JPH0133655B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a ceramic-metal composite piston. Pistons, which are the main components of internal combustion engines, are exposed to high-temperature voltages and have strict requirements for heat resistance, but in order to reduce weight in small engines, pistons made of aluminum alloy instead of regular cast iron have been created. However, problems remained because the heat resistance and thermal properties such as heat insulation were inferior. Incidentally, recently pistons made of ceramic materials have been considered, and by utilizing the heat shielding effect based on the low thermal conductivity of ceramic materials, it is possible to reduce heat loss during operation of internal combustion engines, improve output, and improve the performance of hydrocarbons. Although pistons can be expected to have favorable performance such as reduced concentration and reduced fuel consumption, pistons made using the ceramic shrink-fit casting method that has been considered up to now suffer from metal damage when used for long periods of time in heating and cooling cycles. There is a risk that this may cause deformation or sagging, and a practical product has not yet been realized. The present invention was made in view of this situation, and instead of bonding ceramic and metal through physical contact such as casting or shrink fitting as described above, it combines ceramic and metal using a chemical reaction. The present invention provides a piston for an internal combustion engine that has an extremely strong joint structure by joining together. Next, the piston of the present invention will be explained with reference to the drawings. Figure 1 shows a ring-shaped metallized ceramic molded body 1a that is fitted into the crown of the piston.
It is. The metallization forms the part of the ceramic surface to be soldered in a piston, which will be described later, and here the metallization part 1-m is provided on the lower surface. Second
The figure shows that the metallized ceramic molded body 1a shown in FIG. 1 is fitted onto the upper surface of the crown portion 3 of the cast iron piston body 2a. A copper clad material, iron/nickel 42 alloy, or Kovar plate is placed on the lower surface of the ceramic molded body 1a as a buffer layer 4, and a silver-copper eutectic solder is used to connect the ceramic molded body 1a and the cast iron piston body 2a. It is a piston that is integrated with a soldered joint. The soldered surface of the ceramic molded body 1a is a metallized surface, but is omitted from illustration in FIG. FIG. 3 shows a metalized irregular-shaped ceramic molded body 1b with a space in the upper center in place of the disk-shaped metallized ceramic molded body 1a in FIG. 1, and the area shown by the imaginary line on the outside A metallized layer 1-m is provided corresponding to the brazed portion when the piston is fitted into the piston. Figures 4, 5, 6, 7, 8, and 9 show a metalized irregularly shaped ceramic molded body 1b as shown in Figure 3, which is fitted onto the top surface of the crown portion of the piston body. The figure shows an example of a piston. However, all metallized parts are omitted without being explicitly shown, but since they are soldered, they will be easily understood. Fig. 4 shows a buffer layer such as a cylindrical copper plate having a length equal to the depth of the crown portion of the piston into which the irregularly shaped ceramic molded body 1b is fitted, on the outer cylindrical side surface of the irregularly shaped ceramic molded body 1b whose side surface is metallized. 4
The metallized surface of the irregularly shaped ceramic molded body 1b existing inside and outside of the molded body 1b and the cast iron body 2a of the piston are soldered using a silver-copper eutectic brazing agent 5.
It has been integrated. Fig. 5 shows a modified ceramic molded body 1b whose entire outer surface is metallized, and a buffer layer 4 made of a copper plate or the like that matches the shape is provided on the outer side and is fitted onto the top surface of the crown portion of the piston. 4 is integrated by soldering 5 between the metallized surface of the irregularly shaped ceramic molded body 1b and the cast iron body 2a using a silver-copper eutectic brazing agent. Fig. 6 shows that a buffer layer 4 such as a copper plate is provided on the cylindrical outer surface of an irregularly shaped ceramic molded body 1b whose cylindrical side surface is metallized, and the inside of this layer covers the metallized surface of the irregularly shaped ceramic molded body 1b, and the outer surface thereof is further covered with a buffer layer 4. The cast iron ring 6 to be provided is soldered using a silver-copper eutectic brazing agent, and after the surface of the cast iron ring 6 is subjected to Alfin treatment 7, they are integrally cast together with the aluminum alloy 2b that constitutes the piston body. The layers are chemically bonded and integrated using a waxing agent and Alfin treatment. FIG. 7 shows a shaped ceramic molded body 1b whose side and bottom surfaces are metallized, with a buffer layer 4 such as a copper-molybdenum-copper clad plate adjacent to the metallized part, and a U-shaped cast iron cap 6 on the outside thereof. 5 and solder each layer with silver-copper eutectic solder.
It has been integrated. Next, the outer surface of the cast iron cap 6 is subjected to Alfin treatment 7, and an aluminum alloy constituting the piston body 2b is cast around the outside of the cast iron cap 6, and the aluminum piston is chemically and firmly bonded between the two. . Fig. 8 shows that a buffer layer 4 of copper or Kovar plate or the like is provided on the cylindrical side surface of an irregularly shaped ceramic molded body 1b whose side surface is metallized, the depth of which is equal to the depth of the groove in the crown portion into which the ceramic molded body is fitted. The inside is integrated with the metallized surface of the ceramic molded body 1b, and the outside with the cast iron piston body 2a by soldering 5 using a silver-copper eutectic solder. Figure 9 is almost the same as Figure 8 above, but
In the figure, a buffer layer 4 such as a copper plate is provided on both the cylindrical side and bottom surfaces of the deformed ceramic, and both sides are soldered 5 using a silver-copper eutectic solder to be integrated.
Further, other parts that are the same as those in FIG. 8 are designated by the same reference numerals. As described above, the present invention involves fitting and integrating a ceramic molded body onto the top surface of the crown portion of a piston.
Utilizing the metal film (metallization) strongly formed on the ceramic surface, it is integrated with the outside by soldering, and if necessary, it can be made of copper or copper alloy, copper-based cladding material, iron/nickel 42 alloy, or We provide a piston that achieves integral connection by soldering through a buffer layer such as a Kovar plate that is easy to solder.Furthermore, in the case of aluminum alloy pistons, we provide a cast iron ring or a cast iron cap with a ceramic molded body. The inside is soldered using a silver-copper eutectic solder, and the outside is treated with Alfin, and then an aluminum alloy is cast as the piston body 2b, and the cast iron and aluminum alloy are joined with a chemical agent for Alfin treatment. The present invention provides an aluminum piston in which layers are firmly bonded. When we install these pistons in an actual engine and look at the required strength of the ceramic and piston body, we find that if the force acting on the ceramic is mainly the inertial force of the vertical movement of the piston, the required strength is 100 kg at 400°C. It was also confirmed in the sample of Example 1 that it is good if it is ² cm2 or more. Next, the most important point of the present invention is the use of a metalized ceramic molded body, and the ceramic used here is silicon nitride.
Materials with good heat resistance and strength, such as Si ₃ N ₄ , silicon carbide (SiC), and yttria-stabilized zirconia, are preferable. As a means for providing a metal layer on the surface, a vapor deposition method or an activated metal method is preferable, and these methods will be described in detail below. Example of A vapor deposition method 1 Group A of the periodic table (Ti, Zr, Hf) is applied to the surface of the ceramic molded body requiring vapor deposition by physical vapor deposition.
A first metal layer consisting of one or more selected from the following is provided, and one or more selected from Group B of the periodic table (Cu, Ag, Au) is formed on the first metal layer by physical vapor deposition or chemical plating. A second metal layer consisting of two or more types is provided to form a metal film, and a metallized ceramic molded body is obtained. Example 2 A ceramic material made of one or more members selected from Group A (Ti, Zr, Hf) or Group A (Cr, Mo, W) of the periodic table formed by physical vapor deposition on the surface of a ceramic molded body. A metal film is formed by providing one metal layer, and providing a second metal layer made of one or more metals selected from group B (Cu, Ag, Au) by physical vapor deposition or chemical plating. to obtain a metalized ceramic molded body. Example 3 Metal consisting of one or more selected from Group A (Cr, Mo, W) or Group B (Cu, Ag, Au) of the periodic table, formed by physical vapor deposition on the surface of a ceramic molded body. A film is formed to obtain a metallized ceramic molded body. Preferable ceramic materials for the present invention have already been mentioned, including those with excellent heat resistance and thermal shock resistance, but in addition to these materials, there are also alumina porcelain, mullite porcelain, zircon porcelain, etc., which can withstand use as a piston head. In that case, all ceramics can be applied. Next, the results of comparative tests made by preparing samples of Examples of the present invention and Comparative Examples will be shown. Example 1 Pressure-sintered silicon nitride with a porosity of 1% and a silicon nitride content of 90% was processed to form a ceramic molded body as shown in Figure 1, and the bottom surface was coated with 10 ^-6 torr by vacuum evaporation. After sequentially depositing Zr500Å and Cu5μ in vacuum, a Cu plate with a thickness of 1mm and a diameter of 50mm or a Cu(0.3)-Mo(0.4)
-Cu (0.3) clad material is interposed as an intermediate layer and fitted into the crown of the cast iron piston body, and the joint is brazed at 900℃ in a hydrogen furnace using silver and copper eutectic solder, as shown in Figure 2. I got a piston like this. Example 2 A piston as shown in FIG. 2 was obtained in the same manner as in Example using pressureless sintered silicon carbide having a porosity of 1% and a silicon carbide content of 0.5%. In order to measure the strength of the joint, a cast iron piston was machined and its tensile strength was measured. In addition, in order to investigate heat resistance and durability, we conducted a heating-cooling cycle test of 500 and 1000 cycles by directly roasting the ceramic part of the piston using a commercially available Bunsen burner, and the temperature of the joint at both times was the highest. The temperature was 400℃, the lowest was 300℃. In the comparative example, the ceramic was not metallized, a shrink-fitting allowance of 0.1 mm was taken, and the ceramic was attached to the crown of a cast iron piston and shrink-fitted at 500°C, and the burner test and tensile strength were measured in the same manner as described above. These results are shown in Table 1.

[Table] Example 3 A deformed ceramic molded body as shown in FIG. 3 was made using pressureless sintered silicon nitride having a porosity of 1% and a silicon nitride content of 90%, and its vertical outer surface was metallized. The conditions for metallization were the same as in Example 1.
A metalized irregular shaped ceramic was manufactured by sequentially depositing Ti1000Å, Cr1000Å, and Cu5μ. This metallized irregular shaped ceramic was fitted into the crown of a cast iron piston, a 0.5 mm thick Cu plate was interposed as a buffer layer, and the metallized ceramic was brazed at 900°C in a hydrogen furnace using a silver-copper eutectic solder. A cast iron piston as shown in Figure 4 was obtained. Similarly, a cast iron piston as shown in Fig. 5 was obtained by using deformed ceramics deposited and metallized on the side and bottom surfaces and brazing them at 900°C in a hydrogen furnace using silver-copper eutectic solder. Ta. Furthermore, using metallized irregular ceramics deposited on the side and bottom surfaces, a cast iron ring was brazed at 900°C in a hydrogen furnace using a silver-copper eutectic solder with a Kovar plate interposed. After the surface was subjected to alphite treatment, it was cast with aluminum alloy (AC8A) to obtain an aluminum piston as shown in Fig. 6. Example 4 Using ittria-stabilized zirconia with a porosity of 1% and a zirconia content of 90%, a piston as shown in FIGS. 4, 5, and 6 was produced in the same manner as in Example 3. Manufactured. These Examples 3 and 4
After conducting the same burner test as in Example 1 for the piston shown in 1, the piston was processed and the joint strength was measured. In a comparative example, a ceramic molded body made of Si ₃ N ₄ was wrapped in an aluminum alloy (AC8A) and a burner test was conducted, and then the bonding strength was measured. These results are shown in Table 2.

[Table] Established.
Next, a ceramic molded body was obtained by metallizing silicon nitride in the same manner as in Example 1, using a 1 mm thick Cu plate as an intermediate buffer layer, and bonding it with silver-copper eutectic solder to form a cast iron piston as shown in Figure 2. was obtained, and its hot strength was measured at 100°C, 300°C, and 500°C. The test results of the above examples and comparative examples show that the pistons of each example of the present invention are thermally stable up to 300°C, and have several orders of magnitude higher performance than pistons using conventional shrink-fitting or casting methods. It turned out to be excellent. In each of the above examples, group A of the periodic table (Ti, Zr,
Hf), A group metals (Cr, Mo, W) were selected for the first or second layer because they have good reactivity with the ceramic molded body, excellent adhesion, high bonding strength, and This is because the subsequent heat resistance is good. Moreover, the reason why Group B (Cu, Ag, Au) was selected for the outermost layer is that it has good wettability with various brazing agents, and good soldering can be obtained. Of course, group B comes first.
Even if a metal film is formed as a layer, it is recognized that the adhesion with ceramic is acceptable. In the present invention, the physical vapor deposition method refers to an ion beam method, a sputtering method, a resistance heating method, etc.
Although the thickness of the deposited film is limited by the vapor deposition equipment, it is preferably several thousand angstroms for the B group, and several hundred angstroms for the others. B. Activated metal method The activated metal method is an effective alternative to the vapor deposition method, and is achieved by the following method. (1) Ti or Zr on the surface of the ceramic molded body
At least one of Ag and Cu and foil are placed and heated at 800℃ to 1200℃ in a non-oxidizing atmosphere.
How to heat to ℃. (2) Place Ti foil or Zr foil and at least one type of solder foil among Ag and Cu on the surface of the ceramic molded body and heat it at 800℃ in a non-oxidizing atmosphere.
A method of heating and bonding at 1200℃. When a metallized layer is formed on a predetermined surface of a ceramic molded body using such a method, Ti or Zr diffuses into the ceramic and chemically combines with the oxygen and nitrogen atoms in the ceramic, resulting in a high degree of integrity. can be retained. Example 5 Pressure-sintered silicon nitride with a porosity of 1% and a silicon nitride content of 90% was processed as shown in Fig. 3, and a thickness of 0.05% of Ti 5%, Ag 69%, and Cu 26% by weight was formed on the side of the ceramic.
After installing the foil with a thickness of 10 mm, a Cu plate (0.5 mm thick) was installed, and then an Ag-Cu eutectic solder was placed between the cast iron pistons, and heated at 1000℃ in a vacuum of 10 ^-4 Torr.
After heating and bonding for 30 minutes, a cast iron piston as shown in FIG. 8 was obtained. Example 6 Ti-Ag-Cu foil, Cu plate, Ag-
A cast iron piston with a Cu eutectic solder and similar vacuum heat welding was obtained. After conducting the same burner test as in Example 1 for these, pistons were processed and their joint strength was measured. The results are shown in Table 3.

[Table] As can be seen from these results, a ceramic molded body with a strong metallized layer can be obtained by the activated metal method as well as by the vapor deposition method, so the various effects of the piston using this method are completely different from those by the vapor deposition method. There is nothing that will change.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing an example of a metalized ceramic molded body used in the present invention, FIG. 2 is a partial vertical cross-sectional view showing an example of the structure of a piston of the present invention using this, and FIG. FIGS. 4 to 9 are vertical cross-sectional views showing other examples of the metallized ceramic molded body used in the present invention, and FIGS. 4 to 9 are partial vertical cross-sectional views showing structural examples of the piston of the present invention using the same. . 1a: Metallized ring-shaped ceramic molded body, 1b: Metallized irregular shaped ceramic molded body, 1-m: Metallized part, 2a: Cast iron piston body, 2b: Aluminum alloy piston body,
3: Crown part, 4: Buffer layer, 5: Brazing, 6:
Cast iron ring, cast iron cap, 7: Alfin treatment.

Claims (1)

[Claims] 1. A ceramic molded body metallized by a vapor deposition method can be made of copper, copper alloy, copper/Mo/copper clad material,
A cast iron piston characterized by being brazed to a cast iron piston body through a buffer layer selected from copper/invar/copper clad material, iron/42% Ni alloy, or Kovar. 2 Ceramic molded bodies can be made into copper, copper alloy, copper/Mo/copper clad material, copper/invar/copper clad material, iron by using a mixed activated brazing filler metal of one or more of Ti and Zr and one or more of Ag and Cu. /42%Ni
A cast iron piston characterized in that it is brazed with a buffer layer selected from alloy or Kovar, and the buffer layer and the cast iron piston body are brazed with silver solder. 3 The ceramic molded body and the cast iron ring are made of copper, copper alloy, copper/Mo/copper clad material, copper/invar/
An aluminum piston characterized in that it is brazed by vapor deposition or active brazing material through a buffer layer selected from copper clad material, iron/42% Ni alloy, or Kovar, and is further cast in aluminum.