Cylindrical vibration isolation device

Abstract

This invention provides a novel cylindrical vibration isolation device with a structure that prevents the outer cylindrical member, which is made of resin, from becoming too thick, while more efficiently ensuring the necessary strength for the outer cylindrical member. [Solution] A cylindrical vibration damping device 10 is provided in which an inner shaft member 12 and a resin outer cylindrical member 14 are connected by a main rubber elastic body 16. The outer cylindrical member 14 has a plurality of recesses 26 opening on its outer circumferential surface, arranged in the axial direction. The axial middle portion of the outer cylindrical member 14 is provided with a reinforcing region 38 in which the amount of resin is greater than that on both sides in the axial direction due to the difference in the shape of the recesses 26 arranged in the axial direction.

Description

Technical Field

[0001] The present invention relates to a cylindrical vibration isolator used for engine mounts, member mounts, suspension bushes, etc. of automobiles.

Background Art

[0002] Conventionally, a cylindrical vibration isolator is known as a vibration isolator used for engine mounts, motor mounts, member mounts, suspension bushes, etc. of automobiles. As disclosed in, for example, Japanese Patent No. 5061129 (Patent Document 1), the cylindrical vibration isolator has a structure in which an inner shaft member is inserted into the inner circumference of an outer cylinder member, and the inner shaft member and the 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, recently, for the purpose of improving fuel efficiency and the like, weight reduction of vehicles has been more strongly demanded, and further weight reduction is also required for cylindrical vibration isolators. Therefore, in Patent Document 1, it has been proposed to reduce the weight by making the outer cylinder member, which was conventionally made of metal, into a resin.

[0005] ) However, a resin outer cylinder member is likely to need to be thickened in order to ensure strength as compared with a metal outer cylinder member, and there are problems such that the effect of weight reduction becomes insufficient due to thickening, or molding defects are likely to occur.

[0006] In Patent Document 1, in order to prevent the pair of first side walls from becoming too thick, a number of recesses opening onto the outer surface are formed to provide a press-fitting surface into the cylindrical holder by the lattice-like support wall. However, the inventor's research revealed that the stress acting on the outer cylindrical member when it is press-fitted into the cylindrical holder is not necessarily uniform, and in an outer cylindrical member structure with recesses of the same shape and size as in Patent Document 1, it was conceivable that cracks or other damage might occur in the outer cylindrical member in areas where large stresses are applied.

[0007] The problem to be solved by the present invention is to provide a cylindrical vibration isolation device with a novel structure that can more efficiently secure the necessary strength for the outer cylindrical member while preventing the outer cylindrical member, which is made of resin, from becoming too thick. [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 a resin outer cylindrical member are connected by a main rubber elastic body, wherein the outer cylindrical member has a plurality of recesses opening on its outer circumferential surface arranged in the axial direction, and the axial middle portion of the outer cylindrical member is provided with a reinforcing region in which the amount of resin is greater than that on both sides in the axial direction due to differences in the shape of the recesses arranged in the axial direction.

[0010] Through the inventor's research, it was found that the stress acting on the resin outer cylindrical member during press-fitting is greater in the axial middle portion than at both axial ends. Therefore, in the cylindrical vibration isolation device according to this embodiment, a reinforcing region is provided in the axial middle portion of the outer cylindrical member, where the amount of resin is greater than on both sides due to a difference in the shape of the recess. This ensures sufficient strength of the outer cylindrical member in the axial middle portion where greater stress acts, preventing deformation such as cracking. Furthermore, since the reinforcing region is determined by a difference in the shape of the recess, excessive thickening of the outer cylindrical member in the reinforcing region can be prevented, thereby suppressing an increase in the weight of the outer cylindrical member due to thickening and preventing molding defects.

[0011] The second embodiment is a cylindrical vibration isolation device described in the first embodiment, wherein the reinforcing region is provided by the difference in the axial dimension of the recess.

[0012] According to the cylindrical vibration isolation device with a structure conforming to this embodiment, by making the axial dimension of the recess smaller in the axial middle portion than on both sides, it is easier to set a reinforcement area in the axial direction.

[0013] The third embodiment is a cylindrical vibration isolation device described in the second embodiment, wherein the axial dimension of the openings of the plurality of recesses gradually decreases from the axial end toward the reinforcement region.

[0014] According to the cylindrical vibration isolation device with a structure conforming to this embodiment, stress concentration caused by abrupt changes in the axial dimension of the recess can be prevented, and damage to the outer cylindrical member during press-fitting can be prevented more effectively.

[0015] The fourth embodiment is a cylindrical vibration isolation device described in any one of the first to third embodiments, wherein all of the plurality of recesses open toward the first radial direction of the outer cylindrical member, the inner surface of the side wall of the recess located on the central side of the second radial direction perpendicular to the first radial direction of the outer cylindrical member expands toward the first radial direction, and the inner surface of the side wall of the recess located on the opposite side of the center of the second radial direction of the outer cylindrical member expands toward the radial direction of the outer cylindrical member, and the recess expands toward the outer circumference in the circumferential direction.

[0016] According to the cylindrical vibration isolation device with a structure conforming to this embodiment, the inner surfaces of the side walls on both sides in the circumferential direction of each recess are shaped so as not to be undercut with respect to the first radial direction, and the outer surface of the outer cylindrical member, which has numerous recesses opening, can be molded with two molds that are divided on both sides in the first radial direction.

[0017] Furthermore, the circumferential walls on both sides of the recess are shaped to extend in a direction nearly parallel to the radial direction, which is the direction of force applied by press-fitting. Therefore, the strength of the outer cylindrical member can be efficiently ensured against stress caused by press-fitting, and damage to the outer cylindrical member can be effectively prevented while sufficiently achieving weight reduction of the outer cylindrical member.

[0018] The fifth embodiment is a cylindrical vibration isolation device described in any one of the first to fourth embodiments, wherein the outer cylindrical member is partially provided with an inner circumferential protrusion projecting onto the inner circumferential surface in the circumferential direction, and the recess provided in the portion forming the inner circumferential protrusion in the circumferential direction is of a depth that reaches the inner circumferential protrusion.

[0019] According to the cylindrical vibration isolation device with a structure conforming to this embodiment, by partially providing an inner circumferential protrusion in the circumferential direction, the radial free length of the main rubber elastic body can be changed in the circumferential direction, thereby adjusting the radial spring characteristics.

[0020] By forming a recess in the area where the inner circumferential protrusion is formed, to a depth that reaches the inner circumferential protrusion, it is possible to prevent the area where the inner circumferential protrusion is formed from becoming thick, thereby suppressing the increase in weight caused by the formation of the inner circumferential protrusion and preventing molding defects.

[0021] The sixth aspect is the cylindrical vibration isolator described in any one of the first to fifth aspects, wherein the outer cylindrical member is partially provided with an inner peripheral convex portion protruding from the inner peripheral surface in the circumferential direction, and the main body rubber elastic body is formed with a bore portion opening at the axial end surface, and the bore portion is arranged at a position where the inner peripheral convex portion of the outer cylindrical member is disengaged in the circumferential direction.

[0022] According to the cylindrical vibration isolator having the structure according to this aspect, even if a force due to thermal shrinkage of a portion where the bore portion is not formed in the main body rubber elastic body acts on a portion where the inner peripheral convex portion of the outer cylindrical member is formed and the deformation rigidity of the outer cylindrical member becomes relatively large, the outer cylindrical member is hardly damaged. On the other hand, at a position where the inner peripheral convex portion is disengaged in the circumferential direction, since the bore portion is formed in the main body rubber elastic body, the stress acting on the outer cylindrical member due to thermal shrinkage of the main body rubber elastic body is reduced, and damage to the outer cylindrical member is prevented.

[0023] Also, in a portion where the inner peripheral convex portion is disengaged in the circumferential direction, a soft spring characteristic is realized by forming the bore portion. On the other hand, in the radial direction where the free length of the main body rubber elastic body is shortened by forming the inner peripheral convex portion, since a hard spring characteristic is required, it is easy to realize the required characteristic by not forming the bore portion.

[0024] The seventh aspect is the cylindrical vibration isolator described in any one of the first to sixth aspects, wherein all of the plurality of recesses open toward the first radial direction of the outer cylindrical member, and the main body rubber elastic body is formed with a bore portion opening at the axial end surface, and the bore portion is provided on both sides in a second radial direction orthogonal to the first radial direction.

[0025] According to the cylindrical vibration isolator structured according to this aspect, in the first radial direction where the recess opens, since the deformation rigidity of the outer cylinder member is relatively large due to the wall portion of the recess, even if a relatively large stress due to thermal shrinkage acts on the portion where the groove portion in the main body rubber elastic body is not formed, damage to the outer cylinder member is unlikely to occur. On the other hand, in the second radial direction orthogonal to the opening direction of the recess, since the deformation rigidity of the outer cylinder member tends to be relatively low, the stress acting on the outer cylinder member due to the thermal shrinkage of the main body rubber elastic body is reduced by the formation of the groove portion, and damage to the outer cylinder member is prevented.

[0026] An eighth aspect is the cylindrical vibration isolator according to any one of the first to seventh aspects, wherein high-strength portions where the recesses are not formed are provided at both axial ends of the outer cylinder member.

[0027] According to the cylindrical vibration isolator structured according to this aspect, since both axial ends of the outer cylinder member are high-strength portions with large deformation rigidity, deformation of the outer cylinder member due to press-fitting is efficiently suppressed, damage to the outer cylinder member is prevented, and the press-fitted state of the outer cylinder member is stably maintained. Further, for example, since a high-strength portion is provided at the end on the press-fitting tip side, deformation of the outer cylinder member at the start of press-fitting is suppressed, damage to the outer cylinder member is prevented, and improvement in press-fitting workability is also achieved.

[0028] A ninth aspect is the cylindrical vibration isolator according to any one of the first to eighth aspects, wherein the plurality of recesses arranged in the axial direction of the outer cylinder member are arranged so as to be distributed over the entire circumference of the outer cylinder member, the plurality of recesses arranged in the circumferential direction have the same axial dimension of the opening portion, and the plurality of recesses arranged in the axial direction have the same circumferential dimension of the opening portion.

[0029] According to the cylindrical vibration isolator structured according to this aspect, by providing a plurality of recesses arranged in the axial direction so as to be distributed over the entire circumference of the outer cylinder member, effects such as weight reduction and improvement in formability due to the formation of the recesses can be obtained in a wide range of the outer cylinder member.

[0030] Because the axial dimensions of the recesses arranged in the circumferential direction are the same, the walls on both sides of the recesses in the axial direction are continuous in the circumferential direction, and these continuous walls provide a more advantageous strength for the outer cylindrical member. [Effects of the Invention]

[0031] According to the present invention, in a cylindrical vibration isolation device, it is possible to more efficiently secure the necessary strength for the outer cylindrical member while preventing the outer cylindrical member, which is made of resin, from becoming too thick. [Brief explanation of the drawing]

[0032] [Figure 1] Front view showing a cylindrical vibration damper as the first embodiment of the present invention. [Figure 2] Plan view of the cylindrical vibration isolation device shown in Figure 1. [Figure 3] Section III-III in Figure 1 [Figure 4] Figure 2, section IV-IV [Figure 5] Front view of the outer cylindrical member constituting the cylindrical vibration isolation device shown in Figure 1. [Figure 6] Figure 4 is an enlarged cross-sectional view showing the main parts of a cylindrical vibration isolation device. [Figure 7] Cross-sectional view showing the molding die used to form the outer cylindrical member of Figure 5. [Figure 8A] Figure 5 shows the stress analysis results for the outer cylindrical member. [Figure 8B] Figure showing the stress analysis results of the outer cylindrical member of the comparative structure. [Modes for carrying out the invention]

[0033] Embodiments of the present invention will be described below with reference to the drawings.

[0034] Figures 1 to 4 show a member mount 10 for automobiles as a first embodiment of the cylindrical vibration damping device according to the present invention. The member mount 10 has a structure in which an inner shaft member 12 and an outer cylindrical member 14 are interconnected by a main rubber elastic body 16. In the following description, as a general rule, the vertical direction is the vertical direction in Figure 1 which is the mount axis direction, the front-rear direction which is the first radial direction of the outer cylindrical member 14 is the vertical direction in Figure 2, and the left-right direction which is the second radial direction of the outer cylindrical member 14 is the left-right direction in Figure 2.

[0035] The inner shaft member 12 has a small diameter and is approximately cylindrical in shape. The inner shaft member 12 is a highly rigid member made of metal or fiber-reinforced synthetic resin, and is equipped with a bolt hole 18 that penetrates in the axial direction.

[0036] The outer cylindrical member 14 has a large diameter and is substantially cylindrical in shape. The outer cylindrical member 14 is a resin outer member formed from resin. The resin material forming the outer cylindrical member 14 is not particularly limited, but it is preferably a synthetic resin material, and preferably, for example, polyamide, polyacetal, etc. is used. Furthermore, the material forming the outer cylindrical member 14 is preferably a fiber-reinforced synthetic resin, and for example, reinforcing fibers such as glass or carbon fiber are mixed into the synthetic resin material.

[0037] The upper end of the outer cylindrical member 14 is provided with a tip guide portion 20, which serves as a high-strength section. The outer diameter of the tip guide portion 20 gradually decreases towards the top. The inner circumferential surface of the tip guide portion 20 is a cylindrical surface extending substantially parallel to the axial direction, and its radial thickness gradually decreases towards the top. The tip guide portion 20 does not have a recess 26, which will be described later.

[0038] A flange portion 22, which serves as a high-strength section, is provided at the lower end of the outer cylindrical member 14. The flange portion 22 protrudes outward from the lower end of the outer cylindrical member 14. The flange portion 22 is substantially annular in shape and is provided continuously around its entire circumference. Note that the flange portion 22 does not have a recess 26, which will be described later.

[0039] As shown in Figure 3, the outer cylindrical member 14 is provided with a pair of inner circumferential protrusions 24, 24 that project inward on both sides in one radial direction. Each inner circumferential protrusion 24 has a circumferential length of less than half a circumference and is partially formed in the circumferential direction, preferably with a circumferential length of 1 / 3 of a circumference or less. As shown in Figure 3, the inner circumferential protrusions 24 are provided in the axial middle portion of the outer cylindrical member 14 and do not reach both ends of the outer cylindrical member 14 in the axial direction. In particular, the inner circumferential protrusions 24 are formed on the outer cylindrical member 14 at a position offset from the center in the axial direction relative to the tip guide portion 20 and the flange portion 22. The height of the inner circumferential protrusion 24 gradually decreases outward at both ends in the axial direction and also gradually decreases outward at both ends in the circumferential direction. Furthermore, the inner circumferential protrusion 24 has a substantially constant protrusion height in the intermediate portion in the axial and circumferential directions, and the tip surface of the protrusion in the intermediate portion is a curved surface that extends in the circumferential direction.

[0040] As shown in Figure 1, the outer cylindrical member 14 has a plurality of recesses 26 that open to the outer circumferential surface. In this embodiment, all of the recesses 26 open in the first radial direction (front-to-back direction) toward either the front or rear. The recesses 26 are formed in the portion of the outer cylindrical member 14 that is away from the tip guide portion 20 and the flange portion 22, and are distributed throughout that portion. Multiple recesses 26 are arranged linearly in the axial direction, and rows of multiple recesses 26 arranged linearly in the axial direction are arranged in multiple rows in the circumferential direction and are located around the entire circumference. Multiple recesses 26 that are arranged in the circumferential direction at the same position in the axial direction have the same axial dimensions at the outer circumferential opening. Multiple recesses 26 that are arranged in the axial direction at the same position in the circumferential direction have the same circumferential dimensions at the outer circumferential opening. As a result, the outer cylindrical member 14 is provided with vertical ribs 28 that extend continuously in the vertical direction between adjacent recesses 26, 26 in the circumferential direction, and horizontal ribs 30 that extend continuously in the circumferential direction between adjacent recesses 26, 26 in the axial direction.

[0041] The recess 26 comprises, in the cross-section shown in Figure 3, a first side wall surface 32 which is the inner surface of the side wall located on the left-right center side of the outer cylindrical member 14, a second side wall surface 34 which is the inner surface of the side wall located on the left-right outer side (opposite the left-right center) of the outer cylindrical member 14, and a bottom wall surface 36 which connects the first side wall surface 32 and the second side wall surface 34 to each other at the inner circumferential end. The first side wall surface 32 widens in the front-rear direction. The second side wall surface 34 widens in the radial direction of the outer cylindrical member 14 and is inclined relative to the first side wall surface 32. As a result, the first side wall surface 32 and the second side wall surface 34 move further apart from each other in the circumferential direction as they move toward the outer circumference, and the recess 26 has a shape that widens in the circumferential direction toward the outer circumference. Furthermore, the side walls of the recesses 26 that are composed of vertical ribs 28 and separate adjacent recesses 26, 26 in the circumferential direction are tapered in shape, with the circumferential dimension decreasing towards the outer circumference, except for the parts between recesses 26a, 26a and between recesses 26f, 26f, which will be described later. The bottom wall surface 36 is curved in the circumferential direction and is a curved surface concentric with the outer surface of the outer cylindrical member 14.

[0042] As shown in Figure 3, the multiple recesses 26, which are arranged circumferentially at the same position in the axial direction, have different shapes from each other. Furthermore, the recesses 26 provided on the front half (lower half in Figure 3) and the recesses 26 provided on the rear half (upper half in Figure 3) are symmetrical in the front-to-back direction, while the recesses 26 provided on the right half (right half in Figure 3) and the recesses 26 provided on the left half (left half in Figure 3) are symmetrical in the left-to-right direction.

[0043] As shown in Figure 3, six recesses 26a, 26b, 26c, 26d, 26e, and 26f are arranged in a circumferential direction on the right front quarter circumference of the outer cylindrical member 14. Recesses 26a and 26b are entirely located in the portion where the inner circumferential protrusion 24 is formed, recess 26c is located at the circumferential end of the inner circumferential protrusion 24 so as to partially deviate from the inner circumferential protrusion 24 in the circumferential direction, and recesses 26d, 26e, and 26f are located at positions away from the inner circumferential protrusion 24 in the circumferential direction. The recesses 26a to 26f are arranged sequentially in the circumferential direction from the left and right center to the left and right outer sides on each quarter circumference of the outer cylindrical member 14.

[0044] The recesses 26a and 26b, which are provided in the portion where the inner circumferential protrusion 24 is formed, are each formed with a radial depth that reaches the inner circumferential protrusion 24. In short, the bottom wall surfaces 36 of recess 26a and recess 26b are both located on the inner circumferential side of the base end of the inner circumferential protrusion 24. Furthermore, the recesses 26c to 26f, which are provided in portions that are circumferentially outside the inner circumferential protrusion 24, are formed with a depth that does not reach the inner circumferential protrusion 24, and their respective bottom wall surfaces 36 are located on the outer circumference of the base end of the inner circumferential protrusion 24. Therefore, the radial depth dimensions of recesses 26a and 26b are larger than those of recesses 26c to 26f. Furthermore, the bottom wall surfaces 36, 36 of recesses 26a and 26b are located on the same cylindrical surface concentric with the outer peripheral surface of the outer cylindrical member 14, while the bottom wall surfaces 36 of recesses 26c to 26f are located on a different cylindrical surface from the bottom wall surfaces 36, 36 of recesses 26a and 26b.

[0045] Each longitudinal rib 28 located between the six recesses 26a to 26f in the circumferential direction has approximately the same circumferential width dimension at its outer end. Furthermore, at both the front and rear ends of the outer cylindrical member 14, the longitudinal ribs 28 between mutually adjacent recesses 26a, 26a in the circumferential direction have approximately the same circumferential width dimension at their outer end as each longitudinal rib 28 located between the six recesses 26a to 26f in the circumferential direction. Additionally, at both the left and right ends of the outer cylindrical member 14, the longitudinal ribs 28 between mutually adjacent recesses 26f, 26f in the circumferential direction have a larger circumferential width dimension at their outer end than each longitudinal rib 28 located between the six recesses 26a to 26f in the circumferential direction.

[0046] The five recesses 26a to 26e, excluding recess 26f, have approximately the same circumferential width dimension of their outer openings. Recess 26f has a larger circumferential width dimension of its outer opening than the other recesses 26, in order to ensure sufficient radial depth and prevent excessive thickness of the outer cylindrical member 14, while considering the demolding of the first and second molds 48 and 50 when forming the outer cylindrical member 14, as described later.

[0047] As shown in Figures 1 and 4, the multiple recesses 26, which are aligned axially at the same position in the circumferential direction, have openings whose axial dimensions gradually decrease from both axial ends of the outer cylindrical member 14 toward the axial middle of the outer cylindrical member 14. The axial dimensions of the openings of the multiple recesses 26 aligned axially may change at a substantially constant rate of change, or the rate of change may vary as appropriate. In the following description, the recesses 26 aligned axially are denoted by the letters A to J from top to bottom for distinction. As shown in Figure 5, the recesses are denoted by the letters 26aA to 26fJ, which are combinations of the letters a to f indicating the circumferential position and the letters A to J indicating the axial position, and different recesses that are substantially the same shape (symmetrical shape) are denoted by the same letter.

[0048] As shown in Figure 4, the recesses 26A to 26J, which are aligned in the axial direction, have the smallest axial dimensions at recesses 26E and 26F. The axial dimensions gradually decrease from recess 26A to recess 26E, and gradually increase from recess 26F to recess 26J. In addition, the transverse ribs 30 between adjacent recesses 26, 26 have approximately constant axial dimensions. However, in this embodiment, the transverse rib 30 between recess 26G and recess 26H is narrower in the axial direction than the other transverse ribs 30, so that adjacent recesses 26G and recess 26H have approximately the same axial dimensions.

[0049] As a result, in the outer cylindrical member 14, the distance between the transverse ribs 30 is narrower in the axial intermediate portion close to the recesses 26E and 26F in the axial direction, and the amount of resin is greater in this portion than in the axial portions on both sides close to the recesses 26A and 26J. Furthermore, the portion of the outer cylindrical member 14 close to the recesses 26E and 26F is designated as a reinforced region 38 with a larger amount of resin due to the shape (including size) of the recesses 26. As is clear from the above, the reinforced region 38 in this embodiment is provided by the difference in axial dimensions of the recesses 26A to 26J that are aligned in the axial direction. In the reinforced region 38, the outer cylindrical member 14 has greater radial deformation rigidity than the portions located on both sides of the reinforced region 38 in the axial direction.

[0050] The reinforced region 38 is a region in which the amount of resin per unit length in the axial direction of the outer cylindrical member 14 is greater than that of the adjacent portions on both sides in the axial direction. In the reinforced region 38, which includes the forming portions of the recesses 26E and 26F with small axial dimensions and the transverse ribs 30, 30, 30 adjacent to them in the axial direction and on both sides in the axial direction, there is less of the portion that becomes thin in the radial direction due to the recesses 26, and the amount of resin per unit length in the axial direction is greater compared to other regions of the same axial length as the reinforced region 38 located on both sides of the reinforced region 38.

[0051] The amount of resin per unit length in the outer cylindrical member 14 is, for example, the amount of resin (volume) of the outer cylindrical member 14 within a range of axial unit length L that includes at least a part of the recess 26, starting from one axial end of the recess 26 (the upper end in Figure 6), as shown in Figure 6. In order to understand the difference in the amount of resin of the outer cylindrical member 14 based on the difference in the axial dimensions of the recess 26, in Figure 6, the axial unit length L is made larger than the minimum axial dimension of the recess 26 provided in the reinforcement region 38 (the axial dimension W of the recess 26F in Figure 6), and more preferably larger than the maximum axial dimension of the recess 26 provided in the reinforcement region 38. Therefore, in the reinforcement region 38, the entire axial direction of at least one recess 26 is included within the range of axial unit length L.

[0052] In this embodiment, since the axial dimension of the opening gradually changes in recesses 26A to 26J, the radial deformation stiffness of the outer cylindrical member 14 gradually changes in the axial direction. However, the reinforcement region 38 is a part close to recesses 26E and 26F, where the radial deformation stiffness is sufficiently large, and is located below recess 26D and above recess 26G. The reinforcement region 38 in this embodiment is provided in the axial central part of the outer cylindrical member 14. For recesses 26E and 26F, where the axial dimension of the outer peripheral opening is minimized, it is desirable that the axial dimension of the outer peripheral opening be 2 / 3 or less, and more preferably 1 / 2 or less, compared to recesses 26A and 26J, where the axial dimension of the outer peripheral opening is maximized. Furthermore, it is desirable that the axial dimension of the outer peripheral opening of recesses 26E and 26F be 3 / 4 or less, and more preferably 2 / 3 or less, compared to the axial dimension of the outer peripheral opening of recesses 26D and 26G adjacent to recesses 26E and 26F.

[0053] Furthermore, the lowest recess 26J closest to the flange portion 22 has an inclined surface on the inner surface of its lower wall that slopes downward toward the outer circumference. Therefore, the difference between the axial dimension of the inner circumference end and the axial dimension of the outer circumference end is larger in recess 26J compared to the other recesses 26A to 26I. Because the inner surface of the lower wall of recess 26J is an inclined surface, the base end portion of the flange portion 22 is thickened in the part where recess 26J is formed, and the deformation rigidity of the base end portion of the flange portion 22 is increased.

[0054] The outer cylindrical member 14 has axial ends that consist of a tip guide portion 20 and a flange portion 22, respectively, where the recess 26 is not formed, and thus has greater radial deformation rigidity compared to the axial middle portion where the recess 26 is formed. Therefore, the outer cylindrical member 14 has high deformation rigidity at both axial ends and in the central portion, while the radial deformation rigidity is relatively low between the tip guide portion 20 and the reinforcing region 38, and between the reinforcing region 38 and the flange portion 22.

[0055] Incidentally, the resin outer cylindrical member 14 is molded, for example, using the molding die 40 shown in Figure 7. The molding die 40 consists of an inner mold 42 that molds the inner circumferential surface of the outer cylindrical member 14 and an outer mold 44 that molds the outer circumferential surface of the outer cylindrical member 14.

[0056] The inner mold 42 is generally columnar in shape. The outer surface of the inner mold 42, which forms the inner surface of the outer cylindrical member 14, is generally cylindrical, and a pair of inner circumferential protrusions 24, 24 and a pair of corresponding concave surfaces 46, 46 are formed on both sides in the front-rear direction. The inner mold 42 is divided into an upper and lower portion in the axial direction, thereby avoiding undercuts in the concave surfaces 46, 46.

[0057] The outer mold 44 is composed of a first split mold 48 and a second split mold 50 that are combined with each other in the front-to-back direction. The first split mold 48 and the second split mold 50 are symmetrical in the front-to-back direction. The inner circumferential surface of the outer mold 44 that forms the outer circumferential surface of the outer cylindrical member 14 is substantially cylindrical as a whole, and has a number of protrusions 52 that project inward. The protrusions 52 are shaped to correspond to the recesses 26 of the outer cylindrical member 14, and the surface of the protrusions 52 constitutes the molded surface of the inner surface of the recesses 26. In Figure 7, which is a cross-sectional view, protrusions 52a to 52f are shown aligned in the circumferential direction in a part of the axial direction, but the protrusions 52 are also provided aligned in the axial direction to correspond to the recesses 26.

[0058] The first mold 48 and the second mold 50 are butted together in the front-to-back direction to form the outer mold 44, and the inner mold 42 is inserted radially into the inner circumference of the outer mold 44 with a gap between them, thereby forming a cavity 54 between the inner mold 42 and the outer mold 44. After filling the cavity 54 with molten resin material, it is hardened by cooling or other means to form a resin outer cylindrical member 14 corresponding to the shape of the cavity 54, completing the molding process of the outer cylindrical member 14. Since the outer cylindrical member 14 has numerous recesses 26 that open to the outer surface, localized thickening is prevented, and molding defects such as sink marks and voids caused by excessively large thickness dimensions are prevented. Furthermore, the formation of the recesses 26 also enables weight reduction of the outer cylindrical member 14 and reduction of resin material.

[0059] After the molding process of the outer cylindrical member 14 is completed, the molding die 40 is removed from the molded outer cylindrical member 14. Specifically, the first split mold 48 and the second split mold 50 are separated from each other in the front-rear direction, and the inner mold 42 is pulled out from the outer cylindrical member 14 in the axial direction, thereby removing the outer cylindrical member 14 from the molding die 40 and completing the mold release process of the molding die 40.

[0060] As can be seen from the shape of the recess 26 described above, the projection 52 of the outer mold 44 has a side surface located towards the center in the left-right direction that widens in the front-rear direction, and a side surface located on the outside in the left-right direction that widens radially on the inner circumferential surface of the outer mold 44. Preferably, a draft taper is set on both the upper and lower surfaces of the projection 52, so that both the upper and lower surfaces of the projection 52 are slightly closer to each other towards the protruding tip. These features prevent poor release due to undercutting of the projection 52 when releasing the first split mold 48 and the second split mold 50 from the outer cylindrical member 14.

[0061] The outer cylindrical member 14, with this structure, is positioned in an extrapolated state relative to the inner shaft member 12. The inner shaft member 12 and the outer cylindrical member 14 are elastically connected to each other by the main rubber elastic body 16.

[0062] The main rubber elastic body 16 is a thick-walled cylindrical shape, and as shown in Figures 2 to 4, it is positioned radially between the inner shaft member 12 and the outer cylindrical member 14, with its inner circumferential surface fixed to the outer circumferential surface of the inner shaft member 12 and its outer circumferential surface fixed to the inner circumferential surface of the outer cylindrical member 14. In addition, a stopper rubber 56 integrally formed with the main rubber elastic body 16 is fixed to the lower surface of the flange portion 22 of the outer cylindrical member 14.

[0063] The main rubber elastic body 16 has a grooved hole 58 that penetrates axially. As shown in Figure 3, the grooved hole 58 has a circumferentially curved cross-sectional shape and is formed with a circumferential length of less than half the circumference of the main rubber elastic body 16. The grooved holes 58 are formed on both sides in the left-right direction relative to the inner shaft member 12, and both pairs of grooved holes 58, 58 are located in the center in the front-rear direction.

[0064] The pair of cut holes 58, 58 are provided at positions circumferentially away from the pair of inner circumferential protrusions 24, 24. The outer cylindrical member 14 has greater radial deformation rigidity in the area where the inner circumferential protrusions 24, 24 are formed than on the sides circumferentially away from the inner circumferential protrusions 24. Therefore, for example, even if tensile stress due to thermal shrinkage of the main rubber elastic body 16 after molding acts on the area where the pair of rubber arms 60, 60 are fixed to the inner circumferential protrusions 24, 24, deformation of the outer cylindrical member 14 is unlikely to occur. On the other hand, on the left and right sides away from the inner circumferential protrusions 24, 24, where deformation of the outer cylindrical member 14 due to thermal shrinkage of the main rubber elastic body 16 is likely to occur, the pair of cut holes 58, 58 are formed in the main rubber elastic body 16, so that tensile stress due to thermal shrinkage of the main rubber elastic body 16 hardly acts on the outer cylindrical member 14, and deformation of the outer cylindrical member 14 is prevented. In particular, in this embodiment, the circumferential dimension of the outer peripheral opening of the recess 26f located furthest towards the center in the front-to-back direction is larger than that of the other recesses 26a to 26e, and the deformation rigidity of the outer cylindrical member 14 in the left-to-right direction is relatively low. However, the stress acting on the outer cylindrical member 14 due to the thermal contraction of the main rubber elastic body 16 is reduced by the formation of a pair of recessed holes 58, 58, thereby effectively preventing unintended deformation of the outer cylindrical member 14.

[0065] A pair of rubber arms 60, 60 extending in the front-rear direction are formed between the circumferentially connected holes 58, 58, and these rubber arms 60, 60 connect the inner shaft member 12 and the outer cylindrical member 14 to each other. The main rubber elastic body 16 has a large ratio between the spring constant in the front-rear direction, where the compression spring component of the pair of rubber arms 60, 60 is dominant, and the spring constant in the left-right direction, where the shear spring component of the pair of rubber arms 60, 60 is dominant, resulting in a softer spring characteristic in the left-right direction than in the front-rear direction.

[0066] The pair of rubber arms 60, 60 are fixed to the inner circumferential protrusions 24, 24 of the outer cylindrical member 14 on both outer sides in the front-rear direction. This shortens the free length of the pair of rubber arms 60, 60 positioned between the opposing surfaces of the inner shaft member 12 and the outer cylindrical member 14 in the front-rear direction, thereby achieving a stiff spring characteristic in the front-rear direction. Furthermore, the spring ratio of the main rubber elastic body 16 in the front-rear and left-right directions can also be adjusted by adjusting the protrusion height of the inner circumferential protrusions 24, 24 that project from the inner circumferential surface of the outer cylindrical member 14.

[0067] As shown in Figure 4, the member mount 10, with the structure described above, is mounted to the vehicle by press-fitting the outer cylindrical member 14 into the cylindrical holder 62 of the suspension member. When the outer cylindrical member 14 is press-fitted into the holder 62, the outer peripheral end faces of the longitudinal ribs 28 and transverse ribs 30 are pressed against the inner peripheral surface of the holder 62. In short, the outer peripheral end faces of the longitudinal ribs 28 and transverse ribs 30 serve as the press-fitting surfaces for the outer cylindrical member 14 into the holder 62.

[0068] The outer cylindrical member 14 is press-fitted into the holder 62 from below. The upper end of the outer cylindrical member 14 is a tip guide portion 20 whose outer circumferential surface becomes smaller in diameter towards the top. As the outer circumferential surface of the tip guide portion 20 abuts against the holder 62, the outer cylindrical member 14 is guided to the appropriate radial position relative to the holder 62, making it easy to press-fit the outer cylindrical member 14 into the holder 62. In addition, the lower end of the outer cylindrical member 14 is provided with a flange portion 22 that protrudes outward. As the flange portion 22 abuts against the lower surface of the holder 62, the axial position of the outer cylindrical member 14 relative to the holder 62 is defined.

[0069] When the outer cylindrical member 14 is pressed into the holder 62, a force is applied to the outer cylindrical member 14 toward its inner circumference. In this case, the outer cylindrical member 14, which has numerous recesses 26 formed on its outer circumferential surface, is prone to variations in the stress applied by the press-fitting into the holder 62. Specifically, the stress applied to the outer cylindrical member 14 by press-fitting into the holder 62 tends to be greater in the axial middle portion than at both ends. In particular, if both axial ends of the outer cylindrical member 14 have a structure that is continuous in the circumferential direction without recesses 26, stress tends to concentrate in the axial middle portion.

[0070] Therefore, in this embodiment, the outer cylindrical member 14 has a reinforced region 38 with high deformation rigidity set in the axial middle portion due to the difference in the shape of the recesses 26A to 26J arranged in the axial direction. As a result, in the axial middle portion of the outer cylindrical member 14, where stress tends to concentrate when pressed into the holder 62, the high deformation rigidity of the reinforced region 38 helps to distribute the stress to both sides in the axial direction, preventing deformation and damage to the outer cylindrical member 14 due to stress concentration. In this embodiment, since the stress acting on the outer cylindrical member 14 by press-fitting into the holder 62 tends to be high in the axial central portion of the outer cylindrical member 14, the reinforced region 38 is set in the axial central portion of the outer cylindrical member 14, thereby achieving efficient stress distribution.

[0071] In this embodiment, the reinforcing region 38 is provided by the difference in the axial dimension of the recess 26. As a result, the thickness of the wall portion of the recess 26 is suppressed even in the reinforcing region 38, making it difficult for localized thickened portions to form in the outer cylindrical member 14, and thus preventing molding defects caused by thickening of the outer cylindrical member 14.

[0072] Furthermore, the reinforcing region 38 is provided by differences in the axial dimensions of the recesses 26, and the circumferential dimensions of the outer peripheral openings of the recesses 26, which are aligned axially throughout the entire structure including the reinforcing region 38, are kept substantially constant, so that the vertical ribs 28 extend continuously in the vertical direction. As a result, the outer cylindrical member 14 can be smoothly pressed into the holder 62, compared to, for example, a case where the vertical ribs are discontinuous between the reinforcing region and an adjacent region axially outward.

[0073] Furthermore, in the recess 26, the first side wall surface 32 located on the left and right central side of the outer cylindrical member 14 extends substantially parallel to the front-rear direction, while the second side wall surface 34 located on the left and right outer sides of the outer cylindrical member 14 extends substantially parallel to the radial direction of the outer cylindrical member 14. As a result, the side wall portions (vertical ribs 28) of the recess 26, which have the first side wall surface 32 and the second side wall surface 34 of adjacent recesses 26 in the circumferential direction as both sides in the circumferential direction, have their central axis in the cross-section extending in a direction close to the radial direction. Therefore, the force due to press-fitting into the holder 62 acts mainly as a radial compressive force on the side wall portions of the recess 26, making it difficult to generate a moment that acts to tilt the side wall portions of the recess 26 in the circumferential direction. As a result, even if a large number of recesses 26 opening onto the outer circumferential surface of the outer cylindrical member 14 are formed, damage to the outer cylindrical member 14 due to press-fitting into the holder 62 is less likely to occur, improving the durability of the outer cylindrical member 14.

[0074] The outer cylindrical member 14, which has recesses 26 opening on its outer circumferential surface, has its resistance force when press-fitting into the holder 62 and its fixing force when press-fitting into the holder 62 adjusted by the number, shape (including size), and arrangement of the recesses 26. In addition, the continuous extension of the longitudinal ribs 28 in the axial direction suppresses snagging and increased resistance during press-fitting.

[0075] Furthermore, the stress distribution in the outer cylindrical member 14 equipped with the reinforcing region 38 according to the present invention has also been confirmed by the stress analysis results shown in Figure 8. Figure 8A shows the stress analysis results for the outer cylindrical member 14' according to the present invention, and Figure 8B shows the stress analysis results for the outer cylindrical member 70 of a comparative example in which the axial dimension of the outer peripheral opening of the recess 26 is substantially constant. Although the outer cylindrical member 14' shown in Figure 8A differs from the outer cylindrical member 14 described in the first embodiment in terms of the number of recesses 26 and the relative sizes of the axial dimensions, it has substantially the same structure, and the effect of the reinforcing region 38 is the same. Also, although Figure 8 is shown in grayscale due to restrictions at the time of patent application, in reality, the parts of the outer cylindrical members 14' and 70 with large radial stress are shown in red, and the parts with small radial stress are shown in blue, and the magnitude of the stress is indicated by the change in hue from red to yellow and then to blue.

[0076] In other words, the outer cylindrical member 14' shown in Figure 8A has a reinforced region 38, which reduces the maximum stress in the axial middle portion compared to the outer cylindrical member 70 shown in Figure 8B. Thus, the outer cylindrical member 14' according to the present invention is more susceptible to damage due to stress concentration compared to the comparative example outer cylindrical member 70, as confirmed by the results of stress analysis.

[0077] 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 recesses 26 do not have to be distributed over the entire circumference, but may be provided partially in the circumferential direction. Also, the number of recesses 26 arranged in the axial direction may vary in the circumferential direction, and the region in the outer cylindrical member 14 where the recesses 26 are formed may have a different axial dimension in the circumferential direction.

[0078] In the first embodiment, the circumferential dimensions of the recesses 26A to 26J arranged in the axial direction were assumed to be approximately constant, but the circumferential dimensions of the recesses 26A to 26J arranged in the axial direction may vary. Also, in the first embodiment, the axial dimensions of the recesses 26a to 26f arranged in the circumferential direction were assumed to be approximately constant, but the axial dimensions of the recesses 26a to 26f arranged in the circumferential direction may vary.

[0079] The opening areas of the multiple recesses 26 arranged in the axial direction do not necessarily have to gradually decrease in the axial direction toward the reinforcement region 38. For example, the opening areas of the recesses 26 provided on both sides of the reinforcement region 38 in the axial direction may be set to be approximately constant and larger than the opening areas of the recesses 26 provided in the reinforcement region 38, or the opening areas of the recesses 26 located in areas of high stress may be made smaller than the others, taking into account the stress distribution in the press-fit state into the holder 62.

[0080] The reinforced area 38 can be defined by differences in the shape (including size) of the recesses 26 arranged in the axial direction. For example, the reinforced area 38 can be defined by reducing the circumferential dimension of the recesses 26, or by reducing the depth dimension of the recesses 26. Furthermore, the "shape of the recess" in this invention does not only refer to the hollow interior of the recess, but can also include the circumferential wall of the recess. Therefore, for example, even if the shape of the hollow interior of the recess is the same, it is possible to create a reinforced area with a different amount of resin per unit axial length of the outer cylindrical member by varying the thickness of the circumferential wall of the recess. In other words, the reinforced area can be configured by varying the distance or pitch between adjacent recesses in the axial direction.

[0081] The reinforcement region 38 is not necessarily limited to being provided at only one location in the middle of the axial direction; multiple reinforcement regions 38, each with approximately the same amount of resin, can be set in multiple locations that are separated from each other in the axial direction.

[0082] Multiple transverse ribs 30, which are aligned axially and extend circumferentially, may all have a substantially constant axial width dimension, or they may have different axial width dimensions. Similarly, multiple longitudinal ribs 28, which are aligned circumferentially and extend axially, may all have a substantially constant circumferential width dimension, or they may have different circumferential width dimensions.

[0083] The high-strength portion of the outer cylindrical member is not necessarily limited to a tapered shape like the tip guide portion 20 or a protruding shape on the outer circumference like the flange portion 22, but may also be an annular or cylindrical shape with a substantially constant diameter. Furthermore, while it is desirable for the high-strength portion to be made of resin alone, it can also be constructed by improving strength by, for example, embedding and fixing a metal reinforcing material, and is not limited to areas without recesses or flange structures with enlarged radial dimensions as illustrated. The outer cylindrical member does not necessarily have to be made of resin alone, and can be made of, for example, a composite material of resin and metal. In addition, the outer cylindrical member can be made of multiple types of resin materials by, for example, two-color molding. Note that the high-strength portion of the outer cylindrical member is not essential, and for example, the recess may be located up to the axial end of the outer cylindrical member.

[0084] The inner circumferential protrusion 24 of the outer cylindrical member 14 is not essential; for example, the inner diameter of the outer cylindrical member may be constant around its entire circumference. As shown in Figure 4, the radial thickness of the outer cylindrical member 14, and therefore the amount of resin, changes in the axial direction due to the inner circumferential protrusion 24. However, the amount of resin due to differences in the shape of the recesses 26 is, in principle, compared only in portions with the same radial thickness. Incidentally, even in the embodiment shown in Figure 4, for example, the formation regions of recesses 26E and 26F, which are the axial central portions of the inner circumferential protrusion 24, can be recognized as reinforced regions where the amount of resin is increased due to differences in the shape of the recesses 26, compared to the formation regions of recesses 26D, C, G, and H, which are provided on both sides of the axial direction in portions with the same radial thickness. Alternatively, since the difference in the amount of resin due to differences in the shape of the recesses 26 may be partial in the circumferential direction, for example, the existence of reinforced regions where the amount of resin is increased due to differences in the shape of the recesses 26 may be recognized only in the circumferential portion where the inner circumferential protrusion 24 is not formed (the right half in Figure 4).

[0085] The grooves 58, 58 in the main rubber elastic body 16 are not essential. Three or more grooves 58 can also be provided. Furthermore, the grooves are not necessarily limited to grooves 58 that penetrate axially; for example, they may be recesses opening on the axial end face of the main rubber elastic body 16, thereby reducing the spring's strength by decreasing the axial thickness of the main rubber elastic body 16.

[0086] The cylindrical vibration damping device according to the present invention can be applied to applications other than member mounts, and is suitably applicable to, for example, power unit mounts such as engine mounts and motor mounts of vehicles, suspension bushings, and the like. [Explanation of Symbols]

[0087] 10. Member mount (Cylindrical vibration isolation device, first embodiment) 12 Inner shaft member 14,14' Outer cylindrical member 16 Main body rubber elastic body 18 bolt holes 20 Tip guide part (high strength part) 22 Flange section (high-strength section) 24 Inner Circumference Protrusion 26 (26a~26f, 26A~26J, 26aA~26fJ) recess 28 Vertical Ribs 30 horizontal ribs 32 First side wall 34 Second side wall 36 Bottom wall 38 Reinforcement Area 40 Molding mold 42 Inner mold 44 External mold 46 Concave surface 48 First split type 50 Second split type 52(52a~52f) Protrusion 54 Cavity 56 Stopper rubber 58. Cutting holes (cutting area) 60 Rubber Arms 62 Holder 70 Outer cylindrical member L axial length Axial dimension of the recess provided in the W reinforcement region

Claims

1. A cylindrical vibration isolation device in which an inner shaft member and a resin outer cylindrical member are connected by a main rubber elastic body, The outer cylindrical member has a plurality of recesses that open to the outer surface, arranged in the axial direction. A cylindrical vibration damping device is provided in which the axial middle portion of the outer cylindrical member has a reinforcing region in which the amount of resin is greater than that of the axial side portions due to differences in the shape of the recesses arranged in the axial direction.

2. The cylindrical vibration isolation device according to claim 1, wherein the reinforcing region is provided by the difference in the axial dimension of the recess.

3. The cylindrical vibration isolation device according to claim 2, wherein the axial dimension of the openings of the plurality of recesses gradually decreases from the axial end toward the reinforcement region.

4. Each of the aforementioned recesses opens toward the first radial direction of the outer cylindrical member. The inner surface of the side wall of the recess located on the central side in the second radial direction perpendicular to the first radial direction of the outer cylindrical member is wider in the first radial direction, The inner surface of the side wall of the recess located on the opposite side of the second radial center in the outer cylindrical member extends radially in the outer cylindrical member. The cylindrical vibration isolation device according to any one of claims 1 to 3, wherein the recess expands in the circumferential direction toward the outer circumference.

5. The outer cylindrical member is partially provided with an inner circumferential protrusion that protrudes from the inner circumferential surface in the circumferential direction. A cylindrical vibration damping device according to any one of claims 1 to 3, wherein the recess provided in the portion forming the inner circumferential protrusion in the circumferential direction is deep enough to reach the inner circumferential protrusion.

6. The outer cylindrical member is partially provided with an inner circumferential protrusion that protrudes from the inner circumferential surface in the circumferential direction. The main body of the rubber elastic material has a groove formed on its axial end face, The cylindrical vibration damping device according to any one of claims 1 to 3, wherein the groove is positioned away from the inner circumferential protrusion of the outer cylindrical member in the circumferential direction.

7. Each of the aforementioned recesses opens toward the first radial direction of the outer cylindrical member. The aforementioned main body rubber elastic material has a notched portion that opens to the axial end face, The cylindrical vibration isolation device according to any one of claims 1 to 3, wherein the grooves are provided on both sides in a second radial direction perpendicular to the first radial direction.

8. The cylindrical vibration isolation device according to any one of claims 1 to 3, wherein high-strength portions in which the recess is not formed are provided at both axial ends of the outer cylindrical member.

9. The plurality of recesses, which are arranged in the axial direction of the outer cylindrical member, are distributed around the entire circumference of the outer cylindrical member. The multiple recesses arranged in the circumferential direction have the same axial dimension of their openings. The cylindrical vibration isolation device according to any one of claims 1 to 3, wherein the plurality of recesses arranged in the axial direction have the same circumferential dimensions of the openings.

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