JP2008038920A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for improving the durability of a ball screw device by preventing the damage of loaded surfaces and balls in an internal circulation type ball screw device. <P>SOLUTION: The ball screw device 1 comprises a screw shaft 3 having a helicoidal shaft raceway groove 4 formed on its outer peripheral surface, a nut 5 having a nut raceway groove 6 formed on its inner peripheral surface so as to face the shaft raceway groove 4, a communicating hole 10 formed in the nut 5 along its axial direction, a loading way to be formed by the shaft raceway groove 4 and the nut raceway groove 6, a deflector 11 having connecting passages 12 for connecting both ends of the communicating hole 10 and both ends of the loading way respectively, mounting holes 17 for mounting the deflector 11 provided in the nut 5, and a plurality of balls 2 to circulate in a circulation passage to be formed by the communicating hole 10, the connecting passages 12, and the loading way, wherein the inner surface of the communicating hole 10 of the nut 5 is treated by a shot peening operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an internal circulation type ball screw device used for driving a linear moving mechanism such as positioning of a moving table or conveying for a machine device such as a machine tool or an industrial machine or for transmitting power.

  A conventional internal circulation type ball screw device has a load formed by a shaft raceway groove formed in a spiral shape on the outer peripheral surface of a screw shaft and a nut raceway groove opposed to the shaft raceway groove formed on the inner peripheral surface of the nut. The both ends of the path are communicated by a communicating hole formed along the axial direction of the nut and a connecting path of a deflector attached to a mounting hole provided at both ends of the communicating hole. The load applied to the nut is supported by a plurality of balls that circulate through the circulation path formed by the load path, and the screw shaft is rotated to linearly reciprocate the nut (see, for example, Patent Document 1). ).

Also, a ball screw device in which a shaft raceway groove formed spirally on the outer peripheral surface of the screw shaft and a nut raceway groove facing the shaft raceway groove formed on the inner peripheral surface of the nut are screwed together via a plurality of balls. And the nut raceway groove is subjected to shot peening treatment to improve the surface roughness of the nut raceway groove, and there is also an improvement in the durability of the ball screw device by increasing the surface compressive residual stress ( For example, see Patent Document 2.)
Japanese Patent Laying-Open No. 2005-48845 (mainly third page paragraph 0010 to fourth page paragraph 0013, FIG. 1) Japanese Patent Laying-Open No. 2005-90570 (mainly, page 5 paragraphs 0024-0028, FIGS. 1 and 2)

  However, in the internal circulation type ball screw device of Patent Document 1 described above, when shot peening is applied to the nut raceway groove as in Patent Document 2, burrs formed in the communication path, adhered metal powder, etc. If it is not removed sufficiently, the burrs, metal powder, etc. will enter the load path formed by the nut raceway groove and the shaft raceway groove as foreign matter and will be crushed between the ball and the surface of the load path. There is a problem that there is a possibility that damage such as a biting wound may be caused and an improvement in durability cannot be expected.

  The present invention has been made to solve the above-described problems, and provides means for preventing damage to a load path and a ball in an internal circulation ball screw device and improving the durability of the ball screw device. For the purpose.

  In order to solve the above problems, the present invention provides a screw shaft having a spiral shaft raceway groove formed on the outer peripheral surface, a nut having a nut raceway groove facing the shaft raceway groove on the inner peripheral surface, and the nut A communication hole formed along the axial direction of the shaft, a load path formed by the shaft raceway groove and the nut raceway groove, and a connection path for connecting both ends of the communication hole and both ends of the load path are formed. And a plurality of balls that circulate in a circulation path formed by the communication hole, the connection path, and the load path, and a mounting hole for mounting the connection member provided on the nut. In the screw device, a shot peening process is performed on an inner surface of the communication hole of the nut.

  Thereby, this invention can remove the burr | flash formed in the corner | angular part of the mouth of a communicating hole, the metal powder adhering to an inner surface, etc., preventing damage to a load path or a ball | bowl, and durability of a ball screw apparatus. The effect that property can be improved is acquired.

  Embodiments of a ball screw device according to the present invention will be described below with reference to the drawings.

1 is an explanatory view showing a cross section of a ball screw device of an embodiment, FIG. 2 is an explanatory view showing a side surface of the nut of the embodiment, FIG. 3 is an explanatory view showing an AA cross section of FIG. 2, and FIG. FIG. 5 is a view in the direction of the arrow B in FIG. 4, and FIG. 6 is a view in the direction of the arrow C in FIG.
In FIG. 1, 1 is a ball screw device.
Reference numeral 2 denotes a ball as a rolling element of the ball screw device 1, which is a sphere made of a steel material such as alloy steel.

Reference numeral 3 denotes a screw shaft of the ball screw device 1, which is a rod-shaped member made of a steel material such as alloy steel, and an axial raceway groove 4 having an arc-shaped cross-section is spirally formed with a predetermined lead on the outer peripheral surface thereof. Is formed.
Reference numeral 5 denotes a nut of the ball screw device 1, which is a cylindrical member made of a steel material such as alloy steel, and the inner peripheral surface thereof has a nut raceway groove 6 having an arcuate cross-sectional shape facing the shaft raceway groove 4. Is formed with the same lead as the shaft raceway groove 4.

The nut 5 of this embodiment is tempered, and its cylindrical wall is formed with a Rockwell hardness C scale of about HRC 20-40, and the nut raceway 6 is formed by carburizing or induction hardening. It has a hardness of about HRC60.
Reference numeral 7 denotes a mounting flange, which is provided at one end of the outer peripheral portion of the nut 5 and is fixed to a moving table of a mechanical device (not shown) with a mounting bolt or the like by a mounting bolt hole 8 provided in the mounting flange 7. .

Reference numeral 10 denotes a communication hole having a diameter larger than the diameter of the ball 2 formed on the cylindrical wall of the nut 5 as shown in FIGS. 2 and 3, and the ball 2 formed along the axial direction of the nut 5. It is a relatively long hole for circulation, and is provided corresponding to the number of nut raceway grooves 6 (one in this embodiment).
Denoted at 11 is a deflector as a connecting member. As shown in FIGS. 4 to 6, the nut raceway groove 6 and the shaft raceway groove 4 are arranged to face each other, and both ends of the load path on which the ball 2 rolls and the nut are formed. 5 is formed with a connecting path 12 which is a curved path (see FIG. 5) for connecting the both ends of the communication hole 10 to each other. The connecting path 12 is made of a resin material or the like and is attached to a mounting hole 17 which will be described later. It is arrange | positioned at both ends, respectively.

Reference numeral 13 denotes a tongue portion, as shown in FIG. 4, which is a protrusion having an arcuate cross section that loosely fits along the groove direction of the shaft raceway groove 4 formed on the screw shaft 3 side of the deflector 11 (twist direction). The tip portion of the ball 2 that rolls on the load path is formed in a tangential direction or with a slight scooping angle, and functions as a scooping surface 14 that lifts the ball 2 from the axial raceway groove 4 to the connecting path 12. .
Reference numeral 15 denotes a positioning projection, which is formed by an arc surface protruding toward the communication hole 10 of the deflector 11 as shown in FIG. And the connecting path 12 are positioned in the height direction and the angle direction.

As shown in FIG. 2, the mounting hole 17 is positioned and fitted with an insertion hole 20 penetrating in a tangential direction of the nut raceway groove 6 from a counterbore portion 19 provided on the outer peripheral surface of the nut 5 toward the nut raceway groove 6. It has a joint portion 18 and is formed at both end portions of the communication hole 10 of the nut 5 with the positioning fitting portion 18 facing the communication hole 10.
The deflector 11 of this embodiment is attached by inserting the main body portion into the insertion hole 20 and fitting the positioning projection 15 of the deflector 11 to the positioning fitting portion 18 of the mounting hole 17. Thereby, the nut raceway groove 6 and the communication hole 10 are connected by the connecting path 12 of the deflector 11.

  In the present embodiment, the communication hole 10 is drilled from the mounting flange 7 side of the nut 5 and the mounting hole 17 is drilled from the counterbore 19 by a drill, an end mill or the like, and then the inner surface and the communication hole 10 are attached to both sides. Metal beads or the like were used for the connecting portion 21a (see FIG. 2) of the hole 17 to the fitting portion 18 and the connecting portion 21b (see FIG. 3) of the insertion portion 20 of the mounting hole 17 on both sides and the nut raceway groove 6. A shot peening process is performed.

Thereby, the burr | flash formed in each corner | angular part, the metal powder adhering to each inner surface, etc. are removed, and R chamfering is formed in each corner | angular part.
Further, the nut raceway groove 6 is finished by grinding or the like after the shot peening process.
Both ends of the load path are connected by a communication path formed by the connection path 12 of the deflector 11 and the communication hole 10 of the nut 5 to form a circulation path, and a predetermined amount of lubricant, For example, grease and a plurality of balls 2 are enclosed, and when the screw shaft 3 is rotated, the balls 2 roll on the load path while supporting the load applied to the nut 5, and the tongue 13 of the one deflector 11 scoops. It is lifted by the surface 14 and guided to the connecting path 12, and circulates in the circulating path while being returned to the load path from the tongue 13 of the other connecting path 12 through the communication hole 10.

Thereby, the rotational motion of the screw shaft 3 is converted into the linear motion of the nut 5, and the nut 5 is supported so as to be capable of linear reciprocation along the longitudinal direction of the screw shaft 3.
At this time, the inner surface of the communication hole 10 of the present embodiment has the burr and metal powder removed by the shot peening process, so that foreign matter does not enter the load path, and damage to the load path and the ball 2 is prevented. Thus, the durability of the ball screw device 1 can be improved, and the quality of the ball screw device 1 can be improved with a good initial wear fit.

  Moreover, in each connection part 21a of the communication hole 10 and the attachment hole 17, a corner | angular part is exposed to the connection part 21a by the difference in the elastic coefficient of the nut 5 which consists of a deflector and alloy steel etc. which were formed with the resin material. Even if it does, the burr | flash formed in the corner | angular part by a shot peening process will be removed, R chamfering will be formed, the connection path 12 and the communication hole 10 may be connected smoothly, and the surface of the communication path 10 may remain. Since the surface hardness is increased by the compressive stress, it is possible to prevent damage to the corner of the mouth of the communication hole 10 formed in the cylindrical wall of the nut 5 having a relatively low hardness (about HRC 20 to 40). .

  Further, in each connection portion 21b between the mounting hole 17 and the nut raceway groove 6, the ball 2 entering the connecting path 12 from the load path or the ball 2 returning from the connecting path 12 to the load path suddenly changes the moving direction. Therefore, although the surface hardness (about HRC60) of the nut raceway groove 6 is high, a relatively high stress is generated at the corner of the connecting portion 21b, but the shot at the corner of the connecting portion 21b of the present embodiment. Peening is performed, burrs formed at the corners are removed, R chamfering is formed, and the connection path 12 and the nut raceway groove 6 are smoothly connected. Damage to the part can be prevented.

This is the case in the case of the ball screw device 1 of the preload specification in which the ball 2 returns to the load path while being elastically deformed, or the elastic deformation is released and the connection portion 21b is likely to be damaged because it enters the connecting path 12. It is particularly effective.
Further, the mounting hole 17 of the present embodiment is subjected to shot peening treatment, and burrs formed at the corners of the mouth and metal powder attached to the inner surface are removed. Therefore, when the deflector 11 is inserted, The outer surface is not damaged, and the quality of the ball screw device 1 can be stabilized.

  As described above, in this embodiment, the inner surface of the communication hole that communicates with the mounting hole to which the deflector is attached is subjected to shot peening treatment, so that burrs and inner portions formed at the corners of the communication hole are formed. It can remove metal powder adhering to the surface, prevent these foreign substances from entering the load path, prevent damage to the load path and the ball, and improve the durability of the ball screw device In addition, the quality of the ball screw device can be improved by making the initial wear fit good.

In addition, by performing shot peening on the connection part between the communication hole and the mounting hole of the nut, it is possible to remove the burr formed at the corner of the mouth of the communication path and form an R chamfer, By smoothly connecting the connection path and the communication hole, damage to the corner portion of the communication hole at the connection part between the communication hole and the mounting hole of the nut can be prevented.
Furthermore, the shot peening treatment is applied to the connecting portion between the nut mounting hole and the nut raceway groove, thereby removing burrs formed at the corners at the connecting portion between the nut mounting hole and the nut raceway groove. Chamfering can be formed, and the connecting path of the deflector and the nut raceway groove can be smoothly connected to prevent damage to the corners of the connecting portion due to the balls.

In the above-described embodiment, it has been described that the shot peening process is performed on the communication hole and the mounting hole. However, a buff process using a buff formed of felt or the like may be performed. Even if it does in this way, the burr | flash formed in each corner | angular part, the metal powder etc. which adhered to the inner surface can be removed, and the effect similar to the above can be acquired.
Further, in the above embodiment, the screw shaft of the ball screw device is rotated and the nut is moved in the axial direction. However, the present invention is applied to a ball screw device of a type in which the nut is rotated and the screw shaft is moved in the axial direction. Even if the invention is applied, the same effect can be obtained.

Explanatory drawing which shows the cross section of the ball screw apparatus of an Example Explanatory drawing which shows the side of the nut of an Example Explanatory drawing which shows the AA cross section of FIG. Explanatory drawing which shows the front of the deflector of an Example B direction arrow view of FIG. C direction arrow view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ball screw apparatus 2 Ball 3 Screw shaft 4 Shaft raceway groove 5 Nut 6 Nut raceway groove 7 Mounting flange part 8 Mounting bolt hole 10 Communication hole 11 Deflector 12 Connection path 13 Tongue part 14 Scuff surface 15 Positioning protrusion 17 Mounting hole 18 Positioning fitting Joint part 19 Counterbore part 20 Insertion hole 21a, 21b Connection part

Claims (4)

A screw shaft having a spiral shaft raceway groove formed on the outer peripheral surface, a nut having a nut raceway groove opposed to the shaft raceway groove on the inner peripheral surface, and a communication hole formed along the axial direction of the nut; A load path formed by the shaft raceway groove and the nut raceway groove, a connection member formed with a connection path that connects both ends of the communication hole and both ends of the load path, and the nut. In a ball screw device comprising a mounting hole for attaching the connecting member, and a plurality of balls circulating in a circulation path formed by the communication hole, the connecting path, and the load path,
A ball screw device characterized in that shot peening treatment is performed on the inner surface of the communication hole of the nut. In claim 1,
A ball screw device, wherein a shot peening process is performed on a connection portion between the communication hole of the nut and the mounting hole. In claim 1 or claim 2,
A ball screw device characterized in that shot peening treatment is applied to a connecting portion between the nut mounting hole and the nut raceway groove. In any one of Claims 1 to 3,
A ball screw device characterized in that a buffing process is performed instead of the shot peening process.