JPWO2015129163A1 - Ball screw device - Google Patents

Abstract

Provided is a ball screw device that reduces the vibration of an end portion of a screw shaft even when an excessive load is applied to the screw shaft. For this purpose, the ball screw device (1) supports a screw shaft (10) having a spiral groove (11) formed on the surface and a bearing installation portion (10a) formed at the end of the screw shaft (10). A bearing (20), a diameter-expanding member (50), and a spacer (60). The diameter-expanding member (50) is in contact with the end face with which the spiral groove (11) communicates, and has an annular shape that can be divided into a plurality of divided bodies in the axial direction. The spacer (60) covers at least a part of the diameter-expanding member (50), and fits between the axial end surface of the diameter-expanding member (50) and the inner ring (21) of the bearing (20).

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. 8A, 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. 8B. It has a ring shape. Therefore, as shown in FIG. 8C, 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. 9A, 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. 9B. It has a circular shape. This shape is conspicuous when the interval between the spiral grooves 201 is small (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. 9C, 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, since the radial dimension of the end surface 202a of the screw shaft 200 that contacts the inner ring 211 or the spacer 240 of the bearing 210 is not uniform, an irregular ring shape is formed, and when tightening with the lock nut 220, the spacer When 240 enters the spiral groove 201 beyond the end face 202a or an excessive load is applied to the screw shaft 200, the end portion of the screw shaft 200 is more easily shaken.
When the ball screw device is operated in such a state, the screw shaft 200 is deformed, decentered, or climbs up. As a result, the end of the screw shaft 200 is bent by tightening the lock nut 220 or the screw shaft 200 is bent. Since it may be difficult to install pulleys and couplings on the ends, there is 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.
A ring-shaped diameter-expanding member that is in contact with the end face with which the spiral groove communicates and can be divided into a plurality of divided bodies in the axial direction is provided,
A spacer that covers at least a part of the diameter-expanding member and fits between an end face in the axial direction of the diameter-expanding member and the inner ring of the bearing is provided.

In the ball screw device, it is preferable that the spacer covers the bearing installation portion side of the diameter-expanding member and is fitted between the axial end surface of the diameter-expanding member and the inner ring of the bearing. .
Moreover, in the said ball screw apparatus, it is preferable that the said diameter expansion member is provided in the area | region of the said axial direction where the cross-sectional area of the land part in the said end surface was expanded over the circumferential direction.
Moreover, in the said ball screw apparatus, it is preferable that the said spacer is divided | segmented into the some division body in the axial direction, and these division bodies are integrally molded with each of the division body of the said enlarged diameter member.

Another aspect of the ball screw device for solving the above problems includes a screw shaft having a spiral groove forming portion having a spiral groove and a land portion formed on a surface thereof, and a bearing installation portion supported by the bearing, and the bearing installation portion. And a bearing for supporting
The spiral groove forming portion is formed with a first taper portion in which a land portion is gradually reduced in diameter from the spiral groove forming portion toward the bearing installation portion,
An annular spacer with which the inner peripheral surface is fitted to the first tapered portion is provided,
The axial end surface of the spacer contacts the inner ring of the bearing.

In the ball screw device, the spacer preferably has the same inner diameter dimension at both ends in the axial direction.
Further, in the ball screw device, a second taper portion in which an inner diameter dimension of both end portions is reduced in accordance with a reduced diameter of the land portion is formed on at least a part of the axial direction on the inner peripheral surface of the spacer. It is preferred that

  According to one aspect of the present invention, it is possible 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.

It is a figure which shows the structure in 1st Embodiment of a ball screw apparatus. It is a figure which shows the installation process of the diameter-expansion member in 1st Embodiment of a ball screw apparatus. It is a figure which shows the structure in 2nd Embodiment of a ball screw apparatus. It is a figure which shows the installation process of the diameter-expansion member in 2nd Embodiment of a ball screw apparatus. It is a figure which shows the structure in 3rd Embodiment of a ball screw apparatus. It is a figure which shows the structure in 4th Embodiment of a ball screw apparatus. It is a figure which shows the structure in 5th Embodiment of a ball screw apparatus. 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. .

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without such specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.
Embodiments of a ball screw device according to the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration of a ball screw device according to a first embodiment, where (a) is a left side view of the screw shaft, (b) is a partial cross-sectional view of the screw shaft, and (c) is a view of the ball screw device. It is sectional drawing which follows an axial direction. Moreover, FIG. 2 is a figure which shows the installation process of the diameter expansion member in 1st Embodiment of a ball screw apparatus.
As shown in FIG. 1 (c), the ball screw device 1 includes a screw shaft 10 of a ball screw and double row rolling bearings 20, 20 that support end portions of the screw shaft 10. A spiral groove 11 is formed on the surface of the screw shaft 10. The rolling bearing 20 has two inner rings 21 and 21 that are fitted to a bearing installation portion 10 a formed at an 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 periphery.

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.
Here, as shown in FIG. 1A, a ring-shaped diameter-expanding member 50 is fitted and provided in the bearing installation portion 10 a of the screw shaft 10. One end surface 50a of the diameter expanding member 50 is in contact with the end surface 13a. The diameter-expanding member 50 can be divided into a plurality of divided bodies 50A in the axial direction (see FIG. 2B).

Further, the outer peripheral surface of the diameter-expanding member 50 covers at least a part of the diameter-expanding member 50 and is related to an axial end face (end face opposite to the end face 50a contacting the end face 13a) 50b. A spacer 60 in which a stepped portion 61 is formed is provided. This end face 50 b forms the stepped portion 12. The spacer 60 may cover at least a part of the diameter expanding member 50 on the bearing installation portion 10a side.
The spacer 60 is provided so as to be fitted to the outer periphery of the screw shaft 10 between the end surface 50 b and the inner ring 21. That is, the inner ring 21 of the rolling bearing 20 is pressed against the end surface 50 b by the tightening force of the lock nut 40. The spacer 60 is made of, for example, a disc spring, a coil spring, or a metal having a longitudinal elastic modulus.

Next, a manufacturing process of the screw shaft 10 configured as described above will be described. First, as shown in FIGS. 2 (a) to 2 (c), on the side on which the spiral groove 11 is formed in the bearing installation portion 10a of the screw shaft 10, an expansion composed of two or more divided bodies 50A and 50A. The diameter member 50 is fitted. In FIG. 2B, the diameter-expanding member 50 is divided into two parts. Here, the outer diameter dimension of the diameter-expanding member 50 (divided body 50 </ b> A) is preferably larger than the inner diameter dimension of the inner ring 21 of the bearing 20.
Next, as shown in FIGS. 2B and 2C, the spacer 60 having the shape of the inner peripheral surface that engages with the end surface 50 b of the diameter-expanding member 50 (the divided body 50 </ b> A) is connected to the inner ring 21 of the bearing 20. It is provided so as to fit between them (see FIG. 1C). That is, as shown in FIG. 1C, the end surface 60a on the bearing installation portion 10a side of the spacer 60 is fitted between the inner ring 21 of the bearing 20 and the end surface 50b of the diameter expanding member 50 (divided body 50A). The movement of the bearing 20 in the axial direction is limited.
Here, the spacer 60 may be divided into a plurality of divided bodies in the axial direction similarly to the diameter expanding member 50, and the divided bodies may be integrally formed with each of the divided bodies 50 </ b> A of the diameter expanding member 50.

(Second Embodiment)
FIGS. 3A and 3B are diagrams showing the configuration of the ball screw device according to the second embodiment, wherein FIG. 3A is a left side view of the screw shaft, FIG. 3B is a front view of the screw shaft, and FIG. FIG. 4D is a cross-sectional view along the axial direction of the ball screw device. Moreover, FIG. 4 is a figure which shows the installation process of the diameter expansion member in 2nd Embodiment of a ball screw apparatus.
As shown in FIG. 3D, the ball screw device 1 includes a ball screw screw shaft 10 and double row rolling bearings 20, 20 that support end portions of the screw shaft 10. A spiral groove 11 is formed on the surface of the screw shaft 10. The rolling bearing 20 has two inner rings 21 and 21 that are fitted to a bearing installation portion 10 a formed at an 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 periphery.

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.

Here, as shown in FIG. 3A, the bearing installation portion 10a of the screw shaft 10 is formed with a reduced diameter portion 13 that communicates with the spiral groove 11 and is reduced in diameter by a predetermined dimension in the axial direction. Yes. The reduced diameter portion 13 is provided so as to expand (increase) the cross-sectional area of the land portion 11a in the end surface 13a in the circumferential direction so as not to impair the strength of the screw shaft 10.
And in this reduced diameter part 10, as shown to FIG.3 (b), (c), the annular-shaped enlarged diameter member 50 is fitted and provided. One end face 50 a of the diameter-expanding member 50 is in contact with the end face 13 a of the reduced diameter portion 13. The diameter-expanding member 50 can be divided into a plurality of divided bodies 50A in the axial direction (see FIG. 4B).

Further, the outer peripheral surface of the diameter-expanding member 50 covers at least a part of the diameter-expanding member 50 and is related to an axial end face (end face opposite to the end face 50a contacting the end face 13a) 50b. A spacer 60 in which a stepped portion 61 is formed is provided. This end face 50 b forms the stepped portion 12.
The spacer 60 is provided so as to be fitted to the outer periphery of the screw shaft 10 between the end surface 50 b and the inner ring 21. That is, the inner ring 21 of the rolling bearing 20 is pressed against the end surface 50 b by the tightening force of the lock nut 40. The spacer 60 is made of, for example, a disc spring, a coil spring, or a metal having a longitudinal elastic modulus.

  Next, a manufacturing process of the screw shaft 10 configured as described above will be described. First, as shown in FIGS. 4A to 4C, on the side where the spiral groove 11 is formed in the bearing installation portion 10a of the screw shaft 10, it communicates with the spiral groove 11 and has a predetermined dimension in the axial direction. The reduced diameter portion 13 is formed by a cutting method or the like. At this time, the end surface 13a communicating with the spiral groove 11 receives an axial load corresponding to the diameter of the bearing installation portion 10a reduced to the diameter of the reduced diameter portion 13 by forming the reduced diameter portion 13. The area of the end surface 13a is large. It should be noted that the cutting amount when forming the reduced diameter portion 13 is cut so as to have a smaller diameter than the bottom portion of the spiral groove 11 so as not to impair the strength of the screw shaft 10.

Next, the diameter-expanding member 50 formed of the divided bodies 50 </ b> A and 50 </ b> A divided into two or more is fitted into the reduced diameter portion 13. In FIG. 4B, the diameter-expanding member 50 is divided into two parts. Here, it is preferable that the axial dimension of the diameter-expanding member 50 (divided body 50 </ b> A) is substantially equal to the axial dimension of the reduced diameter portion 13. Moreover, it is preferable that the inner diameter dimension of the diameter-expanding member 50 (divided body 50A) is substantially equal to the outer diameter dimension of the reduced diameter portion. Furthermore, it is preferable that the outer diameter dimension of the diameter expanding member 50 (divided body 50 </ b> A) is larger than the inner diameter dimension of the inner ring 21 of the bearing 20.
Next, as shown in FIGS. 4B and 4C, the spacer 60 having the shape of the inner peripheral surface that engages with the end surface 50 b of the diameter expanding member 50 (the divided body 50 </ b> A) is connected to the inner ring 21 of the bearing 20. It is provided so as to fit between them (see FIG. 3D). That is, as shown in FIG. 3 (d), the end surface 60a on the bearing installation portion 10a side of the spacer 60 is fitted between the inner ring 21 of the bearing 20 and the end surface 50b of the diameter expanding member 50 (divided body 50A). The movement of the bearing 20 in the axial direction is limited.

Here, the spacer 60 may be divided into a plurality of divided bodies in the axial direction similarly to the diameter expanding member 50, and the divided bodies may be integrally formed with each of the divided bodies 50 </ b> A of the diameter expanding member 50.
As described above, the reduced diameter portion 13 is formed on the screw shaft 10 to increase the area of the end surface 13a that receives the load, and the diameter expansion member 50 is assembled to the reduced diameter portion 13 to reduce the vibration of the end portion of the screw shaft 10. can do.
The screw shaft 10 thus configured can be used for a trapezoidal screw or the like other than the ball screw device.

(Third embodiment)
5A and 5B are diagrams showing the configuration of the ball screw device according to the third embodiment, wherein FIG. 5A is a cross-sectional view taken along the axial direction of the ball screw device, FIG. 5B is a perspective view of the screw shaft, and FIG. The side view which shows the process of incorporating a spacer in an axis | shaft, (d) is the left view of a screw axis | shaft.
As shown in FIG. 5A, 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. The screw shaft 10 includes a bearing installation portion 10a and a spiral groove forming portion 10b in the axial direction. A spiral groove 11 is formed on the surface of the screw shaft 10 in the spiral groove forming portion 10b. The rolling bearing 20 has two inner rings 21 and 21 that are fitted to 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 land 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.

Further, as shown in FIGS. 5A and 5B, the screw shaft 10 is provided with an annular spacer 70.
The spacer 70 is provided by being fitted to the outer periphery of the screw shaft 10 between the end surface of the end portion 70 a and the inner ring 21. That is, the inner ring 21 of the rolling bearing 20 is pressed against the end surface of the end portion 70 a by the tightening force of the lock nut 40. The spacer 70 is made of, for example, a disc spring, a coil spring, a metal having a longitudinal elastic modulus (iron / nonferrous), or a resin.

[Tapered part]
As shown in FIG. 5 (c), the spiral groove forming portion 10b of the screw shaft 10 extends from the step portion 13 which is a boundary portion between the bearing installation portion 10a and the spiral groove forming portion 10b toward the spiral groove forming portion 10b. Thus, a first taper portion 10c is formed which is gradually expanded in diameter in a predetermined dimension in the axial direction. The first taper portion 10c is provided such that the land portion 12 is gradually reduced in diameter from the spiral groove forming portion 10b toward the bearing installation portion 10a.
On the other hand, as shown in FIG. 5C, the inner peripheral surface 70 c of the spacer 70 is engaged with the engaging portion 71 that engages with the bearing installation portion 10 a and the first tapered portion 10 c of the screw shaft 10. Two taper portions 72 are formed. That is, the engaging portion 71 is a portion that forms the shape of the inner peripheral surface that engages the stepped portion 13 at the boundary portion between the bearing installation portion 10a and the spiral groove forming portion 10b and the bearing installation portion 10a. The end surface of the axial end portion 70 a of the spacer 70 contacts the inner ring 21 of the bearing 20.
Here, the second taper portion 72 is formed corresponding to the shape of the first taper portion 10 c of the screw shaft 10. For example, as shown in FIG. 5C, in the cross-sectional shape along the axial direction of the spacer 70, the inclination angle θ of the second taper portion 72 with respect to the axial direction of the spacer 70 and the first taper with respect to the axial direction of the screw shaft 10. The inclination angle θ of the portion 10c is provided at substantially the same angle.

Next, a manufacturing process of the screw shaft 10 configured as described above will be described. As shown in FIG. 5C, the screw shaft 10 is opposed to the screw shaft 10 in the direction of the second taper portion 72 and the engagement portion 71 from the opposite side of the screw shaft 10 in the bearing installation portion 10a to the spiral groove forming portion 10b. A cylindrical spacer 70 is inserted. The second taper portion 72 is press-fitted into the first taper portion 10 c and fitted to fix the spacer 70 to the screw shaft 10.
Here, in the ball screw device of the present embodiment, the spacer 70 is firmly fixed to the screw shaft 10 by fitting the second tapered portion 72 and the first tapered portion 10c. For this reason, an excessive axial load is evenly received by the first taper portion 10c instead of the end face of the step portion 13, and the vibration of the end portion of the screw shaft 10 can be reduced.
The screw shaft 10 thus configured can be used for a trapezoidal screw or the like other than the ball screw device.

(Fourth embodiment)
Next, a fourth embodiment of the ball screw device will be described with reference to the drawings. 6 (a) and 6 (b) are diagrams showing a configuration of the ball screw device according to the fourth embodiment, and are left side views corresponding to FIGS. 5 (c) and 5 (d). The ball screw device 1 of the present embodiment has the same configuration as that of the first embodiment except that the aspect of the inner peripheral surface 70c of the spacer 70 is different. Hereinafter, the same components as those in the first embodiment will be denoted by the same reference numerals, description thereof will be omitted or simplified, and different configurations will be mainly described.

As shown in FIG. 6A, in the ball screw device of this embodiment, a first taper portion 10c having an inclination angle θ is formed on the screw shaft 10 in the same manner as in the first embodiment. The inner peripheral surface 70c of the spacer 70 fitted to the first taper portion 10c has an inner diameter dimension of one end portion 70a and an inner diameter of the other end portion 70b in accordance with the inclination angle θ of the first taper portion 10c. A second taper portion 72 whose size is monotonously increased is formed. In other words, the second taper portion 72 in which the inner diameter dimension of the other end portion 70 b and the inner diameter dimension of the one end portion 70 a are monotonically reduced along the axial direction is formed on the inner peripheral surface 70 c of the spacer 70. Yes. That is, the engaging portion 71 is not provided in the spacer 70 used in the ball screw device of the present embodiment. As described above, the spacer 70 may or may not be provided with the engaging portion 71. Moreover, when the engaging part 71 is provided, the formation range of the axial direction is suitably set by the use etc. of a ball screw apparatus.
When such a spacer 70 is incorporated in the screw shaft 10, as shown in FIG. 6B, the spacer 70 is installed deeper on the spiral groove forming portion 10b side with respect to the bearing installation portion 10a than in the first embodiment. Therefore, the spacer 70 is more firmly fixed to the screw shaft 10.

(Fifth embodiment)
Next, a fifth embodiment of the ball screw device will be described with reference to the drawings. FIGS. 7A and 7B are diagrams showing the configuration of the ball screw device according to the fifth embodiment, and are right side views corresponding to FIGS. 1C and 1D. The ball screw device 1 of the present embodiment has the same configuration as that of the first embodiment, except that the aspects of the first tapered portion 10c and the inner peripheral surface 70c of the spacer 70 are different. Hereinafter, the same components as those in the first embodiment will be denoted by the same reference numerals, description thereof will be omitted or simplified, and different configurations will be mainly described.

As shown in FIG. 7A, unlike the first embodiment, the ball screw device of this embodiment has a first taper portion 10c having an inclination angle ψ (ψ <θ) formed on the screw shaft 10. . The inner peripheral surface 70c of the spacer 70 fitted to the first tapered portion 10c has the same inner diameter dimension at one end and the same inner diameter dimension at the other end. That is, the second taper portion 72 is not provided in the spacer 70 used in the ball screw device of this embodiment.
When such a spacer 70 is incorporated in the screw shaft 10, as shown in FIG. 7B, the spacer 70 is installed shallower on the bearing installation portion 10a side with respect to the spiral groove forming portion 10b than in the first embodiment. Therefore, the urging force to the inner ring 21 by the spacer 70 becomes stronger. Moreover, since it is not necessary to process the 2nd taper part 72 in the internal peripheral surface 70c of the spacer 70, reduction of manufacturing cost can be aimed at.

  Although the present invention has been described above with reference to specific embodiments, it is not intended that the present invention be limited by these descriptions. From the description of the invention, other embodiments of the invention will be apparent to persons skilled in the art, along with various variations of the disclosed embodiments. Therefore, it is to be understood that the claims encompass these modifications and embodiments that fall within the scope and spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Ball screw apparatus 10 Screw shaft 10a Bearing installation part 10b Spiral groove formation part 10c 1st taper part 11 Spiral groove 12 Land part 13 Diameter reduction part 13a End surface 20 Bearing 21 Inner ring 50 Diameter expansion member 60 Spacer 70 Spacer 71 Engagement part 72 Second taper part

Claims (7)

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 diameter-expanding member that abuts on the end face that communicates with the spiral groove and can be divided into a plurality of divided bodies in the axial direction is provided.
A ball screw device comprising a spacer that covers at least a part of the diameter-expanding member and fits between an end face in the axial direction of the diameter-expanding member and an inner ring of the bearing.   The ball screw device according to claim 1, wherein the spacer covers the bearing installation portion side of the diameter-expanding member and is fitted between an axial end surface of the diameter-expanding member and an inner ring of the bearing.   The ball screw device according to claim 1 or 2, wherein the diameter-expanding member is provided in a region in the axial direction in which a cross-sectional area of a land portion on the end surface is expanded in a circumferential direction.   The ball screw device according to any one of claims 1 to 3, wherein the spacer is divided into a plurality of divided bodies in the axial direction, and the divided bodies are integrally formed with each of the divided bodies of the diameter-expanding member. A screw shaft having a spiral groove forming portion formed on the surface with a spiral groove and a bearing installation portion supported by the bearing, and a bearing supporting the bearing installation portion;
The spiral groove forming portion is formed with a first taper portion in which a land portion is gradually reduced in diameter from the spiral groove formation portion toward the bearing installation portion, and a circle whose inner peripheral surface is fitted to the first taper portion. An annular spacer is provided,
The ball screw device, wherein an end face of the spacer in an axial direction is in contact with an inner ring of the bearing.   The ball screw device according to claim 5, wherein the spacer has an inner diameter dimension at both ends equal in the axial direction.   6. The ball according to claim 5, wherein a second taper portion in which an inner diameter dimension of both end portions is reduced in accordance with a reduced diameter of the land portion is formed on at least a part of the axial direction on an inner peripheral surface of the spacer. Screw device.

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