JP2019115159A - Electric actuator - Google Patents

Abstract

To reliably prevent the falling-off of a magnet from a holder installed on a linear movement part of an electric actuator.SOLUTION: An electric actuator includes: a motor 10; a nut 21 formed with a screw groove on an inner peripheral surface; a screw shaft 22 formed with a screw groove on an outer peripheral surface, and inserted into an inner periphery of the nut 21; a ball screw mechanism 20 for translating rotational motion of a rotary part R including the nut 21 to linear motion of a linear movement part L including the screw shaft 22; a casing 30 for accommodating the ball screw mechanism 20 inside; a holder 25 installed on an outer periphery of the linear movement part L and a magnet 51 retained to the holder; and a non-contact sensor 52 installed on the casing 30 and detecting a position of the magnet 51 in the shaft direction in the non-contact manner. A cover member (a slip bush 26) covering an outer periphery of the magnet 51 is installed on the linear movement part L.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electric actuator.

  BACKGROUND ART In recent years, electrification has been advanced for the purpose of saving labor and reducing fuel consumption of vehicles and the like. For example, a system that performs operations of an automatic transmission, a brake, a steering, etc. of an automobile by the power of a motor such as a motor has been developed and put into the market. An electric actuator using a screw mechanism (a ball screw mechanism or a slide screw mechanism) for converting a rotational movement generated by driving a motor into a linear movement is known as an actuator used for such applications.

  In this type of electric actuator, the operation target is connected to the linear movement portion of the screw mechanism, and the operation target is operated by advancing and retracting the linear movement portion. In this case, in order to operate the operation target accurately, a means for detecting the stroke amount (axial position) of the linear motion part may be provided. For example, in the electric actuator shown in Patent Document 1 below, a magnet (permanent magnet) is provided on the outer periphery of a screw shaft constituting a ball screw, and the position of the magnet is detected by a non-contact sensor provided on a casing. , The stroke amount of the screw shaft is detected.

JP, 2017-184482, A

  In the above-described electric actuator, the magnet is fixed to the outer periphery of the screw shaft via the holder. For example, when the magnet is fixed to the holder by adhesion, the number of steps is increased, which leads to the deterioration of the assembling property, and the magnet may be detached from the holder when the adhesion is released.

  For example, in Patent Document 1 described above, as shown in FIG. 10, the magnet 102 is mounted in the recess 101a provided in the holder 101, and the pair of claws 101b provided on both sides in the circumferential direction of the recess 101a The magnet 102 is held by engaging with the above. In this case, since the magnet 102 is held only by the engagement with the claw 101 b of the holder 101, it can not be said that the reliability is sufficient. Further, for example, when a magnet having a simple shape such as a cylindrical shape is used, it is difficult to adopt the configuration in which the magnet is held by the claws of the holder as described above.

  Therefore, the present invention has an object of reliably preventing detachment of a magnet from a holder attached to a linear movement part in an electric actuator which converts rotational movement of a motor part into linear movement of a shaft member and outputs the linear movement. .

  In order to solve the above problems, according to the present invention, a motor portion, a nut having a thread groove formed on an inner circumferential surface, and a screw shaft having a thread groove formed on an outer circumferential surface and inserted on the inner periphery of the nut A motion converting mechanism for converting rotational motion of a rotating portion including one of the nut and the screw shaft into linear motion of a linear moving portion including the other of the nut and the screw shaft; Non-contact sensor for detecting the axial position of the sensor target in a non-contact manner, attached to the casing housed inside, the holder attached to the outer periphery of the linear motion part and the sensor target held by this, and the casing And a cover member covering an outer periphery of the sensor target is attached to the linear movement portion.

  As described above, when the cover member covering the outer periphery of the sensor target is attached to the linear movement portion, the sensor target can be reliably prevented from falling off from the holder.

  In the above-described electric actuator, the cover member can be fixed using the rotation restricting member that restricts the rotation of the linear movement portion. Specifically, it is possible to provide a rotation restricting member that protrudes from the outer peripheral surface of the linear moving member and engages with the casing in the rotational direction, and fixes the cover member to the linear moving portion by the rotation restricting member. As described above, by fixing the linear movement portion and the cover member using the rotation restricting member that restricts the rotation of the linear movement portion, it is possible to avoid an increase in the number of parts and the number of steps.

  In the above-described electric actuator, it is preferable to slide the cover member attached to the linear movement portion and the inner circumferential surface of the casing. Thereby, when a moment load is applied to the linear movement portion, the moment load can be supported not only by the screw portion but also by the sliding portion between the cover member and the casing. It can reduce and prevent damage to the thread.

  The maximum stroke position of the linear motion portion can be defined, for example, by axially contacting the linear motion portion and the casing. At this time, if the linear motion part and the metal parts of the casing are abutted in the axial direction, the impact at the time of the abutment is large, so the screw part (screw groove and ball or screw grooves) bites, and then When moving the linear motion portion backward, it may be difficult to rotate the rotating portion in the reverse direction. Therefore, if the above cover member is formed of resin, and the resin cover member and the casing are brought into axial contact with each other to define the maximum stroke position of the linear movement portion, the biting of the screw portion may occur. Since it is difficult to cause the jamming, it is possible to smoothly retreat the linear motion part thereafter.

  If the motor unit of the electric actuator and the motion conversion mechanism are coaxially arranged, it is possible to reduce the size in the direction (radial direction) orthogonal to the axial direction, as compared to the case where these are arranged side by side in parallel. .

  As described above, in the electric actuator according to the present invention, by attaching the cover member covering the outer periphery of the sensor target to the linear movement portion, the sensor target can be reliably prevented from falling off from the holder.

It is a longitudinal cross-sectional view of the electrically-driven actuator which concerns on one Embodiment of this invention. It is a longitudinal cross-sectional view of the said electrically-driven actuator, and shows the cross section orthogonal to the cross section of FIG. It is a division perspective view of a direct-acting part of the above-mentioned electric actuator, and parts attached to this. It is XX sectional drawing of FIG. It is YY sectional drawing of FIG. It is a longitudinal cross-sectional view which shows the state which made the linear_motion | direct_drive part of the said electrically-driven actuator project most from a casing. It is a longitudinal cross-sectional view of the electrically-driven actuator which concerns on other embodiment. It is a disassembled perspective view of the holder of the electric actuator of FIG. 7, a magnet, and a cover member. It is sectional drawing of the holder of the electric actuator of FIG. 7, a magnet, and a cover member. It is sectional drawing of the conventional holder and magnet.

  Hereinafter, embodiments of the present invention will be described based on the drawings.

  FIGS. 1 and 2 are longitudinal sectional views of an electric actuator according to an embodiment of the present invention, each showing a cross section in a plane orthogonal to each other. The electric actuator includes a motor unit 10, a ball screw mechanism 20 as a motion conversion mechanism for converting the rotational movement of the rotary unit R driven by the motor unit 10 into linear movement of the linear movement unit L, the motor unit 10 and And a casing 30 for housing the ball screw mechanism 20 therein. In the following description, the moving direction (horizontal direction in FIGS. 1 and 2) of the linear motion portion L of the ball screw mechanism 20 is referred to as “axial direction”, and the linear motion portion L protrudes from the casing 30 in the axial direction. One side (left side in FIGS. 1 and 2) is referred to as “distal side”, and the opposite side (right side in FIGS. 1 and 2) as “proximal side”.

  The casing 30 has a cylindrical first case 31 provided on the front end side, a cylindrical second case 32 provided on the base end side, and a lid that closes an opening on the base end side of the second case 32. And 33. The first case 31, the second case 32, and the lid 33 are formed of metal or resin. In the present embodiment, the first case 31 and the second case 32 are formed of metal (in particular, aluminum alloy), and the lid 33 is formed of resin.

  The first case 31 is provided on the inner periphery of the small diameter portion 31a provided on the distal end side, the large diameter portion 31b provided on the base end side, the disk portion 31c that connects them, and the large diameter portion 31b. And a cylindrical portion 31d extending from the disc portion 31c to the proximal end side. In the illustrated example, the inner peripheral surface of the small diameter portion 31a and the inner peripheral surface of the cylindrical portion 31d are continuous to form a cylindrical surface. A seal member 36 is mounted at the end of the first case 31 to prevent foreign matter such as dust from entering the casing 30 and water. Specifically, the inner peripheral surface 31a1 at the end of the small diameter portion 31a of the first case 31 is made to face the outer peripheral surface of the linear movement portion L via a minute radial gap, and the inner peripheral surface 31a1 is formed A seal member 36 is disposed inside the groove.

  The second case 32 is provided on the inner periphery of the large diameter portion 32a provided on the tip end side, the small diameter portion 32b provided on the base end side, a disk portion 32c that connects them, and the large diameter portion 32a. And a cylindrical portion 32d extending from the disc portion 32c to the tip end side. The tip of the large diameter portion 32 a of the second case 32 and the base end of the large diameter portion 31 b of the first case 31 are fitted and fixed to each other. The opening on the proximal end side of the small diameter portion 32 b of the second case 32 is covered with a lid 33. A connector portion 34 for connecting a power line or a signal line to the stator 11 of the motor unit 10 is attached to the second case 32. In the illustrated example, the connector portion 34 is provided so as to penetrate the disc portion 32 c of the second case 32 in the axial direction.

  The motor unit 10 is a hollow brushless motor having a stator 11 and a rotor 12. The stator 11 is fixed to the inner peripheral surface of the casing 30, and is fixed to the inner peripheral surface of the large diameter portion 32a of the second case 32 in the illustrated example. The stator 11 has a stator core 11a formed of a plurality of electromagnetic steel plates stacked in the axial direction, a bobbin 11b made of an insulating material mounted on the stator core 11a, and a stator coil 11c wound around the bobbin 11b.

  The rotor 12 is disposed radially inward of the stator 11 so as to face the stator 11 via a gap. The rotor 12 has an annular rotor core 12a, a plurality of magnets 12b attached to the outer peripheral surface of the rotor core 12a, and an annular rotor inner 12c fixed to the inner peripheral surface of the rotor core 12a. The rotor core 12a is formed of, for example, a plurality of steel plates (for example, electromagnetic steel plates) stacked in the axial direction. The rotor inner 12c has a tubular shape, and the stopper 12d is fixed to the base end thereof. The axial length of the rotor inner 12c is longer than the axial length of the rotor core 12a, and bearings 41 and 42 are respectively mounted on outer peripheral surfaces of both end portions of the rotor inner 12c projecting to both sides in the axial direction from the rotor core 12a. In the present embodiment, the inner ring of the bearing 41 on the tip end side is fixed to the outer peripheral surface of the tip end portion of the rotor inner 12c, and the outer ring of the bearing 41 on the tip end side is fixed to the inner peripheral surface of the large diameter portion 31b of the first case 31. . Further, the inner ring of the bearing 42 on the base end side is fixed to the outer peripheral surface of the base end portion of the rotor inner 12 c, and the outer ring of the bearing 42 on the base end side is fixed to the inner peripheral surface of the cylindrical portion 32 d of the second case 32. Thus, the rotor inner 12 c is rotatably supported relative to the casing 30 by the bearings 41 and 42 interposed between the rotor inner 12 c and the casing 30.

  The ball screw mechanism 20 has a cylindrical nut 21 having a screw groove on the inner peripheral surface, a screw shaft 22 having a screw groove on the outer peripheral surface and inserted into the inner periphery of the nut 21, and a screw groove of the nut 21 And a plurality of balls 23 interposed between the screw shaft 22 and the thread groove. In the present embodiment, the nut 21 constitutes a rotating part R rotationally driven by the motor part 10, and the screw shaft 22 constitutes a part of a linear moving part L which linearly moves in the axial direction. The nut 21 and the screw shaft 22 are coaxially arranged with the rotation center of the motor unit 10 (the axial center of the rotor inner 12 c).

  The nut 21 is fixed to the inner peripheral surface of the rotor inner 12 c and is rotatable integrally with the rotor inner 12 c. The nut 21 is provided with means (piece, return tube, etc.) for circulating the ball 23 (not shown).

  The screw shaft 22 has a cylindrical shape. A solid shaft member 24 is inserted into the bore of the screw shaft 22 from the distal end side. The shaft member 24 protrudes from the screw shaft 22 to the tip side, and further protrudes from the casing 30 to the tip side. An abutment member 27 is attached to the proximal end of the screw shaft 22. The contact member 27 protrudes from the screw shaft 22 to the proximal side. The linear movement portion L of the ball screw mechanism 20 is configured by the screw shaft 22, the shaft member 24, the contact member 27 and the like.

  The above-described electric actuator is provided with a stroke detection unit that detects the axial position of the linear movement portion L. Specifically, a magnet 51 as a sensor target is attached to the outer periphery of the linear movement portion L, and a non-contact sensor 52 that detects the axial position of the magnet 51 in a non-contact manner is attached to the casing 30.

  The magnet 51 is attached to the outer periphery of the linear movement portion L. In the illustrated example, a plurality of (for example, two) magnets 51 are provided axially separated. The magnet 51 is attached to the outer periphery of the shaft member 24 via the holder 25. The holder 25 is formed of a nonmagnetic material, and is integrally formed of resin in the present embodiment. As shown in FIG. 3 and FIG. 4, the holder 25 is in the form of a partial cylindrical (a cross-sectional substantially C-shaped) discontinuous in the circumferential direction. A flat surface 25 b and a pair of cylindrical surfaces 25 a extending in the circumferential direction from the flat surface 25 b are provided on the inner peripheral surface of the holder 25. A cylindrical surface 24 a and a flat surface 24 b in which a part of the cylindrical surface 24 a is cut out are provided on the outer peripheral surface of the shaft member 24.

  The holder 25 is attached to the shaft member 24 by pushing the shaft member 24 into the opening of the holder 25. Specifically, the shaft member 24 is pushed into the opening of the holder 25 and elastically spread, and when the shaft member 24 is pushed to a predetermined position, the holder 25 elastically restores and the pair of cylindrical surfaces 25 a The holder 25 is attached to the shaft member 24 by holding it from both sides in the diameter direction. At this time, the flat surface 24 b of the outer peripheral surface of the shaft member 24 and the flat surface 25 b of the inner peripheral surface of the holder 25 are in close contact with each other, whereby the rotation of the holder 25 with respect to the shaft member 24 is restricted. According to the above configuration, the holder 25 can be attached to the outer periphery of the shaft member 24 with one touch.

  A recess 25 c for mounting the magnet 51 is provided on the outer peripheral surface of the holder 25 (see FIGS. 1 and 4). The recess 25 c is open at the outer peripheral surface of the holder 25. In the present embodiment, the outer peripheral surface of the magnet 51 and the inner peripheral surface of the recess 25 c do not engage in the radial direction. In the illustrated example, the magnet 51 has a cylindrical shape, and the inner peripheral surface of the recess 25 c of the holder 25 accommodating the same is a cylindrical surface that fits with the outer peripheral surface of the magnet 51. Further, in the illustrated example, the circumferential region where the flat surface 25b of the inner peripheral surface of the holder 25 is provided is thicker in the radial direction than the other circumferential regions, and the recess 25c is formed in this thick region. Is provided. Thereby, the strength reduction of holder 25 by providing crevice 25c is controlled. The recess 25 c is open to the outer peripheral surface of the holder 25, and the bottom of the recess 25 c is closed. As a result, since the resin holder 25 is interposed between the magnet 51 and the metal shaft member 24 in a state where the magnet 51 and the holder 25 are mounted on the shaft member 24, the magnetic force of the magnet 51 is transmitted to the shaft member 24. It becomes difficult to escape, and a drop in detection accuracy can be avoided.

  A slide bush 26 as a cover member is attached to the outer periphery of the linear movement portion L. The slide bush 26 is formed of a resin material. In the present embodiment, the slide bush 26 has a cylindrical shape (see FIG. 3). The slide bush 26 is provided, for example, on the outer periphery of the holder 25. The slide bush 26 of the present embodiment covers at least the opening of the recess 25c among the outer peripheral surface of the holder 25, and preferably covers the entire opening of the recess 25c, in the illustrated example, the entire outer peripheral surface of the holder 25 1 and 4). As a result, the magnet 51 is covered from the outer periphery by the sliding bush 26. Therefore, even when the holder 25 and the magnet 51 are not engaged in the radial direction as in the present embodiment, the magnet 51 is contained in the recess 25c of the holder 25. Can be held securely. Accordingly, it is possible to prevent the magnet 51 from falling off from the recess 25 c of the holder 25 at the time of assembly or operation of the linear motion actuator. In this case, the step of bonding the magnet 51 and the holder 25 is not necessary, and the assemblability is improved. When the magnet 51 and the holder 25 are bonded and the outer periphery of the magnet 51 is covered with the slide bush 26, the magnet 51 can be more reliably prevented from falling off the holder 25.

  The linear movement portion L is provided with a rotation prevention pin 61 as a rotation restriction member. The locking pin 61 is provided so as to protrude from the outer peripheral surface of the linear movement portion L (see FIG. 2). In the illustrated example, the locking pin 61 passes through the linear movement portion L in the diameter direction, and both ends thereof project from the outer peripheral surface of the linear movement portion L. In the present embodiment, the screw shaft 22, the shaft member 24, and the sliding bush 26 are fixed by the locking pin 61. Specifically, as shown in FIG. 3, through holes 22 a, 24 d and 26 a in the diametrical direction are provided in the screw shaft 22, the shaft member 24 and the slide bush 26 respectively. Then, as shown in FIG. 2, the screw shaft 22 is disposed on the outer periphery of the shaft member 24, and the base end of the sliding bush 26 is disposed on the outer periphery of the distal end of the screw shaft 22. 22a, 24d, and 26a are arranged in a straight line in the diametrical direction. By inserting the locking pin 61 into the through holes 22a, 24d and 26a in this state, the screw shaft 22, the shaft member 24, and the sliding bush 26 are integrated. The locking pin 61 is fixed by press-fitting into at least one of the through holes 22a, 24d and 26a. In the present embodiment, the locking pin 61 is press-fit into the through hole 22a of the screw shaft 22, and the through hole 24d of the shaft member 24 and the through hole 26a of the slide bush 26 are fitted with a gap therebetween.

  As shown in FIG. 5, the end of the detent pin 61 protruding from the outer peripheral surface of the linear movement portion L is fitted in an axial groove 35 provided on the inner peripheral surface of the casing 30. In the illustrated example, an axial groove 35 is formed on the inner peripheral surface of the small diameter portion 31a and the cylindrical portion 31d of the first case 31 of the casing 30 (see FIG. 2). A cylindrical collar 62 is provided at both ends of the locking pin 61, and the collar 62 is fitted into the axial groove 35 of the casing 30. The collar 62 is rotatable relative to the locking pin 61.

  The operation of the above-described electric actuator will be described. When the stator 11 of the motor unit 10 is energized, the rotor 12 and the nut 21 rotate integrally. The rotational movement of the nut 21 is transmitted to the screw shaft 22 via the ball 23, and the linear movement portion L including the screw shaft 22 and the shaft member 24 moves in the axial direction. At this time, the detent pin 61 (collar 62) fixed to the linear movement portion L engages with the axial direction groove 35 of the casing 30 in the rotational direction, so that the claw of the linear movement portion L accompanying the rotation of the nut 21 It is regulated. In addition, when the collar 62 provided on the locking pin 61 rotates and slides on the axial groove 35, the friction between the both is reduced. The tip of the shaft member 24 is provided with a hole (connection portion) 24c for connecting with the operation target (not shown) (see FIGS. 1 and 2), and the linear movement portion L advances and retracts in the axial direction The operation target is operated.

  In the present embodiment, the resin slide bush 26 provided on the outer periphery of the linear movement portion L and the inner peripheral surface of the casing 30 are fitted with a precise radial gap. The radial gap is very small, for example, sufficiently smaller than the radial gap between the inner peripheral surface 31a1 at the end of the first case 31 and the outer peripheral surface of the shaft member 24. As a result, when a load in the bending direction (a load in the direction perpendicular to the axial direction) is applied to the tip of the linear movement portion L, the linear movement portion L corresponds to the screw portion S of the ball screw mechanism 20 (nut 21 and screw shaft 22 As well as the power transmission portion between them, the contact portion (sliding portion) of the sliding bush 26 and the casing 30 is also supported. Therefore, the moment load applied to the screw portion S of the ball screw mechanism 20 is reduced, and damage to the screw portion S can be prevented. In particular, in the case of the top type ball screw mechanism 20 in which the ball 23 is circulated through the top provided on the nut 21, when a moment load is applied to the screw portion S, the ball 23 tries to ride on the hill portion between the screw grooves. By pressing against the edge of the screw groove, there is a possibility that excessive surface pressure may occur. In such a case, it is particularly effective to reduce the moment load applied to the screw portion S by sliding the slide bush 26 provided in the linear movement portion L and the casing 30.

  At this time, by providing the slide bush 26 made of resin on the linear movement portion L side, the axial length of the slide bush 26 is short as compared to the case where the slide bush 26 is provided on the casing 30 side. Cost reduction and weight reduction can be achieved by shortening.

  As described above, when the axial length of the slide bush 26 is shortened, there is a concern that the supporting force against the moment load applied to the linear movement portion L is insufficient. In particular, as shown in FIG. 6, when the linear movement portion L is moved to the extreme end side and the protrusion amount of the shaft member 24 from the casing 30 is maximized, the moment load applied to the screw portion S is maximized. At this time, the slide bush 26 moves toward the tip end, and the linear movement portion L is supported at two points (the slide bush 26 and the screw portion S) axially separated. As a result, even when the axial length of the slide bush 26 is shortened, sufficient supporting force against moment load can be obtained.

  Further, in the illustrated example, since the chamfered portion is provided on the outer periphery of the tip of the slide bush 26, even when the linear movement portion L is slightly inclined with respect to the casing 30 by applying a moment load, Edge contact with the inner circumferential surface of the small diameter portion 31 a of the first case 31 of the casing 30 can be avoided.

  Further, in the present embodiment, since the slide bush 26 is formed separately from the nut 21 and the screw shaft 22 which constitute the screw portion S, regardless of the structure of the screw portion S, the shape of the slide bush 26 and by extension It is possible to freely design the support structure of the linear movement portion L by the sliding bush 26 and the casing 30.

  In the above-described electric actuator, the stroke of the linear movement portion L is managed by detecting the position of the magnet 51 provided on the outer periphery of the linear movement portion L by the touch sensor 52 provided on the housing 30. However, when the non-contact sensor 52 fails due to any cause, the linear movement portion L abuts on the housing 30. At this time, in the present embodiment, the resin sliding bush 26 provided in the linear moving portion L and the first case 31 of the metallic casing 30 abut on each other in the axial direction, whereby the maximum stroke of the linear moving portion L The position is defined. In this manner, by bringing the sliding bush 26 made of resin softer than metal into contact with the casing 30, the screw portion S is engaged as compared with the case where the metals are brought into contact and the maximum stroke of the linear movement portion is defined. It becomes difficult to get involved. As a result, thereafter, the nut 21 can be smoothly rotated in the reverse direction to retract the linear movement portion L.

  When the linear movement portion L is moved to the most proximal end side, as shown in FIG. 1, the abutting member 27 provided at the proximal end of the screw shaft 22 is provided at the proximal end of the rotor inner 12 c of the motor unit 10. It abuts against the stopper 12d, whereby the movement of the linear movement portion L to the further proximal side is restricted. In this embodiment, the linear movement portion L is moved to a position where the proximal end of the linear movement portion L passes through the inner periphery of the motor portion 10 and is disposed closer to the proximal side than the bearing 42 supporting the proximal end portion of the rotor inner 12c. Can be retracted proximally. As described above, by utilizing the space on the inner diameter side of the motor unit 10 as a storage space for the linear motion portion L, the axial travel of the linear motion portion L can be maximized while the axial dimension of the electric actuator is reduced. Can be secured for a long time.

  Since the motor unit 10 and the ball screw mechanism 20 are coaxially arranged in the above-described electric actuator, the compactness in the direction (radial direction) orthogonal to the axial direction is made as compared with the case where these are arranged in parallel. Can be Further, in the present embodiment, the cylindrical portion 31d provided in the casing 30 is extended to the inner periphery of the rotor inner 12c, and the inner peripheral surface of the cylindrical portion 31d and the outer peripheral surface of the sliding bush 26 are slid. As a result, the linear movement portion L can be retracted to a position where the slide bush 26 is disposed on the inner periphery of the rotor inner 12c (inner periphery of the bearing 41 on the tip end side), thereby suppressing the axial dimension of the electric actuator. The stroke of the linear movement portion L can be lengthened.

  The present invention is not limited to the above embodiment. In the following embodiments, duplicate explanations of the same points as the above embodiments will be omitted.

  FIG. 7 shows an example in which the present invention is applied to a parallel axis type electric actuator in which the rotation axis of the motor unit 10 and the rotation axis of the ball screw mechanism 20 are arranged in parallel. In this embodiment, the gear 71 fixed to the output shaft of the motor unit 10 and the gear 72 fixed to the rotating unit R (nut 21) of the ball screw mechanism 20 mesh with each other, whereby the rotational driving force of the motor unit 10 is obtained. Is transmitted to the nut 21. In the illustrated example, the screw shaft 22 having a screw groove on the outer periphery is provided with a hole 22 b as a connecting portion connected to the operation target, and the screw shaft 22 functions as the linear movement portion L. One end of a bellows-like boot 80 is attached near the tip of the screw shaft 22, and the other end of the bellows-like boot 80 is attached to the opening of the casing 30 from which the screw shaft 22 protrudes.

  A holder 25 holding a magnet 51 is attached to the outer periphery of the screw shaft 22, and a cover member 90 is attached to the outer periphery thereof. In this embodiment, as shown in FIG. 8, the magnet 25 is mounted in the concave portions 25A1 and 25B1 formed on the outer peripheral surface of the holder members 25A and 25B and the holder 25 is formed by the pair of holder members 25A and 25B. Be done. A pair of claws 25A2 and 25B2 is provided on both sides in the circumferential direction of the concave portions 25A1 and 25B1 of the holder members 25A and 25B. As shown in FIG. 9, the pair of claws 25A2 and 25B2 is engaged with the side surface of the magnet 51 in the radial direction (vertical direction in FIG. 9) to prevent the magnet 51 from coming off from the holder 25.

  In the illustrated example, a cover member 90 is further provided on the outer periphery of the holder 25. The cover member 90 has a partially cylindrical shape in which a part in the circumferential direction is cut away and covers the entire area of the holder 25. As a result, the detachment of the magnet 51 from the holder 25 is more reliably prevented. In this embodiment, as shown in FIG. 7, a radial gap is provided between the cover member 90 and the casing 30, and they do not slide relative to each other.

  Further, in the embodiment shown in FIGS. 1 to 6, the cover member (slip bush 26) and the holder 25 are fixed to the linear movement portion L using the detent pin 61, but the invention is not limited thereto. 25 may be fixed to the linear movement portion L by adhesion or the like. In this case, the cover member and the holder 25 may be provided at a position axially separated from the locking pin 61.

  In the above embodiment, the rotating portion R of the ball screw mechanism 20 is configured by the nut 21 and the linear moving portion L is configured by the screw shaft 22 or the like. You may comprise a part and may comprise a linear_motion | direct_drive part with a nut. Also, the motion conversion mechanism is not limited to the ball screw mechanism, and for example, a slide screw mechanism may be adopted.

DESCRIPTION OF SYMBOLS 10 motor part 11 stator 12 rotor 20 ball screw mechanism (motion conversion mechanism)
21 nut 22 screw shaft 23 ball 24 shaft member 25 holder 26 sliding bush (cover member)
30 Casing 51 Magnet (Sensor Target)
52 Non-contact sensor 61 Locking pin (rotation restricting member)
L Linear moving part R Rotating part S Threaded part

Claims (5)

It has a motor section, a nut having a thread groove formed on the inner circumferential surface, and a thread shaft having an outer circumferential surface on which a thread groove is formed and inserted into the inner circumference of the nut, one of the nut and the thread shaft A motion conversion mechanism for converting the rotational motion of the rotary portion including the first to the linear motion of the linear motion portion including the other of the nut and the screw shaft; a casing for accommodating the motion conversion mechanism therein; An electric actuator comprising: a holder attached to an outer periphery and a sensor target held by the holder; and a noncontact sensor attached to the casing and detecting an axial position of the sensor target in a noncontact manner.
The electric actuator which attached the cover member which covers the perimeter of the sensor target to the direct-acting part. There is provided a rotation restricting member which protrudes from the outer peripheral surface of the linear movement portion and engages with the casing in the rotational direction.
The electric actuator according to claim 1, wherein the cover member is fixed to the linear movement portion by the rotation restricting member.   The electric actuator according to claim 1, wherein the outer peripheral surface of the cover member is slid with the inner peripheral surface of the casing. The cover member is formed of resin,
The electric actuator according to any one of claims 1 to 3, wherein the maximum stroke position of the linear movement portion is defined by bringing the cover member and the casing into axial contact with each other. The electric actuator according to any one of claims 1 to 4, wherein the motor unit and the motion conversion mechanism are coaxially disposed.

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