Torsional damper

Abstract

To provide a torsional damper capable of suppressing falling of a vibration ring to an engine side.SOLUTION: A torsional damper 10 includes a hub 100, a vibration ring 200 provided concentrically with the hub 100, and an annular elastic body 300 provided between an outer cylinder 130 of the hub 100 and the vibration ring 200, and is disposed in an engine case. A stopper structure for preventing the vibration ring 200 from coming off from the outer cylinder 130 to a region in which an engine is disposed is formed by relation between a dimensional shape of an outer peripheral surface of the outer cylinder 130 and a dimensional shape of an inner peripheral surface of the vibration ring 200.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Conventionally, a torsional damper provided on a crankshaft has a pulley on its outer circumferential surface for rotating a belt, and also plays a role in driving accessories. Therefore, the torsional damper is arranged on the outside of the engine case (outside the front cover). In recent years, engines have become more hybridized to improve fuel efficiency, and belts for driving accessories are becoming unnecessary. Accordingly, development is underway to arrange the torsional damper inside the engine case, aiming at downsizing the engine, suppressing noise emitted from the torsional damper, and eliminating the need for oil seals.

[0003] However, when a torsional damper is placed inside an engine case, the usage environmental conditions change significantly, as the damper is exposed to splashing oil, the temperature inside the engine case increases, etc. This gives rise to various new issues, such as improving oil resistance, improving heat resistance, preventing the annular elastic body provided between the hub and the vibration ring that constitute the torsional damper from becoming too hot, and preventing the vibration ring from falling into the engine even if the annular elastic body is damaged. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-177469 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a torsional damper capable of preventing a vibration ring from falling toward the engine. [Means for solving the problem]

[0006] The present invention employs the following means to solve the above problems.

[0007] That is, the torsional damper of the present invention has the following features: a hub including an inner cylindrical portion, an outward flange portion integral with the inner cylindrical portion, and an outer cylindrical portion integrally provided radially outward of the outward flange portion, the inner cylindrical portion being fixed to a crankshaft; a vibration ring disposed concentrically on the hub; an annular elastic body provided between the outer cylinder portion and the vibration ring; A torsional damper disposed in an engine case, The present invention is characterized in that a stopper structure is formed that prevents the vibrating ring from slipping out of the outer cylinder portion into the area where the engine is located, due to the relationship between the dimensions and shape of the outer peripheral surface of the outer cylinder portion and the dimensions and shape of the inner peripheral surface of the vibrating ring.

[0008] According to the present invention, even if the annular elastic body is damaged and the vibration ring attempts to move toward the engine, the vibration ring can be prevented from falling toward the engine.

[0009] The outer tubular portion has an annular protruding portion at a center in a width direction of an outer circumferential surface thereof, the annular protruding portion protruding radially outward, The maximum outer diameter of the annular protrusion is preferably larger than the minimum inner diameter of the inner circumferential surface of the vibration ring on the opposite side to the area in which the engine is disposed relative to the annular protrusion.

[0010] It should be noted that "the center in the width direction" does not necessarily mean near the center in the width direction, but means excluding the ends in the width direction.

[0011] As a result, even if the vibration ring attempts to move toward the engine, the inner peripheral surface of the vibration ring is caught in the annular protrusion provided on the outer cylindrical portion of the hub, and therefore the vibration ring will not fall toward the engine.

[0012] The maximum outer diameter of the annular protrusion is preferably smaller than the minimum inner diameter of the inner circumferential surface of the vibration ring on the side of the region where the engine is disposed, the region being closer to the annular protrusion.

[0013] This allows the vibration ring to be fitted onto the hub, so that no problems arise during manufacturing.

[0014] The vibration ring has an inner peripheral surface at a center in a width direction thereof, the inner peripheral surface having an annular protruding portion protruding radially inward, It is also preferable that the minimum inner diameter of the annular protrusion is smaller than the maximum outer diameter of the outer peripheral surface of the outer cylinder portion on the side of the region where the engine is disposed, the region being closer to the annular protrusion.

[0015] It should be noted that "the center in the width direction" does not necessarily mean near the center in the width direction, but means excluding the ends in the width direction.

[0016] As a result, even if the vibration ring attempts to move toward the engine, the annular protrusion of the vibration ring catches on the outer peripheral surface of the outer ring, so that the vibration ring will not fall toward the engine.

[0017] The minimum inner diameter of the annular protrusion may be greater than the maximum outer diameter of the outer peripheral surface of the outer cylinder portion on the opposite side to a region in which an engine is disposed relative to the annular protrusion.

[0018] This allows the vibration ring to be fitted onto the hub, so that no problems arise during manufacturing.

[0019] The end face of the annular elastic body is preferably located inside the end face of the outer cylindrical portion and the end face of the vibration ring.

[0020] This makes it possible to prevent the annular elastic body from being significantly deformed.

[0021] The above configurations may be combined as much as possible. Effect of the Invention

[0022] As described above, according to the present invention, it is possible to prevent the vibration ring from falling toward the engine. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a front view of a torsional damper according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the torsional damper according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of the torsional damper according to the first embodiment. [Figure 4] FIG. 4 is a graph showing the vibration characteristics of a torsional damper. [Diagram 5] FIG. 5 is a schematic cross-sectional view of a torsional damper according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, the embodiment of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative positions, and the like of the components described in the embodiment are not intended to limit the scope of the present invention unless otherwise specified.

[0025] Example 1 A torsional damper according to a first embodiment of the present invention will be described with reference to Figs. 1 to 4. Fig. 1 is a front view of the torsional damper according to the first embodiment of the present invention. Fig. 2 is a schematic cross-sectional view of the torsional damper according to the first embodiment of the present invention, taken along line AA in Fig. 1. Fig. 3 is a partially enlarged cross-sectional view of the torsional damper according to this embodiment. Fig. 4 is a graph showing vibration characteristics of the torsional damper, Fig. 4(a) is an explanatory diagram of the influence of the natural frequency of the torsional damper, and Fig. 4(b) is an explanatory diagram of the influence of the moment of inertia of the vibrating ring.

[0026] <Torsion damper> The overall configuration of the torsional damper 10 according to this embodiment will be described. The torsional damper 10 according to this embodiment includes a hub 100, a vibration ring 200 provided concentrically with the hub 100, and an annular elastic body 300.

[0027] The hub 100 is an annular member made of metal. The hub 100 has an inner cylindrical portion 110, an outward flange portion 120 that is provided integrally with the inner cylindrical portion 110, and an outer cylindrical portion 130 that is provided integrally with the radially outer side of the outward flange portion 120. The inner cylindrical portion 110 is fixed to a crankshaft 20 of an engine. Note that in FIG. 2, the crankshaft 20 and the positions of bolts 30 for fixing the torsional damper 10 to the crankshaft 20 are indicated by dotted lines.

[0028] The vibration ring 200 is a metal annular member. The annular elastic body 300 is made of a rubber material and is provided between the outer cylinder portion 130 of the hub 100 and the vibration ring 200. The annular elastic body 300 can be obtained by, for example, vulcanization molding, and is vulcanization-bonded to the outer cylinder portion 130 and the vibration ring 200.

[0029] The torsional damper 10 configured as described above is disposed inside the engine case. In Fig. 2, the position of the inner wall surface of a part of the engine case (a part of the front cover) is indicated by a dotted line C. In Fig. 2, the side to the right of the torsional damper 10 is the area (E) where the engine is disposed.

[0030] In the torsional damper 10, when vibrations of a frequency at which the crankshaft 20 resonates are transmitted, the vibration ring 200 vibrates, thereby exerting a function of suppressing resonance of the crankshaft 20. In other words, the vibration ring 200 is designed to suppress resonance of the crankshaft 20 with respect to vibrations in the rotational direction (torsional direction) of the crankshaft 20.

[0031] <Detailed configuration of each component of the torsional damper> The detailed configuration of each member of the torsional damper 10 will be described. The outer cylinder portion 130 of the hub 100 according to this embodiment has an annular protruding portion 131 that protrudes radially outward at the center of the width direction of the outer circumferential surface (the width direction in the direction in which the central axis of the torsional damper 10 extends). That is, the outer diameter of the outer peripheral surface of the outer cylinder portion 130 is large at the portion where the annular protrusion portion 131 is provided, and the outer diameters on both sides are smaller than the outer diameter of the annular protrusion portion 131. The inner peripheral surface of the vibrating ring 200 has an annular recessed shape at the center in the width direction so as to conform to the shape of the outer peripheral surface of the outer cylinder portion 130. That is, the inner diameter of the inner peripheral surface of the vibrating ring 200 is large at the center in the width direction, and the inner diameters on both sides are smaller than the inner diameter at the center.

[0032] The maximum outer diameter R10 of the annular protrusion 131 is set to be larger than the minimum inner diameter R21 of the inner circumferential surface of the vibration ring 200 on the side opposite the region (E) where the engine is disposed from the annular protrusion 131. The maximum outer diameter R10 of the annular protrusion 131 is set to be smaller than the minimum inner diameter R22 of the inner circumferential surface of the vibration ring 200 on the side closer to the region (E) where the engine is disposed from the annular protrusion 131.

[0033] In the torsional damper 10 according to this embodiment, the amount of positional deviation of the vibration ring 200 on the opposite side to the region (E) where the engine is located after thermal aging (after 533 hours in an environment of 130°C) is set to be 1 mm or less. This prevents the vibration ring 200 from coming into contact with the inner wall surface of a part of the engine case (a part of the front cover).

[0034] <Advantages of the torsional damper according to this embodiment> According to the torsional damper 10 of this embodiment, a stopper structure is configured that prevents the vibration ring 200 from slipping out of the outer cylinder 130 toward the area where the engine is located, due to the relationship between the size and shape of the outer peripheral surface of the outer cylinder 130 and the size and shape of the inner peripheral surface of the vibration ring 200. More specifically, the outer peripheral surface of the outer cylinder 130 is provided with an annular protrusion 131, and as described above, the hub 100 and the vibration ring 200 are configured so that R10>R21. Therefore, even if the annular elastic body 300 is damaged and the vibration ring 200 tries to move toward the engine, the inner peripheral surface of the vibration ring 200 is caught by the annular protrusion 131 provided on the outer cylinder 130 of the hub 100. Therefore, the vibration ring 200 does not fall toward the engine.

[0035] Here, in order to prevent the vibration ring from falling to the engine side, it is also possible to provide a flange-shaped stopper at the end of the outer cylinder of the hub on the engine side to restrict the movement of the vibration ring to the engine side. However, since there is a limit to how wide the entire width of the outer cylinder can be, when such a configuration is adopted, it is necessary to narrow the width of the fitting portion between the annular elastic body and the outer cylinder. Therefore, this becomes a factor of the annular elastic body becoming hot. In contrast, according to the torsional damper 10 of this embodiment, the width of the fitting portion between the annular elastic body 300 and the outer cylinder 130 can be made wider than when a flange-shaped stopper is provided, and the temperature rise of the annular elastic body 300 can be suppressed. This makes it possible to suppress damage to the annular elastic body 300.

[0036] Furthermore, according to the torsional damper 10 of this embodiment, the hub 100 and the vibration ring 200 are configured so that R22>R10, as described above. This makes it possible to fit the vibration ring 200 to the hub 100. That is, by moving the vibration ring 200 relatively to the right in FIG. 2 with respect to the hub 100, the hub 100 and the vibration ring 200 can be brought into the positional relationship shown in FIG. 2. In this state, the annular elastic body 300 can be molded by vulcanization molding to obtain the torsional damper 10. Therefore, no problems are caused during manufacturing.

[0037] Here, it is desirable to adopt a configuration in which the end face of the annular elastic body 300 is located more inward than the end face of the outer cylinder portion 130 and the end face of the vibrating ring 200. This point will be explained with reference to Fig. 3. Fig. 3(a) is an enlarged cross-sectional view of a case in which an end face 310 of the annular elastic body 300 is located more inward than the end face 132 of the outer cylinder portion 130 and the end face 210 of the vibrating ring 200. 1B is an enlarged cross-sectional view of the case where an end face 310 of the annular elastic body 300 is positioned outside the end face 132 of the outer cylinder portion 130 and the end face 210 of the vibrating ring 200.

[0038] When the vibration ring 200 rotates relative to the hub 100 in accordance with the rotation of the crankshaft 20, the annular elastic body 300 is deformed. Here, the deeper the position inside the annular elastic body 300, the greater the restraining force of the annular elastic body 300 by the hub 100 and the vibration ring 200. Therefore, in the annular elastic body 300, the amount of deformation from the original state increases at the deeper position inside (see arrow X1 in the figure), and the amount of deformation from the original state decreases at the position closer to the end face 310 (surface) (see arrow X2 in the figure).

[0039] As shown in FIG. 3(a), when the end face 310 of the annular elastic body 300 is located inside the end face 132 of the outer cylinder 130 and the end face 210 of the vibration ring 200, the difference in the amount of deformation between the deep position X1 inside and the position X2 close to the end face 310 is relatively small. On the other hand, as shown in FIG. 3(b), when the end face 310 of the annular elastic body 300 is located outside the end face 132 of the outer cylinder 130 and the end face 210 of the vibration ring 200, the difference in the amount of deformation between the deep position X1 inside and the position X2 close to the end face 310 becomes large. This makes the annular elastic body 300 more likely to crack. Once a crack occurs, the crack gradually grows larger, making the annular elastic body 300 more likely to break. Therefore, it is desirable to adopt a configuration in which the end face 310 of the annular elastic body 300 is located inside the end face 132 of the outer cylinder 130 and the end face 210 of the vibration ring 200. Although FIG. 3 shows only one end face 310 of the annular elastic body 300, it goes without saying that the opposite end face is similar.

[0040] (Various methods for preventing deterioration of annular elastic bodies) Various methods for suppressing the deterioration of the annular elastic body 300 will be described. In order to suppress the deterioration of the annular elastic body 300 in order to suppress damage (breakage) of the annular elastic body 300, it is necessary to suppress the temperature rise of the annular elastic body 300. In order to suppress the temperature rise of the annular elastic body 300, it is necessary to reduce the amount of distortion of the annular elastic body 300 when the crankshaft 20 rotates at high speed. In the case of a four-cylinder engine, vibrations of various orders occur, but a significant large vibration peak occurs in the fourth and sixth vibrations. Note that the Nth order means the vibration cycle that appears in one rotation of the crankshaft, and for example, in the case of one vibration per rotation, it is the first order. In addition, the vibration peak generated by the crankshaft alone (in a state in which a torsional damper is not provided) is reduced by providing a torsional damper. As a result, a vibration peak smaller than the original vibration peak that is generated on the lower frequency side than the frequency at which the original vibration peak occurs is called the first node, and a vibration peak smaller than the original vibration peak that is generated on the higher frequency side is called the second node. The following findings have also been obtained. That is, when the resonant frequency (natural frequency) of the torsional damper is matched to the frequency at which the crankshaft alone generates a vibration peak, the vibration peak at node 1 and the vibration peak at node 2 become equal. In contrast, when the resonant frequency (natural frequency) of the torsional damper is shifted to a lower frequency side than the frequency at which the crankshaft alone generates a vibration peak, the vibration peak at node 2 becomes higher than the vibration peak at node 1. Conversely, when the resonant frequency (natural frequency) of the torsional damper is shifted to a higher frequency side than the frequency at which the crankshaft alone generates a vibration peak, the vibration peak at node 1 becomes higher than the vibration peak at node 2. In addition, the heavier the inertial mass of the vibrating ring 200 is, the lower the vibration peaks at nodes 1 and 2 become, and the greater the difference between the frequency at which the first vibration peak occurs and the frequency at which the second vibration peak occurs.

[0041] In Fig. 4, a graph is shown in which the horizontal axis represents engine speed (rpm) and the vertical axis represents strain (%) of the annular elastic body 300. The horizontal axis corresponds to frequency, and the vertical axis corresponds to the magnitude of vibration. In the figure, solid lines L11 and L31 represent a graph of the sixth order, and the vibration on the left side of the figure is The peak is the sixth order first node, and the peak on the right is the sixth order second node. In addition, in the figure, the solid lines L21 and L41 show the fourth order graphs, and the vibration peak in the figure is the fourth order first node. These are graphs when the natural frequency of the torsional damper 10 is matched to the resonance frequency of the crankshaft 20. As shown in FIG. 4(a), the fourth order first node and the sixth order second node are coupled at an engine speed of about 5000 rpm, and it can be seen that the heat generation of the annular elastic body 300 becomes high. Therefore, if the natural frequency of the torsional damper 10 is shifted to the high frequency side, the vibration peak of the sixth order second node, which is a higher order, can be reduced. The dotted lines L12 and L22 show the sixth order and fourth order graphs, respectively, when the natural frequency of the torsional damper 10 is shifted to the high frequency side. As can be seen from these graphs, the vibration peak of the sixth order second node can be reduced, but the vibration peak of the fourth order first node tends to increase. Therefore, the effect of reducing the temperature of the annular elastic body 300 is not sufficient simply by adjusting the natural frequency of the torsional damper 10.

[0042] In Fig. 4(b), dotted lines L32 and L42 respectively show graphs of the sixth order and the fourth order when the inertial mass of the vibrating ring 200 is changed to be heavier. As can be seen from these graphs, the vibration peak of the sixth order second node is reduced and shifted to the high frequency side, and the vibration peak of the fourth order first node is reduced and shifted to the low frequency side, so that the coupling of both orders is also suppressed.

[0043] As a method for preventing the annular elastic body 300 from becoming too hot, a configuration that enhances the heat dissipation effect can be adopted. That is, the amount of heat dissipated from the annular elastic body 300 can be increased by increasing the thickness (corresponding to the width in the radial direction) of the vibrating ring 200 or increasing the engagement width (width in the central axis direction) between the vibrating ring 200 and the annular elastic body 300. This makes it possible to prevent the annular elastic body 300 from becoming too hot.

[0044] Furthermore, since the amount of heat generated and stored increases when the thickness of the annular elastic body 300 is large, a thinner thickness can prevent the annular elastic body 300 from becoming too hot. Incidentally, by providing irregularities on the vibrating ring 200 to increase the surface area, the heat dissipation effect from the vibrating ring 200 can be improved and the temperature of the annular elastic body 300 can be prevented from becoming too hot. In this embodiment, as shown in FIG. 2, a configuration is adopted in which irregularities are provided on the side of the vibrating ring 200 in the region (E) where the engine is located.

[0045] The above-mentioned measures can prevent the temperature of the annular elastomer 300 from rising to a high temperature. When H-NBR (hydrogenated acrylonitrile butadiene rubber) is used as the material for the annular elastomer 300, the normal heat resistance limit temperature is 130°C, but the above-mentioned measures can keep the maximum temperature of the annular elastomer 300 below 130°C.

[0046] Example 2 Example 2 of the present invention is shown in Fig. 5. Fig. 5 is a schematic cross-sectional view of a torsional damper according to Example 2 of the present invention, and corresponds to the cross-sectional view taken along line AA in Fig. 1. The overall configuration of a torsional damper 10X according to this example is similar to that of Example 1. That is, the torsional damper 10X according to this example also includes a hub 100X, a vibration ring 200X provided concentrically with the hub 100X, and an annular elastic body 300X.

[0047] Similarly to the first embodiment, the hub 100X is a metal annular member having an inner cylindrical portion 110, an outward flange portion 120, and an outer cylindrical portion 130X. The inner cylindrical portion 110 is fixed to the crankshaft 20 of the engine. Note that in Fig. 5 as well, the crankshaft 20 and the positions of the bolts 30 for fixing the torsional damper 10X to the crankshaft 20 are indicated by dotted lines.

[0048] Similarly to the first embodiment, the vibration ring 200X is a metal annular member. The annular elastic body 300X is made of a rubber material and vibrates together with the outer cylinder portion 130X of the hub 100X. It is provided between the ring 200X.

[0049] The torsional damper 10X configured as above is also disposed inside the engine case. In Fig. 5, the position of the inner wall surface of a part of the engine case (a part of the front cover) is indicated by a dotted line C. In Fig. 5, the right side of the torsional damper 10X is the area (E) where the engine is disposed. The vibration suppression function of the torsional damper 10X is the same as that described in the first embodiment, and therefore will not be described again.

[0050] <Detailed configuration of each component of the torsional damper> The detailed configuration of each member of the torsional damper 10X will be described. The inner peripheral surface of the vibration ring 200X according to this embodiment has an annular protruding portion 220 protruding radially inward at the center of the width direction (the width direction in the direction in which the central axis of the torsional damper 10X extends). That is, the inner diameter of the inner peripheral surface of the vibration ring 200X is small at the portion where the annular protruding portion 220 is provided, and the inner diameters on both sides are larger than the inner diameter of the annular protruding portion 220. The outer peripheral surface of the outer cylinder portion 130X has a shape in which the center in the width direction is annularly recessed so as to follow the shape of the inner peripheral surface of the vibration ring 200X. That is, the inner diameter of the outer peripheral surface of the outer cylinder portion 130X is small at the center in the width direction, and the inner diameters on both sides are larger than the inner diameter of the center.

[0051] The minimum inner diameter R20 of the annular protrusion 220 is set to be smaller than the maximum outer diameter R12 of the outer peripheral surface of the outer cylinder portion 130X on the side of the annular protrusion 220 toward the region (E) where the engine is disposed. The minimum inner diameter R20 of the annular protrusion 220 is set to be larger than the maximum outer diameter R11 of the outer peripheral surface of the outer cylinder portion 130X on the side opposite the region (E) where the engine is disposed from the annular protrusion 220.

[0052] In the torsional damper 10X according to the present embodiment as well, the amount of displacement of the vibration ring 200X to the side opposite to the region (E) where the engine is disposed after heat aging (after 533 hours have elapsed in an environment of 130°C) is set to be 1 mm or less. Thereby, it is possible to suppress the vibration ring 200X from coming into contact with the inner wall surface of a part of the engine case (a part of the front cover).

[0053] In the torsional damper 10X according to the present embodiment as well, due to the relationship between the dimensional shape of the outer peripheral surface of the outer cylinder portion 130X and the dimensional shape of the inner peripheral surface of the vibration ring 200X, a stopper structure is configured such that the vibration ring 200X does not come out from the outer cylinder portion 130X toward the region where the engine is disposed. More specifically, an annular protrusion 220 is provided on the inner peripheral surface of the vibration ring 200X, and as described above, the hub 100X and the vibration ring 200X are configured such that R20 < R12. Further, according to the torsional damper 10X according to the present embodiment, as described above, the hub 100 and the vibration ring 200 are configured such that R11 < R20. With the above configuration, the same effects as those in the first embodiment can be obtained.

[0054] Regarding the point that it is desirable to adopt a configuration in which the end surface of the annular elastic body 300X is located inside the end surface of the outer cylinder portion 130X and the end surface of the vibration ring 200X, it is the same as described in the first embodiment. Regarding various methods for suppressing deterioration of the annular elastic body, it is the same as described in the first embodiment.

Explanation of Reference Numerals

[0055] 10, 10X: Torsional damper 20: Crankshaft 30: Bolt 100, 100X: Hub 110: Inner cylinder portion 120: Outward flange portion 130, 130X: Outer cylinder portion 131: Annular protrusion 132: End surface 200, 200X: Vibration ring 210: End surface 220: Annular protrusion 300, 300X: Annular elastic body 310: End face

Claims

1. a hub including an inner cylindrical portion, an outward flange portion integral with the inner cylindrical portion, and an outer cylindrical portion integrally provided radially outward of the outward flange portion, the inner cylindrical portion being fixed to a crankshaft; a vibration ring disposed concentrically on the hub; an annular elastic body provided between the outer cylinder portion and the vibration ring; A torsional damper disposed in an engine case, A torsional damper characterized in that a stopper structure is formed that prevents the vibrating ring from slipping out of the outer cylindrical portion into the area where the engine is located, due to the relationship between the dimensions and shape of the outer peripheral surface of the outer cylindrical portion and the dimensions and shape of the inner peripheral surface of the vibrating ring.

2. The outer tubular portion has an annular protruding portion at a center in a width direction of an outer circumferential surface thereof, the annular protruding portion protruding radially outward, 2. The torsional damper according to claim 1, wherein the maximum outer diameter of the annular protrusion is larger than the minimum inner diameter of the inner circumferential surface of the vibration ring on the opposite side of the annular protrusion from the area in which the engine is located.

3. 3. The torsional damper according to claim 2, wherein the maximum outer diameter of the annular protrusion is smaller than the minimum inner diameter of the inner circumferential surface of the vibration ring on the side of the engine located closer to the annular protrusion.

4. The vibration ring has an inner peripheral surface at a center in a width direction thereof, the inner peripheral surface having an annular protruding portion protruding radially inward, 2. The torsional damper according to claim 1, wherein the minimum inner diameter of the annular protrusion is smaller than the maximum outer diameter of the outer peripheral surface of the outer cylinder portion on a side of the annular protrusion where an engine is disposed.

5. 5. The torsional damper according to claim 4, wherein the minimum inner diameter of the annular protrusion is greater than the maximum outer diameter of the outer peripheral surface of the outer cylinder portion on the opposite side of the region in which the engine is disposed relative to the annular protrusion.

6. 6. The torsional damper according to claim 1, wherein an end face of the annular elastic body is located inside an end face of the outer cylindrical portion and an end face of the vibration ring.

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