JP7798211B2 - Reducer motor - Google Patents

Description

This disclosure relates to a motor with a reducer.

Patent Document 1 below discloses a motor with a reducer, in which a unit such as a reducer is disposed. The motor with a reducer described in this document comprises a rotatably supported rotor and a unit such as a reducer disposed radially inward of the rotor. The rotation of the rotor is slowed down by the reducer and transmitted to the output shaft.

Patent No. 6278432

The configuration of the geared motor described in Patent Document 1 aims to reduce the axial size of the geared motor by arranging units such as the reducer radially inward of the rotor. However, this configuration leaves room for improvement in terms of reducing the radial size of the geared motor.

The present disclosure takes the above into consideration and aims to provide a motor with a reducer that can be made smaller in the radial direction.

A motor with a reducer that solves the above problem has a ring gear (60) formed in an annular shape and having a plurality of first internal teeth (60A) and a plurality of second internal teeth (60B) formed on its radially inner surface, a rotor (22) in which one of a magnet (32) and a coil (28) is fixed to the radially outer surface of the ring gear, a stator (20) including one of the magnet and the coil arranged opposite one of the magnet and the coil, a first planetary gear (62) arranged radially inside the rotor and meshing with the first internal teeth, a first sun gear (66) arranged radially inside the first planetary gear and meshing with the first planetary gear, and a stator (20) arranged radially inside the rotor. a first carrier (64) positioned radially inside the rotor and on one axial side of the first planetary gear, meshing with the second internal teeth; a second sun gear (72) positioned radially inside the second planetary gear, engaged with the first sun gear in a state where it cannot rotate relative to the first sun gear, and meshing with the second planetary gear; a second carrier (70) positioned radially inside the rotor, supporting the second planetary gear, and rotating as the second planetary gear revolves around the second sun gear; and an output shaft (12) that rotates when the rotational force of the second carrier is transmitted.

By configuring it in this way, the motor with a reducer can be made smaller in the radial direction.

1 is a perspective view showing a motor with a reducer according to a first embodiment; 2 is a cross-sectional perspective view showing the motor with a reducer taken along line 2-2 shown in FIG. 1. 2 is a side cross-sectional view showing a cross section of the speed reducer-equipped motor shown in FIG. 1 taken along the axial direction. FIG. 2 is an exploded perspective view showing the motor with a speed reducer shown in FIG. 1 . FIG. 2 is an exploded perspective view showing the stator. FIG. 2 is an exploded perspective view showing the reducer. FIG. 2 is an exploded perspective view showing a magnet and a magnet covering member. FIG. 6 is a side cross-sectional view corresponding to FIG. 3 and showing a motor with a reducer according to a second embodiment. FIG. 10 is a side cross-sectional view corresponding to FIG. 3 and showing a motor with a reducer according to a third embodiment.

(First embodiment)
A speed reducer-equipped motor 10 according to the first embodiment will be described with reference to Figures 1 to 7. Note that the arrow Z direction, arrow R direction, and arrow C direction shown as appropriate in the figures respectively indicate one side in the rotational axial direction, the outer side in the rotational radial direction, and one side in the rotational circumferential direction of the output shaft 12. Furthermore, hereinafter, when simply referring to the axial direction, radial direction, or circumferential direction, this refers to the rotational axial direction, rotational radial direction, or rotational circumferential direction of the output shaft 12, unless otherwise specified.

As shown in Figures 1 to 4, the reducer-equipped motor 10 of this embodiment is a three-phase, eight-pole, 12-slot reducer-equipped motor with a built-in reducer 14. This reducer-equipped motor 10 includes a motor case 16, a motor cover 18, a stator 20, a rotor 22, and a reducer 14 that slows the rotation of the rotor 22, all of which are arranged within the motor case 16, and an output shaft 12 that protrudes from the motor cover 18. Note that Figure 3 shows only a cross-sectional portion.

As shown in Figures 2, 3, and 5, the motor case 16 is formed in a cylindrical shape with a bottom that is open on one axial side and closed on the other axial side. The motor case 16 has a disk-shaped bottom wall portion 16A and a side wall portion 16B that bends and extends from the radially outer end of the bottom wall portion 16A toward one axial side.

2, 3, and 4, the motor cover 18 includes a disk-shaped lid portion 18A. An insertion hole 18B is formed in the radial center of the lid portion 18A, into which the output shaft 12 (described later) is inserted. The motor cover 18 also includes an annular first flange portion 18C that protrudes axially from the edge of the insertion hole 18B. A bearing 19 that supports the output shaft 12 is fixed to the inner periphery of the first flange portion 18C by press fitting or the like. When the output shaft 12 is inserted into the insertion hole 18B and the motor cover 18 is attached to the motor case 16, the open end (one axial side) of the motor case 16 is closed by the lid portion 18A with the output shaft 12 protruding axially from the motor cover 18. As shown in Figures 2 and 3, the motor cover 18 has an annular second flange portion 18D that protrudes from the radially intermediate portion on the other axial side of the lid portion 18A toward the other axial side. A sealed bearing 21 that supports a ring gear 60 that forms part of the reducer 14 (described below) is fixed to the inner periphery of this second flange portion 18D by press fitting or the like.

As shown in FIG. 4, the stator 20 is fixed to the radially inner surface of the side wall portion 16B of the motor case 16. As shown in FIGS. 4 and 5, the stator 20 includes an annular stator core 24 and a plurality of coil bodies 26 fixed to the inner circumferential surface of the stator core 24. As shown in FIG. 5, in this embodiment, twelve coil bodies 26 are arranged in a circumferential direction.

Here, the coil body 26 includes a coil 28 formed by winding a conductive wire, and an insulator 30 having a locking portion 30A that maintains the shape of the coil 28 and is locked to the stator core 24. The conductive wire that constitutes the coil 28 is a wire assembly formed by bundling conductive wires. The resistance between the bundled wires is greater than the resistance of the wires themselves, thereby reducing eddy current loss. The terminals of the coil 28 of each coil body 26 are connected to a bus bar 31. In this embodiment, as an example, the coil 28 of each coil body 26 is connected in a star connection via the bus bar 31. In addition, this embodiment has a teethless structure in which no part of the stator core 24 is disposed inside the coil 28.

As shown in FIGS. 4 and 7 , the rotor 22 is configured by attaching an annular magnet 32 to the outer peripheral surface of a ring gear 60 that constitutes a part of the reducer 14 (described later). As shown in FIG. 7 , the magnet 32 of this embodiment is an eight-pole magnet with polar anisotropic orientation, in which north and south poles are alternately arranged in the circumferential direction. Note that in FIG. 7 , the direction of magnetic flux within some of the magnets 32 is schematically indicated by arrows W. Note that the magnets 32 may also be magnets with other orientations, such as a Halbach orientation. Furthermore, the magnet 32 of this embodiment is formed using a magnetic compound having a coercive force Hc of 400 kA/m or more and a residual magnetic flux density Br of _1.0 T or more. As an example, the magnet 32 of this embodiment is formed using a magnetic compound such as _NdFe11TiN , _Nd2Fe14B , _Sm2Fe17N3 , _{or FeNi} .

In the magnet 32 of this embodiment, the magnetic flux orientation within the magnet 32 is set so that when the magnetic flux density on the outer peripheral surface 32A, which is the radially outer surface, is measured along the circumferential direction, it reaches its peak value at the centers of the north and south poles. In addition, in the magnet 32 of this embodiment, the magnetic flux orientation within the magnet 32 is set so that when the magnetic flux density on the inner peripheral surface 32B, which is the radially inner surface, is measured along the circumferential direction, it reaches approximately zero at each position along the circumferential direction. This ensures that the ring gear 60 to which the magnet 32 is fixed does not become part of the magnetic circuit, which is a magnetic path. The outer peripheral surface 32A, one axial side surface, and the other axial side surfaces of the magnet 32 attached to the outer peripheral surface of the ring gear 60 are each covered by a magnet covering member 33.

As shown in FIG. 6, the reducer 14 includes a cylindrical ring gear 60 that constitutes part of the rotor 22. The reducer 14 also includes a first planetary gear 62, a first carrier 64, and a first sun gear 66, which are arranged on the other axial side of the ring gear 60. The reducer 14 also includes a second planetary gear 68, a second carrier 70, and a second sun gear 72, which are arranged on one axial side of the ring gear 60.

As shown in Figures 2, 3, and 6, the ring gear 60 is formed in a cylindrical shape using a metal material. In this embodiment, all components constituting the reducer 14 are made of metal. A plurality of first internal teeth 60A are formed circumferentially on the radially inner surface of the ring gear 60 on the other axial side. A plurality of second internal teeth 60B are formed circumferentially on the radially inner surface of the ring gear 60 on one axial side. In this embodiment, the inner diameter of the portion of the inner periphery of the ring gear 60 where the first internal teeth 60A are formed is larger than the inner diameter of the portion of the inner periphery where the second internal teeth 60B are formed. A reduced-diameter portion 60C protruding radially inward is formed at the boundary between the portion of the inner periphery of the ring gear 60 where the first internal teeth 60A are formed and the portion of the inner periphery of the ring gear 60 where the second internal teeth 60B are formed. Furthermore, three stepped portions with different heights in the radial direction are formed on the outer periphery of the ring gear 60. These three steps are referred to as the first step 60D, the second step 60E, and the third step 60F, in order from one axial side. In this embodiment, the outer diameter of the portion of the outer periphery of the ring gear 60 between the second step 60E and the first step 60D is larger than the outer diameter of the portion on one axial side of the first step 60D. Furthermore, the outer diameter of the portion of the outer periphery of the ring gear 60 between the third step 60F and the second step 60E is larger than the outer diameter of the portion between the second step 60E and the first step 60D. Furthermore, the outer diameter of the portion of the outer periphery of the ring gear 60 on the other axial side of the third step 60F is larger than the outer diameter of the portion between the third step 60F and the second step 60E. The second step 60E is formed at the same axial position as the reduced diameter portion 60C. The magnet 32 is fixed to the outer peripheral surface of the ring gear 60, with the inner peripheral end of the magnet 32 on the other axial side engaged with the second step portion 60E. The portion of the ring gear 60 on one axial side of the first step portion 60D, which is the end portion on one axial side, is supported by a first seal bearing 21 fixed to the motor cover 18. The seal bearing 21 is fixed by press fitting or the like to the inner peripheral portion of the portion of the ring gear 60 on the other axial side of the third step portion 60F, which is the end portion on the other axial side.

The first planetary gears 62 are arranged radially inward of the other axial side of the ring gear 60. In this embodiment, three first planetary gears 62 are arranged at equal intervals along the circumferential direction. Furthermore, the three first planetary gears 62 each mesh with the first internal teeth 60A of the ring gear 60.

The first carrier 64 includes a disk-shaped base plate 64A and three shaft portions 64B that protrude axially from the base plate 64A and are equally spaced circumferentially. The three shaft portions 64B rotatably support the three first planetary gears 62. The three first planetary gears 62 are positioned adjacent to the reduced-diameter portion 60C of the ring gear 60, thereby restricting the movement of the three first planetary gears 62 away from the shaft portions 64B. A circular opening 64C is formed at the axial center of the base plate 64A. A bearing 76 that supports the other axial end of the shaft member 74 (described later) is fixed to the inner periphery of this opening 64C by press-fitting or other means. In this embodiment, the base plate 64A is fixed to the bottom wall portion 16A of the motor case 16. Furthermore, the inner race of the seal bearing 21 is engaged with the outer periphery of the base plate portion 64A of the first carrier 64.

The first sun gear 66 is positioned radially inward of the three first planetary gears 62 and is in mesh with these three first planetary gears 62. This first sun gear 66 is fixed by press fitting or the like to a cylindrical shaft member 74 that is positioned coaxially with the output shaft 12. In addition, in this embodiment, the module and pitch circle diameter of the first sun gear 66 are set to be larger than the module and pitch circle diameter of the second sun gear 72, which will be described later.

The second planetary gears 68 are arranged radially inward of one axial side of the ring gear 60. In this embodiment, three second planetary gears 68 are arranged at equal intervals along the circumferential direction. Each of the three second planetary gears 68 meshes with the second internal teeth 60B of the ring gear 60. Furthermore, in this embodiment, the three second planetary gears 68 face each other in the axial direction via the aforementioned first planetary gear 62 and the reduced diameter portion 60C of the ring gear 60.

The second carrier 70 includes a disk-shaped base plate 70A and three shaft portions 70B that protrude from the base plate 70A toward the other axial direction and are equally spaced circumferentially. The three shaft portions 70B rotatably support three second planetary gears 68. The three second planetary gears 68 are positioned adjacent to the reduced-diameter portion 60C of the ring gear 60, restricting the movement of the three second planetary gears 68 toward the shaft portions 70B. A recess 70C, open toward the other axial direction, is formed at the axial center of the base plate 70A. A bearing 76, which supports one axial end of the aforementioned shaft member 74, is fixed to the inner periphery of this recess 70C by press-fitting or the like. The output shaft 12 protrudes toward one axial direction from the radial center of the base plate 70A. In other words, the second carrier 70 is integral with the output shaft 12.

The second sun gear 72 is positioned radially inward of the three second planetary gears 68 and is in mesh with these three second planetary gears 68. The second sun gear 72 is fixed to the shaft member 74 by press fitting or the like. As a result, the second sun gear 72, first sun gear 66, and shaft member 74 form a sun gear assembly 78, allowing the second sun gear 72 to rotate integrally with the first sun gear 66.

(Actions and Effects of the Present Embodiment)
Next, the operation and effects of this embodiment will be described.

In the geared motor 10 of this embodiment described above, the stator 20 generates a rotating magnetic field by switching the current flow to the coils 28 of each coil body 26 that make up the stator 20 using a control circuit (not shown). This causes the rotor 22 to rotate. In other words, the ring gear 60 rotates together with the magnet 32.

When the ring gear 60 rotates, the three first planetary gears 62 that mesh with the first internal teeth 60A of the ring gear 60 also rotate.

When the three first planetary gears 62 rotate, the first sun gear 66, which meshes with the three first planetary gears 62, rotates together with the second sun gear 72.

When the second sun gear 72 rotates, the three second planetary gears 68 that mesh with the second sun gear 72 also rotate. Here, the three second planetary gears 68 also mesh with the ring gear 60. Therefore, the three second planetary gears 68 revolve around the second sun gear 72 at a rotational speed corresponding to the rotational speed of the second sun gear 72 and the ring gear 60. As a result, the second carrier 70 that supports the three second planetary gears 68 rotates together with the output shaft 12 at a rotational speed corresponding to the revolution of the three second planetary gears 68.

In the geared motor 10 of this embodiment, the ring gear 60, which constitutes part of the reducer 14, also constitutes part of the rotor 22. In other words, the ring gear 60, which constitutes part of the reducer 14, serves as the rotor core on which the magnet 32 is supported. This reduces the number of parts stacked radially in the geared motor 10 compared to when the rotor core on which the magnet 32 is supported is provided as a separate component from the ring gear 60. This allows for a reduction in the radial size of the geared motor 10. Furthermore, in this embodiment, a teethless structure is used in which part of the stator core 24 is not disposed inside the coil 28, allowing for a reduction in the radial size of the stator 20. This allows for a reduction in the radial size of the geared motor 10.

In addition, in the geared motor 10 of this embodiment, the second carrier 70 is configured as an integral part of the output shaft 12. This reduces the number of parts that make up the geared motor 10 compared to a configuration in which the second carrier 70 and the output shaft 12 are separate.

In addition, in the geared motor 10 of this embodiment, the first sun gear 66 and the second sun gear 72 are fixed to the shaft member 74 by press-fitting or the like to form the sun gear assembly 78. This allows the sun gear assembly 78 to be handled as a single component during the assembly process of the geared motor 10, facilitating assembly of the geared motor 10. Furthermore, by setting the module and pitch diameter of the first sun gear 66 to be larger than the module and pitch diameter of the second sun gear 72, a one-way assembly procedure can be realized in which the sun gear assembly 78 is inserted into the inner periphery of the ring gear 60 from the other axial side. Depending on the reduction ratio required for the reducer 14, the module and pitch diameter of the second sun gear 72 may also be set to be larger than the module and pitch diameter of the first sun gear 66. In this case, a one-way assembly procedure can be achieved in which the sun gear assembly 78 is inserted into the inner periphery of the ring gear 60 from one axial side.

Furthermore, in the motor with reducer 10 of this embodiment, the space radially inside the ring gear 60 and the space radially outside the ring gear 60 are separated by a pair of sealed bearings 21. This prevents lubricants such as grease in the space radially inside the ring gear 60 and wear debris from the components that make up the reducer 14 from penetrating into the space radially outside the ring gear 60 in which the stator 20 and other components are located.

In addition, in the reducer-equipped motor 10 of this embodiment, the ring gear 60 to which the magnet 32 is fixed is configured not to be part of the magnetic circuit. This prevents wear debris from the components that make up the reducer 14 from accumulating on the inner surface of the ring gear 60.

In addition, in the reducer-equipped motor 10 of this embodiment, the magnet 32 is fixed to the outer peripheral surface of the ring gear 60 while being engaged with the second step portion 60E, and as a result, the magnet 32 and stator 20 are positioned radially opposite the second sun gear 72, second planetary gear 68, and second carrier 70. This ensures that there is sufficient space on the other axial side of the stator 20 for the bus bar 31 to be placed, and the bus bar 31 and stator 20 can be placed overlapping in the axial direction.

Furthermore, the reducer 14 of the reducer-equipped motor 10 of this embodiment is a so-called compound planetary gear mechanism made up of all gears, including the ring gear 60, first planetary gear 62, first carrier 64, first sun gear 66, second planetary gear 68, second carrier 70, and second sun gear 72. This makes it possible to increase the reduction ratio of the reducer 14. In particular, in this embodiment, the first carrier 64 is fixed to the motor case 16, making it possible to particularly increase the reduction ratio of the reducer 14. Note that, depending on the reduction ratio required of the reducer 14, the shaft member 74 of the sun gear assembly 78 may be fixed to the motor case 16, as in the reducer-equipped motor 80 of the second embodiment shown in FIG. 8. Note that components and parts of the reducer-equipped motor 80 of the second embodiment that correspond to those of the reducer-equipped motor 10 of the first embodiment are designated by the same reference numerals as those of the reducer-equipped motor 10 of the first embodiment.

In this embodiment, an example has been described in which the shaft member 74 of the sun gear assembly 78 is supported by a pair of bearings 76. However, as in the geared motor 82 of the third embodiment shown in FIG. 9, the shaft member 74 of the sun gear assembly 78 may be supported by a single bearing 76. By adopting this configuration, the number of bearings 76 used in the geared motor 82 can be reduced compared to the geared motor 10 of the first embodiment. In the geared motor 82 of the third embodiment, components and parts corresponding to those in the geared motor 10 of the first embodiment are designated by the same reference numerals as those corresponding to those in the geared motor 10 of the first embodiment.

In the above-described embodiments, the magnet 32 is attached to the ring gear 60, but the present invention is not limited to this. For example, the ring gear 60 may be configured to have multiple coils and commutators attached.

The above describes one embodiment of the present disclosure, but the present disclosure is not limited to the above and can, of course, be implemented in various other modifications without departing from the spirit of the present disclosure.

10: Geared motor, 12: Output shaft, 20: Stator, 21: Sealed bearing, 22: Rotor, 28: Coil, 31: Bus bar, 32: Magnet, 60: Ring gear, 60A: First internal gear, 60B: Second internal gear, 62: First planetary gear, 64: First carrier, 66: First sun gear, 68: Second planetary gear, 70: Second carrier, 72: Second sun gear, 74: Shaft member, 76: Bearing, 80: Geared motor, 82: Geared motor

Claims (9)

a rotor ( 22) having a ring gear (60) formed in an annular shape and having a plurality of first internal teeth (60A) and a plurality of second internal teeth (60B) formed on a radially inner surface thereof, and a magnet ( 32) fixed to a radially outer surface of the ring gear;
a stator (20) including a coil arranged opposite the magnet ;
a first planetary gear (62) disposed radially inside the rotor and meshing with the first internal teeth;
a first sun gear (66) disposed radially inside the first planetary gear and meshing with the first planetary gear;
a first carrier (64) disposed radially inside the rotor and supporting the first planetary gear;
a second planetary gear (68) disposed radially inside the rotor and on one axial side of the first planetary gear, and meshing with the second internal teeth;
a second sun gear (72) disposed radially inside the second planetary gear, engaged with the first sun gear in a state in which the second sun gear cannot rotate relative to the first sun gear, and meshing with the second planetary gear;
a second carrier (70) disposed radially inside the rotor, supporting the second planetary gear, and rotating as the second planetary gear revolves around the second sun gear;
an output shaft (12) that rotates by transmitting a rotational force of the second carrier;
Equipped with
The orientation of the magnetic flux within the magnet is set so that the magnetic flux density measured along the circumferential direction on the outer circumferential surface of the magnet reaches its peak value at the center of the N and S poles, and the density of the radially oriented magnetic flux on the inner circumferential surface of the magnet measured per unit area of the inner circumferential surface of the magnet is zero at each position in the circumferential direction,
A motor with a reducer (10, 80, 82) in which the ring gear is not part of a magnetic circuit, which is a magnetic path. A motor with a reducer as described in claim 1, wherein the module and pitch circle diameter of one of the first sun gear and the second sun gear are set to be larger than the module and pitch circle diameter of the other of the first sun gear and the second sun gear. A motor with a reducer as described in claim 1 or claim 2, wherein the space radially inside the ring gear and the space radially outside the ring gear are separated by a sealed bearing (21) that rotatably supports the ring gear. The magnet is fixed to a radially outer surface of the ring gear,
A motor with a reducer as described in any one of claims 1 to 3, wherein the coil and a bus bar (31) to which the terminal portion of the coil is connected are arranged in an axially overlapping state on the radial outside of the ring gear. A motor with a reducer according to any one of claims 1 to 4, in which rotation of the first carrier is restricted. The motor with a reducer described in any one of claims 1 to 4, wherein rotation of the first sun gear and the second sun gear is restricted. A motor with a reducer according to any one of claims 1 to 5, wherein the first sun gear and the second sun gear are rotatably supported by a single bearing (76) provided between the first sun gear and the second sun gear. A motor with a reducer according to any one of claims 1 to 7, wherein the first sun gear and the second sun gear are fixed to a single shaft member (74). A motor with a reducer according to any one of claims 1 to 8, wherein the output shaft and the second carrier are integrated.