Speed reducer

Abstract

The invention provides a speed reducer. The speed reducer has a housing, a rotor, a stator, a speed reduction mechanism, an output member, and an output bearing. The housing extends in a cylindrical shape in the axial direction with the central axis as the center. The rotor rotates about a central axis. The stator is fixed to the inner circumferential surface of the housing. The speed reduction mechanism reduces the rotation speed of the rotor. The output member rotates about the central axis at a rotational speed reduced by the reduction mechanism. The output bearing is disposed between the housing and the output member in the radial direction, and supports the output member so as to be rotatable about the central axis. The speed reduction mechanism has an internally toothed gear formed on the inner peripheral surface of the housing, and the internally toothed gear has a plurality of internally toothed teeth arranged in an annular shape around the central axis. 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 internally toothed gear.

Description

Technical Field

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

[0002] Conventionally, a speed reducer that decelerates the rotational motion of a motor and outputs it has been known. For example, the existing speed reducer is described in Japanese Unexamined Patent Application Publication No. 2005-212657. The electric wheel drive device in Japanese Unexamined Patent Application Publication No. 2005-212657 decelerates the rotation of an electric motor using a first planetary speed reducer and a second planetary speed reducer, and transmits this rotation to a wheel via a wheel hub ring.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-212657

[0004] In the above publication, the stator housing constituting the stator portion of the electric motor is an annular member having a substantially U-shaped cross section, and has a fixing portion extending radially outward on the outer diameter side. Moreover, the fixing portion is fastened to a body mounting flange of an external member via fixing bolts. In addition, planetary gears constituting the first planetary speed reducer and the second planetary speed reducer are respectively assembled inside the external member.

[0005] However, in the device of the above publication, the stator housing of the electric motor is fixed to the member on which the first planetary speed reducer and the second planetary speed reducer are assembled by bolts, so it is difficult to ensure the strength of the fixing portion, and it may not be possible to miniaturize the entire device. Summary of the Invention

[0006] An object of the present invention is to provide a technology capable of ensuring the fixing strength between the stator housing on the motor side and the member on which the speed reducer is assembled and achieving miniaturization of the entire device.

[0007] An exemplary first invention of the present application is a speed reducer having: a housing that extends in a cylindrical shape along an axial direction with a central axis as a center; a rotor that can rotate with the central axis as a center; a stator that is fixed to an inner peripheral surface of the housing; a speed reduction mechanism that reduces the rotational speed of the rotor; an output member that rotates with the central axis as a center at a rotational speed reduced by the speed reduction mechanism; and an output bearing that is disposed radially between the housing and the output member and supports the output member so as to be able to rotate with the central axis as a center. The speed reduction mechanism has an internal gear formed on the inner peripheral surface of the housing, and the internal gear has a plurality of internal teeth arranged in a circular ring shape around the central axis. At least one of an outer diameter of an outer ring of the output bearing and an outer diameter of the stator is larger than a root diameter of the internal gear.

[0008] According to the exemplary first invention of the present application, by disposing the stator of the motor and the internal gear of the reduction mechanism inside a single housing, the strength of the housing can be ensured and the overall miniaturization of the reducer can be achieved. Description of the Drawings

[0009] Figure 1 is a longitudinal sectional view of the reducer of the first embodiment.

[0010] Figure 2 is a transverse sectional view of the reducer of the first embodiment.

[0011] Figure 3 is a longitudinal sectional view of the reducer of the second embodiment.

[0012] Figure 4 is a longitudinal sectional view of the reducer of the third embodiment.

[0013] Figure 5 is a longitudinal sectional view of the reducer of the fourth embodiment.

[0014] Figure 6 is a transverse sectional view of the reducer of the fourth embodiment.

[0015] Description of Reference Numerals

[0016] 1, 1B, 1C, 1D: Reducer; 2, 2B, 2C, 2D: Motor; 3, 3B, 3C, 3D: Reduction mechanism; 4, 4B, 4D: Housing; 5: Middle cover; 6: Outer cover; 7, 7B, 7D: Output member; 21: Stator; 22, 22C, 22D: Shaft; 23, 23D: Rotor; 35: Internal gear; 35B: First internal gear; 54: First ring; 55: First retaining ring; 64: Second ring; 65: Second retaining ring; 90, 90B, 90C, 90D: Central axis; 200C: Coupling; 225: Support bearing; 226: Input bearing; 331D: Rigid internal gear; 350: (Tooth) root of internal tooth; 351, 351D: Internal teeth; 401B: Second internal tooth; 751, 751B, 751D: Output bearing; 752, 752B, 752D: Output bearing. Detailed Embodiments

[0017] Hereinafter, exemplary embodiments of the present application will be described with reference to the drawings. In addition, in the present application, the direction parallel to the central axis of the reducer of the present invention is referred to as the "axial direction", the direction perpendicular to the central axis is referred to as the "radial direction", and the direction along the arc centered on the central axis is referred to as the "circumferential direction".

[0018] In addition, in the present application, in Figure 1 and Figures 3 to 5In this description, the axial direction is used as the left - right direction, the left side is taken as the "axial - side", and the right side is taken as the "axial - other - side" to describe the shapes and positional relationships of the respective components. However, it is not intended to limit the orientation during the manufacturing and use of the speed reducer of the present invention by this definition. Additionally, in this application, the "parallel direction" is not limited to the direction that is strictly parallel geometrically. That is, a certain direction and the direction "parallel to it" only need to be approximately parallel to the extent that the effects of the invention are achieved. Also, in this application, the "perpendicular direction" is not limited to the case that is strictly perpendicular geometrically. That is, a certain direction and the direction "perpendicular to it" only need to be approximately perpendicular to the extent that the effects of the invention are achieved.

[0019] <1. First Embodiment>

[0020] Hereinafter, the structure of the speed reducer 1 of the first embodiment of the present invention will be described. Figure 1 is a longitudinal sectional view of the speed reducer 1 of the first embodiment.

[0021] The speed reducer 1 of the present embodiment decelerates and outputs, for example, the rotational motion of a servo motor or the like that can control position or speed. The speed reducer 1 of the present embodiment includes a motor 2, a reduction mechanism 3, a housing 4, a middle cover 5, an outer cover 6, an output member 7, a support bearing 225, an input bearing 226, a planetary bearing 325, and output bearings 751, 752. The speed reducer 1 uses the reduction mechanism 3 to reduce the rotational speed of a rotor 23 (described later) of the motor 2 and transmits it to the output member 7. The output member 7 rotates at the rotational speed reduced by the reduction mechanism 3.

[0022] The motor 2 and the reduction mechanism 3 are respectively arranged along a central axis 90 extending in the horizontal direction ( Figure 1 the left - right direction in it). The housing 4 is a member that extends in a cylindrical shape along the axial direction with the central axis 90 as the center. The housing 4 is formed of a single member.

[0023] The middle cover 5 is arranged radially inside the middle part in the axial direction of the housing 4. As Figure 1 shown, the middle cover 5 is located between a stator 21 (described later) of the motor 2 and the axial direction of the reduction mechanism 3. The middle cover 5 is a member that extends in an annular shape around the central axis 90. The outer diameter of the middle cover 5 is approximately equal to the inner diameter of the part of the housing 4 located radially outside the middle cover 5. Therefore, the outer peripheral surface of the middle cover 5 contacts the inner peripheral surface of the housing 4.

[0024] In addition, an O-ring that extends in a circular ring shape around the central axis 90 is disposed between the outer peripheral surface of the middle cover 5 and the inner peripheral surface of the outer housing 4. Hereinafter, this O-ring will be referred to as the "first ring 54". Thereby, the outer peripheral surface of the middle cover 5 is supported on the inner peripheral surface of the outer housing 4 in a non-rotatable manner. In addition, by disposing the first ring 54, as will be described later, it is possible to suppress the leakage of the lubricant applied to the speed reduction mechanism 3 side to the motor 2 side.

[0025] In addition, a snap ring is disposed on the other axial side of the middle cover 5. Hereinafter, this snap ring will be referred to as the "first snap ring 55". The first snap ring 55 is in contact with the inner peripheral surface of the outer housing 4 and the end surface on the other axial side of the middle cover 5, respectively. Thereby, it is possible to suppress the middle cover 5 from moving to the other axial side. In addition, the inner diameter of the portion of the outer housing 4 adjacent to the axial side of the position where the middle cover 5 is disposed is smaller than the outer diameter of the middle cover 5. Thereby, it is possible to suppress the middle cover 5 from moving to the axial side.

[0026] An outer cover 6 is disposed radially inward of the portion near the end on the other axial side of the outer housing 4. As Figure 1 shown, the outer cover 6 is located on the other axial side of the stator 21 of the motor 2. The outer cover 6 is a member that extends in a disk shape in the radial direction with the central axis 90 as the center. The outer diameter of the outer cover 6 is substantially equal to the inner diameter of the portion of the outer housing 4 located radially outside the outer cover 6. Therefore, the outer peripheral surface of the outer cover 6 is in contact with the inner peripheral surface of the outer housing 4.

[0027] In addition, an O-ring that extends in a circular ring shape around the central axis 90 is disposed between the outer peripheral surface of the outer cover 6 and the inner peripheral surface of the outer housing 4. Hereinafter, this O-ring will be referred to as the "second ring 64". Thereby, the outer peripheral surface of the outer cover 6 is supported on the inner peripheral surface of the outer housing 4 in a non-rotatable manner. In addition, by providing the second ring 64, it is possible to suppress dust from entering the internal space of the outer housing 4 from the outside of the speed reducer 1.

[0028] In addition, a snap ring is disposed on the other axial side of the outer cover 6. Hereinafter, this snap ring will be referred to as the "second snap ring 65". The second snap ring 65 is in contact with the inner peripheral surface of the outer housing 4 and the end surface on the other axial side of the outer cover 6, respectively. Thereby, it is possible to suppress the outer cover 6 from moving to the other axial side. In addition, the end surface on the axial side of the outer cover 6 is in contact with the stator 21 of the motor 2. Thereby, it is possible to suppress the outer cover 6 from moving to the axial side.

[0029] In addition, a concave portion 60 is provided on the end surface on the axial side of the outer cover 6. The concave portion 60 is recessed from the end surface on the axial side of the outer cover 6 to the other axial side. In addition, the shape of the concave portion 60 when viewed in the axial direction is a circle with the central axis 90 as the center. Thereby, a support surface 61 that extends in a cylindrical shape in the axial direction with the central axis 90 as the center is formed on the outer cover 6.

[0030] The motor 2 has a stator 21, a shaft 22, and a rotor 23. The stator 21 is fixed to the inner circumferential surface of the housing 4. The shaft 22 extends in a cylindrical shape along the central axis 90 in the axial direction. The shaft 22 extends from a position axially on one side of the stator 21 to a position axially on the other side of the stator 21. The rotor 23 is fixed around the shaft 22 in a non-rotatable relative manner. The outer circumferential surface of the rotor 23 faces the inner circumferential surface of the stator 21 with a small gap in the radial direction.

[0031] A support bearing 225 is provided between the outer circumferential surface of the portion of the shaft 22 located axially on one side of the stator 21 and the radial direction of the inner circumferential surface of the middle cover 5. The support bearing 225 uses a ball bearing, for example. The inner ring of the support bearing 225 is fixed to the outer circumferential surface of the shaft 22. The outer ring of the support bearing 225 is fixed to the inner circumferential surface of the middle cover 5. Thus, the shaft 22 is supported by the support bearing 225 on the axially one side of the stator 21 so as to be rotatable about the central axis 90 relative to the middle cover 5 and the housing 4. However, as the support bearing 225, other types of bearings such as roller bearings can be used instead of ball bearings. In addition, the outer diameter of the outer ring of the support bearing 225 is smaller than the diameter of the tooth root 350 of the internal gear 35 of the speed reduction mechanism 3 described later.

[0032] An input bearing 226 is provided between the outer circumferential surface of the portion near the end on the axially other side of the shaft 22 and the radial direction of the support surface 61 of the outer cover 6. The input bearing 226 uses a ball bearing, for example. The inner ring of the input bearing 226 is fixed to the outer circumferential surface of the shaft 22. The outer ring of the input bearing 226 is fixed to the support surface 61. Thus, the shaft 22 is supported by the input bearing 226 on the axially other side of the stator 21 so as to be rotatable about the central axis 90 relative to the outer cover 6 and the housing 4. As a result, the shaft 22 rotates while being more stably supported. However, as the input bearing 226, other types of bearings such as roller bearings can be used instead of ball bearings.

[0033] When driving the motor 2, when a drive current is supplied to each coil provided in the stator 21, each coil generates a rotating magnetic field. Thereby, the rotor 23 generates a circumferential torque. As a result, the rotor 23 and the shaft 22 fixed to the rotor 23 rotate circumferentially about the central axis 90 relative to the stator 21 and the housing 4 via the support bearing 225 and the input bearing 226.

[0034] The speed reduction mechanism 3 is a device that decelerates the rotational motion of the input rotational speed N1 of the shaft 22 and the rotor 23 and converts it into a rotational motion of an output rotational speed N2 smaller than the input rotational speed N1. Figure 2 is a transverse cross-sectional view of the speed reducer 1 when viewed from the A-A position Figure 1 when viewed axially. In addition, in Figure 2 order to avoid complication of the drawings, the cross-hatching indicating the cross-section and the illustration of the teeth of each gear are omitted. AsFigure 1 and Figure 2 As shown in Figure 2 , the speed reduction mechanism 3 includes a sun gear 31, a plurality of planetary gears 32, a plurality of carrier pins 33, a carrier 34, and an internal gear 35. The speed reduction mechanism 3 of the present embodiment has three planetary gears 32 and three carrier pins 33. The speed reduction mechanism 3 transmits power by rotating while the sun external teeth 311 (described later) of the sun gear 31 mesh with the planetary external teeth 321 of the plurality of planetary gears 32 and the planetary external teeth 321 of the plurality of planetary gears 32 mesh with the internal teeth 351 of the internal gear 35.

[0035] The sun gear 31 is a gear disposed substantially coaxially with the central axis 90. The sun gear 31 is fixed to the axial side of the shaft 22 in a non-rotatable relative manner. Thus, the sun gear 31 receives the rotation of the motor 2 and rotates about the central axis 90 together with the shaft 22 and the rotor 23 at the input rotational speed N1. In addition, the sun gear 31 has a plurality of external teeth on the outer peripheral surface. Hereinafter, this external tooth is referred to as "sun external tooth 311". The plurality of sun external teeth 311 project radially outward. The plurality of sun external teeth 311 are arranged at a constant pitch along the circumferential direction.

[0036] The three planetary gears 32 are respectively arranged around the sun gear 31 along the self-rotation axis 91. In the present embodiment, the self-rotation axis 91 is substantially parallel to the central axis 90. In addition, as shown in

[0036] , in the present embodiment, three planetary gears 32 are arranged at equal intervals in the circumferential direction around the sun gear 31. However, the number of planetary gears 32 arranged around the sun gear 31 may be one or two, or may be four or more. Each planetary gear 32 has a plurality of external teeth on the outer peripheral surface. Hereinafter, this external tooth is referred to as "planetary external tooth 321". The plurality of planetary external teeth 321 project outward. Figure 2 As shown in Figure 2 , the planetary external teeth 321 of each planetary gear 32 mesh with the sun external teeth 311 of the sun gear 31 from the radially outer side. Thus, 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 self-rotation axis 91 in a direction opposite to the rotation direction of the sun gear 31. In addition, each planetary gear 32 has a through hole 320 extending in the axial direction. The carrier pin 33 passes through each through hole 320 along the self-rotation axis 91.

[0037]

[0038] ​The three carrier pins 33 are components for supporting a planetary gear 32 so that it can rotate. Each carrier pin 33 uses, for example, a columnar component extending along the rotation axis 91. Each carrier pin 33 is inserted into a through hole 320 of a planetary gear 32. In addition, a planetary bearing 325 is inserted between the outer peripheral surface of the carrier pin 33 and the radial direction of the through hole 320 of the planetary gear 32. The planetary bearing 325 uses, for example, a needle bearing. Thus, the planetary gear 32 is supported by the planetary bearing 325 so that it can rotate around the rotation axis 91 relative to the carrier pin 33.

[0039] In addition, in the present embodiment, a lubricant such as grease is applied near the carrier pin 33, the planetary bearing 325, and the planetary gear 32. Thus, it is possible to better lubricate between the planetary bearing 325, which generates a strong contact pressure, and the carrier pin 33 and the planetary gear 32.

[0040] The carrier 34 is a component that expands in a disk shape along the radial direction with the central axis 90 as the center. As Figure 1 shown, the carrier 34 has a through hole 340. In the present embodiment, the carrier 34 has three through holes 340. Each through hole 340 penetrates the carrier 34 along the rotation axis 91 at a position radially outside the central axis 90. In addition, the three through holes 340 are arranged at intervals of approximately 120 degrees from each other in the circumferential direction with the central axis 90 as the center. However, the carrier 34 may have a concave portion that depresses from the end surface on the other axial side to the axial side instead of the through hole 340.

[0041] The portions on the axial one side of the three carrier pins 33 are inserted into one through hole 340. Moreover, each carrier pin 33 is fixed to the carrier 34 in the through hole 340 by bonding or press-fitting or the like. Thus, each carrier pin 33 is fixed at a position radially outside the central axis 90 so that it cannot rotate relative to the carrier 34. When the carrier 34 rotates around the central axis 90, the three carrier pins 33 fixed to the carrier 34 and the planetary gears 32 supported by the respective carrier pins 33 revolve around the central axis 90 in the circumferential direction.

[0042] The output member 7 is fixed to the end portion on the axial one side of the carrier 34 so that they cannot rotate relative to each other. The output member 7 is a component that extends in a cylindrical shape along the axial direction with the central axis 90 as the center. Thus, the output member 7 rotates around the central axis 90 together with the carrier 34. However, the output member 7 and the carrier 34 may be formed of one component.

[0043] Between the outer peripheral surface of the output member 7 and the radial direction of the inner peripheral surface of the housing 4, two output bearings 751 and 752 are arranged. The two output bearings 751 and 752 have the same structure as each other and are arranged along the axial direction. For example, ball bearings are respectively used for the output bearings 751 and 752. The inner rings of the output bearings 751 and 752 are fixed to the outer peripheral surface of the output member 7. The outer rings of the output bearings 751 and 752 are fixed to the inner peripheral surface of the housing 4. Thus, the output member 7 is supported by the output bearings 751 and 752 so as to be able to rotate about the central axis 90 with respect to the housing 4. However, as the output bearings 751 and 752, bearings of other types such as roller bearings can also be respectively used instead of ball bearings. In addition, as long as at least one output bearing is arranged between the outer peripheral surface of the output member 7 and the radial direction of the inner peripheral surface of the housing 4.

[0044] The internal gear 35 is a gear arranged substantially coaxially with the central axis 90. The internal gear 35 extends in an annular cylindrical shape along the axial direction with the central axis 90 as the center. In addition, the internal gear 35 is formed on the inner peripheral surface of the housing 4 and has a plurality of internal teeth 351 arranged in a circular ring shape around the central axis 90. Thus, since the internal gear 35 is composed of a plurality of internal teeth 351 formed on the inner peripheral surface of the housing 4, it has a structure that does not rotate about the central axis 90. The plurality of internal teeth 351 respectively project toward the radial inner side. The plurality of internal teeth 351 are arranged at a constant pitch along the circumferential direction. In addition, the plurality of internal teeth 351 mesh with the planetary external teeth 321 of the three planetary gears 32 from the radial outside.

[0045] When the sun gear 31 rotates about the central axis 90 at the input rotational speed N1, the three planetary gears 32 meshing with both the sun gear 31 and the internal gear 35 respectively rotate about their own rotation axes 91. In addition, while the three planetary gears 32 respectively rotate about their own rotation axes 91, they revolve about the central axis 90 at the output rotational speed N2 together with the carrier pins 33 through the meshing with the sun gear 31 and the internal gear 35. Thus, the carrier 34 to which the three carrier pins 33 are fixed rotates about the central axis 90 at the output rotational speed N2. That is, the carrier 34 supports the three planetary gears 32 and the carrier pins 33 so as to be able to revolve circumferentially about the central axis 90, and rotates about the central axis 90 at the output rotational speed N2 as the three planetary gears 32 and the carrier pins 33 revolve.

[0046] In addition, as described above, the housing 4 of the present embodiment is formed of a single component. In this way, by disposing the motor 2 including the stator 21 and the reduction mechanism 3 including the internal gear 35 inside a single housing 4, compared with the case where the housing for accommodating the motor 2 and the housing for accommodating the reduction mechanism 3 are separately provided and connected to each other, it is possible to more easily ensure the strength of the housing 4. As a result, the entire speed reducer 1 can be further miniaturized. In addition, since the central axis 90 of the motor 2 can be easily and accurately aligned with the central axis 90 of the reduction mechanism 3, the rotational performance is improved.

[0047] In addition, the outer diameters of the outer rings of the output bearings 751 and 752 and the outer diameter of the stator 21 of the motor 2 of the present embodiment 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 the present embodiment, the diameter of the portion of the inner peripheral surface of the housing 4 where a plurality of internal teeth 351 are formed is smaller than the diameter of the portion where the output bearings 751 and 752 are fixed and the diameter of the portion where the stator 21 is fixed. Thereby, when manufacturing the speed reducer 1 and performing cutting processing (broaching) to form the internal gear 35 on the inner peripheral surface of the housing 4, the workability can be improved.

[0048] However, it is sufficient that at least one of the outer diameters of the outer rings of the output bearings 751 and 752 and the outer diameter of the stator 21 is larger than the diameter of the tooth root 350 of the internal gear 35. Thereby, it is possible to more easily perform cutting processing (broaching) of the internal gear 35 on the inner peripheral surface of the housing 4.

[0049] <2. Second Embodiment>

[0050] Next, the structure of the speed reducer 1B of the second embodiment of the present invention will be described. Figure 3 FIG. is a longitudinal sectional view of the speed reducer 1B of the second embodiment. In addition, hereinafter, the description will focus on the structures different from those of the first embodiment, and the repeated description of the same structures as those of the first embodiment will be omitted.

[0051] As Figure 3 shown, the reduction mechanism 3B of the present embodiment includes 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.

[0052] The first sun gear 31B, the plurality of first planetary gears 32B, the plurality of first carrier pins 33B, the first carrier 34B, and the first internal gear 35B of the present embodiment respectively have the same structures as the sun gear 31, the plurality of planetary gears 32, the plurality of carrier pins 33, the carrier 34, and the internal gear 35 of the first embodiment.

[0053] When the first sun gear 31B rotates about the central axis 90B at the input rotational speed N1, the plurality of first planetary gears 32B that mesh with both the first sun gear 31B and the first internal gear 35B respectively rotate about the self-rotation axis 91B. In addition, while the plurality of first planetary gears 32B respectively rotate about the self-rotation axis 91B, they revolve about the central axis 90B at an intermediate rotational speed N15 that is less than the input rotational speed N1 by meshing with the first sun gear 31B and the first internal gear 35B, together with the first carrier pins 33B. As a result, the first carrier 34B to which the plurality of first carrier pins 33B are fixed rotates about the central axis 90B at the intermediate rotational speed N15.

[0054] The second sun gear 36B is a gear disposed substantially coaxially with the central axis 90B. The second sun gear 36B is fixed to the axial side of the first carrier 34B in a manner that they cannot rotate relative to each other. As a result, the second sun gear 36B rotates about the central axis 90B together with the first carrier 34B at the intermediate rotational speed N15. In addition, the second sun gear 36B has a plurality of external teeth on its outer peripheral surface. Hereinafter, these external teeth will be referred to as "second sun external teeth 361B". The plurality of second sun external teeth 361B respectively protrude toward the radially outer side. The plurality of second sun external teeth 361B are arranged at a constant pitch along the circumferential direction.

[0055] The plurality of second planetary gears 37B are respectively arranged around the second sun gear 36B along the self-rotation axis 91B. Each second planetary gear 37B has a plurality of external teeth on its outer peripheral surface. Hereinafter, these external teeth will be referred to as "second planetary external teeth 371B". The plurality of second planetary external teeth 371B respectively protrude toward the outside.

[0056] The second planetary external teeth 371B of each second planetary gear 37B mesh with the second sun external 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 self-rotation axis 91B in a direction opposite to the rotation direction of the second sun gear 36B. In addition, each second planetary gear 37B has a second through hole 370B extending in the axial direction. The second carrier pins 38B pass through each second through hole 370B along the self-rotation axis 91B.

[0057] The plurality of second carrier pins 38B are respectively components for supporting a second planetary gear 37B so as to be rotatable. Each of the second carrier pins 38B uses, for example, a columnar component extending along the rotation axis 91B. Each of the second carrier pins 38B is inserted into a second through-hole 370B of a second planetary gear 37B. In addition, a second planetary bearing 375B is inserted between the outer peripheral surface of the second carrier pin 38B and the radial direction of the second through-hole 370B of the second planetary gear 37B. The second planetary gear 37B is supported by the second planetary bearing 375B so as to be rotatable about the rotation axis 91B with respect to the second carrier pin 38B.

[0058] The second carrier 39B is a component that extends in a disk shape in the radial direction about the central axis 90B. The plurality of second carrier pins 38B are respectively fixed at positions radially outside the central axis 90B in a manner that they cannot rotate relative to the second carrier 39B. When the second carrier 39B rotates about the central axis 90B, the plurality of second carrier pins 38B fixed to the second carrier 39B and the second planetary gears 37B supported by the respective second carrier pins 38B revolve in the circumferential direction about the central axis 90B.

[0059] The output member 7B is fixed to an end portion on the axial side of the second carrier 39B in a manner that they cannot rotate relative to each other. The output member 7B is a component that extends in a cylindrical shape in the axial direction about the central axis 90B. The output member 7B rotates about the central axis 90B together with the second carrier 39B with respect to the housing 4B via output bearings 751B and 752B.

[0060] The second internal gear 40B is a gear disposed substantially coaxially with the central axis 90B. The second internal gear 40B extends in an annular cylindrical shape in the axial direction about the central axis 90B. In addition, the second internal gear 40B is formed on the inner peripheral surface of the housing 4B on the axial side of the first internal gear 35B and has a plurality of second internal teeth 401B arranged in a circular ring shape about the central axis 90B. The plurality of second internal teeth 401B mesh with the respective second planetary external teeth 371B of the plurality of second planetary gears 37B from the radial outside. The second internal gear 40B of the present embodiment and the first internal gear 35B are formed of one component. However, the second internal gear 40B may also be formed separately from the first internal gear 35B.

[0061] When the second sun gear 36B rotates about the central axis 90B at the intermediate speed N15, the plurality of second planetary gears 37B that mesh with both the second sun gear 36B and the second internal gear 40B rotate about their own rotation axes 91B, respectively. In addition, while rotating about their own rotation axes 91B, the plurality of second planetary gears 37B revolve about the central axis 90B at an output speed N2 that is lower than the intermediate speed N15 together with the second carrier pins 38B by meshing with the second sun gear 36B and the second internal gear 40B. As a result, the second carrier 39B to which the plurality of second carrier pins 38B are fixed rotates about the central axis 90B together with the output member 7B at the output speed N2.

[0062] As described above, the reduction mechanism 3B of the present embodiment reduces the input speed N1 from the motor 2B to the intermediate speed N15 through the first sun gear 31B, the plurality of first planetary gears 32B, the plurality of first carrier pins 33B, the first carrier 34B, and the first internal gear 35B. In addition, the reduction mechanism 3B reduces the intermediate speed N15 to the output speed N2 through the second sun gear 36B, the plurality of second planetary gears 37B, the plurality of second carrier pins 38B, the second carrier 39B, and the second internal gear 40B. In this way, the reduction mechanism 3B of the present embodiment can obtain a higher reduction ratio by performing two-stage reduction.

[0063] In addition, the housing 4B of the present embodiment is formed of a single component. In the present embodiment, by disposing the motor 2B and the reduction mechanism 3B inside a single housing 4B, it is also possible to more easily ensure the strength of the housing 4B compared to the case where the housing for housing the motor 2B and the housing for housing the reduction mechanism 3B are separately provided and connected to each other. As a result, the entire speed reducer 1B can be further miniaturized.

[0064] <3. Third Embodiment>

[0065] Next, the structure of the speed reducer 1C according to the third embodiment of the present invention will be described. Figure 4 It is a longitudinal sectional view of the speed reducer 1C according to the third embodiment. In addition, hereinafter, the description will focus on the structure different from that of the first embodiment, and the repeated description of the same structure as that of the first embodiment will be omitted.

[0066] In addition to the components of the speed reducer 1 in the first embodiment, the speed reducer 1C of this embodiment further includes a coupling 200C. The coupling 200C is composed of a cut groove 201C cut axially and a screw 202C screwed in a direction perpendicular to the central axis 90C. In the speed reducer 1C of this embodiment, the shaft 22C of the motor 2 is axially connected to the sun gear 31C of the speed reduction mechanism 3C via the coupling 200C. Specifically, by inserting the shaft 22C into the cut groove 201C and tightening the screw 202C, the sun gear 31C rotates around the central axis 90C using the power obtained from the motor 2C.

[0067] That is, the coupling 200C can connect the shaft 22C of the motor 2C and the speed reduction mechanism 3C. Thus, motors 2C of various specifications can be installed on the speed reduction mechanism 3C using the coupling 200C, so the versatility is improved. In addition, the present invention includes a speed reducer 1C in a state where the motor 2C is installed on the speed reduction mechanism 3C using the coupling 200C.

[0068] <4. Fourth Embodiment>

[0069] Next, the structure of the speed reducer 1D of the fourth embodiment of the present invention will be described. Figure 5 It is a longitudinal sectional view of the speed reducer 1D of the fourth embodiment. Figure 6 It is from Figure 5 The B-B position of the speed reducer 1D is observed in a transverse sectional view. In Figure 6 In order to avoid complicating the drawings, some of the hatching indicating the cross section is omitted. In addition, hereinafter, the description will focus on the structure different from that of the first embodiment, and the repeated description of the same structure as that of the first embodiment will be omitted.

[0070] As Figure 5 shown, the speed reduction mechanism 3D of this embodiment includes a rigid internal gear 331D, a flexible external gear 332D, and a wave generator 333D.

[0071] The rigid internal gear 331D is a gear arranged substantially coaxially with the central axis 90D. The rigid internal gear 331D extends in an annular cylindrical shape along the axial direction with the central axis 90D as the center. In addition, the rigid internal gear 331D is located radially outside a cylindrical portion 334D of the flexible external gear 332D to be described later. 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. Therefore, the rigid internal gear 331D can be substantially regarded as a rigid body.

[0072] In addition, a rigid internal gear 331D is formed on the inner peripheral surface of the housing 4D and has a plurality of internal teeth 351D arranged in an annular shape around the central axis 90D. In this way, the rigid internal gear 331D is composed of the plurality of internal teeth 351D formed on the inner peripheral surface of the housing 4D, and thus has a structure that does not rotate about the central axis 90D. The plurality of internal teeth 351D respectively project toward the radially inner side. The plurality of internal teeth 351D are arranged at a constant pitch along the circumferential direction.

[0073] The flexible external gear 332D is an annular gear capable of flexural deformation. The flexible external gear 332D is supported so as to be rotatable about the central axis 90D. The flexible external gear 332D has a cylindrical portion 334D and a disk portion 335D. The cylindrical portion 334D extends in a cylindrical shape along the axial direction around the central axis 90D. The end portion on the other axial side of the cylindrical portion 334D is located radially outside the wave generator 333D and radially inside the rigid internal gear 331D. Since the cylindrical portion 334D has flexibility, it can be deformed in the radial direction. In particular, the end portion on the other axial side of the cylindrical portion 334D is a free end, and thus can be displaced more greatly in the radial direction than other portions.

[0074] 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 end portion on the other axial side of the cylindrical portion 334D. The plurality of external teeth 336D are arranged at a constant pitch along the circumferential direction. Each external tooth 336D projects toward the radially outer side. The number of internal teeth 351D of the above-mentioned rigid internal gear 331D is slightly different from the number of external teeth 336D of the flexible external gear 332D.

[0075] The disk portion 335D extends in a flat plate shape from the end portion on the axial side of the cylindrical portion 334D toward the radially inner side and extends in an annular shape in a direction perpendicular to the central axis 90D. The disk portion 335D is fixed, for example, by bolt fastening, so as not to rotate relative to each other, to the end surface on the other axial side of the output member 7D. Thus, the output member 7D is supported by the housing 4D together with the flexible external gear 332D via the output bearings 751D, 752D so as to be rotatable about the central axis 90D.

[0076] The wave generator 333D is a mechanism that causes the cylindrical portion 334D of the flexible external gear 332D to generate periodic flexural deformation. The wave generator 333D has a cam 337D and a flexible bearing 338D. The cam 337D is directly or indirectly fixed to the shaft 22D of the motor 2D via other components. Therefore, the cam 337D rotates about the central axis 90D at the input rotational speed N1 together with the shaft 22D and the rotor 23D of the motor 2D. In addition, as Figure 6As shown, when viewed axially, the outer peripheral surface of the cam 337D is elliptical. 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 rotational speeds.

[0077] 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. Therefore, the cylindrical portion 334D of the flexible external gear 332D deforms into an elliptical shape along the outer peripheral surface of the cam 337D. Then, at two positions corresponding to both ends of the major axis of the ellipse, the cylindrical portion 334D is pressed radially outward, whereby a part of the external teeth 336D of the flexible external gear 332D meshes with the internal teeth 351D of the rigid internal gear 331D. At other positions in the circumferential direction, the external teeth 336D do not mesh with the internal teeth 351D.

[0078] When driving the motor 2D, the cam 337D rotates together with the rotor 23D and the shaft 22D of the motor 2D about the central axis 90D at the input rotational speed N1. As a result, the major axis of the above-mentioned ellipse of the flexible external gear 332D also rotates at the input rotational speed N1. Then, the meshing position of the external teeth 336D and the internal teeth 351D also changes in the circumferential direction at the input rotational speed N1. In addition, as described above, the number of the internal teeth 351D of the rigid internal gear 331D is slightly different from the number of the external teeth 336D of the flexible external gear 332D. Due to this difference in the number of teeth, every time the cam 337D rotates one week, the meshing position of the external teeth 336D and the internal teeth 351D slightly changes in the circumferential direction. As a result, the flexible external gear 332D and the output member 7D rotate about the central axis 90D at an output rotational speed N2 that is less than the input rotational speed N1 with respect to the rigid internal gear 331D.

[0079] The housing 4D of the present embodiment is formed of a single component. In addition, in the present embodiment, by disposing the motor 2D and the reduction mechanism 3D inside a single housing 4D, it is possible to more easily ensure the strength of the housing 4D compared with the case where the housing for housing the motor 2D and the housing for housing the reduction mechanism 3D are separately provided and connected to each other. As a result, the entire speed reducer 1D can be further miniaturized.

[0080] <5. Modification Example>

[0081] Above, the exemplary embodiments of the present invention have been described, but the present invention is not limited to the above-described embodiments. Within the scope not departing from the gist of the present invention, a part of the elements appearing in the above-described embodiments may be deleted, or known elements may be added.

[0082] In addition, the shape of the detailed part of the speed reducer may be different from the shape shown in each of the figures of the above-described embodiment.

[0083] <6. Summary>

[0084] In addition, the present technology may adopt the following structure.

[0085] (1) A speed reducer having: a housing extending in a cylindrical shape along an axial direction with a central axis as a center; a rotor capable of rotating about the central axis; a stator fixed to an inner peripheral surface of the housing; a speed reduction mechanism for reducing the rotational speed of the rotor; an output member rotating about the central axis at a rotational speed reduced by the speed reduction mechanism; and an output bearing disposed radially between the housing and the output member to support the output member so as to be capable of rotating about the central axis, wherein the speed reduction mechanism has an internal gear formed on the inner peripheral surface of the housing, the internal gear having a plurality of internal teeth arranged in an annular shape around the central axis, and at least one of an outer diameter of an outer ring of the output bearing and an outer diameter of the stator is larger than a root diameter of the internal gear.

[0086] (2) The speed reducer according to (1), wherein both the outer diameter of the outer ring of the output bearing and the outer diameter of the stator are larger than the root diameter of the internal gear.

[0087] (3) The speed reducer according to (1) or (2), further comprising a middle cover extending in an annular shape around the central axis between the speed reduction mechanism and the stator in the axial direction, an outer peripheral surface of the middle cover being in contact with the inner peripheral surface of the housing and being supported so as not to rotate relative to the housing.

[0088] (4) The speed reducer according to (3), further comprising: a shaft fixed to the rotor in a non-rotatable manner and extending in a columnar shape along the central axis; and a support bearing supporting the shaft on an axial side of the stator so as to be capable of rotating about the central axis relative to the middle cover, an outer diameter of an outer ring of the support bearing being smaller than the root diameter of the internal gear.

[0089] (5) The speed reducer according to (3) or (4), further comprising a first ring as an O-ring extending in an annular shape around the central axis between the inner peripheral surface of the housing and the outer peripheral surface of the middle cover.

[0090] (6) The speed reducer according to any one of (3) to (5), further comprising a first retaining ring as a retaining ring in contact with the inner peripheral surface of the housing and an end surface on an axial other side of the middle cover.

[0091] (7) The speed reducer according to any one of (1) to (6), wherein the speed reducer further has: a shaft that is fixed to the rotor in a non-rotatable manner and extends in a columnar shape along the central axis; an outer cover that extends in a disc shape in the radial direction with the central axis as the center on the other axial side of the stator, and the outer peripheral surface of the outer cover contacts the inner peripheral surface of the housing and is supported so as not to rotate relative to each other; and an input bearing that supports the shaft on the other axial side of the stator so as to be rotatable about the central axis relative to the outer cover.

[0092] (8) The speed reducer according to (7), wherein the speed reducer further has a second ring as an O-ring that extends in a circular ring shape around the central axis between the inner peripheral surface of the housing and the outer peripheral surface of the outer cover.

[0093] (9) The speed reducer according to (7) or (8), wherein the speed reducer further has a second retaining ring as a retaining ring that contacts the inner peripheral surface of the housing and the end surface on the other axial side of the outer cover.

[0094] (10) The speed reducer according to any one of (1) to (9), wherein the speed reducer further has: a shaft that is fixed to the rotor in a non-rotatable manner and extends in a columnar shape along the central axis; and a coupling that can connect the shaft and the speed reduction mechanism.

[0095] Industrial applicability

[0096] This application can be used in speed reducers.

Claims

1. A speed reducer having: A housing extending axially in a cylindrical shape about a central axis; A rotor capable of rotating about the central axis; A stator fixed to the inner peripheral surface of the housing; A speed reduction mechanism for reducing the rotational speed of the rotor; An output member rotating about the central axis at a rotational speed reduced by the speed reduction mechanism; And An output bearing disposed radially between the housing and the output member, supporting the output member to be rotatable about the central axis, The speed reduction mechanism has an internal gear formed on the inner peripheral surface of the housing, the internal gear having a plurality of internal teeth arranged in an annular shape about the central axis, At least one of the outer diameter of the outer ring of the output bearing and the outer diameter of the stator is greater than the root diameter of the internal gear.

2. The speed reducer according to claim 1, wherein Both the outer diameter of the outer ring of the output bearing and the outer diameter of the stator are greater than the root diameter of the internal gear.

3. The speed reducer according to claim 1 or 2, wherein The speed reducer further has a middle cover extending in an annular shape about the central axis axially between the speed reduction mechanism and the stator, the outer peripheral surface of the middle cover being in contact with the inner peripheral surface of the housing and being supported not to rotate relatively.

4. The speed reducer according to claim 3, wherein The speed reducer further has: A shaft fixed to the rotor in a non-rotatable manner and extending in a columnar shape along the central axis; and A support bearing supporting the shaft on the axially one side of the stator to be rotatable about the central axis relative to the middle cover, The outer diameter of the outer ring of the support bearing is smaller than the root diameter of the internal gear.

5. The speed reducer according to claim 3, wherein The speed reducer further has a first ring as an O-ring extending in an annular shape about the central axis between the inner peripheral surface of the housing and the outer peripheral surface of the middle cover.

6. The speed reducer according to claim 3, wherein The speed reducer further has a first snap ring as a snap ring, the first snap ring being in contact with the inner peripheral surface of the housing and the end surface on the axially other side of the middle cover.

7. The speed reducer according to claim 1 or 2, wherein The speed reducer further has: A shaft fixed to the rotor in a non-rotatable manner and extending in a columnar shape along the central axis; An outer cover extending in a circular plate shape radially about the central axis on the axially other side of the stator, the outer peripheral surface of the outer cover being in contact with the inner peripheral surface of the housing and being supported not to rotate relatively; and An input bearing supporting the shaft on the axially other side of the stator to be rotatable about the central axis relative to the outer cover.

8. The speed reducer according to claim 7, wherein The speed reducer further has a second ring as an O-ring extending in an annular shape about the central axis between the inner peripheral surface of the housing and the outer peripheral surface of the outer cover.

9. The speed reducer according to claim 7, wherein The speed reducer further has a second retaining ring serving as a snap ring, and the second retaining ring contacts the inner circumferential surface of the housing and the end surface on the other axial side of the outer cover.

10. The speed reducer according to claim 1 or 2, wherein the speed reducer further has: a shaft that is fixed to the rotor in a non-rotatable manner and extends in a columnar shape along the central axis; and a coupling that can connect the shaft and the speed reduction mechanism.

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