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WO1997011292A1 - Entrainement de synchronisation pour chaine a rouleaux a bruit reduit - Google Patents

Entrainement de synchronisation pour chaine a rouleaux a bruit reduit Download PDF

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Publication number
WO1997011292A1
WO1997011292A1 PCT/US1996/014458 US9614458W WO9711292A1 WO 1997011292 A1 WO1997011292 A1 WO 1997011292A1 US 9614458 W US9614458 W US 9614458W WO 9711292 A1 WO9711292 A1 WO 9711292A1
Authority
WO
WIPO (PCT)
Prior art keywords
chain
sprocket
teeth
tooth
drive assembly
Prior art date
Application number
PCT/US1996/014458
Other languages
English (en)
Inventor
Timothy R. Allen
Original Assignee
Cloyes Gear And Products, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US08/691,350 external-priority patent/US5848948A/en
Application filed by Cloyes Gear And Products, Inc. filed Critical Cloyes Gear And Products, Inc.
Publication of WO1997011292A1 publication Critical patent/WO1997011292A1/fr

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H7/00—Gearings for conveying rotary motion by endless flexible members
    • F16H7/06—Gearings for conveying rotary motion by endless flexible members with chains

Definitions

  • the subject invention is directed to roller chain timing drives, and more particularly, to timing sprockets and chains operable to produce reduced noise.
  • the present invention relates to chain timing drives having added backlash resulting from reduced or thinned sprocket teeth.
  • Chain drives as used in timing operations involve a timing chain wrapped around two or more sprockets of either a drive, driven or idler design. An example is shown in FIG. 1 where the larger driven sprocket has a larger wrap angle than the smaller drive sprocket.
  • Each sprocket has a plurality of teeth thereon where the number of teeth is variable based upon the user' s preference or intended use.
  • each tooth is defined by a drive side tooth surface and a coast side tooth surface either intersecting in some embodiments at a point, or connected in most embodiments by a top land.
  • the top land is the top surface relatively flat surface of each tooth.
  • the drive side and coast side tooth surfaces each include a flank and a fillet. The flank being the portion of the tooth between the point or top land and the tangent point with the fillet, while the fillet is otherwise known as the seating curve .
  • the combination of the teeth on the sprocket defines various overall sprocket dimensions including tip diameter, root diameter, and pitch diameter.
  • the tip or outside diameter is defined as the diameter across a hypothetical circle defined by the cumulation of the top lands of all of the teeth, i.e., where an even number of teeth exist, the tip diameter is the distance from one tooth tip to another tooth tip diametrically opposed thereto.
  • Each sprocket also has a minor diameter referred to as the root diameter defined as the diameter extending across a hypothetical circle defined by the cumulation of the bottom lands of all of the teeth, i.e., the diameter of a circle tangent to the seating curve at the bottom of the tooth gap.
  • the pitch diameter is a theoretical dimension is later defined.
  • the operating pitch radius is half of the diameter of an operating pitch circle which is defined as the distance from the center point of the sprocket known as the gear axis to the center point of a fully seated roller on a chain when the chain is wrapped around the sprocket .
  • Tooth and sprocket designs are typically governed by one of the numerous conventions or standards including ANSI, ISO, British, DIN (German) and other national and international standards.
  • One such standard is the American National Standard, or ANSI standard, as described in ANSI specifications and summarized in Marks' Standard Handbook For Mechanical Engineers on the pages directed to chain drives and design of sprocket teeth for roller chains (as shown in FIG. 2) .
  • This discussion explains the ANSI standards for tooth design to maximize efficiency throughout life of the chain drive. This is one conventional manner in which sprocket teeth have been designed and manufactured for years.
  • FIG. 3 Another such generally accepted and widely used standard is the International Standard, or ISO standard (as shown in FIG. 3) .
  • each tooth is symmetrical in nature and the minor or bottom diameter between adjacent teeth is defined by one continuous roller seating or fillet radius.
  • the tooth profiles are ISO,
  • portions of the sprocket tooth profiles are involute in nature because the involute curve provides numerous advantages and properties well known in the art.
  • One list of some of these properties is found in the twenty-fifth edition of the Machinery's Handbook in the section on gearing.
  • the standard tooth design of a roller chain sprocket 10 has a tooth space 12 having a continuous fillet radius from one tooth flank 14 to the adjacent tooth flank 16.
  • the chain In order for the roller chain 18 to fully seat in a sprocket tooth, the chain must have the same pitch as the sprocket. This, of course, is not practical because of manufacturing tolerances. Accordingly, industry standards suggest that the chain have a pitch which is slightly greater than the sprocket wheel. Moreover, a worn chain theoretically has a longer pitch than a new chain. Thus, after extended use, the pitch length of the roller chain is altered.
  • the present invention adds backlash to the system by reducing or thinning the sprocket teeth.
  • the present invention is a chain drive assembly for reducing noise having a chain and a sprocket.
  • the sprocket has a number of peripherally spaced teeth. Each tooth on the sprocket is reduced in thickness as measured across a tooth from a drive flank to a coast flank of the tooth. The amount of thinning is selected on the basis of compensating for actual pitch of the chain so that the chain and sprocket remain in contact .
  • FIGURE 1 shows a standard timing chain drive having two sprockets and one chain wrapped therearound;
  • FIGURE 2 shows an ANSI standard tooth
  • FIGURE 3 shows an ISO standard tooth
  • FIGURE 4 shows an axial view of a standard tooth design of a prior art roller chain sprocket with a tooth space having a continuous fillet radius from one tooth flank to the adjacent tooth flank;
  • FIGURE 5 shows the present invention in an exaggerated format displaying the chain remaining tightly wrapped around the complete chain wrap even after wearing
  • FIGURE 6 shows an axial view of the present invention tooth design with the thinned teeth
  • FIGURE 7 shows the thinning of the teeth according to the formula of the present invention whereby the thinning is shown in cross hatched lines;
  • FIGURE 8 shows backlash in a new chain wrapped around a sprocket employing the present invention .
  • FIGURE 9 shows backlash in a worn chain at the end of its design life that is wrapped around a sprocket employing the present invention.
  • FIGURE 5 the overall arrangement of the preferred construction of a sprocket A for use with a timing chain B as is generally shown in FIGURE 5 (in an exaggerated fashion) .
  • the invention is a sprocket design that forces the rollers tight against the root diameter so that the chain does not climb up the sprocket as the chain wears, i.e., specifically so that the rollers on the chain do not climb up the flank and then the face of the teeth in the wrap area.
  • This result occurs by adding backlash to the new chain in an amount equivalent to assure that the chain once worn to its design life will have closed all of the backlash but still be tight against the root diameter, i.e., the chain will have stretched and worn to the point of almost climbing up the sprocket.
  • ISO standard teeth are designed to supply relatively tight roller-tooth contact when a chain is new.
  • the rollers come out of tight contact resulting in proper engagement between the teeth and rollers at only the chain wrap entrance and exit spots.
  • the result of this poor contact is increased noise and wear due to rattling of the chain in the middle of the wrap.
  • sprocket modification resulting in a reduced root diameter. This reduction is problematic because the sprocket fails to meet required design and performance standards such as that of ISO.
  • the present invention solves the above mentioned problems of supplying and maintaining roller-tooth contact throughout the wrap as the chain and sprocket wear without reducing the root diameter while continuing to meet all ISO design and performance standards.
  • each sprocket tooth 112 is thinned along the flank radius 114, 116 as shown in FIG. 6, and as represented in exaggerated form by the cross-hatching in FIG. 7 while the root diameter is maintained the same. This thinning of the tooth builds in a backlash when compared to the theoretical sprocket design. Since the root land is elongated, the chain is in hard contact with the root diameter of the sprocket throughout the entire chain wrap.
  • the chain wrapped around standard non-thinned sprockets is usually in hard contact with a standard sprocket root diameter only at the immediate area of entry and exit and not over the remainder of the wrap angle.
  • chain wear and elongation when used on these standard non-thinned sprockets further loosens the chain wrap in the non-entry and non-exit regions. Stated another way, this means there is no backlash in the standard non-thinned sprocket.
  • the chain is able to leave contact with the sprocket.
  • the resultant space between adjacent sprocket teeth has a circular root portion 120 that is concentric with the rotational axis of the sprocket and is tangent with the fillet radii which blend into the tooth flanks. This is shown in exaggerated form in FIG. 6.
  • FIGS. 8 and 9 This thinning to build in backlash is shown in FIGS. 8 and 9.
  • FIG. 8 shows the backlash B of the present invention as is built into the sprocket design.
  • This backlash is correlated to the expected wearing over the expected design life such that at the end of the expected life, all of the backlash has been used up but the rollers are still in tight contact with the chain, i.e., the rollers have not begun to climb up the teeth faces.
  • FIG 9 This elimination of backlash at the end of the expected life is shown in FIG 9 as B' .
  • the amount that the teeth are thinned is calculated based on the allowable chain wear, the angle through which the chain wraps around the sprocket during operation, and the desired operating pitch diameter of the sprocke .
  • a formula for determining the amount of tooth thinning is given by:
  • ⁇ TT Amount teeth are to be thinned WA Chain Wrap Angle in Radians
  • SPD Pitch Diameter (PD) based upon Actual Chain
  • APD Actual (Operating) Pitch Diameter This thinning is used in conjunction with the pitch diameter to define a sprocket with reduced noise. Pitch diameter is calculated using the following formula:
  • N Number of Teeth in Sprocket
  • sprocket is shown in FIG. 7 and can be incorporated into various forms of timing drive layouts including all known drives on the market including drives having more than two sprockets.
  • a desired worn chain pitch is selected (pitch elongation of approximately 0.15 percent for a worn chain) , and this amount is divided over the number of teeth in engagement with the chain, i.e., the wrap angle, and the teeth are then thinned accordingly.
  • the chain rollers remain in contact with the sprocket root diameter and the main source of noise associated with the chain contacting the sprocket teeth is reduced.
  • this backlash concept compensates for chain elongation that is particularly relevant over time by thinning the flank and/or face of each tooth without affecting the bottom land (thereby not affecting the root diameter) .
  • the thinned teeth as thinned according to the formula remove the variability supplied by the worn chain.
  • the root diameter remains unchanged and thus remains within the realm of whatever standard, such as ISO, is called for therefore assuring that the sprocket remains within industry standard tolerances.

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Gears, Cams (AREA)
  • Devices For Conveying Motion By Means Of Endless Flexible Members (AREA)

Abstract

L'amincissement des dents (114, 116) et l'allongement du méplat (120) situé entre chaque dent permet de réduire le bruit produit par l'entraînement de synchronisation d'une chaîne à rouleaux. Plus précisément, l'allongement dudit méplat (120), fruit d'un calcul approfondi, se solde par un amincissement des dents, tel que mesuré transversalement du flanc d'entraînement (114) au flanc de côte (116) de la dent. Il en résulte, durant toute la durée de vie de la chaîne et des pignons, le maintien du contact de tous les rouleaux (118) enroulés autour d'un pignon, ainsi qu'une diminution du bruit.
PCT/US1996/014458 1995-09-19 1996-09-10 Entrainement de synchronisation pour chaine a rouleaux a bruit reduit WO1997011292A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US398395P 1995-09-19 1995-09-19
US60/003,983 1995-09-19
US08/691,350 US5848948A (en) 1996-08-02 1996-08-02 Roller chain timing drive having reduced noise
US08/691,350 1996-08-02

Publications (1)

Publication Number Publication Date
WO1997011292A1 true WO1997011292A1 (fr) 1997-03-27

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0907041A1 (fr) 1997-10-03 1999-04-07 Borg-Warner Automotive, Inc. Pignon aléatoire pour chaíne à rouleaux
US6213905B1 (en) 1999-07-01 2001-04-10 Borgwarner Inc. Roller chain sprockets oriented to minimize strand length variation
EP1235003A1 (fr) 2001-02-23 2002-08-28 Morse Tec Europe S.p.A. Pignon pour chaíne à rouleaux avec differents profils de dents sur le même pignon

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4036071A (en) * 1976-04-02 1977-07-19 Hollis And Company Sprocket and method for producing same

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4036071A (en) * 1976-04-02 1977-07-19 Hollis And Company Sprocket and method for producing same

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0907041A1 (fr) 1997-10-03 1999-04-07 Borg-Warner Automotive, Inc. Pignon aléatoire pour chaíne à rouleaux
US6213905B1 (en) 1999-07-01 2001-04-10 Borgwarner Inc. Roller chain sprockets oriented to minimize strand length variation
EP1235003A1 (fr) 2001-02-23 2002-08-28 Morse Tec Europe S.p.A. Pignon pour chaíne à rouleaux avec differents profils de dents sur le même pignon

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