JPS6240425B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a piston ring for an internal combustion engine, and more specifically, the present invention relates to a method for manufacturing a piston ring for an internal combustion engine. It relates to the method of application.

In recent years, internal combustion engines have been driven to higher speeds and higher compression rates to improve performance, as well as increased heat loads due to exhaust gas countermeasures, which have increased the burden on the sliding parts of the piston, piston rings, and cylinder liners. However, the demands on these things are becoming increasingly strict. Particularly in diesel internal combustion engines, piston rings are increasingly required to have seizure resistance, abrasion resistance, and scuffing resistance as diesel internal combustion engines increase in speed due to the occurrence of carbon suits.

Conventionally, as piston rings with improved mechanical properties, there have been known piston rings whose outer circumferential surface connected to the cylinder liner is plated with chromium (Cr) or sprayed with molybdenum. Among these, chrome-plated piston rings have good wear resistance, but they do not have good seizure resistance with the mating cylinder liner cast iron material, so they have the disadvantage of being prone to seizure and scuffing. ing. For these reasons, molybdenum thermal spraying, carbide, and ceramic thermal spraying have been adopted or are being considered, but because there are various restrictions in the thermal spraying process during manufacturing, they require many steps and are expensive. It is also a contributing factor. In other words, the piston rings are too small to be thermally sprayed one by one, so the first
As shown in the figure, a large number of piston rings 1, 1,
1,... to form a cylindrical body 11, thermal spraying is applied to the outer periphery of this cylindrical body, and then separation into individual rings is conventionally carried out because it is economical. 11, there was a problem that the rings were integrated by the sprayed layer and could not be divided into individual rings. Therefore, conventionally, as shown in FIG. 2, a ring groove 2 is formed at the center of the outer periphery of the ring, and a thermal spray layer 3 is formed within this ring groove 2.

In this conventional method, as shown in FIG. 1, piston rings 1, 1... are stacked to form a cylindrical body 11,
By rotating the cylindrical body 11 about the holders 4.4 at both ends, one of the rings 1, as shown in FIG. 3A,
A predetermined ring groove 2 is cut into one ring, shot blasted, and then preheated and thermally sprayed (Fig. 3B). Continue spraying the sprayed surface until part of the ring surface is scraped off (up to line X-X in Figure 3 B).
The cylindrical bodies are individually separated by grinding to obtain thermal spray rings.

However, when using the above conventional method, compared to the chrome plating method, there is a disadvantage that the number of processes such as groove processing and thermal spray layer grinding increases, and the sliding surface of the product decreases. In addition, since it is more expensive than the chrome plating method, thermal sprayed rings are not used in Japan except for special vehicles, despite their advantages in terms of performance and durability.

An object of the present invention is to provide a new manufacturing method that allows thermal spray piston rings to be manufactured in mass production at low cost without grooving rings in the process of manufacturing thermal spray rings.

The method of the present invention involves chamfering the outer circumferential surface of a ring made of cast iron or steel base material, if necessary, by 0.1 to 0.3 cm at both ends, and then applying fluororesin (Teflon) to the outer circumferential surface, including the chamfered portions. The method is characterized in that after applying a surface treatment such as iron oxide to make it difficult for thermal spray particles to adhere, the surface treatment layer of the area to be thermally sprayed is removed and thermal spraying is carried out.

In the present invention, when chamfering is performed, the entire outer periphery of the cylindrical body is subjected to surface treatment, and then a light grinding process is applied to form a surface treatment layer of Teflon, triiron tetroxide, etc. only on the chamfered part. remains, so the spray particles during thermal spraying do not adhere to this chamfer, but only to the sliding surface with the liner, so the removal by grinding after thermal spraying basically only removes the surface roughness caused by thermal spraying. All that is required is processing, and a thermal sprayed ring with excellent scuffing and seizure resistance can be obtained at a cost comparable to that of chrome plating.

In addition, in the case where a triiron tetroxide film is to be formed, it is sufficient to simply remove the triiron tetroxide film in the portion corresponding to the conventional groove without chamfering.

Next, an example of the present invention will be explained with reference to FIGS. 4A to 4E.

First, as shown in FIG. 4A, piston rings 1 with chamfers 5 on both ends of their outer peripheral surfaces are stacked to form a cylindrical body (mandrel) 11, and then thermal spray particles such as Teflon or triiron tetroxide are attached. After forming a surface treatment layer 6 that is difficult to spray (Fig. 4B), and then grinding only the outer peripheral surface to expose the ring surface to be thermally sprayed and finishing it to the predetermined dimensions (Fig. 4C), preheating is performed. Then, thermal spraying is performed (Fig. 4D). After that, the sprayed surface is finish ground to obtain the desired ring.

In thermal spraying, if the thermal spray coating on the outer peripheral surface has poor adhesion to the base material, a metal material with excellent adhesion and heat resistance is applied as a base thermal spray, and then the coating is coated with abrasion resistance, seizure resistance, and resistance. It is preferable to form a thermal spray coating with excellent scuffing properties on the outer peripheral surface.

Furthermore, the coating treatment with Teflon or the like may be performed before or after forming the cylindrical body, depending on the process.

When obtaining a product ring with a thermal spray coating thickness of 0.2 mm or more, in the conventional method, the ring groove needs to be 0.25 to 0.3 mm, taking into account machining allowance, and the thermal spray thickness needs to be 0.25 mm or more. . At this time, the sprayed coating adheres to areas other than the ring groove as shown in Figure 3B, so the grinding allowance after spraying is equal to the thickness of the sprayed layer.
The total machining allowance for the ring is 0.3-0.4mm, which is 0.25-0.3mm and the machining allowance of 0.05-0.1mm for the ring, and the grinding process is time-consuming. On the other hand, according to the present invention, by thermal spraying of 0.25 to 0.3 mm, the machining allowance is only 0.05 to 0.10 mm, which is less than 1/4 of the conventional machining allowance, and the grinding process can be greatly reduced.

The present invention will be explained in more detail below with reference to Examples.

Example 1 As shown in FIG. 4A, a plurality of piston ring base materials 1 made of spheroidal graphite cast iron having a cross-sectional shape with a chamfer 5 on the outer circumferential end are prepared, and these are stacked to form a cylindrical body 11. The cylindrical body 11 is coated with Teflon while rotating around its axis, and after coating, the outer circumferential surface of the ring is ground to a predetermined size that takes into account the thickness of the sprayed coating, and only the outer circumferential end surface 5 of the ring is coated with Teflon. A cylindrical body in which the surface treatment layer 6 of the coat remains is obtained. Next, this cylindrical body is preheated while rotating, and a NiAl base is thermally sprayed to a thickness of 20 to 60 mm.
μ applied and further 63.3Cr−6.6C−1.9Si−0.02P−
The alloy powder consisting of 0.04S with the remainder being Fe is coated by plasma spraying to a predetermined thickness that allows for grinding machining allowance, and the outer circumferential surface is ground using a cylindrical grinder to finish the piston ring to product dimensions. completed.

The product dimensions and thermal spraying conditions for this piston ring are as follows.

Piston ring nominal diameter 90mm, thickness 3mm, width
2.5mm, outer circumferential chamfering ^0.2c , thermal spray coating thickness 0.20~0.25
mm plasma spraying was carried out using METCO's ``3MB'' in the United States with the company's GH nozzle and No. 2 powder port installed under the following conditions.

Ar gas flow rate 80SCFH H ₂ gas flow rate 15SCFH Arc current 450~500Amp Piston ring cylinder rotation speed 200~500rpm Thermal spray gun feed rate 0.8~2.0m/min Powder supply rate 40g/min Reference example Same as Example 1 A cylindrical body of a piston ring was made, and without Teflon coating, a base coat of NiAl was sprayed and then used in Example 1.
Although Cr-Fe alloy powder was sprayed and the same was ground, the sprayed coating adhered to the chamfered portions of both ends of the outer periphery of the ring, making it impossible to separate the rings one by one.

Example 2 In place of the Teflon coating in Example 1, the surface of the piston ring was subjected to steam treatment to generate triiron tetroxide, and then the same procedure as in Example 1 was carried out.
Following the NiAl base spraying, a Cr-Fe alloy was sprayed and ground to obtain the desired piston ring.

[Brief explanation of the drawing]

Figure 1 is a side view of the piston ring cylindrical body, Figure 2 is a side view of the piston ring cylindrical body;
The figure is a partially cutaway perspective view of a piston ring according to the conventional method, FIGS. 3A and 3B are cross-sectional views of the main part a of the cylindrical body for explaining the conventional method, and FIGS. A sectional view of a main part a of a cylindrical body is shown for purposes of explanation. In the figure, 1... Piston ring base material, 11... Piston ring cylindrical body, 2... Groove, 3... Thermal spray layer,
5... Chamfering, 6... Surface treatment layer.

Claims (1)

[Claims] 1 A large number of piston rings are stacked to form a cylindrical body,
After applying a surface treatment to the entire outer peripheral surface of the cylindrical body to prevent thermal spray particles from adhering to it, the surface treatment layer on the part of the cylindrical body to be thermally sprayed is removed by machining, etc., and metal or ceramic is thermally sprayed. A method for manufacturing a thermal sprayed piston ring, characterized by: