JP2001254803A - Ball screw - Google Patents

Abstract

(57) [Problem] To provide a ball screw which is used in a vacuum environment and has low dust generation and excellent durability. A screw shaft (2) having a spiral screw groove (2a) on the outer peripheral surface, and a screw groove (3) corresponding to the screw groove (2a) of the screw shaft (2).
a to the screw shaft 2 via a plurality of balls 4 which are rotatably fitted in a helical ball rolling space formed between the two screw grooves 2a, 3a. And a ball screw nut 3 to be screwed, and at least the screw shaft 2 and the ball screw nut 3 are made of metal.
A lubricating film 6 containing a fluoropolymer having a functional group and PFPE on the raceway surface 2b of the thread groove 2a of the screw shaft 2 and the raceway surface 3b of the thread groove 3a of the ball screw nut 3; did.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer system and a positioning device in a semiconductor manufacturing apparatus, a sputtering apparatus for a liquid crystal, semiconductor, and solar cell manufacturing equipment, a plasma CVD apparatus,
The present invention relates to a ball screw used in an ion implantation apparatus and the like, and more particularly to a low dust generation and excellent durability ball screw suitably used in a vacuum environment.

[0002]

2. Description of the Related Art Generally, a ball screw has a plurality of balls arranged in a spiral space (hereinafter referred to as a ball rolling space) formed between a screw groove of a screw shaft and a screw groove of a ball screw nut. Then, power is transmitted between the screw shaft and the ball screw nut through the rolling circulation of the ball, but the ball is subject to sliding due to the combined force of the rotational force and the axial force. As the ball rolls, rolling friction and sliding friction occur simultaneously at the contact portion between the ball and the two thread grooves forming the ball rolling space.

[0003] Therefore, a lubricant such as grease or solid lubricant is used inside the ball screw, and the lubricant reduces the coefficient of friction between the screw shaft and the ball screw nut and the ball, thereby reducing the ball screw. Improves screw durability (life). However, when grease is used as a lubricant for a ball screw used in a vacuum environment, inconveniences such as deterioration of lubrication performance and contamination of the use environment may occur due to evaporation of grease oil and scattering of the grease itself. .

Therefore, instead of using grease,
At least one of the raceway surfaces of the thread groove of the screw shaft and the thread groove of the ball screw nut and the surface of the ball,
By coating soft metals such as silver and lead, solid lubricants such as carbon and molybdenum disulfide in a film form,
Lubricity was imparted. Also, Japanese Patent Application Laid-Open No. 8-226516
In Japanese Patent Application Laid-Open Publication No. H11-157, a ball screw having a lubricating film having a thickness of 0.2 μm or less made of a fluoropolymer having a functional group and used in a vacuum environment, a clean environment, and a corrosive environment is disclosed. I have.

Further, JP-A-8-4878 discloses that
A ball screw is disclosed in which a part of a plurality of balls is a non-loaded ball made of a PTFE-based polymer material, and further, a crystalline PTFE coating is provided on the surface of the loaded ball.

[0006]

However, in the case of a coating film made of a solid lubricant or the like as described above, the coating film peels off or falls off little by little due to the load caused by the rolling of the ball, and generates dust. was there.
In particular, under high load conditions, the amount of dust increases,
It has been difficult to apply the present invention to a ball screw used in an environment where particles are extremely disliked, such as a ball screw used in a semiconductor manufacturing apparatus or the like.

Further, when the coating film is peeled or dropped as described above, the lubricating action at the portion where the ball and the screw shaft and the ball screw nut roll and slidably contact with each other is reduced. As a result, the metals come into contact with each other, so that they tend to adhere to each other, and wear at the rolling and sliding contact portions is promoted, so that the life of the ball screw is shortened. Was.

Further, since a lubricating film made of a fluorine-containing polymer having a functional group has fluidity, it does not easily peel off or drop off unlike a coating film of a solid lubricant or the like. Therefore, a ball screw having such a lubricating film is less likely to wear than a ball screw having a coating film of a solid lubricant or the like. However, if the balls collide with each other when the balls roll, the rotational directions of the adjacent balls are reversed (reverse operation), so that the relative sliding speed between the balls is twice that of one ball. Large friction force is generated. Therefore, in the ball screw, the contact between the balls has a great effect on the durability, and the life may be shortened.

Further, when the non-loaded ball is made of a PTFE-based polymer material, the life can be expected to be improved by the phase transition, but abrasion of the non-loaded ball may result in discharge of abrasion powder. However, it is difficult to use it in an application requiring a clean environment such as a silicon wafer processing process. An object of the present invention is to solve the problems of the conventional ball screw as described above, and to provide a ball screw which is used in a vacuum environment and has a small amount of dust generation and excellent durability.

[0010]

In order to solve the above-mentioned problems, the present invention has the following arrangement. That is, the ball screw of the present invention has a screw shaft having a spiral screw groove on the outer peripheral surface, and a screw groove corresponding to the screw groove of the screw shaft on the inner peripheral surface, and is formed between the two screw grooves. A ball screw nut screwed into the screw shaft via a plurality of balls that are rollably fitted into the formed spiral space, and at least the screw shaft and the ball screw nut In a ball screw made of metal, at least one of the raceway surface of the thread groove of the screw shaft and the raceway surface of the thread groove of the ball screw nut has a fluorine-containing polymer having a functional group and a perfluoropolyether (PFPE). And a lubricating film containing

[0011] The ball screw having such a configuration has a small amount of dust generation and excellent durability even when used in a vacuum environment. In the ball screw of the present invention, the lubricating film containing a fluoropolymer having a functional group and PFPE is used as a lubricant, and the raceway surface of the thread groove of the screw shaft and the raceway surface of the thread groove of the ball screw nut are formed. By providing at least one of them, the ball screw is lubricated.

Since the lubricating film contains the fluorinated polymer having a functional group and PFPE as described above, it has fluidity. Therefore, even when a relatively large axial load is applied, unlike a coating film of a conventional solid lubricant or the like, the possibility of peeling or dropping due to the load caused by the rolling of the ball is low. The present invention is applicable to a ball screw used in an environment where particles are extremely disliked, such as a ball screw used in a semiconductor manufacturing apparatus or the like.

[0013] Further, it is difficult for the metal to be in a non-lubricated contact state at the portion where the ball screw rolls and slides,
The state where the lubricant is always adhered to the site is maintained.
Therefore, since the possibility of adhesion or abrasion at the site is low, the durability is excellent and the dust generation is low. Further, the rolling resistance of the ball is smaller than that of the conventional coating film, and the ball can be arranged with a certain negative gap between the screw shaft and the ball screw nut. Operation can be performed with high precision.

Fluoropolymer having functional group and PFPE
The thickness of the lubricating film containing 0.3 μm to 2 μm
It is preferred that If it is less than 0.3 μm, a problem occurs in the durability of the ball screw. In other words, since the ball screw has a lower surface roughness of the raceway surface than the rolling bearing, metal contact between the rolling element and the convex portion of the raceway surface easily occurs. Therefore, it is necessary to increase the thickness of the lubricating film accordingly. is there. Also, 2μ
If it exceeds m, there is a problem that the amount of generated dust is large. 2 μm
There is no problem as long as the thickness is less than or equal to 0.
It is preferable to be closer to 3 μm.

The lubricating film in the ball screw of the present invention contains the fluorinated polymer having a functional group and PFPE as described above. A film may be formed, or a two-layer structure including a layer of a fluoropolymer having a functional group and a layer of PFPE may be used. In the latter case, a layer of a fluorine-containing polymer having a functional group is provided on at least one of the raceway surface of the thread groove of the screw shaft and the raceway surface of the thread groove of the ball screw nut, and PFPE of PFPE is provided thereon. It is necessary to have a two-layer structure in which layers are provided. If so, the wettability between the lower layer of the fluoropolymer and the upper layer of PFPE is good.
PE is thinly and uniformly coated, and PFPE is not easily scattered by the rotation of the ball screw (low dust generation). If the metal surface is directly coated with PFPE, it is difficult to uniformly coat the PFPE because the wettability between the metal and the PFPE is poor.

Further, the surface roughness of each raceway surface of the screw groove of the screw shaft and the screw groove of the ball screw nut is preferably 0.05 Ra or less. Then, the lubricity can be further improved, and the durability can be further improved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a ball screw according to the present invention will be described with reference to the drawings. Note that the present invention is not limited to this embodiment. FIG. 1 is a cross-sectional view of a ball screw 1 in which a ball screw nut 3 and a part of a circulator tube 5 are cut away (a screw groove 2).
a, 3a and the ball 4 which are located at the center of the screw shaft 2 and the ball screw nut 3 are not shown). FIG. 2 is an enlarged cross-sectional view showing a portion A of the ball screw 1 in FIG. 1 in an enlarged manner, and further showing a part of the screw shaft 2 and the ball 4 in a cutaway manner.

A ball screw 1 (manufactured by Nippon Seiko Co., Ltd., shaft diameter 15 mm, lead 10 mm) has a screw shaft 2 having a spiral screw groove 2 a on the outer peripheral surface, and a spiral shaft corresponding to the screw groove 2 a of the screw shaft 2. Of the screw shaft 2 and the screw groove 3a of the ball screw nut 3, and is rotatably fitted into a spiral ball rolling space formed by the screw groove 2a of the screw shaft 2 and the screw groove 3a of the ball screw nut 3. A ball screw nut 3 screwed to the screw shaft 2 via a plurality of balls 4 (only some of which are shown), and a circulator tube 5 (ball circulation path).

The circulator tube 5 rolls and circulates the ball 4 by rotation of either the screw shaft 2 or the ball screw nut 3, and is attached to the ball screw nut 3. With such a configuration, the ball 4 rolling in the ball rolling space moves in the ball rolling space, turns around the screw groove 2 a plurality of times, and then picks up at one end of the circulator tube 5. Then, circulation is repeated through the circulator tube 5 and returning to the ball rolling space from the other end.

The cross-sectional shape of the two screw grooves 2a and 3a is a Gothic arch shape, that is, a substantially V-shape formed by combining two arcs having different centers of curvature. This cross-sectional shape is
The shape may be an arc. The screw shaft 2, ball screw nut 3, ball 4, and circulator tube 5 are made of a corrosion-resistant material. The material of the screw shaft 2 and the ball screw nut 3 is, for example, JIS SU
S440C, alloy component: C: 0.65%, Cr: 13.
0% steel material, alloy component: C: 0.45%, Cr: 13.
0%, N: 0.14% of a martensitic stainless steel such as a steel material subjected to an appropriate hardening heat treatment, and precipitation hardening stainless steel SUS630.

The material of the ball 4 is the same steel material as described above.
In addition to cermets such as ceramic materials and cemented carbide
be able to. As a ceramic material, silicon nitride
(Si _ThreeN_Four) As well as alumina (Al
_TwoO_Three), Silicon carbide (SiC), zirconia (ZrO
_Two) Etc. are preferred. In addition, circu
The material of the generator tube 5 is, for example, SUS304 or the like.
Austenitic stainless steel.

Such a ball screw 1 is provided on the outer peripheral surface of the screw shaft 2 including the raceway surface 2b, the inner peripheral surface of the ball screw nut 3 including the raceway surface 3b, the surface of the ball 4, and the inner surface of the circulator tube 5. A lubricating film 6 made of a mixture of a fluorinated polymer having a functional group and PFPE is provided. As the fluorine-containing polymer having a functional group, a fluoropolyether polymer or a polyfluoroalkyl polymer is preferable. Examples of the fluoropolyether polymer include a polymer having a repeating unit represented by the following chemical formula 1 and having a number average molecular weight of 1,000 to 50,000. In addition, this fluoropolyether polymer has a functional group described later on at least one molecular terminal.

[0023]

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Further, as the polyfluoroalkyl polymer, those represented by the following chemical formula 2 can be mentioned. In addition, chemical formula 2
Y is a functional group having a high affinity for a metal, for example, an epoxy group, an amino group, a carboxyl group, a hydroxyl group,
Preferred are a mercapto group, an isocyanate group, a sulfone group, an ester group and the like. As the polyfluoroalkyl polymer, in addition to chemical formula 2, for example, those represented by chemical formulas 3 and 4 can be suitably used.

[0025]

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[0026]

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[0027]

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Such a functional group includes a lubricating film 6 formed on the screw shaft 2.
And when coated on the surface of the ball screw nut 3, it is combined with the metal constituting the screw shaft 2 and the ball screw nut 3, so that a lubricating film 6 strongly bonded to the surface of the screw shaft 2 and the ball screw nut 3 is formed. Is done. In the case of a fluorine-containing polymer having a plurality of functional groups in one molecule, at least one of them may be bonded to a metal.

The above-mentioned fluoropolymers may be used alone or in combination of two or more.
When two or more kinds are used in combination, it is preferable to select a combination (combination of functional groups) of the fluoropolymer so that the functional groups react with each other and the fluoropolymer has a higher molecular weight. . If the fluorinated polymer has a higher molecular weight, a lubricating film 6 having more excellent wear resistance can be obtained.

Specific examples of such a fluorine-containing polymer having a functional group include, for example, Krytox 157FSL, 157FSM, and 157FSH manufactured by DuPont, and Demnum-modified products SA, SH, SY-3, and S manufactured by Daikin Industries, Ltd.
P, Fomblin Z DEAL, Z of Montecatini
DIAC, Z DISCO, Z DOL, Z DOL
TX2000 and the like.

Next, an example of a method for forming the lubricating film 6 will be described. After assembling the ball screw 1 in a completed state, a mixture of a fluorinated polymer having a functional group and PFPE (hereinafter referred to as lubricating oil) is provided at a position where the ball 4 exists between the screw shaft 2 and the ball screw nut 3. A few drops) with a dropper or the like, and by rotating the ball screw 1 several times,
The rolling and sliding contact portions of the screw shaft 2, the ball screw nut 3, the ball 4, and the circulator tube 5 are coated with the lubricating oil in a film form (supply process). This lubricating oil coating
The coating may be performed by spraying, or may be performed by immersing the ball screw 1 in the lubricating oil.
The method of coating the lubricating oil is not particularly limited.

The lubricating oil is, for example, PF
A PE-based S-200 manufactured by Daikin Industries, Ltd., to which 5% of Krytox 157FSH manufactured by DuPont as a fluoropolymer having a functional group is added, is added to a fluorine-based solvent (for example, AK225 manufactured by Asahi Chemical Industry). ) At 2%
And the like are preferably used. Next, the whole of the ball screw 1 coated with the lubricating oil is dried at room temperature, and then heat-treated at 100 to 200 ° C. for 30 minutes in a thermostat.

The process of providing the lubricating film 6 may be repeated several times as necessary, and the lubricating film 6 is finally formed to a thickness of, for example, 0.3 μm or more. This film thickness can be controlled by the concentration of the fluorine-containing polymer having a functional group and PFPE dissolved in the fluorine-based solvent. By such a method, a lubricating film 6 is formed at a suitable thickness on the rolling and sliding contact portions of the components of the ball screw 1 (the screw shaft 2, the ball screw nut 3, the ball 4, and the circulator tube 5). can do.

If the solvent is removed as described above, unnecessary dust generation does not occur when the ball screw 1 is operated. In particular, dust generation and outgassing in the use environment can be suppressed by the final heat treatment. Since the fluorine-containing polymer having a functional group generally has a higher vapor pressure than that of PFPE, it is preferable to use a small amount when the demand for outgassing is severe.

A fluorine-containing polymer having a functional group diluted with a fluorine-based solvent is coated first, and then heated in a constant temperature bath or the like, and the metal as a base material of each of the above-mentioned components is added to the metal-containing polymer. Are reacted with each other to form a fluoropolymer layer having a functional group bonded to a metal.
The lubricating film 6 may have a two-layer structure by coating FPE diluted with a fluorine-based solvent and forming a PFPE layer on the fluorine-containing polymer layer having the functional group.

As described above, the ball screw 1 of the present embodiment is provided with the lubricating film 6 having fluidity, so that even if a relatively large axial load is applied, a conventional coating film of a solid lubricant or the like is applied. In this environment, the amount of dust generated is small because particles are unlikely to be separated or dropped due to the load caused by rolling of the ball, and the particle is extremely disliked, such as a ball screw used in semiconductor manufacturing equipment. It can be applied to a ball screw used below (contributing to an improvement in the yield of semiconductor products).

In addition, it is difficult for the metal to be in a state in which the metal contacts each other without lubrication at a portion where the ball screw rolls and slides.
The state where the lubricant is always adhered to the site is maintained.
Therefore, adhesion and wear are less likely to occur at the site, so that the durability is excellent and the generation of dust is low (not only the generation of dust from the lubricating film 6 but also the generation of dust from each of the constituent elements described above is suppressed). it can).

Furthermore, the rolling resistance of the ball is smaller than that of the conventional coating film, and the ball can be disposed between the screw shaft and the ball screw nut with a certain negative gap. The operation of the ball screw can be made highly accurate. (Examples 1 to 6 and Comparative Examples 1 to 4) Next, for the above-described ball screw, the type of lubricant, the film thickness of the lubricating film, the material of the ball, and the screw groove of the screw shaft and the ball screw nut The results of testing the durability and outgassing properties (out particles) in vacuum by varying the surface roughness of each raceway surface of the screw groove in various ways will be described.

The durability test was performed using the apparatus shown in FIG. That is, the ball screw 30 mounted in the vacuum chamber 40 was rotated by the AC servomotor 41, and the life thereof was evaluated. 3, reference numeral 31 denotes a screw shaft of the ball screw 30, reference numeral 32 denotes a ball screw nut of the ball screw 30, reference numeral 42 denotes a weight for applying an axial load, reference numeral 43 denotes a rotation stop of the ball screw nut 32, reference numeral 44 denotes a magnetic fluid seal. A unit, 45 is an observation window inside the vacuum chamber 40, 46 is a laser type particle counter, and 47 is a dust collecting funnel.

The test conditions are shown below, and the test results are shown in Table 1. Ball screw: shaft diameter 15 mm, lead 10 mm Ball screw material: screw shaft, ball screw nut, SUS304C circulator tube for SUS304 Rotation speed: 1000 rpm Load: axial load (Fa) 120N Stroke: 120 mm Atmosphere: vacuum (10 ^-4) Pa or lower) Environmental temperature: room temperature

[0041]

[Table 1]

As can be seen from Table 1, the ball screws of Examples 1 to 6 had excellent life. In particular, the ball composed of silicon nitride had a very excellent life. In contrast, when the lubricating film was composed of only one of the fluorine-containing polymer having a functional group and PFPE (Comparative Examples 1 and 2), the life of the ball screw was inferior to those of Examples 1 to 6. .

When the thickness of the lubricating film is insufficient (Comparative Example 3), the life is similarly inferior. When the thickness of the lubricating film is excessive (Comparative Example 4), the life is reduced. Although excellent, dust generation was inferior as described later. Regarding the surface roughness of each raceway surface of the thread groove of the screw shaft and the thread groove of the ball screw nut, since the ball screw has a larger slip compared to the bearing, the surface roughness of the raceway surface of the thread groove should be as small as possible. Is preferred. In this embodiment, Ra0.05
In the following cases, the effect of improving the life was recognized.

Next, the dusting test will be described. The dusting test was also performed using the apparatus shown in FIG. Only the portions of the test conditions that differ from those in the durability test are shown below, and the test results are shown in FIG. Rotation speed: 300 rpm Load: Axial load (Fa) 50N Stroke: 200 mm Evaluation of dust generation: 2 × 10 ⁶ Particle diameter when rotated ⁶ times.
The evaluation was based on the number of dust particles having a size of 21 μm or more.

As for the durability, the larger the film thickness, the more advantageous. However, there is an optimum value for the amount of generated dust, and it can be seen from FIG. 4 that the value is 0.24 to 2.0 μm. (Embodiments 7 and 8 and Comparative Example 5) Next, a ball screw which can prevent a reverse operation of adjacent balls by inserting a spacer between the balls will be described with reference to FIG. However, except for having the spacer 7,
Since the configuration is substantially the same as that of the ball screw 1 of the above-described embodiment, only different portions will be described, and description of the same portions will be omitted. In addition, for convenience of description, the description will be made using the reference numerals in FIGS.

FIG. 5 shows a plurality of balls 4 rotatably fitted in a helical ball rolling space formed by a screw groove 2a of a screw shaft 2 and a screw groove 3a of a ball screw nut 3.
FIG. 4 is a view for explaining an arrangement form with a spacer 7 interposed between the balls 4, and is a partial schematic view of a screw groove 2 a of the screw shaft 2 as viewed from a direction perpendicular to the screw shaft 2. Note that the spacer 7 and a part of the ball 4 are cut away, and the illustration of the ball screw nut 3 is omitted.

On the raceway surface 2b of the screw groove 2a of the screw shaft 2 and the raceway surface 3b of the screw groove 3a of the ball screw nut 3, a lubricating film 6 containing a fluorine-containing polymer having a functional group is provided. Further, a spacer 7 is interposed between the balls 4 as shown in FIG. 5 so that the balls 4 do not directly contact each other. That is, since the spacers 7 are interposed between the balls 4 so that the balls 4 do not directly contact each other, the rotation directions of the adjacent balls 4 are not reversed (the adjacent balls 4 are not rotated). Reverse operation is prevented)
Therefore, a large frictional force is not generated and the ball screw has a long life.

The shape and size of the spacer 7 are as follows.
Screw groove 2a of screw shaft 2 and screw groove 3 of ball screw nut 3
a) and a shape that can be arranged in the ball rolling space formed by the ball 4a, the contact surface with the ball 4 is a curved surface having substantially the same shape as the spherical surface of the ball 4, There is no particular limitation as long as the shape is such that it is interposed.

The material of the spacer 7 is resin,
Metals, sintered products and the like are preferably used. Further, the spacer 7 may be formed of a porous body and impregnated with a lubricant. The lubricating film 6 has a raceway surface 2b of the thread groove 2a of the screw shaft 2 and a raceway surface 3b of the thread groove 3a of the ball screw nut 3.
b, at least one of the surface of the ball 4 and the surface of the spacer 7.

As the fluorine-containing polymer having a functional group,
Those exemplified in the above embodiment are preferably used. More specifically, for example, the brand name of FONBLIN Y Standard of Montecatini Co.,
Fomblin emulsion (FE20, EM04, etc.) or Fomblin Z derivative (FONBLIN Z)
DEAL, FONBLIN Z DIAC, FONBL
IN Z DISOC, FONBLIN Z DOL,
FONBLIN Z DOLTX2000, FONBL
INZ TETRAOL, etc.), 157 from DuPont
FSL, 157FSM, 157FSH and the like are preferably used.

The fluorine-containing polymer having a functional group is
It may be used by mixing with perfluoropolyether (PFPE) or a derivative thereof. Next, the results of a durability test of a ball screw provided with such a spacer 7 will be described. The test conditions are shown below. Ball screw: shaft diameter 15 mm, lead 10 mm Rotation speed: 1000 rpm Load: axial load 30 N Stroke: 200 mm Atmosphere: vacuum (on the order of 10 ^-5 Pa) In this test, the spacer 7 is made of resin (Example 7) or metal (implemented). Example 8), the resin spacer was made by injection molding of 6,6 nylon resin, and the metal spacer was SUS3.
It was manufactured by pressing a steel plate made of 04. The resin spacer may be made of a polyimide resin.

The resin spacer is not covered with the lubricating film 6,
The lubricating film 6 was used to cover the metal spacer. The lubricating film 6 is formed by immersing the screw shaft 2, the ball screw nut 3, the circulator tube 4, and the ball 4 in a lubricating oil containing a fluorine-containing polymer having a functional group, and drying at room temperature.
The coating was performed by performing a heat treatment at 100 to 200 ° C. for 30 minutes in a constant temperature bath and baking. The lubricating film 6 at this time
Was 1 μm.

The lubricating oil is, for example, PF
A PE-based S-200 manufactured by Daikin Industries, Ltd., to which 5% of Krytox 157FSH manufactured by DuPont as a fluoropolymer having a functional group is added, is added to a fluorine-based solvent (for example, AK225 manufactured by Asahi Chemical Industry). ) At 5%
And the like are preferably used. The test results are shown in FIG. The test was performed for each sample at two points, and FIG. 6 shows the results.

As can be seen from FIG. 6, the ball screws provided with the spacers 7 (Examples 7 and 8) were superior in durability to those without the spacers 7 (Comparative Example 5). When the metal spacer and the resin spacer were compared, the durability was almost the same level. As described above, the ball screw in which the spacers 7 are interposed between the balls 4 can prevent the balls 4 from directly contacting each other.
Since the reverse operation of each other can be prevented, the life of the ball screw can be extended.

[0055]

As described above, the ball screw of the present invention
Used in a vacuum environment with low dust generation and excellent durability.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a ball screw of the present invention.

FIG. 2 is an enlarged sectional view of a portion A in FIG.

FIG. 3 is a schematic view of a testing machine for testing durability and dust generation of a ball screw.

FIG. 4 is a graph showing a correlation between the thickness of a lubricating film containing a fluorinated polymer having a functional group and PFPE and the amount of dust generation.

FIG. 5 is a partially enlarged view illustrating an arrangement of balls and spacers.

FIG. 6 is a graph showing a correlation between the presence or absence of a spacer and the life of a ball screw.

[Explanation of symbols]

 Reference Signs List 1 ball screw 2 screw shaft 2a screw groove 2b raceway surface 3 ball screw nut 3a screw groove 3b raceway surface 4 ball 5 circulator tube 6 lubrication film

Claims (1)

[Claims] 1. A screw shaft having a spiral screw groove on an outer peripheral surface and a screw groove corresponding to the screw groove of the screw shaft on an inner peripheral surface, and a spiral formed between the two screw grooves. A ball screw nut screwed to the screw shaft via a plurality of balls rotatably fitted in the space of the shape,
At least one of the raceway surface of the thread groove of the screw shaft and the raceway surface of the thread groove of the ball screw nut, wherein at least one of the raceway surface of the thread groove of the screw shaft and the raceway surface of the thread groove of the ball screw nut has a functional group. Polymer and perfluoropolyether (PF
And a lubricating film containing (PE).