JP2010133519A - Actuator of multi-stage structure - Google Patents

Abstract

Provided is an actuator having a multi-stage structure capable of making inertia relatively small even when positioning with a long stroke.
An actuator 1 having a multi-stage structure includes a plurality of drive units 10A to 10C and a guide unit 20. The guide unit 20 includes a guide member 3 that moves integrally with the drive units 10A to 10C, and the guide member. Each of the drive units 10A to 10C is disposed on the same guide rail 2 and is simultaneously driven by one motor 8 to have two ball screws 11A, 11B. The two ball screws 11A and 11B are driven by the motor 8 through the gear mechanism 19 by rotating the nut, the screw shafts 4 and 4 of the adjacent drive units are connected to each other, and the rotation of the screw shafts is restricted. Thus, the driven body A is conveyed.
[Selection] Figure 1

Description

  The present invention relates to an actuator having a multistage structure suitable for long stroke positioning.

As an actuator for the purpose of long stroke positioning, for example, a technique described in Patent Document 1 is known. The technique described in this document is suitable for a case where a large stroke is required in the vertical direction, and is driven by moving the nut by rotating the screw shaft of the two-axis ball screw arranged vertically with a servo motor. A long stroke is obtained with respect to the driven body by adopting a two-stage multistage structure using a separate guide unit for each vertical slide mechanism.
Japanese Patent Laying-Open No. 2006-102886 (FIG. 1) JP 2007-218285 A (FIGS. 3 and 4)

  However, although the technique described in Patent Document 1 has no problem when used for vertical movement, the slide mechanism is cantilevered when used for horizontal movement. Therefore, as the stroke becomes longer, an excessive moment load is applied to the guide member corresponding to the guide unit due to the influence of gravity. Further, when this has a further multi-stage structure (for example, a three-stage structure), it is difficult to support its own weight in the horizontal direction. Therefore, a separate long guide unit is required to support the drive unit. Furthermore, since it is driven by screw shaft rotation and nut movement, the rotational energy of the ball screw inertia is not consumed during acceleration / deceleration. Especially when positioning a long stroke, the screw shaft becomes longer, and the inertia is correspondingly increased. Therefore, energy loss increases.

  On the other hand, for example, the technique described in Patent Document 2 has a drive unit that drives a biaxial feed screw with a single motor by rotating a nut, and if the feed screw is replaced with a ball screw, the axial direction is precise. Positioning is possible. However, the technique described in Patent Document 2 is not a multistage structure using a plurality of drive units, and is a technique in which the feed screws of the drive units are overlapped (overlapping in the transport direction). It is not something to offer. Therefore, long stroke positioning using a feed screw longer than the length of the drive unit cannot be performed. Accordingly, there still remains a problem to be solved in constructing a multi-stage actuator.

  Therefore, the present invention has been made paying attention to such a problem, and an object of the present invention is to provide an actuator having a multi-stage structure that can make inertia relatively small even when positioning with a long stroke. It is said.

  In order to solve the above-described problems, the present invention provides a multistage actuator including a plurality of drive units and a guide unit that guides the plurality of drive units, and the guide unit is attached to each drive unit. A guide member that moves integrally with the guide member, and a guide rail that supports the guide member so as to be slidable. The drive units are disposed on the same guide rail, and include a single motor, Two ball screws that are simultaneously driven by one motor, and the two ball screws of each drive unit are configured to be driven by a nut rotation via a gear mechanism by the one motor, Furthermore, the screw shafts of adjacent drive units are connected to each other, and the driven body is conveyed by restraining the rotation of the screw shafts. It is characterized in that there.

  According to the actuator having a multistage structure according to the present invention, each drive unit is driven to rotate by a nut, so that the inertia can be reduced as compared with a configuration in which a long screw shaft is rotated. Therefore, energy loss during acceleration / deceleration can be suppressed, and economical operation is possible. Since a plurality of these drive units are arranged on the same guide rail and the screw shafts of adjacent drive units are connected to each other, the multi-stage actuator as a whole can be positioned with a long stroke while keeping the inertia relatively small. Is possible.

  In each drive unit of the multi-stage actuator according to the present invention, as a configuration in which two nuts are driven by a single motor through a gear mechanism, for example, in the case of a ball screw having the same twist direction, the nut is In the case of a ball screw that is rotated in the opposite direction and the twist direction is reversed, the screw shafts can be moved relative to each other by rotating the nut in the same direction. In addition, as a guide unit, a guide member is laid across a guide rail via rolling elements such as balls or rollers, and if the guide rail and the guide member are held with a preload without a gap, the guide unit is driven. This is suitable for smoothly sliding the unit and suppressing its vibration.

Here, in the multi-stage actuator according to the present invention, for example, if the plurality of drive units have the same configuration, it is more economical to configure a multi-stage actuator.
In the actuator having a multistage structure according to the present invention, for example, each of the drive units preferably has a through hole or a notch for avoiding interference with a screw shaft of another drive unit. With such a configuration, a through hole or a notch hole is provided in the mating drive unit to avoid interference. Therefore, when the actuator of the multi-stage structure is extended or contracted, the screw shaft of the ball screw of each drive unit And other drive units are prevented from interfering with each other. Therefore, the screw shafts of the drive units can be arranged so as to overlap each other. Therefore, since a long ball screw can be adopted for each drive unit, the stroke per drive unit can be set larger.

  In the multistage actuator according to the present invention, it is preferable that the screw shafts of the adjacent drive units are coaxially connected to each other in the plurality of drive units. With such a configuration, the ball screw receives an axial force when the driven body is conveyed, but no moment is generated by arranging adjacent screw shafts coaxially.

  As described above, according to the multistage actuator according to the present invention, the inertia can be made relatively small even when positioning with a long stroke.

Hereinafter, embodiments of an actuator having a multistage structure according to the present invention will be described with reference to the drawings as appropriate. In addition, the following 1st and 2nd embodiment is an example which comprised the multistage structure using three drive units.
First, a first embodiment of an actuator having a multistage structure according to the present invention will be described in detail with reference to FIGS. FIG. 1 is a plan view of a first embodiment of an actuator having a multistage structure according to the present invention. 2 is a diagram for explaining the drive unit of FIG. 1. FIG. 2 (a) is a view taken in the direction of arrow A in FIG. 1, and FIG. is there.

  As shown in FIG. 1, the multi-stage actuator 1 includes a plurality of drive units 10A, 10B, and 10C, and a guide unit 20 that guides the plurality of drive units 10A to 10C. The plurality of drive units 10A to 10C all have the same configuration. In this specification, the first drive unit 10A, the second drive unit 10B, and the third drive unit 10C are referred to in order from the right unit in FIG.

  As shown in FIG. 2, each drive unit 10 </ b> A to 10 </ b> C has one servo motor 8 and two ball screws 11 </ b> A and 11 </ b> B that are simultaneously driven by the servo motor 8. Each of the ball screws 11A and 11B includes a screw shaft 4 and a nut 5 that is externally fitted to the screw shaft 4 via a large number of balls (not shown). The nuts 5 and 5 between the two ball screws 11A and 11B are configured to rotate simultaneously via the gear mechanism 19 when the servo motor 8 is driven.

  More specifically, as shown in FIG. 2, each drive unit 10 </ b> A to 10 </ b> C includes a unit housing 9. A servomotor 8 is attached to the unit housing 9, and a gear mechanism 19 and a support bearing 18 are provided in the unit housing 9. Of the two ball screws 11 </ b> A and 11 </ b> B, the nut 5 of the lower ball screw 11 </ b> B is connected to the output shaft 8 a of the servo motor 8 via the gear mechanism 19 in the unit housing 9. Yes. The nuts 5, 5 are arranged in parallel in the height direction of the unit housing 9, and are supported by the support bearing 18 while being freely rotatable and restraining movement in the radial direction and the axial direction.

  In this embodiment, the twist directions of the thread grooves of the two ball screws 11A and 11B are the same (for example, both are right screws), and when the nut 5 of the ball screw 11B is rotationally driven by the servo motor 8, The nut 5 of the other ball screw 11A connected thereto via the gear mechanism 19 is also rotationally driven in the opposite direction at the same time, so that the nuts 5 and 5 between the two ball screws 11A and 11B are opposite to each other. The screw shafts 4 and 4 are rotated so as to move relative to each other in opposite directions. When the twisting directions of the thread grooves 4 and 4 of the two ball screws 11A and 11B are opposite to each other, a gear mechanism 19 having one or an odd number of intermediate gears is interposed between the nuts 5 and 5. The nuts 5 and 5 may be connected to each other. In this embodiment, the gear is directly attached to the output shaft 8a of the servo motor 8. However, the rotating shaft of the gear is supported by a bearing and connected to the motor via a coupling or the like. May be.

On the other hand, the guide unit 20 is attached to each of the drive units 10A to 10C and moves together with the drive units 10A to 10C (two for each drive unit), and the plurality of guide members 3. And two guide rails 2 arranged in parallel on the base B so as to be slidably supported in the axial direction.
Each guide member 3 includes a ball or a roller inside as a rolling element, and straddles the guide rail 2 via the rolling element. Moreover, the guide rail 2 and each guide member 3 have a preload, and are hold | maintained without a gap | interval, Thereby, the vibration of each drive unit 10A-10C can be suppressed, and it aims at noise reduction. Further, by applying preload to the guide unit 20, the rigidity of the drive units 10A to 10C in the direction perpendicular to the axis is increased. Therefore, even when moment force is generated from the adjacent nut, positioning accuracy when converted into the axial direction Has improved.

The multistage actuator 1 supports the drive units 10A to 10C described above so as to be slidable in the axial direction by the same guide rail 2 of the guide unit 20 as shown in FIG.
Hereinafter, the multistage structure by each of the drive units 10A to 10C will be described. In addition, five figures shown to Fig.3 (a)-(e) are each the figures which show the VZ to ZZ cross section in FIG.

  As shown in FIG. 3, this multistage actuator 1 has the second drive unit 10B shifted from the first drive unit 10A by the offset amount F of the nut 5, and further the third drive unit 10C. Are shifted in the vertical direction (left-right direction in FIG. 2A) by the offset amount F of the nut 5 with respect to the second drive unit 10B. A through hole 22 and a notch 44 for avoiding interference with the screw shaft 4 of the drive unit are provided along the axial direction.

  Specifically, the nuts 5 and 5 are arranged with an offset amount F as shown in FIG. This offset amount F is such that in the axial direction of each screw shaft 4, the structure such as the gear mechanism 19 and the support bearing 18 and the screw shafts 4, 4 between the two ball screws 11 A, 11 B do not interfere with each other. It has been established. Furthermore, each unit housing 9 is provided with a through hole 22 and a notch 24 along the axial direction of the screw shaft 4. The through hole 22 and the notch 24 are provided at the same interval as the offset amount F, and are formed at positions facing each other so as to avoid interference with the screw shaft 4 of another drive unit.

  In FIG. 1, the rotation of the screw shaft 4 (BS-1B) of the ball screw 11B of the first drive unit 10A is restricted to the base B via the fixed arm 7 at one end (right end portion in the figure). It is fixed in the state. As shown in FIG. 3E, the first drive unit 10A has its unit housing 9 supported by the guide member 3 on the guide unit 20 so as to be slidable. As the nut 5 rotates, it slides on the guide rail 2.

  Furthermore, the screw shaft 4 (BS-1A) of the ball screw 11A of the first drive unit 10A has one end (the left end portion in FIG. 1), the screw shaft 4 (BS-2A) of the ball screw 11A of the second drive unit 10B. Are connected together by a connecting member 25. Further, between the first drive unit 10A and the second drive unit 10B, as shown in FIG. 3D, a substantially L-shaped connecting arm 6 formed so as not to interfere with the screw shaft 4. Is provided. The connecting arm 6 has a base end attached to a guide member 3 on the guide rail 2 and slides on the guide rail 2. And the front-end | tip part of this connection arm 6 is connected with the said connection member 25, and it becomes movable integrally with the screw shafts 4 and 4 (BS-1A, BS-2A) in the state where rotation was restrained. ing. As shown in FIG. 3C, the second drive unit 10B is attached to the guide member 3 on the guide rail 2 via a support member 26 having a height corresponding to the offset amount F.

  Similarly, the screw shaft 4 (BS-2B) of the ball screw 11B of the second drive unit 10B has one end (the left end portion in FIG. 1) at the screw shaft 4 (ball screw 11B of the third drive unit 10C). BS-3B) and a connecting member 25 are integrally connected to one end (right end portion in FIG. 1). Then, as shown in FIG. 3 (b), a crank-like connection is formed between the second drive unit 10B and the third drive unit 10C so that there is no interference with the screw shaft 4 as described above. The arm 6 is provided so as to be slidable by the guide member 3 on the guide unit 20, and the distal end portion of the connecting arm 6 is connected to the connecting member 25, and the screw shaft in a state in which rotation is constrained. 4 and 4 (BS-2B, BS-3B) are integrated with the guide rail 2 so as to be slidable. As shown in FIG. 3A, the third drive unit 10C is attached to the guide member 3 on the guide rail 2 via a support member 26 having a height corresponding to two offset amounts F. .

  Further, the screw shaft 4 (BS-3A) of the ball screw 11A of the third drive unit 10C is connected with one end (left end portion in FIG. 1) to the tip of the driven body connecting arm 12 in a state where rotation is constrained. The base end portion of the driven body connecting arm 12 is attached to the guide member 3 on the guide rail 2 on the upper side of FIG. 1, thereby sliding on the guide rail 2 integrally with the driven body connecting arm 12. It is like that.

  The multi-stage actuator 1 connects the driven body connecting arm 12 (or the guide member 3 to which the driven body connecting arm 12 is attached) to the target driven body A, thereby allowing the base B and the driven body A to move relative to each other. Can be done. In addition, when there are a plurality of driven bodies A, the driving units 10A to 10C and the connecting arms 6 and the driven body A are connected, and the driving units 10A to 10C are controlled independently, thereby It is good also as a structure which positions the to-be-driven body A independently.

Next, the operation, action and effect of the first embodiment will be described.
FIG. 4 is a diagram showing a state where the distances between the drive units 10A to 10C are clogged.
According to the multistage actuator 1 of the first embodiment, by having the above-described configuration, the two nuts 5 and 5 are rotationally driven by the single servo motor 8 via the gear mechanism 19 and are constrained screws. When the grooves 4 and 4 are ball screws having the same twist direction, the nuts 5 and 5 rotate in the opposite directions. Since each drive unit is formed in a multi-stage structure so as to move relative to each other on 4, 4, long stroke positioning can be performed.

  Further, according to this multistage actuator 1, the guide member 3 is straddled over the guide rail 2 via the rolling elements, and the guide rail 2 and the guide member 3 are held without gaps with a preload. The vibrations of the drive units 10A to 10C can be suppressed and noise reduction can be achieved. Moreover, since the rigidity in the direction perpendicular to the axis of each of the drive units 10A to 10C is increased by applying the preload, the positioning accuracy when converted to the axial direction can be improved even when moment force is generated from the adjacent nut. Can do.

  For example, in the technique described in Patent Document 2, since the guide structure is a sliding guide having a gap, it is insufficient for restraining vibration or the like accompanying rotation of the nut in a direction perpendicular to the axis. Therefore, in the technique described in this document, when the feed screw or the ball screw is rotated at a high speed, the entire unit vibrates and noise is a problem. On the other hand, the configuration of the present embodiment can solve such problems of vibration and noise.

  Further, according to this multistage actuator 1, since the nut is driven to rotate, the inertia becomes lower than that of rotating a long screw shaft. Therefore, energy loss during acceleration / deceleration can be suppressed, and economical operation is possible. A plurality of drive units 10A to 10C are arranged on the same guide rail 2, and the mutual screw shafts 4 and 4 are connected by restricting the rotation thereof, so that a long stroke can be achieved while making the inertia relatively small. Positioning is possible.

  In particular, according to this multi-stage actuator 1, as shown in FIG. 3, the second drive unit 10B has an offset amount F of the nut 5 relative to the first drive unit 10A, and further the third drive unit 10C. Is shifted in the vertical direction (left-right direction in FIG. 2A) by the offset amount F of the nut 5 with respect to the second drive unit 10B, and each of the drive units 10A to 10C includes other Since the through hole 22 and the notch 44 for avoiding interference with the screw shaft 4 of the drive unit are provided along the axial direction, the ball screw of each of the drive units 10A to 10C when the actuator 1 having a multi-stage structure is expanded and contracted Interference between the screw shaft 4 of 11A and 11B and another drive unit is prevented. Therefore, as shown in FIG. 4, the screw shafts 4 of the drive units can be arranged so as to overlap each other. Therefore, according to this multistage actuator 1, a long ball screw can be adopted for each of the drive units 10A to 10C, so that the stroke per drive unit can be set larger.

  That is, FIG. 4A is a diagram focusing on the screw shafts 4 and 4 of the two ball screws 11A and 11B of the first drive unit 10A, but the screw shaft 4 of the ball screw 11B is the second drive unit 10B. And it can project to a position where it interferes with the third drive unit 10C. Similarly, FIG. 4B is a view focusing on the screw shafts 4 and 4 of the two ball screws 11A and 11B of the second drive unit 10B, but the screw shaft 4 of the ball screw 11B is the third drive. The unit 10C and the screw shaft 4 of the ball screw 11A can project to positions that interfere with the first drive unit 10A. Similarly, FIG. 4C is a view focusing on the screw shafts 4 and 4 of the two ball screws 11A and 11B of the third drive unit 10C, but the screw shaft 4 of the ball screw 11B is the first drive. It can project to a position where it interferes with the unit 10A and the second drive unit 10B.

  In this way, each of the drive units 10A to 10C is provided with the through hole 22 and the notch 24 along the axial direction of the screw shaft 4 to avoid interference with the screw shaft 4 of the other drive unit. The overhanging to the interference position does not become a problem, and the distance between the drive units 10A to 10C can be reduced to the position shown in FIGS. 4A to 4C without any problem. Further, as shown in FIGS. 3 (b) and 3 (d), the connecting arm 6 is formed in a substantially L shape or a crank shape so as not to interfere with the screw shaft 4. Interference with the screw shaft 4 at the lower and upper parts of the arm 6 is prevented. Therefore, according to this multistage actuator 1, a long ball screw can be adopted for each of the drive units 10A to 10C, so that the stroke per drive unit can be set to be larger.

Next, a second embodiment will be described.
The second embodiment of the present invention is that the same drive units 10A to 10C as those in the first embodiment are arranged by alternately inverting the drive units 10A to 10C as shown in FIG. Is different. That is, in the second embodiment, odd-numbered drive units (one in this example) and even-numbered drive units face the same direction. Further, in the second embodiment, the screw shafts 4 and 4 connected by the connecting arm 6 are coaxially arranged in the connection between the screw shafts 4 and 4 (see FIGS. 6B and 6D). . About another structure, it is the same as that of 1st embodiment.

With such a configuration, each ball screw receives an axial force when transporting the driven body A, but by arranging the screw shafts 4 and 4 of adjacent drive units coaxially, No moment is generated in the connecting portion (connecting member 25).
Although FIG. 5 shows an example in which the drive units 10A to 10C having the same shape are used and the odd-numbered drive unit 10B is inverted, the offset amount is set between the odd-numbered drive unit and the even-numbered drive unit. A drive unit with F in the opposite direction may be prepared and the servo motors 8 may be aligned.

Next, a third embodiment will be described.
The third embodiment of the present invention uses the same two drive units 10A and 10B as the first embodiment described above. As shown in FIGS. 7 and 8, the drive units 10A to 10B are replaced by nuts 5 and 5, respectively. The point which arrange | positions facing so that arrangement | positioning and the arrangement position of the through-hole 22 may become coaxial at the same height differs from 1st embodiment.

FIG. 9 is a diagram when the drive units 10A and 10B in the third embodiment are close to each other.
FIG. 4A is a view focusing on the screw shafts 4 and 4 of the two ball screws 11A and 11B of the first drive unit 10A, but the screw shaft 4 (BS-1B) of the ball screw 11B is the second one. It overhangs to a position where it interferes with the drive unit 10B. Similarly, FIG. 5B is a view focusing on the screw shafts 4 and 4 of the two ball screws 11A and 11B of the second drive unit 10B, but the screw shaft 4 (BS-2A) of the ball screw 11A. Projecting to positions that interfere with the first drive unit 10A.

  However, as described with reference to FIG. 2A, each of the drive units 10A and 10B has a through hole 22 and a notch 24 for avoiding interference with the screw shaft 4 of the other drive unit. In the present embodiment, the nuts 5 and 5 and the through holes 22 are disposed at the same height so as to face each other coaxially, so that the drive unit 10A, When the 10Bs face each other, as shown in FIG. 8, the screw shafts 4, 4 pass through the mutual through holes 22, so that interference between the drive units 10A to 10B can be avoided.

The multi-stage actuator according to the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in each of the above-described embodiments, the example in which the offset amount F is given to the nuts 5 and 5 of the ball screws 11A and 11B has been described. There may be no offset amount F. That is, as in the modification shown in FIG. 10, the axis CL of the servo motor 8 and the nuts 5 and 5 of the ball screws 11A and 11B may be arranged on one line. However, since the screw shaft interference problem between the drive units occurs in the same manner as described above, through holes and notches are provided in each drive unit at the same intervals as the offset amount F between the drive units (same as above The figure shows an example in which a notch 24 is provided).

Further, as a modification of the above embodiment, for example, as shown in FIGS. 11 and 12, the mounting posture of the drive unit may be rotated by 90 °. In addition, the example shown in FIG. 11 and FIG. 12 is an example which rotated the drive unit 90 degrees in 2nd embodiment.
That is, as shown in FIG. 12, in this modification, the support member 26 and the connecting arm 6 are provided so as to connect the mutual guide members 3 on the two guide rails 2 arranged in parallel on the base B. Yes. The drive units 10A to 10C whose mounting posture is rotated by 90 ° (the servo motor 8 side is the base B side) are placed and fixed on the support member 26, and the connection member 25 is attached to the connection arm 6. Are connected. Even with such a configuration, the same operations and effects as those of the first to second embodiments are achieved.

  In each of the above embodiments, the through hole 22 and the notch 24 are not particularly referred to the diameter of the hole, but in addition to being formed so as not to interfere with the screw shaft 4, the through hole 22 and For example, the gap between the notch 24 and the screw shaft 4 may be adjusted so as to slide with a slight gap therebetween to suppress the vibration of the screw shaft 4. Moreover, in order to make sliding more smooth, you may make it the screw shaft 4 penetrate through a bush.

In each of the above-described embodiments, an example in which a multistage structure is configured using two or three drive units has been described. However, the present invention is not limited to this, and a multistage structure (for example, four or more stages) is further added. It may be.
In addition, when a long ball screw is used for screw shaft rotation drive and high-speed rotation, the critical speed may be a problem. However, since the multi-stage actuator according to the present invention is a nut rotation drive, Is a problem, for example, by adopting a vibration damper as disclosed in Japanese Patent No. 3438286, the problem of dangerous speed can be solved.

1 is a plan view of a first embodiment of an actuator having a multistage structure according to the present invention. FIGS. 2A and 2B are diagrams illustrating the drive unit of FIG. 1, in which FIG. 1A is a view taken in the direction of arrow A in FIG. 1, and FIG. FIG. 5 is a diagram (a) to (e) showing cross sections VV to ZZ in FIG. 1 respectively. It is a figure of the state where the distance between each drive unit was jammed. It is a top view of 2nd embodiment of the actuator of the multistage structure concerning this invention. FIGS. 6A to 6E are cross-sectional views taken from VV to ZZ in FIG. It is a top view of 3rd embodiment of the actuator of the multistage structure concerning this invention. FIGS. 8A to 8E are cross-sectional views taken from VV to ZZ in FIG. It is a figure when each drive unit approaches. It is a figure explaining the modification of the drive unit used for the actuator of the multistage structure concerning the present invention, and the figure shows the figure corresponding to Drawing 2 of a first embodiment. It is a top view of the modification of 2nd embodiment of the actuator of the multistage structure concerning this invention. It is the figure (a)-(e) which each shows the VZ to ZZ cross section in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Actuator of multistage structure 2 Guide rail 3 Guide member 4 Screw shaft 5 Nut 6 Connecting arm 7 Fixed arm 8 Servo motor (motor)
9 Unit housing 10A, 10B, 10C Drive unit 11A, 11B Ball screw 12 Driven body connection arm 18 Support bearing 19 Gear mechanism 20 Guide unit 22 Through hole 24 Notch 25 Connection member 26 Support member A Driven body B Base

Claims (4)

A multi-stage actuator comprising a plurality of drive units and a guide unit for guiding the plurality of drive units,
The guide unit includes a guide member that is attached to each drive unit and moves integrally therewith, and a guide rail that supports the guide member so as to be slidable,
Each drive unit is disposed on the same guide rail, and has one motor and two ball screws driven simultaneously by the one motor,
The two ball screws of each drive unit are configured to be driven by the nut rotation through the gear mechanism by the one motor, and the screw shafts of adjacent drive units are connected to each other. A multistage actuator characterized in that a driven body is conveyed by restraining rotation of a shaft.   The multi-stage actuator according to claim 1, wherein the plurality of drive units have the same configuration.   3. The multistage actuator according to claim 1, wherein each of the drive units has a through hole or a notch for avoiding interference with a screw shaft of another drive unit.   4. The multistage actuator according to claim 1, wherein screw shafts of adjacent drive units are coaxially connected to each other in the plurality of drive units. 5.

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