CN114337090A

CN114337090A - Electric actuator

Info

Publication number: CN114337090A
Application number: CN202111129941.1A
Authority: CN
Inventors: 白井宽; 佐藤伦纪
Original assignee: Nidec Tosok Corp
Current assignee: Nidec Tosok Corp
Priority date: 2020-09-30
Filing date: 2021-09-26
Publication date: 2022-04-12
Also published as: JP2022056524A

Abstract

The present invention provides an electric actuator, comprising: a motor having a motor shaft rotatable about a motor axis; a transmission mechanism connected to one axial side of the motor shaft; and an output shaft extending in the axial direction of the motor shaft, the rotation of the motor shaft being transmitted to the output shaft via the transmission mechanism. The motor shaft is a hollow shaft. At least a portion of the output shaft is located inside the motor shaft. One of the motor shaft and the output shaft rotatably supports the other of the motor shaft and the output shaft.

Description

Electric actuator

Technical Field

The present invention relates to an electric actuator.

Background

An electric actuator including a motor shaft and an output shaft coupled by a transmission mechanism is known. For example, patent document 1 describes a rotary actuator applied as a power source of a shift-by-wire system for switching a shift of an automatic transmission of a vehicle.

Patent document 1: japanese patent laid-open publication No. 2016-109226

In the electric actuator as described above, one of the motor shaft and the output shaft may be inclined with respect to the other.

Disclosure of Invention

In view of the above circumstances, an object of the present invention is to provide an electric actuator having a structure capable of suppressing mutual inclination of a motor shaft and an output shaft.

One embodiment of the present invention is an electric actuator including: a motor having a motor shaft rotatable about a motor axis; a transmission mechanism coupled to one axial side of the motor shaft; and an output shaft extending in an axial direction of the motor shaft, the rotation of the motor shaft being transmitted to the output shaft via the transmission mechanism. The motor shaft is a hollow shaft. At least a portion of the output shaft is located inside the motor shaft. One of the motor shaft and the output shaft rotatably supports the other of the motor shaft and the output shaft.

According to one aspect of the present invention, in the electric actuator, the motor shaft and the output shaft can be suppressed from being inclined to each other.

Drawings

Fig. 1 is a sectional view showing an electric actuator according to the present embodiment.

Fig. 2 is a view showing the transmission mechanism of the present embodiment, and is a sectional view taken along line II-II in fig. 1.

Description of the reference symbols

10: a housing; 11: a housing main body; 12: a cover; 20: a motor; 21: a rotor; 21 a: a motor shaft; 21 b: a rotor body; 21 d: an eccentric shaft portion; 24: 1 st detected part; 30: a transfer mechanism; 31: an external gear; 31 b: a hole portion; 32: an internal gear; 41: an output shaft; 41 a: a connecting portion; 41 b: an extension portion; 42: an output flange portion; 43: a protrusion; 44: a mounting member; 45: the 2 nd detected part; 51: a 1 st bearing; 52: a 2 nd bearing; 53: the 3 rd bearing (bearing); 61. 62: a gasket; 81: 1 st rotation sensor; 82: a 2 nd rotation sensor; 100: an electric actuator; and (2) DS: a driven shaft; j1: a motor axis; j2: an eccentric axis.

Detailed Description

In each figure, the Z-axis direction is a vertical direction with a positive side (+ Z side) as an upper side and a negative side (-Z side) as a lower side. The axial direction of the motor axis J1 shown in the drawings is parallel to the Z-axis direction, i.e., the vertical direction. In the following description, a direction parallel to the axial direction of the motor axis J1 is simply referred to as an "axial direction". The radial direction about the motor axis J1 is simply referred to as the "radial direction", and the circumferential direction about the motor axis J1 is simply referred to as the "circumferential direction".

In the present embodiment, the lower side corresponds to the "one axial side", and the upper side corresponds to the "other axial side". The vertical direction, the upper side, and the lower side are only names for describing the relative positional relationship of the respective parts, and the actual arrangement relationship and the like may be an arrangement relationship other than the arrangement relationship and the like indicated by these names.

The electric actuator 100 of the present embodiment shown in fig. 1 is mounted on a vehicle. More specifically, electric actuator 100 is mounted on, for example, a drive-by-wire actuator device that is driven in accordance with a shift operation by a driver of a vehicle. As shown in fig. 1, the electric actuator 100 includes a housing 10, a motor 20, a transmission mechanism 30, an output portion 40, a 1 st bearing 51, a 2 nd bearing 52, a 3 rd bearing 53, washers 61 and 62, a bus bar unit 70, a substrate 80, a 1 st rotation sensor 81, a 2 nd rotation sensor 82, a 1 st detection target portion 24, a mounting member 44, a 2 nd detection target portion 45, and a partition member 90. The 1 st bearing 51, the 2 nd bearing 52, and the 3 rd bearing 53 are, for example, ball bearings.

The housing 10 houses therein various parts of the electric actuator 100 including the motor 20 and the transmission mechanism 30. The housing 10 has a housing main body 11, a cover 12, and an inner cover 13. The housing body 11 is open on the upper side. The housing body 11 is, for example, cylindrical with the motor axis J1 as the center. The housing body 11 has a 1 st housing portion 11a and a 2 nd housing portion 11 b.

The 1 st housing portion 11a is, for example, a lower portion of the housing main body 11. The 1 st housing portion 11a has a bottom portion 11c located on the lower side and a cylindrical portion 11d extending upward from the radially outer edge portion of the bottom portion 11 c. The bottom portion 11c has a hole portion 11e axially penetrating the bottom portion 11 c. The hole 11e is, for example, a circular hole centered on the motor axis J1. The upper portion of the hole 11e constitutes a 1 st bearing holding portion 11f, and the 1 st bearing holding portion 11f holds the 1 st bearing 51 therein. The 1 st bearing 51 is held by the housing main body 11 by being held inside the 1 st bearing holding portion 11 f. The outer ring of the 1 st bearing 51 is fitted to the inner circumferential surface of the 1 st bearing holding portion 11f, for example.

The 2 nd housing portion 11b is, for example, an upper portion of the case main body 11. The 2 nd housing part 11b is connected to the upper side of the 1 st housing part 11 a. The 2 nd accommodating portion 11b is in a cylindrical shape having an upper opening. The inner diameter of the 2 nd housing part 11b is larger than that of the 1 st housing part 11 a. The outer diameter of the 2 nd housing part 11b is larger than that of the 1 st housing part 11 a. The lower end of the 2 nd accommodating portion 11b is connected to, for example, the radially outer edge of the upper end of the cylindrical portion 11 d. A step having a step surface 11g facing upward is provided on the inner peripheral surface of the 2 nd accommodating portion 11 b. The step surface 11g is, for example, a surface perpendicular to the axial direction.

A substrate 80 is fixed to the step surface 11 g. The base plate 80 has a plate shape with its plate surface facing the axial direction and expands in the radial direction. The radially outer edge portion of the base plate 80 is fixed to the step surface 11g by, for example, screws. The substrate 80 is housed inside the 2 nd housing part 11 b. The substrate 80 is located above the rotor body 21b described later. The substrate 80 has a through hole 80a penetrating the substrate 80 in the axial direction. The through hole 80a is, for example, a circular hole centered on the motor axis J1. An upper portion of the output shaft 41 described later axially extends into the through hole 80 a. A printed wiring, not shown, is provided on the plate surface of the substrate 80. Although not shown, an inverter circuit for supplying electric power to the motor 20 is provided on the substrate 80.

A 1 st rotation sensor 81 and a 2 nd rotation sensor 82 are mounted on the substrate 80. The 1 st rotation sensor 81 is a sensor capable of detecting rotation of the motor shaft 21a described later. The 2 nd rotation sensor 82 is a sensor capable of detecting rotation of the output shaft 41 described later. In the present embodiment, the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 are magnetic sensors. The 1 st rotation sensor 81 and the 2 nd rotation sensor 82 are hall elements such as hall ICs, for example. For example, a plurality of the 1 st rotation sensors 81 and the 2 nd rotation sensors 82 may be provided in the circumferential direction.

In the present embodiment, the 1 st rotation sensor 81 is mounted on the lower surface of the substrate 80. The 1 st rotation sensor 81 is attached to, for example, the peripheral edge of the through hole 80a in the lower surface of the substrate 80. In the present embodiment, the 2 nd rotation sensor 82 is mounted on the upper surface of the substrate 80. The 2 nd rotation sensor 82 is located radially outward of the 1 st rotation sensor 81, for example. That is, in the present embodiment, the radial positions of the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 are different from each other.

The cover 12 is fixed to the housing main body 11. The radially outer edge portion of the cover 12 is fixed to the upper end portion of the 2 nd accommodating portion 11b by, for example, screws. The cover 12 closes an opening on the upper side of the housing main body 11. The cover 12 has: a cover main body 12a that covers an opening on the upper side of the housing main body 11; and a 2 nd bearing holding portion 12b projecting downward from the cover main body 12 a. The 2 nd bearing holding portion 12b is, for example, cylindrical and opens downward around the motor axis J1. The 2 nd bearing 52 is held in the 2 nd bearing holding portion 12 b. Thereby, the 2 nd bearing 52 is held by the cover 12. The outer ring of the 2 nd bearing 52 is fitted to the inner peripheral surface of the 2 nd bearing holding portion 12b, for example.

The inner cover 13 is located inside the housing body 11. The inner lid 13 is, for example, plate-shaped with its plate surface facing in the axial direction. The inner lid 13 is, for example, a circular plate shape centered on the motor axis J1. The inner lid 13 axially partitions the interior of the 1 st housing portion 11a and the interior of the 2 nd housing portion 11 b. The radially outer edge of the inner lid 13 is fixed to the upper end of the 1 st accommodation portion 11a by screws, for example. The inner lid 13 has

hole portions

13a and 13b that penetrate the inner lid 13 in the axial direction. The hole portion 13a is, for example, a circular hole centered on the motor axis J1. The hole 13b overlaps with a stator 22 described later when viewed in the axial direction.

A bus bar unit 70 is disposed on the upper surface of the inner lid 13. The bus bar unit 70 has a bus bar holder 71 and a bus bar 72. The bus bar holder 71 is a resin member that holds the bus bar 72. The bus bar 72 electrically connects a lead wire 22d drawn from a coil 22c of the stator 22 described later to the substrate 80. The bus bar 72 is provided in plurality, for example. The inverter circuit provided on the substrate 80 supplies electric power to the stator 22 via the bus bar 72.

The motor 20 has a rotor 21 and a stator 22. The rotor 21 has a motor shaft 21a and a rotor body 21 b. That is, the motor 20 has a motor shaft 21a and a rotor body 21 b. The motor shaft 21a can rotate about a motor axis J1. The motor shaft 21a is a hollow shaft. The motor shaft 21a is, for example, cylindrical and extends in the axial direction around a motor axis J1. The motor shaft 21a is open on both sides in the axial direction. The inner diameter of the motor shaft 21a is uniform over the entire axial range, for example. The motor shaft 21a extends upward from the inside of the 1 st housing portion 11a and protrudes into the 2 nd housing portion 11b through the hole portion 13 a. The motor shaft 21a includes a main body 21c, an eccentric shaft 21d, and a fixed portion 21 e.

The body portion 21c is a portion to which the rotor body 21b is fixed. The upper end of the body 21c is, for example, inserted into the hole 13a of the inner lid 13. The main body 21c is located inside the 1 st housing portion 11a except for the upper end.

The eccentric shaft portion 21d is connected to the lower side of the body portion 21 c. The eccentric shaft portion 21d is located inside the 1 st housing portion 11 a. The lower end of the eccentric shaft portion 21d is, for example, the lower end of the motor shaft 21 a. The eccentric shaft portion 21d is a portion centered on an eccentric axis J2 eccentric with respect to the motor axis J1. The eccentric axis J2 is parallel to the motor axis J1. The inner race of the 3 rd bearing 53 is fitted and fixed to the eccentric shaft portion 21 d. Thereby, the 3 rd bearing 53 is fixed to the motor shaft 21 a.

The fixed portion 21e is connected to the upper side of the main body portion 21 c. The fixed portion 21e is located inside the 2 nd housing portion 11b, for example. The fixed portion 21e is located above the rotor body 21 b. The upper end of the fixed portion 21e is, for example, the upper end of the motor shaft 21 a. The upper end of the fixed portion 21e is located in, for example, the through hole 80a of the substrate 80. The outer diameter of the fixed portion 21e is smaller than the outer diameter of the body portion 21 c. A step having a stepped surface 21f facing upward is provided between the outer peripheral surface of the fixed portion 21e and the outer peripheral surface of the main body portion 21c in the axial direction. The step surface 21f is perpendicular to the axial direction, for example. The step surface 21f is an upper end surface of the body portion 21 c. The stepped surface 21f is located, for example, above the upper surface of the inner lid 13.

The 1 st detection target portion 24 is fixed to the fixed portion 21 e. Thus, the 1 st detection target portion 24 is provided in a portion of the motor shaft 21a located above the rotor main body 21 b. The 1 st detected part 24 is a part in which the 1 st rotation sensor 81 detects rotation. In the present embodiment, the 1 st detection target portion 24 is a magnet. That is, in the present embodiment, the 1 st rotation sensor 81 detects the rotation of the 1 st detection target portion 24 by detecting the magnetic field of the 1 st detection target portion 24, and detects the rotation of the motor shaft 21a to which the 1 st detection target portion 24 is fixed. The 1 st detection target portion 24 has, for example, an annular shape centered on the motor axis J1. The inner peripheral surface of the 1 st detection target portion 24 is fixed to the outer peripheral surface of the fixed portion 21 e. The lower surface of the 1 st detection target portion 24 is in contact with the step surface 21 f.

The 1 st detection target portion 24 protrudes radially outward from the main body portion 21 c. The outer diameter of the 1 st detection target portion 24 is larger than the inner diameter of the hole portion 13a, for example. The radially outer edge of the 1 st detected portion 24 is located above the inner lid 13 and radially outward of the inner edge of the hole 13 a. The 1 st detected part 24 is located below the substrate 80. The radially outer edge of the 1 st detected part 24 is disposed to face the lower side of the 1 st rotation sensor 81. In the present embodiment, the 1 st rotation sensor 81 and the 1 st detection object 24 overlap each other when viewed in the axial direction.

The rotor body 21b is fixed to the outer peripheral surface of the motor shaft 21 a. The rotor body 21b is fixed to, for example, an axial center portion of the outer peripheral surface of the body 21 c. The rotor body 21b is housed inside the 1 st housing portion 11 a. Although not shown, the rotor body 21b includes a cylindrical rotor core fixed to the outer peripheral surface of the motor shaft 21a, and a rotor magnet fixed to the rotor core.

The stator 22 and the rotor 21 are radially opposed to each other with a gap therebetween. The stator 22 is located radially outside the rotor 21. The stator 22 is housed inside the 1 st housing portion 11 a. The stator 22 has: an annular stator core 22a surrounding the radially outer side of the rotor body 21 b; an insulator 22b mounted on the stator core 22 a; and a plurality of coils 22c, and the plurality of coils 22c are attached to the stator core 22a via an insulator 22 b. The outer peripheral surface of the stator core 22a is fixed to the inner peripheral surface of the cylindrical portion 11d, for example. The lead wire 22d is led out upward from the coil 22 c. The lead wire 22d penetrates the hole 13b in the axial direction and is connected to the bus bar 72.

The transmission mechanism 30 is located below the rotor body 21b and the stator 22 in the 1 st housing portion 11 a. In the present embodiment, the transmission mechanism 30 is a speed reduction mechanism that reduces the speed of rotation of the motor shaft 21a and transmits the rotation to the output shaft 41. The transmission mechanism 30 includes an external gear 31, an internal gear 32, an output flange 42, and a plurality of protrusions 43.

The external gear 31 has a substantially annular plate shape extending along a plane perpendicular to the axial direction with the eccentric axis J2 of the eccentric shaft portion 21d as the center. As shown in fig. 2, a gear portion including a plurality of tooth portions 31a is provided on an outer surface of the external gear 31 in the radial direction. The external gear 31 is coupled to the eccentric shaft portion 21d via a 3 rd bearing 53. Thereby, the transmission mechanism 30 is coupled to the lower side of the motor shaft 21 a. In the present embodiment, the transmission mechanism 30 is coupled to the lower end of the motor shaft 21 a. The external gear 31 is fitted to the outer ring of the 3 rd bearing 53 from the radially outer side. Thus, the 3 rd bearing 53 connects the motor shaft 21a and the externally toothed gear 31 to be relatively rotatable about the eccentric axis J2.

The external gear 31 has a plurality of holes 31b recessed from the lower surface of the external gear 31 toward the upper surface. In the present embodiment, the hole 31b penetrates the external gear 31 in the axial direction. The plurality of holes 31b are disposed so as to surround the motor axis J1. More specifically, the plurality of hole portions 31b are arranged at equal intervals in a circumferential direction around the eccentric axis J2. For example, 8 holes 31b are provided. The hole 31b has a circular shape, for example, when viewed in the axial direction. The inner diameter of the hole 31b is larger than the outer diameter of a portion of the protrusion 43 to be described later, which is inserted into the hole 31 b.

The internal gear 32 surrounds the radially outer side of the external gear 31 and meshes with the external gear 31. The internal gear 32 has an annular shape centered on the motor axis J1. As shown in fig. 1, in the present embodiment, the internal gear 32 is fixed to the housing 10. The outer peripheral surface of the internal gear 32 is fitted and fixed to the inner peripheral surface of the 1 st housing portion 11 a. As shown in fig. 2, a gear portion having a plurality of tooth portions 32a is provided on an inner peripheral surface of the internal gear 32. The gear portion of the internal gear 32 meshes with the gear portion of the external gear 31. More specifically, the gear portion of the internal gear 32 meshes with the gear portion of the external gear 31 in a part of the circumferential direction.

The output flange portion 42 is a part of the output portion 40. As shown in fig. 1, the output flange portion 42 is disposed to face the lower side of the external gear 31. A gap is provided between the output flange portion 42 and the external gear 31 in the axial direction. The output flange portion 42 is, for example, in the form of an annular plate extending radially about the motor axis J1. The output flange 42 extends radially outward from a portion of the output shaft 41, which will be described later, located below the motor shaft 21 a. The output flange 42 extends radially outward from an upper end of the coupling portion 41a, which will be described later.

The output flange portion 42 has a plurality of fixing holes 42a that penetrate the output flange portion 42 in the axial direction. As shown in fig. 2, the plurality of fixing holes 42a are disposed so as to surround the motor axis J1. More specifically, the plurality of fixing holes 42a are arranged at equal intervals in a circumferential direction around the motor axis J1. The number of the fixing holes 42a is 8, for example. The fixing hole 42a has a circular shape as viewed in the axial direction.

As shown in fig. 1, in the present embodiment, the protruding portion 43 is a columnar member extending in the axial direction. The lower portion of each projection 43 is fixed in each fixing hole 42a, for example. The upper portion of each projection 43 is located above the fixing hole 42 a. Thereby, the plurality of projecting portions 43 project from the output flange portion 42 in the axial direction toward the external gear 31. As shown in fig. 2, the plurality of projections 43 are disposed so as to surround the motor axis J1. The plurality of projections 43 are arranged at equal intervals in a circumferential range, for example, along the circumferential direction. The number of the projections 43 is 8, for example.

As shown in fig. 1, the plurality of projections 43 are inserted into the plurality of holes 31b from below, respectively. The outer diameter of the portion of the protruding portion 43 inserted into the hole portion 31b is smaller than the inner diameter of the hole portion 31 b. The outer peripheral surface of the protruding portion 43 is inscribed in the inner surface of the hole portion 31 b. The plurality of projecting portions 43 support the external gear 31 via the inner surface of the hole portion 31b so as to be swingable about the motor axis J1.

The output portion 40 is a portion that outputs the driving force of the electric actuator 100. The rotation of the motor shaft 21a is transmitted to the output unit 40 via the transmission mechanism 30. The output portion 40 has an output shaft 41 and an output flange portion 42. That is, the electric actuator 100 has an output shaft 41 and an output flange portion 42. The output unit 40 is, for example, a single member.

The output shaft 41 extends in the axial direction of the motor shaft 21 a. The output shaft 41 is disposed coaxially with the motor shaft 21 a. That is, the output shaft 41 can rotate about the motor axis J1. The output shaft 41 is rotatably supported by the 1 st bearing 51 and the 2 nd bearing 52. The output shaft 41 has a coupling portion 41a and an extending portion 41 b.

The coupling portion 41a is located below the motor shaft 21 a. The coupling portion 41a has an outer diameter larger than that of the extension portion 41 b. The coupling portion 41a is inserted into the hole 11e, for example. The lower end of the coupling portion 41a is, for example, the lower end of the output shaft 41. The lower end of the coupling portion 41a is located at the same axial position as the lower end of the hole 11e, for example. The coupling portion 41a is supported by the 1 st bearing 51 to be rotatable about the motor axis J1. Thus, the 1 st bearing 51 rotatably supports a portion of the output shaft 41 located below the motor shaft 21 a.

The coupling portion 41a has a coupling recess 41c recessed upward from the lower end surface of the coupling portion 41 a. The coupling recess 41c is open on the lower side and exposed to the outside of the housing 10. For example, the coupling recess 41c has a circular shape centered on the motor axis J1 when viewed from the lower side. Spline grooves are provided on the inner peripheral surface of the coupling recess 41 c. The driven shaft DS is inserted from below into the coupling recess 41c and coupled thereto. Thereby, the driven shaft DS is coupled to the coupling portion 41 a. More specifically, the output shaft 41 is coupled to the driven shaft DS by spline sections provided on the outer peripheral surface of the driven shaft DS being fitted into spline grooves provided on the inner peripheral surface of the coupling recess 41 c. The driving force of the electric actuator 100 is transmitted to the driven shaft DS via the output shaft 41. Thereby, the electric actuator 100 rotates the driven shaft DS about the motor axis J1.

The extending portion 41b extends upward from the coupling portion 41 a. More specifically, the extending portion 41b extends upward from a radially central portion of an upper end of the coupling portion 41 a. The extension 41b has, for example, a cylindrical shape extending in the axial direction around the motor axis J1. The dimension in the axial direction of the extending portion 41b is larger than the dimension in the axial direction of the coupling portion 41a, for example. The extension 41b opens into the inside of the motor shaft 21a as a hollow shaft. Thereby, at least a part of the output shaft 41 is positioned inside the motor shaft 21 a. In the present embodiment, a part of the extension 41b of the output shaft 41 is located inside the motor shaft 21 a.

The extension 41b is inserted into the motor shaft 21a from the lower side of the motor shaft 21a and protrudes upward from the motor shaft 21 a. Thus, the output shaft 41 extends from a position lower than the motor shaft 21a to a position upper than the motor shaft 21a through the inside of the motor shaft 21 a. The extending portion 41b axially extends into the hole portion 13a of the inner lid 13 and the through hole 80a of the base plate 80. The portion of the output shaft 41 located above the motor shaft 21a is located, for example, inside the 2 nd housing portion 11 b. The upper end of the extension 41b is supported by the 2 nd bearing 52 to be rotatable about the motor axis J1. Thus, the 2 nd bearing 52 rotatably supports a portion of the output shaft 41 located above the motor shaft 21 a.

The outer diameter of the extension 41b is slightly smaller than the inner diameter of the motor shaft 21a, for example. In the present embodiment, the extension 41b is fitted to the inside of the motor shaft 21a with a gap therebetween. The radial clearance between the extension 41b and the motor shaft 21a is small enough to support the motor shaft 21a rotatably about the motor axis J1 by the extension 41 b. In this way, in the present embodiment, the output shaft 41 rotatably supports the motor shaft 21a via the extension portion 41 b. The outer peripheral surface of a portion of the output shaft 41 located inside the motor shaft 21a, that is, a portion of the extension 41b, is radially opposed to the inner peripheral surface of the motor shaft 21a and is capable of contacting each other. The motor shaft 21a is radially supported by a portion of the inner peripheral surface of the motor shaft 21a contacting the outer peripheral surface of the output shaft 41. For example, a lubricating oil may be provided in a radial gap between the output shaft 41 and the motor shaft 21 a.

A 2 nd detection target portion 45 is fixed to a portion of the extension portion 41b located above the motor shaft 21 a. That is, in the present embodiment, the 2 nd detection target portion 45 is provided in a portion of the output shaft 41 located above the motor shaft 21 a. The 2 nd detected part 45 is a part in which the 2 nd rotation sensor 82 detects rotation. In the present embodiment, the 2 nd detection target portion 45 is a magnet. In the present embodiment, the 2 nd rotation sensor 82 detects the rotation of the 2 nd detection object part 45 by detecting the magnetic field of the 2 nd detection object part 45, thereby detecting the rotation of the output shaft 41.

In the present embodiment, the 2 nd detection target portion 45 is attached to the output shaft 41 via the attachment member 44. The mounting member 44 has a fixed cylinder portion 44a and a flange portion 44 b. The fixed cylinder portion 44a is, for example, cylindrical with the motor axis J1 as the center and is open on both sides in the axial direction. The fixed cylinder portion 44a is fitted and fixed to the outer peripheral surface of a portion of the extension portion 41b that is above the motor shaft 21a and below the 2 nd bearing 52. Thereby, the mounting member 44 is fixed to the outer peripheral surface of the portion of the output shaft 41 located above the motor shaft 21 a. The fixed cylinder portion 44a is located between the motor shaft 21a and the 2 nd bearing 52 in the axial direction. The flange portion 44b extends radially outward from an upper end of the fixed cylinder portion 44 a. The flange portion 44b is, for example, annular and centered on the motor axis J1. The radially outer edge portion of the lower surface of the flange portion 44b is recessed, for example, upward.

The 2 nd detection target portion 45 has, for example, an annular shape centered on the motor axis J1. The 2 nd detection target portion 45 is fixed to the radially outer edge portion of the lower surface of the flange portion 44 b. The 2 nd detection target portion 45 is located above the substrate 80. The inner diameter and the outer diameter of the 2 nd detection target portion 45 are larger than the outer diameter of the 1 st detection target portion 24. The 2 nd detection target portion 45 is located radially outward of the 1 st detection target portion 24. That is, in the present embodiment, the radial positions of the 1 st detection target portion 24 and the 2 nd detection target portion 45 are different from each other. The radially outer edge of the 2 nd detected part 45 is disposed to face the upper side of the 2 nd rotation sensor 82. In the present embodiment, the 2 nd rotation sensor 82 and the 2 nd detection object 45 overlap each other when viewed in the axial direction. The 2 nd rotation sensor 82 and the 2 nd detected part 45 do not overlap the 1 st rotation sensor 81 and the 1 st detected part 24 as viewed in the axial direction. For example, the 2 nd detection target portion 45 overlaps the rotor main body 21b when viewed in the axial direction.

A washer 61 is provided between the lower end of the motor shaft 21a and the upper end of the coupling portion 41 a. A washer 62 is provided between an upper end of the motor shaft 21a and a lower end of the mounting member 44. In the present embodiment, the lower end of the mounting member 44 is the lower end of the fixed cylinder 44 a. The washers 61 and 62 are annular rings centered on the motor axis J1, for example. The washers 61 and 62 are, for example, plate-shaped with the plate surfaces facing in the axial direction. The washers 61 and 62 are, for example, sliding washers.

The washers 61 and 62 surround the extension 41 b. The lower surface of the washer 61 contacts the peripheral edge of the extending portion 41b on the upper surface of the coupling portion 41 a. The upper surface of the washer 61 contacts the lower end surface of the motor shaft 21 a. The lower surface of the washer 62 contacts the upper end surface of the motor shaft 21 a. The upper surface of the washer 62 contacts the lower end surface of the mounting member 44.

The partition member 90 is located between the stator 22 and the transmission mechanism 30 in the axial direction. The partition member 90 surrounds the motor axis J1. The partition member 90 has a partition member main body 91 and a peripheral wall portion 92. The partition member main body 91 is, for example, annular and centered on the motor axis J1. The partition member main body 91 has a plate shape with a plate surface facing in the axial direction. The radially inner edge of the partition member main body 91 is located radially outward of the radially inner edge of the insulator 22 b. The peripheral wall 92 protrudes upward from the radially outer edge of the partition member main body 91. The peripheral wall portion 92 is, for example, cylindrical with the motor axis J1 as the center. The peripheral wall 92 is fitted and fixed to the inner peripheral surface of the 1 st housing portion 11 a. The upper end of the peripheral wall 92 contacts the radially outer edge of the lower end surface of the stator core 22 a.

When the motor 20 is supplied with electric power to rotate the motor shaft 21a about the motor axis J1, the eccentric shaft portion 21d revolves in the circumferential direction about the motor axis J1. The revolution of the eccentric shaft portion 21d is transmitted to the external gear 31 via the 3 rd bearing 53, and the external gear 31 oscillates while changing the position at which the inner circumferential surface of the hole 31b contacts the outer circumferential surface of the protruding portion 43. Thereby, the position at which the gear portion of the external gear 31 meshes with the gear portion of the internal gear 32 changes in the circumferential direction. Therefore, the rotational force of the motor shaft 21a is transmitted to the internal gear 32 via the external gear 31.

Here, in the present embodiment, the internal gear 32 is fixed to the housing 10 and therefore does not rotate. Therefore, the external gear 31 is rotated about the eccentric axis J2 by the reaction force of the rotational force transmitted to the internal gear 32. At this time, the external gear 31 rotates in a direction opposite to the direction in which the motor shaft 21a rotates. The rotation of the external gear 31 about the eccentric axis J2 is transmitted to the output flange portion 42 via the hole portion 31b and the protruding portion 43. Thereby, the output shaft 41 rotates about the motor axis J1. In this way, the rotation of the motor shaft 21a is transmitted to the output shaft 41 via the transmission mechanism 30. The structure of the transmission mechanism 30 as the speed reduction mechanism is a structure in which rotation is transmitted via the plurality of protrusions 43 as described above, and thus the speed reduction ratio of the rotation of the output shaft 41 with respect to the rotation of the motor shaft 21a can be made relatively large. Therefore, the rotational torque of the output shaft 41 can be made large.

According to the present embodiment, the motor shaft 21a is a hollow shaft, and at least a part of the output shaft 41 is located inside the motor shaft 21 a. The output shaft 41 rotatably supports the motor shaft 21 a. Therefore, even if the motor shaft 21a tries to tilt in the radial direction with respect to the output shaft 41, the motor shaft 21a is supported by the output shaft 41. This suppresses the inclination of the motor shaft 21a with respect to the output shaft 41. Therefore, the motor shaft 21a and the output shaft 41 can be suppressed from being inclined to each other. Further, since the motor shaft 21a can be supported by the output shaft 41, it is not necessary to provide a separate bearing for rotatably supporting the motor shaft 21 a. Therefore, the number of components of the electric actuator 100 can be reduced.

In addition, according to the present embodiment, the outer peripheral surface of the portion of the output shaft 41 located inside the motor shaft 21a and the inner peripheral surface of the motor shaft 21a are radially opposed to each other and can be in contact with each other. Therefore, even if the motor shaft 21a tries to tilt in the radial direction with respect to the output shaft 41, the inner peripheral surface of the motor shaft 21a can be directly supported by the outer peripheral surface of the output shaft 41. This makes it easy to increase the area for supporting the motor shaft 21a, and the motor shaft 21a can be supported more stably by the output shaft 41. Therefore, the motor shaft 21a and the output shaft 41 can be further suppressed from being inclined to each other. In addition, the number of components of the electric actuator 100 can be reduced as compared with a case where another component is provided between the motor shaft 21a and the output shaft 41 in the radial direction.

In addition, according to the present embodiment, the output shaft 41 extends from a position lower than the motor shaft 21a to a position upper than the motor shaft 21a through the inside of the motor shaft 21 a. Therefore, the output shaft 41 can be disposed over the entire axial range inside the motor shaft 21 a. Thereby, the motor shaft 21a can be more appropriately supported by the output shaft 41. Therefore, the motor shaft 21a and the output shaft 41 can be further suppressed from being inclined to each other.

Further, according to the present embodiment, the 1 st bearing 51 for rotatably supporting the portion of the output shaft 41 located below the motor shaft 21a and the 2 nd bearing 52 for rotatably supporting the portion of the output shaft 41 located above the motor shaft 21a are provided. Therefore, the output shaft 41 can be supported with a double arm stably. Since the output shaft 41 is thus stably supported, the motor shaft 21a can be more appropriately supported by the output shaft 41. Therefore, the motor shaft 21a and the output shaft 41 can be further suppressed from being inclined to each other.

Further, since the output shaft 41 protrudes to both axial sides with respect to the motor shaft 21a, the 1 st bearing 51 and the 2 nd bearing 52 that support both axial sides of the output shaft 41 are easily held by the housing 10. Therefore, the 1 st bearing 51 and the 2 nd bearing 52 can be easily assembled while suppressing complication of the configuration of the housing 10. In this way, by adopting the structure in which the output shaft 41 is supported by the 1 st bearing 51 and the 2 nd bearing 52 and the motor shaft 21a is supported by the output shaft 41, it is possible to suppress the structure of the electric actuator 100 from being complicated and to easily assemble the electric actuator 100, compared to, for example, the structure in which the output shaft 41 is supported by the motor shaft 21a supported by bearings.

In addition, according to the present embodiment, the housing 10 has a housing main body 11 that is open on the upper side, and a cover 12 that is fixed to the housing main body 11 and closes the opening on the upper side of the housing main body 11. The 1 st bearing 51 is held by the housing main body 11, and the 2 nd bearing 52 is held by the cover 12. That is, the 2 nd bearing 52 can be held by the cover 12 that closes the opening on the upper side of the housing main body 11. Therefore, the number of components of the electric actuator 100 can be reduced as compared with a case where a component holding the 2 nd bearing 52 is separately provided.

In addition, according to the present embodiment, the substrate 80 has a through hole 80a through which an upper portion of the output shaft 41 passes in the axial direction. Therefore, the substrate 80 can be disposed between the cover 12 and the motor 20 in the axial direction, and the upper end of the output shaft 41 can be held by the 2 nd bearing 52 held by the cover 12. In addition, the substrate 80 can be enlarged in the radial direction. Therefore, it is easy to secure a region where the inverter circuit, the 1 st rotation sensor 81, the 2 nd rotation sensor 82, and other electronic components not shown are disposed on the substrate 80.

Further, according to the present embodiment, the 1 st detection target portion 24 for detecting rotation by the 1 st rotation sensor 81 is provided in a portion of the motor shaft 21a located above the rotor main body 21 b. A 2 nd detection target portion 45 whose rotation is detected by the 2 nd rotation sensor 82 is provided in a portion of the output shaft 41 located above the motor shaft 21 a. Therefore, both the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 can be disposed in the upper portion of the inside of the casing 10. Thus, for example, as compared with the case where the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 are disposed on different sides in the axial direction in the housing 10, the work of assembling the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 can be easily performed. Specifically, in the present embodiment, since both the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 can be disposed in the 2 nd housing part 11b, it is not necessary to pass the wiring of the 2 nd rotation sensor 82 from the 1 st housing part 11a to the substrate 80 in the 2 nd housing part 11b, as compared with a case where the 2 nd rotation sensor 82 is disposed in the 1 st housing part 11a, for example. Therefore, the man-hours and time required for the work of assembling the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 can be reduced. Further, for example, as compared with a case where the housing 10 is provided with a structure for passing the wiring from the inside of the 1 st housing part 11a to the inside of the 2 nd housing part 11b, the structure of the housing 10 can be suppressed from being complicated.

As described above, in the configuration in which the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 can be collectively arranged on the same side in the axial direction, the motor shaft 21a can be made a hollow shaft, and the output shaft 41 can be made to penetrate through the inside of the motor shaft 21a and protrude to the upper side of the motor shaft 21 a. That is, by extending a part of the output shaft 41 connected to the transmission mechanism 30 coupled to the lower side of the motor shaft 21a to a position above the motor shaft 21a through the inside of the motor shaft 21a, the 2 nd detection object 45 can be provided above the motor shaft 21a, and the 2 nd rotation sensor 82 for detecting the 2 nd detection object 45 can be disposed at an upper portion in the housing 10.

In addition, according to the present embodiment, the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 are mounted on the substrate 80. Therefore, by disposing the substrate 80 on which the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 are mounted in the housing 10, the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 can be disposed in the housing 10 together. This can further reduce the number of steps and time required for the assembly operation of the 1 st rotation sensor 81 and the 2 nd rotation sensor 82.

In addition, according to the present embodiment, the 1 st rotation sensor 81 is mounted on the lower surface of the substrate 80, and the 2 nd rotation sensor 82 is mounted on the upper surface of the substrate 80. That is, the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 are respectively attached to surfaces on opposite sides of each other among surfaces on both sides in the axial direction of the substrate 80. Therefore, it is easier to secure a region for mounting each rotation sensor on the substrate 80, compared to a case where the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 are mounted on the same surface of the substrate 80.

Further, since the 2 nd detection target portion 45 is provided in the output shaft 41 at a position above the motor shaft 21a, the 1 st detection target portion 24 provided in the motor shaft 21a is easily disposed below the 2 nd detection target portion 45. Therefore, by mounting the 1 st rotation sensor 81 on the lower surface of the substrate 80 and mounting the 2 nd rotation sensor 82 on the upper surface of the substrate 80, it is easy to dispose each rotation sensor close to each detected portion. Thus, the rotation of each detection target portion can be detected more appropriately by each rotation sensor. Therefore, the accuracy of detecting the rotation of each shaft by each rotation sensor can be improved.

Further, according to the present embodiment, the 1 st rotation sensor 81 and the 1 st detection object 24 overlap each other when viewed in the axial direction, and the 2 nd rotation sensor 82 and the 2 nd detection object 45 overlap each other when viewed in the axial direction. Therefore, the 1 st rotation sensor 81 and the 1 st detection target portion 24 can be made to face each other in the axial direction, and the 1 st rotation sensor 81 can more easily detect the rotation of the 1 st detection target portion 24. Further, the 2 nd rotation sensor 82 and the 2 nd detection target portion 45 are opposed to each other in the axial direction, and the 2 nd rotation sensor 82 can more easily detect the rotation of the 2 nd detection target portion 45. Therefore, the accuracy of detecting the rotation of each shaft by each rotation sensor can be further improved.

The radial positions of the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 are different from each other, and the radial positions of the 1 st detected portion 24 and the 2 nd detected portion 45 are different from each other. Therefore, for example, when the 1 st detected part 24 and the 2 nd detected part 45 are magnets and the 1 st rotation sensor 81 and the 2 nd rotation sensor 82 are magnetic sensors as in the present embodiment, it is possible to suppress the magnetic field of the other detected part from interfering with the other sensor. Thus, the rotation of each detection target portion can be detected more appropriately by each rotation sensor. Therefore, the accuracy of detecting the rotation of each shaft by each rotation sensor can be further improved.

Further, according to the present embodiment, washers 61 and 62 are provided between the lower end of the motor shaft 21a and the upper end of the coupling portion 41a, and between the upper end of the motor shaft 21a and the lower end of the mounting member 44. Therefore, the motor shaft 21a can be pressed from both axial sides by the washers 61 and 62. This can suppress the axial displacement of the motor shaft 21a relative to the output shaft 41. Further, as compared with the case where both axial end portions of the motor shaft 21a are in direct contact with the output shaft 41 or the mounting member 44, friction between the motor shaft 21a and the output shaft 41 and between the motor shaft 21a and the mounting member 44 can be reduced, and smooth relative rotation between the motor shaft 21a and the output shaft 41 can be facilitated. In particular, the washers 61 and 62 are sliding washers, so that the motor shaft 21a and the output shaft 41 can be rotated relative to each other more smoothly.

In addition, according to the present embodiment, the 1 st detection target portion 24 and the 2 nd detection target portion 45 are magnets. The 1 st rotation sensor 81 and the 2 nd rotation sensor 82 are magnetic sensors. Therefore, the rotation of the motor shaft 21a and the rotation of the output shaft 41 can be appropriately detected by the magnetic field generated from the 1 st detection object 24 and the 2 nd detection object 45. Further, as described above, the effect of improving the rotation detection accuracy by disposing the 1 st rotation sensor 81 and the 1 st detection target portion 24 and the 2 nd rotation sensor 82 and the 2 nd detection target portion 45 in a radially displaced manner can be effectively obtained.

The present invention is not limited to the above-described embodiments, and other configurations and methods can be adopted within the scope of the technical idea of the present invention. The motor shaft may rotatably support the output shaft. Even in this case, the motor shaft and the output shaft can be suppressed from being inclined to each other. In this case, the motor shaft may be supported by a bearing, and the output shaft may not be supported by the bearing. The output shaft may not extend to the other side (upper side) in the axial direction than the motor shaft. The output shaft may be entirely located inside the motor shaft. Another member may be provided between the inner peripheral surface of the motor shaft and the outer peripheral surface of the output shaft. In this case, one of the motor shaft and the output shaft may rotatably support the other of the motor shaft and the output shaft via the other member. In this case, the other member may be a bearing such as a ball bearing, a needle bearing, or a slide bearing. The type of the 1 st bearing, the type of the 2 nd bearing, and the type of the 3 rd bearing are not particularly limited. The 2 nd bearing may not be held by the cover.

The 1 st detected part may be any part as long as the 1 st rotation sensor detects rotation. The 1 st rotation sensor may be any sensor as long as it can detect the rotation of the motor shaft by detecting the rotation of the 1 st detected member. The 2 nd detected part may be any part as long as the rotation is detected by the 2 nd rotation sensor. The 2 nd rotation sensor may be any sensor as long as it can detect the rotation of the output shaft by detecting the rotation of the 2 nd detected part. The 1 st detected part may be a part of the motor shaft. The 2 nd detection target portion may be a part of the output shaft. The 1 st rotation sensor and the 2 nd rotation sensor may be optical sensors. The 1 st rotation sensor may be a resolver stator and the 1 st detection target portion may be a resolver rotor. The 2 nd rotation sensor may be a resolver stator and the 2 nd detected object may be a resolver rotor. The 1 st rotation sensor and the 2 nd rotation sensor may be magnetic sensors other than hall elements. The 1 st rotation sensor and the 2 nd rotation sensor may also be magnetoresistance effect elements.

The 1 st rotation sensor may be mounted on the other side (upper side) in the axial direction of the substrate, and the 2 nd rotation sensor may be mounted on the one side (lower side) in the axial direction of the substrate. The 1 st rotation sensor and the 2 nd rotation sensor may also be mounted on different components. The 1 st rotation sensor and the 2 nd rotation sensor may be disposed on different sides in the axial direction in the housing. The 1 st rotation sensor and the 2 nd rotation sensor may not be provided. No washer may be provided between the motor shaft and the coupling portion and between the motor shaft and the mounting member.

The transmission mechanism is not particularly limited as long as it can transmit the rotation of the motor shaft to the output shaft. The transmission mechanism may be a speed increasing mechanism or a mechanism that does not change the speed of rotation of the motor shaft. When the transmission mechanism is a speed reduction mechanism, the structure of the speed reduction mechanism is not particularly limited. The plurality of protruding portions may be provided on the external gear, and the plurality of holes may be provided on the output flange portion. In this case, the protruding portion protrudes from the external gear toward the output flange portion and is inserted into the hole portion.

The use of the electric actuator to which the present invention is applied is not particularly limited. The electric actuator may be mounted on an actuator device of a shift-by-wire system that is driven in accordance with a shift operation by a driver. The electric actuator may be mounted on a device other than the vehicle. Further, the respective structures described above in the present specification may be appropriately combined within a range not inconsistent with each other.

Claims

1. An electric actuator having:

a motor having a motor shaft rotatable about a motor axis;

a transmission mechanism coupled to one axial side of the motor shaft; and

an output shaft extending in an axial direction of the motor shaft, the rotation of the motor shaft being transmitted to the output shaft via the transmission mechanism,

the motor shaft is a hollow shaft and,

at least a portion of the output shaft is located inside the motor shaft,

one of the motor shaft and the output shaft rotatably supports the other of the motor shaft and the output shaft.

2. The electric actuator according to claim 1,

an outer peripheral surface of a portion of the output shaft located inside the motor shaft and an inner peripheral surface of the motor shaft are radially opposed to each other and are capable of contacting each other.

3. The electric actuator according to claim 1 or 2,

the output shaft extends from a position on one side in the axial direction of the motor shaft to a position on the other side in the axial direction of the motor shaft through the inside of the motor shaft.

4. The electric actuator according to claim 3,

the electric actuator further has:

a 1 st bearing that rotatably supports a portion of the output shaft that is located on one axial side of the motor shaft; and

a 2 nd bearing rotatably supporting a portion of the output shaft located on the other axial side than the motor shaft,

the output shaft rotatably supports the motor shaft.

5. The electric actuator according to claim 4,

the electric actuator further has a housing that houses the motor and the transmission mechanism inside,

the housing has:

a housing main body that is open on the other axial side; and

a cover fixed to the housing main body to close an opening on the other axial side of the housing main body,

the 1 st bearing is held by the housing main body,

the 2 nd bearing is held by the cage.

6. The electric actuator according to claim 3,

the electric actuator further has:

a 1 st rotation sensor capable of detecting rotation of the motor shaft; and

a 2 nd rotation sensor capable of detecting rotation of the output shaft,

the motor has a rotor body fixed to an outer peripheral surface of the motor shaft,

a 1 st detection target portion for detecting rotation by the 1 st rotation sensor is provided in a portion of the motor shaft located on the other axial side of the rotor body,

a 2 nd detection target portion for detecting rotation by the 2 nd rotation sensor is provided in a portion of the output shaft located on the other side in the axial direction than the motor shaft.

7. The electric actuator according to claim 6,

the 1 st detected part and the 2 nd detected part are magnets,

the 1 st rotation sensor and the 2 nd rotation sensor are magnetic sensors.

8. The electric actuator according to claim 6 or 7,

the electric actuator further includes a mounting member fixed to an outer peripheral surface of a portion of the output shaft located on the other side in the axial direction than the motor shaft,

the 2 nd detected part is attached to the output shaft via the attachment member,

the output shaft has:

a coupling portion to which a driven shaft is coupled; and

an extension portion extending from the connection portion to the other axial side and extending into the motor shaft,

the coupling portion has an outer diameter larger than an outer diameter of the extension portion,

a washer is provided between an end of the motor shaft on one axial side and an end of the coupling portion on the other axial side, and between an end of the motor shaft on the other axial side and an end of the mounting member on one axial side.

9. The electric actuator according to claim 1,

the motor shaft has an eccentric shaft portion centered on an eccentric axis eccentric with respect to the motor axis,

the transmission mechanism includes:

an external gear coupled to the eccentric shaft portion via a bearing;

an internal gear that surrounds a radially outer side of the external gear and meshes with the external gear;

an output flange portion that protrudes radially outward from a portion of the output shaft that is located on one axial side of the motor shaft, and that is disposed so as to face one axial side of the external gear; and

a plurality of projecting portions that project from one of the output flange portion and the external gear toward the other and are arranged so as to surround the motor axis,

the other of the output flange portion and the external gear has a plurality of holes disposed so as to surround the motor axis,

the plurality of protruding portions are inserted into the plurality of holes, respectively, and support the external gear via inner side surfaces of the holes so as to be swingable around the motor axis.