JP4666436B2 - Linear actuator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a linear actuator capable of reciprocating and repetitively positioning a slider along a track rail with a stroke amount corresponding to the amount of rotation of the screw shaft. The present invention relates to an improvement for facilitating the movement and reducing the size of the slider.
[0002]
[Prior art]
Conventionally, as this type of linear actuator, one disclosed in Japanese Patent Laid-Open No. 4-164540 has been known. As shown in FIGS. 8 and 9, the linear actuator disclosed in this publication includes a track rail 100 having a groove shape along the longitudinal direction and formed in a channel shape, and a groove groove in the track rail 100. And a slider 102 that is screwed to the screw shaft 101 and moves in the concave groove of the track rail 100 in accordance with the rotation of the screw shaft 101. The slider 102 includes a ball screw portion that converts the rotational motion of the screw shaft 101 into linear motion, and a linear guide portion that guides the slider 102 along the track rail 100.
[0003]
The ball screw portion 102 provided in the slider 102 is screwed to the screw shaft 101 via a large number of balls (hereinafter referred to as “driving balls”). Is configured. A spiral ball rolling groove is formed on the outer peripheral surface of the screw shaft 101 with a predetermined lead. When the screw shaft 101 rotates, the drive ball rolls in a spiral manner on the ball rolling groove. Further, the ball screw portion is provided with an infinite circulation path for circulating the driving ball. The infinite circulation path includes a return pipe that jumps over the ball rolling groove of the screw shaft 101 by several turns and returns to the original position, and the driving ball is formed by spirally rolling the ball rolling groove of the screw shaft 101. Is configured to circulate through the return pipe.
[0004]
On the other hand, the slider 102 is provided with a pair of linear guide portions so as to sandwich the ball screw portion. These linear guide portions are engaged with the track rail 100 via a large number of balls 103 (hereinafter referred to as “guide balls”), and together with the track rail 100, constitutes a linear guide device. A plurality of ball rolling grooves 104 are formed along the longitudinal direction of the track rail 100 on the inner surface facing the concave groove of the track rail 100, and the guide ball 103 includes the track rail 100, the slider 102, and the like. The ball rolling groove 104 rolls while applying a load between. Each linear guide portion is provided with an infinite circulation path for circulating the guide ball 103, and the slider 102 continues in the concave groove of the track rail 100 as the guide ball 103 circulates in the infinite circulation path. It is possible to move.
[0005]
With such a configuration, in the linear actuator disclosed in the publication, when the screw shaft 101 rotates, the rotation is converted into linear motion of the slider 102 by the ball screw portion, and the slider 102 is converted into the rotation amount of the screw shaft 101. It is possible to position with high accuracy at a corresponding predetermined position.
[0006]
[Problems to be solved by the invention]
By the way, in recent years, in order to prevent the balls circulating in the endless circulation path from contacting each other, to prevent clogging of the balls in the endless circulation path, and to reduce the generation of noise when the ball runs at high speed, Balls are arranged at predetermined intervals on a conductive spacer belt, and the spacer belt is circulated together with the balls in an infinite circulation path. For example, in the linear guide device disclosed in Japanese Patent Application Laid-Open No. 7-317762, an infinite circulation path for balls is provided on a slider that linearly moves along a track rail, and a flexible spacer belt is provided in the infinite circulation path. An array of balls is incorporated with the spacer belt. Further, in the ball screw device disclosed in Japanese Utility Model Laid-Open No. 5-27408, an infinite circulation path of the ball is provided in a nut member that is screwed to the screw shaft via the ball. Balls arranged in a flexible spacer belt are incorporated together with the spacer belt.
[0007]
Therefore, even in the linear actuator having the structure of the ball screw device and the linear guide device as described above, the drive ball and the guide ball are flexible from the viewpoint of smooth circulation of the ball and consequently smooth movement of the slider with respect to the track rail. It can be said that it is preferable to arrange the drive ball and the guide ball together with these spacer belts in each endless circulation path.
[0008]
However, in the former linear actuator disclosed in Japanese Patent Laid-Open No. 4-164540, the endless circulation path of the drive ball is wound around the outer peripheral surface of the screw shaft in a spiral shape. Even if this spacer belt is incorporated, there is a problem that the spacer belt is easily twisted while circulating in the endless circulation path, and a large resistance acts on the circulation of the driving ball. In addition, it is difficult to incorporate the connecting belt into the infinite circulation path, and there is a problem that production takes time.
[0009]
The present invention has been made in view of such problems, and an object of the present invention is to easily incorporate a flexible spacer belt into the infinite circulation path of the drive ball constituting the ball screw portion. Another object of the present invention is to provide a linear actuator that can ensure smooth circulation of the drive ball and can prevent generation of noise when the screw shaft rotates at high speed as much as possible.
[0010]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention comprises a track rail which is formed in a channel shape having a concave groove along the longitudinal direction and has a plurality of ball rolling grooves facing the concave groove, Via a screw shaft that is rotatably provided in the concave groove of the track rail and has a spiral ball rolling groove formed on the outer peripheral surface, and a number of guide balls that roll on the ball rolling groove of the track rail. And is assembled into the groove groove of the track rail, and is screwed into the screw shaft via a number of drive balls that roll on the ball rolling groove of the screw shaft, and the track according to the rotation of the screw shaft. And a slider that freely moves in the groove of the rail, and the slider is provided with an infinite circulation path for the guide ball and an infinite circulation path for the drive ball. Circulation Are formed in an annular shape circumscribing the screw shaft and at least a pair formed so as to sandwich the screw shaft, and the drive balls are arranged at a predetermined interval on a flexible spacer belt, and the infinite It is characterized by circulating in the circulation path.
[0011]
According to such technical means, the endless circulation path of the drive ball provided in the slider is formed in an annular shape circumscribing the screw shaft, so that the endless circulation path can be formed without winding the screw shaft in a spiral shape. Thus, a flexible spacer belt in which driving balls are arranged at predetermined intervals can be easily incorporated into the endless circuit. Therefore, the spacer belt can circulate in the endless circulation path in a stable posture without being twisted, and the circulation of the driving balls arranged on the spacer belt can be facilitated. By incorporating the drive ball into the endless circulation path together with the spacer belt in this way, it is possible to remarkably reduce the drive sound of the drive ball when the screw shaft rotates at high speed, that is, when the slider moves at high speed. This is a great benefit for linear actuators that require a movable body such as a table to be positioned at high speed.
[0012]
On the other hand, this type of linear actuator has a linear guide part for moving the slider along the track rail, and an infinite circulation path of the guide ball is formed in the linear guide part. As shown, when the linear guide portion G that guides the slider 93 with respect to the track rail 94 and the ball screw portion S that is screwed onto the screw shaft 95 are completely separated, the slider 93 becomes larger and heavier. As a result, there is a problem that the positioning accuracy is deteriorated when the slider is moved at a high speed.
[0013]
Therefore, from such a viewpoint, it is preferable that the endless circulation path of the drive ball is disposed so as to penetrate the inside of the endless circulation path of the guide ball. If such an arrangement is adopted, the area where the infinite circulation path of the guide ball is formed (straight guide part) and the area where the endless circulation path of the drive ball is formed (ball screw part) overlap each other in the slider. Therefore, the slider can be reduced in size, and the slider can be reduced in weight, and the positioning accuracy of the slider can be increased.
[0014]
In the present invention, the spacer belt may be any one as long as the driving balls or guide balls are arranged at a predetermined interval in the infinite circulation path of the slider to prevent collision of the balls during circulation. For example, a synthetic resin belt having flexibility may be formed by simply receiving accommodation holes larger than the ball diameter at predetermined intervals. Further, a spacer may be provided between the front and rear balls, and the ball may be held so as not to fall off with the spacer.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the linear actuator of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a sectional view showing an embodiment of a linear actuator to which the present invention is applied. The linear actuator includes a track rail 1 having a concave groove and formed in a channel shape, a screw shaft 2 disposed in the concave groove of the track rail 1, and a screw shaft 2. In addition, the slider 3 is configured to be movable in the groove of the track rail 1.
[0016]
The track rail 1 has a base portion 10 attached to a fixed portion such as a bed by a bolt (not shown), and has a pair of side wall portions 11 and 11 rising from the base portion 10, and the base portion 10 and the side wall portions. 11 is formed in a channel shape continuous in the direction perpendicular to the paper surface. In addition, two ball rolling grooves 12 are formed on the inner side surface of each side wall portion 11 facing the concave groove. The ball rolling grooves 12 are formed in the longitudinal direction of the track rail 1 (in the direction perpendicular to the paper surface). ).
[0017]
The screw shaft 2 is disposed so that its axis substantially coincides with the centroid of the concave groove of the track rail 1. A spiral ball rolling groove 20 is formed on the outer peripheral surface of the screw shaft 1. It is formed with a predetermined lead. A pair of brackets (not shown) are attached to both ends of the track rail 1 in the longitudinal direction, and both ends of the screw shaft 2 are supported by the brackets via bearings. That is, the screw shaft 2 is rotatably supported in the concave groove of the track rail 1.
[0018]
On the other hand, the slider 3 is formed to have a substantially rectangular cross section, and is configured to move in the concave groove with its upper portion slightly protruding from the concave groove of the track rail 1. Therefore, the upper surface of the slider 3 is a mounting surface 30 for a movable body such as a table, and the movable body is fixed by a bolt (not shown). The slider 3 includes a pair of linear guide portions G for freely guiding the slider 3 along the track rail 1 and a linear movement of the slider 3 according to the rotation of the screw shaft 2. The ball screw portion S is provided.
[0019]
A pair of linear guide portions G are provided so as to sandwich the screw shaft 2, and each linear guide portion G corresponds to one side wall portion 11 of the track rail 1. Each linear guide portion G includes two rows of infinite circulation paths T1 through which the guide balls B1 circulate, and each infinite circulation path T1 corresponds to a ball rolling groove 12 formed in the side wall 11 of the track rail 1. . Each infinite circulation path includes a load rolling groove 31 formed on the outer surface of the slider 3 and a ball return hole 32 formed in parallel with the load rolling groove 31, and a large number of guide balls B 1 receive a load. It rolls between the ball rolling groove 12 of the track rail 1 and the load rolling groove 31 of the slider 3 while being loaded. In addition, the ball B1 that has finished rolling in the load rolling groove 31 is released from the load, and then circulates to the original position before the load rolling by rolling in the ball return hole 32 in an unloaded state. It is like that.
[0020]
As shown in FIG. 2, the guide balls B1 are arranged on a flexible spacer belt 4 made of synthetic resin at a predetermined interval, and each of the infinite circulation paths of the linear guide portion G together with the spacer belt 4. Incorporated into T1. This spacer belt 4 is provided with a spacer 40 so as to separate guide balls adjacent to each other, and the guide balls B1 are prevented from contacting each other while circulating in the infinite circulation path T1. Yes. In addition, an accommodation hole for the ball B1 is formed between the pair of front and rear spacers 40, and the ball is accommodated therein. Thereby, the smooth circulation of the guide ball B1 is ensured.
[0021]
On the other hand, a through hole through which the screw shaft 2 passes is formed at the center of the slider 3, and a pair of the ball screw portions S are formed so as to sandwich the through hole. Each ball screw portion S includes an annular endless circulation path T2 through which the drive ball B2 circulates. As shown in FIG. 3, the endless circulation path T2 is arranged in four rows so as to overlap in the axial direction of the screw shaft 2. Has been. Each infinite circulation path T2 includes a load rolling groove 33 formed on the inner peripheral surface of the through hole and a no-load ball passage 34 formed so as to connect both ends of the load rolling groove 33. It is formed in an annular shape that circumscribes the screw shaft 2. Each infinite circulation path T2 is formed to be inclined in accordance with the lead angle α of the ball rolling groove 20 of the screw shaft 2, so that the ball B2 circulates in a certain plane. The load rolling groove 33 is formed in a range shorter than the half circumference with respect to the inner circumferential surface of the through hole, and the driving ball B2 is a ball formed on the outer circumferential surface of the load rolling groove 33 and the screw shaft 2. It rolls while applying a load between the rolling grooves 20. Therefore, the screw shaft 2 is sandwiched between the drive balls B2 from both sides inside the through hole formed in the slider 3.
[0022]
Similar to the guide ball B1, the drive ball B2 is disposed at a predetermined interval on a flexible spacer belt 4 made of synthetic resin, and each endless circulation path T2 of the ball screw portion S together with the spacer belt 4. Incorporated into. Therefore, contact between the adjacent drive balls B2 is prevented by the spacers 40 provided on the spacer belt 4, and smooth circulation of the drive balls B2 is ensured.
[0023]
As shown in FIG. 7, the endless circulation path T <b> 2 of the drive ball B <b> 2 is formed by attaching several parts to the metal slider 3. A through hole 35 through which the screw shaft 2 passes is formed in the slider 3. A rectangular notch hole 36 communicating with the outer surface of the slider 3 is formed above and below the through hole 35, and the drive ball B2 is configured to enter and exit from the through hole 35 through the cutout hole 36. In addition, a pipe mounting hole 37 for fitting the guide vip 50 is formed in the slider 3 for each infinite circulation path T2. The pipe mounting hole 37 is located between the load rolling groove 31 of the linear guide portion G and the ball return hole 32 and is disposed so as to penetrate the infinite circulation path T1 of the linear guide portion G. A guide groove for guiding the spacer belt 4 along the longitudinal direction is formed on the inner peripheral surface of each guide pipe 50, so that twisting and meandering of the spacer belt 4 circulating in the infinite circulation path T2 can be prevented. It has become. Further, an inner peripheral side guide member 51 is provided between the guide pipe 50 fitted in the pipe mounting hole 37 and the notch hole 36 so as to span between them. An auxiliary plate 52 is fixed to the outer surface of the slider 3, and the inner guide member 51 and the auxiliary plate 52 are fixed to the slider 3 to complete the unloaded ball path 34 of the drive ball B2. Yes.
[0024]
The auxiliary plate 52 is a member common to the infinite circulation path T2 of all the drive balls B2 provided in the slider 3, and covers the outer surface of the slider 3 so as to cover the notch 36 formed in the slider 3. Fixed to. A scooping piece 53 to be inserted into the notch hole 36 is erected at the center of the auxiliary plate 52, and the notch hole 36 is divided into left and right by the scooping piece 53, and the ball of the screw shaft 2. The drive ball B2 can be detached from the rolling groove 20. Accordingly, when the screw shaft 2 rotates with the auxiliary plate 52 attached to the slider 3, the drive ball B 2 that has finished rolling the load rolling groove 33 from one side of the scooping piece 53 is transferred to the screw shaft 2. From the other side of the scooping piece 53, the driving ball B 2 is scooped up from the ball rolling groove 20 of the ball rolling groove 20 and loaded on the ball rolling groove 20 of the screw shaft 2 and the slider 3. It is fed between the rolling grooves 33.
[0025]
According to the linear actuator of this embodiment configured as described above, the endless circulation path T2 of the drive ball B2 is formed in an annular shape that circumscribes the screw shaft 2, and the periphery of the screw shaft 2 is spiral. Therefore, there is no inconvenience that the spacer belt 4 is twisted while circulating in the endless circulation path T2. Further, since the endless circulation path T2 is inclined at an angle that matches the lead angle α of the screw shaft 2, the spacer belt 4 always circulates in a fixed plane. In this respect as well, the spacer belt 4 The circulation of the drive ball B2 and the circulation of the drive ball B2 can be facilitated. Furthermore, since the infinite circulation path T2 is formed in a fixed plane without being spirally wound, the assembly of the spacer belt 4 to the infinite circulation path T2 can be performed very easily.
[0026]
On the other hand, the endless circulation path T2 of the drive ball B2 provided in the ball screw portion S is disposed so as to penetrate the inside of the endless circulation path T1 of the guide ball b1 provided in the straight guide portion G. FIG. 4 is a plan perspective view showing the arrangement of the infinite circulation paths T1 and T2 of the guide ball B1 and the drive ball B2 provided in the slider 3, and each infinite circulation path provided in the linear guide portion G and the ball screw portion S. Only the balls B1 and B2 circulating through are shown. In this way, the endless circulation path T2 of the ball screw part S is arranged so as to pass through the inside of the endless circulation path T1 of the straight guide part G, in other words, so as to intersect in a chain shape. When the G and the ball screw portion S are observed from the axial direction of the screw shaft 2, as shown in FIG. 5, the linear guide portion G and the ball screw portion S are arranged in the slider 3 so as to overlap each other. It will be. Thereby, in the linear actuator of a present Example, size reduction of the slider 2 can be achieved.
[0027]
【The invention's effect】
As described above, according to the linear actuator of the present invention, the infinite circulation path of the drive ball that rolls on the ball rolling groove of the screw shaft is an annular ring circumscribing the screw shaft without winding the screw shaft in a spiral shape. Therefore, a flexible spacer belt in which drive balls are arranged at predetermined intervals can be easily incorporated into the endless circuit, and the spacer belt can be twisted in the endless circuit. It is possible to circulate in a stable posture without any problem, and by using this spacer belt, it is possible to ensure smooth circulation of the drive ball and to prevent the generation of noise during high-speed rotation of the screw shaft as much as possible. It becomes.
[Brief description of the drawings]
FIG. 1 is a front sectional view showing an embodiment of a linear actuator to which the present invention is applied.
FIGS. 2A and 2B are a plan view and a side view showing a connecting belt on which guide balls according to an embodiment are arranged.
3 is a cross-sectional view taken along line III-III in FIG.
FIG. 4 is a perspective plan view showing an arrangement of an infinite circulation path of a straight guide portion and an infinite circulation path of a ball screw portion according to the embodiment.
FIG. 5 is a diagram conceptually showing a linear actuator of the present invention.
FIG. 6 is a diagram conceptually showing a conventional linear actuator.
FIG. 7 is an exploded view showing components of the slider according to the embodiment.
FIG. 8 is a perspective view showing an example of a conventional linear actuator.
9 is a front sectional view of the linear actuator shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Track rail, 2 ... Screw shaft, 3 ... Slider, G ... Linear guide part, S ... Ball screw part, B1 ... Guide ball, B2 ... Drive ball

Claims (7)

A track rail having a plurality of ball rolling grooves formed in a channel shape having a groove along the longitudinal direction and facing the groove,
A screw shaft provided rotatably in a concave groove of the track rail and having a spiral ball rolling groove formed on the outer peripheral surface;
It is assembled in the concave groove of the track rail via a large number of guide balls that roll on the ball rolling groove of the track rail, and via a large number of drive balls that roll on the ball rolling groove of the screw shaft. A slider that is screwed to the screw shaft and moves freely in the groove of the track rail in accordance with the rotation of the screw shaft,
In the linear actuator in which the slider has an infinite circulation path for the guide ball and an infinite circulation path for the drive ball,
Such an infinite circulation path of the drive ball is formed in an annular shape circumscribing the screw shaft and at least a pair is formed so as to sandwich the screw shaft,
The drive balls are arranged at a predetermined interval on a flexible spacer belt, and circulate in the endless circuit with the spacer belt .
The slider has through-holes through which the screw shafts are inserted, and notch holes that communicate the through-holes with the outer surface of the slider are formed at two positions opposite to the through-holes at 180 °. A linear actuator, wherein a drive ball enters or leaves a ball rolling groove of a screw shaft through a notch hole. An auxiliary plate for forming an infinite circulation path of the drive ball is fixed to the outer surface of the slider, and the drive ball inserted into the notch hole is separated from the ball rolling groove of the screw shaft on the auxiliary plate. The linear actuator according to claim 1, wherein the scooping piece is erected. A track rail having a plurality of ball rolling grooves formed in a channel shape having a groove along the longitudinal direction and facing the groove,
A screw shaft provided rotatably in a concave groove of the track rail and having a spiral ball rolling groove formed on the outer peripheral surface;
It is assembled in the concave groove of the track rail via a large number of guide balls that roll on the ball rolling groove of the track rail, and via a large number of drive balls that roll on the ball rolling groove of the screw shaft. A slider that is screwed to the screw shaft and moves freely in the groove of the track rail in accordance with the rotation of the screw shaft,
In the linear actuator in which the slider has an infinite circulation path for the guide ball and an infinite circulation path for the drive ball,
Such an infinite circulation path of the drive ball is formed in an annular shape circumscribing the screw shaft and at least a pair is formed so as to sandwich the screw shaft,
A linear actuator characterized in that the endless circulation path of the driving ball is disposed through the inside of the endless circulation path of the guide ball. 4. The linear actuator according to claim 3, wherein the drive balls are arranged on a flexible spacer belt at a predetermined interval, and circulate in the endless circulation path together with the spacer belt. 5. The linear actuator according to claim 1, wherein the guide balls are also arranged on a flexible spacer belt at a predetermined interval and circulate through the infinite circulation path together with the spacer belt. 6. The spacer belt is formed with receiving holes for arranging guide balls or driving balls at predetermined intervals along the longitudinal direction. The linear actuator described.   4. The linear actuator according to claim 1, wherein the endless circulation path of the drive ball is formed so as to be inclined in accordance with a lead angle of a ball rolling groove formed on the screw shaft.

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