electric actuator

Abstract

Provided is an electric actuator including a motor portion, a magnet, a bus bar, a bus bar holder that holds the bus bar, a magnetic sensor that is fixed to the bus bar holder and is capable of detecting a magnetic field of the magnet, a conductive wire that is electrically connected to the magnetic sensor, and a circuit board that is electrically connected to the motor portion. The magnetic sensor is disposed opposite an axial side of the magnet via a gap, and the conductive wire penetrates the bus bar holder from an inside of the bus bar holder and is electrically connected to the circuit board.

Description

TECHNICAL FIELD

[0001] The present application relates to an electric actuator. BACKGROUND

[0002] In the rotation control of a motor in an electric actuator, it is known to detect a change in a magnetic field by a magnetic sensor. For example, a structure is disclosed in Patent Literature 1 in which a magnet is installed to a motor shaft in a manner that the same phase as a magnetic pole of a rotor is obtained, with a magnetic sensor being disposed on a circuit board. A method is generally used in which the magnetic pole of the rotor is directly detected by the magnetic sensor without the magnet being installed on the motor shaft.

[0003] Patent Literature 1: Japanese Patent Application Publication No. 2019-198191

[0004] In the method in which the magnetic pole of the rotor is directly detected by the magnetic sensor, since a phase shift occurs between the magnet installed in a manner that the same phase as the magnetic pole of the rotor is obtained and the rotor, it is possible that the performance of the motor is reduced due to a delay in the energization timing caused by a deviation in the detection timing of the sensor. SUMMARY

[0005] The present application was completed in consideration of the above points, and aims to provide an electric actuator capable of suppressing a reduction in the performance of a motor.

[0006] One embodiment of the present application is an electric actuator including a motor portion including a rotor that rotates around a central axis extending in an axial direction and a stator that opposes the rotor in a radial direction with a gap therebetween, a magnet fixed to the rotor, a bus bar electrically connected to the motor portion, a bus bar holder disposed on one side of the rotor in the axial direction and holding the bus bar, a magnetic sensor fixed to the bus bar holder and capable of detecting a magnetic field of the magnet, a conductive wire electrically connected to the magnetic sensor, and a circuit board disposed on one side of the bus bar holder in the axial direction and electrically connected to the motor portion, the magnetic sensor being disposed to oppose one side of the magnet in the axial direction with a gap therebetween, the conductive wire penetrating through the bus bar holder from an inside of the bus bar holder and being electrically connected to the circuit board.

[0007] According to one embodiment of the present application, in an electric actuator, it is possible to suppress a reduction in the performance of a motor. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a cross-sectional view illustrating the electric actuator of the present embodiment.

[0009] Figure 2 is a cross-sectional view illustrating the electric actuator of the present embodiment, and Figure 1 is a II-II cross-sectional view of is a II-II cross-sectional view of

[0010] Figure 3 is a schematic cross-sectional view showing a part of the electric actuator of the present embodiment.

[0011] Explanation of Reference Numerals

[0012] 10: electric actuator; 11: housing; 12: support surface; 15: support member (partition member); 20: motor section; 21: motor shaft; 21a: first shaft section; 21b: second shaft section (eccentric shaft section); 22: rotor; 23: stator; 24b: outer peripheral surface; 25: through-hole; 26: recessed section; 30: speed reduction mechanism; 40: magnet; 41: output shaft; 42: linking section; 44: cylindrical section; 45: linking recessed section; 51: second bearing; 52: third bearing; 53: first bearing; 63: magnetic sensor; 64: conductive wire; 70: circuit board; 140: bus bar holder; 141: peripheral wall section; 142: protrusion section; 143: spacer; 150: bus bar; J1: central axis; J2: eccentric axis. DETAILED DESCRIPTION

[0013] Hereinafter, an electric actuator of an embodiment of the present application will be described with reference to the drawings. In addition, the scope of the present application is not limited to the following embodiment, and can be arbitrarily changed within the scope of the technical idea of the present application. In addition, in the following drawings, the actual configuration is sometimes made different from the scale, the number, and the like in each configuration in order to easily understand each configuration.

[0014] In each drawing, the Z-axis direction is a vertical direction with the positive side as the upper side and the negative side as the lower side. The axial direction of the central axis J1, which is appropriately shown in each drawing, is parallel to the Z-axis direction, that is, the vertical direction. In the following description, the direction parallel to the axial direction of the central axis J1 will simply be referred to as the "axial direction" unless otherwise specified. In addition, the radial direction centered on the central axis J1 will simply be referred to as the "radial direction", and the circumferential direction centered on the central axis J1 will simply be referred to as the "circumferential direction" unless otherwise specified.

[0015] In the present embodiment, the upper side corresponds to one side in the axial direction, and the lower side corresponds to the other side in the axial direction. In addition, the upper side and the lower side are merely names for explaining the relative positional relationship of each part, and the actual arrangement relationship and the like can also be an arrangement relationship and the like other than those indicated by these names.

[0016] Figures 1 to 3 The electric actuator 10 of the present embodiment shown is, for example, an electric actuator mounted on a vehicle. As shown in FIG. 1, the electric actuator 10 includes a housing 11, a support surface 12, a support member (partition member) 15, a motor section 20, a speed reduction mechanism 30, a magnet 40, a bus bar 150, and the like. Figure 1 and Figure 3As shown, the electric actuator 10 has a housing 11, a partition component 15, a motor unit 20, a first bearing 53, a second bearing 51, a third bearing 52, a reduction mechanism 30, an output shaft 41, a magnetic sensor 63, a circuit board 70 and a bus bar holder 140, wherein the motor unit 20 has a motor shaft 21 that rotates around a central axis J1.

[0017] like Figure 1 As shown, the housing 11 houses the partition member 15, the motor unit 20, the motor shaft 21, the speed reduction mechanism 30, the output shaft 41, the magnetic sensor 63, the circuit board 70, and the bus bar holder 140. The housing 11 includes a lower housing 11A opened at the top and an upper housing 11B fixed to the opening of the lower housing 11A.

[0018] The lower housing 11A is cylindrical and extends axially about the central axis J1. The lower housing 11A includes a substrate storage portion 13a, a housing tube portion 13b, an output portion storage portion 13c, and a bearing retaining portion 13d. The substrate storage portion 13a is a portion that stores the circuit board 70 and the bus bar holder 140. The substrate storage portion 13a is open on the upper side. The substrate storage portion 13a is formed on the radially inner side of the upper portion of the lower housing 11A. The bottom surface of the substrate storage portion 13a is a support surface 12 that supports and fixes the circuit board 70 and the bus bar holder 140. The support surface 12 faces upward.

[0019] The housing cylindrical portion 13b surrounds the radially outer side of the motor portion 20. The output portion housing portion 13c houses the output portion 46 described later. The bearing holding portion 13d holds the third bearing 52. The bearing holding portion 13d extends upward from the lower end portion of the housing 11 around the central axis J1.

[0020] The upper housing 11B is a container-shaped component having a recessed portion 16a open at the bottom. The upper housing 11B and the lower housing 11A are fastened together by a plurality of bolts that axially penetrate the upper housing 11B. In this embodiment, the upper housing 11B functions as a lid that covers the opening of the lower housing 11A from above. The upper housing 11B includes a bearing retaining portion 16b. The bearing retaining portion 16b retains the first bearing 53. The bearing retaining portion 16b extends downwardly, centered on the central axis J1.

[0021] The central axis of the motor unit 20 is the central axis J1. Figure 1 As shown, the motor unit 20 includes a rotor 22 and a stator 23. The rotor 22 includes a motor shaft 21, a rotor core 22a, and a magnet 40.

[0022] The motor shaft 21 has a first shaft portion 21a, a second shaft portion 21b, and a through-hole 25. The first shaft portion 21a extends in the axial direction and is located on the upper side of the motor shaft 21. The second shaft portion 21b extends in the axial direction and is located on the lower side of the motor shaft 21. The diameter of the second shaft portion 21b is larger than the diameter of the first shaft portion 21a. To be more specific, the outer diameter of the second shaft portion 21b is larger than the outer diameter of the first shaft portion 21a. The second shaft portion 21b is an eccentric shaft portion that is centered on an eccentric axis J2 that is eccentric with respect to the central axis J1. The eccentric axis J2 is parallel to the central axis J1. The through-hole 25 extends centered on the central axis J1. Thus, the first shaft portion 21a is in a cylindrical shape that extends centered on the central axis J1. The second shaft portion 21b has an axial recessed portion 26 on the lower side. The recessed portion 26 extends centered on the eccentric axis J2. Thus, the second shaft portion 21b is in a cylindrical shape that extends centered on the eccentric axis J2. The upper side of the recessed portion 26 is continuous with the lower side of the through-hole 25. The second shaft portion 21b of the motor shaft 21 is supported by the third bearing 52 so as to be rotatable about the eccentric axis J2.

[0023] The rotation of the motor shaft 21 is transmitted to the output shaft 41 via the reduction mechanism 30. The output shaft 41 has a shaft portion 41a and a connecting portion 42. The shaft portion 41a is located on the upper side, and the connecting portion 42 is located on the lower side. The shaft portion 41a is in a cylindrical shape that extends centered on the central axis J1. The upper side of the shaft portion 41a is inserted into the through-hole 25 of the motor shaft 21. The upper side end portion of the shaft portion 41a protrudes toward the upper side of the motor shaft 21. The upper side end portion of the shaft portion 41a that protrudes toward the upper side of the motor shaft 21 is supported by the first bearing 53 so as to be rotatable about the central axis J1. The upper side end portion of the motor shaft 21 is supported on the housing 11 via the first bearing 53.

[0024] The lower side end portion of the connecting portion 42 protrudes toward the lower side of the motor shaft 21. The lower side end portion of the connecting portion 42 that protrudes toward the lower side of the motor shaft 21 is supported by the second bearing 51 so as to be rotatable about the central axis J1. The lower side end portion of the motor shaft 21 is supported on the housing 11 via the second bearing 51. The axial end portion of the output shaft 41 is supported by the first bearing 53 and the second bearing 51 so as to be rotatable about the central axis J1. Thus, the motor shaft 21, into which the shaft portion 41a of the output shaft 41 is inserted in the through-hole 25, is supported by the shaft portion 41a so as to be rotatable about the central axis J1.

[0025] The first bearing 53, the second bearing 51, and the third bearing 52 are each a rolling bearing that has an inner ring and an outer ring located on the radially outer side of the inner ring. In the present embodiment, the first bearing 53, the second bearing 51, and the third bearing 52 are, for example, ball bearings in which the inner ring and the outer ring are connected via a plurality of balls.

[0026] The upper side of the coupling portion 42 is inserted into the recessed portion 26 of the motor shaft 21. By the upper side of the coupling portion 42 being inserted into the recessed portion 26 of the motor shaft 21, the length in the axial direction of the output shaft 41 can be shortened. Thus, the length in the axial direction of the electric actuator 10 can be shortened, and the electric actuator 10 can be downsized.

[0027] The coupling portion 42 has a cylindrical cylindrical portion 44 extending about the center axis J1. A coupling recessed portion 45 is provided at the inner diameter of the cylindrical portion 44. The coupling recessed portion 45 is recessed upward from the lower side end portion of the output shaft 41. When viewed in the axial direction, the coupling recessed portion 45 has a substantially circular shape about the center axis J1. A plurality of spline grooves are provided on the inner peripheral surface of the coupling recessed portion 45 in the circumferential direction. Other components that are coupled to the driving force of the electric actuator 10 are inserted into the coupling recessed portion 45. The other components are, for example, a manual shaft in a vehicle. The electric actuator 10 drives the manual shaft in accordance with a shift operation by a driver, thereby switching the gears of the vehicle.

[0028] By the coupling portion 42 having the coupling recessed portion 45 recessed upward, the length in the axial direction of the output shaft 41 can be shortened compared to a case where the coupling portion 42 is a shaft protruding downward. Thus, the length in the axial direction of the electric actuator 10 can be shortened, and the electric actuator 10 can be downsized. By the first bearing 53 being held by the bearing holding portion 16b provided to the housing 11 and the second bearing 51 being held by the bearing holding portion 13d provided to the housing 11, the coaxiality of the output shaft 41 with respect to the center axis J1 can be improved. By the first bearing 53 being held by the bearing holding portion 16b provided to the housing 11 and the second bearing 51 being held by the bearing holding portion 13d provided to the housing 11, components for holding the first bearing 53 and the second bearing 51 need not be separately provided, and thus the cost and the downsizing of the electric actuator 10 can be facilitated.

[0029] The rotor core 22a is fixed to the outer peripheral surface of the motor shaft 21. More specifically, the rotor core 22a is fixed to the outer peripheral surface of the first shaft portion 21a. The peripheral edge portion of the rotor core 22a is supported from the lower side by a partition member 15 described later, which is supported from the lower side by the lower housing 11A. The partition member 15 is a support member that supports the rotor core 22a from the lower side. The magnets 40 are fixed to the radially outer side of the rotor core 22a. A plurality of the magnets 40 are arranged at intervals in the circumferential direction.

[0030] The stator 23 is located radially outward of the rotor 22. The stator 23 has a stator core 23a and a plurality of coils 23b. The stator core 23a has a circular ring shape that surrounds the radially outer side of the rotor 22. The outer peripheral surface 24a of the stator core 23a is fixed to the inner peripheral surface of the housing cylindrical portion 13b. The plurality of coils 23b are mounted on the teeth of the stator core 23a, for example, with an insulating member not shown therebetween.

[0031] AsFigure 2 As shown, the stator 23 has an outer peripheral surface 24b located radially inward of the outer peripheral surface 24a. The outer peripheral surface 24b is arranged for each magnetic pole. When viewed axially, the outer peripheral surface 24b is perpendicular to the circumferential magnetic pole center. A groove 27 is provided on the outer peripheral surface 24b of the stator 23, which is recessed radially inward. The groove 27 extends axially. The grooves 27 are located above and below the outer peripheral surface 24a of the stator core 23a. A plurality of grooves 27 are arranged at intervals along the circumferential direction.

[0032] The bus bar holder 140 is disposed on the upper side of the rotor 22. The bus bar holder 140 is in the shape of an annular plate. Figure 1 As shown, the busbar holder 140 includes a spacer 143. The spacer 143 is cylindrical and extends in the axial direction. It protrudes upward from the busbar holder 140. The upper end of the spacer 143 contacts the lower side of the circuit board 70. The busbar holder 140 and the circuit board 70 are screw-fastened to the support surface 12 of the lower housing 11A using bolts 144 that penetrate the circuit board 70 and the spacer 143 from above. For example, three bolts 144 are provided. When viewed axially, the busbar holder 140 and the circuit board 70 are screw-fastened from above by the bolts 144 at a position where the spacer 143 overlaps. The screw-fastened circuit board 70 is positioned above the busbar holder 140 with a gap therebetween. The gap between the circuit board 70 and the busbar holder 140 is the size of the spacer 143 protruding upward from the busbar holder 140.

[0033] The bus bar holder 140 has a peripheral wall portion 141 extending downward. The peripheral wall portion 141 is located radially outward of the outer peripheral surface 24b of the stator 23. The peripheral wall portion 141 is located radially inward of the outer peripheral surface 24a of the stator 23. When the bus bar holder 140 is screwed to the support surface 12, the lower end of the peripheral wall portion 141 contacts the upper side of the stator 23.

[0034] When the bus bar holder 140 is screwed to the support surface 12 of the lower case 11A, the lower end of the peripheral wall portion 141 contacts the upper side of the stator 23, thereby positioning and fixing the stator 23 supported by the partition member 15 from the lower side in the axial direction to the lower case 11A.

[0035] like Figure 2As shown, the peripheral wall portion 141 of the bus bar holder 140 has a protrusion portion 142 that protrudes toward the radially inner side. The protrusion portion 142 extends in the axial direction. The circumferential position of the protrusion portion 142 is the same as the circumferential position of the slot portion 27 of the stator 23. The protrusion portion 142 is opposed to the slot portion 27 in the radial direction. The protrusion portion 142 that protrudes toward the radially inner side of the peripheral wall portion 141 is inserted into the slot portion 27. The bus bar holder 140 whose protrusion portion 142 is inserted into the slot portion 27 is positioned in the circumferential direction with the stator 23. When the bus bar holder 140 is housed in the substrate housing portion 13a while the protrusion portion 142 is inserted from the upper side with respect to the slot portion 27 that is open in the upper side, the bus bar holder 140 can be positioned in the circumferential direction with respect to the stator 23 and the lower case 11A. Therefore, when the bus bar holder 140 is fastened to the support surface 12 of the lower case 11A with the screw, the bus bar holder 140, the stator 23, and the lower case 11A can be positioned in the circumferential and axial directions with respect to each other.

[0036] The bus bar holder 140 holds the magnetic sensor 63, the conductive wire 64, and the plurality of bus bars 150. In the present embodiment, the bus bar holder 140, the magnetic sensor 63, the conductive wire 64, the spacer 143, and the plurality of bus bars 150 are a molded body that is integrated by resin molding. In more detail, the bus bar holder 140 is produced by insert molding with the magnetic sensor 63, the conductive wire 64, the spacer 143, and the bus bars 150 as insert parts.

[0037] The magnetic sensor 63 can detect the magnetic field of the magnet 40. The magnetic sensor 63 is, for example, a Hall element. The magnetic sensor 63 is fixed to the lower side of the bus bar holder 140. The magnetic sensor 63 is disposed in opposition to the upper side of the magnet with a gap therebetween. As shown, the magnetic sensor 63 is disposed at three positions that are spaced apart in the circumferential direction. The magnetic sensor 63 detects the rotational position of the magnet 40 by detecting the magnetic field of the magnet 40, thereby detecting the rotation of the motor shaft 21. Figure 2

[0038] ​According to the electric actuator 10 of this embodiment, the magnetic sensor 63, located on the lower side of the bus bar holder 140 so as to be opposed to the magnet 40, directly detects the magnetic field of the magnet 40. Therefore, the detection timing of the magnetic sensor 63 is less likely to vary. Therefore, according to the electric actuator 10 of this embodiment, phase shift between the magnet 40 and the rotor 22 can be suppressed. By suppressing the phase shift between the magnet 40 and the rotor 22, delays in energization timing caused by variations in the detection timing of the magnetic sensor 63 can be suppressed, thereby suppressing degradation in motor performance. According to the electric actuator 10 of this embodiment, since the magnetic sensor 63 is provided on the bus bar holder 140, a separate substrate for mounting the magnetic sensor is not required. According to the electric actuator 10 of this embodiment, the magnetic sensor 63 and the bus bar holder 140 are integrally molded by resin molding. When the bus bar holder 140 is screwed and assembled to the support surface 12 of the lower housing 11A, the magnetic sensor 63 and the bus bar holder 140 are positioned circumferentially and axially relative to the stator 23. According to the electric actuator 10 of the present embodiment, it is possible to suppress a decrease in the accuracy of the rotation control of the motor due to an advance angle deviation caused by assembly accuracy.

[0039] One end of the conductive wire 64 is electrically connected to the magnetic sensor 63. The conductive wire 64 may be a terminal extending from the magnetic sensor 63 or a bus bar having one end connected to the magnetic sensor 63. The conductive wire 64 extends through the bus bar holder 140 from the inside and is electrically connected to the circuit board 70 at its other end by a connection method such as soldering, welding, or press-fitting.

[0040] The circuit board 70 is a plate-shaped structure extending along a plane perpendicular to the axial direction. It is housed in the lower housing 11A. More specifically, it is housed within the substrate housing 13a. The circuit board 70 is electrically connected to the motor unit 20. For example, the circuit board 70 controls the current supplied to the motor unit 20. Specifically, the circuit board 70 carries, for example, an inverter circuit.

[0041] like Figure 3 As shown, the end 150a on one side of the busbar 150 holds the coil lead wire led out from the coil 23b of the stator 23 and is connected to the coil 23b by brazing or welding. The end 150b on the other side of the busbar 150 protrudes upward from the upper surface of the busbar holder 140. In this embodiment, the end 150b on the other side of the busbar 150 passes through the circuit board 70 from the bottom to the top. The end 150b is electrically connected to the circuit board 70 at the position where it passes through the circuit board 70 by a connection method such as brazing, welding, and pressing. As a result, the circuit board 70 is electrically connected to the motor unit 20 via the busbar 150.

[0042] The reduction mechanism 30 is disposed radially outward of the second shaft portion 21b of the motor shaft 21 and radially outward of the coupling portion 42 of the output shaft 41. The reduction mechanism 30 is disposed on the lower side of the motor portion 20. The partition member 15 is disposed between the stator 23 and the reduction mechanism 30 in the axial direction. The reduction mechanism 30 has an external gear 31, an internal gear 32, an output portion 46, and a plurality of protruding portions 43.

[0043] The external gear 31 is a circular ring plate shape that expands in the radial direction of the eccentric axis J2 with the eccentric axis J2 of the eccentric shaft portion 21b as the center. A gear portion is provided on the radially outer side surface of the external gear 31. The gear portion of the external gear 31 has a plurality of tooth portions arranged along the outer periphery of the external gear 31.

[0044] The external gear 31 is coupled to the motor shaft 21. More specifically, the external gear 31 is coupled to the eccentric shaft portion 21b of the motor shaft 21 via a third bearing 52. Thus, the motor shaft 21 is coupled to the reduction mechanism 30. The external gear 31 is fitted to the outer ring of the third bearing 52 from the radially outer side. The eccentric shaft portion 21b is fitted to the inner ring of the third bearing 52 from the radially outer side. Thus, the third bearing 52 couples the motor shaft 21 and the external gear 31 so as to be relatively rotatable about the eccentric axis J2.

[0045] In the present embodiment, the external gear 31 has a plurality of hole portions 31a. In the present embodiment, the hole portions 31a penetrate the external gear 31 in the axial direction. The plurality of hole portions 31a are arranged along the circumferential direction. More specifically, the plurality of hole portions 31a are arranged at equal intervals in one circumferential range along the circumferential direction with the eccentric axis J2 as the center. The hole portions 31a are circular in shape when viewed in the axial direction. The inner diameter of the hole portions 31a is larger than the outer diameter of the protruding portions 43. Note that the hole portions 31a can also be holes having bottoms.

[0046] The internal gear 32 is located radially outward of the external gear 31 and is annular so as to surround the external gear 31. In the present embodiment, the internal gear 32 is a circular ring shape with the central axis J1 as the center. The radially outer edge portion of the internal gear 32 is arranged on and fixed to the step portion 13e recessed radially inward of the inner circumferential surface of the housing cylindrical portion 13b. Thus, the reduction mechanism 30 is held by the lower housing 11A. The internal gear 32 is engaged with the external gear 31. A gear portion is provided on the radially inner side surface of the internal gear 32. The gear portion of the internal gear 32 has a plurality of tooth portions arranged along the inner periphery of the internal gear 32. In the present embodiment, the gear portion of the internal gear 32 is engaged with the gear portion of the external gear 31 only on a part of the circumferential direction.

[0047] The output portion 46 is a circular ring plate shape that expands radially with the center axis J1 as the center. The output portion 46 is located on the lower side of the external tooth gear 31. The output portion 46 is fixed to the outer peripheral surface of the output shaft 41. To be more specific, the output portion 46 is fixed to the outer peripheral surface of the coupling portion 42 of the output shaft 41.

[0048] The plurality of protrusions 43 are fixed to the output portion 46, for example, by welding. The plurality of protrusions 43 protrude upward from the output portion 46. That is, the plurality of protrusions 43 protrude from the output portion 46 toward the external tooth gear 31. The protrusions 43 are cylindrical. The plurality of protrusions 43 are arranged along the circumferential direction. To be more specific, the plurality of protrusions 43 are arranged at equal intervals along the circumferential direction with the center axis J1 as the center over one revolution. The number of the protrusions 43 is, for example, eight.

[0049] The plurality of protrusions 43 are respectively inserted into the plurality of hole portions 31a. The outer peripheral surface of the protrusion 43 is inscribed in the inner peripheral surface of the hole portion 31a. Thereby, the plurality of protrusions 43 support the external tooth gear 31 to be able to oscillate around the center axis J1 via the inner side surface of the hole portion 31a.

[0050] In the present embodiment, the hole portion 31a and the protrusion 43 overlap the third bearing 52 and the second shaft portion 21b when viewed in the radial direction. In other words, the hole portion 31a, the protrusion 43, the third bearing 52, and the second shaft portion 21b each have a portion that is located at the same position in the axial direction as each other.

[0051] When the motor shaft 21 rotates around the center axis J1, the second shaft portion 21b as an eccentric shaft portion revolves in the circumferential direction with the center axis J1 as the center. The revolution of the second shaft portion 21b is transmitted to the external tooth gear 31 via the third bearing 52, and the external tooth gear 31 oscillates while the position at which the inner peripheral surface of the hole portion 31a and the outer peripheral surface of the protrusion 43 are inscribed changes. Thereby, the position at which the gear portion of the external tooth gear 31 and the gear portion of the internal tooth gear 32 mesh changes in the circumferential direction. Thus, the rotational force of the motor shaft 21 is transmitted to the internal tooth gear 32 via the external tooth gear 31.

[0052] Here, in the present embodiment, the internal tooth gear 32 is fixed, and thus does not rotate. Thus, the external tooth gear 31 is rotated around the eccentric axis J2 by the reaction force of the rotational force transmitted to the internal tooth gear 32. At this time, the direction in which the external tooth gear 31 rotates is the direction opposite to the direction in which the motor shaft 21 rotates. The rotation of the external tooth gear 31 around the eccentric axis J2 is transmitted to the output portion 46 via the hole portion 31a and the protrusion 43. Thereby, the output shaft 41 rotates around the center axis J1. In this way, the rotation of the motor shaft 21 is transmitted to the output shaft 41 via the speed reduction mechanism 30

[0053] The rotation of the output shaft 41 is decelerated with respect to the rotation of the motor shaft 21 by the deceleration mechanism 30. Specifically, in the structure of the deceleration mechanism 30 of the present embodiment, the deceleration ratio R of the rotation of the output shaft 41 with respect to the rotation of the motor shaft 21 is represented by R = -(N2-N1) / N2. The negative sign at the beginning of the formula representing the deceleration ratio R indicates the direction of the rotation with respect to the motor shaft 21, and the direction of the rotation of the output shaft 41, which is decelerated, is the opposite direction. N1 is the number of teeth of the outer gear 31, and N2 is the number of teeth of the inner gear 32. As an example, in the case where the number of teeth N1 of the outer gear 31 is 59 and the number of teeth N2 of the inner gear 32 is 60, the deceleration ratio R is -1 / 60.

[0054] Thus, according to the deceleration mechanism 30 of the present embodiment, it is possible to make the deceleration ratio R of the rotation of the output shaft 41 with respect to the rotation of the motor shaft 21 large. Therefore, it is possible to make the rotation torque of the output shaft 41 large.

[0055] The electric actuator to which the present application is applied is only a device that can move an object as a target by being supplied with electric power, and can be a motor that does not have a deceleration mechanism. In addition, the electric actuator can be an electric pump that has a pump portion driven by a motor portion. The use of the electric actuator is not particularly limited. The electric actuator can be mounted on an actuator device of a wire control type that is driven in accordance with a shift operation by a driver. In addition, the electric actuator can be mounted on a device other than a vehicle. In addition, each structure described in the present specification can be appropriately combined within a range where they do not contradict each other.

Claims

1. An electric actuator, comprising: a motor portion having a rotor rotating about a center axis extending in an axial direction and a stator facing the rotor in a radial direction across a gap, the rotor having a motor shaft, a rotor core fixed to an outer peripheral surface of the motor shaft, and a magnet fixed to a radially outer side of the rotor core; a bus bar electrically connected to the motor portion; a bus bar holder disposed on an axial one side of the rotor to hold the bus bar; a magnetic sensor fixed to the bus bar holder to detect a magnetic field of the magnet; an electrically conductive wire electrically connected to the magnetic sensor; and a circuit board disposed on an axial one side of the bus bar holder and electrically connected to the motor portion, the magnetic sensor being disposed facing an axial one side of the magnet fixed to a radially outer side of the rotor core across a gap to directly detect a magnetic field of the magnet, the electrically conductive wire penetrating the bus bar holder from an inside of the bus bar holder and being electrically connected to the circuit board.

2. The electric actuator according to claim 1, wherein the magnetic sensor and the bus bar holder are integrated as a molded body by resin molding.

3. The electric actuator according to claim 1 or 2, wherein a plurality of groove portions recessed toward a radially inner side and extending in an axial direction are provided at intervals in a circumferential direction on an outer peripheral surface of the stator, the bus bar holder has a peripheral wall portion extending toward an axial other side and facing the groove portions at a position radially outward of the outer peripheral surface of the stator, and the peripheral wall portion has a protrusion portion protruding toward a radially inner side and inserted into the groove portions.

4. The electric actuator according to claim 3, wherein the electric actuator has a housing accommodating the motor portion, the housing having a support surface toward an axial one side, the bus bar holder has a spacer protruding toward an axial one side, an axial other side of the circuit board is in contact with the spacer, and the bus bar holder and the circuit board are fastened to the support surface from the axial one side at a position overlapping the spacer when viewed in an axial direction.

5. The electric actuator according to claim 4, wherein the electric actuator has a support member supported on the housing from an axial other side, the support member is in contact with an axial other side of the stator, and an end portion of the peripheral wall portion on the axial other side is in contact with an axial one side of the stator when the bus bar holder is fastened to the support surface.

6. The electric actuator according to claim 1, wherein the magnetic sensor is a Hall element. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Images