JPS6150130B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a combination of two members that come into contact with each other and slide relative to each other, and more specifically, the present invention relates to a combination of two members in which one member is made of a composite material and the other member is made of cast iron. It relates to a sliding member formed by combining. 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 in which various inorganic fibers are used as reinforcing materials and light metals such as aluminum alloys are used as a matrix. ing. As one such fiber-reinforced metal composite material, a fiber-reinforced metal composite material in which alumina fibers are used as a reinforcing material and aluminum, magnesium, or an alloy thereof is used as a matrix is already known. Accordingly, it is possible to improve the specific strength, abrasion resistance, etc. of a member made of them. However, in a combination of two 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 may As a result, 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 have proposed a fiber-reinforced metal composite material, which 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 alumina fibers as a reinforcement and a light metal such as an aluminum alloy as a matrix. In order to minimize the amount of wear on both parts in a combination of parts where the other part is made of cast iron, what is the composition and combination of materials? As a result of conducting various experimental studies on the suitability of these methods, it was found that each of them must have specific characteristics. The present invention is based on the knowledge obtained as a result of the above-mentioned experimental research conducted by the inventor of the present invention, and is based on the findings obtained from the above-mentioned experimental research conducted by the inventor of the present invention. It is a combination of two members that are in contact with each other and slide relatively, the other member being made of cast iron, and the resistance of the sliding surfaces of both members relative to each other is The object is to provide a combination of two parts with improved wear properties. According to the present invention, this object is achieved by providing a sliding member that is a combination of a first member and a second member that are in contact with each other and slide relative to each other, so that at least the first member of the first member The sliding surface for the second member is
It is composed of a composite material consisting of alumina of 80 wt% or more and silica as the balance, with an α-alumina content of 5 to 55 wt%, reinforced with alumina fibers, and an aluminum alloy or magnesium alloy as a matrix. This is achieved by a sliding member characterized in that at least the sliding surface portion of the second member relative to the first member is made of cast iron. According to the present invention, it is a combination of two 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 members in which the amount of wear on each sliding surface of the members can be minimized, and one of the members has excellent specific strength and rigidity. According to one detailed feature of the invention, the alumina fibers preferably have an alpha alumina content (ratio of alpha alumina weight to total alumina weight in the alumina fibers) of 10 to 45 wt%. According to another detailed feature of the invention,
The sliding surface of the second member relative to the first member is preferably treated with a phosphate film,
Moreover, it is preferable that the cast iron forming the sliding surface portion of the second member is spheroidal graphite cast iron. According to another detailed feature of the present invention, the other member is a piston ring, and the one member is an engine piston in which a ring groove portion for receiving the piston ring is made of a fiber-reinforced metal composite material. It's nice and warm. 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. Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. 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 fibers as a reinforcement and a light metal such as an aluminum alloy as a matrix. In a combination of members in which the other member is made of cast iron, the inventors conducted a wear test to determine the appropriate composition and material of each member. I will explain about it. α alumina content is 0wt%, 5wt%, respectively
Prepare 30wt%, 55wt%, and 65wt% alumina fibers (95wt% Al ₂ O ₃ , 5wt% iO ₂ ) with a fiber diameter of 3.0μ, and uniformly spread these five types of alumina fibers separately into colloidal silica. Disperse the fibers, form a fiber molded body of 80 x 80 x 20 mm using a vacuum forming method, and then bake this at 600°C to bond the individual reinforcing fibers with silica. is placed in the mold cavity of the mold, molten aluminum alloy (JIS standard AC8A) is placed in the mold cavity, and the molten metal is pressurized to a pressure of 1000 Kg/cm ² by a flange that fits into the mold. The state was maintained until the molten metal completely solidified, and the bulk density thus obtained was 0.15 g/
A composite material reinforced with randomly oriented alumina fibers in cm ³ is produced, which has dimensions of 16 x 6 x 10 mm by machining, with one side (16 mm x 10 mm) Five types of block test specimens were prepared using the following as the test surface. At the same time, for comparison,
A block test piece having the same dimensions as the above block test piece was prepared, which was made only of an aluminum alloy (JIS standard AC8A) that was not reinforced with fibers. 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.
was brought into contact with the outer circumferential surface of a cylindrical test piece made of spheroidal graphite cast iron (JIS standard FCD70), and while supplying high-temperature (150℃) lubricating oil (castle motor oil 5W-30) to the contact area of the test piece. , pressing force 60Kg, rotation speed
A wear test was conducted by rotating the cylindrical specimen for 1 hour at 160 rpm. The combinations of block test pieces and cylindrical test pieces in this wear test were as shown in Table 1 below.

【table】

[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 K correspond to test piece combinations A to K in Table 1 above. From FIG. 1, it can be seen that the block test pieces made only of aluminum alloy (GH and K) had a very large amount of wear, whereas the block test pieces made of aluminum alloy reinforced with reinforcing fibers (A~
Both FI and J) have a much smaller amount of wear compared to the block test pieces (GH and K) made only of aluminum alloy, especially the block test pieces (A~
It can be seen that the wear amount of E) is smaller than that of the block test piece (F), which is a cylindrical test piece plated with hard chrome. Regarding the wear of the cylindrical test piece as a mating material, the wear amount of the cylindrical test piece of combinations A, E, and F is larger than that of combinations G, H, and K, whereas the wear amount of the cylindrical test piece of combinations B and It can be seen that the wear amount of the cylindrical test pieces of C and D was suppressed to the same level as that of combinations G and H, or only slightly larger than that of combinations G and H. In addition, block test pieces were prepared using composite materials with alumina fibers of various α-alumina compositions consisting of 80 wt% or more of alumina and the balance of silica as reinforcement materials and magnesium alloy (ASTM standard EZ33A) as a matrix. In addition, cylindrical test pieces (both with and without phosphate film treatment) were made from gray cast iron (JIS standard FC25).
When a wear test was conducted in the same manner as the wear test described above, the results showed substantially the same tendency as shown in Figure 1 (however, the amount of wear on the cylindrical test piece in this case was slightly smaller than that on the spheroidal graphite cast iron). The test results showed that Table 2 is a table showing the combinations of test pieces in the test using the above magnesium alloy as a matrix in the same way as Table 1 for the test pieces using the aluminum alloy as the matrix. In this table, 1 to 5 are α as shown below.
It has alumina content. 1α alumina content 65wt% 2α alumina content 55wt% 3α alumina content 30wt% 4α alumina content 5wt% 5α alumina content 0wt% The results of the wear test are shown in Figure 6. In Figure 6, 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 cylindrical test piece, which is the mating material. The symbols A to K correspond to the test piece combinations A to K in Table 2, respectively.

【table】

[Table] From Figure 6, even when the matrix metal is a magnesium alloy, the wear amount of the block test piece and the wear amount of the cylindrical test piece are both greater than the wear amount in the previous wear test using aluminum alloy as the matrix. Although there is a slight increase overall, the characteristics of the change in wear amount with respect to the α-alumina content in the reinforcing fibers are consistent with the characteristics obtained in the previous wear test using an aluminum alloy as a matrix. be understood. 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,
In a combination of two members, one member is made of a composite material reinforced with alumina fibers and has an aluminum alloy or magnesium alloy matrix, and the other member is made of cast iron. , the composite material constituting the one member is composed of 80wt% or more alumina and the balance silica, and the alpha alumina content is 5 to 55wt%.
% alumina fiber as a reinforcing material and an aluminum alloy or a magnesium alloy as a matrix, and the cast iron constituting the other member is phosphoric acid coated cast iron, especially phosphoric acid coated spheroidal graphite. It turns out that cast iron is preferred. In addition, in the above two wear tests using aluminum alloy and magnesium alloy as matrix metals, the bulk density of alumina fiber in the composite material is assumed to be 0.15 g/ ^cm3 ; The influence of the α-alumina content in the alumina fibers thus obtained on the changes in the wear amount of the block test piece and the wear amount of the cylindrical test piece is not substantial depending on the change in the bulk density of the alumina fibers in the composite material. It is not affected by this. When a composite material reinforced with alumina fibers is rubbed together with a mating material, the hardness of the alumina fibers is higher than the hardness of the aluminum alloy or magnesium alloy that constitutes the matrix, so as the composite material wears out, the surface of the matrix becomes The alumina fibers will be somewhat protruding from the layer. As the composite material wears further, the height at which the alumina fibers protrude from the matrix layer further increases, but when that height reaches a certain point, the alumina fibers begin to act on the mating material when sliding together. The alumina fibers cannot withstand the bending moment and break, and the height at which the alumina fibers protrude from the matrix layer is reduced again. By repeating this phenomenon, the wear of the composite material and the mating material due to rubbing progresses, but the mechanism of wear that involves the repeated exposure and breakage of the alumina fibers is that the bulk density of the reinforcing fibers is the same as in the above example. When it is in the range of about 0.15g/cm ³ (approximately 4.5% in terms of volume ratio) to at most 1g/cm ³ (approximately 27% in terms of volume ratio), it is mostly influenced by the reinforcing fiber bulk density. Not done. This fact is demonstrated by the test results in Japanese Patent Application No. 191923/1983, which was filed on the same day as the present application by the same applicant as the present application. Therefore, when manufacturing composite materials by reinforcing aluminum alloys or magnesium alloys with alumina fibers, within the range of fiber mixing ratios of several percent to more than ten percent by volume, The preferred range of conditions for the alpha alumina content of is independent of fiber content. 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. In these figures, 1 is the 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 that receive compression rings 4 and 5 that prevent combustion gases from leaking out of the combustion chamber of the engine through the space between the piston 1 and the cylinder wall of the cylinder block 3. ring groove 6
and 7, and an oil ring 8 for scraping off excess oil.
A ring groove 9 is formed to receive the ring groove. In the illustrated embodiment, the portion from the piston head 10 along the side outer circumferential surface 2 of the piston 1 to below the lower surface 11 of the top ring groove 6 has a fiber diameter of 3.0μ, α
Alumina fiber with alumina content of 30wt% (95wt%)
Al ₂ O ₃ , 5wt% SiO ₂ ) randomly oriented with a bulk density of 0.15 g/cm ³ is used as a reinforcing material, and an aluminum alloy (JIS standard AC8A ) is made of a composite material 12 having 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 in the portion exposed to the side outer peripheral surface 2 of the piston. ing. 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) and has been subjected to Reublat treatment as a surface treatment. 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 piston and piston ring configured as described above (corresponding to combination C in Table 1 above), and the piston and piston ring configured in combinations A, E to H in Table 1 above, are used in a 4 cylinder 4 cylinder. It was installed in a cycle diesel engine, and an actual wear test was conducted under the test conditions shown in Table 3 below. Table 3: 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: 5200 rpm Engine load: Full load test time: 500 hours Figure 5 shows the results of the wear test using this actual machine. In Fig. 5, the upper half and the lower half represent the wear amount (wear scar depth μ) of the top ring groove lower surface 11 and the top ring lower surface 17, respectively.
Symbols A, C, E, FG, and H are shown in Table 1 above, respectively.
It corresponds to the combinations AC, E, F, G, and H in . From FIG. 5, in the case of combinations A, C, E, and F, the amount of wear is smaller on the lower surface 11 of the top ring groove of the piston and the lower surface 17 of the top ring than in the case of combination H, and especially in combination C of the present invention, the amount of wear is smaller. It can be seen that in this case, the amount of wear on the lower surface of the ring groove and the lower surface of the piston ring is smaller than in any combination. Furthermore, the oil consumption and blow-by gas amount in the case of combination C of the present invention were stable and lower than in any other combination. 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, and FIG. 6 is a graph similar to FIG. 1 in the case where the matrix is a magnesium alloy. DESCRIPTION OF SYMBOLS 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... Bottom surface of top ring groove, 1
2... Composite material, 13... Top land, 14... Second land, 15... Molybdenum sprayed layer, 16... Top surface of top ring groove, 17... Bottom surface of top ring.

Claims (1)

[Claims] 1. A sliding member formed by combining a first member and a second member that abut each other and slide relatively,
The sliding surface of the first member relative to at least the second member is composed of 80 wt% or more of alumina and the balance of silica, and has an α-alumina content of 5 to 5%.
It is made of a composite material having 55wt% alumina fiber as a reinforcement material and an aluminum alloy or a magnesium alloy as a matrix, and at least the sliding surface portion of the second member relative to the first member is made of cast iron. A sliding member characterized by: 2. The sliding member according to claim 1,
The alpha alumina content of the alumina fiber is 10~
A sliding member characterized by having a content of 45wt%. 3. The sliding member according to claim 1 or 2, wherein the sliding surface of the second member relative to the first member is treated with a phosphate coating. Element. 4. The sliding member according to any one of claims 1 to 3, wherein the first member is an engine piston and the second member is a piston ring. Moving parts.