WO2018085317A1 - Components and assemblies for a ball-type continuously variable planetary transmission - Google Patents

Abstract

A continuously variable transmission (CVT) having a plurality of balls, each ball having a tiltable axis of rotation and in contact with a first traction ring and a second traction ring. The CVT includes a rotatable shaft aligned along a longitudinal axis of the CVT and positioned radially inward of the balls, the first traction ring, and the second traction ring; a carrier assembly operably coupled to each ball including a first carrier member coaxial to the shaft and a second carrier member operably coupled to the first carrier member; a first cam driver operably coupled to the first traction ring and the first carrier member and adapted to receive a rotational power; and a thrust bearing assembly coupled to the cam driver and the shaft. In one embodiment, the carrier assembly includes lubrication passage channels.

Description

COMPONENTS AND ASSEMBLIES FOR A BALL-TYPE CONTINUOUSLY VARIABLE PLANETARY TRANSMISSION

RELATED APPLICATION

The present application claims the benefit of U.S. Provisional Application No. 62/416,358 filed on November 2, 2016, which is incorporated herein by reference in its entirety.

BACKGROUND

Automatic and manual transmissions are commonly used on

automobiles. Such transmissions have become more and more complicated since the engine speed has to be adjusted to limit fuel consumption and the emissions of the vehicle. A vehicle having a driveline including a tilting ball variator allows an operator of the vehicle or a control system of the vehicle to vary a drive ratio in a stepless manner. A variator is an element of a

Continuously Variable Transmission (CVT) or an Infinitely Variable

Transmission (IVT). Transmissions that use a variator can decrease the transmission's gear ratio as engine speed increases. This keeps the engine within its optimal efficiency while gaining ground speed, or trading speed for torque during hill climbing, for example. Efficiency in this case can be fuel efficiency, decreasing fuel consumption and emissions output, or power efficiency, allowing the engine to produce its maximum power over a wide range of speeds. That is, the variator keeps the engine turning at constant RPMs over a wide range of vehicle speeds.

Over time packaging of transmission components has become an ever increasing issue. As with most parts of a transmission, there is a desire to reduce weight, number and size of components to improve efficiency. The carrier of a variator is made up of multiple pieces to facilitate ease of

manufacture and provide adequate lubrication for traction contacts and cooling of traction rings. Due to tight packaging requirements for lubrication channels within the variator, an improved carrier design is required to facilitate a path for lubrication fluid to route from the main shaft through the carrier and to target the leading and trailing edges of the traction rings with an efficient spray pattern. SUMMARY

Provided herein is a continuously variable transmission (CVT) having a plurality of balls, each ball having a tiltable axis of rotation, each ball in contact with a first traction ring and a second traction ring. The CVT includes a rotatable shaft aligned along a longitudinal axis of the CVT, the shaft positioned radially inward of the balls, the first traction ring and the second traction ring; a carrier assembly operably coupled to each ball, the carrier assembly including a first carrier member arranged coaxial to the shaft and a second carrier member operably coupled to the first carrier member, the second carrier member configured to rotate relative to the first carrier member and arranged coaxial to the shaft; a first cam driver operably coupled to the first traction ring and the first carrier member, the first cam driver adapted to receive a rotational power; and a thrust bearing assembly coupled to the cam driver and to the shaft.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

Novel features of the preferred embodiments are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present embodiments will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the preferred embodiments are utilized, and the accompanying drawings of which:

Figure 1 is a side sectional view of a ball-type variator.

Figure 2 is a plan view of a carrier member that is used in the variator of Figure 1. Figure 3 is an illustrative view of different tilt positions of the ball-type variator of Figure 1.

Figure 4 is a plan view of a ball-type continuously variable transmission depicting a number of section views with respect to a longitudinal axis.

Figure 5 is a cross-sectional view "A-A" of the ball-type continuously variable transmission of Figure 4.

Figure 6 is a detail view "G" of a thrust bearing assembly used in the ball-type continuously variable transmission of Figure 4.

Figure 7 is a detail view "H" of an anti-rotation washer used in the ball- type continuously variable transmission of Figure 4.

Figure 8 is an exploded isometric detail view "L" of the thrust bearing assembly and anit-rotation washer of Figures 6 and 7, respectively.

Figure 9 is a cross-section view "C-C" of certain components of the ball- type continuously variable transmission of Figure 4.

Figure 10 is an isometric cross-section view of the ball-type continuously variable transmission of Figure 4.

Figure 1 1 is an isometric view of a cam driver used in the ball-type continuously variable transmission of Figure 4.

Figure 12 is another isometric view of the cam driver of Figure 1 1.

Figure 13 is an isometric, cross-sectional view "F-F" of the cam driver of

Figure 1 1.

Figure 14 is a plan view of another embodiment of a ball-type

continuously variable transmission depicting a section view with respect to a longitudinal axis.

Figure 15 is a cross-sectional view "T-T" of certain components of the ball-type continuously variable transmission of Figure 14.

Figure 16 is a cross-section detail view "Y" of a bearing hub used in the ball-type continuously variable transmission of Figure 14.

Figure 17 is a cross-section view "J-J" of the ball-type continuously variable transmission of Figure 4.

Figure 18 is a cross-sectional detail view "K" of a shift-stop assembly used in the ball-type continuously variable transmission of Figure 4. Figure 19 is a cross-sectional view "V-V" of certain components of the ball-type continuously variable transmission of Figure 4, depicting a shift-stop assembly.

Figure 20 is a detail view "W" of the shift-stop of Figure 19.

Figure 21 is a detail view "Z" of ramped surfaces of the cam driver of

Figure 1 .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Provided herein are configurations of CVTs based on ball type variators, also known as CVP, for continuously variable planetary. Basic concepts of a ball type Continuously Variable Transmissions are described in United States Patent No. 8,469,856 and United States Patent No. 8,870,71 1 incorporated herein by reference in their entirety. Such a CVT, adapted herein as described throughout this specification, includes a number of balls (planets, spheres) 1 , depending on the application, two ring (disc) assemblies with a conical surface contact with the balls 1 , as a first (input) traction ring 2 and a second (output) traction ring 3, and an idler (sun) assembly 4 as shown on FIG. 1 . The balls 1 are mounted on tiltable axles 5, themselves held in a carrier (stator, cage) assembly having a first carrier member 6 operably coupled to a second carrier member 7. The first carrier member 6 rotates with respect to the second carrier member 7, and vice versa. In some embodiments, the first carrier member 6 is substantially fixed from rotation while the second carrier member 7 is

configured to rotate with respect to the first carrier member, and vice versa. In one embodiment, the first carrier member 6 is provided with a number of radial guide slots 8. The second carrier member 7 is provided with a number of radially offset guide slots 9. The radial guide slots 8 and the radially offset guide slots 9 are adapted to guide the tiltable axles 5. The axles 5 is adjusted to achieve a desired ratio of input speed to output speed during operation of the CVT. In some embodiments, adjustment of the axles 5 involves control of the position of the first carrier member and the second carrier member to impart a tilting of the axles 5 and thereby adjusts the speed ratio of the variator. Other types of ball CVTs also exist, like the one produced by Milner, but are slightly different, !n some embodiments, the conical surfaces of the first traction ring 2 and the second traction ring 3 have angled contact surfaces with respect to the balls 1 in the range of 30 to 45 degrees. The traction surface profile is typically described as a radius, R, of concave or convex nature between 100% conformal and 100% convex, including a straight (0% convex). In some embodiments, the traction surface profile R is generally less than the planet (ball) diameter.

Likewise, in some embodiments, the idler assembly 4 includes rings in contact with each balls 1 having angled contact surfaces with respect to the balls 1 in the range of 7 to 13 degrees. The traction surface shape is between 200% conformal and 200% convex including straight (0% convex). The traction surface profile of the idler assembly rings is less than or equal to two times the planet diameter.

The working principle of such a CVP of FIG. 1 is shown on FIG. 2. The CVP itself works with a traction fluid. The lubricant between the ball and the conical rings acts as a solid at high pressure, transferring the power from the input ring, through the balls, to the output ring. By tilting the balls' axes, the ratio is changed between input and output. When the axis is horizontal the ratio is one, illustrated in FIG. 3, when the axis is tilted the distance between the axis and the contact point change, modifying the overall ratio. All the balls' axes are tilted at the same time with a mechanism included in the carrier and/or idler. Embodiments disclosed here are related to the control of a variator and/or a CVT using generally spherical planets each having a tiltable axis of rotation that is capable of being adjusted to achieve a desired ratio of input speed to output speed during operation. In some embodiments, adjustment of said axis of rotation involves angular misalignment of the planet axis in a first plane in order to achieve an angular adjustment of the planet axis in a second plane that is substantially perpendicular to the first plane, thereby adjusting the speed ratio of the variator. The angular misalignment in the first plane is referred to here as "skew", "skew angle", and/or "skew condition". In one embodiment, a control system coordinates the use of a skew angle to generate forces between certain contacting components in the variator that will tilt the planet axis of rotation. The tilting of the planet axis of rotation adjusts the speed ratio of the variator. As used here, the terms "operationally connected," "operationally coupled", "operationally linked", "operably connected", "operably coupled", "operably linked," and like terms, refer to a relationship (mechanical, linkage, coupling, etc.) between elements whereby operation of one element results in a corresponding, following, or simultaneous operation or actuation of a second element. It is noted that in using said terms to describe inventive

embodiments, specific structures or mechanisms that link or couple the elements are typically described. However, unless otherwise specifically stated, when one of said terms is used, the term indicates that the actual linkage or coupling may take a variety of forms, which in certain instances will be readily apparent to a person of ordinary skill in the relevant technology.

For description purposes, the term "radial" is used here to indicate a direction or position that is perpendicular relative to a longitudinal axis of a transmission or variator. The term "axial" as used here refers to a direction or position along an axis that is parallel to a main or longitudinal axis of a transmission or variator. For clarity and conciseness, at times similar components labeled similarly (for example, ramped surface 52A and ramped surface 52B) will be referred to collectively by a single label (for example, bearing 1011).

It should be noted that reference herein to "traction" does not exclude applications where the dominant or exclusive mode of power transfer is through "friction." Without attempting to establish a categorical difference between traction and friction drives here, generally these may be understood as different regimes of power transfer. Traction drives usually involve the transfer of power between two elements by shear forces in a thin fluid layer trapped between the elements. The fluids used in these applications usually exhibit traction coefficients greater than conventional mineral oils. The traction coefficient (μ) represents the maximum available traction forces which would be available at the interfaces of the contacting components and is a measure of the maximum available drive torque. In some embodiments, the traction coefficient is a design parameter in the range of 0.3 to 0.6. Typically, friction drives generally relate to transferring power between two elements by frictional forces between the elements. For the purposes of this disclosure, it should be understood that the CVTs described here may operate in both tractive and frictional

applications. As a general matter, the traction coefficient μ is a function of the traction fluid properties, the normal force at the contact area, and the velocity of the traction fluid in the contact area, among other things. For a given traction fluid, the traction coefficient μ increases with increasing relative velocities of components, until the traction coefficient μ reaches a maximum capacity after which the traction coefficient μ decays. The condition of exceeding the maximum capacity of the traction fluid is often referred to as "gross slip condition".

As used herein, "creep", "ratio droop", or "slip" is the discrete local motion of a body relative to another and is exemplified by the relative velocities of rolling contact components such as the mechanism described herein. In traction drives, the transfer of power from a driving element to a driven element via a traction interface requires creep. Usually, creep in the direction of power transfer is referred to as "creep in the rolling direction." Sometimes the driving and driven elements experience creep in a direction orthogonal to the power transfer direction, in such a case this component of creep is referred to as "transverse creep."

For description purposes, the terms "prime mover", "engine," and like terms, are used herein to indicate a power source. Said power source may be fueled by energy sources including hydrocarbon, electrical, biomass, solar, geothermal, hydraulic, and/or pneumatic to name but a few. Although typically described in a vehicle or automotive application, one skilled in the art will recognize the broader applications for this technology and the use of alternative power sources for driving a transmission including this technology.

Referring now to FIGS. 4-20, in some embodiments, a continuously variable transmission (CVT) 10 is configured in a similar manner as the variator depicted in FIGS. 1-3. For description purposes, only the differences between the CVT 10 and the variator of FIGS. 1-3 will be described. As a visual aid to depict certain components of the CVT 10, orientation of cross-sectional views are provided with respect to the longitudinal axis in FIGS. 4 and 14. The longitudinal axis is arranged perpendicular to the plane of the page when viewed in FIGS. 4 and 14. Referring now to FIG. 5, in some embodiments, the CVT 10 is provided with a shaft 1 that is arranged along the longitudinal axis. A thrust bearing assembly 12 is operably coupled to the shaft 1 1 . In some embodiments, the CVT 10 is adapted to receive a rotational input power on a first cam driver 13. The first cam driver 13 is coupled to a first array of ball cam bearings 14. The first array of ball cam bearings 14 are configured to cooperate with a number ramped surfaces provided on the first cam driver 13 and/or a first traction ring 15 to provide torque dependent axial force, sometimes referred to as "clamping force", "clamping", or "axial clamp force". The first traction ring 15 is in contact with a number of balls 1 . In some embodiments, the CVT 10 is provided with a second traction ring 16 in contact with the balls 1. The second traction ring 16 is coupled to a second array of ball cam bearings 17. The ball cam bearings 17 are configured to cooperate with a number of ramped surfaces provided on the second traction ring 16 and/or a second cam driver 18. The second cam driver 18 is coupled to the shaft 1 1. In some embodiments, the second cam driver 18 is coupled to the shaft 1 1 with a set of splines. The shaft 1 1 is adapted to transmit a power output from the CVT 10. In some embodiments, the balls 1 are operably coupled to a carrier assembly 19. The carrier assembly 19 is provided with a first carrier member 20 and a second carrier member 21. The carrier assembly 19 is coaxial with the shaft 1 1. In some embodiments, the carrier assembly 19 is operably coupled to the shaft 1 1 with a bearing, a bushing, or some other means of rotatable coupling.

Passing now to FIGS. 6-8, in some embodiments, the thrust bearing assembly 12 is provided with a thrust bearing nut 25. The thrust bearing nut 25 is coupled to the shaft 1 1 with a threaded portion 26. In some embodiments, the threaded portion 26 is on the radially inner surface of the thrust bearing nut 25. In some embodiments, the threaded portion 26 provides a piloting surface for alignment of the thrust bearing assembly 12 with respect to the shaft 1 1. The thrust bearing nut 25 is coupled to an array of thrust bearing balls 27. The thrust bearing balls 27 are configured to couple to an outer bearing race 28. In some embodiments, the outer bearing race 28 is integral to the thrust bearing nut 25. In some embodiments, the outer bearing race 28 is located radially outward with respect to the threaded portion 26. The thrust bearing assembly 12 includes an inner thrust bearing race member 29. The inner thrust bearing race member 29 is operably coupled to the first cam driver 13. In some embodiments, a preload spring 30 is coupled to the first cam driver 13 and the inner thrust bearing race member 29. In some embodiments, the inner thrust bearing race member 29 includes an inner bearing race 31 adapted to couple to the thrust bearing balls 27. In some embodiments, the inner thrust bearing race member 29 is located on an opposite side of the thrust bearing nut 25 with respect to the thrust bearing balls 27. For example, the inner bearing race 31 and the outer bearing race 28 contact opposite surfaces of the thrust bearing balls 27.

The inner thrust bearing race member 29 is provided with an extension portion 32 configured to surround the thrust bearing nut 25. In some

embodiments, the extension portion 32 is an annular ring located radially outward of the inner bearing race 31 on the inner thrust bearing member 29. The extension portion 32 extends axially toward the thrust bearing nut 25. In some embodiments, the extension portion 32 is sized to substantially surround the radial periphery of the thrust bearing nut 25. During operation of the CVT 10, the extension portion 32 provides blockage to a fluid path through the thrust bearing assembly 12. Using accepted bearing-industry rating calculations contained in ISO-281 , a life prediction for this bearing location cannot be calculated due to the low viscosity of traction fluid and the zero- and very low- speed conditions inherent with 1 :1 speed ratio of the CVT 10. To overcome this situation, the extension portion 32 is provided to limit lube flow out of thrust bearing assembly 12, thus resulting in a flooded bearing space. In some embodiments of the thrust bearing assembly 12, a shallow angle angular contact ball bearing is used to allow for standard raceway processing, therefore, lowering cost. Improvements in axial packaging are possible when the raceways 28, 31 are integrated into the thrust bearing nut 25 and the first cam driver 3.

Referring now to FIG. 7, and still referring to FIGS. 6 and 8, in some embodiments, an anti-rotation washer 33 is coupled to the thrust bearing nut 25. The anti-rotation washer 33 includes a protrusion 34 that couples to a set of holes 35 formed in the thrust bearing nut 25. The protrusion 34 is optionally a cylinder-like body configured to fit within one of the holes 35. In some embodiments, the protrusion 34 is sized to be approximately the diameter of one of the holes 35. In some embodiments, the anti-rotation washer 33 is radially located on the shaft 1 1. In some embodiments, the anti-rotation washer 33 has an inner bore that the shaft 11 fits through and the inner bore of the anti-rotation washer 33 is provided with a set of splines configured to couple to mating splines formed on the shaft 11. In some embodiments, the anti-rotation washer 33 is coupled to the shaft 1 1 with a c-clip 36.

Referring now to FIGS. 9 and 10, in some embodiments the shaft 1 1 and the carrier assembly 19 are configured to facilitate flow of fluid, such as traction fluid, through the CVT 10 to provide lubrication and cooling, among other purposes. In some embodiments, the shaft 11 is provided with a hollow central passage 37. The hollow central passage 37 is in fluid communication with a source of pressurized fluid from a pump, for example.

The shaft 11 is provided with a thrust bearing lube port 38 aligned axially to the thrust bearing assembly 12. In some embodiments, the thrust bearing lube port 38 is a drilled radial hole arranged between the hollow central passage 37 and an outer periphery of the shaft 1 1. The shaft 11 is provided with a first carrier member lube port 39 arranged in proximity to the first carrier member 20. In some embodiments, the first carrier member lube port 39 is a drilled hole arranged between the hollow central passage 37 and the outer periphery of the shaft 1 1. The shaft 1 1 is provided with an idler assembly lube port 40 arranged in proximity to the idler assembly 4, for example. In some embodiments, the idler assembly lube port 40 is a radial hole arranged between the hollow central passage 37 and the outer periphery of the shaft 1 1. The shaft 11 is provided with a second carrier member lube port 41 arranged in proximity to the second carrier member 21. In some embodiments, the second carrier member lube port 41 is a radial hole drilled between the hollow central passage 37 and the outer periphery of the shaft 11.

The first carrier member 20 is provided with a first array of radial lubricant passages 42. In some embodiments, the first array of radial lubricant passages 42 are arranged so that one of the radial lubricant passages 42 is between each ball 1. For example, a CVT having six balls is provided with six radial lubricant passages. The second carrier member 21 is provided with a second array of radial lubricant passages 43. In some embodiments, the second array of radial lubricant passages 42 are arranged between each ball 1 in a similar manner as the first array of radial lubricant passages 42. The first array of radial lubricant passages 42 and the second array of radial lubricant passages 43 are arranged to be in fluid communication with the first carrier member lube port 39 and the second carrier member lube port 41 , respectively. In some embodiments, the first carrier member 20 is provided with a first array of orifice lube passages 44. The first array of orifice lube passages 44 are in fluid communication with the first array of radial lubricant passages 42.

Each of the first array of orifice lube passages 44 is located between each ball 1. Each of the first array of orifice lube passages 44 are located radially outward of each of the first array of radial lubricant passages 42. In some embodiments, the second carrier member 21 is provided with a second array of orifice lube passages 45. The second array of orifice lube passages

45 are in fluid communication with the second array of radial lubricant passages 43. Each of the second array of orifice lube passages 45 is located between each ball 1. Each of the second array of orifice lube passages 45 are located radially outward of each of the second array of radial lubricant passages 43. In some embodiments, the first array of orifice lube passages 43 and the second array of orifice lube passages 45 are configured to supply a metered flow of fluid to an array of input traction ring orifice plugs 46 and an array of output traction ring orifice plugs 47. The input traction ring orifice plugs

46 and the output traction ring orifice plugs 47 are arranged to spray fluid at the contacting location between the balls 1 and the first traction ring 15 and the second traction ring 16.

Turning now to FIGS. 1 1 -13, and still referring to FIG. 5, in some embodiments, the first cam driver 13 is a substantially disc shaped body having an inner bore 50. The first cam driver 13 is provided with a splined ring 51 positioned between the inner bore 50 and an outer periphery of the disc shaped body. In some embodiments, the inner bore 50 is configured to be a bearing race adapted to receive a needle bearing or bushing, for example, which is piloted radially and operab!y coupled to the first carrier member 20₌ The splined ring 51 is configured to couple to a source of rotational power. In some embodiments, the splined ring 51 is provided with a number of raised piloting surfaces 49 located radially inward of the splined ring 51 . The raised piloting surfaces 49 provide an alignment feature to the thrust bearing assembly 12. In some embodiments, the raised piloting surfaces 49 are adapted to receive the inner thrust bearing race member 29.

In some embodiments, the first cam driver 13 is provided with an array of ramped surfaces 52 located radially about an outer periphery of the disc shaped body. The ramped surfaces 52 are coupled to the first array of ball cam bearings 14, for example, and provide a means to produce an axial force during operation of the CVT 10. In some embodiments, each of the ramped surfaces 52 are formed adjacent to each other so that the ramped surfaces 52 connect at the crest of each ramp. By connecting ramp crests, the cam ball bearings 14 are able to roll on the ramped surface to the crest and down into the next adjacent ramped surface 52, all the while ensuring radial location of the cam ball bearings 14. This operating condition is sometimes referred to as "cam-hop". In some embodiments, the first cam driver 13 is provided with a ridge 53 coaxially aligned with the splined ring 51 . The ridge 53 is formed on a common side with the ramped surfaces 52. The splined ring 51 is formed on an opposite side of the disc shaped body from the ridge 53. In some

embodiments, the first cam driver 13 is provided with a number of radial legs 54 positioned between the inner bore 50 and the ridge 53. The radial legs 54 and the ridge 53 guide the strain in the first cam driver 13 during operation of the CVT 10. For example, the strain or deflection, in the first cam driver 13 is controlled by the positioning of the ridge 53 with respect to the splined ring 51 and the inner bore 50.

Turning now to FIGS. 14-16, in some embodiments, a continuously variable transmission (CVT) 55 is provided with a shaft 56, a first carrier member 57, and a second carrier member 58. For description purposes, only the differences between the CVT 10 and the CVT 55 will be addressed. In some embodiments, the CVT 55 is provided with a first cam driver 59 adapted to receive a first power. In some embodiments, the CVT 55 is provided with a carrier bearing hub 60. The carrier bearing hub 60 is coupled to the shaft 56 with a bearing 61 , for example. In some embodiments, the carrier bearing hub 60 is coupled to the first cam driver 59 with a need bearing 62, for example. The carrier bearing hub 60 is coupled to an inner bore of the first carrier member 57. In some embodiments, the carrier bearing hub 60 is a different material than the first carrier member 57.

Referring now FIGS. 17-20, in some embodiments, the CVT 10 is provided with a shift stop pin 65 fixedly coupled to the first carrier member 20. In some embodiments, the shift stop pin 65 is a common dowel pin having a cylindrical shape. The second carrier member 21 has a pocket 66 recessed into the second carrier member 21 and adapted to receive the shift stop pin 65. The pocket 66 has a first stop face 67 at one end of the pocket 66, and a second stop face 68 at an opposite end of the pocket 66. During operation of the CVT 10, a relative rotation of the first carrier member 20 with respect to the second carrier member 21 , or vice versa, corresponds to a change in the operating condition of the CVT 10. The first stop face 67 and the second stop face 68 provide a physical limitation to the relative rotation of the first carrier member 20 to the second carrier member 21 to thereby limit the operating speed ratio range of the CVT 10.

Referring now to FIG. 21 , and returning to FIGS. 1 1 -13, in some embodiments, a crest 70 is formed between two adjacent ramped surfaces 52 (labeled as "52A" and "52B" in FIG. 21). During operation of the CVT 10, the ball cam bearing 14 contacts the ramped surface 52. The contacting location between the ball cam bearing 14 and the ramped surface 52 is an elliptical shape, referred to herein as the "contact ellipse". During peak load operation, the contact ellipse of the ball cam bearing 14 to the ramped surface 52 is smaller than the width of the crest to thereby lower contact pressure or stress at the crest 52. For example, the contact stress on the ball cam bearing 14 at the crest 70 is less than the contact stress on the ball cam bearing 14 when on either the ramped surface 52A or the ramped surface 52B. The crest 70 facilitates a transition from the ramped surface 52A to the ramped surface 52B within the stress limits of the materials selected for the ball cam bearing 14 and the ramped surface 52. It should be noted that the description above has provided dimensions for certain components or subassemblies. The mentioned dimensions, or ranges of dimensions, are provided in order to comply as best as possible with certain legal requirements, such as best mode. However, the scope of the embodiments described herein are to be determined solely by the language of the claims, and consequently, none of the mentioned dimensions is to be considered limiting on the inventive embodiments, except in so far as any one claim makes a specified dimension, or range of thereof, a feature of the claim.

The foregoing description details certain embodiments. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the preferred embodiments can be practiced in many ways. As is also stated above, it should be noted that the use of particular terminology when describing certain features or aspects of the preferred embodiments should not be taken to imply that the terminology is being re-defined herein to be restricted to including any specific characteristics of the features or aspects of the preferred

embodiments with which that terminology is associated.

While preferred embodiments have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the preferred embodiments. It should be understood that various alternatives to the embodiments described herein may be employed in practice. It is intended that the following claims define the scope of the preferred embodiments and that methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims

WHAT IS CLAIMED IS:

1. A continuously variable transmission (CVT) having a plurality of balls, each ball having a tiltable axis of rotation, each ball in contact with a first traction ring and a second traction ring, the CVT comprising:

a rotatable shaft aligned along a longitudinal axis of the CVT, the shaft positioned radially inward of the balls, the first traction ring, and the second traction ring;

a carrier assembly operably coupled to each ball, the carrier assembly comprising:

a first carrier member arranged coaxial to the shaft, and

a second carrier member operably coupled to the first carrier member, the second carrier member configured to rotate relative to the first carrier member and arranged coaxial to the shaft;

a first cam driver operably coupled to the first traction ring and the first carrier member, the first cam driver adapted to receive a rotational power; and a thrust bearing assembly coupled to the cam driver and to the shaft.

2. The CVT of Claim 1 , wherein the thrust bearing assembly further comprises:

a thrust bearing nut coupled to the shaft, the thrust bearing nut having an outer bearing race;

a plurality of thrust bearing balls in contact with the outer bearing race; and

an inner thrust bearing race member in contact with the plurality of thrust bearing balls and coupled to the first cam driver,

wherein the inner thrust bearing race member is provided with an extension portion arranged to surround a portion of the thrust bearing nut. 3. The CVT of Claim 2, wherein the thrust bearing assembly further comprises an anti-rotation washer coupled to the thrust bearing nut and the shaft, wherein the anti-rotation washer is provided with a protrusion configured to couple to a hole in the thrust bearing nut.

4. The CVT of Claim 1 , wherein the shaft further comprises:

a hollow central passage positioned axially along the shaft;

a thrust bearing lube port aligned axially with the thrust bearing assembly, the thrust bearing lube port is a radial hole connected to the hollow central passage and an outer periphery of the shaft;

a first carrier member lube port aligned axially with the first carrier member, the first carrier member lube port is a radial hole connected to the hollow central passage and the outer periphery of the shaft;

an idler assembly lube port arranged aligned axially with an idler assembly of the CVT, wherein the idler assembly lube port is a radial hole connected to the hollow central passage and the outer periphery of the shaft; and

a second carrier member lube port aligned axially with the second carrier member, wherein the second carrier member lube port is a radial hole connected to the hollow central passage and the outer periphery of the shaft.

5. The CVT of Claim 4, wherein the first carrier member is provided with a first array of radial lubricant passages, wherein each of the radial lubricant passages is in fluid communication with the first carrier member lube port, and wherein each of the radial lubricant passages is located between adjacent balls.

6. The CVT of Claim 5, wherein the second carrier member is provided with a second array of radial lubricant passages, wherein each of radial lubricant passages is in fluid communication with the second carrier member lube port, and wherein each of the radial lubricant passages is located between adjacent balls.

7. The CVT of Claim 6, wherein the first carrier member further comprises a first array of orifice lube passages in contact with the first array of radial lubricant passages, wherein each of the orifice lube passages is provided with at least one orifice arranged to spray a lubricant onto a contact location between the ball and the first traction ring.

8. The CVT of Claim 7, wherein the second carrier member further comprises a second array of orifice lube passages in contact with the second array of radial lubricant passages, wherein each of the orifice lube passages is provided with at least one orifice arranged to spray a lubricant onto a contact location between the ball and the second traction ring.

9. The CVT of Claim 1 , wherein the first cam driver further comprises:

a disc shaped body having an inner bore, wherein the inner bore is radially piloted by, and operably coupled to, the first carrier member;

a splined ring extending from the disc shaped body, the splined ring positioned between the inner bore and an outer periphery of the disc shaped body;

a plurality of raised piloting surfaces extending radially inward from the splined ring, the plurality of raised piloting surfaces configured to align the thrust bearing assembly;

a plurality of ramped surfaces located on the outer periphery of the disc shaped body, wherein adjacent ramped surfaces connect at a crest;

a ridge aligned with the splined ring, the ridge formed on an opposite side of the disc shaped body from the splined ring; and

a plurality of radial legs extending from the inner bore to the ridge.

10. The CVT of Claim 1 , wherein the carrier assembly further comprises a carrier bearing hub coupled to the first carrier member and operably coupled to the first cam driver and the shaft. 1. The CVT of Claim 1 , wherein the carrier assembly further comprises a shift stop pin coupled to the first carrier member, wherein the second carrier member is provided with a pocket adapted to receive the shift stop pin, the pocket having a first stop face at one end and a second stop face at a distal end.

12. The CVT of claim 2 wherein the thrust bearing assembly further comprises a spring operably coupled to the inner thrust bearing race member and coupled to the first cam driver.

13. The CVT of claim 9, wherein the position of the ridge controls strain in the disc shaped body during operation of the CVT.