Dual clutch transmission with a torque converter

A multi-speed transmission for transmitting power from a power source includes a torque converter as well as dual clutches which may be arranged as dual input clutches or dual output clutches. To combine the smoothness and ratio boosting effects of a torque converter with the low spin loses associated with synchronizers used in dual clutch designs. The torque converter and dual clutches as well as synchronizers and a plurality of intermeshing gears are utilized to transfer torque from an input member to an output member at a plurality of speed ratios.

TECHNICAL FIELD

This invention relates to a multi-speed, dual clutch transmission connectable with a torque converter.

BACKGROUND OF THE INVENTION

Dual input clutch transmissions have been designed with friction launch clutches to connect a vehicle engine to selectively engaged gears in a lay shaft transmission. Dual input clutch transmissions are designed to permit engine power to be distributed through power paths that are dependent upon which input clutch is engaged. Dual input clutch power transmissions are typically designed as countershaft-type transmissions (i.e., lay shaft transmissions) wherein engagement of a first of the input clutches creates a power path from an input shaft through a first countershaft to an output shaft, and engagement of a second of the input clutches creates a power path through a second countershaft to the output shaft. Synchronizers engage gears with the countershafts to complete the powerflow to the output shaft. Layshaft designs and other transmission configurations that use synchronizers for selectively engaging gears with a shaft provide relatively low spin losses, thus enhancing overall operating efficiency.

The art has also employed the clutch of a planetary transmission as a friction launch mechanism that provides launch slip in connecting a set of interconnected planetary gear sets with an input shaft connected to an engine to transfer power from the input shaft to an output shaft. One such power transmission with a friction launch torque-transmitting mechanism is disclosed in commonly-assigned U.S. Pat. No. 6,471,616, issued to Paul D. Stevenson on Oct. 29, 2002, which is hereby incorporated by reference in its entirety.

Furthermore, the art has also employed a torque converter connectable with planetary or layshaft gear sets in a transmission to transfer power from a power source, such as an engine, to an output shaft. The torque converter provides a torque multiplier and speed differential between the engine and the gearing. The fluid coupling function of the torque converter enables a smooth transmission of power during launch, shifting, as well as coasting. A torque converter clutch may or may not be employed to connect the engine to the transmission (bypassing the torque converter) and thereby improve the overall efficiency of the transmission. An example of a powertrain including an engine, a torque converter and a transmission including three planetary gear sets is described in commonly-assigned U.S. Pat. No. 6,729,993, issued to Norman Kenneth Bucknor et al. on May 4, 2004, which is hereby incorporated by reference in its entirety.

SUMMARY OF THE INVENTION

By utilizing a torque converter with a dual clutch transmission, the invention combines smoothness and ratio-boosting effects of a torque converter with the low spin losses associated with the synchronizers of the dual clutch designs. With respect to a conventional dual clutch transmission, a damper and two launching clutches are replaced by a torque converter and two shifting clutches. Shifting clutches may be more compact, require less heat sink and require less cooling than launching clutches. They may, therefore, be less expensive and may weigh less than launching clutches, as the torque converter provides some of the heat absorbing capability otherwise required by launching clutches. It should be noted that a damper is employed within the torque converter, but such a damper may be smaller than a damper required to be used in conjunction with friction launch clutches, as the inertia of the torque converter itself provides a portion of the required inertia capability.

A powertrain having a torque converter and a dual shifting clutch design may be especially advantageous for a vehicle having a low power to weight ratio, as the torque converter provides greater heat sink capability than conventional friction launch clutches. Vehicles having a low ratio of engine speed to vehicle velocity (i.e., a low N/V, where N is the speed of the engine in revolutions per minute (rpm) and V is the velocity of the vehicle in miles per hour (mph)), may be well-suited for a design having a torque converter with dual shifting clutches, due to the heat sink capability and ratio-boosting effect of the torque converter. Additionally, the relatively low spin losses of the synchronizers and wide ratios available in higher gears may improve fuel economy with respect to other powertrain designs. The use of a torque converter with its torque multiplication can allow the use of gear ratios with smaller steps or fewer gear ratios for the same performance.

Accordingly, a multi-speed transmission is provided for transmitting power from a power source. The transmission includes an input member and an output member as well as a torque converter operatively connected between the input member and the power source to create a fluid coupling therebetween. The transmission further includes a first shaft and a second shaft as well as a plurality of synchronizers and a plurality of intermeshing gears. One or more of the input member, the output member and the first and second shafts has some of the gears continuously connected thereto for rotation therewith. Others of the gears are selectively interconnectable for rotation with others of the shafts and/or input or output member via selective engagement of the synchronizers.

The transmission also includes a first and a second clutch which are alternately selectively engageable for operatively interconnecting the first and second shafts, respectively, with either the input member or the output member. The first and second clutches may be referred to as dual shifting clutches. When the dual shifting clutches are engageable for operatively interconnecting the first shaft and second shaft with the input member, they are referred to as dual input clutches. Likewise, when the first and second clutches are engageable for operatively interconnecting the first and second shaft with the output member, they are referred to as dual output clutches. By selectively engaging the clutches and the synchronizers as described above, the input member is operatively interconnected with the output member through the intermeshing gears to transfer power provided from the power source to the output member. The power source may be a conventional internal combustion engine, but may also be a hybrid engine, diesel engine or other form of power source.

In one aspect of the invention, the transmission includes a torque converter clutch which is engageable to establish a mechanical connection between the power source and the input member to bypass the torque converter and effectively establishing a direct one-to-one ratio between the power source and the input member.

A variety of different transmission configurations may employ the torque converter and dual shifting clutch combination. For instance, the first and second shaft may be spaced generally parallel to the input member and to the output member in a typical countershaft design. Alternatively, the first and second shafts may be coaxial. Whether of the countershaft or the coaxial design, the alternate engagement of the first and second shifting clutches may operatively interconnect the first and second shaft with the input member or, alternatively, with the output member. The operative interconnection by the first and second clutches of the first and second shaft with either the input member or the output member may be a direct interconnection or an indirect interconnection, i.e., where the interconnection is through some of the intermeshing gears, which in that instance, may be referred to as transfer gears.

The input member, output member and first and second countershafts may be physically arranged with respect to one another to establish two axes or three or more axis. For instance, the input member and the output member may be aligned with one another, to establish an axis. Alternatively, the first and second shafts, the input member and the output member may be arranged to establish three or more axis. For instance, in a dual input clutch design, the first and second shafts may be arranged as countershafts spaced apart from one another and parallel to the aligned input and output members, thereby establishing three axes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment: Dual Input Clutch, Counter Shaft Design on Three Axes

Referring to the drawings, wherein like reference numbers represent the same or corresponding parts throughout the several views, there is shown inFIG. 1a vehicle10having a powertrain12. The powertrain12includes a power source or engine14, a torque converter16and a transmission15. The torque converter16is connected with the engine14and with the transmission input member18via a turbine22. Selective engagement of a torque converter clutch20allows the engine14to be directly connected with the input shaft18, bypassing the torque converter16. The input member18is typically a shaft, and may be referred to as an input shaft herein. Preferably, the torque converter clutch20is electronically controlled and may be enhanced with a multitude of clutch plates to provide a large clutch torque capacity, thus making the converter clutch20able to transmit a large amount of torque. The torque converter16includes the turbine22, a pump24and a stator26. The converter stator26is grounded to a casing30through a typical one-way clutch that is not shown. A damper28is operatively connected to the engaged torque converter clutch20for absorbing vibration.

An input transfer gear set32includes a first transfer gear34, a second transfer gear36, and third transfer gear38. The third transfer gear38is continuously interconnected with and rotatable with the input shaft18. The first transfer gear34intermeshes with the third transfer gear38. The first transfer gear34is rotatable about a first countershaft40. The first transfer gear34is selectively engageable with the first countershaft40via a first shifting clutch42. Similarly, the second transfer gear36intermeshes with the third transfer gear38. The second transfer gear36is rotatable about a second countershaft44. The second transfer gear36is selectively engageable with the second countershaft44via a second shifting clutch46. Notably, the first and second shifting clutches42,46, respectively, are placed on separate axes (i.e., the first countershaft40and the second countershaft44, respectively, in the embodiment illustrated inFIG. 1). The transmission15establishes three primary axes plus a minor axis I for an idler gear86. The input shaft18and the output shaft84are aligned with one another to establish an axis, as illustrated inFIG. 1. The first and second countershafts40,44are on two separate axes, parallel to the input and output shafts18,84.

Within the scope of the invention, the shifting clutches may be connected to the input shaft and may be engageable with concentric first and second shafts for torque transfer from the engine to the first and second shafts as described below with respect to the embodiments ofFIGS. 3 and 6. However, placing the shifting clutches on the parallel countershafts40,44, may afford placement of the clutches in close proximity to the stationary transmission casing (not shown, but generally surrounding the outer periphery of the transmission15), enabling the use of nonrotating shifting pistons to be employed within the shifting clutches. Other shaft configurations may also be employed with a torque converter and dual shifting clutch combination, such as a “delta configuration” (i.e., a triangular configuration having an input member and an output member disposed at one corner of a triangle formed with respect to first and second countershafts disposed at the other two corners).

Referring again toFIG. 1, the powertrain12further includes a first, second, third, fourth, fifth and sixth intermeshing gear48,50,52,54,56and58, respectively. The first, third and fifth intermeshing gears,48,52and56, respectively, are each rotatable about and selectively engageable with the first countershaft40. Similarly, the second, fourth and sixth intermeshing gears,50,54and58, respectively, are each rotatable about and selectively engageable with the second countershaft44. A seventh/reverse gear60is rotatable about and selectively engageable with the second countershaft44as well.

A first synchronizer62is selectively engageable to interconnect the first intermeshing gear48with the first countershaft40. A second synchronizer64is selectively engageable to interconnect the second intermeshing gear50with the second countershaft44for common rotation therewith. A third synchronizer66is selectively engageable to interconnect the third intermeshing gear52with the first countershaft40for common rotation therewith. A fourth synchronizer68is selectively engageable to interconnect the fourth intermeshing gear54with the second countershaft44for common rotation therewith. A fifth synchronizer70is selectively engageable to interconnect the fifth intermeshing gear56with the first countershaft40for common rotation therewith. A sixth synchronizer72is selectively engageable to interconnect the sixth intermeshing gear58with the second countershaft44for common rotation therewith. A seventh synchronizer74is selectively engageable to interconnect the reverse gear60with the second countershaft44for common rotation therewith.

An eighth intermeshing gear76, a ninth intermeshing gear78, a tenth intermeshing gear80, and an eleventh intermeshing gear82are each continuously connected to and rotatable with an output member84, which in this embodiment is a shaft and may be referred to as an output shaft. The output shaft84is connected with a final drive mechanism85. The eighth intermeshing gear76intermeshes with the first intermeshing gear48and with the second intermeshing gear50. The ninth intermeshing gear78intermeshes with the third intermeshing gear52and with the fourth intermeshing gear54. The tenth intermeshing gear80intermeshes with the fifth intermeshing gear56and with the sixth intermeshing gear58. The idler gear86rotates about an axis I that is generally parallel with the output shaft84and with the second countershaft44. The idler gear86intermeshes with both the reverse gear60and with the eleventh intermeshing gear82.

The transmission15is operable for providing six forward speed ratios as well as a reverse speed ratio. Within the scope of the invention, a dual clutch transmission may provide a different number of forward speed ratios, such as five or seven. For instance, a transmission with seven forward speed ratios would require only one more gear interconnectable with the first countershaft40via one additional synchronizer. The additional gear would intermesh with the eleventh intermeshing gear82. Each of the intermeshing gears is designed with a specific number of teeth to establish desirable torque ratio steps between adjacent torque ratios, as well as to affect the overall speed ratio obtainable with the transmission15. (The torque converter16also has a ratio-boosting effect that contributes to the overall speed ratio).

To establish the reverse speed ratio, the seventh synchronizer74is engaged. Additionally, the second shifting clutch46is engaged. With the engagement of the second shifting clutch46and the seventh synchronizer74, torque is transferred from the input shaft18to the output shaft84in a reverse direction. Torque is transferred from the input shaft18to the second countershaft44via the intermeshing second transfer gear36and third transfer gear38. Torque is transferred from the second countershaft44to the output shaft84via the seventh intermeshing or reverse gear60, idler gear86and eleventh intermeshing gear82. The idler gear86reverses the direction of rotation between the seventh/reverse gear60and the eleventh intermeshing gear82, thereby reversing the direction of rotation between the input shaft18and the output shaft84.

To shift from the reverse speed ratio to the first forward speed ratio, the first synchronizer62is preselected (i.e., engaged) prior to shifting from the second shifting clutch46to the first shifting clutch42. The first shifting clutch42is then engaged as the second shifting clutch46is disengaged. The seventh synchronizer74is then disengaged.

In the first forward speed ratio, torque is transferred from the input shaft18to the first countershaft40via the intermeshing first transfer gear34and third transfer gear38. Torque is transferred from the first countershaft40to the output shaft84via the intermeshing first intermeshing gear48and eighth intermeshing gear76.

To shift from the first forward speed ratio to the second forward speed ratio, the second synchronizer64is preselected during the first forward speed ratio. The first shifting clutch42is then disengaged as the second shifting clutch46is engaged. The first synchronizer62is then disengaged. With the engagement of the second shifting clutch46and the second synchronizer64, torque is transferred from the input shaft18to the second countershaft44via the intermeshing third transfer gear38and second transfer gear36. Torque is transferred from the second countershaft44to the output shaft84via the intermeshing second intermeshing gear50and eighth intermeshing gear76to establish the second forward speed ratio.

Because the second shifting clutch46is not engaged during the first forward speed ratio, preselection of the second synchronizer64does not effect the first forward speed ratio. Preselection of the synchronizer required for the subsequent speed ratio occurs during each previous speed ratio in the transmission15. Such preselection allows dynamic shifting to occur. “Dynamic shifting” means that output torque is present during a clutch shift to an oncoming speed ratio.

To shift from the second speed ratio to the third speed ratio, the third synchronizer66is preselected (i.e., engaged) during the second speed ratio. The second shifting clutch46is then disengaged as the first shifting clutch42is engaged. The second synchronizer64is then disengaged. With the engagement of the first shifting clutch42and the third synchronizer66, torque is transferred from the input shaft18to the first countershaft40via the intermeshing first transfer gear34and third transfer gear38. Torque is transferred from the first countershaft40to the output shaft84via the intermeshing third intermeshing gear52and ninth intermeshing gear78to establish the third forward speed ratio.

To shift from the third forward speed ratio to the fourth forward speed ratio, the fourth synchronizer68is preselected (i.e., engaged) during the third forward speed ratio. The second shifting clutch46is then engaged as the first shifting clutch42is disengaged. The third synchronizer66is then disengaged. With the engagement of the second shifting clutch46and the fourth synchronizer68, torque is transferred from the input shaft18to the second countershaft44via the intermeshing second transfer gear36and third transfer gear38. Torque is transferred from the second countershaft44to the output shaft84via the fourth intermeshing gear54and ninth intermeshing gear78to establish the fourth forward speed ratio.

To shift from the fourth forward speed ratio to the fifth forward speed ration, the fifth synchronizer70is preselected (i.e., engaged) during the fourth forward speed ratio. The second shifting clutch46is disengaged as the first shifting clutch42is engaged. The fourth synchronizer68is then disengaged. With the engagement of the first shifting clutch42, torque is transferred from the input shaft18to the first countershaft40via the intermeshing first transfer gear34and third transfer gear38. The engaged fifth synchronizer70permits torque to be transferred from the first countershaft40to the output shaft84via the fifth intermeshing gear56and tenth intermeshing gear80to establish the fifth forward speed ratio.

To shift from the fifth forward speed to the sixth forward speed ratio, the sixth synchronizer72is preselected (i.e., engaged) during the fifth forward speed ratio. The second shifting clutch46is then engaged as the first shifting clutch42is disengaged. The fifth synchronizer70is then disengaged. With the engagement of the second shifting clutch46and the sixth synchronizer72, torque is transferred from the input shaft18to the second countershaft44via the intermeshing second transfer gear36and third transfer gear38, and from the second countershaft44to the output shaft84via the sixth and tenth intermeshing gears58,80, to establish the sixth forward speed ratio.

The eighth, ninth, tenth and eleventh gears are a first group, each being continuously connected with the output shaft84. The first transfer gear34, and the first, third and fifth intermeshing gears48,52,56, respectively, are a second group, each being selectively interconnectable with the first shaft40. The second transfer gear36, and the second, fourth, sixth and seventh intermeshing gears50,54,58and60are a third group, each being selectively interconnectable with the second shaft44.

Second Embodiment: Dual Input Clutch, Countershaft Design on Three Axes with Torque Converter Clutch External to Torque Converter

Referring toFIG. 2, a vehicle10′ having a powertrain12′, similar to the powertrain train12ofFIG. 1, is illustrated. The powertrain12′ is different from that shown inFIG. 1in that the torque converter clutch20′ is moved outside of the torque converter16′. Otherwise, each of the components of the vehicle10′ operates substantially the same as the correspondingly numbered components of the vehicle ofFIG. 1. As discussed above, such relocation of the torque converter clutch enables spacing flexibility to permit an increased size and or/number of plates in the torque converter clutch and avoids the influence of torque converter pressure on the torque converter clutch.

Third Embodiment: Dual Input Clutch, Coaxial Shaft Design on Two Axes

Referring toFIG. 3, a vehicle110having a powertrain112including a torque converter16and transmission115is illustrated. The engine14and torque converter16are connected with the input shaft18in identical fashion to that ofFIG. 1. Dual input clutches142,146may be alternately selectively engaged to provide torque from the input shaft18to the first and second shafts140,144, respectively. First, third and fifth intermeshing gears148,152,156, respectively, are selectively engageable with the first shaft140via the first, third and fifth synchronizers,162,166,170, respectively. Second, fourth and sixth intermeshing gears,150,154,158, respectively, are rotatable about and selectively engageable with the second countershaft144via second, fourth and sixth synchronizers164,168and172, respectively. Additionally, a seventh or reverse gear160is selectively engageable with the second shaft144via a seventh synchronizer174. Eighth, ninth, tenth, eleventh, twelfth, thirteenth and fourteenth intermeshing gears176,178,180,182,175,177and179, respectively, are continuously connected with an output member184which connects to the final drive mechanism85. In this embodiment, the output member184is a shaft, and may be referred to as an output shaft. Idler gear186is rotatable about an axis I and intermeshes with both the seventh/reverse gear160and the eleventh intermeshing gear182.

The eighth through fourteenth gears175,176,177,178,179,180,182are a first group continuously connected with the output shaft84. The first, third and fifth gears148,152,156are a second group, each being selectively interconnectable with the first shaft140. The second, fourth, sixth and seventh gears150,154,158,160are a third group, each selectively interconnectable with the second shaft144.

The input shaft18and the coaxial first and second countershafts140,144establish a first axis. The output shaft184establishes a second axis spaced form the first axis.

The clutches142,146and synchronizers162,164,166,168,170,172and174are selectively engageable to transfer torque through the intermeshing gears from the input shaft18to the output shaft184and establish multiple speed ratios as will be well understood by those skilled in the art based upon the description of clutch and synchronizer engagements with respect toFIG. 1.

Fourth Embodiment: Dual Output Clutch, Coaxial Shaft Design on Two Axes

Referring toFIG. 4, a vehicle210having a powertrain212including a torque converter16and transmission215is illustrated. The torque converter16is connected between the engine14and the input shaft18in an identical manner as that described with respect toFIG. 1. The transmission215includes a plurality of intermeshing gears some of which are continuously connected with the input shaft18and transfer torque to one of a first shaft240or a coaxial second shaft244depending upon synchronizer engagements. Dual output clutches242,246are alternately selectively engageable with the first and second shaft240,244, respectively to transfer torque to an output member284and to the final drive mechanism85. In this embodiment, the output member284is a shaft and may be referred to as an output shaft.

A first intermeshing gear248intermeshes with a twelfth intermeshing gear275which is selectively engageable with (i.e., interconnectable for rotation with) the first shaft240via a first synchronizer262. A third intermeshing gear252is continuously connected with the input shaft18and intermeshes with a thirteenth intermeshing gear277which is selectively engageable with the first shaft240via a third synchronizer266. A fifth intermeshing gear256is continuously interconnected with the input shaft18and intermeshes with a fourteenth intermeshing gear279which is selectively engageable with the first shaft240via a fifth synchronizer270. A seventh intermeshing gear260is continuously connected with the input shaft18and intermeshes with an idler gear286which rotates about an idler axis I. The idler gear286also intermeshes with an eleventh intermeshing gear282which is selectively engageable with the second shaft244via the seventh synchronizer274. A second intermeshing gear250is continuously connected with the input shaft18and intermeshes with an eighth intermeshing gear276which is selectively engageable with the second shaft244via a second synchronizer264. A fourth intermeshing gear254is continuously connected with the input shaft18and intermeshes with a ninth intermeshing gear278which is selectively engageable with the second shaft244via a fourth synchronizer268. A sixth intermeshing gear258is continuously connected and rotates with an input shaft18. The sixth intermeshing gear258intermeshes with a tenth intermeshing gear280which is selectively engageable with the second shaft244via a sixth synchronizer272.

The first, second, third, fourth, fifth, sixth and seventh gears248,250,252,254,256,258and260, respectively, are a first group continuously connected with the input shaft18. The twelfth, thirteenth and fourteenth gears275,277and279, respectively, are a second group, each being selectively interconnectable with the first shaft240. The eighth, ninth, tenth and eleventh gears276,278,280and282are a third group, each selectively connectable with the second shaft244.

The input shaft18establishes a first axis. The coaxial first and second shafts240,244and the output shaft284establish a second axis.

The output clutches242,246and synchronizers262,264,266,268,270,272and274are selectively engageable to establish six forward speed ratios and a reverse speed ratio in a similar manner as described with respect toFIG. 1, as will be readily understood by those skilled in the art.

Fifth Embodiment: Dual Output Clutch, Counter Shaft Design on Three Axes

Referring toFIG. 5, a vehicle310having a powertrain312is illustrated. The powertrain312includes an engine14, a torque converter16, with a transmission315having an input shaft18and an output member384, and a final drive385. The torque converter16is connected between the engine14and the input shaft18in an identical manner to that described with respect toFIG. 1, above.

An eighth intermeshing gear376, a thirteenth intermeshing gear377, a ninth intermeshing gear378, a tenth intermeshing gear380and a fourteenth intermeshing gear379are continuously connected to and rotate with the input shaft18. First and second counter shafts340,344, respectively, are spaced from the input shaft18and are substantially parallel thereto. A first intermeshing gear348intermeshes with an eighth intermeshing gear376and is selectively engageable with the first shaft340via a first synchronizer362. A third intermeshing gear352intermeshes with the thirteenth intermeshing gear377and is selectively engageable with the first shaft340via a third synchronizer366. A fifth intermeshing gear356intermeshes with the tenth intermeshing gear380and is selectively engageable with the first shaft340via a fifth synchronizer370. An idler gear386rotates about an idler axis I and intermeshes with the eighth intermeshing gear376. A seventh intermeshing gear360also intermeshes with the idler gear386and is selectively engageable with the second shaft344via a seventh synchronizer374. A second intermeshing gear350intermeshes with the thirteenth intermeshing gear377and is selectively engageable with the second shaft344via a second synchronizer364. A fourth intermeshing gear354intermeshes with the ninth intermeshing gear378and is selectively engageable with the second counter shaft344via a fourth synchronizer368. A sixth intermeshing gear358intermeshes with the fourteenth intermeshing gear379and is selectively engageable with the second shaft344via a sixth synchronizer372. First and second clutches342,346, respectively, form dual output clutches and when selectively engaged transfer torque from the first and second shaft340,344, respectively. The first clutch342may be selectively engaged to transfer torque from the first shaft340to a sixteenth intermeshing gear383which intermeshes with a seventeenth intermeshing gear387, which may be referred to as the final drive ring gear. The seventeenth intermeshing gear387may be referred to as a final drive ring gear, and intermeshes with an output differential389to transfer torque to the output member384. The second clutch346is selectively engageable to transfer torque from the second shaft344to a fifteenth intermeshing gear381.

The eighth, ninth, tenth, thirteenth and fourteenth gears376,378,380,377and379, respectively, are a first group, each being continuously connected with the input shaft18for rotation therewith. The first, third and fifth gears348,352and356, respectively, are a second group, each being selectively interconnectable with the first shaft340. The second, fourth, sixth and seventh gears350,354,358and360, respectively, are a third group, each being selectively interconnectable with the second shaft344.

The input shaft18establishes a first axis. The first and second shafts340,344, respectively, establish second and third axes spaced from and parallel to the input shaft18. The output member384is on a fourth axis.

The clutches342and346as well as the synchronizers362,364,366,368,370,372and374are selectively engageable to transfer torque between the input shaft18and the output member384to establish six forward speed ratios and a reverse speed ratio as will be well understood by those skilled in the art based upon the description of clutch and synchronizer engagements ofFIG. 1.

Sixth Embodiment: Dual Input Clutch, Coaxial Shaft Design on Three Axes

Referring toFIG. 6, a vehicle410having a powertrain412is illustrated. The powertrain includes an engine14and a torque converter16connected between the engine14and the input shaft18in an identical manner as that described with respect toFIG. 1. The powertrain further includes a transmission415that has dual input clutches442,446and a plurality of intermeshing gears and synchronizers selectively engageable to transfer torque from the input shaft18to an output member484. First and second clutches442,446are alternately engageable to transfer torque from the input shaft18to first and second shafts440,444, respectively.

A thirteenth intermeshing gear477, a twelfth intermeshing gear475, and a tenth intermeshing gear480are continuously connected to and rotate with the first shaft440. An eighth intermeshing gear476and a ninth intermeshing gear478are continuously connected to and rotate with the second shaft444. A second intermeshing gear450intermeshes with the eighth intermeshing gear476and is selectively engageable with a third shaft443via a second synchronizer464. A fourth intermeshing gear454intermeshes with the ninth intermeshing gear478and is selectively engageable with the third shaft443via a fourth synchronizer468. A third intermeshing gear452intermeshes with the thirteen intermeshing gear477and is selectively engageable with the third shaft443via a third synchronizer466. A first intermeshing gear448intermeshes with the twelfth intermeshing gear475and is selectively engageable with the third shaft443via a first synchronizer462. A sixteenth intermeshing gear483is continuously connected to shaft443and intermeshes with a seventeen intermeshing gear487(a final drive ring gear) which in turn intermeshes with a differential489to transfer torque to the output member484.

A sixth intermeshing gear458intermeshes with the ninth intermeshing gear478and is selectively engageable with the fourth shaft445via a sixth synchronizer472. A fifth intermeshing gear456intermeshes with the tenth intermeshing gear480and is selectively engageable with the fourth shaft445via a fifth synchronizer470. A seventh or reverse gear460rotates about and is selectively engageable with the fourth shaft445via a seventh synchronizer474. The first idler gear486A is continuously connected to a shaft that rotates about axis I and intermeshes with the seventh intermeshing gear460when the second clutch446is engaged. The second idler gear486B intermeshes with the twelfth intermeshing gear475and, although not shown geometrically in the two-dimensional layout ofFIG. 6, is continuously connected to the same shaft that rotates about the axis I as the first idler gear486A and is therefore able to transfer torque between the first shaft440and the fourth shaft445when the first clutch442and the seventh synchronizer474are engaged. A fifteen intermeshing gear481is continuously connected with the fourth shaft445and, although not shown in the two dimensional schematic ofFIG. 6, also intermeshes with the seventeenth intermeshing gear487to transfer torque to the differential489and the output member484, as will be well understood by those skilled in the art. The fifteenth intermeshing gear481, the sixteenth intermeshing gear483, the seventeenth intermeshing gear487and the differential489together establish a final drive485.

The tenth, twelfth and thirteenth gears480,475and477, respectively, are a first group, each being continuously connected with the first shaft440. The first, second, third and fourth gears448,450,452, and454, respectively, are a second group, each being selectively interconnectable with the third shaft443. The fifth, sixth and seventh gears456,458and460, respectively, are a third group, each being selectively interconnectable with the fourth shaft445. The eighth and ninth intermeshing gears476,478are continuously connected to the second shaft444.

The input shaft and coaxial first and second shafts440,444establish a first axis. The third and fourth shafts443,445, respectively, establish second and third axes spaced from and parallel to the input shaft18. The output member484is on a fourth axis.