Dust cover

Abstract

Dust cover (10, 50, 60) with a bellows section (12, 52, 62) comprising a plurality of annular vertex sections (14a, 14b, 14c, 14d, 14e, 14f, 14g, 14h) which are convex radially outward and successively arranged in an axial direction, wherein each of the vertex sections (14a, 14b, 14c, 14d, 14e, 14f, 14g, 14h) comprises a pair of inclined wall sections (16a, 16b, 16c, 16d, 16e, 16f, 16g, 16h) which are inclined radially inward toward opposite axial ends, wherein: the bellows section (12, 52, 62) is structured such that an upper region (12a, 52a, 62d, 62e) having a plurality of vertex sections and a lower region (12b, 52b, 62e, 62f) having a plurality of vertex sections are provided continuously or consecutively on both axial sides of an intermediate region (12c, 52c, 62g, 62h) having at least one of the vertex sections, The pair of inclined wall sections (16c, 16g, 16h), of at least one of the vertex sections (14c, 14g, 14h) of the intermediate region (12c, 52c, 62g, 62h), has the same angle of inclination θ, where the angle of inclination θ is less than an angle of inclination α of the pair of inclined wall sections (16a, 16d, 16e), the plurality of vertex sections (14a, 14d, 14e) of the upper region (12a, 52a, 62d, 62e), and as an angle of inclination β of the pair of inclined wall sections (16b, 16e, 16f), the plurality of vertex sections (14b, 14e, 14f) of the lower region (12b, 52b, 62e, 62f), where the inclination angles θ, α, β form the angles between the inclined wall sections (16a, 16b, 16c, 16d, 16e, 16f, 16g, 16h) and a plane orthogonal to the axis of the dust cover (10, 50, 60); the intermediate area (12c, 52c, 62g, 62h) contracts more easily in the axial direction than the upper area (12a, 52a, 62d, 62e) and the lower area (12b, 52b, 62e, 62f) when axial compression is applied or exerted on the bellows section (12, 52, 62). wherein the angle of inclination θ of the inclined wall sections (16c, 16g, 16h) in the intermediate region (12c, 52c, 62g, 62h) is 25° or greater and 35° or less; and wherein the angle of inclination α of the inclined wall sections (16a, 16d, 16e) in the upper area (12a, 52a, 62d, 62e) is 35° or greater and 50° or less, and the angle of inclination β of the inclined wall sections (16b, 16e, 16f) in the lower area (12b, 52b, 62e, 62f) is 35° or greater and 50° or less.

Description

[Technical field]

[0001] The present invention relates to a dust cover for preventing the adhesion of dust, water and the like by covering, for example, a piston rod of a shock absorber and the like which constitutes a suspension mechanism of an automobile. [State of the art]

[0002] Conventionally, a dust cover for preventing the adhesion of foreign matter such as dust and water is known, and is used, for example, to prevent the adhesion of foreign matter to a piston rod by mounting it on a shock absorber to cover a portion of a piston rod projecting from a cylinder. For example, as described in Japanese Unexamined Patent Publication JP H10-331897 A (Patent Literature 1), the dust cover is in the shape of a thin tube as a whole and can be extended and contracted in an axial direction according to a projecting amount of the piston rod from the cylinder by including a bellows portion in which a plurality of annular apex portions convex radially outward are sequentially provided.

[0003] The dust cover is desired to have a large extension / contraction deformation stroke of the bellows portion to follow a large extension or contraction of the shock absorber, and desirably a maximum axial length during extension or extension is long and a minimum axial length during contraction or contraction is short.

[0004] However, when attempting to ensure a large extension / contraction deformation stroke of the bellows portion, a lateral force is likely to act on the bellows portion during compression of the bellows portion due to errors in the thickness and shape of the bellows portion, causing bending to radially deflect and bend an intermediate part of the bellows portion. Specifically, when the bellows portion is formed of a resin, a reaction force against compression tends to become larger, and the acting lateral force also tends to become larger, than when the bellows portion is formed of a rubber-elastic material, thus causing large bending.

[0005] Accordingly, in the dust cover of Patent Literature 1, the bellows portion includes a large pitch portion and a small pitch portion, in which the respective plurality of apex portions are arranged at mutually different pitches. Accordingly, the small pitch portion and the large pitch portion are contractively deformed in a stepwise manner during compression, thereby shortening a substantial length of a part of the bellows portion to be deformed, and bending is expected to be reduced.

[0006] However, an effect was not sufficient by merely providing the bellows portion with the large pitch portion and the small pitch portion having mutually different pitches, and causing this large pitch portion and this small pitch portion to be deformed in a step-like manner as in Patent Literature 1. Specifically, when the small pitch portion is provided to have a small axial dimension relative to the entire bellows portion, the large pitch portion becomes too long, and bending of the bellows portion may possibly occur during deformation of the large pitch portion.On the other hand, when the low pitch portion is provided to have a long axial dimension relative to the entire bellows portion, the number of the crest portions necessary to realize the entire maximum axial length of the bellows portion increases, thereby posing a problem that the minimum axial length of the bellows portion is made long.

[0007] Patent Literature 2 further describes a bellows structure having wall portions whose inclination angles can be varied in order to be able to design the wall thickness of the bellows structure, particularly in a hollow molding process.

[0008] Patent Literature 3 describes a bellows structure in which the bellows structure is axially divided into several sections with different inner diameters. Accordingly, wear of the inner surface of the bellows structure can be prevented upon contraction of the bellows structure.

[0009] Patent Literature 4 describes a bellows structure which is axially divided into three sections, wherein the wall thickness of the intermediate section is made larger than the wall thickness in the upper and lower sections of the bellows structure.

[0010] Patent literature 5 describes a bellows structure for a dust cover having a plurality of inclined wall portions, wherein the wall portions have a smaller angle of inclination at their radially outer peripheral portion than at their radially inner peripheral portion. [Literature list][Patent literature] Patent Literature 1: Japanese Unexamined Patent Publication JP H10- 331 897 A Patent Literature 2: JP S60 215163A Patent literature 3: US 2007 / 0187197 A1 Patent literature 4: US 2012 / 0241267 A1 Patent literature 5: JP 2015 55298 A [Summary of the invention][Problem the invention seeks to solve]

[0011] The present invention has been developed with the above situation as a background, and an object thereof is to provide a dust cover having a novel structure and capable of preventing bending of a bellows portion. [Means for solving the problem]

[0012] Aspects of the present invention, which were developed to solve such a problem, are described below. It should be noted that components employed in each aspect described below can be used in any combination as long as possible.

[0013] Specifically, a first aspect of the present invention is directed to a dust cover having a bellows portion including a plurality of annular apex portions convexly provided radially outward and sequentially in an axial direction, each of the apex portions including a pair of inclined wall portions inclined radially inward toward opposite axial ends, the bellows portion being structured such that an upper region having a plurality of apex portions and a lower region having a plurality of apex portions are continuous.adjacent to each other on both axial sides of an intermediate region having at least one of the apex portions, the pair of inclined wall portions of the at least one of the apex portions of the intermediate region has the same inclination angle, the inclination angle being smaller than that of the inclined wall portions of the plurality of apex portions of the upper region and than that of the inclined wall portions of the plurality of apex portions of the lower region, and the intermediate region contracts more easily than the upper region and the lower region when axial compression is applied to the bellows portion.

[0014] According to the dust cover structured according to the first aspect of the present invention, by making the inclination angle of the inclined wall portions of the apex portion small in the intermediate region provided in an axial intermediate region of the bellows portion, it is difficult for bending to occur in the intermediate region during the contracting deformation of the bellows portion.

[0015] Furthermore, the intermediate portion is preferentially contracted across the upper and lower portions, and deflection and deformation (bending) of the preferentially contracted intermediate portion are reduced, thereby making inclination angles of connected ends of the intermediate portion with the upper and lower portions smaller. In this way, the inclinations of the upper and lower portions relative to a vertical plane are limited not only to axially outer ends supported by a shock absorber and the like, but also to connected ends with the intermediate portion spaced apart from the axially outer ends of the bellows portion. Thus, bending of the upper and lower portions is reduced.

[0016] In addition, due to the preferential contraction of the intermediate portion, a substantial effective length of the bellows portion is short, bending is difficult to occur during the deformation of the upper and lower portions, and the amount of bending is also reduced when the upper and lower portions are greatly contracted.

[0017] As just described, since bending is reduced in each of the upper, intermediate, and lower regions constituting the bellows portion, bending of the entire bellows portion is effectively reduced to reduce interference of the bellows portion with other members and the like.

[0018] Furthermore, by restricting the inclination angles at the connected ends of the upper and lower portions with the intermediate portion, an effect of reducing bending is effectively demonstrated by also providing the intermediate portion in a narrow range of the bellows portion. Therefore, the upper and lower portions, which consist of, for example, the apex portions having a large axial width, can be provided even at large ratios to the entire length of the bellows portion, and it is also possible to ensure a large extension / contraction stroke of the bellows portion.

[0019] A second aspect of the present invention is such that in the dust cover according to the first aspect, a minimum inner diameter of the bellows portion is the same in the intermediate region, the upper region, and the lower region, and a maximum outer diameter of the bellows portion is the same in the intermediate region, the upper region, and the lower region.

[0020] According to the second aspect, the bending reducing effect can be obtained by causing the intermediate region having the inclined wall portions having a small inclination angle to be contracted preferentially over the upper and lower regions without providing the bellows portion with a special thickness change or the like.

[0021] The first aspect of the present invention is further such that in the dust cover, the inclination angle of the inclined wall portions in the intermediate region is 25° or greater and 35° or less.

[0022] According to the inclination angle of the inclined wall portions in the intermediate region, it is possible to realize the preferential contraction of the intermediate region while suppressing the bending while ensuring an extension / contraction stroke of the intermediate region.

[0023] The first aspect of the present invention is further such that in the dust cover, the inclination angle of the inclined wall portions in the upper region is 35° or greater and 50° or less, and that of the inclined wall portions in the lower region is 35° or greater and 50° or less.

[0024] According to the inclination angle of the inclined wall portions in the upper region, it is possible to stably effect the extension / contraction deformation of the upper and lower regions while ensuring large extension / contraction strokes in the upper and lower regions.

[0025] A fifth aspect of the present invention is such that in the dust cover according to any one of the first to fourth aspects, the intermediate region is composed of an apex portion.

[0026] According to the fifth aspect, the upper and lower regions can be provided at large ratios at the bellows portion, and a large extension / contraction stroke of the bellows portion can be obtained by forming the intermediate region by a minimum number of the apex portion.

[0027] A sixth aspect of the present invention is such that in the dust cover according to any one of the first to fifth aspects, the apex portion of the upper region and the apex portion of the lower region are equal in size.

[0028] According to the sixth aspect, each of the apex portions of the upper and lower regions undergoes a similar diameter change during extension / contraction deformation. Thus, each apex portion can be provided with good space efficiency, and a large extension / contraction stroke of the bellows portion can be obtained, as if, for example, spaces on the inner and outer peripheral sides of the bellows portion are restricted by other members.

[0029] A seventh aspect of the present invention is such that in the dust cover according to any one of the first to sixth aspects, a recessed annular small trough portion open radially outward is formed on an outer peripheral end part of the at least one apex portion.

[0030] According to the seventh aspect, a larger axial dimension can be obtained in an extended state of the bellows portion by the deformation of the small trough portions. In addition, when radial depths of the small trough portions are made smaller than depths of troughs between the apex portions adjacent in the axial direction, an increase in an axial dimension in a contracted state of the bellows portion caused by the overlap of inner circumferential ends of the small trough portions and those of the apex portions can be prevented, and a large extension / contraction stroke of the bellows portion can be obtained.

[0031] An eighth aspect of the present invention is such that in the dust cover according to any one of the first to seventh aspects, the intermediate region is provided in a central one of three parts of the bellows portion which is equally divided in the axial direction.

[0032] According to the eighth aspect, the bending of the upper and lower portions is more effectively reduced by arranging the connected ends of the upper and lower portions with the intermediate portion in an axial central part of the bellows section spaced from the upper and lower outer ends of the upper and lower portions. [Effect of the invention]

[0033] According to the present invention, the inclination angle of the inclined wall portions in the intermediate region is smaller than that of the inclined wall portions in the upper region and that of the inclined wall portions in the lower region, and the intermediate region is contracted more easily than the upper and lower regions, and therefore the bending of the bellows portion is reduced. [Brief description of the drawings] Fig. 1 is a longitudinal section of a dust cover as a first embodiment of the present invention, Fig. Figure 2 is an enlarged section showing an essential part A of Fig. 1 shows, Fig. 3 is a longitudinal section showing an assembled state of the dust cover shown in Fig. 1 is shown on a vehicle, Fig. 4 are diagrams showing an effect of reducing bending in the dust cover according to the present invention, wherein Fig. 4(a) shows a bellows section of a conventional structure and Fig. 4(b) shows a bellows section according to the present invention, Fig. Fig. 5 is a longitudinal section of a dust cover as a second embodiment of the present invention, and Fig. 6 is a longitudinal sectional view of a dust cover as a third embodiment of the present invention. [Embodiments of the invention]

[0034] Embodiments of the present invention will be described below with reference to the drawings.

[0035] Fig. Fig. 1 shows a dust cover 1 as a first embodiment of the present invention. In the following description, a vertical direction basically means a vertical direction of Fig. 1, which is an axial direction.

[0036] The dust cover 10 is in the shape of a thin tube as a whole and is made of a resin in this embodiment. A material in which ethylene propylene rubber (EPDM) is mixed and dispersed in polypropylene (PP), which is a thermoplastic resin, is suitably employed as a material constituting the dust cover 10 because it is excellent in weather resistance, moldability, and the like. Of course, in the case of forming the dust cover 10 from a thermoplastic resin, any of polyolefin-based resins such as polypropylene and polyethylene, polyamide-based resins, polyvinyl chloride-based resins, polyester-based resins, urethane-based resins, styrene-based resins, olefin-based resins, and the like, for example, can be employed.Furthermore, blow molding is suitably employed as a method for molding the dust cover 10, but injection molding may also be employed.

[0037] Furthermore, the dust cover 10 includes a bellows portion 12. The bellows portion 12 is structured such that a plurality of apex portions 14a to 14c, which are convex radially outward, are integrally formed while being sequentially provided one above the other in the axial direction. This apex portion 14a to 14c includes a pair of inclined wall portions 16a to 16c, 16a to 16c, which are inclined axially outward toward an inner peripheral side, and is continuously circular over the entire circumference while having a substantially V-shaped cross section rotated by 90°. It should be noted that the bellows portion 12 of this embodiment becomes progressively thinner toward an outer peripheral side, and such a thickness difference is realized by the blow molding of the dust cover 10.

[0038] Furthermore, a small trough portion 18a to 18c, which opens radially outward, is formed on a tip part of the apex portion 14a to 14c. The small trough portion 18a to 18c is formed on an outer peripheral part of the bellows portion 12 and is continuously provided over the entire circumference while having a substantially V-shaped cross section widened toward an outer peripheral side. Note that the small trough portions 18a to 18c are narrower and shallower than trough portions formed between the apex portions 14a to 14c, 14a to 14c adjacent in the axial direction.

[0039] Here, the bellows portion 12 consists of three regions, including an upper region 12a, a lower region 12b, and an intermediate region 12c. The upper region 12a is formed by integrally and sequentially providing a plurality of apex portions 14a, and the lower region 12b is formed by integrally and sequentially providing a plurality of apex portions 14b. In this embodiment, the upper region 12a is formed by approximately three and a half apex portions 14a, and the lower region 12b is formed by five apex portions 14b. Note that, in this embodiment, the apex portions 14a constituting the upper region 12a and the apex portions 14b constituting the lower region 12b are substantially the same.

[0040] On the other hand, the intermediate section 12c is formed by an apex section 14c. The apex section 14c has the same minimum inner diameter r and maximum outer diameter R as the apex sections 14a of the upper region 12a and the apex sections 14b of the lower region 12b and has an axial width p less than an axial width P of the apex sections 14a, 14b. An inclination angle θ of the inclined wall sections 16c, 16c, which form the apex section 14c of the intermediate region 12c, which in Fig. 2, relative to a plane orthogonal to the axis of the dust cover is smaller than an inclination angle α of the inclined wall portions 16a, 16a constituting the apex portions 14a of the upper region 12a relative to the plane orthogonal to the axis of the dust cover, and an inclination angle β of the inclined wall portions 16b, 16b constituting the apex portions 14b of the lower region 12b relative to the plane orthogonal to the axis of the dust cover (θ < α, θ < β).

[0041] More preferably, the inclination angle θ of the inclined wall sections 16c, 16c constituting the apex section 14c of the intermediate region 12c relative to the vertical plane is set within a range of 25° ≤ θ ≤ 35°. Furthermore, the inclination angle α of the inclined wall sections 16a, 16a constituting the apex sections 14a of the upper region 12a relative to the vertical plane is set within a range of 35° ≤ α ≤ 50°, and the inclination angle β of the inclined wall sections 16b, 16b constituting the apex sections 14b of the lower region 12b relative to the vertical plane is set within a range of 35° ≤ β ≤ 50°. Since the apex portions 14a of the upper region 12a and the apex portions 14b of the lower region 12b are the same in this embodiment, the inclination angle α of the inclined wall portions 16a, 16a constituting the apex portions 14a and 14b of the lower region 12b are the same.build up, and the inclination angle β of the inclined wall sections 16b, 16b, which represent the apex sections 14b, are equal to each other (α = β).

[0042] Furthermore, the intermediate portion 12c need only be provided in an axially intermediate part of the bellows portion 12, but is preferably provided in a central one of three parts of the bellows portion 12 that are equally divided in the axial direction. In short, the intermediate portion 12c is desirably provided at a position sufficiently spaced from both axial ends of the bellows portion 12, and more desirably at a position close to an axial center of the bellows portion 12, which largely protrudes laterally upon bending of the bellows portion 12.

[0043] Note that the small trough portion 18c formed in the apex portion 14c of the intermediate region 12c has the same depth in a radial direction as the small trough portions 18a formed on the apex portions 14a of the upper region 12a and the small trough portions 18b formed on the apex portions 14b of the lower region 12b, and a smaller width in the axial direction than these. This causes wall portions on both axial sides of the small trough portion 18c to widen at a smaller inclination angle than wall portions on both axial sides of the small trough portions 18a, 18b.

[0044] The upper portion 12a is continuously provided axially above the intermediate portion 12c, the lower portion 12b is continuously provided axially below the intermediate portion 12c, and the lower end of the upper portion 12a and the upper end of the lower portion 12b are integrally connected to the intermediate portion 12c.

[0045] Furthermore, an upper mounting portion 26 is provided axially above the bellows portion 12. The upper mounting portion 26 has a substantially cylindrical shape as a whole, and an engaging groove 28 is formed in an axially intermediate portion. The engaging groove 28 is a recessed groove open on the outer peripheral surface and extending over the entire circumference, and the upper mounting portion 26 is partially narrowed in diameter in a portion where the engaging groove 28 is formed.

[0046] On the other hand, a lower mounting portion 30 is formed axially below the bellows portion 12. The lower mounting portion 30 has a substantially cylindrical shape as a whole, and a circumferential groove 32 open on the inner circumferential surface is formed in an axially intermediate part. Furthermore, diameter-enlarged portions 34 are formed at a plurality of circumferential positions of the lower mounting portion 30. The diameter-enlarged portion 34 protrudes radially outward and extends substantially straight in the axial direction while having a zigzag-like cross section whose circumferential width is progressively narrowed toward a protruding end. The diameter-enlarged portions 34 of this embodiment are provided radially while being arranged at substantially equal intervals in the circumferential direction.

[0047] As this is Fig. 3, the dust cover 10 is mounted on a vehicle, with the upper mounting portion 26 mounted on a spring receiving member (not illustrated) supporting an upper end portion of a coil spring 36, and the lower mounting portion 30 mounted on a shock absorber 38.

[0048] The structure of the spring receiving member is not particularly limited, and various known structures are employed. Thus, the spring receiving member is not shown here at all, but includes, for example, an unillustrated spring seat mounted on a piston rod 44 (described later) of the shock absorber 38 to support the upper end of the coil spring 36, and an unillustrated sheet rubber similarly disposed between the coil spring 36 and the spring seat. A mounting fixture 40 provided on the spring receiving member is inserted into and engaged with the engaging groove 28 formed on the upper mounting portion 26 of the dust cover 10, whereby an upper end part of the dust cover 10 is mounted on the spring receiving member.

[0049] The shock absorber 38 is structured such that the piston rod 44 extends upward from a cylinder 42 and includes a cylinder cap 46 constituting an upper end portion of the cylinder 42. This cylinder cap 46 is provided with a locking protrusion 48 projecting radially outward, and the locking protrusion 48 is fitted into the circumferential groove 32 formed on the lower mounting portion 30 of the dust cover 10, thereby mounting a lower end portion of the dust cover 10 to the cylinder 42.

[0050] As just described, the dust cover 10 has the upper end part mounted on the piston rod 44 via the spring receiving member and the lower end part mounted on the cylinder 42, and is deformed in an extending and contracting manner according to the extension and contraction (change of an exposed length of the piston rod 44 from the cylinder 42) of the shock absorber 38.

[0051] Specifically, the bellows portion 12 of the dust cover 10 can be axially extended and contracted by deforming the respective apex portions 14a to 14c so as to change the inclination angles of the inclined wall portions 16a to 16c, 16a to 16c. Furthermore, in this embodiment, the bellows portion 12 is also expansively and compressively deformed by deforming the small trough portions 18a to 18c so as to change the inclination angles of the side wall portions on both axial sides, thus ensuring a larger expansible / contractible deformation amount (extension / contraction stroke) of the bellows portion 12. In addition, inner end parts in the circumferential direction of the small trough sections 18a to 18c are arranged radially outward from those of the apex sections 14a to 14c, whereby the inner end parts in the circumferential direction orCircumferential end portions of the small trough portions 18a to 18c and those of the apex portions 14a to 14c in the axial direction are avoided. Thus, an axial dimension of the bellows portion 12 in a most compressed state (minimum axial dimension) is made shorter.

[0052] In addition, in the mounted state of the dust cover 10 on the vehicle, which is in Fig. 3, the bellows portion 12 is compressed more axially than in a single state, which in Fig. 1, where no load is applied thereto by the contraction of the shock absorber 38 due to a shared supporting load of the vehicle weight.

[0053] As is also the case in Fig. 3, the intermediate region 12c is preferably contracted across the upper and lower regions 12a, 12b in response to an axially applied compressive load in the bellows portion 12. Specifically, the inclined wall portions 16c, 16c of the apex portion 14c constituting the intermediate region 12c have a larger inclination angle than the inclined wall portions 16a, 16a of the apex portions 14a constituting the upper region 12a and those of the apex portions 14b constituting the lower region 12b, and have substantially the same thickness as those, and are more easily deformed in response to the axially applied compressive load.This causes the apex portion 14c to preferentially fold over the apex portions 14a, 14b during contraction of the shock absorber 38, and the upper and lower regions 12a, 12b to further contract, preventing buckling of the intermediate region 12c. Specifically, against large compression, the intermediate region 12c is compressed to a most compressed state earlier than the upper and lower regions 12a, 12b, and the upper and lower regions 12a, 12b are contracted, substantially obstructing the expansion and contraction of the intermediate region 12c.

[0054] By preferentially constructing the intermediate portion 12a over the upper and lower portions 12a, 12b in this manner, the deflection and deformation of the bellows portion 12 into a buckled state (bending) can be reduced or prevented. Specifically, since the deformation of the intermediate portion 12c is restricted, with the intermediate portion 12c being preferentially contracted, the lower end of the upper portion 12a and the upper end of the lower portion 12b are restrained by the intermediate portion 12c, spaced apart by a restricted portion by the shock absorber 38. Thus, compared with the conventional structure in which deformation of the intermediate portion is permitted, amounts of lateral deflection / deformation of the upper and lower portions 12a, 12b are restrained, and the bending of the bellows portion 12 is reduced.

[0055] In particular, when the intermediate portion 12c is compressed to the most contracted state earlier than the upper and lower portions 12a, 12b, any further extensible / compressive deformation of the intermediate portion 12c is hardly permitted, and the shape is stabilized. Thus, the lower end of the upper portion 12a and the upper end of the lower portion 12b are effectively restrained by the intermediate portion 12c, and bending is effectively prevented.

[0056] It should be noted that such an effect of reducing the bending of the dust cover 10 according to this embodiment is thought to be exhibited based on a change in a deformation mode of the bellows portion 12 due to the provision of the intermediate region 12c, which is different in shape from the apex portion 14c of the upper and lower regions 12a, 12b. Accordingly, a difference between a deformation mode of a bellows portion 100 of a conventional structure as a comparative example and that of the bellows portion 12 according to the present invention as an example will be described below with reference to FIG. Fig. 4, which schematically show these bellows sections 100, 12. It should be noted that the bellows section 100 as the comparative example is structured such that the apex portions having a predetermined shape are continuously provided over the entire circumference, and apex portions of an upper and lower region 100a, 100b are the same as those of an intermediate region 100c. Furthermore, the small trough portions 18a to 18c are not included in the Fig. 4 for easier viewing. In addition, the bellows sections 100, 12 in an original or initial state before compressive deformation are shown schematically in a double-dashed line in the Fig. 4 to make the deformation modes or types easy to understand.

[0057] Specifically, in the bellows portion 100 of the conventional structure shown in Fig. As shown in Fig. 4(a), when an axial compressive force acts, not only the upper portion 100a and the lower portion 100b, but also the intermediate portion 100c, which is formed from the same apex portion as the upper and lower portions 100a, 100b, are also deformed and deflected laterally. Thus, in the bellows portion 100, bending also occurs due to the deflection and deformation of the intermediate portion 100c, and opposite axial ends of the intermediate portion 100c are greatly inclined relative to a vertical plane, and therefore bending due to the deflection and deformation of the upper and lower portions 100a, 100b may become greater. On the other hand, in the bellows portion 12 according to this embodiment, which is shown in Fig. As shown in Fig. 4(b), when an axial compressive force acts, the intermediate portion 12c is compressed vertically without being greatly deflected, the inclinations of the two axial ends of the intermediate portion 12c to the vertical plane are suppressed, and the inclinations of the lower end of the upper portion 12a and the upper end of the lower portion 12b are restricted by the intermediate portion 12c. In this way, an amount d of lateral deflection / deformation of the bellows portion 12 according to the example becomes smaller than an amount D of lateral deflection / deformation of the bellows portion 100 according to the comparative example.

[0058] As just described, in the dust cover 10 structured according to this embodiment, the intermediate portion 12c is preferably contracted over the upper and lower portions 12a, 12b, and the inclination angle θ of the inclined wall portions 16c of the intermediate portion 12c is smaller than the inclination angle α of the inclined wall portions 16a, 16a of the upper portion 12a and the inclination angle β of the inclined wall portions 16b, 16b of the lower portion 12b, thereby reducing bending due to deflection and deformation of the upper and lower portions 12a, 12b. In addition, since the intermediate portion 12c is easily contracted with a small reaction force, bending of the intermediate portion 12c is also avoided.

[0059] Furthermore, the inclined wall sections 16a of the upper region 12a and the inclined wall sections 16b of the lower region 12b have a larger inclination angle relative to the vertical plane than the inclined wall sections 16c of the intermediate region 12c. Thus, long axial lengths are ensured by a small number of the apex sections 14a, 14b in the upper and lower regions 12a, 12b. In this way, in the upper and lower regions 12a, 12b, the maximum axial lengths during expansion are long, and the minimum axial lengths during contraction, which are set by the axial overlap of the inclined wall sections 16a, 16b, are short, thus realizing a large extension / compression stroke.

[0060] Additionally, this embodiment is structured such that only one apex portion 14c, which constitutes the intermediate region 12c and has a short axial dimension, is provided, and the ratios of the upper and lower regions 12a, 12b in the bellows portion 12 are large. Thus, the extension / compression stroke of the bellows portion 12 is increased more efficiently.

[0061] Moreover, since the apex portions 14a of the upper portion 12a and the apex portions 14b of the lower portion 12b have the same shape in this embodiment, any of extension / contraction strokes, deformation characteristics, and the like of the apex portions 14a of the upper portion 12a and the apex portions 14b of the lower portion 12b can be most efficiently set when spaces on inner and outer peripheral sides of the bellows portion 12 are restricted by other members.

[0062] Furthermore, since the intermediate region 12c is arranged in a third region at the center relative to the entire axial length of the bellows portion 12, the upper and lower regions 12a, 12b can be restrained by the preferably deformed intermediate region 12c at the positions spaced from the upper and lower ends of the bellows portion 12, which is restrained by the shock absorber 38, and the effect of preventing bending due to the deflection of the upper and lower regions 12a, 12b is effectively exhibited.

[0063] Furthermore, by setting the inclination angle θ of the inclined wall portions 16c, 16c constituting the apex portion 14c of the intermediate portion 12c in the range of 25° ≤ θ ≤ 35°, a large extension / contraction stroke of the intermediate portion 12c can be ensured while facilitating the deformation of the intermediate portion 12c in response to axially applied compression.

[0064] Furthermore, by setting the inclination angle α of the inclined wall portions 16a, 16a constituting the apex portions 14a of the upper portion 12a in the range of 35° ≤ α ≤ 50° and the inclination angle β of the inclined wall portions 16b, 16b constituting the apex portions 14b of the lower portion 12b in the range of 35° ≤ β ≤ 50°, the upper and lower portions 12a, 12b can be stably deformed in an extending and compressing manner while ensuring large extension / contraction strokes of the upper and lower portions 12a, 12b, and excessive increases in changing amounts of the inner and outer diameters of the upper and lower portions 12a, 12b during an extension or lengthening and a contraction or contraction are also avoided.

[0065] Fig. 5 shows a dust cover 50 as a second embodiment of the present invention. This dust cover 50 includes a bellows portion 52, and the bellows portion 52 is composed of an upper portion 52a, a lower portion 52b, and an intermediate portion 52c. Note that in the following description, members and parts that are understood to be substantially the same as those of the first embodiment will be denoted by the same reference numerals and will not be described.

[0066] More specifically, the upper portion 52a is substantially the same as the upper portion 12a of the first embodiment and is structured such that a plurality of apex portions 14a are provided sequentially in an axial direction. On the other hand, the lower portion 52b has a smaller number of apex portions 14b than the lower portion 12b of the first embodiment and is structured such that three apex portions 14b are provided sequentially in the axial direction.

[0067] The intermediate region 52 is structured such that a plurality of apex portions 14c are provided sequentially in the axial direction. In this embodiment, four apex portions 14c are provided sequentially in the axial direction. In short, the bellows portion 52 of this embodiment has a larger ratio of the intermediate region 52c in the axial direction and a smaller ratio of the bottom region 52b compared to the bellows portion 12 of the first embodiment.

[0068] According to the dust cover 50 of this embodiment described above, an effective length of the bellows portion 52 becomes shorter due to the preferential contraction of the intermediate region 52c. Thus, it is difficult for bending of the bellows portion 52 to occur during the contraction of the upper and lower regions 12a, 52b. Moreover, the intermediate region 52c, which is provided in an axially wider range than in the first embodiment, is easily contracted because an inclination angle θ of the inclined wall portions 16c constituting the apex portions 14c is made smaller. Thus, it is difficult for bending to occur even during the contraction of the intermediate region 52c.

[0069] Fig. 6 shows a dust cover 60 as a third embodiment of the present invention. This dust cover 60 includes a bellows portion 62.

[0070] More specifically, the bellows portion 62 has a first region 62d, a second region 62e and a third region 62f, a first intermediate region 62g is provided between the first and second regions 62d, 62e and a second intermediate region 62h is provided between the second and third regions 62e, 62f.

[0071] The first region 62d is structured such that a plurality of apex portions 14d are provided sequentially in an axial direction. The apex portions 14d are substantially the same as the apex portions 14a (14b) in the first embodiment and include inclined wall portions 16d, 16d and small trough portions 18d, which have substantially the same structures as the inclined wall portions 16a, 16a (16b, 16b) and the small trough portions 18a (18b).Moreover, the second region 62e is structured such that a plurality of apex portions 14e are provided sequentially in the axial direction, and the apex portions 14e are substantially the same as the apex portions 14d, and includes inclined wall portions 16e, 16e and the small trough portions 18e, which have substantially the same structures as the inclined wall portions 16d, 16d and the small trough portions 18d. Moreover, the third region 62f is structured such that a plurality of apex portions 14f are provided sequentially in the axial direction, and the apex portions 14f are substantially the same as the apex portions 14d, and includes inclined wall portions 16f, 16f and small trough portions 18f having substantially the same structures as the inclined wall portions 16d, 16d and the small trough portions 18d.

[0072] On the other hand, the first intermediate region 62g consists of an apex portion 14g. The apex portion 14g is substantially the same as the apex portion 14c in the first embodiment and includes wall portions 16g, 16g, and a small trough portion 18g, which have substantially the same structures as the inclined wall portions 16c, 16c and the small trough portion 18c. The second intermediate region 62h consists of an apex portion 14h, and the apex portion 14h is substantially the same as the apex portion 14g of the first intermediate region 62g and includes inclined wall portions 16h, 16h, and a small trough portion 18h, which have substantially the same structures as the inclined wall portions 16c, 16c, and the small trough portion 18c.

[0073] Moreover, the first region 62d is an upper region relative to the first intermediate region 62g and the second region 62e is a lower region relative to the first intermediate region 62g, an inclination angle θ1 of the inclined wall portions 16g of the first intermediate region 62g is smaller than both an inclination angle α1 of the inclined wall portions 16d of the first region 62d and an inclination angle β1 of the inclined wall portions 16e of the second region 62d.

[0074] Furthermore, the second region 62e is an upper region relative to the second intermediate region 62h, and the third region 62f is a lower region relative to the second intermediate region 62h. An inclination angle θ2 of the inclined wall portions 16h of the second intermediate region 62h is smaller than both an inclination angle α2 (= β1) of the inclined wall portions 16e of the second region 62e and an inclination angle β2 of the inclined wall portions 16f of the third region 62f (θ2 < α2 = β1, θ2 = β2). It should be noted that the second region 62e is a lower region relative to the first intermediate region 62g and an upper region relative to the second intermediate region 62h.

[0075] Furthermore, during compression of the bellows portion 62 in the axial direction, the first intermediate region 62g is preferably contracted via the first and second regions 62d and 62e, and the second intermediate region 62h is preferably contracted via the second and third regions 62e and 62f.

[0076] Also, in such a dust cover 60 structured according to this embodiment, bending during contraction is reduced in a similar manner to the dust cover 10 according to the first embodiment.

[0077] Specifically, since the inclined wall portions 16g of the first intermediate region 62g and the inclined wall portions 16h of the second intermediate region 62h have smaller inclination angles than the inclined wall portions 16d to 16f of the first to third regions 62d to 62f, the first and second intermediate regions 62g, 62h are smoothly folded in response to an axial compressive force, making it more difficult for bending to occur.

[0078] Furthermore, during the contractive deformation of the first to third regions 62d to 62f, the lower end of the first region 62d, the upper and lower ends of the second region 62e, and the upper end of the third region 62f are restrained by the preferentially contracted first and second intermediate regions 62g, 62h. As a result, each of the amounts of lateral deflection / deformation of the first to third regions 62d to 62f becomes smaller to reduce the bending of the bellows portion 62.

[0079] Since the intermediate regions 62g, 62h are provided at two axially intermediate positions of the bellows portion 62 in the dust cover 60 of this embodiment, each of the axial lengths of the first to third regions 62d to 62f divided by these intermediate regions 62g, 62h becomes shorter, and lateral deflection in each of the first to third regions 62d to 62f becomes smaller. Furthermore, since an effective length of the bellows portion 62 is made shorter during contraction of the first to third regions 62d to 62f by the preferential contraction of the intermediate regions 62g, 62h, bending of the bellows portion 62 is reduced.

[0080] Furthermore, when both the first and second intermediate regions 62g, 62h are provided in a central one of three parts of the bellows portion 62 which is equally divided in the axial direction, the deflection of the first to third regions 62d to 62f is effectively prevented by the preferentially deformed first and second intermediate regions 62g, 62h.

[0081] It should be noted that the apex portions 14d to 14f of the first to third regions 62d to 62f may be mutually different in shape and size, and the inclination angles of the inclined wall portions 16d to 16f of the apex portions 14d to 14f may be mutually different. Furthermore, the apex portions 14g, 14h of the first and second intermediate regions 62g, 62h may be mutually different in shape and size, and the inclination angles of the inclined wall portions 16d to 16f of the apex portions 14d to 14f may be mutually different. It should be noted that the intermediate regions may be provided at three or more positions of the bellows portion.

[0082] Although the embodiments of the present invention have been described in detail above, the present invention is not limited by the specific description thereof. For example, all of the plurality of apex portions constituting the upper region need not be the same, and the upper region may be configured by combining a plurality of types of apex portions that differ in shape, size, and the like. This also applies to the lower region and the intermediate region.

[0083] Furthermore, the specific number, shape, size, etc. of the apex portion(s) of each region are merely illustrative and can be appropriately changed based on the maximum axial length, minimum axial length, etc. required for the bellows portion. Furthermore, it is not essential to form the small trough portions at the apex portions, and the small trough portions may be omitted.

[0084] Furthermore, the entire inclined wall section does not need to be inclined at a uniform inclination angle. For example, as disclosed in Japanese Unexamined Patent Publication No. 2015-55298, an inclination angle of an outer peripheral part of the inclined wall section may be smaller than that of an inner peripheral part of the inclined wall section. In this case, a maximum inclination angle of the inclined wall sections of the intermediate region is desirably smaller than the minimum inclination angles of the inclined wall sections of the upper region and those of the lower region.

[0085] Further, the intermediate region can preferably be made slightly contracted across the upper and lower regions by making a thickness of the inclined wall portions of the intermediate region smaller than those of the inclined wall portions in the upper and lower regions in addition to making the inclination angle of the inclined wall portions of the intermediate region smaller than those of the inclined wall portions in the upper region and that of the inclined wall portions in the lower region. [List of reference symbols]

[0086] 10: dust cover, 12, 52, 72: bellows section, 12a, 52a: upper section, 12b, 52b: lower section, 12c, 52c: intermediate section, 14a to 14h: crest section, 16a to 16h: inclined wall section, 18a to 18h: small trough section, 62d: first section (upper section), 62e: second section (upper section, lower section), 62f: third section (lower section), 62g: first intermediate section (intermediate section), 62h: second intermediate section (intermediate section).

Claims

[1] A dust cover (10, 50, 60) having a bellows portion (12, 52, 62) including a plurality of annular apex portions (14a, 14b, 14c, 14d, 14e, 14f, 14g, 14h) convexly provided radially outward and sequentially in an axial direction, each of the apex portions (14a, 14b, 14c, 14d, 14e, 14f, 14g, 14h) including a pair of inclined wall portions (16a, 16b, 16c, 16d, 16e, 16f, 16g, 16h) inclined radially inward toward opposite axial ends, wherein: the bellows portion (12, 52, 62) is structured such that an upper region (12a, 52a, 62d, 62e) having a plurality of apex portions and a lower region (12b, 52b, 62e, 62f) having a plurality of apex portions are provided continuously or adjacent to each other on both axial sides of an intermediate region (12c, 52c, 62g, 62h) having at least one of the apex portions, the pair of inclined wall sections (16c, 16g, 16h) of at least one of the apex sections (14c, 14g, 14h) of the intermediate region (12c, 52c, 62g, 62h) has the same inclination angle θ, wherein the inclination angle θ is less than an inclination angle α of the pair of inclined wall sections (16a, 16d, 16e) of the plurality of apex sections (14a, 14d, 14e) of the upper region (12a, 52a, 62d, 62e), and than an inclination angle β of the pair of inclined wall sections (16b, 16e, 16f) of the plurality of apex sections (14b, 14e, 14f) of the lower region (12b, 52b, 62e, 62f), wherein the inclination angles θ, α, β form the angles between the inclined wall sections (16a, 16b, 16c, 16d, 16e, 16f, 16g, 16h) and a plane orthogonal to the axis of the dust cover (10, 50, 60); the intermediate region (12c, 52c, 62g, 62h) contracts more easily than the upper region (12a, 52a, 62d, 62e) and the lower region (12b, 52b, 62e, 62f) in the axial direction when axial compression is applied or exerted on the bellows section (12, 52, 62), wherein the angle of inclination θ of the inclined wall sections (16c, 16g, 16h) in the intermediate region (12c, 52c, 62g, 62h) is 25° or greater and 35° or less; and wherein the angle of inclination α of the inclined wall sections (16a, 16d, 16e) in the upper region (12a, 52a, 62d, 62e) is 35° or greater and 50° or less, and the angle of inclination β of the inclined wall sections (16b, 16e, 16f) in the lower region (12b, 52b, 62e, 62f) is 35° or greater and 50° or less. [2] The dust cover (10, 50, 60) according to claim 1, wherein a minimum inner diameter of the bellows portion (12, 52, 62) is the same in the intermediate region (12c, 52c, 62g, 62h), the upper region (12a, 52a, 62d, 62e) and the lower region (12b, 52b, 62e, 62f), and a maximum outer diameter of the bellows portion (12, 52, 62) is the same in the intermediate region (12c, 52c, 62g, 62h), the upper region (12a, 52a, 62d, 62e) and the lower region (12b, 52b, 62e, 62f). [3] Dust cover (10, 50, 60) according to one of claims 1 or 2, wherein the intermediate region (12c, 62g, 62h) consists of an apex portion (14c, 14g, 14h). [4] Dust cover (10, 50, 60) according to one of claims 1 to 3, wherein the apex portion (14a, 14d, 14e) of the upper region (12a, 52a, 62d, 62e) and the apex portion (14b, 14e, 14f) of the lower region (12b, 52b, 62e, 62f) are of the same dimension. [5] The dust cover (10, 50, 60) according to any one of claims 1 to 4, wherein a recessed annular small trough portion (18a, 18b, 18c, 18d, 18e, 18f, 18g, 18h) which is open radially outward is formed on an outer peripheral end part of the at least one apex portion (14a, 14b, 14c, 14d, 14e, 14f, 14g, 14h). [6] A dust cover (10, 50, 60) according to any one of claims 1 to 5, wherein the intermediate region (12c, 52c, 62g, 62h) is provided in a central one of three parts of the bellows portion (12, 52, 62) which is equally divided in the axial direction. [7] The dust cover (60) according to any one of claims 1 to 5, wherein the bellows portion (62) has a first region (62d), a second region (62e), a third region (62f), a first intermediate region (62g) between the first region (62d) and the second region (62e), and a second intermediate region (62h) between the second region (62e) and the third region (62f), and the first region (62d) forms the upper region relative to the first intermediate region (62g), the second region (62e) forms the lower region relative to the first intermediate region (62g), the second region (62e) forms the upper region relative to the second intermediate region (62h), and the third region (62f) forms the lower region relative to the second intermediate region (62h).

Images