Electric Actuator

Abstract

To provide an electric actuator in which a nut is axially miniaturized.SOLUTION: An electric actuator includes a screw shaft, a driving part, a nut, a plurality of balls, and a rotary stopper. The nut has a nut main body provided with an inner peripheral raceway surface and an S-groove surface formed by forging on an inner peripheral surface; and a cylindrical extension portion extending in a first direction from the nut main body and provided with a flange projecting to a radial outer side from an outer peripheral surface of the nut main body on an outer peripheral surface. The extension portion has: a first end face directing in the first direction; a circular arc-shaped recess recessed in a second direction from the first end face and extending in a rotating direction with respect to the screw shaft as a center; and a first stopper disposed on an extension line in the rotating direction with respect to the recess and composed of a remaining part of a thick portion of the extension portion. The driving part has a second end face opposed to the recess. The rotary stopper has the first stopper, and a second stopper disposed in a second direction of the second end face, rotates with the driving part, and capable of entering the recess.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Electric actuators are equipped with a ball screw device to convert rotary motion generated by a motor into linear motion. In some cases, the ball screw device transmits rotary motion to a screw shaft, causing a nut to move linearly. In this configuration, when the motor rotates, the nut advances from its initial position, and when the motor rotates in the reverse direction, the nut retreats.

[0003] However, when the nut retreats and returns to its initial position, the reverse rotation of the motor stops. Meanwhile, a moment of inertia acts on the transmission components that transmit power from the motor to the screw shaft. Therefore, the screw shaft may continue to rotate after the motor stops, causing the nut to retreat further from its initial position. To address this issue, the ball screw device of Patent Document 1 is equipped with a rotation stopper. The rotation stopper has a first stopper that protrudes from the end face of the nut and a second stopper that is fixed to the screw shaft so that it cannot rotate. When the nut returns to its initial position, the first stopper and the second stopper come into contact, restricting the rotation of the screw shaft. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-70281 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the rotation stopper of the above-mentioned patent document, the first stopper protrudes from the end face of the nut, which increases the size of the nut in the axial direction. Therefore, there is a demand for a smaller nut in the axial direction.

[0006] The present disclosure has been made in view of the above, and aims to provide an electric actuator in which the nut is made smaller in size in the axial direction. [Means for solving the problem]

[0007] To achieve the above object, an electric actuator according to one aspect of the present disclosure includes: a screw shaft having one end pointing in a first direction and the other end pointing in a second direction; a drive component coupled to one end of the screw shaft and transmitting rotational motion to the screw shaft; a nut inserted through the screw shaft and movable in an axial direction parallel to the screw shaft; a plurality of balls disposed between the screw shaft and the nut; and a rotation stopper that restricts rotation of the drive component when the nut moves in the first direction and returns to its initial position. The nut includes a nut body having an inner peripheral raceway surface and an S-groove surface formed by forging on its inner peripheral surface, and a cylindrical extension portion extending from the nut body in the first direction and provided with a flange that protrudes radially outward beyond the outer peripheral surface of the nut body. The extension portion has a first end face facing the first direction, an arc-shaped recess recessed from the first end face in the second direction and extending in a rotational direction around the screw shaft, and a first stopper that is a remaining solid portion of the extension portion and is arranged on an extension line of the rotational direction from the recess. The driving component has a second end face facing the second direction and facing the recess. The rotation stopper has the first stopper and a second stopper that is arranged in the second direction on the second end face, rotates together with the driving component, and can enter the recess.

[0008] When forming an S-groove surface on the inner peripheral surface of a nut by forging, if there is a flange on the outer peripheral side, it is difficult for the solid portion of the nut body to escape to the outer peripheral side, making it difficult to form the S-groove surface. For this reason, the nut of the present disclosure has an extension portion, and the flange is offset in the axial direction from the S-groove surface. Also, in the present disclosure, a recess is provided in the extension portion. This reduces the weight of the nut and improves the operability of the nut. Furthermore, a first stopper is disposed in the recess in the extension portion. Therefore, the nut is smaller in the axial direction than when the first stopper is provided on the first end face of the nut (extension portion). In addition, the nut and the first stopper are integrated. Therefore, there is no need to provide a separate first stopper, and the number of parts can be reduced.

[0009] In a preferred embodiment of the electric actuator, the first stopper is continuous with the nut on the radially outer side and in the second direction.

[0010] According to this configuration, the rigidity of the first stopper is improved, and therefore the electric actuator can be used for a long period of time.

[0011] In a preferred embodiment of the electric actuator, the electric actuator further comprises a rotation prevention member disposed on the outer periphery of the flange and extending in the axial direction. The outer periphery of the flange is provided with a concave surface into which the rotation prevention member fits.

[0012] According to the above configuration, the rotation of the nut is restricted. Furthermore, when the second stopper comes into contact with the first stopper, torque is input to the first stopper, and a torsional load acts between the first stopper and the concave surface. If the concave surface and the first stopper were arranged separately at one end and the other end of the axial direction of the nut, the nut body between them would twist, generating a load on the ball. On the other hand, the concave surface and the first stopper of the present disclosure are arranged at the end of the nut in the first direction. Therefore, the torsional load acts on the extension and flange, not on the nut body. This reduces the load on the ball.

[0013] In a preferred embodiment of the electric actuator, the first stopper and the concave surface are out of phase with each other in the circumferential direction.

[0014] According to this configuration, the load acting on the extension portion is dispersed in the circumferential direction, thereby improving the durability of the extension portion.

[0015] In a preferred embodiment of the electric actuator, the second stopper is continuous with the second end surface and is integral with the driving component.

[0016] According to the above configuration, there is no need to separately provide a second stopper, and the number of parts can be reduced.

[0017] In a preferred embodiment of the electric actuator, the driving component has a cylindrical tubular portion protruding in the second direction from the second end face. The inner peripheral surface of the tubular portion is circular. The screw shaft is fitted to the inner peripheral surface of the tubular portion and positioned coaxially with the driving component. The second stopper is disposed on the outer peripheral side of the tubular portion and is continuous with the outer peripheral side of the tubular portion.

[0018] According to the above configuration, the screw shaft is positioned coaxially with the driving component, thereby improving the operability of the ball screw device. Also, the rigidity of the second stopper is improved, allowing the electric actuator to be used for a long period of time.

[0019] In a preferred embodiment of the electric actuator, the second stopper has an annular fitting portion that fits onto the screw shaft and is prevented from rotating, and a protrusion that protrudes radially outward from the fitting portion.

[0020] According to the above configuration, the second stopper can be replaced, improving convenience.

[0021] In a preferred embodiment of the electric actuator, the driving component is a planetary gear mechanism having a sun gear, a ring gear, planetary gears, and a carrier.

[0022] According to the above configuration, the torque reduced by the planetary gear mechanism can be transmitted to the screw shaft.

[0023] A preferred embodiment of the electric actuator includes a housing, an outer ring fitted into the housing and having an inner circumferential groove surface on its inner circumferential surface, an outer circumferential groove surface provided on the outer circumferential surface of the carrier, and a plurality of bearing balls arranged between the inner circumferential groove surface and the outer circumferential groove surface.

[0024] According to the above configuration, there is no need to prepare a separate inner ring for the bearing device, and the number of parts can be reduced.

[0025] In a preferred embodiment of the electric actuator, the electric actuator includes a small diameter gear and a large diameter gear meshing with the small diameter gear, and the driving component is the large diameter gear.

[0026] According to the above configuration, torque reduced by the small diameter gear and the large diameter gear can be transmitted to the screw shaft.

[0027] The electric actuator includes a drive pulley, a driven pulley, and an endless belt that is stretched between the drive pulley and the driven pulley. The drive component may be the driven pulley. [Effects of the Invention]

[0028] According to the electric actuator of the present disclosure, the nut can be made smaller in size in the axial direction. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a cross-sectional view of the electric actuator of the first embodiment, taken along the axial direction, when the nut is in the initial position. [Figure 2] FIG. 2 is a perspective view of the carrier of the first embodiment as viewed from a second direction. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4]FIG. 4 is a perspective view of the nut of the first embodiment viewed from a first direction. [Figure 5] FIG. 5 is a perspective view of a part of the electric actuator of the second embodiment, viewed from a second direction. [Figure 6] FIG. 6 is a perspective view of a part of the electric actuator of the second embodiment, viewed from a first direction. [Figure 7] FIG. 7 is a perspective view of a part of the electric actuator of the third embodiment, viewed from a first direction. DETAILED DESCRIPTION OF THE INVENTION

[0030] The embodiments of the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited to the contents described below. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the components described below can be combined as appropriate.

[0031] (Embodiment 1) Fig. 1 is a cross-sectional view of the electric actuator of embodiment 1, cut in the axial direction, with the nut in the initial position. As shown in Fig. 1, the electric actuator 100 of embodiment 1 includes a motor (not shown) that generates rotational motion, a reduction gear 1 that reduces the speed of the rotational motion, a ball screw device 20 that converts the rotational motion into linear motion, a rotation stopper 50, and a housing 70.

[0032] In the following description, the direction parallel to the axis O of the screw shaft 21 of the ball screw device 20 will be referred to as the axial direction. Within the axial direction, the direction in which the reduction gear transmission 1 is disposed as viewed from the ball screw device 20 will be referred to as the first direction X1. Furthermore, the direction opposite to the first direction X1 will be referred to as the second direction X2.

[0033] The reduction gear 1 is a planetary gear mechanism and includes an input shaft 2, a sun gear 3, a ring gear 4, a plurality of planetary gears 5, a plurality of transmission shafts 6, and a carrier 7.

[0034] Rotational motion generated by the motor is input to the input shaft 2. The input shaft 2 extends in the axial direction. The input shaft 2 is also arranged coaxially with an axis O. The sun gear 3 passes through the input shaft 2 and is fixed to the input shaft 2 so as not to rotate. The ring gear 4 is an internal gear centered on the axis O. The outer peripheral surface of the ring gear 4 is fitted into the housing 70. As a result, the ring gear 4 is fixed to the housing 70 so as not to rotate.

[0035] The planetary gear 5 is disposed between the sun gear 3 and the ring gear 4 and is in mesh with the sun gear 3 and the ring gear 4. A transmission shaft 6 passes through the planetary gear 5. The planetary gear 5 is supported so as to be rotatable about the transmission shaft 6.

[0036] FIG. 2 is a perspective view of the carrier of embodiment 1 as viewed from a second direction. As shown in FIG. 2, the carrier 7 is an annular component centered on an axis O. An outer peripheral groove surface 8 is provided on the outer peripheral surface of the carrier 7. As shown in FIG. 1, an outer ring 72 is disposed on the outer peripheral side of the carrier 7. The outer peripheral surface of the outer ring 72 is fitted into the housing 70. An inner peripheral groove surface 73 is provided on the inner peripheral surface of the outer ring 72. A plurality of bearing balls 74 are disposed between the outer peripheral groove surface 8 and the inner peripheral groove surface 73 of the carrier 7. Thus, the carrier 7 is rotatably supported by the housing 70.

[0037] As shown in Fig. 2, a through hole 10 is provided in the center of the carrier 7. A female spline 11 is provided on the inner peripheral surface of the through hole 10. As shown in Fig. 1, a spline shaft 22 of a screw shaft 21 is inserted into the through hole 10. The female spline 11 is spline-fitted with the spline shaft 22. Therefore, the carrier 7 and the screw shaft 21 are connected so as not to rotate relative to each other.

[0038] As shown in Fig. 2, the carrier 7 has a fitting hole 12 at a position eccentric from the center toward the outside in the radial direction. As shown in Fig. 1, the transmission shaft 6 fits into the fitting hole 12. Therefore, the transmission shaft 6 and the carrier 7 are integrated.

[0039] According to the above configuration, when rotational motion is input to the input shaft 2, the sun gear 3 rotates about the axis O. Then, the planetary gear 5 rotates (revolves) about the axis O while rotating (spinning) about the transmission shaft 6. This causes the carrier 7 and the screw shaft 21 to rotate about the axis O. Furthermore, the rotational speed of the screw shaft 21 is reduced below the rotational speed of the input shaft 2. From the above, among the components of the reduction gear device 1, the carrier 7 is a driving component that transmits rotational motion to the screw shaft 21.

[0040] As shown in Fig. 2, the carrier 7 has a second end surface 14 facing the second direction X2. A cylindrical tubular portion 15 is provided on the second end surface 14 and protrudes in the second direction X2. The tubular portion 15 has a cylindrical shape centered on the axis O. Therefore, the inner circumferential surface 16 of the tubular portion 15 has a circular shape.

[0041] 3 is a cross-sectional view taken along the line III-III in FIG. 1. As shown in FIG. 3, the cylindrical portion 23 of the screw shaft 21 is inserted into the inside of the cylindrical portion 15. The outer peripheral surface 25 of the cylindrical portion 23 is circular, with the axis O as the center. The outer peripheral surface 25 of the cylindrical portion 23 is fitted into the inner peripheral surface 16 of the cylindrical portion 15. This positions the screw shaft 21 coaxially with the carrier 7. In other words, the axis O of the screw shaft 21 and the center of rotation of the carrier 7 coincide with each other. As a result, the screw shaft 21 rotates smoothly, improving the operability of the ball screw device 20.

[0042] As shown in FIG. 2, a second stopper 52 of the rotation stopper 50 is provided on the second end face 14. The second stopper 52 protrudes from the second end face 14 in the second direction X2. The second stopper 52 is made of the same metal material as the carrier 7 and is integrated with the carrier 7. The second stopper 52 is disposed radially outward from the cylindrical portion 15. The radially inner side of the second stopper 52 is continuous with the outer periphery of the cylindrical portion 15. This improves the rigidity of the second stopper 52.

[0043] As shown in FIG. 1, the ball screw device 20 includes a screw shaft 21, a nut 30, and balls 49. The screw shaft 21 is a solid part with one end pointing in a first direction X1 and the other end pointing in a second direction X2. The screw shaft 21 includes a spline shaft 22, a cylindrical portion 23, and a screw shaft body 24, arranged in this order from the first direction X1. The spline shaft 22, the cylindrical portion 23, and the screw shaft body 24 are each formed by processing a shaft-shaped metal material. Therefore, the spline shaft 22, the cylindrical portion 23, and the screw shaft body 24 are continuous and integrated in the axial direction. An outer circumferential raceway surface 26 is provided on the outer circumferential surface of the screw shaft body 24.

[0044] The nut 30 has a cylindrical shape centered on the axis O. The nut 30 includes a nut body 31 and an extension portion 40, which are arranged in this order from the second direction X2. The nut body 31 and the extension portion 40 are each formed by processing a cylindrical metal material. Therefore, the nut body 31 and the extension portion 40 are continuous and integrated in the axial direction. An inner circumferential surface of the nut body 31 is provided with an inner circumferential raceway surface 32 and an S-groove surface 33. A plurality of balls are arranged between the inner circumferential raceway surface 32 and the outer circumferential raceway surface 26 of the screw shaft 21.

[0045] The S-shaped groove surface 33 is a circulation portion that returns the ball 49 that has moved one lead by one lead. The nut body 31 is provided with a plurality of S-shaped groove surfaces 33 (only one is shown in FIG. 1). The S-shaped groove surface 33 is formed by forging. That is, the S-shaped groove surface 33 is formed by applying pressure to the inner peripheral surface of the nut body 31 and plastically deforming the solid portion of the nut body 31 toward the outer periphery. Therefore, if there is a flange on the outer peripheral surface 34 of the nut body 31, it will be difficult for the solid portion of the nut body 31 to plastically deform radially outward, making forming difficult. For this reason, no flange 41 is provided on the outer peripheral surface 34 of the nut body 31.

[0046] The extension portion 40 is a portion for providing a flange 41 at a position axially spaced from the S-groove surface 33 of the nut body 31. The extension portion 40 extends in the first direction X1 from the nut body 31 and has a cylindrical shape. The extension portion 40 is provided on its outer periphery with the flange 41 protruding radially outward beyond the outer periphery 34 of the nut body 31.

[0047] Fig. 4 is a perspective view of the nut of the first embodiment, viewed from a first direction. As shown in Fig. 4, three concave surfaces 42 that are recessed radially inward and open in the axial direction are provided on the outer periphery of the flange 41. The concave surfaces 42 are arc-shaped when viewed from the axial direction. Note that, although the concave surfaces 42 in the embodiment are arc-shaped corresponding to the outer periphery of the anti-rotation component 76, the present disclosure is not limited to the arc-shaped concave surfaces 42. The concave surfaces 42 are only required to be able to hook onto the anti-rotation component 76 in the circumferential direction, and may be, for example, rectangular when viewed from the axial direction, and are not particularly limited.

[0048] As shown in FIG. 3, a rotation prevention component 76 is disposed on the outer periphery of the flange 41. The rotation prevention component 76 is a cylindrical component extending in the axial direction. A portion of the rotation prevention component 76 is fitted into a groove 77 in the housing 70. Therefore, the rotation prevention component 76 is disposed in a state where it protrudes inward from an inner periphery surface 78 of the housing 70. Furthermore, the portion of the rotation prevention component 76 that protrudes inward from the inner periphery surface 78 is fitted into the concave surface 42 of the flange 41. Therefore, when torque is applied to the nut 30, the concave surface 42 catches on the rotation prevention component 76. As a result, rotation of the nut 30 is restricted.

[0049] As shown in FIG. 4, the extension portion 40 has a first end face 43 facing the first direction X1. The first end face 43 faces the second end face 14 (see FIG. 2) of the carrier 7. The first end face 43 is provided with a recess 44 recessed in the second direction X2. When viewed from the axial direction, this recess 44 has an arc shape centered on the axis O. Therefore, the recess 44 extends in the rotational direction around the screw shaft 21. The inner peripheral side of the recess 44 is open toward the screw shaft 21. As described above, the recess 44 reduces the thickness of the nut 30, thereby reducing the weight of the nut 30.

[0050] A first stopper 51 of the rotation stopper 50 is provided on the extending portion 40. An arc-shaped recess 44 is formed in the extending portion 40 by cutting or the like, but this first stopper 51 is a portion that was not cut, i.e., a remaining solid portion of the extending portion 40. Therefore, the first stopper 51 is disposed on an extension line of the recess 44 in the rotation direction. Furthermore, the first stopper 51 is positioned further in the second direction X2 than the first end face 43. According to the nut 30 of the first embodiment, the nut 30 is smaller in the axial direction than when the first stopper 51 is provided on the first end face 43.

[0051] The concave surface 42 is not disposed on the radially outer side of the first stopper 51. In other words, the first stopper 51 and the concave surface 42 are out of phase with each other. Therefore, the load acting from the first stopper 51 to the extension portion 40 and the load acting from the concave surface 42 to the extension portion 40 are dispersed in the circumferential direction. In addition, the first stopper 51 is continuous with the nut in the axial direction and on the radially outer side, and has high rigidity.

[0052] 3, the rotation stopper 50 has a first stopper 51 provided on the extension portion 40 of the nut 30 and a second stopper 52 provided on the second end face 14 of the carrier 7. Hereinafter, regarding the rotation direction, the counterclockwise direction (left-handed) when viewed from the second direction X2 will be referred to as a first rotation direction A1. Furthermore, the direction opposite to the second rotation direction A2 will be referred to as a second rotation direction A2.

[0053] The first stopper 51 has a first contact surface 53 facing the second rotational direction A2. The second stopper 52 has a second contact surface 54 facing the first rotational direction A1. When the nut 30 is in the initial position, the first stopper 51 and the second stopper 52 are adjacent to each other in the circumferential direction. Furthermore, the first contact surface 53 of the first stopper 51 and the second contact surface 54 of the second stopper 52 are in contact with each other.

[0054] Next, a description will be given of the operation of the electric actuator 100 of embodiment 1. In embodiment 1, when the carrier 7 rotates in the second rotation direction A2, the nut 30 moves in the second direction X2. Also, when the carrier 7 rotates in the first rotation direction A1, the nut 30 moves in the first direction X1.

[0055] When the nut 30 moves in the first direction X1 and returns to its initial position, the second stopper 52 enters the recess 44 of the nut 30 while rotating in the first rotational direction A1. Then, when the nut 30 returns to its initial position, the second contact surface 54 of the second stopper 52 comes into contact with the first contact surface 53 of the first stopper 51. This restricts the carrier 7 from further rotating in the first rotational direction A1 due to the moment of inertia. Therefore, the nut 30 stops at its initial position.

[0056] Furthermore, a torque T1 (see FIG. 3) in the first rotation direction A1 is input to the first stopper 51. Meanwhile, a torque T2 (see FIG. 3) in the second rotation direction A2 acts on the outer periphery of the flange 41 as a reaction force from the anti-rotation component 76 caught on the concave surface 42. Therefore, a torsional load acts on the extension portion 40 and the flange 41 located between the first stopper 51 and the concave surface 42.

[0057] On the other hand, the nut body 31 of this embodiment is not disposed between the first stopper 51 and the concave surface 42. Therefore, the torsional load acting on the nut body 31 is extremely small. As a result, the load acting on the balls 49 is reduced.

[0058] As described above, the electric actuator 100 of the first embodiment includes the screw shaft 21 having one end pointing in the first direction X1 and the other end pointing in the second direction X2, a drive component (carrier 7) connected to one end of the screw shaft 21 and transmitting rotational motion to the screw shaft 21, a nut 30 inserted through the screw shaft 21 and movable in an axial direction parallel to the screw shaft 21, a plurality of balls 49 disposed between the screw shaft 21 and the nut 30, and a rotation stopper 50 that restricts rotation of the drive component when the nut 30 moves in the first direction X1 and returns to its initial position. The nut 30 includes a nut body 31 having an inner peripheral raceway surface 32 and an S-groove surface 33 formed by forging on its inner peripheral surface, and a cylindrical extension 40 extending from the nut body 31 in the first direction X1 and having a flange 41 on its outer peripheral surface that protrudes radially outward beyond the outer peripheral surface 34 of the nut body 31. The extension portion 40 has a first end face 43 facing the first direction X1, an arc-shaped recess 44 recessed from the first end face 43 in the second direction X2 and extending in the rotational direction around the screw shaft 21, and a first stopper 51 that is located on an extension of the recess 44 in the rotational direction and is a remaining solid portion of the extension portion 40. The driving component (carrier 7) has a second end face 14 that faces the second direction X2 and faces the recess 44. The rotation stopper 50 has the first stopper 51 and a second stopper 52 that is located on the second end face 14 in the second direction X2, rotates together with the driving component, and can enter the recess 44.

[0059] The nut 30 is made smaller in size in the axial direction. Furthermore, the nut 30 and the first stopper 51 are integrated together. This eliminates the need to provide a separate first stopper 51, reducing the number of parts.

[0060] Furthermore, the radially outer side and the second direction X2 of the first stopper 51 of the first embodiment are continuous with the nut 30.

[0061] The first stopper 51 has high rigidity, so the electric actuator 100 can be used for a long period of time.

[0062] In addition, in the first embodiment, there is provided a rotation prevention member 76 that is disposed on the outer periphery of the flange 41 and extends in the axial direction. The outer periphery of the flange 41 is provided with a concave surface 42 into which the rotation prevention member 76 fits.

[0063] This restricts the rotation of the nut 30. Furthermore, the torsional load acting between the first stopper 51 and the concave surface 42 is less likely to act on the nut body 31. This reduces the load on the balls 49.

[0064] In the first embodiment, the first stopper 51 and the recessed surface 42 are out of phase with each other in the circumferential direction.

[0065] This allows the load acting on the extension portion 40 to be dispersed in the circumferential direction, improving the durability of the extension portion 40.

[0066] Moreover, the second stopper 52 of the first embodiment is continuous with the second end face 14 and is integral with the driving part (carrier 7).

[0067] There is no need to prepare a separate second stopper 52, which reduces the number of parts.

[0068] The driving component (carrier 7) of the first embodiment has a cylindrical tubular portion 15 that protrudes in the second direction X2 from the second end face 14. The inner peripheral surface 16 of the tubular portion 15 is circular. The screw shaft 21 is fitted into the inner peripheral surface 16 of the tubular portion 15 and is positioned coaxially with the driving component. The second stopper 52 is disposed on the outer peripheral side of the tubular portion 15 and is continuous with the outer peripheral side of the tubular portion 15.

[0069] The cylindrical portion 15 allows the screw shaft 21 to be coaxially positioned, improving the operability of the ball screw device. Also, the rigidity of the second stopper 52 can be increased, allowing the electric actuator 100 to be used for a long period of time.

[0070] Moreover, in the first embodiment, a planetary gear mechanism is provided which includes a sun gear 3, a ring gear 4, a planetary gear 5, and a carrier 7. The carrier 7 is a driving component.

[0071] With the above configuration, the torque reduced by the planetary gear mechanism can be transmitted to the screw shaft 21.

[0072] In addition, in embodiment 1, the bearing includes a housing 70, an outer ring 72 fitted into the housing 70 and having an inner circumferential groove surface 73 on its inner circumferential surface, an outer circumferential groove surface 8 provided on the outer circumferential surface of the carrier 7, and a plurality of bearing balls 74 arranged between the inner circumferential groove surface 73 and the outer circumferential groove surface 8.

[0073] There is no need to prepare a separate inner ring for the bearing device, which reduces the number of parts.

[0074] The electric actuator of the first embodiment has been described above, but the electric actuator of the present disclosure is not limited to the example shown in the first embodiment. The first stopper 51 of the first embodiment is continuous with the nut 30 on the radially outer side and in the second direction X2, but in the present disclosure, the first stopper 51 may be continuous with the nut 30 on the radially outer side or in the second direction X2. Furthermore, the nut 30 has an inner circumferential side of the recess 44 that is open toward the screw shaft 21, but may have a wall portion that surrounds the inner circumferential side of the recess 44.

[0075] Furthermore, although the flange 41 is used to prevent rotation of the nut 30, in the present disclosure, it may also be used, for example, to press a piston fitted onto the outside of the nut body 31. In other words, there is no particular limitation on how the flange 41 is used. In addition, in the present disclosure, the first stopper 51 and the concave surface 42 may be in the same phase.

[0076] Furthermore, although an outer peripheral groove surface 8 is provided on the outer periphery of the carrier 7, eliminating the need for an inner ring, in the present disclosure, the carrier 7 may be supported by a bearing device having an inner ring separate from the carrier 7. The second stopper 52 in the first embodiment is continuous with the cylindrical portion 15, but the second stopper 52 in the present disclosure does not have to be continuous with the cylindrical portion 15. Furthermore, the second stopper 52 is continuous with and integral with the carrier 7 (driving component), but may be separate from the carrier 7 (driving component). Furthermore, the driving component in the present disclosure is not limited to the carrier 7. Below, in the second embodiment, an example in which the second stopper 52 and the carrier 7 (driving component) are separate will be described. In the third embodiment, an example in which a driving component other than the carrier 7 is used will be described.

[0077] (Embodiment 2) Fig. 5 is a perspective view of a portion of the electric actuator of embodiment 2, viewed from a second direction. Fig. 6 is a perspective view of a portion of the electric actuator of embodiment 2, viewed from a first direction. As shown in Figs. 5 and 6, the electric actuator 100A of embodiment 2 differs from the electric actuator 100 of embodiment 1 in that the second stopper 52A is separate (a separate component) from the carrier 7 (a driving component). The following description focuses on these differences.

[0078] The second stopper 52A is disposed in the second direction X2 with respect to the second end face 14 of the carrier 7. The second stopper 52A has an annular fitting portion 55 that fits onto the screw shaft 21 and a protruding portion 56 that protrudes radially outward from the fitting portion 55. Note that the screw shaft 21 of the second embodiment does not have a cylindrical portion 23. Therefore, the screw shaft 21 includes a spline shaft 22 and a screw shaft main body 24. A female spline (not shown) is provided on the inner peripheral surface of the fitting portion 55. The female spline is spline-fitted onto the spline shaft 22. Therefore, the second stopper 52A is prevented from rotating on the screw shaft 21.

[0079] Furthermore, the protrusion 56 extends into the recess 44 and abuts against the first stopper 51 when the nut 30 is in its initial position. In this second embodiment, when the nut 30 returns to its initial position, it comes into contact with the first stopper 51, restricting the rotation of the second stopper 52A in the first rotational direction A1. Furthermore, the rotation of the carrier 7 in the first rotational direction A1 is also restricted via the spline shaft 22 of the screw shaft 21. Therefore, the nut 30 does not move further in the first direction X1 from its initial position. Furthermore, in the electric actuator 100A of the second embodiment, the nut 30 can be made smaller in the axial direction. Furthermore, the second stopper 52A is a separate component from the driving component (carrier 7). Therefore, the second stopper 52A can be replaced, improving convenience.

[0080] (Embodiment 3) FIG. 7 is a perspective view of a portion of the electric actuator of the third embodiment, viewed from a first direction. As shown in FIG. 7, the electric actuator 100B of the third embodiment differs from the electric actuator 100 of the first embodiment in that, instead of the reduction gear 1, which is a planetary gear mechanism, a reduction gear 1B including a small-diameter gear (not shown) and a large-diameter gear 7B is provided. In this reduction gear 1B, the large-diameter gear 7B is spline-fitted to the spline shaft 22 of the screw shaft 21. Therefore, the large-diameter gear 7B serves as a driving component that transmits rotational motion to the screw shaft. In addition, a second stopper (not shown) is integrally provided on the end face of the large-diameter gear 7B facing the second direction X2. As described above, even with the electric actuator 100B of the third embodiment, the nut 30 can be made smaller in the axial direction. Note that, in the present disclosure, a second stopper separate from the large-diameter gear 7B (separate component) may be used, as shown in the second embodiment.

[0081] Although the third embodiment has been described above, the present disclosure does not necessarily have to include the reduction gears 1 and 1B. Instead, a power transmission device such as a pulley may be included. Although not specifically illustrated, the pulley includes a drive pulley, a driven pulley, and an endless belt wound around the drive pulley and the driven pulley. When such a pulley is included, the driven pulley corresponds to the driving component. Therefore, the driven pulley is connected to the screw shaft so as not to rotate relative to it. A second stopper may be provided on the end face of the driven pulley facing the second direction. Alternatively, as shown in the second embodiment, a second stopper separate from the driven pulley (separate component) may be used. Furthermore, the output shaft of the motor itself may be the driving component. In other words, the present disclosure may be configured so that the output shaft of the motor is connected to the screw shaft.

[0082] The present disclosure may also be implemented as a combination of the following configurations. (1) a screw shaft having one end pointing in a first direction and the other end pointing in a second direction; a drive part coupled to one end of the screw shaft and transmitting rotational motion to the screw shaft; a nut inserted through the screw shaft and movable in an axial direction parallel to the screw shaft; a plurality of balls disposed between the screw shaft and the nut; and a rotation stopper that restricts rotation of the drive part when the nut moves in the first direction and returns to an initial position, the nut comprising a nut body having an inner peripheral raceway surface and an S-groove surface formed by forging on its inner peripheral surface; and a cylindrical extension portion provided with a flange protruding toward the screw shaft, wherein the extension portion has a first end face facing the first direction, an arc-shaped recess recessed from the first end face in the second direction and extending in a rotational direction around the screw shaft, and a first stopper that is a remainder of a solid portion of the extension portion and is arranged on an extension line of the rotational direction with respect to the recess, wherein the driving component has a second end face facing the second direction and facing the recess, and the rotation stopper has the first stopper and a second stopper that is arranged in the second direction of the second end face, rotates together with the driving component, and is capable of entering the recess. (2) The electric actuator according to (1), wherein the first stopper is continuous with the nut on the radially outer side and in the second direction. (3) An electric actuator as described in (1) or (2), which is provided with a rotation prevention component arranged on the outer periphery of the flange and extending in the axial direction, and the outer periphery of the flange is provided with a concave surface into which the rotation prevention component fits. (4) The electric actuator according to (3), wherein the first stopper and the concave surface are in different phases in the circumferential direction. (5) The electric actuator according to any one of (1) to (4), wherein the second stopper is continuous with the second end surface and is integral with the driving component. (6) The driving component has a cylindrical tubular portion protruding from the second end face in the second direction, the inner peripheral surface of the tubular portion is circular, the screw shaft is fitted into the inner peripheral surface of the tubular portion and positioned coaxially with the driving component, and the second stopper is arranged on the outer peripheral side of the tubular portion and is continuous with the outer peripheral side of the tubular portion. (5) An electric actuator as described in the above. (7) The electric actuator described in any one of (1) to (4), wherein the second stopper has an annular fitting portion that fits onto the screw shaft and is prevented from rotating, and a protrusion that protrudes radially outward from the fitting portion. (8) The electric actuator according to any one of (1) to (7), comprising a planetary gear mechanism having a sun gear, a ring gear, planetary gears, and a carrier, wherein the driving component is the carrier. (9) An electric actuator as described in (8) comprising a housing, an outer ring fitted into the housing and having an inner circumferential groove surface on its inner circumferential surface, an outer circumferential groove surface provided on the outer circumferential surface of the carrier, and a plurality of bearing balls arranged between the inner circumferential groove surface and the outer circumferential groove surface. (10) The electric actuator according to any one of (1) to (7), comprising a small diameter gear and a large diameter gear meshing with the small diameter gear, wherein the driving component is the large diameter gear. (11) An electric actuator according to any one of (1) to (7), comprising a drive pulley, a driven pulley, and an endless belt stretched between the drive pulley and the driven pulley, wherein the drive component is the driven pulley. [Explanation of symbols]

[0083] 1 Reducer 2 input shafts 3 Sun gear 4 ring gear 5 Planetary Gear 6 Transmission shaft 7 Carrier (drive part) 7B Large diameter gear (drive part) 8 Peripheral groove surface 11 female spline 14 Second end face 15 Cylinder part 20 Ball screw device 21 Screw shaft 22 Spline shaft 23 Cylindrical part 24 Screw shaft body 30 nuts 31 Nut body 32 Inner raceway surface 33 S-shaped groove surface 40 Extension 41 flange 42 Concave 43 First end surface 44 depression 49 balls 50 rotation stopper 51 First stopper 52, 52A Second stopper 53 1st contact surface 54 Second contact surface 55 Fitting part 56 Protrusion 70 Housing 72 outer ring 76 Anti-rotation parts 100, 100A, 100B electric actuator

Claims

1. a screw shaft having one end pointing in a first direction and the other end pointing in a second direction; A drive part that is connected to one end of the screw shaft and transmits rotational motion to the screw shaft; A nut that is inserted through the screw shaft and is movable in an axial direction parallel to the screw shaft; a plurality of balls disposed between the screw shaft and the nut; a rotation stopper that restricts rotation of the driving component when the nut moves in the first direction and returns to its initial position; Equipped with The nut is a nut body having an inner raceway surface and an S-groove surface formed by forging on its inner circumferential surface; A cylindrical extension portion extending from the nut body in the first direction and having a flange on its outer periphery that protrudes radially outward beyond the outer periphery of the nut body; and The extension portion is a first end surface facing the first direction; an arc-shaped recess recessed from the first end surface in the second direction and extending in a rotational direction around the screw shaft; a first stopper that is disposed on an extension line of the recess in the rotational direction and is a remaining portion of the extended portion; and the driving component has a second end surface facing the second direction and facing the recess; The rotation stopper is The first stopper; a second stopper disposed in the second direction of the second end surface, rotating together with the driving component and capable of entering the recess; and The second stopper is continuous with the second end surface and is integral with the driving component. Electric actuator.

2. the driving component has a cylindrical portion that protrudes in the second direction from the second end surface, The inner circumferential surface of the cylindrical portion is circular, The screw shaft is fitted to the inner peripheral surface of the cylindrical portion and positioned coaxially with the driving component, The second stopper is disposed on the outer circumferential side of the cylindrical portion and is continuous with the outer circumferential side of the cylindrical portion. The electric actuator according to claim 1 .

3. A small diameter gear, a large diameter gear that meshes with the small diameter gear; Equipped with The driving part is the large diameter gear. The electric actuator according to claim 1 .

4. A drive pulley; A driven pulley; an endless belt stretched between the drive pulley and the driven pulley; Equipped with The driving component is the driven pulley. The electric actuator according to claim 1 .

5. a screw shaft having one end pointing in a first direction and the other end pointing in a second direction; A drive part that is connected to one end of the screw shaft and transmits rotational motion to the screw shaft; A nut that is inserted through the screw shaft and is movable in an axial direction parallel to the screw shaft; a plurality of balls disposed between the screw shaft and the nut; a rotation stopper that restricts rotation of the driving component when the nut moves in the first direction and returns to its initial position; Equipped with The nut is a nut body having an inner raceway surface and an S-groove surface formed by forging on its inner circumferential surface; A cylindrical extension portion extending from the nut body in the first direction and having a flange on its outer periphery that protrudes radially outward beyond the outer periphery of the nut body; and The extension portion is a first end surface facing the first direction; an arc-shaped recess recessed from the first end surface in the second direction and extending in a rotational direction around the screw shaft; a first stopper that is disposed on an extension line of the recess in the rotational direction and is a remaining portion of the extended portion; and the driving component has a second end surface facing the second direction and facing the recess; The rotation stopper is The first stopper; a second stopper disposed in the second direction of the second end surface, rotating together with the driving component and capable of entering the recess; and a planetary gear mechanism having a sun gear, a ring gear, a planetary gear, and a carrier; the driving component is the carrier; Housing and an outer ring fitted into the housing and having an inner peripheral groove surface on its inner peripheral surface; an outer circumferential groove surface provided on the outer circumferential surface of the carrier; a plurality of bearing balls disposed between the inner peripheral groove surface and the outer peripheral groove surface; Equipped with Electric actuator.

6. The second stopper is an annular fitting portion that is fitted onto the screw shaft and is prevented from rotating; a protruding portion protruding radially outward from the fitting portion; 6. The electric actuator according to claim 5, further comprising:

7. The first stopper is continuous with the nut in the radially outer side and in the second direction. The electric actuator according to any one of claims 1 to 6.

8. a rotation prevention member disposed on an outer circumferential side of the flange and extending in the axial direction; The flange has a recessed surface on the outer periphery into which the anti-rotation component fits. The electric actuator according to any one of claims 1 to 6.

9. The first stopper and the concave surface are out of phase with each other in the circumferential direction. The electric actuator according to claim 8.

Images