JPS5925868B2 - internal combustion engine piston - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston for an internal combustion engine, in particular a reciprocating piston engine.

In general, a reciprocating piston engine as shown in Japanese Utility Model Application Publication No. 50-27210 has a piston 2 that reciprocates up and down within a cylinder body 1, as shown in FIG. The combustion chamber 4 is made to undergo each stroke of intake, compression, explosion, expansion, and exhaust in order.

Note that 5 to 7 are piston rings attached to the outer peripheral surface of the piston 2, of which 5 is a top ring, 6 is a second ring, and 7 is an oil ring.

8 is an intake port, 9 is an intake valve, 10 is an exhaust port, 11
1 is an exhaust valve, 12 is a spark plug, and 13 is a connecting rod that connects the piston 2 and a crankshaft (not shown).

As mentioned above, since the reciprocating piston engine structurally forms the hemispherical combustion chamber 4, the combustion chamber 4 is surrounded by the surface of the top land portion 2a on the outer peripheral surface of the piston 2, the inner peripheral wall of the cylinder body 1, and the top ring 5. One side is combustion chamber 4
The hemispherical combustion chamber 4 has an air gap (hereinafter referred to as the ΔH portion) that communicates with the combustion chamber 4 all around.

This △H part has a small gas flow and is cooled from both the walls of the cylinder body 1 and the piston 2, making it difficult for the temperature to rise. This results in an increase in the HC (hereinafter referred to as Raw HC) component.

In order to prevent this, the △H part in the reciprocating piston engine should be made structurally and dimensionally free from clearance, but when the piston 2 reciprocates up and down and under unbalanced thermal expansion of each part of the engine, In order to obtain sufficient clearance for vertical movement, a considerable amount of △
H (usually about 400μ) is required and cannot be eliminated mechanically.

Furthermore, since the piston 2 in the reciprocating piston engine performs crank motion with the crankshaft via the connecting rod 13, some clearance is provided between the outer surface of the skirt portion 2b of the piston 2 and the inner circumferential wall of the cylinder body 1. Even if the skirt portion 2b of the piston 2 collides with the inner circumferential wall of the cylinder body 1 due to pressure fluctuations, etc., the skirt portion 2b may
There is a problem in that it causes seizure of the engine 1 and generates noise, which contributes to the noise of the engine 1.

Therefore, in order to reduce the above-mentioned piston noise, Japanese Unexamined Patent Publication No. 50-128046 discloses that an outer cylinder is inserted into the skirt portion of the piston body, and oil or a leaf spring is interposed between the piston body and the outer cylinder. A device is disclosed that reduces the impact force between the liner and the liner.

However, this makes the structure of the piston complicated, and the compatibility between the outer cylinder and the liner is not very good.

In addition, the applicant of the present application has considered forming a fluororesin coating on the surfaces of both side skirt portions of the piston to reduce wear and noise of the piston (see Japanese Patent Application No. 71167/1983).

However, when applying and baking fluororesin, the boiling point of the solvent is high, so it is difficult to coat the coating layer that has been baked at a normal temperature. In some cases, the solvent does not drain completely, so when it is applied thickly and then baked at a normal temperature, it becomes foamy and easily peels off, which limits the range of use due to the thickness of the coating layer. It is.

The present invention has been made in view of this point, and the above-mentioned △
By coating the top land surface of the piston outer peripheral surface in the H part with a material having the following physical properties and making the clearance of the ΔH part as small as possible, RawH
We have discovered that it is possible to reduce C and have developed a material that has the physical properties required as a coating material for the outer circumferential surface of a piston.
The present invention provides a piston for a reciprocating piston engine that can effectively reduce HC.

In other words, the physical properties necessary for the coating material for the outer circumferential surface of the piston are: (1) heat resistance that does not change in quality at 300°C, @ (that) it does not wear itself and damage the other party when it collides with the cylinder body 1, and (0) that it itself is wear resistant. *No peeling due to seizure or lack of shear resistance when in contact with the inner peripheral wall of the cylinder body; *Easy to apply thick coatings and multiple coats; @Preferably a material with elasticity and a cushioning effect. (1) Sufficient adhesion to the piston.

In order to satisfy these physical properties, the present invention has developed a coating material made of an epoxy resin in which 10 to 25 weight percent of flaky aluminum and 15 to 30 weight percent of molybdenum disulfide (MoS2) are dispersed, and this coating material The material is baked onto the top land surface of the outer peripheral surface of the piston of a reciprocating piston engine to a thickness of 30 μm or more.

Furthermore, the present invention bakes the coating material to a layer thickness of 30 μm or more on the top land surface of the piston outer peripheral surface of a reciprocating piston engine, and bakes the coating material to a layer thickness of 5 to 150 μm or more on the outer surface of the skirt portion below the oil ring groove. As a result, in addition to reducing the Raw HC, it is possible to improve the fit of the skirt portion to the inner circumferential wall of the cylinder body, and to prevent noise.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

Incidentally, since the schematic structure of the reciprocating piston engine has already been described with reference to FIG. 1, detailed explanation thereof will be omitted.

In FIGS. 1 to 3, 14 is a first coating layer provided on the surface of the top land portion 2a of the outer peripheral surface of the piston, and 15 is the outer surface of the skirt portion 2b below the ring groove of the oil ring 7 on the outer peripheral surface of the piston. The second coating layer provided, the first coating layer 14 has a layer thickness of 30 mm.
μ or more, and the layer thickness of the second coating layer 15 is 5 to 1
It is set to 50μ, and both coating layers 14 and 15
As shown in FIG. 3, 10 to 25% by weight of flaky aluminum 16 and molybdenum disulfide (MO82) 1
A coating material made of epoxy resin 18 in which 15 to 30% by weight of 7 is dispersed is applied and baked.

Among the components of the coating material, the epoxy resin 18 has the properties of @, ■, θ, and ■ among the physical properties necessary for the coating material for the piston outer circumferential surface (i.e., it does not wear itself and do not damage the other party, it is not coated thickly, and It has sufficient properties of ■, 0 and ○ (i.e. heat resistance, abrasion resistance,
However, the flaky aluminum 16 improves the peeling resistance of ○, that is, the shear strength, and also improves the heat resistance (properties of ■) of the coating layers 14 and 15. In addition, molybdenum disulfide 17 prevents the peeling resistance of @, especially seizure, and ensures the lubricity between the cylinder body 1 and improves the wear resistance of O. It is.

Therefore, by containing the flaky aluminum 16 and molybdenum disulfide 17 in the epoxy resin 18, the necessary physical properties as a coating material for the outer peripheral surface of a piston can be achieved.
will hold all of the following.

In addition, the content of the above-mentioned scaly aluminum 16 is 10% by weight.
If it is less than 25% by weight, it is insufficient to achieve the above effects (i.e., improved peeling resistance and heat resistance), and if it exceeds 25% by weight, the effect is saturated and the strength (i.e., adhesion) of the coating layers 14 and 15 is reduced. Therefore, the content is set in the range of 10 to 25% by weight.

In addition, the content of molybdenum disulfide 17 is 15% by weight.
If it is less than 30% by weight, it is insufficient to achieve the above effects (i.e., improved peeling resistance and abrasion resistance), and if it exceeds 30% by weight, the effect is saturated, which leads to a decrease in the adhesion strength of the coating layers 14 and 15, which is not preferable. , so 15 to 30
It is set in the weight% range.

Furthermore, if the thickness of the first coating layer 14 is less than 30μ, the coating will not be able to sufficiently reduce the clearance, so it needs to be at least 30μ, and the upper limit is usually about 400μ for the clearance of the ΔH portion.
Since it is about μ, it is limited to about 200μ.

Further, if the thickness of the second coating layer 15 is less than 5 μm, it is insufficient to achieve a coating effect, and if it exceeds 150 μm, the coating effect is saturated, and on the contrary, the noise due to contact with the cylinder body 1 increases. 150μ
Next, to explain an example of the present invention, an example of the coating material of the present invention is a coating material consisting of 20% by weight of flaky aluminum, 25% by weight of molybdenum disulfide, and the remainder of epoxy resin. Dissolve in thinner and apply with a brush to the top land surface of the piston outer circumferential surface, the piston ring land portion, and the outer surface of the skirt portion below the ring groove of the oil ring 7. After application, heat and bake at 180°C for 30 minutes. As a result, a first coating layer with a thickness of 150 μm was formed on the top land surface of the outer peripheral surface of the piston, and a second coating layer with a thickness of 30 μm was formed on the outer surface of the skirt portion.

The coating layer on the piston ring land portion is formed to improve the conformability when the piston ring land portion occasionally makes weak contact with the inner peripheral wall of the cylinder body 1, and its thickness is 5 to 10μ. thin.

In addition, the coating layer on the piston ring land portion is Ra
Since it has little effect on reducing wHC and piston noise, it is not necessarily necessary to form it.

Furthermore, among the components of the coating material, epoxy resin (silicon type) and flaky aluminum were used as a mixture thereof, commercially available "Santomo DHxM-1" (manufactured by Mitsui Bussan Kakoki Sales Co., Ltd.).

2000 pistons with such a coating layer
Used in a CC 4-cylinder reciprocating piston engine, full load operation at engine speed 4000 r, p, m for 100
After this time, the next Raw HC measurement and decomposition test were performed.

In addition, when full load operation of 4000r, p, m was performed for 100 hours, the layer thickness of the first coating layer was 120μ on average,
The average layer thickness of the second coating layer was 20μ, which was worn by 30μ and 10μ compared to the original thickness, respectively.

First, as a measurement of RawHC, the engine speed is 700.
At idling operation of r, p, m, air fuel ratio A/F 1
Under the conditions of 4, unburned HC
The amount of discharged components was measured and the results are shown in Table 1 below.

As is clear from Table 1 above, it can be seen that in the example of the present invention, Raw HC is reduced by 25% compared to the conventional example.

In addition, as a disassembly test, a case using a coating material in which scale-like aluminum was removed from the above-mentioned example of the present invention and the above-mentioned coating material according to the present invention (Comparative Example 1), and a case in which a coating material was used in which molybdenum disulfide was removed from the above-mentioned coating material ( In Comparative Example 2), the presence or absence of peeling of each coating layer and the presence or absence of combustion deterioration due to heat were examined,
The results are shown in Table 2 below.

Similarly, the skirt portions of the present invention example, conventional example, comparative example 1, and comparative example 2 were inspected for presence of seizure and measured for noise, and the results are shown in Table 3 below.

Furthermore, when the layer thickness of the first coating layer (provided on the top land) was measured, it was found that the initial layer thickness was 150 μm, and the engine break-in operation (4000 r, p, m full load operation) was 20 hours. When this is done, the layer thickness is abraded to approximately 120μ, and even if the break-in operation is continued, the layer thickness does not change and remains approximately constant (120μ).

That is, it can be seen that the layer thickness of the first coating layer becomes a constant value after running-in for a certain period of time.

As explained above, according to the present invention, an epoxy resin containing 10 to 25 parts by weight of flaky aluminum and 15 to 30 parts by weight of molybdenum disulfide is dispersed on the surface of the top land portion of the outer peripheral surface of the piston of a reciprocating piston engine. By baking it to a layer thickness of 30μ or more, it is possible to reduce the clearance of the △H part and reduce Raw HC, and the coating material has excellent heat resistance, adhesion, lubricity, peeling resistance, etc. Since it has excellent physical properties necessary as a coating material for the outer circumferential surface and is highly durable, it also has the advantage that it can be used without affecting the performance of reciprocating piston engines.

Furthermore, the above-mentioned coating material is baked on the surface of the top land portion of the outer peripheral surface of the piston to a thickness of 30μ or more, and the outer surface of the skirt portion below the oil ring groove is coated with a layer of 5 to 150μ.
By μ baking, in addition to reducing the Raw HC described above, it is possible to improve the fit of the skirt portion of the piston to the cylinder body and to reduce the generation of noise.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the present invention, and FIG. 1 is a longitudinal sectional view showing the schematic structure of a reciprocating piston engine, FIG. 2 is a longitudinal sectional view of the piston part, and FIG. 3 is an enlarged sectional view of the coating layer. It is. 1...Cylinder body, 2...Piston, 2a...Top land portion, 2b...
Skirt portion, 3... Cylinder head, 4...
...Combustion chamber, 5...Top ring, 6...
...Second ring, 7...Oil ring,
8...Intake port, 9...Intake valve, 1
0...Exhaust port, 11...Exhaust valve,
12... Spark plug, 13... Connecting rod, 1
゛4...First coating layer, 15...
- Second coating layer, 16... scale-like aluminum, 17... molybdenum disulfide, 18...
····Epoxy resin.

Claims (1)

[Claims] 1. On the surface of the top land portion of the outer peripheral surface of the piston of a reciprocating piston engine, 10 to 25 pieces of aluminum flakes are applied.
A piston for an internal combustion engine, characterized in that it is made by baking an epoxy resin in which a weight factor and a weight factor of 15 to 30 molybdenum disulfide are dispersed to a layer thickness of 30 μm or more. 2. Baking an epoxy resin in which 10 to 25 weight percent of flaky aluminum and 15 to 30 weight percent of molybdenum disulfide are dispersed on the surface of the top land portion of the outer peripheral surface of the piston of a reciprocating piston engine to a layer thickness of 30 μ or more, and applying oil 5 to 1 on the outer surface of the skirt below the ring groove.
A piston for an internal combustion engine characterized by being baked to 50μ.