Cylindrical vibration isolation device

Abstract

To provide a cylindrical vibration control device of a new structure, capable of obtaining stable fixing force for a long term, by pressing a resinous outer cylinder member into an installing hole.SOLUTION: A cylindrical vibration control device 10 has a structure in which an inner shaft member 12 and a synthetic resinous outer cylinder member 14 are coupled by a body rubber elastic body 16. The body rubber elastic body 16 is equipped with a pair of rubber arms 34 and 34 extending out from the inner shaft member 12 to both sides and coupling the inner shaft member 12 and the outer cylinder member 14 in a diametrical direction. The outer cylinder member 14 is equipped with a division portion 28 in a circumferential direction on an outer peripheral side of the rubber arm 34. On the division portion 28, a coupling rubber 42 coupling both sides of the division portion 28 in the circumferential direction is arranged. At an outer peripheral end portion of the rubber arm 34, a void 44 penetrating in an axial direction on an inner periphery of the coupling rubber 42 is formed.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a cylindrical vibration isolator applied to an engine mount or the like of an automobile.

Background Art

[0002] Conventionally, cylindrical vibration isolators have been adopted as engine mounts, sub-frame mounts, suspension bushes, etc. of automobiles. As disclosed in, for example, Japanese Patent Application Laid-Open No. 5-126183 (Patent Document 1), the cylindrical vibration isolator has a structure in which an inner shaft member and an outer cylinder member are connected by a main body rubber elastic body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, although the conventional outer cylinder member was made of metal, conversion of the outer cylinder member to a synthetic resin has been studied for the purpose of weight reduction of the cylindrical vibration isolator. Also in Patent Document 1, an outer cylinder member made of synthetic resin is exemplified.

[0005] However, if the outer cylinder member to be press-fitted into the mounting hole of the mounting object is made of synthetic resin, the outer cylinder member is likely to plastically deform due to the continuous action of the stress caused by the press-fitting into the mounting hole, and there is a risk that the fixing force to the mounting object may decrease due to the plastic deformation (sagging) of the outer cylinder member.

[0006] The problem to be solved by the present invention is to provide a cylindrical vibration isolator having a novel structure that can obtain a long-term stable fixing force by press-fitting a resin-made outer cylinder member into a mounting hole.

Means for Solving the Problems

[0007] 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.

[0008] The first embodiment is a cylindrical vibration damping device in which an inner shaft member and an outer cylindrical member made of synthetic resin are connected by a main rubber elastic body, the main rubber elastic body comprises a pair of rubber arms extending from the inner shaft member to both sides and connecting the inner shaft member and the outer cylindrical member in the radial direction, the outer cylindrical member comprises a circumferential division on the outer circumference side of the rubber arms, a connecting rubber is provided in the division to connect both sides of the division in the outer cylindrical member in the circumferential direction, and a cavity is formed at the outer circumference end of the rubber arm that penetrates axially through the inner circumference of the connecting rubber.

[0009] According to the cylindrical vibration isolation device constructed in accordance with this embodiment, when the outer cylindrical member is press-fitted into the mounting hole, the connecting rubber arranged at the divided portion of the outer cylindrical member is compressed in the circumferential direction. This reduces the stress (press-fit reaction force) acting on the outer cylindrical member, while allowing a relatively stable fixing force to be obtained over a long period of time based on the elasticity of the connecting rubber.

[0010] By forming the segmented portion of the outer cylindrical member on the outer circumference of the rubber arm connecting the inner shaft member and the outer cylindrical member, the rubber arm is less likely to be compressed radially between the inner shaft member and the outer cylindrical member when the outer cylindrical member is press-fitted into the mounting hole. This reduces variations in the fixing force during press-fitting and the spring characteristics of the main rubber elastic body, thereby achieving stable performance.

[0011] A cavity is formed on the inner circumference of the connecting rubber, with the outer end of the rubber arm passing through it axially. This allows the connecting rubber to bulge into the cavity when compressed in the circumferential direction. As a result, the circumferential elasticity of the connecting rubber is effectively utilized, and the desired press-fit reaction force can be effectively obtained through the elasticity of the connecting rubber.

[0012] The second embodiment is a cylindrical vibration isolation device described in the first embodiment, wherein the inner surface of the connecting rubber constituting the inner surface of the wall of the cavity has a concave cross-section that opens toward the inner circumference and extends in the axial direction.

[0013] According to the cylindrical vibration isolation device with a structure conforming to this embodiment, when the connecting rubber is compressed in the circumferential direction by press-fitting the outer cylindrical member into the mounting hole, the connecting rubber is less likely to deform toward the inner circumference of the outer cylindrical member, and the press-fit reaction force based on the circumferential compression spring of the connecting rubber is effectively exerted.

[0014] A third embodiment is a cylindrical vibration isolation device described in the first or second embodiment, wherein the maximum circumferential width dimension of the cavity is greater than the circumferential width dimension of the divided portion of the outer cylindrical member.

[0015] According to the cylindrical vibration isolation device constructed in accordance with this embodiment, the connecting rubber provided at the divided portion of the outer cylindrical member is allowed to bulge outward towards the inner circumference by the void over the entire circumferential direction, thereby enabling the appropriate press-fit reaction force based on the compression spring of the connecting rubber to be obtained.

[0016] The fourth embodiment is a cylindrical vibration isolation device described in any one of the first to third embodiments, wherein the outer cylindrical member is a divided structure composed of a pair of outer divided bodies, a pair of divided parts are formed between the circumferential ends of the pair of outer divided bodies, and the pair of divided parts are provided on the outer circumference of each of the pair of rubber arms.

[0017] According to the cylindrical vibration isolator structured according to this aspect, when the pair of outer divided bodies constituting the outer cylinder member are in a state of approaching each other and the outer cylinder member is press-fitted into the mounting hole, the pull-out resistance by the compression springs of the connecting rubbers provided in the pair of divided portions respectively is exerted. Therefore, while further reducing the deformation of the outer cylinder member (the acting stress on the outer cylinder member), the press-fitting fixing force based on the elasticity of the connecting rubber can be effectively obtained.

Effect of the Invention

[0018] According to the present invention, in the cylindrical vibration isolator, a long-term stable fixing force can be obtained by press-fitting a synthetic resin-made outer cylinder member into the mounting hole.

Brief Description of the Drawings

[0019] [Figure 1] Perspective view showing the cylindrical vibration isolator as the first embodiment of the present invention [Figure 2] Front view of the cylindrical vibration isolator shown in FIG. 1 [Figure 3] Right side view of the cylindrical vibration isolator shown in FIG. 2 [Figure 4] Cross-sectional view taken along line IV-IV of FIG. 2 [Figure 5] Cross-sectional view taken along line V-V of FIG. 2 [Figure 6] Cross-sectional view taken along line VI-VI of FIG. 3 [Figure 7] Cross-sectional view showing the state in which the cylindrical vibration isolator shown in FIG. 1 is mounted on a holder, corresponding to the cross-sectional view taken along line VII-VII of FIG. 8 [Figure 8] Cross-sectional view taken along line VIII-VIII of FIG. 7 [Figure 9] Front view showing the cylindrical vibration isolator as the second embodiment of the present invention

Modes for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0021] Figures 1 to 6 show a cylindrical vibration isolation device 10 as a first embodiment of the present invention. The cylindrical vibration isolation device 10 has a structure in which an inner shaft member 12 and an outer cylindrical member 14 are 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 2, the left-right direction refers to the left-right direction in Figure 2, and the front-back direction refers to the left-right direction in Figure 3.

[0022] The inner shaft member 12 has a thick, small-diameter, substantially cylindrical shape. The inner shaft member 12 is made of a metal such as iron. The inner shaft member 12 is provided with a bolt insertion hole 18 that penetrates axially, and is fixed to an object to be mounted, such as a power unit (not shown), by a mounting bolt (not shown) inserted through the bolt insertion hole 18.

[0023] The outer cylindrical member 14 is made of synthetic resin, for example, polyamide. The outer cylindrical member 14 has a thin-walled, large-diameter, substantially cylindrical shape and comprises a cylindrical portion 20 that is cylindrical overall, and a flange portion 22 that is an annular plate shape overall and protrudes from the front end of the cylindrical portion 20 outward.

[0024] In this embodiment, the outer cylindrical member 14 is a divided structure composed of a pair of outer divided bodies 24, 24, each having a substantially semi-cylindrical shape, arranged facing each other in the vertical direction. Each outer divided body 24 integrally comprises a half-circumferential portion of the cylindrical part 20 and a half-circumferential portion of the flange part 22. The outer divided body 24 has divided ends 26 at both circumferential ends that protrude inward and are thickened radially, thus increasing the area of ​​the circumferential end face. In this embodiment, divided ends 26 are provided at both circumferential ends of each outer divided body 24. When no external force is acting on the outer cylindrical member 14, the outer diameter dimension in the vertical direction, which is the opposing direction of the pair of outer divided bodies 24, 24, is larger than the outer diameter dimension in the horizontal direction.

[0025] Furthermore, a dividing portion 28 is formed between the circumferential ends of the pair of outer divided bodies 24, 24 in the outer cylindrical member 14. In other words, the cylindrical outer cylindrical member 14 is divided circumferentially at the dividing portions 28, 28, thereby forming a pair of semi-cylindrical outer divided bodies 24, 24. The dividing portion 28 extends continuously and linearly along the entire axial length of the outer cylindrical member 14.

[0026] The outer cylindrical member 14 is arranged to surround the outer circumference of the inner shaft member 12, and the main rubber elastic body 16 is provided radially between the inner shaft member 12 and the outer cylindrical member 14. The main rubber elastic body 16 is substantially cylindrical in shape overall, with its inner circumferential surface vulcanized and bonded to the outer circumferential surface of the inner shaft member 12, and its outer circumferential surface vulcanized and bonded to the inner circumferential surface of the outer cylindrical member 14. More specifically, the main rubber elastic body 16 has an inner circumferential surface that is fixed to the inner shaft member 12 as a substantially cylindrical surface, and an outer circumferential surface that is fixed to the outer cylindrical member 14 as a substantially elongated cylindrical surface. In the state in which the inner shaft member 12 and the outer cylindrical member 14 are connected by the main rubber elastic body 16, the inner shaft member 12 protrudes axially from both sides relative to the outer cylindrical member 14.

[0027] The main rubber elastic body 16 has a groove 30 extending in an annular shape in the circumferential direction, which opens to both axial ends. The main rubber elastic body 16 has a pair of groove holes 32, 32 that penetrate in the axial direction. The groove holes 32 are formed on both sides in the vertical direction relative to the inner shaft member 12, and extend in the left-right direction, with both ends reaching outside the inner shaft member 12 in the left-right direction. Both groove holes 32, 32 are shorter than half a circumference in the circumferential direction and are formed off-center on both sides in the vertical direction relative to the center of the inner shaft member 12.

[0028] Between the upper and lower parts of a pair of grooves 32, 32 in the main rubber elastic body 16, a pair of rubber arms 34, 34 are formed, extending in the left-right direction to connect the inner shaft member 12 and the outer cylindrical member 14 in the left-right direction. The pair of rubber arms 34, 34 are provided to connect an inner circumferential cylindrical portion 36 fixed to the outer circumferential surface of the inner shaft member 12 and an outer circumferential cylindrical portion 38 fixed to the inner circumferential surface of the outer cylindrical member 14 to each other in the left-right direction. As a result, on both the left and right sides of the inner shaft member 12, the inner shaft member 12 and the outer cylindrical member 14 are connected in the left-right direction by the pair of rubber arms 34, 34. The pair of rubber arms 34, 34 are arranged in series in the left-right direction, which is the direction in which the inner shaft member 12 and the outer cylindrical member 14 are connected, and the elastic principal shafts extending in the connection direction extend from the inner shaft member 12 toward the outer cylindrical member 14 on both sides in the left-right direction. The axial end face of the rubber arm 34 is formed by the bottom surface of the groove 30, and the inner circumferential cylindrical portion 36 and the outer circumferential cylindrical portion 38 protrude axially from the axial end face of the rubber arm 34.

[0029] A pair of stopper rubbers 40, 40 are formed above and below the pair of cut holes 32, 32 in the main rubber elastic body 16, projecting inward and upward from the outer cylindrical member 14 toward the inner shaft member 12. The relative vertical displacement between the inner shaft member 12 and the outer cylindrical member 14 is limited by the contact between the stopper rubbers 40 and the inner shaft member 12.

[0030] A divided portion 28 of the outer cylindrical member 14 is located on the outer circumference of each of the pair of rubber arms 34, 34. A connecting rubber 42 is provided at each divided portion 28. The connecting rubber 42 is integrally formed with the rubber arms 34, protruding outward, and its outer circumference is positioned at the divided portion 28 of the outer cylindrical member 14. The outer circumference of the connecting rubber 42 is fixed to the circumferential end faces of the pair of outer divided bodies 24, 24 that constitute the inner surfaces on both sides of the divided portion 28 in the circumferential direction, and the circumferential ends of the pair of outer divided bodies 24, 24 are connected circumferentially at the divided portion 28, 28 by the connecting rubber 42, 42. The connecting rubber 42 does not protrude outward beyond the cylindrical portion 20 of the outer cylindrical member 14, and its outer circumference end face is located slightly inward from the outer circumference of the cylindrical portion 20. The connecting rubber 42 in this embodiment is composed not only of the outer peripheral portion arranged on the divided portion 28, but also of a part of the outer peripheral cylindrical portion 38 located on the inner peripheral side of the divided portion 28 and on the outer peripheral side of the rubber arm 34. The connecting rubber 42 has a longer axial length than the rubber arm 34 and is approximately the same axial length as the outer peripheral cylindrical portion 38.

[0031] A cavity 44 is formed at the outer peripheral end of the rubber arm 34, penetrating in the axial direction. The cavity 44 is a hole-like structure with a substantially constant cross-sectional shape that penetrates in the axial direction, and is formed on the inner peripheral side of the connecting rubber 42. Therefore, the cavity 44 is located between the rubber arm 34 and the connecting rubber 42. As shown in Figure 6, the cavity 44 is composed of an inner circumferential concave surface 46, which is a curved surface with a concave arc shape toward the outer circumference, an outer circumferential concave surface 48, which is a curved surface with a concave arc shape toward the inner circumference, and connecting surfaces 50, 50 that connect the open end of the inner circumferential concave surface 46 and the open end of the outer circumferential concave surface 48 to each other. The width dimension of the opening of the inner circumferential concave surface 46 toward the outer circumference is larger than the width dimension of the opening of the outer circumferential concave surface 48 toward the inner circumference, and the open end of the inner circumferential concave surface 46 and the open end of the outer circumferential concave surface 48 are continuous by the connecting surfaces 50, 50 that extend substantially in the circumferential direction. Therefore, the cavity 44 has an inner circumference and an outer circumference that are both approximately semicircular in shape, with the inner circumference having a larger diameter than the outer circumference. The inner circumferential concave surface 46, the outer circumferential concave surface 48, and the connecting surfaces 50, 50 are a series of smoothly continuous curved surfaces without any bends or broken lines. In this embodiment, the curvature of the inner circumferential concave surface 46 is smaller in both the outer and vertical portions than in the central portion in the vertical direction. The connecting surface 50 of the cavity 44 constitutes a part of the inner circumference of the outer cylindrical portion 38, but it protrudes slightly inward in correspondence with the divided end 26 of the outer divided body 24.

[0032] The cavity 44 is located on the inner circumference side of the connecting rubber 42, and its outer concave surface 48 is aligned with the connecting rubber 42 in the circumferential direction. Therefore, the inner surface of the connecting rubber 42 is composed of the outer concave surface 48 of the cavity 44, and is a concave curved surface that extends axially with a concave cross-section that opens toward the inner circumference. Since the curvature of the outer concave surface 48 on the connecting rubber 42 side of the cavity 44 is greater than the curvature of the inner concave surface 46 on the rubber arm 34 side, the inner surface of the connecting rubber 42 is a concave curved surface with greater curvature. Furthermore, since the connecting rubber 42 is provided to protrude axially outward from the rubber arm 34, the outer concave surface 48 that constitutes the inner surface of the connecting rubber 42 is provided to extend axially outward from the inner concave surface 46 (see Figures 1 and 4).

[0033] The maximum width dimension w1 of the circumferential cavity 44 is greater than the width dimension w2 of the dividing portion 28 (width dimension of the connecting rubber 42) in the circumferential direction. The maximum width dimension w1 of the circumferential cavity 44 is greater than the circumferential width dimension w2 of the dividing portion 28 located on the outer circumference side of the cavity 44 in the outer cylindrical member 14. In this embodiment, the cavity 44 has a substantially constant cross-sectional shape in the axial direction, and the maximum width dimension w1 of the cavity 44 is substantially constant in the axial direction, and the dividing portion 28 extends in the axial direction with a substantially constant width dimension w2. Therefore, at any position in the axial direction, the maximum width dimension w1 of the cavity 44 is greater than the width dimension w2 of the dividing portion 28. In this embodiment, the maximum width dimension w1 of the cavity 44 is the width dimension at the outer circumference end of the inner circumferential concave surface 46, as shown in Figure 6.

[0034] The outer surface of the connecting rubber 42 is a substantially flat surface that extends perpendicular to the left-right direction, and the curvature of the inner surface, which is composed of the outer concave surface 48, is greater than the curvature of the outer surface. Therefore, the radial thickness dimension of the connecting rubber 42 decreases from both ends in the circumferential direction towards the circumferential center.

[0035] As shown in Figures 7 and 8, the cylindrical vibration damping device 10, with the structure described above, has an outer cylindrical member 14 that is press-fitted into a mounting hole 52 provided in the mounting object, such as a vehicle body. The mounting hole 52 is, for example, formed by the inner hole of a cylindrical holder 54, and by press-fitting the outer cylindrical member 14, the outer cylindrical member 14 is attached to the mounting object equipped with the holder 54.

[0036] The outer cylindrical member 14 is press-fitted into the mounting hole 52 with a pair of outer segmented bodies 24, 24 brought closer together vertically by a jig or the like to reduce its maximum outer diameter. When the outer cylindrical member 14 is press-fitted into the mounting hole 52, the outer diameter in the vertical direction is reduced due to the displacement of the pair of outer segmented bodies 24, 24 as they move closer together, resulting in an overall shape that is approximately cylindrical, with the outer diameter in the vertical direction being approximately the same as the outer diameter in the horizontal direction.

[0037] As the pair of outer segments 24, 24 move closer to each other in the vertical direction, the connecting rubbers 42, 42 are compressed in the circumferential direction between the circumferential ends of the pair of outer segments 24, 24. As a result, the outer cylindrical member 14, which is press-fitted into the mounting hole 52, is pressed against the inner surface of the wall of the mounting hole 52 based on the elasticity of the compressed connecting rubbers 42, 42, and a resistance force against axial slippage acts between the outer circumferential surface of the outer cylindrical member 14 and the inner surface of the wall of the mounting hole 52 (the inner circumferential surface of the holder 54).

[0038] Since the divided portions 28, 28 of the outer cylindrical member 14 are located on the outer circumference side of the rubber arms 34, 34, even when the pair of outer divided bodies 24, 24, which are divided circumferentially at the divided portions 28, 28, approach each other, the pair of rubber arms 34, 34 hardly undergo any compressive deformation in the direction of connection between the inner shaft member 12 and the outer cylindrical member 14 (the left-right direction, which is the extension direction of the rubber arms 34). Therefore, variations in the press-fit fixing force due to the elasticity of the rubber arms 34 are prevented, and the influence on the spring characteristics of the rubber arms 34 is reduced.

[0039] The pair of outer segmented bodies 24, 24 constituting the outer cylindrical member 14 are displaced to move closer to each other from their initial positions before press-fitting when pressed into the mounting hole 52, while hardly any elastic deformation occurs due to external force (press-fitting reaction force). Therefore, plastic deformation (sagging) of the outer cylindrical member 14 caused by the continuous action of external force is suppressed, and even though the outer cylindrical member 14 is made of synthetic resin, which is more prone to sagging than metal, problems such as a decrease in press-fit fixing force due to sagging of the outer cylindrical member 14 are less likely to occur. Consequently, with the cylindrical vibration isolation device 10, the fixing force of the outer cylindrical member 14 by press-fitting into the mounting hole 52 is exerted more stably over a longer period of time.

[0040] Furthermore, since the fixing force exerted by press-fitting the outer cylindrical member 14 into the mounting hole 52 is based on the elasticity of the connecting rubbers 42, 42 compressed between the circumferential directions of the pair of outer segmented bodies 24, 24, the press-fit fixing force into the mounting hole 52 can be easily adjusted by the shape, size, and material of the connecting rubbers 42. The connecting rubbers 42 are separated from the rubber arms 34 by a void 44 and have almost no effect on the spring characteristics of the main rubber elastic body 16, and consequently on the vibration isolation performance of the cylindrical vibration isolation device 10. Therefore, their shape and size can be designed with a large degree of freedom, and the press-fit fixing force can be set accurately over a wide adjustment range.

[0041] The circumferential end of the outer segment 24 is made into a thick segmented end 26, which increases the area (radial width dimension) of the circumferential end face of the outer segment 24 to which the connecting rubber 42 is fixed. This ensures that the size of the portion of the connecting rubber 42 that is compressed between the circumferential end faces of the outer segment 24, 24 can be adjusted, thereby controlling the press-fit fixing force of the connecting rubber 42 due to its elasticity.

[0042] Because a void 44 is formed on the inner circumference side of the connecting rubber 42, when the connecting rubber 42 is compressed in the circumferential direction, the void 44 allows for bulging deformation of the connecting rubber 42 toward the inner circumference. This prevents the circumferential spring of the connecting rubber 42 from becoming excessively stiff, and prevents the bulging deformation of the connecting rubber 42 toward the inner circumference from affecting the spring characteristics of the rubber arm 34. Furthermore, because the connecting rubber 42 is allowed to deform toward the inner circumference, it is difficult for the connecting rubber 42 to deform by bulging toward the outer circumference due to circumferential compression, and this prevents the connecting rubber 42 from protruding toward the outer circumference beyond the outer surface of the outer cylindrical member 14 and obstructing press-fitting into the mounting hole 52.

[0043] In this embodiment, since the circumferential width dimension of the cavity 44 is larger than the circumferential width dimension of the connecting rubber 42, the entire connecting rubber 42 is allowed to deform inward. Although the connecting rubber 42 protrudes outward on both sides in the axial direction from the rubber arm 34, and therefore both ends in the axial direction are located outward in the axial direction from the cavity 44, there is no rubber arm 34 on the inner circumference of both ends of the connecting rubber 42, and the deformation of both ends of the connecting rubber 42 inward in the axial direction is allowed by the groove 30.

[0044] The inner circumferential surface of the connecting rubber 42 is composed of a concave curved surface (outer circumferential concave surface 48) that opens inward. The cavity 44 and the groove 30 allow deformation of the connecting rubber 42 toward the inner circumferential side, while the arch shape of the inner circumferential portion of the connecting rubber 42 restricts excessive deformation toward the inner circumferential side. As a result, the circumferential spring of the connecting rubber 42 is appropriately adjusted, and an effective press-fit fixing force can be obtained for the mounting hole 52 of the outer cylindrical member 14. The size of the outer circumferential concave surface 48 that is convex toward the outer circumferential side of the cavity 44 is not limited, but preferably the circumferential width dimension w3 is 0.5*w2≦w3≦2*w2. Furthermore, as can be seen from Figure 6, a narrowed portion is formed between the connecting rubber 42 and the outer cylindrical portion 38, where the rubber thickness is reduced between the inner edge portion of the circumferential end face of the outer divided body 24 (the portion forming the divided end 26 in this embodiment) and the outer concave surface 48 of the cavity 44. This allows for a more effective suppression of the adverse effects of compression strain and stress on the rubber arm 34 side of the connecting rubber 42 caused by press-fitting the outer cylindrical member 14 into the mounting hole 52.

[0045] A cavity 44 with an inner circumferential concave surface 46 is formed at the outer circumferential end of the rubber arm 34, so that the outer circumferential end of the rubber arm 34 is bifurcated to both sides in the circumferential direction of the cavity 44. As a result, the spring characteristics of the cylindrical vibration damping device 10 are adjusted using the cavity 44. The maximum circumferential width w1 of the cavity 44 is not limited, but for example, when ensuring spring rigidity in the left-right direction by a pair of rubber arms 34, 34, it is desirable that it be 1 / 3 or less of the circumferential dimension of the rubber arm 34 at the location where the cavity 44 is formed. Furthermore, it is also desirable that the radial size of the cavity 44 be 1 / 3 or less of the radial dimension of the rubber arm 34.

[0046] Figure 9 shows 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 16. In the description of this embodiment, components and parts that are substantially the same as those in the first embodiment are denoted by the same reference numerals in the figure and their description is omitted.

[0047] The outer cylindrical member 62 is C-shaped overall and has only one dividing section 28 in a part of its circumferential direction. Therefore, the cylindrical portion 20, which is roughly cylindrical in shape, and the flange portion 22, which is roughly annular plate shaped, are divided in the circumferential direction at one point in the circumferential direction.

[0048] The divided section 28 is located on the outer circumference of one of the rubber arms 34 (the right rubber arm 34 in Figure 9), with a connecting rubber 42 provided on the outer circumference of one rubber arm 34, while the other rubber arm 34 does not have a connecting rubber. Furthermore, the void 44 is formed only at the outer end of one of the rubber arms 34.

[0049] A cylindrical vibration damping device 60 equipped with such a C-shaped outer cylindrical member 62 can also obtain the same effects as the first embodiment. That is, when the outer cylindrical member 62 is inserted into a mounting hole (52) (not shown), the connecting rubber 42 arranged in the divided portion 28 is compressed in the circumferential direction, thereby reducing the stress acting on the outer cylindrical member 62, while effectively obtaining a fixing force (pull-out resistance) for the outer cylindrical member 62 to the mounting hole (52) through the elasticity of the connecting rubber 42.

[0050] As shown in this embodiment, the outer cylindrical member is not necessarily limited to a divided structure consisting of a pair of outer divided parts; the divided portion of the outer cylindrical member only needs to be provided on the outer circumference of at least one of the pair of rubber arms.

[0051] 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 shape of the cavity 44 is not limited by the specific description of the first embodiment above, and may be, for example, a simple circular hole, or a hole cross-sectional shape that extends for a predetermined length in the circumferential direction. Furthermore, the cross-sectional shape and size of the cavity 44 may vary in the axial direction.

[0052] The width dimension of the connecting rubber 42 in the circumferential direction, in other words, the width dimension of the divided portion 28, does not need to be constant in the axial direction and may vary in the axial direction. If at least one of the width dimension of the connecting rubber 42 and the maximum width dimension of the space 44 varies in the axial direction, it is desirable that the maximum width dimension of the space 44 is larger than the width dimension of the connecting rubber 42 at any point in the axial direction. [Explanation of symbols]

[0053] 10. Cylindrical Vibration Isolator (First Embodiment) 12 Inner shaft member 14 Outer cylindrical member 16 Main body rubber elastic body 18 bolt insertion holes 20 Cylindrical part 22 Flange section 24 Outer divisions 26 Split end 28 Division 30 slit grooves 32 slit holes 34 Rubber Arms 36 Inner cylindrical part 38 Outer cylindrical portion 40 Stopper rubber 42 Connecting rubber 44 Blanks 46 Inner circumferential concave surface 48 Outer periphery concave surface 50 connection surface 52 mounting holes 54 Holder 60. Cylindrical Vibration Isolator (Second Embodiment) 62 Outer cylindrical member

Claims

1. A cylindrical vibration isolation device in which an inner shaft member and an outer cylindrical member made of synthetic resin are connected by a main body rubber elastic material, The main body rubber elastic body is provided with a pair of rubber arms that extend from the inner shaft member to both sides and connect the inner shaft member and the outer cylindrical member in the radial direction. The outer cylindrical member has a circumferential division on the outer circumference side of the rubber arm, The divided portion is provided with connecting rubber that connects both sides of the divided portion in the outer cylindrical member in the circumferential direction. A cylindrical vibration damping device having a cavity formed at the outer peripheral end of the rubber arm, which penetrates the inner circumference of the connecting rubber in the axial direction.

2. The cylindrical vibration isolation device according to claim 1, wherein the inner circumferential surface of the connecting rubber constituting the inner surface of the wall of the cavity has a concave cross-section that opens toward the inner circumference and extends in the axial direction.

3. The cylindrical vibration isolation device according to claim 1 or 2, wherein the maximum width dimension of the cavity in the circumferential direction is greater than the circumferential width dimension of the divided portion of the outer cylindrical member.

4. The outer cylindrical member is a divided structure composed of a pair of outer divided bodies. A pair of the aforementioned divisions are formed between the circumferential ends of the pair of outer divisions. The cylindrical vibration damping device according to claim 1 or 2, wherein the pair of dividing parts are provided on the outer circumference of each of the pair of rubber arms.

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