WO2019209299A1

WO2019209299A1 - Continuously variable transmission snubber assembly

Info

Publication number: WO2019209299A1
Application number: PCT/US2018/029539
Authority: WO
Inventors: Joseph P. GOODSELL; Sean Simmons; James R. CAPP
Original assignee: Borgwarner, Inc.
Priority date: 2018-04-26
Filing date: 2018-04-26
Publication date: 2019-10-31

Abstract

A snubber assembly for guiding a chain in a continuously variable transmission (CVT) includes a friction element formed from a first material, including a first pad having a surface that faces a first side of the chain and a second pad having a surface that faces a second side of the chain! a friction element spacer, connecting the first pad and the second pad, that supports the first pad and the second pad on opposite sides of the chain! a support element formed from a second material including a first flange that engages the first pad of the friction element and a second flange that engages the second pad of the friction element! and a support element spacer, connecting the first flange and the second flange, that supports the first pad and the second pad.

Description

CONTINUOUSLY VARIABLE TRANSMISSION SNUBBER ASSEMBLY

TECHNICAL FIELD

The present application relates to continuously variable transmissions (CVTs) and, more particularly, to snubbers used with CVTs.

BACKGROUND

A wide assortment of vehicles use CVTs to transfer power from the output of an engine to a mechanism that propels the vehicle. In one example, some automobiles use CVTs to transfer the rotational force generated by the output of an internal combustion engine (ICE) into rotational force that drives one or more wheels of the automobile at a continuously variable gear ratio between an input shaft and an output shaft. CVTs can be implemented in a number of ways. For example, a CVT can include an input pulley attached to the input shaft and an output pulley attached to an output shaft. The input pulley and the output pulley can each include a sheave with sides that slide axially relative to each other and change the diameter of the pulley. An endless loop, such as a chain or belt, can link the input pulley to the output pulley and as the sides of the sheaves slide axially, the effective gear ratio of the input shaft relative to the output shaft can change.

As the input pulley rotates and communicates rotational force to the output pulley via the endless loop, a CVT can experience some amount of noise, vibration, and harshness (NVH) in a variety of ways. For example, as the diameter of the pulleys change, a portion of the endless loop located between the input pulley and the output pulley can unnecessarily oscillate and impute NVH to the CVT. This oscillation of the endless loop can be reduced using a snubber that reduces the oscillating motion of the endless loop. However, improving NVH reduction performance can be challenging. For instance, an improvement in NVH reduction of the snubber may involve increasing the amount of material used to create the snubber. But increasing material quantity can increase the cost of manufacturing the snubber. It would be helpful to increase the NVH performance of the snubber without also increasing the quantity of material used to create each snubber.

SUMMARY

In one embodiment, a snubber assembly for guiding a chain in a CVT includes a friction element formed from a first material, including a first pad having a surface that faces a first side of the chain and a second pad having a surface that faces a second side of the chain! a friction element spacer, connecting the first pad and the second pad, that supports the first pad and the second pad on opposite sides of the chain! a support element formed from a second material including a first flange that engages the first pad of the friction element and a second flange that engages the second pad of the friction element! and a support element spacer, connecting the first flange and the second flange, that supports the first pad and the second pad.

In another embodiment, a snubber assembly for guiding a chain in a CVT includes a friction element formed from a first material, including a first pad having a surface that faces the chain and a second pad having a surface that faces the chain! a support element formed from a second material including a first flange that engages the first pad of the friction element and a second flange that engages the second pad of the friction element! a support element spacer, connecting the first flange and the second flange, that supports the first pad and the second pad! and one or more alignment features, wherein one portion of the alignment feature is included with the friction element and another portion of the alignment feature is included with the support element.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view depicting an implementation of a CVT including a snubber assembly! Figure 2 is a profile view depicting an implementation of a CVT including a snubber assembly!

Figure 3 is another profile view depicting an implementation of a CVT including a snubber assembly!

Figure 4 is a perspective view depicting an implementation of a snubber assembly used with a CVT!

Figure 5 is another perspective view depicting an implementation of a snubber assembly used with a CVT! and

Figure 6 is an exploded perspective view depicting an implementation of a snubber assembly used with a CVT.

DETAILED DESCRIPTION

A snubber assembly used with an endless loop of a continuously variable transmission (CVT) includes a friction element formed from a first material and a support element formed from a second material. When combined, the friction element can provide a sliding surface that contacts the endless loop, such as a CVT chain or belt, while the support element engages the friction element to provide additional stiffness and/or rigidity to the assembly. Together, the friction element and the support element can confine the endless loop within a chain path to prevent oscillation or other unwanted movement that creates noise, vibration, and harshness (NVH).

In the past, snubbers have been made from two identically-shaped and formed components made from the same material that mate together along matching surfaces. These identically-constructed components may share a common part number rather than using differently-constructed components in an effort to reduce cost. In assemblies that incorporate these identically- shaped components, each component is made from the same material and includes a friction surface that contacts an endless loop. The two identically-shaped components join via vertically-oriented surfaces to surround the chain with each of the components providing a friction surface. However, the side-byside mating of identically constructed components comprising the same material may not optimally reduce NVH.

In contrast, the snubber assembly disclosed herein includes a friction element providing a unitary friction surface formed from a first type of material, such as a non-glass reinforced polymer. The first material can be optimized for its ability to minimize friction with respect to the chain operation yet remain durable in the face of extended chain operation. However, the qualities that make the first material desirable for minimizing friction and durability may not also be optimal for reducing NVH. For example, an increase in the reduction of NVH abatement may correspond to an increase in the stiffness of the snubber assembly. But increasing stiffness often involves increasing the amount of material use. Or selecting a different material may increase stiffness yet increase friction and/or decrease durability in response to chain abrasion. NVH may be more effectively reduced by a snubber assembly that uses a friction element comprising a first material that provides an uninterrupted and unitary surface for the chain to slidably contact that is combined with a support element comprising a second material that engages the friction element and increases the stiffness of the assembly.

Turning to FIGS. 1-3, an implementation of a continuously variable transmission (CVT) 10 including a CVT chain 12 and a snubber assembly 14 is shown. CV s can be used in a variety of applications including the transmission of power from an internal combustion engine (ICE) to an output shaft. Vehicles commonly uses CV s to transmit power from an output shaft of an internal combustion engine to the wheels propelling the vehicle. The CVT 10 includes an input pulley 16 attached to an input shaft 18 and an output pulley 20 attached to an output shaft 22. The input pulley 16 can include an input sheave with sheave sides 24 that slide axially relative to each other and the input shaft 18 along the axis of input shaft rotation to change the diameter of the input pulley 16. The output pulley 20 can be implemented in a similar way with an output sheave having sheave sides 26 that slide axially relative to each other and the output shaft 22 along the axis of output shaft rotation. An endless loop, such as a chain or belt, can link the input pulley to the output pulley. In this implementation the endless loop will be described with respect to the CVT chain 12. As the sides of the sheaves 24, 26 slide axially, the effective gear ratio of the input shaft 18 relative to the output shaft 20 can change.

The snubber assembly 14 is assembled to encircle or encapsulate the CVT chain 16 as it passes through a chain path 28 and attach to a movable pivot 30 on the CVT 10. The snubber assembly 14 includes a friction element 32 and a support element 34 that are securely attached to each other using one or more attachment features 36 shown in FIGS. 4-6. The support element 34 can include a pivoting slot 38 that engages with the movable pivot 30 and permits the assembly 14 to move in response to a change in profile shape of the CVT chain 12 as would occur when the diameter of the input pulley 16 and output pulley 20 changes. The friction element 32 can be secured to the CVT 10 by virtue of its attachment to the support element 34 via attachment feature(s) 36. When attached to the support element 34, the friction element 32 is positioned so that a surface of the friction element 32 faces the CVT chain 12. The support element 34 of the snubber assembly 14 can then be secured to the CVT 10 so that it engages the pivot 30 through the pivoting slot 38 of the support element 34 on an opposite side of the CVT chain 12. The support element 34 is positioned so that a portion of the support element 34 engages an outer surface of the friction element 32 and mates with the attachment feature(s) 36 to provide support to the friction element 32. The pivoting slot 38 included with the support element 34 permits the snubber assembly 16 to rotate about the pivot 30 as well as move nearer and farther from the input shaft 18 and/or output shaft 20 as the diameters of the sheaves 24, 26 change.

For example, the input pulley 16 is shown in FIG. 1 with its sheave sides 24 spaced nearest each other along the axis of rotation of the input pulley 16. The decreased length of axial distance between the sheave sides 24 increases the diameter (di) of the input pulley 16 causing the input pulley 16 to engage a greater length of the CVT chain 12 than if the sheave sides 24 were farther apart. The decreased axial distance between the sheave sides 24 of the input pulley 16 corresponds to an increased axial distance between the sheave sides 26 of the output pulley 20 and causes the output pulley 20 to have a reduced diameter (do) to engage a smaller length of the CVT chain 12 than the input pulley 16. When the sheaves 24, 26 are so positioned, the input pulley 16 may rotate at an angular velocity that is slower than the angular velocity at which the output pulley 20 rotates. Conversely, the sheave sides 24 of the input pulley 16 can be moved apart such that the axial distance between the sheave sides 24 along the input shaft axis of rotation increases. Positioning the sheave sides 24 in this way can decrease the diameter of the input pulley 16 causing the input pulley 16 to engage a smaller length of the CVT chain 12. The sheave sides 26 of the output pulley 18 can move axially about the axis of output shaft rotation to increase the diameter of the output pulley 20. The output pulley 20 then engages a greater length of the CVT chain 12. The output pulley 20 may then rotate at an angular velocity that is slower than the angular velocity at which the input pulley 16 rotates. As the sheave sides 24, 26 move, the snubber assembly 14 can rotate about the CVT pivot 30 as well as move linearly but constrained by the pivoting slot 38 to move closer to or further away from a baseline (b). The baseline (b) can be measured by drawing a chord between the axis of rotation of the input shaft 18 and the axis of rotation of the output shaft 22.

FIGS. 4-6 depict the snubber assembly 16 in more detail. The snubber assembly 16 includes the friction element 32, the support element 34, and the pivoting slot 38. The friction element 32 engages with the support element 34 to orient the friction element 32 relative to the support element 34 at a predetermined spatial orientation that can be governed via one or more alignment features 42. And the orientation of the friction element 32 relative to the support element 34 can be achieved and maintained using the one or more attachment features 42. The friction element 32 is formed from the first material and includes a first pad 44 having a surface 46 that faces the CVT chain 12 and a second pad 48 having a surface 50 that faces the CVT chain 12. The first pad 44 and the second pad 48 may be elongated elements each having a substantially planar surface 46, 50 that faces opposite sides of the CVT chain 12. The first pad 44 and the second pad 48 can be connected by a friction element spacer 52 that supports the first pad 44 and the second pad 48 and positions the first pad 44 and the second pad 48 so that the surface 46 of the first pad 44 faces one side of the CVT chain 12 and the surface 50 of the second pad 48 faces another side of the CVT chain 12. The friction element spacer 52 can also include a surface 54 that faces a pin side 56 of the CVT chain 12 and partially defines the chain path 28 through which the CVT chain 12 passes. The surface 54 of the friction element spacer 52 can make contact with the CVT chain 12 and assist in reducing NVH during transmission operation. With respect to sides of the CVT chain 12, the CVT chain 12 includes four sides— two pin sides 56 and two link sides 58 shown in FIG. 1. The link sides 58 of the CVT chain 12 can refer to the top of the CVT chain 12 and the bottom of the CVT chain 12 such that the top and bottom of the chain 12 solely exposes the links in the CVT chain 12 to the surface 46 of the first pad 44 and the surface 50 of the second pad 48 rather than pins. The pin sides 56 of the CVT chain 12 refer to the side of the chain that exposes the pivot and/or the pivot is perpendicular to.

The support element 34 is formed from a second material that is different from the material used to form the friction element 32. The support element 34 can be made from a material that provides an increased level of stiffness relative to the material used to form the friction element 32. The material used for the support element 34 can be a glass-reinforced polymer and the glass content of the polymer can be varied to change the performance characteristics of the snubber assembly 14. The support element 34 includes a first flange 58 that engages the first pad 44 of the friction element 32 and a second flange 60 that engages the second pad 48 of the friction element 32. The first flange 58 and the second flange 60 can be formed to at least partially conform to the shape of the first pad 44 and second pad 48 of the friction element 32, respectively, so that at least a portion of a surface 62 of the first flange 58 abuts and supports an outer surface 64 of the first pad 44 and at least a portion of a surface 66 of the second flange 60 abuts and supports the second pad 48. The first flange 58 is located radially outward from to the first pad 44 relative to the CVT chain 12 and the second flange 60 is located radially outward from the second pad 48 relative to the CVT chain 12. A support element spacer 68 connects the first flange 58 and the second flange 60 supporting the first pad 44 and the second pad 48 as well as adding stiffness to the friction element 32. The support element spacer 68 can also include a surface 70 that faces a pin side 56 of the CVT chain 12 and partially defines the chain path 28 through which the CVT chain 12 passes. The surface 54 of the friction element spacer 52 can make contact with the CVT chain 12 and assist in reducing NVH during transmission operation. The surface 70 of the support element spacer 68 can face the surface 54 of the friction element spacer 52. The snubber assembly 14 includes the surfaces 46, 50 of the first pad 44 and the second pad 48 along with the surface 54 of the friction element spacer 52 and the surface 70 of the support element spacer 68 that confine the radial displacement of the CVT chain 12 as it passes through the snubber assembly 14.

In this implementation, the friction element 32, including the first pad 44, the second pad 48, and the friction element spacer 52 can be formed entirely from a first material that facilitates chain motion against it such that the friction element 32 comprises a homogeneous material. And the support element 34 including the first flange 58, the second flange 60, and the pivoting slot 38 is formed entirely from a second material, that is homogeneous and is relatively stiffer than the first material. However, in other implementations it should be appreciated portions of the support element 34 could be formed from both the first material and the second material. For example, the pivoting slot 38 could be made from the first, relatively more pliable material whereas the first flange 58 and the second flange 60 could be formed from the second material. The first material can be implemented using a non-glass-reinforced polymer. Examples of non-glass-reinforced polymers include Nylon, such as PA6, Nylon, PA46 Nylon, or PA66 Nylon. The second material could be a metal or metal alloy or a glass- filled or glass-reinforced polymer. For example, the support element 34 could be stamped from a second material comprising steel or aluminum alloy. Or the second material could be any one of the varieties of Nylon identified above combined with glass reinforcement. The relative glass content amount of the second material can be increased or decreased to change the overall stiffness of the snubber assembly 14. Table 1 below depicts the relative stiffness of glass- reinforced polymer relative to non-glass reinforced polymer. The non-glass reinforced polymer is PA66 Nylon and the glass-reinforced polymer is PA66 Nylon with varying amounts of glass content. The increase in glass content corresponds to different increases in secant modulus and stiffness ratio values measured at a temperature of 80°C.

Table 1

The friction element 32 can include one or more attachment features 36, alignment features 42, or both attachment features 36 and alignment features 42 that are configured to mate or engage the friction element 32 with the support element 34. In this implementation, the alignment features 36 include tapered projections 72 that fit with similarly shaped recesses 74 to form a mortise and tenon joint between the friction element 32 and the supporting element 34. The friction element 32 includes the tapered projections 72 that extend radially outwardly from the outer surface of the friction element 32 in a direction extending away from the CVT chain 12. However, it should be appreciated that other implementations of alignment features are possible. In addition, the friction element 32 and the support element 34 can be secured to each other using a deflectable member 76 and an engaging receptacle 78 that comprise the attachment feature 36. The deflectable member 76 can extend outwardly from the first pad 44. The engaging receptacle 78 can be a slot included in the support element spacer 68 having a defined width and height such that when the deflectable member 76 is inserted into the slot one or more elements deflect from a resting position against a surface of the slot allowing the member 76 to slide into the slot. When the deflectable member 76 is inserted a particular distance, the deflectable member 76 returns to its resting position and engages a surface of the support element spacer 68. After engaging the support element 34, the deflectable member 76 prevents movement of the friction element 32 relative to the support element 34. It is to be understood that the foregoing is a description of one or more embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims. As used in this specification and claims, the terms“e.g.”“for example,”

“for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open- ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.

Claims

What is claimed is:

1. A snubber assembly for guiding a chain in a continuously variable transmission (CVT), comprising:

a friction element formed from a first material, including a first pad having a surface that faces a first side of the chain and a second pad having a surface that faces a second side of the chain!

a friction element spacer, connecting the first pad and the second pad, that supports the first pad and the second pad on opposite sides of the chain!

a support element formed from a second material including a first flange that engages the first pad of the friction element and a second flange that engages the second pad of the friction element! and

a support element spacer, connecting the first flange and the second flange, that supports the first pad and the second pad.

2. The snubber assembly recited in claim 1, wherein the first material comprises a non- glass -filled polymer.

3. The snubber assembly recited in claim 2, wherein the non-glass filled polymer comprises nylon.

4. The snubber assembly recited in claim 2, wherein the non-glass filled polymer comprises nylon 46.

5. The snubber assembly recited in claim 1, wherein the second material comprises a glass-filled polymer.

6. The snubber assembly recited in claim 5, wherein the glass-filled polymer comprises glass -filled nylon.

7. The snubber assembly recited in claim 1, wherein the second material comprises metal or metal alloy.

8. The snubber assembly recited in claim 1, wherein the friction element comprises a different shape than the support element.

9. The snubber assembly recited in claim 1, wherein further comprising a pivoting slot configured to slidably engage a pivot of the CVT and permit the snubber assembly to move in response to a change in pulley diameter of sheaves used with the CVT.

10. The snubber assembly recited in claim 1, wherein the first pad, the second pad, the friction element spacer, and the support element spacer define a chain path through which the chain passes.

11. The snubber assembly recited in claim 1, wherein the first pad is radially closer to the chain than the first flange or the second pad is radially closer to the chain relative to the second flange.

12. A snubber assembly for guiding a chain in a continuously variable transmission (CVT), comprising:

a friction element formed from a first material, including a first pad having a surface that faces the chain and a second pad having a surface that faces the chain!

a support element formed from a second material including a first flange that engages the first pad of the friction element and a second flange that engages the second pad of the friction element!

a support element spacer, connecting the first flange and the second flange, that supports the first pad and the second pad! and

one or more alignment features, wherein one portion of the alignment feature is included with the friction element and another portion of the alignment feature is included with the support element.

13. The snubber assembly recited in claim 12, wherein the first material comprises a non- glass -filled polymer.

14. The snubber assembly recited in claim 13, wherein the non-glass filled polymer comprises nylon.

15. The snubber assembly recited in claim 12, wherein the second material comprises a glass-filled polymer.

16. The snubber assembly recited in claim 15, wherein the glass-filled polymer comprises glass-filled nylon.

17. The snubber assembly recited in claim 12, wherein the second material comprises metal or metal alloy.

18. The snubber assembly recited in claim 12, wherein one portion of the alignment feature comprises a tapered projection and the other portion comprises a tapered recess.

19. The snubber assembly recited in claim 12, wherein further comprising a pivoting slot configured to slidably engage a pivot of the CVT and permit the snubber assembly to move in response to a change in pulley diameter of sheaves used with the CVT.