KR100328606B1 - Heat barrier and wear resistant coating combination for internal combustion engines - Google Patents

Abstract

The present invention is a heat barrier and wear resistant coating having high strength, low thermal conductivity, low coefficient of thermal expansion and good adhesion, wherein the wear resistant coating is self lubricated and has high thermal resistance, strong wear resistant matrix, low coefficient of friction and smooth A wear resistant coating that is easy to machine to a surface, wherein the thermal barrier is applied to an internal combustion engine cylinder to reduce heat rejection and thereby reduce the need to cool with air or liquid, and the self-lubricating wear resistant coating layer is heated. It prevents contact between the internal combustion engine portion and the thermal barrier that is applied to the barrier and operates, and the wear resistant coating hides the low coefficient of friction and is self-lubricating with good resistance to temperatures up to 900 ° C. without actually producing more heat.

Description

Heat barrier and wear resistant coating combination for internal combustion engines

FIELD OF THE INVENTION The present invention relates to heat resistant coatings and wear resistant coatings for internal combustion engines, and in particular to combinations of heat barriers and wear resistant coatings that provide improved coatings for use in cylinder walls of internal combustion engines, wherein the wear resistant coatings provide abrasion of coated engines. It can withstand high operating temperatures with self-lubrication to reduce

Inadequate cooling of the internal combustion engine is a limiting factor on how much more constant power can be provided by the internal combustion engine. Therefore, the amount of heat conduction from the operating chamber (piston and cylinder or rotor and rotor housing) of the internal combustion engine to the cooling apparatus of the internal combustion engine is preferably kept to a minimum, so that the cooling apparatus conducts heat appropriately and the internal combustion engine is removed. To maintain an acceptable operating temperature. Low heat dissipation internal combustion engines used ceramic insulating coatings to receive combustion energy in the operating chambers of these internal combustion engines. In addition to the thermal protection provided by such an insulated coil, various types of ceramics have been tested to obtain reasonable heat resistance characteristics.

As published in the 1988 S.A.E publication, recent developments in adiabatic internal combustion engines have shown the use of ceramics as thermal insulators for internal combustion engine components.

Although such a ceramic is an excellent insulator, the surface of such a ceramic is poor in abrasion resistance, and the surface density also falls rapidly by friction.

Ceramic thermal barrier coatings are very successful in terms of reducing heat transfer through the housing of the engine, but in doing so, the temperature of the internal combustion engine surface rises beyond the desired lubrication performance to maintain the lubrication film. Recently, high temperature, self-lubricating materials have been developed for applications in which temperatures exceed the performance of known lubricants.

The NASA PS-200 itself, which is composed of a chromium carbide (or silicon carbide) matrix of nickel alloy junctions with dispersed particles of a process mixture of silver and calcium fluoride-barium fluoride, for example, was developed by NASA. Lubricating synthetic coating. Silver and fluoride form films with low shear strength on sliding surfaces. Silver provides lubrication until it reaches 500 ° C. and provides process lubrication of fluorides that withstands brittleness to ductility at temperatures above 500 ° C.

However, there are complex problems in completing thermal barrier coatings and self-lubricating antiwear coatings that are compatible with each other and that can be economically and practically applied to operating members of an engine.

It is therefore an object of the present invention to provide a compatible mixture of thermal barrier material and antiwear material in order to provide an improved coating for the cylinder wall to reduce the cooling load of an air cooled or water cooled engine.

Another object of the invention is to reduce the heat exhausted from the operating chamber of an internal combustion engine.

Another object of the present invention is to provide an improved type of wear resistant coating to improve the wear resistance of the combustion chamber surface.

Another object of the invention is to rule out the need for continuous lubrication of the cylinder inner wall of the engine.

It is another object of the present invention to allow a wider selection of usable thermal barrier coating materials by eliminating the need for consideration of the wear resistance of the thermal barrier material.

Another object of the present invention is to provide a means for reducing the temperature of the piston ring and the sliding seal when the piston ring and the sliding seal move in a portion of the movement path.

Preferred embodiments of the present invention include a mixture of a thermal barrier coating and a self-lubricating wear resistant coating, the coating being easy to machine to a smooth surface to provide an improved cylinder inner wall for an internal combustion engine. Such thermal barrier coatings have high strength, low conductivity, low coefficient of thermal expansion and good adhesion properties, and self-lubricating wear resistant coatings have high temperature resistance, a hard wear resistant matrix, and a low coefficient of friction. Thermal barriers are formed primarily on the inner surface of the engine cylinders to reduce the flow of heat and thereby reduce the need for water or air cooling. Since the thermal barrier is not wear resistant, an anti-lubrication wear coating is formed on the thermal barrier to prevent contact with the thermal barrier due to the movement of the engine parts. This wear resistant coating has a low coefficient of friction so that no additional heat is generated due to engagement with the engine piston.

One of the important advantages of the present invention is to provide an insulating thermal barrier with a self-lubricating wear resistant coating that maintains the wear and friction resistance of the surface to an acceptable value.

Another advantage of the present invention is to improve the efficiency of the engine by reducing the heat exhausted from the operating chamber of the internal combustion engine to the cooling device of the engine.

Another advantage of the present invention is to provide a coating for the cylinder inner wall with improved wear resistance.

Another advantage of the present invention is to eliminate the need for continuous lubrication of the cylinder inner wall of the internal combustion engine.

Another advantage of the present invention is that the need to consider the wear resistance of the thermal barrier material used is eliminated, resulting in greater selectivity for the thermal barrier material.

Another advantage of the present invention is provided by means for reducing the temperature of the piston ring or sliding ring sufficient to prevent lubrication breakage in the piston ring or sliding seal.

These and other objects and advantages of the present invention are apparent from the description of the preferred embodiments with reference to the accompanying drawings.

According to a preferred embodiment of the present invention, a combination of conventional thermal barrier technology with recently developed high temperature and self lubricating wear resistant materials provides a synthetic coating for wear resistant surfaces of internal combustion engines having two advantages.

Preferred features in the selection of the material constituting the thermal barrier of the present invention are 1) low thermal conductivity (ie, 10 BTU.ft / hr.ft2. ° F), 2) low coefficient of thermal expansion, and 3) base material. 4) maintains high durability with increasing temperature. Representative examples of preferred thermal barrier materials include zirconia and silicon oxide.

Preferred properties for the wear resistant coating of the present invention are 1) low coefficient of friction (ie, .02 or less), 2) ease of machining to smooth surfaces, 3) high temperature resistance, and 4) rough surfaces. 5) the ability to form a compliant film on the surface to prevent contact with the engine part in friction, and 5) a hard, abrasion resistant matrix for supporting the film as soft as it is not rubbed. A representative example of a preferred abrasion resistant coating material is NASA's PS-200, which is a self-lubricating coating material used for turbine bearings and steering engines where lubrication of inner walls and piston rings is not possible.

In order to harmonize these two technologies, one must find two coatings of thermal barriers and self-lubricating antiwear coatings that are compatible with each other and can be economical to put these technologies to practical use. The combination of these two coils consists of a self-lubricating antiwear coating of NASA PS-200 combined with zirconium and an excellent thermal barrier with very low wear resistance. The combination of these two coatings can be formed by plasma arc spraying on conventional engine component materials and adheres well to the base material and to each other. The description of the present invention is that zirconium and PS-200 are used as examples of thermal barrier and anti-wear coatings respectively, and this use example is not intended to limit the scope of the present invention but is intended to assist in understanding the contents of the present invention. It is only. Other types of materials and other application techniques may be used so long as the materials are compatible with each other and with the application techniques used.

In FIG. 1 an engine housing 12 is shown, in partial cross-sectional view, provided with a synthetic coating 10 applied according to the invention on a perforated or machined surface 14 forming a cylinder 16. This synthetic coating 10 consists of a heat barrier layer 18 attached to the surface 14 and a self-lubricating wear resistant layer 20 arranged on top of the heat barrier layer 18. Also shown in FIG. 1 is a partial cross sectional view of a piston 22 having a piston ring 24 for fastening the wear resistant layer 20 to a frictional force. Alternatively, the piston 22 and piston ring 24 shown may be the means for sealing the rotor and apex of the rotary engine.

In particular, a cooling device 21 having fins 26 and an inner chamber 12 for air cooling the engine housing 12 is installed inside the engine housing, through which heat absorbing liquid flows to cool the engine. . The chiller 21 scatters and absorbs the combustion energy delivered through the synthetic coating 10.

The surface 14 must be provided prior to forming the thermal barrier coating layer 18. Most engine components consist of aluminum or iron-based materials. To reinforce the adhesion of the coating, small square sand must be crushed and sprayed onto the surface 14, which must be washed to remove particles of the metal or sand prior to forming the coating. This metallic housing 12 must be preheated to a temperature above the predetermined temperature expected in operation so that the coating can always be applied under compression by differential thermal expansion. The adhesive 30 may be painted on the surface 14 immediately prior to forming the thermal barrier coating layer 18. According to one embodiment of the invention, a thin (ie 0.001 inch) adhesive film made of a mixture of molybdenum, chromium, aluminum and yttrium applied to the aluminum surface enhances the adhesion of the thermal barrier 18 to the surface 14. do.

Since it is not necessary to consider the wear resistance of the thermal barrier, the material including the thermal barrier 18 can be selected from a wide variety of coating materials. Zirconia is a conventional type of ceramic used as a thermal barrier and used herein as an example of the coating layer 18. Preferably, zirconia is a plasma that is partially stabilized with a low proportion of yttrium oxide and sprayed onto the heated surface 14. Self-regulating plasma guns are most desirable to maintain a constant distance and always vertical spray to maintain optimal spraying techniques. The thickness of zirconia depends on the amount of insulating material required and balanced by the structural preservation of the coating. Typically, a 0.02 inch zirconia layer is preferred.

No intermediate process is required during the application of the zirconia coating layer 18 and the wear resistant coating 20, but the coating 20 must be applied immediately after the zirconia layer as it is practical to avoid contamination of the zirconia surface. An example of a suitable wear resistant coating 20 compatible with zirconia is the PS-200 auto-lubricating coating developed by NASA. The screw's PS-200 self-lubricating coating should be applied with optimized plasma parameters for the coating. This will vary from the plasma parameters for the zirconia layer. The screw's PS-200 self-lubricating coating is applied enough to cover all irregular faces of zirconia and to smoothly finish the screw's PS-200 self-lubricating coating without exposing the zirconia. The screw's PS-200 self-lubricating coating will typically be applied to a thickness of 0.01.

The wear resistant coating layer 20 finishes smoothly (eg 10 microns or less), which can be achieved by grinding, lapping or honing. Grinding requires the use of a harder wheel than any wear resistant element in the coating for clean cutting. This requires two different wheels for a "rough" process and a "close" process. The lapping may be accomplished using cast iron covered with alcohol as a cleaning medium to remove debris. Lapping is easiest for application to planar surfaces. Hoonyl is well suited for curved surfaces that are internally independent of shape. Sufficient hornstone pressure must be maintained for cutting, but the surface must be flushed to avoid scratching by debris. The hornstone must be perpendicular to the surface and pressurized to maintain contact at all times. The axis and rotation of the stones are important to keep them clean and flat.

In operation, the piston 22 moves vertically in the cylinder 16 such that thermal energy is generated in the cylinder and conducted to and transmitted to the cooling system 21 in the direction shown by the arrow 32. However, most of the thermal energy is prevented from reaching the cooling system 21 by the thermal barrier layer 18. The wear resistant coating layer 20 prevents contact between the piston ring 24 and the thermal barrier layer 18. The self-lubricating feature of the coating layer 20 should be carried out at elevated temperatures, above which temperatures (216 ° C. and above) are not only generated in the cylinder 16 but also due to the heat generated by the piston ring friction wear resistant coating material. Conventional lubricants may be used because they make the surface very hot. The low coefficient of friction of the wear resistant coating prevents wear of the piston ring 24 and substantially reduces the heat normally generated by the frictional contact between the piston ring 24 and the wear resistant coating.

Although the piston 22, the piston mold 24 and the cylinder 16 are used in the embodiments described above, friction-coupled mechanical parts or friction or size that require control of thermal conduction, such as, for example, rotors and rotor housings. The use of the thermal barrier / abrasion resistant coating of the present invention on at least one surface of the working part will also benefit from the use of a bearing device that is optimal or desirable at elevated temperatures.

In the case of a rotary internal combustion engine, the second advantage can be achieved using the invention. By selectively applying a ceramic coating to the hot zone of the center and to the walls of the combustion chamber in the end housing, the seals have the opportunity to reduce their temperature as they pass through the uncooled and cooled surface. This makes it possible to maintain the seal at a low enough temperature to prevent damage to lubrication in the slot. This is because it is impossible to prevent some oil from entering the combustion chamber through coking.

The ceramic is applied by computer control and is reduced from the maximum thickness at maximum heat flux to zero thickness outside the combustion zone. The heat flux for the walls of the same internal combustion engine without the ceramic coating is shown in FIG. 2 and is used as a basis for establishing an approximate pattern of ceramic coating thickness lying on the wall of the trochoid housing, with a maximum thickness (1 mm + ) Is used at the point of maximum heat flux and the coating will be reduced to either side. Solid lubricants are applied uniformly on all coated and uncoated surfaces. More specifically, using the small axis 42 of the crocoid 40 as 0 °, the maximum thickness is applied at 30 ° and the thickness is reduced to 90 at 0 °. On the other hand, in the case of the long axis 44, the thickness is reduced to or close to zero at -30 ℃. In the end housing, the coating mixture as shown in cross hatched area 46 covers the area exposed to the combustion temperature. However, it can normally cover the entire 120 ° region up to the edge of the football-shaped opening 48 as indicated by the region 50. In these end wall regions, the thickness of the ceramic layer also decreases from the maximum thickness at + 30 ° to zero, the minimum thickness at -30 ° and 90 °.

As a result, the temperature distribution around the housing becomes more uniform. That is, it decreases on the combustion side and increases on the suction side. This provides the advantage of reducing contamination by helping to maintain a more constant setting of engine clearance for reducing quenching and sealing of fuel-air mixtures and the like. It contributes to the control of contamination by reducing blow-by and other gas leaks by better clearance control.

While the invention has been described in the above specific embodiments, it will be apparent to those skilled in the art that other embodiments of the invention may be altered and modified. For example, for the same or similar reason as the embodiment of the rotary internal combustion engine described above, the thickness of the ceramic coating layer 18 becomes smaller as suggested by the dotted line 52 in FIG. 1 or decreases to zero at the bottom of the cylinder. There may be an embodiment of the engine of the reciprocating piston being. Accordingly, the following claims should be construed as including all changes and modifications falling within the spirit and scope of the present invention.

1 is a cross sectional view of an engine housing comprising a combination of a heat barrier and a wear resistant coating arranged on an inner wall of a cylinder in accordance with a preferred embodiment of the present invention and a portion of the cylinder mill piston;

FIG. 2 is a diagram showing the heat flux distribution for the combustion chamber inner wall forming the combustion chamber of the rotary engine prior to coating with the heat barrier and wear resistant coating of the present invention.

Explanation of symbols on the main parts of the drawings

10: synthetic coating 12: engine housing

14 surface 16: cylinder

18: heat barrier layer 20: automatic lubrication wear-resistant layer

22: piston 24: piston ring

26: pin 28: inner chamber

30: adhesive layer 40: trochiod (trochiod)

42: secondary axis 44: main axis

48: hole

Claims (12)

A protective coating for a friction-bearing combustion chamber wall surface of an internal combustion engine, having a low coefficient of thermal expansion, good adhesion to the base material and high strength maintained even at elevated temperatures, A first thermal barrier material layer made of a ceramic material having a thermal conductivity of 0.0 or more and 10 BTU.ft / hr.ft2 ° F or less and fixed to the wall surface, and A second self-lubricating wear resistant layer consisting of a material comprising a nickel alloy bonded chromium carbide matrix having silver and calcium fluoride-barium fluoride process particles dispersed therein, wherein the process has a friction coefficient of at least 0.0 and no greater than 0.2. And a second self-lubricating wear resistant layer, wherein the second wear resistant layer adheres to the first material layer, A protective coating having similar thermal expansion properties that can cause the first material layer and the second wear resistant layer to expand and contract in tight contact. The protective coating of claim 1, wherein the second wear resistant layer is maintained unaffected at least between about 316 ° C. (600 ° F.) and up to about 482 ° C. (900 ° F.). The protective coating of claim 1 wherein said first layer of material consists of zirconia. The protective coating of claim 1 further comprising a bonding coating for securing the first layer of material to the combustion chamber wall surface. The protective coating of claim 4 wherein the bonding coating for fixation is a composite of molybdenum, chromium, aluminum and yttrium. The protective coating of claim 1 wherein the thickness of the first material layer is proportional to the operational heat flux distribution characteristic and the engine material is free of the first material layer. In a friction bearing mechanical part having a low thermal expansion coefficient, good adhesion to the base material and a protective coating having a high strength maintained even at elevated temperatures, Friction bearing machine surface, A first thermal barrier material layer made of a ceramic material having a thermal conductivity of 0.0 or more and 10 BTU.ft / hr.ft2 ° F or less and fixed to the wall surface, and A second self-lubricating wear resistant layer consisting of a material comprising a nickel alloy bonded chromium carbide matrix having silver and calcium fluoride-barium fluoride process particles dispersed therein, wherein the process has a friction coefficient of at least 0.0 and no greater than 0.2. And a second self-lubricating wear resistant layer, wherein the second wear resistant layer adheres to the first material layer, A friction bearing mechanical surface having similar thermal expansion properties that can be expanded and contracted while the first material layer and the second wear resistant layer are in intimate contact. 8. The friction bearing mechanical surface of claim 7 wherein said second wear resistant layer remains largely unaffected from about 316 ° C. up to 482 ° C. 8. The friction bearing mechanical surface of claim 7, wherein said first layer of material is made of zirconia. 8. The friction bearing machine surface of claim 7, further comprising a bond coating for securing the first layer of material to the machine surface. 8. The mechanical surface of claim 7, wherein the thickness of the first material layer is proportional to the operational heat flux distribution characteristic and wherein the wall forming the mechanical surface is free of the first material layer. The mechanical surface of claim 10, wherein the bond coating for fixation is a composite of molybdenum, chromium, aluminum, and yttrium.