JP7796071B2 - Dynamic Damper - Google Patents

Description

The present invention relates to a dynamic damper that is attached to a vibration source, such as the body of an automobile, to attenuate vibrations of a specific frequency.

A conventional dynamic damper is known, as described in Patent Document 1 below. Figure 6 is a front view of a conventional dynamic damper.

As shown in Figure 6, this dynamic damper 1 comprises a gate-shaped outer metal fitting 2 that is attached to a vibration source such as a member of an automobile body, a mass member 5 that is positioned inside the outer metal fitting 2 and is surrounded by a pair of side walls 3, 3 and an upper end wall 4 that connects the upper ends of both side walls 3, 3, and a pair of left and right rubber elastic bodies 6, 6 that are vulcanized and bonded between the outer surfaces of the mass member 5 and the opposing inner surfaces of the both side walls 3, 3.

The outer metal fitting 2 is fixed to a vibrating member 8, such as a member constituting the vehicle body, by fixing bolts 7, 7 inserted through mounting holes provided in a pair of fixing bracket pieces 3a, 3a integrally formed at the lower ends of both side walls 3, 3.

A through hole 4a is formed in the center of the upper end wall 4, and an engaging protrusion 9 made of rubber is provided on the upper surface of the mass member 5, protruding upward from the through hole 4a. Even if the rubber elastic bodies 6, 6 break and the mass member 5 falls, the engaging protrusion 9 will catch on the through hole 4a between the outer metal fitting 2 and the vibrating member 8, preventing the mass member 5 from falling off.

This dynamic damper 1 is used to reduce vibrations in the vertical direction of the vehicle (X direction in the figure) of a vibrating member 8, such as a member of the vehicle body, and is set to the desired resonant frequency (Hz) by tuning the spring constant of the rubber elastic bodies 6, 6 and the mass of the mass member 5.

JP 2004-353826 A (FIG. 1)

However, in the dynamic damper 1 described in Patent Document 1, the rubber elastic bodies 6, 6 are arranged linearly in the horizontal direction (Y direction in the figure) relative to the mass member 5. Therefore, when the mass of the rubber elastic bodies 6, 6 and the mass member 5 is tuned to match the desired resonant frequency in the vertical direction (X direction), the resonant frequency in the Y direction is fixed to a constant resonant frequency corresponding to the resonant frequency in the X direction. In other words, the resonant frequency in the Y direction is determined depending on the resonant frequency in the X direction, and it is not possible to set the resonant frequencies relative to the X and Y directions.

In other words, because conventional rubber elastic bodies 6, 6 are arranged linearly in the Y direction relative to the mass member 5, a pure shear force acts in the X direction, while a linear pure compressive force acts in the Y direction, which can result in the resonant frequency in the Y direction being approximately 2 to 2.5 times higher than the resonant frequency in the X direction. As a result, it may become impossible to set a low resonant frequency in the Y direction, and the tuning range may become smaller.

The present invention was devised in consideration of the technical issues with conventional dynamic dampers. It provides a dynamic damper that allows the left-right resonance frequency to be adjusted freely and relatively to the up-down resonance frequency by adjusting the inclination angle of each pair of left and right elastic bodies provided between the outer member and the mass member.

The invention according to claim 1 of the present application is an apparatus comprising: an outer member made of a metal material attached to a vibration source and having a pair of left and right side walls and end walls provided between ends of the both side walls in the longitudinal direction; a mass member arranged inside the outer member; and four elastic bodies arranged on top, bottom, left, and right sides between the inner surfaces of the both side walls of the outer member and the outer surfaces of the mass member facing the both inner surfaces, the elastic bodies being arranged with a certain gap between them in the vertical direction,
The four elastic bodies are each formed at an angle from the inner surfaces of both side walls of the outer member toward the outer surfaces of the mass member, and by adjusting the angle of inclination of each elastic body, the left-right resonance frequency of the vibration source can be adjusted relative to the up-down resonance frequency.

According to the present invention, by adjusting the inclination angle of each elastic body, it is possible to adjust the left-right resonance frequency relative to the up-down resonance frequency, making it possible to damp the desired up-down and left-right resonance frequencies according to the required specifications of the dynamic damper.

1 is a plan view showing a first embodiment of a dynamic damper according to the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. FIG. 4 is a characteristic diagram showing the relationship between the Y/X resonance frequency ratio of the dynamic damper and the inclination angle of each elastic body in the first embodiment. FIG. 10 is a plan view showing a second embodiment of the dynamic damper of the present invention. FIG. FIG. 1 is a front view showing a conventional dynamic damper.

Each embodiment of the dynamic damper according to the present invention will be described below with reference to the drawings. In this embodiment, the dynamic damper is attached to the front suspension member of an automobile. Figure 1 is a plan view showing a first embodiment of the dynamic damper according to the present invention, and Figure 2 is a cross-sectional view taken along line A-A in Figure 1.

The front suspension member (not shown) is a source of vibration in automobiles, and as is well known, it suppresses twisting of the vehicle body while driving, absorbs shock from the road surface, and improves ride comfort and handling stability. It is made up of a square frame formed from highly rigid hot-rolled steel plates for welded structures. In addition to the front suspension, this front suspension member also supports the engine, steering, etc.

As shown in Figure 2, the dynamic damper 11 is positioned so that its vertical direction (arrow X direction) roughly corresponds to the vertical direction of the vehicle body, and its left-right direction (arrow Y direction) roughly corresponds to the width direction of the vehicle body.

As shown in Figures 1 and 2, the dynamic damper 11 comprises a base plate 12 fixed to the frame of the front suspension member, which is the vibration source (vibration member), by two bolts (not shown); an outer metal fitting 13, a gate-shaped outer member fixed to the upper surface 12a of the base plate 12 by welding; a mass member 14, a mass member positioned inside the outer metal fitting 13; and a total of four rubber elastic bodies 19a, 19b, 20a, 20b, one pair above, one pair below, one pair left, and one pair left, positioned between the outer metal fitting 13 and the mass member 14.

The base plate 12 is made of metal and formed into a rectangular shape that is elongated horizontally in the drawing. Its lower surface is placed in contact with a predetermined upper surface of the frame of the front suspension member, and two bolt insertion holes 12b, 12b are formed vertically through both ends in the longitudinal direction, into which the two bolts are inserted.

The outer metal fitting 13 is formed by bending a long, narrow metal plate into a U-shape and has rectangular side walls 16, 17 and an upper wall 18 located between the upper longitudinal edges of the side walls 16, 17. The side walls 16, 17 are formed as vertical flat plates with their inner surfaces 16a, 17a facing each other and their lower edges 16b, 17b welded to the upper surface 12a of the base plate 12 by, for example, arc welding. The welds 21, 22 are located on the inside of the lower edges 16b, 17b.

The upper end wall 18 is formed as a horizontal flat plate, and a retaining hole 24 that forms part of the fall prevention mechanism 23 (described later) is formed through it in the vertical direction at the center of its length.

As shown in Figure 2, the mass member 14 is formed in a roughly cubic shape of a predetermined mass, with its outer surfaces 14a, 14b positioned laterally opposite the inner surfaces 16a, 17a of both side walls 16, 17 of the outer metal fitting 13, and its lower surface 14c positioned a predetermined distance S from the upper surface 12a of the base plate 12. The upper surface 14d of the mass member 14 is positioned a predetermined distance from the lower surface of the upper end wall 18 via a retaining bolt 25 of the fall prevention mechanism 23, which will be described later. A female threaded hole 14e is formed in the center of the upper surface 14d of the mass member 14, extending vertically, into which the male threaded portion 25c of the shaft 25b of the retaining bolt 25 screws.

The four elastic bodies 19a-20b have their outer axial ends vulcanized and bonded to the opposing inner surfaces 16a, 17a of the side walls 16, 17, and their inner axial ends vulcanized and bonded to the outer surfaces 14a, 14b of the mass member 14.

Each of these elastic bodies 19a-20b is inclined from the inner surfaces 16a, 17a of the side walls 16, 17 of the outer metal fitting 13 toward the outer surfaces 14a, 14b of the mass member 14, and is arranged symmetrically in the vertical and left-right directions about the center line P of the mass member 14 in the width direction and the center line P1 of the mass member 14 in the vertical direction. In other words, in Figure 2, the pair of upper and lower elastic bodies 19a, 19b on the left side and the pair of upper and lower elastic bodies 20a, 20b on the right side are inclined from their respective outer ends in the axial direction toward their respective inner ends toward the center of gravity GP of the mass member 14, and are arranged in an X-shape when viewed from the front, and are arranged symmetrically in the vertical and left-right directions about the center line P of the mass member 14 in the width direction and the center line P1 of the mass member 14 in the vertical direction.

As shown in Figure 2, the elastic bodies 19a-20b are arranged so that the central position OP of the arrangement of the four elastic bodies 19a-20b at the intersection of the center lines P and P1 of the mass member 14 coincides with the center of gravity GP of the mass member 14. Note that "matching" here is a concept that includes cases where the center of gravity GP and the central position OP coincide perfectly, as well as cases where they are close to but not perfectly aligned.

Furthermore, the inclination angle θ of each of the elastic bodies 19a-20b relative to the horizontal direction is set within a range of approximately 20° to 70°. The inclination angle θ of each of the elastic bodies 19a-20b is determined according to the ratio of the resonance frequencies (Hz) in the vertical direction (X direction) and the horizontal direction (Y direction) required for the dynamic damper 11.

In this way, the tilt angle θ of each elastic body 19a-20b in the present invention is set to approximately 20°-70°, which was determined by the inventors through analytical experiments on the relationship between the Y/X resonance frequency ratio shown in Figure 3 and the tilt angle θ. In this analytical experiment, as shown in Figure 3, the tilt angle θ (°) of the elastic bodies 19a-20b is shown as a horizontal line, and the resonance frequency ratio in the left-right Y direction/up-down X direction is shown as a vertical line.

This analytical experiment revealed that the Y/X resonance frequency ratio changes depending on the inclination angle θ of each elastic body 19a-20b. When the inclination angle θ is set to 0°, i.e., when the elastic bodies are set in a linear horizontal direction as in the prior art described in the publication, the Y/X resonance frequency ratio is 2.0 to 2.5 times greater than 1.80 times. Furthermore, when the inclination angle θ is gradually increased, for example to approximately 80° or greater, the Y/X resonance frequency ratio becomes sufficiently small, at approximately 1.00 times or less.

The typical required specifications for the dynamic damper 11 in the front suspension member of a vehicle body are for the Y/X resonance frequency ratio to be 1.70 to 1.20, so in this invention, the tilt angle θ that satisfies this Y/X resonance frequency ratio is set between 20° and 70°. In this embodiment, the tilt angle θ is set to approximately 35° to 50° to further narrow the required Y/X resonance frequency ratio to approximately 1.55 to 1.40, and can be adjusted as desired depending on the required specifications of the dynamic damper 11.

A fall prevention mechanism 23 for the mass member 14 is provided between the upper end wall 18 and the mass member 14. This fall prevention mechanism 23 has a retaining hole 24 formed vertically through the approximate center of the upper end wall 18, and a retaining bolt 25, which is a fall prevention member that can be held by the edge of this retaining hole 24.

The retaining hole 24 has a predetermined inner diameter d, which is smaller than the outer diameter d1 of the head 25a of the retaining bolt 25, which will be described later.

The retaining bolt 25 has a generally hexagonal head 25a and a shank 25b that is integrally formed below the head 25a and is inserted into the retaining hole 24 while being fixed to the upper end of the mass member 14. The head 25a is positioned above the retaining hole 24, and its outer diameter d1 is larger than the inner diameter d of the retaining hole 24 as described above, so that the outer periphery of the lower end surface will catch on the edge of the retaining hole 24 if the mass member 14 is accidentally dropped. The large-diameter portion of the shank 25b on the head 25a side is inserted into the retaining hole 24, and a male thread 25c is formed on the outer periphery of the stepped, smaller-diameter tip located below the large-diameter portion.

Furthermore, when the male threaded portion 25c of the retaining bolt 25 is screwed and fixed into the female threaded hole 14e of the mass member 14, the distance S1 between the underside of the head 25a and the upper surface of the upper end wall 18 is set to be smaller than the distance S between the upper surface of the base plate 12 and the underside of the mass member 14.
[Actions and Effects of the Dynamic Damper in the Present Embodiment]
According to the dynamic damper 11 of this embodiment having the above-described configuration, by adjusting the inclination angle θ of each elastic body 19a to 20b, it is possible to arbitrarily adjust the resonant frequency in the left-right direction (Y direction) relative to the resonant frequency in the up-down direction (X direction), thereby making it possible to damp the resonant frequencies in the up-down and left-right directions according to the required specifications of the dynamic damper 11.

In this embodiment, by adjusting the inclination angle θ of each elastic body 19a-20b to within a range of, for example, approximately 35°-50°, it is possible to further narrow the required Y/X resonance frequency ratio to approximately 1.55-1.40 times.

In this way, it is possible to lower the resonance frequency in the Y direction relative to the resonance frequency in the X direction, and the tuning range can be expanded. As a result, an excellent vibration damping effect can be achieved depending on the object to which the dynamic damper 11 is attached and the installation direction.

Furthermore, according to this embodiment, by aligning the central position OP of the arrangement of the four elastic bodies 19a-20b with the center of gravity GP of the mass member 14, the translational movement of the mass member 14 along with the center of gravity GP due to resonance is not affected by the rotational movement around the center of gravity GP. This makes it possible to suppress the mass effect of the mass member 14, i.e., the reduction in the damping effect due to mass. As a result, the resonance suppression effect of the mass member 14 in the vertical and horizontal directions is enhanced.

In other words, if the central position OP of the arrangement of the four elastic bodies 19a-20b were to be offset, for example, vertically, from the center of gravity GP of the mass member 14, rotational motion would occur in conjunction with translational motion, which could reduce the damping effect of the mass member 14. However, in this embodiment, by aligning the central position OP of the arrangement of the elastic bodies 19a-20b with the center of gravity GP of the mass member 14, the occurrence of such rotational motion can be suppressed, thereby enhancing the resonance suppression effect of the mass member 14.

In addition, because the lower edges 16b, 17b of both side walls 16, 17 of the outer metal fitting 13 are welded to the upper surface 12a of the base plate 12, the support force for both side walls 16, 17, i.e., the support force for both side walls 16, 17 against left-right vibrations, is particularly strong. As a result, left-right vibrations of the outer metal fitting 13 are suppressed, and the left-right vibration damping effect of the dynamic damper 11 is increased.

In addition, in the fall prevention mechanism 23 of this embodiment, under normal circumstances, as shown in FIG. 2, when the male threaded portion 25c of the retaining bolt 25 is threadedly secured to the female threaded hole 14e of the mass member 14, the head 25a is positioned above the retaining hole 24 via the large diameter portion of the shaft 25b. However, if each elastic body 15 breaks due to deterioration over time or the like and the mass member 14 falls, the underside of the head 25a catches on the edge of the retaining hole 24, and the mass member 14 is suspended from the upper end wall 18 via the retaining bolt 25 and retaining hole 24, eliminating interference with the upper surface 12a of the base plate 12.

Furthermore, the fall prevention mechanism 23 has a simplified structure, being simply constituted by the retaining hole 24 and the retaining bolt 25, which simplifies manufacturing and prevents costs from rising.
Second Embodiment of the Present Invention
A second embodiment of the present invention will now be described. Figure 4 is a plan view showing a dynamic damper according to a second embodiment of the present invention, and Figure 5 is a front view of the same second embodiment.

As shown in Figures 4 and 5, the dynamic damper 11 of this second embodiment comprises a base plate 12 fixed to the frame of the front suspension member by three bolts (not shown); a gate-shaped outer metal fitting 13 positioned approximately in the center of the upper surface 12a of the base plate 12 and having a pair of left and right side walls 16 and 17; an inner metal fitting 27, which serves as an inner member positioned inside the outer metal fitting 13; a mass member 14 positioned inside the inner metal fitting 27; multiple rubber elastic bodies 19a-20b (four, one on top and one on bottom in this embodiment) vulcanized and bonded between the inner surfaces 16a, 17a of the side walls 16, 17 of the outer metal fitting 13 and the outer surfaces of the side pieces 27b, 27c of the inner metal fitting 27; and four fastening bolts 28, which serve as connecting members that secure the mass member 14 to the inner metal fitting 27.

The base plate 12 is made of metal and has an irregular V-shape when viewed from above, with three bolt insertion holes 12b formed through it at both ends and the center as shown in Figure 4, into which the three bolts are inserted.

The outer metal fitting 13, like that of the first embodiment, is formed by bending a metal plate into a roughly U-shape, and has left and right side walls 16, 17 and an upper end wall 18 connecting the upper edges of the side walls 16, 17. The side walls 16, 17 are longer in the vertical direction than those of the first embodiment, and the other side wall 17 on the right side of Figure 5 has an inclined concave upper end 18a to avoid interference with other components.

Like the outer fitting 13, the inner fitting 27 is made by bending a metal plate into an inverted U-shape. It has a bottom wall piece 27a and side pieces 27b, 27c that stand upright from both longitudinal edges of the bottom wall piece 27a and are arranged opposite the side walls 16, 17 from the left and right. Furthermore, the thickness t1 of the inner fitting 27 is thinner than the thickness t of the outer fitting 13, and the side pieces 27b, 27c are arranged parallel to the side walls 16, 17 of the outer fitting 13 with a specified gap between them.

The bottom wall piece 27a is formed horizontally, parallel to the base plate 12, and a gap of a predetermined distance S is formed between its lower surface and the upper surface of the base plate 12.

The upper ends of both side pieces 27b and 27c each have an insertion hole (not shown) through which the small-diameter male threaded portion at the tip of the shaft of each fastening bolt 28 (described below) is inserted.

The mass member 14 is made of, for example, an iron-based metal material and is formed as a roughly rectangular parallelepiped that is elongated in the vertical direction. The vertical length L (X direction) is greater than the horizontal length L1 (Y direction), and is housed and positioned inside the inner metal fitting 27. Furthermore, the mass member 14 is fixed at both sides of its upper end to the side pieces 27b, 27c of the inner metal fitting 27 by four fastening bolts 28.

As shown in Figures 4 and 5, the four elastic bodies 19a-20b are each formed in a cylindrical shape, with their outer and inner axial ends vulcanized and bonded to the inner surfaces 16a, 17a of both side walls 16, 17 of the outer metal fitting 13 and the outer surfaces of both side pieces 27b, 27c of the inner metal fitting 27.

As shown in FIG. 5, each pair of left and right elastic bodies 19a-20b is angled from the inner surfaces 16a, 17a of the side walls 16, 17 of the outer metal fitting 13 toward the outer surfaces of the side pieces 27b, 27c of the inner metal fitting 27, forming a diamond shape when viewed from the front. In other words, the pair of upper and lower elastic bodies 19a, 19b on the left side of FIG. 5 and the pair of upper and lower elastic bodies 20a, 20b on the right side of FIG. 5 are angled from their respective axial outer ends toward the inner ends of the side pieces 27b, 27c of the inner metal fitting 27, vertically separating them from each other, forming a diamond shape when viewed from the front. Furthermore, as in the first embodiment, each elastic body 19a-20b is arranged symmetrically in the vertical and left directions about the widthwise center line P and the vertical center line P1 of the mass member 14. Therefore, the center position OP of the arrangement of the four elastic bodies 19a-20b coincides with the center of gravity GP of the mass member 14.

Furthermore, the inclination angle θ of each elastic body 19a-20b is set between 20° and 70° in the present invention, since the normal required specifications for the dynamic damper 11 generally require a Y/X resonance frequency ratio of 1.70 to 1.20. However, in this embodiment, as in the first embodiment, the inclination angle θ is set to approximately 35° to 50° in order to achieve a Y/X resonance frequency ratio of approximately 1.55 to 1.40 in the required specifications for the dynamic damper 11.

Furthermore, the fall prevention mechanism 23 is the same as that in each embodiment, so it is given the same reference number and a detailed description will be omitted.

As described above, in the dynamic damper 11 of the second embodiment, each elastic body 19a-20b is formed at an angle rather than horizontally, as in the first embodiment. By adjusting this angle θ, it is possible to arbitrarily adjust the resonant frequency in the left-right direction (Y direction) relative to the resonant frequency in the up-down direction (X direction). This makes it possible to damp the resonant frequencies in the up-down, left-right directions according to the required specifications of the dynamic damper 11. In particular, it is possible to lower the resonant frequency in the Y direction relative to the resonant frequency in the X direction, and the tuning range can be expanded. As a result, an excellent vibration damping effect can be achieved according to the attachment target and attachment direction of the dynamic damper 11.

In addition, in this second embodiment, the central position OP of the arrangement of the elastic bodies 19a-20b coincides with the center of gravity GP of the mass member 14, so, as in the first embodiment, the translational movement of the mass member 14 along with the center of gravity GP due to resonance is not affected by the rotational movement around the center of gravity GP. This makes it possible to suppress the mass effect of the mass member 14, i.e., the reduction in the damping effect due to mass. As a result, the resonance suppression effect of the mass member 14 is enhanced in the up/down and left/right directions.

Furthermore, unlike the first embodiment, the second embodiment is provided with an inner metal fitting 27, which allows the vibration source to be set to a specific fixed frequency for a different target.

Also, as in the first embodiment, the fall prevention mechanism 23 prevents the mass member 14 from accidentally falling.

The present invention is not limited to the configurations of the above-described embodiments. For example, the shape of the outer metal fitting 13 and the shape of the mass member 5 can be further modified. Furthermore, the outer diameter, length, and inclination angle θ of each elastic body 19a-20b can be modified as desired depending on the object to which the dynamic damper 11 is attached, i.e., the natural frequency of the vibration to be reduced.

In addition, dynamic dampers can also be used on other vibrating components of vehicle bodies and on vibrating components other than automobiles, such as ships, and the mounting position on the vibrating component can be set arbitrarily.

11... Dynamic damper 12... Base plate 13... Outer metal fitting (outer member)
14: Mass member 14a, 14b: Both outer surfaces 16: One side wall 16a: Inner surface 17: Other side wall 17a: Inner surface 18: Upper end wall 19a, 19b, 20a, 20b: Elastic body 23: Fall prevention mechanism 25: Bolt 27: Inner metal fitting (inner member)
27a...Bottom wall piece 27b, 27c...Side pieces θ...Inclination angle of elastic body GP...Center of gravity position of mass member OP...Center position of arrangement of each elastic body P...Center line of mass member in width direction P1...Center line of mass member in up-down direction

Claims (6)

the vibration source is attached to a vibration source and comprises an outer member made of a metal material having a pair of left and right side walls and end walls provided between longitudinal ends of the both side walls; a mass member arranged inside the outer member; and four elastic bodies arranged vertically and horizontally between the inner surfaces of the both side walls of the outer member and the outer surfaces of the mass member facing the both inner surfaces, the elastic bodies being arranged with a certain gap between them in the vertical direction;
a dynamic damper characterized in that the four elastic bodies are each formed at an angle from the inner surfaces of both side walls of the outer member toward the outer surfaces of the mass member, and that the left-right resonance frequency of the vibration source can be adjusted relatively to the up-down resonance frequency by adjusting the angle of inclination of each elastic body. 2. The dynamic damper according to claim 1,
A dynamic damper characterized in that the inclination angles of the four elastic bodies are set to 20° to 70°, respectively , so that the resonance frequency in the left-right direction is 1.2 to 1.7 times the resonance frequency in the up-down direction. 2. The dynamic damper according to claim 1,
The four elastic bodies are arranged at an angle in an X-shape when viewed from the front, and are arranged in vertically and horizontally symmetrical positions around the center line of the width direction and the center line of the up-down direction of the mass member, so that the center position of the arrangement of the four elastic bodies coincides with the center of gravity of the mass member. an outer member made of a metal material attached to a vibration source and having a pair of left and right side walls and end walls provided between ends of the side walls in the longitudinal direction; an inner member made of a metal material arranged inside the outer member and having side pieces facing the side walls of the outer member; a mass member arranged inside the inner member; and four elastic bodies arranged vertically and at upper, lower, left and right positions with a certain gap between them, the elastic bodies being arranged between the inner surfaces of the side walls of the outer member and the outer surfaces of the side pieces of the inner member facing the inner surfaces,
A dynamic damper characterized in that the four elastic bodies are each formed at an angle from the inner surfaces of both side walls of the outer member toward the outer surfaces of both side pieces of the inner member, and that by adjusting the angle of inclination of each elastic body, the left-right resonance frequency of the vibration source can be adjusted relatively to the up-down resonance frequency. 5. The dynamic damper according to claim 4,
A dynamic damper characterized in that the inclination angles of the four elastic bodies are set to 20° to 70°, respectively , so that the resonance frequency in the left-right direction is 1.2 to 1.7 times the resonance frequency in the up-down direction. 6. The dynamic damper according to claim 5,
The dynamic damper is characterized in that the four elastic bodies are arranged in a slanted diamond shape when viewed from the front, and are arranged symmetrically about the center line of the width direction and the center line of the length direction of the mass member, so that the center position of the arrangement of the four elastic bodies coincides with the center of gravity of the mass member.