Dynamic damper

Abstract

To provide a dynamic damper which can sufficiently reduce vibration in a predetermined frequency band.SOLUTION: A dynamic damper 10 includes an outer cylinder 11, a mass member 12 which is provided spaced apart from the outer cylinder 11 at a position which is located at the inner side of the outer cylinder 11 and through which a center axis 17 of the outer cylinder 11 passes; and rubber members 13 connecting the outer cylinder 11 with the mass member 12. In the dynamic damper 10, the number, which is three or larger and an odd number, of the rubber members 13 are provided arranged at an equal interval in a direction around the center axis 17.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a dynamic damper. [Background technology]

[0002] Dynamic dampers that are attached to a rotating body are known as devices for reducing vibrations of a rotating body such as a vehicle wheel. The dynamic damper includes an outer cylinder that is attached to the rotating body, a mass member that is disposed inside the outer cylinder, and a member that connects the outer cylinder and the mass member. When the rotating body vibrates, the mass member vibrates relative to the outer cylinder, thereby reducing the vibrations of the rotating body.

[0003] Dynamic dampers are designed to reduce vibrations in a specific frequency band, but the direction in which they can reduce vibrations in that frequency band is fixed. For example, the dynamic damper in Patent Document 1 includes a ring-shaped member (outer cylinder), a weight (mass member) disposed inside the ring-shaped member, and a spring element disposed between the ring-shaped member and the weight. Such a dynamic damper can reduce vibrations in a specific frequency band only when the arrangement of the spring element and the weight meets a specific condition, for example, only once when the spring element is above the weight, or only twice when the spring element is above and below the weight. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-17356 A Summary of the Invention [Problem to be solved by the invention]

[0005] When a conventional dynamic damper such as the one described above is fixed to a rotating body and rotates together with the rotating body, the dynamic damper can reduce vibrations in a predetermined frequency band only when the arrangement of the spring elements and weights satisfies certain conditions, for example, only once or twice per rotation of the rotating body. Therefore, the conventional dynamic damper was not able to sufficiently reduce the vibrations of the rotating body.

[0006] In addition, many conventional dynamic dampers have a structure with two-fold rotational symmetry, with spring elements provided on both sides of the weight, but such dynamic dampers can only reduce vibrations in a given frequency band twice per rotation, and therefore cannot sufficiently reduce vibrations in a rotating body.

[0007] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a dynamic damper that can sufficiently reduce vibrations in a predetermined frequency band. [Means for solving the problem]

[0008] The present invention includes the embodiments set forth below.

[0009] [1] A dynamic damper comprising an outer tube, a mass member disposed inside the outer tube and separated from the outer tube at a location through which the central axis of the outer tube passes, and an elastic body connecting the outer tube and the mass member, wherein an odd number of the elastic bodies, three or more in number, are arranged at equal intervals in a direction around the central axis.

[0010] [2] The dynamic damper described in [1], wherein all of the elastic bodies have the same shape.

[0011] [3] A dynamic damper as described in [1] or [2], wherein, when viewed from the extension direction of the central axis, the ratio of the area occupied by the elastic body to the area between the outer tube and the mass member is 10% or more and 70% or less.

[0012] [4] The dynamic damper according to any one of [1] to [3], wherein a stress is applied to the outer cylinder in a direction toward the central axis.

[0013] [5] The dynamic damper described in [4], in which the stress is applied to the outer tube by drawing the outer tube.

[0014] [6] A dynamic damper described in any one of [1] to [5], wherein a buffer member fixed to the outer tube and spaced apart from the mass member is provided between adjacent elastic bodies inside the outer tube.

[0015] [7] The dynamic damper described in [6], wherein the cushioning member is provided at the midpoint between the adjacent elastic bodies in every location where two of the elastic bodies are adjacent to each other.

[0016] [8] A dynamic damper as described in [6] or [7], wherein a plurality of the buffer members are arranged at positions that are rotationally symmetric with respect to the central axis.

[0017] [9] The dynamic damper described in any one of [6] to [8], wherein the buffer member has a shape tapered toward the central axis. Effect of the Invention

[0018] The dynamic damper of the above embodiment can sufficiently reduce vibrations in a predetermined frequency band. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a view of the dynamic damper of the first embodiment as viewed from the central axis direction. [Diagram 2] Cross-sectional view taken along line AA in Figure 1. [Diagram 3] FIG. 2 is a view of the dynamic damper of the first embodiment as viewed from the central axis direction. [Figure 4] A diagram explaining the drawing process. (a) is a diagram when the dynamic damper is placed in the center of the drawing die. (b) is a diagram when force is applied from the periphery of the drawing die. [Diagram 5] FIG. 13 is a diagram showing the rotation of a dynamic damper when the number of rubber members is two. [Figure 6] A diagram showing the rotation of a dynamic damper when the number of rubber members is four. [Figure 7] A diagram showing the rotation of a dynamic damper when the number of rubber members is three. [Figure 8] FIG. 13 is a graph showing the change in frequency of vibration reduced by the dynamic damper when the number of rubber members is four. [Figure 9] FIG. 13 is a graph showing the change in frequency of vibration reduced by the dynamic damper when the number of rubber members is three. [Figure 10] 1A is a diagram of a dynamic damper according to a second modified example of the first embodiment, viewed from the central axis direction, in which (a) is a diagram in which the outer cylinder and the mass member are triangular, (b) is a diagram in which the outer cylinder and the mass member are rectangular, and (c) is a diagram in which the outer cylinder is triangular and the mass member is circular. [Figure 11] FIG. 13 is a cross-sectional view taken along the central axis of a dynamic damper according to a fifth modified example of the first embodiment. [Figure 12] FIG. 11 is a view of the dynamic damper of the second embodiment as viewed from the central axis direction. [Figure 13] FIG. 11 is a view of a dynamic damper according to a second modified example of the second embodiment, as viewed from the central axis direction. [Figure 14] 13A and 13B are diagrams of a dynamic damper in which a buffer member is provided at the midpoint between adjacent rubber members in a third modification of the second embodiment, as viewed from the central axis direction. (a) is a diagram in which the outer cylinder and mass member are triangular, (b) is a diagram in which the outer cylinder and mass member are square, and (c) is a diagram in which the outer cylinder is triangular and the mass member is circular. [Figure 15] FIG. 11 is a view of a dynamic damper in a case where a buffer member is provided in a location where the mass member is likely to hit in the third modification of the second embodiment, as viewed from the central axis direction. [Figure 16] FIG. 11 is a view of a dynamic damper in a case where a buffer member is provided in a location where the mass member is likely to hit in the third modification of the second embodiment, as viewed from the central axis direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The following describes the first and second embodiments with reference to the drawings. Note that the embodiments described below are merely examples, and any appropriate modifications that do not depart from the spirit of the present invention are included in the scope of the present invention.

[0021] 1. Embodiment 1 As shown in Figures 1 and 2, the dynamic damper 10 of embodiment 1 comprises an outer tube 11, one mass member 12 provided inside the outer tube 11 and spaced apart from the outer tube 11, and a plurality of rubber members 13 connecting the outer tube 11 and the mass member 12.

[0022] The outer cylinder 11 is cylindrical, i.e., has a hole 14 in the center, and the mass member 12 is cylindrical with no hole (the hole is filled). The inner circumferential surface 15 and outer circumferential surface 16 of the outer cylinder 11 and the outer circumferential surface of the mass member 12 are shaped like right cylinders. The dynamic damper 10 rotates in the circumferential direction of the outer cylinder 11, with the central axis 17 of the outer cylinder 11 as the axis of rotation. The central axis 17 of the outer cylinder 11 coincides with the central axes of the inner circumferential surface 15 and outer circumferential surface 16.

[0023] In this specification, the extension direction of the central axis 17 of the outer cylinder 11 is referred to as the "central axis direction." The central axis direction is indicated by an arrow X in FIG.

[0024] The outer cylinder 11 has a predetermined rigidity and is made of, for example, a metal. The mass member 12 has a predetermined mass and is made of, for example, a metal. The rubber member 13 is connected to the outer cylinder 11 and the mass member 12 by vulcanization adhesion. Because the rubber member 13 is an elastic body, the mass member 12 can move relative to the outer cylinder 11.

[0025] The multiple rubber members 13 are arranged between the outer tube 11 and the mass member 12, at equal intervals in a direction around the central axis 17 of the outer tube 11 (this direction is indicated by arrow Y in FIG. 1). The multiple rubber members 13 are also arranged at positions that are rotationally symmetric with respect to the central axis 17 of the outer tube 11. The number of rubber members 13 arranged in the direction around the central axis 17 is an odd number equal to or greater than three, and is three in the case of FIG. 1.

[0026] The rubber member 13 is thick on the outer cylinder 11 side and thin on the mass member 12 side, and is approximately trapezoidal when viewed from the central axis direction in Fig. 1. Due to this shape, the cross-sectional area of ​​the rubber member 13 gradually decreases as it approaches the mass member 12. Here, the cross-sectional area refers to the area in a plane perpendicular to the direction in which the rubber member 13 extends from the outer cylinder 11 toward the mass member 12. All of the rubber members 13 provided in the dynamic damper 10 have the same shape and size. Furthermore, all of the rubber members 13 are provided in a direction that is thick on the outer cylinder 11 side and thin on the mass member 12 side.

[0027] The number of rubber members 13 is an odd number of 3 or more, but preferably not too many. Also, each rubber member 13 preferably has an appropriate thickness. When viewed from the extension direction of the central axis 17, the ratio of the area occupied by all of the rubber members 13 (the area shown by the portion shaded diagonally downward to the right in addition to the portion shaded diagonally downward to the left in FIG. 3) to the area between the outer tube 11 and the mass member 12 (the area shown by the portion shaded diagonally downward to the right in FIG. 3) is 10% or more and 70% or less.

[0028] Moreover, it is preferable that the outer tube 11 is subjected to a stress in a direction toward the central axis 17 of the outer tube 11 by the drawing process of the outer tube 11. The drawing process is a process for reducing the diameter of the outer tube 11. An example of the drawing process is shown in FIG. 4. In the method of FIG. 4, first, as shown in (a), the dynamic damper 10 is placed in the center of a drawing die consisting of a plurality of die pieces 30. Next, a force is applied from the periphery of the drawing die, and the inner diameter of the cylindrical shape formed by the die pieces 30 is reduced as shown by the arrows in (b). As a result, the dynamic damper 10 in the center of the drawing die is pushed by the die pieces 30, and the outer diameter of the outer tube 11 of the dynamic damper 10 is reduced. As the outer diameter of the outer tube 11 is reduced, a stress is applied to the outer tube 11 in a direction toward the central axis 17.

[0029] By applying such stress through the drawing process, the rubber member 13 is maintained in a compressed state at least when the dynamic damper 10 is stopped. The drawing ratio is, for example, 2% to 3%. The drawing ratio is the ratio of the change in the outer diameter of the outer tube 11 before and after the drawing process to the outer diameter of the outer tube 11 before the drawing process, and is calculated as 100×(L1-L2) / L1, where L1 is the outer diameter of the outer tube 11 before the drawing process and L2 is the outer diameter of the outer tube 11 after the drawing process.

[0030] This dynamic damper 10 can be attached to various rotating bodies for use. For example, it can be attached to vehicle wheels, axles for cars and railways, rotating drums such as drums for tire drive-over tests and tire molding drums, and the like. In any rotating body, it is preferable to attach the dynamic damper 10 so that the rotation axis of the rotating body coincides with the central axis 17 of the outer cylinder 11 of the dynamic damper 10. When the rotating body vibrates, the mass member 12 vibrates relative to the outer cylinder 11 in the opposite direction to the vibration direction of the rotating body, thereby reducing the vibration of the rotating body.

[0031] In the first and second embodiments, the vibration is assumed to be vertical vibration. The dynamic damper 10 is designed to reduce the vertical vibration of a rotating body. In the following description, unless otherwise specified, the term "vibration" refers to vertical vibration, and the term "frequency" refers to the frequency of the vertical vibration.

[0032] Here, the number and function of the rubber members 13 will be described with reference to Figures 5 to 9. In all of Figures 5 to 9, a plurality of rubber members 13 are arranged at equal intervals in the direction around the central axis 17 of the outer cylinder 11.

[0033] Fig. 5 is a diagram of the dynamic damper 10 when the number of rubber members 13 is two. If it is possible to reduce vibrations in a predetermined frequency band when two rubber members 13 are arranged horizontally as in Fig. 5(a), this dynamic damper 10 can reduce vibrations in a predetermined frequency band twice during one rotation: at a rotation angle of 0° shown in Fig. 5(a) (the rubber member 13 on the left side at this time is indicated by an arrow) and at a rotation angle of 180° shown in Fig. 5(b).

[0034] 6 is a diagram of the dynamic damper 10 when the number of rubber members 13 is four. Assuming that vibrations in a predetermined frequency band can be reduced when the rubber members 13 are arranged above and below the mass member 12 as in Fig. 6(a), this dynamic damper 10 can reduce vibrations in a predetermined frequency band four times during one rotation: at a rotation angle of 0° as shown in Fig. 6(a) (the upper rubber member 13 at this time is indicated by an arrow), at a rotation angle of 90° as shown in Fig. 6(b), at a rotation angle of 180° as shown in Fig. 6(c), and at a rotation angle of 270° as shown in Fig. 6(d).

[0035] In this way, when the number of rubber members 13 is an even number, the dynamic damper 10 can reduce vibrations in a predetermined frequency band the same number of times as the number of rubber members 13 during one rotation.

[0036] On the other hand, Fig. 7 is a diagram of the dynamic damper 10 in which the number of rubber members 13 is three. If it is assumed that vibrations in a predetermined frequency band can be reduced when the rubber members 13 are disposed on the mass member 12 as in Fig. 7(a), this dynamic damper 10 can reduce vibrations in a predetermined frequency band six times during one rotation: when the rotation angle is 0° as shown in Fig. 7(a), when the rotation angle is 60° as shown in Fig. 7(b), when the rotation angle is 120° as shown in Fig. 7(c), when the rotation angle is 180° as shown in Fig. 7(d), when the rotation angle is 240° as shown in Fig. 7(e), and when the rotation angle is 300° as shown in Fig. 7(f).

[0037] In this way, when the number of rubber members 13 is an odd number, the dynamic damper 10 can reduce vibrations in a predetermined frequency band twice the number of rubber members 13 during one rotation.

[0038] 8 and 9 are diagrams showing, by using thick lines, the relationship between the rotation angle of the dynamic damper 10 and the frequency of vibration that the dynamic damper 10 can reduce at that angle when the number of rubber members 13 is 3 and 4. In addition, in Figs. 8 and 9, the frequency band in which it is desired to reduce vibration is shown by thin hatching lines.

[0039] The frequency of vibration that the dynamic damper 10 can reduce is the natural frequency of the dynamic damper 10 in the vertical direction at that rotation angle, and is calculated by the following formula.

[0040]

number

[0041] Furthermore, by adjusting the mass m and spring constant k of the mass member 12, the frequency of vibration that can be reduced by the dynamic damper 10 can be adjusted so as to overlap as closely as possible with the frequency band in which vibration reduction is desired.

[0042] Fig. 8 illustrates the calculation results when the number of rubber members 13 is four. From Fig. 8, it can be seen that the frequency of vibration that the dynamic damper 10 can reduce overlaps with the frequency band in which vibration reduction is desired four times during one rotation (360° rotation) of the dynamic damper 10.

[0043] On the other hand, Fig. 9 illustrates the calculation results when the number of rubber members 13 is three. From Fig. 9, it can be seen that the frequency of vibration that the dynamic damper 10 can reduce overlaps with the frequency band in which vibration reduction is desired six times during one rotation (360° rotation) of the dynamic damper 10.

[0044] In this way, the number of times that the dynamic damper 10 can reduce vibrations in a specified frequency band during one rotation is the same as the number of rubber members 13 if the number of rubber members 13 is an even number, and is twice the number of rubber members 13 if the number of rubber members 13 is an odd number.

[0045] 8 and 9, the more times the dynamic damper 10 can reduce vibrations in a specified frequency band during one rotation, the shorter the period of change in the frequency of vibration that the dynamic damper 10 can reduce (i.e., the period of change in the thick line) and the smaller the range of change in the frequency of vibration that the dynamic damper 10 can reduce (i.e., the range of change up and down the thick line). Because this range of change is small, the frequency of vibration that the dynamic damper 10 can reduce overlaps with the frequency band in which vibration reduction is desired for a long period of time. In this way, if the numbers of rubber members 13 are close, the frequency of vibration that the dynamic damper 10 can reduce overlaps with the frequency band in which vibration reduction is desired for a long period of time when the number is an odd number rather than an even number.

[0046] As described above, the dynamic damper 10 of the first embodiment includes the outer cylinder 11, the mass member 12, and the rubber member 13, and three or more odd number of rubber members 13 are arranged at equal intervals in the direction around the central axis 17 of the outer cylinder 11. Therefore, as described above, during one rotation of the dynamic damper 10, vibrations in a predetermined frequency band are reduced twice the number of rubber members 13. Therefore, the dynamic damper 10 of the first embodiment can sufficiently reduce vibrations in a predetermined frequency band.

[0047] Furthermore, since all of the rubber members 13 have the same shape, the structure of the dynamic damper 10 has rotational symmetry, and vibrations in a specified frequency band can be reduced each time the dynamic damper 10 rotates at a precise angle.

[0048] In addition, as the ratio of the area occupied by the rubber member 13 to the area between the outer tube 11 and the mass member 12 is 10% or more when viewed in the extension direction of the central axis 17 of the outer tube 11, the mass member 12 can vibrate appropriately relative to the outer tube 11, and the function of reducing vibration in a predetermined frequency band works sufficiently. Moreover, as this ratio is 70% or less, the vibration of the mass member 12 is not easily hindered, and the rubber members 13 are less likely to come into contact with each other when the mass member 12 vibrates and the rubber members 13 are deformed.

[0049] In addition, since stress is applied to the outer cylinder 11 in the direction toward the central axis 17, the rubber member 13 is compressed. Therefore, the rubber member 13 is less likely to develop defects such as cracks, and has a long life.

[0050] Various modifications can be made to the first embodiment. Any one of the modifications described below may be applied to the first embodiment, or any two or more of them may be combined and applied to the first embodiment. The combination may be arbitrary.

[0051] <Change Example 1> Instead of the rubber members 13 connecting the outer cylinder 11 and the mass member 12, other elastic bodies such as springs may be provided.

[0052] <Change Example 2> The shapes of the outer cylinder and the mass member when viewed from the central axial direction of the outer cylinder are not limited to the circular shape as described above. For example, the shapes of either or both of the outer cylinder and the mass member when viewed from the central axial direction of the outer cylinder may be polygonal, such as a regular polygon.

[0053] As a specific example, the outer cylinder 111a and the mass member 112a may be equilateral triangles as shown in Fig. 10(a), and the outer cylinder 111b and the mass member 112b may be squares as shown in Fig. 10(b). Fig. 10(a) and Fig. 10(b) are examples in which the outer cylinder and the mass member have the same regular polygonal shape. Also, as shown in Fig. 10(c), the shape of the outer cylinder 111c and the shape of the mass member 112c when viewed from the central axis direction of the outer cylinder may be different.

[0054] In all of the modified examples, the outer cylinder and the mass member are connected by a rubber member 13. In all of the modified examples, the number of rubber members 13 is an odd number equal to or greater than three, and they are disposed at equal intervals in the direction around the central axis of the outer cylinder. When the dynamic damper 10 is at rest, the central axis of the outer cylinder passes through the mass member.

[0055] <Change Example 3> The number of rubber members arranged in the dynamic damper in the direction around the central axis may be three or more and may be an odd number, but is preferably five or seven other than three.

[0056] If the number of rubber members is 3, 5, or 7, the number of rubber members is not too large, so the mass member moves easily inside the outer cylinder and the rubber members are less likely to come into contact with each other. Also, since the rubber members are arranged in a way that they can reduce vibrations in a specified frequency band a sufficient number of times during one rotation of the dynamic damper, vibrations in the specified frequency band are easily reduced.

[0057] Furthermore, if the number of rubber members is 3 or 5, the mass member is particularly likely to move inside the outer cylinder because the number of rubber members is relatively small. Therefore, there is no risk that the vibration reduction effect will be difficult to achieve. Furthermore, if the number of rubber members is 5 or 7, an arrangement of rubber members that can reduce vibrations in a specified frequency band a particularly large number of times during one rotation of the dynamic damper is realized, so vibrations in a specified frequency band are particularly likely to be reduced.

[0058] <Change Example 4> When the rubber member is thick on the outer cylinder side and thin on the mass member side, the shape of the rubber member does not have to be trapezoidal when viewed from the central axis of the outer cylinder as described above.

[0059] Furthermore, the cross-sectional area of ​​the rubber member may be constant from the outer cylinder 11 side to the mass member 12 side, and may be rectangular when viewed from the central axis direction of the outer cylinder, for example.

[0060] <Change Example 5> In addition to being arranged side by side in the direction around the central axis 17 of the outer cylinder 11 as in Fig. 1, the multiple rubber members 113 may be arranged at intervals in the central axis direction of the outer cylinder 11 as in Fig. 11. In this case, the mass member 12 is more likely to move than when there is no such interval.

[0061] <Change Example 6> As part of the dynamic damper, an outer member having a hole shaped to fit the outer tube 11 may be provided, and the outer tube 11 may be fitted into the hole. In this case, the inner diameter of the hole is set to be slightly smaller than the outer diameter of the outer tube 11. By fitting the outer tube 11 into such a hole, a stress toward the central axis 17 is applied to the outer tube 11, and the rubber member 13 is compressed.

[0062] 2. Embodiment 2 The dynamic damper 210 of embodiment 2 differs from the dynamic damper 10 of embodiment 1 only in that a buffer member 220 fixed to the outer tube 11 and separated from the mass member 12 is provided between adjacent rubber members 13 inside the outer tube 11.

[0063] 12, in all locations where two rubber members 13 are adjacent to each other, a buffer member 220 is provided at the midpoint between the adjacent rubber members 13. Since the rubber members 13 are lined up at equal intervals in the direction around the central axis 17 of the outer tube 11, the multiple buffer members 220 are also lined up at equal intervals in the direction around the central axis 17 of the outer tube 11. In addition, these buffer members 220 are disposed at positions that are rotationally symmetrical with respect to the central axis 17 of the outer tube 11.

[0064] The buffer member 220 has a tapered shape toward the mass member 12, or in other words, is thick on the outer tube 11 side and thin on the mass member 12 side. Therefore, the cross-sectional area of ​​the buffer member 220 is large on the outer tube 11 side and gradually becomes smaller as it approaches the mass member 12. Examples of such shapes include polygonal pyramids such as triangular pyramids and square pyramids, and cones.

[0065] All of the buffer members 220 provided in the dynamic damper 210 have the same shape and the same size. In addition, all of the buffer members 220 are provided in a direction tapering toward the mass member 12.

[0066] The buffer member 220 is preferably made of a material having buffer properties, and more preferably made of an elastic material such as rubber. The buffer member 220 is adhered to the outer tube 11 by an adhesive means suitable for the material. For example, when the buffer member 220 is made of rubber, the buffer member 220 is adhered to the outer tube 11 by vulcanization adhesion.

[0067] In this way, in the second embodiment, the buffer member 220 fixed to the outer cylinder 11 and separated from the mass member 12 is provided between the adjacent rubber members 13, so that even if the mass member 12 moves significantly, the mass member 12 will not hit the outer cylinder 11 but will hit the buffer member 220. This makes it possible to prevent the mass member 12 from hitting the outer cylinder 11, thereby preventing the generation of hitting sounds and the breakdown of the dynamic damper 210. Note that the buffer member 220 is not connected to the mass member 12, so it does not affect the characteristics of the dynamic damper 210.

[0068] Here, without the buffer member 220, the mass member 12 is likely to hit the outer tube 11, particularly at the midpoint between the adjacent rubber members 13, when it moves significantly. However, because the buffer member 220 is provided at the midpoint between the adjacent rubber members 13 in all locations where two rubber members 13 are adjacent to each other, it is possible to prevent the mass member 12 from hitting the outer tube 11.

[0069] In addition, because the buffer member 220 has a tapered shape toward the mass member 12, the contact area between the mass member 12 and the buffer member 220 gradually increases as the mass member 12 moves toward the outer tube 11, and the force with which the buffer member 220 tries to push back the mass member 12 gradually increases. This makes it possible to effectively suppress the movement of the mass member 12. In addition, the stronger the mass member 12 hits the buffer member 220, the greater the force with which the buffer member 220 tries to push back the mass member 12, making it possible to prevent the mass member 12 from hitting the outer tube 11.

[0070] Various modifications can be made to the second embodiment. Any one of the modifications described below and the above modifications of the first embodiment may be applied to the second embodiment, or any two or more of them may be combined and applied to the second embodiment. The combination may be arbitrary.

[0071] <Change Example 1> The cushioning member does not have to have a shape that tapers toward the mass member 12. For example, the cushioning member may have a shape that has the same thickness from the bonding surface with the outer tube 11 to the tip on the mass member 12 side. An example of such a shape is a rectangular parallelepiped.

[0072] <Change Example 2> 13, a recess 321 may be formed on the inner circumferential surface 315 of the outer tube 311, and a part of the buffer member 320 may be embedded in the recess 321. In this case, the part of the buffer member 320 that protrudes inward from the inner circumferential surface 315 of the outer tube 311 has the same shape and size as the buffer member 220 described above.

[0073] In this modification, since a cushioning effect is also produced from the portion of cushioning member 320 that is embedded in recess 321, the impact when mass member 12 hits cushioning member 320 can be significantly reduced.

[0074] <Change Example 3> As in Modification 2 of Embodiment 1, even when one or both of the outer cylinder and the mass member have a shape other than a circle when viewed from the central axis direction of the outer cylinder, cushioning members 420a, 420b, and 420c may be provided at the midpoints of adjacent rubber members 13 as shown in Fig. 14. In the case of Fig. 14, cushioning members 420a, 420b, and 420c are provided at all locations where two rubber members 13 are adjacent to each other.

[0075] In addition, when one or both of the outer cylinder and the mass member have a shape other than circular, cushioning members can be provided at various locations where the mass member is likely to come into contact with the outer cylinder when it moves significantly.

[0076] For example, when the mass member is polygonal and rubber members are connected to its edges, the location where the mass member is likely to come into contact with the outer cylinder is the location that is closest to the vertices of the polygon of the mass member when viewed from the central axial direction of the outer cylinder.

[0077] A specific example where a buffer member is provided in such a location is shown in Fig. 15. As shown in Fig. 15, when the outer tube 111a and the mass member 112a form an equilateral triangle whose sides are connected by rubber members 13, the mass member 112a is likely to hit the two locations of the outer tube 111a that are the closest to the vertices of the equilateral triangle of the mass member 112a. Therefore, in Fig. 15, buffer members 420d are provided in those locations.

[0078] Further, other locations where the mass member is likely to hit the outer cylinder include, for example, a location that is the shortest distance from the mass member when the dynamic damper is stopped.

[0079] In addition, the location where the mass member is likely to hit the external cylinder may be determined based on the direction in which the dynamic damper rotates. For example, if the mass member is polygonal and the rubber members are connected to its sides when viewed from the central axis direction of the external cylinder, the mass member is likely to hit the location that is closest to the apex of the polygon and on the opposite side of the rotation direction of the dynamic damper. Therefore, a buffer member is provided at that location.

[0080] For example, as shown in Fig. 16, the outer cylinder 111a and the mass member 112a form an equilateral triangle whose sides are connected by the rubber member 13, and when the dynamic damper rotates to the right, the mass member 112a is likely to hit a location on the outer cylinder 111a that is the shortest distance from the apex of the equilateral triangle of the mass member 112a and is on the left side of the apex of the equilateral triangle. Therefore, in Fig. 16, a buffer member 420d is provided at that location.

[0081] <Change Example 4> When the outer cylinder 11 is cylindrical, the buffer member 220 may be provided at a location away from the midpoint between the two rubber members 13 . [Explanation of symbols]

[0082] 10...dynamic damper, 11...outer cylinder, 12...mass member, 13...rubber member, 14...hole, 15...inner peripheral surface, 16...outer peripheral surface, 17...center axis, 30...mold piece, 111a...outer cylinder, 111b...outer cylinder, 111c...outer cylinder, 112a...mass member, 112b...mass member, 112c...mass member, 113...rubber member, 210...dynamic damper, 220...cushion member, 311...outer cylinder, 315...inner peripheral surface, 320...cushion member, 321...recess, 420a...cushion member, 420b...cushion member, 420c...cushion member, 420d...cushion member

Claims

1. A dynamic damper including an outer cylinder, a mass member provided inside the outer cylinder at a location through which a central axis of the outer cylinder passes and spaced apart from the outer cylinder, and an elastic body connecting the outer cylinder and the mass member, A dynamic damper, characterized in that an odd number of the elastic bodies, which are three or more, are arranged at equal intervals in a direction around the central axis.

2. 2. The dynamic damper according to claim 1, wherein all of said elastic bodies have the same shape.

3. 3. The dynamic damper according to claim 1, wherein a ratio of an area occupied by said elastic body to an area between said outer cylinder and said mass member when viewed from an extension direction of said central axis is 10% or more and 70% or less.

4. 3. The dynamic damper according to claim 1, wherein a stress is applied to the outer cylinder in a direction toward the central axis.

5. 5. The dynamic damper according to claim 4, wherein the stress is applied to the outer cylinder by drawing the outer cylinder.

6. 3. The dynamic damper according to claim 1, further comprising a buffer member fixed to the outer cylinder and spaced apart from the mass member, the buffer member being disposed between adjacent ones of the elastic bodies inside the outer cylinder.

7. 7. The dynamic damper according to claim 6, wherein the buffer member is provided at a midpoint between the adjacent elastic bodies at every location where two of the elastic bodies are adjacent to each other.

8. 7. The dynamic damper according to claim 6, wherein a plurality of said buffer members are provided at positions rotationally symmetrical with respect to said central axis.

9. The dynamic damper according to claim 6 , wherein the buffer member is tapered toward the mass member.

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