WO2001033108A1

WO2001033108A1 - Pulley assembly

Info

Publication number: WO2001033108A1
Application number: PCT/US2000/029274
Authority: WO
Inventors: Rolf Schaad; Joseph W. Zamm
Original assignee: Dayco Products, Inc.
Priority date: 1999-10-29
Filing date: 2000-10-19
Publication date: 2001-05-10
Also published as: AR026251A1; AU1227401A

Abstract

A power transmission system having a pulley assembly (41, 26) operatively associated therewith. The pulley assembly is formed of a stamped or rolled steel body (43), and contacts the non-driving or driving surface (23, 24) of the belt (21) and has two substantially identical ball bearing assemblies (50, 51) axially adjacent one another which are press fitted into the rolled steel body (43) of the pulley assembly (41, 26). Each of the ball bearing assemblies (50, 51) comprises an inner and an outer race (56, 55; 59, 58) and a single row of balls (54, 57) supported therebetween.

Description

PULLEY ASSEMBLY

Technical Field

This invention relates to a pulley assembly, and more particularly to such assembly used as a routing pulley or in conjunction with belt tensioners, for automotive power transmission systems applications. Such pulley assemblies are used as a routing pulley to change the direction of belt travel, or as a belt wrap; or used with tensioners to apply tension to belts used in the systems. Such assemblies normally utilize ball bearing assemblies in their operation. Background Art

Pulley assemblies are commonly used in conjunction with belt transmission systems as routing pulleys to change belt direction, or as a belt wrap, or with tensioners for applying tension to the outer non- driving surface of a power transmission belt; this outer surface being opposite the driving surface. The driving surface of the belt may be of a conventional trapezoidal configuration, multi-ribbed, or toothed synchronous drive. Typical pulley assemblies are shown in Kawashima et al., U.S. Patent No. 5,234,385; Yamamoto, U.S. Patent No. 5,312,302; and Henderson, U.S. Patent No. 4,886,483. Such pulley assemblies utilize ball bearing assemblies between the principal body which is secured to the engine, a bracket, or to the tensioner, and the outer belt-contacting portion, the bearing assemblies thus minimizing friction as the outer portion rotates in contact with the belt surface. As shown in Kawashima et al. and Henderson for example, a single ball bearing assembly may be utilized; or as shown in Yamamoto, a single assembly having two rows of balls within single inner and outer races may be provided. Standard ball bearing assemblies are primarily constructed of plastic materials, machined metals, or powdered metal.

These standard assemblies are usually costly, have a limited bearing life, and require special designs or heavier bearings to improve life, thus rendering them even more costly. The single row bearings which are in normal use also allow rocking of the assembly, leading to misalignment and poor sealing of the bearings. Such an arrangement is shown in the Henderson and Kawashima patents. The present invention solves these problems by the use of a less expensive stamped or rolled steel pulley body, combined with two separate bearing assemblies in axial alignment. This minimizes the rocking effect of single bearings and also results in superior wear characteristics, less tendency for misalignment, and a greatly lowered cost. While the Yamamoto patent referred to above discloses a tension pulley (9) which is similar in appearance to the present idler pulley, the construction of the body is not discussed nor claimed. It is also noted that Yamamoto utilizes two rows of spherical balls (10), these are retained within a single outer and inner race, rather than the dual bearing assemblies of the present invention. It has been found that this arrangement, coupled with the stamped or rolled steel body construction, achieves the desired result. Disclosure of the Invention

The present invention relates to a tensioner having an associated pulley assembly which is an improvement over the prior art.

The assembly is primarily formed of a stamped or rolled steel body which utilizes two substantially identical ball bearing assemblies which are adjacent one another so that the balls are in axial alignment, the assemblies being press fitted or bonded against the inner wall of the body. Each of the ball bearing assemblies comprises an inner and an outer race and a single row of balls supported therebetween. The use of two ball bearing assemblies may be used in conjunction with a rolled steel construction to overcome problems arising from using a single bearing assembly, particularly a tendency of the pulley assembly to rock and create misalignment, poor sealing, reduced life, and uneven pressure against the belt surface. Attempts have been made to avoid this problem by using larger balls; by using two rows of balls with a single set of races (referred to above); or by using specially constructed bearing assembles instead of standard ones. Such constructions have been found to be more costly.

It is an object of this invention to provide a belt tensioner having an improved pulley assembly.

It is another object of the present invention to provide a pulley assembly which will eliminate rocking and improve performance. It is a further object to provide a pulley assembly with a pair of axially adjacent ball bearing assemblies. It is a further object to form the pulley assembly of stamped or rolled steel construction which will cooperate with the ball bearing assemblies.

It is a further object to provide each of said ball bearing assemblies with a single row of balls contained within a single set of races.

Brief Description of the Drawings

These and other objects, uses, and advantages of this invention are apparent from a reading of the specification in conjunction with the accompanying schematic drawings, which form a part thereof and wherein:

FIG. 1 is a view looking toward the front end of an automobile engine utilizing a typical belt tensioner and pulley assembly.

FIG. 2 is a sectional view of the pulley assembly taken along line 2-2 of FIG. 1 , with parts omitted for clarity. Detailed Description of Preferred Embodiments While the various features of this invention are hereinafter illustrated and described as applicable to using a pulley assembly of this invention with a power transmission belt on motor vehicle engine, it is to be understood that the various features of this invention can be utilized singly or in any combination thereof to provide a pulley assembly for other arrangements as desired.

Therefore, this invention is not to be limited to only the embodiments illustrated in the drawings, because the drawings are merely utilized to illustrate one of the wide variety of uses of this invention. Referring now to FIG. 1 , an automobile engine is generally indicated by the reference numeral 20 and utilizes an endless power transmission belt 21 for driving a plurality of driven accessories as is well known in the art, the belt tensioner of this invention being generally indicated by the reference numeral 22 and being utilized to provide a tensioning force on the belt 21 in a manner hereinafter set forth.

The endless power transmission belt 21 may be of any suitable type known in the art and is preferably made primarily of a polymeric material because the unique features of the tensioner 22 of this invention readily permit the tensioner 22 to tension a belt having a load-carrying cord in an efficient manner as fully set forth in U.S. Patent to Henderson, U.S. Patent No. 4,886,483. Also, because many of the parts of the belt tensioner 22 of this invention and the details of the operation thereof are fully described and illustrated in the aforementioned U.S. Patent to Henderson, this patent is being incorporated into this disclosure by this reference thereto whereby a further discussion of the engine 21 and the operation of the tensioner 22 on the belt 21 is deemed unnecessary.

Thus, the belt tensioner 22 of this invention will now be described by using many of the same reference numerals as used in the U.S. Patent to Henderson, U.S. Patent No. 4,886,483, in order to facilitate the understanding of the various features of this invention.

The belt tensioner 22 of this invention comprises a metallic support means 36 adapted to be fixed to a mounting bracket or structure of the engine 20 by fastening means 37 as illustrated in FIG. 1. A belt engaging means that is generally indicated by the reference numeral 38 is movably carried by the support means 36 in a manner hereinafter set forth. The tensioner 22 has mechanical spring means operatively associated with the support means 36 in a manner hereinafter set forth. The tensioner 22 has mechanical spring means operatively associated with the support means 36 and the belt engaging means 38 to tend to urge the belt engaging means 38 against the belt 21.

The belt tensioner 22 also includes a friction dampening means operatively associated with the support means 36 and the belt engaging means 38 to dampen movement of the belt engaging means 38 relative to the support means 36 in a manner hereinafter set forth. The friction dampening means and spring means are coaxially aligned and the support means 36 includes an integral tubular member or shaft means 39 that has a cylindrical opening passing completely therethrough to receive a fastening member that is adapted to fasten an end plate to the support means 36 of the tensioner 22.

The support means 36 has mounting openings disposed parallel to the shaft means 39 in offset relation thereto for receiving the fastening members 37 therein for securing the tensioner 22 to the engine 20 whereby the support means 36 will be stationary.

The belt engaging means 38 comprises a pulley assembly 41 shown in detail in FIG. 2, operatively connected to the belt tensioner as described above, and supported to structure such as detailed in the

Henderson Patent 4,886,483. The pulley assembly which applies direct pressure to the non-driven surface 23 of the belt which is opposite driving surface 24 is pivotally supported on a rocker arm mounted on a shaft 25. The pulley assembly utilizes the roller bearing assemblies for rotational support. As shown in FIG. 2 the pulley assembly comprises a rolled steel pulley body 43 of generally U- shaped construction. The pulley assembly extends annularly around a central axis 44 and the body 43 comprises an inner wall 45 and an outer wall 46, the inner and outer walls joined by a connecting wall 47. Inner wall 45 has a generally cylindrical inner surface 48 and outer wall

46 has a generally cylindrical outer surface 49 parallel to surface 48. A pair of substantially identical ball bearing assemblies 50 and 51 are axially aligned and are press fitted or bonded adjacent one another against the inner surface 48. The wall 52 of bearing assembly 50 is thus in contact with the wall 53 of bearing assembly 51 as shown. The ball bearing assembly 50 has a single row of spherical balls 54 which are retained in a conventional manner between an outer race 55 and an inner race 56; and similarly, the assembly 51 has a similar row of balls 57 retained between outer race 58 and inner race 59. The inner races 59 and 56 are secured to the support shaft 25 in a manner well- known is the art, the shaft being omitted from FIG. 2 for clarity. Free rocking is prevented by reason of the fact that two rows of balls are provided, which is found to be practical when associated with a stamped or rolled steel construction. The cost of this construction is minimized because standard ball bearing assemblies instead of specially formulated assemblies may be used. As a result, improved performance is obtained at a low cost.

While the invention is described in the form of a preferred embodiment, it is understood that other embodiments are contemplated as being within the spirit of the invention. For example, the pulley assembly 41 may be used as a routing pulley for contacting the back side of a belt in systems other than belt tensioners. Also, the pulley assembly 26 shown in FIG. 1 may be of the same construction as pulley assembly 41 and contacts the outer belt surface to function as a wrap belt.

Claims

CLAIMS:

1. A power transmission system comprising driving and driven members, a belt (21) providing power transmission between said driving and driven members and having an inner driving surface (24) and an opposite outer surface (23), and a cylindrical pulley assembly (41 , 26) having an outer wall (46) contacting one of said belt surfaces (23, 24) and an inner wall (45) extending cylindrically about a central axis (44); characterized in that said pulley assembly (41 , 26) is principally formed of stamped or rolled steel and comprises first and second ball bearing assemblies (50,

51) axially adjacent one another and against said inner wall (45), each of said ball bearing assemblies (50, 51) comprising an outer race (55, 58) in frictional contact with said inner wall (45), an inner race (56, 59) positioned radially inward of said outer race (55, 58), and a single row of balls (54, 57) supported between said outer and inner races for providing minimal friction during rotation of said pulley assembly.

2. The pulley assembly of claim 1 , characterized in that said ball bearing assemblies (50, 51) are substantially identical.

3. The pulley assembly of claim 1 , characterized in that said ball bearing assemblies (50, 51) are pressed fitted against said inner wall (45).

4. A power transmission system comprising driving and driven members, a belt (21) providing power transmission between said driving and driven members and having an inner driving surface (24) and an opposite outer surface (23), said system comprising a tensioner (22) with an operatively associated cylindrical pulley assembly (41) having an outer wall (46) contacting said outer belt surface (23) and an inner wall (45) extending cylindrically about a central axis (44); characterized in that said pulley assembly (41) is formed of stamped or rolled steel and comprises first and second ball bearing assemblies (50, 51) axially adjacent one another and against said inner wall (45), each of said ball bearing assemblies (50, 51) comprising an outer race (55, 58) in frictional contact with said inner wall (45), an inner race (56, 59) positioned radially inward of said outer race (55, 58), and a single row of balls (54, 57) supported between said outer and inner races for providing minimal friction during rotation of said pulley assembly.

5. The system of claim 4, characterized in that said ball bearing assemblies (50, 51) are substantially identical.

6. The system of claim 4, characterized in that said ball bearing assemblies (50, 51) are press fitted against said inner wall (45).

7. The system of claim 4, characterized in that said ball bearing assemblies (50, 51) are bonded against said inner wall (45).

8. A method of forming a pulley assembly for a power transmission system comprising driving and driven members, a belt (21) providing power transmission between said driving and driven members and having an inner driving surface (24) and an opposite outer surface (23), said cylindrical pulley assembly (41 ,

26) having an outer wall (46) contacting one of said belt surfaces (23, 24) and an inner wall (45) extending cylindrically about a central axis (44); the method characterized by the steps of forming said pulley assembly (41 , 26) of stamped or rolled steel, forming first and second ball bearing assemblies (50, 51) with an inner and an outer race (56, 55; 59, 58) in each of said ball bearing assemblies, placing a single row of spherical balls (54, 57) between said inner and outer race in each of said ball bearing assemblies (50, 51), and placing said first and second ball bearing assemblies axially adjacent one another in frictional contact with said inner wall (45) of said pulley assembly (41 , 26).

9. The method of claim 8, characterized by the further step of press fitting said ball bearing assemblies (50, 51) against said inner wall (45).

10. The method of claim 8, characterized by the further step of bonding said ball bearing assemblies (50, 51) against said inner wall (45).