speed reducer

Abstract

To provide a speed reducer in which fretting is hard to occur between an input shaft and a motor shaft.SOLUTION: A speed reducer 10 has an input shaft 21 having a connected hole 28 connected to a motor shaft 11, and input shaft bearings 39, 40 that support the input shaft 21, and has first connection means 3 of connecting the input shaft 21 and the motor shaft 11. The first connection means 3 is configured such that a load in a direction toward a bottom part of the connected hole 28 acts on the motor shaft 11 as the first connection means 3 is fastened. The input shaft bearings 39, 40 are axially movable toward an opening part 284 of the connected hole 28.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] A speed reducer having an input shaft to which rotation is transmitted from a motor shaft is known. The applicant has disclosed in Patent Document 1 a speed reducer having an input shaft that rotates by the rotational power input from a motor. This speed reducer has a connecting hole opened axially from the end face on the side where the motor of the input shaft is disposed, and is configured to be able to connect the motor shaft using a key.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to connect the motor shaft to the input shaft of the speed reducer, it is conceivable to insert the motor shaft into a connecting hole provided in the input shaft and connect it using a key. In this case, from the viewpoint of ensuring assemblability, a slight gap is provided between the connecting hole and the motor shaft. If there is a gap, the connecting hole and the motor shaft are welded by fretting, making it difficult to disassemble during maintenance. The speed reducer described in Patent Document 1 has room for improvement from the viewpoint of suppressing the occurrence of fretting.

[0005] The present invention has been made in view of such problems, and one of the objects is to provide a speed reducer in which fretting is difficult to occur.

Means for Solving the Problems

[0006] To solve the above problems, a gearbox according to one aspect of the present invention is a gearbox having an input shaft having a connecting hole for connecting to a motor shaft, and an input shaft bearing supporting the input shaft, wherein the gearbox has a first connecting means for connecting the input shaft and the motor shaft. The first connecting means is configured such that when the first connecting means is fastened, a load acting toward the bottom of the connecting hole is applied to the motor shaft, and the input shaft bearing is axially movable toward the opening side of the connecting hole.

[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. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view showing an example of a gearbox according to the embodiment. [Figure 2] This figure shows a magnified view of the area around the input shaft bearing of the gearbox in Figure 1. [Figure 3] This is a side cross-sectional view showing a second example of the gearbox of the embodiment. [Figure 4] This is a side cross-sectional view showing a third example of the gearbox of the embodiment. [Figure 5] This is a side cross-sectional view showing a speed reducer according to the first modified example. [Modes for carrying out the invention]

[0009] 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.

[0010] 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.

[0011] [Embodiment] The configuration of the gearbox 10 according to the embodiment will be described with reference to Figures 1 and 2. Figure 1 is a side cross-sectional view showing the gearbox 10 according to an embodiment of the present invention. Figure 2 is an enlarged view showing the area around the input shaft bearings 39 and 40 of the gearbox 10. Hereinafter, the direction along the central axis La of the internal gear 41 of the gearbox 10 will be referred to as the "axial direction," and the circumferential direction and radial direction of the circle centered on the central axis La will be referred to as the "circumferential direction" and "radial direction," respectively. Also, for convenience, one side of 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 non-input side.

[0012] First, the overall configuration of the reduction gear 10 will be explained. The reduction gear 10 reduces the rotation input from the motor 1 and outputs it to the driven member 81. As for the motor 1, there are no restrictions as long as it is capable of outputting rotation to the reduction gear 10 via the motor shaft 11, and motors based on various principles can be used. In this embodiment, the motor 1 is a brushless DC motor (sometimes called an AC servo motor). In the example in Figure 1, the motor shaft 11 of the motor 1 transmits rotation using a key.

[0013] The reduction gear 10 will now be described. There are no restrictions on the reduction gear 10 as long as it is capable of reducing the input rotation to a reduced output, and various reduction mechanisms can be used. The reduction gear 10 of this embodiment is an eccentric oscillating type reduction gear that generates rotation of one of the internal gears and the external gears by oscillating the external gear that meshes with the internal gear, and outputs the resulting rotation component from the output member to the driven member. The reduction gear 10 of this embodiment is a center crank type in which the rotation centerline of the input shaft 21 is located on the same axis as the central axis La.

[0014] The gearbox 10 mainly includes an input shaft 21, external gears 13, 14, 15, internal gear 41, carriers 35, 36, internal pin 48, eccentric bearings 16, 17, 18, main bearings 37, 38, input shaft bearings 39, 40, casing 71, and mounting member 72. The casing 71 has a cylindrical shape that surrounds the gearbox 10, and the internal gear 41 is provided on its inner circumferential surface. The mounting member 72 is a plate-shaped member having a hollow portion 73 through which the input shaft 21 passes. The mounting member 72 is positioned to close the input side of the casing 71 and is fixed to the casing 71 by bolts B4. The motor 1 is fixed to the input side of the mounting member 72 by bolts B5. A first seal member S1 is positioned between the hollow portion 73 of the mounting member 72 and the input shaft 21. The first sealing member S1 functions as an oil seal to prevent lubricant leakage from the second input shaft bearing 40 of the reduction gear 10. The lip portion L1 of the first sealing member S1 abuts against the sliding portion 27 of the input shaft 21, which will be described later.

[0015] The input shaft 21 is rotated around its centerline by the rotational power input from the motor 1. The outer circumference of the input shaft 21 is provided with, in order from the non-input side toward the input side, a first shaft portion 22, a first eccentric portion 23, a second eccentric portion 24, a third eccentric portion 25, a second shaft portion 26, and a sliding portion 27. The first shaft portion 22 and the second shaft portion 26 support the inner rings 391 and 401 of the input shaft bearings 39 and 40. The first eccentric portion 23, the second eccentric portion 24, and the third eccentric portion 25 are cylindrical portions with a larger diameter than the first shaft portion 22 and are eccentric as described later. The second shaft portion 26 is a cylindrical portion with the same diameter as the first shaft portion 22. The sliding portion 27 is a cylindrical portion with the same diameter as the second shaft portion 26.

[0016] The input shaft 21 has a connecting hole 28 that connects to the motor shaft 11. In the example shown in Figure 1, the connecting hole 28 is a blind hole formed axially from the input-side end face of the input shaft 21 and is configured to accommodate the motor shaft 11. In this embodiment, a key 51 is provided as a second connecting means 5 that connects the input shaft 21 and the motor shaft 11 in the circumferential direction. The connecting hole 28 is a circular hole coaxial with the rotational centerline (coaxial with the central axis La) of the input shaft 21 and has a keyway 29 at a predetermined position on its inner circumferential surface into which the key 51 engages. In particular, the connecting hole 28 in this example has a cylindrical shape.

[0017] The speed reducer 10 has a first connecting means 3 for connecting the input shaft 21 and the motor shaft 11. In the embodiment, the first connecting means 3 is a bolt B1, and has a bolt insertion hole 30 that communicates from the end face of the input shaft 21 on the side opposite to the motor to the bottom surface of the connected hole 28, and a bolt hole 12 provided axially from the tip end face of the motor shaft 11. By screwing the bolt B1 inserted into the bolt insertion hole 30 from the side opposite to the motor of the input shaft 21 into the bolt hole 12 of the motor shaft 11, the motor shaft 11 and the input shaft 21 are connected. In the example of FIG. 1, the bolt insertion hole 30 is a through hole formed axially from the end face of the input shaft 21 on the side opposite to the input. The bolt hole 12 in this example is a tap hole provided at a position overlapping the bolt insertion hole 30 when viewed axially.

[0018] As shown in FIG. 1, with the motor shaft 11 in a state where the key 51 is attached inserted into the connected hole 28, the bolt B1 penetrates the bolt insertion hole 30 and is screwed into the bolt hole 12 of the motor shaft 11, whereby the input shaft 21 is connected to the motor shaft 11. In this state, the input shaft 21 has a fixed positional relationship in the circumferential direction with respect to the motor shaft 11 by the key 51 and has no play in the circumferential direction with respect to the motor shaft 11. Further, the input shaft 21 has a fixed positional relationship in the axial direction with respect to the motor shaft 11 by the bolt B1 and has no play in the axial direction with respect to the motor shaft 11. A washer W1 is provided between the bolt B1 and the input shaft 21.

[0019] In the embodiment, the input shaft 21 is an eccentric shaft having a plurality of eccentric portions 23, 24, 25 for swinging the external gears 13, 14, 15, and may be referred to as a crank shaft. The axial centers of the eccentric portions 23, 24, 25 are eccentric with respect to the rotation center line of the input shaft 21. In this embodiment, three eccentric portions 23, 24, 25 are provided, and the eccentric phases of adjacent eccentric portions 23, 24, 25 are shifted by 120°.

[0020] The first shaft portion 22 on the anti-input side of the input shaft 21 is supported by the first carrier 35 via the input shaft bearing 39. The second shaft portion 26 on the input side of the input shaft 21 is supported by the second carrier 36 via the second input shaft bearing 40. That is, the input shaft 21 is rotatably supported with respect to the first carrier 35 and the second carrier 36.

[0021] The input shaft bearings 39 and 40 are disposed between the hollow portions 352 and 362 of the carriers 35 and 36 and the shaft portions 22 and 26 of the input shaft 21. The input shaft bearings 39 and 40 can employ various known bearing mechanisms. In this example, the input shaft bearings 39 and 40 are ball bearings having spherical rolling elements 393 and 403, and outer rings 392 and 402 and inner rings 391 and 392.

[0022] In the embodiment, an axial movement suppressing member 6 for suppressing the axial movement of the outer rings of the input shaft bearings 39 and 40 and the supporting members 35 and 36 that support the outer rings 392 and 402 is disposed therebetween. In this example, the supporting members 35 and 36 are carriers. The axial movement suppressing member 6 is not limited in configuration as long as it can suppress the axial movement of the outer rings 392 and 402. In this example, the axial movement suppressing member 6 is O-rings R1 and R2. The O-rings R1 and R2 are accommodated in circumferential recesses 355 and 365 formed in the hollow portions 352 and 362 of the supporting members 35 and 36, and the axial movement is restricted.

[0023] The external gear wheels 13, 14, and 15 are individually provided corresponding to the plurality of eccentric portions 23, 24, and 25, respectively. The external gear wheels 13, 14, and 15 are swingably incorporated on the outer circumferences 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 gear wheels 13, 14, and 15 are internally meshed with the internal gear wheel 41 while swinging respectively. Wave-shaped teeth are formed on the outer circumferences of the external gear wheels 13, 14, and 15, and by moving while this tooth contacts the internal gear wheel 41, the external gear wheels 13, 14, and 15 can swing within a plane having the central axis as the normal line.

[0024] The internal gear 41 meshes with the external gears 13, 14, and 15. The internal gear 41 in this embodiment has an internal gear body 42 integrally provided on the inner circumference side of the casing 71, and a plurality of external pins 43 arranged in pin grooves formed at predetermined intervals in the circumferential direction on the inner circumference surface of the internal gear body 42. The external pins 43 are cylindrical pin members that are rotatably supported in the pin grooves of the internal gear body 42. The external pins 43 constitute the internal teeth of the internal gear 41. The number of external pins 43 (number of internal teeth) of the internal gear 41 is slightly greater (only 1 in this example) than the number of external teeth of the external gears 13, 14, and 15.

[0025] 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 input shaft 21 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 input shaft 21. The internal pin 48 contributes to the transmission of power between the carriers 35 and 36 and the external gears 13, 14, and 15.

[0026] The carriers 35 and 36 have a ring shape with hollow sections 352 and 362. The first carrier 35 is positioned on the side of the external gears 13, 14, and 15 that is not the input side, and the second carrier 36 is positioned on the side of the external gears 13, 14, and 15 that is the input side. The first carrier 35 is rotatably supported by the casing 71 via a first main bearing 37. The second carrier 36 is rotatably supported by the casing 71 via a second main bearing 38. The first carrier 35 rotatably supports the side of the input shaft 21 that is not the input side via a first input shaft bearing 39. The second carrier 36 rotatably supports the input side of the input shaft 21 via a second input shaft bearing 40.

[0027] A first inward flange portion 353 is provided in the first hollow portion 352, and a second inward flange portion 363 is provided in the second hollow portion 362. The first inward flange portion 353 is a ring-shaped portion that extends axially inward from the first hollow portion 352 and faces the outer ring 392 in the axial direction on the non-input side of the first input shaft bearing 39. The second inward flange portion 363 is a ring-shaped portion that extends axially inward from the second hollow portion 362 and faces the outer ring 402 in the axial direction on the input side of the second input shaft bearing 40.

[0028] The main bearings 37 and 38 are positioned between the casing 71 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.

[0029] The second sealing member S2 is positioned between the casing 71 and the first carrier 35, on the side opposite to the input of the first main bearing 37, to prevent leakage of lubricant from the first main bearing 37.

[0030] 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 B3 through a through hole in the second carrier 36 into a bolt hole provided at the end of the internal pin 48.

[0031] One of the carriers 35, 36 and the casing 71 becomes an output member that outputs rotational power to the driven member, and the other becomes a fixed member that is fixed to a mounting member for supporting the reduction gear 10. In this example, the first carrier 35 functions as an output member that outputs rotational power to the driven member 81, and the casing 71 functions as a fixed member that is fixed to a mounting member 72. In the example in Figure 1, the driven member 81 and the first carrier 35 are connected to each other by screwing a bolt B2 through a through hole in the driven member 81 into a bolt hole provided at the non-input end of the first carrier 35.

[0032] The operation of the reduction gear 10 will now be explained. When rotational power is transmitted from the motor 1 to the input shaft 21, the eccentric parts 23, 24, and 25 of the input shaft 21 rotate around the rotational centerline passing through the input shaft 21, 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 input shaft 21. 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, for each rotation of the input shaft 21, 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 of 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 81 connected to the first carrier 35 is rotated.

[0033] Next, the characteristic configuration of this disclosure will be described with reference to Figures 1 and 2.

[0034] In the gearbox 10, the motor shaft 11 is connected to the input shaft 21 by inserting the motor shaft 11 into a connecting hole 28 provided in the input shaft 21 and connecting them using a key 51. If the gap between the connecting hole 28 and the motor shaft 11 is too small, it becomes difficult to insert the input shaft 21 into the connecting hole 28, so this gap is set to a size that ensures practical assembly. However, due to this gap, the connecting hole 28 and the motor shaft 11 rub against each other during rotation, causing fretting, and there is a possibility that they may weld to each other. If the motor shaft 11 is welded to the connecting hole 28, it becomes difficult to disassemble during maintenance, etc.

[0035] The reduction gear 10 of this embodiment is a reduction gear having an input shaft 21 having a connecting hole 28 for connecting to a motor shaft 11, and input shaft bearings 39 and 40 for supporting the input shaft 21, and has a first connecting means 3 (bolt B1 in this example) for connecting the input shaft 21 and the motor shaft 11. The first connecting means 3 is configured such that when the first connecting means 3 is fastened, a load acting toward the bottom of the connecting hole 28 is applied to the motor shaft 11. The input shaft bearings 39 and 40 are axially movable toward the opening 284 side of the connecting hole 28.

[0036] In particular, in the gearbox 10, the input shaft 21 and the motor shaft 11 are fixed to each other using bolts B1 while the input shaft 21 is inserted into the connecting hole 28, thereby suppressing fretting. However, in this configuration, excessive axial load is applied to the input shaft bearings 39 and 40 that support the input shaft 21 when the bolts are fixed, which may reduce the lifespan of the input shaft bearings 39 and 40. It is conceivable to use larger bearings with a greater load capacity, but in this case, the device will become larger, which is disadvantageous in terms of miniaturization, weight reduction, and cost. Therefore, in the gearbox 10 of this embodiment, the input shaft bearings 39 and 40 are configured to move axially toward the connecting hole 28. By moving the input shaft bearings 39 and 40 axially, the axial load acting on the input shaft bearings 39 and 40 can be reduced.

[0037] There are no limitations on the configuration that allows the input shaft bearings 39 and 40 to move in the axial direction; various configurations can be adopted.

[0038] (Example 1) A first example will be described with reference to Figures 1 and 2. In order to make the input shaft bearings 39 and 40 movable, the inner ring side of the input shaft bearings 39 and 40 may be a clearance fit, or the outer ring side may be a clearance fit. In the example in Figure 2, the outer ring side of the input shaft bearings 39 and 40 is a clearance fit. That is, the input shaft bearings 39 and 40 are supported by clearance fitting in the hollow sections 352 and 362 of the carriers 35 and 36. The fitting clearance between the input shaft bearings 39 and 40 and the hollow sections 352 and 362 can be set by calculation or simulation according to the desired movement resistance.

[0039] To ensure the movable range of the input shaft bearings 39 and 40, axial gaps G1 and G2 are provided between the inward flange portions 353 and 363. Specifically, gap G1 is provided between the first inward flange portion 353 and the outer ring 392 of the first input shaft bearing 39, and gap G2 is provided between the second inward flange portion 363 and the outer ring 402 of the second input shaft bearing 40. The size of gaps G1 and G2 can be set by calculation or simulation according to the desired movable range. In this example, gaps G1 and G2 are set to 0.5 mm or more when the input shaft bearings are moved to the opposite side of the gap. In other words, these gaps are not gaps that may occur due to design errors.

[0040] If the input shaft bearings 39 and 40 mounted in the hollow sections 352 and 362 are allowed to move freely, assembly becomes difficult. Therefore, in the reduction gear 10 of this embodiment, O-rings R1 and R2 are placed on the outside of the outer rings of the input shaft bearings 39 and 40. The input shaft bearings 39 and 40 are held within a certain range by the O-rings R1 and R2, improving assembly efficiency. In addition, the creep phenomenon can be suppressed by the O-rings R1 and R2.

[0041] From the viewpoint of effectively suppressing fretting, it is desirable that the gap between the motor shaft 11 and the connecting hole 28 does not increase due to thermal expansion or changes over time. Therefore, in this embodiment, the input shaft 21 has a bolt insertion hole 30 into which a bolt B1 protruding into the connecting hole 28 is inserted, and is configured so that the load caused by fastening the bolt B1 to the motor shaft 11 is applied to the input shaft 21 in the axial direction.

[0042] In the example shown in Figure 1, when bolt B1 is screwed into the bolt hole 12 of the motor shaft 11, a tensile load is applied to the motor shaft 11 on the non-input side, and the end face of the input shaft 21 is pushed toward the input side from the screw head of bolt B1, thereby applying an axial load to the input shaft 21. This load is a bias load due to the elasticity of these structures, and within a certain range, it can absorb the effects of thermal expansion and changes over time, thereby suppressing the increase in the gap.

[0043] Furthermore, when the input shaft 21 moves axially due to the tightening of bolt B1, if the eccentric bearings 16, 17, and 18 detach from the external gears 13, 14, and 15, an uneven load will be applied to them, which may cause problems such as abnormal noise and insufficient transmission capacity. For this reason, in this embodiment, the shape, dimensions, and material of each component of the reducer 10 are determined so that when bolt B1 is tightened, the eccentric bearings 16, 17, and 18 do not detach from the external gears 13, 14, and 15, and the eccentric bearings 16, 17, and 18 do not come into contact with each other.

[0044] (Second example) A second example will be described with reference to Figure 3. The second example shown in Figure 3 differs from the first example shown in Figure 1 in that the carriers 35 and 36 do not have inward-facing flange portions 353 and 363, but the other configurations are the same. Repeated explanations will be omitted, and the differing configurations will be explained in detail. Figure 3 is a side cross-sectional view showing a gearbox 10 of an embodiment to which the second example is applied. In this example, since the carriers 35 and 36 do not have inward-facing flange portions 353 and 363, the movable range of the input shaft bearings 39 and 40 can be increased.

[0045] (Third example) A third example will be described with reference to Figure 4. The third example shown in Figure 4 differs from the first example shown in Figure 1 in the configuration of the input shaft bearings 39 and 40, and in the absence of O-rings R1 and R2; the other configurations are the same. Duplication will be omitted, and the differing configurations will be explained in detail. Figure 4 is a side cross-sectional view showing a gearbox 10 of an embodiment to which the third example is applied.

[0046] In the third example, the input shaft bearings 39 and 40 are roller bearings having axially movable rollers 393 and 403. The input shaft bearings 39 and 40 have cylindrical rollers 393 and 403 as rolling elements, outer rings 392 and 402, and inner rings 391 and 392. The fitting of the outer rings 392 and 402 to the hollow portions 352 and 362 of the carriers 35 and 36 may be a clearance fit, an intermediate fit, or an interference fit. The fitting of the inner rings 391 and 392 to the second shaft portion 26 of the input shaft 21 may be a clearance fit, an intermediate fit, or an interference fit. Because the outer rings 392 and 402 and the inner rings 391 and 392 can move relative to each other in the axial direction, the input shaft bearings 39 and 40 are hardly subjected to the axial load acting on them.

[0047] The features of the reduction gear 10 configured as described above will now be explained. The reduction gear 10 of this embodiment is a reduction gear having an input shaft 21 having a connecting hole 28 that connects to a motor shaft 11, and input shaft bearings 39 and 40 that support the input shaft 21, wherein the input shaft bearings 39 and 40 are axially movable toward the connecting hole 28.

[0048] With this configuration, the input shaft bearings 39 and 40 move in the axial direction, which reduces the axial load acting on the input shaft bearings 39 and 40, even when the input shaft 21 is fixed to the motor shaft 11 with bolts or the like. As a result, fretting between the input shaft 21 and the motor shaft 11 can be effectively suppressed.

[0049] 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.

[0050] (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.

[0051] [First variation] In the description of the embodiment, an example was shown in which the connecting hole 28 has a cylindrical shape with a constant inner diameter in the axial direction, but the present invention is not limited thereto. The shape of the connecting hole 28 can be any shape as long as the input shaft 21 can be connected to the motor shaft 11. For example, the connecting hole 28 may have a tapered shape. Figure 5 is a side cross-sectional view showing a reduction gear 10 according to the first modified example. The first modified example shown in Figure 5 differs from the embodiment shown in Figure 1 in that the connecting hole 28 and the motor shaft 11 have a tapered shape, but the other configurations are the same. Repeated explanations will be omitted, and the differing configurations will be explained in detail.

[0052] In the first modified example, the connected hole 28 has a tapered surface 282 that gradually decreases in diameter toward the non-input side, and the motor shaft 11 has a tapered surface 112 that gradually decreases in diameter toward the non-input side. The inclination of the tapered surface 282 with respect to the axial direction can be set in accordance with the inclination of the tapered surface 112 with respect to the axial direction, and in this example it is set to be the same as the tapered surface 112. With this configuration, since the tapered surface 282 and the tapered surface 112 are in contact over a wide area in the circumferential direction, rotational torque can be transmitted between the surfaces and fretting is less likely to occur.

[0053] [Other variations] In the description of the embodiments, an example was shown in which the input shaft 21 is connected to the motor shaft 11 using a key, but the present invention is not limited thereto. The input shaft and the motor shaft may be connected by various known coupling methods.

[0054] In the description of the embodiments, an example was shown in which the reduction gear is a center-crank type eccentric oscillating reduction gear, but the present invention is not limited thereto. For example, the reduction gear may be an eccentric oscillating reduction gear of the type in which the eccentric shaft is offset from the axis of the internal gear, or it may be a flexible meshing type reduction gear (sometimes called a wave reduction gear) having a cylindrical external gear. The reduction gear may also be a cup-type or top-hat-type flexible meshing type reduction gear. Furthermore, it can be applied to reduction gears having various reduction mechanisms such as parallel-axis reduction mechanisms and orthogonal-axis reduction mechanisms.

[0055] The description of the embodiments shows an example in which three external gears 13, 14, and 15 are provided, but the present invention is not limited thereto. The reduction gear may be provided with two or fewer external gears or four or more external gears.

[0056] In the description of the embodiment, a bolt B1 was exemplified as the first connecting means for axially connecting the motor shaft 11 and the input shaft 21, but the invention is not limited to this, and various connecting means can be applied. For example, a rivet connection may be used. Also, a key connection was exemplified as the second connecting means for circumferentially (rotationally) connecting the motor shaft 11 and the input shaft 21, but the invention is not limited to this, and various connecting means can be applied. For example, a spline connection or a D-cut connection may be used.

[0057] In the description of the embodiment, an example was shown in which the axial movement suppression member 6 is an O-ring R1, R2, but it is not limited to this, and the axial movement suppression member 6 is a broad concept that also includes a surface treatment layer, etc.

[0058] Each of these modifications produces the same functions and effects as the embodiments.

[0059] 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]

[0060] 1 Motor, 3 First connecting means, 5 Second connecting means, 6 Axial movement suppressing member, 10 Reducer, 11 Motor shaft, 13, 14, 15 External gears, 21 Input shaft, 23, 24, 25 Eccentric parts, 28 Connecting hole, 30 Bolt insertion hole, 35, 36 Carrier, 37, 38 Main bearings, 39, 40 Input shaft bearings, 41 Internal gear.

Claims

1. A reduction gear having an input shaft having a connecting hole for connecting to a motor shaft, and an input shaft bearing for supporting the input shaft, It has a first connecting means for connecting the input shaft and the motor shaft, and a second connecting means for connecting the input shaft and the motor shaft in the circumferential direction, The first connecting means is configured such that when the first connecting means is fastened, a load acting toward the bottom of the connected hole is applied to the motor shaft. The input shaft bearing is axially movable toward the opening of the connected hole, The aforementioned connected hole is a cylindrical portion with a constant inner diameter in the axial direction, and is connected to the motor shaft of the reduction gear.

2. The gearbox according to claim 1, wherein the input shaft and the motor shaft are connected by a first connecting means, with an axial gap between the axial end face of the motor shaft and the bottom of the connecting hole.

3. The gear reducer according to claim 1 or 2, wherein the fitting on the outer ring side of the input shaft bearing is a clearance fit.

4. The gearbox according to any one of claims 1 to 3, wherein the input shaft bearing is a bearing having rollers that are movable in the axial direction.

5. The gearbox according to any one of claims 1 to 4, wherein an axial movement suppression member is disposed between the outer ring of the input shaft bearing and a support member that supports the outer ring, the member that suppresses the axial movement of the outer ring.

6. The gearbox according to claim 5, wherein the axial movement suppressing member is an O-ring disposed in a recess provided in the outer ring or the support member.

7. The first connecting means is a bolt, The input shaft has a bolt insertion hole that communicates with the bottom surface of the connected hole from the end face on the side opposite the motor, and a bolt hole provided axially from the tip surface of the motor shaft. The motor shaft and the input shaft are connected by screwing the bolt, which has been inserted through the bolt insertion hole from the motor side of the input shaft, into the bolt hole of the motor shaft. A washer is provided between the bolt and the input shaft. The gearbox according to any one of claims 1 to 6, wherein the outer shape of the portion of the bolt that protrudes axially from the input shaft is within the outer diameter of the input shaft as viewed from the axial direction.

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