Double-clutch Transmission For Vehicles

Abstract

A double-clutch transmission (DCT)includes, but is not limited to an inner input shaft inside an outer input shaft. Two clutches of the DCT are connected to the input shafts respectively. The DCT has three layshafts that are parallel to the input shafts. One or more pinions are fixed onto the layshafts respectively. Seven forward gearwheel groups and one reverse gearwheel group of the DCT are arranged on the shafts. Each one of the gearwheel groups comprises a fixed gearwheel on one of the input shafts, meshing with an idler gearwheel on one of the layshafts. In particular, a third fixed gearwheel meshes with a third idler gearwheel and a fifth idler gearwheel. Especially, the DCT includes, but is not limited to a park-lock.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a U.S. National-Stage entry under 35 U.S.C. .sctn.371 based on International Application No. PCT/EP2009/002355, filed Mar. 31, 2009, which was published under PCT Article 21(2) and which claims priority to European Application No. 08006645.9, filed Mar. 31, 2008, and which claims priority to European Application No. 08006638.4, filed Mar. 31, 2008, and which claims priority to European Application No. 08006639.2, filed Mar. 31, 2008, and which claims priority to European Application No. 08006640.0, filed Mar. 31, 2008, and which claims priority to European Application No. 08006641.8, filed Mar. 31, 2008, and which claims priority to European Application No. 08006642.6, filed Mar. 31, 2008, and which claims priority to European Application No. 08006635.0, filed Mar. 31, 2008, and which claims priority to European Application No. 08006643.4, filed Mar. 31, 2008, and which claims priority to European Application No. 08006644.2, filed Mar. 31, 2008, and which claims priority to European Application No. 08006486.8, filed Mar. 31, 2008, and which claims priority to European Application No. 08006606.1, filed Mar. 31, 2008, and which claims priority to European Application No. 08006607.9, filed Mar. 31, 2008, and which claims priority to European Application No. 08006608.7, filed Mar. 31, 2008, and which claims priority to European Application No. 08006646.7, filed Mar. 31, 2008, and which claims priority to European Application No. 08006616.7, filed Mar. 31, 2008, and which claims priority to European Application No. 08006617.8, filed Mar. 31, 2008, and which claims priority to European Application No. 08006609.5, filed Mar. 31, 2008, and which claims priority to European Application No. 08006610.3, filed Mar. 31, 2008, and which claims priority to European Application No. 08006611.1, filed Mar. 31, 2008, and which claims priority to European Application No. 08006612.9, filed Mar. 31, 2008, and which claims priority to European Application No. 08006621.0, filed Mar. 31, 2008, and which claims priority to European Application No. 08006622.8, filed Mar. 31, 2008, and which claims priority to European Application No. 08006623.6, filed Mar. 31, 2008, and which claims priority to European Application No. 08006624.4, filed Mar. 31, 2008, and which claims priority to European Application No. 08006569.1, filed Mar. 31, 2008, and which claims priority to European Application No. 08006637.6, filed Mar. 31, 2008, and which claims priority to European Application No. 08006615.2, filed Mar. 31, 2008, and which claims priority to European Application No. 08006636.8, filed Mar. 31, 2008, and which claims priority to European Application No. 08006625.1, filed Mar. 31, 2008, and which claims priority to European Application No. 08006626.9, filed Mar. 31, 2008, and which claims priority to European Application No. 08006627.7, filed Mar. 31, 2008, and which claims priority to European Application No. 08006628.5, filed Mar. 31, 2008, and which claims priority to European Application No. 08006629.3, filed Mar. 31, 2008, and which claims priority to European Application No. 08006630.1, filed Mar. 31, 2008, and which claims priority to European Application No. 08006631.9, filed Mar. 31, 2008, and which claims priority to European Application No. 08006619.4, filed Mar. 31, 2008, and which claims priority to European Application No. 08006620.2, filed Mar. 31, 2008, and which claims priority to European Application No. 08006618.6, filed Mar. 31, 2008, and which claims priority to European Application No. 08006614.5, filed Mar. 31, 2008, and which claims priority to European Application No. 08006613.7, filed Mar. 31, 2008, and which claims priority to European Application No. 08006634.3, filed Mar. 31, 2008, and which claims priority to European Application No. 08006633.5, filed Mar. 31, 2008, and which claims priority to European Application No. 08006632.7, filed Mar. 31, 2008, and which claims priority to European Application No. 08006649.1, filed Mar. 31, 2008, and which claims priority to European Application No. 08006648.3, filed Mar. 31, 2008, and which claims priority to European Application No. 08006647.5, filed Mar. 31, 2008, which are all hereby incorporated in their entirety by reference.

TECHNICAL FIELD

[0002] The present application relates to a double-clutch transmission for vehicles, such as cars.

BACKGROUND

[0003] A double-clutch transmission comprises two input shafts that are connected to and that are actuated by two clutches separately. The two clutches are often combined into a single device that permits actuating any of the two clutches at a time. The two clutches transmit driving torque from an engine to the two input shafts of the double-clutch transmission.

[0004] U.S. Pat. No. 6,634,247 B2 discloses a six-gear double clutch transmission with an electric unit. The double clutch transmission has not been widely used in the cars for street driving. Problems that hinder the wide application of double clutch transmission comprise of providing a compact, reliable, and fuel-efficient double clutch transmission. Therefore, there exists a need for providing such a double clutch transmission that is also affordable by consumers.

SUMMARY

[0005] The present application provides a double-clutch transmission (DCT) that comprises an inner input shaft and an outer input shaft. The inner input shaft can be either solid or hollow. The outer input shaft encloses a portion of the inner input shaft in a radial direction. The radial direction of the shaft indicates a direction that points away from a central longitudinal axis of the shaft following a radius direction of the shaft.

[0006] The DCT comprises a first clutch that is non-rotatably connected to the inner input shaft and a second clutch that is also non-rotatably connected to the outer input shaft. For example, the first clutch is fixed to the inner input shaft and the second clutch is fixed to the outer input shaft. Alternatively, the non-rotatable connection can be provided by a universal joint.

[0007] The DCT also comprises a first layshaft, a second layshaft, and a third layshaft that are radially spaced apart from the input shafts. The layshafts are essentially parallel to the input shafts. One or more of the layshafts comprise a pinion or pinions for outputting a drive torque to a vehicle. Examples of the vehicle include a car or a motorcycle. Pinions of the DCT comb with an output gearwheel respectively such that the output gearwheel transmits torques from the pinions to an output shaft for driving the vehicle.

[0008] The DCT has gearwheels arranged on the first layshaft, on the second layshaft, on the third layshaft, on the inner input shaft, and on the outer input shaft. The gearwheels includes a first gearwheel group, a second gearwheel group, a third gearwheel group, a fourth gearwheel group, a fifth gearwheel group, a sixth gearwheel group, a seventh gearwheel group and a reverse gearwheel group for providing seven sequentially increasing forward gears and one reverse gear respectively. Typically, a gearwheel is typically mounted to its carrying shaft coaxially. The fact that a gearwheel and its carrying shaft having the same rotational axis ensures uniform gear meshing of the gearwheel with its neighboring gearwheel on a parallel shaft.

[0009] The sequentially increasing gears describe an escalating order that members of the order follow each other. Gears of a car are typically arranged in a sequentially increasing manner from first gear to seventh gear. For example, in a vehicle can have a transmission with a first gear having a gear ratio of 2.97:1. A second gear has a gear ratio of 2.07:1. A third gear has a gear ratio of 1.43:1. A fourth gear has a gear ratio of 1.00:1. A fifth gear has a gear ratio of 0.84:1. A sixth gear has a gear ratio of 0.56:1. Lastly, a seventh gear has a gear ratio of 0.45:1. The seven gears provide an increasing order of output speed of the transmission for driving the vehicle.

[0010] The first gearwheel group comprises a first fixed gearwheel on the outer input shaft, meshing with a first idler gearwheel on one of the layshafts. Similarly, the third gearwheel group comprises a third fixed gearwheel on the outer input shaft, meshing with a third driven gearwheel on one of the layshafts. The fifth gearwheel group comprises a fifth fixed gearwheel on the outer input shaft, meshing with a fifth idler gearwheel on one of the layshafts. The seventh gearwheel group comprises a seventh fixed gearwheel on the outer input shaft, meshing with a seventh idler gearwheel on one of the layshafts.

[0011] The second gearwheel group comprises a second fixed gearwheel on the inner input shafts, meshing with a second idler gearwheel on one of the layshafts. The fourth gearwheel group comprises a fourth fixed gearwheel on the inner input shafts, meshing with a fourth idler gearwheel on one of the layshafts. The sixth gearwheel group comprises a sixth fixed gearwheel on the inner input shafts, meshing with a sixth idler gearwheel on one of the layshafts. The reverse gearwheel group comprises a fixed driving gearwheel on one of the input shafts, meshing directly or indirectly with a reverse idler gearwheel on one of the layshafts, wherein the layshaft includes or carries the pinion.

[0012] The direct meshing can be provided by two gearwheels that are physically in contact with each other. The indirect meshing can be provided by one or more intermediate gearwheels that mesh with the fixed driving gearwheel and the reverse gearwheel.

[0013] Each of these gearwheel groups comprises a coupling device, which is arranged on one of the layshafts to selectively engage one of the gearwheels to its carrying shaft for selecting one the seven sequentially increasing forward gears and the one reverse gear. The carrying shaft is a shaft that carries the weight of the gearwheel. The third fixed gearwheel meshes with both the third idler gearwheel and the fifth idler gearwheel.

[0014] Two coupling devices for engaging two gearwheels can form a coupling unit. The coupling unit is also called a double-sided coupling unit or a double-sided synchronizer.

[0015] The DCT provides seven forward gears and one reverse gear. A dual-clutch of the DCT enables gear switching between odd and even ratios to be swift and efficient because the gearwheels for the odd gears and even gears are driven by different clutches respectively. A double-meshing feature is provided by the third fixed gearwheel on the outer input shaft meshing with the third idler gearwheel and the fifth idler gearwheel. The double-meshing feature makes the DCT to be compact and lightweight at low cost because one fixed gearwheel is reduced from the input shafts. The reverse gear enables a vehicle with the DCT to be more maneuverable.

[0016] The double-clutch transmission can further comprise a park-lock gearwheel that is fixed onto one of the layshafts for providing a park-lock. The layshaft with the park-lock also carries the pinion for engaging and for locking a differential of the DCT. The differential comprises the output gearwheel on the output shaft. The park-lock enables a vehicle with the park-lock to park at a place in a secure manner, even on a slope. The park-lock is easy to implement as it is placed on the layshaft that carries the pinion.

[0017] The double clutch transmission can provide two coupling devices that engage two of the idler gearwheels of the seven gears respectively at the same time. The process of multiple engagements of the two idler gearwheels on different layshafts is known as pre-selection of gears. Especially, the two idlers of two consecutive gears that are driven by different input shafts of the DCT can be both engaged for shifting from one of the two gears to the other. For example, idler gearwheels of the third gear and the fourth gear of the DCT are both engaged to their weight-carrying layshaft by their neighboring coupling devices when only one of the input shafts receives an input torque. Since incoming torque from any of the input shafts is constantly delivered to an idler gearwheel of the two consecutive gears, there is little or no interruption in torque flow during the gearshift. Therefore, the double-clutch transmission provides continuous and more efficient torque transmission, as compared to the gearshift process in single clutch transmissions.

[0018] According to the application, different input shafts can provide the first forward gear and the reverse gear. For example, the outer input shaft can drive the first gearwheel group and the inner input shaft can drive the reverse gearwheel group. Since the first forward gear and the reverse gear are provided on two different input shafts, the two clutches of the DCT can enable efficient switching between the two input shafts to provide a rocking motion. In this, a driving scheme that the DCT engages one of the two input shafts alternatively drive the vehicle back and forth rapidly using the first gear and the reverse gear without much loss in momentum. The swaying back and forth of the vehicle pulls the vehicle out of mud.

[0019] The reverse gearwheel group can also comprise a further reverse gear for providing second reverse gear, in addition to the previously mentioned first gear. The further reverse gear meshes with a further fixed driving gearwheel that is provided on one of the input shafts. One of the two reverse gears can provide a powerful and slower reverse gear whilst the other reverse gear can provide a faster reverse gear with less strength. The two reverse gears at different speeds enable some special vehicles, such as a Leopard II Main Battle Tank, to increase their maneuverability and operation efficiency.

[0020] Furthermore, different input shafts can drive the two reverse gears for providing the two reverse gears. This scheme makes the interchange between the two reverse gears to be fast, just by alternatively engaging one of the two clutches of the DCT. In a special case, the two reverse gears are driven either by the same inner input shaft or by the same outer input shaft. For easier design and implementation, the two reverse gears can be provided on the same layshaft. In certain implementation, the second forward gear and the further reverse gear are driven by different input shafts for providing a rocking motion to pull out a vehicle that is stuck in mud.

[0021] The DCT can also comprise an eighth gearwheel group for providing an eighth forward gear. The eighth gearwheel group comprises a fixed eighth fixed gearwheel on one of the input shafts, meshing with an eighth idler gearwheel on one of the layshafts. The eighth gear is useful for some high-end cars that have more powerful engine for achieving high speed driving. More gears also mean more choices for a driver.

[0022] The sixth fixed gearwheel can further mesh with the eighth idler gearwheel. In other words, the DCT can provide two double-meshing features. One double meshing feature includes the eighth idler gearwheel meshing with the sixth idler gearwheel via the sixth fixed gearwheel, which also serves as the eight fixed gearwheel. The two double meshing features save or reduce two driving gearwheels on the input shafts such that the weight, cost and size of the DCT is reduced. Furthermore, since the two double-meshing features are provided on the inner input shaft and the outer input shaft separately, gear changing between the idler gearwheels of these double-meshing features can be performed efficiently by engaging any of the input shafts using the double clutch.

[0023] In the application, the DCT has a distance between one of the layshafts with gearwheels of low gears and the inner input shaft is greater than a distance between the other layshaft with gearwheels of high gears and the inner input shaft. The layshaft with gearwheels of low gears can be any of the layshafts. Since gearwheels of low gears, for example first, second, or third gear, can be larger than the gearwheels of high gears, such as fifth, sixth, seventh, or eighth gear, the layshaft with the gearwheels of high gears can be brought closer to the input shafts such that the DCT can be made more compact.

[0024] In the application, the DCT can have two pinions are mounted on two of the layshafts respectively. In a further alternative, each of the three layshafts can have a pinion on it for outputting a torque of its carrying layshaft. A gearwheel or pinion-carrying shaft is a shaft that bears the weight of the gearwheel. The pinion can be used as a fixed gearwheel for providing the park-lock. In fact, any one of the pinions on the layshafts can be made into or be adapted to the park-lock.

[0025] Two or more of the first idler gearwheel, the second idler gearwheel, the third driven gearwheel, and the fourth idler gearwheel can be provided on the same layshaft. These gearwheels of low gears transmit larger torques and thus require a thicker layshaft, as compared to the layshaft carrying the gearwheels of high gears. The thicker layshaft can be more fully utilized when more gearwheels of the low gears are installed on it. For example, the first idler gearwheel, the second idler gearwheel, and the third idler gearwheel can be mounted on the upper layshaft.

[0026] Similarly, two or more of the fifth idler gearwheel, the sixth idler gearwheel, the seventh idler gearwheel, and the eighth idler gearwheel can be provided on the same layshaft. Gearwheels of higher gears are advantageous to be installed on the same shaft because the shaft can be made slim for the reduction of cost and size of the double-clutch transmission. For example, the fifth idler gearwheel, the sixth idler gearwheel, and the seventh idler gearwheel can be provided on the same layshaft. More gearwheels of high gears mounted on the same shaft provide further opportunity for installing gearwheels of low gears on another shaft. The other shaft can thus be made short for carrying less number of gearwheels.

[0027] The DCT can further comprise bearings for supporting the layshafts and the input shafts. One or more of the bearings can be provided next to the pinions. Since each of the pinions output torque of its carrying shaft, support from its neighboring bearing can help with reducing the carrying shaft's deflection unload, minimizing the carrying shaft's size and improving the pinion's meshing accuracy for better efficiency.

[0028] One or more of the bearings can be provided next to one of the driven gearwheels of low gears. Bearings that support a shaft are more advantageously provided next to gearwheels of low gears. The supporting shaft can be made slim and have less deflection when the bearings are next to the gearwheels of low gears. For example, the bearing can be located immediately adjacent to the first idler gearwheel or the second idler gearwheel. The driven gearwheels of low gears, such as first, second, or third gear, carries heavier load and torque, which need stronger support from the bearings at their vicinity.

[0029] In the application, there can be provided a gearbox an output gearwheel on an output shaft that meshes with the pinion of the DCT for outputting the drive torque to a torque drain. The torque drain can be a differential of a drive train. In a motor vehicle, the term drive train is also known as power train or power plant that refers to the group of components that generate power and deliver it to the road surface, water, or air. This includes the engine, transmission, drive shafts, differentials, and the final drive. The final drive can be drive wheels, continuous track like with tanks or Caterpillar tractors, propeller, etc. Sometimes the "power train" is used to refer to simply the engine and transmission, including the other components only if they are integral to the transmission. In a carriage or wagon, running gear designates the wheels and axles in distinction from the body.

[0030] According to the application, a power train device with the gearbox is provided. The power train device comprises one or more power source for generating a driving torque. The power source is preferred to be onboard with the power train such that a vehicle with the power train device can be more mobile.

[0031] The power source can comprise a combustion engine. The vehicle having the combustion engine and the double-clutch transmission is easy to manufacture. The combustion engine can consume less petrol for environmental protection. Furthermore, a combustion engine for other types of fuel can have even less polluting emission, such as hydrogen fuel.

[0032] The power source can further comprise an electric motor. Electric motor used in a hybrid car, or in an electrical car enables reduction of pollution, as compared to typical combustion using petrol. The electric motor can even recuperate brake energy in a generator mode.

[0033] In the application, there can be provided a vehicle that comprises the power train device. The vehicle having the power train device is efficient in energy usage by using the double-clutch transmission.

[0034] The double clutch transmission enables pre-selection of gears for smooth gear transmission. Two coupling devices can engage the idler gearwheel of the current gear and the idler gearwheel of the next sequential gear at the same time. This allows the next sequential gear to be connected rapidly and thus in a more smooth manner. In particular, the two idlers of two consecutive gears that are driven by different input shafts of the DCT can be both engaged simultaneously. For example, idler gearwheels of the third gear and the fourth gear of the DCT can be both engaged to their weight-carrying layshaft by their respectively coupling devices when one of the input shafts receives an input torque. One engaged idler gearwheel is driven directly by the input torque whilst the other engaged idler gearwheel is driven via the pinion by the input torque. In this manner, little or no interruption in torque flow during gearshift. Therefore, the double-clutch transmission provides continuous and more efficient torque transmission, as compared to other gearshift process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and

[0036] FIG. 1 illustrates a front view of an embodiment of a double clutch transmission of the application;

[0037] FIG. 2 illustrates the path of torque flow of a first gear transmission ratio;

[0038] FIG. 3 illustrates the path of torque flow of a second gear transmission ratio;

[0039] FIG. 4 illustrates the path of torque flow of a third gear transmission ratio;

[0040] FIG. 5 illustrates the path of torque flow of a fourth gear transmission ratio;

[0041] FIG. 6 illustrates the path of torque flow of a fifth gear transmission ratio;

[0042] FIG. 7 illustrates the path of torque flow of a sixth gear transmission ratio;

[0043] FIG. 8 illustrates the path of torque flow of a seventh gear transmission ratio;

[0044] FIG. 9 illustrates the path of torque flow of a reverse gear transmission ratio;

[0045] FIG. 10 illustrates an assembly of a double-sided coupling device with its neighboring gearwheels for engagement;

[0046] FIG. 11 illustrates an assembly of a single-sided coupling device with its neighboring gearwheel for engagement;

[0047] FIG. 12 illustrates an assembly of an idler gearwheel that is rotatably supported by a shaft on a bearing;

[0048] FIG. 13 illustrates an assembly of a fixed gearwheel that is supported on a shaft;

[0049] FIG. 14 illustrates a cross-section through a detail of a crankshaft of an internal combustion engine according to embodiment of the double-clutch transmission;

[0050] FIG. 15 illustrates a front view of a further embodiment of a double clutch transmission of the application;

[0051] FIG. 16 illustrates an expanded side view of the double clutch transmission of FIG. 16;

[0052] FIG. 17 illustrates a front view of a further embodiment of a double clutch transmission of the application;

[0053] FIG. 18 illustrates an expanded side view of the double clutch transmission of FIG. 17;

[0054] FIG. 19 illustrates a front view of a further embodiment of a double clutch transmission of the application;

[0055] FIG. 20 illustrates an expanded side view of the double clutch transmission of FIG. 19;

[0056] FIG. 21 illustrates a front view of a further embodiment of a double clutch transmission of the application; and

[0057] FIG. 22 illustrates an expanded side view of the double clutch transmission of FIG. 21.

[0058] FIG. 23 illustrates an alternative front view of the expanded side view of the double clutch transmission in FIG. 18.

DETAILED DESCRIPTION

[0059] The following detailed description is merely exemplary in nature and is not intended to limit or the application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description.

[0060] In the following description, details are provided to describe the embodiments of the application. It shall be apparent to one skilled in the art, however, that the embodiments may be practiced without such details.

[0061] FIGS. 1 to 9 and FIGS. 11 to 15 provide detailed description of an embodiment of a double clutch transmission (DCT) of the application.

[0062] FIG. 1 illustrates a front view of an embodiment of a double clutch transmission 1 of the application. The DCT 1 comprises a reverse gear idler shaft 38, a relatively large output gearwheel 12 on an output shaft 14, an upper pinion 41 on an upper layshaft 40, a solid input shafts 20, a hollow input shaft 22, and a lower pinion 51 on a lower layshaft 50.

[0063] The input shaft 20 is also called K1. The input shaft 22 is also called K2. The solid input shaft 20 and the hollow input shaft 22 share the same longitudinal axis of rotation and are non-rotatably connected to two clutches 8, 10 of a double clutch 6, separately. The clutches 8, 10 and the double clutch 6 are shown in FIG. 15.

[0064] The two pinions 41, 51 are fixed to the upper layshaft 40 and the lower layshaft 50 respectively at their longitudinal axes of rotation. The output gearwheel 12 is also fixed to the output shaft 14 at its rotation axis. The two pinions 41, 51 mesh separately with the output gearwheel 12 at different positions of the output gearwheel 12.

[0065] The reverse gear idler shaft 38, the upper layshaft 40, the input shafts 20, 22, and the lower layshaft 50 are parallel to each other with predetermined distances in-between. The distances are provided in radial directions of these shafts, which are better seen in FIG. 2. Other gearwheels are mounted on these shafts that mesh with each other according to predetermined manners. The manners of these gearwheels' mounting and meshing are better seen in some of the following figures.

[0066] Functionally, the gearwheel 12 acts as a ring gear of a differential that is used as a carrier of differential gears. The carrier is contained in a housing. Driving shafts for wheels of a car, which are not shown in the figure, can be connected to corresponding tapered gears of the differential. Therefore, the output shaft 14 acts essentially as an axis of the differential.

[0067] FIG. 1 further shows a cutting plane A-A for illustrating an expanded cross-section view through the DCT 1, which is shown in FIGS. 2 to 9. The cutting plane A-A passes through the rotational axes of the reverse gear idler shaft 38, the upper layshaft 40, the input shafts 20, 22, the lower layshaft 50, and the output shaft 14. One of the goals of FIGS. 2 to 9 is to illustrate further structure and torque flows of the DCT 1.

[0068] FIG. 2 illustrates the expanded view of the DCT that shows the manners of the gearwheels mounting, which corresponds to FIG. 1.

[0069] According to FIG. 2, the DCT 1 comprises the following shafts, from top to bottom, the reverse gear idler shaft 38, the upper layshaft 40, the hollow input shaft 22, the solid input shaft 20, the lower layshaft 50, and the output shaft 14. The solid input shaft 20 is partially disposed inside the hollow input shaft 22. The solid input shaft 20 also protrudes outside the hollow input shaft 22 at two ends. The hollow input shaft 22 is mounted onto the solid input shaft 20 by a pair of solid shaft bearings 71 that are disposed between the solid input shaft 20 and the hollow input shaft 22 at two ends of the hollow input shaft 22. As a result, the two input shafts 20, 22 are coupled together such that the solid input shaft 20 is free to rotate inside the hollow input shaft 22. The hollow input shaft 22 surrounds a right portion of the solid input shaft 20, and a left portion of the solid input shaft 20 is exposed outside the hollow input shaft 22. The assembly of the input shafts 20, 22 is supported by a solid shaft bearing 71 at a protruding end of the solid shaft 20 on the left and by a hollow shaft bearing 72 on the hollow input shaft 22 on the right.

[0070] According to FIG. 2, the outer input shaft 22 surrounds a portion of the solid input shaft 20 in a radial direction of the solid input shaft 20. There are four gearwheels mounted on the left exposed portion of the solid input shaft 20. These gearwheels are a fixed wheel second gear 30, a fixed wheel reverse gear 34, a fixed wheel fourth gear 31, and a fixed wheel sixth gear 32 from left to right sequentially. All of the fixed wheel second gear 30, the fixed wheel reverse gear 34, the fixed wheel fourth gear 31, and the fixed wheel sixth gear 32 are mounted onto the solid input shaft 20 coaxially. On the hollow input shaft 22, which is mounted on the right portion of the solid input shaft 20, there is attached with a fixed wheel third gear 25, a fixed wheel seventh gear 27, and a fixed wheel first gear 24 from left to right. The fixed wheel third gear 25 also serves as a fixed wheel fifth gear 26. The fixed wheel second gear 30 is fixed onto the hollow input shaft 22 coaxially.

[0071] The upper layshaft 40 is provided above the input shafts 20, 22. There are gearwheels and coupling devices provided on the upper layshaft 40, which includes, from right to the left, the upper pinion 41, an idler seventh gear 66, a double-sided coupling device 80, an idler fifth gear 64, an idler sixth gear 65, a double-sided coupling device 81, and an reverse gear idler wheel 37. One layshaft bearing 73 is positioned at a left end of the upper layshaft 40 and another layshaft bearing 73 is positioned between the upper pinion 41 and the idler seventh gear 66. The idler seventh gear 66, the idler fifth gear 64, the idler sixth gear 65, and the reverse gear idler wheel 37 are mounted on the upper layshaft 40 by bearings respectively such that these gearwheels are free to rotate around the upper layshaft 40. The double-sided coupling device 80 is configured to move along the upper layshaft 40 to engage or disengage the idler seventh gear 66 or the idler fifth gear 64 to the upper layshaft 40. Similarly, the double-sided coupling device 81 is configured to move along the upper layshaft 40 to engage the idler sixth gear 65 or the reverse gear idler wheel 37 to the upper layshaft 40. The idler seventh gear 66 meshes with the fixed wheel seventh gear 27. The idler fifth gear 64 meshes with the fixed wheel fifth gear 26. The idler sixth gear 65 meshes with the fixed wheel sixth gear 32.

[0072] The reverse gear idler shaft 38 is provided further above the upper layshaft 40. A first reverse gear wheel 35 is fixed onto the reverse gear idler shaft 38 in the middle. An idler shaft bearing 74 supports each end of the reverse gear idler shaft 38 such that the first reverse gear wheel 35 and the reverse gear idler shaft 38 are free to rotate together. The upper layshaft 40, the reverse gear idler shaft 38, and the input shafts 20 are positioned at vertexes of a triangle such that the first reverse gear wheel 35 meshes with the fixed wheel reverse gear 34 and with the reverse gear idler wheel 37.

[0073] The lower layshaft 50 is provided below the input shafts 20, 22. There are a number of gearwheels and coupling devices mounted on the lower layshaft 50, which include, from right to the left, the lower pinion 51, an idler first gear 60, a double-sided coupling device 83, an idler third gear 62, an park-lock 42, an idler fourth gear 63, a double-sided coupling device 82, and an idler second gear 61. One layshaft bearing 73 is provided between the lower pinion 51 and the idler first gear 60. Another layshaft bearing 73 is provided next to the idler second gear 61 at the left end of the lower layshaft 50. The lower pinion 51 is fixed onto the lower layshaft 50 at its rotational axis. The idler first gear 60, the idler third gear 62, the idler fourth gear 63, and the idler second gear 61 are mounted on the lower layshaft 50 by bearings separately such that these gearwheels become idlers, being free to rotate around the lower layshaft 50.

[0074] The double-sided coupling devices 83 is configured to move along the lower layshaft 50 such that it can engage either the idler first gear 60 or the idler third gear 62. Similarly, the double-sided coupling devices 82 is configured to move along the lower layshaft 50 such that it can engage either the idler fourth gear 63 or the idler second gear 61 to the lower layshaft 50 respectively. The idler first gear 60 meshes with the fixed wheel first gear 24. The idler third gear 62 meshes with the fixed wheel third gear 25. The idler fourth gear 63 meshes with the fixed wheel fourth gear 31. The idler second gear 61 meshes with the fixed wheel second gear 30.

[0075] The park-lock 42 includes a fixed gear wheel that is fixed to the lower layshaft 50. The park-lock 42 locks the lower layshaft 50 when parking a vehicle that has the double-clutch transmission 1. The park-lock is provided with a ratchet device, with a click device having a rack element, a claw or similar. The park-lock 42 keeps the lower layshaft 50 and the output shaft 14 from rotating, which thereby stops the vehicle from moving when it is a parked. Functions of the park-lock 42 are easy to implement as it is placed the lower layshaft 50 that carries the pinion 51. In a generic sense, the park-lock 42 can be placed on any layshaft that carries the pinion.

[0076] The DCT 1 with the park-lock is controlled by a gearshift lever located in a driving compartment and movable by a vehicle operator between positions corresponding to transmission gear ranges, such as Park, Reverse, Neutral, Drive, and Low. A linear actuation cable is attached at its first end to the gearshift lever, and movement of the gearshift lever alternatively pushes or pulls on the cable to move a transmission mode select lever attached to the other end of the cable. The mode select lever is mechanically connected to a shift valve within a DCT housing, and movement of the shift valve effects shifting between different gears.

[0077] When the gearshift lever is placed in a park position, two related mechanical actuations take place within the DCT 1. First, the mode select lever is moved, depending on a clutch system, to disengage or to engage the input shafts 20, 22 from an engine. Second, a park-lock pawl is moved into locking engagement with the ratchet device of the park-lock 42 on the lower layshaft 50 to thereby lock the output shaft 14 against rotation. A linear actuation cable that actuates the mode select lever moves the lock pawl.

[0078] In other words, there are two double-meshing features provided in the DCT 1. A first double-meshing feature comprises that the fixed wheel third gear 25 meshes with both the idler third gear 62 and the idler fifth gear 64. A second double meshing feature comprises that the first reverse gear wheel 35 meshes with both the reverse gear idler wheel 37 and the fixed wheel reverse gear 34.

[0079] In addition, FIG. 2 shows a distance 56 that extends between the input shafts 20, 22 and the upper layshaft 40 and a distance 58 that extends between the input shafts 20, 22 and the lower layshaft 50.

[0080] The distance 56 the input shafts 20, 22 and the upper layshaft 40 is measured from a common longitudinal axis of the input shafts 20, 22 to a longitudinal axis of the upper layshaft 40. The gearwheels 64, 65, 66 that reflect high gears are provided on the upper layshaft 40. Similarly, the distance 58 is measured from the common longitudinal axis of the input shafts 20, 22 to a longitudinal axis of the lower layshaft 50. The gearwheels 60, 61, 62, 63 that reflect low gears are provided on the lower layshaft 50. Since the high gears are smaller than the low gears, the distance 56 is longer than the distance 58.

[0081] The output shaft 14 is further provided below the lower layshaft 50. Two output shaft bearings 75 at two opposite ends of the output shaft 14 respectively for supporting. The output gearwheel 12 is fixed onto the output shaft 14 coaxially. The output gearwheel 12 meshes with the lower pinion 51 and the upper pinion 41.

[0082] In the present specification, the expressions "mesh" and "comb" with respect to geared wheels or engaged gearwheels are provided as synonyms. The solid input shaft 20 is alternatively termed as an inner input shaft 20, while the hollow input shaft 22 is alternatively termed as an outer input shaft 22. The solid input shaft 20 is replaced alternatively by a hollow shaft and is disposed inside the hollow input shaft 22. The term "coupling device" is alternatively termed as "shifting mechanism" or "synchronizer" for engaging or disengaging gearwheels on its carrying shaft. The double-clutch transmission (DCT) can be alternatively termed as a double clutch, or a dual clutch transmission.

[0083] The fixed wheel first gear 24 is also known as the first fixed gearwheel 24. The fixed wheel third gear 25 is also known as the third fixed gearwheel 25. The fixed wheel fifth gear 26 is also known as the fifth fixed gearwheel 26. The fixed wheel seventh gear 27 is also known as the seventh fixed gearwheel 27. The fixed wheel second gear 30 is also known the second fixed gearwheel 30. The fixed wheel fourth gear 31 is also known as the fourth fixed gearwheel 31. The fixed wheel sixth gear 32 is also known as the sixth fixed gearwheel 32. The first reverse gear wheel 35 is also known as a first reverse idler gearwheel 35. The reverse gear idler wheel 37 is also known as the reverse idler gearwheel 37. The idler first gear 60 is also known as the first idler gearwheel 60. The idler second gear 61 is also known as the second idler gearwheel 61. The idler third gear 62 is also known as the third fixed gearwheel 62. The idler fourth gear 63 is also known as the fourth idler gearwheel 63. The idler fifth gear 64 is also known as the fifth idler gearwheel 64. The idler sixth gear 65 is also known as the sixth idler gearwheel 65. The idler seventh gear 66 is also known as the seventh idler gearwheel 66.

[0084] In the drawings of the present application, dash lines indicate either alternative positions of the illustrated parts or combing relationship between the gearwheels.

[0085] The DCT 1 permits gearshift operations with less loss of driving torque. This is because the gearshift operations can selectively connect of one of the two clutches 8, 10 of the DCT 1. Therefore, an associated additional main drive clutch can be avoided. The selective connections between the two clutches 8, 10 also enable a realization of an automatic transmission that can be operated without interruptions in propulsive power. The propulsive power comprises momentum derived from rotating gearwheels and rotating shafts inside the DCT 1. Such a transmission is also similar in design to a mechanical manual transmission. The DCT 1 further provides a parallel manual transmission that can be used for transverse installation in a front-wheel drive vehicle.

[0086] The DCT 1 according to the application can be connected similar to a known manual transmission, such as a parallel manual transmission. In the known manual transmission, a drive shaft for the front axle of a vehicle extends outward from its DCT case, and parallel to the output shaft 14 of the main DCT 1. The arrangement of the known manual transmission provides little space left for actuation of the manual transmission and clutch and for an optional electric motor. The optional electric motor can act as a starter device for a combustion engine, as an energy recuperation device for brake operation or as an additional drive means in hybrid vehicles. Having such little space presents a number of difficulties that are solved or are at least alleviated by the application. The application provides a DCT 1 that has two clutches for connecting to an electrical motor and the manual transmission in a compact manner.

[0087] The application provides a compact structure of a parallel transmission. The parallel transmission includes two input shafts 20, 22, each of which can be coupled non-rotatably via its own clutch to a shaft that is powered by a drive engine of a vehicle. The DCT 1 of the application further provides the output shaft 14 that is parallel to the input shafts 20, 22.

[0088] The DCT 1 according to the application is particularly well suited for transverse installation in front-wheel drive vehicles, in which the front differential, for example, is positioned below the pinions 41, 51. A short overall length of the power train for transmitting torques can be achieved.

[0089] The application provides at least two relatively small pinions 41, 51 on intermediately arranged layshafts 40, 50 that comb with one relatively big output gearwheel 12. The output gearwheel 12 in turn is fixed onto the output shaft 14. This arrangement provides a compact and lightweight DCT 1.

[0090] The application further allows a design in which the output gearwheel 12 is integrated into a transmission differential device without providing an intermediate output shaft of the DCT 1. This allows a very dense packaging situation for the DCT 1.

[0091] It is further not only of advantage to provide fixed wheels for the even gearwheels on one input shaft and fixed gearwheels for the odd gears on another input shaft. This arrangement provides the above-mentioned power-shift operation in a smooth and efficient manner when gearshift is performed sequentially. This is because the DCT 1 can alternatively engage one of the two clutches 8, 10 in the process of increasing or decreasing gear. For example, the power-shift operation from the third gear to the fourth gear causes the solid input shaft 20 and the hollow input shaft 22 being engaged alternatively, which is energy efficient and fast.

[0092] Some gearwheels of the low gears, for example a first, second, third or fourth gear, provided on the same layshaft are advantageous. In FIG. 2, the idler first gear 60, the idler second gear 61, the idler third gear 62, and the idler fourth gear 63 are installed on the same lower layshaft 50. In contrast, gearwheels of high gears, for example fifth, sixth, or seventh gear, provided on another layshaft. According to FIG. 2, the idler fifth gear 64, the idler sixth gear 65, and the idler seventh gear 66 are provided on the upper layshaft 40. This is because the lower layshaft 50 has lower rotational speed with larger size for higher torque transmission, as compared to that of the upper layshaft 40. This arrangement eliminates the need of providing multiple layshafts with larger size for carrying those heavily loaded idler gearwheels 60, 61, 62, 63 of the low gears, for example first, second, third, or fourth gear, on different shafts. Furthermore, the reverse gear idler shaft 38 with even lower rotational speed, heavier load and lesser number of gearwheels can be made shorter and thicker. These arrangements offer the feasibility of making the DCT 1 lightweight with less cost.

[0093] The layshaft bearings 73 of the DCT 1 are next to the pinions 41, 51. The layshaft bearings 73 offer strong support to the pinions carrying layshafts 40, 50 for reducing shaft deflection. Excessive shaft deflection can lower gear transmission efficiency or cause gearwheels early worn out. The idler shaft bearing 74 next to the reverse gear idler shaft 38 also provides strong support to the first reverse gear wheel 35. In a like manner, the output shaft bearing 75 at two ends of the output shaft 14 offer sturdy support to the output shaft 14.

[0094] In other words, it is beneficial to provide the idler first gear 60, the idler second gear 61, the reverse gear idler wheel 37, and the pinions 41, 51 close to the bearings for supporting. The pinions 41, 51 and especially these gearwheels of low gears, for example first and second gears, undergo heavier load than those of the higher gears because the drive ratio is higher for the lower gears and reverse gears. Therefore, a carrying shaft of low gears, for example lower layshaft 50, must take up higher driving forces. If those forces are taken up close to the support points of the layshaft, shaft bending will be reduced.

[0095] FIG. 2 illustrates the path of torque flow of a first gear transmission ratio. In FIG. 2, an input torque of the first gear is received from a crankshaft 2 of a combustion engine, which is not shown in the figure. According to FIG. 2, the hollow input shaft 22 of the double-clutch 6 of the DCT 1 receives the input torque of the first gear. A torque of the first gear is transmitted from the hollow input shaft 22, via the fixed wheel first gear 24, via the idler first gear 60, via the double-sided coupling device 83, via the lower layshaft 50, via lower pinion 51, and via the output gearwheel 12 to the output shaft 14. The double-sided coupling device 83 is engaged to the idler first gear 60 when transmitting the torque of the first gear, which provides the first gear of the DCT 1. The number of tooth engagements or engaged gear pairs for the torque transfer of the first gear is two.

[0096] FIG. 3 illustrates the path of torque flow of a second gear transmission ratio. In FIG. 3, an input torque of the second gear is received from the crankshaft 2 of the combustion engine, which is not shown in the figure. According to FIG. 3, the solid input shaft 20 of the double-clutch 6 of the DCT 1 receives the input torque of the second gear. The torque of the second gear is transmitted from the solid input shaft 20, via the fixed wheel second gear 30, via the idler second gear 61, via the double-sided coupling device 82, via the lower layshaft 50, via the lower pinion 51, via the output gearwheel 12, to the output shaft 14. The double-sided coupling device 82 is engaged to the idler second gear 61 when transmitting the torque of the second gear, which provides the second gear of the DCT 1. The number of tooth engagements or engaged gear pairs for the torque transfer of the second gear is two.

[0097] FIG. 4 illustrates the path of torque flow of a third gear transmission ratio. In FIG. 4, an input torque of the third gear is received from the crankshaft 2 of the combustion engine, which is not shown in the figure. According to FIG. 4, the hollow input shaft 22 of the double clutch of the DCT 1 receives the input torque of the third gear. The torque of the third gear is transmitted from the hollow input shaft 22, via the fixed wheel third gear 25, via the idler third gear 62, via the double-sided coupling device 83, via the lower layshaft 50, via the lower pinion 51, via the output gearwheel 12, to the output shaft 14. The double-sided coupling device 83 is engaged to the idler wheel third gear 62 when transmitting the torque of the third gear, which provides the third gear of the DCT 1. The number of tooth engagements or engaged gear pairs for the torque transfer of the third gear is two.

[0098] FIG. 5 illustrates the path of torque flow of a fourth gear transmission ratio. In FIG. 5, an input torque of the fourth gear is received from the crankshaft 2 of the combustion engine, which is not shown in the figure. According to FIG. 5, the solid input shaft 20 of the double-clutch 6 of the DCT 1 receives the input torque of the fourth gear. The torque of the fourth gear is transmitted from the solid input shaft 20, via the fixed wheel fourth gear 31, via the idler fourth gear 63, via the double-sided coupling device 82, via the lower layshaft 50, via the lower pinion 51, via the output gearwheel 12, to the output shaft 14. The double-sided coupling device 82 is engaged to the idler fourth gear 63 when transmitting the torque of the fourth gear, which provides the fourth gear of the DCT 1. The number of tooth engagements or engaged gear pairs for the torque transfer of the fourth gear is two.

[0099] FIG. 6 illustrates the path of torque flow of a fifth gear transmission ratio. In FIG. 6, an input torque of the fifth gear is received from the crankshaft 2 of a combustion engine, which is not shown in the figure. According to FIG. 6, the hollow input shaft 22 of the double-clutch 6 of the DCT 1 receives the input torque of the fifth gear. The torque of the fifth gear is transmitted from the hollow input shaft 22, via the fixed wheel fifth gear 26, via the idler fifth gear 64, via the double-sided coupling device 80, via the upper layshaft 40, via the upper pinion 41, via the output gearwheel 12, to the output shaft 14. The double-sided coupling device 80 is engaged to the idler fifth gear 64 when transmitting the torque of the fifth gear, which provides the fifth gear of the DCT 1. The number of tooth engagements or engaged gear pairs for the torque transfer of the fifth gear is two.

[0100] FIG. 7 illustrates the path of torque flow of a sixth gear transmission ratio. In FIG. 7, an input torque of the sixth gear is received from the crankshaft 2 of a combustion engine, which is not shown in the figure. The solid input shaft 20 of the double-clutch 6 of the DCT 1 receives the input torque of the sixth gear. The torque of the sixth gear is transmitted from the solid input shaft 20, via the fixed wheel sixth gear 32, via the idler sixth gear 65, via the double-sided coupling device 81, via the upper layshaft 40, via the upper pinion 41, via the output gearwheel 12, to the output shaft 14. The double-sided coupling device 81 is engaged to the idler sixth gear 65 when transmitting the torque of the sixth gear, which provides the sixth gear of the DCT 1. The number of tooth engagements or engaged gear pairs for the torque transfer of the sixth gear is two.

[0101] FIG. 8 illustrates the path of torque flow of a seventh gear transmission ratio. In FIG. 8, an input torque of the seventh gear is received from the crankshaft 2 of a combustion engine, which is not shown in the figure. According to FIG. 8, the hollow input shaft 22 of the double-clutch 6 of the DCT 1 receives the input torque of the seventh gear. The torque of the seventh gear is transmitted from the hollow input shaft 22, via the fixed wheel seventh gear 27, via the idler seventh gear 66, via the double-sided coupling device 80, via the upper layshaft 40, via the upper pinion 41, via the output gearwheel 12, to the output shaft 14. The double-sided coupling device 80 is engaged to the idler seventh gear 66 when transmitting the torque of the seventh gear, which provides the seventh gear of the DCT 1. The number of tooth engagements or engaged gear pairs for the torque transfer of the seventh gear is two.

[0102] FIG. 9 illustrates the path of torque flow of a reverse gear transmission ratio, which is a first reverse gear. In FIG. 9, an input torque of the reverse gear is received from the crankshaft 2 of a combustion engine, which is not shown in the figure. According to FIG. 9, the solid input shaft 20 of the double-clutch 6 of the DCT 1 receives the input torque of the reverse gear. The torque of the reverse gear is transmitted from the solid input shaft 20, via the fixed wheel reverse gear 34, and via the first reverse gear wheel 35. The torque is then transmitted via the reverse gear idler wheel 37, via the double-sided coupling device 81, via the upper layshaft 40, via the upper pinion 41, and via the output gearwheel 12 to the output shaft 14. The double-sided coupling device 81 is engaged to the reverse gear idler wheel 37 when transmitting the torque of the reverse gear, which provides the reverse gear of the DCT 1. The number of tooth engagements or engaged gear pairs for the torque transfer of the reverse gear is three.

[0103] FIG. 10 illustrates an assembly 100 of a double-sided coupling device 102 with its neighboring gearwheels 101, 103 for engagement. The assembly 100 comprises a shaft 104 with the two coaxially mounted idler gears 101, 103 on two bearings respectively. The coupling device 102 is provided between the idler gear 101 on the left and the idler gear 103 on the right. The coupling device 102 is configured to move along the shaft 104 to selectively engage any of the idler gears 101, 103 at one time. In other words, the idler gears 101, 103 can alternatively be brought into non-rotating engagement with the shaft 104 by the coupling device 102. Symbols for showing the assembly 100 is provided at the right hand side of FIG. 10.

[0104] FIG. 11 illustrates an assembly 110 of a single-sided coupling device 112 with its neighboring gearwheel 113 for engagement. The assembly 110 comprises a shaft 114 with the one coaxially mounted idler gear 113 on a bearing. The coupling device 112 is provided next to the idler gear 113 on the left side. The coupling device 112 is configured to move along the shaft 114 to engage or disengage the idler gears 113. In other words, the idler gear 113 can be brought into non-rotating engagement with the shaft 114 by the single-sided coupling device 112. Symbols for showing the assembly 110 are provided at the right hand side of FIG. 11.

[0105] FIG. 12 illustrates an assembly 120 of an idler gearwheel 121 that is supported rotatably by a shaft 122 on a bearing 123. The idler gearwheel 121 is mounted coaxially onto the shaft 122 via the bearing 123. The bearing 123 enables the idler gearwheel 121 to be rotated freely around the shaft 122. Symbols that represent the assembly 120 are provided at the right hand side of the FIG. 12.

[0106] FIG. 13 illustrates an assembly 130 of a fixed gearwheel 132 that is supported on a shaft 131. The fixed gearwheel 132 is mounted coaxially onto the shaft 131 such that the gearwheel 132 is fixed to the shaft 132. The fixed gearwheel 132 and the shaft 131 are joined as one single body such that torque of the fixed gearwheel 132 is transmitted to the shaft 131 directly, and vice versa.

[0107] A number of fixed gearwheels are connected rigidly to the input shafts 20, 22 and other shafts 12, 38, 40, 50 in a manner that is similar to the assembly 130. A symbol as used in the previous figures for such a fixed gearwheel is provided on the left side in FIG. 13. The more commonly used symbol for such a fixed gearwheel is provided on the right side in FIG. 13.

[0108] FIG. 14 illustrates a cross-section through a detail of a crankshaft 2 of an internal combustion engine according to the embodiment of the DCT 1. According to FIG. 14, the crankshaft 2 of the internal combustion engine, which is not shown here, is non-rotatably connected to a housing 4 of a double clutch 6. The double clutch 6 includes an inner clutch disc 8 and an outer clutch disc 10, which can be brought into non-rotating engagement with the housing 4 via control elements that are not illustrated here. The solid input shaft 20 is connected non-rotatably to the inner clutch disc 8, and extends all the way through the hollow shaft 22. Similarly, the hollow input shaft 22 is connected non-rotatably to the other clutch disc 10.

[0109] An outer diameter around the inner clutch disc 8 is larger than an outer diameter around the outer clutch disc 10. Correspondingly, an outer diameter of the inner clutch disc 8 is larger than an outer diameter of the outer clutch disc 10.

[0110] Alternative paths for transmitting some of the above-mentioned torque flow paths of the DCT 1 are possible to be provided.

[0111] The above-mentioned nine torque flow paths not only provide viable solutions to generate nine gears of the DCT 1, but also offer possibilities of switching from one gear to another gear efficiently. The gear switching can be achieved by switching between the two input shafts, between gearwheels of double meshing features, or both.

[0112] For example, the DCT 1 can provide odd gears, such as a first, third, fifth, or seventh gear, by driving the gearwheels of the DCT 1 using the hollow input shaft 22. The DCT 1 also provides even gears, such as second, fourth, or sixth gear, by driving the gearwheels of the DCT 1 using the solid input shaft 20. Gear switching between the odd and even can be obtained simply by alternating between the two input shafts 20, 22.

[0113] One double meshing feature provides efficient and fast gear switching between gears of two driven gearwheels that comb with a shared driving gearwheel. For example, the DCT 1 provides the convenience of selecting the third gear or the fifth gear without stopping their shared driving gearwheel, the fixed wheel third gear 25. The selection can be achieved by engaging either the driven idler third gear 62 or the driven idler fifth gear 64.

[0114] The double-meshing feature of the fixed wheel third gear 25 reduces the number of driving gearwheels, which is commonly engaged by the driven gearwheels idler third gear 62 and the driven gearwheel idler fifth gear 64. For example, the driving fixed wheel third gear 25 and the driving fixed wheel fifth gear 26 become one single gearwheel that is shared by the idler third gear 62 and the idler fifth gear 64. As a result, the number of gearwheels on the hollow input shaft 22 has been reduced and less space is required on the hollow input shaft 22 such that the DCT 1 can be made cheaper and lighter.

[0115] The park-lock 42 gives a useful safety feature for a car with the DCT 1. As the park-lock 42 is placed on the lower shaft 50 that carries the final drive pinion 51, the park-lock 42 can easily keep the lower layshaft 50 and the output shaft 14 from rotating. A vehicle with the DCT 1 is then hindered from moving when the vehicle is in a park mode.

[0116] In providing gear meshing or combing for torque transmission, less number of gear tooth engagement, that is gear engagement, is preferred. The less number of gear tooth engagement provides lower noise and more efficient torque transmission. Examples of the less gear tooth engagement are provided in FIGS. 2-10.

[0117] The DCT 1 drives the gearwheel groups of the first gear and the reverse gear by different input shafts 20, 22. This provides the ability to drive a vehicle change between a slow forward and a slow backward by engaging and disengaging the respective clutches 8, 10 that are connected to the two input shafts 20, 22. The DCT 1 enables the vehicle to move back and forth quickly with little loss of the transmission power or gearwheels momentum. This helps in many situations in which a wheel of a vehicle with the DCT 1 is stuck in a hostile environment such as a snow hole or a mud hole. The vehicle can then be swayed free just by switching between the two clutches 8, 10 of the DCT 1.

[0118] FIGS. 16 to 17 illustrate a further embodiment of the application. The embodiment includes parts that are similar to the parts of previously described embodiments. The similar parts are labeled with the same or similar part reference number. Descriptions related to the similar parts are hereby incorporated by reference.

[0119] FIG. 15 shows a front view of the gearbox of the application. A relatively big output gearwheel 12 meshes with a lower pinion 51, which is provided on a lower layshaft 50. The output gearwheel 12 further meshes with an upper pinion 41, which is provided on an upper layshaft 40. A reverse gear idler shaft 38, a solid input shaft 20, and a hollow input shaft 22 are provided to be parallel to the upper layshaft 40 and the lower layshaft 50. In some variants of the application, at least one a further layshaft with a further pinion can be provided but this is not shown here. Such a further pinion would then also mesh or comb with the output gearwheel 12.

[0120] FIG. 15 further comprises a cutting plane A-A for illustrating the cross-section through the gearbox 1, which is shown in FIG. 16. For an embodiment, which has more than two layshafts or an additional idler shaft, a cutting plane, which leads through all shafts, is applied similarly. FIG. 16 illustrates a simplified cross-section through the double clutch transmission gearbox 1 of FIG. 15. It illustrates the structure and various torque flows for the several gears of the double clutch transmission gearbox 1.

[0121] According to FIG. 16, the double clutch transmission gearbox 1 comprises the following shafts, from top to bottom, the reverse gear idler shaft 38, the upper layshaft 40, the solid input shaft 20, the hollow shaft 22, and the lower layshaft 50. The above-mentioned shafts are provided parallel to each other at predetermined mutual distances inside the gearbox 1. The hollow shaft 22 is arranged concentrically around the solid shaft 20. The solid input shaft 20 protrudes outside the hollow input shaft 22 at a right end.

[0122] The solid input shaft 20 comprises, from the right end to the left end, a solid shaft bearing 71, a hollow shaft bearing 72 that serves also as a solid shaft bearing 71, a fixed wheel sixth gear 32, a fixed wheel fourth gear 31, a fixed wheel second gear 30, and a solid shaft bearing 71.

[0123] The hollow input shaft 22 comprises, from the right end to the left end, a hollow shaft bearing 72, a fixed wheel first gear 24, a fixed wheel seventh gear 27, and a fixed wheel third gear 25, which serves also as a fixed wheel fifth gear 26.

[0124] The upper layshaft 40 comprises, from the right end to the left end, an upper pinion 41, a layshaft bearing 73, an idler seventh gear 66, a double-sided coupling device 80, an idler fifth gear 64, an idler sixth gear 65, a double-sided coupling device 81, and a reverse gear idler wheel 37, and a layshaft bearing 73. The idler seventh gear 66 combs with the fixed wheel seventh gear 27. The idler fifth gear 64 combs with the fixed wheel fifth gear 26. The idler sixth gear 65 combs with the fixed wheel sixth gear 32.

[0125] The reverse gear idler shaft 38 comprises, from the right end to the left end, an idle shaft bearing 74, a first reverse gear wheel 35, combing with the fixed wheel first gear 24, a second reverse gear wheel 36, combing with the reverse gear idler wheel 37, and an idle shaft bearing 74.

[0126] The lower layshaft 50 comprises, from the right end to the left end, a lower pinion 51,a layshaft bearing 73, an idler first gear 60, a double-sided coupling device 83, an idler third gear 62, a park-lock 42, an idler fourth gear 63, a double-sided coupling device 82, an idler second gear 61, and a layshaft bearing 73. In particular, the idler first gear 60 combs with the fixed wheel first gear 24. The idler third gear 62 combs with the fixed wheel third gear 25. The idler fourth gear 63 combs with the fixed wheel fourth gear 31. The idler second gear 61 combs with the fixed wheel second gear 30.

[0127] Several torque flows for different gears are possible.

[0128] A torque flow of the first gear can start from the hollow input shaft 22, via the fixed wheel first gear 24, via the idler first gear 60, via the double-sided coupling device 83, via the lower layshaft 50, via the lower pinion 51, and via the output gear wheel 12 to the output shaft 14.

[0129] Similarly, a torque flow of the second gear can start from the solid input shaft 20, via the fixed wheel second gear 30, via the idler second gear 61, via the double-sided coupling device 82, via the lower layshaft 50, via lower pinion 51, and via the output gear wheel 12 to the output shaft 14.

[0130] A torque flow of the third gear can start from the hollow input shaft 22, via the fixed wheel third gear 25, via the idler third gear 62, via the double-sided coupling device 83, via the lower layshaft 50, via the lower pinion 51, and via the output gear wheel 12 to the output shaft 14.

[0131] A torque flow of the fourth gear can start from the solid input shaft 20, via the fixed wheel fourth gear 31, via the idler fourth gear 63, via the double-sided coupling device 82, via the lower layshaft 50, via the lower pinion 51, and via the output gear wheel 12 to the output shaft 14.

[0132] A torque flow of the fifth gear can start from the hollow input shaft 22, via the fixed wheel fifth gear 26, via the idler fifth gear 64, via the double-sided coupling device 80, via the upper layshaft 40, via the upper pinion 41, and via the output gear wheel 12 to the output shaft 14.

[0133] A torque flow of the sixth gear can start from the solid input shaft 20, via the fixed wheel sixth gear 32, via the idler sixth gear 65, via the double-sided coupling device 81, via the upper layshaft 40, via the upper pinion 41, and via the output gear wheel 12 to the output shaft 14.

[0134] A torque flow of the seventh gear can start from the hollow input shaft 22, via the fixed wheel seventh gear 27, via the idler seventh gear 66, via the double-sided coupling device 80, via the upper layshaft 40, via the upper pinion 41, and via the output gear wheel 12 to the output shaft 14.

[0135] A torque flow of the reverse gear can start from the hollow input shaft 22, via the fixed wheel first gear 24, and via the first reverse gear wheel 35. The torque is then transmitted via the reverse gear idler shaft 38, via the second reverse gear wheel 36, via the reverse gear idler wheel 37, via the double-sided coupling device 81, via the upper layshaft 40, via the upper pinion 41, and via the output gear wheel 12 to the output shaft 14.

[0136] FIGS. 17 and 18 illustrate a further embodiment of the application. The embodiment includes parts that are similar to the parts of previously described embodiments. The similar parts are labeled with the same or similar part reference number. Descriptions related to the similar parts are hereby incorporated by reference.

[0137] FIG. 17 shows a front view of a gearbox 1 of the application. A relatively big output gearwheel 12 on an output shaft 14 meshes with a lower pinion 51, which is provided on a lower layshaft 50. The output gearwheel 12 further meshes with an upper pinion 41, which is provided on an upper layshaft 40. A reverse gear idler shaft 38, a solid input shaft 20, and a hollow input shaft 22 are provided parallel to the upper layshaft 40 and the lower layshaft 50. In some variants of the application, at least one a further layshaft with a further pinion can be provided but this is not shown here. Such a further pinion would then also mesh or comb with the output gearwheel 12.

[0138] FIG. 17 further comprises a cutting plane A-A for illustrating the cross-section through the gearbox 1, which is shown in FIG. 18. For an embodiment, which has more than two layshafts or an additional idler shaft, a cutting plane, which leads through all shafts, is applied similarly.

[0139] FIG. 18 illustrates a simplified cross-section through the double clutch transmission gearbox 1 of FIG. 18. It illustrates its structure and various torque flows for the several gears of the double clutch transmission gearbox 1.

[0140] The double clutch transmission gearbox 1 comprises the following shafts, from top to bottom, the upper layshaft 40, the solid input shaft 20, the hollow input shaft 22, the lower layshaft 50, and the reverse gear idler shaft 38.

[0141] The above-mentioned shafts are provided parallel to each other at predetermined mutual distances inside gearbox 1.

[0142] The hollow shaft 22 is arranged concentrically around the solid input shaft 20. The solid input shaft 20 protrudes outside the hollow input shaft 22 at the right end.

[0143] The solid input shaft 20 comprises, from the right end to the left end, a solid shaft bearing 71, a hollow shaft bearing 72, which serves also as a solid shaft bearing 71, a fixed wheel sixth gear 32, a fixed wheel fourth gear 31, a fixed wheel second gear 30, a solid shaft bearing 71, and a fixed wheel reverse gear 34.

[0144] The hollow input shaft 22 comprises, from the right end to the left end, a hollow shaft bearing 72, a fixed wheel first gear 24, a fixed wheel seventh gear 27, and a fixed wheel third gear 25 which serves also as a fixed wheel fifth gear 26.

[0145] The upper layshaft 40 comprises, from the right end to the left end, an upper pinion 41, a layshaft bearing 73, an idler first gear 60, combing with the fixed wheel first gear 24, a double-sided coupling device 80, an idler third gear 62, combing with the fixed wheel third gear 25, an idler fourth gear 63, combing with the fixed wheel fourth gear 31, a double-sided coupling device 81, an idler second gear 61, combing with the fixed wheel second gear 30, and a layshaft bearing 73.

[0146] The lower layshaft 50 comprises, from the right end to the left end, a lower pinion 51, a layshaft bearing 73, an idler seventh gear 66, a double-sided coupling device 83, an idler fifth gear 64, an idler sixth gear 65, a park-lock 42, a double-sided coupling device 82, a second reverse gear wheel 36, and a solid shaft bearing 73. In particular, the idler seventh gear 66 combs with the fixed wheel seventh gear 27. The idler fifth gear 64 combs with the fixed wheel fifth gear 26. The idler sixth gear 65 combs with the fixed wheel sixth gear 32.

[0147] The reverse gear idler shaft 38 comprises, from the right end to the left end, an idle shaft bearing 74, a first reverse gear wheel 35, combing with the second reverse gear wheel 36 and combing with the fixed wheel reverse gear 34, an idle shaft bearing 74.

[0148] Several torque flows are possible.

[0149] A torque flow of the first gear to FIG. 18 can start from the hollow input shaft 22, via the fixed wheel first gear 24, via idler first gear 60, via the double-sided coupling device 80, via the upper layshaft 40, via the upper pinion 41, and via the output gear wheel 12 to the output shaft 14.

[0150] Similarly, a torque flow of the second gear can start from the solid input shaft 20, via the fixed wheel second gear 30, via the idler second gear 61, via the double-sided coupling device 81, via the upper layshaft 40, via the upper pinion 41, and via the output gear wheel 12 to the output shaft 14.

[0151] A torque flow of the third gear can start from the hollow input shaft 22, via the fixed wheel third gear 25, via the idler third gear 62, via the double-sided coupling device 80, via the upper layshaft 40, via the upper pinion 41, and via the output gear wheel 12 to the output shaft 14.

[0152] A torque flow of the fourth gear can start from the solid input shaft 20, via the fixed wheel fourth gear 31, via the idler fourth gear 63, via the double-sided coupling device 81, via the upper layshaft 40, via the upper pinion 41, and via the output gear wheel 12 to the output shaft 14.

[0153] A torque flow of the fifth gear can start from the hollow input shaft 22, via the fixed wheel fifth gear 26, via the idler fifth gear 64, via the double-sided coupling device 83, via the lower layshaft 50, via the lower pinion 51, and via the output gear wheel 12 to the output shaft 14.

[0154] A torque flow of the sixth gear can start from the solid input shaft 20, via the fixed wheel sixth gear 32, via the idler sixth gear 65, via the double-sided coupling device 82, via the lower layshaft 50, via the lower pinion 51, and via the output gear wheel 12 to the output shaft 14.

[0155] A torque flow of the seventh gear can start from the hollow input shaft 22, via the fixed wheel seventh gear 27, via the idler seventh gear 66, via the double-sided coupling device 83, via the lower layshaft 50, via the lower pinion 51, and via the output gear wheel 12 to the output shaft 14.

[0156] A torque flow of the reverse gear can start from the solid input shaft 20, via the fixed wheel reverse gear 34, via the first reverse gear wheel 35, via the second reverse gear wheel 36, via the double-sided coupling device 82, via the lower layshaft 50, via the lower pinion 51, and via the output gear wheel 12 to the output shaft 14.

[0157] FIGS. 19 to 20 illustrate a further embodiment of the application. The embodiment includes parts that are similar to the parts of previously described embodiments. The similar parts are labeled with the same or similar part reference number. Descriptions related to the similar parts are hereby incorporated by reference.

[0158] FIG. 19 shows a front view of the gearbox of the application. A relatively big output gearwheel 12 meshes with a lower pinion 51, which is provided on a lower layshaft 50. The output gearwheel 12 further meshes with an upper pinion 41, which is provided on an upper layshaft 40. There is also a reverse pinion 55 on a reverse gear solid shaft 38. A reverse gear hollow shaft 39 is mounted onto the reverse gear solid shaft 38 by two reverse gear hollow shaft bearings 76 at opposite ends such that the reverse gear hollow shaft 39 can freely rotate around the reverse gear solid shaft 38. The reverse pinion 55 also meshes with the output gear wheel 12. A solid input shaft 20 and a hollow input shaft 22 are provided in parallel with the reverse gear solid shaft 38, the upper layshaft 40, and the lower layshaft 50. In some variants of the application, at least one a further layshaft with a further pinion can be provided but this is not shown here. Such a further pinion would then also mesh or comb with the output gearwheel 12.

[0159] FIG. 19 further comprises a cutting plane A-A for illustrating the cross-section through the gearbox, which is shown in FIG. 20. For an embodiment, which has more than two layshafts or an additional idler shaft, a cutting plane that leads through all shafts is applied similarly.

[0160] FIG. 20 illustrates a simplified cross-section of the double clutch transmission gearbox 1 of FIG. 19. It illustrates structure and various torque flows for the several gears of the double clutch transmission gearbox 1.

[0161] The double clutch transmission gearbox 1 comprises the following shafts, from top to bottom, the reverse gear idler shaft 38, a reverse gear hollow shaft 39, the upper layshaft 40, the solid input shaft 20, the hollow input shaft 22, the lower layshaft 50 and an output shaft 14.

[0162] The above-mentioned shafts are provided parallel to each other at predetermined mutual distances inside gearbox 1. The hollow shaft 22 is arranged concentrically around the solid input shaft 20. The solid input shaft 20 protrudes outside the hollow input shaft 22 at the right end.

[0163] The solid input shaft 20 comprises, from the right end to the left end, a solid shaft bearing 71, a hollow shaft bearing 72 that serves also as a solid shaft bearing 71, a fixed wheel fourth gear 31, a fixed wheel second gear 30, a fixed wheel sixth gear 32, and a solid shaft bearing 71.

[0164] The hollow input shaft 20 comprises, from the right end to the left end, a hollow shaft bearing 72, a fixed wheel seventh gear 27, and a fixed wheel third gear 25, which serves also as a fixed wheel fifth gear 26.

[0165] The upper layshaft 40 comprises, from the right end to the left end, the upper pinion 41, a layshaft bearing 73, an idler first gear 60, a double-sided coupling device 80, an idler third gear 62, an attached idler third gear 62', an idler second gear 61, a single-sided coupling device 81, a layshaft bearing 73. The idler third gear 62 combs with the fixed wheel third gear 25. The idler second gear 61 combs with the fixed wheel second gear 30. The idler third gear 62 is attached or is fused to the idler third gear 62' such that they become one integral body.

[0166] The reverse gear idler shaft 38 comprises, from the right end to the left end, the reverse pinion 55, an idler shaft bearing 74, a reverse gear hollow shaft 39, a park lock 42, a single-sided coupling device 85, and an idler shaft bearing 74.

[0167] The reverse gear hollow shaft 39 comprises, from the right end to the left end, a second reverse gear wheel 36, combing with the idler first gear 60, and a first reverse gear wheel 35, combing with the attached idler third gear 62'.

[0168] The lower layshaft 50 comprises, from the right end to the left end, the lower pinion 51, a layshaft bearing 73, an idler seventh gear 66, a double-sided coupling device 83, an idler fifth gear 64, an idler fourth gear 63, a double-sided coupling device 82, an idler sixth gear 65, and a layshaft bearing 73. The idler seventh gear 66 combs with the fixed wheel seventh gear 27. The idler fifth gear 64 combs with the fixed wheel fifth gear 26. The idler fourth gear 63 combs with the fixed wheel fourth gear 31. The idler sixth gear 65 combs with the fixed wheel sixth gear 32.

[0169] Torque flow of the first gear according to FIG. 20 starts from the hollow input shaft 22, via the fixed wheel third gear 25, via the idler third gear 62, via the attached idler third gear 62', via the first reverse gear wheel 35. The torque flow is then transmitted via the reverse gear hollow shaft 39, via the second reverse gear wheel 36, via the idler first gear 60, via the double-sided coupling device 80, via the upper layshaft 40, via the upper pinion 41, and via the output gear wheel 12 to the output shaft 14.

[0170] Torque flow of the second gear according to FIG. 20 starts from the solid input shaft 20, via the fixed wheel second gear 30, via the idler second gear 61, via the single-sided coupling device 81, via the upper layshaft 40, via the upper pinion 41, via the output gear wheel 12, to the output shaft 14.

[0171] Torque flow of the third gear according to FIG. 20 starts from the hollow input shaft 22, via the fixed wheel third gear 25, via the idler third gear 62, via the double-sided coupling device 80, via the upper layshaft 40, via the upper pinion 41, via the output gear wheel 12, to the output shaft 14.

[0172] Torque flow of the fourth gear according to FIG. 20 starts from the solid input shaft 20, via the fixed wheel fourth gear 31, via the idler fourth gear 63, via the double-sided coupling device 82, via the lower layshaft 50, via the lower pinion 51, via the output gear wheel 12, to the output shaft 14.

[0173] Torque flow of the fifth gear according to FIG. 20 starts from the hollow input shaft 22, via the fixed wheel fifth gear 26, via the idler fifth gear 64, via the double-sided coupling device 83, via the lower layshaft 50, via the lower pinion 51, via the output gear wheel 12, to the output shaft 14.

[0174] Torque flow of the sixth gear according to FIG. 20 starts from the solid input shaft 20, via the fixed wheel sixth gear 32, via the idler sixth gear 65, via the double-sided coupling device 82, via the lower layshaft 50, via the lower pinion 51, via the output gear wheel 12, to the output shaft 14.

[0175] Torque flow of the seventh gear according to FIG. 20 starts from the hollow input shaft 22, via fixed wheel seventh gear 27, via the idler seventh gear 66, via the double-sided coupling device 83, via the lower layshaft 50, via the lower pinion 51, via the output gear wheel 12, to the output shaft 14.

[0176] Torque flow of the reverse gear according to FIG. 20 starts from the hollow input shaft 22, via the fixed wheel third gear 25, via the idler third gear 62, and via the attached idler third gear 62'. The torque is then transmitted via the first reverse gear wheel 35, via the reverse gear hollow shaft 39, via the single-sided coupling device 85, via the reverse gear idle shaft 38, via the reverse pinion 55, via the output gear wheel 12, to the output shaft 14.

[0177] FIGS. 24 and 25 illustrate a further embodiment of the application. The embodiment includes parts that are similar to the parts of previously described embodiments. The similar parts are labeled with the same or similar part reference number. Descriptions related to the similar parts are hereby incorporated by reference.

[0178] FIG. 21 shows a front view of the gearbox of the application. A relatively big output gearwheel 12 meshes with a lower pinion 51, which is provided on a lower layshaft 50. The output gearwheel 12 further meshes with an upper pinion 41, which is provided on an upper layshaft 40. There is also a reverse pinion 55 on a reverse gear solid shaft 38. A reverse gear hollow shaft 39 is mounted onto the reverse gear solid shaft 38 by two reverse gear hollow shaft bearings 76 at opposite ends such that the reverse gear hollow shaft 39 can freely rotate around the reverse gear solid shaft 38. The reverse pinion 55 also meshes with the output gear wheel 12. A solid input shaft 20 and a hollow input shaft 22 are provided in parallel with the reverse gear solid shaft 38, the upper layshaft 40, and the lower layshaft 50. In some variants of the application, at least one a further layshaft with a further pinion can be provided but this is not shown here. Such a further pinion would then also mesh or comb with the output gearwheel 12.

[0179] FIG. 21 further comprises a cutting plane A-A for illustrating the cross-section through the gearbox, which is shown in FIG. 21. It illustrates structure and various torque flows for the several gears of the double clutch transmission gearbox 1. For an embodiment, which has more than two layshafts or an additional idler shaft, a cutting plane, which leads through all shafts, is applied similarly.

[0180] The double clutch transmission gearbox 1 comprises the following shafts from top to bottom, the reverse gear idler shaft 38, the reverse gear hollow shaft 39, the upper layshaft 40, the solid input shaft 20, the hollow input shaft 22, the lower layshaft 50, and the output shaft 14.

[0181] The above-mentioned shafts are provided parallel to each other at predetermined mutual distances inside gearbox 1. The hollow shaft 22 is arranged concentrically around the solid input shaft 20. The solid input shaft 20 protrudes outside the hollow input shaft 22 at the right end.

[0182] The solid input shaft 20 comprises, from the right end to the left end, a solid shaft bearing 71, a hollow shaft bearing 72, a fixed wheel fourth gear 31, a fixed wheel second gear 30, a fixed wheel sixth gear 32, and a solid shaft bearing 71. The hollow shaft bearing 72 serves also as a solid shaft bearing 71. The fixed wheel sixth gear 32 also serves as a fixed wheel eighth gear 32'.

[0183] The hollow input shaft 20 comprises, from the right end to the left end, a hollow shaft bearing 72, a fixed wheel seventh gear 27, and a fixed wheel third gear 25, which is at the same time a fixed wheel fifth gear 26.

[0184] The upper layshaft 40 comprises, from the right end to the left end, the upper pinion 41, a layshaft bearing 73, an idler first gear 60, a double-sided coupling device 80, an idler third gear 62, and an attached idler third gear 62'. Further, the upper layshaft 40 includes an idler second gear 61, a double-sided coupling device 81'', an idler sixth gear 65', and a layshaft bearing 73. The idler third gear 62 combs with the fixed wheel third gear 25 whilst the idler sixth gear 65' combs with the fixed wheel sixth gear 32.

[0185] The reverse gear idler shaft 38 comprises, from the right end to the left end, the reverse pinion 55, an idler shaft bearing 74, the reverse gear hollow shaft 39, a single-sided coupling device 85, and an idler shaft bearing 74.

[0186] The reverse gear hollow shaft 39 comprises, from the right end to the left end, a second reverse gear wheel 36, combing with the idler first gear 60, a first reverse gear wheel 35, combing with the attached idler third gear 62'.

[0187] The lower layshaft 50 comprises, from the right end to the left end, the lower pinion 51, a layshaft bearing 73, an idler seventh gear 66, a double-sided coupling device 83, an idler fifth gear 64, an idler fourth gear 63, a double-sided coupling device 82, a park-lock 42, an idler eighth gear 67, and a layshaft bearing 73. In particular, the idler seventh gear 66 combs with the fixed wheel seventh gear 27. The idler fifth gear 64 combs with fixed wheel fifth gear 26. The idler fourth gear 63 combs with the fixed wheel fourth gear 31. The idler eighth gear 67 combs with the fixed wheel eighth gear 32'.

[0188] Torque flow of the first gear according to FIG. 22 starts from the hollow input shaft 22, via the fixed wheel third gear 25, via the idler third gear 62, and via the attached idler third gear 62'. The torque flow is then transmitted via the first reverse gear wheel 35, via the reverse gear hollow shaft 39, via the second reverse gear wheel 36, via the idler first gear 60, via the double-sided coupling device 80, via the upper layshaft 40, via upper pinion 41, and via the output gear wheel 12 to the output shaft 14.

[0189] Similarly, torque flow of the second gear according to FIG. 22 starts from the solid input shaft 20, via the fixed wheel second gear 30, via the idler second gear 61, via the single-sided coupling device 81, via the upper layshaft 40, via the upper pinion 41, via the output gear wheel 12, to the output shaft 14.

[0190] Torque flow of the third gear according to FIG. 22 starts from the hollow input shaft 22, via the fixed wheel third gear 25, via the idler third gear 62, via the double-sided coupling device 80, via the upper layshaft 40, via the upper pinion 41, and via the output gear wheel 12 to the output shaft 14.

[0191] Torque flow of the fourth gear according to FIG. 22 starts from the solid input shaft 20, via the fixed wheel fourth gear 31, via the idler fourth gear 63, via the double-sided coupling device 82, via the lower layshaft 50, via the lower pinion 51, and via the output gear wheel 12 to the output shaft 14.

[0192] Torque flow of the fifth gear according to FIG. 22 starts from the hollow input shaft 22, via the fixed wheel fifth gear 26, via the idler fifth gear 64, via the double-sided coupling device 83, via the lower layshaft 50, via the lower pinion 51, and via the output gear wheel 12 to the output shaft 14.

[0193] Torque flow of the sixth gear according to FIG. 22 starts from the solid input shaft 20, via the fixed wheel sixth gear 32, via the idler sixth gear 65', via the double-sided coupling device 81'', via the upper layshaft 40, via the upper pinion 41, and via the output gear wheel 12 to the output shaft 14.

[0194] Torque flow of the seventh gear according to FIG. 22 starts from the hollow input shaft 22, via the fixed wheel seventh gear 27, via the idler seventh gear 66, via the double-sided coupling device 83, via the lower layshaft 50, via the lower pinion 51, and via the output gear wheel 12 to the output shaft 14.

[0195] Torque flow of the eighth gear according to FIG. 22 starts from the solid input shaft 20, via the fixed wheel eighth gear 32', via the idler eighth gear 67, via the double-sided coupling device 82, via the lower layshaft 50, via the lower pinion 51, and via the output gear wheel 12 to the output shaft 14.

[0196] Torque flow of the reverse gear according to FIG. 22 starts from the hollow input shaft 22, via the fixed wheel third gear 25, via the idler third gear 62, via the attached idler third gear 62', via the first reverse gear wheel 35, via the reverse gear hollow shaft 39, and via the single-sided coupling device 85. The torque flow is afterward sent via the reverse gear idle shaft 38, via the reverse pinion 55, and via the output gear wheel 12 to the output shaft 14.

[0197] 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 practice. Thus, the scope of the embodiments should be determined by the claims, rather than by the examples given.

[0198] While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

Claims

1. A double-clutch transmission, comprising: an inner input shaft and an outer input shaft, at least a portion of the inner input shaft surrounded by the outer input shaft; a first clutch disc connected to the inner input shaft and a second clutch disc connected to the outer input shaft; a first layshaft, a second layshaft and a third layshaft spaced apart from the input shafts and arranged in parallel to the input shafts, at least one of the layshafts comprising a pinion for outputting a drive torque, gearwheels arranged on the first layshaft, on the second layshaft, on the third layshaft, on the inner input shaft and on the outer input shaft, the gearwheels comprising a first gearwheel group, a second gearwheel group, a third gearwheel group, a fourth gearwheel group, a fifth gearwheel group, a sixth gearwheel group, a seventh gearwheel group, and a reverse gearwheel group for providing seven sequentially increasing forward gears and one reverse gear respectively, the first gearwheel group comprising a first fixed gearwheel on the outer input shaft, meshing with a first idler gearwheel on one of the layshafts, the third gearwheel group comprising a third fixed gearwheel on the outer input shaft, meshing with a third driven gearwheel on one of the layshafts, the fifth gearwheel group comprising a fifth fixed gearwheel on the outer input shaft, meshing with a fifth idler gearwheel on one of the layshafts, the seventh gearwheel group comprising a seventh fixed gearwheel on the outer input shaft, meshing with a seventh idler gearwheel on one of the layshafts, the second gearwheel group comprising a second fixed gearwheel on the inner input shafts, meshing with a second idler gearwheel on one of the layshafts, the fourth gearwheel group comprising a fourth fixed gearwheel on the inner input shafts, meshing with a fourth idler gearwheel on one of the layshafts, the sixth gearwheel group comprising a sixth fixed gearwheel on the inner input shafts meshing with a sixth idler gearwheel on one of the layshafts, the reverse gearwheel group comprising a fixed driving gearwheel on one of the input shafts meshing with a reverse gearwheel on one of the layshafts, the reverse gearwheel meshes with a reverse idler gearwheel on the layshaft that comprises the pinion, each of these gearwheel groups comprising a coupling device which is arranged on one of the layshafts to selectively engage one of the gearwheels for providing one of the seven sequentially increasing forward gears and the one reverse gear, and the third fixed gearwheel further meshing with the fifth idler gearwheel, wherein the double-clutch transmission further comprises a fixed gearwheel on one of the layshafts that carries the pinion as a final drive for providing a park-lock.

2. The double-clutch transmission according to claim 1, wherein the first forward gear and the reverse gear are driven via different input shafts.

3. The double-clutch transmission according to claim 1, wherein the second forward gear and the reverse gear are driven by different input shafts.

4. The double-clutch transmission according to claim 1, wherein the reverse gear group comprises a reverse gear wheel and a second reverse gear wheel on a same reverse gear idler shaft, the reverse gear wheel and the second reverse gear wheel meshes with two gearwheels on the two layshafts.

5. The double-clutch transmission according claim 1, wherein a distance between one of the layshafts with gearwheels of higher gear ratios and the inner input shaft is lesser than a distance between the other layshaft with gearwheels of lower gear ratios and the inner input shaft.

6. The double-clutch transmission according to claim 1, wherein the idler gearwheels of the first gear, the third gear, the fifth gear and the seventh gear are driven by the hollow input and the idler gearwheels of the second, fourth, and the sixth gears are driven by the solid input shaft.

7. The double-clutch transmission according to claim 1, wherein at least two coupling devices are configured to engage two of the idler gearwheels simultaneously to pre-select a gear for gear shift.

8. The double-clutch transmission device according to claim 1, wherein at least two of the first idler gearwheel, the second idler gearwheel, the third driven gearwheel, and the fourth idler gearwheel are provided on the same layshaft.

9. The double-clutch transmission device according to claim 1, wherein at least two of the fifth idler gearwheel, the sixth idler gearwheel, and the seventh idler gearwheel are provided on the same layshaft.

10. The double-clutch transmission according to claim 1, further comprising bearings for supporting the layshafts, at least one of the bearings provided next to one of the pinions.

11. A gearbox, comprising: an inner input shaft and an outer input shaft, at least a portion of the inner input shaft surrounded by the outer input shaft; a first clutch disc connected to the inner input shaft and a second clutch disc connected to the outer input shaft; a first layshaft, a second layshaft and a third layshaft spaced apart from the input shafts and arranged in parallel to the input shafts, at least one of the layshafts comprising a pinion for outputting a drive torque. gearwheels arranged on the first layshaft, on the second layshaft, on the third layshaft, on the inner input shaft and on the outer input shaft, the gearwheels comprising a first gearwheel group, a second gearwheel group, a third gearwheel group, a fourth gearwheel group, a fifth gearwheel group, a sixth gearwheel group, a seventh gearwheel group, and a reverse gearwheel group for providing seven sequentially increasing forward gears and one reverse gear respectively, the first gearwheel group comprising a first fixed gearwheel on the outer input shaft, meshing with a first idler gearwheel on one of the layshafts, the third gearwheel group comprising a third fixed gearwheel on the outer input shaft, meshing with a third driven gearwheel on one of the layshafts, the fifth gearwheel group comprising a fifth fixed gearwheel on the outer input shaft, meshing with a fifth idler gearwheel on one of the layshafts, the seventh gearwheel group comprising a seventh fixed gearwheel on the outer input shaft, meshing with a seventh idler gearwheel on one of the layshafts, the second gearwheel group comprising a second fixed gearwheel on the inner input shafts, meshing with a second idler gearwheel on one of the layshafts, the fourth gearwheel group comprising a fourth fixed gearwheel on the inner input shafts, meshing with a fourth idler gearwheel on one of the layshafts, the sixth gearwheel group comprising a sixth fixed gearwheel on the inner input shafts meshing with a sixth idler gearwheel on one of the layshafts, the reverse gearwheel group comprising a fixed driving gearwheel on one of the input shafts meshing with a reverse gearwheel on one of the layshafts, the reverse gearwheel meshes with a reverse idler gearwheel on the layshaft that comprises the pinion, each of these gearwheel groups comprising a coupling device which is arranged on one of the layshafts to selectively engage one of the gearwheels for providing one of the seven sequentially increasing forward gears and the one reverse gear, and the third fixed gearwheel further meshing with the fifth idler gearwheel, wherein the double-clutch transmission further comprises a fixed gearwheel on one of the layshafts that carries the pinion as a final drive for providing a park-lock; and an output gearwheel on an output shaft that meshes with the pinion for outputting the drive torque to a torque drain.

12. A power train device, comprising: an inner input shaft and an outer input shaft, at least a portion of the inner input shaft surrounded by the outer input shaft; a first clutch disc connected to the inner input shaft and a second clutch disc connected to the outer input shaft; a first layshaft, a second layshaft and a third layshaft spaced apart from the input shafts and arranged in parallel to the input shafts, at least one of the layshafts comprising a pinion for outputting a drive torque, gearwheels arranged on the first layshaft, on the second layshaft, on the third layshaft, on the inner input shaft and on the outer input shaft, the gearwheels comprising a first gearwheel group, a second gearwheel group, a third gearwheel group, a fourth gearwheel group, a fifth gearwheel group, a sixth gearwheel group, a seventh gearwheel group, and a reverse gearwheel group for providing seven sequentially increasing forward gears and one reverse gear respectively, the first gearwheel group comprising a first fixed gearwheel on the outer input shaft, meshing with a first idler gearwheel on one of the layshafts, the third gearwheel group comprising a third fixed gearwheel on the outer input shaft, meshing with a third driven gearwheel on one of the layshafts, the fifth gearwheel group comprising a fifth fixed gearwheel on the outer input shaft, meshing with a fifth idler gearwheel on one of the layshafts, the seventh gearwheel group comprising a seventh fixed gearwheel on the outer input shaft, meshing with a seventh idler gearwheel on one of the layshafts, the second gearwheel group comprising a second fixed gearwheel on the inner input shafts, meshing with a second idler gearwheel on one of the layshafts, the fourth gearwheel group comprising a fourth fixed gearwheel on the inner input shafts, meshing with a fourth idler gearwheel on one of the layshafts, the sixth gearwheel group comprising a sixth fixed gearwheel on the inner input shafts meshing with a sixth idler gearwheel on one of the layshafts, the reverse gearwheel group comprising a fixed driving gearwheel on one of the input shafts meshing with a reverse gearwheel on one of the layshafts, the reverse gearwheel meshes with a reverse idler gearwheel on the layshaft that comprises the pinion, each of these gearwheel groups comprising a coupling device which is arranged on one of the layshafts to selectively engage one of the gearwheels for providing one of the seven sequentially increasing forward gears and the one reverse gear, and the third fixed gearwheel further meshing with the fifth idler gearwheel, wherein the double-clutch transmission further comprises a fixed gearwheel on one of the layshafts that carries the pinion as a final drive for providing a park-lock; an output gearwheel on an output shaft that meshes with the pinion for outputting the drive torque to a torque drain; and at least one power source for generating a driving torque.

13. The power train device according to claim 12, wherein the power source comprises a combustion engine.

14. The power train device of claim 12, wherein the power source comprises an electric motor.

15. (canceled)