Reduction gear

Abstract

This reduction gear comprises: a wave generator (1) that has a cam (10); an internal gear (2); a first link mechanism (31); a second link mechanism (32) that rotates together with the first link mechanism (31); and an interlocking part (4) that rotates together with the second link mechanism (32). The first link mechanism (31) has first transmission parts that can be accommodated in tooth grooves of the internal gear (2). The second link mechanism (32) has second transmission parts that can be inserted into insertion parts provided in the interlocking part (4). A plurality of each of the first and second transmission parts are aligned along the outer circumference of the wave generator 1. The cam (10) engages the internal gear (2) with a first transmission part at a position corresponding to a pole part. The number of first transmission parts is less than the number of teeth of the internal gear (2). The number of second transmission parts is the same as the number of first transmission parts or less than the number of first transmission parts.

Description

reducer

[0001] The present invention relates to a reducer.

[0002] An example of a reducer is a wave gear device described in Patent Document 1. The wave gear device includes a circular spline, which is a rigid internal gear, a flexspline, which is a flexible external gear, and a wave generator with an elliptical cam. The wave generator bends the flexspline with the cam to mesh with the circular spline, thereby generating relative rotation between the two splines according to the difference in the number of teeth between the two splines. This relative rotation can be used to obtain output from the flexspline, which rotates at a speed slower than the rotation of the cam.

[0003] Japanese Patent Application Laid-Open No. 2011-7206

[0004] The flexspline of a strain wave gearing device is made of a thin-walled, cup-shaped elastic metal body to ensure flexibility, so there is a risk of it breaking if a large torque is applied, which poses a durability problem for strain wave gearing devices.

[0005] An object of the present invention is to provide a reducer with good durability.

[0006] In order to achieve the above object, the reducer of the present invention comprises: a wave generator having a cam that rotates around an axis in response to a rotational input; an internal gear surrounding the cam; a first link mechanism having a plurality of first links configured in a shape that surrounds the outer periphery of the wave generator and positioned between the internal gear and the cam; a second link mechanism having a plurality of second links configured in a shape that surrounds the outer periphery of the wave generator, positioned alongside the first link mechanism in the axial direction that is the direction in which the axis extends and connected to the first link mechanism to rotate together with the first link mechanism around the axis; and an interlocking part that rotates together with the second link mechanism around the axis, wherein the first link mechanism has a first transmission part that can be received in a tooth groove of the internal gear and has an outer periphery in the shape of a cylindrical surface, and the second link mechanism has a second transmission part that can be inserted into an insertion part provided in the interlocking part and has an outer periphery in the shape of a cylindrical surface, and a plurality of first transmission parts are arranged along the outer periphery of the wave generator, and a plurality of second transmission parts are arranged along the outer periphery of the wave generator, The cam has a plurality of pole portions positioned at equal intervals in the circumferential direction around the axis, and meshes the first transmission portion with the internal gear at positions corresponding to the pole portions; the number of first transmission portions is less than the number of teeth of the internal gear; the wave generator generates relative rotation between the internal gear and the first link mechanism according to the difference between the number of teeth of the internal gear and the number of first transmission portions; and the number of second transmission portions is the same as or less than the number of first transmission portions.

[0007] According to the present invention, a reducer with good durability can be provided.

[0008] 5 is a cross-sectional view of a reducer according to an embodiment of the present invention. A cross-sectional view of the reducer according to the same embodiment taken along line II-II shown in FIG. 1. A cross-sectional view of the reducer according to the same embodiment taken along line II-II shown in FIG. 1. A perspective view of a link device, a spacer, and a wave bearing according to the same embodiment. A partial exploded view of the link device and the spacer according to the same embodiment. A cross-sectional view of the link device, the spacer, and the wave bearing according to the same embodiment taken along line III-III shown in FIG. 5. A cross-sectional view of a reducer according to a first modification. A diagram for explaining an interlocking portion according to a second modification. A diagram for explaining a link device and an interlocking portion according to a third modification. A cross-sectional view of a reducer according to a fourth modification. A cross-sectional view of a reducer according to a fourth modification taken along line IV-IV shown in FIG. 10. A diagram for explaining a link device and an interlocking portion according to a fifth modification. A diagram for explaining a cam according to a sixth modification. A diagram for explaining a cam according to a seventh modification.

[0009] An embodiment of the present invention will be described with reference to the drawings.

[0010] As shown in Fig. 1, a reducer according to one embodiment of the present invention includes a wave generator 1, an internal gear 2, a link device 3, an interlocking portion 4, a spacer 5, a case 6 that houses these components, and a support portion 8. This reducer is a differential device of an entirely new type that generates a differential motion based on the same principle as a wave gear device, without using a conventional flexspline. In the following, when describing the configuration of the reducer, the expressions input side (Si in the figure) and output side (So in the figure) may be used.

[0011] The wave generator 1 includes a cam 10 , a cylindrical shaft 10 a formed integrally with the cam 10 , and a wave bearing (flex bearing) 11 .

[0012] The cam 10 and cylindrical shaft 10a rotate about axis AX in response to a rotational input. Rotational power from a motor (not shown) is transmitted to the cylindrical shaft 10a via a known transmission mechanism. An annular bearing B1 is interposed between the case 6 and a portion of the cylindrical shaft 10a on the input side of the cam 10. An annular bearing B2 is interposed between the interlocking part 4 and a portion of the cylindrical shaft 10a on the output side of the cam 10. This allows the cam 10 and cylindrical shaft 10a to rotate relative to the case 6. The bearings B1 and B2 are, for example, ball bearings.

[0013] The cam 10 is formed to protrude from the outer peripheral surface of the cylindrical shaft 10a. The cam 10 has N (N is an integer of 2 or more) pole portions positioned at equal intervals in the circumferential direction (hereinafter simply referred to as the "circumferential direction") about the axis AX. Hereinafter, the number of pole portions that the cam 10 has will be referred to as the "pole number." For example, when the number of poles is N=2, the cam 10 will have an elliptical shape when viewed in the direction in which the axis AX extends (hereinafter also referred to as the "axial direction"), as shown in FIG. 2.

[0014] The wave bearing 11 is an annular bearing that surrounds the outer periphery of the cam 10. The wave bearing 11 has an inner ring fixed to the outer periphery of the cam 10, a flexible outer ring, and a plurality of balls inserted in a rollable state between the inner ring and the outer ring. The outer ring of the wave bearing 11 elastically deforms via the balls. The inner ring may be formed from a portion that includes the outer periphery of the cam 10. In this embodiment, two wave bearings 11 are provided adjacent to each other in the axial direction. Of the two wave bearings 11, the wave bearing 11 located on the input side is surrounded by a first link mechanism 31, which will be described later, and the wave bearing 11 located on the output side is surrounded by a third link mechanism 33, which will be described later.

[0015] The internal gear 2 is made of metal and has rigidity, and is fixed to the case 6. As shown in Figure 2, the internal gear 2 is ring-shaped and surrounds the cam 10, and has a plurality of teeth 2t arranged circumferentially at a constant pitch on its inner periphery. Hereinafter, the grooves formed between adjacent teeth 2t will be referred to as tooth spaces 2g.

[0016] The link device 3 surrounds the outer periphery of the wave generator 1 and has a first link mechanism 31 , a second link mechanism 32 , and a third link mechanism 33 .

[0017] The first link mechanism 31 faces the internal gear 2 via the wave bearing 11 in a radial direction (hereinafter simply referred to as the "radial direction") centered on the axis AX. The second link mechanism 32 faces the interlocking part 4 in the radial direction. The third link mechanism 33 is located between the first link mechanism 31 and the second link mechanism 32 in the axial direction. The first link mechanism 31, the second link mechanism 32, and the third link mechanism 33 are connected by a common shaft S and move together.

[0018] As shown in Figure 2, the first link mechanism 31 has a first link L1 and a first transmission part T1, and is located between the internal gear 2 and the cam 10. There are multiple first links L1, which are connected in order to form a shape that surrounds the outer periphery of the wave generator 1. Specifically, the first link L1 surrounds the outer ring of the wave bearing 11. The first transmission part T1 can be accommodated in the tooth grooves 2g of the internal gear 2, and its outer periphery has a cylindrical surface shape.

[0019] Specifically, as shown in Fig. 4, the first transmission unit T1 has a first shaft S1 extending in the axial direction and a first roller R1 that rotates relative to the first shaft S1. The first shaft S1 is a columnar member made of a rigid material such as metal, and functions as a joint that connects adjacent first links L1 together. The first roller R1 is a cylindrical member made of a rigid material such as metal, and its hollow portion is supported by the first shaft S1. The first roller R1 forms the outer periphery of the first transmission unit T1.

[0020] The first link L1 is composed of a pair of plates facing each other in the axial direction and is made of a rigid material such as metal. As shown in Figure 5, adjacent first links L1 are a pair of inner plates, one located inside the other, and a pair of outer plates, one located outside the other. In other words, the pair of inner plates constituting one of the adjacent first links L1 and the pair of outer plates constituting the other are connected by the first shaft S1.

[0021] Of the outer plates constituting the first link L1, the outer plate located on the output side is shared with the third link L3 and also functions as the inner plate of the third link L3. Also, of the inner plates constituting the first link L1, the inner plate located on the output side is shared with the third link L3 and also functions as the outer plate of the third link L3.

[0022] 2, a plurality of first transmission parts T1 are arranged along the outer periphery of the wave generator 1, with the link device 3 surrounding the outer periphery of the wave generator 1. The arrangement pitch of the first transmission parts T1 (i.e., the arrangement pitch of the first shafts S1) is set to be uniform.

[0023] The number of first transmission parts T1 is less than the number of teeth, which is the number of teeth 2t, of the internal gear 2. Specifically, the number of first transmission parts T1 is less than the number of teeth of the internal gear 2 by N, which is the number of poles of the cam 10 (in this embodiment, N = 2). Here, if the number of teeth of the internal gear 2 is M and the number of first transmission parts T1 is m, then M - m = N holds for a cam 10 with N poles. FIG. 2 shows an example in which there are 40 first transmission parts T1 and the number of teeth of the internal gear 2 is 42 (that is, the number of teeth 2t and the number of tooth spaces 2g are each 42).

[0024] As shown in Figure 2, the second link mechanism 32 has a second link L2 and a second transmission part T2. There are multiple second links L2, which are connected in order to form a shape that surrounds the outer periphery of the wave generator 1. In this embodiment, the second link L2 surrounds the portion of the cylindrical shaft 10a that is closer to the output side than the cam 10. The second transmission part T2 can be inserted into an insertion part 40 (described later) of the interlocking part 4, and its outer periphery has a cylindrical surface shape.

[0025] Specifically, as shown in FIG. 4 , the second transmission unit T2 includes a second shaft S2 extending in the axial direction and a second roller R2 that rotates relative to the second shaft S2. In this embodiment, as described below, due to the relationship between the number of second transmission units T2 and the first transmission unit T1, the second link mechanism 32 also includes a second shaft S2 that does not support a second roller R2. The second shaft S2 is a cylindrical member made of a rigid material such as metal, and functions as a joint that connects adjacent second links L2 together. The second roller R2 is a cylindrical member made of a rigid material such as metal, and its hollow portion is supported by the second shaft S2. The second roller R2 forms the outer periphery of the second transmission unit T2.

[0026] The second link L2 is composed of a pair of plates facing each other in the axial direction and is made of a rigid material such as metal. As shown in Figure 5, adjacent second links L2 are a pair of inner plates, one located inside the other, and a pair of outer plates, one located outside the other. In other words, the pair of inner plates constituting one of the adjacent second links L2 and the pair of outer plates constituting the other are connected by the second shaft S2.

[0027] Of the outer plates constituting the second link L2, the outer plate located on the input side is shared with the third link L3 and also functions as the inner plate of the third link L3. Also, of the inner plates constituting the second link L2, the inner plate located on the input side is shared with the third link L3 and also functions as the outer plate of the third link L3.

[0028] 3, a plurality of second transmission parts T2 are arranged along the outer periphery of the wave generator 1, with the link device 3 surrounding the outer periphery of the wave generator 1. The arrangement pitch of the second transmission parts T2 (i.e., the arrangement pitch of the second shafts S2) is set to be uniform.

[0029] In this embodiment, the number of second transmission units T2 is smaller than the number of first transmission units T1. Specifically, as can be seen from a comparison of Figures 2 and 3, the arrangement of the second transmission units T2 corresponds to an arrangement in which the first transmission units T1 are alternately arranged. That is, Figure 3 shows an example in which there are 20 second transmission units T2.

[0030] In the second link mechanism 32, the second shaft S2 of the second transmission part T2 (i.e., the second shaft S2 supporting the second roller R2) is integral with the first shaft S1 of the first link mechanism 31 and constitutes a common shaft S. In other words, the first shaft S1 includes a common shaft S that is integral with the second shaft S2.

[0031] As shown in FIG. 2 , in this embodiment, the third link mechanism 33 surrounds the outer ring of the wave bearing 11 located on the output side of the two wave bearings 11. As shown in FIGS. 4 and 5 , the third link mechanism 33 includes a third link L3 and a third transmission unit T3. The third transmission unit T3 includes a third shaft S3 extending axially and a third roller R3 that rotates relative to the third shaft S3. The third link mechanism 33 is configured in the same manner as the first link mechanism 31, and the number of third transmission units T3 is the same as the number of first transmission units T1. In this embodiment, all of the third shafts S3 are integral with the first shaft S1. Furthermore, in this embodiment, the common shaft S is configured integrally with not only the first shaft S1 and the second shaft S2, but also the third shaft S3.

[0032] Here, the first transmission unit T1 is configured to transmit a force applied to the first link mechanism 31 to the internal gear 2. The second transmission unit T2 is configured to transmit a force applied to the second link mechanism 32 to the interlocking unit 4. On the other hand, the third link mechanism 33 is provided to increase the strength of the link device 3, and the third roller R3 of the third transmission unit T3 does not transmit force to any object. Therefore, the third roller R3 may be omitted from the third link mechanism 33. Note that, like the first link mechanism 31, a configuration in which the internal gear 2 is also meshed with the third link mechanism 33 may also be adopted. In this case, the third link mechanism 33 functions as the first link mechanism 31.

[0033] The link device 3 configured as described above can also be said to be a roller chain manufactured with high precision in terms of the pitch between the joints and the diameters of the first to third transmission portions T1 to T3. As shown in Figure 4, the link device 3 has the joint positions of the first to third links L1 to L3 regularly arranged along the circumferential direction and aligned. Therefore, the first to third link mechanisms 31 to 33 that make up the link device 3 can be deformed into the same shape when viewed in the axial direction.

[0034] The cam 10 meshes the first transmission parts T1 with the internal gear 2 at positions corresponding to the extreme parts. Figure 2 shows an example in which four first transmission parts T1 located within each of two meshing positions E, E indicated by dashed line boxes are fitted into tooth grooves 2g of the internal gear 2 and mesh with the internal gear 2.

[0035] When the cam 10 rotates, the first link mechanism 31 and the third link mechanism 33 deform in response to the rotation of the cam 10 via the wave bearing 11, and the second link mechanism 32 connected to the first link mechanism 31 and the third link mechanism 33 also deforms in a similar manner. The meshing position E between the internal gear 2 and the first transmission part T1 moves sequentially in response to the rotation of the cam 10. During one rotation of the cam 10, the first link mechanism 31 moves in the opposite rotational direction to the cam 10 by an amount equal to the difference between the number of teeth of the internal gear 2 and the number of first transmission parts T1 (M-m=N). Because the third link mechanism 33 and the second link mechanism 32 are connected to the first link mechanism 31, the entire link device 3 moves in the opposite rotational direction to the cam 10 as described above during one rotation of the cam 10. As a result, as will be described later, the interlocking portion 4, which rotates together with the second link mechanism 32 of the link device 3, is decelerated relative to the rotational speed of the cam 10 at a reduction ratio i=(Mm) / m=N / m.

[0036] Using the above principle, the wave generator 1 generates relative rotation between the internal gear 2 and the first link mechanism 31 in accordance with the difference between the number of teeth of the internal gear 2 and the number of the first transmission part T1. In this way, the principle of differential motion using the wave generator 1 is the same as that of a wave gear device, but the reducer according to this embodiment is completely different from conventional devices in that it uses a link device 3 made up of a combination of rigid materials rather than a flexible thin-film flexspline.

[0037] Although the link device 3 deforms in response to the rotation of the cam 10, it is made of a combination of rigid materials, and so there is a risk of a gap occurring between the link device 3 and the outer periphery of the wave generator 1. To fill this gap, the reducer according to this embodiment is provided with a spacer 5.

[0038] As shown in Figure 1, the spacer 5 is provided between the link device 3 and the cam 10, and is located on the outer periphery of the wave bearing 11 as shown in Figures 1 and 4. That is, the spacer 5 according to this embodiment has a first portion 51 located between one of the two wave bearings 11 and the first link mechanism 31, and a second portion 52 located between the other of the two wave bearings 11 and the third link mechanism 33. As shown in Figure 5, the spacer 5 is a plate-shaped member extending in the axial direction, and is made of metal formed by, for example, machining. The surface of the spacer 5 may be coated with an electroplated grinding stone, a resin lining, or any other coating.

[0039] The first portion 51 is located between the first link mechanism 31 and the wave generator 1, and applies a radial preload centered on the axis AX to each of the first link mechanism 31 and the wave generator 1. As shown in Figure 6, the first portion 51 has a recess 51a into which the outer peripheral edge of the wave generator 1 (i.e., the outer ring of the wave bearing 11) fits. The recess 51a is formed on the side of the first portion 51 facing the wave generator 1.

[0040] The second portion 52 is located between the third link mechanism 33 and the wave generator 1, and applies a radial preload centered on the axis AX to each of the third link mechanism 33 and the wave generator 1. As shown in Figure 6, the second portion 52 has a recess 52a into which the outer peripheral edge of the wave generator 1 (i.e., the outer ring of the wave bearing 11) fits. The recess 52a is formed on the wave generator 1 side of the second portion 52.

[0041] 5 and 6, grooves D1, D2, and D3 are formed in the spacer 5 in this order from the input side. The grooves D1, D2, and D3 extend in the width direction (short direction of the spacer 5) of the spacer 5, which is long in the axial direction. (i) As shown in Fig. 6, when the input sides of a pair of inner plates constituting the first link L1 fit into groove D1, the output sides of a pair of inner plates constituting the first link L1 (which are the same as the input sides of a pair of outer plates constituting the third link L3) fit into groove D2, and the output sides of a pair of outer plates constituting the third link L3 (which are the same as the input sides of a pair of inner plates constituting the second link L2) fit into groove D3. (ii) Although not shown, when the input sides of the pair of outer plates constituting the first link L1 fit into groove D1, the output sides of the pair of outer plates constituting the first link L1 (which are the same as the input sides of the pair of inner plates constituting the third link L3) fit into groove D2, and the output sides of the pair of inner plates constituting the third link L3 (which are the same as the input sides of the pair of outer plates constituting the second link L2) fit into groove D3. Recesses are provided on the inner peripheries of each of the first to third links L1 to L3, and these recessed portions fit into grooves D1, D2, and D3 in accordance with the rules (i) and (ii) above.

[0042] The first portions 51 of the spacers 5 are provided between each of the plurality of first links L1 and the wave generator 1. The second portions 52 of the spacers 5 are provided between each of the plurality of third links L3 and the wave generator 1. In other words, the number of spacers 5 provided is the same as the number of first links L1 and third links L3.

[0043] The spacer 5 provided as described above strengthens the fit between the outer ring of the wave bearing 11 and the link device 3. Furthermore, by providing the spacer 5 with a preload function, it is possible to adjust or absorb errors and deformations that may occur in at least one of the link device 3 and the wave bearing 11 due to wear over long periods of use, etc. Furthermore, the grooves D1 to D3 and recesses 51a, 52a of the spacer 5 prevent the spacer 5 from coming out from between the link device 3 and the wave generator 1, and also prevent the relative positions of the link device 3 and the wave generator 1 from shifting in the axial direction.

[0044] The interlocking unit 4 rotates about the axis AX together with the second link mechanism 32. The interlocking unit 4 has a main portion on the inner circumferential side of the second link mechanism 32 and is formed in an annular shape as shown in FIG. 3 . As shown in FIG. 1 , the interlocking unit 4 is supported on the case 6 via a support 8. The support 8 is formed, for example, by a cross roller bearing, and includes an inner ring 81 fixed to the interlocking unit 4 and an outer ring 82 fixed to the case 6. The support 8 supports the interlocking unit 4 rotatably about the axis AX relative to the case 6. The inner ring 81, which rotates together with the interlocking unit 4, is connected to an output target (not shown). This allows a decelerated output to be obtained via the interlocking unit 4, which is decelerated as described above.

[0045] 3, the interlocking part 4 has insertion parts 40 into which the second transmission parts T2 of the second link mechanism 32 are inserted. The number of insertion parts 40 is the same as the number of second transmission parts T2, and in this embodiment, the insertion parts 40 are formed in the shape of grooves recessed from the outer periphery of the interlocking part 4 toward the axis AX.

[0046] Here, because the link devices 3 deform in response to the rotation of the cam 10, the vectors of the forces imparted from the rotating link devices 3 to the respective second transmission parts T2 do not face uniformly in the circumferential direction, but rather the phase shifts depending on the position of the second transmission parts T2. Furthermore, when the link devices 3 rotate relative to the internal gear 2, the first link mechanisms 31 move while meshing with the internal gear 2, causing radial pulsation in the link devices 3. If no measures are taken to address these issues, unnecessary stress that does not contribute to the torque required to rotate the interlocking part 4 may be generated in the link devices 3, and unnecessary torsional force may be applied.

[0047] In consideration of the above, the insertion portion 40 is formed in a shape that allows circumferential and radial displacement of the second transmission portion T2. ​​Specifically, the circumferential length (groove width) of the insertion portion 40 is greater than the outer diameter of the second transmission portion T2, and the radial length (groove depth) of the insertion portion 40 is also greater than the outer diameter of the second transmission portion T2. ​​This reduces the generation of unnecessary stress in the link device 3 that does not contribute to the rotation of the interlocking portion 4, allowing the interlocking portion 4 to rotate with good transmission efficiency.

[0048] Figure 3, which corresponds to Figure 2, shows the positional relationship between each insertion portion 40 and each second transmission portion T2 when the pole portions of the cam 10 relative to the internal gear 2 are located in the 12 o'clock and 6 o'clock directions as shown in Figure 2. When the second link mechanism 32 of the link device 3 rotates the interlocking portion 4 clockwise in Figure 3, the three second transmission portions T2 located in each of the two transmission positions F, F shown in the dashed-line box push the insertion portion 40 clockwise. On the other hand, when the second link mechanism 32 of the link device 3 rotates the interlocking portion 4 counterclockwise in Figure 3, the three second transmission portions T2 located in each of the two transmission positions G, G shown in the dashed-line box push the insertion portion 40 counterclockwise.

[0049] (Modifications) The present invention is not limited to the above-described embodiment and drawings. Modifications (including the elimination of components) can be made as appropriate within the scope of the present invention. Various modifications in which the configuration of the reducer according to the above-described embodiment is modified are described below. Note that components having the same functions as those in the above-described embodiment are designated by the same reference numerals as those in the above-described embodiment.

[0050] (Variation 1) As shown in FIG. 7 , the link device 3 included in the reducer according to Variation 1 is configured with two first link mechanisms 31 and two second link mechanisms 32. The two first links L1 according to Variation 1 face the cam 10 in the radial direction via two wave bearings 11 and mesh with the internal gear 2. The two second links L2 according to Variation 1 rotate the interlocking unit 4 about the axis line AX. The cross-sectional view of the reducer shown in FIG. 7 , taken along a line perpendicular to the axis line AX, is similar to that shown in FIG. 2 . The cross-sectional view of the reducer shown in FIG. 7 , taken along a line perpendicular to the axis line AX, is similar to that shown in FIG. 3 . In other words, the internal gear 2 according to Variation 1 has a plurality of teeth 2t surrounding one of the two first links L1 and a plurality of teeth 2t surrounding the other. In addition, the interlocking portion 4 in variant example 1 has an insertion portion 40 into which the second transmission portion T2 of one of the two second links L2 is inserted, and an insertion portion 40 into which the second transmission portion T2 of the other second link L2 is inserted.

[0051] In the first modification, the first portion 51 of the spacer 5 is located between one of the two first link mechanisms 31 and the corresponding wave bearing 11. The second portion 52 of the spacer 5 is located between the other of the two first link mechanisms 31 and the corresponding wave bearing 11.

[0052] (Variation 2) As shown in Figure 8, the insertion portion 40 provided in the interlocking portion 4 in Variation 2 may be formed so that the end on the outer periphery of the interlocking portion 4 is closed, and may have the shape of a hole that surrounds the second transmission portion T2 when viewed from the axial direction.

[0053] (Variation 3) As shown in FIG. 9 , the number of second transmission parts T2 included in the second link mechanism 32 of the link device 3 according to Variation 3 is the same as the number of first transmission parts T1 included in the first link mechanism 31. In the link device 3 according to Variation 3, the first shaft S1 of the first link mechanism 31 and the second shaft S2 of the second link mechanism 32 are integrally formed into a common shaft S. FIG. 9 is a diagram corresponding to FIG. 2 and shows the positional relationship between each insertion part 40 and each second transmission part T2 when the pole parts of the cam 10 relative to the internal gear 2 are positioned in the 12 o'clock and 6 o'clock directions as shown in FIG. 2 . When the second link mechanism 32 according to Variation 3 rotates the interlocking part 4 clockwise in FIG. 9 , the three second transmission parts T2 located within each of the two transmission positions H, H enclosed by dashed lines push the insertion part 40 clockwise. On the other hand, when the second link mechanism 32 according to Modification 3 rotates the interlocking unit 4 counterclockwise in Fig. 9, the three second transmission units T2 located within each of the two transmission positions I, I enclosed by dashed lines push the insertion unit 40 counterclockwise. The interlocking unit 4 according to Modification 3 is formed in the shape of an external gear. The tooth gaps located between adjacent teeth of this gear and formed with curved surfaces are the insertion units 40 into which the second transmission units T2 are inserted.

[0054] In addition, the features of the interlocking portion 4 of Modification 2, or the features of the second link mechanism 32 and the interlocking portion 4 of Modification 3 may be applied to the above-mentioned embodiment or to Modification 1.

[0055] 10 , the link device 3 included in the reducer according to Modification 4 is configured to have one first link mechanism 31 and one second link mechanism 32. The first link L1 according to Modification 4 faces the cam 10 in the radial direction via the wave bearing 11, and meshes with the internal gear 2. The second link L2 according to Modification 4 faces the cam 10 in the radial direction via the wave bearing 11, and rotates the interlocking part 4 around the axis line AX.

[0056] The cross-sectional view of the reducer taken along a line perpendicular to the axis AX at the location of the first link L1 shown in FIG. 10 is the same as that shown in FIG. 2 . Meanwhile, a cross-sectional view of the reducer taken along line IV-IV in FIG. 10 is shown in FIG. 11 . The interlocking unit 4 according to the above-described embodiment and Modifications 1 to 3 has a configuration in which a main portion is located on the inner periphery of the second link mechanism 32 (hereinafter, this configuration will be referred to as "inside output"). On the other hand, the interlocking unit 4 according to Modification 4, as shown in FIG. 11 , has a main portion located on the outer periphery of the second link mechanism 32 (hereinafter, this configuration will be referred to as "outside output"). The insertion unit 40 according to Modification 4 is formed in a groove shape recessed from the inner periphery toward the outer periphery of the interlocking unit 4. The configuration of the second link mechanism 32 according to Modification 4 is the same as that of the above-described embodiment.

[0057] Figure 11 is a diagram corresponding to Figure 2 and shows the positional relationship between each insertion portion 40 and each second transmission portion T2 when the pole portions of the cam 10 relative to the internal gear 2 are located in the 12 o'clock and 6 o'clock directions as shown in Figure 2. When the second link mechanism 32 according to Modification 4 rotates the interlocking portion 4 clockwise in Figure 11, the two second transmission portions T2 located in each of the two transmission positions J, J enclosed in dashed lines push the insertion portion 40 clockwise. On the other hand, when the second link mechanism 32 of the link device 3 rotates the interlocking portion 4 counterclockwise in Figure 11, the two second transmission portions T2 located in each of the two transmission positions K, K enclosed in dashed lines push the insertion portion 40 counterclockwise.

[0058] 10 , in Modification 4, the first portion 51 of the spacer 5 is located between the first link mechanism 31 and the wave bearing 11. The second portion 52 of the spacer 5 is located between the second link mechanism 32 and the wave bearing 11. The reducer according to Modification 4 also includes a connecting portion 7 that connects the inner ring 81 of the support portion 8 and the interlocking portion 4. The support portion 8 supports the interlocking portion 4 and the connecting portion 7 so that they can rotate about the axis AX relative to the case 6. Note that the connecting portion 7 may be integral with the interlocking portion 4.

[0059] (Variation 5) Figure 12 is a diagram for explaining the interlocking unit 4 and the second link mechanism 32 according to Variation 5, in which the interlocking unit 4 is an outside output type and can be applied instead of the interlocking unit 4 and the second link mechanism 32 according to Variation 4.

[0060] The number of second transmission parts T2 included in the second link mechanism 32 according to Modification 5 is the same as the number of first transmission parts T1 included in the first link mechanism 31. In the link device 3 according to Modification 5, the first shaft S1 of the first link mechanism 31 and the second shaft S2 of the second link mechanism 32 are integrally formed as a common shaft S. FIG. 12 is a view corresponding to FIG. 2 and shows the positional relationship between each insertion part 40 and each second transmission part T2 when the pole parts of the cam 10 relative to the internal gear 2 are positioned in the 12 o'clock and 6 o'clock directions as shown in FIG. 2. When the second link mechanism 32 according to Modification 5 rotates the interlocking part 4 clockwise in FIG. 12, the three second transmission parts T2 located within each of the two transmission positions P, P enclosed by dashed lines push the insertion part 40 clockwise. On the other hand, when the second link mechanism 32 according to Modification 5 rotates the interlocking unit 4 counterclockwise in Fig. 12, the three second transmission units T2 located within each of the two transmission positions Q, Q enclosed by dashed lines push the insertion unit 40 counterclockwise. The interlocking unit 4 according to Modification 5 is formed in the shape of an internal gear. The tooth gaps located between adjacent teeth of this gear and formed with curved surfaces are the insertion units 40 into which the second transmission units T2 are inserted.

[0061] (Variations 6 and 7) In the above, the case where the number of poles of the cam 10 is N=2 has been described. However, instead of the cam 10 with N=2, a cam 10 with N≧3 may be used. When the number of poles of the cam 10 is N≧3, the shape of the cam 10 as viewed from the axial direction is a regular N-sided polygon, and, for example, each pole portion and the space between adjacent pole portions have a curved surface that bulges gently in the outer diameter direction. Figure 13 shows a cam 10 according to Variation 6 with three poles. Figure 14 shows a cam 10 according to Variation 7 with four poles.

[0062] Although not shown, the number of poles of the cam 10 may be N≧5. Regardless of the number of poles, the cam 10 meshes the first transmission part T1 of the first link mechanism 31 with the internal gear 2 at a position corresponding to the pole part. Even if the number of poles of the cam 10 is N≧3, the interlocking part 4, which rotates together with the second link mechanism 32 of the link device 3, is decelerated with respect to the rotational speed of the cam 10 at a reduction ratio i=(M−m) / m=N / m. Meanwhile, the position at which the second transmission part T2 of the second link mechanism 32 meshes with the insertion part 40 of the interlocking part 4 varies depending on (i) the number of poles of the cam 10, (ii) the number of second transmission parts T2, and (iii) whether the interlocking part 4 is in the inside output mode or the outside output mode.

[0063] (Other Modifications) The link device 3 may be configured with any number of link mechanisms as long as it includes at least one first link mechanism 31 and at least one second link mechanism 32. The number of link mechanisms to be included in the link device 3 may be determined according to the required strength. In addition, (i) the number of first transmission parts T1 and second transmission parts T2, (ii) the number of third transmission parts T3 when a third link mechanism 33 is provided, and (iii) whether the interlocking part 4 is an inside output type or an outside output type may also be determined as required.

[0064] The first to third rollers R1 to R3 may be needle bearings. The first and second rollers R1, R2 may be omitted from the first and second transmission parts T1, T2. In other words, the first transmission part T1 may be a first shaft S1 whose outer periphery is cylindrical, and the second transmission part T2 may be a second shaft S2 whose outer periphery is cylindrical.

[0065] It should be noted that the term "cylindrical surface" naturally includes not only the side surface of a cylinder, but also the side surface of a column, as is commonly used.

[0066] When rollers are omitted as described above, the first shaft S1 of the first link mechanism 31 meshes with the internal gear 2, and the second shaft S2 of the second link mechanism 32 is inserted into the insertion portion 40 of the interlocking portion 4. Note that the third roller R3 may be omitted from the third transmission portion T3. A link device 3 without rollers in this manner can also be considered a bushing chain manufactured with high precision. The resistance between the first transmission portion T1 and the internal gear 2 and the resistance between the second transmission portion T2 / second link mechanism 32 and the interlocking portion 4 is rolling resistance when rollers are used, and sliding resistance when rollers are omitted. The choice of which resistance to use can be determined according to the purpose.

[0067] The material of each part constituting the link device 3 is not limited to metal and may be any material as long as it can obtain the required rigidity. Furthermore, the material of each part constituting the reducer is also any material and may be not limited to metal but may be engineering plastic, resin, ceramic, etc.

[0068] The reducer described above can be used in a wide range of applications from small to large (for example, reducer diameters of 50 mm to 500 mm) and from low reduction ratios to high reduction ratios (for example, 1 / 20 to 1 / 300). This reducer can be applied to various reduction mechanisms used in robots as well as automobiles that require high durability and safety. When used in automobiles, this reducer can be applied to EV (Electric Vehicle) motors, in-wheel motors, etc. Specifically, the reducer has the advantages described in (1) to (5) below, for example.

[0069] (1) Conventional strain wave gearing devices are prone to fatigue failure due to deformation and bending of the flexspline, which limits their ability to handle large torques. On the other hand, the link device 3 of the speed reducer is made of a combination of rigid materials, making it less likely to break even at high speeds and with large torques. Therefore, the speed reducer has good durability and can handle large torque fluctuations, such as those that occur when an EV suddenly starts, accelerates, or decelerates.

[0070] (2) Conventional strain wave gearing devices have been primarily small for the reasons described in (1). On the other hand, the above-described reducer has fewer size restrictions than conventional strain wave gearing devices, and can be made larger, for example, up to a diameter of 500 mm.

[0071] (3) Conventional strain wave gearing devices have large resistance due to deformation and bending of the flexspline, resulting in a reduction efficiency of approximately 50 to 80%, which is lower than other types of differential devices (planetary gears, Cyclo Reducer (registered trademark), etc.). On the other hand, the above-mentioned reducer can reduce this resistance using the link device 3, and can improve reduction efficiency by 20 to 30% compared to conventional strain wave gearing devices, achieving a level equivalent to that of the other types of differential devices.

[0072] (4) Conventional wave gear devices are difficult to use at low reduction ratios, which cause greater deformation of the flexspline and lead to fatigue failure. On the other hand, the above-described reducer equipped with the link device 3 allows for a low reduction ratio of, for example, 1 / 10. Of course, the above-described reducer also allows for a high reduction ratio of, for example, 1 / 300.

[0073] (5) In particular, the speed reducer including the first transmission unit T1 having the first roller R1 and the second transmission unit T2 having the second roller R2 can use the resistance between the first and second transmission units T1, T2 and the objects with which they mesh as rolling resistance. This makes it easy to achieve high strength and high precision with the speed reducer.

[0074] The reducer described above includes the contents described in the following supplementary notes.

[0075] (Notes) (Note 1) A wave generator having a cam that rotates around an axis in response to a rotational input; an internal gear surrounding the cam; a first link mechanism having a plurality of first links configured in a shape that surrounds the outer periphery of the wave generator and positioned between the internal gear and the cam; a second link mechanism having a plurality of second links configured in a shape that surrounds the outer periphery of the wave generator, positioned alongside the first link mechanism in the axial direction that is the direction in which the axis extends and connected to the first link mechanism to rotate together with the first link mechanism around the axis; and an interlocking part that rotates together with the second link mechanism around the axis, wherein the first link mechanism has a first transmission part that can be received in a tooth groove of the internal gear and has an outer periphery in the shape of a cylindrical surface, and the second link mechanism has a second transmission part that can be inserted into an insertion part provided in the interlocking part and has an outer periphery in the shape of a cylindrical surface, and a plurality of first transmission parts are arranged along the outer periphery of the wave generator, and a plurality of second transmission parts are arranged along the outer periphery of the wave generator, a reduction gear, wherein the cam has a plurality of pole portions positioned at equal intervals in a circumferential direction around the axis, and meshes the first transmission portion with the internal gear at positions corresponding to the pole portions; the number of the first transmission portions is smaller than the number of teeth of the internal gear; the wave generator generates relative rotation between the internal gear and the first link mechanism in accordance with the difference between the number of teeth of the internal gear and the number of the first transmission portions; and the number of the second transmission portions is the same as or smaller than the number of the first transmission portions.

[0076] (Supplementary Note 2) The reducer according to Supplementary Note 1, wherein the first transmission unit has a first shaft extending in the axial direction, the second transmission unit has a second shaft extending in the axial direction, the first shaft includes a common shaft that is integral with the second shaft, and the first link mechanism and the second link mechanism are connected by the common shaft.

[0077] (Supplementary Note 3) The reducer according to Supplementary Note 2, wherein the first transmission part has a first roller that rotates relative to the first shaft and forms an outer periphery of the first transmission part, and the second transmission part has a second roller that rotates relative to the second shaft and forms an outer periphery of the second transmission part.

[0078] (Supplementary Note 4) The reducer according to any one of Supplementary Notes 1 to 3, wherein the insertion portions allow displacement of the second transmission portion in the circumferential direction and in the radial direction about the axis, and the number of the insertion portions is the same as the number of the second transmission portions.

[0079] (Supplementary Note 5) The reducer according to any one of Supplementary Notes 1 to 4, wherein there are a plurality of at least one of the first link mechanisms and the second link mechanisms, and the reducer includes the first link mechanisms and the second link mechanisms adjacent to each other in the axial direction.

[0080] (Supplementary Note 6) The reducer according to any one of Supplementary Notes 1 to 4, further comprising a third link mechanism located between the first link mechanism and the second link mechanism in the axial direction, the third link mechanism having a plurality of third links configured in a shape surrounding an outer periphery of the wave generator, and connected to the first link mechanism and the second link mechanism to rotate together with the first link mechanism and the second link mechanism about the axis.

[0081] (Supplementary Note 7) The reducer according to any one of Supplementary Notes 1 to 6, further comprising a spacer positioned between the first link mechanism and the wave generator, the spacer applying a radial preload about the axis to each of the first link mechanism and the wave generator.

[0082] (Supplementary Note 8) The reducer according to Supplementary Note 7, wherein the spacer is provided between the first link and the wave generator.

[0083] (Supplementary Note 9) The reducer according to Supplementary Note 8, wherein the spacer has a groove into which the first link fits and a recess into which an outer peripheral end of the wave generator fits.

[0084] In the above description, in order to facilitate understanding of the present invention, descriptions of well-known technical matters have been omitted as appropriate.

[0085] This invention allows various embodiments and modifications without departing from the broad spirit and scope of this invention. Furthermore, the above-described embodiments are intended to explain this invention and do not limit the scope of this invention. That is, the scope of this invention is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and the meaning of the invention equivalent thereto are considered to be within the scope of this invention.

[0086] This application is based on Japanese Patent Application No. 2023-197191, filed on November 21, 2023. The entire specification, claims, and drawings of Japanese Patent Application No. 2023-197191 are incorporated herein by reference.

[0087] REFERENCE SIGNS LIST 1...wave generator 10...cam, 10a...cylindrical shaft, 11...wave bearing 2...internal gear, 2t...tooth, 2g...tooth space 3...link device 31...first link mechanism L1...first link T1...first transmission section, S1...first shaft, R1...first roller 32...second link mechanism T2...second transmission section, S2...second shaft, R2...second roller 33...third link mechanism T3...third transmission section, S3...third shaft, R3...first roller S...common shaft 4...interlocking section, 40...insertion section 5...spacer, D1 to D3...groove 51...first portion, 51a...recess 52...second portion, 52a...recess 6...case, 7...connecting section 8...support section B1, B2...bearing E...engagement position F, G, H, I, J, K, P, Q...transmission position

Claims

a first link mechanism having a plurality of first links configured to surround the outer periphery of the wave generator and positioned between the internal gear and the cam; a second link mechanism having a plurality of second links configured to surround the outer periphery of the wave generator, positioned alongside the first link mechanism in the axial direction in which the axis extends and connected to the first link mechanism to rotate together with the first link mechanism around the axis; and an interlocking portion which rotates together with the second link mechanism around the axis, wherein the first link mechanism has a first transmission portion capable of being received in a tooth groove of the internal gear and having an outer periphery in the shape of a cylindrical surface; the second link mechanism has a second transmission portion capable of being inserted into an insertion portion provided in the interlocking portion and having an outer periphery in the shape of a cylindrical surface; a first transmission part for engaging with the internal gear at a position corresponding to the first pole part; a number of the first transmission parts for engaging with the internal gear at a position corresponding to the first pole part; a number of the first transmission parts for engaging with the internal gear at a position corresponding to the first pole part; a number of the first transmission parts for engaging with the internal gear at a position corresponding to the first pole part; a number of the first transmission parts for engaging with the internal gear at a position corresponding to the first pole part; a number of the second transmission parts for engaging with the internal gear at a position corresponding to the first pole part; 2. A reducer as described in claim 1, wherein the first transmission part has a first shaft extending in the axial direction, the second transmission part has a second shaft extending in the axial direction, the first shaft includes a common shaft integral with the second shaft, and the first link mechanism and the second link mechanism are connected by the common shaft.

3. A reducer as described in claim 2, wherein the first transmission part has a first roller that rotates relative to the first shaft and forms the outer periphery of the first transmission part, and the second transmission part has a second roller that rotates relative to the second shaft and forms the outer periphery of the second transmission part.

4. A reducer as claimed in claim 1, wherein the insertion sections allow displacement of the second transmission section in the circumferential direction and in the radial direction about the axis, and the number of the insertion sections is the same as the number of the second transmission sections.

5. The reducer according to claim 1, wherein there are a plurality of at least one of the first link mechanisms and the second link mechanisms, and the reducer includes the first link mechanisms and the second link mechanisms adjacent to each other in the axial direction.

6. The reducer according to claim 1, further comprising a third link mechanism located between the first link mechanism and the second link mechanism in the axial direction, the third link mechanism having a plurality of third links configured in a shape surrounding the outer periphery of the wave generator, and connected to the first link mechanism and the second link mechanism to rotate about the axis together with the first link mechanism and the second link mechanism.

7. A reducer according to any one of claims 1 to 6, further comprising a spacer positioned between said first link mechanism and said wave generator, for applying a radial preload about said axis to each of said first link mechanism and said wave generator.

8. The reducer according to claim 7, wherein the spacer is provided between the first link and the wave generator.

9. The reducer according to claim 8, wherein the spacer has a groove into which the first link fits, and a recess into which the outer peripheral end of the wave generator fits.

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