CN216599290U - Electric actuator - Google Patents

Abstract

The present invention provides an electric actuator, comprising: a motor having a motor shaft rotatable about a motor axis; a transmission mechanism connected to the motor shaft; a housing that houses the motor and the transmission mechanism therein; and a support shaft extending in the axial direction of the motor axis, portions of both sides of the support shaft in the axial direction being supported by the housing. The motor shaft is a hollow shaft. The support shaft is inserted into the motor shaft and supports the motor shaft so that the motor shaft can rotate around the motor axis.

Description

Electric actuator

Technical Field

The present invention relates to an electric actuator.

Background

An electric actuator including a motor and a transmission mechanism is known. For example, patent document 1 describes a rotary actuator that is applied as a power source of a shift-by-wire system for switching a shift of an automatic transmission of a vehicle.

Patent document 1: japanese patent laid-open publication No. 2016-109226

In the electric actuator as described above, further downsizing of the motor shaft in the axial direction is desired.

SUMMERY OF THE UTILITY MODEL

In view of the above circumstances, an object of the present invention is to provide an electric actuator having a structure that can be reduced in size in the axial direction.

A first aspect of the present invention provides an electric actuator including: a motor having a motor shaft rotatable about a motor axis; a transmission mechanism coupled to the motor shaft; a housing that houses the motor and the transmission mechanism therein; and a support shaft extending in an axial direction of the motor axis, portions of both sides of the support shaft in the axial direction being supported by the housing, the motor shaft being a hollow shaft, the support shaft being inserted into the motor shaft and supporting the motor shaft so that the motor shaft can rotate around the motor axis.

An electric actuator according to a second aspect of the present invention is the electric actuator according to the first aspect, wherein the housing includes: a 1 st housing member that supports a portion of the support shaft that protrudes to one side in an axial direction of the motor; and a 2 nd housing member fixed to the 1 st housing member and supporting a portion of the support shaft that protrudes further than the motor shaft in the axial direction than the other side.

In an electric actuator according to a third aspect of the present invention, in the electric actuator according to the second aspect, one of the 1 st and 2 nd casing members has a fixing hole portion for fixing the support shaft, and the other of the 1 st and 2 nd casing members has a fitting hole portion for fitting the support shaft with a gap therebetween.

An electric actuator according to a fourth aspect of the present invention is the electric actuator according to the first aspect, wherein the housing has a hole for supporting the support shaft, and a washer is provided between a peripheral edge portion of the hole in the housing and an axial direction of the motor shaft.

An electric actuator according to a fifth aspect of the present invention is the electric actuator according to any one of the first to fourth aspects, wherein the motor shaft has an eccentric shaft portion centered on an eccentric axis that is eccentric with respect to the motor axis, and the transmission mechanism includes: an external gear coupled to the eccentric shaft portion via a 1 st bearing; an internal gear that meshes with the external gear and surrounds a radially outer side of the external gear; an output gear coupled to the motor shaft via a 2 nd bearing and disposed to be axially opposite to the external gear; and a plurality of protruding portions that protrude from one of the output gear and the external gear toward the other and are arranged so as to surround the motor axis, the other of the output gear and the external gear having a plurality of holes arranged so as to surround the motor axis, the plurality of protruding portions being inserted into the plurality of holes, respectively, and supporting the external gear via inner side surfaces of the holes so as to be swingable around the motor axis.

According to the present invention, the electric actuator can be downsized in the axial direction.

Drawings

Fig. 1 is a sectional view showing an electric actuator according to the present embodiment.

Fig. 2 is a sectional view showing the transmission mechanism of the present embodiment, and is a sectional view II-II in fig. 1.

Description of the reference symbols

10: an electric actuator; 11: a housing; 12: a 1 st housing part; 14: a 2 nd housing part; 14 d: a fixing hole portion; 32 d: a fitting hole portion; 40: a motor; 41: a motor shaft; 41 b: an eccentric shaft portion; 44 a: a 1 st bearing; 44 b: a 2 nd bearing; 50: a transfer mechanism; 51: an external gear; 51 b: a hole portion; 52: an internal gear; 53: an output gear; 54: a protrusion; 90: a support shaft; 91: a gasket; j1: a motor axis; j2: an eccentric axis.

Detailed Description

In the following description, unless otherwise specified, an axial direction along which the motor axis J1, which is an imaginary axis appropriately shown in the drawings, extends will be simply referred to as an "axial direction". Unless otherwise specified, the radial direction about the motor axis J1 is simply referred to as the "radial direction", and the circumferential direction about the motor axis J1 is simply referred to as the "circumferential direction".

The Z-axis appropriately shown in each figure represents the axial direction. In the following description, a positive side (+ Z side) facing an arrow of the Z axis in the axial direction is referred to as an "upper side", and a negative side (Z side) opposite to the arrow of the Z axis is referred to as a "lower side". In the present embodiment, the upper side corresponds to the "one axial side", and the lower side corresponds to the "other axial side".

The vertical direction, the upper side, and the lower side are only names for describing the relative positional relationship of the respective parts, and the actual arrangement relationship may be an arrangement relationship other than the arrangement relationship indicated by the names.

The electric actuator 10 of the present embodiment shown in fig. 1 is mounted on a vehicle. More specifically, the electric actuator 10 is mounted on, for example, an actuator device of a shift-by-wire system that is driven in accordance with a shift operation by a driver of the vehicle. As shown in fig. 1, the electric actuator 10 includes: the motor includes a housing 11, a motor 40, a 1 st bearing 44a, a 2 nd bearing 44b, a support shaft 90, a transmission mechanism 50, an output portion 60, a substrate 70, a rotation sensor 74, and a stator fixing member 80. The 1 st bearing 44a and the 2 nd bearing 44b are, for example, ball bearings.

The housing 11 houses the motor 40, the 1 st bearing 44a, the 2 nd bearing 44b, the support shaft 90, the transmission mechanism 50, the output unit 60, the substrate 70, the rotation sensor 74, and the stator fixing member 80. The housing 11 has: a 1 st housing member 12 having openings 12a and 12b on both sides in the axial direction; a cover 13 for closing the opening 12a on the upper side of the 1 st housing member 12; and a 2 nd case member 14 that closes the opening 12b on the lower side of the 1 st case member 12.

The 1 st housing part 12 is made of metal, for example. The 1 st housing part 12 is a die-cast product molded as a single part by die-casting, for example. The material constituting the 1 st housing part 12 is, for example, aluminum or the like. The 1 st housing part 12 has: a cylindrical outer wall portion 30 that constitutes a housing of the electric actuator 10; a bottom wall portion 31 that extends radially inward from a lower end of the outer wall portion 30; a motor housing portion 32 and an output shaft holding portion 33, the motor housing portion 32 and the output shaft holding portion 33 being provided to the bottom wall portion 31; and a cylindrical wall 39 projecting downward from the bottom wall portion 31.

Although not shown, the outer wall portion 30 has a square tubular shape, for example. The outer wall portion 30 surrounds the motor housing portion 32 from the radially outer side. In the present embodiment, the upper opening of the outer wall portion 30 is the upper opening 12a of the 1 st case member 12.

The motor housing portion 32 is located inside the outer wall portion 30. The motor housing portion 32 internally houses the motor 40. The motor housing portion 32 has a cylindrical shape surrounding the motor 40 from the radially outer side. In the present embodiment, the inner peripheral surface of the motor case portion 32 is cylindrical and is open on the lower side with respect to the motor axis J1. The motor housing portion 32 holds the motor 40 inside. More specifically, a stator 43, which will be described later, of the motor 40 is fixed to an inner peripheral surface of the motor case 32. The motor case 32 includes a peripheral wall portion 32b, a lid portion 32a, and a 1 st support portion 32 c.

The peripheral wall portion 32b has a cylindrical shape extending upward from the bottom wall portion 31. The inner peripheral surface of the peripheral wall portion 32b is, for example, cylindrical with the motor axis J1 as the center. The peripheral wall portion 32b surrounds a radially outer side of a stator 43 described later. The outer peripheral surface of the peripheral wall portion 32b is continuous with the inner side surface of the outer wall portion 30. A part of the peripheral wall portion 32b is constituted by a part of the outer wall portion 30, for example.

The lid portion 32a extends radially inward from an upper end of the peripheral wall portion 32b, for example. The cover portion 32a covers at least a part of the motor 40 from the upper side. In the present embodiment, the cover portion 32a covers the motor shaft 41, the rotor body 42, and the stator 43, which will be described later, from above.

The 1 st support portion 32c protrudes downward from the radial center of the cover portion 32 a. The 1 st support portion 32c has a cylindrical shape centered on the motor axis J1, for example. The 1 st support portion 32c has a fitting hole portion 32d recessed from the lower surface of the 1 st support portion 32c toward the upper surface. That is, the 1 st housing part 12 has a fitting hole portion 32 d. The fitting hole 32d is, for example, a hole having a bottom on the upper side and an opening on the lower side. The fitting hole portion 32d is, for example, a circular hole centered on the motor axis J1.

The output shaft holding portion 33 is located inside the outer wall portion 30. The output shaft holding portion 33 is located radially outward of the motor housing portion 32. The output shaft holding portion 33 protrudes upward from the bottom wall portion 31. A part of the side surface of the output shaft holding portion 33 is connected to a part of the side surface of the motor housing portion 32, for example. The output shaft holding portion 33 has a hole portion 33a axially penetrating the output shaft holding portion 33. The hole portion 33a is, for example, a circular hole centered on the output axis J3. The output axis J3 is a central axis of the output shaft 61 described later. The output axis J3 is parallel to the motor axis J1 and is disposed radially spaced from the motor axis J1. A cylindrical sliding bearing 65 is fitted inside the hole 33 a.

The cylindrical wall 39 protrudes downward from the lower surface of the bottom wall 31. The cylindrical wall 39 is cylindrical surrounding the motor axis J1 and the output axis J3. The cylindrical wall 39 is open on the lower side. In the present embodiment, the lower opening of the cylindrical wall 39 is the lower opening 12b of the 1 st case member 12.

In the present embodiment, the cover 13 is a plate-shaped member having a plate surface facing in the axial direction. The cover 13 is made of metal, for example. The cover 13 is manufactured by, for example, forming a plate-shaped metal member by press working. The cover 13 is fixed to the 1 st housing member 12 by a plurality of bolts, for example. The cover 13 covers the substrate 70 from above, for example.

The 2 nd housing part 14 covers the transfer mechanism 50 from the lower side. The 2 nd housing member 14 is made of metal, for example. The 2 nd housing part 14 is molded by die casting, for example. The 2 nd housing member 14 has a bottom wall portion 14a, a cylindrical portion 14b, a flange portion 14c, a fitting cylindrical portion 14g, and an annular convex portion 14 f.

The bottom wall portion 14a expands in the radial direction. The bottom wall portion 14a is located below the motor 40, the transmission mechanism 50, and the support shaft 90. The bottom wall portion 14a has a 2 nd support portion 14 h. The 2 nd support portion 14h is a radial center portion of the bottom wall portion 14 a. For example, the 2 nd support portion 14h has a circular shape centered on the motor axis J1 when viewed in the axial direction. The 2 nd support portion 14h is located below the motor shaft 41 and the support shaft 90.

The 2 nd support portion 14h has a fixing hole portion 14d recessed from the upper surface of the 2 nd support portion 14h toward the lower side. That is, the 2 nd housing member 14 has a fixing hole portion 14 d. The fixing hole portion 14d is, for example, a hole having a bottom on the lower side and an opening on the upper side. The fixed hole portion 14d is, for example, a circular hole centered on the motor axis J1. The inner diameter of the fixing hole 14d is smaller than the inner diameter of the fitting hole 32d, for example.

The cylindrical portion 14b extends upward from the outer peripheral edge of the bottom wall portion 14 a. The cylindrical portion 14b is, for example, cylindrical with the motor axis J1 as the center. The cylindrical portion 14b is open on the upper side. An internal gear 52 described later is fitted inside the cylindrical portion 14 b.

The flange portion 14c extends radially outward from the cylindrical portion 14 b. The upper surface of the flange portion 14c contacts, for example, the lower end surface of the cylindrical wall 39. The flange portion 14c is fixed to the cylindrical wall 39 with screws, for example. Thereby, the 2 nd housing part 14 is fixed to the 1 st housing part 12. The flange portion 14c has an opening portion 14e that overlaps the output portion 60 in the axial direction. The opening 14e is open on the lower side.

The fitting tube portion 14g protrudes upward from the flange portion 14 c. The fitting cylindrical portion 14g has a cylindrical shape surrounding the motor axis J1 and the output axis J3. The fitting tube portion 14g is fitted into the cylindrical wall 39.

The annular projecting portion 14f projects upward from a portion of the upper surface of the bottom wall portion 14a that is radially inward of the cylindrical portion 14 b. The annular projection 14f is annular and surrounds the motor axis J1. The annular protrusion 14f is, for example, annular centered on the motor axis J1. The inner diameter of the annular projection 14f is larger than the inner diameter of the fixing hole 14 d. The annular projection 14f surrounds the fixing hole 14d when viewed from above. The upper end of the annular protrusion 14f is located below the upper end of the cylindrical portion 14 b.

The central axis of the motor 40 is the motor axis J1. The motor 40 has a rotor 40a and a stator 43. The rotor 40a is rotatable about a motor axis J1 extending in the axial direction. The rotor 40a has a motor shaft 41 and a rotor main body 42. That is, the motor 40 has a motor shaft 41 and a rotor main body 42.

The motor shaft 41 extends in the axial direction. The motor shaft 41 can rotate about a motor axis J1. The motor shaft 41 is a hollow shaft. The motor shaft 41 is, for example, cylindrical and extends in the axial direction around a motor axis J1. The motor shaft 41 is open on both sides in the axial direction. The inner diameter of the motor shaft 41 is uniform over the entire axial range, for example. The inner peripheral surface of the motor shaft 41 is, for example, cylindrical in shape centered on the motor axis J1 over the entire axial range. The motor shaft 41 has a main body portion 41a and an eccentric shaft portion 41 b.

The main body 41a is a portion to which the rotor body 42 is fixed. The body portion 41a is cylindrical with the motor axis J1 as the center. The upper end of the body 41a is, for example, the upper end of the motor shaft 41. The upper end of the main body 41a is disposed to face the lower side of the peripheral edge of the fitting hole 32d on the lower surface of the 1 st support portion 32 c. A gasket 91 is provided between an upper end of the body 41a and a lower end of the 1 st supporting portion 32 c. That is, a washer 91 is provided between the peripheral edge of the fitting hole 32d in the housing 11 and the axial direction of the motor shaft 41.

The washer 91 is, for example, annular and centered on the motor axis J1. The washer 91 is, for example, plate-shaped with its plate surface facing in the axial direction. The washer 91 is, for example, a wave washer. A washer 91 surrounds the support shaft 90. The lower surface of the washer 91 contacts the upper end surface of the motor shaft 41. The upper surface of the washer 91 contacts the peripheral edge of the fitting hole 32d in the lower end surface of the 1 st support portion 32 c.

The body portion 41a has an enlarged diameter portion 41c having an enlarged outer diameter at a central portion in the axial direction. The enlarged diameter portion 41c is connected to portions of the body portion 41a located on both sides in the axial direction of the enlarged diameter portion 41c via a step.

The eccentric shaft portion 41b is connected to the lower side of the body portion 41 a. The lower end of the eccentric shaft portion 41b is, for example, the lower end of the motor shaft 41. The lower end of the eccentric shaft portion 41b is located above the peripheral edge of the fixing hole 14d in the upper surface of the bottom wall portion 14 a. The lower end of the eccentric shaft portion 41b is axially opposed to the peripheral edge of the fixed hole portion 14d with a gap therebetween. The eccentric shaft portion 41b is a portion centered on an eccentric axis J2 that is eccentric with respect to the motor axis J1. The eccentric axis J2 is parallel to the motor axis J1. The inner race of the 1 st bearing 44a is fitted and fixed to the eccentric shaft portion 41 b. Thereby, the 1 st bearing 44a is fixed to the motor shaft 41.

In the present specification, the term "the eccentric shaft portion is centered on the eccentric axis" means that the outer peripheral surface of the eccentric shaft portion is centered on the eccentric axis, and the inner peripheral surface of the eccentric shaft portion may not be centered on the eccentric axis. In the present embodiment, the outer peripheral surface of the eccentric shaft portion 41b is cylindrical with the eccentric axis J2 as the center. The inner peripheral surface of the eccentric shaft portion 41b is cylindrical about the motor axis J1.

The rotor main body 42 has a ring shape surrounding the motor shaft 41. The rotor body 42 is fixed to the outer peripheral surface of the motor shaft 41. More specifically, the rotor body 42 is fixed to the outer peripheral surface of a portion of the body 41a located above the enlarged diameter portion 41 c. Although not shown, the rotor body 42 includes a rotor core fixed to the motor shaft 41 and a rotor magnet fixed to the rotor core. The radially inner peripheral edge of the rotor body 42 contacts, for example, the upper end surface of the enlarged diameter portion 41 c.

The stator 43 is located radially outward of the rotor 40 a. The stator 43 is disposed radially outward of the rotor body 42 with a gap therebetween. The stator 43 is annular surrounding the radially outer side of the rotor main body 42. The stator 43 includes, for example, a stator core 43a, an insulator 43b, and a plurality of coils 43 c. Each coil 43c is attached to a tooth of the stator core 43a via an insulator 43 b.

The stator core 43a is annular and surrounds the rotor body 42 from the radially outer side. The stator core 43a is fitted into the peripheral wall portion 32 b. In the present embodiment, the stator core 43a is fixed inside the peripheral wall portion 32b by press fitting. The stator core 43a is, for example, lightly pressed into the inside of the peripheral wall portion 32 b. A radially outer peripheral edge portion of the upper end portion of the stator core 43a contacts a step provided on the inner peripheral surface of the peripheral wall portion 32b from below. The stator core 43a is formed by laminating a plurality of electromagnetic steel plates in the axial direction, for example.

The support shaft 90 extends in the axial direction of the motor axis J1. The support shaft 90 has a cylindrical shape centered on the motor axis J1, for example. The bearing shaft 90 opens into the interior of the motor shaft 41. The support shaft 90 protrudes axially to both sides of the motor shaft 41. Both axial side portions of the support shaft 90 are supported by the housing 11. The two axial side portions of the support shaft 90 include a portion of the support shaft 90 that protrudes upward from the motor shaft 41 and a portion of the support shaft 90 that protrudes downward from the motor shaft 41.

In the present embodiment, the upper end of the support shaft 90 is fitted into the fitting hole 32d with a gap therebetween and is supported by the inner circumferential surface of the fitting hole 32 d. That is, the housing 11 has the fitting hole portion 32d as a hole for supporting the support shaft 90. Thereby, the 1 st housing member 12 supports a portion of the support shaft 90 that protrudes upward from the motor shaft 41. The radial clearance between the outer peripheral surface of the upper end of the support shaft 90 and the inner peripheral surface of the fitting hole 32d is small enough to support the support shaft 90 by the inner peripheral surface of the fitting hole 32 d. The outer peripheral surface of the upper end of the support shaft 90 and the inner peripheral surface of the fitting hole 32d are radially opposed to each other and can contact each other. A part of the outer peripheral surface of the support shaft 90 contacts the inner peripheral surface of the fitting hole portion 32d, thereby radially supporting the support shaft 90. The upper end surface of the support shaft 90 faces the upper bottom of the fitting hole 32d with a gap therebetween in the axial direction.

The lower end of the support shaft 90 is fixed to the fixing hole 14 d. Thereby, the 2 nd housing member 14 supports a portion of the support shaft 90 that protrudes downward from the motor shaft 41. The lower end of the support shaft 90 is, for example, press-fitted into the fixing hole portion 14 d. The lower end surface of the support shaft 90 contacts, for example, the bottom of the fixing hole portion 14 d.

The support shaft 90 supports the motor shaft 41 rotatably about a motor axis J1. The outer diameter of the support shaft 90 is slightly smaller than the inner diameter of the motor shaft 41, for example. In the present embodiment, the support shaft 90 is fitted into the motor shaft 41 with a gap therebetween. The radial clearance between the support shaft 90 and the motor shaft 41 is small enough to support the motor shaft 41 rotatably about the motor axis J1 by the support shaft 90. The outer peripheral surface of the portion of the support shaft 90 located inside the motor shaft 41 and the inner peripheral surface of the motor shaft 41 are radially opposed to each other and can be in contact with each other. A part of the inner peripheral surface of the motor shaft 41 contacts the outer peripheral surface of the support shaft 90, thereby radially supporting the motor shaft 41. For example, a lubricating oil may be provided in the radial gap between the support shaft 90 and the motor shaft 41.

The transmission mechanism 50 is located on the lower side of the motor 40. The transmission mechanism 50 is located, for example, below the rotor body 42 and the stator 43. The transmission mechanism 50 is coupled to the rotor 40 a. The transmission mechanism 50 is coupled to a lower portion of the motor shaft 41, for example. In the present embodiment, the transmission mechanism 50 is a deceleration mechanism that decelerates the rotation of the rotor 40a and transmits the decelerated rotation to the output unit 60. The transmission mechanism 50 has an external gear 51, an internal gear 52, an output gear 53, and a plurality of protrusions 54.

The external gear 51 has an annular plate shape extending in the radial direction of the eccentric axis J2 around the eccentric axis J2 of the eccentric shaft portion 41 b. The external gear 51 is supported from below by the annular convex portion 14f, for example. As shown in fig. 2, a gear portion including a plurality of tooth portions 51a is provided on an outer surface of the external gear 51 in the radial direction. The external gear 51 is coupled to the eccentric shaft portion 41b via the 1 st bearing 44 a. Thereby, the transmission mechanism 50 is coupled to the motor shaft 41. More specifically, the transmission mechanism 50 is coupled to a lower end of the motor shaft 41. The external gear 51 is fitted to the outer ring of the 1 st bearing 44a from the radially outer side. Thus, the 1 st bearing 44a couples the motor shaft 41 and the externally toothed gear 51 so that the motor shaft 41 and the externally toothed gear 51 can rotate relatively around the eccentric axis J2.

As shown in fig. 1, the external gear 51 has a plurality of holes 51b recessed from the upper surface to the lower surface of the external gear 51. In the present embodiment, the hole 51b penetrates the external gear 51 in the axial direction. As shown in fig. 2, the plurality of holes 51b are disposed so as to surround the motor axis J1. More specifically, the plurality of holes 51b are arranged at equal intervals in a circumferential direction around the eccentric axis J2. For example, 8 holes 51b are provided. The hole 51b has a circular shape, for example, when viewed in the axial direction. The inner diameter of the hole 51b is larger than the outer diameter of the portion of the protruding portion 54 inserted into the hole 51 b. In addition, the hole portion 51b may be a hole having a bottom.

The internal gear 52 surrounds the radially outer side of the external gear 51 and meshes with the external gear 51. The internal gear 52 has an annular shape centered on the motor axis J1. As shown in fig. 1, in the present embodiment, the internal gear 52 is fixed to the housing 11. The internal gear 52 is, for example, press-fitted and fixed to the inside of the cylindrical portion 14 b. As shown in fig. 2, a gear portion having a plurality of tooth portions 52a is provided on an inner peripheral surface of the ring gear 52. The gear portion of the internal gear 52 meshes with the gear portion of the external gear 51. More specifically, the gear portion of the internal gear 52 meshes with the gear portion of the external gear 51 in a part of the circumferential direction.

As shown in fig. 1, the output gear 53 is disposed above the external gear 51 and the internal gear 52. The output gear 53 is disposed axially opposite the external gear 51. The output gear 53 is disposed so as to overlap the external gear 51 when viewed in the axial direction. The output gear 53 is coupled to the motor shaft 41 via the 2 nd bearing 44 b. More specifically, the output gear 53 is coupled to a portion of the main body 41a located below the diameter-enlarged portion 41c via the 2 nd bearing 44 b. The inner ring of the 2 nd bearing 44b is in contact with, for example, the lower end surface of the enlarged diameter portion 41 c.

The output gear 53 is, for example, annular and centered on the motor axis J1. A gear portion is provided on the radially outer side surface of the output gear 53. The gear portion of the output gear 53 has a plurality of tooth portions arranged along the outer periphery of the output gear 53. The output gear 53 meshes with a drive gear 62 described later.

The output gear 53 has a plurality of fixing holes 53a that penetrate the output gear 53 in the axial direction. Although not shown, the plurality of fixing holes 53a are disposed so as to surround the motor axis J1. More specifically, the plurality of fixing holes 53a are arranged at equal intervals in a circumferential direction around the motor axis J1. The number of the fixing holes 53a is 8, for example. The shape of the fixing hole 53a as viewed in the axial direction is, for example, a circular shape.

In the present embodiment, the protruding portion 54 is a columnar member extending in the axial direction. The upper portion of each projection 54 is fixed in each fixing hole 53a, for example. The lower portion of each projection 54 is located below the fixing hole 53 a. Thereby, the plurality of projecting portions 54 project from the output gear 53 toward the external gear 51 in the axial direction. As shown in fig. 2, the plurality of projections 54 are disposed so as to surround the motor axis J1. The plurality of projections 54 are arranged at equal intervals in a circumferential range, for example, along the circumferential direction. The number of the projections 54 is 8, for example.

As shown in fig. 1, the plurality of projections 54 are inserted into the plurality of holes 51b from above, respectively. The outer diameter of the portion of the protruding portion 54 inserted into the hole portion 51b is smaller than the inner diameter of the hole portion 51 b. The outer peripheral surface of the projection 54 is inscribed in the inner surface of the hole 51 b. The plurality of projecting portions 54 support the external gear 51 via the inner surface of the hole portion 51b so as to be swingable around the motor axis J1.

The output portion 60 is a portion that outputs the driving force of the electric actuator 10. The output portion 60 is disposed radially outward of the motor 40. The output unit 60 includes an output shaft 61, a drive gear 62, a slide bearing 65, and a sensor magnet 63.

The output shaft 61 has a cylindrical shape extending in the axial direction of the motor shaft 41. In this way, the output shaft 61 extends in the same direction as the motor shaft 41, and therefore the structure of the transmission mechanism 50 that transmits the rotation of the motor shaft 41 to the output shaft 61 can be simplified. The output shaft 61 is coupled to the motor shaft 41 via the transmission mechanism 50. In the present embodiment, the output shaft 61 is cylindrical with the output axis J3 as the center. In the following description, the radial direction of the output shaft 61, i.e., the radial direction centered on the output axis J3 is referred to as an "output radial direction".

The motor shaft 41 and the output shaft 61 are arranged apart from each other in a direction perpendicular to the axial direction. In other words, the motor shaft 41 and the output shaft 61 are arranged apart from each other in the radial direction of the motor shaft 41. Therefore, the electric actuator 10 can be downsized in the axial direction compared to the case where the motor shaft 41 and the output shaft 61 are arranged in the axial direction.

The lower end of the output shaft 61 is exposed downward through the opening 14e of the 2 nd housing member 14. The output shaft 61 is open on the lower side. The output shaft 61 has a spline groove on an inner peripheral surface. The output shaft 61 is disposed at a position overlapping the rotor body 42 in the radial direction of the motor shaft 41, for example. A shaft flange portion 61b is provided at a lower portion of the output shaft 61. The shaft flange portion 61b protrudes outward in the output radial direction. The shaft flange portion 61b is annular and centered on the output axis J3. The shaft flange portion 61b is supported from below by the 2 nd housing member 14.

The driven shaft DS is inserted from below into the output shaft 61 and coupled thereto. More specifically, the output shaft 61 and the driven shaft DS are coupled by fitting a spline portion provided on the outer peripheral surface of the driven shaft DS into a spline groove provided on the inner peripheral surface of the output shaft 61. The driving force of the electric actuator 10 is transmitted to the driven shaft DS via the output shaft 61. Thereby, the electric actuator 10 rotates the driven shaft DS about the output axis J3.

The drive gear 62 is fixed to the output shaft 61. The drive gear 62 extends from the output shaft 61 toward the output gear 53. The drive gear 62 meshes with the output gear 53. Although not shown, the drive gear 62 has a substantially fan-like shape when viewed in the axial direction, for example. The dimension of the drive gear 62 in the circumferential direction centered on the output axis J3 becomes larger toward the outer side in the output radial direction. The drive gear 62 has a gear portion at an outer end portion in the output radial direction. The gear portion of the drive gear 62 has a plurality of tooth portions arranged along a circumferential direction centered on the output axis J3. The gear portion of the drive gear 62 meshes with the gear portion of the output gear 53. Thereby, the drive gear 62 is connected to the transmission mechanism 50. The rotation of the motor 40 is transmitted to the drive gear 62 via the transmission mechanism 50.

The sensor magnet 63 is fixed to the output shaft 61. The sensor magnet 63 is fitted into a recess provided at the upper end of the output shaft 61, for example. For example, the sensor magnet 63 has a circular shape centered on the output axis J3 when viewed in the axial direction. The sensor magnet 63 is disposed below the rotation sensor 74 with a gap therebetween.

When the motor shaft 41 rotates about the motor axis J1, the eccentric shaft 41b revolves in the circumferential direction around the motor axis J1. The revolution of the eccentric shaft portion 41b is transmitted to the external gear 51 via the 1 st bearing 44a, and the external gear 51 oscillates while changing the position at which the inner circumferential surface of the hole 51b contacts the outer circumferential surface of the protruding portion 54. Thereby, the position at which the gear portion of the external gear 51 meshes with the gear portion of the internal gear 52 changes in the circumferential direction. Therefore, the rotational force of the motor shaft 41 is transmitted to the internal gear 52 via the external gear 51.

Here, in the present embodiment, the internal gear 52 is fixed to the housing 11 and therefore does not rotate. Therefore, the external gear 51 is rotated about the eccentric axis J2 by the reaction force of the rotational force transmitted to the internal gear 52. At this time, the external gear 51 rotates in a direction opposite to the direction in which the motor shaft 41 rotates. The rotation of the external gear 51 about the eccentric axis J2 is transmitted to the output gear 53 via the hole 51b and the protruding portion 54. Thereby, the output gear 53 rotates about the motor axis J1. The rotation of the motor shaft 41 is reduced and transmitted to the output gear 53.

When the output gear 53 rotates, the drive gear 62 meshed with the output gear 53 rotates about the output axis J3. Thereby, the output shaft 61 fixed to the drive gear 62 rotates about the output axis J3. Thus, the rotation of the rotor 40a is transmitted to the output shaft 61 via the transmission mechanism 50. With such a configuration of the transmission mechanism 50, the rotation of the output shaft 61 can be greatly reduced with respect to the rotation of the motor shaft 41. Therefore, the rotational torque of the output shaft 61 can be made relatively large. Therefore, the electric actuator 10 can be miniaturized and the output of the electric actuator 10 can be easily ensured. In the electric actuator 10, the output shaft 61 rotates bidirectionally in a range of less than 1 cycle, for example.

The substrate 70 has a plate shape with a plate surface facing in the axial direction. The plate surface of the substrate 70 is, for example, perpendicular to the axial direction. The substrate 70 is positioned above the motor 40 with the motor case 32 interposed therebetween. The substrate 70 is positioned on the upper side of the cover portion 32 a. The base plate 70 overlaps the motor shaft 41 and the output shaft 61 as viewed in the axial direction. Although not shown, a wiring pattern is provided on the plate surface of the substrate 70. An inverter circuit capable of adjusting power supplied to the motor 40 is provided on the substrate 70.

The rotation sensor 74 is fixed to the lower surface of the substrate 70. More specifically, the rotation sensor 74 is fixed to a portion of the lower surface of the substrate 70 that faces the sensor magnet 63 with a gap therebetween in the axial direction. The rotation sensor 74 is located above the sensor magnet 63 and the output shaft 61. The rotation sensor 74 is a magnetic sensor capable of detecting the magnetic field of the sensor magnet 63. The rotation sensor 74 is, for example, a magnetoresistive effect element. The rotation sensor 74 detects the magnetic field of the sensor magnet 63, thereby detecting the rotational position of the sensor magnet 63 and detecting the rotation of the output shaft 61. The rotation sensor 74 may be a hall element such as a hall IC.

The stator fixing member 80 is fixed inside the motor housing portion 32. The stator fixing member 80 has a fixing cylinder portion 81 and a partition portion 82. The fixed cylinder portion 81 has a cylindrical shape surrounding the motor axis J1. The fixed cylinder portion 81 has, for example, a cylindrical shape centered on the motor axis J1. The fixed cylinder 81 is open on the upper side. The fixed cylinder part 81 is fitted into the peripheral wall part 32 b. In the present embodiment, the fixed cylinder portion 81 is fixed inside the peripheral wall portion 32b by press fitting. Thus, in the present embodiment, the stator fixing member 80 is fixed inside the peripheral wall portion 32b by press fitting. The fixed cylinder portion 81 is press-fitted from below to an end portion below the peripheral wall portion 32b, for example. The upper end of the fixed cylinder 81 contacts the radially outer edge of the lower surface of the stator core 43 a.

The partition portion 82 protrudes radially inward from the inner peripheral surface of the fixed cylinder portion 81. In the present embodiment, the partition portion 82 protrudes radially inward from the inner circumferential surface of the lower end portion of the fixed cylinder portion 81. The partition 82 is annular surrounding the motor axis J1. The partition 82 has, for example, an annular shape centered on the motor axis J1. The partition 82 is, for example, plate-shaped with its plate surface facing in the axial direction. The plate surface of the partition 82 is, for example, perpendicular to the axial direction.

The partition 82 is located between the motor 40 and the transmission mechanism 50 in the axial direction. The partition portion 82 is disposed, for example, across the axial direction between the stator 43 and the output gear 53 and the axial direction between the stator 43 and the drive gear 62. The partition 82 covers, for example, a portion where the output gear 53 meshes with the drive gear 62 from above.

According to the present embodiment, the motor shaft 41 is a hollow shaft. The support shaft 90 is inserted into the motor shaft 41 and supports the motor shaft 41 rotatably about a motor axis J1. Therefore, it is not necessary to use a bearing such as a ball bearing to rotatably support the motor shaft 41. This eliminates the need to provide bearing-supported portions at both axial ends of the motor shaft 41, and thus the axial dimension of the motor shaft 41 can be reduced. Therefore, the electric actuator 10 can be downsized in the axial direction.

In the case where the motor shaft 41 is supported by a rolling bearing such as a ball bearing, it is necessary to perform an operation of press-fitting an inner ring of the rolling bearing to an outer peripheral surface of the motor shaft 41 and fixing the rolling bearing to the motor shaft 41. Therefore, there is a problem that the number of steps and time required for assembling the motor shaft 41 are increased. In contrast, according to the present embodiment, since it is not necessary to provide a bearing for rotatably supporting the motor shaft 41, the number of steps and time required for assembling the motor shaft 41 can be reduced.

In addition, according to the present embodiment, the housing 11 has: a 1 st housing member 12 that supports a portion of the support shaft 90 that protrudes upward from the motor shaft 41; and a 2 nd housing member 14 fixed to the 1 st housing member 12 and supporting a portion of the support shaft 90 that protrudes downward from the motor shaft 41. Therefore, by fixing the 1 st and 2 nd case members 12 and 14, both axial side portions of the support shaft 90 can be easily supported. Further, the support shaft 90 is supported by the housing parts, so that the 1 st housing part 12 and the 2 nd housing part 14 can be aligned in the radial direction. This makes it possible to easily and accurately dispose the 1 st housing part 12 and the 2 nd housing part 14.

In addition, according to the present embodiment, the 2 nd housing member 14 has the fixing hole portion 14d for fixing the support shaft 90. Therefore, when the 1 st housing member 12 and the 2 nd housing member 14 are fixed, the support shaft 90 can be prevented from falling off by fixing the support shaft 90 to the fixing hole portion 14d of the 2 nd housing member 14 in advance. This makes it possible to easily perform the fixing operation of the 1 st housing part 12 and the 2 nd housing part 14. In addition, according to the present embodiment, the 1 st housing part 12 has the fitting hole portion 32d into which the support shaft 90 is fitted with a gap therebetween. Therefore, when the 1 st and 2 nd housing members 12 and 14 are fixed, the support shaft 90 fixed to the 2 nd housing member 14 and the fitting hole portion 32d of the 1 st housing member 12 are fitted with a gap therebetween, whereby the support shaft 90 can be easily supported by the 1 st housing member 12. Accordingly, for example, the fixing operation of the 1 st housing part 12 and the 2 nd housing part 14 can be performed more easily than in the case where the support shaft 90 is supported by the 1 st housing part 12 by press-fitting or the like.

Further, according to the present embodiment, a gasket 91 is provided between the peripheral edge portion of the fitting hole portion 32d in the housing 11 and the axial direction of the motor shaft 41. Therefore, as compared with the case where the upper end of the motor shaft 41 directly contacts the peripheral edge of the fitting hole 32d, friction between the motor shaft 41 and the 1 st housing part 12 can be reduced, and the motor shaft 41 can be easily rotated smoothly. Further, the washer 91 is a wave washer, so that the motor shaft 41 can be pressed from above. Therefore, the motor shaft 41 can be suppressed from being displaced in the axial direction. Further, the motor shaft 41 is pressed from the upper side to the lower side by the washer 91, whereby the preload can be applied to the 1 st bearing 44a and the 2 nd bearing 44 b.

Further, according to the present embodiment, the transmission mechanism 50 includes: an external gear 51 coupled to the eccentric shaft portion 41b via a 1 st bearing 44 a; and an output gear 53 coupled to the motor shaft 41 via a 2 nd bearing 44 b. In this way, when a plurality of bearings are required to connect the transmission mechanism 50 to the motor shaft 41, the axial dimension of the motor shaft 41 is likely to increase in order to attach the bearings to the motor shaft 41. In contrast, according to the present embodiment, there is no need to provide a bearing for rotatably supporting the motor shaft 41, and the motor shaft 41 can be downsized in the axial direction. That is, the effect of being able to reduce the size of the motor shaft 41 in the axial direction is more effectively obtained in the electric actuator 10 having the transmission mechanism 50 coupled to the motor shaft 41 via a plurality of bearings.

The present invention is not limited to the above-described embodiments, and other configurations may be adopted within the scope of the technical idea of the present invention. The support shaft may have any shape as long as it extends in the axial direction of the motor axis, is inserted into the hollow motor shaft, and can support the motor shaft so as to be rotatable about the motor axis. The support shaft may be supported by the housing in any manner as long as both axial side portions thereof are supported by the housing. The support shaft may support both axial side portions by the same single member constituting at least a part of the housing. The support shaft may be supported by the housing via a separate member fixed to the housing.

The support shaft may be supported by the housing except for the axial end portion thereof. For example, in the above embodiment, a portion of the support shaft 90 protruding upward from the motor shaft 41 may be supported by the 1 st housing member 12, the portion being located below the upper end of the support shaft 90.

Both axial side portions of the support shaft may be fixed to the housing or may be not fixed to the housing. Both the 1 st and 2 nd housing parts may have fitting hole portions into which the support shafts are fitted with gaps therebetween to support the support shafts. Both the 1 st and 2 nd housing members may have fixing hole portions for fixing and supporting the support shaft by press-fitting or the like. In the above embodiment, the 1 st housing part 12 may have the fixing hole portion 14d, and the 2 nd housing part 14 may have the fitting hole portion 32 d. The fitting hole and the fixing hole may be through holes penetrating a part of the housing. The support shaft may be fixed to the fixing hole portion in any manner. The support shaft may be fixed to the fixing hole portion by an adhesive. The support shaft may be configured to be rotatable in a case where both axial side portions of the support shaft are not fixed to the housing.

In the above embodiment, the washer 91 is provided between the upper end of the motor shaft 41 and the peripheral edge of the fitting hole 32d, but the present invention is not limited thereto. A washer may be provided between the lower end portion of the motor shaft 41 and the peripheral edge portion of the fixing hole portion 14d serving as a hole for supporting the support shaft 90. In this case, the washer 91 may be provided between the upper end of the motor shaft 41 and the peripheral edge of the fitting hole 32d, or the washer 91 may not be provided. The type of the washer is not particularly limited, and the washer may be a slide washer. The washer may be provided at any position between both ends of the motor shaft in the axial direction and the housing in the axial direction.

The transmission mechanism is not particularly limited as long as it can transmit the rotation of the motor shaft. The transmission mechanism may be a speed increasing mechanism or a mechanism that does not change the speed of rotation of the motor shaft. When the transmission mechanism is a speed reduction mechanism, the structure of the speed reduction mechanism is not particularly limited. The plurality of protruding portions may be provided on the external gear, and the plurality of holes may be provided on the output gear. In this case, the protruding portion protrudes from the external gear toward the output gear and is inserted into the hole portion. In the case where the projection is provided to the output gear, the projection and the output gear may be part of the same one component. In the case where the protruding portion is provided to the external gear, the protruding portion and the external gear may be part of the same one component.

The use of the electric actuator to which the present invention is applied is not particularly limited. The electric actuator may be mounted on an actuator device of a shift-by-wire system that is driven in accordance with a shift operation by a driver. The electric actuator may be mounted on a device other than a vehicle. In addition, the respective configurations described above in the present specification can be appropriately combined within a range not inconsistent with each other.

Claims (5)

1. An electric actuator, characterized in that,

the electric actuator includes:

a motor having a motor shaft rotatable about a motor axis;

a transmission mechanism coupled to the motor shaft;

a housing that houses the motor and the transmission mechanism therein; and

a support shaft extending in an axial direction of the motor axis, portions of both sides of the support shaft in the axial direction being supported by the housing,

the motor shaft is a hollow shaft and,

the support shaft is inserted into the motor shaft and supports the motor shaft so that the motor shaft can rotate around the motor axis.

2. Electric actuator according to claim 1,

the housing has:

a 1 st housing member that supports a portion of the support shaft that protrudes to one side in an axial direction of the motor; and

and a 2 nd housing member fixed to the 1 st housing member and supporting a portion of the support shaft that protrudes further than the motor shaft toward the other side.

3. The electric actuator according to claim 2,

one of the 1 st and 2 nd case members has a fixing hole portion for fixing the support shaft,

the other of the 1 st and 2 nd housing parts has a fitting hole portion into which the support shaft is fitted with a gap therebetween.

4. The electric actuator according to claim 1,

the housing has a hole supporting the support shaft,

a gasket is provided between a peripheral edge portion of the hole in the housing and an axial direction of the motor shaft.

5. The electric actuator according to any one of claims 1 to 4,

the motor shaft has an eccentric shaft portion centered on an eccentric axis eccentric with respect to the motor axis,

the transmission mechanism includes:

an external gear coupled to the eccentric shaft portion via a 1 st bearing;

an internal gear that meshes with the external gear and surrounds a radially outer side of the external gear;

an output gear coupled to the motor shaft via a 2 nd bearing and disposed to be axially opposite to the external gear; and

a plurality of protruding portions that protrude from one of the output gear and the external gear toward the other and are arranged so as to surround the motor axis,

the other of the output gear and the external gear has a plurality of holes disposed so as to surround the motor axis,

the plurality of protruding portions are inserted into the plurality of holes, respectively, and support the external gear via inner side surfaces of the holes so as to be swingable around the motor axis.

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