DESC:FIELD OF THE DISCLOSURE

The present disclosure generally relates to a transmission system of a vehicle.

Particularly, the present disclosure relates to dual clutch transmissions.

Definition(s):
Forward and Reverse shuttling - Shifting of gears between forward and reverse gears for facilitating movement of vehicle in forward and reverse direction

BACKGROUND

A clutch is a device that facilitates transmission of power and therefore usually motion from one component (a driving element) to another (a driven element) when engaged. Also, a clutch is adapted to disengage a driving element form a driven element as per requirement. Clutches are used whenever transmission of power or motion needs to be controlled either in amount or over time.

A dual-clutch transmission (DCT) is a semi-automatic or an automated manual automotive transmission. A dual-clutch transmission (DCT) uses two separate clutches for odd and even gear sets. Two separate clutches of a dual-clutch transmission (DCT) may be contained within a housing and may work as a single unit. A dual-clutch transmission (DCT) may be operated in a fully automatic mode or may also allow the driver to manually shift gears.

Existing dual-clutch transmissions include two input shafts concentric to each other and carry input gears with a clutch mounted on the front end of each shaft. The first input shaft is relatively long as compared to the second input shaft and has two integral drive gears and one fixed gear. The second input shaft is relatively shorter and hollow and has two integral drive gears. A reverse drive gear is common with the drive gear mounted on the first input shaft. The existing dual-clutch transmissions include a compound idler. The compound idler has two gears integral on it, one big gear and the other a small gear. The big gear is driven by the first drive gear and the small gear drives the reverse driven gear on the first countershaft.

However, the existing dual-clutch transmissions have numerous limitations. For example, existing dual-clutch transmissions need a separate long idler shaft. Further, the existing dual-clutch transmissions do not facilitate FORWARD/ REVERSE shuttling. Furthermore, the existing dual-clutch transmissions provide delayed shifting while shifting gears from 1st to Reverse or Reverse to 1st.

Accordingly, there is need of a dual-clutch transmission (DCT) that facilitates FORWARD/ REVERSE shuttling. Further, there is need of a dual-clutch transmission (DCT) that does not require a dedicated output shaft for a reverse gear. Furthermore, there is need of a dual-clutch transmission (DCT) that provides an efficient control system.

OBJECTS

Some of the objects of the system of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the system of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

An object of the present disclosure is to provide a dual-clutch transmission (DCT) that facilitates smooth (no torque interruption) shifting for FORWARD/ REVERSE shuttling.

Another object of the present disclosure is to provide a dual-clutch transmission (DCT) that does not require a dedicated output shaft for a reverse gear.

Further, an object of the present disclosure is to provide a dual-clutch transmission (DCT) that provides an efficient control system.

Also, an object of the present disclosure is to provide a dual-clutch transmission (DCT) that can compactly packaged.

Other objects and advantages of the system of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figure, which is not intended to limit the scope of the present disclosure.

SUMMARY

A dual clutch transmission system includes a first clutch, a set of odd drive gears, a second clutch, a set of even drive gears and a set of reverse gears. The first clutch is functionally coupled to a power source and a first output shaft. The first clutch selectively transmits driving power from the power source to the first output shaft. The driving gears of the set of odd drive gears are mounted on the first output shaft and engage with driven gears of the set of odd drive gears that are rotatably supported on either of first and second counter-shafts supported within a transmission housing to define odd gear transmission ratios. The second clutch is functionally coupled to the power source and a second output shaft concentrically disposed with respect to said first output shaft. The second clutch selectively transmits driving power from the power source to the second output shaft. The driving gears of the set of even drive gears are mounted on the second output shaft and engage with driven gears of the set of even drive gears rotatably supported on either of the first and second counter-shafts to define even gear transmission ratios. A driving gear of the set of reverse gears is mounted on the first countershaft and is functionally coupled to a driven gear of a set of second drive gears mounted on the second output shaft. The driving gear of the set of reverse gears is independently mounted with respect to the driving gear of a set of first drive gears mounted on the first output shaft, thereby facilitating forward and reverse shuttling and facilitating parking wherein the first gear and reverse gear are used alternatively.

Typically, the power source is an I.C. engine.

Generally, the first and second counter-shafts are rotatably supported within the transmission housing by using a set of tapered roller bearings.

Typically, the driven gears of the set of odd drive gears are rotatably supported on either of the first and second counter-shafts by using needle bearings.

Alternatively, the driven gears of the set of even drive gears are rotatably supported on either of the first and second counter-shafts by using needle bearings.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWING

The dual-clutch transmission (DCT) of the present disclosure will now be explained in relation to the non-limiting accompanying drawing, in which:
Figure 1 illustrates a schematic representation of a dual-clutch transmission (DCT) that provides 7 speeds, in accordance with one embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWING

The dual-clutch transmission (DCT) of the present disclosure will now be described with reference to the accompanying drawing which does not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The description hereinafter, of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Referring to Figure 1, the dual clutch transmission 100 includes a pair of clutches 102 and 104, the input sides of which are connected to an engine and output sides to output shafts 106 and 108 which are concentric to each other. More specifically, the first output shaft 106 is relatively long as compared to the second output shaft 108. The second output shaft 108 is relatively shorter and is hollow to receive the first output shaft 106. The output shaft 106, also referred to as the first output shaft or the inner output shaft carries the odd drive gears D1, D3 and D57, and the outer output shaft 108, also referred to as the second output shaft or the outer output shaft, carries the even drive gears D46, and D21. The reverse drive gear Dr is functionally coupled to the 2nd driven gear D24 and the driven gear D23, wherein the 2nd driven gear D24 is on the other countershaft LS2 and the driven gear D23 is mounted on the output shaft 108. The dual clutch transmission 100 includes a pair of idler gears. One idler gear is placed on the input shaft and the other on a separate shaft.
The transmission includes a transmission housing, first, second, third, fourth, fifth gear sets, the first transmission output shaft also referred to as inner output shaft 106, the second transmission output shaft also referred to as outer output shaft 108, a first counter shaft LS1, a second countershaft LS2 and four synchronizer assemblies.

The pair of output shafts 106 and 108 are concentric to each other, carrying input /driving/driver gears with a clutch mounted on the front end of each shaft. The inner shaft 106 is long and has two integral gears and one fixed gear. The outer shaft 108 is short and hollow. It has two integral gears and one free rotating gear.

The first and second countershafts LS1 and LS2 are rotatably supported within the transmission housing by a set of tapered roller bearings. Each countershaft LS1 and LS2 has four freely rotating gears, two synchronizer full packs and one fixed final drive gear. The final drive gear meshes with the differential ring gear. The first countershaft LS1 has one square toothed wheel which acts as a park gear.

The transmission includes six coplanar gear sets, two of the six coplanar gear sets produce two ratios each and the remaining three coplanar gear sets produce individual ratios.

The first gear set has the first drive gear D1 integrally mounted on the inner shaft 106 and the first driven gear D1’ freely rotating on a needle bearing on the first countershaft LS1. The second gear set has the driven gear D23 integral on the inner shaft 106 and the third driven gear D24 freely rotating on a needle bearing on the second countershaft LS2. The third gear set has the common driving gear D57 for the fifth and the seventh speed fixed on the inner shaft 106. The corresponding fifth driven gear D5 freely rotates on a needle bearing on the first countershaft LS1 and seventh driven gear D7 freely rotates on a needle bearing on the second countershaft LS2.

The fourth gear set has the common drive gear D46 for fourth and sixth gear D4 and D6 integral on the outer output shaft 108. The corresponding fourth driven gear D4 freely rotates on a needle bearing on the first countershaft LS1 and sixth driven gear D6 freely rotates on a needle bearing on the second countershaft LS2.

The fifth gear set consists of second drive gear D57 integral to the first output shaft 106. The second speed driven gear D24 is located on a needle bearing in the second countershaft LS2. The reverse drive gear Dr is mounted on the first countershaft LS1 and mounted on a needle bearing and allowed to rotate freely on the first countershaft but is functionally coupled to the second driven gear D23. The reverse drive gear Dr then drives a free gear mounted on a needle bearing on the outer shaft 108. The torque is then transferred to a dedicated idler gear mounted on an idler shaft. The idler shaft is supported at both ends with the help of thrust bearings. This idler gear drives the reverse drive gear on the first countershaft LS1. The reverse drive gear Dr is mounted on a needle bearing and allowed to freely rotate on the first countershaft.

Park gear is fixed on the second countershaft LS2 and is provided for placing the transmission in a park mode that prevents the output member from rotating. The park gear is axially aligned with the first gear set plane. This reduces the axial length of the transmission. The park gear includes a park lock 110.

The transmission includes four synchronizer assemblies driven by four rail shafts and forks. The synchronizer pack selectively couple at least one of the gears of the first, second ,third , fourth and fifth gear sets with at least one of the inner shaft 106, the outer shaft 108, the first countershaft and second countershaft. The selective engagement of the dual clutch assembly 100 interconnects the dual clutch housing with at least one of the inner shaft 106 and the outer shaft 108 and selective engagement of at least one of the four synchronizer assemblies establish at least one of the seven forward ratios.

The reverse drive gear Dr is integrated to one of the forward gears. The power then flows to the free gear in the input shaft to the idler gear. This idler gear drives the reverse drive gear on the other countershaft. Thus the direction is reversed and the required ratio is also obtained. The reverse drive gear Dr includes a reverse idler 112.

In one embodiment, the dual clutch transmission 100 of the present disclosure is a seven speed dual clutch transmission. However, the present disclosure is not limited to any number of speeds achieved by the dual clutch transmission 100 of the present disclosure. Further, in one embodiment, the dual clutch transmission 100 of the present disclosure is a wet clutch transmission. However, in another embodiment, the dual clutch transmission 100 can be a dry clutch transmission. In one embodiment, the gear train architecture utilized in the dual clutch transmission (DCT) 100 of the present disclosure is the same parallel shaft arrangement as the conventional manual transmission. However, the present disclosure is not limited to any particular gear train architecture described.

The dual-clutch transmission (DCT) 100 of the present disclosure facilitates smooth (no torque interruption) shifting for FORWARD/ REVERSE shuttling. FORWARD/REVERSE shuttling corresponds to a Garage parking phenomenon, where generally the 1st gear and the reverse drive gear is used alternatively at very low speeds less than 10km/hr. For this to happen, the 1st and the reverse drive gear should be mounted at different output shafts. The transmission Controller enables this when the vehicle speed is less than 10km/hr. So when in 1st gear below 10km/hr, the reverse drive gear is pre-selected. If the reverse drive gear is demanded then the even clutch 104 is engaged and power flow changes to the even input shaft 108 and reverse drive gear is in operation. Conversely, if the reverse drive gear is in operation, the 1st gear is always preselected. During the 1st gear driving (Reverse drive gear is preselected), clutch changes from odd clutch 102 to even clutch 104. Thus for shuttling between the reverse (REVERSE) and forward (FORWARD) gears, only there is a clutch change operation (time duration approximately 0.6 sec). So the shuttling is quick, smooth and seamless.

Also, in the dual-clutch transmission (DCT) 100 of the present disclosure, the REVERSE drive gear is functionally coupled to the even output shaft 108 and 1st gear is on the odd input shaft 106. So FORWARD/REVERSE shuttling is enabled. In a conventional layout, both the 1st and reverse drive gear are mounted on the same shaft (odd output shaft in most cases). Accordingly, in the present disclosure, for shifting from 1st gear to reverse gear, the operations would be like a manual transmission. Accordingly, the sequence of gear changing is: Odd clutch disengage - 1st gear disengage - Reverse drive gear engage - Odd Clutch engage. Accordingly, FORWARD/REVERSE shuttling is prevented.

The dual-clutch transmission (DCT) 100 of the present disclosure facilitates reduction of shifting time while performing gear shifting from 1st Gear to Reverse gear or Reverse gear to 1st gear. This happens because of FWD/REV shuttling is possible, then shifting from 1st to Rev or Rev to 1st to Rev is only a clutch changing process. In one embodiment, the gear shifting time from 1st Gear to Reverse gear or Reverse gear to 1st gear is approximately 0.6 sec. However, in the conventional dual-clutch transmission systems without FWD/REV shuttling, the shifting time is around 1.4 sec.

TECHNICAL ADVANCEMENTS AND ECONOMICAL SIGNIFICANCE

The technical advancements offered by the system of the present disclosure which add to the economic significance of the disclosure include the realization of:

• a dual-clutch transmission (DCT) that facilitates smooth (no torque interruption) shifting for FORWARD/ REVERSE shuttling;

• a dual-clutch transmission (DCT) that does not require dedicated output shaft for a reverse gear;

• a dual-clutch transmission (DCT) that provides efficient control system as the dual-clutch transmission (DCT) of the present disclosure has four synchronizer packs;
• a dual-clutch transmission (DCT) that provides compact packaging;

• a dual-clutch transmission (DCT) that achieves reverse gear ratio greater or equal to 1st speed;
• a dual-clutch transmission (DCT) that provides flexible reverse ratio;

• a dual-clutch transmission (DCT) that takes drive for reverse gear from an even gear driving input shaft;

• a dual-clutch transmission (DCT) that provides 1st and reverse gears at either ends to rationalize bearing loads; and

• a dual clutch transmission that is fuel efficient.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary. ,CLAIMS:
1. A dual clutch transmission system comprising:
• a first clutch functionally coupled to a power source and a first output shaft, said first clutch adapted to selectively transmit driving power from said power source to said first output shaft;
• a set of odd drive gears, wherein driving gears of set of odd drive gears are mounted on said first out-put shaft and are adapted to engage with driven gears of said set of odd drive gears rotatably supported on either of first and second counter-shafts supported within a transmission housing to define odd gear transmission ratios;
• a second clutch functionally coupled to said power source and a second output shaft concentrically disposed with respect to said first output shaft, said second clutch adapted to selectively transmit driving power from said power source to said second output shaft;
• a set of even drive gears, wherein driving gears of set of even drive gears are mounted on said second output shaft and are adapted to engage with driven gears of said set of even drive gears rotatably supported on either of said first and second counter-shafts to define even gear transmission ratios; and
• a set of reverse gears, wherein a driving gear of said set of reverse gears is mounted on said first countershaft and is functionally coupled to a driven gear of a set of second drive gears mounted on said second output shaft, said driving gear of said set of reverse gears is independently mounted with respect to said driving gear of a set of first drive gears mounted on said first output shaft, thereby facilitating forward and reverse shuttling and facilitating parking wherein first gear and reverse gear are used alternatively.

2. The dual clutch transmission system as claimed in claim 1, wherein said power source is an I.C. engine.
3. The dual clutch transmission system as claimed in claim 1, wherein said first and second counter-shafts are rotatably supported within said transmission housing by using a set of tapered roller bearings.

4. The dual clutch transmission system as claimed in claim 1, wherein said driven gears of said set of odd drive gears are rotatably supported on either of said first and second counter-shafts by using needle bearings.

5. The dual clutch transmission system as claimed in claim 1, wherein driven gears of said set of even drive gears are rotatably supported on either of said first and second counter-shafts by using needle bearings.