JP2005127379A - Ball screw unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw unit capable of reducing the level of noises that occurs at the circulation of a ball. <P>SOLUTION: A ball circulation member 17 formed by injection-molding a resin material having a melt type liquid crystal polymer as the main component is used as a ball circulation member for circulating a ball 15. Since the inner structure of the ball circulation member 17 is multi-layered, vibration caused by a collision with the ball is attenuated between the layers of the multi-layered structure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an improvement of a ball screw device used as a machine part for converting a rotational motion into a linear motion, for example, in a feeding device of a machine tool.

  2. Description of the Related Art Conventionally, in a machine tool feeder or the like, for example, a ball screw device as shown in FIG. 11 is used as a machine part for converting a rotary motion of a motor or the like into a linear motion. This ball screw device includes a screw shaft 1 and a nut 2 having an inner diameter larger than the outer diameter of the screw shaft 1, and a ball screw groove 3 is formed at one end of the screw shaft 1 on the outer peripheral surface of the screw shaft 1. It is formed from the part to the other end part. The ball screw groove 3 faces a ball screw groove 4 formed on the inner peripheral surface of the nut 2, and a large number of balls 5 are provided between the ball screw groove 3 and the ball screw groove 4 so as to be able to roll. It has been. These balls 5 roll along a spiral ball rolling path 6 formed between the ball screw grooves 3 and 4 with the rotational movement of the screw shaft 1 or the nut 2. When the rolling path 6 rolls, the nut 2 moves in a relative linear motion in the axial direction of the screw shaft 1.

Since such a ball screw device includes a ball circulation tube 7 for infinite circulation of the ball 5, the nut 2 can be continuously moved in a relative linear motion in the axial direction of the screw shaft 1. It had a problem. That is, in the above-described ball screw device, the ball 5 collides with the tongue portion of the ball circulation tube 7 made of metal and is rolled up into the ball circulation tube 7. For this reason, there is a problem that noise or the like is generated when the ball 5 collides with the tongue portion of the ball circulation tube 7.
The present invention has been made paying attention to such problems, and an object of the present invention is to provide a ball screw device capable of reducing the noise level generated when a ball is circulated.

  In order to solve this problem, the invention according to claim 1 of the present invention has a screw shaft having a ball screw groove on the outer peripheral surface and a ball screw groove facing the ball screw groove of the screw shaft on the inner peripheral surface. A plurality of balls that roll with a rotational movement of the screw shaft or the nut and a ball rolling path formed between the screw shaft and the ball screw groove of the nut, and the ball rolling path. A ball screw device including a ball circulating member for scooping and circulating the ball to the outside of the nut, wherein the ball circulating member positions the ball on a center track circle of the ball And a ball scooping portion that scoops up along the tangent line of the central orbit circle, and is formed by injection molding a material mainly composed of a molten liquid crystal polymer.

  According to a second aspect of the present invention, a screw shaft having a ball screw groove on an outer peripheral surface, a nut having a ball screw groove facing the ball screw groove of the screw shaft on an inner peripheral surface, the screw shaft, and the A large number of balls that are provided to freely roll between the ball screw grooves of the nut, and a tongue portion that is disposed at both end portions in the axial direction of the nut and scoops up the ball from the ball screw groove of the nut. A ball screw device comprising a pair of end deflectors having a ball return guide path for guiding the raised balls to a ball return path formed inside the nut, wherein the end deflector is composed mainly of a melt-type liquid crystal polymer. The material is formed by injection molding.

According to a third aspect of the present invention, in the ball screw device according to the first or second aspect, the material having the molten liquid crystal polymer as a main component is at least one of glass fiber, carbon fiber, and potassium titanate whisker. It is characterized by including the filler.
According to a fourth aspect of the present invention, in the ball screw device according to the third aspect, the content of the filler is 10 to 40 wt%.

  In the ball screw device according to the first aspect of the present invention, the ball rolling on the ball rolling path is tangent to the center orbit circle from the ball scooping point positioned on the center orbit circle of the ball by the ball scooping portion of the ball circulation member. Can be crawl along. As a result, the ball can be scooped up without colliding with the tongue or the like, so that generation of noise or the like can be suppressed. Further, since the ball circulation member is formed by injection molding a material mainly composed of a melt-type liquid crystal polymer, the internal structure of the ball circulation member becomes a multilayer structure. Thereby, when the vibration generated by the collision with the ball is transmitted through the inside of the ball circulation member, it is attenuated by the multilayer structure, so that the noise of the entire ball screw device can be reduced.

In the ball screw device according to the second aspect of the present invention, the end deflector is formed by injection molding a material mainly composed of a melt-type liquid crystal polymer, so that the internal structure of the end deflector has a multilayer structure. As a result, the vibration generated by the collision with the ball is attenuated by the multilayer structure when it propagates inside the end deflector, so that the noise of the entire ball screw device can be reduced.
In the ball screw device according to the third and fourth aspects of the invention, in addition to the above-described effects, the strength, wear resistance, and impact resistance are improved, the damage due to the collision with the ball is prevented, and the low resistance for a long time. Noise reduction can be achieved.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
In FIG. 1, reference numeral 11 denotes a screw shaft of the ball screw device according to the first embodiment of the present invention, and 12 denotes a nut having an inner diameter larger than the outer diameter of the screw shaft 11. The ball screw groove 13 is formed from one end of the screw shaft 11 to the other end. The ball screw groove 13 faces a ball screw groove 14 (see FIG. 2) formed on the inner peripheral surface of the nut 12, and a large number of balls 15 are interposed between the ball screw groove 13 and the ball screw groove 14. It is provided to roll freely. These balls 15 roll on a spiral ball rolling path 16 (see FIG. 3) formed between the ball screw grooves 13 and 14 as the screw shaft 11 or the nut 12 rotates. A ball circulating member 17 for infinitely circulating the ball 15 is assembled to the nut 12.

  The ball circulating member 17 is fixed to a flat circulating member mounting surface 18 (see FIGS. 1 and 4) formed on the outer diameter surface of the nut 12 by set screws 19 and 20 (FIGS. 6 and 7). A plate-like main body portion 171 having a cylindrical shape, and cylindrical leg portions 172 and 173 projecting from a fixing surface 171a of the main body portion 171. The main body portion 171 and the leg portions 172 and 173 are formed inside the main body portion 171 and the leg portions 172 and 173. Is formed with a ball return passage 174 communicating with the ball rolling path 16. In addition, ball circulation holes 21 and 22 (see FIG. 4) that fit into the leg portions 172 and 173 of the ball circulation member 17 are formed in the circulation member mounting surface 18 of the nut 12.

  The leg portions 172 and 173 of the ball circulation member 17 have a ball scooping portion 176 (see FIG. 6) at the tip, and therefore the ball 15 rolling on the ball rolling path 16 is as shown in FIG. Further, the ball scooping part 176 of the leg 172 or 173 is scooped up along the tangent line T of the central orbit circle BCD from the ball scooping point P located on the central orbit circle BCD of the ball 15.

  The ball circulation member 17 is formed by injection molding. As the injection molding material, a resin material mainly composed of a melt type liquid crystal polymer represented by the following general formulas (1) to (3) is used. Yes. Examples of specific material names of the general formula (1) include “Econol (trade name)” manufactured by Sumitomo Chemical Co., Ltd., “Zider (trade name)” manufactured by Nippon Petrochemical Co., Ltd. Can do. As a specific material name of the general formula (2), “Vectra (trade name)” manufactured by Polyplastics Co., Ltd. can be exemplified, and as a specific material name of the general formula (3), Mitsubishi Chemical ( “Novacute (trade name)” manufactured by Co., Ltd., “rod run ((trade name))” manufactured by Unitika Ltd., and the like can be exemplified.

  As described above, the main body portion 171 having the fixing surface 171a for fixing the ball circulating member 17 to the circulating member mounting surface 19 of the nut 12, and the columnar leg portions 172 protruding from the fixing surface 171a of the main body portion 171. The ball scooping portion 176 that scoops up the ball 15 from the ball scooping point P located on the center orbit circle BCD along the tangent line T of the center orbit circle BCD is formed on the leg portion 172 of the ball circulation member 17. , 173, the ball 15 rolling on the ball rolling path 16 is positioned on the center orbit circle BCD of the ball 15 by the ball scooping part 176 of the leg 172 or 173. It is scooped up from P along the tangent line T of the center orbit circle BCD. Thereby, since the ball 15 can be scooped up without colliding with the tongue or the like, it is possible to suppress the generation of noise and the like.

Next, the reason why a resin material mainly composed of a melt type liquid crystal polymer is used as the injection molding material for the ball circulation member 17 will be described.
Molten liquid crystal polymer (hereinafter referred to as “liquid crystal polymer”) has a rigid molecule, maintains a crystal structure substantially even in a molten state, has little entanglement, and exhibits orientation by shearing during flow. That is, when injection molding is performed, the shear rate is large near the mold, and the shear rate is small at the center of the mold cavity. Due to the difference in shear rate, the resin material containing the liquid crystal polymer as a main component has a surface portion and an internal form (morphology) different as the internal structure, and has a multilayer structure despite being the same material. This is because when the liquid crystal polymer passes through the mold at a high speed during injection molding, a velocity gradient is generated in the flowing liquid crystal polymer from the mold wall surface toward the center in the thickness direction of the fluidized portion, and the liquid crystal polymer is aligned. Because.

Therefore, by using a resin material mainly composed of a melt-type liquid crystal polymer as an injection molding material for the ball circulation member 17, the internal structure of the ball circulation member 17 has a multilayer structure, and vibration generated by collision with the ball 15 is generated. Since it is attenuated by the multilayer structure when traveling inside the ball circulating member 17, the noise of the entire ball screw device can be reduced.
Next, a second embodiment of the present invention will be described with reference to FIGS.
In FIG. 8, reference numeral 31 denotes a screw shaft of a ball screw device according to the second embodiment of the present invention, and 32 denotes a nut having an inner diameter larger than the outer diameter of the screw shaft 31. A ball screw groove 33 is formed from one end of the screw shaft 31 to the other end. The ball screw groove 33 faces a ball screw groove 34 formed on the inner peripheral surface of the nut 32, and a large number of balls 35 are provided between the ball screw groove 33 and the ball screw groove 34 so as to be able to roll. It has been.

  The ball 35 rolls along a spiral ball rolling path 36 formed between the ball screw grooves 33 and 34 as the screw shaft 31 or the nut 32 rotates. A ball return passage 36 for infinite circulation of the ball 36 rolling on the ball rolling path 36 is formed. The ball return passage 36 is open to both end surfaces of the nut 32, and end deflectors 37 are incorporated in both end portions of the nut 32 in the axial direction.

  The end deflector 37 has a tongue portion 37 a (see FIGS. 9 and 10), and the ball 35 rolling on the ball screw grooves 33 and 34 of the screw shaft 31 and the nut 32 is formed on the tongue portion 37 a of the end deflector 37. As a result, the ball screw groove 34 of the nut 32 can be scooped up. The end deflector 37 has a ball return guide path 37b (see FIGS. 8 and 10), and the ball 35 scooped up from the ball screw groove 34 of the nut 32 by the tongue portion 37a is the ball of the end deflector 37. The ball is guided to the ball return passage 36 of the nut 32 by the return guide path 37b so as to circulate infinitely.

The end deflector 37 is formed by injection molding. As the injection molding material, a resin material whose main component is the melt type liquid crystal polymer represented by the general formulas (1) to (3) is used. .
As described above, the end deflector 37 is formed by injection molding a resin material mainly composed of a melt-type liquid crystal polymer, so that the internal structure of the end deflector 37 has a multilayer structure, and vibrations generated by collision with the ball 35 are generated. Since it is attenuated by the multilayer structure when traveling inside the end deflector 37, the noise of the entire ball screw device can be reduced.

The present invention is not limited to the embodiment described above. For example, an injection molding material for the ball circulation member 17 or the end deflector 37 is obtained by mixing a resin material mainly composed of a melt-type liquid crystal polymer with a reinforcing material such as glass fiber, carbon fiber, or potassium titanate Whistler as a filler. It may be used. Among these, carbon fiber and potassium titanate Whistler are particularly preferable because the filler itself has vibration damping properties. By mixing these fillers, strength, wear resistance, and impact resistance are improved, damage due to collision with a ball or the like is prevented, and good noise reduction can be achieved over a long period of time.
In addition, since the improvement of the above-mentioned strength etc. is not seen so much as the mixing amount of the filler is less than 10 wt%, and if it exceeds 40 wt%, the moldability may be lowered, it is preferably 10 to 40 wt%. Is preferably 20 to 30 wt%.
Next, examples of the present invention will be described with reference to Tables 1 and 2.

In Table 1, Example 1 is an example using “Vectra A950 (trade name): unfilled great” manufactured by Polyplastics Co., Ltd. as an injection molding material of the ball circulating member 17, and Example 2 is an example of the ball circulating member 17. This is an example using “Vectra B230 (trade name): carbon fiber 30 wt% containing great” manufactured by Polyplastics Co., Ltd. as an injection molding material. Comparative Example 1 is a comparative example using polyacetal resin as an injection molding material for the ball circulation member 17. The ball screw device of Examples 1 and 2 and the ball screw device of Comparative Example 1 have a shaft diameter of 25 mm and lead. : The noise level was measured and compared under the test conditions of 25 mm and the rotation speed: 2500 min ⁻¹ .
As shown in Table 1, it can be seen that the noise levels of the ball screw devices of Examples 1 and 2 are lower than that of the ball screw device of Comparative Example 1. Further, comparing Example 1 and Example 2, it can be seen that the noise level is further reduced in Example 2 in which a melt type liquid crystal polymer containing carbon fiber is used as the injection molding material of the ball circulation member 17.

In Table 2, Example 3 is an example using “Vectra A950 (trade name): unfilled great” manufactured by Polyplastics Co., Ltd. as an injection molding material of the end deflector 37, and Example 4 is an injection molding of the end deflector 37. This is an example using “Vectra B230 (trade name): carbon fiber containing 30 wt% great” manufactured by Polyplastics Co., Ltd. as a material. Comparative Example 2 is a comparative example using polyacetal resin as an injection molding material for the end deflector 37. For the ball screw devices of Examples 3 and 4 and the ball screw device of Comparative Example 2, the shaft diameter: 36 mm, the lead: The noise level was measured and compared under the test conditions of 25 mm and rotation speed: 1500 min ⁻¹ .
As shown in Table 2, it can be seen that the noise levels of the ball screw devices of Examples 3 and 4 are lower than those of the ball screw device of Comparative Example 2. Further, comparing Example 3 and Example 4, it can be seen that the noise level is further reduced in Example 4 in which a melt type liquid crystal polymer containing carbon fiber is used as the injection molding material of the end deflector 37.

1 is a plan view of a ball screw device according to a first embodiment of the present invention. It is II-II sectional drawing of FIG. FIG. 3 is a sectional view taken along line III-III in FIG. 1. It is a top view of the nut shown in FIG. It is a top view of the ball | bowl circulation member shown in FIG. It is a side view of the ball | bowl circulation member shown in FIG. It is a front view of the ball | bowl circulation member shown in FIG. It is sectional drawing of the ball screw apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the nut and end deflector of the ball screw apparatus which concern on the 2nd Embodiment of this invention. It is a perspective view of the end deflector shown in FIG. It is a figure which shows an example of the conventional ball screw apparatus.

Explanation of symbols

1,11,31 Screw shaft 2,12,32 Nut 3,13,33 Ball screw groove 4,14,34 Ball screw groove 5,15,35 Ball 6,16,36 Ball rolling path 7 Ball circulation tube 17 Ball Circulating member 171 Main body portion 172, 173 Leg portion 175 Ball return passage 176 Ball scooping portion 18 Circulating member mounting surface 19, 20 Set screw 21, 22 Ball circulation hole 37 End deflector 37a Tongue portion 37b Ball return guide passage

Claims (4)

  A screw shaft having a ball screw groove on the outer peripheral surface, a nut having a ball screw groove facing the ball screw groove on the screw shaft on the inner peripheral surface, and a ball roller formed between the screw shaft and the ball screw groove of the nut. A number of balls that roll along the rotational path of the screw shaft or the nut along with the rotational movement of the nut, and a ball circulation member that circulates the balls rolling along the ball rolling path outside the nut The ball circulating device includes a ball scooping unit that scoops up the ball from a ball scooping point located on a center trajectory circle of the ball along a tangent line of the central trajectory circle. And a ball screw device formed by injection molding a material mainly composed of a melt-type liquid crystal polymer.   A screw shaft having a ball screw groove on the outer peripheral surface, a nut having a ball screw groove facing the ball screw groove of the screw shaft on the inner peripheral surface, and rolling freely between both screw screw shafts of the screw shaft and the nut. A large number of balls provided on each of the nuts, and a tongue portion that is disposed at both axial end portions of the nut and scoops up the ball from the ball screw groove of the nut, and a ball scooped up by the tongue portion is formed inside the nut. A ball screw device including a pair of end deflectors having a ball return guide path for guiding to the ball return path, wherein the end deflector is formed by injection molding a material mainly composed of a molten liquid crystal polymer. A ball screw device characterized by comprising:   3. The ball screw device according to claim 1, wherein the material mainly composed of the molten liquid crystal polymer contains at least one filler selected from glass fiber, carbon fiber, and potassium titanate whisker.   The ball screw device according to claim 3, wherein a content of the filler is 10 to 40 wt%.

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