JP2017137962A - Electric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric actuator with a position keeping function, capable of keeping a position of a linear motion member at an output side without enlarging the entire shape and increasing the number of components.SOLUTION: In an electric actuator 1 in which torque from an electric motor 4 is transmitted to a ball screw 6 supported by housings 2, 3, and which includes a detent mechanism 13 for restricting rotation around a shaft to the housing 2, 3, of a screw shaft 7 as a linear motion member axially moved by the torque from the electric motor 4, of the screw shaft 7 and a nut 8 configuring the ball screw 6, the restriction in rotation around the shaft to the housings 2, 3 of the screw shaft 7 by the detent mechanism 13, is released by adding torque Tlim as external force around the shaft of a prescribed value or more to the screw shaft 7.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electric actuator provided with a ball screw. More specifically, the present invention relates to an electric actuator provided with a ball screw having an overload input preventing function.

  Conventionally, in general industrial electric motors, automobile transmissions, parking brakes, and the like, an electric actuator provided with a ball screw is used to convert a rotary motion of an output shaft of an electric motor into a linear motion and output it. The electric actuator transmits the rotational movement of the electric motor to a nut or a screw shaft that is a rotating member of the ball screw. The ball screw converts the rotational motion of the rotating member into an axially linear motion by the action of the screw groove and transmits it to the screw shaft or nut that is the linear motion member. In such an electric actuator, when the rotating member of the ball screw is rotated by the rotating motion from the electric motor, the conversion efficiency from the rotating motion to the rectilinear motion is lowered when the linear moving member rotates together with the rotating member. Therefore, an electric actuator in which a ball screw is provided with a detent mechanism is known. For example, as described in Patent Document 1.

  In the electric actuator described in Patent Document 1, a detent mechanism is configured by engaging a pin provided on a linear motion member of a ball screw and a groove formed in a sleeve fixed to the housing of the electric actuator. Yes. The anti-rotation mechanism allows the linear motion of the linear motion member to move in the axial direction by the groove formed in the axial direction of the sleeve, while the rotational motion of the linear motion member generated by the rotation of the rotary member between the groove and the pin. Regulate by engagement. However, in the electric actuator described in Patent Document 1, when an axial external force is applied to the linear motion member, the linear motion of the linear motion member is converted into the rotational motion of the rotary member by a highly efficient ball screw. The external force converted into the rotational motion is transmitted to the electric motor through the rotating member. In the electric actuator, when the electric motor does not output rotational torque or when an external force larger than the rotational torque of the electric motor is transmitted to the electric motor, the electric motor is rotated by the external force. When the linear motion member reaches the end of the movable range, the linear motion is restricted in the axial direction. The rotating member is rotated by the inertia of the electric motor even if the linear motion member stops. In other words, the rotational force around the axis of the linear motion member is transmitted from the rotational member in a state where the rotational motion and the linear motion are restricted. As a result, the ball screw of the electric actuator generates excessive surface pressure on the thread groove of the rotating member that is the rolling surface of the ball that is the rolling element and the thread groove of the linear motion member. There was a possibility of damage.

JP 2014-80994 A

  The present invention has been made in view of the above situation, and an electric actuator capable of preventing damage to a thread groove as a rolling surface and a ball as a rolling element even when a rotational force as an excessive external force is applied. The purpose is to provide.

  That is, the rotational force from the electric motor is transmitted to the ball screw supported by the housing, and the linear movement member that is moved in the axial direction by the rotational force from the electric motor among the screw shaft and nut constituting the ball screw. In the electric actuator having a rotation preventing mechanism for restricting rotation about the shaft relative to the housing, the linear motion member that is moved in the axial direction by the rotational force from the electric motor among the screw shaft and the nut constituting the ball screw. An anti-rotation mechanism that restricts rotation about the axis relative to the housing, and an external force around the axis that is greater than or equal to a predetermined value is applied to the linear motion member to prevent rotation of the linear motion member about the axis relative to the housing by the anti-rotation mechanism; Regulations will be lifted.

  The electric actuator includes a sleeve that is fixed to the housing and into which the linear motion member is inserted, and the anti-rotation mechanism includes a groove provided along an axial direction on an inner peripheral surface of the sleeve, and the linear motion member A projecting portion provided on the outer peripheral surface of the shaft and configured to move to the outer peripheral surface side by a load equal to or greater than a predetermined value. The shaft of the linearly moving member with respect to the sleeve is engaged by the engagement of the groove and the projecting portion. Rotational rotation is restricted, and when the rotational force of a predetermined value or more is applied to the linear motion member, the protrusion is moved to the outer peripheral surface side of the linear motion member by the groove, and the relationship between the groove and the protrusion is The match is released.

  The electric actuator includes a sleeve that is fixed to the housing and into which the linear motion member is inserted, and the anti-rotation mechanism includes a groove that is provided along an axial direction on an outer peripheral surface of the linear motion member; A projecting portion provided on the inner peripheral surface and configured to move toward the inner peripheral surface side by a load greater than or equal to a predetermined value, and the engagement of the groove with the projecting portion causes the linearly moving member to move against the sleeve. Rotation around the axis is restricted, and when the rotational force of a predetermined value or more is applied to the linear motion member, the protrusion is moved to the outer peripheral surface side of the linear motion member by the groove, and the groove and the protrusion The engagement is released.

  The electric actuator includes a sleeve that is fixed to the housing and into which the linear motion member is inserted, and the anti-rotation mechanism includes a groove provided along an axial direction on an inner peripheral surface of the sleeve, and the linear motion member And a projecting portion configured to move in the circumferential direction by a load greater than or equal to a predetermined value. The shaft of the linearly moving member with respect to the sleeve is formed by engagement of the groove and the projecting portion. The rotation of the linear motion member is restricted, and when the rotational force of a predetermined value or more is applied to the linear motion member, the protrusion is moved in the circumferential direction by the groove, and the rotational motion of the linear motion member around the shaft is restricted. It is to be canceled.

  The electric actuator includes a sleeve that is fixed to the housing and into which the linear motion member is inserted, and the anti-rotation mechanism includes a groove that is provided along an axial direction on an outer peripheral surface of the linear motion member; A shaft provided on the inner peripheral surface and configured to move in the circumferential direction by a load of a predetermined value or more, and the shaft of the linearly moving member with respect to the sleeve by the engagement between the groove and the protrusion. The rotation of the linear motion member is restricted, and when the rotational force of a predetermined value or more is applied to the linear motion member, the protrusion is moved in the circumferential direction by the groove, and the rotational motion of the linear motion member around the shaft is restricted. It is to be canceled.

  In the electric actuator, the protrusion is composed of a ball member supported by an elastic body.

  In the electric actuator, the projecting portion includes an annular member having a convex portion and a sliding member that supports the annular member.

  In the electric actuator, a plurality of the detent mechanisms are provided.

  As effects of the present invention, the following effects can be obtained.

  That is, in the electric actuator, when an external force about an axis greater than or equal to a predetermined value is applied to the linear motion member, the linear motion member is rotated about the axis together with the rotation member. Thereby, even if an excessive external force is applied, it is possible to prevent damage to the thread groove that is the rolling surface and the ball that is the rolling element.

  In the electric actuator, when an external force about a predetermined value or more is applied to the linear motion member, the linear motion member rotates about the axis until the projection is engaged with the groove again after the engagement between the groove and the projection is released. It is rotated. Thereby, even if an excessive external force is applied, it is possible to prevent damage to the thread groove that is the rolling surface and the ball that is the rolling element.

  In the electric actuator, the linear motion member is rotated about the axis only while an external force about the axis greater than a predetermined value is applied to the linear motion member. Thereby, even if an excessive external force is applied, it is possible to prevent damage to the thread groove that is the rolling surface and the ball that is the rolling element. Thereby, even if an excessive external force is applied, it is possible to prevent damage to the thread groove that is the rolling surface and the ball that is the rolling element.

  In the electric actuator, the magnitude of the external force that rotates the linear motion member around the axis is set by adjusting the magnitude of the elastic force of the elastic body. Thereby, even if an excessive external force is applied, it is possible to prevent damage to the thread groove that is the rolling surface and the ball that is the rolling element.

  In the electric actuator, the magnitude of the external force that rotates the linear motion member around the axis is set by adjusting the friction coefficient of the sliding member and the shape of the annular member. Thereby, even if an excessive external force is applied, it is possible to prevent damage to the thread groove that is the rolling surface and the ball that is the rolling element.

  In the electric actuator, the magnitude of the external force that causes the linear motion member to rotate about the axis is set by adjusting the number of rotation prevention mechanisms. Thereby, even if an excessive external force is applied, it is possible to prevent damage to the thread groove that is the rolling surface and the ball that is the rolling element.

Sectional drawing which shows the whole structure in 1st embodiment of an electric actuator. (A) Sectional drawing which shows the operation | movement aspect of the anti-rotation mechanism in 1st embodiment of an electric actuator, (b) The same as A arrow sectional drawing in Fig.2 (a). (A) Sectional view and B arrow sectional view showing a state in which the ball screw in the first embodiment of the electric actuator is engaged with the sleeve by the detent mechanism, (b) Engagement with the sleeve by the detent mechanism Sectional drawing and C arrow sectional drawing which show the state by which is cancelled. (A) Sectional drawing which shows the operation | movement aspect of other embodiment of the rotation prevention mechanism in 1st embodiment of an electric actuator, (b) D arrow sectional drawing similarly in Fig.4 (a). (A) Cross-sectional view and F sectional view showing a configuration in which three or more protrusions are provided on the same plane in the detent mechanism in the first embodiment of the electric actuator, (b) Similarly, the protrusion is shifted in the axial direction. Sectional drawing and the E arrow sectional drawing which show the form which provided two or more. (A) Sectional drawing which shows the rotation prevention mechanism in 2nd embodiment of an electric actuator, (b) Similarly G arrow sectional drawing in Fig.6 (a). (A) Sectional drawing and H arrow sectional view which show the state in which the ball screw in 2nd embodiment of an electric actuator is engaged with the sleeve by the rotation prevention mechanism, (b) Engagement with the sleeve by the rotation prevention mechanism Sectional drawing and the arrow I sectional view which show the state from which the is cancelled | released. (A) Sectional drawing which shows the operation | movement aspect of other embodiment of the rotation prevention mechanism in 2nd embodiment of an electric actuator, (b) J arrow sectional drawing in Fig.8 (a). Sectional drawing which shows the whole structure in 3rd embodiment of an electric actuator.

  Below, the electric actuator 1 which is 1st embodiment of an electric actuator is demonstrated using FIG. 1 and FIG.

  As shown in FIG. 1, the electric actuator 1 converts a rotary motion from an electric power source into a linear motion and outputs the linear motion. The electric actuator 1 includes a storage-side housing 2, an extension-side housing 3, an electric motor 4, a sleeve 5, a ball screw 6 that is a linear motion mechanism, a protrusion 12, and a gear reduction mechanism 11. The electric actuator 1 is configured to be able to move the screw shaft 7 to an arbitrary position by controlling the movement of the electric motor 4.

  The storage side housing 2 and the extension side housing 3 are main structural members of the electric actuator 1. The storage-side housing 2 and the extension-side housing 3 are formed from an aluminum alloy such as A6061 or ADC12 or die cast. The aluminum alloy and die cast forming the storage housing 2 and the extension housing 3 are heated to a high temperature to form a solid solution, a quenching process in which it is rapidly cooled in water, and then brought to room temperature. Precipitation hardening treatment is performed in which a large lattice strain is generated in the precipitated phase and hardened by heat treatment constituted by age-hardening treatment (tempering treatment) in which the precipitate is heated or precipitated at a low temperature (100 to 200 ° C.). As a result, the storage-side housing 2 and the extension-side housing 3 can be mass-produced and can be reduced in cost, and at the same time, the strength can be increased and the amount of aluminum used can be reduced to achieve weight reduction. . The storage-side housing 2 and the extension-side housing 3 are fixed integrally with a ball 9 or the like (not shown) with their side surfaces abutting each other.

  The storage side housing 2 is formed with a storage portion 2a and a ball bearing holding portion 2b. The storage portion 2 a is formed in a hollow bottomed cylindrical shape capable of storing a screw shaft 7 of a ball screw 6 described later on the other side surface of the storage-side housing 2. The storage portion 2a is integrally provided with a sleeve 5 fitted therein. The ball bearing holding portion 2 b is formed in the opening portion of the storage portion 2 a that is on the same axis as the storage portion 2 a and is one side surface of the storage side housing 2. The ball bearing holding portion 2b is formed so as to hold a ball bearing 10 that rotatably supports a nut 8 of a ball screw 6 to be described later.

  The extension-side housing 3 is formed with an electric motor attachment portion 3a, a gear reduction mechanism arrangement portion 3b, a ball bearing holding portion 3c, and a communication hole 3d. The electric motor attachment portion 3 a is formed in a shape that allows the electric motor 4 to be attached to the other side surface of the extending side housing 3. The gear reduction mechanism arrangement portion 3b is formed in a concave shape on one side surface of the extension side housing 3 in which the drive side gear 11a, the driven side gear 11b, and the idle gear 11c constituting the gear reduction mechanism 11 can be arranged. . The ball bearing holding portion 3 c is formed on one side surface of the extension side housing 3 and on the same axis as the ball bearing holding portion 2 b of the storage side housing 2. The ball bearing holding portion 3c is formed so as to hold a ball bearing 10 that rotatably supports a nut 8 of the ball screw 6. The communication hole 3d is formed on the same axis as that of the ball bearing holding portion 3c so as to communicate one side surface and the other side surface of the extending side housing 3. That is, the communication hole 3 d communicates the inside of the storage portion 2 a of the storage side housing 2 with the outside.

  The electric motor 4 generates a rotational driving force. The electric motor 4 is attached to the electric motor attachment portion 3a of the extension side housing 3 so that the output shaft 4a protrudes into the recessed portion of the gear reduction mechanism arrangement portion 3b. The electric motor 4 is configured to be driven at an arbitrary torque, rotation speed, rotation angle, and the like by a control current from a control device (not shown). That is, the electric motor 4 outputs rotational power at a rotational speed and torque according to the control current.

  The sleeve 5 regulates the rotation of the screw shaft 7. The sleeve 5 is formed in a cylindrical shape by cold forging from medium carbon steel such as S55C or case-hardened steel such as SCM415 or SCM420, and the surface thereof is hardened in a range of 55 to 62 HRC by induction hardening or carburizing quenching. It has been subjected. Thereby, mass productivity improves and it can aim at low cost. The sleeve 5 is provided integrally with the storage portion 2 a of the storage-side housing 2. That is, the sleeve 5 is configured so as not to rotate relative to the storage-side housing 2. On the inner peripheral surface of the sleeve 5, grooves 5a along the axial direction are provided at two locations so as to face each other. The groove 5 a is formed in a V shape in a sectional view of the sleeve 5 in the axial direction. The sleeve 5 forms a detent mechanism 13 by forming a groove 5a. In the present embodiment, the groove 5a is formed in the sleeve 5 that is integrally provided by being fitted to the storage portion 2a of the storage side housing 2, but the present invention is not limited to this. 2 may be formed.

  The ball screw 6 converts rotational motion into linear motion. The ball screw 6 includes a screw shaft 7, a nut 8, a plurality of balls 9, a ball bearing 10, and the like.

  The screw shaft 7 is made of medium carbon steel such as S55C or case-hardened steel such as SCM415 or SCM420, and is subjected to a hardening process of about 55 to 62 HRC by induction hardening or vacuum carburizing and hardening. The screw shaft 7 has a plurality of one-side shaft-side thread grooves 7a for rolling the ball 9 on the outer peripheral surface thereof. A substantially cylindrical sliding portion 7 b (not required to slide) is formed at one end of the screw shaft 7. The sliding portion 7b is formed to have a diameter that can be slidably inserted into the sleeve 5. The sliding portion 7b is provided with protrusions 12 to be described later at positions facing the two grooves 5a of the sleeve 5. The protruding portion 12 constitutes a detent mechanism 13. In the present embodiment, the shaft-side thread groove 7a formed in the screw shaft 7 is a right-hand thread, but is not limited thereto. The other end of the screw shaft 7 is threaded so that a driven object (not shown) can be connected.

  The nut 8 is formed in a hollow cylindrical shape into which the screw shaft 7 can be inserted. The nut 8 is made of case-hardened steel such as SCM415 or SCM420, and is subjected to a hardening process of about 55 to 62HRC by vacuum carburizing and quenching. A nut-side thread groove 8 a for rolling the ball 9 is formed on the inner peripheral surface of the nut 8 with the same lead and pitch as the shaft-side thread groove 7 a of the screw shaft 7. Further, a piece member 8 b is fitted into a part of the inner peripheral surface of the nut 8. The top member 8b is configured to return the ball 9 to the original shaft-side thread groove 7a even if it climbs over the peak portion (land portion) of the shaft-side thread groove 7a of the screw shaft 7. On the outer peripheral surface of the nut 8, a flange portion 8 c that is a stepped portion whose outer diameter is partially enlarged is formed. The screw shaft 7 is inserted into the nut 8 so that the shaft-side screw groove 7a and the nut-side screw groove 8a face each other. A plurality of balls 9 are housed in a space formed by the shaft-side screw groove 7a and the nut-side screw groove 8a so as to be able to roll. The ball 9 is made of a high carbon chrome bearing steel such as SUJ2, and is hardened in the range of 58 to 64 HRC up to the core by quenching. The nut 8 supports the screw shaft 7 through a plurality of balls 9 so as to be rotatable around the axis of the nut 8. Further, ball bearings 10 are provided at both end portions of the nut 8. In addition, in this embodiment, although the shaft side thread groove 7a of the screw shaft 7 was 1 turn, it is not limited to this.

  In the ball screw 6 configured in this way, one ball bearing 10 provided on the nut 8 is held by the ball bearing holding portion 2 b of the storage side housing 2, and the other ball bearing 10 is connected to the extension side housing 3. It is held by the ball bearing holding portion 3c. That is, the nut 8 is rotatably supported by the storage side housing 2 and the extension side housing 3 via the ball bearing 10. In the ball screw 6, the screw shaft 7 is disposed in the storage portion 2a of the storage-side housing 2 and the communication hole 3d of the extension-side housing 3, and the sliding portion 7b at one end of the screw shaft 7 is the storage portion 2a. The sleeve 5 is slidably inserted. At this time, each groove 5a of the sleeve 5 is engaged with a protruding portion 12 provided on the sliding portion 7b. As described above, the ball screw 6 is rotated with respect to the storage-side housing 2 by the anti-rotation mechanism 13 including the groove 5a of the sleeve 5 and the projecting portion 12 while the screw shaft 7 is rotatably supported by the nut 8 around the shaft. Is inserted in a regulated state. When the nut 8 is rotated, the ball screw 6 is applied to the screw shaft 7 via a plurality of balls 9 accommodated in the shaft-side screw groove 7a and the nut-side screw groove 8a (hereinafter simply referred to as a rotational torque around the shaft). ("Rotational force") is transmitted. Since the rotation of the screw shaft 7 with respect to the storage-side housing 2 is restricted, the rotational motion of the nut 8 is converted into linear motion in the axial direction of the screw shaft 7 by the inclination of the shaft-side screw groove 7a. In this manner, the screw shaft 7 of the ball screw 6 extends or retracts from the storage side 2 of the storage side housing 2 through the communication hole 3d of the extension side housing 3 to the outside from the extension side housing 3.

  The gear reduction mechanism 11 decelerates and outputs the rotational power from the electric motor 4. The gear reduction mechanism 11 includes a driving gear 11a that is a pinion gear, a driven gear 11b that has more teeth than the driving gear 11a, and an idle gear 11c that connects the driving gear 11a and the driven gear 11b. The idle gear 11c is used when the rotational direction of the driven gear 11b is reversed or when the distance between the axes of the driving gear 11a and the driven gear 11b is large. The drive side gear 11a, the driven side gear 11b, and the idle gear 11c are made of sintered metal.

  The drive side gear 11a, the driven side gear 11b, and the idle gear 11c are arranged in the gear reduction mechanism arrangement portion 3b of the extension side housing 3 in an engaged state. The drive side gear 11 a is provided so as to be rotatable integrally with the output shaft 4 a of the electric motor 4. A nut 8 is inserted into the driven gear 11b and is provided so as to be integrally rotatable. The idle gear 11 c is rotatably supported by the storage side housing 2 and the extension side housing 3. The idle gear 11c is disposed so as to mesh with the driving side gear 11a and the driven side gear 11b simultaneously. Thereby, the gear reduction mechanism 11 decelerates the input rotational speed from the electric motor 4 according to the reduction ratio between the drive side gear 11a and the driven side gear 11b, and increases and outputs the rotational force. In the present embodiment, the gear reduction mechanism 11 is constituted by three gears including a driving side gear 11a, a driven side gear 11b, and an idle gear 11c, but is not limited thereto. Moreover, although the drive side gear 11a, the driven side gear 11b, and the idle gear 11c are comprised from the sintered metal, it is not limited to this.

  When the control current based on any one of the torque, the rotation speed, and the rotation angle is supplied to the electric motor 4 from the control device or the like (not shown), the electric actuator 1 configured as described above is supplied with the control current. The output shaft 4a of the electric motor 4 rotates in one direction or the other direction in a corresponding operation mode. The electric actuator 1 converts the input rotation speed and the input torque of the electric motor 4 into an output rotation speed and an output torque corresponding to the reduction ratio of the gear reduction mechanism 11 and transmits them to the ball screw 6. The electric actuator 1 rotates the nut 8 of the ball screw 6 on which the driven gear 11b is provided so that the screw shaft 7 is rotated at a speed and axial thrust according to the lead of the nut 8 (screw shaft 7). It moves linearly in the axial direction (see black arrow in FIG. 1). At this time, in the ball screw 6, the rotation of the screw shaft 7 is suppressed by the anti-rotation mechanism 13 constituted by the groove 5 a of the sleeve 5 and the protrusion 12 provided on the screw shaft 7.

  Hereinafter, the rotation preventing mechanism 13 will be described with reference to FIG. The anti-rotation mechanism 13 suppresses rotation around the axis of the linear motion member. The anti-rotation mechanism 13 includes a groove 5 a of the sleeve 5 and a protrusion 12 provided on the screw shaft 7.

  As shown in FIG. 2, the projecting portion 12 includes an engaging spring 12a and an engaging ball 12b, which are elastic members. The engaging spring 12a is made of a compression coil spring, and is hardened in the range of 58 to 64 HRC up to the core portion by quenching. The engaging ball 12b is rotatably held at one end of the engaging spring 12a. The protrusions 12 are respectively provided on straight lines orthogonal to the axis of the screw shaft 7. That is, the protrusions 12 are arranged on the outer peripheral surface of the sliding part 7b around the axis about every 180 °. In the protrusion 12, the engagement spring 12 a and the engagement ball 12 b are inserted into the holding holes 7 c formed every 180 ° from the outer peripheral surface of the sliding portion 7 b of the screw shaft 7 toward the shaft center. At this time, the protruding portion 12 is configured such that the engaging ball 12b protrudes from the outer peripheral surface of the sliding portion 7b. Further, when the engaging ball 12b is pressed by a load of a predetermined value or more, the protruding portion 12 is bent by the engaging spring 12a, and the engaging ball 12b is moved to the outer peripheral surface side of the sliding portion 7b (the axial center side of the screw shaft 7). ) (See arrows).

  The anti-rotation mechanism 13 suppresses the rotation of the screw shaft 7, which is a linear motion member, about the axis by engaging the sleeve 5 and the screw shaft 7 with the engagement ball 12 b of the protrusion 12 and the groove 5 a of the sleeve. ing. The anti-rotation mechanism 13 is provided at two locations around the axis of the sleeve 5 or the screw shaft 7 every 180 °. The anti-rotation mechanism 13 is configured such that the groove 5a and the engagement ball 12b engage with each other in a state where the engagement spring 12a is compressed. That is, in the rotation preventing mechanism 13, the engagement ball 12b is pressed against the groove 5a by a force (hereinafter simply referred to as “spring force”) according to the deflection amount of the engagement spring 12a (see white arrow).

  Next, an operation mode of the ball screw 6 in the electric actuator 1 when a rotational force is applied to the screw shaft 7 which is a linear motion member will be described with reference to FIG. In the present embodiment, the ball screw 6 has a shaft-side thread groove that is a rolling surface when a rotational force equal to or greater than the rotational force Tlim is transmitted to the screw shaft 7 in a state where the linear movement of the screw shaft 7 is restricted. 7a and the nut side thread groove 8a and the contact surface of the ball 9 which is a rolling element, a stress greater than a reference value is generated.

  As shown in FIG. 3A, when the rotational motion is transmitted from the electric motor 4 (see FIG. 1) to the nut 8 (see the arrow), the ball screw 6 of the electric actuator 1 is screwed on the shaft side of the screw shaft 7. By the inclination of the groove 7a, the screw shaft 7 is converted into a linear motion in the axial direction (see thin ink arrow) and a rotational motion around the axis. The anti-rotation mechanism 13 is configured such that the engagement ball 12b rolls along the groove 5a as the screw shaft 7 moves in the axial direction. Therefore, the rotation preventing mechanism 13 does not suppress the linear movement of the screw shaft 7 in the axial direction. The anti-rotation mechanism 13 is a force in the expansion / contraction direction of the engagement spring 12a of the protrusion 12 (black arrow) generated when the engagement ball 12b of the protrusion 12 is pressed against the wall surface of the groove 5a by the rotational force applied to the screw shaft 7. The spring force of the engagement spring 12a (see the white arrow) is greater than that of the reference spring. That is, in the rotation preventing mechanism 13, the component force in the expansion / contraction direction of the engagement spring 12a generated by the action of the wall surface of the groove 5a in contact with the engagement ball 12b out of the rotational force applied to the screw shaft 7 is the engagement spring 12a. As long as the spring force is smaller than this, the engagement between the groove 5a and the engagement ball 12b is maintained. With this configuration, in the electric actuator 1, the rotational movement around the axis of the screw shaft 7 due to the rotation of the nut 8 is suppressed by the rotation prevention mechanism 13.

  On the other hand, in the electric actuator 1, when an external force in the axial direction is applied to the screw shaft 7 in a state where the electric motor 4 does not output a rotational force, the screw shaft 7 moves straight in the axial direction and the nut-side screw groove 8 a The nut 8 and the electric motor 4 are rotated by the inclination. In the electric actuator 1, the nut 8 is rotated by the inertial force of the electric motor 4 even if the screw shaft 7 reaches the end of the movable range and the linear movement in the axial direction is restricted. Thereby, the rotational force due to the inertia of the electric motor 4 is transmitted to the screw shaft 7 via the nut 8.

  As shown in FIG. 3 (b), the detent mechanism 13 contacts the ball 9 with the shaft side screw groove 7 a and the nut 8 side screw groove 8 a on the screw shaft 7 in a state where the linear movement of the screw shaft 7 is restricted. When a rotational force equal to or greater than the rotational force Tlim that generates a stress greater than a reference value is transmitted to the surface, the engagement spring 12a of the protrusion 12 is generated by pressing the engagement ball 12b of the protrusion 12 against the wall surface of the groove 5a. The spring force of the engaging spring 12a (see white arrow) is configured to be smaller than the force in the expansion / contraction direction (see black arrow). That is, the rotation preventing mechanism 13 has a component force in the expansion / contraction direction of the engagement spring 12a generated by the action of the wall surface of the groove 5a in contact with the engagement ball 12b out of the rotation force greater than the rotation force Tlim applied to the screw shaft 7. Is larger than the spring force of the engaging spring 12a, the engaging ball 12b of the protrusion 12 is moved to the outer peripheral surface side of the sliding portion 7b of the screw shaft 7 by the wall surface of the groove 5a, and the groove 5a and the engaging ball 12b are moved. Is disengaged. With this configuration, the electric actuator 1 is configured such that when the rotational force equal to or greater than the rotational force Tlim is transmitted to the screw shaft 7 in a state where the linear motion of the screw shaft 7 is restricted, the screw shaft 7 rotates about the axis. It is rotated. The screw shaft 7 of the electric actuator 1 is rotated until the engagement ball 12b of the protrusion 12 is engaged with the other groove 5a.

  Further, as shown in FIG. 4, as another embodiment of the anti-rotation mechanism 13, the anti-rotation mechanism 14 may be configured such that the protruding portion 12 is provided on the sleeve and the groove 7 d is provided on the sliding portion 7 b of the screw shaft 7.

  On the inner peripheral surface on a straight line passing through the axial center of the sleeve 5, a projecting portion 12 constituting the detent mechanism 14 is provided. That is, the protrusion 12 is arranged on the inner peripheral surface of the sleeve 5 around the axis thereof every 180 °. In the protrusion 12, the engagement spring 12 a and the engagement ball 12 b are inserted into the holding holes 5 b formed every 180 ° from the inner peripheral surface of the sleeve 5 toward the outer peripheral surface. At this time, the protruding portion 12 is disposed so that the engaging ball 12 b protrudes from the inner peripheral surface of the sleeve 5. Further, the protrusion 12 is configured such that when the engagement ball 12b is pressed by a predetermined load, the engagement spring 12a bends and moves toward the inner peripheral surface side (the outer peripheral surface side of the sleeve 5) of the sleeve 5. (See arrow). In the present embodiment, the protruding portion 12 is configured as a sleeve 5 that is integrally provided by being fitted to the storage portion 2a of the storage-side housing 2, but is not limited thereto. The housing 2 may be configured.

  The sliding portion 7b of the screw shaft 7 is provided at two locations so that the grooves 7d along the axial direction face each other. On the outer peripheral surface of the sliding portion 7b, grooves 7d are arranged around the axis every 180 °. The groove 7d is formed in a V shape in a sectional view of the screw shaft 7 in the axial direction. The screw shaft 7 forms a detent mechanism 14 by forming a groove 7d.

  The anti-rotation mechanism 14 suppresses the rotation of the screw shaft 7 around the axis by engaging the sleeve 5 and the screw shaft 7 with the engagement ball 12 b of the protruding portion 12 and the groove 7 d of the screw shaft 7. The anti-rotation mechanism 14 is provided at two positions every 180 ° around the axis of the sleeve 5 or the screw shaft 7. The detent mechanism 14 is configured such that the groove 7d and the engagement ball 12b engage with each other in a state where the engagement spring 12a is compressed. That is, in the rotation preventing mechanism 14, the engagement ball 12b is pressed against the groove 7d by the spring force (see the white arrow).

  With the configuration as described above, the electric actuator 1 has a stress greater than a reference value on the contact surface between the shaft side screw groove 7d and the nut 8 side screw groove 7d and the ball by the rotational force applied to the screw shaft 7 of the ball screw 6. When the torque is less than the generated torque Tlim, the engagement between the sleeve 5 of the anti-rotation mechanism 13 or the anti-rotation mechanism 14 and the screw shaft 7 is maintained. On the other hand, in the electric actuator 1, when the linear movement of the screw shaft 7 is restricted and a rotational force greater than the rotational force Tlim is applied to the screw shaft 7, the engagement ball 12b of the anti-rotation mechanism 13 or the anti-rotation mechanism 14 is pressed, The engagement between the sleeve 5 and the screw shaft 7 is released. That is, when the electric actuator 1 generates a stress greater than the reference value on the contact surface between the shaft side screw groove 7d and the nut 8 side screw groove 7d and the ball due to the rotational force applied to the screw shaft 7, the electric actuator 1 or The screw shaft 7 and the nut 8 are integrally rotated around the shaft by the action of the stop mechanism 14. In the electric actuator 1, the predetermined value of the rotational force at which the screw shaft 7 starts rotating around the axis is set to an appropriate value by adjusting the magnitude of the elastic force of the engagement spring 12a. As a result, the electric actuator 1 prevents the ball screw 6 from being damaged because stress exceeding the reference value does not occur on the contact surface between the shaft side screw groove 7d and the nut 8 side screw groove 7d and the ball even when an excessive external force is applied. can do.

  In the present embodiment, the anti-rotation mechanism 13 and the anti-rotation mechanism 14 are provided at two places so as to face each other with the axis of the ball screw 6 interposed therebetween, but the present invention is not limited to this. As shown in FIG. 5A, only one anti-rotation mechanism 13 and anti-rotation mechanism 14 may be provided on the ball screw 6, or three or more anti-rotation mechanisms 14 and 14 may be provided. Further, as shown in FIG. 5B, a plurality of anti-rotation mechanisms 13 and anti-rotation mechanisms 14 may be provided at positions shifted in the axial direction.

  Next, the electric actuator 15 which is 2nd embodiment of an electric actuator is demonstrated using FIG. In addition, the electric actuator 15 which concerns on the following 2nd embodiment is replaced with the electric actuator 1 in the electric actuator 1 shown in FIGS. 1-5, and the name, figure number, and symbol which were used for the description are used. In the following embodiments, the same points as those of the already described embodiments will be omitted, and different portions will be mainly described.

  As shown in FIG. 6, the electric actuator 15 converts the rotary motion from the electric power source into a linear motion and outputs it. The electric actuator 15 includes a storage-side housing 2 (see FIG. 1), an extension-side housing 3 (see FIG. 1), an electric motor 4 (see FIG. 1), a sleeve 5, a ball screw 6 that is a linear motion mechanism, and a rotation prevention mechanism 17. And a gear reduction mechanism 11 (see FIG. 1). The electric actuator 15 is configured to be able to move the screw shaft 7 to an arbitrary position by controlling the movement of the electric motor 4.

  The ball screw 6 converts rotational motion into linear motion. The ball screw 6 includes a screw shaft 7, a nut 8, a plurality of balls 9, a ball bearing 10 (see FIG. 1), and the like.

  A substantially cylindrical sliding portion 7 b (not required to slide) is formed at one end of the screw shaft 7. The sliding portion 7b is formed to have a diameter that can be slidably inserted into the sleeve 5. Further, a small diameter stepped portion 7e is formed at one end of the sliding portion 7b. The small-diameter stepped portion 7e is formed with protruding portions 16 that are movable in the circumferential direction at positions facing the two grooves 5a of the sleeve 5. The protruding portion 16 constitutes a detent mechanism 17.

  As described above, the ball screw 6 includes the rotation preventing mechanism 17 including the groove 5 a of the sleeve 5 and the protruding portion 16 of the screw shaft 7. That is, the screw shaft 7 is inserted into the sleeve 5 of the storage-side housing 2 in a state in which the rotational movement with respect to the storage-side housing 2 is suppressed by the anti-rotation mechanism 17 while being supported rotatably on the nut 8. Yes. When the nut 8 of the ball screw 6 is rotated, the electric actuator 15 causes the screw shaft 7 to linearly move in the axial direction at a speed and axial thrust according to the lead of the nut 8 (screw shaft 7) (see FIG. See arrow). At this time, the ball screw 6 is restrained from rotating about the screw shaft 7 by the rotation prevention mechanism 17.

  The protruding portion 16 includes a resistance member 16a (light ink portion) that is a sliding member and an engaging member 16b that has a pin 16c that is a convex portion. The resistance member 16a is made of an engineering plastic having wear resistance and a predetermined coefficient of friction. The resistance member 16a is formed in an annular shape having an inner diameter slightly smaller than the outer diameter of the small-diameter stepped portion 7e of the screw shaft 7. The resistance member 16 a is supported by the screw shaft 7 by inserting a small diameter stepped portion 7 e of the screw shaft 7 into the inner diameter thereof. A frictional force is generated between the resistance member 16 a and the screw shaft 7. The engaging member 16b is made of high carbon chrome bearing steel such as SUJ2, and is hardened in the range of 58 to 64 HRC up to the core portion by quenching. The engaging member 16b is formed in an annular shape having an inner diameter slightly smaller than the outer diameter of the resistance member 16a. On the outer peripheral surface of the engaging member 16b, pins 16c are provided on straight lines orthogonal to the axis of the engaging member 16b. That is, on the outer peripheral surface of the engaging member 16b, the pins 16c are arranged every 180 ° around the axis. The engaging member 16b has a resistance member 16a supported by the screw shaft 7 inserted in its inner diameter. A frictional force is generated between the engaging member 16b and the resistance member 16a.

  Thus, as for the protrusion part 16, the engaging member 16b is supported by the screw shaft 7 via the resistance member 16a. At this time, the protruding portion 16 is configured such that the pin 16c protrudes from the outer peripheral surface of the sliding portion 7b. In addition, the protrusion 16 is a screw between the inner peripheral surface of the engagement member 16b and the outer peripheral surface of the resistance member 16a or a screw on the inner peripheral surface of the resistance member 16a by applying a force of a predetermined value or more to the pin 16c in the circumferential direction. Sliding occurs between the shaft 7 and the outer peripheral surface of the small-diameter stepped portion 7e so that the shaft 7 moves in the circumferential direction.

  The anti-rotation mechanism 17 suppresses the rotation of the screw shaft 7 around the axis by engaging the sleeve 5 and the screw shaft 7 with the engaging member 16b of the protruding portion 16 and the groove 5a of the sleeve. The anti-rotation mechanism 17 is provided at two locations around the axis of the sleeve 5 or the screw shaft 7 every 180 °. The anti-rotation mechanism 17 is configured such that the groove 5a of the sleeve 5 and the pin 16c of the engagement member 16b engage with each other while being slidable in the axial direction.

  Next, an operation mode of the electric actuator 15 when a rotational force is applied to the screw shaft 7 will be described with reference to FIG.

  As shown in FIG. 7 (a), when the electric actuator 15 receives rotational movement from the electric motor 4 (see FIG. 1) to the nut 8 of the ball screw 6 (see arrow), the screw on the shaft side of the screw shaft 7 is rotated. By the inclination of the groove 7a, the screw shaft 7 is converted into a linear movement in the axial direction and a rotational movement around the axis (see thin ink arrow). The anti-rotation mechanism 17 is configured such that the pin 16c of the protruding portion 16 rolls along the groove 5a as the screw shaft 7 moves in the axial direction. Therefore, the rotation preventing mechanism 17 does not suppress the linear movement of the screw shaft 7 in the axial direction. The anti-rotation mechanism 17 is supported by the screw shaft 7 via a resistance member 16a of the protrusion 16 having an engagement member 16b of the protrusion 16 having a predetermined friction coefficient. The anti-rotation mechanism 17 has an inner peripheral surface of the engaging member 16b that is more than a circumferential force generated in the pin 16c provided on the engaging member 16b through the wall surface of the groove 5a by the rotational force applied to the screw shaft 7. And the outer peripheral surface of the resistance member 16a and the frictional force generated between the inner peripheral surface of the resistance member 16a and the outer peripheral surface of the small-diameter stepped portion 7e of the screw shaft 7 (hereinafter simply referred to as “predetermined frictional force”). It is comprised so that it may become large. That is, the rotation preventing mechanism 17 maintains the engagement between the groove 5a and the engaging member 16b as long as the circumferential force generated on the pin 16c by the rotational force applied to the screw shaft 7 is smaller than the predetermined frictional force. . With this configuration, in the electric actuator, the rotational movement around the axis of the screw shaft 7 due to the rotation of the nut 8 is suppressed by the rotation prevention mechanism 17.

  As shown in FIG. 7B, the rotation preventing mechanism 17 causes the wall surface of the groove 5 a to move when a rotational force equal to or greater than the rotational force Tlim is transmitted to the screw shaft 7 in a state where the linear movement of the screw shaft 7 is restricted. The predetermined frictional force of the protrusion 16 is configured to be smaller than the circumferential force generated in the engaging member 16b of the protrusion 16 via That is, when the rotational force greater than the rotational force Tlim is applied to the screw shaft 7 (see the arrow), the anti-rotation mechanism 17 moves the engaging member 16b of the protrusion 16 in the circumferential direction of the screw shaft 7 by the wall surface of the groove 5a. Thus, the position of the screw shaft 7 with respect to the engaging member 16b is shifted (see the arrow in the arrow I direction). With this configuration, the electric actuator 15 can rotate around the axis of the screw shaft 7 when a rotational force equal to or greater than the rotational force Tlim is transmitted to the screw shaft 7 in a state where the linear movement of the screw shaft 7 is restricted. The restriction on the rotation is released. The screw shaft 7 of the electric actuator 15 is rotated until the circumferential force generated in the engaging member 16 b is smaller than a predetermined frictional force of the protruding portion 16.

  Furthermore, as shown in FIG. 8, as another embodiment of the anti-rotation mechanism 17, the anti-rotation mechanism 18 may be configured such that the protruding portion 16 is provided on the sleeve 5 and the groove 7 d is provided on the sliding portion 7 b of the screw shaft 7.

  An enlarged diameter portion 5 c is formed on the inner peripheral surface of the sleeve 5. The resistance member 16a constituting the protruding portion 16 is formed in an annular shape having an outer diameter slightly larger than the inner diameter of the enlarged diameter portion 5c of the sleeve 5. The resistance member 16 a is inserted into the enlarged diameter portion 5 c and supported by the sleeve 5. A frictional force is generated between the resistance member 16 a and the sleeve 5. The engaging member 16b constituting the protruding portion 16 is formed in an annular shape having an outer diameter slightly larger than the inner diameter of the resistance member 16a. On the inner peripheral surface of the engaging member 16b, pins 16c, which are convex portions, are respectively provided on straight lines passing through the axis. That is, the pin 16c is arrange | positioned every 180 degrees around an axial center on the internal peripheral surface of the engaging member 16b. The engaging member 16b is inserted into the resistance member 16a supported by the sleeve 5. A frictional force is generated between the engaging member 16b and the resistance member 16a.

  Thus, the engaging part 16b of the protrusion 16 is supported by the sleeve 5 via the resistance member 16a. At this time, the protruding portion 16 is configured such that the pin 16 c protrudes from the inner peripheral surface of the sleeve 5. Further, the protrusion 16 has a sleeve 5 on the pin 16c between the outer peripheral surface of the engagement member 16b and the inner peripheral surface of the resistance member 16a or on the outer peripheral surface of the resistance member 16a by applying a force equal to or greater than a predetermined value to the pin 16c. The large diameter portion 5c is configured to slide in the inner peripheral surface and move in the circumferential direction of the sleeve 5.

  On the outer peripheral surface of the sliding portion 7b of the screw shaft 7, two grooves 7d along the axial direction are provided so as to face each other. That is, the grooves 7d are arranged around the axis at every 180 ° on the outer peripheral surface of the sliding portion 7b. The screw shaft 7 forms a detent mechanism 18 by forming a groove 7d.

  The anti-rotation mechanism 18 suppresses the rotation of the screw shaft 7 around the axis by engaging the engaging member 16b of the protruding portion 16 with the groove 7d of the screw shaft 7. The anti-rotation mechanisms 18 are provided at two positions every 180 ° around the axis of the sleeve 5 or the screw shaft 7. The anti-rotation mechanism 18 is configured such that the groove 7d and the pin 16c of the engagement member 16b are engaged with each other while being slidable in the axial direction. In the present embodiment, the protruding portion 16 is configured as a sleeve 5 that is integrally provided by being fitted to the storage portion 2a (see FIG. 1) of the storage-side housing 2, but is not limited thereto. Instead, the housing 2 may be configured.

  With the configuration as described above, the electric actuator 15 allows the rotation prevention mechanism 17 with respect to the screw shaft 7 or the protrusion 16 of the rotation prevention mechanism 18 to be applied to the screw shaft 7 when the rotational force applied to the screw shaft 7 of the ball screw 6 is less than the rotational force Tlim. The position of the engaging member 16b is maintained. On the other hand, in the electric actuator 15, when the linear movement of the screw shaft 7 is restricted and a rotational force equal to or greater than the rotational force Tlim is applied to the screw shaft 7, the locking member 17 of the rotation prevention mechanism 17 or the rotation prevention mechanism 18 is connected to the screw shaft 7. The position of the engaging member 16b with respect to the screw shaft 7 is shifted in the circumferential direction. That is, when the rotational force applied to the screw shaft 7 is greater than or equal to the rotational force Tlim, the electric actuator 15 causes the screw shaft 7 and the nut 8 to rotate integrally around the shaft by the action of the anti-rotation mechanism 17 or the anti-rotation mechanism 18. Is done. In addition, the electric actuator 15 has an appropriate value of the rotational force at which the screw shaft 7 starts rotating around the axis by adjusting the friction coefficient of the resistance member 16a and the fit between the resistance member 16a and the engagement member 16b. Set to the correct value. Thereby, even if an excessive external force is applied, the electric actuator 15 prevents the ball screw 6 from being damaged because no stress exceeding the reference value is generated on the contact surface between the shaft side screw groove 7d and the nut 8 side screw groove 7d and the ball. can do.

  Next, the electric actuator 19 which is 3rd embodiment of an electric actuator is demonstrated using FIG. In this embodiment, the anti-rotation mechanism 26 has the same configuration as the anti-rotation mechanism 26 in the first embodiment, but is not limited to this, and the anti-rotation mechanism 14 and the anti-rotation mechanism in the second embodiment. The structure similar to the mechanism 17 and the rotation prevention mechanism 18 may be sufficient.

  As shown in FIG. 9, the electric actuator 19 converts the rotary motion from the electric power source into a linear motion and outputs it. The electric actuator 19 includes a storage side housing 20, an extension side housing 3, a shaft end housing 21, an electric motor 4, a ball screw 22 that is a linear motion mechanism, a sleeve 25, and a gear reduction mechanism 11. The electric actuator 19 is configured to be able to move a nut 24 described later to an arbitrary position by controlling the movement of the electric motor 4.

  The storage housing 20 is formed with a ball bearing holding portion 20a. The ball bearing holding portion 20 a is formed on one side surface of the storage side housing 20. Further, the ball bearing holding portion 20a is formed so as to hold a ball bearing 10 that rotatably supports a screw shaft 23 of a ball screw 22 described later.

  The shaft end housing 21 supports the screw shaft 23 of the ball screw 22. The shaft end housing 21 is fixed to a base (not shown) to which the extension side housing 3 and the storage side housing 20 are fixed. The shaft end housing 21 is formed so as to hold the ball bearing 10 that rotatably supports the screw shaft 23.

  The ball screw 22 converts rotational motion into linear motion. The ball screw 22 includes a screw shaft 23, a nut 24, a plurality of balls 9, a ball bearing 10, and the like.

  A cylindrical one-side support portion 17a and another-side support portion 17b are formed at one end and the other end of the screw shaft 23, respectively. Ball bearings 10 are provided at both end portions of the one side support portion 17a. The ball bearings 10 are respectively held by the ball bearing holding part 3 c of the extension side housing 3 and the ball bearing holding part 20 a of the storage side housing 20. Similarly, the ball bearing 10 is provided in the other side support part 17b. The ball bearing 10 is held by the shaft end housing 21. That is, the screw shaft 23 is rotatably supported by the extension side housing 3, the storage side housing 20, and the shaft end housing 21 via the ball bearing 10.

  The outer peripheral surface of the nut 24 has a diameter that can be inserted into the sleeve 25. The nut 24 is supported via a plurality of balls 9 so as to be rotatable about the axis of the screw shaft 23. Further, the nut 24 is provided with a projecting portion 12 constituting a detent mechanism 26 at a position facing a groove 25a of a sleeve 25 described later.

  The sleeve 25 regulates the rotation of the nut 24. The sleeve 25 is fixed to a base (not shown) to which the extension side housing 3 and the storage side housing 20 are fixed. That is, the sleeve 25 is configured so as not to rotate relative to the nut 24. The inner peripheral surface of the sleeve 25 is formed to have a diameter into which the nut 24 can be inserted. On the inner peripheral surface of the sleeve 25, a groove 25 a extending in the axial direction is formed at a position facing the engaging ball 12 b of the protruding portion 12 provided on the nut 24. The groove 25a constitutes a detent mechanism 26.

  In the ball screw 22 configured in this way, the ball bearing 10 provided on the one side support portion 17a of the screw shaft 23 is held by the extension side housing 3 and the storage side housing 20, and the other side support portion 17b The provided ball bearing 10 is held by the shaft end housing 21. That is, the screw shaft 23 is rotatably supported by the storage side housing 20, the extension side housing 3 and the shaft end housing 21 via the ball bearing 10. The ball screw 22 is slidably inserted into a sleeve 25 in which a nut 24 is integrally fixed to a base (not shown) (it does not need to slide). At this time, the engaging ball 12b of the protruding portion 12 of the nut 24 is engaged with the groove 25a of the sleeve 25 so as to roll freely. That is, the nut 24 is inserted into the sleeve 25 in a state in which the rotational movement is restricted while the nut 24 is rotatably supported around the axis. In the ball screw 22, the rotational force is transmitted to the nut 24 when the screw shaft 23 is rotated. Since the nut 24 is restricted in rotational movement by the sleeve 25, the rotational movement of the nut 24 is converted into a linear movement in the axial direction of the screw shaft 23. In this way, the nut 24 of the ball screw 22 reciprocates in the axial direction on the screw shaft 23 while being inserted into the sleeve 25.

  The drive side gear 11a, the driven side gear 11b, and the idle gear 11c are arranged in the gear reduction mechanism arrangement portion 3b of the extension side housing 3 in an engaged state. The driven gear 11b is provided so that the one-side support portion 17a of the screw shaft 23 is inserted into a support shaft insertion hole formed at the center thereof so as to be integrally rotatable. In the electric actuator 19, when the screw shaft 23 of the ball screw 22 provided with the driven gear 11b is rotated, the nut 24 linearly moves in the axial direction at a speed and axial thrust according to the lead of the screw shaft 23. (See black arrow in FIG. 9).

  The anti-rotation mechanism 26 of the electric actuator 19 is based on the force in the expansion / contraction direction of the engagement spring 12a of the protrusion 12 that is generated when the engagement ball 12b of the protrusion 12 is pressed against the wall surface of the groove by the rotational force applied to the screw shaft 7. Also, the spring force of the engaging spring 12a is configured to be large. With this configuration, the electric actuator 19 is prevented from rotating about the axis of the nut 24 relative to the housing by the rotation prevention mechanism 26.

  Further, when the rotational force greater than the rotational force Tlim is transmitted to the screw shaft 23 in a state in which the straight movement of the nut 24 is restricted, the anti-rotation mechanism 26 presses the engagement ball 12b of the protrusion 12 against the wall surface of the groove. The spring force of the engagement spring 12a of the protrusion 12 is configured to be smaller than the force in the expansion / contraction direction of the engagement spring 12a of the protrusion 12 caused by the deformation. That is, when the rotational force equal to or greater than the rotational force Tlim is applied to the nut 24, the anti-rotation mechanism 26 moves the engagement ball 12b of the protrusion 12 to the outer peripheral surface side of the nut 24 by the wall surface of the groove and engages the groove. The engagement with the ball 12b is released. By being configured in this way, the electric actuator 19 can move around the axis of the nut 24 relative to the housing when a rotational force equal to or greater than the rotational force Tlim is transmitted to the nut 24 in a state where the linear movement of the nut 24 is restricted. The restriction on rotation is released.

  In the above, the anti-rotation mechanism 13 using the compression coil spring, the anti-rotation mechanism 14 and the anti-rotation mechanism 26 in the electric actuator, and the anti-rotation mechanism 17 and the anti-rotation mechanism 18 using the sliding member have been described. However, any elastic member or sliding member that slides on the linear motion member by a force by a predetermined rotational force may be used. It goes without saying that the present invention can be implemented in various forms without departing from the gist of the present invention, and the scope of the present invention is shown by the description of the claims and further described in the claims. Including the equivalent meaning of and all changes within the scope.

DESCRIPTION OF SYMBOLS 1 Electric actuator 2 Storage side housing 3 Extension side housing 4 Electric motor 6 Ball screw 7 Screw shaft 8 Nut 13 Anti-rotation mechanism

Claims (8)

The housing of the linear motion member that transmits the rotational force from the electric motor to the ball screw supported by the housing and is moved in the axial direction by the rotational force from the electric motor among the screw shaft and nut constituting the ball screw. In the electric actuator provided with a detent mechanism that restricts rotation around the axis with respect to
An electric actuator in which the restriction of rotation of the linear motion member around the axis of the linear motion member relative to the housing by the anti-rotation mechanism is canceled by applying an external force about a predetermined value or more to the linear motion member. A sleeve fixed to the housing and into which the linear motion member is inserted;
The anti-rotation mechanism is provided on the inner peripheral surface of the sleeve along the axial direction and on the outer peripheral surface of the linear motion member, and is configured to move to the outer peripheral surface side by a load greater than a predetermined value. And a protruding part
The rotation of the linear motion member around the shaft with respect to the sleeve is restricted by the engagement between the groove and the projection, and the projection is moved by the groove when the rotational force of a predetermined value or more is applied to the linear motion member. The electric actuator according to claim 1, wherein the electric actuator is moved to the outer peripheral surface side of the moving member, and the engagement between the groove and the protrusion is released. A sleeve fixed to the housing and into which the linear motion member is inserted;
The anti-rotation mechanism is provided on the outer peripheral surface of the linear motion member along the axial direction, and provided on the inner peripheral surface of the sleeve, and is configured to move to the inner peripheral surface side by a load greater than a predetermined value. Consisting of a protruding part,
The rotation of the linear motion member around the shaft with respect to the sleeve is restricted by the engagement between the groove and the projection, and the projection is moved by the groove when the rotational force of a predetermined value or more is applied to the linear motion member. The electric actuator according to claim 1, wherein the electric actuator is moved to the outer peripheral surface side of the moving member, and the engagement between the groove and the protrusion is released. A sleeve fixed to the housing and into which the linear motion member is inserted;
The anti-rotation mechanism is provided on the inner circumferential surface of the sleeve along the axial direction and on the outer circumferential surface of the linear motion member, and is configured to move in the circumferential direction by a load greater than a predetermined value. And a protruding part
The rotation of the linear motion member around the axis with respect to the sleeve is restricted by the engagement between the groove and the projection, and the projection is caused to be circumferential by the groove when a rotational force of a predetermined value or more is applied to the linear motion member. The electric actuator according to claim 1, wherein the restriction of rotation about the axis of the linearly moving member with respect to the sleeve is released. A sleeve fixed to the housing and into which the linear motion member is inserted;
The anti-rotation mechanism is provided on the outer peripheral surface of the linear motion member along the axial direction and on the inner peripheral surface of the sleeve, and is configured to move in the circumferential direction by a load greater than a predetermined value. And a protruding part
The rotation of the linear motion member around the axis with respect to the sleeve is restricted by the engagement between the groove and the projection, and the projection is caused to be circumferential by the groove when a rotational force of a predetermined value or more is applied to the linear motion member. The electric actuator according to claim 1, wherein the restriction of rotation about the axis of the linearly moving member with respect to the sleeve is released.   The electric actuator according to claim 2, wherein the protrusion is configured by a ball member supported by an elastic body.   The electric actuator according to claim 4, wherein the protruding portion includes an annular member having a convex portion and a sliding member that supports the annular member.   The electric actuator according to any one of claims 1 to 7, wherein a plurality of the detent mechanisms are provided.

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