Gearing

Abstract

To provide a gear device that can be made light-weight.SOLUTION: A gear device comprises a crank shaft 14 having an eccentric body 12A, an external gear 16A swinging by the eccentric body 12A, and an internal gear 18A meshing with the external gear 16A, wherein the external gear 16A comprises a plurality of external teeth 40, which form an N-gonal outer peripheral shape on the whole when N is a natural number equal to or larger than 3, the outer peripheral shape of the external teeth 40 being a circular-arc shape which is convex to radially outside a line L1 connecting adjacent vertexes 42 of the N-gonal shape.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to gear arrangements. [Background technology]

[0002] Patent Document 1 discloses a gear device incorporating a planetary gear mechanism as a gear mechanism. This type of gear device typically includes a sun gear that rotates integrally with a high-speed shaft, multiple planetary gears that mesh with the sun gear, and an internal gear that meshes with the planetary gears. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-220496 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a planetary gear mechanism is used as the gear mechanism, it is necessary to place the sun gear and planetary gears inside the internal gear, which increases the number of gears in a cross section perpendicular to the axial direction of the high-speed shaft, resulting in a problem of increased weight.

[0005] One object of the present disclosure is to provide a gear device that can be made lighter. [Means for solving the problem]

[0006] The gear device of the present disclosure is a gear device comprising a crankshaft having an eccentric body, an external gear that oscillates due to the eccentric body, and an internal gear that meshes with the external gear, wherein the external gear has a plurality of external teeth, and the entirety of the plurality of external teeth forms an N-sided polygon when N is a natural number greater than or equal to 3, and the outer circumferential shape of the external teeth forms an arc that is convex radially outward with respect to a line connecting adjacent vertices of the N-sided polygon. Effect of the Invention

[0007] According to the gear device of the present disclosure, weight reduction can be achieved. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a side cross-sectional view of the gear device according to the embodiment. [Diagram 2] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 3] FIG. 4 is a first explanatory diagram showing a motion locus of a first external gear. [Figure 4] FIG. 2 is a second explanatory diagram showing the movement locus of the first external gear. [Diagram 5] FIG. 4 is a diagram showing a part of the movement trajectory of FIG. 3. [Figure 6] FIG. 2 is a cross-sectional view of FIG. [Figure 7] FIG. 3 is a first explanatory diagram showing an operating state of the first external gear and the second external gear. [Figure 8] FIG. 2 is a second explanatory diagram showing an operating state of the first external gear and the second external gear. [Figure 9] FIG. 2 is a diagram showing a first external gear set of the embodiment. [Figure 10] FIG. 2 is a cross-sectional view taken along CC in FIG. [Figure 11] Fig. 2 is a diagram showing a part of the cross section DD of Fig. 1. Fig. 3 is a cross section DD of Fig. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment will be described. The same components are given the same reference numerals, and duplicated explanations will be omitted. In each drawing, for the sake of convenience, components are omitted, enlarged, or reduced as appropriate. The drawings should be viewed according to the orientation of the reference numerals.

[0010] Referring to Fig. 1, the gear device 10 includes a crankshaft 14 having at least one eccentric body 12A, 12B, external gears 16A-16D that oscillate due to the eccentric bodies 12A, 12B, and internal gears 18A-18D that mesh with the external gears 16A-16D. The gear device 10 includes a low speed shaft 20 connected to the crankshaft 14 via a power transmission path that passes through the external gears 16A-16D and the internal gears 18A-18D, and a casing 22 that houses the external gears 16A-16D.

[0011] One of the crankshaft 14 and the low speed shaft 20 is an input shaft to which rotational power is input from a drive source (not shown), and the other is an output shaft that outputs rotational power to a driven device. In this embodiment, the crankshaft 14 is the input shaft, and the low speed shaft 20 is the output shaft. The drive source is, for example, a motor, a gear motor, an engine, etc. When the input shaft rotates, the crankshaft 14 becomes a high speed shaft that rotates at a relatively high speed, and the low speed shaft 20 rotates at a relatively low speed. Hereinafter, for convenience of explanation, one side of the crankshaft 14 in the axial direction X (the right side in FIG. 1) will be referred to as the input side, and the opposite side will be referred to as the anti-input side.

[0012] The eccentric bodies 12A and 12B are provided at a midpoint in the axial direction X of the crankshaft 14. Axial centers C1 of the eccentric bodies 12A and 12B are eccentric by an eccentricity amount e1 from a rotation center line CL1 of the crankshaft 14. The eccentric bodies 12A and 12B have a circular shape centered on the axis C1.

[0013] In this embodiment, at least one eccentric body 12A, 12B is provided, which is a first eccentric body 12A arranged on the input side and a second eccentric body 12B arranged on the opposite input side. The multiple eccentric bodies 12A, 12B have different eccentric phases from each other. The eccentric phase here refers to the phase around the rotation center line CL1 in the eccentric direction from the rotation center line CL1 of the crankshaft 14 toward the axis C1 of the eccentric bodies 12A, 12B. When the number of the eccentric bodies 12A, 12B is M (M is a natural number of 2 or more), the eccentric phases of the multiple eccentric bodies 12A, 12B are shifted by 360° / M. Since M is 2 in this embodiment, the eccentric phases of the first eccentric body 12A and the second eccentric body 12B are shifted by 180° (=360° / 2).

[0014] The crankshaft 14 is composed of multiple shaft members 24A, 24B, 24C having a shape obtained by dividing the crankshaft 14 in the axial direction X. The multiple shaft members 24A, 24B, 24C include split shaft members 24A, 24B in which the individual eccentric bodies 12A, 12B are provided, and a connecting shaft member 24C that connects adjacent split shaft members 24A, 24B. The split shaft members 24A, 24B include a first split shaft member 24A in which the first eccentric body 12A is provided, and a second split shaft member 24B in which the second eccentric body 12B is provided. The split shaft members 24A, 24B and the connecting shaft member 24C are connected to each other so as to be rotatable together by spline fitting or the like.

[0015] The crankshaft 14 is rotatably supported by crank bearings 26A and 26B. The crank bearings 26A and 26B include a first crank bearing 26A disposed between the casing 22 and the crankshaft 14, and a second crank bearing 26B disposed between the low speed shaft 20 and the crankshaft 14.

[0016] The low speed shaft 20 is rotatably supported by a low speed bearing 28. The low speed bearing 28 is disposed between the casing 22 and the low speed shaft 20.

[0017] The gear device 10 includes a plurality of external gear units 30A, 30B having at least one external gear 16A-16D. Each of the plurality of external gear units 30A, 30B oscillates due to an individual eccentric body 12A, 12B. The plurality of external gear units 30A, 30B includes a first external gear unit 30A oscillated due to a first eccentric body 12A, and a second external gear unit 30B oscillated due to a second eccentric body 12B. The first external gear unit 30A includes a first external gear 16A arranged on the input side and a second external gear 16B arranged on the opposite input side. The second external gear unit 30B includes a third external gear 16C arranged on the input side and a fourth external gear 16D arranged on the opposite input side.

[0018] The external gear units 30A, 30B include flange bodies 32A-32C integrated with the external gears 16B-16D in addition to the external gears 16A-16D. The flange bodies 32A-32C are part of the first external gear unit 30A and include a first flange body 32A integrated with the second external gear 16B. In addition, the flange bodies 32A-32C include a second flange body 32B integrated with the third external gear 16C and a third flange body 32C integrated with the fourth external gear 16D. The second flange body 32B and the third flange body 32C are part of the second external gear unit 30B. The flange bodies 32A-32C in this embodiment are provided as part of the same member as the external gears 16B-16D integrated with the flange bodies 32A-32C, but may be provided separately from the external gears 16B-16D. The flange bodies 32A-32C are disposed axially outward from meshing portions 40a of the external teeth 40 of the external gears 16B-16D that are integrated with the flange bodies 32A-32C, and are provided so as to protrude radially outward from the meshing portions 40a (see FIG. 11). The meshing portions 40a of the external teeth 40 here refer to the locations that mesh with the internal teeth 48 of the internal gears 18B-18D.

[0019] The external gears 16A to 16D are rotatably supported by the eccentric bodies 12A, 12B by eccentric bearings 34. The eccentric bearings 34 are disposed between the eccentric bodies 12A, 12B of the crankshaft 14 and through holes 36 formed in the external gears 16A to 16D of the external gear units 30A, 30B corresponding to the eccentric bodies 12A, 12B. The eccentric bearings 34 are rolling bearings such as roller bearings or ball bearings. In this embodiment, a common eccentric bearing 34 is disposed between the multiple external gears 16A to 16D belonging to one external gear unit 30A, 30B and the eccentric bodies 12A, 12B.

[0020] The gear device 10 includes a plurality of internal gear units 38A, 38B each including at least one internal gear 18A-18D. The plurality of internal gear units 38A, 38B correspond to the plurality of external gear units 30A, 30B, respectively, and mesh with the external gears 16A-16D of the corresponding external gear units 30A, 30B. The plurality of internal gear units 38A, 38B include a first internal gear unit 38A corresponding to the first external gear unit 30A, and a second internal gear unit 38B corresponding to the second external gear unit 30B. The first internal gear unit 38A includes a first internal gear 18A meshing with the first external gear 16A, and a second internal gear 18B meshing with the second external gear 16B. The second internal gear unit 38B includes a third internal gear 18C that meshes with the third external gear 16C, and a fourth internal gear 18D that meshes with the fourth external gear 16D. The internal gears 18A to 18D are integrated with the casing 22.

[0021] One of the external gears 16A-16D and the internal gears 18A-18D is a rotating gear that rotates on its own axis, and the other is a constrained gear whose rotation is constrained. In this embodiment, the external gears 16A-16D are rotating gears, and the internal gears 18A-18D are constrained gears. In this case, the casing 22 is fixed to an external member that is separate from the driven device driven by the gear device 10, so that the internal gears 18A-18D function as constrained gears whose rotation is constrained. In addition, the external gears 16A-16D that serve as rotating gears are connected to the low-speed shaft 20 by carriers 74A, 74B and pin members 76A, 76B described later so as to synchronize the rotation component of the rotating gear with the low-speed shaft 20.

[0022] Please refer to Fig. 2. In the following cross-sectional views, the eccentric bearing 34 is shown in schematic form, and the external shapes of the internal gears 18A to 18D are mainly shown. In addition, here, the first external gear 16A and the first internal gear 18A are illustrated, and the contents common to the other external gears 16B to 16D and internal gears 18B to 18D are explained.

[0023] The external gears 16A to 16D each have a plurality of external teeth 40. When N is a finite natural number equal to or greater than 3, the plurality of external teeth 40 as a whole form an N-sided polygon on the outer periphery. In this specification, the term "shape" includes not only a shape that strictly matches the shape being referred to geometrically, but also a shape similar to the shape being referred to. In this embodiment, N is 3, and the plurality of external teeth 40 as a whole form an N-sided Reuleaux polygon (more specifically, a Reuleaux triangle), that is, an odd-sided shape on the outer periphery. This condition is satisfied in a cross section perpendicular to the axial direction X of the crankshaft 14.

[0024] The N-sided polygon formed by the multiple external teeth 40 has N vertices 42. The N vertices 42 are equidistant from the center C2 of the N-sided polygon, and are provided at positions shifted in central angle by 360° / N (120° in this embodiment). The external teeth 40 are formed by each side of the N-sided polygon formed by the multiple external teeth 40, and the number of external teeth is N (three in this embodiment). The center C2 of the N-sided polygon becomes the axis C2 of the external gears 16A to 16D.

[0025] The outer peripheral shape of each of the multiple external teeth 40 forms an arc shape that is convex radially outward with respect to a line L1 connecting adjacent vertices 42 of the N-gon. In order to satisfy this condition, the outer peripheral shape of the external teeth 40 may be a single curve, or may be a combination of multiple curves having different curvatures, or a combination of curves and straight lines.

[0026] The internal gears 18A to 18D have a number of internal teeth 48 that are linear along each side 46 of the (N+1) polygon 44 in the inner peripheral shape. The number of internal teeth of the internal gears 18A to 18D is the same as the number of sides of the (N+1) polygon 44, that is, N+1 (four in this embodiment). The (N+1) polygon 44 here has (N+1) vertices 50 in addition to the (N+1) sides 46. The (N+1) vertices 50 are provided at equal distances from the center C3 of the (N+1) polygon 44 and at positions shifted by the central angle of 360° / (N+1) (90° in this embodiment). Since N is 3 in this embodiment, the (N+1) polygon 44 is a quadrangle, that is, an even-numbered polygon. Sides 46 of the (N+1) polygon 44 need only be linear as a whole, and may be a shape represented by a single straight line or a shape combining straight lines and curves. This condition is satisfied in a cross section perpendicular to the axial direction X of the crankshaft 14. The center C3 of the (N+1) polygon corresponds to the axis C3 of the internal gears 18A-18D.

[0027] The inner peripheral shape of the internal teeth 48 at least partially overlaps with the side 46 of the (N+1) polygon 44. In this embodiment, the overlapping range in which the inner peripheral shape of the internal teeth 48 overlaps with the side 46 is a range excluding the vertex of the (N+1) polygon 44. This overlapping range is, for example, a range of 3 / 4 or more of the length of the side 46 of the (N+1) polygon 44. Alternatively, the inner peripheral shape of the internal teeth 48 may overlap with the side 46 of the (N+1) polygon 44 over the entire length. The inner peripheral shape of the internal teeth 48 will be generally linear, like the side 46 of the (N+1) polygon 44.

[0028] The operation of the above gear device 10 will be described below. Here, the operation will be described when the rotating gears are the external gears 16A-16D, the restraint gears are the internal gears 18A-18D, the crankshaft 14 is the input shaft, and the low speed shaft 20 is the output shaft. Please refer to Figures 3 and 4. Figures 3 and 4 show the movement locus of the first external gear 16A when the crankshaft 14 rotates half a circumference, with Figure 3 showing the movement locus of the first half and Figure 4 showing the movement locus of the latter half.

[0029] When rotational power is transmitted from the drive device to the input shaft (crankshaft 14), the external gears 16A-16D oscillate with relative rotation to the eccentric bodies 12A, 12B in response to rotation of the input shaft in the rotation direction Da by the eccentric bodies 12A, 12B. The oscillating here refers to the movement of the axis C2 of the external gears 16A-16D rotating in the rotation direction Da around the rotation center line CL1 in a state where they are eccentric to the rotation center line CL1 of the crankshaft 14.

[0030] In the process in which the external gears 16A-16D oscillate with the relative rotation with respect to the eccentric bodies 12A, 12B, the external gears 16A-16D move so as to change the meshing position with the internal gears 18A-18D in the circumferential direction (direction Db) of the crankshaft 14. In this process, the external gears 16A-16D can be said to move as if rolling with respect to the internal gears 18A-18D. At this time, as shown in FIG. 5, the external gears 16A-16D and the internal gears 18A-18D mesh with each other, and a rotational force Fa acts on the rotating gears (external gears 16A-16D). When the external gears 16A-16D serve as rotating gears, this rotational force Fa acts in the opposite direction to the rotational direction Da of the input shaft. As a result, when the external gears 16A to 16D oscillate, the rotating gears (external gears 16A to 16D) rotate on their own axes due to the rotational force Fa acting on the rotating gears in response to the oscillation of the external gears. When the rotating gears rotate on their own axes, the rotation component of the rotating gears is transmitted to the output shaft (low speed shaft 20), causing the output shaft (low speed shaft 20) to rotate.

[0031] As described above, when the input shaft rotates, the external gears 16A-16D oscillate, changing the meshing positions of the external gears 16A-16D and the internal gears 18A-18D, thereby rotating the output shaft. Here, the speed ratio, which is the ratio of the rotation speed of the output shaft to that of the input shaft, is the number of teeth of the rotating gears. In this embodiment, the number of teeth of the external gears 16A-16D, which serve as the rotating gears, is three, and the low speed shaft 20 serves as the output shaft, so the reduction ratio as the speed ratio is three. If the internal gears 18A-18D serve as the rotating gears, the reduction ratio as the speed ratio is four.

[0032] The effects of the above gear device 10 will now be described.

[0033] When using the N-angled external gears 16A-16D as the gear mechanism, it is sufficient to simply place the external gears 16A-16D inside the internal gears 18A-18D. Therefore, compared to using a planetary gear mechanism, the number of gears can be reduced in a cross section perpendicular to the axial direction of the crankshaft 14, thereby making it possible to reduce the weight of the gear device 10.

[0034] The outer circumferential shape of the external teeth 40 of the external gears 16A to 16D forms an arc shape that is convex radially outward with respect to a line L1 connecting adjacent vertices 42 of the N-gon. Therefore, the outer circumferential shape of the external teeth 40 is a shape that has no significant recesses as a whole, that is, a shape without a tooth base as referred to as an involute tooth profile, making it possible to eliminate the need to consider tooth base strength.

[0035] The internal teeth 48 of the internal gears 18A to 18D are linear along the side 46 of the (N+1) polygon 44. When involute tooth profiles mesh with each other, the curved external teeth and internal teeth with a relatively large curvature mesh with each other, and the curvature at the meshing points becomes large. In contrast, according to this embodiment, the arc-shaped (curved) external teeth 40 and the linear internal teeth 48 that are close to a straight line mesh with each other, and the curvature at the meshing points becomes significantly smaller. As a result, the contact stress (Hertz stress) between the external teeth 40 and the internal teeth 48 can be reduced, which is advantageous for transmitting large torque.

[0036] Next, other features of the gear train 10 will be described.

[0037] Please refer to FIG. 2 and FIG. 6. The first external gear 16A and the second external gear 16B of the first external gear unit 30A oscillate with a common eccentric phase. The axis C2 of the first external gear 16A and the second external gear 16B move to rotate in the same direction around the rotation center line CL1 of the crankshaft 14 while being eccentric with the same eccentric amount and in the same eccentric direction. To satisfy this condition, the first external gear 16A and the second external gear 16B of this embodiment oscillate by a common first eccentric body 12A. In addition, to satisfy this condition, the first external gear 16A and the second external gear 16B may be oscillated by a plurality of eccentric bodies that are separate from each other and have a common eccentric phase. The first external gear 16A and the second external gear 16B are connected by a restricting member 56 (described later) as a connecting member so as to restrict the relative rotation.

[0038] The phases of the first external gear 16A and the second external gear 16B of the first external gear unit 30A are shifted from each other by 360 / (N×2)°. The phases of the external gears 16A to 16D here refer to the phases around the axis C2 of the external gears 16A to 16D. In this embodiment, since N=3, the phases of the first external gear 16A and the second external gear 16B are shifted from each other by 60°.

[0039] The phases of the first internal gear 18A and the second internal gear 18B of the first internal gear unit 38A are shifted from each other by 360 / {(N+1)×2}[°]. The phases of the internal gears 18A to 18D here refer to the phases around the axis C3 of the internal gears 18A to 18D. In this embodiment, since N=3, the phases of the first internal gear 18A and the second internal gear 18B are shifted from each other by 45°.

[0040] The above advantages will be explained with reference to Figs. 7 and 8. Fig. 8 shows a state in which the eccentric phase of the first eccentric body is shifted by 45° from the state in Fig. 7. The external teeth 40 of the external gears 16A, 16B can mesh with the internal gears 18A, 18B at locations close to the vertices 42 of the N-gon. On the other hand, the external teeth 40 of the external gears 16A, 16B cannot mesh with the internal gears 18A, 18B at locations close to the midpoint 52 in the middle of the adjacent vertices 42.

[0041] Here, by satisfying the above-mentioned conditions, as shown in FIG. 7, even when the first external gear 16A cannot mesh with the first internal gear 18A at a point P1 close to the midpoint 52 of the first external gear 16A, the second external gear 16B can mesh with the second internal gear 18B at a point P2 close to the apex 42 of the second external gear 16B. Similarly, as shown in FIG. 8, even when the second internal gear 18B cannot mesh with the first external gear 16A at a point P3 close to the midpoint 52 of the second external gear 16B, the first external gear 16A can mesh with the first internal gear 18A at a point P4 close to the apex 42 of the first external gear 16A. In other words, the first external gear 16A and the second external gear 16B can alternately mesh with the internal gears 18A and 18B of the first internal gear unit 38A. As a result, the first external gear unit 30A as a whole can maintain a state of meshing with the internal gears 18A and 18B of the first internal gear unit 38A regardless of the rotation phase of the input shaft. As a result, torque can be transmitted stably and continuously between the external gear units 30A, 30B and the internal gear units 38A, 38B.

[0042] The phase relationship described above with respect to the first external gear unit 30A is similarly satisfied by the third external gear 16C and the fourth external gear 16D of the second external gear unit 30B. Moreover, the phase relationship described above with respect to the first internal gear unit 38A is similarly satisfied by the third internal gear 18C and the fourth internal gear 18D of the second internal gear unit 38B. Therefore, the effect of stably and continuously transmitting torque described above can also be obtained between the second external gear unit 30B and the second internal gear unit 38B.

[0043] Please refer to Fig. 1 and Fig. 9. The two external gear units 30A, 30B are provided with two gear sets 54A, 54B consisting of two external gears 16A-16D belonging to the different external gear units 30A, 30B. The two gear sets 54A, 54B include a first gear set 54A and a second gear set 54B. The first gear set 54A consists of a first external gear 16A belonging to the first external gear unit 30A and a fourth external gear 16D belonging to the second external gear unit 30B. The second gear set 54B consists of a second external gear 16B belonging to the first external gear unit 30A and a third external gear 16C belonging to the second external gear unit 30B.

[0044] The two external gears 16A, 16D of the first gear set 54A have a phase difference of the same magnitude as the eccentric phase difference between the two eccentric bodies 12A, 12B, that is, a phase difference of 180° (=360 / 2) between them. The two internal gears 18A, 18D that mesh with the two external gears 16A, 16D of the first gear set 54A also have a phase difference of 180°. The phase here refers to the phase around the axis C3 of the internal gears 18A, 18D. In FIG. 9, the two internal gears 18A, 18D are located in rotational symmetry (four-fold symmetry), so the phase difference of 180° does not appear. The phase relationship described here for the first gear set 54A is also satisfied for the second gear set 54B, although not shown.

[0045] This allows the external gears 16A-16D of the gear sets 54A, 54B to mesh with the internal gears 18A-18D at the same time. This reduces the load on the gears 16A-16D, 18A-18D, thereby increasing the transmission capacity. In addition, the radial moment of the crankshaft 14 caused by the load acting on the axis C1 of the individual eccentric bodies 12A, 12B and the eccentricity of the eccentric bodies 12A, 12B can be offset, improving the rotational balance of the crankshaft 14.

[0046] Please refer to Figures 1, 2 and 6. The gear device 10 includes a regulating member 56 disposed between the multiple external gears 16A, 16B of the first external gear unit 30A and the first eccentric body 12A. The regulating member 56 in this embodiment is a ring member. The regulating member 56 in this embodiment is provided separately from the eccentric bearing 34. The outer ring 34a of the eccentric bearing 34 is attached to the inside of the regulating member 56 by an interference fit.

[0047] The regulating member 56 includes an outer peripheral fitting portion 58 provided on the outer peripheral portion of the regulating member 56. The multiple external gears 16A, 16B include inner peripheral fitting portions 60 into which the outer peripheral fitting portions 58 of the regulating member 56 are fitted. The inner peripheral fitting portions 60 are provided on the inner peripheral portion of the through holes 36 of the external gears 16A, 16B. The outer peripheral fitting portions 58 and the inner peripheral fitting portions 60 are shaped to be fitted together so as to be able to transmit rotational force by contacting each other in the circumferential direction. As a shape that satisfies this condition, in this embodiment, a combination of a male spline and a female spline is used. In addition to this, for example, a combination of a key and a key groove may be used. The multiple external gears 16A, 16B are connected by the common regulating member 56 so as to restrict relative rotation.

[0048] In this way, the multiple external gears 16A, 16B can be connected by utilizing the restricting member 56 disposed in the space between the first eccentric body 12A and the external gears 16A, 16B. Therefore, it is not necessary to secure space at other locations of the external gears 16A, 16B to provide a connecting member (e.g., a pin) that connects the multiple external gears 16A, 16B. As a result, the outer diameter dimensions of the external gears 16A, 16B can be reduced.

[0049] The configuration described here with respect to the regulating member 56 is similarly satisfied in the second external gear unit 30B and the second eccentric body 12B. A similar regulating member 56 is also disposed between the multiple external gears 16C, 16D of the second external gear unit 30B and the second eccentric body 12B.

[0050] Referring to FIG. 2, a configuration common to the multiple internal gears 18A to 18D will be described with reference to the first internal gear 18A. The internal gears 18A to 18D each include an internal gear member 62 on which the internal teeth 48 are provided, and a gear body 64 integrated with the internal gear member 62. The internal gear member 62 in this embodiment includes multiple internal gear members 62 on which the multiple internal teeth 48 are individually provided. The multiple internal teeth 48 are composed of multiple internal gear members 62 separated in the circumferential direction. The internal gear member 62 has a plate shape extending in a direction along the side 46 of the (N+1) polygon 44 as a whole.

[0051] The gear body 64 is integrated with the casing 22. In this embodiment, the gear body 64 is separate from the casing 22 and is disposed inside the casing 22. The gear body 64 is detachably fixed to the casing 22. To achieve this, in this embodiment, the casing 22 is formed by a pair of casing members 68 that are paired above and below, and the multiple casing members 68 are detachably connected by bolts. The gear body 64 can be detached from the casing 22 by disassembling the multiple casing members 68.

[0052] The gear body 64 has an accommodating hole 72 that accommodates a fastener 70. The accommodating hole 72 opens on the radially opposite side of the gear body 64 from the internal teeth member 62. The fastener 70 is, for example, a bolt, which is screwed into the internal teeth member 62 to detachably fix the internal teeth member 62 to the gear body 64. In this way, the internal teeth member 62 is detachably fixed to the gear body 64. With the above configuration, it becomes possible to replace only the internal teeth member 62 that needs to be replaced, while leaving the other internal teeth members 62 in place.

[0053] The external teeth 40 of the above external gears 16A to 16D are harder than the internal teeth 48. This means that the surface hardness of the external teeth 40 is harder than the surface hardness of the internal teeth 48. The surface hardness here refers to, for example, Vickers hardness measured by a method in accordance with JIS Z2244. This condition only needs to be satisfied between at least one external tooth 40 and at least one internal tooth 48. In this embodiment, all the external teeth 40 of one external gear 16A are harder than all the internal teeth 48 of one internal gear 18A.

[0054] As a result, even if fatigue occurs due to the meshing of the external gears 16A-16D and the internal gears 18A-18D, the occurrence location can be limited to the internal teeth 48, which have a lower hardness than the external teeth 40. Furthermore, even if fatigue occurs due to the meshing, the replacement work can be completed by simply replacing the internal teeth member 62 provided with the internal teeth 48, which has a simpler configuration than the external gears 16A-16D.

[0055] Referring to Fig. 1, the gear device 10 includes carriers 74A, 74B disposed axially laterally of the external gear units 30A, 30B, and pin members 76A, 76B inserted into the external gear units 30A, 30B.

[0056] The carriers 74A, 74B include an intermediate carrier 74A arranged between adjacent external gear units 30A, 30B, and an end carrier 74B arranged axially outward with respect to the multiple external gear units 30A, 30B. The end carrier 74B is integrated with the low speed shaft 20. In this embodiment, the end carrier 74B is provided integrally as part of the same member as the low speed shaft 20, but may be provided separately from the low speed shaft 20. The end carrier 74B is provided so as to protrude radially outward from the low speed shaft 20. A bearing 78 is provided between the end carrier 74B and the casing 22.

[0057] The pin members 76A, 76B connect the external gear units 30A, 30B to the side members 80A, 80B so as to be synchronized with the rotation components of the external gear units 30A, 30B. The side members 80A, 80B refer to members arranged axially to the external gear units 30A, 30B, and are the carriers 74A, 74B in this embodiment. Here, "connected so as to be synchronized with the rotation components" refers to maintaining the rotation components of the two objects mentioned at the same magnitude within a numerical range including zero. When the external gears 16A to 16D are rotating gears, the pin members 76A, 76B maintain the rotation components of the external gear units 30A, 30B and the side members 80A, 80B at the same magnitude within a numerical range exceeding zero. When the external gears 16A-16D are constrained gears that do not rotate, the pin members 76A, 76B maintain the rotation components of the external gear units 30A, 30B and the side members 80A, 80B at zero. In this case, by constraining the rotation components of the external gear units 30A, 30B by the side members 80A, 80B and the pin members 76A, 76B, the external gears 16A-16D function as constrained gears.

[0058] The pin members 76A and 76B of this embodiment include an intermediate pin member 76A that connects the first external gear unit 30A to the intermediate carrier 74A as the first side member 80A, and an end pin member 76B that connects the second external gear unit 30B to the end carrier 74B as the second side member 80B. The intermediate pin member 76A of this embodiment connects the second external gear unit 30B in addition to the intermediate carrier 74A so as to be synchronized with the rotation component of the first external gear unit 30A. The end pin member 76B connects the end carrier 74B so as to be synchronized with the rotation component of the second external gear unit 30B. As a result, all the external gear units 30A and 30B are connected by the intermediate pin member 76A and the end pin member 76B so that the rotation components of the carriers 74A and 74B are synchronized.

[0059] Please refer to Figures 1 and 10. The intermediate pin members 76A are provided at intervals around the axis C3 of the internal gears 18A to 18D. The intermediate pin member 76A includes an intermediate carrier pin portion 82 inserted into the intermediate carrier 74A, and gear pin portions 84A, 84B inserted into the external gear units 30A, 30B. The gear pin portions 84A, 84B include a first gear pin portion 84A inserted into the first external gear unit 30A, and a second gear pin portion 84B inserted into the second external gear unit 30B.

[0060] The intermediate carrier 74A has intermediate carrier pin holes 86 through which the intermediate carrier pin portions 82 are inserted so as to be rotatable relative to one another. A bearing 88 is disposed between the intermediate carrier pin holes 86 and the intermediate carrier pin portions 82. The intermediate carrier pin portions 82 are rotatably supported by the intermediate carrier 74A via the bearing 88.

[0061] The external gear units 30A, 30B are provided with gear pin holes 90 through which the gear pin portions 84A, 84B of the intermediate pin member 76A are inserted so as to be relatively rotatable. In this embodiment, the gear pin holes 90 are formed in the first flange body 32A of the first external gear unit 30A and the second flange body 32B of the second external gear unit 30B. The intermediate pin member 76A is inserted through the first flange body 32A and the second flange body 32B. A bearing 92 is disposed between the gear pin hole 90 and the gear pin portions 84A, 84B. The gear pin holes 90 may be formed in the external gears 16A, 16B of the external gear units 30A, 30B instead of the flange bodies 32A to 32C.

[0062] The axis C4 of the first gear pin portion 84A is eccentric by an eccentricity amount e2 from the axis C5 of the intermediate carrier pin portion 82. This eccentricity direction and eccentricity amount e2 are the same as the eccentricity direction and eccentricity amount e1 of the first eccentric body 12A that oscillates the first external gear unit 30A. This condition is satisfied for all intermediate pin members 76A.

[0063] The axis C6 of the second gear pin portion 84B is eccentric by an eccentricity amount e2 from the axis C5 of the intermediate carrier pin portion 82. This eccentricity direction and eccentricity amount e2 are the same as the eccentricity direction and eccentricity amount e2 of the second eccentric body 12B that oscillates the second external gear unit 30B. This condition is satisfied for all intermediate pin members 76A.

[0064] This allows the intermediate pin member 76A to swing so that the axis centers C4, C6 of the gear pin portions 84A, 84B rotate around the axis center C5 of the intermediate carrier pin portion 82. Furthermore, while the intermediate pin member 76A remains supported by the intermediate carrier 74A, the intermediate pin member 76A can also swing, as described above, following the swing of the external gear units 30A, 30B.

[0065] In this way, the gear device 10 includes the intermediate carrier 74A that rotatably supports the intermediate pin member 76A. This makes it possible to support the intermediate pin member 76A by the intermediate carrier 74A while allowing the first eccentric body 12A of the first external gear unit 30A to swing. Another advantage is that the first external gear unit 30A and the second external gear unit 30B, which have different eccentric phases, can be connected by the intermediate pin member 76A while allowing the eccentric bodies 12A and 12B of the external gear units 30A and 30B to swing.

[0066] Referring to Fig. 1, the end side pin members 76B are provided at intervals around the axis C3 of the internal gears 18A to 18D. The end side pin member 76B includes an end side carrier pin portion 96 inserted into the end side carrier 74B, and a third gear pin portion 98 inserted into the second external gear unit 30B. In this embodiment, the gear pin portion 98 is inserted into the third flange body 32C of the second external gear unit 30B.

[0067] The axis C7 of the third gear pin portion 98 is eccentric from the axis C8 of the end carrier pin portion 96 by an eccentricity e2. The eccentricity direction and the eccentricity amount e2 are the same as the eccentricity direction and the eccentricity amount e1 of the second eccentric body 12B that swings the second external gear unit 30B. This condition is satisfied for all the end pin members 76B. This allows the end pin members 76B to swing so that the axis C7 of the third gear pin portion 98 rotates around the axis C8 of the end carrier pin portion 96. In addition, the end pin members 76B can also swing in response to the swing of the second external gear unit 30B while the second external gear unit 30B is supported by the end pin members 76B.

[0068] Refer to FIG. 11. When viewed from the axial direction X of the crankshaft 14, the pin member 76A is integrated with the flange body 32A through which the pin member 76A is inserted, and is disposed radially outside the meshing portion 40a of the external gear 16B adjacent to the flange body 32A. This position condition only needs to be satisfied by at least one of the multiple pin members 76A inserted into the flange body 32A. This position condition only needs to be satisfied by the portion of the pin member 76A that is inserted into the flange body 32A (the gear pin portion 84A in this embodiment). To satisfy this position condition, it is sufficient that a part of the pin member 76A is disposed radially outside the external gear 16B, and it is not essential that the entire pin member 76A is disposed radially outside the external gear 16B. In this embodiment, the above position condition is satisfied by seven pin members 76A out of a total of eight pin members 76A. Of these, the three pin members 76A, 76B have their entire portions (gear pin portions 84A) inserted into the flange body 32A positioned radially outside the meshing portion 40a of the external gear 16B.

[0069] As a result, when using the pin members 76A that are synchronized with the rotation component of the external gear 16B, the outer diameter dimension of the external gear 16B can be made smaller than in the case where the pin members 76A are inserted through the external gear 16B itself.

[0070] The positional conditions described here are similarly satisfied for the intermediate pin member 76A, the second flange body 32B, and the third external gear 16C. Moreover, these positional conditions are similarly satisfied for the end pin member 76B, the third flange body 32C, and the fourth external gear 16D. In these cases as well, the outer diameter dimensions of the external gears 16C, 16D can be made smaller than when the pin members 76A, 76B are inserted through the external gears 16C, 16D themselves.

[0071] Other variations of each component are described.

[0072] So far, the operation has been described in the case where the rotating gears are the external gears 16A-16D and the constraint gears are the internal gears 18A-18D. Alternatively, the rotating gears may be the internal gears 18A-18D and the constraint gears may be the external gears 16A-16D. In this case, the rotation of the external gears 16A-16D may be constrained by inserting the pin members 76A, 76B into the side members 80A, 80B fixed to the external member. In this case, when the input shaft rotates, the external gears 16A-16D (constraint gears) oscillate in a state where their rotation is constrained. In this case, for example, a casing 22 may be used as a connecting means for connecting the rotation components of the internal gears 18A-18D that are the rotating gears to the low-speed shaft 20 so as to synchronize them.

[0073] So far, the gear device 10 has been described as being used as a reduction gear in which the crankshaft 14 is the input shaft and the low speed shaft 20 is the output shaft. Alternatively, the gear device 10 may be used as a speed increasing device in which the low speed shaft 20 is the input shaft and the crankshaft 14 is the output shaft. In this case, the gear device 10 as a speed increasing device may be used, for example, as a wind power generator or the like.

[0074] In the above embodiment, the crankshaft 14 is provided on the axis C3 of the internal gears 18A to 18D. Alternatively, the crankshaft 14 may be provided at a position offset from the axis C3 of the internal gears 18A to 18D and spaced apart in the radial direction.

[0075] So far, an example has been described in which the outer peripheral shapes of the external gears 16A to 16D have an odd-numbered polygonal shape, and the inner peripheral shapes of the internal gears 18A to 18D have an even-numbered polygonal shape. However, the present invention is not limited to this, and the outer peripheral shapes of the external gears 16A to 16D may have an even-numbered polygonal shape, and the inner peripheral shapes of the internal gears 18A to 18D may have an odd-numbered polygonal shape. In any case, the outer peripheral shapes of the external gears 16A to 16D may have an N-gonal shape, and the inner peripheral shapes of the internal gears 18A to 18D may have an (N+1)-gonal shape. Furthermore, N may be 3 or more, and is not particularly limited to a particular number, and may be 4 or more.

[0076] The number of external gears 16A-16D of the external gear units 30A, 30B is not particularly limited. For example, the number of external gears 16A-16D of the external gear units 30A, 30B may be one, or may be three or more. Furthermore, the number of external gears 16A-16D used in the gear device 10 is not particularly limited. The number of external gears 16A-16D may be one, or may be five or more, for example.

[0077] The phase relationship between the two external gears 16A to 16D belonging to the gear sets 54A and 54B is not particularly limited. For example, the two external gears 16A to 16D may be shifted in phase with each other in any desired manner.

[0078] The multiple internal teeth 48 of the internal gears 18A to 18D do not have to be linear along the sides 46 of the (N+1) polygon 44. The multiple internal teeth 48 may have, for example, an involute tooth profile, a trochoid tooth profile, or the like.

[0079] When the multiple internal teeth 48 are configured by multiple internal teeth members 62 separated in the circumferential direction, there is no particular limitation on the number of internal teeth 48 provided on each internal teeth member 62. For example, in addition to the case where one internal teeth 48 is provided on one internal teeth member 62 as in the embodiment, multiple internal teeth 48 may be provided on one internal teeth member 62.

[0080] There is no particular limitation on the means for detachably fixing the internal teeth member 62 to the gear body 64. The internal teeth member 62 may be detachably fixed to the gear body 64 by, for example, press fitting or the like. The multiple internal teeth 48 of the internal gears 18A-18D may be constituted by a single internal teeth member 62.

[0081] Shims for adjusting the position of the internal teeth 48 may be disposed between the internal teeth member 62 and the casing 22. The shims are used to adjust the backlash between the external gears 16A to 16D and the internal gears 18A to 18D by adjusting the thickness of the shims.

[0082] Although the example has been described in which the gear bodies 64 of the internal gears 18A to 18D are separate from the casing 22, the casing 22 may also serve as the gear bodies 64. Alternatively, the gear bodies 64 may be provided individually in correspondence with each of the multiple internal teeth 48.

[0083] There is no particular limitation on the hardness relationship between the external teeth 40 and the internal teeth 48. The external teeth 40 may have the same hardness as the internal teeth 48, or may be softer than the internal teeth 48.

[0084] The restricting member 56 may be any member capable of coupling the external gears 16A to 16D so as to restrict the relative rotation of the external gears 16A to 16D, and a specific example of the restricting member 56 is not limited to a ring member. The restricting member 56 may also be a pin member penetrating the external gears 16A to 16D. Although the restricting member 56 is configured as a separate member from the eccentric bearing 34 in the above example, the restricting member 56 may be configured as the outer ring 34a of the eccentric bearing 34.

[0085] The pin members 76A, 76B may directly connect the external gears 16A-16D to the side members 80A, 80B in order to synchronize the rotation components of the external gear units 30A, 30B with the side members 80A, 80B. The side members 80A, 80B connected to the external gear units 30A, 30B by the pin members 76A, 76B are not limited to the carriers 74A, 74B. The side members 80A, 80B may be, for example, the casing 22, etc.

[0086] Gear train 10 does not necessarily have to include intermediate carrier 74A.

[0087] The above-mentioned embodiment and modified forms are examples. The technical ideas abstracted from these should not be interpreted as being limited to the contents of the embodiment and modified forms. The contents of the embodiment and modified forms are subject to many design changes, such as changes, additions, and deletions of components. In the above-mentioned embodiment, the contents subject to such design changes are emphasized by adding the notation "embodiment". However, design changes are also permitted even in contents without such notation. The hatching on the cross section of the drawing does not limit the material of the hatched object. The structures referred to in the embodiment and modified forms naturally include structures that are shifted by an error amount that can be considered to be the same when considering manufacturing errors, etc. [Explanation of symbols]

[0088] 10...gear device, 12A, 12B...eccentric body, 14...crankshaft, 16A-16D...external gear, 16A...first external gear, 16B...second external gear, 18A-18D...internal gear, 30A, 30B...external gear unit, 32A-32C...flange body, 40...external tooth, 42...apex, 44...(N+1)-gon, 46...side, 48...internal tooth, 50...apex, 56...regulating member, 62...internal tooth member, 64...gear body, 74A...intermediate carrier, 76A, 76B...pin member.

Claims

1. A crankshaft having an eccentric body; an external gear that is oscillated by the eccentric body; An internal gear meshing with the external gear, The external gear has a plurality of external teeth, The plurality of external teeth as a whole have an N-sided polygonal outer periphery, where N is a natural number of 3 or more. The outer circumferential shape of the external teeth is an arc shape that is convex radially outward with respect to a line connecting adjacent vertices of the N-gon, The internal gear is a gear device having a plurality of internal teeth that are linearly arranged along each side of an (N+1) polygon on its inner circumference.

2. The plurality of internal teeth are constituted by a plurality of internal teeth members separated in a circumferential direction, The gear device according to claim 1 , wherein the internal gear comprises a gear body to which the plurality of internally toothed members are removably fixed.

3. 3. A gear arrangement according to claim 1 or 2, wherein the external teeth are harder than the internal teeth.

4. A crankshaft having an eccentric body; an external gear that is oscillated by the eccentric body; An internal gear meshing with the external gear, The external gear has a plurality of external teeth, The plurality of external teeth as a whole have an N-sided polygonal outer periphery, where N is a natural number of 3 or more. The outer circumferential shape of the external teeth is an arc shape that is convex radially outward with respect to a line connecting adjacent vertices of the N-gon, the external gear includes a first external gear and a second external gear that oscillate with a common eccentric phase, A gear device in which the phases of the first external gear and the second external gear are shifted from each other by 360 / (N×2) [°].

5. a restricting member disposed between the first external gear and the eccentric body, and between the second external gear and the eccentric body, The gear device according to claim 4 , wherein the first external gear and the second external gear are connected to each other so that relative rotation between them is restricted by the restricting member.

6. A crankshaft having an eccentric body; an external gear that is oscillated by the eccentric body; An internal gear meshing with the external gear, The external gear has a plurality of external teeth, The plurality of external teeth as a whole have an N-sided polygonal outer periphery, where N is a natural number of 3 or more. The outer circumferential shape of the external teeth is an arc shape that is convex radially outward with respect to a line connecting adjacent vertices of the N-gon, a flange body disposed axially outside the meshing portion of the external teeth; a pin member that is inserted through the flange body and synchronized with a rotation component of the external gear, A gear device in which the pin member is disposed radially outward of the meshing portion when viewed from the axial direction.

7. A crankshaft having an eccentric body; an external gear that is oscillated by the eccentric body; An internal gear meshing with the external gear, The external gear has a plurality of external teeth, The plurality of external teeth as a whole have an N-sided polygonal outer periphery, where N is a natural number of 3 or more. The outer circumferential shape of the external teeth is an arc shape that is convex radially outward with respect to a line connecting adjacent vertices of the N-gon, A plurality of external gear units each having at least one of the external gears; a pin member that is inserted into the external gear unit and synchronized with a rotation component of the external gear unit; an intermediate carrier disposed between adjacent external gear units and configured to rotatably support the pin member.

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