DE19646524A1 - Wear-resistant parts, especially the piston ring of an internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to wear-resistant parts, Strictly wear-resistant parts with a Aluminum alloy can be brought into contact and on a Impact aluminum alloy. In particular, the present invention a piston ring, the one has wear-resistant surface and is suitable in Assembly with an aluminum alloy piston Internal combustion engine to be used.

2. Description of the prior art

With the recent trend, the power and revolution of one Internal combustion engine will increase the pressure and the increased thermal stress on the piston rings, especially the first piston ring. There one Aluminum alloy widely used for the piston Motor vehicle internal combustion engine is used, the adhering wear described below easily occur.

Referring to Fig. 11, a four stroke gasoline engine of a motor vehicle, strictly speaking a piston and its surrounding parts, is shown. The four stroke gasoline engine performs four strokes consisting of intake, compression, combustion and exhaust during the two reciprocating operations of the piston 11 which are repeated. A crankshaft, which is hidden behind the counterweight 18 and does not appear in the drawing, is rotated via the connecting rod 17 by means of the piston 11 , which moves back and forth as described above.

The stroke shown in Fig. 11 is the final stage of the suction stroke in which the suction valve is kept closed; and further the gas mixture, which has been introduced into a cylinder bore via the intake manifold 29 and then the intake opening 22 of a cylinder head 21 , is compressed by the piston 11 which is displaced upwards. When the candle 24 is excited, the compressed gas mixture burns in an explosive manner and causes the piston 11 to move downward.

The first and second piston rings 12 and 13 create gas-tight contact between the piston 11 and the cylinder sleeve 15 , while the oil control ring 14 adjusts the supply of lubricating oil to an appropriate amount. These rings 12 , 13 and 14 are arranged one behind the other in the downward direction and fitted into the ring grooves of the piston 11 . Of these piston rings, the first pressure ring 12 in particular is exposed to the high temperature of the combustion gas.

The intake valve 23 is only kept open in the intake stroke. The exhaust valve, which is covered by the suction valve 23 and therefore does not appear in FIG. 11, is only kept open in the exhaust stroke. The valves are opened and closed by a closing arm 27 which is coupled to the cam 28 and driven together. A pressure force is continuously applied to the valves by the valve springs 26 in order to be displaced in a closing direction.

Referring are to FIGS. 9 and 10, which are enlarged views of the piston rings and the piston ring grooves 11 are on the piston 11 a, 11 b and 11 c formed. The first pressure ring 12 , the second pressure ring 13 and the oil scraper ring 14 are fitted in the ring grooves 11 a, 11 b and 11 c in such a way that a slight play is formed between the rings and both sides of the ring grooves.

In general, the wear-resistant parts should have properties such that their wear is low; furthermore, the wear of the opposite element that is brought into contact with these elements should be low. The "wear resistance" meant here appears particularly indicated for the piston ring, so that its wear on the top and bottom is low, while the wear of the ring grooves is low. The “wear resistance” required for the piston ring is described in more detail with reference to FIGS. 9 and 10.

When the piston 11 is displaced downwardly ejected and collide with the first and the second pressure ring 12 and 13 on the top of the annular grooves 11 a and b. 11 On the other hand, the first and second pressure rings 12 and 13 collide and bump onto the underside of the ring grooves 11 a and 11 b, respectively, when the piston is moved upwards. Since this impact and impact effect is repeated at a frequency proportional to the number of revolutions of an engine, the piston rings are subjected to a strong blow at a higher number of revolutions of the engine. While the piston is reciprocating, the first and second pressure rings 12 , 13 are shifted unevenly around the piston circumference in the ring grooves 11 a, 11 b. The first and second pressure rings 12 , 13 are therefore not only subjected to an impact contact, but also to a sliding contact.

Furthermore, the first pressure ring 12 in particular is exposed to the high temperature of the explosion gas. The environment to which the first pressure ring 12 is exposed is therefore very unsparing.

The aluminum alloy of the piston softens due to the high temperature, is scraped off by the piston rings and deposited on the first pressure ring 12 . The so-called adherent wear therefore occurs between the first pressure ring 12 and the aluminum alloy of the piston 11 . The wear of the piston progresses in this way on its ring grooves, and one suffers the so-called "blow-by", that is, the combustion gas is blown through the ring grooves. The performance of the engine is reduced.

After countermeasures that have been taken to date The piston had to solve the piston problem described above be subjected to anodic oxidation to a hard one Aluminum coating while taking countermeasures, which have been undertaken to address the above piston ring problem  loosen the piston ring of a phosphating chemical Conversion, especially a manganese phosphate coating had to be subordinated. The anodic oxidation treatment is expensive. The manganese phosphate coating is suitable for the adherent wear in the initial operating phase of an engine to prevent it, however, due to its low level Persistence does not expect it to be over effective maintains an extended operating phase.

The release of the unchecked Japanese Utility Model No. 60-82 552 disclosed, at least that Top and bottom of a piston ring of a phosphating chemical transformation and then the formation of a heat-resistant and wear-resistant resin coating with subject to a solid lubricant. The publication Japanese Unexamined Utility Model No. 1-307 568 discloses the top and bottom of a piston ring one Nitriding and then the formation of a heat-resistant and wear-resistant resin coating with subject to a solid lubricant. The one in these Publications revealed solid lubricant that in the heat-resistant and wear-resistant coating included is, can wear or peel to an extent that the Sliding effect of the coating is lost and therefore adherent wear is suffered.

SUMMARY OF THE INVENTION

The aim of the present invention is to be wear-resistant Parts, in particular to create a piston ring, the Wear is low, the opposite Touch parts slightly worn and an excellent one Wear resistance over an extended period of time shows.

According to the objectives of the present invention wear-resistant parts created that have a layered structure have, comprising a carrier material, a first Coating on the substrate by a chemical  Conversion phosphatization is formed, and a second Coating formed on the first coating and contains a solid lubricant, characterized in that between the crystal grains of the chemical Conversion phosphate on its top part gaps are formed and these spaces have a width and depth to have particles of the solid lubricant embed. Most particles are preferably solid Lubricant embedded in the gaps.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferably the chemical conversion phosphate is Manganese phosphate, since very small spaces with a large one Depth-to-width ratio on top of the first Coating can be formed. The average Solid lubricant particle diameter preferably from 1 to 2 µm, and the second coating is preferably from 3 to 13 µm thick, since the solid lubricant in can be embedded to a high degree in the gaps. The The thickness of the second coating is determined by means of an optical Microscope by observing the cross section of the second Coating measured and from the lowest position of the tiny bumps in the chemical conversion phosphate certainly.

According to the embodiment described above, there is second coating of particles of molybdenum disulfide or the like, with an average diameter from 1 to 2 µm, and heat-resistant and wear-resistant resin, in which contain the molybdenum disulfide or the like or is dispersed. This second coating is permanent good lubrication and low friction. Next Molybdenum disulfide can be tungsten disulfide, boron nitride (hBN), Graphite and other substances known in tribology as solid Lubricant can be used.  

The wear-resistant elements according to the present Invention are suitable because they are in sliding contact with the Aluminum alloy stand. In particular, the first and the second coating according to the present invention at least on the top and bottom of a piston ring applied. In this embodiment, a satisfactory one permanent wear resistance can be achieved without the Aluminum alloy is subjected to anodic oxidation. However, the anodic oxidation can take place at the Aluminum alloy can be applied, but does not get strong Wear of a piston ring.

Polyamide imide and other binder resins such as epoxy and Polyamide resins and polytetrafluoroethylene (PTFE) can be used as Solid lubricant binders can be used.

So far, the chemical transformation phosphate is the first Layer that in the publication of the unchecked Japanese Utility Model No. 60-82 552 is disclosed, mainly for anchoring and connecting the heat-resistant and wear-resistant resin and thus for Improvement in the adhesive properties of such a resin been used. The well-known chemical transformation phosphate is not effective in peeling off such a resin contained solid lubricant from the surface of such To prevent resin layer. Along with the wear and tear of the heat-resistant and wear-resistant resin occurs adherent wear on the surface of such Resin coating.

In contrast to the prior art, the size of the Solid lubricant particles and the gap between the crystals of chemical transformation phosphatization, which is an underlying layer. That is, if the phosphate crystals by a certain Type of chemical transformation phosphatization are formed, grow out of a carrier material and eventually growth there are tiny bumps on the top the phosphate layer. The particles of the solid  Lubricant are in the spaces between the Embedded crystals of the underlying layer, provided that the size of the solid lubricant particles is considerably smaller than the diameter or the width and Depth of intercrystalline spaces. If the like above built-up surface layer worn out over time the solid lubricant particles keep theirs Lubrication function until the wear is close to the Carrier material progresses because the particles of the Solid lubricant practically not from the connecting Resin layer to be separated. According to the present invention it is therefore possible to prevent the occurrence of scuffing wear to prevent a longer period of time than by standing technology, and thus the durability of the surface layer of wear-resistant parts.

Regarding the crystal morphology of the Phosphate coating by chemical conversion are in the Japanese Patent Examined Publication No. 3-25,514 Leaf shape or a rectangular parallelepiped shown. It However, the particles of the solid lubricant is difficult between the crystals of this publication. Even if it is possible, the proportion of embedded solid lubricant particles to be extremely low.

According to a special procedure for forming the second Coating become particles of solid lubricant, heat-resistant and wear-resistant resin and its Solvents mixed together continuously and then dried to evaporate the solvent. The heat-resistant and wear-resistant resin is baked to make that Trapping resin. The second coating is preferred of such strength that the recesses of the phosphate crystals the underlying layer completely through the second Coating to be covered, desirably with 3 to 13 µm.

Since the present invention as described above there is a preferred relationship between the  Diameter of the solid lubricant particles and intercrystalline spaces between the underlying chemically converted phosphate layer. That is, one finer particle size is more advantageous because the Solid lubricant particles in the intergranular Spaces need to be embedded. If the average particle size is finer than 1 µm, the solid lubricant particles in the heat-resistant and wear-resistant resin coagulate as a binder in the Coating step is used. In this case, the Coagulate solid lubricant particles in the binder resin, whereby the diameter of the coagulated particles increases is that the particles are not in the intergranular Gaps can penetrate the underlying layer.

On the other hand, if the average diameter is more than 2 µm, the proportion of solid lubricant Particles that enter the intercrystalline spaces of the underlying layer occur so reduced that their Separation from the second coating will easily occur. In addition, the solid lubricant particles in the second Coating unstable when the average diameter is more than 2 µm. For example, the proportion of Solid lubricant particles that are not due to the binder are covered, but from the surface of the second Protruding coating. The clout is on the tips of the protruding solid lubricant particles during the repeated, powerful collision against the opposite Element and sliding on that element focused with the consequence that the solid lubricant particles easily from can peel off the second coating. In the worst case can not only the solid lubricant particles, but occasionally also the entire second coating such particles and the resin from the wear-resistant Peel off parts.  

A manganese phosphate coating is advisable to ensure that to form intercrystalline spaces into which the Solid lubricant particles with an average Diameters from 1 to 2 µm can penetrate. Since that Manganese phosphate on a steel substrate in the form of Pyramid crystals grow, the solid lubricants penetrate Particles easily into the intergranular spaces. Of the heat-resistant and wear-resistant resin also becomes good tied up on these crystals.

If the average particle diameter of the solid Lubricant is 1 to 2 µm, the second wears out Coating layer on its surface evenly while local wear is prevented. Because the wear of the second coating layer further to the lowest level is depressed, the wear-resistant element according to the present invention over a long period of time permanently be used. As a binder resin, for example, polyamide Imide resin recommended. The proportion of solid lubricant, such as Molybdenum disulfide, based on its total amount including binders, preferably 40 to 60 Weight percent to the sliding and lubricating properties and To bring adhesive properties into balance. The application the wear-resistant surface layer according to the invention Recommended for wear-resistant elements that come in contact with be brought to an aluminum alloy part.

The present invention is described below with reference to described several drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an enlarged cross-sectional view of a pressure piston ring.

Fig. 2 and 3 are photographs conversion coating of a surface scanning electron microscope image of the manganese phosphate chemical.

Fig. 4 is a photograph of a scanning electron microscope surface image of the solid lubricant layer (the second layer) of Example 3.

Fig. 5 is a photograph of a scanning electron microscope surface image of the solid lubricant layer (the second layer) of Example 6.

Fig. 6 is a cross sectional view of the wear tester and shows its essential parts.

Fig. 7 is a graph showing the amounts of wear in the inventive examples compared with those of the comparative examples.

Fig. 8 is a photograph of a surface scanning electron microscope study of the solid lubricant layer after the wear test in Example 3.

Fig. 9 is an enlarged view of piston rings, ring grooves and a piston, and shows the positional relationship between the piston rings and the ring grooves during the downward displacement of the piston.

Fig. 10 is an enlarged view of piston rings, ring grooves and a piston, and shows the positional relationship between the piston rings and the ring grooves during the upward displacement of the piston.

Fig. 11 is a cross-sectional view of the piston and the surrounding parts of a gasoline engine.

Referring now to FIGS . 2 and 3, the crystal grains of manganese phosphate 31 , 32 formed by chemical conversion are shown by surface scanning electron microscope images. The manganese phosphate crystals are arranged in polyhedral shapes on the top of the first coating. The ridges of the polyhedral crystals face upward and a number of spaces are formed between the ridges facing upward, which are slightly smaller than 10 μm. The present invention is described below with reference to examples in which the present invention is applied to a piston ring.

EXAMPLES

First, details are described which all Examples are common.

Referring to FIG. 1, an enlarged first piston ring is shown. The first piston ring has a nominal diameter of 78 mm, a width (B) of 1.5 mm and a thickness of 2.8 mm. The carrier material 1 is made of oil-tempered silicon-chrome steel for use with valve springs, which steel corresponds to the SWOSC-V under the JIS name. The manganese phosphate layer (the first coating 2 ) is formed on the substrate 1 except for the outer peripheral surface. The second coating 3 with the binder resin (polyamide imide) is formed on the first coating 2 , the particles of molybdenum disulfide being dispersed in the binder resin. On the outer peripheral surface of the support material a hard chromium plating film 4 is formed, which is in sliding contact with the cylinder liner, which is designated in FIGS. 9 and 10 15. Instead of the hard chromium plating layer 4 , a nitride layer or a flame-sprayed layer made of Mo or the like can be formed. The second pressure ring can have the same structure as in FIG. 1.

The first pressure ring 8 was manufactured by the following method. It should be noted that both the typical values used in the examples and the preferred range of values applicable to the present invention are described.

The above-mentioned oil-coated SWOSC-V, which was made into a wire with a rectangular cross section of 1.5 mm × 2.8 mm, is plastically worked into a ring shape with a nominal diameter of 78 mm in the free state. First, the hard chrome plating layer 4 is formed on the outer peripheral surface of the annular wire material by a conventional method. This material is then subjected to the subsequent chemical conversion phosphating under the following procedure (1) - (4) to form the manganese phosphate layer (the first coating 1 ) while the hard chromium plating layer 4 is covered.

• 1) First, the carrier material in a 16% aqueous Solution from the mixture of sodium hydroxide and sodium carbonate (Temperature: from 50 to 90 ° C, typically 90 ° C) for 3 to 7 Minutes, typically 3 minutes immersed in the Degrease carrier material.
• 2) The carrier material is then in a 5% aqueous Solution from a mixture of sulfuric acid and phosphoric acid in the Ratio of 4: 6 immersed (temperature: from 15 to 35 ° C, typically 35 ° C) to the surface of the substrate clean.
• 3) Then the carrier material for 30 to 70 Seconds (typically 60 seconds) one Surface treatment with titanium colloid using a Surface treatment agent for the manganese phosphate coating, which is sold under the trade name PP-VMA, B (Nihon Parkerizing Co. Ltd.) is available.
• 4) The backing material is then used an agent sold under the trade name PF-M5 (Nihon Parkerizing Co. Ltd.) is available, a chemical Transformation phosphatization at a temperature from 82 to 85 ° C for 2 to 5 minutes (typically 5 minutes) to form the manganese phosphate. The total acidity (TA) of the phosphating liquid is 21 to 25 points, typically 23 points. The free acid is 4 to 7 Points, typically 6 points. The iron content is 0.4 up to 3 g / L (typically 1 g / L). The total acidity and the free Acids are analyzed using titrants.

The lubricating layer (second coating 3 ) is then formed on the top and bottom of the piston rings by applying the polyamide-imide binder with dispersed molybdenum disulfide particles. The amount of molybdenum disulfide is 50 percent by weight.

Finally, the hard chrome plating layer 4 is finished on the outer peripheral surface of the piston rings by lapping. The pressure piston rings shown in Fig. 1 are completed in this way.

Examples 1-7

As shown in Table 1 below, the average is Particle diameter of the molybdenum disulfide in Examples 1 to 6, d. H. in the examples of piston rings according to the invention varies. In addition, the molybdenum disulfide Particles due to graphite dispersed in 50% by weight Particles with an average particle size of 1.5 µm replaced. The other features of the example are the same like those of Examples 1 to 6.

Comparative Example 1

For comparison purposes, the phosphating agent is for Form a zinc phosphate coating used under the Name Palbond 880 (Nihon Parkerizing Co. Ltd.) is available. The other details are the same as in Example 1.

Table 1

Referring to FIG. 4, a surface scanning electron microscope image of the solid lubricant layer (the second coating layer) of Example 3 is shown, while referring to FIG. 5, a surface scanning electron microscopic image of the solid lubricant layer (the second coating layer) of Example 6 is shown. In Figs. 4 and 5, the binder resin (polyamide-imide) is designated 20, and the molybdenum disulfide particles 10 are designated 10. They, 10 and 20 , are embedded between manganese phosphate crystals.

The wear resistance test of the above Workflow made piston rings was carried out to the relationship between the materials of the piston rings and that The piston rings slide in the piston grooves of a piston evaluate.

Referring to FIG. 6, a wear tester includes a vertically moving part 5 for knocking and a rotating part 6 opposite to the vertically moving part 5 . The vertically moved member 5 is vertically driven by a motor via a crank mechanism (not shown). The rotating part 6 is attached to the vertical rotary shaft 6 a and is driven by a motor via the shaft 6 a. The rotating part 6 can be rotated continuously or in the opposite direction. A disc 7 made for an aluminum alloy piston is horizontally attached to the underside of the vertically moving part 5 . A heater is mounted inside the vertically moving part 5 and heats the aluminum alloy to a predetermined temperature. A piston ring 8 is inserted on the top of the rotating part 6 and fixed horizontally and arranged opposite the disc 7 .

With the structure described above, the vertically moving disk 7 driven by the crank mechanism is knocked on the rotating piston ring 8 which is driven on the rotating member 6 . The tester shown in Fig. 6 reproduces the collision and sliding of the piston rings and ring grooves in which the piston rings are fitted. The knocking load can optionally be set by means of the hydraulic mechanism (not shown) which is provided for the rotating part 6 . The knock frequency (per time) and the speed of rotation can also be set optionally.

The treated pressure rings 8 and the washer 7 made of aluminum alloy for the piston (AC8A-T 6) were mounted in the tester. The wear test was carried out under the following conditions:
Lubrication: dry
Knock load: 150 kgf
Knock frequency: eight times per second
Rotation speed: continuous in one direction, 2.0 mm / second
Disc temperature: 280 ° C

The results of the test are shown in Fig. 7.

As can be seen from FIG. 7, the piston rings according to the examples according to the invention have both less piston ring wear and less disk wear (piston wear) than all the comparative examples. The durability achieved by the present invention is improved beyond that of the comparative examples. The durability is excellent when the average particle diameter of the solid lubricant is 1 to 2 µm.

After the wear test of Example 3, the surface of the piston ring was observed by a surface scanning electron microscope. The surface raster electron microscope image is shown in Fig. 8. In Fig. 8, the intergranular spaces which appear dark gray are formed between the crystal grains 9 of the manganese phosphate which appear light gray. Most of the molybdenum sulfide particles 10 , which appear bright black, penetrate into the intergranular spaces 9 and fill them. In contrast, in example 6 the proportion of the particles embedded in the intercrystalline interstices 9 is smaller than in example 3, since the molybdenum sulfide particles used in example 6 are coarser than those of example 3. In other words, the majority of the molybdenum sulfide Particle is only bound by the binder. In Example 6, the lubricating layer peels off, albeit very slightly, in part from the manganese phosphate layer underneath. However, the wear resistance is improved in Example 6 compared to the comparative examples.

Various modifications can be made to the above Examples are made provided that such Modifications within the technical concept of present invention.

Claims (9)

1. Wear-resistant parts, in particular a piston ring, which have a layer structure, comprising a carrier material ( 1 ), a first coating ( 2 ) which is formed on the carrier material ( 1 ) by chemical conversion phosphating, and a second coating ( 3 ), which is formed on the first coating ( 2 ) and contains a solid lubricant, characterized in that spaces are formed between the crystal grains ( 31 , 32 ) of the chemical conversion phosphate on its upper part and these spaces have a width and depth to accommodate particles of the solid Embed lubricant ( 10 , 31 , 32 ) in itself. 2. Wear-resistant parts according to claim 1, wherein most of the particles of the solid lubricant ( 10 , 31 , 32 ) are embedded in the spaces. 3. Wear-resistant parts according to claim 1 or 2, wherein said first coating ( 2 ), which is formed by chemical conversion phosphating, consists of manganese phosphate. 4. Wear-resistant parts according to one of claims 1 to 3, wherein an average diameter of said particles of the solid lubricant ( 10 , 31 , 32 ) is from 1 to 2 µm. 5. Wear-resistant parts according to one of claims 1 to 4, the solid lubricant being molybdenum disulfide. 6. Wear-resistant parts according to one of claims 1 to 5, being in sliding contact with an aluminum alloy brought, which can be anodized.   7. Wear-resistant parts according to one of claims 1 to 6, wherein said first coating ( 2 ) and said second coating ( 3 ) are formed on an upper and a lower surface of a piston ring ( 8 ) which in a piston made of an aluminum alloy ( 11 ) is to be assembled. 8. Wear-resistant parts according to one of claims 2 to 7, wherein said carrier material ( 1 ) has been subjected to a surface treatment with titanium colloid before said chemical conversion phosphating. 9. Wear-resistant parts according to one of claims 4 to 8, wherein said second coating ( 3 ) has a thickness from 3 to 13 microns.