JP7019083B2 - Combination oil ring and piston with oil ring - Google Patents

Description

The present invention relates to a three-piece combined oil ring comprising a pair of upper and lower segments (side rails) and expander spacers arranged between the segments.

The piston of the internal combustion engine is provided with a ring groove for sequentially arranging a compression ring and an oil ring on the outer wall thereof, and the compression ring and the oil ring are arranged in the grooves, respectively. Of these, the oil ring has the function of scraping off excess engine oil adhering to the inner wall of the cylinder of the internal combustion engine to form an appropriate oil film.

Since the outer peripheral surface of the oil ring slides at high speed with the inner wall of the cylinder, wear resistance is required. Therefore, a technique for providing a diamond-like carbon (hereinafter, also referred to as DLC) coating having high wear resistance has been proposed (see Patent Document 1).

On the other hand, in order to realize the demand for low fuel consumption of the internal combustion engine, it is required to reduce the friction between the oil ring and the inner wall of the cylinder. Specifically, there is a need to reduce the tension of the oil ring and the friction of the film formed on the outer periphery of the oil ring. However, in that case, it may cause an increase in engine oil consumption, and in order to solve such a problem, a technique has been proposed in which the contour shape of the upper and lower segments of the three-piece oil ring is characteristic. (See Patent Document 2).

Japanese Unexamined Patent Publication No. 11-315924 Patent No. 5833276

The three-piece combined oil ring comprises a pair of upper and lower segments and expander spacers arranged between the segments, but according to the studies of the present inventors, the segments arranged closer to the combustion chamber (the segments arranged closer to the combustion chamber). Hereinafter, it was found that the coating film covering the outer peripheral surface of the upper segment wears significantly due to long-term use because the upper segment slides with the inner wall of the cylinder under more severe conditions. Therefore, when the same type of coating is formed on the outer peripheral surface of the upper and lower segments, the amount of coating wear on the outer peripheral surface of the segment differs between the upper segment and the lower segment due to long-term sliding, and the balance between the upper and lower segments pressing the inner wall of the cylinder is balanced. It was found that it became worse and reduced the function of the combined oil ring.
Specifically, as the coating on the outer peripheral surface of the upper segment wears more, the lower segment presses more strongly against the inner wall of the cylinder. In that case, the function of the outer periphery of the upper segment to scrape off the engine oil adhering to the inner wall of the cylinder is reduced, and the force of the outer peripheral surface of the upper segment to press the inner wall of the cylinder is reduced, so that the engine oil existing between the upper and lower segments is removed. , There is a concern that it will slip between the upper segment and the inner wall of the cylinder.

The present invention solves a problem that may occur due to deterioration of the balance in which such upper and lower segments press the inner wall of the cylinder.

The present inventors have studied to solve the above problems, and by making the wear resistance of the coating film covering the outer peripheral surface of the upper and lower segments different from each other, it is possible to prevent the deterioration of the balance in which the upper and lower segments press the inner wall of the cylinder. He found out what he could do and completed the invention.

The present invention is a combined oil ring provided with a pair of upper and lower segments whose outer peripheral surface slides on the inner wall of the cylinder and an expander spacer arranged between the segments.
The upper and lower segments are a combination oil ring having a coating film having different wear resistance on its outer peripheral surface.

Further, when a coating film such as DLC having high wear resistance is provided on the outer peripheral surface of one segment, the DLC generally has low friction, so that the DLC does not have sufficient compatibility with the inner wall of the cylinder at the initial stage of sliding. There was room for improvement in fuel efficiency. To solve such a problem, it is preferable to increase the friction coefficient of the coating film having low wear resistance among the coating films of the upper and lower segments from the viewpoint of improving fuel efficiency. By increasing the coefficient of friction of the coating film having low wear resistance, the inner wall of the cylinder and the coating film are quickly adapted to each other, so that friction can be reduced and fuel efficiency can be improved.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a combined oil ring that can prevent problems that may occur due to deterioration of the balance in which the upper and lower segments press the inner wall of the cylinder during long-term use. Further, in a preferred embodiment, a combination oil ring capable of improving the familiarity between the outer peripheral surface of the segment and the inner wall of the cylinder at an early stage and improving the fuel efficiency is provided.

It is sectional drawing which shows the state which the piston which attached the combination oil ring which concerns on one Embodiment is inserted into a cylinder. It is sectional drawing of the piston which attached the oil ring. It is a graph which shows the result of the segment wear test.

An embodiment of the present invention is a combination oil ring provided with a pair of upper and lower segments in which an outer peripheral surface slides on an inner wall of a cylinder and an expander spacer arranged between the segments, and is provided on the outer peripheral surface of the upper and lower segments. , Each has a coating with different wear resistance. The usage embodiment of the combination oil ring of this embodiment will be described with reference to FIG.

FIG. 1 is a cross-sectional view showing the configuration of the combined oil ring 10 and showing a state in which the piston 2 equipped with the combined oil ring is inserted into the cylinder 1.
In FIG. 1, a reciprocating piston 2 is arranged inside the cylinder 1 of the engine. Two or three annular grooves are provided on the outer peripheral surface 3 of the piston 2, and an oil ring groove 14 is provided on the crankshaft side (not shown) farthest from the combustion chamber.
The combination oil ring 10 is a three-piece type combination oil ring, and has a pair of upper and lower segments 11 and 12 and an expander spacer 13 arranged between the upper segment 11 and the lower segment 12. The right end portion in the figure of the upper segment 11 and the right end portion in the figure of the lower segment 12 are sliding surfaces that slide in contact with the inner wall of the cylinder 1 and are covered with a coating film.

FIG. 2 is a cross-sectional view of a piston equipped with an oil ring.
The piston 2 is formed with a first groove 24, a second groove 34, and a third groove 14 from the combustion chamber side. A top ring 20 which is a compression ring is attached to the first groove 24, a second ring 30 which is a compression ring is attached to the second groove 34, and a combination oil ring 10 is attached to the third groove 14. Is installed.

The upper segment 11 of the combined oil ring 10 is located closer to the combustion chamber and the lower segment 12 is located farther from the combustion chamber. According to the study by the present inventors, the upper segment 11 arranged at a position closer to the combustion chamber slides under more severe conditions, and therefore, after long-term use, the sliding surface of the outer peripheral surface of the segment with the cylinder bore. However, it was found that the wear was large (hereinafter, also simply referred to as the sliding surface of the segment). The tests for which such findings were obtained are shown below.

<Test 1: Segment wear test>
The engine of a passenger car with a displacement of 2 L after traveling 100,000 km, which is a product recovered on the market, was disassembled to obtain a combined oil ring. The amount of wear on the sliding surface of the obtained combination oil ring between the upper segment located closer to the combustion chamber and the lower segment located farther from the combustion chamber with the cylinder bore on the outer peripheral surface of the segment. It was measured using a contour shape measuring machine. The sliding surfaces of the upper segment and the lower segment were PVD coatings (coating hardness 1150Hv). As a result of the measurement, the wear ratio of the sliding surface of the upper segment and the lower segment is as shown in FIG. 3, the upper segment: the lower segment = 1.0: 0.7, and the upper segment is about 1.43 times. It turned out to be easy to wear.

Based on the findings obtained from the above tests, if the outer peripheral surface of the upper segment 11 and the outer peripheral surface of the lower segment 12 have the same coating, the amount of wear on the outer peripheral surface of the segment due to long-term sliding depends on the upper segment and the lower segment. It was found that the difference causes the balance between the upper and lower segments to press the inner wall of the cylinder to deteriorate, and new problems such as oil leakage from the gap between the upper segment 11 of the combined oil ring 10 and the inner wall of the cylinder may occur. Obtained.

In the present embodiment, the above-mentioned new problem is solved by making the wear resistance of the coating film different between the outer peripheral surface of the upper segment 11 and the outer peripheral surface of the lower segment 12. As one form, the coating on the outer peripheral surface of the upper segment 11 which is close to the combustion chamber and can slide under harsh conditions is a DLC coating having excellent wear resistance, and the coating on the outer peripheral surface of the lower segment 12 is a PVD coating. , Nitride coating, or hard chrome plating. As another form, the coating on the outer peripheral surface of the upper segment 11 is a PVD coating, and the coating on the outer peripheral surface of the lower segment 12 is a nitride coating or a hard chrome plating.
It should be noted that the outer peripheral surface of the upper segment 11 may have a different wear resistance while the coating on the outer peripheral surface of the upper segment 11 and the coating on the outer peripheral surface of the lower segment 12 are both DLC coatings. The film and the film on the outer peripheral surface of the lower segment 12 may both be a PVD film, and the wear resistance of the PVD film may be different.

As shown in the above specific example, the coating film on the outer peripheral surface of the lower segment 12 is a coating film having a lower wear resistance than the coating film on the outer peripheral surface 11 of the upper segment 11, while the outer peripheral surface of the upper segment 11 is from the viewpoint of the coefficient of friction. It is preferable that the film is higher than the film of. For example, since the DLC coating illustrated above has a low coefficient of friction, the outer peripheral surface of the segment and the inner wall of the cylinder are not sufficiently familiar at the initial stage of the reciprocating movement of the piston, and there is room for improvement in engine fuel efficiency. rice field. By increasing the coefficient of friction of the coating film on the outer peripheral surface of the lower segment 12, the outer peripheral surface of the lower segment 12 and the inner wall of the cylinder become familiar at an early stage, friction can be reduced, and fuel efficiency can be improved.

In the present embodiment, that is, the thickness of the coating film formed on the outer peripheral surface of the segment is not particularly limited, but may be usually 0.5 μm or more, preferably 1 μm or more, and usually 150 μm or less, preferably 50 μm or less.
Further, the hardness of the coating film formed on the outer peripheral surface of the segment is not particularly limited, but the hardness of the segment on the side having low wear resistance is usually 700 Hv or more, preferably 800 Hv or more, and usually 2000 Hv or less, preferably 1500 Hv or less.
On the other hand, the hardness of the segment on the high wear resistance side is usually 800 Hv or more, preferably 1200 Hv or more, and usually 3500 Hv or less, preferably 2500 Hv or less.

Regarding the surface roughness of the coating film formed on the outer peripheral surface of the segment, the initial surface roughness Ra of the coating film on the high wear resistance side is usually 0.1 μm or less, but the initial surface roughness of the coating film on the low wear resistance side. The surface roughness Ra of the above may be usually 0.3 μm or less, and it is preferable to make the initial surface roughness Ra of the coating film on the side having low wear resistance higher.

The present invention will be described in detail with reference to specific embodiments and examples, but those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Is obvious.

1 Cylinder 2 Piston 3 Piston outer peripheral surface 10 Combination oil ring 11 Upper segment 12 Lower segment 13 Expander spacer 14 Third groove 20 Top ring (compression ring)
24 First groove 30 Second ring (compression ring)
34 Second groove

Claims (5)

A combination oil ring having a pair of upper and lower segments whose outer peripheral surface slides on the inner wall of the cylinder and an expander spacer arranged between the segments.
The upper and lower segments each have a coating film having different wear resistance on the outer peripheral surface thereof, and the friction coefficient of the coating film having low wear resistance is higher than the friction coefficient of the coating film having high wear resistance. The hardness of the coating on the surface is 800 Hv or more, the hardness of the coating on the outer peripheral surface of the lower segment is 700 Hv or more, and the hardness of the coating on the outer peripheral surface of the upper segment is the hardness of the outer peripheral surface of the lower segment. The surface roughness Ra of the coating on the outer peripheral surface of the upper segment is 0.1 μm or less, which is larger than the hardness of the coating, and the surface roughness Ra of the coating on the outer peripheral surface of the lower segment is 0.3 μm or less. A combination oil ring to prevent the balance of the upper and lower segments from pressing against the inner wall of the cylinder. The combination oil ring according to claim 1, wherein the amount of wear on the sliding surface of the upper segment in the engine after traveling 100,000 km is less than 1.43 times the amount of wear on the sliding surface of the lower segment. The combination oil ring according to claim 1 or 2, wherein among the coatings on the outer peripheral surface of the upper and lower segments, the coating having high wear resistance is the DLC coating, and the coating having low wear resistance is the PVD coating. The combination oil ring according to any one of claims 1 to 3, which is used by being mounted on the outer peripheral surface of a piston together with a compression ring. A piston for an internal combustion engine located between the combustion chamber and the crank chamber of an internal combustion engine and having at least an oil ring groove in which an oil ring is mounted, and a combination oil ring mounted in the oil ring groove of the piston.
It is an oil ring mounted piston consisting of
The combined oil ring includes a pair of upper and lower segments whose outer peripheral surface slides on the inner wall of the cylinder, and an expander spacer arranged between the segments, and the outer peripheral surface of the upper segment arranged on the combustion chamber side. The wear resistance of the covering coating is higher than the abrasion resistance of the coating covering the outer peripheral surface of the lower segment, and the friction coefficient of the coating covering the outer peripheral surface of the upper segment is higher than the friction coefficient of the coating covering the outer peripheral surface of the lower segment. The hardness of the coating film on the outer peripheral surface of the upper segment is 800 Hv or more, the hardness of the coating film on the outer peripheral surface of the lower segment is 700 Hv or more, and the hardness of the coating film on the outer peripheral surface of the upper segment is 800 Hv or more. The surface roughness Ra of the coating on the outer peripheral surface of the upper segment is 0.1 μm or less, which is larger than the hardness of the coating on the outer peripheral surface of the lower segment, and the surface of the coating on the outer peripheral surface of the lower segment. Roughness Ra is 0.3 μm or less, in order to prevent deterioration of the balance in which the upper and lower segments press the inner wall of the cylinder.
Oil ring mounted piston.

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