JP5260220B2 - piston ring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston ring of such a structure that the contact pressure over its whole may periphery become uniform while it is in operation actually. <P>SOLUTION: The piston ring 1 is equipped with an oversurface and undersurface having approximately a circular shape and intersecting the peripheral sliding surface 2 and inside circumferential surface 3 and an abutment 4 to cut the circular shape into sections in the radial direction, wherein the position of the outermost point where the distance between the cylinder center 5 and the inside circumferential surface 3 maximizes lies between 44.6&deg; and 46.1&deg; from the middle point between the two ends of the abutment 4. On this piston ring 1, the value R<SB>max</SB>/R<SB>180</SB>obtained by dividing the distance R<SB>max</SB>from the cylinder center 5 to the cylinder center 5 and the outermost point by the distance R<SB>180</SB>from the cylinder center 5 to the antipode lying on the reference axis passing the middle point between the two ends of the abutment 4 and the cylinder center 5 and located in a place as 180&deg; rotated from the middle point ranges 1.044 thru 1.053 while the value obtained by dividing the distance R<SB>abutment</SB>from the cylinder center 5 to one end of the abutment 4 by the distance R<SB>180</SB>from the cylinder center 5 to the antipode ranges 1.032 thru 1.040. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention relates to a piston ring for an internal combustion engine, and more particularly to the shape of the piston ring.

For setting the shape of the ring of a piston ring for an internal combustion engine, a ring curve or the like designed based on the conventional theory such as Arnold or Prescott is generally used. Considering the case of using a ring with a ring curve design based on these theories, a temperature gradient is generated inside the piston ring due to the temperature difference between the cylinder wall surface and the piston during actual operation. As a result, a difference occurs in the amount of thermal expansion due to a temperature difference (50 ° C. to 60 ° C. during actual operation), causing deformation in which the curvature of the piston ring is reduced. Further, the abutment portion is locally heated by high-temperature blow-by gas blow-through. As a result, the surface pressure at the end of the abutment portion increases, the surface pressure balance of the piston ring is lost, and cracks, excessive wear, scuffing, etc. of the wear-resistant surface treatment film occur. In addition, a contact failure that is in a non-contact state with the cylinder bore occurs at a part away from the joint end by a certain distance. Such a phenomenon occurs particularly notably in the pressure ring of a high-supercharged diesel engine with an intake air cooler having a high heat load.

In order to solve the above problems, in Japanese Patent Laid-Open No. 2004-278378, a notch portion is formed over a predetermined circumferential length portion starting from the end portion of the joint portion on the inner peripheral surface of the piston ring. The piston ring is described. In this piston ring, the thickness in the radial direction at the predetermined circumferential length portion is smaller than the radial thickness at the portion other than the predetermined circumferential length portion due to the formation of the notch. Thereby, the surface pressure with respect to the cylinder wall surface of an abutment part can be reduced.

Furthermore, in Japanese Patent Laid-Open No. 2001-263488, the surface pressure in the vicinity of the abutment portion can be reduced by performing curve correction based on the core metal shape to reduce the piston ring overlap (ellipticity). In particular, since the joint portion is a free end, the surface pressure distribution change margin due to the change in curvature is large, and the effect becomes more remarkable. In the state where the piston ring is closed, the overhead is a distance of an axis passing through the center of the piston ring perpendicular to the axis from a distance B of the axis passing through the joint portion of the piston ring shown in FIG. The value obtained by subtracting A.
2004-278378 2001-263488

However, if a notch is made in the predetermined circumferential length portion from the joint portion as in the conventional (Patent Document 1) piston ring, the number of processing steps increases and the processing cost increases. Furthermore, blow-by gas blow-off causes a so-called hit-out in which the surface pressure at a predetermined distance from the abutment portion decreases, causing blow-by that combustion gas escapes to the crankcase without being sealed by the pressure ring, and problems such as pollution due to discharge of raw gas Occurs. In addition, the presence of the notch at the joint portion reduces the thickness in the radial direction and carries a risk that the strength decreases.

In addition, there is no established theory for the setting of the overflow in the piston ring, and since it depends heavily on experience, it is difficult to set the ideal surface pressure distribution.

Accordingly, the present invention has an object to provide a piston ring in which the surface pressure of the entire circumference of the piston ring is uniform during actual operation without providing a notch from the viewpoint of reducing the piston ring processing cost and maintaining a predetermined performance. And

In order to achieve the above object, an outer peripheral sliding surface that slides with respect to a cylinder, an inner peripheral surface that faces the piston, an outer peripheral sliding surface, and an upper surface and a lower surface that intersect the inner peripheral surface are formed. A piston ring for an internal combustion engine comprising a single abutment that divides a substantially circular shape in the radial direction, wherein the distance between the cylinder center and the inner peripheral surface is the maximum from the cylinder center that is the center point of the cylinder The distance (Rmax) to the outermost point is a pair located on a reference axis passing through the center of the cylinder and the center of both ends of the joint and the center of the cylinder and rotated by 180 ° from the center. The value (Rmax / R180) divided by the distance (R180) to the saddle point is 1.044 to 1.053, and the distance from the center of the cylinder to one end of the joint (R joint) is determined from the center of the cylinder. The value divided by the distance to the opposite point (R180) is 1.03 To a 1.040 is the position of the outermost point a 44.7 ° to 46.1 ° from the neutral point, the outer diameter of the piston ring for the internal combustion engine is a 90 to 112 mm, the internal combustion The piston ring for an internal combustion engine is characterized in that the thickness of the piston ring for the engine is uniform over the entire circumference .

According to the piston ring of the first aspect, since the surface pressure is designed to be uniform over the entire circumference of the piston ring during actual operation by the analysis by the finite element method, the increase in the surface pressure near the joint portion is prevented. Can be prevented. Thereby, cracks, excessive wear, scuffing, etc. of the wear-resistant surface treatment film at the joint can be prevented. Further, by preventing the increase in the surface pressure near the abutment portion, the contact pressure of the portion at a predetermined distance from the abutment portion does not occur, and problems such as pollution due to the discharge of raw gas can be prevented. .

Furthermore, since it is not necessary to process the inner peripheral surface of the ring, it is possible to reduce the processing cost by reducing the number of steps. In particular, the piston ring that has undergone surface processing such as nitriding or plating is difficult to process due to its high hardness, but the piston ring of the present embodiment does not apply special processing to the joint part, etc. Reduction effect can be obtained.

A piston ring according to a first embodiment of the present invention will be described with reference to FIGS. The piston ring 1 shown in FIG. 1 has a substantially circular shape, and an outer peripheral sliding surface 2 that slides on a cylinder wall (not shown), an inner peripheral surface 3 that faces a piston ring groove (not shown), and a substantially circular shape in the radial direction. It has the joint part 4 to divide. The distance between the outer circumferential sliding surface 2 and the inner peripheral surface 3 (thickness in the radial direction of the piston ring) and a _1. R _joint is a distance from the cylinder center 5 to one end of the joint part (nominal diameter of the piston ring), and R _{180 °} is a distance from the cylinder center 5 to a part rotated 180 ° from the center of the joint part.

FIG. 2 shows the relationship between the distance from the cylinder center and the circumferential angle from the ring joint in the piston ring according to the embodiment of the present invention and the conventional piston ring. Since the piston ring is line-symmetric with respect to the axis passing through the center of the joint portion as a reference axis, only one side of the reference axis is shown in FIG. In this graph, a piston ring in a static state at normal temperature is fixed _at a position of R _{180 °} , and the distance from the cylinder center 5 is measured by a shape measurement program of a contact type three-dimensional measuring instrument. The piston ring according to the present embodiment is indicated by a solid line, and the point where the distance from the cylinder center 5 is farthest is R _max . The piston ring designed with zero zero (A = B) is indicated by a dotted line, the point where the distance from the cylinder center 5 is farthest is R _max0, and the distance from the cylinder center 5 to one end of the _joint is the R _{joint Set} to ₀ . The piston ring designed with minus (A> B) is indicated by a one-dot chain line, the point where the distance from the cylinder center 5 is farthest is R _max-, and the distance from the cylinder center 5 to one end of the joint is R _joint- .

The piston ring according to the embodiment of the present invention uses a finite element method (FEM) to analyze the thermal expansion due to the temperature gradient inside the piston ring, and the surface pressure is uniform over the entire circumference of the piston ring outer peripheral sliding surface during actual operation. It is designed to be. More specifically, the shape of the piston ring indicated by the solid line in the graph of FIG. Here, a graph of one-dot chain line is a conventional low point ring (over Rithy negative), as the surface pressure of the R _max- part increases, to increase the design values of R _max-, the R _max- parts The surface pressure in the vicinity of the joint is reduced by increasing the surface pressure. On the other hand, in the solid line graph (this embodiment), the values of R _max and R _joint are designed to be low in order to keep the surface pressure around the entire circumference of the piston ring uniform. When the conventional design is negative, R _max−− R _max0 > 0 and R _joint−− R _{joint 0} <0, but in this embodiment, R _max −R _max0 <0 and R _joint -R _{abutment 0} <0. Due to such a ring curve shape, the surface pressure of the entire circumference of the piston ring during actual operation becomes uniform. Table 1 shows detailed numerical values of φ104 and φ112 that are mainstream in the size of the piston ring. The ring h ₁ was all 2.5 mm, and the a ₁ dimension was 3.75 mm for the ring outer diameter φ104 and 4.15 mm for φ112.

The conventional design is a ring curve designed based on theories such as Arnold and Prescott. From Table 1, in the piston ring according to the embodiment of the present invention, R _max / The value of R _{180 °} is about 1% lower. This is because _Rmax is designed to be low in order to keep the surface pressure uniform over the entire circumference of the piston ring. Furthermore, the angle from R _max is also about 3 to 15 ° higher. In addition, R _joint / The value of R _{180 °} is reduced by about 1%. The angle of the R joint is θ shown in FIGS. 1 and 2.

The specific dimensions of the present embodiment JIS B8032-1: shown in 1998, the outer diameter _{d 1} is 90～150Mm, piston ring width _{a 1} is 2.5 to 4.5, free closed gap m is 5 25 mm, it is preferable axial thickness _{h 1} of the piston ring is 2.0 to 4.0 mm.

Next, a unit test was performed on the piston ring. In the unit test, the surface pressure distribution at room temperature and warm time was measured for the φ104 conventional ring. Here, normal temperature means that the piston ring and the cylinder liner are both 20 ° C. Also, when warm, the piston ring is 230 ° C. and the cylinder liner is 90 ° C. Incidentally, the axial thickness and the outer peripheral sliding surface shape of each ring, the radial thickness a ₁ using the same thing with respect to the measurement.

  FIG. 3 shows the left half of the surface pressure distribution measuring device 5. The cylinders 52 and 53 are supported by the cylinder holder 51, and a recess 53 a is formed in a part of the outer peripheral surface 2 of the cylinder 53 to form the thinnest part. It becomes. A piston ring as a test piece is mounted in the ring groove 55 a of the piston 55, and the outer peripheral sliding surface 4 of the piston ring is brought into contact with the inner peripheral surface 3 of the cylinder 53. Then, the surface pressure from the piston ring acts on the thinnest portion of the cylinder 53, and distortion occurs. Therefore, the strain gauge 54 was attached to the bottom of the recess 53a, the strain gauge 54 was connected to the strain amplifier 57, and the strain value was recorded on the pen recorder 58, thereby measuring the strain value as the surface pressure. Further, a temperature was measured by providing a J-type thermocouple 59 near the piston ring groove 55a and the inner peripheral surface of the cylinder 53 at a position facing the piston ring, and connecting it to the high-speed dot meter 60. Further, a heater 56 is attached to the upper side of the piston 55 that holds the piston ring to heat the piston ring, while cooling water is brought into contact with the outer peripheral side of the cylinder 53 to cool the cylinder 53. A temperature gradient close to that during actual operation was distributed to the cylinder 53.

4 and 5 are graphs in which the vertical axis represents the surface pressure and the horizontal axis represents the circumferential direction angle when the midpoint of the joint portion is 0 °. FIG. 4 shows the test results at room temperature, and FIG. 5 shows the test results at warm time.

In the figure, not only the φ104 conventional ring but also φ104 steel, φ112 steel (high temperature), and φ112 steel (medium temperature), which are embodiments of the present invention, are shown together. For φ104 steel, φ112 steel (high temperature), and φ112 steel (intermediate temperature), the results are calculated. A shows the experimental results for φ104 steel, B for φ112 steel (high temperature), C for φ112 steel (medium temperature), and D for φ104 conventional ring.

In the comparative material φ104 conventional ring D, the contact pressure in the range of the joint portion ± 10 ° has already increased at room temperature. This phenomenon becomes more pronounced when the heat load action shown in FIG. 5 is applied, and the surface pressure in the vicinity of the joint is increased to about 1.8 Mpa. Then, when the vicinity of the abutment portion was strongly pressed against the cylinder liner, a contact drop in which the surface pressure became extremely low in a range of ± 5 to 30 ° from the abutment portion occurred.

On the other hand, in the piston rings φ104 steel A, φ112 steel (high temperature) B, and φ112 steel (medium temperature) C according to the embodiment of the present invention, the surface pressure becomes zero in the range of ± 30 ° at normal temperature, and hitting occurs. ing. Further, the surface pressure increases rapidly as the circumferential angle moves away from the abutment, and the surface pressure is substantially constant when the circumferential angle becomes ± 90 ° or more. Such a tendency applies to any of φ104 steel, φ112 steel (high temperature), and φ112 steel (medium temperature).

However, in the warm state, the surface pressure in the range of ± 15 ° is low for φ104 steel A, φ112 steel (high temperature) B, and φ112 steel (medium temperature) C, which are the piston rings of this embodiment. The surface pressure is substantially constant as the circumferential angle moves away from the abutment. This is particularly noticeable in φ104 steel A and φ112 steel (high temperature) B. Further, in any piston ring of the present embodiment, the surface pressure in the vicinity of the abutment portion is low. There has been no omission in which the contact pressure decreases. From the above, the shape of the piston ring as shown in Table 1 makes it possible to obtain a uniform surface pressure over the entire circumference during warm operation assuming actual operation.

  The piston ring by this invention is not limited to embodiment mentioned above, A various change is possible within the range of the summary of the invention described in the claim. For example, in order to improve wear resistance and durability, the surface of the piston ring may be subjected to surface treatment such as plating or nitriding. Furthermore, you may perform a PVD film process to an outer peripheral sliding surface, after giving a nitriding process. Although steel is used in the present embodiment, the present invention is not limited to this, and the same effect can be obtained even when cast iron or the like is used. In the above-described embodiment, the notch has a linear shape that is substantially parallel to the outer sliding surface. However, the shape of the notch is not limited to this, and the shape of the unevenness or the abutment end on the inner peripheral surface side. A linear shape in which the thickness in the radial direction decreases toward the part toward the part may be used. Furthermore, the sliding surface shape may be a symmetric barrel shape, an eccentric barrel shape, or a tapered shape.

Schematic diagram showing the shape of the piston ring The graph which shows the shape of the piston ring by embodiment of this invention Sectional drawing which shows the left half of the surface pressure distribution measuring apparatus which tested the piston ring by embodiment of this invention The graph showing the calculation result performed about the piston ring by embodiment of this invention, and the conventional ring, and the result of the unit test at normal temperature The graph showing the calculation result performed about the piston ring by the embodiment of the present invention, and the conventional ring, and the result of the unit test at the time of actual operation

Explanation of symbols

1: Piston ring
2: Outer peripheral sliding surface 3: Inner peripheral surface 4: Joint portion 5: Center of cylinder

Claims (1)

It has a substantially circular shape, and the outer peripheral sliding surface that slides relative to the cylinder, the inner peripheral surface that faces the piston, the outer peripheral sliding surface, the upper and lower surfaces that intersect the inner peripheral surface, and the substantially circular shape are divided in the radial direction. A piston ring for an internal combustion engine comprising one abutment
The distance (Rmax) from the cylinder center, which is the center point of the cylinder, to the outermost point where the distance between the cylinder center and the inner peripheral surface is the maximum, and the midpoint between both ends of the joint portion from the cylinder center A value (Rmax / R180) divided by a distance (R180) to a counterpoint located on a reference axis passing through the cylinder center and rotated by 180 ° from the midpoint is 1.044 to 1.053. The value obtained by dividing the distance from the cylinder center to one end of the joint (R joint) by the distance (R180) from the cylinder center to the opposite point is 1.032 to 1.040. The position of the outermost point is 44.7 ° to 46.1 ° from the midpoint;
The internal diameter of the piston ring for the internal combustion engine is 90 to 112 mm,
A piston ring for an internal combustion engine, characterized in that the thickness of the piston ring for the internal combustion engine is uniform over the entire circumference .

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