JP2004068866A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw device capable of facilitating its assembling works and maintaining stable operations for a long period of time. <P>SOLUTION: The ball screw device includes a nut 6 and a circulating piece 8 attached to the nut 6, wherein the inside surface of the nut 6 is distinctly divided by the circulating piece 8 into a screw groove 4a where a ball 5 rolls actually and a portion 4c where the ball 5 does not roll, wherein the screw groove 4a is solely formed at the inside surface of the nut 6, and the portion 4c (the inside surfaces at both ends of the nut 6 and a part of around the center in axial direction of the inside surface of the nut 6) is made in the same dimension with the nut inside diameter. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ball screw device used for a feed mechanism of various devices.
[0002]
[Prior art]
FIG. 3 shows an example of a conventional ball screw device of this type. In the ball screw device 1, a nut 6 having a spiral screw groove 2 on an outer peripheral surface and extending in the axial direction and a nut 6 having a spiral screw groove 4 on the inner peripheral surface corresponding to the screw groove 2 is provided. It is screwed.
[0003]
The screw groove 4 of the nut 6 and the screw groove 2 of the screw shaft 3 are opposed to each other to form a spiral load track between them, and a number of balls 5 as rolling elements are rolled on the load track. It is movably loaded. The rotation of the screw shaft 3 (or the nut 6) causes the nut 6 (or the screw shaft 3) to move in the axial direction through the rolling of the ball 5.
[0004]
When the nut 6 (or the screw shaft 3) moves in the axial direction, the ball 5 moves while rolling on the load track formed between the two screw grooves 2 and 4. In order to move the shaft 3) continuously, it is necessary to circulate the ball 5 infinitely.
For this reason, for example, a circulating frame fitting hole 7 is provided on the outer peripheral surface of the nut 6 and a circulating frame 8 having a ball circulating groove (ball circulating path) 8 a as a ball circulating member is fitted into the fitting hole 7. The ball 5 forms an infinite circulation path.
[0005]
That is, the ball 5 rolling on the load track between the two screw grooves 2 and 4 is guided by the scooping portion of the circulation frame 8 over the land 3a of the screw shaft 3 into the ball circulation groove 8a inside the circulation frame 8. It is returned to the load track between the adjacent two screw grooves 2 and 4 via the ball circulation groove 8a.
[0006]
[Problems to be solved by the invention]
In the conventional ball screw device, the screw groove 4 on the nut 6 is formed continuously from one end to the other end of the inner peripheral surface of the nut 6. Does not roll, and is distinguished into a thread groove 4 in which the ball 5 actually rolls when the circulation frame 8 is attached to the nut 6, and a thread groove 4 in which the ball 5 does not roll.
[0007]
For example, in the nut 6 shown in FIG. 4, reference numeral 4a is a thread groove on which the ball 5 actually rolls, and reference numeral 4b is a thread groove on which the ball 5 does not roll, and is a functionally unnecessary groove.
However, if the functionally unnecessary thread groove 4b that prevents the ball 5 from rolling on the inner peripheral surface of the nut 6 is formed, the ball may enter the thread groove 4b during the ball insertion and assembly operation, There is a problem that foreign matter easily adheres to and mixes into the groove 4b, and the operability of the device becomes unstable.
[0008]
The present invention has been made to solve such inconvenience, and provides a ball screw device capable of facilitating assembly work and maintaining stable operability for a long period of time. The purpose is to:
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 includes a screw shaft having a spiral screw groove on an outer peripheral surface, and a screw groove corresponding to the screw groove of the screw shaft on an inner peripheral surface. A nut screwed onto the screw shaft, a number of balls rollably loaded between the two screw grooves, and a ball circulation path for infinitely circulating the balls rolling between the two screw grooves. In a ball screw device having a ball circulation member fixed to the nut,
The thread groove on the nut side is formed only in a portion where the ball actually rolls.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view for explaining a nut of a ball screw device as an example of an embodiment of the present invention, and FIG. 2 is a partially enlarged view of FIG. In this embodiment, only different parts from the nut of the conventional ball screw device described with reference to FIG. 4 will be described.
[0011]
As shown in FIGS. 1 and 2, the ball screw device according to the embodiment of the present invention actually rotates the ball 5 on the inner peripheral surface of the nut 6 by the circulation top 8 attached to the nut 6. The moving screw groove 4a and the portion 4c where the ball 5 does not roll are clearly separated, and only the screw groove 4a where the ball actually rolls is formed on the inner peripheral surface of the nut 6, so that the ball 5 The portion 4c that does not roll (in this embodiment, the inner peripheral surfaces of both ends of the nut 6 and part of the axially substantially central portion of the inner peripheral surface of the nut 6) has the same size as the inner diameter of the nut. In addition, an angle for the center which is a setting reference for the outer diameter grinding may be provided on the inner peripheral surfaces on both ends of the nut 6.
[0012]
As described above, in this embodiment, only the screw groove 4a on which the ball 5 actually rolls is formed on the inner peripheral surface of the nut 6, and the screw groove 4a on which the ball 5 actually rolls and the ball 5 are rolled. Since the non-moving portion 4c is clearly separated, the ball 5 can be accurately and easily inserted into the screw groove 4a and assembled. Can be completely prevented.
[0013]
Further, unlike the related art, foreign matter does not adhere to or enter the screw groove 4b where the ball 5 does not roll, so that stable operability can be maintained for a long time.
Furthermore, since the sharp edge of the thread line cut-up portion 10 of the screw groove 4 is located substantially at the center of the inner peripheral surface of the nut 6 in the axial direction, the sharp edge is formed on the inner peripheral surface of both ends of the nut 6. As a result, the safety can be improved, and the sharp edge deburring work by hand becomes unnecessary, thereby reducing the processing load.
[0014]
In addition, it is needless to say that each configuration of the ball screw device of the present invention is not limited to the above embodiment, and can be appropriately changed without departing from the gist of the present invention.
[0015]
【The invention's effect】
As is clear from the above description, according to the present invention, since the thread groove on the nut side is formed only in the portion where the ball actually rolls, the assembling work can be facilitated and the stable The effect that the improved operability can be maintained for a long period is obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a nut of a ball screw device which is an example of an embodiment of the present invention.
FIG. 2 is a partially enlarged view of FIG.
FIG. 3 is a sectional view showing an example of a conventional ball screw device.
FIG. 4 is a sectional view showing a nut of a conventional ball screw device.
[Explanation of symbols]
2: Screw groove (screw shaft side)
3 Screw shaft 4a Screw groove on which ball actually rolls (nut side)
5 ball 6 nut 8a ball circulation groove (ball circulation path)
8. Circulation top (ball circulation member)

Claims (1)

A screw shaft having a helical screw groove on the outer peripheral surface, a nut screwed to the screw shaft having a screw groove corresponding to the screw groove of the screw shaft on the inner peripheral surface, and between the two screw grooves; A ball screw device comprising: a number of balls rotatably mounted; and a ball circulation member fixed to the nut to form a ball circulation path for infinitely circulating the balls rolling between the two screw grooves. ,
A ball screw device wherein the thread groove on the nut side is formed only in a portion where the ball actually rolls.

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