Electric actuator

Abstract

The present invention provides an electric actuator comprising: a motor having a motor shaft; a transmission mechanism connected to one axial side of the motor shaft; an output shaft extending in the axial direction of the motor shaft; a first bearing and a second bearing, the first bearing and the second bearing supporting the output shaft; and a housing. The housing comprises: a housing body opening on the other axial side; and a cover closing the opening on the other axial side of the housing body. The motor shaft is a hollow shaft. The output shaft extends from a position axially one side of the motor shaft through the interior of the motor shaft to a position axially the other side of the motor shaft. The first bearing rotatably supports a portion of the output shaft located axially one side of the motor shaft, and the first bearing is retained by the housing body. The second bearing rotatably supports a portion of the output shaft located axially the other side of the motor shaft, and the second bearing is retained by the cover.

Description

Technical Field

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

[0002] Electric actuators having a motor shaft and an output shaft connected by a transmission mechanism are known. For example, Patent Document 1 describes a rotary actuator used as a power source for a shift-by-wire system for switching gears in an automatic transmission of a vehicle.

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

[0004] In the electric actuator described above, for example, it is necessary to provide bearings for rotatably supporting the motor shaft and the output shaft, respectively, and this has a problem in that the number of components tends to increase. Summary of the Invention

[0005] In view of the above-mentioned circumstances, one object of the present invention is to provide an electric actuator having a structure capable of reducing the number of parts.

[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 coupled to one axial side of the motor shaft; an output shaft extending axially along the motor shaft, the rotation of the motor shaft being transmitted to the output shaft via the transmission mechanism; a first bearing and a second bearing rotatably supporting the output shaft; and a housing that internally houses the motor and the transmission mechanism. The housing comprises: a housing body that is open on the other axial side; and a cover that is fixed to the housing body and closes the opening on the other axial side of the housing body. The motor shaft is a hollow shaft. The output shaft extends from a position axially one side of the motor shaft through the interior of the motor shaft to a position axially the other side of the motor shaft. The first bearing rotatably supports a portion of the output shaft located axially to one side of the motor shaft, and the first bearing is held by the housing body. The second bearing rotatably supports a portion of the output shaft located axially to the other side of the motor shaft, and the second bearing is held by the cover.

[0007] According to one aspect of the present invention, the number of components of the electric actuator can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0010] Label Description

[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; 42: Output flange portion; 43: Protrusion; 45: Second detected portion; 51: First bearing; 52: Second bearing; 53: Third bearing (bearing); 80: Substrate; 80a: Through hole; 81: First rotation sensor; 82: Second rotation sensor; 100: Electric actuator; J1: Motor axis; J2: Eccentric axis. DETAILED DESCRIPTION

[0012] In each figure, the Z-axis direction is a vertical 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, as shown in the figures, is parallel to the Z-axis direction, that is, the vertical 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." Furthermore, 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 corresponds to "one axial side" and the upper side corresponds to "the other axial side." Furthermore, the terms "upper and lower directions," "upper side," and "lower side" are merely names used to describe the relative positional relationships of the components, and the actual arrangement relationships may be other than those indicated by these names.

[0014] Figure 1 The electric actuator 100 of the present embodiment shown 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 by a driver of the vehicle. Figure 1 As shown, electric actuator 100 includes housing 10, motor 20, transmission mechanism 30, output unit 40, first bearing 51, second bearing 52, third bearing 53, washers 61, 62, bus bar unit 70, substrate 80, first rotation sensor 81, second rotation sensor 82, first detected portion 24, mounting member 44, second detected portion 45, and partition member 90. First bearing 51, second bearing 52, and third bearing 53 are, for example, ball bearings.

[0015] The housing 10 houses various components 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. For example, the housing body 11 has a cylindrical shape centered on the motor axis J1. 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 of the bottom portion 11c. The bottom portion 11c has a hole portion 11e that passes through 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 into 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 cylindrical 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 to 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 above 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 portion of the output shaft 41 described later passes through the through hole 80a in the axial direction. Printed wiring, not shown in the figure, is provided on the plate surface of the substrate 80. Although not shown in the figure, 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 the motor shaft 21a (described later). The second rotation sensor 82 is a sensor capable of detecting the rotation of the output shaft 41 (described later). In this embodiment, the first rotation sensor 81 and the second rotation sensor 82 are magnetic sensors. For example, the first rotation sensor 81 and the second rotation sensor 82 are Hall elements such as Hall ICs. For example, multiple first rotation sensors 81 and multiple second rotation sensors 82 may be provided along the circumference.

[0020] In this embodiment, the first rotation sensor 81 is mounted on the lower surface of the substrate 80. For example, the first rotation sensor 81 is mounted on the peripheral edge of the through-hole 80a in the lower surface of the substrate 80. In this embodiment, the second rotation sensor 82 is mounted on the upper surface of the substrate 80. For example, the second rotation sensor 82 is positioned radially outward of the first rotation sensor 81. That is, in this embodiment, the radial positions of the first rotation sensor 81 and the second rotation sensor 82 are different.

[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 by, for example, screws. The cover 12 closes the upper opening of the housing body 11. The cover 12 has: 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, in the shape of a cylinder centered on the motor axis J1 and open at the bottom. 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 into 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 of the inner cover 13 is fixed to the upper end of the first housing portion 11a by, for example, screws. The inner cover 13 has holes 13a and 13b that pass through the inner cover 13 in the axial direction. The hole 13a is, for example, a circular hole centered on the motor axis J1. When viewed in the axial direction, the hole 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 wires 22d extending from the coils 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 bars 72.

[0024] The motor 20 includes a rotor 21 and a stator 22. The rotor 21 includes a motor shaft 21a and a rotor body 21b. That is, the motor 20 includes the motor shaft 21a and the rotor body 21b. The motor shaft 21a is rotatable about the motor axis J1. The motor shaft 21a is a hollow shaft. The motor shaft 21a is, for example, cylindrical, centered about 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 interior of the first housing portion 11a and protrudes into the interior of the second housing portion 11b through the hole portion 13a. The motor shaft 21a includes a main body portion 21c, an eccentric shaft portion 21d, and a fixed portion 21e.

[0025] The main body 21c is the 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 centered around 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. As a result, 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 located, for example, 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 located, for example, within 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 axially between the outer circumferential surface of the fixed portion 21e and the outer circumferential surface of the main body 21c, and the step has a step surface 21f facing upward. 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 a ring centered on the motor axis J1. The inner peripheral surface of the first detected portion 24 is fixed to the outer peripheral 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 larger than the inner diameter of the hole portion 13a, for example. 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 this embodiment, when viewed in the axial direction, the first rotation sensor 81 and the first detected portion 24 overlap with each other.

[0030] The rotor body 21b is fixed to the outer circumference of the motor shaft 21a. For example, the rotor body 21b is fixed to the axial center of the outer circumference of the main body 21c. The rotor body 21b is housed within the first housing portion 11a. Although not shown, the rotor body 21b includes a cylindrical rotor core fixed to the outer circumference of the motor shaft 21a and rotor magnets 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 via the insulator 22b. 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 from the coil 22c toward 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 within the first housing portion 11a, below the rotor body 21b and stator 22. In this embodiment, the transmission mechanism 30 is a speed reduction mechanism that reduces the rotation of the motor shaft 21a and transmits it to the output shaft 41. The transmission mechanism 30 includes an externally toothed gear 31, an internally toothed gear 32, an output flange 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 consisting of a plurality of teeth 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. As a result, the transmission mechanism 30 is connected to the lower side of the motor shaft 21a. In this 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 radial outside. As a result, 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 upward from the lower surface of the external gear 31. In this embodiment, the hole 31b extends axially through the external gear 31. The plurality of holes 31b are arranged to surround the motor axis J1. More specifically, the plurality of holes 31b are arranged at equal intervals around the motor axis J1 along the circumferential direction centered on the eccentric axis J2. For example, eight holes 31b are provided. The shape of the hole 31b when viewed 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 circumference.

[0036] The output flange portion 42 is a part of the output portion 40. Figure 1 As shown, the output flange 42 is disposed opposite the lower side of the externally toothed gear 31. A gap is provided axially between the output flange 42 and the externally toothed gear 31. The output flange 42 has, for example, a circular plate shape extending radially about the motor axis J1. The output flange 42 extends radially outward from a portion of the output shaft 41 (described later) located below the motor shaft 21a. The output flange 42 extends radially outward from, for example, the upper end 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, multiple fixing holes 42a are arranged around the motor axis J1. More specifically, the multiple fixing holes 42a are arranged at equal intervals around the motor axis J1. For example, eight fixing holes 42a are provided. The fixing holes 42a are circular when viewed along the axial direction.

[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. As a result, the plurality of protrusions 43 protrude axially from the output flange portion 42 toward the external gear 31. Figure 2 As shown, a plurality of protrusions 43 are arranged around the motor axis J1. The plurality of protrusions 43 are arranged at equal intervals around the circumference, for example. For example, eight protrusions 43 are provided.

[0039] like Figure 1 As shown, multiple protrusions 43 are inserted from below into the multiple holes 31b. 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 circumferential surface of the protrusion 43 is in contact with the inner surface of the hole 31b. The multiple protrusions 43 support the externally toothed gear 31 via the inner surface of the hole 31b so that it can swing about the motor axis J1.

[0040] The output unit 40 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. In other words, 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 axially along the motor shaft 21a. It is coaxially arranged with the motor shaft 21a. That is, the output shaft 41 is rotatable about the motor axis J1. The output shaft 41 is rotatably supported by a first bearing 51 and a second bearing 52. The output shaft 41 includes a connecting portion 41a and an extending portion 41b.

[0042] The connecting portion 41a is located below 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 inserted into the interior of the hole portion 11e, for example. 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 about the motor axis J1. Thus, the first bearing 51 rotatably supports the portion of the output shaft 41 located below the motor shaft 21a.

[0043] The connecting portion 41a has a connecting recess 41c that is recessed upward from the lower end surface of the connecting portion 41a. 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 bottom, the connecting recess 41c is circular with the motor axis J1 as the center. A spline groove is provided on the inner circumferential surface of the connecting recess 41c. The driven shaft DS is inserted from the bottom inside the connecting recess 41c and connected. Thus, the driven shaft DS is connected to the connecting portion 41a. More specifically, the output shaft 41 is connected to the driven shaft DS by engaging 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 causes the driven shaft DS to rotate around the motor axis J1.

[0044] The extension portion 41b extends upward from the connecting portion 41a. More specifically, 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, cylindrical in shape, 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 this 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 bottom side and protrudes upward from the motor shaft 21a. Thus, the output shaft 41 extends from a position below the motor shaft 21a through the interior of the motor shaft 21a to a position above the motor shaft 21a. The extension portion 41b axially penetrates the hole 13a of the inner cover 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, within the second housing portion 11b. The upper end of the extension portion 41b is supported by the second bearing 52 for rotation about the motor axis J1. Thus, the second bearing 52 rotatably supports the portion of the output shaft 41 located above the motor shaft 21a.

[0046] The outer diameter of the extension portion 41b is, for example, slightly smaller than the inner diameter of the motor shaft 21a. In this embodiment, the extension portion 41b fits into the interior 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 allow the extension portion 41b to support the motor shaft 21a so that it can rotate about the motor axis J1. Thus, in this embodiment, the output shaft 41 rotatably supports the motor shaft 21a via the extension portion 41b. The outer circumferential surface of the portion of the output shaft 41 located inside the motor shaft 21a, i.e., a portion of the extension portion 41b, is radially opposed to and contactable with the inner circumferential surface of the motor shaft 21a. The contact between a portion of the inner circumferential surface of the motor shaft 21a and the outer circumferential surface of the output shaft 41 supports the motor shaft 21a in the radial direction. For example, lubricating oil may be provided in the radial gap between the output shaft 41 and the motor shaft 21a.

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

[0048] In this embodiment, the second detected portion 45 is mounted on the output shaft 41 via a mounting member 44. The mounting member 44 includes a fixed cylindrical portion 44a and a flange portion 44b. The fixed cylindrical portion 44a is, for example, cylindrical in shape, centered on the motor axis J1 and open on both axial sides. The fixed cylindrical portion 44a is fitted into and fixed to the outer circumferential surface of the 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 circumferential surface of the portion of the output shaft 41 that is located above the motor shaft 21a. The fixed cylindrical portion 44a is located axially between the motor shaft 21a and the second bearing 52. The flange portion 44b extends radially outward from the upper end of the fixed cylindrical portion 44a. The flange portion 44b is, for example, annular in shape, centered on the motor axis J1. The radial outer edge of the lower surface of the flange portion 44b is, for example, recessed upward.

[0049] The second detected portion 45 is, for example, in the shape of a ring centered on the motor axis J1. The second detected portion 45 is fixed to the radially outer edge 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 radially outward of the first detected portion 24. That is, in this 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 of the second detected portion 45 is arranged opposite to the upper side of the second rotation sensor 82. In this embodiment, when viewed in the axial direction, the second rotation sensor 82 and the second detected portion 45 overlap with 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 this embodiment, the lower end of the mounting member 44 corresponds to the lower end of the fixed cylindrical portion 44a. Washers 61 and 62 each have, for example, an annular shape centered on the motor axis J1. They each have, for example, a plate-like shape with the plate surface facing the axial direction. Washers 61 and 62 are, for example, sliding washers.

[0051] Washers 61 and 62 surround the extension 41b. The lower surface of washer 61 contacts the periphery of the extension 41b on the upper surface of the connecting portion 41a. The upper surface of washer 61 contacts the lower end surface of the motor shaft 21a. The lower surface of washer 62 contacts the upper end surface of the motor shaft 21a. The upper surface of 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 main body 91 and a peripheral wall portion 92. The partition member main body 91 is, for example, in the shape of an annulus centered on the motor axis J1. The partition member main 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 main 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 main 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 is fixed. The upper end of the peripheral wall portion 92 contacts the radial outer edge portion of the lower end face of the stator core 22a.

[0053] When power is supplied to the motor 20, causing the motor shaft 21a to rotate about the motor axis J1, the eccentric shaft portion 21d orbits circumferentially about the motor axis J1. This orbital motion of the eccentric shaft portion 21d is transmitted to the external gear 31 via the third bearing 53. The external gear 31 oscillates as the position at which the inner circumferential surface of the hole 31b and the outer circumferential surface of the protrusion 43 are internally inscribed changes. This causes the position at which the gear portion of the external gear 31 meshes with the gear portion of the internal gear 32 to change circumferentially. Consequently, the rotational force of the motor shaft 21a is transmitted to the internal gear 32 via the external gear 31.

[0054] In this embodiment, the internal gear 32 is fixed to the housing 10 and therefore does not rotate. Therefore, the reaction force of the rotational force transmitted to the internal gear 32 causes the external gear 31 to rotate about the eccentric axis J2. At this time, the direction of rotation of the external gear 31 is opposite to the direction of rotation of the motor shaft 21a. The rotation of the external gear 31 about the eccentric axis J2 is transmitted to the output flange 42 via the hole 31b and the protrusion 43. As a result, 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 transmission mechanism 30, as a speed reduction mechanism, is configured to transmit rotation via the multiple protrusions 43 described above. This allows the rotation of the output shaft 41 to be significantly reduced relative to the rotation of the motor shaft 21a. Consequently, the rotational torque of the output shaft 41 can be increased.

[0055] According to this 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 attempts to tilt radially relative to the output shaft 41, the motor shaft 21a is supported by the output shaft 41. This prevents the motor shaft 21a from tilting relative to the output shaft 41. Therefore, it is possible to prevent the motor shaft 21a and the output shaft 41 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 separate bearing to support the motor shaft 21a so that it can rotate. Therefore, the number of components of the electric actuator 100 can be reduced.

[0056] Furthermore, according to this embodiment, the outer circumferential surface of the portion of the output shaft 41 located inside the motor shaft 21a is radially opposed to and in contact with the inner circumferential surface of the motor shaft 21a. Therefore, even if the motor shaft 21a attempts to tilt radially relative to the output shaft 41, the outer circumferential surface of the output shaft 41 can directly support the inner circumferential surface of the motor shaft 21a. This makes it easier to increase the area supporting the motor shaft 21a, allowing the output shaft 41 to more stably support the motor shaft 21a. Consequently, mutual tilting of the motor shaft 21a and the output shaft 41 can be further suppressed. Furthermore, compared to a case where other components are provided radially between the motor shaft 21a and the output shaft 41, the number of components in the electric actuator 100 can be reduced.

[0057] Furthermore, according to this embodiment, the output shaft 41 extends from a position below the motor shaft 21a through the interior of the motor shaft 21a to a position above the motor shaft 21a. Therefore, the output shaft 41 can be arranged within the entire axial range of the interior of the motor shaft 21a. This allows the output shaft 41 to more appropriately support the motor shaft 21a. Consequently, it is possible to further prevent the motor shaft 21a and the output shaft 41 from tilting relative to each other.

[0058] Furthermore, according to this embodiment, a first bearing 51 is provided to rotatably support the portion of the output shaft 41 located below the motor shaft 21a, and a second bearing 52 is provided to rotatably support the portion of the output shaft 41 located above the motor shaft 21a. This allows for stable dual-arm support of the output shaft 41. This stable support of the output shaft 41 allows for more appropriate support of the motor shaft 21a. Consequently, it is possible to further suppress relative tilting of the motor shaft 21a and the output shaft 41.

[0059] Furthermore, since the output shaft 41 protrudes axially to both sides relative to the motor shaft 21a, the first and second bearings 51, 52 supporting the output shaft 41 on both axial sides are easily retained in the housing 10. This reduces the structural complexity of the housing 10 and facilitates assembly of the first and second bearings 51, 52. Thus, by adopting a structure in which the output shaft 41 is supported by the first and second bearings 51, 52, and the motor shaft 21a is supported by the output shaft 41, the structural complexity of the electric actuator 100 can be reduced, and assembly of the electric actuator 100 can be facilitated, compared to, for example, a structure in which the output shaft 41 is supported by the motor shaft 21a, which is supported by bearings.

[0060] Furthermore, according to this embodiment, the housing 10 includes a housing body 11 with an upper opening, and a 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. In other words, the second bearing 52 can be held by the cover 12 closing the upper opening of the housing body 11. Therefore, the number of components of the electric actuator 100 can be reduced compared to a case where a separate component is provided to hold the second bearing 52.

[0061] Furthermore, according to this embodiment, the substrate 80 includes a through-hole 80a through which the upper portion of the output shaft 41 passes axially. This allows a structure in which the substrate 80 is positioned axially between the cover 12 and the motor 20, and the upper end of the output shaft 41 is held by the second bearing 52 held by the cover 12. Furthermore, the substrate 80 can be radially enlarged. This makes it easier to secure space 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).

[0062] Furthermore, according to this embodiment, the first detected portion 24, whose rotation is detected by the first rotation sensor 81, is provided in the 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 in the portion of the output shaft 41 located above the motor shaft 21a. Therefore, both the first rotation sensor 81 and the second rotation sensor 82 can be arranged in the upper portion of the interior of the housing 10. This facilitates assembly of the first rotation sensor 81 and the second rotation sensor 82, compared to, for example, a case where the first rotation sensor 81 and the second rotation sensor 82 are arranged on different axial sides within the housing 10. Specifically, in this embodiment, since both the first rotation sensor 81 and the second rotation sensor 82 can be placed within the second housing portion 11b, compared to, for example, a case where the second rotation sensor 82 is placed within the first housing portion 11a, there is no need to route the wiring of the second rotation sensor 82 from within the first housing portion 11a to the substrate 80 within the second housing portion 11b. Consequently, the man-hours and time required to assemble the first and second rotation sensors 81, 82 can be reduced. Furthermore, compared to, for example, a case where the housing 10 is provided with a structure for routing wiring from within the first housing portion 11a to the second housing portion 11b, the complexity of the housing 10 can be minimized.

[0063] As described above, in a configuration 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 hollow, and the output shaft 41 can be made to extend through the interior of the motor shaft 21a and project above the motor shaft 21a. Specifically, by extending a portion of the output shaft 41 connected to the transmission mechanism 30 connected to the lower side of the motor shaft 21a through the interior of the motor shaft 21a to a position above the motor shaft 21a, the second detected portion 45 can be positioned above the motor shaft 21a, and the second rotation sensor 82 for detecting the second detected portion 45 can be positioned in the upper portion of the housing 10.

[0064] Furthermore, according to this embodiment, the first rotation sensor 81 and the second rotation sensor 82 are mounted on the substrate 80. Therefore, by placing the substrate 80, to which the first rotation sensor 81 and the second rotation sensor 82 are mounted, within the housing 10, the first rotation sensor 81 and the second rotation sensor 82 can be collectively placed within the housing 10. This further reduces the man-hours and time required to assemble the first rotation sensor 81 and the second rotation sensor 82.

[0065] Furthermore, according to this 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. Specifically, the first rotation sensor 81 and the second rotation sensor 82 are mounted on opposite sides of the substrate 80 in the axial direction. Therefore, compared to a 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 easier to secure areas on the substrate 80 for mounting each rotation sensor.

[0066] Furthermore, since the second detected portion 45 is disposed on the output shaft 41 above the motor shaft 21a, the first detected portion 24 disposed on the motor shaft 21a can be easily positioned below the second detected portion 45. Consequently, by mounting the first rotation sensor 81 on the lower surface of the substrate 80 and the second rotation sensor 82 on the upper surface of the substrate 80, it is easy to position each rotation sensor close to each detected portion. This allows each rotation sensor to more appropriately detect the rotation of each detected portion. Consequently, the accuracy of each rotation sensor's rotation detection of each shaft can be improved.

[0067] Furthermore, according to this embodiment, when viewed axially, the first rotation sensor 81 and the first detected portion 24 overlap, and when viewed axially, the second rotation sensor 82 and the second detected portion 45 overlap. Therefore, the first rotation sensor 81 and the first detected portion 24 can be axially opposed, making it easier for the first rotation sensor 81 to detect the rotation of the first detected portion 24. Furthermore, when the second rotation sensor 82 and the second detected portion 45 are axially opposed, making it easier for the second rotation sensor 82 to detect the rotation of the second detected portion 45. Consequently, the accuracy of rotation detection for each axis by each rotation sensor can be further improved.

[0068] Furthermore, the radial positions of the first rotation sensor 81 and the second rotation sensor 82 differ from each other, and the radial positions of the first detected portion 24 and the second detected portion 45 differ from each other. Therefore, for example, when the first detected portion 24 and the second detected portion 45 are magnets, and the first rotation sensor 81 and the second rotation sensor 82 are magnetic sensors, as in this embodiment, interference between the magnetic field of the other detected portion and the other sensor can be suppressed. This allows each rotation sensor to more appropriately detect the rotation of each detected portion. Consequently, the accuracy of each rotation sensor's rotation detection of each axis can be further improved.

[0069] Furthermore, according to this 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, washers 61 and 62 can press the motor shaft 21a from both sides in the axial direction. This prevents axial displacement of the motor shaft 21a relative to the output shaft 41. Furthermore, compared to a case where both axial ends 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, thereby facilitating smooth relative rotation of the motor shaft 21a and the output shaft 41. In particular, by configuring washers 61 and 62 as sliding washers, the motor shaft 21a and the output shaft 41 can rotate more smoothly relative to each other.

[0070] Furthermore, according to this 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 using the magnetic fields generated by the first detected portion 24 and the second detected portion 45. Furthermore, as described above, the improvement in rotation detection accuracy can be effectively achieved by radially staggering the first rotation sensor 81 and the first detected portion 24 from the second rotation sensor 82 and the second detected portion 45.

[0071] The present invention is not limited to the above-mentioned embodiment, and other structures and methods can be adopted within the scope of the technical concept of the present invention. Alternatively, the motor shaft supports the output shaft so that it can rotate. 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, the motor shaft can be supported by a bearing, and the output shaft can be not supported by a bearing. Other components can also be provided between the inner circumference of the motor shaft and the outer circumference of the output shaft. In this case, one of the motor shaft and the output shaft can also support the other of the motor shaft and the output shaft so that it can rotate via the other component. In addition, in this case, the other component can also be a bearing such as a ball bearing, a needle bearing, or a sliding bearing. Alternatively, the motor shaft does not support the output shaft and the output shaft does not support the motor shaft. In this case, the motor shaft and the output shaft can also be supported by bearings so that they can rotate. The type of the first bearing, the type of the second bearing, and the type of the third bearing are not particularly limited.

[0072] The first detected part may be any part as long as its 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 its 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. The first rotation sensor may also be a resolver stator and the first detected part may be a resolver rotor. The second rotation sensor may also be a resolver stator and the second detected part may be a resolver 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 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 the one axial side (lower side) of the substrate. The first and second rotation sensors may also be mounted on different components. The first and second rotation sensors may also be positioned on different axial sides within the housing. The first and second rotation sensors may not be provided. Washers may not be provided between the motor shaft and the coupling 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 motor shaft's rotation. If the transmission mechanism is a speed-reducing mechanism, the structure of the speed-reducing mechanism is not particularly limited. Alternatively, multiple protrusions may be provided on the externally toothed gear, and multiple holes may be provided in the output flange. In this case, the protrusions project from the externally toothed gear toward the output flange and are inserted into the holes.

[0075] The applications of the electric actuator of the present invention are not particularly limited. The electric actuator may also be installed in a shift-by-wire actuator system driven by a driver's shift operation. Furthermore, the electric actuator may be installed in equipment other than vehicles. Furthermore, the various configurations described above in this specification may be combined as appropriate within the scope of non-inconsistency.

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; 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; a mounting member fixed to an outer peripheral surface of a portion of the output shaft located axially on the other side of the motor shaft; a second rotation sensor capable of detecting the rotation of the output shaft; a substrate on which the second rotation sensor is mounted; a second detected portion, which is mounted on the output shaft via the mounting member and detects rotation thereof by the second rotation sensor; a first bearing and a second bearing that rotatably support the output shaft; and 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 and closing the opening on the other axial side of the housing body, The motor shaft is a hollow 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 output shaft has: a connecting portion connected to the driven shaft; and an extension portion extending from the connecting portion to the other axial side and passing into the interior of the motor shaft, The first bearing rotatably supports a portion of the output shaft located axially closer to the motor shaft, and the first bearing is held by the housing body. The second bearing rotatably supports a portion of the output shaft located axially to the other side of the motor shaft, and the second bearing is held by the cover. 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.

2. The electric actuator according to claim 1, wherein The base plate has a through hole through which a portion of the output shaft on the other axial side passes in the axial direction.

3. The electric actuator according to claim 2, wherein: The electric actuator further includes a first rotation sensor capable of detecting the rotation of the motor 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. The second detection portion is provided at a portion of the output shaft located on the other side of the motor shaft in the axial direction. The first rotation sensor is mounted on the substrate.

4. The electric actuator according to claim 3, wherein: One of the first rotation sensor and the second rotation sensor is mounted on one axial side surface of the substrate. The other of the first rotation sensor and the second rotation sensor is mounted on the surface on the other axial side of the substrate.

5. The electric actuator according to claim 4, wherein: The first rotation sensor and the second rotation sensor have radial positions different from each other.

6. The electric actuator according to any one of claims 1 to 5, 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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