WO2016138365A1

WO2016138365A1 - Isolator gear

Info

Publication number: WO2016138365A1
Application number: PCT/US2016/019744
Authority: WO
Inventors: Sathya Dev KONDASANI
Original assignee: Linamar Corporation
Priority date: 2015-02-26
Filing date: 2016-02-26
Publication date: 2016-09-01

Abstract

An isolator gear includes an outer gear, an Inner gear and a corrugated elastic ring disposed between internal teeth of the outer gear and external teeth of the Inner gear. In use, the inner gear external teeth engage the outer gear internal teeth via corrugated elastic the ring.

Description

ISOLATOR GEAR

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and all the benefits of U.S. Provisional Application No. 62/121,224, filed on February 26, 2015, and entitled "Isolator Gear", which is incorporated herein by reference

FIELD OF THE INVENTION

This invention relates to resilient couplings that couple a driving shaft to a driven shaft while isolating the driving shaft from vibration developed by cyclic irregularities due to eccentricities of the driven shaft.

BACKGROUND

It is known to employ an isolator gear in a gear system including a driving shaft having a driving gear coupled to a driven shaft via a driven gear. The isolator gear is used to address, for example, an imbalance in the driven system. Such an imbalance can be caused, for example, by manufacturing variability in forming the driven shaft or driven gear, and/or tolerances between the driven gear and driving gear, and can sometimes cause an eccentric motion on the gears, which in turn affects the performance of the gear system. In some cases, the effect of imbalance is a reduction in the load transmission efficiency and durability of the gear system, and increased noise levels. By employing an isolator gear in the gear system, the eccentric motion is reduced or eliminated by placement of a damping element between the gear teeth and the shaft on which it is mounted.

SUMMARY

An isolator gear system includes a driven gear assembly that includes an outer gear, an inner gear concentric with the outer gear, and an elastic member disposed between the outer gear and the inner gear. The elastic member is in the form of a corrugated elastic ring that conforms to the shape of interior teeth formed on the outer gear. The ring covers the contact surfaces of the outer gear interior teeth and stays with (e.g., moves in concert with) the outer gear. The inner gear includes external teeth that engage the interior teeth of the outer gear via the ring, whereby the inner gear floats to provide isolation between the driving shaft and the driven shaft. Advantageously, the isolator gear system is simple to manufacture to an extent that little or no experience is required to manufacture the system. In addition, the gear system has fewer parts relative to some conventional isolation gear assemblies.

The isolator gear system can be used in any gear system, but has particular advantage when used in engines that require balance shaft, or engines that cannot overcome the imbalance at crank shaft with a damper.

The isolator gear system including the corrugated elastic ring provides advantages compared to some conventional isolator gear systems, for example, those which include a spring pack 100 disposed between an inner gear 106 and an outer gear 101 such as the one shown in Figs. 1-3. The spring pack 100 is secured to an inner surface of the outer gear 101, and includes a plurality of leaf springs 105 spaced apart by stationary wedges 104. The leaf springs 105 engage external teeth 107 formed on the inner gear 106, isolating itself from the eccentric motion. The spring pack 100 is retained on the outer gear 101 via a cover 103 that is pressed into the outer gear and retained in place by a retaining ring 102. Although such conventional isolator gear systems provide a high degree of isolation, they require many precision-formed leaf springs, and include a complex design having a large number of parts that require skilled assembly, resulting in a system that is difficult and expensive to manufacture.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 is a front perspective view of a conventional isolator gear. Fig. 2 is a partially exploded front perspective view of the conventional isolator gear of Fig. 1 showing the cover exploded relative to the remaining portions of the conventional isolator gear.

Fig. 3 is a fully exploded front perspective view of the conventional isolator gear of Fig. 1.

Fig. 4 is an end view of a gear system including an isolator gear as a driven gear. Fig. 5 is a front perspective view of an isolator gear including a corrugated elastic ring, with the cover partially cut away to illustrate the engagement between the outer gear, the ring and the inner gear.

Fig. 6 is a fully exploded front perspective view of the isolator gear of Fig. 5.

Fig. 7 is a cross-sectional view of the isolator gear of Fig. 5.

Fig. 8a is a front view of the isolator gear of Fig. 6.

Fig. 8b is an exploded side view of the isolator gear of Fig. 6.

Fig. 9a is a front view of one aspect of the elastic ring of Fig. 6.

Fig. 9b is a front view of another aspect of the elastic ring of Fig. 6.

Fig. 10 is an exploded perspective view of yet another aspect of the elastic ring of

Fig.6.

DETAILED DESCRIPTION

Referring to Fig. 4, a gear system 1 includes a driving gear 3 mounted on a driving shaft 4 and a driven gear assembly 5 mounted on a driven shaft 2. The external teeth 7 of the driving gear 3 engage external teeth 12 of the driven gear assembly 5, whereby the driving shaft 4 is coupled to, and drives, the driven shaft 2. The driven gear assembly 5 is an isolator gear that isolates an outer gear 10 from vibrations of the driven shaft 2 due to eccentric rotations of the driven shaft 2 resulting from imperfections of the driven shaft 2 and/or manufacturing tolerances.

Referring to Figs. 5-7, the driven gear assembly 5 includes an inner gear 50, an outer gear 10 concentric with and surrounding the inner gear 50, an elastic ring 20 disposed between the inner gear 50 and the outer gear 10, a cover 30, and a retaining ring 40.

The inner gear 50 includes a hollow, cylindrical hub 52 including a central opening 53 that receives the driven shaft 2. The inner gear 50 includes a radially protruding flange 56 formed at one end of the hub 52. External teeth 55 are formed on an outer surface of the hub 52 adjacent to the radially protruding flange 56. A groove 54 is formed on an outer surface of the hub 52 at a location axially spaced apart from the external teeth 55 such that the external teeth 55 are disposed between the groove 54 and the radially protruding flange 56. The groove 54 is configured to receive the retaining ring 40 therein, as discussed further below. The flange 56 protrudes radially a greater extent than the external teeth 55.

The outer gear 10 includes a flange receiving face 16 and an opposed, cover receiving face 17. The flange receiving face 16 includes a central flange recess 16a dimensioned to receive the inner gear radially protruding flange 56 therein. Likewise, the cover receiving face 17 includes a central cover recess 17a dimensioned to receive the cover 30 therein (Fig. 7). The outer gear 10 includes external teeth 12 formed on an outer periphery thereof that are configured to cooperatively engage with the external teeth 7 of the driving gear 3, and internal teeth 13 that define an outer gear central opening 18. The internal teeth 13 are configured to indirectly cooperate with the inner gear external teeth 55, as discussed further below, and are dimensioned so that a small gap 22 exists between an outer surface of the inner gear external teeth 55 and an outer surface of the outer gear internal teeth 13 (Fig. 5).

The elastic ring 20 is a continuous member that is disposed between the inner gear 50 and the outer gear 10. More specifically, the elastic ring 20 is corrugated when viewed in cross section, and conforms to the shape of the outer gear internal teeth 13. The elastic ring 20 covers contact surfaces 13a of the outer gear internal teeth 13 and is configured to move in concert with the outer gear internal teeth 13. Opposing contact surfaces 13a define spaces 14 for receipt of the inner gear external teeth 55. When the inner gear 50, the outer gear 10 and the elastic ring 20 are assembled, the elastic ring 20 fills the gap 22, and the inner gear external teeth 55 are disposed within the spaces 14 formed by the contact surfaces 13a to thereby engage the outer gear internal teeth 13 via the elastic ring 20. The elastic ring 20 and the gap 22 between the outer gear 10 and the internal gear 50 are engineered to provide adequate stiffness to mitigate the torsional excitations of the shaft. In some embodiments, the elastic ring 20 is formed of a polymer, but the elastic ring 20 is not limited to this material.

The cover 30 is an annular plate having a cover central opening 33 that defines an inner peripheral edge 32 dimensioned to correspond to an outer dimension of the inner gear hub 52, and an outer peripheral edge 31 dimensioned to be received within the central recess 17a of the outer gear cover receiving face 17. When the driven gear assembly 5 is assembled with the outer gear 10 surrounding the inner gear 50, and the elastic ring 20 is disposed between the respective teeth 55, 13 of the inner and outer gears 50, 10, the hub 52 protrudes through the cover central opening 33 and the cover 30 is disposed in the central cover recess 17a. In addition, the cover 30 is disposed on the hub 52 such that the inner peripheral edge 32 is positioned axially between the groove 54 and the hub external teeth 55. By this configuration, the elastic ring 20 is axially positioned between the radially protruding flange 56 and the cover 30 and thus retained in the desired axial position relative to the respective teeth 55, 13 of the inner and outer gears 50, 10.

The elastic ring 20 and cover 30 can be molded as one single piece or two separate pieces used together. In one aspect, as shown in Figs. 5 and 9a, the elastic ring 20 is dual sided and includes corrugated surfaces containing lands 20a and grooves 20b connected by dual side surfaces 20c. As shown in Fig. 9a, lands 20a, grooves 20b and connecting dual side surfaces 20c form a u-shaped configuration. The lands 20a, grooves 20b and connecting dual side surfaces 20c cover contact surfaces 13a of the outer gear internal teeth 13 when the inner gear 50, the outer gear 10 and the elastic ring 20 are assembled. Connecting dual side surfaces 20c may include features such as undulations that assist with damping and noise control.

In another aspect, as detailed in Fig. 9b, the elastic ring 20 is single sided and includes corrugated surface that may be z-shaped wherein the lands 20a and grooves 20b are connected by a single interconnecting member 20d. The interconnecting member 20d may also include features such as undulations that assist with damping and noise control. Similarly, lands 20a, grooves 20b and interconnecting member 20d cover contact surfaces 13a of the outer gear internal teeth 13 when the inner gear 50, the outer gear 10 and the elastic ring 20 are assembled.

In yet another aspect, as shown in Fig. 10, the elastic ring 20 may include a back plate 21 molded as one piece therewith. Back plate 21 provides added stiffness and deflection resistance to the elastic ring 20 from the vibration developed by cyclic irregularities due to eccentricities of the driven shaft. The addition of the back plate 21 also assists with maintaining the elastic ring 20 in position to ensure that the inner gear 50 is isolated enough with respect to the outer gear 10 thereby allowing the inner gear to float unimpeded. When assembled, the back plate 21 is disposed adjacent to a side of the cover 30 opposite placement of the retainer ring 40, while the lands 20a and grooves 20b of the elastic ring 20 cover contact surfaces 13a of the internal teeth 13 of the outer gear 10.

The retaining ring 40 is, for example, a snap ring that is received within the groove 54 and retains the cover 30 within the central cover recess 17a.

Since the inner gear 50 includes the external teeth 55 that engage the interior teeth 13 of the outer gear 10 via the elastic ring 10, the inner gear 50 floats relative to the outer gear 10, thus providing isolation between the driving shaft 4 and the driven shaft 2.

Advantageously, the gear assembly 5 including the elastic ring 20 as an isolator feature is simple to manufacture to an extent that little or no experience is required to manufacture the system. In addition, the gear assembly 5 has fewer parts (for example, 5 parts) relative to some conventional isolation gear assemblies such as shown in Pigs 1-3, which may include 52 parts or more.

Claims

What is claimed, is

1. An isolator gear comprising

an outer gear including outer gear external teeth and outer gear internal teeth, the outer gear internal teeth defining an outer gear central opening;

an inner gear including a central opening configured to receive a shaft and inner gear external teeth, the inner gear disposed within the outer gear central opening such that the inner gear external teeth are disposed in spaces defined between the outer gear internal teeth;

an elastic ring disposed between the inner gear external teeth and the outer gear internal teeth, the elastic ring having a corrugated shape that conforms to the shape of the outer gear internal teeth ,

wherein the inner gear external teeth engage the outer gear internal teeth via the ring.

2. The isolator gear of claim 1 wherein the inner gear is disposed to float relative to the outer gear.

3. The isolator gear of claim 1 wherein the corrugated shapes of the elastic ring are u-shaped.

4. The isolator gear of claim 1 wherein the corrugated shapes of the elastic ring are z-shaped.

5. The isolator gear of claim 3 wherein the elastic ring includes a back plate.

6. The isolator gear of claim 4 wherein the elastic ring includes a back plate.

7. The isolator gear of claim 1 wherein the inner gear includes a hollow, cylindrical hub that forms the central opening and a radially protruding flange formed at one end of the hub, the hollow, cylindrical hub includes an outer surface including a groove configured to receive a retaining ring therein.

8. The isolator gear of claim 7 wherein the outer gear includes a flange receiving face and an opposed, cover receiving face, the flange receiving face includes a central flange recess configured to receive the radially protruding flange of the inner gear therein, and the cover receiving face includes a central cover recess configured to receive a cover therein.

9. An isolator gear system that comprises a drive gear mounted on a drive shaft, and a driven gear assembly mounted on a driven shaft, driven gear assembly including an outer gear comprising outer gear external teeth and outer gear internal teeth, an inner gear concentric with the outer gear, the inner gear comprising a central opening configured to receive a shaft and inner gear external teeth, and

an elastic ring disposed between the outer gear and the inner gear,

wherein

the elastic ring conforms to the shape of the outer gear internal teeth,

the elastic ring covers contact surfaces of the outer gear internal teeth and is configured to move in conceit with the outer gear,

the inner gear external teeth engage the interior teeth of the outer gear via the ring, and the outer gear external teeth engage corresponding teeth of the drive gear.

10. The isolator gear of claim 9 wherein the inner gear includes a hollow, cylindrical hub that forms the central opening and a radially protruding flange formed at one end of the hub, the hollow, cylindrical hub includes an outer surface including a groove configured to receive a retaining ring therein.

1 1. The isolator gear of claim 10 wherein the outer gear includes a flange receiving face 16 and an opposed, cover receiving face, the flange receiving face includes a central flange recess 16a configured to receive the radially protruding flange of the inner gear therein, and the cover receiving face includes a central cover recess configured to receive a cover therein.

12. The isolator gear of claim 1 1 wherein the inner gear is disposed to float relative to the outer gear thereby providing isolation between the driving shaft and the driven shaft.