JP2006258110A - Steel combination oil control ring - Google Patents

Abstract

[PROBLEMS] To provide an excellent oil sludge adhesion / deposition prevention function even in an in-cylinder injection type gasoline engine in which operating conditions for repeated high-speed operation and stop, apparently less oil consumption, and gasoline is particularly likely to be mixed into engine oil. A combination oil ring is provided.
In a combined oil control ring comprising a pair of side rails and a spacer expander that supports the side rail, at least the spacer expander or the side rail of the side rail facing the spacer expander Combination oil control ring characterized by providing a hydrophilic film.
[Selection] Figure 1

Description

  The present invention relates to a steel combined oil control ring mounted on an engine piston.

  As part of protecting the global environment, there is a strong demand for improved fuel economy and exhaust gas purification. Therefore, in an engine, it is important to improve fuel efficiency by reducing friction loss of each part and to reduce the amount of engine oil (oil consumption) that flows into the combustion chamber and is discharged as combustion gas. It has become. The piston ring plays a major role in solving these problems. In piston ring design, lowering the piston ring tension to reduce frictional force (an attempt to reduce the tension of the oil ring to a level of 10 N) and piston rings to improve oil consumption Attention has been paid to the reduction in width. Thinning improves the oil consumption by reducing the section modulus of the piston ring and improving the ability to follow the cylinder wall.

  Fig. 2 shows a cross-sectional configuration of a general piston ring in a gasoline engine. The piston 100 is formed with ring grooves 110, 120, and 130 for mounting piston rings, and in these ring grooves, two pressure rings 200 and 210 mainly for gas sealing action, and an oil control The steel combined oil control ring (hereinafter referred to as “combined oil ring”) 220 is mounted. As the piston 100 reciprocates, the outer peripheral sliding surfaces of these rings slide with the inner wall of the cylinder 300.

  The combination oil ring shown in the figure includes a pair of upper and lower side rails 222 in the axial direction, and a spacer expander 224 that is combined between the two and presses from the inner peripheral side of the side rail 222 to generate tension on the side rail 222. Consists of pieces. The spacer expander includes a radial corrugated shape in addition to the axial corrugated shape shown in the figure, but the function and structure for supporting the side rail and generating the tension are basically the same.

  In the combined oil ring, the side rail 222 has a radial force toward the cylinder wall and a component force toward the upper and lower surfaces of the ring groove of the piston depending on the angle of the ear portion (side rail pressing piece) 224a of the spacer expander 224 that presses the side rail. Is pressed. Therefore, the side rail 222 is characterized in that it can exhibit a sealing function (side sealing function) on the cylinder wall surface and the upper and lower surfaces of the ring groove. In particular, the thin combination oil ring has good followability to the cylinder wall and also has the above-mentioned side seal function, so it can reduce friction loss without increasing oil consumption even at low tension. Has advantages.

  However, in combination oil rings, hydrocarbon unburned substances in engine oil and modified products of oil additives (hereinafter collectively referred to as “oil sludge”) are used as spacer expanders, There is a drawback that the oil control function and the oil seal function described above are deteriorated by adhering to and accumulating on the surface of the side rail, in particular, in the gap between the spacer expander and the side rail, and in a severe case, it adheres. In the combination oil ring with low tension, the functional deterioration was remarkable.

  Oil sludge is generated when engine oil is exposed to blow-by gas, and hydrocarbon unburned substances are mixed in engine oil or produced by modified oil additives. Circulate. Further, when the in-cylinder injection method is adopted in the gasoline engine as the fuel efficiency improving means, the oil tends to be mixed with the engine oil and the oil sludge tends to increase.

 Since the combined oil ring has a complicated shape, engine oil mixed with oil sludge, which is fine or highly viscous liquid, easily adheres to the combined oil ring, and the flat recess 224b on the side of the spacer expander 224 and the side rail spacer Since the space 226 formed between the side surface 222b facing the expander is narrow, it tends to deposit in a sludge shape. Once the oil sludge has accumulated, the oil flow in that portion is obstructed, so that a vicious cycle occurs in which the sludge further accumulates. The combined oil ring is in a temperature environment of 100 to 150 ° C when the engine is running, but when stopped, the oil sludge becomes thicker and becomes more liable to accumulate when it is stopped to the room temperature level. The rail sticks.

  When the sticking occurs, the force that presses the cylinder wall surface of the side rail is weakened, and the force that presses with the component force in the axial direction toward the upper and lower surfaces of the piston ring groove is also weakened, so both the oil control function and the oil seal function are impaired, This leads to an increase in oil consumption.

  As a countermeasure against sticking, it is effective to increase the side clearance of the ring groove, which is the difference between the axial width of the piston oil ring groove and the combined nominal width of the combined oil ring. Along with the movement, the width of the side rail that vibrates up and down in the ring groove is increased, which causes groove wear, deterioration of the sealing function, and abnormal noise problems. Therefore, there is a limit to increasing the clearance.

  As a means for preventing the oil sludge from adhering or sticking to the combination oil ring, a method of applying a fluorine resin film or a resin film containing a fluorine resin has been proposed. For example, JP 2002-310299 (Patent Document 1) discloses a side for a combined oil ring in which a synthetic resin film such as polytetrafluoroethylene (hereinafter referred to as “PTFE”) is formed on at least one side of a side rail. A rail is disclosed. JP-A-2003-254155 (Patent Document 2) discloses a film made of polyamideimide or polyimide containing at least one of molybdenum disulfide, graphite, and PTFE at a portion where the side rail contacts the ring groove side surface. A formed combined oil ring is disclosed. However, Patent Document 1 describes that the thickness of the resin film is preferably 1 to 10 μm, and Patent Document 2 forms a resin film having a thickness of 10 μm in the embodiment. Since the combined nominal width h1 of the combined oil ring is increased by at least twice the thickness of the coating, it is necessary to increase the width dimension of the ring groove. However, when the width dimension of the ring groove is increased, when the resin film is worn, the side clearance is increased as described above, the ring groove is worn, and oil consumption is likely to be deteriorated.

  Also, in response to the problem of the thickness of the resin film, it is possible to form a thin film having a thickness of 10 to 100 nm by applying a solution containing a fluoroalkyl group-substituted alkoxide and baking it. It is disclosed in Patent Document 3).

  However, although the above resin film is excellent in terms of water repellency, when it is used in an engine, sticking occurs under operating conditions that repeat high-speed operation and stoppage, and under apparently low oil consumption, Further, it is a serious problem in a gasoline engine of an in-cylinder injection type in which gasoline is easily mixed into engine oil.

JP 2002-310299 A JP 2003-254155 A JP 2000-27995 JP

  Accordingly, an object of the present invention is to provide excellent oil sludge adhesion even in a driving engine that repeats high-speed operation and stopping, in a situation where oil consumption is apparently low, and in a gasoline engine of a cylinder injection type in which gasoline is particularly likely to be mixed into engine oil. To provide a combined oil ring in which a thin film having a deposition preventing function is formed.

  According to the engine test, the sticking does not occur in the continuous high-speed test, but occurs under conditions that repeat high-speed operation and stop. In addition, the tendency of sticking to occur is that the engine oil is hot, the blow-by gas is large, and the oil consumption is not high, but rather the engine oil is cold, the blow-by gas is small, and the oil consumption is low. In many cases, groove wear associated with the top ring often occurs. The groove wear of the top ring is because engine oil is not supplied properly. As a cause of this state, “fuel dilution” in which gasoline is mixed with engine oil is considered. Engine tests have also confirmed that when "fuel dilution" occurs, engine oil is apparently increased and oil consumption is reduced. From the above situation, it is estimated that the sticking phenomenon is particularly likely to occur in a situation where “fuel dilution” occurs, that is, in a situation where the oil sludge source increases.

  In addition, the combustion gas itself contains a lot of moisture. Moisture contained in the blowby gas is returned to the crankcase via the oil hole of the piston while passing through the oil ring and the ring groove. The temperature in the vicinity of the oil ring is usually 100 to 150 ° C., and in some cases, it becomes 100 ° C. or less. The high temperature / high pressure blow-by gas becomes low temperature / low pressure, and vaporized water is liquefied. The liquefied water is evaporated again in the crankcase having a relatively high temperature and returned to the intake pipe together with the blow-by gas. Also, in the crankcase after several hours have elapsed since the engine was operated, moisture contained in the engine oil or the air in the crankcase is condensed and condensed on the crankcase inner surface, crankshaft, connecting rod, piston, etc. It has been confirmed. Considering the above phenomenon, it can be estimated that a relatively large amount of water is mixed in the engine oil.

  When the engine oil contains moisture, the water-repellent resin film having a large contact angle with water, such as a fluorine-based resin film, repels water and becomes oleophilic. On the contrary, because of the characteristics of the fluororesin film that is easily attracted by the nature, the combustion soot contained in the blow-by gas is adsorbed by static electricity, so it may not exhibit the adhesion prevention function, Focusing on the affinity of the film with engine oil and water, the mechanism of oil sludge adhesion when water is contained in the engine oil was considered from the viewpoint of contact angle and surface tension, and the present invention was conceived.

The mechanism for preventing sticking by the hydrophilic film can be estimated as follows.
If the film formed on the combined oil ring is a hydrophilic film having a small contact angle with water, water enters between the oil sludge and the film to prevent oil sludge from adhering and accumulating. The adhesion of water does not lead to sticking, and as a result, sticking by oil sludge is prevented.

  That is, the steel combined oil control ring of the present invention is a combined oil control ring comprising a pair of side rails and a spacer expander that supports the side rails, and at least the spacer expander or the spacer expander of the side rail. A hydrophilic film is provided on the outermost surface of the side surface facing the surface. This hydrophilic film is preferably a silica glass of 2 μm or less, and the silica glass is formed by coating a precursor polymer containing an inorganic polysilazane, and the precursor polymer converts the inorganic polysilazane to silica at room temperature or 100 ° C. or less. It is preferable to have the function of

  An antifouling coating solution capable of imparting such a hydrophilic effect and antifouling effect to the surface of an article is disclosed in International Publication No. WO02 / 088269 (Patent Document 4). Specifically, 0.5 to 10% inorganic polysilazane, a catalyst that promotes silica conversion of 0.5 to 10% with respect to the pure polysilazane, and a coating solution comprising a solvent such as mineral spirit, paraffinic solvent and / or xylene. Yes, this is commercialized under the trade name “AQUAMICA” (AZ Electronic Materials Co., Ltd.). These can be conveniently used in the present invention.

Examples of applications using the above antifouling coating solution include automobile bodies, automobile wheels, dentures, tombstones, interior / exterior of houses, toilets, kitchens, toilets, bathtubs, water-use products, toilets, Examples include signboards, signs, plastic products, and glass products. JP-A-2004-148520 (Patent Document 5) proposes a coating on color titanium used in the fields of equipment, home appliances, and building materials. Japanese Patent Application Laid-Open No. 2002-332561 (Patent Document 6) is an example applied to a part in an engine, but it is used as an anti-nitriding film and is used only in a manufacturing process and used as a film of a final product. Absent.

International Publication WO02 / 088269 JP 2004-148520 A JP 2002-332561 A

  The combination oil ring of the present invention is a hydrophilic silica glass of 2 μm or less by coating a precursor polymer containing inorganic polysilazane on at least the outermost surface of the side surface of the spacer expander or the side rail facing the spacer expander. Since the coating is provided, the engine operating conditions that repeat high-speed operation and stop, the condition that apparently consumes less oil, and the excellent oil sludge adherence even in the gasoline engine of the in-cylinder injection method, where gasoline is particularly likely to be mixed into the engine oil. Has a function to prevent deposition. In addition, the hydrophilic silica glass film of the present invention is an extremely thin film of 2 μm or less, so it does not affect the dimensions, tension, and side clearance of the combined oil ring. Including a catalyst that promotes silica conversion in the case of the present invention eliminates the need for firing at a particularly high temperature, so that it is suitable for providing a high-accuracy thin-width low-tension combined oil ring from the viewpoint of variation in the tension of the spacer expander. .

  FIG. 1 schematically shows an example of a portion where a hydrophilic film 31 is coated in a combination oil ring showing an embodiment of the present invention. Fig. 1 (a) is only between the edge of the spacer expander and the outer peripheral projection that supports the side rail, Fig. 1 (b) is only the side facing the spacer expander of the side rail, and Fig. 1 (c) is Between the ears of the spacer expander and the protrusion on the outer periphery that supports the side rail, and the side of the side rail facing the spacer expander, Fig. 1 (d) is the entire surface of the spacer expander, and Fig. 1 (e) is the side rail. In Fig. 1 (f), the entire surface of the spacer expander and side rail is covered with a hydrophilic film.

  Oil sludge is particularly likely to adhere to and accumulate in the space between the flat recess between the ear 12 and the protrusion 11 of the spacer expander 13 and the side rail 5. Therefore, if the hydrophilic film 13 is coated as shown in FIGS. 1 (a) to (e), an oil sludge adhesion preventing effect can be obtained. As shown in FIG. 1 (f), when the hydrophilic film 13 is formed on almost the entire combination oil ring, the effect of preventing oil sludge from adhering to the oil ring is further improved.

  The material of the spacer expander 13 and the side rail 5 and the surface treatment applied thereto may be known ones and are not particularly limited. If a material obtained by nitriding austenitic stainless steel such as SUS304 is used as the spacer expander 13, the ear portion is excellent in wear resistance. From the viewpoint of reducing variation in tension, it is preferable to nitride only the ears. As side rails, the outer peripheral surface of a commonly used hard steel wire is provided with a hard chromium plating film or a CrN film by an ion plating method, and the base metal made of martensitic stainless steel is nitrided. Processed ones are suitable.

  In order to ensure high adhesion of the hydrophilic film, both the spacer expander and the side rail are sufficiently cleaned with an organic solvent-based cleaning solution or an alkali cleaning solution to remove surface dirt, particularly oil. In the case of alkali cleaning, if moisture remains, the problem of adhesion remains, so it is sufficiently dried.

  The hydrophilicity of the film is expressed as the degree of contact angle with water, and the surface of the film usually showing 40 ° or less is called hydrophilic. Silica glass, which is highly hard and chemically stable, is known as a film having a high hydrophilicity of 10 to 20 °, and as a coating method, inorganic polysilazane, which is a precursor polymer of silica glass,-(SiH2- A method of coating a solution containing NH)-(perhydropolysilazane) and converting it to silica glass is known. In order to convert the perhydropolysilazane solution into silica, for example, atmospheric baking at 450 ° C. for 1 hour is required. However, baking the spacer expander at 450 ° C. may cause new tension variations such as deformation. is there. Therefore, it is preferable to include a catalyst having a function of converting inorganic polysilazane into silica at room temperature or 100 ° C. or less.

  Further, since the hydrophilic film converted to silica according to the present invention is a thin film having a thickness of 2 μm or less, the adhesion with the base material is extremely high, it is hard and can follow a certain degree of deformation, and a spacer expander or Even if the rail is covered, it is a highly scratch-resistant film even if the spacer expander and the rail collide with each other due to the behavior during engine operation or the piston ring groove collides with the friction. .

  The coating method of the inorganic polysilazane on the spacer expander and / or the side rail is preferably a spray method or a dipping method, and the film thickness can be freely set by adjusting the content of the inorganic polysilazane in the diluting solvent. The film thickness set in this way is 2 μm or less, preferably 1 μm or less. If it exceeds 2μm, it will affect the tension and side clearance of the combined oil ring, so it cannot be used. The dilution solvent may be any solvent that can dissolve the inorganic polysilazane and the catalyst, but is preferably a stable solvent that does not generate gas such as silane, hydrogen, and ammonia. Xylene is an example.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Examples 1 to 5 (J1 to J5) and Comparative Examples 1 to 2 (H1 to H2)
A SUS440 side rail and a SUS304 spacer expander with a combined oil ring nominal diameter of 75 mm, combined nominal width of 2.0 mm, combined thickness of 2.5 mm, and side rail width of 0.4 mm were molded. The obtained side rail was subjected to plasma nitriding treatment, and the spacer expander was subjected to salt bath nitriding. Thereafter, each was subjected to predetermined post-processing and washed with acetone.

Next, using the “AQUAMICA” NL series or NP series from AZ Electronic Materials Co., Ltd., facing the spacer expander side rail using the prescribed inorganic polysilazane content, coating method, and baking method shown in Table 1. The surface (J1 to J3) or the entire surface (J4 to J5, H1) was coated with a hydrophilic film. Table 1 shows that for each sample of three conditions, the average film thickness from the cross-sectional thickness of the film observed with a scanning electron microscope of the cut surface, and the Cp value and Cpk value of the data measured for tension from the 50 samples of each condition Was described.
Cp = (Standard range / 6σ)
Cpk = {(standard range / 2-average value) / 3σ}
Calculated by

  In Examples 1 to 5, both the Cp value and the Cpk value of the tension data were 1.33 or more, but in Comparative Example 1 having a film thickness of 2.5 μm, the Cp value was 1.10, the Cpk value was 0.82, and the tension variation was large. It was a level that became a problem in terms of process capability.

  The engine test was conducted using a 4-cylinder gasoline engine with a displacement of 1500cm3. The top ring of the outer peripheral barrel face and the second ring of the outer peripheral tapered face, which are common to each cylinder, were installed. As shown in Examples 1, 3, 5 (J1, J3, J5) and Comparative Example 2 (H2), each cylinder is equipped with a combined oil ring using spacer expanders and side rails that are not formed with a hydrophilic film made of inorganic polysilazane. did. The engine oil was deteriorated oil, which became a problem in the market, and cyclic evaluation was repeated in which the operating conditions from the stopped state to the maximum output speed and the oil / water temperature conditions from low temperature to high temperature were repeated continuously. After completion of the evaluation for a predetermined time, the engine was disassembled and the appearance was observed with the oil ring attached. Next, the oil ring was removed, and the presence or absence of sticking between the spacer expander and the side rail was investigated. Further, the spacer expander and the side rail were washed away with acetone and then sufficiently dried. All the adhered / deposits adhered to the spacer expander and the side rail after drying were scraped off, and the collected adhered / deposited materials were dried at 120 ° C. for 60 minutes, and then allowed to cool in a desiccator and weighed. The results are shown in Table 2. The amount of deposit was expressed as a relative value with the value of Comparative Example 2 as 100, but the oil rings of Examples 1, 3 and 5 clearly had less adhesion and deposit than the oil ring of Comparative Example 2. Also, no sticking was observed. Moreover, the uneven distribution of the deposit | attachment by peeling etc. was not recognized by the spacer expander.

Examples 6 to 8 (J6 to J8) and Comparative Example 3 (H3)
A side expander made of SUS440 and a spacer expander made of SUS304 having the same dimensions as in Example 1 were formed, and a CrN film was formed on the outer peripheral sliding surface of the side rail by ion plating, and the ear of the spacer expander was the ear. Only the part was subjected to salt bath nitriding. Thereafter, each was subjected to predetermined post-processing and washed with acetone. These side rails and spacer expanders were used in Examples 6 to 8 and Comparative Example 3.

As the hydrophilic film, AZ Electronic Materials Co., Ltd.'s `` Aquamica '' NP series is used, a solution with an inorganic polysilazane content of 5%, in Example 6, the surface facing the spacer expander of the side rail, Example In Example 7, the entire surface of the side rail was applied to the entire surface of both the side rail and the spacer expander in Example 8, using a spray method or a dipping method, and dried at room temperature. Table 3 shows the film thickness of the formed silica glass hydrophilic film.

As Comparative Example 3, a water repellent fluororesin film was formed by the following procedure.
First, 300 g tetraethoxysilane, 9.06 g heptadecafluoro-1, 1, 2, 2-tetrahydro-decyl-triethoxysilane, 647.9 g ethanol were put in a beaker and stirred for 20 minutes, then 123 g water and 158 g 0.1N Hydrochloric acid was added and the mixture was further stirred for 2 hours. The solution was sealed and left at 25 ° C. for 24 hours. The side rail and spacer expander were dipped into the obtained solution, dried at room temperature, and then heat-treated in an electric furnace at 250 ° C. for 1 hour. The obtained side rail with a water-repellent fluororesin film and a spacer expander were combined into an oil ring.

For Examples 6 to 8 and Comparative Example 3, engine tests similar to those of Examples 1, 3, 5 and Comparative Example 2 were performed. After completion of the evaluation for a predetermined time, the engine was disassembled, the appearance of the oil ring was observed, the presence or absence of occurrence of sticking, and the adhesion and deposits were weighed. The results are shown in Table 3. Also in these results, the amount of deposits was expressed as a relative value with the value of Comparative Example 2 being 100, but the oil rings of Examples 6 to 8 clearly adhered and deposited compared to the oil ring of Comparative Example 2. There was little, and adhesion was not recognized. Moreover, although the comparative example 3 was remarkably excellent compared with the comparative example 2, compared with Examples 6-8, the amount of the deposit was about several dozen times larger. From this comparison, it was confirmed that the hydrophilic film is superior in adhesion / deposition prevention function compared to the water-repellent film.

In Examples 7 and 8 in which a silica glass hydrophilic film was applied to the entire surface of the side rail, a silica glass film of 2 μm or less was further formed on the CrN film on the outer peripheral sliding surface. The dynamic characteristics were not affected at all. However, according to observation after completion of the engine test, there was no silica glass film on the outer peripheral sliding surface of the side rail.

FIG. 1 is a diagram schematically showing a combined oil control ring according to the present invention, in which FIG. 1 (a) covers a hydrophilic film only between an outer edge of a spacer expander and an outer peripheral protrusion supporting a side rail. Cross-sectional view showing an example, FIG. 1 (b) is a cross-sectional view showing an example in which a hydrophilic film is coated only on the side surface of the side rail facing the spacer expander, and FIG. 1 (c) is an ear portion of the spacer expander. FIG. 1D is a cross-sectional view showing an example in which a hydrophilic film is coated on the side surface of the side rail that faces the spacer expander between the outer peripheral projections supporting the side rail and the side rail, and FIG. 1 (e) is a cross-sectional view showing an example in which a hydrophilic film is coated on the entire surface of the side rail, and FIG. 1 (f) is an entire surface of the spacer expander and the side rail. Coated with hydrophilic film And a cross-sectional view showing an example. It is sectional drawing which shows a state when the piston with which the conventional piston ring was mounted | worn is in a cylinder, The oil ring shown in the figure shows the typical steel combination oil control ring of an axial direction waveform.

Explanation of symbols

11 Protrusion
12 Ear
13 Connecting surface of ear and protrusion
21 Side rail
31 Hydrophilic film

Claims (6)

In a combined oil control ring comprising a pair of side rails and a spacer expander that supports the side rails, a hydrophilic film is formed on at least the outermost surface of the side surface of the side expander or the side rail facing the spacer expander. A combination oil control ring characterized by providing The combined oil control ring according to claim 1, wherein the hydrophilic film is silica glass of 2 μm or less. The combined oil control ring according to claim 2, wherein the silica glass is formed by coating a precursor polymer containing inorganic polysilazane. The combined oil control ring according to claim 3, wherein the precursor polymer containing the inorganic polysilazane contains a catalyst having a function of converting the inorganic polysilazane into silica at room temperature. The combined oil control ring according to any one of claims 1 to 4, wherein the combined oil control ring is used in a gasoline engine. The combined oil control ring according to claim 5, wherein the gasoline engine is an in-cylinder injection type engine.

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