Two-piece molded pulley exhibiting radial bearing distortion-reducing properties

Abstract

Pulley for use with a pulley belt, the pulley comprising the following: a pulley main housing comprising a central axis, a pulley surface having a rim, a belt running surface perpendicular to the rim, and a bearing recess formed in the surface coaxial to the axis; a bearing arranged in the recess, the bearing comprising an inner raceway having a side wall and an outer raceway having a side wall, wherein at least one of the inner raceway and the outer raceway has a raised surface formed on the side wall, wherein the raised surface is knurling and / or raised points; and an outer pulley shell which is attached to the main pulley housing, wherein the bearing is axially clamped between the housing and the shell.

Description

TECHNICAL FIELD

[0001] The disclosed inventive concept generally relates to pulley systems for vehicle engines. More specifically, the disclosed inventive concept relates to a two-piece pulley that is formed without the bearing in place, thereby eliminating an overmolding step. According to the disclosed manufacturing design and method, radial bearing warpage is reduced or eliminated. GENERAL STATE OF THE ART

[0002] The modern internal combustion engine typically includes a pulley drive system for driving accessories, driven by the engine crankshaft. The accessories typically include an air conditioning compressor, a power steering pump, a water pump, and an alternator. A front-end accessory drive belt is wound around pulleys to deliver power from the engine crankshaft to the accessories. The drive belt makes frictional contact with the running surface of the pulleys.

[0003] The drive belt is most commonly a flexible reinforced polymer belt.

[0004] Each of the accessories requires a driven pulley. Furthermore, operating multiple accessories, especially with a multi-V-ribbed drive belt, requires careful handling of the belt to allow for proper placement of the belt where needed to drive the accessories without slippage. Precise belt positioning often requires the use of one or more idler pulleys.

[0005] Pulleys such as idler pulleys incorporate a ball bearing (or other cartridge bearing) that is secured by either press-fitting the ball bearing into a recess or overmolding the ball bearing to retain it. While these are conventional approaches, both of these processes can result in distortion of the ball bearing's outer race, which can lead to an irregular internal radial clearance of the bearing itself. Such outer race distortion is known to contribute to undesirable NVH (noise, vibration, harshness) problems, while also reducing bearing life.

[0006] Another undesirable consequence of the assembly process is that the average inner radial gap of the bearing is altered during press-fitting or over-forming operations. As a consequence, the resulting inner radial gap tolerance of the bearing after press-fitting or over-forming cannot be precisely controlled.

[0007] Pulleys according to the prior art are known from the documents US 2 631 474 A, US 2 137 987 A, US 1 848 144 A, US 1 679 691 A, US 1 627 558 A, US 1 482 579 A, ​​US 1 177 046 A, US 859 099 A, US 2 669 878 A, US 2 655 814 A, US 2 655 813 A, US 2 349 281 A, US 2 315 357 A.

[0008] As in so many areas of automotive engineering, there is always room for improvement when designing a pulley for use in an internal combustion engine. In particular, it would be advantageous to precisely control the bearing's internal radial clearance, maximizing bearing life and minimizing negative NVH effects. SUMMARY OF THE INVENTION

[0009] The above-mentioned object is achieved by pulleys according to the independent claims. Preferred embodiments are the subject of the subclaims.

[0010] The disclosed inventive concept avoids the problems of known pulley designs by providing a two-piece pulley design in which the pulley main housing and outer pulley shell are molded without the bearing in place, thereby eliminating an over-molding process. The pulley main housing is molded with a mate for the bearing. A bearing assembly is mate into the mate. At least one of the bearing races of the bearing assembly includes an axially projecting raised surface. The raised surface may be knurled or may have another configuration, such as bosses. The pulley main housing and outer shell include a bearing shield.

[0011] During assembly, the bearing is inserted into the recess on the pulley main housing and the outer shell is then ultrasonically welded to the main housing, compressing the pulley material axially into the raised surface of the bearing race, securing the bearing outer race to the pulley in an axial direction.

[0012] By forming the two housing halves without the bearing in place, overmolding is eliminated, thus eliminating radial compression and distortion of the outer race. The raised surface on the bearing race allows the bearing assembly to grip the pulley in an axial direction.

[0013] The assembly process of the disclosed inventive concept avoids subjecting the bearing assembly itself to the type of high temperatures that commonly accompany the overmolding process. Furthermore, axially securing the ball bearing assembly within the pulley, rather than radially securing it, results in minimal impact on the roundness of the outer ball bearing race or the inner bearing radial gap. This design also provides a continuous (one-piece) belt running surface, unlike other two-piece pulley designs that split the running surface between the two parts of the pulley. Furthermore, the disclosed inventive concept provides a molded pulley that utilizes the two halves of the pulley as the radial structure, eliminating the need for an inner band, which is known to contribute to belt / pulley running surface NVH interactions.

[0014] The above advantages and other advantages and features will be readily apparent from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] For a more complete understanding of the present invention, reference will now be made to the embodiments shown in more detail in the accompanying drawings and described below by way of example, in which: Fig. 1 is a sectional view of a pulley according to existing art; Fig. 2 is a perspective view of a two-piece pulley according to the disclosed inventive concept; Fig. 3 is a front view of the two-piece pulley according to the disclosed embodiment of the invention; Fig. 4 illustrates a perspective view of the main pulley housing according to the disclosed inventive concept; Fig. 5 is a perspective view of the outer pulley shell according to the disclosed inventive concept; and Fig. 6 illustrates a sectional view of the two-piece pulley according to the disclosed inventive concept. DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] In the following figures, the same reference numbers are used to refer to the same components. The following description describes various operating parameters and components for various constructed embodiments. These specific parameters and components are included as examples and are not intended to be limiting.

[0017] In general, the disclosed inventive concept provides a two-piece pulley design including a main pulley housing, a mating recess for a bearing assembly, and an outer pulley shell. The main pulley housing is ultrasonically welded to the outer pulley shell. This arrangement differs significantly from known pulleys, where interference fitting or overmolding often results in distortion of the outer race of the ball bearing, resulting in an irregular internal radial clearance of the bearing, which, as noted above, contributes to NVH problems and reduces overall bearing life.

[0018] The arrangement of the disclosed inventive concept eliminates radial compression and distortion of the outer race of the bearing assembly. Furthermore, the design of the disclosed inventive concept also provides a continuous (one-piece) belt running surface, unlike other two-piece pulley designs that split the running surface between the two parts of a conventional pulley.

[0019] Accordingly, the design as presented and discussed avoids the problems typically associated with known pulley designs.

[0020] A pulley according to the state of the art is in Fig. 1. As shown, and as will be understood, assembling parts according to known pulley designs by interference fitting or overmolding often results in distortion of the ball bearing outer race, resulting in an irregular internal radial clearance of the bearing, which, as noted above, contributes to NVH problems and reduces overall bearing life.

[0021] Referring to Fig. Figure 1 is a sectional view of a pulley according to the prior art. The pulley, generally indicated at 10, includes a first half 12 and a second half 14. The halves 12 and 14 are conventionally secured, for example, by fasteners 16 and 16'. When the two halves 12 and 14 are secured together, a pulley surface 18 is defined between a peripheral wall 20 formed on the first half 12 and a peripheral wall 20' formed on the second half 14. A central bore 22 is defined through the assembled halves 12 and 14, and a bearing recess 24 is formed therebetween. A bearing 26 is installed, typically by an interference fit, into the bearing recess 24.

[0022] The disclosed inventive concept represents a desirable alternative to the Fig. 1, which is described herein with reference thereto. In particular, the design of the disclosed inventive concept provides a pulley in which the radial compression and distortion of the outer race of the bearing assembly have been eliminated. The disclosed inventive concept is shown in Fig. 2 to 6 and is described below.

[0023] The disclosed inventive concept represents a desirable alternative to the Fig. 1, which is described here with reference to it.

[0024] Referring to Fig. Figure 2 is a perspective view of a two-piece pulley according to the disclosed inventive concept, generally shown as 30. In Fig. 3 shows a side view of the two-part pulley 30.

[0025] The two-piece pulley 30 includes a pulley main housing 32 and an outer pulley shell 34. The pulley main housing 32 and the outer pulley shell 34 are attached to form the housing for the two-piece pulley 30, which includes a belt running surface 36 perpendicular to the pulley main housing 32. The belt running surface 36 is integrally connected to the pulley main housing 32. It should be understood that the specific shape and size of the pulley 30 as shown in the figures is merely a suggestion and is not intended to be limiting. For example, the width of the pulley 30, as well as its diameter, could be varied. The pulley main housing 32 and the outer pulley shell 34 are molded without the bearing in place, thereby eliminating an over-molding process.Although the pulley main housing 32 and the outer pulley shell 34 are preferably composed of a polymerized material, one or both could be constructed of a metal such as steel or aluminum.

[0026] A central bore 38 is formed through the pulley main housing 32 and the outer pulley shell 34. A bearing assembly 40 is provided centrally in the central bore 38. The bearing assembly 40 includes both an inner race 42 and an outer race, explained below. An inner bearing shield 44 is provided, preferably formed as part of the pulley main housing 32. An outer bearing shield is also provided, preferably formed as part of the outer pulley shell 34, as also explained below. The side view of the pulley 30 shown in Fig. 3 is from the outer pulley shell side 34.

[0027] Referring to Fig. Figure 4 is a perspective view of the pulley main housing 32 shown in isolation. Centrally formed within the pulley main housing 32 is a plug-in bearing recess 46 defined by a peripheral bearing wall 48. As will be understood, the shape of the plug-in bearing recess 46 can be varied as needed to accommodate different types and sizes of bearings. The plug-in bearing recess 46 is formed as part of the pulley main housing 32, thereby eliminating radial compression and distortion of the outer race. Fig. 5 illustrates a perspective view of the outer pulley shell 34 in isolation.

[0028] Referring to Fig.6 is a sectional view of pulley 30. The sectional view of pulley 30 illustrates pulley main housing 32, outer pulley cup 34, belt race 36, central bore 38, and bearing assembly 40 positioned within bearing recess 46. Bearing assembly 40 includes an outer race 50 in addition to inner race 42. Sandwiched between inner race 42 and outer race 50 are a plurality of bearings 52 retained by any known method, including a bearing cage. Inner bearing shield 44, formed as part of pulley main housing 32, and outer bearing shield 51, formed as part of outer pulley cup 34, prevent dirt and other foreign matter from entering bearing assembly 40.By integrating the inner bearing shield 44 into the pulley main housing 32 and by integrating the outer bearing shield 51 into the outer pulley shell 34, the need for additional bearing shields is thus eliminated.

[0029] The illustrated bearing assembly 40 is of the radial ball bearing type, however, it is understood that other bearing types may be used, including, but not limited to, other ball bearing types, including angular contact ball bearings and deep groove ball bearings, and may further include, without limitation, roller bearing types such as spherical roller bearings, thrust bearings, needle roller bearings, and tapered roller bearings. Thus, the disclosed inventive concept can be readily adapted for use in virtually any application requiring a pulley.

[0030] At least one of the sidewalls of the bearing races, preferably the sidewalls of the outer race 50, includes a raised surface 54, defined, for example, as a knurled surface or as raised protrusions projecting axially around one or both sides of the bearing race. The raised surfaces 54 are provided to axially engage the pulley main housing 32 and the outer pulley shell 34.

[0031] To assemble the pulley 30 of the disclosed inventive concept, the bearing assembly is inserted into the bearing insertion recess 46 of the pulley main housing 32. The outer pulley shell 34 is then positioned over the pulley main housing 32 and is secured thereto, preferably but not exclusively, by ultrasonic welding, which axially compresses the pulley material into the raised surfaces 54 of the outer race 50, thus axially securing the outer race 50 of the bearing assembly 40 to the pulley. Preferably but not exclusively, the outer pulley shell 34 is welded to the pulley main housing at the insertion recess weld 58 and the belt race weld 60.

[0032] The pulley 30 of the disclosed inventive concept provides several advantages over known pulley designs. For example, the pulley 30 is a molded pulley, which does not require a bearing overmolding process that exposes the bearing to high temperatures. The axial retention of the ball bearing assembly 40 within the pulley 30, rather than radial retention, results in minimal impact on the roundness of the outer ball bearing race 50 or the inner bearing radial gap. This design of the pulley 30, as set forth herein, also allows for a continuous (one-piece) belt running surface, unlike other two-piece pulley designs that split the belt running surface between the two parts of the pulley.Furthermore, the disclosed inventive concept provides a molded pulley 30 that utilizes the two halves of the pulley 30, the outer pulley shell 34 and the pulley main housing 32, as a radial structure, thereby eliminating the need for an inner band, which is known to contribute to belt / pulley raceway NVH interactions. From the above discussion and the accompanying drawings and claims, it will be readily apparent to one skilled in the art that various changes, modifications, and variations may be made without departing from the true spirit and legitimate scope of the invention as set forth in the following claims.

Claims

[1] Pulley for use with a pulley belt, the pulley comprising: a pulley main housing including a central axis, a pulley surface having a rim, a belt running surface perpendicular to the rim, and a bearing recess formed in the surface coaxial with the axis; a bearing disposed in the recess, the bearing including an inner race having a sidewall and an outer race having a sidewall, at least one of the inner race and the outer race including a raised surface formed on the sidewall, the raised surface being knurling and / or raised points; and an outer pulley shell fixed to the pulley main housing, with the bearing axially clamped between the housing and the shell. [2] A pulley for use with a pulley belt according to claim 1, wherein the pulley main housing and the outer pulley shell are formed from a material selected from the group consisting of a molded polymerized material and a metal. [3] A pulley for use with a pulley belt according to claim 2, wherein the pulley main body and the outer pulley shell are secured by ultrasonic welding. [4] A pulley for use with a pulley belt according to claim 1, wherein the pulley main housing and the outer pulley shell include a bearing shield positioned adjacent to the bearing when assembled. [5] A pulley for use with a pulley belt, the pulley comprising: a pulley main housing including a central axis, a pulley surface having a rim, a belt running surface perpendicular to the rim, and a bearing recess formed in the surface coaxial with the axis; a bearing disposed in the recess, the bearing having a sidewall having at least one axially raised surface, the raised surface being knurling and / or raised points; and an outer pulley shell attached to the pulley main housing. [6] A pulley for use with a pulley belt according to claim 5, wherein the bearing is axially clamped between the housing and the shell. [7] A pulley for use with a pulley belt according to claim 6, wherein the pulley main housing and the outer pulley shell are formed from a material selected from the group consisting of a molded polymerized material and a metal. [8] A pulley for use with a pulley belt according to claim 7, wherein the pulley main body and the outer pulley shell are secured by ultrasonic welding. [9] A pulley for use with a pulley belt according to claim 5, wherein the bearing includes an inner race having a sidewall and an outer race having a sidewall. [10] A pulley for use with a pulley belt according to claim 9, wherein the at least one axially raised surface is formed on a side wall of the inner race and / or the outer race. [11] A pulley for use with a pulley belt according to claim 5, wherein the pulley main housing and the outer pulley shell include a bearing shield positioned adjacent to the bearing when assembled.

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