GEAR ARRANGEMENTS FOR 7-SPEED DUAL CLUTCH TRANSMISSION

Abstract

Double-clutch transmission (DCT) includes, but is not limited to two input shafts that are connected to two clutch discs respectively. The DCT further includes, but is not limited to gearwheels on layshafts and the input shafts. The gearwheels include, but are not limited to six gearwheel groups for providing six gears respectively. Each of the gearwheel groups include, but are not limited to a fixed gearwheel on one of the input shafts, meshing with an idler gearwheel on one of the layshafts. A third fixed gearwheel meshes with the third gear idler gearwheel and the fifth gear idler gearwheel. Additionally, the DCT device further includes, but is not limited to a seventh gearwheel group for providing a seventh gear. The seventh gearwheel group includes, but is not limited to a seventh fixed gearwheel, meshing with a seventh gear idler gearwheel. The DCT further includes, but is not limited to a reverse gear idler shaft and one reverse gearwheel on the reverse gear idler shaft for providing a reverse gear.

Description

TECHNICAL FIELD

The present application relates to a double-clutch transmission for vehicles.

BACKGROUND

A double-clutch transmission (DCT) comprises two input shafts that are connected to and 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 are connected to two input shafts of the DCT separately for providing driving torques.

U.S. Pat. No. 7,246,534 B2 discloses a six-gear double clutch transmission. The six-gear double clutch transmission has not yet been widely used in cars for street driving. Problems that hinder the application of DCT for street driving comprise of providing a compact, reliable and fuel-efficient DCT. Therefore, there exists a need for providing such a DCT that is also affordable by consumers.

SUMMARY

The application provides a double-clutch transmission with an inner input shaft and an outer input shaft. The inner shaft can be hollow or solid. A portion of the inner input shaft is surrounded by the outer input shaft in a radial direction. The radial direction of a shaft indicates a direction pointing away from a central axis of the shaft following a radius of the shaft.

There is provided a first clutch and a second clutch that are non-rotatably connected to the inner input shaft and to the outer input shaft respectively. 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.

The transmission further comprises a first layshaft, a second layshaft radially spaced apart from the input shafts and arranged in parallel to the input shafts.

At least one of the layshafts comprises a fixed output gearwheel for outputting a drive torque to a torque drain, such as a differential gearbox of 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 the output shaft for driving the vehicle.

Gearwheels are arranged on the first layshaft, on the second layshaft, on the inner input shaft and on the outer input shaft. The gearwheels comprise a first gearwheel group, a second gearwheel group, a third gearwheel group, a fourth gearwheel group, a fifth gearwheel group and a sixth gearwheel group for providing six sequentially increasing gears. The sequentially increasing gears describe an escalating order that members of the order follow each other. Gear ratios of a car are typically arranged in a sequentially decreasing manner from first gear to sixth gear. For example, in a vehicle having a transmission, a first gear has the gear ratio of approximately 2.97:1; a second gear has the gear ratio of approximately 2.07:1; a third gear has the gear ratio of approximately 1.43:1; a fourth gear has the gear ratio of approximately 1.00:1; a fifth gear has the gear ratio of approximately 0.84:1; and a sixth gear has the gear ratio of approximately 0.56:1. The six gears provide an increasing order of output speed of the transmission for driving the vehicle.

The first gearwheel group comprises a first fixed gearwheel on the inner input shaft, meshing with a first gear idler gearwheel on one of the layshafts. The third gearwheel group comprising a third fixed gearwheel on the inner input shaft, meshing with a third gear idler gearwheel on one of the layshafts. The fifth gearwheel group comprises a fifth fixed gearwheel on the inner input shaft, meshing with a fifth gear idler gearwheel on one of the layshafts. The second gearwheel group comprises a second fixed gearwheel on the outer input shafts, meshing with a second gear idler gearwheel on one of the layshafts. The fourth gearwheel group comprises a fourth fixed gearwheel on the outer input shafts, meshing with a fourth gear idler gearwheel on one of the layshafts. The sixth gearwheel group comprises a sixth fixed gearwheel on the outer input shafts, meshing with a sixth gear idler gearwheel on one of the layshafts. Each gearwheel group comprises a coupling device that is arranged on one of the layshafts to selectively engage one of the idler gearwheels for selecting one of the six gears.

The third fixed gearwheel on the inner input shaft meshes with the third gear idler gearwheel and the fifth gear idler gearwheel.

Additionally, the double-clutch transmission device comprises a seventh gearwheel group for providing a seventh gear, the seventh gearwheel group comprising a seventh fixed gearwheel on the inner input shaft, meshing with a seventh gear idler gearwheel on one of the layshafts. The seventh gearwheel group further comprises a coupling device which is arranged on one of the layshafts to selectively engage one of the idler gearwheels for selecting the seventh gear. The double-clutch transmission device further comprises a reverse gear idler shaft and at least one reverse gearwheel mounted on the reverse gear idler shaft for providing a reverse gear.

The double-clutch transmission provides seven forward gears through the double-clutch. The double-clutch enables gear switching between odd and even ratios to be swift and efficient because the gearwheels for the odd gear and even gear are distributed to different clutches respectively. A double-meshing is provided by the third fixed gearwheel on the inner input shaft meshing with the third gear idler gearwheel and the fifth gear idler gearwheel. The double-meshing makes the double-clutch transmission to be compact, light-weight at low cost because one fixed gearwheel is avoided on one of the input shafts.

In the application, different input shafts may provide the first forward gear and the reverse gear respectively. The DCT put the first forward gear and the reverse gear on two different input shafts. A double-clutch of the DCT enables that the switching between the two input shafts can be achieved quickly. As a result, a driving scheme that the DCT engages the two input shafts alternatively can drive the vehicle back & forth rapidly. This scheme is useful for moving the vehicle out of a muddy puddle because the vehicle can simply be driven back & forth to get out the puddle. Less loss of momentum of the gearwheels and the layshafts of the DCT can be achieved.

In the application, the at least one reverse gearwheel may comprise a first reverse gearwheel and a second reverse gearwheel that mesh with two of the gearwheels respectively. The double-clutch transmission further provides a reverse gear that enables the vehicle to reverse. The reverse gear makes the vehicle more maneuverable. The two reverse gearwheels enable the DCT to eliminate a pinion only for the use of reverse gear. The absence of the pinion reduces the weight and cost of the DCT.

In the application, the first reverse gearwheel may mesh with the second fixed gearwheel, while the second reverse gearwheel may mesh with a reverse gear idler wheel. Both the first reverse gearwheel and the second reverse gearwheel share the same rotational axis with the reverse gear idler shaft, which is coaxial. In fact, a gearwheel is typically mounted to its supporting shaft coaxially, unless otherwise stated. The fact that a gearwheel and its supporting shaft having the same rotational axis ensures uniform gear meshing of the gearwheel with its neighboring gearwheel on a parallel shaft.

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 comprises a final drive pinion for locking a differential of the DCT. The differential comprises the output gearwheel on the output shaft. The park-lock enables the vehicle to park at a place in a secure manner, even on a slope. The park-lock is easy to implement and beneficial for vehicle and passengers' safety.

In the application, at least two of the first gear idler gearwheel, the second gear idler gearwheel, the third gear idler gearwheel and the fourth gear idler gearwheel may be mounted on the same layshaft. Gearwheels of lower gears (e.g. 1st, 2nd, 3rd & 4th gears) are desired to be installed on the same shaft because only one of the layshafts 40, 50 needs to be made strong for carrying heavy torque.

In the application, at least two of the fifth gear idler gearwheel, the sixth gear idler gearwheel and the seventh gear idler gearwheel are mounted 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.

In the application, the fifth gear idler gearwheel, the sixth gear idler gearwheel and the seventh gear idler gearwheel may be mounted on the lower layshaft. Gearwheels of higher gears (e.g., 5th, 6^th, & 7th gears) are desired to be installed on the same shaft because the shaft can be made slim for carrying less torque. Consequently, the DCT can be made with low cost and lightweight. Three gearwheels of high gears mounted on the same layshaft greatly help to reduce weight of the layshaft. The DCT with the layshaft can also be made lighter. Bearings for supporting the layshaft of high gears become less demanding.

In the application, the coupling device may comprise a double-sided coupling device for engaging a gearwheel on the left side or right side of the coupling device to a shaft that carries the coupling device.

In the application, there may be further provided bearings for supporting the layshafts, at least one of the bearings being provided next to one of the first gear idler gearwheel and the second gear idler gearwheel. 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.

In the application, the DCT may further comprise an output gearwheel that meshes with pinions on the layshafts for providing an output torque. The output gearwheel receives driving torques from pinions and offer a single output to the exterior of the double-clutch transmission. No multiple external connections that are associated to the layshafts are required. Connection to the double-clutch transmission is thus made simple.

In the application, there may be provided a power train device with the gearbox. The power train device may comprise at least one power source for generating a driving torque. The power train device is alternatively known as power train.

In the application, the power source comprises 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.

In the application, the power source may comprise an electric motor. Electric motor used in as 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.

In the application, there may be provided a vehicle comprising the power train device. The vehicle having the power train device is efficient in energy usage by using the double-clutch transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

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

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

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

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

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

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

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

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

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

FIG. 14 illustrates a cross-section through a crankshaft of an internal combustion engine according to the embodiment of the DCT; and

FIG. 15 illustrates an alternative front view of the expanded side view of the double clutch transmission in FIG. 2.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and is not intended to limit 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. In the following description, details are provided to describe the embodiment of the application. It shall be apparent to one skilled in the art, however, that the embodiment may be practiced without such details.

FIGS. 1-14 provide detailed description of an embodiment of a double clutch transmission (DCT) of the application.

FIG. 1 illustrates a front view of an embodiment of a double clutch transmission 1 of the application. The DCT 1 comprises a relatively large output gearwheel 12, two input shafts 20, 22, two pinions 41, 51 and a reverse gear idler shaft 38. The two input shafts 20, 22 are a solid input shaft 20 (i.e. K1) and a hollow input shaft 22 (i.e. K2). The solid input shaft 20 and the hollow input shaft 22 share the same rotational axis and are non-rotatably connected to two clutch discs 8, 10 of a double clutch 6 separately. The two pinions 41, 51 are the upper pinion 41 and the lower pinion 51. The two pinions 41, 51 are fixed to an upper layshaft 40 and a lower layshaft 50 at their rotational axes respectively. The output gearwheel 12 is fixed to an output shaft 14 at its rotation axis. The two pinions 41, 51 mesh with the output gearwheel 12 separately at different positions of the output gearwheel 12.

The input shafts 20, 22, the upper layshaft 40, the lower layshaft 50, the reverse gear idler shaft 38 and the output shaft 14 are parallel to each other at predetermined distances. The distances are provided in radial directions of these shafts 20, 22, 40, 50, 38, 14 which are better seen in FIG. 2. Other gearwheels are mounted on these shafts 20, 22, 40, 50, 38, 14 respectively and 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.

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 lower pinion 51, the output gearwheel 12, the input shafts 20, 22, the upper pinion 41 and the reverse gear idler shaft 38. One of the goals of FIGS. 2 to 9 is to further illustrate structure and torque flows of the DCT 1.

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

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 solid input shaft 20, the hollow input shaft 22, the lower layshaft 50 and the output shaft 14. The solid input shaft 20 is partially disposed inside the hollow input shaft 22, while the solid input shaft 20 protrudes outside the hollow input shaft 22 at its 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, while 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 right.

As shown in FIG. 2, a portion of the solid input shaft 20 is surrounded by the outer input shaft 22 in a radial direction of the input shafts 20, 22. There are three gearwheels 25, 27, 24 mounted on the left exposed portion of the solid input shaft 20. These gearwheels 25, 27, 24 are a fixed wheel third gear 25, a fixed wheel seventh gear 27 and a fixed wheel first gear 24. The fixed wheel third gear 25, the fixed wheel seventh gear 27 and the fixed wheel first gear 24 are disposed on the exposed portion of the solid shaft 20 from right to left sequentially. The fixed wheel third gear 25 also serves as a fixed wheel fifth gear 26. On the hollow input shaft 22, which is mounted on the right portion of the solid input shaft 20, there is mounted with a fixed wheel second gear 30, a fixed wheel fourth gear 32 and a fixed wheel fourth gear 31 from right to left. The fixed wheel second gear 30, the fixed wheel fourth gear 32 and the fixed wheel fourth gear 31 are fixed to the hollow input shaft 22 coaxially.

The lower layshaft 50 is provided below the solid input shaft 20 and the hollow input shaft 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 second gear 61, a double-sided coupling device 83, an idler fourth gear 63, an idler third gear 62, a double-sided coupling device 82 and an idler first gear 60. One layshaft bearing 73 is provided next to both the lower pinion 51 and the idler second gear 61. The other layshaft bearing 73 is provided next to the idler first gear 60 at the left end of the lower layshaft 50. The lower pinion 51 is fixed to the lower layshaft 50 at its rotational axis. The idler second gear 61, the idler fourth gear 63, the idler third gear 62 and the idler first gear 60 are mounted on the lower layshaft 50 by bearings separately such that these gearwheels 61, 63, 62, 60 are idlers, being free to rotate around the lower layshaft 50. In other words, gearwheels of low gears 60, 61, 62, 63 are provided on the same layshaft 50, while the two layshafts' bearings 73 are next to the gearwheels of the lowest gears 60, 61. The double-sided coupling device 83 is provided between the idler second gear 61 and the idler fourth gear 63. The other double-sided coupling device 82 is provided between the idler third gear 62 and the idler first gear 60. Both the double-sided coupling devices 82, 83 are configured to move along the lower layshaft 50 such that they can either engage a gearwheel on their left or right to the lower layshaft 50 respectively. The idler second gear 61 meshes with the fixed wheel second gear 30. The idler fourth gear 63 meshes with the fixed wheel fourth gear 31. The idler third gear 62 meshes with the fixed wheel third gear 25. The idler first gear 60 meshes with the fixed wheel first gear 24.

The upper layshaft 40 is provided above the input shafts 20, 22. There is provided gearwheels and coupling devices on the upper layshaft 40, which includes, from right to the left, the upper pinion 41, a reverse gear idler wheel 37, a double-sided coupling device 80, an idler sixth gear 65, a park-lock gearwheel 39, an idler fifth gear 64, a double-sided coupling device 81 and an idler seventh gear 66. One layshaft bearing 73 is positioned next to and between the upper pinion 41 and the reverse gear idler wheel 37. Another layshaft bearing 73 is positioned at another end of the upper layshaft 40, next to the idler seventh gear 66. The reverse gear idler gear wheel 37, the idler sixth gear 65, the idler fifth gear 64, the idler seventh gear 66 are mounted on the upper layshaft 40 by bearings respectively such that these gearwheels 37, 65, 64, 66 are free to rotate around the upper layshaft 40. In other words, gearwheels of high gears 64, 65, 66 are mounted on the same shaft 40. The double-sided coupling device 80 is configured to move along the upper layshaft 40 to engage or disengage either the reverse gear idler wheel 37 or the idler sixth gear 65 to the upper layshaft 40 at a time. The other double-sided coupling device 81 is configured to move along the upper layshaft 40 to engage or disengage any of the idler fifth gear 64 and the idler seventh gear 66 to the upper layshaft 40 at a time. The idler sixth gear 65 meshes with the fixed wheel sixth gear 32. The idler fifth gear 64 meshes with fixed wheel fifth gear 26. The idler seventh gear 66 meshes with the fixed wheel seventh gear 27.

In other words, there is only one double-meshing provided between the two layshafts 40, 50. The double-meshing comprises the idler fifth gear 64 that meshes with the idler third gear 62 via the fixed wheel third gear 25. The fixed wheel third gear 25 also serves as the fixed wheel fifth gear 26.

The reverse gear idler shaft 38 is provided further above the upper layshaft 40. There is provided gearwheels on the reverse gear idler shaft 38, which includes, from right to the left, a first reverse gearwheel 35 and a second reverse gearwheel 36. Two idler shaft bearings 74 are provided at two ends of the reverse gear idler shaft 38 respectively. Both the first reverse gearwheel 35 and the second reverse gearwheel 36 are fixed on the reverse gear idler shaft 38 coaxially. The first reverse gearwheel 35 meshes with the idler second gear 61 via an intermediate gearwheel, which is the fixed wheel second gear 30. The second reverse gearwheel 36 meshes with the reverse gear idler wheel 37.

The output shaft 14 is provided below the lower layshaft 50. A pair of output shaft bearings 75 is provided at two opposite ends of the output shaft 14 for supporting. The output gearwheel 12 is fixed on the output shaft 14 coaxially. The output gearwheel 12 meshes with both the lower pinion 51 and the upper pinion 41.

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 alternatively replaced by a hollow shaft that is disposed inside the hollow input shaft 22. The term “coupling device” is alternatively termed as “shifting mechanism” for engaging or disengaging gearwheels on a shaft. The double-clutch transmission (DCT) is alternatively termed as double-clutch, double clutch transmission or dual clutch transmission (DCT). Any on of the input shafts 20, 22 can be held by more than two bearings for better support.

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 idler first gear 60 is also known as the first gear idler gearwheel 60. The idler second gear 61 is also known as the second gear idler gearwheel 61. The idler third gear 62 is also known as the third gear idler gearwheel 62. The idler fourth gear 63 is also known as the fourth gear idler gearwheel 63. The idler fifth gear 64 is also known as the fifth gear idler gearwheel 64. The idler sixth gear 65 is also known as the sixth gear idler gearwheel 65. The idler seventh gear 66 is also known as the seventh gear idler gearwheel 66. The coupling devices are alternatively known as synchronizers.

The application provides the DCT 1 that permits gear shift operations with less loss of driving torque. This is because the gear shift operations can be achieved by selectively connecting one of the two clutch discs 8, 10 of the DCT 1. Therefore, an associated additional main drive clutch can be avoided. The selective connection between the two clutch discs 8, 10 also enables the realization of an automatic transmission that can be operated without interruptions in propulsive power. The propulsive power comprises momentum derived from the rotating gearwheels and shafts inside the DCT 1. Such a transmission is similar in design to a mechanical manual transmission and it has correspondingly very low friction losses. The double-clutch transmission 1 further provides a parallel manual transmission that can be used for transverse installation in a front-wheel drive vehicle.

The DCT 1 according to the application can be connected similar to a known manual transmission, such as a parallel manual transmission. In the know 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 also 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 at least alleviated by the application. The application provides a double-clutch transmission 1 that has two clutches for connecting to an electrical motor and the manual transmission in a compact manner.

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

The double-clutch transmission 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 the torques can be achieved.

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

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.

It is further advantageous 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 gear shift is performed sequentially. This is because the DCT 1 can alternatively engage one of the two clutch discs 8, 10. For example, the power-shift operation from the first 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.

The single double-meshing of the idler third gear 62 and the idler fifth gear 64 via the intermediate fixed wheel third gear 25 (i.e. fixed wheel fifth gear 26) provides efficient gear shifts between the third and the fifth. No input shaft or clutch change is required for the direct gear shift between the third gear and the fifth gear. Since the fixed wheel third gear 25 is the same as the fixed wheel fifth gear 26, no additional gearwheel is required for providing each of the third and fifth gears. The solid input shaft 20 can thus be made shorter and one gearwheel is saved for reducing cost and weight of the DCT 1.

Gearwheels 60, 61, 62, 63 of the low gears (i.e. 1st, 2nd, 3rd & 4th gears) are provided on the same lower layshaft 50, which is advantageous. This is because the lower layshaft 50 has lower rotational speed with larger size for higher torque, as compared to that of the upper layshaft 40. This arrangement eliminates the need of providing multiple layshafts with larger sizes for carrying those heavy-load gearwheels 60, 61, 62, 63 of the low gears separately. Therefore, the DCT 1 can be made light with less cost.

Bearings 73 of the DCT 1 are mounted next to gearwheels 60, 61 of low gears and the pinions 41, 51. This arrangement provides stronger mechanical support to the shafts 40, 50 for less shaft deflection. Similarly, the bearings 74, 75 for the reverse gear idler shaft 38 and the output shaft 14 are also close to the gearwheels 12, 35, 36. As a result, the shafts 14, 38 can be reduced in weight for lower cost.

It is also of advantage to drive the gearwheel groups of the first gear and the reverse gear by different input shafts 20, 22 of the DCT 1. This provides the ability to drive a vehicle change between a slow forward and a slow backward without engaging and disengaging the same group of gearwheels. Just by engaging and disengaging the respective clutches 8, 10 of 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 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 clutch discs 8, 10 of the DCT 1.

A variant of the embodiment with one double-shared gearwheel on one or both of the input shafts 20, 22 has the advantage of providing a higher ratio-flexibility and of less dependency. It is beneficial to provide the gearwheels of the first gear, of the reverse gear and of the second gear close to the bearings for supporting. The gearwheels of these gearwheels of low gears (e.g. 1st gear, 2nd gear, reverse gear, etc) undergo bigger forces than those of the higher gears because the drive ratio is larger for the lower gears and reverse gears. Therefore, their shafts 38, 50 must take up higher driving forces. If those forces are taken up close to the support points of the shafts 38, 50, excessive shafts' bending will be reduced.

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 (not shown). According to FIG. 2, the input torque of the first gear is received by the solid input shaft 20 from the double-clutch 6 of the DCT 1. A torque of the first gear is transmitted from the solid input shaft 20, via the fixed wheel first gear 24, via the idler first gear 60, 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 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.

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 (not shown). According to FIG. 3, the input torque of the second gear is received by the hollow input shaft 22 from the double-clutch 6 of the DCT 1. A torque of the second gear is transmitted from the hollow input shaft 22, via the fixed wheel second gear 30, via the idler second gear 61, 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 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.

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 (not shown). According to FIG. 4, the input torque of the third gear is received by the solid input shaft 20 from the double-clutch of the DCT 1. A torque of the third gear is transmitted from the solid input shaft 20, via the fixed wheel third gear 25, via the idler third gear 62, 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 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.

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 (not shown). According to FIG. 5, the input torque of the fourth gear is received by the hollow input shaft 22 from the double-clutch 6 of the DCT 1. A torque of the fourth gear is transmitted from the hollow input shaft 22, via the fixed wheel fourth gear 31, via the idler fourth gear 63, 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 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.

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 (not shown). According to FIG. 6, the input torque of the fifth gear is received by the solid input shaft 20 from the double-clutch 6 of the DCT 1. A torque of the fifth gear is transmitted from the solid input shaft 20, via the fixed wheel fifth gear 26, via the idler fifth gear 64, 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 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.

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 (not shown). According to FIG. 7, the input torque of the sixth gear is received by the hollow input shaft 22 from the double-clutch 6 of the DCT 1. A torque of the sixth gear is transmitted from the hollow input shaft 22, via the fixed wheel sixth gear 32, via the idler sixth gear 65, 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 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.

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 (not shown). According to FIG. 8, the input torque of the seventh gear is received by the solid input shaft 20 from the double-clutch 6 of the DCT 1. A torque of the seventh gear is transmitted from the solid input shaft 20, via the fixed wheel seventh gear 27, via the idler seventh gear 66, 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 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.

FIG. 9 illustrates the path of torque flow of a reverse gear transmission ratio. In FIG. 9, an input torque of the reverse gear is received from the crankshaft 2 of a combustion engine (not shown). According to FIG. 9, the input torque of the reverse gear is received by the hollow input shaft 22 from the double-clutch 6 of the DCT 1. A torque of the reverse gear is transmitted from the hollow input shaft 22, via the fixed wheel second gear 30, via the first reverse gearwheel 35, via the reverse gear idler shaft 38, via the second reverse gearwheel 36, via the reverse gear idler wheel 37, 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 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.

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

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.

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.

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

FIG. 13 illustrates an assembly 130 of a fixed gearwheel 132 that is supported on a shaft 131. The fixed gearwheel 132 is coaxially mounted 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.

A number of fixed gearwheels are rigidly connected to the input shafts 20, 22 and other shafts 14, 38, 40, 50. 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.

FIG. 14 illustrates a cross-section through a crankshaft 2 of an internal combustion engine according to the embodiment of the DCT 1. In FIG. 14, a crankshaft 2 of an internal combustion engine, which is not shown here, is non-rotatably connected to the housing 4 of a double clutch 6. The double clutch 6 includes an inner clutch disk 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 non-rotatably connected to the clutch disk 8, and extends all the way through the hollow shaft 22. Similarly, the hollow input shaft 22 is non-rotatably connected to the other clutch disc 10.

The clutch housing 4 has a larger outer diameter around the inner clutch disc 8 than that around the outer clutch disc 10. Correspondingly, the inner clutch disc 8 has a larger outer diameter than that of the outer clutch disc 10 inside the clutch housing 4. The fact that the larger inner clutch disc 8 on the solid input shaft 20 drives the first gear makes the DCT 1 robust.

The above-mentioned eight torque flow paths not only provide viable solutions to generate eight gears (i.e. seven-forward & one rearward gears) of the DCT 1, but also offer possibilities of switching from one gear to the other efficiently. For example, gear jumping from the third gear to the fifth gear is efficiently provided by the double-meshing of the idler fifth gear 64 and the idler third gear 62, via an intermediate gearwheel, namely the fixed wheel third gear 25. The fixed wheel third gear 25 also serves as the fixed wheel fifth gear 26. The gear jump between the third and the fifth does not require stopping the solid input shaft 20. Furthermore, the double-meshing of the idler third gear 62 and idler fifth gear 64 avoids the need of providing two separate fixed gearwheels on an input shaft. In other words, less space is required on the hollow input shaft 22 because two fixed gearwheels 25, 26 are combined into a single one. The DCT 1 can thus be made lighter and cheaper by the reduction of one gearwheel.

The park-lock gearwheel 39 is a gearwheel fixed onto the upper layshaft 40 for providing a park-lock. The park-lock is a wheel which is provided with a ratchet device, with a click device having a rack element, a claw or similar. The park-lock keeps the upper layshaft 40 and the output shaft 14 from rotating, which stop a vehicle with the DCT 1 from running when the vehicle is parked. When using the park-lock, the park-lock gearwheel 39 on the upper layshaft 40 can be easily engaged to lock the output shaft 14, via the upper pinion 41, via the output gearwheel 12 and stopping the output shaft 14 from rotating.

FIG. 15 illustrates an alternative front view of the expanded side view of the double clutch transmission 1 in FIG. 2. FIG. 15 comprises parts that are similar to that of FIGS. 1 to 14. The similar parts have similar or same part reference numbers. Descriptions of the similar or the same parts are hereby incorporated by reference.

Although the above description contains much specificity, these should not be construed as limiting the scope of the embodiment but merely providing illustration of the foreseeable embodiment. Especially the above stated advantages of the embodiment should not be construed as limiting the scope of the embodiment but merely to explain possible achievements if the described embodiment is put into practice. Thus, the scope of the embodiment should be determined by the claims, rather than by examples given.

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 of the invention, 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 connected to the inner input shaft and a second clutch connected to the outer input shaft;a first layshaft and a second layshaft radially spaced apart from the inner input shaft and the outer input shaft and arranged in parallel to the inner input shaft and the outer input shaft,gearwheels arranged on the first layshaft, on the second 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, and a sixth gearwheel group, which are adapted to provide six gears,the first gearwheel group comprising a first fixed gearwheel on the inner input shaft, meshing with a first gear idler gearwheel on one of the first layshaft or the second layshaft,the third gearwheel group comprising a third fixed gearwheel on the inner input shaft, meshing with a third gear idler gearwheel on one of the first layshaft or the second layshaft,the fifth gearwheel group comprising a fifth fixed gearwheel on the inner input shaft, meshing with a fifth gear idler gearwheel on one of the first layshaft or the second layshaft,the second gearwheel group comprising a second fixed gearwheel on the outer input shafts, meshing with a second gear idler gearwheel on one of the first layshaft or the second layshaft,the fourth gearwheel group comprising a fourth fixed gearwheel on the outer input shafts, meshing with a fourth gear idler gearwheel on one of the first layshaft or the second layshaft,the sixth gearwheel group comprising a sixth fixed gearwheel on the outer input shafts, meshing with a sixth gear idler gearwheel on one of the first layshaft or the second layshaft, andeach gearwheel group comprising a coupling device arranged on one of the first layshaft or the second lay shaft to selectively engage one of the first idler gearwheel, the second idler gearwheel, the third idler gearwheel, the fourth idler gear wheel, the fifth idler gearwheel, or sixth idler gearwheel, which are adapted to select one of the six gears, andthe third fixed gearwheel further meshing with the fifth gear idler gearwheel,a seventh gearwheel group adapted to provide a seventh gear, the seventh gearwheel group comprising a seventh fixed gearwheel on the inner input shaft, meshing with a seventh gear idler gearwheel on one of the first layshaft or the second layshaft,the seventh gearwheel group further comprises a coupling device arranged on one of the first layshaft or the second layshaft to selectively engage the seventh gear idler gearwheel and provide the seventh gear; anda reverse gear idler shaft and at least one reverse gearwheel mounted on the reverse gear idler shaft adapted to provide a reverse gear.

2. The double-clutch transmission of claim 1, wherein the first forward gear and the reverse gear are provided by different input shafts.

3. The double-clutch transmission according to claims, wherein the at least one reverse gearwheel comprises a first reverse gearwheel and a second reverse gearwheel that mesh with two gearwheels of the seven gearwheel groups, respectively.

4. The double-clutch transmission of claim 3, wherein the first reverse gearwheel meshes with the second fixed gearwheel, while the second reverse gearwheel meshes with a reverse gear idler wheel.

5. The double-clutch transmission according to claim 1, further comprising: a park-lock gearwheel fixed onto one of the first layshaft of the second layshaft and adapted to provide a park-lock.

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

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

8. The double-clutch transmission according to claim 7, wherein the fifth gear idler gearwheel, the sixth gear idler gearwheel and the seventh gear idler gearwheel are mounted on the second layshaft, which is lower then the first layshaft.

9. The double-clutch transmission according to claim 1, wherein the coupling device comprises a double-sided coupling device for engaging a gearwheel on a side of the coupling device to a shaft that carries the coupling device.

10. The double-clutch transmission according to claim 1 further comprising bearings adapted to support the first layshaft and the second layshaft, at least one of the bearings provided next to one of the first gear idler gearwheel or the second gear idler gearwheel.

11. A gearbox, comprising: 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 connected to the inner input shaft and a second clutch connected to the outer input shaft;a first layshaft and a second layshaft radially spaced apart from the inner input shaft and the outer input shaft and arranged in parallel to the inner input shaft and the outer input shaft,gearwheels arranged on the first layshaft, on the second 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, and a sixth gearwheel group, which are adapted to provide six gears,the first gearwheel group comprising a first fixed gearwheel on the inner input shaft, meshing with a first gear idler gearwheel on one of the first layshaft or the second layshaft,the third gearwheel group comprising a third fixed gearwheel on the inner input shaft, meshing with a third gear idler gearwheel on one of the first layshaft or the second layshaft,the fifth gearwheel group comprising a fifth fixed gearwheel on the inner input shaft, meshing with a fifth gear idler gearwheel on one of the first layshaft or the second layshaft,the second gearwheel group comprising a second fixed gearwheel on the outer input shafts, meshing with a second gear idler gearwheel on one of the first layshaft or the second layshaft,the fourth gearwheel group comprising a fourth fixed gearwheel on the outer input shafts, meshing with a fourth gear idler gearwheel on one of the first layshaft or the second layshaft,the sixth gearwheel group comprising a sixth fixed gearwheel on the outer input shafts, meshing with a sixth gear idler gearwheel on one of the first layshaft or the second layshaft, andeach gearwheel group comprising a coupling device arranged on one of the first layshaft or the second lay shaft to selectively engage one of the first idler gearwheel, the second idler gearwheel, the third idler gearwheel, the fourth idler gear wheel, the fifth idler gearwheel, or sixth idler gearwheel, which are adapted to select one of the six gears, andthe third fixed gearwheel further meshing with the fifth gear idler gearwheel,a seventh gearwheel group adapted to provide a seventh gear, the seventh gearwheel group comprising a seventh fixed gearwheel on the inner input shaft, meshing with a seventh gear idler gearwheel on one of the first layshaft or the second layshaft,the seventh gearwheel group further comprises a coupling device arranged on one of the first layshaft or the second layshaft to selectively engage the seventh gear idler gearwheel and provide the seventh gear;a reverse gear idler shaft and at least one reverse gearwheel mounted on the reverse gear idler shaft adapted to provide a reverse gear; andan output gearwheel that meshes with pinions on the first layshaft and second layshaft, respectively, for providing an output torque.

12. A power train device, comprising: 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 connected to the inner input shaft and a second clutch connected to the outer input shaft;a first layshaft and a second layshaft radially spaced apart from the inner input shaft and the outer input shaft and arranged in parallel to the inner input shaft and the outer input shaft,gearwheels arranged on the first layshaft, on the second 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, and a sixth gearwheel group, which are adapted to provide six gears,the first gearwheel group comprising a first fixed gearwheel on the inner input shaft, meshing with a first gear idler gearwheel on one of the first layshaft or the second layshaft,the third gearwheel group comprising a third fixed gearwheel on the inner input shaft, meshing with a third gear idler gearwheel on one of the first layshaft or the second layshaft,the fifth gearwheel group comprising a fifth fixed gearwheel on the inner input shaft, meshing with a fifth gear idler gearwheel on one of the first layshaft or the second layshaft,the second gearwheel group comprising a second fixed gearwheel on the outer input shafts, meshing with a second gear idler gearwheel on one of the first layshaft or the second layshaft,the fourth gearwheel group comprising a fourth fixed gearwheel on the outer input shafts, meshing with a fourth gear idler gearwheel on one of the first layshaft or the second layshaft,the sixth gearwheel group comprising a sixth fixed gearwheel on the outer input shafts, meshing with a sixth gear idler gearwheel on one of the first layshaft or the second layshaft, andeach gearwheel group comprising a coupling device arranged on one of the first layshaft or the second lay shaft to selectively engage one of the first idler gearwheel, the second idler gearwheel, the third idler gearwheel, the fourth idler gear wheel, the fifth idler gearwheel, or sixth idler gearwheel, which are adapted to select one of the six gears, andthe third fixed gearwheel further meshing with the fifth gear idler gearwheel,a seventh gearwheel group adapted to provide a seventh gear, the seventh gearwheel group comprising a seventh fixed gearwheel on the inner input shaft, meshing with a seventh gear idler gearwheel on one of the first layshaft or the second layshaft,the seventh gearwheel group further comprises a coupling device arranged on one of the first layshaft or the second layshaft to selectively engage the seventh gear idler gearwheel and provide the seventh gear;a reverse gear idler shaft and at least one reverse gearwheel mounted on the reverse gear idler shaft adapted to provide a reverse gear;an output gearwheel that meshes with pinions on the first layshaft and second layshaft, respectively, for providing an output torque; andat least one power source adapted to generate a driving torque.

13. The power train device of 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)