JP2010270887A - Electric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric actuator whose reliability is improved by simplifying a loosening preventing mechanism while reducing cost by reducing the number of parts and processing man-hours. <P>SOLUTION: A ball screw mechanism 8 is coupled to a speed reducing mechanism 6. The electric actuator is made up of a nut 16 supported in rotatable and axially immovable manners via a rolling bearing 18 mounted on a housing 2, and a screw shaft 15 inserted into the nut 16 via a plurality of balls to be integrated coaxially with a driving shaft 7. A tubular blind hole 21 with a flat plane opposed mutually to the housing 2 is formed. The loosening preventing mechanism 9 is formed in a nearly square shape with a flat plane engaging with the flat plane and is movably inserted axially. A spiral protrusion 9a is formed in an inner periphery of the loosening preventing member 9. Then, the protrusion 9a is allowed to engage with a screw groove 15a for the screw shaft 15 to be supported in non-rotatable and axially-movable manners in relation to the housing 2. <P>COPYRIGHT: (C)2011,JPO&INPIT

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 a linear motion of a drive shaft through a shaft.

  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.

  Generally, in an electric actuator provided with a ball screw mechanism and configured to enclose a nut in a housing, a non-rotating groove is provided on the inner periphery of the housing in order to provide a detent for suppressing rotation of the nut. Need to be provided, or the inner periphery must have an irregular (non-cylindrical) shape. However, if a groove is formed in the inner periphery of the housing by machining or if an irregular shape is to be formed, machining of the elongated housing is difficult, so the overall length of the housing is limited, and as a result, a long actuator stroke is secured. There is a problem that you can not. On the other hand, it is conceivable to form a groove on the inner periphery of the housing or to form an irregular shape by molding using a mold, but there is a problem that the mold becomes complicated and the cost is increased. In addition, in order to engage the nut with the inner circumferential groove of the housing, it is necessary to provide a protrusion on the nut, and there is a problem that the cost of the nut is unavoidable. Furthermore, both the inner periphery of the housing and the nut shape must be complicated, which leads to an increase in the size of the actuator.

  As a solution to such a problem, an electric actuator as shown in FIG. 7 is known. This electric actuator is movable so as to be axially movable with respect to the housing 51, the screw shaft 56 having a male screw groove 56a formed on the outer peripheral surface thereof, and is disposed so as to surround the screw shaft 56. A nut 53 having an internal thread groove 53a formed on the inner peripheral surface, a plurality of balls 57 disposed so as to roll along a rolling path formed between the opposing screw grooves 56a and 53a, and the housing 51 A guide member 63 having a guide part 63 a extending along the inner peripheral surface and an engaging part 63 b engaging with the housing 51 is provided.

  The housing 51 includes a substantially hollow cylindrical main body 51a and a cup-shaped lid member 51b fixed so as to close one end of the main body 51a. A cylindrical output shaft 52, which is a driven member, and a nut 53 connected to the output shaft 52 are disposed inside the main body 51a having a cylindrical inner periphery. The output shaft 52 has a left end protruding from the main body in the figure, and a bag hole 52a is formed at the right end in the figure. The outer periphery of the output shaft 52 is slidably supported by the bush 54 with respect to the main body 51a. A seal member 55 is disposed adjacent to the bush 54 and seals between the output shaft 52 and the main body 51a, thereby preventing dust and the like from entering from the outside.

  A screw shaft 56 penetrates the inside of the nut 53 and enters the bag hole 52a of the output shaft 52 so as to freely enter and exit. A male screw groove 56 a is formed on the outer peripheral surface of the screw shaft 56. On the other hand, the nut 53 arranged so as to surround the screw shaft 56 has a groove 53b formed in the axial direction on the outer peripheral lower surface thereof, and a female screw groove 53a formed on the inner peripheral surface thereof. A plurality of balls 57 are movably disposed along a rolling path formed between the opposing screw grooves 56a and 53a. A nut 53 having a tube-type ball circulation member, a screw shaft 56, a ball 57, and a guide member 63 constitute a ball screw mechanism.

  A ball bearing 59 is disposed at the end of the main body 51a via a bearing spacer 58, and supports the screw shaft 56 rotatably. The outer ring of the ball bearing 59 is fixed to the bearing spacer 58 by a fixing member 60. On the other hand, the inner ring of the ball bearing 59 is fixed to the screw shaft 56 by a retaining ring 61. Therefore, the screw shaft 56 can only rotate with respect to the main body 51a. A gear 62 is connected to the right end of the screw shaft 56 so as to rotate integrally by serration.

  The guide member 63 formed by pressing the metal plate material includes a linear guide portion 63a that is engaged with the thread groove 53a of the nut 53, and a member that is bent at a right angle with respect to the guide portion 63a at the right end in the drawing. And a joint part 63b. Further, a groove-like recess 51c is formed on the right end surface of the main body 51a, and the engaging portion 63b is engaged with a recess 51c having the same width (see FIG. 8). The surface of the guide portion 63a is subjected to a surface treatment including a coating treatment such as manganese phosphate or zinc phosphate for reducing friction.

  When the operator operates the switch, the rotation shaft of a motor (not shown) rotates, power is transmitted through the speed reduction mechanism, and the screw shaft 56 rotates with it. Here, since the nut 53 is smoothly guided only in the axial direction by the guide member 63 that exhibits a detent function, the rotational motion of the screw shaft 56 is efficient for the axial motion of the nut 53. The output shaft 52 that has been converted and thus connected to the nut 53 can be moved in the axial direction.

  At the time of assembly, the guide member 63 is inserted from the right end of the main body 51a to which the bush 54 is assembled, the tip of the guide portion 63a is inserted into the notch 54a, and the bent engaging portion 63b is engaged with the concave portion 51c of the main body 51a. According to this configuration, the guide member 63 can be easily attached to the main body 51a without using a special tool. Thereafter, the nut 53 and the output shaft 52 are inserted into the main body 51a so that the guide portion 63a is engaged with the groove 53b, and the screw shaft 56 and the like are assembled.

  In particular, when the guide portion 63a is long, if only one of the guide members 63 is supported, the guide member 63 may be twisted on the unsupported side, and the anti-rotation function may be insufficient. Here, the front end of the guide portion 63a is engaged with the notch 54a of the bush 54, so that both ends of the guide member 63 can be fixed to the main body 51a. Therefore, even if the guide portion 63a is long, It is possible to suppress the twist and realize an effective detent function (see, for example, Patent Document 1).

JP 2008-232338 A

  In such a conventional electric actuator, a groove 53b for preventing the rotation of the nut 53 is formed on the inner periphery of the housing 51 that houses the ball screw as a rotation stopper for the nut 53, and the guide portion 63a is engaged with the groove 53b. At the same time, the front end of the guide portion 63a is engaged with the notch 54a of the bush 54. This not only increases the number of parts, but also increases the number of assembly steps and becomes complicated, resulting in a problem of increased manufacturing costs.

  The present invention has been made in view of such problems of the prior art, and is an electric actuator in which the number of parts and the number of processing steps are reduced to reduce the cost and the rotation prevention mechanism is simplified to improve the reliability. The purpose is to provide.

  In order to achieve the object, the invention according to claim 1 of the present invention transmits a cylindrical housing, an electric motor attached to the housing, and a rotational force of the electric motor via a motor shaft. An electric actuator comprising a speed reduction mechanism and a ball screw mechanism that converts the rotational motion of the electric motor into an axial linear motion of the drive shaft via the speed reduction mechanism, wherein the ball screw mechanism is connected to the speed reduction mechanism. A nut rotatably supported through a rolling bearing mounted on the housing and supported so as not to move in the axial direction, and inserted into the nut through a number of balls, and is coaxially integrated with the drive shaft. A cylindrical bag hole having an engaging portion extending in the axial direction is formed in the housing, and a rotation stopper member is engaged with the engaging portion in the bag hole. And a spiral protrusion is formed on the inner periphery of the anti-rotation member. The protrusion is engaged with a screw groove of the screw shaft, and the screw shaft is inserted into the housing. Is supported so as to be non-rotatable and movable in the axial direction.

  As described above, in the electric actuator including the speed reduction mechanism that transmits the rotational force of the electric motor and the ball screw mechanism that converts the rotational motion of the electric motor to the linear motion in the axial direction of the drive shaft via the speed reduction mechanism. A ball screw mechanism is connected to the speed reduction mechanism, is rotatably supported via a rolling bearing mounted on the housing and is supported so as not to move in the axial direction, and is inserted into the nut via a large number of balls. A cylindrical bag hole having an engaging portion extending in the axial direction is formed in the housing, and the rotation preventing member is engaged with the engaging portion. In a combined state, it is inserted so as to be movable in the axial direction, and a spiral protrusion is formed on the inner periphery of the rotation preventing member. The protrusion is engaged with a screw groove of the screw shaft so that the screw shaft is in the housing. Non-rotatable And because it is axially movably supported, by reducing the number of parts and processing steps together with the cost reduction, the detent mechanism can be provided an electric actuator with improved reliability and simplified.

  According to a second aspect of the present invention, there is provided a cylindrical housing, an electric motor attached to the housing, a reduction mechanism for transmitting the rotational force of the electric motor via a motor shaft, An electric actuator comprising 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 a speed reduction mechanism, wherein the ball screw mechanism is connected to the speed reduction mechanism and is connected to the housing. A screw shaft that is rotatably supported via the mounted rolling bearing and is not axially movable, and is extrapolated to the screw shaft via a large number of balls, and is coaxially integrated with the drive shaft. A cylindrical bag hole having an engaging portion extending in the axial direction is formed in the housing, and the rotation preventing member is engaged with the engaging portion in the bag hole and moves in the axial direction. A concave and convex portion extending in the axial direction is formed on the outer periphery of the nut, and the detent member is externally fitted to the nut while being engaged with the concave and convex portion. And is supported so as to be non-rotatable and movable in the axial direction.

  As described above, in the electric actuator including the speed reduction mechanism that transmits the rotational force of the electric motor and the ball screw mechanism that converts the rotational motion of the electric motor to the linear motion in the axial direction of the drive shaft via the speed reduction mechanism. A ball screw mechanism is connected to the speed reduction mechanism, is rotatably supported via a rolling bearing mounted on the housing, and is supported so as not to move in the axial direction, and is extrapolated to the screw shaft via a number of balls. A cylindrical bag hole having an engaging portion extending in the axial direction is formed in the housing, and a rotation prevention member is formed in the bag hole. In the engaged state, the shaft is movably inserted in the axial direction, and an uneven portion extending in the axial direction is formed on the outer periphery of the nut, and the anti-rotation member is externally fitted to the nut and engaged with the uneven portion. Nut is how Since it is supported so that it cannot rotate with respect to the ring and is movable in the axial direction, it is possible to reduce the number of parts and the number of processing steps, thereby reducing the cost and simplifying the detent mechanism and improving the reliability. it can.

  Further, as in the invention described in claim 3, the engaging portion may be formed of a flat surface, and, as in the invention described in claim 4, the engaging portion is a convex portion or You may be comprised by the recessed part.

  Further, as in the invention described in claim 5, even if the concavo-convex portion is formed of a flat knurled, the anti-rotation member is pressed into the concavo-convex portion while being scraped off, and the nut and the anti-rotation member are integrally fixed. In addition, as in the invention described in claim 6, the uneven portion is formed of serrations, and an uneven portion that engages with the uneven portion is formed on an inner periphery of the rotation preventing member, and the nut and the rotation stop The member may be integrally fixed.

  According to a seventh aspect of the present invention, a recess extending in the axial direction is formed at an end of the drive shaft, a connecting portion is formed at an opening of the recess, and the nut is connected to the connecting shaft. If it is inserted into the part and connected in the axial direction, the screw shaft can be disposed in the recess so as to freely advance and retract, and the drive shaft and the nut can be integrated coaxially with high accuracy.

  In addition, as in the invention according to claim 8, a plurality of perforations are formed in the circumferential direction of the connecting portion, and a plurality of pin holes are formed in the outer periphery of the nut. If the connecting pin is press-fitted into the pin hole, the nut can be further prevented from rotating, and the drive shaft and the nut can be reliably integrated to improve the reliability.

  Moreover, if the housing is formed by an aluminum die casting method and subjected to T6 treatment as in the invention described in claim 9, it prevents wear of the inner peripheral surface of the bag hole where the detent member slides. And durability can be improved.

  Further, if the anti-rotation member is formed of synthetic resin by injection molding as in the invention described in claim 10, the anti-rotation member is prevented from being worn, and the number of processing steps is reduced to reduce the cost. As a result, strength and rigidity are increased, and durability can be improved over a long period of time.

  An electric actuator according to the present invention includes a cylindrical 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 electric motor via the reduction mechanism. An electric actuator comprising a ball screw mechanism that converts the rotational motion of the motor into a linear motion in the axial direction of the drive shaft, wherein the ball screw mechanism is coupled to the speed reduction mechanism and via a rolling bearing attached to the housing. And a nut that is supported so as to be rotatable and immovable in the axial direction, and a screw shaft that is inserted into the nut via a large number of balls and is coaxially integrated with the drive shaft, and the housing A cylindrical bag hole having an engaging portion extending in the axial direction is formed in the bag hole, and a locking member is fitted in the bag hole so as to be movable in the axial direction in a state of being engaged with the engaging portion. In addition, a spiral protrusion is formed on the inner periphery of the rotation preventing member, and the protrusion is engaged with a thread groove of the screw shaft so that the screw shaft cannot rotate with respect to the housing. Since it is supported so as to be movable in the axial direction, it is possible to reduce the number of parts and the number of processing steps, thereby reducing the cost, and it is possible to provide an electric actuator that has an improved reliability by simplifying the detent mechanism.

It is a longitudinal section showing a 1st embodiment of an electric actuator concerning the present invention. It is sectional drawing which shows the ball screw mechanism of FIG. It is a cross-sectional view along the III-III line of FIG. It is a cross-sectional view showing a modification of FIG. It is a longitudinal cross-sectional view which shows 2nd Embodiment of the electric actuator which concerns on this invention. (A) is a principal part enlarged view of FIG. 5, (b) is a side view of (a). It is a longitudinal cross-sectional view which shows the conventional electric actuator. FIG. 8 is a transverse sectional view taken along line IV-IV in FIG. 7.

  A cylindrical 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 a rotational movement of the electric motor via the reduction mechanism. An electric actuator including a ball screw mechanism that converts linear motion in an axial direction, wherein the ball screw mechanism is coupled to the speed reduction mechanism and is rotatable via a rolling bearing attached to the housing, and in an axial direction. The nut is configured to be immovably supported, and a screw shaft that is inserted into the nut via a large number of balls and is coaxially integrated with the drive shaft, and has flat surfaces that face each other on the housing. When a cylindrical bag hole is formed, and the anti-rotation member is formed in a substantially rectangular shape having a flat surface that engages with the flat surface, and is inserted and movably inserted in the axial direction. In addition, a spiral protrusion is formed on the inner periphery of the anti-rotation member, and the protrusion is engaged with a thread groove of the screw shaft so that the screw shaft cannot rotate with respect to the housing. It is supported movably.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view showing a first embodiment of the electric actuator according to the present invention, FIG. 2 is a sectional view showing the ball screw mechanism of FIG. 1, and FIG. 3 is taken along the line III-III of FIG. FIG. 4 is a cross-sectional view showing a modification of FIG.

  The electric actuator 1 includes a cylindrical housing 2, an electric motor 3 attached to the housing 2, and a pair of spur gears 4 and 5 for transmitting the rotational force of the electric motor 3 through a motor shaft 3a. A speed reduction mechanism 6, a ball screw mechanism 8 that converts the rotational motion of the electric motor 3 into an axial linear motion of the drive shaft 7 via the speed reduction mechanism 6, and a detent member 9 of the drive shaft 7 are provided. .

  The housing 2 includes a first housing 2a and a second housing 2b assembled to the end surface. An electric motor 3 is disposed inside the first housing 2a. The electric motor 3 is fixed to a disk-shaped motor bracket 10. The motor bracket 10 is attached so that the outer ring of the ball bearing 18 is sandwiched between the second housing 2b and the first housing 2a and the second housing 2b are closed.

  A motor shaft 3a of the electric motor 3 protrudes from the motor bracket 10, and a small spur gear 4 is attached to the end of the motor shaft 3a so as not to be relatively rotatable by press fitting. The large spur gear 5 is press-fitted into a nut 16 constituting a ball screw mechanism 8 described later, and meshes with the small spur gear 4.

  As shown in an enlarged view in FIG. 2, the ball screw mechanism 8 has a screw shaft 15 having a spiral thread groove 15a formed on the outer periphery thereof, and is opposed to the screw groove 15a of the screw shaft 15, and has a spiral shape on the inner periphery thereof. The nut 16 is formed with a thread groove 16a, and a large number of balls 17 are rotatably accommodated in a spiral space formed by the thread grooves 15a and 16a. The above-described large spur gear 5 is press-fitted and fixed to the outer periphery of the nut 16, and the ball bearing 18 fitted to the first housing 2 a and the motor bracket 10 is positioned and fixed via a retaining ring 19, and is relatively relative to the axial direction. It cannot move and can rotate relatively.

  The cross-sectional shape of each thread groove 15a, 16a may be a circular arc shape or a Gothic arc shape, but here, it has a Gothic arc shape that allows a large contact angle with the ball 17 and a small axial clearance. Is formed. Thereby, the rigidity with respect to an axial load becomes high and generation | occurrence | production of a vibration can be suppressed.

  Here, as shown in FIG. 1, the drive shaft 7 is configured integrally with a screw shaft 15 constituting the ball screw mechanism 8, and is connected to a link member (not shown) at the left end portion of the drive shaft 7. The outer periphery of the drive shaft 7 is slidably supported by the bush 11 with respect to the first housing 2b. A seal member 12 is mounted adjacent to the bush 11 to seal between the drive shaft 7 and the first housing 2b, thereby preventing dust and the like from entering from the outside.

  In the present embodiment, the rotation preventing member 9 is attached to the right end portion of the screw shaft 15. A helical protrusion 9a that engages with the screw groove 15a is formed on the inner peripheral surface of the rotation preventing member 9, and the degree of freedom of rotation of the screw shaft 15 is suppressed. The cross-sectional shape of the protrusion 9a is formed in a Gothic arc shape corresponding to the thread groove 15a. Note that the cross-sectional shape of the protrusion 9a is not limited to the Gothic arc shape, and may be a shape composed of a single R having an approximate shape with respect to the screw groove 15a as long as the backlash with the screw shaft 15 can be minimized. good.

  The screw shaft 15 linearly moves in the left-right direction in the figure as the nut 16 rotates, and the rotation-preventing member 9 also moves in the axial direction as indicated by the arrow in conjunction with the linear motion of the screw shaft 15. When the screw shaft 15 reaches the stroke end position in the linear motion range, the allowable stroke range of the anti-rotation member 9 is restricted so that the anti-rotation member 9 does not interfere with the nut 16.

  A cylindrical bag hole 20 is formed in the first housing 2a, and as shown in FIG. 3, a detent member 9 is inserted into the bag hole 20 so as to be movable in the axial direction through a predetermined radial clearance. Has been. On the inner periphery of the bag hole 20, flat surfaces 20a and 20a facing each other are formed. On the other hand, the cross-sectional shape of the anti-rotation member 9 is formed in a substantially square shape having a flat surface 21 that engages with the flat surfaces 20 a and 20 a of the bag hole 20. As a result, the anti-rotation member 9 can be guided in the axial direction, the degree of freedom in the rotational direction can be suppressed, and the screw shaft 15 can be supported so as to be non-rotatable and axially movable with respect to the first housing 2a.

  The housing 2 including the second housing 2a is formed by an aluminum die casting method, and the flat surfaces 20a and 20a of the bag hole 20 are cut and finished as necessary. The housing 2 is subjected to a precipitation hardening process as a heat treatment, so-called a T6 process, because the anti-rotation member 9 slides. Thereby, abrasion of the inner peripheral surface of the bag hole 20 can be prevented and durability can be improved.

  On the other hand, the anti-rotation member 9 is formed by injection molding from a thermoplastic synthetic resin such as polyphenylene sulfide (PPS), and a reinforcing material such as GF (glass fiber) is added in an amount of 30 to 50 wt%. As a result, it is possible to provide an electric actuator that suppresses wear of the anti-rotation member 9, reduces the number of processing steps, reduces costs, increases strength and rigidity, and improves durability over a long period of time. it can. The anti-rotation member 9 can be exemplified by synthetic resins such as PA (polyamide) 66, PA11, PA6.12, PPA (polyphthalamide), polybutylene terephthalate (PBT) in addition to the materials described above. Moreover, as a fibrous reinforcement, not only GF but CF (carbon fiber), an aramid fiber, a boron fiber, etc. can be illustrated other than this.

  Next, the operation of the electric actuator according to the present invention will be described with reference to FIG. When the electric motor 3 is driven, the rotational force of the motor shaft 3 a is decelerated and transmitted to the nut 16 of the ball screw mechanism 8 via the speed reduction mechanism 6, and the screw shaft 15 is moved in the axial direction as the nut 16 rotates. Perform linear motion within the desired linear motion range. The anti-rotation member 9 that is mounted on the first housing 2 a and engages with the end of the screw shaft 15 moves in the axial direction in conjunction with the linear motion of the screw shaft 15 while being guided by the bag hole 20. The drive shaft 7 can be supported so as to be non-rotatable and movable in the axial direction with respect to the second housing 2b while suppressing the degree of freedom in the rotation direction without disturbing the linear motion of the screw shaft 15.

  FIG. 4 shows a modification of the above-described detent mechanism. In addition, the same code | symbol is attached | subjected to the components site | part similar to the embodiment mentioned above, or the components and site | part which have the same function, and detailed description is abbreviate | omitted.

  A cylindrical bag hole 22 is formed in the second housing 2b, and an anti-rotation member 23 is fitted into the bag hole 22 so as to be movable in the axial direction through a predetermined radial clearance. A convex portion 22 a extending in the axial direction is formed on the inner periphery of the bag hole 22. On the other hand, the rotation preventing member 23 is formed in a cylindrical shape corresponding to the cross-sectional shape of the bag hole 22, and an axially recessed portion 23 a that engages with the protruding portion 22 a is formed on the outer periphery. Accordingly, the rotation preventing member 23 can be guided in the axial direction, the degree of freedom in the rotational direction can be suppressed, and the screw shaft 15 can be supported so as to be non-rotatable and axially movable with respect to the first housing 2a.

  Here, a convex portion 22a is formed on the inner periphery of the bag hole 22, and a concave portion 23a is formed on the outer periphery of the rotation preventing member 23. By engaging the concave portion 23a with the convex portion 22a, a screw shaft is formed. 15 is supported so as to be non-rotatable and movable in the axial direction. However, the present invention is not limited to this. You may make it form in the outer periphery of a member.

  FIG. 5 is a longitudinal sectional view showing a second embodiment of the electric actuator according to the present invention, FIG. 6 (a) is an enlarged view of a main part of FIG. 5, and (b) is a side view of (a). . In this embodiment, the first embodiment of the nut rotation type described above is applied to the shaft rotation type, and the same reference numerals are used for the same parts and parts having the same functions as those of the first embodiment. The detailed description is omitted.

  The electric actuator 13 includes a cylindrical housing 25, an electric motor 3 attached to the housing 25, and a pair of spur gears 26 and 27 that transmit the rotational force of the electric motor 3 via a motor shaft 3a. A speed reduction mechanism 28, a ball screw mechanism 30 that converts the rotational motion of the electric motor 3 into the linear motion in the axial direction of the drive shaft 29 via the speed reduction mechanism 28, and a detent member 31 of the drive shaft 29 are provided. .

  The housing 25 includes a first housing 25a and a second housing 25b assembled to the end surface. The electric motor 3 is disposed inside the first housing 25a. The electric motor 3 is fixed to a disk-shaped motor bracket 10. The motor bracket 10 is attached so that the outer ring of the ball bearing 32 is sandwiched between the support bracket 33 fixed to the inside of the first housing 25a and the first housing 25a and the second housing 25b are closed. Yes.

  The motor shaft 3a of the electric motor 3 protrudes from the motor bracket 10, and a small spur gear 26 is attached to the end of the motor shaft 3a so as not to be relatively rotatable by press fitting. The large spur gear 27 is press-fitted into the end portion of the support shaft 34 protruding from the end portion of the screw shaft 36 and meshes with the small spur gear 26.

  The drive shaft 29 is disposed coaxially with a screw shaft 36 constituting a ball screw mechanism 30 described later, and a hole 7a for connecting to a link member (not shown) is formed at the left end portion of the drive shaft. In addition, a recess 35 extending in the axial direction is formed at the right end, and a nut 37 constituting the ball screw mechanism 30 is attached to the opening, and the screw shaft 36 is disposed in the recess 35 so as to be able to advance and retract.

  As shown in FIG. 6, the ball screw mechanism 30 includes a screw shaft 36 having a spiral thread groove 15a formed on the outer periphery thereof, a screw thread 15a facing the screw groove 15a of the screw shaft 36, and a spiral screw groove formed on the inner periphery thereof. The nut 37 is formed with a nut 16a, and a large number of balls 17 are rotatably accommodated in a spiral space formed by the screw grooves 15a and 16a. A concavo-convex portion 38 made of a flat knurled or the like is formed on the outer periphery of the nut 37, and a stopper member 31 is pressed and integrated into the concavo-convex portion 38 while being scraped off, and retaining rings 40, 40 mounted on both sides. The positioning is fixed through.

  Here, an example is shown in which an uneven portion 38 is formed on the outer periphery of the nut 37, and the rotation preventing member 31 is press-fitted and fixed to the uneven portion 38. However, the present invention is not limited to this. An uneven portion made of serration or the like is formed on the outer periphery, an uneven portion is formed on the inner periphery of the rotation preventing member that engages with the uneven portion, and the rotation preventing member is integrally fixed to the nut by engaging these uneven portions. You may do it.

  A cylindrical bag hole 41 is formed in the second housing 25b, and a rotation preventing member 31 is fitted into the bag hole 41 so as to be movable in the axial direction through a predetermined radial clearance. On the inner periphery of the bag hole 41, flat surfaces 41a and 41a facing each other are formed. On the other hand, the cross-sectional shape of the anti-rotation member 31 is formed in a substantially rectangular shape having a flat surface 42 that engages with the flat surfaces 41 a and 41 a of the bag hole 41. Thus, the rotation preventing member 31 can be guided in the axial direction, the degree of freedom in the rotational direction can be suppressed, and the nut 37 can be supported so as to be non-rotatable and axially movable with respect to the second housing 25b.

  Further, the connecting portion 14 is formed in the opening portion of the recess 35 of the drive shaft 29, and a plurality of (here, two) perforations 43 are formed in the circumferential direction of the connecting portion 14. On the other hand, a plurality (two in this case) of pin holes 44 are formed on the outer periphery of the nut 37, and the connecting pin 45 is press-fitted into the pin hole 44 from the outer diameter direction of the hole 43, so that the drive shaft 29 and the nut 37 are moved in the axial direction. It is connected. Note that a simple connection method in which a nut is press-fitted into the connection portion of the drive shaft may be used, but by using such a connection pin 45, the rotation of the nut 37 can be further strengthened. The drive shaft 29 and the nut 37 can be reliably integrated, and the reliability can be improved.

  Next, the operation of the electric actuator will be described with reference to FIG. When the electric motor 3 is driven, the rotational force of the motor shaft 3a is decelerated and transmitted to the screw shaft 36 via the speed reduction mechanism 28. As the screw shaft 36 rotates, the nut 37 moves in a desired linear motion in the axial direction. Make a linear motion within the range. Then, the anti-rotation member 31 fixed to the outer periphery of the nut 37 and slidably fitted into the bag hole 41 of the second housing 25 b is interlocked with the linear motion of the nut 37 while being guided by the bag hole 41. The drive shaft 29 is supported so as to be non-rotatable and axially movable with respect to the second housing 25b while suppressing the degree of freedom in the rotation direction without disturbing the linear motion of the nut 37. it can.

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

DESCRIPTION OF SYMBOLS 1, 13 Electric actuator 2, 25 Housing 2a, 25a 1st housing 2b, 25b 2nd housing 3 Electric motor 3a Motor shaft 4, 26 Small spur gear 5, 27 Large spur gear 6, 28 Reduction mechanism 7, 29 Drive shaft 7a Holes 8, 30 Ball screw mechanism 9, 23, 31 Anti-rotation member 9a Projection 10 Motor bracket 11 Bush 12 Seal member 14 Connecting portion 15, 36 Screw shaft 15a, 16a Screw groove 16, 37 Nut 17 Ball 18, 32 Ball bearing 19, 40 Retaining ring 20, 22, 41 Bag hole 20a, 21, 41a, 42 Flat surface 22a Convex portion 23a Concavity 33 Support bracket 34 Support shaft 35 Concavity 38 Concavity and convexity 43 Perforation 44 Pin hole 45 Connecting pin 51 Housing 51a Main body 51b Lid member 51c Recess 52 Output shaft 52a Bag hole 53 Nut 53a, 56a Feed groove 53b Groove 54 Bush 54a Notch 55 Seal member 56 Screw shaft 57 Ball 58 Bearing spacer 59 Ball bearing 60 Fixing member 61 Retaining ring 62 Gear 63 Guide member 63a Guide portion 63b Engagement portion

Claims (10)

A cylindrical 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;
In an electric actuator comprising 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,
The ball screw mechanism is connected to the speed reduction mechanism and is rotatably supported via a rolling bearing mounted on the housing and is not axially movable. Inserted and configured with a screw shaft that is coaxially integrated with the drive shaft,
A cylindrical bag hole having an engaging portion extending in the axial direction is formed in the housing, and a rotation stopper member is fitted into the bag hole so as to be movable in the axial direction while being engaged with the engaging portion.
A spiral ridge is formed on the inner periphery of the anti-rotation member, and this ridge is engaged with the screw groove of the screw shaft so that the screw shaft cannot rotate with respect to the housing and can move in the axial direction. It is supported by the electric actuator characterized by the above-mentioned. A cylindrical 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;
In an electric actuator comprising 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,
The ball screw mechanism is coupled to the speed reduction mechanism and is supported by a rolling bearing mounted on the housing so as to be rotatable and non-movable in the axial direction. And is constituted by a nut integrated coaxially with the drive shaft,
A cylindrical bag hole having an engaging portion extending in the axial direction is formed in the housing, and a rotation stopper member is fitted into the bag hole so as to be movable in the axial direction while being engaged with the engaging portion.
An uneven portion extending in the axial direction is formed on the outer periphery of the nut, and the rotation preventing member is fitted on the nut in a state of being engaged with the uneven portion, so that the nut cannot rotate with respect to the housing, and the shaft An electric actuator characterized by being supported so as to be movable in a direction.   The electric actuator according to claim 1, wherein the engaging portion is formed of a flat surface.   The electric actuator according to claim 1, wherein the engaging portion is configured by a convex portion or a concave portion.   5. The electric actuator according to claim 2, wherein the concavo-convex portion is formed of a flat knurled, and is pressed into the concavo-convex portion while the anti-rotation member is scraped off, and the nut and the anti-rotation member are integrally fixed.   The uneven part which consists of the said uneven part which consists of serrations, the uneven part engaged with the said uneven part is formed in the inner periphery of the said anti-rotation member, and the said nut and the anti-rotation member are integrally fixed. Electric actuator.   A recess extending in the axial direction is formed at the end of the drive shaft, and a connecting portion is formed in the opening of the recess, and the nut is fitted into the connecting portion and connected in the axial direction. The electric actuator according to claim 2.   8. A plurality of perforations are formed in a circumferential direction of the connecting portion, a plurality of pin holes are formed in an outer periphery of the nut, and a connecting pin is press-fitted into the pin hole from the outer diameter direction of the perforations. The electric actuator described in 1.   The electric actuator according to any one of claims 1 to 8, wherein the housing is formed by an aluminum die casting method and subjected to T6 treatment.   The electric actuator according to claim 1, wherein the anti-rotation member is formed of a synthetic resin by injection molding.

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