JP2009030628A - Rectilinear drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rectilinear drive device having no harmful substance and hard to cause rusting. <P>SOLUTION: This rectilinear drive device comprises a guide rail 1 having an axially extending rolling element rolling groove 10, a slider 2 having a rolling element rolling groove 11 opposed to the rolling element rolling groove 10, and a plurality of rolling elements 3 rollingly charged in a rolling element rolling passage 14 formed by the rolling element rolling grooves 10, 11. The slider 2 is rectilinearly moved through the rolling of the rolling elements 3 in the axial direction along the guide rail 1. At least one of the guide rail 1 and the slider 2 is coated, at least partly on the surface thereof, with a rust preventive film containing zinc, tin, and triiron tetroxide. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a linear motion device such as a ball screw, a linear motion guide device, a linear motion bearing, and a ball spline.

The members constituting the linear motion device as described above are usually made of a steel material such as carburized steel (equivalent to SCR 420) or steel equivalent to SAE 1055, S45C, S58C, and on the surface for rust prevention. Plating is performed (for example, refer to Patent Documents 1 and 2).
Examples of plating methods employed in this case include hard chrome plating, electroless nickel plating, and low-temperature electrolytic chrome plating. In particular, when the linear motion device is used in an optical mechanical device, the surface of the member is required not to reflect light irregularly, and therefore, black low temperature electrolytic chrome plating is employed.

Further, Patent Document 3 discloses a method for imparting rust prevention while maintaining the mounting accuracy. In other words, low-temperature electrolytic chromium plating and fluororesin coating are applied to coat the rust-preventive layer and then grinding is performed on the reference surface and raceway surface, or low-temperature electrolysis is performed after grinding is performed on the reference surface and raceway surface. In this method, the rust prevention layer is coated by performing chromium plating and fluororesin coating treatment, and further, pressure is applied to press the rust prevention layer.
JP-A-1-96394 JP 2005-195165 A JP-A-6-66319

However, low-temperature electrolytic chrome plating uses hexavalent chrome, which is prohibited by the RoHS directive, and has a problem that it remains in the product. In addition, electroless nickel plating has been pointed out for problems related to environmentally hazardous substances such as the inclusion of lead compounds.
Furthermore, another chemical plating has a problem that the mounting accuracy of the rolling sliding member is lowered because a plating layer having a thickness of several μm is formed. If the plating layer is thin, cracks and bits are likely to be generated in the plating layer, resulting in insufficient rust prevention. If the plating layer is thick, it is easily peeled off when a surface pressure is applied by rolling of the rolling elements. Although chemical plating has these problems, it is often used as a rust-proofing treatment for rolling and sliding members because the rolling and sliding members are required to have rust prevention properties.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems of the prior art and to provide a linear motion device in which rust is not easily generated in addition to containing no harmful substances.

  In order to solve the above problems, the present invention has the following configuration. That is, the linear motion device according to claim 1 of the present invention includes a first member having a raceway surface extending in the axial direction, a second member having a raceway surface facing the raceway surface of the first member, and both the raceways. A plurality of rolling elements arranged between the surfaces so as to be freely rollable, and the first member and the second member move relative to each other in the axial direction through the rolling of the rolling elements. In the linear motion device, at least one of the first member and the second member is such that at least a part of the surface thereof is coated with a rust-preventing film containing zinc, tin, and triiron tetroxide. Features.

The linear motion device according to claim 2 of the present invention is the linear motion device according to claim 1, wherein the coating amount of the rust preventive coating is 0.3 g / m ² or more and less than 3 g / m ^2. Features.
The present invention can be applied to various linear motion devices. For example, a ball screw, a linear motion guide device, a linear motion bearing and the like. The first member and the second member in the present invention are a screw shaft and a nut when the linear motion device is a ball screw, a guide rail and a slider when the linear motion guide device is the same, and a linear motion bearing. Means a shaft and an outer cylinder, respectively.

  In addition to containing no harmful substances, the linear motion device of the present invention is less susceptible to rust.

An embodiment of a linear motion device according to the present invention will be described in detail with reference to the drawings.
[First embodiment]
FIG. 1 is a perspective view showing a linear motion guide device that is an embodiment of the linear motion device according to the present invention, and FIG. 2 is a front view of the linear motion guide device of FIG. The end cap is omitted in the figure).
On a guide rail 1 having a substantially square cross section extending in the axial direction, a slider 2 having a substantially U-shaped cross section is mounted so as to be capable of relative linear movement in the axial direction. The guide rail 1 and the slider 2 are made of steel.

  Rolling element rolling grooves 10 and 10 each formed of a concave groove having a substantially arc-shaped cross section extending in the axial direction are formed at a ridge line portion where the upper surface of the guide rail 1 and both side surfaces 1a and 1a intersect. Rolling element rolling grooves 10 and 10 each having a substantially semicircular cross section extending in the axial direction are formed at intermediate positions of both side surfaces 1a and 1a of the guide rail 1. The inner surface of the rolling element rolling groove 10 forms a raceway surface on which a rolling element 3 described later rolls.

The slider 2 includes a slider body 2A and end caps 2B and 2B that are detachably attached to both ends in the axial direction. Further, both ends of the slider 2 (end surfaces of the end caps 2B). ) Are provided with side seals 5 and 5 for sealing the opening of the gap between the guide rail 1 and the slider 2.
Furthermore, rolling element rolling grooves 11 and 11 having a substantially semicircular cross section facing the rolling element rolling grooves 10 and 10 of the guide rail 1 are formed at the corners of the inner surfaces of both sleeve portions 6 and 6 of the slider body 2A. Formed at the center of the inner surface of the sleeves 6 and 6 are rolling element rolling grooves 11 and 11 having a substantially semicircular cross section facing the rolling element rolling grooves 10 and 10 of the guide rail 1. Yes. The inner surface of the rolling element rolling groove 11 forms a raceway surface on which a rolling element 3 described later rolls.

  The rolling element rolling grooves 10, 10, 10, 10 of the guide rail 1 and the rolling element rolling grooves 11, 11, 11, 11 of both sleeve portions 6, 6 have a substantially circular cross section. 14, 14, 14, and 14 are formed, and these rolling element rolling paths 14 extend in the axial direction. The number of rolling element rolling grooves 10 and 11 provided in the guide rail 1 and the slider 2 is not limited to two rows on one side, and may be one row on one side or three rows or more, for example. Moreover, the cross-sectional shape of the rolling element rolling grooves 10 and 11 may be an arc shape formed of a single arc as described above, but is substantially V-shaped (Gothic arc shape) formed by combining two arcs having different centers of curvature. Groove).

Furthermore, the slider 2 is formed of a through-hole having a circular cross-section that penetrates in the axial direction in parallel to the rolling element rolling path 14 at the upper and lower portions of the thick portions of the sleeve portions 6 and 6 of the slider body 2A. A moving body return path 13, 13, 13, 13 is provided.
On the other hand, although not shown, the end caps 2B and 2B having a substantially U-shaped cross section have a rolling element rolling path 14 and a rolling element return path parallel to the rolling element rolling path 14 on the contact surface (back surface) with the slider body 2A. The rolling element rolling path 14, the rolling element return path 13, and the curved paths at both ends form a substantially annular rolling element circulation path. . In this rolling element circulation path, a large number of rolling elements (balls) 3 made of, for example, steel balls are loaded so as to freely roll.

When the slider 2 assembled to the guide rail 1 is moved in the axial direction along the guide rail 1, the rolling element 3 loaded in the rolling element rolling path 14 rolls in the rolling element rolling path 14. It moves in the same direction as the slider 2 with respect to the guide rail 1 while moving. When the rolling element 3 reaches one end of the rolling element rolling path 14, it is scooped up from the rolling element rolling path 14 by the tongue provided in the end cap 2B and sent to the curved path.
The rolling element 3 having entered the curved path makes a U-turn and is introduced into the rolling element return path 13, and reaches the opposite curved path through the rolling element return path 13. Here, the U-turn is performed again to return to the rolling element rolling path 14, and the circulation in the rolling element circulation path is repeated infinitely.

  At least one of the guide rail 1 and the slider 2 of such a linear motion guide device is coated with a rust preventive film (not shown) containing zinc, tin, and triiron tetroxide on at least a part of its surface. ing. Therefore, the guide rail 1 and the slider 2 are not easily rusted. If at least part of the surface is coated with a rust preventive film, the effect of suppressing rusting can be obtained, but in order to give better rust preventive properties, the entire surface should be coated with a rust preventive film. Is preferred. Moreover, since this rust preventive film does not contain a harmful substance, there is no possibility that the environment around the linear motion guide device is contaminated with the harmful substance.

  Since zinc has a redox potential lower than that of steel (ie, it is a base metal rather than steel), zinc is selectively oxidized by local cell action between different metals. That is, rusting and corrosion of the guide rail 1 and the slider 2 made of steel are suppressed by the self-sacrificial anticorrosive action. In addition, since a self-sacrificial anticorrosive action can be obtained if the metal is baser than steel, aluminum, vanadium, bismuth, or the like can be used instead of zinc.

  In addition, since tin has a higher oxidation-reduction potential than steel (that is, it is a noble metal than steel), it has an action of slowing down the local battery action. Therefore, oxidation and elution of zinc are controlled, and rust prevention is maintained for a long period. In addition, since the above effects can be obtained if the metal is nobler than steel, other types of metals nobler than steel may be used instead of tin. In particular, copper, chromium, and the like that easily form a passivity (becomes inactive by changing to an oxide) are preferable, but tin that is not a harmful substance is most preferable.

Furthermore, since the anticorrosive film is black due to triiron tetroxide, it does not diffusely reflect light. Therefore, the linear motion guide device can be used for the optical system device. In addition, it is possible to form a black rust preventive film even if iron oxide, copper sulfide, copper oxide, or the like is used instead of triiron tetroxide.
The coating amount of the rust preventive coating is preferably 0.3 g / m ² or more and less than 3 g / m ² . If it is less than 0.3 g / m ² , the coating amount is too small and the rust prevention property may be insufficient. On the other hand, if it is 3 g / m ² or more, the rust-proof coating is easily peeled off. In addition, when this coating amount is converted into the thickness of the antirust coating, it is 0.04 μm or more and less than 0.43 μm.

  The method for coating the anticorrosive film is not particularly limited, but powder projection is preferred. That is, it is good to inject | pour each powder of zinc, tin, and ferric tetroxide on the surface of the guide rail 1 and the slider 2, and to form a rust prevention film. If a rust preventive film is coated by such a method, a film having almost no pinholes or cracks can be formed, so that a rust preventive film having excellent rust preventive properties can be obtained with a small amount of coating. The spraying pressure of the powder is preferably 0.2 MPa or more and 0.7 MPa or less, and the spraying time is preferably 5 minutes or more and 30 minutes or less.

  When projecting, the zinc powder and the tin powder may be sprayed separately or simultaneously. At this time, the triiron tetroxide powder is preferably mixed with at least one of zinc powder and tin powder. However, if zinc powder is sprayed to form a zinc coating, then tin powder is sprayed onto the coating to form a tin coating, and then a two-layer anticorrosive coating is formed. It is possible to slow down the speed. Moreover, if zinc powder and tin powder are mixed and sprayed, a rust preventive film made of an alloy of zinc and tin can be formed. In order to form a more uniform alloy film, it is preferable to spray a powder of an alloy of zinc and tin.

  In addition, when a linear motion guide apparatus is used in an acidic atmosphere, you may coat | cover a protective film further on a rust prevention film, and may improve rust prevention property further. Examples of the protective film include a film made of a resin such as a fluororesin. As the fluororesin, polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluorovinyl ether copolymer (PFA), fluorinated ethylene propylene copolymer (FEP) and the like are preferable.

[Second Embodiment]
FIG. 3 is a cross-sectional view of a ball screw which is an embodiment of the linear motion device according to the present invention. The ball screw has a screw shaft 21 having a spiral thread groove 21a having an arcuate cross section on the outer peripheral surface and a spiral screw groove 22a having an arc cross section facing the screw groove 21a of the screw shaft 21 on the inner peripheral surface. Rolling into a spiral ball rolling path 26 having a substantially circular cross section formed by a cylindrical nut 22 screwed to the internal thread shaft 21, a thread groove 21 a of the screw shaft 21, and a thread groove 22 a of the nut 22. And a large number of balls 23 loaded freely.

  The screw shaft 21 and the nut 22 are made of steel. Further, the inner surfaces of the thread grooves 21a and 22a form a raceway surface on which the ball 23 rolls. Further, a lubricant such as lubricating oil or grease may be disposed in the ball rolling path 26. Further, a seal for sealing the opening of the gap between the outer peripheral surface of the screw shaft 21 and the inner peripheral surface of the nut 22 may be provided in the vicinity of the opening. When a lubricant is disposed in the ball rolling path 26, it is preferable to provide a seal to seal the lubricant inside the ball screw.

The nut 22 is provided with a return tube 27 bent in a substantially U-shape so that the ball 23 in the ball rolling path 26 is circulated through the return tube 27. That is, the ball 23 rolling in the ball rolling path 26 moves in the ball rolling path 26 and rotates around the screw shaft 21 a plurality of times, and then the return tube 27 of one end of the ball rolling path 26 is Scooped up at one end. The scooped ball 23 passes through the return tube 27 and is returned from the other end of the return tube 27 to the other end of the ball rolling path 26.
Then, the nut 22 screwed into the screw shaft 21 via the ball 23 and the screw shaft 21 perform relative rotational movement through the rolling of the many balls 23, whereby the screw shaft 21 and the nut 22 are moved. And move relative to each other in the axial direction.

  At least one of the screw shaft 21 and the nut 22 of such a ball screw is coated with a rust preventive film (not shown) containing zinc, tin, and triiron tetroxide on at least a part of its surface. . Therefore, the screw shaft 21 and the nut 22 are not easily rusted. If at least part of the surface is coated with a rust preventive film, the effect of suppressing rusting can be obtained, but in order to give better rust preventive properties, the entire surface should be coated with a rust preventive film. Is preferred. Moreover, since this rust preventive film does not contain harmful substances, the environment around the ball screw is not likely to be contaminated with harmful substances. Furthermore, since the anticorrosive film is black due to triiron tetroxide, it does not diffusely reflect light. Therefore, the linear motion guide device can be used for the optical system device. Since other points are the same as those in the first embodiment, description thereof is omitted.

〔Example〕
Hereinafter, the present invention will be described with reference to more specific examples. A linear motion guide device and a ball screw having substantially the same configuration as the linear motion guide device of the first embodiment and the ball screw of the second embodiment were manufactured.
In the case of the linear motion guide device, the entire surface of the guide rail and the slider (including the rolling element rolling groove) was coated with a rust preventive coating by shot peening. Shot peening was performed by spraying a mixed powder of zinc powder, tin powder, and triiron tetroxide powder for 10 minutes at an injection pressure of 0.7 MPa using a shot peening apparatus 30 as shown in FIG. That is, the projection material (mixed powder) 35 in the tank 32 is sprayed from the nozzle 33a at the tip of the metal tube 33 by the compressed gas 34, and is applied to the guide rail and the slider (the guide rail is shown in FIG. 4). The surface was coated with a rust-proof coating. When the surface of the guide rail is coated with a rust-proof coating, it is preferable to perform shot peening while arranging the nozzle 33a on the side of the guide rail and moving the nozzle 33a in the longitudinal direction of the guide rail.

The mixing ratio of the zinc powder, tin powder and triiron tetroxide powder in the mixed powder is 20% by mass for zinc powder, 60% by mass for tin powder and 20% by mass for triiron tetroxide powder. The average particle size of each powder (according to JIS R6001) is 45 μm. Furthermore, air, nitrogen, or the like can be used as the gas 34.
In the case of a ball screw as well, in the same way as in the case of a linear motion guide device, a shot peening device 30 as shown in FIG. . The mixing ratio of the zinc powder, tin powder and triiron tetroxide powder in the mixed powder is 30% by mass for zinc powder, 30% by mass for tin powder and 40% by mass for triiron tetroxide powder. The injection pressure is 0.4 MPa and the injection time is 10 minutes.

Next, a method for evaluating rust resistance will be described. The guide rail of the linear guide device obtained as described above and the screw shaft of the ball screw were left in an environment of a temperature of 70 ° C. and a humidity of 95%, and the state of rusting was visually observed. And the situation of rusting was ranked as follows.
When there is no rusting at "0 rank", when white rust consisting of zinc oxide or tin oxide is found in less than 20% of the entire surface, it is "1 rank", white rust is 20% or more of the entire surface and 100% The case where it was seen in the following part was set to "2 ranks". In addition, when the rust further progresses and the red rust made of iron oxide is found in less than 20% of the entire surface, “3 rank”, the case where the red rust is found in the entire surface of 20% or more and less than 50% The case where “4 ranks” and red rust were found in the portion of 50% or more and 100% or less of the entire surface was designated as “5 ranks”. The case where red rust further progressed and the layered rust was raised was designated as “6 rank”, and the case where damage such as perforation or breakage occurred was designated as “7 rank”.

The results are shown in the graph of FIG. Example 1 is a guide rail of a linear motion guide device that is subjected to a running-in operation for 4 hours at a contact surface pressure of 1.5 GPa and a slider speed of 0.6 m / s after coating with a rust-proof coating. Example 2 This is a screw shaft of a ball screw that was subjected to a running-in operation for 2 hours at a contact surface pressure of 1.2 GPa and a nut speed of 0.2 m / s after coating with a rust-proof coating. Moreover, the comparative example 1 is the steel material which coat | covered the film by the low temperature electrolytic chromium plating.
In Comparative Example 1, the time until red rust was generated was less than 72 hours, while Examples 1 and 2 were excellent in rust prevention properties over a long period of time. In particular, rusting is also suppressed in concave portions such as rolling elements rolling grooves of the guide rail and screw grooves of the screw shaft, and the rust prevention property is remarkably superior to conventional low-temperature electrolytic chrome plating.

It is a perspective view which shows the structure of the linear motion guide apparatus which is one Embodiment of the linear motion apparatus which concerns on this invention. It is the front view which looked at the linear motion guide apparatus of FIG. 1 from the axial direction. It is sectional drawing which shows the structure of the ball screw which is one Embodiment of the linear motion apparatus which concerns on this invention. It is explanatory drawing of a shot peening apparatus. It is a graph which shows the evaluation result of rust prevention property.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Guide rail 2 Slider 2A Slider main body 2B End cap 3 Rolling body 10 Rolling body rolling groove 11 Rolling body rolling groove 21 Screw shaft 21a Screw groove 22 Nut 22a Screw groove 23 Ball

Claims (2)

  A first member having a raceway surface extending in the axial direction, a second member having a raceway surface facing the raceway surface of the first member, and a plurality of rolling elements arranged to be freely rollable between the both raceway surfaces A linear motion device in which the first member and the second member are relatively linearly moved in the axial direction through the rolling of the rolling element, the first member and the second member At least one of the linear motion apparatus is characterized in that at least a part of the surface thereof is coated with a rust-preventing film containing zinc, tin, and triiron tetroxide. The linear motion device according to claim 1, wherein a coating amount of the rust preventive coating is 0.3 g / m ² or more and less than 3 g / m ² .

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