JP2010255038A - Surface treatment method and sliding member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve sliding properties of a sliding member such as a piston by fundamentally improving surface qualities of a film for lubrication. <P>SOLUTION: This surface treatment method includes: forming a film for lubrication on a piston-skirt part 13 of a piston 10 formed from aluminum or aluminum alloy; and immersing the film in a treatment liquid containing a fluorine compound and ammonium silicofluoride in a temperature range of 70-100°C. Thereby, the surface qualities of the film for lubrication formed on the piston-skirt part 13 are changed, and an affinity for (wettability with) engine oil is improved. In addition, a chemical conversion coating film formed from an Al-OH-F compound, an NH<SB>4</SB>-Mg-Al-F compound, or a blended material of both compounds is formed on a piston ring groove 12, a piston pin boss 14, a piston head 11 and a piston inner wall, which further improves the affinity (wettability) while co-operating with the film for lubrication of which the surface qualities have been changed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface treatment method for aluminum or an aluminum alloy, and more particularly to a technique for reducing friction loss of a sliding member such as a piston skirt portion of an internal combustion engine.

  Patent Document 1 (Japanese Utility Model Publication No. 63-196450) discloses a technique for reducing the friction loss by coating the outer peripheral surface of the piston of the internal combustion engine with a lubricating film to reduce the friction coefficient during boundary lubrication. ing.

  Non-Patent Document 1 (Invention Association Open Technical Report, Official Technical Number 89-20142) is provided with a lubricating film such as a fluororesin on the piston skirt to improve oil retention (and reduce oil rise). In addition, it is disclosed that a plurality of cut portions not forming a film are formed. According to this technique, the retainability of oil around the film can be improved. However, there is a problem that the cut portion overlaps a portion where the surface pressure with the cylinder bore is high, and the skirt portion and the cylinder bore come into contact with each other to increase the impact force (impact noise increases).

  Therefore, Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-182612) discloses that a groove portion into which oil flows is formed at the lower end of the skirt portion where the surface pressure between the piston skirt portion and the cylinder bore is low. The impact sound when the cylinder bore hits is reduced.

Japanese Utility Model Publication No. 63-196450 JP 2001-182612 A

Japan Society for Invention and Innovation Public Technical Bulletin Number 89-20142

  The lubrication film formed on the sliding member such as the piston skirt has a problem that it is likely to be boundary lubrication because it has low affinity (wetability) with the lubricating oil (engine oil). However, the techniques disclosed in Patent Document 1 and Patent Document 2 do not fundamentally improve the familiarity (wetability) between the lubricating film and the engine oil, that is, the lubricating film and the lubricating oil.

  The present invention has been made in view of the actual situation, and improves the sliding characteristics of the sliding member by avoiding boundary lubrication and fundamentally improving the surface properties for reducing friction loss. With the goal.

In the surface treatment method of the present invention, a lubricating film is formed on a part or all of a member made of aluminum or an aluminum alloy, and the member is treated with a fluorine compound in a temperature range of 70 to 100 ° C. and ammonium silicofluoride. It is characterized by being immersed in a liquid.
Further, the sliding member of the present invention is a sliding member made of aluminum or an aluminum alloy, and a lubricating film is formed on a part or all of the sliding member, and the lubricating film is 70 to 100 ° C. It is characterized by being subjected to chemical conversion treatment by being immersed in a treatment liquid containing a fluorine compound in a temperature range and ammonium silicofluoride.

  According to the present invention, it is possible to improve the familiarity (wetting property) of the lubricating film with the lubricating oil, and it is possible to improve the sliding characteristics of the lubricating film.

It is a figure which shows the piston of the internal combustion engine which concerns on embodiment of this invention. It is the figure which showed the evaluation value of the contact angle in Example 1. FIG.

  Embodiments of the present invention will be described below.

  The surface treatment method according to the present invention is a surface treatment method suitable for use in a sliding member, and aims to improve sliding characteristics by realizing reduction of friction loss of the sliding member. As a summary, a lubricating film is formed on a part or all of a sliding member made of aluminum or an aluminum alloy, and thereafter, the sliding member is subjected to chemical conversion treatment. This will be described in detail below.

  First, the material or material of the sliding member targeted by the surface treatment method according to the present invention is aluminum or an aluminum alloy. Aluminum or aluminum alloy includes pure aluminum, aluminum wrought material, aluminum casting, aluminum die-cast material, etc. In the present invention, sliding members made of such material or material are used for lubrication. Surface treatment consisting of film formation and chemical conversion treatment is performed.

  The lubrication film to be formed on a part or all of the sliding member uses polyamide imide that is excellent in lubricity, wear resistance, heat resistance, workability, etc. It is formed by using a solid lubricant such as graphite (graphite), PTFE (polytetrafluoroethylene) or molybdenum disulfide as an agent. In addition, the formation of the lubricating film is performed at an arbitrary location by a printing method or a spray method.

  The chemical conversion treatment according to the present invention is performed after degreasing, etching, and desmutting. Degreasing removes oils and dirt adhered to the aluminum surface, etching removes dirt and scratches on the aluminum surface that cannot be removed by degreasing, and desmutting removes the aluminum remaining on the surface during etching. Impurities contained are removed with an acidic aqueous solution. Degreasing, etching and desmutting are performed after the formation of the lubricating film, but there is no damage such as poor adhesion to the lubricating film due to this process.

  The chemical conversion treatment performed after degreasing, etching, and desmutting is performed by immersing the sliding member in a chemical conversion treatment aqueous solution containing a fluorine compound and ammonium silicofluoride in a temperature range of 70 to 100 ° C. for 3 to 5 minutes.

Here, the fluorine compound means a fluorine compound excluding ammonium silicofluoride, specifically, magnesium silicofluoride (MgSiF ₆ .6H ₂ O), zinc silicofluoride (ZnSiF ₆ .6H ₂ O), Silicate fluoride such as potassium silicofluoride (K ₂ SiF ₆ ), sodium silicofluoride (Na ₂ SiF ₆ ), manganese silicofluoride (MnSiF ₆ .6H ₂ O), borofluoride, zirconium fluoride, titanium fluoride, etc. Is included. Among these fluorine compounds, silicofluoride salts are preferably used, and magnesium silicofluoride and manganese silicofluoride are particularly preferred.

  Moreover, in the chemical conversion treatment aqueous solution, 0.1 to 20 parts by weight of a fluorine compound, more preferably 0.2 to 15 parts by weight, and 0.05 to 15 parts by weight of ammonium silicofluoride with respect to 100 parts by weight of water, More preferably, 0.1 to 10 parts by weight are included.

  Moreover, the reason why the temperature range of the chemical conversion treatment aqueous solution is set to 70 to 100 ° C. is that the reaction is slow when it is less than 70 ° C., and the evaporation is increased when it is higher than 100 ° C. In addition, if the immersion time is 3 to 5 minutes, the reaction may be insufficient when the immersion time is less than 3 minutes. This is because there is no change.

In the surface treatment method according to the present invention, a chemical conversion treatment is performed after the coating as described above is formed. In the sliding member after the chemical conversion treatment, the surface properties of the lubricating film are changed by the chemical conversion treatment, the familiarity (wetting property) with the lubricating oil (engine oil or the like) is remarkably improved, and the oil retention performance is improved. In the portion where the lubricating film is not formed, on its surface, Al-OH-F compound or NH 4 _-Mg-Al-F compound, or a chemical conversion film consisting of a mixture of both is formed, the properties are Combined with the modified lubricating film portion, the sliding characteristics of the entire sliding member are significantly improved.

  FIG. 1 is a view showing a piston 10 in an internal combustion engine that has been surface-treated by the surface treatment method according to the present invention. As shown in FIG. 1, the piston 10 includes a piston head 11, a piston ring groove 12 formed on the peripheral surface of the piston head 11, a piston skirt portion 13 formed from the lower end of the piston head 11, and a piston through which a piston pin is inserted. A pin boss 14 is included. In the piston 10, a space is formed on the back surface of the piston skirt portion 13, and a portion below the piston head 11 of the piston 10 is hollow.

  The piston 10 used in the internal combustion engine comes into contact with the cylinder liner and the piston skirt portion 13 when sliding. Therefore, in the piston 10, a lubricating film (resin coat) is formed on the piston skirt portion 13 (the portion marked with the node in FIG. 1) to suppress an increase in the coefficient of friction, but thereafter the chemical conversion treatment according to the present invention is performed. As a result, the sliding characteristics are further improved.

  After the chemical conversion treatment according to the present invention for the piston 10, the surface property of the lubricating film formed on the piston skirt portion 13 changes, and the familiarity (wetting property) with the engine oil will be significantly improved. Engine oil retention performance is improved. Since this holding performance is exhibited from a low temperature to a high temperature, lubrication is smoothly performed when the engine is started, and an increase in the friction coefficient can be significantly suppressed even at a high load.

In addition, it has been pointed out that lubricating oil may not be sufficiently supplied to the sliding portion of the piston ring groove 12 and the piston ring and piston pin boss 14 fitted therein and the piston pin inserted through the groove. Yes. However, in the piston 10, chemical conversion treatment is performed on portions other than the portion (piston skirt portion 13) where the lubricating film is formed. Therefore, the surface of a portion other than a portion where the lubricating film has been formed, Al-OH-F compound or NH 4 _-Mg-Al-F compound, or a chemical conversion film consisting of a mixture of both is formed. Specifically, a chemical conversion film is formed on the piston head 11, the piston ring groove 12, the piston pin boss 14 and the inner surface of the insertion hole, and the inner surface of the piston 10. As a result, the sliding characteristics of the entire piston 10 are further improved together with the lubricating film portion (surface of the piston skirt portion 13) modified by the chemical conversion treatment, and the fuel consumption and output of the internal combustion engine are improved. Will be.

  In addition, although the piston 10 which performed the surface treatment which concerns on this invention was demonstrated here, if it is components (for example, pistons and bearings for other power engines) in which the film for lubrication is formed, the effect will be the same As expressed, the scope of the present invention is broad.

  As described above, according to the surface treatment method of the present invention, it is possible to improve the familiarity (wetting property) of the lubricating film with the lubricating oil, and to reduce the sliding loss of the lubricating film by reducing friction loss. Can be improved.

  And if the piston which gave such a surface treatment is used, the holding | maintenance performance of engine oil will improve by improving familiarity (wetability) with engine oil. And since this holding performance is exhibited from low temperature to high temperature, lubrication at the start of the engine is performed smoothly, and the increase in the coefficient of friction can be greatly suppressed even at high loads, resulting in sliding. It is possible to avoid boundary lubrication, and to obtain a fuel efficiency improvement effect and an output improvement effect. Moreover, since the lubricating film is formed on one surface of the piston skirt portion, it is possible to suppress an impact sound when the piston skirt portion hits the cylinder bore.

  Further, in the piston 10, no lubricating film is formed on portions other than the piston skirt portion 13. However, in such an aspect, the dissolution of aluminum affects the chemical conversion treatment of the lubricating coating, and the chemical conversion treatment of the lubricating coating is performed. It is considered that the reforming by means of smoothing.

  In addition, although the object of the surface treatment is aluminum or aluminum alloy in the present invention, it can be applied even if other iron materials are cast or fitted to the target member, and the target member is other The possibility of application to steel materials is also expected.

  Example 1 according to the present invention will be described. In Example 1, a reference test piece manufactured from a JIS AC8A casting material, which is a typical aluminum alloy used for a piston, is made of polyamideimide as a resin binder, and graphite for lubrication as a solid lubricant is 20 to 20%. A film containing 30% was formed to 8 μm.

  Then, the test piece was immersed in an aqueous solution (treatment liquid) containing magnesium silicofluoride and ammonium silicofluoride heated to 80 to 90 ° C., and subjected to chemical conversion treatment for 3 to 5 minutes.

  The familiarity (wetability) of the test piece with the engine oil was evaluated by dropping 0.017 g of 5W30 oil on the treated test piece. As test piece temperature, it carried out at 25 degreeC, 50 degreeC, and 75 degreeC. As a result, the lubricating film without chemical conversion treatment had a wettability with oil of 5W30 having a low viscosity of about 25 to 30 °, whereas the lubricating film subjected to chemical conversion treatment had 10 to 10 It was about 15 °, almost half that of the case where no chemical conversion treatment was performed, and it was confirmed that the wettability with oil was very high. The result is shown in FIG.

The contact angle is calculated from the following formula: γ _S = γ _L cos θ + γ _{SL based on} the solid surface tension (γ _S ), liquid surface tension (γ _L ), and solid-liquid interface tension (γ _SL ). Specifically, θ is obtained from tan (θ / 2) = h / r (where r is 1/2 of the bottom side and h is the height of the droplet). The contact angle θ is an evaluation value of the familiarity (wetting property), and the smaller the contact angle θ, the better the familiarity.

  Next, Example 2 will be described. In Example 2, a standard test piece manufactured from a JIS AC8A casting material, which is a typical aluminum alloy used for a piston, is made of polyamideimide as a resin binder and molybdenum disulfide for lubrication as a solid lubricant. A film containing about 20% was formed to 7 μm.

  Thereafter, the test piece was immersed in an aqueous solution containing magnesium silicofluoride and ammonium silicofluoride heated to 80 to 90 ° C. and subjected to chemical conversion treatment for 3 to 5 minutes.

  The familiarity (wetability) with the engine oil was evaluated by dropping 0.017 g of 5W30 oil onto the treated specimen in the same manner as in Example 1. The test piece temperature was 25 degreeC, 50 degreeC, and 75 degreeC. As a result, almost the same result as in Example 1 was obtained, and the contact angle of the lubricating film that was subjected to the chemical conversion treatment on the lubricating film without the chemical conversion treatment was approximately half.

  Next, Example 3 will be described. In Example 3, a standard test piece manufactured with a JIS AC8A casting material, which is a typical aluminum alloy used for a piston, is made of polyamideimide as a resin binder, and a lubricating film 10 μm containing no solid lubricant is formed. Formed.

  Then, the test piece was immersed in an aqueous solution containing magnesium silicofluoride and ammonium silicofluoride heated to 80 to 90 ° C. and subjected to chemical conversion treatment for 3 to 5 minutes.

  The familiarity (wetability) with the engine oil was evaluated by dropping 0.017 g of 5W30 oil onto the treated test piece in the same manner as in Examples 1 and 2. The test piece temperature was 25 degreeC, 50 degreeC, and 75 degreeC. As a result, almost the same result as in Example 1 was obtained, and the contact angle of the lubricating film that was subjected to the chemical conversion treatment on the lubricating film without the chemical conversion treatment was approximately half.

  Next, Example 4 will be described. In Example 4, 20% of molybdenum disulfide for lubrication as a solid lubricant is used by using polyamideimide as a resin binder for a piston manufactured from a JIS AC8A casting material, which is a typical aluminum alloy used for pistons. A film containing 6 to 15 μm was formed on the piston skirt (see FIG. 1).

  Then, the piston was immersed in an aqueous solution containing magnesium silicofluoride and ammonium silicofluoride heated to 80 to 90 ° C. and subjected to chemical conversion treatment for 3 to 5 minutes.

As a result, a lubricating coating whose surface properties are modified by chemical conversion treatment is formed on the piston skirt, and Al-OH which is a chemical conversion coating is formed on the piston ring groove, piston piston boss, piston head, and piston inner surface. A chemical conversion film composed of the —F compound, the NH ₄ —Mg—Al—F compound, or a mixture of both was formed. By modifying the surface properties of the piston skirt and forming a film by surface treatment of the piston ring groove, piston pin boss, piston head, and piston inner surface, friction loss can be greatly reduced, resulting in improved output and improved fuel efficiency. I was able to.

10 Piston 11 Piston Head 12 Piston Ring Groove 13 Piston Skirt 14 Piston Pin Boss

Claims (8)

  A lubricating film is formed on part or all of a member made of aluminum or an aluminum alloy, and the member is immersed in a treatment solution containing a fluorine compound and ammonium silicofluoride in a temperature range of 70 to 100 ° C. Surface treatment method.   The surface treatment method according to claim 1, wherein the lubricating film is formed of polyamideimide or polyamideimide containing a solid lubricant.   The surface treatment method according to claim 2, wherein the solid lubricant contains any one of graphite, polytetrafluoroethylene, and molybdenum disulfide. A sliding member made of aluminum or an aluminum alloy,
A lubricating film is formed on part or all of the sliding member,
A sliding member, wherein the lubricating film is subjected to a chemical conversion treatment by being immersed in a treatment liquid containing a fluorine compound having a temperature range of 70 to 100 ° C. and ammonium silicofluoride. The lubricating film is formed on a part of the sliding member,
A chemical conversion film made of an Al—OH—F compound, an NH ₄ —Mg—Al—F compound, or a mixture of both is formed in a portion other than the portion where the lubricating film is formed. The sliding member according to claim 4. The sliding member is a piston,
The lubricating coating is formed on the piston skirt, and the lubricating coating is immersed in a treatment solution containing a fluorine compound and ammonium silicofluoride in a temperature range of 70 to 100 ° C., and is subjected to chemical conversion treatment.
The piston ring groove, piston pin boss, piston head, and piston inner surface on which the lubricating film is not formed are formed of an Al—OH—F compound or NH ₄ —Mg—Al—F compound, or a mixture of both. The sliding member according to claim 5, wherein a treatment film is formed.   The sliding member according to any one of claims 4 to 6, wherein the lubricating film is formed of polyamideimide or polyamideimide containing a solid lubricant.   The sliding member according to claim 7, wherein the solid lubricant includes any one of graphite, polytetrafluoroethylene, and molybdenum disulfide.

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