JP5367649B2 - Electric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric actuator that can easily be applied to an industrial machine or the like, and is superior in durability. <P>SOLUTION: The electric actuator 1 includes: a cylinder 2 having a screw groove 7 at its internal periphery and an opening 8 at its end; a rod 3 having a base end 3a inserted into the cylinder 2 from the opening 8 and a tip 3b outside the cylinder 2 at a side opposite to the base end; a screw member 5 which can relatively rotate around the center axis of the screw groove 7 coaxially therewith with respect to the base end 3a of the rod 3, is connected to the rod 3 so as to be integrally movable together with the rod in the direction of the center axis, and has a thread 11 screwed into the screw groove 7 at an external periphery; and a motor 4 which linearly moves the screw member 5 and the rod 3 in the direction of the center axis by relatively rotationally driving the screw member 5 with respect to the rod 3. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to an electric actuator that performs an expansion and contraction motion, which is used in industrial machines and construction machines.

  In fields such as industrial machinery and construction machinery, hydraulic cylinders are widely used as actuators that perform linear drive with large thrust. However, since the hydraulic cylinder is controlled by adjusting the hydraulic pressure, there is a problem that it is difficult to improve the accuracy and responsiveness of the position control.

  Therefore, in recent years, various electric actuators have been developed as actuators that can improve the accuracy and responsiveness of position control.

  For example, the electric actuators described in Patent Documents 1 and 2 have a structure in which a conversion mechanism such as a ball screw structure that converts rotational driving force into linear driving force is coupled to the electric motor. In these electric actuators, the rotational driving force of the electric motor is converted into a linear driving force by a conversion mechanism, and the rod inside the cylinder is reciprocated linearly.

  The electric actuators disclosed in Patent Document 1 and Patent Document 2 have a so-called external configuration in which an electric motor and a speed reduction mechanism are attached to the outside of the cylinder portion. Therefore, the entire electric actuator unit is larger than the hydraulic cylinder. Therefore, it is difficult to apply such an electric actuator to an industrial machine or a construction machine due to the limitation of installation space.

  Therefore, as described in Patent Document 3, as a small electric actuator, an electric actuator having a structure in which a wave gear device (for example, a harmonic drive (registered trademark)) and a screw structure portion are housed in the rotor of the electric motor. Has been proposed. The screw structure portion is composed of a male screw formed on the outer peripheral surface of the rod on the output side and a female screw on the inner peripheral surface of the cylindrical body covering the rod outer peripheral surface. The cylinder is connected to a flex spline on the driven side of the wave gear device.

  In the electric actuator described in Patent Document 3, when the rotor of the motor rotates, the rotational motion of the rotor is reduced by the wave gear device inside the rotor, and the reduced rotational motion is converted into linear motion by the screw structure portion. Thus, the rod is moved linearly. As described above, since the speed reduction mechanism and the motion conversion mechanism are built in the rotor, the entire actuator is compact.

International Publication No. 2006/106817 Japanese Patent Laid-Open No. 2-273049 Japanese Patent Laid-Open No. 7-123631

  However, since the electric actuator described in Patent Document 3 has a structure that linearly moves while the output-side rod rotates, it is used as it is in conventional industrial machines and construction machines to which a hydraulic cylinder that performs only linear movement is applied. It is difficult to apply.

  For this reason, in order to apply the electric actuator described in Patent Document 3 to an industrial machine or a construction machine, a bearing or a jig that can be coupled to the end of the rod while receiving the rotation of the rod is required at an attachment site of the industrial machine or the like. Therefore, it is necessary to change the structure of an industrial machine or the like.

  Further, in the electric actuator described in Patent Document 3, since the thread groove is formed on the outer peripheral surface of the rod, when it is desired to increase the rod stroke, a long rod is required and the thread groove on the outer peripheral surface is formed. It is necessary to widen the range.

  Accordingly, when the long rod is extended and contracted, the thread groove on the outer peripheral surface of the rod may be exposed to the outside of the actuator casing. If the screw groove is exposed to the outside, dust and dust are attached to the screw groove, and foreign matter is likely to be caught in the meshing portion of the screw. Further, when the screw groove is exposed to the outside and exposed to a poor environment (for example, an environment with high humidity), the screw groove portion is easily corroded, and the meshing portion of the screw is easily worn or damaged.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electric actuator that can be easily applied to industrial machines and has excellent durability.

In order to solve the above-described problems, an electric actuator according to the present invention includes a cylinder having a thread groove formed on an inner peripheral surface and having an opening at an end, and a base end that is inserted into the cylinder from the opening. And a rod having a tip portion which is an end portion located outside the cylinder on the opposite side, a relative rotation about the center axis of the screw groove relative to the base end portion of the rod, and the center A screw member that is coupled so as to move integrally with the rod in the axial direction, and has a screw thread that engages with the screw groove on an outer peripheral surface; and the screw member is driven to rotate relative to the rod. by, and a motor for linearly moving the screw member and the rod in the direction of the central axis, said motor comprises a motor body provided inside the rod, relative to the rod A rotating drive shaft, and the screw member is coupled to the drive shaft. The screw member includes a screw member body having an outer peripheral surface on which the thread is formed, and an interior of the screw member body. And a speed reduction mechanism for transmitting the rotational driving force of the motor from the drive shaft to the screw member main body (Claim 1).

  According to this configuration, in the electric actuator, the thread groove is formed on the inner peripheral surface of the cylinder, and the screw member that meshes with the thread groove is the center of the thread groove with respect to the base end portion of the rod inserted into the cylinder. It is connected so as to be able to rotate relative to the shaft coaxially and to move integrally with the rod in the direction of the central axis. Then, by rotating the screw member relative to the rod by the motor, the screw member receiving the rotational driving force of the motor rotates while meshing with the screw groove inside the cylinder, and the screw member and the rod are screw grooves. The cylinder moves linearly in the direction of the center axis of the cylinder. Thus, by converting the rotational motion of the motor into a linear motion that expands and contracts the cylinder and the rod, it is possible to expand and contract similarly to the conventional hydraulic cylinder without rotating the cylinder and the rod.

  Furthermore, since the screw member is attached to the proximal end portion of the rod inside the cylinder, the screw member is not exposed to the outside of the cylinder even if the rod extends to the outside of the cylinder. Therefore, there is no possibility that dust or dust adheres to the thread of the screw member, or foreign matter is caught in the meshing portion of the screw. Further, since the corrosion of the thread can be suppressed, the durability of the electric actuator is improved.

Moreover, according to said structure, since the motor main body is incorporated in the rod, the whole electric actuator can be reduced in size. Moreover, since the motor main body is provided inside the non-rotating rod, the entire electric actuator can be reduced in size, and the motor can be easily mounted and wired. In particular, mounting and wiring of the motor becomes easier as compared with the case where the motor body is provided inside the screw member.

Furthermore, according to said structure, since the speed-reduction mechanism is provided in the inside of a screw member main body, it is possible to transmit the rotational motion of a motor to a screw member main body with a big reduction ratio.

Further, the speed reduction mechanism is composed of a planetary gear device, and the planetary gear device is fixed to the drive shaft and the screw member main body, and is arranged to surround the sun gear. An internal gear, a planetary gear disposed inside the internal gear and transmitting a driving force from the sun gear to the internal gear, and a planet carrier fixed to a base end portion of the rod and supporting the planetary gear. It is preferable to have (claim 2 ).

  According to this configuration, the speed reduction mechanism includes a planetary gear device, the driving-side sun gear is fixed to the driving shaft, the driven-side internal gear is fixed to the screw member body, and the base end portion of the rod on which the planetary carrier does not rotate. Therefore, the sun gear, the planetary gear and the internal gear can be accommodated in a small space inside the screw member main body, and a large reduction ratio can be obtained.

The speed reduction mechanism is composed of a planetary gear device, and the planetary gear device is fixed to the sun gear fixed to the drive shaft and the base end portion of the rod, and is arranged so as to surround the periphery of the sun gear. An internal gear, a planetary gear that is disposed inside the internal gear, transmits a driving force from the sun gear to the internal gear, and a planet carrier that is fixed to the screw member body and supports the planetary gear. It is preferable to have (Claim 3 ).

  According to this configuration, the speed reduction mechanism includes a planetary gear device, the driving-side sun gear is fixed to the driving shaft, the driven-side planetary carrier is fixed to the screw member body, and the base end portion of the rod where the internal gear does not rotate. Therefore, the sun gear, the planetary gear and the internal gear can be accommodated in a small space inside the screw member main body, and an even greater reduction ratio can be obtained.

Further, the speed reduction mechanism is composed of a planetary gear device, and the planetary gear device is coupled to a sun gear fixed to a base end portion of the rod and the drive shaft so as to surround the periphery of the sun gear. An internal gear, a planetary gear that is disposed inside the internal gear, transmits a driving force from the sun gear to the internal gear, and a planet carrier that is fixed to the screw member body and supports the planetary gear. It is preferable to have (claim 4 ).

  According to this configuration, the speed reduction mechanism includes a planetary gear device, the driving-side internal gear is coupled to the driving shaft, the driven-side planetary carrier is fixed to the screw member body, and the base end portion of the rod where the sun gear does not rotate. Therefore, the sun gear, the planetary gear and the internal gear can be accommodated in a small space inside the screw member main body, and a large reduction ratio can be obtained.

Further, the speed reduction mechanism comprises a wave gear device, the wave gear device being fixed to the drive shaft and the screw member main body, along the outer peripheral surface of the wave generator. A flexspline that is elastically deformed and has teeth on the outer peripheral surface, and is fixed to a base end portion of the rod inside the cylinder and is disposed so as to surround the flexspline, and the flexspline is disposed on an inner peripheral surface. preferably it has a circular circular spline having teeth meshing with the teeth (claim 5).

  According to this configuration, the speed reduction mechanism is composed of a wave gear device, the drive-side wave generator is fixed to the drive shaft, the driven-side flexspline is fixed to the screw member body, and the base end of the rod where the circular spline does not rotate Therefore, the wave generator, flex spline and circular spline can be accommodated in a small space inside the screw member main body, and a very large reduction ratio can be obtained. Moreover, since the wave gear device has a small number of parts, it is easy to assemble.

  As described above, according to the electric actuator of the present invention, it can be replaced with a conventional hydraulic cylinder, and thus can be easily applied to industrial machines and construction machines. In addition, since the thread of the screw member is not exposed to the outside of the cylinder, the durability of the electric actuator is improved.

It is a longitudinal cross-sectional view of the electric actuator concerning 1st Embodiment of this invention. FIG. 2 is an enlarged cross-sectional view of the vicinity of a screw member of the electric actuator of FIG. 1. It is an expanded sectional view near the screw member of the electric actuator concerning a 2nd embodiment of the present invention. It is the figure which looked at the planetary gear mechanism of FIG. 3 from the direction where a drive shaft extends. It is an expanded sectional view near the screw member of the electric actuator concerning the modification of a 2nd embodiment of the present invention. It is the figure which looked at the planetary gear mechanism of FIG. 5 from the direction in which a drive shaft extends. It is an expanded sectional view near the screw member of the electric actuator concerning other modifications of the 2nd embodiment of the present invention. It is the figure which looked at the planetary gear mechanism of FIG. 7 from the direction in which a drive shaft extends. It is an expanded sectional view near the screw member of the electric actuator concerning a 3rd embodiment of the present invention. It is the figure which looked at the wave gear mechanism of Drawing 9 from the direction where a drive shaft extends, and is a figure showing the state when the rotation angle of a drive shaft is 0 degrees. It is a figure which shows the state of a wave gear mechanism when the rotation angle of a drive shaft is 90 degree | times. It is a figure which shows the state of a wave gear mechanism when the rotation angle of a drive shaft is 180 degree | times. It is a figure which shows the state of a wave gear mechanism when the rotation angle of a drive shaft is 360 degree | times.

    Embodiments of an electric actuator according to the present invention will be described below in detail with reference to the drawings.

(First embodiment)
The electric actuator 1 shown in FIGS. 1 and 2 includes a cylinder 2, a rod 3, a motor 4, and a screw member 5.

  The cylinder 2 is formed of a cylindrical tube. An opening 8 is formed at one end 2 a of the cylinder 2. The other end 2b of the cylinder 2 is closed and a bracket 12 is attached. The bracket 12 is connected to a movable part such as an industrial machine or a construction machine or the vicinity thereof (for example, an arm or a base of an arm).

  A thread groove 7 is formed on the inner peripheral surface 2 c of the cylinder 2. The thread groove 7 is formed over almost the entire length of the cylinder 2. In addition, when forming the thread groove 7 inside the cylinder 2, the inner surface of the trunk | drum of the cylinder 2 in the state which does not have both ends 2a and 2b is cut, the thread groove 7 is formed, and then both ends 2a, What is necessary is just to braze or weld 2b to a trunk | drum.

  The rod 3 is a rod-shaped member having a base end portion 3 a inserted into the cylinder 2 from the opening 8 and a tip end portion 3 b which is an end portion located outside the cylinder 2 on the opposite side. An opening 13 is formed in the base end portion 3 a of the rod 3. The tip 3b of the rod 3 is closed and a bracket 14 is attached. The bracket 14 is connected to a movable part such as an industrial machine or a construction machine or the vicinity thereof (for example, an arm or a base of the arm).

  A space 15 for accommodating the motor body 9 is formed inside the rod 3. The motor 4 includes a motor main body 9 provided inside the rod 3 and a drive shaft 10. The motor body 9 includes a casing 16, a stator (stator) 17 housed inside the casing 16, and a rotor (rotor) 18 that is rotatably installed inside the stator 17. The drive shaft 10 is coaxially fixed to the rotor 18.

  The motor 4 drives the screw member 5 to rotate relative to the rod 3 to linearly move the screw member 5 and the rod 3 in the direction of the central axis CL.

  The casing 16 is fixed to the inner wall 19 of the space 15 of the rod 3 by brazing or the like. In addition, as another fixing method of the casing 16, for example, the inner wall 19 of the rod 3 and the casing 16 may be provided with recesses or protrusions, respectively, and the casing 16 may be fixed by combining these recesses and protrusions. . Furthermore, the rod 3 itself may be used as the casing of the motor body 9 by directly fitting the stator 17 of the motor into the space 15 of the rod 3.

  The drive shaft 10 protrudes into the cylinder 2 from the opening 13 of the base end portion 3 a of the rod 3.

  Since the motor 4 has the motor body 9 built in the rod 3, the entire electric actuator can be reduced in size. Moreover, since the motor body 9 is provided inside the non-rotating rod 3, the motor 4 can be easily mounted and wired. The motor body 9 may be provided inside the screw member 5.

  The electric wire 20 that supplies electric power to the motor 4 passes through the space 15 of the rod 3, is drawn out from the vicinity of the tip 3 b of the rod 3, and is connected to an external power source (not shown). By switching the direction of the current flowing through the electric wire 20, the rotation direction of the motor 4 can be switched to either forward or reverse.

  The screw member 5 shown in FIG. 2 is rotatable relative to the base end portion 3a of the rod 3 around the center axis CL of the screw groove 7, and moves integrally with the rod 3 in the direction of the center axis CL. To be connected. On the outer peripheral surface of the rod 3, a screw thread 11 that is screwed into the screw groove 7 is formed.

  The screw member 5 of the first embodiment is a solid cylindrical body having a thread 11 formed on the outer peripheral surface thereof, and is directly fixed to the drive shaft 10. Therefore, the rotational driving force of the motor 4 is directly transmitted to the screw member 5. Therefore, the structure of the screw member is simple. Furthermore, since the screw member 5 is a solid cylindrical body, its strength is high.

  The screw groove 7 and the screw thread 11 shown in FIG. 2 employ a screw structure having a triangular cross-sectional shape (triangular screw structure), but other screw thread shapes may be employed. For example, if the trapezoidal screw structure is used, the durability strength of the meshing portion of the screw is improved, and a large tensile load or compressive load acting on the cylinder 2 and the rod 3 can be withstood.

  In the electric actuator 1 according to the first embodiment configured as described above, the screw groove 7 is formed on the inner peripheral surface of the cylinder 2, and the screw member 5 that meshes with the screw groove 7 is inserted into the cylinder 2. The rod 3 is connected to the base end portion 3a so as to be rotatable about the same axis as the center axis CL of the screw groove 7 and to move integrally with the rod 3 in the direction of the center axis CL. The motor 4 drives the screw member 5 to rotate relative to the rod 3 to linearly move the screw member 5 and the rod 3 in the direction of the central axis.

  As a result, when the screw member 5 is rotated forward or reversely by the rotational driving force of the motor 4 inside the rod 3, the screw member 5 is engaged with the screw groove 7 of the inner peripheral surface 2 c of the cylinder 2. The screw member 5 and the rod 3 reciprocate linearly in the cylinder 2 in the direction of the central axis CL of the screw groove 7. As a result, the rotational motion of the motor 4 can be converted into a linear motion that relatively expands and contracts the cylinder 2 and the rod 3.

  Since the tip 3b of the rod 3 is connected to a movable part such as an industrial machine or a construction machine or in the vicinity thereof, the rod 3 is a cylinder even if it receives a reaction force generated when the screw member 5 rotates. The cylinder 2 can be moved linearly without rotating relative to the cylinder 2.

  A detent may be provided between the rod 3 and the cylinder 2 in order to prevent the rod 3 from rotating relative to the cylinder 2.

  The screw member 5 also has a function of decelerating when converting the rotational motion of the motor 4 to linear motion. That is, when the screw member 5 rotates in the cylinder 2 by the driving force of the motor 4, it can be decelerated to a linear moving speed that is much slower than the peripheral speed of the screw member 5. The reduction ratio related to this reduction is determined by the thread pitch of the thread 11 of the screw member 5.

  In the electric actuator 1 configured as described above, the screw member 5 moves linearly while rotating inside the cylinder 2, but the rod 3 itself moves linearly relative to the cylinder 2 without rotating. Therefore, it is possible to realize only the expansion / contraction motion similar to that of the conventional hydraulic cylinder without rotating the cylinder 2 and the rod 3. As a result, the electric actuator 1 of the present invention can be easily applied without changing the structure of an industrial machine or construction machine to which a conventional hydraulic cylinder is applied.

  Furthermore, in this electric actuator 1, even if the cylinder 2 and the rod 3 extend and contract over a long distance, the screw member 5 positioned at the proximal end portion 3a of the rod 3 is not exposed to the outside of the cylinder 2. Therefore, since the thread 11 of the screw member 5 is not exposed to the outside, the durability of the electric actuator 1 is improved.

  Further, the rod 3 exposed to the outside of the cylinder 2 has a smooth outer peripheral surface in which no thread is formed on the outer peripheral surface, like the rod of the hydraulic cylinder. For this reason, if the outer circumferential surface of the rod 3 is coated with the same wear resistance and corrosion resistance as the rod outer circumferential surface of the hydraulic cylinder, the rod 3 can be used while maintaining high durability even in a poor environment. Is possible.

  In the present invention, the motor 4 accommodated in the rod 3 may be any electric motor as long as it can be accommodated in the rod 3 and the screw member 5 can be rotated. Any type, method, or structure of electric motor may be employed.

(Second Embodiment)
In the first embodiment described above, the screw member 5 is decelerated when converting the rotational driving force of the motor 4 into a linear driving force. However, if it is desired to further increase the reduction ratio, the planetary member is placed inside the screw member. A structure having a speed reduction mechanism such as a gear mechanism may be used.

  That is, in the electric actuator 21 of the second embodiment, as shown in FIGS. 3 to 4, the screw member 22 includes a screw member main body 23 and a planetary gear mechanism 24. In addition, in FIGS. 3-4, the part to which the code | symbol same as the code | symbol of FIGS. 1-2 was attached | subjected points out the part same as FIGS.

  The screw member main body 23 is a circular cast body in which a screw thread 11 is formed on the outer peripheral surface thereof. A recess 23 b is formed in the end 23 a of the screw member main body 23.

  The planetary gear mechanism 24 is provided inside the recess 23 b of the screw member main body 23. The planetary gear mechanism 24 is a speed reduction mechanism that transmits the rotational driving force of the motor 4 from the drive shaft 10 to the screw member main body 23.

  Specifically, the planetary gear mechanism 24 includes a sun gear 25, an internal gear 26, a plurality of planetary gears 27, and a planet carrier 28.

  The sun gear 25 is fixed to the drive shaft 10 and functions as a drive-side gear.

  The internal gear 26 is fixed to the inner peripheral surface of the recess 23b of the screw member main body 23, and functions as a driven gear. The internal gear 26 is disposed so as to surround the sun gear 25.

  The plurality of planetary gears 27 are arranged inside the internal gear 26 and transmit driving force from the sun gear 25 to the internal gear 26.

  The planet carrier 28 is a member that rotatably supports a plurality of planetary gears 27 at predetermined intervals. The planet carrier 28 is fixed to the proximal end portion 3 a of the rod 3. Therefore, the plurality of planetary gears 27 can only rotate without revolving around the sun gear 25.

  In the planetary gear mechanism 24 shown in FIGS. 3 to 4, the sun gear 25 is rotated by the rotational driving force input from the drive shaft 10 of the motor 4. The planetary gear 27 that meshes with the sun gear 25 rotates in the direction opposite to the rotation direction of the sun gear 25. The internal gear 26 that meshes with the planetary gear 27 rotates while decelerating in the same direction as the planetary gear 27. The screw member main body 23 to which the internal gear 26 is fixed rotates together with the internal gear 26.

  In this case, since the ratio (N1 / N2) of the number of teeth N1 of the sun gear 25 to the number of teeth N2 of the internal gear 26 is a reduction ratio, the rotational motion of the motor 4 is greatly reduced and transmitted to the screw member body 23. It is possible.

  As described above, in the second embodiment, the planetary gear mechanism 24 is provided inside the screw member main body 23, the driving-side sun gear 25 is fixed to the drive shaft 10, and the driven-side internal gear 26 is connected to the screw member main body 23. Since the planetary carrier 28 is fixed to the base end portion 3a of the rod 3 that does not rotate, the sun gear 25, the planetary gear 27, and the internal gear 26 can be accommodated in a small space inside the screw member main body 23. In addition, a large reduction ratio can be obtained. As a modification of the second embodiment, as shown in FIGS. 5 to 6, the planetary carrier 28 of the planetary gear mechanism 24 is fixed to the screw member main body 23 as the driven side, and the internal gear 26 is fixed to the sun gear 25. You may fix to the base end part 3a of the rod 3 so that it may not revolve around. The drive-side sun gear 25 is fixed to the drive shaft 10 as in FIGS.

  That is, the planetary gear mechanism 24 of the modification shown in FIGS. 5 to 6 is fixed to the sun gear 25 fixed to the drive shaft 10 and the base end portion 3 a of the rod 3 so as to surround the sun gear 25. The arranged internal gear 26, the planetary gear 27 arranged inside the internal gear 26 and transmitting the driving force from the sun gear 25 to the internal gear 26, and the planets fixed to the screw member body 23 and supporting the planetary gear 27. The carrier 28 is configured. The planet carrier 28 is fixed to the inner back surface 23 c of the recess 23 b of the screw member main body 23.

  The planetary gear mechanism 24 of the modification shown in FIGS. 5 to 6 performs a speed reduction operation as follows. First, when the sun gear 25 is rotated by the rotational driving force input from the drive shaft 10 of the motor 4, the planetary gear 27 that meshes with the sun gear 25 rotates in the direction opposite to the rotation direction of the sun gear 25. At this time, the planetary gear 27 revolves in the same direction as the rotation direction of the sun gear 25 while meshing with the internal gear 26 fixed to the base end portion 3 a of the rod 3. At the same time, the planet carrier 28 for fixing the planetary gear 27 revolves together with the planetary gear 27. As a result, the screw member main body 23 to which the planet carrier 28 is fixed rotates together with the planet carrier 28.

  In this case, the ratio of the number of teeth N1 of the sun gear 25 to the sum of the number of teeth N1 of the sun gear 25 and the number of teeth N2 of the internal gear 26 (N1 / (N1 + N2)) is the reduction ratio. It is possible to decelerate at a larger reduction ratio and transmit it to the screw member main body 23.

  As another modification of the second embodiment, as shown in FIGS. 7 to 8, the internal gear 26 is connected to the drive shaft 10 on the drive side, and the planet carrier 28 of the planetary gear mechanism 24 is driven. As a side, the sun gear 25 may be fixed to the base end portion 3 a of the rod 3 by fixing to the screw member main body 23.

  That is, the planetary gear mechanism 24 of the modification shown in FIGS. 7 to 8 is coupled to the sun gear 25 fixed to the base end portion 3 a of the rod 3 and the drive shaft 10 so as to surround the sun gear 25. The arranged internal gear 26, the planetary gear 27 arranged inside the internal gear 26 and transmitting the driving force from the sun gear 25 to the internal gear 26, and the planets fixed to the screw member body 23 and supporting the planetary gear 27. The carrier 28 is included. The planet carrier 28 is fixed to the inner back surface 23 c of the recess 23 b of the screw member main body 23.

  Further, the internal gear 26 shown in FIG. 7 receives the rotational driving force of the motor 4, so that the drive shaft 10 is connected via the output gear 10 a of the drive shaft 10 and the transmission shaft 29 having gears 29 a and 29 b at both ends. 10 is connected. The input side gear 29 a of the transmission shaft 29 meshes with the output gear 10 a, and the output side gear 29 b meshes with the internal gear 26.

  The planetary gear mechanism 24 of the modification shown in FIGS. 7 to 8 performs a speed reduction operation as follows. First, when the internal gear 26 is rotated by the rotational driving force input from the drive shaft 10 of the motor 4 via the transmission shaft 29, the planetary gear 27 that meshes with the internal gear 26 rotates in the same direction as the rotation direction of the internal gear 26. To do. At this time, the planetary gear 27 revolves in the same direction as the rotation direction of the internal gear 26 while meshing with the sun gear 25 fixed to the base end portion 3 a of the rod 3. At the same time, the planet carrier 28 that fixes the planetary gear 27 revolves together with the planetary gear 27. As a result, the screw member main body 23 to which the planet carrier 28 is fixed rotates together with the planet carrier 28.

  In this case, the ratio of the number of teeth N2 of the internal gear 26 to the sum of the number of teeth N1 of the sun gear 25 and the number of teeth N2 of the internal gear 26 (N2 / (N1 + N2)) is the reduction ratio. It is possible to decelerate at a large reduction ratio and transmit it to the screw member main body 23.

(Third embodiment)
Further, if a wave gear mechanism (for example, Harmonic Drive (registered trademark)) as described below is used as the speed reduction mechanism inside the screw member, a larger speed reduction ratio can be obtained.

  That is, in the electric actuator 31 of the third embodiment, as shown in FIGS. 9 to 10, the screw member 32 includes a screw member main body 33 and a wave gear mechanism 34. 9-13, the part to which the code | symbol same as the code | symbol of FIGS. 1-2 was attached | subjected points out the part same as FIGS. 1-2.

  The screw member main body 33 is a circular casting having a thread 11 formed on the outer peripheral surface thereof. A recess 33 b is formed in the end 33 a of the screw member main body 33.

  The wave gear mechanism 34 is provided inside the recess 33 b of the screw member main body 33. The wave gear mechanism 34 is a speed reduction mechanism that transmits the rotational driving force of the motor 4 from the drive shaft 10 to the screw member main body 33.

  Specifically, the wave gear mechanism 34 includes a wave generator 35, a flex spline 36, and a circular spline 37.

  The wave generator 35 is fixed to the drive shaft 10 and functions as a drive-side gear. The wave generator 35 includes an elliptical cam 41 and a ball bearing 42 attached to the outer periphery thereof.

  The ball bearing 42 is configured by inserting a plurality of balls 43 having a small diameter between an inner ring 44 and an outer ring 45. The inner ring 44 is fixed to the elliptical cam 41. The outer ring 45 is elastically deformed by the ball 43.

  The flex spline 36 is fixed to the screw member main body 33 and functions as a driven gear. The flexspline 36 is a thin cup-shaped metal elastic part, and teeth 36a are formed on the outer peripheral side. The flex spline 36 is disposed by being elastically deformed along the outer peripheral surface of the wave generator 35. The inner peripheral surface of the flex spline 36 is in contact with the outer ring 45 of the ball bearing 42. A bottom portion 36 a (see FIG. 9) of the flex spline 36 is fixed to the inner back surface 33 c of the concave portion 33 b of the screw member main body 33.

  The circular spline 37 is a rigid ring-shaped part, and teeth 37a are carved on the inner periphery. The circular spline 37 is fixed to the proximal end portion 3 a of the rod 3, is arranged so as to surround the periphery of the flexspline 36, and meshes with the outer teeth 36 a of the flexspline 36. The number of teeth of the circular spline 37 is two more than the number of teeth of the fresco spline 36.

  In the wave gear mechanism 34, as shown in FIG. 10, the flex spline 36 fixed to the screw member main body 33 is bent elliptically by the wave generator 35. For this reason, the teeth 36a of the flexspline 36 are engaged with the teeth 37a of the circular spline 37 at the elliptical long axis portion, but are completely disengaged at the short axis portion.

  As shown in FIG. 11, when the wave generator 35 fixed to the drive shaft 10 is rotated in the clockwise direction C <b> 1 by the rotational driving force of the motor 4 with the circular spline 37 fixed to the proximal end portion 3 a of the rod 3. The fresco spline 36 is elastically deformed, and the position where it engages with the teeth 37a of the circular spline 37 moves sequentially.

  Then, as shown in FIG. 12, when the wave generator 35 rotates 180 degrees in the clockwise direction C1, the fresco line 36 moves in the counterclockwise direction C2 by the number of teeth.

  Further, as shown in FIG. 13, when the wave generator 35 makes one rotation (360 degrees), the fresco line 36 has two teeth less than the circular spline 37. Therefore, the counterclockwise direction C2 is equivalent to two teeth difference. Move to.

  In this case, each time the wave generator 35 makes one rotation, the flex spline 36 reversely rotates by the amount of two teeth, so that the rotational motion of the motor 4 is reduced to a very large reduction ratio and transmitted to the screw member body 33. It is possible.

  In the third embodiment, a wave gear mechanism 34 is provided inside the screw member main body 33, the drive-side wave generator 35 is fixed to the drive shaft 10, and the driven-side flex spline 36 is fixed to the screw member main body 33. Since the spline 37 is fixed to the base end portion 3a of the rod 3 that does not rotate, the wave generator 35, the flexspline 36, and the circular spline 37 can be accommodated in a small space inside the screw member main body 33, and a very large reduction ratio. It is possible to obtain In addition, the main components of the wave gear mechanism 34 are only three (wave generator 35, flex spline 36, circular spline 37). Therefore, the number of parts is very small, and the assembly of the wave gear device 34 is easy.

1, 2, 31 Electric actuator 2 Cylinder 3 Rod 4 Motor 5, 22, 32 Screw member 7 Screw groove 8 Opening 9 Motor body 10 Drive shaft 11 Thread 12 Bracket 23, 33 Screw member body 24 Planetary gear mechanism 34 Wave gear mechanism

Claims (5)

A cylinder having a thread groove formed on the inner peripheral surface and having an opening at the end;
A rod having a proximal end portion inserted into the cylinder from the opening and a distal end portion located on the opposite side to the outside of the cylinder;
It is connected to the base end of the rod relative to the central axis of the screw groove and coaxially, and is connected to move integrally with the rod in the direction of the central axis. A screw member having a screw thread to be screwed onto,
A motor that linearly moves the screw member and the rod in the direction of the central axis by rotationally driving the screw member relative to the rod ;
The motor has a motor body provided inside the rod and a drive shaft that is rotatable relative to the rod;
The screw member is coupled to the drive shaft;
The screw member includes a screw member main body having the thread formed on an outer peripheral surface thereof, and a speed reduction mechanism that is provided inside the screw member main body and transmits a rotational driving force of the motor from the drive shaft to the screw member main body. And having
An electric actuator characterized by that. The speed reduction mechanism comprises a planetary gear device,
The planetary gear device is
A sun gear fixed to the drive shaft;
An internal gear fixed to the screw member body and arranged to surround the sun gear;
A planetary gear disposed inside the internal gear and transmitting a driving force from the sun gear to the internal gear;
Is fixed to a base end portion of the rod, the electric actuator according to claim 1 and a planetary carrier for supporting the planetary gears. The speed reduction mechanism comprises a planetary gear device,
The planetary gear device is
A sun gear fixed to the drive shaft;
An internal gear fixed to the base end of the rod and arranged to surround the sun gear;
A planetary gear disposed inside the internal gear and transmitting a driving force from the sun gear to the internal gear;
Fixed to said screw member body, the electric actuator according to claim 1 and a planetary carrier for supporting the planetary gears. The speed reduction mechanism comprises a planetary gear device,
The planetary gear device is
A sun gear fixed to the proximal end of the rod;
An internal gear coupled to the drive shaft and arranged to surround the sun gear;
A planetary gear disposed inside the internal gear and transmitting a driving force from the sun gear to the internal gear;
Fixed to said screw member body, the electric actuator according to claim 1 and a planetary carrier for supporting the planetary gears. The speed reduction mechanism comprises a wave gear device,
The wave gear device is
An elliptical wave generator fixed to the drive shaft;
A flexspline that is fixed to the screw member body, is elastically deformed and arranged along the outer peripheral surface of the wave generator, and has teeth on the outer peripheral surface;
A circular circular spline that is fixed to the base end of the rod and is arranged so as to surround the flexspline and has teeth that mesh with the teeth of the flexspline on the inner peripheral surface;
The electric actuator according to claim 1 .

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