Transmission mechanism
The transmission mechanism addresses the challenge of axial thickness by fixing the sun gear and using a housing to accommodate engaging gears, achieving efficient speed change and compact design with improved efficiency and reduced noise.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-03-25
- Publication Date
- 2026-03-19
AI Technical Summary
Conventional transmission mechanisms with a fixed gear on the outermost diameter necessitate a bearing layout in the axial direction, limiting their ability to be made thinner in this direction.
A transmission mechanism design that includes a sun gear fixed to a housing, with a planetary gear and internal gear engaging through eccentric rotation, allowing for a thinner axial configuration by fixing the sun gear to prevent rotation and utilizing a housing to accommodate these gears.
Enables speed change through eccentric rotation while reducing the mechanism's axial thickness, improving power transmission efficiency and reducing noise, and allowing for a compact design without reversing input and output rotation directions.
Smart Images
Figure JP2025011898_19032026_PF_FP_ABST
Abstract
Description
Transmission mechanism
[0001] The present invention relates to a transmission mechanism. This application claims the benefit of the priority of Japanese Patent Application No. 2024-159471 filed on September 13, 2024, the content of which is incorporated herein by reference.
[0002] As a conventional transmission mechanism, for example, there is known a speed reduction mechanism in which a planetary gear disposed between a sun gear and an internal gear is eccentrically rotated, with the planetary gear serving as an input gear and the sun gear serving as an output gear (see, for example, Patent Document 1).
[0003] International Publication No. 2019 / 077886
[0004] However, in the transmission mechanism having the above-described configuration, since the internal gear disposed on the outermost diameter of the transmission mechanism is a fixed gear, it is necessary to arrange the bearing layout of the rotating gears in the axial direction. Therefore, there is room for improvement in the transmission mechanism having the above-described configuration in terms of making the transmission mechanism thinner by shortening it in the axial direction.
[0005] An object of the present invention is to provide a transmission mechanism that enables speed change using eccentric rotation and can be made thinner in the axial direction.
[0006] (1) The transmission mechanism according to the present invention includes a sun gear having external teeth, a planetary gear located on the outer peripheral side of the sun gear and having internal teeth and external teeth, an internal gear located on the outer peripheral side of the planetary gear and having internal teeth, an eccentric rotating shaft having an eccentric shaft that eccentrically rotates together with the planetary gear, and a rotating shaft that rotates together with the internal gear. The internal teeth of the planetary gear are locally engaged with the external teeth of the sun gear, and the external teeth of the planetary gear are locally engaged with the internal teeth of the internal gear. The sun gear is a fixed gear.
[0007] (2) The transmission mechanism according to (1) above may further include a housing that houses the sun gear, the planetary gear, and the internal gear, and the sun gear may be fixed to the housing so as not to rotate.
[0008] (3) In the gear shifting mechanism described in (2) above, the sun gear may be provided with an annular base and be fixed to the housing so as not to rotate by the annular base.
[0009] (4) In the gear shifting mechanism described in (3) above, it is preferable that the sun gear is positioned at an axial distance from the annular base.
[0010] (5) In the gear shifting mechanism described in (2) above, it is preferable that the sun gear is fixed to the housing so as not to rotate by press-fitting.
[0011] (6) In the gear shifting mechanism described in (3) above, it is preferable that the annular base is fixed to the housing so as not to rotate by press-fitting.
[0012] (7) The gear shifting mechanism described in (1) above further comprises a housing that accommodates the sun gear, the planetary gear and the internal gear, and the sun gear may be fixed to a fixed shaft fixed to the housing in a manner that prevents rotation.
[0013] (8) In the gear shifting mechanism described in (7) above, the sun gear may be integrally formed with the fixed shaft.
[0014] (9) In any one of the transmission mechanisms described in (1) to (8) above, the eccentric rotating shaft may be the input rotating shaft, and the rotating shaft may be the output rotating shaft.
[0015] According to the present invention, it is possible to provide a speed change mechanism that enables speed change using eccentric rotation and can be made thinner in the axial direction.
[0016] This is a cross-sectional view of a transmission mechanism according to the first embodiment of the present invention, taken in a section including the central axis of the transmission mechanism. This is a cross-sectional view of the transmission mechanism in Figure 1 taken along section A-A. This is a schematic cross-sectional view of a transmission mechanism according to the second embodiment of the present invention, taken in a section including the central axis of the transmission mechanism.
[0017] Hereinafter, an exemplary embodiment of the present invention, a gear shift mechanism, will be described with reference to the drawings.
[0018] In Figure 1, reference numeral 1A denotes a transmission mechanism that is a first embodiment of the present invention. The transmission mechanism 1A in Figure 1 is shown as a cross-sectional view of a plane that includes the central axis O1 of the transmission mechanism 1A (hereinafter also simply referred to as "axis O1").
[0019] In the following explanation, unless otherwise specified, the meanings of the terms are defined as follows.
[0020] For example, "axial direction" refers to the direction in which the axis O1 extends. "Input side" refers to one side in the axial direction. "Output side" refers to the other side in the axial direction. "Circumferential direction" refers to the circumferential direction of the axis O1. Furthermore, "radial direction" refers to the direction perpendicular to the axis O1. Specifically, "radial inner side" refers to the side closer to the axis O1. "Radial outer side" refers to the side further away from the axis O1.
[0021] The gear shifting mechanism 1A includes a sun gear 2 having external teeth 2a, a planetary gear 3 located on the outer circumference of the sun gear 2 and having internal teeth 3a and external teeth 3b, an internal gear 4 located on the outer circumference of the planetary gear 3 and having internal teeth 4b, an eccentric rotating shaft 5 having an eccentric shaft 5a that rotates eccentrically with the planetary gear 3, and a rotating shaft 6 that rotates with the internal gear 4. In this disclosure, the rotating shaft 6 is a concentric rotating shaft extending along the axis O1 (hereinafter, "rotating shaft 6" is also referred to as "concentric rotating shaft 6").
[0022] The gear shift mechanism 1A is configured such that the internal teeth 3a of the planetary gear 3 locally mesh with the external teeth 2a of the sun gear 2, while the external teeth 3b of the planetary gear 3 locally mesh with the internal teeth 4b of the internal gear 4. Furthermore, in the gear shift mechanism 1A, the sun gear 2 is a fixed gear.
[0023] The gear shifting mechanism 1A further comprises a housing 7 that accommodates the sun gear 2, planetary gears 3, and internal gear 4.
[0024] In this disclosure, the housing 7 comprises a housing body 71 and a housing cover 72. The housing body 71 has a through hole A1 through which an eccentric rotating shaft 5 passes. In this disclosure, the housing cover 72 has a through hole A2 through which a concentric rotating shaft 6 passes. In this disclosure, the housing 7 is positioned on the same axis as the central axis O1 of the transmission mechanism 1A. For convenience, the central axis of the housing 7 is defined here as axis O1.
[0025] In this disclosure, the housing body 71 comprises an annular bottom wall 71a and a housing cylinder wall 71b extending axially from the bottom wall 71a. In this disclosure, the housing body 71 is positioned on the same axis as the central axis O1 of the transmission mechanism 1A. Therefore, here again, the central axis of the housing body 71 is defined as axis O1.
[0026] The bottom wall 71a extends in an annular shape in the circumferential direction. In this disclosure, the housing body 71 further comprises a cylindrical wall 71c. The cylindrical wall 71c extends in the axial direction. In this disclosure, the cylindrical wall 71c constitutes the radially inner edge of the bottom wall 71a. In this disclosure, the through hole A1 is formed in the bottom wall 71a. In this disclosure, the through hole A1 is a through hole formed on the inside of the cylindrical wall 71c. The housing cylindrical wall 71b, together with the bottom wall 71a, forms a recessed space that houses the sun gear 2, planetary gear 3, and internal gear 4 radially inward.
[0027] In this disclosure, the housing body 71 is rotatably mounted on the eccentric rotating shaft 5 via a bearing B2. In this disclosure, the eccentric rotating shaft 5 includes a central shaft 5b that, together with the eccentric shaft 5a, lies on the same axis as the axis O1. In this disclosure, the bearing B1 connects the central shaft 5b of the eccentric rotating shaft 5 to the cylindrical wall 71c of the housing body 71. As a result, in this disclosure, the eccentric rotating shaft 5 and the housing body 71 can rotate relative to each other in the circumferential direction. Therefore, in this disclosure, the eccentric rotating shaft 5 and the housing 7 can rotate relative to each other about the axis O1.
[0028] On the other hand, in this disclosure, the housing cover 72 comprises an annular top wall 72a and a mounting cylinder wall 72b extending axially from the top wall 72a. In this disclosure, the housing cover 72 is also positioned on the same axis as the central axis O1 of the transmission mechanism 1A. Therefore, here again, the central axis of the housing cover 72 is defined as axis O1.
[0029] The top wall 72a extends in an annular shape in the circumferential direction. In this disclosure, the through hole A2 is formed in the top wall 72a. In this disclosure, the through hole A2 is a through hole formed radially inward of the top wall 72a. In this disclosure, the mounting cylinder wall 72b can be attached to the mounting end 71b1 provided on the housing cylinder wall 71b of the housing body 71. As a result, as shown in Figure 1, a housing space for housing the sun gear 2, planetary gear 3, and internal gear 4 is formed between the housing body 71 and the housing cover 72.
[0030] As shown in Figure 2, the sun gear 2 is an annular sun gear. In this disclosure, the sun gear 2 extends annularly in the circumferential direction. In this disclosure, the sun gear 2 is positioned on the same axis as the central axis O1 of the transmission mechanism 1A. Therefore, here again, the central axis of the sun gear is defined as axis O1.
[0031] On the other hand, the planetary gear 3 is also an annular planetary gear, as shown in Figure 2. However, as shown in Figure 1, in this disclosure, the planetary gear 3 is attached to the eccentric shaft 5a of the eccentric rotating shaft 5. In this disclosure, the eccentric axis O2 of the eccentric shaft 5a is positioned radially eccentric with respect to the axis O1. As a result, the central axis of the planetary gear 3 is located on the same axis as the eccentric axis O2, which is radially eccentric with respect to the axis O1. Therefore, here, the central axis of the planetary gear 3 is defined as the eccentric axis O2.
[0032] The planetary gear 3 is rotatably mounted on the eccentric rotating shaft 5. In this disclosure, the planetary gear 3 is rotatably mounted on the eccentric shaft 5a.
[0033] In this disclosure, the planetary gear 3 is configured as a planetary gear member 3A. In this disclosure, the planetary gear member 3A comprises a planetary gear 3, an annular connecting portion 31, and an inner cylinder wall 32. The annular connecting portion 31 extends annularly in the circumferential direction around the central axis (eccentric axis O2) of the planetary gear 3. In this disclosure, the radially outer end of the annular connecting portion 31 is connected to the planetary gear 3. On the other hand, the radially inner end of the annular connecting portion 31 is connected to the inner cylinder wall 32. In particular, in this disclosure, the annular connecting portion 31 is connected to the ends of the planetary gear 3 and the inner cylinder wall 32 on the side of the concentric rotation axis 6. Accordingly, in this disclosure, the planetary gear member 3A is configured such that the planetary gear 3 is the outer cylinder, the inner cylinder wall 32 is the inner cylinder, and the opening on the side of the concentric rotation axis 6 between the planetary gear 3 and the inner cylinder wall 32 is closed by an annular connecting portion 31.
[0034] In this disclosure, the planetary gear 3 is mounted on the eccentric shaft 5a via a bearing B2 so as to be rotatable relative to it. In this disclosure, the bearing B2 connects the eccentric shaft 5a of the eccentric rotating shaft 5 to the inner cylinder wall 32 of the planetary gear 3. As a result, in this disclosure, the eccentric rotating shaft 5 and the planetary gear 3 (planetary gear member 3A) can rotate circumferentially relative to each other about the central axis (eccentric axis O2) of the eccentric shaft 5a. Therefore, in this disclosure, the eccentric rotating shaft 5 and the planetary gear 3 can rotate relative to each other about the central axis (eccentric axis O2) of the eccentric shaft 5a.
[0035] In this disclosure, the planetary gear 3 can rotate relative to the eccentric axis 5a at a position on the eccentric axis O2 which is eccentric with respect to the axis O1 of the eccentric rotation shaft 5. That is, in this disclosure, the planetary gear 3 can rotate on its own axis around the eccentric axis 5a (eccentric axis O2) of the eccentric rotation shaft 5 while revolving around the central axis 5b (axis O1) of the eccentric rotation shaft 5.
[0036] Next, the internal gear 4 is connected to the concentric rotating shaft 6. In this disclosure, the internal gear 4 is connected to the concentric rotating shaft 6 by a connecting plate 8. In this disclosure, the concentric rotating shaft 6 is located on the same axis as the central axis O1 of the transmission mechanism 1A. Therefore, here, the central axis of the concentric rotating shaft 6 is defined as axis O1. Furthermore, in this disclosure, the internal gear 4 is also located on the same axis as the central axis O1 of the transmission mechanism 1A. Therefore, here again, the central axis of the internal gear 4 is defined as axis O1. As a result, in this disclosure, the internal gear 4 and the concentric rotating shaft 6 can rotate integrally and synchronously in the circumferential direction around axis O1.
[0037] As shown in Figure 2, the internal gear 4 extends in an annular shape in the circumferential direction. In this disclosure, the internal teeth 3a of the planetary gear 3 locally mesh with the external teeth 2a of the sun gear 2, while the external teeth 3b of the planetary gear 3 locally mesh with the internal teeth 4b of the internal gear 4. In this disclosure, the internal gear 4 is mounted to the housing 7 so as to be rotatable relative to it via a bearing B3. In this disclosure, the bearing B3 connects the internal gear 4 to the housing cylinder wall 71b of the housing body 71. As a result, in this disclosure, the internal gear 4 and the housing 7 can rotate circumferentially relative to each other around the axis O1. Therefore, in this disclosure, the internal gear 4 and the housing 7 can rotate relative to each other about the axis O1.
[0038] In this disclosure, the external teeth 2a of the sun gear 2 and the internal teeth 3a of the planetary gear 3 have different numbers of teeth Z. In this disclosure, the number of teeth ZS of the external teeth 2a of the sun gear 2 is smaller than the number of teeth Zp1 of the internal teeth 3a of the planetary gear 3. For example, the number of teeth ZS is one less than the number of teeth Zp1 (Zp1 - ZS = 1). Also in this disclosure, the external teeth 3b of the planetary gear 3 and the internal teeth 4b of the internal gear 4 have different numbers of teeth Z. In addition, in this disclosure, the number of teeth Zp2 of the external teeth 3b of the planetary gear 3 is less than or equal to the number of teeth Zi of the internal teeth 4b of the internal gear 4. As a result, in this disclosure, the internal teeth 3a of the planetary gear 3 can locally mesh with the external teeth 2a of the sun gear 2, while the external teeth 3b of the planetary gear 3 can locally mesh with the internal teeth 4b of the internal gear 4. Therefore, in this disclosure, if the planetary gear 3 rotates on its own axis around the eccentric axis 5a (eccentric axis O2) of the eccentric rotation shaft 5 while revolving around the central axis 5b (axis O1) of the eccentric rotation shaft 5 as described above, the planetary gear 3 can rotate so as to oscillate around axis O1 while locally meshing with the sun gear 2 and the internal gear 4 in the circumferential direction. In this disclosure, if the number of teeth Zp2 is the same as the number of teeth Zi, the reduction ratio can be maximized when the eccentric rotation shaft 5 is used as input.
[0039] In the transmission mechanism 1A, the sun gear 2 is fixed to the housing 7 in a way that prevents it from rotating.
[0040] As shown in Figure 1, in the gear shifting mechanism 1A, the sun gear 2 is provided with an annular base 21. In this disclosure, the sun gear 2 is fixed to the housing 7 in a non-rotatable manner by the annular base 21.
[0041] In this disclosure, the annular base 21 extends annularly in the circumferential direction around the axis O1. In this disclosure, the annular base 21 is a plate-like, annular base.
[0042] The annular base 21 can be fixed to the housing 7, for example, by bonding, welding, screwing, fastening with bolts and nuts, fitting or other coupling means so as to prevent rotation around the axis O1 with respect to the housing 7. In the present disclosure, the annular base 21 is non-rotatably fixed to the housing body 71.
[0043] In the present disclosure, the annular base 21 is disposed between the housing cylinder wall 71b and the cylinder wall 71c of the housing body 71. In this case, the sun gear 2 can fix the annular base 21 to the bottom wall 71a of the housing body 71.
[0044] In addition, as shown in FIG. 1, in the present disclosure, the sun gear 2 is disposed at an axial interval C with respect to the annular base 21.
[0045] In the present disclosure, the sun gear 2 is disposed at an axial interval C with respect to the annular base 21 by a connecting piece 22. The connecting piece 22 connects the sun gear 2 and the annular base 21. Thus, in the present disclosure, the sun gear 2 is disposed at an axial interval C with respect to the annular base 21. In the present disclosure, the connecting piece 22 is a cylindrical connecting piece. In the present disclosure, the outer diameter of the connecting piece 22 is smaller than the outer diameter of the sun gear 2. Specifically, the outer diameter of the connecting piece 22 is made smaller than the outer diameter of the sun gear 2 so that a gap space is ensured by the amount of the interval C between the outer teeth 2a of the sun gear 2 and the base 21. However, the connecting piece 22 can also be a plurality of connecting pieces intermittently arranged around the axis O1.
[0046] In addition, in the present disclosure, an extension cylinder portion 21b1 extending in the axial direction by the amount of the interval C is provided at the outer peripheral edge portion 21b of the annular base 21. Thus, in the present disclosure, the annular base 21 is configured as a bottomed cylindrical base.
[0047] In the present disclosure, the annular base 21 is non-rotatably fixed to the housing 7 by press-fitting. [[ID=1In the present disclosure, the sun gear 2 is non-rotatably fixed to the housing main body 71, that is, the housing 7 by press-fitting the outer peripheral edge portion 21b of the annular base portion 21 into the housing cylinder wall 71b of the housing main body 71. In the present disclosure, as described above, the annular base portion 21 is a bottomed cylindrical base portion. Therefore, when the outer peripheral surface of the outer peripheral edge portion 21b of the base portion 21 is press-fitted into the inner peripheral surface of the housing cylinder wall 71b of the housing main body 71, the fitting force due to the press-fitting is larger by the amount of the extension cylinder portion 21b1 than when there is no extension cylinder portion 21b1.
[0049] Note that the sun gear 2 can also be non-rotatably fixed to the housing main body 71, that is, the housing 7 by press-fitting the inner peripheral edge portion 21a of the annular base portion 21 into the cylinder wall 71c of the housing main body 71. In the present disclosure, the cylinder wall 71c includes a protruding cylinder wall 71c1 that protrudes in the axial direction from the bottom wall 71a. Thereby, in the present disclosure, by press-fitting the inner peripheral surface of the inner peripheral edge portion 21a of the annular base portion 21 onto the outer peripheral surface of the protruding cylinder wall 71c1 of the housing main body71, it can be non-rotatably fixed to the housing main body 71, that is, the housing 7. Further, the sun gear 2 can also be press-fitted with respect to both the inner peripheral edge portion 21a and the outer peripheral edge portion 21b of the annular base portion 21 to the housing main body 71. Further, the annular base portion 21 can be non-rotatably fixed to the housing 7, for example, the housing main body 71 by fitting having a function of preventing rotation, such as keyway fitting, spline fitting, serration fitting, etc., using a key and a keyway that fits with the key.
[0050] As shown in FIG. 1, the transmission mechanism 1A is composed of six components: a sun gear 2, a planetary gear 3, an internal gear 4, an eccentric rotating shaft 5, a concentric rotating shaft 6, a housing main body 71, and a housing cover 72. The transmission mechanism 1A has a configuration in which the sun gear 2 is used as a fixed gear and meshes with the internal teeth 3a of the planetary gear 3 that rotates together with the eccentric rotating shaft 5, while the external teeth 3b of the planetary gear 3 mesh with the internal gear 4 that rotates together with the concentric rotating shaft 6.
[0051] In this disclosure, the transmission mechanism 1A has an eccentric rotating shaft 5 as the input rotating shaft and a concentric rotating shaft 6 as the output rotating shaft. In this case, the transmission mechanism 1A can function as a reduction mechanism, as described below.
[0052] In the transmission mechanism 1A, when the eccentric rotating shaft 5 is rotated, the planetary gear 3 performs eccentric motion around the axis O1 due to its eccentric axis 5a, which is eccentric with respect to the central axis 5b of the eccentric rotating shaft 5. At this time, the planetary gear 3 moves circumferentially with respect to the sun gear 2, which functions as a fixed gear, due to its eccentric motion, and engages locally with respect to the sun gear 2. As a result, the planetary gear 3 is decelerated by oscillating motion around the axis O1. On the other hand, the internal gear 4 eliminates the oscillating motion of the planetary gear 3 by engaging with it. That is, the internal gear 4 obtains decelerated rotation by engaging with the planetary gear 3 in a way that extracts only decelerated rotation.
[0053] According to the gear shifting mechanism 1A, the sun gear 2 is a fixed gear, and the sun gear 2 is meshed with the internal teeth 3a of a planetary gear 3 that rotates with the eccentric rotation shaft 5, while the external teeth 3b of the planetary gear 3 are meshed with an internal gear 4 that rotates with the concentric rotation shaft 6. As shown in Figure 1, this configuration makes it possible to place the bearing B3 on the outer circumference of the internal gear 4. Therefore, according to the gear shifting mechanism 1A, the gear shifting mechanism 1A can be made thinner by shortening it in the axial direction.
[0054] Therefore, the gear shift mechanism 1A makes it possible to provide a gear shift mechanism that enables gear shifting using eccentric rotation and can be made thinner in the axial direction.
[0055] By the way, in the transmission mechanism described in Patent Document 1, the input rotation and output rotation are reversed due to the mechanism. In contrast, with the mechanism of transmission mechanism 1A, the rotation direction of the input rotation and the rotation direction of the output rotation can be the same. That is, with transmission mechanism 1A, the input rotation and output rotation do not reverse. Therefore, with transmission mechanism 1A, it is possible to obtain an output rotation that rotates in the same direction as the input and output rotations without reversing the input rotation.
[0056] Furthermore, in this disclosure, the sun gear 2 is fixed to the housing 7 in a non-rotatable manner. In this case, by arranging each gear inside the housing 7, the transmission mechanism 1A can be made smaller.
[0057] Furthermore, in this disclosure, the sun gear 2 is provided with an annular base 21, which is fixed to the housing 7 in a non-rotatable manner. In this case, the sun gear 2 is press-fitted into the housing 7 via the annular base 21, thereby suppressing the effect of press-fitting on the sun gear 2. As a result, the meshing between the sun gear 2 and the planetary gear 3 is maintained in a normal state compared to when the sun gear 2 is directly press-fitted. Therefore, in this case, the power transmission efficiency of the transmission mechanism 1A can be improved and the noise generated during power transmission can be suppressed. In particular, in this disclosure, the annular base 21 functions as a cylindrical base 21, acting as a partition that separates the radially inner side of the sun gear 2 from the radially outer side of the sun gear 2. As a result, even when a lubricant such as grease is applied to the radially inner transmission part of the sun gear 2, it is possible to prevent it from scattering beyond the annular base 21 to the radially outer side of the sun gear 2.
[0058] Furthermore, in this disclosure, the sun gear 2 is positioned with an axial gap C between it and the annular base 21. In this case, by leaving a gap C between the sun gear 2 and the annular base 21, even when the base 21 is provided as in this disclosure, axial interference between the annular base 21 and the external teeth 2a of the sun gear 2 and the internal teeth 3a of the planetary gear 3 when they mesh can be suppressed. This makes it possible to further improve the power transmission efficiency of the transmission mechanism 1A and further suppress noise generated during power transmission.
[0059] In this disclosure, when the sun gear 2 is made a fixed gear, the sun gear 2 is fixed so as not to rotate by press-fitting its annular base 21 into the housing 7. In this case, the sun gear 2 can be easily fixed to the housing 7.
[0060] Furthermore, in this disclosure, the eccentric rotating shaft 5 is the input rotating shaft, and the concentric rotating shaft 6 is the output rotating shaft. In this case, the speed change mechanism 1A is effective when applied as a reduction mechanism that is thin and aims to improve transmission efficiency.
[0061] In this case, the reduction ratio of the transmission mechanism 1A can be expressed by the following formula.
[0062] [Formula 1]
[0063] Figure 3 is a schematic cross-sectional view showing a transmission mechanism 1B, which is a second embodiment of the present invention, in a cross-section including the central axis O1 of the transmission mechanism 1B. In the transmission mechanism 1B, the same reference numerals are used for parts that are substantially the same as those of the transmission mechanism 1A.
[0064] In the transmission mechanism 1A, the sun gear 2 is fixed to the housing 7 itself in a non-rotatable manner. In contrast, in this disclosure, the sun gear 2 is fixed not to the housing 7 itself, but to a fixed shaft 9 fixed to the housing 7 in a non-rotatable manner. The transmission mechanism 1B can be applied, for example, when it is arranged inside the housing 7 together with a power source such as a motor.
[0065] The sun gear 2 can be fixed to the fixed shaft 9, for example, by means of bonding such as adhesive, welding, fastening with screws or bolts and nuts, or fitting, such that rotation around the axis O1 is prevented from being performed on the fixed shaft 9. In this disclosure, the fixed shaft 9 is fixed to the housing body 71 in a way that prevents rotation.
[0066] In this disclosure, the sun gear 2 is integrally formed with the fixed shaft 9.
[0067] In this disclosure, the eccentric rotating shaft 5 is a cylindrical shaft. The speed change mechanism 1B includes two bearings B1 spaced apart in the axial direction. In this disclosure, the bearings B1 connect the eccentric rotating shaft 5 and the fixed shaft 9. As a result, in this disclosure, the eccentric rotating shaft 5 and the fixed shaft 9 can rotate relative to each other in the circumferential direction. Therefore, in this disclosure, the sun gear 2, which is integrally formed on the eccentric rotating shaft 5 and the fixed shaft 9, can rotate relative to each other about the axis O1.
[0068] Furthermore, in this disclosure, the internal gear 4 is rotatably mounted on the fixed shaft 9 via a bearing B4. In this disclosure, the connecting plate 8 of the internal gear 4 is an annular connecting plate. In this disclosure, the fixed shaft 9 passes through the inside of the connecting plate 8. In this disclosure, the bearing B4 connects the radially inner edge of the connecting plate 8 connected to the internal gear 4 to the fixed shaft 9. As a result, in this disclosure, the internal gear 4 and the fixed shaft 9 can rotate relative to each other in the circumferential direction. Therefore, in this disclosure, the internal gear 4 and the fixed shaft 9 can rotate relative to each other about the axis O1. In this case, the fixed shaft 9 is more firmly supported by the housing 7 by being supported by the housing cylinder wall 71b of the housing body 71 without being attached to the housing cover 72. However, in this disclosure, the connecting plate 8 can be connected to the concentric rotating shaft 6, similar to the speed change mechanism 1A, without being supported by the fixed shaft 9 via the bearing B4.
[0069] According to the transmission mechanism 1B, similar to the transmission mechanism 1A, the sun gear 2 is a fixed gear, and the sun gear 2 is meshed with the internal teeth 3a of the planetary gear 3 which rotates together with the eccentric rotating shaft 5, while the external teeth 3b of the planetary gear 3 are meshed with the internal gear 4 which rotates together with the concentric rotating shaft 6 (omitted in Figure 3) connected to the connecting plate 8. This configuration makes it possible to place the bearing B3 on the outer circumference of the internal gear 4, as shown in Figure 3. Therefore, according to the transmission mechanism 1B, similar to the transmission mechanism 1A, the transmission mechanism 1B can be made thinner by shortening it in the axial direction. In addition, according to the transmission mechanism 1B, similar to the transmission mechanism 1A, the direction of rotation of the input rotation and the direction of rotation of the output rotation can be the same. That is, according to the transmission mechanism 1B, similar to the transmission mechanism 1A, the input rotation and the output rotation will not reverse.
[0070] Therefore, the transmission mechanism 1B, like the transmission mechanism 1A, enables speed change using eccentric rotation without reversing the input rotation and output rotation, and also provides a transmission mechanism that can be made thinner in the axial direction.
[0071] Furthermore, in this disclosure as well, the eccentric rotating shaft 5 is the input rotating shaft, and the concentric rotating shaft 6 is the output rotating shaft. In this case, the gear shift mechanism 1B is also effective when applied as a reduction mechanism that is thin and aims to improve transmission efficiency. In this disclosure as well, the reduction ratio of the gear shift mechanism 1B can be expressed by the above formula (1), similar to the gear shift mechanism 1A.
[0072] Furthermore, in this disclosure, the sun gear 2 is fixed non-rotatably to a fixed shaft 9 that is fixed to the housing 7. In this case, the sun gear 2 can be fixed in a position closer to the central axis O1 of the transmission mechanism 1B. This allows the transmission mechanism 1B to be miniaturized radially inward. In this case, when the transmission mechanism 1B is used as part of the powertrain of a mobility device (such as an automobile), the input and output rotating shafts of the transmission mechanism are generally arranged on the same axis, which is effective for use in mobility devices, for example, as it allows for a larger interior space to be secured.
[0073] Furthermore, in this disclosure, the sun gear 2 is integrally formed with the fixed shaft 9. In this case, it is possible to suppress the deformation of the sun gear 2 and other centering deviations that may occur in the sun gear 2, which may occur when the sun gear 2 is assembled to the fixed shaft 9 as a separate part. This makes it possible to improve the power transmission efficiency of the transmission mechanism 1B and suppress noise generated during power transmission.
[0074] The above describes only exemplary embodiments of the present invention, and various modifications are possible according to the claims. For example, the sun gear 2, planetary gear 3, internal gear 4, housing body 71, and housing cover 72 can be formed from a resin such as engineering plastic. However, they can also be formed from metal. The eccentric rotating shaft 5 and concentric rotating shaft 6 can be formed from metal. However, they can also be formed from a resin such as engineering plastic. Furthermore, the transmission mechanisms 1A and 1B can use the concentric rotating shaft 6 as the input rotating shaft and the eccentric rotating shaft 5 as the output rotating shaft. Moreover, the components (items) used in each of the above embodiments can be added to and substituted for one another.
[0075] 1A: Gear shifting mechanism (first embodiment), 1B: Gear shifting mechanism (second embodiment), 2: Sun gear, 2a: External teeth, 21: Annular base, 21a: Inner peripheral edge of the annular base, 21b: Outer peripheral edge of the annular base, 21b1: Extension cylinder portion of the outer peripheral edge, 22: Connecting piece, 3: Planetary gear, 3A: Planetary gear member, 3a: Internal teeth, 3b: External teeth, 31: Annular connecting portion, 32: Inner cylinder wall, 4: Internal gear, 4b: Internal teeth, 5: Eccentric rotating shaft, 5a: Eccentric shaft, 5b: Central shaft, 6: Concentric rotating shaft (rotating shaft), 7: Housing, 71: Housing body, 71a: Bottom wall, 71b: Housing cylinder wall, 71b1: Mounting end provided on the housing cylinder wall, 71c: Cylinder wall, 71c1: Protruding cylindrical wall, 72: Housing cover, 72a: Top wall, 72b: Mounting cylindrical wall, 8: Connecting plate, 9: Fixed shaft, A1: Through hole, A2: Through hole, B1-B4: Bearings, C: Spacing, O1: Center axis of the transmission mechanism, O2: Eccentric axis of the eccentric shaft
Claims
1. A speed change mechanism comprising: a sun gear having external teeth; a planetary gear located on the outer circumference of the sun gear and having internal and external teeth; an internal gear located on the outer circumference of the planetary gear and having internal teeth; an eccentric rotating shaft having an eccentric shaft that rotates eccentrically together with the planetary gear; and a rotating shaft that rotates together with the internal gear, wherein the internal teeth of the planetary gear locally mesh with the external teeth of the sun gear, while the external teeth of the planetary gear locally mesh with the internal teeth of the internal gear, and the sun gear is a fixed gear.
2. The gear shift mechanism according to claim 1, further comprising a housing for housing the sun gear, the planetary gear and the internal gear, wherein the sun gear is fixed to the housing in a manner that prevents rotation.
3. The gear shifting mechanism according to claim 2, wherein the sun gear is provided with an annular base and is fixed to the housing in a non-rotatable manner by the annular base.
4. The gear shifting mechanism according to claim 3, wherein the sun gear is arranged at an axial distance from the annular base.
5. The gear shifting mechanism according to claim 2, wherein the sun gear is fixed to the housing so as not to rotate by press-fitting.
6. The gear shift mechanism according to claim 3, wherein the annular base is fixed to the housing so as not to rotate by press-fitting.
7. The gear shift mechanism according to claim 1, further comprising a housing for housing the sun gear, the planetary gear, and the internal gear, wherein the sun gear is non-rotatably fixed to a fixed shaft fixed to the housing.
8. The gear shifting mechanism according to claim 7, wherein the sun gear is integrally formed with the fixed shaft.
9. The gear shift mechanism according to any one of claims 1 to 8, wherein the eccentric rotating shaft is an input rotating shaft and the rotating shaft is an output rotating shaft.
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