JP2003307263A - Ball screw mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw mechanism of high reliability capable of reducing labor and cost for assembling. <P>SOLUTION: A circulating path 6 is integrally formed on a nut member 3 which dispenses with an independently frame, reduces the labor and the cost for assembling, and prevents a problem on accuracy and reliability relating to frame connection. Further the nut member 3 is integrally molded in a state that divisional faces do not exist at least in the circumferential direction, lightweight and high strength can be achieved, and the labor in assembling can be reduced. Further, conventional quenching and tempering (including carburizing) can be of cause applied in the heat treatment of the nut member 3, and the problem such as partial overheating can be prevented even when the high-frequency heat treatment is applied because of the absence of a frame hole. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw mechanism capable of converting rotary motion into linear motion.

[0002]

2. Description of the Related Art A ball screw mechanism is a mechanism capable of converting the rotational output of a motor as an axial output, and is often used in electric actuators. By the way, the ball screw mechanism is capable of converting a rotational motion into a linear motion with low friction by a ball rolling in a spiral space between the ball screw and the nut member. However, since the ball rolls relative to the nut member as the ball screw rotates, if it is left as it is, it will come out of the nut member. Therefore, a so-called circulation path is required to return the rolling balls to the upstream side.

For example, in the ball screw mechanism disclosed in Japanese Patent Publication No. 55-21225, an opening is provided in the peripheral surface of a nut member, and when the nut member rotates with respect to the screw shaft, it rolls along a spiral groove. A ball guide is formed in a rigid body that has a passage that connects over the ridges on the screw shaft to allow the moving balls to move over the ridges of the screw shaft and return to the adjacent spiral groove for internal circulation. I will do it. That is, the ball guide is formed by inserting the ball guide portion from the inside of the nut member into the opening to attach the ball guide portion to the ball nut.

However, in this conventional ball screw mechanism, the ball guide portion as the internal circulation path in the nut member is formed as a separate component (called a top) from the nut member main body. Apart from the main body, the internal circulation path forming parts are manufactured, and then
It is necessary to perform processing such as holes for mounting it on the nut member main body, and to fix them by combining them, which causes a problem that processing cost, parts cost, assembly cost, etc. increase and the product itself becomes expensive. . There is also a problem regarding the strength and reliability of the ball guide portion of another component (coma) in which the internal circulation path is formed, and its retaining.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a ball screw mechanism which can reduce the labor and cost of assembling and is excellent in reliability.

[0006]

A ball screw mechanism of the present invention is a nut having a screw shaft having a male spiral groove formed on the outer peripheral surface and a female spiral groove formed on the inner peripheral surface of the screw shaft so as to face the male spiral groove of the screw shaft. A nut, and a ball that is rollable in a space formed by the male spiral groove of the screw shaft and the female spiral groove of the nut member, and does not have a dividing surface in the circumferential direction. A circular path projecting in a radial direction that connects both ends of at least one female spiral groove, and the circular path adjoins the balls rolling along the male spiral groove, It is characterized in that the guide is made so as to return to the male spiral groove on the rolling side beyond the peaks separating the spiral grooves.

[0007]

According to the ball screw mechanism of the present invention, the nut member which does not have a dividing surface in the circumferential direction has a radially projecting circulation path which connects both ends of at least one female spiral groove. The circulation path guides the ball rolling along the male spiral groove so as to return to the male spiral groove on the rolling side, beyond the peak separating the adjacent male spiral grooves. Therefore, since the nut member is integrated, it is lightweight and has high strength, and it is not necessary to provide a separate piece as in the conventional case, and the labor and cost of assembly are not required,
In addition, it is possible to avoid accuracy and reliability problems related to frame connection.

Further, when a plurality of circulation paths are provided,
Changing the phase in the circumferential direction is preferable because interference between the circulation paths can be suppressed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. 1 is a sectional view of a ball screw mechanism according to an embodiment of the present invention.
FIG. 3 is a sectional view of the nut member shown in FIG. 1, and FIG. 3 is a view of the nut member shown in FIG. The ball screw mechanism has a screw shaft 1, a nut member 3, and a ball 5.

In FIG. 1, a screw shaft 1 is provided with a male spiral groove 2 having an arcuate cross section on its outer peripheral surface. Nut member 3
Has an inner peripheral surface close to the outer peripheral surface of the screw shaft 1, and a female spiral groove 4 is formed on the inner peripheral surface so as to face the spiral groove 2 of the screw shaft 1. Female spiral groove 4 formed with three threads on the nut member 3
Are spirally formed only once, and both ends thereof are connected by a circulation path 6 described later. A large number of balls 5 are rotatably arranged in a space defined by the spiral grooves 2 and 4 of the screw shaft 1 and the nut member 3, and the balls 5 are relative spirals of the screw shaft 1 and the nut member 3. It is possible to roll along the spiral grooves 2 and 4 during exercise.

The nut member 3 is integrally formed from a metal such as steel by cutting or forging (without a dividing surface at least in the circumferential direction), and the inner peripheral surface of the nut member 3 is formed with a female member. A long S-shaped circulation path 6 having a portion deeper than the spiral groove 4 (protruding outward in the radial direction) smoothly connects both ends of the female spiral groove 4. The balls 5 rolling in the male spiral groove 2 of the screw shaft 1 while rolling are guided along the ridges 8 separating the adjacent male spiral grooves 2 of the screw shaft 1,
Further, by being guided to the circulation path 6, the ridge 8 is overcome and returned to the adjacent (rolling) male spiral groove 2, that is, circulation is possible.

When the screw shaft 1 is rotated when the nut member 3 is supported in a non-rotating state, the three ball guide paths (spiral grooves 2, 4 and the circulation path 6) that are closed in FIG. Each time the ball 5 rolls and the endless circulation is repeated, the nut member 3 moves linearly in the forward or backward direction according to the rotation direction of the screw shaft 1. In the infinite circulation motion of the ball 5, when the ball 5 passes through the circulation path 6 and goes over the ridge 8 of the screw shaft 1, the ball 5 is guided by the guide projection 12 and can move extremely smoothly.

According to the present embodiment, the nut member 3 has
Since the circulation path 6 is formed integrally, there is no need to provide a separate type top, and the labor and cost of assembly are eliminated,
In addition, it is possible to avoid accuracy and reliability problems related to frame connection. Further, by integrally molding the nut member 3 so as not to have a dividing surface at least in the circumferential direction, it is possible to obtain a lightweight and high strength, and the labor at the time of assembling can be suppressed.
Further, as the heat treatment of the nut member 3, the conventional quenching and tempering (including carburizing) can be used, of course, and since there is no coma hole, local overheating and the like even if the high frequency heat treatment is used. There is an advantage that no trouble occurs.

By the way, in the structure shown in FIGS. 1 to 3, since the axial width of the ridge 8 is relatively large, the allowable thrust force with respect to the axial length of the nut member 3 is relatively small. Therefore, in order to receive a large thrust force with such a configuration,
Although it is necessary to increase the axial length of the nut member 3,
This leads to an increase in the size of the ball screw mechanism, which is not preferable. Therefore, it is conceivable to form a larger number of female spiral grooves in the nut member 3 without changing the axial length of the nut member 3 by reducing the axial width of the peak 8 as much as possible. In such a case, how to make the circulation path becomes a problem. This problem is solved by the embodiments described below.

FIG. 4 is a partial cross-sectional view of the ball screw mechanism according to the second embodiment. FIG. 5 is a cross-sectional view of the nut member according to the second embodiment, but the spiral groove is partially omitted in the drawing.

As shown in FIG. 4, the ridge 8'of the screw shaft 1 '
Has a smaller axial width than the first embodiment. Therefore, when the circulation paths are formed in the same phase, the circulation paths may interfere with each other. Therefore, as shown in FIG. 5, the phases of the adjacent circulation paths 6'are shifted in the circumferential direction. This provides a ball screw mechanism capable of receiving a high thrust load while suppressing the interference between the circulation paths 6 '.

Although the present invention has been described above with reference to the embodiments, the present invention should not be construed as being limited to the above embodiments, and it goes without saying that appropriate modifications and improvements are possible. is there.

[0018]

According to the ball screw mechanism of the present invention, the nut member which does not have the dividing surface in the circumferential direction connects the both ends of at least one female spiral groove to the radially projecting circulation path. And the circulation path returns the ball rolling along the male spiral groove to the male spiral groove on the rolling side beyond the peak separating the adjacent male spiral grooves. Since the nut member is integrated, it is lightweight and has high strength, and there is no need to provide a separate piece as in the prior art, which does not require assembly labor and cost, and is involved in connecting pieces. Avoid accuracy and reliability issues.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a ball screw mechanism according to a first embodiment.

FIG. 2 is a cross-sectional view of the nut member shown in FIG.

FIG. 3 is a view of the nut member shown in FIG. 2 as viewed in the III direction.

FIG. 4 is a partial cross-sectional view of the ball screw mechanism according to the second embodiment.

FIG. 5 is a sectional view of a nut member according to a second embodiment.

[Explanation of symbols]

1, 1'screw shaft 2 Male thread groove 3,3 'nut member 4 female thread groove 6,6 'circuit 8,8 'peak

Claims (2)

[Claims] 1. A screw shaft having a male spiral groove formed on an outer peripheral surface, a nut member having a female spiral groove formed on an inner peripheral surface, the female spiral groove facing the male spiral groove of the screw shaft, and a male spiral groove of the screw shaft. The nut member having a ball that can roll in a space formed by the female spiral groove of the nut member and having no dividing surface in the circumferential direction is at least one end of the female spiral groove. Has a radially projecting circulation path connecting the parts, and the circulation path rolls a ball rolling along the male spiral groove over a ridge separating the adjacent male spiral grooves. A ball screw mechanism which guides to return to the male spiral groove on the moving side. 2. The ball screw mechanism according to claim 1, wherein when a plurality of the circulation paths are provided, the phase in the circumferential direction is changed.