Cylindrical vibration isolation device

Abstract

To provide a cylinder type vibration control device with a new structure capable of realizing excellent durability against input in a torsion direction.SOLUTION: A cylinder type vibration control device 10 is such that: a swelling part 22 projecting to an outer periphery is disposed in an inner shaft member 12; inner recessed grooves 24 opened to the outer peripheral surface of the inner shaft member 12 and extending in the circumferential direction are disposed on both outer sides in the axial direction of the swelling part 22; a filling part 40 of a body rubber elastic body 16 is filled into the inner recessed groove 24; rubber recessed grooves 42 opened to both end surfaces in the axial direction of the body rubber elastic body 16 and extending in the circumferential direction are disposed; the opening end of the rubber recessed groove 42 is positioned in an axial outward direction than the inner recessed groove 24; the rubber recessed groove 42 is superposed on at least a part of the inner recessed groove 24 in projection in an axial perpendicular direction; a bottom face 48 of the rubber recessed groove 42 is constituted of an intermediate curve part 50, an inner periphery curve part 52 and an outer periphery curve part 54 which are each a curve surface; and the curvature radius of the intermediate curve part 50 is larger than the curvature radiuses of the inner periphery curve part 52 and the outer periphery curve part 54.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cylindrical vibration isolator used for, for example, bogies of railway vehicles.

Background Art

[0002] Conventionally, elastomeric bearings such as those disclosed in Japanese National Publication of International Patent Application No. 2008-509344 (Patent Document 1) have been used for bogies of railway vehicles and the like. The elastomeric bearing has a structure in which a plurality of non-elastic laminated members and a plurality of elastic laminated members are alternately stacked and arranged in the radial direction between an inner shaft member and an outer cylindrical member, and is expected to ensure durability against input in the prying direction while obtaining a soft spring in the torsional direction.

[0003] Further, application of a cylindrical vibration isolator in place of the elastomeric bearing having a complicated structure has also been studied. The cylindrical vibration isolator has a structure in which an inner shaft member and an outer cylindrical member are connected by a main rubber elastic body, like a vibration-proof bush disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2020-067157 (Patent Document 2), and can simplify the structure as compared with an elastomeric bearing in which a plurality of non-elastic laminated members and a plurality of elastic laminated members are alternately stacked and arranged.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of Invention

Problems to be Solved by the Invention

[0005] Incidentally, when applying cylindrical vibration damping devices to, for example, the bogies of railway vehicles or the suspension mechanisms of automobiles, durability is required to withstand repeated loads in the twisting direction. For example, the vibration damping bush described in Patent Document 2 improves durability against twisting input by the shape of the axial end of the main rubber elastic body.

[0006] However, when applying cylindrical vibration damping devices to parts where torsional input loads are particularly large, such as the bogies of railway vehicles, conventional cylindrical vibration damping devices with structures like those described in Patent Document 2, which are mainly applied to automobile suspension mechanisms, still lack sufficient durability against torsional inputs.

[0007] The problem to be solved by the present invention is to provide a cylindrical vibration isolation device with a novel structure that can achieve excellent durability against twisting input. [Means for solving the problem]

[0008] The following describes preferred embodiments for understanding the present invention. However, each embodiment described below is illustrative and can be combined with others as appropriate. Furthermore, the multiple components described in each embodiment can be recognized and adopted as independently as possible, and can be combined with any component described in another embodiment as appropriate. Thus, the present invention is not limited to the embodiments described below, and various other embodiments can be realized.

[0009] The first embodiment is a cylindrical vibration damping device in which an inner shaft member and an outer cylindrical member are connected by a main rubber elastic body, wherein the inner shaft member is provided with a bulge that protrudes outward, and the inner shaft member is provided with inner grooves that open to the outer surface and extend in the circumferential direction on both axial sides of the bulge, and the filling portion of the main rubber elastic body is filled into the inner grooves, and rubber grooves that open to both axial ends of the main rubber elastic body and extend in the circumferential direction are provided, the opening ends of the rubber grooves on the main rubber elastic body are located axially outward from the inner grooves, and the rubber grooves overlap with at least a part of the inner grooves in a projection perpendicular to the axis, and the bottom surface of the rubber grooves is composed of an intermediate curved portion, an inner circumferential curved portion and an outer circumferential curved portion, respectively, and the radius of curvature of the intermediate curved portion is larger than the radii of curvature of the inner circumferential curved portion and the outer circumferential curved portion.

[0010] According to the cylindrical vibration isolation device constructed in accordance with this embodiment, the inner shaft member is provided with a bulge, which reduces the tensile stress acting on the main rubber elastic body when subjected to twisting input (an input that causes relative tilting between the inner shaft member and the outer cylindrical member), thereby ensuring durability. At the same time, by limiting the thickness of the main rubber elastic body in the direction perpendicular to the axis at the outer circumference of the bulge, the spring in the direction perpendicular to the axis can be set to be stiffer.

[0011] Inner grooves are provided on both axial outer sides of the bulging portion, and the thickness of the main rubber elastic body (filling portion) fixed to the inner grooves is ensured. As a result, the strain of the main rubber elastic body is reduced in the filling portion when subjected to twisting input, thereby improving the durability of the main rubber elastic body.

[0012] By providing rubber grooves that open onto the axial end face of the main rubber elastic body, the compressive and tensile forces acting on the axial end of the main rubber elastic body during twisting input are reduced, thereby improving durability.

[0013] Since at least a portion of the rubber groove overlaps with the inner groove in a projection perpendicular to the axis, the twisting input does not directly act on the filling portion within the inner groove. Instead, the deformation of the main rubber elastic body axially inward from the rubber groove is transmitted to the filling portion, thereby reducing the strain on the main rubber elastic body.

[0014] By making the radius of curvature of the intermediate curved portion that constitutes the radial middle portion of the bottom surface of the rubber groove larger than the radii of curvature of the inner and outer curved portions that constitute the inner and outer ends of the bottom surface of the rubber groove, it is possible to set a larger groove width dimension for the rubber groove while ensuring the axial dimension of the main rubber elastic body. Therefore, a large free surface area of ​​the main rubber elastic body is secured on the inner surface of the rubber groove, improving the durability of the main rubber elastic body.

[0015] The second embodiment is a cylindrical vibration damping device in which an inner shaft member and an outer cylindrical member are connected by a main rubber elastic body, wherein rubber grooves are provided on both axial ends of the main rubber elastic body and extending in the circumferential direction, the inner shaft member is provided with a bulge that protrudes outward, the inner shaft member is provided with inner grooves that protrude in the circumferential direction and open on the outer surface of the inner shaft member on both axial sides of the bulge, the filling portion of the main rubber elastic body is filled into the inner grooves, and the open end of the rubber groove in the main rubber elastic body is the inner groove The rubber groove is located axially outward from the groove, and the rubber groove overlaps with at least a portion of the inner groove in a projection perpendicular to the axis, the inner shaft member is provided with mounting portions that protrude axially outward on both sides from the inner groove, and between the mounting portion and the inner groove on the inner shaft member, a projection is provided that protrudes circumferentially from the mounting portion toward the outer circumference, and the axial end of the main rubber elastic body on the inner circumference side from the rubber groove is located on the outer circumferential surface of the projection and is thinner than the filling portion.

[0016] According to the cylindrical vibration isolation device constructed in accordance with this embodiment, the inner shaft member is provided with a bulge, which reduces the tensile stress acting on the main rubber elastic body when subjected to twisting input (an input that causes relative tilting between the inner shaft member and the outer cylindrical member), thereby ensuring durability. At the same time, by limiting the thickness of the main rubber elastic body in the direction perpendicular to the axis at the outer circumference of the bulge, the spring in the direction perpendicular to the axis can be set to be stiffer.

[0017] Inner grooves are provided on both axial outer sides of the bulging portion, and the thickness of the main rubber elastic body (filling portion) fixed to the inner grooves is ensured. As a result, the strain of the main rubber elastic body is reduced in the filling portion when subjected to twisting input, thereby improving the durability of the main rubber elastic body.

[0018] By providing rubber grooves that open onto the axial end face of the main rubber elastic body, the compressive and tensile forces acting on the axial end of the main rubber elastic body during twisting input are reduced, thereby improving durability.

[0019] Since at least a portion of the rubber groove overlaps with the inner groove in a projection perpendicular to the axis, the twisting input does not directly act on the filling portion within the inner groove. Instead, the deformation of the main rubber elastic body axially inward from the rubber groove is transmitted to the filling portion, thereby reducing the strain on the main rubber elastic body.

[0020] The presence of a protrusion on the axially outward side of the inner groove limits the axial outward deformation of the thickened filling portion fixed within the inner groove when the main rubber elastic body deforms by being pushed outward in the axial direction due to a twisting input. This prevents increased strain and crack formation due to excessive deformation in the filling portion, which is prone to large deformations due to its thickness, thereby improving durability.

[0021] Further, the axial end of the inner peripheral end portion of the main rubber elastic body is made thinner than the filling portion, and the amount of deformation at the axial end of the inner peripheral end portion of the main rubber elastic body is smaller than that of the filling portion. This makes it difficult for the axial end face of the inner peripheral end portion of the main rubber elastic body to deform in a bulging manner when an input in the prying direction is applied, thereby improving the durability of the main rubber elastic body.

[0022] A third aspect is a cylindrical vibration isolator in which an inner shaft member and an outer cylindrical member are connected by a main rubber elastic body, wherein the inner shaft member is provided with a bulging portion protruding toward the outer periphery, the surface of the bulging portion is formed in an arc shape in a longitudinal cross-section, the center of curvature of the surface of the bulging portion is offset toward the protruding tip side of the bulging portion relative to the center of the inner shaft member, the inner shaft member is provided with inner concave grooves opening to the outer peripheral surface and extending in the circumferential direction on both axially outer sides of the bulging portion respectively, the filling portion of the main rubber elastic body is filled into the inner concave grooves, rubber concave grooves opening to the axial end face of the main rubber elastic body and extending in the circumferential direction are provided on both axially outer sides of the bulging portion respectively, the opening end of the rubber concave groove in the main rubber elastic body is located axially outward of the inner concave groove, and the rubber concave groove overlaps with at least a part of the inner concave groove in projection in the direction perpendicular to the axis.

[0023] According to the cylindrical vibration isolator structured in accordance with this aspect, by providing the bulging portion on the inner shaft member, while ensuring durability by reducing the tensile stress acting on the main rubber elastic body during input in the prying direction (input that causes relative tilting between the inner shaft member and the outer cylindrical member), the spring in the direction perpendicular to the axis can be set to be hard by limiting the thickness of the main rubber elastic body in the direction perpendicular to the axis at the outer periphery of the bulging portion.

[0024] Inner concave grooves are provided on both axially outer sides of the bulging portion, and the thickness of the main rubber elastic body (filling portion) fixed to the inner concave grooves is secured, so that the strain of the main rubber elastic body during input in the prying direction is reduced at the filling portion, and the durability of the main rubber elastic body is improved.

[0025] By providing the rubber concave groove that opens at the axial end face of the main rubber elastic body, the compressive force and tensile force acting on the axial end portion of the main rubber elastic body upon input in the prying direction are reduced, so that the durability is improved.

[0026] Since at least a part of the rubber concave groove overlaps with the inner concave groove in projection in the direction perpendicular to the axis, the input in the prying direction does not directly act on the filling portion in the inner concave groove, and the deformation of the main rubber elastic body located axially inward of the rubber concave groove is transmitted to the filling portion, whereby the strain of the main rubber elastic body is reduced.

[0027] Since the center of curvature of the surface of the arc-shaped bulging portion is deviated toward the protruding tip side of the bulging portion relative to the center of the inner shaft member, compared with the case where the center of curvature of the surface of the bulging portion coincides with the center of the inner shaft member, the axial dimension can be reduced by reducing the curvature radius of the bulging portion while keeping the protruding dimension to the outer periphery of the bulging portion the same. As a result, it is possible to secure a space for providing the inner concave groove and the rubber concave groove on both axially outer sides of the bulging portion while appropriately setting the radial spring constant.

[0028] A fourth aspect is the cylindrical vibration isolator according to any one of the first to third aspects, wherein the entire inner concave groove is located axially inward of the axial end of the outer cylindrical member.

[0029] According to the cylindrical vibration isolator structured in accordance with this aspect, for example, in a case where the portion of the inner shaft member that protrudes axially outward beyond the outer cylindrical member serves as a mounting portion to a member to be mounted, it is possible to prevent the shape of the mounting portion from being restricted by the formation of the inner concave groove.

[0030] A fifth aspect is the cylindrical vibration isolator according to the fourth aspect, wherein the inner peripheral end of the main rubber elastic body is located axially outward of the inner concave groove and axially inward of the axial end of the outer cylindrical member.

[0031] According to the cylindrical vibration isolation device with a structure conforming to this embodiment, for example, when the portion of the inner shaft member that protrudes axially outward from the outer cylindrical member is used as the mounting portion to the mounting target member, it is possible to avoid the mounting structure to the mounting target member being restricted by the fixing of the main body rubber elastic body.

[0032] The sixth embodiment is a cylindrical vibration damping device described in any one of the first to fifth embodiments, wherein a thin-walled portion is provided in the main body rubber elastic body axially inward from the filling portion, the thin-walled portion having a thickness smaller than the maximum thickness dimension of the filling portion.

[0033] In a cylindrical vibration damping device with a structure according to this embodiment, when the deformation of the main rubber elastic body axially inward from the rubber groove is transmitted to the filling portion, the deformation of the main rubber elastic body axially inward from the rubber groove is restrained by the thin-walled portion, and the amount of deformation transmitted to the filling portion is regulated by the thin-walled portion. Therefore, damage due to excessive deformation of the main rubber elastic body is prevented, and durability is improved.

[0034] The seventh embodiment is a cylindrical vibration isolation device described in any one of the first to sixth embodiments, wherein the outer cylindrical member has a large-diameter cylindrical portion in which the portion facing the bulging portion of the inner shaft member in a direction perpendicular to the axis has a larger inner diameter than the portions at both ends in the axial direction.

[0035] According to the cylindrical vibration isolation device constructed in accordance with this embodiment, the rubber volume of the main rubber elastic body can be adjusted in the radial direction between the bulging portion and the large-diameter cylindrical portion of the outer cylindrical member. Therefore, for example, it becomes easier to appropriately set the balance between the spring characteristics in the direction perpendicular to the axis and the durability of the main rubber elastic body against twisting input.

[0036] The eighth aspect is a cylindrical vibration damping device as described in the seventh aspect, wherein on both axial sides of the large-diameter cylindrical portion of the outer cylindrical member, there are small-diameter cylindrical portions that are thickened to protrude inward and have a smaller inner diameter than the large-diameter cylindrical portion, and these small-diameter cylindrical portions are located on the outer circumference of the inner groove, facing the inner groove in the radial direction.

[0037] According to the cylindrical vibration isolation device constructed in this embodiment, the rubber volume of the main rubber elastic body can be secured in the large-diameter cylindrical section while the spring characteristics can be adjusted in the small-diameter cylindrical section. In particular, the axial end of the main rubber elastic body is located on the inner circumference of the small-diameter cylindrical section, which reduces the radial width dimension. This increases the compression ratio when the outer cylindrical member is processed to reduce its diameter, thereby improving the durability of the main rubber elastic body against tensile load input.

[0038] The ninth embodiment is a cylindrical vibration isolation device described in any one of the first to eighth embodiments, wherein the groove width dimension in the direction perpendicular to the axis of the rubber groove is larger than the groove depth dimension in the axial direction.

[0039] According to the cylindrical vibration isolation device constructed in accordance with this embodiment, the groove depth dimension of the rubber groove is reduced, which ensures sufficient rubber volume of the main rubber elastic body, allowing for the setting of a straight-axis spring, etc., while the groove width dimension of the rubber groove is increased, which ensures sufficient free length at the axial end of the main rubber elastic body, thereby improving durability during twisting input.

[0040] The tenth embodiment is a cylindrical vibration damping device described in any one of the first to ninth embodiments, wherein the bottom surface of the rubber groove is composed of an intermediate curved section, an inner curved section, and an outer curved section, and the radius of curvature of the inner curved section is less than or equal to the radius of curvature of the outer curved section.

[0041] According to the cylindrical vibration isolation device with a structure conforming to this embodiment, the inner circumferential curved portion of the rubber groove can be brought closer to the inner shaft member locally without increasing the depth of the rubber groove. As a result, the amount of deformation of the main rubber elastic body can be adjusted at the portion of the inner circumferential curved portion that approaches the inner shaft member, thereby improving the durability of the main rubber elastic body. [Effects of the Invention]

[0042] According to the present invention, excellent durability against twisting input can be achieved in a cylindrical vibration isolation device. [Brief explanation of the drawing]

[0043] [Figure 1] This is a cross-sectional view showing a cylindrical vibration isolation device as a first embodiment of the present invention, corresponding to cross-section II in Figure 2. [Figure 2] Section II-II in Figure 1 [Figure 3] Front view of the cylindrical vibration isolation device shown in Figure 1. [Figure 4] Sectional view of IV-IV in Figure 1 [Figure 5] This is a cross-sectional view showing a cylindrical vibration isolation device as a second embodiment of the present invention, and corresponds to the VV section of Figure 6. [Figure 6] Figure 5, section VI-VI [Modes for carrying out the invention]

[0044] Embodiments of the present invention will be described below with reference to the drawings.

[0045] Figures 1 to 4 show a cylindrical vibration damping device 10 used in the bogie of a railway vehicle as a first embodiment of the present invention. The cylindrical vibration damping device 10 has a structure in which an inner shaft member 12 and an outer cylindrical member 14 are elastically connected by a main rubber elastic body 16. In the following description, as a general rule, the vertical direction refers to the vertical direction in Figure 1, the left-right direction refers to the vertical direction in Figure 2, and the front-rear direction refers to the left-right direction in Figure 1, which is the axial direction. Also, as a general rule, the circumferential direction refers to the circumferential direction of the inner shaft member 12 and the outer cylindrical member 14.

[0046] The inner shaft member 12 is a highly rigid member made of metal or the like, and comprises a central portion 18 which is cylindrical overall, and a pair of mounting portions 20, 20 which protrude outward from the central portion 18 in the axial direction.

[0047] The central portion 18 is provided with a bulge portion 22 that protrudes toward the outer circumference. The bulge portion 22 has a surface shaped like a revolved body obtained by rotating a circular arc around its central axis, and its axial length gradually decreases toward the outer circumference. As shown in Figures 1 and 2, in the longitudinal section, the surface of the bulge portion 22 is arc-shaped, and the center of curvature C1 of the surface of the bulge portion 22 is set at a position shifted by a distance d toward the protruding tip of the bulge portion 22 with respect to the inner central axis passing through the center C0 of the portion of the inner shaft member 12 where the bulge portion 22 is provided (hereinafter, the center C0 of the inner shaft member 12). The distance d between the inner central axis passing through the center C0 of the inner shaft member 12 and the center of curvature C1 of the surface of the bulge portion 22 is not particularly limited, but it is desirable that it be smaller than the radius of curvature of the surface of the bulge portion 22, for example, this prevents the radius of curvature of the surface of the bulge portion 22 from becoming excessively small. Furthermore, the center of curvature C1 of the surface of the bulging portion 22 is set to the same position as the center C0 of the inner shaft member 12 in the axial direction. The center of curvature C1 of the surface of the bulging portion 22 is continuous in the circumferential direction in an arc shape centered on the center C0 of the inner shaft member 12, and as shown in Figures 1 and 2, it is located on both radial sides with respect to the center C0 of the inner shaft member 12 in the longitudinal cross-section.

[0048] Inner grooves 24 are provided on both the axial sides of the bulging portion 22 in the central portion 18. The inner grooves 24 open to the outer circumferential surface of the central portion 18 and extend continuously around the entire circumference of the central portion 18. The inner surface of the inner grooves 24 has a concave, curved cross-sectional shape and deepens towards the middle in the groove width direction (axial direction). The inner grooves 24 have a smooth inner surface shape composed of a curved surface, with the axial inner end smoothly continuing to the surface of the bulging portion 22, and the axial outer end smoothly continuing to the surface of the projection portion 26, which will be described later.

[0049] In the central portion 18, protrusions 26 are provided that project outward from the inner grooves 24, 24 in the axial direction. The end face of the protrusion 26 is a curved surface that is continuous with the inner surface of the inner groove 24, while the end face that is axially outer is a stepped surface 28 that widens perpendicular to the axis. The tip surface of the protrusion 26 is a cylindrical tip surface 30 that extends straight in the axial direction. The protrusions 26 are provided continuously with a substantially constant cross-sectional shape over the entire circumference in the circumferential direction. The projection height of the protrusion 26 to the outer circumference is smaller than the projection height of the bulging portion 22 to the outer circumference, for example, it is less than or equal to the depth dimension of the inner groove 24. However, the projection height of the protrusion 26 to the outer circumference may be greater than the depth dimension of the inner groove 24.

[0050] Cylindrical connecting portions 32 are provided axially outward from the protrusions 26, 26 in the central portion 18. The connecting portions 32 have a smaller outer diameter than the protrusions 26, and the axial end face of the protrusion 26 on the connecting portion 32 side is a stepped surface 28.

[0051] The mounting portion 20 is roughly rectangular in shape, and as shown in Figure 3, both sides in the thickness direction (left-right direction) are flat to form a two-sided width, while both sides in the width direction (up-down direction) are curved surfaces that widen in the circumferential direction. The mounting portion 20 has circular bolt holes 34 that penetrate in the thickness direction. The mounting portion 20 is provided axially outward from the inner groove 24, and a projection 26 is provided between the inner groove 24 and the mounting portion 20, extending circumferentially and protruding outward from the mounting portion 20.

[0052] The outer cylindrical member 14 is substantially cylindrical in shape, and as shown in Figures 1 and 2, its inner diameter is larger than the maximum outer diameter of the bulge 22, which is the maximum outer diameter of the inner shaft member 12. The outer cylindrical member 14 has an outer circumferential surface that is a cylindrical surface extending straight in the axial direction along its entire length in the axial direction. The outer cylindrical member 14 has an inner circumferential surface that is a concave surface 35 that opens inward in the axial central portion. In a longitudinal cross-section, the concave surface 35 is tapered, with both axial ends inclined outward inward in the axial direction, and the axial central portion is a cylindrical surface extending straight in the axial direction. The concave surface 35 extends continuously along the entire circumference in the circumferential direction with a substantially constant cross-sectional shape. The axial dimension of the concave surface 35 is greater than or equal to the axial dimension of the bulge 22 of the inner shaft member 12. However, the axial dimension of the concave surface 35 may be less than or equal to the axial dimension of the bulge 22 of the inner shaft member 12.

[0053] The axial central portion of the outer cylindrical member 14 is provided with a concave surface 35, resulting in a large-diameter cylindrical portion 36 with a larger inner diameter than the axial end. The large-diameter cylindrical portion 36 is thinner in the radial direction compared to the axial end (the small-diameter cylindrical portion 38, described later). The axially outer portion of the outer cylindrical member 14 beyond the concave surface 35 is a small-diameter cylindrical portion 38 that protrudes inward relative to the large-diameter cylindrical portion 36 and is thicker. The inner surface of the small-diameter cylindrical portion 38 is a cylindrical surface that extends straight in the axial direction.

[0054] The central portion 18 of the inner shaft member 12 and the outer cylindrical member 14 are positioned such that their axial and radial centers coincide, and the inner shaft member 12 is inserted through the outer cylindrical member 14. The protruding portions 26, 26 of the inner shaft member 12 are located inside the axial end of the outer cylindrical member 14, while the connecting portion 32 is located outside the axial end of the outer cylindrical member 14. The bulging portion 22 of the inner shaft member 12 is positioned opposite the concave surface 35 of the outer cylindrical member 14, spaced apart on the inner circumference, and the axial center of the bulging portion 22 and the axial center of the concave surface 35 are approximately the same in the axial direction. The surface of the bulging portion 22 is closest to the concave surface 35 at its axial center, and the separation distance gradually increases toward the axial outward direction. The small-diameter cylindrical portion 38 of the outer cylindrical member 14 is positioned radially opposite the inner groove 24, spaced apart on the outer circumference relative to the inner groove 24. The inner grooves 24, 24 are all located axially inward from the axial end of the outer cylindrical member 14. The center of the central portion 18 of the inner shaft member 12 and the center of the outer cylindrical member 14 may be offset from each other in at least one of the axial and radial directions. For example, their centers may be offset from each other due to thermal shrinkage after vulcanization molding of the main rubber elastic body 16 or due to drawing of the outer cylindrical member 14. The protrusions 26, 26 may also be located axially outward from the axial end of the outer cylindrical member 14.

[0055] A main rubber elastic body 16 is positioned radially between the inner shaft member 12 and the outer cylindrical member 14. The main rubber elastic body 16 is substantially cylindrical in shape, with its inner circumferential surface fixed to the outer circumferential surface of the central portion 18 of the inner shaft member 12, and its outer circumferential surface fixed to the inner circumferential surface of the outer cylindrical member 14. The inner shaft member 12 and the outer cylindrical member 14 are elastically connected to each other by the main rubber elastic body 16. The main rubber elastic body 16 is formed, for example, as an integrally vulcanized molded product comprising the inner shaft member 12 and the outer cylindrical member 14. To alleviate tensile stress due to thermal shrinkage after vulcanization of the main rubber elastic body 16, it is desirable to reduce the diameter of the outer cylindrical member 14 (drawn) after molding the main rubber elastic body 16. In the diameter reduction process of the outer cylindrical member 14, for example, the outer cylindrical member 14 may be reduced in diameter by a substantially constant amount along its entire axial length, or the amount of diameter reduction deformation of the outer cylindrical member 14 may differ in the axial direction, such as the outer cylindrical member 14 being reduced in diameter more at both axial ends than at the axial center.

[0056] The inner circumferential end of the main rubber elastic body 16 is fixed to the inner shaft member 12 at the surface of the bulging portion 22, the inner groove surface of the inner recess 24, and the surface of the protruding portion 26. Both axial ends of the inner circumferential end of the main rubber elastic body 16 are located on the cylindrical tip surfaces 30, 30 of the protruding portions 26, 26, and the stepped surfaces 28, 28 of the protruding portions 26, 26 are exposed without being covered by the main rubber elastic body 16. It is desirable that the axial end of the inner circumferential end of the main rubber elastic body 16 is located axially inward from the axial end of the outer cylindrical member 14. The portion of the main rubber elastic body 16 fixed to the inner recess 24 is a filling portion 40 that is thicker than the axial end of the inner circumferential end of the main rubber elastic body 16. The filling portion 40 fills the entire inner recess 24 and extends to the outer circumference beyond the opening end of the inner recess 24. Furthermore, the outer circumferential surfaces of the stepped surfaces 28, 28 and the connecting portions 32, 32 may be covered with thin rubber extending from the main rubber elastic body 16. The axial end of the inner circumferential end of the main rubber elastic body 16 may extend to the same position as the axial end of the outer cylindrical member 14, or it may protrude axially outward beyond the axial end of the outer cylindrical member 14.

[0057] The outer peripheral end of the main rubber elastic body 16 extends axially outward beyond the concave surface 35 relative to the outer cylindrical member 14, and is located axially inward from the axial end of the outer cylindrical member 14, with both axial ends located on the inner circumferential surface of the small-diameter cylindrical portion 38. In this embodiment, the axial positions of the inner and outer axial ends of the main rubber elastic body 16 are approximately the same. The outer peripheral end of the main rubber elastic body 16 may extend to the same position as the axial end of the outer cylindrical member 14, or it may protrude axially outward beyond the axial end of the outer cylindrical member 14.

[0058] Rubber grooves 42 are formed at both axial ends of the main rubber elastic body 16. The rubber grooves 42 open to the axial end faces of the main rubber elastic body 16 and extend with a substantially constant cross-sectional shape around the entire circumference. The inner surface of the rubber grooves 42 has an inner circumferential side surface 44 and an outer circumferential side surface 46 that extend straight in the axial direction, as shown in an enlarged view in Figure 1, and a bottom surface 48 that connects these inner and outer circumferential side surfaces 44 and 46. The rubber grooves 42 have a groove cross-sectional shape in which the radial groove width dimension is larger than the axial groove depth dimension. The inner circumferential side wall portion of the rubber groove 42 having the inner circumferential side surface 44 is fixed to the inner shaft member 12 as the axial end on the inner side of the main rubber elastic body 16, and the outer circumferential side wall portion of the rubber groove 42 having the outer circumferential side surface 46 is fixed to the outer cylindrical member 14 as the axial end on the outer side of the main rubber elastic body 16. The inner circumferential axial end of the main rubber elastic body 16, which is the inner circumferential side wall portion of the rubber groove 42, is a filling portion 40 in which the axially inner portion is fixed to the inner groove 24, and the axially outer portion is fixed to the cylindrical tip surface 30 of the protruding portion 26 and is thinner than the filling portion 40. The inner circumferential axial end of the main rubber elastic body 16 is located axially outward from the inner groove 24 and axially inward from the axial end of the outer cylindrical member 14. The outer circumferential axial end of the main rubber elastic body 16, which is the outer circumferential side wall portion of the rubber groove 42, is fixed almost entirely to the small diameter cylindrical portion 38 of the outer cylindrical member 14 and has a substantially constant thickness.

[0059] The axial position of the opening of the rubber groove 42 is located axially outward from the inner groove 24 and is on the outer circumference side of the protrusion 26. The rubber groove 42 overlaps with the inner groove 24 in a projection perpendicular to the axis, and the bottom surface 48 of the rubber groove 42 reaches the inner groove 24 of the inner shaft member 12 in the axial direction. The rubber groove 42 overlaps with the concave surface 35 of the outer cylindrical member 14 in a projection perpendicular to the axis, and the bottom surface 48 of the rubber groove 42 reaches the concave surface 35 of the outer cylindrical member 14.

[0060] The bottom surface 48 of the rubber groove 42 is a curved surface composed of an intermediate curved portion 50, an inner circumferential curved portion 52, and an outer circumferential curved portion 54. In this embodiment, the intermediate curved portion 50 is a concave curved surface and has an arc-shaped longitudinal cross-section with a radius of curvature of Ra in the longitudinal cross-section. In this embodiment, the inner and outer ends of the intermediate curved portion 50 are located at approximately the same position in the axial direction, and the center of curvature is located approximately in the radial center. The inner circumferential curved portion 52 is a concave curved surface connecting the inner circumferential side surface 44 and the intermediate curved portion 50 and has an arc-shaped longitudinal cross-section with a radius of curvature of Rb in the longitudinal cross-section. The outer circumferential curved portion 54 is a concave curved surface connecting the outer circumferential side surface 46 and the intermediate curved portion 50 and has an arc-shaped longitudinal cross-section with a radius of curvature of Rc in the longitudinal cross-section.

[0061] The radius of curvature Ra of the intermediate curved section 50 is greater than the radius of curvature Rb of the inner curved section 52 and the radius of curvature Rc of the outer curved section 54. Furthermore, the radius of curvature Rb of the inner curved section 52 is smaller than the radius of curvature Rc of the outer curved section 54. In this embodiment, the radius of curvature Ra of the intermediate curved section 50 is greater than the sum of the radius of curvature Rb of the inner curved section 52 and the radius of curvature Rc of the outer curved section 54. For example, the radius of curvature Ra of the intermediate curved section 50 is preferably in the range of 1.4 to 100 times the radius of curvature Rb of the inner curved section 52. Also, the radius of curvature Rc of the outer curved section 54 is preferably in the range of 1.1 to 10 times the radius of curvature Rb of the inner curved section 52.

[0062] The main rubber elastic body 16 is partially thinned between the bottom surface 48 of the rubber groove 42 and the bulging portion 22 of the inner shaft member 12. The thickness t of this thinned portion 56 is smaller than the maximum thickness T of the filling portion 40. Therefore, on both sides of the filling portion 40, there are portions that are thinner than the maximum thickness T of the filling portion 40.

[0063] The cylindrical vibration damping device 10, having such a structure, is attached, for example, to a railway bogie, car body, axle box, etc. (not shown) by bolts (not shown) inserted through bolt holes 34, 34 at the mounting portions 20, 20 of the inner shaft member 12, and the outer cylindrical member 14 is press-fitted and fixed to cylindrical portions provided at the ends of links or dampers of a railway bogie (not shown).

[0064] In this configuration mounted on a railway bogie, the cylindrical vibration damping device 10 is required to have high durability against twisting input (twisting input) caused by the relative tilting of the inner shaft member 12 and the outer cylindrical member 14.

[0065] Therefore, in this embodiment, the cylindrical vibration damper 10 is provided with a bulge 22 on the inner shaft member 12, and when twisting input occurs, the main rubber elastic body 16 mainly undergoes shear deformation, thus preventing the occurrence of cracks in the main rubber elastic body 16 due to excessive tension. In this embodiment, the surface of the outer cylindrical member 14 facing the bulge 22 is a concave surface 35, so that the reduction of strain during twisting input can be achieved more effectively. Damage such as cracks in the main rubber elastic body 16 due to twisting input can occur at the axial end of the main rubber elastic body 16, the joint surface of the main rubber elastic body 16 to the inner shaft member 12 and the outer cylindrical member 14, and inside the main rubber elastic body 16, but with the cylindrical vibration damper 10 according to this embodiment, a damage suppression effect can be achieved in any of the parts where such damage is expected to occur.

[0066] A rubber groove 42 is provided at the axial end of the main rubber elastic body 16, making it difficult for the axial end of the main rubber elastic body 16 to undergo significant compressive or tensile deformation between the inner shaft member 12 and the outer cylindrical member 14 during twisting input. This prevents the occurrence of cracks at the axial end of the main rubber elastic body 16 during twisting input.

[0067] The bottom surface 48 of the rubber groove 42 is provided with an intermediate curved portion 50 with a large radius of curvature, and an inner circumferential curved portion 52 and an outer circumferential curved portion 54 with a smaller radius of curvature than the intermediate curved portion 50. This ensures a large radial width of the bottom surface 48 of the rubber groove 42, improving durability by ensuring the free length of the rubber groove 42 in the radial direction. The rubber groove 42 in this embodiment has a flat groove cross-sectional shape in which the width dimension W is larger than the depth dimension D, making it possible to ensure the free length in the radial direction without setting the depth excessively deep.

[0068] Inner grooves 24 are provided on both the axial sides of the bulging portion 22 of the inner shaft member 12, and the filling portion 40 of the main rubber elastic body 16 is placed within the inner grooves 24. The filling portion 40 is relatively thick because it is provided within the inner grooves 24, and when a twisting input is applied, the deformation of the filling portion 40 reduces the strain of the main rubber elastic body 16, and furthermore, the strain at the axial end on the inner circumference side of the main rubber elastic body 16.

[0069] Because the rubber groove 42 is provided with a depth that overlaps with the inner groove 24 in a projection perpendicular to the axis, the thin-walled portion 56 is provided axially inward of the filling portion 40 in the main rubber elastic body 16. As a result, the deformation transmission rate between the axially inward portion of the main rubber elastic body 16 (the axial central portion fixed to the bulging portion 22 of the inner shaft member 12) and the filling portion 40 is regulated by the thin-walled portion 56, preventing damage to the filling portion 40 due to excessive deformation.

[0070] In this embodiment, the rubber groove 42 has a radius of curvature Rb of the inner circumferential curved portion 52 smaller than the radius of curvature Rc of the outer circumferential curved portion 54 at the bottom surface 48. This makes it easier to bring the rubber groove 42 closer to the inner shaft member 12 in a narrow area, and it is possible to limit the deformation of the filling portion 40 while ensuring the rubber volume of the main rubber elastic body 16.

[0071] The curvature center C1 of the bulge 22 of the inner shaft member 12 is shifted toward the protruding tip of the bulge 22 relative to the center C0 of the inner shaft member 12. As a result, the radius of curvature of the surface of the bulge 22 is smaller compared to the case where the bulge 22 has a spherical surface with the center of curvature C0 of the inner shaft member 12, and the axial length dimension is smaller if the position of the outer peripheral end is the same. Therefore, while appropriately setting the spring characteristics in the direction perpendicular to the axis, it is possible to secure space for forming inner grooves 24 and rubber grooves 42 on both axial outer sides of the bulge 22, inward from the axial ends of the outer cylindrical member 14.

[0072] The axial end face of the main rubber elastic body 16 is located axially outward from the bulge portion 22, thereby ensuring a large radial free length. This improves durability against torsional input. Furthermore, since the radial thickness dimension of the main rubber elastic body 16 is smaller on the outer circumference side of the bulge portion 22, the spring of the main rubber elastic body 16 in the direction perpendicular to the axis can be set to be stiffer.

[0073] The axial end of the main rubber elastic body 16, on the inner circumference side of the rubber groove 42, is fixed to the protruding portion 26 of the inner shaft member 12 axially outward from the filling portion 40, and is thinner in the radial direction than the filling portion 40. As a result, when the main rubber elastic body 16 deforms, the axial end face on the inner circumference of the main rubber elastic body 16 is less likely to deform excessively, and damage to the axial end face is prevented. Because the thin axial end, which is subjected to a large restraining force due to its fixation to the inner shaft member 12, is located axially outward from the relatively thicker filling portion 40, deformation of the axial end face on the inner circumference of the main rubber elastic body 16 is suppressed even when the filling portion 40 deforms.

[0074] Figures 5 and 6 show a cylindrical vibration isolation device 60 as a second embodiment of the present invention. The cylindrical vibration isolation device 60 has a structure in which an inner shaft member 12 and an outer cylindrical member 62 are connected by a main rubber elastic body 64. In the following description, components and parts that are substantially the same as those in the first embodiment are denoted by the same reference numerals in the figures, and their descriptions are omitted.

[0075] The outer cylindrical member 62 has an inner circumferential surface that is a cylindrical surface extending linearly in the axial direction, does not have a concave surface 35 on its inner circumferential surface, and has a substantially constant thickness dimension along its entire length in the axial direction.

[0076] The main rubber elastic body 64 is provided with rubber grooves 66 at both ends in the axial direction. As shown in an enlarged view in Figure 5, the radius of curvature Ra of the intermediate curved portion 50 that constitutes the bottom surface 48 is larger than the radius of curvature Rb of the inner curved portion 52 and the radius of curvature Rc of the outer curved portion 54, while the radius of curvature Rb of the inner curved portion 52 and the radius of curvature Rc of the outer curved portion 54 are the same size. Furthermore, the center of curvature of the intermediate curved portion 50 is set in the radial direction to be closer to the outer surface 46 than to the inner surface 44 of the rubber groove 66, and the deepest part of the rubber groove 66 is located on the outer side than the widthwise center of the rubber groove 42. Consequently, the depth dimension of the inner end of the rubber groove 66 is smaller than the depth dimension of the outer end.

[0077] With this embodiment of the cylindrical vibration isolation device 60, while appropriately setting the spring characteristics in each direction, the durability against torsional input can be improved.

[0078] Furthermore, the main body rubber elastic body 16 of the first embodiment and the outer cylindrical member 62 of the second embodiment can be used in combination, or the main body rubber elastic body 64 of the second embodiment and the outer cylindrical member 14 of the first embodiment can be used in combination.

[0079] Although embodiments of the present invention have been described in detail above, the present invention is not limited by its specific description. For example, the rubber groove 42 may have a depth that extends axially inward from the inner groove 24, and the bottom surface 48 may be located on the outer circumference side of the bulge 22.

[0080] The intermediate curved portion that constitutes the bottom surface of the rubber groove is not necessarily limited to a concave curved surface. For example, it may be a convex curved surface or a flat surface with an infinite radius of curvature, at least in part. Even when the intermediate curved portion is a convex curved surface or a flat surface, the radius of curvature of the intermediate curved portion is made larger than the radius of curvature of the inner curved portion and the radius of curvature of the outer curved portion.

[0081] The intermediate curved section may be pre-formed as a concave curved surface, or it may be formed as a flat or convex curved surface and then made into a concave curved surface by drawing. Similarly, the intermediate curved section may be pre-formed as a convex curved surface, or it may be formed as a flat or concave curved surface and then made into a convex curved surface by drawing.

[0082] The intermediate curved section, inner circumference curved section, and outer circumference curved section are not limited to arc-shaped curved surfaces with a constant radius of curvature throughout. In particular, after drawing, the radius of curvature may not be constant in each curved section. When the radius of curvature of each curved section is not constant, the cylindrical vibration damping device according to the first embodiment only needs to have a maximum value of the radius of curvature of the intermediate curved section that is greater than the maximum value of the radius of curvature of the inner circumference curved section and the maximum value of the radius of curvature of the outer circumference curved section.

[0083] In the above embodiment, a rubber groove 42(66) extending with a constant groove cross-sectional shape over the entire circumference in the circumferential direction was illustrated, but the groove cross-sectional shape of the rubber groove may change in the circumferential direction. For example, at least one of the groove width dimension and groove depth dimension of the rubber groove may change in the circumferential direction, or the cross-sectional shape may change while maintaining the groove width dimension and groove depth dimension of the rubber groove.

[0084] The rubber groove is not necessarily limited to annular grooves that extend continuously around the entire circumference, but may be provided partially in the circumferential direction, for example. More specifically, for example, rubber grooves extending in the circumferential direction for a length of less than half a circumference may be provided on both radial sides of the main rubber elastic body 16. Alternatively, for example, there may be one rubber groove that is C-shaped in an axial view and extends in the circumferential direction for a length of less than one circumference, or there may be three or more rubber grooves extending in the circumferential direction.

[0085] The structure of the mounting portion 20 of the inner shaft member 12 is merely an example and can be appropriately modified according to the structure of the object to be mounted. Specifically, for example, the outer shape of the mounting portion when viewed from the front may be a shape other than a rectangle, such as a trapezoid or a semicircle, and it may not be limited to a plate shape but may be rod-shaped or the like. Furthermore, the pair of mounting portions may have different shapes and sizes from each other, and the connecting structures of the pair of mounting portions may also be different from each other. In addition, the connecting structure of the mounting portion to the object to be mounted is not limited to bolt fixing, but may be pin fixing, fitting, press-fitting, or a combination of these. As can be seen from this, the bolt holes 34 provided in the mounting portion 20 in the above embodiment are not essential and can be appropriately modified according to the connecting structure with the object to be mounted. Furthermore, the bolt holes can be made into elongated holes to allow for errors in the relative position of the mounting portion with respect to the object to be mounted. Moreover, by making the bolt holes provided in the pair of mounting portions have different diameters from each other, the mounting direction of the cylindrical vibration damper with respect to the object to be mounted can also be defined.

[0086] The connecting portion 32 of the inner shaft member 12 is not mandatory; for example, the mounting portion 20 may be directly connected to the axially outer side of the portion where the protruding portion 26 is provided. Furthermore, the specific shape of the connecting portion 32 is not particularly limited; for example, its outer shape in an axial view may be a plate-like shape or a shape other than a cylinder.

[0087] Furthermore, the surface shape of the bulge 22 of the inner shaft member 12 may be, for example, an ellipse with a focal point radially outward from the center C0 of the inner shaft member 12 in a longitudinal cross-section. As can be seen from this, the curvature of the surface of the bulge 22 does not have to be constant, and can change gradually or in steps, for example, by becoming smaller or larger toward the axial outward direction. Also, a cylindrical surface extending linearly in the axial direction in a longitudinal cross-section can be set as the protruding tip of the bulge 22. Moreover, the bulge 22 may be trapezoidal or the like in a longitudinal cross-section, and is not limited to having an arc-shaped surface.

[0088] The inner groove is not limited to having a constant groove cross-sectional shape over its entire circumference in the circumferential direction; the groove cross-sectional shape may change in the circumferential direction. Furthermore, the inner groove does not necessarily have to be provided over its entire circumference in the inner shaft member; it may be provided only in part in the circumferential direction. Moreover, it is possible to provide multiple inner grooves that are partially spaced apart in the circumferential direction, and the groove shapes of these multiple inner grooves may be the same or different.

[0089] The outer circumferential surface of the outer cylindrical member 14 in the above embodiment is not limited to a straight cylindrical shape, but may, for example, be a convex curved surface corresponding to the concave surface 35 of the inner circumferential surface, or the axial end may be tapered to reduce in diameter to serve as a guide surface during press-fitting.

[0090] In addition to being applicable to the illustrated railway bogie, the cylindrical vibration damping device according to the present invention can also be applied to, for example, automobile suspension bushings, torque rod bushings, engine mounts, and the like. [Explanation of symbols]

[0091] 10. Cylindrical Vibration Isolator (First Embodiment) 12 Inner shaft member 14 Outer cylindrical member 16 Main body rubber elastic body 18 Central part 20 Mounting part 22 Bulge 24 inner groove 26 Protrusion 28 Stepped surface 30 Cylindrical tip surface 32 Connection part 34 bolt holes 35 concave surface 36 Large diameter cylindrical section 38 Small diameter cylinder part 40 Filling section 42 Rubber grooves 44 Inner side 46 Outer perimeter side 48 Bottom 50 Intermediate curve 52 Inner curved section 54 Outer curved section 56 Thin-walled section 60. Cylindrical Vibration Isolator (Second Embodiment) 62 Outer cylindrical member 64 Main body rubber elastic body 66 Rubber groove

Claims

1. A cylindrical vibration isolation device in which an inner shaft member and an outer cylindrical member are connected by a main body rubber elastic material, The inner shaft member is provided with a bulge that protrudes outward, The inner shaft member has inner grooves that open to the outer surface and extend in the circumferential direction on both axially outer sides of the bulging portion, and the filling portion of the main body rubber elastic material is filled into these inner grooves. Each of the main body's rubber elastic material is provided with a single rubber groove that opens to the axial end face and extends in the circumferential direction, the opening end of the rubber groove in the main body's rubber elastic material is located axially outward from the inner groove, and the rubber groove overlaps with at least a portion of the inner groove in a projection perpendicular to the axis. The bottom surface of the rubber groove is composed of an intermediate curved section, an inner curved section, and an outer curved section, each of which is a curved surface. The radius of curvature of the intermediate curved section is larger than the radii of curvature of the inner and outer curved sections. A cylindrical vibration isolation device in which the surface of the bulge is in the shape of a circular arc with a single radius in a longitudinal cross-section, and each of the outer ends on both sides of the bulge in the axial direction is directly connected to the inner ends of each of the inner grooves in the axial direction.

2. The cylindrical vibration damping device according to claim 1, wherein the bulging portion has a rotating body shape around the central axis of the inner shaft member.

3. The cylindrical vibration damping device according to claim 1 or 2, wherein the axial end of the inner circumference end of the main body rubber elastic body is located axially inward from the axial end of the outer cylindrical member.

4. The inner shaft member is provided with mounting portions that protrude outward in both axial directions from the inner groove, Between the mounting portion and the inner groove of the inner shaft member, a protruding portion is provided that extends circumferentially and protrudes outward from the mounting portion. The cylindrical vibration damping device according to claim 1 or 2, wherein the axial end of the main rubber elastic body on the inner circumference side of the rubber groove is located on the outer circumference surface of the protrusion and is thinner than the filling portion.

5. The cylindrical vibration damping device according to claim 1 or 2, wherein the center of curvature of the surface of the bulging portion is shifted toward the protruding tip of the bulging portion with respect to the central axis of the inner shaft member.

6. The cylindrical vibration damping device according to claim 1 or 2, wherein the entire inner groove is located axially inward from the axial end of the outer cylindrical member.

7. The cylindrical vibration damping device according to claim 6, wherein the inner circumferential end of the main body rubber elastic body is located outside the inner groove in the axial direction and inside the axial end of the outer cylindrical member.

8. The cylindrical vibration damping device according to claim 1 or 2, wherein a thin-walled portion is provided in the main body rubber elastic body axially inward from the filling portion, and the thickness dimension is smaller than the maximum thickness dimension of the filling portion.

9. The cylindrical vibration damping device according to claim 1 or 2, wherein the outer cylindrical member has a large-diameter cylindrical portion in which the portion facing the bulging portion of the inner shaft member in a direction perpendicular to the axis has a larger inner diameter than the portions at both ends in the axial direction.

10. The cylindrical vibration damping device according to claim 9, wherein on both axial sides of the large diameter cylindrical portion of the outer cylindrical member, there are small diameter cylindrical portions that are thickened to protrude toward the inner circumference and have a smaller inner diameter than the large diameter cylindrical portion, and the small diameter cylindrical portions are located on the outer circumference of the inner groove, facing the inner groove in the radial direction.

11. The cylindrical vibration damping device according to claim 1 or 2, wherein the groove width dimension in the direction perpendicular to the axis of the rubber groove is larger than the groove depth dimension in the axial direction.

12. The bottom surface of the rubber groove is composed of an intermediate curved section, an inner curved section, and an outer curved section, each of which is a curved surface. The cylindrical vibration isolation device according to claim 1 or 2, wherein the radius of curvature of the inner curved portion is less than or equal to the radius of curvature of the outer curved portion.

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