Electric actuator, and actuator device

Abstract

To provide an electric actuator capable of suppressing rotation of an output shaft even if rotational torque is applied to the output shaft.SOLUTION: A transmission mechanism comprises: an external tooth gear and an internal tooth gear to which rotation of a motor shaft is transmitted; and a flange part which transmits rotation of the external tooth gear to an output shaft. The external tooth gear includes a plurality of through-hole parts. A plurality of protrusions is provided in the flange part. The plurality of protrusions is inserted into the through-hole parts which are different from each other. The plurality of through-hole parts includes: an inner end portion which is a radially inside end portion; an outer end portion which is a radially outside end portion; an inside circular arc portion passing the inner end portion; a first outside portion connecting the inside circular arc portion with the outer end portion; and a second outside portion connecting the inside circular arc portion with the outer end portion. When a distance between the inner end portion and the outer end portion is defined as a diameter and a circle passing both the inner end portion and the outer end portion is defined as a virtual circle, the inside circular arc portion overlaps the virtual circle, and at least one of the first outside portion and the second outside portion is positioned on the side of a center of the virtual circle rather than the virtual circle.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an electric actuator and an actuator device. [Background technology]

[0002] BACKGROUND ART Electric actuators that drive objects such as parking switch mechanisms based on vehicle operations are known (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-247798 Summary of the Invention [Problem to be solved by the invention]

[0004] In the electric actuator described above, when a rotational torque is applied to the output shaft connected to the object, the output shaft may rotate, which may cause the position of the components constituting the object to fluctuate. If a detent plate, stopper, or other components are provided on the object to suppress the positional fluctuation of the components constituting the object, the number of parts of the object and the manufacturing cost increase.

[0005] In view of the above circumstances, an object of the present invention is to provide an electric actuator and an actuator device that can prevent the output shaft from rotating even when a rotational torque is applied to the output shaft. [Means for solving the problem]

[0006] One aspect of the electric actuator of the present invention includes a motor having a motor shaft rotatable about a motor axis, a transmission mechanism connected to the motor shaft, an output shaft to which rotation of the motor shaft is transmitted via the transmission mechanism, and a case accommodating the motor, the transmission mechanism, and the output shaft. The motor shaft has an eccentric shaft portion centered on an eccentric axis extending in the direction of the motor axis. The transmission mechanism includes an annular external gear connected to the outer peripheral surface of the eccentric shaft portion via a bearing and to which rotation of the motor shaft is transmitted, an annular internal gear disposed radially outward of the external gear and fixed to the case, and an annular flange portion that transmits rotation of the external gear to the output shaft. The external gear has a plurality of through-holes that axially penetrate the external gear and are arranged around the motor axis. The flange portion has a plurality of protrusions that axially protrude from the flange portion and are arranged around the motor axis. Each of the multiple protrusions is inserted into a different through-hole portion. A portion of the internal gear portion provided along the inner peripheral surface of the internal gear meshes with a portion of the external gear portion provided along the outer peripheral surface of the external gear. The external gear portion and the internal gear portion are each an involute gear. Each of the multiple through-hole portions has an inner end portion that is the radially inner end, an outer end portion that is the radially outer end, an arc-shaped inner arc portion that passes through the inner end portion and protrudes radially inward, a first outer portion that connects one end of the inner arc portion to the outer end, and a second outer portion that connects the other end of the inner arc portion to the outer end. When viewed from the axial direction, the distance between the inner end portion and the outer end portion is the diameter, and a circle that passes through both the inner end portion and the outer end portion is defined as a virtual circle, the inner arc portion overlaps the virtual circle, and at least one of the first outer portion and the second outer portion is curved and located closer to the center of the virtual circle than the virtual circle. is.

[0007] One aspect of the actuator device of the present invention includes the electric actuator described above and an object connected to the output shaft, wherein the electric actuator drives the object based on a shift operation of a vehicle. [Effects of the Invention]

[0008] According to one aspect of the present invention, in an electric actuator and an actuator device, even if a rotational torque is applied to the output shaft, the output shaft can be prevented from rotating. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view showing a drive device according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing an electric actuator according to one embodiment. [Figure 3] FIG. 3 is a first view of the transmission mechanism of the embodiment as seen from one axial side. [Figure 4] FIG. 4 is a first view of a part of the transmission mechanism of one embodiment as seen from one axial side. [Figure 5] FIG. 5 is a second view of the transmission mechanism of the embodiment as seen from one axial side. [Figure 6] FIG. 6 is a third view of the transmission mechanism of the embodiment as viewed from one axial side. [Figure 7] FIG. 7 is a second view of a part of the transmission mechanism of the embodiment as seen from one axial side. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the following embodiment, as an example, a case will be described in which the object displaced and driven by the electric actuator 9 based on vehicle operation is the parking switch mechanism 70. A drive unit 90 will be described as a device equipped with the electric actuator 9 and parking switch mechanism 70 of this embodiment. Note that the present invention is also applicable to actuator devices used in continuously variable transmissions connected to a hydraulic motor in a closed circuit, such as so-called HST (Hydraulic Static Transmission).

[0011] In the following description, the vertical direction is defined based on the positional relationship when the drive device 90 of this embodiment shown in FIG. 1 is mounted on a vehicle positioned on a horizontal road surface. The drawings also appropriately illustrate an XYZ coordinate system as a three-dimensional Cartesian coordinate system. In the XYZ coordinate system, the Z axis direction is the vertical direction with the +Z side as the upper side and the −Z side as the lower side. The X axis direction is a direction perpendicular to the Z axis direction and is the direction in which the motor axis line J1 of the electric actuator 9, shown appropriately in each drawing, extends. The motor axis line J1 is a virtual axis. In this embodiment, the +X side is one side in the axial direction, and the −X side is the other side in the axial direction. The Y axis direction is a direction perpendicular to both the X axis direction and the Z axis direction and is the left-right direction of the vehicle. In this embodiment, the +Y side is one side in the left-right direction of the vehicle, and the −Y side is the other side in the left-right direction of the vehicle.

[0012] In this embodiment, the direction parallel to the Z-axis direction is referred to as the "vertical direction," the direction parallel to the X-axis direction is referred to as the "axial direction," and the direction parallel to the Y-axis direction is referred to as the "left-right direction." The positive side (+Z side) of the Z-axis direction is referred to as the "upper side," and the negative side (-Z side) of the Z-axis direction is referred to as the "lower side." The positive side (+X side) of the X-axis direction is referred to as the "one axial side," and the negative side (-X side) of the X-axis direction is referred to as the "other axial side." The positive side (+Y side) of the Y-axis direction is simply referred to as the "one left-right side," and the negative side (-Y side) of the Y-axis direction is simply referred to as the "other left-right side." Note that the terms "upper side" and "lower side" are merely names used to describe the relative positional relationships of the various parts, and the actual positional relationships may be other than those indicated by these names.

[0013] In the following description, the radial direction centered on the motor axis J1 will be simply referred to as the "radial direction," and the circumferential direction centered on the motor axis J1 will be simply referred to as the "circumferential direction." The circumferential direction is indicated by the arrow θ1 in each drawing. The side of the circumferential direction toward which the arrow θ1 points (+θ1 side) will be referred to as the "one circumferential side." The opposite side of the circumferential direction toward which the arrow θ1 points (-θ1 side) will be referred to as the "other circumferential side." The one circumferential side is the side that advances clockwise around the motor axis J1 as viewed from one axial side. The other circumferential side is the side that advances counterclockwise around the motor axis J1 as viewed from one axial side.

[0014] The first direction D1 shown in each drawing is a direction perpendicular to the axial direction. In the following description, the side toward which the arrow of the first direction D1 points (+D1 side) will be referred to as "one side of the first direction D1," and the side opposite to the side toward which the arrow of the first direction D1 points (-D1 side) will be referred to as "the other side of the first direction D1." The second direction D2 shown in each drawing as appropriate is a direction perpendicular to both the axial direction and the first direction D1. In the following description, the side toward which the arrow of the second direction D2 points (+D2 side) will be referred to as "one side of the second direction D2," and the side opposite to the side toward which the arrow of the second direction D2 points (-D2 side) will be referred to as "the other side of the second direction D2."

[0015] 1 is mounted on a vehicle powered by a motor, such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHV), or an electric vehicle (EV). The drive device 90 includes a housing 92, a drive motor 93, a reduction gear 94, a differential 95, a parking lock gear 96, and an actuator device 100. The actuator device 100 includes a parking switch mechanism 70 and an electric actuator 9.

[0016] The housing 92 accommodates the drive motor 93, the reduction gear 94, the differential gear 95, and the parking switch mechanism 70 inside. Although not shown, oil is contained inside the housing 92. The reduction gear 94 is connected to the drive motor 93. The differential gear 95 is also connected to the reduction gear 94 and transmits torque output from the drive motor 93 to an axle of the vehicle (not shown). The park lock gear 96 is connected to the axle of the vehicle via the reduction gear 94 and the differential gear 95. The park lock gear 96 has a plurality of teeth 96a.

[0017] The parking switching mechanism 70 is driven by the electric actuator 9 based on the shift operation of the vehicle. The parking switching mechanism 70 switches the parking lock gear 96 between a locked state and an unlocked state. The parking switching mechanism 70 locks the parking lock gear 96 when the vehicle is in parking gear, and unlocks the parking lock gear 96 when the vehicle is in a gear other than parking. Examples of situations where the vehicle is in a gear other than parking include situations where the vehicle is in drive, neutral, reverse, etc. The parking switching mechanism 70 has a parking shaft 78, a rod 76, an annular member 73, a parking lock arm 77, and a support member 75.

[0018] The parking shaft 78 is coupled to the electric actuator 9 and rotated about the motor axis J1 by the electric actuator 9. In this embodiment, the parking shaft 78 extends in the axial direction along the motor axis J1. As shown in Fig. 2, one axial end of the parking shaft 78 is provided with a plurality of spline grooves extending in the axial direction and arranged along the circumferential direction.

[0019] As shown in FIG. 1, the rod 76 is connected to a parking shaft 78. When the parking shaft 78 rotates around the motor axis J1, the rod 76 moves in the left-right direction (Y-axis direction). The annular member 73 is connected to the rod 76. The annular member 73 has a generally conical shape extending in the left-right direction. The annular member 73 is movable in the left-right direction. Although not shown in the figure, the outer peripheral surface of the annular member 73 is a tapered surface whose outer diameter increases toward one side in the left-right direction (+Y side). When the rod 76 moves in the left-right direction, the annular member 73 moves in the left-right direction together with the rod 76.

[0020] The support member 75 supports the annular member 73 so as to be movable in the left-right direction. In this embodiment, the support member 75 supports the annular member 73 from below. The support member 75 is fixed to the housing 92.

[0021] The park lock arm 77 is disposed above the annular member 73 and below the park lock gear 96. The park lock arm 77 is supported by a cylindrical support shaft 79 that extends left and right around a rotation axis J3 that also extends left and right, so as to be rotatable about the rotation axis J3. The park lock arm 77 has an arm main body 77a, a meshing portion 77b, and a contact portion 77c.

[0022] The arm main body 77a extends from the support shaft 79 to one side in the axial direction. The contact portion 77c protrudes to one side in the axial direction from the end portion on one side of the arm main body 77a in the axial direction. The contact portion 77c contacts the outer peripheral surface of the annular member 73 from above. The meshing portion 77b protrudes upward from the arm main body 77a. A coil spring (not shown) is attached to the support shaft 79. The coil spring applies an elastic force to the park lock arm 77 around the rotation axis J3 in a counterclockwise direction when viewed from one side in the left-right direction (+Y side).

[0023] As described above, the outer diameter of the annular member 73 increases from the other side in the left-right direction (-Y side) to one side in the left-right direction (+Y side). Therefore, when the annular member 73 moves to the other side in the left-right direction as the parking shaft 78 rotates, the contact portion 77c is lifted upward, and the parking lock arm 77 rotates clockwise around the rotation axis J3 as viewed from the one side in the left-right direction (+Y side). As a result, although not shown in the figures, the meshing portion 77b meshes with the teeth 96a of the parking lock gear 96, and the parking lock gear 96 is put into a locked state.

[0024] Furthermore, when the annular member 73 moves to one side in the left-right direction (the +Y side) in conjunction with the rotation of the parking shaft 78, the contact portion 77c, which had been lifted by the outer circumferential surface of the annular member 73, moves downward due to its own weight and the elastic force of a coil spring (not shown), and the parking lock arm 77 rotates counterclockwise around the rotation axis J3 as viewed from the one side in the left-right direction (the +Y side). As a result, the meshing portion 77b disengages from between the tooth portions 96a, and the parking lock gear 96 enters an unlocked state. As a result, when the electric actuator 9 is driven based on a shift operation of the vehicle, the parking lock arm 77 rotates about the rotation axis J3 via the parking shaft 78, the rod 76, and the annular member 73, and the parking lock gear 96 can be switched between a locked state and an unlocked state.

[0025] As will be described later, the electric actuator 9 of this embodiment can prevent the output shaft 46, which is connected to the parking shaft 78, from rotating even when rotational torque is applied from the parking shaft 78 to the output shaft 46. Therefore, even when rotational torque is applied from the parking shaft 78 to the output shaft 46, fluctuations in the position of the parking lock arm 77 can be prevented. Therefore, the parking switch mechanism 70 of this embodiment is not provided with a member such as a detent plate or a stopper member that suppresses fluctuations in the position of the parking lock arm 77.

[0026] The electric actuator 9 drives the parking switching mechanism 70, i.e., an object, based on the shift operation of the vehicle. In this embodiment, the electric actuator 9 moves the parking lock arm 77 upward or downward via a member such as a parking shaft 78, thereby switching the parking lock gear 96 between a locked state and an unlocked state.

[0027] 2, the electric actuator 9 includes a case 10, a motor 20, a transmission mechanism 30, an output shaft 46, a first bearing 51, a second bearing 52, a third bearing 53, a control board 80, a rotation sensor 81, and a sensor magnet 45. Each of the first bearing 51, the second bearing 52, and the third bearing 53 is, for example, a ball bearing.

[0028] The case 10 accommodates the various components of the electric actuator 9, including the motor 20, the transmission mechanism 30, and the output shaft 46. The case 10 includes a case body 11 and a cover member 12. The case body 11 is substantially cylindrical and has its center on the motor axis J1. The case body 11 has an opening 11h that opens to one axial side. The case body 11 includes a first housing portion 11a and a second housing portion 11b.

[0029] The first housing portion 11a is a portion on the other axial side of the case body 11. The first housing portion 11a has a bottom portion 11c located on the other axial side and a peripheral wall portion 11d extending from the radial outer edge of the bottom portion 11c to one axial side. A hole portion 11e is provided in the bottom portion 11c, penetrating the bottom portion 11c in the axial direction. The hole portion 11e is a substantially circular hole centered on the motor axis J1. The portion on the one axial side of the hole portion 11e constitutes a first bearing holder portion 11f that holds the first bearing 51.

[0030] The second housing portion 11b is a portion on one axial side of the case body 11. The second housing portion 11b is axially connected to the first housing portion 11a. The second housing portion 11b is cylindrical and opens to one axial side. The inner peripheral surface of the second housing portion 11b is provided with a step having a step surface 11g facing one axial side.

[0031] The cover member 12 is fixed to one axial end of the case body 11. The cover member 12 closes the opening 11h of the case body 11 from one axial side. The cover member 12 has a cover main body portion 12a that closes the opening 11h from one axial side, and a second bearing holder portion 12b that protrudes from the cover main body portion 12a to the other axial side. The second bearing holder portion 12b is cylindrical and has its center on the motor axis J1 and opens to the other axial side. The second bearing 52 is held on the inner circumferential surface of the second bearing holder portion 12b.

[0032] The motor 20 has a rotor 21 and a stator 22. The rotor 21 is rotatable about the motor axis J1. The rotor 21 has a motor shaft 23, a rotor core 24a, and a magnet 24b. The motor shaft 23 is rotatable about the motor axis J1. The motor shaft 23 is substantially cylindrical and extends axially about the motor axis J1. The motor shaft 23 is a hollow shaft. The motor shaft 23 is open on both sides in the axial direction. The motor shaft 23 extends axially across the interior of the first housing portion 11a and the interior of the second housing portion 11b. The motor shaft 23 has a main body portion 23a and an eccentric shaft portion 23b.

[0033] The main body portion 23a is a portion on one axial side of the motor shaft 23. A rotor core 24a is fixed to the outer peripheral surface of the main body portion 23a. One axial end of the main body portion 23a is disposed inside the second housing portion 11b. The rest of the main body portion 23a other than the one axial end is disposed inside the first housing portion 11a.

[0034] The eccentric shaft portion 23b is the portion on the other axial side of the motor shaft 23. The eccentric shaft portion 23b is axially connected to the main body portion 23a. The eccentric shaft portion 23b is disposed inside the first housing portion 11a. The eccentric shaft portion 23b is disposed on the other axial side of the rotor core 24a. When viewed from the axial direction, the inner peripheral surface of the eccentric shaft portion 23b is circular and centered on the motor axis J1. When viewed from the axial direction, the outer peripheral surface of the eccentric shaft portion 23b is circular and centered on an eccentric axis J2 that is eccentric with respect to the motor axis J1. The eccentric axis J2 is a virtual axis that extends in the same direction as the motor axis J1. When the motor shaft 23 rotates, the eccentric axis J2 revolves around the motor axis J1. An inner ring of a third bearing 53 is fitted and fixed to the outer peripheral surface of the eccentric shaft portion 23b. As a result, the third bearing 53 is fixed to the eccentric shaft portion 23b of the motor shaft 23.

[0035] The rotor core 24a has an annular shape centered on the motor axis J1. The rotor core 24a is disposed inside the first housing portion 11a. The rotor core 24a is fixed to the outer peripheral surface of the main body portion 23a. The magnet 24b is fixed to the outer peripheral surface of the rotor core 24a. In this embodiment, a plurality of magnets 24b are disposed at intervals along the circumferential direction.

[0036] The stator 22 is disposed radially outside the rotor 21 with a gap between them. The stator 22 includes an annular stator core 22a that surrounds the rotor core 24a from the radial outside, an insulator 22b attached to the stator core 22a, and a plurality of coil portions 22c attached to 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 peripheral wall portion 11d. This fixes the stator 22 to the case 10.

[0037] The transmission mechanism 30 is disposed inside the first housing portion 11a. The transmission mechanism 30 is disposed on the other axial side of the rotor core 24a and the stator 22. The transmission mechanism 30 is coupled to the motor shaft 23 and the output shaft 46. The transmission mechanism 30 transmits the rotation of the motor shaft 23 about the motor axis J1 to the output shaft 46. That is, the rotation of the motor shaft 23 is transmitted to the output shaft 46 via the transmission mechanism 30. In this embodiment, the transmission mechanism 30 is a reduction mechanism that reduces the rotation of the motor shaft 23 and transmits it to the output shaft 46. The transmission mechanism 30 may be a speed-up mechanism that increases the rotation of the motor shaft 23 and transmits it to the output shaft 46, or may be a transmission mechanism that transmits rotation at the same rotational speed as the rotation of the motor shaft 23 to the output shaft 46. The transmission mechanism 30 has an external gear 31, an internal gear 32, a flange portion 42, and multiple protrusions 43.

[0038] The external gear 31 is annular and centered on the eccentric axis J2. In this embodiment, the external gear 31 is annular and centered on the eccentric axis J2. The external gear 31 is fitted to the outer ring of the third bearing 53. The external gear 31 is connected to the outer peripheral surface of the eccentric shaft portion 23b via the third bearing 53. This allows the rotation of the motor shaft 23 to be transmitted to the external gear 31. The external gear 31 is rotatable relative to the motor shaft 23 around the eccentric axis J2. As shown in FIG. 3, the external gear 31 has a plurality of through-hole portions 34 and an external gear portion 31c.

[0039] In this embodiment, each of the multiple through-hole portions 34 is a hole that penetrates the external gear 31 in the axial direction. The through-hole portions 34 are arranged surrounding the motor axis J1. The through-hole portions 34 are arranged at approximately equal intervals along the circumferential direction. In this embodiment, eight through-hole portions 34 are provided. As shown in FIG. 4, each of the multiple through-hole portions 34 has an inner end portion 34a, an outer end portion 34b, an inner arc portion 34d, a first outer portion 34f, and a second outer portion 34h.

[0040] The inner end 34a is the radially inner end of the through-hole portion 34. The outer end 34b is the radially outer end of the through-hole portion 34. The imaginary circle Vc shown in FIG. 4 is a circle whose diameter is the distance between the inner end 34a and the outer end 34b when viewed in the axial direction, and which passes through the inner end 34a and the outer end 34b. The imaginary center Ch is the center of the imaginary circle Vc. The imaginary line Ls is an imaginary straight line that passes through the inner end 34a and the outer end 34b. In this embodiment, the imaginary line Ls passes through the eccentric axis J2 and the imaginary center Ch.

[0041] The inner arc portion 34d is a radially inner portion of the through-hole portion 34. The inner arc portion 34d has an arc shape that is centered on the imaginary center Ch and protrudes radially inward. When viewed from the axial direction, the inner arc portion 34d passes through the inner end portion 34a. When viewed from the axial direction, the inner arc portion 34d overlaps with the imaginary circle Vc. In this embodiment, the central angle αi of the inner arc portion 34d is 180° or greater. The central angle αi of the inner arc portion 34d may be smaller than 180°. In this embodiment, the central angle αi of the inner arc portion 34d is approximately 185°. When viewed from the axial direction, the shape of the inner arc portion 34d is line-symmetrical with respect to the imaginary line Ls as the axis of symmetry.

[0042] The first outer portion 34f and the second outer portion 34h are each a radially outer portion of the through-hole portion 34. When viewed in the axial direction, the first outer portion 34f has a curved shape connecting one end of the inner arc portion 34d and the outer end portion 34b. In the present embodiment, one end of the inner arc portion 34d is an end portion on the other circumferential side (-θ1 side) of the inner arc portion 34d. The second outer portion 34h has a curved shape connecting the other end of the inner arc portion 34d and the outer end portion 34b. In the present embodiment, the other end of the inner arc portion 34d is an end portion on one circumferential side (+θ1 side) of the inner arc portion 34d. The first outer portion 34f and the second outer portion 34h are connected to each other at the outer end portion 34b.

[0043] When viewed from the axial direction, the first outer portion 34f is located closer to the imaginary center Ch than the imaginary circle Vc, i.e., closer to the center of the imaginary circle Vc. As a result, at least one of the first outer portion 34f and the second outer portion 34h is located closer to the imaginary center Ch than the imaginary circle Vc. When viewed from the axial direction, the second outer portion 34h is located closer to the imaginary center Ch than the imaginary circle Vc. As a result, in this embodiment, each of the first outer portion 34f and the second outer portion 34h is located closer to the center of the imaginary circle Vc than the imaginary circle Vc. Note that when viewed from the axial direction, one of the first outer portion 34f and the second outer portion 34h may overlap with the imaginary circle Vc. In this embodiment, when viewed from the axial direction, the shape of the first outer portion 34f and the shape of the second outer portion 34h are line-symmetrical with respect to each other with the imaginary line Ls as the axis of symmetry. As described above, when viewed from the axial direction, the shape of the inner arc portion 34d is line-symmetrical with respect to the imaginary line Ls as the axis of symmetry. Therefore, when viewed from the axial direction, the shape of each of the multiple through-hole portions 34 is line-symmetric with respect to the imaginary line Ls as the axis of symmetry. When viewed from the axial direction, the shape of each of the multiple through-hole portions 34 does not have to be line-symmetric with respect to the imaginary line Ls as the axis of symmetry.

[0044] As shown in FIG. 3 , the external gear portion 31c is provided along the outer peripheral surface of the external gear 31. The external gear portion 31c is composed of a plurality of externally toothed portions 31d arranged along the outer peripheral surface of the external gear 31. In this embodiment, the external gear portion 31c is composed of 79 externally toothed portions 31d. That is, the number of teeth N1 of the external gear portion 31c is 79. The number of teeth N1 of the external gear portion 31c may be 78 or less or 80 or more. In this embodiment, the external gear portion 31c is an involute gear. A first imaginary line L1 is an imaginary line passing through the eccentric axis J2 and the pitch point of the externally toothed portion 31d when viewed from the axial direction. The pitch point of the externally toothed portion 31d is a portion of the tooth surface of the externally toothed portion 31d that contacts the internally toothed portion 32b of the internal gear 32, which will be described later. The first tangent line L3 is a tangent line that is tangent to the tooth flank of the external tooth portion 31d and is a tangent line that is tangent to the pitch point of the external tooth portion 31d. The angle between the first virtual line L1 and the first tangent line L3 is the pressure angle α1 of the external tooth portion 31d. In this embodiment, the pressure angle α1 of each of the multiple external tooth portions 31d is equal to or greater than 22° and equal to or less than 25.5°.

[0045] The internal gear 32 is disposed radially outside the external gear 31. The internal gear 32 surrounds the external gear 31 from the radial outside. The internal gear 32 is annular and centered on the motor axis J1. In this embodiment, the internal gear 32 is annular and centered on the motor axis J1. As shown in FIG. 2, the outer peripheral surface of the internal gear 32 is fixed to the inner peripheral surface of the peripheral wall portion 11d. This fixes the internal gear 32 to the case 10. As shown in FIG. 3, the internal gear 32 has an internal gear portion 32a.

[0046] The internal gear portion 32a is provided along the inner circumferential surface of the internal gear 32. The internal gear portion 32a is composed of a plurality of internal tooth portions 32b arranged along the inner circumferential surface of the internal gear 32. In this embodiment, the internal gear portion 32a is composed of 80 internal tooth portions 32b. That is, the number of teeth N2 of the internal gear portion 32a is 80. The number of teeth N2 of the internal gear portion 32a may be 79 or less or 81 or more. A portion of the internal gear portion 32a meshes with a portion of the external gear portion 31c. In this embodiment, the internal gear portion 32a is an involute gear. The second virtual line L2 is a virtual line connecting the motor axis J1 and the pitch point of the internal tooth portion 32b when viewed from the axial direction. The pitch point of the internal tooth portion 32b is the portion of the tooth surface of the internal tooth portion 32b that contacts the pitch point of the external tooth portion 31d. The second tangent line L4 is a tangent line that is tangent to the pitch point of the internal tooth portion 32b among the tangent lines that are tangent to the tooth flank of the internal tooth portion 32b. The angle between the second virtual line L2 and the second tangent line L4 is the pressure angle α2 of the internal tooth portion 32b. In this embodiment, the pressure angle α2 of each of the multiple internal tooth portions 32b is equal to or greater than 22° and equal to or less than 25.5°. The pressure angle α1 and the pressure angle α2 may be the same angle or different angles.

[0047] As shown in FIG. 2, the flange portion 42 is disposed on the other axial side of the external gear 31. The flange portion 42 is disposed axially apart from the external gear 31. The flange portion 42 is annular and centered on the motor axis J1. In this embodiment, the flange portion 42 is annular and centered on the motor axis J1. The flange portion 42 is fixed to a portion of the output shaft 46 that is on the other axial side of the motor shaft 23. The flange portion 42 is provided with a plurality of protrusions 43.

[0048] Each of the multiple protrusions 43 protrudes in the axial direction from the flange portion 42. In this embodiment, each of the multiple protrusions 43 is cylindrical and protrudes from the flange portion 42 toward one axial side. In this embodiment, the multiple protrusions 43 and the flange portion 42 are part of the same single member. As shown in FIG. 3 , the outer diameter of each of the protrusions 43 is smaller than the inner diameter of each of the through-hole portions 34. The multiple protrusions 43 are arranged surrounding the motor axis J1. In this embodiment, eight protrusions 43 are provided. The protrusions 43 are provided at approximately equal intervals along the circumferential direction. Each of the multiple protrusions 43 is inserted into a different through-hole portion 34 from the other axial side. Each protrusion 43 supports the external gear 31 via the inner surface of the through-hole portion 34 so that the external gear 31 can swing about the motor axis J1.

[0049] The output shaft 46 outputs the driving force of the electric actuator 9 to the parking switch mechanism 70. As shown in FIG. 2 , the output shaft 46 extends in the axial direction. The output shaft 46 is rotatable about the motor axis J1. The rotation of the motor shaft 23 is transmitted to the output shaft 46 via the transmission mechanism 30. The output shaft 46 passes through the motor shaft 23 in the axial direction. The output shaft 46 protrudes from the motor shaft 23 on both axial sides. That is, a portion of the output shaft 46 is located inside the motor shaft 23. The output shaft 46 and the flange portion 42 may be part of the same single member. The output shaft 46 has an output shaft main body 41 and an attachment member 44 fixed to the outer circumferential surface of the output shaft main body 41.

[0050] The output shaft body 41 extends in the axial direction. The output shaft body 41 is supported rotatably around the motor axis J1 by a first bearing 51 and a second bearing 52. The output shaft body 41 has a connecting portion 41a and an extending portion 41b.

[0051] The connecting portion 41a is a portion on the other axial side of the output shaft main body 41. The connecting portion 41a is cylindrical and extends axially with the motor axis J1 as its center. The connecting portion 41a opens on the other axial side. The other axial end of the connecting portion 41a is inserted into the hole 11e. The one axial end of the connecting portion 41a is inserted into the eccentric shaft portion 23b. The connecting portion 41a is supported by a first bearing 51 so as to be rotatable around the motor axis J1.

[0052] A portion of one axial side of the parking shaft 78 can be inserted into the interior of the connecting portion 41a from the other axial side. When a plurality of spline grooves provided on the outer circumferential surface of the parking shaft 78 are fitted into a plurality of spline grooves provided on the inner circumferential surface of the connecting portion 41a, the connecting portion 41a and the parking shaft 78 are connected to each other. As a result, the parking switch mechanism 70, i.e., the object, is connected to the output shaft 46. The rotation of the motor shaft 23 is transmitted to the parking shaft 78 via the output shaft 46. As a result, the electric actuator 9 drives the parking switch mechanism 70.

[0053] The extension portion 41b is a portion on one axial side of the output shaft main body 41. The extension portion 41b is cylindrical and extends axially around the motor axis J1. The extension portion 41b is axially connected to the connecting portion 41a. The extension portion 41b passes axially through the interior of the motor shaft 23. The portion on one axial side of the extension portion 41b protrudes from the motor shaft 23 to one axial side. The end portion on one axial side of the extension portion 41b is supported by the second bearing 52 so as to be rotatable around the motor axis J1.

[0054] In this embodiment, the outer diameter of the extension 41b is slightly smaller than the inner diameter of the main body 23a of the motor shaft 23. The extension 41b is loosely fitted inside the main body 23a. For example, lubricating oil may be placed in the gap between the extension 41b and the main body 23a.

[0055] The mounting member 44 is fixed to a portion of the outer circumferential surface of the extension portion 41b on one axial side of the motor shaft 23. The mounting member 44 has a fixed cylindrical portion 44a and an annular portion 44b. The fixed cylindrical portion 44a is cylindrical and has its center on the motor axis J1 and is open on both axial sides. The fixed cylindrical portion 44a is fixed to the outer circumferential surface of the extension portion 41b. The annular portion 44b is a generally annular plate that extends radially outward from the end of the fixed cylindrical portion 44a on the other axial side.

[0056] The sensor magnet 45 is annular and surrounds the motor axis J1. The sensor magnet 45 is fixed to the outer peripheral surface of the fixed cylindrical portion 44a. The radial outer edge of the sensor magnet 45 is located radially outward of the annular portion 44b and faces the rotation sensor 81 in the axial direction.

[0057] A washer 61 is disposed axially between the main body 23a of the motor shaft 23 and the connecting portion 41a of the output shaft 46. A washer 62 is disposed axially between the main body 23a and the annular portion 44b. The washers 61 and 62 are annular plates with their plate surfaces facing the axial direction. The washers 61 and 62 are, for example, slip washers. The washers 61 and 62 each reduce the frictional force between the motor shaft 23 and the output shaft 46. This increases the output efficiency of the electric actuator 9.

[0058] The control board 80 is disposed on one axial side of the stator 22. The control board 80 is fixed to the stepped surface 11g of the case 10. The control board 80 is plate-shaped and extends in the radial direction. Although not shown, the control board 80 is electrically connected to each of the multiple coil portions 22c of the stator 22. The control board 80 controls the power supplied to each of the multiple coil portions 22c. A through hole 80a is provided in the control board 80. When viewed from the axial direction, the through hole 80a has a circular shape centered on the motor axis J1. The extension portion 41b of the output shaft 46 passes through the through hole 80a in the axial direction. A rotation sensor 81 is attached to the control board 80.

[0059] The rotation sensor 81 is fixed to a surface of the control board 80 facing one axial side. The rotation sensor 81 faces the sensor magnet 45 in the axial direction. In this embodiment, the rotation sensor 81 is a magnetic sensor. The rotation sensor 81 is, for example, a Hall element such as a Hall IC. The rotation sensor 81 detects the magnetic field of the sensor magnet 45 to detect the rotation of the sensor magnet 45. In this way, the rotation sensor 81 detects the rotation of the output shaft 46.

[0060] When power is supplied from the control board 80 to the motor 20 and the motor shaft 23 rotates about the motor axis J1, the eccentric shaft portion 23b revolves circumferentially around the motor axis J1. The revolution of the eccentric shaft portion 23b is transmitted to the external gear 31 via the third bearing 53. The external gear 31 revolves around the motor axis J1 while changing the position at which the inner peripheral surface of the through-hole portion 34 contacts the outer peripheral surface of the protrusion 43. As the external gear 31 revolves around the motor axis J1, the meshing position between the external gear portion 31c of the external gear 31 and the internal gear portion 32a of the internal gear 32 changes circumferentially. As a result, the driving force of the motor shaft 23 is transmitted to the internal gear 32 via the external gear 31.

[0061] As described above, the internal gear 32 is fixed to the case 10. Therefore, the external gear 31 rotates around the eccentric axis J2 due to the reaction force of the driving force transmitted to the internal gear 32. In this embodiment, the rotation of the external gear 31 is decelerated relative to the rotation of the motor shaft 23.

[0062] The rotation of the external gear 31 about the eccentric axis J2 is transmitted to the flange portion 42 via the inner surface of the through-hole portion 34 and the protrusion 43, and the flange portion 42 rotates about the motor axis J1. As described above, the output shaft 46 is fixed to the flange portion 42, and therefore the output shaft 46 rotates together with the flange portion 42 about the motor axis J1. In other words, the rotation of the external gear 31 is transmitted to the output shaft 46 by the flange portion 42. In this way, the rotation of the motor shaft 23 is transmitted to the output shaft 46 via the transmission mechanism 30.

[0063] 4 and 5 , a first thrust force F1 that is a force that the internal gear 32 applies to the external gear 31 and a first pressure force Fp1 that is a force that the first protrusion 43a applies to the external gear 31 when a rotational torque directed toward the other circumferential side (-θ1 side) is applied to the output shaft 46 to reversely drive the electric actuator 9 will be described. When the electric actuator 9 is reversely driven, a rotational torque is applied to the output shaft 46 to rotate the output shaft 46 about the motor axis J1, and the rotation of the output shaft 46 is transmitted to the motor shaft 23 via the transmission mechanism 30 to drive the motor shaft 23 about the motor axis J1. When a rotational torque directed toward the other circumferential side is applied to the output shaft 46, the external gear 31 attempts to rotate about the eccentric axis J2 toward the other circumferential side. As shown by the arrow Rh in FIG. 5, the eccentric axis J2, which is the center of the external gear 31, attempts to revolve around the motor axis J1 toward one circumferential side (+θ1 side). This causes the motor shaft 23 to rotate around the motor axis J1 toward one circumferential side. In the following description, the eccentric axis J2 is located on one side (+D1 side) of the motor axis J1 in the first direction D1. The first external tooth portion 31e is the external tooth portion 31d that is located furthest to one side in the first direction D1 among the multiple external tooth portions 31d. The first external tooth portion 31e meshes with the internal gear portion 32a. The first protruding portion 43a is the protruding portion 43 that is located approximately 135° toward the other circumferential side from the first external tooth portion 31e among the multiple protruding portions 43. The first through hole portion 35 is the through hole portion 34 into which the first protruding portion 43a is inserted.

[0064] When a rotational torque directed toward the other circumferential side (-θ1 side) is applied to the output shaft 46, each protrusion 43 attempts to rotate toward the other circumferential side around the motor axis J1. As a result, a force directed toward the other circumferential side from the protrusion 43 is applied to the inner surface of the through-hole 34 from the protrusion 43, and the first external tooth portion 31e attempts to rotate toward the other circumferential side around the eccentric axis J2. Therefore, a first pressing force Fg1, which is a force directed toward the other circumferential side from the first external tooth portion 31e, is applied to the pitch point 32d of the first internal tooth portion 32c located on the other circumferential side of the first external tooth portion 31e.

[0065] The first pressing force Fg1 is a force applied to the pitch point 32d of the first internal tooth portion 32c in a direction perpendicular to the first virtual line L1. The first normal force Fn1 is a component of the first pressing force Fg1 that is directed in a normal direction to the tooth surface of the first external tooth portion 31e at the pitch point 31f. As viewed from the pitch point 31f, the first normal force Fn1 is directed between the other circumferential side (-θ1 side) and the radially outer side. The first tangential force Ft1 is a component of the first pressing force Fg1 that is directed in a tangential direction to the tooth surface of the first external tooth portion 31e at the pitch point 31f. As viewed from the pitch point 31f, the first tangential force Ft1 is directed between the other circumferential side and the radially inner side.

[0066] As described above, because the internal gear 32 is fixed to the case 10, a reaction force Fr1 of the first normal force Fn1 is applied to the first external tooth portion 31e from the first internal tooth portion 32c. The reaction force Fr1 is a force of the same magnitude as the first normal force Fn1 but directed in the opposite direction to the first normal force Fn1. As a result, a first thrust force F1, which is a resultant force of the first tangential force Ft1 and the reaction force Fr1, is applied to the first external tooth portion 31e. As viewed from the pitch point 31f, the first thrust force F1 is a force directed between the other side (-D1 side) of the first direction D1 and the other side (-D2 side) of the second direction D2. In other words, the external gear 31 is subjected to the first thrust force F1 directed between the other side of the first direction D1 and the other side of the second direction D2.

[0067] When the eccentric axis J2 is located on one side (+D1 side) of the motor axis J1 in the first direction D1, each protrusion 43 is located on the other side (-D1 side) of the through-hole 34 into which the protrusion 43 is inserted. Therefore, as shown in FIG. 4, the first protrusion 43a contacts the inner surface of the first outer portion 34f. As described above, when viewed in the axial direction, the first outer portion 34f is located closer to the imaginary center Ch than the imaginary circle Vc. Therefore, the end of each protrusion 43 on the other side in the first direction D1 is located closer to one side in the first direction D1 than the end of the imaginary circle Vc on the other side in the first direction D1. The distance between the end of each protrusion 43 on the other side in the first direction D1 and the end of the imaginary circle Vc on the other side in the first direction D1 is a distance G1. In this case, the protrusion 43c arranged adjacent to the first protrusion 43a on one circumferential side (+θ1 side) is arranged away from the through-hole 34. Furthermore, the protrusion 43d, which is arranged adjacent to the first protrusion 43a on the other circumferential side (-θ1 side), is arranged away from the through-hole portion 34. Therefore, when each protrusion 43 attempts to rotate toward the other circumferential side around the motor axis J1 due to a rotational torque acting toward the other circumferential side and applied to the output shaft 46, only the first protrusion 43a of the multiple protrusions 43 applies force to the inner surface of the through-hole portion 34.

[0068] The first pressure force Fp1 shown in FIG. 4 is a force applied by the first protrusion 43a to the inner surface of the first through-hole portion 35. The first pressure force Fp1 is a force directed toward the other circumferential side (-θ1 side). The first pressure force Fp1 is a force directed between the other side (-D1 side) of the first direction D1 and the other side (-D2 side) of the second direction D2. In other words, the first pressure force Fp1 directed between the other side of the first direction D1 and the other side of the second direction D2 is applied to the external gear 31. As described above, the first thrust force F1 is a force directed between the other side of the first direction D1 and the other side of the second direction D2. As shown in FIG. 5, in this embodiment, the direction of the first pressure force Fp1 and the direction of the first thrust force F1 are approximately parallel to each other. Therefore, in this embodiment, the external gear 31 cannot rotate toward the other circumferential side about the eccentric axis J2 due to the rotational torque applied to the output shaft 46 toward the other circumferential side. Therefore, even if rotational torque toward the other circumferential side is applied to the output shaft 46, the meshing state between the first external tooth portion 31e and the internal gear portion 32a is maintained. As a result, in this embodiment, even if rotational torque toward the other circumferential side is applied to the output shaft 46, it is possible to prevent the electric actuator 9 from being reverse-driven.

[0069] As shown in FIG. 4, in this embodiment, the central angle αi of the inner arc portion 34d is 180° or greater. Unlike this embodiment, if the central angle αi of the inner arc portion 34d is smaller than 180°, both ends of the inner arc portion 34d are located on the radially inner side of the through-hole portion 34, although this is not shown in the drawings. Therefore, the radially inner ends of the first outer portion 34f and the second outer portion 34h extend radially inward. Therefore, the protruding portion 43c is likely to come into contact with the first outer portion 34f of the through-hole portion 37 through which the protruding portion 43c passes. When the protruding portion 43c comes into contact with the inner surface of the first outer portion 34f of the through-hole portion 37, the first protruding portion 43a may not come into contact with the inner surface of the first through-hole portion 35. In this case, when a rotational torque is applied to the output shaft 46 in the other circumferential direction (-θ1 side), the protrusion 43c applies a third pressure force Fp3 to the inner surface of the through-hole portion 37.

[0070] The third pressure force Fp3 is a force directed toward the other side (-D1 side) in the first direction D1. As described above, the first thrust force F1 is a force directed between the other side in the first direction D1 and the other side (-D2 side) in the second direction D2. Therefore, when the central angle αi of the inner arc portion 34d is smaller than 180°, the direction of the third pressure force Fp3 and the direction of the first thrust force F1 are significantly different. As a result, when a rotational torque directed toward the other circumferential side (-θ1 side) is applied to the output shaft 46, the external gear 31 is likely to rotate toward the other circumferential side about the eccentric axis J2, and the electric actuator 9 is likely to be reverse-driven. Therefore, when the central angle αi of the inner arc portion 34d is smaller than 180°, when a rotational torque directed toward the other circumferential side is applied to the output shaft 46, the output shaft 46 is likely to rotate.

[0071] Next, using Figures 6 and 7, a second thrust force F2, which is a force applied by the internal gear 32 to the external gear 31, and a second pressure force Fp2, which is a force applied by the second protrusion 43b to the external gear 31, will be described when a rotational torque directed toward one circumferential side (+θ1 side) is applied to the output shaft 46 to reversely drive the electric actuator 9. When a rotational torque directed toward one circumferential side is applied to the output shaft 46, the external gear 31 attempts to rotate about the eccentric axis J2 toward one circumferential side. The eccentric axis J2, which is the center of the external gear 31, attempts to revolve around the motor axis J1 toward the other circumferential side (-θ1 side), as shown by arrow Rh in Figure 6. This causes the motor shaft 23 to rotate about the motor axis J1 toward the other circumferential side. In the following description, the second protruding portion 43b is the protruding portion 43 that is provided at a position approximately 135° forward from the first external teeth portion 31e to one circumferential side among the multiple protruding portions 43. The second through-hole portion 36 is the through-hole portion 34 into which the second protruding portion 43b is inserted.

[0072] When a rotational torque directed toward one circumferential side (+θ1 side) is applied to the output shaft 46, each protrusion 43 attempts to rotate toward one circumferential side around the motor axis J1. As a result, a force directed toward one circumferential side is applied from the protrusion 43 to the inner surface of the through-hole 34, and the first external tooth portion 31e attempts to rotate toward one circumferential side around the eccentric axis J2. Therefore, a second pressing force Fg2, which is a force directed toward one circumferential side from the first external tooth portion 31e, is applied to the pitch point 32f of the second internal tooth portion 32e located on one circumferential side of the first external tooth portion 31e.

[0073] The second normal force Fn2 is a component of the second pressing force Fg2 that is directed in the normal direction to the tooth flank of the first external toothing portion 31e at the pitch point 31g of the first external toothing portion 31e. The second tangential force Ft2 is a component of the second pressing force Fg2 that is directed in the tangential direction to the tooth flank of the first external toothing portion 31e at the pitch point 31g. As described above, since the internal gear 32 is fixed to the case 10, a reaction force Fr2 of the second normal force Fn2 is applied to the first external toothing portion 31e from the second internal toothing portion 32e. The reaction force Fr2 is a force of the same magnitude as the second normal force Fn2 but is directed in the opposite direction to the second normal force Fn2. As a result, a second thrust force F2, which is a resultant force of the second tangential force Ft2 and the reaction force Fr2, is applied to the first external toothing portion 31e. When viewed from the pitch point 31g, the second thrust force F2 is a force directed between the other circumferential side (-θ1 side) and the radially inward direction. The second thrust force F2 is also a force directed between the other side (-D1 side) in the first direction D1 and one side (+D2 side) in the second direction D2.

[0074] As shown in FIG. 7, when the eccentric axis J2 is located on one side (+D1 side) of the motor axis J1 in the first direction D1, the second protrusion 43b comes into contact with the inner surface of the second outer portion 34h. As described above, the second outer portion 34h is located closer to the imaginary center Ch than the imaginary circle Vc when viewed in the axial direction. As described above, the distance between the end of each protrusion 43 on the other side (-D1 side) in the first direction D1 and the end of the imaginary circle Vc on the other side in the first direction D1 is the distance G1. At this time, the protrusion 43e arranged adjacent to the second protrusion 43b on the other circumferential side (-θ1 side) is arranged away from the through-hole portion 34. The protrusion 43d arranged adjacent to the second protrusion 43b on the one circumferential side (+θ1 side) is arranged away from the through-hole portion 34, as described above. Therefore, when each protrusion 43 tries to rotate around the motor axis J1 toward one circumferential side, only the second protrusion 43b applies force to the inner surface of the through-hole portion .

[0075] The second pressure force Fp2 is a force that the second protrusion 43b applies to the inner surface of the second through-hole portion 36. The second pressure force Fp2 is a force that is directed toward one circumferential side (+θ1 side). The second pressure force Fp2 is a force that is directed between the other side (-D1 side) of the first direction D1 and one side (+D2 side) of the second direction D2. In other words, the second pressure force Fp2 that is directed between the other side of the first direction D1 and one side of the second direction D2 is applied to the external gear 31. As described above, the second thrust force F2 is a force that is directed between the other side of the first direction D1 and one side of the second direction D2. As shown in FIG. 6, in this embodiment, the direction of the second pressure force Fp2 and the direction of the second thrust force F2 are approximately parallel. Therefore, in this embodiment, the external gear 31 cannot rotate toward one circumferential side about the eccentric axis J2 due to rotational torque acting toward one circumferential side on the output shaft 46. Therefore, even if rotational torque acting toward one circumferential side is applied to the output shaft 46, the first externally toothed portion 31e and the internal gear portion 32a remain meshed. As a result, in this embodiment, even if rotational torque acting toward one circumferential side is applied to the output shaft 46, it is possible to prevent the electric actuator 9 from being reverse-driven.

[0076] Unlike the present embodiment, when the central angle αi of the inner arc portion 34d is smaller than 180°, the radially inner ends of the first outer portion 34f and the second outer portion 34h extend radially inward, as described above (not shown). Therefore, the protruding portion 43e shown in FIG. 7 is likely to come into contact with the second outer portion 34h of the through-hole 38 through which the protruding portion 43e passes. When the protruding portion 43e comes into contact with the inner surface of the through-hole 38, the second protruding portion 43b may not come into contact with the inner surface of the second through-hole 36. In this case, when a rotational torque directed toward one circumferential side (+θ1 side) is applied to the output shaft 46, the protruding portion 43e applies a fourth pressure force Fp4 to the inner surface of the through-hole 38.

[0077] The fourth pressure force Fp4 is a force directed toward the other side (-D1 side) in the first direction D1. As described above, the second thrust force F2 is a force directed between the other side in the first direction D1 and one side (+D2 side) in the second direction D2. Therefore, when the central angle αi of the inner arc portion 34d is smaller than 180°, the direction of the fourth pressure force Fp4 and the direction of the second thrust force F2 are significantly different. As a result, when a rotational torque directed toward one circumferential side (+θ1 side) is applied to the output shaft 46, the external gear 31 is likely to rotate toward one circumferential side about the eccentric axis J2, and the electric actuator 9 is likely to be reverse-driven. Therefore, when the central angle αi of the inner arc portion 34d is smaller than 180°, when a rotational torque directed toward one circumferential side is applied to the output shaft 46, the output shaft 46 is likely to rotate.

[0078] According to this embodiment, each of the multiple through-hole portions 34 has an inner end portion 34a which is the radially inner end portion, an outer end portion 34b which is the radially outer end portion, an arc-shaped inner arc portion 34d which passes through the inner end portion 34a and protrudes radially inward, a first outer portion 34f which connects one end of the inner arc portion 34d to the outer end portion 34b, and a second outer portion 34h which connects the other end of the inner arc portion 34d to the outer end portion 34b. When viewed from the axial direction, the distance between the inner end portion 34a and the outer end portion 34b is the diameter, and if a circle passing through both the inner end portion 34a and the outer end portion 34b is defined as an imaginary circle Vc, the inner arc portion 34d overlaps with the imaginary circle Vc, and at least one of the first outer portion 34f and the second outer portion 34h is curved and located closer to the imaginary center Ch than the imaginary circle Vc, i.e., closer to the center of the imaginary circle Vc. Therefore, when the first outer portion 34f is positioned closer to the imaginary center Ch than the imaginary circle Vc, the first protrusion 43a and the first outer portion 34f of the first through-hole portion 35 can be stably contacted with each other, as described above. Therefore, when a rotational torque directed toward the other circumferential side (-θ1 side) is applied to the output shaft 46, the direction of the first pressure force Fp1 applied to the external gear 31 and the direction of the first thrust force F1 become substantially parallel, as described above. This prevents the external gear 31 from rotating about the eccentric axis J2 toward the other circumferential side, as described above, thereby preventing the electric actuator 9 from being reversely driven. Therefore, even if a rotational torque directed toward the other circumferential side is applied to the output shaft 46, the output shaft 46 can be prevented from rotating.

[0079] Furthermore, in this embodiment, when the second outer portion 34h is positioned closer to the imaginary center Ch than the imaginary circle Vc, the second protrusion 43b can be stably contacted with the second outer portion 34h of the second through-hole portion 36, as described above. Therefore, when a rotational torque directed toward one circumferential side (+θ1 side) is applied to the output shaft 46, the direction of the second pressurizing force Fp2 applied to the external gear 31 and the direction of the second thrust force F2 become substantially parallel, as described above. This prevents the external gear 31 from rotating toward one circumferential side about the eccentric axis J2, as described above, thereby preventing the electric actuator 9 from being reversely driven. Therefore, even if a rotational torque directed toward one circumferential side is applied to the output shaft 46, the output shaft 46 can be prevented from rotating.

[0080] According to this embodiment, each of the first outer portion 34f and the second outer portion 34h has a curved shape that is located closer to the center of the imaginary circle Vc than the imaginary circle Vc. Therefore, regardless of whether a rotational torque directed toward one circumferential side (+θ1 side) or a rotational torque directed toward the other circumferential side (−θ1 side) is applied to the output shaft 46, as described above, it is possible to prevent the electric actuator 9 from being reverse-driven. Therefore, even if a rotational torque is applied to the output shaft 46, it is possible to more suitably prevent the output shaft 46 from rotating.

[0081] According to the present embodiment, the central angle αi of the inner arc portion 34d is 180° or greater when viewed in the axial direction. As described above, if the central angle αi of the inner arc portion 34d is smaller than 180°, the protruding portion 43c may come into contact with the inner surface of the first outer portion 34f of the through hole 37, and the protruding portion 43e may come into contact with the inner surface of the second outer portion 34h of the through hole 38. In this case, when a rotational torque directed toward the other circumferential side (−θ1 side) is applied to the output shaft 46, as described above, the direction of the third pressurizing force Fp3 and the direction of the first thrust force F1 are significantly different, and therefore the external gear 31 is likely to rotate toward the other circumferential side about the eccentric axis J2. Furthermore, when a rotational torque directed toward one circumferential side (+θ1 side) is applied to the output shaft 46, the direction of the fourth pressurizing force Fp4 and the direction of the second thrust force F2 are significantly different, as described above. Therefore, the electric actuator 9 is likely to rotate toward one circumferential side about the eccentric axis J2. Therefore, when the central angle αi of the inner arc portion 34d is smaller than 180°, the electric actuator 9 is likely to reversely drive. In contrast, in the present embodiment, the central angle αi of the inner arc portion 34d is equal to or greater than 180°. This allows stable contact between the first protruding portion 43a and the first outer portion 34f of the first through-hole portion 35, and stable contact between the second protruding portion 43b and the second outer portion 34h of the second through-hole portion 36. Therefore, regardless of whether a rotational torque directed toward one circumferential side or a rotational torque directed toward the other circumferential side is applied to the output shaft 46, reverse driving of the electric actuator 9 can be more effectively prevented. Therefore, even if a rotational torque is applied to the output shaft 46, the output shaft 46 can be more suitably prevented from rotating.

[0082] According to this embodiment, when viewed in the axial direction, the shape of each of the multiple through-hole portions 34 is line-symmetric with respect to the imaginary line Ls that passes through the inner end portion 34a and the outer end portion 34b. Therefore, it is easy to arrange the first outer portion 34f and the second outer portion 34h of each through-hole portion 34 closer to the imaginary center Ch than the imaginary circle Vc. This more effectively prevents the electric actuator 9 from being reversely driven when a rotational torque directed toward one circumferential side (+θ1 side) or another circumferential side (−θ1 side) is applied to the output shaft 46. Therefore, even if a rotational torque is applied to the output shaft 46, the output shaft 46 can be more suitably prevented from rotating.

[0083] According to this embodiment, the pressure angle α1 of the multiple external tooth portions 31d that make up the external gear portion 31c and the pressure angle α2 of the multiple internal tooth portions 32b that make up the internal gear portion 32a are each 22° or greater and 25.5° or less. If the pressure angle α1 of the external tooth portions 31d and the pressure angle α2 of the internal tooth portions 32b were each smaller than 22°, the circumferential dimensions of the roots of the external tooth portions 31d and the internal tooth portions 32b would be too small, which could result in damage to the external tooth portions 31d and the internal tooth portions 32b when the electric actuator 9 is operating. Furthermore, if the pressure angle α1 of the external toothing portion 31d and the pressure angle α2 of the internal toothing portion 32b are each greater than 25.5°, the circumferential component of the force applied from the external toothing portion 31d to the internal toothing portion 32b during operation of the electric actuator 9 becomes too small, thereby reducing the circumferential component of the reaction force applied from the internal toothing portion 32b to the external toothing portion 31d. This reduces the rotational torque with which the external gear 31 rotates about the eccentric axis J2, which is likely to reduce the drive efficiency of the electric actuator 9. In contrast, in this embodiment, as described above, the pressure angle α1 of the multiple external toothing portions 31d and the pressure angle α2 of the multiple internal toothing portions 32b are each greater than or equal to 22° and less than 25.5°. This makes it possible to prevent damage to the external toothing portion 31d and the internal toothing portion 32b and to prevent a decrease in the drive efficiency of the electric actuator 9.

[0084] According to this embodiment, the motor shaft 23 is a hollow shaft, at least a portion of the output shaft 46 is located inside the motor shaft 23, and the output shaft 46 is rotatable about the motor axis line J1. Therefore, compared to when the output shaft 46 is located radially outward of the motor shaft 23, it is possible to prevent the electric actuator 9 from becoming larger in size in the radial direction.

[0085] According to this embodiment, the actuator device 100 includes an electric actuator 9 and an object connected to an output shaft 46, and the electric actuator 9 drives the object based on a shift operation of the vehicle. Therefore, even if a rotational torque is applied from the object to the output shaft 46 when the electric actuator 9 and the object are stopped, the electric actuator 9 is prevented from reversely driving, and therefore the output shaft 46 is prevented from rotating. This prevents the positions of the components constituting the object from fluctuating when the electric actuator 9 and the object are stopped. Therefore, there is no need to provide the actuator device 100 with components such as a detent plate or a stopper member for preventing the positions of the components constituting the object from fluctuating. This prevents an increase in the number of parts and manufacturing costs of the actuator device 100.

[0086] According to this embodiment, the target object is the parking switch mechanism 70 that is driven based on a shift operation of the vehicle. Therefore, when the electric actuator 9 is mounted on a park-by-wire type actuator device 100, even if a rotational torque is applied from the parking switch mechanism 70 to the output shaft 46, the electric actuator 9 can be prevented from reverse driving, and therefore the output shaft 46 can be prevented from rotating. Therefore, there is no need to provide components such as a detent plate and a stopper member in the actuator device 100, and an increase in the number of parts and manufacturing costs of the actuator device 100 can be prevented.

[0087] Although the embodiments of the present invention have been described above, the configurations and combinations thereof in the embodiments are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the embodiments.

[0088] The configuration of the transmission mechanism is not limited to this embodiment, and for example, the pressure angle of the external gear portion and the pressure angle of the internal gear portion may be smaller than 22° or larger than 25.5°. Furthermore, the number of teeth of the external gear portion and the number of teeth of the internal gear portion are not particularly limited.

[0089] Alternatively, the plurality of protrusions may be provided on the external gear, and the plurality of through-holes may be provided on the flange. In this case, each of the plurality of protrusions protrudes from the external gear toward the flange, i.e., toward the other axial side, and is inserted into a through-hole. The number of protrusions and the number of through-holes provided on the transmission mechanism may each be seven or less, or nine or more.

[0090] The plurality of protrusions and the flange may be separate bodies, in which case the plurality of protrusions are fixed by press-fitting or the like into the plurality of holes that pass through the flange.

[0091] Furthermore, when viewed in the axial direction, the shape of each of the plurality of through holes does not have to be line symmetrical with respect to an imaginary line passing through the inner end and the outer end. Even in this case, by positioning each of the first outer portion and the second outer portion closer to the center of the imaginary circle than the imaginary circle, it is possible to suppress rotation of the output shaft even when rotational torque is applied to the output shaft.

[0092] The application of the electric actuator to which the present invention is applied is not particularly limited. The electric actuator may be mounted in a shift-by-wire type actuator device that is driven based on the driver's shift operation. The electric actuator may also be mounted in equipment other than a vehicle. Note that the configurations described above in this specification can be combined as appropriate within the scope of not mutually contradicting each other.

[0093] The present technology can be configured as follows. (1) A motor having a motor shaft rotatable about a motor axis, a transmission mechanism connected to the motor shaft, an output shaft to which rotation of the motor shaft is transmitted via the transmission mechanism, and a case accommodating the motor, the transmission mechanism, and the output shaft, wherein the motor shaft has an eccentric shaft portion centered on an eccentric axis extending in the direction of extension of the motor axis, the transmission mechanism is connected to the outer circumferential surface of the eccentric shaft portion via a bearing and comprises an annular external gear to which rotation of the motor shaft is transmitted, an annular internal gear disposed radially outside the external gear and fixed to the case, and an annular flange portion that transmits rotation of the external gear to the output shaft, wherein the external gear has a plurality of through-hole portions that penetrate the external gear in the axial direction and are arranged surrounding the motor axis, and the flange portion is provided with a plurality of protrusions that protrude from the flange portion in the axial direction and are arranged surrounding the motor axis. wherein each of the plurality of protrusions is inserted into a different one of the through-hole portions, a portion of the internal gear portion provided along the inner peripheral surface of the internal gear meshes with a portion of the external gear portion provided along the outer peripheral surface of the external gear, the external gear portion and the internal gear portion are each an involute gear, and each of the plurality of through-hole portions has an inner end portion that is the radially inner end portion, an outer end portion that is the radially outer end portion, an arc-shaped inner arc portion that passes through the inner end portion and protrudes radially inward, a first outer portion that connects one end of the inner arc portion and the outer end portion, and a second outer portion that connects the other end of the inner arc portion and the outer end portion, wherein, when viewed from the axial direction, the distance between the inner end portion and the outer end portion is a diameter, and when a circle that passes through both the inner end portion and the outer end portion is taken as a virtual circle, the inner arc portion overlaps the virtual circle, and at least one of the first outer portion and the second outer portion is curved and located closer to the center of the virtual circle than the virtual circle. (2) The electric actuator according to (1), wherein each of the first outer portion and the second outer portion has a curved shape that is positioned closer to the center of the imaginary circle than the imaginary circle. (3) The electric actuator according to (1) or (2), wherein the central angle of the inner arc portion is 180° or more when viewed from the axial direction. (4) An electric actuator described in any one of (1) to (3), wherein, when viewed from the axial direction, the shape of each of the plurality of through-hole portions is linearly symmetrical with respect to a virtual line passing through the inner end portion and the outer end portion as the axis of symmetry. (5) An electric actuator according to any one of (1) to (4), wherein the pressure angles of the plurality of external tooth portions constituting the external gear portion and the pressure angles of the plurality of internal tooth portions constituting the internal gear portion are each 22° or more and 25.5° or less. (6) An electric actuator described in any one of (1) to (5), wherein the motor shaft is a hollow shaft, a portion of the output shaft is located inside the motor shaft, and the output shaft is rotatable around the motor axis. (7) An actuator device comprising the electric actuator described in any one of (1) to (6) and an object connected to the output shaft, wherein the electric actuator drives the object based on a shift operation of a vehicle. (8) The actuator device according to (7), wherein the object is a parking switching mechanism that is driven based on a shift operation of a vehicle. [Explanation of symbols]

[0094] 9...electric actuator, 10...case, 20...motor, 23...motor shaft, 23b...eccentric shaft portion, 30...transmission mechanism, 31...external gear, 31c...external gear portion, 31d...external gear portion, 32...internal gear, 32a...internal gear portion, 32b...internal gear portion, 34...through hole portion, 34a...inner end portion, 34b...outer end portion, 34d...inner arc portion, 34f...first outer portion, 34h...second outer portion, 42...flange portion, 43...protrusion portion, 46...output shaft, 53...third bearing (bearing), 70...parking switch mechanism (object), 100...actuator device, J1...motor axis, J2...eccentric axis, Ls...virtual line, Vc...virtual circle, α1...pressure angle of external gear portion, α2...pressure angle of internal gear portion, αi...central angle of inner arc portion

Claims

1. a motor having a motor shaft rotatable about a motor axis; a transmission mechanism coupled to the motor shaft; an output shaft to which the rotation of the motor shaft is transmitted via the transmission mechanism; a case that accommodates the motor, the transmission mechanism, and the output shaft; Equipped with the motor shaft has an eccentric shaft portion having an eccentric axis extending in the direction of the motor axis, The transmission mechanism includes: an annular external gear connected to an outer peripheral surface of the eccentric shaft portion via a bearing, to which rotation of the motor shaft is transmitted; an annular internal gear disposed radially outside the external gear and fixed to the case; an annular flange portion that transmits rotation of the external gear to the output shaft; and the external gear has a plurality of through-holes that pass through the external gear in the axial direction and are arranged around the motor axis, The flange portion is provided with a plurality of protruding portions that protrude from the flange portion in the axial direction and are arranged around the motor axis, the plurality of protrusions are inserted into different through-hole portions, a portion of the internal gear portion provided along the inner peripheral surface of the internal gear meshes with a portion of the external gear portion provided along the outer peripheral surface of the external gear; the external gear portion and the internal gear portion are each an involute gear, Each of the plurality of through-hole portions has an inner end portion which is an end portion on the inner side in the radial direction, an outer end portion which is an end portion on the outer side in the radial direction, an inner arc portion which is an arc-shaped portion passing through the inner end portion and protruding radially inward, a first outer portion which connects one end of the inner arc portion and the outer end portion, and a second outer portion which connects the other end of the inner arc portion and the outer end portion, an electric actuator, wherein, when viewed from the axial direction, the distance between the inner end and the outer end is a diameter, and when a circle passing through both the inner end and the outer end is defined as a virtual circle, the inner arc portion overlaps the virtual circle, and at least one of the first outer portion and the second outer portion is curved and located closer to the center of the virtual circle than the virtual circle.

2. The electric actuator according to claim 1 , wherein each of the first outer portion and the second outer portion has a curved shape that is positioned closer to a center of the imaginary circle than the imaginary circle.

3. The electric actuator according to claim 1 , wherein a central angle of the inner arc portion is equal to or greater than 180° when viewed in the axial direction.

4. The electric actuator according to claim 1 , wherein, when viewed in the axial direction, the shape of each of the plurality of through-hole portions is line-symmetric with respect to an imaginary line passing through the inner end portion and the outer end portion as an axis of symmetry.

5. 2. The electric actuator according to claim 1, wherein a pressure angle of the plurality of external tooth portions constituting the external gear portion and a pressure angle of the plurality of internal tooth portions constituting the internal gear portion are each equal to or greater than 22° and equal to or less than 25.5°.

6. the motor shaft is a hollow shaft; a portion of the output shaft is located inside the motor shaft; The electric actuator according to claim 1 , wherein the output shaft is rotatable around the motor axis.

7. The electric actuator according to any one of claims 1 to 5; an object connected to the output shaft; Equipped with The electric actuator is an actuator device that drives the object based on a shift operation of a vehicle.

8. The actuator device according to claim 7 , wherein the object is a parking switching mechanism that is driven based on a shift operation of a vehicle.

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