JP6582603B2 - Ball screw preload recovery device - Google Patents

Description

  The present invention relates to a ball screw preload recovery device provided with a preload applying mechanism between adjacent nuts screwed to a screw shaft.

This type of ball screw includes a screw shaft and a plurality of nuts that are screwed to the screw shaft via a plurality of rolling elements (for example, balls), and is configured by a flat spacer between adjacent nuts. A preload applying mechanism is interposed between the adjacent nuts.
As this preloading mechanism, as described in Patent Document 1, piezoelectric sheets are alternately stuck on both sides of a spacer inserted between adjacent nuts, and when sandwiched strongly between both nuts, It has been proposed to adjust the preload freely from outside by causing elastic deformation and adjusting the voltage supplied to the piezoelectric sheet from outside.

  Further, as another preload applying mechanism, as described in Patent Document 2, an anti-rotation means and an urging element that applies forces in opposite directions in the axial direction are arranged between adjacent nuts. It has been proposed to externally adjust the fixed position preload and the variable preload type constant pressure preload by applying a biasing force to the thruster by a biasing means including a pressure source, a fluid pressure supply path, a pressure chamber, and the like. Yes.

Japanese Patent No. 2876614 Japanese Patent Laid-Open No. 06-235446

However, in the ball screws described in Patent Documents 1 and 2, it is possible to adjust the preload from the outside, and it is possible to adjust the preload constantly, but in order to adjust the preload, It is necessary to provide a detection device and a drive device for supplying a DC voltage, or to provide an urging means including a fluid pressure source, a fluid pressure supply path, a pressure chamber, etc. There is an unresolved issue that cannot be solved.
In a ball screw that does not have an external preload adjusting mechanism as in the above-described conventional example, it is common to assemble a flat spacer between adjacent nuts and apply a preload between adjacent nuts depending on the thickness of the spacer. .

In this case, the preload imparting mechanism can be a simple configuration by simply providing a flat spacer, but when the ball screw is incorporated into a machine tool or the like and operated, it is formed in the rolling groove of the ball screw. When foreign matter such as chips adheres, this foreign matter causes wear of the rolling element or rolling groove or both of the rolling element and the rolling groove, and the preload gradually decreases. Therefore, it is necessary to stop the machine tool, and it is necessary to arrange a new ball screw and replace the ball screw.
Therefore, the present invention has been made paying attention to the unsolved problems of the conventional examples described in Patent Documents 1 and 2, and can recover the preload when the preload is reduced without providing an external drive unit. It is an object of the present invention to provide a preload recovery device for a ball screw that can be used.

  In order to achieve the above object, a ball screw preload recovery device according to an aspect of the present invention includes a screw shaft, a plurality of nuts screwed to the screw shaft via a plurality of rolling elements, and an interval between adjacent nuts. Between the adjacent nuts and a spacer formed with a cylindrical portion having a cylindrical inner surface disposed at a joint between adjacent nuts. And a spacer housing portion having a small-diameter cylindrical portion for housing the cylindrical portion of the seat, a male screw portion formed on one of the contact surfaces of the spacer and the spacer housing portion, and screwed into the male screw portion on the other When the preload between the adjacent nuts is reduced, the internal thread portion between the spacer and the spacer storage portion and the screwing position of the male screw portion are adjusted to restore the preload between the adjacent nuts.

According to one aspect of the present invention, since the preload applying mechanism has a preload recovery function, foreign matter enters the rolling groove of the ball screw and both the rolling element or the rolling groove or both the rolling element and the rolling groove are When the preload decreases due to wear, the preload can be recovered by adjusting the screwing position of the cylindrical spacer, and the ball screw can be used for a long time while maintaining the initial performance of the ball screw. . For this reason, the preparation period required for the replacement of the ball screw can be lengthened, and when the ball screw to be replaced has been procured, the ball screw replacement operation is performed to shorten the stop period of the machine incorporating the ball screw. And a decrease in productivity can be suppressed.
In addition, it is not necessary for the user of the machine incorporating the ball screw to have a spare stock of the ball screw, which can lead to a reduction in inventory costs.

1 is a cross-sectional view illustrating a first embodiment of a preload recovery device for a ball screw according to an aspect of the present invention. It is sectional drawing which shows 2nd Embodiment of the preload recovery apparatus of the ball screw which concerns on 1 aspect of this invention.

  Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

Further, the embodiment described below exemplifies an apparatus and a method for embodying the technical idea of the present invention, and the technical idea of the present invention includes the material, shape, structure, The layout is not specified as follows. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.
First, an embodiment of a ball screw preload recovery apparatus representing one aspect of the present invention will be described.

As shown in FIG. 1, the ball screw 10 includes a screw shaft 11 and a plurality of, for example, two nuts 13 </ b> A and 13 </ b> B screwed to the screw shaft 11 via balls 12 as rolling elements.
The screw shaft 11 is formed with a screw shaft side spiral groove 14 on which the ball 12 rolls on the outer peripheral surface.
The nut 13A includes a cylindrical body 16 having a flange portion 15 formed at one end, and a nut-side spiral groove 17 on which the ball 12 rolls on the inner peripheral surface of the cylindrical body 16 so as to face the screw shaft-side spiral groove 14. Is formed.

The nut 13B has the same configuration as the nut 13A except that the flange portion 15 is omitted, and the ball 12 rolls on the inner peripheral surface of the cylindrical body 16 so as to face the screw shaft side spiral groove 14. A nut-side spiral groove 17 is formed.
Although not shown, the nuts 13A and 13B are formed with a circulation path on the outer peripheral surface for returning the ball 12 from one end side to the other end side in the axial direction. The ball 12 is circulated through the circulation path. ing.

Here, the screw shaft side spiral groove 14 has a Gothic arc shape in which a cross-sectional shape perpendicular to the spiral groove is a substantially V shape in which two identical arcs having different centers of curvature are combined. On the other hand, the nut-side spiral groove 17 has a Gothic arc shape in which a cross-sectional shape perpendicular to the spiral groove has a radius of curvature larger than the radius of the ball 12.
A nut 13B is disposed adjacent to the flange 13 on the opposite side of the nut 13A.

Between the nuts 13A and 13B, a preload applying mechanism 20 for applying a preload to the ball 12 is provided. The preload applying mechanism 20 includes a spacer 21 that applies a preload to the ball 12, and a spacer housing portion 22 formed at one end of the nut 13A, 13B, for example, the nut 13B side of the nut 13A.
The spacer 21 is disposed between the cylindrical portion 23 accommodated in the spacer accommodating portion 22 and the opposing end surfaces of the nuts 13A and 13B fixed to the end portion of the cylindrical portion 23 on the nut 13B side. And an initial preloading spacer 24 for applying an initial preload.

The cylindrical portion 23 has a configuration of a tightening nut in which an internal thread 23a is formed on the inner peripheral surface.
The initial preload spacer 24 is formed of an annular plate in which a through hole having an inner diameter equal to or larger than the inner diameter between the bottom surfaces of the nut-side spiral grooves 17 of the nuts 13A and 13B is formed. An initial preload is applied to the.
Here, the cylindrical portion 23 and the initial preload spacer 24 may be formed separately and combined, or the cylindrical portion 23 and the initial preload spacer 24 may be integrally formed. Also good.

  The spacer housing portion 22 is formed to house the cylindrical portion 23 of the spacer 21 at the end of the cylindrical body 16 of the nut 13A on the nut 13B side. The spacer storage portion 22 is formed as an annular notch portion in which a small-diameter cylindrical portion 25 having a diameter smaller than the outer diameter of the cylindrical body 16 is formed at an end portion of the cylindrical body 16 and the end surface side and the outer peripheral surface are opened. On the outer peripheral surface of the small-diameter cylindrical portion 25 of the spacer housing portion 22, a male screw portion 26 that is screwed into the female screw portion 23a formed in the cylindrical portion 23 of the spacer 21 is formed.

Here, an annular recess 23 b is formed on the inner peripheral surface joined to the end face of the initial preloading spacer 24 of the cylindrical portion 23, and the initial preloading spacer is stored in the spacer storage 22 of the spacer 21. It is preferable that the inner end face of the portion 24 is reliably brought into contact with the end face of the small diameter cylindrical portion 25.
The nuts 13A and 13B are made of chromium molybdenum steel (thermal expansion coefficient: 11.2 × 10 ⁻⁶ / K), which is a metal material having a relatively small thermal expansion coefficient, and the spacer 21 is connected to the nuts 13A and 13B. On the other hand, it is made of brass (thermal expansion coefficient: 19 × 10 ⁻⁶ / K), stainless steel SUS304 (thermal expansion coefficient: 17.3 × 10 ⁻⁶ / K), which is a metal material having a large thermal expansion coefficient.

Next, the operation of the above embodiment will be described.
When attaching the nuts 13 </ b> A and 13 </ b> B to the screw shaft 11, first, the nut 13 </ b> A is screwed onto the screw shaft 11 via the ball 12. At this time, the male screw portion 26 of the small-diameter cylindrical portion 25 is screwed into the female screw portion 23 a formed in the cylindrical portion 23 of the spacer 21, and the cylindrical portion 23 is inserted into the back side of the spacer housing portion 22, and is used for initial preloading. The inner end surface of the seat portion 24 is mounted so as to contact the end surface of the small diameter cylindrical portion 25 of the nut 13A.

Next, the nut 13B is screwed through the ball 12 from the end of the nut 13A of the screw shaft 11 on the small diameter cylindrical portion 25 side, and the end surface of the nut 13A is brought into contact with the end surface of the initial preload spacer 24. Thus, a predetermined initial preload in the pulling direction is applied to the ball 12 between the nuts 13 </ b> A and 13 </ b> B and the screw shaft 11 by the initial preload spacer 24 so as to be in a two-point contact state.
Thus, by adopting a double nut configuration in which the nuts 13A and 13B are mounted adjacent to the screw shaft 11, the rigidity can be increased as compared with the case of a single nut, and the positioning accuracy of the feed system using the ball screw 10 is improved. Can be improved.

  By the way, the ball screw 10 having the above configuration is used by being incorporated in a machine tool, an injection molding machine, a semiconductor manufacturing apparatus, or the like that requires positioning accuracy. Foreign matter such as chips and wear powder easily enters the side spiral groove 14 and the nut side spiral groove 17 of the nuts 13A and 13B. When foreign matter enters the screw shaft side spiral groove 14 or the nut side spiral groove 17 in this way, the foreign matter is caught between the screw shaft side spiral groove 14 or the nut side spiral groove 17 and the ball 12 due to the contact angle. At least one of the ball 12, the screw shaft side spiral groove 14, and the nut side spiral groove 17 is worn and preload loss occurs.

Further, when the nuts 13A and 13B are driven to rotate by causing the nuts 13A and 13B to rotate, the amount of heat generated between the nut-side spiral groove 17 and the ball 12 increases as compared with the amount of heat generated at other parts.
When foreign matter such as chips or wear powder enters between the nut-side spiral groove 17 and the ball depending on the contact angle, the amount of heat generated increases as the frictional resistance increases, so the nuts 13A and 13B of the cylindrical portion 23 are increased. And the temperature of the preload application mechanism 20 rises.

  At this time, since the thermal expansion coefficient of the spacer 21 of the preload applying mechanism 20 is set to be larger than the thermal expansion coefficients of the nuts 13A and 13B, the axial extension amount of the cylindrical portion 23 of the spacer 21 is the small diameter of the nut 13A. The amount of elongation of the cylindrical portion 25 is larger than the amount of elongation in the axial direction, and there is no play between the female screw portion 23a and the male screw portion 226. And the preload of 13B is increased, and the preload by the spacer 21 is recovered.

  However, when the wear amount of at least one of the ball 12, the screw shaft side spiral groove 14, and the nut side spiral groove 17 increases, the preload is insufficient for the increase in the preload due to the difference in thermal expansion coefficient between the spacer 21 and the small diameter cylindrical portion 25. Will do. In this case, if the female threaded portion 23a of the cylindrical portion 23 of the spacer 21 and the male threaded portion 26 of the small diameter cylindrical portion 25 are right-handed, the spacer 21 is rotated clockwise toward the nut 13B. Accordingly, the spacer 21 moves in the axial direction toward the nut 13B, and the preload between the nuts 13A and 13B can be reliably recovered. For this reason, rigidity proportional to the preload of the ball screw 10 can be ensured, and a decrease in the positioning accuracy of the feed system can be compensated.

  Therefore, even if the ball screw 10 has a decrease in preload due to wear of at least one of the ball 12, the screw shaft side spiral groove 14, and the nut side spiral groove 17, the preload is recovered and can be continuously used. When this preload recovery operation is performed, a new ball screw 10 is prepared, and until this new ball screw 10 is delivered, rigidity is secured by preload recovery to maintain positioning accuracy of the feed system. The feed system can be operated as it is.

Then, when a new ball screw 10 is delivered, the driving of the feed system is stopped, and an operation of replacing the deteriorated ball screw 10 with a new ball screw 10 is performed. Thereby, the mechanism of the feed system can be updated and the stop time of the feed system can be shortened, so that the production volume can be reduced as much as possible.
Furthermore, it is no longer necessary to have a spare stock of the ball screw 10 at a manufacturer or a production site that uses a machine tool, an injection molding machine, a semiconductor manufacturing apparatus or the like incorporating the ball screw 10, thereby contributing to a reduction in inventory costs. Can do.

In addition, in the said embodiment, although the case where the spacer accommodating part 22 was formed in the nut 13A side was demonstrated, it is not limited to this, respecting the small diameter cylindrical part 25 on the nut 13B side, a spacer The storage portion 22 may be formed, and the spacer 21 may be screwed into the spacer storage portion 22.
Moreover, in the said embodiment, although the case where the cylindrical part 23 of the spacer 21 was screwed on the outer peripheral side of the small diameter cylindrical part 25 of the spacer accommodating part 22 was demonstrated, it is not limited to this, FIG. You may comprise as shown in 2. FIG. That is, the internal thread portion 23a is omitted on the inner peripheral surface of the cylindrical portion 23 of the spacer 21, and the external thread portion 31 is formed on the outer peripheral surface instead. Accordingly, the spacer accommodating portion 22 formed on the end surface of the nut 13A on the nut 13B side is formed as an annular recess 32 instead of the annular notch, and an external thread is formed on the outer peripheral side inner peripheral surface of the annular recess 32. A female screw portion 32 a that is screwed into the portion 31 is formed.

Then, the spacer 21 is movably held in the spacer storage portion 22 in the axial direction by screwing the male screw portion 31 of the spacer 21 with the female screw portion 32a of the spacer storage portion 22 of the nut 13A.
Even with this configuration, when the ball screw 10 is deteriorated due to wear of at least one of the ball 12, the screw shaft side spiral groove 14 and the nut side spiral groove 17, the spacer 21 is rotated. Thus, the preload can be recovered by adjusting the screwing position so as to be moved in the axial direction toward the nut 13B.

  Therefore, it is possible to obtain the same operation and effect as the embodiment of FIG. In the configuration shown in FIG. 2, the spacer housing 22 can be formed on the nut 13B side.

  DESCRIPTION OF SYMBOLS 10 ... Ball screw, 11 ... Screw shaft, 12 ... Ball, 13A, 13B ... Nut, 14 ... Screw shaft side spiral groove, 16 ... Cylindrical body, 17 ... Nut side spiral groove, 20 ... Preload imparting mechanism, 21 ... Spacer , 22 ... spacer housing part, 23 ... cylindrical part, 23a ... female screw part, 24 ... initial preload spacer part, 25 ... small diameter cylindrical part, 26 ... male screw part, 31 ... male screw part, 32 ... annular concave part, 32a ... Female thread

Claims (3)

A screw shaft, a plurality of nuts screwed to the screw shaft via a plurality of rolling elements, and a preload application mechanism disposed between adjacent nuts,
The preload applying mechanism houses a spacer formed with a cylindrical portion having a cylindrical inner surface disposed at a joint between the adjacent nuts, and a cylindrical portion of the spacer formed on at least one of the adjacent nuts. Including a spacer housing portion having a small diameter cylindrical portion,
A male thread part is formed on one of the contact surfaces of the spacer and the spacer housing part, and a female thread part is formed on the other to be screwed to the male thread part. When the preload between the adjacent nuts is reduced, the spacer and By adjusting the screwing position of the female screw part and the male screw part between the spacer housing parts, the preload between the adjacent nuts is recovered ,
The spacer includes a tightening nut that forms a cylindrical portion, an end surface of the small-diameter cylindrical portion that is fixed to an inner surface of an end portion of the tightening nut that is opposite to a nut that forms the spacer housing portion, A preload recovery device for a ball screw, characterized by comprising an initial preload spacer that contacts an end of an opposite nut and applies an initial preload . A screw shaft, a plurality of nuts screwed to the screw shaft via a plurality of rolling elements, and a preload application mechanism disposed between adjacent nuts,
The preload applying mechanism houses a spacer formed with a cylindrical portion having a cylindrical inner surface disposed at a joint between the adjacent nuts, and a cylindrical portion of the spacer formed on at least one of the adjacent nuts. Including a spacer housing portion having a small diameter cylindrical portion,
A male thread part is formed on one of the contact surfaces of the spacer and the spacer housing part, and a female thread part is formed on the other to be screwed to the male thread part. When the preload between the adjacent nuts is reduced, the spacer and By adjusting the screwing position of the female screw part and the male screw part between the spacer housing parts, the preload between the adjacent nuts is recovered,
The spacer includes a cylindrical portion having a male thread portion formed on an outer peripheral surface thereof, and a small diameter cylindrical portion fixed to an inner surface of an end portion of the cylindrical portion opposite to a nut on which the spacer storage portion is formed. preload recovery device characteristics and to Rubo Lumpur screw that is configured with an initial preload for spacer portion to provide an initial preload in contact with the end portion of the end face and the opposite side of the nut. 3. The ball screw preload recovery device according to claim 1, wherein the spacer is formed of a metal material having a thermal expansion coefficient larger than that of the nut. 4.

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