Speed reducer

Abstract

To provide a technique which allows a whole device to be downsized while securing fixing strength between a stator housing on a motor side and a member in which a speed reducer is assembled.SOLUTION: A speed reducer has a casing, a rotor, a stator, a speed reduction mechanism, an output member, and an output bearing. The casing cylindrically extends in an axial direction centering on a center shaft. The rotor rotates centering on the center shaft. The stator is fixed to an inner peripheral surface of the casing. The speed reduction mechanism reduces rotational speed of the rotor. An output member rotates around the center shaft at the rotational speed which has been reduced by the speed reduction mechanism. The output bearing is disposed in the diameter direction between the casing and the output member and supports the output member rotatably centering on the center shaft. The speed reduction mechanism has a plurality of internal teeth which are formed on the inner peripheral surface of the casing and arranged annularly around the center shaft. At least either an outer diameter of an outer ring of the output bearing or an outer diameter of the stator is larger than a diameter of a tooth bottom of the internal gear.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reducer. [Background technology]

[0002] Conventionally, reducers that reduce the speed of rotation of a motor and output the reduced speed have been known. A conventional reducer is described, for example, in Japanese Patent Application Laid-Open No. 2005-212657. The electric wheel drive device disclosed in Japanese Patent Application Laid-Open No. 2005-212657 reduces the speed of rotation of an electric motor using first and second planetary reducers and transmits the reduced speed to a wheel via a hub wheel. [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-212657 Summary of the Invention [Problem to be solved by the invention]

[0003] In the above publication, the stator housing constituting the stator portion of the electric motor is an annular member having a generally U-shaped cross section and a fixing portion extending radially outward on the outer diameter side. The fixing portion is fastened to a vehicle body mounting flange of the outer member via fixing bolts. Planetary gears constituting the first and second planetary reducers are respectively mounted inside the outer member.

[0004] However, in the device described in the above publication, the stator housing of the electric motor is fixed with bolts to the member in which the first and second planetary reducers are incorporated, making it difficult to ensure the strength of the fixed parts and potentially making it impossible to miniaturize the entire device.

[0005] An object of the present invention is to provide a technology that can reduce the size of the entire device while ensuring the fixing strength between the stator housing on the motor side and the member in which the reducer is incorporated. [Means for solving the problem]

[0006] A first exemplary invention of the present application is a reducer comprising: a casing extending cylindrically in the axial direction about a central axis; a rotor rotating about the central axis; a stator fixed to the inner peripheral surface of the casing; a speed reduction mechanism for reducing the rotational speed of the rotor; an output member rotating about the central axis at the rotational speed reduced by the speed reduction mechanism; and an output bearing disposed radially between the casing and the output member for supporting the output member rotatably about the central axis. The speed reduction mechanism includes an internal gear formed on the inner peripheral surface of the casing and having a plurality of internal teeth arranged in an annular shape around the central axis. At least one of the outer diameter of an outer ring of the output bearing and the outer diameter of the stator is larger than the diameter of the tooth root of the internal gear. [Effects of the Invention]

[0007] According to the first exemplary aspect of the present application, the stator of the motor and the internal gear of the reduction mechanism are disposed inside a single casing, thereby ensuring the strength of the casing while realizing a reduction in the size of the entire reducer. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a vertical cross-sectional view of a reducer according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the reducer according to the first embodiment. [Figure 3] FIG. 3 is a vertical cross-sectional view of a reducer according to a second embodiment. [Figure 4] FIG. 4 is a vertical cross-sectional view of a reducer according to a third embodiment. [Figure 5] FIG. 5 is a vertical cross-sectional view of a reducer according to a fourth embodiment. [Figure 6] FIG. 6 is a cross-sectional view of a reducer according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, exemplary embodiments of the present application will be described with reference to the drawings. In this application, a direction parallel to the central axis of a reducer according to the present invention will be referred to as the "axial direction," a direction perpendicular to the central axis will be referred to as the "radial direction," and a direction along an arc centered on the central axis will be referred to as the "circumferential direction."

[0010] In addition, in this application, the axial direction is defined as the left-right direction in Figures 1 and 3 to 5, with the left side defined as "one axial side" and the right side defined as "the other axial side," and the shapes and positional relationships of the various parts will be described. However, this definition is not intended to limit the orientation of the reducer according to the present invention during manufacture and use. In addition, in this application, the term "parallel direction" is not limited to being geometrically strictly parallel. In other words, it is sufficient that a certain direction and a "parallel direction" to that direction are approximately parallel to each other to the extent that the effects of the invention are achieved. In addition, in this application, the term "orthogonal direction" is not limited to being geometrically strictly orthogonal. In other words, it is sufficient that a certain direction and a "orthogonal direction" to that direction are approximately orthogonal to each other to the extent that the effects of the invention are achieved.

[0011] 1. First Embodiment The configuration of a reducer 1 according to a first embodiment of the present invention will be described below. Fig. 1 is a vertical cross-sectional view of the reducer 1 according to the first embodiment.

[0012] The reducer 1 of this embodiment reduces the rotational speed of, for example, a servo motor or the like that can control the position or speed, and outputs the reduced speed. The reducer 1 of this embodiment has a motor 2, a reduction mechanism 3, a casing 4, an inner lid 5, an outer lid 6, an output member 7, a support bearing 225, an input bearing 226, a planetary bearing 325, and output bearings 751 and 752. The reducer 1 reduces the rotational speed of a rotor 23 (described later) of the motor 2 using the reduction mechanism 3, and transmits the reduced rotational speed to the output member 7. The output member 7 rotates at the rotational speed reduced by the reduction mechanism 3.

[0013] The motor 2 and the reduction mechanism 3 are each disposed along a central axis 90 that extends horizontally (the left-right direction in FIG. 1). The casing 4 is a member that extends cylindrically in the axial direction around the central axis 90. The casing 4 is formed from a single member.

[0014] An inner lid 5 is disposed radially inside an intermediate portion of the casing 4 in the axial direction. As shown in FIG. 1 , the inner lid 5 is located axially between a stator 21 (described later) of the motor 2 and the reduction mechanism 3. The inner lid 5 is a member that extends in an annular shape around a central axis 90. The outer diameter of the inner lid 5 is approximately equal to the inner diameter of a portion of the casing 4 that is located radially outside the inner lid 5. Therefore, the outer peripheral surface of the inner lid 5 contacts the inner peripheral surface of the casing 4.

[0015] Additionally, an O-ring extending in an annular shape around the central axis 90 is disposed between the outer peripheral surface of the inner lid 5 and the inner peripheral surface of the casing 4. Hereinafter, this O-ring will be referred to as the "first ring 54." This allows the outer peripheral surface of the inner lid 5 to be supported on the inner peripheral surface of the casing 4 so as not to rotate relative to it. Furthermore, by disposing the first ring 54, it is possible to prevent the lubricant applied to the side of the reduction mechanism 3 from leaking to the side of the motor 2, as will be described later.

[0016] A retaining ring is disposed on the other axial side of the inner lid 5. Hereinafter, this retaining ring will be referred to as the "first retaining ring 55." The first retaining ring 55 contacts the inner circumferential surface of the casing 4 and the end face on the other axial side of the inner lid 5. This prevents the inner lid 5 from moving in the other axial direction. The inner diameter of a portion of the casing 4 adjacent to one axial side of the position where the inner lid 5 is disposed is smaller than the outer diameter of the inner lid 5. This prevents the inner lid 5 from moving in the one axial direction.

[0017] An outer lid 6 is disposed radially inside a portion of the casing 4 near the other axial end thereof. As shown in FIG. 1 , the outer lid 6 is located on the other axial side of the stator 21 of the motor 2. The outer lid 6 is a member that extends radially in a disk shape about a central axis 90. The outer diameter of the outer lid 6 is approximately equal to the inner diameter of a portion of the casing 4 that is located radially outside the outer lid 6. Therefore, the outer peripheral surface of the outer lid 6 contacts the inner peripheral surface of the casing 4.

[0018] Additionally, an O-ring extending in an annular shape around the central axis 90 is disposed between the outer peripheral surface of the outer lid 6 and the inner peripheral surface of the casing 4. Hereinafter, this O-ring will be referred to as the "second ring 64." As a result, the outer peripheral surface of the outer lid 6 is supported on the inner peripheral surface of the casing 4 so as not to rotate relative to it. Furthermore, by disposing the second ring 64, it is possible to prevent dust from entering the inner space of the casing 4 from outside the reducer 1.

[0019] A retaining ring is also disposed on the other axial side of the outer lid 6. Hereinafter, this retaining ring will be referred to as the "second retaining ring 65." The second retaining ring 65 contacts the inner circumferential surface of the casing 4 and the end face of the outer lid 6 on the other axial side. This prevents the outer lid 6 from moving in the other axial direction. Furthermore, the end face of the outer lid 6 on one axial side contacts the stator 21 of the motor 2. This prevents the outer lid 6 from moving in the one axial direction.

[0020] A recess 60 is provided on one axial end face of the outer lid 6. The recess 60 is recessed from the one axial end face of the outer lid 6 to the other axial end. When viewed in the axial direction, the recess 60 has a circular shape centered on the central axis 90. This forms a support surface 61 on the outer lid 6 that expands cylindrically in the axial direction with the central axis 90 as the center.

[0021] The motor 2 has a stator 21, a shaft 22, and a rotor 23. The stator 21 is fixed to the inner peripheral surface of the casing 4. The shaft 22 extends cylindrically in the axial direction along a central axis 90. The shaft 22 extends from one axial side of the stator 21 to the other axial side of the stator 21. The rotor 23 is fixed around the shaft 22 so as not to rotate relative to the shaft 22. The outer peripheral surface of the rotor 23 faces the inner peripheral surface of the stator 21 with a small radial gap therebetween.

[0022] A support bearing 225 is provided radially between the outer peripheral surface of a portion of the shaft 22 located axially on one side of the stator 21 and the inner peripheral surface of the inner lid 5. The support bearing 225 is, for example, a ball bearing. An inner ring of the support bearing 225 is fixed to the outer peripheral surface of the shaft 22. An outer ring of the support bearing 225 is fixed to the inner peripheral surface of the inner lid 5. As a result, the shaft 22 is supported by the support bearing 225 on one axial side of the stator 21 so as to be rotatable about the central axis 90 relative to the inner lid 5 and the casing 4. However, instead of a ball bearing, another type of bearing such as a roller bearing may be used for the support bearing 225. The outer diameter of the outer ring of the support bearing 225 is smaller than the diameter of a tooth root 350 of an internal gear 35 (described later) of the reduction mechanism 3.

[0023] An input bearing 226 is provided radially between the outer circumferential surface of the shaft 22 near the other axial end thereof and the support surface 61 of the outer lid 6. The input bearing 226 may be, for example, a ball bearing. An inner ring of the input bearing 226 is fixed to the outer circumferential surface of the shaft 22. An outer ring of the input bearing 226 is fixed to the support surface 61. As a result, the shaft 22 is supported by the input bearing 226 on the other axial end of the stator 21 so as to be rotatable about the central axis 90 relative to the outer lid 6 and the casing 4. As a result, the shaft 22 rotates while being supported more stably. However, instead of a ball bearing, another type of bearing such as a roller bearing may be used for the input bearing 226.

[0024] When motor 2 is driven, a driving current is supplied to each coil of stator 21, generating a rotating magnetic field in each coil. This generates a circumferential torque in rotor 23. As a result, rotor 23 and shaft 22 fixed to rotor 23 rotate circumferentially about central axis 90 relative to stator 21 and casing 4 via support bearing 225 and input bearing 226.

[0025] The reduction mechanism 3 is a device that reduces the speed of rotation of the shaft 22 and rotor 23 at an input rotation speed N1 and converts it into rotation at an output rotation speed N2, which is slower than the input rotation speed N1. FIG. 2 is a cross-sectional view of the reducer 1 as viewed axially along the line AA in FIG. 1. Note that in FIG. 2, hatching indicating the cross section and the teeth of each gear are partially omitted to avoid cluttering the drawing. As shown in FIGS. 1 and 2, the reduction mechanism 3 includes a sun gear 31, multiple planetary gears 32, multiple carrier pins 33, a carrier 34, and an internal gear 35. The reduction mechanism 3 of this embodiment includes three planetary gears 32 and three carrier pins 33. The reduction mechanism 3 transmits power by rotating the sun outer teeth 311 of the sun gear 31, which will be described later, and the planet outer teeth 321 of the multiple planetary gears 32, and the planet outer teeth 321 of the multiple planetary gears 32 and the internal teeth 351 of the internal gear 35 while meshing with each other.

[0026] The sun gear 31 is a gear disposed approximately coaxially with the central axis 90. The sun gear 31 is fixed to one axial side of the shaft 22 so as to be unable to rotate relative to each other. As a result, the sun gear 31 receives rotation from the motor 2 and rotates together with the shaft 22 and the rotor 23 at an input rotation speed N1 around the central axis 90. The sun gear 31 also has a plurality of external teeth on its outer circumferential surface. Hereinafter, these external teeth will be referred to as "sun outer teeth 311." Each of the plurality of sun outer teeth 311 protrudes radially outward. The plurality of sun outer teeth 311 are arranged at a constant pitch along the circumferential direction.

[0027] Each of the three planetary gears 32 is arranged along a rotation axis 91 around the sun gear 31. In this embodiment, the rotation axis 91 is substantially parallel to the central axis 90. Also, as shown in FIG. 2, in this embodiment, the three planetary gears 32 are arranged around the sun gear 31 at equal intervals in the circumferential direction. However, the number of planetary gears 32 arranged around the sun gear 31 may be one to two, or may be four or more. Each planetary gear 32 has a plurality of external teeth on its outer circumferential surface. Hereinafter, these external teeth will be referred to as "planetary external teeth 321." Each of the plurality of planetary external teeth 321 protrudes outward.

[0028] The outer planetary teeth 321 of each planetary gear 32 mesh with the outer sun teeth 311 of the sun gear 31 from the radially outer side. As a result, when the sun gear 31 rotates about the central axis 90, each planetary gear 32 receives power from the sun gear 31 and rotates about the rotation axis 91 in the direction opposite to the rotation direction of the sun gear 31. Each planetary gear 32 also has a through hole 320 extending in the axial direction. A carrier pin 33 passes through each through hole 320 along the rotation axis 91.

[0029] Each of the three carrier pins 33 is a member for rotatably supporting one planetary gear 32. For example, a columnar member extending along the rotation axis 91 is used for each carrier pin 33. Each carrier pin 33 is inserted into a through hole 320 of one planetary gear 32. Furthermore, a planetary bearing 325 is inserted radially between the outer circumferential surface of the carrier pin 33 and the through hole 320 of the planetary gear 32. For example, a needle bearing is used for the planetary bearing 325. As a result, the planetary gear 32 is supported by the planetary bearing 325 so as to be rotatable about the rotation axis 91 relative to the carrier pin 33.

[0030] In this embodiment, a lubricant such as grease is applied to the vicinity of the carrier pin 33, the planetary bearing 325, and the planetary gear 32. This allows for better lubrication between the planetary bearing 325 and the carrier pin 33 and the planetary gear 32, where strong contact pressure is generated.

[0031] The carrier 34 is a member that expands in a disk shape in the radial direction about a central axis 90. As shown in FIG. 1 , the carrier 34 has a through hole 340. In this embodiment, the carrier 34 has three through holes 340. Each through hole 340 penetrates the carrier 34 along a rotation axis 91, radially outward of the central axis 90. The three through holes 340 are provided at intervals of approximately 120 degrees from one another in the circumferential direction about the central axis 90. However, instead of the through holes 340, the carrier 34 may have a recess that is recessed from an end face on the other axial side toward one axial side.

[0032] One axial side portion of each of the three carrier pins 33 is inserted into one of the through holes 340. Each carrier pin 33 is fixed to the carrier 34 in the through hole 340 by bonding, press-fitting, or the like. As a result, each carrier pin 33 is fixed to the carrier 34 radially outward of the central axis 90 so as to be unable to rotate relative to the carrier 34. When the carrier 34 rotates about the central axis 90, the three carrier pins 33 fixed to the carrier 34 and the planetary gears 32 supported by each carrier pin 33 revolve in the circumferential direction about the central axis 90.

[0033] The output member 7 is fixed to one axial end of the carrier 34 so as to be non-rotatable relative to the carrier 34. The output member 7 is a member that extends cylindrically in the axial direction around a central axis 90. This allows the output member 7 to rotate together with the carrier 34 around the central axis 90. However, the output member 7 and the carrier 34 may be formed from a single member.

[0034] Two output bearings 751, 752 are disposed radially between the outer peripheral surface of the output member 7 and the inner peripheral surface of the casing 4. The two output bearings 751, 752 have the same structure and are aligned in the axial direction. Each of the output bearings 751, 752 is, for example, a ball bearing. The inner rings of the output bearings 751, 752 are fixed to the outer peripheral surface of the output member 7. The outer rings of the output bearings 751, 752 are fixed to the inner peripheral surface of the casing 4. As a result, the output member 7 is supported by the output bearings 751, 752 to be rotatable about the central axis 90 relative to the casing 4. However, instead of ball bearings, other types of bearings such as roller bearings may be used for each of the output bearings 751, 752. Furthermore, it is sufficient that at least one output bearing is disposed radially between the outer peripheral surface of the output member 7 and the inner peripheral surface of the casing 4.

[0035] The internal gear 35 is a gear disposed approximately coaxially with the central axis 90. The internal gear 35 extends in the axial direction in the shape of an annular cylinder centered on the central axis 90. The internal gear 35 has a plurality of internal teeth 351 formed on the inner circumferential surface of the casing 4 and arranged in an annular shape around the central axis 90. As described above, the internal gear 35 is composed of a plurality of internal teeth 351 formed on the inner circumferential surface of the casing 4, and is therefore structured not to rotate around the central axis 90. Each of the plurality of internal teeth 351 protrudes radially inward. The plurality of internal teeth 351 are arranged at a constant pitch along the circumferential direction. The plurality of internal teeth 351 mesh with the planetary external teeth 321 of each of the three planetary gears 32 from the radially outer side.

[0036] When the sun gear 31 rotates around the central axis 90 at the input rotational speed N1, the three planetary gears 32 that mesh with both the sun gear 31 and the internal gear 35 each rotate around a rotation axis 91. Furthermore, while rotating around their rotation axes 91, the three planetary gears 32 revolve together with the carrier pins 33 around the central axis 90 at an output rotational speed N2 due to their meshing with the sun gear 31 and the internal gear 35. As a result, the carrier 34 to which the three carrier pins 33 are fixed rotates around the central axis 90 at the output rotational speed N2. In other words, the carrier 34 supports the three planetary gears 32 and the carrier pins 33 so that they can revolve circumferentially around the central axis 90, and rotates around the central axis 90 at the output rotational speed N2 in conjunction with the revolution of the three planetary gears 32 and the carrier pins 33.

[0037] Furthermore, as described above, the casing 4 of this embodiment is formed from a single member. In this way, by arranging the motor 2 including the stator 21 and the reduction mechanism 3 including the internal gear 35 inside a single casing 4, the strength of the casing 4 can be more easily ensured compared to when a casing for accommodating the motor 2 and a casing for accommodating the reduction mechanism 3 are provided separately and connected to each other. As a result, the entire reducer 1 can be made more compact. Furthermore, since the central axis 90 of the motor 2 and the central axis 90 of the reduction mechanism 3 can be easily and accurately aligned, rotational performance is improved.

[0038] Furthermore, in this embodiment, the outer diameter of the outer rings of the output bearings 751, 752 and the outer diameter of the stator 21 of the motor 2 are each larger than the diameter of the tooth root 350 of the internal gear 35. Here, the tooth root 350 refers to the bottom surface of the tooth groove between adjacent internal teeth 351. That is, in this embodiment, the diameter of the portion of the inner circumferential surface of the casing 4 where the multiple internal teeth 351 are formed is smaller than the diameter of the portion to which the output bearings 751, 752 are fixed and the diameter of the portion to which the stator 21 is fixed. This improves the workability when forming the internal gear 35 by cutting (broaching) the inner circumferential surface of the casing 4 during manufacturing of the reducer 1.

[0039] However, it is sufficient if at least one of the outer diameter of the outer rings of the output bearings 751, 752 and the outer diameter of the stator 21 is made larger than the diameter of the tooth bottom 350 of the internal gear 35. This makes it easier to cut (broach) the internal gear 35 on the inner peripheral surface of the casing 4.

[0040] 2. Second Embodiment Next, the configuration of a reducer 1B according to a second embodiment of the present invention will be described. Fig. 3 is a vertical cross-sectional view of the reducer 1B according to the second embodiment. Note that the following description will focus on configurations that differ from the first embodiment, and redundant description of configurations that are the same as those in the first embodiment will be omitted.

[0041] As shown in FIG. 3, the reduction gear mechanism 3B of this embodiment has a first sun gear 31B, a plurality of first planetary gears 32B, a plurality of first carrier pins 33B, a first carrier 34B, a first internal gear 35B, a second sun gear 36B, a plurality of second planetary gears 37B, a plurality of second carrier pins 38B, a second carrier 39B, and a second internal gear 40B.

[0042] The first sun gear 31B, the multiple first planetary gears 32B, the multiple first carrier pins 33B, the first carrier 34B, and the first internal gear 35B of this embodiment have configurations equivalent to the sun gear 31, the multiple planetary gears 32, the multiple carrier pins 33, the carrier 34, and the internal gear 35 of the first embodiment, respectively.

[0043] When the first sun gear 31B rotates about the central axis 90B at the input rotational speed N1, the multiple first planetary gears 32B, which mesh with both the first sun gear 31B and the first internal gear 35B, each rotate about their own rotation axis 91B. Furthermore, while rotating about their own rotation axis 91B, the multiple first planetary gears 32B revolve together with the first carrier pin 33B around the central axis 90B at an intermediate rotational speed N15 that is lower than the input rotational speed N1 due to their meshing with the first sun gear 31B and the first internal gear 35B. As a result, the first carrier 34B, to which the multiple first carrier pins 33B are fixed, rotates about the central axis 90B at the intermediate rotational speed N15.

[0044] The second sun gear 36B is a gear arranged approximately coaxially with the central axis 90B. The second sun gear 36B is fixed to one axial side of the first carrier 34B so that they cannot rotate relative to each other. As a result, the second sun gear 36B rotates together with the first carrier 34B at an intermediate rotation speed N15 around the central axis 90B. The second sun gear 36B also has multiple external teeth on its outer circumferential surface. Hereinafter, these external teeth will be referred to as "second sun outer teeth 361B." Each of the multiple second sun outer teeth 361B protrudes radially outward. The multiple second sun outer teeth 361B are arranged at a constant pitch along the circumferential direction.

[0045] The multiple second planetary gears 37B are each arranged around the second sun gear 36B along the rotation axis 91B. Each second planetary gear 37B has multiple external teeth on its outer circumferential surface. Hereinafter, these external teeth will be referred to as "second planetary external teeth 371B." Each of the multiple second planetary external teeth 371B protrudes outward.

[0046] The second outer planetary teeth 371B of each second planetary gear 37B mesh with the second outer sun teeth 361B of the second sun gear 36B from the radially outer side. As a result, when the second sun gear 36B rotates about the central axis 90B, each second planetary gear 37B receives power from the second sun gear 36B and rotates about the rotation axis 91B in the direction opposite to the rotation direction of the second sun gear 36B. Each second planetary gear 37B also has a second through hole 370B extending in the axial direction. A second carrier pin 38B passes through each second through hole 370B along the rotation axis 91B.

[0047] Each of the multiple second carrier pins 38B is a member for rotatably supporting one second planetary gear 37B. For example, a columnar member extending along the rotation axis 91B is used for each second carrier pin 38B. Each second carrier pin 38B is inserted into a second through hole 370B of one second planetary gear 37B. A second planetary bearing 375B is inserted radially between the outer circumferential surface of the second carrier pin 38B and the second through hole 370B of the second planetary gear 37B. The second planetary gear 37B is supported by the second planetary bearing 375B to be rotatable about the rotation axis 91B relative to the second carrier pin 38B.

[0048] The second carrier 39B is a member that expands radially in a disk shape about a central axis 90B. Each of the multiple second carrier pins 38B is fixed to the second carrier 39B radially outward of the central axis 90B so as to be unable to rotate relative to the second carrier 39B. When the second carrier 39B rotates about the central axis 90B, the multiple second carrier pins 38B fixed to the second carrier 39B and the second planetary gears 37B supported by each second carrier pin 38B revolve circumferentially about the central axis 90B.

[0049] An output member 7B is fixed to one axial end of the second carrier 39B so as to be non-rotatable relative to the second carrier 39B. The output member 7B is a member that extends in the axial direction in a cylindrical shape centered on a central axis 90B. The output member 7B rotates together with the second carrier 39B about the central axis 90B relative to the casing 4B via output bearings 751B and 752B.

[0050] The second internal gear 40B is a gear arranged approximately coaxially with the central axis 90B. The second internal gear 40B extends in the axial direction in the shape of an annular cylinder centered on the central axis 90B. The second internal gear 40B has a plurality of second internal teeth 401B formed on the inner peripheral surface of the casing 4B on one axial side of the first internal gear 35B and arranged in an annular shape around the central axis 90B. The second internal gear 401B meshes with the second planetary external teeth 371B of each of the second planetary gears 37B from the radially outer side. In this embodiment, the second internal gear 40B and the first internal gear 35B are formed from a single member. However, the second internal gear 40B may be formed separately from the first internal gear 35B.

[0051] When the second sun gear 36B rotates about the central axis 90B at the intermediate rotation speed N15, the multiple second planetary gears 37B that mesh with both the second sun gear 36B and the second internal gear 40B each rotate about their own rotation axis 91B. Furthermore, while rotating about their own rotation axis 91B, the multiple second planetary gears 37B revolve together with the second carrier pins 38B around the central axis 90B at an output rotation speed N2 that is lower than the intermediate rotation speed N15 due to their meshing with the second sun gear 36B and the second internal gear 40B. As a result, the second carrier 39B to which the multiple second carrier pins 38B are fixed rotates together with the output member 7B about the central axis 90B at the output rotation speed N2.

[0052] As described above, the reduction mechanism 3B of this embodiment reduces the input rotation speed N1 from the motor 2B to an intermediate rotation speed N15 using the first sun gear 31B, the multiple first planetary gears 32B, the multiple first carrier pins 33B, the first carrier 34B, and the first internal gear 35B. The reduction mechanism 3B also reduces the intermediate rotation speed N15 to an output rotation speed N2 using the second sun gear 36B, the multiple second planetary gears 37B, the multiple second carrier pins 38B, the second carrier 39B, and the second internal gear 40B. Thus, the reduction mechanism 3B of this embodiment can achieve a higher reduction ratio by performing two-stage reduction.

[0053] Furthermore, in this embodiment, the casing 4B is formed from a single member. In this embodiment, too, by arranging the motor 2B and the reduction mechanism 3B inside the single casing 4B, the strength of the casing 4B can be more easily ensured compared to when a casing for accommodating the motor 2B and a casing for accommodating the reduction mechanism 3B are provided separately and connected to each other. As a result, the entire reducer 1B can be made more compact.

[0054] 3. Third Embodiment Next, the configuration of a reducer 1C according to a third embodiment of the present invention will be described. Fig. 4 is a vertical cross-sectional view of the reducer 1C according to the third embodiment. Note that the following description will focus on configurations that differ from the first embodiment, and redundant description of configurations that are the same as those in the first embodiment will be omitted.

[0055] A reducer 1C of this embodiment further includes a shaft coupling 200C in addition to the components of the reducer 1 of the first embodiment. The shaft coupling 200C is composed of a slot 201C cut in the axial direction and a screw 202C that is threaded in a direction perpendicular to the central axis 90C. In the reducer 1C of this embodiment, a shaft 22C of a motor 2 is axially connected to a sun gear 31C of a reduction mechanism 3C via the shaft coupling 200C. Specifically, by inserting the shaft 22C into the slot 201C and tightening the screw 202C, the sun gear 31C rotates about the central axis 90C by power obtained from the motor 2C.

[0056] That is, the shaft coupling 200C can connect the shaft 22C of the motor 2C to the reduction mechanism 3C. This allows motors 2C of various specifications to be attached to the reduction mechanism 3C using the shaft coupling 200C, improving versatility. Note that the present invention also includes a reducer 1C in which the motor 2C is attached to the reduction mechanism 3C using the shaft coupling 200C.

[0057] 4. Fourth Embodiment Next, the configuration of a reducer 1D according to a fourth embodiment of the present invention will be described. Fig. 5 is a longitudinal sectional view of the reducer 1D according to the fourth embodiment. Fig. 6 is a transverse sectional view of the reducer 1D as seen from position BB in Fig. 5. In Fig. 6, some of the hatching indicating cross sections has been omitted to avoid complicating the drawing. Note that the following description will focus on configurations that differ from the first embodiment, and redundant description of configurations that are equivalent to those in the first embodiment will be omitted.

[0058] As shown in FIG. 5, a speed reduction mechanism 3D of this embodiment has a rigid internal gear 331D, a flexible external gear 332D, and a wave generator 333D.

[0059] The rigid internal gear 331D is a gear arranged approximately coaxially with the central axis 90D. The rigid internal gear 331D extends in the axial direction in the shape of an annular cylinder centered on the central axis 90D. The rigid internal gear 331D is also located radially outside a cylindrical portion 334D (described later) of the flexible external gear 332D. The rigidity of the rigid internal gear 331D is much higher than the rigidity of the cylindrical portion 334D of the flexible external gear 332D. For this reason, the rigid internal gear 331D can be considered to be a substantially rigid body.

[0060] The rigid internal gear 331D has a plurality of internal teeth 351D formed on the inner circumferential surface of the casing 4D and arranged in an annular shape around the central axis 90D. As such, the rigid internal gear 331D is composed of a plurality of internal teeth 351D formed on the inner circumferential surface of the casing 4D, and is therefore structured not to rotate around the central axis 90D. Each of the plurality of internal teeth 351D protrudes radially inward. The plurality of internal teeth 351D are arranged at a constant pitch along the circumferential direction.

[0061] The flexible external gear 332D is a flexible, deformable annular gear. The flexible external gear 332D is supported rotatably around a central axis 90D. The flexible external gear 332D has a cylindrical portion 334D and a disk portion 335D. The cylindrical portion 334D extends cylindrically in the axial direction around the central axis 90D. The other axial end of the cylindrical portion 334D is located radially outside the wave generator 333D and radially inside the rigid internal gear 331D. The cylindrical portion 334D is flexible and therefore capable of radial deformation. In particular, the other axial end of the cylindrical portion 334D is a free end and therefore capable of greater radial displacement than other portions.

[0062] The flexible external gear 332D has a plurality of external teeth 336D. The plurality of external teeth 336D are provided on the outer peripheral surface near the other axial end of the cylindrical portion 334D. The plurality of external teeth 336D are arranged at a constant pitch in the circumferential direction. Each of the external teeth 336D protrudes radially outward. The number of internal teeth 351D of the rigid internal gear 331D described above is slightly different from the number of external teeth 336D of the flexible external gear 332D.

[0063] The disk portion 335D extends radially inward from one axial end of the cylindrical portion 334D in a flat plate shape and also extends in an annular shape in a direction perpendicular to the central axis 90D. The disk portion 335D is fixed to the other axial end face of the output member 7D by, for example, bolting so that they cannot rotate relative to each other. As a result, the output member 7D, together with the flexible external gear 332D, is supported rotatably about the central axis 90D relative to the casing 4D via output bearings 751D and 752D.

[0064] The wave generator 333D is a mechanism that generates periodic bending deformation in the cylindrical portion 334D of the flexible external gear 332D. The wave generator 333D has a cam 337D and a flexible bearing 338D. The cam 337D is fixed to the shaft 22D of the motor 2D directly or indirectly via a separate member. Therefore, the cam 337D rotates at an input rotation speed N1 around the central axis 90D together with the shaft 22D and rotor 23D of the motor 2D. Furthermore, as shown in FIG. 6, the outer peripheral surface of the cam 337D is elliptical when viewed in the axial direction. The flexible bearing 338D is interposed between the outer peripheral surface of the cam 337D and the inner peripheral surface of the cylindrical portion 334D of the flexible external gear 332D. Therefore, the cam 337D and the cylindrical portion 334D can rotate at different rotation speeds.

[0065] The inner ring of the flexible bearing 338D contacts the outer peripheral surface of the cam 337D. The outer ring of the flexible bearing 338D contacts the inner peripheral surface of the cylindrical portion 334D of the flexible external gear 332D. As a result, the cylindrical portion 334D of the flexible external gear 332D deforms into an elliptical shape that follows the outer peripheral surface of the cam 337D. As a result, the cylindrical portion 334D is pushed radially outward at two locations corresponding to both ends of the major axis of the ellipse, causing some of the external teeth 336D of the flexible external gear 332D to mesh with the internal teeth 351D of the rigid internal gear 331D. At other circumferential positions, the external teeth 336D and the internal teeth 351D do not mesh with each other.

[0066] When the motor 2D is driven, the cam 337D rotates around the central axis 90D at the input rotational speed N1 together with the rotor 23D and shaft 22D of the motor 2D. As a result, the major axis of the ellipse described above of the flexible external gear 332D also rotates at the input rotational speed N1. As a result, the meshing position between the external teeth 336D and the internal teeth 351D also changes circumferentially at the input rotational speed N1. Also, as described above, the number of internal teeth 351D of the rigid internal gear 331D is slightly different from the number of external teeth 336D of the flexible external gear 332D. Due to this difference in the number of teeth, the meshing position between the external teeth 336D and the internal teeth 351D changes slightly circumferentially with each rotation of the cam 337D. As a result, the flexible external gear 332D and the output member 7D rotate relative to the rigid internal gear 331D about the central axis 90D at an output rotation speed N2 that is lower than the input rotation speed N1.

[0067] The casing 4D of this embodiment is formed from a single member. Also, in this embodiment, by arranging the motor 2D and the reduction mechanism 3D inside a single casing 4D, the strength of the casing 4D can be more easily ensured compared to when a casing for accommodating the motor 2D and a casing for accommodating the reduction mechanism 3D are provided separately and connected to each other. As a result, the entire reducer 1D can be made more compact.

[0068] <5. Variations> Although exemplary embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. Some of the elements appearing in the above-described embodiments may be deleted or known elements may be added without departing from the spirit of the present invention.

[0069] Furthermore, the detailed shape of the reducer may differ from the shape shown in each drawing of the above embodiment.

[0070] <6. Summary> The present technology can be configured as follows. (1): a casing extending cylindrically in an axial direction around a central axis; a rotor that rotates around the central axis; a stator fixed to an inner peripheral surface of the casing; a speed reduction mechanism that reduces the rotational speed of the rotor; an output member that rotates about the central axis at a rotational speed reduced by the reduction mechanism; an output bearing disposed radially between the casing and the output member, the output bearing supporting the output member rotatably about the central axis; and The reduction mechanism is an internal gear formed on the inner peripheral surface of the casing and having a plurality of internal teeth arranged in an annular shape around the central axis. and At least one of the outer diameter of the outer ring of the output bearing and the outer diameter of the stator is larger than the diameter of the tooth root of the internal gear.

[0071] (2): The reducer according to (1), a reduction gear, wherein both the outer diameter of the outer ring of the output bearing and the outer diameter of the stator are larger than the diameter of the tooth root of the internal gear.

[0072] (3): The reducer according to (1) or (2), an inner cover that extends annularly around the central axis between the reduction mechanism and the stator in the axial direction, and whose outer circumferential surface is in contact with the inner circumferential surface of the casing and supported so as to be non-rotatable relative to the casing; The reducer further comprises:

[0073] (4): (3) The reducer according to the present invention, a shaft fixed to the rotor so as not to be rotatable relative to the rotor and extending in a columnar shape along the central axis; a support bearing that supports the shaft relative to the inner cover on one axial side of the stator so as to be rotatable about the central axis; and an outer diameter of the outer ring of the support bearing is smaller than a diameter of a tooth root of the internal gear.

[0074] (5): The reducer according to (3) or (4), The reducer further includes a first ring, which is an O-ring extending in an annular shape around the central axis, between the inner peripheral surface of the casing and the outer peripheral surface of the inner lid.

[0075] (6): A reducer according to any one of (3) to (5), The reducer further includes a first retaining ring that is in contact with the inner peripheral surface of the casing and the other axial end face of the inner lid.

[0076] (7): A reducer according to any one of (1) to (6), a shaft fixed to the rotor so as not to be rotatable relative to the rotor and extending in a columnar shape along the central axis; an outer cover that extends radially in a disk shape around the central axis on the other axial side of the stator, and whose outer peripheral surface is in contact with the inner peripheral surface of the casing and supported so as to be non-rotatable relative to the inner peripheral surface of the casing; an input bearing that supports the shaft rotatably about the central axis relative to the outer cover on the other axial side of the stator; The reducer further comprises:

[0077] (8): (7) The reducer according to the present invention, The reducer further includes a second ring, which is an O-ring extending in an annular shape around the central axis, between the inner peripheral surface of the casing and the outer peripheral surface of the outer lid.

[0078] (9): The reducer according to (7) or (8), The reducer further includes a second retaining ring that is in contact with the inner peripheral surface of the casing and the other axial end face of the outer lid.

[0079] (10): A reducer according to any one of (1) to (9), a shaft fixed to the rotor so as not to be rotatable relative to the rotor and extending in a columnar shape along the central axis; a shaft coupling capable of connecting the shaft and the reduction mechanism; The reducer further comprises: [Industrial Applicability]

[0080] The present invention can be used in a reducer. [Explanation of symbols]

[0081] 1,1B,1C,1D reducer 2, 2B, 2C, 2D motors 3,3B,3C,3D reduction mechanism 4,4B,4D casing 5 Inner lid 6 Outer lid 7, 7B, 7D Output member 21 Stator 22, 22C, 22D shaft 23,23D rotor 35 Internal gear 35B 1st internal gear 54 First Ring 55 First retaining ring 64 Second Ring 65 Second retaining ring 90,90B,90C,90D Center axis 200C shaft coupling 225 Support bearing 226 Input bearing 331D Rigid Internal Gear 350 (internal tooth) root 351,351D internal teeth 401B 2nd internal tooth 751, 751B, 751D output bearing 752, 752B, 752D output bearing

Claims

1. a casing extending cylindrically in an axial direction around a central axis; a rotor that rotates around the central axis; a stator fixed to an inner peripheral surface of the casing; a speed reduction mechanism that reduces the rotational speed of the rotor; an output member that rotates about the central axis at a rotational speed reduced by the reduction mechanism; an output bearing disposed radially between the casing and the output member, the output bearing supporting the output member rotatably about the central axis; and The reduction mechanism is an internal gear formed on the inner peripheral surface of the casing and having a plurality of internal teeth arranged in an annular shape around the central axis. and At least one of the outer diameter of the outer ring of the output bearing and the outer diameter of the stator is larger than the diameter of the tooth root of the internal gear.

2. The reducer according to claim 1, a reduction gear, wherein both the outer diameter of the outer ring of the output bearing and the outer diameter of the stator are larger than the diameter of the tooth root of the internal gear.

3. The reducer according to claim 1 or 2, an inner cover that extends annularly around the central axis between the reduction mechanism and the stator in the axial direction, and whose outer circumferential surface is in contact with the inner circumferential surface of the casing and supported so as to be non-rotatable relative to the casing; The reducer further comprises:

4. The reducer according to claim 3, a shaft fixed to the rotor so as not to be rotatable relative to the rotor and extending in a columnar shape along the central axis; a support bearing that supports the shaft relative to the inner cover on one axial side of the stator so as to be rotatable about the central axis; and an outer diameter of the outer ring of the support bearing is smaller than a diameter of a tooth root of the internal gear.

5. The reducer according to claim 3, The reducer further includes a first ring, which is an O-ring extending in an annular shape around the central axis, between the inner peripheral surface of the casing and the outer peripheral surface of the inner lid.

6. The reducer according to claim 3, The reducer further includes a first retaining ring that is in contact with an inner peripheral surface of the casing and an end face of the inner cover on the other axial side.

7. The reducer according to claim 1 or 2, a shaft fixed to the rotor so as not to be rotatable relative to the rotor and extending in a columnar shape along the central axis; an outer cover that extends radially in a disk shape around the central axis on the other axial side of the stator, and whose outer peripheral surface is in contact with the inner peripheral surface of the casing and supported so as to be non-rotatable relative to the inner peripheral surface of the casing; an input bearing that supports the shaft rotatably about the central axis relative to the outer cover on the other axial side of the stator; The reducer further comprises:

8. The reducer according to claim 7, The reducer further includes a second ring, which is an O-ring extending in an annular shape around the central axis, between the inner peripheral surface of the casing and the outer peripheral surface of the outer lid.

9. The reducer according to claim 7, The reducer further includes a second retaining ring that is in contact with the inner peripheral surface of the casing and the other axial end face of the outer lid.

10. The reducer according to claim 1 or 2, a shaft fixed to the rotor so as not to be rotatable relative to the rotor and extending in a columnar shape along the central axis; a shaft coupling capable of connecting the shaft and the reduction mechanism; The reducer further comprises:

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