JP2011214662A - Pressure ring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure ring whose upper and lower surfaces are changed into flat surfaces substantially perpendicular to a piston shaft during fitting of the pressure ring to a piston when the pressure ring is fitted to a piston ring groove, which suppresses an increase in the amount of blowby gas and oil consumption, and also suppresses an increase in manufacturing cost.SOLUTION: A stepped cutout portion is formed by cutting out a corner formed by a lower surface having an axial cross-sectional surface formed into a substantially rectangular shape and a peripheral surface. The pressure ring has the upper surface formed into the shape of a substantially coned disc spring inclined downward toward a radially outward direction in a free state. The inclination angle θ of the upper surface of the pressure ring, with respect to a surface perpendicular to the shaft of the pressure ring, is set to be 0°<θ≤2°.

Description

  The present invention relates to a pressure ring attached to a piston ring groove provided in a piston for an internal combustion engine.

  With the recent market demand for longer life and improved fuel consumption of automobile engines, the pressure ring used in the engine has low friction against the inner wall of the cylinder in order to achieve smooth reciprocation of the piston in the cylinder. There is a need for a product that can be integrated. In order to reduce the friction of the pressure ring against the inner wall surface of the cylinder, it is necessary to reduce the tension of the pressure ring with a small width and light weight.

  The pressure ring is referred to as a top ring and a second ring in order from a pressure ring that is mounted in a piston ring groove provided in the piston and disposed at a position closest to the combustion chamber side. The top ring must have a gas seal function that can withstand the explosion shock in the combustion chamber and stably seal high-temperature combustion gas for a long period of time, and an oil seal function that seals oil without entering the combustion chamber. Is done. On the other hand, the second ring mounted between the top ring and an oil ring that requires an oil control function is required to function to assist the top ring and the oil ring. Therefore, when the pressure ring is thin and light, and the tension is reduced, the second ring that is not affected by the explosion impact in the combustion chamber or the high-temperature combustion gas compared to the top ring is particularly thin and light. There is a demand for lower tension. Therefore, a scraper ring in which the outer peripheral surface is tapered and the stepped notch is provided at the lower end of the outer peripheral surface is often used for the second ring.

  In addition, when a pressure ring whose axial cross-sectional shape of the ring is not vertically symmetrical, such as a scraper ring, is mounted on the piston ring groove, the pressure ring is bent with its outer peripheral sliding surface inclined with respect to the cylinder inner wall surface. There is a problem that causes a twist proportional to the cost. Since the pressure ring attached to the piston moves following the reciprocating motion of the piston while contacting the inner wall surface of the cylinder via an oil film, the pressure ring is twisted in the state of being attached in the piston ring groove. If so, the posture of the pressure ring in the piston ring groove tends to become unstable due to the reciprocating motion of the piston. In this case, depending on the operating conditions of the internal combustion engine, the oil seal function, the gas seal function, and the oil control function by the pressure ring are lowered, leading to an increase in blow-by gas amount and oil consumption amount.

  In order to avoid the above problem, for example, Patent Document 1 (Japanese Utility Model Publication No. 63-141357) relates to a pressure piston ring for an internal combustion engine (that is, a pressure ring) and is inclined toward the sliding surface side with respect to the upper surface. Disclosed is to provide an upper cut portion that is cut as described above, a lower surface, and a lower cut portion that is cut at the corners of the sliding surface. In Patent Document 1, by providing the pressure piston ring with an upper cut portion and a lower cut portion, the twist caused by the upper cut portion and the twist caused by the lower cut portion, which are in different twist directions, are offset. There is a disclosure that the twist when the pressure piston ring is mounted in the piston ring groove is eliminated.

  Patent Document 2 (Japanese Patent Laid-Open No. 2001-124204) relates to a piston ring for a first groove (that is, a pressure ring) facing the combustion space side of a piston of an internal combustion engine, and has a spherical shape. In the piston ring which is arranged on the side of the piston ring on the combustion space side below the half of the height of the piston ring, the lower side facing the combustion space side Disposing a groove extending in the axial direction from the side surface of the piston ring to the top of the spherical shape on the sliding surface. And in patent document 2, it is a state without a twist when a piston ring is assembled | attached by forming a cross-sectional discontinuity part as a notch part in the side orient | assigned to the combustion space of the area | region of the internal peripheral surface of a piston ring. There is a disclosure to do so.

Japanese Utility Model Publication No. 63-141357 JP 2001-124204 A

  However, the pressure ring of Patent Document 1 described above is provided with an upper cut portion in addition to the lower cut portion on the outer peripheral sliding surface side of the pressure ring, and further, the lower cut portion is interrupted near the joint portion. Because of its shape, the lower cut portion must be processed after the piston ring wire is made into a ring shape. In this case, the pressure ring of the cited document 1 requires time and labor for forming the lower cut portion except for the vicinity of the abutment portion, so that the time required for the processing increases and the cost increases.

  In addition, the above-described piston ring of Patent Document 2 forms a groove from the side surface of the lower pressure ring facing the combustion space side to the sliding surface, and on the side facing the combustion space in the region of the inner peripheral surface. In addition, since the cutout portion is formed and the groove is interrupted in the vicinity of the abutment portion, the time required for processing to form the groove is increased as in Patent Document 1, and the cost is increased. . Further, the piston ring of Patent Document 2 has a spherical sliding surface on the outer peripheral surface, and the cutout portion is formed on either the upper side or the lower side of the inner peripheral surface region facing the combustion space. However, since the contact area between the pressure ring and the piston ring groove is small, the posture stability of the pressure ring is lacking, and the oil sealability on the lower surface side of the pressure ring is deteriorated.

  That is, the pressure rings disclosed in Patent Document 1 and Patent Document 2 are formed below the outer peripheral surface of the pressure ring in order to prevent twisting of the pressure ring when the pressure ring is mounted on the piston. Another cut part (or notch part) is further formed at a position in a twist direction different from the twist direction by the cut part (or groove). By the way, these pressure rings have a cut portion (or groove) formed on the lower side of the outer peripheral surface thereof, so that the area that contacts the cylinder inner wall surface of the sliding portion of the outer peripheral surface of the pressure ring is reduced. This is a shape frequently used as a second ring because the effect of preventing the oil from rising can be improved by increasing the surface pressure against the water.

  From the above, the present invention is a pressure ring in which when the pressure ring is mounted in the piston ring groove, the upper and lower surfaces of the pressure ring are flat surfaces (flat surfaces) substantially perpendicular to the piston shaft. An object of the present invention is to provide a pressure ring that can suppress an increase in gas amount and oil consumption, and can suppress an increase in manufacturing cost.

  Therefore, as a result of intensive studies, the present inventors have solved the above-mentioned problem by making the shape before mounting in the piston ring groove of the pressure ring a shape that satisfies a predetermined condition. It was. According to the pressure ring of the present invention, when the pressure ring is installed in the piston ring groove, the upper and lower surfaces of the pressure ring are flat surfaces that are substantially perpendicular to the piston shaft. Can be effectively suppressed from changing in the piston ring groove. Hereinafter, the present invention will be described.

  A pressure ring according to the present invention is a pressure ring that is mounted in a piston ring groove of a piston for an internal combustion engine, and has a step in which a corner formed by a lower surface and an outer peripheral surface having a substantially rectangular cross section in the axial direction is cut out. In the free state, the pressure ring has a substantially disc spring shape with the upper surface of the pressure ring inclined downward in the radial direction in the free state. The inclination angle θ of the upper surface with respect to a plane perpendicular to the axis of the pressure ring is 0 ° <θ ≦ 2 °.

  The pressure ring according to the present invention is preferably a second ring.

  The pressure ring according to the present invention preferably has a tapered portion whose outer peripheral surface has a diameter reduced from the lower surface side to the upper surface side of the pressure ring.

  In the pressure ring according to the present invention, it is preferable that a hard layer is formed on at least the outer peripheral surface of the pressure ring.

  The pressure ring according to the present invention is such that the ring shape in the free state before being mounted in the piston ring groove is a shape that satisfies the conditions specified in the present invention, and the pressure ring is mounted after being mounted in the piston ring groove. The upper and lower surfaces can be flat surfaces substantially perpendicular to the piston axis. As described above, the upper and lower surfaces of the pressure ring mounted in the piston ring groove are flat surfaces substantially perpendicular to the piston shaft, so that the piston ring groove that is normally formed perpendicular to the piston shaft is formed. The upper and lower surfaces of the pressure ring can maintain a stable parallel state with respect to the upper and lower side surfaces, and the change of the ring posture can be suppressed even during the reciprocating motion of the piston. Note that the free state of the pressure ring means a state in which the substance is not subjected to external stress other than the force (gravity, air pressure, etc.) normally received in a stationary state.

It is the figure which showed the state which looked at one Example of the pressure ring which concerns on this invention from the axial direction upper direction of the said pressure ring. It is the figure cut | disconnected and shown in the said pressure ring axial direction, in order to demonstrate the shape before attaching to the piston of the pressure ring which concerns on this invention. It is sectional drawing cut | disconnected and shown in the piston axial direction, in order to demonstrate the state which mounted | wore the piston ring groove | channel with the pressure ring which concerns on this invention. It is the figure which cut | disconnected and showed the pressure ring which concerns on this invention in the axial direction of the said pressure ring. It is the graph which showed the relationship between the inclination angle of a pressure ring, and oil consumption.

  The preferred embodiment of the pressure ring according to the present invention will be described below in more detail with reference to the drawings.

  FIG. 1 shows a state of an embodiment of a pressure ring according to the present invention as viewed from above in the axial direction of the pressure ring, and is a perspective view of a main part of a joint portion (portion indicated by a) provided in the pressure ring (a ). As shown in FIG. 1, the pressure ring 1 has a ring shape and includes an abutment portion 1 a. Further, FIG. 1A shows that a notch portion 1b formed by cutting a corner portion formed between the pressure ring and the outer peripheral surface is provided on the lower surface side of the pressure ring. As shown in FIG. 1A, the pressure ring of the present invention is provided with the notch 1b on the outer peripheral surface side of the pressure ring 1, so that the outer peripheral surface side of the pressure ring 1 is connected to the pressure ring. Since the piston ring groove is twisted upward, the upper and lower surfaces of the pressure ring become flat surfaces substantially perpendicular to the piston shaft, and the oil scraping function can be improved. Further, by providing the pressure ring 1 with the notch 1b, the area of the outer peripheral surface of the pressure ring that contacts the cylinder inner wall surface is reduced, and the surface pressure of the pressure ring 1 against the cylinder inner wall surface due to the movement of the piston in the combustion stroke. By increasing the value, the effect of suppressing oil rise can be obtained.

  FIG. 2 is a cross-sectional view taken along the axial direction of the pressure ring in order to explain the shape of the pressure ring according to the present invention before being attached to the piston. FIG. 2 shows the details of the outer shape as (b) using the cut portion (the portion indicated by b) of the pressure ring. As shown in FIG. 2, the pressure ring 1 according to the present invention has a substantially disc spring shape in which the upper surface 2 of the pressure ring is inclined downward in the radial direction. The pressure ring of the present invention is formed in the pressure ring 1 when the piston is mounted on the piston by preliminarily forming a ring shape in a free state before mounting on the piston as shown in FIG. The posture of the pressure ring in the piston ring groove can be corrected to a flat state substantially perpendicular to the piston axis by the twisting action toward the upper side on the outer peripheral surface 4 side, which is acted by the notch 1b. Below, the external shape of the pressure ring which concerns on this invention is demonstrated in detail using FIG.

  As shown in FIG. 2B, the pressure ring 1 of the present invention has a radial width of the pressure ring a1, an axial width of the pressure ring h1, a radial length of the notch portion X, Let Y be the axial length of the notch. The condition is preferably set such that the inclination angle θ of the upper surface of the pressure ring with respect to the plane H perpendicular to the axis of the pressure ring is 0 ° <θ ≦ 2 °. By setting the outer shape of the pressure ring of the present invention to this condition, when the pressure ring is mounted on the piston, the posture of the pressure ring can be in a flat state substantially perpendicular to the piston shaft.

  That is, the pressure ring 1 according to the present invention has the pressure ring 1 attached to the piston by making the upper surface 2 of the pressure ring slightly inclined downward in the radial direction. When the pressure ring 1 is provided with the notch 1b, the upper and lower surfaces of the pressure ring in the piston ring groove are moved relative to the piston shaft by the twisting action toward the upper side on the outer peripheral surface 4 side. It becomes a substantially vertical flat surface. Therefore, in order to make the posture of the pressure ring 1 in the piston ring groove flat, the size of the notch 1b formed in the pressure ring 1 should be taken into consideration. Therefore, in the pressure ring 1 of the present invention, the notch portion 1b has a radial width of the pressure ring set as a size that can be assumed by those skilled in the art to satisfy the function required for a pressure ring. When the axial width of the pressure ring is h1, the radial length X of the notch 1b is 0 <X ≦ a1 / 3, and the axial length Y of the notch is The condition that the posture of the pressure ring in the piston ring groove is in a flat state was set for the case where 0 <Y ≦ h1 / 2.

  The pressure ring 1 according to the present invention has a cut formed in the pressure ring 1 when the inclination angle θ of the upper surface 2 of the pressure ring 1 with respect to a plane H perpendicular to the axis of the pressure ring is 0 °. The presence of the notch 1b acts to twist upward when the pressure ring is attached to the piston, making it impossible to keep the pressure ring in a flat state. On the other hand, when the inclination angle θ of the upper surface 2 of the pressure ring 1 with respect to the plane H perpendicular to the axis of the pressure ring is θ> 2 °, the posture is changed when the pressure ring is attached to the piston. In order to keep the flat state, the size (diameter length X, axial direction length Y) of the notch 1b provided in the pressure ring 1 shown in FIG. 2 must be larger than the set size. In this case, the ratio of the notch 1b formed in the pressure ring 1 to the pressure ring 1 is too large, so that the contact area between the lower surface 3 of the pressure ring 1 and the piston ring groove (not shown) is small. Therefore, the posture stability of the pressure ring is lacking, and the oil sealability on the lower surface side of the pressure ring 1 is deteriorated.

  FIG. 3 is a cross-sectional view showing the pressure ring according to the present invention cut in the piston axial direction in order to explain a state where the pressure ring is mounted in the piston ring groove. As shown in FIG. 3, the pressure ring 1 is self-tensioned with respect to the cylinder inner wall surface 10 by reciprocating movement of the piston 5 while controlling the gas seal and oil while being mounted in the piston ring groove 6. The outer peripheral surface 4 of the pressure ring pressed by the pressure moderately controls the thickness of the oil film. The pressure ring 1 follows the reciprocating motion of the piston 5 (in the direction of the arrow in the figure) while contacting the cylinder inner wall surface 10 through an oil film, whereby the upper surface 2 and the lower surface of the pressure ring 1 3, contact with the upper and lower side surfaces 7 and 8 of the piston ring groove is repeated. When the pressure ring 1 is mounted on a piston, if the posture of the pressure ring is not maintained in a flat state substantially perpendicular to the piston axis, the posture of the pressure ring 1 is likely to be unstable in the reciprocating motion of the piston. In addition, the oil control function and the gas seal function are deteriorated.

  The pressure ring of the present invention is preferably a second ring. As shown in FIG. 1, the pressure ring according to the present invention cuts a part of the outer peripheral surface 4 in order to form the cutout portion 1 b, so that the area of the pressure ring 1 that contacts the cylinder inner wall surface is reduced. The oil control function required as a second ring is improved.

  In the pressure ring of the present invention, it is preferable that the outer peripheral surface includes a tapered portion whose diameter is reduced from the lower surface side to the upper surface side of the pressure ring. The pressure ring according to the present invention includes a tapered portion on the outer peripheral surface thereof, thereby making it possible to further reduce the contact area with the inner wall surface of the cylinder and to improve the oil scraping performance with a high surface pressure. . Further, by setting the taper angle α shown in FIG. 2 to 30 ′ to 4 °, a thick oil film is formed due to the wedge effect of the taper surface clearance in the upward stroke of the piston, and the lower end is sharpened in the downward stroke of the piston. The edge can scrape the oil positively. Note that the taper angle is an angle α formed between the perpendicular B and the taper surface provided on the outer peripheral surface 4 with respect to the extension line A on the lower surface of the pressure ring as shown in FIG. Say. And this taper angle is measured based on the measuring method of the outer peripheral surface taper shown to JISB8032 (1993).

  Moreover, it is preferable that the pressure ring which concerns on this invention has a hard layer formed in the at least outer peripheral surface of the said pressure ring. The pressure ring according to the present invention can improve wear resistance and scuff resistance by forming a hard layer on at least the outer peripheral surface. FIG. 3 shows that the hard layer 11 is formed on the outer peripheral surface 4 of the pressure ring 1. However, the hard layer 11 is not limited to the outer peripheral surface 4 of the pressure ring 1 according to the present invention. FIG. 4 is a cross-sectional view showing the pressure ring according to the present invention cut in the axial direction of the pressure ring. For example, as shown to (A) of FIG. 4, the pressure ring which concerns on this invention may form the hard layer 11 in the said pressure ring perimeter. In this case, in the upper surface 2 and the lower surface 3 of the pressure ring shown in FIG. 3, wear due to contact with the upper and lower side surfaces 7 and 8 of the piston ring groove can be effectively suppressed. 3 shows that the hard layer 11 is formed on the outer peripheral surface 4 of the pressure ring 1, the pressure ring 1 according to the present invention has the hard layer 11 notched during the formation process. It may be formed on the outer surface of the portion 1b.

  Further, the pressure ring according to the present invention is formed by forming a nitriding layer, a chromium plating layer, or a PVD layer as the hard layer 11 formed on at least the outer peripheral surface 4 of the pressure ring 1, so that the wear resistance of the pressure ring is increased. And scuff resistance are dramatically improved. In addition, chrome plating, composite plating, thermal spraying, physical vapor deposition (PVD), chemical vapor deposition (CVD), etc. are applied to the surface of the nitriding treatment layer or chromium plating layer or PVD layer formed on at least the outer peripheral surface 4 of the pressure ring 1. Further surface treatment can be performed using the technique.

  Moreover, the pressure ring 1 of the present invention can also form a diamond-like carbon layer (hereinafter referred to as “DLC layer”) on the surface thereof. This DLC layer may be provided in the outermost layer 4 of the outer peripheral surface 4 on which the above-described nitriding layer, chrome plating layer, or PVD layer of the pressure ring 1 is formed, and the hard layer formed on the surface of the pressure ring 1 is omitted. Then, it may be formed directly on the outer peripheral surface 4. This DLC layer is known as a low-friction material having a low friction coefficient compared to hard wear materials such as TiN and CrN. The DLC layer is provided on the upper surface 2 and the lower surface 3 in addition to the outer peripheral surface 4. As a result, the wear resistance can be dramatically improved.

  It should be noted that it is not absolutely necessary for the pressure ring according to the present invention to form a hard layer on the surface of the pressure ring. Although the improvement effect of abrasion resistance and scuffing resistance when a hard layer is formed on the surface of the pressure ring according to the present invention has been described, as shown in FIG. The hard layer 11 may not be formed at all on the surface.

  As described above, according to the pressure ring of the present invention, when the piston is mounted on the piston, the posture of the pressure ring is stably maintained in a flat state substantially perpendicular to the piston shaft, so that the oil consumption The increase in the amount and the amount of blow-by gas can be suppressed. The basis for this is shown in the examples below.

Oil consumption confirmation test: In this confirmation test, an in-line four-cylinder gasoline engine with a displacement of 2000 cc and a cylinder bore diameter of 86.0 mm was tested and satisfied the condition of the inclination angle θ of the pressure ring specified in the present invention. It was confirmed whether there was a difference in oil consumption between what was and what was not.

  In carrying out this confirmation test, the engine was operated under full load (WOT) at a rotational speed of 6000 rpm for 5 hours. The combination of rings was a top ring, a second ring, and an oil ring, and those with different conditions of the inclination angle θ were prepared only for the second ring. The top ring used was a barrel-shaped outer peripheral surface having an axial width of 1.0 mm and a radial width of 2.7 mm and subjected to gas nitriding treatment. Further, the second ring has a tapered portion whose outer peripheral surface is reduced in diameter from the lower surface side to the upper surface side of the second ring, and is made of a SWRH62B material expressed in JIS standard, and has an axial width. Having a diameter of 1.0 mm and a radial width of 2.7 mm was used.

  Here, the 10Cr steel constituting the top ring and the SWRH62B material constituting the second ring used in this confirmation test will be described. The 10Cr steel mentioned here is carbon 0.50 mass%, silicon 0.21 mass%, manganese 0.30 mass%, chromium 10.1 mass%, phosphorus 0.02 mass%, sulfur 0.01 mass%, and the balance. It has a composition of iron and inevitable impurities and has been subjected to gas nitriding treatment. And SWRH62B material said here is carbon 0.62 mass%, silicon 0.21 mass%, manganese 0.75 mass%, phosphorus 0.02 mass%, sulfur 0.01 mass%, remainder iron and inevitable impurities The composition is provided.

  The oil ring used in this confirmation test is a two-piece oil ring composed of an oil ring body and a coil expander. The oil ring body is composed of carbon 0.70% by mass, silicon 0.28% by mass, manganese 0. A so-called 8Cr steel having a composition of 35 mass%, chromium 8.1 mass%, phosphorus 0.01 mass%, sulfur 0.01 mass%, the balance iron and inevitable impurities, and subjected to gas nitriding treatment Using.

  And about the second ring used in this confirmation test, the example sample (Example 1 to Example) in which the inclination angle θ of the pressure ring defined in the present invention satisfies the condition of 0 ° <θ ≦ 2 ° 4) and those corresponding to conventional products and those not satisfying the conditions were used as comparative sample (Comparative Example 1 and Comparative Example 2). Specifically, the inclination angle θ of the example sample was 15 ′ in Example 1, 30 ′ in Example 2, 1 ° in Example 3, and 2 ° in Example 4. On the other hand, the inclination angle θ of the comparative sample was 0 ° in Comparative Example 1 and 2 ° 30 ′ in Comparative Example 2. Here, as the example samples and the comparative example samples, all samples were provided with a tapered portion on the outer peripheral surface, and the taper angle α was 2 ° and the sliding surface width was unified to 0.1 mm. The sample used in this confirmation test was prepared using a pressure ring processing method generally adopted by those skilled in the art. Moreover, the shape of the outer peripheral surface of these samples was measured using a shape measuring instrument.

  Table 1 and FIG. 5 show the results of the oil consumption confirmation test based on the above conditions. Table 1 confirms the condition of the notch provided in the pressure ring and the condition of the inclination angle θ of the pressure ring in the example sample within the condition range of the present invention and the comparative example sample outside the condition range of the present invention. The result of having performed is shown. FIG. 5 is a graph showing the relationship between the inclination angle of the pressure ring (second ring) and the oil consumption. In Table 1, the value of the oil consumption index (LOC) is the value of a sample (Comparative Example 1) corresponding to a conventional product having an inclination angle θ of 0 ° in a free state before the pressure ring is mounted on the piston. It is shown as a relative value in the case of “100”.

  From Table 1, the oil consumption index of Example 1, which is an example sample, is 90, the oil consumption index of Example 2 is 80, the oil consumption index of Example 3 is 70, and the oil consumption index of Example 4 is 70. became.

  Further, from Table 1, the oil consumption index of Comparative Example 1, which is a comparative sample, was 100, and the oil consumption index of Comparative Example 2 was 98.

  Based on the above results, Examples 1 to 4 which are Example Samples are Comparative Example Samples that are out of the range of the inclination angle of the pressure ring defined in the present invention (0 ° <θ ≦ 2 °). The oil consumption was smaller than in Example 1 and Comparative Example 2. From the results shown in Table 1 and FIG. 5, in the pressure ring having a notch, the condition of the inclination angle θ of the upper surface of the pressure ring with respect to the plane perpendicular to the axis of the pressure ring is the present invention. If it is out of the range specified in (1), it is considered that the posture of the pressure ring when the piston is mounted is inclined. This is because, when the pressure ring is attached to the piston in a tilted posture, the contact area with the lower surface of the piston ring groove decreases, so the posture stability of the pressure ring in the piston ring groove deteriorates. This can be easily assumed because the oil sealability deteriorates and the oil consumption increases.

  In addition, from Table 1, regarding Comparative Example 2 of the comparative sample, the inclination angle of the pressure ring deviates from the upper limit side within the range defined in the present invention, but the size of the notch provided in the pressure ring is also The largest of all samples. In Table 1, when comparing the oil consumption index of Example 1 to Example 4, there is shown a tendency that the numerical value of the oil consumption index decreases as the inclination angle of the pressure ring increases. Nevertheless, the oil consumption index of Comparative Example 2 shows a numerical value close to that of Comparative Example 1 with an inclination angle θ of 0 °. Considering based on the result of Comparative Example 2, the pressure ring of Comparative Example 2 is formed into a pressure ring due to the shape deviating from the inclination angle range (0 ° <θ ≦ 2 °) of the pressure ring defined in the present invention. The ratio of the notch to be provided to the pressure ring increases, and the contact area between the lower surface of the pressure ring and the piston ring groove decreases, resulting in lack of ring posture stability and oil sealability on the lower surface of the pressure ring. Is thought to have declined.

  As described above, in the pressure ring of the present invention, the condition of the inclination angle θ of the upper surface of the pressure ring with respect to the plane perpendicular to the axis of the pressure ring is within the condition range defined in the present invention. Therefore, the oil consumption can be reduced.

  In the pressure ring of the present invention, since the upper and lower surfaces of the pressure ring are flat surfaces substantially perpendicular to the piston shaft when the piston is mounted, an increase in oil consumption and blow-by gas amount can be suppressed.

DESCRIPTION OF SYMBOLS 1 Pressure ring 2 Pressure ring upper surface 3 Pressure ring lower surface 4 Pressure ring outer peripheral surface 1a Joint part 1b Notch part 1b
θ Inclination angle α Taper angle a1 Radial width h1 of pressure ring Axial width A of pressure ring Extension line B on the lower surface of the pressure ring Vertical line X drawn on the extension line on the lower surface of the pressure ring Radial length Y of the notch Axial length of section

Claims (4)

A pressure ring mounted in a piston ring groove of a piston for an internal combustion engine,
A cut-out portion having a step shape by cutting off a corner formed by a lower surface and an outer peripheral surface having a substantially rectangular cross section in the axial direction is provided,
In the free state, the pressure ring has a substantially disc spring shape with the upper surface of the pressure ring inclined downward in the radial direction,
The pressure ring, wherein an inclination angle θ of the upper surface of the pressure ring with respect to a plane perpendicular to the axis of the pressure ring is 0 ° <θ ≦ 2 °.   The pressure ring according to claim 1, wherein the pressure ring is a second ring.   The pressure ring according to claim 1 or 2, wherein an outer peripheral surface of the pressure ring includes a tapered portion having a diameter reduced from the lower surface side to the upper surface side of the pressure ring.   The pressure ring according to claim 1, wherein a hard layer is formed on at least an outer peripheral surface of the pressure ring.

Images