Vibration isolating bush

Abstract

To provide a vibration isolating bush that can reduce a spring property in a torsional direction while securing the degree of freedom of setting of a spring property in a direction perpendicular to an axis, and has a new structure.SOLUTION: In a vibration isolating bush 10, an inner shaft member 12 and an outer cylinder member 14 are elastically connected by a body rubber elastic body 16. The inner shaft member 12 comprises a split structure comprising a body shaft member 20 and a bulge member 22. The bulge member 22 is attached to the body shaft member 20 so as to be relatively movable in a circumferential direction in an unfixed state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a substantially cylindrical vibration-isolating bushing that can be used, for example, as a suspension bushing for an automobile. [Background technology]

[0002] Conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2010-159860 (Patent Document 1), there have been known vibration-damping bushes used in automobile suspension bushings, etc. Such vibration-damping bushings are generally cylindrical in shape, with an inner shaft member and an outer cylindrical member connected by a main rubber elastic body, and the inner shaft member and the outer cylindrical member are attached to each of the members in the vibration-damping connection, so that the vibration-damping effect is achieved by elastic deformation of the main rubber elastic body.

[0003] In suspension bushings and the like, it is sometimes necessary to achieve both high spring characteristics in response to inputs in the direction perpendicular to the central axis of the bushing, and low spring characteristics in response to inputs in the torsional direction around the central axis of the bushing.

[0004] Therefore, as shown in Patent Document 1, it is conceivable to provide a bulging portion that bulges out on the outer periphery at the axial center portion of the inner shaft member, thereby increasing the spring strength in the axis-perpendicular direction.

[0005] However, when such a bulging portion is provided in the inner shaft member, although the increase in springiness in the prying direction in which the central axes of the inner shaft member and the outer cylindrical member tilt relative to each other can be reduced, there is a problem that the increase in springiness in the torsional direction cannot be avoided. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-159860 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved by the present invention is to provide a vibration-damping bushing with a novel structure that prevents the bushing from becoming too stiff in the torsional direction around the central axis, while ensuring a large degree of freedom in tuning the spring characteristics in the direction perpendicular to the axis. [Means for solving the problem]

[0008] The following describes preferred embodiments for understanding the present invention, but the embodiments described below are merely examples and may be appropriately combined with one another. Multiple components described in each embodiment may be recognized and employed independently to the greatest extent possible, and may also be appropriately combined with any of the components described in other embodiments. Accordingly, the present invention is not limited to the embodiments described below, and various other embodiments may be realized.

[0009] A first aspect of the present invention is as follows. In a vibration-isolating bushing in which an inner shaft member and an outer cylindrical member are connected by a main rubber elastic body, the inner shaft member has a divided structure including a main body shaft member extending over the entire axial length and a bulge member located in an axially intermediate portion of the main body shaft member and assembled to the outer peripheral surface of the main body shaft member, the bulge member is a hard member having greater rigidity than the main rubber elastic body, The bulge member is assembled to the main shaft member in a non-fixed state so as to be movable relative to the main shaft member in the circumferential direction.

[0010] In the vibration-damping bushing according to this aspect, the inner axial member is configured as a divided structure with a composite structure of a main axial member and a bulge member assembled so as to be rotatable relative to each other about a central axis. As a result, when a torsional force about the central axis is applied between the inner axial member and the outer cylindrical member, the main axial member and the bulge member move relative to each other in the circumferential direction inside the inner axial member, reducing the torsional force applied to the main rubber elastic body and the deformation stress of the main rubber elastic body, thereby achieving low springiness.

[0011] Furthermore, by designing the outer peripheral surface shape of the bulge member, a great degree of freedom in design can be ensured for the radial thickness dimension of the main rubber elastic body, and therefore for the spring characteristics in the axis-transverse direction. Therefore, with this vibration-damping bushing, a great degree of freedom in design can be ensured for the spring characteristics in the axis-transverse direction, making it possible to achieve, for example, high spring characteristics in the axis-transverse direction, while achieving sufficiently low spring characteristics in the torsional direction.

[0012] The second aspect of the present invention is as follows. The vibration-isolating bushing according to the first aspect, wherein the main shaft member is fixed to the main rubber elastic body at portions that are spaced apart from the bulge member on both sides in the axial direction.

[0013] In the vibration-damping bushing according to this aspect, both axial ends of the main rubber elastic body are fixed to the main shaft member constituting the inner shaft member, which exerts a certain degree of restraint on the elastic deformation of the inner peripheral portion of the main rubber elastic body. Therefore, when an input is applied in the axis-perpendicular direction, for example, elastic deformation of the main rubber elastic body that would cause it to escape to both axial ends is suppressed, which can more effectively suppress springiness in the axis-perpendicular direction.

[0014] The third aspect of the present invention is as follows. The vibration-isolating bushing according to the first or second aspect is provided with an engaging portion that positions the main shaft member and the bulge member relative to each other in the axial direction.

[0015] In the vibration-isolating bushing according to this aspect, the provision of the engaging portion makes it possible to position the bulge member with respect to the main shaft member with high precision and to limit relative movement in the axial direction.

[0016] A fourth aspect of the present invention is as follows. The vibration-isolating bushing according to any one of the first to third aspects, wherein the bulge member is composed of a plurality of divided structures in the circumferential direction.

[0017] In the vibration-damping bushing of this aspect, not only is the bulge member easier to manufacture than when a bulge member made of a circumferentially continuous, cylindrical, one-piece structure is used, but the assembly work to the main shaft member can also be facilitated. For example, by combining it with the third aspect, in which an axial engagement portion is provided between the bulge member and the main shaft member, it is possible to ensure ease of assembly between the main shaft member and the bulge member, while still making it easier to realize an axial engagement portion using a concave-convex engagement or the like.

[0018] A fifth aspect of the present invention is as follows. The vibration-isolating bushing according to any one of the first to fourth aspects, wherein the bulge member is fixed to the main rubber elastic body.

[0019] In the vibration-damping bushing according to this aspect, the bulge member to which the inner peripheral surface of the main rubber elastic body is fixed exerts a certain degree of restraint on elastic deformation of the inner peripheral portion of the main rubber elastic body. Therefore, when an input is applied in the axis-perpendicular direction, for example, elastic deformation of the main rubber elastic body that would cause it to escape in the circumferential or axial direction is suppressed, thereby more effectively suppressing low springiness in the axis-perpendicular direction. Meanwhile, because the main shaft member and the bulge member move relative to each other in the circumferential direction inside the inner shaft member, low springiness can be achieved in the torsional direction of the main rubber elastic body.

[0020] A sixth aspect of the present invention is as follows. A vibration-damping bushing according to any one of the first to fifth aspects, wherein the outer diameter dimension of the axially intermediate portion of the main shaft member to which the bulge member is assembled is equal to or smaller than the outer diameter dimensions of both axial end portions.

[0021] In the vibration-damping bushing according to this aspect, the outer diameter of the main shaft member is reduced, which increases the degree of freedom in designing the shape of the outer peripheral surface of the bulge member, its radial thickness, etc. Furthermore, it becomes easier to ensure the radial thickness of the bulge member, and when the bulge member is made of synthetic resin or the like, it becomes easier to ensure the strength, durability, and other properties of the bulge member.

[0022] A seventh aspect of the present invention is as follows. A vibration-damping bushing according to any one of the first to sixth aspects, wherein the assembly surface between the outer peripheral surface of the axially middle portion of the main shaft member and the inner peripheral surface of the bulge member has a cylindrical assembly surface that extends straight in the axial direction.

[0023] In the vibration-damping bushing of this embodiment, it becomes easier to control the dimensions and precision of the outer surface of the main shaft member and the inner surface of the bulge member, and it is possible to, for example, reduce uneven contact during relative rotation and stabilize the desired circumferential movement characteristics. [Effects of the Invention]

[0024] According to the present invention, by constructing the inner shaft member with a composite structure of the main shaft member and the bulge member, it is possible to ensure a large degree of design freedom in the radial thickness dimension of the main rubber elastic body and therefore in the spring characteristics perpendicular to the axis based on the large degree of design freedom in the outer surface shape of the bulge member, while also achieving low torsional spring strength based on the allowance for relative movement in the circumferential direction between the main shaft member and the bulge member. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 5 is a longitudinal cross-sectional view showing a suspension bushing according to an embodiment of the present invention, which corresponds to cross section II of FIG. 4. [Figure 2] 2 is a cross-sectional view of the suspension bushing shown in FIG. 1, which corresponds to the cross section II-II of FIG. 3; [Figure 3] Front view of the suspension bushing shown in Figure 1 [Figure 4] Side view of the suspension bushing shown in Figure 1 [Figure 5] FIG. 2 is a perspective view of an inner shaft member that constitutes the suspension bushing shown in FIG. 1; [Figure 6] Graph showing the results of a simulation of the spring characteristics in the axis-perpendicular direction of the suspension bush shown in FIG. 1, along with a comparative example. [Figure 7] Graph showing the results of a simulation showing the spring characteristics in the torsional direction of the suspension bushing shown in FIG. 1, along with a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0027] 1 to 4 show an anti-vibration bushing 10 used as a suspension bushing for automobiles as one embodiment of the present invention.

[0028] The vibration-damping bushing 10 of this embodiment has an inner shaft member 12 having a small diameter and a roughly cylindrical shape, and an outer cylindrical member 14 having a large diameter and a roughly cylindrical shape is arranged on the outer peripheral side of the inner shaft member 12. The inner shaft member 12 and outer cylindrical member 14 are arranged on roughly the same central axis, and the inner shaft member 12 and outer cylindrical member 14 are arranged facing each other and separated from each other in the radial direction.

[0029] A main rubber elastic body 16 having a thick, approximately cylindrical shape is arranged radially between the inner shaft member 12 and the outer cylindrical member 14, and this main rubber elastic body 16 elastically connects the inner shaft member and the outer cylindrical member 14.

[0030] Such a vibration-damping bushing 10 is used by being installed between the components to be connected in a vibration-damping manner, with the inner shaft member 12 attached to one of the components to be connected in a vibration-damping manner (for example, a vehicle body side component) using bolts or the like, and the outer tubular member 14 attached to the other component to be connected in a vibration-damping manner (for example, a vehicle suspension arm) by press-fitting or the like.

[0031] The inner axial member 12, the outer tubular member 14, and the main rubber elastic body 16 are not limited to specific shapes or structures, and various modifications can be made based on the knowledge of those skilled in the art, taking into account the required vibration-damping characteristics and functions. For example, the inner axial member 12 in this embodiment has a generally cylindrical shape with a central hole 18 through which a fastening member such as a bolt is inserted. However, it may also have a solid rod shape with a fixing bolt hole, a bolt shank, or the like. Furthermore, the outer tubular member 14 in this embodiment has a thin-walled, generally cylindrical shape. However, for example, a flange-like portion may be provided at the axial end to form an axial stopper mechanism, or the axial end may be tapered to reduce in diameter toward the tip to improve press-fitting workability. Furthermore, the main rubber elastic body 16 may also have a reinforcing member embedded and fixed in the radial middle portion to tune its spring characteristics, or a recessed hole or slit that opens into the axial end surface and extends axially to adjust the radial spring characteristics in a specific direction. Furthermore, in this embodiment, the inner shaft member 12, outer cylindrical member 14, and main rubber elastic body 16 are rotationally symmetrical around the center axis of the bushing, but it is also possible to tune the spring ratio in different radial directions by embedding and fixing a reinforcing member in a specific radial direction, providing a recessed hole or slit, or varying the radial thickness dimension of the main rubber elastic body 16.

[0032] Here, in the vibration-damping bushing 10 of this embodiment, as shown in Figure 5, the inner shaft member 12 has a divided structure and is composed of a main shaft member 20 and a bulge member 22, which are separate members.

[0033] The main body shaft member 20 extends on the inner central axis over the entire axial length of the inner shaft member 12, and is generally cylindrical, forming a central hole 18. A bulge member 22 is assembled to the main body shaft member 20 at a position intermediate in the axial direction (in this embodiment, the central portion in the axial direction).

[0034] The bulge member 22 has an overall cylindrical shape and is assembled in an externally fitted state onto the main shaft member 20. The axial length of the bulge member 22 is shorter than that of the main shaft member 20, and the axial ends of the main shaft member 20 protrude a predetermined length from both axial sides of the bulge member 22. The inner circumferential surface 24 of the bulge member 22 is cylindrical with a diameter that is the same as or slightly larger than that of the central outer circumferential surface 26 of the main shaft member 20, and the bulge member 22 is assembled to the main shaft member 20 in an unfixed manner so as to be relatively movable in the circumferential direction.

[0035] In particular, in this embodiment, the main shaft member 20 and the bulge member 22 are both rotationally symmetrical about the same central axis, which is the central axis of the inner shaft member 12, and the main shaft member 20 and the bulge member 22 are capable of rotating relatively about that central axis.

[0036] Furthermore, in this embodiment, the outer diameter of the axially central portion 30 of the main body shaft member 20, to which the bulge member 22 is assembled, is made smaller by a predetermined dimension than the outer diameter of the axially opposite end portions 32, 32 protruding from the bulge member 22. As a result, the main body shaft member 20 has large-diameter axially opposite end portions 32, 32 on both axial sides of the small-diameter axially central portion 30, and annular steps 34, 34 extending in the radial direction are formed at each boundary between the axially central portion 30 and the axially opposite end portions 32, 32.

[0037] The radial thickness of the bulge member 22 at both axial ends is approximately the same as the stepped portion 34. As a result, the outer circumferential surfaces of the axial ends of the bulge member 22 are smoothly (almost flush) connected to the outer circumferential surfaces of the axial ends 32 of the main shaft member 20 in the axial direction, with almost no steps. That is, the main shaft member 20 of this embodiment has a recessed portion with a reduced diameter along a predetermined axial length in the axial center, and the inner circumferential portion of the bulge member 22 is fitted into this recessed portion when assembled. As a result, the stepped portions 34, 34 of the main shaft member 20 and the axial end faces of the bulge member 22 abut against each other in the axial direction, forming an engagement portion 36 that positions the main shaft member 20 and the bulge member 22 relative to each other in the axial direction. Note that a slight gap may exist between the stepped portion 34 of the main shaft member 20 and the axial end faces of the bulge member 22.

[0038] Furthermore, the outer peripheral surface 38 of the bulge member 22 in this embodiment has a gradually increasing diameter from both axial end portions toward the center, with the center portion being the most bulged in the axial direction. In particular, the outer peripheral surface 38 in this embodiment has a bulged shape that is smoothly curved without steps or corners in the axial direction and has a varying inclination angle, and the axially central portion has a cylindrical portion that extends with a substantially constant maximum outer diameter over a short axial length.

[0039] In this embodiment, the inner circumferential portion of the main rubber elastic body 16 extends axially from the bulge member 22 as described above to both axial end portions 32, 32 of the main shaft member 20. In other words, the outer circumferential surface of the inner shaft member 12, including the entire outer circumferential surface of the bulge member 22 and predetermined regions of both axial end portions 32, 32 of the main shaft member 20, is covered in a substantially tight contact state by the inner circumferential surface of the main rubber elastic body 16.

[0040] The inner peripheral surface of the main rubber elastic body 16 does not need to be fixed to the outer peripheral surface of the bulge member 22 or the outer peripheral surface of the main shaft member 20 (both axial end portions 32, 32). However, it is desirable that the outer peripheral surfaces of the both axial end portions 32, 32 are bonded to the main rubber elastic body 16, and more preferably, the bulge member 22 and the main rubber elastic body 16 are also bonded. It is also desirable that the outer peripheral surface of the main rubber elastic body 16 is fixed to the inner peripheral surface of the outer tubular member 14 by adhesive or the like.

[0041] Furthermore, the bulge member 22 is made of a hard member that is at least more rigid than the main rubber elastic body 16, so that the amount of deformation when a load is applied is kept at least smaller than that of the main rubber elastic body 16. Specifically, the material of the bulge member 22 is not limited, but it is preferable to use one made of, for example, metal or synthetic resin (including those that are fiber-reinforced, etc.).

[0042] The material of the main rubber elastic body is not limited, and various conventionally known rubber materials can be used taking into consideration the required vibration-damping properties, load characteristics, durability, etc. The materials of the main shaft member 20 and the outer cylindrical member 14 are also not limited, but generally, those formed from highly rigid metals or hard resins can be used.

[0043] In the vibration-damping bushing 10 constructed as described above, when an external force such as vibration is applied between the inner axial member 12 and the outer cylindrical member 14 in the torsional direction around the central axis of the bushing, relative rotational movement in the torsional direction between the inner axial member 12 and the outer cylindrical member 14 is permitted based on the elastic deformation of the main rubber elastic body 16. The elastic properties and damping characteristics of the main rubber elastic body 16 then provide a vibration-damping effect.

[0044] Here, the bulge member 22, which constitutes the axially central portion of the inner shaft member 12, is assembled to the main shaft member 20 so as to be rotatable about the central axis, thereby reducing torsional deformation of the main rubber elastic body 16 during relative torsional rotation between the inner shaft member 12 and the outer cylindrical member 14. The main shaft member 20 of the inner shaft member 12 is fixedly attached to a vehicle body or the like, and the bulge member 22 remains rotatable even in this attached state. Therefore, the main rubber elastic body 16, which is provided on the outer peripheral surface of the bulge member 22, does not rotate together with the main shaft member 20 at its inner peripheral portion, and circumferential deformation is reduced by the relative rotation of the bulge member 22 with respect to the main shaft member 20. As a result, the main rubber elastic body 16, and in turn the vibration-damping bushing 10, can achieve substantially lower torsional spring force.

[0045] On the other hand, when vibrations or the like are input in the axis-perpendicular direction perpendicular to the bushing central axis, the inner shaft member 12 and the outer cylindrical member 14 undergo relative displacement (eccentric movement) in the radial direction, and therefore the radial spring characteristics of the main rubber elastic body 16 are effectively exhibited, regardless of whether relative rotation is permitted between the bulge member 22 and the main shaft member 20. As a result, the main rubber elastic body 16, and ultimately the vibration-damping bushing 10, can effectively maintain and exhibit the desired axis-perpendicular spring characteristics (e.g., high spring characteristics).

[0046] In particular, in this embodiment, the bulge member 22 has an outer diameter dimension larger than both axial end portions 32 of the main shaft member 20, making it possible to set a small radial thickness dimension of the main rubber elastic body 16. Therefore, the bulge member 22 makes it easy to design the outer diameter dimension and outer peripheral surface shape of the inner shaft member 12, increasing the degree of freedom in tuning the spring characteristics in the axis-perpendicular direction (radial direction), and making it possible to achieve, for example, even higher springiness in the axis-perpendicular direction.

[0047] Furthermore, the vibration-damping bushing 10 of this embodiment can employ a structure in which the outer peripheral surfaces of both axial end portions 32 of the main shaft member 20 are fixed to the main rubber elastic body 16. This improves durability by preventing foreign matter (including water) from entering between the sliding surfaces of the main shaft member 20 and the bulge member 22. Furthermore, by suppressing axial outward bulging deformation of the main rubber elastic body 16 when an external force is applied in the axis-perpendicular direction, it is possible to achieve even higher springiness in the axis-perpendicular direction.

[0048] Furthermore, the vibration-damping bushing 10 of this embodiment can employ a structure in which at least a portion of the outer peripheral surface of the bulge member 22 is fixed to the main rubber elastic body 16. This makes it possible to avoid wear and other problems caused by the main rubber elastic body 16 sliding against the bulge member 22, and because the amount of elastic deformation of the inner peripheral portion of the main rubber elastic body 16 is limited by the bulge member 22, it is possible to reduce the amount of elastic deformation of the main rubber elastic body 16 when an input is applied in the axis-perpendicular direction, for example, thereby achieving even higher springiness.

[0049] In the vibration-damping bushing 10 of this embodiment, the central outer peripheral surface 26 to which the bulge member 22 is assembled in the main shaft member 20 is reduced in diameter. This ensures a sufficient radial thickness dimension of the bulge member 22 to ensure member strength and formability, while also ensuring a great degree of freedom in designing the shape of the outer peripheral surface of the bulge member 22.

[0050] Furthermore, in the vibration-damping bushing 10 of this embodiment, the central outer peripheral surface 26 of the main body shaft member 20, which comes into sliding contact with the inner peripheral surface of the bulge member 22, is configured as a cylindrical assembly surface that extends in a substantially straight line over the entire axial length. This allows the main body shaft member 20 to stably support the radial contact force of the bulge member 22, and also stabilizes sliding performance during relative rotation.

[0051] The spring characteristics in the axis-perpendicular direction and the spring characteristics in the torsional direction of the vibration-damping bushing 10 constructed in accordance with the present embodiment shown in Figures 1 to 4 were determined by simulation, and the results are shown in the graphs of Figures 6 and 7 as an example. Furthermore, the spring characteristics in the axis-perpendicular direction and the spring characteristics in the torsional direction of the same vibration-damping bushing, but in which the bulge member 22 is fixed to the main shaft member 20 and integrally formed so as not to rotate relative to it, were also determined by simulation, and the results are also shown in the graphs of Figures 6 and 7 as a comparative example. From the results shown in Figures 6 and 7, it can be confirmed that the vibration-damping bushing constructed in accordance with the present invention achieves low spring characteristics in the torsional direction while maintaining the spring characteristics in the axis-perpendicular direction. In the graph of Figure 6, the example and the comparative example roughly overlap.

[0052] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to those specific descriptions. For example, the outer peripheral surface shape of the bulge member 22 is not limited and can be designed appropriately depending on the required spring characteristics, etc. Furthermore, the inner peripheral surface shape of the bulge member 22 and the outer peripheral surface shape of the main shaft member 20 are not limited and can be designed appropriately taking into account the expected direction and magnitude of external force, required characteristics, etc.

[0053] Specifically, for example, in the vibration-damping bushing 10 of the above embodiment, the outer peripheral surface of the bulge member 22 may be formed into a cylindrical shape that extends with a substantially constant outer diameter over the entire axial length. In this case, the outer diameter of the bulge member 22 may be made larger than the outer diameter of both axial end portions 32 of the main shaft member 20, or it may be made substantially the same as the outer diameter of both axial end portions 32, for example.

[0054] Furthermore, a mechanism for positioning the main shaft member 20 and the bulge member 22 in the axial direction is not necessarily required; for example, the main shaft member 20 may be formed with a cylindrical outer surface having an approximately constant outer diameter dimension along the entire axial length, and the bulge member 22, which has large-diameter, straight cylindrical inner and outer peripheral surfaces, may be fitted on top and assembled.

[0055] Furthermore, even when an engaging portion is employed to position the main shaft member 20 and the bulge member 22 in the axial direction, in addition to providing a circumferentially extending recessed portion on the outer peripheral surface of the main shaft member 20 as in the above embodiment and fitting the bulge member 22 into it to engage, it is also possible to form an engaging portion for axial positioning by providing an engaging protrusion that protrudes partially in the axial direction and extends circumferentially on one of the outer peripheral surface of the main shaft member 20 and the inner peripheral surface of the bulge member 22, and providing a corresponding engaging recessed portion on the other to engage with the recessed and concave portions.

[0056] Furthermore, the bulge member 22 need only be able to rotate relative to the main shaft member 20 by a predetermined angle in the circumferential direction, taking into consideration the spring characteristics required of the vibration-damping bushing 10, and there is no limit to the allowable angle of relative rotation in the circumferential direction. Therefore, for example, it is possible to provide a stopper mechanism that limits the amount of relative movement of the bulge member 22 in the circumferential direction with respect to the main shaft member 20.

[0057] Furthermore, the bulge member does not have to be a single, integrally molded part. For example, in the vibration-damping bushing 10 of the above embodiment, if the bulge member 22 is configured as a single, integrally molded part made of a synthetic resin material or the like, it is possible to form the bulge member 22 on the outer circumferential surface of the main shaft member 20 by injection molding or the like in a molding cavity in which a preformed and prepared main shaft member 20 is set, and then assemble the bulge member 22 to the main shaft member 20 at the same time as molding. Alternatively, for example, the bulge member 22 can be configured as a divided structure in which it is divided into two or more parts circumferentially (divided by a dividing surface extending in the axial direction), and the multiple divided structures divided circumferentially can be combined with each other on the outer circumferential surface of the main shaft member 20 and fixed to each other as necessary to form a cylindrical bulge member 22 as a whole.

[0058] In addition, it is possible for not only the main shaft member 20 and the main rubber elastic body 16 but also the bulge member 22 to have cross-sectional shapes that differ partially in the circumferential direction. For example, by making the outer diameter dimensions of the bulge member 22 different in two perpendicular radial directions, it is possible to make the radial thickness of the main rubber elastic body 16 different in the two perpendicular directions, thereby tuning the spring ratio of the vibration-damping bushing 10 in the two perpendicular directions.

[0059] In addition, although not listed individually, the present invention can be implemented in various forms with various changes, modifications, improvements, etc. made based on the knowledge of those skilled in the art, and all such embodiments are included within the scope of the present invention as long as they do not deviate from the spirit of the present invention. [Explanation of symbols]

[0060] 10 Anti-vibration bushing 12 Inner shaft member 14 outer cylindrical member 16 Main body rubber elastic body 18 Center hole 20 Main body shaft member 22 Bulge member 24 Inner surface (bulge member) 26 Central outer peripheral surface (main body shaft member) 30 Axial center portion (main body shaft member) 32 Axial end portions (main shaft member) 34 Step 36 Engagement part 38 Outer surface (bulge member)

Claims

1. In a vibration-isolating bushing in which an inner shaft member and an outer cylindrical member are connected by a main rubber elastic body, the inner shaft member has a divided structure including a main body shaft member extending over the entire axial length and a bulge member located in an axially intermediate portion of the main body shaft member and assembled to the outer peripheral surface of the main body shaft member, the bulge member is a hard member having greater rigidity than the main rubber elastic body, The bulge member is assembled to the main shaft member in a non-fixed state so as to be movable relative to the main shaft member in the circumferential direction.

2. 2. The vibration-isolating bushing according to claim 1, wherein the main shaft member is fixed to the main rubber elastic body at portions spaced apart from the bulge member on both sides in the axial direction.

3. 3. The vibration-isolating bushing according to claim 1, further comprising an engaging portion for axially positioning the main shaft member and the bulge member relative to each other.

4. 3. The vibration-isolating bushing according to claim 1, wherein the bulge member is composed of a plurality of divided structures in the circumferential direction.

5. 3. The vibration-isolating bushing according to claim 1, wherein the bulge member is fixed to the main rubber elastic body.

6. 3. The vibration-isolating bushing according to claim 1, wherein the outer diameter of the axially intermediate portion of the main shaft member to which the bulge member is attached is equal to or smaller than the outer diameter of both axial end portions.

7. 3. The vibration-isolating bushing according to claim 1, wherein the outer peripheral surface of the axially intermediate portion of the main shaft member and the inner peripheral surface of the bulge member have an assembly surface that is cylindrical and extends straight in the axial direction.

Images