Vibration isolation device

Abstract

To provide a vibration isolation device that eliminates the need to attach a mass to the bracket while efficiently adjusting the natural frequency of the bracket. [Solution] Since the mass portion 22 is formed on the outer circumferential surface 21a of the annular portion 21 provided on the lower end side of the bracket 2, the mass portion 22 can be positioned away from the insertion holes 20c to 20e, which are the pivot points for the vibration of the bracket 2 (i.e., in a region where the amplitude of the bracket 2 tends to be large). Therefore, even if the mass of the mass portion 22 is relatively small, the natural frequency of the bracket 2 can be changed significantly, so the natural frequency of the bracket 2 can be adjusted efficiently. In addition, since the mass portion 22 is integrally formed on the outer circumferential surface 21a of the annular portion 21, unlike conventional techniques in which a separate mass is retrofitted to the bracket 2, the work of attaching the mass can be eliminated.

Description

Technical Field

[0001] The present invention relates to a vibration isolation device, and more particularly to a vibration isolation device that can efficiently adjust the natural frequency of a bracket while eliminating the need for attaching a mass to the bracket.

Background Art

[0002] For example, Patent Document 1 describes a technique of attaching a dynamic damper 50 to a mount bracket 38 (bracket) interposed between a subframe 12 on the vehicle body side and a power unit P on the vibration source side. The dynamic damper 50 includes a dynamic damper bracket 64 attached to the mount bracket 38, and a weight 70 (mass) elastically supported on the dynamic damper bracket 64 via an elastic coupling body 68. In this technique, a collar member 60 of the mount bracket 38 and the dynamic damper bracket 64 of the dynamic damper 50 are clamped together by bolts 36.

[0003] Also, for example, Patent Document 2 describes a technique of directly attaching a weight mass 62 to an attachment member 50 (bracket) interposed between a subframe 12 on the vehicle body side and a power unit P on the vibration source side. Also in this technique, the weight mass 62 is fastened to the attachment member 50 by bolts 70.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described in the aforementioned Patent Documents 1 and 2, the structure in which a mass is bolted to a bracket has the problem that the installation of the mass is time-consuming.

[0006] This invention was made to solve the above-mentioned problems, and aims to provide a vibration isolation device that can efficiently adjust the natural frequency of a bracket while eliminating the need for mounting a mass to the bracket. [Means for solving the problem]

[0007] To achieve this objective, the vibration isolation device of the present invention comprises a fastening member fastened to either the vibration receiving side or the vibration source side, a bracket having an insertion hole formed at one end for inserting the fastening member from the front side and a press-fit hole formed at the other end, and a vibration isolation bush attached to the press-fit hole of the bracket, wherein the vibration isolation bush comprises a cylindrical outer member press-fitted into the press-fit hole, an inner member arranged on the inner circumference side of the outer member and fixed to the other of the vibration receiving side or the vibration source side, and an elastic body connecting the outer member and the inner member, and the bracket comprises a mass portion integrally formed on the outer circumference opposite to the insertion hole, with the press-fit hole in between. [Effects of the Invention]

[0008] According to the vibration isolation device described in claim 1, the bracket is provided with a mass portion formed on the outer circumferential surface opposite the insertion hole, straddling the press-fit hole. This allows the mass portion to be positioned away from the insertion hole (the part where the fastening member is fastened), which is the pivot point for the vibration of the bracket. By positioning the mass portion in a region where the amplitude of the bracket tends to be large, the natural frequency of the bracket can be significantly changed even if the mass of the mass portion is relatively small. Therefore, this has the effect of efficiently adjusting the natural frequency of the bracket. Furthermore, since the mass portion is integrally formed with the bracket, unlike conventional techniques in which a separate mass is retrofitted to the bracket, this eliminates the need for mass installation work.

[0009] The vibration isolation device according to claim 2 provides the following effects in addition to the effects of the vibration isolation device according to claim 1. The mass portion comprises a pair of side walls protruding from the outer circumferential surface of the bracket and a tip wall connecting the tips of the pair of side walls. Since a first weight-reducing hole is formed in the mass portion surrounded by the pair of side walls and the tip wall, the center of gravity of the mass portion can be moved away from the fulcrum (insertion hole) of the bracket's vibration compared to when the first weight-reducing hole is not formed. Therefore, the natural frequency of the bracket can be adjusted efficiently.

[0010] The vibration isolation device according to claim 3 provides the following effects in addition to the effects of the vibration isolation device according to claim 2. The mass portion is provided with a bottom wall that closes the first weight-reducing hole on the rear side of the bracket, and the rear surface of the bottom wall is a plane perpendicular to the axial direction of the vibration isolation bush and is connected to the edge of the press-fit hole. As a result, when pressing the vibration isolation bush into the press-fit hole with the bracket placed on the mounting surface of the press-fit jig, a support surface (the rear surface of the bottom wall) for supporting the load during press-fitting can be formed adjacent to the edge of the press-fit hole. Therefore, the bracket can be stably supported when the vibration isolation bush is pressed in, which has the effect of improving the workability of the work of pressing in the vibration isolation bush.

[0011] The vibration isolation device according to claim 4 provides the following effects in addition to the effects of the vibration isolation device according to claim 3. The bracket is provided with a plurality of second weight-reducing holes formed around the insertion hole. Since the second weight-reducing holes are not formed on the rear surface of the bracket, when inserting a pin rising from the mounting surface of the press-fitting jig into the insertion hole from the rear side, the insertion hole into which the pin should be inserted can be easily identified. Therefore, the workability of the press-fitting operation of the vibration isolation bush can be improved.

[0012] According to the vibration isolation device of claim 5, in addition to the effects of the vibration isolation device of claim 1, the bracket is formed in an annular shape surrounding the press-fit hole and has an annular portion in which a mass portion is integrally formed on the outer surface. Therefore, when a load due to the displacement of the inner member of the vibration isolation bush is input to the bracket, the stress due to that load tends to concentrate at the boundary between the mass portion and the annular portion. By pre-forming such a stress-concentrating area in the annular portion, it is possible to simplify the strength design of the bracket (annular portion).

[0013] The mounting structure for the vibration isolation device described in claim 6 is a mounting structure for mounting the vibration isolation device described in claim 5 between the vibration receiving side and the vibration source side, wherein the mass portion is positioned to overlap with the inner member when viewed in the direction of load input from the vibration receiving side or the vibration source side, so that the load from the vibration receiving side or the vibration source side acts more easily on the boundary between the mass portion and the annular portion. As a result, the stress due to such load is more likely to concentrate at the boundary between the mass portion and the annular portion, which has the effect of making the strength design of the bracket (annular portion) easier.

[0014] The mounting structure for the vibration isolation device described in claim 7, in addition to the effects of the mounting structure for the vibration isolation device described in claim 6, is positioned such that the boundary between the end of the mass portion in the circumferential direction of the annular portion and the outer surface of the annular portion overlaps with the inner member when viewed in the direction of load input. This makes it easier for loads from the vibration receiving side or vibration source side to act on the boundary portion between the mass portion and the annular portion. As a result, stress due to such loads is more easily concentrated at the boundary portion between the mass portion and the annular portion, which has the effect of making the strength design of the bracket (annular portion) even easier. [Brief explanation of the drawing]

[0015] [Figure 1] This is a front view of a vibration isolation device in one embodiment of the present invention. [Figure 2] This is a cross-sectional view of the vibration isolation device along line II-II in Figure 1. [Figure 3](a) is a partially enlarged cross-sectional view of the vibration isolation device along the line IIIa-IIIa in Figure 1, and (b) is a partially enlarged cross-sectional view of the vibration isolation device along the line IIIb-IIIb in Figure 1. [Figure 4] This is a rear perspective view of the bracket. [Modes for carrying out the invention]

[0016] The following describes preferred embodiments with reference to the attached drawings. First, the overall configuration of the vibration isolation device 1 will be described with reference to Figures 1 and 2. Figure 1 is a front view of the vibration isolation device 1 in one embodiment of the present invention, and Figure 2 is a cross-sectional view of the vibration isolation device 1 along line II-II in Figure 1, both illustrating the vibration isolation device 1 in an unloaded state where no vibration (load) is input.

[0017] In Figures 1 and 2, the external shapes of the mounting members 100 and 101 to which the vibration damping device 1 is attached are schematically shown with dashed lines. In Figure 1, the bolts 4 and 5 fastened to the mounting members 100 and 101 (see Figure 2) are omitted from the illustration to simplify the drawing. Also, the arrows UD, FB, and LR in Figures 1 and 2 indicate the vertical, longitudinal, and lateral directions of the vibration damping device 1, respectively (the same applies to subsequent figures). However, these directions of the vibration damping device 1 do not necessarily coincide with the directions of the vehicle to which the vibration damping device 1 is attached.

[0018] As shown in Figures 1 and 2, the vibration isolation device 1 is an engine mount that elastically supports the vehicle's engine. The vibration isolation device 1 comprises a metal bracket 2 attached to a mounting member 100 on the engine (vibration source) side, and a vibration isolation bush 3 attached to a mounting member 101 on the vehicle body (vibration receiver) side.

[0019] Bracket 2 comprises a main body portion 20 fixed to the mounting member 100 by bolts 4 (see Figure 2), an annular (semi-annular) portion 21 formed on the lower end side (arrow D side) of the main body portion 20, and a mass portion 22 formed on the outer peripheral surface 21a of the annular portion 21, with each of these portions 20 to 22 being integrally formed.

[0020] In the main body portion 20, a plurality of insertion holes 20c to 20e (for the insertion hole 20e, refer to FIG. 1) penetrating through its front surface 20a and rear surface 20b (for the rear surface 20b, refer to FIG. 2) are formed. Further, on the front surface 20a of the main body portion 20, a plurality of relief holes 20f are uniformly formed (dispersedly arranged) over substantially the entire surface. These relief holes 20f are recesses for ensuring the formability (such as the fluidity of the casting in the mold) when integrally forming each part 20 to 22 of the bracket 2 by casting.

[0021] Among the plurality of insertion holes 20c to 20e, the one formed on the uppermost end side (arrow U side) of the bracket 2 is the insertion hole 20c, and the ones formed below this insertion hole 20c are the insertion holes 20d and 20e. The main body portion 20 of the bracket 2 extends downward (lower right side in FIG. 1) from these insertion holes 20c to 20e, and an annular portion 21 is formed at the lower end portion of this main body portion 20.

[0022] On the inner peripheral side of the annular portion 21, a press-fitting hole 21b having a circular cross-section (refer to FIG. 1) is formed, and a vibration isolation bush 3 is attached to this press-fitting hole 21b. In the following description, the axial direction O of the vibration isolation bush 3 in the state of being press-fitted into the press-fitting hole 21b will be simply described as the "axial direction O".

[0023] The vibration isolation bush 3 includes a cylindrical outer cylinder 30 (outer member) (refer to FIG. 1) that is press-fitted into the press-fitting hole 21b, and a cylindrical inner cylinder 31 (inner member) is arranged on the inner peripheral side of the outer cylinder 30. These outer cylinder 30 and inner cylinder 31 are members made of metal respectively. An elastic body 32 (refer to FIG. 1) is vulcanized and adhered to the inner peripheral surface of the outer cylinder 30 and the outer peripheral surface of the inner cylinder 31, and the outer cylinder 30 and the inner cylinder 31 are connected by this elastic body 32.

[0024] The vibration isolation device 1 is mounted between the mounting members 100 and 101 by fastening a bolt 5 (see Figure 2) inserted into the inner cylinder 31 of the vibration isolation bush 3 to the mounting member 101, while fastening a bolt 4 (see Figure 2) inserted into the insertion holes 20c to 20e of the bracket 2 (main body portion 20) to the mounting member 100. In this embodiment, the axis O direction in this mounting state is considered to be the front-to-back direction (arrow FB direction) of the vibration isolation device 1 for explanation purposes.

[0025] In a view of the vibration isolation device 1 in the front-to-back direction (axis O direction), the longitudinal direction of the bracket 2 (vibration isolation device 1) is the direction connecting the centers of insertion hole 20c, which is formed at the position furthest from the press-fit hole 21b (upper end side) among the insertion holes 20c to 20e, and the press-fit hole 21b. The transverse direction of the bracket 2 is perpendicular to both the longitudinal direction and the front-to-back direction.

[0026] In the installed state of the vibration isolation device 1, the longitudinal direction of the bracket 2 is inclined with respect to the vertical direction (arrow UD direction), and the insertion holes 20c to 20e are positioned eccentrically to one side in the left-right direction (arrow R side in this embodiment) with respect to the center (axis O) of the press-fit hole 21b. Furthermore, the pair of insertion holes 20d and 20e are spaced apart in the short direction of the bracket 2, and the dimensions of the bracket 2 (main body 20) in the short direction gradually increase from the area where the insertion hole 20c is formed to the area where the insertion holes 20d and 20e are formed.

[0027] The dimensions of bracket 2 in the short direction are maximized in the region where the insertion holes 20d and 20e are formed. If this maximum dimension is taken as the width of bracket 2, the thickness of bracket 2 in the front-to-back direction (the direction perpendicular to the long and short directions) is formed to be smaller than the width of bracket 2. Naturally, the length dimension of bracket 2 is also larger than the width dimension.

[0028] The press-fit hole 21b is formed at a distance from the insertion holes 20c to 20e in the longitudinal direction of the bracket 2, and in the mounted state of the vibration isolation device 1, the press-fit hole 21b is positioned below (downward in the vertical direction) the insertion holes 20c to 20e. The outer circumferential surface 21a of the annular portion 21 that surrounds approximately half the circumference of the press-fit hole 21b is an arcuate surface centered on axis O, except for the region where the mass portion 22 is formed. Hereafter, the direction around the outer circumferential surface 21a of this annular portion 21 will be simply referred to as the "circumferential direction". The mass portion 22 formed on the outer circumferential surface 21a of the annular portion 21 is a part that is configured as a mass body for adjusting the natural frequency of the bracket 2.

[0029] As described above, the vibration isolation device 1 of this embodiment is configured such that the upper end (one end in the longitudinal direction) of the bracket 2 is fixed (rigidly connected) to the mounting member 100 by a bolt 4, and the lower end (the other end in the longitudinal direction) is elastically supported by the mounting member 101 via a vibration isolation bush 3 (elastic body 32). Therefore, when vibration is input to the bracket 2, the vibration is more easily restrained at the upper end of the bracket 2, while the lower end of the bracket 2 can vibrate relatively more freely compared to the upper end. In other words, when such vibration is input, the upper end of the bracket 2 acts as a pivot point for vibration, so the amplitude at the lower end of the bracket 2 tends to be larger.

[0030] In contrast, in this embodiment, the mass portion 22 is formed on the outer circumferential surface 21a of the annular portion 21 provided on the lower end side of the bracket 2 (opposite the insertion holes 20c to 20e, with the press-fit hole 21b in between), so that the mass portion 22 can be positioned away from the pivot point of the bracket 2's vibration (insertion holes 20c to 20e). By positioning the mass portion 22 in a region where the amplitude of the bracket 2 tends to be large, the natural frequency of the bracket 2 can be significantly changed even if the mass of the mass portion 22 is relatively small, thus allowing for efficient adjustment of the natural frequency of the bracket 2.

[0031] Furthermore, since the mass portion 22 (mass body) for adjusting the natural frequency of the bracket 2 is integrally formed on the outer circumferential surface 21a of the annular portion 21, unlike conventional techniques in which a separate mass is retrofitted to the bracket 2, the installation work of the mass can be eliminated.

[0032] The mass portion 22 is provided with a pair of side walls 22a and 22b (see Figure 1 for side wall 22a) that project downward (towards the outer circumference of the annular portion 21) from the outer circumferential surface 21a of the annular portion 21, and the projection directions of this pair of side walls 22a and 22b are substantially parallel to each other. The projection length of side wall 22a from the outer circumferential surface 21a of the annular portion 21 is formed to be longer than the projection length of side wall 22b (see Figure 1), and the tips (lower ends) of the pair of side walls 22a and 22b are connected in the circumferential direction (arrows LR direction) by tip wall 22c.

[0033] The rear ends (the ends on the far side in the vertical direction of the paper in Figure 1) of the pair of side walls 22a, 22b and the front end wall 22c are connected by the bottom wall 22d, thereby forming a weight-reducing hole 22e on the front surface of the mass portion 22, surrounded by these walls 22a to 22d. In other words, the weight-reducing hole 22e is a recess that is closed off from the rear side of the bracket 2 by the bottom wall 22d, and this weight-reducing hole 22e is a recess that mainly ensures moldability when integrally forming the entire bracket 2, including the walls 22a to 22d of the mass portion 22, by casting.

[0034] While it is possible to form the mass portion 22 by omitting the weight-reducing holes 22e, for example, in a configuration where the weight-reducing holes 22e are filled and the mass portion 22 is formed in a simple rectangular parallelepiped shape, the formability when casting the bracket 2 tends to decrease. Also, if we consider forming the mass portion 22 with the same mass (volume), in a configuration where the weight-reducing holes 22e are omitted, the center of gravity of the mass portion 22 approaches the pivot point of the bracket 2's vibration (insertion holes 20c to 20e). When the center of gravity of the mass portion 22 approaches the pivot point of the bracket 2's vibration, it becomes impossible to broadly adjust the natural frequency of the bracket 2 even if the mass of the mass portion 22 is changed.

[0035] In contrast, the mass portion 22 of this embodiment comprises a pair of side walls 22a and 22b protruding from the outer circumferential surface of the bracket 2, and a tip wall 22c connecting the tips of the pair of side walls 22a and 22b. The mass portion 22 has a weight-reducing hole 22e surrounded by these walls 22a to 22c. This allows the center of gravity of the mass portion 22 to be moved away from the pivot point of vibration of the bracket 2, compared to the configuration in which the weight-reducing hole 22e is omitted as described above. Therefore, the natural frequency of the bracket 2 can be efficiently adjusted by changing the mass of the mass portion 22.

[0036] Here, when engine vibrations or vehicle vibrations associated with vehicle movement are input to the vibration isolation device 1, the bracket 2 (annular portion 21) and the inner cylinder 31 of the vibration isolation bush 3 are displaced relative to each other, and a load Fa (a load in the direction indicated by the arrow Fa in Figure 1; hereinafter simply referred to as "load Fa") acting on the bracket 2 is generated by this displacement of the inner cylinder 31. The input direction of this load Fa is mainly perpendicular to the axis O and is inclined at an angle of 20 to 40° (30° in this embodiment) with respect to the vertical direction.

[0037] In other words, since the load Fa acts mainly in a direction that is roughly coincide with the longitudinal direction of the bracket 2, stress due to the load Fa is generated in the main body portion 20 and the annular portion 21 located on both sides of the press-fit hole 21b in the longitudinal direction of the bracket 2. In contrast, the main body portion 20 is formed to be relatively thick (compared to the annular portion 21), while the annular portion 21 is formed to be relatively thin (in the form of a flat plate with a plate thickness of roughly constant). Therefore, when the load Fa is repeatedly applied to the bracket 2, fatigue failure is likely to occur mainly in the annular portion 21.

[0038] In particular, in this embodiment, since the mass portion 22 is integrally formed with the annular portion 21, stress due to the load Fa tends to concentrate at the circumferential ends of the mass portion 22 (the sides of the pair of side walls 22a, 22b) and the boundary portions B1, B2 (see Figure 1) between the outer circumferential surface 21a of the annular portion 21. This is because the rigidity of the annular portion 21 in the region where the mass portion 22 is not present is relatively lower than in the region where the mass portion 22 is formed (between the boundaries B1, B2).

[0039] Therefore, when the load Fa due to vehicle vibration repeatedly acts on the bracket 2, failure is likely to occur starting from the boundaries B1 and B2 between the annular portion 21 and the mass portion 22. In this way, by pre-forming areas where stress is likely to concentrate (where failure is likely to occur) on the annular portion 21, the strength design of the bracket 2 (annular portion 21) can be made easier.

[0040] Furthermore, in the input direction view of the load Fa acting on bracket 2 (direction indicated by arrow Fa in Figure 1), the mass portion 22 and the inner cylinder 31 are positioned to overlap, so the load Fa due to vehicle vibrations is more likely to act on the boundaries B1 and B2 between the annular portion 21 and the mass portion 22. Therefore, stress due to the load Fa is more likely to concentrate at the boundaries B1 and B2 between the annular portion 21 and the mass portion 22, making it easier to design the strength of bracket 2.

[0041] Furthermore, in this embodiment, one of the boundaries B1 and B2 between the annular portion 21 and the mass portion 22, boundary B1 (on the side wall 22a side), is positioned to overlap with the inner cylinder 31 when viewed in the direction of the input load Fa. Therefore, the load Fa is more likely to act on one of the boundaries B1. Consequently, stress due to the load Fa is more likely to concentrate at boundary B1 between the annular portion 21 and the mass portion 22, making the strength design of the bracket 2 even easier.

[0042] Next, the detailed configuration of the mass section 22 will be explained with reference to Figures 3 and 4, with reference to Figures 1 and 2 as appropriate. Figure 3(a) is a partially enlarged cross-sectional view of the vibration isolation device 1 along the line IIIa-IIIa in Figure 1, and Figure 3(b) is a partially enlarged cross-sectional view of the vibration isolation device 1 along the line IIIb-IIIb in Figure 1. Figure 4 is a rear perspective view of the bracket 2. Note that Figure 4 shows the vibration isolation bush 3 removed from the press-fit hole 21b of the bracket 2.

[0043] As shown in Figures 3 and 4, in a cross-sectional view (see Figure 3(a)) taken by cutting with a plane perpendicular to the protruding direction of the pair of side walls 22a and 22b, the side wall 22b extends in a substantially straight line along the front-rear direction (axis O direction) (arrow FB direction), while the side wall 22a has a partially bent shape.

[0044] More specifically, the side wall 22a has a first wall portion 220a that constitutes its front end (the end on the side of arrow F), and a second wall portion 221a is connected to the rear end (the end on the side of arrow B) of the first wall portion 220a which extends in the front and rear directions (in the direction of arrow FB). The second wall portion 221a is bent inward in the circumferential direction from the first wall portion 220a (inward in the opposing direction of the side walls 22a and 22b), and a third wall portion 222a is connected to the circumferentially inward end of this second wall portion 221a.

[0045] The third wall portion 222a extends from the second wall portion 221a toward the rear (towards arrow B) and is connected to the bottom wall 22d. The thickness of each wall portion 220a to 222a that constitute these side walls 22a is approximately constant.

[0046] By forming the side wall 22a from the bent wall portions 220a to 222a in this manner, a recess 22f is formed on the side surface of the mass portion 22 (side wall 22a) that is recessed toward the circumferential inward direction of the mass portion 22. This recess 22f is mainly for preventing interference with mating parts (other parts assembled to the vehicle) around the bracket 2. Furthermore, by bending a part of the side wall 22a as described above, a first recess 220e, which is relatively shallow in depth from the front surface of the mass portion 22 (the surface facing the arrow F side), and a second recess 221e, which is deeper than the first recess 220e, are formed side by side (connected) in the circumferential direction.

[0047] Thus, in this embodiment, a portion of the side wall 22a from its front end to its rear end is bent, while the side wall 22b is formed in a straight line from front to back. This configuration makes it possible to increase the rigidity of the side wall 22a compared to the side wall 22b. In other words, it is possible to create a difference in rigidity between the pair of side walls 22a and 22b. Furthermore, with this configuration, of the boundaries B1 and B2 (see Figure 1) between the annular portion 21 and the mass portion 22, the boundary line between the annular portion 21 and the mass portion 22 is bent at one boundary B1, while the boundary line between the annular portion 21 and the mass portion 22 is formed in a straight line at the other boundary B2.

[0048] As described above, by creating a difference in rigidity between the pair of side walls 22a and 22b, and by making the boundary lines between the annular section 21 and the pair of side walls 22a and 22b have different shapes, it becomes easier to predict in advance which of the two boundary lines B1 and B2 (see Figure 1) between the annular section 21 and the mass section 22 will be prone to stress concentration (and thus prone to failure) when a load Fa (see Figure 1) due to vehicle vibration is applied to the bracket 2. Therefore, the strength design of the bracket 2 can be simplified.

[0049] The projection height of the side wall 22a from the outer peripheral surface 21a of the annular portion 21 is highest in the central part in the front-to-back direction compared to the front and rear ends of the side wall 22a (see Figure 3(b)), and the same shape is formed for the side wall 22b (see Figure 2). That is, each of the pair of side walls 22a and 22b has a tapered shape toward the lower end (arrow D side). For this reason, the front surface 223a of the side wall 22a (first wall portion 220a) and the bottom surface of the first recess 220e of the weight-reducing hole 22e are inclined so that they approach the center of the mass portion 22 in the front-to-back direction as they move toward their lower end (see Figure 3(b)).

[0050] Furthermore, the front wall 22c, which connects the lower ends of the side walls 22a and 22b in the circumferential direction, is also inclined to move away from the annular portion 21 from the rear end (bottom wall 22d side) to the front end (see Figure 3(b)). By forming the mass portion 22 with such a tapered shape toward the lower end, interference between the mass portion 22 and mating parts present around (front and rear of) the mass portion 22 can be suppressed.

[0051] Here, when the outer cylinder 30 (see Figure 3(b)) of the vibration-damping bush 3 is pressed into the press-fit hole 21b, a press-fit jig (not shown) having a mounting surface on which the bracket 2 is placed is used. This press-fit jig has a plurality of pins (for example, three) rising from the mounting surface, and when the bracket 2 is placed on this mounting surface, the plurality of pins of the press-fit jig are inserted into the insertion holes 20c to 20e (see Figure 4) from the rear surface 20b side of the bracket 2.

[0052] The vibration isolation device 1 is assembled by fitting the vibration isolation bush 3 (outer cylinder 30) into the press-fit hole 21b with the pin inserted. For this reason, if, for example, the mass portion 22 is not formed on the outer circumferential surface 21a of the annular portion 21, it becomes difficult to form a support surface (a surface supported by the mounting surface of the press-fit jig) around the annular portion 21 that supports the load when pressing the vibration isolation bush 3 into the press-fit hole 21b.

[0053] In contrast, in this embodiment, since a mass portion 22 is formed on the outer circumferential surface 21a of the annular portion 21, the mass portion 22 can form a support surface when pressing the vibration-damping bush 3 into the press-fit hole 21b. In particular, the rear surface 220d (see Figure 4) of the bottom wall 22d of the mass portion 22 in this embodiment is a plane perpendicular to the axis O direction and is a plane that is connected to the edge of the press-fit hole 21b. By supporting this rear surface 220d of the bottom wall 22d with the press-fit jig described above, the load during the press-fitting of the vibration-damping bush 3 can be supported at a position adjacent to the annular portion 21 (press-fit hole 21b). Therefore, the vibration-damping bush 3 can be pressed in with the bracket 2 stably placed on the mounting surface of the press-fit jig, thus improving the workability of the press-fitting operation of the vibration-damping bush 3.

[0054] Furthermore, as described above, multiple weight-reducing holes 20f (see Figure 1 or Figure 2) are formed on the front surface 20a of the bracket 2, but no such weight-reducing holes are formed on the rear surface 20b of the bracket 2 (see Figure 4). This makes it easier for the operator to identify the insertion holes 20c to 20e into which the pins of the press-fitting jig should be inserted, allowing the bracket 2 to be easily set into the press-fitting jig. Thus, the work efficiency of press-fitting the vibration-damping bush 3 (outer cylinder 30) can be improved.

[0055] Although the present invention has been described above based on the above embodiments, it can be easily inferred that the present invention is not limited in any way to the above embodiments, and that various modifications and improvements are possible without departing from the spirit of the present invention.

[0056] In the above embodiment, the engine mount was given as an example of an application target for the vibration damping device 1, but the application target is arbitrary. Other examples of application targets include motor mounts, member mounts, differential mounts, etc. Furthermore, it is not limited to attaching the bracket 2 to the vibration source side such as the engine and attaching the vibration damping bush 3 to the vibration receiving side such as the vehicle body; the vibration damping bush 3 may be attached to the vibration source side and the bracket 2 may be attached to the vibration receiving side.

[0057] In the above embodiment, a case was described in which a weight-reducing hole 22e surrounded by side walls 22a, 22b, a front wall 22c, and a bottom wall 22d is formed in the mass portion 22, but it is not necessarily limited to this. For example, the weight-reducing hole 22e may be omitted and the mass portion 22 may be formed in the shape of a rectangular parallelepiped or a cube, or the mass portion 22 may be made into the shape of another polyhedron. Also, the bottom wall 22d may be omitted and the weight-reducing hole 22e may be formed as a through hole, or in addition to the weight-reducing hole 22e, or in place of the weight-reducing hole 22e, other holes (holes) or recesses may be formed in the mass portion 22.

[0058] In other words, if the mass portion 22 is integrally formed on the outer circumferential surface 21a of the annular portion 21, the shape of the mass portion 22 can be arbitrarily changed. Therefore, for example, in the above embodiment, the case was described in which the rear surface 220d of the bottom wall 22d (the bottom surface of the mass portion 22) is a plane perpendicular to the axis O direction and is a plane that is connected to the edge of the press-fit hole 21b. However, the rear surface 220d of the bottom wall 22d may be a plane or curved surface that is not perpendicular to the axis O direction, and a step may be formed between the rear surface 220d of the bottom wall 22d and the edge of the press-fit hole 21b (the rear surface of the annular portion 21).

[0059] In the above embodiment, a case was described in which a weight-reducing hole 20f is formed on the front surface 20a of the bracket 2, while no such weight-reducing hole is formed on the rear surface 20b of the bracket 2. However, the embodiment is not limited to this. For example, the weight-reducing hole 20f of the bracket 2 may be omitted, or a weight-reducing hole 20f may be formed on the rear surface 20b of the bracket 2.

[0060] In the above embodiment, a case was described in which one mass portion 22 is formed on the outer circumferential surface 21a of the annular portion 21 surrounding the press-fit hole 21b, but this is not necessarily the case. For example, the shape of the outer circumferential surface 21a of the annular portion 21 can be changed as appropriate (it does not have to be formed in an annular shape), and multiple mass portions 22 may be integrally formed on the outer circumferential surface 21a of the annular portion 21.

[0061] In the above embodiment, the definition of the boundaries B1 and B2 between the annular portion 21 and the mass portion 22 has been omitted. However, for example, if the curved surface connecting the outer circumferential surface 21a of the annular portion 21 and the side surface of the mass portion 22 (side walls 22a, 22b) is used as the connecting surface, then the midpoint of that connecting surface is the boundary B1 and B2 between the annular portion 21 and the mass portion 22.

[0062] In the above embodiment, we have described a case where one of the boundaries B1 and B2 between the annular portion 21 and the mass portion 22, B1, is formed at a position that overlaps with the inner cylinder 31 when viewed in the direction of load Fa input (where the mass portion 22 and the inner cylinder 31 overlap when viewed in the same direction), but this is not necessarily the only case. For example, when viewed in the direction of load Fa input, the other boundary B2 may be formed at a position that overlaps with the inner cylinder 31, or both boundaries B1 and B2 may be formed at positions that overlap with the inner cylinder 31.

[0063] Furthermore, the mass portion 22 may be formed in a position that does not overlap with the inner cylinder 31 when viewed in the direction of the input load Fa. In other words, the arrangement and size of the mass portion 22 in the circumferential direction of the annular portion 21 are not limited to the above configuration and can be changed as appropriate. [Explanation of Symbols]

[0064] 1. Vibration isolation device 2 brackets 20c~20e Insertion hole 20f Weight reduction hole (2nd weight reduction hole) 21 Ring section 21a Outer surface of the annular portion 21b Press-fit hole 22 Mass Section 22a,22b side wall 22c Tip wall 22d bottom wall 220d Rear of the bottom wall 22e Weight reduction hole (1st weight reduction hole) 3. Vibration-damping bushings 30 Outer cylinder (outer component) 31 Inner cylinder (inner component) 32 Elastic body 4 bolts (fastening members) B1, B2 Boundary between the mass section and the outer surface of the annular section O-axis

Claims

1. A fastening member that is fastened to either the vibration receiving side or the vibration source side, A bracket having an insertion hole formed on one end for inserting the fastening member from the front side, and a press-fit hole formed on the other end, The bracket comprises a vibration-damping bush that is attached to the press-fit hole of the bracket, The aforementioned vibration-damping bushing is A cylindrical outer member that is pressed into the aforementioned press-fit hole, An inner member is positioned on the inner circumference side of the outer member and fixed to the other side of the vibration receiving side or the vibration source side, The system comprises an elastic body connecting the outer member and the inner member, The vibration isolation device is characterized in that the bracket comprises a mass portion integrally formed on the outer circumferential surface opposite to the insertion hole, with the press-fit hole in between.

2. The mass portion comprises a pair of side walls protruding from the outer circumferential surface of the bracket, and an end wall connecting the ends of the pair of side walls. The vibration isolation device according to claim 1, characterized in that a first weight-reducing hole is formed in the mass portion, surrounded by a pair of side walls and a front wall.

3. The mass portion is provided with a bottom wall that closes the first weight-reducing hole on the rear side of the bracket, The vibration isolation device according to claim 2, characterized in that the rear surface of the bottom wall is a plane perpendicular to the axial direction of the vibration isolation bush and is connected to the edge of the press-fit hole.

4. The bracket is provided with a plurality of second weight-reducing holes formed around the insertion hole, The vibration isolation device according to claim 3, characterized in that the second weight-reducing hole is not formed on the rear surface of the bracket.

5. The vibration isolation device according to claim 1, characterized in that the bracket is formed in an annular shape surrounding the press-fit hole and has an annular portion on which the mass portion is integrally formed on the outer circumferential surface.

6. A mounting structure for installing the vibration isolation device according to claim 5 between the vibration receiving side and the vibration source side, The mounting structure for a vibration isolation device is characterized in that the mass portion is positioned to overlap with the inner member when viewed in the direction of load input from the vibration receiving side or the vibration source side.

7. The mounting structure for the vibration isolation device according to claim 6, characterized in that the boundary between the end of the mass portion in the circumferential direction of the annular portion and the outer surface of the annular portion is positioned to overlap with the inner member when viewed in the direction of the load input.

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