Pulley structure

Abstract

To provide a pulley structure capable of inhibiting vibration of an outer rotating body or an inner rotating body due to force applied from a sliding bearing or a portion composed of the sliding bearing and rust to generate an abnormal noise.SOLUTION: A pulley structure 1 comprises a cylindrical outer rotating body 2 that is rotated about a rotation axis A by a torque applied from a wound belt B, an inner rotating body 3 that is provided on the inner side in the radial direction of the outer rotating body 2 and can be rotated about the rotation axis A relatively to the outer rotating body 2, and a pair of bearings 6, 7 that intervene between the outer rotating body 2 and the inner rotating body 3 on each of one end side and the other end side in an axial direction along the rotation axis A and connect the outer rotating body 2 and the inner rotating body 3 in a relatively-rotatable manner. An elastic sleeve 5 is provided between an outer cylinder portion 3b of the inner rotating body 3, on which the sliding bearing 6, one of the pair of bearings 6, 7, is provided, and the sliding bearing 6. The elastic sleeve 5 is formed to be compressive-elastically deformable in the radial direction when force is applied from the belt B.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pulley structure provided with a sliding bearing.

Background Art

[0002] The pulley structure described in Patent Document 1 includes an outer rotating body, an inner rotating body, and a pair of bearings. The outer rotating body is a cylindrical member around which a belt is wound and which rotates about a predetermined rotation axis by the torque applied from this belt. The inner rotating body is provided radially inside the outer rotating body and is relatively rotatable with respect to the outer rotating body about the rotation axis. The pair of bearings are disposed between the outer rotating body and the inner rotating body at one end side and the other end side in the axial direction along the rotation axis, and connect the outer rotating body and the inner rotating body so as to be relatively rotatable. Further, one of the pair of bearings is a sliding bearing, and the other bearing is a rolling bearing. This sliding bearing is made of a thermoplastic resin and is formed in an endless annular shape.

[0003] In Patent Document 1, since the thicknesses of both circumferential ends of the sliding bearing produced by the injection molding method are slightly larger than the thicknesses of the portions other than both circumferential ends, when a force is applied from the belt of the outer rotating body, the gap between the outer rotating body and the inner rotating body is widened. Thus, in order to solve the problem that vibrations occur in the outer rotating body or the inner rotating body and abnormal noises are generated due to the periodic application of force from the sliding bearing (both circumferential ends) to the outer rotating body or the inner rotating body, attention is paid to the configuration of the sliding bearing, and a pulley structure is disclosed in which the sliding bearing is formed such that the thicknesses of both circumferential ends are smaller than the thicknesses of the portions other than both circumferential ends.

[0004] The above problem (the problem that the outer rotating body or the inner rotating body vibrates and abnormal noise occurs) is that when the outer rotating body and the inner rotating body rotate relative to each other, every time a portion where the thickness of the sliding bearing is larger than the reference dimension (the portions with large thickness at both circumferential ends) reaches a position facing the portion where force is applied from the belt of the outer rotating body, the sliding bearing applies a force radially outward to the outer rotating body so as to widen the gap between the outer rotating body and the inner rotating body, thereby causing the problem. That is to say, the above problem is, so to speak, caused by the convex portion of the sliding bearing itself where the thickness of the sliding bearing is larger than the reference dimension.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the above problem (the problem that the outer rotating body or the inner rotating body vibrates and abnormal noise occurs) may also be caused by rust due to corrosion occurring in the portion of the outer rotating body or the inner rotating body where the sliding bearing is provided, as inferred by the inventors' more detailed observations (described below).

[0007] (Regarding the occurrence of rust) Previously, a lubricant (rust preventive agent) such as grease was enclosed in the space U (see FIG. 1 of Patent Document 1), and when the pulley structure is operated, the lubricant diffuses throughout the space U. However, it was found that the more the following conditions a to c overlap, the more likely it is that rust that has progressed due to corrosion of the portion of the outer rotating body or the inner rotating body where the sliding bearing is provided (hereinafter, this portion) will occur in this portion.

[0008] a. During assembly, if an operator accidentally touches the part (e.g., the outer peripheral surface of the outer cylinder 3b of the inner rotating body) with bare hands, the salt content of the sweat on the hands will adhere to the part, promoting the progress of rust due to corrosion of the part.

[0009] b. For example, in the final inspection (engine start test) of an alternator provided with a pulley structure, which is carried out by the manufacturer of the alternator or the like, in a pulley structure configured such that a lubricant diffuses throughout the internal space of the pulley structure by operating the pulley structure, it will be left for about three months after manufacturing until the diffusion operation of the lubricant is performed.

[0010] c. Since the part is provided with a sliding bearing, depending on the degree of contact (adhesion) of the sliding bearing with the part, there is a possibility that the lubricant may not spread sufficiently even when the pulley structure is operated.

[0011] (Speculation) That is, not only the convex part of the sliding bearing itself (the part where the thickness of the sliding bearing is larger than the reference dimension), but also the so-called convex part composed of the sliding bearing and rust (the part where the overall thickness of the part composed of the sliding bearing and rust is larger than the reference dimension of the thickness of the sliding bearing), every time the convex part composed of the sliding bearing and rust reaches a position facing the part where the force is applied from the belt of the outer rotating body while the outer rotating body and the inner rotating body are relatively rotating, there is a possibility that the convex part composed of the sliding bearing and rust applies a force radially outward to the outer rotating body so as to widen the gap between the outer rotating body and the inner rotating body.

[0012] In this case, merely adopting the solution described in Patent Document 1 (using a sliding bearing formed such that the thicknesses of both circumferential ends are smaller than the thicknesses of portions other than both circumferential ends) is insufficient to solve the problem (the problem that the outer rotating body or the inner rotating body vibrates and abnormal noise is generated). It can be seen that there is potentially a need for a pulley structure capable of suppressing the generation of abnormal noise due to vibration of the outer rotating body or the inner rotating body even if rust occurs in the portion of the outer rotating body or the inner rotating body where the sliding bearing is provided.

[0013] Therefore, an object of the present invention is to provide a pulley structure capable of suppressing the occurrence of vibration of the outer rotating body or the inner rotating body and the generation of abnormal noise due to the force applied from a sliding bearing or a portion composed of a sliding bearing and rust.

Means for Solving the Problem

[0014] The present invention includes a cylindrical outer rotating body around which a belt is wound and which rotates about a rotation axis by torque applied from the belt, an inner rotating body provided on the radially inner side of the outer rotating body and relatively rotatable with respect to the outer rotating body about the rotation axis, a pair of bearings interposed between the outer rotating body and the inner rotating body at one end side and the other end side in the axial direction along the rotation axis, and connecting the outer rotating body and the inner rotating body so as to be relatively rotatable, and is a pulley structure comprising: at least one of the pair of bearings is a sliding bearing, further comprising an elastic sleeve provided between a portion of the outer rotating body or the inner rotating body where the sliding bearing is provided and the sliding bearing, characterized in that when a force is applied from the belt, the elastic sleeve is formed to be elastically compressible and deformable in the radial direction.

[0015] According to the above configuration, an elastic sleeve formed to be elastically compressible and deformable in the radial direction when a force is applied from the belt is provided between a portion of the outer rotating body or the inner rotating body where the sliding bearing is provided and the sliding bearing. Therefore, even when rust due to corrosion occurs in the portion of the outer rotating body or the inner rotating body where the sliding bearing is provided, so-called a convex portion composed of the sliding bearing and rust (a portion where the overall thickness of the portion composed of the sliding bearing and rust is larger than the reference dimension of the thickness of the sliding bearing), the elastic sleeve can absorb the dimensional expansion in the radial (thickness) direction with respect to the reference dimension of the thickness of the sliding bearing (that is, the length dimension obtained by subtracting the reference dimension of the thickness of the sliding bearing from the overall thickness of the portion composed of the sliding bearing and rust). (That is, by the elastic sleeve being elastically deformed by compression by the amount of dimensional expansion, the displacement in the radial direction of the outer rotating body can be sufficiently suppressed). Thereby, when a force is applied from the belt of the outer rotating body while the outer rotating body and the inner rotating body are relatively rotating, every time the convex portion composed of the sliding bearing and rust reaches a position facing the portion where the force is applied from the belt of the outer rotating body, a force is periodically applied from the sliding bearing and rust to the outer rotating body or the inner rotating body, so that vibration and abnormal noise can be prevented from occurring in the outer rotating body or the inner rotating body. In addition, the impact transmitted from one rotating body to the other rotating body through the sliding bearing can be alleviated by the elastic sleeve. Therefore, the effect of suppressing the generation of abnormal noise due to the vibration of the outer rotating body or the inner rotating body can be further improved. In addition, the sliding surface facing the outer rotating body or the inner rotating body that forms a gap (hereinafter, sliding gap) generated when the outer rotating body or the inner rotating body slides with the sliding bearing is one end surface in the radial direction of the sliding bearing, not one end surface in the radial direction of the elastic sleeve. Therefore, there is no possibility of inhibiting the characteristics (low friction slidability and wear resistance) that the sliding bearing should have when the outer rotating body and the inner rotating body relatively rotate.

[0016] In addition, in the present invention, in the pulley structure, the elastic sleeve is in close contact with the inner rotating body by the self-elastic restoring force in the diameter-reducing direction because the inner peripheral surface is in contact with the inner rotating body in an expanded diameter state, The sliding bearing may be characterized in that, in an enlarged diameter state, the inner peripheral surface thereof is in contact with the inner rotating body via the elastic sleeve, and thus it is in close contact with the inner rotating body via the elastic sleeve by its own elastic restoring force in the diameter reducing direction.

[0017] According to the above configuration, when a force is applied from the belt, while ensuring the design freedom of the substitute characteristics (hardness, elastic modulus, etc.) related to the elasticity of the elastic sleeve so that it can be elastically compressed and deformed in the diameter (thickness) direction, the adhesion between the sliding bearing and the elastic sleeve, and the sliding bearing and the elastic sleeve and the part of the rotating body (inner rotating body) where they are provided can be made higher.

[0018] Further, the present invention may be characterized in that, in the pulley structure, the elastic sleeve is made of synthetic rubber.

[0019] According to the above configuration, the elastic sleeve has excellent heat resistance, oil resistance, etc. As a result, it can be suitably used as a pulley structure provided in a belt system for driving auxiliary machines of an automobile engine.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0021] (Embodiment) Hereinafter, the pulley structure 1 of the embodiment of the present invention will be described.

[0022] 〈Structure of Pulley Structure 1〉 The pulley structure 1 according to the embodiment of the present invention shown in FIG. 1 is attached to the drive shaft S of the alternator, for example, in an accessory drive system of an automobile. The accessory drive system includes a drive pulley attached to the crankshaft of the engine, a driven pulley that drives accessories such as an alternator, and the pulley structure 1, and a belt B wound around these pulleys and the pulley structure 1. By transmitting the rotation of the crankshaft to the driven pulley and the pulley structure 1 via the belt B, accessories such as the alternator are driven. As the rotational speed of the crankshaft varies according to the combustion of the engine, the running speed of the belt B also varies.

[0023] As shown in FIGS. 1 and 2, the pulley structure 1 includes an outer rotating body 2, an inner rotating body 3, a torsion coil spring 4 (hereinafter simply referred to as "spring 4"), an elastic sleeve 5, a pair of bearings 6 and 7 including a sliding bearing 6 and a rolling bearing 7, and an end cap 8.

[0024] (Outer rotating body 2 and inner rotating body 3) Both the outer rotating body 2 and the inner rotating body 3 are substantially cylindrical and have the same rotation axis A (the rotation axis of the pulley structure 1, hereinafter simply referred to as "rotation axis A"). The rotation axis A extends along the left - right direction (axial direction) of FIG. 1. Also, hereinafter, the right side of FIG. 1 is referred to as one end side in the axial direction, and the left side of FIG. 1 is referred to as the other end side in the axial direction.

[0025] The outer rotating body 2 has a belt B wound around its outer peripheral surface. As shown in FIG. 1, the inner diameter of the outer rotating body 2 decreases in two steps from the other end to one end. The inner peripheral surface of the outer rotating body 2 at the smallest inner diameter portion is referred to as the pressure contact surface 2a, and the inner peripheral surface of the outer rotating body 2 at the second - smallest inner diameter portion is referred to as the annular surface 2b. The inner diameter of the outer rotating body 2 at the pressure contact surface 2a is smaller than the inner diameter of the outer cylindrical portion 3b of the inner rotating body 3. The inner diameter of the outer rotating body 2 at the annular surface 2b is the same as or larger than the inner diameter of the outer cylindrical portion 3b of the inner rotating body 3.

[0026] The inner rotating body 3 is provided inside the outer rotating body 2 and is relatively rotatable with respect to the outer rotating body 2. The inner rotating body 3 has a cylindrical main body 3a into which the drive shaft S of the alternator is fitted, an outer cylindrical portion 3b disposed outside the other end of the cylindrical main body 3a, and an annular plate portion 3c connecting the other end of the cylindrical main body 3a and the other end of the outer cylindrical portion 3b. The drive shaft S is screwed into the screw groove on the inner peripheral surface of the cylindrical main body 3a.

[0027] The outer diameter of the cylindrical main body 3a of the inner rotating body 3 increases at the other end side. The outer peripheral surface of the cylindrical main body 3a of the inner rotating body 3 at this portion is referred to as the contact surface 3ax.

[0028] (Spring 4) The spring 4 is disposed between the outer rotating body 2 and the inner rotating body 3. Specifically, the spring 4 is accommodated in a space U that is defined by the inner circumferential surface of the outer rotating body 2, the inner circumferential surface of the outer cylindrical portion 3b of the inner rotating body 3, the outer circumferential surface of the cylindrical main body 3a of the inner rotating body 3, and the annular plate portion 3c of the inner rotating body 3, and is on the other end side of the rolling bearing 7. The spring 4 is composed of a wire rod having a square cross section (for example, oil-tempered wire for springs (conforming to JIS G3560:1994), etc.), and is wound left (counterclockwise from the other end side to the one end side of the spring 4).

[0029] The space U is filled with a lubricant such as grease. The lubricant is put into the space U in the state of a paste-like mass when the pulley structure 1 is assembled. The amount of input is, for example, about 0.2 g. When the pulley structure 1 is operated, the viscosity of the lubricant decreases due to the temperature rise and shear heat generation (frictional heat) in the space U, and the lubricant diffuses throughout the space U.

[0030] The spring 4 has a one end side region 4a that contacts the outer rotating body 2 at one end side, a other end side region 4b that contacts the inner rotating body 3 at the other end side, and a middle region 4c that does not contact either the outer rotating body 2 or the inner rotating body 3 between the one end side region 4a and the other end side region 4b. The one end side region 4a and the other end side region 4b each refer to a region extending over half a turn or more (180° or more around the rotation axis) from one end and the other end of the spring 4. Also, in the other end side region 4b, the position near 90° away from the other end of the spring 4 around the rotation axis is called the second region 4b2, the portion on the other end side of the second region 4b2 is called the first region 4b1, and the remaining portion is called the third region 4b3 (see FIG. 2).

[0031] In a state where the spring 4 is not receiving an external force, the diameter is constant over the entire length, and the outer diameter of the spring 4 at this time is smaller than the inner diameter of the outer rotating body 2 on the annular surface 2b and larger than the inner diameter of the outer rotating body 2 on the pressure contact surface 2a. That is, the spring 4 is accommodated in the space U in a state where the one end side region 4a has a reduced diameter.

[0032] Further, the spring 4 is axially compressed in a state where no external force is applied to the pulley structure 1 (i.e., the state where the pulley structure 1 has stopped). At this time, the outer peripheral surface of one end side region 4a of the spring 4 is pressed against the pressure contact surface 2a by the self-elastic restoring force of the spring 4 in the diameter-expanding direction, and the other end side region 4b of the spring 4 is in contact with the contact surface 3ax in a slightly diameter-expanded state. That is, the inner peripheral surface of the other end side region 4b of the spring 4 is pressed against the contact surface 3ax by the self-elastic restoring force of the spring 4 in the diameter-reducing direction.

[0033] As shown in FIG. 2, a contact surface 3d facing the other end surface 4bx of the spring 4 is formed at the other end portion of the inner rotating body 3. Further, a protrusion 3e protruding radially inward of the outer cylinder portion 3b and facing the outer peripheral surface of the other end side region 4b is provided on the inner peripheral surface of the outer cylinder portion 3b. The protrusion 3e faces the second region 4b2.

[0034] In a state where the inner peripheral surface of the other end side region 4b of the spring 4 is in contact with the contact surface 3ax, a gap is formed between the outer peripheral surface of the other end side region 4b of the spring 4 and the inner peripheral surface of the outer cylinder portion 3b of the inner rotating body 3. Also, a gap is formed between the annular surface 2b of the outer rotating body 2 and the outer peripheral surface of the spring 4. In the present embodiment, in a state where no external force is applied to the pulley structure 1, as shown in FIG. 2, the outer peripheral surface of the torsion coil spring 4 and the protrusion 3e are separated from each other, and a gap is formed between them, but they may be in contact with each other.

[0035] (Elastic sleeve 5) The elastic sleeve 5 is a cylindrical elastic member formed of a synthetic rubber (for example, a rubber composition containing a rubber component such as chloroprene rubber, urethane rubber, nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, silicone rubber, fluorine rubber, etc.) (see FIGS. 4 and 5). This cylindrical elastic sleeve 5 is provided between the outer peripheral surface of the outer cylinder portion 3b of the inner rotating body 3 and the inner peripheral surface 6a of the sliding bearing 6 as shown in FIGS. 1 and 2.

[0036] Specifically, the elastic sleeve 5 is mounted on the outer peripheral surface of the outer cylindrical portion 3b of the inner rotating body 3 in a slightly expanded diameter state, and the inner peripheral surface of the elastic sleeve 5 is in close contact with the outer peripheral surface of the outer cylindrical portion 3b by its own elastic restoring force in the diameter-reducing direction. Further, the inner peripheral surface of the elastic sleeve 5 has a substantially constant diameter over its entire circumference, and the entire circumference of the inner peripheral surface of the elastic sleeve 5 is in close contact with the outer peripheral surface of the outer cylindrical portion 3b.

[0037] Note that the inner diameter of the elastic sleeve 5 may be formed to be the same as the outer diameter of the outer peripheral surface of the outer cylindrical portion 3b of the inner rotating body 3, or may be formed slightly smaller. When the inner diameter of the elastic sleeve 5 is made slightly smaller than the outer diameter of the outer peripheral surface of the outer cylindrical portion 3b of the inner rotating body 3, it is preferably formed about 5% smaller.

[0038] Also, a part or all of the inner peripheral surface of the elastic sleeve 5 and the outer peripheral surface of the outer cylindrical portion 3b may be subjected to an adhesion treatment.

[0039] The reference thickness of the elastic sleeve 5 is the dimension increase amount in the radial (thickness) direction with respect to the reference dimension of the thickness of the sliding bearing 6 in the convex portion composed of the sliding bearing 6 and rust (the portion where the overall thickness of the portion composed of the sliding bearing 6 and rust is larger than the reference dimension of the thickness of the sliding bearing 6), and may be determined after confirming the vibration width in the radial direction of the outer rotating body 2, the vibration acceleration of the alternator, and the noise reduction effect obtained by evaluation using, for example, an idle tester described later.

[0040] The axial length of the elastic sleeve 5 may be the same as or slightly larger than the axial length of the sliding bearing 6, and may be formed to be substantially the same as the inner width of the protrusions provided on both sides of the sliding bearing 6 and the elastic sleeve 5 on the outer peripheral surface of the outer cylindrical portion 3b.

[0041] The hardness of the elastic sleeve 5 is preferably in the range of 50 to 90, more preferably 60 to 80, in terms of durometer A hardness (conforming to JIS K6253:2012). When the Shore A hardness is less than 50, the elastic sleeve 5 will reach the bottoming state prematurely. When the outer rotating body 2 and the inner rotating body 3 rotate relative to each other and a force is applied from the belt B of the outer rotating body 2, the elastic sleeve 5 cannot sufficiently absorb the dimensional expansion in the radial (thickness) direction with respect to the reference dimension of the thickness of the sliding bearing 6 in the convex portion composed of the sliding bearing 6 and rust. That is, when the elastic sleeve 5 cannot sufficiently suppress the displacement of the outer rotating body 2 in the radial direction, it may be difficult to prevent vibrations and abnormal noises from occurring in the outer rotating body 2 or the inner rotating body 3. On the other hand, when the Shore A hardness exceeds 90, it becomes difficult for the elastic sleeve 5 to undergo compressive elastic deformation in its thickness direction. Similarly, when a force is applied from the belt B of the outer rotating body 2, it may be difficult to prevent vibrations and abnormal noises from occurring in the outer rotating body 2 or the inner rotating body 3.

[0042] (A pair of bearings 6, 7) The pair of bearings 6 and 7 are interposed between the outer rotating body 2 and the inner rotating body 3 at each of the one end side and the other end side. Specifically, a sliding bearing 6 is interposed through an elastic sleeve 5 in a gap (hereinafter referred to as a "cylindrical gap") between the inner peripheral surface on the other end side of the outer rotating body 2 and the outer peripheral surface of the outer cylindrical portion 3b of the inner rotating body 3. Also, a rolling bearing 7 is interposed between the inner peripheral surface on the one end side of the outer rotating body 2 and the outer peripheral surface on the one end side of the cylindrical main body 3a of the inner rotating body 3. The outer rotating body 2 and the inner rotating body 3 are connected so as to be relatively rotatable by the pair of bearings 6 and 7. The outer rotating body 2 and the inner rotating body 3 rotate clockwise (in the direction of the arrow in FIG. 2. Hereinafter referred to as the "positive direction") when viewed from the direction from the other end side to the one end side.

[0043] (Sliding bearing 6) The sliding bearing 6 is an end-ring-shaped member, and there is a gap 6d between both circumferential ends of the sliding bearing 6 (see FIGS. 2 and 3). The sliding bearing 6 is formed of a hard thermoplastic resin with a Rockwell R scale (conforming to JIS K7202-2:2001) of 80 to 130. Specifically, the sliding bearing 6 is made of polyacetal resin, polyamide resin, polycarbonate, modified polyphenylene ether, polyester (such as polybutylene terephthalate, polyethylene terephthalate, etc.), fluororesin, polyphenylene sulfide, polysulfone, amorphous polyarylate, polyetherimide, polyethersulfone, polyether ketones, liquid crystal polymer, polyamideimide, thermoplastic polyimides, syndiotactic polystyrene, olefin resins (such as polyethylene, polypropylene, etc.), styrene resins (such as ABS resin, polystyrene, etc.), polyvinyl chloride, vinylidene chloride resins, methacrylic resins, polyvinyl alcohol, styrene-based block copolymer resins, etc. However, from the viewpoints of low friction slidability and wear resistance, etc., it is more preferable that the sliding bearing 6 is formed of polyacetal resin and polyamide resin among these materials. Also, the hardness of the sliding bearing 6 according to the Rockwell R scale is more preferably about 85 to 125.

[0044] Also, the sliding bearing 6 may be a single-layer one formed of one kind of resin composition, or a multi-layer one formed of two or more kinds of resin compositions. However, from the viewpoint of manufacturing cost, it is more preferable that the sliding bearing 6 is a single-layer one formed of one kind of resin composition.

[0045] The sliding bearing 6 is mounted on the outer peripheral surface of the outer cylinder portion 3b of the inner rotating body 3 via the elastic sleeve 5 in a slightly enlarged diameter state. The inner peripheral surface 6a of the sliding bearing 6 is in close contact with the outer peripheral surface of the outer cylinder portion 3b via the elastic sleeve 5 by its self-elastic restoring force in the diameter-reducing direction. Further, the inner peripheral surface 6a of the sliding bearing 6 has a substantially constant diameter over its entire circumference, and the entire circumference of the inner peripheral surface 6a is in close contact with the outer peripheral surface of the outer cylinder portion 3b via the elastic sleeve 5. On both sides of the sliding bearing 6 and the elastic sleeve 5 on the outer peripheral surface of the outer cylinder portion 3b, protrusions for preventing the sliding bearing 6 and the elastic sleeve 5 from coming off are provided. The sliding bearing 6 and the elastic sleeve 5 are slightly axially movable between the protrusions.

[0046] There is a gap R (sliding gap R) of about 0.1 mm, for example, between the outer peripheral surface 6b of the sliding bearing 6 and the inner peripheral surface of the outer rotating body 2. When the lubricant enclosed in the space U enters the gap R, wear of the friction surface of the sliding bearing 6 (the contact surface with the outer rotating body 2 in the sliding bearing 6) is suppressed. Note that the lubricant hardly leaks out from this gap R to the other end side.

[0047] Also, the sliding bearing 6 has a greater thickness at both circumferential ends than at portions other than both circumferential ends. That is, the thickness of the sliding bearing 6 at both circumferential ends is greater than the reference dimension of the thickness of the sliding bearing 6. In other words, the sliding bearing 6 has a main portion with a substantially constant thickness and both ends with a greater thickness. Note that the reference dimension of the thickness of the sliding bearing 6 refers to the design reference dimension of the thickness of the sliding bearing 6, and is, for example, 1.40 mm in the case of Examples 1 and 2 described later.

[0048] (Rolling bearing 7) The rolling bearing 7 is a contact seal type sealed ball bearing, which includes an outer ring 7a fixed to the inner peripheral surface of the outer rotating body 2, an inner ring 7b fixed to the outer peripheral surface of the cylindrical main body 3a of the inner rotating body 3, a plurality of balls (rolling elements) 7c rotatably arranged between the outer ring 7a and the inner ring 7b, and annular contact seal members 7d arranged on both axial sides of the plurality of balls 7c. By enclosing a lubricant such as grease (for example, the same lubricant as the lubricant enclosed in the space U) inside the rolling bearing 7, wear of the friction surface of the rolling bearing 7 (the contact surface of the balls 7c with the outer ring 7a and / or the inner ring 7b) is suppressed.

[0049] (End cap 8) The end cap 8 is arranged on the other end sides of the outer rotating body 2 and the inner rotating body 3.

[0050] 〈Operation of the pulley structure〉 Here, the operation of the pulley structure 1 will be described.

[0051] First, the case where the rotational speed of the outer rotating body 2 becomes higher than the rotational speed of the inner rotating body 3 (that is, the case where the outer rotating body 2 accelerates) will be described.

[0052] In this case, the outer rotating body 2 rotates relative to the inner rotating body 3 in the positive direction (the direction of the arrow in FIG. 2). Along with the relative rotation of the outer rotating body 2, one end side region 4a of the spring 4 moves together with the pressure contact surface 2a and rotates relative to the inner rotating body 3. As a result, the spring 4 is twisted in the diameter-expanding direction. The pressure contact force of the one end side region 4a of the spring 4 against the pressure contact surface 2a increases as the twist angle of the spring 4 in the diameter-expanding direction increases. The second region 4b2 is most susceptible to torsional stress, and as the twist angle of the spring 4 in the diameter-expanding direction increases, it moves away from the contact surface 3ax. At this time, the first region 4b1 and the third region 4b3 are in pressure contact with the contact surface 3ax. At substantially the same time as the second region 4b2 moves away from the contact surface 3ax, or when the twist angle of the spring 4 in the diameter-expanding direction further increases, the outer peripheral surface of the second region 4b2 abuts against the protrusion 3e. When the outer peripheral surface of the second region 4b2 abuts against the protrusion 3e, the deformation of the other end side region 4b in the diameter-expanding direction is restricted, and the torsional stress is dispersed to portions of the spring 4 other than the other end side region 4b, particularly increasing the torsional stress acting on the one end side region 4a of the spring 4. As a result, the difference in the torsional stress acting on each part of the spring 4 is reduced, and since the spring 4 can absorb strain energy as a whole, local fatigue failure of the spring 4 can be prevented.

[0053] In addition, the pressing force of the contact surface 3ax of the third region 4b3 decreases as the torsional angle of the spring 4 in the diameter-expanding direction increases. When the second region 4b2 comes into contact with the protrusion 3e, or when the torsional angle of the spring 4 in the diameter-expanding direction becomes even larger, the pressing force of the contact surface 3ax of the third region 4b3 becomes substantially zero. Let the torsional angle of the spring 4 in the diameter-expanding direction at this time be θ1 (for example, θ1 = 3°). When the torsional angle of the spring 4 in the diameter-expanding direction exceeds θ1, the third region 4b3 moves away from the contact surface 3ax by deforming in the diameter-expanding direction. However, near the boundary between the third region 4b3 and the second region 4b2, the spring 4 does not bend (flex), and the other-end-side region 4b is maintained in an arc shape. That is, the other-end-side region 4b is maintained in a shape that is easy to slide with respect to the protrusion 3e. Therefore, when the torsional angle of the spring 4 in the diameter-expanding direction increases and the torsional stress acting on the other-end-side region 4b increases, the other-end-side region 4b slides in the circumferential direction of the outer rotating body 2 with respect to the protrusion 3e and the contact surface 3ax against the pressing force of the protrusion 3e of the second region 4b2 and the pressing force of the contact surface 3ax of the first region 4b1. Then, by pressing the contact surface 3d with the other end surface 4bx, torque can be reliably transmitted between the outer rotating body 2 and the inner rotating body 3.

[0054] When the torsional angle of the spring 4 in the diameter-expanding direction is θ1 or more and less than θ2 (for example, θ2 = 45°), the third region 4b3 is separated from the contact surface 3ax and does not contact the inner peripheral surface of the outer cylinder portion 3b of the inner rotating body 3, and the second region 4b2 is pressed against the protrusion 3e. Therefore, in this case, the effective number of turns of the spring 4 is larger and the spring constant is smaller than when the torsional angle of the spring 4 in the diameter-expanding direction is less than θ1. When the torsional angle of the spring 4 in the diameter-expanding direction reaches θ2, the outer peripheral surface of the middle region 4c of the spring 4 comes into contact with the annular surface 2b, or when the torsional angle of the spring 4 in the diameter-expanding direction reaches the limit, further deformation of the spring 4 in the diameter-expanding direction is restricted, and the outer rotating body 2 and the inner rotating body 3 rotate integrally. Thereby, breakage due to deformation of the spring in the diameter-expanding direction can be prevented.

[0055] Next, the case where the rotational speed of the outer rotating body 2 becomes smaller than the rotational speed of the inner rotating body 3 (that is, the case where the outer rotating body 2 decelerates) will be described.

[0056] In this case, the outer rotating body 2 rotates relative to the inner rotating body 3 in the reverse direction (the direction opposite to the direction of the arrow in FIG. 2). As the outer rotating body 2 rotates relatively, one end side region 4a of the spring 4 moves together with the pressure contact surface 2a and rotates relative to the inner rotating body 3. As a result, the spring 4 is twisted in the direction of reducing the diameter. When the torsional angle of the spring 4 in the direction of reducing the diameter is less than θ3 (for example, θ3 = 10°), the pressing force of the one end side region 4a against the pressure contact surface 2a is slightly reduced compared to the case where the torsional angle is zero, but the one end side region 4a is in pressure contact with the pressure contact surface 2a. Also, the pressing force of the other end side region 4b against the contact surface 3ax is slightly increased compared to the case where the torsional angle is zero. When the torsional angle of the spring 4 in the direction of reducing the diameter is θ3 or more, the pressing force of the one end side region 4a against the pressure contact surface 2a becomes substantially zero, and the one end side region 4a slides in the circumferential direction of the outer rotating body 2 with respect to the pressure contact surface 2a. Therefore, torque is not transmitted between the outer rotating body 2 and the inner rotating body 3.

[0057] Thus, the spring 4 engages with each of the outer rotating body 2 and the inner rotating body 3 when the inner rotating body 3 rotates relative to the outer rotating body 2 in the forward direction to transmit torque between the outer rotating body 2 and the inner rotating body 3, while when the inner rotating body 3 rotates relative to the outer rotating body 2 in the reverse direction, the spring 4 slides with respect to at least one of the outer rotating body 2 and the inner rotating body 3 (in this embodiment, the pressure contact surface 2a) (in this embodiment, slides in the circumferential direction of the outer rotating body 2) so as not to transmit torque between the outer rotating body 2 and the inner rotating body 3. Further, the pulley structure 1 is configured to transmit or block torque between the outer rotating body 2 and the inner rotating body 3 by the expansion or contraction of the spring 4.

[0058] In the case of this embodiment, during the operation of the pulley structure 1, even when the outer rotating body 2 and the inner rotating body 3 rotate relative to each other, the three members of the sliding bearing 6, the elastic sleeve 5, and the inner rotating body 3 provided with the sliding bearing 6 and the elastic sleeve 5 do not shift in the circumferential direction relative to each other, and the relative positional relationship in the circumferential direction between them hardly changes.

[0059] (Effect) According to the above configuration, an elastic sleeve 5 is provided between the outer cylindrical portion 3b of the inner rotating body 3 provided with the sliding bearing 6 and the sliding bearing 6, which is formed to be elastically compressively deformable in the radial direction when a force is applied from the belt B. Therefore, even when rust due to corrosion occurs on the outer peripheral surface of the outer cylindrical portion 3b of the inner rotating body 3 where the sliding bearing 6 is provided, so-called in the convex portion composed of the sliding bearing 6 and rust (the portion where the overall thickness of the portion composed of the sliding bearing 6 and rust is larger than the reference dimension of the thickness of the sliding bearing 6), the elastic sleeve 5 can absorb the dimensional expansion in the radial (thickness) direction with respect to the reference dimension of the thickness of the sliding bearing 6 (that is, the length dimension obtained by subtracting the reference dimension of the thickness of the sliding bearing 6 from the overall thickness of the portion composed of the sliding bearing 6 and rust). (That is, by elastically compressing and deforming the elastic sleeve 5 by the amount of dimensional expansion, the displacement of the outer rotating body 2 in the radial direction can be sufficiently suppressed). Thereby, while the outer rotating body 2 and the inner rotating body 3 are relatively rotating, every time the convex portion composed of the sliding bearing 6 and rust reaches a position facing the portion where the force is applied from the belt B of the outer rotating body 2, a force is periodically applied from the sliding bearing 6 and rust to the outer rotating body 2 or the inner rotating body 3, so that vibration and abnormal noise can be prevented from occurring in the outer rotating body 2 or the inner rotating body 3. In addition, the impact transmitted from the outer rotating body 2 to the inner rotating body 3 via the sliding bearing 6 can be mitigated by the elastic sleeve 5. Therefore, the effect of suppressing the generation of abnormal noise due to the vibration of the outer rotating body 2 or the inner rotating body 3 can be further improved. Further, the sliding surface facing the outer rotating body 2, which forms the sliding gap R generated when the outer rotating body 2 and the sliding bearing 6 slide, is on the outer side in the radial direction of the sliding bearing 6 and not on the inner side in the radial direction of the elastic sleeve 5. Therefore, there is no possibility of inhibiting the characteristics (low friction slidability and wear resistance) that the sliding bearing 6 should possess when the outer rotating body 2 and the inner rotating body 3 relatively rotate.

[0060] Further, since the elastic sleeve 5 is in contact with the outer cylinder portion 3b in the expanded diameter state, it is in close contact with the outer cylinder portion 3b by its own elastic restoring force in the diameter-reducing direction. Also, since the sliding bearing 6 is in contact with the outer cylinder portion 3b through the elastic sleeve 5 in the expanded diameter state, it is in close contact with the outer cylinder portion 3b through the elastic sleeve 5 by its own elastic restoring force in the diameter-reducing direction. Therefore, when a force is applied from the belt B, while ensuring the design freedom of the substitute characteristics (hardness, elastic modulus, etc.) related to the elasticity of the elastic sleeve 5 so that it can be elastically compressed and deformed in the diameter (thickness) direction, the adhesion between the sliding bearing 6 and the elastic sleeve 5 and the outer cylinder portion 3b of the inner rotating body 3 can be made higher.

[0061] Also, since the elastic sleeve 5 is made of synthetic rubber, it has excellent heat resistance, oil resistance, etc. As a result, it can be suitably used as the pulley structure 1 provided in the belt system for auxiliary machine drive of an automobile engine.

[0062] (Other embodiments) The elastic sleeve 5 being in close contact with the inner rotating body 3 in the expanded diameter state and the sliding bearing 6 being in close contact with the inner rotating body 3 (outer cylinder portion 3b) through the elastic sleeve 5 in the expanded diameter state is not limited thereto. The inner diameter of the elastic sleeve 5 in the free state is formed to be the same size as the outer diameter of the inner rotating body 3 (outer cylinder portion 3b) where the elastic sleeve 5 is provided, and the elastic sleeve 5 is in contact with the inner rotating body 3 (outer cylinder portion 3b) in a state where its own elastic restoring force in the diameter-reducing direction hardly acts, and the sliding bearing 6 may be in close contact with the inner rotating body 3 (outer cylinder portion 3b) through the elastic sleeve 5 in the expanded diameter state. Also, the outer diameter of the elastic sleeve 5 in the free state is formed to be the same size as the inner diameter of the outer rotating body 2 where the elastic sleeve 5 is provided, and the elastic sleeve 5 is in contact with the outer rotating body 2 in a state where its own elastic restoring force in the diameter-expanding direction hardly acts, and the sliding bearing 6 may be in close contact with the outer rotating body 2 through the elastic sleeve 5 in the diameter-reduced state (see Fig. 10).

[0063] Also, in the above-described embodiment, the elastic sleeve 5 was made of synthetic rubber, but it is not particularly limited thereto, and it may be formed of an elastic material.

[0064] Also, there is no limitation that there must be a gap 6d between both circumferential ends of the sliding bearing 6. The circumferential ends of the sliding bearing 6 may be in contact with each other, and there may be almost no gap 6d between the circumferential ends of the sliding bearing 6.

[0065] Also, in the pulley structure 1, torque may be transmitted or interrupted between the outer rotating body 2 and the inner rotating body 3 by a clutch having a configuration different from the coil spring type clutch including the torsion coil spring 4. Further, the pulley structure 1 may be provided without a clutch for transmitting or interrupting torque between the outer rotating body 2 and the inner rotating body 3. That is, in the pulley structure 1, torque may always be transmitted between the outer rotating body 2 and the inner rotating body 3, or torque may always be interrupted between the outer rotating body 2 and the inner rotating body 3.

[0066] Also, in the present embodiment, the sliding bearing 6 and the rolling bearing 7 are adopted as a pair of bearings, but both of the pair of bearings may be sliding bearings. In this case, it is preferable to arrange the elastic sleeve 5 in the cylindrical gap between the outer rotating body 2 and the inner rotating body 3 in both sliding bearings to interpose the sliding bearings.

Example

[0067] Using the test specimens (pulley structures) of Example 1, 2, Comparative Example (conventional example), and Reference Examples 1, 2 shown below, an idle tester 80 as shown in FIG. 7 was formed, and this idle tester 80 was operated to evaluate the presence or absence of abnormal noise.

[0068] (Idle tester 80) The idle tester 80 includes an alternator 81, a specimen (pulley structure) 1x attached to the drive shaft S of the alternator 81, a crank pulley 83, a V-ribbed belt 84 wound around the crank pulley 83 and the specimen 1x, a timing pulley 85 fixed coaxially with the crank pulley 83, a motor 86, a timing pulley 87 connected to the drive shaft of the motor 86, and a timing belt 88 wound around the timing pulleys 85 and 87. Further, a space including the alternator 81, the specimen 1x, the crank pulley 83, and the V-ribbed belt 84 was used as a thermostat 82 to keep the ambient temperature constant.

[0069] Also, when the above evaluation was performed, in the idle tester 80, the rotational speed of the crank pulley 83 was about 700 rpm, and the rotational speeds of the alternator 81 (auxiliary machine) and the specimen 1x were about 1500 rpm. Also, the fluctuation rate of these rotational speeds was about 10%. Further, the surface temperatures of the alternator 81 (auxiliary machine) and the specimen 1x were set to about 130 °C (the thermostat 82 was maintained at the same 130 °C as the idle ring state of the actual vehicle). Also, in Examples 1 and 2, the comparative example, and Reference Examples 1 and 2, the idle tester 80 was operated for about 3 minutes after about 20 minutes of running-in operation for measurement. Also, the belt tension at this time was about 300 N per belt.

[0070] (Specimen 1x (pulley structure)) A total of five pulley structures in Examples 1 and 2, the comparative example, and Reference Examples 1 and 2 were prepared as specimens. In Examples 1 and 2, the pulley structure 1 according to the above embodiment was used as the specimen. Also, in the specimens of the comparative example and Reference Examples 1 and 2, they did not have an elastic sleeve, and the configuration of the pulley structure other than the sliding bearing and the elastic sleeve was the same as that of Example 1.

[0071] Specifically, each specimen has the following configuration. · Cylindrical gap (reference dimension) in the state before the belt is hung: 2.1 mm · Sliding gap R (reference dimension) in the state before the belt is hung: 0.1 mm ·Reference dimension of the thickness of the sliding bearing (thickness other than both circumferential ends): It corresponds to the thickness of the sliding bearing at X = 2 (position 2 mm from the circumferential end face) in Table 1. The thickness of the sliding bearing in Example 1 and Example 2 is 1.40 mm. The thickness of the sliding bearing in the Comparative Example, and Reference Examples 1 and 2 is 2.00 mm.

[0072] Note that the reference dimension of the thickness of the sliding bearing in Example 1 and Example 2 (1.40 mm) is the dimension obtained by subtracting the thickness of the elastic sleeve (0.60 mm) in Example 1 and Example 2 described below from the reference dimension of the thickness of the sliding bearing in the Comparative Example (conventional) (2.00 mm). In other words, in Example 1 and Example 2, the total thickness of the sliding bearing and the elastic sleeve (2.00 mm) was made to match the reference dimension of the thickness of the sliding bearing in the Comparative Example (conventional) (2.00 mm).

[0073] ·Thickness of both circumferential ends of the sliding bearing: It corresponds to the thickness of the portion located in the range less than 2 mm from both circumferential end faces in Table 1, and refers to the thickness of the sliding bearing at, for example, X = 0 (circumferential end face) and X = 1 (position 1 mm from the circumferential end face). ·Cross-section of both circumferential ends of the sliding bearing: Example 1 and Example 2 are shown in Fig. 6(a), the Comparative Example is shown in Fig. 6(b), and Reference Examples 1 and 2 are shown in Fig. 6(c) ·Axial length (width) (W) of the sliding bearing: 6 mm ·Inner diameter of the portion other than both circumferential ends of the sliding bearing: Approximately 55 mm.

[0074]

Table 1

[0075] (Elastic sleeve used in the specimens of Example 1 and Example 2) ·Reference thickness of the elastic sleeve: 0.6 mm (Table 1) · Inner diameter of the elastic sleeve: The inner diameter of the elastic sleeve was made slightly smaller (by about 5%) than the outer diameter of the outer cylindrical surface of the inner rotating body. As a result, the elastic sleeve is mounted on the outer cylindrical part (inner rotating body) with its inner peripheral surface in contact with the outer cylindrical part in an expanded state and is in a state of being closely attached to the outer cylindrical part (inner rotating body) by its self-elastic restoring force in the diameter-reducing direction. Note that no adhesion treatment was performed.

[0076] · Axial length of the elastic sleeve: The axial length of the elastic sleeve was set to 6 mm, which was made to match the axial length of the sliding bearing. · Hardness: The durometer A hardness (conforming to JIS K6253:2012) of the elastic sleeve (after vulcanization molding) was approximately 70.

[0077] (Manufacturing method of the sliding bearing) · In Examples 1 and 2, the comparative example, and Reference Examples 1 and 2, the sliding bearing was made of a polyacetal resin (trade name "BESTAL G" (manufactured by Mitsuboshi Belting Ltd.)) with a Rockwell R scale of 114. · Also, in Examples 1 and 2, the comparative example, and Reference Examples 1 and 2, the sliding bearing was manufactured using the same mold (injection molding mold) (not shown) having four cavities. Note that among the four cavities, two cavities were used for Examples 1 and 2 and were formed so that the reference dimension of the thickness of the sliding bearing would be 1.40 mm, and the remaining two cavities were used for the comparative example and Reference Examples 1 and 2 and were formed so that the reference dimension of the thickness of the sliding bearing would be 2.00 mm (see Table 1). · However, in Reference Examples 1 and 2, the sliding bearing was manufactured in the same manner as the comparative example, and then polishing was performed so that the thickness would be substantially constant over the entire circumference in the circumferential direction (see Fig. 6(c)).

[0078] · Note that in Examples 1 and 2, the comparative example, and Reference Examples 1 and 2, after confirming that the sliding bearing with the thickness of each part as described in Table 1 could be manufactured with good reproducibility by the injection molding method as described above, a pulley structure was formed using the sliding bearing having the thickness described in Table 1.

[0079] ·Regarding the injection molding conditions, the temperature of the resin during injection molding was about 170°C at the rear part of the plasticizing cylinder (the part opposite to the nozzle), about 200°C at the front part of the plasticizing cylinder (the part on the nozzle side), and about 210°C at the nozzle part. Also, the mold temperature was about 70°C. Further, the injection pressure of the resin was about 80 MPa, and the injection speed of the resin was about 30 mm / second. Also, the molding shrinkage rate was about 2%.

[0080] (Method for manufacturing elastic sleeve) ·The elastic sleeves of the specimens (pulley structures) used in Examples 1 and 2 were produced as follows. First, a rubber composition having a hydrogenated nitrile rubber as a rubber component (the one with the formulation shown in Table 2) was kneaded with a Banbury mixer and made into a rubber sheet using a rolling mill. The rubber sheet was put into the cavity of a mold set consisting of a core and a split outer mold, and while clamping the mold using a press molding machine, heat and pressure were applied for vulcanization molding. As a result, the elastic sleeve became excellent in heat resistance, oil resistance, etc. Note that although the elastic sleeve was molded by press molding, it may be molded by any other optional method (for example, rubber injection molding, rubber transfer molding, rubber extrusion molding, etc.).

[0081]

Table 2

[0082] (Regarding the presence or absence of rust on each specimen (see Table 3)) (Example 1) Example 1: It reproduced a state where no rust occurred (see Figure 3). Note that the proper state during the operation of the pulley structure (without rust) when a force was applied from the belt was shown in Figure 8(a).

[0083] (Manufacturing procedure of the pulley structure (without rust) (in the case of Example 1)) (1) At the time of assembly, on the outer peripheral surface of the outer cylinder part of the newly manufactured inner rotating body (without rust), an elastic sleeve was attached, and on top of that, a sliding bearing for Example 1 (Figure 6(a)) was attached. (2) The pulley structure completed using this inner rotating body (rust-free) was used as the test specimen in Example 1 for this evaluation (evaluation of the presence or absence of abnormal noise by the idle tester 80).

[0084] (Example 2) Example 2: It reproduces the state where rust has occurred on the outer peripheral surface (inner rotating body) of the outer cylinder part facing both ends of the sliding bearing. Specifically, the pulley structure was fabricated according to the procedure shown below. Note that the proper state during the operation of the pulley structure (with rust) (when force is applied from the belt) is shown in Fig. 8(b).

[0085] (Fabrication procedure of the pulley structure (with rust) (in the case of Example 2)) (1) Manufacture of the pulley structure (2) In the completion inspection (operation confirmation test involving engine start) of the alternator provided with a conventional pulley structure (corresponding to the comparative example) that had been left for about three months after the manufacture of the pulley structure, a pulley structure with rust on the inner rotating part (outer peripheral surface of the outer cylinder part) where the sliding bearing was provided was detected by disassembling and visually observing the pulley structure in which significant abnormal noise occurred. Incidentally, the ratio of such rust detection was, for example, about 0.03% (about 3 out of 10,000 completed inspections). When detailing the state of the observed rust, the rust was in a flat plate shape, the number of rust occurrence locations in that part (outer peripheral surface of the outer cylinder part) was about 1 to 2, and the thickness of the rust was about 0.05 to 0.09 mm. (3) Among these pulley structures with rust, an inner rotating body (with rust) was secured in which the thickness of the rust was significantly large (about 0.09 mm) and the number of rust occurrence locations was 1. The approximate dimensions of the rust (at one location) occurring on the secured inner rotating body (with rust) were a maximum thickness of 0.09 mm × a maximum circumferential length of about 7 mm × a maximum axial length of about 3 mm. (4) In the case of the secured inner rotating body (rusted), once the conventional sliding bearing (Fig. 6(b)) is removed, an elastic sleeve is attached, and when the sliding bearing (Fig. 6(a)) used in Example 2 is attached again, the circumferential central portion of the rust (at one location) is arranged in a positional relationship facing the circumferential central portions of both ends of the sliding bearing. The relative positional relationship in the circumferential direction between the sliding bearing and the inner rotating body was adjusted. Such adjustment is for facilitating the confirmation (verification) of whether the effects of the present invention described above are obtained. (5) The pulley structure completed using this inner rotating body (rusted) was used as the test specimen in Example 2 for this evaluation (evaluation of the presence or absence of abnormal noise by the idle tester 80).

[0086] (Comparative Example) Comparative Example: Rust occurred. The inner rotating body (rusted) was the same as that in Example 2. Note that the proper mode during the operation of the pulley structure (when force is applied from the belt) is shown in Fig. 9.

[0087] (Reference Example 1 and Reference Example 2) Reference Example 1: Rust occurred. The inner rotating body (rusted) was the same as that in Example 2. Reference Example 2: No rust occurred. The inner rotating body (rust-free) was the same as that in Example 1.

[0088] (Evaluation Items) Regarding Example 1, 2, the Comparative Example, and Reference Example 1, 2, evaluations were respectively conducted on the radial vibration amplitude of the outer rotating body, the vibration acceleration of the alternator 81, and the presence or absence of abnormal noise. Note that the results are shown in Table 3.

[0089] (Evaluation Method) The radial vibration amplitude of the outer rotating body is the amount of displacement in the radial position of the outer rotating body when both circumferential ends of the sliding bearing are at positions facing the belt winding portion of the outer rotating body and when they are at positions rotated 180° around the rotation axis from this position. Table 3 shows the measurement results obtained using a displacement meter (dial gauge) with the idle tester 80 not operating.

[0090] Regarding the vibration acceleration of the alternator 81, an acceleration pickup was fixed to the outer surface (radially inward) of the alternator for measurement. This was done because when the outer rotating body vibrates radially, the vibration of the outer rotating body is transmitted to the alternator connected to the pulley structure via the alternator shaft, causing the housing covering the alternator main body to resonate, and this housing is considered to act as a substitute for the speaker and generate abnormal noise.

[0091] In the evaluation of the presence or absence of abnormal noise, five evaluators without hearing impairments determined whether they could hear other abnormal noises based on the sound generated in the case of Reference Example 2. Specifically, when the idle tester 80 was operated as described above, it was determined whether abnormal noise could be heard by the evaluators' hearing at a position 2 m behind the alternator (on the side opposite to the pulley structure).

[0092] When none of the five evaluators could hear the abnormal noise, the evaluation was marked as '○'. Also, when the abnormal noise was heard by two or fewer (less than a majority) of the five evaluators, the evaluation was marked as '△'. When the abnormal noise was heard by three or more (a majority or more) of the five evaluators, the evaluation was marked as '×'. Note that in this evaluation, since Reference Example 2 is the reference, the evaluation result for Reference Example 2 is not shown. Also, as can be seen from Table 3, there were no examples where the evaluation was '△'.

[0093] (Evaluation Results)

Table 3

[0094] In Examples 2, Comparative Examples, and Reference Example 1, no changes (such as cracks, chips, changes in the maximum thickness, etc.) were observed in the shape and dimensions of the rust before and after the evaluation.

[0095] (Obtained effects) From the results in Table 3, in the sliding bearings as in Examples 1 and 2, even when, similar to the comparative example (Fig. 6(b)), in the circumferential direction, both end portions have portions that are thicker than the portions other than both end portions in the circumferential direction (Fig. 6(a)), if a configuration (Fig. 3) is adopted in which an elastic sleeve formed to be radially elastically deformable is provided between the portion of the outer rotating body or the inner rotating body where the sliding bearing is provided and the sliding bearing when a force is applied from the belt, then while the outer rotating body and the inner rotating body are relatively rotating, when a force is applied from the belt to the outer rotating body, not only when rust has not occurred on the portion of the outer rotating body or the inner rotating body where the sliding bearing is provided (in the case of Example 1, Fig. 8(a)), but also when rust has occurred on the portion of the outer rotating body or the inner rotating body where the sliding bearing is provided and that faces both end portions of the sliding bearing (in the case of Example 2, Fig. 8(b)), as in the comparative example (Fig. 9), it was found that the vibration acceleration of the outer rotating body (alternator) is small and abnormal noise due to the vibration of the outer rotating body is less likely to occur, as compared with the case of a configuration not provided with the elastic sleeve.

[0096] Also, in a state where rust has occurred on the portion of the outer rotating body or the inner rotating body where the sliding bearing is provided and that faces both end portions of the sliding bearing, in the comparative example, the radial vibration width of the outer rotating body is larger than that in Example 2. From this, it was confirmed that when the radial vibration width of the outer rotating body increases, the above abnormal noise is more likely to occur.

[0097] Also, in the comparative example, the vibration acceleration of the alternator is higher than that in Example 2. From this, as described above, it was confirmed that abnormal noise is more likely to occur due to the resonance of the alternator.

Explanation of reference numerals

[0098] 1 Pulley structure 2 Outer rotating body 3 Inner rotating body 4 Coil spring 5 Elastic sleeve 6 Sliding bearing 7 Rolling bearing B Belt

Claims

1. A pulley structure provided in a belt system for driving auxiliary machines of an automobile engine, comprising: a cylindrical outer rotating body around which a belt is wound and which rotates about a rotating shaft by torque applied from the belt; an inner rotating body provided radially inside the outer rotating body and relatively rotatable with respect to the outer rotating body about the rotating shaft; a pair of bearings interposed between the outer rotating body and the inner rotating body at one axial end side and the other axial end side along the rotating shaft, and connecting the outer rotating body and the inner rotating body so as to be relatively rotatable; at least one of the pair of bearings is a sliding bearing; further comprising an elastic sleeve provided between a portion of the outer rotating body or the inner rotating body where the sliding bearing is provided and the sliding bearing; the outer rotating body and the inner rotating body are made of a material capable of generating rust; the sliding bearing is an end-ring-shaped member formed of resin; the hardness of the elastic sleeve is in the range of 50 to 90 in terms of durometer A hardness (conforming to JIS K6253:2012); a pulley structure, characterized in that when a force is applied from the belt, the elastic sleeve is formed to be elastically compressible and deformable in the radial direction.

2. The elastic sleeve is in close contact with the inner rotating body by its own elastic restoring force in the diameter-reducing direction because its inner peripheral surface is in contact with the inner rotating body in an expanded state; The pulley structure according to claim 1, characterized in that the sliding bearing is in close contact with the inner rotating body through the elastic sleeve by its own elastic restoring force in the diameter-reducing direction because its inner peripheral surface is in contact with the inner rotating body through the elastic sleeve in an expanded state.

3. The pulley structure according to claim 1 or 2, characterized in that the elastic sleeve is made of synthetic rubber.

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