JP4165119B2 - Piston ring of internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a piston ring used as a compression ring in an internal combustion engine, mainly an automobile gasoline engine.
[0002]
[Prior art]
The compression ring of an internal combustion engine is required to have good oil consumption performance at the same time as the combustion gas seal. Japanese Utility Model Laid-Open No. 5-14733 discloses a barrel in which both the combustion chamber side portion and the crankcase side portion of the outer peripheral surface of the piston ring are substantially arc-shaped curved surfaces, and the central portion in the ring width direction is a loosely tapered surface. A face-type piston ring is disclosed. Note that the tapered surface is inclined in the direction in which the combustion chamber side has a smaller diameter, and therefore the connecting portion with the curved surface on the crankcase side protrudes most on the outer peripheral side.
[0003]
Japanese Patent Application Laid-Open No. 6-185620 discloses that a combustion chamber side portion including a ring width central portion that is most convex on the outer peripheral side is a barrel face type curved surface, and a chamfered taper is formed on a crank case side portion. A piston ring with a face is disclosed.
[0004]
[Problems to be solved by the invention]
In the former configuration, the vicinity of the connecting portion between the tapered surface and the curved surface on the crankcase side is in sliding contact with the cylinder wall surface in a form close to line contact, and the tapered surface and the cylinder immediately above the contact portion (combustion chamber side). Both the angle formed by the wall surface and the angle formed by the curved surface immediately below the contact portion (crankcase side) and the cylinder wall surface are small. Therefore, when the piston moves downward, a clear edge effect on the oil film on the cylinder wall surface cannot be obtained, and the oil scraping performance is low. In particular, when the piston moves upward or downward with respect to the oil film on the cylinder wall surface, the operation is almost the same, so the function of transporting oil in one direction, that is, to the crankcase side is hardly obtained. .
[0005]
In the latter configuration, the taper surface is used to scrape off the oil. However, the most convex part in the radial direction is the curved surface part, and this part is in sliding contact with the cylinder wall surface in a form close to line contact. After all, a clear edge effect cannot be obtained. In particular, in the vicinity of the contact portion, the upper and lower portions are almost symmetrical with respect to the contact portion, so that the action of transporting oil in one direction is weak.
[0006]
Further, in the case of the line contact with the cylinder wall surface as described above, the shape change due to wear over time is large, and characteristics such as oil consumption performance become unstable over time.
[0007]
[Means for Solving the Problems]
The piston ring of the internal combustion engine according to the present invention has, as a contour shape of the piston ring in a cross section including the ring central axis, a linear portion parallel to the ring central axis at the center portion in the ring width direction of the outer peripheral surface. Therefore, this linear portion is in surface contact with the cylinder wall surface. The length (L1) of the linear portion is, for example, in the range of 1/5 to 2/3 with respect to the ring width (L). Especially when used as a top ring, in order to increase the surface pressure at this straight portion, it is desirable to set the range of 1/5 to 1/3. When used as a second ring, the surface pressure is compared. It is desirable to set it within a range of 1/4 to 2/3 so that an oil film can be formed when the piston is lowered. On one side of the straight line portion, a chamfered taper portion inclined with respect to the ring central axis is provided. The inclination angle of the tapered portion is desirably in the range of 45 ° to 60 °. Since the taper portion is bent sharply from the straight portion, an edge effect is obtained with respect to the oil film on the cylinder wall surface, and the oil on the cylinder wall surface can be scraped off effectively. The tapered portion intersects with one end surface of the piston ring at a point retracted by 0.2 mm to 0.4 mm radially inward from the radial position of the linear portion . And on the other side of the straight line portion, there is an arc portion formed of an arc having an appropriate curvature. In the arc constituting the arc portion, the straight line portion is continuous as a tangent. The arc portion has a radius of curvature that intersects the other end surface of the piston ring at a point that is 0.2 mm to 0.4 mm backward from the radial position of the linear portion toward the radially inner periphery. Yes.
[0008]
Therefore, paying attention to the surface pressure distribution in the state where it is in pressure contact with the cylinder wall surface, the surface pressure changes gently at the portion where the straight portion transitions to the arc portion, while at the portion where the straight portion transitions to the tapered portion, both The surface pressure changes abruptly at the boundary. Therefore, when the piston rises, the oil easily passes from the arc portion to the linear portion, and when the piston descends, the oil is scraped by the edge effect at the boundary between the tapered portion and the linear portion. Be dropped. As a result, the oil on the cylinder wall surface is effectively conveyed in one direction.
[0009]
【The invention's effect】
According to this invention, when the piston ring moves up and down together with the piston, the oil on the cylinder wall surface can be reliably conveyed to the crankcase side, and oil consumption is reduced. Further, since the straight portion is in surface contact with the cylinder wall surface, the shape change due to wear over time is small, and stable performance can be obtained from the initial stage over a long period of time.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
First, the basic cross-sectional shape of the piston ring 1 according to the present invention will be described with reference to FIG. The piston ring 1 is used as a compression ring, is mounted in the ring groove 3 of the piston 2, and is in sliding contact with the cylinder wall surface 4. The overall structure, material, or surface treatment of the piston ring 1 is not particularly different from known ones.
[0012]
The cross-sectional shape of the piston ring 1 is a substantially rectangular cross section surrounded by the outer peripheral surface on the cylinder wall surface 4 side, the upper and lower end surfaces 5 and 6, and the inner peripheral surface 7, and the ring width L (FIG. 3). Has a flat cross-sectional shape smaller than the thickness in the radial direction. And the said outer peripheral surface is comprised from three parts. The first portion is a straight portion 11 constituting the central portion in the ring width direction, and the second portion located below, that is, on the crankcase side, is a tapered portion 12 that forms a straight line inclined in the cross section. . Further, the third portion above the straight portion 11, that is, on the combustion chamber side is an arc portion 13 that forms an arc having a constant radius of curvature in the cross section.
[0013]
The linear portion 11 is formed in parallel with the ring center axis m (see FIG. 4), and forms a cylindrical surface in surface contact with the cylinder wall surface 4. The taper portion 12 is a chamfered inclined surface so as to have an inclination angle θ (see FIG. 3) with respect to the linear portion 11. The circular arc portion 13 is continuous with the linear portion 11 so that the linear portion 11 forms a tangent to the circular arc, and the upper end surface 5 intersects the plane of the end surface 5 with the circular arc. It has become.
[0014]
Therefore, the surface pressure distribution when the outer peripheral surface composed of the three parts as described above is in pressure contact with the cylinder wall surface 4 is as shown in FIG. On the other hand, in the portion where the linear pressure portion 11 transitions from the linear portion 11 to the tapered portion 12, the surface pressure changes abruptly at the boundary between the two. That is, the surface pressure distribution is asymmetrical in the vertical direction, and the rising gradient of the surface pressure at each boundary is gentle on the arc portion 13 side and steep on the taper portion 12 side. Therefore, when the piston 2 moves up, the surface pressure changes gently, so that oil easily passes from the arc portion 13 to the straight portion 11. Conversely, when the piston 2 descends, an abrupt change in surface pressure causes an edge effect at the boundary between the taper portion 12 and the straight portion 11, thereby scraping off the oil. Therefore, when the piston ring 1 reciprocates together with the piston 2, the oil on the cylinder wall surface 4 is positively carried to the crankcase side, and oil consumption is suppressed.
[0015]
Next, the dimensional relationship of each part will be described with reference to FIG. The axial length L1 of the linear portion 11 is preferably in the range of 1/5 to 2/3 of the ring width L of the entire piston ring 1. When this L1 is reduced, the surface pressure increases and the oil film formation decreases both when the piston is raised and when it is lowered, so that oil consumption is reduced, but wear resistance and seizure resistance are deteriorated. Range exists. The range varies depending on oil consumption performance requirements, durability requirements, wear resistance and seizure resistance due to surface treatment differences, ring tension, etc. Within the above range. In particular, when used as a top ring, considering the blow-by gas sealing property and ring behavior, in order to increase the surface pressure at this straight portion 11, it is desirable to set the range of 1/5 to 1/3, Further, when used as a second ring, it is desirable that the surface pressure is set to a range of 1/4 to 2/3 so that the surface pressure is relatively low and an oil film can be formed when the piston is lowered. In the present invention, since the oil can be positively conveyed to the crankcase side, the oil consumption can be equivalent with a surface pressure relatively lower than that of the conventional one. The balance with the seizure property can be taken at a higher level.
[0016]
The dimension t2 in the radial direction of the tapered portion 12 is preferably 0.2 mm to 0.4 mm as a piston ring of an internal combustion engine for automobiles. If this is excessively large, the tapered portion 12 enters the ring groove 3, and the lower end edge of the tapered portion 12 interferes with the inner surface of the ring groove 3, which is not preferable. The limit that the tapered portion 12 does not overlap with the ring groove 3 is generally about 0.4 mm in an automobile internal combustion engine. On the other hand, if this t2 is excessively small, the lower end edge of the taper portion 12 may interfere with the cylinder wall surface 4 when the piston ring 1 is tilted or wear progresses. Therefore, at least about 0.1 mm is necessary, and it is preferable to add a margin of allowance of about 0.1 mm to allow a processing error to at least 0.2 mm.
[0017]
Further, the inclination angle θ of the tapered portion 12 is preferably 45 ° to 60 °. In order to enhance the effect of oil scraping by making the gradient of the surface pressure change abrupt, it is advantageous that the inclination angle θ is large. However, if the inclination angle θ is increased, the boundary with the straight portion 11 during processing is increased. Since the burrs are likely to be generated at the edges and the burrs are similarly generated due to the progress of wear, the maximum is set to 60 ° in order to suppress the occurrence of burrs due to workability and wear. If the angle is at least 45 °, a sufficient edge effect can be obtained.
[0018]
The axial dimension L2 of the tapered portion 12 is determined accordingly by appropriately determining the above-described t2 and the inclination angle θ.
[0019]
The dimension t1 in the radial direction of the arc portion 13 is preferably 0.2 mm to 0.4 mm for the same reason as t2. In order to make the gradient of the change in surface pressure at the boundary between the straight line part 11 and the circular arc part 13 more gradual, it is desirable to increase the radius of curvature R of the circular arc part 13 where the straight line part 11 is a tangent line. In this case, it is necessary to make t1 small. However, if t1 is made excessively small, a processing error is not allowed. Therefore, it is desirable to make t1 as small as possible within the above range.
[0020]
As described above, the radius of curvature R of the arc portion 13 is desirably as large as possible in order to make the gradient of the change in surface pressure at the boundary between the linear portion 11 and the arc portion 13 more gradual. However, this is uniquely determined by determining the required sizes L1 and L2 for the ring width L and the radial dimension t1. Therefore, it is desirable to set the radius of curvature R as large as possible while making the dimension t1 in the radial direction as small as possible. As a piston ring of an internal combustion engine for automobiles, it is desirable that the radius of curvature R is about 0.7 mm to 2.2 mm.
[0021]
In general, in an internal combustion engine for automobiles, the bore diameter of a cylinder is about 65 mm to 100 mm for a gasoline engine and about 150 mm at maximum for a diesel engine for a large truck. The ring width L of the piston ring 1 is about 0.8 mm to 1.5 mm for a gasoline engine, about 2.0 mm to 3.9 mm for a top ring and about 1.5 mm to 3.0 mm for a second ring for a diesel engine. It will be about. The above-described dimensional relationships of the respective parts can be applied to the piston rings of these automobile internal combustion engines.
[0022]
Next, more specific examples 1 to 5 will be described.
[0023]
FIG. 4 shows a piston 2 for a gasoline engine of a two-ring type, and includes a top ring 101 that becomes a single compression ring and an oil ring 103. Note that the oil ring 103 is generally configured as a combination ring having upper and lower rails, unlike the piston ring targeted by the present invention. FIG. 5 shows a piston 2 for a three-ring type gasoline engine, and includes two compression rings, that is, a top ring 101 and a second ring 102, and an oil ring 103.
[0024]
Examples 1 to 3 are used as the second ring 102 in the configuration of FIG. In this case, a general barrel face type piston ring or the like can be used as the top ring 101, or the piston ring of the present invention can be further combined as the top ring 101. In this second ring 102 example, the bore diameter is 95 mm and the ring width L is 1.5 mm.
[0025]
Examples 4 and 5 are used as the top ring 101 in the configuration of FIG. 4 or the configuration of FIG. When the top ring 101 is used in the configuration of FIG. 5, a general tapered piston ring or the like can be used as the second ring 102, or the piston ring of the present invention can be further combined as the second ring 102. It is. In the example of the top ring 101, the bore diameter is 95 mm and the ring width L is 1.2 mm.
[0026]
{Example 1}
As a balance between oil consumption performance and durability at a high level, L1 = 0.7 mm, t2 = 0.3 mm, θ = 45 °, t1 = 0.2 mm, and R = 0.7 mm. The cross-sectional shape is shown in FIG. Note that L2 is 0.3 mm from t2 and θ. Therefore, in this example, the linear portion 11 is provided in a range straddling the center of the ring width L.
[0027]
{Example 2}
As settings for maximizing oil consumption performance, L1 = 0.4 mm, t2 = 0.3 mm, θ = 60 °, t1 = 0.2 mm, and R = 2.2 mm. The cross-sectional shape is shown in FIG. Thus, by setting the length L1 of the linear portion 11 to be small, the surface pressure is increased, and coupled with the fact that the inclination angle θ is set to be large in order to enhance the edge effect, oil can be scraped off reliably.
[0028]
{Example 3}
L1 = 0.8 mm, t2 = 0.2 mm, θ = 60 °, t1 = 0.2 mm, R = 0.7 mm were obtained to obtain higher durability while satisfying the oil consumption performance. The cross-sectional shape is shown in FIG. Thus, by setting the length L1 of the straight portion 11 to be large, the surface pressure is lowered, and the wear resistance and seizure resistance are improved. And by setting the inclination angle θ large, the oil can be scraped off reliably.
[0029]
{Example 4}
L1 = 0.4 mm, t2 = 0.3 mm, θ = 45 °, t1 = assuming that oil consumption performance and durability are balanced at a high level while considering the blow-by gas sealing performance necessary for the top ring 101. 0.2 mm and R = 0.9 mm. The cross-sectional shape is shown in FIG. Note that L2 is 0.3 mm from t2 and θ. Therefore, in this example, the linear portion 11 is provided in a range straddling the center of the ring width L.
[0030]
{Example 5}
As settings for maximizing oil consumption performance and blow-by gas sealing performance, L1 = 0.25 mm, t2 = 0.3 mm, θ = 60 °, t1 = 0.2 mm, and R = 1.7 mm. The cross-sectional shape is shown in FIG. Thus, by setting the length L1 of the linear portion 11 to be small, the surface pressure is increased, and coupled with the fact that the inclination angle θ is set to be large in order to enhance the edge effect, oil can be scraped off reliably. Moreover, blow-by gas sealing performance also becomes high because surface pressure is high.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a cross-sectional shape of a piston ring according to the present invention.
FIG. 2 is a characteristic diagram showing the surface pressure distribution.
FIG. 3 is an explanatory diagram of dimensions of each part of the piston ring.
FIG. 4 is a sectional view of a two-ring type piston.
FIG. 5 is a cross-sectional view of a three-ring type piston.
FIG. 6 is a cross-sectional view of the piston ring according to the first embodiment.
7 is a cross-sectional view of a piston ring of Example 2. FIG.
8 is a cross-sectional view of a piston ring of Example 3. FIG.
9 is a cross-sectional view of a piston ring of Example 4. FIG.
10 is a sectional view of a piston ring of Example 5. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Piston ring 11 ... Linear part 12 ... Tapered part 13 ... Arc part

Claims (5)

As the contour shape of the piston ring in the cross section including the ring center axis, the ring center in the ring width direction of the outer peripheral surface has a straight line portion parallel to the ring center axis, and the ring center is located on one side across the straight line portion It has a tapered portion inclined with respect to the axis, and on the other side, have a circular arc portion made of an arc in which the straight portion are continuous as tangents,
The length (L1) of the linear portion is in the range of 1/5 to 2/3 with respect to the ring width (L),
The inclination angle of the tapered portion is within a range of 45 ° to 60 °;
The taper portion intersects one end surface of the piston ring at a point that is receded from 0.2 mm to 0.4 mm radially inward from the radial position of the linear portion ,
The radius of curvature of the arc portion is set so that the arc portion intersects with the other end surface of the piston ring at a point that is 0.2 mm to 0.4 mm backward from the radial position of the straight portion to the radially inner side. is, piston rings of an internal combustion engine, characterized in that.   2. The piston ring for an internal combustion engine according to claim 1, wherein the arc portion is provided on the combustion chamber side, and the tapered portion is provided on the crankcase side.   The piston ring for an internal combustion engine according to claim 1 or 2, wherein the linear portion is formed in a range straddling the center of the ring width. Used as the top ring, the length of the straight portion (L1) is, relative ring width (L), in any one of claims 1 to 3, characterized in that in the range of 1 / 5-1 / 3 The piston ring of the internal combustion engine described. It is used as a second ring, and the length (L1) of the straight portion is in the range of 1/4 to 2/3 of the ring width (L). The piston ring of the internal combustion engine described.

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