Power transmission mechanism

Abstract

To provide a power transmission mechanism which inhibits deterioration of an elastic member while maintaining vibration control performance by the elastic member.SOLUTION: A power transmission mechanism includes: a rotatable shaft member; a gear which encloses the shaft member; an inner cylinder part 30 which encloses the shaft member; an outer cylinder part 40 which is fixed to the gear and encloses the inner cylinder part 30; and an annular elastic member installed between the inner cylinder part 30 and the outer cylinder part 40. A plurality of first projections 81 is installed on an outer peripheral surface of the inner cylinder part 30. A plurality of second projections 82 is installed on an inner peripheral surface of the outer cylinder part 40. The respective first projections 81 and the respective second projections 82 are arranged in a circumferential direction at intervals. When power does not act on the gear, an interval D1 between each of the first projections 81 and the second projection 82 located adjacent to the first projection 81 in a circumferential direction C1 is different from an interval D2 between the first projection 81 and the second projection 82 located adjacent to the first projection 81 in a circumferential direction C2 opposite to the circumferential direction C1.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power transmission mechanism. [Background technology]

[0002] Power transmission mechanisms that transmit power generated by a power source require vibration-damping performance to suppress vibration. Patent Document 1 discloses a structure in which a damper is installed in a power transmission mechanism in which a driven gear is installed on an intermediate shaft. The damper is composed of an inner cylinder fixed to the intermediate shaft by spline fitting, an outer cylinder fixed to the driven gear, and an elastic member between the inner and outer cylinders. When the power is low, the power is transmitted via the elastic member, thereby absorbing vibration. Therefore, for example, gear rattle noise can be reduced. On the other hand, when the power is high, the power is transmitted without passing through the elastic member. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-100271 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a configuration in which the range of power over which the power is maintained to pass through the elastic member is wide, the elastic member is subject to excessive deformation, which can lead to deterioration of the elastic member. On the other hand, in a configuration in which the range of power over which the power is maintained to pass through the elastic member is narrow, the elastic member may not be able to provide sufficient vibration-damping performance. In consideration of the above circumstances, one aspect of the present disclosure aims to suppress deterioration of the elastic member while maintaining the vibration-damping performance of the elastic member. [Means for solving the problem]

[0005] In order to solve the above problems, a power transmission mechanism according to one embodiment of the present disclosure comprises a rotatable shaft member, a gear surrounding the shaft member, an inner cylindrical portion surrounding the shaft member, an outer cylindrical portion fixed to the gear and surrounding the inner cylindrical portion, and an annular elastic member installed between the inner cylindrical portion and the outer cylindrical portion, wherein a plurality of first protrusions are provided on the outer peripheral surface of the inner cylindrical portion and a plurality of second protrusions are provided on the inner peripheral surface of the outer cylindrical portion, the first protrusions and the second protrusions are arranged circumferentially at intervals from each other, and when no power is applied to the gear, a first distance between each of the plurality of first protrusions and a second protrusion adjacent to the first protrusion in a first circumferential direction is different from a second distance between the first protrusion and a second protrusion adjacent to the first protrusion in a second circumferential direction opposite the first circumferential direction. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 2 is a cross-sectional view of the power transmission mechanism according to the embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 10 is an explanatory diagram of a path through which power is transmitted in a vibration-absorbing state. [Figure 4] FIG. 4 is an explanatory diagram of a path through which power is transmitted in an engaged state. [Figure 5] 10 is a graph illustrating the relationship between the number of times of durability and the amount of deformation of an elastic member. [Figure 6] FIG. 10 is a cross-sectional view of a power transmission mechanism in a comparative example. [Figure 7] FIG. 1 is a diagram illustrating the configuration of an automobile (internal combustion engine vehicle) that utilizes a power transmission mechanism. [Figure 8] This is a diagram showing the configuration of a vehicle (BEV) that uses a power transmission mechanism. [Figure 9] This is a diagram showing the configuration of an automobile (HEV) that uses a power transmission mechanism. [Figure 10] This is a diagram showing the configuration of an automobile (HEV) that uses a power transmission mechanism. [Figure 11] This is a diagram of a vehicle (PHEV) that uses a power transmission mechanism. DETAILED DESCRIPTION OF THE INVENTION

[0007] The embodiments for carrying out the present disclosure will be described with reference to the drawings. Note that the dimensions and scale of each element in each drawing may differ from those of the actual product. Furthermore, the embodiment described below is an exemplary embodiment that may be envisioned when carrying out the present disclosure. Therefore, the scope of the present disclosure is not limited to the embodiment exemplified below.

[0008] A: Embodiment FIG. 1 is a cross-sectional view of a power transmission mechanism 100 according to one embodiment of the present disclosure. The power transmission mechanism 100 is used in a drive mechanism (e.g., a transmission or a differential) that transmits power generated by a power source such as an internal combustion engine or an electric motor in a moving body such as an automobile. As illustrated in FIG. 1, the power transmission mechanism 100 includes a shaft member 10, a gear member 20, an inner cylindrical portion 30, an outer cylindrical portion 40, an elastic member 50, and a mounting ring 60. Note that the power transmission mechanism 100 constitutes, for example, a gear unit including one or more shaft members, but in this embodiment, for convenience, attention will be focused on a portion of the gear unit related to one shaft member 10.

[0009] In the following description, the direction along the rotation axis X of the shaft member 10 will be referred to as the axial direction Z. The axial direction Z is divided into axial direction Z1 and axial direction Z2. The axial direction Z1 is one direction along the rotation axis X, and the axial direction Z2 is the opposite direction to the axial direction Z1. Furthermore, the direction along the circumference of an imaginary circle of any diameter centered on the rotation axis X will be referred to as the circumferential direction C, and the direction of the radius of the imaginary circle will be referred to as the "radial direction." In the radial direction, the direction toward the rotation axis X will be referred to as the "inner side," and the direction away from the rotation axis X will be referred to as the "outer side."

[0010] The shaft member 10 is a cylindrical shaft that can rotate around a rotation axis X. The shaft member 10 is supported, for example, by a ball bearing 71 and a ball bearing 72 that are spaced apart from each other. The shaft member 10 includes a first portion 11 and a second portion 12. The first portion 11 is a portion that is located in the axial direction Z1 of the second portion 12. The first portion 11 has a smaller diameter than the second portion 12.

[0011] The gear member 20 is a hollow structure that surrounds the shaft member 10. The gear member 20 is installed coaxially with the shaft member 10. Specifically, the gear member 20 surrounds the shaft member 10 with a small gap between it and the outer peripheral surface of the second portion 12 of the shaft member 10. The gear member 20 of this embodiment includes a gear 21 and a connecting portion 22.

[0012] The gear 21 is a spur gear that receives power from an external mechanism such as a power source. That is, a plurality of gear teeth 23 are arranged on the outer circumferential surface of the gear 21 in the circumferential direction C. As can be seen from FIG. 1 , the gear 21 surrounds the shaft member 10.

[0013] The connecting portion 22 is a cylindrical portion connected to the gear 21 in the axial direction Z1. A plurality of protrusions 24 extending in the axial direction Z are formed on the outer peripheral surface of the connecting portion 22. The plurality of protrusions 24 are arranged in the circumferential direction C at intervals from one another.

[0014] The inner cylinder portion 30 is a cylindrical structure that surrounds the shaft member 10. The inner cylinder portion 30 is installed coaxially with the shaft member 10. Specifically, the inner cylinder portion 30 is fixed to the outer peripheral surface of the first portion 11 of the shaft member 10. Therefore, the inner cylinder portion 30 rotates integrally with the shaft member 10 around the rotation axis X. The inner cylinder portion 30 includes a first portion 31 and a second portion 32. The first portion 31 is located in the axial direction Z1 of the second portion 32.

[0015] The outer cylindrical portion 40 is a cylindrical structure that surrounds the inner cylindrical portion 30. The outer cylindrical portion 40 is installed coaxially with the shaft member 10. The outer cylindrical portion 40 includes a first portion 41, a second portion 42, and a third portion 43. The first portion 41 is located in the axial direction Z1 of the second portion 42, and the third portion 43 is located in the axial direction Z2 of the second portion 42. In other words, the second portion 42 is located between the first portion 41 and the third portion 43.

[0016] A plurality of second protrusions 82 are formed on the inner circumferential surface of the outer cylindrical portion 40. Each second protrusion 82 extends in the axial direction Z across the second portion 42 and the third portion 43. The plurality of second protrusions 82 are arranged in the circumferential direction C at intervals from one another.

[0017] The outer cylinder portion 40 is fixed to the gear member 20. Specifically, the third portion 43 of the outer cylinder portion 40 is fixed to the connecting portion 22 of the gear member 20. That is, the outer cylinder portion 40 is fixed to the gear member 20 by meshing (i.e., spline fitting) between the multiple protrusions 24 formed on the outer peripheral surface of the connecting portion 22 and the multiple second protrusions 82 formed on the inner peripheral surface of the third portion 43. Each protrusion 24 meshes with each second protrusion 82 without any gap. Therefore, the outer cylinder portion 40 rotates integrally with the gear member 20 around the rotation axis X. As explained above, the outer cylinder portion 40 is fixed to the gear 21.

[0018] The elastic member 50 is an annular (specifically, cylindrical) elastic body disposed between the inner tubular portion 30 and the outer tubular portion 40. Specifically, the elastic member 50 is disposed in the annular space between the first portion 31 of the inner tubular portion 30 and the first portion 41 of the outer tubular portion 40.

[0019] The elastic member 50 is formed of an elastic material such as a rubber material. Examples of rubber materials used for the elastic member 50 include various rubber materials such as chloroprene rubber (CR), silicone rubber (SR), acrylic rubber (ACM), urethane rubber (U), polyurethane rubber (PUR), vinyl methyl silicone rubber (VMQ), ethylene propylene diene rubber (EPDM), and fluororubber (FKM).

[0020] The mounting ring 60 is a cylindrical structure for fixing the elastic member 50 to the inner tubular portion 30 and the outer tubular portion 40. Specifically, the mounting ring 60 includes an inner ring 61 and an outer ring 62. The outer ring 62 has a larger diameter than the inner ring 61.

[0021] The inner ring 61 is located between the outer peripheral surface of the first portion 31 of the inner tubular portion 30 and the inner peripheral surface of the elastic member 50. The outer ring 62 is located between the inner peripheral surface of the first portion 41 of the outer tubular portion 40 and the outer peripheral surface of the elastic member 50. A structure in which the elastic member 50 is formed in the annular space between the inner ring 61 and the outer ring 62 is fitted into the annular space between the inner tubular portion 30 and the outer tubular portion 40, thereby placing the elastic member 50 between the inner tubular portion 30 and the outer tubular portion 40. In other words, the inner peripheral surface of the elastic member 50 is fixed to the inner tubular portion 30, and the outer peripheral surface of the elastic member 50 is fixed to the outer tubular portion 40. Note that one or both of the inner ring 61 and the outer ring 62 may be omitted.

[0022] Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. That is, Fig. 2 shows a cross section passing through the second portion 32 of the inner cylindrical portion 30 and the second portion 42 of the outer cylindrical portion 40.

[0023] FIG. 2 illustrates the second portion 32 of the inner cylindrical portion 30 and the second portion 42 of the outer cylindrical portion 40 in a state where no power is applied to the power transmission mechanism 100 (e.g., the gear 21) (hereinafter referred to as the "unloaded state"). The unloaded state refers to a state where no power is applied to one shaft member 10 of the power transmission mechanism 100, which is the focus of attention in this embodiment for convenience, and does not matter whether or not power is applied to the other shaft members. In FIG. 2, the circumferential direction C is divided into a circumferential direction C1 and a circumferential direction C2. The circumferential direction C1 and the circumferential direction C2 are opposite directions along an imaginary circle centered on the rotation axis X. Specifically, the circumferential direction C1 is a clockwise direction, and the circumferential direction C2 is a counterclockwise direction. The circumferential direction C1 is an example of a "first circumferential direction," and the circumferential direction C2 is an example of a "second circumferential direction."

[0024] 2, a plurality of first protrusions 81 are provided on the outer peripheral surface of the second portion 32 of the inner cylindrical portion 30. The plurality of first protrusions 81 are gear teeth arranged at intervals from one another in the circumferential direction C. As described above, a plurality of second protrusions 82 are provided on the inner peripheral surface of the second portion 42 of the outer cylindrical portion 40. The plurality of second protrusions 82 are gear teeth arranged at intervals from one another in the circumferential direction C.

[0025] The multiple first protrusions 81 and the multiple second protrusions 82 mesh with each other. That is, the first protrusions 81 and the second protrusions 82 are alternately arranged along the circumferential direction C. Specifically, one first protrusion 81 is located between two second protrusions 82 that are adjacent to each other along the circumferential direction C, and one second protrusion 82 is located between two first protrusions 81 that are adjacent to each other along the circumferential direction C. The first protrusions 81 and the second protrusions 82 are arranged in the circumferential direction C at intervals. Therefore, the inner cylinder portion 30 and the outer cylinder portion 40 can rotate relatively by an angle corresponding to the interval between each first protrusion 81 and each second protrusion 82.

[0026] In the above configuration, when the power acting on the gear 21 is small, the power is transmitted to the shaft member 10 via the gear member 20, the outer cylindrical portion 40, the elastic member 50, and the inner cylindrical portion 30, as illustrated in FIG. 3 (this state is called the "vibration-absorbing state"). In the vibration-absorbing state, the power passes through the elastic member 50, and the vibration of the power transmission mechanism 100 (particularly the gear 21) is absorbed by the elastic member 50. Therefore, for example, the teeth rattle noise of the gear 21 can be reduced. As can be understood from the above explanation, the inner cylindrical portion 30, the outer cylindrical portion 40, and the elastic member 50 function as a vibration-proof mechanism (damper) that absorbs the vibration of the shaft member 10 or the gear member 20.

[0027] On the other hand, when the power acting on the gear 21 is large, the elastic member 50 deforms in the circumferential direction C, causing the second protrusions 82 and the first protrusions 81 to come into contact with each other. Therefore, as illustrated in FIG. 4 , the power is transmitted to the shaft member 10 via the gear 21, the outer cylindrical portion 40, and the inner cylindrical portion 30 (this state is referred to as the "engaged state"). In other words, the power is transmitted to the shaft member 10 without passing through the elastic member 50. In the engaged state, the second protrusions 82 and the first protrusions 81 come into contact with each other, causing the deformation of the elastic member 50 to stop. In other words, the second protrusions 82 and the first protrusions 81 function as stoppers that prevent elastic deformation. Therefore, excessive deformation of the elastic member 50 is reduced, and deterioration of the elastic member 50 due to excessive deformation can be suppressed.

[0028] 2, for the sake of convenience, attention will be focused on one arbitrary first protrusion 81a among the multiple first protrusions 81 of the inner cylindrical portion 30 and two second protrusions 82 (82a, 82b) adjacent to the first protrusion 81a among the multiple second protrusions 82 of the outer cylindrical portion 40. The second protrusion 82a is the second protrusion 82 among the multiple second protrusions 82 of the outer cylindrical portion 40 that is adjacent to the first protrusion 81a in the circumferential direction C1. The second protrusion 82b is the second protrusion 82 among the multiple second protrusions 82 of the outer cylindrical portion 40 that is adjacent to the first protrusion 81a in the circumferential direction C2. In other words, the first protrusion 81a is located between the second protrusion 82a and the second protrusion 82b.

[0029] In FIG. 2, the distance D1 is the distance between the first protrusion 81a and the second protrusion 82a in an unloaded state. The distance D2 is the distance between the first protrusion 81a and the second protrusion 82b in an unloaded state. As illustrated in FIG. 2, the distance D1 and the distance D2 are different. Specifically, the distance D1 is greater than the distance D2 (D1>D2). For example, the distance D1 is at least twice the distance D2 (D1≧2·D2).

[0030] As explained above, in this embodiment, the distance D1 and the distance D2 are different. Therefore, the range of power transmitted via the elastic member 50 differs between when power acts on the gear 21 in the circumferential direction C1 and when power acts on the gear 21 in the circumferential direction C2. In other words, the range of power maintained in the vibration-absorbing state and the range of power maintained in the engaged state change depending on the direction (C1, C2) of the power. Therefore, as will be described in detail below, this embodiment makes it possible to suppress deterioration of the elastic member 50 while maintaining the vibration-damping performance of the elastic member 50.

[0031] FIG. 5 is a graph illustrating the relationship between the number of times of durability (horizontal axis) of the elastic member 50 and the amount of deformation (vertical axis) of the elastic member 50. The number of times of durability in FIG. 5 is, for example, the number of times power is applied to the power transmission mechanism 100 until the elastic member 50 is damaged. FIG. 5 also illustrates the characteristic F1 of the above-described embodiment and the characteristic F2 of the comparative example. FIG. 6 is a cross-sectional view of the comparative example. As illustrated in FIG. 6, the comparative example has a configuration in which the distance D1 and the distance D2 are equal in an unloaded state.

[0032] 5, the number of cycles of durability when the elastic member 50 is deformed by a specific deformation amount in the embodiment is significantly greater than the number of cycles of durability in the comparison example. That is, according to the embodiment, as described above, it is possible to suppress deterioration of the elastic member 50 while maintaining the vibration-damping performance of the elastic member 50.

[0033] B: Example of use of power transmission mechanism 100 The following describes an example of the use of the power transmission mechanism 100 described above. In the following description, various types of automobiles 90 (90A, 90B, 90C, 90D, 90E) will be described as examples of the use of the power transmission mechanism 100.

[0034] B-1: Internal combustion engine vehicle 7 is an internal combustion engine vehicle that uses an internal combustion engine 91 as a power source. In the automobile 90A, for example, a power transmission mechanism 100 is used as a mechanism for transmitting the power generated by the internal combustion engine 91 to tires 92.

[0035] B-2:BEV(Battery Electric Vehicle) 8 is a BEV that operates an electric motor 93 using power stored in a battery. In the vehicle 90B, a power transmission mechanism 100 is used as a mechanism for transmitting the power generated by the electric motor 93 to tires 92.

[0036] B-3:HEV(Hybrid Electric Vehicle) 9 is an HEV that uses an internal combustion engine 91 and an electric motor 93 as power sources. In the automobile 90C, a power transmission mechanism 100 is used as a mechanism for transmitting the power generated by the internal combustion engine 91 and the electric motor 93 to tires 92.

[0037] An automobile 90D illustrated in Fig. 10 is another example of an HEV. The automobile 90D is equipped with a charging motor 94 that charges a battery 95 with power generated by an internal combustion engine 91. In the automobile 90D, the above-described power transmission mechanism 100 is used as a mechanism for transmitting the power generated by the internal combustion engine 91 to the charging motor 94, a mechanism for transmitting the power generated by the internal combustion engine 91 to tires 92, and a mechanism for transmitting the power generated by the electric motor 93 using power supplied from the battery 95 to tires 92.

[0038] B-4:PHEV(Plug-in Hybrid Electric Vehicle) 11 is a PHEV equipped with a battery 95 that can be charged using an external power source. In the vehicle 90E, the above-described power transmission mechanism 100 is used as a mechanism for transmitting power generated by an internal combustion engine 91 to an electric motor 94 for charging, and as a mechanism for transmitting power generated by an electric motor 93 supplied with power from the battery 95 to tires 92.

[0039] C: Modified Example Specific modified embodiments that can be added to the embodiments exemplified above are shown below. Two or more embodiments arbitrarily selected from the following examples may be combined as appropriate within the scope of not being mutually contradictory.

[0040] (1) In the above embodiment, the distance D1 is greater than the distance D2, but the relationship between the distances D1 and D2 is not limited to the above example. For example, the distance D2 may be greater than the distance D1 (D2>D1), or the distance D2 may be at least twice the distance D1 (D2≧2·D1).

[0041] (2) As can be seen from Fig. 2, when the inner cylindrical portion 30 rotates in the circumferential direction C1 relative to the outer cylindrical portion 40, the first protrusions 81 and the second protrusions 82 come into contact with each other as the inner cylindrical portion 30 rotates by an angle corresponding to the distance D1. On the other hand, when the inner cylindrical portion 30 rotates in the circumferential direction C2 relative to the outer cylindrical portion 40, the first protrusions 81 and the second protrusions 82 come into contact with each other as the inner cylindrical portion 30 rotates by an angle corresponding to the distance D2. Therefore, a preferred embodiment has a relationship between the distances D1 and D2 that is set in accordance with the tendency (for example, time or frequency) for the inner cylindrical portion 30 to rotate more frequently in the circumferential direction C1 or the circumferential direction C2 relative to the outer cylindrical portion 40.

[0042] For example, consider time T1 during which the inner cylindrical portion 30 rotates in the circumferential direction C1 relative to the outer cylindrical portion 40, and time T2 during which the inner cylindrical portion 30 rotates in the circumferential direction C2 relative to the outer cylindrical portion 40. Time T1 is the total time during a predetermined unit time during which power acts to rotate the inner cylindrical portion 30 in the circumferential direction C1 relative to the outer cylindrical portion 40. For example, time T1 is the time during which power acts on the gear 21 in the circumferential direction C2. On the other hand, time T2 is the total time during the unit time during which power acts on the gear 21 in the circumferential direction C1. Note that time T1 is an example of a "first time" and time T2 is an example of a "second time."

[0043] When time T1 is longer than time T2, priority should be given to the rotation of the inner cylindrical portion 30 in the circumferential direction C1 relative to the outer cylindrical portion 40. Therefore, when time T1 is longer than time T2, a configuration in which distance D1 is greater than distance D2 is preferable. On the other hand, when time T2 is longer than time T1, priority should be given to the rotation of the inner cylindrical portion 30 in the circumferential direction C2 relative to the outer cylindrical portion 40. Therefore, when time T2 is longer than time T1, a configuration in which distance D2 is greater than distance D1 is preferable. As described above, according to the configuration in which the relationship between distance D1 and distance D2 is set depending on the direction of relative rotation between the inner cylindrical portion 30 and the outer cylindrical portion 40, the aforementioned effect of suppressing deterioration of the elastic member 50 while maintaining the vibration-damping performance of the elastic member 50 is particularly effective.

[0044] (3) In the above embodiment, both the distance D1 and the distance D2 are positive numbers, but one of the distances D1 and D2 may be zero. For example, in an embodiment in which the distance D1 is greater than the distance D2, the distance D2 may be zero. That is, in an unloaded state, the first protrusion 81a and the second protrusion 82b may be in contact with each other (D2=0). Similarly, in an embodiment in which the distance D2 is greater than the distance D1, the distance D1 may be zero. That is, in an unloaded state, the first protrusion 81a and the second protrusion 82a may be in contact with each other (D1=0).

[0045] (4) In the above-described embodiment, an example was given in which the inner tube portion 30, which is separate from the shaft member 10, is fixed to the shaft member 10, but the shaft member 10 and the inner tube portion 30 may also be manufactured integrally as a single structure.

[0046] (5) In the above-described embodiment, an example is given in which the outer cylinder portion 40, which is separate from the gear member 20, is fixed to the gear member 20, but the gear member 20 and the outer cylinder portion 40 may be manufactured integrally as a single structure.

[0047] (6) The structure for fixing the outer tubular portion 40 and the gear member 20 to each other is not limited to the above example (spline fitting). For example, the outer tubular portion 40 may be fixed to the gear member 20 by fasteners such as screws or bolts.

[0048] (9) The term "nth" (n is a natural number) in this application is used only as a formal and convenient label to distinguish each element in the description and does not have any substantive meaning. Therefore, there is no room for restrictive interpretation of the position of each element or the order of manufacture, etc., based on the term "nth."

[0049] D: Notes From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0050] A power transmission mechanism according to one aspect (aspect 1) of the present disclosure comprises a rotatable shaft member, a gear surrounding the shaft member, an inner cylindrical portion surrounding the shaft member, an outer cylindrical portion fixed to the gear and surrounding the inner cylindrical portion, and an annular elastic member installed between the inner cylindrical portion and the outer cylindrical portion, wherein a plurality of first protrusions are provided on the outer peripheral surface of the inner cylindrical portion, and a plurality of second protrusions that mesh with the plurality of first protrusions are provided on the inner peripheral surface of the outer cylindrical portion, and when no power is applied to the gear, a first distance between each of the plurality of first protrusions and a second protrusion adjacent to the first protrusion in a first circumferential direction is different from a second distance between the first protrusion and a second protrusion adjacent to the first protrusion in a second circumferential direction opposite the first circumferential direction.

[0051] In the above configuration, when the power acting on the gear is small, the power is transmitted to the shaft member via the gear, the outer cylindrical portion, the elastic member, and the inner cylindrical portion. Vibrations are absorbed by the elastic member as the power passes through the elastic member. Therefore, for example, gear rattle noise can be reduced. On the other hand, when the power acting on the gear is large, the first protrusion and the second protrusion come into contact due to deformation of the elastic member, and the power is transmitted to the shaft member via the gear, the outer cylindrical portion, and the inner cylindrical portion. In other words, the power is transmitted to the shaft member without passing through the elastic member. As described above, the contact between the first protrusion and the second protrusion stops the deformation of the elastic member. Therefore, excessive deformation of the elastic member is reduced, and deterioration of the elastic member due to excessive deformation can be suppressed.

[0052] In the above configuration, the first distance between the first protrusion and the second protrusion adjacent thereto in the first circumferential direction is different from the second distance between the first protrusion and the second protrusion adjacent thereto in the second circumferential direction. Therefore, the range of power transmitted via the elastic member differs between when power acts on the gear in the first circumferential direction and when power acts on the gear in the second circumferential direction. According to the above aspect, it is possible to suppress deterioration of the elastic member while maintaining the vibration-damping performance of the elastic member, compared to a configuration in which the first distance and the second distance are equal.

[0053] In a specific example (Aspect 2) of Aspect 1, the first distance is at least twice the second distance. According to the above aspect, the first distance is ensured to be at least twice the second distance, which is particularly effective in suppressing deterioration of the elastic member while maintaining the vibration-damping performance of the elastic member.

[0054] In the first aspect or a specific example of the first aspect (aspect 3), the first time during which the inner cylindrical portion rotates in the first circumferential direction relative to the outer cylindrical portion is longer than the second time during which the inner cylindrical portion rotates in the second circumferential direction relative to the outer cylindrical portion, and the first interval exceeds the second interval. When the inner cylindrical portion rotates in the first circumferential direction relative to the outer cylindrical portion, the first protrusion and the second protrusion come into contact when the inner cylindrical portion rotates through an angle corresponding to the first interval. On the other hand, when the inner cylindrical portion rotates in the second circumferential direction relative to the outer cylindrical portion, the first protrusion and the second protrusion come into contact when the inner cylindrical portion rotates through an angle corresponding to the second interval. Therefore, when the first time during which the inner cylindrical portion rotates in the first circumferential direction relative to the outer cylindrical portion is longer than the second time during which the inner cylindrical portion rotates in the second circumferential direction, a preferred embodiment is one in which the first interval exceeds the second interval. According to the above embodiment, the effect of suppressing deterioration of the elastic member while maintaining the vibration-damping performance of the elastic member is particularly effective.

[0055] In a specific example (Aspect 4) of any one of Aspects 1 to 3, the power transmission mechanism is a mechanism for transmitting power generated by a power source of an automobile. However, the application of the power transmission mechanism according to the present disclosure is not limited to automobiles. [Explanation of symbols]

[0056] 100...power transmission mechanism, 10...shaft member, 11...first part, 12...second part, 20...gear member, 21...gear, 22...connecting part, 23...gear teeth, 24...protrusion, 30...inner cylinder part, 31...first part, 32...second part, 40...outer cylinder part, 41...first part, 42...second part, 43...third part, 50...elastic member, 60...mounting ring, 61...inner ring, 62...outer ring, 71, 72...ball bearing, 81, 81a...first protrusion, 82, 82a, 82b...second protrusion, 90, 90A, 90B, 90C, 90D, 90E...automobile, 91...internal combustion engine, 92...tire, 93...electric motor, electric motor for charging, 95...battery.

Claims

1. a rotatable shaft member; a gear surrounding the shaft member; an inner cylindrical portion surrounding the shaft member; an outer cylindrical portion fixed to the gear and surrounding the inner cylindrical portion; an annular elastic member disposed between the inner cylindrical portion and the outer cylindrical portion; a plurality of first protrusions are provided on the outer peripheral surface of the inner cylindrical portion; a plurality of second protrusions are provided on the inner circumferential surface of the outer cylindrical portion; The first protrusions and the second protrusions are arranged in the circumferential direction at intervals from each other, When no power is applied to the gear, a first distance between each of the plurality of first protrusions and a second protrusion adjacent to the first protrusion in a first circumferential direction is different from a second distance between the first protrusion and a second protrusion adjacent to the first protrusion in a second circumferential direction opposite to the first circumferential direction. Power transmission mechanism.

2. The first distance is at least twice the second distance. The power transmission mechanism of claim 1.

3. a first time period during which the inner cylindrical portion rotates in the first circumferential direction relative to the outer cylindrical portion is longer than a second time period during which the inner cylindrical portion rotates in the second circumferential direction relative to the outer cylindrical portion; The first distance is greater than the second distance. The power transmission mechanism of claim 1.

4. It is a mechanism that transmits the power generated by the power source of a vehicle. The power transmission mechanism according to any one of claims 1 to 3.

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