JP2003028264A - Feed screw device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low cost, small loss and long life feed screw device capable of miniaturizing the whole of the feed screw device and coping with extremely small diameter balls and easy to assemble with a simple structure. SOLUTION: This feed screw device includes a screw shaft 11 provided with at least one spiral shaped screw groove 11a on an outer circumference surface, a moving member 12 enclosing surroundings of the screw shaft 11, a plurality of rolling rings 13 movably fitted in an inner space 12b of an inside of the moving member 12 in an axial direction, balls 14 provided between the screw groove 11a of the screw shaft 11 and each rolling ring. The rolling ring 13 is provided with an annular V-shaped groove 13a for storing the ball in an inner circumference surface. The V-shaped groove is divided with a dividing surface perpendicular to an axial direction at the deepest part. The rolling ring 13 is retained movably in the axial direction by thrust adjusting means 15, 12c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feed screw device, and more particularly to a feed screw device provided with a ball in a spiral thread groove provided on a screw shaft.

[0002]

2. Description of the Related Art Conventionally, such a feed screw device has, for example, a screw shaft provided with a spiral screw groove along an outer peripheral surface, and a spiral groove formed on the inner surface so as to surround the screw shaft. A moving member provided, a ball housed in a spiral thread groove formed by the thread groove of the screw shaft and the groove of the moving member,
It consists of According to the feed screw device having such a configuration, the ball is formed by the screw groove of the screw shaft and the groove of the moving member along with the rotation of the screw shaft, for example, when the screw shaft is rotationally driven by the driving unit. Roll along a spiral thread groove. As a result, the moving member moves along the axial direction due to the rotation of the screw shaft.

At this time, the balls roll in the screw groove along one direction, so that only rolling friction due to the balls is generated between the screw shaft and the moving member, and the moving member moves on the screw shaft. On the other hand, it can move smoothly in the axial direction. Then, when the balls roll in the thread groove along one direction to reach the terminal end portion, the ball is returned from the terminal end portion to the starting end portion of the thread groove through the reflux bypass provided inside the moving member, It rolls in the thread groove again in one direction. As a result, even if the screw shaft is long, the moving member can be smoothly moved along the axial direction of the screw shaft by rolling of the ball.

[0004]

By the way, in such a feed screw device, high precision is required at the contact point between the ball and the screw shaft and between the ball and the moving member, and if this precision is not satisfied, the screw shaft is required. There is a problem that noise and vibration are generated when the moving member is moved by the rotation of the moving member, and the moving member cannot be smoothly moved.
Moreover, in the conventional feed screw device, it is not possible to adjust the contact points between the ball and the screw shaft or between the ball and the moving member. Need to be manufactured, resulting in high cost.

Further, even if each of the above parts is manufactured with high accuracy, if the balls are worn out due to use, the accuracy of these parts deteriorates, and noise and vibration similarly occur. Further, conventionally, it is difficult to process the spiral screw on the inner circumference of the moving member, and at present, there is a problem that the ball screw shaft having a diameter of less than 4 mm cannot be dealt with, and in this respect, the size cannot be reduced. Further, if a reflux bypass is provided for the above-described ball circulation, there is a problem that the moving member becomes large in the radial direction.

In view of the above points, the present invention can reduce the size of the entire feed screw device with a simple structure, can handle balls with a very small diameter, can be easily assembled, and can be manufactured at low cost and with low loss. The purpose is to provide a long-lived lead screw device.

[0007]

According to the present invention, the above object is to provide a screw shaft having at least one spiral thread groove on an outer peripheral surface thereof, a moving member surrounding the screw shaft from the periphery, and a moving member. A plurality of rolling rings fitted in an inner space inside the member so as to be movable in the axial direction; and balls arranged respectively between the thread groove of the screw shaft and each rolling ring. Each of the rolling rings has an annular V-shaped groove for accommodating a ball on the inner peripheral surface thereof, and is divided by a dividing surface perpendicular to the axial direction at the deepest portion of the V-shaped groove. The above-mentioned rolling ring is held by a thrust adjusting means so as to be able to advance and retreat in the axial direction.

In the lead screw device according to the present invention, preferably, the balls fitted in the annular V-shaped groove of the rolling ring and the screw groove of the screw shaft are arranged at substantially equal angular intervals as viewed in the axial direction. Thus, the axial thickness of the rolling ring is selected.

In the feed screw device according to the present invention, preferably, the thrust adjusting means presses the end wall that closes the internal space of the moving member at one end in the axial direction and each rolling ring in the axial direction against the end wall. Therefore, the adjusting screw member is screwed with the moving member.

In the lead screw device according to the present invention, preferably, with respect to the axially adjacent rolling rings, the axially divided portions which come into contact with each other back to back are integrally formed with each other.

According to the above construction, each ball is fitted in the thread groove of the screw shaft and the annular V-shaped groove of the rolling ring,
When the screw shaft rotates, each ball rolls in the annular V-shaped groove of the rolling ring and in the screw groove of the screw shaft. As a result, the moving member is moved only in the axial direction by the ball rolling along the thread groove of the screw shaft and rolling in the annular V-shaped groove of the rolling ring.

In this case, when the ball is worn during assembly or during use and a gap is generated between the ball and the thread groove of the screw shaft and the annular V-shaped groove of the rolling ring, By pressing the rolling ring in the axial direction by the thrust adjusting means, the divided parts of the rolling ring forming the annular V-shaped grooves are brought closer to each other in the axial direction. Therefore,
Due to the axial compression of the V-shaped groove, each ball is pushed out inward in the radial direction, and the ball is adjusted so as to surely contact the screw groove of the screw shaft.

Further, when each ball rolls due to the rotation of the screw shaft, each ball rolls in the annular groove of the rolling ring, but the ball recirculates for each ball as in the conventional lead screw device. Bypass is unnecessary. As a result, the moving member has a small diameter, and the entire feed screw device can be downsized. Further, since the rolling ring itself is axially divided into two parts so as to have an annular groove, it can be easily processed and formed. For example, even if the ball screw shaft is less than 4 mm, the rolling ring can be easily formed. And can be assembled.

The rolling ring has a thickness in the axial direction such that balls which fit in the annular V-shaped groove and the thread groove of the screw shaft are arranged at substantially equal angular intervals when viewed in the axial direction. Is selected, the rolling rings are held substantially concentrically with respect to the screw shaft without being eccentric by the balls distributed in the circumferential direction at substantially equal angular intervals.

The thrust adjusting means is screwed with the end wall that closes the inner space of the moving member at one end in the axial direction, and the moving member so that each rolling ring can be axially pressed against the end wall. If it is composed of an adjusting screw member,
By screwing the adjusting screw member into the moving member,
Each rolling ring is pressed against the end wall of the internal space of the moving member, and the divided parts of the rolling ring sandwiching the annular V-shaped groove are brought closer to each other, so that the ball is attached to the screw shaft. It is pushed toward and adjustment is performed.

When the rolling rings adjacent to each other in the axial direction are integrally formed with each other in the axially divided rolling contact portions, the number of parts is reduced and the distance between the rolling rings is reduced. Since foreign matter does not enter the device, assembly errors can be reduced, and misalignment due to foreign matter can be eliminated.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below based on the embodiments shown in the drawings. FIG. 1 shows an embodiment of a lead screw device according to the present invention. In FIG. 1, a feed screw device 10 is configured as a moving lens driving unit of a zoom lens, for example, and includes a screw shaft 11, a housing 12 as a moving member, a rolling ring 13,
It comprises a ball 14 and an adjusting nut 15 as an adjusting member (thrust adjusting means).

The screw shaft 11 is similar to the screw shaft used in the conventional feed screw device, and has two spiral thread grooves 11a and 11a 'on the outer peripheral surface thereof. It is adapted to be rotationally driven by a driving means.

The housing 12 is formed so as to surround the screw shaft 11 from the entire circumference, and an inner space 12b whose one axial end is closed by an end wall 12a is formed on the inner peripheral surface thereof. There is. In addition, the housing 12
At the other end of the internal space 12b, is provided with a female screw portion 12c with which the adjusting nut 15 is screwed, and a flange portion 12d for connecting to a member to be driven.

A plurality of rolling rings 13, five in the illustrated case, are provided, and they are sequentially fitted into the internal space 12b of the housing 12 from the other end. As shown in FIG. 1, each rolling ring 13 is provided with an annular groove 13a having a substantially V-shaped cross section on the inner peripheral surface thereof, and at the deepest part of the annular groove 13a, a surface perpendicular to the axial direction is formed. Two parts 13
It is divided into b and 13c. And each rolling ring 1
3 is movable in the axial direction by inserting the rotation stopping pin 12e extending in the axial direction in the housing 12, but is prevented from rotating around the axis.

The balls 14 are made of steel balls, and those having a diameter of 1 mm, for example, and those having an extremely small diameter less than that can be used. Here, one ball 14 is provided for each rolling ring 13 for each thread groove 11a of the screw shaft 11, that is, two balls 14 are provided in the case of the double thread groove of FIG. When viewed from above, the balls 14 are arranged for each rolling ring 13 at substantially equal angular intervals, that is, at substantially 90 ° intervals, as shown in FIG.

The adjusting nut 15 constitutes a thrust adjusting means together with the end wall 12a of the housing 12.
The adjusting nut 15 is the same as the housing 1 described above.
2 is screwed into the female threaded portion 12c, and is screwed to the left in the axial direction in FIG. 1 to press the rolling rings 13 fitted in the internal space 12b of the housing 12 in the axial direction. Thus, each rolling ring 13 is axially compressed with the end wall 12a forming one end of the internal space 12b of the housing 12.

Lead screw device 10 according to an embodiment of the present invention.
Is configured as described above and operates as shown below. First, a drive shaft of a drive means such as a servomotor is connected to one end of the screw shaft 11, and the flange portion 12d of the housing 12 as a moving member is driven by the feed screw device 10 (see FIG. (Not shown).

When the screw shaft 11 is rotationally driven from this state, the balls 14 fitted in the screw grooves 11a and 11a 'of the screw shaft 11 roll with the rotation of the screw shaft 11. . At that time, each ball 14 has a thread groove 11a, 11a '.
Along with the rolling ring 13, the rolling ring 13 also rolls in the annular groove 13a. As a result, each ball 14
While rolling in the screw grooves 11a and 11a 'of the screw shaft 11, the screw shaft 11 moves in the axial direction.

Therefore, the balls 14 roll along the screw grooves 11a, 11a 'and the annular groove 13a, respectively, so that the rolling ring 13 and the housing 12 move in the axial direction. At that time, each ball 1
4 sequentially from the rolling ring 13 on the left side in FIG.
As shown in FIG. 3, the screw shafts 11 are held concentrically with respect to the rolling ring 13 and the housing 12 by being arranged so as to be displaced from each other at substantially equal angular intervals when viewed in the axial direction. Therefore, the rolling ring 13 and the housing 12 can be smoothly moved in the axial direction.

Here, when each ball 14 has a rattling in the radial direction with respect to the screw shaft 11, for example, at the time of manufacturing and assembling the feed screw device 10, or when the ball 1 is used.
When the diameter of the ball 14 becomes small due to wear of No. 4,
The adjustment is performed as follows. That is, when the adjusting nut 15 constituting the thrust adjusting means is screwed into the female screw portion 12c of the housing 12, the adjusting nut 15 moves toward the end wall 12a at one end of the housing 12 in the axial direction. As a result, the adjusting nut 15 compresses the rolling rings 13 fitted into the internal space 12b of the housing 12 in the axial direction between the adjusting nut 15 and the end wall 12a of the housing 12.

Therefore, each ball 14 fitted in each annular groove 13a is compressed by axial compression of each rolling ring 13.
Are both portions 13b and 13c forming the annular groove 13a.
Due to the approaching of the slopes of each other, they are extruded radially inward with respect to the screw shaft 11. And each ball 14
Are pressed against the screw grooves 11a and 11a 'of the screw shaft 11, and the rattling of each ball 14 in the radial direction is eliminated. Thus, the adjustment is completed, and the housing 1 as the moving member is
By rotating the screw shaft 11, the screw shaft 2 can be smoothly moved in the axial direction without generating noise or vibration.

As described above, according to the lead screw device 10 of the present invention, by screwing the adjusting nut 15 as the thrust adjusting means, the axially divided parts 13b and 13c of the rolling ring 13 are compressed to each other. Then, the annular groove 13a is narrowed. As a result, the balls 14 fitted in the annular groove 13 a are pushed toward the inner side of the screw shaft 11 in the radial direction, and the screw groove 11 of the screw shaft 11 is pushed.
It comes into contact with a and 11a 'without rattling.

Further, the balls 14, the housing 12, the rolling ring 13, and the screw shaft 11 which are the respective parts are formed into a shape capable of being processed with high precision, and when the housing 12 is moved by the rotation of the screw shaft 11, Without any noise or vibration
Smooth movement is possible.

Since the compression distance of the rolling ring 13 due to the above adjustment is short, the compression of the rolling ring 13 causes the screw groove 11a of the screw shaft 11 to be inside the annular groove 13a of each rolling ring 13. , 1a 'held on the ball 1
The position of 4 does not largely deviate from the equiangular interval as viewed in the axial direction, and is maintained at an approximately equiangular interval.
Therefore, the eccentricity of the rolling ring 13 and the housing 12 from the center of the screw shaft 11 due to the compression of the rolling ring 13 is negligible, and does not hinder the smooth movement of the housing 12 in the axial direction with respect to the screw shaft 11. Absent. Also,
The axial load is changed by increasing or decreasing the number of rolling rings 13.
It can be adjusted appropriately.

In the embodiment shown in FIGS. 1 and 2, the screw shaft 11 is provided with two thread grooves 11a and 11a '. However, when the screw shaft 11 is one thread, the screw groove 11a is formed.
Only will be equipped. In this case, each rolling ring 13
For each rolling ring 13, one ball 14 is fitted in the thread groove 11a. And
In order that each rolling ring 13 and the housing 12 are held substantially concentric with the screw shaft 11 by these balls 14, for example, as shown in FIG. 4, sequentially from the rolling ring 13 on the left side of FIG. 1, The thickness of the rolling ring 13 is selected with respect to the pitch of the thread groove 11a of the screw shaft 11 so that the balls 14 in the rolling ring 13 are displaced from each other by an angle of 360 ° + 120 ° when viewed in the axial direction. There is. This can be easily realized by setting the thickness of the rolling ring 13 to approximately 4 mm when the pitch of the thread grooves 11a is 3 mm, for example.

In the above-mentioned embodiment, each rolling ring 13 is formed so as to be divided in the axial direction at the deepest portion of the annular groove 13a, but the present invention is not limited to this, and as shown in FIG. In addition, the respective portions 13b and 13c that contact back to back of the adjacent rolling rings 13 may be integrally formed. As a result, the number of parts can be reduced, and the parts cost and the assembly cost can be reduced.

Further, in the above-mentioned embodiment, the screw shaft 11 has two or one thread grooves, but the invention is not limited to this, and three or more thread grooves may be provided. If the screw shaft has three or more thread grooves,
Three or more balls are fitted in the annular groove of each rolling ring at substantially equal angular intervals. As a result, the axial thickness of each rolling ring can be arranged such that the positions of the balls fitted in the annular grooves of the other rolling rings can be equally distributed.

[0034]

As described above, according to the present invention, each ball is fitted in the thread groove of the screw shaft and the annular V-shaped groove of the rolling ring, and when the screw shaft rotates. In the above, each ball rolls in the annular V-shaped groove of the rolling ring and the thread groove of the screw shaft. As a result, the moving member is moved only in the axial direction by the ball rolling along the thread groove of the screw shaft and rolling in the annular V-shaped groove of the rolling ring.

In this case, when the ball is worn during assembly or during use and a gap is generated between the ball and the thread groove of the screw shaft and the annular V-shaped groove of the rolling ring, By pressing the rolling ring in the axial direction by the thrust adjusting means, the divided parts of the rolling ring forming the annular V-shaped grooves are brought closer to each other in the axial direction. Therefore,
Due to the axial compression of the V-shaped groove, each ball is pushed out inward in the radial direction, and the ball is adjusted so as to surely contact the screw groove of the screw shaft.

Further, when each ball rolls due to the rotation of the screw shaft, each ball rolls in the annular groove of the rolling ring, but the ball returns for each ball as in the conventional lead screw device. Bypass is not necessary. As a result, the moving member has a small diameter, and the entire feed screw device can be downsized. Furthermore, since the rolling ring itself is divided into two in the axial direction so as to have an annular groove, for example, 4 mm
Even with less than a ball screw shaft, the rolling ring can be easily processed and can be easily assembled.

Thus, according to the present invention, it is not necessary to select the respective parts including the ball, that is, to combine them,
We can provide lead screw devices with balls of any class (size).

[Brief description of drawings]

FIG. 1 is an axial sectional view showing a configuration of an embodiment of a feed screw device according to the present invention.

2 is a right side view of the feed screw device of FIG. 1. FIG.

FIG. 3 is a schematic view sequentially showing an example of the positional relationship between each rolling ring and balls in the lead screw device of FIG.

FIG. 4 is a schematic view sequentially showing an example of a positional relationship between each rolling ring and balls in a modified example of the feed screw device of FIG.

5 is a schematic cross-sectional view showing a modified example of the rolling ring in the feed screw device of FIG.

[Explanation of symbols]

10 Lead screw device 11 screw shaft 11a, 11a 'screw groove 12 Housing (moving member) 12a End wall (thrust adjusting means) 12b Internal space 12c female thread 12d flange 12e Anti-rotation pin 13 Rolling ring 13a annular groove 13b, 13c part 14 balls 15 Adjustment nut (thrust adjustment means)

Claims (4)

[Claims] 1. A screw shaft having at least one spiral thread groove on an outer peripheral surface thereof, a moving member surrounding the screw shaft from the periphery, and an axially movable inside space of the moving member. It includes a plurality of rolling rings that are inserted and inserted, and balls that are respectively arranged between the thread groove of the screw shaft and each rolling ring. An annular V-shaped groove for accommodating the balls is provided, and the rolling ring is divided in the axial direction by the thrust adjusting means, the dividing ring being divided at a deepest portion of the V-shaped groove by a dividing surface perpendicular to the axial direction. A lead screw device characterized by being held so that it can move forward and backward. 2. The rolling ring of the rolling ring is arranged such that the balls that fit into the annular V-shaped groove of the rolling ring and the thread groove of the screw shaft are arranged at substantially equal angular intervals as viewed in the axial direction. The feed screw device according to claim 1, wherein the axial thickness is selected. 3. The moving member and the screw so that the thrust adjusting means can press the end wall that closes the inner space of the moving member at one end in the axial direction and each rolling ring in the axial direction against the end wall. The feed screw device according to claim 1 or 2, wherein the lead screw device is configured by a matching adjusting member. 4. With regard to axially adjacent rolling rings,
The part that is divided in the axial direction and contacts back to back,
The lead screw device according to claim 1, wherein the lead screw devices are formed integrally with each other.