JPH01199017A - Support structure for rotary shaft and thrust bearing - Google Patents

Abstract

PURPOSE:To reduce the occurrence of swing and bending and to facilitate structure and assembly, by a method wherein by using a ball support hole, formed in a surface positioned facing the end of a rotary shaft, and a radial non- constraining thrust bearing formed with a plane and a ball, a feed screw is formed between a radial bearing and the other thrust bearing. CONSTITUTION:A rotary shaft 11 is provided with a feed screw part 12 and a rotation providing part 13 and supported by means of a radial bearing 21 and a thrust bearing 22 of a support frame 20, and the end part on the rotation providing part 13 side of the rotary shaft 11 is supported by a radial non- constraining thrust bearing 30. The radial non-constraining thrust bearing 30 is formed such that a conical ball support hole 32 having an inclination angle alphais formed in the end part of the rotary shaft 11, and is positioned facing a plane 32 of a thrust member 31, securely threadedly joined with an auxiliary base frame 23, with a ball therebetween. This constitution constrains an axis substantially only by two points, reduces swinging and bending of the rotary shaft 11 to a minimum, and simplifies structure and facilitates assembly.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a support structure for a rotating shaft, and in particular to a supporting structure for a rotating shaft suitable for use in an ultra-precision rotating shaft that extremely dislikes roughness and deflection of the rotating shaft, and a thrust support structure for the rotating shaft. Regarding bearings.

"Prior Art and Problems Therewith" For example, a feed screw mechanism works by rotating a rotating shaft having a feed screw to feed an object to be moved whose rotation is restricted by being screwed together with the feed screw.

This feeding mechanism has conventionally been used in many fields, but in the field of ultra-precision, it is used, for example, in a moving mechanism that moves a magnetic head while maintaining a fixed distance relationship with a magnetic recording medium.

The rotating shaft having the feed screw has a feed screw portion and a rotation imparting portion, and must be supported at at least three points, the middle and both ends of the feed screw portion and the rotation imparting portion. The intermediate bearing is a radial bearing that freely supports only rotation, and both end portions are thrust bearings that receive thrust in opposite directions.For example, a motor rotor is fixed to the zero rotation imparting portion, or a rotor that does not rotate. A pulley for transmission is fixed.

There is also a four-point support structure. Both ends of the feed screw section are rotatably supported by a pair of radial bearings, and the ends of an extension shaft (rotation imparting section) extending from the feed screw section to both sides are received by thrust bearings.

However, all of the conventional thrust bearings have a stepped portion such as a seven flange or a small diameter portion on the rotating shaft, and receive thrust through the stepped portion, and also restrict movement in the radial direction. For this reason, in these three-point or four-point supported rotating shafts, it is impossible to position the axes of the three or four points on a geometric straight line.

Conventional rotary shaft support structures aim to improve the accuracy of the radial and thrust rotary bearings and their mounting accuracy in order to position the axes of these three or four points on a geometric straight line. However, there is a limit to the machining accuracy, and when viewed microscopically, there is always some vibration or deflection of the rotating shaft between the bearings.

However, this runout and deflection cannot be ignored in a feed screw mechanism that requires feed accuracy on the order of microns.

Additionally, in order to receive thrust, conventionally it is necessary to form a step, a flange, etc. on the rotating shaft, and these steps and flange portions worsen the support load of the rotating shaft and make assembly, especially automatic assembly, difficult. I have to.

[Object of the Invention] An object of the present invention is to obtain a support structure that does not cause runout or deflection in a rotating shaft structure with three-point support or four-point support without relying on machining accuracy.

Another object of the present invention is to obtain a thrust bearing that does not require forming a step or a flange on a rotating shaft to receive thrust.

"Summary of the Invention" The present invention provides a rotating shaft support structure with three or four points support, in which it is virtually impossible to position these three or four points in a straight line along the axis. This was done by focusing on the fact that if it is supported at two points, the two points will automatically be located on a straight line. In other words, if the 3rd (and 4th) support part (@ part) receives only thrust force without restraining the 1-rotation shaft in the radial direction, the 3rd or 4th point support part (@ part) will be able to receive only thrust force. This was completed based on the idea that the vibration and deflection of the rotating shaft could be eliminated.

The present invention provides a three-point support structure for a rotating shaft in which the middle portion of the rotating shaft is supported by a single radial bearing and both ends are supported by thrust bearings. It is characterized by being constructed from a radial non-constraint thrust bearing that does not constrain the shaft.

In addition, in a four-point support structure for a rotating shaft, in which the middle part of the rotating shaft is supported by a pair of radial bearings separated by a predetermined distance, and each end is supported by a thrust bearing, each of the pair of thrust bearings is supported in the radial direction. It consists of a radial unconstrained thrust bearing that does not constrain the rotating shaft.

A radial non-restricted thrust bearing includes, for example, a thrust member facing one end of a rotating shaft, a ball support hole centered on the axis of the rotating shaft formed on one of the opposing surfaces of the thrust member and the rotating shaft, and It can be composed of a plane formed on the other side in a direction orthogonal to the axis of the rotating shaft, and a ball inserted between the ball support hole and the plane. This radial non-restricted thrust bearing has a simple structure and is easy to process, so that the present invention can be realized most easily.

In the case of a rotating shaft with a feed screw, the feed screw portion is used between the radial bearing and the other thrust bearing in the case of three-point support, and between the pair of radial bearings in the case of four-point support, and the rotation is restricted to this feed screw portion. By screwing these moving objects together, a feed screw mechanism that is not affected by vibration or deflection of the rotating shaft can be obtained.

In addition, the thrust bearing of the present invention includes a radial bearing that rotatably supports an end of a rotating shaft without a step, a thrust member that faces the end of the rotating shaft, and a surface that faces the thrust member and the rotating shaft. A ball support hole centered on the axis of the rotating shaft formed on one side, a plane perpendicular to the axis of the rotating shaft formed on the other side, and a ball inserted between the ball support hole and the plane. It is composed of According to this bearing structure, there is no need for a step or a flange at the end of the rotating shaft, which increases the rust resistance of the support and simplifies assembly. This thrust bearing is suitable for use, for example, as the other thrust bearing of a rotating shaft in a three-point support structure.

"Embodiments of the Invention" The present invention will be described below with reference to illustrated embodiments. Figure 1 is 3
2 shows an embodiment of the present invention in the case of point support. The rotating shaft 11 has a feed screw portion 12 and a rotation imparting portion 13,
The support base 2 is located between the feed screw portion 12 and the rotation imparting portion 13.
It is rotatably supported by a radial bearing 21 fixed at zero. The radial bearing 21 may be a sliding bearing (plain metal) or a rolling bearing (ball bearing, roller bearing). The rotating shaft 11 has the same diameter at least in the portion supported by the radial bearing 21.

A small diameter portion 14 is provided at the end of the rotating shaft 11 on the feed screw portion 12 side.
The small diameter portion 14 is rotatably supported by a thrust bearing 22 fixed to the support base 20 and supported by the stepped portion of the small diameter portion 14 so as to receive the thrust force. The structure of this thrust bearing 22 is also not limited.

The above is a normal support structure, but the present invention provides a support structure for the rotating shaft 11.
The end portion on the rotation imparting portion 13 side is supported by a radial non-constraint thrust bearing 30. This radial non-constraint thrust bearing 30 does not constrain the rotating shaft 11 in the radial direction, but only receives thrust force, and in this embodiment is configured as follows.

A thrust member 31 is screwed onto the auxiliary base 23 that is integrated with the support base 20 so as to be positioned on the axis of the rotating shaft 11 . This thrust member 31 has a plane 32 at its end on the rotating shaft 11 side that is perpendicular to the axis of the rotating shaft 11 .

On the other hand, the end of the rotating shaft 11 facing this plane 32 has an apex angle α of, for example, 60 to 90 degrees, centered on the axis.
A ball support hole 33 consisting of a conical hole is formed,
A steel ball 34 is inserted between the ball support hole 33 and the thrust member 31. Therefore, by adjusting the screwing position of the thrust member 31 with respect to the auxiliary base 23, it is possible to receive the thrust while rotatably supporting the rotary shaft 11, and the rotary shaft 11 is not restrained in the radial direction. The flat surface 32 of the thrust member 31, the ball support hole 33 of the rotating shaft 11, and the steel ball 34
All are made of hard materials and processed with ultra-precision. The ball support hole 33 may be formed of an inner spherical hole 33'', as shown in FIG.

According to the above support structure, the rotating shaft 11 is only restrained in the radial direction at two points, the radial bearing 21 and the thrust bearing 22. In the third radially unconstrained thrust bearing 30, the thrust of the rotating shaft 11 is rotatably supported by the bearing, but is not constrained in the radial direction. Therefore, the rotating shaft 11 in the radial unconstrained thrust bearing 30
The axial center of is automatically located on the geometrical axis of the rotating shaft 11 determined by the radial bearing 21 and the thrust bearing 22. That is, since the steel balls 34 of the radial non-restricted thrust bearing 30 are located at the axis of the rotating shaft 11 and can move on the plane 32, the point of contact between the steel balls 34 and the plane 32 is at the radial bearing of the rotating shaft 11. 21 and the thrust bearing 22, automatically and accurately located on the straight line determined by the two points. Therefore, the runout and deflection occurring in the feed screw portion 12 supported between the radial bearing 21 and the thrust bearing 22 are minimized, and the vibration in the direction perpendicular to the axis of the movable body 16 screwed into the feed screw portion 12 is minimized. The amount of runout can be reduced to the order of microns or less. Note that the rotation imparting unit 13 includes a drive system 17 such as a motor rotor and a pulley.
is connected.

FIG. 3 shows an embodiment in which the left thrust bearing 22 is replaced with a thrust bearing 40 according to the present invention in the structure shown in FIG. A ball support hole 41 centered on the axis of the rotation shaft is formed in the end face of the support base 20.The ball support hole 41 may be a conical hole or a spherical hole. A bottomed cylindrical body 42 having a larger diameter than this is fixed, and a radial bearing 43 is provided between the bottomed cylindrical body 42 and the rotating shaft 11 to support the rotating shaft 11 freely only in rotation. This bottomed cylindrical body 42 also constitutes a thrust member, and its bottom constitutes a plane 44 that faces the ball support hole 41 and is orthogonal to the axis of the rotating shaft 11, and this plane 44 and the ball A steel ball 45 is inserted between the support hole 41 and the support hole 41 .

According to this radial bearing 40, since there is no stepped portion on the rotating shaft 11, precision machining is easy and assembly is also easy. In addition, since rotation is applied by the radial bearing 43 and thrust is applied by point contact between the ball 45 and the flat surface 44, the structure of the rotating shaft is simplified and the rotational resistance exerted on the rotating shaft by the thrust member is extremely small.

4A to 4E show modified examples of the thrust bearing according to the present invention. FIG. 4A shows a bottomed cylindrical body 42 screwed onto the support base 20 so that its axial position can be adjusted, and FIG. 4B shows a bottomed cylindrical body 42 with a flat end surface 44 and a bottomed cylindrical body. Thrust member 46 having ball support hole 41 in body 42
4C, the relationship between the ball support hole and the plane in FIG. 4B is reversed, and the ball support hole 41 is provided at the end of the rotating shaft 11, and the flat surface 44 is provided at the end of the thrust member 46.
was formed. Furthermore, FIG. 4D shows the bottomed cylindrical body 4.
2 has a ball support hole 41 formed therein, and the end surface of the rotating shaft 11 is made into a flat surface 44. In FIG. 4E, the bottomed cylindrical body 42 is screwed onto the support base 20 in FIG. 4D, and the axial position is adjusted. is adjustable.

FIG. 5 shows an example of a support structure for a rotating shaft in the case of four-point support. This embodiment corresponds to an embodiment in which the intermediate portion of the feed screw portion 12 in the embodiment shown in FIG. 1 has a line-symmetric structure with respect to an imaginary line. That is, the rotation shaft 11 has a rotation imparting section 13 and an extension shaft section 1 on both sides of the feed screw section 12 at the center thereof.
3 degrees, the feed screw part 12 and the rotation imparting part! During 3,
The portion between the feed screw portion 12 and the extended shaft portion 13° is supported by radial bearings 21A and '21B, respectively. The ends of the rotation imparting portion 13 and the extended shaft portion 13° are each supported by a radial non-constraint thrust bearing 3°. The other parts are common to the first embodiment, and the same elements are given the same reference numerals.

In this four-point supported embodiment, the rotating shaft 11 is only restrained in the radial direction at two points, radial bearings 21A and 21B. In the third and fourth radially unconstrained thrust bearings 30, the thrust of the rotating shaft 11 is rotatably supported by the bearing, but is not constrained in the radial direction. Therefore, the axis of the rotating shaft 11 in the radial unconstrained thrust bearing 30, that is, the steel ball 34 and the plane 32
The point of contact with the radial bearings 21A and 21B is automatically located on the axis of the geometric axis of rotation 11 determined by the radial bearings 21A and 21B, so that the radial bearings 21A and 21B
There is a very low possibility that the portion of the feed screw portion 12 supported between the two portions will be shaken or bent. For this reason, the feed screw part 1
The amount of deflection of the movable body 16 screwed into the movable body 16 can be sufficiently suppressed to the micron order.

The thrust member 31 of the radial unrestricted thrust bearing 30 may apply a biasing force toward the rotating shaft 11 by means of a spring means 35, as schematically shown in FIG. Alternatively, the thrust member 31 is fixed to the auxiliary base 23, and this auxiliary base 2
3 may be adjustable toward and away from the support base 20.

Further, the relationship between the plane 32 and the ball support hole 33 may be reversed. In other words, as shown in FIG.
A bearing with the same effect can be obtained by forming a ball support hole 33 on the side and forming a flat surface 32 at the end of the rotating shaft 11 facing the ball support hole 33. However, if the ball support hole 33 is formed at the same time as the rotary shaft 11 is machined, a highly accurate ball support hole 33 can be easily obtained.

"Effects of the Invention" As described above, the rotating shaft support structure of the present invention substantially restrains the position of the axis of a rotating shaft supported at three or four points at only two points.

As a result, runout and deflection of the rotating shaft can be suppressed to a minimum, so if used in an ultra-precise feed screw device, etc., it is possible to obtain a feed mechanism that does not run out in the direction perpendicular to the axis. In addition, according to the thrust bearing of the present invention, there is no need to provide a step or a flange on the rotating shaft, and the rotation is received by the radial bearing, and the thrust is received by the point contact between the ball and the plane, so the structure of the rotating shaft is simple. At the same time, the rotational resistance exerted by the thrust member on the rotating shaft becomes extremely small. Therefore, a thrust bearing with higher precision can be obtained, and assembly is easier. Therefore, if this thrust bearing is used as the other thrust bearing of the three-point supported rotating shaft according to the present invention, it is possible to support the rotating shaft with no stepped portions with extremely high precision, and the assembly becomes simple and automatic assembly is possible. can open the way.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of the rotating shaft support structure of the present invention, FIG. 2 is a sectional view showing another example of the ball support hole, and FIG. 3 is a sectional view showing the rotating shaft support structure of the present invention. 48 to 4E are sectional views showing other embodiments of the structure; FIG. 5 is a sectional view showing the second embodiment of the thrust bearing; FIG. 7 are sectional views of essential parts showing a modification of the present invention. 11--Rotation shaft, 12--Feed screw part, 13-Rotation imparting part, 14-Small diameter part, 20-Support base, 21.21A, 2
1B-Radial bearing, 22-Thrust bearing, 23-Auxiliary base, 30-Radial unconstrained thrust bearing, 31-Thrust member, 32-Plane, 33-Ball support hole, 34-Steel ball, 40-Thrust bearing, 41 - Ball support hole, 42 - Bottomed cylindrical body (thrust member), 43 - Radial bearing, 44 - Plane, 45 - Steel ball, 46
- Thrust members.

Claims (8)

[Claims] (1) In a rotating shaft support structure in which the middle part of the rotating shaft is supported by a single radial bearing and both ends are supported by thrust bearings, one of the thrust bearings is connected to a radial shaft that does not restrain the rotating shaft in the radial direction. A support structure for a rotating shaft characterized by being composed of a non-restricted thrust bearing. (2) A radial non-restricted thrust bearing consists of a thrust member facing one end of the rotating shaft; and a ball support hole centered on the axis of the rotating shaft formed on one of the opposing surfaces of the thrust member and the rotating shaft. 2. The rotating shaft support structure according to claim 1, comprising:; a plane formed on the other side in a direction perpendicular to the axis of the rotating shaft; and a ball inserted between the ball support hole and the plane. (3) Support for the rotating shaft according to claim 1 or 2, wherein the rotating shaft constitutes a feed screw between the radial bearing and the other thrust bearing, and a moving object whose rotation is restrained is screwed onto the feed screw. structure. (4) The other thrust bearing includes a radial bearing that rotatably supports the end of the rotating shaft without a step; a thrust member that faces the end of the rotating shaft; and a surface that faces the thrust member and the rotating shaft. A ball support hole centered on the axis of the rotating shaft formed on one side; a plane perpendicular to the axis of the rotating shaft formed on the other side; and a ball inserted between the ball support hole and the plane. A support structure for a rotating shaft according to any one of claims 1 to 3, comprising: (5) In a rotating shaft support structure in which the middle portion of the rotating shaft is supported by a pair of radial bearings separated by a predetermined distance, and each end portion is supported by a thrust bearing, the pair of thrust bearings are rotated in the radial direction. A support structure for a rotating shaft characterized by being constructed from a radial non-constraint thrust bearing that does not constrain the shaft. (6) A radial non-restricted thrust bearing consists of a thrust member facing one end of the rotating shaft; a ball support hole centered on the axis of the rotating shaft formed on one of the opposing surfaces of the thrust member and the rotating shaft; 5. The rotating shaft support structure according to claim 4, comprising:; a plane formed on the other side in a direction perpendicular to the axis of the rotating shaft; and a ball inserted between the ball support hole and the plane. (7) The rotary shaft support structure according to claim 1 or 2, wherein the rotary shaft constitutes a feed screw between the pair of radial bearings, and a moving object whose rotation is restrained is screwed onto the feed screw. (8) A radial bearing that rotatably supports the end of the rotating shaft without a step; a thrust member that faces the end of the rotating shaft; and a radial bearing formed on one of the opposing surfaces of the thrust member and the rotating shaft. , a ball support hole centered on the axis of the rotating shaft; a plane formed on the other side in a direction orthogonal to the axis of the rotating shaft; and a ball inserted between the ball support hole and the plane.