JPH04360723A - Manufacture of piston ring - Google Patents

Abstract

PURPOSE:To form a lubricating oil film even in condition of a cylinder not yet warmed and prevent breakage of a piston ring and generation of scuffing on the cylinder wall by forming a non-contact part or a low contact pressure part in the vicinity of the gap of the ring. CONSTITUTION:A piston ring 1 formed into a nearly circular form of prescribed outer diameter on the outer circumferential face and finished into the product condition is mounted in a cylindrical gauge 4 of bore D nearly same as a ring nominal diameter. The gauge 4 is formed out of an insulating body such as resin or ceramics and actually into a rigid body. Further, high frequency coils 5 are fitted to the ring 1 in the range from the center of the gap 2 to 5 deg.-20 deg., and after high frequency heating in a short time the ring is radiatedly cooled. The ring is plastically deformed by thermal stress generated in the vicinity of the gap 2, cooled as it is, the vicinity of the gap 2 is bent inside by compressive residual stress, what is called roll-over is generated, and it is prevented to protrude the gap 2 into the port of a cylinder or strongly contact the gap with the cylinder wall, even if the ring is thermally expanded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for manufacturing piston rings used in internal combustion engines, etc., and in particular to piston rings that can reduce the contact pressure with the cylinder wall near the ring abutment. Relating to a manufacturing method.

0002

[Prior Art] In a two-stroke engine in which a cylinder is provided with ports for intake, scavenging, and exhaust, when a piston ring passes through these ports, the tip of the ring abutment protrudes into the port, and the port end The ring may break due to strong interference. As a countermeasure, a method has been adopted in which only the vicinity of the ring abutment is kept in a non-contact state with the cylinder wall.

[0003] Also, with regard to four-stroke engines, as output increases, lubrication problems associated with increases in combustion pressure and temperature in the ring grooves have become more prominent. In particular, with regard to piston rings, scuffing between the piston rings and the cylinder wall has become a problem due to increased temperature and increased back pressure. Because blow-by gas accompanied by combustion gas passes through the ring joint,
Scuffing is particularly likely to occur in this area because the temperature tends to increase, the oil film ruptures due to blow-by gas blowing down, and since the piston ring abutment is a free end, locally high surface pressure tends to occur.

[0004] As a means to solve this problem, a ring is used in which the contact surface pressure near the abutment of the piston ring is lower than that in other parts, and the contact with the cylinder wall near the abutment is weakened or prevented. things are being done.

As shown in FIG. 3, a conventional piston ring manufacturing method is used to reduce the surface pressure against the cylinder wall in the vicinity of the piston ring abutment compared to other parts, or to make it non-contact. By applying pressure in the direction of the axis 3 passing through the abutment 2, it is slightly deformed into an oval shape as shown by the broken line 1', and when this is installed in the ring groove of the piston and fitted into the cylinder, A method is known in which the surface pressure near the abutment is reduced or there is no contact.

This method has disadvantages in that the hard coating forming the surface of the piston ring is easily damaged and it is difficult to control the amount of inward protrusion of the abutment. In addition, the entire piston ring deforms into a slightly oval shape, resulting in the same condition as an undersized ring, and if the cylinder is not warm enough when the piston temperature rises, the lubricating oil film will not be formed sufficiently. As the ring thermally expands, the abutment comes into strong contact with the cylinder wall.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the conventional manufacturing method in which the surface pressure with the cylinder wall near the abutment end of the piston ring is reduced or made non-contact. When the cylinder is hot, a sufficient lubricating oil film is formed even when the cylinder is not sufficiently warm, and even when the ring is thermally expanded, the area near the abutment may protrude into the intake or scavenging air or exhaust hole, or it may hit the cylinder wall strongly, causing scuffing. An object of the present invention is to provide a manufacturing method that can manufacture piston rings without causing any damage.

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the method for manufacturing a piston ring according to the present invention provides a piston ring whose outer circumferential surface has an approximately perfect circular shape with a predetermined outer diameter and is finished in a product state. , by charging the ring into a rigid cylindrical gauge with an inner diameter approximately equal to the ring nominal diameter, and heating and cooling the inner periphery in a predetermined range near the ring abutment in a short period of time, the area near the ring abutment end is heated and cooled. It is characterized by being able to be in a non-contact state or a low contact pressure state with the cylinder wall.

[0009]

[Operation] As described above, a piston ring finished in a product state with an approximately perfect circular shape is inserted into a cylindrical gauge whose inner diameter is approximately equal in rigidity to the nominal diameter of the piston ring, and the inner circumferential local area near the abutment is inserted. By heating at high temperature in a short time,
A thermal stress exceeding the compressive stress limit is generated in the heated local area, resulting in a plastic deformation state. Then, when the ring is cooled from this state, the vicinity of the ring abutment part is curved inward due to the action of compressive residual stress, and is in a state of non-contact or low contact pressure with the inner surface of the cylindrical gauge.

In this case, by limiting the local heating and cooling range to the area near the abutment, a sufficient lubricating oil film is formed even when the cylinder is not sufficiently warm when the piston temperature rises.
Even when the ring thermally expands, the vicinity of the abutment portion is prevented from protruding into the port or from strongly hitting the cylinder wall and causing scuffing.

It is appropriate that the local heating and cooling positions be within a range of 5° to 20° on both sides from the center of the ring abutment.

[0012] As a means of heating a local area to a high temperature in a short time, it is preferable to maintain the cylindrical gauge and the outer periphery of the ring in an insulated state and heat the area using a high frequency heating method.

[0013]

EXAMPLES Examples of the manufacturing method of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing the piston ring manufacturing method of the present invention. The piston ring 1 has a generally perfect circular shape with a predetermined outer diameter slightly larger than the nominal diameter, and after being finished into a product state, the piston ring 1 is placed in a circular gauge 4 having an internal diameter D approximately equal to the nominal diameter of the ring 1. will be installed on the The gauge 4 is formed of an insulator such as resin or ceramic as a substantially rigid body.

5° to 20° from the center of the abutment 2 of the ring 1
A high-frequency coil 5 is attached to the inner circumferential surface of the ring within a range of 50°, and the ring is restrained from outward deformation by the highly rigid gauge 4. In this state, both sides of the abutment are heated to high temperatures, generating thermal stress exceeding the compressive stress limit and causing plastic deformation. When it is cooled in that state, it curves inward due to the action of compressive residual stress, as shown in FIG. 2, and a so-called sagging occurs only in the vicinity of the abutment.

[0015] As a result of experiments with various heating positions by the high-frequency coil, it was found that when heating was performed at a position 5° or less from the abutment, there was almost no gap from the inner surface of the gauge; It was found that the gap would be too large at this position, so the local high temperature heating position was set at 5° from the center of the abutment.
It is judged that a range of ~20° is appropriate.

In addition to the above-mentioned high-frequency heating, an oxygen-acetylene combustion gas torch can also be used as the rapid high-temperature heating means, and as with high-frequency heating, the hardness of the outer surface treatment film decreases and Although adhesion deterioration and oxidation prevention can be achieved, high-frequency heating or laser heating is more appropriate in that the heat-affected zone is small.

As a specific example, the nominal diameter is 120 mm,
Using a cast iron piston ring (outer circumference chrome plated) with cross-sectional dimensions of 3 mm x 5 mm, after attaching it to a perfect circular gauge with an inner diameter of 120 mm, a high frequency coil was set at a position 15 degrees from the center of the abutment of the ring, and the voltage was 12.5 KV and the frequency was 200 KHz.
Heating was performed by applying a high frequency voltage of 0.5 seconds. The ring, which was in contact with the inner surface of the gauge with uniform pressure over its entire circumference before heating, was heated under the above conditions and after cooling, the gap between the abutment and the inner surface of the gauge was measured, and the gap between the ring and the inner surface of the gauge at the abutment was between 0.015 mm and 0.01 mm. 040 mm, with an average of 0.026 mm. Moreover, there was no change in the hardness of the ring outer chrome plating before and after treatment.

[0018]

As described above, according to the piston ring manufacturing method of the present invention, a non-contact part or a low contact pressure part with the cylinder wall is formed near the ring abutment, so that when the piston temperature rises, the cylinder is sufficiently heated. A sufficient lubricating oil film is formed even when the piston ring is not in contact with the piston, and even when the ring is thermally expanded, the abutment will rush into the cylinder port and break the piston ring, or it will come into strong contact with the cylinder wall to prevent scuffing. be able to.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram illustrating the manufacturing method of the present invention.

FIG. 2 is an explanatory diagram illustrating its effect.

FIG. 3 is an explanatory diagram illustrating a conventional manufacturing method for reducing the surface pressure of the abutment part of a piston ring or making it non-contact.

[Explanation of symbols]

1 Piston ring 2 Entrance 3 Axis line ４　Perfect circle gauge 5 High frequency coil

Claims (3)

[Claims] Claim 1: A piston ring whose outer circumferential surface has a generally perfect circular shape with a predetermined outer diameter and which has been finished as a product is placed in a rigid cylindrical gauge whose inner diameter is approximately equal to the nominal diameter of the ring. Manufacture of a piston ring that enables the vicinity of the ring abutment end to be in a non-contact state or a low contact pressure state with the cylinder wall by heating and cooling a predetermined area of the inner periphery near the abutment end in a short period of time at high temperature. Method. 2. The method for manufacturing a piston ring according to claim 1, wherein the local heating and cooling position is within a range of 5° to 20° on both sides from the center of the ring abutment. 3. The method of manufacturing a piston ring according to claim 1, wherein the local heating is performed by high-frequency heating while maintaining the cylindrical gauge and the outer periphery of the ring in an insulated state.