JP6424458B2 - Ball screw device - Google Patents

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 single axis actuator and includes a ball screw and a bearing that supports the screw shaft.

  BACKGROUND ART Conventionally, there has been known a ball screw apparatus which is used for 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 (Patent Document 1). In such a ball screw device, the diameter of the outer peripheral surface of the screw shaft is reduced to fit 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 and the bearing It is common to insert a spacer between the two and tighten with a lock nut.

JP 2009-162314 A, FIG.

Here, as a form of a screw shaft of a ball screw device, there are those in which a spiral groove formed on the surface is formed up to an end face of a bearing installation portion and one not formed.
As shown in FIG. 4 (a), in the screw shaft 100 in which the spiral groove 101 is not formed up to the end face 102a of the bearing installation portion 102, as shown in FIG. 4 (b), the shape of the end face 102a is a uniform circle. It has an annular shape. Therefore, as shown in FIG. 4C, the inner ring 111 of the bearing 110 is sandwiched between the lock nut 120 and the spacer 130 provided between the lock ring 120 and the inner ring 111 of the bearing 110 and the end face 102a to move the bearing 110 in the axial direction. It can be restricted.

  On the other hand, as shown in FIG. 5A, 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, as shown in FIG. 5B, the shape of the end surface 202a is uneven. It has an annular shape. This shape is remarkable when the lead of the spiral groove 201 is small, and a portion where the bottom portion 201 a of the spiral groove 201 is exposed may occur. In the screw shaft 200 having such a configuration, as shown in FIG. 5C, the spacer 230 provided between the lock nut 220 and the inner ring 211 of the bearing 210, and between the end face 202a and the inner ring 211 of the bearing 210. The spacer 240 provided on the upper side restricts the axial movement of the bearing 210 in which the inner ring 211 is sandwiched.

As described above, when the radial dimension of the end face 202a of the screw shaft 200 in contact with the inner ring 211 of the bearing 210 or the spacer 240 is uneven, the screw shaft 200 is too large if it has an irregular ring shape. When a load is applied, the end of the screw shaft 200 is easily shaken.
This causes deformation, eccentricity, or riding up of the screw shaft 200, and as a result, the end of the screw shaft 200 is bent due to the tightening of the lock nut 220, or pulleys or couplings against the end of the screw shaft 200. There was room for consideration, as it may be difficult to set up.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a ball screw device that reduces the swing of the end portion of the screw shaft even when an excessive load is applied to the screw shaft.

According to another aspect of the present invention, there is provided a ball screw device including a screw shaft having a first helical groove formed on an outer peripheral surface on which a rolling element rolls and a bearing installation portion formed at an end of the screw shaft. With a bearing to support,
The screw shaft includes a screw shaft main body having a first spiral groove and a second spiral groove, a nut screwed to the second spiral groove, a fourth spiral groove screwed to the second spiral groove, and the bearing installed And an adapter having a step portion,
An end face in the axial direction of the step portion contact the inner ring of the bearing, one end face of the nut is in contact with the end surface of the screw shaft, the other end face of the nut that Sessu the end face of the adapter.
In the ball screw device, the axial dimension of the nut is preferably shorter than the axial dimension of the fourth helical groove.

  According to the present invention, it is possible to provide a ball screw device that reduces the deflection of the end of the screw shaft even when an excessive load is applied to the screw shaft.

It is a side view showing composition in a certain mode of a ball screw device of the present invention. It is a side view showing composition of a screw axis in a certain mode of a ball screw device of the present invention. It is a side view which shows the structure of the screw shaft in the other 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 side view of a screw shaft, (b) is a front view of a screw shaft, (c) is a sectional view along the axial direction of a ball screw apparatus. . It is a figure which shows the structure of the conventional ball screw apparatus, (a) is a right side view of a screw shaft, (b) is a front view of a screw shaft, (c) is a sectional view along the axial direction of a ball screw apparatus. .

Hereinafter, an embodiment of a ball screw device according to the present invention will be described with reference to the drawings.
FIG. 1 is a side view showing a configuration of an embodiment of a ball screw device. Moreover, FIG. 2 is a side view which shows the structure of the screw shaft in the one aspect | mode of the ball screw apparatus of this invention, (a) is a side view which shows the integrated screw shaft, (b) is a screw shaft main-body part Fig. 18 is a side view disassembled into a nut, a nut and an adapter.

As shown in FIG. 1, the ball screw device 1 has a screw shaft 10 and double-row rolling bearings 20, 20 supporting the end of the screw shaft 10. The screw shaft 10 is formed with a first spiral groove 11 which is a spiral groove on which a rolling element (not shown) in the ball screw device 1 rolls.
The rolling bearing 20 has two inner rings 21 and 21 fitted in a bearing installation portion 10 a formed on an adapter 10 C constituting the screw shaft 10 and rotated integrally with the screw shaft 10. Outer rings 23 that rotatably support the inner ring 21 via a plurality of rolling elements 22 are provided on the outer circumferences of the inner rings 21 and 21, respectively.

Further, the ball screw device 1 is provided with a cylindrical housing 30 for housing the rolling bearing 20, and the outer peripheral surface (the outer peripheral surface of the outer ring 23) of the rolling bearing 20 is slidably fitted with the inner peripheral surface of the housing 30. It is correct.
The inner ring 21 of the rolling bearing 20 is positioned at a predetermined position by a step 12 formed on the screw shaft 10 and a lock nut 40. The lock nut 40 is screwed into 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 or a coil spring or a metal having a longitudinal elastic coefficient.

<Screw shaft>
The screw shaft 10 has a screw shaft main body 10A, a nut 10B, and an adapter 10C, as shown in FIGS. 2 (a) and 2 (b).
The screw shaft main body 10A has a first helical groove forming portion 10A ₁ and a second helical groove forming portion 10A _{2. On} an outer peripheral surface of the first spiral groove forming portion 10A1, a first spiral groove 11 which is a spiral groove on which a rolling element (not shown) in the ball screw device 1 rolls is formed. On the other hand, on the outer peripheral surface of the second spiral groove forming portion 10A2, a _second spiral groove 12 which is coaxial with and opposite to the first spiral groove 11 is formed.

The nut 10 </ b> B has a third spiral groove (not shown) formed in its inner circumferential surface to be screwed into the second spiral groove 12.
The adapter 10C has a bearing installation portion 10a and a step portion 13 in which a step is formed in the axial direction with respect to the bearing installation portion 10a. The stepped portion 13 has a recess formed along the axial direction on the end face 13b opposite to the bearing installation portion 10a, and the fourth spiral groove 14 engaged with the second spiral groove 12 is formed on the inner peripheral surface thereof. It is formed.

The screw shaft main body 10A, the nut 10B, and the adapter 10C configured in this way have a second spiral groove in which the nut 10B is screwed into the second spiral groove 12 of the screw shaft main body 10A and further protrudes axially from the nut 10B. The fourth helical groove 14 is screwed to be integrated with 12 to form a screw shaft 10.
Here, the dimension in the axial direction of the second spiral groove 12 is longer than the dimension in the axial direction of the nut 10B, and the difference is set equal to or less than the dimension in the axial direction of the fourth spiral groove 14. Further, the axial dimension of the nut 10B is set shorter than the axial dimension of the fourth spiral groove 14 formed in the adapter 10C.

As described above, by fixing the nut 10B and the adapter 10C in the form of a double nut in the second spiral groove 12 of the screw shaft main body 10A, each fastening force is increased, and the screw shaft 10 is rotated forward or reverse It becomes difficult to loosen even if it rotates.
The axial end face 13 a of the step 13 abuts on the inner ring 21 of the bearing 20. The stepped portion 13 is fitted to the outer periphery of the screw shaft 10 between the end surface 13 a and the inner ring 21. That is, the inner ring 21 of the rolling bearing 20 is pressed against the end face 13 a by the tightening force of the lock nut 40. The stepped portion 13 is made of, for example, metal (iron / non-ferrous metal) or resin of longitudinal elastic coefficient.

(Other embodiments)
FIGS. 3A and 3B are side views showing the configuration of a screw shaft in another aspect of the ball screw device of the present invention. As shown in FIGS. 3 (a) and 3 (b), in order to correspond to bearings of various inner diameter dimensions, the second of the screw shaft main body 10A with respect to the adapter 10C having the bearing installation portion 10a of various outer diameter dimensions. it is possible to change the shape of the spiral groove forming portion 10A ₂ (dimensions).

Thus, simply by changing the second helical groove forming portion 10A ₂ of the shape of the screw shaft main body 10A constituting the screw shaft 10 (dimension), the screw shaft 10 which can be attached a variety of bearing inner diameter is different Can be provided.
As described above, in the ball screw device according to the present embodiment, the step portion 13 of the adapter 10C screwed tightly to the screw shaft main body portion 10A together with the nut 10B receives an excessive axial load on the end surface 13a. The deflection of the end of the screw shaft 10 can be reduced.

In addition, the screw shaft 10 comprised in this way can be used for a trapezoidal screw etc. other than a ball screw apparatus.
As mentioned above, although the ball screw apparatus concerning the present invention was explained, the ball screw apparatus concerning the present invention is not limited to the above-mentioned embodiment, and various modification is possible if it does not deviate from the meaning of the present invention .

DESCRIPTION OF SYMBOLS 1 ball screw apparatus 10 screw shaft 10A screw shaft main body 10B nut 10C adapter 10a bearing installation part 11 1st spiral groove 12 2nd spiral groove 13 step part 14 4th spiral groove 20 bearing 21 inner ring

Claims (2)

A screw shaft having a first helical groove formed on an outer peripheral surface on which the rolling element rolls, and a bearing for supporting a bearing installation portion formed at an end of the screw shaft;
The screw shaft includes a screw shaft main body having a first spiral groove and a second spiral groove, a nut screwed to the second spiral groove, a fourth spiral groove screwed to the second spiral groove, and the bearing installed And an adapter having a step portion,
Contact the inner ring of the axial end face the bearing of the step portion, one end face of said nut is in contact with the end face of the screw shaft, the other end face of said nut the Rukoto that Sessu the end face of said adapter Features a ball screw device.   The ball screw device according to claim 1, wherein an axial dimension of the nut is smaller than an axial dimension of the fourth helical groove.

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