JPH0134683Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a piston having a wear-resistant ring made of a composite material inserted therein. For example, pistons made of aluminum alloy or the like used in vehicle engines, particularly pistons for diesel engines, suffer from particularly severe wear at the tip of the piston because the combustion chamber reaches high temperature and pressure during operation. Therefore, the ring-shaped wear ring used at the tip of the piston must be made of a material that has excellent wear resistance and thermal conductivity, has a small coefficient of thermal expansion, and has high high temperature strength and fatigue strength. Conventionally, for aluminum alloy pistons,
As a wear-resistant ring for reducing wear at the tip, a cast iron wear-resistant ring (Niresto) is known, and this wear-resistant ring is cast around the tip of the piston, but it has the following drawbacks: It was hot. Cast iron wear rings and piston rings (coefficient of thermal expansion
11.5 to 12.0×10 ^-6 /°C), there is a large difference in the coefficient of thermal expansion, so a large clearance tends to occur between the two. Cast iron wear rings have poor thermal conductivity, so if the piston temperature rises, the piston strength and thermal fatigue strength will decrease, and if the dimensions of the wear ring increase due to thermal expansion, it will be necessary to increase the clearance with the liner. , noise is likely to be generated, and seizure with the liner is likely to occur. Poor wear resistance. Because the cast iron wear-resistant ring and the aluminum alloy piston body have poor adhesion, Alfin treatment (surface treatment) is required, and when the piston is subjected to solution treatment, the boundary between the piston body and the wear-resistant ring is Cracks occur in the parts, resulting in poor yield. Also, pistons in which a composite wear ring is attached to an aluminum alloy piston body are known, but such pistons have the following drawbacks. This is made by press-fitting molten Al into reinforcing materials such as Al ₂ O ₃ fibers under high pressure, so there is no
It is difficult to fill the Al alloy uniformly, and special molding methods such as creating a vacuum atmosphere are required. When the cross-sectional shape of a composite wear ring made of an Al alloy and a reinforcing material is simply U-shaped, the mechanical bonding force between the wear ring and the piston body is weak. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a piston with a wear-resistant ring that overcomes the above-mentioned drawbacks of the conventional piston. The present invention will be explained in detail below based on FIGS. 1 and 2. As shown in the figure, the piston has a ring-shaped composite wear-resistant ring 3 with a substantially horizontal T-shaped cross section inserted into a top ring groove 2 provided around the tip of the piston body 1, made of cast aluminum alloy, magnesium alloy, or the like. It is made up of cast iron. The wear-resistant ring 3 includes SiC, Al ₂ O ₃ , carbon,
Granular powder with a particle size of 2 to 100μ selected from Si ₃ N ₄ , SiO ₂ , stainless steel, boron, etc., length of 0.2 to 0.155μ
Whiskers of 50 to 300μ, or wire diameter of 2 to 100μ,
Short fibers with a length of 0.5 to 5 mm for JIS die casting
5-30wt% in molten light alloy for casting such as ADC10 alloy
The aluminum base composite material added and stirred is molded by die-casting, but the wear-resistant ring 3 can be formed by molding methods other than the above-mentioned die-casting, such as die casting, molten metal forging, low-pressure casting, or low-speed casting. It is also possible to use a molded product. Further, as described above, the wear ring 3 has a substantially horizontal T-shaped cross section, that is, a vertical plate portion 3a, and a horizontal plate portion 3b extending outward from the center of the vertical plate portion 3a at a substantially right angle. The horizontal plate portion 3b is integrally formed with an outward ring groove 3c in the center thereof. Then, the wear ring 3 is inserted and set in the mold cavity corresponding to the top ring groove 2 of the piston body 1, and the piston body 1 is made of AC8A alloy for JIS Al casting, AC8B alloy, etc. 3 and are integrally molded by casting. With this structure, the wear-resistant ring 3 cast into the top ring groove 2 is formed in the piston body 1 due to thermal expansion or contraction that occurs when the temperature changes.
The wear-resistant ring 3 is mechanically clamped and held by the piston body 1 by forces in opposite directions that press the upper and lower ends of the vertical plate portion 3a from inside and outside, respectively, and the piston body 1 and the wear-resistant ring 3 are The generation of gaps between the two is prevented. Furthermore, since the matrix alloy of the wear-resistant ring 3 and the material of the piston body 1 are of the same type of Al alloy, a strong bonding layer is formed at the interface between the wear-resistant ring 3 and the piston body 1 by welding. Next, an example in which the piston of the present invention was actually manufactured will be described. <Example> 15wt% of SiC powder with a diameter of around 100μ was added to the molten metal of ADC10 alloy kept at 650°C to 750°C, stirred and mixed for 20 minutes, and then the casting pressure ( Gauge pressure) 150Kg/cm ² (pressure on metal 1000Kg/cm ² ), casting plunger speed 1.2m/sec, casting temperature 750℃, mold temperature 200℃~
Casting was performed at 250℃. We obtained a wear-resistant ring made of Al-based composite material that has good dimensional accuracy due to die-casting and can be used as a filler in the as-cast state. Next, this wear ring was preheated to room temperature or 250°C, and then set as a filler metal in a mold, and the piston body 1 was formed using molten AC8A alloy under normal die casting conditions. Note that other molding methods such as die casting, molten metal forging, low pressure casting, or low speed casting are also possible. Table 1 shows the general properties of the composite wear ring formed in this manner in comparison with the AC8A alloy that forms the piston body.

[Table] Oil From Table 1, the wear-resistant ring of the present invention has an appropriate thermal expansion coefficient, excellent wear resistance, and high strength under high temperatures. Next, Table 2 shows the measured values of the coefficient of thermal expansion, which is a characteristic of the wear-resistant ring of the present invention, in the operating temperature range in comparison with that of ADC10 alloy.

[Table] The cross-section of the wear-resistant ring of the present invention is approximately T-shaped, and from the measured values in Table 2, the coefficient of thermal expansion is smaller than that of a cast iron wear-resistant ring in the operating temperature range, so the diameter increases as the temperature rises. Since a tightening force acts on the wear ring 3 from the outer circumferential portion 1a of the piston body 1, the coupling force between the piston body 1 and the wear ring 3 becomes strong. As explained above, according to the piston with a composite wear-resistant ring according to the present invention, reinforcing materials such as SiC, Al ₂ O ₃ , etc.
Using a material added to a molten metal of the same type as the piston body 1 and stirred, a wear ring 3 is formed into a substantially horizontal T-shape in cross section by die casting or the like, and the wear ring 3 is attached to the tip of the piston body 1. Since the wear-resistant ring 3 is integrally molded with casting aluminum alloy or the like, the cross section of the wear-resistant ring 3 is approximately horizontally T.
The piston body 1 and the wear ring 3 have a strong mechanical connection, and the piston body 1 and the wear ring 3 have a small thermal expansion coefficient.
The matrix alloy and the material of the piston body 1 are of the same type, and by adding the above-mentioned reinforcing material to the molten light alloy for casting and stirring and mixing, the reinforcing material is uniformly distributed in the alloy. Then,
Since both have a strong metallurgical bond, the bond between the two is stronger than that of conventional products, so even when operated for long periods of time at high temperatures, they are always held tightly and no clearance occurs, and the wear-resistant ring 3 is Since products with excellent wear resistance, high temperature strength, and high dimensional accuracy can be mass-produced by die-casting, machining can be omitted. Due to the strong bonding, the conventionally required Alphin treatment can be omitted, resulting in excellent productivity and cost reduction.Furthermore, it is lighter than conventional products, so it can be used not only for low-speed engines but also for high-speed engines. It can also be applied to commercial engines, and has the effect of improving engine performance.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view showing an example of a piston with a composite wear ring according to the present invention, and FIG. 2 is a perspective view showing a composite wear ring in the same piston. 1... Piston body, 2... Top spring groove, 3... Wear-resistant ring.

Claims (1)

[Scope of utility model registration request] A wear-resistant ring 3 is made of a material obtained by adding reinforcing materials such as SiC, Al ₂ O _3, etc. to a molten metal of the same type as the piston body 1 and stirring it. A piston with a wear-resistant ring made of a composite material, characterized in that it is integrally formed by casting an aluminum alloy or the like into the tip of a body 1.