JP2000120866A - Piston ring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston ring which causes neither non-contact parts in all circumferences at room temperature, nor increase of surface pressure at an abutment portion under thermal load. SOLUTION: A substantially circular piston ring has an outer peripheral surface 3 slid relative to a cylinder, an inner peripheral surface 4 opposed to a piston, and an abutment portion 2 which splits the substantially circular form in a radial direction. A cutout portion 4a serving a part of the inner peripheral surface 4 is formed on the surface 4, within a specified range starting an end face of the abutment portion 2. Radial thickness in the specified circumferential length range is smaller than the radial thickness a1 at other portions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston ring,
In particular, it relates to a low point piston ring.

[0002]

2. Description of the Related Art A piston ring has a surface pressure distribution.
A high point piston ring whose surface pressure near the abutment is higher than other portions and a low point piston ring whose surface pressure near the abutment is lower than other portions are roughly classified. Although both are used properly depending on the use environment and application, a low-point piston ring tends to be used in a high-output diesel engine or the like in which abrasion 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 changes depending on the circumferential shape at free time. Rings were being manufactured.

[0003]

However, during operation of the engine, the piston ring is thermally deformed as described below, so that the contact state between the piston ring and the cylinder changes as compared with that at normal temperature. It changes greatly. Due to this change, the surface pressure distribution of the piston ring at the time of engine operation has a tendency that the surface pressure at the abutment end rises, and even if it is a low point piston ring, it tends to shift to the same surface pressure distribution as the high point piston ring. Have.

First, a deformation occurs in which the piston ring diameter is apparently larger than the cylinder diameter due to the difference in thermal expansion due to the temperature difference between the cylinder and the piston ring. Also, a temperature difference between the cylinder and the piston causes a temperature difference between the outer and inner circumferences of the piston ring (60 ° C. to 70 ° C. at full load). Occurs. 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 end of the abutment increases, and so-called hitting, which is not in contact with the cylinder bore, is likely to occur at a portion beside the end of the abutment.

Further, due to the heating by blow-by of the blow-by gas, the temperature in the vicinity of the junction rises from that of other parts (about 30 ° C.).
To 50 ° C.), the vicinity of the joint expands more thermally than the other parts, and deformation occurs in which the curvature becomes smaller. By this action, the surface pressure distribution is such that the surface pressure at the end of the abutment becomes extremely large. Also, if this action is extremely strong, hitting occurs at a portion beside the joint end.

In addition, since the circumferential shape changes greatly due to the expansion of the entire piston ring due to the above-mentioned thermal load and the thermal stress generated by the temperature difference between the inner and outer circumferences of the piston ring, the state of contact with the cylinder bore changes. In particular, at the joint, the surface pressure increases as the temperature increases. Therefore, when the engine is operated under extremely strict lubrication conditions, the abutment particularly shows an extremely abraded state, and sometimes the PVD coating formed on the outer peripheral surface of the piston ring may be damaged or cracked. generate.

On the other hand, if the abutment is designed to have an extremely low surface pressure at the time of cold in consideration of the surface pressure at the time of heat load, the abutment is likely to be hit or miss in production (the defect rate is high). Therefore, it is not suitable for mass production. Also, there is a piston ring that is intentionally made non-contact at the abutment portion so as to have an equal pressure surface distribution at the time of high load operation, and is brought into contact when a heat load is applied,
Oil rising at the time of starting and idling becomes a problem,
Manufacturing control is also difficult, which is also unsuitable for mass production. Furthermore, in these piston rings, a so-called blow-by occurs in which the combustion gas escapes to the crankcase without being sealed by the pressure ring due to the contact of the abutting portion, which causes problems such as deterioration of lubricating oil and pollution due to discharge of raw gas. Had occurred.

Therefore, in the case of a conventional low-point piston ring whose peripheral shape is merely adjusted, if it is designed in consideration of occurrence of hitting and falling, it is not sufficient for measures against abrasion, and the surface pressure at the end of the abutment increases. When trying to suppress, there was a hit. In particular, it has been very difficult to design the vicinity of the joint portion of the piston ring, which causes significant wear due to engine operation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a piston ring which does not come off at all times even at room temperature and does not cause an increase in surface pressure at the abutment even under heat load.

[0010]

In order to achieve the above-mentioned object, the present invention has a substantially circular shape, and has an outer peripheral surface that slides on a cylinder, an inner peripheral surface facing a piston, and the substantially circular shape. And a single abutment portion radially dividing the inner peripheral surface, a part of the inner peripheral surface on the inner peripheral surface side, over a predetermined peripheral portion starting from the end surface of the abutment portion A piston ring, wherein a radial thickness at the predetermined circumferential portion is smaller than a radial thickness at a portion other than the predetermined circumferential portion. ing.

The notch has a first surface and a second surface, and the first surface is in contact with the end face of the abutment portion and has a substantially circular arc surface having the same central axis as the plane or the outer peripheral surface. And the radial thickness defined between the outer peripheral surface and the first surface is 0.7 to 0.8 times the radial thickness at a portion other than the predetermined circumferential portion. A central angle defined by a central axis of the outer peripheral surface is formed in a range of 15 ° to 20 ° (a preferable angle is about 15 °), and the second surface is formed by combining the first surface with the abutment. It is preferable to form an arbitrary curved surface in contact with the first surface at an end opposite to the part in contact with the end surface.

The notch has a flat shape gradually approaching the outer peripheral surface toward the end face of the abutting portion, and the radial thickness at the end face of the abutting portion is changed in the radial direction at a portion other than the predetermined circumferential portion. 0.5 to 0.6 times the thickness of the outer peripheral surface, and the predetermined peripheral portion has a central angle 20 defined by the central axis of the outer peripheral surface.
It may be formed over a range of degrees to 30 degrees (a preferred angle is about 20 degrees).

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A piston ring according to a first embodiment of the present invention will be described with reference to FIG.

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 on a cylinder (not shown), and an inner peripheral surface 4 that faces the piston (not shown).
And one abutment 2 for dividing the substantially circular shape in the radial direction.

The distance (thickness in the radial direction of the piston ring) between the outer peripheral surface 3 and the inner peripheral surface 4 is a ₁ , and the inner peripheral surface 4 has a predetermined circumference starting from the end surface of the abutment 2. Notch 4a, ABC which forms a part of inner peripheral surface 4 over the long part
Is formed, and the thickness in the radial direction at the predetermined circumferential portion is formed smaller than the radial thickness at portions other than the predetermined circumferential portion.

Specifically, the notch 4a is formed on the first surface AB.
And a second surface BC. The first surface AB is a joint 2
And has a substantially arc-shaped surface having the same central axis as the outer peripheral surface 3, and a radial thickness defined between the outer peripheral surface 3 and the first surface is equal to that of a portion other than the predetermined peripheral portion. It is 0.7 to 0.8 times the thickness a _{1 in} the radial direction. Here, if the thickness is less than 0.7 times, the surface pressure at the end of the joint becomes too low during operation of the engine, which is a problem with respect to the consumption of lubricating oil.
Further, the gas sealing property of the lower surface of the ring is reduced. On the other hand, if the thickness exceeds 0.8 times, the bending rigidity is not sufficiently reduced,
Surface pressure rises during engine operation. The thickness of the portion where the first surface AB is formed is set to be 2 times larger than the thickness of the entire piston ring 1.
By reducing the amount by 0% to 30%, the second moment of area can be reduced to about 、, and the bending rigidity in the radial direction is also reduced to about ２. By reducing the bending stiffness in the radial direction to about ２, the contact pressure at the end of the abutment becomes about の of that of a piston ring with a uniform cross-sectional shape. Be superior.

The first surface AB is formed by a central axis O of the outer peripheral surface 3.
Are formed over a range of a central angle of 15 ° to 20 ° (15 ° in the present embodiment). Here, if the central angle is less than 15 °, the width of reduction in bending rigidity in the radial direction is not sufficient, and a rise in surface pressure occurs during engine operation. On the other hand, if the central angle exceeds 20 °, the surface pressure at the end of the joint becomes too low during operation of the engine, which poses a problem with respect to lubricating oil consumption.

The second surface BC is formed by connecting the first surface AB with the joint 2
Is an arbitrary curved surface that is in contact with the first surface AB at the end opposite to the portion that is in contact with the end surface.

Although not shown in the drawing, a similar notch 4a is formed from the other abutting surface facing the abutting surface shown in the drawing.

A piston ring according to a second embodiment of the present invention will be described with reference to FIG.

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 notch 14 a forms a plane A′-B ′ that gradually approaches the outer peripheral surface 13 toward the end face of the abutment 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 abutment portion 12, and the thickness at A ′ is 0.5 or the 0.6a _1. Also, the plane A′-B ′ is
Is formed over a range of a central angle 20 ° to 30 ° (20 ° in the present embodiment) defined by the central axis O ′.
Here, if the central angle is less than 20 °, the reduction in bending rigidity in the radial direction is not sufficient, and a rise in surface pressure occurs during engine operation. On the other hand, if the central angle exceeds 30 °, the surface pressure at the end of the joint becomes too low during operation of the engine, causing a problem with respect to the consumption of lubricating oil.

This piston ring 10 also has a bending rigidity of about 1/2, similar to the piston ring 1 of the first embodiment.
And the surface pressure at the end of the abutment is about half that of a piston ring with a uniform cross-sectional shape, so it is superior to local wear, cracks and peeling of the PVD film during engine operation. .

Although not shown in the drawing, a similar notch 14a is formed from the other abutting surface facing the abutting surface shown in the drawing.

The surface pressure distribution of the piston ring according to the first embodiment of the present invention and the surface pressure distribution of the conventional piston ring were measured by a surface pressure distribution measuring device shown in FIG. 3 and compared. Incidentally, for the measurement, the axial thickness and the outer peripheral surface shape, the radial thickness a ₁ using the same.

As shown in FIG. 3, a part of the cylinder 101 is cut out, and a strain gauge 102 is attached to a notch 101a (the thinnest part) of the cylinder 101, and the piston ring 1 of the present invention or the piston ring of the conventional example is formed. The strain due to the contact load was measured as the surface pressure. Heaters 104 are attached above and below the piston 103 holding the piston ring to heat the piston ring, while cooling water is supplied to the outer periphery of the cylinder 101 to cool the cylinder 101. A close temperature gradient was distributed.

FIG. 4 shows the surface pressure on the vertical axis and the circumferential angle from the abutment on the horizontal axis. As is apparent from FIG. 4, in the case of a piston ring having a uniform cross-sectional shape as in the conventional example, the surface pressure near the end of the abrupt portion when the heat load is applied increases rapidly even if the abutment portion has a low surface pressure during cold. Rose. This tendency was further enhanced by increasing the temperature.

On the other hand, in the piston ring 1 according to the present invention, as is apparent from FIG. 5, the surface pressure at the joint at the time of cold is lower than the surface pressure of the conventional piston ring, and the surface pressure due to the decrease in bending stiffness. Reduction was realized. When a thermal load was applied, an increase in the surface pressure was observed, but no increase in the surface pressure was observed as in the case of a conventional piston ring in which the end of the abutment was extremely protruded, and the distribution became iso-surface pressure. Further, even in the cold state, the surface pressure at the end of the abutment does not become 0, and it can be seen that no hitting occurs.

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 at the time of cold was experimentally manufactured, and the experiment was conducted. It goes without saying that various settings can be made according to the requirements.

The piston ring according to the present invention is not limited to the embodiment described above, and various modifications and improvements can be made within the scope described in the claims. For example, the first surface A- which constitutes a part of the notch 4a in the first embodiment.
B has a substantially arc-shaped surface having the same central axis as the outer peripheral surface 3, but may be a flat surface instead of the arc-shaped surface as long as the thickness is within the above-described thickness range. Further, the second surface BC may not be a curved surface but may be a flat surface. However, it is easier to manufacture the second surface BC as a curved surface than a flat surface. Further, the piston ring of the present invention is made of steel, cast iron,
Any of them can be manufactured, and a desired effect can be obtained.

[0030]

According to the piston ring of the present invention, in order to suppress the high surface pressure abutment end of the piston rings the radial vicinity abutment portion thickness dimension a ₁ is reduced approximately 20% to 30% And the bending stiffness is reduced to about 1/2. As a result, the surface pressure at the end of the abutment can be reduced to about half that of a piston ring having a uniform cross-sectional shape. Therefore, even in a cold state, there is no dropout in the entire circumference, and no increase in the surface pressure of the joint portion occurs even under a thermal load. Since there is no slippage around the entire circumference even in the cold state, a desired sealing property can be exhibited even in the early stage of engine operation, and blow-by can be prevented. or,
At the time of thermal load, the surface pressure of the joint does not increase, so that extreme wear of the joint is prevented, and at the same time, when PVD coating is applied to the outer peripheral surface of the piston ring, cracks, peeling, etc. of the film may occur. You can prevent obstacles.

[Brief description of the drawings]

FIG. 1 is a plan view showing a shape near an abutment portion of a piston ring according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a shape near an abutment 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 device used for measuring a surface pressure distribution of a piston ring according to the first embodiment of the present invention and a surface pressure distribution of a conventional piston ring.

FIG. 4 is a line diagram showing a surface pressure distribution of a conventional piston ring.

FIG. 5 is a 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 abutment 3, 13, outer peripheral surface 4, 14 inner peripheral surface 4a, 14a notch

Claims (3)

[Claims] 1. A piston ring having a substantially circular shape and having an outer peripheral surface sliding with respect to a cylinder, an inner peripheral surface facing a piston, and one abutment for radially dividing the substantially circular shape. In addition, on the inner peripheral surface side, a cutout portion forming a part of the inner peripheral surface is formed over a predetermined peripheral portion starting from an end surface of the abutment portion, and A piston ring, wherein a thickness in a radial direction is smaller than a thickness in a radial direction of a portion other than the predetermined peripheral portion. 2. The notch has a first surface and a second surface, and the first surface is in contact with the end face of the abutment portion, and has a substantially circular arc surface having the same central axis as the plane or the outer peripheral surface. None, the outer peripheral surface and the first
The radial thickness defined between the outer peripheral surface and the outer peripheral surface is 0.7 to 0.8 times the radial thickness at a portion other than the predetermined peripheral portion. The second surface is an arbitrary curved surface that is 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 abutment portion. The piston ring according to claim 1, wherein 3. The notch has a flat shape gradually approaching the outer peripheral surface toward the end face of the abutment, and the radial thickness at the end face of the abutment is radial in a portion other than the predetermined circumferential portion. 0.5 to 0.
The piston ring according to claim 1, wherein the predetermined circumferential length is formed over a range of a central angle of 20 ° to 30 ° defined by a central axis of the outer peripheral surface.