JPS59108850A - Engine piston - Google Patents

Abstract

PURPOSE:To reduce a slap sound by baking a lagging material consisting of 35- 75wt% heat resistant resin, 10-40wt% scaly aluminium, and 15-55wt% fluoro- resin powder onto the outer surface of a piston skirt part and covering said surface with said material. CONSTITUTION:The outer surface of a part downward an oil ring groove 3 in the skirt part 2 of a piston 1 is baked and covered with a lagging material 4 obtained by allowing scaly aluminium 6 and fluoro-resin powder 7 to be dispersed and contained in heat resistant resin 5. The heat resistant resin 5 consists of epoxy resin and phenolic resin, by 35-75wt%, and scaly aluminium 6 and fluoro-resin powder 7 by 10-40wt% and 15-55wt% respectively. The thickness of the lagging material 4 is adjusted to be more than 15mu, and surface roughness to be 5-20mu.

Description

[Detailed description of the invention] The present invention relates to a piston for a reciprocating engine.

In a reciprocating engine, reducing the piston clearance between the outer surface of the piston and the inner wall surface of the cylinder is effective in reducing engine noise, particularly the slap noise of the screws. However, this piston clearance is
Even in an autothermatic piston designed to suppress thermal expansion of the skirt portion, the limit is about 40μ, and further shrinkage will result in increased sliding resistance of the piston and consequent seizure of the piston. Therefore, the actual situation is that the above-mentioned slap sound cannot be sufficiently reduced.

To solve this problem, we can coat the outer surface of the piston with a coating material that has the required properties.
Attempts have been made to reduce piston clearance without increasing sliding resistance. For example, according to the applicant's prior patent application (Japanese Patent Application No. 54-3312),
A coating material made by dispersing 10 to 25% by weight of flaky aluminum and 15 to 30% by weight of heptanosulfide (MOS2') in an epoxy resin is baked on the outer surface of the piston to a predetermined thickness. An invention characterized by the following is disclosed.

According to this invention, the fit of the piston, especially the skirt portion, to the inner circumferential wall of the cylinder improves, and noise is reduced. However, since the coating material with the composition described above has the property of being easily worn, it is advantageous to quickly form an R-suitable bis-line profile by lap operation of the engine. It is difficult to maintain the clearance for a long period of time, and the disadvantage is that the clearance gradually increases and the noise increases.

In addition, other patent applications by the applicant (Japanese Patent Application No. 53-7
No. 1167) discloses an invention in which a fluororesin coating is formed on the surfaces of the pistons on both sides to reduce wear and noise of the piston. The above-mentioned fluororesin coating has excellent wear resistance, and the piston clearance does not gradually increase as the engine is used. However, the boiling point of the solvent is high, and it is difficult to apply further layers to a coating layer baked at normal temperatures. Since it does not need to be cut, the range of use is limited due to the thickness of the prefecture, such as when applying a thick compress and finally baking with normal ffM If. Also,
Since the wear resistance is too good, it is impossible to form an optimal profile by short-time lapping operation under normal conditions.

The present invention was made in order to solve the problems in view of the actual situation as described in Section 1F regarding pistons of reciprocating engines. When reducing the screw clearance, it is possible to obtain the optimum piston profile in a short time without increasing the sliding resistance, and by running the engine in laps, and to reduce the profile or the optimum screw clearance. It is designed to last for a long time. The object of the present invention is to realize a highly reliable piston that maintains the effect of reducing slap noise for a long period of time and consumes less lubricating oil.

That is, the bis 1-bond of the present invention has scaly aluminum lx 1 in 35 to 75% by weight of a heat-resistant resin on the outer surface of the skirt portion.
0~7! IO weight % and fluororesin powder 15-55%
The present invention is characterized in that the surface roughness of the coating material is adjusted to 5 to 20μ by baking a coating material made of a dispersed material with a layer thickness of 15 μm or more. According to such a configuration, since the friction coefficient of the coating material is small, the piston clearance can be reduced without increasing the anti-failure resistance, and the movement of the fluororesin also improves wear resistance. The gender increases by 1 or more,
The piston clearance after the formation of the optimum profile is maintained substantially constant, and this optimum profile can be formed quickly by adjusting the surface roughness of the coating material within the above range.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 shows screws 1 to 1 according to the present invention, and the outer surface of the screw 1 part 2 of the screws 1 to 1, that is, the part below the oil ring groove 3, is covered with a covering material 4. has been done. As shown in FIG. 2, this covering material 4 consists of a heat-resistant resin 5, scale-like aluminum 6, and fluororesin powder 7.
This is obtained by dispersing and curing the mixture.

The above-mentioned heat-resistant resin can withstand temperatures of about 250 degrees Celsius, as the temperature of the piston skirt can exceed 200 degrees Celsius, especially in the case of diesel engines. It has to be something that doesn't exist. This is compatible with the following:
There are epoxy resins, phenolic resins, silicone resins, polyimide resins, etc. In addition, the resin needs to function as an adhesive for the outer surface of the screws 1 to 1.
For this purpose, the ratio of the covering material to the whole must be at least 35m%. Incidentally, the upper limit of the ratio of the resin is 75% by weight, which is the minimum required level of the scale-like aluminum and the fluororesin powder.

Aluminum flakes are added to improve the heat resistance of the coating material and improve the abrasion resistance against shear loads, and in order to achieve these effects, it is necessary to add 10% or more. However, if it exceeds 40% by weight, the effect will be saturated, and on the contrary, the strength 1a of the coating material, that is, the adhesion to the outer surface of the bis 1-bond will decrease.

Fluororesin powder is an abrasion resistance improver for coating materials.The reason why powder is used is that liquid fluororesin has the following drawbacks.
-Because it is. In other words, liquid fluororesin has extremely poor miscibility with base resin, and if it is not thermally cured at a high temperature of 300°C or higher, its original properties cannot be improved by 1q, but at this temperature aluminum alloy screws In the case of 1-ton, the strength of the piston is drastically reduced. Note that the particle size of the fluororesin powder is preferably 24 μm or less in relation to the surface roughness of the coating material.

The graph in FIG. 3 shows how this fluororesin powder is involved in improving the abrasion resistance of the coating material.

This graph shows the ratio of fluororesin powder to 10.15.1
9, 26. 32. We compared the amount of wear (amount of reduction in piston diameter) in test runs under certain conditions for each of the coating materials using epoxy resin and heat-resistant resin. As a conventional example, the above-mentioned patent application (Japanese Patent Application
Data are shown for a coating material disclosed in 4-33 December 2003, which is composed of 20% by weight of molybdenum disulfate, 25% by weight of flaky aluminum, and 55% by weight of epoxy resin. The test conditions were: coat thickness of coating material 20μ, surface roughness 2-3μ, screw clearance during coating 0μ, heat curing condition of coating material 225℃, 30 minutes (conventional example: 180℃, 30 minutes), the ratio of fluororesin powder was reduced to 1.
For the 5% by weight coating material, the heat curing conditions were set to 180%.
℃ for 30 minutes.
This is shown in the bar graph of broken X31 in FIG. and,
The engine used was a 1.5j2 gasoline engine, and the operating conditions were 3000 PPM, full load, and 50 hours. According to this, when the fluororesin powder is 10% by weight, the significant difference from the conventional example is small, but when it is 15% or more, the wear and tear is significantly reduced. It can be seen that the wear resistance is improved.

Furthermore, the abrasion resistance of the υ material to be covered is also affected by the heat setting thread 1'1, as shown in FIG. That is, the higher the thermosetting temperature is, the better the wear resistance is, but it is saturated around 225°C, and the wear resistance is not sufficient at 160°C. Therefore, considering the effect on piston strength, 180℃~
The temperature is preferably 225°C, and in that case baking time is required to be 30 minutes or more.

Here, the data in FIG. 4 shows that the composition of the coating material is 26% by weight of fluororesin powder, 30% of scale-shaped aluminum,
1% and 44% by weight of epoxy resin, and the des-l-conditions are the same as the test shown in FIG. 3 above.

In addition, as each component of the above-mentioned coating H, for example, the heat-resistant resin and flaky aluminum include Santomo DI-IX-Ml (trade name), which is made by containing flaky aluminum in an epoxy resin, and the fluororesin powder includes: Sangatsu Fluorochemical TLP-10 (trade name) is used. Coating methods for the coating material include spraying, transfer, sheet adhesion, electrostatic coating, and the like.

As described above, by adding the fluororesin powder, a coating material with excellent wear resistance can be realized. However, if the wear resistance is too good, it will be difficult to achieve the appropriate screw profile or piston clearance by a short lapping operation after coating (A coating). By adjusting the surface roughness during coating to a relatively rough fixed range, reducing the apparent wear resistance and accelerating initial wear, an optimum profile is formed for short-term lapping operations. In order to form this optimal profile, the wear amount of the covering material must be 2.5μ or more (radius).

However, the current clearance for screws 1 to 1 is for the diameter,
In other words, the difference between the cylinder inner diameter and piston outer diameter is 30 to 60μ for gasoline engines and 4μ for diesel engines.
0 to 200μ, but in the case of a piston coated with a coating material, in the case of a gasoline engine, it is 10 to 30μ,
In the case of a diesel engine, the rotational resistance can be reduced to 20 to 40μ without any increase in rotational resistance. Clearance 40 without coating material
If we take as an example the screws I and N with a clearance of 20μ and the covering material, we can see that the fifth
As shown in the figure, there is almost no resistance loss between the two, and it can be seen that by coating with a covering material, the bis-1 hem clearance can be halved.

Note that even if the piston is coated with a coating material, the resistance loss will be large if the clearance is Oμ.

Here, the coating material used in this test was a mixture of 26% fluororesin powder, 30% scaly aluminum, and 14% epoxy resin, which was heat-cured at 225°C for 30 minutes. The surface roughness is 2-3μ. Also, the engine used is 2. It is a gasoline engine of O.g.

In other words, for bis-1-hen coated with coating material (
Well, due to initial wear due to lap operation, it is 10 to 30μ for gasoline engines and 2μ for diesel engines.
If an R-appropriate screw clearance of 0 to 40μ can be obtained, and if an optimum profile of the screw skirt can be obtained during this initial wear. To achieve this, the surface roughness during coating is adjusted.

FIG. 6 shows the relationship between the surface roughness during coating of the coating material and the initial wear due to lap operation, and there is a certain range depending on the displacement per cylinder for both gasoline engines and diesel engines. Now, coating material is coated so that the piston clearance becomes Oμ for the current screws 1 to 1, and this is coated with a coating material so that the piston clearance becomes Oμ. The optimum screw clearance shall be obtained.

First, in the case of a gasoline engine, the current piston clearance is 30 to 60μ (diameter), so the coating thickness is 15 to 30μ (radius), and this is applied until the optimum clearance is 10 to 30μ (diameter). To wear out, the amount of wear is 5 to 15 rl (radius), remaining] -1 ~
The thickness is 10 to 15μ (radius). In order to obtain this amount of wear, the surface roughness at the time of coating may be adjusted to about 7 to 20 microns, as shown at point a, 1] in FIG. In addition, in the case of Diegel engines, the current piston clearance is 40 to 200μ (diameter), so 1-1 to
The thickness is 20-100μ (radius), and in order to wear this to the optimum clearance of 20-40μ (diameter), a wear amount of 10-20μ (radius) is required, and the remaining coat thickness is 10-20μ (radius). It becomes 80μ (radius). In order to obtain this amount of wear, the surface roughness at the time of coating should be adjusted to about 10 to 12μ, as shown at points c and d in FIG.

Taking all of this into consideration, when coating the coating material, it is only necessary to adjust the tool thickness to 15μ or more and the surface roughness to a range of 5 to 20μ, and this surface The roughness range is 2.5μ or more.

, 1-(radius) Because the coating material wears, the piston 7
J-1 partial optimal profiles can also be created.

Furthermore, the test conditions were 26% fluororesin powder, 30% aluminum flakes, and 44% epoxy resin by weight.
The coating material was thermally cured at 225°C for 30 minutes, and each engine was lapped for 20 hours while changing from no load to full load depending on each engine. Above J: Sea urchin surface roughness adjusted rH
As shown in Figure 7.8, the initial wear is almost complete after 10 hours of lapping operation, and there is almost no wear thereafter. Here, the experimental data shown in Figure 7.8 are 26% by weight of fluororesin powder and 30% by weight of scaly aluminum.
, 225°C for 1 boxy resin 44% coating material
Figure 7 shows 1.5 after heat curing for 130 minutes.
1 gasoline engine, 3500RPlvl, 3/4
In the case of 10 hours of lap operation under load, Fig. 8 shows 3. OJ2. Diesel engine, 2500RP
This is a case where lap operation was performed for 10 hours at M, 3/4 load.

Next, based on the above study results, the durability of the coating material (during operation 118 vs.
We will explain the convergence of the changes in the amount of wear (changes in the amount of wear caused by the wear and tear) and the changes in noise over time.Here, the coating material is made of 26% suspended fluororesin powder, 30ffiω% flaky aluminum,
The epoxy resin is 44%, and the heat curing conditions are 225℃, 3
1st Example A of 0 minutes, fluororesin powder 15 weight%, scaly aluminum 34%, epoxy 4fii fat 51%, thermosetting thread (!1
or 1-2 Second Example B similar to First Example A, 20% by weight of molybdenum disulfide, 25,000 m% of scaly aluminum,
Epoxy resin 55% basis weight, heat curing conditions 180℃, 3
A comparison was made regarding the conventional example of 0 minutes.

Figure ε) shows that the screw clearance at the start of the test is Oμ, the coating thickness of the coating material is 20μ, and the surface roughness is 2 to 3.
μ, 3000 for a 1.5il gasoline engine
PPM, which shows the results when operating at full load.
The amount of wear in the actual eggplants A and B is significantly smaller than that of the conventional example, and moreover, the amount of wear hardly changes within a short period of time after the start of operation.

Also, in Fig. 10, the piston clearance at the start of the test was 10μ, the coating thickness of the coating material was 35μ, the surface roughness was 2 to 3μ, and 3.0! About the diesel engine 3
The results are similar to those shown in FIG. 9 when operating at 800 RPM and full load.

Furthermore, Fig. 11 shows that the screw clearance is 0μ (the conventional example of non-cone is 170μ) and the surface roughness of the coating material is 1
This shows the change in the noise level over time when operation is started from a state of 5μ, and is a case where a 2.51 diesel engine is operated at 3000PPM and full load. As a result, in the conventional example, the noise level reaches the same level as in the case of the non-coal type (over a short traveling distance), but in the example A,
B is both held at a low level.

As mentioned above, according to the present invention, it is possible to reduce the piston clearance in the piston of a reciprocating engine without causing an increase in the learning resistance.
The optimum piston clearance and the optimum profile of the screw force section can be obtained by a short lap operation and will be maintained for a long period of time. As a result, the effect of reducing slap noise and the like can be maintained for a long period of time, and a highly reliable screw 1 with low lubricant consumption can be realized.

[Brief explanation of the drawing]

FIG. 1 is a partial longitudinal cross-sectional view of a bis-1 hem in which the present invention is implemented;
Fig. 2 is an enlarged vertical cross-sectional view of the coating material in Fig. 1, and Fig. 3 shows the relationship between wear resistance 14 due to the addition of fluororesin powder to the coating material.
Graph showing the system, Figure 4 is a J-graph showing the relationship between heat curing temperature and wear resistance of the coating material, Figure 5 is a graph showing the sliding resistance of a piston coated with Ya material, Figure 6 7 and 8 are graphs showing the relationship between the surface roughness of the coating material and the amount of wear.
The country has graphs showing the state of initial wear of the covering material, Nos. 9 and 10.
The figure is a graph comparing the durability of the embodiment of the present invention and the conventional example, and FIG. 11 is a graph comparing the noise level as well. 1...Bis 1~n, 2...Scar 1 part, 4...
Covering material, 5... heat resistant (11 resin, 6... scaly aluminum, 7... fluororesin powder applicant Toyo) Nigyo Co., Ltd. Fig. 1 Fig. 2 1 (2) , Ishi 58 gl-C　Fig. 5 and 1 stone force - to once (@C) Fig. 6 surface sum jC voice) Fig. 7 Fig. 8 between 1 and 9 (h) Fig. 10 Operating time ( h) Figure 11 Travel route M (X10'km) -307-

Claims (1)

[Claims] (1) A coating material made by dispersing 10-40% by weight of flaky aluminum and 15-55% by weight of fluororesin powder in 35-75% by weight of a heat-resistant resin is baked onto the outer surface of the skirt in a layer thickness of 15 μm or more. 1. An engine piston, characterized in that the piston is coated with a surface roughness of the coating material adjusted to 5 to 20μ.