Speed reducer and actuator

Abstract

The present application relates to a speed reducer and an actuator, the speed reducer having a sun gear, a plurality of planetary gears, a fixed portion, an output portion, a first bearing, and a second bearing. The sun gear rotates at a first rotational speed relative to the fixed portion. The plurality of planetary gears are disposed around the sun gear and each engages with the sun gear. The output portion includes a ring gear that engages with the plurality of planetary gears. The output portion rotates at a second rotational speed lower than the first rotational speed relative to the fixed portion. The first bearing is located between the fixed portion and the output portion at a position on an input side relative to the plurality of planetary gears. The second bearing is located between the fixed portion and the output portion at a position on an output side relative to the plurality of planetary gears. The second bearing has a radial size smaller than a radial size of the first bearing.

Description

[0001] This application is a divisional application of Chinese invention patent application No. 201710475160.5, filed on June 21, 2017, entitled "Gear Reducer and Actuator". Technical Field

[0002] This invention relates to a speed reducer and an actuator having a speed reducer. Background Technology

[0003] In devices such as electric wheelchairs and automated guided vehicles, torque is increased by slowing down the rotation from the motor, thereby causing the wheels to rotate. In these devices, in-wheel reducers, where a reducer is located inside the wheel, are conventionally used. An example of an in-wheel reducer is described, for instance, in Japanese Patent Application Publication No. 2015-110382.

[0004] In the speed reducer disclosed in Japanese Patent Application Publication No. 2015-110382, a planetary gear mechanism having a sun gear and planetary gears is used to transmit power. Furthermore, in the speed reducer of this publication, the internal gear is supported by two bearings 71 and 72 so that it can rotate relative to the frame (see paragraph 0024). Figure 1 wait).

[0005] This type of in-wheel reducer, because it is housed inside the wheel, is advantageous for meeting miniaturization requirements. Especially in recent years, there has been a demand for in-wheel reducers capable of supporting smaller wheels. However, in Japanese Patent Application Publication No. 2015-110382, the two bearings 71 and 72 have the same diameter. Furthermore, the wheel is fixed to an internal gear on the radially outer side of these two bearings 71 and 72. This structure presents a problem that makes it difficult to further miniaturize the wheel.

[0006] Furthermore, this problem is not limited to wheels; it can also occur in gearboxes located inside driven objects such as fans. Summary of the Invention

[0007] The purpose of this invention is to provide a structure in a speed reducer disposed inside a driven object that can accommodate the miniaturization of the driven object.

[0008] Methods for solving technical problems

[0009] One exemplary embodiment of this application is a speed reducer that converts rotation at a first speed centered on a rotational axis extending between an input side and an output side into rotation at a second speed lower than the first speed. The speed reducer includes: a fixed portion; a sun gear that rotates relative to the fixed portion at the first speed about the rotational axis; a plurality of planetary gears arranged around and meshing with the sun gear; an output portion including an annular internal gear meshing with the plurality of planetary gears and rotating relative to the fixed portion at the second speed; a first bearing located between the fixed portion and the output portion at a position closer to the input side than the plurality of planetary gears; and a second bearing located between the fixed portion and the output portion at a position closer to the output side than the plurality of planetary gears, the second bearing having a smaller radial size than the first bearing.

[0010] An actuator includes: a speed reducer; and a motor directly or indirectly connected to the sun gear, wherein the sun gear rotates at a first rotational speed by being driven by the motor.

[0011] According to one embodiment illustrated in this application, by using a second bearing with a small diameter, the portion of the output section located on the output side, which is closer to the output side than the plurality of planetary gears, can be made smaller. Therefore, the driven object rotating at a reduced second rotational speed can also be miniaturized.

[0012] The above and other features, elements, steps, characteristics, and advantages of the present invention will become clearer with reference to the accompanying drawings and through the following detailed description of preferred embodiments of the invention. Attached Figure Description

[0013] Figure 1 This is a longitudinal cross-sectional view of the actuator.

[0014] Figure 2 From Figure 1 A partial cross-sectional view of the reducer observed at position II-II.

[0015] Figure 3 This is a longitudinal section view of the speed reducer involved in the modified example. Detailed Implementation

[0016] Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In this application, the direction parallel to the rotation axis of the sun gear is referred to as "axial direction," the direction orthogonal to the rotation axis is referred to as "radial direction," and the direction along an arc centered on the rotation axis is referred to as "circumferential direction." However, the aforementioned "parallel direction" also includes substantially parallel directions. Furthermore, the aforementioned "orthogonal direction" also includes substantially orthogonal directions. And, hereinafter, the direction along the rotation axis... Figure 1 The right side of the input is called the "input side". Figure 1 The left side of the diagram is called the "output side".

[0017] Figure 1 This is a longitudinal cross-sectional view of the actuator 100 of the speed reducer 1 according to an embodiment of the present invention. Figure 2 From Figure 1 A partial cross-sectional view of the reducer 1 observed at position II-II. Additionally, in Figure 2 To avoid complicating the diagram, the shadow lines representing the cross sections have been omitted.

[0018] The actuator 100 is a device that converts rotation from the motor 8 at a first speed into rotation at a second speed, which is lower than the first speed, and rotates the wheel 9. The actuator 100 is used, for example, to rotate the wheels of wheelchairs, automated guided vehicles, self-balancing vehicles, electric walking aids, chair-type electric vehicles, etc. However, the speed reducer and actuator of the present invention can also be used for other purposes.

[0019] like Figure 1 As shown, the actuator 100 includes a motor 8, a reducer 1, and a wheel 9. The reducer 1 includes a sun gear 10, multiple planetary gears 20, multiple support pins 30, a fixed part 40, and an output part 50.

[0020] The sun gear 10 is a gear coaxially configured with respect to the axis of rotation A. For example... Figure 2 As shown, the sun gear 10 has multiple external teeth on its outer circumferential surface. The sun gear 10 is directly or indirectly connected to the motor 8, which serves as a drive source. In this embodiment, the sun gear 10 is connected to the motor 8 via the input shaft 11. The sun gear 10 and the input shaft 11 can be either integral components or separate components fixed together. When driven by the motor 8, the input shaft 11 and the sun gear 10 rotate at a first rotational speed about the rotation axis A.

[0021] Multiple planetary gears 20 are arranged around the sun gear 10. For example... Figure 2 As shown, in this embodiment, three planetary gears 20 are arranged at equal intervals around the sun gear 10. However, the reducer 1 may have two or more planetary gears 20. Each planetary gear 20 has a plurality of external teeth on its outer circumferential surface. In this embodiment, the diameter of each planetary gear 20 is larger than the diameter of the sun gear 10. Furthermore, the number of external teeth of a planetary gear 20 is greater than the number of external teeth of the sun gear 10. The external teeth of the sun gear 10 mesh with the external teeth of each of the plurality of planetary gears 20.

[0022] Multiple support pins 30 are components used to support the planetary gears 20 so that they can rotate. The support pins 30 are, for example, cylindrical components extending axially. Each planetary gear 20 has a pin hole 21. The pin hole 21 extends axially through the center of the planetary gear 20. Each support pin 30 is inserted into the pin hole 21. Furthermore, a needle roller bearing 211 is inserted between the inner circumferential surface of the planetary gear 20 and the support pin 30. Thus, each planetary gear 20 is supported so that it can rotate about the support pin 30.

[0023] The fixing part 40 is a portion that is stationary relative to the frame of the device on which the speed reducer 1 is mounted. In this embodiment, the fixing part 40 has a first fixing member 41 and a second fixing member 42. The first fixing member 41 and the second fixing member 42 are fixed together by bolts 43. Furthermore, the first fixing member 41 is fixed to the frame of the device on which the speed reducer 1 is mounted by bolts 44.

[0024] The second fixing member 42 includes: a gear retainer portion 421 for holding a plurality of planetary gears 20; and a protrusion 422. Both ends of each support pin 30 are fixed axially to the gear retainer portion 421. The gear retainer portion 421 has a plurality of notches 420 for receiving the planetary gears 20. Each planetary gear 20 rotates while being supported by the support pins 30 inside the notches 420. The protrusion 422 protrudes from the gear retainer portion 421 along the rotation axis A toward the output side. The protrusion 422 has a cylindrical outer peripheral surface centered on the rotation axis A.

[0025] The output section 50 is the part that rotates at a reduced second speed. The output section 50 has an internal gear 51 and a bearing cage 52. The internal gear 51 is a ring-shaped gear surrounding a plurality of planetary gears 20. Figure 2 As shown, the internal gear 51 has multiple internal teeth on its inner circumferential surface. The number of internal teeth in the internal gear 51 is greater than the number of external teeth in a single planetary gear 20. The internal teeth of the internal gear 51 mesh with the external teeth of each of the multiple planetary gears 20. That is, each planetary gear 20 meshes with both the sun gear 10 and the internal gear 51.

[0026] The bearing cage 52 is an annular component located on the output side of the internal gear 51. The bearing cage 52 has a cylindrical portion 521 and a flange portion 522. The cylindrical portion 521 extends axially in a cylindrical shape and is coaxially arranged with the rotation axis A. The flange portion 522 extends radially outward from the input side end of the cylindrical portion 521. The internal gear 51 and the flange portion 522 are fixed together by bolts 53. Furthermore, the internal gear 51, the flange portion 522, and the wheel 9 are fixed together by bolts 91. Therefore, the internal gear 51, the bearing cage 52, and the wheel 9 rotate as a single unit around the rotation axis A.

[0027] If the motor 8, which serves as the drive source, is driven, the input shaft 11 and the sun gear 10 rotate relative to the fixed part 40 at a first rotational speed. Furthermore, as the sun gear 10 rotates, the plurality of planetary gears 20 meshing with the sun gear 10 rotate around the support pin 30. Moreover, if each planetary gear 20 rotates, the internal gear 51 meshing with the planetary gear 20 rotates around the rotation axis A. At this time, the rotational speed of the internal gear 51 relative to the fixed part 40 is a second rotational speed, lower than the first rotational speed. Furthermore, the output part 50, including the internal gear 51, and the wheel 9 fixed to the output part 50 rotate around the rotation axis A at the second rotational speed.

[0028] In addition, lubricating oil (e.g., grease) is applied to the surface of each component of the reducer 1. This reduces friction between components, allowing the reducer 1 to operate smoothly.

[0029] like Figure 1 As shown, the reducer 1 has a first bearing 61, a second bearing 62 and a third bearing 63.

[0030] The first bearing 61 is located between the fixed part 40 and the output part 50, closer to the input side than the plurality of planetary gears 20. The first bearing 61 is, for example, a ball bearing. However, other types of bearings, such as roller bearings, may be used instead of ball bearings. The inner ring of the first bearing 61 is fixed to the outer peripheral surface of the gear cage portion 421 of the second fixed member 42. The outer ring of the first bearing 61 is fixed to the inner peripheral surface of the internal gear 51 at a position where no internal teeth are provided.

[0031] The second bearing 62 is located between the fixed portion 40 and the output portion 50, closer to the output side than the plurality of planetary gears 20. The second bearing 62 is, for example, a ball bearing. However, other types of bearings, such as roller bearings, may be used instead of ball bearings. The inner ring of the second bearing 62 is fixed to the outer peripheral surface of the protrusion 422 of the second fixed member 42. The outer ring of the second bearing 62 is fixed to the inner peripheral surface of the cylindrical portion 521 of the bearing cage 52.

[0032] Furthermore, a retaining ring 45 is fixed near the output side end of the outer peripheral surface of the protrusion 422. The retaining ring 45 is in axial contact with the output side end face of the inner ring of the second bearing 62. This prevents the second bearing 62 from falling off to the output side.

[0033] A third bearing 63 is located between the input shaft 11 and the fixed part 40. The third bearing 63 may be a ball bearing, for example. However, other types of bearings, such as roller bearings, may be used instead of ball bearings. The inner ring of the third bearing 63 is fixed to the outer circumferential surface of the input shaft 11. The outer ring of the third bearing 63 is fixed to the inner circumferential surface of the first fixed part 41. In this way, the presence of the third bearing 63 between the input shaft 11 and the fixed part 40 allows the input shaft 11 to rotate relative to the fixed part 40.

[0034] As described above, two bearings, a first bearing 61 and a second bearing 62, are located between the fixed part 40 and the output part 50. Therefore, the output part 50 is supported relative to the fixed part 40 so that it can rotate about the rotation axis A. Furthermore, the first bearing 61 and the second bearing 62 are arranged axially spaced apart. This prevents the output part 50 from tilting relative to the rotation axis A.

[0035] In this reducer 1, the radial dimension of the second bearing 62, located closer to the output side than the planetary gear 20, is smaller than the radial dimension of the first bearing 61, located closer to the input side than the planetary gear 20. Specifically, the outer diameter of the outer ring of the second bearing 62 is smaller than the outer diameter of the outer ring of the first bearing 61. By using a smaller diameter second bearing 62, the portion of the output section 50 located closer to the output side than the planetary gear 20 can be made smaller in diameter. In this embodiment, the outer diameter of the cylindrical portion 521 of the bearing cage 52 can be reduced. As a result, it becomes easier to install a small wheel 9 in the output section 50. Especially in this embodiment, the second bearing 62 is located radially inside the wheel 9. Therefore, by making the second bearing 62 smaller in diameter, the wheel 9 can also be made smaller.

[0036] However, if the diameter of the second bearing 62 is made extremely small, there is a concern that the support of the second bearing 62 for the output section 50 may become unstable. Therefore, in order to obtain sufficient supporting force, it is preferable that the second bearing 62 has a diameter of a predetermined size or larger. For example, it is preferable that the second bearing 62 has a diameter that at least partially coincides with the support pin 30 when viewed axially. Figure 1 In the example, the radial distance from the rotation axis A to the inner circumferential surface of the second bearing 62 is smaller than the radial distance from the rotation axis A to the radially inner end edge of the support pin 30. Furthermore, the radial distance from the rotation axis A to the outer circumferential surface of the second bearing 62 is larger than the radial distance from the rotation axis A to the radially outer end edge of the support pin 30.

[0037] And, as Figure 1 As shown, in this embodiment, the cross-section of the second bearing 62, which is orthogonal to the circumference, is larger than that of the first bearing 61. Specifically, the axial dimension of the second bearing 62 is larger than that of the first bearing 61. Furthermore, the radial dimension of the second bearing 62, from its inner circumferential surface to its outer circumferential surface, is larger than that of the first bearing 61. In this way, by increasing the cross-sectional dimension of the second bearing 62, a second bearing 62 with a smaller diameter can be used, and the supporting force of the second bearing 62 can be ensured.

[0038] Furthermore, in this embodiment, the second fixing member 42 of the fixing part 40 has a gear retainer portion 421 and a protrusion 422 protruding from the gear retainer portion 421 toward the output side. The diameter of the outer peripheral surface of the protrusion 422 is smaller than the diameter of the outer peripheral surface of the gear retainer portion 421. Moreover, the space S on the output side of the gear retainer portion 421 and the internal gear 51 and radially outward of the protrusion 422 accommodates the second bearing 62, the bearing retainer 52, the head 531 of the bolt 53, and the head 911 of the bolt 91. In this way, it is possible to prevent these parts from protruding to the output side beyond the end face of the protrusion 422 on the output side. It is also possible to prevent these parts from protruding radially outward beyond the outer peripheral surface of the internal gear 51. As a result, the reducer 1 can be further miniaturized in both the axial and radial directions.

[0039] Furthermore, in this embodiment, a circular hole 423 is provided in the second fixing member 42 for the output end of the fixing support pin 30. This circular hole 423 is a through hole that opens on both the input and output sides. Therefore, the diameter of the circular hole 423 can be easily changed by machining. Therefore, the diameter of the support pin 30 can be easily changed. In particular, if the diameter of the support pin 30 is increased, a needle roller bearing 211 that can withstand a higher load can be used. Therefore, the service life of the reducer 1 can be extended. Furthermore, the output torque of the actuator 100 can be increased.

[0040] As described above, the output section 50 of this embodiment has an internal gear 51 and a bearing cage 52. The internal gear 51 and the bearing cage 52 are separate parts, and are fixed together by bolts 53 and 91.

[0041] By making the internal gear 51 and the bearing cage 52 separate components, materials that meet their respective strength requirements can be used for both. Specifically, the bearing cage 52 requires less strength than the internal gear 51. Therefore, for example, a high-strength alloy can be used for the internal gear 51, while a lightweight and inexpensive die-cast aluminum can be used for the bearing cage 52. Furthermore, making the internal gear 51 and the bearing cage 52 separate components simplifies the shape of each component. Consequently, the machining of each component becomes easier. As a result, the material cost and machining cost of the output section 50 can be reduced.

[0042] Furthermore, in this embodiment, a bearing cage 52 is clamped between the internal gear 51 and the wheel 9 and connected by bolts 91. Therefore, the so-called "alignment" operation, which aligns the central axis of the wheel 9 with the central axis of the internal gear 51, can be performed directly between the wheel 9 and the internal gear 51. Moreover, torque is directly transmitted from the internal gear 51 to the wheel 9. Therefore, it is less likely to cause a decrease in installation accuracy or a decrease in transmitted torque due to making the internal gear 51 and the bearing cage 52 separate components.

[0043] The exemplary embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments.

[0044] Figure 3 This is a longitudinal cross-sectional view of the reducer 1A involved in a modified example. Figure 3 The speed reducer 1A is assembled inside the impeller of the ceiling fan to rotate the impeller. In the case of a ceiling fan, such as... Figure 3 As shown, the reducer 1A is configured with the output side facing downwards. Therefore, Figure 3 The reducer 1A has an oil catch cover 70A. The oil catch cover 70A is located on the output side closer to the second bearing 62A. Furthermore, the oil catch cover 70A is in the shape of a circular plate and is arranged perpendicularly to the axis of rotation A. The periphery of the oil catch cover 70A is fixed to the cylindrical portion 521A of the bearing cage 52A by bolts 71A.

[0045] In this way, even if lubricating oil (e.g., grease) inside the reducer 1A drips downwards from the second bearing 62A, it will be caught by the oil catcher 70A. Therefore, it is possible to prevent lubricating oil from dripping to a position lower than the oil catcher 70A.

[0046] Furthermore, in the above embodiment, the internal gear and bearing cage of the output section are separate components. However, the internal gear or bearing cage and wheel can also be an integral component. That is, the wheel can also be part of the reducer. Similarly, in Figure 3 In some examples, the internal gear or bearing cage can be an integral part of the impeller.

[0047] Furthermore, in the above embodiments, the sun gear, planetary gear, and internal gear are all toothed gears that transmit power through tooth meshing. However, the sun gear, planetary gear, and internal gear can also be friction gears that transmit power through friction.

[0048] Furthermore, the speed reducer of the present invention can also be a speed reducer that rotates a drive object other than a wheel and impeller.

[0049] Furthermore, the shapes of the detailed parts of the reducer and actuator may differ from those shown in the figures of this application. Also, the elements described in the above embodiments and variations may be appropriately combined without causing contradiction.

[0050] This invention can be used in speed reduction devices and wheel units.

Claims

1. A speed reducer that converts rotation at a first rotational speed centered on a rotational axis extending between an input side and an output side to rotation at a second rotational speed lower than the first rotational speed, the speed reducer having: a fixed portion; a sun gear that rotates at the first rotational speed with respect to the fixed portion centered on the rotational axis; a plurality of planetary gears that are disposed around the sun gear and each mesh with the sun gear; an output portion that includes a ring-shaped inner gear that meshes with the plurality of planetary gears and rotates at the second rotational speed with respect to the fixed portion; a first bearing that is located between the fixed portion and the output portion at a position closer to the input side than the plurality of planetary gears; a second bearing that is located between the fixed portion and the output portion at a position closer to the output side than the plurality of planetary gears; a bearing holder that is located at a position closer to the output side than the inner gear; and a wheel that rotates with the output portion, the fixed portion having: a gear holder portion that holds the plurality of planetary gears; and a convex portion that protrudes in an axial direction from the gear holder portion and has a cylindrical outer peripheral surface that is smaller in diameter than an outer peripheral surface of the gear holder portion, an inner ring of the second bearing is fixed to the outer peripheral surface of the convex portion, the bearing holder having: a cylindrical portion that extends in a cylindrical shape in an axial direction and is disposed coaxially with the rotational axis; and a flange portion that expands to an outer radial side from an end portion of the cylindrical portion on the input side, an outer ring of the second bearing is fixed to an inner peripheral surface of the bearing holder, a radial size of the second bearing is smaller than a radial size of the first bearing, the inner gear, the flange portion, and the wheel are fixed to each other by a bolt, a space on an output side of the gear holder portion and the inner gear and on an outer radial side of the convex portion accommodates the second bearing, the bearing holder, and a head portion of the bolt, an end surface of the bolt on the output side is disposed at a position closer to the input side than an end surface of the second bearing on the output side, an inner ring of the first bearing is fixed to an outer peripheral surface of the gear holder portion, the speed reducer is characterized in that the second bearing is located on an inner radial side of the wheel, the first bearing is disposed outside an axial range of the wheel.

2. The speed reducer according to claim 1, characterized by Further having: a support pin that extends in an axial direction from the fixed portion and supports the planetary gears so as to be able to rotate on their own, the second bearing and the support pin at least partially coincide when viewed in an axial direction.

3. The speed reducer according to claim 2, characterized in that a radial distance from the rotational axis to an inner peripheral surface of the second bearing is smaller than a radial distance from the rotational axis to an end edge on an inner radial side of the support pin.

4. The speed reducer according to claim 2 or claim 3, characterized in that a radial distance from the rotational axis to an outer peripheral surface of the second bearing is larger than a radial distance from the rotational axis to an end edge on an outer radial side of the support pin.

5. The speed reducer according to any one of claims 1 to 3, characterized in that A cross section of the second bearing orthogonal to a circumferential direction is larger than a cross section of the first bearing orthogonal to the circumferential direction.

6. The speed reducer according to any one of claims 1 to 3, characterized in that, An axial dimension of the second bearing is larger than an axial dimension of the first bearing.

7. The speed reducer according to any one of claims 1 to 3, characterized in that, A radial dimension of the second bearing from an inner peripheral surface to an outer peripheral surface is larger than a radial dimension of the first bearing from an inner peripheral surface to an outer peripheral surface.

8. The speed reducer according to any one of claims 1 to 3, characterized in that, The inner gear or the bearing holder is an integral part with the wheel.

9. The speed reducer according to any one of claims 1 to 3, characterized in that, An end surface of the output side of the wheel is flush with an end surface of the output side of the cylindrical portion.

10. The speed reducer according to any one of claims 1 to 3, characterized in that, An end surface of the input side of the wheel is disposed at a position closer to the input side than an end surface of the input side of the planetary gear.

11. The speed reducer according to any one of claims 1 to 3, characterized in that, The fixed portion is fixed to an end portion of the input side of the gear holder portion, and the fixed portion further has a first fixed portion that extends in a radial direction, An end surface of the input side of the wheel is axially opposed to an end surface of the output side of the first fixed portion.

12. The speed reducer according to any one of claims 1 to 3, characterized in that, A material of the inner gear is higher in strength than a material of the bearing holder.

13. The speed reducer according to any one of claims 1 to 3, characterized by, Further comprising: Lubricating oil applied to a surface of at least a portion of the components; and An oil receiving pan disposed on the output side of the second bearing.

14. The speed reducer according to claim 13, characterized in that, The oil receiving pan is disposed vertically with respect to the rotational axis and is fixed to the fixed portion.

15. An actuator, characterized by Having: The speed reducer according to any one of claims 1 to 14; and A motor connected directly or indirectly to the sun gear, The sun gear is rotated at the first rotational speed by driving of the motor.

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