JPS59162342A - Processing method of cylinder or cylinder liner and its surface for internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve wearing resistance and corrosion resistance, by filling chrome oxide to be solidified between ceramic particles of a ceramic layer which forms peripheral and internal peripheral surfaces of a cylinder or a cylinder liner for use of internal-combustion engine. CONSTITUTION:After applying ceramic slurry of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, etc. on the surface of a cylinder liner, its preliminary firing furnace 15, and water in an applied film 13 is evaporated. And then, the ceramic film 13, after being impregnated with a chromic acid solution, is fired. In this way, filling fine chrome oxide 18 to be solidified in a void part between ceramic particles 17, wearing resistance and corrosion resistance are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cylinder or cylinder liner for an internal combustion engine, and a surface processing method thereof, and particularly relates to a cylinder or cylinder liner for an internal combustion engine, and particularly to a method for processing the inner peripheral surface and/or the cylinder liner.
The present invention also relates to a cylinder or cylinder liner in which a ceramic layer is formed on the outer peripheral surface, and a surface processing method thereof.

In a dry cylinder liner that is attached to a cylinder block that constitutes an internal combustion engine, wear resistance and corrosion resistance are important because the entire inner circumferential surface of the liner forms a sliding surface for the piston. In particular, the upper part of the inner peripheral surface of the cylinder liner, that is, the part where the combustion explosion takes place, is exposed to high temperatures and has insufficient lubricating oil film formation, so it is easy to suffer from rolling wear. Therefore, it is necessary that the cylinder liner, especially the upper end side, has wear resistance and corrosion resistance. Conventionally, the inner circumferential surface of the cylinder liner of such an internal combustion engine has been plated with hard chrome to meet the above objective. However, even with these measures, wear resistance and corrosion resistance have not been sufficiently solved, and abnormal wear has caused problems such as blow-pipe of combustion gas.

In addition, in wet cylinder liners used in internal combustion engines, not only the wear resistance and corrosion resistance on the inner circumferential surface are issues, but also the outer circumferential surface is in direct contact with cooling water, so the outer circumferential surface of the cylinder liner is They were susceptible to damage due to cavitation pitting, and to solve this problem, the outer circumference was also coated with chrome plating.

However, even with this chrome plating, the problem of cavitation pitting described in Section 2 could not be solved satisfactorily.

Furthermore, in conventional cylinder liners, chrome plating with a thickness of about 100 μm is applied electrically, which has the disadvantage of increasing costs.

The present invention has been made in view of these problems, and it is an object of the present invention to provide a cylinder or cylinder liner for an internal combustion engine that has excellent wear resistance and corrosion resistance, and a surface processing method thereof. .

A feature of the invention is that a ceramic slurry is first applied to the surface of the cylinder or cylinder liner. The ceramic slurry used here is made as follows. First, as a ceramic material, silicon oxide (S!02
), fine particles of oxide ceramics such as aluminum oxide (A1203), zirconium oxide (ZrOz), titanium oxide (T!Oz), or silicon carbide (Si C)
, silicon nitride (S! 3N4), aluminum nitride (Aβ
The material may be selected from fine particles of non-oxide ceramics such as N), tungsten carbide (WC), and the like. Therefore, for example, fine particles of silicon oxide and aluminum oxide, which are relatively easily available and have excellent wear resistance and corrosion resistance, may be used.

When silicon oxide and aluminum oxide are selected, flaky chromium [
ll(CrO3) and water, which makes it possible to obtain the desired ceramic slurry. The reason why chromic acid is mixed here is that by converting it into chromium oxide (Cr203) in the subsequent firing, it fills the gaps between the ceramic particles of silicon oxide and aluminum oxide and bonds the ceramic particles together. This is to allow the chromium oxide to act as a binder, and to take advantage of the abrasion resistance and corrosion resistance specific to chromium oxide.

This ceramic slurry will be applied to the inner or outer peripheral surface of the cylinder or cylinder liner. For example, when applying ceramic slurry to the inner surface of the cylinder liner 6 to form a coating film, as shown in FIG.
This is done by a dipping method in which the ceramic slurry 7 is immersed in the ceramic slurry 7 in the tank 8 and then pulled up.

The thickness of the coating film on the inner surface of the cylinder liner 6 thus formed is approximately 50 to 200 microns. In addition, if the thickness obtained by the above-mentioned coating film formation is thin, after drying and baking the coating film, the above-mentioned dipping method can be applied again to increase the thickness of the coating film. .

This operation can be repeated until the desired thickness is obtained.

Furthermore, according to the apparatus shown in FIG. 1, a coating film is formed only on the inner circumferential surface of the cylinder liner 6, but if it is necessary to form a coating film on both the inner circumferential surface and the outer circumferential surface by the dipping method, In this case, masking 5 described above may be omitted. Alternatively, the ceramic coating film 13 may be formed on the outer peripheral surface by spraying a ceramic slurry with a spray gun.

The ceramic material 13 thus formed on the inner or outer surface of the cylinder liner 6 is prefired. Note that it is preferable to perform preliminary drying prior to this preliminary baking. After pre-drying,
The cylinder liner 6 is placed in a pre-firing furnace 15 equipped with a heater as shown in FIG. 2, and pre-firing is performed. The purpose of pre-baking the coating film 13 is to evaporate the moisture in the coating film 13 and to make it durable for the subsequent impregnation work with a chromic acid solution, and the temperature is generally 400°C to 400°C.
Preferably, the temperature is in the range of 600°C.

Once the preliminary firing has been performed, the ceramic coating formed on the surface of the cylinder liner 6 is then impregnated with a chromic acid solution. And ceramic coating film 13 of this chromic acid solution
The impregnation is carried out, for example, by simply applying a chromic acid solution-soaked channel 16 onto the surface of the coating film 13, as shown in FIG. As a result, as shown in FIG. 4, the chromic acid 18 is impregnated and filled between the ceramic particles 17 forming the ceramic coating film.

Next, the ceramic coating film 13 impregnated with the above chromic acid solution
to be fired. The purpose of this firing is to convert the chromic acid 18 in the ceramic coating 13 to chromium oxide.

That is, as shown in FIG. 2, the cylinder liner 6 is introduced into a firing furnace 19 and heated to about 510°C. The higher the firing temperature is, the faster the rate of conversion of chromic acid into chromium oxide becomes, so the firing time can be shortened.

However, since the thermal influence on the cylinder liner 6, which is the base material, such as thermal deformation and softening, is taken into consideration, it is not preferable to employ a firing temperature that is too high. Typical firing temperatures are approximately within the range of 450-600°C. On the contrary, it is extremely advantageous to solidify and harden the ceramic coating 13 at such a low temperature.

By such firing, as shown in FIG. 5, the chromic acid 18 filled between the ceramic particles 17 constituting the ceramic coating 13 is converted into chromium oxide 20. In addition, in one cycle of impregnating the ceramic coating 11!13 with chromic acid 18 and firing, the pores of the ceramic coating 13 are only partially filled with the chromium oxide 20, so the pores are filled more completely. for,
It is necessary to repeat the cycle of chromic acid impregnation and calcination described above multiple times.

As described above, in the cylinder or cylinder liner for an internal combustion engine according to the present invention, a ceramic coating film made of fine particles of ceramic such as silicon oxide or aluminum oxide is formed on the inner or outer surface thereof. Furthermore, the ceramic particles themselves are coated with chromium oxide, and the pores existing between the ceramic particles are filled with chromium oxide. Since chromium oxide itself constitutes a type of ceramic, it can be used in cylinders or cylinder liners for internal combustion engines with excellent corrosion resistance. In general, according to the present invention, since the ceramic coating film can be composed of extremely small chromium oxide particles, the anti-friction effect on the surface of the cylinder or cylinder liner that constitutes the sliding surface is increased, and therefore the resistance is increased. It becomes possible to provide a cylinder or cylinder liner that is also excellent in terms of wear resistance.

Next, the present invention will be explained in more detail with reference to examples.

Example 1 A ceramic slurry was obtained from a mixture consisting of 55% by weight of finely divided silicon oxide, IOI of finely divided aluminum oxide, 10% by weight of flaky chromic acid, and 25% by weight of water.

Next, the outer peripheral surface of a dry type cylinder liner with an inner diameter of 90T [III, which constitutes an internal combustion engine, is masked and immersed in ceramic slurry 7 in tank 8 shown in FIG. Formation was avoided on the inner circumferential surface of the liner 6. The thickness of this coating film 13 was approximately 100-odd microns, but since this thickness was insufficient, the liner 6 was immersed in the tank 8 again as shown in FIG. 1, and the method described above was performed. Slurry 7 was applied in the same manner. As a result, liner 6
A ceramic coating film 13 with a thickness of approximately 300 μm was obtained on the inner surface. Next, as shown in FIG. 2, this cylinder liner 6 was introduced into a preliminary firing furnace 15, heated at 510° C. for about 10 minutes to solidify the coating film 13, and then cooled to room temperature.

Next, a chromic acid solution consisting of 60 parts by weight of chromic acid and 40 parts by weight of water is applied to the ceramic coating 13 of the cylinder liner 6 with a brush 16 as shown in FIG. The chromic acid solution 18 was impregnated into the coating film 13 in the same manner. Next, this cylinder liner 6 was introduced into a firing furnace 19 (see FIG. 2) and heated at 510° C. for about 10 minutes.

As a result, chromic acid 18 was converted to chromium oxide 20 as shown in FIG. The steps of applying the chromic acid solution and firing were repeated 12 times. Then, the surface of the coating film 13 of this cylinder liner 6 was ground to obtain the desired finishing accuracy.

When the Pinkers hardness of the ceramic layer of the cylinder liner 6 thus obtained was measured, a value of 1200 was obtained. This value means that the material is very hard and therefore has great wear resistance.

Furthermore, when we measured the wear of the cylinder liner 6 obtained in this way, we obtained results not shown in FIG. 6. In this graph, the wear ω of the cylinder liner according to this example is shown by a solid line. The wear amount results shown by the dotted line and the chain line show the characteristics of cylinder liners made of sintered silicon carbide and silicon nitride, respectively. Therefore, as is clear from the results, the cylinder liner according to this example has less leakage than the cylinder liner formed with a sintered body of silicon carbide or the cylinder liner formed with a sintered body of silicon nitride. It is clear that wear is reduced. Note that all of these measurements were conducted under conditions where no lubricating oil was used.

Example 2 A ceramic coating film 13 was formed on the inner circumferential surface of a wet cylinder liner for an internal combustion engine having an inner diameter of 140 mm by the same method as in Example 1 above. Further, the ceramic slurry prepared in Example 1 was sprayed onto the outer peripheral surface of this liner to form a coating film on the outer surface as well. In other words, the cylinder liner is placed on a table rotating at 4 Orpm, and the liner is rotated, so that the outer peripheral surface of the liner is coated with 30 cm.
Spray ceramic slurry with a spray gun at a pressure of 1.5 kg/cJ from a distance of about 10 m to the outer surface.
A ceramic coating film of 0μ was formed. Next, this liner was subjected to the chromic acid impregnation and firing process 12 times in the same manner as in Example 1 to convert the chromic acid in the ceramic coating formed on the inner and outer surfaces of the cylinder liner to chromium oxide. I filled it up and did it. In this way, it is possible to obtain a wet type cylinder liner whose inner circumferential surface has excellent wear resistance and whose outer circumferential surface has excellent cavitation resistance.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view showing an apparatus for applying slurry to cylinder liners by dipping, Fig. 2 is a longitudinal cross-sectional view of a pre-calcination furnace or firing furnace, and Fig. 3 is a longitudinal cross-sectional view showing a device for applying slurry to cylinder liners by dipping. 4 is an enlarged sectional view of a 1ζ ceramic coating film with pores filled with chromic acid; FIG. 5 is an enlarged sectional view of a ceramic coating film with pores filled with chromium oxide; FIG. 6 is a graph showing test results of the wear resistance of a cylinder liner according to an embodiment of the present invention. The symbols used in the drawings are as follows: 6... Cylinder liner 7... Slurry 13... Ceramic coating film 17... Ceramic particles 18... Chromic acid 20... Chromium oxide. Agent Osamu Matsumura

Claims (1)

[Claims] 1. In a cylinder or cylinder liner for an internal combustion engine in which a ceramic layer is formed on the inner peripheral surface and/or the outer peripheral surface, the ceramic layer is formed by firing and solidifying a ceramic slurry, and the ceramic layer is formed by firing and solidifying a ceramic slurry. A cylinder or cylinder liner for an internal combustion engine, characterized in that chromium oxide is filled and solidified between ceramic particles of a ceramic layer. 2. In a method for forming a ceramic layer on the inner circumferential surface and/or outer circumferential surface of a cylinder or cylinder liner for an internal combustion engine, a ceramic slurry is applied to the surface of the cylinder or cylinder liner (preliminary firing, and then A method for surface processing a cylinder or cylinder liner for an internal combustion engine, characterized in that the ceramic layer is impregnated with a chromium solution, and then the ceramic layer is fired to convert the chromic acid into chromium oxide.