Dynamic damper

Abstract

To provide a dynamic damper that can suppress the generation of abnormal noise while suppressing a decrease in vibration damping performance. [Solution] The elastic body 5 is provided with a lower projection 52 that protrudes from the side surface 60 of the mass 6 facing left and right toward the fastening portion 40. Therefore, if the mass 6 vibrates excessively, the lower projection 52 of the elastic body 5 can come into contact with the fastening portion 40. This suppresses the generation of abnormal noise due to contact between the fastening portion 40 and the mass 6. Furthermore, since the lower projection 52 is formed in a position that does not overlap with the insertion hole 40a of the bolt 2 when viewed in the vertical direction, even if the mass 6 vibrates excessively, it is possible to suppress contact between the lower projection 52 and the bolt 2. Therefore, loosening of the bolt 2 due to such contact can be suppressed, and the bracket 4 can be stably attached to the mounting member 100. Thus, a decrease in the vibration damping performance of the dynamic damper 1 can be suppressed.

Description

Technical Field

[0001] The present invention relates to a dynamic damper, and particularly to a dynamic damper that can suppress the generation of abnormal noise while suppressing a decrease in vibration damping performance.

Background Art

[0002] For example, Patent Document 1 describes a dynamic damper 10 including a mounting member 12 (bracket) attached to a vibration damping target member 60 by a bolt 24, and a mass body 14 connected to the mounting member 12 via a connecting rubber elastic body 16. A stopper rubber 50 is fixed to the lower surface of a mass mounting member 32 attached to the mass body 14, and a buffer projection 56 is provided on the stopper rubber 50. When the mass body 14 is displaced (vibrated), the mass mounting member 32 contacts the head of the bolt 24 via the buffer projection 56, so that abnormal noise generated at the time of contact can be reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a configuration in which the buffer projection 56 contacts the head of the bolt 24 when the mass body 14 is displaced as in the above-described conventional technology, the bolt 24 is likely to loosen due to repeated contact. When such loosening of the bolt 24 occurs, there is a problem that the vibration damping performance of the dynamic damper 10 cannot be sufficiently exhibited.

[0005] The present invention has been made to solve the above-described problems, and an object thereof is to provide a dynamic damper that can suppress the generation of abnormal noise while suppressing a decrease in vibration damping performance. [Means for solving the problem]

[0006] To achieve this objective, the dynamic damper of the present invention comprises a fastening member fastened to the vibration source side, a bracket having a fastening portion in which an insertion hole for inserting the fastening member is formed, and a pair of connecting portions rising from both sides in a first direction of the fastening portion, a mass disposed between the pair of connecting portions of the bracket and facing the fastening portion in a second direction perpendicular to the first direction, and an elastic body covering portions on both sides of the mass in the first direction, wherein the elastic body comprises a leg portion connecting the surface of the mass facing the first direction and the connecting portion, and a first convex portion projecting from the surface of the mass facing the first direction toward the fastening portion, the first convex portion being formed in a position that does not overlap with the insertion hole in the second direction view. [Effects of the Invention]

[0007] According to the dynamic damper described in claim 1, the elastic body includes a leg portion that connects the surface of the mass facing a first direction (the direction in which the bracket's connecting portion and the mass face each other; hereinafter referred to as the "left-right direction") to the connecting portion, and a first protrusion that projects from the surface of the mass facing the left-right direction toward the fastening portion. Therefore, if the mass vibrates excessively, the first protrusion of the elastic body can be brought into contact with the fastening portion of the bracket. This has the effect of suppressing the generation of abnormal noise caused by contact between the fastening portion and the mass.

[0008] Furthermore, since the first protrusion is formed in a position that does not overlap with the insertion hole when viewed in the second direction (the direction in which the fastening portion of the bracket and the mass face each other; hereinafter referred to as the "up and down direction"), even if the mass vibrates excessively, it is possible to suppress contact between the first protrusion and the fastening member inserted into the insertion hole. Therefore, loosening of the fastening member due to such contact can be suppressed, and the bracket can be stably attached to the vibration source side. Thus, there is an effect of suppressing a decrease in the vibration damping performance of the dynamic damper.

[0009] According to the dynamic damper of claim 2, in addition to the effects of the dynamic damper of claim 1, the thickness of the first protrusion in the left-right direction gradually increases as it approaches the fastening portion, so that the impact when the fastening portion and the first protrusion come into contact can be effectively mitigated. Therefore, there is an effect of reducing the abnormal noise generated when such contact occurs.

[0010] The dynamic damper according to claim 3 provides the following effects in addition to the effects of the dynamic damper according to claim 2. The bracket has a facing portion that rises from the end of the fastening portion in a third direction (hereinafter referred to as the "front-rear direction") perpendicular to the first and second directions and faces the mass. Since the first protrusion is formed in a position that does not overlap with the facing portion when viewed in the front-rear direction, even when the mold for vulcanizing the first protrusion (elastic body) is demolded in the front-rear direction, it is possible to suppress the occurrence of undercuts between the mass and the facing portion. Therefore, there is an effect of simplifying the mold used when forming the first protrusion.

[0011] The dynamic damper according to claim 4 provides the following effects in addition to the effects of the dynamic damper according to claim 3. The thickness of the first protrusion in the left-right direction increases as it approaches the fastening portion, so that the distance between the first protrusion and the connecting portion gradually narrows. This makes it possible to form the first protrusion in a position that does not overlap with the opposing portion in the front-rear direction, while gradually increasing the thickness of the first protrusion as it approaches the fastening portion. Therefore, it is possible to simplify the mold used when forming the first protrusion, while also reducing the noise generated when the fastening portion and the first protrusion come into contact.

[0012] According to the dynamic damper of claim 5, in addition to the effects of the dynamic damper of claim 1, the elastic body has a second protrusion that protrudes from the surface of the mass facing left and right on the opposite side from the first protrusion, so that the center of gravity of the mass including the elastic body (first and second protrusions) does not become biased toward the first protrusion. Therefore, it is possible to make it easier to give the dynamic damper a desired frequency characteristic. Furthermore, if there is another mating part on the opposite side from the first protrusion, the second protrusion can suppress contact between that mating part and the mass, so that it is possible to suppress the generation of abnormal noise caused by such contact.

[0013] The dynamic damper according to claim 6 provides the following effects in addition to those of the dynamic damper according to claim 5. The elastic body covers the surfaces of both masses in the front-rear direction and includes a third and a fourth protrusion that connect the first and second protrusions in the vertical direction. As a result, compared to, for example, the case where the first and second protrusions are divided vertically, when the first protrusion and the fastening part come into contact, the stress due to the deformation of the first protrusion is more easily distributed to the third and fourth protrusions. Therefore, the durability of the first protrusion can be improved.

[0014] The dynamic damper according to claim 7 provides the following effects in addition to those of the dynamic damper according to claim 6. The elastic body includes a covering portion that covers the surface of the mass facing left and right around the legs, and the first, second, third, and fourth protrusions are connected to the legs via the covering portion. As a result, even if deformation of the legs occurs due to vibration of the mass, or deformation of the first protrusion occurs due to contact with the fastening portion, the stress caused by that deformation is more easily distributed to each part of the elastic body. Therefore, the durability of the elastic body can be improved.

[0015] According to the dynamic damper of claim 8, in addition to the effects of the dynamic damper of claim 1, the first protrusion is provided with a plurality of projections formed on the end face facing the fastening portion, so that when the mass vibrates excessively, the first protrusion and the fastening portion do not come into surface contact with each other. Therefore, there is an effect of reducing the abnormal noise generated when the first protrusion and the fastening portion come into contact.

[0016] According to the dynamic damper of claim 9, in addition to the effects of the dynamic damper of claim 8, multiple projections extending in the front-rear direction are arranged along the left-right direction. Therefore, when the first projection vibrates so as to slide back and forth relative to the fastening portion, the projections extending along the sliding direction can come into contact with the fastening portion. This reduces the frictional resistance when the fastening portion and the projections come into contact, thus reducing the noise generated at the time of contact.

[0017] According to the dynamic damper of claim 10, in addition to the effects of the dynamic damper of claim 8, since multiple projections extending in the left-right direction are arranged along the front-rear direction, when the first projection vibrates in a way that it slides back and forth relative to the fastening portion, the projections extending in a direction perpendicular to the sliding direction can be brought into contact with the fastening portion. As a result, the projections are less likely to slide relative to the fastening portion, which has the effect of quickly dampening excessive vibrations of the mass. [Brief explanation of the drawing]

[0018] [Figure 1] This is a front perspective view of the dynamic damper in the first embodiment. [Figure 2] This is a cross-sectional view of the dynamic damper along line II-II in Figure 1. [Figure 3] (a) is a cross-sectional view of the dynamic damper along the line IIIa-IIIa in Figure 2, and (b) is a partially enlarged cross-sectional view of the dynamic damper along the line IIIb-IIIb in Figure 3(a). [Figure 4] (a) is a cross-sectional view of the dynamic damper of the second embodiment, and (b) is a partially enlarged cross-sectional view of the dynamic damper along the line IVb-IVb in Figure 4(a). [Figure 5] (a) is a partially enlarged cross-sectional view of the dynamic damper of the third embodiment, and (b) is a partially enlarged cross-sectional view of the dynamic damper of the fourth embodiment. [Modes for carrying out the invention]

[0019] Hereinafter, preferred embodiments will be described with reference to the accompanying drawings. First, referring to FIGS. 1 and 2, the overall configuration of the dynamic damper 1 in the first embodiment will be described. FIG. 1 is a front perspective view of the dynamic damper 1 in the first embodiment, and FIG. 2 is a cross-sectional view of the dynamic damper 1 taken along line II-II in FIG. 1.

[0020] In addition, the arrow directions U-D, F-B, and L-R in FIGS. 1 and 2 indicate the vertical direction, the front-rear direction, and the left-right direction of the dynamic damper 1, respectively (the same applies to the subsequent figures). However, the directions of the dynamic damper 1 do not necessarily coincide with the directions of the vehicle to which the dynamic damper 1 is attached.

[0021] As shown in FIGS. 1 and 2, the dynamic damper 1 is a backdoor damper attached to a metal mounting member 100 (a bracket on the vehicle body side) provided on the backdoor of the vehicle. The dynamic damper 1 includes a bracket 4 attached to the mounting member 100 by bolts 2 and nuts 3.

[0022] The bracket 4 includes a flat plate-shaped fastening portion 40 extending in the left-right direction (arrow L-R direction) (the first direction), and a pair of flat plate-shaped connecting portions 41 rising from both left and right sides of the fastening portion 40. These portions �, 41 are integrally formed by bending a metal plate. In the fastening portion 40, a pair of insertion holes 40a (see FIG. 2) for inserting the bolts 2 are formed at intervals on the left and right. This pair of insertion holes 40a are formed at positions corresponding to the insertion holes 101 (see FIG. 2) formed in the mounting member 100. By fastening the nuts 3 to the bolts 2 inserted from the upper side into these insertion holes 40a, 101, the bracket 4 is attached to the mounting member 100.

[0023] An elastic body 5 made of rubber or thermoplastic elastomer is vulcanized and bonded to the inner surfaces (surfaces facing inward in the left-right direction) of a pair of left and right connecting parts 41, and a metal mass 6 (mass body) is supported between the opposing connecting parts 41 by this elastic body 5. The mass 6 is formed in the shape of a rectangular parallelepiped, with its left-right dimension being longer than its dimensions in the up-down direction (arrow UD direction) (second direction) and the front-back direction (arrow FB direction) (third direction), and the elastic body 5 is vulcanized and bonded to the left and right side surfaces 60 (surfaces facing outward in the left-right direction) of this mass 6. The pair of left and right elastic bodies 5 have a plane symmetrical (mirror image) shape with respect to a plane perpendicular to the left-right direction as the plane of symmetry.

[0024] The elastic body 5 comprises leg portions 50 that connect the connecting portion 41 of the bracket 4 to the left and right side surfaces 60 of the mass 6, and a covering portion 51 that extends around the leg portions 50 (the entire circumference of the outer surface) and covers the side surfaces 60 of the mass 6. The vibration of the mass 6, which is elastically supported by the leg portions 50, reduces harmful vibrations of the back door.

[0025] On the other hand, since the fastening portion 40 of the mass 6 and the bracket 4 face each other vertically, excessive vibration of the mass 6 may cause abnormal noise due to contact between the fastening portion 40 and the mass 6. In particular, since the dynamic damper 1 of this embodiment is attached to the back door, the mass 6 is more likely to come into contact with the bracket 4 when the back door is closed forcefully.

[0026] In order to prevent contact between the fastening portion 40 and the mass 6, configurations such as making the leg portion 50 thicker or increasing the hardness of the leg portion 50 (elastic body 5) would make it difficult to give the dynamic damper 1 the desired frequency characteristics. Therefore, in this embodiment, a configuration is adopted in which contact between the fastening portion 40 and the mass 6 is prevented by the lower convex portion 52 (first convex portion) of the elastic body 5.

[0027] The lower projection 52 is a projection that protrudes from the side surface 60 of the mass 6 toward the fastening portion 40 (downward). By making this lower projection 52 protrude below the lower surface 61 (the surface facing downward) of the mass 6, for example, if the back door is closed forcefully and the mass 6 vibrates excessively, the lower projection 52 of the elastic body 5, rather than the mass 6, can come into contact with the fastening portion 40. Therefore, the abnormal noise generated when they come into contact can be reduced.

[0028] The lower protrusion 52 is formed in a position that does not overlap with the bolt insertion hole 40a (see Figure 2) when viewed in the vertical direction (direction of arrow UD) of the dynamic damper 1. Therefore, even if the mass 6 vibrates excessively, contact between the lower protrusion 52 and the head of the bolt 2 can be suppressed. Thus, loosening of the bolt 2 due to such contact can be suppressed, and the bracket 4 can be stably attached to the mounting member 100 (back door). Therefore, a decrease in the vibration damping performance of the dynamic damper 1 can be suppressed.

[0029] A semicircular projection 52b is integrally formed on the lower surface 52a of the lower protrusion 52 (see enlarged portion in Figure 2). Since multiple projections 52b are formed on the lower surface 52a of the lower protrusion 52, it is possible to suppress surface-to-surface contact between the fastening portion 40 and the lower surface 52a of the lower protrusion 52 when the mass 6 vibrates excessively. As a result, compared to, for example, the case where the lower surface 52a of the lower protrusion 52 is a flat surface, the abnormal noise generated when the fastening portion 40 and the lower protrusion 52 come into contact can be reduced.

[0030] Thus, when the objective is to suppress contact between the fastening portion 40 and the mass 6 by the lower protrusion 52, it is possible to form the lower protrusion 52 only on the fastening portion 40 side. However, the elastic body 5 of this embodiment is equipped with an upper protrusion 53 (second protrusion) formed on the upper part of the side surface 60 of the mass 6. The upper protrusion 53 is a projection that protrudes from the side surface 60 of the mass 6 on the side opposite to the lower protrusion 52 (fastening portion 40).

[0031] By forming a lower protrusion 52 and an upper protrusion 53 on both the upper and lower sides of the side 60 of the mass 6, it is possible to suppress the center of gravity of the mass 6, including the elastic body 5, from being biased towards the lower protrusion 52 side with respect to the axis of the leg portion 50 (i.e., the weight balance of the mass 6, including the elastic body 5, can be made uniform from top to bottom). Therefore, it is possible to make the dynamic damper 1 have the desired frequency characteristics. In addition, by forming an upper protrusion 53 on the upper part of the side 60 of the mass 6, if there is another mating part (another part assembled to the vehicle) above the mass 6, the upper protrusion 53 can be made to contact the mating part when the mass 6 vibrates excessively. Therefore, the abnormal noise generated when that contact occurs can be reduced.

[0032] As described above, the lower convex portion 52 has a projection 52b (see enlarged portion in Figure 2), but the upper surface of the upper convex portion 53 does not have a projection 52b like the lower convex portion 52. Except for the fact that this projection 52b is not formed on the upper convex portion 53, the lower convex portion 52 and the upper convex portion 53 (elastic body 5) have a plane symmetrical (mirror image) shape with respect to a plane perpendicular to the vertical direction. This makes it possible to make the weight balance of the mass 6 including the elastic body 5 uniform from top to bottom, making it easier to give the dynamic damper 1 the desired frequency characteristics.

[0033] The left and right ends of the lower surface 61 (see Figure 2) of the mass 6 are covered by the lower protrusions 52, and the left and right ends of the upper surface 62 of the mass 6 are also covered by the upper protrusions 53. Furthermore, the lower protrusions 52 and upper protrusions 53 extend in the front-to-back direction and protrude from the front surface 63 (see Figure 1) and rear surface 64 of the mass 6, respectively, and these protruding portions are connected by the front protrusions 54 and rear protrusions 55 (both see Figure 1).

[0034] The front protrusion 54 (third protrusion) covers both the left and right ends of the front surface 63 of the mass 6, and although not shown in the illustration, the rear protrusion 55 (fourth protrusion) similarly covers both the left and right ends of the rear surface 64 of the mass 6. As a result, if there is another mating part (another part to be assembled to the vehicle) on the front or rear side of the mass 6, for example, contact between the mating part and the mass 6 can be suppressed by the front protrusion 54 and the rear protrusion 55.

[0035] The front protrusion 54 and the rear protrusion 55 extend vertically, respectively, connecting the lower protrusion 52 and the upper protrusion 53 to each other, and the entire circumference of the outer edge (4 sides) of the side surface 60 of the mass 6 is covered by the respective protrusions 52 to 55.

[0036] Here, for example, it is also possible to omit the front protrusion 54 and the rear protrusion 55 and expose the front surface 63 of the mass 6 between the lower protrusion 52 and the upper protrusion 53 (dividing the lower protrusion 52 and the upper protrusion 53 into upper and lower parts). However, in such a configuration, when the lower protrusion 52 comes into contact with the fastening part 40, the stress due to the deformation of the lower protrusion 52 tends to concentrate at the boundary between the lower protrusion 52 and the front surface 63 of the mass 6. Therefore, the lower protrusion 52 tends to peel off from the mass 6.

[0037] In contrast, in this embodiment, the lower protrusion 52 and the upper protrusion 53 are connected by the front protrusion 54 and the rear protrusion 55. Therefore, even if the lower protrusion 52 deforms due to contact with the fastening portion 40, stress concentration at the boundary between the lower protrusion 52 and the front surface 63 of the mass 6 can be suppressed. That is, the stress caused by the deformation of the lower protrusion 52 is more easily distributed to the front protrusion 54 and the rear protrusion 55, thereby improving the durability of the lower protrusion 52 (it is possible to suppress the lower protrusion 52 from peeling off the mass 6).

[0038] Furthermore, in this embodiment, the leg portion 50 is connected to each of the protrusions 52-55 via the covering portion 51. However, it is also possible to omit a portion of the covering portion 51 located between the leg portion 50 and each of the protrusions 52-55, and expose a portion of the side surface 60 of the mass 6 around the leg portion 50. However, in a configuration where the side surface 60 of the mass 6 is exposed around the leg portion 50, stress due to the deformation of the leg portion 50 tends to concentrate at the boundary between the side surface 60 of the mass 6 and the leg portion 50 when the mass 6 vibrates. Therefore, the leg portion 50 tends to peel off from the mass 6.

[0039] In particular, in a configuration in which the covering portion 51 connecting the leg portion 50 and the lower protrusion portion 52 is omitted, when the lower protrusion portion 52 comes into contact with the fastening portion 40, the stress due to the deformation of the lower protrusion portion 52 tends to concentrate at the boundary between the lower protrusion portion 52 and the side surface 60 of the mass 6. Therefore, not only is the leg portion 50 more likely to peel off from the mass 6 as described above, but the lower protrusion portion 52 is also more likely to peel off.

[0040] In contrast, in this embodiment, since each of the protrusions 52 to 55 of the elastic body 5 is connected to the leg portion 50 via the covering portion 51, even if deformation of the leg portion 50 occurs due to vibration of the mass 6, or deformation of the lower protrusion 52 occurs due to contact with the fastening portion 40, the stress caused by such deformation is easily distributed to each of the parts 51 to 55 of the elastic body 5 via the covering portion 51. Therefore, it is possible to suppress the concentration of stress caused by such deformation in a part of the elastic body 5, thereby improving the durability of the elastic body 5.

[0041] In the enlarged portion of Figure 2, a virtual line V1 is shown extending outward in the left-right direction from the lower surface 61 of the mass 6. This virtual line V1 indicates the boundary between the covering portion 51 and the lower protrusion 52. That is, the area above the virtual line V1 is the covering portion 51, and the area below it is the lower protrusion 52.

[0042] Of the sides of the covering portion 51 facing outward in the left-right direction, the side 51a that connects the leg portion 50 and the lower protrusion 52 vertically is inclined so as it moves downward, it moves away from the side 60 of the mass 6. That is, the thickness of the covering portion 51 located between the leg portion 50 and the lower protrusion 52 gradually increases in the left-right direction as it approaches the fastening portion 40.

[0043] A side surface 52c facing outward in the left-right direction (arrow L in the enlarged portion of Figure 2) of the lower protrusion 52 is connected to the lower end of the side surface 51a of the covering portion 51. This side surface 52c is composed of an inclined surface 520c that is connected to the side surface 51a of the covering portion 51, and a flat surface 521c that is connected to the lower end of the inclined surface 520c. The inclined surface 520c is a flat surface that is inclined at the same angle as the side surface 51a of the covering portion 51, and the flat surface 521c is a flat surface that is perpendicular to the left-right direction.

[0044] Furthermore, the side surface 52d of the lower protrusion 52 facing inward in the left-right direction (towards arrow R in the enlarged portion of Figure 2) is a plane extending downward (vertically) from the lower surface 61 of the mass 6, and each side surface 52c, 52d (plane 521c) of the lower protrusion 52 is connected to the lower surface 52a of the lower protrusion 52 via a smooth curved surface 52e.

[0045] Specifically, in the region where the inclined surface 520c of the lower protrusion 52 is formed, the thickness of the lower protrusion 52 in the left-right direction gradually increases as it approaches the fastening portion 40. This allows for a reduction in the amount of rubber in the lower protrusion 52 on the leg portion 50 side (the amount of rubber in the covering portion 51 connecting the leg portion 50 and the lower protrusion 52) while ensuring a larger amount of rubber in the lower protrusion 52 on the fastening portion 40 side. Reducing the amount of rubber in the lower protrusion 52 (covering portion 51) on the leg portion 50 side suppresses the impact on the spring characteristics of the leg portion 50, making it easier to give the dynamic damper 1 the desired frequency characteristics. Furthermore, by ensuring sufficient rubber in the lower protrusion 52 on the fastening portion 40 side, the impact during contact between the fastening portion 40 and the lower protrusion 52 can be effectively mitigated, thereby reducing the abnormal noise generated during contact.

[0046] As shown in Figure 1, the elastic body 5 has notches 56 formed by cutting out a portion of the covering portion 51 and the front protrusion portion 54. The notches 56 are formed in pairs, spaced apart vertically, and when the elastic body 5 is vulcanized (molded) in a mold, the side surface 60 of the mass 6 exposed through the notches 56 is clamped by the mold. The configuration of the dynamic damper 1 related to this vulcanization molding will be explained with reference to Figures 2 and 3.

[0047] Figure 3(a) is a cross-sectional view of the dynamic damper 1 along the line IIIa-IIIa in Figure 2, and Figure 3(b) is a partially enlarged cross-sectional view of the dynamic damper 1 along the line IIIb-IIIb in Figure 3(a). Note that the imaginary line V2 shown in Figure 3(a) is an imaginary line indicating the split surface of the mold (for example, one comprising an upper mold and a lower mold) when vulcanizing the elastic body 5.

[0048] As shown in Figures 2 and 3, a flat, facing portion 42 is integrally formed on the fastening portion 40 of the bracket 4. The facing portion 42 rises from the rear end of the fastening portion 40 (the end on the side of arrow B) and faces the rear surface 64 of the mass 6 (see Figure 3(b)).

[0049] The lower surface 52a of the lower protrusion 52 is composed of a first inclined surface 520a and a second inclined surface 521a formed with the imaginary line V2 as the boundary. The first inclined surface 520a is inclined so as to move away from the fastening portion 40 as it moves forward from the imaginary line V2 (towards arrow F), and the second inclined surface 521a is inclined so as to move away from the fastening portion 40 as it moves backward from the imaginary line V2 (towards arrow B). These inclined surfaces 520a and 521a form a draft angle for the mold on the lower surface 52a of the lower protrusion 52.

[0050] Furthermore, the side surface 52c of the lower protrusion 52, the upper surface 53a and side surface 53b of the upper protrusion 53 (see Figure 3(a)), and the side surface 51a of the covering portion 51 are also provided with the same draft angle as the lower surface 52a of the lower protrusion 52. In other words, the dynamic damper 1 is formed by demolding the elastic body 5 in the front-rear direction (arrow FB direction) after vulcanization molding.

[0051] Therefore, if, for example, a lower protrusion 52 (elastic body 5) is formed at a position that overlaps with the opposing portion 42 when viewed in the front-to-back direction, the mold for vulcanizing the elastic body 5 becomes more complex. In particular, if the portion of the rear surface 64 of the mass 6 that faces the opposing portion 42 is covered by the elastic body 5, the elastic body 5 will be undercut in the direction of mold removal during vulcanization molding, making it difficult to mold the elastic body 5.

[0052] In contrast, in this embodiment, the elastic body 5 (lower protrusion 52) is not provided in the region where the opposing portion 42 and the mass 6 overlap in a front-to-back view, and the rear surface 64 of the mass 6 is exposed in that region. In other words, the lower protrusion 52 is formed in a position that does not overlap with the opposing portion 42 in a front-to-back view, and a gap S (see enlarged portion in Figure 2) is formed between the opposing portion 42 and the lower protrusion 52 in that view. With this configuration, it is possible to suppress undercuts in the demolding direction when the elastic body 5 is vulcanized. Therefore, the structure of the mold for vulcanizing the elastic body 5 can be simplified, and the manufacturing cost (mold cost) of the dynamic damper 1 can be reduced.

[0053] Furthermore, as described above, the thickness of the lower protrusion 52 in the left-right direction gradually increases as it approaches the fastening portion 40 (see Figure 2). However, the thickness of this lower protrusion 52 increases as it approaches the fastening portion 40, narrowing the gap between the connecting portion 41 and the lower protrusion 52. This allows for the formation of a gap S between the lower protrusion 52 and the opposing portion 42 (see enlarged portion of Figure 2), while increasing the amount of rubber in the lower protrusion 52 toward the fastening portion 40. Thus, the structure of the mold for vulcanizing the elastic body 5 can be simplified, and the abnormal noise generated when the fastening portion 40 and the lower protrusion 52 come into contact can be reduced.

[0054] Furthermore, as shown in Figure 3, the projection 52b formed on the lower surface 52a of the lower convex portion 52 extends in the front-rear direction, and this projection 52b is also provided with the same draft angle as the lower surface 52a of the lower convex portion 52. By extending the projection 52b in the same direction as the mold release direction during vulcanization molding of the elastic body 5, it is possible to suppress the projection 52b from being forcibly removed, thereby improving the release properties of the elastic body 5.

[0055] Here, if excessive vibration is input to the dynamic damper 1, for example, when the back door is closed forcefully, the vibration of the mass 6 may not only be a displacement along the vertical direction, but also a displacement in which the mass 6 rotates due to the twisting of the elastic body 5 (see arrow A in Figure 3(a)), or a displacement in which the mass 6 moves linearly toward the front and downward (see arrow B in Figure 3(a)). In other words, the lower protrusion 52 may be displaced so as to slide back and forth relative to the fastening portion 40.

[0056] In contrast, in this embodiment, since multiple projections 52b extending in the front-rear direction are arranged side by side in the left-right direction (in this embodiment, at three locations), when the lower projection 52 slides back and forth relative to the fastening portion 40 as described above, the projections 52b extending in the sliding direction can come into contact with the fastening portion 40. This reduces the frictional resistance when the fastening portion 40 and the projections 52b come into contact, thereby reducing the abnormal noise generated by such contact.

[0057] Next, the dynamic damper 201 of the second embodiment will be described with reference to Figure 4. Note that parts identical to those of the first embodiment described above are denoted by the same reference numerals, and their descriptions are omitted. Figure 4(a) is a cross-sectional view of the dynamic damper 201 of the second embodiment, and Figure 4(b) is a partially enlarged cross-sectional view of the dynamic damper 201 along the line IVb-IVb in Figure 4(a). Note that Figure 4(a) is a cross-sectional view corresponding to Figure 3(a).

[0058] As shown in Figure 4, the dynamic damper 201 of the second embodiment is equipped with a plurality of protrusions 252b formed on the lower surface 52a of the lower protrusion 52, so that when the mass 6 vibrates excessively, the lower surface 52a of the lower protrusion 52 and the upper surface of the fastening portion 40 do not come into surface contact with each other. Therefore, the abnormal noise generated when the lower protrusion 52 and the fastening portion 40 come into contact can be reduced.

[0059] The projections 252b are formed to extend in the left-right direction (arrows LR direction) and are also arranged in multiples (16 locations in this embodiment) in the front-back direction (arrows FB direction). Therefore, as shown by arrows A and B in Figure 4(a), when the lower projection 52 of the bracket 4 slides back and forth relative to the fastening portion 40, the projections 252b extending in a direction perpendicular to the sliding direction can come into contact with the fastening portion 40. This makes it difficult for the projections 252b to slide relative to the fastening portion 40, and the vibration energy of the mass 6 is more easily absorbed by the contact between the fastening portion 40 and the projections 252b, thus allowing excessive vibrations of the mass 6 to subside quickly.

[0060] Next, the dynamic dampers 301 and 401 of the third and fourth embodiments will be described with reference to Figure 5. Figure 5(a) is a partially enlarged cross-sectional view of the dynamic damper 301 of the third embodiment, and Figure 5(b) is a partially enlarged cross-sectional view of the dynamic damper 401 of the fourth embodiment. Note that Figures 5(a) and 5(b) are cross-sectional views corresponding to Figure 4(b), respectively.

[0061] As shown in Figure 5, in the dynamic dampers 301 and 401 of the third and fourth embodiments, multiple protrusions 352b and 452b are formed on the lower surface 52a of the lower protrusion 52. This prevents the lower surface 52a of the lower protrusion 52 from coming into surface contact with the upper surface of the fastening portion 40 of the bracket 4 (see Figure 4(a)) when the mass 6 vibrates excessively. Therefore, it is possible to reduce the abnormal noise generated when the lower protrusion 52 and the fastening portion 40 come into contact.

[0062] Furthermore, the projection 352b of the third embodiment (see Figure 5(a)) is formed to extend in a direction that is inclined with respect to both the front-rear, left-right, and right directions (arrows FB direction and arrows LR direction), and is provided in multiples (16 locations in this embodiment) in the front-rear direction. As a result, when the lower projection 52 is displaced so as to slide diagonally relative to the fastening portion 40 (see Figure 4(a)), the same effect as the projections 52b and 252b of the first and second embodiments can be obtained.

[0063] Furthermore, the projection 452b of the fourth embodiment (see Figure 5(b)) is a projection formed in a circular shape when viewed from below, and such projections 452b (textures) with no directionality are uniformly formed (distributed) over substantially the entire lower surface 52a of the lower convex portion 52. As a result, even if the lower convex portion 52 is displaced to slide relative to the fastening portion 40 (see Figure 4(a)) in any direction, the projection 252b will not easily slide relative to the fastening portion 40.

[0064] 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.

[0065] In the embodiments described above, the dynamic dampers 1,201,301,401 were described as being attached to the vehicle's tailgate, but the dynamic dampers 1,201,301,401 may also be attached to other parts of the vehicle that are subject to vibration damping (such as the vehicle frame or other doors).

[0066] In the embodiments described above, the case in which the thickness of the lower protrusion 52 in the left-right direction gradually increases as it approaches the fastening portion 40 has been explained, but this is not necessarily the only case. For example, the thickness of the lower protrusion 52 may gradually decrease as it approaches the fastening portion 40, or the thickness of the lower protrusion 52 may be substantially constant from the upper end to the lower end.

[0067] In the embodiments described above, a facing portion 42 that faces the mass 6 is formed on the bracket 4, and a lower protrusion 52 is formed at a position that does not overlap with the facing portion 42 when viewed in the front-rear direction. However, the invention is not limited to these cases. For example, the lower protrusion 52 (rear protrusion 55) may be formed at a position that overlaps with the facing portion 42 when viewed in the front-rear direction, or the facing portion 42 of the bracket 4 may be omitted.

[0068] In the embodiments described above, the upper protrusion 53 projecting above the mass 6 is formed symmetrically with the lower protrusion 52, but this is not necessarily the only case. For example, the lower protrusion 52 and the upper protrusion 53 may have asymmetrical shapes, or the upper protrusion 53 may be omitted.

[0069] In the embodiments described above, the case in which the lower protrusion 52 and the upper protrusion 53 are connected vertically by the front protrusion 54 and the rear protrusion 55 has been explained. However, either or both of the front protrusion 54 and the rear protrusion 55 may be omitted, and the lower protrusion 52 and the upper protrusion 53 may be divided vertically.

[0070] In the embodiments described above, the cases in which the lower protrusion 52, upper protrusion 53, front protrusion 54, and rear protrusion 55 are connected to the leg portion 50 via the covering portion 51 have been explained, but the invention is not limited to this. For example, part or all of the covering portion 51 may be omitted, and part or all of the protrusions 52 to 55 may be separated from the leg portion 50.

[0071] In the embodiments described above, the cases in which protrusions 52b, 252b, 352b, and 452b are formed on the lower surface 52a of the lower protrusion 52 have been explained. However, the protrusions 52b, 252b, 352b, and 452b of the lower protrusion 52 may be omitted, or protrusions 52b, 252b, 352b, and 452b similar to those of the lower protrusion 52 may be formed on any or all of the upper protrusion 53, front protrusion 54, and rear protrusion 55. [Explanation of symbols]

[0072] 1,201,301,401 Dynamic Damper 2 bolts (fastening members) 4 brackets 40 Fastening part 40a Insertion hole 41 Connecting part 42 Face-to-face section 5 Elastic body 50 Legs 51 Covering part 52 Lower protrusion (first protrusion) 52b,252b,352b,452b protrusion 53 Upper convex portion (second convex portion) 54 Front protrusion (third protrusion) 55 Rear convex portion (fourth convex portion) 6 squares

Claims

1. A fastening member fastened to the vibration source side, A bracket having a fastening portion in which an insertion hole for inserting the fastening member is formed, and a pair of connecting portions rising from both sides in a first direction of the fastening portion, A mass is positioned between the pair of connecting portions of the bracket and facing the fastening portion in a second direction perpendicular to the first direction, The mass comprises an elastic body covering portions on both sides in the first direction, The elastic body comprises a leg portion connecting the surface of the mass facing the first direction to the connecting portion, and a first protrusion projecting from the surface of the mass facing the first direction toward the fastening portion. The dynamic damper is characterized in that the first protrusion is formed in a position that does not overlap with the insertion hole when viewed from the second direction.

2. The dynamic damper according to claim 1, characterized in that the thickness of the first protrusion in the first direction gradually increases as it approaches the fastening portion.

3. The bracket rises from the end of the fastening portion in a third direction perpendicular to the first and second directions, and has a facing portion that faces the mass. The dynamic damper according to claim 2, characterized in that the first protrusion is formed in a position that does not overlap with the opposing portion in the third viewing direction.

4. The dynamic damper according to claim 3, characterized in that the thickness of the first protrusion in the first direction increases such that the distance between the mass and the connecting portion gradually narrows as it approaches the fastening portion.

5. The dynamic damper according to claim 1, characterized in that the elastic body has a second protrusion that protrudes from the surface of the mass facing the first direction on the side opposite to the first protrusion.

6. The dynamic damper according to claim 5, characterized in that the elastic body covers the surfaces of the mass on both sides in a third direction perpendicular to the first and second directions, and comprises a third and fourth protrusion connecting the first and second protrusions in the second direction.

7. The elastic body includes a covering portion that covers the surface of the mass facing the first direction around the leg portion, The dynamic damper according to claim 6, characterized in that the first protrusion, the second protrusion, the third protrusion, and the fourth protrusion are connected to the leg portion via the covering portion.

8. The dynamic damper according to claim 1, characterized in that the first protrusion comprises a plurality of projections formed on the end face facing the fastening portion.

9. The projection extends in a third direction perpendicular to the first and second directions, The dynamic damper according to claim 8, characterized in that a plurality of the protrusions are arranged along the first direction.

10. The projection extends in the first direction, The dynamic damper according to claim 8, characterized in that a plurality of the protrusions are arranged along a third direction perpendicular to the first and second directions.

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