JP6829028B2 - Rolling device - Google Patents

Description

The present invention relates to various rolling devices such as a ball screw device, a linear guide device, and a rolling bearing.

For example, as shown in FIGS. 1 and 2 (AA cross-sectional view of FIG. 1), in the ball screw device 1, a screw shaft 3 in which a screw groove 3a is spirally formed on the outer periphery thereof and a screw facing the screw groove 3a A cylindrical nut 7 having a groove 5 spirally formed on the inner circumference thereof and a large number of balls 9 arranged in a space formed by the double-threaded grooves 3a and 5 are main constituent members. The nut 7 is formed with a flange 11 at one end for fixing to a table or the like (not shown), and a flat surface (notch surface) 13 is machined on a part of the outer peripheral surface (upper side in FIG. 2). A pair of front and rear steel pipe tubes 15 are fixed to the nut 7 as a circulation path for the balls 9, and the balls 9 rotated between the screw grooves 3a and 5 a predetermined number of times circulate through the tubes 15. It has a structure. In the figure, reference numeral 17 indicates a tube retainer for fixing the tube 15 on the flat surface 13 of the nut 7, and reference numeral 19 indicates dust-proof plastic seals attached to both ends of the nut 7. Further, in order to prevent collisions between the balls 9, a spacer 21 may be interposed between the balls 9.

However, in the ball screw device 1, the ball 9 and the screw grooves 3a and 5 come into contact with each other due to vibration or the like, and the surface of the screw grooves 3a and 5 is damaged, which is a major cause of shortening the life. Therefore, various coatings are formed on the outer diameter surface of the screw shaft 3 and the inner diameter surface of the nut 7 to improve wear resistance and the like to improve durability.

For example, Patent Document 1 describes a mechanical part in which a sliding portion is treated with Kanigen and coated with an electroless nickel plating film. Although the electroless nickel plating film by this Kanigen treatment has the advantages of high impact strength (high toughness), high hardness, excellent lubricity such as sliding characteristics, and high speed formation. Abrasion resistance is not sufficient.

Further, in Patent Document 2, the surface of the frame of the electric actuator is subjected to raident treatment, chrome plating, kanizen plating, etc., and the rolling groove of the inner wall surface of the frame and the rolling groove of the guide block are surface-treated by kanizen plating. ing. However, an electroless nickel plating film is formed on the surface of the rolling groove by a Kanigen treatment, and it cannot be said that the wear resistance is sufficient as in Patent Document 1.

Further, the ball screw device 1 is used for applications in which it comes into contact with various chemicals, and corrosion resistance may be required. However, the screw shaft 3 and the nut 7 are generally made of steel, and have sufficient corrosiveness. I can not say.

The above is not limited to the ball screw device 1, but the same can be said for various rolling devices such as linear guide devices and rolling bearings.

Japanese Patent No. 3027515 Japanese Unexamined Patent Publication No. 2000-88071

The present invention has been made in view of such a situation, and the track groove of the outer member such as the thread groove 5 of the nut 7 and the track groove of the inner member such as the thread groove 3a of the screw shaft 3 The purpose is to further improve wear resistance, impact resistance and corrosion resistance.

In order to solve the above problems, the present invention provides the following rolling devices.
(1) an outer member having a raceway groove on the inner diameter surface, an inner member having a raceway groove in the outer diameter surface, rolling is rotatably disposed between both raceway grooves of the outer member and the inner member In a rolling device including a plurality of rolling elements,
At least one of the inner diameter surface of the outer member and the outer diameter surface of the inner member
Having a porous low-temperature chrome plating film via an electroless nickel plating film or a base layer composed of a metal plating film having a lower ionization tendency than the outer member and the base material forming the inner member. A featured rolling device.
(2) The rolling apparatus according to (1) above, wherein the surface roughness of the track groove of the low temperature chrome plating film is at least 1 μmRa or less.

According to the present invention, the wear resistance, impact resistance, and corrosion resistance of the track groove can be improved, and the durability of the rolling element can be significantly improved.

It is a top view which shows an example of the ball screw device. It is a cross-sectional view of AA of FIG. It is an enlarged view of the part X of FIG.

Hereinafter, the present invention will be described in detail with reference to the drawings. In this embodiment, the ball screw device will be described as an example, but it can be generally applied to rolling devices such as linear guide devices and rolling bearings.

In the present invention, the type of the ball screw device is not limited, and various ball screw devices including the ball screw device 1 shown in FIGS. 1 and 2 are targeted. FIG. 3 is an enlarged view of a portion X of FIG. 2, but in the present invention, at least one of the outer diameter surface of the screw shaft 3 and the inner diameter surface of the nut 7, preferably both, is an electroless nickel-plated coating or the screw shaft 3. The low-temperature chrome plating film 30 is formed via the base layer 20 made of a metal plating film having a lower ionization tendency than the base material forming the nut 7.

The nickel-plated coating as the base layer 20 has excellent impact resistance, and in the ball screw device, the durability against collision with the ball 9 due to vibration is enhanced. Further, the screw shaft 3 and the nut 7 are generally made of steel materials such as SCM material and SAE material, and nickel is a metal having a lower ionization tendency than iron, so that it has better corrosion resistance than the case where an electroless nickel film is not formed. become.

Further, even if the base layer 20 is a metal plating film having a lower ionization tendency than the base material forming the screw shaft 3 and the nut 7, the corrosion resistance can be similarly improved. Among them, tin, copper, silver, gold and the like are preferable as the metal species because they are relatively soft and also have impact resistance.

On the other hand, since the low-temperature chrome plating film 30 has excellent wear resistance, it suppresses wear due to contact with the balls 9. Further, the low-temperature chrome plating film 30 is porous and has a property of being easily deformed. On the other hand, the electroless nickel plating film which is the base layer 20 and the metal having a low ionization tendency are not easily deformed, and cracks are likely to occur when a load is applied through the balls 9. However, when the low-temperature chrome plating film 30 is placed on the base layer 20, the easily deformable low-temperature chrome plating film 30 relaxes the load and suppresses the generation of cracks in the base layer 20. By laminating the base layer 20 and the low-temperature chrome plating film 30 in this way, the durability of the film as a whole is improved.

In order to fully exhibit these effects, it is preferable that the film thickness of the base layer 20 is 3 to 100 μm. If the base layer 20 is thinner than 3 μm, the effect of improving corrosion resistance and wear resistance cannot be sufficiently obtained.

Further, a gap is formed between the thread groove 3a of the screw shaft 3 on which the base layer 20 and the low-temperature chrome plating film 30 are formed, the thread groove 5 of the nut 7, and the ball 9, and the gap becomes narrower as a load is applied. Become. At that time, in order to form an appropriate gap against the load, it is necessary to make the base layer 20 a certain film thickness or more, and make it 3 μm or more as described above. However, if the base layer 20 becomes thick, it becomes difficult to control the film thickness, so it is preferable that the film thickness is 100 μm or less as described above.

The film thickness of the low-temperature chrome plating film 30 is preferably 0.1 to 3 μm, more preferably 0.5 to 2 μm. If the low-temperature chrome plating film 30 is thinner than 0.1 μm, the effect of improving wear resistance cannot be sufficiently obtained, and if it is thicker than 3 μm, the compressive stress becomes low and the adhesion to the base layer 20 becomes low.

The electroless nickel plating film to be the base layer 20 may contain other elements such as Ni-B and Ni-P-B in addition to Ni-P. The electroless nickel plating film can be formed by a general electroless plating method, but is preferably formed by a Kanigen treatment.

As an example of the Kanigen treatment, a Ni-P-B film can be formed on a nickel salt by using a plating bath containing a phosphorus compound and a boron compound as a reducing agent. As the nickel salt, nickel chloride, nickel sulfate, nickel acetate, nickel carbonate and the like can be used. As the phosphorus compound, sodium hypophosphite, potassium hypophosphite, nickel hypophosphate and the like can be used, and as the boron compound, dimethylaminoboron, diethylaminoboron, sodium borohydride and the like can be used. The ratio of the nickel salt, the phosphorus compound and the boron compound in the plating bath can be appropriately adjusted according to the composition of the obtained coating film. Further, the concentration of each component can be determined in consideration of the stability of the plating bath, the precipitation rate, etc. For example, it is appropriate that the nickel salt concentration is in the range of 15 to 30 g / L.

Further, an organic acid such as acetic acid, malic acid and citric acid and a chelating agent such as ethylenediaminetetraacetic acid can be added to the plating bath in consideration of stability and pH buffering action. Further, as a stabilizer, a trace amount of lead nitrate, bismuth nitrate, antimony salt, sulfur compound and the like can be added. Further, in the plating bath, the pH is preferably adjusted to the range of 6 to 7 in consideration of stability, precipitation rate and the like.

Then, by immersing the screw shaft 3 and the nut 7 in the above plating bath for a certain period of time, a plating film is formed on the outer diameter surface of the screw shaft 3 and the inner diameter surface of the nut 7. The temperature of the plating bath is determined in consideration of the stability of the bath, the precipitation rate, etc., and is, for example, 60 to 95 ° C, preferably 70 to 90 ° C. Further, the film thickness of the plating film can be adjusted by adjusting the immersion time in the plating bath.

It is preferable that the outer diameter surface of the screw shaft 3 and the inner diameter surface of the nut 7 are subjected to pretreatment performed in a normal plating step in order to improve the adhesion to the plating film. Examples of the pretreatment include degreasing using a solvent or an alkaline solution, zinc substitution treatment, acid immersion treatment and the like.

Further, the film hardness can be increased by heat-treating the plating film. The heat treatment conditions can be determined according to the hardness and the like required for the plating film, but the heat treatment temperature can be 150 to 400 ° C., more preferably 200 to 350 ° C. The heat treatment time is appropriately 30 to 120 minutes. The atmosphere of the heat treatment can be air, an inert gas, a reducing gas, or the like, and can be appropriately selected in consideration of workability, cost, and the like.

On the other hand, the low temperature chrome plating film 30 can be formed by a low temperature plating treatment, which is also called a raydent treatment. This low-temperature chromium plating treatment is a method in which a catalyst component is appropriately added to an aqueous solution of chromic acid and DC electrolysis is performed at a low temperature of −5 to −10 ° C. to form a porous black film of chromium fine particles. The voltage and processing time can be appropriately adjusted according to the film thickness and the like, and it is appropriate to carry out the voltage and processing time at 6 V to 12 V for 5 minutes to 60 minutes, for example. In the low-temperature chrome plating treatment, a part of the porous film diffuses inside the base layer 20 to form a diffusion layer (alloy layer), which exerts excellent adhesion and provides abrasion resistance for a long period of time. Can be maintained.

As described above, according to the present invention, the base layer 20 and the low-temperature chrome plating film 30 are excellent in impact resistance, wear resistance, and corrosion resistance, and the durability of the ball screw device 1 can be improved.

Further, considering the rolling property of the ball 9, it is preferable that the surface roughness of the low temperature chrome plating film 30 is small, and at least the surface roughness of the low temperature chrome plating film 30 of both screw grooves 3a and 5 is set to 1 μmRa or less. It is preferably 0.8 μmRa or less, and more preferably 0.8 μmRa or less. Such surface roughness may be mechanically polished after the low-temperature chrome plating film 30 is formed. The entire outer diameter surface of the screw shaft 3 and the entire inner diameter surface of the nut 7 including both screw grooves 3a and 5 may have such surface roughness.

Further, the screw shaft 3 and the nut 7 (hereinafter, also referred to as “base material”) are made of an iron-based alloy such as stainless steel, and have a higher ionization tendency than the nickel alloy which is the material for forming the base layer 20 on the base material and the base material. Since the potential difference between the small metal and the metal is large, the adhesion between the base material and the base layer 20 may be low. Further, depending on the surface condition of the base material, or when the base layer 20 is thin, a part of the base material may be exposed without forming the base layer 20, and similarly, the base material and the base layer 20 may be exposed. Adhesion may decrease. Therefore, it is preferable to interpose an electrolytic nickel plating film (strike nickel plating) between the screw shaft 3 or the nut 7 and the base layer 20.

Further, it is preferable to coat the surface of the low temperature chrome plating film 30 with a fluororesin. Since the fluorine coating film serves as a protective film for the low temperature chrome plating film 30, and the fluororesin also has lubricity, durability is improved. Further, the electroless nickel plating film cannot fill the recesses of the base material. The low-temperature chrome plating film 30 is considered to have an effect of filling the recesses and an effect of enhancing the adhesion between the electroless nickel plating film and the low-temperature chrome plating film 30. When the fluorine coating film is formed on the low temperature chrome plating film 30, the fluorine coating film acts as a weight stone and the electroless nickel plating film and the low temperature chrome plating film 30 are in close contact with each other, so that the durability is further improved. .. As the fluororesin, polytetrafluoroethylene (PTFE) or the like is suitable.

The present invention will be further described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Example 1)
Thrust ball bearings (nominal number "51305") including upper and lower races made of SCM material and balls made of SUJ material were prepared. Then, S-780 or SK-100 manufactured by Japan Kanigen Co., Ltd. is diluted 5 times with pure water, a small amount of stabilizer is added, then an appropriate amount of dimethylaminoboron is added, and the pH is adjusted to 6.2 with caustic soda. , A plating bath in which the liquid temperature was heated to 80 to 82 ° C. was prepared, and each raceway surface of the upper race and the lower race was immersed therein. By this Kanigen treatment, electroless electrolessness was applied to each raceway surface of the upper race and the lower race. A Ni-P plating film was formed. Next, a low-temperature chrome plating film was formed on the electroless Ni-P plating film by low-temperature chrome plating treatment to prepare a test piece. The film thickness of the electroless Ni-P plating film is 10 μm, and the film thickness of the low temperature chrome plating film is 1 μm.

(Comparative Example 1)
Only the same low-temperature chrome plating film as in Example 1 was formed on each raceway surface of the same upper race and lower race as in Example 1 to prepare a test body. The film thickness of the low-temperature chrome plating film was the same as that of the chrome plating film of Example 1.

(Comparative Example 2)
The same low-temperature chrome plating film as in Example 1 was formed on each raceway surface of the same upper race and lower race as in Example 1, and a fluorine coating film was formed on the low temperature chrome plating film to prepare a test piece. The film thickness of the low-temperature chrome plating film was the same as that of the chrome plating film of Example 1.

(Comparative Example 3)
Only the electroless Ni-P plating film was formed on each raceway surface of the same upper race and lower race as in Example 1 by the same Kanigen treatment as in Example 1 to prepare a test piece.

(Comparative Example 4)
An electroless Ni-P plating film was formed on each raceway surface of the same upper race and lower race as in Example 1 by the same Kanigen treatment as in Example 1, and a boron coating was formed on the electroless Ni-P plating film by the canivoron plating treatment. It was used as a test body. The electroless Ni-P plating film thickness was the same as that of the electroless Ni-P plating film of Example 1.

Then, each test piece was subjected to (1) corrosion resistance test and (2) high surface pressure test shown below. The results are shown in Table 1.

(1) Corrosion resistance test Based on JIS Z 2371, the upper race and lower race of the test piece were immersed in an aqueous solution of sodium chloride (concentration 5 ± 0.5%) for 120 hours each, and after immersion, the raceway surface was visually corroded. I confirmed the degree. In the evaluation, those without corrosion were judged as "○", those with slight corrosion were judged as "Δ", and those with corrosion were judged as "×".

(2) High surface pressure test Using the test piece, the peeling condition of each coating film formed on the raceway surface was confirmed under the following conditions. Moreover, since a high surface pressure is applied, the impact resistance can be evaluated at the same time. The evaluation was "○" for those with inseparable peeling, "△" for those with slight peeling, and "×" for those with slight peeling.
<Test conditions>
-Test piece: Thrust ball bearing (nominal number "51305")
・ Number of balls: 3 balls ・ Number of rotations: 1000min ^-1
-Load: 620 kg (pure axial load)
・ Surface pressure: 3.0 GPa
-Number of cycles (rotation amount x number of balls): 120,000 rev.
-Lubricating oil: Oil (FBK R068)
・ Lubrication method: Oil bath

As shown in Table 1, by using an electroless nickel plating film as a base layer and forming a low-temperature chrome plating film on it, all of the corrosion resistance, abrasion resistance, and impact resistance are improved as compared with each single film. It turns out to be excellent.

The ball screw device and the thrust ball bearing have been described above with reference to the present invention. For example, the outer diameter surface of the guide shaft (inner member) of the linear guide device, the inner diameter surface of the slider (outer member), and the rolling bearing. Even if the chrome plating film 30 is formed on the inner ring raceway surface of the inner ring (inner member) and the outer ring raceway surface of the outer ring (outer member) via the base layer 20 as described above, the same corrosion resistance and wear resistance are obtained. Properties and impact resistance can be obtained.

1 Ball screw device 3 Screw shaft 3a, 5 Thread groove 7 Nut 9 Ball 20 Base layer 30 Chrome plating film

Claims (2)

An outer member having a raceway groove on the inner diameter surface, an inner member having a raceway groove on the outer diameter surface, and a plurality of rollable arrangements between the outer member and both raceway grooves of the inner member. In a rolling device provided with a rolling element,
At least one of the inner diameter surface of the outer member and the outer diameter surface of the inner member
Having a porous low-temperature chrome plating film via an electroless nickel plating film or a base layer composed of a metal plating film having a lower ionization tendency than the outer member and the base material forming the inner member. A featured rolling device. The rolling apparatus according to claim 1, wherein the surface roughness of the track groove of the low-temperature chrome-plated coating film is at least 1 μmRa or less.

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