Dual clutch transmission with continuously variable final drive assembly

A dual clutch transmission includes a pair of concentric clutches which selectively drive a pair of concentric drive shafts, pairs of gears in constant mesh, a first portion of which are associated with the first drive shaft and a first, parallel countershaft and a second portion of which are associated with the second drive shaft and a second, parallel countershaft. Synchronizer clutches disposed adjacent the gears on the countershafts selectively connect the gears to the countershafts. Both countershafts drive a single output shaft through transfer gears. The output shaft is coupled to a drive (input) pulley of a continuously variable final drive assembly which receives a chain which drives a driven (output) pulley which is coupled to and drives the cage of a differential assembly. A pair of axles are driven by the side gears of the differential and, in turn, drive the vehicle wheel.

FIELD

The present disclosure relates to dual clutch transmissions and more particularly to a dual clutch transmission having a continuously variable final drive assembly.

BACKGROUND

For the last several years, dual clutch transmissions have represented a significant alternative to more conventional automatic motor vehicle transmissions which typically comprise several planetary gear sets, clutches and brakes. A defined sequence of engagement and disengagement of the clutches and brakes steps the transmission through the available gear ratios. In contrast to such direct, sequenced operation, a dual clutch transmission includes a pair of main clutches that alternately engage to provide torque through a previously selected gear pair disposed between a shaft driven by the clutch and a countershaft.

One of the drawbacks of dual clutch transmissions, especially when they include six, seven eight or more gear ratios is their axial length. Given certain motor vehicle platforms, axial length is critical and may limit the number of gears provided by a dual clutch transmission. Current market demand is for vehicles with relatively high numbers of gear ratios, i.e., seven, eight and higher and thus a vehicle with only five or six gears, though desirable from every other standpoint, may be viewed by the consumer as having lesser value. A second, though less apparent drawback of such transmissions, is their relatively high spin losses resulting from the large number of gears sets in constant mesh and rotation in spite of the fact that only one gear set at a time is active and transferring torque.

The present invention addresses these problems and provides a dual clutch transmission with reduced length and reduced spin losses.

SUMMARY

The present invention provides a dual clutch transmission having a continuously variable final drive assembly. The dual clutch transmission includes a pair of concentric clutches which selectively drive a pair of concentric drive shafts, pairs of gears in constant mesh, a first portion of which are associated with the first drive shaft and a first, parallel countershaft and a second portion of which are associated with the second drive shaft and a second, parallel countershaft. Synchronizer clutches disposed adjacent the gears on the countershafts selectively synchronize and connect the gears to the countershafts. Both countershafts drive a single output shaft through transfer gears. The output shaft is coupled to a drive (input) pulley of a continuously variable final drive assembly which receives a chain which drives a driven (output) pulley. The output pulley is coupled to and drives the cage of a differential assembly. A pair of output shafts or axles are driven by the side gears of the differential and, in turn, drive the vehicle wheels.

Thus it is an aspect of the present invention to provide a motor vehicle transmission having a continuously variable final drive assembly.

It is a further aspect of the present invention to provide a dual clutch motor vehicle transmission having a continuously variable final drive assembly.

It is a still further aspect of the present invention to provide a dual clutch transmission having concentrically disposed input clutches and a continuously variable final drive assembly.

It is a still further aspect of the present invention to provide a dual clutch transmission having concentrically disposed input clutches and drive shafts and a continuously variable final drive assembly.

It is a still further aspect of the present invention to provide a dual clutch transmission having concentrically disposed input clutches and drive shafts, a pair of parallel countershafts and a continuously variable final drive assembly.

It is a still further aspect of the present invention to provide a dual clutch transmission having concentrically disposed input clutches and drive shafts, a pair of parallel countershafts, pairs of meshing gears disposed between the drive shafts and the countershafts and a continuously variable final drive assembly.

It is a still further aspect of the present invention to provide a dual clutch transmission having concentrically disposed input clutches and drive shafts, a pair of parallel countershafts, pairs of meshing gears disposed between the drive shafts and the countershafts, synchronizer clutches disposed adjacent the gears on the countershafts and a continuously variable final drive assembly.

It is a still further aspect of the present invention to provide a dual clutch transmission having concentrically disposed input clutches and drive shafts, a pair of parallel countershafts, pairs of meshing gears disposed between the drive shafts and the countershafts, synchronizer clutches disposed adjacent the gears on the countershafts and a continuously variable final drive assembly having a pair of adjustable diameter pulleys and a chain encircling both pulleys.

It is a still further aspect of the present invention to provide a dual clutch transmission having concentrically disposed input clutches and drive shafts, a pair of parallel countershafts, pairs of meshing gears disposed between the drive shafts and the countershafts, synchronizer clutches disposed adjacent the gears on the countershafts and a continuously variable final drive assembly including a differential.

DETAILED DESCRIPTION

With reference toFIG. 1, a dual clutch transmission having a continuously variable final drive assembly is illustrated and generally designated by the reference number10. The dual clutch transmission10includes a cast metal housing12which surround, protects and locates the various internal components of the dual clutch transmission10such as the dual clutch assembly20, the transmission assembly100and the continuously variable final drive assembly200.

The dual clutch assembly20includes an input plate or member22which is secured to the output flange of a prime mover such as an internal combustion engine or hybrid power plant (all not illustrated) by suitable threaded fasteners24. The input plate or member22is a component of a damper assembly30having a plurality of circumferentially disposed compression springs32operably disposed between the input plate or member22and a similarly configured output plate or member34which is coupled to and rotationally drives an input member or housing38of the dual clutch assembly20.

First and second clutch drive plates42and44rotate with the clutch housing38. A first driven clutch plate46is splined to and drives a first or inner drive shaft48and a second driven clutch plate52is splined to and drives a second or outer drive shaft or quill54. A ball bearing assembly50is disposed on the outer drive shaft or quill54between the first driven clutch plate46and the second driven clutch plate52. The first driven clutch plate46is engaged to transfer torque to the first or inner drive shaft48by a first hydraulic operator56through a first throw out bearing58and the second driven clutch plate52is engaged to transfer torque to the second or outer drive shaft or quill54by a second hydraulic operator62through a second throw out bearing64. The hydraulic circuit which provides pressurized hydraulic fluid to the hydraulic operators56and62is illustrated inFIG. 2.

Turning now to the transmission assembly100, the second or outer drive shaft or quill54includes a first smaller diameter gear102and an axially spaced apart second, larger diameter gear104. The gears102and104may be integrally formed with the outer drive shaft or quill54or may be fabricated separately and secured thereto by welding, staking, splines, an interference fit or a combination of these approaches. The outer drive shaft or quill54is preferably supported on a ball bearing assembly106. The first or inner drive shaft48includes a third gear108having a diameter intermediate the gears102and104and typically is rotationally secured to the inner drive shaft48by an interengaging spline set112. The inner shaft48may also be supported on a ball bearing assembly114.

The transmission assembly100also includes a first countershaft or layshaft120and a second countershaft or layshaft140. The first countershaft or layshaft120is preferably supported on a pair of tapered roller bearings122. Freely rotatably disposed on the first countershaft or layshaft120is a first, larger diameter gear124that, in cooperation with other gears, provides reverse. Axially spaced from the first, larger diameter gear124is a second, smaller diameter gear126which, in cooperation with another gear, provides third gear. Both the gears124and126are preferably supported on needle bearings128.

Disposed between the first gear124and the second gear126is a dual synchronizer clutch assembly130. A three position actuator or operator132which may be hydraulically or electrically operated, translates the synchronizer clutch assembly130to the left to synchronize and connect the first, larger diameter gear124to the first countershaft or layshaft120to provide reverse, to the right to synchronize and connect the second, smaller diameter gear126to the first countershaft or layshaft120to provide third gear or to a middle or intermediate position in which both gears124and126are disconnected from and free to rotate on the first countershaft or layshaft120. The first counter shaft or layshaft120also includes a first helical output gear134.

The second countershaft or layshaft140is preferably supported on a pair of tapered roller bearings142. Freely rotatably disposed on the first countershaft or layshaft120is a compound gear144having a first smaller diameter gear146that, in cooperation with a reverse idler gear147behind the cutting plane ofFIG. 1, and the first, larger diameter gear124on the first countershaft or layshaft120provides reverse, as noted above. The compound gear144also includes a second, larger diameter gear148which is in constant mesh with the first, smaller diameter gear102on the second or outer drive shaft or quill54and provides first gear. The compound gear144is preferably supported on needle bearing assemblies149. The compound gear144may be a unitary component or the smaller diameter gear146and the larger diameter gear148may be fabricated separately and assembled by welding, staking, splines, an interference fit or a combination of these approaches. Immediately adjacent the compound gear144is a first, single synchronizer clutch assembly150. A two position actuator or operator152which may be hydraulically or electrically operated, translates the synchronizer clutch assembly130to the left to synchronize and connect the compound gear144to the second countershaft or layshaft140to provide first gear or to the right to disconnect the compound gear144from the second countershaft or layshaft140so that it is free to rotate thereon.

Axially spaced from the compound gear144is a second, smaller diameter gear156which, is in constant mesh with the third gear108on the first or inner drive shaft48and provides second gear. The gear156is preferably supported on needle bearing assemblies158. Immediately adjacent the second, smaller diameter gear156is a second, single synchronizer clutch assembly160. A two position actuator or operator162which may be hydraulically or electrically operated, translates the synchronizer clutch assembly160to the left to synchronize and connect the second, smaller diameter gear156to the second countershaft or layshaft140to provide second gear or to the right to disconnect the second, smaller diameter gear156from the second countershaft or layshaft140so that it is free to rotate thereon. The second counter shaft or layshaft140also includes a second helical output gear164.

It will be appreciated that, according to conventional dual clutch transmission operation, when one of the four gears124,126,148and156(three forward and one reverse) is synchronized and connected to their associated countershaft or layshaft120or140, the clutch of the dual clutch assembly20driving the drive shaft48or54associated with the respective drive gear102,104and108of the above-recited four gears is engaged.

Finally, turning to the continuously variable final drive assembly200, an input shaft or quill202includes a helical gear204which is in constant mesh with and driven by the first helical output gear134of the first counter shaft120and the second helical output gear164of the second countershaft140. The input shaft or quill202is coupled to and drives a variable diameter input pulley assembly206of the continuously variable final drive assembly200. The input pulley assembly206includes a pair of symmetrically opposed drive pulley faces or segments212which are translated toward one another by a first hydraulic actuator214. Partially encircling the pair of drive pulley segments212is a multi-link drive chain216which is shown on phantom in multiple positions. The multilink drive chain216also partially encircles a variable diameter output pulley assembly218which includes a pair of symmetrically opposed driven pulley faces or segments222which are translated toward one another by a second hydraulic actuator224. Both of the hydraulic actuators214and224are, like the multi-link chain216, shown in multiple positions. The circuit supplying hydraulic fluid to the actuators214and224is illustrated inFIG. 2

It will be appreciated that, first of all, the spacing of the drive pulley segments212and the driven pulley segments222occurs oppositely, that is, when the drive pulley segments212are close together and thus exhibit their largest effective diameter, the driven pulley segments222are far apart and exhibit their smallest effective diameter and vice versa and, second of all, pressurized hydraulic fluid is provided to the hydraulic actuators214and224to drive the pulley segments212and222together to create their largest effective diameters whereas hydraulic fluid is simply exhausted from the hydraulic actuators214and224to allow the pulley segments212and222to separate and achieve their smallest effective diameters.

The driven pulley segments222are coupled to and drive a differential assembly230having a cage232which may be integrally formed with one of the pulley segments222and which supports, in conventional fashion, a pair of center gears234on a stub shaft236and a pair of side gears238which are in constant mesh with the center gears234. The side gears238include female splines242which receive and engage complementary male splines244on a pair of half shafts or axles246which preferably extend to and drive the vehicle wheels (not illustrated).

Referring now toFIG. 2, a hydraulic circuit300for the dual clutch transmission10according to the present invention is illustrated. The hydraulic circuit300includes a hydraulic pump302which draws hydraulic fluid (transmission oil) from a transmission sump304through a filter306. Pressurized hydraulic fluid from the pump302is supplied in a line308to a pair of proportioning control valves, a first control valve314associated with the actuator214of the input pulley assembly206and a second control valve316associated with the actuator224of the output pulley assembly218.

The control valves314and316may be any type of proportioning valves such as, for example, spool valves, capable of providing a modulating or proportioning supply of hydraulic fluid to the actuators214and224to increase the effective diameters of the pulleys segments212and222, maintaining the pressure of such supplied fluid to maintain a position of the actuators214and224and the pulley segments212and222and to control release of hydraulic fluid from the actuators214and224to reduce the effective diameters of the pulley segments212and222. Thus, they may be hydraulically or electrically controlled. Of course, and as noted above, the actions of increasing or decreasing the effective diameters of the pulley segments212and222occur in opposition, that is, as the effective diameter of one pulley and its segments increases, the effective diameter of the other pulley and its segments decreases to provide an essentially constant length path for the multi-link chain216.

Preferably, the circuit300also includes a pressure relief valve318which may return fluid to the sump304under certain operating conditions. Preferably as well, pressurized hydraulic fluid may be supplied to multiple valves322controlled by a control module such as a transmission control module (TCM)330which selectively supply pressurized hydraulic fluid to the first and second hydraulic clutch operators56and62and either hydraulic fluid or electrical signals to the actuators or operators132,152and162of the synchronizer clutch assemblies130,150and160as well as a respective pair of operators332and334of the control valves314and316.

The dual clutch transmission10of the present design provides excellent ratio flexibility due to the use of both fixed ratio gear sets and the variable ratio final drive. The elimination of several gear pairs from the dual clutch portion of the transmission results in a transmission having shorter length and thus reduced mass and concomitant cost savings. The shorter length provides increased application options, especially in compact vehicle platforms. Finally, elimination of several gear pairs also results in lower spin losses relative to a dual clutch transmission with a full complement of gears and gear ratios.

It should be appreciated, however, that although the transmission assembly100of the present invention is illustrated and described as having three forward gears, this configuration is exemplary only. Due to the wide ratio range available from the continuously variable final drive assembly200, which need not necessarily be entirely utilized, a transmission assembly100having but two forward gears or four five or six, for example, would be practical and appropriate with certain prime movers and in certain applications.