JP2014206196A - Lock nut for ball screw device, and ball screw device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lock nut for a ball screw device, which prevents loosening of screwing of the ball screw device to a screw shaft, and the ball screw device comprising the lock nut.SOLUTION: A lock nut for a ball screw device includes a soft metal piece 18 which is arranged on the screw shaft side of the ball screw device with respect to a setscrew 20 within a fixing hole 15a formed in the lock nut 6 and which bites into a male screw part of the screw shaft by screwing of the setscrew 20, and loosening prevention means 19 which is arranged in the fixing hole 15a to prevent loosening of the setscrew 20.

Description

  The present invention relates to a lock nut used for fixing a ball screw device used as, for example, a steering device, a heavy object moving device, a processing device, a precision positioning device, or the like as a mechanical element that converts rotational motion into linear motion, and the lock nut. The present invention relates to a ball screw device provided with

  Conventionally, an inner ring of a bearing that rotatably supports a screw shaft of a ball screw device, and a lock nut that fixes the inner ring of the bearing and the screw shaft by screwing into a male screw portion formed near the end of the screw shaft. Some have a compression spring interposed between the inner ring and the lock nut to generate a tensile stress on the screw shaft (see, for example, Patent Document 1).

  According to this, even when the screw shaft of the ball screw device is extended by thermal expansion, the screw shaft is smoothly extended, and the feed accuracy and rigidity of the feed screw shaft can be kept high.

Japanese Patent No. 3535327

  However, in the conventional ball screw device, there is a possibility that the screw engagement between the lock nut and the screw shaft is loosened due to vibration or the like.

  In view of such a problem, an object of the present invention is to provide a lock nut for a ball screw device that prevents loosening of screwing with a screw shaft, and a ball screw device including the lock nut.

In order to solve the above problems, in the present invention,
Used in a ball screw device having a nut and a screw shaft inserted into the nut,
Having a generally donut-shaped body,
The inner ring of the bearing that rotatably supports the screw shaft is fixed by screwing the first female screw portion formed on the inner peripheral surface of the main body with the male screw portion formed on the screw shaft. And
In the main body, a fixing hole that penetrates from the outer peripheral surface to the inner peripheral surface and has a second female thread portion is formed,
In a lock nut for preventing loosening of the screwing with the male screw part by screwing a set screw into the second female screw part,
Within the fixing hole, a soft metal piece disposed on the screw shaft side with respect to the set screw and biting into the male screw portion by screwing of the set screw;
It shall have a loosening prevention means which is arranged in the fixed hole and prevents loosening of the set screw.

  Preferably, the loosening prevention means includes an elastic member disposed between the soft metal piece and the set screw.

  Preferably, the loosening prevention means includes a slit disposed in the fixing hole on the side that moves when the set screw is loosened, and a retaining ring fitted in the slit.

  Further preferably, the loosening prevention means further includes a washer interposed between the set screw and the retaining ring.

  Preferably, the loosening prevention means includes a slit provided in the fixing hole on the side that moves when the set screw is loosened, and an elliptical plate fitted into the slit.

  Further preferably, the loosening prevention means further includes a washer interposed between the set screw and the elliptical plate.

  In order to solve the above problems, in the present invention, it is assumed that the ball screw device includes any one of the above-described lock nuts for the ball screw device.

  ADVANTAGE OF THE INVENTION According to this invention, the ball screw apparatus provided with the lock nut for the ball screw apparatus which prevents the loosening of screwing with a screw shaft, and the said lock nut can be provided.

It is a side view of the ball screw device concerning a 1st embodiment of this application. It is an enlarged side view showing a lock nut with which a ball screw device concerning a 1st embodiment of this application is provided. It is sectional drawing which shows the loosening prevention means of the set screw which concerns on 1st Embodiment of this application. It is sectional drawing which shows the loosening prevention means of the set screw which concerns on 2nd Embodiment of this application.

(First embodiment)
Hereinafter, a first embodiment of the present application will be described with reference to FIGS. 1 to 3. FIG. 1 is a side view of the ball screw device 1 according to the first embodiment. Bearings, lock nuts, and spacers are shown in cross section. In FIG. 1, only the side provided with the lock nut is shown, and the display of the other end side is omitted. In the drawings of the present application, a portion where a thread groove is formed is indicated by a double line.

  The ball screw device 1 according to the first embodiment is made entirely of a metal material, and is fitted with a nut 2, a screw shaft 3 inserted through the nut 2, and a screw shaft 3 so that the screw shaft 3 can rotate. A pair of bearings 4 that are supported on the cylindrical shaft 5, a cylindrical spacer 5 that is fitted on the end side of the screw shaft 3 with respect to the bearing 4, and a lock nut 6 that is disposed further on the end side than the spacer 5. ing.

  The nut 2 includes a cylindrical cylindrical portion 7 and a flange 8 formed integrally with one end portion of the cylindrical portion 7 and having a larger outer diameter than the cylindrical portion 7. A spiral outer rolling groove (not shown) is formed on the inner peripheral surface of the cylindrical portion 7. A plurality of rolling elements (not shown) are arranged between the outer rolling groove and the screw shaft 3. The cylindrical portion 7 is attached with a circulation path 9 that communicates with the two outer rolling grooves and circulates the rolling elements that roll on the outer rolling grooves.

  On the outer peripheral surface of the screw shaft 3, a spiral inner rolling groove 10 that faces the outer rolling groove of the cylindrical portion 7 is formed. The rolling elements roll the nut 2 smoothly in the axial direction of the screw shaft 2 by rolling between the outer rolling groove and the inner rolling groove as the screw shaft 13 rotates.

  On the lock nut 6 side of the inner rolling groove 10, an enlarged stepped portion 11 is formed adjacent to the inner rolling groove 10 and having a diameter larger than that of a portion where the pair of bearings 4 are fitted. Further, a male screw portion 12 having a thread groove formed on the outer periphery is provided at a portion where the lock nut 6 is fitted.

  The pair of bearings 4 is press-fitted into the screw shaft 3 from the end portion on the lock nut 6 side, and is disposed at a position where the inner ring of the bearing on the diameter expansion step portion 11 side contacts the diameter expansion step portion 11. The pair of bearings 4 uses a combination of angular ball bearings that can receive axial loads in opposite directions.

  The screw shaft 3 is connected to the end of the lock nut 6 on the rotating shaft of the motor M, and is rotated by driving the motor M to move the nut 7 in the axial direction.

  FIG. 2 is an enlarged side view of the lock nut 6 as viewed from the pair of bearings 4 side. The lock nut 6 has a substantially donut shape, and a first screw groove is formed on the inner peripheral surface 13 to be screwed into the male screw portion 12 formed on the screw shaft 3. Further, the lock nut 6 has a protruding portion 14 that protrudes in an annular shape toward the pair of bearings 4 on the inner diameter side of the pair of bearings 4 side (the surface shown in FIG. 2). The lock nut 6 is screwed into the male screw portion 12 and presses the inner rings of the pair of bearings 4 against the diameter-expanded step portion 11 via the spacer 5 between the protruding portion 14 and the inner rings of the pair of bearings 4. The inner ring of the shaft 3 and the pair of bearings 4 is fixed (see FIG. 1).

  The lock nut 6 is formed with fixing holes 15 a and 15 b extending toward the central axis and penetrating from the outer peripheral surface to the inner peripheral surface 13. The fixing holes 15a and 15b are disposed at positions that are 90 ° apart from each other about the central axis.

  FIG. 3 is a sectional view showing a means for preventing loosening of the set screw 20 according to the first embodiment of the present application. The fixing hole 15a formed in the lock nut 6 has a second female threaded portion 16 formed slightly below the midpoint between the upper end (outer peripheral surface) and the lower end (inner peripheral surface), and is continuously below the lower portion. Thus, a circular hole 17 is formed.

  To prevent the lock nut 6 from loosening, after the lock nut 6 is screwed into the male threaded portion 12 (see FIG. 1) of the screw shaft 3, a disk-shaped soft metal piece 18 is inserted into the fixing hole 15a, and a cylindrical shape is formed thereon. The elastic member 19 is inserted, and a set screw 20 is inserted from above the elastic member 19 and screwed into the second female screw portion 16. A hexagon hole (not shown) is formed in the upper portion of the set screw 20 and can be easily tightened using a hexagon wrench. The soft metal piece 18 and the elastic member 19 are compressed between the set screw 20 and the male screw portion 12 of the screw shaft 3.

  As a material of the soft metal piece 18, tin (Sn), tin alloy, pure iron (Fe), aluminum (Al), zinc (Zn), zinc alloy, copper (Cu), copper alloy, or the like can be used. As a material of the elastic member 19, resin, rubber, or the like can be used. The other fixing hole 15b is the same as the fixing hole 15a.

  Thereby, it is possible to prevent the soft metal piece 18 from biting into the irregularities of the male screw portion 12 and loosening the screw engagement between the lock nut 6 and the screw shaft 3. In addition, the compressed elastic member 19 constantly presses the set screw 20 upward (outward in the radial direction), thereby increasing the frictional force between the set screw 20 and the second female screw portion 16, and the set screw 20 vibrates. It is possible to prevent loosening due to the above. Therefore, loosening of the set screw 20 can prevent the screw nut 6 and the screw shaft 3 from loosening.

(Second Embodiment)
Next, a ball screw device according to a second embodiment of the present application will be described with reference to FIG. The ball screw device according to the second embodiment is the same as the ball screw device 1 according to the first embodiment except for the lock nut loosening prevention means. Only the means will be described.

  FIG. 4 is a cross-sectional view showing the setscrew loosening prevention means according to the second embodiment of the present application. The lock nut 26 is formed with a fixing hole 215a penetrating in the radial direction. The fixing hole 215a is formed with an enlarged diameter portion 222 having a retaining ring slit 221 extending in the circumferential direction on the inner peripheral surface in order from the upper end (outer peripheral surface) to the lower end (inner peripheral surface), and an internal thread. The second female screw portion 216 and the circular hole portion 217 are configured.

  To prevent the lock nut 26 from loosening, after the lock nut 26 is screwed into a male screw portion (not shown) formed on the screw shaft, a disk-shaped soft metal piece 218 is placed in the circular hole portion 217 and then stopped from above. The screw 220 is inserted into the fixing hole 215a and screwed into the second female screw portion 216. The soft metal piece 218 is pressed against the male screw portion of the screw shaft by screwing the set screw 220. Thereafter, a metal washer 223 is placed on the upper side of the set screw 220 and the retaining ring 224 is fitted into the retaining ring slit 221 so as to press the washer 223 against the set screw 220. By providing the washer 223, the contact surface with the set screw can be increased, and stable loosening prevention can be achieved. In FIG. 4, the retaining ring 224 indicates a surface that is on the upper side (outer diameter side) when fitted to the retaining ring slit 221.

  Thereby, it is possible to prevent the soft metal piece 218 from biting into the irregularities of the male threaded portion of the screw shaft and loosening the engagement between the lock nut 26 and the screw shaft. In addition, since the washer 223 and the retaining ring 224 restrict the set screw 220 from moving upward (outward in the radial direction), the set screw 220 can be prevented from loosening due to vibration or the like. The loosening of 220 can prevent the lock nut 26 and the screw shaft from loosening.

  Although the present invention has been described with reference to specific embodiments, the present invention is not limited to this, and various modifications and improvements can be made.

  For example, it is possible to change the arrangement of locking nuts made of fixing holes, set screws, soft metal pieces, and the like, and the locking nuts may be arranged to face each other in the radial direction. Moreover, the said locking prevention can also be made into one place or three places or more according to the magnitude | size of a lock nut.

  As the washer 223 of the second embodiment, for example, a plain washer, a spring washer, a toothed washer, a wave washer, or the like can be used.

  In the second embodiment, an elliptical flat plate may be used instead of the retaining ring 224. By adopting an elliptical shape, it can be fitted into a slit similar to the retaining ring slit.

  The shape of the soft metal pieces 18 and 218 is not limited to a disk shape, and the shape of the elastic member 19 is not limited to a cylindrical shape. For example, a rectangular parallelepiped shape and a quadrangular prism shape can be used, respectively. Further, the shape of the circular hole portion 17 can be changed in accordance with the change of these shapes.

  As a means for preventing the set screw from loosening, in addition to the first and second embodiments, the means for applying an adhesive to the set screw, means for caulking the upper part (outer diameter side portion) of the fixing hole, etc. Known means for preventing can be used, and these means can be used in combination.

  As described above, according to the present invention, it is possible to provide a ball screw device lock nut that prevents loosening of screw engagement with the screw shaft, and a ball screw device provided with the lock nut.

DESCRIPTION OF SYMBOLS 1 Ball screw apparatus 2 Nut 3 Screw shaft 4 A pair of bearing 5 Spacer 6, 26 Lock nut 7 Cylindrical part 8 Flange 9 Circulation path 10 Inner rolling groove 11 Expanded step part 12 Male thread part 13 Inner peripheral surface 14 Protruding part 15a, 15b, 215a, 215b Fixing hole 16, 216 Second female screw portion 17, 217 Circular hole portion 18, 218 Soft metal piece 19 Elastic member 20, 220 Set screw 221 Retaining ring slit 222 Expanded portion 223 Washer 224 Retaining ring

Claims (7)

Used in a ball screw device having a nut and a screw shaft inserted into the nut,
Having a generally donut-shaped body,
The inner ring of the bearing that rotatably supports the screw shaft is fixed by screwing the first female screw portion formed on the inner peripheral surface of the main body with the male screw portion formed on the screw shaft. And
In the main body, a fixing hole that penetrates from the outer peripheral surface to the inner peripheral surface and has a second female thread portion is formed,
In a lock nut for preventing loosening of the screwing with the male screw part by screwing a set screw into the second female screw part,
Within the fixing hole, a soft metal piece disposed on the screw shaft side with respect to the set screw and biting into the male screw portion by screwing of the set screw;
A lock nut for a ball screw device, wherein the lock nut is disposed in the fixing hole and has a loosening prevention means for preventing the setscrew from loosening.   2. The lock nut for a ball screw device according to claim 1, wherein the loosening prevention means includes an elastic member disposed between the soft metal piece and the set screw.   2. The loosening prevention means comprises a slit disposed in the fixed hole on the side that moves when the set screw is loosened, and a retaining ring fitted in the slit. A lock nut for the ball screw device according to 1.   4. The ball screw device lock nut according to claim 3, wherein the loosening prevention means further includes a washer interposed between the set screw and the retaining ring.   The said loosening prevention means is provided with the slit provided in the said fixing hole of the side which moves when the said set screw loosens, and the ellipse board fitted to this slit, The Claim 1 characterized by the above-mentioned. A lock nut for a ball screw device as described.   The ball screw device lock nut according to claim 5, wherein the loosening prevention means further includes a washer interposed between the set screw and the elliptical plate.   A ball screw device comprising the lock nut for the ball screw device according to any one of claims 1 to 6.

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