SAMIE FARZAD (US)
DUAN CHENGWU (CN)
| WO2012091469A2 | 2012-07-05 |
| CN201705873U | 2011-01-12 | |||
| CN201100387Y | 2008-08-13 | |||
| CN1408057A | 2003-04-02 | |||
| US20010024987A1 | 2001-09-27 | |||
| EP1188956A2 | 2002-03-20 |
| CLAIMS 1. A continuously variable transmission comprising: an input shaft extending along an input axis; an input pulley attached to the input shaft and rotatable with the input shaft about the input axis, wherein the input pulley defines an annular input groove; an output shaft extending along an output axis; an output pulley attached to the output shaft and rotatable with the output shaft about the output axis, wherein the output pulley defines an annular output groove; an endless rotatable device looped around the input shaft and the output shaft, disposed within the annular input groove and the annular output groove, and operable to transmit a torque from the input pulley to the output pulley; wherein the endless rotatable device is movable radially relative to the input axis and the output axis respectively, within the annular input groove and the annular output groove respectively, to change a torque ratio between the input shaft and the output shaft; wherein at least one of the annular input groove and the annular output groove defines a cross sectional shape having a variable rate of radial change along the input axis and the output axis respectively, to adjust a force required to move the endless rotatable device radially relative to the input shaft and the output shaft respectively. 2. The continuously variable transmission as set forth in claim 1 wherein: the input pulley includes a movable input sheave axially movable along the input axis relative to the input shaft, and a stationary input sheave disposed opposite the movable input sheave and axially fixed along the input axis relative to the input shaft; the movable input sheave and the stationary input sheave each include an input groove surface disposed opposite each other to define the annular input groove therebetween disposed perpendicular to the input axis; and the input groove surfaces of the movable input sheave and the stationary input sheave each define a cross sectional shape having a variable rate of radial change along the input axis to define the cross sectional shape of the annular input groove. 3. The continuously variable transmission as set forth in claim 2 wherein the cross sectional shape of the input groove surfaces of the movable input sheave and the stationary input sheave includes two linear segments defining an angle therebetween less than one hundred eighty degrees (180°). 4. The continuously variable transmission as set forth in claim 2 wherein the cross sectional shape of the input groove surfaces of the movable input sheave and the stationary input sheave includes at least one of a concave region and a convex region. 5. The continuously variable transmission as set forth in claim 1 wherein: the output pulley includes a movable output sheave axially movable along the output axis relative to the output shaft, and a stationary output sheave disposed opposite the movable output sheave and axially fixed along the output axis relative to the output shaft; the movable output sheave and the stationary output sheave each include an output groove surface disposed opposite each other to define the annular output groove therebetween disposed perpendicular to the output axis; and the output groove surfaces of the movable output sheave and the stationary output sheave each define a cross sectional shape having a variable rate of radial change along the output axis to define the cross sectional shape of the annular output groove. 6. The continuously variable transmission as set forth in claim 5 wherein the cross sectional shape of the output groove surfaces of the movable output sheave and the stationary output sheave includes two linear segments defining an angle therebetween less than one hundred eighty degrees (180°). 7. The continuously variable transmission as set forth in claim 5 wherein the cross sectional shape of the output groove surfaces of the movable output sheave and the stationary output sheave includes at least one of a concave region and a convex region. 8. The continuously variable transmission as set forth in claim 1 wherein both of the annular input groove and the annular output groove define a cross sectional shape having a variable rate of radial change along the input axis and the output axis respectively, to adjust a force required to move the endless rotatable device radially relative to the input shaft and the output shaft respectively. 9. The continuously variable transmission as set forth in claim 8 wherein the variable rate of radial change of the annular input groove and the annular output groove respectively is operable to decrease a force required to change the torque ratio in at least a first region of the annular input groove and the annular output groove respectively, relative to a constant force value, and is operable to increase the force required to change the torque ratio in at least a second region of the annular input groove and the annular output groove respectively, relative to the constant force value. 10. The continuously variable transmission as set forth in claim 1 characterized by the absence of a tensioning device for tensioning and removing slack in the endless rotatable device. 11. The continuously variable transmission as set forth in claim 1 wherein: the input pulley includes a plurality of sliding teeth assemblies disposed radially about the input axis, and radially movable relative to the input axis in response to axial movement of the movable input sheave relative to the stationary input sheave to define a variable diameter of the input pulley; the output pulley includes a plurality of sliding teeth assemblies disposed radially about the output axis, and radially movable relative to the output axis in response to axial movement of the movable output sheave relative to the stationary output sheave to define a variable diameter of the output pulley; and the endless rotatable device is looped around the sliding teeth assemblies of the input pulley and the sliding teeth assemblies of the output pulley; 12. The continuously variable transmission as set forth in claim 11 wherein the endless rotatable device includes a plurality of fixed teeth disposed on a radially inner surface thereof, and extending radially inward into meshing engagement with the sliding teeth assemblies of the input pulley and the sliding teeth assemblies of the output pulley. 13. The continuously variable transmission as set forth in claim 12 wherein each of the sliding teeth assemblies of the input pulley and the output pulley includes a holder slideably attached to both the movable input sheave and the stationary input sheave, and the movable output sheave and the stationary output sheave, respectively, and wherein each holder is slideably movable in a radial direction relative to the input axis and the output axis respectively. 14. The continuously variable transmission as set forth in claim 13 wherein the holder of each of the sliding teeth assemblies of the input pulley moves radially inward toward the input axis in response to movement of the movable input sheave away from the stationary input sheave along the input axis, and moves radially outward away from the input axis in response to movement of the movable input sheave inward toward the stationary input sheave along the input axis, and wherein the holder of each of the sliding teeth assemblies of the output pulley moves radially inward toward the output axis in response to movement of the movable output sheave away from the stationary output sheave along the output axis, and moves radially outward away from the output axis in response to movement of the movable output sheave inward toward the stationary output sheave along the output axis. 15. The continuously variable transmission as set forth in claim 14 wherein each of the sliding teeth assemblies of the input pulley and the output pulley includes a plurality of teeth slideably supported by their respective holder, and movable radially outward relative to the input axis and the output axis respectively, into meshing engagement with the fixed teeth of the endless rotatable device in response to a centrifugal force. 16. A continuously variable transmission comprising: an input shaft extending along an input axis; an input pulley attached to the input shaft and rotatable with the input shaft about the input axis, wherein the input pulley defines an annular input groove; wherein the input pulley includes a movable input sheave axially movable along the input axis relative to the input shaft, and a stationary input sheave disposed opposite the movable input sheave and axially fixed along the input axis relative to the input shaft; wherein the input pulley includes a plurality of sliding teeth assemblies disposed radially about the input axis, and radially movable relative to the input axis in response to axial movement of the movable input sheave relative to the stationary input sheave to define a variable diameter of the input pulley; an output shaft extending along an output axis; an output pulley attached to the output shaft and rotatable with the output shaft about the output axis, wherein the output pulley defines an annular output groove; wherein the output pulley includes a plurality of sliding teeth assemblies disposed radially about the output axis, and radially movable relative to the output axis in response to axial movement of the movable output sheave relative to the stationary output sheave to define a variable diameter of the output pulley; wherein the output pulley includes a movable output sheave axially movable along the output axis relative to the output shaft, and a stationary output sheave disposed opposite the movable output sheave and axially fixed along the output axis relative to the output shaft; the endless rotatable device is looped around the sliding teeth assemblies of the input pulley and the sliding teeth assemblies of the output pulley; an endless rotatable device looped around the input shaft and the sliding teeth assemblies of the input pulley, looped around the output shaft and the sliding teeth assemblies of the output pulley, disposed within the annular input groove and the annular output groove, and operable to transmit a torque from the input pulley to the output pulley; wherein the endless rotatable device includes a plurality of fixed teeth disposed on a radially inner surface thereof, and extending radially inward into meshing engagement with the sliding teeth assemblies of the input pulley and the sliding teeth assemblies of the output pulley; wherein the endless rotatable device is movable radially relative to the input axis and the output axis respectively, within the annular input groove and the annular output groove respectively, to change a torque ratio between the input shaft and the output shaft; and wherein the annular input groove and the annular output groove each define a cross sectional shape having a variable rate of radial change along the input axis and the output axis respectively, to adjust a force required to move the endless rotatable device radially relative to the input shaft and the output shaft respectively. 17. The continuously variable transmission as set forth in claim 16 wherein: the movable input sheave and the stationary input sheave each include an input groove surface disposed opposite each other to define the annular input groove therebetween disposed perpendicular to the input axis; the input groove surfaces of the movable input sheave and the stationary input sheave each define a cross sectional shape having a variable rate of radial change along the input axis to define the cross sectional shape of the annular input groove; the movable output sheave and the stationary output sheave each include an output groove surface disposed opposite each other to define the annular output groove therebetween disposed perpendicular to the output axis; and the output groove surfaces of the movable output sheave and the stationary output sheave each define a cross sectional shape having a variable rate of radial change along the output axis to define the cross sectional shape of the annular output groove. 18. The continuously variable transmission as set forth in claim 17 wherein: the cross sectional shape of the input groove surfaces of the movable input sheave and the stationary input sheave includes two adjacent linear segments defining an angle therebetween less than one hundred eighty degrees (180°); and the cross sectional shape of the output groove surfaces of the movable output sheave and the stationary output sheave includes two adjacent linear segments defining an angle therebetween less than one hundred eighty degrees (180°) 19. The continuously variable transmission as set forth in claim 17 wherein: the cross sectional shape of the input groove surfaces of the movable input sheave and the stationary input sheave includes at least one of a concave region and a convex region; and wherein the cross sectional shape of the output groove surfaces of the movable output sheave and the stationary output sheave includes at least one of a concave region and a convex region. 20. The continuously variable transmission as set forth in claim 17 wherein: the input groove surface of the movable input sheave and the output groove surface of the stationary output sheave are identical; the input groove surface of the stationary input sheave and the output groove surface of the movable output sheave are identical; the input groove surface of the movable input sheave and the input groove surface of the stationary input sheave are mirror images of each other; and the output groove surface of the movable output sheave and the output groove surface of the stationary output sheave are mirror images of each other. |
| AMENDED CLAIMS received by the International Bureau on 30 September 2014 (30.09.2014) 1. A continuously variable transmission comprising: an input shaft extending along an input axis; an input pulley attached to the input shaft and rotatable with the input shaft about the input axis, wherein the input pulley defines an annular input groove; an output shaft extending along an output axis; an output pulley attached to the output shaft and rotatable with the output shaft about the output axis, wherein the output pulley defines an annular output groove; an endless rotatable device looped around the input shaft and the output shaft, disposed within the annular input groove and the annular output groove, and operable to transmit a torque from the input pulley to the output pulley; wherein the endless rotatable device is movable radially relative to the input axis and the output axis respectively, within the annular input groove and the annular output groove respectively, to change a torque ratio between the input shaft and the output shaft; wherein at least one of the annular input groove and the annular output groove defines a cross sectional shape that is disposed perpendicular to the input axis and the output axis, and includes a variable rate of radial change with axial movement along the input axis and the output axis respectively, to adjust a force required to move the endless rotatable device radially relative to the input shaft and the output shaft respectively. 2. The continuously variable transmission as set forth in claim 1 wherein: the input pulley includes a movable input sheave axially movable along the input axis relative to the input shaft, and a stationary input sheave disposed opposite the movable input sheave and axially fixed along the input axis relative to the input shaft; the movable input sheave and the stationary input sheave each include an input groove surface disposed opposite each other to define the annular input groove therebetween disposed perpendicular to the input axis; and AMENDED SHEET (ARTICLE 19) the input groove surfaces of the movable input sheave and the stationary input sheave each define a cross sectional shape having a variable rate of radial change along the input axis to define the cross sectional shape of the annular input groove. 3. The continuously variable transmission as set forth in claim 2 wherein the cross sectional shape of the input groove surfaces of the movable input sheave and the stationary input sheave includes two linear segments defining an angle therebetween less than one hundred eighty degrees (180°). 4. The continuously variable transmission as set forth in claim 2 wherein the cross sectional shape of the input groove surfaces of the movable input sheave and the stationary input sheave includes at least one of a concave region and a convex region. 5. The continuously variable transmission as set forth in claim 1 wherein: the output pulley includes a movable output sheave axially movable along the output axis relative to the output shaft, and a stationary output sheave disposed opposite the movable output sheave and axially fixed along the output axis relative to the output shaft; the movable output sheave and the stationary output sheave each include an output groove surface disposed opposite each other to define the annular output groove therebetween disposed perpendicular to the output axis; and the output groove surfaces of the movable output sheave and the stationary output sheave each define a cross sectional shape having a variable rate of radial change along the output axis to define the cross sectional shape of the annular output groove. 6. The continuously variable transmission as set forth in claim 5 wherein the cross sectional shape of the output groove surfaces of the movable output sheave and the stationary output sheave includes two linear segments defining an angle therebetween less than one hundred eighty degrees (180°). AMENDED SHEET (ARTICLE 19) 7. The continuously variable transmission as set forth in claim 5 wherein the cross sectional shape of the output groove surfaces of the movable output sheave and the stationary output sheave includes at least one of a concave region and a convex region. 8. The continuously variable transmission as set forth in claim 1 wherein both of the annular input groove and the annular output groove define a cross sectional shape having a variable rate of radial change along the input axis and the output axis respectively, to adjust a force required to move the endless rotatable device radially relative to the input shaft and the output shaft respectively. 9. The continuously variable transmission as set forth in claim 8 wherein the variable rate of radial change of the annular input groove and the annular output groove respectively is operable to decrease a force required to change the torque ratio in at least a first region of the annular input groove and the annular output groove respectively, relative to a constant force value, and is operable to increase the force required to change the torque ratio in at least a second region of the annular input groove and the annular output groove respectively, relative to the constant force value. 10. The continuously variable transmission as set forth in claim 1 characterized by the absence of a tensioning device for tensioning and removing slack in the endless rotatable device. 11. The continuously variable transmission as set forth in claim 1 wherein: the input pulley includes a plurality of sliding teeth assemblies disposed radially about the input axis, and radially movable relative to the input axis in response to axial movement of the movable input sheave relative to the stationary input sheave to define a variable diameter of the input pulley; AMENDED SHEET (ARTICLE 19) the output pulley includes a plurality of sliding teeth assemblies disposed radially about the output axis, and radially movable relative to the output axis in response to axial movement of the movable output sheave relative to the stationary output sheave to define a variable diameter of the output pulley; and the endless rotatable device is looped around the sliding teeth assemblies of the input pulley and the sliding teeth assemblies of the output pulley. 12. The continuously variable transmission as set forth in claim 11 wherein the endless rotatable device includes a plurality of fixed teeth disposed on a radially inner surface thereof, and extending radially inward into meshing engagement with the sliding teeth assemblies of the input pulley and the sliding teeth assemblies of the output pulley. 13. The continuously variable transmission as set forth in claim 12 wherein each of the sliding teeth assemblies of the input pulley and the output pulley includes a holder slideably attached to both the movable input sheave and the stationary input sheave, and the movable output sheave and the stationary output sheave, respectively, and wherein each holder is slideably movable in a radial direction relative to the input axis and the output axis respectively. 14. The continuously variable transmission as set forth in claim 13 wherein the holder of each of the sliding teeth assemblies of the input pulley moves radially inward toward the input axis in response to movement of the movable input sheave away from the stationary input sheave along the input axis, and moves radially outward away from the input axis in response to movement of the movable input sheave inward toward the stationary input sheave along the input axis, and wherein the holder of each of the sliding teeth assemblies of the output pulley moves radially inward toward the output axis in response to movement of the movable output sheave away from the stationary output sheave along the output axis, and moves radially outward away from the output axis in response to movement of the movable output sheave inward toward the stationary output sheave along the output axis. AMENDED SHEET (ARTICLE 19) 15. The continuously variable transmission as set forth in claim 14 wherein each of the sliding teeth assemblies of the input pulley and the output pulley includes a plurality of teeth slideably supported by their respective holder, and movable radially outward relative to the input axis and the output axis respectively, into meshing engagement with the fixed teeth of the endless rotatable device in response to a centrifugal force. 16. A continuously variable transmission comprising: an input shaft extending along an input axis; an input pulley attached to the input shaft and rotatable with the input shaft about the input axis, wherein the input pulley defines an annular input groove; wherein the input pulley includes a movable input sheave axially movable along the input axis relative to the input shaft, and a stationary input sheave disposed opposite the movable input sheave and axially fixed along the input axis relative to the input shaft; wherein the input pulley includes a plurality of sliding teeth assemblies disposed radially about the input axis, and radially movable relative to the input axis in response to axial movement of the movable input sheave relative to the stationary input sheave to define a variable diameter of the input pulley; an output shaft extending along an output axis; an output pulley attached to the output shaft and rotatable with the output shaft about the output axis, wherein the output pulley defines an annular output groove; wherein the output pulley includes a plurality of sliding teeth assemblies disposed radially about the output axis, and radially movable relative to the output axis in response to axial movement of the movable output sheave relative to the stationary output sheave to define a variable diameter of the output pulley; wherein the output pulley includes a movable output sheave axially movable along the output axis relative to the output shaft, and a stationary output sheave disposed opposite the movable output sheave and axially fixed along the output axis relative to the output shaft; AMENDED SHEET (ARTICLE 19) the endless rotatable device is looped around the sliding teeth assemblies of the input pulley and the sliding teeth assemblies of the output pulley; an endless rotatable device looped around the input shaft and the sliding teeth assemblies of the input pulley, looped around the output shaft and the sliding teeth assemblies of the output pulley, disposed within the annular input groove and the annular output groove, and operable to transmit a torque from the input pulley to the output pulley; wherein the endless rotatable device includes a plurality of fixed teeth disposed on a radially inner surface thereof, and extending radially inward into meshing engagement with the sliding teeth assemblies of the input pulley and the sliding teeth assemblies of the output pulley; wherein the endless rotatable device is movable radially relative to the input axis and the output axis respectively, within the annular input groove and the annular output groove respectively, to change a torque ratio between the input shaft and the output shaft; and wherein the annular input groove and the annular output groove each define a cross sectional shape that is disposed perpendicular to the input axis and the output axis, and includes a variable rate of radial change with axial movement along the input axis and the output axis respectively, to adjust a force required to move the endless rotatable device radially relative to the input shaft and the output shaft respectively. 17. The continuously variable transmission as set forth in claim 16 wherein: the movable input sheave and the stationary input sheave each include an input groove surface disposed opposite each other to define the annular input groove therebetween disposed perpendicular to the input axis; the input groove surfaces of the movable input sheave and the stationary input sheave each define a cross sectional shape having a variable rate of radial change along the input axis to define the cross sectional shape of the annular input groove; AMENDED SHEET (ARTICLE 19) the movable output sheave and the stationary output sheave each include an output groove surface disposed opposite each other to define the annular output groove therebetween disposed perpendicular to the output axis; and the output groove surfaces of the movable output sheave and the stationary output sheave each define a cross sectional shape having a variable rate of radial change along the output axis to define the cross sectional shape of the annular output groove. 18. The continuously variable transmission as set forth in claim 17 wherein: the cross sectional shape of the input groove surfaces of the movable input sheave and the stationary input sheave includes two adjacent linear segments defining an angle therebetween less than one hundred eighty degrees (180°); and the cross sectional shape of the output groove surfaces of the movable output sheave and the stationary output sheave includes two adjacent linear segments defining an angle therebetween less than one hundred eighty degrees (180°). 19. The continuously variable transmission as set forth in claim 17 wherein: the cross sectional shape of the input groove surfaces of the movable input sheave and the stationary input sheave includes at least one of a concave region and a convex region; and wherein the cross sectional shape of the output groove surfaces of the movable output sheave and the stationary output sheave includes at least one of a concave region and a convex region. 20. The continuously variable transmission as set forth in claim 17 wherein: the input groove surface of the movable input sheave and the output groove surface of the stationary output sheave are identical; the input groove surface of the stationary input sheave and the output groove surface of the movable output sheave are identical; AMENDED SHEET (ARTICLE 19) the input groove surface of the movable input sheave and the input groove surface of the stationary input sheave are mirror images of each other; and the output groove surface of the movable output sheave and the output groove surface of the stationary output sheave are mirror images of each other. AMENDED SHEET (ARTICLE 19) |
CHANGE PULLEY SHEAVES
TECHNICAL FIELD
[0001] The invention generally relates to a continuously variable transmission, and more specifically to a non-traction based continuously variable transmission having pulleys with sliding teeth assemblies for positively engaging an endless rotatable device, such as a chain or belt. BACKGROUND
[0002] In general, a continuously variable transmission is a transmission that can change steplessly through an infinite number of effective gear ratios between a maximum gear ratio and a minimum gear ratio. A typical continuously variable transmission includes two pulleys, each having two sheaves. A belt typically runs between the two pulleys, with the two sheaves of each of the pulleys sandwiching the belt therebetween. Frictional engagement between the sheaves of each pulley and the belt couples the belt to each of the pulleys to transfer a torque from one pulley to the other. One of the pulleys may function as a drive pulley so that the other pulley can be driven by the drive pulley via the belt. The gear ratio is the ratio of the torque of the driven pulley to the torque of the drive pulley. The gear ratio may be changed by moving the two sheaves of one of the pulleys closer together and the two sheaves of the other pulley farther apart, causing the belt to ride higher or lower on the respective pulley.
SUMMARY
[0003] A continuously variable transmission is provided. The continuously variable transmission includes an input shaft and an output shaft. The input shaft extends along an input axis. The output shaft extends along an output axis. An input pulley is attached to the input shaft, and defines an annular input groove. The input pulley is rotatable with the input shaft about the input axis. An output pulley is attached to the output shaft, and defines an annular output groove. The output pulley is rotatable with the output shaft about the output axis. An endless rotatable device is looped around the input shaft and the output shaft, and is disposed within the annular input groove and the annular output groove. The endless rotatable device is operable to transmit a torque from the input pulley to the output pulley. The endless rotatable device is movable radially relative to the input axis and the output axis respectively, within the annular input groove and the annular output groove respectively. The endless rotatable device is radially movable to change a torque ratio between the input shaft and the output shaft. At least one of the annular input groove and the annular output groove defines a cross sectional shape having a variable rate of radial change along the input axis and the output axis respectively. The variable rate of radial change adjusts a force required to move the endless rotatable device radially relative to the input shaft and the output shaft respectively.
[0004] A higher rate of radial change of the input groove/output groove provides faster, more responsive changes in the gear ratio, but requires a higher force to move the movable input sheave and the movable output sheave along the input axis and the output axis respectively. In contrast, a lower rate of radial change of the input groove/output groove provides slower changes in the gear ratio, but requires a lower force to move the movable input sheave and the movable output sheave along the input axis and the output axis respectively. Accordingly, the variable rate of radial change of either the input groove and/or the output groove allows the continuously variable transmission to be designed to satisfy a specific resistance load and/or performance requirement. For example, the input groove and/or the output groove may be configured to have one or more regions having a higher rate of radial change to provide quicker changes in the effective gear ratio, and may also include one or more regions having a lower rate of radial change to reduce the force required to move the movable input sheave and the movable output sheave.
[0005] The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS [0006] Figure 1 is a schematic perspective view of a continuously variable transmission.
[0007] Figure 2 is a schematic cross sectional view of the continuously variable transmission along a horizontal plane bisecting and parallel with both an input axis and an output axis of the continuously variable transmission.
[0008] Figure 3 is a schematic cross sectional view of the continuously variable transmission perpendicular to both the input axis and the output axis.
[0009] Figure 4 is an enlarged schematic cross sectional view of a sliding teeth assembly of the continuously variable transmission.
[0010] Figure 5 is a schematic cross sectional view of a pulley of the continuously variable transmission showing a first alternative cross sectional shape of a groove of the pulley.
[0011] Figure 6 is a schematic cross sectional view of a pulley of the continuously variable transmission showing a second alternative cross sectional shape of a groove of the pulley.
[0012] Figure 7 is a schematic cross sectional view of a pulley of the continuously variable transmission showing a third alternative cross sectional shape of a groove of the pulley. DETAILED DESCRIPTION
[0013] Those having ordinary skill in the art will recognize that terms such as
"above," "below," "upward," "downward," "top," "bottom," etc., are used descriptively for the figures, and do not represent limitations on the scope of the invention, as defined by the appended claims. Furthermore, the invention may be described herein in terms of functional and/or logical block components and/or various processing steps. It should be realized that such block components may be realized by any number of hardware, software, and/or firmware components configured to perform the specified functions.
[0014] Referring to the Figures, wherein like numerals indicate like parts throughout the several views, a continuously variable transmission is generally shown at 20. The continuously variable transmission 20 can change steplessly through an infinite number of effective gear ratios, between a maximum gear ratio and a minimum gear ratio. The continuously variable transmission 20 transfers power from a power source (not shown), such as but not limited to an internal combustion engine, to an output device, such as but not limited to a drive wheel of a vehicle. The continuously variable transmission 20 uses the effective gear ratio to convert the rotational output speed of the power source into a desired torque for the output device.
[0015] Referring to Figures 1 through 3, the continuously variable transmission
20 includes an input shaft 22 and an output shaft 24. The input shaft 22 may be referred to as a drive shaft, and is configured for attachment to the power source to receive a torque therefrom. For example, the input shaft 22 may be coupled to a crankshaft of an engine for rotation therewith. Accordingly, the input shaft 22 receives a rotational input. The input shaft 22 extends along and rotates about an input axis 26. An input pulley 28 is attached to the input shaft 22. The input pulley 28 may alternatively be referred to as a drive pulley. The input pulley 28 is rotatable with the input shaft 22 about the input axis 26. The input pulley 28 is split perpendicular to the input axis 26 to define an annular input groove 30 therebetween. The annular input groove 30 is disposed perpendicular to the input axis 26.
[0016] The input pulley 28 includes a movable input sheave 32, and a stationary input sheave 34. The movable input sheave 32 is axially movable along the input axis 26 relative to the input shaft 22. For example, the movable input sheave 32 may be attached to the input shaft 22 via a splined connection, thereby allowing axial movement of the movable input sheave 32 along the input axis 26. The stationary input sheave 34 is disposed opposite the movable input sheave 32. The stationary input sheave 34 is axially fixed along the input axis 26 relative to the input shaft 22. As such, the stationary input sheave 34 does not move in the axial direction of the input axis 26 along the input shaft 22. The movable input sheave 32 and the stationary input sheave 34 each include an input groove surface 36. The input groove surface 36 of each of the movable input sheave 32 and the stationary input sheave 34 are disposed opposite each other to define the annular input groove 30 therebetween.
[0017] The output shaft 24 may be referred to as a driven shaft, and is configured for attachment to the output device to provide torque thereto. For example, the output shaft 24 may be coupled to a vehicle driveshaft or axle to rotate a drive wheel. The output shaft 24 extends along and rotates about an output axis 38. The input axis 26 and the output axis 38 are parallel with each other and spaced from each other a fixed distance 40. An output pulley 42 is attached to the output shaft 24. The output pulley 42 may alternatively be referred to as a driven pulley. The output pulley 42 is rotatable with the output shaft 24 about the output axis 38. The output pulley 42 is split perpendicular to the output axis 38 to define an annular output groove 44 therebetween. The annular output groove 44 is disposed perpendicular to the output axis 38.
[0018] The output pulley 42 includes a movable output sheave 46, and a stationary output sheave 48. The movable output sheave 46 is axially movable along the output axis 38 relative to the output shaft 24. For example, the movable output sheave 46 may be attached to the output shaft 24 via a splined connection, thereby allowing axial movement of the movable output sheave 46 along the output axis 38. The stationary output sheave 48 is disposed opposite the movable output sheave 46. The stationary output sheave 48 is axially fixed along the output axis 38 relative to the output shaft 24. As such, the stationary output sheave 48 does not move in the axial direction of the output axis 38 along the output shaft 24. The movable output sheave 46 and the stationary output sheave 48 each include an output groove surface 50. The output groove surface 50 of each of the movable output sheave 46 and the stationary output sheave 48 are disposed opposite each other to define the annular output groove 44 therebetween.
[0019] Each of the input pulley 28 and the output pulley 42 include a plurality of sliding teeth assemblies 52 arranged annularly around the input axis 26 and the output axis 38 respectively. The sliding teeth assemblies 52 of the input pulley 28 are coupled to the stationary input sheave 34 and the movable input sheave 32, and move radially inward and outward within the annular input groove 30 of the input pulley 28. The outer radial circumference of the sliding teeth assemblies 52 of the input pulley 28 defines an effective pulley diameter of the input pulley 28. The sliding teeth assemblies 52 of the output pulley 42 are coupled to the stationary output sheave 48 and the movable output sheave 46, and move radially inward and outward within the annular output groove 44 of the output pulley 42. The outer radial circumference of the sliding teeth assemblies 52 of the output pulley 42 defines an effective pulley diameter of the output pulley 42. [0020] The sliding teeth assemblies 52 of the input pulley 28 and the output pulley 42 may be attached to the input pulley 28 and the output pulley 42 respectively in any suitable manner. An exemplary connection between the sliding teeth assemblies 52 and the input pulley 28 and the output pulley 42 is herein described with reference to the input pulley 28. It should be appreciated that the description of the connection between the sliding teeth assemblies 52 and the input pulley 28 is likewise applicable to the connection between the sliding teeth assemblies 52 and the output pulley 42. The movable input sheave 32 and the stationary input sheave 34 may each include a plurality of radially extending undercuts 54 formed into their respective input groove surfaces 36. As best shown in Figure 1, the sliding teeth assemblies 52 include a roller mechanism 56 disposed at each axial end of the sliding teeth assemblies 52. The roller mechanisms 56 at each axial end of the sliding teeth assemblies 52 are disposed within the undercuts 54 formed in the input groove surfaces 36 of the movable input sheave 32 and the stationary input sheave 34. The sliding teeth assemblies 52 are radially movable inward toward the input axis 26, and outward away from the input axis 26, within their respective undercuts 54. It should be appreciated that the sliding teeth assemblies 52 may be attached to the input pulley 28 in some other manner that allows the sliding teeth assemblies 52 to move radially inward and outward relative to the input axis 26. Furthermore, it should be appreciated that the sliding teeth assemblies 52 of the output pulley 42 may be attached to the output pulley 42 in a similar manner.
[0021] Referring to Figure 4, each of the sliding teeth assemblies 52 includes a holder 58. The holder 58 includes the roller mechanisms 56 disposed at each axial end thereof. The holder 58 supports a plurality of teeth 60, i.e., plates stacked adjacent to each other. The plurality of teeth 60 includes one end sheet 62, disposed at an end of the stack of teeth 60. The end sheet 62 operates as the primary load bearing sheet of the sliding teeth assemblies 52. Each of the teeth 60 defines a center slot 64. A pin 66 is attached to the holder 58 and extends through the center slots 64 of the teeth 60. The center slots 64 define a radial opening that is larger than a radial thickness of the pin 66, such that the teeth 60 may move radially relative to the pin 66.
[0022] Referring to Figures 1 through 3, an endless rotatable device 68 is looped around the input shaft 22 and the output shaft 24, and is disposed within the annular input groove 30 and the annular output groove 44. The endless rotatable device 68 is operable to transmit torque from the input pulley 28 to the output pulley 42. The endless rotatable device 68 may include, but is not limited to, a chain, a belt, or some other similar device. The endless rotatable device 68 includes a plurality of fixed teeth 70 disposed on a radial inner surface thereof, which extend radially inward toward the sliding teeth assemblies 52.
[0023] Referring to Figure 4, during rotation of the input pulley 28 and the output pulley 42, a centrifugal force causes the teeth 60 of the sliding teeth assemblies 52 to slide radially outward into positive engagement with the fixed teeth 70 of the endless rotatable device 68, thereby rotating the endless rotatable device 68 with the input pulley 28 and the output pulley 42. The gear ratio of the continuously variable transmission 20 is changed by moving the two sheaves of either the input pulley 28 or the output pulley 42 closer together, and simultaneously moving the two sheaves of the other of the input pulley 28 and the output pulley 42 farther apart. The cross sectional shape of the input groove 30 and the output groove 44, parallel with the input axis 26 and the output axis 38 respectively, causes the sliding teeth assemblies 52 to ride higher on the pulley in which the two sheaves move closer together, i.e., increase the radial distance from an axis of rotation of the respective pulley, and causes the sliding teeth assemblies 52 to ride lower on the other pulley in which the two sheaves move farther apart, i.e., decrease the radial distance from an axis of rotation of the respective pulley. Changing the radial distances between the sliding teeth assemblies 52 and the axes of rotation of the respective pulleys changes the effective diameters of the pulleys, which in turn changes the overall gear ratio. The endless rotatable device 68 is movable radially with the sliding teeth assemblies 52 relative to the input axis 26 and the output axis 38 respectively.
[0024] Referring to Figure 2, at least one actuator 72 is coupled to at least one of the movable input sheave 32 or the movable output sheave 46. The actuator 72 applies a force parallel to the input axis 26 and the output axis 38 to move the movable input sheave 32 and/or the movable output sheave 46 axially along the input axis 26 and the output axis 38 respectively. The continuously variable transmission 20 may include one actuator 72 for each of the input pulley 28 and the output pulley 42, such that the input pulley 28 and the output pulley 42 are actuated independently of each other.
Alternatively, the continuously variable transmission 20 may include a single actuator 72 for both the input pulley 28 and the output pulley 42, with the movable input sheave 32 and the movable output sheave 46 attached and movable together. As best shown in Figure 2, the movable input sheave 32 and the movable output sheave 46 are disposed on opposite sides of the endless rotatable device 68, and the stationary input sheave 34 and the stationary output sheave 48 are disposed on opposite sides of the endless rotatable device 68. It should be appreciated that when the actuator 72 moves one of the movable input sheave 32 or the movable output sheave 46 toward the stationary input sheave 34 or the stationary output sheave 48 respectively, the other of the movable input sheave 32 and the movable output sheave 46 moves away from the stationary input sheave 34 or the stationary output sheave 48 respectively.
[0025] At least one of the annular input groove 30 and the annular output groove
44 defines a cross sectional shape, parallel with the input axis 26 and the output axis 38 respectively, and having a variable rate of radial change along the input axis 26 and the output axis 38 respectively. The variable rate of radial change is used to adjust a force required to move the endless rotatable device 68 radially relative to the input shaft 22 and the output shaft 24 respectively. The variable rate of radial change of the annular input groove 30 and the annular output groove 44 may be configured to decrease a force required to change the torque ratio in at least a first region of the annular input groove 30 and the annular output groove 44 respectively, relative to a constant force value. The constant force value may include any reference value, such as but not limited to the force required to change the torque ratio of a continuously variable transmission having a constant angled V-groove. Furthermore, the variable rate of radial change may be operable to increase the force required to change the torque ratio in at least a second region of the annular input groove 30 and the annular output groove 44 respectively, relative to the constant force value. Additionally, the variable rate of radial change may be operable to increase and/or decrease the speed at which the gear ratio changes, relative to benchmark speed. The benchmark speed may include any reference value, such as but not limited to the speed at which the gear ratio changes in a continuously variable transmission having a constant angled V-groove. A higher rate of radial change of the input groove and/or the output groove provides faster, more responsive changes in the gear ratio, but requires a higher force to move the movable input sheave 32 and the movable output sheave 46 along the input axis 26 and the output axis 38 respectively. In contrast, a lower rate of radial change of the input groove and/or the output groove provide a slower change in the gear ratio, but requires a lower force to move the movable input sheave 32 and the movable output sheave 46 along the input axis 26 and the output axis 38 respectively.
[0026] Preferably, both of the annular input groove 30 and the annular output groove 44 may define a cross sectional shape having a variable rate of radial change along the input axis 26 and the output axis 38 respectively. More preferably, the annular input groove 30 and the annular output groove 44 each include identical cross sectional shapes. However, the scope of the invention should not be limited to requiring both of the annular input groove 30 and the annular output groove 44 to include a cross sectional shape having a variable rate of radial change along the input axis 26, nor having identical cross sectional shapes.
[0027] Referring to Figure 2, both the input pulley 28 and the output pulley 42 are shown having a cross sectional shape with a variable rate of radial change. The variable rate of radial change is herein described with reference to the input pulley 28. It should be appreciated that the description of the variable rate of change relative to the input pulley 28 is likewise applicable to the output pulley 42. The input groove surfaces 36 of the movable input sheave 32 and the stationary input sheave 34 each define a cross sectional shape having a variable rate of radial change along the input axis 26 to define the cross sectional shape of the annular input groove 30. The input groove surface 36 of the movable input sheave 32 is a mirror image of the input groove surface 36 of the stationary input sheave 34.
[0028] Referring to Figures 5-7, the variable rate of radial change along the input axis 26 is defined as a change in the radial distance 74 of the input groove surfaces 36 measured relative to the input axis 26, divided by a change in axial location 76 of the input groove surfaces 36 measured along the input axis 26. Accordingly, the cross sectional shapes of the input groove surfaces 36 of the movable input sheave 32 and the stationary input sheave 34 perpendicular to the input axis 26 defines two different and distinct regions, with each region having a different, i.e., variable, rate of radial change. It should be appreciated that the rate of radial change of the annular output groove 44 is defined in the same manner as the rate of radial change of the annular input groove 30 described in detail above.
[0029] Referring to Figures 5-7, various possible configurations of the cross sectional shape of the input groove surfaces 36 of the movable input sheave 32 and the stationary input sheave 34 are shown. The cross sectional shape of the input groove surfaces 36 of the movable input sheave 32 and the stationary input sheave 34 may include, for example, at least one of a concave region 78, a convex region 80, and/or a linear region 82. For example, Figure 5 shows a cross sectional shape of the annular input groove 30 having multiple linear regions 82, separated by a convex region 80 and a concave region 78, whereas Figures 6 and 7 show a cross sectional shape of the annular input groove 30 having only a single convex region 80 and a single concave region 78. Furthermore, the cross sectional shape of the input groove surfaces 36 of the movable input sheave 32 and the stationary input sheave 34 may include, for example, two adjacent linear regions 82 defining an angle therebetween, with the angle having a value less than one hundred eighty degrees (180°). It should be appreciated that the cross sectional shape of the annular input groove 30 and the annular output groove 44 may differ from the exemplary embodiments shown and described herein.
[0030] If the cross sectional shape of the annular input groove 30 and the annular output groove 44 are properly designed, then the continuously variable transmission 20 may be constructed without the need for a tensioning device for tensioning and removing slack in the endless rotatable device 68. The cross sectional shape of the annular input groove 30 and the annular output groove 44 are determined by the fixed distance 40, and the maximum and minimum effective pulley diameters of the input pulley 28 and the output pulley 42 respectively. However, for any given specific fixed distance 40, and maximum and minimum effective pulley diameters, various alternative designs are possible. The optimized design needs to be defined considering factors including but not limited to axial size and closeness to a linear shape.
[0031] The detailed description and the drawings or figures are supportive and descriptive of the invention, but the scope of the invention is defined solely by the claims. While some of the best modes and other embodiments for carrying out the claimed invention have been described in detail, various alternative designs and embodiments exist for practicing the invention defined in the appended claims.
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