Electric actuator

Abstract

We provide an electric actuator that can accurately learn the rotation angle of the output shaft. [Solution] The electric actuator comprises an output shaft connected to a first member, a motor, a rotation sensor, and a control unit. The valley portion of the outer edge of the first member has a first inclined surface, a second inclined surface, and a bottom. The control unit acquires the rotation angle of the bottom position when the contact position is the bottom, and alternately repeats a first rotation drive that rotates the output shaft to one side in the circumferential direction and a second rotation drive that rotates the output shaft to the other side in the circumferential direction, and includes making the output torque of the motor in the first rotation drive less than the output torque that the contact portion can overcome the first inclined surface, switching the first rotation drive to the second rotation drive when it is determined that the output shaft has stopped in the first rotation drive, and decreasing the output torque of the motor in the first rotation drive each time the first rotation drive is performed.

Description

Technical Field

[0001] The present invention relates to an electric actuator.

Background Art

[0002] An electric actuator that drives a switching mechanism such as a park lock mechanism based on vehicle operation is known (for example, Patent Document 1). The switching mechanism driven by the electric actuator has, for example, a positioning mechanism that holds the rotation angle of a detent plate by fitting a part of a leaf spring member into a groove provided on the outer peripheral edge of the detent plate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the case of the electric actuator described above, it may be possible to implement a learning method to learn the rotation angle of the output shaft that rotates the detent plate, so that a part of the leaf spring member fits precisely into the groove provided on the outer edge of the detent plate. One such learning method is known to use abutment learning control, in which a wall is provided on the outer edge of the detent plate, the force applied to the detent plate from the electric actuator is released after the leaf spring member abuts against the wall, and the rotation angle of the output shaft is learned when the position of the detent plate is corrected by the elastic force of the leaf spring member. However, this method has the problem that the rotation angle of the output shaft cannot be learned accurately when it is not possible to provide a wall on the outer edge of the detent plate due to some constraint, or when the rotation angle of the output shaft does not change even when the force applied to the detent plate is released after abutting against the wall due to a self-holding function or the like.

[0005] In view of the above circumstances, one of the objectives of the present invention is to provide an electric actuator that can accurately learn the rotation angle of the output shaft. [Means for solving the problem]

[0006] One embodiment of the electric actuator of the present invention is an electric actuator that rotates a plate-shaped first member having a plate surface and an outer peripheral edge around a central axis perpendicular to the plate surface, thereby changing the contact position of a second member having a contact portion that contacts the outer peripheral edge, comprising: an output shaft connected to the first member; a motor that rotates the output shaft around the central axis; a rotation sensor that detects the rotation angle of the output shaft; and a control unit that controls the motor. The outer peripheral edge has a valley. The valley has a first inclined surface, a second inclined surface located on one side of the first inclined surface in the circumferential direction around the central axis, and a bottom portion connecting the first inclined surface and the second inclined surface. The control unit is capable of performing acquisition control to acquire the rotation angle of the output shaft when the contact position becomes the bottom portion as the bottom position rotation angle. The acquisition control includes: alternating between a first rotational drive that rotates the output shaft to one side in the circumferential direction around the central axis and a second rotational drive that rotates the output shaft to the other side in the circumferential direction around the central axis, starting from a state where the rotation angle of the output shaft is at a starting angle where the contact position is the valley; reducing the output torque of the motor in the first rotational drive to less than the output torque that allows the contact portion to overcome the first inclined surface; switching the first rotational drive to the second rotational drive when it is determined that the output shaft has stopped in the first rotational drive; and reducing the output torque of the motor in the first rotational drive each time the first rotational drive is performed. [Effects of the Invention]

[0007] According to one aspect of the present invention, the rotation angle of the output shaft can be accurately learned in an electric actuator. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows a drive device according to one embodiment. [Figure 2] Figure 2 is a perspective view showing a switching mechanism of one embodiment. [Figure 3]Figure 3 shows a detent plate according to one embodiment. [Figure 4] Figure 4 is a cross-sectional view showing an electric actuator of one embodiment. [Figure 5] Figure 5 shows a part of an electric actuator according to one embodiment. [Figure 6] Figure 6 is a block diagram showing the system configuration of an electric actuator according to one embodiment. [Figure 7] Figure 7 is a block diagram showing the functional block of an electric actuator in one embodiment. [Figure 8] Figure 8 is a flowchart showing an example of acquisition control for a valley in one embodiment. [Figure 9A] Figure 9A shows the first rotational drive in acquisition control for a valley in one embodiment. [Figure 9B] Figure 9A shows the second rotational drive in acquisition control for a valley in one embodiment. [Figure 10] Figure 10 shows an example of the change in motor output torque and the change in output shaft rotation angle during acquisition control for a valley in one embodiment. [Figure 11] Figure 11 is a flowchart showing an example of acquisition control for another valley in one embodiment. [Figure 12A] Figure 12A shows the first rotational drive in acquisition control for another valley in one embodiment. [Figure 12B] Figure 12B shows the second rotational drive in acquisition control for another valley in one embodiment. [Figure 12C] Figure 12C shows the second first rotational drive in acquisition control for another valley in one embodiment. [Figure 13] Figure 13 shows an example of the change in motor output torque and the change in output shaft rotation angle during acquisition control for another valley in one embodiment. [Modes for carrying out the invention]

[0009] The drawings show, as appropriate, a hypothetical central axis J1 in the output shaft 46 of the electric actuator 10 described below. In the following description, unless otherwise specified, the axial direction of the central axis J1 will simply be referred to as the "axial direction". The radial direction centered on the central axis J1 will simply be referred to as the "radial direction". The circumferential direction centered on the central axis J1, i.e., the circumferential direction around the central axis J1, will simply be referred to as the "circumferential direction". The X-axis shown in each figure indicates the direction in which the central axis J1 extends. The Y-axis shown in each figure indicates one direction perpendicular to the X-axis direction. The Z-axis shown in each figure indicates a direction perpendicular to both the X-axis direction and the Y-axis direction. In the following description, the direction along the Y-axis will be referred to as the "width direction", and the direction along the Z-axis will be referred to as the "vertical direction". The width direction is the left-right direction of the vehicle on which the drive unit 1 is mounted in the following embodiment, i.e., the vehicle width direction. The vertical direction is the vertical direction of the vehicle on which the drive unit 1 is mounted in the following embodiment. The axial direction is the front-rear direction of the vehicle on which the drive unit 1 is mounted in the following embodiment.

[0010] Furthermore, within the axial direction, the side in which the X-axis arrow points (+X side) is called the "axial direction side," and the side opposite to the direction in which the X-axis arrow points (-X side) is called the "axial direction side." Within the width direction, the side in which the Y-axis arrow points (+Y side) is called the "width direction side," and the side opposite to the direction in which the Y-axis arrow points (-Y side) is called the "width direction side." Within the vertical direction, the side in which the Z-axis arrow points (+Z side) is called the "upper side," and the side opposite to the direction in which the Z-axis arrow points (-Z side) is called the "lower side." Note that the vertical direction, width direction, upper side, and lower side are merely names used to describe the relative positional relationships of each part, and the actual arrangement relationships may be other than those indicated by these names.

[0011] The drawings will show arrows θ indicating the circumferential direction as appropriate. In the following explanation, unless otherwise specified, the side of the circumferential direction that moves counterclockwise around the central axis J1 when viewed from one axial side (+X side) (+θ side) will be referred to as the "one circumferential side," and the side of the circumferential direction that moves clockwise around the central axis J1 when viewed from one axial side (+X side) (-θ side) will be referred to as the "other circumferential side."

[0012] The electric actuator 10 shown in FIG. 1 is an electric actuator mounted on the drive device 1 mounted on a vehicle. The vehicle on which the drive device 1 is mounted is a vehicle powered by a motor, such as a hybrid electric vehicle (HEV), a plug-in hybrid vehicle (PHV), or an electric vehicle (EV). The drive device 1 of the present embodiment is used as a power source of the mounted vehicle. The drive device 1 rotates the vehicle axle.

[0013] As shown in FIG. 1, the drive device 1 includes a housing 2, a drive motor 3, a reduction gear 4, a differential device 5, a park lock gear 6, and a parking mechanism 100. The parking mechanism 100 includes an electric actuator 10 and a switching mechanism 70. The switching mechanism 70 has a connection shaft 80 connected to the electric actuator 10. The connection shaft 80 extends in the axial direction about the central axis J1. The electric actuator 10 rotates the connection shaft 80 about the central axis J1.

[0014] The housing 2 houses the drive motor 3, the reduction gear 4, the differential device 5, and the switching mechanism 70 inside. Although not shown, for example, oil is housed inside the housing 2. The reduction gear 4 is connected to the drive motor 3. The differential device 5 is connected to the reduction gear 4 and transmits the torque output from the drive motor 3 to the vehicle axle. The park lock gear 6 is fixed to a gear provided in the reduction gear 4. The park lock gear 6 is connected to the vehicle axle via the reduction gear 4 and the differential device 5. The park lock gear 6 has a plurality of tooth portions 6a.

[0015] The switching mechanism 70 is driven by the electric actuator 10 based on the vehicle's shift operation. The switching mechanism 70 switches the park lock gear 6 between a locked state and an unlocked state. The switching mechanism 70 locks the park lock gear 6 when the vehicle's shift position is the parking position (P range), and unlocks the park lock gear 6 when the vehicle's shift position is a non-parking position other than the parking position. A non-parking position of the vehicle includes, for example, the drive position (D range), neutral position (N range), reverse position (R range), etc. As shown in Figure 2, the switching mechanism 70 has a connecting shaft 80, a movable part 70a, a park lock arm 77, a base member 75, and a leaf spring member 76.

[0016] The connecting shaft 80 connects the electric actuator 10 and the movable part 70a. The connecting shaft 80 transmits power from the electric actuator 10 to the movable part 70a. One end 81 on the axial side (+X side) of the connecting shaft 80 is connected to the electric actuator 10. Multiple spline grooves extending in the axial direction are provided on the end 81 along the circumferential direction. The connecting shaft 80 is also connected to the detent plate 71 of the movable part 70a. The connecting shaft 80 rotates around the central axis J1 together with the detent plate 71 by the power of the electric actuator 10.

[0017] The movable part 70a moves in the width direction (Y-axis direction) based on the vehicle's shift operation. In this embodiment, the movable part 70a is moved by the electric actuator 10 via the connecting shaft 80. The width direction position of the movable part 70a is switched between at least a non-parking position and a parking position. That is, the movable part 70a is moved between a parking position and a non-parking position by the electric actuator 10. The non-parking position is the width direction position of the movable part 70a when the vehicle's shift position is other than the parking position. The parking position is the width direction position of the movable part 70a when the vehicle's shift position is the parking position. The parking position is one side (+Y side) in the width direction from the non-parking position. Figure 2 shows the case where the movable part 70a is in the non-parking position.

[0018] The movable part 70a includes a detent plate 71, a rod 72, a conical member 73, and a coil spring 74. The detent plate 71 is fixed to the connecting shaft 80. The detent plate 71 is rotated around the central axis J1 by the connecting shaft 80. The detent plate 71 extends radially outward from the connecting shaft 80. In this embodiment, the detent plate 71 extends upward from the connecting shaft 80. In this embodiment, the detent plate 71 is plate-shaped with its plate surface 71f facing axially (X-axis direction). The detent plate 71 is substantially fan-shaped. The detent plate 71 has a plate surface 71f perpendicular to the central axis J1 and an outer peripheral edge 71a which is the radially outward edge. In this embodiment, the detent plate 71 corresponds to the "first member".

[0019] As shown in Figure 3, in this embodiment, the outer peripheral edge 71a of the detent plate 71 has three or more valleys 79 arranged in a circumferential direction around the central axis J1. In this embodiment, there are three valleys 79: valley 79a, valley 79b, and valley 79c. Valley 79c is the valley 79 located furthest to one side (+θ side) in the circumferential direction of the three valleys 79. Valley 79b is the valley 79 located furthest to the other side (-θ side) in the circumferential direction of the three valleys 79. Valley 79a is the valley 79 located between valley 79c, which is furthest to one side (+θ side) in the circumferential direction around the central axis J1, and valley 79b, which is furthest to the other side (-θ side). Valley 79c corresponds, for example, to the parking position. Valleys 79a and 79b correspond, for example, to the non-parking position. Each valley 79 is recessed radially inward at the outer peripheral edge 71a of the detent plate 71, with respect to the central axis J1. Each valley 79 penetrates the detent plate 71 axially. A peak 71c is provided in the portion between valley 79a and valley 79b in the circumferential direction, projecting radially outward. A peak 71d is provided in the portion between valley 79a and valley 79c in the circumferential direction, projecting radially outward.

[0020] The valley portion 79a has a first inclined surface 79d, a second inclined surface 79e, and a bottom portion 79f. The first inclined surface 79d and the second inclined surface 79e are surfaces that are inclined radially with respect to the circumferential direction. The first inclined surface 79d is located radially inward as it is directed toward one side of the circumferential direction (+θ side). The second inclined surface 79e is located radially inward as it is directed toward the other side of the circumferential direction (-θ side). The second inclined surface 79e is located on one side (+θ side) of the first inclined surface 79d in the circumferential direction around the central axis J1. The first inclined surface 79d and the second inclined surface 79e are inclined in different directions from each other. Viewed in the axial direction, the absolute value of the inclination angle of the first inclined surface 79d with respect to the circumferential direction and the absolute value of the inclination angle of the second inclined surface 79e with respect to the circumferential direction are the same. In this embodiment, the first inclined surface 79d and the second inclined surface 79e are arranged symmetrically with respect to a virtual line L1 that passes through the central axis J1 and the bottom portion 79f and extends radially, when viewed in the axial direction. The first inclined surface 79d and the second inclined surface 79e move circumferentially away from each other as they extend radially outward. Note that, when viewed in the axial direction, the absolute values ​​of the inclination angle of the first inclined surface 79d with respect to the circumferential direction and the absolute values ​​of the inclination angle of the second inclined surface 79e with respect to the circumferential direction may be different from each other.

[0021] The bottom portion 79f connects the first inclined surface 79d and the second inclined surface 79e. More specifically, the bottom portion 79f connects the circumferential end of the first inclined surface 79d (+θ side) and the circumferential end of the second inclined surface 79e (-θ side). The bottom portion 79f is the part perpendicular to the radial direction centered on the central axis J1. The first inclined surface 79d and the bottom portion 79f are smoothly connected to each other. The second inclined surface 79e and the bottom portion 79f are smoothly connected to each other. The portion of the first inclined surface 79d that connects to the bottom portion 79f and the portion of the second inclined surface 79e that connects to the bottom portion 79f and the portion including the bottom portion 79f are arc-shaped, concave radially inward when viewed in the axial direction.

[0022] The valley section 79b has a first inclined surface 79g, a second inclined surface 79h, and a bottom section 79i. Viewed axially, the absolute value of the inclination angle of the first inclined surface 79g with respect to the circumferential direction is greater than the absolute value of the inclination angle of the second inclined surface 79h with respect to the circumferential direction. Viewed axially, the first inclined surface 79g is inclined circumferentially with respect to the central axis J1 and a virtual line L2 that passes through the first inclined surface 79g and extends radially. Other points in each part of the valley section 79b are the same as other points in each part of the valley section 79a.

[0023] The valley section 79c has a first inclined surface 79j, a second inclined surface 79k, and a bottom section 79m. Viewed axially, the absolute value of the inclination angle of the first inclined surface 79j with respect to the circumferential direction is greater than the absolute value of the inclination angle of the second inclined surface 79k with respect to the circumferential direction. Viewed axially, the first inclined surface 79j is inclined circumferentially with respect to the central axis J1 and a virtual line L3 that passes through the first inclined surface 79j and extends radially. The second inclined surface 79k is located on the other circumferential side (-θ side) of the first inclined surface 79j. The radial dimension of the first inclined surface 79j is smaller than the radial dimension of the first inclined surface 79g in the valley section 79b. The radially outer end of the first inclined surface 79j is located radially inward than the radially outer end of the first inclined surface 79g. The other points of valley 79c are the same as the other points of valley 79b, except that they are arranged symmetrically with respect to the imaginary line L1 when viewed in the axial direction. Note that valleys 79b and 79c may be asymmetrical with respect to the imaginary line L1 when viewed in the axial direction. Furthermore, valley 79a may be provided in the circumferential direction between valleys 79b and 79c, and may be provided in the center of the circumferential direction between valleys 79b and 79c, or may be provided at a position offset in the circumferential direction from the center of the circumferential direction between valleys 79b and 79c.

[0024] As shown in Figure 2, the rod 72 is arranged to be movable in the width direction (Y-axis direction). The rod 72 has a connecting portion 72a and a rod body portion 72b. The connecting portion 72a is rod-shaped and extends in the axial direction (X-axis direction). One end of the connecting portion 72a on one axial side (+X side) passes through the detent plate 71 in the axial direction and is fixed to the detent plate 71. In this way, the rod 72 is connected to the connecting shaft 80 via the detent plate 71. The rod body portion 72b is rod-shaped and extends in the width direction. In this embodiment, the rod body portion 72b extends from the other end of the connecting portion 72a on the other axial side (-X side) to one side in the width direction (+Y side). The rod body portion 72b has a projection 72c in the portion located on the other side in the width direction (-Y side) than the conical member 73. A cylindrical member 72d, which extends in the width direction, is fitted and fixed to one end of the rod body 72b in the width direction.

[0025] The conical member 73 is conical in shape through which the rod body 72b passes. The conical member 73 extends in the width direction (Y-axis direction). The portion of the outer circumferential surface of the conical member 73 on one side in the width direction (+Y side) is a tapered surface 73a, where the outer diameter decreases as it moves toward that side in the width direction. The conical member 73 is movable in the width direction relative to the rod body 72b.

[0026] The coil spring 74 extends in the width direction (Y-axis direction). The coil spring 74 is positioned between the conical member 73 and the projection 72c in the width direction. The rod body 72b passes through the coil spring 74. The other end of the coil spring 74 in the width direction (-Y side) contacts the projection 72c. The other end of the coil spring 74 in the width direction (+Y side) contacts the other side of the conical member 73 in the width direction. The coil spring 74 expands and contracts as the conical member 73 moves relative to the rod body 72b in the width direction, applying an elastic force in the width direction to the conical member 73.

[0027] The park lock arm 77 is located on the other axial side (-X side) of the movable part 70a. The park lock arm 77 is rotatably supported by a support shaft 78 centered on a rotation axis J3 that extends in the width direction (Y axis direction). The park lock arm 77 has a park lock arm body 77a and a meshing part 77b.

[0028] The park lock arm body 77a extends from the support shaft 78 in one axial direction (+X side). The axial end 77c of the park lock arm body 77a contacts the movable part 70a from above. The meshing part 77b protrudes upward from the park lock arm body 77a. A coil spring (not shown) is attached to the support shaft 78. The coil spring (not shown) applies an elastic force to the park lock arm 77 in a clockwise direction when viewed from the other side in the width direction (-Y side) with respect to the rotation axis J3.

[0029] The park lock arm 77 moves in conjunction with the movement of the movable part 70a. More specifically, the park lock arm 77 rotates around the axis of rotation J3 as the rod 72 and the conical member 73 move in the width direction (Y-axis direction). As the connecting shaft 80 rotates, the detent plate 71 rotates from the non-parking position to the parking position, causing the rod 72 and the conical member 73 to move to one side in the width direction (+Y side).

[0030] The outer diameter of the tapered surface 73a of the conical member 73 increases from one side in the width direction (+Y side) to the other side in the width direction (-Y side). Therefore, when the conical member 73 moves to one side in the width direction, the tapered surface 73a lifts the end 77c of the park lock arm 77 upward, causing the park lock arm 77 to rotate counterclockwise around the rotation axis J3 when viewed from the other side in the width direction (-Y side). As a result, although not shown in the illustration, the meshing portion 77b approaches the park lock gear 6 and meshes with the teeth 6a of the park lock gear 6.

[0031] When the park lock gear 6 and the park lock arm 77 engage, the conical member 73 also moves into the parking position, and the entire movable part 70a moves into the parking position. In other words, the park lock arm 77 engages with the park lock gear 6 connected to the axle when the movable part 70a is in the parking position. In the parking position, the conical member 73 is sandwiched between the support part 75b of the base member 75 (described later) and the park lock arm 77, in contact with each other. When the park lock arm 77 engages with the park lock gear 6, the park lock gear 6 is locked.

[0032] As the connecting shaft 80 rotates, the detent plate 71 rotates from the parking position to the non-parking position, causing the rod 72 and the conical member 73 to move to the other side in the width direction (-Y side). When the conical member 73 moves to the other side in the width direction, the end 77c of the park lock arm 77, which was lifted by the conical member 73, moves downward due to its own weight and the elastic force from a coil spring (not shown), causing the park lock arm 77 to rotate clockwise around the rotation axis J3 when viewed from the other side in the width direction (-Y side). As a result, the meshing portion 77b of the park lock arm 77 separates from the park lock gear 6 and disengages from between the teeth 6a. Figure 2 shows the park lock arm 77 in the state of being disengaged from the park lock gear 6. With the park lock arm 77 disengaged from the park lock gear 6, the park lock gear 6 becomes unlocked.

[0033] The base member 75 supports the movable part 70a so that it can move in the width direction (Y-axis direction). In this embodiment, the base member 75 supports the movable part 70a from below. The base member 75 is fixed to the inner surface of the housing 2. The base member 75 has a base plate 75a, a support part 75b, and a leaf spring fixing part 75c.

[0034] In this embodiment, the base plate 75a is plate-shaped with its surface facing vertically. The support portion 75b protrudes upward from the base plate 75a. The support portion 75b is the part that contacts the movable portion 70a and supports the movable portion 70a. In this embodiment, the support portion 75b contacts the conical member 73 of the movable portion 70a from below and supports the movable portion 70a from below. The surface of the support portion 75b on the side facing the movable portion 70a is an arc-shaped curved surface that is concave on the opposite side from the movable portion 70a when viewed in the width direction (Y-axis direction). Therefore, the conical member 73 having a tapered surface 73a can be stably supported. The leaf spring fixing portion 75c protrudes upward from the base plate 75a. The leaf spring fixing portion 75c is, for example, rectangular parallelepiped-shaped. The leaf spring fixing portion 75c is located on one axial side (+X side) of the support portion 75b.

[0035] The leaf spring member 76 is fixed to the leaf spring fixing portion 75c of the base member 75. In this embodiment, the leaf spring member 76 is fixed to the end on the other side (-Y side) in the width direction of the upper surface of the leaf spring fixing portion 75c. In this embodiment, the leaf spring member 76 corresponds to the "second member". The leaf spring member 76 has a leaf spring body portion 76a and a contact portion 76b.

[0036] The leaf spring body portion 76a is plate-shaped with its plate surface facing vertically. The leaf spring body portion 76a extends from the leaf spring fixing portion 75c to the other side in the width direction (-Y side). The leaf spring body portion 76a extends to the upper side of the detent plate 71. The leaf spring body portion 76a has a slit 76c at the end on the other side in the width direction. The slit 76c penetrates the leaf spring body portion 76a in the vertical direction. The slit 76c extends in the width direction (Y axis direction). The slit 76c extends to the other end of the leaf spring body portion 76a in the width direction, and divides the other end of the leaf spring body portion 76a in the width direction into two branches.

[0037] The contact portion 76b is provided at the other end (-Y side) in the width direction of the leaf spring body portion 76a. In this embodiment, the contact portion 76b is a roller attached to the leaf spring body portion 76a so as to be rotatable around an axis extending in the axial direction (X-axis direction). The contact portion 76b is provided between the two tip portions of the leaf spring body portion 76a, which are divided into two by the slit 76c.

[0038] The contact portion 76b is pressed against the outer peripheral edge 71a of the detent plate 71 by the elastic force generated in the leaf spring member 76. In the following description, the position where the contact portion 76b contacts the outer peripheral edge 71a is referred to as the contact position P. The contact position P is the contact position of the leaf spring member 76 with respect to the outer peripheral edge 71a. When the movable portion 70a is in the parking position, the contact portion 76b is located within the valley portion 79c. As a result, the contact portion 76b is circumferentially hooked against the inner surface of the valley portion 79c, and the detent plate 71 and rod 72 are maintained in the parking position. When the movable portion 70a is in the non-parking position, the contact portion 76b is located within the valley portion 79a or valley portion 79b. As a result, the contact portion 76b is circumferentially hooked against the inner surface of the valley portion 79a or valley portion 79b, and the detent plate 71 and rod 72 are maintained in the non-parking position.

[0039] As the detent plate 71 rotates around the central axis J1, the contact portion 76b moves relative to the inside of one valley 79, overcoming the peaks 71c and 71d provided between the valleys 79 to move to the inside of another valley 79. When the contact portion 76b overcomes the peak 71c or peak 71d, the leaf spring member 76 receives a radially outward force from the peak 71c or peak 71d via the contact portion 76b and undergoes elastic deformation. In other words, in this embodiment, the leaf spring member 76 is an elastic member that is pushed upward by the peaks 71c and 71d of the detent plate 71 and undergoes elastic deformation when the movable portion 70a moves between a non-parking position and a parking position. Thus, the leaf spring member 76 in this embodiment is an elastic member having a contact portion 76b that contacts one of the multiple valleys 79 due to the elastic force generated as the detent plate 71 rotates. In this embodiment, when the contact portion 76b moves relative to the outer peripheral edge 71a of the detent plate 71, the contact portion 76b, which is a roller, moves while rolling along the outer peripheral edge 71a of the detent plate 71.

[0040] The electric actuator 10 shown in Figure 4 drives a switching mechanism 70 based on the vehicle's shift operation. In this embodiment, the electric actuator 10 drives the switching mechanism 70 by moving the movable part 70a in the width direction (Y-axis direction) via the connecting shaft 80, and switches the park lock gear 6 between a locked state and an unlocked state. More specifically, the electric actuator 10 rotates the detent plate 71 around a central axis J1 perpendicular to the plate surface 71f, changing the contact position P of the leaf spring member 76 having a contact portion 76b that contacts the outer edge 71a. As shown in Figure 4, the electric actuator 10 comprises a case 10A, a motor 20, a reduction gear 30, an output shaft 46, a first bearing 51, a second bearing 52, a third bearing 53, a control unit 90, a rotation sensor 95, a sensor magnet 45, and a current sensor 96. The first bearing 51, the second bearing 52, and the third bearing 53 are, for example, ball bearings.

[0041] Case 10A houses the components of the electric actuator 10, including the motor 20, the reduction gear 30, and the output shaft 46. Case 10A comprises a case body 11 and a lid member 12. The case body 11 is cylindrical with a central axis J1. The case body 11 has an opening 11h that opens on one axial side (+X side). The case body 11 has a first housing section 11a and a second housing section 11b.

[0042] The first housing section 11a is the part of the case body 11 on the other axial side (-X side). The first housing section 11a has a bottom plate section 11c located on the other axial side, and a peripheral wall section 11d extending from the radial outer edge of the bottom plate section 11c to one axial side. The bottom plate section 11c is provided with a hole section 11e that penetrates the bottom plate section 11c in the axial direction. The hole section 11e is a substantially circular hole centered on the central axis J1. The part of the hole section 11e on one axial side (+X side) constitutes the first bearing holding section 11f that holds the first bearing 51. The first bearing 51 is held in the first bearing holding section 11f.

[0043] The second housing section 11b is the portion of the case body 11 on one axial side (+X side). The second housing section 11b is connected to the first housing section 11a in the axial direction. The second housing section 11b is cylindrical and opens to one axial side. The inner circumferential surface of the second housing section 11b is provided with a step having a stepped surface 11g facing one axial side.

[0044] The lid member 12 is fixed to one axial end (+X side) of the case body 11. The lid member 12 closes the opening 11h of the case body 11 from one axial side. The lid member 12 has a lid body portion 12a that closes the opening 11h from one axial side, and a second bearing holding portion 12b that protrudes from the lid body portion 12a to the other axial side. The second bearing holding portion 12b is cylindrical with a central axis J1 as its center and opening to the other axial side (-X side). The second bearing 52 is held on the inner circumferential surface of the second bearing holding portion 12b.

[0045] The motor 20 is, for example, a three-phase brushless DC motor. The motor 20 rotates the output shaft 46 around the central axis J1. The motor 20 has a rotor 21 and a stator 22. The rotor 21 is rotatable about the central 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 central axis J1. The motor shaft 23 is substantially cylindrical and extends axially about the central axis J1. The motor shaft 23 is a hollow shaft. The motor shaft 23 opens on both sides in the axial direction. The motor shaft 23 extends across the interior of the first housing 11a and the interior of the second housing 11b. The motor shaft 23 has a main body 23a and an eccentric shaft 23b.

[0046] The main body portion 23a is the axial side (+X side) portion of the motor shaft 23. The rotor core 24a is fixed to the outer circumferential surface of the main body portion 23a. The axial end of the main body portion 23a is located inside the second housing portion 11b. The portion of the main body portion 23a other than the axial end is located inside the first housing portion 11a.

[0047] The eccentric shaft portion 23b is the portion of the motor shaft 23 on the other axial side (-X side). The eccentric shaft portion 23b is connected to the main body portion 23a in the axial direction. The eccentric shaft portion 23b is located inside the first housing portion 11a. The eccentric shaft portion 23b is located on the other axial side of the rotor core 24a. Viewed in the axial direction, the inner circumferential surface of the eccentric shaft portion 23b is circular in shape with the central axis J1 as the center. Viewed in the axial direction, the outer circumferential surface of the eccentric shaft portion 23b is circular in shape with the eccentric axis J2 as the center, which is eccentric with respect to the central axis J1. The eccentric axis J2 is a virtual axis parallel to the central axis J1. The inner ring of the third bearing 53 is fitted and fixed to the outer circumferential surface of the eccentric shaft portion 23b. In this way, the third bearing 53 is fixed to the motor shaft 23. The eccentric shaft portion 23b rotates eccentrically as the rotor 21 rotates around its central axis J1. In other words, the motor 20 has an eccentric shaft portion 23b that rotates eccentrically.

[0048] The rotor core 24a is annular in shape with a central axis J1. The rotor core 24a is located inside the first housing 11a. The rotor core 24a is fixed to the outer circumferential surface of the main body 23a. The magnets 24b are fixed to the outer circumferential surface of the rotor core 24a. In this embodiment, multiple magnets 24b are arranged at intervals in the circumferential direction.

[0049] The stator 22 is positioned radially opposite the rotor 21. The stator 22 is positioned radially outward from the rotor 21, with a gap between them. The stator 22 is positioned inside the first housing 11a. The stator 22 has an annular stator core 22a surrounding the rotor core 24a from the radial outward, an insulator 22b mounted on the stator core 22a, and a plurality of coil portions 22c mounted on the stator core 22a via the insulator 22b. The outer circumferential surface of the stator core 22a is fixed to the inner circumferential surface of the peripheral wall portion 11d. In this way, the stator 22 is fixed to the case 10A.

[0050] The reduction gear 30 is located inside the first housing 11a. The reduction gear 30 is located on the other axial side (-X side) of the rotor core 24a and stator 22. The reduction gear 30 is connected to the motor shaft 23 and the output shaft 46. The reduction gear 30 reduces the rotation of the motor 20 and transmits it to the output shaft 46, causing the output shaft 46 to rotate around the central axis J1. The reduction gear 30 has an external gear 31, an internal gear 32, a flange portion 42, and a plurality of protrusions 43.

[0051] The external gear 31 is annular in shape with respect to the eccentric axis J2. The external gear 31 is fitted onto the outer ring of the third bearing 53. The external gear 31 is connected to the eccentric shaft portion 23b of the motor shaft 23 via the third bearing 53. As a result, the rotation of the motor shaft 23 is 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 Figure 5, the reduction gear 30 of this embodiment is an internal gear reduction gear. In this specification, "internal gear reduction gear" means a reduction gear having an external gear 31 and an internal gear 32, which reduces rotation when the meshing point between the external gear 31 and the internal gear 32 moves in the circumferential direction.

[0052] The external gear 31 has a plurality of through holes 31b and an external gear portion 31c. In this embodiment, each of the plurality of through holes 31b is a hole that penetrates the external gear 31 in the axial direction. Viewed in the axial direction, each of the plurality of through holes 31b is circular in shape. The plurality of through holes 31b are arranged around the central axis J1. In this embodiment, eight through holes 31b are provided. The external gear portion 31c is provided along the outer circumferential surface of the external gear 31. The external gear portion 31c is composed of a plurality of teeth 31d arranged along the outer circumferential surface of the external gear 31. The tooth profile of the plurality of teeth 31d in the external gear 31 is, for example, an involute tooth profile.

[0053] The internal gear 32 is positioned radially outward of the external gear 31. The internal gear 32 surrounds the external gear 31 from the radially outward direction. The internal gear 32 is annular in shape with a central axis J1. As shown in Figure 4, the outer circumferential surface of the internal gear 32 is fixed to the inner circumferential surface of the circumferential wall portion 11d. In this way, the internal gear 32 is fixed to the case 10A. As shown in Figure 5, the internal gear 32 has an internal gear portion 32a.

[0054] A portion of the internal gear portion 32a meshes with a portion of the external gear portion 31c. 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 teeth 32b arranged along the inner circumferential surface of the internal gear 32. The tooth profile of the plurality of teeth 32b in the internal gear 32 is, for example, an involute tooth profile.

[0055] As shown in Figure 4, the flange portion 42 is positioned on the other axial side (-X side) of the external gear 31. The flange portion 42 is positioned with an axial gap between it and the external gear 31. The flange portion 42 is annular in shape with the central axis J1 as its center. The flange portion 42 is fixed to the portion of the output shaft 46 that is on the axial side of the motor shaft 23. The flange portion 42 is provided with a plurality of protrusions 43.

[0056] In this embodiment, each of the multiple protrusions 43 is cylindrical and protrudes from the flange portion 42 in one axial direction (+X side). In this embodiment, the multiple protrusions 43 and the flange portion 42 are part of the same single member. As shown in Figure 5, the outer diameter of each of the multiple protrusions 43 is smaller than the inner diameter of each of the multiple through-holes 31b. The multiple protrusions 43 are arranged around the central axis J1. In this embodiment, eight protrusions 43 are provided. As shown in Figure 4, each of the multiple protrusions 43 is inserted into each of the multiple through-holes 31b from the other axial direction (-X side). As shown in Figure 5, each protrusion 43 supports the external gear 31 so that it can swing around the central axis J1 via the inner surface of the through-hole 31b.

[0057] The output shaft 46 outputs the driving force of the electric actuator 10 to the switching mechanism 70 via the connecting shaft 80. As shown in Figure 4, the output shaft 46 extends axially around the central axis J1. The output shaft 46 is rotatable around the central axis J1. The rotation of the motor shaft 23 is transmitted to the output shaft 46 via the reduction gear 30. The output shaft 46 passes axially through the inside of the motor shaft 23. The output shaft 46 protrudes from the motor shaft 23 on both axial sides. Note that the output shaft 46 and the flange portion 42 may be part of the same single component.

[0058] The output shaft 46 comprises an output shaft body 41 and a mounting member 44 fixed to the outer circumferential surface of the output shaft body 41. The output shaft body 41 extends in the axial direction. The output shaft body 41 is rotatably supported about the central axis J1 by a first bearing 51 and a second bearing 52. The output shaft body 41 has a connecting portion 41a and an extension portion 41b.

[0059] The connecting portion 41a is the axially opposite (-X side) portion of the output shaft body 41. The connecting portion 41a is cylindrical in shape and extends axially around the central axis J1. The connecting portion 41a opens to the axially opposite side. The axially opposite end of the connecting portion 41a is inserted into the hole 11e. The axially opposite end of the connecting portion 41a (+X side) is inserted into the eccentric shaft portion 23b. The connecting portion 41a is rotatably supported around the central axis J1 by the first bearing 51.

[0060] The end 81 of the connecting shaft 80 can be inserted into the connecting portion 41a from the other axial side (-X side). When the multiple spline grooves provided on the outer circumferential surface of the end 81 of the connecting shaft 80 are fitted into the multiple spline grooves provided on the inner circumferential surface of the connecting portion 41a, the connecting portion 41a and the connecting shaft 80 are connected to each other. As a result, the output shaft 46 is connected to the first member, the detent plate 71, via the connecting shaft 80. The rotation of the output shaft 46 is transmitted to the detent plate 71 via the connecting shaft 80. As a result, the electric actuator 10 drives the switching mechanism 70.

[0061] The extension portion 41b is the axial side (+X side) of the output shaft body 41. The extension portion 41b is cylindrical in shape and extends axially around the central axis J1. The extension portion 41b is connected axially to the connecting portion 41a. The extension portion 41b is passed axially inside the motor shaft 23. The axial side portion of the extension portion 41b protrudes axially beyond the motor shaft 23. The axial end of the extension portion 41b is supported by the second bearing 52 so as to be rotatable around the central axis J1.

[0062] In this embodiment, the outer diameter of the extension portion 41b is smaller than the inner diameter of the main body portion 23a of the motor shaft 23. The extension portion 41b is fitted into the main body portion 23a. The radial gap between the extension portion 41b and the main body portion 23a is small enough that the extension portion 41b can support the motor shaft 23 so that it can rotate around the central axis J1. Thus, the motor shaft 23 is supported by the case 10A via the output shaft 46, the first bearing 51, and the second bearing 52. This prevents the motor shaft 23 from moving radially relative to the case 10A.

[0063] The mounting member 44 is fixed to the outer circumferential surface of the extension portion 41b on one axial side (+X 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 with a central axis J1 as its center and openings 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 substantially annular plate shape that extends radially outward from the other axial side (-X side) end of the fixed cylindrical portion 44a.

[0064] The sensor magnet 45 is annular in shape, surrounding the central axis J1. The sensor magnet 45 is fixed to the outer circumferential surface of the fixed cylindrical portion 44a. The radially outer edge of the sensor magnet 45 is located radially outward from the annular portion 44b and faces the rotation sensor 95 in the axial direction.

[0065] In the axial direction, a washer 61 is positioned between the other axial end (-X side) of the main body portion 23a of the motor shaft 23 and the one axial end (+X side) of the connecting portion 41a of the output shaft 46. The washer 61 is an annular plate shape surrounding the extension portion 41b. The plate surface of the washer 61 faces axially. The washer 61 contacts both the main body portion 23a and the connecting portion 41a in the axial direction. In the axial direction, a washer 62 is positioned between the one axial end of the main body portion 23a and the annular portion 44b. The washer 62 is an annular plate shape surrounding the extension portion 41b. The plate surface of the washer 62 faces axially. The washer 62 contacts both the main body portion 23a and the annular portion 44b in the axial direction. Washers 61 and 62 are, for example, slip washers.

[0066] When power is supplied to the motor 20 and the motor shaft 23 rotates around the central axis J1, the eccentric shaft portion 23b revolves circumferentially around the central 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 central axis J1 while the contact position between the inner circumferential surface of the through hole portion 31b and the outer circumferential surface of the protrusion portion 43 changes. As the external gear 31 revolves around the central 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.

[0067] As described above, the internal gear 32 is fixed to the case 10A. 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. At this time, the rotation of the external gear 31 is reduced relative to the rotation of the motor shaft 23. The rotation of the external gear 31 around the eccentric axis J2 is transmitted to the flange portion 42 via the inner surface and protrusion 43 of the through hole portion 31b, and the flange portion 42 rotates around the central axis J1. As described above, the output shaft 46 is fixed to the flange portion 42, so the output shaft 46 rotates around the central axis J1 together with the flange portion 42. That is, the flange portion 42 transmits the rotation of the external gear 31 to the output shaft 46. In this way, the rotation of the motor shaft 23 is transmitted to the output shaft 46 via the reduction gear 30.

[0068] The electric actuator 10 has a function to maintain the rotation angle θa of the output shaft 46 when power is not supplied to the motor 20, i.e., a self-holding function. This self-holding function is achieved, for example, by mechanically locking the rotation of the output shaft 46 when power is not supplied to the motor 20. For example, the reduction gear 4 may have a structure that has this self-holding function, or a separate mechanism for adding this self-holding function may be provided. The electric actuator 10 may have a self-holding function using cogging torque. Any known self-holding function can be adopted as the self-holding function mounted on the electric actuator 10.

[0069] The control unit 90 controls the motor 20. In this embodiment, the control unit 90 controls the motor 20 by pulse width modulation (PWM) control. The control unit 90 is located on one axial side (+X side) of the stator 22. The control unit 90 has a substrate 91. The substrate 91 is fixed to the stepped surface 11g of the case 10A. The substrate 91 is a plate that expands radially. The substrate 91 is provided with a through hole 91a that penetrates the substrate 91 in the axial direction. The extended portion 41b of the output shaft 46 passes through the through hole 91a in the axial direction.

[0070] As shown in Figure 6, the control unit 90 includes a calculation unit 92 and an inverter circuit unit 93. Although not shown, the inverter circuit unit 93 is composed of multiple switching elements. The inverter circuit unit 93 supplies current I to the motor 20. More specifically, the inverter circuit unit 93 supplies three-phase current I to multiple coil units 22c of the stator 22. The inverter circuit unit 93 is controlled by the calculation unit 92.

[0071] The calculation unit 92 is the part of the control unit 90 that can perform the acquisition control described later. The calculation unit 92 is a processor such as a CPU (Central Processing Unit). The calculation unit 92 inputs pulse signals used for pulse width modulation control to the inverter circuit unit 93 and drives the inverter circuit unit 93. More specifically, the calculation unit 92 inputs pulse signals to each switching element of the inverter circuit unit 93 and switches each switching element between the ON state and the OFF state. The calculation unit 92 receives the output signal of the current sensor 96 mounted on the circuit board 91. The current sensor 96 detects the three-phase current I supplied to the motor 20 by the inverter circuit unit 93. The calculation unit 92 also receives the output signal of the angular velocity sensor 97 mounted on the circuit board 91. The angular velocity sensor 97 detects the rotational angular velocity ω of the motor shaft 23 of the motor 20. Alternatively, a sensor that detects the rotation angle of the motor shaft 23 may be provided instead of the angular velocity sensor 97. In this case, the calculation unit 92 may detect the rotational angular velocity ω of the motor shaft 23 based on the output of the sensor. Alternatively, the calculation unit 92 may detect the back electromotive force generated in the motor 20 using a sensor that detects the voltage applied to the motor 20 from the inverter circuit unit 93, and calculate the rotational angular velocity ω of the motor shaft 23 based on the back electromotive force.

[0072] The arithmetic unit 92 receives the output signal from a voltage sensor 98 mounted on the circuit board 91. The voltage sensor 98 detects the input voltage applied from an external power supply E that supplies power to the control unit 90. The arithmetic unit 92 also receives the output signal from a rotation sensor 95 mounted on the circuit board 91. The rotation sensor 95 detects the rotation angle θa of the output shaft 46. In this embodiment, the rotation sensor 95 is a magnetic sensor. The rotation sensor 95 is, for example, a Hall element such as a Hall IC. The rotation sensor 95 detects the rotation of the sensor magnet 45 by detecting the magnetic field of the sensor magnet 45. As a result, the rotation sensor 95 detects the rotation angle of the output shaft 46. Note that the rotation sensor 95 can be any sensor as long as it is capable of detecting the rotation angle θa of the output shaft 46.

[0073] As shown in Figure 7, the calculation unit 92 includes an angle control unit 92a, an angular velocity control unit 92b, a current control unit 92c, and a pulse generation unit 92d. The angle control unit 92a performs PID control in which the rotation angle θa of the output shaft 46 is fed back. The angle control unit 92a receives a value obtained by subtracting the current rotation angle θa from the command value θr of the rotation angle θa. The command value θr is input from a higher-level device of the electric actuator 10. This higher-level device may be a control device mounted on the drive unit 1, or it may be a control device that controls various parts of the vehicle. The angle control unit 92a outputs a command value ωr of the rotational angular velocity ω. The angular velocity control unit 92b performs PID control in which the rotational angular velocity ω of the motor shaft 23 is fed back. The angular velocity control unit 92b receives a value obtained by subtracting the current rotational angular velocity ω from the command value ωr output from the angle control unit 92a. The angular velocity control unit 92b outputs a command value Ir of the three-phase current I. The current control unit 92c performs PID control in which the three-phase current I is fed back. The current control unit 92c receives a value obtained by subtracting the current current I from the command value Ir output from the angular velocity control unit 92b. The current control unit 92c outputs a command value Vr of the output voltage Vm applied to the motor 20 to the pulse generation unit 92d. The pulse generation unit 92d generates a pulse signal to be input to the inverter circuit unit 93 based on the input command value Vr. In pulse width modulation control, the duty cycle of the pulse signal input to the inverter circuit unit 93 changes periodically within a range from 0 to a maximum value set appropriately based on the phase information of the motor 20.

[0074] The control unit 90 can perform acquisition control to acquire the rotation angle θa of the output shaft 46 as the bottom position rotation angle when the contact position P is at the bottom of the valley 79. The acquisition control is performed before the electric actuator 10 is used for the first time. In this embodiment, the acquisition control is performed after the electric actuator 10 is attached to the switching mechanism 70 and before the drive unit 1 is used for the first time. The acquisition control is a learning control included in a learning method in which the electric actuator 10 self-learns the rotation angle θa of the output shaft 46. In this embodiment, the control unit 90 performs the acquisition control by the calculation unit 92.

[0075] In this embodiment, the control unit 90 performs acquisition control for each of the three valleys 79. Figure 8 is a flowchart showing an example of acquisition control for valley 79a. As shown in Figure 8, in acquisition control for valley 79a, the control unit 90 rotates the output shaft 46 to a starting angle θs1 (step S101). The starting angle θs1 is an angle pre-stored in the control unit 90 as the rotation angle θa when the contact position P becomes the bottom 79f of the valley 79a. Ideally, the contact portion 76b contacts the bottom 79f when the rotation angle θa of the output shaft 46 becomes the pre-stored starting angle θs1. However, in reality, due to assembly tolerances of the electric actuator 10, assembly tolerances of the switching mechanism 70, and assembly tolerances between the electric actuator 10 and the switching mechanism 70, even if the rotation angle θa of the output shaft 46 is set to the starting angle θs1, the contact portion 76b contacts the outer peripheral edge 71a of the detent plate 71 at a position offset from the bottom 79f. Therefore, in order to learn the rotation angle θa when the contact portion 76b contacts the bottom portion 79f, the electric actuator 10 needs to perform acquisition control. Note that the contact position P of the contact portion 76b at the starting angle θs1 will shift relative to the bottom portion 79f due to the tolerances mentioned above, but it will not shift so much as to shift from the valley portion 79a. In other words, the starting angle θs1 is the angle at which the contact position P is at the valley portion 79a.

[0076] In explaining the flowchart in Figure 8, we will describe the case where the contact portion 76b contacts the second inclined surface 79e when the output shaft 46 is rotated to the starting angle θs1, as shown in Figure 9A. Note that it is also possible that the contact portion 76b contacts the first inclined surface 79d when the output shaft 46 is rotated to the starting angle θs1. In Figure 9A, the contact portion 76b when the rotation angle θa of the output shaft 46 is the starting angle θs1 is shown by a dashed line.

[0077] As shown in Figure 8, after rotating the output shaft 46 to a starting angle θs1, the control unit 90 reduces the output torque Tm of the motor 20 and starts the first rotational drive D1a (step S102). The first rotational drive D1a is a drive that rotates the output shaft 46 in one direction (+θ side) in the circumferential direction around the central axis J1. The output torque Tm of the motor 20 in the first rotational drive D1a is smaller than the output torque Tm that the contact portion 76b can overcome the first inclined surface 79d. In other words, the acquisition control includes making the output torque Tm of the motor 20 in the first rotational drive D1a smaller than the output torque Tm that the contact portion 76b can overcome the first inclined surface 79d. In this embodiment, the control unit 90 adjusts the output torque Tm of the motor 20 by adjusting the maximum value of the duty cycle in the pulse signal of pulse width modulation control generated by the pulse generation unit 92d. The larger the maximum value of the duty cycle in the pulse signal of pulse width modulation control, the larger the output torque Tm of the motor 20. The smaller the maximum duty cycle in the pulse signal of pulse width modulation control, the smaller the output torque Tm of the motor 20.

[0078] As shown in Figure 9A, when the first rotational drive D1a is performed and the output shaft 46 is rotated to one side in the circumferential direction (+θ side), the contact portion 76b moves to the other side in the circumferential direction (-θ side) relative to the detent plate 71. When the first rotational drive D1a is performed, the contact portion 76b, which was in contact with the second inclined surface 79e in the example of Figure 9A, descends the second inclined surface 79e, passes the bottom 79f, and then ascends the first inclined surface 79d. Here, as described above, the output torque Tm of the motor 20 in the first rotational drive D1a is smaller than the output torque Tm that the contact portion 76b can overcome to overcome the first inclined surface 79d. Therefore, when the first rotational drive D1a is performed, after the contact portion 76b begins to ascend the first inclined surface 79d, there is a timing when the contact portion 76b can no longer ascend the first inclined surface 79d and the output shaft 46 stops rotating. Specifically, when the electric actuator 10 is unable to rotate the detent plate 71 in the circumferential direction against the elastic force that presses the leaf spring body 76a against the contact portion 76b of the outer edge 71a, the output shaft 46 stops rotating.

[0079] As shown in Figure 8, after starting the first rotation drive D1a, the control unit 90 determines whether or not the rotation angle θa of the output shaft 46 has stopped changing (step S103). In this embodiment, the control unit 90 obtains the rotation angle θa of the output shaft 46 based on the output of the rotation sensor 95 and makes various determinations. In step S103, the control unit 90 determines that the rotation angle θa of the output shaft 46 has stopped changing in the first rotation drive D1a if the rotation angle θa of the output shaft 46 has stopped changing at all during the execution of the first rotation drive D1a, or if the rotation angle θa of the output shaft 46 has stopped changing substantially during the execution of the first rotation drive D1a.

[0080] The condition that the rotation angle θa of the output shaft 46 has virtually stopped changing includes, for example, a case where, even if the rotation angle θa of the output shaft 46 changes, the amount of change is small enough to fall within the range of what is caused by the elastic deformation of each component and the variation in the detected value by the rotation sensor 95, and the output shaft 46 is substantially not rotating. The control unit 90 stores a first predetermined value determined based on the maximum value of the slight change in rotation angle θa that may occur when the output shaft 46 is substantially not rotating. The first predetermined value is a value greater than or equal to the maximum value of the slight change in rotation angle θa that may occur when the output shaft 46 is substantially not rotating. In step S103, the control unit 90 determines that the rotation angle θa of the output shaft 46 has stopped changing if, during the execution of the first rotation drive D1a, the amount of change in rotation angle θa remains below the first predetermined value for a first predetermined time (step S103: YES). The first predetermined time is appropriately determined based on the speed at which the output shaft 46 rotates when the first rotation drive D1a is executed. The first predetermined time is, for example, a few seconds or less.

[0081] If the control unit 90 determines in step S103 that the rotation angle θa of the output shaft 46 has changed (step S103: NO), it continues the first rotation drive D1a. If the control unit 90 determines in step S103 that the rotation angle θa of the output shaft 46 has stopped changing (step S103: YES), it terminates the first rotation drive D1a, reduces the output torque Tm of the motor 20, and starts the second rotation drive D2a (step S104). In other words, the acquisition control includes switching from the first rotation drive D1a to the second rotation drive D2a when it determines that the output shaft 46 has stopped during the first rotation drive D1a.

[0082] Figure 9A shows an example where the output shaft 46 stops rotating when the rotation angle θa becomes angle θ1 due to the first rotation drive D1a. In the example in Figure 9A, angle θ1 is the rotation angle θa where the difference between angle θ1 and the bottom position rotation angle θe1 ​​(the rotation angle θa when the contact portion 76b is in contact with the bottom portion 79f) is greater than the starting angle θs1. However, depending on the position of the contact portion 76b at the starting angle θs1, the difference between angle θ1 and the bottom position rotation angle θe1 ​​may be less than or equal to the difference between the starting angle θs1 and the bottom position rotation angle θe1.

[0083] The second rotational drive D2a is a drive that rotates the output shaft 46 in the other circumferential direction (-θ side) around the central axis J1. The output torque Tm of the motor 20 in the second rotational drive D2a is smaller than the output torque Tm that the contact portion 76b can overcome the second inclined surface 79e. In other words, the acquisition control includes making the output torque Tm of the motor 20 in the second rotational drive D2a smaller than the output torque Tm that the contact portion 76b can overcome the second inclined surface 79e. In this embodiment, the output torque Tm of the motor 20 in the second rotational drive D2a is smaller than the output torque Tm of the motor 20 in the first rotational drive D1a performed immediately before the second rotational drive D2a. In other words, in this embodiment, the acquisition control includes making the output torque Tm of the motor 20 in the second rotational drive D2a smaller than the output torque Tm of the motor 20 in the first rotational drive D1a performed immediately before the second rotational drive D2a.

[0084] As shown in Figure 9B, when the second rotational drive D2a is performed and the output shaft 46 is rotated to the other side in the circumferential direction (-θ side), the contact portion 76b moves to one side in the circumferential direction (+θ side) relative to the detent plate 71. When the second rotational drive D2a is performed, the contact portion 76b, which was in contact with the first inclined surface 79d by the first rotational drive D1a, descends the first inclined surface 79d, passes the bottom 79f, and then ascends the second inclined surface 79e. Here, as described above, the output torque Tm of the motor 20 in the second rotational drive D2a is smaller than the output torque Tm that the contact portion 76b can overcome to overcome the second inclined surface 79e. Therefore, when the second rotational drive D2a is performed, similar to when the first rotational drive D1a is performed, there is a timing when the contact portion 76b begins to ascend the second inclined surface 79e, after which the contact portion 76b is unable to ascend the second inclined surface 79e and the output shaft 46 stops rotating.

[0085] As shown in Figure 8, in this embodiment, after the second rotation drive D2a is started, the control unit 90 determines whether or not the rotation angle θa of the output shaft 46 has changed since the start of the second rotation drive D2a (step S105). In step S105, the control unit 90 determines that the rotation angle θa of the output shaft 46 has not changed since the start of the second rotation drive D2a if the rotation angle θa of the output shaft 46 does not change at all even after the start of the second rotation drive D2a, or if the rotation angle θa of the output shaft 46 does not change substantially even after the start of the second rotation drive D2a.

[0086] The case in which the rotation angle θa of the output shaft 46 does not substantially change even when the second rotation drive D2a is started includes, for example, the case in which, even if the rotation angle θa of the output shaft 46 changes after the second rotation drive D2a is started, the amount of change is less than or equal to the first predetermined value described above, and the output shaft 46 is not rotating in substance. In step S105, the control unit 90 determines that the rotation angle θa of the output shaft 46 has not changed since the start of the second rotation drive D2a if the amount of change in the rotation angle θa remains less than or equal to the first predetermined value even after a second predetermined time has elapsed since the start of the second rotation drive D2a (step S105: NO). In step S105, the control unit 90 determines that the rotation angle θa of the output shaft 46 has changed since the start of the second rotation drive D2a if, after a second predetermined time has elapsed since the start of the second rotation drive D2a, the amount of change in the rotation angle θa is greater than the first predetermined value (step S105: YES). The second predetermined time is determined appropriately based on the speed at which the output shaft 46 rotates when the second rotational drive D2a is executed. The second predetermined time may be the same as or different from the first predetermined time described above. The second predetermined time is, for example, a few seconds or less.

[0087] If the control unit 90 determines in step S105 that the rotation angle θa of the output shaft 46 has changed since the start of the second rotation drive D2a (step S105: YES), it continues the second rotation drive D2a and determines whether the rotation angle θa of the output shaft 46 has stopped changing (step S106). In step S106, the control unit 90 determines that the rotation angle θa of the output shaft 46 has stopped changing if, during the execution of the second rotation drive D2a, the amount of change in the rotation angle θa remains below the first predetermined value described above for a third predetermined time (step S106: YES). The third predetermined time is appropriately determined based on the speed at which the output shaft 46 rotates when the second rotation drive D2a is executed. The third predetermined time may be the same as or different from the first and second predetermined times described above. The third predetermined time may be, for example, a few seconds or less.

[0088] If the control unit 90 determines in step S106 that the rotation angle θa of the output shaft 46 has changed (step S106: NO), it continues the second rotation drive D2a. If the control unit 90 determines in step S106 that the rotation angle θa of the output shaft 46 has stopped changing (step S106: YES), it terminates the second rotation drive D2a, then reduces the output torque Tm of the motor 20 and starts the first rotation drive D1a again (step S107). In other words, the acquisition control includes switching the second rotation drive D2a to the first rotation drive D1a when it determines that the rotation angle θa of the output shaft 46 has stopped changing during the second rotation drive D2a.

[0089] Figure 9B shows an example where the output shaft 46 stops rotating when the rotation angle θa becomes angle θ2 due to the second rotation drive D2a. In this embodiment, the first inclined surface 79d and the second inclined surface 79e are arranged symmetrically with respect to a virtual line L1 that passes through the bottom 79f and extends radially, when viewed in the axial direction. Also, the output torque Tm of the motor 20 in the second rotation drive D2a is smaller than the output torque Tm of the motor 20 in the first rotation drive D1a. Therefore, the angle θ2 at which the output shaft 46 stops rotating in the second rotation drive D2a is closer to the bottom position rotation angle θe1 ​​than the angle θ1 at which the output shaft 46 stops rotating in the first rotation drive D1a performed immediately before the second rotation drive D2a.

[0090] In step S107, the output torque Tm of the motor 20 in the first rotational drive D1a, which is started again, is smaller than the output torque Tm of the motor 20 in the previous first rotational drive D1a. In other words, the acquisition control includes reducing the output torque Tm of the motor 20 in the first rotational drive D1a each time the first rotational drive D1a is performed. In step S107, the output torque Tm of the motor 20 in the first rotational drive D1a, which is started again, is smaller than the output torque Tm of the motor 20 in the second rotational drive D2a that was performed immediately before. In other words, the acquisition control includes reducing the output torque Tm of the motor in the second rotational drive D2a to be smaller than the output torque Tm of the motor 20 in the second rotational drive D2a that was performed immediately before the first rotational drive D1a.

[0091] As shown in Figure 8, after the first rotational drive D1a is started again, the control unit 90 determines whether or not the rotation angle θa of the output shaft 46 has changed since the time the first rotational drive D1a was started (step S108). In step S108, if the amount of change in the rotation angle θa remains less than or equal to the first predetermined value described above even after a fourth predetermined time has elapsed since the time the first rotational drive D1a was started, the control unit 90 determines that the rotation angle θa of the output shaft 46 has not changed since the time the first rotational drive D1a was started (step S108: NO). In step S108, if the amount of change in the rotation angle θa is greater than the first predetermined value after a fourth predetermined time has elapsed since the time the first rotational drive D1a was started, the control unit 90 determines that the rotation angle θa of the output shaft 46 has changed since the time the first rotational drive D1a was started (step S108: YES). The fourth predetermined time is appropriately determined based on the speed at which the output shaft 46 rotates when the first rotational drive D1a is executed. The fourth predetermined time may be the same as or different from the first to third predetermined times described above. The fourth predetermined time may be, for example, a few seconds or less.

[0092] If the control unit 90 determines in step S108 that the rotation angle θa of the output shaft 46 has changed since the start of the first rotation drive D1a (step S108: YES), it executes step S103 again. If the control unit 90 determines again in step S103 that the rotation angle θa of the output shaft 46 has stopped changing, it starts the second rotation drive D2a again. The output torque Tm of the motor 20 in the second rotation drive D2a that is started again is smaller than the output torque Tm of the motor 20 in the second rotation drive D2a that was performed previously. In other words, the acquisition control includes reducing the output torque of the motor 20 in the second rotation drive D2a each time the second rotation drive D2a is performed.

[0093] As described above, in the acquisition control for the valley section 79a, the first rotational drive D1a and the second rotational drive D2a are repeated alternately. In other words, the acquisition control for the valley section 79a includes repeating the first rotational drive D1a and the second rotational drive D2a alternately from a state where the rotation angle θa of the output shaft 46 is the starting angle θs1. If the control unit 90 determines in step S105 that the rotation angle θa of the output shaft 46 has not changed since the start of the second rotational drive D2a (step S105: NO), and if it determines in step S108 that the rotation angle θa of the output shaft 46 has not changed since the start of the first rotational drive D1a (step S108: NO), it terminates the alternate execution of the first rotational drive D1a and the second rotational drive D2a, and acquires the rotation angle θa of the output shaft 46 at that time as the bottom position rotation angle θe1 ​​in the valley section 79a (step S109). In other words, the acquisition control includes acquiring the rotation angle θa of the output shaft 46 as the bottom position rotation angle θe1 ​​when switching from one of the rotation drives, D1a, or D2a, to the other, and the rotation angle θa of the output shaft 46 does not change even when the other rotation drive is executed.

[0094] In step S109, the rotation angle θa acquired as the bottom position rotation angle θe1 ​​is the rotation angle θa when the output shaft 46 does not rotate even if the second rotation drive D2a is executed after the first rotation drive D1a has finished, or when the output shaft 46 does not rotate even if the first rotation drive D1a is executed after the second rotation drive D2a has finished. In step S109, the control unit 90 determines in step S105 or step S108 that the output shaft 46 is not rotating, and acquires the rotation angle θa after stopping the power supply to the motor 20 as the bottom position rotation angle θe1. With this, the acquisition control for the valley portion 79a is completed.

[0095] According to this embodiment, the acquisition control for the valley portion 79a includes, from a state where the rotation angle θa of the output shaft 46 is the starting angle θs1 at which the contact position P becomes the valley portion 79a, alternating between a first rotational drive D1a that rotates the output shaft 46 to one side in the circumferential direction around the central axis J1 and a second rotational drive D2a that rotates the output shaft to the other side in the circumferential direction around the central axis J1; making the output torque Tm of the motor 20 in the first rotational drive D1a smaller than the output torque Tm that the contact portion 76b can overcome the first inclined surface 79d; switching the first rotational drive D1a to the second rotational drive D2a when it is determined that the output shaft 46 has stopped in the first rotational drive D1a; and decreasing the output torque Tm of the motor 20 in the first rotational drive D1a each time the first rotational drive D1a is performed. Each time the first rotational drive D1a is performed, the output torque Tm of the motor 20 decreases. As a result, the rotation angle θa at which the output shaft 46 stops rotating during the first rotational drive D1a approaches the bottom position rotation angle θe1 ​​with each subsequent rotation. Consequently, as the first rotational drive D1a is repeated, the contact position P of the contact portion 76b at which the output shaft 46 stops rotating approaches the bottom 79f, until finally the contact position P at which the output shaft 46 stops rotating becomes the bottom 79f. Therefore, the bottom position rotation angle θe1 ​​can be accurately obtained based on the rotation angle θa of the output shaft 46 during the first rotational drive D1a. Thus, the rotation angle θa of the output shaft 46 can be accurately learned.

[0096] Furthermore, according to this embodiment, the acquisition control for the valley portion 79a includes making the output torque Tm of the motor 20 in the second rotation drive D2a smaller than the output torque Tm that the contact portion 76b can overcome the second inclined surface 79e; switching the second rotation drive D2a to the first rotation drive D1a when it is determined that the rotation angle θa of the output shaft 46 has stopped changing in the second rotation drive D2a; decreasing the output torque Tm of the motor 20 in the second rotation drive D2a each time the second rotation drive D2a is performed; and acquiring the rotation angle θa of the output shaft 46 as the bottom position rotation angle θe1 ​​when switching from one rotation drive to the other between the first rotation drive D1a and the second rotation drive D2a, if the rotation angle θa of the output shaft 46 does not change even when the other rotation drive is performed. Each time the second rotational drive D2a is performed, the output torque Tm of the motor 20 decreases. Therefore, the rotation angle θa at which the output shaft 46 stops rotating during the second rotational drive D2a approaches the bottom position rotation angle θe1 ​​with each subsequent D2a. Consequently, even when the second rotational drive D2a is repeated, the contact position P at which the output shaft 46 stops rotating approaches the bottom 79f, and eventually the contact position P becomes the bottom 79f. In this case, when the contact position P becomes the bottom 79f, the output shaft 46 will not rotate whether the first rotational drive D1a or the second rotational drive D2a is performed. Therefore, if the output shaft 46 does not rotate even after the second rotation drive D2a is executed following the execution of the first rotation drive D1a and the output shaft 46 has stopped rotating, and if the output shaft 46 does not rotate even after the first rotation drive D1a is executed following the execution of the second rotation drive D2a and the output shaft 46 has stopped rotating, it can be determined that the rotation angle θa of the output shaft 46 is at the bottom position rotation angle θe1, where the contact portion 76b contacts the bottom portion 79f. Therefore, in steps S105 and S108 described above, if it is determined that the rotation angle θa of the output shaft 46 has not changed from the time each rotation drive is started, the rotation angle θa of the output shaft 46 can be obtained as the bottom position rotation angle θe1, thereby obtaining the bottom position rotation angle θe1 ​​with greater accuracy. Consequently, the rotation angle θa of the output shaft 46 can be learned with greater accuracy.

[0097] Furthermore, according to this embodiment, the acquisition control for the valley portion 79a includes making the output torque Tm of the motor 20 in the second rotational drive D2a smaller than the output torque Tm of the motor 20 in the first rotational drive D1a performed immediately before the second rotational drive D2a. Therefore, compared to the case where the output torque Tm of the motor 20 in the second rotational drive D2a is the same as the output torque Tm of the motor 20 in the first rotational drive D1a performed immediately before, the rotation angle θa at which the output shaft 46 stops can be set to the bottom position rotation angle θe1 ​​with fewer rotational drive executions. Consequently, the time required for acquisition control can be shortened, and the bottom position rotation angle θe1 ​​can be acquired quickly.

[0098] Furthermore, according to this embodiment, the control unit 90 performs acquisition control in the valley 79a located between the valley 79 located on one side and the valley 79 located on the other side in the circumferential direction around the central axis J1, among the three or more valleys 79. In the valley 79a provided between the valleys 79 in this way, it is necessary to move the contact portion 76b between the valleys 79, so it is not possible to provide an inclined surface (wall) that the contact portion 76b cannot overcome. Therefore, as in the conventional method, it is not possible to employ abutting learning control to acquire the bottom position rotation angle θe1 ​​by abutting the contact portion 76b against the inclined surface of the valley 79a. In contrast, by using the acquisition control of this embodiment for the valley 79a as described above, the first rotation drive D1a and the second rotation drive D2a are executed alternately, and the output torque Tm of the motor 20 in each rotation drive is reduced, thereby bringing the rotation angle θa at which the output shaft 46 stops rotating closer to the bottom position rotation angle θe1. Therefore, even in the valley section 79a where there is no wall to abut against, the bottom position rotation angle θe1 ​​can be obtained with high accuracy.

[0099] Figure 10 shows an example of the change in the output torque Tm of the motor 20 and the change in the rotation angle θa of the output shaft 46 during acquisition control for the valley section 79a. In the upper graph of Figure 10, the vertical axis is the output torque Tm and the horizontal axis is time t. In the lower graph of Figure 10, the vertical axis is the rotation angle θa of the output shaft 46 and the horizontal axis is time t. In Figure 10, at time t0, the rotation angle θa becomes the starting angle θs1. From time t0 to time t1, from time t2 to time t3, from time t4 to time t5, and from time t6 to time t7, the first rotation drive D1a is executed. From time t1 to time t2, from time t3 to time t4, from time t5 to time t6, and from time t7 to time t8, the second rotation drive D2a is executed. From time t7 to time t8, the second rotation drive D2a is executed, but since the output shaft 46 did not rotate from the time the second rotation drive D2a started, the rotation angle θa did not change. In the example in Figure 10, the bottom position rotation angle θe1 ​​is obtained at time t8.

[0100] As shown in the lower graph of Figure 10, the rotation angle θa approaches the bottom position rotation angle θe1 ​​each time the first rotation drive D1a and the second rotation drive D2a are performed. As shown in the upper graph of Figure 10, the output torque Tm decreases each time the first rotation drive D1a and the second rotation drive D2a are performed. The torque Ta shown in the upper graph of Figure 10 is the output torque Tm of the motor 20 when driving the switching mechanism 70. Torque Ta is the output torque Tm that allows the contact portion 76b to overcome the first inclined surface 79d and the second inclined surface 79e, and the output torque Tm that allows it to overcome the peaks 71c and 71d. When the control unit 90 rotates the output shaft 46 to the starting angle θs1, it sets the output torque Tm to torque Ta. Note that the output torque Tm when rotating the output shaft 46 to the starting angle θs1 can be any torque as long as the output shaft 46 can be rotated to the starting angle θs1. In the acquisition control for the valley section 79a, the maximum value of the duty cycle of the pulse signal input to the inverter circuit section 93 changes in the same way as the output torque Tm shown in the upper graph of Figure 10.

[0101] Furthermore, if the starting angle θs1 is the rotation angle θa at which the contact portion 76b contacts the first inclined surface 79d, then after the first rotational drive D1a is executed, the contact portion 76b stops on the first inclined surface 79d without contacting the second inclined surface 79e.

[0102] Furthermore, in the above description, the control unit 90 reduced the output torque Tm of the motor 20 each time it performed the first rotational drive D1a and the second rotational drive D2a, but this is not limited to this. The control unit 90 may reduce the output torque Tm of the motor 20 each time it performs the first rotational drive D1a and the second rotational drive D2a once. In other words, the control unit 90 may perform the first rotational drive D1a and the second rotational drive D2a with the same output torque Tm, and then reduce the output torque Tm to perform the next first rotational drive D1a and second rotational drive D2a.

[0103] Figure 11 is a flowchart showing an example of acquisition control for the valley portion 79b. As shown in Figure 11, in acquisition control for the valley portion 79b, the control unit 90 rotates the output shaft 46 to a starting angle θs2 (step S201). The starting angle θs2 is the rotation angle θa at which the contact position P becomes the valley portion 79b, and is stored in the control unit 90 in advance. The starting angle θs2 is a predetermined angle at which the contact position P becomes the second inclined surface 79h. The starting angle θs2 is the angle at which the contact position P becomes the second inclined surface 79h even if the contact position P is shifted due to tolerances. In Figure 12A, the contact portion 76b when the rotation angle θa of the output shaft 46 becomes the starting angle θs2 is shown by a dashed line.

[0104] As shown in Figure 11, after rotating the output shaft 46 to the starting angle θs2, the control unit 90 reduces the output torque Tm of the motor 20 and starts the first rotational drive D1b (step S202). The first rotational drive D1b is a drive that rotates the output shaft 46 in one direction (+θ side) in the circumferential direction around the central axis J1. The output torque Tm of the motor 20 in the first rotational drive D1b is smaller than the output torque Tm that the contact portion 76b can overcome to overcome the first inclined surface 79g. Other aspects of the first rotational drive D1b are the same as other aspects of the first rotational drive D1a in the acquisition control for the valley portion 79a.

[0105] As shown in Figure 12A, when the first rotational drive D1b is executed and the output shaft 46 is rotated to one side in the circumferential direction (+θ side), the contact portion 76b moves to the other side in the circumferential direction (-θ side) relative to the detent plate 71. When the first rotational drive D1b is executed, the contact portion 76b that was in contact with the second inclined surface 79h descends the second inclined surface 79h, passes the bottom 79i, and then ascends the first inclined surface 79g. Here, as described above, the output torque Tm of the motor 20 in the first rotational drive D1b is smaller than the output torque Tm that the contact portion 76b can overcome to overcome the first inclined surface 79g. Therefore, when the first rotational drive D1b is executed, after the contact portion 76b begins to ascend the first inclined surface 79g, there is a timing when the contact portion 76b can no longer ascend the first inclined surface 79g and the output shaft 46 stops rotating.

[0106] As shown in Figure 11, after starting the first rotation drive D1b, the control unit 90 determines whether the rotation angle θa of the output shaft 46 has stopped changing, similar to step S103 described above (step S203). If the control unit 90 determines in step S203 that the rotation angle θa of the output shaft 46 has changed (step S203: NO), it continues the first rotation drive D1b. If the control unit 90 determines in step S203 that the rotation angle θa of the output shaft 46 has stopped changing (step S203: YES), it determines whether the rotation angle θa of the stopped output shaft 46 is the same as the rotation angle θa when it stopped during the previous first rotation drive D1b (step S204).

[0107] In step S204, the control unit 90 states that the case where the rotation angle θa of the stopped output shaft 46 is the same as the rotation angle θa when it stopped during the previous first rotation drive D1b includes the case where the rotation angle θa of the stopped output shaft 46 is exactly the same as the rotation angle θa when it stopped during the previous first rotation drive D1b, and the case where the rotation angle θa of the stopped output shaft 46 is approximately the same as the rotation angle θa when it stopped during the previous first rotation drive D1b. The case where the rotation angle θa of the stopped output shaft 46 is approximately the same as the rotation angle θa when it stopped during the previous first rotation drive D1b includes, for example, a case where, even if the rotation angles θa are different values ​​from each other, the difference between the rotation angles θa is small enough to fall within the tolerance range of the variation in the detected value by the rotation sensor 95, and the rotation angles θa can be considered to be substantially the same. The control unit 90 stores a second predetermined value determined based on the maximum value of the difference between rotation angles θa when the rotation angles θa can be considered to be substantially the same. The second predetermined value is greater than or equal to the maximum difference between rotation angles θa when they can be considered to be substantially the same. The second predetermined value may be the same as or different from the first predetermined value described above. In step S204, the control unit 90 determines that the rotation angle θa of the stopped output shaft 46 is the same as the rotation angle θa when it stopped during the previous first rotation drive D1b if the difference between the rotation angle θa of the stopped output shaft 46 and the rotation angle θa when it stopped during the previous first rotation drive D1b is less than or equal to the second predetermined value (step S204: YES). In step S204, the control unit 90 determines that the rotation angle θa of the stopped output shaft 46 is not the same as the rotation angle θa when it stopped during the previous first rotation drive D1b if the difference between the rotation angle θa of the stopped output shaft 46 and the rotation angle θa when it stopped during the previous first rotation drive D1b is greater than the second predetermined value (step S204: NO).

[0108] If the first rotational drive D1b is executed for the first time since the acquisition control started, there is no previous first rotational drive D1b. In this case, the control unit 90 determines that the rotation angle θa of the output shaft 46 is not the same as the rotation angle θa at which it stopped during the previous first rotational drive D1b (step S204: NO). If the control unit 90 determines in step S204 that the rotation angle θa of the output shaft 46 that has stopped is not the same as the rotation angle θa at which it stopped during the previous first rotational drive D1b (step S204: NO), it terminates the first rotational drive D1b and starts the second rotational drive D2b (step S205). Figure 12A shows the case where the rotation of the output shaft 46 stops at an angle θa of θ3 due to the first rotational drive D1b. Note that the timing for terminating the first rotational drive D1b may be after step S203 and before step S204 is executed.

[0109] The second rotational drive D2b is a drive that rotates the output shaft 46 in the other circumferential direction (-θ side) around the central axis J1. The second rotational drive D2b is a drive that returns the rotation angle θa of the output shaft 46 to the starting angle θs2. The output torque Tm of the motor 20 in the second rotational drive D2b is greater than the output torque Tm of the motor 20 in the first rotational drive D1b. The output torque Tm of the motor 20 in the second rotational drive D2b is, for example, the torque Ta described above. As shown in Figure 12B, when the second rotational drive D2b is executed and the output shaft 46 is rotated in the other circumferential direction (-θ side), the contact portion 76b moves to one circumferential direction (+θ side) relative to the detent plate 71. When the second rotational drive D2b is executed, the contact portion 76b that was in contact with the first inclined surface 79g descends the first inclined surface 79g, passes the bottom 79i, and then ascends the second inclined surface 79h.

[0110] As shown in Figure 11, after starting the second rotation drive D2b, the control unit 90 determines whether the rotation angle θa of the output shaft 46 has become the starting angle θs2 (step S206). In step S206, the control unit 90 determines that the rotation angle θa has become the starting angle θs2 if the rotation angle θa is exactly the same as the starting angle θs2, or if the rotation angle θa is approximately the same as the starting angle θs2. The case where the rotation angle θa is approximately the same as the starting angle θs2 includes the case where the difference between the rotation angle θa and the starting angle θs2 is small enough to fall within the tolerances of the position control in the second rotation drive D2b and the variation of the detected value by the rotation sensor 95, and the rotation angle θa can be considered to be substantially the starting angle θs2. The control unit 90 stores a third predetermined value determined based on the maximum value of the difference between the rotation angle θa and the starting angle θs2 in the case where the rotation angle θa can be considered to be substantially the starting angle θs2. The third predetermined value is greater than or equal to the maximum difference between the rotation angle θa and the starting angle θs2 when the rotation angle θa can be considered to be substantially the same as the starting angle θs2. The third predetermined value may be the same as or different from the first and second predetermined values ​​described above. In step S206, the control unit 90 determines that the rotation angle θa has become the starting angle θs2 if the difference between the rotation angle θa and the starting angle θs2 is less than or equal to the third predetermined value (step S206: YES). In step S206, the control unit 90 determines that the rotation angle θa has not become the starting angle θs2 if the difference between the rotation angle θa and the starting angle θs2 is greater than the third predetermined value (step S206: NO).

[0111] If the control unit 90 determines in step S206 that the rotation angle θa of the output shaft 46 is not the starting angle θs2 (step S206: NO), it continues the second rotation drive D2b. If the control unit 90 determines in step S206 that the rotation angle θa of the output shaft 46 has reached the starting angle θs2 (step S206: YES), it executes step S202 again and starts the first rotation drive D1b. In other words, the acquisition control includes switching the second rotation drive D2b to the first rotation drive D1b when it determines that the rotation angle θa of the output shaft 46 has reached a predetermined angle, the starting angle θs2, during the second rotation drive D2b. When the control unit 90 executes the first rotation drive D1b again in step S202, it reduces the output torque Tm of the motor 20 to be less than the output torque Tm of the motor 20 during the previous first rotation drive D1b. In other words, the control unit 90 reduces the output torque Tm of the motor 20 in the first rotational drive D1b each time the first rotational drive D1b is performed.

[0112] After restarting the first rotation drive D1b, the control unit 90 executes steps S203 and S204. In step S204, if it determines that the rotation angle θa of the output shaft 46 is not the same as the rotation angle θa at which it stopped during the previous first rotation drive D1b (step S204: NO), it restarts the second rotation drive D2b (step S205). In this way, the first rotation drive D1b and the second rotation drive D2b are repeated alternately in the acquisition control of the valley portion 79b. Figure 12C shows the state after the first rotation drive D1b has been executed for the second time. Figure 12C shows the case where the rotation of the output shaft 46 stops at a rotation angle θa of angle θ4 due to the first rotation drive D1b. Angle θ4 is the rotation angle θa at which the contact portion 76b is closer to the bottom portion 79i than at angle θ3. The output torque Tm of the motor 20 during the first rotational drive D1b decreases each time the first rotational drive D1b is performed. Therefore, the distance that the contact portion 76b can climb on the first inclined surface 79g decreases with each execution of the first rotational drive D1b. Consequently, the contact position P of the contact portion 76b at the end of the first rotational drive D1b approaches the bottom portion 79i with each execution of the first rotational drive D1b.

[0113] If the control unit 90 determines in step S204 that the rotation angle θa of the output shaft 46 is the same as the rotation angle θa at which it stopped during the previous first rotation drive D1b (step S204: YES), it determines whether the rotation angle θa at which the output shaft 46 stopped during the first rotation drive D1b has remained the same for a predetermined number of consecutive times (step S207). The predetermined number of times is an integer of 2 or more. For example, the predetermined number of times is 3. If the control unit 90 determines in step S207 that the rotation angle θa at which the output shaft 46 stopped during the first rotation drive D1b has not remained the same for a predetermined number of consecutive times (step S207: NO), it starts the second rotation drive D2b again (step S205). In step S207, the control unit 90 determines that the rotation angle θa when the output shaft 46 stops in the first rotation drive D1b has remained the same for a predetermined number of consecutive times (step S207: YES), and acquires this rotation angle θa as the bottom position rotation angle θe2 of the valley 79b (step S208). In other words, the acquisition control includes acquiring the rotation angle θa of the output shaft 46 as the bottom position rotation angle θe2 if the rotation angle θa of the output shaft 46 has remained the same for two or more consecutive times when it is determined that the rotation angle θa of the output shaft 46 has stopped changing in the first rotation drive D1b. In step S208, the acquisition control acquires the rotation angle θa after the power supply to the motor 20 is stopped as the bottom position rotation angle θe2. With this, the acquisition control for the valley 79b is completed.

[0114] According to this embodiment, the acquisition control for the valley portion 79b includes alternating between a first rotational drive D1b that rotates the output shaft 46 to one side in the circumferential direction around the central axis J1 and a second rotational drive D2b that rotates the output shaft to the other side in the circumferential direction around the central axis J1, starting from a state where the rotation angle θa of the output shaft 46 is the starting angle θs2 when the contact position P becomes the valley portion 79b; making the output torque Tm of the motor 20 in the first rotational drive D1b smaller than the output torque Tm that the contact portion 76b can overcome the first inclined surface 79g; switching the first rotational drive D1b to the second rotational drive D2b when it is determined that the output shaft 46 has stopped in the first rotational drive D1b; and decreasing the output torque Tm of the motor 20 in the first rotational drive D1b each time the first rotational drive D1b is performed. Therefore, similar to the acquisition control for the valley portion 79a described above, the bottom position rotation angle θe2 can be acquired with high accuracy. Therefore, the rotation angle θa of the output shaft 46 can be learned with high accuracy.

[0115] Furthermore, according to this embodiment, the acquisition control for the valley portion 79b includes acquiring the rotation angle θa of the output shaft 46 as the bottom position rotation angle θe2 when it is determined that the rotation angle θa of the output shaft 46 has stopped changing in the first rotation drive D1b and the rotation angle θa of the output shaft 46 has been the same for two or more consecutive times. In the acquisition control for the valley portion 79b, the output torque Tm of the motor 20 decreases each time the first rotation drive D1b is performed, so the rotation angle θa at which the output shaft 46 stops rotating in the first rotation drive D1b approaches the bottom position rotation angle θe2 each time the first rotation drive D1b is performed. Therefore, if the first rotation drive D1b is repeated with the second rotation drive D2b in between, the contact position P of the contact portion 76b at which the output shaft 46 stops rotating in the first rotation drive D1b approaches the bottom portion 79i, and finally the contact position P becomes the bottom portion 79i. When the contact position P becomes the bottom 79i, even if the output torque Tm is then reduced to execute the first rotational drive D1b, the rotation angle θa at which the output shaft 46 stops rotating will remain the same. Therefore, if the rotation angle θa at which the output shaft 46 stops when the first rotational drive D1b is executed is the same two or more times, it can be determined that the rotation angle θa of the output shaft 46 is at the bottom position rotation angle θe2, where the contact portion 76b contacts the bottom 79i. Thus, in step S207 described above, if it is determined that the rotation angle θa at which the output shaft 46 stops in the first rotational drive D1b is the same rotation angle θa for two or more predetermined consecutive times, the rotation angle θa is acquired as the bottom position rotation angle θe2, thereby enabling accurate acquisition of the bottom position rotation angle θe2. Consequently, the rotation angle θa of the output shaft 46 can be learned with high accuracy. Furthermore, by setting the above predetermined number of times to 3 or more, even if a misjudgment occurs in step S204, it is possible to suppress the acquisition of an incorrect rotation angle θa as the bottom position rotation angle θe2.

[0116] The above predetermined number of times may be 2. In this case, the control unit 90 may omit step S207 and execute step S208 if it determines in step S204 that the rotation angle θa of the output shaft 46 is the same as the rotation angle θa when it stopped during the previous first rotation drive D1b.

[0117] Furthermore, according to this embodiment, the acquisition control for the valley portion 79b includes switching the second rotation drive D2b to the first rotation drive D1b when it is determined that the rotation angle θa of the output shaft 46 in the second rotation drive D2b has reached a predetermined angle, i.e., the starting angle θs2, at which point the contact position P is the second inclined surface 79h. Therefore, in the acquisition control for the valley portion 79b, there is no need to adjust the output torque Tm of the motor 20 in the second rotation drive D2b, and the second rotation drive D2b simply drives the rotation angle θa to a predetermined angle, i.e., the starting angle θs2. Consequently, it is possible to suppress the contact position P from moving away from the valley portion 79b when the second rotation drive D2b is executed, and the execution of the second rotation drive D2b can be made easier. In the above description, the predetermined angle which is the target value of the rotation angle θa in the second rotation drive D2b was set to the starting angle θs2, but it is not limited to this. The predetermined angle is not particularly limited as long as the contact position P is at the second inclined surface 79h, and may be an angle other than the starting angle θs2.

[0118] Furthermore, according to this embodiment, the electric actuator 10 has a function to maintain the rotation angle θa of the output shaft 46 when power is not supplied to the motor 20. Viewed in the axial direction of the central axis J1, the absolute value of the inclination angle of the first inclined surface 79g with respect to the circumferential direction around the central axis J1 is greater than the absolute value of the inclination angle of the second inclined surface 79h with respect to the circumferential direction around the central axis J1. Conventionally, for valleys 79b having such first inclined surfaces 79g and second inclined surfaces 79h, it is conceivable to obtain the bottom position rotation angle θe2 by abutting learning control in which the contact portion 76b abuts against the first inclined surface 79g, which has a large inclination angle with respect to the circumferential direction. However, if the electric actuator 10 has a self-holding function to maintain the rotation angle θa of the output shaft 46, when the contact portion 76b rises above the first inclined surface 79g when it abuts against the first inclined surface 79g, the position of the contact portion 76b will not change even if it receives force from the leaf spring member 76 after the power supply to the motor 20 is stopped. Therefore, when the electric actuator 10 has a self-holding function, conventional abutment learning control has the problem of not being able to accurately obtain the bottom position rotation angle θe2. In contrast, according to this embodiment, by performing the acquisition control for the valley portion 79b described above, the bottom position rotation angle θe2 of the valley portion 79b can be obtained with accuracy.

[0119] Figure 13 shows an example of the change in the output torque Tm of the motor 20 and the change in the rotation angle θa of the output shaft 46 during acquisition control for the valley section 79b. In the upper graph of Figure 13, the vertical axis is the output torque Tm and the horizontal axis is time t. In the lower graph of Figure 13, the vertical axis is the rotation angle θa of the output shaft 46 and the horizontal axis is time t. In Figure 13, at time t9, the rotation angle θa becomes the starting angle θs2. From time t9 to time t10, from time t11 to time t12, from time t13 to time t14, from time t15 to time t16, from time t17 to time t18, and from time t19 to time t20, the first rotation drive D1b is executed. The second rotational drive D2b is executed from time t10 to time t11, from time t12 to time t13, from time t14 to time t15, from time t16 to time t17, and from time t18 to time t19.

[0120] As shown in the lower graph of Figure 13, in the acquisition control for the valley 79b, the rotation angle θa approaches the bottom position rotation angle θe2 in the valley 79b each time the first rotation drive D1b is executed. As shown in the upper graph of Figure 13, the output torque Tm in the first rotation drive D1b decreases each time the first rotation drive D1b is performed. In the example of Figure 13, the output torque Tm in the second rotation drive D2b is torque Ta in all second rotation drives D2b. In the example of Figure 13, the rotation angle θa becomes the bottom position rotation angle θe2 due to the first rotation drive D1b executed from time t15 to time t16. In the example of Figure 13, the control unit 90 acquires the rotation angle θa as the bottom position rotation angle θe2 when the same rotation angle θa is achieved three times in a row: from time t15 to time t16, from time t17 to time t18, and from time t19 to time t20.

[0121] The acquisition control for valley 79c is the same as the acquisition control for valley 79a or valley 79b. Here, unlike valley 79a, valley 79c is not a valley 79 provided between two valleys 79. Therefore, conventionally, it is conceivable to acquire the bottom position rotation angle by abutment learning control by setting the radial dimension of the first inclined surface 79j to a height that the contact portion 76b cannot overcome. However, due to the arrangement of other equipment, the radial dimension of the first inclined surface 79j may not be large enough. In this case, the conventional abutment learning control cannot be used, as with valley 79a. Furthermore, even if the first inclined surface 79j can be made to a size that allows for abutment learning control, as with valley 79b described above, the bottom position rotation angle may not be acquired accurately due to the self-holding function of the electric actuator 10. In response to these, by performing the acquisition control for valley 79a or valley 79b described above on valley 79c as well, the control unit 90 can acquire the bottom position rotation angle of valley 79c. In the acquisition control for valley 79c, the +θ side is the other side in the circumferential direction, and the -θ side is the one side in the circumferential direction.

[0122] The acquisition control described above for valley 79a can also be applied to valley 79b. The acquisition control described above for valley 79b can also be applied to valley 79a.

[0123] The control unit 90 is a computer that executes the learning method, including the acquisition control described above in this embodiment. The control unit 90 has a program installed that causes the computer, the control unit 90, to execute the learning method, including the acquisition control described above. At least some of the functions of each component of the control unit 90 are realized, for example, by executing a program, i.e., software, stored in a memory unit (not shown).

[0124] At least some of the functions of each component of the control unit 90 may be implemented by hardware including circuit sections such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), and GPU (Graphics Processing Unit), or by the cooperation of software and hardware. The storage unit (not shown) that stores the program that causes the control unit 90, which is a computer, to execute the learning method including the acquisition control of this embodiment described above, may be implemented by a storage medium such as RAM (Random Access Memory), ROM (Read Only Memory), HDD (hard disk drive), and flash memory. The storage unit is not particularly limited as long as it can store the program that causes the computer to execute the learning method including the acquisition control of this embodiment described above, and may be a microcomputer or a disk medium such as a CD-ROM. The storage unit may be provided separately from the control unit 90. In this case, the control unit 90 may communicate with the storage unit by wired communication or wireless communication and execute the program stored in the storage unit.

[0125] The present invention is not limited to the embodiments described above, and other configurations and methods can be adopted within the scope of the technical idea of ​​the present invention. The number of valleys provided on the outer edge of the first member (detent plate) is not particularly limited, as long as there is one or more. The number of valleys may be two, or four or more. The first rotational drive and the second rotational drive, which are repeated alternately, may be started from either rotational drive.

[0126] In the embodiments described above, the rotor of the motor of the electric actuator is configured to rotate around the central axis J1 of the output shaft, but it is not limited to this configuration. The rotor may be rotatable around an axis different from the central axis J1 of the output shaft. This axis different from the central axis J1 may be an axis parallel to the central axis J1 but at a different radial position, or it may be an axis extending in a direction intersecting the axial direction of the central axis J1. The applications of the electric actuator to which the present invention is applied are not particularly limited. The electric actuator may be mounted on any equipment.

[0127] Furthermore, this technology can be configured as follows: (1) An electric actuator that rotates a plate-shaped first member having a plate surface and an outer edge around a central axis perpendicular to the plate surface, thereby changing the contact position of a second member having a contact portion that contacts the outer edge, comprising: an output shaft connected to the first member; a motor that rotates the output shaft around the central axis; a rotation sensor that detects the rotation angle of the output shaft; and a control unit that controls the motor, wherein the outer edge has a valley, the valley has a first inclined surface, a second inclined surface located on one side of the first inclined surface in the circumferential direction around the central axis, and a bottom portion connecting the first inclined surface and the second inclined surface, and the control unit performs acquisition control to acquire the rotation angle of the output shaft when the contact position becomes the bottom portion as the bottom position rotation angle. An electric actuator is possible, and the acquisition control includes alternatingly performing a first rotational drive that rotates the output shaft to one side in the circumferential direction around the central axis and a second rotational drive that rotates the output shaft to the other side in the circumferential direction around the central axis, starting from a state where the rotation angle of the output shaft is at a starting angle where the contact position is the valley; making the output torque of the motor in the first rotational drive less than the output torque that the contact portion can overcome the first inclined surface; switching the first rotational drive to the second rotational drive when it is determined that the output shaft has stopped in the first rotational drive; and decreasing the output torque of the motor in the first rotational drive each time the first rotational drive is performed. (2) The electric actuator according to (1), wherein the acquisition control includes: reducing the output torque of the motor in the second rotation drive to less than the output torque that allows the contact portion to overcome the second inclined surface; switching the second rotation drive to the first rotation drive when it is determined that the rotation angle of the output shaft has stopped changing in the second rotation drive; reducing the output torque of the motor in the second rotation drive each time the second rotation drive is performed; and acquiring the rotation angle of the output shaft as the bottom position rotation angle when switching from one rotation drive of the first rotation drive or the second rotation drive to the other rotation drive, if the rotation angle of the output shaft does not change even when the other rotation drive is performed. (3) The electric actuator according to (2), wherein the acquisition control includes making the output torque of the motor in the second rotational drive less than the output torque of the motor in the first rotational drive performed immediately before the second rotational drive. (4) The electric actuator according to (1), wherein the acquisition control includes acquiring the rotation angle of the output shaft as the bottom position rotation angle when it is determined that the rotation angle of the output shaft has not changed in the first rotation drive and the rotation angle of the output shaft has been the same for two or more consecutive times. (5) The electric actuator according to (4), wherein the acquisition control includes switching the second rotation drive to the first rotation drive when it is determined that the rotation angle of the output shaft in the second rotation drive has reached a predetermined angle in which the contact position is the second inclined surface. (6) The electric actuator according to any one of (1) to (5), wherein the outer periphery has three or more valleys arranged in a circumferential direction about the central axis, and the control unit performs the acquisition control in the valley located between the valley located on the far side and the valley located on the far side in the circumferential direction about the central axis. (7) An electric actuator according to any one of (1) to (6), having a function to maintain the rotation angle of the output shaft when power is not supplied to the motor, wherein the absolute value of the inclination angle of the first inclined surface with respect to the circumferential direction around the central axis is greater than the absolute value of the inclination angle of the second inclined surface with respect to the circumferential direction around the central axis when viewed in the axial direction of the central axis.

[0128] The configurations and methods described herein can be combined as appropriate, within the bounds of non-inconsistency. [Explanation of Symbols]

[0129] 10…Electric actuator, 20…Motor, 46…Output shaft, 71…Detent plate (first member), 71a…Outer edge, 71f…Plate surface, 76…Leaf spring member (second member), 76b…Contact part, 79, 79a, 79b, 79c…Valley part, 79d, 79g, 79j…First inclined surface, 79e, 79h, 79k…Second inclined surface, 79f, 79i, 79m…Bottom part, 90…Control unit, 95…Rotation sensor, D1a, D1b…First rotation drive, D2a, D2b…Second rotation drive, J1…Center axis, P…Contact position, Tm…Output torque, θa…Rotation angle, θe1, θe2…Bottom position rotation angle, θs1…Starting angle, θs2…Starting angle (predetermined angle)

Claims

1. An electric actuator that rotates a plate-shaped first member having a plate surface and an outer edge around a central axis perpendicular to the plate surface, thereby changing the contact position of a second member having a contact portion that contacts the outer edge, An output shaft connected to the first member, A motor that rotates the output shaft around the central axis, A rotation sensor for detecting the rotation angle of the output shaft, A control unit that controls the motor, Equipped with, The outer edge has a valley, The aforementioned valley section is The first inclined surface and A second inclined surface located on one side of the first inclined surface in the circumferential direction around the central axis, A bottom portion connecting the first inclined surface and the second inclined surface, It has, The control unit is capable of performing acquisition control to acquire the rotation angle of the output shaft when the contact position becomes the bottom as the bottom position rotation angle. The acquisition control described above is: The rotation angle of the output shaft is such that, starting from a state where the contact position is the valley, a first rotational drive that rotates the output shaft to one side in the circumferential direction around the central axis and a second rotational drive that rotates the output shaft to the other side in the circumferential direction around the central axis are alternately repeated. The output torque of the motor in the first rotational drive is made smaller than the output torque that the contact portion can overcome the first inclined surface, When it is determined that the output shaft has stopped during the first rotational drive, the first rotational drive is switched to the second rotational drive, The output torque of the motor in the first rotational drive is reduced each time the first rotational drive is performed, Electric actuators, including

2. The acquisition control described above is: The output torque of the motor in the second rotational drive is made smaller than the output torque that the contact portion can overcome the second inclined surface, When it is determined that the rotation angle of the output shaft has stopped changing in the second rotation drive, the second rotation drive is switched to the first rotation drive. The output torque of the motor in the second rotational drive is reduced each time the second rotational drive is performed, When switching from one of the first rotational drive and the second rotational drive to the other rotational drive, if the rotation angle of the output shaft does not change even when the other rotational drive is executed, the rotation angle of the output shaft is obtained as the bottom position rotation angle. The electric actuator according to claim 1, including the following:

3. The electric actuator according to claim 2, wherein the acquisition control includes making the output torque of the motor in the second rotational drive less than the output torque of the motor in the first rotational drive performed immediately before the second rotational drive.

4. The electric actuator according to claim 1, wherein the acquisition control includes acquiring the rotation angle of the output shaft as the bottom position rotation angle when it is determined that the rotation angle of the output shaft has not changed in the first rotation drive and the rotation angle of the output shaft has been the same for two or more consecutive times.

5. The electric actuator according to claim 4, wherein the acquisition control includes switching the second rotation drive to the first rotation drive when it is determined that the rotation angle of the output shaft in the second rotation drive has reached a predetermined angle such that the contact position is the second inclined surface.

6. The outer edge has three or more valleys arranged in the circumferential direction around the central axis, The electric actuator according to any one of claims 1 to 5, wherein the control unit performs the acquisition control in the valley located between the valley located on the furthest side in the circumferential direction around the central axis and the valley located on the farther side among three or more valleys.

7. The motor has a function to maintain the rotation angle of the output shaft when power is not supplied to it. The electric actuator according to any one of claims 1 to 5, wherein, when viewed in the axial direction of the central axis, the absolute value of the inclination angle of the first inclined surface with respect to the circumferential direction about the central axis is greater than the absolute value of the inclination angle of the second inclined surface with respect to the circumferential direction about the central axis.

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