Torsional damper

Abstract

To reduce radiation noise from a hub regardless of the size of a torsional damper.SOLUTION: A torsional damper 100 comprises a hub 10, a vibration ring 30, and a damper rubber 20. The hub 10 is fixed to a shaft member. The vibration ring 30 is an annular mass body that surrounds the hub 10. The damper rubber 20 is an annular elastic body that is fitted between the hub 10 and the vibration ring 30. In the hub 10, two first holes 15 and four second holes 16 of different shapes open along a circumferential direction of the hub 10.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a torsional damper.

Background Art

[0002] Structures for reducing noise radiated from damper devices such as crankshafts in internal combustion engines have been proposed conventionally. For example, Patent Document 1 discloses that a cavity formed along the outer edge of the front surface of a boss portion attached to the front end of a crankshaft uses interference of sound waves to cancel the radiated sound emitted from the center of the front surface of the boss portion through the crankshaft.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the technique of Patent Document 1, a sufficient noise cancellation effect cannot be obtained unless the cavity volume and the opening area of the cavity are set according to the frequency of the radiated sound, and there is a problem that the conditions for effectively canceling the sound do not hold depending on the size of the torsional damper.

[0005] The present invention has been made to solve the above problems, and an object thereof is to effectively reduce the radiated sound from the hub regardless of the size of the torsional damper.

Means for Solving the Problems

[0006] In order to solve the above problems, a torsional damper according to one aspect of the present invention includes a hub fixed to a shaft member, an annular vibration ring surrounding the hub, and an annular damper rubber fitted between the hub and the vibration ring. One or more first holes and one or more second holes having different shapes from each other are opened along the circumferential direction of the hub.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0008] Preferred embodiments of the present invention will be described below with reference to the drawings. Note that the dimensions and scales of the elements in each drawing are appropriately different from those of actual products.

[0009] A: First Embodiment A-1: Structure of Torsional Damper FIG. 1 is a plan view of a torsional damper 100 according to the first embodiment. FIG. 2 is an enlarged view of a part including the first hole in FIG. 1. FIG. 3 is a cross-sectional view taken along line a-a in FIG. 1.

[0010] The torsional damper 100 of the present embodiment is used as a damper pulley for an internal combustion engine such as an in-line four-cylinder engine. The internal combustion engine includes a shaft member that rotates about a rotation axis A. Examples of the shaft member include a crankshaft. The torsional damper 100 is a dynamic vibration absorber that reduces vibrations generated in the shaft member. The vibrations generated in the shaft member mainly include torsional vibrations and bending vibrations.

[0011] In the following description, the circumferential direction on an imaginary circle with an arbitrary diameter centered on the rotation axis A is referred to as the "circumferential direction", and the radial direction of the radius of the imaginary circle is referred to as the "radial direction". Also, the direction parallel to the rotation axis A is referred to as the "axial direction".

[0012] As illustrated in FIGS. 1, 2, and 3, the torsional damper 100 includes a hub 10, a damper rubber 20, and a vibration ring 30. The hub 10 is fixed to the shaft member of the internal combustion engine. The hub 10 of the present embodiment is a structure in which a boss portion 11, a stay portion 12, and a rim portion 13 are integrally formed.

[0013] The boss portion 11 is a cylindrical portion fixed to the shaft member. A key groove 14 extending in the axial direction is formed on the inner peripheral surface of the boss portion 11. The inner peripheral surface of the boss portion 11 can also be referred to as the inner peripheral surface of the hub 10. The key groove 14 is a groove portion with a predetermined width that fits a key protruding from the outer peripheral surface of the shaft member.

[0014] The rim portion 13 is an annular portion that surrounds the boss portion 11. A recess 19 is formed on the outer peripheral surface of the rim portion 13. The outer peripheral surface of the rim portion 13 can also be referred to as the outer peripheral surface of the hub 10. The recess 19 is a depression extending in the circumferential direction on the outer peripheral surface.

[0015] The stay portion 12 is a disk-shaped part that connects the boss portion 11 and the rim portion 13. The thickness of the stay portion 12 is constant. The thickness of the stay portion 12 is less than the height of the boss portion 11 in the axial direction and the height of the rim portion 13 in the axial direction. In the stay portion 12, two first holes 15, four second holes 16, and two third holes 17 open along the circumferential direction of the hub 10. The first hole 15, the second hole 16, and the third hole 17 are holes with different shapes from each other. Note that the thickness of the stay portion 12 does not necessarily have to be constant. For example, the thickness of the stay portion 12 may vary along the radial direction.

[0016] The vibration ring 30 is an annular mass body that surrounds the hub 10. The vibration ring 30 is installed concentrically with the hub 10. A convex portion 31 is formed on the inner peripheral surface of the vibration ring 30. The convex portion 31 is a protrusion that extends in the circumferential direction on the inner peripheral surface. The outer peripheral surface of the hub 10 and the inner peripheral surface of the vibration ring 30 face each other with an annular gap therebetween. A plurality of pulley grooves 32 are formed on the outer peripheral surface of the vibration ring 30. The plurality of pulley grooves 32 are V-grooves for winding an endless belt that transmits the rotational torque of the rotation axis A to an external mechanism. Note that, for example, in a configuration where an endless belt is not wound around the vibration ring 30, the plurality of pulley grooves 32 may be omitted.

[0017] The damper rubber 20 is an annular elastic body that is fitted into the gap between the hub 10 and the vibration ring 30. The inner peripheral surface of the damper rubber 20 is in close contact with the outer peripheral surface of the hub 10. The outer peripheral surface of the damper rubber 20 is in close contact with the inner peripheral surface of the vibration ring 30. The damper rubber 20 is formed of an elastic material. As understood from the above description, the hub 10 and the vibration ring 30 are elastically connected by the damper rubber 20. Note that a convex portion may be formed on the outer peripheral surface of the hub 10 and a concave portion may be formed on the inner peripheral surface of the vibration ring 30.

[0018] A-2: Explanation of the holes in the stay portion Hereinafter, the first hole 15, the second hole 16, and the third hole 17 will be described in detail respectively.

[0019] The first hole 15 is a rectangular hole. The first hole 15 is a through-hole that penetrates the stay portion 12. The two first holes 15 are arranged in the stay portion 12 so as to be point-symmetrical with each other about the rotation axis A. By arranging the first holes 15 in this way, it is possible to suppress the deviation of the center of gravity position of the hub 10 from the rotation axis A.

[0020] Also, the position where the first hole 15 opens in the radial direction is closer to the rim portion 13 than the boss portion 11. By arranging the first hole 15 in this way, the distance LI between the side SI closest to the boss portion 11 among the sides of the first hole 15 and the boss portion 11 is longer than the distance LO between the side SO closest to the rim portion 13 among the sides of the first hole 15 and the rim portion 13. Therefore, more of the thickness of the stay portion 12 can be left around the boss portion 11 where stress concentration occurs. For this reason, for example, compared with the case where the first hole 15 is arranged at the center of the stay portion 12 in the radial direction, mechanical strength can be more ensured.

[0021] The second hole 16 is a fan-shaped hole. The second hole 16 is a through-hole that penetrates the stay portion 12. The four second holes 16 are arranged in the stay portion 12 at 90-degree intervals about the rotation axis A. By arranging the second holes 16 in this way, it is possible to suppress the deviation of the center of gravity position of the hub 10 from the rotation axis A. The four second holes 16 are arranged such that the arc portions of the sectors face the rim portion 13 and the centers of the sectors face the boss portion 11, respectively. The second hole 16 is provided as a hole for inserting a jig for preventing the torsional damper 100 from rotating when the torsional damper 100 is attached to a shaft member such as a crankshaft.

[0022] The third hole 17 is a threaded hole. The third hole 17 is a through-hole that penetrates the stay portion 12. The two third holes 17 are arranged in the stay portion 12 so as to be point-symmetrical with each other about the rotation axis A. As shown in FIG. 1, the third hole 17 is smaller than the first hole 15 and the second hole 16. The third hole 17 is a hole for screwing in a tool used when removing the torsional damper 100 from a shaft member such as a crankshaft.

[0023] Note that the first hole 15, the second hole 16, and the third hole 17 may be formed by cutting the cast hub 10, or may be formed by casting.

[0024] The area of the first hole 15, the area of the second hole 16, and the area of the third hole 17 are correlated with the equivalent radiation power of the radiated sound from the hub 10. The equivalent radiation power is the total amount of energy radiated into the acoustic space per unit time, and is the energy given by the velocity component of the structure orthogonal to the surface of the structure to the acoustic space. More specifically, there is a relationship of the following formula (1) between the equivalent radiation power ERP of the radiated sound from the hub 10, the radiation loss coefficient σ of the hub 10, the material density ρ of the hub 10, the projected area Sp of the hub 10, the vibration velocity Vo of the hub 10, and the sound velocity Vs.

[0025] ERP = σ×(Vs / 2)×ρ×Sp×Vo 2 ···(1)

[0026] The radiation loss coefficient σ is a coefficient that depends on the shape of the object. For example, the radiation loss coefficient σ of an object with a thin shape like a piano wire is smaller than the radiation loss coefficient σ of a flat plate-shaped object.

[0027] The material density ρ depends on the physical properties of the material. For example, the material density ρ depends on whether the material is a sponge-like object or a high-density object without air bubbles. For example, the hub 10 is made of general cast iron, and in this case, the material density ρ is constant.

[0028] The projected area Sp is the area where the hub 10 is projected onto a plane orthogonal to the rotation axis A of the hub 10. In other words, the projected area Sp is the area obtained by subtracting the projected area of the first hole 15, the projected area of the second hole 16, and the projected area of the third hole from the projected area of a circle having the same diameter as the radius of the hub 10.

[0029] Therefore, the parameters that depend on the shape of the hub 10 are the radiation loss coefficient σ and the projected area Sp. As understood from equation (1), the equivalent radiated power ERP is proportional to the radiation loss coefficient σ and proportional to the projected area Sp. Therefore, by reducing the radiation loss coefficient σ or reducing the projected area Sp, the equivalent radiated power ERP can be reduced. Furthermore, since the equivalent radiated power ERP is proportional to the square of the vibration velocity, the equivalent radiated power ERP can also be reduced by reducing the vibration velocity.

[0030] In order to reduce the projected area Sp, for example, it is considered effective to increase the opening area of the stay portion 12. Here, the opening area means the sum of the areas of the first hole 15, the second hole 16, and the third hole 17.

[0031] In order to reduce the radiation loss coefficient σ, for example, it is considered effective to increase the opening area of the stay portion 12. Furthermore, even if the opening area of the stay portion 12 is the same, reducing the area of each opening in the stay portion 12 and increasing the number of each opening are also considered effective for reducing the radiation loss coefficient σ.

[0032] In order to reduce the vibration velocity Vo, for example, it is considered effective to increase the opening area of the stay portion 12. More specifically, by increasing the opening area of the stay portion 12 to reduce the projected area Sp, the rigidity of the hub 10 in the axial direction becomes lower. When the rigidity of the hub 10 in the axial direction becomes lower, the force generated for the same displacement in the axial direction of the hub 10 becomes weaker, so the vibration velocity Vo of the hub 10 decreases.

[0033] A-3: Effects of the First Embodiment According to the above description, the torsional damper 100 according to the first embodiment includes a hub 10, a vibration ring 30, and a damper rubber 20. The hub 10 is fixed to the shaft member. The vibration ring 30 is an annular mass body that surrounds the hub 10. The damper rubber 20 is an elastic body that is fitted between the hub 10 and the vibration ring 30. Two first holes 15 and four second holes are opened in the hub 10 along the circumferential direction of the hub 10. The two first holes 15 and the four second holes are holes having different shapes from each other.

[0034] According to this aspect, in addition to the second hole 16, the first hole 15 different from the second hole 16 opens in the hub 10, so that the projected area Sp in the axial direction of the hub 10 is reduced. Therefore, the radiated sound from the hub 10 can be reduced. Further, since the radiated sound is reduced as the projected area Sp is smaller, the reduction effect of the radiated sound can be achieved only by arranging the first hole 15 in the hub 10 in addition to the second hole 16. Further, according to this aspect, since it is not a method using the interference of sound waves, it is not necessary to set the opening area of the hole according to the frequency of the radiated sound. Therefore, the radiated sound from the hub 10 can be reduced without being restricted by the size of the torsional damper.

[0035] Further, two third holes 17 smaller than the first hole 15 and the second hole 16 are opened in the hub 10. The two third holes 17 are threaded holes.

[0036] According to this aspect, the first hole 15 is a hole larger than the threaded hole. Therefore, the radiated sound from the hub 10 can be reduced more effectively.

[0037] Further, the hub 10 includes a boss portion 11 and a rim portion 13. The boss portion 11 is fixed to the shaft member. The rim portion 13 is an outer peripheral portion of the hub 10. The position where the first hole 15 opens in the radial direction of the hub 10 is closer to the rim portion 13 than to the boss portion 11.

[0038] According to this aspect, by leaving the thickness of the stay portion 12 around the boss portion 11 where stress concentrates and arranging the first hole 15 at a position close to the rim portion 13, a substantial strength reduction of the hub 10 due to opening the stay portion 12 can be suppressed.

[0039] Further, the area of the first hole 15 correlates with the equivalent radiated power ERP of the radiated sound from the hub 10.

[0040] According to this aspect, since the required area of the first hole 15 can be estimated from the allowable equivalent radiated power ERP of the radiated sound, the design of the first hole 15 becomes easier.

[0041] Further, between the equivalent radiated power ERP, the radiation loss coefficient σ of the hub 10, the material density ρ of the hub 10, the projected area Sp on which the hub 10 is projected onto a virtual plane perpendicular to the rotation axis A of the hub 10, the vibration velocity Vo of the hub 10, and the speed of sound Vs, there is an equivalent radiated power ERP = radiation loss coefficient σ × speed of sound Vs / 2 × material density ρ × projected area Sp × vibration velocity Vo 2 such a relationship holds.

[0042] According to this aspect, since the required area of the first hole 15 can be estimated from the allowable equivalent radiated power ERP of the radiated sound, the design of the first hole 15 becomes even easier.

[0043] Further, the second hole 16 is a hole through which a jig used when attaching the torsional damper 100 to the internal combustion engine passes.

[0044] According to this aspect, although the second hole 16 has shape restrictions in order to function as a hole for passing the jig, the first hole 15 does not have shape restrictions like those of the second hole 16. Therefore, the shape of the first hole 15 can be designed relatively freely.

[0045] B: Second Embodiment B-1: Structure of Torsional Damper Figure 4 is a plan view of the torsional damper 100A according to the second embodiment. As shown in Figure 4, the first hole 15A in the torsional damper 100A includes two holes 15a and 15b. The two holes 15a and 15b are arranged in the radial direction of the hub 10A.

[0046] The two first holes 15A are arranged on the stay portion 12A so as to be point-symmetrical with each other about the rotation axis A. By arranging the first holes 15A in this way, it is possible to suppress the deviation of the center-of-gravity position of the hub 10A from the rotation axis A.

[0047] The torsional damper 100A according to the second embodiment is different from the torsional damper 100 according to the first embodiment in that the first hole 15A includes a plurality of holes 15a and 15b arranged in the radial direction of the hub 10A.

[0048] As shown in Figure 4, a beam 18 is formed between the two holes 15a and 15b. The longitudinal direction of the beam 18 is perpendicular to the direction in which the two holes 15a and 15b are arranged. Therefore, the beam 18 is effective against circumferential stress. That is, the beam 18 has the effect of suppressing a decrease in the strength of the hub 10A due to the opening of the first hole 15A.

[0049] B-2: Effects achieved by the second embodiment According to the above description, in the torsional damper 100A according to the second embodiment, the first hole 15A includes two holes 15a and 15b arranged in the radial direction of the hub 10.

[0050] According to this aspect, by arranging the first holes 15A side by side in the radial direction, it is possible to suppress a decrease in the strength of the hub 10A due to the opening of the first hole 15A.

[0051] C: Third embodiment C-1: Structure of the torsional damper Figure 5 is a plan view of the torsional damper 100B according to the third embodiment. As shown in Figure 5, the first hole 15B in the torsional damper 100B is a semi-elliptical hole.

[0052] The torsional damper 100B according to the third embodiment is different from the torsional damper 100 according to the first embodiment and the torsional damper 100A according to the second embodiment in that the first hole 15B is a semi-elliptical hole.

[0053] As shown in FIG. 5, the two first holes 15B are arranged such that the arc portions of the semi-ellipses face the boss portion 11 and the flat portions of the semi-ellipses face the rim portion 13, respectively. Therefore, the stay portion 12B sandwiched between the second hole 16 and the arc portion of the first hole 15B becomes wider as it is closer to the boss portion 11 where stress concentrates. Therefore, there is an effect of suppressing a decrease in the strength of the hub 10B due to the opening of the first hole 15B.

[0054] C-2: Effects of the Third Embodiment According to the above description, in the torsional damper 100B according to the third embodiment, the first hole 15B is a semi-elliptical hole. The arc portion of the first hole 15B faces the boss portion 11, and the flat portion of the first hole 15B faces the rim portion 13.

[0055] According to this aspect, it is possible to suppress a decrease in the strength of the hub 10B due to the opening of the first hole 15B.

[0056] D: Fourth Embodiment D-1: Structure of the Torsional Damper FIG. 6 is a plan view of the torsional damper 100C according to the fourth embodiment. As shown in FIG. 6, the first holes 15 in the torsional damper 100C are arranged in the stay portion 12C at intervals of 90 degrees in the circumferential direction.

[0057] The torsional damper 100C according to the fourth embodiment is different from the torsional dampers 100, 100A, and 100B according to the above embodiments in that the first holes 15 are arranged in the stay portion 12C at intervals of 90 degrees in the circumferential direction.

[0058] In this embodiment, the shape of the first hole 15 is the same as that of the first hole 15 according to the first embodiment. Among the four first holes 15, two first holes 15 open in place of the third hole 17 in the first to third embodiments.

[0059] D-2: Effects achieved by the third embodiment When the third hole 17 is functionally unnecessary, as in this embodiment, it is desirable that the first hole 15 be arranged in the stay portion 12C in place of the third hole 17. According to this aspect, since the projected area Sp of the hub 10C is smaller than each of the projected areas Sp of the hub 10, the hub 10A, and the hub 10B, the equivalent radiated power ERP from the hub 10C can be reduced more effectively.

[0060] E: Modifications Specific modifications added to each of the embodiments illustrated above are exemplified below. Two or more forms arbitrarily selected from the following examples may be appropriately combined within a non - conflicting range.

[0061] (1) In the first to third embodiments, the two first holes 15, 15A, or 15B are arranged in the stay portions 12, 12A, or 12B, respectively, so as to be point - symmetric with respect to the rotation axis A. However, the two first holes 15, 15A, or 15B do not necessarily have to be arranged to be point - symmetric. Also, the number of the first holes 15, 15A, or 15B is not limited to two. At least one of the first holes 15, 15A, and 15B may be open.

[0062] (2) In each of the above embodiments, the shapes of the first holes 15, 15A, and 15B were rectangular or semi - elliptical. However, the shapes of the first holes 15, 15A, and 15B are not limited to rectangular or semi - elliptical.

[0063] (3) In each of the above embodiments, the shape of the second hole 16 was fan - shaped. However, the shape of the second hole 16 is not limited to fan - shaped. Any shape may be used as long as it allows a jig for preventing the torsional damper from rotating to be inserted.

[0064] (4) In the second embodiment, the first holes 15A are arranged side by side in the radial direction. However, the arrangement of the first holes 15A is not limited to the above examples. For example, three or more first holes 15A may be arranged in the radial direction. Also, the first holes 15A do not necessarily have to be arranged side by side in the radial direction. For example, the first holes 15A may be arranged side by side in a direction perpendicular to the radial direction. FIG. 7 is a plan view of the torsional damper 100D according to the fourth modification. As shown in FIG. 7, the first holes 15D in the torsional damper 100D include two holes 15c and 15d. The two holes 15c and 15d are formed in the stay portion 12D. The two holes 15c and 15d are arranged in the circumferential direction of the hub 10D.

[0065] F: Supplementary Note From the forms exemplified above, for example, the following configurations can be understood.

[0066] A torsional damper according to one aspect (Aspect 1) of the present disclosure includes a hub fixed to a shaft member, an annular vibration ring surrounding the hub, and an annular damper rubber fitted between the hub and the vibration ring. One or more first holes and one or more second holes having different shapes from each other open along the circumferential direction of the hub.

[0067] According to this aspect, the radiated noise from the hub can be reduced regardless of the size of the torsional damper.

[0068] In a torsional damper according to one aspect (Aspect 2) of the present disclosure, one or more third holes smaller than the first holes and the second holes open in the hub, and the third holes are screw holes.

[0069] According to this aspect, since the first hole is larger than the screw hole, the radiated noise from the hub can be reduced more effectively.

[0070] In the torsional damper according to one aspect (Aspect 3) of the present disclosure, the one or more first holes include a plurality of holes arranged in the radial direction of the hub.

[0071] According to this aspect, by arranging the first holes in the radial direction, it is possible to suppress a decrease in the strength of the hub due to the opening of the first holes.

[0072] In the torsional damper according to one aspect (Aspect 4) of the present disclosure, the hub includes a boss portion fixed to the shaft member and a rim portion that is an outer peripheral portion of the hub, and a position in the radial direction of the hub where the first hole opens is closer to the rim portion than to the boss portion.

[0073] According to this aspect, by leaving the thickness of the stay portion 12 around the boss portion 11 where stress concentrates and arranging the first hole 15 at a position closer to the rim portion 13, it is possible to suppress a substantial decrease in the strength of the hub 10 due to the opening of the stay portion 12.

[0074] In the torsional damper according to one aspect (Aspect 5) of the present disclosure, the area of the first hole correlates with the equivalent radiation power of the radiated sound from the hub.

[0075] According to this aspect, since the required area of the first hole can be estimated from the equivalent radiation power of the allowed radiated sound, the design of the first hole becomes easier.

[0076] In the torsional damper according to one aspect (Aspect 6) of the present disclosure, between the equivalent radiation power, the radiation loss coefficient of the hub, the material density of the hub, the projected area obtained by projecting the hub onto a virtual plane orthogonal to the rotation axis of the hub, the vibration velocity of the hub, and the speed of sound, the following relationship holds: equivalent radiation power = radiation loss coefficient × (speed of sound / 2) × material density × projected area × vibration velocity 2 holds.

[0077] According to this aspect, since the required area of the first hole can be estimated from the equivalent radiated power of the allowed radiated sound, the design of the first hole becomes easier.

[0078] In a torsional damper according to one aspect (Aspect 7) of the present disclosure, the second hole is a hole for passing a jig used when attaching the torsional damper to an internal combustion engine.

[0079] According to this aspect, the second hole has shape constraints in order to function as a hole for passing a jig, but the first hole does not have shape constraints like the second hole. Therefore, the shape of the first hole can be designed relatively freely.

Explanation of Reference Numerals

[0080] 100, 100A, 100B, 100C... Torsional damper, 10, 10A, 10B, 10C... Hub, 11... Boss portion, 12... Stay portion, 13... Rim portion, 15, 15A, 15a, 15B, 15b, 15C... First hole, 16... Second hole, 17... Third hole, 20... Damper rubber, 30... Vibration ring, ERP... Equivalent radiated power, Sp... Projected area, Vo... Vibration velocity, Vs... Sound velocity, ρ... Material density, σ... Radiation loss coefficient.

Claims

1. A hub fixed to a shaft member, An annular vibration ring surrounding the hub, An annular damper rubber fitted between the hub and the vibration ring, Comprising, In the hub, one or more first holes and one or more second holes having different shapes open along the circumferential direction of the hub, A torsional damper.

2. In the hub, one or more third holes smaller than the first hole and the second hole are open, The third hole is a threaded hole, The torsional damper according to Claim 1.

3. The one or more first holes include a plurality of holes arranged in the radial direction of the hub, The torsional damper according to Claim 1.

4. The hub includes a boss portion fixed to the shaft member and a rim portion that is the outer peripheral portion of the hub, The position where the first hole opens in the radial direction of the hub is closer to the rim portion than to the boss portion, The torsional damper according to Claim 1.

5. The area of the first hole correlates with the equivalent radiation power of the radiated sound from the hub, The torsional damper according to Claim 1.

6. Between the equivalent radiation power, the radiation loss coefficient of the hub, the material density of the hub, the projected area obtained by projecting the hub onto a virtual plane perpendicular to the rotation axis of the hub, the vibration velocity of the hub, and the speed of sound, Equivalent radiation power = radiation loss coefficient × (speed of sound / 2) × material density × projected area × vibration velocity ２ The following relationship holds, The torsional damper according to Claim 5.

7. The second hole is a hole for passing a jig used when attaching the torsional damper to an internal combustion engine, The torsional damper according to Claim 1.

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