JPS594984A - Production of piston ring - Google Patents

Abstract

PURPOSE:To obtain a piston ring having an abrasion resistant layer with good productivity by delivering separately a base material for the piston ring and the 2nd wire rod dissimilar from said material, supplying both in the space between a pair of rotary discs, and welding the same then subjecting the welded material to a curling treatment. CONSTITUTION:A base material 11 for a piston ring is fed to a rotary disc electrode 31, and the 2nd wire rod 12 forming an outside circumference is fed to a rotary disc electrode 32 and both materials are press-welded between both electrodes 31 and 32. At the same instant, electricity is conducted to both electrodes 31, 32 to melt and weld the joined parts between the material 11 and the rod 12. The welded material is curved to roundness by means of the 5-point rolls formed of 3-point rolls 61, 62, 63 for forming the curled part and additive rolls 64, 65. The curled piston ring is cut at every one turn, and is subjected to a heat treatment. The piston ring wherein the rod 12 is securely bound to the material 1 is obtd. by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a piston ring for an internal combustion engine, particularly a piston ring whose outer peripheral surface is provided with a wear-resistant layer.

A piston ring is required to have special wear resistance on the outer peripheral surface that forms the sliding surface with the cylinder litchi, and normally a wear-resistant layer 12 is provided on the piston ring base material 11 as shown in FIG. It will be done. This wear-resistant layer includes surface coatings formed by thermal spraying of chrome plating, molypide, iron-based alloys, ceramics, etc., and hardening heat treatments such as soft nitriding, ion nitriding, surface remelting, and surface layer fusion alloying. This is usually done. Among these, surface-coated ones do not have sufficient bonding properties with the M' base material, and peeling and chipping of the coating layer is likely to occur, and those that undergo hardening heat treatment require a long processing time or a short processing time such as surface melting means. However, the surface roughness is significant and requires post-processing time, resulting in low productivity.

On the other hand, there are piston rings manufactured by filling different materials, such as ferrox insert piston rings, and piston rings filled with soft metals such as copper or lead. In these piston rings filled with dissimilar materials, grooves are formed in the piston ring base material in advance, and the grooves are filled with powder or a paste made by kneading the powder with a binding liquid, and the piston ring itself is fired, or it is formed into a sheet. Alternatively, it is manufactured by press-fitting or swaging a ribbon-shaped wire into the groove of a piston ring.

However, in general, piston rings that are made of different materials are limited to soft materials that are easily plastically deformed or materials that require low firing temperatures, and the purpose of these piston rings is to improve conformability and lubricate. It is not a matter of selecting a wear-resistant material for the dissimilar material itself to be embedded.

Therefore, even if an attempt is made to insert a wire made of a hard material such as martensitic high chromium stainless steel, the trenched wire will not be press-fitted or swaged into the groove of the piston ring base material because it is difficult to be plastically deformed. It cannot be fixed by other means.

The present invention is a method for manufacturing a piston ring in which a different member made of such a hard material is joined to a piston ring, and an object of the present invention is to provide a method for manufacturing a piston ring that is not only highly productive but also functions well as a piston ring. shall be.

First, the gist of the present invention is a method of manufacturing a piston ring that is manufactured according to the following seven constituent elements as described in the claims.

(1) Prepare a piston ring base material made of a wire material and a thin second wire material that forms the outer peripheral surface of the piston ring.

(2) (First step) The piston ring base material is sent out at a speed ^ by roll feeding, and the second wire is sent out separately from the piston ring base material.

(3) (Second step) Supply the piston ring base material and the second wire to a pair of rotating disk electrodes, and
The wire is pressure-welded between rotating disk electrodes.

(4) (Third step) The piston ring base material and the second wire are welded by applying electricity between the rotating disk electrodes.

(5) (Fourth step) Curling the piston ring.

(6) (Step s) Cutting off the joint of the piston ring 0
(7) (Sixth Step) Heat Treating the Piston Ring The method for manufacturing the piston ring of the present invention described above will be described below with reference to Examples.

First, FIG. 2 is a schematic front view of the apparatus used in the piston ring manufacturing method of the present invention, in which 11 is a wire material of the piston ring base material, and 12 is a second wire material forming the piston ring outer periphery.
It is a wire rod. The wire material of the piston ring base material 11 is fed from a stock (not shown) by feed rollers 21 and 21, and sent to the rotating disk electrode 31 via the guide 22. On the other hand, the second wire 12 forming the outer periphery of the piston ring is also sent to the rotating disk electrode 32 by the guy troller 41 and the feed roller 42. The feeding speed preferably depends on the amount of thermal deformation between the second wire rod and the piston ring base material, but by increasing the feeding speed of the second wire rod relatively, the function as a piston ring can be improved as described later. The wire material 11 of the piston ring base material and the second wire material 12 sent out in this way are connected to a pair of rotating disk electrodes 31.3.
2 and are pressed into contact with rotating disk electrodes 31 and 32. At the same time, the joint between the piston ring base material and the second wire is melted by the heat generated by continuous or intermittent current application to the rotating disk electrodes 31 and 32.

The thus melted joint is cooled by the heat capacity of the piston ring itself, and the piston ring base material and the second wire are welded together. Further, since this melting occurs from the joint between the piston ring base material and the second wire material, which has a high electrical resistance, the piston ring base material and the second wire material are affected by heat, but their surfaces are not melted.

The piston ring base material and the second wire rod welded in this way are guided by guide rollers 5, and three-point rollers 61, 62, 63 forming a curling part, or a roller 64 added for the purpose of stabilizing curling. It is bent into a perfect circle by a three-point roller formed by .65.

This curling is the same as the method for forming ordinary steel piston rings. For example, by controlling the position of the bending edge/roller 63, it is possible to bend the piston ring into a cam shape. It is also possible to form a coil shape by shifting it in the axial direction of .63 (the front-rear direction in FIG. 1).

Next, the curled piston ring is fitted by cam-forming each turn, or by cutting the coiled material in one place in the axial direction. The heat treatment is performed for the purpose of removing distortion caused by time, a heat-affected layer remaining in the base material and the second wire, and internal distortion caused by curling.

In this invention, in addition to achieving a strong bond due to the welded structure similar to a normal seam welded plate, the surface roughness can be reduced to the material roughness or lower, but it is not suitable for practical use as a piston ring. In this case, the following embodiments are preferred.

First, the piston ring material used in the present invention is one that requires less wear resistance than the second wire material used in ordinary engines, but requires stiffness and plastic workability, such as high carbon steel or low alloy steel. Carbon steel is preferred. For diesel engines and EGR engines that require particularly high corrosion resistance, it is also possible to use austenitic stainless steel or other steels with excellent corrosion resistance.

On the other hand, for the second wire that forms the outer peripheral surface, a material with high hardness is selected because it needs to have excellent wear resistance, especially scuffing resistance. Specifically, materials such as martensitic stainless steel, high carbon high alloy steel, etc. are selected. High speed steel is used.

Furthermore, in the present invention, since the straight wire rod stock is finally plastically worked into a ring shape with a diameter of 50 to 150 +++ m, the amount of plastic deformation is large, and the internal stress applied to the welded part and the second wire rod is extremely high.

Therefore, there is a high possibility that cracks will occur in the second wire rod, which is usually highly hard and has a large tendency to become brittle, and cracks are likely to occur in the welded part. However, as shown in the embodiment in FIG. is made faster than the feed rate of the piston ring base material 11, and the circumferential speed of the rotating disk electrode 32 is made faster than the circumferential speed of the rotating disk electrode 31 (specifically, the diameter of the electrode 32 is increased) during welding. It is preferable to apply compressive stress to the second wire in advance.

Further, as shown in FIG. 3, a concave groove 1 is formed in the piston ring base material 11.
3 is provided, and the second wire 12 is welded into this groove 13. In this embodiment, the upper and lower surfaces 14 of the piston ring.
Since 15 is the uniform piston ring base material 11, this surface has high rigidity and can be precisely processed. When welding at the same time, only the bottom 16 of the groove 13 is welded,
Since no nuggets 19 are formed on the side surface, the outer circumference of the piston ring is not made rough, and non-uniformity of the outer circumference of the piston ring due to nuggets appearing on the surface is also prevented.

At the same time, the piston ring with the concave groove 13 formed thereon and the second wire rod 12 welded thereto is curled, as shown in FIG. Therefore, even if the concave groove 13 and the second wire 12 are assembled with a loose fit during welding, they will be a tight fit after being formed into a piston ring.

In the embodiment in which the second wire is welded to the concave groove of the fifth
As shown in the figure, it is preferable to form a chamfered portion 7 in advance on the upper surface end of the second wire rod 12 and/or the concave groove 13 of the piston ring base material. In addition to preventing it from reaching the outer peripheral surface,
An acute edge is formed on the outer circumferential side of the second wire to prevent it from scratching the cylinder liner, and furthermore, this chamfered portion 7 also functions as a lubricating oil retaining groove. Although it is preferable that the chamfered portion 7 is formed in advance on the piston ring base material and the wire material of the second wire material, it can also be formed by cutting after the piston ring is completed.

Further, as shown in FIG. 6, a projection 71 is provided on the piston ring base material and welded to the second wire to improve weldability. This projection is formed on the wire by rolling or other means before the welding process.

As another embodiment of the present invention, as shown in FIG. 7, the piston ring base material 11 to be supplied to the rotating disk electrodes 31, 32 is formed in advance to a predetermined curvature, welded, and then applied to curling rolls 61, 62, 63. By curling the wire, it is possible to prevent the generation of internal stress on the welded portion and the second wire during curling.

At this time, it is also possible to form the piston ring base material 11 to a predetermined curvature so that the curvature is approximately the same as the final curling curvature of the piston ring. However, if there is an axial velocity that occurs during coiling in the traveling direction of the piston ring base material just before and after the rotating disk electrode to be welded, torsional stress will remain in the welded part when it is finally formed as a piston ring. It is preferable that the piston ring is welded at least in the initial stage of curling in a range where the piston ring is bent on one plane.

The present invention has been described above, but the present invention first improves productivity by continuously molding the piston ring in the same way as ordinary steel piston rings, and also improves productivity by molding the piston ring continuously in the same manner as ordinary steel piston rings, and also improves productivity by molding the piston ring with a highly hard and difficult-to-plastic material on the outer peripheral surface of the piston ring. It is possible to achieve a wear-resistant effect that can be applied to the outer circumferential surface, and a bonding strength of the wear-resistant layer formed on the outer peripheral surface.

Furthermore, the present invention can also exhibit a bimetallic effect that cannot be achieved with ordinary surface coatings. That is, usually 0.1~
A surface coating of about 0.5 m is not as strong as a piston ring and is hardly affected by tension, surface pressure, etc. However, with a piston ring that has a welded structure as in the present invention, there is also the purpose of preventing the welded ragget from reaching the outer circumferential surface. Usually, a relatively thick second wire of 0.5+mm or more is used, and the second wire and the piston ring are strongly connected by welding, so the mechanical properties of the second wire on the outer circumferential surface are different from those of the piston ring. The impact is significant. As an example of applying this to a function specific to piston rings, the present invention makes it possible to utilize the difference in coefficient of thermal expansion between the second wire and the piston ring base material. In other words, during processing, the joint state is designed so that the joint part has a curvature dog (so-called low point joint), and if the second wire is selected to have a high coefficient of thermal expansion relative to the piston ring base material, the engine rotation range will be high. (i.e., as the piston ring becomes hot), the piston ring abutment changes to a small curvature (so-called high point), which is effective in preventing fluffing during high speed rotation.

On the other hand, in engines such as 2-cycle engines and diesel engines where there is concern about the intake and scavenging air ports and the joints at high speeds, by increasing the thermal expansion coefficient of the piston ring base material relative to the second wire material, high speeds and rotations can be achieved. As the piston ring increases, the piston ring tends to meet at a low point, reducing galling wear and blow-by.

Further, in the present invention, it is preferable to preheat the piston ring base material and the second wire for the purpose of controlling the nugget thickness when welding the piston ring base material and the second wire using a rotating disk electrode.

The present invention can also be achieved using the conventional three-point roll method shown in FIG. 1, or a method other than three-point roll forming, such as curling on a mandrel. First of all, it is necessary to eliminate welding distortion, curling distortion, and heat effects during welding, but if the quenching process, opening, and shrinking heat treatment process conventionally used in piston ring technology is performed, these Since stress relief can be achieved by heat treatment, heat treatment solely for strain relief is omitted.

[Brief explanation of drawings]

FIG. 1: A sectional view of a conventional piston ring. FIG. 2: A front view of main parts for explaining the manufacturing method of the first embodiment of the present invention. FIGS. 3 to 6 are cross-sectional views of other embodiments of the present invention. FIG. 7 are front views of main parts 1 for explaining the manufacturing method of other embodiments of the present invention. Explanation of numbers 11; Piston ring base material 12; Second wire rod 13; Concave groove 21; Feed roll 31, 32; Rotating disc electrode 41; Feed roll 61, 62, 63; Curling roll Patent applicant Nippon Piston Ring Co., Ltd. Company Figure 3 Figure 4

Claims (4)

[Claims] (1) A piston ring for an internal combustion engine, in which a piston ring manufacturing method involves joining dissimilar materials to the outer circumferential surface forming the sliding surface, in which a piston ring base material made of a wire material and a thin wall forming the piston ring outer circumferential surface are used. A second wire is prepared, and as a first step, the piston ring base material is rolled and sent out, and the second wire is sent out separately from the piston ring base material, and as a second step, the piston ring base material and the piston ring base material are fed to a pair of rotating disk electrodes. A second wire is supplied, the piston ring base material and the second wire are pressed together between the rotating disk electrodes, and in the third step, electricity is applied between the rotating disk electrodes to weld the piston ring base material and the second wire. The first to sixth steps include curling the piston ring as a fourth step, cutting off the piston ring as a fifth step, and heat treating the piston ring as a sixth step.
A method for manufacturing a piston ring, characterized in that it is manufactured by a process. (2) A patented piston ring manufacturing method characterized in that in the first step, the second wire feeding speed is made faster than the feeding speed of the piston ring base material. (3) The piston ring manufacturing method according to claim 1, wherein a groove into which the second wire is fitted is formed in advance on the outer peripheral side of the piston ring base material. (4) The piston ring manufacturing method according to claim 1, characterized in that a projection is provided in a groove provided in the piston ring base material.