JPH10169778A - Piston ring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the wavy deformation of a seal ring for more sealing ability by absorbing the thermal expansion of the seal ring under high load and temperature. SOLUTION: A piston ring has a resin seal ring 101 inserted in a ring groove 6 formed on the outer periphery of a piston 5 and a ring spring member 2 to thrust the seal ring 101 outward so that the seal ring 101 inserted in the ring groove 6 can contact a cylinder wall 7. Plural grooves are formed in the seal ring 101, which are extended across the peripheral direction of the seal ring 101 to partly divide the seal ring 101 only in an area where they are stored in the ring groove 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston ring fitted in a ring groove formed in a piston head to fill a gap between a piston body and a cylinder in an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, a piston of an internal combustion engine usually has a total of three compression rings for sealing gas and one oil ring for scraping off oil.
A piston ring is attached. In recent years, various improvements have been made to the piston ring from the viewpoint of improving sealing performance, reducing oil consumption, reducing friction loss, and the like.

[0003] For example, Japanese Utility Model Laid-Open Publication No. Sho 57-148036 discloses that a piston ring composed of a synthetic resin seal ring in contact with a cylinder wall surface and an expander ring for pressing the seal ring from inside to outside is used as an oil ring. It is disclosed to do.

FIG. 1 shows a piston ring composed of a seal ring 1 made of synthetic resin and an expander ring 2.
FIG. 3 is a cross-sectional view showing a state in which it is fitted into a ring groove 6 formed in a head of a piston 5 and comes into contact with a cylinder wall surface 7.
According to the seal ring 1 made of synthetic resin, a seal structure without a joint (a break in the ring) can be obtained by utilizing its elasticity.

[0005]

However, in the piston ring as shown in FIG. 1, when a high load and high temperature state is reached, as shown in FIG. 2, the seal ring 1 undergoes undulating deformation. There is a problem. FIG. 2 is based on FEM (finite element method) calculation, in which the displacement in the radial direction is shown to be magnified 10 times, and the seal ring 1 and the expander ring 2 are separated. Although shown, this is for the sake of clarity of the deformed state, and is actually in contact. The cause of such undulation is that the resin has a larger coefficient of thermal expansion than metal, so that when the temperature becomes high, the seal ring 1 expands in the ring circumferential direction. This is due to deformation in the inward direction, that is, in the direction toward the bottom of the ring groove by overcoming the urging force in the radially outward direction. Therefore, under high load and high temperature conditions, the sealing performance is impaired.

As a countermeasure, it is possible to suppress the thermal expansion of the seal ring by mixing fibers having a small coefficient of thermal expansion into a resin to form a composite material. It will be difficult to assemble it. That is, such a measure does not make it possible to reduce the thermal expansion and increase the elastic elongation.

In view of such circumstances, an object of the present invention is to provide a seal ring made of resin inserted into a ring groove formed on an outer peripheral surface of a piston, and a seal such that the seal ring inserted into the ring groove comes into contact with a cylinder wall surface. A ring-shaped spring member that presses the ring outward, and by absorbing the thermal expansion of the seal ring under high load and high temperature conditions, reduces the undulating deformation of the seal ring, thereby improving the sealing performance. The goal is to achieve further improvements.

[0008]

Means for Solving the Problems A piston ring according to the first invention of the present invention devised to achieve the above object is a resin seal ring inserted into a ring groove formed on the outer peripheral surface of the piston. And a ring-shaped spring member that presses the seal ring outward so that the seal ring inserted into the ring groove is in contact with the cylinder wall surface.
A plurality of grooves extending in a direction intersecting the circumferential direction and partially dividing the seal ring are formed only in a range accommodated in the ring groove.

In the piston ring configured as described above, the plurality of grooves formed in the seal ring can absorb the expansion of the seal ring in the circumferential direction of the ring, thereby reducing the undulation of the piston ring. be able to. Further, since the plurality of grooves are formed only in the region inside the ring groove, the opening of the groove of the seal ring is closed by the wall of the ring groove, and as a result, gas blows through the groove. Cannot occur.

In the piston ring according to the second aspect of the present invention, a resin seal ring inserted into a ring groove formed on an outer peripheral surface of the piston and the seal ring inserted into the ring groove are provided on a cylinder wall surface. A ring-shaped spring member that presses the seal ring outward so as to be in contact with the seal ring, wherein the thickness of the seal ring extends in a direction intersecting the circumferential direction of the seal ring. An elastic ring having a plurality of grooves partially dividing the seal ring in a direction, and having an outer peripheral surface that is in close contact with an inner peripheral surface of the seal ring between the ring-shaped spring member and the seal ring; Characterized by intervening.

In the piston ring configured as described above, the deformation that occurs as a result of forming the groove extending in the vertical direction (the cylindrical axis direction) occurs in the vertical direction, and the undulation of the seal ring can be prevented. Further, since an elastic ring that closes the opening of the formed groove is in close contact with the back surface of the seal ring, a situation in which gas leaks through the formed groove cannot occur.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

A piston ring according to the present invention includes a seal ring made of a synthetic resin and a ring-shaped spring member (for example, a coil-shaped or plate-shaped expander ring) for pressing the seal ring outward. However, the structure of the seal ring is characteristic. As shown in FIG. 3, the basic structure of such a seal ring is a ring made of a synthetic resin (for example, a polyimide resin). Unlike a metal ring, there is no need to have an abutment (a break in the ring). It is the same as the conventional one in that the property is improved, but the detailed structure is devised.

FIG. 4 is an enlarged perspective view showing a part of the seal ring 101 according to the first embodiment of the present invention, that is, a part corresponding to the portion A in FIG. As shown in this figure, a plurality of slits or grooves are formed in the seal ring 101 from the inside in a direction crossing the circumferential direction, that is, in a radial direction. At the time of thermal expansion of the seal ring, in the case of the seal ring 1 having no slit, as described above, the seal ring 101 having the slit is deformed in a swell shape as shown in FIG.
In the case of (1), it is deformed as shown in FIG. That is, since the slit acts as a relief field at the time of thermal expansion, the gap between the cylinder wall surface 7 and the seal ring 101 is reduced, and the sealing performance on their sliding surfaces is improved. In addition, according to the result of calculation by FEM (finite element method), it has been found that the contact portion between the cylinder and the seal ring occurs at four places when viewed from the top of the cylinder. Therefore, five or more such slits are provided. Is preferred.

FIG. 6 is a sectional view showing a state in which the piston ring including the seal ring 101 and the expander ring 2 of FIG. 4 is inserted into the ring groove 6 of the piston 5 together with the cylinder wall surface 7. 4) shows the case where the seal ring is cut along the cutting line XX in FIG. 4, and FIG. 4 (B) shows the case where the seal ring is cut along the cutting line YY in FIG. I have. As shown in this figure,
The seal ring 101 inserted into the ring groove 6 is pressed outward by the expander ring 5 disposed inside the ring groove 6, that is, in the direction of the cylinder wall surface 7, so that the seal ring 101 is in close contact with the cylinder wall surface 7.

At this time, as shown in FIG. 1B, the slit of the seal ring 101 is designed to have a size that is completely accommodated in the ring groove 6. That is, the slit is not exposed in the gap between the piston 5 and the cylinder wall 7, in other words, the slit is formed in the ring groove 6.
It is made to be closed by the wall of. As a result, a situation (blow-by) in which gas blows through the slit cannot occur. In this way, it is possible to prevent the thermal expansion of the seal ring in the circumferential direction by the slit while preventing blow-by. Thus, the sealing performance under high load and high temperature conditions is guaranteed.

FIG. 7 is an enlarged perspective view showing a part of the seal ring 201 according to the second embodiment of the present invention, that is, a part corresponding to the portion A in FIG. As shown in this figure, the seal ring 201 has a plurality of slits or grooves extending in a direction intersecting the circumferential direction thereof and partially dividing the seal ring in a thickness direction of the seal ring. And on the lower surface.

That is, the seal ring 101 according to the first embodiment is a seal ring provided with slits in the radial direction, whereas the seal ring 2 according to the second embodiment is
Reference numeral 01 denotes a seal ring provided with a slit in a cylindrical axis direction (stroke direction). Therefore, the seal ring 20
In 1, thermal expansion occurs in the cylinder axis direction. That is, since the direction in which the thermal expansion is released is changed to the cylindrical axis direction, the above-described circumferential undulation is prevented, and the sealing property between the cylinder wall surface and the seal ring is ensured. The reason why the slits formed on the upper surface are deeper than the slits formed on the lower surface is to facilitate scraping off unnecessary oil downward, but may have the same shape. .

When a slit is provided in the cylindrical axial direction as shown in FIG. 7, the seal between the upper surface of the seal ring and the upper wall surface of the ring groove and the lower surface of the seal ring and the lower wall surface of the ring groove are provided. The sealability between them is impaired. Therefore, in the second embodiment, as described below, inner ring is employed.

FIG. 8 is a sectional view showing a state in which the piston ring including the seal ring 201, the expander ring 2, and the inner ring 3 of FIG. 7 is inserted into the ring groove 6 of the piston 5, together with the cylinder wall surface 7. 7A shows a case where the seal ring is cut along a cutting line XX of FIG. 7, and FIG. 7B shows a case where the seal ring is cut along a cutting line YY of FIG. Shows the case. As in the first embodiment, the seal ring 2 inserted into the ring groove 6
01 is pressed outward by the expander ring 5 arranged inside, that is, in the direction of the cylinder wall surface 7, but unlike the first embodiment, between the seal ring 201 and the expander ring 2, An inner ring 3 as an elastic ring (for example, made of PTFE (polytetrafluoroethylene)) is interposed.

The inner peripheral surface of the seal ring 201 and the outer peripheral surface of the inner ring 3 are in close contact with each other. Also, the inner ring 3 is in close contact with the upper wall surface and the lower wall surface of the ring groove 6. Therefore, as easily understood from FIGS. 8A and 8B, the gas flowing into the upper surface side slit is stopped by the inner ring 3 and does not leak downward through the lower surface side slit. As described above, in the second embodiment, the hard seal ring 201 having excellent wear resistance and heat resistance ensures the sealing performance on the sliding surface between the piston and the cylinder, while the soft inner ring 3 is The sealing property in the ring groove, that is, in the back surface of the seal ring is ensured. Although the slit in FIG. 7 was U-shaped,
A V-shaped slit as shown in FIG. 9 may be employed.

[0022]

As described above, according to the first aspect of the present invention, a seal ring having a plurality of grooves (slits) in a radial direction is employed, so that thermal expansion of the seal ring in the ring circumferential direction is prevented. As a result, the undulation of the piston ring can be reduced, and since the plurality of grooves (slits) are formed only in the area within the ring groove, blow-by through the slits is prevented. You. Therefore, the sealing performance under high load and high temperature is guaranteed.

According to the second aspect of the present invention, since a seal ring having a plurality of grooves (slits) in the cylinder axis direction is employed, thermal expansion can be released in the cylinder axis direction, and the piston and the cylinder can be separated. The sealing performance of the sliding surface is ensured, and the elasticity is interposed between the ring-shaped spring member and the sealing ring that presses the sealing ring outward, so that the sealing performance in the ring groove is also ensured, Sealability at high load and high temperature is guaranteed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a conventional piston ring.

FIG. 2 is a view showing a state in which a conventional piston ring is deformed by thermal expansion.

FIG. 3 is a perspective view showing an outline (basic structure) of a seal ring.

FIG. 4 is an enlarged perspective view showing a part of the seal ring according to the first embodiment of the present invention.

5A and 5B are diagrams showing deformation of the seal ring during thermal expansion in the case where there is no slit and in the case where there is a slit.

6 is a cross-sectional view showing the piston ring according to the first embodiment of the present invention together with a ring groove and a cylinder wall surface, wherein (A) a seal ring is cut along a cutting line XX in FIG. 4; 5 (B) is a view showing a case where the seal ring is cut along a cutting line YY in FIG. 4.

FIG. 7 is an enlarged perspective view showing a part of a seal ring according to a second embodiment of the present invention.

8 is a cross-sectional view showing a piston ring according to a second embodiment of the present invention together with a ring groove and a cylinder wall surface, wherein (A) a seal ring is cut along a cutting line XX in FIG. 7; 8 (B) is a view showing a case where the seal ring is cut along a cutting line YY in FIG. 7.

FIG. 9 is an enlarged perspective view showing a part of a modification of the seal ring according to the second embodiment of the present invention.

[Explanation of symbols]

 1, 101, 201 ... seal ring 2 ... expander ring 3 ... inner ring 5 ... piston 6 ... ring groove 7 ... cylinder wall surface

Claims (2)

[Claims] 1. A resin seal ring inserted into a ring groove formed on an outer peripheral surface of a piston, and the seal ring pressed outward so that the seal ring inserted into the ring groove contacts a cylinder wall surface. A ring-shaped spring member, and the seal ring, wherein the seal ring extends partially in a direction intersecting the circumferential direction thereof and partially covers the seal ring only in a range accommodated in the ring groove. A piston ring having a plurality of divided grooves. 2. A resin seal ring inserted into a ring groove formed on an outer peripheral surface of a piston, and the seal ring pressed outward so that the seal ring inserted into the ring groove contacts a cylinder wall surface. A ring-shaped spring member, which extends in a direction intersecting the circumferential direction of the seal ring and partially divides the seal ring in a thickness direction of the seal ring. A piston ring, wherein a plurality of grooves are formed, and an elastic ring having an outer peripheral surface in close contact with an inner peripheral surface of the seal ring is interposed between the ring-shaped spring member and the seal ring. .