Processing device for nut of ball screw

Abstract

To provide a processing device for a nut of a ball screw, capable of projecting a shot agent precisely to sites for removing processing traces.SOLUTION: A processing device for a nut of a ball screw including a screw shaft, a nut, a plurality of balls, and a ball circulation part includes a work holder for holding a raw material of the nut, a tube holder for holding a tube projecting a shot agent, a rotation unit for causing relative rotation of the work holder and the tube holder around the axis of the raw material of the nut, and a direct advance drive unit for causing relative displacement of the work holder and the tube holder along the axis of the raw material of the nut.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a processing device for a nut of a ball screw. [Background technology]

[0002] Linear motion devices such as ball screws and linear guides are used in machine tools and transport equipment, but there is strong demand for smoother operation, quieter operation, higher speeds, and improved durability, and measures to meet these demands are being sought.

[0003] In the manufacturing process of ball screws, cutting and grinding are performed to form the raceway surface. However, after this cutting and grinding process, streaky processing marks are formed on the raceway surface along a certain direction. These streaky processing marks may indicate an insufficient ability to retain lubricant, which can cause seizure due to a lack of lubricant, damage to the surface of the balls, or damage such as peeling, reducing durability.

[0004] In response to this, Patent Document 1 discloses a technique in which a nozzle having a shot outlet is set at a fixed distance from the end face of a nut that has been hardened and ground, the position of the nozzle is fixed, and the nut is also fixed, and the shot is sprayed toward the inner surface of the nut, thereby removing the machining marks. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 04-203549 Summary of the Invention [Problem to be solved by the invention]

[0006] However, as shown in Patent Document 1, when blasting is performed using a shot such as shot peening, the shot is dispersed and projected during processing. Therefore, if the shot is directly sprayed against the screw shaft or nut of a ball screw, there is a risk that the shot will collide with areas other than the area where it is desired to remove the processing marks, which may result in a deterioration of the surface precision of those areas.

[0007] In addition, when spraying shot material while keeping the nozzle and nut in fixed positions, the distance from the nozzle's shot material outlet differs between the top surface of the nut, which is close to the nozzle, and the bottom surface of the nut, which is far from the nozzle. This causes problems such as unevenness in the amount of shot material that hits the workpiece and the impact force when the shot material hits the workpiece.

[0008] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a processing device for a nut of a ball screw that can accurately project shot material onto an area where it is desired to remove processing marks. [Means for solving the problem]

[0009] The above object of the present invention can be achieved by the following configuration. (1) a screw shaft having a helical outer peripheral thread groove formed on an outer peripheral surface thereof; A nut is disposed around the screw shaft, and has an inner peripheral surface on which a helical inner peripheral thread groove is formed opposite to the outer peripheral thread groove; A plurality of balls are accommodated in a rolling path formed by the outer peripheral screw groove and the inner peripheral screw groove that face each other; a circulation unit for circulating the plurality of balls in the rolling paths; A processing device for a nut of a ball screw, comprising: A work holding device for holding the nut material; A tube holding device that holds a tube for projecting the shot material; a rotation unit that rotates the work holding device and the tube holding device relatively around an axis of the nut material; A linear drive unit that moves the work holding device and the tube holding device relative to each other along an axis of the nut material; 1. A processing device for a nut of a ball screw, comprising: (2) The axis of the projection port of the tube for projecting the shot material is inclined at an acute angle to the axis of the material. A processing device for a nut of a ball screw as described in (1). (3) The axis of the projection port of the tube through which the shot is projected is inclined at a right angle or an obtuse angle to the axis of the material. A processing device for a nut of a ball screw as described in (1). (4) The rotation unit and the linear drive unit are driven in synchronization with each other to move a projection port of the tube through which the shot material is projected in a spiral shape along the internal thread groove. The processing device for a nut of a ball screw according to any one of (1) to (3). Effect of the Invention

[0010] According to the present invention, it is possible to provide a processing device for a nut of a ball screw that can accurately project shot material onto an area where it is desired to remove processing marks. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view of a circulating ball screw that can be processed by the blast processing device according to the first embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a state in which a nut material is attached to the blast processing device according to the first embodiment. [Diagram 3] FIG. 3 is a schematic cross-sectional view showing a blast processing step for a nut material. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a blast processing step for a nut material. [Diagram 5] FIG. 5 is a schematic cross-sectional view similar to FIG. 2, showing a blast processing device according to a modified example. [Figure 6]FIG. 6 is a schematic cross-sectional view similar to FIG. 2, showing a blast processing apparatus according to another modified example. [Figure 7] FIG. 7 is a schematic cross-sectional view similar to FIG. 2, showing a blast processing apparatus according to another modified example. [Figure 8] FIG. 8 is a schematic cross-sectional view similar to FIG. 2, illustrating a state in which a nut of a circulating-type ball screw is blasted using the blast processing device according to the first embodiment. [Figure 9] Fig. 9(a) is a schematic cross-sectional view similar to Fig. 8, showing a blast processing device according to a second embodiment, and Fig. 9(b) is an enlarged view showing the vicinity of the projection port of the tube shown in Fig. 9(a). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a blast processing device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a circulating ball screw that can be machined by the blast processing device according to this embodiment.

[0013] The ball screw 1 includes a screw shaft 10, a nut 20, a plurality of balls 30, and a plurality of circulation pieces 40 as a circulation section. The screw shaft 10 is formed in a cylindrical shape centered on a central axis CL, and a helical outer peripheral screw groove 11 having a predetermined lead is formed on the outer peripheral surface thereof.

[0014] The nut 20 is substantially cylindrical. The inner diameter of the nut 20 is larger than the outer diameter of the screw shaft 10, and the nut 20 is fitted onto the screw shaft 10 with a predetermined gap. One end of the nut 20 is provided with a flange 25 for coupling with a guide target (another component). The inner peripheral surface of the nut 20 has an inner peripheral thread groove 21 that has the same lead as the outer peripheral thread groove 11 of the screw shaft 10 and faces the outer peripheral thread groove 11 and is formed in a spiral shape.

[0015] A rolling path 23 having a substantially circular cross section is formed by the outer peripheral thread groove 11 of the screw shaft 10 and the inner peripheral thread groove 21 of the nut 20. A plurality of balls 30 are housed and arranged in the rolling path 23 so as to be able to roll.

[0016] In addition, a plurality of circulating pieces 40 for returning the balls 30 to the preceding rolling path 23 are attached to the inner peripheral surface of the nut 20. Each circulating piece 40 is formed with a ball return passage 42 connecting one end of the rolling path 23 to the other end of the rolling path 23 one turn before. This ball return passage 42 scoops up the balls 30 rolling along the rolling path 23 toward each circulating piece 40 in the radial direction of the screw shaft 10, and causes them to go over the outer land portion (a portion other than the outer peripheral thread groove 11 on the outer peripheral surface of the screw shaft 10) 13 of the screw shaft 10 and return them to the rolling path 23 one turn before (one lead before), thereby enabling the balls 30 to circulate.

[0017] The ball return passage 42 and the rolling passage 23 form a substantially annular endless circulation passage on the outside of the screw shaft 10. As a result, as the screw shaft 10 rotates relative to the nut 20, the multiple balls 30 circulate in the endless circulation passage, making it possible to linearly move the nut 20 relative to the screw shaft 10 in the axial direction of the screw shaft 10.

[0018] [First embodiment] 2 is a diagram showing a blast processing device of the first embodiment, which is a processing device for a nut of a ball screw, with a cut-machined material M attached to it. The blast processing device has a stage (workpiece holding device) ST on which a holder HD for holding a flange 25 of the material M is placed, a rotation unit RU for a tube BT that sprays shot material, and a linear drive unit SU for the tube BT.

[0019] The rotation unit RU holds a gripping portion (tube holding device) CK that grips the tube BT, and is capable of rotating the tube BT together with the gripping portion CK around the axis L of the material M by an actuator ACT. The fixed linear drive unit SU includes a slider SL connected to the rotation unit RU, and is capable of driving the slider SL along the axis L of the material M together with the rotation unit RU. The stage ST is fixed to a base (not shown).

[0020] In this embodiment, the axis O of the projection port BTO of the tube BT through which the shot charge is projected is inclined at an angle θ1 with respect to the axis L of the material M. The axis O is parallel to the average projection direction of the shot charge projected from the projection port BTO. Here, the angle θ1 is greater than 0 degrees (when the axis O coincides with the axis L) and less than 90 degrees (acute angle), but for example, θ1 = 45 degrees ± 10 degrees is preferable because it allows the shot charge to be projected smoothly from the projection port BTO. The inner peripheral surface of the tube BT is connected by a smooth curved surface from the side along the axis L to the projection port BTO. The other end of the tube BT is connected to a storage tank for the shot charge and a high-pressure air source, etc., not shown.

[0021] The blasting process of the material M performed by using the blasting device shown in Fig. 2 will be described with reference to Figs. 3 and 4. Figs. 3 and 4 are schematic cross-sectional views showing the blasting process of the material M for a nut.

[0022] The manufacturing process of the nut 20 of the ball screw 1 will be described. First, in a pre-process, a flange 25 is formed on the outer peripheral end of a cylindrical material by cutting and grinding. Then, a groove cutting tool is inserted into the inside of the material, and an inner circumferential screw groove 21 is formed by cutting and grinding. On the inner peripheral surface 20a of the material, the area other than the inner circumferential screw groove 21 is made into an inner land portion 26. The inner diameter of the inner land portion 26 is uniform. Then, the flange 25 of the material M is held by a holder HD on a stage ST.

[0023] When performing blast processing, as shown in Figure 3, the linear drive unit SU moves the rotation unit RU and the tube BT closer to the stage ST, and the projection port BTO of the tube BT is inserted into the inner side of the material M, and the projection port BTO of the tube BT is positioned opposite the inner surface 20a of the material M.

[0024] Thereafter, as shown in FIG. 4, while the tube BT is rotated around its axis by the rotation unit RU and moved axially by the linear drive unit SU, shot material pumped from the storage tank through the tube BT is sprayed from the projection port BTO to blast the entire circumference and length of the inner surface 20a.

[0025] The shot ejected from the ejection tube BT is sprayed onto the inner circumferential thread groove 21 and the inner land portion 26 on the inner circumferential surface 20a of the blank M2, removing the machining marks formed by the cutting process and forming minute irregularities. The lubricant is retained by these irregularities, forming the nut 20 with excellent lubricity.

[0026] Note that by using a control device (not shown), the rotational movement of the tube BT by the rotation unit RU and the axial movement of the tube BT by the linear drive unit SU can be synchronized and driven to drive the projection port BTO in a spiral shape along the inner thread groove 21 while maintaining the projection port BTO facing the inner thread groove 21. In this way, the shot ejected from the projection port BTO can be caused to collide intensively with the inner thread groove 21, making it possible to reduce the amount of machining of the inner land portion 26 compared to the amount of machining of the inner thread groove 21, thereby shortening the machining time and saving the shot, thereby improving machining efficiency.

[0027] The blow-out port BTO moves relative to the inner peripheral surface 20a of the material M at a constant speed over the entire circumference and length, which prevents the amount of blasting from becoming uneven. When the blow-out port BTO reaches the lower end of the material M, the blasting ends. The blow-out port BTO can also be driven back and forth multiple times. After that, the material M is subjected to post-processing such as heat treatment to complete the nut 20 (FIG. 1).

[0028] Furthermore, the screw shaft 10 and the nut 20, which are manufactured in a separate process, are assembled together, and the balls 30 are then fitted inside, completing the ball screw 1.

[0029] According to the blast processing device of this embodiment, the shot material is projected after the outlet BTO is moved to the inner periphery of the material M by the linear drive unit SU, so that the blast processing is performed only on the inner periphery 20a of the material M, and the blast processing is not performed on, for example, the end faces or outer periphery of the material M to which other components are attached. Therefore, even when cutting or grinding is performed on the end faces or outer periphery of the material M, the surface condition is not deteriorated by collision of the shot material.

[0030] Fig. 5 is a schematic cross-sectional view similar to Fig. 2, showing a blast processing apparatus according to a modified example. In this embodiment, a gripping part CK that grips a tube BT is rotatably held by a fixed rotation unit RU, while a stage ST is attached so as to be movable along an axis L by a fixed linear drive unit SU. Therefore, the axial drive unit SU can move the material M relative to the tube BT along the axial direction, and the rotation unit RU can rotate the projection port BTO of the tube BT relative to the inner peripheral surface of the material M about the axis L.

[0031] Fig. 6 is a schematic cross-sectional view similar to Fig. 2, showing a blast processing apparatus according to another modified example. In this embodiment, a gripping part CK that grips a tube BT is attached so as to be movable along an axis L by a linear drive unit SU, while a stage ST is rotatably held by a fixed rotation drive unit RU. Therefore, the tube BT can be moved along the axial direction relative to the material M by the axis drive unit SU, and the inner peripheral surface of the material M can be rotated around the axis L relative to the projection port BTO of the tube BT by the rotation unit RU.

[0032] Fig. 7 is a schematic cross-sectional view similar to Fig. 2, showing a blast processing apparatus according to yet another modified example. In this embodiment, a gripping part CK for gripping a tube BT is fixed, while a stage ST is held rotatably and movable along an axis L via a fixed rotation drive unit RU and linear drive unit SU. Therefore, the axial drive unit SU can move the material M relative to the tube BT along the axial direction, and the rotation unit RU can rotate the inner peripheral surface of the material M relative to the projection port BTO of the tube BT about the axis L.

[0033] Here, the problems encountered when blasting a nut of a circulating ball screw by applying the above embodiment will be described. Fig. 8 is a schematic cross-sectional view similar to Fig. 2, showing a state in which a nut of a circulating ball screw is blasted using the blasting device according to the first embodiment, but for ease of understanding, hatching of the nut cross-section, the inner peripheral screw groove, the rotating unit, and the linear driving unit are omitted.

[0034] As shown in Fig. 8, an elongated mounting hole 20b for mounting a circulating top 40 (Fig. 1) is formed penetrating the inner and outer periphery on the inner peripheral surface 20a of the nut 20 of the circulating top type ball screw. Since the mounting hole 20b is formed so as to intersect with the inner peripheral screw groove 21, even if the projection port BTO of the tube BT is moved in a spiral shape along the inner peripheral screw groove 21 using the blast processing device according to the first embodiment, it will face the mounting hole 20b at some position.

[0035] In such a case, as shown in Figure 8, the shot ejected from the projection port BTO of the tube BT may pass through the mounting hole 20b and collide with, for example, a flange 25 held by a holder HD of the stage ST. The flange 25 is normally cut or ground as it is the part that is connected to other components, but the collision of the shot may deteriorate the condition of its surface, which may prevent good connection with other components.

[0036] To avoid this, it is sufficient to protect the surface of the flange 25 by applying masking tape or the like to the flange 25 before the blasting process. However, applying masking tape or the like increases costs, and it is also time-consuming to peel off the masking tape or the like after the blasting process. The second embodiment described below can solve this problem.

[0037] [Second embodiment] Fig. 9(a) is a schematic cross-sectional view similar to Fig. 8 showing the blast processing device according to the second embodiment, but hatching etc. are omitted for ease of understanding. Fig. 9(b) is an enlarged view showing the vicinity of the projection port BTO of the tube BT shown in Fig. 9(a).

[0038] In this embodiment, as shown in Fig. 9(b), the axis O of the projection port BTO is arranged to intersect with the axis L of the tube BT at an angle θ2 of 90 degrees with respect to the axis L of the material M. Also, the inner peripheral surface of the tube BT is connected by a smooth curved surface from the side along the axis L to the projection port BTO. The other configurations are the same as those of the first embodiment.

[0039] According to this embodiment, the axis O of the projection port BTO is arranged to intersect with the axis L of the tube BT at θ2=90 degrees, so that when the projection port BTO of the tube BT is opposed to the mounting hole 20b of the nut 20 as shown in FIG. 9(a), the shot material projected from the projection port BTO is ejected from the mounting hole 20b toward the radially outward direction of the nut 20. Since the flange 25 is positioned axially away from the mounting hole 20b, the shot material ejected from the mounting hole 20b does not collide with the flange 25, and deterioration of the machined or ground surface is suppressed. Therefore, the application of masking tape or the like is not required. The angle θ2 is sufficient as long as it is 90 degrees or more and 180 degrees or less (right angle or obtuse angle).

[0040] The present invention is not limited to the above-described embodiment. Any of the components of the above-described embodiment can be modified within the scope of the present invention. Any of the components can be added or omitted in the above-described embodiment. For example, the rotation unit and the linear drive unit used in the blast processing device can be of any type. The present invention is not limited to the circulating ball screw, but can be applied to various ball screws such as a tube type ball screw, a deflector type ball screw, and an end cap type ball screw. [Explanation of symbols]

[0041] 1. Ball screw 10 Screw shaft 11 Outer Circumferential Thread Groove 20 Nut 20a Inner surface 20b Mounting hole 21 Internal thread groove 23 Rolling Path 25 Flange 26 Inner Land Section 30 Ball 40 Circulation Top M Nut Material BTO shot nozzle BT Tube for blowing shot material CK grip part RU Rotating Unit SU linear drive unit ST Stage

Claims

1. A screw shaft having a helical outer peripheral thread groove formed on an outer peripheral surface thereof; A nut is disposed around the screw shaft, and has an inner peripheral surface on which a helical inner peripheral thread groove is formed opposite to the outer peripheral thread groove; A plurality of balls are accommodated in a rolling path formed by the outer peripheral screw groove and the inner peripheral screw groove that face each other; a circulation unit for circulating the plurality of balls in the rolling paths; A processing device for a nut of a ball screw, comprising: A work holding device for holding the nut material; A tube holding device that holds a tube for projecting the shot material; a rotation unit that rotates the work holding device and the tube holding device relatively around an axis of the nut material; A linear drive unit that moves the work holding device and the tube holding device relative to each other along an axis of the nut material; 1. A processing device for a nut of a ball screw, comprising:

2. The axis of the projection port of the tube for projecting the shot material is inclined at an acute angle to the axis of the material.

2. The apparatus for machining a nut of a ball screw according to claim 1.

3. The axis of the projection port of the tube for projecting the shot material is inclined at a right angle or an obtuse angle to the axis of the material.

2. The apparatus for machining a nut of a ball screw according to claim 1.

4. The rotation unit and the linear drive unit are driven in synchronization with each other to move a projection port of the tube through which the shot material is projected in a spiral shape along the inner peripheral screw groove. The processing device for a nut of a ball screw according to any one of claims 1 to 3.

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