Double-layer lubrication coating composition, double-layer lubrication coating and piston having same coating

(54) Title: COMPOSITION FOR DOUBLE LAYER LUBRICATION COATING, DOUBLE LAYER LUBRICATION COATING AND PISTON THAT HAS THE SAME COAT (30) Unionist Priority: 30/08/2006 jp 2006-232961 (71) Depositor (s): Honda Motor Co., LTD. (JP) (72) Inventor (s): Yoshimi Kuroda, Kentaro Sugimura (74) Attorney: Dannemann .Siemsen, Bigler & Ipanema Moreira (57) Abstract: COMPOSITION FOR DOUBLE LAYER LUBRICATION COATING, DOUBLE LAYER COATING AND PISTON WHICH HAS THE SAME COATING The present invention relates to a coating composition for double layer lubrication consisting of an upper layer coating composition and a lower layer coating composition. The top layer coating composition consists of 50 to 70% by weight of an epoxy resin or polyamide-imide resin, 5 to 20% by weight of boron nitride and 15 to 30% by weight of silicone nitride or alumina. The bottom layer coating composition consists of 50 to 70% by weight of an epoxy resin or polyamide-imide resin, 15 to 30% by weight of polytetrafluoroethylene and 5 to 20% by weight of molybdenum disulfide and can include graphite when needed.

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Description of the Invention Patent for COMPOSITION FOR DOUBLE LAYER LUBRICATION COATING, DOUBLE LAYER LUBRICATION COATING AND PISTON THAT HAS THE SAME COATING.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lubricating coating composition that can form a dry coating that has superior adhesion properties to a base material such as a piston skirt and superior sliding properties and more particularly, the coating coating composition. double layer lubrication having an upper layer coating composition and a lower layer coating composition.

2. Description of the Related Art

Conventionally, a process for forming a coating for lubrication on a sliding component surface of an internal combustion engine has been adopted as one of the means to improve the wear resistance and the jam resistance of the relevant component. Then, a composition was proposed in which a solid lubricant is composed of a resin that acts as a binder as a means to improve the sliding property of the lubrication coating.

For example, Japanese Patent Publication JP-A-01-261514 describes a slip material that is composed of 20 to 80% by volume of a polyimide resin or a polyamide-imide resin, 10 to 60% by volume of polytetrafluoroethylene as a solid lubricant, 0.5 to 20% by volume of alumina and the like.

In addition, Japanese Patent Unexamined Publication JP-A-64-087851 describes that a coating is applied to a piston by using a solid lubricant film consisting of the composition of 25 to 125 parts by weight of polytetrafluoroethylene per 100 parts in weight of polyimide resin to increase the wear resistance of an engine component such as a piston.

In addition, Japanese Patent Unexamined Publication JP-A-06-279708 describes a low-friction lubrication paint designed to form a coating that has a low friction coefficient and superior wear resistance in which 5 to 300 parts by weight of a solid lubricant, such as molybdenum disulfide, graphite, boron nitride or the like, and 5 to 100 parts by weight of a modifier, such as a vinyl resin, polybutadiene or the like are mixed per 100 parts by weight of a high-strength, heat-resistant binder such as an epoxy resin.

In addition, Japanese Patent Unexamined Publication JP-A-07-097517 describes a slip resin composition designed to achieve a low friction coefficient and a high wear resistance that is made up of 50 to 73% by weight of hair. at least one of a polyamide-imide resin and a polyimide resin and, as solid lubricants, 3 to 15% by weight of polytetrafluoroethylene, 20 to 30% by weight of molybdenum disulfide and 2 to 8% by weight of graphite, a total sum of the solid lubricants being 27 to 50% by weight.

To reduce the friction coefficient of a lubrication coating in which a solid lubricant is composed in a resin, the amount of polytetrafluoroethylene to be composed needs to be increased. However, on the other hand, when the amount of polytetrafluoroethylene to be composed needs to be increased, as polytetrafluoroethylene and the heat resistant resin have no adhesion force, the amount of wear on the resin coating layer is increased. Therefore, it was not possible to achieve a low friction coefficient and high wear resistance simultaneously.

In addition, it is known that among solid lubricants, when the amounts of molybdenum disulfide and graphite to be mixed are increased, the resistance to binding is increased. However, in the event that molybdenum disulfide and graphite are mixed more than necessary, the strength of the resin layer itself is noticeably reduced to the extreme and this tends to increase the wear of the resin coating layer.

Furthermore, it has been known that the composition, for example, of alumina and / or silicone nitride as a hard filler material is effective in increasing the wear resistance of the resin coating layer. However, it is also known that in the event that the amount of alumina and / or silicone nitride to be mixed is increased, the friction coefficient on the surface of the resin coating is increased, while the resistance to binding is increased. decreased.

SUMMARY OF THE INVENTION

The invention was carried out in view of these conventional situations and its objective is to provide a coating composition for lubrication that can form a dry coating that has an adhesion property superior to a base material such as an aluminum alloy piston and a superior sliding property and more particularly, a coating composition for lubrication that has a low coefficient of friction and superior wear resistance and that can increase the property of initial operation (running-in) and resistance to jamming.

With a focus on achieving the goal, the inventor and others have studied in depth about bonding resins by which coating properties such as thermal resistance, oil resistance, adhesion property to aluminum alloy base materials, wear resistance and similar products can be obtained with good balance, solid lubricants that can reduce friction on the surface of a coating, increasing at the same time the property of initial operation and resistance to binding of the same and, in addition, hard particles that are used in order to increase the wear resistance of a resin coating in relation to its formulation and composition and the coating properties obtained in this way and which the present invention has achieved as a result of the studies.

According to one aspect of the invention, a coating position is provided for double layer lubrication which includes:

a top layer coating composition that includes:

at 70% by weight of a resin for bonding which includes at least one of an epoxy resin and a polyamide-imide resin;

20% by weight of a solid lubricant that includes boron nitride; and 30% by weight of a hard particle that includes at least one of silicon nitride and alumina; and a bottom layer coating composition that includes:

at 70% by weight of a resin for bonding which includes at least one of an epoxy resin and a polyamide-imide resin; and a solid lubricant that includes 15 to 30% by weight of a polyflamethylene trifluoroethylene and 5 to 20% by weight of a molybdenum disulfide.

According to another aspect of the invention, a coating composition for double-layer lubrication is provided which includes:

a topcoat composition that includes:

50 at 70% by weight of a resin for bonding which includes at least one of an epoxy resin and a polyamide-imide resin;

20% by weight of a solid lubricant that includes boron nitride; and 30% by weight of hard particles that include at least 25 µm between silicon nitride and alumina and a bottom layer coating composition that includes:

at 70% by weight of a resin for bonding which includes at least one of an epoxy resin and a polyamide-imide resin; a solid lubricant that includes:

15 to 30% by weight of polytetrafluoroethylene; and a molybdenum and graphite disulfide, the total amount of molybdenum disulfide and graphite being 5 to 20% by weight and a quantity of graphite being 1 to 10% by weight.

In addition, according to a further aspect of the invention, a double layer lubrication coating formed from the double layer lubrication coating composition is provided.

In addition, according to another aspect of the invention, an internal combustion engine piston is provided which includes a double-layer lubrication coating formed from the double-layer lubrication coating composition on an outer circumferential surface of a piston skirt. .

According to the invention, by using the coating composition for double layer lubrication which includes the upper layer coating composition and the lower layer coating composition, the upper layer coating or the lower layer coating can be formed and the top layer coating that has superior adhesion properties to the base material, low friction coefficient and superior wear resistance, property of initial operation and resistance to binding. Consequently, on a sliding member that has the double-layer lubrication coating of the invention, the top layer coating which has initial operation property and resistance to sticking constitutes a good smooth sliding surface when it comes in sliding contact with a fitting member and the wear resistance also becomes good due to the amount of wear in steady state which is reduced by the action of the lower layer coating which is superior in decreasing friction.

Because of this, the double-layer lubrication coating according to the invention is effective in a field that requires jamming resistance, wear resistance and low friction coefficient and is therefore particularly effective for a combustion engine piston. internal, for example. In addition, the double-layer lubrication coating composition of the invention can be calcined at a temperature of 200 ° C or lower which can be applied to an aluminum alloy piston of an internal combustion engine and, in particular, to coating composition for double layer lubrication has superior adhesion property to aluminum alloys and also has good initial operation property, resistance to binding and wear resistance. Consequently, the durability of a sliding member is noticeably increased and the pressure of the binding surface is increased. In addition, a reduction in the friction coefficient can be expected due to the advantage of the lower layer coating after the initial operation has ended.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a graph showing the amount of wear of the respective coatings for lubricating Samples 1 and 3 under a dry lubrication environment in Example 1;

Figure 2 is a graph showing friction coefficients of the respective coatings for lubricating Samples 1 and 3 under the dry lubrication environment in Example 1;

Figure 3 is a graph showing the amount of wear of the respective coatings for lubricating Samples 1 to 3 under an oil-lubricated environment in Example 2;

Figure 4 is a graph showing friction coefficients of the respective coatings for lubricating Samples 1 to 3 under the oil-lubricated environment in Example 2;

Figure 5 is a graph showing friction before the pistons having full operation for the lubrication of Samples 2 to 4 in Example 4;

Figure 6 is a graph showing friction after 20 hours of full operation of the pistons that have the respective coatings for lubricating Samples 2 to 4 in Example 4;

Figure 7 is a graph showing friction before full operation and after the elapsed time of 20 hours and 150 hours of a piston that has the lubrication coating for Sample 2 in Example 4; and

Figure 8 is of photos showing the conditions of the top of the pistons that have the respective coatings for lubricating Samples 2 to 4 in Example 4 after the durability tests DETAILED DESCRIPTION OF EXAMPLES OF MODALITIES OF THE INVENTION

The double-layer lubrication coating composition of the invention includes an upper layer coating composition and a lower layer coating composition and employs, as a bonding resin, an epoxy resin or a polyamide-imide resin, which has superior thermal resistance, wear resistance and bonding properties or both resins. In addition, as hard particles are used only in the topcoat composition, one or both of silicon nitride (SÍNN4) and alumina (AI₂O₃). When the average particle diameter of a hard particle becomes less than 0.1 pm, the wear resistance is reduced, whereas when the average particle diameter of the particle exceeds 5 pm, the wear of a plug-in material is increased. Because of this, the average particle diameter is preferably in the range of 0.1 to 5 pm and is more preferably in the range of 0.1 to 2 pm.

The topcoat composition includes 50 to 70% by weight of an epoxy resin and / or polyamide-imide resin as a bonding resin, 5 to 20% by weight of boron nitride (BN) as a lubricant solid and 15 to 30% by weight of silicon nitride and / or alumina as a hard particle. When the bonding resin becomes less than 50% by weight, the wear resistance and adhesion property are reduced due to a reduction in bonding strength, while the bonding resin exceeds 70% by weight, as 0 solid lubricant and hard particles are relatively reduced, lubricity and wear resistance are reduced. When boron nitride, which is the solid lubricant, becomes less than 5% by weight, lubricity is reduced, whereas if it exceeds 20% by weight, wear resistance is reduced. Moreover, when the hard particles become smaller in amount than 20% by weight, the wear resistance is reduced, the quan8 they exceed 30 wt%, lubricity is reduced.

The lower layer coating composition consists of 50 to 70% by weight of an epoxy resin and / or a polyamide-imide resin as a bonding resin, which is similar to the upper layer coating composition and as a lubricant solid, basically 15 to 30% by weight of polytetrafluoroethylene and 5 to 20% by weight of molybdenum disulfide (MoS₂). When the resin for bonding is reduced to less than 50% by weight, wear resistance and adhesion property are reduced, whereas when it exceeds

70% by weight, the solid lubricant is reduced, and low friction and resistance to binding are impaired. In addition, when polytetrafluoroethylene is reduced to less than 15% by weight, lubricity is reduced, while when it exceeds 30% by weight, the amount of wear is increased. In addition, when molybdenum disulfide is less than 5% by weight, the resistance to binding is reduced, while when it exceeds 20% by weight, the resistance of the coating is reduced, and the amount of wear is increased.

In addition, with molybdenum disulfide as the solid lubricant, an improvement in the resistance to binding can be achieved by a synergistic effect with graphite. Namely, in the composition for coating in the lower layer, as the solid lubricant, in addition to polytetrafluoroethylene, molybdenum disulfide and graphite can be used in parallel with it. When this occurs, a total amount of molybdenum disulfide and graphite is in the range of 5 to 20% by weight and in addition, it is desirable to use 1 to 10% by weight of graphite. When graphite becomes less than 1% by weight, the resulting advantage cannot be obtained from the increased resistance to binding due to the parallel use of graphite, whereas when it exceeds 10% by weight, the wear resistance is reduced.

To adjust the top layer coating composition and the bottom layer coating composition that make up the coating composition for double layer lubrication, for example, an organic solvent is mixed with the epoxy resin and / or the polyamideimide resin that is the resin for bonding and a solid lubricant is added to the resulting resin solution with hard particles also added to it when necessary, so that, the result can be mixed and dispersed using a ball mill.

In addition, the mixing amounts of the resin for bonding, the solid lubricant such as PTEF, M0S2 and graphite and the hard particles are adjusted to be 100% by weight in total.

In addition, the coating composition for double-layer lubrication of the invention is diluted with an organic solvent when necessary, so as to be applied as a coating on a base material such as paint. Namely, a lower layer coating and an upper layer coating are applied sequentially over the base material in that order and are then calcined so that the paints thus applied are hardened, with a coating for double layer lubrication being obtained. There is no specific limitation regarding the organic solvent that is used for dilution, as long as the organic solvent used is a solvent system and can dissolve the resin for bonding. The calcination conditions such as calcination temperature and calcination time can be adjusted accordingly and since calcination at a temperature of 200 ° C or lower is possible, the invention can be applied to aluminum alloy base materials. In addition, although the coating thickness for double-layer lubrication can be selected appropriately, taking into account the processability of the coating and costs, the thickness is desirably in the range of 5 to 40 pm

Specifically, a surface of a base material on which a coating for double layer lubrication must be formed is pre-treated with degreasing solvent or with alkaline degreasing in order to remove oils and / or dirt from it. Then, a paint for the lower layer coating is first applied to the surface of the base material using a known process such as air spraying or screen printing and after that, an upper layer coating paint is applied. After that, the base material is dried to remove the organic solvent and is then calcined, for example, for 30 minutes at 180 ° C or 20 minutes at 200 ° C, where a coating for double lubrication can be formed layer consisting of the lower layer coating and the upper layer coating.

The invention's double layer lubrication coating can be widely applied to sliding members that have various applications under oil-lubricated and dry-lubricated environments. Epoxy resin and polyamide-imide resin, which act as the resin for bonding the coating for double layer lubrication, have superior adhesion properties and therefore can be used for any types of base materials. In this way, the double-layer lubrication coating of the invention can be applied to base materials of various types of aluminum alloys, cast irons, steels and copper alloys. Among these, the double-layer lubrication coating of the invention is preferably applied to a piston of an internal combustion engine, particularly to a piston skirt.

Examples

Example 1

An epoxy resin (EP) and a polyamide-imide resin (PAI) were used as bonding resin, boron nitride (BN), polytetrafluoroethylene (PTFE) and molybdenum disulfide (M0S2), graphite (GF) was used as solid lubricants and silicone nitride (SYNN4) was used as hard particles and they were mixed to provide compositions for an upper layer coating composition and for a lower layer coating composition presented as Samples 1 to 3 in Table 1 below. Note that Sample 3 is a comparative example and was a single layer coating composition.

<td rowspan="2">Samples</td><td colspan="4">Top layer coating composition (% by weight)</td><td colspan="5">Lower layer coating composition (% by weight)</td>

<td>EP</td><td>DAD</td><td>BN</td><td>SYNN4</td><td>EP</td><td>DAD</td><td>PTFE</td><td>MoS₂</td><td>GF</td>

<td> 1</td><td> 62,5</td><td> -</td><td> 12,5</td><td> 25,0</td><td> 60,2</td><td> -</td><td> 21,7</td><td> 14,5</td><td> 3,6</td>

<td> 2</td><td> -</td><td> 62,5</td><td> 12,5</td><td> 25,0</td><td> -</td><td> 63,7</td><td> 21,9</td><td> 14,3</td><td> -</td>

<td> 3*</td><td> -</td><td> -</td><td> -</td><td> -</td><td> -</td><td> 63,7</td><td> 21,9</td><td> 14,3</td><td> -</td>

*: Comparative example.

An organic solvent was added to and mixed with each of the coating compositions for Samples 1 to 3 in Table 1 above and after that it was dispersed for 30 minutes by a ball mill, in which top coat and inks were obtained. respective lower layer coating. The top coat paints and the respective lower coat paints were applied on specimens made of AC8A aluminum alloy (according to the Japanese Industrial Standard JIS) and having an average surface roughness of 0.10 at 0.15 pm in Ra (arithmetic mean roughness) so that a lower layer coating has a coating thickness of 5 to 10 pm and an upper layer coating had a coating thickness from 5 to 10 pm and the specimens thus coated with the paints were calcined for 30 minutes at 180 ° C. However, as for Sample 3, which was the comparative example, the paint was applied so that the coating of the single layer had a coating thickness of 10 +/- 2 pm and was calcined for 60 minutes at 180 ° C.

The respective lubrication coatings for Sample 1, which was the example according to the invention and Sample 3, which was the comparative example, were tested using a Suzuki machine for friction and wear testing under a dry environment. lubrication in which a sliding speed: 0.5 m / s; a plug-in member: AC8A; a sliding distance: 1800 m and a pressure on the surface: 2.52 to 5.04 MPa in order to measure amounts of wear and friction coefficients over the entire sliding distance. The results of tests and measurements are shown in Figure 1, which shows wear quantities (wear depths) and in Figure 2, which shows friction coefficients. In addition, as for the resistance to binding, a wear amount of 10 pm or greater was determined as binding.

As is obvious from Figure 1, it is indicated that the double layer lubrication coating of Sample 1, which was the example of the invention, had a small amount of wear and high resistance to binding under the dry lubrication environment. Furthermore, as is obvious from the

Figure 2, it is observed that the friction coefficient was also reduced. This is considered to be because the double-layer lubrication coating had a good initial operating property, that is, the surface of the double-layer lubrication coating was worn regularly due to sliding contact with a locking member in order to form a good sliding surface at an early sliding stage. As the amount of wear at steady state was reduced as a result of the good sliding surface that is obtained, the wear resistance was good.

On the other hand, as is obvious from Figure 1, the coating for single layer lubrication of Sample 3, which was the comparative example, had a greater amount of wear than that of Sample 1, which was the example of the invention, under the same surface pressure and low resistance to binding. Furthermore, as is obvious from Fig. 2, the reduction in the friction coefficient was not achieved. This is considered to be because the hardness of the Sample 3 lubrication layer itself was low and, therefore, a good sliding surface could not be formed due to the sliding contact with a fitting material in an initial sliding stage.

From the results that were described above, Sample 1, which is the example of the invention, has a high resistance to binding and superior initial operation property under dry lubrication and it is obvious that when the sliding phase is shifted to a sliding with the coating13 lubrication in the lower layer after the initial operation has been completed, a much lower friction coefficient can be obtained.

Example 2

The respective coatings for lubricating Samples 1 to 5 2, which were the examples of the invention and Sample 3, which was the comparative example, shown in Table 1 of Example 1 were tested using the Suzuki machine for friction testing and wear under an oil-lubricated environment where a sliding speed: 0.5 m / s; a plug-in member: AC8A; sliding distance: 1800 m;

a surface pressure: 3.78 MPa and an oil: 0.3 ml of synthetic oil (PAO-4) in order to measure the amount of wear and friction coefficients over the entire sliding distance. The results of the tests and the measurements are shown in Figure 3 which shows wear quantities (wear depths) and in Figure 4 which shows friction coefficients. In addition, for resistance to binding, an amount of wear of 10 pm or greater was determined as binding.

As is obvious from Figure 3, with the coatings for double layer lubrication of Samples 1 to 2, which were the examples of the invention, under the oil-lubricated environment, the amount of wear was small and the high resistance to binding was high, compared to Sample 3, which was the comparative example. In addition, as is obvious from Figure 4, it is observed that the friction coefficient was also reduced. This is considered to be because the double-layer lubrication coating had a good initial operating property even under the oil-lubricated environment and, therefore, the surface of the double-layer lubrication coatings was regularly worn due to the contact of sliding with the fitting parts to form good sliding surfaces at an initial sliding stage. As the amount of wear was reduced as a result of having good sliding surfaces, wear resistance was also good.

On the other hand, as Sample 3, which was the comparative example, formed the lubrication coating in a single layer and the hardness of the lubrication coating itself was low, the amount of wear was increased compared to Samples 1 to 2, which were the examples of the invention. In addition, as is obvious from Figure 4, although Sample 3 had a low friction coefficient when an initial operation reached under the oil-lubricated environment, the amount of wear was large in the initial slip state.

From the results that were described above, Samples 1 to 2, which are the examples of the invention, have the high resistance to binding and the superior property of initial operation even under oil lubrication and it is obvious that when the sliding phase is displaced for sliding with the lower layer coating after the initial operation has been completed, a much lower friction coefficient can be obtained.

Example 3

The single layer coating compositions for Samples 5 to 20 were prepared as shown in Table 2 below. When they were prepared, an epoxy resin (EP), a polyamide-imide resin (PAI), a phenolic resin (PH) and a polyimide resin (PI) were used as glue resins and boron nitride (BN), polytetrafluoroethylene (PTFE), molybdenum disulfide (M0S2) θ graphite (GF) were used as solid lubricants and, in addition, silicone nitride (SÍNN4), zirconia (ZrO₂), alumina (AI₂O₃) and iron oxide (Fe₂The) were used as hard particles.

Table 2

<td colspan="2">Total rating</td><td> &lt;</td><td> &lt;</td><td>Q</td><td>Q</td><td>Q</td><td>ü</td><td>O</td><td>co</td><td>CD</td><td>The</td><td>co</td><td>co</td><td>Q</td><td>O</td><td>O</td><td>Q</td><td>co</td><td>O</td><td>Q</td><td>O</td>

<td rowspan="4">Composition for lower layer coating (% by weight)</td><td>GF</td><td> 3,6</td><td></td><td> 1</td><td> 1</td><td> 3,6</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> • 1</td><td> 1</td><td> 1</td><td> 1</td>

<td>CM ω O</td><td> 14,5</td><td> 14,3</td><td> 14,3</td><td> 1</td><td> 12,0</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td>

<td>PTFE</td><td> 21,7</td><td> 21,9</td><td> 21,9</td><td> 1</td><td> 21,7</td><td> 1</td><td> &gt;</td><td> 1</td><td>t</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td>

<td>Resin</td><td>EP / 60.2</td><td>FATHER / 63.7</td><td>FATHER / 63.7</td><td> 1</td><td>EP / 60.2</td><td> 1</td><td> 1</td><td> 1</td><td>t</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> (</td><td> 1</td>

<td rowspan="4">Top layer coating composition (% by weight)</td><td>Particles</td><td> 1</td><td> &lt;</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td>O in CM CM O N</td><td>O in CM O CM &lt;</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td> 1</td><td>m cm ' O CM ω LL</td><td> 1</td><td> 1</td>

<td>z C * 5 ώ</td><td> 25,0</td><td> 25,0</td><td> 1</td><td></td><td> 1</td><td> 25,0</td><td> 25,0</td><td> 25,0</td><td> 25,0</td><td> 1</td><td> 1</td><td> 18,8</td><td> 12,5</td><td> 50,0</td><td> 37,5</td><td> 16,7</td><td> 28,1</td><td> 16,6</td><td> 33,3</td><td> 50,0</td>

<td>BN</td><td> 12,5</td><td> 12,5</td><td> 1</td><td> 1</td><td> 1</td><td> 12,5</td><td> 12,5</td><td> 12,5</td><td> 12,5</td><td> 12,5</td><td> 12,5</td><td> 18,8</td><td> 25,0</td><td> 1</td><td> 1</td><td> 1</td><td>σ&gt;</td><td> 8,4</td><td> 1</td><td> 1</td>

<td>Resin</td><td>EP / 62.5</td><td>FATHER / 62.5</td><td> 1</td><td> 1</td><td> 1</td><td>PH / 62.5</td><td>PI / 62.5</td><td>FATHER / 62.5</td><td>EP / 62.5</td><td>EP / 62.5</td><td>EP / 62.5</td><td>EP / 62.5</td><td>EP / 62.5</td><td>EP / 50.0</td><td>EP / 62.5</td><td>EP / 83.3</td><td>EP / 62.5</td><td>EP / 62.5</td><td>FATHER / 66.7</td><td>FATHER / 50.0</td>

<td>Sample</td><td></td><td> -</td><td>CM</td><td>* CO</td><td> *</td><td>* LO</td><td> ♦ &lt;0</td><td> *</td><td> * 00</td><td>9 Hi</td><td>♦ O</td><td> ♦</td><td>♦ C \ j</td><td>♦ co</td><td>* Xf-</td><td> 15*</td><td> 16*</td><td>* r-</td><td> * 00</td><td>* O) T "</td><td> 20*</td>

An organic solvent was added to and mixed with each of the coating compositions for Samples 5 to 20 shown in Table 2, which were comparative examples and Samples 1 to 2, which were the examples of the invention and Sample 3, which was the example comparative, shown in Table 1 in Example 1 and was dispersed for 30 minutes in a ball mill. The respective coating paints thus obtained were applied to piston skirts made of an aluminum alloy AC8A and were then calcined to form coatings for lubrication. When this occurred, coating paints were applied as for Samples 1 to 2, which were the examples of the invention, the lower layer coatings had a coating thickness of 5 to 10 pm and the upper layer coatings had a thickness of coating from 5 to 10 pm and for the respective Samples, which were the comparative examples, a single layer coating had a coating thickness of 10 to 20 pm. In addition, as calcining conditions, Samples 1 to 2 were calcined for 30 minutes at 180 ° C and the other Samples were calcined for 60 minutes at 180 ° C. Note that Sample 4 was a Sample that had no coating for lubrication.

The respective pistons were each built on a single cylinder gasoline engine with a 160 cm aluminum layer³ and were subjected to a 20 hour test run with full operation at 3600 rpm. The respective coatings for lubricating the Samples were fully evaluated based on wear and scratch marks on the piston surface and oil consumption after completing the engine test run, the results of which are also shown in Table 2 above. Note that the results of the total assessments were presented using A which indicates that the results were good, B which indicates that they were mild marks of wear and scratches, C which indicates that they were evident marks of wear and scratches and D which indicates that they were notable marks of wear and scratches. It is observed from the results presented in Table 2 that Samples 1 to 2 according to the examples of the invention, which were coatings for double layer lubrication, are extremely superior when compared not only to Sample 4 which had no coating for lubrication but also to Samples 3 and 5 to 20.

Example 4

The pistons that have the double layer lubrication coating for Sample 2, which was the example of the invention and the single layer lubrication coatings for Samples 3 to 4, which were the comparative examples, presented in Table 2 were prepared in a similar to that used in Example 3. These pistons were subjected to a 150 hour durability test with a full operating speed at 3600 rpm by using, similar to Example 3, a gas engine. single cylinder blade with a 160 cm aluminum layer³. Friction was applied before the full operating regime and after 15 seconds, 20 hours and 150 hours were measured while the engine speed varied up to 2000 rpm, 2500 rpm, 3000 rpm and 4000 rpm and the conditions of wear on the surfaces of the engines were investigated. pistons, the results of which are shown in Figures 5 to 8.

As is obvious from Figure 5, which shows friction from the Samples

2 to 4 before full operation was applied and the Figure showing friction from Samples 2 to 4 after 20 hours of full operation has elapsed, with the piston having the double layer lubrication coating of Sample 2, which was the example of the invention, on an outer circumferential surface of its piston skirt, compared to Samples 3 to 4, which were the comparative example, an output that indicates that friction was evidently reduced and it is also evident that Sample 2 had superior resistance to jamming and initial operating property.

' . . . .

In addition, it is obvious from Figure 7 that it shows the transition of friction conditions on Sample 2 of the invention before the full operation regime was applied and after 20 hours and 150 hours have elapsed since the Sample 2 piston, which was the example of the invention, is superior in little friction because the output decreased with the passage of the evaluation period. In addition, it is seen from Figure 8 that it shows photos of surfaces of the pistons of Samples 2 to 4 after the durability tests that the wear and scratches on Sample 2 of the invention were improved remarkably over Samples 3 to 4 of the comparative examples.

It is observed by the results that have been described so far that the piston on which the double layer lubrication coating was formed using the double layer lubrication coating composition of the invention presented the good initial operation property, less wear and high resistance to binding when used in the internal combustion engine. This is considered to be because the double-layer lubrication coating of the invention has been worn regularly due to the sliding contact with the socket material to thereby form a good sliding surface in the initial sliding stage. In addition, a reduction in friction can be expected due to the advantage of the coating for lower layer lubrication after the initial operation is completed.

Although the invention has been described in association with the exemplary embodiments, it will be obvious to those skilled in the art that various changes and variations can be made without departing from the present invention and the aim is therefore to cover such changes and variations in the appended claims when stay within the true spirit and scope of the present invention.