Planetary gear mechanism

Abstract

To provide a planetary gear mechanism that can suppress meshing vibration by giving the pinion itself elasticity due to rigidity fluctuations while ensuring strength. [Solution] The stepped pinions 16 (16a, 16b, 16c) have a circumferential stiffness variation characteristic G in which the radial stiffness varies depending on the circumferential position, and rotational phase differences θb, θc of the circumferential stiffness variation characteristic G are provided between the stepped pinions 16a, 16b, 16c, respectively, so that the composite component of vibration generated when each of the stepped pinions 16a, 16b, 16c meshes with the sun gear 12 is reduced. This reduces the magnitude and range of vibration fluctuations of the entire vibration caused by the meshing of the stepped pinions 16a, 16b, 16c with the sun gear 12. Therefore, by giving the pinions themselves a stiffness variation characteristic while ensuring strength, meshing vibration is suppressed.

Description

[Technical Field]

[0001] The present invention relates to a vibration suppression structure for a planetary gear mechanism. [Background technology]

[0002] A planetary gear mechanism is well known, which includes a sun gear, a carrier, a ring gear, and multiple pinions of the same shape supported by the carrier so that they can rotate and revolve. In a planetary gear mechanism with helical gears, a technique has been disclosed for suppressing friction torque fluctuations that occur between the pinion and other gears, thereby suppressing noise and vibration, by setting the number of teeth of each gear and the meshing interval between the pinion and other gears. Patent Document 1 (JP-A-2005-102566) discloses an example of such a planetary gear device.

[0003] In planetary gear mechanisms, noise and vibration are generated by friction torque fluctuations between the pinion and other gears, as described above, as well as vibrations (hereinafter referred to as meshing vibrations) that occur when the gear teeth of the pinion and other gears collide with each other when they mesh. Conventional countermeasures to this meshing vibration include reducing meshing transmission errors through precision machining of gears and providing soundproof covers or dynamic dampers to absorb vibrations at locations where meshing vibrations are generated and propagated. On the other hand, a possible countermeasure to suppress meshing vibrations is to impart elasticity to the pinion itself, i.e., to impart a variable rigidity characteristic to the pinion, thereby reducing the forcing force when the teeth mesh and collide. For example, Patent Document 2 discloses a helical gear that has multiple through-holes in the disk portion (flange) between the hub portion (rotating shaft) and rim portion (gear) of the helical gear, thereby ensuring strength and imparting a variable rigidity characteristic to the gear itself, thereby suppressing vibrations. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-60694 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-69401 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the content disclosed in Patent Document 2 is a technology relating to a single helical gear, and there is room for further improvement in a planetary gear mechanism in which multiple gears mesh.

[0006] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a planetary gear mechanism that can suppress meshing vibration by imparting rigidity fluctuation characteristics to the pinion itself while ensuring strength. [Means for solving the problem]

[0007] The gist of the present invention is a planetary gear mechanism comprising: (a) a sun gear, a carrier, a ring gear, and a plurality of pinions of the same shape supported by the carrier so as to be able to rotate and revolve, (b) the pinions have a circumferential stiffness variation characteristic in which the radial stiffness varies depending on the circumferential position, and (c) a rotational phase difference of the circumferential stiffness variation characteristic is provided between each of the pinions so that the composite component of vibrations generated when each of the pinions meshes with the sun gear is reduced. [Effects of the Invention]

[0008] According to the present invention, the pinions have a circumferential stiffness variation characteristic in which radial stiffness varies depending on the circumferential position, and a rotational phase difference in the circumferential stiffness variation characteristic is provided between each of the pinions so that the composite component of vibrations generated when each of the pinions meshes with the sun gear is reduced. This reduces the magnitude and range of vibration fluctuations of the overall vibration caused by the meshing of each of the pinions with the sun gear. Therefore, it is possible to provide a planetary gear mechanism that can suppress meshing vibrations by providing the pinions themselves with stiffness variation characteristics while ensuring strength. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating a schematic configuration of a planetary gear mechanism to which the present invention is applied; [Figure 2] 2 is a diagram illustrating an arrangement of a pinion included in the planetary gear mechanism of FIG. 1 for suppressing vibration. FIG. [Figure 3] 10A and 10B are diagrams illustrating the configuration of a pinion included in a planetary gear mechanism according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the various parts are not necessarily drawn accurately. [Example]

[0011] FIG. 1 is a diagram illustrating the schematic configuration of a planetary gear mechanism 10 to which the present invention is applied. FIG. 1(a) is a perspective view of the planetary gear mechanism 10, which is a known stepped pinion type planetary gear mechanism including a sun gear 12, a carrier (not shown), a ring gear 14, and three stepped pinions 16 (16a, 16b, 16c) supported by the carrier so as to be rotatable and revolvable. A shaft center CL is the rotational axis of the sun gear 12, the ring gear 14, and the carrier. The stepped pinions 16 (16a, 16b, 16c) correspond to the "pinion" in this invention.

[0012] Each of the stepped pinions 16a, 16b, and 16c includes a large-diameter gear 16a1, 16b1, and 16c1 that meshes with the sun gear 12, and a small-diameter gear 16a2, 16b2, and 16c2 that meshes with the ring gear 14, and the large-diameter gear 16a1 and the small-diameter gear 16a2, the large-diameter gear 16b1 and the small-diameter gear 16b2, and the large-diameter gear 16c1 and the small-diameter gear 16c2 rotate integrally. The operation of the planetary gear mechanism 10 is well known, so a description thereof will be omitted.

[0013] FIG. 1(b) is a perspective view of the stepped pinion 16a as viewed from the axis CL toward the front of the perspective view of FIG. 1(a). The large-diameter gear 16a1 of the stepped pinion 16a, which meshes with the sun gear 12, is supported by a disk-shaped flange F. As shown in FIG. 1(b), the flange F has three approximately semicircular through holes h, whose outer diameters vary circumferentially and are equally spaced circumferentially along the outer periphery RF of the flange F. The stepped pinions 16b and 16c are also configured with the same shape as the stepped pinion 16a. The provision of the through holes h ensures the strength of the stepped pinion 16 (16a, 16b, 16c), while also providing it with a circumferential stiffness variation characteristic G, in which the radial stiffness varies depending on the circumferential position of the gear teeth.

[0014] 1(c) shows a conventional stepped pinion 16NA to which the present invention does not apply, in which no through-hole is provided in the flange FA of the large-diameter gear 16NA1, meaning that the circumferential stiffness fluctuation characteristic G is not provided and the stiffness in the radial direction does not fluctuate.

[0015] FIG. 1(d) illustrates the effectiveness of the through-hole h in suppressing meshing vibrations (hereinafter referred to as meshing vibrations) that occur when the gear teeth of the stepped pinion 16 (16a, 16b, 16c) and the sun gear 12 collide with each other when they mesh. The solid line in FIG. 1(d) corresponds to FIG. 1(b), and the dashed-dotted line corresponds to FIG. 1(c). When the through-hole h is present at the meshing point with the sun gear 12 as the stepped pinion 16 (16a, 16b, 16c) rotates, the meshing point forcing force, which is the force exerted when the teeth mesh and collide, is modulated by stiffness fluctuation due to the circumferential stiffness fluctuation characteristic G. As a result, the peak of the first-order frequency component generated when the through-hole h is absent is dispersed, as shown in FIG. 1(d). This suppresses meshing vibrations at the meshing point.

[0016] Next, the arrangement of the stepped pinions 16 (16a, 16b, 16c) for suppressing meshing vibration and the synthesis of meshing vibration will be described with reference to Figure 2. Figure 2(a) is a view of the stepped pinions 16 (16a, 16b, 16c) and the sun gear 12 as seen from the axis CL in the forward direction of the perspective view of Figure 1(a), showing the arrangement for suppressing meshing vibration. The stepped pinions 16 (16a, 16b, 16c) are provided with rotational phase differences in the circumferential stiffness fluctuation characteristics G between them so that the synthesized components of the meshing vibrations generated at the meshing points between each of the stepped pinions 16a, 16b, 16c and the sun gear 12 are reduced. For example, in Figure 2(a), the stepped pinion 16a is arranged with its meshing point with the sun gear 12 located at the center of the through hole h, whereas the stepped pinion 16b is arranged with a counterclockwise rotational phase difference θb, and the stepped pinion 16c is arranged with a clockwise rotational phase difference θc.

[0017] 2(b) and 2(c) are diagrams illustrating the circumferential stiffness fluctuation characteristic G of each of the stepped pinions 16a, 16b, and 16c at the meshing point with the sun gear 12, as well as its combined component. FIG. 2(b) illustrates an example of an embodiment of the present invention, while FIG. 2(c) illustrates a comparative example. In both FIGS. 2(b) and 2(c), the horizontal axis represents the rotation angle of each of the stepped pinions 16a, 16b, and 16c when rotated 360 degrees counterclockwise from the position shown in the balloon on the right side of the figure, while the vertical axis represents the amount of fluctuation in stiffness of the stepped pinions 16a, 16b, and 16c and their combined component at the meshing point with the sun gear 12. The larger the value on the vertical axis, the greater the stiffness at the meshing point with the sun gear 12, which in turn increases the meshing point forcing force, resulting in greater meshing vibration. That is, in FIGS. 2(b) and 2(c), the larger the value on the vertical axis, the greater the meshing vibration.

[0018] In the comparative example of FIG. 2(c), as shown in the balloons on the right side of the page, the stepped pinions 16a, 16b, and 16c are positioned such that the meshing points with the sun gear 12 are located at the centers of their respective through holes h, i.e., the rotational phase difference θb = rotational phase difference θc = 0°. When the stepped pinions 16a, 16b, and 16c rotate 360 ​​degrees counterclockwise from this state, the stiffness of the stepped pinions 16a, 16b, and 16c at the meshing points with the sun gear 12 periodically varies within a range from the minimum stiffness fluctuation value (the line of the vertical axis 0) to the maximum stiffness fluctuation value S, as shown in FIG. 2(c). This stiffness fluctuation characteristic corresponds to the circumferential stiffness fluctuation characteristic G (the circumferential stiffness fluctuation characteristics corresponding to the stepped pinions 16a, 16b, and 16c are designated Ga, Gb, and Gc). The periodic fluctuation is repeated three times because three through holes h are provided at equal intervals in the circumferential direction. In the comparative example, the rotational phases of the stepped pinions 16a, 16b, and 16c at the meshing points with the sun gear 12 are the same (θb = θc = 0°), so the circumferential stiffness fluctuation characteristics Ga, Gb, and Gc have the same waveform. Therefore, the combined component (= Ga + Gb + Gc) of the circumferential stiffness fluctuation characteristic G has a waveform that fluctuates three times as large as the aforementioned identical waveform, as shown in Figure 2(c), and therefore the overall meshing vibration between the stepped pinions 16a, 16b, and 16c and the sun gear 12 also occurs and fluctuates in accordance with this fluctuating waveform.

[0019] In contrast to the comparative example, Fig. 2(b) shows an example in which the rotational phase difference θb is 40° and the rotational phase difference θc is -40°. As shown in Fig. 2(b), rotational phase differences θb and θc occur between the circumferential stiffness fluctuation characteristics Ga, Gb, and Gc of the stepped pinions 16a, 16b, and 16c, so the maximum value of the combined component (= Ga + Gb + Gc) is smaller and the fluctuation range is also smaller than in the comparative example of Fig. 2(c). As a result, the magnitude of the overall meshing vibration between the stepped pinions 16a, 16b, and 16c and the sun gear 12 is reduced, and the fluctuation range of the generated meshing vibration is also reduced.

[0020] 2(b) shows an example in which the rotational phase difference θb=40° and the rotational phase difference θc=−40°, but the rotational phase differences θb and θc are suitably set in advance through design or experimentation depending on the design and manufacturing conditions of the planetary gear mechanism 10, the mounting conditions on a vehicle, etc. Similarly, the number, dimensions, shape, etc. of the through holes h are also suitably set in advance through design or experimentation.

[0021] As described above, according to the planetary gear mechanism 10 of this embodiment, the stepped pinions 16 (16a, 16b, 16c) have a circumferential stiffness variation characteristic G in which the radial stiffness varies depending on the circumferential position, and rotational phase differences θb and θc of the circumferential stiffness variation characteristic G are provided between the stepped pinions 16a, 16b, 16c, respectively, so that the composite component of vibrations generated when the stepped pinions 16a, 16b, 16c mesh with the sun gear 12 is reduced. This reduces the magnitude and fluctuation range of the overall vibration caused by the meshing of the stepped pinions 16a, 16b, 16c with the sun gear 12. Therefore, by providing the pinions themselves with a stiffness variation characteristic while ensuring strength, meshing vibration is suppressed.

[0022] Next, another embodiment of the present invention will be described. In the following description, parts common to the embodiments will be given the same reference numerals and the description thereof will be omitted. [Example]

[0023] 3 is a diagram illustrating the configuration of a stepped pinion 26 included in a planetary gear mechanism 20 according to another embodiment of the present invention, and corresponds to FIG. 2(a) of the first embodiment. The planetary gear mechanism 20 is an embodiment in which the stepped pinions 16 (16a, 16b, 16c) of the planetary gear mechanism 10 of the first embodiment are replaced with stepped pinions 26 (26a, 26b, 26c). The large-diameter gears (26a1, 26b1, 26c1) of the stepped pinion 26 are supported, for example, by a disk-shaped flange F2 that has elasticity and low rigidity, and three ribs LB that are equally spaced circumferentially and longitudinally disposed in the radial direction and have high rigidity for ensuring strength. This ensures strength while realizing a circumferential rigidity variation characteristic G2 in which radial rigidity varies depending on the circumferential position. As in the first embodiment, the stepped pinion 26b has a rotational phase difference θb2 with respect to the stepped pinion 26a, and the stepped pinion 26c has a rotational phase difference θc2 with respect to the stepped pinion 26a at the meshing point with the sun gear 12. The material, dimensions, shape, and rotational phase differences θb2 and θc2 of the flange F2 and rib LB are suitably set in advance through design or experimentation.

[0024] The planetary gear mechanism 20 configured as above also provides the same effects as those of the planetary gear mechanism 10 of the first embodiment described above.

[0025] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0026] For example, in the first and second embodiments described above, the planetary gear mechanisms 10 and 20 are equipped with stepped pinions 16 and 26, but the present invention is not limited to this and can be applied to planetary gear mechanisms having a single-diameter pinion.

[0027] Furthermore, in the first and second embodiments described above, the stepped pinions 16 and 26 are configured with three pinions, but the present invention is not limited to three and can be applied to any suitable number of pinions.

[0028] It should be noted that the above is merely one embodiment, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0029] 10, 20: Planetary gear mechanism 12: Sun gear 14: Ring gear 16, 26: Stepped pinion (pinion) G, G2 circumferential stiffness fluctuation characteristics θb, θb2, θc, θc2: Rotational phase difference

Claims

[Claim 1] A planetary gear mechanism comprising a sun gear, a carrier, a ring gear, and a plurality of pinions of the same shape supported by the carrier so as to be able to rotate and revolve, the pinion has a circumferential stiffness variation characteristic in which radial stiffness varies depending on a circumferential position, In the meshing between each of the pinions and the sun gear, a rotational phase difference of the circumferential stiffness fluctuation characteristics is provided between each of the pinions so that the combined component of the vibrations generated by each pinion is reduced. A planetary gear mechanism characterized by the following features.

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