Reduction gear

Abstract

To provide a reduction gear with high durability.SOLUTION: A reduction gear includes: a wave generator 1 having 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 section 4 that rotates together with the second link mechanism 32. The first link mechanism 31 has a first transmission section which can fit in a tooth groove of the internal gear 2. The second link mechanism 32 has a second transmission section which can be inserted into an insertion portion provided in the interlocking section 4. A plurality of the first and second transmission sections are arranged along an outer periphery of the wave generator 1. A cam 10 makes the first transmission section engaged with the internal gear 2 at a position corresponding to a pole section. The number of the first transmission sections is smaller than the tooth number of the internal gear 2. The number of the second transmission sections is the same as the number of the first transmission sections or smaller than the number of the first transmission sections.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a speed reducer.

Background Art

[0002] As a speed reducer, there is, for example, a harmonic gear device described in Patent Document 1. The harmonic gear device includes a circular spline which is a rigid internal gear, a flex spline which is a flexible external gear, and a wave generator having an elliptical cam. The wave generator bends the flex spline with the cam and meshes it with the circular spline, thereby generating a relative rotation between the two splines according to the difference in the number of teeth of the two splines. By utilizing this relative rotation, an output can be obtained from the flex spline that rotates at a speed lower than the rotation of the cam.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since the flex spline of the harmonic gear device is composed of a thin-walled cup-shaped metal elastic body to ensure flexibility, there is a risk of breakage when a large torque is applied. In this regard, the harmonic gear device has a problem of durability.

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

Means for Solving the Problems

[0006] To achieve the above object, the speed reducer according to the present invention has a wave generator having a cam that rotates about an axis in response to a rotational input, an internal gear surrounding the cam, It has a plurality of first links configured in a shape surrounding the outer periphery of the wave generator, a first link mechanism positioned between the internal gear and the cam, It has a plurality of second links configured in a shape surrounding the outer periphery of the wave generator, is positioned side by side with the first link mechanism in the axial direction which is the direction in which the axis extends, and is a second link mechanism that is connected to the first link mechanism and rotates about the axis together with the first link mechanism, It includes an interlocking part that rotates about the axis together with the second link mechanism. The first link mechanism has a first transmission part that can fit into the tooth groove of the internal gear and has a cylindrical outer peripheral surface. The second link mechanism has a second transmission part that can be inserted into an insertion part provided in the interlocking part and has a cylindrical outer peripheral surface. The plurality of first transmission parts are arranged along the outer periphery of the wave generator. The plurality of second transmission parts are arranged along the outer periphery of the wave generator. The cam has a plurality of pole parts that are equally spaced in the circumferential direction about the axis, and meshes the first transmission part with the internal gear at positions corresponding to the pole parts. The number of the first transmission parts 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 the first transmission parts. The number of the second transmission parts is the same as the number of the first transmission parts or less than the number of the first transmission parts.

Advantages of the Invention

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

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Figure 10

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Mode for Carrying Out the Invention

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

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

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

[0012] The cam 10 and the cylindrical shaft 10a rotate about the axis AX in response to a rotational input. The rotational power of a motor (not shown) is transmitted to the cylindrical shaft 10a via a known transmission mechanism. An annular bearing B1 is interposed between a portion of the cylindrical shaft 10a on the input side of the cam 10 and the case 6. An annular bearing B2 is interposed between a portion of the cylindrical shaft 10a on the output side of the cam 10 and the interlocking part 4. Thereby, the cam 10 and the cylindrical shaft 10a are rotatable with respect to the case 6. The bearings B1 and B2 are composed of, 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 parts that are equally spaced in the circumferential direction centered on the axis AX (hereinafter, also simply referred to as the "circumferential direction"). In the following, the number of pole parts of the cam 10 is referred to as the number of poles. For example, when the number of poles is N = 2, the cam 10 has an elliptical shape as viewed from 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 peripheral surface of the cam 10, a flexible outer ring, and a plurality of balls inserted between the inner ring and the outer ring in a rollable state. The outer ring of the wave bearing 11 is elastically deformed via the balls. Note that the inner ring may be composed of a portion including the outer peripheral surface of the cam 10. In the present embodiment, two wave bearings 11 are provided adjacent to each other in the axial direction. Among the two wave bearings 11, the wave bearing 11 located on the input side is surrounded by the first link mechanism 31 described later, and the wave bearing 11 located on the output side is surrounded by the third link mechanism 33 described later.

[0015] The internal gear 2 is formed with rigidity by metal and fixed to the case 6. As shown in FIG. 2, the internal gear 2 has a ring shape surrounding the cam 10 and has a plurality of teeth 2t arranged along the circumferential direction at a constant pitch on its inner circumference. Hereinafter, the groove formed between adjacent teeth 2t is referred to as a tooth groove 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 the radial direction centered on the axis AX (hereinafter, also simply referred to as the "radial direction"). The second link mechanism 32 faces the interlocking portion 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 Fig. 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 a plurality of first links L1, and they are configured in a shape that surrounds the outer periphery of the wave generator 1 by being sequentially coupled. Specifically, the first link L1 surrounds the outer ring of the wave bearing 11. The first transmission part T1 can fit into the tooth groove 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 part T1 has a first shaft S1 extending in the axial direction and a first roller R1 rotating with respect to the first shaft S1. The first shaft S1 is a columnar member formed of a rigid material such as metal, and functions as a joint that couples adjacent ones of the plurality of first links L1. The first roller R1 is a cylindrical member formed of a rigid material such as metal, and its hollow part is supported by the first shaft S1. The first roller R1 constitutes the outer periphery of the first transmission part T1.

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

[0021] Among 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, among 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] As shown in Fig. 2, the first transmission part T1 is arranged in a plurality 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 part T1 (that is, the arrangement pitch of the first shaft S1) is set evenly.

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

[0024] As shown in Fig. 2, the second link mechanism 32 has a second link L2 and a second transmission part T2. There are a plurality of second links L2, and they are configured in a shape surrounding the outer periphery of the wave generator 1 by being sequentially coupled. The second link L2 of this embodiment surrounds a part on the output side of the cam 10 among the cylindrical shafts 10a. The second transmission part T2 can be inserted into an insertion part 40 of the interlocking part 4 described later, and its outer periphery has the shape of a cylindrical surface.

[0025] Specifically, as shown in Fig. 4, the second transmission part T2 has a second shaft S2 extending in the axial direction and a second roller R2 rotating with respect to the second shaft S2. In this embodiment, as will be described later, due to the relationship between the number of the second transmission parts T2 and the number of the first transmission parts T1, the second link mechanism 32 also has a second shaft S2 that does not support the second roller R2. The second shaft S2 is a columnar member formed of a rigid material such as metal, and functions as a joint that couples adjacent ones among the plurality of second links L2. The second roller R2 is a cylindrical member formed of a rigid material such as metal, and its hollow part is supported by the second shaft S2. The second roller R2 constitutes the outer periphery of the second transmission part T2.

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

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

[0028] As shown in FIG. 3, the second transmission parts T2 are arranged in a plurality along the outer periphery of the wave generator 1 in a state where the link device 3 surrounds the outer periphery of the wave generator 1. The arrangement pitch of the second transmission parts T2 (that is, the arrangement pitch of the second shafts S2) is set evenly.

[0029] In the present embodiment, the number of the second transmission parts T2 is less than the number of the first transmission parts T1. Specifically, as can be seen by comparing FIG. 2 and FIG. 3, the arrangement of the second transmission parts T2 corresponds to a mode in which the first transmission parts T1 are arranged skipping one. That is, FIG. 3 is an example where there are 20 second transmission parts T2.

[0030] Among the second link mechanisms 32, the second shaft S2 (that is, the second shaft S2 that supports the second roller R2) that the second transmission part T2 has is integral with the first shaft S1 of the first link mechanism 31 and constitutes a common shaft S. That is, the first shaft S1 includes the 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 one of the two wave bearings 11 located on the output side. As shown in FIGS. 4 and 5, the third link mechanism 33 includes a third link L3 and a third transmission portion T3. The third transmission portion T3 includes a third shaft S3 extending in the axial direction and a third roller R3 rotating with respect 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 the third transmission portions T3 is the same as the number of the first transmission portions T1. In this embodiment, all of the third shafts S3 are integral with the first shaft S1. Further, in this embodiment, the common shaft S is integrally formed not only with the first shaft S1 and the second shaft S2 but also with the third shaft S3.

[0032] Here, the first transmission portion T1 is configured to transmit the force applied to the first link mechanism 31 to the internal gear 2. The second transmission portion T2 is configured to transmit the force applied to the second link mechanism 32 to the interlocking portion 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 portion T3 does not transmit force to any object. Therefore, the third roller R3 may be omitted from the third link mechanism 33. Similar to the first link mechanism 31, a configuration in which the internal gear 2 is also meshed with the third link mechanism 33 can 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 in which the pitch between joints, the diameters of the first to third transmission portions T1 to T3, etc. are manufactured with high precision. As shown in FIG. 4, in the link device 3, the joint positions of the first to third links L1 to L3 are regularly arranged and coincide with each other along the circumferential direction. For this reason, the first to third link mechanisms 31 to 33 constituting the link device 3 can be deformed into similar shapes when viewed from the axial direction.

[0034] The cam 10 meshes the first transmission part T1 with the internal gear 2 at a position corresponding to the pole part. Fig. 2 shows an example in which four first transmission parts T1 located in each of two meshing positions E, E shown by a dashed line enclosure are fitted into the tooth grooves 2g of the internal gear 2 and are meshing with the internal gear 2.

[0035] When the cam 10 rotates, the first link mechanism 31 and the third link mechanism 33 are deformed according 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 is deformed in the same way. Then, according to the rotation of the cam 10, the meshing position E between the internal gear 2 and the first transmission part T1 sequentially moves. And during one rotation of the cam 10, the first link mechanism 31 moves in the rotation direction opposite to that of the cam 10 by an amount equal to the difference (M - m = N) between the number of teeth of the internal gear 2 and the number of the first transmission parts T1. Since the third link mechanism 33 and the second link mechanism 32 are connected to the first link mechanism 31, that is, during one rotation of the cam 10, the entire link device 3 moves in the rotation direction opposite to that of the cam 10 as described above. Thereby, as will be described later, the interlocking part 4 that rotates together with the second link mechanism 32 of the link device 3 is decelerated at a reduction ratio i = (M - m) / m = N / m with respect to the rotation speed of the cam 10.

[0036] Based on the above principle, the wave generator 1 generates relative rotation between the internal gear 2 and the first link mechanism 31 according to the difference between the number of teeth of the internal gear 2 and the number of the first transmission parts T1. Thus, although the differential principle using the wave generator 1 is the same as that of the wave gear device, in the speed reducer according to the present embodiment, instead of the flexible thin film flex spline, a link device 3 composed of a combination of rigid materials is used, which is completely different from the conventional device.

[0037] Although the link device 3 is deformed according to the rotation of the cam 10, since it is composed of a combination of rigid materials, there is a possibility of generating a gap between the outer periphery of the wave generator 1. In order to fill this gap, a spacer 5 is provided in the speed reducer according to the present embodiment.

[0038] The spacer 5 is provided between the link device 3 and the cam 10 as shown in FIG. 1 and is located on the outer peripheral side of the wave bearing 11 as shown in FIGS. 1 and 4. That is, the spacer 5 according to the present 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. The spacer 5 is a plate-like member extending in the axial direction as shown in FIG. 5 and is composed of, for example, metal formed by machining. An electrodeposited grinding wheel, a resin lining, or any other optional coating may be applied to the surface of the spacer 5.

[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 FIG. 6, the first portion 51 has a recess 51a into which the outer peripheral end of the wave generator 1 (that is, 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 FIG. 6, the second portion 52 has a recess 52a into which the outer peripheral end of the wave generator 1 (that is, the outer ring of the wave bearing 11) fits. The recess 52a is formed on the side of the second portion 52 facing the wave generator 1.

[0041] As shown in FIGS. 5 and 6, the spacer 5 is provided with grooves D1, D2, and D3 in order from the input side. The grooves D1, D2, and D3 extend in the width direction (the short side direction of the spacer 5) of the spacer 5 that is long in the axial direction. (i) As shown in FIG. 6, when the input sides of the pair of inner plates constituting the first link L1 are fitted into the groove D1, the output sides of the pair of inner plates constituting the first link L1 (the same as the input sides of the pair of outer plates constituting the third link L3) are fitted into the groove D2, and the output sides of the pair of outer plates constituting the third link L3 (the same as the input sides of the pair of inner plates constituting the second link L2) are fitted into the groove D3. (ii) Although not shown, when the input sides of the pair of outer plates constituting the first link L1 are fitted into the groove D1, the output sides of the pair of outer plates constituting the first link L1 (the same as the input sides of the pair of inner plates constituting the third link L3) are fitted into the groove D2, and the output sides of the pair of inner plates constituting the third link L3 (the same as the input sides of the pair of outer plates constituting the second link L2) are fitted into the groove D3. Dents are provided on the inner circumferential sides of each of the first to third links L1 to L3, and these dented portions are fitted into the grooves D1, D2, and D3 according to the rules of (i) and (ii) above.

[0042] The first portion 51 of the spacer 5 is provided between each of the plurality of first links L1 and the wave generator 1. The second portion 52 of the spacer 5 is provided between each of the plurality of third links L3 and the wave generator 1. That is, the number of spacers 5 provided is the same as the number of the first link L1 and the third link L3.

[0043] With the spacer 5 provided as described above, the fitting between the outer ring of the wave bearing 11 and the link device 3 can be strengthened. Further, by providing the spacer 5 with a preloading function, it is possible to adjust or absorb errors and deformations that may occur in at least either the link device 3 or the wave bearing 11 due to wear or the like caused by long-term use. Further, the grooves D1 to D3 and the depressions 51a and 52a of the spacer 5 can suppress the spacer 5 from coming off between the link device 3 and the wave generator 1, and can also suppress the relative position of the link device 3 and the wave generator 1 from shifting in the axial direction.

[0044] The interlocking part 4 rotates about the axis AX together with the second link mechanism 32. The interlocking part 4 has a main part on the inner peripheral 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 part 4 is supported by the case 6 via the support part 8. The support part 8 is composed of, for example, a cross roller bearing, and includes an inner ring 81 fixed to the interlocking part 4 and an outer ring 82 fixed to the case 6. By the support part 8, the interlocking part 4 is rotatably supported with respect to the case 6 about the axis AX. The inner ring 81 that rotates together with the interlocking part 4 is connected to an output target (not shown). Thereby, a decelerated output can be obtained through the interlocking part 4 decelerated as described above.

[0045] As shown in FIG. 3, the interlocking part 4 has an insertion part 40 into which the second transmission part T2 of the second link mechanism 32 is inserted. The number of the insertion parts 40 is the same as that of the second transmission parts T2. In the present embodiment, the insertion parts 40 are formed in groove shapes that are recessed from the outer periphery of the interlocking part 4 toward the axis AX.

[0046] Here, since the link device 3 deforms in response to the rotation of the cam 10, the vectors of the forces applied from the rotating link device 3 to each of the second transmission parts T2 do not uniformly point in the circumferential direction, and a phase shift occurs according to the position of the second transmission part T2. Further, when the link device 3 rotates relative to the internal gear 2, since the first link mechanism 31 moves while meshing with the internal gear 2, a radial pulsation occurs in the link device 3. If no countermeasures are taken against these events, useless stress that does not contribute to the torque for rotating the interlocking part 4 may occur in the link device 3, and a useless torsional force may be applied.

[0047] Based on the above events, the insertion part 40 is formed in a shape that allows displacement in the circumferential direction and the radial direction of the second transmission part T2. Specifically, the insertion part 40 has a length (groove width) in the circumferential direction that is larger than the outer diameter of the second transmission part T2, and a length (groove depth) in the radial direction that is larger than the outer diameter of the second transmission part T2. Thereby, it is possible to reduce the occurrence of useless stress in the link device 3 that does not contribute to the rotation of the interlocking part 4, and to rotate the interlocking part 4 with good transmission efficiency.

[0048] FIG. 3 is a diagram corresponding to FIG. 2, and shows the positional relationship between each insertion part 40 and each second transmission part T2 in a state where the extreme parts of the cam 10 with respect to the internal gear 2 are located in the 12 o'clock direction and the 6 o'clock direction as in FIG. 2. When the second link mechanism 32 of the link device 3 rotates the interlocking part 4 in the clockwise direction in FIG. 3, the three second transmission parts T2 located in each of the two transmission positions F, F indicated by the dashed line enclosures push the insertion part 40 in the clockwise direction. On the other hand, when the second link mechanism 32 of the link device 3 rotates the interlocking part 4 in the counterclockwise direction in FIG. 3, the three second transmission parts T2 located in each of the two transmission positions G, G indicated by the dashed line enclosures push the insertion part 40 in the counterclockwise direction.

[0049] (Modification example) The present invention is not limited to the above embodiments and drawings. Within the scope of not changing the gist of the present invention, modifications (including deletion of components) can be appropriately made. Various modifications of a part of the configuration of the speed reducer according to the above embodiment will be described below. Note that, for configurations having the same functions as those in the above embodiment, the same reference numerals as those in the above embodiment are used.

[0050] (Modification Example 1) As shown in FIG. 7, the link device 3 included in the speed reducer according to Modification Example 1 is configured to include two first link mechanisms 31 and two second link mechanisms 32. The two first links L1 according to Modification Example 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 Modification Example 1 rotate the interlocking portion 4 about the axis AX. The cross-sectional view of the speed reducer obtained by cutting each location of the two first links L1 shown in FIG. 7 with a line perpendicular to the axis AX is the same as FIG. 2. Also, the cross-sectional view of the speed reducer obtained by cutting each location of the two second links L2 shown in FIG. 7 with a line perpendicular to the axis AX is the same as FIG. 3. That is, the internal gear 2 according to Modification Example 1 has a plurality of teeth 2t surrounding one of the two first links L1 and a plurality of teeth 2t surrounding the other. Further, the interlocking portion 4 according to Modification 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 is inserted.

[0051] In Modification Example 1, the first portion 51 of the spacer 5 is located between one of the two first link mechanisms 31 and the wave bearing 11 corresponding to the one. The second portion 52 of the spacer 5 is located between the other of the two first link mechanisms 31 and the wave bearing 11 corresponding to the other.

[0052] (Modification Example 2) As shown in FIG. 8, the insertion portion 40 provided in the interlocking portion 4 according to Modification Example 2 may be formed such that the end on the outer peripheral side of the interlocking portion 4 closes, and has a shape of a hole surrounding the second transmission portion T2 when viewed from the axial direction.

[0053] (Modification Example 3) As shown in Fig. 9, the number of second transmission parts T2 of the second link mechanism 32 of the link device 3 according to Modification 3 is the same as the number of first transmission parts T1 of the first link mechanism 31. In the link device 3 according to Modification 3, the first shaft S1 of the first link mechanism 31 and the second shaft S2 of the second link mechanism 32 integrally form a common shaft S. Fig. 9 is a figure corresponding to Fig. 2, and shows the positional relationship between each insertion part 40 and each second transmission part T2 in a state where the extreme parts of the cam 10 with respect to the internal gear 2 are located in the 12 o'clock direction and the 6 o'clock direction as shown in Fig. 2. When the second link mechanism 32 according to Modification 3 rotates the interlocking part 4 in the clockwise direction in Fig. 9, the three second transmission parts T2 located in each of the two transmission positions H, H indicated by the dashed line enclosures push the insertion part 40 in the clockwise direction. On the other hand, when the second link mechanism 32 according to Modification 3 rotates the interlocking part 4 in the counterclockwise direction in Fig. 9, the three second transmission parts T2 located in each of the two transmission positions I, I indicated by the dashed line enclosures push the insertion part 40 in the counterclockwise direction. Further, the interlocking part 4 according to Modification 3 is formed in the shape of an external gear. The tooth groove formed by a curved surface and located between adjacent teeth in this gear is the insertion part 40 into which the second transmission part T2 is inserted.

[0054] Note that the features of the interlocking part 4 of Modification 2, or the features of the second link mechanism 32 and the interlocking part 4 of Modification 3, may be applied to the foregoing embodiment, or may be applied to Modification 1.

[0055] (Modification 4) As shown in Fig. 10, the link device 3 provided in the speed reducer according to Modification 4 is configured to include 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 about the axis AX.

[0056] The cross-sectional view of the speed reducer obtained by cutting the portion of the first link L1 shown in FIG. 10 with a line orthogonal to the axis AX is the same as FIG. 2. On the other hand, the cross-sectional view of the speed reducer along the line IV-IV shown in FIG. 10 is shown in FIG. 11. The interlocking part 4 according to the above-described embodiment and Modifications 1 to 3 had a mode in which the main part was on the inner peripheral side of the second link mechanism 32 (hereinafter, this mode is referred to as "inside output"). On the other hand, as shown in FIG. 11, the interlocking part 4 according to Modification 4 has a mode in which the main part is on the outer peripheral side of the second link mechanism 32 (hereinafter, this mode is referred to as "outside output"). In the insertion part 40 according to Modification 4, it is formed in a groove shape that is recessed from the inner periphery to the outer periphery of the interlocking part 4. The configuration of the second link mechanism 32 according to Modification 4 is the same as that of the above-described embodiment.

[0057] FIG. 11 is a diagram corresponding to FIG. 2, and shows the positional relationship between each insertion part 40 and each second transmission part T2 in a state where the pole parts of the cam 10 with respect to the internal gear 2 are located in the 12 o'clock direction and the 6 o'clock direction as shown in FIG. 2. When the second link mechanism 32 according to Modification 4 rotates the interlocking part 4 in the clockwise direction in FIG. 11, the two second transmission parts T2 located in each of the two transmission positions J and J indicated by the dashed-line enclosure push the insertion part 40 in the clockwise direction. On the other hand, when the second link mechanism 32 of the link device 3 rotates the interlocking part 4 in the counterclockwise direction in FIG. 11, the two second transmission parts T2 located in each of the two transmission positions K and K indicated by the dashed-line enclosure push the insertion part 40 in the counterclockwise direction.

[0058] As shown in FIG. 10, in Modification 4, the first part 51 of the spacer 5 is located between the first link mechanism 31 and the wave bearing 11. The second part 52 of the spacer 5 is located between the second link mechanism 32 and the wave bearing 11. Further, the speed reducer according to Modification 4 includes a connecting part 7 that connects the inner ring 81 of the support part 8 and the interlocking part 4. By the support part 8, the interlocking part 4 and the connecting part 7 are rotatably supported with respect to the case 6 about the axis AX. Note that the connecting part 7 may be integral with the interlocking part 4.

[0059] (Modification 5) FIG. 12 is a diagram for explaining the interlocking part 4 and the second link mechanism 32 according to Modification 5, which can be applied instead of the interlocking part 4 and the second link mechanism 32 according to Modification 4, where the interlocking part 4 is in the outside output mode.

[0060] The number of the second transmission parts T2 of the second link mechanism 32 according to Modification 5 is the same as the number of the first transmission parts T1 of 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 form an integral common shaft S. FIG. 12 is a diagram corresponding to FIG. 2, showing the positional relationship between each insertion part 40 and each second transmission part T2 in a state where the extreme parts of the cam 10 with respect to the internal gear 2 are located in the 12 o'clock direction and the 6 o'clock direction as shown in FIG. 2. When the second link mechanism 32 according to Modification 5 rotates the interlocking part 4 in the clockwise direction in FIG. 12, the three second transmission parts T2 located in each of the two transmission positions P, P shown by the dashed-line enclosures push the insertion part 40 in the clockwise direction. On the other hand, when the second link mechanism 32 according to Modification 5 rotates the interlocking part 4 in the counterclockwise direction in FIG. 12, the three second transmission parts T2 located in each of the two transmission positions Q, Q shown by the dashed-line enclosures push the insertion part 40 in the counterclockwise direction. Further, the interlocking part 4 according to Modification 5 is formed in an internal gear shape. The tooth groove formed by a curved surface and located between adjacent teeth in this gear is the insertion part 40 into which the second transmission part T2 is inserted.

[0061] (Modifications 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 viewed from the axial direction forms a regular N-sided shape, and for example, each extreme part and the surface between adjacent extreme parts have a gently bulging shape in the outer diameter direction. FIG. 13 shows the cam 10 according to Modification 6 with 3 poles. FIG. 14 shows the cam 10 according to Modification 7 with 4 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 that rotates together with the second link mechanism 32 of the link device 3 is decelerated at a reduction ratio of i = (M - m) / m = N / m with respect to the rotational speed of the cam 10. On the other hand, the position where the second transmission part T2 of the second link mechanism 32 meshes with the insertion part 40 of the interlocking part 4 changes according to (i) the number of poles of the cam 10, (ii) the number of the second transmission parts T2, and (iii) whether the interlocking part 4 is in an inside output mode or an outside output mode.

[0063] (Other modification examples) The link device 3 may be composed of 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 constituting the link device 3 may be determined according to the required strength. Moreover, (i) the number of the first transmission part T1 and the second transmission part T2, (ii) the number of the third transmission part T3 when the third link mechanism 33 is provided, and (iii) whether the interlocking part 4 is in an inside output mode or an outside output mode are also arbitrary according to the requirements.

[0064] Note that the first to third rollers R1 to R3 may be needle bearings. Also, the first and second rollers R1 and R2 may be omitted from the first and second transmission parts T1 and T2. That is, the first transmission part T1 may be a first shaft S1 whose outer periphery has a cylindrical surface shape, and the second transmission part T2 may be a second shaft S2 whose outer periphery has a cylindrical surface shape.

[0065] Note that the term "cylindrical surface" includes not only the side surface of a cylinder but also the side surface of a circular column as per the generally used meaning.

[0066] When the roller is 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. Incidentally, the third roller R3 may be omitted from the third transmission portion T3. The link device 3 with the roller omitted in this way can be said to be a bush chain manufactured with high precision. Regarding the resistance between the first transmission portion T1 and the internal gear 2 and the resistance between the second transmission portion T2, the second link mechanism 32, and the interlocking portion 4, it is rolling resistance when a roller is used, and sliding resistance when the roller is omitted. Which one to select may be determined according to the purpose.

[0067] Regarding the materials of the respective parts constituting the link mechanism 3, as long as the necessary rigidity can be obtained, it is not limited to metal and is arbitrary. Moreover, the materials of the respective parts constituting the speed reducer are also arbitrary and are not limited to metal, and may be engineering plastics, resins, ceramics, etc.

[0068] The speed reducer described above can handle from small to large sizes (for example, the diameter of the speed reducer is 50 mm to 500 mm), and can handle from low reduction ratios to high reduction ratios (for example, 1 / 20 to 1 / 300). This speed reducer is applicable to various speed reduction mechanisms used not only in robots but also in automobiles that require high durability and high safety. When this speed reducer is used in an automobile, it is applicable to an EV (Electric Vehicle) motor, an in-wheel motor, etc. Specifically, the above speed reducer has, for example, the advantages described in the following (1) to (5).

[0069] (1) In the conventional harmonic gear device, since fatigue failure is likely to occur due to deformation and deflection of the flexspline, there is a limit to large torque. On the other hand, since the link device 3 included in the above speed reducer is composed of a combination of rigid materials, it is difficult to break even at high speed and with large torque. Therefore, the above speed reducer has good durability and can handle, for example, large fluctuating torques such as sudden acceleration and sudden deceleration of an EV.

[0070] (2)Conventional harmonic gear devices were mainly small in size for the reasons described in (1). On the other hand, the speed reducer has fewer size restrictions compared to conventional harmonic gear devices, and can be enlarged, for example, to a diameter of 500 mm.

[0071] (3)In a conventional harmonic gear device, the resistance due to the deformation and deflection of the flexspline is large, and the deceleration efficiency is about 50 - 80%, which is lower than that of other types of differential devices (such as planetary gears, cycloidal speed reducers (registered trademarks), etc.). On the other hand, the above speed reducer can reduce the said resistance by the link device 3, can improve the deceleration efficiency by 20% - 30% compared to the conventional harmonic gear device, and can achieve a level equivalent to that of the said other types of differential devices.

[0072] (4)Using a conventional harmonic gear device at a low reduction ratio where the deformation of the flexspline becomes larger is difficult because it is a factor of fatigue failure. On the other hand, according to the above speed reducer equipped with the link device 3, a low reduction ratio such as 1 / 10 is possible. Of course, the above speed reducer can also achieve a high reduction ratio such as 1 / 300.

[0073] (5)In particular, according to the above speed reducer provided with the first transmission part T1 having the first roller R1 and the second transmission part T2 having the second roller R2, the resistance between the first and second transmission parts T1, T2 and the object with which they mesh can be made into rolling resistance. Thereby, according to the above speed reducer, it is easy to achieve high strength and high precision.

[0074] The speed reducer described above includes the content described in the following supplementary note.

[0075] (Supplementary Note) (Supplementary Note 1) A wave generator having a cam that rotates about 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 surrounding the outer periphery of the wave generator and located between the internal gear and the cam, It has a plurality of second links configured in a shape surrounding the outer periphery of the wave generator, is positioned side by side with the first link mechanism in the axial direction which is the direction in which the axis extends, and is connected to the first link mechanism to rotate about the axis together with the first link mechanism, and includes an interlocking part that rotates about the axis together with the second link mechanism. The first link mechanism has a first transmission part that can fit into the tooth groove of the internal gear and has an outer periphery in the shape of a cylindrical surface. 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. A plurality of the first transmission parts are arranged along the outer periphery of the wave generator. A plurality of the second transmission parts are arranged along the outer periphery of the wave generator. The cam has a plurality of pole parts that are equally spaced in the circumferential direction about the axis, and meshes the first transmission part with the internal gear at a position corresponding to the pole part. The number of the first transmission parts 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 the first transmission parts. The number of the second transmission parts is the same as the number of the first transmission parts or less than the number of the first transmission parts. Reducer.

[0076] (Appendix 2) 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 that is integral with the second shaft. The first link mechanism and the second link mechanism are connected by the common shaft. The reducer according to Appendix 1.

[0077] (Appendix 3) The first transmission part rotates with respect to the first shaft and has a first roller that constitutes the outer periphery of the first transmission part. The second transmission part rotates with respect to the second shaft and has a second roller that constitutes the outer periphery of the second transmission part. The speed reducer according to Supplementary Note 2.

[0078] (Supplementary Note 4) The insertion part allows displacement in the circumferential direction and the radial direction centered on the axis of the second transmission part, and is the same number as the second transmission part, The speed reducer according to any one of Supplementary Notes 1 to 3.

[0079] (Supplementary Note 5) At least one of the first link mechanism and the second link mechanism is plural, The speed reducer includes the first link mechanism and the second link mechanism adjacent to each other in the axial direction. The speed reducer according to any one of Supplementary Notes 1 to 4.

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

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

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

[0083] (Supplementary Note 9) 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. The speed reducer according to Supplementary Note 8.

[0084] In the above description, for the sake of facilitating the understanding of the present invention, the description of known technical matters has been appropriately omitted.

[0085] The present invention can be implemented in various embodiments and modifications without departing from the broad spirit and scope of the present invention. Also, the above-described embodiments are for explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is indicated by the claims rather than the embodiments. And various modifications made within the scope of the claims and within the scope of the meaning of the invention equivalent thereto are regarded as being within the scope of the present invention.

Explanation of Reference Numerals

[0086] 1... Wave generator 10... Cam, 10a... Cylindrical shaft, 11... Wave bearing 2... Internal gear, 2t... Teeth, 2g... Tooth groove 3... Link device 31... First link mechanism L1... First link T1... First transmission part, S1... First shaft, R1... First roller 32... Second link mechanism T2... Second transmission part, S2... Second shaft, R2... Second roller 33... Third link mechanism T3... Third transmission part, S3... Third shaft, R3... First roller S... Common shaft 4... Interlocking part, 40... Insertion part 5... Spacer, D1~D3... Grooves 51…Part 1, 51a…Depression 52…Part 2, 52a…Depression 6…Case, 7…Connecting part 8…Support part B1, B2…Bearings E…Engagement position F, G, H, I, J, K, P, Q…Transmission positions

Claims

1. A wave generator having a cam that rotates about an axis in response to a rotational input, an internal gear surrounding the cam, a plurality of first links configured in a shape surrounding the outer periphery of the wave generator, and a first link mechanism positioned between the internal gear and the cam, a plurality of second links configured in a shape surrounding the outer periphery of the wave generator, positioned side by side with the first link mechanism in the axial direction, which is the direction in which the axis extends, and a second link mechanism connected to the first link mechanism and rotating about the axis together with the first link mechanism, and an interlocking portion that rotates about the axis together with the second link mechanism. The first link mechanism has a first transmission portion that can fit into the tooth groove of the internal gear and has a cylindrical outer peripheral surface. The second link mechanism has a second transmission portion that can be inserted into an insertion portion provided in the interlocking portion and has a cylindrical outer peripheral surface. A plurality of the first transmission portions are arranged along the outer periphery of the wave generator. A plurality of the second transmission portions are arranged along the outer periphery of the wave generator. The cam has a plurality of pole portions that are equally spaced in the circumferential direction about the axis, and the first transmission portion is meshed with the internal gear at a position corresponding to the pole portion. The number of the 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 the first transmission portions. The number of the second transmission portions is the same as the number of the first transmission portions or less than the number of the first transmission portions. A speed reducer.

2. The first transmission portion has a first shaft extending in the axial direction. The second transmission portion has a second shaft extending in the axial direction. The first shaft includes a common shaft that is integral with the second shaft. The first link mechanism and the second link mechanism are connected by the common shaft. The speed reducer according to Claim 1.

3. The first transmission portion rotates with respect to the first shaft and has a first roller that constitutes the outer periphery of the first transmission portion. The second transmission portion rotates with respect to the second shaft and has a second roller that constitutes the outer periphery of the second transmission portion. The speed reducer according to Claim 2.

4. The insertion portion Permit displacement in the circumferential direction and the radial direction centered on the axis of the second transmission part, The same number as that of the second transmission part, The speed reducer according to claim 1.

5. At least one of the first link mechanism and the second link mechanism is plural, The speed reducer includes the first link mechanism and the second link mechanism adjacent to each other in the axial direction. The speed reducer according to claim 1.

6. Further include a third link mechanism located between the first link mechanism and the second link mechanism in the axial direction, The third link mechanism has a plurality of third links configured in a shape surrounding the outer periphery of the wave generator, and is 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. The speed reducer according to claim 1.

7. Further include a spacer located between the first link mechanism and the wave generator, and applying radial preload centered on the axis to each of the first link mechanism and the wave generator. The speed reducer according to any one of claims 1 to 6.

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

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

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