Gear mechanism

Abstract

To provide a gear mechanism that has excellent transmission efficiency and in which self-locking does not occur.SOLUTION: In a gear mechanism (1) comprising a first gear (2) and a second gear (3) having tooth grooves (3Ag) meshing with the first gear (2), the second gear (3) is composed of a torsion gear in which the tooth grooves (3Ag) are formed into a shape that includes an arc shape in a cross section perpendicular to an axial direction of a second axis (AX2), the first gear (2) is configured such that an outer shape in a cross section perpendicular to the axial direction is circular at any cross section in the axial direction of a first axis (AX1), and the centers of the plurality of circular shapes aligned in the axial direction are each eccentric with respect to the first axis (AX1) and are arranged at different circumferential positions around the first axis (AX1) when viewed in the axial direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a gear mechanism including a first gear and a second gear meshing with the first gear. [Background technology]

[0002] Generally, there are various gear mechanisms in which a first gear and a second gear mesh with each other to rotate in conjunction with each other and thereby transmit rotation. Among these gear mechanisms, a worm gear including a cylindrical worm with a cylindrical outer shape and teeth formed thereon, and a worm wheel meshing with the cylindrical worm, has been proposed (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-314464 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned worm gears have the problem of poor transmission efficiency due to frequent slippage between the teeth of the cylindrical worm and the teeth of the worm wheel when transmitting rotation. Furthermore, worm gears, particularly as the reduction ratio increases, can transmit the rotation of the cylindrical worm to the worm wheel, but cannot transmit the rotation of the worm wheel to the cylindrical worm, resulting in a phenomenon known as self-locking. This limits their applications, making them difficult to use in, for example, automobile transmissions that switch between drive and non-drive modes.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a gear mechanism that has good transmission efficiency and does not self-lock. [Means for solving the problem]

[0006] One aspect of the present invention is a gear mechanism including a first gear rotatably arranged on a first shaft, and a second gear having tooth grooves meshing with the first gear and rotatably arranged on a second shaft, wherein the second gear is a torsion gear in which the tooth grooves are formed into a shape including an arc shape in a cross section perpendicular to the axial direction of the second shaft, The first gear is a gear mechanism in which the outer shape in a cross section perpendicular to the axial direction of the first shaft is circular at any cross section in the axial direction of the first shaft, and the central positions of multiple circular shapes aligned in the axial direction of the first shaft, when viewed in the axial direction of the first shaft, are each eccentric with respect to the first shaft and are arranged at different circumferential positions centered on the first shaft.

[0007] One aspect of the present invention is a gear mechanism comprising a first gear rotatably arranged on a first axis, and a second gear having a tooth groove that meshes with the first gear and arranged rotatably on a second axis, wherein the second gear is composed of a plurality of spur gears, the tooth grooves of which are formed into a shape that includes an arc in a cross section perpendicular to the axial direction of the second axis, and which are arranged in the axial direction of the second axis and have different phases in the circumferential direction; the first gear has a plurality of cylindrical portions arranged in the axial direction of the first axis to correspond to the plurality of spur gears, and its outer shape in the cross section perpendicular to the axial direction of the first axis is circular in any cross section in the axial direction of the first axis; and when viewed in the axial direction of the first axis, the center positions of the plurality of cylindrical portions are each eccentric with respect to the first axis and are arranged at different circumferential positions centered on the first axis. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a gear mechanism that has good transmission efficiency and does not cause self-locking. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a side view showing the gear mechanism according to the first embodiment. [Figure 2]1A is a perspective view showing the gear mechanism according to the first embodiment as viewed from the side and above, and FIG. 1B is a perspective view showing the gear mechanism according to the first embodiment as viewed from the side and in the axial direction. [Figure 3] 1. (a) is a cross-sectional view taken along the line AA in FIG. 1. (b) is a cross-sectional view taken along the line BB in FIG. 1. (c) is a cross-sectional view taken along the line CC in FIG. [Figure 4] 1. (a) is a cross-sectional view taken along the line DD in FIG. 1. (b) is a cross-sectional view taken along the line EE in FIG. 1. (c) is a cross-sectional view taken along the line FF in FIG. [Figure 5] 1. (a) is a cross-sectional view taken along the line GG in FIG. 1. (b) is a cross-sectional view taken along the line HH in FIG. 1. (c) is a cross-sectional view taken along the line II in FIG. [Figure 6] 6(a) is an axial view showing a gear mechanism according to a second embodiment, (b) is a perspective view showing the gear mechanism according to the second embodiment as seen from the side and above, and (c) is a perspective view showing the gear mechanism as seen from an angle different from that of FIG. 6(b). [Figure 7] 7(a) is a perspective view showing a gear mechanism according to a third embodiment, (b) is a perspective view of the gear mechanism according to the third embodiment viewed from an angle different from that of FIG. 7(a), and (c) is a perspective view of the gear mechanism according to the third embodiment viewed from an angle different from that of FIG. 7(a) and FIG. 7(b). [Figure 8] FIG. 10 is a cross-sectional view showing a gear mechanism according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] First Embodiment The gear mechanism 1 according to the first embodiment will be described below with reference to the drawings.

[0011] [Outline of gear mechanism] First, the schematic configuration of a gear mechanism 1 according to the first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a side view showing the gear mechanism according to the first embodiment. Also, Figure 2(a) is a perspective view showing the gear mechanism according to the first embodiment as viewed from the side and above, and Figure 2(b) is a perspective view showing the gear mechanism according to the first embodiment as viewed from the side and in the axial direction.

[0012] As shown in FIGS. 1, 2(a), and 2(b), the gear mechanism 1 according to the first embodiment is generally configured to include a torsion cylindrical gear 2 and an external gear 3 circumscribing the torsion cylindrical gear 2. The torsion cylindrical gear 2 and the external gear 3 of the gear mechanism 1 according to the first embodiment are each formed (manufactured) by a three-dimensional printing device, i.e., a 3D printer. However, they may be manufactured by other methods, such as cutting, forging, or casting, as long as they can be formed into the shapes described below. The torsion cylindrical gear 2 and the external gear 3 may be made of metal or resin, i.e., any material may be used. When the gear mechanism 1 is used to transmit a large driving force, such as in an automobile, it may be formed of metal. When the gear mechanism 1 is used to transmit a small driving force, such as in an electrical device, it may be formed of resin.

[0013] The torsion cylindrical gear 2 includes a gear body 2A, which is a torsion gear serving as a first gear and is disposed about the first axis AX1 as its center of rotation, and shaft portions 2B, 2B formed on both sides of the gear body 2A in the axial direction of the first axis AX1. In this first embodiment, the torsion cylindrical gear 2 is formed using a 3D printer as described above, so the gear body 2A and the shaft portions 2B, 2B are integrally formed. Each of the shaft portions 2B includes a support shaft 2Ba and a large-diameter portion 2Bb formed in a flange shape on the outer periphery of the support shaft 2Ba, i.e., a large-diameter portion 2Bb having a larger diameter than the support shaft 2Ba. The support shaft 2Ba is rotatably supported about the first axis AX1 by a support member (not shown), for example, via a bearing or bushing. Therefore, the torsion cylindrical gear 2 (i.e., the gear body 2A) is disposed rotatably on the first axis AX1. The detailed shape of the gear body 2A will be described later.

[0014] The large diameter portion 2Bb of the torsion cylindrical gear 2 functions to disperse stress generated on the support shaft 2Ba or to function as a spacer to prevent contact between a bearing (not shown) and the gear body 2A, but it does not necessarily have to be formed as such. In this embodiment, the shaft portion 2B and the gear body 2A are integrally formed, but the shaft portion 2B may be formed as a separate member from the gear body 2A, and the gear body 2A may be supported rotatably relative to the shaft portion 2B. In this case, a snap ring or the like may be provided at the position of the large diameter portion 2Bb to position the gear body 2A axially on the support shaft 2Ba.

[0015] Meanwhile, the external gear 3 includes a gear body 3A serving as a second gear and arranged around a second axis AX2, which is parallel to the first axis AX1, as its rotation center, and shaft portions 3B, 3B formed on both sides of the gear body 3A in the axial direction of the second axis AX2. Similarly, in this first embodiment, the external gear 3 is formed using a 3D printer, so the gear body 3A and the shaft portions 3B, 3B are integrally formed. Each shaft portion 3B includes a support shaft 3Ba and a large-diameter portion 3Bb formed in a flange shape on the outer periphery of the support shaft 3Ba, i.e., a large-diameter portion 3Bb having a larger diameter than the support shaft 3Ba. The support shaft 3Ba is rotatably supported around the second axis AX2 by a support member (not shown), for example, via a bearing or bushing. In other words, the external gear 3 (i.e., the gear body 3A) is rotatably arranged on the second axis AX2. The detailed shape of the gear body 3A will be described later. In the first embodiment, the first axis AX1 and the second axis AX2 are arranged in parallel.

[0016] The large diameter portion 2Bb of the external gear 3 also functions to disperse stress generated on the support shaft 3Ba or as a spacer to prevent contact between a bearing (not shown) and the gear body 3A, but it does not have to be formed as such. In this embodiment, the shaft portion 3B and the gear body 3A are integrally formed, but the shaft portion 3B may be formed as a separate member from the gear body 3A, and the gear body 3A may be rotatably supported relative to the shaft portion 3B. In this case, a snap ring or the like may be provided at the position of the large diameter portion 3Bb to position the gear body 3A axially on the support shaft 3Ba.

[0017] [Gear body and tooth groove shape of the external gear of the twisted cylindrical gear] Next, the shape of the gear body 2A of the torsion cylindrical gear 2 and the shape of the circumscribing gear 3 (shape of the tooth grooves 3Ag) will be described in detail with reference to Figures 3, 4, and 5, along with Figures 1 and 2. Figure 3(a) is a cross-sectional view taken along the line AA in Figure 1, Figure 3(b) is a cross-sectional view taken along the line BB in Figure 1, Figure 3(c) is a cross-sectional view taken along the line CC in Figure 1, Figure 4(a) is a cross-sectional view taken along the line DD in Figure 1, Figure 4(b) is a cross-sectional view taken along the line EE in Figure 1, Figure 4(c) is a cross-sectional view taken along the line FF in Figure 1, Figure 5(a) is a cross-sectional view taken along the line GG in Figure 1, Figure 5(b) is a cross-sectional view taken along the line HH in Figure 1, and Figure 5(c) is a cross-sectional view taken along the line II in Figure 1.

[0018] 3 to 5 show the shape of a cross section perpendicular to the first and second axes. As will be described in detail later, the gear body 2A of the torsion cylindrical gear 2 is composed of one helical cycle. Since FIGS. 3(a) and 5(c) are in the same position, the cross section is taken at a position where the length XL of one cycle of the gear body 2A is divided into eight equal parts in the axial direction. The torsion cylindrical gear 2 and the circumscribing gear 3 shown in FIGS. 3 to 5 are shown in a stationary, non-rotating state. The positions of the circular shape Cir (i.e., center position CT), which is the outer diameter shape of the gear body 2A, and the positions of the concave shapes CON of the tooth grooves 3Ag (i.e., arrangement angle θ) are shifted in each figure, but this shows that they are formed at different positions due to the difference in the axial positions of the first and second axes. The circular shape Cir, its center position CT, and the concave shapes CON, and their arrangement angle θ are given suffixes "A" to "I" to distinguish the state of each cross section.

[0019] As shown in Figures 3 to 5, the torsion cylindrical gear 2 has a circular shape Cir (Cir-A to Cir-I) that is a substantially perfect circle in any cross section (cross section perpendicular to the axial direction) in the axial direction X1-X2 (see Figure 1). The center positions CT (CT-A to CT-I) of the circular shapes Cir aligned in the axial direction, i.e., the center positions CT (CT-A to CT-I) of the circular shapes Cir in cross sections at multiple different positions in the axial direction, are positioned so as to be eccentric with respect to the first axis AX1 when viewed in the axial direction of the first axis AX1. In this embodiment, the circular shapes are positioned on a spiral Spi-CT orbit around the first axis AX1 so that their circumferential phases differ, i.e., they are arranged in a spiral shape in the axial direction. As a result, the outer shape of the gear body 2A is a twisted cylinder (twisted column) because the multiple circular shapes Cir are continuously connected in the axial direction to form a spiral shape. In this way, the torsion cylindrical gear 2 has a circular shape Cir that is an approximately perfect circle in cross section at any position in the axial direction, and as described in Patent Publication No. 7185424, for example, the cross section of a worm gear is a distorted circle, so its shape is different from that of a worm gear.

[0020] On the other hand, the circumferential gear 3 has a plurality of groove-shaped tooth grooves 3Ag on the outer peripheral surface of the gear body 3A, with the short side direction being the circumferential direction and the long side direction being the axial direction, and the plurality of tooth grooves 3Ag are formed in parallel in the circumferential direction, for example, nine tooth grooves 3Ag. Each tooth groove 3Ag is formed in a shape including an arc shape that can mesh with the circular shape Cir of the gear body 2A at any cross section in the axial direction of the second axis, i.e., the X1-X2 direction (see FIG. 1). In this embodiment, the tooth grooves 3Ag are formed in a concave shape Con. The plurality of concave shapes Con at different positions in the X1-X2 direction, which is the axial direction of the second axis AX2, are formed to be at different positions as viewed in the axial direction in accordance with the outer shape of the torsion cylindrical gear 2. In other words, the tooth grooves 3Ag are formed in a spiral shape with multiple concave shapes Con connected in the axial direction to match the spiral outer shape of the gear body 2A. In this embodiment, the concave shape Con (arc shape) in each cross section perpendicular to the axial direction is formed in the shape of a cycloid curve. Note that, although the concave shape Con (arc shape) in this embodiment is described as being formed in a cycloid curve, it is not limited to this, and may be, for example, a circular arc or a U-shaped groove, in other words, any shape that allows the circular shape Cir of the gear body 2A of the torsion cylindrical gear 2 to roll and advance on the bottom surface of the tooth grooves 3Ag of the gear body 3A of the circumscribing gear 3.

[0021] 3(a), at the position of the cross section along the arrow AA in Fig. 1 in the axial direction, the center position CT-A of the circular shape Cir-A, which is the outer shape of the gear main body 2A, is eccentric (offset) by a predetermined distance from the first axis AX1 and is located on the orbit of the spiral Spi-CT, i.e., the circular shape Cir-A is located at a position eccentric to the first axis AX1. When the gear main body 2A configured in this manner is rotated around the first axis AX1, the circular shape Cir-A moves eccentrically at a position eccentric to the first axis AX1.

[0022] In one of the external gears 3, the concave shape Con-A, which can mesh with the circular shape Cir-A, is positioned so that its center, the bottom of the tooth (the most concave position), is at an angle θA with respect to an imaginary line connecting the first axis AX1 and the second axis AX2, for example.

[0023] Similarly, as shown in FIG. 3(b), at the cross section along arrow BB in FIG. 1 in the axial direction, the center position CT-B of the circular shape Cir-B, which is the outer shape of the gear main body 2A, is eccentric (offset) by a predetermined distance from the first axis AX1 and is located on the orbit of the spiral Spi-CT. In other words, the circular shape Cir-B is located eccentrically with respect to the first axis AX1. Furthermore, the center position CT-B of the circular shape Cir-B is located 45 degrees counterclockwise in FIG. 3(b) from the center position CT-A of the circular shape Cir-A (see FIG. 3(a)) on the orbit of the spiral Spi-CT, which is moved in the axial direction X1 from the cross section along arrow AA to the cross section along arrow BB (see FIG. 1) (here, one cycle is divided into eight equal parts in the axial direction). Similarly, when the gear main body 2A configured in this manner is rotated around the first axis AX1, the circular shape Cir-B moves eccentrically with respect to the first axis AX1.

[0024] In one of the external gears 3, the concave shape Con-B, which can mesh with the circular shape Cir-B, is positioned so that its center, the tooth bottom (the most recessed position), is at an angle θB that is 5 degrees clockwise from the above angle θA, relative to an imaginary line connecting the first axis AX1 and the second axis AX2, for example, when the center position CT-B of the circular shape Cir-B moves in the spiral direction from the center position CT-A of the circular shape Cir-A to a 45-degree phase shift.

[0025] Similarly, at the cross section indicated by the arrow CC in FIG. 1 in the axial direction, as shown in FIG. 3(c), the center position CT-C of the circular shape Cir-C, which is the outer shape of the gear main body 2A, is eccentric (offset) by a predetermined distance from the first axis AX1 and is located on the orbit of the spiral Spi-CT. In other words, the circular shape Cir-C is located eccentrically with respect to the first axis AX1. Furthermore, the center position CT-C of the circular shape Cir-C is located 45 degrees counterclockwise in FIG. 3(c) from the center position CT-B of the circular shape Cir-B (see FIG. 3(b)) on the orbit of the spiral Spi-CT, which is moved in the axial direction X1 from the cross section indicated by the arrow BB to the cross section indicated by the arrow CC (see FIG. 1). Similarly, when the gear main body 2A configured in this manner is rotated about the first axis AX1, the circular shape Cir-C moves eccentrically with respect to the first axis AX1.

[0026] In one of the external gears 3, the concave shape Con-C, which can mesh with the circular shape Cir-C, is positioned so that its center, the tooth bottom (the most recessed position), is at an angle θC that is 5 degrees clockwise from the above angle θB, relative to an imaginary line connecting the first axis AX1 and the second axis AX2, for example, when the center position CT-C of the circular shape Cir-C moves in the spiral direction from the center position CT-B of the circular shape Cir-B, resulting in a 45-degree phase shift.

[0027] Similarly, as shown in FIG. 4(a), in the axial cross section of arrow DD in FIG. 1, the center position CT-D of the circular shape Cir-D, which is the outer shape of the gear main body 2A, is eccentric (offset) by a predetermined distance from the first axis AX1 and is located on the orbit of the spiral Spi-CT. In other words, the circular shape Cir-D is located eccentrically with respect to the first axis AX1. Furthermore, the center position CT-D of the circular shape Cir-D is located 45 degrees counterclockwise in FIG. 4(a) from the center position CT-C of the circular shape Cir-C (see FIG. 3(c)) on the orbit of the spiral Spi-CT, which is moved in the axial direction X1 from the position on the cross section of arrow CC to the position on the cross section of arrow DD (see FIG. 1). Similarly, when the gear main body 2A configured in this manner is rotated around the first axis AX1, the circular shape Cir-D moves eccentrically with respect to the first axis AX1.

[0028] In one of the external gears 3, the concave shape Con-D that can mesh with the circular shape Cir-D is positioned so that its center, the tooth bottom (the most concave position), is at an angle θD that is 5 degrees clockwise from the above angle θC, relative to an imaginary line connecting the first axis AX1 and the second axis AX2, for example, when the center position CT-D of the circular shape Cir-D moves in the spiral direction from the center position CT-C of the circular shape Cir-C, resulting in a 45-degree phase shift.

[0029] Similarly, in the axial cross section of FIG. 1 taken along the arrow EE, as shown in FIG. 4(b), the center position CT-E of the circular shape Cir-E, which is the outer shape of the gear main body 2A, is eccentric (offset) by a predetermined distance from the first axis AX1 and is located on the orbit of the spiral Spi-CT. In other words, the circular shape Cir-E is located eccentrically with respect to the first axis AX1. Furthermore, the center position CT-E of the circular shape Cir-E is located on the orbit of the spiral Spi-CT, slightly displaced counterclockwise in FIG. 4(b) from the center position CT-D of the circular shape Cir-D (see FIG. 4(a)) by the amount of movement in the axial direction X1 from the position on the cross section of the arrow DD to the position on the cross section of the arrow EE (see FIG. 1). Similarly, when the gear main body 2A configured in this manner is rotated around the first axis AX1, the circular shape Cir-E moves eccentrically with respect to the first axis AX1.

[0030] In one of the external gears 3, the concave shape Con-E, which can mesh with the circular shape Cir-E, is positioned so that its center, the tooth bottom (the most recessed position), is at an angle θE that is 5 degrees clockwise from the above angle θD, relative to an imaginary line connecting the first axis AX1 and the second axis AX2, for example, when the center position CT-E of the circular shape Cir-E moves in the spiral direction from the center position CT-D of the circular shape Cir-D, resulting in a 45-degree phase shift.

[0031] Similarly, at the axial cross section of arrow FF in FIG. 1, as shown in FIG. 4(c), the center position CT-F of the circular shape Cir-F, which is the outer shape of the gear main body 2A, is eccentric (offset) by a predetermined distance from the first axis AX1 and is located on the orbit of the spiral Spi-CT. In other words, the circular shape Cir-F is located eccentrically with respect to the first axis AX1. Furthermore, the center position CT-F of the circular shape Cir-F is located on the orbit of the spiral Spi-CT, slightly displaced counterclockwise in FIG. 4(c) from the center position CT-E of the circular shape Cir-E (see FIG. 4(b)) by the amount of movement in the axial direction X1 on the orbit of the spiral Spi-CT from the position on the cross section of arrow EE to the position on the cross section of arrow FF (see FIG. 1). Similarly, when the gear main body 2A configured in this manner is rotated around the first axis AX1, the circular shape Cir-F moves eccentrically at a position eccentric with respect to the first axis AX1.

[0032] In one of the external gears 3, the concave shape Con-F that can mesh with the circular shape Cir-F is positioned so that its center, the bottom of the tooth (the most recessed position), is at an angle θF that is 5 degrees clockwise from the above angle θE, relative to an imaginary line connecting the first axis AX1 and the second axis AX2, for example, when the center position CT-F of the circular shape Cir-F moves in the spiral direction from the center position CT-E of the circular shape Cir-E, resulting in a 45-degree phase shift.

[0033] Similarly, at the cross section of arrows GG in FIG. 1 in the axial direction, as shown in FIG. 5(a), the center position CT-G of the circular shape Cir-G, which is the outer shape of the gear main body 2A, is eccentric (offset) by a predetermined distance from the first axis AX1 and is located on the orbit of the spiral Spi-CT. In other words, the circular shape Cir-G is located at an eccentric position relative to the first axis AX1. Furthermore, the center position CT-G of the circular shape Cir-G is located at a position slightly displaced counterclockwise in FIG. 5(a) from the center position CT-F of the circular shape Cir-F (see FIG. 4(c)) on the orbit of the spiral Spi-CT by the amount of movement in the axial direction X1 from the cross section of arrows FF to the cross section of arrows GG (see FIG. 1). Similarly, when the gear main body 2A configured in this manner is rotated about the first axis AX1, the circular shape Cir-G moves eccentrically at a position eccentric to the first axis AX1.

[0034] In one of the external gears 3, the concave shape Con-G that can mesh with the circular shape Cir-G is positioned so that its center, the bottom of the tooth (the most recessed position), is at an angle θG that is shifted 5 degrees clockwise from the above angle θF, relative to an imaginary line connecting the first axis AX1 and the second axis AX2, for example, when the center position CT-G of the circular shape Cir-G moves in the spiral direction from the center position CT-F of the circular shape Cir-F, resulting in a 45-degree phase shift.

[0035] Similarly, at the position of the cross section of arrow HH in FIG. 1 in the axial direction, as shown in FIG. 5(b), the center position CT-H of the circular shape Cir-H, which is the outer shape of the gear main body 2A, is eccentric (offset) by a predetermined distance from the first axis AX1 and is located on the orbit of the spiral Spi-CT. In other words, the circular shape Cir-H is located at a position eccentric to the first axis AX1. Furthermore, the center position CT-H of the circular shape Cir-H is located at a position slightly moved counterclockwise in FIG. 5(b) from the center position CT-G of the circular shape Cir-G (see FIG. 5(a)) on the orbit of the spiral Spi-CT by the amount of movement in the axial direction X1 from the position of the cross section of arrow GG to the position of the cross section of arrow HH on the orbit of the spiral Spi-CT (see FIG. 1). Similarly, when the gear main body 2A configured in this manner is rotated around the first axis AX1, the circular shape Cir-H moves eccentrically at a position eccentric to the first axis AX1.

[0036] In one of the external gears 3, the concave shape Con-H that can mesh with the circular shape Cir-H is positioned so that its center, the bottom of the tooth (the most recessed position), is at an angle θH that is 5 degrees clockwise from the above angle θG, relative to an imaginary line connecting the first axis AX1 and the second axis AX2, for example, when the center position CT-H of the circular shape Cir-H moves in the spiral direction from the center position CT-G of the circular shape Cir-G, resulting in a 45-degree phase shift.

[0037] Similarly, at the position of the cross section of arrow II in FIG. 1 in the axial direction, as shown in FIG. 5(c), the center position CT-I of the circular shape Cir-I, which is the outer shape of the gear main body 2A, is eccentric (offset) by a predetermined distance from the first axis AX1 and is located on the orbit of the spiral Spi-CT. In other words, the circular shape Cir-I is located at a position eccentric with respect to the first axis AX1. Furthermore, the center position CT-I of the circular shape Cir-I is located at a position slightly moved counterclockwise in FIG. 5(c) from the center position CT-H of the circular shape Cir-H (see FIG. 5(b)) on the orbit of the spiral Spi-CT by an amount equivalent to the amount of movement in the axial direction X1 from the position of the cross section of arrow HH to the position of the cross section of arrow II (see FIG. 1). Similarly, when the gear main body 2A configured in this manner is rotated about the first axis AX1, the circular shape Cir-I moves eccentrically at a position eccentric with respect to the first axis AX1. It should be noted that the circular shape Cir-I shown in FIG. 5(c) has a shape that returns to the circular shape Cir-A shown in FIG. 3(a) when viewed in the axial direction.

[0038] In one of the external gears 3, the concave shape Con-I that can mesh with the circular shape Cir-I is positioned so that its center, the tooth bottom (the most recessed position), is at an angle θI that is 5 degrees clockwise from the above angle θH, relative to an imaginary line connecting the first axis AX1 and the second axis AX2, for example, when the center position CT-I of the circular shape Cir-I moves in the spiral direction from the center position CT-H of the circular shape Cir-H, resulting in a 45-degree phase shift.

[0039] In the above explanation of Figures 3 to 5, the gear body 2A of the torsion cylindrical gear 2 and the circumscribing gear 3 are described as being divided into eight equal parts in the axial direction. However, as described above, the torsion cylindrical gear 2 and the circumscribing gear 3 are formed using a so-called 3D printer, and each layer can be formed to, for example, 0.01 mm, etc., so the circular shape Cir that forms the outer surface 2As of the gear body 2A of the torsion cylindrical gear 2 forms a continuously smooth surface across multiple layers, and the concave shape Con that forms the inner surface of the tooth groove 3Ag of the circumscribing gear 3 forms a continuously smooth surface across multiple layers.

[0040] [Gear mechanism operation] The gear body 2A of the torsion cylindrical gear 2 configured as described above has circular shapes Cir-A to Cir-I in each cross section perpendicular to the axial direction that are aligned axially and continuously connected to form the outer surface 2As of the gear body 2A, and is configured like a twisted cylinder having such an outer surface 2As. The circular shapes Cir-A and Cir-I are in the same position when viewed from the axial direction, that is, the gear body 2A of the torsion cylindrical gear 2 is configured as a twisted cylindrical shape that goes around the first axis AX1 for one cycle.

[0041] In the gear body 2A of the torsion cylindrical gear 2 configured in this manner, the circular shape Cir-A shown in Figure 3(a) is in a non-meshing state with the concave shape Con-A of the tooth space 3Ag of the circumscribing gear 3, but the circular shape Cir-B shown in Figure 3(b) begins to mesh with the concave shape Con-B and gradually becomes more deeply meshed, so that the circular shape Cir-E shown in Figure 4(b) meshes most deeply with the concave shape Con-E, and then the meshing gradually becomes shallower, and the circular shape Cir-I shown in Figure 5(c) is disengaged from the concave shape Con-I of the tooth space 3Ag of the circumscribing gear 3.

[0042] In this state, for example, when the torsion cylindrical gear 2 is rotated around the first axis AX1, the circular shape Cir meshes with the concave shape Con, and the eccentric motion of the circular shape Cir relative to the first axis AX1 generates a rotational moment around the first axis AX1 in the torsion cylindrical gear 2, and the rotation of the torsion cylindrical gear 2 is transmitted to the circumscribing gear 3. At this time, when the torsion cylindrical gear 2 rotates once around the first axis AX1, one tooth groove 3Ag of the circumscribing gear 3 rotates in one cycle of rotation, and since nine tooth grooves 3Ag are formed on the outer periphery of the circumscribing gear 3, the gear ratio is 1:9 (=0.111), which means that the gear mechanism 1 achieves a large reduction ratio.

[0043] Conversely, for example, when the external gear 3 is rotated around the second axis AX2, the concave shape Con meshes with the circular shape Cir, and the circular shape Cir moves eccentrically relative to the first axis AX1, generating a rotational moment around the first axis AX1 in the torsion cylindrical gear 2, and the rotation of the external gear 3 is transmitted to the torsion cylindrical gear 2. At this time, when the external gear 3 rotates once around the second axis AX2, nine tooth grooves 3Ag are formed on the outer periphery of the external gear 3, and therefore the nine tooth grooves 3Ag cause the torsion cylindrical gear 2 to rotate nine times around the first axis AX1, which means that the gear ratio becomes 9:1 (=9), and therefore a large speed-up ratio is obtained in the gear mechanism 1.

[0044] In this way, the gear body 2A of the torsion cylindrical gear 2 moves eccentrically while meshing with the tooth groove 3Ag of the circumscribed gear 3, so this twisted cylindrical shape itself can be said to be a single gear tooth, or in other words, the gear body 2A of the torsion cylindrical gear 2 can be said to be composed only of the tooth base.

[0045] Furthermore, the gear ratio of the torsion cylindrical gear 2 and the circumscribing gear 3 in the first embodiment is merely an example, and the diameter of the circular shape Cir of the torsion cylindrical gear 2 can be changed depending on the allowable torque that can be transmitted, and the diameter of the circumscribing gear 3 can be changed depending on the constraints on the overall size, etc. In other words, the gear ratio can be freely designed within a feasible range depending on the application of the gear mechanism 1.

[0046] [Summary of the first embodiment] In the gear mechanism 1 according to the first embodiment described above, the circular shape Cir of the gear body 2A of the torsion cylindrical gear 2 meshes with the concave shape Con of the tooth groove 3Ag of the circumscribing gear 3, and the meshed portion moves in response to rotation. This reduces slippage between the circular shape Cir and the concave shape Con (i.e., slippage of the tooth surfaces), and therefore provides a gear mechanism 1 with good transmission efficiency.

[0047] Furthermore, even if the size of the circular shape Cir of the gear body 2A of the torsion cylindrical gear 2, i.e., the diameter of the circular shape Cir, is reduced, sufficient strength can be obtained to withstand the load applied to the gear body 2A, which is entirely composed of teeth. Therefore, the curvature of the concave shape Con of the circumscribing gear 3 that meshes with the circular shape Cir can also be reduced, which means that a larger number of tooth grooves 3Ag can be formed on the circumscribing gear 3. In other words, even if the diameter of the circumscribing gear 3 is reduced, the number of tooth grooves 3Ag can be ensured. Therefore, the gear mechanism 1 can increase the reduction ratio (or speed-up ratio) even if the axial distance between the first shaft AX1 and the second shaft AX2 is shortened. Furthermore, because slippage on the tooth flanks is small even when the reduction ratio (or speed-up ratio) is increased, self-locking does not occur, as occurs with worm gears. Overall, a gear mechanism 1 with good transmission efficiency and no self-locking can be provided.

[0048] Second Embodiment Next, a second embodiment, which is a partial modification of the first embodiment, will be described with reference to Fig. 6. Fig. 6(a) is an axial view showing a gear mechanism according to the second embodiment, Fig. 6(b) is a perspective view showing the gear mechanism according to the second embodiment as seen from the side and above, and Fig. 6(c) is a perspective view showing the gear mechanism as seen from an angle different from that of Fig. 6(b). In the description of this second embodiment, the same reference numerals will be used to refer to the same parts as in the first embodiment, and parts not specifically described below have the same configurations, actions, and effects as in the first embodiment.

[0049] A gear mechanism 101 according to the second embodiment is different from the gear mechanism 1 of the first embodiment in that the external gear 3 is replaced with an internal gear 103. In detail, as shown in Figures 6(a), 6(b), and 6(c), the gear mechanism 101 according to the second embodiment is roughly configured to include a torsion cylindrical gear 102 and an internal gear 103 inscribed in the torsion cylindrical gear 102.

[0050] The torsion cylindrical gear 102 is configured with a gear body 102A formed of a torsion gear serving as a first gear arranged with the first axis AX1 as its center of rotation, and shaft portions 102B formed on both sides of the gear body 102A in the axial direction of the first axis AX1. The configuration of the torsion cylindrical gear 102 is similar to that of the torsion cylindrical gear 2 in the first embodiment (see FIGS. 1 and 2), that is, the configurations of the gear body 102A and shaft portion 102B are similar to those of the gear body 2A and shaft portion 2B in the first embodiment (see FIGS. 1 and 2). Therefore, the outer shape of the gear body 102A is a circular shape Cir (see FIGS. 3 to 5) such that the cross section of the gear body 102A at any position in the axial direction of the first axis AX1 is a substantially perfect circle. The center positions CT of the circular shapes Cir in the cross sections at different positions in the axial direction are arranged so as to be eccentric with respect to the first axis AX1 when viewed in the axial direction of the first axis AX1, and are arranged on the orbit of the spiral Spi-CT, that is, arranged so as to form a spiral in the axial direction. As a result, the outer shape of the gear body 102A has an outer peripheral surface 102As where the plurality of circular shapes Cir are continuously connected in the axial direction and form a spiral, and has a shape like a twisted cylinder (twisted column).

[0051] On the other hand, the inscribed gear 103 is configured to include a gear body 103A as a second gear disposed about a second axis AX2 disposed parallel to the first axis AX1 as its center of rotation, and shaft portions (not shown) formed on both sides of the gear body 103A in the axial direction of the second axis AX2. The inscribed gear 103 has a plurality of groove-shaped tooth grooves 103Ag on the inner peripheral surface of the gear body 103A, with the short side direction being the circumferential direction and the long side direction being the axial direction, and the plurality of tooth grooves 103Ag are formed in parallel in the circumferential direction, for example, nine tooth grooves 103Ag. Each tooth groove 103Ag is formed in a concave shape Con (see FIGS. 3 to 5) that can mesh with the circular shape Cir of the gear body 102A at any cross section in the axial direction of the second axis. The plurality of concave shapes Con at different positions in the axial direction of the second shaft are formed so as to be at different positions as viewed in the axial direction in accordance with the outer shape of the torsion cylindrical gear 102. In other words, the tooth grooves 103Ag are formed so as to have a spiral shape with a plurality of concave shapes Con connected in the axial direction in accordance with the spiral outer shape of the gear body 102A. Also in this second embodiment, the concave shapes Con in each cross section perpendicular to the axial direction are formed in the shape of a cycloid curve.

[0052] In the gear mechanism 101 according to the second embodiment described above, the circular shape Cir of the gear body 102A of the torsion cylindrical gear 102 meshes with the concave shape Con of the tooth groove 103Ag of the inscribed gear 103, and the meshed portion moves in response to rotation. This reduces slippage between the circular shape Cir and the concave shape Con (i.e., slippage of the tooth surfaces), and therefore provides a gear mechanism 101 with good transmission efficiency.

[0053] Furthermore, even if the size of the circular shape Cir of the gear body 102A of the torsion cylindrical gear 102, i.e., the diameter of the circular shape Cir, is reduced, sufficient strength can be obtained to withstand the load applied to the gear body 102A, which is entirely composed of teeth. Therefore, the curvature of the concave shape Con of the inscribed gear 103 that meshes with the circular shape Cir can also be reduced, which means that a large number of tooth grooves 103Ag can be formed in the inscribed gear 103. In other words, even if the diameter of the inscribed gear 103 is reduced, the number of tooth grooves 103Ag can be ensured. Therefore, the gear mechanism 101 can also have a large reduction ratio (or speed-up ratio). Furthermore, because slippage on the tooth flanks is small even when the reduction ratio (or speed-up ratio) is increased, self-locking does not occur, as occurs with worm gears. Overall, a gear mechanism 101 with good transmission efficiency and no self-locking can be provided.

[0054] Third Embodiment Next, a third embodiment, which is a partial modification of the first embodiment, will be described with reference to Figures 7 and 8. Figure 7(a) is a perspective view of a gear mechanism according to the third embodiment. Figure 7(b) is a perspective view of the gear mechanism according to the third embodiment, viewed from an angle different from that of Figure 7(a). Figure 7(c) is a perspective view of the gear mechanism according to the third embodiment, viewed from an angle different from that of Figures 7(a) and 7(b). Figure 8 is a cross-sectional view of the gear mechanism according to the third embodiment. In the description of this third embodiment, parts similar to those in the first embodiment will be described using the same reference numerals, and parts not particularly described below have the same configurations, actions, and effects as those in the first embodiment.

[0055] The gear mechanism 201 according to the third embodiment differs from the gear mechanism 1 according to the first embodiment in that the torsion cylindrical gear 2 is replaced by a cylindrical gear 202, and the external gear 3, which is made up of a torsion gear, is replaced by an external gear 203, which is made up of a spur gear.

[0056] 7(a), 7(b), 7(c), and 8, the cylindrical gear 202 is arranged with the first axis AX1 as its rotation center and is configured to include a gear body 202A as a first gear composed of multiple (two in this embodiment) cylindrical portions 202A1 and 202A2, and shaft portions 202B and 202B formed on both sides of the gear body 202A in the axial direction of the first axis AX1. Each of the shaft portions 202B is supported by a support member (not shown) via, for example, a bearing or a bushing so as to be rotatable about the first axis AX1, that is, the cylindrical gear 202 (i.e., the gear body 202A) is arranged to be rotatable on the first axis AX1.

[0057] The cylindrical portions 202A1 and 202A2 have center positions CT1 and CT2, respectively, parallel to the first axis AX1, and are formed into linear cylindrical shapes centered on these center positions CT1 and CT2. That is, the outer peripheral surface 202As of the gear body 202A (cylindrical portions 202A1 and 202A2) has an outer shape that is a circular shape Cir in a cross section perpendicular to the first axis AX1 at any position on the first axis AX1.

[0058] The center position CT1 of the cylindrical portion 202A1 and the center position CT2 of the cylindrical portion 202A2 are eccentric with respect to the first axis AX1 and are arranged so that their circumferential positions (phases in the rotational direction) are different about the first axis AX1. In this embodiment, the center position CT1 of the cylindrical portion 202A1 and the center position CT2 of the cylindrical portion 202A2 are arranged on a circular orbit CirAX1 centered on the first axis AX1 and are arranged so that their phases are different by 180 degrees, that is, they are arranged on opposite sides of the first axis AX1. The cylindrical portions 202A1 and 202A2 are arranged side by side in the axial direction of the first axis AX1 so as to correspond to spur gears 203A1 and 203A2 of the circumscribed gear 203, which will be described later.

[0059] The circumscribing gear 203 includes a gear body 203A as a second gear composed of a plurality of spur gears 203A1 and 203A2, and shaft portions 203B, 203B formed on both sides of the gear body 203A in the axial direction of the second axis AX2. Similar to the cylindrical gear 202, each of the shaft portions 203B is supported on a support member (not shown) via, for example, a bearing or a bushing, so as to be rotatable about the second axis AX2. In other words, the circumscribing gear 203 (i.e., the gear body 203A) is arranged rotatably on the second axis AX1. These spur gears 203A1 and 203A2 are arranged in the axial direction of the second axis AX2. In other words, in the axial direction of the second axis AX2, the spur gear 203A1 is arranged to correspond to the cylindrical portion 202A1, and the spur gear 203A2 is arranged to correspond to the cylindrical portion 202A2. In other words, in the axial direction of the first axis AX1, the cylindrical portion 202A1 is arranged to correspond to the spur gear 203A1, and the cylindrical portion 202A2 is arranged to correspond to the spur gear 203A2.

[0060] Each of the spur gears 203A1, 203A2 has a plurality of groove-shaped tooth grooves 203Ag on its outer circumferential surface, and the plurality of tooth grooves 203Ag are formed in a straight line in the axial direction with, for example, nine tooth grooves 203Ag arranged in parallel in the circumferential direction. In a cross section perpendicular to the axial direction of the second shaft, each tooth groove 203Ag is formed in a concave shape Con including an arc shape that can mesh with the outer diameter shape (circular shape Cir) of the cylindrical parts 202A1, 202A2 of the gear body 202A of the cylindrical gear 202, and in this embodiment, the concave shape Con (arc shape) is formed in the shape of a cycloid curve. The spur gears 203A1 and 203A2 are arranged so that their tooth grooves 203Ag are out of phase with each other in the circumferential direction. In other words, the phases of the spur gears 203A1 and 203A2 are shifted by 0.5 pitches in correspondence with the cylindrical portions 202A1 and 202A2, which are arranged so that their phases are out of phase with respect to the first axis AX1 as described above.

[0061] In the gear mechanism 201 according to the third embodiment configured as described above, when the cylindrical gear 202 is rotated around the first axis AX1, the outer peripheral surfaces 202As (circular shape Cir) of the cylindrical portions 202A1 and 202A2 mesh with the concave shapes Con of the spur gears 203A1 and 203A2, and the outer peripheral surfaces 202As move eccentrically relative to the first axis AX1, generating a rotation moment about the first axis AX1 in the cylindrical gear 202, and the rotation of the cylindrical gear 202 is transmitted to the circumscribing gear 203. At this time, when the torsion cylindrical gear 202 rotates once around the first axis AX1, one tooth groove 203Ag of the circumscribing gear 203 rotates in one rotation cycle, and nine tooth grooves 203Ag are formed on the outer periphery of the circumscribing gear 203, i.e., the gear ratio is 1:9 (=0.111), and thus a large reduction ratio is obtained in the gear mechanism 201.

[0062] Conversely, for example, when the circumferential gear 203 is rotated about the second axis AX2, the concave shapes Con of the spur gears 203A1, 203A2 mesh with the outer peripheral surfaces 202As (circular shapes Cir) of the cylindrical portions 202A1, 202A2, and the outer peripheral surfaces 202As move eccentrically with respect to the first axis AX1, causing a rotation moment about the first axis AX1 to be generated in the cylindrical gear 202, and the rotation of the circumferential gear 203 is transmitted to the cylindrical gear 202. At this time, when the circumferential gear 203 rotates once about the second axis AX2, nine tooth grooves 203Ag are formed on the outer periphery of the circumferential gear 203, and therefore the nine tooth grooves 203Ag cause the cylindrical gear 202 to rotate nine times about the first axis AX1, which means that the gear ratio is 9:1 (=9), and therefore a large speed-up ratio is obtained in the gear mechanism 1.

[0063] The gear ratio of the cylindrical gear 202 and the circumscribing gear 203 in the third embodiment is merely an example, and the diameter of the cylindrical portions 202A1 and 202A2 of the cylindrical gear 202 can be changed depending on the allowable torque that can be transmitted, and the diameter of the circumscribing gear 203 can be changed depending on the constraints on the overall size, etc. In other words, the gear ratio can be freely designed within a feasible range depending on the application of the gear mechanism 201.

[0064] In the gear mechanism 201 according to the third embodiment described above, the outer peripheral surface 202As (circular shape Cir) of the cylindrical portions 202A1, 202A2 of the gear body 202A of the cylindrical gear 202 meshes with the concave shape Con of the tooth groove 203Ag of the circumscribing gear 203, and the meshed portion moves in response to rotation. This reduces slippage between the outer peripheral surface 202As (circular shape Cir) and the concave shape Con (i.e., slippage of the tooth surface), and therefore provides a gear mechanism 201 with good transmission efficiency.

[0065] Furthermore, even if the size of the outer circumferential surface 202As (circular shape Cir) of the cylindrical portions 202A1 and 202A2 of the gear body 202A of the cylindrical gear 202, i.e., the diameter of the circular shape Cir (i.e., the diameter of the cylindrical portions 202A1 and 202A2), is reduced, sufficient strength can be obtained to withstand the load applied to the gear body 202A, which is entirely configured as teeth. Therefore, the curvature of the concave shape Con of the circumscribing gear 203 meshing with the circular shape Cir can also be reduced, which means that a large number of tooth grooves 203Ag can be formed in the circumscribing gear 203. In other words, even if the diameter of the circumscribing gear 203 is reduced, the number of tooth grooves 203Ag can be ensured. Therefore, the gear mechanism 201 can also have a large reduction ratio (or speed-up ratio). Furthermore, even if the reduction ratio (or speed increase ratio) is increased, slippage on the tooth surface is small, so self-locking does not occur as occurs with worm gears, and overall, a gear mechanism 201 can be provided that has good transmission efficiency and does not cause self-locking.

[0066] <Possibilities for other embodiments> In the third embodiment described above, the gear body of the first gear is configured with two cylindrical portions 202A1 and 202A2. However, this is not limited to this. Two or more cylindrical shapes may be arranged with a phase shift relative to the circumferential direction when viewed in the axial direction, i.e., the cylindrical shapes may be arranged with steps in the spiral direction. Furthermore, when two or more cylindrical shapes are arranged with a phase shift relative to the circumferential direction when viewed in the axial direction, it is preferable that the phases are shifted at equal intervals in the circumferential direction. Furthermore, when the first gear is configured in this manner, the tooth grooves of the second gear are also formed to match the gear body of the first gear. Note that the torsion cylindrical gear 2 in the first and second embodiments is also stacked in the axial direction using a 3D printer, so strictly speaking, minute steps will occur between each layer. However, since this can generally be recognized as a continuous surface, it is defined as a continuously connected surface in this specification.

[0067] Furthermore, in the third embodiment, the gear body of the first gear is described as being composed of two cylindrical portions 202A1, 202A2, but this is not limited to this. If the gear body of the first gear is configured to have, for example, three or more cylindrical portions (cylindrical shapes), it is sufficient that at least two cylindrical portions (cylindrical shapes) are arranged so that their circumferential positions (i.e., circumferential phases) are different around the first axis AX1 when viewed in the axial direction. In other words, the gear body of the first gear may have cylindrical portions (cylindrical shapes) that have the same circumferential phase.

[0068] In the first and second embodiments, the helix Spi-CT at which the center position CT of the circle Cir in the torsion cylindrical gear 2 (or the torsion cylindrical gear 102) is located is a perfect circle when viewed in the axial direction (see FIGS. 3 to 5). However, this is not limiting, and the helix Spi-CT may be an ellipse when viewed in the axial direction. In this case, the outer shape of the gear body 2A of the torsion cylindrical gear 2 is cylindrical, but has irregularities that bulge outward and contract toward the inner diameter. Furthermore, the tooth grooves 3Ag of the circumscribed gear 3 (or the tooth grooves 103Ag of the inscribed gear 103) have irregularities in the groove depth direction to match the outer shape of the gear body 2A (or the gear body 102A).

[0069] Furthermore, in the first to third embodiments, the first axis AX1 on which the torsion cylindrical gear 2 (or the torsion cylindrical gear 102, or the cylindrical gear 202) is disposed and the second axis AX2 on which the circumscribing gear 3 (or the inscribing gear 103, or the circumscribing gear 203) is disposed are described as being parallel, but this is not limiting, and for example, the first axis AX1 and the second axis AX2 may be positioned such that they are spaced apart by about 10 degrees in one direction, that is, the first axis AX1 and the second axis AX2 do not necessarily have to be parallel. Furthermore, the first axis AX1 and the second axis AX2 may be disposed coaxially; in other words, in this specification, the definition of "parallel" includes the "coaxial" state in which the axes are overlapping.

[0070] Furthermore, in the first to third embodiments, the concave shape Con (see Figures 3 to 5 and Figure 8) of the tooth groove 3Ag of the circumscribing gear 3 (or the tooth groove 103Ag of the inscribing gear 103, or the tooth groove 203Ag of the circumscribing gear 203) has been described as being formed by a cycloidal curve, but this is not limited to this and may be, for example, a semicircular shape. In other words, any shape is acceptable as long as it can mesh with the circular shape Cir of the gear main body 2A of the torsion cylindrical gear 2 (or the outer peripheral surface 202As of the cylindrical portions 202A1 and 202A2).

[0071] Furthermore, in the first to third embodiments, a gear mechanism has been described in which two gears, the torsion cylindrical gear 2 (or the torsion cylindrical gear 102 or the cylindrical gear 202) as the first gear and the external gear 3 (or the internal gear 103 or the external gear 203) as the second gear, mesh together. However, the present invention is not limited to this, and may be applied to a planetary gear mechanism (so-called planetary gear) in which the torsion cylindrical gear 2 (or the torsion cylindrical gear 102 or the cylindrical gear 202) is used as a pinion gear, the external gear as a sun gear, and the internal gear as a ring gear. Furthermore, when configuring a planetary gear mechanism, it is not limited to one configured with three rotating elements, and various modifications are possible, such as one having two rotating elements, or one having four rotating elements by combining two planetary gears as a set.

[0072] In the first and second embodiments, the gear body 2A of the torsion cylindrical gear 2 has a circular shape Cir that spirals around once, i.e., one gear cycle per rotation. However, the present invention is not limited to this. For example, the gear body 2A may have a half-cycle (half the length of the gear body 2A), or multiple gears each having one cycle connected continuously in the axial direction, i.e., two or more gear cycles. In particular, when a gear with a half-cycle is configured, it is possible that the first gear and the second gear rotate without completing one full rotation, rather than transmitting rotation. Furthermore, when multiple gear bodies 2A of the torsion cylindrical gear 2 are connected continuously in the axial direction, a helical gear can be configured by switching the circumferential direction of the spiral (for example, by configuring the first gear as a counterclockwise spiral as shown in FIGS. 3 to 5 and the second gear as a clockwise spiral as shown in FIGS. 3 to 5). [Explanation of symbols]

[0073] 1...Gear mechanism / 2A...Gear body (first gear) / 3A...Gear body (second gear) / 3Ag...Tooth groove / 101...Gear mechanism / 102A...Gear body (first gear) / 103A...Gear body (second gear) / 103Ag...Tooth groove / 201...Gear mechanism / 202A...Gear body (first gear) / 202A1...Cylindrical portion / 202A2...Cylindrical portion / 203A...Gear body (second gear) / 203Ag...Tooth groove / AX1...First axis / AX2...Second axis / Cir...Circular shape / CT...Center position / CT1...Center position / CT2...Center position / Con...Concave shape

Claims

1. A gear mechanism including: a first gear rotatably disposed on a first shaft; and a second gear having a tooth groove meshing with the first gear and rotatably disposed on a second shaft, the second gear is a torsion gear in which the tooth grooves are formed in a shape including an arc shape in a cross section perpendicular to the axial direction of the second shaft, The first gear is an outer shape in a cross section perpendicular to the axial direction of the first shaft is circular at any position in the cross section in the axial direction of the first shaft, When viewed in the axial direction of the first axis, the central positions of the plurality of circular shapes arranged in the axial direction of the first axis are eccentric with respect to the first axis and are arranged so that the positions in the circumferential direction about the first axis are different. Gear mechanism.

2. A gear mechanism including: a first gear rotatably disposed on a first shaft; and a second gear having a tooth groove meshing with the first gear and rotatably disposed on a second shaft, the second gear is composed of a plurality of spur gears, each of which has a tooth groove formed in a shape including an arc shape in a cross section perpendicular to the axial direction of the second shaft, and which are arranged side by side in the axial direction of the second shaft and have different phases in the circumferential direction, The first gear is a plurality of cylindrical portions arranged in the axial direction of the first shaft so as to correspond to the plurality of spur gears, and an outer shape in a cross section perpendicular to the axial direction of the first shaft is circular at any position in the cross section in the axial direction of the first shaft, When viewed in the axial direction of the first axis, the central positions of the plurality of cylindrical portions are eccentric with respect to the first axis and are arranged so that their positions in the circumferential direction about the first axis are different. Gear mechanism.

3. The second axis is arranged parallel to the first axis.

3. The gear mechanism according to claim 1 or 2.

4. the arc shape is a cycloid curve shape in a cross section perpendicular to the axial direction of the second axis, 3. The gear mechanism according to claim 1 or 2.

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