Electric Actuator

Abstract

The present invention provides an electric actuator, which has: a motor having a motor shaft that can rotate around a motor axis; a transmission mechanism that is connected to one axial side of the motor shaft; and an output shaft that extends along the axial direction of the motor shaft, and the rotation of the motor shaft is 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 supports the other of the motor shaft and the output shaft so that it can rotate.

Description

Technical Field

[0001] The present invention relates to electric actuators. Background Art

[0002] There is known an electric actuator including a motor shaft and an output shaft connected by a transmission mechanism. For example, Patent Document 1 describes a rotary actuator used as a power source for a shift-by-wire system for switching the gears of an automatic transmission of a vehicle.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2016-109226

[0004] In the electric actuator as described above, there is a possibility that one of the motor shaft and the output shaft may be inclined relative to the other. Summary of the invention

[0005] The present invention has been made in view of the above circumstances, and one object of the present invention is to provide an electric actuator having a structure capable of suppressing a motor shaft and an output shaft from being tilted relative to each other.

[0006] One embodiment of the present invention is 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 along the axial direction of the motor shaft, wherein the rotation of the motor shaft is 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 supports the other of the motor shaft and the output shaft so that it can rotate.

[0007] According to one aspect of the present invention, in the electric actuator, it is possible to suppress the motor shaft and the output shaft from being tilted relative to each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a cross-sectional view showing the electric actuator according to the present embodiment.

[0009] Figure 2 is a diagram showing a transmission mechanism of this embodiment. Figure 1 Sectional view II-II in FIG.

[0010] Description of symbols

[0011] 10: Housing; 11: Housing body; 12: Cover; 20: Motor; 21: Rotor; 21a: Motor shaft; 21b: Rotor body; 21d: Eccentric shaft portion; 24: First detected portion; 30: Transmission mechanism; 31: External gear; 31b: Hole portion; 32: Internal gear; 41: Output shaft; 41a: Connecting portion; 41b: Extension portion; 42: Output flange portion; 43: Protrusion; 44: Mounting component; 45: Second detected portion; 51: First bearing; 52: Second bearing; 53: Third bearing (bearing); 61, 62: Washers; 81: First rotation sensor; 82: Second rotation sensor; 100: Electric actuator; DS: Driven shaft; J1: Motor axis; J2: Eccentric axis. DETAILED DESCRIPTION

[0012] In each figure, the Z-axis direction is an up-down direction with the positive side (+Z side) as the upper side and the negative side (-Z side) as the lower side. The axial direction of the motor axis J1 shown appropriately in each figure is parallel to the Z-axis direction, that is, the up-down direction. In the following description, the direction parallel to the axial direction of the motor axis J1 is simply referred to as the "axial direction". In addition, the radial direction centered on the motor axis J1 is simply referred to as the "radial direction", and the circumferential direction centered on the motor axis J1 is simply referred to as the "circumferential direction".

[0013] In this embodiment, the lower side is equivalent to "one side in the axial direction", and the upper side is equivalent to "the other side in the axial direction". In addition, the up-down direction, the upper side, and the lower side are merely names used to describe the relative positional relationship of each part, and the actual configuration relationship may also be a configuration relationship other than the configuration relationship represented by these names.

[0014] Figure 1 The electric actuator 100 of the present embodiment shown in FIG. 1 is mounted on a vehicle. More specifically, the electric actuator 100 is mounted on a wire-controlled actuator device that is driven according to a shift operation of a driver of the vehicle. Figure 1 As shown, the electric actuator 100 includes a housing 10, a motor 20, a transmission mechanism 30, an output portion 40, a first bearing 51, a second bearing 52, a third bearing 53, washers 61, 62, a bus bar unit 70, a substrate 80, a first rotation sensor 81, a second rotation sensor 82, a first detected portion 24, a mounting member 44, a second detected portion 45, and a partition member 90. The first bearing 51, the second bearing 52, and the third bearing 53 are, for example, ball bearings.

[0015] The housing 10 accommodates various parts of the electric actuator 100 including the motor 20 and the transmission mechanism 30. The housing 10 includes a housing body 11, a cover 12, and an inner cover 13. The housing body 11 is open at the top. The housing body 11 is, for example, cylindrical with the motor axis J1 as the center. The housing body 11 includes a first housing portion 11a and a second housing portion 11b.

[0016] The first housing portion 11a is, for example, the lower portion of the housing body 11. The first housing portion 11a has a bottom portion 11c located at the lower side and a cylindrical portion 11d extending upward from the radial outer edge portion of the bottom portion 11c. The bottom portion 11c has a hole portion 11e that penetrates the bottom portion 11c in the axial direction. The hole portion 11e is, for example, a circular hole centered on the motor axis J1. The upper portion of the hole portion 11e constitutes a first bearing retaining portion 11f, which retains the first bearing 51 inside. The first bearing 51 is retained by the housing body 11 by being retained inside the first bearing retaining portion 11f. The outer ring of the first bearing 51 is, for example, fitted with the inner circumferential surface of the first bearing retaining portion 11f.

[0017] The second housing portion 11b is, for example, the upper portion of the shell body 11. The second housing portion 11b is connected to the upper side of the first housing portion 11a. The second housing portion 11b is in the shape of a tube that is open on the upper side. The inner diameter of the second housing portion 11b is larger than the inner diameter of the first housing portion 11a. The outer diameter of the second housing portion 11b is larger than the outer diameter of the first housing portion 11a. The lower end portion of the second housing portion 11b is, for example, connected to the radial outer edge portion of the upper end portion of the cylinder portion 11d. A step is provided on the inner circumferential surface of the second housing portion 11b, the step having a step surface 11g facing upward. The step surface 11g is, for example, a surface perpendicular to the axial direction.

[0018] A substrate 80 is fixed on the step surface 11g. The substrate 80 is in the shape of a plate with the plate surface facing the axial direction and extending in the radial direction. The radial outer edge of the substrate 80 is fixed to the step surface 11g, for example, by screws. The substrate 80 is housed inside the second housing portion 11b. The substrate 80 is located at a position higher than the rotor body 21b described later. The substrate 80 has a through hole 80a that passes through the substrate 80 in the axial direction. The through hole 80a is, for example, a circular hole centered on the motor axis J1. The upper part of the output shaft 41 described later is axially inserted into the through hole 80a. A printed wiring not shown in the figure is provided on the plate surface of the substrate 80. Although the figure is omitted, an inverter circuit for supplying power to the motor 20 is provided on the substrate 80, for example.

[0019] A first rotation sensor 81 and a second rotation sensor 82 are mounted on the substrate 80. The first rotation sensor 81 is a sensor capable of detecting the rotation of a motor shaft 21a described later. The second rotation sensor 82 is a sensor capable of detecting the rotation of an output shaft 41 described later. In the present embodiment, the first rotation sensor 81 and the second rotation sensor 82 are magnetic sensors. The first rotation sensor 81 and the second rotation sensor 82 are, for example, Hall elements such as Hall ICs. For example, a plurality of the first rotation sensor 81 and the second rotation sensor 82 may be provided along the circumferential direction.

[0020] In the present embodiment, the first rotation sensor 81 is mounted on the lower surface of the substrate 80. The first rotation sensor 81 is mounted, for example, on the peripheral edge of the through hole 80a in the lower surface of the substrate 80. In the present embodiment, the second rotation sensor 82 is mounted on the upper surface of the substrate 80. The second rotation sensor 82 is, for example, located radially outward of the first rotation sensor 81. That is, in the present embodiment, the radial positions of the first rotation sensor 81 and the second rotation sensor 82 are different from each other.

[0021] The cover 12 is fixed to the housing body 11. The radial outer edge of the cover 12 is fixed to the upper end of the second housing portion 11b, for example, by screws. The cover 12 closes the upper opening of the housing body 11. The cover 12 includes: a cover body 12a, which covers the upper opening of the housing body 11; and a second bearing retaining portion 12b, which protrudes downward from the cover body 12a. The second bearing retaining portion 12b is, for example, cylindrical in shape with the motor axis J1 as the center and opening at the lower side. The second bearing 52 is retained inside the second bearing retaining portion 12b. Thus, the second bearing 52 is retained by the cover 12. The outer ring of the second bearing 52 is, for example, fitted with the inner circumferential surface of the second bearing retaining portion 12b.

[0022] The inner cover 13 is located inside the housing body 11. The inner cover 13 is, for example, in the shape of a plate with the plate surface facing the axial direction. The inner cover 13 is, for example, in the shape of a circular plate centered on the motor axis J1. The inner cover 13 separates the interior of the first housing portion 11a from the interior of the second housing portion 11b in the axial direction. The radial outer edge portion of the inner cover 13 is fixed to the upper end of the first housing portion 11a, for example, by screws. The inner cover 13 has hole portions 13a and 13b that penetrate the inner cover 13 in the axial direction. The hole portion 13a is, for example, a circular hole centered on the motor axis J1. When viewed in the axial direction, the hole portion 13b overlaps with the stator 22 described later.

[0023] A bus bar unit 70 is disposed on the upper surface of the inner cover 13. The bus bar unit 70 includes a bus bar holder 71 and a bus bar 72. The bus bar holder 71 is a resin component that holds the bus bar 72. The bus bar 72 electrically connects the lead wire 22d led out from the coil 22c of the stator 22 described later to the substrate 80. For example, a plurality of bus bars 72 are provided. The inverter circuit provided on the substrate 80 supplies power to the stator 22 via the bus bar 72.

[0024] The motor 20 has a rotor 21 and a stator 22. The rotor 21 has a motor shaft 21a and a rotor body 21b. That is, the motor 20 has a motor shaft 21a and a rotor body 21b. The motor shaft 21a can rotate around the motor axis J1. The motor shaft 21a is a hollow shaft. The motor shaft 21a is, for example, cylindrical, centered on the motor axis J1 and extending in the axial direction. The motor shaft 21a is open on both sides in the axial direction. The inner diameter of the motor shaft 21a is, for example, uniform over the entire axial range. The motor shaft 21a extends upward from the inside of the first housing portion 11a and protrudes into the inside of the second housing portion 11b through the hole portion 13a. The motor shaft 21a has a main body portion 21c, an eccentric shaft portion 21d, and a fixed portion 21e.

[0025] The main body 21c is a portion to which the rotor body 21b is fixed. The upper end of the main body 21c is inserted into, for example, the hole 13a of the inner cover 13. The portion of the main body 21c other than the upper end is located inside the first housing portion 11a.

[0026] The eccentric shaft portion 21d is connected to the lower side of the main body portion 21c. The eccentric shaft portion 21d is located inside the first housing portion 11a. The lower end of the eccentric shaft portion 21d is, for example, the lower end of the motor shaft 21a. The eccentric shaft portion 21d is a portion centered on an eccentric axis J2 that is eccentric relative to the motor axis J1. The eccentric axis J2 is parallel to the motor axis J1. The inner ring of the third bearing 53 is fitted and fixed to the eccentric shaft portion 21d. Thus, the third bearing 53 is fixed to the motor shaft 21a.

[0027] The fixed portion 21e is connected to the upper side of the main body 21c. The fixed portion 21e is, for example, located inside the second housing portion 11b. The fixed portion 21e is located above the rotor main body 21b. The upper end of the fixed portion 21e is, for example, the upper end of the motor shaft 21a. The upper end of the fixed portion 21e is, for example, located in the through hole 80a of the substrate 80. The outer diameter of the fixed portion 21e is smaller than the outer diameter of the main body 21c. A step is provided between the outer peripheral surface of the fixed portion 21e and the outer peripheral surface of the main body 21c in the axial direction, and the step has a step surface 21f facing the upper side. The step surface 21f is, for example, perpendicular to the axial direction. The step surface 21f is the upper end surface of the main body 21c. The step surface 21f is, for example, located above the upper surface of the inner cover 13.

[0028] The first detected portion 24 is fixed to the fixed portion 21e. Thus, the first detected portion 24 is provided in a portion of the motor shaft 21a that is located above the rotor body 21b. The first detected portion 24 is a portion whose rotation is detected by the first rotation sensor 81. In the present embodiment, the first detected portion 24 is a magnet. That is, in the present embodiment, the first rotation sensor 81 detects the rotation of the first detected portion 24 by detecting the magnetic field of the first detected portion 24, thereby detecting the rotation of the motor shaft 21a to which the first detected portion 24 is fixed. The first detected portion 24 is, for example, in the shape of an annulus centered on the motor axis J1. The inner circumferential surface of the first detected portion 24 is fixed to the outer circumferential surface of the fixed portion 21e. The lower surface of the first detected portion 24 is in contact with the step surface 21f.

[0029] The first detected portion 24 protrudes radially outward from the main body portion 21c. The outer diameter of the first detected portion 24 is, for example, larger than the inner diameter of the hole portion 13a. The radial outer edge of the first detected portion 24 is located on the upper side of the inner cover 13, and is located radially outward from the inner edge of the hole portion 13a. The first detected portion 24 is located on the lower side of the substrate 80. The radial outer edge of the first detected portion 24 is arranged opposite to the lower side of the first rotation sensor 81. In the present embodiment, when viewed in the axial direction, the first rotation sensor 81 and the first detected portion 24 overlap each other.

[0030] The rotor body 21b is fixed to the outer peripheral surface of the motor shaft 21a. The rotor body 21b is fixed, for example, to the axial center portion of the outer peripheral surface of the main body 21c. The rotor body 21b is accommodated in the first accommodation portion 11a. Although not shown in the figure, the rotor body 21b has a cylindrical rotor core fixed to the outer peripheral surface of the motor shaft 21a and a rotor magnet fixed to the rotor core.

[0031] The stator 22 is radially opposed to the rotor 21 with a gap therebetween. The stator 22 is located radially outside the rotor 21. The stator 22 is housed inside the first housing portion 11a. The stator 22 includes: an annular stator core 22a that surrounds the radially outer side of the rotor body 21b; an insulator 22b that is mounted on the stator core 22a; and a plurality of coils 22c that are mounted on the stator core 22a with the insulator 22b therebetween. The outer circumferential surface of the stator core 22a is fixed to, for example, the inner circumferential surface of the cylinder 11d. The lead wire 22d is led out from the coil 22c to the upper side. The lead wire 22d passes through the hole 13b in the axial direction and is connected to the bus bar 72.

[0032] The transmission mechanism 30 is located inside the first housing portion 11a below the rotor body 21b and the stator 22. In the present embodiment, the transmission mechanism 30 is a speed reduction mechanism that reduces the speed of the rotation of the motor shaft 21a and transmits it to the output shaft 41. The transmission mechanism 30 includes an external gear 31, an internal gear 32, an output flange portion 42, and a plurality of protrusions 43.

[0033] The external gear 31 is in the shape of a substantially annular plate extending along a plane perpendicular to the axial direction with the eccentric axis J2 of the eccentric shaft portion 21d as the center. Figure 2 As shown, a gear portion composed of a plurality of tooth portions 31a is provided on the radially outer side surface of the external gear 31. The external gear 31 is connected to the eccentric shaft portion 21d via the third bearing 53. Thus, the transmission mechanism 30 is connected to the lower side of the motor shaft 21a. In the present embodiment, the transmission mechanism 30 is connected to the lower end of the motor shaft 21a. The external gear 31 is engaged with the outer ring of the third bearing 53 from the radially outer side. Thus, the third bearing 53 connects the motor shaft 21a and the external gear 31 in a manner that allows relative rotation around the eccentric axis J2.

[0034] The external gear 31 has a plurality of holes 31b recessed from the lower surface of the external gear 31 toward the upper side. In the present embodiment, the hole 31b penetrates the external gear 31 in the axial direction. The plurality of holes 31b are arranged to surround the motor axis J1. In more detail, the plurality of holes 31b are arranged at equal intervals within a circle along the circumferential direction centered on the eccentric axis J2. For example, eight holes 31b are provided. The shape of the hole 31b when observed along the axial direction is, for example, circular. The inner diameter of the hole 31b is larger than the outer diameter of the portion of the protrusion 43 to be described later that is inserted into the hole 31b.

[0035] 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 is annular with the motor axis J1 as the center. Figure 1 As shown in FIG. 1 , in this embodiment, the internal gear 32 is fixed to the housing 10. The outer peripheral surface of the internal gear 32 is fitted into the inner peripheral surface of the first housing portion 11a and fixed. Figure 2 As shown, a gear portion having a plurality of teeth 32a is provided on the inner circumferential 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 over a portion of the circumferential direction.

[0036] The output flange portion 42 is a part of the output portion 40. Figure 1As shown, the output flange portion 42 is arranged opposite to 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 shape of an annular plate centered on the motor axis J1 and extending in the radial direction. The output flange portion 42 extends radially outward from a portion of the output shaft 41 described later that is located below the motor shaft 21a. The output flange portion 42 extends radially outward from, for example, an upper end portion of the connecting portion 41a described later.

[0037] The output flange portion 42 has a plurality of fixing holes 42a that penetrate the output flange portion 42 in the axial direction. Figure 2 As shown, a plurality of fixing holes 42a are arranged around 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. For example, eight fixing holes 42a are provided. The shape of the fixing hole 42a viewed along the axial direction is circular.

[0038] like Figure 1 As shown, in this embodiment, the protrusion 43 is a cylindrical component extending in the axial direction. The lower part of each protrusion 43 is fixed in each fixing hole 42a. The upper part of each protrusion 43 is located above the fixing hole 42a. Thus, the plurality of protrusions 43 protrude in the axial direction from the output flange portion 42 toward the external gear 31. Figure 2 As shown, a plurality of protrusions 43 are arranged to surround the motor axis J1. The plurality of protrusions 43 are arranged at equal intervals in the circumferential direction, for example. For example, eight protrusions 43 are provided.

[0039] like Figure 1 As shown, the plurality of protrusions 43 are respectively inserted into the plurality of holes 31b from the lower side. The outer diameter of the portion of the protrusion 43 inserted into the hole 31b is smaller than the inner diameter of the hole 31b. The outer peripheral surface of the protrusion 43 is inscribed with the inner side surface of the hole 31b. The plurality of protrusions 43 support the external gear 31 via the inner side surface of the hole 31b so as to be able to swing around the motor axis J1.

[0040] The output unit 40 is a part 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 unit 40 includes an output shaft 41 and an output flange 42. That is, the electric actuator 100 includes the output shaft 41 and the output flange 42. The output unit 40 is, for example, a single component.

[0041] The output shaft 41 extends in the axial direction of the motor shaft 21a. The output shaft 41 is arranged coaxially with the motor shaft 21a. That is, the output shaft 41 can rotate around the motor axis J1. The output shaft 41 is rotatably supported by the first bearing 51 and the second bearing 52. The output shaft 41 has a connecting portion 41a and an extending portion 41b.

[0042] The connecting portion 41a is located at the lower side of the motor shaft 21a. The outer diameter of the connecting portion 41a is larger than the outer diameter of the extension portion 41b. The connecting portion 41a is, for example, inserted into the interior of the hole portion 11e. The lower end of the connecting portion 41a is, for example, the lower end of the output shaft 41. The lower end of the connecting portion 41a is, for example, located at the same axial position as the lower end of the hole portion 11e. The connecting portion 41a is supported by the first bearing 51 so as to be rotatable around the motor axis J1. Thus, the first bearing 51 supports the portion of the output shaft 41 located at the lower side of the motor shaft 21a so as to be rotatable.

[0043] The connecting portion 41a has a connecting recess 41c that is recessed from the end surface of the lower side of the connecting portion 41a toward the upper side. The connecting recess 41c is open at the lower side and exposed to the outside of the housing 10. For example, when viewed from the lower side, the connecting recess 41c is a circular shape centered on the motor axis J1. A spline groove is provided on the inner circumferential surface of the connecting recess 41c. The driven shaft DS is inserted from the lower side inside the connecting recess 41c and connected. Thus, the driven shaft DS is connected to the connecting portion 41a. In more detail, the output shaft 41 is connected to the driven shaft DS by fitting the spline portion provided on the outer circumferential surface of the driven shaft DS with the spline groove provided on the inner circumferential surface of the connecting recess 41c. The driving force of the electric actuator 100 is transmitted to the driven shaft DS via the output shaft 41. Thus, the electric actuator 100 rotates the driven shaft DS around the motor axis J1.

[0044] The extension portion 41b extends upward from the connecting portion 41a. In more detail, the extension portion 41b extends upward from the radial center portion of the upper end portion of the connecting portion 41a. The extension portion 41b is, for example, in the shape of a cylinder centered on the motor axis J1 and extending in the axial direction. The axial dimension of the extension portion 41b is, for example, larger than the axial dimension of the connecting portion 41a. The extension portion 41b passes into the interior of the motor shaft 21a, which is a hollow shaft. Thus, at least a portion of the output shaft 41 is located inside the motor shaft 21a. In the present embodiment, a portion of the extension portion 41b in the output shaft 41 is located inside the motor shaft 21a.

[0045] The extension portion 41b is inserted into the interior of the motor shaft 21a from the lower side of the motor shaft 21a and protrudes upward from the motor shaft 21a. Thus, the output shaft 41 extends from a position lower than the motor shaft 21a through the interior of the motor shaft 21a to a position higher than the motor shaft 21a. The extension portion 41b is axially inserted into the hole portion 13a of the inner cover 13 and the through hole 80a of the substrate 80. The portion of the output shaft 41 located higher than the motor shaft 21a is located, for example, inside the second housing portion 11b. The upper end of the extension portion 41b is supported by the second bearing 52 so as to be rotatable around the motor axis J1. Thus, the second bearing 52 supports the portion of the output shaft 41 located higher than the motor shaft 21a so as to be rotatable.

[0046] The outer diameter of the extension portion 41b is, for example, slightly smaller than the inner diameter of the motor shaft 21a. In the present embodiment, the extension portion 41b is fitted into the inside of the motor shaft 21a with a gap therebetween. The radial gap between the extension portion 41b and the motor shaft 21a is small enough to support the motor shaft 21a so as to be rotatable around the motor axis J1 by the extension portion 41b. Thus, in the present embodiment, the output shaft 41 supports the motor shaft 21a so as to be rotatable by the extension portion 41b. The outer peripheral surface of the portion of the output shaft 41 located inside the motor shaft 21a, that is, a portion of the extension portion 41b, is radially opposed to the inner peripheral surface of the motor shaft 21a and can contact each other. The motor shaft 21a is supported in the radial direction 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, lubricating oil may also be provided in the radial gap between the output shaft 41 and the motor shaft 21a.

[0047] The second detected portion 45 is fixed to a portion of the extension portion 41b located above the motor shaft 21a. That is, in the present embodiment, the second detected portion 45 is provided at a portion of the output shaft 41 located above the motor shaft 21a. The second detected portion 45 is a portion whose rotation is detected by the second rotation sensor 82. In the present embodiment, the second detected portion 45 is a magnet. In the present embodiment, the second rotation sensor 82 detects the rotation of the second detected portion 45 by detecting the magnetic field of the second detected portion 45, thereby detecting the rotation of the output shaft 41.

[0048] In the present embodiment, the second detected portion 45 is mounted on the output shaft 41 via the mounting member 44. The mounting member 44 includes a fixed cylinder portion 44a and a flange portion 44b. The fixed cylinder portion 44a is, for example, in the shape of a cylinder centered on the motor axis J1 and open on both axial sides. 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 second bearing 52. Thus, the mounting member 44 is fixed to the outer peripheral surface of a portion of the output shaft 41 that is located above the motor shaft 21a. The fixed cylinder portion 44a is located between the motor shaft 21a and the second bearing 52 in the axial direction. The flange portion 44b extends radially outward from the upper end of the fixed cylinder portion 44a. The flange portion 44b is, for example, in the shape of a ring centered on the motor axis J1. The radial outer edge portion of the lower surface of the flange portion 44b is, for example, recessed toward the upper side.

[0049] The second detected portion 45 is, for example, in the shape of an annulus centered on the motor axis J1. The second detected portion 45 is fixed to the radial outer edge portion of the lower surface of the flange portion 44b. The second detected portion 45 is located on the upper side of the substrate 80. The inner diameter and outer diameter of the second detected portion 45 are larger than the outer diameter of the first detected portion 24. The second detected portion 45 is located at a position radially outward of the first detected portion 24. That is, in the present embodiment, the radial positions of the first detected portion 24 and the second detected portion 45 are different from each other. The radial outer edge portion of the second detected portion 45 is arranged opposite to the upper side of the second rotation sensor 82. In the present embodiment, when viewed in the axial direction, the second rotation sensor 82 and the second detected portion 45 overlap each other. When viewed in the axial direction, the second rotation sensor 82 and the second detected portion 45 do not overlap with the first rotation sensor 81 and the first detected portion 24. For example, when viewed in the axial direction, the second detected portion 45 overlaps with the rotor body 21 b.

[0050] A washer 61 is provided between the lower end of the motor shaft 21a and the upper end of the connecting portion 41a. A washer 62 is provided between the upper end of the motor shaft 21a and the 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 44a. The washer 61 and the washer 62 are, for example, in the shape of an annulus centered on the motor axis J1. The washer 61 and the washer 62 are, for example, in the shape of a plate with the plate surface facing the axial direction. The washer 61 and the washer 62 are, for example, sliding washers.

[0051] The washer 61 and the washer 62 surround the extension portion 41b. The lower surface of the washer 61 contacts the peripheral edge of the extension portion 41b in the upper surface of the connecting portion 41a. The upper surface of the washer 61 contacts the lower end surface of the motor shaft 21a. The lower surface of the washer 62 contacts the upper end surface of the motor shaft 21a. The upper surface of the washer 62 contacts the lower end surface of the mounting member 44.

[0052] 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 body 91 and a peripheral wall portion 92. The partition member body 91 is, for example, in the shape of an annulus centered on the motor axis J1. The partition member body 91 is in the shape of a plate with the plate surface facing the axial direction. The radial inner edge portion of the partition member body 91 is located radially outward of the radial inner edge portion of the insulating member 22b. The peripheral wall portion 92 protrudes upward from the radial outer edge portion of the partition member body 91. The peripheral wall portion 92 is, for example, in the shape of a cylinder centered on the motor axis J1. The peripheral wall portion 92 is fitted into the inner circumferential surface of the first housing portion 11a and fixed. The upper end of the peripheral wall portion 92 contacts the radial outer edge portion of the lower end surface of the stator core 22a.

[0053] When power is supplied to the motor 20 to rotate the motor shaft 21a around the motor axis J1, the eccentric shaft portion 21d revolves in the circumferential direction around the motor axis J1. The revolving of the eccentric shaft portion 21d is transmitted to the external gear 31 via the third bearing 53, and the external gear 31 oscillates while the position where the inner circumferential surface of the hole portion 31b and the outer circumferential surface of the protrusion 43 are inscribed changes. As a result, the position where the gear portion of the external gear 31 and the gear portion of the internal gear 32 mesh 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.

[0054] 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 around the eccentric axis J2 by ​​the reaction force of the rotational force transmitted to the internal gear 32. At this time, the direction in which the external gear 31 rotates is the opposite direction to the direction in which the motor shaft 21a rotates. The rotation of the external gear 31 around the eccentric axis J2 is transmitted to the output flange portion 42 via the hole portion 31b and the protrusion 43. Thus, the output shaft 41 rotates around 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 transmission mechanism 30 as a speed reduction mechanism is structured to transmit the rotation via the plurality of protrusions 43 as described above, thereby enabling the speed reduction ratio of the rotation of the output shaft 41 to be relatively large relative to the rotation of the motor shaft 21a. Therefore, the rotation torque of the output shaft 41 can be relatively large.

[0055] According to the present embodiment, the motor shaft 21a is a hollow shaft, and at least a portion of the output shaft 41 is located inside the motor shaft 21a. The output shaft 41 supports the motor shaft 21a so that it can rotate. Therefore, even if the motor shaft 21a is about to tilt radially relative to the output shaft 41, the motor shaft 21a is supported by the output shaft 41. Thus, the motor shaft 21a is suppressed from tilting relative to the output shaft 41. Therefore, the motor shaft 21a and the output shaft 41 can be suppressed from tilting relative to each other. In addition, since the motor shaft 21a can be supported by the output shaft 41, there is no need to provide a bearing that supports the motor shaft 21a so that it can rotate. Therefore, the number of components of the electric actuator 100 can be reduced.

[0056] 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 is radially opposed to the inner peripheral surface of the motor shaft 21a and can contact each other. Therefore, even if the motor shaft 21a is about to tilt radially relative 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. As a result, it is easy to increase the area supporting the motor shaft 21a, and the motor shaft 21a can be supported more stably by the output shaft 41. Therefore, it is possible to further suppress the motor shaft 21a and the output shaft 41 from tilting relative to each other. In addition, compared with the case where other components are provided between the motor shaft 21a and the output shaft 41 in the radial direction, the number of components of the electric actuator 100 can be reduced.

[0057] In addition, according to the present embodiment, the output shaft 41 passes through the inside of the motor shaft 21a from a position lower than the motor shaft 21a and extends to a position higher than the motor shaft 21a. Therefore, the output shaft 41 can be arranged within the entire axial range of the inside of the motor shaft 21a. Thus, 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 tilting relative to each other.

[0058] In addition, according to the present embodiment, the first bearing 51 that rotatably supports the portion of the output shaft 41 located below the motor shaft 21a and the second bearing 52 that rotatably supports the portion of the output shaft 41 located above the motor shaft 21a are provided. Therefore, the output shaft 41 can be stably supported with both arms. In this way, since the output shaft 41 is 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 tilted relative to each other.

[0059] In addition, since the output shaft 41 protrudes to both sides in the axial direction relative to the motor shaft 21a, it is easy to hold the first bearing 51 and the second bearing 52 that support both sides in the axial direction of the output shaft 41 on the housing 10. Therefore, it is possible to suppress the complexity of the structure of the housing 10, and to easily assemble the first bearing 51 and the second bearing 52. In this way, by adopting a structure in which the output shaft 41 is supported by the first bearing 51 and the second bearing 52 and the motor shaft 21a is supported by the output shaft 41, it is possible to suppress the complexity of the structure of the electric actuator 100 and to easily assemble the electric actuator 100, compared with, for example, a structure in which the output shaft 41 is supported by the motor shaft 21a supported by the bearings.

[0060] In addition, according to the present embodiment, the housing 10 includes the housing body 11 opened at the upper side and the cover 12 fixed to the housing body 11 and closing the upper opening of the housing body 11. The first bearing 51 is held by the housing body 11, and the second bearing 52 is held by the cover 12. That is, the second bearing 52 can be held by the cover 12 closing the upper opening of the housing body 11. Therefore, compared with the case where a component for holding the second bearing 52 is separately provided, the number of components of the electric actuator 100 can be reduced.

[0061] In addition, according to the present embodiment, the substrate 80 has a through hole 80a for the upper portion of the output shaft 41 to pass through in the axial direction. Therefore, it is possible to adopt a structure in which the substrate 80 is arranged between the cover 12 and the motor 20 in the axial direction and the upper end of the output shaft 41 is held by the second bearing 52 held by the cover 12. In addition, the substrate 80 can be enlarged in the radial direction. Therefore, it is easy to ensure an area on the substrate 80 for arranging the inverter circuit, the first rotation sensor 81, the second rotation sensor 82, and other electronic components not shown in the figure.

[0062] In addition, according to the present embodiment, the first detected portion 24 whose rotation is detected by the first rotation sensor 81 is provided at a portion of the motor shaft 21a located above the rotor body 21b. The second detected portion 45 whose rotation is detected by the second rotation sensor 82 is provided at a portion of the output shaft 41 located above the motor shaft 21a. Therefore, the first rotation sensor 81 and the second rotation sensor 82 can be both arranged at the upper portion inside the housing 10. Thus, for example, compared with a case where the first rotation sensor 81 and the second rotation sensor 82 are arranged at different sides in the axial direction inside the housing 10, the operation of assembling the first rotation sensor 81 and the second rotation sensor 82 can be easily performed. Specifically, in the present embodiment, since both the first rotation sensor 81 and the second rotation sensor 82 can be arranged in the second housing portion 11b, it is not necessary to pass the wiring of the second rotation sensor 82 from the first housing portion 11a to the substrate 80 in the second housing portion 11b, as compared to, for example, the case where the second rotation sensor 82 is arranged in the first housing portion 11a. Therefore, it is possible to reduce the number of man-hours and time required for the work of assembling the first rotation sensor 81 and the second rotation sensor 82. In addition, it is possible to suppress the complexity of the structure of the housing 10, as compared to, for example, the case where a structure for passing the wiring from the first housing portion 11a to the second housing portion 11b is provided in the housing 10.

[0063] As described above, in a structure in which the first rotation sensor 81 and the second rotation sensor 82 can be arranged together 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 the inside of the motor shaft 21a and protrude to the upper side of the motor shaft 21a. That is, by extending a part of the output shaft 41 connected to the transmission mechanism 30 connected to the lower side of the motor shaft 21a through the inside of the motor shaft 21a to a position higher than the motor shaft 21a, the second detection portion 45 can be provided at a position higher than the motor shaft 21a, and the second rotation sensor 82 that detects the second detection portion 45 can be arranged at the upper part of the housing 10.

[0064] In addition, according to the present embodiment, the first rotation sensor 81 and the second rotation sensor 82 are mounted on the substrate 80. Therefore, by arranging the substrate 80 on which the first rotation sensor 81 and the second rotation sensor 82 are mounted in the housing 10, the first rotation sensor 81 and the second rotation sensor 82 can be arranged together in the housing 10. Thus, the man-hours and time required for the work of assembling the first rotation sensor 81 and the second rotation sensor 82 can be further reduced.

[0065] In addition, according to the present embodiment, the first rotation sensor 81 is mounted on the lower surface of the substrate 80, and the second rotation sensor 82 is mounted on the upper surface of the substrate 80. That is, the first rotation sensor 81 and the second rotation sensor 82 are mounted on the surfaces on the opposite sides of the axial direction of the substrate 80. Therefore, compared with the case where the first rotation sensor 81 and the second rotation sensor 82 are mounted on the same surface of the substrate 80, it is easy to ensure the area for mounting each rotation sensor on the substrate 80.

[0066] In addition, since the second detected portion 45 is provided at a portion of the output shaft 41 located above the motor shaft 21a, the first detected portion 24 provided on the motor shaft 21a is easily arranged at a position below the second detected portion 45. Therefore, by installing the first rotation sensor 81 on the lower surface of the substrate 80 and installing the second rotation sensor 82 on the upper surface of the substrate 80, it is easy to arrange each rotation sensor close to each detected portion. Thus, the rotation of each detected portion can be more appropriately detected by each rotation sensor. Therefore, the rotation detection accuracy of each rotation sensor for each axis can be improved.

[0067] In addition, according to the present embodiment, when viewed in the axial direction, the first rotation sensor 81 and the first detected portion 24 overlap each other, and when viewed in the axial direction, the second rotation sensor 82 and the second detected portion 45 overlap each other. Therefore, the first rotation sensor 81 and the first detected portion 24 can be axially opposed, and the rotation of the first detected portion 24 can be more easily detected by the first rotation sensor 81. In addition, the second rotation sensor 82 and the second detected portion 45 are axially opposed, and the rotation of the second detected portion 45 can be more easily detected by the second rotation sensor 82. Therefore, the rotation detection accuracy of each rotation sensor for each axis can be further improved.

[0068] In addition, the radial positions of the first rotation sensor 81 and the second rotation sensor 82 are different from each other, and the radial positions of the first detected part 24 and the second detected part 45 are different from each other. Therefore, for example, when the first detected part 24 and the second detected part 45 are magnets and the first rotation sensor 81 and the second 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 sensor of the other party. Thus, the rotation of each detected part can be more appropriately detected by each rotation sensor. Therefore, the rotation detection accuracy of each rotation sensor for each axis can be further improved.

[0069] In addition, 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 sides in the axial direction by the washers 61 and 62. Thus, the motor shaft 21a can be prevented from being displaced in the axial direction relative to the output shaft 41. In addition, compared with the case where both axial ends of the motor shaft 21a are in direct contact with the output shaft 41 or the mounting member 44, the 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, so that the motor shaft 21a and the output shaft 41 can be easily rotated relatively smoothly. In particular, by making the washers 61 and 62 as sliding washers, the motor shaft 21a and the output shaft 41 can be rotated relatively more smoothly.

[0070] In addition, according to the present embodiment, the first detected portion 24 and the second detected portion 45 are magnets. The first rotation sensor 81 and the second 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 using the magnetic field generated from the first detected portion 24 and the second detected portion 45. In addition, as described above, the effect of improving the rotation detection accuracy can be effectively obtained by arranging the first rotation sensor 81 and the first detected portion 24 and the second rotation sensor 82 and the second detected portion 45 in a radially staggered manner.

[0071] The present invention is not limited to the above-mentioned embodiments, and other structures and methods can also be adopted within the scope of the technical idea of ​​the present invention. It is also possible that the motor shaft supports the output shaft so as to be rotatable. Even in this case, the motor shaft and the output shaft can be prevented from tilting relative to each other. In addition, in this case, it is also possible that the motor shaft is supported by a bearing and the output shaft is not supported by a bearing. The output shaft may not extend to a position axially on the other side (upper side) than the motor shaft. It is also possible that the output shaft is located entirely inside the motor shaft. It is also possible to provide other components between the inner circumferential surface of the motor shaft and the outer circumferential surface of the output shaft. In this case, it is also possible that one of the motor shaft and the output shaft supports the other of the motor shaft and the output shaft so as to be rotatable via the other component. In addition, in this case, the other component may also be a bearing such as a ball bearing, a needle bearing, or a sliding bearing. The type of the first bearing, the type of the second bearing, and the type of the third bearing are not particularly limited. The second bearing may also not be held by a cover.

[0072] The first detected part may be any part as long as the rotation is detected by the first rotation sensor. The first rotation sensor may be any sensor as long as it can detect the rotation of the motor shaft by detecting the rotation of the first detected part. The second detected part may be any part as long as the rotation is detected by the second rotation sensor. The second rotation sensor may be any sensor as long as it can detect the rotation of the output shaft by detecting the rotation of the second detected part. The first detected part may also be a part of the motor shaft. The second detected part may also be a part of the output shaft. The first rotation sensor and the second rotation sensor may also be optical sensors. Alternatively, the first rotation sensor may be a rotary transformer stator and the first detected part may be a rotary transformer rotor. Alternatively, the second rotation sensor may be a rotary transformer stator and the second detected part may be a rotary transformer rotor. The first rotation sensor and the second rotation sensor may also be magnetic sensors other than Hall elements. The first rotation sensor and the second rotation sensor may also be magnetoresistive effect elements.

[0073] Alternatively, the first rotation sensor may be mounted on the other axial side (upper side) of the substrate, and the second rotation sensor may be mounted on one axial side (lower side) of the substrate. The first rotation sensor and the second rotation sensor may be mounted on different components. The first rotation sensor and the second rotation sensor may be arranged on different axial sides in the housing. The first rotation sensor and the second rotation sensor may not be provided. Washers may not be provided between the motor shaft and the connecting portion and between the motor shaft and the mounting component.

[0074] 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 the rotation of the motor shaft. In the case where the transmission mechanism is a speed-reducing mechanism, the structure of the speed-reducing mechanism is not particularly limited. Alternatively, a plurality of protrusions may be provided on the external gear and a plurality of holes may be provided on the output flange. In this case, the protrusions protrude from the external gear toward the output flange and are inserted into the holes.

[0075] The application of the electric actuator of the present invention is not particularly limited. The electric actuator may also be mounted on an actuator device of a shift-by-wire type that is driven according to a shift operation of a driver. In addition, the electric actuator may also be mounted on equipment other than a vehicle. In addition, the various structures described above in this specification may be appropriately combined within a range that does not contradict each other.

Claims

1. 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, to which the rotation of the motor shaft is transmitted 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. The output shaft extends from a position on one side of the motor shaft in the axial direction to a position on the other side of the motor shaft in the axial direction. The electric actuator also features: a first bearing rotatably supporting a portion of the output shaft located axially toward one side of the motor shaft; and a second bearing rotatably supporting a portion of the output shaft located axially on the other side of the motor shaft; The output shaft rotatably supports the motor shaft. The electric actuator further includes a housing that houses the motor and the transmission mechanism. The housing has: a housing body opened on the other axial side; and a cover fixed to the housing body to close the opening on the other axial side of the housing body; The first bearing is held by the housing body. The second bearing is held by the cover.

2. The electric actuator according to claim 1, wherein 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 and can contact each other.

3. The electric actuator according to claim 1, wherein: The electric actuator also features: a first rotation sensor capable of detecting the rotation of the motor shaft; and a second rotation sensor capable of detecting the rotation of the output shaft, The motor has a rotor body fixed to the outer peripheral surface of the motor shaft. A first detected portion, the rotation of which is detected by the first rotation sensor, is provided at a portion of the motor shaft located axially to the other side of the rotor body. A second detected portion, whose rotation is detected by the second rotation sensor, is provided at a portion of the output shaft located on the other axial side relative to the motor shaft.

4. The electric actuator according to claim 3, wherein: The first detected portion and the second detected portion are magnets, The first rotation sensor and the second rotation sensor are magnetic sensors.

5. The electric actuator according to claim 3 or 4, wherein: The electric actuator further includes a mounting member fixed to the outer peripheral surface of a portion of the output shaft located axially on the other side of the motor shaft. The second detected portion is mounted on the output shaft via the mounting member. The output shaft has: a connecting portion to which the driven shaft is connected; and an extension portion extending from the connecting portion to the other axial side and passing into the interior of the motor shaft, The outer diameter of the connecting portion is larger than the outer diameter of the extending portion, Washers are provided between one axial end portion of the motor shaft and the other axial end portion of the coupling portion, and between the other axial end portion of the motor shaft and one axial end portion of the mounting member.

6. The electric actuator according to claim 1, wherein The motor shaft has an eccentric shaft portion centered around an eccentric axis that is eccentric with respect to the motor axis. The transmission mechanism comprises: an externally toothed gear connected to the eccentric shaft portion via a bearing; an internally toothed gear surrounding a radially outer side of the externally toothed gear and meshing with the externally toothed gear; an output flange portion projecting radially outward from a portion of the output shaft located axially to one side relative to the motor shaft, the output flange portion being arranged to face one axial side of the externally toothed gear; as well as a plurality of protrusions, the plurality of protrusions protruding from one of the output flange portion and the externally toothed gear toward the other and arranged to surround the motor axis; The other of the output flange and the externally toothed gear has a plurality of holes arranged to surround the motor axis. The plurality of protrusions are respectively inserted into the plurality of holes, and support the externally toothed gear via inner side surfaces of the holes so as to be swingable about the motor axis.

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