JPH0428767B2 - - Google Patents

Description

[Detailed description of the invention]

A. Purpose of the invention (1) Industrial field of application The present invention relates to a method for molding a reinforcing cylindrical fiber molded article, and in particular, to a method for molding a reinforcing cylindrical fiber molded article, and in particular, to a method for molding a reinforcing cylindrical fiber molded article, and in particular, to a method for molding a reinforcing cylindrical fiber molded article. The present invention relates to an improvement in a method for molding the fiber molded article by applying a suction action inside a shaped mold and causing a molding material to adhere to the outer peripheral surface of the mold. (2) Prior art Conventionally, as a molding method of this type, a method is known in which the molding material is stirred by rotating a stirring blade disposed in a tank (Japanese Patent Application Laid-Open No. 126357-1982).
(see publication). (3) Problems to be solved by the invention In the conventional method described above, in order to sufficiently stir the molding material, it is sufficient to increase the rotational speed of the stirring blade to form a spiral flow of the molding material. In this case, the molding material flows rapidly along the outer periphery of the molding die, resulting in poor adhesion of the molding material to the molding die, and the adhering molding material may be removed by the flow. Therefore, the production efficiency of fiber molded bodies is poor, and it is difficult to obtain fiber molded bodies having a uniform thickness. In view of the above, an object of the present invention is to provide the above-mentioned molding method which can improve the production efficiency of fiber molded bodies and obtain fiber molded bodies having a uniform thickness. B. Structure of the Invention (1) Means for Solving Problems The present invention provides a method for applying a suction action to an air-permeable cylindrical mold that is installed upright in a tank containing an aqueous solution of a molding material containing reinforcing fibers. , when attaching the molding material to the outer peripheral surface of the mold and molding the reinforcing cylindrical fiber molded article, rotation of the tank around the axis of the mold held immovably and the inner peripheral surface of the tank; or a plurality of rectifying plates disposed around the outer periphery of the mold, forming a turbulent flow of the molding material along the circumferential direction near the inner peripheral surface of the tank due to the stirring action of a plurality of stirring blades existing in the vicinity; The method is characterized in that the flow of the molding material collides with the flow of the molding material to convert the flow into a laminar flow toward the outer peripheral surface of the mold. (2) Effect By forming a turbulent flow of the molding material near the inner peripheral surface of the tank as described above, stagnation of the molding material at the inner bottom of the tank can be prevented. When the turbulent flow of molding material collides with each straightening plate, the flow velocity is weakened, and also because there is a suction effect inside the mold, the flow becomes laminar toward the outer circumferential surface of the mold. is converted to This improves the adhesion of the molding material to the mold,
Furthermore, the adhered molding material is hardly removed by the flow. (3) Example Figure 1 shows a reinforcing cylindrical fiber molded body 1 obtained through a molding process, a drying process, a firing process, etc. The fiber molded body 1 contains carbon fibers and carbon fibers as reinforcing fibers. Mixed short fibers of alumina fibers are partially bonded by silica sol, alumina sol, or a mixed sol thereof as an inorganic binder.
There are countless spaces into which the matrix can penetrate. This fiber molded body 1 is used, for example, in order to obtain a fiber-reinforced composite cylinder sleeve by combining it with an aluminum alloy matrix when casting an aluminum alloy cylinder block. In this case, the carbon fibers mainly contribute to improving the sliding characteristics of the inner circumferential surface of the cylinder sleeve due to their lubricating ability, and the alumina fibers mainly contribute to improving the strength around the cylinder bore. The fiber molded body 1 is obtained through the manufacturing process shown in FIG. In Figure 2a, the mold 2 is made of shell sand (grain size
It is formed into a breathable cylindrical shape using AFS35), and has the property of completely collapsing when heated to 330-480°C. First, the outer peripheral surface of the mold 2 is made of a thin film body that has air permeability and burns out at the collapse temperature of the mold 2;
For example, it is covered with a stockinette-knit stretchable thin fabric F made of 6-nylon and having a thickness of 0.10 mm. As shown in FIG. 2b, holders 3 ₁ and 3 ₂ are attached to the openings at both ends of the mold 2 by gluing, bolting, etc., and the openings are sealed. As shown in FIG. 2c, the mold 2 is set upright in a cylindrical tank 5 of the molding device 4 containing an aqueous solution of a molding material containing mixed short fibers of carbon fibers and alumina fibers, alumina sol, etc. The pump 6 applies suction into the mold 2 through the opening 7 of the holder ₃₂ , and the molding material is transferred to the mold 2 through the thin cloth F.
to a predetermined thickness on the outer peripheral surface of the fiber molded body 1.
to form. This molding operation using the water pump 6 is performed for approximately 2 minutes. As shown in FIG. 2d, the mold 2 is placed in a pressure container 8 of a rubber press, and pressurized air is supplied from an air pressure source 9 into the pressure container 8 to mold the fiber molded product 1 through the rubber 10. The outer peripheral surface of the mold 2 is pressed with a pressure of 10 kg/cm ² to adjust the shape of the fiber molded body 1 and at the same time determine the fiber volume fraction. In this case, the diameter of the mold 2 is slightly reduced by the pressing force, but since the thin fabric F follows the shrinking action due to its shrinking action, wrinkles do not occur in the thin fabric F. Roughening of the inner circumferential surface of the fiber molded body 1 due to transfer of wrinkles can be prevented. After the pressing force is released, the mold 2 is restored to its original state, but since the thin fabric F is stretched at this time, no problem occurs. As shown in Figure 2e, both holders are removed from the mold 2.
Remove 3 ₁ and 3 ₂ . As shown in FIG. 2f, the mold 2 is placed in a drying oven 11 kept in an air atmosphere,
A drying process is performed for 60 minutes at an oven temperature of 120°C to evaporate and remove moisture. During this heat drying process, the thin fabric F starts to burn out. Furthermore, the mold 2 expands, but the amount of expansion is absorbed by the void created by partially burning off the thin fabric F and the buffering effect of the remaining thin fabric F. No cracks will occur due to the expansion of item 2. As shown in Figure 2g, the mold 2 is placed in a firing furnace 12 maintained in an air atmosphere, and the mold 2 is subjected to a collapse treatment for 30 minutes at a furnace temperature of 450°C, and the temperature is increased. Thin cloth F is completely burned out in the process. The mold 2 collapses 100% by this collapse process. The mold 2 expands before collapsing, but the amount of expansion is absorbed by the void g generated as the thin fabric F is burned out, and as a result, cracks occur in the fiber molded product 1 in the same manner as described above. There's nothing to do. In addition, since the fiber molded body 1 is in contact with the mold 2 through the thin cloth F, the shell sand that is the constituent material of the mold 2 does not adhere to and remain on the fiber molded body 1 after the mold 2 collapses. As a result, the inner circumferential surface of the fiber molded body 1 becomes smooth. As shown in FIG. 2h, only the fiber molded body 1 is placed in a firing furnace 12 kept in an argon atmosphere, and the fiber molded body 1 is heated for 30 minutes at a furnace temperature of 800°C.
The mixed short fibers are partially bonded by the alumina sol by a calcination treatment for 1 minute. In this case, since the firing process is performed in an argon atmosphere, oxidation of the carbon fibers is avoided and their weight loss is prevented. Note that other inert gases may be used instead of argon. Next, the molding apparatus 4 used to carry out the molding method of the present invention will be described in detail with reference to FIGS. 3 and 4. The tank 5 containing the aqueous solution L of the molding material is open at the top and has a hollow shaft 13 on the outer surface of the bottom, and the hollow shaft 13 is connected to a hole 16 formed in the base 15 via a bearing 14. Supported by In order to erect the mold 2 in the tank 5, a hollow rod 18 with a mounting flange 17 at the upper end is attached to the hollow shaft 13.
It is inserted through the seal member 19. The hollow shaft portion 13 is connected to a drive source (not shown),
Further, the hollow rod 18 is fixed to the base 15 and its through hole 20 is connected to the water pump 6. The mold 2 has an opening 7 in one of the holders ₃₂ through the through hole 2.
0 and the mounting flange 17 of the hollow rod 18
Therefore, the mold 2 is held immovably within the tank 5, and the tank 5 is configured to be rotatable around the axis of the mold 2. On the outer periphery of the mold 2, a plurality of rectifying plates 21 extending in the axial direction and radial direction of the mold 2 are arranged at equal intervals in the circumferential direction. The upper end of each rectifying plate 21 is fixed to the annular ceiling surface of a cover 23 covering the tank 5 via an annular mounting plate 22, and the lower end of each rectifying plate 21 is arranged near the bottom of the tank 5. The cover 23 is fixed to the upper surface of the base 15 with a plurality of bolts 24, so that each rectifying plate 21 is immovably disposed around the outer periphery of the mold 2. Between the virtual circle C (FIG. 4) passing through the radially outer surface of the mold 2 of each rectifying plate 21 and the inner peripheral surface of the tank 5,
A plurality of rotating shafts 26 each having a plurality of stirring blades 25 ₁ in the axial direction are arranged along the circumferential direction of the tank 5 , and a motor 27 for driving each rotating shaft 26 is fixed to the top surface of the cover 23 . In forming the fiber molded body 1, for example, the tank 5 and each stirring blade ₂₅₁ are rotated clockwise in FIG. 4, and the water pump 6 is operated to apply suction into the mold 2. As a result, near the inner peripheral surface of the tank 5, the tank 5
The flow of the molding material becomes turbulent due to the rotation of the molding material and the stirring action of each stirring blade 25 ₁ , so that the molding material does not stagnate at the inner bottom of the tank 5 . When the flow of the molding material in a turbulent state collides with each rectifying plate 21, the flow velocity of the flow is weakened, and also because a suction action is applied within the mold 2,
The flow is converted into a laminar flow toward the outer peripheral surface of the mold 2 as shown by the arrow in FIG. This improves the adhesion of the molding material to the mold 2, and the adhered molding material is hardly removed by the flow. Therefore, the production efficiency of the fiber molded body 1 is improved, and the fiber molded body 1 having a uniform thickness can be obtained. Next, an example of the fiber molded body 1 will be described. (a) Preparation of aqueous solution L of molding material Reinforcing fibers with an average diameter of 18 μm and an average length
0.02-0.20% by weight of carbon fibers of 0.8 mm and 0.22-0.40% by weight of alumina fibers with an average diameter of 3-4 μm and an average length of 100-200 μm and 4-6% by weight of silica sol or alumina sol as an inorganic binder.
and 0.2% by weight of the antifoaming agent and surfactant in total, and 93.4 to 95.4% by weight of water (32). The calculated fiber concentration in the tank 5 of the molding material obtained in this way is 4.2 g/Kg.
It is. (b) Dimensions of mold 2 The upper outer diameter is 78 mm, the lower outer diameter is 74 mm, and the thickness is 5 mm. Using the aqueous solution L of the molding material and the mold 2, two types of fiber molded bodies 1 are molded by the apparatus 4 under the conditions shown in the table.

[Table] The fiber adhesion rate is determined from: Fiber adhesion rate=Amount of attached fibers/Amount of filtrated water x Fiber concentration x 100. Using the conventional method, the rotation speed of the stirring blade was set to 300,520 rpm.
Two types of fiber molded bodies were formed with the filtration water amount and fiber concentration approximately the same as above, and the fiber adhesion rate was determined. When the stirring blade rotation speed was 300 rpm, it was 94.3%, and the rotation rate was 94.3%. number
At 520 rpm, it was 91.8%, so it is clear that the fiber molded article obtained by the method of the present invention is superior in terms of fiber adhesion rate. The table shows the variation in fiber concentration around the outer periphery of the mold 2 surrounded by each rectifying plate 21 when the molding operation is performed under the conditions shown in the table (however, the tank rotation speed is 40 rpm).

【table】

[Table] As is clear from the table, the difference between the part with the highest fiber concentration and the part with the lowest fiber concentration is 0.02 g/Kg, which means that the fiber distribution on the outer periphery of the mold 2 is approximately uniform throughout. As a result, the thickness of the fiber molded body 1 can be made uniform. In the case of the conventional method, the above difference is 0.04 g/Kg, which is twice the above value. FIG. 5 shows another example of a molding apparatus for carrying out the molding method of the present invention, in which a plurality of stirring blades ₂₅₂ extending in the generatrix direction are provided on the inner peripheral surface of the tank 5 at equal intervals on the circumference. be. C. Effects of the Invention According to the present invention, as described above, the rotation of the tank,
Due to the stirring action of each stirring blade and the converting action of the flow of the molding material by each rectifying plate, the molding material can be sufficiently stirred and adhered to the outer circumferential surface of the mold efficiently and uniformly. The production efficiency can be improved and the thickness of the fiber molded article can be made uniform.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a fiber molded article, FIG. 2 is an explanatory diagram of the manufacturing process of the fiber molded article, FIG. 3 is a longitudinal sectional front view of a molding apparatus for carrying out the molding method of the present invention, and FIG. 4 is a third
5 is a sectional view showing another example of a molding apparatus used for carrying out the molding method of the present invention, and corresponds to FIG. 4. L...Aqueous solution of molding material, 2...Mold, 5...
... Tank, 6 ... Lifting pump, 21 ... Rectifier plate,
25 ₁ , 25 ₂ ... Stirring blade.

Claims (1)

[Claims] 1 A suction action is applied to an air-permeable cylindrical mold installed upright in a tank containing an aqueous solution of a molding material containing reinforcing fibers, and the molding material is adhered to the outer peripheral surface of the mold to form a reinforcing cylinder. When molding a fibrous molded product, the rotation of the tank around the axis of the immovably held mold and the stirring action of a plurality of stirring blades existing on or near the inner circumferential surface of the tank cause the inner circumferential surface of the tank to be A turbulent flow of the molding material is formed along the circumferential direction of the mold, and the flow of the molding material collides with a plurality of rectifying plates arranged around the outer periphery of the mold, so that the flow is directed around the mold. A method for forming a reinforcing cylindrical fiber molded body, characterized by converting the flow into a laminar flow toward the outer peripheral surface.