Electric actuator

Abstract

To provide an electric actuator capable of suppressing an increase in size in an axial direction.SOLUTION: An electric actuator 1 includes: a motor 20 that has a rotor 24 fastened to an outer circumferential surface of a hollow motor shaft 23; a transmission mechanism 30 that is coupled to the motor shaft; an output shaft 46 to which the rotation of the motor shaft is transmitted via the transmission mechanism; a circuit board 80 that is arranged at one side in an axial direction relative to the rotor; a first rotation member 71 that is attached to a portion of the output shaft at the one side in the axial direction relative to the motor shaft; and a second rotation member 72 to which the decelerated rotation of the first rotation member is transmitted. At least a part of the output shaft is positioned inside the motor shaft. The second rotation member is arranged at the one side in the axial direction relative to the circuit board. A magnet 45 is fastened to the second rotation member. A magnetic sensor 81 that is arranged so as to face the magnet in the axial direction and detects a magnetic flux of the magnet is mounted on a surface of the circuit board directed to the one side in the axial direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] An electrically controlled actuator is known in which the rotation of the drive shaft is reduced and transmitted to a detection rotor via a pinion attached to one axial end of the drive shaft, and the magnetic field of a magnet member possessed by the detection rotor is detected by a sensor mounted on a circuit board positioned on one axial side of the magnet member, thereby controlling the rotation of the drive shaft (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-263777 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the electrically controlled actuator as described above, the magnet member, the sensor, and the circuit board are disposed on one axial side of the drive shaft, which poses a problem of increasing the size of the electrically controlled actuator in the axial direction.

[0005] In view of the above circumstances, one object of the present invention is to provide an electric actuator that can prevent an increase in size in the axial direction. [Means for solving the problem]

[0006] One embodiment of the electric actuator of the present invention includes a motor having a hollow motor shaft rotatable around a motor axis and a rotor fixed to the outer peripheral surface of the motor shaft, a transmission mechanism connected to the motor shaft, an output shaft extending in the axial direction and to which the rotation of the motor shaft is transmitted via the transmission mechanism, a circuit board arranged on one axial side of the rotor, a first rotating member attached to a portion of the output shaft on one axial side of the motor shaft, and a second rotating member to which the rotation of the first rotating member is transmitted at a reduced speed. At least a portion of the output shaft is located inside the motor shaft. The second rotating member is arranged on one axial side of the circuit board. A magnet is fixed to the second rotating member. A magnetic sensor is mounted on a surface of the circuit board facing one axial side, and is arranged to face the magnet in the axial direction and detect the magnetic flux of the magnet. Effect of the Invention

[0007] According to one aspect of the present invention, it is possible to suppress an increase in size in the axial direction of an electric actuator. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing an electric actuator according to a first embodiment. [Diagram 2] FIG. 2 is a view of the transmission mechanism of the first embodiment as seen from above. [Diagram 3] FIG. 3 is a cross-sectional view showing the electric actuator of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In each figure, 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. The direction in which the motor axis J1, as shown appropriately in each figure, extends is parallel to the Z-axis direction, i.e., the up-down direction. In the following description, the direction parallel to the extension of the motor axis J1 will simply be referred to as the "axial direction." Additionally, the radial direction centered on the motor axis J1 will simply be referred to as the "radial direction," and the circumferential direction centered on the motor axis J1 will simply be referred to as the "circumferential direction."

[0010] In this embodiment, the upper side corresponds to “one axial side,” and the lower side corresponds to “the other axial side.” Note that the terms “up-down direction,” “upper side,” and “lower side” are names used simply to describe the relative positional relationships of the various parts, and the actual positional relationships may be other than those indicated by these names.

[0011] First Embodiment 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 the vehicle driver. The electric actuator 1 includes a housing 10, a motor 20, a transmission mechanism 30, an output shaft 46, a first rotating member 71, a second rotating member 72, an axis member 73, a magnet 45, a circuit board 80, and a magnetic sensor 81.

[0012] The housing 10 accommodates each component of the electric actuator 1, such as the motor 20, the transmission mechanism 30, the output shaft 46, the first rotating member 71, the second rotating member 72, the magnet 45, and the circuit board 80. The housing 10 has a housing main body 11 and a cover member 12. The housing main body 11 is, for example, cylindrical with the motor axis J1 as its center. The housing main body 11 opens upward. The housing main body 11 has a first housing portion 11a and a second housing portion 11b.

[0013] The first accommodating portion 11a is a lower portion of the housing main body 11. The first accommodating portion 11a has a bottom portion 11c and a peripheral wall portion 11d extending upward from a radial outer edge portion of the bottom portion 11c. The bottom portion 11c is provided with a hole portion 11e penetrating the bottom portion 11c in the axial direction. The hole portion 11e is a circular hole centered on the motor axis line J1. The upper portion of the hole portion 11e constitutes a third bearing holding portion 11f that holds a third bearing 51. In this embodiment, the third bearing 51 is, for example, a ball bearing.

[0014] The second housing portion 11b is an upper portion of the housing body 11. The second housing portion 11b is axially connected to the first housing portion 11a. The second housing portion 11b is cylindrical and opens upward. The inner peripheral surface of the second housing portion 11b is provided with a step having a step surface 11g facing upward. A circuit board 80 is fixed to the step surface 11g.

[0015] The cover member 12 is fixed to the upper end of the housing body 11. The cover member 12 closes the upper opening of the housing body 11. The cover member 12 has a cover body portion 12a that closes the upper opening of the housing body 11, a fourth bearing holding portion 12b, and a shaft member holding portion 12d. The fourth bearing holding portion 12b protrudes downward from the cover body portion 12a. The fourth bearing holding portion 12b is cylindrical and opens downward, centered on the motor axis J1. A fourth bearing 52 is held on the inner peripheral surface of the fourth bearing holding portion 12b. The fourth bearing 52 is, for example, a ball bearing. The shaft member holding portion 12d protrudes downward from the cover body portion 12a. The shaft member holding portion 12d is cylindrical and extends in the axial direction. The shaft member holding portion 12d opens downward. The shaft member holding portion 12d is disposed radially outward from the fourth bearing holding portion 12b. A shaft member 73 is held on the inner circumferential surface of the shaft member holding portion 12d.

[0016] The motor 20 has a stator 22, a motor shaft 23, and a rotor 24. The motor shaft 23 is rotatable about the motor axis J1. The motor shaft 23 is substantially cylindrical and extends in the axial direction about the motor axis J1. The motor shaft 23 is a hollow shaft. The motor shaft 23 is open on both sides in the axial direction. The motor shaft 23 is disposed inside the first housing portion 11a. The motor shaft 23 has a main body portion 23a and an eccentric shaft portion 23d.

[0017] The main body 23a is an upper part of the motor shaft 23. The main body 23a has a first main body 23b and a second main body 23c. The first main body 23b and the second main body 23c are substantially cylindrical with the motor axis J1 as the center. The second main body 23c is located on the upper side of the first main body 23b. The second main body 23c is connected to the first main body 23b in the axial direction. The inner diameter of the second main body 23c is the same as the inner diameter of the first main body 23b. The outer diameter of the second main body 23c is smaller than the outer diameter of the first main body 23b. The second bearing 62 is held on the outer peripheral surface of the second main body 23c. In this embodiment, the second bearing 62 is, for example, a ball bearing.

[0018] The eccentric shaft portion 23d is a lower portion of the motor shaft 23. The eccentric shaft portion 23d is connected to the main body portion 23a in the axial direction. The eccentric shaft portion 23d is disposed inside the first housing portion 11a. The eccentric shaft portion 23d is disposed below the rotor 24. A first bearing 61 is held on the inner peripheral surface of the eccentric shaft portion 23d. In this embodiment, the first bearing 61 is, for example, a roller bearing. When viewed in the axial direction, the outer peripheral surface of the eccentric shaft portion 23d is circular with the eccentric axis J2, which is eccentric with respect to the motor axis J1, as the center. The eccentric axis J2 is a virtual axis extending in a direction parallel to the motor axis J1. A fifth bearing 53 is held on the outer peripheral surface of the eccentric shaft portion 23d. In this embodiment, the fifth bearing 53 is, for example, a ball bearing.

[0019] The rotor 24 is accommodated inside the first accommodating portion 11a. The rotor 24 has a rotor core 24a and a rotor magnet 24b. The rotor core 24a is annular about the motor axis J1. The rotor core 24a is fixed to the outer peripheral surface of the first main body portion 23b. As a result, the rotor 24 is fixed to the outer peripheral surface of the motor shaft 23. The rotor magnet 24b is fixed to the rotor core 24a.

[0020] The stator 22 faces the rotor 24 in the radial direction with a gap therebetween. The stator 22 is disposed radially outside the rotor 24. The stator 22 is accommodated inside the first accommodation portion 11a. The stator 22 has an annular stator core 22a surrounding the rotor 24 from the radial outside, an insulator 22b attached to the stator core 22a, and a plurality of coils 22c attached to the stator core 22a via the insulator 22b. The outer peripheral surface of the stator core 22a is fixed to the inner peripheral surface of the peripheral wall portion 11d. In this way, the stator 22 is fixed to the housing 10.

[0021] The transmission mechanism 30 is accommodated inside the first accommodation portion 11a. The transmission mechanism 30 is disposed below the rotor 24 and the stator 22. The transmission mechanism 30 is connected to the eccentric shaft portion 23d via a fifth bearing 53. The transmission mechanism 30 is connected to the output shaft 46. In this embodiment, the transmission mechanism 30 is a reduction mechanism that reduces the rotation of the motor shaft 23 and transmits it to the output shaft 46. The transmission mechanism 30 has an external gear 31, an internal gear 32, a flange portion 42, and a plurality of protrusions 43.

[0022] The external gear 31 is a substantially circular ring shape that expands in a direction perpendicular to the axial direction with the eccentric axis J2 as the center. The inner peripheral surface of the external gear 31 is fixed to the outer peripheral surface of the fifth bearing 53. As a result, the external gear 31 is connected to the eccentric shaft portion 23d of the motor shaft 23 via the fifth bearing 53. The external gear 31 is rotatable relative to the motor shaft 23 around the eccentric axis J2. As shown in FIG. 2, an external gear portion 31c constituted by a plurality of external teeth portions 31d is provided on the outer peripheral surface of the external gear 31.

[0023] As shown in FIG. 1, the external gear 31 has a plurality of holes 31b recessed upward from a surface of the external gear 31 facing downward. In this embodiment, the holes 31b are circular holes penetrating the external gear 31 in the axial direction. As shown in FIG. 2, the holes 31b are arranged surrounding the motor axis J1. The holes 31b are arranged at equal intervals around one circumference in the circumferential direction centered on the eccentric axis J2. In this embodiment, eight holes 31b are provided. The inner diameter of the holes 31b is larger than the outer diameter of the portion of the protrusion 43 that is inserted into the holes 31b.

[0024] The internal gear 32 is disposed radially outside the external gear 31. The internal gear 32 is substantially annular about the motor axis J1. The internal gear 32 surrounds the external gear 31 from the radial outside. As shown in FIG. 1, the outer peripheral surface of the internal gear 32 is fixed to the inner peripheral surface of the peripheral wall portion 11d. This fixes the internal gear 32 to the housing 10. As shown in FIG. 2, an internal gear portion 32a having a plurality of internal teeth portions 32b is provided on the inner peripheral surface of the internal gear 32. The internal gear portion 32a meshes with the external gear portion 31c. More specifically, the internal gear portion 32a meshes with the external gear portion 31c at a portion in the circumferential direction.

[0025] The flange portion 42 transmits the rotation of the motor shaft 23 to the output shaft 46. As shown in FIG. 1, the flange portion 42 is substantially disk-shaped and centered on the motor axis J1. The flange portion 42 is disposed below the external gear 31. The flange portion 42 faces the external gear 31 in the axial direction with a gap therebetween. In this embodiment, the flange portion 42 is axially connected to an output shaft body 41 of the output shaft 46, which will be described later. In this embodiment, the flange portion 42 and the output shaft body 41 are part of the same single member. The flange portion 42 and the output shaft body 41 may be different members.

[0026] The flange portion 42 is provided with a plurality of protrusions 43. Each protrusion 43 is cylindrical and protrudes upward from the flange portion 42. As shown in FIG. 2, each protrusion 43 is arranged surrounding the motor axis J1. Each protrusion 43 is arranged at equal intervals around the circumference in the circumferential direction. In this embodiment, eight protrusions 43 are provided. Each protrusion 43 is inserted from below into a different hole 31b. A part of the outer circumferential surface of each protrusion 43 contacts a part of the inner circumferential surface of the hole 31b. Each protrusion 43 supports the external gear 31 via the inner circumferential surface of the hole 31b so as to be swingable around the motor axis J1.

[0027] The output shaft 46 outputs the driving force of the electric actuator 1. The rotation of the motor shaft 23 is reduced and transmitted to the output shaft 46 via the transmission mechanism 30. As shown in FIG. 1, the output shaft 46 extends in the axial direction. The output shaft 46 is rotatable about the motor axis J1. The output shaft 46 passes through the inside of the motor shaft 23 in the axial direction. At least a portion of the output shaft 46 is located inside the motor shaft 23. The output shaft 46 protrudes from the motor shaft 23 on both sides in the axial direction. The output shaft 46 has an output shaft main body 41 and a retaining member 44 fixed to the outer circumferential surface of the output shaft main body 41.

[0028] The output shaft body 41 extends in the axial direction. The output shaft body 41 is supported rotatably about the motor axis J1 by a third bearing 51 and a fourth bearing 52. The output shaft body 41 has a connecting portion 41a, a first extending portion 41b, and a second extending portion 41c.

[0029] The connecting portion 41a is a lower portion of the output shaft main body 41. The connecting portion 41a is cylindrical and extends in the axial direction centered on the motor axis J1. The connecting portion 41a opens downward. The upper end of the connecting portion 41a is axially connected to a surface of the flange portion 42 facing downward. The lower end of the connecting portion 41a is inserted inside the hole portion 11e.

[0030] The driven shaft DS can be inserted into the connecting part 41a from below. When the spline part on the outer circumferential surface of the driven shaft DS is fitted into the spline groove on the inner circumferential surface of the connecting part 41a, the connecting part 41a and the driven shaft DS are connected to each other. As a result, the rotation of the motor shaft 23 is transmitted to the driven shaft DS via the output shaft 46.

[0031] The first extension portion 41b has a cylindrical shape extending in the axial direction around the motor axis J1. The lower end of the first extension portion 41b is axially connected to the upward surface of the flange portion 42. The first extension portion 41b is disposed inside the eccentric shaft portion 23d. The first extension portion 41b is supported by the first bearing 61 so as to be rotatable around the motor axis J1. The first bearing 61 determines the radial position of the motor shaft 23 relative to the output shaft 46.

[0032] The second extension portion 41c has a cylindrical shape extending in the axial direction around the motor axis J1. The second extension portion 41c is located above the first extension portion 41b and is connected to the first extension portion 41b in the axial direction. The second extension portion 41c passes through the inside of the main body portion 23a in the axial direction. An upper portion of the second extension portion 41c protrudes upward beyond the motor shaft 23. An upper end of the second extension portion 41c is supported by the fourth bearing 52 to be rotatable around the motor axis J1.

[0033] The retaining member 44 is fixed to the outer circumferential surface of the second extending portion 41c at a portion above the motor shaft 23. The retaining member 44 has a cylindrical portion 44a and a second bearing retaining portion 44c. The cylindrical portion 44a is cylindrical and has a center on the motor axis J1 and is open on both axial sides. The cylindrical portion 44a is fixed to the outer circumferential surface of the second extending portion 41c.

[0034] The second bearing holder 44c is cylindrical and has a center on the motor axis J1 and opens downward. The upper end of the second bearing holder 44c is axially connected to the lower end of the cylindrical portion 44a. The second bearing holder 44c faces the motor shaft 23 with a gap therebetween in the radial direction. A second bearing 62 is held on the inner circumferential surface of the second bearing holder 44c. The radial position of the motor shaft 23 relative to the output shaft 46 is determined by the second bearing 62.

[0035] The circuit board 80 is in the form of a plate extending in the radial direction. The plate surface of the circuit board 80 faces the axial direction. The circuit board 80 is accommodated inside the second accommodation portion 11b. The circuit board 80 is disposed above the rotor 24, i.e., on one axial side. When viewed from the radial direction, the circuit board 80 is disposed at a position overlapping the output shaft 46. The circuit board 80 is provided with a board hole 80a penetrating the circuit board 80 in the axial direction. The board hole 80a is a substantially circular hole centered on the motor axis J1. The output shaft 46 passes through the board hole 80a in the axial direction. The board hole 80a faces the cylindrical portion 44a in the radial direction with a gap therebetween.

[0036] The first rotating member 71 is annular about the motor axis J1. The first rotating member 71 is accommodated in the second accommodation portion 11b. The first rotating member 71 is disposed above the motor shaft 23, the holding member 44, and the circuit board 80. The second extension portion 41c passes through the first rotating member 71 in the axial direction. The first rotating member 71 is attached to the outer peripheral surface of the second extension portion 41c. The first rotating member 71 is attached to a portion of the output shaft 46 above the motor shaft 23, that is, on one axial side. The first rotating member 71 can rotate together with the output shaft 46 about the motor axis J1. The first rotating member 71 may be attached to the cylindrical portion 44a. A first gear portion 71a is provided on the radial outer peripheral surface of the first rotating member 71. The first gear portion 71a extends around the circumference in the circumferential direction. The first gear portion 71a is configured by a plurality of first teeth portions (not shown) that are arranged side by side in the circumferential direction.

[0037] The shaft member 73 has a cylindrical shape extending in the axial direction. In this embodiment, the shaft member 73 is made of resin. In the axial direction, the shaft member 73 is disposed between the lid main body portion 12a and the circuit board 80. An upper portion of the shaft member 73 is held by the inner peripheral surface of the shaft member holding portion 12d. This allows the shaft member 73 to be held in the housing 10. In this embodiment, the shaft member 73 faces the circuit board 80 in the axial direction via a gap. Note that a lower portion of the shaft member 73 may be passed through a hole that axially penetrates the circuit board 80 and held by the inner peripheral surface of the hole.

[0038] The second rotating member 72 is annular and surrounds the shaft member 73. The second rotating member 72 is disposed above the circuit board 80, i.e., on one axial side. The second rotating member 72 faces the circuit board 80 via a gap in the axial direction. The second rotating member 72 is disposed radially outward of the motor axis J1 relative to the first rotating member 71. The outer diameter of the second rotating member 72 is larger than the outer diameter of the first rotating member 71. In this embodiment, the second rotating member 72 is made of resin. The second rotating member 72 is provided with a through hole 72a, a recess 72c, and a second gear portion 72e.

[0039] The through hole 72a is a hole that passes through the center of the second rotating member 72 in the axial direction. When viewed in the axial direction, the through hole 72a is circular. The shaft member 73 is passed through the through hole 72a in the axial direction. In this embodiment, the shaft member 73 is gap-fitted into the through hole 72a. As a result, the shaft member 73 rotatably supports the second rotating member 72. Therefore, according to this embodiment, since the second rotating member 72 can be rotatably supported by the shaft member 73, the configuration for rotatably supporting the second rotating member 72 can be simplified. This makes it possible to suppress an increase in the number of parts of the electric actuator 1. Therefore, it is possible to suppress an increase in the manufacturing cost and manufacturing man-hours of the electric actuator 1.

[0040] The recess 72c is a hole recessed upward, i.e., toward one axial direction side, from the surface facing downward, i.e., the surface facing the other axial direction side, of the second rotating member 72. When viewed from the axial direction, the recess 72c is circular. When viewed from the axial direction, the recess 72c may be another shape, such as a square shape.

[0041] The second gear portion 72e is provided on the outer peripheral surface of the second rotating member 72 in the radial direction centered on the shaft member 73. The second gear portion 72e extends around the entire circumference along the outer peripheral surface of the second rotating member 72. The second gear portion 72e is configured by a plurality of second tooth portions (not shown) arranged side by side along the outer peripheral surface of the second rotating member 72. The second gear portion 72e meshes with the first gear portion 71a. As a result, the rotation of the output shaft 46 is transmitted to the second rotating member 72 via the first rotating member 71. As described above, the outer diameter of the second rotating member 72 is larger than the outer diameter of the first rotating member 71. Therefore, the number of teeth of the second gear portion 72e is larger than the number of teeth of the first gear portion 71a. Therefore, the rotation of the first rotating member 71, i.e., the rotation of the output shaft 46, is transmitted to the second rotating member 72 at a reduced speed.

[0042] According to this embodiment, the first gear portion 71a is provided on the radial outer peripheral surface of the first rotating member 71, and the second gear portion 72e that meshes with the first gear portion 71a is provided on the second rotating member 72. Therefore, the rotation of the output shaft 46 can be decelerated and transmitted to the second rotating member 72 by a simple configuration via only the first rotating member 71 attached to the output shaft 46. This makes it possible to simplify the configuration for decelerating and transmitting the rotation of the output shaft 46 to the second rotating member 72. Therefore, it is possible to more appropriately prevent the number of parts of the electric actuator 1 from increasing. Therefore, it is possible to more appropriately prevent the manufacturing cost and manufacturing man-hours of the electric actuator 1 from increasing.

[0043] The magnet 45 is annular and surrounds the shaft member 73. When viewed from the axial direction, the magnet 45 may have another shape, such as a square shape. In this embodiment, an upper portion of the magnet 45 is disposed inside the recess 72c. When viewed from the radial direction, the magnet 45 is disposed at a position overlapping the output shaft 46. An upper portion of the magnet 45 is fixed to the inner surface of the recess 72c. That is, at least a portion of the magnet 45 is fixed to the inner surface of the recess 72c. In this way, the magnet 45 is fixed to the second rotating member 72. The magnet 45 is fixed to the second rotating member 72 by, for example, an adhesive. Note that the entire magnet 45 may be disposed inside the recess 72c. The second rotating member 72 may be molded by insert molding using the magnet 45 as an insert member. In this case, at least a portion of the magnet 45 is embedded inside the second rotating member 72. The magnet 45 is provided with an insertion hole 45a.

[0044] The insertion hole 45a is a hole that axially passes through the center of the magnet 45. The shaft member 73 is passed through the insertion hole 45a in the axial direction. The hole diameter of the insertion hole 45a is sufficiently larger than the diameter of the shaft member 73.

[0045] The magnetic sensor 81 detects the magnetic flux of the magnet 45. The magnetic sensor 81 is mounted on the upper side of the circuit board 80, that is, on a surface facing one axial direction. When viewed from the radial direction, the magnetic sensor 81 is disposed at a position overlapping the output shaft 46. In this embodiment, the magnetic sensor 81 is, for example, a Hall element such as a Hall IC. The magnetic sensor 81 is disposed facing the magnet 45 in the axial direction. The magnetic sensor 81 detects the rotation of the second rotating member 72 by detecting the magnetic flux of the magnet 45. As described above, the rotation of the output shaft 46 is decelerated and transmitted to the second rotating member 72. Therefore, the magnetic sensor 81 detects the magnetic flux of the magnet 45 fixed to the second rotating member 72 to which the rotation of the output shaft 46 is decelerated and transmitted. Therefore, the magnetic sensor 81 can detect the phase of the output shaft 46 at a rotation angle of 360° or more.

[0046] A groove (not shown) is provided on the outer circumferential surface of the shaft member 73 at a portion located below the second rotating member 72 and the magnet 45. A retaining member 75 is fixed to the groove. That is, the retaining member 75 is fixed to a portion of the shaft member 73 on the other axial side of the second rotating member 72 and the magnet 45. In this embodiment, the retaining member 75 is, for example, an E-type retaining ring. The retaining member 75 may be another member such as a C-type retaining ring. In addition, when a hole penetrating the shaft member 73 in a direction perpendicular to the axial direction is provided, the retaining member 75 may be a pin that is passed through the hole. The outer diameter of the retaining member 75 is larger than the inner diameter of the through hole 72a and the inner diameter of the insertion hole 45a. In this embodiment, the retaining member 75 contacts the surface of the magnet 45 facing downward in the axial direction. The retaining member 75 does not have to contact the magnet 45. The retaining member 75 restricts the second rotating member 72 and the magnet 45 from moving downward, thereby preventing the second rotating member 72 and the magnet 45 from coming off the shaft member 73. Furthermore, although not shown, the shaft member 73 may have a structure (e.g., a stepped shape) that restricts the second rotating member 72 and the magnet 45 from moving upward. In this case, the second rotating member 72 and the magnet 45 can be restricted from moving in both axial directions, so that the first gear portion 71a and the second gear portion 72e can be meshed more stably.

[0047] According to this embodiment, the electric actuator 1 includes a circuit board 80 disposed above the rotor 24, i.e., on one axial side, a first rotating member 71 attached to a portion of the output shaft 46 above the motor shaft 23, and a second rotating member 72 to which the rotation of the first rotating member 71 is transmitted at a reduced speed. The second rotating member 72 is disposed above the circuit board 80, and a magnet 45 is fixed to the second rotating member 72. A magnetic sensor 81 is mounted on the surface of the circuit board 80 facing the magnet 45 in the axial direction and detects the magnetic flux of the magnet 45. Thus, the magnet 45, the magnetic sensor 81, and the circuit board 80 can be disposed at positions overlapping the output shaft 46 as viewed from the radial direction. Thus, the electric actuator 1 can be prevented from becoming larger in the axial direction compared to a case in which the magnet 45, the magnetic sensor 81, and the circuit board 80 are disposed above the output shaft 46.

[0048] In a configuration in which the magnetic sensor 81 detects the magnetic flux of the magnet 45 directly fixed to the output shaft 46, in order to detect the phase of the output shaft 46 at a rotation angle of 360° or more, it is necessary to store the rotation number of the output shaft 46 detected by a pulse sensor or the like in a memory or the like. In this case, if a momentary interruption or the like occurs in the power supply of the electric actuator 1, the rotation number of the output shaft 46 stored in the memory or the like is lost, and there is a risk that the phase of the output shaft 46 becomes unclear. In contrast, in this embodiment, as described above, the magnetic sensor 81 detects the magnetic flux of the magnet 45 fixed to the second rotating member 72 to which the rotation of the output shaft 46 is transmitted at a reduced speed. Therefore, as described above, the magnetic sensor 81 can detect the phase of the output shaft 46 at a rotation angle of 360° or more without storing the rotation number of the output shaft 46 in a memory or the like. As a result, in the electric actuator 1 of this embodiment, even if a momentary interruption or the like occurs in the power supply, the phase of the output shaft 46 can be detected at a rotation angle of 360° or more. Therefore, the phase of the output shaft 46 can be stably detected over a rotation angle of 360° or more while preventing the electric actuator 1 from becoming large in size in the axial direction.

[0049] According to this embodiment, the second rotating member 72 is provided with a recess 72c recessed from the lower side, i.e., the surface facing the other axial side, to the upper side, i.e., to one axial side, and at least a part of the magnet 45 is fixed to the inner surface of the recess 72c. This allows at least a part of the second rotating member 72 to be arranged in a position overlapping with the magnet 45 when viewed from the radial direction. Therefore, it is easier to arrange the second rotating member 72 on the lower side compared to a configuration in which the magnet 45 is attached to the surface facing the lower side of the second rotating member 72, i.e., a configuration in which the second rotating member 72 is arranged in a position not overlapping with the magnet 45 when viewed from the radial direction. Therefore, it is possible to more suitably suppress the electric actuator 1 from becoming large in size in the axial direction.

[0050] According to this embodiment, the retaining member 75 is fixed to the shaft member 73 on the lower side of the second rotating member 72 and the magnet 45, i.e., on the other axial side, and the outer diameter of the retaining member 75 is larger than the inner diameter of the through hole 72a and the inner diameter of the insertion hole 45a. Therefore, the retaining member 75 can prevent the second rotating member 72 from falling off the shaft member 73 downward, and can accurately determine the axial position of the second rotating member 72 relative to the first rotating member 71. This allows the first gear part 71a and the second gear part 72e to be stably engaged with each other, and therefore the rotation of the output shaft 46 can be stably transmitted to the second rotating member 72 via the first rotating member 71. Therefore, the magnetic sensor 81 can accurately detect the phase of the output shaft 46, and therefore the stability of the operation of the electric actuator 1 can be improved.

[0051] Furthermore, in this embodiment, as described above, the retaining member 75 comes into axial contact with the downward surface of the magnet 45. This allows the retaining member 75 to accurately determine the axial position of the magnet 45 relative to the magnetic sensor 81. Therefore, the magnetic flux of the magnet 45 can be detected with high accuracy by the magnetic sensor 81, and the operational stability of the electric actuator 1 can be more suitably improved.

[0052] <Second embodiment> FIG. 3 is a cross-sectional view showing an electric actuator 201 of this embodiment. In the following description, the same components as those in the above-mentioned first embodiment are given the same reference numerals, and the description thereof will be omitted. In this embodiment, the second rotating member 72 faces the first rotating member 71 in the radial direction with a gap therebetween. The other configurations of the first rotating member 71 and the second rotating member 72 are similar to the other configurations of the first rotating member 71 and the second rotating member 72 in the above-mentioned first embodiment. In this embodiment, the electric actuator 201 includes a drive member 277.

[0053] The driving member 277 is a circular timing belt driven by the first rotating member 71. The driving member 277 surrounds both the first rotating member 71 and the second rotating member 72 from the radial outside. The driving member 277 is wound around both the first rotating member 71 and the second rotating member 72. When viewed from the radial direction, the driving member 277 is disposed at a position overlapping the output shaft 46. Although not shown, a plurality of protrusions protruding inward are provided on the inner peripheral surface of the driving member 277. The plurality of protrusions are provided along the inner peripheral surface of the driving member 277. Some of the plurality of protrusions mesh with the first gear portion 71a of the first rotating member 71. In addition, another portion of the plurality of protrusions mesh with the second gear portion 72e of the second rotating member 72. As a result, when the first rotating member 71 rotates around the motor axis J1 together with the output shaft 46, the second rotating member 72 rotates following the first rotating member 71 via the driving member 277. That is, the rotation of the first rotating member 71 is transmitted to the second rotating member 72 via the driving member 277. As described above, the number of teeth of the second gear portion 72e is greater than the number of teeth of the first gear portion 71a. Therefore, the rotation of the first rotating member 71 is transmitted to the second rotating member 72 via the driving member 277 at a reduced speed.

[0054] According to this embodiment, the electric actuator 201 includes an annular driving member 277 wound around both the first rotating member 71 and the second rotating member 72, and the rotation of the first rotating member 71 is transmitted to the second rotating member 72 via the driving member 277. Therefore, even if the dimensional tolerance between the rotation center of the first rotating member 71 and the rotation center of the second rotating member 72 is large, the rotation of the first rotating member 71 is easily transmitted to the second rotating member 72. As described above, in this embodiment, only the upper end of the shaft member 73 is held by the housing 10. Therefore, it is difficult to accurately determine the radial position of the lower part of the shaft member 73 relative to the motor axis J1. Therefore, it is difficult to accurately determine the position of the rotation center of the second rotating member 72 relative to the motor axis J1, which is the rotation center of the first rotating member 71. Therefore, in the case of a configuration in which the rotation of the first rotating member 71 is transmitted to the second rotating member 72 by bringing the first rotating member 71 and the second rotating member 72 into contact with each other, there is a risk that the rotation of the first rotating member 71 cannot be stably transmitted to the second rotating member 72. In contrast, in this embodiment, even if the dimensional tolerance between the center of rotation of the second rotating member 72 and the center of rotation of the first rotating member 71 is large, the dimensional error can be absorbed by utilizing the elastic deformation or bending of the driving member 277, so that the rotation of the first rotating member 71 can be stably transmitted to the second rotating member 72. Therefore, the configuration for holding the shaft member 73 can be simplified, and an increase in the number of parts and manufacturing costs of the electric actuator 201 can be suppressed.

[0055] Furthermore, in this embodiment, the magnet 45, the magnetic sensor 81, the circuit board 80, and the driving member 277 can be disposed at positions overlapping the output shaft 46 when viewed from the radial direction. Therefore, compared to a case in which the magnet 45, the magnetic sensor 81, the circuit board 80, and the driving member 277 are disposed above the output shaft 46, it is possible to prevent the electric actuator 201 from becoming large in size in the axial direction.

[0056] 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.

[0057] The second rotating member does not necessarily have to have a recess. In this case, the magnet is preferably fixed to the surface of the second rotating member facing downward.

[0058] The shaft member may be rotatably supported by the housing. In this case, the second rotating member may be fixed to the shaft member or may be rotatably supported by the shaft member.

[0059] 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. The transmission mechanism may be a speed-increasing mechanism or a mechanism that does not change the speed of the rotation of the motor shaft. The multiple protrusions and the flange portion may be separate from each other. In this case, each of the multiple protrusions is fixed to each of the multiple holes penetrating the flange portion. The multiple protrusions may be provided on the external gear, and the multiple holes may be provided on the flange portion. In this case, each of the multiple protrusions protrudes from the external gear toward the flange portion and is inserted into the hole of the flange portion. The number of holes and the number of protrusions may each be seven or less, or nine or more.

[0060] 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.

[0061] The present technology can be configured as follows. (1) An electric actuator comprising: a motor having a hollow motor shaft rotatable about a motor axis and a rotor fixed to an outer peripheral surface of the motor shaft; a transmission mechanism connected to the motor shaft; an output shaft extending in the axial direction and to which rotation of the motor shaft is transmitted via the transmission mechanism; a circuit board arranged on one axial side of the rotor; a first rotating member attached to a portion of the output shaft on one axial side of the motor shaft; and a second rotating member to which rotation of the first rotating member is transmitted at a reduced speed, wherein at least a portion of the output shaft is located inside the motor shaft, the second rotating member is arranged on one axial side of the circuit board, a magnet is fixed to the second rotating member, and a magnetic sensor is mounted on a surface of the circuit board facing one axial side, the magnetic sensor being arranged axially opposite the magnet and detecting magnetic flux of the magnet. (2) The electric actuator described in (1), wherein a first gear portion is provided on the radial outer surface of the first rotating member, and a second gear portion is provided on the second rotating member that meshes with the first gear portion. (3) The electric actuator described in (1) is provided with a ring-shaped drive member that is wound around both the first rotating member and the second rotating member, and rotation of the first rotating member is transmitted to the second rotating member via the drive member. (4) An electric actuator described in any one of (1) to (3), wherein the second rotating member has a recess recessed toward one axial direction from a surface facing the other axial direction, and at least a portion of the magnet is fixed to an inner surface of the recess. (5) An electric actuator described in any one of (1) to (4), comprising a housing that accommodates the motor, the transmission mechanism, and the output shaft, and a shaft member that is held in the housing and extends in the axial direction, wherein the second rotating member has a through hole that passes through the second rotating member in the axial direction, and the shaft member is passed axially through the through hole to rotatably support the second rotating member. (6) An electric actuator as described in (5), wherein the magnet has an insertion hole that passes through the magnet in the axial direction, the shaft member passes axially through the insertion hole, a retaining member is fixed to a portion of the shaft member on the other axial side of the second rotating member and the magnet, and an outer diameter of the retaining member is larger than an inner diameter of the through hole and an inner diameter of the insertion hole. [Explanation of symbols]

[0062] 1,201...electric actuator, 10...housing, 20...motor, 23...motor shaft, 24...rotor, 30...transmission mechanism, 45...magnet, 46...output shaft, 71...first rotating member, 71a...first gear portion, 72...second rotating member, 72a...through hole, 72c...recess, 72e...second gear portion, 73...shaft member, 75...prevention member, 80...circuit board, 81...magnetic sensor, 277...driving member, J1...motor axis

Claims

1. a motor having a hollow motor shaft rotatable about a motor axis and a rotor fixed to an outer circumferential surface of the motor shaft; a transmission mechanism coupled to the motor shaft; an output shaft extending in an axial direction and to which rotation of the motor shaft is transmitted via the transmission mechanism; a circuit board disposed on one axial side of the rotor; a first rotating member attached to a portion of the output shaft on one axial side of the motor shaft; a second rotating member to which the rotation of the first rotating member is transmitted at a reduced speed; Equipped with At least a portion of the output shaft is located inside the motor shaft; the second rotating member is disposed on one side of the circuit board in the axial direction, A magnet is fixed to the second rotating member, An electric actuator, wherein a magnetic sensor is mounted on a surface of the circuit board facing one axial side, the magnetic sensor being arranged opposite the magnet in the axial direction and detecting magnetic flux of the magnet.

2. A first gear portion is provided on a radially outer peripheral surface of the first rotating member, The electric actuator according to claim 1 , wherein the second rotating member is provided with a second gear portion that meshes with the first gear portion.

3. a ring-shaped driving member that is wound around both the first rotating member and the second rotating member; The electric actuator according to claim 1 , wherein the rotation of the first rotating member is transmitted to the second rotating member via the drive member.

4. The second rotating member is provided with a recess that is recessed toward one side in the axial direction from a surface facing the other side in the axial direction, The electric actuator according to claim 1 , wherein at least a portion of the magnet is fixed to an inner surface of the recess.

5. a housing that accommodates the motor, the transmission mechanism, and the output shaft therein; a shaft member held by the housing and extending in an axial direction; Equipped with The second rotating member is provided with a through hole passing through the second rotating member in an axial direction, The electric actuator according to claim 1 , wherein the shaft member is axially passed through the through hole and rotatably supports the second rotating member.

6. The magnet is provided with an insertion hole passing through the magnet in an axial direction, The shaft member is passed through the insertion hole in the axial direction, a retaining member is fixed to a portion of the shaft member that is on the other axial side of the second rotating member and the magnet; The electric actuator according to claim 5 , wherein an outer diameter of the retaining member is larger than an inner diameter of the through hole and an inner diameter of the insertion hole.

Images