WO2018218026A1

WO2018218026A1 - Torque splitting device for use with a ball variator continuously variable transmission

Info

Publication number: WO2018218026A1
Application number: PCT/US2018/034400
Authority: WO
Inventors: Charles B. Lohr
Original assignee: Dana Limited
Priority date: 2017-05-25
Filing date: 2018-05-24
Publication date: 2018-11-29

Abstract

Provided herein is a powersplit variator provided with a variator having a number of balls in contact with a first traction ring assembly and a second traction ring assembly, each provided with an axial force generator that provides torque dependent axial force. The powersplit variator is provided with a traction planetary set having a number of traction planets in contact with an inner race and an outer race. The traction planets are operably coupled to a source of input power. The inner race is operably coupled to the first traction ring assembly. The outer race is operably coupled to a rotatable shaft configured to transfer power out of the powersplit variator.

Description

TORQUE SPLITTING DEVICE FOR USE WITH A BALL VARIATOR CONTINUOUSLY VARIABLE TRANSMISSION

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 62/510,800 filed May 25, 2017, which is incorporated herein by reference in its entirety.

BACKGROUND

A driveline including a continuously variable transmission (CVT) allows an operator or a control system to vary a drive ratio in a stepless manner, permitting a power source to operate at its most advantageous rotational speed. Continuously variable transmissions (CVT) and transmissions that are substantially continuously variable are increasingly gaining acceptance in various applications. The process of controlling the ratio provided by the CVT is complicated by the continuously variable or minute gradations in ratio presented by the CVT. Furthermore, the range of ratios that are available to be implemented in a CVT are not sufficient for some applications. A transmission is capable of implementing a combination of a CVT with one or more additional CVT stages, one or more fixed ratio range splitters, or some combination thereof in order to extend the range of available ratios.

SUMMARY

Provided herein is a powersplit variator having a ball-type variator comprising a plurality of balls in contact with a first traction ring and a second traction ring, the transmission having: an input coupling operably coupleable to a source of rotational power; a traction planetary set operably coupled to the input coupling, the traction planetary set including: a plurality of traction planets, an inner race in contact with each traction planet, and an outer race in contact with each traction planet; a first axial force driver coupled to the inner race, wherein the first axial force driver is operably coupled to the first traction ring; and a second axial force driver coupled to the outer race, wherein the second axial force driver is operably coupled to the second traction ring. In some embodiments, a first axial force generator is coupled to the first traction ring and the first axial force driver.

In some embodiments, a second axial force generator is coupled to the second traction ring and the second axial force driver.

In some embodiments, the traction planets are tapered rollers.

In some embodiments, each traction planet contacts the inner race at an inner traction interface.

In some embodiments, each traction planet contacts the outer race at an outer traction interface.

In some embodiments, the traction planetary set is a fixed ratio planetary set.

In some embodiments, a rotatable shaft is coupled to the outer race and the second axial force driver.

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 embodiments are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present disclosure will be obtained by reference to the following detailed description that sets forth illustrative embodiments 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 schematic diagram of an embodiment of a torque splitting device for use with a ball variator having a traction planetary set. Figure 5 is a schematic diagram of another embodiment of a torque splitting device for use with a ball variator having a traction planetary set.

Figure 6 is a cross-sectional view of the traction planetary set depicted in Figure 4.

DETAILED DESCRIPTION

The preferred embodiments will now be described with reference to the accompanying figures, wherein like numerals refer to like elements throughout. The terminology used in the descriptions below is not to be interpreted in any limited or restrictive manner simply because it is used in conjunction with detailed descriptions of certain specific embodiments. Furthermore, the embodiments include several novel features, no single one of which is solely responsible for its desirable attributes or which is essential to practicing the embodiments described.

Provided herein are configurations of CVTs based on a ball-type variators, also known as CVPs, for continuously variable planetary. Basic concepts of a ball-type Continuously Variable Transmissions are described in United States Patent No. 8,469,856 and 8,870,711 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 in contact with the balls, an input (first) traction ring 2, an output (second) traction ring 3, and an idler (sun) assembly 4 as shown on FIG. 1. The balls 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 fixed from rotation while the second carrier member 7 is configured to rotate with respect to the first carrier member 6, 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, as illustrated in FIG. 2. The radial guide slots 8 and the radially offset guide slots 9 are adapted to guide the tiltable axles 5. The axles 5 are 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 6 and second carrier members 7 to impart a tilting of the axles 5 and thereby adjusts the speed ratio of the variator. Other types of ball CVTs also exist, but are slightly different.

The working principle of such a CVP of FIG. 1 is shown on FIG. 3. The CVP itself works with a traction fluid. The lubricant (traction fluid) 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 use and control of a variator and/or a CVT using generally spherical planets each having a tiltable axis of rotation that are 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 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.

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, bearing 1011 A and bearing 1011 B) will be referred to collectively by a single label (for example, bearing 1011).

As used here, the terms "operationally connected," "operationally coupled", "operationally linked", "operably connected", "operably coupled", "operably linked," "operably coupleable" 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 take a variety of forms, which in certain instances will be readily apparent to a person of ordinary skill in the relevant technology.

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 are typically 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 force which would be available at the interfaces of the contacting components and is the ratio of the maximum available drive torque per contact force. 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 operate in both tractive and frictional applications. For example, in the embodiment where a CVT is used for a bicycle application, the CVT operates at times as a friction drive and at other times as a traction drive, depending on the torque and speed conditions present during operation. As used herein, "creep" 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. "Creep" is

characterized by the slowing of the output because the transmitted force is stretching the fluid film in the direction of rolling. As used herein, the term "ratio droop" refers to the shift of the tilt angle of the ball axis of rotation (sometimes referred to as the ratio angle or gamma angle) due to a compliance of an associated control linkage in proportion to a control force that is in proportion to transmitted torque, wherein the compliance of the control linkage corresponds to a change in the skew angle of the ball axis of rotation. As used herein, the term "load droop" refers to any operating event that reduces the ratio of output speed to input speed as transmitted torque increases.

Referring now to FIG. 4, in some embodiments, a powersplit variator 20 includes a variator 21 having a number of balls 22 in contact with a first traction ring 23 and a second traction ring 25.

In some embodiments, the variator 21 is substantially similar to the variator described in FIGS. 1 -3.

In some embodiments, the first traction ring 23 is operably coupled to a first axial force generator 24. The second traction ring 25 is operably coupled to a second axial force generator 26.

In some embodiments, the first axial force generator 24 and the second axial force generator 26 are ball-and-cam clamping type mechanisms similar to those described in United States Patent No. 9,086, 145 and Patent Cooperation Treaty Application No. PCT/US2017/059430, which are hereby incorporated by reference. In some embodiments, the first axial force generator 24 and the second axial force generator 26 provide a torque dependent axial force between the traction rings 23, 25 and the balls 22.

In some embodiments, an input coupling 27 is operably coupled to a rotational source of power, such as an internal combustion engine or an electric motor.

The input coupling 27 is coupled to a traction planetary set 28. The traction planetary set 28 includes an array of traction planets 29 coupled to an inner race 30 at an inner traction interface 31. Each traction planet 29 is coupled to an outer race 32 at an outer traction interface 33.

In some embodiments, the inner traction interface 31 is a substantially flat interface when viewed in the plane of the page of Figure 4.

In some embodiments, the inner traction interface 31 is a conformal interface having a nested curvature.

In some embodiments, the inner traction interface 31 is a non-conformal interface having opposing convex curvatures.

In some embodiments, the input coupling 27 is operably coupled to each traction planet 29.

In some embodiments, the outer race 32 is coupled to a rotatable shaft 34 in a non-rotatable manner.

In some embodiments, the inner race 30 is operably coupled to a first axial force driver 35. The first axial force driver 35 is coupled to the first axial force generator 24.

In some embodiments, the rotatable shaft 34 is coupled to a second axial force driver 36. The second axial force driver 36 is coupled to the second axial force generator 26.

In some embodiments, the second axial force generator 26 is located between the rotatable shaft 34 and the outer race 32, in proximity to the outer race 32.

In some embodiments, the second axial force driver 36 is constrained axially by a clip 37 or similar restraint device.

In some embodiments, a power output is transmitted from the rotatable shaft 34 out of the powersplit variator 20.

During operation of the powersplit variator 20, an input power is received from a source of rotational power source (not shown) on the input coupling 27 and transmitted to the traction planetary set 28. The inner race 30 transmits a portion of the input power to the first axial force driver 35 through the inner traction interface 31. The outer race 32 transmits a portion of the input power to the rotatable shaft 34 through the outer traction interface 33.

In some embodiments, the traction planetary set 28 is a fixed ratio traction planetary set. In some embodiments, the traction planetary set 28 is designed for minimal to theoretically zero spin on the traction interfaces 31 , 33.

In some embodiments, the fixed ratio traction planetary set 28 is similar to a tapered roller thrust bearing, as depicted in FIG. 4.

When the tangents to the traction interfaces 31 , 33 between the traction planets 29 and the inner race 30 and outer races 32 cross the axis of rotation of the traction planet 29 at the same point where the axis of rotation of the traction planets 29 cross the axis or rotation of the CVP, there is zero spin at the interfaces or in other terms, zero ratio creep. For example referring to FIG. 6, a first construction line 60 depicts a tangent line to the inner traction interface 31 , and a second construction line 61 depicts a tangent line to the outer traction interface 33. A third construction line 62 depicts axis of rotation of the traction planet 29. The first construction line 60 and the second construction line 61 converge at a point 63 located on the third construction line 62.

In some embodiments, the ratio of available traction coefficients μ between the fixed ratio traction planetary 28 and variator 21 may be in the range of 1:1 to 2.5:1.

In some embodiments, the axial force that provides normal force for the variator 21 also provides normal force for the fixed ratio planetary set 28. This allows the fixed ratio planetary set 28 to be reduced in size by having a smaller traction diameter.

Turning now to FIG. 5, in some embodiments, a powersplit variator 40 includes a variator 41 having a number of balls 42 in contact with a first traction ring 43 and a second traction ring 45.

In some embodiments, the variator 41 is substantially similar to the variator described in FIGS. 1-3.

In some embodiments, the first traction ring 43 is operably coupled to a first axial force generator 44. The second traction ring 45 is operably coupled to a second axial force generator 46.

In some embodiments, the first axial force generator 44 and the second axial force generator 46 are ball-and-cam clamping type mechanisms similar to those described in United States Patent No. 9,086,145, which is hereby incorporated by reference. For example, the first axial force generator 44 and the second axial force generator 46 generally provide a torque dependent axial force between the traction rings and the balls 42.

In some embodiments, an input coupling 47 is operably coupled to a rotational source of power including, but not limited to, an internal combustion engine or an electric motor. The input coupling 47 is coupled to a traction planetary set 48. The traction planetary set 48 includes an array of traction planets 49 coupled to an inner race 50. Each traction planet 49 is coupled to an outer race 51 .

In some embodiments, the traction planet 49 has a convex curved outer surface configured to engage a concave surface of the inner race 50 also referred to as a conformal interface.

In some embodiments, the traction planet 49 has a convex curved outer surface configured to engage a concave surface of the outer race 51.

In other embodiments, the traction planet 49 has a convex curved outer surface configured to engage a convex surface of the inner race 50 also referred to as a non-conformal interface.

In other embodiments, the traction planet 49 has a convex curved outer surface configured to engage a convex surface of the outer race 51.

In some embodiments, the input coupling 47 is operably coupled to each traction planet 49.

In some embodiments, the outer race 5,1 is coupled to a rotatable shaft 52 in a non-rotatable manner.

In some embodiments, the inner race 50 is operably coupled to the first axial force generator 44.

In some embodiments, the rotatable shaft 52 is coupled to a second axial force driver 53. The second axial force driver 53 is coupled to the second axial force generator 46.

In some embodiments, a power output is transmitted from the rotatable shaft 53.

Provided herein is a variable transmission including the powersplit variators described above. Provided herein is a vehicle driveline including a power source, a variable transmission of any of described above drivingly engaged with the power source, and a vehicle output drivingly engaged with the variable transmission.

Provided herein is a vehicle including the variable transmission of any one of the transmissions described above.

Provided herein is a method including providing a variable transmission of any one of the transmissions described above.

Provided herein is a method including providing a vehicle driveline of the kind described above.

Provided herein is a method including providing a vehicle having any one of the transmission described above.

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.

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 invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the embodiments. It is intended that the following claims define the scope of the invention and that methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims

WHAT IS CLAIMED IS:

1. A powersplit variator having a ball-type variator comprising a plurality of balls in contact with a first traction ring and a second traction ring, the transmission comprising:

an input coupling operably coupleable to a source of rotational power;

a traction planetary set operably coupled to the input coupling, the traction planetary set comprising:

a plurality of traction planets,

an inner race in contact with each traction planet, and an outer race in contact with each traction planet;

a first axial force driver coupled to the inner race, wherein the first axial force driver is operably coupled to the first traction ring; and

a second axial force driver coupled to the outer race, wherein the second axial force driver is operably coupled to the second traction ring.

2. The powersplit variator of Claim , further comprising a first axial force generator coupled to the first traction ring and the first axial force driver.

3. The powersplit variator of Claim 1 , further comprising a second axial force generator coupled to the second traction ring and the second axial force driver.

4. The powersplit variator of Claim 1 , wherein the traction planets are

tapered rollers.

5. The powerspilt variator of Claim 1 , wherein each traction planet contacts the inner race at an inner traction interface.

6. The powersplit variator of Claim 1 , wherein each traction planet contacts the outer race at an outer traction interface. The powersplit variator of Claim 1 , wherein the traction planetary set is fixed ratio planetary.

The powersplit variator of Claim , further comprising a rotatable shaft coupled to the outer race and the second axial force driver.