Electric actuator and manufacturing method of electric actuator

Abstract

To provide an electric actuator capable of suppressing an increase in the number of components of the electric actuator.SOLUTION: The electric actuator includes: a motor case 12 having an opening 12a opening to one axial side; and a cover member 17 closing the opening. The motor case and the cover member are each made of resin. The cover member has a first supporting portion 17a which supports a portion of a motor shaft located on one axial side than a stator and is disk-shaped with a center of a center axis J1. The motor case has: a bottom wall portion 14 provided with a second support portion 14a supporting a portion of the motor shaft located on the other axial side than the stator and a through hole 14c through which the motor shaft passes in the axial direction, and extending in a direction intersecting the axial direction; and an annual cover fixing portion 13b axially contacting with a surface of the cover member facing the other axial side, and surrounding the center axis. The cover member and the cover fixing portion are peripherally connected to each other.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an electric actuator and a method for manufacturing an electric actuator. [Background technology]

[0002] 2. Description of the Related Art There is known an electric actuator in which a housing for accommodating a motor is constituted by a motor case that supports one axial end of a motor shaft and a cover that supports the other axial end of the motor shaft (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-053986 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the manufacturing process of the electric actuator as described above, there have been cases where the coaxiality between the motor shaft and the housing is increased by assembling one axial end of the motor shaft to a support part of the motor case and assembling the other axial end of the motor shaft to a support part of the cover while holding both axial ends of the motor shaft with a jig or the like. In this case, it was necessary to provide holes in the motor case and the cover to pass the jig or the like holding the motor shaft through. Therefore, in order to increase the airtightness of the electric actuator, it was necessary to block the holes with a member such as a cap, which increased the number of parts of the electric actuator.

[0005] In consideration of the above circumstances, one object of the present invention is to provide an electric actuator that can increase the concentricity between the motor shaft and the housing while suppressing an increase in the number of parts of the electric actuator, and a manufacturing method for the electric actuator. [Means for solving the problem]

[0006] One embodiment of the electric actuator of the present invention includes a rotor having a motor shaft rotatable around a central axis, a stator disposed radially outside the rotor, a motor case having an opening opening to one axial side and housing the rotor and the stator inside, and a cover member closing the opening. The motor case and the cover member are each made of resin. The cover member has a first support portion supporting a portion of the motor shaft located on one axial side of the stator, and is disk-shaped with the central axis as its center. The motor case has a second support portion supporting a portion of the motor shaft on the other axial side of the stator, a through hole through which the motor shaft passes, a bottom wall portion extending in a direction intersecting the axial direction, and an annular cover fixing portion that axially contacts a surface of the cover member facing the other axial side and surrounds the central axis. The cover member and the cover fixing portion are joined to each other over the entire circumference in the circumferential direction.

[0007] One aspect of the manufacturing method of the electric actuator of the present invention is a manufacturing method of an electric actuator including a rotor having a motor shaft rotatable around a central axis, a stator disposed radially outside the rotor, a motor case having an opening opening to one axial side and housing the rotor and the stator inside, and a cover member closing the opening, and includes an assembly process of assembling the rotor and the cover member to the motor case. The motor case and the cover member are each made of resin. The cover member has a first support part supporting a portion of the motor shaft located on one axial side of the stator, and is disk-shaped with the central axis as its center. The motor case has a second support part, a through hole through which the motor shaft passes, a bottom wall part extending in a direction intersecting the axial direction, and an annular cover fixing part surrounding the central axis. The assembly process includes a first process of inserting the rotor into the motor case through the opening to cause the second support portion to support the other axial side of the motor shaft, and passing the motor shaft through the through hole; a second process of fixing the portion of the motor shaft that protrudes further toward the other axial side than the bottom wall portion through the through hole to a shaft fixing jig; a third process of moving the cover member from one axial side of the motor case to the other axial side to cause the portion of the motor shaft on one axial side to be supported by the first support portion; and a fourth process of rotating the cover member around the central axis to spin-weld the surface of the cover member facing the other axial side to the cover fixing portion. Effect of the Invention

[0008] According to one aspect of the present invention, in an electric actuator and a manufacturing method for an electric actuator, it is possible to improve the concentricity between a motor shaft and a housing while suppressing an increase in the number of parts of the electric actuator. [Brief description of the drawings]

[0009] [Figure 1]FIG. 1 is a perspective view showing an electric actuator according to one embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing an electric actuator according to one embodiment. [Diagram 3] FIG. 3 is a flow chart showing an assembly process according to one embodiment. [Figure 4] FIG. 4 is a first cross-sectional view showing an assembly process of an embodiment. [Diagram 5] FIG. 5 is a second cross-sectional view showing an assembly process of the embodiment. [Figure 6] FIG. 6 is a third cross-sectional view showing an assembly process of an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In each drawing, the Z-axis direction is the up-down direction with the positive side (+Z side) on the top and the negative side (-Z side) on the bottom. In this embodiment, the top side (+Z side) corresponds to one axial side, and the bottom side (-Z side) corresponds to the other axial side.

[0011] In each drawing, the first direction D1 is a direction perpendicular to the Z-axis direction. In this embodiment, the first direction D1 is the left-right direction of the electric actuator. In the following description, the side toward which the arrow of the first direction D1 points (+D1 side) is referred to as the "right side," and the side opposite to the side toward which the arrow of the first direction D1 points (-D1 side) is referred to as the "left side."

[0012] In each drawing, the second direction D2 is a direction perpendicular to both the Z-axis direction and the first direction D1. In this embodiment, the second direction D2 is the front-rear direction of the electric actuator. In the following description, the side toward which the arrow of the second direction D2 points (+D2 side) is referred to as the "rear side", and the side opposite to the side toward which the arrow of the second direction D2 points (-D2 side) is referred to as the "front side". Note that the upper side, lower side, right side, left side, front side, and rear side are names simply for describing the relative positional relationship of each part, and the actual positional relationship, etc. may be a positional relationship, etc. other than the positional relationship, etc. indicated by these names.

[0013] The direction in which the central axis J1 shown in each drawing extends is parallel to the Z-axis direction. In this embodiment, the central axis J1 is a virtual axis. The central axis J1 is the central axis of the motor shaft. In the following description, the direction parallel to the central axis J1 is simply referred to as the "axial direction." The radial direction centered on the central axis J1 is simply referred to as the "radial direction." The circumferential direction centered on the central axis J1 is simply referred to as the "circumferential direction." In each drawing, the circumferential direction is indicated by the arrow θ1.

[0014] The electric actuator 1 of this embodiment shown in Fig. 1 is attached to a vehicle. More specifically, the electric actuator 1 is mounted on, for example, a park-by-wire type actuator device that is driven based on a shift operation by a vehicle driver. As shown in Fig. 2, the electric actuator 1 includes a housing 10, a motor 9, a transmission mechanism 60, an output shaft 66, and a circuit board 80.

[0015] The housing 10 accommodates the motor 9, the transmission mechanism 60, the output shaft 66, and the circuit board 80 therein. The housing 10 has a case body 11, a cover member 17, and a lower case 18. In this embodiment, the case body 11 and the cover member 17 are made of resin. The lower case 18 may be made of resin or metal. The case body 11 is cylindrical and surrounds the central axis J1. The case body 11 has a lower opening 11b that opens downward. The case body 11 has a motor case 12, a connector case 15, and a fixing portion 11a.

[0016] The motor case 12 is generally cylindrical and centered on the case axis J2. In this embodiment, the case axis J2 is a virtual axis extending in a direction parallel to the central axis J1. The case axis J2 overlaps with the central axis J1. Thus, the motor case 12 is generally cylindrical and extends in the axial direction and centered on the central axis J1. The motor case 12 is made of resin. The motor case 12 accommodates the motor 9 therein. The motor case 12 opens downward. The motor case 12 has an opening 12a that opens upward, i.e., on one axial side (+Z side). The motor case 12 has a peripheral wall portion 13, a cover fixing portion 13b, and a bottom wall portion 14. In the present invention, the axis of one member overlaps with the axis of the other member not only includes the case where the axis of one member completely overlaps with the axis of the other member, but also the case where the coaxiality of both members deviates to approximately the design tolerance obtained by adding the design tolerance of the roundness, etc. of one member and the design tolerance of the roundness, etc. of the other member.

[0017] The peripheral wall portion 13 has a generally cylindrical shape extending in the axial direction centered on the central axis J1. The peripheral wall portion 13 surrounds the motor 9 from the radially outer side. The peripheral wall portion 13 has a stepped surface 13a. The stepped surface 13a is a stepped surface facing upward. The stepped surface 13a is a part of the inner surface of the peripheral wall portion 13. When viewed in the axial direction, the stepped surface 13a is annular and centered on the central axis J1.

[0018] The cover fixing portion 13b protrudes upward from the peripheral wall portion 13. The cover fixing portion 13b is annular and surrounds the central axis J1. In this embodiment, the cover fixing portion 13b is annular and centered on the central axis J1. The upper end of the cover fixing portion 13b is the upper end of the motor case 12. The cover fixing portion 13b is located on the upper side of the motor case 12, i.e., at the end on one axial side (+Z side). The inner diameter of the cover fixing portion 13b is the same dimension as the inner diameter of the peripheral wall portion 13. The outer diameter of the cover fixing portion 13b is smaller than the outer diameter of the peripheral wall portion 13.

[0019] The bottom wall portion 14 is generally disk-shaped and extends in a direction intersecting the axial direction. In this embodiment, the bottom wall portion 14 extends in a direction perpendicular to the axial direction. The bottom wall portion 14 is generally disk-shaped and centered on the central axis J1. The radially outer end of the bottom wall portion 14 is connected to the lower end of the peripheral wall portion 13. The bottom wall portion 14 is provided with a second support portion 14a, a through hole 14c, a first bottom wall hole portion 14e, a second bottom wall hole portion 14f, and a first substrate holding portion 14h.

[0020] The second support portion 14a protrudes upward from the bottom wall portion 14. The second support portion 14a is cylindrical and centered on the central axis J1. The second support portion 14a opens upward. The through hole 14c is a hole that penetrates the bottom wall portion 14 in the axial direction. In this embodiment, the through hole 14c is substantially circular and centered on the central axis J1 when viewed from the axial direction. The through hole 14c may be of other shapes, such as a square shape, when viewed from the axial direction. The inner diameter of the through hole 14c is smaller than the inner diameter of the second support portion 14a.

[0021] The first bottom wall hole portion 14e is a hole penetrating the bottom wall portion 14 in the axial direction. The first bottom wall hole portion 14e is arranged radially outward from the second support portion 14a. Although not shown, in this embodiment, three first bottom wall holes 14e are provided in the bottom wall portion 14. The first bottom wall holes 14e are arranged at intervals from each other along the circumferential direction. The second bottom wall hole portion 14f is a hole penetrating the bottom wall portion 14 in the axial direction. When viewed from the axial direction, the second bottom wall hole portion 14f has a circular shape centered on the output axis J4. The second bottom wall hole portion 14f is arranged on the left side (-D1 side) of the second support portion 14a. The second bottom wall hole portion 14f is arranged at an interval from the second support portion 14a in the first direction D1.

[0022] In this embodiment, the output axis J4 is a virtual axis extending in a direction parallel to the central axis J1. The output axis J4 is located on the left side (-D1 side) of the central axis J1. In the following description, the radial direction centered on the output axis J4 is simply referred to as the "output radial direction," and the circumferential direction centered on the output axis J4 is simply referred to as the "output circumferential direction." The output circumferential direction is indicated by an arrow θ4 in each drawing.

[0023] The first board holding portion 14h holds the circuit board 80. The first board holding portion 14h is a generally cylindrical shape protruding downward from the bottom wall portion 14. The first board holding portion 14h is disposed radially outward from the first bottom wall hole portion 14e. Although not shown, in this embodiment, three first board holding portions 14h are provided on the bottom wall portion 14. The first bottom wall hole portions 14e are disposed at intervals along the circumferential direction. Each first board holding portion 14h has a first shaft portion 14i, a first insertion portion 14j, and a first board support portion 14k. The first shaft portion 14i is a generally cylindrical shape protruding downward from the bottom wall portion 14. The first insertion portion 14j is a generally cylindrical shape protruding downward from the first shaft portion 14i. The outer diameter of the first insertion portion 14j is smaller than the outer diameter of the first shaft portion 14i. The first substrate support portion 14k protrudes downward from the first insertion portion 14j. The outer diameter of the first substrate support portion 14k is larger than the outer diameter of the first insertion portion 14j.

[0024] The connector case 15 is cylindrical and extends in the axial direction. The connector case 15 opens downward. The connector case 15 is disposed on the left side (-D1 side) of the motor case 12. The connector case 15 is connected to the motor case 12 in the first direction D1. As shown in FIG. 1, the connector case 15 is substantially rectangular in shape with the right side (+D1 side) recessed in an arc shape toward the left side when viewed from the axial direction. As shown in FIG. 2, the connector case 15 is provided with a second board holding portion 15a and a connector accommodating portion 16.

[0025] The second board holding portion 15a holds the circuit board 80. The second board holding portion 15a is a substantially cylindrical shape protruding downward from the connector case 15. Although not shown, in this embodiment, two second board holding portions 15a are provided in the connector case 15. The second board holding portions 15a are arranged at intervals in the second direction D2. Each second board holding portion 15a has a second shaft portion 15b, a second insertion portion 15c, and a second board support portion 15d. The second shaft portion 15b is a substantially cylindrical shape protruding downward from the connector case 15. The second insertion portion 15c is a substantially cylindrical shape protruding downward from the second shaft portion 15b. The outer diameter of the second insertion portion 15c is smaller than the outer diameter of the second shaft portion 15b. The second board support portion 15d protrudes downward from the second insertion portion 15c. The outer diameter of the second substrate supporting portion 15d is larger than the outer diameter of the second insertion portion 15c.

[0026] As shown in FIG. 1, the connector accommodating portion 16 has a generally rectangular tubular shape that protrudes upward from the connector case 15. The connector accommodating portion 16 opens upward. As shown in FIG. 2, the connector accommodating portion 16 holds a plurality of connector pins 97a. Each connector pin 97a extends in the axial direction. An upper end of each connector pin 97a is located inside the connector accommodating portion 16. A lower end of each connector pin 97a is connected to the circuit board 80.

[0027] As shown in FIG. 1, the fixing portion 11a protrudes radially outward from the motor case 12 or the connector case 15. The fixing portion 11a is provided with a hole penetrating the fixing portion 11a in the axial direction. In this embodiment, the case body 11 has three fixing portions 11a. One fixing portion 11a protrudes from the peripheral wall portion 13 to the right side (+D1 side). One of the other two fixing portions 11a protrudes from the connector case 15 to the front side (-D2 side), and the other fixing portion 11a protrudes from the connector case 15 to the rear side (+D2 side). A bolt (not shown) is passed through the hole of each fixing portion 11a in the axial direction, and when the bolt is fastened into a screw hole (not shown) provided in the vehicle, the electric actuator 1 is fixed to the vehicle body.

[0028] As shown in FIG. 2, the cover member 17 is disk-shaped and centered on the cover axis J3. In this embodiment, the cover axis J3 is a virtual axis extending in a direction parallel to the central axis J1. The cover axis J3 overlaps with the central axis J1. Thus, the cover member 17 is disk-shaped and centered on the central axis J1. The cover member 17 is disposed on the upper side of the motor case 12. The cover member 17 closes the opening 12a of the motor case 12 from above. The cover member 17 has a first support portion 17a, a cover welded portion 17b, and a cover annular portion 17d.

[0029] The first support portion 17a protrudes downward from the cover member 17. The first support portion 17a is cylindrical and centered on the central axis J1. The first support portion 17a opens downward. The cover welding portion 17b is a radially outer edge portion of the surface of the cover member 17 facing the lower side. The cover welding portion 17b extends around the circumferential direction along the radially outer edge of the cover member 17. When viewed from the axial direction, the cover welding portion 17b is substantially annular and centered on the central axis J1. The cover welding portion 17b contacts the cover fixing portion 13b in the axial direction. That is, the cover fixing portion 13b contacts the lower side of the cover member 17, i.e., the surface facing the other axial side (-Z side) in the axial direction. The cover welding portion 17b is joined to the cover fixing portion 13b by welding. As a result, the cover member 17 is fixed to the motor case 12. The cover member 17 and the cover fixing portion 13b are joined to each other over the entire circumferential direction, thereby sealing the gap between the cover member 17 and the motor case 12 over the entire circumferential direction. As will be described later, in this embodiment, the cover welding portion 17b and the cover fixing portion 13b are joined by spin welding.

[0030] The cover annular portion 17d protrudes downward from the radially outer end of the cover member 17. The cover annular portion 17d is annular about the central axis J1. The cover annular portion 17d is disposed radially outside the cover fixing portion 13b. The cover annular portion 17d faces the cover fixing portion 13b in the radial direction. In this embodiment, the cover annular portion 17d may be disposed with a gap from the cover fixing portion 13b in the radial direction, or may be disposed in contact with the cover fixing portion 13b in the radial direction. The cover annular portion 17d is disposed with a gap from the peripheral wall portion 13 in the axial direction.

[0031] The lower case 18 is box-shaped and opens upward. The lower case 18 is disposed below the case body 11. The lower case 18 closes the lower opening 11b of the case body 11 from below. The lower case 18 is fixed to the lower end of the case body 11. The lower case 18 and the case body 11 may be fixed by adhesion or by screws (not shown). The inside of the lower case 18 is isolated from the inside of the motor case 12 by the bottom wall portion 14. The inside of the lower case 18 is connected to the inside of the connector case 15. The transmission mechanism 60 is housed inside the lower case 18. The lower case 18 has a first wall portion 18a and a second wall portion 18b.

[0032] The first wall portion 18a is cylindrical and protrudes in the axial direction. The first wall portion 18a opens upward. The first wall portion 18a surrounds the central axis J1 and the output axis J4. The right side (+D1 side) of the first wall portion 18a is annular about the central axis J1. The right side of the first wall portion 18a is fixed to the lower end of the peripheral wall portion 13. The left side (-D1 side) of the first wall portion 18a is substantially rectangular and opens to the right. The left side of the first wall portion 18a is fixed to the lower end of the connector case 15. As a result, the lower case 18 is fixed to the lower end of the case main body 11.

[0033] The second wall portion 18b is a plate-like portion that extends in a direction perpendicular to the axial direction. The outer edge of the second wall portion 18b is connected to the lower end of the first wall portion 18a. The second wall portion 18b is provided with a third support portion 18d and an output hole portion 18f. The third support portion 18d protrudes downward from the second wall portion 18b. The third support portion 18d is cylindrical and centered on the central axis J1. The third support portion 18d opens upward. The output hole portion 18f is a hole that penetrates the second wall portion 18b in the axial direction. When viewed from the axial direction, the output hole portion 18f is circular and centered on the output axis J4.

[0034] The motor 9 has a rotor 20 and a stator 30. The rotor 20 and the stator 30 are housed inside a motor case 12. The rotor 20 is rotatable about a central axis J1. The rotor 20 has a rotor core 21, a magnet (not shown), and a motor shaft 23. The rotor core 21 is annular about the central axis J1. The magnet (not shown) is fixed to the rotor core 21. In this embodiment, a plurality of magnets are arranged at intervals in the circumferential direction.

[0035] The motor shaft 23 is rotatable about the central axis J1. The motor shaft 23 is generally cylindrical and extends in the axial direction about the central axis J1. The motor shaft 23 extends in the axial direction across the interior of the motor case 12 and the interior of the lower case 18. The motor shaft 23 passes through the interior of the rotor core 21 in the axial direction. The rotor core 21 is fixed to the outer circumferential surface of the motor shaft 23. A portion of the motor shaft 23 below the rotor core 21 passes through the through hole 14c in the axial direction and protrudes into the interior of the lower case 18. In other words, a portion of the motor shaft 23 below the bottom wall portion 14 protrudes into the interior of the lower case 18.

[0036] The stator 30 is disposed radially outward of the rotor 20. The stator 30 is disposed radially opposite the rotor 20 with a gap therebetween. The stator 30 includes a stator core 31, an insulator 32, and a coil portion .

[0037] The stator core 31 is annular and surrounds the rotor core 21 from the radial outside. The stator core 31 faces the rotor 20 with a gap in the radial direction. The stator core 31 has a core back portion 31a and a plurality of teeth portions 31b. The core back portion 31a is annular and centered on the central axis J1. The core back portion 31a is fixed to the inner peripheral surface of the peripheral wall portion 13. This fixes the stator 30 to the case body 11. The surface of the core back portion 31a facing downward is in contact with the step surface 13a in the axial direction. This determines the axial position of the stator 30 relative to the case body 11. Each tooth portion 31b protrudes radially inward from the core back portion 31a. Although not shown, each tooth portion 31b is arranged at intervals along the circumferential direction. The insulator 32 is attached to the stator core 31. The insulator 32 insulates the stator core 31 from the coil portion 35 .

[0038] The coil portion 35 has a plurality of coil body portions 35a and a coil lead wire 35b. Each coil body portion 35a is attached to a different tooth portion 31b via an insulator 32. The coil lead wire 35b is drawn downward from the coil body portion 35a and passed axially through a first bottom wall hole portion 14e of the bottom wall portion 14. The lower end of the coil lead wire 35b is connected to the circuit board 80. As a result, the coil portion 35 is electrically connected to the circuit board 80.

[0039] The first bearing 91 is annular about the central axis J1. The first bearing 91 is attached to the inner peripheral surface of the first support portion 17a. The first bearing 91 supports a portion of the motor shaft 23 above the stator 30 so as to be rotatable about the central axis J1. As a result, the first support portion 17a supports a portion of the motor shaft 23 above the stator 30, i.e., on one axial side (+Z side), via the first bearing 91. In other words, the first support portion 17a supports a portion of the motor shaft 23 above the stator 30. In this embodiment, the first bearing 91 is a sliding bearing. The first bearing 91 may be a ball bearing.

[0040] The second bearing 92 is annular about the central axis J1. The second bearing 92 is attached to the inner peripheral surface of the second support portion 14a. The second bearing 92 supports a portion of the motor shaft 23 below the stator 30 so as to be rotatable about the central axis J1. As a result, the second support portion 14a supports a portion of the motor shaft 23 below the stator 30, i.e., the other axial side (-Z side), via the second bearing 92. In other words, the second support portion 14a supports a portion of the motor shaft 23 below the stator 30. In this embodiment, the second bearing 92 is a ball bearing. The second bearing 92 may be a sliding bearing.

[0041] The third bearing 93 has an annular shape centered on the central axis J1. The third bearing 93 is attached to an inner circumferential surface of the third support portion 18d. The third bearing 93 supports the lower end of the motor shaft 23 rotatably about the central axis J1. In this embodiment, the third bearing 93 is a ball bearing. The third bearing 93 may be a sliding bearing.

[0042] The circuit board 80 is a plate-like shape that spreads in a direction perpendicular to the axial direction. The circuit board 80 is disposed below the stator 30 and the bottom wall portion 14. As described above, a plurality of connector pins 97a are connected to the circuit board 80. When the plurality of connector pins 97a are electrically connected to an external power source (not shown), power is supplied from the external power source to the circuit board 80. Also, as described above, a plurality of coil lead wires 35b are connected to the circuit board 80. As a result, power from the external power source is supplied to the coil portion 35 via the circuit board 80. The circuit board 80 is provided with a first board hole 80a, a second board hole 80b, a third board hole 80c, and a fourth board hole 80d. Each of the first board hole 80a, the second board hole 80b, the third board hole 80c, and the fourth board hole 80d is a hole that penetrates the circuit board 80 in the axial direction.

[0043] When viewed in the axial direction, the first board hole 80a is substantially circular. Although not shown in the drawings, in this embodiment, three first board holes 80a are provided in the circuit board 80. When viewed in the axial direction, each first board hole 80a overlaps with a different first board holding portion 14h. The first insertion portion 14j passes through each first board hole 80a in the axial direction. The surface of the circuit board 80 facing upward is in contact with the first shaft portion 14i in the axial direction. The surface of the circuit board 80 facing downward is supported in the axial direction by the first board support portion 14k. As a result, the circuit board 80 is held in the housing 10.

[0044] When viewed in the axial direction, the second board hole 80b is substantially circular. Although not shown in the drawings, in this embodiment, two second board holes 80b are provided in the circuit board 80. When viewed in the axial direction, each second board hole 80b overlaps with a different second board holding portion 15a. The second insertion portion 15c passes through each second board hole 80b in the axial direction. The surface of the circuit board 80 facing upward is in contact with the second shaft portion 15b in the axial direction. The surface of the circuit board 80 facing downward is supported in the axial direction by the second board support portion 15d. As a result, the circuit board 80 is held in the housing 10.

[0045] When viewed in the axial direction, the third board hole 80c is substantially circular and centered on the central axis J1. The motor shaft 23 is passed through the third board hole 80c in the axial direction. When viewed in the axial direction, the fourth board hole 80d is substantially circular and centered on the output axis J4. The output shaft 66 is passed through the fourth board hole 80d in the axial direction.

[0046] The transmission mechanism 60 is disposed below the circuit board 80. The transmission mechanism 60 is housed inside the lower case 18. The transmission mechanism 60 is connected to both the motor shaft 23 and the output shaft 66. The transmission mechanism 60 is connected to a portion of the motor shaft 23 located below the bottom wall portion 14, i.e., on the other axial side (-Z side). The transmission mechanism 60 transmits the rotation of the motor shaft 23 to the output shaft 66. In this embodiment, the transmission mechanism 60 transmits the rotation of the rotor 20 to the output shaft 66 at a reduced speed. The transmission mechanism 60 may transmit the rotation of the rotor 20 to the output shaft 66 at an increased speed, or may transmit the rotation of the rotor 20 to the output shaft 66 at the same rotational speed as that of the rotor 20. The transmission mechanism 60 has a motor gear 61, a first stage gear 62, a second stage gear 63, and an output gear 64. The rotation of the motor shaft 23 is transmitted through the motor gear 61, the first stage gear 62, the second stage gear 63, the output gear 64, and the output shaft 66 in this order.

[0047] The motor gear 61 transmits the rotation of the motor shaft 23 to the first stage gear 62. The motor gear 61 is in the shape of an annular plate centered on a central axis J1. The inner circumferential surface of the motor gear 61 is fixed to the motor shaft 23. This causes the motor gear 61 to rotate together with the motor shaft 23 around the central axis J1. A motor gear portion is provided on a surface of the motor gear 61 facing radially outward.

[0048] The first stage gear 62 transmits the rotation of the motor gear 61 to the second stage gear 63. The first stage gear 62 is in the shape of an annular plate centered on the output axis J4. An output shaft 66 passes through the inside of the first stage gear 62 in the axial direction. The first stage gear 62 is supported by the output shaft 66 so as to be rotatable about the output axis J4. The first stage gear 62 has a first large diameter gear 62a and a first small diameter gear 62b. The first large diameter gear 62a and the first small diameter gear 62b are part of the same single member.

[0049] The first large diameter gear 62a is annular plate-shaped and centered on the output axis J4. The first large diameter gear 62a faces the motor gear 61 in the radial direction. A first large diameter gear part that meshes with the motor gear part is provided on the surface of the first large diameter gear 62a facing outward in the output radial direction. The number of teeth of the first large diameter gear part is greater than the number of teeth of the motor gear part. As a result, the rotation of the motor shaft 23 and the motor gear 61 is transmitted to the first stage gear 62 at a reduced speed. The first small diameter gear 62b is annular plate-shaped and centered on the output axis J4. The first small diameter gear 62b is disposed on the upper side of the first large diameter gear 62a. A first small diameter gear part is provided on the surface of the first small diameter gear 62b facing outward in the output radial direction.

[0050] The second stage gear 63 transmits the rotation of the first stage gear 62 to the output gear 64. The second stage gear 63 is in the shape of an annular plate centered on the central axis J1. The motor shaft 23 passes through the inside of the second stage gear 63 in the axial direction. The second stage gear 63 is supported by the motor shaft 23 so as to be rotatable about the central axis J1. The second stage gear 63 has a second large diameter gear 63a and a second small diameter gear 63b. The second large diameter gear 63a and the second small diameter gear 63b are part of the same single member.

[0051] The second large diameter gear 63a is annular plate-shaped with the center at the central axis J1. The second large diameter gear 63a faces the first small diameter gear 62b in the radial direction. A second large diameter gear portion that meshes with the first small diameter gear portion is provided on the surface of the second large diameter gear 63a facing radially outward. The number of teeth of the second large diameter gear portion is greater than the number of teeth of the first small diameter gear portion. As a result, the rotation of the first stage gear 62 is transmitted to the second stage gear 63 at a reduced speed. The second small diameter gear 63b is annular plate-shaped with the center at the central axis J1. The second small diameter gear 63b is disposed on the upper side of the second large diameter gear 63a. A second small diameter gear portion is provided on the surface of the second small diameter gear 63b facing radially outward.

[0052] The output gear 64 transmits the rotation of the second stage gear 63 to the output shaft 66. The output gear 64 is annular and has an output axis J4 as its center. The inner peripheral surface of the output gear 64 is fixed to the output shaft 66. As a result, the output shaft 66 rotates together with the output gear 64 around the output axis J4. An output gear portion that meshes with the second small diameter gear portion is provided on the surface of the output gear 64 facing outward in the output radial direction. The number of teeth of the output gear portion is greater than the number of teeth of the second small diameter gear portion. As a result, the rotation of the second stage gear 63 is reduced and transmitted to the output gear 64. As described above, the rotation of the motor gear 61 is reduced and transmitted to the first stage gear 62, and the rotation of the first stage gear 62 is reduced and transmitted to the second stage gear 63. As a result, the transmission mechanism 60 reduces the speed of the rotation of the motor shaft 23 and transmits it to the output shaft 66.

[0053] The output shaft 66 outputs the driving force of the electric actuator 1. The output shaft 66 is substantially cylindrical and extends axially around the output axis J4. The output shaft 66 is rotatable around the output axis J4. The output shaft 66 is axially passed through the fourth board hole 80d, the first stage gear 62, and the output gear 64. The upper end of the output shaft 66 is disposed inside the second bottom wall hole 14f. The upper end of the output shaft 66 is supported by the inner peripheral surface of the second bottom wall hole 14f via the fourth bearing 94. The output shaft 66 is rotatably supported around the output axis J4 by the inner peripheral surface of the second bottom wall hole 14f. The lower part of the output shaft 66 is axially passed through the output hole 18f and protrudes to the outside of the housing 10. The part of the output shaft 66 protruding to the outside of the housing 10 is connected to a driven member (not shown). This enables the electric actuator 1 to drive a driven member.

[0054] Next, a description will be given of an assembly process Pf of the electric actuator 1 of this embodiment. The assembly process Pf is part of the manufacturing process of the electric actuator 1. In the assembly process Pf, the rotor 20 and the cover member 17 are each assembled to the motor case 12. 3, the assembly process Pf includes a first process P01 in which the rotor 20 is inserted into the motor case 12 through the opening 12a to support a lower portion of the motor shaft 23 on the second support portion 14a and the motor shaft 23 is passed through the through hole 14c, a second process P02 in which the portion of the motor shaft 23 that protrudes below the bottom wall portion 14 through the through hole 14c is fixed to the shaft fixing jig 96, a third process P03 in which the cover member 17 is moved from the upper side to the lower side of the motor case 12 to support the upper portion of the motor shaft 23 on the first support portion 17a, and a fourth process P04 in which the cover member 17 is rotated about the central axis J1 to spin-weld the surface of the cover member 17 facing downward to the cover fixing portion 13b. In this specification, the term "workers, etc." includes workers who perform each task of the assembly process Pf and assembly devices, etc. Each task may be performed by a worker alone, by an assembly device alone, or by both a worker and the assembly device.

[0055] 4, in a first step P01, an operator first inserts the stator 30 into the motor case 12 through the opening 12a of the case body 11 fixed to a jig (not shown) and attaches the stator 30 to the motor case 12. At this time, the core back portion 31a of the stator core 31 is fixed to the inner circumferential surface of the peripheral wall portion 13, and the surface facing downward of the core back portion 31a is in axial contact with the stepped surface 13a. In addition, the coil lead wire 35b is passed axially through the first bottom wall hole portion 14e of the bottom wall portion 14.

[0056] Next, the worker moves the rotor 20 to which the first bearing 91 and the second bearing 92 are attached from the upper side to the lower side of the case body 11, and inserts it into the inside of the motor case 12 through the opening 12a. Next, as shown in FIG. 5, the worker moves the rotor 20 further downward, inserts the second bearing 92 into the inside of the second support portion 14a, and attaches the second bearing 92 to the inner circumferential surface of the second support portion 14a. As a result, the worker supports the part of the motor shaft 23 that is lower than the stator 30, i.e., the other axial side (-Z side), on the second support portion 14a through the second bearing 92. In other words, the worker supports the lower part of the motor shaft 23 on the second support portion 14a. The worker also passes the motor shaft 23 through the inside of the second support portion 14a and through the through hole 14c. As a result, the lower part of the motor shaft 23 protrudes downward from the bottom wall portion 14. When the motor shaft 23 is supported by the second support portion 14a and passed through the through hole 14c, the first step P01 is completed.

[0057] In the second step P02, the worker or the like fixes the portion of the motor shaft 23 that protrudes downward from the bottom wall portion 14, i.e., toward the other axial side (-Z side), through the through hole 14c to the shaft fixing jig 96. In this embodiment, the portion of the motor shaft 23 that protrudes downward from the bottom wall portion 14 is inserted into a shaft fixing hole 96a provided in the shaft fixing jig 96 and fixed to the inner circumferential surface of the shaft fixing hole 96a. The shaft fixing hole 96a is a circular hole recessed downward from the surface facing the upper side of the shaft fixing jig 96. Although not shown in the figure, the central axis of the shaft fixing hole 96a overlaps with the case axis J2, which is the central axis of the motor case 12. As a result, the central axis J1, which is the central axis of the motor shaft 23, and the case axis J2 overlap, so that the coaxiality between the motor shaft 23 and the motor case 12 can be improved. When the portion of the motor shaft 23 that protrudes downward beyond the bottom wall portion 14 is fixed to the shaft fixing jig 96, the second step P02 is completed.

[0058] In the third step P03, the worker moves the cover member 17 from the upper side to the lower side of the motor case 12, and inserts the upper part of the motor shaft 23 into the first support part 17a as shown in FIG. 6. As a result, the worker supports the first support part 17a with the first bearing 91 at the part of the motor shaft 23 that is above the stator 30. That is, the worker supports the upper part of the motor shaft 23 on the first support part 17a. As a result, the central axis J1 of the motor shaft 23 and the cover axis J3 of the cover member 17 overlap, so that the concentricity between the motor shaft 23 and the cover member 17 can be improved. At this time, the radial outer edge of the surface facing the lower side of the cover member 17 comes into contact with the cover fixing part 13b in the axial direction. In addition, the cover annular part 17d is disposed radially outside the cover fixing part 13b. When the upper part of the motor shaft 23 is supported by the first support part 17a, the third step P03 is completed.

[0059] In the fourth step P04, the worker rotates the cover member 17 around the central axis J1 to spin-weld the cover member 17 and the cover fixing portion 13b. In this embodiment, the cover member 17 is rotated around the central axis J1 while pressing the cover member 17 against the cover fixing portion 13b by a cover rotation jig (not shown). As described above, the radial outer edge of the surface facing the lower side of the cover member 17 is in axial contact with the cover fixing portion 13b, so frictional heat is generated between the radial outer edge of the surface facing the lower side of the cover member 17 and the cover fixing portion 13b. Also, as described above, the motor case 12 and the cover member 17 are each made of resin, so the radial outer edge of the surface facing the lower side of the cover member 17 and the cover fixing portion 13b are melted by the frictional heat involved. Next, the worker stops the rotation of the cover member 17. As a result, when the temperatures of the cover welding portion 17b and the cover fixing portion 13b shown in Fig. 2 drop and solidify, the cover welding portion 17b and the cover fixing portion 13b are joined by welding. At this time, the cover welding portion 17b and the cover fixing portion 13b are joined around the entire circumference. When the cover member 17 and the cover fixing portion 13b are spin-welded, the fourth step P04 is completed. When the fourth step P04 is completed, the rotor 20 and the cover member 17 are each assembled to the motor case 12, and the assembly step Pf of the electric actuator 1 is completed.

[0060] According to this embodiment, the motor case 12 and the cover member 17 are each made of resin, and the cover member 17 has a first support portion 17a that supports a portion of the motor shaft 23 located above the stator 30, i.e., on one axial side (+Z side), and is disk-shaped with the center at the central axis J1. The motor case 12 has a second support portion 14a that supports a portion of the motor shaft 23 located below the stator 30, i.e., on the other axial side (-Z side), a bottom wall portion 14 that is provided with a through hole 14c through which the motor shaft 23 passes in the axial direction and that extends in a direction intersecting the axial direction, and an annular cover fixing portion 13b that axially contacts a surface facing the lower side of the cover member 17 and surrounds the central axis J1. The cover member 17 and the cover fixing portion 13b are joined to each other over the entire circumference in the circumferential direction. Therefore, since the lower portion of the motor shaft 23 passes through the through hole 14c in the axial direction, in the second step P02, the lower portion of the motor shaft 23 can be fixed to the shaft fixing jig 96 from outside the motor case 12. As a result, the motor shaft 23 can be supported by the motor case 12 in a state in which the coaxiality between the motor case 12 and the motor shaft 23 is increased. In addition, since the cover member 17 has the first support portion 17a that supports the upper portion of the motor shaft 23, the coaxiality between the cover member 17 and the motor shaft 23 can be increased by adjusting the radial position of the first support portion 17a to match the motor shaft 23 fixed by the shaft fixing jig 96. Therefore, in the fourth step P04, the cover member 17 can be rotated around the central axis J1 with high precision, and the cover member 17 can be joined to the motor case 12 by spin welding while increasing the coaxiality between the cover member 17 and the motor shaft 23. These improve the coaxiality between the motor shaft 23 and the motor case 12 and the cover member 17, thereby improving the coaxiality between the motor shaft 23 and the housing 10. Also, because it is sufficient to fix the lower portion of the motor shaft 23 with the shaft fixing jig 96, there is no need to provide a hole in the cover member 17 for holding down the upper portion of the motor shaft 23 with a jig, etc.Therefore, compared to a case where the motor case 12 and the cover member 17 are assembled to the motor shaft 23 with both axial ends of the motor shaft 23 fixed with a jig or the like, there is no need to provide a hole in the cover member 17 for passing such a jig or the like. Therefore, in this embodiment, a member such as a cap for closing the hole provided in the cover member 17 is not required to improve the airtightness of the electric actuator 1. This makes it possible to suppress an increase in the number of parts of the electric actuator 1. This makes it possible to suppress an increase in the number of parts of the electric actuator 1 while improving the coaxiality between the motor shaft 23 and the housing 10.

[0061] In addition, in this embodiment, since the cover member 17 and the cover fixing portion 13b are joined to each other over the entire circumference in the circumferential direction, the gap between the cover member 17 and the motor case 12 can be sealed over the entire circumference in the circumferential direction. Therefore, the airtightness of the electric actuator 1 can be improved.

[0062] In addition, in this embodiment, since the motor case 12 and the cover member 17 are both made of resin, the manufacturing costs of the electric actuator 1 can be prevented from increasing and the weight of the electric actuator 1 can be reduced compared to when the motor case 12 and the cover member 17 are both made of metal.

[0063] According to this embodiment, the cover member 17 has a cover welding portion 17b that is joined to the cover fixing portion 13b by welding. Therefore, the gap between the cover member 17 and the motor case 12 can be suitably sealed, which can more suitably improve the airtightness of the electric actuator 1. In addition, since there is no need to separately provide a sealing member such as an O-ring for sealing the gap between the cover member 17 and the motor case 12, an increase in the number of parts of the electric actuator 1 can be suppressed.

[0064] According to this embodiment, the first support portion 17a supports, via the first bearing 91, a portion of the motor shaft 23 located above the stator 30, i.e., on one axial side (+Z side), and the second support portion 14a supports, via the second bearing 92, a portion of the motor shaft 23 located below the stator 30, i.e., on the other axial side (-Z side). Thus, when the motor shaft 23 rotates about the central axis J1 during operation of the electric actuator 1, it is possible to suppress an increase in the frictional force between the motor shaft 23 and the cover member 17 and the frictional force between the motor shaft 23 and the motor case 12. Thus, it is possible to increase the output efficiency of the electric actuator 1 and suppress vibration and noise during operation of the electric actuator 1.

[0065] According to this embodiment, the electric actuator 1 includes a transmission mechanism 60 that transmits the rotation of the motor shaft 23 to the output shaft 66, and the transmission mechanism 60 is connected to a portion of the motor shaft 23 that is located below the bottom wall portion 14, i.e., on the other axial side (-Z side). Therefore, the portion of the motor shaft 23 that is below the bottom wall portion 14, i.e., the portion fixed to the shaft fixing jig 96 in the second step P02, can be used as the portion connected to the transmission mechanism 60. Therefore, compared to the case where the transmission mechanism 60 is connected to the upper portion of the motor shaft 23, it is possible to prevent the axial dimension of the motor shaft 23 from becoming larger. Therefore, it is possible to prevent the electric actuator 1 from becoming larger in size in the axial direction.

[0066] Furthermore, in this embodiment, as described above, the transmission mechanism 60 reduces the rotation of the motor shaft 23 and transmits it to the output shaft 66. Therefore, the transmission mechanism 60 can increase the rotation torque of the output shaft 66 relative to the rotation torque of the motor shaft 23, so that the driven member connected to the output shaft 66 can be smoothly driven.

[0067] According to this embodiment, the method for manufacturing the electric actuator 1 includes an assembly process Pf for assembling each of the rotor 20 and the cover member 17 to the motor case 12. The assembly process Pf includes a first process P01 for inserting the rotor 20 into the motor case 12 through the opening 12a to support the lower side of the motor shaft 23, i.e., the other axial side (-Z side) of the motor shaft 23 on the second support portion 14a and passing the motor shaft 23 through the through hole 14c; The method includes a second step P02 of fixing the portion of the motor shaft 23 protruding downward from the bottom wall 14 to the shaft fixing jig 96 through the hole 14c, a third step P03 of moving the cover member 17 downward from the upper side of the motor case 12, i.e., from one axial side (+Z side) to support the upper portion of the motor shaft 23 on the first support portion 17a, and a fourth step P04 of rotating the cover member 17 about the central axis J1 to spin-weld the downward surface of the cover member 17 to the cover fixing portion 13b. Therefore, in the second step P02, the portion of the motor shaft 23 protruding downward from the bottom wall 14 can be fixed to the shaft fixing jig 96 from the outside of the motor case 12, so that the motor shaft 23 can be assembled to the motor case 12 with the coaxiality between the motor shaft 23 and the motor case 12 increased. In addition, in the fourth step P04, the cover member 17 is joined to the motor case 12 by spin welding, which joins the cover member 17 to the motor case 12 while rotating the cover member 17 around the central axis J1, so that the coaxiality between the motor shaft 23 and the cover member 17 can be increased. As a result, the coaxiality between the motor shaft 23 and the motor case 12 and the cover member 17 can be increased. That is, the coaxiality between the motor shaft 23 and the housing 10 can be increased. Also, as described above, compared to the case where the motor case 12 and the cover member 17 are fixed to the motor shaft 23 with both ends of the motor shaft 23 in the axial direction fixed by a jig or the like, it is not necessary to provide holes in the motor case 12 and the cover member 17 for passing such a jig or the like, and a member such as a cap for closing such a hole is not required. Therefore, it is possible to suppress an increase in the number of parts of the electric actuator 1 while increasing the coaxiality between the motor shaft 23 and the housing 10.

[0068] In addition, in this embodiment, since the cover weld portion 17b and the cover fixing portion 13b are joined by spin welding in the fourth step P04, it is easy to reduce the circumferential variation in the amount of frictional heat generated by friction between the cover weld portion 17b and the cover fixing portion 13b. Therefore, it is easy to reduce the circumferential variation in the joining strength compared to, for example, joining the cover member 17 and the cover fixing portion 13b by laser welding. Therefore, it is possible to more suitably improve the airtightness of the electric actuator 1.

[0069] In this embodiment, in the fourth step P04, the cover member 17 is rotated about the central axis J1 while the upper side of the motor shaft 23 is supported by the first support portion 17a, and the cover member 17 and the cover fixing portion 13b are spin-welded to each other. Therefore, even if there is play between the cover annular portion 17d of the cover member 17 and the cover fixing portion 13b, the concentricity between the motor shaft 23 and the cover member 17 can be improved.

[0070] Furthermore, in this embodiment, the degree of coaxiality between the motor shaft 23 and the motor case 12 and the cover member 17 can be improved, so that the motor shaft 23 can be smoothly rotated about the central axis J1 when the electric actuator 1 operates. Therefore, the output efficiency of the electric actuator 1 can be improved, and an increase in vibration and noise during operation of the electric actuator 1 can be suppressed.

[0071] According to this embodiment, the cover fixing portion 13b is located on the upper side of the motor case 12, that is, at the end on one axial side (+Z side). Therefore, in the fourth step P04, when the cover member 17 is rotated around the central axis J1, the cover member 17 is easily pressed in the axial direction against the cover fixing portion 13b. This makes it easy to increase the amount of frictional heat generated by friction between the cover welding portion 17b and the cover fixing portion 13b, and also makes it easy to reduce the variation in the amount of frictional heat in the circumferential direction. Therefore, it is easy to more suitably reduce the variation in the joining strength between the cover welding portion 17b and the cover fixing portion 13b in the circumferential direction. Therefore, the airtightness of the electric actuator 1 can be more suitably increased.

[0072] According to this embodiment, in the first step P01, the portion of the motor shaft 23 below the stator 30, i.e., the other axial side (-Z side), is supported by the second support portion 14a via the second bearing 92, and in the third step P03, the portion of the motor shaft 23 above the stator 30, i.e., the one axial side (+Z side), is supported by the first support portion 17a via the first bearing 91. Thus, when the cover member 17 is rotated about the central axis J1 in the fourth step P04 to spin-weld the cover welding portion 17b and the cover fixing portion 13b, it is possible to suppress an increase in the frictional force between the motor shaft 23 and the first support portion 17a and the frictional force between the motor shaft 23 and the second support portion 14a. Therefore, in the fourth step P04, it is easy to suppress the position of the motor shaft 23 from fluctuating, so that the coaxiality between the motor shaft 23 and the cover member 17 can be more suitably increased.

[0073] Although the embodiments of the present invention have been described above, each configuration and their combinations in the embodiments are merely examples, and addition, omission, substitution, and other modifications of the configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the embodiments.

[0074] The cover weld part and the cover fixing part may be joined by other welding methods, such as laser welding, ultrasonic welding, etc. In this case as well, the motor shaft is supported by the first support part of the cover member, and the cover weld part and the cover fixing part are welded together in a state in which the coaxiality between the motor shaft and the cover member is increased, thereby increasing the coaxiality between the motor shaft and the cover member.

[0075] Also, at least one of the first bearing and the second bearing does not have to be provided. If the first bearing is not provided, the upper part of the motor shaft is directly supported by the first support part, and if the second bearing is not provided, the lower part of the motor shaft is directly supported by the second support part. However, if the cover member and the motor case are joined by spin welding, it is preferable that the first support part supports the motor shaft via the first bearing in order to suppress an increase in frictional force between the motor shaft and the cover member.

[0076] The configuration of the transmission mechanism is not particularly limited as long as it can transmit the rotation of the motor shaft to the output shaft. For example, the motor shaft and the motor gear may be part of the same single member, and the output shaft and the output gear may be part of the same single member. Also, the transmission mechanism does not have to have a first stage gear and a second stage gear. In this case, the motor gear and the output gear are directly connected.

[0077] The use of the electric actuator to which the present invention is applied is not particularly limited. The electric actuator may be mounted on a shift-by-wire type actuator device that is driven based on the driver's shift operation. The electric actuator may also be mounted on equipment other than a vehicle. Note that the configurations described above in this specification can be appropriately combined within a range that does not contradict each other.

[0078] The present technology can be configured as follows. (1) An electric actuator comprising: a rotor having a motor shaft rotatable about a central axis; a stator arranged radially outward of the rotor; a motor case having an opening that opens to one axial side and houses the rotor and the stator inside; and a cover member that closes the opening, wherein the motor case and the cover member are each made of resin, the cover member has a first support portion that supports a portion of the motor shaft that is located on one axial side of the stator and is disk-shaped centered on the central axis, the motor case has a second support portion that supports a portion of the motor shaft that is on the other axial side of the stator, and a bottom wall portion that is provided with a through hole through which the motor shaft passes and extends in a direction intersecting the axial direction, and a ring-shaped cover fixing portion that is in axial contact with a surface of the cover member facing the other axial side and surrounds the central axis, and the cover member and the cover fixing portion are joined to each other around the circumference in the circumferential direction. (2) The electric actuator according to (1), wherein the cover member has a cover weld portion that is joined to the cover fixing portion by welding. (3) An electric actuator described in (1) or (2), wherein the first support portion supports a portion of the motor shaft located on one axial side of the stator via a first bearing, and the second support portion supports a portion of the motor shaft located on the other axial side of the stator via a second bearing. (4) An electric actuator described in any one of (1) to (3), further comprising a transmission mechanism that transmits rotation of the motor shaft to an output shaft, the transmission mechanism being connected to a portion of the motor shaft that is located on the other axial side of the bottom wall portion. (5) A manufacturing method of an electric actuator including a rotor having a motor shaft rotatable about a central axis, a stator disposed radially outward of the rotor, a motor case having an opening that opens to one axial side and accommodating the rotor and the stator therein, and a cover member that closes the opening, the method including an assembly process of assembling each of the rotor and the cover member to the motor case, the motor case and the cover member being each made of resin, the cover member having a first support portion that supports a portion of the motor shaft that is located on one axial side of the stator, and being disk-shaped with the central axis as its center, the motor case being provided with a second support portion and a through hole through which the motor shaft passes in the axial direction, and a second support portion that extends in a direction intersecting the axial direction a bottom wall portion and an annular cover fixing portion surrounding the central axis, the assembly process comprising: a first step of inserting the rotor into the motor case through the opening to cause the second support portion to support a portion of the motor shaft on the other axial direction and passing the motor shaft through the through hole; a second step of fixing a portion of the motor shaft that protrudes beyond the bottom wall portion through the through hole to a shaft fixing jig; a third step of moving the cover member from one axial side of the motor case to the other axial side to cause the portion of the motor shaft on one axial side to be supported by the first support portion; and a fourth step of rotating the cover member around the central axis to spin-weld a surface of the cover member facing the other axial side to the cover fixing portion. (6) The method for manufacturing an electric actuator according to (5), wherein the cover fixing portion is located at one end portion of the motor case in the axial direction. (7) A method for manufacturing an electric actuator described in (5) or (6), wherein in the first step, a portion of the motor shaft on the other axial side of the stator is supported by the second support portion via a second bearing, and in the third step, a portion of the motor shaft on one axial side of the stator is supported by the first support portion via a first bearing. [Explanation of symbols]

[0079] 1...electric actuator, 12...motor case, 12a...opening, 13b...cover fixing portion, 14...bottom wall portion, 14a...second support portion, 14c...through hole, 17...cover member, 17a...first support portion, 17b...cover welding portion, 20...rotor, 23...motor shaft, 30...stator, 60...transmission mechanism, 66...output shaft, 91...first bearing, 92...second bearing, J1...center axis, Pf...assembly step, P01...first step, P02...second step, P03...third step, P04...fourth step

Claims

1. a rotor having a motor shaft rotatable about a central axis; a stator disposed radially outside the rotor; a motor case having an opening that opens to one axial side and that houses the rotor and the stator therein; A cover member that closes the opening; Equipped with each of the motor case and the cover member is made of resin; the cover member has a first support portion that supports a portion of the motor shaft that is located on one axial side of the stator, and is disk-shaped about the central axis, The motor case includes: a second support portion supporting a portion of the motor shaft on the other axial side of the stator; and a bottom wall portion having a through hole through which the motor shaft passes and extending in a direction intersecting the axial direction; a ring-shaped cover fixing portion that is in axial contact with a surface of the cover member facing the other axial direction and that surrounds the central axis; having The cover member and the cover fixing portion are joined to each other over a circumferential direction of the electric actuator.

2. The electric actuator according to claim 1 , wherein the cover member has a cover weld portion that is joined to the cover fixing portion by welding.

3. the first support portion supports a portion of the motor shaft located on one axial side of the stator via a first bearing, The electric actuator according to claim 1 , wherein the second support portion supports a portion of the motor shaft located on the other axial side of the stator via a second bearing.

4. a transmission mechanism for transmitting rotation of the motor shaft to an output shaft; The electric actuator according to claim 1 , wherein the transmission mechanism is connected to a portion of the motor shaft that is located on the other axial side of the bottom wall portion.

5. A method for manufacturing an electric actuator including: a rotor having a motor shaft rotatable about a central axis; a stator disposed radially outward of the rotor; a motor case having an opening that opens to one axial side and that houses the rotor and the stator therein; and a cover member that closes the opening, an assembly process for assembling the rotor and the cover member to the motor case, each of the motor case and the cover member is made of resin; the cover member has a first support portion that supports a portion of the motor shaft that is located on one axial side of the stator, and is disk-shaped about the central axis, the motor case has a second support portion, a bottom wall portion having a through hole through which the motor shaft passes in the axial direction and extending in a direction intersecting the axial direction, and a ring-shaped cover fixing portion surrounding the central axis, The assembling step includes: a first step of inserting the rotor into the motor case through the opening to cause the second support portion to support a portion of the motor shaft on the other axial side, and passing the motor shaft through the through hole; a second step of fixing a portion of the motor shaft, the portion protruding beyond the bottom wall portion toward the other axial side through the through hole, to a shaft fixing jig; a third step of moving the cover member from one axial side to the other axial side of the motor case to cause the one axial side portion of the motor shaft to be supported by the first support portion; a fourth step of rotating the cover member around the central axis line to spin-weld the surface of the cover member facing the other axial direction to the cover fixing portion; A manufacturing method of an electric actuator having the above-mentioned features.

6. The method for manufacturing an electric actuator according to claim 5 , wherein the cover fixing portion is located at one end portion of the motor case in the axial direction.

7. In the first step, a portion of the motor shaft on the other axial side of the stator is supported by the second support portion via a second bearing; 7. The method for manufacturing an electric actuator according to claim 5, wherein in the third step, a portion of the motor shaft on one axial side of the stator is supported by the first support portion via a first bearing.

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