JP2015215038A - Ball screw device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw device for reducing the shake of a screw shaft at its end when an excessive load is applied to the screw shaft.SOLUTION: A ball screw device 1 includes a screw shaft 10 having a spiral groove 11 formed in the surface, and a bearing 20 for supporting a bearing installation part 10a formed at the end of the screw shaft 10. Herein, an annularly shaped spacer 50 is provided which is fitted to the bearing installation part 10a. An end face 50a in the axial direction of the spacer 50 abuts on an inner ring 21 of the bearing 20. Knurling work is applied to the inner peripheral face of the spacer 50.

Description

  The present invention relates to a ball screw device, and more particularly, to a ball screw device that is used in various machine tools such as a uniaxial actuator and includes a ball screw and a bearing that supports the screw shaft.

  2. Description of the Related Art Conventionally, a ball screw device that is used in various machine tools such as a uniaxial actuator and includes a ball screw and a bearing that supports both ends or one end of the screw shaft is known (Patent Document 1). In such a ball screw device, the outer peripheral surface of the screw shaft is reduced in diameter so as to be fitted to the inner peripheral surface of the inner ring of the bearing to form a bearing installation portion, and the end surface of the bearing installation portion, the bearing, In general, a spacer is inserted between the two and tightened with a lock nut.

Japanese Unexamined Patent Publication No. 2009-162314, FIG.

Here, as a form of the screw shaft of the ball screw device, there are one in which the spiral groove formed on the surface thereof is formed up to the end face of the bearing installation portion and the one not formed.
As shown in FIG. 2A, in the screw shaft 100 in which the spiral groove 101 is not formed up to the end surface 102a of the bearing installation portion 102, the shape of the end surface 102a is a uniform circle as shown in FIG. It has a ring shape. Therefore, as shown in FIG. 2 (c), the inner ring 111 of the bearing 110 is sandwiched between the spacer 130 and the end surface 102a provided between the lock nut 120 and the inner ring 111 of the bearing 110, and the axial movement of the bearing 110 is controlled. Can be limited.

  On the other hand, as shown in FIG. 3A, in the screw shaft 200 in which the spiral groove 201 is formed up to the end surface 202a of the bearing installation portion 202, the shape of the end surface 202a is uneven as shown in FIG. It has a circular shape. This shape is conspicuous when the lead of the spiral groove 201 is small, and a portion where the bottom 201a of the spiral groove 201 is exposed may occur. In the screw shaft 200 having such a configuration, as shown in FIG. 3C, the spacer 230 provided between the lock nut 220 and the inner ring 211 of the bearing 210, and between the end face 202 a and the inner ring 211 of the bearing 210. The movement of the bearing 210 in which the inner ring 211 is sandwiched between the spacer 240 and the spacer 240 is limited.

  As described above, if the radial dimension of the end surface 202a of the screw shaft 200 that is in contact with the inner ring 211 or the spacer 240 of the bearing 210 is uneven, the screw shaft 200 is excessively large. When a load is applied, the end of the screw shaft 200 is likely to swing.

This leads to deformation, eccentricity, and climbing of the screw shaft 200. As a result, the end of the screw shaft 200 is bent by tightening the lock nut 220, or a pulley or coupling is coupled to the end of the screw shaft 200. Because it may be difficult to install, there was room for consideration.
The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a ball screw device that reduces the vibration of the end of the screw shaft even when an excessive load is applied to the screw shaft.

An aspect of the ball screw device for solving the above-described problem includes a screw shaft having a spiral groove formed on a surface thereof, and a bearing that supports a bearing installation portion formed at an end of the screw shaft.
An annular spacer that is fitted to the bearing installation portion is provided, and an axial end surface of the spacer contacts the inner ring of the bearing,
The inner peripheral surface of the spacer is knurled.

Moreover, in the said ball screw apparatus, it is preferable that it is knurled in the range which the said spacer fits among the outer peripheral surfaces of the said bearing installation part.
Moreover, in the said ball screw apparatus, it is preferable that the surface shape of the inner peripheral surface of the said knurled said spacer is the same pitch space | interval.
Moreover, in the said ball screw apparatus, it is preferable that the said knurling process is an oblique knurling process.

Moreover, in the said ball screw apparatus, it is preferable that the said knurling process is a flat knurling process.
In the ball screw device, the knurling process is preferably a twill knurling process.

  ADVANTAGE OF THE INVENTION According to this invention, even when an excessive load is applied to the screw shaft, it is possible to provide a ball screw device that reduces the deflection of the end portion of the screw shaft.

It is a figure which shows the structure in a certain aspect of the ball screw apparatus of this invention. It is a figure which shows the structure of the conventional ball screw apparatus, (a) is a right view of a screw shaft, (b) is a front view of a screw shaft, (c) is sectional drawing in alignment with the axial direction of a ball screw device. . It is a figure which shows the structure of the conventional ball screw apparatus, (a) is a right view of a screw shaft, (b) is a front view of a screw shaft, (c) is sectional drawing in alignment with the axial direction of a ball screw device. .

Hereinafter, an embodiment of a ball screw device according to the present invention will be described with reference to the drawings.
1A and 1B are diagrams showing a configuration of an embodiment of a ball screw device, wherein FIG. 1A is a sectional view along the axial direction of the ball screw device, and FIG. 1B is a right side view showing a process of incorporating a spacer into the screw shaft. c) is a right side view of a screw shaft incorporating a spacer.
As shown in FIG. 1A, the ball screw device 1 includes a screw shaft 10 and double row rolling bearings 20 and 20 that support end portions of the screw shaft 10. A spiral groove 11 is formed on the surface of the screw shaft 10. This rolling bearing 20 has two inner rings 21, 21 that fit together with a bearing installation portion 10 a formed at the end of the screw shaft 10 and rotate integrally with the screw shaft 10. Outer rings 23 that rotatably support the inner ring 21 via a plurality of rolling elements 22 are respectively provided on the outer circumferences of the inner rings 21 and 21.

The ball screw device 1 includes a cylindrical housing 30 that houses the rolling bearing 20, and the outer peripheral surface of the rolling bearing 20 (the outer peripheral surface of the outer ring 23) is slidably fitted to the inner peripheral surface of the housing 30. Match.
The inner ring 21 of the rolling bearing 20 is positioned at a predetermined position by a step portion 12 formed on the screw shaft 10 and a lock nut 40. The lock nut 40 is screwed onto the end of the screw shaft 10, and a spacer 41 is provided on the outer periphery of the screw shaft 10 between the lock nut 40 and the inner ring 21. The spacer 41 is made of, for example, a disc spring, a coil spring, or a metal having a longitudinal elastic modulus.

The screw shaft 10 is provided with an annular spacer 50 as shown in FIG. The diameter of the inner peripheral surface of the spacer 50 is set to be equal to or smaller than the diameter of the outer peripheral surface of the bearing installation portion 10a so that the spacer 50 is fitted and installed in the bearing installation portion 10a.
The spacer 50 has one end surface 50a in the axial direction in contact with the end surface 12a of the step 12 at the boundary portion between the bearing installation portion 10a and the spiral groove 11, and the other end surface 50b in the axial direction is the bearing. It is installed so as to contact the 20 inner rings 21.

[Knurled part]
Here, the inner peripheral surface 50c of the spacer 50 is knurled. The range to be knurled on the inner peripheral surface 50c does not have to be the entire inner peripheral surface 50c, and is appropriately set as necessary. Hereinafter, the knurled portion on the inner peripheral surface 50c is referred to as a knurled portion 51 (indicated by dot hatching in FIG. 1).

Further, the outer peripheral surface of the bearing installation portion 10a may be knurled in a range where the spacer 50 is fitted. In this case, it is preferable that the knurled shape of the inner peripheral surface 50c of the spacer 50 is different from the knurled shape formed on the outer peripheral surface of the bearing installation portion 10a.
Moreover, it is preferable that the surface shape of the knurl processing part 51 formed in the internal peripheral surface 50c of the spacer 50 is the same pitch space | interval. As the surface shape of the knurled portion 10b, for example, those specified in JIS B0951 can be suitably used. This surface shape is measured using, for example, a contour shape measuring machine manufactured by Tokyo Seimitsu Co., Ltd.

  Examples of the knurling include oblique knurling, flat knurling, and twill knurling. By adopting an oblique knurling process, it is possible to easily insert the spacer. Further, by adopting a flat knurling process as the knurling process, an effect that the spacer can be more easily inserted is obtained. In addition, by adopting a twill knurling process as the knurling process, an effect of strengthening the fastening force is obtained.

Since the spacer 50 provided in this way has the knurled portion 51 formed on the inner peripheral surface 50c, the spacer 50 is fitted (press-fitted) into the outer peripheral surface of the bearing installation portion 10a and is firmly fitted to the screw shaft 10. Combined.
Further, the inner ring 21 of the rolling bearing 20 is pressed against the other end surface 50 b of the spacer 50 by the tightening force of the lock nut 40. The spacer 50 is preferably made of, for example, a disc spring, a coil spring, a metal having a longitudinal elastic modulus (iron / nonferrous), or a resin.

  Next, a manufacturing process of the screw shaft 10 configured as described above will be described. As shown in FIGS. 1B and 1C, the spacer 50 is inserted from the side opposite to the side where the spiral groove 11 is formed in the bearing installation portion 10 a of the screw shaft 10. Then, the spacer 50 is press-fitted into the bearing installation portion 10a until the one end surface 50a is engaged with the end surface 12a, and the spacer 50 is fitted to the screw shaft 10.

  Thus, in the ball screw device of this embodiment, the spacer 50 having the knurled portion 51 formed on the inner peripheral surface 50c is press-fitted into the screw shaft 10, so that the fastening force due to the frictional force is increased, and the screw shaft 10 On the other hand, the spacer 50 is firmly fixed. As a result, an excessive load in the axial direction is evenly received by the spacer 50 firmly fixed to the screw shaft 10 instead of the end face 12, and the vibration of the end portion of the screw shaft 10 can be reduced.

Further, by forming the knurled portion 51 on the inner peripheral surface 50c of the spacer 50, it is not necessary to manage the tolerance of the outer peripheral surface of the bearing installation portion 10a fitted to the knurled portion 51, thereby realizing low cost. .
Conventionally, the screw shaft 10 and the bearing 20 are positioned with the dimension in the width direction of the spacer 50. However, by adopting the configuration of the present invention, the fastening force by knurling is improved and the fastening in the width direction is performed. There is no need to put effort into securing the power, and the production efficiency can be improved.

The screw shaft 10 thus configured can be used for a trapezoidal screw or the like other than the ball screw device.
The ball screw device according to the present invention has been described above. However, the ball screw device according to the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. .

DESCRIPTION OF SYMBOLS 1 Ball screw apparatus 10 Screw shaft 10a Bearing installation part 11 Spiral groove 20 Bearing 21 Inner ring 50 Spacer 50c Inner peripheral surface 51 Knurled part

Claims (6)

A screw shaft having a spiral groove formed on the surface, and a bearing that supports a bearing installation portion formed at an end of the screw shaft;
An annular spacer that is fitted to the bearing installation portion is provided, and an axial end surface of the spacer contacts the inner ring of the bearing,
A ball screw device, wherein an inner peripheral surface of the spacer is knurled.   2. The ball screw device according to claim 1, wherein the ball screw device is knurled in a range in which the spacer is fitted in an outer peripheral surface of the bearing installation portion.   The ball screw device according to claim 1 or 2, wherein the surface shape of the inner circumferential surface of the knurled spacer is the same pitch interval.   The ball screw device according to any one of claims 1 to 3, wherein the knurling process is an oblique knurling process.   The ball screw device according to any one of claims 1 to 3, wherein the knurling is flat knurling.   The ball screw device according to any one of claims 1 to 3, wherein the knurling is a twill knurling.

Images