JP2015215040A - 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 forming part 10b having a spiral groove 11 and a land portion 11a formed in and on the surface, and a bearing installation part 10a supported by a bearing 20, the bearing 20 supporting the bearing installation part 10a, a diameter enlarging member 50, and a spacer 60. The diameter enlarging member 50 abuts on the end face with which the spiral groove 11 is communicated, and it is annularly shaped to be split into a plurality of split bodies 50A, 50B in the peripheral direction. The split bodies 50A, 50B have opposite faces 50Aa, 50Ba formed opposite to the other split bodies while being further inclined than the axial direction of the diameter enlarging member 50. The diameter enlarging member 50 is provided so that the opposite end faces of the split bodies 50A, 50B are distant from the spiral groove forming part 10b to the bearing installation part 10a.

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 Patent Laid-Open No. 2007-178002, 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. 6 (a), 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. 6 (b). It has a ring shape. Therefore, as shown in FIG. 6C, 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 movement of the bearing 110 in the axial direction is controlled. Can be limited.

  On the other hand, as shown in FIG. 7A, 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. 7C, 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.

In one aspect of the ball screw device for solving the above-described problem, a screw shaft including 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 includes: Bearing to support,
A ring-shaped diameter-expanding member that abuts on an end surface that communicates with the spiral groove and can be divided into a plurality of divided bodies in the circumferential direction is provided,
At least one of the divided bodies is formed such that a facing surface facing the other divided body is inclined with respect to the axial direction of the diameter-expanding member,
The diameter-expanding member is provided so that the opposing surfaces of the divided bodies are separated from the spiral groove forming portion toward the bearing installation portion,
It has 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.

  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.

  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 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 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 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. .

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 right 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. 3 (a) to 3 (d) are diagrams showing the configuration of the diameter-expanding member in the first embodiment of the ball screw device, and FIGS. 3 (e) to 3 (g) are virtual expansions for comparison. It is a figure which shows the structure of a diameter member.

  As shown in FIG. 1C, 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 (spiral groove forming portion 10b). 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 lock nut 40 via a stepped portion 13a formed on the screw shaft 10 and a diameter increasing member 50 in contact with the stepped portion 13a and a spacer 60. 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 and 50B in the circumferential direction (see FIG. 2B).

3 (a) and 3 (b) are a front view and a plan view showing the configuration of the diameter-expanding member 50 composed of the divided bodies 50A and 50B.
As illustrated in FIGS. 3A and 3B, the diameter-expanding member 50 includes, for example, two divided bodies 50 </ b> A and 50 </ b> B that are divided along the axial direction of the diameter-expanding member 50.
The divided bodies 50A and 50B are formed with opposing surfaces 50Ac and 50Bc that are inclined, for example, α (°) from the axial direction of the diameter-enlarging member 50 with respect to the respective end surfaces 50Aa and 50Ba. These end surfaces 50 </ b> Aa and 50 </ b> Ba are surfaces constituting one end surface 50 a of the diameter expanding member 50.
That is, when the divided bodies 50A and 50B are arranged so that the end faces 50Aa and 50Ba are flush with each other to form one end face 50a of the diameter-expanding member 50, the opposing faces 50Ac and 50Bc face each other. As a result, the ring-shaped enlarged member 50 is formed.
As shown in FIGS. 2B and 2C, the diameter-enlarging member 50 in which the divided bodies 50A and 50B are arranged in this way is formed with spiral grooves formed on the opposing surfaces 50Ac and 50Bc of the divided bodies 50A and 50B. The screw shaft 10 is provided in a direction away from the portion 10b toward the bearing installation portion 10a.

FIGS. 3C and 3D are a front view and a plan view of the base material 51 viewed from the circumferential direction as a process of obtaining the divided bodies 50A and 50B.
Here, as shown in FIGS. 3C and 3D, the divided bodies 50A and 50B are inclined at a predetermined angle (for example, α (°)) with respect to the axial direction of the annular base material 51. Obtained by cutting. The end surfaces 51Aa and 51Ba are flush with each other so that the cut surfaces 51Ac and 51Bc of the divided bodies 51A and 51B thus obtained are opened at a predetermined angle (for example, α (°)) in the axial direction. Thus, the divided bodies 50A and 50B can be easily obtained from one annular base material 51.
On the other hand, as shown in FIGS. 3E and 3F, when the base material is cut parallel to the axial direction to obtain divided bodies 150A and 150B, the dimensions of the circumferential divided bodies 150A and 150B are reduced by the cutting. The cutting allowance d2 may be reduced. As a result, a gap d3 including a cutting allowance is generated even if the expanded member 50 is configured by the divided bodies 150A and 150B.
The bearing 20 may not be sufficiently loaded through the spacer 60.
In the ball screw device of the present embodiment, an angle α (°) is formed with respect to the axis of the cylindrical base material 51 so that one of the cut surfaces becomes the center line of the upper end surface, and the other Cutting is performed so that the cut surface passes through the center line of the lower end surface, and the circular arc section viewed from the axial direction is cut into a semicircle. Thus, by assembling the ones having larger arc sections (51Aa, 51Ba) in contact with each other, the load can be more reliably received when assembled, and misalignment hardly occurs. Note that the same effect can be obtained by cutting into six parts (six pieces).

  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. 2 (a) to 2 (c), on the side where the spiral groove 11 is formed in the bearing installation portion 10a of the screw shaft 10, an expansion made up of two or more divided bodies 50A and 50B. The diameter member 50 is fitted. In FIG. 2B, the diameter-expanding member 50 is divided into two parts. Here, it is preferable that the outer diameter of the diameter-expanding member 50 (divided bodies 50A and 50B) is larger than the inner diameter 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 bodies 50 </ b> A and 50 </ b> B) is replaced with the inner ring 21 of the bearing 20. (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 bodies 50A and 50B). The movement of the bearing 20 in the axial direction is limited.

(Second Embodiment)
4A and 4B are diagrams showing the configuration of the ball screw device according to the second embodiment, wherein FIG. 4A is a right side view of the screw shaft, FIG. 4B is a front view of the screw shaft, and FIG. 4C is a partial cross section of the screw shaft. FIG. 4D is a cross-sectional view along the axial direction of the ball screw device. FIG. 5 is a diagram showing an installation process of the diameter-expanding member in the second embodiment of the ball screw device.

  As shown in FIG. 4D, the ball screw device 1 includes a ball screw 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. 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. 4A, 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.

  Then, as shown in FIGS. 4B and 4C, the diameter-reduced portion 10 is provided with a ring-shaped diameter-expanding member 50 fitted therein. 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 and 50B in the circumferential direction (see FIG. 5B).

  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. 5A to 5C, 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 composed of the divided bodies 50A and 50B divided into two or more is fitted into the reduced diameter portion 13. In FIG. 5B, the diameter-expanding member 50 is divided into two parts. Here, the axial dimension of the diameter-expanding member 50 (divided bodies 50A, 50B) is preferably 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 bodies 50A and 50B) is substantially equal to the outer diameter dimension of the reduced diameter portion. Furthermore, it is preferable that the outer diameter of the diameter-expanding member 50 (divided bodies 50A, 50B) is larger than the inner diameter of the inner ring 21 of the bearing 20.

  Next, as shown in FIGS. 5B and 5C, 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 bodies 50 </ b> A and 50 </ b> B) is replaced with the inner ring 21 of the bearing 20. (See FIG. 4D). That is, as shown in FIG. 4D, 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 enlarged member 50 (divided bodies 50A, 50B). The movement of the bearing 20 in the axial direction is limited.

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.

  The screw shaft of 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. Is possible.

DESCRIPTION OF SYMBOLS 1 Ball screw apparatus 10 Screw shaft 10a Bearing installation part 11 Spiral groove 13 Reduced diameter part 13a End surface 20 Bearing 21 Inner ring 50 Diameter expansion member 60 Spacer

Claims (2)

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;
A ring-shaped diameter-expanding member that abuts on an end surface that communicates with the spiral groove and can be divided into a plurality of divided bodies in the circumferential direction is provided,
At least one of the divided bodies is formed such that a facing surface facing the other divided body is inclined with respect to the axial direction of the diameter-expanding member,
The diameter-expanding member is provided so that the opposing surfaces of the divided bodies are separated from the spiral groove forming portion toward the bearing installation portion,
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.   2. The ball screw device according to claim 1, wherein the diameter increasing 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.

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