JPS5950465B2 - Cylinder liner Oyobi Sonohoning Hohou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for honing the inner peripheral surface of a cylinder liner (including cylinders and cylinder sleeves, hereinafter the same) used in internal combustion engines and the like.

The cylinder liner is a liner formed on the inner circumferential surface of the cylinder to smoothly guide the reciprocating movement of the piston and to facilitate replacement when the inner wall of the cylinder becomes worn.

In the case of cylinder liners for internal combustion engines, the piston slides on the inner peripheral surface of the cylinder liner at a maximum speed of about 10 to 20 m/s while sealing the high-temperature gas burned in the combustion chamber. The lubrication conditions and sliding conditions between the piston or piston cylinder and cylinder liner are extremely severe.

Therefore, it is an important issue how to maintain a good lubrication state on the inner circumferential surface of the cylinder liner and how to avoid the intrusion of foreign matter in order to prevent "galling" between the sliding surfaces, and this application is based on this perspective. The aim is to improve this. Conventionally, in order to improve the wear resistance of a cylinder liner, it has been widely practiced to form an extremely thin soft-nitrided layer of about 30 microns on the inner circumferential surface of the cylinder liner.

After this soft nitriding treatment, a soft nitrided layer is generated on the surface that has greater roughness than the surface before treatment, and the areas along the graphite are raised higher than other areas.
The surface roughness is becoming even greater. Therefore, if it is assembled into an internal combustion engine, etc. in this state, the high surface parts and the weak parts of the base surrounded by graphite will break off due to sliding contact with the piston or piston ring, and these missing pieces will As a result, there was a risk of "galling" occurring between the contact surfaces between the cylinder liner and the piston or piston ring. Furthermore, even if no missing pieces occur, when a piston ring or the like slides, the pressure-receiving area is initially extremely small, so there is a risk of "cauling" due to lack of oil film. An object of the present invention is to provide a method for honing the inner circumferential surface of a cylinder liner, which eliminates the above-mentioned defects and also aims to maintain and improve quality characteristics through nitrocarburizing treatment. Hereinafter, the present invention will be explained in detail with reference to the drawings of the embodiment.

FIG. 1 is a cross-sectional view showing the inner circumferential surface of a cast iron cylinder liner before soft nitriding treatment. Graphite 2 is precipitated and distributed in the base 1 of the cylinder liner material, and some of it is distributed on the inner circumferential surface 3. is also precipitated.

FIG. 2 is a cross-sectional view of the cylinder liner shown in FIG. 1 after soft nitriding treatment, and a hardened soft nitrided layer 4 is formed on the surface thereof. As can be seen from the drawing, the surface subjected to soft nitriding treatment is rougher than the surface before treatment, has many protruding parts 5, and furthermore, the part a of base 1 weakened by graphite 2 is missing. If a missing piece is interposed between the sliding surfaces, it will easily damage the cylinder liner and the sliding surface of the piston or piston ring, causing 'galling'.

In order to eliminate the cause of such galling, the present invention removes the protruding portion of the soft nitrided layer and the weakened portion of the base by honing, and the remaining area of the smoothed soft nitrided layer is equal to the inner circumferential surface area of the cylinder liner. (However, the area of the chamfered relief part on the inner circumferential surface near the cylinder liner end face is excluded) is a method for honing the inner circumferential surface of a cylinder liner. This is the summary. When honing the inner circumferential surface of a hardened cylinder liner, when honing the hard base material with a whetstone containing abrasive grains, the protruding portion 5
In addition to the easily chipped portion a, other thin nitrocarburized layers. As a result, the remaining area of the soft nitrided layer 4 becomes extremely small.

However, when honing is performed with a rubber bond grindstone under specific conditions, only the protrusion j portion 5 of the soft nitrided layer 4 and the portion a where the base 1 is weakened by the graphite 2 are accurately removed, and the other portions are removed. Since the lower portion of the liner having the thin nitrocarburizing layer is not excessively removed, it is possible to secure a residual area of the smooth nitrocarburizing layer that is 80% or more of the area of the inner circumferential surface of the liner.

- Fig. 3 is a cross-sectional view of the cylinder liner shown in Fig. 2 honed with a rubber bond grindstone. As can be seen from FIG. 3, since the abrasive grains of the rubber bond grinding wheel are held elastically inside the rubber, the protruding portions 5 of the soft nitrided layer 4 on the inner circumferential surface of the cylinder liner are scraped off, but the lower portions remains as is. In addition, the weak portion a of the base 1 surrounded by graphite or the nitrocarburized layer along the graphite is chipped off during honing with a rubber bond grindstone, resulting in grooves as shown in FIG. 3b. This groove b retains lubricating oil and significantly improves the lubricating performance during engine operation. Fourth
Figure 5 is a graph showing the surface roughness measured before and after honing with a rubber bond grindstone (magnification, vertical x
5000, horizontal x 50).

This shows that before honing, the surface was extremely uneven (Fig. 4), but after honing, the surface was smooth as shown in Fig. 5. In addition, when honing with a rubber bond whetstone, the grain size of the whetstone is 240-2 to obtain a uniform surface over the entire circumference and to minimize the working time.
It is 80 meshes.

The reason for this is that if the grain size is larger than this, the soft-nitrided layer may be partially scraped off, and if the grain size is smaller than this, the machining time will be prolonged and furthermore, the parts that are likely to fall off will not be removed sufficiently. It is from. In addition, when using a rubber bond grindstone, the grinding speed is 43 to 65 m/min, and the honing shoe pressure, that is, the contact pressure is 6 to 10 kg/min.
Cm・, and the above grinding conditions are expressed as follows.

Note that similar surfaces can be obtained by using resinoid bond grindstones, human rib art bond grindstones, etc. other than rubber bond grindstones, but it is difficult to obtain a uniform surface condition over the entire circumference due to poor elasticity. In addition, whetstones made by mixing cork as a binder have the same elasticity as rubber bond whetstones, but they are less sharp and require a long time to scrape off the protruding parts of the nitrocarburized layer. However, it is not economical because the grinding wheel is subject to large amounts of wear and tear.

Furthermore, in the present invention, the residual area of the nitrocarburized layer smoothed by honing is set to approximately 80% or more (more preferably 90% or more) of the cylinder liner inner circumferential surface area because of its wear resistance. This is because it is the lower limit value for the surface condition that simultaneously satisfies the prevention of galling.

In other words, the "galling" and wear resistance when the residual area of the soft-nitrided layer smoothed by honing was varied using a 6-cylinder water-cooled diesel Edgin as a test engine, and the cylinder hole diameter x strotor size was 155 mm x 170
Fig. 6 shows the experimental results investigated under the measurement conditions of 440 horsepower/2000 rotations, and 250 hours of bench test time.

The galling test was conducted under the following conditions: The chrome-plated sliding surface of the piston ring piece and the soft-nitrided sliding surface of the cylinder liner piece were coated on the entire surface of both sliding surfaces. After finishing by sliding until a contact is achieved, approximately 0.01cc of motor oil (SAElOW) is dripped onto the sliding surface of the cylinder liner, the piston ring piece is fixed, and the cylinder liner piece is moved at a stroke of 50mm at 5/min.
It was reciprocated at a speed of 0.00 reciprocating, and both sliding surfaces were slid with a sliding contact pressure of 50 kg until ``casino'' occurred, and the sliding distance and amount of wear until ``casing'' occurred were measured.

As can be seen from FIG. 6, when the residual area of the nitrocarburized layer relative to the inner peripheral surface area of the liner becomes approximately 80% or more, the "degree curvature" curve becomes approximately vertical, although it is not shown in FIG. When the sliding distance reached 15,000 m, no "degree galling" was observed in I.

On the other hand, the amount of wear on the cylinder liner sliding surface per 100 hours (
μ) gradually decreases as the residual area of the nitrocarburized layer increases, and at a residual area of 80%, the wear amount is 10 μ, 100 μ
%, and therefore the residual area is approximately 80
% or more, the best results for both galling and wear were obtained. As described above, the present invention eliminates the occurrence of "galling" in a soft-nitrided cylinder liner by ensuring a smooth residual area of the soft-nitrided layer that is approximately 80% or more of the inner circumferential surface area of the cylinder liner. The present invention provides a simple and inexpensive method for honing the inner circumferential surface of a cylinder liner, which reduces wear and further improves the reliability and durability of the cylinder liner, and has extremely great practical effects.

[Brief explanation of the drawing]

FIG. 2 is a cross-sectional view showing the inner circumferential surface of the cylinder liner before soft-nitriding treatment, and FIG. 2 after soft-nitriding treatment. FIG. 3 is a sectional view showing the inner peripheral surface of the cylinder liner according to the present invention. Figure 4 shows the roughness curve of the inner circumferential surface of the soft-nitrided cylinder liner measured with a roughness meter at 5000x vertically and 50x horizontally. Figure 5 shows the roughness curve of the cylinder liner of the present invention. Similar roughness curves, FIG. 6, are graphs of galling and wear curves for cylinder liners. 1: base of cylinder liner material, 2: graphite, 3: inner peripheral surface, 4: nitrocarburizing layer, 5: protruding portion, a: weakened portion of base 1,
b: Groove.

Claims (1)

[Claims] 1 The inner circumferential surface of the cylinder liner that has been soft-nitrided is 240~2
Rubber bond whetstone with 80 mesh abrasive grains from 43 to
The inner peripheral surface of the cylinder liner is honed smoothly under the conditions of a grinding speed of 65 m/min and a shoe pressure of 6 to 10 kg/cm^2, and more than 80% of the inner peripheral surface is formed into a smooth nitrocarburized surface layer. Honing method.