KR101468495B1 - Ball screw nut module of fixed type and small linear actuator having the same - Google Patents

Abstract

The present invention relates to a fixed ball screw nut module and a small-sized linear actuator having the fixed ball screw nut module, and is capable of downsizing the linear actuator even when a ball screw nut module is applied, and having a gravity compensation function. A screw shaft, a nut, a plurality of balls, a ball fixing tube, and an output shaft according to the present invention. The screw shaft is formed with threads and threads in the axial direction. The nut is coupled to the screw shaft, and a plurality of ball insertion holes are formed along the direction of the thread of the screw shaft. A plurality of balls are respectively inserted into the ball insertion holes. The ball fixing tube is engaged with an outer circumferential surface of a nut into which a plurality of balls are inserted, so that the plurality of balls are constrained to the ball insertion holes of the nut so that the plurality of balls rotate in the ball insertion hole. The output shaft is connected to the nut and protrudes to one side.

Description

Technical Field The present invention relates to a fixed ball screw nut module and a small linear actuator having the ball screw nut module.

The present invention relates to a small-sized linear actuator, and more particularly, to a small-sized linear actuator to which a fixed ball screw nut module is applied and which has a gravity compensation function.

Recent mechatronics machines and robots often require linear motion, so linear actuators are used in various devices. Here, the linear actuator means a motor that moves linearly in a horizontal direction.

Such linear actuators include a linear actuator having a linear AC motor linearly wound, a linear actuator using a rotary motor and a rack and pinion mechanism, and the like. In addition, solenoids that use electromagnets for mechanical motion are also types of linear actuators.

For the linear actuator, a circulating ball screw nut module is used. The circulating ball screw nut module has a structure in which a ball for supporting friction or load is circulated in the ball screw nut. Therefore, the volume of the circulating ball screw nut module in the linear actuator is large and it is difficult to miniaturize the linear actuator .

On the other hand, when the circulating ball screw nut module is not applied, the linear actuator can be manufactured in a small size. However, the small linear actuator without the circulating ball screw nut module has a problem in that the accuracy can not be maintained.

Korean Patent Publication No. 10-2011-0103402 (September 20, 2011)

Accordingly, it is an object of the present invention to provide a fixed ball screw nut module capable of downsizing a linear actuator even when a ball screw nut module is applied, and a small-sized linear actuator having the same.

Another object of the present invention is to provide a fixed ball screw nut module having gravity compensation function and a small linear actuator having the same.

In order to achieve the above object, the present invention provides a fixed ball screw nut module for a small linear actuator including a screw shaft, a nut, a plurality of balls, a ball fixing tube, and an output shaft. The screw shaft is formed with threads and threads in the axial direction. The nut is coupled to the screw shaft, and a plurality of ball insertion holes are formed along the direction of the thread of the screw shaft. The plurality of balls are inserted into the ball insertion holes, respectively. The ball fixing tube is coupled to an outer peripheral surface of the nut into which the plurality of balls are inserted, so that the plurality of balls are constrained to the ball insertion holes of the nut so that the plurality of balls rotate in the ball insertion hole. The output shaft is connected to the nut and protruded to one side.

In the fixed ball screw nut module according to the present invention, the screw shaft includes a connecting shaft, a threaded shaft and a stopper ring. The connection shaft is connected to a drive shaft of the motor. The threaded shaft is formed to extend axially in the connecting shaft, and a thread is formed on the outer peripheral surface. The stopper ring is formed at a boundary between the connection shaft and the threaded shaft, and has a larger diameter than the connection shaft and the threaded shaft.

In the fixed ball screw nut module according to the present invention, the ball contacts the threaded shaft of the screw shaft through the ball insertion hole of the nut.

In the fixed ball screw nut module according to the present invention, the size of the ball insertion hole of the nut corresponds to the width of the thread of the screw shaft.

In the fixed ball screw nut module according to the present invention, engineering plastic may be used as the material of the ball fixing tube.

The fixed ball screw nut module according to the present invention may further include a frame, an elastic support, and an elastic body. The frame includes a screw shaft, a nut, a plurality of balls, and a ball fixing tube excluding the output shaft, and a guide hole capable of reciprocating linearly in a direction in which the output shaft protrudes is formed. The elastic supporter is provided on one side of the frame facing the output shaft. The elastic body connects one side of the output shaft and the elastic support. At this time, an object is connected to the other side of the output shaft.

The present invention also relates to a fixed ball screw nut module as described above, and a small linear actuator including a motor that is connected to the screw shaft to rotate the screw shaft and linearly move the output shaft along the screw shaft according to rotation of the screw shaft Lt; / RTI >

In the small-sized linear actuator according to the present invention, the drive shaft of the motor is installed parallel to the screw shaft, and the drive shaft and the screw shaft are connected to each other via gears to transmit power.

According to the present invention, a small linear actuator can provide a linear actuator with a small size and high load, and high accuracy, by disposing a structure in which the ball is circulated and restricting the ball in the ball insertion hole of the nut to implement a mechanism for rotating the ball .

Further, since the small linear actuator according to the present invention has a structure in which a ball fixing tube having a slight elasticity is coupled to the nut, the ball is smoothly rotated in the ball insertion hole while restraining the ball constrained in the ball insertion hole of the nut So that the small linear actuator can perform a stable linear motion.

The miniature linear actuator according to the present invention includes a small motor that is connected to a screw shaft on which a nut is installed to lift a heavy object You can get a great deal of power.

1 is a perspective view showing a small-sized linear actuator having a fixed ball screw nut module according to an embodiment of the present invention.
Fig. 2 is an exploded perspective view showing the miniature linear actuator of Fig. 1;
3 is an exploded perspective view showing the fixed ball screw nut module of FIG.
FIG. 4 is a perspective view showing a state where the fixed ball screw nut module of FIG. 1 is coupled.
5 and 6 are views showing an operation example of a small linear actuator having a fixed ball screw nut module according to an embodiment of the present invention.
FIGS. 7 and 8 are views showing an operation example in which a small linear actuator having a fixed ball screw nut module according to an embodiment of the present invention lifts an object by gravity compensation by an elastic body.

In the following description, only parts necessary for understanding the embodiments of the present invention will be described, and the description of other parts will be omitted so as not to obscure the gist of the present invention.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings and the inventor is not limited to the meaning of the terms in order to describe his invention in the best way. It should be interpreted as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention, so that various equivalents And variations are possible.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view showing a small-sized linear actuator having a fixed ball screw nut module according to an embodiment of the present invention. Fig. 2 is an exploded perspective view showing the miniature linear actuator of Fig. 1;

1 and 2, a small linear actuator 100 according to an embodiment of the present invention includes a motor 10 and a fixed ball screw nut module 20. The motor 10 and the stationary ball screw nut module 20 are coupled to each other. The motor 10 includes a drive shaft 12 and transmits driving force to the stationary ball screw nut module 20 through the drive shaft 12 to rotate the output shaft 70 connected to the screw shaft 40 of the ball screw nut module 20 ).

The motor 10 rotates the output shaft 70 along the screw shaft 40 as the drive shaft 12 is connected to the screw shaft 40 to rotate the screw shaft 40, Exercise. The drive shaft 12 of the motor 10 is installed parallel to the screw shaft 40 and the drive shaft 12 and the screw shaft 40 are connected to each other via a pair of gears 14 and 21 to transmit power .

The pair of gears 14 and 21 includes a first gear 14 coupled to the drive shaft 12 of the motor 10 and a second gear 14 coupled to the screw shaft 40 of the ball screw nut module 20. [ 21).

The ball screw nut module 20 according to the present embodiment implements a mechanism that allows the ball 53 to be constrained and rotated in the ball insertion hole 51 formed in the nut 50, do. Accordingly, the ball screw nut module 20 according to the present embodiment can provide a compact linear actuator 100 that is small in size, high in load, and high in precision.

The ball screw nut module 20 according to this embodiment will be described in detail with reference to FIGS. 1 to 4. FIG. 3 is an exploded perspective view showing the fixed ball screw nut module of FIG. FIG. 4 is a perspective view showing a state where the fixed ball screw nut module of FIG. 1 is coupled.

The ball screw nut module 20 according to the present embodiment includes a screw shaft 40, a nut 50, a plurality of balls 53, a ball fixing tube 60, and an output shaft 70. The ball screw nut module 20 according to the present embodiment may further include a frame 30, an elastic support 80, and an elastic body 90.

The screw shaft 40 is formed with a screw thread 45 and a screw thread 47 in the axial direction. The screw shaft 40 includes a connecting shaft 41, a threaded shaft 43 and a stopper ring 49. The screw shaft 40 is connected to the drive shaft 12 of the motor 10. The threaded shaft 43 extends axially in the connecting shaft 41 and has threads 45 and threaded holes 47 formed on its outer circumferential surface. The stopper ring 49 is formed at the boundary between the connecting shaft 41 and the threaded shaft 43 and has a larger diameter than the connecting shaft 41 and the threaded shaft 43.

The second gear 21 is coupled to the connection shaft 41 and engaged with the first gear 14 coupled to the drive shaft 12 of the motor 10 via the second gear 21, Receive power.

The threaded shaft 43 is formed with threads 45 between the threaded bores 47 formed at a predetermined pitch in the axial direction. The threaded shaft 43 is pivoted to the frame 30 via a pair of bearings 23, 25. The pair of bearings 23 and 25 includes a first bearing 23 coupled to one end of a threaded shaft 43 under the stopper ring 49 and a second bearing 25 coupled to the other end of the threaded shaft 43 ). The second bearing 25 is fixed to the frame 30 via the bolt 27. The bolt 27 is fastened to the fastening groove formed at the end of the threaded shaft 43.

When the stopper ring 49 is provided with the screw shaft 40 on the frame 30, the threaded shaft 43 is inserted into the mounting space 31 of the frame 30, and the connecting shaft 41 is inserted into the frame 30 So that it can protrude outward.

At this time, the threaded shaft 43 is formed longer than the connecting shaft 41 with respect to the stopper ring 49.

The second gear 21 is coupled to the connection shaft 41 and engaged with the first gear 14 coupled to the drive shaft 14 of the motor 10 via the second gear 21, Receive power.

The nut 50 is screwed to the screw shaft 40 and a plurality of ball insertion holes 51 are formed in the direction of the threaded screw 47 of the screw shaft 40. The nut 50 is screwed to the screw shaft 40 and moves in a linear direction along the screw shaft 40 as the screw shaft 40 rotates. The ball insertion hole 51 is formed at a position corresponding to the threaded hole 47 of the screw shaft 40.

The nut 50 has threaded threads and threaded threads on the inner circumferential surface opposite to the threads 45 and threads 47 of the screw shaft 40 so as to be screwed onto the screw shaft 40. The ball insertion hole 51 is formed along the threaded hole 47 of the nut 50.

The length of the nut 50 is designed in consideration of the distance that the screw 50 moves in a linear direction to the left and right. Of course, the length of the nut 50 is shorter than the length of the threaded shaft 43.

The plurality of balls 53 are inserted into the ball insertion holes 51 of the nut 50, respectively. At this time, a metal or a hard plastic ball may be used as the ball 53. The balls 53 come into contact with the threads 47 of the screw shaft 40 through the ball insertion holes 51 of the nut 50. [ The size of the ball insertion hole 51 of the nut 50 may be formed to correspond to the width of the threaded bore 47 of the screw shaft 40 so that the ball 53 can stably contact the threaded bore 47 . The ball 53 inserted into the ball insertion hole 51 is exposed on the outer circumferential surface of the nut 50.

Since the nut 50 is screwed to the screw shaft 50 via the ball 53 inserted in the ball insertion hole 51, the contact area between the nut 50 and the screw shaft 50 is reduced . As a result, the nut 50 smoothly moves linearly along the screw shaft 50 as the screw shaft 50 rotates.

The ball fixing tube 60 is engaged with the outer circumferential surface of the nut 50 into which the plurality of balls 53 are inserted so that the plurality of balls 53 are inserted into the nut insertion hole 51, (50). As the material of the ball fixing tube 60, an engineering plastic having a slight elasticity may be used. Therefore, the ball fixing tube 60 is coupled to the outer peripheral surface of the nut 50 with a predetermined elasticity.

At this time, the engineering plastic used as the material of the ball fixing tube (60) is not only excellent in strength and elasticity but also excellent in impact resistance, abrasion resistance, heat resistance, cold resistance, chemical resistance and electrical insulation. Although engineering plastics differ in performance and characteristics depending on their chemical structure, for example, polyamide, polyacetyl, polycarbonate, polyester resin (PBT), modified polyphenylene oxide (PPO) Can be used. The common point of engineering plastics is that they are high molecular materials ranging from several hundreds to several million, unlike conventional plastics having a molecular weight of several tens to several hundreds of low molecular weight substances.

Since the nut 50 has a structure in which the ball fixing tube 60 having a slight elasticity is coupled to the nut 50 so as to smoothly rotate the ball 53 while fixing the ball 53 from the nut 50, So that the small linear actuator 100 to be manufactured can be stably driven.

The output shaft 70 is connected to the nut 50 and protrudes out through the guide hole 33 of the frame 30. The output shaft 70 is provided with a first connection ring 71 through which an object or an elastic body 90 can be connected to both opposite surfaces in a direction parallel to the screw shaft 40.

The frame 30 is formed therein with an installation space 31 in which a screw shaft 40, a nut 50, a plurality of balls 53, and a ball fixing tube 60, except for the output shaft 70, A guide hole 33 is formed which can reciprocate linearly in a direction in which the output shaft 70 is projected. Of course, the installation space 31 and the guide hole 33 are connected to each other, and the guide hole 33 corresponds to the linear reciprocating distance of the output shaft 70 or is formed to be long. The frame 30 includes an installation frame 35 in which an installation space 31 is formed and a motor mounting plate 37 and an elastic mounting plate 39 which are formed to extend on both sides of the upper and lower portions of the mounting frame 35 do.

The motor (10) is fixed to the frame (30). The frame 30 is fixed to the motor mounting plate 37 extending to the side where the first gear 14 is to be mounted with respect to the mounting frame 35 in which the mounting space 30 is formed. Or the frame 30 may be fixedly mounted to the motor 10.

The elastic supporter 80 is fixed to one side of the frame 30 facing the output shaft 70. The output shaft 70 and the elastic member mounting plate 39 of the frame 30 facing the output shaft 70 via a coupling nut 83. [ And a second linking ring 81 to which the elastic body 90 can be connected is provided at the tip of the elastic support base 80 facing the output shaft 70.

The elastic body 90 connects one side of the output shaft 70 and the elastic support 80 and provides elasticity to the output shaft 70. The elastic support 80 and the elastic body 90 are installed side by side with the screw shaft 40. In this embodiment, an example in which a coil spring is used as the elastic body 90 is disclosed. At this time, one end of the coil spring is fitted in the first connection ring 71, and the other end of the coil spring can be fitted in the second connection ring 81. An object may be connected to the other side of the output shaft 70.

The ball screw nut module 20 according to the present embodiment has the structure in which the nut 50 is connected to the frame 30 by the elastic body 90 to realize the gravity compensation mechanism, The small motor 10 connected to the installed screw shaft 40 can also lift a heavy object or generate a large force.

An operation example of the small linear actuator 100 according to this embodiment will be described with reference to FIGS. 5 and 6. FIG. 5 and 6 are views showing an operation example of a small linear actuator 100 having a fixed ball screw nut module 20 according to an embodiment of the present invention.

5, when the driving shaft 12 of the motor 10 rotates the first gear 14 in the clockwise direction, the second gear 21 engaged with the first gear 14 rotates counterclockwise do.

As the second gear 21 rotates in the counterclockwise direction, the nut 50 screwed to the screw shaft 40 is linearly moved in the + Y axis direction along which the second gear 21 is provided along the screw shaft 40 Exercise. The nut 50 rotates in contact with the threaded bore 47 in the ball insertion hole 51 as the ball 53 of the nut 50 rotates in accordance with the rotation of the screw shaft 40, Axis direction in the + Y-axis direction.

The output shaft 70 also linearly moves in the + Y-axis direction in accordance with the linear motion of the nut 50 in the + Y-axis direction.

6, when the driving shaft 12 of the motor 10 rotates the first gear 14 counterclockwise, the second gear 21 engaged with the first gear 14 rotates clockwise do.

As the second gear 21 rotates clockwise, the nut 50 threadedly engaged with the screw shaft 40 moves along the screw shaft 40 to the opposite side of the side where the second gear 21 is installed, Direction. The nut 50 rotates while the ball 53 of the nut 50 contacts the thread 45 in the ball insertion hole 51 in accordance with the rotation of the screw shaft 40, Axis direction in the + Y-axis direction.

The output shaft 70 also linearly moves in the -Y-axis direction in accordance with the linear motion of the nut 50 in the -Y-axis direction.

An operation example in which the small linear actuator 100 according to the present embodiment lifts an object will be described with reference to FIGS. 7 and 8. FIG. 7 and 8 are views showing an operation example in which a small linear actuator 100 having a fixed ball screw nut module 20 according to an embodiment of the present invention lifts an object by gravity compensation by an elastic body 90 .

Referring to FIG. 7, an object is connected to the upper portion of the output shaft 70. At this time, since the output shaft 70 has a structure connected to the frame 30 via the elastic body 90, gravity compensation according to the weight of the object is performed through the elastic body 90.

When the motor 10 rotates the first gear 14 in the clockwise direction, the second gear 21 engaged with the first gear 14 rotates counterclockwise.

Then, the output shaft 70 coupled to the screw shaft 40 through the nut 50 moves upward and lifts the object upward. In this case, when the coil spring is used as the elastic body 90, the length is increased and the elastic force is accumulated.

Next, referring to FIG. 8, an object is connected to the lower portion of the output shaft 70. At this time, since the output shaft 70 has a structure connected to the frame 30 via the elastic body 90, gravity compensation according to the weight of the object is performed through the elastic body 90.

When the motor 10 rotates the first gear 14 in the counterclockwise direction, the second gear 21 engaged with the first gear 14 rotates clockwise.

The output shaft 70 coupled to the screw shaft 40 via the nut 50 moves upward to lift the object upward. In this case, when the coil spring is used as the elastic body 90, the length is reduced and the elastic force is accumulated.

It should be noted that the embodiments disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

10: motor 12: drive shaft
14: First gear 20: Fixed ball screw nut module
21: second gear 23: first bearing
25: second bearing 30: frame
31: installation space 33: guide hole
40: screw shaft 41: connecting shaft
43: threaded shaft 45: threaded
47: Screw ball 49: Stopper ring
50: Nut 51: Ball insertion hole
53: ball 60: ball fixing tube
70: Output shaft 80: Elastic support
90: Elastic body 100: Small linear actuator

Claims (8)

A screw shaft having threads and threads formed in the axial direction;
A nut coupled to the screw shaft and having a plurality of ball insertion holes formed along the direction of a thread of the screw shaft;
A ball which contacts the threaded bore of the screw shaft through the ball insertion hole and is exposed on an outer circumferential surface of the nut;
Wherein the plurality of balls are coupled to an outer circumferential surface of the nut into which the plurality of balls are inserted so that the plurality of balls are rotated in the ball insertion hole, A ball fixing tube which abuts on the ball exposed on the outer circumferential surface to support rotation of the ball;
An output shaft connected to the nut and projecting to one side;
And a fixed ball screw nut module for a small linear actuator. 2. The screw according to claim 1,
A connection shaft connected to a drive shaft of the motor;
A threaded shaft formed on the connection shaft and extending in the axial direction, the threaded shaft having a thread and a thread on an outer peripheral surface thereof;
A stopper ring formed at a boundary between the connection shaft and the threaded shaft and having a larger diameter than the connection shaft and the threaded shaft;
And a fixed ball screw nut module for a small linear actuator. delete The method according to claim 1,
And the size of the ball insertion hole of the nut corresponds to the width of the thread of the screw shaft. The method according to claim 1,
Characterized in that the material of the ball fixing tube is an engineering plastic. The method according to claim 1,
A frame including a screw shaft, a nut, a plurality of balls, and a ball fixing tube excluding the output shaft, the guide hole being capable of reciprocating linearly in a direction in which the output shaft protrudes;
An elastic support provided on one side of the frame facing the output shaft;
And an elastic body connecting one side of the output shaft and the elastic support,
And the output shaft is connected to the other side of the output shaft. A fixed ball screw nut module according to any one of claims 1 to 6;
A driving shaft connected to the screw shaft to rotate the screw shaft and linearly move the output shaft along the screw shaft according to rotation of the screw shaft;
And a plurality of linear actuators. 8. The method of claim 7,
Wherein the drive shaft of the motor is installed parallel to the screw shaft, and the drive shaft and the screw shaft are connected to each other via gears to transmit power.

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