JPS6229499B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a combination of two sliding members that abut each other and slide relative to each other, and more specifically, one member is made of a composite material and the other member is made of a hard chrome-plated metal. The present invention relates to a combination of two sliding members. Components and members of various machines often require special mechanical properties. For example, in automobile engines, as demands for engine performance become higher, members such as pistons not only have excellent specific strength and rigidity, but also require that their sliding surfaces have excellent wear resistance. It has become a strong requirement to be present. As a means of improving the specific strength and abrasion resistance of such members, attempts have been made to construct them from composite materials made of various inorganic fibers as reinforcements and light metals such as aluminum alloys as a matrix. ing. As one such fiber-reinforced metal composite material,
Fiber-reinforced metal composite materials that use alumina fibers as reinforcement and aluminum, magnesium, or their alloys as a matrix are already known.
According to such fiber-reinforced metal composite materials, it is possible to improve the specific strength, abrasion resistance, etc. of members made of the fiber-reinforced metal composite materials. However, in a combination of two sliding members that are in contact with each other and slide relative to each other, if one of the members is made of a fiber-reinforced metal composite material as described above, the material of the other member In some cases, the wear of the other member increases significantly, so that they cannot be used as a combination of sliding members that abut and slide relative to each other. The present inventors proposed a combination of two members that come into contact with each other and slide relative to each other, one of which has alumina-silica fibers or alumina fibers as a reinforcing material and a light metal such as an aluminum alloy as a matrix. In combinations of parts made of fiber-reinforced metal composite material and the other part made of metal such as cast iron or hard chromium-plated metal, the amount of wear on both parts can be minimized. As a result of various experimental studies on the appropriate combination of these compositions and materials, it was determined that each must have a specific composition and specific material in order to suppress the I found it. The present invention is based on the knowledge obtained as a result of the above-mentioned experimental research conducted by the inventors of the present invention, and the present invention is based on the findings obtained from the above-mentioned experimental research conducted by the inventors of the present invention. A combination of two members made of a metal composite material and the other member made of hard chrome-plated metal, which abut each other and slide relative to each other. It is an object of the present invention to provide a combination of two sliding members with improved wear resistance on the sliding surfaces relative to the other. According to the present invention, this object is achieved by combining a first member and a second member that are in contact with each other and sliding relative to each other, so that the sliding movement of the first member with respect to at least the second member is achieved. The surface part is made of a composite material, which is reinforced with alumina-silica fibers made of 40 to 65 wt% alumina and the balance is silica, and whose matrix is a metal selected from the group consisting of aluminum, magnesium, and their alloys. This is achieved by a combination of sliding members characterized in that at least the sliding surface of the second member relative to the first member is made of hard chromium-plated metal. According to the present invention, it is a combination of two sliding members that are in contact with each other and slide relative to each other, and the sliding surfaces of both members relative to each other have excellent wear resistance. It is possible to obtain a combination of sliding members in which the amount of wear on the respective sliding surfaces of both members can be minimized, and one of the members has excellent specific strength and rigidity. . According to one detailed feature of the invention, the other member is a piston ring, and the one member is an engine piston in which a ring groove for receiving the piston ring is made of a fiber-reinforced metal composite material. It's fine. According to such a combination of a piston and a piston ring, the amount of wear on both the piston ring groove wall surface and the piston ring upper and lower surfaces can be minimized, thereby ensuring normal operation of the engine over a long period of time. can. DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures. First, it is a combination of two members that come into contact with each other and slide relative to each other, one of which is made of a fiber-reinforced metal composite material with alumina-silica fibers as a reinforcement and a light metal such as an aluminum alloy as a matrix. In a combination of parts where the other part is made of metal such as cast iron or metal plated with hard chrome, what is the appropriate composition and material of each part? A wear test conducted by the inventors of the present application will be explained to see if there is any. Alumina-silica fiber (55wt%) with a fiber diameter of 2.8μ
Producing a composite material in which a randomly oriented fiber molded body (Al ₂ O ₃ , 45 wt% SiO ₂ ) with a bulk density of 0.16 g/cm ³ is used as a reinforcing material, and an aluminum alloy (JIS standard AC8A) is used as aluminum, Size is 16 x 6 x 10mm
A block test piece was prepared using one surface (16 mm x 10 mm) as the test surface. For comparison, alumina fiber with a fiber diameter of 3.0μ (95wt%
Composite materials made of randomly oriented fiber molded bodies (Al ₂ O ₃ , 5wt% SiO ₂ ) with a bulk density of 0.16 g/cm ³ as reinforcement materials and aluminum alloy (JIS standard AC8A) as a matrix, and fibers. A block test piece with the same dimensions as the above-mentioned block test piece was prepared from only an unreinforced aluminum alloy (JIS standard AC8A). These test pieces were sequentially set in a friction and wear tester, and the mating parts were 35 mm in outer diameter, 30 mm in inner diameter, and 10 mm in width.
of spheroidal graphite cast iron (JIS standard FCD70).
-30), pressing force 60Kg, rotation speed
A wear test was conducted by rotating the cylindrical specimen for 1 hour at 160 rpm. In this wear test, two types of cylindrical test pieces were prepared, one with hard chrome plating and one without, and tests were conducted on combinations A to D of block test pieces and cylindrical test pieces shown in Table 1 below. Summer.

[Table] Figure 1 shows the results of the above wear test. Furthermore, the first
In the figure, the upper half represents the wear amount (wear scar depth μ) of the block test piece, and the lower half represents the wear amount (wear loss mg) of the mating cylindrical test piece. A to D correspond to test piece combinations A to D in Table 1 above, respectively. From FIG. 1, it can be seen that block test piece D made only of aluminum alloy has a very large amount of wear, while block test pieces A to C made of aluminum alloy reinforced with reinforcing fibers are all made of aluminum alloy. It can be seen that the amount of wear is much smaller than that of the block test piece D made of solid wood. Regarding the wear of the cylindrical test piece as a mating material, the wear amount of the cylindrical test pieces of combinations B and C is larger than that of the cylindrical test piece of combination D, whereas the wear amount of the cylindrical test piece of combination A is It can be seen that it is smaller than in cases B to D. In addition, block test pieces were prepared using composite materials with alumina-silica fibers of various compositions consisting of 40 to 65 wt% alumina and the balance silica as reinforcement materials, and aluminum, magnesium, and magnesium alloy as a matrix. In addition, cylindrical test pieces were made from various cast irons such as black core malleable cast iron.
When a wear test similar to the above-mentioned wear test was conducted, test results showing substantially the same tendency as the results shown in FIG. 1 were obtained. From the results of these wear tests, it was found that the combination of two members that come into contact with each other and slide relative to each other,
A combination of two members, where one member is made of a composite material with alumina-silica fiber as a reinforcement and a light metal such as an aluminum alloy as a matrix, and the other member is made of cast iron. In this case, the composite material constituting the one member is reinforced with alumina-silica fibers consisting of 40 to 65 wt% alumina and the balance silica, and is selected from the group consisting of aluminum, magnesium, and alloys thereof. It is understood that the sliding surface of the cast iron constituting the other member is preferably plated with hard chromium. Next, a specific example of a combination of members according to the present invention applied to a combination of an engine piston and a piston ring will be described. FIG. 2 is an illustrative longitudinal sectional view showing the above-mentioned embodiment;
FIG. 3 is an illustrative enlarged partial longitudinal sectional view showing the main parts thereof, and FIG. 4 is an illustrative partial longitudinal sectional view showing an enlarged piston ring (top ring). In these figures, 1 is a piston, which is made of aluminum alloy (JIS standard AC8A). The side outer circumferential surface 2 of the piston 1 has two compression rings 4 and 5 for receiving compression rings 4 and 5 that prevent combustion gases from leaking from the combustion chamber of the engine through the space between the piston 1 and the cylinder wall surface of the cylinder block 3. Ring grooves 6 and 7 and a ring groove 9 for receiving an oil ring 8 for scraping off excess oil are formed. In the illustrated embodiment, the portion from the piston ring 10 along the side outer peripheral surface 2 of the piston 1 to below the bottom surface 11 of the top ring groove 6 is made of alumina-silica fiber (55wt%) with a fiber diameter of 3 μm.
A fiber molded body made of randomly oriented Al ₂ O ₃ , 45 wt% SiO ₂ ) with a bulk density of 0.14 g/cm ³ is used as a reinforcement material,
The other parts of the piston 1 are made of a composite material 12 having an aluminum alloy (JIS standard AC8A) as a matrix. This composite material 12
defines the wall surface of the top ring groove 6 that receives the top ring 4, and also defines a part of the top land 13 and second land 14 at the portion exposed to the side outer circumferential surface 2 of the piston. In addition, such a piston is made by placing a fiber molded body on the bottom wall of a mold cavity of a mold for casting the piston, pouring molten aluminum alloy into the mold, and fitting the piston into the mold in a fluid-tight manner. The aluminum alloy is solidified while being pressurized by a plunger to form a piston preform, which is heat treated (T6 treatment) and then machined to a predetermined size.
9. The top ring 4, which contacts and slides relative to the piston 1 as described above, is made of spheroidal graphite cast iron (JIS standard FCD70). In particular, the illustrated embodiment is configured as a 7° keystone ring, and a molybdenum sprayed layer 15 is formed on the sliding surface of the cylinder block 3 with the cylinder wall surface. The pistons and piston rings configured as described above and the pistons and piston rings configured in combinations B to D in Table 1 above were assembled into a 4-cylinder 4-stroke diesel engine, and the test conditions shown in Table 2 below were applied. We conducted a wear test using an actual machine. Table 2: Test conditions Engine used: 4-cylinder 4-cycle diesel engine Cylinder bore diameter: 90mm Stroke: 86mm Compression ratio: 21.5 Displacement: 2188c.c. Cylinder material: Gray cast iron (JIS standard FC25) Fuel used: Light oil Engine speed: 5200rpm Engine load: Full load Test time: 500 hours Figure 5 shows the results of the wear test using this actual machine. From FIG. 5, it can be seen that the combination of the piston and piston ring according to the above-mentioned embodiment is more effective than the lower surface 11 of the top ring groove 6 of the piston and the lower surface 17 of the top ring 4 than any of the other three combinations.
The amount of wear can be kept small, especially when using aluminum alloys (JIS standard), which are currently widely used.
Compared to the combination of a piston made of AC8A) and a cast iron piston ring or a cast iron piston ring with a chrome-plated bottom surface, the amount of wear on the bottom surface of the ring groove is reduced to 1/8, and the amount of wear on the bottom surface of the piston ring is reduced to 1/8. It can be seen that the amount of wear is also reduced to 1/4. Furthermore, when we conducted wear tests similar to the wear test using the actual machine described above while varying the alumina composition of the alumina-silica fibers in the composite material, we found that when the alumina composition value was 65wt% or more, the bottom surface of the top In addition, if the alumina composition value is less than 40wt%, the amount of wear on the bottom surface of the top spring groove will increase, and the effect of reinforcing the aluminum alloy with alumina-silica fibers may not be obtained. Admitted. From this, alumina-silica fibers are used as reinforcing fibers for composite materials.
It can be seen that a material consisting of 65 wt% alumina and the balance silica is preferred. Although the present invention has been described above in detail with respect to one embodiment applied to a combination of a piston and a piston ring, the present invention is not limited to such an embodiment. It will be appreciated that other combinations of sliding members are also applicable.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the results of a wear test conducted by the inventors of the present application, and Fig. 2 is an illustration showing an example of a combination of members according to the present invention applied to a combination of a piston and a piston ring. Fig. 3 is a schematic enlarged partial longitudinal sectional view showing the main parts of the embodiment shown in Fig. 2; Fig. 4 is an enlarged diagram showing the piston ring (top ring). FIG. 5 is a graph showing the results of a wear test using an actual machine. 1...Piston, 2...Side outer peripheral surface, 3...Cylinder liner, 4...Top ring, 5...Second ring, 6...Top ring groove, 7...Second ring groove, 8...Oil ring , 9... Ring groove, 10... Piston head, 11... Lower surface of top ring groove, 12... Composite material, 13... Top land, 14... Second land, 15...
Molybdenum sprayed layer, 16...upper surface of the top ring groove, 17... lower surface of the top ring.

Claims (1)

[Scope of Claims] 1. A combination of a first member and a second member that are in contact with each other and slide relative to each other, and at least a sliding surface portion of the first member with respect to the second member is
It is composed of a composite material made of 40 to 65 wt% alumina and the balance silica, reinforced with alumina-silica fibers, and a matrix of metals selected from the group consisting of aluminum, magnesium, and their alloys. A combination of sliding members, characterized in that at least a sliding surface of the second member relative to the first member is made of hard chromium-plated metal. 2. The combination of sliding members according to claim 1, wherein the first member is an engine piston, and the second member is a piston ring. .