JP2016114118A - Electric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric actuator which secures the rigidity and durability of a housing, is suppressed in cost by using a simple screw shaft whirl-stop mechanism, and improved in reliability.SOLUTION: A cylindrical bag hole 12 is formed at a housing 2b, a bottomed cylindrical sleeve 17 in which a recessed groove 17 extending to an axial direction is fit up to a bottom 33 of the bag hole 12 at an internal periphery, the sleeve 17 is formed into a cup shape which is composed of a large-diameter part 29 and a bottomed cylinder part 30 extending to the axial direction from the large-diameter part 29 at one end, a flat part 29a is formed at a position opposing the large-diameter part 29, an opening part 31 along a shape of the large-diameter part 29 of the sleeve 17 is formed at the bag hole 12, the sleeve 17 is whirl-stopped with respect to the bag hole 12, a lock pin 15 arranged at an end of a screw shaft 10 is engaged with the recessed groove 17a, the screw shaft 10 is non-rotatably movably supported in the axial direction, and a bottom 32 of the sleeve 17 is formed into a simple circular arc shape.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electric actuator provided with a ball screw mechanism used in a drive unit of a general industrial electric motor or automobile, and more specifically, a rotation input from an electric motor is applied to a ball screw mechanism in an automobile transmission or a parking brake. The present invention relates to an electric actuator that converts linear motion of a drive shaft via

  In electric actuators used in various drive units, a gear mechanism such as a trapezoidal screw or a rack and pinion is generally used as a mechanism for converting the rotational motion of the electric motor into a linear motion in the axial direction. Since these conversion mechanisms involve a sliding contact portion, the power loss is large, and it is necessary to increase the size of the electric motor and increase the power consumption. Therefore, a ball screw mechanism has been adopted as a more efficient actuator.

  2. Description of the Related Art Conventionally, for example, an electric actuator shown in FIG. 5 is known as an electric actuator used by converting the rotation of an electric motor into a linear motion through a ball screw mechanism. The electric actuator 51 includes a cylindrical housing 52, an electric motor M attached to the housing 52, an intermediate gear 54 meshing with an input gear 53 attached to a motor shaft 53a of the electric motor M, and an intermediate A reduction mechanism 56 comprising an output gear 55 meshing with the gear 54 and a ball screw mechanism 58 for converting the rotational movement of the electric motor M into the linear movement of the drive shaft 57 via the reduction mechanism 56 are provided. .

  The housing 52 includes a first housing 52a and a second housing 52b abutted on the end surface thereof, and is integrally fixed by a fixing bolt (not shown). An electric motor M is attached to the first housing 52a, and a through hole 61 and a bag hole 62 for accommodating the screw shaft 60 are formed at the abutting portions of the first housing 52a and the second housing 52b. Is formed.

  The motor shaft 53a of the electric motor M has an input gear 53 attached to its end portion so as not to be relatively rotatable by press fitting, and is rotatably supported by a rolling bearing 63 attached to the second housing 52b. The output gear 55 that meshes with the intermediate gear 54 is integrally fixed to a nut 68 constituting the ball screw mechanism 58 via a key 64.

  The drive shaft 57 is configured integrally with a screw shaft 60 that constitutes the ball screw mechanism 58, and a locking pin 65 is implanted at one end of the drive shaft 57. Further, a sleeve 67 described later is fitted into the bag hole 62 of the second housing 52b. The sleeve 67 is positioned and fixed in the axial direction by a retaining ring 66 attached to the bag hole 62 of the second housing 52b. Then, the engaging pin 65 of the screw shaft 60 is engaged with the concave grooves 67a and 67a formed in the axial direction at positions facing the circumferential direction of the sleeve 67, so that the screw shaft 60 cannot rotate and moves in the axial direction. Supported as possible.

  The ball screw mechanism 58 includes a screw shaft 60 and a nut 68 that is externally inserted to the screw shaft 60 via a ball 69. The screw shaft 60 has a spiral thread groove 60a formed on the outer periphery. On the other hand, the nut 68 is extrapolated to the screw shaft 60, and a helical screw groove 68a corresponding to the screw groove 60a of the screw shaft 60 is formed on the inner periphery, and a large number of nuts 68 are formed between the screw grooves 60a and 68a. A ball 69 is accommodated so as to roll freely. The nut 68 is supported on the housings 52a and 52b via the two support bearings 59 and 59 so as to be rotatable and not movable in the axial direction. 68b is a piece member that constitutes a circulation member by connecting the thread groove 68a of the nut 68, and a large number of balls 69 can circulate infinitely by this piece member 68b.

  As shown in FIGS. 6A and 6B, the sleeve 67 that supports the screw shaft 60 so as not to rotate and is capable of axial movement is fitted into the bag hole 62 of the second housing 52b. The one end portion includes a large diameter portion 70 and a cylindrical portion 71 extending from the large diameter portion 70 in the axial direction. The large-diameter portion 70 is provided with flat portions 70a and 70a facing each other, and a protruding ridge 72 extending in the axial direction is formed slightly projecting at the approximate center of the flat portion 70a.

  On the other hand, a flat surface (not shown) corresponding to the flat portion 70 a of the sleeve 67 is formed in the bag hole 62 of the second housing 52 b into which the sleeve 67 is fitted. Then, when the flat portion 70a of the sleeve 67 is lightly press-fitted into the flat surface, the sleeve 67 can be prevented from rotating without play.

  Further, the sleeve 73 shown in FIG. 7 is formed in a cup shape, and has a bottom portion 74 that is fitted to the bottom portion of the bag hole (not shown), and extends in an axial direction to a position facing the inner periphery. The concave grooves 67a and 67a with which locking pins (not shown) are engaged are formed by grinding. Further, flat surfaces 75 and 75 are formed at positions facing the outer periphery and substantially orthogonal to the concave groove 67a.

  On the other hand, in the bag hole of the second housing (not shown), a flat portion is formed corresponding to the flat surfaces 75, 75 of the sleeve 73, and the flat portion 75 and the flat surface 75 of the sleeve 73 are fitted to each other. 73 is a detent.

  In such a conventional electric actuator 51, in order to ensure the strength and rigidity of the sleeves 67 and 73, the concave groove 67a is formed at a position shifted by 90 ° from the flat portion 70a or the flat surfaces 75 and 75. Therefore, it is possible to optimize the amount of allowable backlash caused by wear and wear of the press-fitted portion over time (for example, see Patent Document 1).

JP 2014-80995 A

  In such a conventional electric actuator 51, the relationship between the bag hole 62 of the second housing 52b and the sleeve 67 is such that the flat portion 70a or the flat surface 75 formed in the large-diameter portion 70 of the sleeve 67 surrounds the sleeves 67 and 73. Stopped.

  In this type of electric actuator, there is an event that the tip of the screw shaft 60 collides with the bottom 76 of the second housing 52b during operation or when the system is down. However, in the case of the sleeve 67, the sleeve 67 does not have a bottom. When a load is applied from the shaft 60, the screw shaft 60 may directly collide with the bottom 76 of the second housing 52b, and excessive stress may be generated. On the other hand, in the case of the sleeve 73, since the bottom 74 of the sleeve 73 has an irregular shape, the bottom 74 may collide with the bottom 76 of the second housing 52b, and stress may concentrate on the corner of the bottom 76. There is a problem that the strength and durability of the second housing 52b are reduced due to the concentration of the stress.

  The present invention has been made in view of such problems of the prior art, and pays attention to the fact that the bottom is made into a simple circle so that stress due to collision does not concentrate on the bottom of the bag hole of the housing. An object of the present invention is to provide an electric actuator that ensures durability and is reduced in cost by a simple screw shaft detent mechanism and improved in reliability.

  In order to achieve such an object, the invention according to claim 1 of the present invention includes an aluminum alloy housing, an electric motor attached to the housing, and a rotational force of the electric motor via a motor shaft. A transmission speed reduction mechanism, and a ball screw mechanism that converts the rotational motion of the electric motor to a linear motion in the axial direction of the drive shaft via the speed reduction mechanism, the ball screw mechanism being supported by the housing. A nut rotatably supported through a bearing and non-movable in the axial direction and having a helical thread groove formed on the inner periphery, and inserted into the nut through a number of balls, are coaxial with the drive shaft. In an electric actuator composed of a screw shaft formed with a spiral screw groove corresponding to the screw groove of the nut on the outer periphery, a cylindrical bag hole is formed in the housing, A bottomed cylindrical sleeve formed with a groove extending in the axial direction on the periphery is fitted to the bottom of the bag hole to prevent the sleeve from rotating against the bag hole, and the groove is A locking pin provided at an end of the screw shaft is engaged to support the screw shaft so as not to rotate and to be movable in the axial direction, and the bottom portion of the sleeve is formed in a simple circular shape.

  As described above, a reduction mechanism that transmits the rotational force of the electric motor and a ball screw mechanism that converts the rotational movement of the electric motor into the linear movement in the axial direction of the drive shaft via the reduction mechanism are provided. , A nut that is rotatably supported through a support bearing mounted on the housing and is not movable in the axial direction, and has a helical thread groove formed on the inner periphery, and the nut is inserted through a number of balls. A cylindrical bag hole is formed in the housing of the electric actuator composed of a screw shaft that is coaxially integrated with the drive shaft and has a spiral screw groove corresponding to the screw groove of the nut on the outer periphery. The bottomed cylindrical sleeve having a groove extending in the axial direction on the inner periphery is fitted to the bottom of the bag hole to prevent the sleeve from rotating against the bag hole, and the screw shaft is inserted into the groove. Lock pin provided at the end of Since the screw shaft is engaged and supported so as to be non-rotatable and movable in the axial direction, and the bottom of the sleeve is formed in a simple circular shape, the bottom of the housing (bag hole) also has a simple circular shape and operates. Even if the tip of the screw shaft moves to the bottom side of the housing when the system is down or the system goes down, the screw shaft does not directly collide with the bottom portion, but collides with the bottom of the sleeve, so excessive stress is generated at the bottom of the housing. In addition, it is possible to prevent stress from concentrating on the corners of the bottom, ensuring the strength and durability of the housing and reducing the cost with a simple screw shaft detent mechanism. An electric actuator with improved reliability can be provided.

  According to a second aspect of the present invention, the sleeve is formed in a cup shape including a large-diameter portion at one end portion and a bottomed cylindrical portion extending in the axial direction from the large-diameter portion. If the flat part is formed in the diameter part and the opening part along the shape of the large diameter part of the sleeve is formed in the bag hole, the sleeve is prevented from rotating with a simple configuration with respect to the bag hole. be able to.

  According to a third aspect of the present invention, the sleeve includes a cylindrical sleeve main body and a separate bottom plate fitted to the sleeve main body, and the sleeve main body is large at one end. It comprises a diameter portion and a cylindrical portion extending in the axial direction from the large diameter portion, and a flat portion is formed in the large diameter portion, and an opening along the shape of the large diameter portion of the sleeve body in the bag hole If the bottom plate is formed in a simple circle along the shape of the cylindrical portion of the sleeve body, the tip of the screw shaft does not directly collide with the bottom of the housing, and the bottom plate of the sleeve Because of the collision, the stress due to the collision is relaxed, the strength and durability of the housing are ensured, the shape and structure of the sleeve body are simplified, and the mass productivity is further improved.

  According to a fourth aspect of the present invention, a pair of protrusions are integrally formed on the side surface of the bottom plate that is fitted to the end of the sleeve body, and these protrusions are engaged with the concave grooves of the sleeve body. If combined, the bottom plate can be integrally fitted to the sleeve body with a simple structure.

  Further, if the sleeve is formed of a sintered alloy formed by MIM as in the invention described in claim 5, even if the sleeve has a high workability and a complicated shape, it can be easily and accurately obtained. Can be formed into shapes and dimensions.

  An electric actuator according to the present invention includes an aluminum alloy housing, an electric motor attached to the housing, a reduction mechanism that transmits the rotational force of the electric motor via a motor shaft, and the reduction mechanism. A ball screw mechanism that converts the rotational motion of the electric motor into a linear motion in the axial direction of the drive shaft, and the ball screw mechanism is rotatable through a support bearing mounted on the housing and moved in the axial direction. A nut that is unsupported and has a spiral thread groove formed on the inner periphery, and is inserted into the nut via a number of balls and integrated coaxially with the drive shaft. In the electric actuator composed of a screw shaft formed with a helical screw groove corresponding to the groove, a cylindrical bag hole is formed in the housing, and a concave groove extending in the axial direction on the inner periphery The formed bottomed cylindrical sleeve is fitted to the bottom of the bag hole so that the sleeve is prevented from rotating with respect to the bag hole, and is provided at the end of the screw shaft in the concave groove. Since the locking pin is engaged and the screw shaft is supported so as to be non-rotatable and axially movable, and the bottom portion of the sleeve is formed in a simple circular shape, the bottom portion of the housing (bag hole) is also simple. Even if the tip of the screw shaft moves toward the bottom of the housing during operation or when the system is down, the screw shaft does not directly collide with the bottom but collides with the bottom of the sleeve. Excessive stress can be prevented, and stress can be prevented from concentrating at the bottom corner, ensuring the strength and durability of the housing, and a simple screw shaft detent mechanism. Reduce costs , It is possible to provide an electric actuator with improved reliability.

It is a longitudinal section showing one embodiment of an electric actuator concerning the present invention. It is a longitudinal cross-sectional view which expands and shows the ball screw mechanism of FIG. (A) is a perspective view which shows the sleeve of FIG. 1, (b) is a perspective view which shows the bag hole part of the housing which inserts the sleeve of (a). 3A is a front view, FIG. 3B is a cross-sectional view taken along line IV-IV in FIG. 3A, and FIG. 3C is a rear view. It is a longitudinal cross-sectional view which shows the conventional electric actuator. (A) is a front view which shows the sleeve of FIG. 5, (b) is a side view of (a). 6 shows a modification of the sleeve of FIG. 6, (a) is a front view, and (b) is a longitudinal sectional view taken along line VII-VII in (a).

  An aluminum alloy housing, an electric motor attached to the housing, a reduction mechanism that transmits the rotational force of the electric motor via a motor shaft, and the rotational movement of the electric motor is driven via the reduction mechanism A ball screw mechanism for converting the shaft into a linear motion in the axial direction.The ball screw mechanism is supported by a pair of support bearings mounted on the housing so as to be rotatable and non-movable in the axial direction. A nut having a spiral thread groove formed on the circumference, and a nut corresponding to the screw groove of the nut on the outer periphery, which is inserted into the nut via a large number of balls and is coaxially integrated with the drive shaft. In the electric actuator comprising a screw shaft that is formed so as to be non-rotatable and supported so as to be axially movable with respect to the housing, a cylindrical bag hole is formed in the housing. A bottomed cylindrical sleeve formed with a concave groove extending in the axial direction on the inner periphery is fitted to the bottom of the bag hole, and the sleeve has a large diameter portion at one end and the large diameter portion. Formed in the shape of a cup having a bottomed cylindrical portion extending in the axial direction from the flat portion, and a flat portion is formed at a position opposed to the large diameter portion, along the shape of the large diameter portion of the sleeve in the bag hole. An opening is formed so that the sleeve is prevented from rotating with respect to the bag hole, and a locking pin provided at an end of the screw shaft is engaged with the concave groove so that the screw shaft cannot rotate. The sleeve is supported so as to be axially movable, and the bottom of the sleeve is formed in a simple circular shape.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 is a longitudinal sectional view showing an embodiment of an electric actuator according to the present invention, FIG. 2 is an enlarged longitudinal sectional view showing a ball screw mechanism of FIG. 1, and FIG. 3 (a) is a sleeve of FIG. (B) is a perspective view showing a bag hole portion of a housing into which the sleeve of (a) is inserted, FIG. 4 shows a modification of the sleeve of FIG. 3 (a), (a) A front view, (b) is a cross-sectional view along line IV-IV in (a), and (c) is a rear view.

  As shown in FIG. 1, the electric actuator 1 meshes with a cylindrical housing 2, an electric motor M attached to the housing 2, and an input gear 3 attached to a motor shaft 3a of the electric motor M. A speed reduction mechanism 6 comprising an intermediate gear 4 and an output gear 5 meshed with the intermediate gear 4, and a ball for converting the rotational motion of the electric motor M into an axial linear motion of the drive shaft 7 via the speed reduction mechanism 6. And a screw mechanism 8.

  The housing 2 is made of an aluminum alloy such as A6063TE or ADC12, and includes a first housing 2a and a second housing 2b abutted on the end face thereof, and is fixed integrally by a fixing bolt (not shown). . An electric motor M is attached to the first housing 2a, and a through hole 11 for accommodating the screw shaft 10 (drive shaft 7) is provided at an abutting portion between the first housing 2a and the second housing 2b. A bag hole 12 is formed.

  The motor shaft 3a of the electric motor M is rotatably supported by a rolling bearing 13 composed of a deep groove ball bearing mounted on the second housing 2b. Yes. The output gear 5 that meshes with the intermediate gear 4 that is a spur gear is integrally fixed to a nut 18 that constitutes a ball screw mechanism 8 described later via a key 14.

  The drive shaft 7 is formed integrally with a screw shaft 10 constituting the ball screw mechanism 8, and a locking pin 15 is implanted at one end portion (right end portion in the figure) of the drive shaft 7. A sleeve 17 described later is fitted into the bag hole 12 of the second housing 2b. The sleeve 17 is fitted to the bottom 33 of the bag hole 12 of the second housing 2b and is positioned and fixed in the axial direction by a retaining ring 16 attached to the opening of the bag hole 12. Then, the locking pin 15 of the screw shaft 10 is engaged with the concave grooves 17a and 17a formed in the axial direction at positions facing the circumferential direction of the sleeve 17, so that the screw shaft 10 is not rotatable and moves in the axial direction. Supported as possible.

  The locking pin 15 is made of a high carbon chromium bearing steel such as SUJ2 or a carburized bearing steel such as SCr435, and a carbonitriding layer having a carbon content of 0.80 wt% or more and 58 HRC or more is formed on the surface thereof. . In addition, by applying the needle roller used for the needle roller bearing to the locking pin 15, a surface hardness of 58HRC or more can be obtained, the wear resistance is excellent, the availability is good, and the cost is low. Can be achieved.

  In the present embodiment, the retaining ring 16 is tapered so that the tip thereof is tapered and the inner diameter thereof does not interfere with the locking pin 15. As a result, when the retaining ring 16 is attached to the retaining ring groove, the retaining ring 16 presses the sleeve 17 to the opposite side (right side in the figure) while abutting against the end surface of the sleeve 17, so that the sleeve 17 can be positioned and fixed without backlash in the axial direction. In addition, even if the locking pin 15 approaches the opening of the concave groove 17a of the sleeve 17 as the screw shaft 10 moves in the axial direction, the retaining ring 16 and the locking pin 15 do not interfere with each other. Although not shown in the figure, the axial play of the sleeve 17 can be prevented even if the end face of the sleeve 17 is pressed with a wave washer instead of the retaining ring 16.

  Reference numeral 22 denotes a gear shaft, which is implanted in the first and second housings 2a and 2b. The intermediate gear 4 is rotatably supported on the gear shaft 22 via a rolling bearing 23. Of the end portions of the gear shaft 22, for example, when the end portion on the first housing 2 a side is press-fitted, the end portion on the second housing 2 b side is set as a clearance fit, thereby misalignment (assembly error). And smooth rotation performance can be ensured. In the present embodiment, the rolling bearing 23 includes a steel plate press-made outer ring 24 that is press-fitted into the inner diameter of the intermediate gear 4, and a plurality of needle rollers 26 that are rotatably accommodated in the outer ring 24 via a cage 25. It is comprised with what is called a shell type needle roller bearing provided with. Thereby, availability is high and cost reduction can be achieved.

  Further, ring-shaped washers 27 and 27 are mounted on both sides of the intermediate gear 4 to prevent the intermediate gear 4 from directly contacting the first and second housings 2a and 2b. Furthermore, the width of the rolling bearing 23 is set smaller than the tooth width of the intermediate gear 4. Thereby, wear and deformation of the bearing side surface due to friction can be prevented, and smooth rotation performance can be obtained.

  As shown in an enlarged view in FIG. 2, the ball screw mechanism 8 includes a screw shaft 10 and a nut 18 that is externally inserted to the screw shaft 10 via a ball 19. The screw shaft 10 has a spiral thread groove 10a formed on the outer periphery. On the other hand, the nut 18 is extrapolated to the screw shaft 10, and a helical screw groove 18 a corresponding to the screw groove 10 a of the screw shaft 10 is formed on the inner periphery, and a large number of screws 18 a and 18 a are formed between these nuts 18. A ball 19 is accommodated so as to roll freely. The nut 18 is supported to the housings 2a and 2b via the two support bearings 20 and 20 so as to be rotatable and not movable in the axial direction. Reference numeral 21 denotes a piece member that constitutes a circulation member by connecting the thread grooves 18a of the nut 18, and the piece member 21 allows an infinite circulation of a large number of balls 19.

  The cross-sectional shape of each of the thread grooves 10a and 18a may be a circular arc shape or a gothic arc shape, but here, a gothic arc shape that allows a large contact angle with the ball 19 and a small axial clearance can be set. Is formed. Thereby, the rigidity with respect to an axial load becomes high and generation | occurrence | production of a vibration can be suppressed.

  The nut 18 is made of case-hardened steel such as SCM415 or SCM420, and its surface is subjected to hardening treatment in a range of 55 to 62 HRC by vacuum carburizing and quenching. Thereby, the buffing etc. for the scale removal after the heat treatment can be omitted, and the cost can be reduced. On the other hand, the screw shaft 10 is made of medium carbon steel such as S55C or case-hardened steel such as SCM415 or SCM420, and its surface is hardened in the range of 55 to 62 HRC by induction hardening or carburizing hardening.

  The output gear 5 constituting the speed reduction mechanism 6 is integrally fixed to the outer peripheral surface 18b of the nut 18, and two support bearings 20 and 20 are press-fitted on both sides of the output gear 5 via a predetermined shimiro. . Thereby, even if a thrust load is applied from the drive shaft 7, it is possible to prevent the axial displacement between the support bearings 20 and 20 and the output gear 5. Further, the two support bearings 20 and 20 are constituted by sealed deep groove ball bearings having shield plates 20a and 20a attached to both ends, and leakage of the lubricating grease enclosed in the bearings to the outside and from the outside This prevents wear powder from entering the bearing.

  Further, in the present embodiment, the support bearing 20 that rotatably supports the nut 18 is composed of deep groove ball bearings having the same specifications, and thus is loaded from the drive shaft 7 through the thrust load and the output gear 5 described above. Both radial loads can be applied, and confirmation work for preventing misassembly during assembly can be simplified, and assembling workability can be improved. Here, the “deep groove ball bearing of the same specification” refers to a bearing having the same inner diameter, outer diameter, width dimension, rolling element size, number, bearing internal clearance, and the like.

  In addition, here, one of the pair of support bearings 20, 20 is mounted on the first housing 2 a via a washer 28 made of a ring-shaped elastic member. The washer 28 is formed by press working from an austenitic stainless steel plate (JIS standard SUS304 type or the like) having high strength and wear resistance or a rust-proof cold rolled steel plate (JIS standard SPCC type or the like). It consists of a wave washer. The inner diameter D is formed larger than the inner ring outer diameter d of the support bearing 20. As a result, the axial backlash of the pair of support bearings 20 and 20 can be eliminated, smooth rotation performance can be obtained, and the washer 28 is in contact with only the outer ring of the support bearing 20 and is an inner ring that becomes a rotating ring. Therefore, even if a reverse thrust load is generated and the nut 18 is pressed against the first housing 2a, the inner ring of the support bearing 20 is prevented from coming into contact with the housing 2a and the frictional force is prevented from increasing, and the locked state Can be surely prevented.

  As shown in FIG. 3A, the sleeve 17 is fitted in the bag hole 12 of the second housing 2b and supports a screw shaft (not shown) so as not to rotate and to be movable in the axial direction. It is formed in a cup shape including a large-diameter portion 29 at one end and a bottomed cylindrical portion 30 extending from the large-diameter portion 29 in the axial direction. The large diameter portion 29 is formed with flat portions 29a and 29a at opposing positions. In order to ensure the strength and rigidity of the sleeve 17, the flat portions 29 a and 29 a are formed at positions shifted from the concave grooves 17 a and 17 a by 90 °.

  The sleeve 17 is made of a sintered alloy prepared by adjusting a metal powder into a plastic shape and molded by an injection molding machine. In this injection molding, first, metal powder and a binder made of plastic and wax are kneaded by a kneader, and the kneaded product is granulated into pellets. The granulated pellets are molded by so-called MIM (Metal Injection Molding), which is supplied to a hopper of an injection molding machine and pushed into a mold in a heated and melted state. A sintered alloy formed by such an MIM can be easily and accurately formed into a desired shape / dimension even if it has a high workability and a complicated shape.

  As the metal powder, a material that can be subsequently carburized and hardened, for example, C (carbon) is 0.13 wt%, Ni (nickel) is 0.21 wt%, Cr (chromium) is 1.1 wt%, Cu (copper) Exemplifies SCM415 which is 0.04 wt%, Mn (manganese) is 0.76 wt%, Mo (molybdenum) is 0.19 wt%, Si (silicon) is 0.20 wt%, and the rest is Fe (iron). Can do. The sleeve 42 is performed by adjusting the carburizing quenching and tempering temperatures. In addition to this, the sleeve 42 is made of a material containing 3.0 to 10.0 wt% of Ni and having excellent workability and corrosion resistance (FEN8 of Japanese Powder Metallurgy Industry Standard), or C of 0.07 wt%. %, Cr is 17 wt%, Ni is 4 wt%, Cu is 4 wt%, and the remainder is precipitation hardened stainless steel SUS630 made of Fe or the like. This SUS630 can appropriately increase the surface hardness in the range of 20 to 33 HRC by solution heat treatment, and can ensure toughness and high hardness. The sleeve 17 is formed by cold forging from medium carbon steel such as S55C or case-hardened steel such as SCM415 or SCM420, and the surface is hardened in the range of 55 to 62HRC by induction quenching or carburizing quenching. Also good.

  On the other hand, the bag hole 12 of the second housing 2b into which the sleeve 17 is fitted is formed in a cylindrical shape corresponding to the cylindrical portion 30 of the sleeve 17 as shown in FIG. An opening 31 along the shape of the diameter portion 29 is formed by an aluminum die casting method. That is, flat surfaces 31 a and 31 a corresponding to the flat portion 29 a of the sleeve 17 are formed in the opening 31. The flat portion 31a of the sleeve 17 is lightly press-fitted into the flat surface 31a, so that the sleeve 17 can be prevented from rotating with respect to the second housing 2b without play. In this example, the flat portion 29a of the sleeve 17 and the flat surface 31a of the second housing 2b are opposed to each other. However, the sleeve 17 can be basically prevented from being rotated at one place.

  Here, the sleeve 17 according to the present invention includes a cylindrical portion 30 and a bottom portion 32 that are integrally provided. The bottom portion 32 is formed in a simple circular shape that continues to the cylindrical portion 30. As a result, the bottom 33 of the second housing 2b with which the bottom 32 of the sleeve 17 abuts also becomes a simple circle, and the tip of the screw shaft moves toward the bottom 33 of the second housing 2b during operation or when the system is down. However, the screw shaft does not directly collide with the bottom 33 but collides with the bottom 32 of the sleeve 17 (see FIG. 1). Accordingly, it is possible to prevent an excessive stress from being generated at the bottom 33 of the second housing 2b and to concentrate the stress at the corner of the bottom 33, and the strength of the second housing 2b can be prevented. It is possible to provide an electric actuator that ensures durability and is reduced in cost by a simple screw shaft detent mechanism and improved in reliability.

  A sleeve 34 shown in FIG. 4 is a modification of the sleeve 17 described above. The sleeve 34 includes a cylindrical sleeve main body 35 and a separate bottom plate (bottom portion) 36 fitted to the sleeve main body 35, as shown in FIG. The sleeve body 35 includes a large-diameter portion 29 at one end and a cylindrical portion 30 extending in the axial direction from the large-diameter portion 29, as shown in (a) and (b). Flat portions 29a and 29a are formed on the outer periphery of the large-diameter portion 29 at positions facing each other, and concave grooves 17a and 17a are formed at positions substantially orthogonal to the flat portion 29a.

  The bottom plate 36 of the sleeve 34 is formed in a simple circular shape along the shape of the cylindrical portion 30 of the sleeve main body 35 and is fitted to the end of the sleeve main body 35 as shown in (b) and (c). A pair of protrusions 36a, 36a are integrally formed. These protrusions 36 a and 36 a engage with the concave grooves 17 a and 17 a of the sleeve body 35, so that the bottom plate 36 is fitted to the sleeve body 35. Accordingly, the bottom plate 36 can be integrally fitted to the sleeve main body 35 with a simple structure, and the sleeve 34 has a two-body structure of the sleeve main body 35 and the bottom plate 36. The tip of the screw shaft does not directly collide with the bottom of the second housing, but collides with the bottom plate 36 of the sleeve 34, so the stress due to the collision is alleviated and the strength and durability of the second housing are ensured. In addition, the shape and structure of the sleeve main body 35 are simplified, and the mass productivity is further improved.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.

  An electric actuator according to the present invention includes a ball screw mechanism that is used in a drive unit of a general industrial electric motor, an automobile, or the like, and that converts a rotational input from an electric motor into a linear motion of a drive shaft via the ball screw mechanism. Applicable to electric actuators.

DESCRIPTION OF SYMBOLS 1 Electric actuator 2 Housing 2a 1st housing 2b 2nd housing 3 Input gear 3a Motor shaft 4 Intermediate gear 5 Output gear 6 Reduction mechanism 7 Drive shaft 8 Ball screw mechanism 10 Screw shaft 10a, 18a Screw groove 11 Through-hole 12 Bag Holes 13 and 23 Rolling bearing 14 Key 15 Locking pin 16 Retaining ring 17 and 34 Sleeve 17a Groove 18 Nut 18b Nut outer peripheral surface 19 Ball 20 Support bearing 20a Shield plate 21 Piece member 22 Gear shaft 24 Outer ring 25 Cage 26 Needle Rollers 27, 28 Washers 29 Large diameter portion 29a Flat portion 30 Cylindrical portion 31 Opening portion 31a of bag hole Flat surface 32 Bottom portion of sleeve 33 Bottom portion of bag hole 35 Sleeve body 36 Bottom plate 36a Protrusion 51 Electric actuator 52 Housing 52a First Housing 52b Second housing 53 Input gear 5 a motor shaft 54 intermediate gear 55 output gear 56 speed reduction mechanism 57 drive shaft 58 ball screw mechanism 59 support bearing 60 screw shaft 60a, 68a thread groove 61 through hole 62 bag hole 63 rolling bearing 64 key 65 locking pin 66 retaining ring 67, 73 Sleeve 67a Concave groove 68 Nut 68b Piece member 69 Ball 70 Large diameter portion 70a Flat portion 71 Cylindrical portion 72 Projection strip 74 Bottom portion 75 Flat surface 76 The bottom portion of the bag hole of the second housing D The inner diameter of the washer d The outer ring of the support bearing Diameter M Electric motor

Claims (5)

An aluminum alloy housing;
An electric motor attached to the housing;
A speed reduction mechanism for transmitting the rotational force of the electric motor via the motor shaft;
A ball screw mechanism that converts the rotational motion of the electric motor to linear motion in the axial direction of the drive shaft via the speed reduction mechanism;
The ball screw mechanism is rotatably supported via a support bearing mounted on the housing and is not axially movable, and a nut having a helical thread groove formed on the inner periphery,
The nut is inserted through a large number of balls, is integrated with the drive shaft coaxially, and is configured with a screw shaft in which a spiral screw groove corresponding to the screw groove of the nut is formed on the outer periphery. In the electric actuator,
A cylindrical bag hole is formed in the housing, and a bottomed cylindrical sleeve having a concave groove extending in the axial direction on the inner periphery is fitted to the bottom of the bag hole so that the sleeve is in the bag hole. A locking pin provided at an end of the screw shaft is engaged with the concave groove, and the screw shaft is supported so as to be non-rotatable and movable in the axial direction. An electric actuator characterized in that the bottom of the actuator is formed in a simple circular shape.   The sleeve is formed in a cup shape including a large-diameter portion at one end and a bottomed cylindrical portion extending in the axial direction from the large-diameter portion, and a flat portion is formed in the large-diameter portion, and the bag The electric actuator according to claim 1, wherein an opening along the shape of the large diameter portion of the sleeve is formed in the hole.   The sleeve includes a cylindrical sleeve main body and a separate bottom plate fitted to the sleeve main body, and the sleeve main body has a large diameter portion at one end and an axial direction extending from the large diameter portion. A cylindrical portion, a flat portion is formed in the large diameter portion, an opening along the shape of the large diameter portion of the sleeve main body is formed in the bag hole, and the bottom plate is a cylindrical portion of the sleeve main body. The electric actuator according to claim 1, wherein the electric actuator is formed in a simple circular shape along the shape of the actuator.   4. The electric actuator according to claim 3, wherein a pair of protrusions are integrally formed on a side surface of the bottom plate that is fitted to an end portion of the sleeve body, and the protrusions are engaged with concave grooves of the sleeve body.   The electric actuator according to claim 1, wherein the sleeve is formed of a sintered alloy formed by MIM.

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