Torsion damper

Abstract

To reduce a radiation sound caused by the resonance of a vibration ring.SOLUTION: A torsional damper 101 comprises: a hub 111 in which a boss which is fixed to a rotating shaft such as a crankshaft of an engine, and a circular rim 114 are integrally arranged via a stay 113, and a circular vibration ring 131 is connected to an external peripheral face of the rim 114 via an elastic body 121. The vibration ring 131 comprises an end face 133 having a protrusive curved face shape RS which draws a circle in a radial direction RD defined within a range of, for example, curvature radii R1 to R20 (mm). The curved face shape RS of the end face 133 of the vibration ring 131 may be arranged over an entire length of a radial length L possessed by the end face 133, or may be arranged at only a part of the entire length, and also, may be arranged at one end face 133 (133E or 133F), or may be arranged at both the end faces 133 (133E and 133F).SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] A torsional damper is used, for example, as a crank pulley that drives accessories in an automobile engine. The crank pulley is attached to an end portion of a crankshaft provided in the engine and drives the accessories via a belt.

[0003] A torsional damper used as a crank pulley has a hub fixed to the crankshaft and has a structure in which a vibration ring is connected to an outer peripheral surface of the hub via an elastic body. When regarded as a dynamic vibration absorber, the elastic body forms a spring and the vibration ring forms a mass (mass body). Therefore, the vibration ring that rotates following the rotation of the crankshaft resonates in the rotational direction, and the torsional damper suppresses the torsional resonance of the crankshaft. This is the mechanism of vibration suppression by the torsional damper.

[0004] Due to the structure of the engine, vibration occurs in the rotating crankshaft. The vibration of the crankshaft is transmitted to the torsional damper and radiated from the torsional damper to generate radiation noise. Since the radiation noise becomes noise, various techniques have been considered to suppress this.

[0005] For example, Patent Document 1 discloses an invention in which a sound absorption plate is attached to the front side of the hub of a torsional damper to suppress the radiation noise radiated from the hub.

[0006] As another method, for example, as disclosed in Patent Document 2, a torsional damper in which a cavity is provided in the hub is also known. Since a part of the radiation noise guided to the cavity is converted into sound waves having a phase opposite to that of the radiation noise generated from the hub, it is an attempt to cancel the radiation noise by the interference of sound waves (see paragraph

[0030] of Document 2).

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Patent Application Publication No. 05-202987 [Patent Document 2] Japanese Patent Publication No. 2020-041684 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The torsional dampers described in Patent Documents 1 and 2 focus on and aim to suppress the radiated sound generated by the resonance of the hub. However, it is presumed that the radiated sound from a torsional damper is not necessarily caused solely by the hub, but also by the resonance of the vibrating ring. The torsional dampers described in Patent Documents 1 and 2 do not have any measures in place to address the radiated sound generated by the resonance of the vibrating ring.

[0009] Suppression of radiated sound generated by the resonance of the vibrating ring is desirable. [Means for solving the problem]

[0010] One embodiment of a torsional damper comprises a hub in which a boss fixed to a rotating shaft and an annular rim are integrally provided via a stay, and an annular vibrating ring connected to the outer circumferential surface of the rim via an elastic body, wherein the end face of the vibrating ring has a radially arc-shaped projection. Furthermore, the curved shape of the end face of the vibrating ring is provided along the entire length of the radial length of the end face of the vibrating ring. Yes, they are. Another embodiment of the torsional damper comprises a hub in which a boss fixed to a rotating shaft and an annular rim are integrally provided via a stay, and an annular vibrating ring connected to the outer circumferential surface of the rim via an elastic body, wherein one end face of the vibrating ring and the other end face of the vibrating ring each have a radially arc-shaped projection, the curved shape of one end face of the vibrating ring is provided along the entire radial length of the end face of the vibrating ring, and the curved shape of the other end face of the vibrating ring is provided only in a portion of the radial length of the end face of the vibrating ring. [Effects of the Invention]

[0011] This can reduce the noise radiated by the resonance of the vibrating ring. [Brief explanation of the drawing]

[0012] [Figure 1] A schematic diagram of a torsional damper, which is fixed to the crankshaft of a four-cylinder engine and also used as a pulley. [Figure 2] Front view of the torsional damper of the present embodiment. [Figure 3] Vertical side view of the torsional damper. [Figure 4] Perspective view of the torsional damper shown in a vertical cross-section at the central position. [Figure 5] (A) is a vertical side view showing the enlarged end face shape of the vibration ring of the present embodiment, and (B) is a vertical side view showing the enlarged end face shape of the vibration ring of the comparative example.

Embodiment for Carrying Out the Invention

[0013] An embodiment will be described based on the drawings. This embodiment is an application example to a pulley used in a four-stroke engine with four cylinders in series. It will be described along the following items. 1. Configuration (1) Engine (2) Basic configuration of the torsional damper (3) End face shape of the vibration ring 2. Effects (1) Basic effects (2) Causes of noise generation (3) Noise suppression (a) Equivalent radiation power (b) Devising the end face shape of the vibration ring (c) Summary 3. Variations

[0014] 1. Configuration (1) Engine As shown in FIG. 1, a crankshaft 12 (rotating shaft) is rotatably attached to the engine 11. The crankshaft 12 is horizontally arranged and fixes a torsional damper 101 configured as a pulley 31 at one end side.

[0015] The crankshaft 12 is equipped with a counterbalance 13 for each cylinder, and the piston 16 is attached to the pin 14 via a connecting rod 15. The piston 16 is slidably housed in the cylinder 17. The direction of sliding movement of the piston 16 is perpendicular to the axis of the crankshaft 12.

[0016] (2) Basic configuration of torsional damper As shown in Figures 2 to 4, the torsional damper 101 connects an annular vibrating ring 131 to a hub 111 via an elastic body 121, and has a belt groove 141 on the outer surface of the vibrating ring 131.

[0017] The hub 111 has a boss 112 at its center that is fixed to the crankshaft 12 of the engine 11, which is the axis of rotation, and a rim 114 is provided via a stay 113 that rises radially outward from the boss 112.

[0018] The boss 112 is a cylindrical component with a mounting hole 112a at its center for fitting the rotating shaft. The hub 111 is fixed to the crankshaft 12 by fixing one end of the crankshaft 12, which is fitted into the mounting hole 112a, with a bolt 21. In this state, the boss 112 aligns its axis A (see Figure 3) with the axis X that forms the rotation center of the crankshaft 12, and rotates in conjunction with the rotation of the crankshaft 12.

[0019] The stays 113 are interposed between the boss 112 and the rim 114, and are members that connect the boss 112 and the rim 114. Four stays 113 are provided, and each is arranged at equal intervals on a circumference concentric with the axis A of the boss 112. These stays 113 are formed by four holes 115 provided in the portion that connects the boss 112 and the rim 114. These holes 115 are also arranged at equal intervals on a circumference concentric with the axis A of the boss 112.

[0020] The rim 114 is an annular member that extends from the end of the stay 113 along the axial direction of the hub 111 and is positioned concentrically with the axis A of the boss 112. Therefore, the outer circumferential surface of the rim 114 is located on the circumference concentric with the axis A of the boss 112. However, the diameter of the outer circumferential surface of the rim 114 is not constant, and at approximately the center in the axial direction, the diameter is shortened by the rim recess 116. The rim recess 116 is for forming a convolution portion 151 together with the vibration ring 131, and its details will be described later.

[0021] The hub 111, which consists of a boss 112, a stay 113, and a rim 114, is formed integrally from a material such as metal.

[0022] The elastic body 121 is an annular member with a uniform diameter, interposed between the rim 114 and the vibrating ring 131, and elastically connecting the rim 114 and the vibrating ring 131. Such an elastic body 121 is formed from, for example, rubber and has a uniform thickness around its entire circumference.

[0023] The vibrating ring 131 is an annular member whose inner surface faces the outer surface of the rim 114 of the boss 112, with a gap G in which an elastic body 121 is interposed. Due to its structure, in which it is held via the elastic body 121, such a vibrating ring 131 functions as a mass (body of mass) with its own inherent frequency.

[0024] On the inner circumferential surface of the vibrating ring 131, a ring projection 132 is formed, matching the shape of the rim recess 116 formed on the outer circumferential surface of the rim 114. These rim recess 116 and ring projection 132 are provided along the circumferential direction around the entire circumference of the rim 114 and the vibrating ring 131, constituting a convolution portion 151. The convolution portion 151 increases the sliding resistance of the elastic body 121 between the rim 114 and the vibrating ring 131, suppressing displacement and detachment of the elastic body 121.

[0025] The vibrating ring 131 has multiple belt grooves 141 formed along its outer circumferential surface. These belt grooves 141 have a V-shaped cross-section and are structures around which an endless belt for power transmission is wound to drive various auxiliary devices (none of which are shown). By providing the belt grooves 141, the torsional damper 101 functions as a pulley 31.

[0026] (3) End face shape of the vibrating ring Figure 5(A) is an enlarged longitudinal cross-sectional side view showing the shape of the end face 133 of the vibrating ring 131 in this embodiment, and Figure 5(B) is an enlarged longitudinal cross-sectional side view showing the shape of the end face 133C of the vibrating ring 131C in the comparative example. In Figures 5(A) and (B), the right side is the engine side E facing the engine 11 (see Figure 1), and the left side is the opposite front side F.

[0027] The vibrating ring 131 of the torsional damper 101 in this embodiment has a unique shape at its end face 133 (see Figure 5(A)). To explain the end face shape of such a vibrating ring 131, it will be explained here in comparison with a comparative example (see Figure 5(B)). This comparative example is not necessarily prior art, but merely illustrates a vibrating ring 131C having a typical end face shape.

[0028] As shown in Figure 5(A), the vibrating ring 131 of this embodiment has a curved surface shape RS that curves in the radial direction RD on both end faces 133 (133E, 133F). This curved surface shape RS is provided on both the engine side E, where the engine 11 (drive source) that drives the crankshaft 12 (rotating shaft) is located, and on the opposite front side F end face 133F.

[0029] The curved shape RS of the end face 133 of the vibrating ring 131 is provided only in a portion of the radial length L of the end face 133E on the engine side E, and along the entire length of the end face 133F on the front side F. The curved shape RS of the end face 133E on the engine side E is positioned closer to the region that contacts the outer circumferential surface of the vibrating ring 131.

[0030] The curved shape RS provided on the end face 133 of the vibrating ring 131 is, for example, defined within the range of radius of curvature R1 to R20 (mm). Furthermore, the curved shape RS is continuously provided around the entire circumference of either end face 133E or 133F of the vibrating ring 131.

[0031] As shown in Figure 5(B), the unique end face shape of the vibrating ring 131 in this embodiment is immediately apparent when compared with a comparative example having a conventional end face shape. The end face 133C of the vibrating ring 131C in the comparative example is a flat surface that is cut straight in a direction perpendicular to the axis A of the torsional damper 101 (see Figure 3), both on the engine side E and the front side F. Such an end face 133C shape of the vibrating ring 131C is a general and typical shape.

[0032] 2. Effects (1) Basic effects

[0033] In this configuration, when the engine 11 starts and the crankshaft 12 rotates, the torsional damper 101 also rotates. At this time, since the torsional damper 101 also constitutes the pulley 31, power is transmitted to the auxiliary components.

[0034] The torsional damper 101 has a natural frequency in the torsional direction because the vibrating ring 131 functions as a mass. Therefore, when the crankshaft 12 rotates and torsional vibration occurs, if the natural frequency of the torsional damper 101 in the torsional direction is tuned to match the torsional resonance frequency, the torsional vibration generated in the crankshaft 12 can be absorbed and reduced.

[0035] Generally, the torsional resonance frequency that occurs in the crankshaft 12 is often around 300 to 600 Hz. Therefore, the natural frequency of the torsional damper 101 in the torsional direction is also tuned to around 300 to 600 Hz to match the torsional resonance frequency that occurs in the crankshaft 12.

[0036] (2) Causes of noise The crankshaft 12 also vibrates in the axial X direction. Therefore, the torsional damper 101 also resonates in the direction of axis A (hereinafter abbreviated as "axial direction") which coincides with axis X. At this time, the axial resonance frequency of the vibrating ring 131 is slightly higher than that of the torsional vibration, at about 500 to 900 Hz. When the vibrating ring 131 resonates in this way, its end face 133 pushes out the surrounding air, causing pressure fluctuations and generating radiated sound from the vibrating ring 131. This generated radiated sound then propagates as noise.

[0037] Looking at it in more detail, the sound radiated from the front end face 133F of the vibrating ring 131 is directly radiated into the engine compartment, causing high-frequency noise to resonate in the passenger compartment beyond the dashboard, creating a booming sound in the engine compartment, or leaking out from the front grille or under the vehicle. It can be said that this is radiated sound that is the direct cause of noise.

[0038] So what about the radiated sound generated from the engine-side end face 133E of the vibrating ring 131? Depending on the layout of the engine compartment, the radiated sound emitted from the engine-side end face 133E may be directed towards resonant components such as the chain or the case covering the timing belt, in which case it can induce reverberant noise.

[0039] Therefore, the axial resonance of the torsional damper 101 due to the axial vibration of the crankshaft 12 causes radiated sound from both end faces 133E and 133F of the vibrating ring 131, resulting in noise that cannot be ignored.

[0040] (3) Noise reduction The torsional damper 101 of this embodiment focuses on the sound radiation generated from the end face 133 of the vibrating ring 131 as described above, and suppresses this sound radiation by a curved shape RS provided on the end face 133 (end face 133E, end face 133F). The principle of sound radiation suppression by the curved shape RS will be explained next. (i) Equivalent radiant power To understand the noise generated from the end face 133 of the vibrating ring 131, let's consider it from the perspective of equivalent radiated power. Equivalent radiated power is an indicator that represents the degree of sound generated by an object. If the equivalent radiated power can be reduced, it is possible to reduce the radiated sound emitted from the end face 133 of the vibrating ring 131.

[0041] The formula for calculating the equivalent radiated power is given by equation (1). P = τ × (sv / 2) × md × a × v 2 ………(1) However, P: Equivalent Radiation Power τ: Radiation loss coefficient sv:Sonic speed md: material density a:Area v: Vibration speed

[0042] The radiation loss coefficient τ is a coefficient that depends on the shape of the object. For example, objects with curved shapes such as piano wire or round columns emit less sound, while objects with flat shapes such as rectangular columns or flat walls emit more sound. Thus, it represents the degree of sound emission.

[0043] Material density (md) is a material-dependent factor. For example, the material density is determined by the structure, such as whether it is spongy or a dense material without air bubbles.

[0044] Area 'a' represents the projected area of ​​the vibrating body.

[0045] (b) Improvement of the end face shape of the vibrating ring When considering the noise generation principle from the end face 133 of the vibrating ring 131 as described in the section "(2) Causes of Noise Generation" above, the factor that can be considered to be effective in suppressing noise in equation (1) above is the radiation loss coefficient τ. Under this assumption, in this embodiment, the end face 133 of the vibrating ring 131 is given a curved shape RS.

[0046] As mentioned above, the radiation loss coefficient τ depends on the shape of the object; objects with a planar shape have a large value, while objects with a curved shape have a small value. For this reason, the vibration ring 131 of this embodiment, which has a curved shape RS, can achieve a smaller radiation loss coefficient τ value compared to the planar end face 133C of the comparative example vibration ring 131C shown in Figure 5(B).

[0047] (h) Summary According to the torsional damper 101 of this embodiment, the radiation loss coefficient τ of the vibrating ring 131 is smaller compared to the comparative example, and therefore the transmitted radiation power P can be reduced from equation (1) above. As a result, the radiated sound generated from the end faces 133 (133E, 133F) of the vibrating ring 131 is reduced, and the noise level can be kept low.

[0048] In this embodiment, the effect of reducing radiated noise is achieved simply by making the shape of the end faces 133 (133E, 133F) of the vibrating ring 131 a curved shape RS. Therefore, it is possible to reduce radiated noise while avoiding disadvantages such as the addition of additional elements as in the invention described in Patent Document 1, or the enlargement as in the invention described in Patent Document 2.

[0049] In addition, the torsional damper 101 of this embodiment has the following effects and advantages.

[0050] The curved shape of the end face 133 of the vibrating ring 131 is provided on the front end face 133F, which is opposite to the engine 11, the drive source for the crankshaft 12 (rotating shaft). The curved shape RS of this end face 133F extends along the entire radial length L of the end face 133 of the vibrating ring 131.

[0051] Therefore, the radiated sound generated from the front end face 133F of the vibrating ring 131 can be reduced. In this case, the curvature of the curved surface shape RS becomes relatively small, so the effect of reducing radiated sound is obtained over the entire area of ​​the front side F.

[0052] The curved shape RS of the end face 133 of the vibrating ring 131 is also provided on the end face 133E on the engine side E. The curved shape RS of the end face 133E is provided only in a portion of the radial length L of the end face 133 of the vibrating ring 131 that is close to the region that contacts the outer circumferential surface of the vibrating ring 131.

[0053] Therefore, it is possible to reduce the radiated sound generated from the engine-side end face 133E of the vibrating ring 131 and suppress the generation of reverberating sound that occurs when such reflected sound echoes off other components. In this case, the curvature of the curved shape RS becomes relatively large, and since the curved shape RS can be set to a desired position on the end face 133F of the vibrating ring 131, the curvature and position of the curved shape RS can be appropriately set to be more effective in suppressing reverberating sound.

[0054] The curved shape RS of the end face 133 of the vibrating ring 131 is set to a radius of curvature R1 to R20 (mm). This makes it possible to more reliably reduce the radiated sound generated from the end face 133 of the vibrating ring 131.

[0055] The curved shape RS of the end face 133 of the vibrating ring 131 is continuously provided around the entire circumference of the vibrating ring 131. This makes it possible to more reliably reduce the radiated sound generated from the end face 133 of the vibrating ring 131.

[0056] 3. Variant Various modifications and changes are permitted during implementation.

[0057] For example, in this embodiment, a curved shape RS is provided on the front end face 133F along the entire radial length L of the end face 133 of the vibrating ring 131, and on only a portion of the end face 133E on the engine side E. This is not the only example, and the proportion and position of the curved shape RS on the end face 133 of the vibrating ring 131 can be determined as appropriate. It is also optional whether or not to provide the curved shape RS on both end faces 133E and 133F of the vibrating ring 131. For example, it is permissible to provide the curved shape RS only on the front end face 133F or only on the end face 133E on the engine side E.

[0058] The curvature of the curved surface shape RS can also be determined as appropriate; for example, the curvature of the curved surface shape RS may be set to a range that deviates from the radius of curvature R1 to R20 (mm).

[0059] In this embodiment, an example is shown in which a curved surface RS is provided around the entire circumference of the vibrating ring 131. However, this is not mandatory for implementation, and it is also permissible to provide a discontinuous curved surface RS on the circumferential surface of the vibrating ring 131, or to provide a curved surface RS only on a part of it.

[0060] Any other modifications or alterations are permitted. [Explanation of symbols]

[0061] 11 Engine 12. Crankshaft (rotating shaft) 13 Counterbalance 14 pins 15 Connecting Rod 16 pistons 17 Cylinders 21 volts 31 Pulley 101 Torsional Damper 111 Hub 112 Boss 112a Mounting hole 113 Stay 114 rim 115 holes 116 Rim recess 121 Elastic body 131 Vibration Ring 131C Comparative example vibration ring 132 Ring protrusion 133 End face 133C Comparative Example End Face 133E End face (engine side) 133F End face (front side) 141 Belt groove 151 Convolution Section Axle of torsional damper E Engine side F Front side G Gap L is the radial length. RD radial direction RS curved shape X Crankshaft axis

Claims

1. A hub in which a boss fixed to the axis of rotation and an annular rim are integrally provided via a stay, An annular vibrating ring connected to the outer circumferential surface of the rim via an elastic body, Equipped with, The end face of the vibrating ring has a curved surface shape that curves radially, The curved shape of the end face of the vibrating ring is provided along the entire length of the radial length of the end face of the vibrating ring. Torsional damper.

2. A hub comprising a boss fixed to a rotating shaft and an annular rim integrally provided via a stay, An annular vibrating ring connected to the outer circumferential surface of the rim via an elastic body, Equipped with, Both ends of the aforementioned vibrating ring have a curved surface shape that curves radially, The curved shape of one of the end faces of the vibrating ring is provided along the entire length of the radial length of the end face of the vibrating ring. The curved shape of the other end face of the vibrating ring is provided only in a portion of the radial length of the end face of the vibrating ring. Torsional damper.

3. The curved shape of the other end face of the vibrating ring is provided closer to the region that contacts the outer circumferential surface of the vibrating ring. The torsional damper according to claim 2.

4. The curved shape of the end face of the aforementioned vibrating ring is defined to have a radius of curvature in the range of R1 to R20 (mm). A torsional damper according to any one of claims 1 to 3.

5. The curved shape of one end face of the vibrating ring is provided on the end face side opposite to the drive source of the rotating shaft. The torsional damper according to claim 2 or 3.

6. The other end face of the vibrating ring is provided on the drive source side of the rotating shaft. The torsional damper according to claim 2 or 3.

7. The curved shape of the end face of the vibrating ring is provided around the entire circumference of the vibrating ring. A torsional damper according to any one of claims 1 to 6.

8. The curved shape of the end face of the vibrating ring is provided discontinuously within the circumferential surface of the vibrating ring. A torsional damper according to any one of claims 1 to 6.

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