JP3792413B2 - piston ring - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a piston ring, and more particularly to a low point piston ring.
[0002]
[Prior art]
Due to the surface pressure distribution of the piston ring, the high-point piston ring whose surface pressure near the joint is high compared to other parts, and the low-point piston ring whose surface pressure near the joint is low compared to other parts. It is roughly divided into two. Both can be used properly depending on the usage environment and application, but there is a tendency to use a low-point piston ring in a high-power diesel engine or the like where the wear near the joint is severe. Conventionally, a piston that exhibits a desired surface pressure distribution by changing the circumferential shape with a uniform cross-sectional shape utilizing the property that the contact surface pressure distribution with respect to the cylinder bore of the piston ring varies depending on the circumferential shape when free. A ring was manufactured.
[0003]
[Problems to be solved by the invention]
However, since the piston ring is thermally deformed as described below during engine operation, the contact state between the piston ring and the cylinder changes as compared with that at room temperature, and the surface pressure distribution also changes greatly. Due to this change, the surface pressure distribution of the piston ring during actual engine operation tends to increase to the same surface pressure distribution as the high point piston ring even at the low end piston ring. Have.
[0004]
First, due to a difference in thermal expansion due to a temperature difference between the cylinder and the piston ring, a deformation is generated in which the piston ring diameter is apparently larger than the cylinder diameter. In addition, the temperature difference between the cylinder and piston causes a temperature difference between the inner and outer circumferences of the piston ring (60 ° C to 70 ° C at full load), and the deformation becomes smaller due to the difference in thermal expansion between the inner and outer peripheral surfaces. Arise. These effects produce the same effect as when a piston ring having a nominal diameter larger than the bore diameter is inserted. In other words, the surface pressure at the abutment end increases, and so-called hitting that does not come into contact with the cylinder bore at the side of the abutment end tends to occur.
[0005]
Furthermore, the temperature near the abutment rises from the other part due to the heating by blow-by gas blow-off (about 30 ° C. to 50 ° C.), and the vicinity of the abutment greatly expands compared to the other part, resulting in a smaller curvature. Produce. By this action, the surface pressure distribution is such that the surface pressure at the end of the joint becomes extremely large. Also, if this action is extremely strong, a hit will occur at the side of the end of the joint.
[0006]
In addition, since the circumferential shape changes greatly due to the expansion of the entire piston ring due to the thermal load as described above and the thermal stress caused by the temperature difference between the inner and outer sides of the piston ring, the contact state with the cylinder bore changes. Then, the surface pressure increases as the temperature increases. Therefore, when the engine is operated under extremely severe conditions for lubrication, the abutment portion shows an extremely worn state, and sometimes the PVD coating formed on the outer peripheral surface of the piston ring has troubles such as cracking and peeling. generate.
[0007]
On the other hand, if the joint portion is designed to have an extremely low surface pressure when it is cold in consideration of the surface pressure at the time of heat load, the contact portion of the joint portion is likely to come off in production (the defect rate is high). For this reason, it is not suitable for mass production. In addition, some piston rings have been designed so that the abutment is intentionally non-contacted and contacted when a thermal load is applied so that an isobaric surface distribution is obtained during high-load operation. However, there is a problem with oil rising during start-up and idling. Therefore, management in manufacturing is difficult, and this is also not suitable for mass production. Further, in these piston rings, the so-called blow-by occurs that the combustion gas escapes to the crankcase without being sealed by the pressure ring due to the contact of the joint part, and there are problems such as deterioration of the lubricating oil and pollution due to exhaust of raw gas. It was happening.
[0008]
Therefore, the conventional low-point piston ring with just the circumferential shape adjusted is not sufficient for anti-abrasion measures if it is designed so that it will not come into contact with it. Then, a hit was made. In particular, it was very difficult to design the vicinity of the piston ring joint where significant wear was caused by engine operation.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to provide a piston ring that does not come off around the entire circumference even at room temperature and does not cause an increase in surface pressure at the joint portion even under a heat load.
[0010]
[Means for Solving the Problems]
To achieve the above object, the present invention has a substantially circular shape, an outer peripheral surface that slides with respect to a cylinder, an inner peripheral surface that faces the piston, and one abutment that divides the substantially circular shape in the radial direction. A cutout portion forming a part of the inner peripheral surface is formed on the inner peripheral surface side over a predetermined peripheral length portion starting from the end surface of the joint portion. In the piston ring, the notch has a first surface and a second surface, and the notch has a first surface and a second surface. One surface is in contact with the end surface of the joint portion and forms a substantially circular arc surface having the same central axis as the outer peripheral surface, and the radial thickness defined between the outer peripheral surface and the first surface is the predetermined thickness. It is 0.7 to 0.8 times the radial thickness in the portion other than the circumferential length portion, and is defined by the central axis of the outer circumferential surface. Is formed over a range of angular 15 ° to 20 °, the range capable of suppressing surface pressure increase of該合opening when the thermal load it is possible to prevent loss per the entire circumference of the outer peripheral surface at the time of a normal temperature operation The second surface is provided with a piston ring having an arbitrary curved surface in contact with the first surface at an end opposite to a portion where the first surface is in contact with the end surface of the joint portion .
[0011]
The present invention further comprises a substantially circular outer peripheral surface that slides relative to the cylinder, an inner peripheral surface that faces the piston, and a single abutment that divides the substantially circular shape in the radial direction. On the peripheral surface side, a notch portion forming a part of the inner peripheral surface is formed over a predetermined peripheral length portion starting from the end surface of the joint portion, and the radial thickness at the predetermined peripheral length portion is formed. However, in the piston ring which is smaller than the radial thickness of the portion other than the predetermined circumferential length portion, the notch portion has a planar shape gradually approaching the outer peripheral surface toward the end surface of the joint portion, and the joint portion The radial thickness at the end face is 0.5 to 0.6 times the radial thickness at the portion other than the predetermined circumferential length portion, and the predetermined circumferential length portion is defined by the central axis of the outer circumferential surface. Formed at a central angle of 20 ° to 30 °, and at the time of operation and at room temperature. Provided is a piston ring that is set in a range that can prevent the entire outer peripheral surface from being knocked out and can suppress an increase in surface pressure at the joint portion during a thermal load.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
A piston ring according to a first embodiment of the present invention will be described with reference to FIG.
[0014]
The piston ring 1 shown in FIG. 1 has a substantially circular shape made of steel, and has an outer peripheral surface 3 that slides against a cylinder (not shown), an inner peripheral surface 4 that faces the piston (not shown), and a substantially circular shape with a radius. And one abutment portion 2 that is divided in the direction.
[0015]
The distance between the outer peripheral surface 3 and the inner peripheral surface 4 (thickness dimension in the piston ring radial direction) is a ₁ , but on the inner peripheral surface 4 side, a predetermined peripheral length portion starting from the end surface of the joint portion 2 is used. A notch 4a and A-B-C forming part of the inner peripheral surface 4 are formed, and the radial thickness of the predetermined peripheral length portion is the radial direction of the portion other than the predetermined peripheral length portion. It is formed smaller than the thickness.
[0016]
Specifically, the notch 4a has a first surface AB and a second surface BC. The first surface A-B is in contact with the end surface of the abutment portion 2, forms a substantially arc surface having the same central axis as the outer peripheral surface 3, and has a radial thickness defined between the outer peripheral surface 3 and the first surface. The thickness is 0.7 to 0.8 times the radial thickness a ₁ in a portion other than the predetermined circumferential length portion. Here, if the thickness is less than 0.7 times, the surface pressure at the abutment end is excessively lowered during engine operation, which is a problem with respect to the amount of lubricant consumed. Moreover, the gas sealing performance of the lower surface portion of the ring is lowered. On the other hand, if the thickness exceeds 0.8 times, the bending rigidity is not sufficiently reduced, and the surface pressure increases during engine operation. By reducing the thickness dimension of the first surface A-B forming portion by 20% to 30% from the thickness dimension of the entire piston ring 1, the second moment of section can be reduced to about ½, and the radial bending The rigidity is also about ½. By reducing the radial bending rigidity to about 1/2, the surface pressure at the end of the joint becomes about 1/2 of that of a piston ring with a uniform cross-sectional shape, which prevents local wear, cracks in the PVD film, peeling, etc. during engine operation. And become superior.
[0017]
The first surface A-B is formed over a range of a central angle of 15 ° to 20 ° (15 ° in the present embodiment) defined by the central axis O of the outer peripheral surface 3. Here, if the central angle is less than 15 °, the radial bending rigidity reduction width is not sufficient, and the surface pressure rises during engine operation. On the other hand, if the central angle exceeds 20 °, the surface pressure at the end of the joint is too low during engine operation, which is a problem with respect to the amount of lubricant consumed.
[0018]
The second surface BC is an arbitrary curved surface that contacts the first surface AB at the end opposite to the portion where the first surface AB contacts the end surface of the abutment portion 2.
[0019]
Although not shown in the drawing, a similar notch 4a is formed also from the other abutment surface facing the abutment surface shown in the drawing.
[0020]
A piston ring according to a second embodiment of the present invention will be described with reference to FIG.
[0021]
The piston ring 10 shown in FIG. 2 differs from the piston ring 1 of the first embodiment in the shape of the notch 14a. The cutout portion 14 a forms a plane A′-B ′ that gradually approaches the outer peripheral surface 13 toward the end surface of the joint portion 12. That is, the thickness in the ring radial direction at B ′ is a ₁ , but the thickness in the ring radial direction gradually decreases toward A ′ existing on the end face of the abutting portion 12. To 0.6a ₁ . The plane A′-B ′ is formed over a range of a central angle of 20 ° to 30 ° (20 ° in the present embodiment) defined by the central axis O ′ of the outer peripheral surface 13. Here, if the center angle is less than 20 °, the radial bending rigidity reduction width is not sufficient, and the surface pressure increases during engine operation. On the other hand, if the central angle exceeds 30 °, the surface pressure at the end of the joint is too low during engine operation, which is a problem with respect to the amount of lubricating oil consumed.
[0022]
Similarly to the piston ring 1 of the first embodiment, this piston ring 10 can also reduce the bending rigidity to about 1/2, and the surface pressure at the joint end is about 1 of that of a piston ring having a uniform cross-sectional shape. Therefore, it is superior to local wear, PVD coating cracks, peeling, and the like during engine operation.
[0023]
Although not shown in the drawing, a similar notch portion 14a is formed also from the other abutment surface facing the abutment surface shown in the drawing.
[0024]
The surface pressure distribution of the piston ring according to the first embodiment of the present invention and the surface pressure distribution of the piston ring of the conventional example were measured and compared using the surface pressure distribution measuring apparatus shown in FIG. In the measurement, the same axial thickness, outer peripheral surface shape, and radial thickness a ₁ were used.
[0025]
As shown in FIG. 3, a part of the cylinder 101 is cut out, a strain gauge 102 is attached to the cutout 101a (the thinnest part) of the cylinder 101, and the contact load of the piston ring 1 of the present invention or the conventional piston ring is applied. Strain was measured as surface pressure. While the heaters 104 are attached to the upper and lower sides of the piston 103 that holds the piston ring to heat the piston ring, cooling water is supplied to the outer periphery of the cylinder 101 to cool the cylinder 101, and the piston 103 to the cylinder 101 are operated during actual operation. A close temperature gradient was distributed.
[0026]
In FIG. 4, the vertical axis represents the surface pressure, and the horizontal axis represents the circumferential angle from the joint portion. As is clear from FIG. 4, in the piston ring having a uniform cross-sectional shape as in the conventional example, the surface pressure in the vicinity of the abutment end abruptly when the action of the heat load is applied even if the abutment is low in cold contact pressure. Rose. Moreover, this tendency became stronger as the temperature was increased.
[0027]
On the other hand, in the piston ring 1 of the present invention, as is apparent from FIG. 5, the surface pressure of the abutment portion is lower than the surface pressure of the piston ring of the conventional example when cold, and the surface pressure is reduced by lowering the bending rigidity. Was. When a thermal load was applied, an increase in surface pressure was observed, but no increase in surface pressure was observed where the end of the abutment was excessively protruding as in the conventional piston ring, resulting in an isosurface pressure distribution. In addition, it can be seen that even when cold, the surface pressure at the end of the joint does not become 0, and no contact failure occurs.
[0028]
In this experiment, a piston ring having a surface pressure of about 1.5 kgf / cm ^{2 at} a portion other than the vicinity of the abutment portion in the cold state was prototyped and tested. It goes without saying that it can be set to.
[0029]
The piston ring according to the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made within the scope described in the claims. For example, the first surface A-B constituting a part of the notch 4a in the first embodiment forms a substantially arc surface having the same central axis as the outer peripheral surface 3, but the thickness range described above. As long as it is, a flat surface may be used instead of the arc surface. Further, the second surface BC may not be a curved surface but may be a flat surface. However, the second surface B-C is easier to manufacture if it is a curved surface than a flat surface. Furthermore, the piston ring of the present invention can be manufactured by any of steel and cast iron, and a desired effect can be obtained.
[0030]
【The invention's effect】
According to the piston ring of the present invention, in order to suppress the high surface pressure at the abutment end, the piston ring radial thickness a ₁ in the vicinity of the abutment is reduced by about 20% to 30%, and the bending rigidity is about It is reduced to 1/2. Thereby, the surface pressure of the joint end can be reduced to about ½ of the piston ring having a uniform cross-sectional shape. Therefore, there is no omission in the entire circumference even when it is cold, and no increase in the surface pressure at the joint portion occurs even when there is a thermal load. Since there is no omission in the entire circumference even when it is cold, the desired sealing performance can be exhibited even in the initial stage of engine operation, and blow-by can be prevented. In addition, since the surface pressure of the abutment portion does not increase even under thermal load, extreme wear of the abutment portion is prevented, and at the same time, especially when a PVD coating is applied to the outer peripheral surface of the piston ring, the film cracks and peels off. Etc. can be prevented.
[Brief description of the drawings]
FIG. 1 is a plan view showing a shape in the vicinity of a joint portion of a piston ring according to a first embodiment of the present invention.
FIG. 2 is a plan view showing a shape in the vicinity of a joint portion of a piston ring according to a second embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a surface pressure distribution measuring apparatus used for measuring the surface pressure distribution of the piston ring and the surface pressure distribution of the piston ring of the conventional example according to the first embodiment of the present invention.
FIG. 4 is a broken line diagram showing a surface pressure distribution of a piston ring of a conventional example.
FIG. 5 is a broken line diagram showing a surface pressure distribution of the piston ring according to the first embodiment of the present invention.
[Explanation of symbols]
1, 10 Piston ring 2, 12 Joint portion 3, 13 Outer peripheral surface 4, 14 Inner peripheral surface 4a, 14a Notch

Claims (2)

It has a substantially circular shape, and includes an outer peripheral surface that slides relative to the cylinder, an inner peripheral surface that faces the piston, and a single abutment that divides the substantially circular shape in the radial direction, and on the inner peripheral surface side, A notch that forms a part of the inner peripheral surface is formed over a predetermined circumferential length portion starting from the end surface of the joint portion, and the radial thickness of the predetermined circumferential length portion is the predetermined circumferential length. In the piston ring that is small compared to the radial thickness of the part other than the long part,
The notch has a first surface and a second surface;
The first surface is in contact with the end surface of the joint portion and forms a substantially arc surface having the same central axis as the outer peripheral surface, and the radial thickness defined between the outer peripheral surface and the first surface is: The thickness is 0.7 to 0.8 times the radial thickness in a portion other than the predetermined peripheral length portion, and is formed over a range of a central angle of 15 ° to 20 ° defined by the central axis of the outer peripheral surface. is it, is set in a range capable of suppressing surface pressure increase of該合opening when the thermal load it is possible to prevent loss per the entire circumference of the outer circumferential surface at a normal temperature during operation is,
The piston ring , wherein the second surface is an arbitrary curved surface that contacts the first surface at an end opposite to a portion that contacts the end surface of the joint portion . It has a substantially circular shape, and includes an outer peripheral surface that slides relative to the cylinder, an inner peripheral surface that faces the piston, and a single abutment that divides the substantially circular shape in the radial direction, and on the inner peripheral surface side, A notch that forms a part of the inner peripheral surface is formed over a predetermined circumferential length portion starting from the end surface of the joint portion, and the radial thickness of the predetermined circumferential length portion is the predetermined circumferential length. In the piston ring that is small compared to the radial thickness of the part other than the long part,
The notch has a planar shape that gradually approaches the outer peripheral surface toward the end surface of the joint portion,
The radial thickness at the end face of the joint portion is 0.5 to 0.6 times the radial thickness at a portion other than the predetermined circumferential length portion,
The predetermined circumferential length portion is formed over a range of a central angle of 20 ° to 30 ° defined by the central axis of the outer peripheral surface, and can prevent the entire outer peripheral surface from hitting and falling during operation and normal temperature. A piston ring, wherein the piston ring is set in a range in which an increase in surface pressure of the joint portion during heat load can be suppressed.

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