JP2018168898A - Electric actuator - Google Patents

Abstract

To provide an electric actuator which can achieve improvement in positioning accuracy in a linear motion direction and miniaturization.SOLUTION: In an electric actuator, a drive part having an electric motor and a motion conversion mechanism part for converting a rotation motion of the drive part into a linear motion are arranged in series. The motion conversion mechanism part includes a nut 30 rotating by receiving rotation movement of the drive part, and a screw shaft 31 arranged on an inner periphery of the nut 30 and for making a linear motion according to the rotation of the nut 30. The nut 30 is rotatably supported by bearings 13, 14. Each of the bearings 13, 14 includes: an inside raceway surface 30c formed on an outer peripheral surface of the nut 30; an outer ring 20 arranged on an outer periphery of the nut 30, and having an outside raceway surface 20a on an inner peripheral surface; and a rolling element 21 arranged between the inside raceway surface 30c and the outside raceway surface 20a. The rolling element 21 is arranged by having a contact angle α with respect to the inside raceway surface 30c and the outside raceway surface 20a.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an electric actuator.

  In recent years, in vehicles such as automobiles, electrification has progressed to save labor and reduce fuel consumption. For example, a system that uses the power of an electric motor to operate automatic transmissions, brakes, steering, etc. has been developed. Has been put on the market. As a so-called linear motion type electric actuator used for such applications, there is known one using a ball screw as a motion conversion mechanism for converting the rotational motion of a motor into a linear motion.

  For example, Patent Document 1 describes a linear motion type electric actuator that employs a ball screw in a motion conversion mechanism, in which an electric motor and a ball screw are arranged in series (arranged in an axial direction). . In the actuator described in Patent Document 1, a radial ball bearing that mainly receives a radial load is used as a member that supports the ball screw with respect to the housing.

JP 2010-124579 A

  By the way, the radial ball bearing generally has a lower rigidity against an axial load than a rigidity against a radial load. For this reason, when a radial ball bearing is used as a bearing for supporting the ball screw, the axial load generated during the linear motion of the ball screw causes rattling in the axial direction, which causes a positioning error in the linear motion direction of the ball screw. It is possible.

  In this type of electric actuator, it is desired to reduce the number of parts as much as possible from the viewpoint of miniaturization.

  Accordingly, an object of the present invention is to provide an electric actuator capable of improving the positioning accuracy in the linear motion direction and reducing the size.

  As a technical means for achieving the above-described object, the present invention provides a motion conversion mechanism in which a drive unit having an electric motor and a motion conversion mechanism unit that converts the rotational motion of the drive unit into a linear motion are arranged in series. The nut has a nut that rotates in response to the rotational movement of the drive section, and a screw shaft that is arranged on the inner periphery of the nut and linearly moves with the rotation of the nut. The nut is rotatably supported by the bearing. In the electric actuator, the bearing is disposed between the inner raceway surface formed on the outer peripheral surface of the nut, the outer ring disposed on the outer periphery of the nut and having the outer raceway surface on the inner peripheral surface, and the inner raceway surface and the outer raceway surface. The rolling elements are arranged with contact angles with respect to the inner raceway surface and the outer raceway surface.

  As described above, the rolling elements are arranged with contact angles with respect to the inner raceway surface and the outer raceway surface, so that the rolling elements are arranged in the axial direction in comparison with a bearing in which the rolling elements are not arranged with contact angles with respect to both raceway surfaces. The rigidity with respect to the load can be improved. Thereby, it becomes possible to reduce the shakiness in the axial direction of the bearing, and the positioning accuracy of the electric actuator in the linear motion direction is improved. Further, since the inner raceway surface is formed on the outer peripheral surface of the nut, it is not necessary to separately provide the inner ring having the inner raceway surface on the outer peripheral surface of the nut. As a result, the electric actuator can be downsized in the radial direction.

  Further, by using an outer ring having a deep groove type outer raceway as the outer ring of the bearing, it is not necessary to use a specially designed outer ring, so that an increase in design cost can be suppressed.

  The inner raceway surface formed on the nut may be an angular raceway surface. In this case, by forming the outer diameter of the nut larger from the axial end side toward the axial center side, it is possible to form an angular inner raceway surface integral with the nut.

  In addition, by providing an elastic member and preloading the outer ring in the axial direction, shakiness in the axial direction (especially rattling at the initial stage of manufacture) can be reduced more reliably, and the electric actuator positioning accuracy can be further improved. Can be made.

  According to the present invention, since the rigidity of the bearing with respect to the axial load increases, the positioning accuracy of the electric actuator in the linear motion direction can be improved. In addition, according to the present invention, since the inner raceway surface is formed on the outer peripheral surface of the nut, the inner ring of the bearing can be omitted, so that the radial size can be reduced.

It is a longitudinal section of the electric actuator concerning a 1st embodiment of the present invention. FIG. 2 is a partially exploded perspective view of the electric actuator shown in FIG. 1. FIG. 2 is a partially exploded perspective view of the electric actuator shown in FIG. 1. FIG. 2 is a partially exploded perspective view of the electric actuator shown in FIG. 1. It is a disassembled perspective view of the screw shaft in the state where the permanent magnet was attached. It is the elements on larger scale of the electric actuator shown in FIG. It is sectional drawing of a common deep groove type bearing. It is sectional drawing of the bearing which concerns on embodiment of this invention. It is a longitudinal cross-sectional view of the electric actuator which concerns on 2nd Embodiment of this invention. FIG. 10 is a partially exploded perspective view of the electric actuator shown in FIG. 9. FIG. 10 is a cross-sectional view taken along line AA in FIG. 9. FIG. 10 is a cross-sectional view taken along line B-B in FIG. 9. It is a longitudinal cross-sectional view of the electric actuator which concerns on 3rd Embodiment of this invention. FIG. 14 is a partially exploded perspective view of the electric actuator shown in FIG. 13.

  Hereinafter, the present invention will be described with reference to the accompanying drawings. In the drawings for explaining the present invention, components such as members and components having the same function or shape are denoted by the same reference numerals as much as possible, and once described, the description will be given. Omitted.

  FIG. 1 is a longitudinal sectional view of the electric actuator according to the first embodiment of the present invention, and FIG. 2 is an exploded perspective view of the electric actuator according to the first embodiment.

  As shown in FIG. 1, the electric actuator 1 according to the first embodiment includes a drive unit 2, a motion conversion mechanism unit 3 that converts a rotational motion of the drive unit 2 into a linear motion, and a linear motion of the motion conversion mechanism unit 3. And an operation unit 6 for operating an operation target not shown. The drive unit 2 of the present embodiment has an electric motor 7. The “axial direction” referred to below is a direction along the rotation center X of the electric motor 7 shown in FIG. In the following, for convenience in explaining the directionality in the axial direction, the side on which the drive unit 2 is disposed (the right side in FIG. 1) and the side on which the operation unit 6 is disposed (the left side in FIG. 1). Are referred to as one axial side and the other axial side, respectively.

  As shown in FIGS. 1 and 2, each of the drive unit 2 and the motion conversion mechanism unit 3 includes a member that constitutes a housing 1 </ b> A of the electric actuator 1. Specifically, the drive unit 2 is provided with a first case 9 that houses the electric motor 7 and a pair of bus bars 19 as conductive members that electrically connect a power source (not shown) and the electric motor 7. The motion conversion mechanism unit 3 includes a second case 10 and a third case 11 that houses a ball screw 12 as a motion conversion mechanism. The housing 1A is completed by combining and integrating the cases 9 to 11 arranged in a line in the axial direction using the bolt members 27 shown in FIG.

  In order to improve the sealing performance between adjacent cases, the flange portion 16 of the first case 9 and the flange portion 25 of the second case 10 and the flange portion 25 of the second case 10 and the flange portion 26 of the third case 11 are used. O-rings 28 and 29 are interposed between the two.

  The drive unit 2 includes an electric motor 7 that generates a driving force (rotational driving force), a first case 9 that houses the electric motor 7, a bus bar 19, and a second case 10 in which the bus bar 19 is provided. The first case 9 integrally includes a bottomed cylindrical case main body 15 and a flange portion 16 provided with an insertion hole for the bolt member 27 shown in FIG.

  The inner peripheral surface 15a of the case body 15 is gradually reduced in diameter from the other side in the axial direction (opening side of the case body 15) toward one side in the axial direction (bottom side of the case body 15). The outer periphery of the end on one side in the direction is in contact with the end on the one side in the axial direction of the inner peripheral surface 15a of the case main body 15 in a state avoiding contact with the surface. Moreover, the electric motor 7 has the protrusion part 7a fitted to the inner periphery of the motor fitting part 17 of the 2nd case 10 mentioned later. Therefore, the electric motor 7 is supported by the case main body 15 of the first case 9 and the motor fitting portion 17 of the second case 10. An O-ring 18 is interposed between the electric motor 7 and the inner bottom surface 15b of the case body 15 to prevent the electric motor 7 from rattling in the axial direction and external leakage of lubricant such as grease. .

  The second case 10 has a cylindrical case body 23, a cylindrical fitting portion 24 fitted to the inner periphery of the third case 11, and a protrusion 7a of the electric motor 7 fitted to the inner periphery. An annular motor fitting portion 17 and a flange portion 25 provided with an insertion hole for the bolt member 27 shown in FIG. 2 are integrally provided. Since the second case 10 integrally includes the fitting portion 24 and the motor fitting portion 17, the centering between the first case 9 to the third case 11 can be easily performed. The rotation center X and the rotation center of the nut 30 of the ball screw 12 described later can be easily matched.

  As shown in FIG. 3, a pair of bus bars 19 is provided on the case body 23 of the second case 10. One end 19a of each bus bar 19 protrudes in the axial direction from the case body 23 and is exposed to the outside, and the other end 19b protrudes in the radial direction from the case body 23 and is exposed to the outside. One end portion 19a protruding in the axial direction of each bus bar 19 is formed in a substantially cylindrical shape, and a pair of motor terminals 7c provided on the electric motor 7 is a shaft with respect to the one end portion 19a formed in the substantially cylindrical shape. The motor terminal 7c and each bus bar 19 are connected to each other by being inserted in the direction. Further, the other end 19b protruding in the radial direction of each bus bar 19 is connected to a power source (not shown).

  As shown in FIG. 1, the motion conversion mechanism unit 3 includes a ball screw 12 and a third case 11 in which the ball screw 12 is accommodated. The ball screw 12 includes a screw shaft 31 disposed coaxially (in series) with the output shaft 7 b of the electric motor 7, a nut 30 rotatably fitted to the outer periphery of the screw shaft 31 via a large number of balls 32, A top 33 as a circulation member is provided. A large number of balls 32 are filled between a spiral groove 30 a formed on the inner peripheral surface of the nut 30 and a spiral groove 31 a formed on the outer peripheral surface of the screw shaft 31, and a top 33 is incorporated. With such a configuration, when the screw shaft 31 moves back and forth (linear motion) in the axial direction as the nut 30 rotates, the ball 32 circulates between the spiral grooves 30a and 31a.

  A coupling 62 is provided on the output shaft 7 b of the electric motor 7 so as to be able to rotate integrally with the output shaft 7 b, and the electric motor 7 and the nut 30 of the ball screw 12 are connected via the coupling 62. As shown in FIG. 2, the coupling 62 has a flat surface 62a on the outer periphery, and is fitted and fixed to the inner peripheral surface 30b (see FIG. 1) on the other axial end side of the nut 30 by fitting or the like. . Thereby, the rotational driving force of the electric motor 7 is transmitted to the nut 30 via the coupling 62, and the nut 30 rotates in either the forward or reverse direction. On the other hand, the rotation of the screw shaft 31 is restricted by a detent described later. For this reason, when the nut 30 rotates in response to the rotational driving force of the drive unit 2, the screw shaft 31 moves forward and backward in the axial direction according to the rotational direction of the nut 30. The end of the screw shaft 31 on the other side in the axial direction functions as an operation unit (actuator head) 6 that operates an operation target (not shown). Therefore, the operation target is operated in the axial direction as the screw shaft 31 moves back and forth in the axial direction.

  The third case 11 includes a large diameter cylindrical portion 35, a small diameter cylindrical portion 36 located on the other axial side of the large diameter cylindrical portion 35, and an annular flange portion provided with an insertion hole for the bolt member 27 shown in FIG. 26 integrally. An inner peripheral surface 37 of the large-diameter cylindrical portion 35 is formed in a cylindrical surface having a constant diameter, and the nut 30 is rotatably supported on the inner peripheral surface 37 with respect to the housing 1A (third case 11). Bearings (ball bearings) 13 and 14 are attached and fixed apart in the axial direction.

  The third case 11 has a metallic cylindrical member 38 disposed on the inner periphery of the large-diameter cylindrical portion 35, and the inner peripheral surface 37 to which the bearings 13 and 14 (outer rings) are attached and fixed is as follows. It is comprised by the internal peripheral surface of the cylindrical member 38. FIG. An annular portion 39 extending inward in the radial direction is integrally provided at the other axial end of the tubular member 38, and the annular portion 39 and the bearing 13 are opposed to each other in the axial direction. A wave washer 42, which is an annular elastic member that has been compressed and deformed, and an annular spacer washer 43 are interposed. Further, the bearing 14 positioned on one side in the axial direction is urged toward the other side in the axial direction by the fitting portion 24 of the second case 10. With the above configuration, axial preload is applied to the bearings 13 and 14 formed of rolling bearings.

  As shown in FIG. 1, a cylindrical slide bearing 40 formed of sintered metal and having a screw shaft 31 inserted in the inner periphery is provided on the inner periphery of the small-diameter cylindrical portion 36 constituting the third case 11. ing. A sliding surface 34 on which the screw shaft 31 can slide is provided on the inner peripheral surface of the slide bearing 40. The internal pores of the sliding bearing 40 made of a sintered metal porous body are preferably impregnated with a lubricant such as grease or lubricating oil. In this way, an oil film can be formed between the inner peripheral surface (sliding surface 34) of the slide bearing 40 and the outer peripheral surface of the screw shaft 31, so that the screw shaft 31 can be smoothly linearly moved. it can. A retaining ring 41 for positioning the slide bearing 40 in the axial direction is fixed at a predetermined position in the axial direction of the screw shaft 31.

  In the present embodiment, an anti-rotation function of the screw shaft 31 is given to the inner peripheral surface (sliding surface 34) of the slide bearing 40. More specifically, as shown in FIG. 4, the sliding surface 34 includes one flat surface 34 a provided in a partial region in the circumferential direction and an arc surface (partial cylindrical surface) 34 b. On the other hand, in the sliding region 31b that slides with the sliding surface 34 of the outer peripheral surface of the screw shaft 31, a flat surface portion 31b1 that faces the flat surface 34a of the sliding surface 34 and a partial cylinder that faces the partial cylindrical surface 34b. A surface portion 31b2 is provided.

  The third case 11 of the present embodiment having the above configuration is a resin injection-molded product using the cylindrical member 38 and the slide bearing 40 as insert parts. In this case, the third case 11 is provided with a hole 11a so as to follow the outer peripheral surface of the positioning pin in which the cylindrical member 38 is positioned in the mold in the axial direction. Alternatively, after the resin-made third case 11, the metal cylindrical member 38, and the sintered metal slide bearing 40 are individually manufactured, they may be fixed by appropriate means.

  As shown in FIG. 1, a boot 44 is installed between the small diameter cylindrical portion 36 of the third case 11 and the screw shaft 31 to prevent foreign matter from entering the third case 11. The boot 44 is made of resin or rubber, and integrally includes a large-diameter cylindrical portion 44a and a small-diameter cylindrical portion 44b, and a bellows portion 44c interposed between the cylindrical portions 44a and 44b. The large-diameter cylindrical portion 44a and the small-diameter cylindrical portion 44b of the boot 44 are fastened and fixed to the outer peripheral surface of the small-diameter cylindrical portion 36 of the third case 11 and the outer peripheral surface of the screw shaft 31 by using boot bands 45 and 46, respectively. A boot cover 47 covering the boot 44 is disposed on the outer periphery of the boot 44, and the boot cover 47 is attached to, for example, the third case 11 adjacent in the axial direction.

  Further, the electric actuator 1 is provided with a position detection device for detecting the axial position (the amount of movement in the axial direction) of the screw shaft 31. As shown in FIG. 1, the position detection device includes a permanent magnet 53 as a sensor target provided on the screw shaft 31 and a magnetic sensor 54 as a position detection sensor provided on the boot cover 47. As the magnetic sensor 54, any type can be used, and among them, a type capable of detecting the direction and magnitude of the magnetic field using the Hall effect, such as Hall IC and linear Hall IC, can be preferably used.

  As shown in FIGS. 1 and 4, the magnetic sensor 54 is formed integrally with a sensor substrate 55, and the sensor substrate 55 is fixed to a sensor case 57 by a connecting member 56. Then, by attaching a sensor assembly 58 in which the sensor substrate 55 is attached to the sensor case 57 to a sensor attachment portion 47 a provided at a predetermined position in the circumferential direction of the boot cover 47, the magnetic sensor 54 is arranged in the circumferential direction of the boot cover 47. While being installed at a predetermined position, it is in a state of facing the permanent magnet 53 through the boot 44 and the boot cover 47. In this case, the magnetic sensor 54 is covered with the boot cover 47 and the sensor case 57 as shown in FIG. The sensor case 57 and the boot cover 47 that cover the periphery of the magnetic sensor 54 are both formed of a nonmagnetic material such as a resin material.

  FIG. 5 shows an exploded perspective view of the sensor target unit 59 including the permanent magnet 53 and the screw shaft 31. As shown in FIG. 5, a notch 31c is formed at a predetermined position in the axial direction of the screw shaft 31, and a sensor target unit 59 is attached to the notch 31c.

  The sensor target unit 59 includes a permanent magnet 53 and first and second magnet holders 60 and 61 that hold the permanent magnet 53. The first magnet holder 60 is formed in a substantially arc shape as a whole, and has a fitting claw 60 a fitted in the notch 31 c of the screw shaft 31 and a housing portion 60 b that can house the permanent magnet 53. The housing part 60 b has an end on the other axial side opening in the end face on the other axial side of the first magnet holder 60. Then, the permanent magnet 53 is inserted into the accommodating portion 60b of the magnet holder 60 from the opening side, and then the second magnet holder 61 formed in an arc shape so as to close the opening is attached to the screw shaft 31. It is positioned in the axial direction by fitting into the notch 31c.

  The material of the first and second magnet holders 60 and 61 is basically arbitrary. For example, when the influence of the permanent magnet 53 on the magnetic field formed around the permanent magnet 53 is taken into consideration, each of the magnet holders 60 and 61 is preferably made of a non-magnetic material, and the attachment property (fit) of the magnet holders 60 and 61 to the screw shaft 31 is good. In consideration of the elastic deformability of the joint claw 60a, it is preferable to use resin.

  Since the position detection device is configured as described above, when the screw shaft 31 moves back and forth in the axial direction, the relative position of the permanent magnet 53 in the axial direction with respect to the magnetic sensor 54 changes. The magnetic field at the location also changes. The magnetic sensor 54 detects a change in the magnetic field (for example, the direction and strength of the magnetic flux density), and acquires the axial position of the permanent magnet 53 and, in turn, the axial position of the screw shaft 31 (operation unit 6).

  Hereinafter, regarding the electric actuator 1 according to the present embodiment, a configuration that improves the positioning accuracy of the ball screw in the linear motion direction and a configuration that is advantageous for downsizing will be described.

  As described above, in the electric actuator 1 according to this embodiment, the nut 30 of the ball screw 12 is rotatably supported by the two bearings 13 and 14. As shown in FIG. 6, each of the bearings 13 and 14 includes an inner raceway surface 30c formed on the outer circumferential surface of the nut 30, a pair of outer rings 20 having an outer raceway surface 20a on the inner circumferential surface, and an inner raceway surface 30c. It has a plurality of rolling elements (spheres) 21 arranged between the outer raceway surface 20a and a retainer (not shown) that holds each rolling element 21. Each rolling element 21 is arranged with a contact angle α with respect to the inner raceway surface 30c and the outer raceway surface 20a. Here, the contact angle α is an angle formed by a plane (radial plane) perpendicular to the bearing center axis and a line of action of the resultant force transmitted from the raceway surface to the ball.

  In the present embodiment, the outer raceway surface 20a of each outer ring 20 is a so-called deep groove type raceway surface in which the height (diametrical dimension) from the bottom surface of the raceway surface to both ends of the raceway surface is equal. Here, in a general deep groove ball bearing in which the rolling element does not contact the outer raceway surface with a contact angle, as shown in FIG. 7, the center (Ob) of the rolling element 400 and the center of curvature radius of the outer raceway surface 300 are obtained. (O) are arranged at the same position in the axial direction. On the other hand, in this embodiment, as shown in FIG. 8, the center (O ′) of the radius of curvature of the outer raceway surface 20a is shifted from the center (Ob ′) of the rolling element 21 by a distance e in the axial direction. The rolling element 21 is in contact with the outer raceway surface 20a with a contact angle α.

  Further, as shown in FIG. 8, each inner raceway surface 30 c formed on the nut 30 is formed so that the outer diameter of the nut 30 is increased from the axial end side toward the axially central side, whereby the raceway bottom portion is formed. To the both ends of the raceway surface (radial dimension) are formed on a so-called angular raceway surface. In the present embodiment, the center of curvature (O ″) of the inner raceway surface 30c is shifted from the center (Ob ′) of the rolling element 21 by a distance f in the axial direction, so that the rolling element 21 is moved with respect to the inner raceway surface 30c. To make contact with a contact angle α.

  As described above, in the present embodiment, each rolling element 21 is arranged with a contact angle α with respect to the inner raceway surface 30c and the outer raceway surface 20a, so that the rolling element has a contact angle with respect to both raceway surfaces. As compared with a configuration in which the load is not disposed, rigidity against an axial load can be improved. Thereby, the shakiness of the axial direction in each bearing 13 and 14 can be reduced, and the positioning accuracy of the ball screw 21 in the linear motion direction is improved.

  Further, in the present embodiment, the inner raceway surface 30 c is formed on the outer peripheral surface of the nut 30, so that the inner ring having the inner raceway surface may not be provided separately on the outer peripheral surface of the nut 30. Thereby, since the number of parts decreases, the electric actuator can be downsized in the radial direction.

  Further, in the present embodiment, since the preload is applied to the outer ring 20 in the axial direction using the wave washer 42, the shakiness in the axial direction (particularly, rattling at the initial stage of manufacture) can be more reliably reduced. Thereby, the positioning accuracy of the ball screw 21 can be further improved.

  Further, as in the present embodiment, as the outer ring 20 of each of the bearings 13 and 14, an outer ring having a general deep groove type raceway surface (outer raceway surface 20a) can be used without using a specially designed outer ring. Since it is good, an increase in design cost can be suppressed. In addition, it is also possible to use the outer ring | wheel which has an angular type track surface as the outer ring | wheel 20 of each bearing 13 and 14. FIG.

  Hereinafter, regarding the electric actuator according to the second embodiment of the present invention, a longitudinal sectional view shown in FIG. 9, an exploded perspective view shown in FIG. 10, a sectional view taken along line AA in FIG. It demonstrates based on the BB arrow sectional drawing of FIG.

  As shown in FIGS. 9 and 10, the electric actuator 101 according to the second embodiment includes a speed reducer 8 that decelerates and transmits a driving force (rotation) from the electric motor 7 to the ball screw 12. The speed reducer 8 is accommodated in the second case 10. In this case, since the electric motor 7 is connected to the ball screw 12 via the speed reducer 8 so that torque can be transmitted, the coupling 62 is not used. Therefore, in 2nd Embodiment, the drive part 2 is provided with the electric motor 7, the 1st case 9 in which the electric motor 7 was accommodated, the reduction gear 8, and the 2nd case 10 in which the reduction gear 8 was accommodated.

  The speed reducer 8 is a planetary gear speed reducer. As shown in FIGS. 10 and 12, the planetary gear speed reducer is integrated with or separated from a sun gear 49 provided so as to be integrally rotatable with the output shaft 7 b of the electric motor 7, and the inner peripheral surface of the second case 10. Ring gear 48 provided integrally in the embodiment), a plurality (three in this embodiment) of planetary gears 50 arranged to rotate and revolve between the ring gear 48 and the sun gear 49, and the planetary gear 50 can rotate. And the planetary gear carrier 51 for taking out the revolving motion of the planetary gear 50. As shown in FIG. 9, the planetary gear carrier 51 has a cylindrical portion 51 a disposed on the radially outer side of the nut 30 constituting the ball screw 12, and the cylindrical portion 51 a and the nut 30 generate rotational torque between them. It is connected so that it can be transmitted.

  Since the reduction gear 8 having the above configuration transmits the high torque rotational power decelerated by the reduction gear 8 to the motion conversion mechanism 3, the electric actuator 101 according to the second embodiment has the first Compared with the electric actuator 1 according to the embodiment, a small electric motor 7 can be employed. Thereby, since the drive part 2 can be reduced in weight and size as a whole, a lightweight and compact electric actuator can be realized.

  As shown in FIGS. 10 and 11, the electric actuator 101 according to the second embodiment includes the bus bar 19 as means for supplying electric power by electrically connecting the electric motor 7 and a power source (not shown). Instead, a pair of terminals 65 are provided. The pair of terminals 65 are held by a terminal holder 66 fitted to the outer periphery of the electric motor 7. One end 65a of each terminal 65 is electrically connected to the electric motor 7 by being inserted into an insertion groove 7d (see FIG. 11) of the electric motor 7, and an electric wire (not shown) is connected to the other end 65b. As shown in FIG. 9, a through hole 15c is provided at the bottom of the case body 15, and a grommet 64 is fitted into the through hole 15c. An unillustrated electric wire connected to the other end 65b of the terminal 65 is drawn out of the first case 9 through a hole 64a (see FIG. 10) provided in the grommet 64.

  The configuration other than the above is the same as that of the electric actuator 1 according to the first embodiment. That is, parts common to the electric actuator 1 according to the first embodiment can be used for the motion conversion mechanism unit 3 (the ball screw 12 and the third case 11). By adopting such a configuration, the types of parts to be prepared can be reduced, so that it is possible to reduce costs when developing various types of electric actuators in series. Specific examples of the development of various products include electric mechanisms that conventionally use solenoids, such as EGR valves and transmission control valves for automobiles including motorcycles.

  As described above, also in the electric actuator 101 according to the second embodiment, the configurations of the bearings 13 and 14 that support the motion conversion mechanism unit 3 (ball screw 12) are the same as those in the first embodiment. As with the electric actuator 1 according to the embodiment, the axial rattling of the bearings 13 and 14 can be reduced, and the positioning accuracy of the ball screw 21 in the linear motion direction is improved. Furthermore, since the inner raceway surface 30c is formed on the outer peripheral surface of the nut 30, the bearings 13 and 14 can be downsized.

  Next, an electric actuator according to a third embodiment of the present invention will be described based on a longitudinal sectional view shown in FIG. 13 and an exploded perspective view shown in FIG.

  As shown in FIGS. 13 and 14, the electric actuator 201 according to the third embodiment is different from the electric actuator 101 according to the second embodiment shown in FIG. 9 in that the speed reducer 8 is not provided. For this reason, in the electric actuator 201 according to the third embodiment, the output shaft 7b of the electric motor 7 is coupled to the nut 30 of the ball screw 12 via the coupling 62 similar to that of the first embodiment. Other configurations are the same as those of the electric actuator 101 according to the second embodiment.

  As described above, in the electric actuator 101 according to the second embodiment and the electric actuator 201 according to the third embodiment, only a part of the parts (the reducer 8 and the coupling 62) is replaced, and many other parts are replaced. It can be composed of common parts. By adopting such a configuration, it is possible to provide an electric actuator suitable for cost reduction and series production when developing a variety of products as described above.

  In addition, also in the electric actuator 201 according to the third embodiment, the configurations of the bearings 13 and 14 that support the motion conversion mechanism unit 3 (ball screw 12) are the same as those in the first embodiment or the second embodiment. Similar to the electric actuator according to the embodiment, it is possible to reduce the shakiness in the axial direction of each of the bearings 13 and 14, and the positioning accuracy of the ball screw 21 in the linear motion direction is improved. Furthermore, since the inner raceway surface 30c is formed on the outer peripheral surface of the nut 30, the bearings 13 and 14 can be downsized.

  As mentioned above, although each embodiment of the electric actuator concerning the present invention was described, the electric actuator concerning the present invention is not restricted to the above-mentioned embodiment. For example, the speed reducer 8 of the second embodiment may be added to the configuration including the bus bar 19 as in the first embodiment.

  Further, as the speed reducer 8, in addition to the above planetary gear speed reducer, for example, a traction drive type planetary speed reducer (planet roller speed reducer) may be employed.

  Further, in the above-described embodiment, the ball screw 12 is employed as the motion conversion mechanism unit 3, but instead of the ball screw 12, a so-called slide screw in which a nut is assembled to the screw shaft without using a ball is used. It may be adopted.

DESCRIPTION OF SYMBOLS 1 Electric actuator 2 Drive part 3 Motion conversion mechanism part 7 Electric motor 12 Ball screw 13 Bearing 14 Bearing 20 Outer ring 20a Outer raceway surface 21 Rolling element 30 Nut 30c Inner raceway surface 31 Screw shaft 42 Wave washer (elastic member)
101 Electric actuator 201 Electric actuator α Contact angle

Claims (4)

A drive unit having an electric motor and a motion conversion mechanism unit that converts the rotational motion of the drive unit into a linear motion are arranged in series, and the motion conversion mechanism unit rotates by receiving the rotational motion of the drive unit. And an electric actuator that is arranged on the inner periphery of the nut and linearly moves with the rotation of the nut, and the nut is rotatably supported by a bearing.
The bearing includes an inner raceway surface formed on an outer circumferential surface of the nut, an outer ring disposed on an outer circumference of the nut and having an outer raceway surface on an inner circumferential surface, and between the inner raceway surface and the outer raceway surface. Rolling elements arranged in the
The electric actuator according to claim 1, wherein the rolling element is disposed with a contact angle with respect to the inner raceway surface and the outer raceway surface.   The electric actuator according to claim 1, wherein the outer ring is an outer ring having a deep groove type outer raceway surface.   3. The electric actuator according to claim 1, wherein an outer diameter of the nut is formed to increase from an axial end side toward an axial center, and the inner raceway surface is an angular raceway surface.   The electric actuator according to any one of claims 1 to 3, further comprising an elastic member that applies a preload in an axial direction to the outer ring.

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