Eccentric oscillation type reduction gear

Abstract

To provide an eccentric oscillation type speed reduction device that can efficiently secure connection strength between members in the eccentric oscillation type speed reduction device or a whole machine provided with the eccentric oscillation type speed reduction device.SOLUTION: An eccentric oscillation type speed reduction device 100 according to an embodiment comprises external gears 13, 14, and 15, and a first carrier 35 and a second carrier 36 arranged in parts on both sides of the external gears 13, 14, and 15, and comprises a carrier connection member 71 connecting the first carrier 35 and the second carrier 36, and a second connection member 72 attached to the speed reduction device separately from the carrier connection member 71, and connecting at least two members. Tensile strength of the carrier connection member 71 is higher than that of the second connection member 72.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an eccentric swing type reduction gear.

Background Art

[0002] An eccentric swing type gear device including two members connected to each other is known. For example, Patent Document 1 describes an eccentric swing type gear device having a first member and a second member connected to each other. This device includes a first member provided with a first connection hole, a second member provided with a second connection hole, a bolt inserted through the first connection hole and the second connection hole, and a positioning member inserted so as to straddle the first connection hole and the second connection hole and having a second screw hole that engages with a portion on the base end side of the screw portion of the bolt.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventor has obtained the following new recognition regarding an eccentric swing type reduction gear. Regarding an eccentric swing type reduction gear having carriers connected to each other, it is required to ensure the connection strength of various members. However, Patent Document 1 cannot be said to disclose sufficiently regarding the connection strength of various members. Here, for example, if an attempt is made to improve the connection strength between all members of an eccentric swing type reduction gear, demerits may occur in terms of cost, size, etc.

[0005] The present invention has been made in view of such problems, and one object of the present invention is to provide an eccentric swing type reduction gear capable of efficiently ensuring the connection strength between members as an entire eccentric swing type reduction gear or as an entire machine provided with the eccentric swing type reduction gear by ensuring the connection strength of the carrier of the eccentric swing type reduction gear. [Means for solving the problem]

[0006] To solve the above problems, an eccentric oscillating type reduction gear according to one aspect of the present invention is an eccentric oscillating type reduction gear having an external gear and a first carrier and a second carrier arranged on both sides of the external gear, wherein the reduction gear includes a carrier connecting member that connects the first carrier and the second carrier, and a second connecting member that is attached to the reduction gear separately from the carrier connecting member and connects at least two members. The carrier connecting member has greater tensile strength than the second connecting member.

[0007] Furthermore, any combination of the above components, or in which the components or expressions of the present invention are mutually substituted among methods, systems, etc., are also valid embodiments of the present invention. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an eccentric oscillating type reduction gear that can efficiently ensure the connection strength between components of the entire machine equipped with the eccentric oscillating type reduction gear. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing an example of an eccentric oscillating type reduction gear according to an embodiment. [Figure 2] This table shows the chemical composition of the material of the second connecting member. [Modes for carrying out the invention]

[0010] The present invention will be described below with reference to the drawings, based on preferred embodiments. In embodiments and modifications, the same or equivalent components and members will be denoted by the same reference numerals, and redundant explanations will be omitted as appropriate. In addition, the dimensions of the members in each drawing will be enlarged or reduced as appropriate for ease of understanding. Furthermore, some members that are not important for explaining the embodiments will be omitted from the drawings.

[0011] Furthermore, while terms including ordinal numbers such as "first" and "second" are used to describe various components, these terms are used solely to distinguish one component from others, and do not limit the components themselves.

[0012] [Embodiment] Referring to Figures 1 and 2, the overall configuration of the eccentric oscillating type reduction gear 100 according to this embodiment will be described. Figure 1 is a side cross-sectional view showing the eccentric oscillating type reduction gear 100. Hereinafter, the eccentric oscillating type reduction gear 100 may be referred to as the reduction gear 100. The reduction gear 100 of this embodiment includes a crankshaft 20 to which the motor shaft 11 of the motor 10 is connected. Hereinafter, the direction along the central axis La of the crankshaft 20 will be referred to as the "axial direction," the side of the crankshaft 20 to which the motor shaft 11 is connected in the axial direction (right side in the figure) will be referred to as the input side, and the other side (left side in the figure) will be referred to as the anti-input side. In other words, the crankshaft 20 extends from the input side to the anti-input side in the axial direction. Furthermore, the circumferential direction and radial direction of a circle centered on the central axis La will be referred to as the "circumferential direction" and "radial direction," respectively.

[0013] The reduction gear 100 reduces the rotation input from the motor shaft 11 to the crankshaft 20 and outputs it to the driven member 60. There are no restrictions on the motor 10 as long as it is capable of outputting rotation to the reduction gear 100, and motors based on various principles can be used. In this embodiment, the motor 10 is a brushless DC motor (sometimes called an AC servo motor). In the example in Figure 1, the motor shaft 11 of the motor 10 transmits rotation using a key.

[0014] There are no restrictions on the reduction gear 100 as long as it is capable of reducing the input rotation and outputting it, and various reduction gears can be used. The reduction gear 100 of this embodiment causes the external gear that meshes with the internal gear to oscillate, thereby generating rotation of one of the internal gears and the external gear, and outputs the resulting rotation component from the output member to the driven member 60. The reduction gear 100 of this embodiment is a center crank type in which the central axis La of the crankshaft 20 is located coaxially with the central axis of the internal gear.

[0015] The reduction gear 100 mainly includes a crankshaft 20, external gears 13, 14, 15, internal gear 41, carriers 35, 36, internal pin 48, eccentric bearings 16, 17, 18, main bearings 37, 38, crankshaft bearings 39, 40, casing 51, and motor adapter 52. The carriers 35, 36 include a first carrier 35 and a second carrier 36 positioned on the input side of the first carrier 35. The main bearings 37, 38 include a first main bearing 37 and a second main bearing 38 positioned on the input side of the first main bearing 37.

[0016] The casing 51 has a cylindrical shape that forms the outer shell of the reduction gear 100. An internal gear 41 is provided on the inner circumferential surface of the casing 51. The motor adapter 52 is positioned on the side of the second carrier 36 and is attached to the motor 10. In this embodiment, the motor adapter 52 is connected to the input side of the casing 51.

[0017] The motor adapter 52 has a cylindrical portion 521 connected to the casing 51 and a hollow disc portion 522 covering the input side of the cylindrical portion 521. The cylindrical portion 521 surrounds the second carrier 36 and the second main bearing 38 with a gap in between. The cylindrical portion 521 and the disc portion 522 are integrally formed. At the center of the disc portion 522 is a circular recess 523 for the non-input side cylindrical portion of the motor 10 to be fitted into, and a seal placement portion 524, which is a through hole for arranging the oil seal S2.

[0018] The first carrier 35 is positioned on the non-input side of the external gears 13, 14, and 15, and the second carrier 36 is positioned on the input side of the external gears 13, 14, and 15. The reduction gear 100 includes a carrier connecting member 71 that connects the first carrier 35 and the second carrier 36, and a second connecting member 72 that is attached to the reduction gear 100 separately from the carrier connecting member 71. There are no limitations on the configuration of the carrier connecting member 71, but in this example it is a bolt B1. There are no limitations on the configuration of the second connecting member 72, but in this example it is bolts B2 and B3. Bolt B2 connects the casing 51 and the motor adapter 52. Bolt B3 connects the driven member 60 and the first carrier 35. At least a portion of the motor adapter 52 defines a space in which the flow of air to the outside is suppressed, and the carrier connecting member 71 is exposed to this space on the second carrier 36 side.

[0019] The crankshaft 20 is rotated around the rotational centerline La by rotational power input from the motor shaft 11. The crankshaft 20 has an insertion hole 21 into which the motor shaft 11 is inserted. The crankshaft 20 and the motor shaft 11 are connected, for example, by a key. They may be connected by various other coupling methods. Multiple eccentric portions 23, 24, and 25 are provided on the outer circumference of the crankshaft 20 for oscillating the external gears 13, 14, and 15. The axes of the eccentric portions 23, 24, and 25 are eccentric with respect to the rotational centerline La of the crankshaft 20. In this embodiment, three eccentric portions 23, 24, and 25 are provided, and the eccentric phases of adjacent eccentric portions 23, 24, and 25 are shifted by 120°. The crankshaft 20 is sometimes referred to as the input shaft.

[0020] The non-input side of the crankshaft 20 is supported by the first carrier 35 via a crankshaft bearing 39. The input side of the crankshaft 20 is supported by the second carrier 36 via a second crankshaft bearing 40. In other words, the crankshaft 20 is rotatably supported relative to the first carrier 35 and the second carrier 36.

[0021] The crankshaft bearings 39 and 40 are arranged between the carriers 35 and 36 and the crankshaft 20. For the crankshaft bearings 39 and 40, various known bearing mechanisms can be adopted. In this example, the crankshaft bearings 39 and 40 are ball bearings.

[0022] The external gears 13, 14, and 15 are individually provided corresponding to each of the plurality of eccentric portions 23, 24, and 25. The external gears 13, 14, and 15 are swingably incorporated on the outer periphery of the eccentric portions 23, 24, and 25 via the eccentric bearings 16, 17, and 18. The eccentric bearings 16, 17, and 18 in this example are roller bearings. The external gears 13, 14, and 15 are internally meshed with the internal gear 41 while swinging respectively. Wave-shaped teeth are formed on the outer periphery of the external gears 13, 14, and 15, and by moving while these teeth contact the internal gear 41, the external gears 13, 14, and 15 can swing in a plane with the normal line being the central axis.

[0023] The internal gear 41 meshes with the external gears 13, 14, and 15. The internal gear 41 of the present embodiment has an internal gear main body 42 integrally provided on the inner peripheral side of the casing 51, and a plurality of external pins 43 arranged in pin grooves formed at predetermined intervals in the circumferential direction on the inner peripheral surface of the internal gear main body 42. The external pin 43 is a columnar pin member rotatably supported in the pin groove of the internal gear main body 42. The external pin 43 constitutes the internal teeth of the internal gear 41. The number of external pins 43 (the number of internal teeth) of the internal gear 41 is slightly (by 1 in this example) more than the number of external teeth of the external gears 13, 14, and 15.

[0024] Multiple internal pin holes 45, 46, and 47 are formed in the external gears 13, 14, and 15 at positions offset from their axes. An internal pin 48 passes through the internal pin holes 45, 46, and 47. A cylindrical sleeve 49 is positioned around the outer circumference of the internal pin 48. The sleeve 49 functions as a sliding accelerator to facilitate smooth sliding with the internal pin holes 45, 46, and 47. The outer diameter of the sleeve 49 is smaller than the inner diameter of the internal pin holes 45, 46, and 47 by an amount equivalent to twice the eccentricity. A gap is provided between the sleeve 49 and the internal pin 48 to absorb the oscillation component of the external gears 13, 14, and 15, and the internal pin 48 is always in contact with a portion of the internal pin holes 45, 46, and 47 via the sleeve 49. The internal pin 48 revolves around the axis of the crankshaft 20 in synchronization with the rotational component of the external gears 13, 14, and 15, causing the carriers 35 and 36 to rotate around the axis of the crankshaft 20. The internal pin 48 contributes to the transmission of power between the carriers 35 and 36 and the external gears 13, 14, and 15.

[0025] The carriers 35 and 36 have a hollow ring shape. The first carrier 35 is rotatably supported on the casing 51 via the first main bearing 37. The second carrier 36 is rotatably supported on the casing 51 via the second main bearing 38. The first carrier 35 rotatably supports the non-input side of the crankshaft 20 via the first crankshaft bearing 39. The second carrier 36 rotatably supports the input side of the crankshaft 20 via the second crankshaft bearing 40.

[0026] The main bearings 37 and 38 are positioned between the casing 51 and the carriers 35 and 36. The main bearings 37 and 38 can employ various known bearing mechanisms; in this example, the main bearings 37 and 38 are angular contact ball bearings. The inner rolling surfaces of the main bearings 37 and 38 are formed in the carriers 35 and 36.

[0027] The internal pin 48 is integrally formed with the first carrier 35 and extends axially from the input side of the first carrier 35 toward the second carrier 36. The carriers 35 and 36 are connected to each other by screwing a bolt B1 through a through hole 362 provided in the second carrier 36 into a tapped hole 482 provided at the end of the internal pin 48. The head B12 of the bolt B1 is housed in the large diameter portion 364 of the through hole 362.

[0028] One of the carriers 35, 36 and the casing 51 becomes an output member that outputs rotational power to the driven member 60, while the other becomes a fixed member that is fixed to a mounting member (not shown) for supporting the reduction gear 100. In this example, the first carrier 35 functions as an output member that outputs rotational power to the driven member 60, and the casing 51 and motor adapter 52 function as fixed members that are fixed to the mounting member.

[0029] An oil seal S1 is positioned between the first carrier 35 and the casing 51. An oil seal S2 is positioned between the motor adapter 52 and the crankshaft 20. The oil seal S2 is fixed in a fitted state on the seal placement portion 524 of the disc portion 522 of the motor adapter 52. The oil seals S1 and S2 prevent foreign matter from entering the inside of the reduction gear 100.

[0030] The operation of the reduction gear 100 will now be explained. When rotational power is transmitted from the motor shaft 11 to the crankshaft 20, the eccentric parts 23, 24, and 25 of the crankshaft 20 rotate around the rotational centerline passing through the crankshaft 20, and the external gears 13, 14, and 15 oscillate due to these eccentric parts 23, 24, and 25. At this time, the external gears 13, 14, and 15 oscillate so that their own axes rotate around the rotational centerline of the crankshaft 20. As the external gears 13, 14, and 15 oscillate, the meshing positions of the external gears 13, 14, and 15 and the external pins 43 of the internal gear 41 shift sequentially. As a result, with each rotation of the crankshaft 20, one of the external gears 13, 14, and 15 and the internal gear 41 rotates by an amount equivalent to the difference between the number of teeth on the external gears 13, 14, and 15 and the number of external pins 43 of the internal gear 41. In this embodiment, the external gears 13, 14, and 15 rotate on their own, and a reduced rotation is output from the first carrier 35. As the first carrier 35 rotates, the driven member 60 connected to the first carrier 35 is rotated.

[0031] Next, the characteristic configuration of this disclosure will be described with reference to Figures 1 and 2. The inventors have gained the following new insights: From the viewpoint of expanding the scope of application, miniaturization and weight reduction of the reduction gear 100 are desirable. To miniaturize and weight reduction of the reduction gear 100, it has been found that the important parts are particularly in the connecting parts of the carriers 35 and 36. When connecting the carriers 35 and 36 located on both sides of the external gears 13, 14, and 15, the space available for connection is limited due to the presence of the external gears 13, 14, and 15. Therefore, in order to ensure the connection strength of the carriers, there is little room to reduce the number of bolts B1, which are carrier connecting members 71 that connect the carriers 35 and 36, or to reduce their diameter. To address these issues, it is conceivable to use high-strength bolts to ensure the connection strength of the carriers 35 and 36 and to cope with the increased load on each bolt B1. However, high-strength bolts have risks such as delayed fracture and are limited to use within a certain strength range.

[0032] Therefore, in this embodiment, the carrier connecting member 71 (bolt B1) connecting the first carrier 35 and the second carrier 36 is set to have a higher tensile strength than a second connecting member 72 (for example, bolts B2 and B3) that is separate from the carrier connecting member 71. Here, the second connecting member 72 is not limited to a connecting member inside the reduction gear 100, but also includes mounting bolts on the mating machine side, such as bolt B2 connecting the casing 51 and the motor adapter 52, and bolt B3 connecting the driven member 60 and the first carrier 35. The tensile strength of a bolt is determined according to the nominal tensile strength (N / millimeter square MPa) of the strength classification (hereinafter simply referred to as "strength classification") specified in JIS, and a bolt with a higher nominal tensile strength is said to have a higher tensile strength.

[0033] As an example, the carrier connecting member 71 (bolt B1) uses a bolt with a strength class of 14.9 [nominal tensile strength of 1400 MPa], and the second connecting member 72 (bolts B2, B3) uses a bolt with a strength class of 12.9 [nominal tensile strength of 1200 MPa].

[0034] Conventionally, when steel has high tensile strength, there is a problem that "delayed fracture" occurs when a tensile load is applied while hydrogen is present in the steel, causing it to suddenly break without plastic deformation. Therefore, in the carrier connecting member 71 (bolt B1), after trial and error, the delayed fracture characteristics are improved by the following (1) to (3) methods. In this way, when the tensile strength of the steel is increased, it is possible to make improvements to various properties. However, there may be disadvantages in aspects other than tensile strength, such as delayed fracture characteristics and cost, compared to the commonly used bolts B2 and B3. Therefore, as mentioned above, a higher-strength bolt is used in the carrier connecting member 71 where space is limited, while the second connecting member 72 uses a bolt made of a material with lower tensile strength than the carrier connecting member. (1) Reduction of impurity elements The grain boundaries are strengthened by minimizing impurities P and S, as well as reducing Mn, which promotes grain boundary segregation of P and S. (2) Refinement of crystal grains The addition of Ti, Nb, V, etc. refines the crystal grains, strengthens the grain boundaries, and improves the toughness and ductility of the steel. (3) Precipitation of fine carbonitrides By adding precipitation-hardening elements such as Mo, V, and Ti, and performing high-temperature tempering treatment, fine carbonitrides are precipitated. These compounds trap diffusible hydrogen, reducing harmful hydrogen.

[0035] Figure 2 is a table showing the chemical composition of the material (stainless steel) of the second connecting member 72, where the remaining main component is iron. The carrier connecting member 71 has a higher carbon (C) component compared to the second connecting member 72. In addition, the carrier connecting member 71 has lower levels of P, S, and Mn compared to the second connecting member 72. Furthermore, the carrier connecting member 71 has lower levels of impurities P, S, and Mn compared to the other materials. In addition, the material of the carrier connecting member 71 has a higher addition rate of the additive component Mo compared to the second connecting member 72, and further additions of the additive components Ti, Nb, and V. For example, the second connecting member 72 also contains at least one of the additive components Ti, Nb, and V, and the carrier connecting member 71 may contain a higher amount of the additive component than the second connecting member 72.

[0036] In this embodiment, the second connecting member 72 is a bolt exposed to the outside of the reduction gear 100. In this case, since the member covering the second connecting member 72 can be omitted, the motor adapter 52 and the driven member 60 can be easily attached to the outside of the reduction gear 100. Also, because it is exposed to the outside, it can be easily maintained and replaced. Furthermore, it uses a material with lower tensile strength than the carrier connecting member, making delayed fracture less likely.

[0037] In this embodiment, the carrier connecting member 71 is a bolt that is not exposed to the outside of the reduction gear 100. In this case, the reduction in brittleness caused by environmental factors can be suppressed. Since the reduction in brittleness is reduced, the load can be increased, and thus the number of carrier connecting members 71 used can be reduced. In this embodiment, the carrier connecting member 71 is located in a space 78 between the input-side end face of the reduction gear section 90 of the reduction gear 100, excluding the motor adapter 52, and the disc portion 522 of the motor adapter 52, and is surrounded by the cylindrical portion 521 of the motor adapter 52. The space 78 is sealed by an oil seal S2, and the flow of air to the outside is suppressed (hereinafter referred to as a "closed space"). Since the reduction in brittleness is suppressed, the frequency of maintenance and replacement can be reduced.

[0038] As described above, the reduction gear 100 of the embodiment has a motor adapter 52 that is positioned on the side of the second carrier 36 and attached to the motor 10, and the second connecting member 72 is attached to the motor adapter 52. In this case, the motor adapter 52 and the reduction gear 90 are provided in a connected state, so the bolts are less likely to deteriorate during storage.

[0039] The present invention has been described above based on the embodiments. These embodiments are illustrative, and it will be understood by those skilled in the art that various modifications and changes are possible within the scope of the claims of the present invention, and that such modifications and changes are also within the scope of the claims of the present invention. Accordingly, the descriptions and drawings herein should be treated as illustrative rather than limiting.

[0040] (modified version) The following describes modified examples. In the drawings and descriptions of the modified examples, components and parts that are the same as or equivalent to those in the embodiments are denoted by the same reference numerals. Descriptions that overlap with those in the embodiments will be omitted as appropriate, and the descriptions will focus on the configurations that differ from those in the embodiments.

[0041] In the description of the embodiments, an example was shown in which the eccentric oscillating reduction gear is a so-called center crank type eccentric oscillating reduction gear. However, the present invention is not limited to this, and various reduction mechanisms can be employed. For example, the reduction gear may be a so-called distribution type eccentric oscillating reduction gear in which multiple crankshafts are arranged at positions offset from the axis of the internal gear.

[0042] In the description of the embodiment, an example was shown in which the motor shaft 11 is inserted into the insertion hole 21 of the crankshaft 20, but the present invention is not limited to this. For example, the shaft of a gear that meshes with the motor pinion of the motor shaft may be inserted into the insertion hole of the crankshaft.

[0043] In the description of the embodiments, an example was shown in which the crankshaft 20 is connected to the motor shaft 11 using a key, but the present invention is not limited thereto.

[0044] In the description of the embodiments, an example was shown in which the number of teeth of the external gears 13, 14, and 15 is 3, but the present invention is not limited thereto. The number of teeth may be 2 or less, or 4 or more.

[0045] Each of these modifications produces the same functions and effects as the embodiments.

[0046] Any combination of the embodiments and modifications described above is also useful as an embodiment of the present invention. The new embodiments resulting from these combinations possess the combined effects of both the respective embodiments and modifications. [Explanation of Symbols]

[0047] 13, 14, 15 External gears, 35 First carrier, 36 Second carrier, 41 Internal gear, 51 Casing, 52 Motor adapter, 60 Driven member, 71 Carrier connecting member, 72 Second connecting member, 78 Space, 100 Eccentric oscillating reduction gear.

Claims

1. In an eccentric oscillating type reduction gear having an external gear and a first carrier and a second carrier arranged on both sides of the external gear, A carrier connecting member that connects the first carrier and the second carrier, The device has a second connecting member that is attached separately to the carrier connecting member and connects at least two members, The carrier connecting member has greater tensile strength than the second connecting member, and is an eccentric oscillating type reduction gear.

2. The eccentric oscillating type reduction device according to claim 1, wherein the second connecting member is exposed to the outside of the eccentric oscillating type reduction device.

3. The eccentric oscillating type reduction gear according to claim 1 or claim 2, wherein the carrier connecting member is arranged in a space inside the eccentric oscillating type reduction gear in which the flow of air to the outside is suppressed.

4. The carrier connecting member is exposed on the second carrier side. The second carrier has a motor adapter that is positioned on the side and attached to the motor, The eccentric oscillating type reduction gear according to claim 3, wherein at least a portion of the motor adapter defines a space in which the flow of air to and from the outside is suppressed.

5. The eccentric oscillating type reduction device according to claim 4, wherein the second connecting member is attached to the motor adapter and exposed to the outside of the eccentric oscillating type reduction device.

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