JPH02120575A - Piston ring - Google Patents

Abstract

PURPOSE:To prevent engine trouble due to agglutination and improve the durability of an engine by forming a pressure ring of a surface layer made of chemical conversion coating of forming a stannum phosphate film on the manganese phosphate crystal film formed on the upper and lower surfaces. CONSTITUTION:In a pressure ring 1, a nitriding drum 3 is formed on the whole periph eral surface of the base material made of cast iron or steel, a manganese phosphate crystal film surface layer 4 is formed on the layer 3, and a stannum phosphate film 5 is further formed on the layer 4. In addition, a hard chrome plating layer 6 is formed on the peripheral surface of the pressure ring 1 as a barrel face form. As the film of the surface layer 4 made of the manganese phosphate film is formed of a cellular crystal body, the absorptivity and the retentivity of lubricating oil is improved and the contact of metal against the metal in the rotating and sliding part is avoided by the film so as to prevent phenomena such as baking, scuffing, and the like. Further more, the film 5 of stannum phosphate is excellent in corrosion and abrasion resistance compared to the manganese phosphate crystal body as well as in the absorptivity and the retentivity of lubricating oil due to the cellurarity of the crystal body, and displays the lubricating ability and the characteristic of the initial conformability of stannum.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a piston ring whose upper and lower surfaces are improved.

(Prior Art) In recent years, many internal combustion engines have a double-over-hood cam structure or a structure equipped with a turbocharger, and the compression ratio is further increased to improve output. Therefore,
Thermal load on the piston ring, especially in the vicinity of the first pressure ring, is increasing.

For aluminum alloy pistons, when the heat load increases, the aluminum piston material adheres to the top and bottom surfaces of the piston rings, causing wear in the piston ring grooves.
May result in blow-by and increased oil consumption. This aluminum adhesion to the upper and lower surfaces of the piston rings often occurs on the first pressure ring, which is most exposed to the heat load.

Conventionally, this has been a problem in air-cooled two-stroke engines that have a large heat load. However, recently, even water-cooled gasoline engines and diesel engines have been changed to structures that increase the heat load as described above, so aluminum adhesion has become a problem.

(Problems to be Solved by the Present Invention) As a method for preventing aluminum adhesion, the first method is to use a phosphate film with a thickness of 5 μm or more, an iron plating layer, an ethylene tetrafluoride film, or a molybdenum disulfide thermosetting resin coating film. Attempts have been made to provide aluminum on the upper and lower surfaces of the pressure ring, or to apply alumite treatment to the surface of the piston ring groove, but none of these treatments on the piston ring side have been able to sufficiently prevent aluminum adhesion. In addition, alumite treatment of piston ring grooves prevents aluminum adhesion, but is viewed as a problem due to surface roughness and cracks, which can lead to blow pie and increased oil consumption.

The present invention has been made in view of the above circumstances, and includes:
The problem to be solved is to provide a piston ring that does not cause aluminum adhesion even in engines with a large heat load.

(Means for Solving the Problems and Their Effects) That is, the present invention relates to a piston ring having a surface layer with a chemical conversion coating consisting of a double layer of phosphate having corrosion resistance and wear resistance on the upper and lower surfaces.

As a result of repeated studies of the present invention through actual machine tests, it was found that aluminum adhesion occurs in the early stages of operation after the piston ring is assembled. Therefore, it is only necessary to prevent aluminum adhesion from occurring in the early stages of operation, and for this purpose, it is necessary to promptly make the upper and lower surfaces of the piston ring fit in with the side surfaces of the ring groove of the piston. The present invention has been made based on the above findings.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of the pressure ring. Pressure ring 1 is
A nitriding layer 3 is formed on the entire circumferential surface of a base material 2 made of cast iron or steel, a manganese phosphate crystal coating surface layer 4 is formed on the layer 3, and a tin phosphate coating 5 is further formed on the surface layer 4. is formed.

The outer peripheral surface of this pressure ring 1 has a barrel face shape and is plated with hard chrome N6.

The surface layer 4 made of manganese phosphate film is made of porous crystalline material. Therefore, it has good lubricating oil absorption and retention properties, and the coating avoids metal-to-metal contact in rotating and sliding parts, so it is a layer provided to prevent phenomena such as seizure and galling. The thickness of these four layers is preferably 5 to 15 μm; if it is less than 5 μm, the above-mentioned contact avoidance effect will not be noticeable, and if it is thicker than 15 μm, the surface will become too rough and cause partial exfoliation of crystals. It becomes like this.

The thickness of the surface layer 4 needs to be at least 5 μm in order to improve the initial fit and prevent aluminum adhesion. The upper limit is determined by the clearance formed by the difference between the width of the ring groove of the piston and the width of the piston ring, and is usually set to 5 to 15 μm. If the surface layer 4 is too thick, it will be difficult to attach the piston ring to the piston, the increase in the above effects will not be significant, and the cost will increase. Furthermore, the tin phosphate film 5 formed thereon has better corrosion resistance and wear resistance than the manganese phosphate crystals on the surface Ji4, and since the crystals are porous, it has excellent lubricating oil absorption and oil retention. The lubricity and initial run-in properties of this material also make it even more effective. The thickness of the surface layer 5 having initial break-in lubricity may be 1 to 2 μm; if it is less than 1 μm, tin phosphate crystals will not develop and the above effect will be insufficient;
If the thickness exceeds m, the crystals become more porous and the crystal bonding force decreases, and because the bonding force is insufficient, there is a problem that the film will come off by the time it is assembled.

Experiment: In the piston ring shown in Fig. 1, the base material 2 is 62% mX.
1.5m x 3.1m heat-resistant steel 5US440B (C: 0
．． 80-0.95%, Si: 1.0% or less, Mn:
1.0% or less, P: 0.045% or less, Cr: 17. O
~18.0%, Mo: 0.8~1.5%, V: 0.
05 to 0.15%) to a depth of 50 μm on the entire circumferential surface of the base metal.
After forming the nitrided layer 3, 1 is applied to one of the upper and lower surfaces.
A manganese phosphate crystal film 4 with a thickness of 0 μm was formed, and a tin phosphate film 5 with a thickness of 2 μm was formed thereon.

Figure 2 shows an outline of the test equipment used for the adhesion test.

The piston ring holder 12 is connected to the rod 13a of the air cylinder 13 via a universal joint 14, and holds the piston ring 1) with the surface layer 4 facing downward. The piston material holder 16 has recesses 16a, 16.
A heater is inserted into the lower recess 16b, and a piston material sample 15 made of casting aluminum alloy Ac-8A, which is widely used as a piston material, is inserted into the upper recess 16a. Fixed.

The heater 17 is connected to a power source (not shown) through a lead 18 to heat the piston material sample 15 to a predetermined temperature. A shaft 19 is fixed to the piston material holder 16 , the shaft 19 is rotatably supported by a hair ring 20 , and a spur gear 2 attached to the shaft 23 of a motor 22 is attached to the shaft 19 .
A spur gear 21 that meshes with motor 2 is set aside.
2, the piston material sample 15 is rotated in forward and reverse directions at a predetermined period, and the rotating piston material sample 15 is repeatedly struck to examine adhesion.

The test conditions are as follows.

Temperature of piston material sample: 250℃±5℃ Contact surface pressure: 14
kg/cd Stroke: 10 fI Cycle: 4 times/sec Forward/reverse rotation period = 2.5 times/min Rotation angle: 180' The reason why the piston ring sample and piston material are rotated in the forward and reverse directions relative to each other is due to the engine. During operation, the piston reciprocates and the top and bottom surfaces of the piston ring collide with the sides of the piston ring groove, and the piston ring rotates randomly in the piston ring groove. be.

The results of the tests conducted in this manner are shown in Table 1 below. For comparison, the same table shows that the surface layer contains 3 to 7 μm.
Sample coated with m-thick Teflon, sample coated with 5-7 μm thick hard chrome plating, heat-resistant steel JIS 5US44
The results of similar tests conducted on a sample subjected to a nitriding treatment and a sample coated only with a manganese phosphate crystal film with a thickness of 10 to 12 μm are also shown. In the table, OK indicates that no adhesion was observed, and NO indicates that adhesion occurred.

Table 1 From Table 1, it can be seen that all of the comparative samples caused peeling or adhesion during short-term tests, whereas the example samples did not cause adhesion or peeling and had excellent resistance to aluminum adhesion. It can be seen that

Actual machine test: Equipped with a cylinder with a bore diameter of 67, and a piston stroke of 5
An actual machine test was conducted using a 6mm, 200cc, air-cooled, 4-stroke, single-cylinder gasoline engine.

FIG. 3 shows the piston and piston rings in the cylinder, and the first ring groove 33a, the second ring groove 33b, and the oil scraper ring groove 33c of the piston 33 have a first pressure ring 1, a second pressure ring 31, an oil The raking rings 32 are fitted into each piston ring 1, and the outer circumferential surface of each piston ring 1, 31, 32 is in pressure contact with the inner circumferential surface of the cylinder 34.

The structure shown in Fig. 1 is used for the first pressure culling 1, and the base material 2 is made of heat-resistant steel 5O3440B (C: 0.8
0 to 0.95%, Si: 1.0% or less, Mn: 1.
0% or less, P: 0.045% or less, Cr: 17. O~1
8.0%, Mo: 0.8-1.5%, V: 0.05
~0.15%) material to a depth of 20% on the entire circumferential surface of the base material.
After forming the nitrided layer 3 with a thickness of μm, a manganese phosphate crystal film 4 with a thickness of 10 μm is formed on the upper and lower surfaces, and a 2 μm thick manganese phosphate crystal film 4 is formed on the top and bottom surfaces.
A thick tin phosphate film 5 was formed. piston ring 1
The dimensions are 67 tm x 1.2w x 2.3m+
It is.

This piston ring 1 is used as a first pressure ring, and is assembled into the engine as shown in FIG.
After operation, the engine was disassembled and aluminum alloy adhesion on the first pressure ring 1 was observed.
The amount of wear on the side surface of the first pressure ring groove 33a was measured.

For comparison, instead of the surface layer 4.5, a 3-5 μm thick Teflon coating, a 5-6 μm thick hard chrome plating, and a 4-6 μm iron plating were used. , 1) A manganese phosphate crystallized film of ~13βm and a base material of heat-resistant steel 5US440B with 15
A similar actual test was conducted using a nitrided layer with a thickness of ~20m for the first pressure culling.

The experimental results are shown in Table 2 below.

In all of the piston rings compared in Table 2, the piston material has adhered, and the side surfaces of the ring groove of the piston are also worn due to repeated collisions with the upper and lower surfaces of the piston ring, whereas in the piston ring of the example There is no adhesion of the piston material, and there is almost no wear on the side surface of the ring groove of the piston, demonstrating extremely excellent aluminum adhesion resistance.

(Effects) The piston ring of the present invention has extremely fine and uniform tin phosphate crystal surfaces on its upper and lower surfaces, as shown in the electron micrograph of FIG. As a result, even under severe engine operating conditions with a large heat load, adhesion does not occur between the upper and lower surfaces of the piston ring and the side surfaces of the piston ring groove (the adhesion caused by the engine No trouble will occur.Furthermore, the wear on the side surfaces of the piston ring grooves will be extremely minimal, improving the durability of the engine.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a piston ring showing an embodiment of the present invention, Fig. 2 is a sectional view of an adhesion test device, and Fig. 3 is a sectional view of a piston, piston ring, and cylinder assembled into an engine. Figures 4 and 4 are electron micrographs of the crystal structure of the film magnified 1000 times. In the diagram: 1. First pressure ring, 2. Base material, 3. Nitriding layer, 4. Manganese phosphate crystallized film, 5. Tin phosphate film, 6. Hard chromium on outer peripheral surface. Plating layer.

Claims (2)

[Claims] (1) A piston ring having a surface layer made of a chemical conversion treatment in which a crystallized manganese phosphate film is formed on the upper and lower surfaces, and a tin phosphate film is further formed thereon. (2) The piston ring according to claim (1), which is used in a ring groove of a piston made of an aluminum alloy material.