JP2015040595A - Electric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric actuator for improving durability of a housing by loosening a collision force even when a screw shaft of a ball screw mechanism collides with the housing.SOLUTION: An aluminum alloy housing 2 is constituted by two housings 2a, 2b, and a through hole 11 and a bag hole 12 for housing the screw shaft 10 are formed at a butt-jointing part. A sleeve 17 for preventing rotation of the screw shaft 10 is fitted with the bag hole 12, and a liquid gasket made of a hardenable material is coated on a jointing face of the housings 2a, 2b and fastened with a stationary bolt 21. An elastic ring 28 made of a rubber material having a predetermined elasticity coefficient is interposed between a seat face of the stationary bolt 21 and the housing 2a. Thereby, even when a tip of the screw shat 10 collides with a bottom part 17b of the sleeve 17, the housing 2b spontaneously moves in an axial direction and rises due to collision. At the same time, the elastic ring 28 is deformed, and therefore, a collision force can be absorbed and softened.

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 transmitted to a ball screw in an automobile transmission or a parking brake. The present invention relates to an electric actuator that converts a linear motion of a drive shaft through a mechanism.

  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. For this reason, a ball screw mechanism has been adopted as a more efficient actuator with very low friction.

  As a conventional electric actuator, for example, a nut constituting a ball screw can be driven to rotate by an electric motor supported by a housing, and the output member coupled to the nut is displaced in the axial direction by rotating the nut. It is possible. As a typical example, an electric actuator as shown in FIG. 5 is known. The electric actuator 51 includes a cylindrical housing 52, an electric motor 53 attached to the housing 52, a reduction mechanism 56 that transmits the rotational force of the electric motor 53 via a motor shaft 53a, and the reduction mechanism 56. And a ball screw mechanism 58 for converting the rotational motion of the electric motor 53 into the linear motion of the drive shaft 57 in the axial direction.

  The speed reduction mechanism 56 includes an input gear 54 that is a spur gear fixed to the motor shaft 53 a of the electric motor 53, and an output gear 55 that meshes with the input gear 54 and is fixed to the outer peripheral surface of the nut 60. Yes.

  The ball screw mechanism 58 is connected to the speed reduction mechanism 56 and is supported so as to be rotatable and non-movable in the axial direction via a rolling bearing 59 mounted on the housing 52, and a helical thread groove 60a is formed on the inner periphery. And a screw shaft 62 that is inserted into the nut 60 via a large number of balls 61 and is integrated coaxially with the drive shaft 57.

  The screw shaft 62 is formed with one turn of a screw groove 62a corresponding to the screw groove 60a of the nut 60 on the outer periphery. The screw groove 62a is individually closed loop, and the downstream ball sinks to the inner diameter side. A ball circulation groove 63 meandering in an S-shape so as to get over the land portion and return to the upstream side is formed.

  The drive shaft 57 is integrally formed with the screw shaft 62, and a hole 57a for connecting to a wire (not shown) of an electric parking brake mechanism is formed at one end of the drive shaft 57, for example. The drive shaft 57 is slidably supported by a bush 64 made of a sintered alloy attached to the housing 52, and a parallel key 66 attached to the outer periphery engages with a key groove 65 formed in the housing 52. As a result, relative movement in the axial direction is possible, and relative rotation is impossible.

  Thus, since the screw groove 62a is formed only once in the screw shaft 62, the length of the screw shaft 62 can be shortened, the electric actuator 51 can be made compact, and the number of parts can be reduced. Thus, the processing man-hours can be reduced, the cost can be reduced, and the ball circulation mechanism can be simplified (for example, see Patent Document 1).

JP 2011-117513 A

  In such a conventional electric actuator 51, when control fails, the screw shaft 62 of the ball screw mechanism 58 may collide with the housing 52. Accordingly, when the housing 52 is formed of an aluminum alloy or the like, the housing 52 may be deformed if the impact at the time of collision is large.

  The present invention has been made in view of such problems of the prior art, and provides an electric actuator that reduces the impact force even when the screw shaft of the ball screw mechanism collides with the housing and improves the durability of the housing. The purpose is to do.

  In order to achieve such an object, the invention described in claim 1 of the present invention includes an aluminum alloy housing, an electric motor attached to the housing, a speed reduction mechanism for transmitting the rotational force of the electric motor, 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 via the speed reduction mechanism, and the ball screw mechanism is rotatable via a support bearing mounted on the housing. And a nut that is supported so as not to move in the axial direction and has a helical thread groove formed on the inner periphery thereof, and is inserted into the nut via a number of balls, and is coaxially integrated with the drive shaft, An electric actuator comprising a screw shaft which is formed on the outer periphery with a spiral screw groove corresponding to the screw groove of the nut and is supported so as not to rotate with respect to the housing and to be movable in the axial direction. The housing is composed of two housings, and these housings are fastened by fixing bolts, and the axial direction of the housing is such that the sealing performance is not lost between the seating surface of the fixing bolts and the housing. An elastic ring having a deformation amount allowing displacement is interposed.

  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 a 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 screw shaft that is coaxially integrated with the drive shaft, has a helical screw groove corresponding to the screw groove of the nut on the outer periphery, and is supported so as to be non-rotatable and axially movable with respect to the housing. In the electric actuator constituted by the above, the housing is constituted by two housings, and these housings are fastened by fixing bolts, and between the seating surface of the fixing bolts and the housing. Since an elastic ring having a deformation amount that allows the axial displacement of the housing to such an extent that the sealing performance is not lost is interposed, the tip of the screw shaft collides with the sleeve or the bottom of the housing due to an unexpected input signal or the like. Even so, the other housing instantaneously moves in the axial direction and rises due to the impact, and at the same time, the elastic ring is deformed, and the impact force can be absorbed and relaxed. As a result, the deformation of the housing can be prevented, and the occurrence of defects such as indentations in the thread groove and ball of the ball screw mechanism via the support bearing can be prevented, and an electric actuator with improved durability is provided. can do.

  Preferably, if the elastic ring is formed of a rubber material as in the invention described in claim 2, an appropriate elastic modulus, shape, thickness, etc. can be easily selected, and an impact force is generated. It is possible to easily regulate the amount of lifting of the housing when it hits.

  Further, as in the third aspect of the present invention, if a liquid gasket is applied to the mating surface of the housing, the internal sealing performance can be ensured.

  If the elastic ring is selected so that the sealing performance of the liquid gasket is not lost as in the invention described in claim 4, when the one housing is lifted momentarily by an impact force, the lift is lifted. The amount can be regulated.

  Further, as in the invention described in claim 5, if the liquid gasket is made of a curable material, the liquid gasket can be cured and exhibit sealing properties after a certain period of time.

  Further, as in the sixth aspect of the present invention, if a washer is sandwiched between the seating surface of the fixing bolt and the elastic ring, it is possible to reduce friction during fastening of the fixing bolt.

  Further, as in the invention according to claim 7, if the housing is fastened by a plurality of fixing bolts, and the elastic ring is interposed between the seating surface of these fixing bolts and the housing, each fixing is performed. Even if the impact force is not evenly generated on the bolt, it can be recovered instantaneously by the restoring force of the elastic ring which is deformed by the impact force, and the impact force is not adversely affected.

  If the sleeve is formed in a cup shape having a bottom as in the invention described in claim 8, the tip of the screw shaft directly collides with the aluminum alloy housing due to an unexpected input signal or the like. Prevent and do no great damage.

  An electric actuator according to the present invention includes an aluminum alloy housing, an electric motor attached to the housing, a speed reduction mechanism for transmitting a rotational force of the electric motor, and a rotational motion of the electric motor via the speed reduction mechanism. A ball screw mechanism that converts the drive shaft into a linear motion in the axial direction of the drive shaft, and this ball screw mechanism is supported by a support bearing 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. An electric actuator comprising a screw shaft that is supported so as to be non-rotatable and axially movable with respect to the housing. These housings are fastened by fixing bolts, and a deformation that allows axial displacement of the housing between the seating surface of the fixing bolts and the housing without losing the sealing performance. Since an elastic ring having a certain amount is interposed, even if the tip of the screw shaft collides with the sleeve or the bottom of the housing due to an unexpected input signal, the other housing instantaneously moves in the axial direction due to the impact. The elastic ring is deformed at the same time, and the impact force can be absorbed and relaxed. As a result, the deformation of the housing can be prevented, and the occurrence of defects such as indentations in the thread groove and ball of the ball screw mechanism via the support bearing can be prevented, and an electric actuator with improved durability is provided. can do.

It is a longitudinal section showing one embodiment of an electric actuator concerning the present invention. It is II arrow directional view of FIG. It is a longitudinal cross-sectional view which shows the actuator main body of FIG. It is explanatory drawing which shows the state which the screw shaft collided with the housing. It is a longitudinal cross-sectional view which shows the conventional electric actuator.

  An aluminum alloy housing, an electric motor attached to the housing, a speed reduction mechanism for transmitting the rotational force of the electric motor, and a rotational movement of the electric motor via the speed reduction mechanism in a straight line in the axial direction of the drive shaft A ball screw mechanism for converting into motion, and this ball screw mechanism is supported by a support bearing mounted on the housing so as to be rotatable and non-movable in the axial direction. The formed nut and the nut are inserted through a large number of balls, are integrated coaxially with the drive shaft, and a helical thread groove corresponding to the thread groove of the nut is formed on the outer periphery. An electric actuator composed of a screw shaft supported so as to be non-rotatable with respect to the housing and movable in the axial direction. A through-hole and a bag hole for accommodating the screw shaft are formed in the cylindrical hole, and a cylindrical sleeve for preventing the screw shaft from rotating is fitted into the bag hole, and a liquid made of a curable material is provided on the mating surface of the housing. An elastic ring that is fastened by a fixing bolt in a state where a gasket is applied, and has a deformation amount that allows the axial displacement of the housing to the extent that the sealing performance is not lost between the seating surface of the fixing bolt and the housing. Is intervening.

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 a sectional view taken along arrow II in FIG. 1, FIG. 3 is a longitudinal sectional view showing an actuator body in FIG. FIG. 5 is an explanatory view showing a state where the screw shaft collides with the housing.

  As shown in FIG. 1, the electric actuator 1 includes a cylindrical housing 2, an electric motor (not shown) attached to the housing 2, and an input gear 3 attached to a motor shaft 3a of the electric motor. A speed reduction mechanism 6 comprising an intermediate gear 4 meshing with the output gear 5 and an output gear 5 meshing with the intermediate gear 4, and a ball for converting the rotational motion of the electric motor into the linear motion of the drive shaft 7 via the speed reduction mechanism 6. A screw mechanism 8 and an actuator body 9 including the ball screw mechanism 8 are provided.

  The housing 2 is formed by die casting from an aluminum alloy such as A6063TE or ADC12, and includes a first housing 2a and a second housing 2b abutted on an end surface thereof, and is fixed integrally by a fixing bolt 21 described later. Yes. An electric motor is attached to the first housing 2a, and an abutting portion between the first housing 2a and the second housing 2b is for accommodating a screw shaft 10 constituting a ball screw mechanism 8 described later. A through hole 11 and a bag hole 12 are formed.

  The motor shaft 3a of the electric motor is rotatably supported by a rolling bearing 13 comprising a deep groove ball bearing mounted on the second housing 2b. . 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 the ball screw mechanism 8 via a key 14.

  The drive shaft 7 is configured integrally with the screw shaft 10, and a locking pin 15 is implanted at one end (right end in the figure). Further, a bottomed sleeve 17 described later is fitted into the bag hole 12 of the second housing 2b, and concave grooves 17a, 17a extending in the axial direction are formed on the inner periphery of the sleeve 17 by grinding. The concave grooves 17a and 17a are arranged to oppose each other in the circumferential direction, and the locking pin 15 of the screw shaft 10 is engaged, and the screw shaft 10 is supported so as not to rotate but to be movable in the axial direction. .

  As shown in FIG. 2, the upper mating surfaces 22 of the first housing 2a and the second housing 2b are formed in a substantially circular shape, and a fixing portion 23 to be coupled by fixing bolts (not shown) is partly from the outer peripheral surface. A plurality (four in this case) are formed so as to protrude. Bolt holes 23 a through which fixing bolts are inserted are formed in these fixing portions 23. Here, the “substantially circular” is sufficient if the mating surface 22 to which a sealing material to be described later is applied is at least circular. For example, the outer peripheral portion has a partial flange or a rectangular or non-circular mounting portion. Is also included. Further, the lower mating surfaces 24 (see FIG. 1) of the first and second housings 2a and 2b in which the through hole 11 and the bag hole 12 are formed are coupled by a pair of left and right fixing bolts 21.

  In the present embodiment, the mating surfaces 22 and 24 of the first and second housings 2a and 2b are filled (applied) with a sealing material made of a curable material. Examples of the sealing material to be filled include a solventless silicon liquid gasket (packing) and a synthetic rubber liquid gasket. Since the curable material of these liquid gaskets is cured after a certain period of time, the sealing performance is exhibited in approximately 24 hours. Here, the sealing material is not limited to a liquid gasket made of a curable material, but may be, for example, an O-ring made of synthetic rubber or the like, a metal gasket made of copper, stainless steel, an aluminum alloy, or the like. A semi-metal gasket in which the cushion material is covered with a thin metal plate, or a sheet gasket made of synthetic rubber or fluorine resin may be interposed.

  As shown in an enlarged view in FIG. 3, 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 formed with a helical thread groove 18a corresponding to the thread groove 10a of the screw shaft 10 on the inner periphery, and a large number of balls 19 are accommodated between these thread grooves 10a and 18a so as to be able to roll. ing. The nut 18 is supported by the first and second housings 2a and 2b via the two support bearings 20 and 20 so as to be rotatable and non-movable in the axial direction. Reference numeral 16 denotes a piece member that constitutes a circulation member by connecting the thread groove 18a of the nut 18, and the piece member 16 allows an endless 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. 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.

  An output gear 5 constituting the speed reduction mechanism 6 is fixed to the outer peripheral surface 18b of the nut 18 via a key 14, and two support bearings 20 and 20 are provided on both sides of the output gear 5 via a predetermined tightening allowance. It is press-fitted. 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 bearings having the same specifications refer to bearings having the same inner diameter, outer diameter, width dimension, rolling element size, number, bearing internal clearance, and the like.

  In addition, an annular recess 25 in which the support bearing 20 is mounted is formed in the second housing 2b, and a disc-shaped spacer 26 is interposed in a shoulder portion 25a of the annular recess 25. That is, the support bearing 20 is positioned and fixed in a state of being clamped in the axial direction by the flange portion 18 c protruding from the outer peripheral surface of the nut 18 and the spacer 26. The spacer 26 is made of an austenitic stainless steel sheet (JIS standard SUS304 system, etc.) having high strength and wear resistance, or a cold rolled steel sheet (JIS standard SPCC system, etc.) that is rich in mass production and rust-proof. It is formed by press working, protrudes in the axial direction at the outer diameter portion, has a convex portion 26 a at the end surface and is in contact with the outer ring 27 of the support bearing 20. On the other hand, the inner diameter portion is formed smaller than the inner diameter of the bag hole 12 of the second housing 2b (see FIG. 1).

  As a result, as compared with the conventional structure in which the sleeve 17 is prevented from being detached by the retaining ring, the assembling work is facilitated and the working efficiency is improved, and the retaining ring for attaching the retaining ring to the second housing 2b. There is no need to form a ring groove, the number of processing steps is reduced, the ball screw mechanism 8 and other parts can be easily disassembled and assembled during maintenance, and the cost can be reduced. Further, the spacer 26 is in a perfect circular surface contact with the end surface of the sleeve 17 to increase the frictional force, so that the rotation of the sleeve 17 can be prevented simultaneously with the second housing 2b.

  The sleeve 17 that supports the screw shaft 10 is fitted in the bag hole 12 of the second housing 2b. The sleeve 17 is cold-forged from medium carbon steel such as S55C or case-hardened steel such as SCM415 and SCM420. It is formed into a cup shape by the method, and its surface is subjected to hardening treatment in the range of 55 to 62 HRC by induction hardening or carburizing and hardening.

  Here, the embodiment in which the sleeve 17 is formed by the cold heading method is illustrated, but the present invention is not limited to this. For example, the sleeve 17 is formed of a sintered alloy that is adjusted to a plastic shape and molded by an injection molding machine. You may do it. 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 17 is performed by adjusting the carburizing quenching and tempering temperatures. In addition to this, as the material of the sleeve 17, Ni is contained in an amount of 3.0 to 10.0 wt% and has excellent workability and corrosion resistance (FEN8 of Japanese Powder Metallurgy Industry Standard), or C is 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.

  Here, in the present embodiment, the two first and second housings 2a and 2b are fastened by the fixing bolt 21, but an elastic member is provided between the seating surface of the fixing bolt 21 and the first housing 2a. The elastic ring 28 which consists of is interposed. Preferably, the washer 29 is sandwiched between the seating surface of the fixing bolt 21 and the elastic ring 28, so that the friction during fastening of the fixing bolt 21 can be reduced. The elastic ring 28 is made of silicon rubber having excellent weather resistance, heat resistance, and chemical resistance.

  By inserting such an elastic ring 28 between the fixing bolt 21 and the first housing 2a, as shown in FIG. In the case of a cylindrical shape not having a ring, when it collides with the bottom of the housing), the other second housing 2b is instantaneously moved by δ in the axial direction (left side in the figure) and lifted up at the same time due to the impact. 28 is deformed. Then, the deformation of the elastic ring 28 can absorb and mitigate the impact force, and the electric actuator 1 with improved durability by preventing the deformation of the second housing 2b can be provided. Furthermore, it is possible to prevent the occurrence of defects such as indentations in the thread grooves 10 a and 18 a and the ball 19 of the ball screw mechanism 8 through the support bearing 20.

  The material of the elastic ring 28 is not limited to the exemplified silicon rubber, and may be formed of, for example, sponge rubber made of foam rubber called porous rubber. This sponge rubber is excellent in heat insulation, shock absorption, cushioning, and the like. Furthermore, the material of the elastic ring 28 includes NBR (acrylonitrile-butadiene rubber), HNBR (hydrogenated acrylonitrile-butadiene rubber) with excellent heat resistance, EPM, EPDM (ethylene / propylene rubber), etc., heat resistance and chemical resistance. Examples thereof include ACM (polyacrylic rubber) and FKM (fluororubber) having excellent properties.

  In the present embodiment, the liquid gasket is applied to the mating surfaces 22 and 24 of the first and second housings 2a and 2b to ensure the internal sealing performance. The elastic modulus of the ring 28 is taken into account. That is, the elastic modulus and the shape / thickness of the elastic ring 28 are taken into consideration. Since the elastic ring 28 is designed to such an extent that the sealing performance of the liquid gasket is not lost, the floating amount δ of the second housing 2b is restricted, and the tip of the screw shaft 10 collides with the bottom 17b of the sleeve 17. When the second housing 2b momentarily rises due to the impact, the liquid gasket is pulled away and extended, so that the sealing performance can be maintained.

  In addition, when the first and second housings 2a and 2b are fastened by the fixing bolt 21, a female screw is formed in the second housing 2b where an impact force is generated. Bolt holes (bucker holes) through which the fixing bolts 21 are inserted are formed. Although not limited to this, although not shown, conversely, a female screw may be formed on the first housing 2a side, a bolt hole may be formed on the second housing 2b side, or the first and second housings 2a. The bolt holes may be formed in 2b and fastened by the fixing bolt 21 and a nut fastened to the fixing bolt 21. In this case, the elastic ring 28 is interposed between the seat surface of the nut and the first and second housings 2a and 2b as well as the seat surface of the fixing bolt 21 and the first and second housings 2a and 2b. Just wear it.

  Here, the first and second housings 2a and 2b are fastened by a plurality of (here, five) fixing bolts 21, and elastic rings 28 are interposed in the plurality of fixing bolts 21, respectively. . In this case, even if the impact force is not evenly generated in each fixing bolt 21, it can be instantaneously recovered (equalized) by the restoring force of the elastic ring 28 deformed by the impact force, and the impact force is reduced. Will not be adversely affected.

  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 9 Actuator body 10 Screw shaft 10a, 18a Screw groove 11 Through Hole 12 Bag hole 14 Key 15 Locking pin 16 Frame member 17 Sleeve 17a Concave groove 17b Sleeve bottom 18 Nut 18b Nut outer peripheral surface 18c Hook 19 Ball 20 Support bearing 20a Shield plate 21 Fixing bolt 22 Upper mating surface 23 Fixing 23a Bolt hole 24 Lower fitting surface 25 Annular recess 25a Shoulder 26 Spacer 26a Spacer convex 27 Support bearing outer ring 28 Elastic ring 29 Washer 51 Electric actuator 52 Housing 53 Electric motor 53a Motor shaft 54 Input gear 55 Output gear 56 Reduction mechanism 57 Drive 57a hole 58 a ball screw mechanism 59 rolling 60 nut 60a, 62a screw groove 61 a ball 62 screw shaft 63 ball circulation groove 64 bushing 65 weight lifting keyway 66 keys δ housing

Claims (8)

An aluminum alloy housing;
An electric motor attached to the housing;
A speed reduction mechanism for transmitting the rotational force of the electric motor;
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 and is integrated coaxially with the drive shaft. A spiral screw groove corresponding to the screw groove of the nut is formed on the outer periphery, and the nut cannot rotate with respect to the housing. And an electric actuator composed of a screw shaft supported so as to be axially movable,
The housing is composed of two housings, and these housings are fastened by fixing bolts, and the axial displacement of the housing is made between the seating surface of the fixing bolts and the housing to such an extent that the sealing performance is not lost. An electric actuator comprising an elastic ring having an allowable deformation amount.   The electric actuator according to claim 1, wherein the elastic ring is formed of a rubber material.   The electric actuator according to claim 1, wherein a liquid gasket is applied to a mating surface of the housing.   The electric actuator according to claim 3, wherein the elastic ring is selected to such an extent that the sealing performance of the liquid gasket is not lost.   The electric actuator according to claim 3 or 4, wherein the liquid gasket is made of a curable material.   The electric actuator according to claim 1, wherein a washer is sandwiched between a seating surface of the fixing bolt and the elastic ring.   The electric actuator according to claim 1, wherein the housing is fastened by a plurality of fixing bolts, and the elastic ring is interposed between a seating surface of the fixing bolts and the housing.   The electric actuator according to claim 1, wherein the sleeve is formed in a cup shape having a bottom portion.

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