GB2224805A

GB2224805A - Gear train anti-rattle device

Info

Publication number: GB2224805A
Application number: GB8923593A
Authority: GB
Inventors: David Stanley Totten
Original assignee: Borg Warner Automotive Inc
Current assignee: BorgWarner Inc
Priority date: 1988-11-09
Filing date: 1989-10-19
Publication date: 1990-05-16
Also published as: GB8923593D0; DE3934377A1; FR2638804A1; JPH02173457A

Description

2.2-, 2 4 9 0 5 086140-BWL GEAR TRAIN ANTIRATTLE DEVICE

FIELD OF THE 1 M NTION

The present invention relates to a gear train in a vehicle manual transmission having backlash space between pairs of gears and to elimination of gear rattle resulting from the backlash space.

BACKGROUND OF THE I M NTION optimizing shiftability and minimizing gear rattle are major challenges for the design of a manual transmission. Conventionally, a pair of meshing gears has a spacing between the meshing gear teeth due to manufacturing tolerances and dimensioning which is commonly referred to as backlash space. Engine angular accelerations are the major cause of gear rattle, which accelerations are cyclic in nature. The high inertia of an engine flywheel tends to reduce the magnitude of the angular accelerations, but a high inertia flywheel also reduces acceleration of the vehicle resulting in sluggish performance.

Transmissions and drivelines are subjected to greater magnitudes of angular acceleration with the trend to smaller vehicle engines with low inertia 086140-BWL f lywheels. Accessory loads significantly increase angular accelerations, with the increase being particularly large at the idle condition. Neutral rattle occurs at idle with the vehicle at rest, the transmission in neutral and the clutch engaged. The cyclic angular acceleration imparted to the transmission input shaft via the engine causes the spline teeth and the gear teeth to impact through the backlash space, which causes noise. Gear rattle can be eliminated by using zero backlash gears and splines. This is accomplished through tighter tolerances,, but manufacturing becomes more difficult and expensive, and zero backlash gears often cause a gear growl. All gear meshes in the transmission are possible neutral rattle sources since they are all essentially unloaded at neutral.

However, meshed gears which are not under torque in the drive condition for the vehicle are also potential sources of rattle. When engaging gears are transmitting sufficient mean or drive torque,, there will be nc rattle connected therewith. In a multispeed manual transmission, there are obviously more meshing gears that are not transmitting torque than the specific driving gear train, and all of these unloaded meshing gears can produce noise. The present 086140-BWL invention has the capability to reduce or eliminate rattle between any unloaded meshing gears.

SUMMARY OF THE INVENTION

The present invention relates to a gear train anti-rattle device for a pair of interengaging or meshing gears in a vehicle manual transmission. The device comprises an elastomeric extension on at least one side of at least one of a pair of gears, the extension having teeth on its periphery of the same prof ile as the teeth of the associated gear but of a slightly larger dimension. In an unloaded condition, a meshing gear will normally engage the elastomeric teeth of the extension to cushion the vibration. When transmitting mean or drive torque, the elastomeric material progressively def orms to allow the metallic teeth of both gears to engage.

Further objects are to provide a construction of maximum simplicity, efficiency, economy and case of assembly and operation. and such further objects, advantages and capabilities as will later more fully appear and are inherently possessed thereby.

086140-BWL DESCRIPTION OF THE-DRAWINGS

Figure 1 is a partial cross sectional view of a pair of meshing gears before the addition of the present invention.

Figure 2 is a partial perspective view of one of the pair of meshing gears with the anti-rattle device applied thereto.

Figure 3 is a partial cross sectional view of the gear containing the device taken on the line 3-3 of Figure 2.

Figure 4 is a cross sectional view similar to Figure 3, but with torque applied to the gears.

Figure 5 is a partial cross sectional view of a variation of the gear with an anti-rattle extension.

Figure 6 is a partial perspective view of a gear with an extension on both sIdes.

Figure 7 is an enlarged elevational view of a variation of a gear tooth on the device.

11 086140-BWL Figure 8 is a side elevational view of a pair of gears, each having an extension thereon.

Figure 9 Is a side elevational view of a pair of meshing helical gears with an extension on one gear.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring more particularly to the disclosure in the drawings wherein are shown illustrative embodiments of the present invention, Figure 1 discloses a pair of meshing gears 10 and 12 t each having teeth 11 and 13 on their peripheries with a backlash space 14 between the gear teeth. The backlash space 14 is present due to the various tolerances of manufacture and fit between the gears, which may be any two meshing gears in a multispeed manual transmission (not shown). Due to the backlash space and the torsional vibrations occurring in the drive train from the vehicle engine. gear rattle and noise results from the movement of the gear teeth through the backlash space and Impact on the meshing gear teeth.

To overcome gear rattle for gears that are not under torque loads,, an elastomeric extension 21 (Figure 2) is added to at least one side or surface of 086140-BWL the gear, the extension being in the form of an annular ring 22 with teeth 23 on its periphery having substantially the same profile as the gear teeth 11 of the gear 10 carrying the extension. As shown in Figure 3. the extension 21 may be of substantially the same radial dimensions with an inner diameter defining a central opening 24 (Figure 2) axially aligned with the shaft receiving central opening 15 through the gear 10 or 12. In the alternative, the side surface 17 of a gear 16 may be shouldered as at 18 (Figure 5) to receive an elastomeric extension 31 having a central opening 32 encompassing the shoulder 18 on the gear 16.

The elastomeric extension 21 or 31 is a flat annular disc of a material having the characteristics of a low absorption coefficient (moisture resistant) and a high heat deflection temperature to withstand the heat generated in a vehicle manual transmission. Suitable elastomers would be a heat resistant rubber or a plastic such as nylon. acetal or a polyethersulphone. A desirable thickness of the extension is approximately one-eighth inch,, although the width of the extension can range between one-sixteenth and one quarter inch, depending on space limitations within the transmission and the desired deformation of the material.

1 1 086140-BWL The extension 21 or 31 is suitably secured to the surface of the companion gear 10 or 16 to rotate therewith. Such securement may be accomplished through a suitable adhesive that will withstand high temperatures of up to 3000F.,, such as an epoxy resin, a splined connection between the gear and extension or screws or pins that project through the extension Into the body of the gear. For a splined connection, there also must be axial retention between the gear and extension such as heading or swaging the end of the shoulder. Where the extension is adhesively joined to the gear, only the annular body or ring 22 or 33 is secured to the gear and the teeth 23 or 34 are free to be deformed as at 25 (Figure 4) due to the application of torque in the meshing gears. As seen in Figure 5, the surface of the gear 16 abutting the extension 31 is undercut at 19 to provide space to receive an adhesive 20.

AS previously stated. the teeth 23 or 34 of the extension 21 or 31 have the same profile as the teeth 11 or 16a of the metallic spur gear 10 or 16,, however, the extension teeth are slightly oversized compared to the gear teeth. As seen in Figure 3,, the extension overlaps the gear teeth by a dimension t which is in the range of a 0.002 to 0.007 inches depending on the 086140-BWL -a- backlash space 14. As the backlash space averages 0.005 inches, the amount of overlap is nominally set at 0.0025. Thus,, if the extension is applied to the gear 10, then the teeth 13 of gear 12 will be spaced from the teeth 11 of gear 10 by the backlash space 14, but will engage the oversize teeth 23 of the extension 21 (Figure 3).

When subjected to primarily oscillatory torque, the oversized extension teeth will cushion any impact of the backlash space between the gears to prevent gear rattle and noise. The material forming the extension is selected so that the teeth of the extension will deform under a torque load and the metal teeth of the two gears engage when a predetermined level of mean torque is exceeded.

The extension teeth are of a suitable material subject to deformation where the teeth are of solid elastomeric material that will suitably deform relative to the gear teeth. However,, if the elastomeric material has a high hardness to prevent undue surface wear of the extension teeth, the teeth may not be sufficiently compliant to optimally absorb the torsional vibrations. Figure 7 discloses a portion of an extension 36 with gear teeth 37, each having a i 086140-BWL perforation or opening 38 therethrough to enhance its deformability.

Although shown as an extension at one side of one gear for a pair of meshing gears (Figure 1), Figure 6 discloses a gear 41 having elastomeric extensions 42.43. on both sides. This will reduce the width of the metal gear or the width of the meshing gear (not shown) must be increased so the meshing gear will engage both extensions. Another possibility shown in Figure 8 is the addition of an elastomeric extension 47 to one side of meshing gear 46 and a second extension 49 to the opposite side of the second meshing gear 48 so that each metallic gear 46 or 48 will engage an extension on the opposite meshing gear.

Finally,, although shown for meshing pairs of spur gears 10,12 in Figure 1, a similar elastomeric extension could be utilized for meshing pairs of helical gears 51 and 52,, as seen In Figure 9. An elastomeric extension 55 is suitably secured to the side of one of the two gears 51 or 52. Each gear 51 or 52 has helical teeth 53 or 54. while the extension 55 also has helical teeth 56 which are appropriately aligned with the teeth of the associated gear but slightly oversized as previously described. Also, 086140-BWL although shown f or a pair of meshing gears, an elastomeric extension could be applied to a surface of a middle or Intermediate gear in a train of three gears, such as f or reverse in a manual transmission. All of these variations will cushion the gears for oscillatory torque and deform when a predetermined level of mean torque is exceeded.

Claims

C L A I M S

1. A gear train anti-rattle device for a pair of meshing gears having backlash space therebetween comprising an elastomeric extension provided on at least one side of a gear having gear teeth adapted to mesh with a second gear, said extension being in the form of a flat annular disc having gear teeth of the same profile as and axially aligned with the teeth of the gear, said extension teeth being slightly oversized in all dimensions relative to the gear teeth so as to occupy the backlash space, said extension being secured to the gear without the extension teeth themselves being secured to the gear teeth so that the extension teeth are capable of deforming under a predetermined applied load.

2. A gear train anti-rattle device as claimed in claim 1, wherein said extension has a thickness in the range of 1/16 to 1/411 (1.6 to 6.4

3. A gear train anti-rattle device as claimed in claim 1 or 2, wherein said extension is formed of an elastomeric material having a low absorption coefficient and a high heat deflection temperature.

4. A gear train anti-rattle device as claimed in claim 3, wherein said elastomeric material is a polyethersulphone.

5. A gear train anti-rattle device as claimed in any preceding claim, wherein said extension teeth are oversized in a range of 0.002 to 0.00711 (0.0052 to 0.018 mm).

6. A gear train anti-rattle device as claimed in any preceding claim, wherein each said extension tooth has a transverse perforation therethrough to enhance the deformability of the extension teeth.

7. A gear train anti-rattle device as claimed in any preceding claim, wherein said extension is secured to the gear by an adhesive able to withstand temperatures of up to 300OF (149OC).

8. A gear train anti-rattle device as claimed in any preceding claim, wherein an elastomeric extension is secured to each side of the gear.

9. A gear train anti-rattle device for a pair of meshing metallic gears having gear teeth with backlash space therebetween, comprising an elastomeric extension secured to at least one side of at least one of the two gears, said extension including an annular flat body with gear teeth on the outer periphery thereof of the same profile as but oversized in all dimensions relative to the teeth of the associated gear, said extension teeth being axially aligned with said gear teeth to occupy the backlash space, said flat body being secured to the abutting gear surface but with the elastomeric teeth being unsecured to the teeth of the metallic gear, said meshing gear teeth initially contacting only the extension teeth to provide a cushion for vibratory torque.

10. An anti-rattle device as claimed in claim 9, in which said extension teeth are deformable so that the metallic gear teeth of the meshing gears engage when a threshold mean torque is exceeded.

11. An anti-rattle device as claimed in claim 9 or 10, wherein elastomeric extensions are secured to the opposite sides of one of the pair of gears.

12. An anti-rattle device as claimed in claim 9 or 10, in which each of said gears has opposed sides, a first elastomeric extension being secured to one side of one of the meshing gears, and a second elastomeric extension being secured to the opposite side of the second meshing gear.

13. An anti-rattle device as claimed in claim 12, in which the metal portion of each meshing gear engages the elastomeric extension of the opposite gear.

14. An anti-rattle device as claimed in any one of claims 9 to 13, wherein the meshing gears are spur gears.

15. An anti-rattle device as claimed in any one of claims 9 to 13, wherein the meshing gears are helical gears and said extension is provided with mating helical teeth.

16. An anti-rattle device to operate substantially as herein to and as illustrated in Figures 2 drawings.

17. A gear train including an anti-rattle device as claimed in any preceding claim.

18. A method of preventing gear rattle between a pair of meshing gears having backlash space between the gear teeth, comprising the steps of adding an elastomeric extension to the side of at least one gear to occupy the backlash space so that under no load the metallic teeth of one gear engages only the extension teeth, and when a threshold of mean torque is exceeded, the extension teeth deform so that the metallic teeth of both gears engage.

19. A method of preventing gear rattle substantially as herein described with reference to Figures 2 to 9 of the accompanying drawings.

constructed and arranged described with reference to 9 of the accompanying Published 1990 at The Pa,,er.O-flice. State HVuse.66 711-IighHolborn. LondorWC1R4TF Further copies maybe obtained from The Patent Of:ice