Electrically operated traction sheaves for a continuously variable transmission

Abstract

Continuously variable transmission (CVT), including: a rotating traction sheave (60, 62) having a first traction sheave half (61, 63) and a second traction sheave half (67, 68), wherein a distance between the first and second traction sheaves (61, 63, 67, 68) is variable, a screw actuator (78, 124) having a screw (86, 132) engaging the first drive pulley half (61, 63), and a motor (74, 120) connected to the screw (86, 132) and operable to move the first drive pulley half (61, 63) to vary the distance through the screw (86, 132), wherein the screw actuator (78, 124) comprises a planetary roller (88, 134) meshing with the screw (86, 132) and a nut (84, 130) meshing with the planetary roller (88, 134), wherein the motor (74, 120) drives the nut (84, 130) to rotate the planetary roller (88, 134), which moves the screw (86, 132) linearly, wherein the continuously variable transmission (CVT) comprises a planetary gear set having a sun gear (92, 138), a planetary gear (94, 142) meshing with the sun gear (92, 138), and a ring gear (98, 144) meshing with the planetary gear (94, 142), wherein the planetary gear set is connected between the motor (74, 120) and the nut (84, 130) and provides a reduction from the motor (74, 120) to the nut (84, 130), and wherein the motor (120) comprises a rotor (162) having a shaft (126) connected to the planetary gear set and to a brake (128), the brake (128) engaging the shaft (126) to prevent the shaft (126) from rotating, and to fix the first traction sheave half (63) in its position.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 62 / 306,582, filed March 11, 2016. TECHNICAL FIELD

[0002] The field to which the disclosure generally relates includes electrically actuated devices, and more particularly includes electrically actuated drive pulleys in continuously variable transmissions (CVTs). BACKGROUND

[0003] A CVT can be used to continuously vary the gear ratios between an input shaft and an output shaft. A vehicle's drivetrain may include a CVT between the engine and the drive wheels to provide a range of relative speeds between the input and output shafts.

[0004] Document DE 600 01 108 T2 relates to a pulley set for a continuously variable transmission unit comprising a pair of pulleys (halves) mounted on a shaft and a screw mechanism concentric with respect to the pulleys for moving the pulleys toward and away from each other. The pulleys include a V-shaped groove for accommodating a belt, and the screw mechanism is controllable by a control device.

[0005] DE 693 01 875 T2 describes a continuously variable V-belt transmission with a belt that runs on a primary and a secondary pulley, each consisting of two conical pulleys.

[0006] DE 10 2008 046 305 A1 describes an oil pressure control device. Furthermore, document US 2002 / 0 183 146 A1 refers to a belt drive with continuously variable speed control and a recirculating ball screw. SUMMARY OF EXEMPLARY EMBODIMENTS

[0007] The present invention relates to a continuously variable transmission according to claim 1 and claim 5. The dependent claims describe advantageous embodiments of the continuously variable transmission.

[0008] Further illustrative embodiments falling within the scope of the invention will become apparent from the detailed description given below. It should be understood that the detailed description and specific examples, while disclosing variations within the scope of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Selected examples of variations within the scope of the invention will become clear from the detailed description and the accompanying drawings, in which: Fig. 1 is a schematic illustration of a product or a continuously variable transmission according to a number of variations. Fig. Figure 2 is a schematic illustration of a portion of a continuously variable transmission according to a number of variations. Fig. 3 is a schematic illustration of a portion of a continuously variable transmission according to a number of variations. Fig. Figure 4 is a schematic illustration of a continuously variable transmission according to a number of variations. DETAILED DESCRIPTION OF EMBODIMENTS

[0010] In a number of variations, a product 10 or a continuously variable transmission CVT, as in Fig. 1, may include an input drive 12 and an output drive 14. The input drive 12 may be in the form of a rotationally driven shaft 16. The shaft 16 may be connected to a powerplant 18, which may be an engine, such as an internal combustion engine, or an alternative powerplant or hybrid arrangement. The output drive 14 may be in the form of a rotationally driving shaft 20. The shaft 20 may be connected to and may drive one or more road wheels 22 through a gear mechanism 24. The gear mechanism 24 may include a differential unit to split the torque and may include additional gear ratios to transmit the motion to the road wheel 22. The road wheel 22 may require a range of speed inputs from the shaft 20 and may operate under a variety of conditions with varying torque requirements.As a result, the engine 18 can operate over a range of speeds and the product 10 or the continuously variable transmission CVT can provide different gear ratios between the shafts 16 and 20.

[0011] In a number of variations, the shaft 16 may be connected to a torque-transmitting member 26 through a clutch 28. The torque-transmitting member 26 may transmit drive input to a downstream load, which may include a road wheel 22. If the powerplant 18 comprises an internal combustion engine, the clutch 28 may be a torque converter-type fluid coupling. The shaft 16 may be connected to an impeller 30. The torque-transmitting member 26 may be connected to a turbine 32 through a housing portion 34. A stator 36 may be positioned between the impeller 30 and the turbine 32 and may influence the transfer of power through the clutch 28 from the shaft 16 to the torque-transmitting member 26. The stator 36 may be fixed to a gear box 38.The rotation of the impeller 30 may act through a fluid in the clutch 28 to rotate the turbine 32 such that the torque-transmitting member 26 is driven by the shaft 16. The clutch 28 may allow the impeller 30 to rotate relative to the turbine 32, and the stator 36 may effect torque multiplication between the impeller 30 and the turbine 32. A lock-up clutch 40 may be provided to lock the impeller 30 to the turbine 32 through the housing portion 34 so that the two rotate together.

[0012] In a number of variations, the torque-transmitting member 26 may be connected to a shaft 42 through a drive reversing unit 44, which can effect a number of operating modes. The operating modes may include neutral, forward, and reverse operation. The torque-transmitting member 26 may be connected to or formed as part of a carrier member 46. The carrier member 46 may support a number of planet gears 48 in a spaced-apart relationship. The planet gears 48 may be meshed with the external teeth of a sun gear member 50 and may be meshed with the internal teeth of a ring gear member 52. A forward clutch 54 may be connected between the carrier member 46 and the sun gear member 50.The forward clutch 54 may be a wet friction disc-type clutch, which may include a number of inner discs fixed for rotation with either the carrier 46 or the sun gear 50, and a number of intermeshing outer discs fixed for rotation with the other of the carrier 46 or the sun gear 50. An actuator (not shown) may selectively cause the inner and outer discs to compress so that they rotate together and drive the sun gear 50 from the carrier 46 to provide the forward drive mode, with the ring gear 52 free to rotate. A reverse clutch 55 may be a wet friction disc-type clutch, which may include a number of discs fixed for rotation with the ring gear 52, and a number of intermeshing discs fixed to the housing 56.An actuator (not shown) can selectively cause compression of the discs so that the ring gear 52 is locked to the housing 56 to reverse the rotation of the sun gear 50 when driven by the carrier 46 through the planetary gears 48, thereby providing the reverse drive mode. In the forward drive mode, the reverse clutch 55 can be opened or disengaged, and in the reverse drive mode, the forward clutch 54 can be opened or disengaged. Both clutches 54, 55 can be opened to provide a neutral mode.

[0013] In a number of variations, the shaft 42 may be connected to a drive pulley 60 having a variator unit 58. The power unit 18 may drive the pulley 60 through the shaft 42. The drive pulley 60 may be connected to a driven pulley 62 by a connecting element 64, which may be a belt or chain surrounding the pulleys 60, 62. The drive and driven pulleys 60, 62 may each be in the form of a pulley having an adjustable working diameter for use with the connecting element 64. The left (in the view of Fig. 1) Traction sheave halves 61, 63 and the right (in the view from Fig. 1) Traction sheave halves 67, 68 of the traction sheaves 60, 62 can be moved closer together or further apart to vary the working diameter of the traction sheaves 60, 62. Changing the distance between the two traction sheave halves 61 and 67 on the one hand and traction sheave halves 63 and 68 on the other hand results in the connecting element 64 sitting higher or lower in the respective groove of the traction sheaves 60, 62. This can change the effective drive ratio between the driving traction sheave 60 and the driven traction sheave 62. One or more actuator units 70 and / or 72 can be provided in the variator unit 58 to effect the movement of the traction sheave halves 61 and 67 relative to one another and / or to effect the movement of the traction sheave halves 63 and 68 relative to one another. The actuator units 70 and / or 72 may each be a planetary roller screw type actuator.An electronic control unit (not shown) may control the operation of the actuator units 70 and / or 72 in a pre-programmed manner in response to operating conditions.

[0014] In a number of variations, the actuator unit 70 may generally include a motor 74, a gear reduction unit 76, and a screw actuator unit 78. The motor 74 may have a relatively high power-to-volume ratio and thus be a brushless DC motor or another type. The motor 74 may drive a shaft 80, which may be connected to a brake 82. The brake 82 may be an electromagnetic friction brake and may be normally closed to prevent the shaft 80 from rotating when no power is supplied to the brake 82. The brake 82 may, by normally holding the shaft 80, fix the drive sheave half 61 in position relative to the drive sheave half 67. This may reduce the duty cycle on the motor 7 and may maximize the efficiency of the product 10 or the continuously variable transmission (CVT) by minimizing power consumption during non-transient vehicle maneuvers.The screw actuator unit 78 may be a planetary roller screw-type unit including a nut 84, a screw 86, and a number of planetary rollers 88 positioned between the nut 84 and the screw 86. The planetary rollers 88 may include threads that engage threads on the nut 84 and the screw 86. Rotation of the nut 84 may rotate the planetary rollers 88, which in turn may cause the screw 86 to translate linearly. The screw 86 may be hollow, and the shaft 42 may extend entirely through its hollow center.

[0015] The screw 86 may engage the drive sheave half 61 to drive it toward and away from the drive sheave half 67. The nut 84 may include an external gear 90 that may engage and be driven by the gear reduction unit 76.

[0016] In a number of variations, the gear reduction unit 76 can provide reduced speed and increased torque between the shaft 80 and the nut 84. The shaft 80 can provide input to a double reduction planetary arrangement at a first stage thereof through a sun gear 92. The sun gear 92 can be meshed with a number of planet gears 94 carried by a carrier 96. The planet gears 94 can be meshed with a ring gear 98 that can be fixed to a housing 100. The ring gear can extend across the first and second stages of the planetary arrangement. The carrier 96 can be fixedly connected to a sun gear 102 that provides input to the second stage. The sun gear 102 can be meshed with a number of planet gears 104 carried by a carrier 106. The planet gears 104 can be meshed with the ring gear 98.The carrier 106 may be fixedly connected to a torque-transmitting member 108, which may provide an output from the double-reduction planetary arrangement. The input from the shaft 80 may be communicated sequentially through the sun gear 92, the planet gears 94, the carrier 96, the sun gear 102, the planet gears 104, and the carrier 106 to the torque-transmitting member 108. With the fixed ring gear 98, the speed can be reduced through two stages and the torque can be multiplied through the two stages of the double-reduction planetary arrangement.

[0017] In a number of variations, the torque-transmitting element 108 may be a fixed connection or a one-piece structure between the carrier 106 and a gear 110. The gear 110 may mesh with and drive a gear 112. The gear 112 may have a larger diameter and a greater number of teeth than the gear 110 to provide a speed reduction. The gear 112 may be connected to or integral with a gear 114. The gear 114 may mesh with and drive the external gear 90 on the nut 84. The external gear 90 may have a larger diameter and a greater number of teeth than the gear 114 to provide a speed reduction. The motor 74 may be reversible and provide linear displacement of the drive sheave half 61 through the gear reduction unit 76, the screw actuator unit 78, and the plurality of idler gears.

[0018] In a number of variations, the traction sheave half 63 can similarly be driven by an actuator unit 72. The traction sheave 62 can be varied by an intermediate motor 120 in the actuator unit 72. In a number of variations, the actuator unit 72 can include the motor 120, a gear reduction unit 122, and a screw actuator unit 124. The motor 120 can have a relatively high power-to-volume ratio and thus can be a brushless DC motor. The motor 120 can drive a shaft 126, which can be connected to a brake unit 128. The brake unit 128 can be an electromagnetic friction brake and can be normally closed to prevent the shaft 126 from rotating when no power is supplied to the brake unit 128.The screw actuator unit 124 may be a planetary roller screw-type unit including a nut 130, a screw 132, and a number of planetary rollers 134 positioned between the nut 130 and the screw 132. The planetary rollers 134 may include threads that engage threads on the nut 130 and the screw 132. Rotation of the nut 130 may rotate the planetary rollers 134, which in turn may cause the screw 132 to translate linearly. The screw 132 may be hollow, and the shaft 20 may extend entirely through its hollow center. The screw 132 may engage the drive sheave half 63 to drive it toward and away from the drive sheave half 68. The nut 130 may include an external gear 136 that may engage and be driven by the gear reduction unit 122.

[0019] In a number of variations, the gear reduction unit 122 can provide reduced speed and increased torque between the shaft 126 and the nut 130. The shaft 126 can provide input to a double reduction planetary arrangement at a first stage thereof through a sun gear 138. The sun gear 138 can be meshed with a number of planet gears 142 carried by a carrier 140. The planet gears 142 can be meshed with a ring gear 144 that can be fixed to a housing 100. The ring gear can extend across the first and second stages of the planetary arrangement. The carrier 140 can be fixedly connected to a sun gear 146 that provides input to the second stage. The sun gear 146 can be meshed with a number of planet gears 148 carried by a carrier 150. The planet gears 148 can be toothed with the ring gear 144.The carrier 150 may be fixedly connected to a torque-transmitting member 152, which may provide an output from the double-reduction planetary arrangement. The input from the shaft 126 may be communicated sequentially through the sun gear 138, the planet gears 142, the carrier 140, the sun gear 146, the planet gears 148, and the carrier 150 to the torque-transmitting member 152. With the fixed ring gear 144, the speed can be reduced through two stages and the torque can be multiplied through two stages of the double-reduction planetary arrangement.

[0020] In a number of variations, the torque-transmitting member 152 may be a fixed connection or a one-piece structure between the carrier 150 and a gear 154. The gear 154 may mesh with and drive a gear 156. The gear 156 may have a larger diameter and a greater number of teeth than the gear 154 to provide a speed reduction. The gear 156 may be connected to or formed integrally with a gear 158. The gear 158 may mesh with and drive the external gear 136 on the nut 130. The external gear 136 may have a larger diameter and a greater number of teeth than the gear 158 to provide a speed reduction. The motor 120 may be reversible and cause a linear displacement of the traction sheave half 63 through the gear reduction unit 122, the screw actuator unit 124 and the number of intermediate gears.

[0021] With reference to Fig. 2, the screw actuator unit 124 is illustrated according to a number of variations. The motor 120 may include a stator 160 and a rotor 162, which may be connected to the shaft 126. The input from the shaft 126 may be communicated sequentially through the sun gear 138, the planet gears 142, the carrier 140, the sun gear 146, the planet gears 148, and the carrier 150 to the torque-transmitting member 152. The brake unit 128 may be connected to one end 164 of the shaft 126, with a disc 165 fixed for rotation with the shaft 126. A pressure plate 168 may be disposed adjacent the disc 165, with a friction material 170 disposed between the pressure plate 168 and the disc 165. A base plate 172 may be positioned on one side of the disc 165, opposite the pressure plate 168. A friction material 174 may be disposed between the base plate 172 and the disc 165.A spring retainer 178 may be positioned against the pressure plate 168 and may normally compress the disc 165 between the pressure plate 168 and the base plate 172 through the friction material 170, 174 to prevent the shaft 126 from rotating. A coil 176 may be positioned adjacent the pressure plate 168 and may be energized to compress the spring retainer 178 by attracting the pressure plate 168 to release the disc 165 and allow the shaft 126 to rotate.

[0022] The screw actuator assembly 124 may include the nut 130, the screw 132, and the planetary rollers 134. The drive sheave half 63 may be supported on the shaft 20, and the drive sheave half 63 may translate along the length of the shaft 20.

[0023] The sheave half 63 and the shaft 20 may include a keyway connection to allow translation but prevent relative rotation. The screw 132 may be hollow, and the shaft 20 may extend completely through its hollow center. The screw 132 may be actuable in two directions, against the sheave half 63 by thrust washers 180 and against the housing 100 by a thrust washer 182. To illustrate translation, the sheave half 63 is shown in a first position at the top of the shaft 20 and a second position at the bottom of the shaft 20 with the screw 132 extending to the right. The sheave half 63 may have an annular shape, and its upper and lower portions may move together in aligned relationship.The nut 130 and the planetary rollers 134 may be supported on the housing 100 so that they rotate but do not translate with the screw 132. The drive sheave half 63 may be linearly translated in opposite directions from the drive sheave half 68 when driven sequentially by the sun gear 138, the planetary gears 142, the carrier 140, the sun gear 146, the planetary gears 148, the carrier 150, the torque transmitting member 152, the gears 154, 156, and 158, the nut 130, the planetary rollers 134, and the screw 132. Referring to FIG. Fig. 3, which shows a section through the actuator assembly 72, the screw 132 may be surrounded by the nut 130, and the planetary rollers 134 may be supported between the two. The planetary rollers 134 may be arranged around the circumference of the screw 132 and evenly spaced, and the engaging surfaces of the screw 132, the planetary rollers 134, and the nut 130 may all have intermeshing teeth, a portion of which 190 is shown.

[0024] In a number of variations, as in Fig.4 illustrates, both the driving sheave 60 and the driven sheave 62 can be varied by power supplied from a common motor. For example, the sheave half 63 can be driven by the motor 120 through the gear reduction unit 122, the gears 154, 156, 158, and the screw actuator unit 124. The shaft 126 of the motor 120 can extend through the brake unit 128 and be connected at its end 184 to a gear reduction unit 183. The gear reduction unit 183 can be a double planetary gear reduction unit. The output of the gear reduction unit 183 can be supplied to a shaft 185. The sheave half 67 can be driven by the screw actuator unit 78. The screw actuator unit 78 may be oriented to engage the shaft 185 through gears 186, 187 and 188.Accordingly, the traction sheave half 67 can be driven by the motor 120 through the gear reduction unit 183, the gears 188, 187, 186, and the screw actuator unit 78. The motor 120 can drive the variation of both the driving traction sheave 60 and the driven traction sheave 62. The housing 191 can provide the structure to support the components in the dual drive arrangement.

[0025] In all of the variations described above, the drive pulleys of a CVT can be varied using a screw actuator. The following description of exemplary embodiments is merely illustrative of components, elements, acts, products, and methods that are considered to be within the scope of the invention and is in no way intended to limit the scope by what is disclosed in detail or not expressly set forth. The components, elements, acts, products, and methods described herein may be combined and rearranged other than as expressly described herein and still be considered to be within the scope of the invention.

[0026] Although the present invention has been described above and defined in the appended claims, it should be understood that the invention may alternatively be defined according to the following variations: Variation 1 may include a product that may comprise a rotatable traction sheave having a first traction sheave half and a second traction sheave half, wherein a distance between the first and second traction sheave halves may be variable. A screw actuator may include a screw that may engage the first traction sheave half. A motor may be connected to the screw and may be operable to move the first traction sheave half and vary the distance by the screw. Variation 2 may include a product according to Variation 1, wherein the screw actuator may comprise a planetary roller that may mesh with the screw. A nut may mesh with the planetary roller. The motor may drive the nut to rotate the planetary roller, which may move the screw linearly. Variation 3 may include a product according to Variation 2 and may include a planetary gear set that may include a sun gear. A planetary gear may mesh with the sun gear. A ring gear may mesh with the planetary gear. The planetary gear set may be connected between the motor and the nut and may provide a reduction gear from the motor to the nut. Variation 4 may include a product according to Variation 3, wherein the motor may comprise a rotor having a shaft that may be connected to the planetary gear set and to a brake. The brake may engage the shaft and may prevent the shaft from rotating and may lock the first drive sheave half in position. Variation 5 may include a product according to any of Variations 1 to 4 and may include a road wheel that can be driven by the traction sheave. Variation 6 may include a product according to any one of Variations 1 to 5 and may comprise a power unit and a drive reversing unit that may be configured to reverse the rotation of the traction sheave. The power unit may drive the traction sheave to rotate through the drive reversing unit. Variation 7 may include a product according to any of Variations 1 to 6, wherein the screw actuator may comprise a plurality of planetary rollers that may mesh with the screw. A nut may mesh with and surround the plurality of planetary rollers. The nut may include an internal gear that may mesh with the plurality of planetary rollers and may include an external gear that may be driven by the motor. Variation 8 may include a product according to any of variations 1 to 7, wherein the drive sheave may rotate on a shaft. The propeller may have a hollow center. The shaft may extend through the hollow center of the propeller. Variation 9 may include a product that may include a first traction sheave. A second traction sheave may be drivingly connected to the first traction sheave by a connecting member. At least one of the first or second traction sheaves may include a first traction sheave half and an opposing second traction sheave half, and may have a variable working diameter effected by movement of the first traction sheave half relative to the second traction sheave half. A screw actuator may include a screw engageable with the first traction sheave half. A motor may engage the screw through a drive train that may effect displacement of the screw. Variation 10 may include a product according to Variation 9. It may include a planetary roller that may mesh with the screw. A nut may mesh with the planetary roller. The motor may be connected to the screw through the nut and the planetary roller. Variation 11 may include a product according to Variation 10 and may include a double reduction planetary gear set that may be connected between the motor and the nut. Variation 12 may include a product according to Variation 11, wherein the motor may comprise a rotor having a shaft that may be connected to the double-reduction planetary gear set. A brake may be engaged with the shaft and may prevent the shaft from rotating and may lock the first drive sheave half in position. Variation 13 may include a product according to any of Variations 10 to 12 and may include a power unit. A drive reversing unit may include a planetary gear set. The power unit may drive the first drive sheave through the drive reversing unit. Variation 14 may include a product according to any of Variations 10 to 13 and may include a power unit and a torque converter. The power unit may drive the first drive pulley through the torque converter. Variation 15 may include a product according to Variation 14 and may include a drive wheel and a gear mechanism. The second drive pulley may be connected to the drive wheel through the gear mechanism.

Claims

[1] Continuously variable transmission (CVT), comprising: a rotating traction sheave (60, 62) having a first traction sheave half (61, 63) and a second traction sheave half (67, 68), wherein a distance between the first and second traction sheaves (61, 63, 67, 68) is variable, a screw actuator (78, 124) having a screw (86, 132) engaging the first drive pulley half (61, 63), and a motor (74, 120) connected to the screw (86, 132) and operable to move the first drive pulley half (61, 63) to vary the distance through the screw (86, 132), wherein the screw actuator (78, 124) comprises a planetary roller (88, 134) meshing with the screw (86, 132) and a nut (84, 130) meshing with the planetary roller (88, 134), wherein the motor (74, 120) drives the nut (84, 130) to rotate the planetary roller (88, 134), which moves the screw (86, 132) linearly, wherein the continuously variable transmission (CVT) comprises a planetary gear set having a sun gear (92, 138), a planetary gear (94, 142) meshing with the sun gear (92, 138), and a ring gear (98, 144) meshing with the planetary gear (94, 142), wherein the planetary gear set is connected between the motor (74, 120) and the nut (84, 130) and provides a reduction from the motor (74, 120) to the nut (84, 130), and wherein the motor (120) comprises a rotor (162) having a shaft (126) connected to the planetary gear set and to a brake (128), the brake (128) engaging the shaft (126) to prevent the shaft (126) from rotating, and to fix the first traction sheave half (63) in its position. [2] A continuously variable transmission (CVT) according to claim 1, comprising a power unit (18) and a drive reversing unit (44) configured to reverse the rotation of the drive sheave (60), wherein the power unit (18) drives the drive sheave (60) to rotate through the drive reversing unit (44). [3] A continuously variable transmission (CVT) according to claim 1, wherein the screw actuator (78, 124) comprises a plurality of planetary rollers (88, 134) meshing with the screw (86, 132) and a nut (84, 130) meshing with and surrounding the plurality of planetary rollers (88, 134), the nut (84, 130) having an internal gear meshing with the plurality of planetary rollers (88, 134) and an external gear (90, 136) driven by the motor (74, 120). [4] A continuously variable transmission (CVT) according to claim 1, wherein the drive pulley (60, 62) rotates on a shaft (42, 20), and wherein the screw (86, 132) has a hollow center, the shaft (42, 20) extending through the hollow center of the screw (86, 132). [5] Continuously variable transmission (CVT), comprising: a first traction sheave (60), a second traction sheave (62) which is drivingly connected to the first traction sheave (60) by a connecting element (64), wherein at least one of the first or second traction sheaves (60, 62) comprises a first traction sheave half (61, 63) and an opposite second traction sheave half (67, 68) and has a variable working diameter caused by the movement of the first traction sheave half (61, 63) relative to the second traction sheave half (67, 68), a screw actuator (78, 124) having a screw (86, 132) engaging the first drive pulley half (61, 63), and a motor (74, 120) which engages the screw (86, 132) through a drive train and causes the displacement of the screw (86, 132), wherein the continuously variable transmission (CVT) comprises a planetary roller (88, 134) which is in toothed engagement with the screw (86, 132) and a nut (84, 130) which is in toothed engagement with the planetary roller (88, 134), wherein the motor (74, 120) is connected to the screw (86, 132) by the nut (84, 130) and the planetary roller (88, 134), wherein the continuously variable transmission (CVT) comprises a double reduction planetary gear set connected between the motor (74, 120) and the nut (84, 130), and wherein the motor (74, 120) comprises a rotor (162) having a shaft (126) connected to the double reduction planetary gear set, and comprising a brake (128) engaged with the shaft (126) to prevent the shaft (126) from rotating and to fix the first drive sheave half (63) in position. [6] A continuously variable transmission (CVT) according to claim 5, comprising a power unit (18) and a drive reversing unit (44) having a planetary gear set, wherein the power unit (18) drives the first drive sheave (60) through the drive reversing unit (44). [7] A continuously variable transmission (CVT) according to claim 5, comprising a power unit (18) and a torque converter (28), wherein the power unit (18) drives the first drive pulley (60) through the torque converter (28).

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