JP4459328B2 - Rolling linear motion device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rolling linear motion device (hereinafter referred to as “linear motion device”) such as a ball screw, a linear guide way, and a ball spline.
[0002]
[Prior art]
One member having a ball rolling groove on the outer surface, the other member having a ball rolling groove facing the ball rolling groove on the inner surface, and the other member inserted between the both ball rolling grooves A linear motion device having a plurality of balls which can be circulated by a ball circulation mechanism provided in the field is used in various fields.
One member, the other member, and the ball circulation mechanism are:
(1) In the case of ball screws, each corresponds to a screw shaft, ball nut, return tube, top, end cap or guide plate,
(2) In the case of a so-called end cap type linear guide way, it corresponds to a guide rail, a carriage, a ball direction changing groove of the end cap, and a ball return passage in the thickness of the carriage body.
[0003]
In such a linear motion device, the balls that support the load are closely arranged and move while rolling in the load region, that is, between both ball rolling grooves.
However, it is thought that this is caused by the non-uniformity of the effective diameter of the ball rolling groove. However, in the conventional linear motion device, the balls passing through the load region are pressed against each other, and a compression force acts between the balls. It was easy to have a part to do.
When such a compressive force acts on the ball, it slides and contacts in a direction that prevents the balls from rolling at each portion, so that a large resistance that prevents the ball from rolling occurs and the dynamic friction torque fluctuates greatly. Furthermore, a ball clogging phenomenon may occur.
When using a linear motion device, fluctuations in the dynamic friction torque cause unevenness in the feed speed of the object or affect the positioning accuracy, so that there are an increasing number of cases where the fluctuation in the dynamic friction torque is a problem.
[0004]
Therefore, the applicant of the present application has proposed that spacers having concave surfaces that follow the spherical surfaces of the balls are formed on both end surfaces in the axial direction between all adjacent balls of the linear motion device (Japanese Patent Application No. Hei. No. 10-32411, Japanese Patent Application No. 11-108066, and Japanese Patent Application No. 11-149430.)
[0005]
[Problems to be solved by the invention]
However, the proposed linear motion device has the following problems.
(1) The spherical surface of the ball in the load region for supporting the load always moves while rolling while in surface contact with one concave surface of the spacer. For this reason, if a portion where a compressive force acts between the spherical surface of the ball and the concave surface of the spacer due to non-uniformity of the effective diameter of the ball rolling groove, a resistance that prevents the ball from rolling occurs. The dynamic friction torque sometimes fluctuated.
(2) When the linear motion device is a ball screw, both ball rolling grooves are largely twisted spirally. For this reason, even if the concave surface of the spacer is formed so as to follow the spherical surface of the ball, the concave surface of the spacer may partially deviate from the spherical surface of the ball and may not circulate smoothly. In addition, the staggered spacer may be crushed by being caught between the front ball and the ball moving from the rear.
[0006]
[Means for Solving the Problems]
The present invention is interposed between one of the members having a ball rolling groove on the outer surface, the other member having a ball rolling groove facing the ball rolling groove on the inner surface, and both the ball rolling grooves. A plurality of balls, which can be circulated by a ball circulation mechanism provided on the other member, are disposed between the adjacent balls and a part of the spherical surface of the ball is slid on both end surfaces in the axial direction. In the rolling linear motion device having a spacer formed with a concave surface to be movably fitted, convex portions are formed on the same circumference of the concave surface of the spacer, and the convex portion and the spherical surface of the ball are The above problem has been solved by a point contact device.
[0008]
Furthermore, it is preferable that the outer circumferential surface in the axial direction of the spacer is formed in a concave shape.
[0009]
According to the present invention, the spherical surface of the ball in the load region for supporting the load is always fitted in one concave surface of the spacer in a stable manner, and moves while rolling in a point contact state. Therefore,
(1) Even if a portion where a compressive force acts between the spherical surface of the ball and the concave surface of the spacer due to non-uniformity of the effective diameter of the ball rolling groove, the area of the portion is very small. A linear motion device can be obtained in which the resistance to prevent the ball from rolling is extremely small and the dynamic friction torque hardly fluctuates.
(2) Even if both ball rolling grooves are largely twisted, the concave surface of the spacer does not deviate from the spherical surface of the ball. As a result, a smooth circulation between the ball and the spacer can be obtained.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Since the configuration of the linear motion device of the present invention is the same as the conventional configuration except for the ball and spacer described later, illustration and description of the overall configuration are omitted.
FIG. 1 shows a ball 10 and a spacer 20 in a state where the ball 10 is inserted between the ball rolling grooves and a ball infinite circulation path composed of a ball circulation mechanism in the linear motion device of the present invention.
Similar to what the applicant previously proposed, a cylindrical (or disk-shaped) spacer 20 made of metal or plastic is disposed between all adjacent balls 10 and 10.
[0011]
Concave surfaces 22 and 22 into which a part of the spherical surface of the ball 10 is slidably fitted are formed on both axial end surfaces of the spacer 20. Further, the diameter S of the spacer 20 is set to 60% to 80% of the diameter D of the ball 10 from the viewpoint of the holding stability of the spacer 20 by the ball 10 and the viewpoint of smooth circulation between the ball 10 and the spacer 20. ing. Furthermore, the length L of the spacer 20 in the axial direction is set so that the adjacent balls 10 and 10 are adjacent to each other from the viewpoint of securing a high load capacity by inserting as many balls 10 as possible and from the viewpoint of smoothly circulating the balls 10 and the spacers 20. The interval T between the vertices is set to be 0.1 mm to 0.5 mm. Reference numeral 28 denotes an axial outer peripheral surface of the spacer 20.
[0012]
As shown in FIGS. 2 and 3, the convex portions 30 are equally formed at three locations on the same circumference of the concave surface 22. 2A and 2B show the concave surface 22 having a spherical shape and a conical shape, respectively.
The convex portion 30 and the spherical surface of the ball 10 are in point contact with the ball 10 and the axis 34 of the spacer 20 at a predetermined angle θ (preferably around 30 °). The symbol O indicates the center point of the ball 10 on the axis 34.
Moreover, although said embodiment illustrated what integrally formed the convex part 30 in the concave surface 22 using means, such as injection molding, as shown in FIG. It may be installed. In this case, there exists an advantage which can make the convex part 30 into a different material.
In addition, although the thing which formed the convex part 30 equally on the concave surface 22 was illustrated, it cannot be overemphasized that it is not limited to this embodiment.
[0014]
In the first embodiment , the outer circumferential surface 28 in the axial direction of the spacer 20 is exemplified as a straight line, but the outer circumferential surface 28 may be concave as shown in FIG. When both the ball rolling grooves are twisted greatly like a ball screw, the interference between the outer circumferential surface 28 and both ball rolling grooves can be further prevented by making the outer circumferential surface 28 concave. This embodiment is also effective when the ball circulation mechanism is bent largely like a return tube of a ball screw.
[0015]
When the spacer is made of plastic, plastic such as Duracon (Polyplastic Co., Ltd.) is suitable, but sintered oil-impregnated alloy known as a self-lubricating material or Teflon (DuPont Co., Ltd.) Etc. may be used. In addition, the spacer is made of a lubricant-containing plastic (for example, see Japanese Patent Publication No. 47-3455) or a porous plastic that can be impregnated with a lubricant (for example, see Japanese Patent Laid-Open No. 61-283634). It can also be formed.
[0016]
By the way, the ball screw used for an ultra-precision lathe or the like is cooled by making the screw shaft hollow and flowing lubricating oil or the like into the hollow portion from the viewpoint of suppressing heat generation. However, with such a cooling mechanism, a considerable increase in cost is inevitable.
When the ball material used in the present invention is made of ceramics (specifically, silicon nitride) and used in combination with a spacer of the above-mentioned material, the degree of heat generation can be reduced to almost half that of the prior art. . Therefore, the manufacturing cost of the entire apparatus including the ball screw can be considerably reduced.
In addition, the combination of ceramic balls and plastic spacers does not appear to cause damage to the ball surface or break the ball.
[0017]
According to the present invention, the spherical surface of the ball in the load region where the load is supported, that is, between the two ball rolling grooves, is always fitted into one concave surface of the spacer in a stable manner and is in a point contact state. Move while moving. Therefore,
(1) Even if a portion where a compressive force acts between the spherical surface of the ball and the concave surface of the spacer due to non-uniformity of the effective diameter of the ball rolling groove, the area of the portion is very small. The resistance that prevents the ball from rolling is extremely small, and a linear motion device with almost no fluctuation of the dynamic friction torque can be obtained.
(2) Even if both ball rolling grooves are largely twisted, the concave surface of the spacer does not deviate from the spherical surface of the ball. As a result, a smooth circulation between the ball and the spacer can be obtained. There is an effect.
[0018]
Furthermore, by forming the outer circumferential surface in the axial direction of the spacer in a concave shape, interference between the outer circumferential surface in the axial direction and both ball rolling grooves can be further prevented. This embodiment is also effective when the ball circulation mechanism is greatly bent, such as a ball screw return tube.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a ball and a spacer in a state where they are inserted in a ball infinite circulation path in a linear motion device according to a first embodiment of the present invention.
2 is a longitudinal sectional view of the spacer of FIG. 1 (however, a sectional view taken along line 2-2 in FIG. 3). In addition, (a) and (b) of the same figure show that a concave surface is spherical and conical, respectively.
3 is a left side view of FIG. 2 (however, it is also a right side view).
4 is a partial longitudinal sectional view showing a modified embodiment of the spacer in FIG. 1. FIG.
FIG. 5 is a partial longitudinal sectional view showing a deformation mode of the outer circumferential surface in the axial direction of the spacer.
[Explanation of symbols]
10 Ball 20 Spacer 22 Concave surface 28 Spacer axial outer peripheral surface 30 Convex portion

Claims (2)

One member having a ball rolling groove on the outer surface, the other member having a ball rolling groove facing the ball rolling groove on the inner surface, and the other member inserted between the both ball rolling grooves A plurality of balls that can be circulated by a ball circulation mechanism provided on the ball and adjacent balls are disposed, and a part of the spherical surface of the ball is slidably fitted to both axial end surfaces thereof. In a rolling linear motion device comprising a spacer formed with a concave surface to be inserted,
Convex portions are formed on the same circumference of the concave surface of the spacer, and the convex portions and the spherical surface of the ball are in point contact,
Rolling linear motion device.   The rolling linear motion device according to claim 1, wherein an axial outer peripheral surface of the spacer is formed in a concave shape.

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