Eccentric Oscillation Type Reduction Gear Unit Series, Reduction Gear Unit Manufacturing Method, and Design Method

Abstract

The present invention provides a series of eccentric swing type reduction devices that can reduce the trouble in parts management by making parts common. The series of eccentric swing type reduction devices of the present invention includes a first reduction device and a second reduction device. Among them, the first reduction device includes: a first external gear; a first crankshaft having a first eccentric body that swings the first external gear; and a first eccentric body bearing disposed between the first external gear and the first eccentric body. The second reduction device includes: a second external gear; a second crankshaft having a second eccentric body that swings the second external gear; and a second eccentric body bearing disposed between the second external gear and the second eccentric body. The pitch circle diameter of the rolling elements of the first eccentric body bearing is smaller than the pitch circle diameter of the rolling elements of the second eccentric body bearing. The shape of the rolling elements of the first eccentric body bearing is the same as the shape of the rolling elements of the second eccentric body bearing. The shape of the cage of the first eccentric body bearing is different from the shape of the cage of the second eccentric body bearing.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2019-228044 filed on December 18, 2019. The entire content of the Japanese application is incorporated herein by reference. Technical Field

[0002] The present invention relates to a series of eccentric swing type reduction devices, a method for manufacturing a reduction device, and a method for designing a reduction device. Background Art

[0003] There is known a reduction gear set including a first reduction gear and a second reduction gear having different structures. For example, Patent Document 1 discloses a reduction gear set including: a first reduction gear having a first crank assembly; and a second reduction gear having a second crank assembly. In this reduction gear set, the first crank assembly rotates around a first transmission shaft separated from a first main shaft by a first distance, and the second crank assembly rotates around a second transmission shaft separated from a second main shaft by a second distance (different from the first distance). The first crank assembly includes a first gear support bearing disposed between a first eccentric portion and a first swing gear, and the second crank assembly includes a second gear support bearing disposed between a second eccentric portion and a second swing gear. The shape of the first gear support bearing is the same as the shape of the second shaft support bearing.

[0004] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2016-121766

[0005] In the reduction gear set described in Patent Document 1, the first gear support bearing and the second shaft support bearing are made common to reduce the types of bearings. However, the common use of the bearings is limited to the case where the diameters of the supported bodies supported by the bearings are the same. Summary of the Invention

[0006] An object of the present invention is to provide a series of eccentric swing type reduction devices that can reduce the trouble in parts management by making parts common.

[0007] A series of eccentric swing type reduction devices according to an embodiment of the present invention includes a first reduction device and a second reduction device. The first reduction device includes: a first external gear; a first crankshaft having a first eccentric body that swings the first external gear; and a first eccentric body bearing disposed between the first external gear and the first eccentric body. The second reduction device includes: a second external gear; a second crankshaft having a second eccentric body that swings the second external gear; and a second eccentric body bearing disposed between the second external gear and the second eccentric body. The pitch circle diameter of the rolling elements of the first eccentric body bearing is smaller than the pitch circle diameter of the rolling elements of the second eccentric body bearing, and the shape of the rolling elements of the first eccentric body bearing is the same as the shape of the rolling elements of the second eccentric body bearing.

[0008] In addition, any combination of the above-mentioned constituent elements, or a manner in which the constituent elements or expressions of the present invention are mutually replaced between methods, systems, etc. is also effective as an embodiment of the present invention.

[0009] According to the present invention, it is possible to provide a series of eccentric swing type reduction devices that can reduce the trouble in parts management by making parts common. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a cross-sectional view of the first reduction device of the series of eccentric swing type reduction devices according to the first embodiment.

[0011] Figure 2 It is a cross-sectional view of the second reduction device of the series of eccentric swing type reduction devices according to the first embodiment.

[0012] Figure 3 It shows Figure 1 a layout diagram of the rolling elements of the first reduction device.

[0013] Figure 4 It shows Figure 2 a layout diagram of the rolling elements of the second reduction device.

[0014] Figure 5 It is a cross-sectional view of the first reduction device of the series of eccentric swing type reduction devices according to the first modification.

[0015] Figure 6 It is a cross-sectional view of the second reduction device of the series of eccentric swing type reduction devices according to the first modification.

[0016] In the drawings: 1 - series of eccentric swing type reduction devices, 10 - first reduction device, 50 - second reduction device, 12 - crankshaft, 12a - eccentric body, 14 - external gear, 16 - internal gear, 18, 20 - wheel carriers, 24, 26 - main bearings, 30 - eccentric body bearing, 30b - rolling elements, 30c - cage, 30h - movement restricting member, 33 - crankshaft bearing, 33b - rolling elements, 33c - cage, 100 - series of eccentric swing type reduction devices. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] Hereinafter, preferred embodiments of the present invention will be described with reference to the respective drawings. In the embodiments, comparative examples, and modifications, the same or equivalent constituent elements and components are denoted by the same reference numerals, and repeated descriptions are appropriately omitted. Also, for ease of understanding, in each drawing, the sizes of the components are appropriately enlarged or reduced. Further, in each drawing, a part of the components that are not important for explaining the embodiments is omitted.

[0018] Moreover, terms numbered as the first, second, etc. are used to describe various components, but such terms are only for the purpose of differentiating one component from others and are not used to define the components.

[0019] [First Embodiment]

[0020] Hereinafter, with reference to the drawings, the structure of Series 1 of the eccentric swing type reduction gear device according to the first embodiment will be described. Series 1 of the eccentric swing type reduction gear device includes a first reduction gear 10 and a second reduction gear 50 having different structures. Figure 1 It is a side cross-sectional view showing the first reduction gear 10 of Series 1 of the eccentric swing type reduction gear device according to the first embodiment. Figure 2 It is a side cross-sectional view showing the second reduction gear 50 of Series 1 of the eccentric swing type reduction gear device. The first reduction gear 10 and the second reduction gear 50 of the present embodiment are eccentric swing type reduction gear devices that swing an external gear meshing with an internal gear so that one of the internal gear and the external gear rotates and the generated motion component is output from the output member to the driven device.

[0021] Hereinafter, the same names and symbols will be used to label the components common to the first reduction gear 10 and the second reduction gear 50. And sometimes, "first" is added to the beginning of the name of the component constituting the first reduction gear 10, or "-1" is added to the end of the symbol. And sometimes, "second" is added to the beginning of the name of the component constituting the second reduction gear 50, or "-2" is added to the end of the symbol.

[0022] First, the common structure of the first reduction gear 10 and the second reduction gear 50 will be described. The first reduction gear 10 and the second reduction gear 50 mainly include a crankshaft 12, an external gear 14, an internal gear 16, a carrier 18, a carrier 20, a housing 22, a main bearing 24, a main bearing 26, an eccentric body bearing 30, a crankshaft bearing 33, and a crankshaft bearing 34. Hereinafter, the direction along the central axis La of the internal gear 16 will be referred to as the "axial direction", and the circumferential direction and the radial direction of the circle centered on the central axis La will be referred to as the "circumferential direction" and the "radial direction", respectively. And hereinafter, for convenience, one side in the axial direction (the right side in the figure) will be referred to as the input side, and the other side (the left side in the figure) will be referred to as the input opposite side.

[0023] The crankshaft 12 rotates about the rotation center line by the rotational power input from a driving device (not shown). In the first reduction gear 10 and the second reduction gear 50 of the present embodiment, the rotation center line of the crankshaft 12 and the central axis La of the internal gear 16 are arranged on the same axis, which is a central crank type reduction gear device. The driving device is, for example, a motor, a gear motor, an engine, etc.

[0024] The crankshaft 12 of the present embodiment is an eccentric shaft having a plurality of eccentric bodies 12a for swinging the external gears 14. The crankshaft 12 may be a solid shaft, but in the present embodiment, it is a hollow shaft having a prescribed hollow portion 12d. The axis of the eccentric body 12a is eccentric with respect to the rotation center line of the crankshaft 12. In the present embodiment, two eccentric bodies 12a are provided, and the eccentric phases of the adjacent eccentric bodies 12a are offset from each other by 180°.

[0025] On the outer periphery of the eccentric body 12a, two external gears 14 are assembled via the eccentric bearings 30. In the present embodiment, the rolling elements 30b of the eccentric bearings 30 are exemplified by rollers (cylindrical bodies). In addition to this, known rolling elements such as spheres and cones can also be used as the rolling elements 30b of the eccentric bearings 30. Each external gear 14 is internally meshed with the internal gear 16. The purpose of arranging the external gears 14 in two rows for assembly is to increase the load-carrying capacity and achieve low vibration and low noise based on the offset of the eccentric phases. The structures of the external gears in each row are the same except for the different eccentric phases.

[0026] The external gears 14 are respectively provided corresponding to the plurality of eccentric bodies 12a. The external gears 14 are rotatably supported on the corresponding eccentric bodies 12a via the eccentric bearings 30. The external gears 14 are provided with internal pin holes 13 through which the internal pins 32 penetrate and center holes 15 that abut against the eccentric bearings 30.

[0027] The internal pin holes 13 are provided at positions offset from the center of the external gears 14. A plurality of internal pin holes 13 are provided corresponding to the internal pins 32 described later. In this example, three internal pin holes 13 are provided at intervals of 120° in the circumferential direction. The center holes 15 are provided at the centers of the external gears 14, and they are holes through which the eccentric bodies 12a are inserted.

[0028] As Figure 1 shown, the housing 22 is generally cylindrical, and an internal gear 16 is provided on its inner peripheral portion. The internal gear 16 is meshed with the external gear 14. The internal gear 16 of the present embodiment includes an internal gear main body integrated with the housing 22 and external pins 16a (pin members) that are rotatably supported on the internal gear main body and constitute the internal teeth of the internal gear 16. The number of internal teeth of the internal gear 16 (the number of external pins 16a) is slightly more than the number of external teeth of the external gear 14 (in this example, only one more).

[0029] The wheel carriers 18, 20 are arranged on the axial side portions of the external gears 14. The wheel carriers 18, 20 include: an input side wheel carrier 18, arranged on the side portion of the input side of the external gear 14; and an input opposite side wheel carrier 20, arranged on the side portion of the input opposite side of the external gear 14. The wheel carriers 18, 20 are disk-shaped, and they are rotatably supported by the crankshaft 12 via the crankshaft bearings 33, 34.

[0030] The input-side wheel carrier 18 and the wheel carrier 20 on the side opposite to the input are connected together via the inner pin 32. The inner pin 32 axially penetrates a plurality of external gears 14 at positions radially offset from the axis of the external gear 14. The inner pin 32 of the present embodiment is formed integrally with the wheel carrier 20 on the side opposite to the input. The inner pin 32 may also be separately provided from the wheel carriers 18 and 20. A plurality of inner pins 32 are provided at a predetermined interval around the central axis La of the internal gear 16. In the present embodiment, three inner pins 32 are provided at intervals of 120° in the circumferential direction.

[0031] Regarding the inner pin 32, the front end portion thereof is inserted into the bottomed recess 18c formed in the input-side wheel carrier 18, and the input-side wheel carrier 18 and the wheel carrier 20 on the side opposite to the input are connected together with a bolt 36 inserted from the input side of the input-side wheel carrier 18.

[0032] The inner pin 32 penetrates the inner pin hole 13 formed in the external gear 14. A roller 35 is rotatably sleeved on the outer periphery of the inner pin 32 as a sliding promotion member. The axial movement of the roller 35 is restricted by the side opposite to the input of the input-side wheel carrier 18 and the input side of the wheel carrier 20 on the side opposite to the input. A clearance (i.e., gap) for absorbing the swinging component of the external gear 14 is provided between the roller 35 and the inner pin hole 13. The roller 35 is in partial contact with the inner wall surface of the inner pin hole 13.

[0033] Here, the component that outputs rotational power to the driven device (not shown) is referred to as the output component, and the component fixed to the external component for supporting the first reduction gear 10 and the second reduction gear 50 is referred to as the fixed component. The output component of the present embodiment is the wheel carrier 20 on the side opposite to the input, and the fixed component is the housing 22. The output component is rotatably supported by the fixed component via the main bearings 24 and 26.

[0034] The main bearings 24 and 26 include: an input-side main bearing 24 disposed between the input-side wheel carrier 18 and the housing 22; and a main bearing 26 on the side opposite to the input disposed between the wheel carrier 20 on the side opposite to the input and the housing 22. In the present embodiment, the main bearings 24 and 26 are arranged in a so-called back-to-back combination state. The outer peripheries of the wheel carriers 18 and 20 respectively constitute the inner rings of the main bearings 24 and 26. In the present embodiment, as the main bearings 24 and 26, angular contact ball bearings having spherical rolling elements 42 are exemplified. In addition, the main bearings 24 and 26 may also be rolling bearings such as tapered roller bearings and angular contact roller bearings.

[0035] The crankshaft bearings 33 and 34 include: an input-side crankshaft bearing 33 disposed between the input-side wheel carrier 18 and the crankshaft 12; and an input-opposite-side crankshaft bearing 34 disposed between the input-opposite-side wheel carrier 20 and the crankshaft 12. As the crankshaft bearings 33 and 34 of the first reduction gear 10 and the second reduction gear 50, various known types of bearings can be used. In the present embodiment, ball bearings are used as the crankshaft bearings 33 and 34 of the first reduction gear 10. Further, in the second reduction gear 50 of the present embodiment, a ball bearing is used as the input-opposite-side crankshaft bearing 34, and a roller bearing having rollers (cylindrical bodies) as rolling elements 30b is used as the input-side crankshaft bearing 33.

[0036] Next, the operations of the first reduction gear 10 and the second reduction gear 50 configured as described above will be described. When rotational power is transmitted from the drive device to the crankshaft 12, the eccentric body 12a of the crankshaft 12 rotates about the rotation center line passing through the crankshaft 12. When the eccentric body 12a performs an eccentric motion, it causes the external gear 14 to swing via the eccentric body bearing 30 disposed around the eccentric body 12a. At this time, the external gear 14 swings in such a manner that it rotates about the rotation center line of the crankshaft 12 with its own axis as the center. When the external gear 14 swings, the meshing positions of the external gear 14 and the internal gear 16 are sequentially displaced. As a result, for each rotation of the crankshaft 12, one of the external gear 14 and the internal gear 16 rotates by an amount corresponding to the difference in the number of teeth between the external gear 14 and the internal gear 16. In the present embodiment, the external gear 14 rotates, and the reduced rotation is output from the input-opposite-side wheel carrier 20 via the inner pin 32.

[0037] Next, the characteristic structure of Series 1 of the eccentric swing type reduction gear of the present embodiment will be described.

[0038] Reference Figures 1 to 4 。 Figure 3 is a layout view showing the arrangement of the rolling elements 30b of the first eccentric body bearing 30-1 in the first reduction gear 10. Figure 4 is a layout view showing the arrangement of the rolling elements 30b of the second eccentric body bearing 30-2 in the second reduction gear 50. These views show the arrangement of the rolling elements 30b when viewed axially. The eccentric body bearing 30 may have an inner ring and / or an outer ring, but in the present embodiment, it does not have an inner ring and an outer ring. The first eccentric body bearing 30-1 has rolling elements 30b and a first cage 30c-1. The first cage 30c-1 rotatably holds 30 rolling elements 30b at specified positions on the pitch circle C1. The second eccentric body bearing 30-2 has rolling elements 30b and a second cage 30c-2. The second cage 30c-2 rotatably holds 37 rolling elements 30b at specified positions on the pitch circle C2.

[0039] The pitch circle diameter D1 (e.g., 71 mm) of the rolling elements 30b of the first eccentric body bearing 30-1 is smaller than the pitch circle diameter D2 (e.g., 102 mm) of the rolling elements 30b of the second eccentric body bearing 30-2. In addition, in this specification, the pitch circle diameter of the rolling elements of a bearing, including other bearings, refers to the diameter of the circle (pitch circle) passing through the centers of the rolling elements when assembled as a reduction gear. For example, the pitch circle diameters D1 and D2 of the rolling elements 30b of the eccentric body bearing 30 refer to the diameters of the circles (pitch circles C1 and C2) passing through the centers of the rolling elements 30b in the state where the eccentric body 12a is engaged. The pitch circle diameter is sometimes also referred to as PCD (Pitch Circle Diameter).

[0040] The rolling elements 30b of the first eccentric body bearing 30-1 and the rolling elements 30b of the second eccentric body bearing 30-2 have the same shape. In this case, even if the diameter of the supported body supported by the bearing is different or the bearing load is different, the rolling elements can be made common. As a result, the trouble in parts management of Series 1 of the eccentric swing type reduction gear can be reduced. In addition, in this specification, components of the same shape refer to components manufactured according to the same design, including components with manufacturing deviations or errors and not including components made of different materials.

[0041] As Figure 3 and Figure 4 shown, the rolling elements 30b are arranged at equal intervals along the pitch circles C1, C2, etc. In this case, by changing the number of rolling elements or the assembly rate, it is possible to flexibly achieve the desired load-carrying capacity in bearings using rolling elements of the same shape. In addition, in this specification, the assembly rate of the rolling elements refers to the proportion of the rolling elements on the pitch circle.

[0042] As described above, the number of rolling elements 30b of the second eccentric body bearing 30-2 is more than the number of rolling elements 30b of the first eccentric body bearing 30-1, and the assembly rate of the rolling elements 30b of the second eccentric body bearing 30-2 is lower than the assembly rate of the rolling elements 30b of the first eccentric body bearing 30-1. The distance B2 between two adjacent rolling elements 30b of the second eccentric body bearing 30-2 is greater than the distance B1 between two adjacent rolling elements 30b of the first eccentric body bearing 30-1. In this case, by changing the number of rolling elements or the assembly rate, it is possible to flexibly achieve the desired load-carrying capacity in bearings using rolling elements of the same shape.

[0043] Since the number of rolling elements 30b held and the pitch circle diameters D1 and D2 are different, the shape of the first cage 30c-1 is different from the shape of the second cage 30c-2. In this case, the number of rolling elements and the size of the cage can be flexibly selected, so that a structure suitable for the bearing capacity can be easily achieved compared with the case where the shapes of the cages are the same. In addition, the shape of the cage is different, for example, based on differences in the number, diameter, and shape of the roller arrangement portions.

[0044] In the present embodiment, the eccentricity of the eccentric body 12a of the second reduction gear 50 is set to be greater than the eccentricity of the eccentric body 12a of the first reduction gear 10.

[0045] As Figure 1 and Figure 2 shown, the first reduction gear 10 and the second reduction gear 50 each include a plurality (for example, two) of eccentric body bearings 30. In the first reduction gear 10, when viewed axially, the two first cages 30c-1 adjacent to each other of the two first eccentric body bearings 30-1 overlap each other. Therefore, the cages themselves can contact each other to restrict movement, and thus the axial position of the eccentric body bearing can be restricted.

[0046] On the other hand, in the second reduction gear 50, since the eccentricity of the second eccentric body 12a-2 is large, the eccentricity of the second cage 30c-2 is also large. When viewed axially, the two second cages 30c-2 adjacent to each other do not overlap at the maximum separation position (the position farthest apart in the eccentric direction). Therefore, a movement restricting member 30h is provided between the plurality of second eccentric body bearings 30-2 of the second reduction gear 50 of the present embodiment. In this case, even in a structure where the cages themselves cannot restrict the axial position, the axial position of the eccentric body bearing can be restricted. The movement restricting member 30h of the present embodiment is a hollow circular plate-like member present between two adjacent second cages 30c-2, and has a shape that overlaps with these cages when viewed axially. In addition, at positions in the direction orthogonal to the eccentric direction, these cages do not shift, so these second cages 30c-2 overlap each other. That is, when viewed axially, these cages can partially overlap at positions other than the maximum separation position.

[0047] In the present embodiment, the first crankshaft 12-1 and the second crankshaft 12-2 are hollow shafts, and the hollow diameter E2 (for example, 81 mm) of the second crankshaft 12-2 is larger than the hollow diameter E1 (for example, 49 mm) of the first crankshaft 12-1. As a result, compared with the case where the hollow diameter E2 and the hollow diameter E1 are the same, the wall thickness of the second crankshaft 12-2 can be reduced, which is beneficial to the lightening of the second reduction gear 50.

[0048] In the second reduction gear 50 of the present embodiment, the second crankshaft bearing 33-2 is supported by the input-side wheel carrier 18 into which the inner pin 32 of the second reduction gear 50 is inserted and supports the second crankshaft 12-2. The second crankshaft bearing 33-2 may have an inner ring and / or an outer ring, but in the present embodiment, it does not have an inner ring and an outer ring. The second crankshaft bearing 33-2 has rolling elements 33b and a cage 33c. The inner peripheral surface 18h of the through-hole of the input-side wheel carrier 18 functions as the outer ring of the second crankshaft bearing 33-2. The outer peripheral surface 12h of the second crankshaft 12-2 functions as the inner ring of the second crankshaft bearing 33-2.

[0049] In the present embodiment, the pitch circle diameter D1 of the rolling elements 30b of the first eccentric bearing 30-1 is smaller than the pitch circle diameter F2 of the rolling elements 33b of the second crankshaft bearing 33-2. And, the shape of the rolling elements 30b of the first eccentric bearing 30-1 in the present embodiment is the same as the shape of the rolling elements 33b of the second crankshaft bearing 33-2. In this case, parts can be made more common. And, the shape of the first cage 30c-1 of the first eccentric bearing 30-1 in the present embodiment is different from the shape of the cage 33c of the second crankshaft bearing 33-2. In this case, the number of rolling elements and the size of the cage can be flexibly selected, so a structure suitable for the bearing capacity can be easily achieved compared to the case where the shape of the cage is fixed.

[0050] The above is the description of the first embodiment.

[0051] Next, the second embodiment and the third embodiment of the present invention will be described. In the drawings and descriptions of the second embodiment and the third embodiment, the same or equivalent components and parts as those in the first embodiment are denoted by the same reference numerals. The description repeated with the first embodiment is appropriately omitted, and the structures different from the first embodiment are mainly described.

[0052] [Second Embodiment]

[0053] Here, a manufacturing method S100 of the reduction gear 10 according to the second embodiment of the present invention will be described. The manufacturing method S100 is a manufacturing method of the first reduction gear 10 having a structure different from that of the second reduction gear 50. The description in the first embodiment is applicable to both the first reduction gear 10 and the second reduction gear 50.

[0054] The manufacturing method S100 includes the following steps:

[0055] (1) Manufacture a crankshaft 12-1 having a first eccentric body 12a such that the pitch circle diameter D1 of the rolling elements of the first eccentric bearing 30-1 assembled to the first eccentric body 12a-1 is smaller than the pitch circle diameter D2 of the rolling elements of the second eccentric bearing 30-2 assembled to the second eccentric body 12a-2;

[0056] (2) Arrange rolling elements with the same shape as the rolling elements 30b of the second eccentric body bearing 30-2 on the first eccentric body 12a.

[0057] The above manufacturing method S100 is only an example, and the order of the processes can also be replaced, or some processes can be added, deleted, or changed.

[0058] According to this embodiment, the same effects as those of the first embodiment can be obtained, and parts can be made common, thereby reducing the part management man-hours.

[0059] [Third Embodiment]

[0060] Here, a design method S200 for the speed reduction device 10 according to the third embodiment of the present invention will be described. The design method S200 is a design method for the first speed reduction device 10 having a structure different from that of the second speed reduction device 50. The description in the first embodiment is applicable to both the first speed reduction device 10 and the second speed reduction device 50.

[0061] The design method S200 includes the following processes:

[0062] (1) Design the first eccentric body 12a such that the pitch circle diameter D1 of the rolling elements of the first eccentric body bearing 30-1 assembled on the first eccentric body 12a-1 is smaller than the pitch circle diameter D2 of the rolling elements of the second eccentric body bearing 30-2 assembled on the second eccentric body 12a-2;

[0063] (2) Design the rolling elements of the first eccentric body bearing 30-1 to have the same shape as the rolling elements 30b of the second eccentric body bearing 30-2.

[0064] The above design method S200 is only an example, and the order of the processes can also be replaced, or some processes can be added, deleted, or changed.

[0065] According to this embodiment, the same effects as those of the first embodiment can be obtained, and parts can be made common, thereby reducing the design man-hours.

[0066] The above has described in detail examples of the embodiments of the present invention. The above embodiments are merely specific examples for implementing the present invention. The content of the embodiments does not limit the technical scope of the present invention, and various design changes such as changes, additions, and deletions of the constituent elements can be made without departing from the idea of the invention defined in the technical solution. In the above embodiments, regarding the content that allows such design changes, words such as "embodiment of" and "in the embodiment" are added for explanation, but this does not mean that design changes are not allowed for the content without such words.

[0067] Hereinafter, a modified example will be described. In the drawings and descriptions of the modified example, the same reference numerals are assigned to the constituent elements and components that are the same as or equivalent to those of the embodiment. The description that duplicates the embodiment will be omitted as appropriate, and the structure different from the first embodiment will be mainly described.

[0068] [First Modified Example]

[0069] In the description of the first embodiment, an example in which each speed reduction device is a center crank type eccentric swing type speed reduction device is shown, but the present invention is not limited thereto. The speed reduction devices constituting the series of eccentric swing type speed reduction devices of the present invention may be speed reduction devices based on various principles having a crankshaft with an eccentric body and an eccentric body bearing.

[0070] Hereinafter, a series 1 of eccentric swing type speed reduction devices according to the first modified example will be described. The series 1 of eccentric swing type speed reduction devices of this modified example includes a first speed reduction device 10 and a second speed reduction device 50 having different structures. Figure 5 is a side cross-sectional view showing the first speed reduction device 10 of this modified example, which corresponds to Figure 1 correspondingly. Figure 6 is a side cross-sectional view showing the second speed reduction device 50 of this modified example, which corresponds to Figure 2 correspondingly.

[0071] The first speed reduction device 10 and the second speed reduction device 50 mainly include an input gear 70, a crankshaft 12, an external gear 14, an internal gear 16, a wheel carrier 18, a wheel carrier 20, a housing 22, a main bearing 24, a main bearing 26, an eccentric body bearing 30, a crankshaft bearing 33, and a crankshaft bearing 34. The first speed reduction device 10 and the second speed reduction device 50 of this modified example have a plurality of input gears 70 and crankshafts 12. The first speed reduction device 10 and the second speed reduction device 50 are so-called distributed eccentric swing type speed reduction devices in which a plurality of crankshafts 12 are arranged at positions offset from the central axis La of the internal gear 16, which is different from the first embodiment.

[0072] A plurality of input gears 70 are arranged around the central axis La of the internal gear 16. Only one input gear 70 is shown in Figure 5 . The input gear 70 is supported by the crankshaft 12 inserted into its central portion and is arranged to be rotatable integrally with the crankshaft 12. The input gear 70 meshes with the external tooth portion of a rotating shaft (not shown) provided on the central axis La. The rotational power is transmitted from a driving device (not shown) to the rotating shaft, and the input gear 70 and the crankshaft 12 rotate integrally by the rotation of this rotating shaft.

[0073] In this modified example, a plurality of (for example, three) crankshafts 12 are arranged at intervals in the circumferential direction at positions offset from the central axis La of the internal gear 16. In Figure 5Only one crankshaft 12 is shown. On each crankshaft 12, two eccentric bodies 12a with eccentric phases staggered by 180° from each other are arranged axially.

[0074] On the outer periphery of the eccentric body 12a, two outer gears 14 are assembled via the eccentric body bearings 30. Each outer gear 14 is internally meshed with the inner gear 16. The structures of the outer gears 14 are the same except for the different eccentric phases.

[0075] In the first reduction gear 10 and the second reduction gear 50 of this modification, a movement restricting member 30h is provided between the plurality of eccentric body bearings 30. The movement restricting member 30h exists between two adjacent cages 30c, and has a shape that overlaps with each cage 30c when viewed axially.

[0076] In the first reduction gear 10 and the second reduction gear 50 of this modification, the crankshaft bearings 33, 34 are roller bearings using rollers (cylindrical bodies) as rolling elements. The crankshaft bearings 33, 34 have rolling elements 33b, 34b and cages 33c, 34c, and do not have inner rings and outer rings.

[0077] Next, the operations of the first reduction gear 10 and the second reduction gear 50 of this modification configured as above will be described. If rotational power is transmitted from the driving device to the rotating shaft, the rotational power is distributed from the rotating shaft to the plurality of input gears 70, and each input gear 70 rotates with the same phase. If each input gear 70 rotates, the eccentric body 12a of the crankshaft 12 rotates around the rotation center line passing through the crankshaft 12, and the eccentric body 12a swings the outer gear 14. If the outer gear 14 swings, the meshing positions of the outer gear 14 and the inner gear 16 are sequentially staggered in the same manner as in the first embodiment, and one of the outer gear 14 and the inner gear 16 rotates. The rotation of the crankshaft 12 is decelerated at a reduction ratio corresponding to the tooth number difference between the outer gear 14 and the inner gear 16 and output from the output member to the driven device.

[0078] Next, the characteristic structure of Series 1 of the eccentric swing type reduction gear of this modification will be described.

[0079] The pitch circle diameter D1 of the rolling element 30b of the first eccentric body bearing 30-1 is smaller than the pitch circle diameter D2 of the rolling element 30b of the second eccentric body bearing 30-2. The shape of the first cage 30c-1 is different from the shape of the second cage 30c-2. The shape of the rolling element 30b of the first eccentric body bearing 30-1 is the same as the shape of the rolling element 30b of the second eccentric body bearing 30-2. The number of rolling elements 30b of the second eccentric body bearing 30-2 is larger than the number of rolling elements 30b of the first eccentric body bearing 30-1, and the fitting rate of the rolling elements 30b of the second eccentric body bearing 30-2 is lower than the fitting rate of the rolling elements 30b of the first eccentric body bearing 30-1.

[0080] The shape of the rolling elements 30b of the first eccentric body bearing 30-1 in this modification is the same as the shape of the rolling elements 33b, 34b of the second crankshaft bearings 33-2, 34-2. Also, the shape of the rolling elements 30b of the second eccentric body bearing 30-2 in this modification is the same as the shape of the rolling elements 33b, 34b of the first crankshaft bearings 33-1, 34-1.

[0081] In addition, the shape of the rolling elements 33b, 34b of the first crankshaft bearings 33-1, 34-1 of the first speed reduction device 10 may be the same as the shape of the rolling elements 30b of the second eccentric body bearing 30-2 of the second speed reduction device 50. Also, the shape of the rolling elements 33b, 34b of the first crankshaft bearings 33-1, 34-1 may be the same as the shape of the rolling elements 33b, 34b of the second crankshaft bearings 33-2, 34-2. In this case, parts can be made more general-purpose. In addition, these are not limited to the shapes of the first eccentric body bearing 30-1 and the second eccentric body bearing 30-2 being the same; the shapes of other parts may also be the same.

[0082] This modification obtains the same operational effects as the first embodiment.

[0083] [Other modifications]

[0084] In the description of the first embodiment, an example in which both the first speed reduction device 10 and the second speed reduction device 50 are center crank type eccentric swing type speed reduction devices is shown, but the present invention is not limited to this. One of the first speed reduction device and the second speed reduction device may be a center crank type eccentric swing type speed reduction device, and the other speed reduction device may be a distributed eccentric swing type speed reduction device. Also, as in the first modification, both the first speed reduction device 10 and the second speed reduction device 50 may be distributed eccentric swing type speed reduction devices.

[0085] In the description of the first embodiment, an example in which there are two outer gears 14 is shown, but according to the desired characteristics, there may be three or more outer gears 14.

[0086] In the description of the first embodiment, an example in which the main bearings 24, 26 do not have inner rings is given, but the present invention is not limited to this. One or both of the main bearings 24, 26 may be bearings having inner rings.

[0087] In the embodiment, an example in which the output members are the wheel carriers 18, 20 and the housing 22 is fixed to an external member is described. In addition to this, the housing 22 may be used as the output member and the wheel carriers 18, 20 may be fixed to an external member.

[0088] In the description of the first embodiment, an example in which the maximum separation positions where the two second cages 30c-2 of the second reduction gear 50 are farthest apart in the eccentric direction do not overlap when viewed from the axial direction was described. However, when viewed from the axial direction, these two second cages 30c-2 may also overlap each other at the maximum separation positions and the closest positions where they are closest to each other in the eccentric direction.

[0089] In the description of the first embodiment, an example in which the maximum separation positions where the two second cages 30c-2 of the second reduction gear 50 are farthest apart in the eccentric direction do not overlap when viewed from the axial direction was described. However, when viewed from the axial direction, these two second cages 30c-2 may also overlap each other at the maximum separation positions and other positions in the eccentric direction.

[0090] Moreover, in the first embodiment, the shapes of the rolling elements 33b, 34b of the first crankshaft bearings 33-1, 34-1 may also be the same as the shapes of the rolling elements 33b, 34b of the second crankshaft bearings 33-2, 34-2.

[0091] In the description of the first embodiment and the first modification, examples in which the eccentric bearings and the crankshaft bearings have cages were described. However, some or all of these bearings may also be bearings without cages, for example, full complement roller bearings.

[0092] Each of the above modifications achieves the same effects as the first embodiment.

[0093] Any combination of the above embodiments and modifications is also effective as an embodiment of the present invention. The new embodiments produced by the combination have the effects of the respective embodiments and modifications being combined.

Claims

1. A series of eccentric swing type reduction devices, which includes a first reduction device and a second reduction device different from the first reduction device, and the series of eccentric swing type reduction devices is characterized in that, The first reduction device includes: a first external gear; a first crankshaft having a first eccentric body for swinging the first external gear; and a first eccentric body bearing disposed between the first external gear and the first eccentric body, the second reduction device includes: a second external gear; a second crankshaft having a second eccentric body for swinging the second external gear; and a second eccentric body bearing disposed between the second external gear and the second eccentric body, the pitch circle diameter of the rolling elements of the first eccentric body bearing is smaller than the pitch circle diameter of the rolling elements of the second eccentric body bearing, the shape of the rolling elements of the first eccentric body bearing is the same as the shape of the rolling elements of the second eccentric body bearing, the number of the rolling elements of the second eccentric body bearing is more than the number of the rolling elements of the first eccentric body bearing, the fitting rate of the rolling elements of the second eccentric body bearing is lower than the fitting rate of the rolling elements of the first eccentric body bearing, where the fitting rate of the rolling elements refers to the proportion of the rolling elements on the pitch circle.

2. The series of eccentric swing type reduction devices according to claim 1, characterized in that, the rolling elements of the first eccentric body bearing and the second eccentric body bearing are rollers.

3. The series of eccentric swing type reduction devices according to claim 1 or 2, characterized in that, the shape of the rolling elements of the first eccentric body bearing is the same as the shape of the rolling elements of the second crankshaft bearing that supports the second crankshaft.

4. The series of eccentric swing type reduction devices according to claim 3, characterized in that, the shape of the rolling elements of the first eccentric body bearing is the same as the shape of the rolling elements of the second crankshaft bearing that supports the second crankshaft and is embedded in the wheel carrier of the second reduction device with an inner pin.

5. The series of eccentric swing type reduction devices according to claim 1 or 2, characterized in that, the first crankshaft and the second crankshaft are hollow shafts, the hollow diameter of the second crankshaft is larger than the hollow diameter of the first crankshaft.

6. The series of eccentric swing type reduction devices according to claim 1 or 2, characterized in that, the second reduction device has a plurality of the second eccentric body bearings, a movement restricting member is provided between the plurality of the second eccentric body bearings, the eccentricity of the second crankshaft is larger than the eccentricity of the first crankshaft.

7. A manufacturing method of a reduction device, which is a manufacturing method of a first reduction device different in structure from the structure of the second reduction device, and the manufacturing method of the reduction device is characterized in that, The first reduction device includes: a first external gear; a first crankshaft having a first eccentric body for swinging the first external gear; and a first eccentric body bearing disposed between the first external gear and the first eccentric body, the second reduction device includes: a second external gear; a second crankshaft having a second eccentric body for swinging the second external gear; and a second eccentric body bearing disposed between the second external gear and the second eccentric body, The number of rolling elements of the second eccentric body bearing is greater than that of the first eccentric body bearing. The assembly rate of the rolling elements of the second eccentric body bearing is lower than that of the first eccentric body bearing, where the assembly rate of the rolling elements refers to the proportion of the rolling elements on the pitch circle. The manufacturing method of the reduction gear includes the following steps: Manufacturing the crankshaft of the first eccentric body with a pitch circle diameter of the rolling elements of the first eccentric body bearing assembled to the first eccentric body smaller than that of the rolling elements of the second eccentric body bearing assembled to the second eccentric body; and Arranging rolling elements having the same shape as the rolling elements of the second eccentric body bearing on the first eccentric body.

8. A design method of a reduction gear, which is a design method of a first reduction gear different in structure from the second reduction gear, the design method of the reduction gear being characterized in that The first speed reduction device includes: A first external gear; A first crankshaft having a first eccentric body for swinging the first external gear; And a first eccentric body bearing disposed between the first external gear and the first eccentric body, The second reduction gear includes: a second external gear; a second crankshaft having a second eccentric body for swinging the second external gear; and a second eccentric body bearing disposed between the second external gear and the second eccentric body, The number of rolling elements of the second eccentric body bearing is greater than that of the first eccentric body bearing. The assembly rate of the rolling elements of the second eccentric body bearing is lower than that of the first eccentric body bearing, where the assembly rate of the rolling elements refers to the proportion of the rolling elements on the pitch circle. The design method of the reduction gear includes the following steps: Designing the first eccentric body such that the pitch circle diameter of the rolling elements of the first eccentric body bearing assembled to the first eccentric body is smaller than that of the rolling elements of the second eccentric body bearing assembled to the second eccentric body; and Designing the rolling elements of the first eccentric body bearing to have the same shape as the rolling elements of the second eccentric body bearing.

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