Speed reducing mechanism

Abstract

In a speed reduction mechanism, the reduction ratio is increased while miniaturization is achieved. The speed reduction mechanism (30) is provided with: a rotating shaft (10); a pinion gear (11) including a first tooth portion (11a) extending helically along the longitudinal direction (Q1) of the rotating shaft (10); three planetary gears (12) each including a helical second tooth portion (12e) and arranged side by side in the circumferential direction (Q2) of the rotating shaft (10); a housing part (14) that houses the three planetary gears (12); and an internal gear (13) including a spiral third tooth portion (13a) that meshes with the second tooth portion (12e). The tooth profile cross-section of at least a portion of the first tooth portion (11a) is formed in an arc shape, and the second tooth portion (12e) engages with the first tooth portion (11a) in a state of being in contact with the portion having the arc-shaped tooth profile cross-section.

Description

Technical Field

[0001] The present invention relates to a speed reduction mechanism using a planetary gear. Background Art

[0002] As an example of a reduction mechanism using planetary gears, the following reduction mechanism is shown in Patent Document 1, that is, the reduction mechanism has: a sun gear; three planetary gears, each of which revolves around the sun gear while rotating while meshing with the sun gear; and a fixed internal gear meshing with the three planetary gears.

[0003] [Prior art literature]

[0004] [Patent Document]

[0005] [Patent Document 1] Japanese Patent Publication No. 2001-90792 Summary of the invention

[0006] [Problems to be solved by the invention]

[0007] In the speed reduction mechanism described in Patent Document 1, it is desired to ensure a larger output torque while maintaining the size of the speed reduction mechanism. Therefore, it is necessary to further increase the speed reduction ratio while maintaining the size of the speed reduction mechanism.

[0008] In the case of the speed reduction mechanism of Patent Document 1, if the speed reduction ratio is to be further increased, the number of planetary gears must be reduced. When the number of planetary gears is reduced, the strength of the speed reduction mechanism is reduced.

[0009] On the other hand, if the strength of the speed reduction mechanism is to be ensured while reducing the number of planetary gears, the diameter of each planetary gear must be increased, which may increase the size of the speed reduction mechanism.

[0010] An object of the present invention is to provide a speed reduction mechanism capable of increasing the speed reduction ratio while achieving miniaturization.

[0011] [Technical means to solve the problem]

[0012] One embodiment of the present invention comprises: a rotating shaft; a first gear, which is arranged on the outer periphery of the rotating shaft and includes a first tooth portion extending in a spiral shape along the length direction of the rotating shaft; a plurality of second gears, each including a spiral second tooth portion meshing with the first tooth portion, and arranged along the circumferential direction of the rotating shaft; a housing portion, which accommodates the plurality of second gears; and a third gear, which is arranged on the inner periphery of the housing portion and includes a spiral third tooth portion meshing with the second tooth portion, wherein a tooth profile of at least a portion of the first tooth portion is formed in an arc shape, and the second tooth portion meshes with the first tooth portion while contacting the portion with the arc shape of the tooth profile.

[0013] In another embodiment of the present invention, at least three second gears are arranged along the circumferential direction of the rotating shaft.

[0014] In another embodiment of the present invention, when the pitch circle radius of the second gear is set to R1, the center-to-center distance from the rotation center of the rotating shaft to the rotation center of the second gear is set to L1, and the angle calculated using the formula (180° (sum of the interior angles of the triangle) - 90°) - (360° ÷ the number of the second gears ÷ 2) is set to θ, the pitch circle radius R1 < (the center-to-center distance L1 × cosθ).

[0015] [Effects of the Invention]

[0016] In the speed reduction mechanism, the speed reduction ratio can be increased while achieving miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is an external perspective view for explaining the structure of the speed reduction mechanism of the present invention.

[0018] Figure 2 Yes Figure 1 A cross-sectional view illustrating the internal structure of the reduction mechanism.

[0019] Figure 3 Yes Figure 1 An internal plan view illustrating the configuration of the planetary gear (second gear) of the speed reduction mechanism.

[0020] Figure 4 Yes Figure 1 A three-dimensional diagram illustrating the meshing state of the sun gear and the planetary gears and the meshing state of the planetary gears and the fixed internal gear (third gear) in the reduction mechanism.

[0021] Figure 5 Yes Figure 1 An external perspective view illustrating the structure of the sun gear (first gear) of the reduction mechanism.

[0022] Figure 6 Yes Figure 1 A plan view illustrating the structure of the planetary gear (second gear) of the speed reduction mechanism.

[0023] Figure 7 is used to calculate Figure 1 A diagram showing the non-interference conditions of the gears in a reduction gear mechanism having three planetary gears.

[0024] Figure 8 is used to calculate Figure 1 A diagram showing the non-interference conditions of the gears in a reduction gear mechanism having a structure with four planetary gears.

[0025] Fig. 9 This is a plan view for explaining the pitch circle diameter of an involute gear as a comparative example.

[0026] Fig.10 It is for Figure 1 A perspective view illustrating the structure of a robot as an application example of a speed reduction mechanism.

[0027] Fig.11 Yes Fig.10 In the robot Figure 1 The internal structure diagram of the reduction mechanism is used to illustrate the application structure.

[0028] [Explanation of Symbols]

[0029] 10: Rotation axis

[0030] 10a: Center of rotation

[0031] 10b, 10c: Bearings

[0032] 10d: Pin

[0033] 11: Pinion (first gear)

[0034] 11a: First tooth

[0035] 11b: Arc-shaped part

[0036] 11c: Pitch circle

[0037] 12, 12a, 12b, 12c, 12d: Planetary gear (second gear)

[0038] 12e: Second tooth

[0039] 12f: Pitch circle

[0040] 12g: Addendum circle

[0041] 12h: Rotation center

[0042] 12i: Fixed axle

[0043] 12j, 12k: bearings

[0044] 13: Internal gear (third gear)

[0045] 13a: Third tooth

[0046] 14: Containment

[0047] 15: Output shaft

[0048] 15a: Fixed part

[0049] 16: Planet carrier

[0050] 17: Bearing retaining part

[0051] 17a: Bearing

[0052] 18: Bearing retaining part

[0053] 18a: Bearing

[0054] 19: Fixed part

[0055] 19a: Pin

[0056] 30: Speed ​​reduction mechanism

[0057] 31: Motor

[0058] 32: Encoder

[0059] 33: Driver substrate

[0060] 34: Motor unit

[0061] 35: Robot

[0062] 35a: Body

[0063] 35b: Shoulders

[0064] 35c: Elbow

[0065] 35d: Wrist

[0066] 40: Involute gear

[0067] 40a: Pitch circle

[0068] 40b: Addendum circle

[0069] L1: Center-to-center distance

[0070] Q1: Length direction

[0071] Q2: Circumferential

[0072] Q3: Radial

[0073] R1: Pitch circle radius

[0074] R2: Tip radius

[0075] S1, S2, S3, T1, T2, T3, T4: Interference avoidance limit lines

[0076] θ: Angle DETAILED DESCRIPTION

[0077] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0078] Figure 1 is an external perspective view for explaining the structure of the speed reduction mechanism of this embodiment. Figure 2 Yes Figure 1 A cross-sectional view illustrating the internal structure of the reduction mechanism. Figure 3 Yes Figure 1 The internal plan view of the planetary gear (second gear) of the speed reduction mechanism is explained. Figure 4 Yes Figure 1 A perspective view illustrating the meshing state of the sun gear and the planetary gears and the meshing state of the planetary gears and the fixed internal gear (third gear) in the reduction mechanism. Figure 5 Yes Figure 1 The appearance perspective view of the sun gear (first gear) of the speed reduction mechanism is explained. Figure 6 Yes Figure 1 A plan view illustrating the structure of the planetary gear (second gear) of the speed reduction mechanism.

[0079] The speed reduction mechanism 30 of the present embodiment is a mechanism as follows: by causing the sun gear provided on the rotating shaft 10 serving as the input shaft to rotate, more than three planetary gears 12 respectively meshing with the sun gear and the fixed internal gear revolve, thereby enabling the rotation of the output shaft 15 rotating together with the revolution of the planetary gears 12 to be reduced relative to the rotation of the input shaft.

[0080] use Figure 1 to Figure 6 The structure of the speed reduction mechanism 30 will be described. First, the case where three planetary gears 12 are provided will be described. Figure 3 and Figure 4 As shown, the speed reduction mechanism 30 includes: a rotating shaft 10, which is an input shaft; a pinion (first gear) 11, which is provided on the outer periphery of the rotating shaft 10 and includes a first tooth portion 11a; and three planetary gears 12a, 12b, and 12c, which are second gears, respectively meshing with the first tooth portion 11a. In addition, the three planetary gears 12a, 12b, and 12c respectively include a second tooth portion 12e meshing with the first tooth portion 11a, and are arranged at substantially equal intervals along the circumferential direction Q2 of the rotating shaft 10.

[0081] In addition, the reduction mechanism 30 has: a cylindrical housing portion 14 for housing the three planetary gears 12a, 12b, and 12c; and an internal gear (third gear) 13, which is arranged on the inner periphery of the housing portion 14 and includes a third tooth portion 13a that meshes with the second tooth portion 12e of the three planetary gears 12a, 12b, and 12c.

[0082] The pinion gear 11 as the first gear is a sun gear that rotates in the speed reduction mechanism 30. The pinion gear 11 is provided integrally with the rotating shaft 10 at the outer periphery of the rotating shaft 10, and Figure 5As shown, it includes a first tooth portion 11a extending in a spiral shape along the length direction Q1 of the rotating shaft 10. The first tooth portion 11a is a single tooth, and the pinion 11 is also called a single-tooth pinion. That is, it is a structure in which only one tooth portion (first tooth portion 11a) is formed in the cut surface of the radial direction Q3 at any position on the length direction Q1 of the rotating shaft 10. Furthermore, in the tooth shape (tooth profile) of the cut surface of the radial direction Q3 of the rotating shaft 10, at least a part of the first tooth portion 11a has an arc-shaped portion 11b formed in a circular arc shape.

[0083] The three planetary gears 12a, 12b, and 12c as the second gears are as follows: Figure 4 As shown, they are arranged along the circumferential direction Q2 of the rotating shaft 10, and as shown Figure 6 As shown, each includes a spiral second tooth portion 12e. The second tooth portion 12e is located at and Figure 5 The pinion gear 11 shown meshes with the first tooth portion 11a while the tooth profile (tooth profile section) of the cut surface is in contact with the arc-shaped portion. That is, the second tooth portion 12e of each of the three planetary gears 12a, 12b, and 12c meshes with the arc-shaped portion 11b of the first tooth portion 11a of the pinion gear 11.

[0084] like Figure 3 and Figure 4 As shown, the internal gear 13 as the third gear is provided at the inner circumference of the cylindrical receiving portion 14, and includes a third tooth portion 13a meshing with the second tooth portion 12e of each of the planetary gears 12a, 12b, and 12c. The third tooth portion 13a is formed in a spiral shape at the inner circumference of the cylindrical receiving portion 14. In addition, in the speed reduction mechanism 30 of the present embodiment, the internal gear 13 is a fixed internal gear.

[0085] Next, the detailed structure of the interior of the speed reduction mechanism 30 will be described. Figure 1 and Figure 2 As shown, a rotating shaft 10 as an input shaft and having a pinion 11 disposed on the outer periphery is rotatably supported by bearings 10b and 10c. The rotating shaft 10 rotates around a rotation center 10a. The bearings 10b and 10c are respectively fixed to a planetary carrier 16, and the planetary carrier 16 is rotatably mounted relative to the rotating shaft 10 via the bearings 10b and 10c.

[0086] The planetary carrier 16 is formed in a cylindrical shape, and its outer peripheral portion is rotatable relative to the outer peripheral frame of the speed reduction mechanism 30 via bearings 17a and 18a. That is, the planetary carrier 16 is rotatable relative to the bearing holding portions 17 and 18 as the outer peripheral frame of the speed reduction mechanism 30 via bearings 17a and 18a.

[0087] In addition, the fixed portion 15a including the output shaft 15 is attached to the planetary carrier 16 via the pin 10d. Therefore, when the planetary carrier 16 rotates, the fixed portion 15a and the output shaft 15 rotate together with the rotation of the planetary carrier 16. Similarly, when the planetary carrier 16 rotates, the fixed portion 19 fixed to the planetary carrier 16 via the pin 19a rotates together with the rotation of the planetary carrier 16. In the speed reduction mechanism 30, the rotating shaft 10 and the output shaft 15 are arranged on substantially the same axis.

[0088] The three planetary gears 12a, 12b, and 12c, each including a second tooth portion 12e meshing with a first tooth portion 11a of a pinion gear 11 provided on the rotating shaft 10, are provided on three fixed shafts 12i mounted on the planetary carrier 16. Specifically, each of the three fixed shafts 12i is fixed to the planetary carrier 16 and is rotatable around the rotating shaft 10. The three planetary gears 12a, 12b, and 12c are rotatably provided on the fixed shafts 12i via bearings 12j and 12k, respectively. Figure 4 As shown in FIG. 1 , the second tooth portions 12e of the three planetary gears 12a, 12b, and 12c are twisted relative to the gear shaft. That is, the three planetary gears 12a, 12b, and 12c are helical gears.

[0089] Furthermore, since the three planetary gears 12a, 12b, and 12c are provided so as to be rotatable with respect to the fixed shaft 12i, respectively, the rotation center 12h of each of the three planetary gears 12a, 12b, and 12c is also the axial center of the fixed shaft 12i.

[0090] In addition, a cylindrical receiving portion 14 is provided on the inner circumference of the bearing holding portion 17. Figure 2 to Figure 4 As shown, an internal gear 13 is formed on the inner periphery of the receiving portion 14, and the internal gear 13 has a third tooth portion 13a meshing with the second tooth portion 12e of each of the three planetary gears 12a, 12b, and 12c. In addition, in the speed reduction mechanism 30 of this embodiment, the internal gear 13 is a gear fixed in a non-rotating manner. Moreover, the third tooth portion 13a is formed to be twisted relative to the gear shaft, and the internal gear 13 of the receiving portion 14 meshing with the three planetary gears 12a, 12b, and 12c is also a helical gear.

[0091] According to the above structure, in the speed reduction mechanism 30 of the present embodiment, the first tooth portion 11a of the pinion gear 11 of the rotating shaft 10 meshes with the second tooth portion 12e of each of the three planetary gears 12a, 12b, and 12c, and further, the second tooth portion 12e of each of the three planetary gears 12a, 12b, and 12c meshes with the third tooth portion 13a of the internal gear 13. Therefore, when the rotating shaft 10 rotates, each of the three planetary gears 12a, 12b, and 12c rotates (rotates). At this time, the internal gear 13 meshing with the three planetary gears 12a, 12b, and 12c is a non-rotating gear, and the three planetary gears 12a, 12b, and 12c are respectively provided to be rotatable relative to the fixed shaft 12i installed to be rotatable around the rotating shaft 10. As a result, each of the three planetary gears 12a, 12b, and 12c revolves around the rotating shaft 10. As the three planetary gears 12a, 12b, and 12c revolve, the planetary carrier 16 rotates, and the output shaft 15 fixed to the planetary carrier 16 also rotates. Therefore, when the rotating shaft 10 rotates, the output shaft 15 disposed on the substantially same axis as the rotating shaft 10 rotates at a reduced speed.

[0092] In addition, the second tooth portions 12e of the three planetary gears 12a, 12b, and 12c are respectively Figure 5 The tooth profile (tooth profile section) of the cut surface of the pinion 11 shown in the figure is in a state of contact with the arc-shaped portion of the first tooth portion 11a of the pinion 11. That is, the second tooth portion 12e of each of the three planetary gears 12a, 12b, and 12c is meshed with the arc-shaped portion 11b of the first tooth portion 11a of the pinion 11. In other words, the second tooth portion 12e of each of the three planetary gears 12a, 12b, and 12c abuts against and meshes with the arc-shaped portion 11b of the first tooth portion 11a of the pinion 11.

[0093] Here, for example, in a reduction mechanism including a sun gear and three planetary gears meshing with the sun gear and revolving around the sun gear while rotating (rotating) and orbiting, if the sun gear and the three planetary gears are spur gears, the number of planetary gears needs to be reduced from 3 to 2 if the reduction ratio is to be further increased. In this case, when the number of planetary gears is reduced from 3 to 2, the strength of the reduction mechanism is reduced to 2 / 3. On the other hand, if the strength of the reduction mechanism is to be ensured when the number of planetary gears is reduced to 2, the diameter of each planetary gear needs to be increased. As a result, the problem of large-scale reduction mechanism arises.

[0094] However, in the speed reduction mechanism 30 of the present embodiment, the second tooth portion 12e of each of the three planetary gears 12a, 12b, and 12c is formed in a spiral shape, and the spiral second tooth portion 12e meshes with the first tooth portion 11a of the pinion gear 11 serving as the sun gear. At this time, the first tooth portion 11a of the pinion gear 11 is also formed in a spiral shape. In addition, while the pinion gear 11 meshes with the three planetary gears 12a, 12b, and 12c, the three planetary gears 12a, 12b, and 12c also mesh with the internal gear 13 including the third tooth portion 13a formed in a spiral shape. As a result, the meshing rate between the gears becomes higher, and thus the strength of each tooth surface becomes higher, and the strength of the speed reduction mechanism 30 can be ensured.

[0095] In addition, since the pinion 11 including the helical first tooth portion 11a meshes with the three planetary gears 12a, 12b, 12c including the helical second tooth portion 12e, and the internal gear 13 including the helical third tooth portion 13a, and the meshing of each gear is performed continuously, the rotation of each gear becomes smooth. As a result, the vibration caused by the rotation of each gear can be suppressed, and the vibration of the speed reduction mechanism 30 can be suppressed.

[0096] In addition, the second tooth portions 12e of each of the three planetary gears 12a, 12b, and 12c mesh with the arc-shaped portion 11b of the first tooth portion 11a of the pinion gear 11. Figure 6 As shown in FIG. 1 , each of the three planetary gears 12a, 12b, and 12c is in a shape where the tooth tip circle 12g is smaller than the pitch circle 12f. Originally, in the meshing of gears, the tooth tip circle 12g is larger than the pitch circle 12f in most cases. However, in the case of the planetary gear 12 meshing with the single-tooth pinion 11, the pitch circle 12f is larger than the tooth tip circle 12g. Therefore, in the speed reduction mechanism 30 of the present embodiment, each of the three planetary gears 12a, 12b, and 12c is in a shape where the tooth tip circle 12g is smaller than the pitch circle 12f. Figure 6 Since the tooth tip circles 12g shown are meshed, the diameters of the three planetary gears 12a, 12b, and 12c can be reduced. As a result, the speed reduction mechanism 30 can be miniaturized.

[0097] That is, in the reduction mechanism 30, even if the structure has three planetary gears 12a, 12b, 12c, the strength of the reduction mechanism 30 can be ensured without increasing the diameter of each planetary gear. In other words, the strength of the reduction mechanism 30 can be ensured while miniaturizing the reduction mechanism 30. That is, in the reduction mechanism 30, the reduction ratio can be increased while miniaturizing.

[0098] Next, the arrangement conditions of the planetary gears 12 for meshing adjacent planetary gears 12 without interference in the reduction mechanism 30 including the single-tooth pinion 11 and the plurality of planetary gears 12 meshing with the pinion 11 are described. In the reduction mechanism 30 of the above structure, when the number of the planetary gears 12 is three or more, it is necessary to avoid interference between the planetary gears 12 and the adjacent planetary gears 12, and this also involves the strength of the reduction mechanism 30, so it is necessary to determine the number of the planetary gears 12 to be set in the early stage of the design of the reduction mechanism 30 for design.

[0099] First, the use of Fig. 9 The interference of the planetary gears of the general involute gear 40 shown will be described. In the case of the general involute gear 40, the formula (A) for judging whether there is interference is as follows.

[0100] 2+Zb<(Za+Zb)×sin(180° / N)…Formula (A). Here, Za is the number of teeth of the sun gear, Zb is the number of teeth of the planetary gear 12, and N is the number of planetary gears. In formula (A), the value of sin is a variable that becomes a value between 1 and -1. In addition, since the value of sin in formula (A) is not a function that increases the value on the right, it is considered to ignore the number of planetary gears N and assume that the value of sin is the maximum value, that is, 1. At this time, when the sun gear is a single-tooth pinion 11, Za=1, so formula (A) becomes (2+Zb)<(1+Zb). In the formula (2+Zb)<(1+Zb), all values ​​of the value on the right are lower than the value on the left, and this inequality does not hold. The formula (A) is only valid when the number of teeth Za of the sun gear is 3 or more, and is not suitable for the case where the sun gear is a single-tooth pinion 11 as in the reduction mechanism 30 of the present embodiment. Therefore, it is necessary to design conditions suitable for the case where the sun gear is a single-tooth pinion 11 .

[0101] First, the conditions for avoiding interference between adjacent planetary gears when three planetary gears 12 are provided in the reduction mechanism 30 in which the sun gear is a single-tooth pinion 11. The addendum circle 12g of the planetary gear 12 is determined by the specifications of the single-tooth pinion 11 and has a characteristic of being smaller in diameter than the pitch circle 12f of the planetary gear 12. In the case where the specifications of the single-tooth pinion 11 are not determined, the conditions for avoiding interference are studied instead of the addendum circle 12g of the planetary gear 12.

[0102] like Figure 6 As shown in FIG. 1 , the radius of the pitch circle 12f of the planetary gear 12 is set to R1, and as shown in FIG. Figure 7As shown, the interference avoidance limit lines S1, S2 and S3 are set. If the distance (center-to-center distance) between the center of the pitch circle 11c of the single-tooth pinion 11 (rotation center 10a) and the center of the pitch circle 12f of the planetary gear 12 (rotation center 12h) is set to L1, then when the sun gear is a single-tooth pinion 11, the following formula (B) holds.

[0103] The pitch circle radius R1 of the planetary gear 12 < (center distance L1×cosθ) ... formula (B)

[0104] In addition, the planetary gear 12 is as follows Fig. 9 In the case of a general involute gear 40 as shown, it is considered to use a tooth tip circle 40b larger than the pitch circle 40a in the involute gear 40. That is, if the tooth tip circle radius of the involute gear 40 is set to R2, and the distance (center-to-center distance) between the center of the pitch circle 11c of the single-tooth pinion 11 (rotation center 10a) and the center of the tooth tip circle 40b of the involute gear 40 (rotation center 40c) is set to L1, the following formula (C) is established.

[0105] The tip circle radius R2 of the involute gear 40 < (center distance L1×cosθ) ... formula (C)

[0106] At this time, the angle θ can be calculated by the following formula (D).

[0107] θ=(180°(sum of the interior angles of the triangle)-90°)-(360°÷number of planetary gears÷2)…Formula (D)

[0108] That is, in the speed reduction mechanism 30 of the present embodiment, by setting the relationship of the pitch circle radius R1 of the planetary gear 12 <(center distance L1×cosθ), interference between adjacent planetary gears can be avoided when three planetary gears 12 are provided.

[0109] Next, the conditions for avoiding interference between adjacent planetary gears when four planetary gears 12 are provided in the speed reduction mechanism 30 whose sun gear is a single-tooth pinion 11 will be described. That is, the case where four planetary gears 12a, 12b, 12c, and 12d meshing with the single-tooth pinion 11 are provided.

[0110] First, if Figure 8 As shown in FIG. 1 , interference avoidance limit line T1, interference avoidance limit line T2, interference avoidance limit line T3, and interference avoidance limit line T4 are set. Figure 6The radius of the pitch circle 12f of the planetary gear 12 shown is set to R1, and the distance (center-to-center distance) between the center of the pitch circle 11c of the single-tooth pinion 11 (rotation center 10a) and the center of the pitch circle 12f of the planetary gear 12 (rotation center 12h) is set to L1. Then, when the sun gear is a single-tooth pinion 11, the following formula (B) holds, similarly to the case where three planetary gears 12 are provided.

[0111] The pitch circle radius R1 of the planetary gear 12 < (center distance L1×cosθ) ... formula (B)

[0112] In this case, similarly to the case where three planetary gears 12 are provided, the angle θ can be calculated by the following formula (D).

[0113] θ=(180°(sum of the interior angles of the triangle)-90°)-(360°÷number of planetary gears÷2)…Formula (D)

[0114] That is, in the speed reduction mechanism 30 of the present embodiment, even when four planetary gears 12 are provided, interference between adjacent planetary gears can be avoided by setting the relationship of the pitch circle radius R1 of the planetary gear 12 to be less than (center distance L1×cosθ).

[0115] Next, an application example of the speed reduction mechanism 30 of the present embodiment will be described.

[0116] The speed reduction mechanism 30 can be applied to, for example, Fig.10 As shown in FIG. 3 , the robot 35 includes a body 35a, a shoulder 35b mounted on the body 35a, an elbow 35c connected to the shoulder 35b, and a wrist 35d connected to the elbow 35c. Fig.11 The motor unit 34 is provided with the reduction mechanism 30 as shown. Each motor unit 34 includes a motor 31, the reduction mechanism 30 of this embodiment, an encoder 32, and a driver substrate 33. The rotating shaft 10 of the motor 31 is the input shaft of the reduction mechanism 30. The rotating shaft 10 rotates by the driving of the motor 31, and the output shaft 15 (refer to Figure 1 )Rotate.

[0117] By incorporating the motor unit 34 including the speed reduction mechanism 30 of the present embodiment into various parts of the robot 35 , the speed reduction mechanism 30 can be miniaturized, and thus the robot 35 can be miniaturized.

[0118] Furthermore, the reduction mechanism 30 of the present embodiment can be miniaturized, thereby reducing the load on the motor 31 that operates the reduction mechanism 30. As a result, the motor unit 34 including the reduction mechanism 30 can be operated efficiently. This can contribute to the Sustainable Development Goals (SDGs) led by the United Nations, especially Goal 7 (ensuring access to affordable, reliable, sustainable and modern energy for all) and Goal 13 (taking urgent action to combat climate change and its impacts).

[0119] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the reduction mechanism 30 is applied to the motor unit 34 incorporated in various parts provided on the robot 35, but it can also be applied to a motor unit including a drive source of a wiper device mounted on a vehicle, or other drive sources such as an electric window device or a sunroof device.

Claims

1. A speed reduction mechanism, comprising: Axis of rotation; A first gear, disposed on the outer periphery of the rotating shaft, and comprising a first tooth portion extending in a spiral shape along the length direction of the rotating shaft; a plurality of second gears, each including a helical second tooth portion meshing with the first tooth portion, and arranged along the circumferential direction of the rotating shaft; a receiving portion for receiving the plurality of second gears; and a third gear, which is disposed on the inner periphery of the receiving portion and includes a spiral third tooth portion meshing with the second tooth portion, The tooth profile cross section of at least a portion of the first tooth portion is formed in an arc shape, The second tooth portion meshes with the first tooth portion while being in contact with the arc-shaped portion of the tooth profile cross section.

2. The speed reduction mechanism according to claim 1, wherein: At least three second gears are arranged along the circumferential direction of the rotating shaft.

3. The speed reduction mechanism according to claim 1 or 2, wherein: When the pitch circle radius of the second gear is set to R1, The center-to-center distance from the rotation center of the rotation shaft to the rotation center of the second gear is L1, When the angle calculated by the formula (180° (sum of the interior angles of the triangle) - 90°) - (360° ÷ the number of the second gears ÷ 2) is defined as θ, The pitch circle radius R1<(the center-to-center distance L1×cosθ).

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