JPH06137432A - Piston ring and manufacture therefor - Google Patents

Abstract

PURPOSE:To provide a piston ring having a satisfactory initial fitting property while being excellent in exfoliation resistance of its film and in antiscuffing property. CONSTITUTION:This piston ring 2 is a double structured one having a hard chrome plating layer 3 and solid lubricant grain dispersion soft composite alloy plated layer 5 at least on the outer peripheral slide surface. The surface of the hard chrome plating layer 3 is roughened to form a plurality of recesses 4 on which the solid lubricant grain dispersion soft alloy composite plating layer 5 is formed in the piston ring.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston ring for an internal combustion engine having a two-layer structure of a hard chrome plating layer and a soft alloy plating layer on a sliding surface and a method for manufacturing the piston ring, and more particularly to an initial fitting property with a cylinder. The present invention relates to a piston ring that is excellent in peeling resistance and scuff resistance of a coating, and a method for manufacturing the piston ring.

[0002]

2. Description of the Related Art Conventionally, in order to improve wear resistance of a piston ring, hard piston plating is applied to the base material for the piston ring, or in order to improve initial conformability, It has been put to practical use that the surface of hard chrome plating is soft-plated with tin, lead, copper or the like, or that the surface is channelized by anodizing.

However, the method of applying soft plating such as tin on the hard chrome plating layer is easily softened at the initial stage of starting because the soft plating layer is too soft under the condition of high temperature and high load, and is familiar. There was a problem that the effect of was almost gone. Further, the method of anodizing the hard chrome plating layer has a problem that the seizure resistance is good but the initial conformability is insufficient.

Furthermore, since the surface of the hard chrome plating layer is covered with a relatively stable oxide, the adhesion between the soft plating layer and the hard chrome plating layer is weakened, and the film peels off. was there. Therefore, in order to enhance this adhesion, it has been proposed to provide a nickel strike layer between the soft plating layer and the hard chromium plating layer. However, when the soft plating layer is worn and the nickel strike layer is exposed during the operation of the piston ring, there is a problem that the nickel strike layer is burned. Therefore, there is a demand for a piston ring having an improved adhesion between the soft plating layer and the hard chromium plating layer without the nickel strike layer.

Therefore, an object of the present invention is to provide a piston ring having good initial conformability, excellent peeling resistance of the coating, and excellent scuffing resistance.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors roughened the surface of the hard chrome plating layer and applied friction to the roughened surface. While applying the solid lubricant particle-dispersed soft alloy composite plating, it was discovered that it is possible to provide a piston ring having good initial running-in properties and also excellent in peeling resistance and scuffing resistance of the coating, and the present invention completed.

That is, the piston ring of the present invention has a double structure of a hard chrome plating layer and a solid lubricant particle-dispersed soft alloy composite plating layer on at least the outer peripheral sliding surface thereof. The surface of the layer is roughened, and a solid lubricant particle dispersed soft alloy composite plating layer is formed on the surface of the roughened hard chromium plating layer.

Further, the method of the present invention for producing the above-mentioned piston ring comprises (1) forming a hard chromium plating layer on the outer peripheral surface of the piston ring, (2) roughening the surface of the hard chromium plating layer, and (3) ) On the surface of the roughened hard chrome plating layer,
It is characterized in that plating is performed while applying friction to form a solid lubricant particle-dispersed soft alloy composite plating layer.

[0009]

In the piston ring of the present invention, on the hard chromium plating layer (first layer) having good wear resistance,
Solid lubricant particle-dispersed soft alloy composite plating layer that improves compatibility with the cylinder at the initial stage of engine startup (second
Layer) is formed, but since the surface of the first layer is roughened, there is no need to provide a layer having poor seizure resistance, such as a nickel strike layer, which has high adhesion with the second layer. . Furthermore, since the second layer is plated while rubbing the roughened surface of the first layer, the adhesion between the second layer and the first layer is further enhanced, and the peeling resistance and the resistance of the coating are improved. The scuffing property is improved.

[0010]

The present invention will be described in detail with reference to the accompanying drawings by the following embodiments. FIG. 1 is a plan view of a piston ring according to an embodiment of the present invention. 2 is a sectional view taken along the line AA of FIG.

[1] Formation of Hard Chromium Plating Layer The hard chromium plating layer 3 applied to the outer peripheral surface of the base material 2 of the piston ring 1 can be obtained by electroplating using a plating bath mainly containing chromic acid. As such a plating bath, a Sargent bath or a silicofluoride bath which is a kind of a fluoride bath can be used. The hard chrome plating layer has high hardness and excellent wear resistance.

The preferred hard chrome plating layer thickness is 100
~ 500 μm. If the thickness is less than 100 μm, the durability is insufficient, while if it exceeds 500 μm, the hard chrome plating layer is likely to be chipped, causing chipping or cracking during use, causing engine trouble. The more preferable thickness of the hard chrome plating layer is 200 to 400 μm.

Further, it is preferable that the hard chrome plated layer has a shape suitable for further improving the initial conformability, for example, a tapered shape shown in FIG. In this case, as shown in FIG. 2, it is preferable that the outer peripheral surface of the piston ring base material 2 before the hard chrome plating is also tapered in advance.

[2] Roughening of hard chrome plating layer When the solid lubricant particle-dispersed soft alloy composite plating layer, which will be described later, wears in the initial stage of operation of the piston ring, the hard chrome plating layer is exposed and seizure easily occurs. Become. In this case, if the exposed surface of the hard chromium plating layer is roughened, the seizure resistance is high. Further, if the solid lubricant particle-dispersed soft alloy composite plating is applied after roughening the surface, the hard chrome plating layer and the solid chrome plating layer are solid as compared with the case where the hard chrome plating layer has a flat surface without being roughened. The adhesive force with the lubricant particle-dispersed soft alloy composite plating layer can be improved.

As one of the roughening methods, there is a blast honing method. The blast honing method is a method in which hard particles such as SiC are strongly blown to the surface of the plating layer with compressed air to roughen the surface of the plating layer.

As shown in FIG. 2, a large number of fine depressions 4 are formed on the surface of the roughened hard chromium plating layer. The preferred density of the depressions is 50,000 to 90,000 / cm ² , and the preferable depth of the depressions is 2 to 5 μm. When the density of the depressions is less than 50,000 / cm ² or the depth of the depressions is less than 2 μm, the adhesion to the hard chromium plating layer is insufficient, while the density exceeds 90,000 / cm ² or the depth of the depressions is large. When the thickness exceeds 5 μm, the surface roughness of the hard chrome plating layer becomes large and the sealing property deteriorates.

Before the solid lubricant particle-dispersed soft alloy composite plating is performed, the roughened surface of the hard chrome plating layer is removed in order to enhance the adhesion with the hard chrome plating layer and activate the surface. It is preferable to keep it clean.

As a cleaning method, electrolytic degreasing and acid activated electrolysis are preferably performed. The electrolytic degreasing is performed, for example, by subjecting the surface of the hard chromium plating layer to a cathode treatment in an alkaline solution such as NaOH. By this electrolytic degreasing, it is possible to remove the oil and fat adhering to the surface of the hard chromium plating layer in a thin film form. Then, the surface of the electrolytically degreased hard chromium plating layer is subjected to acidic activation electrolysis, which is performed by subjecting the surface to an electrode treatment in an acid such as sulfuric acid, hydrochloric acid or hydrofluoric acid. This acid-activated electrolysis can remove the oxide-altered film adhered in a thin film on the surface of the plating layer.

[3] Formation of Solid Lubricant Particle-Dispersed Soft Alloy Composite Plating Layer The soft alloy of the solid lubricant particle-dispersed soft alloy composite plating layer 5 may be any alloy that can enhance the initial familiarity, for example, Copper-tin alloy, nickel alloy, cobalt alloy, etc. can be used. The preferred alloy is a copper-tin alloy.

On the other hand, it is preferable to use molybdenum disulfide, boron nitride or the like as the solid lubricant particles. Such solid lubricant particles have an excellent effect in improving the scuffing resistance of the coating. Solid lubricant particles have low wettability with metals, do not form alloys, and have a small friction coefficient, so self-lubricating action even in the state of insufficient oil film during initial operation or starting improves seizure resistance and scuff resistance. Also contribute to. The amount of solid lubricant particles is a base soft alloy 1
The amount is preferably 5 to 30% by volume with respect to 00% by volume, and the average particle size is preferably 1 to 10 μm. If the capacity is less than 5% or the particle size is less than 1 μm, the area of the solid lubricant particles occupying the surface of the base is small, and the effect of improving seizure resistance and scuff resistance is small. Also, the volume exceeds 30% or the particle size is 10μ.
If it exceeds m, the strength and adhesion of the composite coating will also decrease, and the solid lubricant particles will easily fall off. More preferably, the solid lubricant particles have an average particle size of 1.0 to 5.0 μm and a content of 10 to 25% by volume.

The thickness of the solid lubricant particle-dispersed soft alloy composite plating layer is preferably 5 to 50 μm. If the thickness is less than 5 μm, the effect of improving the initial conformability cannot be sufficiently exhibited. On the other hand, if the thickness exceeds 50 μm, the solid lubricant particle-dispersed soft alloy composite plating layer disappears in the initial stage of operation, and the increase in the gap between the piston rings becomes excessive, resulting in gas blowout into the crank chamber (compression leakage). Will increase.
The more preferable thickness of the solid lubricant particle-dispersed soft alloy composite plating layer is 10 to 30 μm.

In order to form such a solid lubricant particle-dispersed soft alloy composite plating layer, a plating bath prepared by dispersing solid lubricant particles in an aqueous solution in which a water-soluble compound of the above soft alloy is dissolved is used. .

The plating bath is used to form a composite plating layer while applying friction by using, for example, a brush pressing method. FIG. 3 schematically shows an apparatus for performing plating by the brush pressing method. A brush type plating device 7 is installed so as to cover a part of the outer circumference of the piston ring 6 having the hard chromium plating layer 3 whose surface is roughened. The brush type plating device 7 includes a brush 7a that contacts the outer peripheral surface of the piston ring 6, a graphite anode plate 17 that holds the brush 7a,
Anode fixing cover 10 covering the brush 7a and the graphite anode plate 17
And an anode supporting rod 11 attached to the anode fixing cover 10 so as to come into contact with the graphite anode plate 17. Brush 7
a is pressed against the surface of the hard chrome plating layer 3 of the piston ring 6. In addition, the cathode terminal 12 is the pressing spring 13
Is in contact with the surface of the hard chromium plating layer of the piston ring 6.

On the other hand, an example of an apparatus for continuously feeding the plating solution to the brush 7 will be described. The plating solution in the solution tray 14 is filtered by the filter 15 and sent to the solution tank 9 with a cooling device by the pump 16. Next, the plating solution adjusted to a predetermined temperature is poured into the brush 7 from the solution tank 9 with a cooling device. Further, it is economically preferable that the plating solution overflowing from the surface of the hard chrome plating layer of the piston ring 6 is collected in the solution tray 14 and repeatedly used.

To perform plating with this apparatus, the piston ring 6 is rotated by a rotating device (not shown) while continuously injecting the plating solution into the brush 7a from the solution injection pipe 8.
To rotate. At this time, since the brush 7a is pressed against the piston ring 6, the hard chrome plating layer 3 of the piston ring 6 is coated with the solid lubricant particle-dispersed soft alloy composite plating layer while being constantly rubbed. In order to obtain appropriate friction, it is preferable to adjust the rotational speed of the piston ring, the shape of the brush and the brush, the hardness, the pressure of the brush on the piston ring, and the like to increase the adhesion between the piston ring and the brush.

The reason why the adhesion between the solid lubricant particle-dispersed soft alloy composite plating layer and the hard chromium plating layer is improved by performing electrodeposition while rubbing the surface of the hard chromium plating layer is not necessarily clear, This is probably due to the following reasons.

Although the surface of the hard chrome plating layer is easily oxidized, the surface of the hard chrome plating layer can be plated while the relatively soft oxide film gradually formed during the plating operation is scraped off with a brush. The solid lubricant particle-dispersed soft alloy composite plating layer is formed with almost no oxidation, that is, the surface of the plating layer is active. Since the solid lubricant particle-dispersed soft alloy composite plating layer can be formed without oxidation of the surface of the hard chrome plating layer, which is considered to be one of the causes of the deterioration of adhesion, the hard chromium plating layer and the solid lubricant particle-dispersed soft alloy composite can be formed. It is considered that the adhesion with the plating layer is improved.

Although a brush is used as an example for rubbing the surface of the hard chrome plating layer, it is not limited to a brush, and a non-woven fabric or the like may be used. The material of the brush, the non-woven fabric or the like is preferably animal fiber, plant fiber or synthetic fiber.

Further, although it has been described that only the piston ring is rotated to apply friction, conversely, only the brush may be rotated to generate friction.

Further, although the example in which the brush 7 contains the plating solution has been described, the surface of the hard chrome plating layer of the piston ring 6 other than the portion covered with the brush without injecting the plating solution into the brush 7 is also described. It is also possible to feed the plating solution to the plate and perform plating. The present invention has an outer diameter of 50 to 60
Can be applied to 0mm piston ring.

The present invention will be described in more detail with reference to the following specific examples. Example 1 A first step of forming a hard chrome plating layer as a first layer on the outer peripheral sliding surface of a piston ring, a second step of roughening the surface of the first hard chrome plating layer, and a roughening A film was formed on the surface of the hard chromium plating layer by the third step of performing plating while applying friction to form a solid lubricant particle-dispersed soft alloy composite plating layer.

First, in the first step, the nominal diameter × width × thickness is
Using an SKD-61 piston ring of 110 mm × 3.0 mm × 4.5 mm as a base material, the outer peripheral sliding surface was tapered as shown in Fig. 2. The outer peripheral sliding surface of the piston ring processed in this way was plated with hard chromium under the conditions shown in Table 1 using a plating bath having a bath composition shown in Table 1.

Table 1 Bath composition Cr ₂ O ₃ 250 g / liter H ₂ SO ₄ 1 g / liter Na ₂ SiF ₆ 5 g / liter Plating conditions Bath temperature 55 ° C Current density (cathode) 50 A / dm ² Plating time 8 hours

The thickness of the obtained hard chrome plating layer is 300
was μm. Next, as shown in FIG. 2, the hard chromium plating layer was finished in a tapered shape by lapping, and the thickness of the flat portion other than the end portion of the hard chromium plating layer was set to 200 μm.

Next, in the second step, while rotating the piston ring having the obtained hard chrome plating layer at 10 rpm, Si particles as hard particles were formed on the surface of the hard chrome plating layer.
C # 180 was blown at an air pressure of 3 atm for blast honing to roughen the surface and form a large number of fine depressions 4 having an average depth of about 3 μm.

Next, the roughened surface of the obtained hard chromium plating layer was subjected to electrolytic degreasing under the conditions shown in Table 2.

Table 2 Electrolyte solution NaOH 75 g / liter Na ₃ PO ₄ 10 g / liter Na ₂ CO ₃ 14 g / liter Conditions Bath temperature 80 ° C. Voltage 8 V Current density (anode) 7.5 A / dm ² Electrolysis time 30 seconds

Next, the surface of the hard chromium plating layer subjected to electrolytic degreasing was subjected to acidic activation electrolysis under the conditions shown in Table 3.

Table 3 Electrolyte H ₂ SO ₄ 200 g / liter Conditions Bath temperature 40 ° C. Current density 0.5 A / dm ² Electrolysis time 15 seconds

Then, in a third step, the surface of the hard chrome plated layer which had been subjected to the cleaning treatment was subjected to molybdenum disulfide particle dispersed copper-tin alloy composite plating by a brush pressing method using the apparatus shown in FIG.

The plating solution having the composition shown in Table 4 was placed in the solution tray 14, filtered by the filter 15, sent to the solution tank 9 with a cooling device by the pump 16, and then the plating solution adjusted to 65 ° C. was installed by the cooling device. It was poured into the brush 7a from the solution tank 9.

While rotating the piston ring by a rotating device (not shown) and applying friction to the surface of the piston ring,
Electric power was applied under the conditions shown in Table 4, and molybdenum disulfide particle-dispersed copper-tin alloy composite plating was applied on the hard chromium plating layer by electrodeposition. The obtained molybdenum disulfide particle dispersed copper
Table 4 shows the alloy composition of the tin alloy composite plating layer. The average particle size of the molybdenum disulfide particles was 1.5 μm.

[0043] Table 4 plating solution CuCN 35 g / l _{Na 2 SnO 3 · 3H 2 O} 38g / l NaCN 54 g / l NaOH 7.5 g / l MoS ₂ 30 g / l pH 12.6 conditions Bath temperature 65 ° C. Current density 3A / dm ² hours 30 minutes Electrodeposited alloy composition Copper 85% by weight Tin 15% by weight Molybdenum disulfide 15% by volume

The thickness of the obtained molybdenum disulfide particle-dispersed copper-tin alloy composite plating layer was 30 μm.

Comparative Example 1 As in Example 1, only a flat hard chromium plating layer having a thickness of 250 μm was formed on the outer peripheral sliding surface of the piston ring base material made of the same material as in Example 1.

Comparative Example 2 A porous chromium plating layer having a flat porosity of 30% was formed on the outer peripheral sliding surface of a piston ring base material made of the same material as in Example 1.
Only (thickness 250 μm) was formed.

Comparative Example 3 A hard chromium plating layer having a thickness of 250 μm was formed on the outer peripheral sliding surface of a piston ring base material made of the same material as in Example 1, and a tin plating layer having a thickness of 5 μm was formed thereon. .

Comparative Example 4 On the outer peripheral sliding surface of the piston ring base material made of the same material as in Example 1, a flat porous chrome plating layer having a porosity of 30% (
A thickness of 250 μm) was formed, and a nickel strike layer having a thickness of 5 μm was formed thereon. Further, a flat molybdenum disulfide particle-dispersed copper-tin alloy composite plating layer having a thickness of 20 μm was provided thereon under the bath composition and plating conditions shown in Table 5.

[0049] Table 5 plating solution CuCN 30 g / l _{K 2 SnO 3 · 3H 2 O} 40g / l KCN 60 g / l KOH 12 g / l MoS ₂ 30 g / liter Plating conditions bath temperature 65 ° C. Current density 3A / dm ² hours 20 minutes

Actual machine test A four-cycle water-cooled six-cylinder engine cylinder made of cast iron (FC-25) for a 5000cc diesel engine was assembled with the above-mentioned various piston rings as the first pressure ring, without habituation, under no load and at full load. The state of the sliding surface of the piston ring and the sliding surface of the cylinder was observed by carrying out a continuous cycle operation of 2900 rpm for 60 hours and 2 hours. The results are shown in Table 6.

Table 6 Surface condition after test Piston ring Cylinder outer peripheral surface Inner peripheral surface Example 1 No scuffing No scuffing Comparative example 1 3 places Scuffing 3 places Scuffing Comparative example 2 No scuffing 2 places Scuffing Comparative example 3 3 places scuffed 3 places scuffed Comparative example 4 2 places scuffed 2 places scuffed

As is clear from Table 6, in the piston ring subjected to the surface treatment of Example 1, scuffing was not observed on either the outer peripheral surface of the piston ring or the inner peripheral surface of the cylinder, and Comparative Examples 1 to 4 It can be seen that the film is superior in peeling resistance and scuffing resistance as compared with the piston ring. In addition, the surface-treated piston ring of Example 1 was superior to the piston ring of Comparative Example 4 provided with the nickel strike in the peeling resistance and the scuffing resistance of the film, and thus, there was no nickel strike. However, it can be seen that the film has good peel resistance and scuff resistance.

[0053]

As described in detail above, according to the present invention, the surface of the hard chromium plating layer is roughened, and the surface of the hard chromium plating layer is subjected to solid lubricant particle dispersion soft alloy composite plating while applying friction. The piston ring has good initial running-in properties, and also has excellent film peeling resistance and scuffing resistance.

[Brief description of drawings]

FIG. 1 is a plan view of a piston ring according to an exemplary embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a schematic diagram of an apparatus for performing plating by a brush pressing method.

[Explanation of symbols]

 1 ... Piston ring 2 ... Piston ring base metal 3 ... Hard chromium plating layer 4 ... Dimple 5 ... Solid lubricant particle dispersion soft alloy composite plating layer 6 ... Piston ring 7 ...・ Brush type plating device 7a ・ Brush 8 ・ ・ ・ Solution injection pipe 9 ・ ・ ・ Solution tank with cooling device 10 ・ ・ ・ Anode fixing cover 11 ・ ・ ・ Anode support rod 12 ・ ・ ・ Cathode terminal 13 ・ ・ ・ Pressing Spring 14 ... Solution tray 15 ... Filter 16 ... Pump 17 ... Graphite anode plate

Claims (4)

[Claims] 1. A piston ring having a double structure of a hard chrome plating layer and a solid lubricant particle-dispersed soft alloy composite plating layer on at least the outer peripheral sliding surface thereof, wherein the surface of the hard chrome plating layer is roughened. The piston ring is characterized in that the solid lubricant particle-dispersed soft alloy composite plating layer is formed on the surface of the roughened hard chromium plating layer. 2. The piston ring according to claim 1, wherein the hard chrome plating layer has a thickness of 100 to 500 μm, and the solid lubricant particle-dispersed soft alloy composite plating layer has a thickness of 5 to 50 μm. Piston ring characterized by. 3. A method for manufacturing a piston ring having a double structure of a hard chromium plating layer and a solid lubricant particle-dispersed soft alloy composite plating layer on at least an outer peripheral sliding surface thereof, comprising: (1) an outer peripheral surface of the piston ring. The hard chrome plating layer is formed on (2) the surface of the hard chrome plating layer is roughened, (3) the surface of the roughened hard chrome plating layer is plated while applying friction, A method for producing a piston ring, which comprises forming a solid lubricant particle-dispersed soft alloy composite plating layer. 4. The manufacturing method according to claim 3, wherein at least one kind of solid lubricant particles is compound-dispersed in the soft alloy to form the solid lubricant particle-dispersed soft alloy composite plating layer. Manufacturing method of piston ring. [0001]