torsional damper
By optimizing the shape of the strut in the torsional damper, reducing the circumferential width and axial thickness of the strut, and adopting an inclined design, the problems of radiating sound and large size of the torsional damper are solved, achieving the effects of noise suppression and cost reduction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NOK CORP
- Filing Date
- 2022-12-20
- Publication Date
- 2026-07-24
Smart Images
Figure CN118043569B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to a torsional damper. Background Technology
[0002] Torsional dampers, for example, are crankshaft pulleys used in motor vehicle engines as drive auxiliary equipment. The crankshaft pulley is mounted at the end of the engine's crankshaft and drives the auxiliary equipment via a belt.
[0003] The torsional damper used as a crankshaft pulley has a hub fixed to the crankshaft and a structure in which a vibrating ring is connected to the outer circumferential surface of the hub via an elastic body. When viewed as a dynamic vibration absorber, the elastic body becomes a spring, and the vibrating ring becomes a mass. Therefore, the vibration ring, which rotates in tandem with the crankshaft, resonates in the direction of rotation, thus suppressing the torsional resonance of the crankshaft—this is the vibration-suppressing structure based on the torsional damper.
[0004] Depending on the engine's structure, vibrations occur in the rotating crankshaft. These crankshaft vibrations are transmitted to the torsional damper and primarily radiate from the hub, producing radial noise. This radial noise becomes general noise, hence various techniques for suppressing it have been considered.
[0005] For example, Japanese Patent Application Publication No. 05-202987 (Patent Document 1) discloses an invention that installs a sound-absorbing plate on the front side of the hub of a torsional damper to suppress the emitted sound from the hub.
[0006] As another approach, for example, as disclosed in Japanese Patent Application Publication No. 2020-041684 (Patent Document 2), a torsional damper with a cavity in the wheel hub is known. A portion of the radiated sound introduced into the cavity is converted into a sound wave with the opposite phase to the radiated sound generated from the wheel hub, and thus an attempt is made to eliminate the radiated sound by interference of the sound waves (paragraph
[0030] of Reference 2).
[0007] Existing technical documents
[0008] Patent documents
[0009] Patent Document 1: Japanese Patent Application Publication No. 05-202987
[0010] Patent Document 2: Japanese Patent Application Publication No. 2020-041684 Summary of the Invention
[0011] The technical problem that the invention aims to solve
[0012] As described in Japanese Patent Application Publication No. 05-202987 (Patent Document 1), when the sound-absorbing panel is installed on the torsional damper, the number of parts increases, thus increasing the cost of the parts. The increase in manufacturing steps is also something that needs to be avoided.
[0013] The invention described in Japanese Patent Application Publication No. 2020-041684 (Patent Document 2) is recognized as superior in terms of the number of parts and manufacturing steps because it does not require other parts such as sound-absorbing panels. However, it requires a dedicated space for the cavity, making large-scale production inevitable.
[0014] Both of the inventions described in the aforementioned documents (Patent Documents 1 and 2) aim to achieve improvements. The goal is to reduce radiated sound while avoiding the disadvantages of adding additional elements and increasing size.
[0015] Solution for solving the problem
[0016] One form of torsional damper includes: a hub, which integrally mounts a boss fixed to a rotation axis and an annular rim via multiple struts; and an annular vibrating ring, which is connected to the outer circumferential surface of the rim via an elastomer, wherein the struts have a circumferential width dimension not exceeding 1 / 4 of the wavelength of the resonant frequency of the axial direction of the hub.
[0017] Invention Effects
[0018] It can reduce radioactive sound. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of a crankshaft fixed to a four-cylinder engine, which is also used as a torsional damper for pulleys.
[0020] Figure 2 This is a front view of the torsional damper of this embodiment.
[0021] Figure 3 This is a longitudinal sectional side view of a torsional damper.
[0022] Figure 4 This is a perspective view of the torsional damper shown in longitudinal section at the central position.
[0023] Figure 5 It is a graph showing the equivalent radiated power by frequency.
[0024] Figure 6 It is a graph showing the magnitude of the axial vibration of the vibrating ring generated by the axial vibration of the crankshaft, in terms of frequency. Detailed Implementation
[0025] An embodiment will be described with reference to the accompanying drawings. This embodiment is an example of the application of a pulley to an inline four-cylinder four-stroke engine. The following sections will describe the embodiment.
[0026] 1. Structure
[0027] (1) Engine
[0028] (2) Basic structure of torsional damper
[0029] (3) Support rod
[0030] 2. Effects
[0031] (1) Basic effects
[0032] (2) Noise suppression
[0033] (a) Equivalent radiated power
[0034] (b) Circumferential width of the strut
[0035] (c) Axial thickness of the strut
[0036] (d) Inclined shape of the strut
[0037] (e) Summary
[0038] 3. Variations
[0039] 1. Structure
[0040] (1) Engine
[0041] like Figure 1 As shown, the crankshaft 12 (rotation shaft) is rotatably mounted on the engine 11. The crankshaft 12 is horizontally positioned, and a torsional damper 101 configured as a pulley P is fixed to one end.
[0042] The crankshaft 12 is equipped with a counterweight 13 on each cylinder and mounts the piston 16 to the pin 14 via a connecting rod 15. The piston 16 is slidably received in the cylinder 17. The sliding direction of the piston 16 is perpendicular to the axis of the crankshaft 12.
[0043] (2) Basic structure of torsional damper
[0044] like Figures 2 to 4 As shown, the torsional damper 101 connects the annular vibrating ring 131 to the hub 111 via the elastic body 121, and a groove 141 is provided on the outer peripheral surface of the vibrating ring 131.
[0045] The hub 111 has a boss 112 fixed to the crankshaft 12 of the engine 11, which serves as the axis of rotation, at the center position, and the rim 114 is mounted via a strut 113 that rises radially outward from the boss 112.
[0046] The boss 112 is a cylindrical component with a mounting hole 112a at its center for fitting a rotating shaft. The hub 111 is fixed to the crankshaft 12 by bolts 21, which secure one end of the crankshaft 12 fitted into the mounting hole 112a. In this state, the boss 112 aligns its shaft A with the shaft X, which is the center of rotation of the crankshaft 12, and rotates along with the crankshaft 12.
[0047] The strut 113 is a component that connects the boss 112 and the rim 114. There are four struts 113, arranged at equal intervals on a circumference concentric with the axis A of the boss 112. Four holes 115 are formed between each strut 113. These holes 115 are also arranged at equal intervals on a circumference concentric with the axis A of the boss 112.
[0048] The rim 114 is an annular member extending axially from the end of the strut 113 along the hub 111, and is positioned concentrically with the shaft A of the boss 112. Therefore, the outer circumferential surface of the rim 114 is positioned on a circle concentric with the shaft A of the boss 112. Of course, the diameter of the outer circumferential surface of the rim 114 is not constant; it shortens approximately at the center position along the axial direction due to the rim recess 116. The rim recess 116 is used to form a winding portion C together with the vibrating ring 131, as detailed later.
[0049] The hub 111, which consists of the boss 112, the strut 113 and the rim 114, is formed integrally from metal, for example.
[0050] The elastomer 121 is a uniformly shaped annular component located between the rims 114 and the vibrating rings 131, elastically connecting the rims 114 and the vibrating rings 131. Such an elastomer 121 is formed, for example, of rubber, and has a uniform wall thickness throughout its circumference.
[0051] The vibrating ring 131 is an annular component whose inner circumferential surface faces the outer circumferential surface of the rim 114 of the boss 112 across a gap G. An elastic body 121 is provided in the gap G between the inner circumferential surface of the vibrating ring 131 and the outer circumferential surface of the rim 114 of the boss 112. Based on the structure held by the elastic body 121, the vibrating ring 131 functions as a mass with an inherent vibration frequency.
[0052] On the inner circumferential surface of the vibrating ring 131, annular protrusions 132 are formed to match the shape of the rim recesses 116 formed on the outer circumferential surface of the rim 114. These rim recesses 116 and annular protrusions 132 cover the entire circumference of the rim 114 and the vibrating ring 131 and are arranged along their circumferential direction, constituting a winding portion C. The winding portion C increases the sliding resistance of the elastic body 121 between the rim 114 and the vibrating ring 131, and suppresses the positional displacement and disengagement of the elastic body 121.
[0053] The vibrating ring 131 has multiple grooves 141 formed circumferentially on its outer peripheral surface. These grooves 141 are V-shaped in cross-section and are structures for winding a seamless belt for power transmission to drive various auxiliary equipment (not shown). By providing the grooves 141, the torsional damper 101 functions as a pulley P.
[0054] (3) Support rod
[0055] In this embodiment, the strut 113 of the torsional damper 101 has a circumferential width dimension (reference) that does not exceed 1 / 4 of the wavelength of the resonant frequency in the axial direction of the hub 111, i.e., in the direction of axis A. Figure 1 ).
[0056] The resonant frequency of hub 111 is, for example, 3.7 kHz. The wavelength of the resonant frequency is:
[0057] Wavelength = approximately 340 m / s / frequency (Hz)
[0058] Therefore, the wavelength of the axial resonant frequency of the hub 111 is approximately 0.092 m (92 mm). Therefore, the strut 113 has a circumferential width of 23 mm, which is no more than 1 / 4 of 92 mm.
[0059] In this embodiment, the support rod 113 is thickened within a range where the axial thickness dimension does not exceed half the length of the wavelength of the axial resonant frequency of the hub 111.
[0060] As mentioned earlier, the wavelength of the axial resonant frequency of the hub 111 is approximately 92 mm. Therefore, the strut 113 is thickened within a range of 46 mm, which is no more than half of 92 mm.
[0061] The wall thickness mentioned here, as an example, refers to a wall thickness that is more than 1 / 4 of the wavelength of the axial resonant frequency of the strut 113. In this example, the axial thickness of the strut 113 is set in the range of 23 to 46 mm.
[0062] As another example, wall thickness refers to a wall thickness that is greater than or equal to the circumferential width dimension. The circumferential width dimension of the strut 113 is set to a range not exceeding 23 mm, as described above. For example, if the circumferential width dimension of the strut 113 is set to 20 mm, the axial thickness of the strut 113 is set to a range of 20 to 46 mm.
[0063] If we explicitly describe the shape of the strut 113, we can say that, compared to a typical strut with torsional damping, it has a shape that is wide and narrow in the circumferential direction but thick in the axial direction. The increased axial thickness is to improve the rigidity of the strut 113.
[0064] In terms of ensuring rigidity, the strut 113 of this embodiment has a shape that is inclined axially (see reference). Figure 2-3 At this point, the back surface of the strut 113 is inclined at the same angle. That is, the back surface of the strut 113, which is in an axially inclined shape, has parallel portions.
[0065] 2. Effects
[0066] (1) Basic effects
[0067] In this configuration, when the crankshaft 12 rotates due to the starting of the engine 11, the torsional damper 101 also rotates. At this time, the torsional damper 101 also forms a pulley P, so power is transmitted to auxiliary equipment.
[0068] Since the vibrating ring 131 functions as a mass, the torsional damper 101 has a natural vibration frequency in the torsional direction. Therefore, when the crankshaft 12 rotates and generates torsional vibration, if the natural vibration frequency in the torsional direction of the torsional damper 101 is tuned to a suitable torsional resonance frequency, the torsional vibration generated in the crankshaft 12 can be absorbed and reduced.
[0069] Generally, the torsional resonance frequency generated in crankshaft 12 is around 300 to 600 Hz. Therefore, the natural vibration frequency of torsional damper 101 in the torsional direction is also tuned to around 300 to 600 Hz to match the torsional resonance frequency generated in crankshaft 12.
[0070] (2) Noise suppression
[0071] The crankshaft 12 also vibrates in the X-axis direction. Therefore, the torsional damper 101 also resonates in the direction of axis A (hereinafter referred to as "axial direction"), which is consistent with axis X. At this time, the axial resonant frequency of the vibrating ring 131 is about several hundred Hz, which is the same as that of the torsional vibration.
[0072] On the other hand, the hub 111 resonates axially at a higher frequency of several kilohertz. When the hub 111 resonates at a high frequency, the radiated sound emitted from the hub 111 becomes noise and propagates.
[0073] (a) Equivalent radiated power
[0074] To understand the noise generated from hub 111, we assume equivalent radiated power. Equivalent radiated power is an indicator of the degree of sound produced from an object. If the equivalent radiated power can be reduced, the radiated sound emitted from hub 111 can be reduced.
[0075] The formula for calculating equivalent radiated power is shown in equation (1).
[0076] P=τ×(sv / 2)×md×a×v 2 .........(1)
[0077] in,
[0078] P: Equivalent radiated power
[0079] τ: Radiation loss coefficient
[0080] sv: speed of sound
[0081] md: Material density
[0082] a: area
[0083] v: Vibration velocity
[0084] The reverberation loss coefficient τ is a coefficient that depends on the shape of the object. For example, one can imagine that the sound reverberates weakly from thin piano strings and strongly from a wide, flat surface, thus representing the degree of sound reverberation.
[0085] The density md of a material depends on the material's characteristics. For example, the density of a material is determined by its structure, such as a sponge-like or bubble-free high-density mass.
[0086] Area 'a' refers to the projected area of the vibrating body.
[0087] For the torsional damper 101, the hub 111 is typically made of metal such as cast iron, leaving little room for improvement in suppressing noise caused by radiating sound. The main factors considered effective in suppressing noise are, in terms of shape, the radiation loss coefficient τ and area a, and in other aspects, the vibration velocity v. By reducing the values of these three factors—the radiation loss coefficient τ, area a, and vibration velocity v—the radiating sound emitted from the hub 111 can be reduced.
[0088] Of course, it is difficult to reduce the values of the above three factors for the boss 112 in the hub 111 and the rim 114. Therefore, in this embodiment, the shape of the strut 113 is studied to reduce the values of the above three factors.
[0089] (b) Circumferential width of the strut
[0090] In this embodiment, the circumferential width of the strut 113 is narrowed. As mentioned earlier, the width is no more than 1 / 4 of the wavelength of the resonant frequency of the axial direction of the hub 111. As a result, both the radiation loss coefficient τ and the area a decrease, and the equivalent radiated power P decreases accordingly, thereby reducing the radiated sound emitted from the hub 111.
[0091] Please provide a detailed explanation.
[0092] The sound emitted from a vibrating body depends on its size and is categorized into frequencies with effective emission and frequencies with inefficient emission. In the case of a rectangular vibrating body, sounds with wavelengths shorter than the minimum width dimension of the vibrating body are emitted forward as compression waves of air. In contrast, frequencies with wavelengths longer than the minimum width dimension cause diffraction, causing surrounding air to travel along the sides of the vibrating body to the back, and do not propagate as compression waves. In particular, if the vibrating body has a minimum amplitude of 1 / 4 of its wavelength, there is no emitted sound at all. The emission loss coefficient τ should be minimized to the extreme.
[0093] Therefore, in this embodiment, the circumferential width of the strut 113 is set to a width that does not exceed 1 / 4 of the wavelength of the axial resonant frequency of the hub 111, for example, 1 / 4 of the length. This suppresses radiating noise generated from the hub 111.
[0094] (c) Axial thickness of the strut
[0095] In this embodiment, the strut 113 is thickened in the axial direction to improve rigidity. When the rigidity of the strut 113 is increased, the axial vibration of the strut 113 decreases, and the vibration state shifts to a higher frequency. As a result, the vibration velocity v decreases, and the corresponding equivalent radiated power P decreases, thereby reducing the radiated sound emitted from the hub 111.
[0096] However, when the strut 113 is excessively thickened in the axial direction, it is difficult to induce the aforementioned diffraction phenomenon. Since diffraction is the phenomenon of air circulating around the side of the vibrating body to the back, as the length of the side of the vibrating body increases, it becomes difficult for air to circulate around to the back. Thus, the radiation loss coefficient τ will not be sufficiently small.
[0097] Therefore, in this embodiment, the thickness of the strut 113 is limited to a length not exceeding half the wavelength of the axial resonant frequency of the hub 111 to prevent passivation due to diffraction.
[0098] (d) Inclined shape of the strut
[0099] By tilting the strut 113, the axial stiffness can be significantly improved. In this embodiment, the axial stiffness of the strut 113 is improved by tilting its shape, rather than simply by increasing the wall thickness. Therefore, it is possible to suppress the radiated noise from the hub 111 based on diffraction phenomena while shifting the axial vibration of the strut 113 to higher frequencies.
[0100] In situations where it is difficult to increase the axial wall thickness of strut 113, the inclination shape of strut 113 becomes particularly significant. As mentioned earlier, the axial thickness of strut 113 is limited to a length not exceeding half the wavelength of the axial resonant frequency of hub 111. However, it is conceivable that its wall thickness would be insufficient to provide adequate axial rigidity. The inclination shape of strut 113 contributes to improving its rigidity when the wall thickness of strut 113 is limited.
[0101] (e) Summary
[0102] The limitation on the circumferential width of the strut 113 contributes to reducing the radiation loss coefficient τ and area a in equation (1) above, which defines the equivalent radiated power P. On the other hand, due to the decrease in the rigidity of the strut 113, it may lead to unfavorable conditions for the vibration velocity v in equation (1).
[0103] In this respect, in this embodiment, the increase in vibration velocity v is suppressed or reduced by thickening the wall of the strut 113 in the axial direction. However, if the strut 113 is excessively thickened in the axial direction, it is not easy to generate diffraction phenomena that cause air to flow around the side of the strut 113 to the back, and the radiation loss coefficient τ will not be small enough.
[0104] Therefore, in this embodiment, the axial wall thickness of the strut 113 is limited to prevent the passivation of diffraction phenomena. At this time, the inclined shape of the strut 113 suppresses the decrease in axial stiffness, contributing to the reduction of vibration velocity v.
[0105] As a result, the values of the three elements, "radiation loss coefficient τ", "area a" and "vibration velocity v", can be reduced in a balanced manner, thereby reducing the equivalent radiation power P and reducing the radiation sound emitted from the hub 111.
[0106] Figure 5 and Figure 6 These are graphs showing the simulation results. In these figures, the simulation results for the torsional damper 101 of this embodiment are shown with solid lines, while the simulation results for the reference example are shown with dashed lines. The reference example is a known torsional damper that does not have the numerical range of this embodiment in terms of the circumferential width and axial thickness of the strut 113.
[0107] like Figure 5 As shown, compared to the reference example, the equivalent radiated power of the torsional damper 101 in this embodiment is smaller over a wide frequency band from 400 to 4000 Hz. Particularly in the range of 1600 to 3200 Hz, where the peak frequency is slightly above 2500 Hz, a significant reduction in equivalent radiated power is observed. In other words, it is superior to the reference example in that the equivalent radiated power does not exhibit large variations across the entire frequency band.
[0108] Figure 6 The magnitude of the axial vibration of the vibrating ring 131 is shown by frequency.
[0109] As previously stated, when axial vibration occurs in the crankshaft 12, the vibrating ring 131 of the torsional damper 101 resonates axially at several hundred Hz. Simulation results from the reference example show that the vibrating ring resonates with peak frequencies around 630 Hz, 1000 Hz, and 2500 Hz. In this reference example, the axial stiffness of the hub is low, so it is foreseeable that the force generated by the axial resonance of the vibrating ring is transmitted through the elastic body to the rim located at the outer periphery of the hub, causing forced displacement of the rim and generating radiating noise.
[0110] In this embodiment, the vibration generated in the vibrating ring 131 is lower than in the reference example in any of the three frequency regions described above. This is believed to be due to the high axial rigidity of the strut 113. Therefore, even if the forced displacement force accompanying the axial resonance of the vibrating ring 131 is transmitted to the rim 114, the rim 114 is not easily deformed, which can reduce the radiated sound in the same frequency band.
[0111] 3. Variations
[0112] During implementation, various modifications and alterations are permitted.
[0113] For example, the axial wall thickness of the strut 113 is not necessarily necessary as long as the strut 113 does not require more than the required rigidity.
[0114] The inclined shape of the strut 113 is not necessary. If the strut 113 can be made sufficiently rigid without having an inclined shape, or if the strut 113 is not required to have the above rigidity, then the strut 113 can also be a straight shape extending from the boss 112 in a direction orthogonal to the axial direction.
[0115] Otherwise, all changes and modifications are permitted.
[0116] Explanation of reference numerals in the attached figures
[0117] 11 Engine
[0118] 12. Crankshaft (rotating shaft)
[0119] 13 Counterweights
[0120] 14 sales
[0121] 15-link
[0122] 16 Pistons
[0123] 17 cylinders
[0124] 21 bolts
[0125] 101 Torsional Damper
[0126] 111 rims
[0127] 112 convex platform
[0128] 112a Mounting Hole
[0129] 113 Support pole
[0130] 114 rims
[0131] 115 holes
[0132] 116 Wheel Rim Recess
[0133] 121 Elastomer
[0134] 131 Vibration Ring
[0135] 132 Ring protrusion
[0136] 141 with groove
[0137] A-axis (torsional damper)
[0138] C. Winding section
[0139] G gap
[0140] P pulley
[0141] X-axis (crankshaft)
Claims
1. A torsional damper, wherein, include: The wheel hub is integrated with the boss fixed to the rotating shaft and the circular rim via multiple struts; and A circular vibrating ring is connected to the outer circumferential surface of the wheel rim via an elastic body. The strut has a circumferential width dimension not exceeding 1 / 4 of the wavelength of the resonant frequency of the axial direction of the hub.
2. The torsional damper according to claim 1, wherein, The strut is thickened within a length that does not exceed half the wavelength of the axial resonant frequency of the hub.
3. The torsional damper according to claim 1, wherein, The strut has an axial thickness dimension that is limited to a range of 1 / 4 to 1 / 2 of the wavelength of the resonant frequency in the axial direction of the hub.
4. The torsional damper according to claim 1, wherein, The strut has an axial thickness that is limited to a range above the circumferential width dimension and below half the length of the wavelength of the axial resonant frequency of the hub.
5. The torsional damper according to claim 1, wherein, The strut is thickened within a length whose axial thickness does not exceed half the wavelength of the axial resonant frequency of the hub. The strut has an axial thickness dimension that is limited to a range of 1 / 4 to 1 / 2 of the wavelength of the resonant frequency in the axial direction of the hub.
6. The torsional damper according to claim 1, wherein, The strut is thickened in the axial direction within a range that does not exceed half the wavelength of the axial resonant frequency of the hub. The strut has an axial thickness that is limited to a range above the circumferential width dimension and below half the length of the wavelength of the axial resonant frequency of the hub.
7. The torsional damper according to claim 1, wherein, The circumferential width of the strut is one-quarter the length of the wavelength of the axial resonant frequency of the hub.
8. The torsional damper according to any one of claims 1 to 7, wherein, The strut has a shape that is inclined axially.
9. The torsional damper according to claim 8, wherein, The support rod has a parallel portion on its axially inclined back surface.