JP2013141826A - Method of manufacturing fiber substrate and method of manufacturing resin rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a fiber substrate which enables continuous manufacturing with less variation in short fiber quantity among products, while preventing damage to a metal mold.SOLUTION: A method of stacking short fibers in a cylindrical metal mold by preparing slurry which is formed by dispersing the short fibers in dispersion media, supplying the slurry in the cylindrical metal mold, and discharging the dispersion media from the cylindrical metal mold. The manufacturing process includes: (a) a step of supplying the slurry from above of the cylindrical metal mold toward a slurry dispersion pin of a circular cone or pyramid shape with a sharp tip and arranged in the center of the cylindrical metal mold; (b) a step of removing the short fiber attached to the slurry dispersion pin by pouring the same dispersion media or water toward the slurry dispersion pin from above after the (a) step, and (c) a step of discharging the dispersion media from the cylindrical metal mold and stacking the short fibers in the cylindrical metal mold to produce a fiber aggregate.

Description

  The present invention relates to a method for producing a fiber substrate by paper making means and a method for producing a resin rotating body using the fiber substrate by the above-described production method.

A resin rotating body constituted by holding a resin on a fiber base material has excellent durability performance, and is suitably used as a material for resin gears used for vehicle parts, industrial parts and the like.
As a fiber base material for producing a resin gear, there is a fiber base material in which a tubular body in which yarn is woven or knitted is turned into a donut shape while being turned over from an end portion. It is described in. Patent Document 1 also describes a resin gear in which the fiber base material is impregnated and held to form a tooth portion.
Furthermore, in Patent Document 1, in order to improve the bonding strength between the fiber base material and the retaining member provided on the metal bush, two fiber base materials are interposed between the metal bushes in the molding die. It is described that two layers are stacked.

Unlike the doughnut-shaped fiber substrate described above, a sheet made from a thermosetting resin and short fibers is punched out, and a plurality of sheet-shaped sheets are laminated and heated in a molding die. A method for manufacturing a resin gear to be pressure-molded is described in Patent Document 2.
The resin gears described in Patent Documents 1 and 2 have almost no fiber entanglement at the overlapping interface of the two fiber base materials or the laminated interface of the paper sheet body, and depending on the intended use, it is peeled off on the laminated surface. There is a problem that is likely to occur.
There is also a problem that the bonding strength between the fiber base and the metal bush is insufficient. For these reasons, depending on the application, there is a concern that the durability of the resin gear is insufficient.

In order to solve these problems, it has also been proposed to make an assembly of short fibers using short fibers with a paper mold.
Patent Document 3 discloses a manufacturing method in which a mixed slurry of short fibers and thermosetting resin is pressurized or dehydrated in a water-permeable mold to obtain an aggregate of short fibers and thermosetting resin. Yes.
However, a thermosetting resin that can be dispersed in water has low fluidity and insufficient wettability at the interface between the thermosetting resin and the fiber, so that durability that can withstand practical use cannot be obtained.

Further, Patent Document 4 discloses a method for producing a fiber-reinforced resin composite by filling a short fiber with a molding die having a fluid outlet and further performing resin injection for heating and pressurization with the same die. Has been.
However, in this method, it is difficult to dispose a metal bush at the center of the resin rotating body, and the injected resin leaks to the entire molding die made of a metal mesh or the like, and the molded product can be taken out after curing. In addition to being difficult, the molding die is clogged, which makes it difficult to use it repeatedly (continuous production).

Patent Document 5 discloses a resin gear manufacturing method in which a fiber base material seamlessly formed into a cylindrical shape obtained by a papermaking method as a collection of short fibers is heat-pressed in a molding die. Has been.
However, this Patent Document 5 does not disclose any method for improving the bonding strength between the fiber base material and the metal bush.

In order to solve the problems of Patent Documents 3 to 5 described above, a fiber assembly is manufactured by collecting short fibers around the outer periphery of a metal bush by a papermaking method and surrounding the outer periphery of the bush. Patent Document 6 discloses a method in which a body is compressed by driving a press from the vertical direction, which is the axial direction of the rotation axis, and the fiber substrate is manufactured using the same mold and apparatus.
With such a method, since the thermosetting resin is impregnated after the paper making without using the thermosetting resin at the time of paper making, there is no problem with wetting at the resin and fiber interface, and the central part of the resin rotating body In addition, the metal bush can be easily arranged, there is no fear of resin leakage, and the bonding strength between the fiber base and the metal bush can be improved.

JP 2001-295913 A JP-A-11-227061 Japanese Patent Laid-Open No. 2001-1413 JP 2005-96173 A JP 2007-138146 A JP 2011-152729 A

  However, what is described in Patent Document 6 is to inject liquid while applying a slurry to a member called "upper support base", there is a possibility that short fibers remain in this "upper support base", If it remains, there is a problem that the amount of short fibers per product varies. Furthermore, when the fiber assembly is compressed, there is a problem that the base material bites the short fibers into the gaps between the mold members, damages the mold, and the continuous production cannot be performed.

An object of this invention is to provide the manufacturing method of the fiber base material which has few dispersion | variation in the amount of short fibers of a product, and can perform continuous production without metal mold | die damage.
Moreover, it aims at providing the manufacturing method of the resin-made rotary body which made the fiber base material impregnate and harden, and the resin-made rotary body manufactured by this manufacturing method.

(1) A slurry in which short fibers are dispersed in a dispersion medium is prepared, and the short fibers are accumulated in the cylindrical mold by introducing the slurry into the cylindrical mold and discharging the dispersion medium from the cylindrical mold. A method of manufacturing a fiber base material manufactured by the following steps.
(A) A step of throwing slurry into the cylindrical mold from above toward a slurry diffusion pin having a conical or pyramid shape that is arranged at the center of the cylindrical mold and has a sharp top.
(B) After the step (a), a step of pouring the same dispersion medium or water as the dispersion medium from above toward the slurry diffusion pin to drop the short fibers attached to the slurry diffusion pin.
(C) A step of discharging the dispersion medium from the cylindrical mold to form a fiber assembly in which short fibers are accumulated in the cylindrical mold.
(2) The method for producing a fiber base material according to item (1), wherein (c) a step of compressing the fiber aggregate is further performed during or after the dispersion medium is discharged.
(3) The method for producing a fiber substrate according to item (1) or (2), wherein (c) the dispersion medium is discharged in a reduced-pressure atmosphere.
(4) The method for producing a fiber substrate according to item (2) or (3), wherein (d) the step of compressing the fiber assembly is performed while applying heat.
(5) The method for producing a fiber base material according to any one of items (1) to (4), wherein the fiber assembly is imparted with a gear shape in a cylindrical mold.
(6) A method for producing a resin rotating body, wherein the fiber base material produced by any one of the methods (1) to (5) is subjected to a step of (e) impregnating and curing a resin.
(7) In the item (6), after the step of (e) impregnating and curing the resin, (f) the step of gear cutting is performed on the outer periphery of the fiber base impregnated and cured. Body manufacturing method.

According to the present invention, the basis weight of the fiber base material to be manufactured is obtained by pouring the dispersion medium or water toward the slurry diffusion pin and dropping the short fibers adhering to the slurry diffusion pin into the cylindrical mold. It is possible to perform continuous production by making the amount (mass) uniform and preventing the base material bite that bites the short fiber into the gap between the mold members. In addition, the mold life can be extended.
(C) When the step of discharging the dispersion medium from the cylindrical mold and (d) the step of compressing the fiber assembly are performed at the same time, the number of steps can be reduced, so that the fiber base material is manufactured in a shorter time. be able to.
(C) When the dispersion medium is discharged in a reduced pressure atmosphere, the dispersion medium can be discharged in a shorter time.
(D) When the step of compressing the fiber assembly is performed while applying heat, the dispersion medium contained in the fiber assembly can be separated in a short time as in the case of being performed in a reduced pressure atmosphere. If the heating is further performed in a reduced pressure atmosphere, the dispersion medium can be separated in a shorter time.

  When the fiber assembly is given the shape of a gear in a cylindrical mold, the final cutting process can be simplified and the material yield can be improved when finally producing the gear. it can.

  The resin rotator of the present invention has a uniform basis weight of the fiber base material, and therefore has a uniform strength, excellent durability, and can withstand high temperature and high load use conditions such as vehicle parts and industrial parts. It can be used as a resin rotating body to be obtained.

It is a longitudinal cross-sectional view of the resin gears manufactured by the present invention. The metal bush of the resin gear shown in FIG. 1 is shown, (A) shows a top view, (B) shows a longitudinal cross-sectional view. It is a schematic process drawing which shows operation | movement of the papermaking compressor which is one Example of this invention. (A) shows the longitudinal cross-sectional view of the fiber base material integrated with the bush, (B) shows the longitudinal cross-sectional view of a papermaking compressor. It is a general | schematic process figure which shows the preparation process of the resin gears which are one Example of this invention.

  Hereinafter, before explaining the manufacturing method of the fiber base material of this invention, an example of the papermaking compressor used for this manufacturing method is demonstrated.

<Paper making compressor>
The paper-making compressor 13 used for the manufacturing method of the fiber base material of this invention is provided with the base 1, the hollow lower compression type | mold 2, the cylindrical metal mold | die 3, and the hollow upper compression type | mold 4, as shown, for example in FIG.
Further, the hollow lower compression mold 2 has a bush support 5 and a lower elastic body 6 therein, the cylindrical mold 3 has a slurry diffusion pin 7 therein, and the hollow upper compression mold 4 has a depression. A member 8 and an upper elastic body 9 are provided.
Hereinafter, the individual members will be described in detail.

(pedestal)
The pedestal 1 supports the entire paper compressor, and the hollow lower compression mold 2 is directly placed on the upper surface of the pedestal 1. There is no particular limitation.
The material of the pedestal 1 is not particularly limited, but stainless steel, carbon steel, aluminum, aluminum alloy, magnesium alloy and the like can be used, and stainless steel is preferably used from the viewpoint of corrosion resistance.
The size of the pedestal 1 is not particularly limited, but the installation site can be easily selected by allowing the entire paper-making compressor to enter the projection area on the horizontal plane of the pedestal 1.
The base 1 can also be provided with counterbores and through holes for reducing the weight within a range in which rigidity can be maintained.

(Hollow compression type)
The hollow lower compression mold 2 is installed on the upper surface of the pedestal 1 described above, and as the installation method, various methods such as bolt fixing, groove fixing, fitting fixing, and welding can be used, and easy disassembly is possible. In view of the properties, it is preferable to fix the bolts.
The hollow lower compression mold 2 has a hollow portion opened in the vertical direction inside, and a bush support 5 for placing the bush on the upper surface thereof is disposed in the hollow portion.

The lower surface of the bush support 5 is supported by a lower elastic body 6 erected on the base 1, and the height from the base 1 can be changed by expansion and contraction of the elastic body. In addition, the lower elastic body 6 may be erected not only directly on the pedestal 1 but also indirectly on the pedestal. Further, a plurality of lower elastic bodies 6 may be installed.
As described above, the lower elastic body 6 only needs to change the height of the bush support 5 by expansion and contraction, and a coil spring, a disc spring, a leaf spring, a molded body of natural / synthetic rubber, or the like is used. However, a spring is preferable in terms of durability under use conditions in which a high compressive force is applied to the elastic body. The material of the spring is not particularly limited, but stainless steel excellent in corrosion resistance and a spring subjected to rust prevention treatment are preferable. A rubber spring or the like can also be used.

As the bush support 5, a bush is placed on the upper surface thereof, and a bush in which a groove for preventing displacement of the bush is dug can be preferably used. Further, if the bush is a magnetic body, a magnet can be used instead of the groove.
Further, the connection between the bush support 5 and the lower elastic body 6 may be bonded or fixed, but it is preferable that the bush support 5 is detachably connected so that the bush support can be exchanged according to the type of the bush.

  The relationship between the hollow lower compression mold 2 and the bush support base 5 is that at least a part of the bush support base 5 enters the hollow portion of the hollow lower compression mold 2 when viewed from the horizontal direction, and the elastic body expands and contracts. The amount of insertion into the hollow portion changes. During normal operation, the bush support 5 is separated from the hollow portion of the hollow lower compression mold 2 when viewed in the horizontal direction due to the extension of the elastic body. When returning into the compression mold 2, there is a possibility of causing a displacement, which is not practical.

A step portion 10 is provided on the inner wall of the hollow lower compression mold 2 that forms the hollow portion. The step portion 10 is in contact with the lower portion of the bush support base 5 to prevent the bush support base 5 from descending due to expansion and contraction of the lower elastic body 6, and changes the inner diameter of the hollow portion or provides a protrusion on the inner wall. It is preferable to form by providing.
The step portion 10 does not necessarily have to be provided over the entire circumference of the inner wall, and may be provided on a part of the inner wall. And it is preferable to provide in three or more places. Specifically, when the hollow portion is viewed from above and below, three steps 10 can be provided at intervals of 120 degrees, four at intervals of 90 degrees, and six at intervals of 60 degrees.

  The position of the step portion can be changed depending on the final thickness of the fiber assembly, but it is preferable that a fiber base layer having a thickness equal to the vertical direction can be formed from the center of the bush thickness direction, specifically, The position of the step 10 of the hollow lower compression mold 2 and the step 11 of the hollow upper compression mold 4 described later is hollow when the step 10 of the hollow lower compression mold 2 and the bush support 5 are in contact with each other. The distance from the upper end of the lower compression die 2 to the center in the bush thickness direction, and from the lower end of the hollow upper compression die 4 to the center in the bush thickness direction when the step portion 11 of the hollow upper compression die 4 and the pressing member 8 are in contact with each other. It is preferable to make the distances equal.

  On the upper surface of the hollow lower compression mold 2, a portion excluding a portion where the upper portion of the hollow portion is opened becomes a portion into which a slurry described later is introduced. Therefore, it is preferable to provide a discharge port 12 for discharging the liquid component in the slurry on the upper surface of the hollow lower compression mold 2, and it is more preferable to connect a vacuum suction pump to the discharge port 12. When such a hollow lower compression mold 2 is used, the paper making time can be further shortened.

(Cylindrical mold)
The cylindrical mold 3 has an opening opened up and down, and the hollow lower compression mold 2 is inserted into the lower opening so as to be in close contact with the outer periphery thereof, and the slurry leaks to the outside of the mold. I am trying not to. A hollow upper compression mold 4 to be described later is inserted into the upper opening.
The material of the cylindrical mold 3 is preferably the same as that of the hollow lower compression mold because it is necessary to make the compression strain rate the same in consideration of the coefficient of thermal expansion.
The length in the vertical direction of the cylindrical mold is not particularly limited, but it is sufficient that a predetermined amount of slurry is inserted at least when the slurry is charged so that it does not leak.

A slurry diffusion pin 7 is disposed at the center inside the cylindrical mold 3. The slurry diffusion pin 7 is located on the upper surface of the bush placed on the bush support base 5, and the lower surface thereof has a groove for preventing the displacement of the bush as described in the upper surface of the bush support base 5. What has been used can be preferably used. Further, if the bush is a magnetic body, a magnet can be used instead of the groove.
The top surface of the slurry diffusion pin 7 has a conical or pyramid shape with a sharp top, and when the slurry is thrown into the cylindrical mold from above, the short fibers in the slurry are evenly distributed around the bush. Let A spiral groove may be provided on the surface of the slurry diffusion pin 7. When the spiral groove is provided, the slurry flows like a vortex and the dispersibility can be further improved.
The slurry diffusion pin 7 does not need to be fixed to the upper surface of the bush as long as it does not cause a positional shift, and may simply be placed.

(Hollow top compression type)
The hollow upper compression mold 4 is disposed opposite to the hollow lower compression mold 2 and is inserted into the upper opening of the cylindrical mold 3. The outer periphery of the hollow upper compression mold 4 and the inner wall of the cylindrical mold 3 are in close contact with each other when the hollow upper compression mold 4 is inserted, and prevent leakage of slurry.
In addition, the material of the hollow upper compression mold 4 should be the same as the hollow lower compression mold 2 and the cylindrical mold 3 since it is necessary to make the compression strain rate the same in consideration of the coefficient of thermal expansion. Is preferred.

The hollow upper compression mold 4 has a pressing member 8 in its hollow portion, and the pressing member 8 abuts on the slurry diffusion pin 7. The upper surface of the pressing member 8 is supported by the upper elastic body 9, and the position of the pressing member 8 is changed by expansion and contraction of the elastic body.
The upper elastic body 9 may be the same as or different from the lower elastic body 6 described above, but the hollow lower compression mold 2 is heated or a high compressive force is applied to the elastic body. In use conditions, a spring is preferable in terms of durability. Moreover, it is preferable that the upper elastic body 9 and the lower elastic body 6 are both springs having the same spring constant, and in this way, compression from above and compression from below are performed at equal speeds. The variation in fiber density in the vertical direction can be reduced.
Further, the connection between the pressing member 8 and the upper elastic body 9 may be bonded or fixed, but it is preferable that the pressing member 8 is detachably connected so that the pressing member 8 can be replaced depending on the type of the bush.

  The relationship between the hollow upper compression mold 4 and the pressing member 8 is that at least a part of the pressing member 8 enters the hollow portion of the hollow upper compression mold 4 when viewed in the horizontal direction, and the elastic body expands and contracts. The amount of insertion into the part changes. During normal operation, when the pressing member 8 is separated from the hollow portion of the hollow upper compression mold 4 when viewed in the horizontal direction due to the expansion of the elastic body, the pressing member 8 becomes hollow upper compression mold due to the contraction of the elastic body. When returning to 4, there is a possibility of misalignment, which is not practical.

A step portion 11 is provided on the inner wall of the hollow upper compression mold 4 that forms the hollow portion. The step portion 11 is in contact with the upper portion of the pressing member 8 to prevent the pressing member 8 from rising due to the expansion and contraction of the upper elastic body 9, and the inner diameter of the hollow portion is changed or a projection is provided on the inner wall. It is preferable to form by.
The step portion 11 does not necessarily have to be provided over the entire circumference of the inner wall, and may be provided on a part of the inner wall. It is preferable to provide at three or more locations. Specifically, when the hollow portion is viewed from above and below, three steps 11 can be provided at intervals of 120 degrees, four at intervals of 90 degrees, and six at intervals of 60 degrees.

  As described in the step 10 of the hollow lower compression mold 2, the position of the step 11 is the position of the step 10 of the hollow lower compression mold 2 and the step 11 of the hollow upper compression mold 4. The distance from the upper end of the hollow lower compression mold 2 to the center of the bush thickness direction when the step 10 of the hollow lower compression mold 2 and the bush support 5 are in contact with each other, and the step 11 of the hollow upper compression mold 4 The distance from the lower end of the hollow upper compression mold 4 to the center of the bush thickness direction when the member 8 is in contact is preferably set to be equal.

The temperature of the lower surface of the hollow upper compression mold 4 is preferably adjustable, and the liquid adhering to the short fibers can be quickly dried by heating at the time of pressure compression.
The temperature adjustment may be performed by changing the resistance value of the heater using a variable resistor, or simply by controlling the heater on and off.

(Slurry injection upper mold)
The papermaking compressor can be provided with an upper mold for injecting slurry as required (see FIG. 3B). The slurry injection hole 21 of the slurry injection upper mold 20 is disposed above the slurry diffusion pin 7 in order to produce a fiber base material with a uniform basis weight of fibers accumulated around the bush, but is disposed directly above. It is preferable to do this.
Furthermore, it is preferable to arrange a nozzle that protrudes toward the slurry diffusion pin 7 at the tip of the slurry injection hole 21. This occurs when short fibers remain attached to the slurry diffusion pin 7 after slurry injection. (D) Prevents damage to the mold caused by biting of fibers into the mold during the process (process of compressing the fiber assembly). Therefore, when the dispersion medium or water is injected after the slurry injection, it is possible to efficiently drop the short fibers attached to the slurry diffusion pin 7 with a small amount.

  Moreover, it is preferable that the slurry injection | pouring upper mold | type 20 is the structure which adheres to the cylindrical metal mold | die 3 at the time of slurry injection | pouring, and becomes a sealing state. This is because when the dispersion medium is discharged with a vacuum pump from the discharge port of the hollow lower compression mold 2 at the time of slurry injection or after injection, it can be efficiently discharged by sealing the inside of the cylindrical mold. Slurry will not overflow and spill.

<Bush>
The bush is sandwiched between the bush support 5 and the slurry diffusion pin 7. Hereinafter, the bush will be described in detail.
If the bush is located at the center of the fiber base in the radial direction and the final desired one is a resin gear, it is used by being fixed to the rotating shaft. The material of the bush is not particularly limited, but a metal one is preferable in view of strength.
FIG. 1 is a longitudinal sectional view of a resin gear schematically shown. The resin gear 30 includes a metal bush 31 that is fixed to a rotating shaft (not shown) and rotates. A through hole 32 into which a rotating shaft (not shown) is fitted is formed at the center of the metal bush 31.
In addition, on the outer peripheral portion of the metal bush 31, protrusions 33 constituting a plurality of detent portions are integrally formed with a predetermined interval in the circumferential direction. This interval is determined as appropriate, but when viewed from the central portion of the metal bush 31, it is possible to make the strength against dropping uniform by providing it at equiangular intervals.
In addition, the metal bush 31 may have a shaft integrally formed.

  The metal bush 31 will be described with a specific example. The thickness dimension L2 measured in the axial direction of the plurality of protrusions 33 is smaller than the thickness dimension L1 measured in the axial direction of the metal bush 31. . And the protrusion part 33 which comprises a rotation prevention part is an undercut shape with a thick top part and a thin base part. This undercut prevents interface breakage from occurring at the interface with the surrounding resin molding part and prevents only the metal bush 31 from spinning around. The angle θ of the metal bush 31 in the cross section in the rotation axis direction is 5 to 40 °.

In order to enhance the action of the anti-rotation portion that can withstand the load in the rotation direction, as shown in FIG. 2, the protrusion 33 serving as the anti-rotation portion includes at least a protrusion 33 having a height h 1 and two protrusions 33. It is preferable that the recesses 34 formed between them and having a bottom portion having a height h2 are alternately arranged. When the projecting portion 33 having such an undercut shape and having an angle θ of 5 to 40 °, preferably 10 to 35 ° is used, a plurality of projecting portions 33 serving as detents are provided in the fiber base material. Is completely filled, and the strength of mechanical coupling between the two can be made sufficient.
In addition, the above-mentioned mechanical strength naturally increases also when a part of the fiber base material enters the recess 34 formed between the two adjacent protrusions 33.

  The projecting portion 33 constituting the anti-rotation portion having the undercut shape can be accurately produced as designed if it is formed by a sintering method. For example, in the case of a resin gear having an outer diameter of 60 mm, the optimal structure of the protrusion 33 is 30. The number of protrusions (crests) is 30, and the number of recesses or valleys formed between the protrusions is 29. is there. These numbers are appropriately changed according to the diameter and thickness of the resin gear and the tooth structure.

<Slurry>
Next, the slurry used in the present invention will be described. The slurry used in the present invention is not limited to the one described below.

(Slurry dispersion)
The dispersion medium used for the slurry is not particularly limited as long as it can disperse the short fibers and does not deteriorate the properties of the short fibers to be used, and is an organic solvent, a mixture of an organic solvent and water. Water can be used, and it is particularly preferable to use water that is economical and has a low environmental impact.
When using an organic solvent, it is possible to use an organic solvent such as methanol, ethanol, acetone, toluene, diethyl ether, etc., paying sufficient attention to safety.

(Short fiber)
The short fibers dispersed in the dispersion medium are preferably made of short fibers having a melting point or decomposition temperature of 250 ° C. or higher. By using such short fibers, at the molding temperature and processing temperature at the time of molding, the ambient temperature at the time of actual use, the short fiber does not cause thermal degradation, and the fiber base material or resin gear having excellent heat resistance can do.
Such short fibers include para-aramid fibers, meta-aramid fibers, carbon fibers, glass fibers, boron fibers, ceramic fibers, ultra-high strength polyethylene fibers, polyketone fibers, polyparaphenylene benzobisoxazole fibers, wholly aromatic. It is preferable to use at least one kind of short fiber selected from polyester fiber, polyimide fiber, and polyvinyl alcohol fiber, especially when a mixed fiber of para aramid fiber and meta aramid fiber is used. Has an excellent balance of heat resistance, strength, and workability after resin molding.

  The short fibers preferably contain at least 20% by volume or more of high-strength and high-modulus fibers having a tensile strength of 15 cN / dtex or more and a tensile modulus of 350 cN / dtex or more. When such a short fiber is used, it can withstand a high load applied during use.

  The single fiber fineness (thickness) of the short fibers is preferably in the range of 0.1 to 5.5 dtex, more preferably 0.3 to 2.5 dtex. If it is less than 0.1 dtex, there are many points that are difficult in terms of the spinning technique, and not only is it difficult to use fibers of good quality due to the occurrence of yarn breakage and fluff, but this is not preferable because the cost increases. If it exceeds 5.5 dtex, the decrease in fiber strength gradually increases, which is not preferable.

  Although the length of a short fiber is not specifically limited, Preferably, it is 1-12 mm, More preferably, it is 2-6 mm. When the fiber length is less than 1 mm, the mechanical properties of the fiber reinforced resin molded product are gradually lowered. If the fiber length exceeds 12 mm, the short fibers are too entangled, making it difficult to form a uniform texture, as well as in the piping that transports the short fibers dispersed in the dispersion to the paper compaction device. Thus, clogging with short fibers is likely to occur gradually, which is not preferable.

The ratio of the short fiber contained in the resin molded body varies depending on the strength of the molded body such as a desired resin gear, but is preferably 30 to 50% by volume. When the proportion of the short fibers in the resin molded body is less than 30% by volume, the effect of reinforcing the resin with the short fibers is hardly seen, and filling of the short fibers into the non-rotating portion of the metal bush to be described later Is also insufficient. When the proportion of the short fibers exceeds 50% by volume, the proportion of the short fibers is too high, so that problems such as insufficient resin impregnation tend to occur during the molding of impregnating the fiber base material with resin.
Therefore, the proportion of the short fibers contained in the resin molded body is preferably selected so that there is strength, the short fibers are reliably filled, and the impregnation of the resin is not inhibited, and 35 to 45% by volume is particularly preferable. .

  In order to give strength to maintain the shape when moving or transporting the fiber base material 35 integrated with the metal bush 31 to the next process using the paper making compression device shown in FIG. In addition, the short fibers include fine fibers obtained by fibrillation of aramid fibers, the fineness of the fine fibers is 100 to 400 ml, and the content of the fine fibers is 30% by mass or less in the short fibers. Is desirable.

  As a desirable embodiment, it is preferable to mix fibrillated aramid fine fibers which are cleaved in the fiber axis direction by mechanical shearing of para-aramid fibers. When the freeness exceeds 400 ml, the fibrillation is insufficient, which is not preferable for imparting strength for maintaining the shape of the fiber base 5. When the freeness is less than 100 ml, not only to cleave in the fiber axis direction, but also in a powder state due to shearing in the radial direction, the entanglement of the fibers is deteriorated, and the shape of the fiber base material is maintained. This is not preferable for imparting strength. Moreover, filterability deteriorates and becomes impeded by resin impregnation.

  If the fibrillated aramid fine fibers exceed 30% by mass, the fibrillated fine fibers are filled in the gaps between the fibers, and the resin impregnation of the resin is hindered during resin injection molding, resulting in defects such as poor impregnation. May end up. More preferably, it is preferable to blend 5 to 10% by mass of fibrillated fine fibers that impart appropriate strength and do not impair resin impregnation.

(Dispersion concentration of short fibers)
The dispersion concentration of short fibers is preferably 0.3 to 20 g / liter or less. When the fiber length is shorter than 1 mm, the dispersion concentration can be increased from 20 g / liter, but the mechanical properties in the case of a resin molded body are deteriorated. In addition, when the fiber length of the short fiber is longer than 12 mm, the fibers are too long, so that the fibers are entangled and cannot be sufficiently dispersed even if the dispersion concentration is lower than 0.3 g / liter.

<Resin gear>
Hereinafter, the resin gear suitably manufactured using the resin rotating body of the present invention will be described.
The resin gear is formed by impregnating and curing a resin to a fiber base material and molding it into a gear shape. More specifically, one having a metal bush fitted to a rotating shaft for rotating a gear and a tooth portion arranged around the metal bush can be preferably used.

(Tooth part)
A tooth | gear part is arrange | positioned on the outer periphery of metal bushes mentioned above. More specifically with reference to FIG. 1 described above, one fiber base material 35 is disposed at a position outside the outer peripheral portion 36 of the metal bush 31 in a state of being fitted to the outer peripheral portion 36. Yes. And the fiber base material 35 becomes the resin molding 37 formed by impregnating the resin and curing the resin. The tooth portion is formed on the outer periphery of the resin molded body 37.
When the resin is impregnated with the resin, the tooth portion may be formed using a mold having a final tooth shape, or may be formed by cutting or the like after the resin molded body 37 is once formed. However, if a highly accurate tooth part is formed, it is preferable to carry out by cutting. Further, the cutting can be performed in multiple stages so that the cutting is performed with high accuracy after the roughing is performed.

<Driving compressor drive>
The papermaking compressor has a driving device that can change the separation distance between the upper and lower hollow compression molds described above, but the driving source is not particularly limited, and the moving speed and the applied pressure can be controlled. An electric press can be used.
In addition, the upper and lower hollow compression molds may be driven, but it is preferable to drive the hollow upper compression mold up and down because it is easy to disassemble and clean.

<Method for producing fiber substrate>
Hereinafter, the manufacturing method of the fiber base material of the present invention will be described when used as a gear.
As schematically shown in FIG. 3, the fiber base material 35 forms a fiber assembly 38 at an outer position of the outer peripheral portion 36 of the metal bush 31 using the paper-making compression device 13. It is formed by compressing in the axial direction of a rotating shaft (not shown) for rotating the metal bush 31.
First, the step (a) in which short fibers are accumulated around the outer periphery of a metal bush by a papermaking method will be described.

<Process (a)>
In the step (a), the slurry is thrown into the cylindrical mold from above toward the slurry diffusion pin. This slurry is temporarily stored in the cylindrical mold, or the dispersion medium is discharged out of the cylindrical mold in parallel with the addition.
First, the paper compaction device 13 will be described. As shown in FIG. 3A, the mold used in the paper compaction device has a fiber assembly 38 (see FIG. 3C) of the metal bush 31 during the compression operation. A cylindrical mold 3 that restricts spreading outward in the radial direction, and a portion that is arranged inside the cylindrical mold 3 and that is located inside the outer peripheral portion 36 of the metal bush 31 from both sides in the axial direction. The bush support 5 and the slurry diffusion pin 7, and the cylindrical mold 3, the bush support 5 and the slurry diffusion pin that restrict the fiber assembly 38 from spreading radially inward of the metal bush 31 during the sandwiching and compression operation. 7, the hollow upper compression mold 4 and the hollow lower compression mold 2 that compress the fiber aggregate 38 from both sides in the axial direction during the compression operation, and the slurry diffusion pin when the fiber aggregate 38 is pressurized and compressed. Press part to hold 7 It is equipped with a 8.

The hollow lower compression mold 2 has a discharge port 12 for discharging the dispersion medium in order to impart the liquid permeability of the dispersion medium contained in the fiber assembly 38. A vacuum suction pump (not shown) is attached to the discharge port 12, and the discharge of the dispersion medium can be completed in a short time. In this example, a bottom member 39 is disposed on the upper surface of the hollow lower compression mold 2 in order to prevent short fibers from flowing out when the dispersion medium is discharged from the discharge port 12.
A metal mesh can be used for the bottom member 39, and the mesh size is preferably 10 to 250 mesh. When it becomes larger than 250 mesh, the filtration resistance of the dispersion gradually increases. From the slurry described later including the short fibers placed inside the mold, the liquid is discharged by suction with a pump. The time for performing the separation becomes longer and the manufacturing cycle becomes longer. On the other hand, if it is smaller than 10 mesh, even if a fiber having a long fiber length is used, most of the fiber flows out together with the liquid because the mesh is large. In this case, there arises a problem that the fiber density of the fiber assembly 38 is remarkably lowered.
Note that the mesh size used in the present specification conforms to that defined in JIS G 3555.

The bush support 5 and the slurry diffusing pin 7 are provided with a cylindrical metal portion located on the inner side of the outer peripheral portion 36 of the metal bush 31 so that short fibers do not enter the inner side of the outer peripheral portion of the metal bush 31. The mold 3 is supported by being sandwiched from both sides in the direction in which the center line extends. In the example shown in FIG. 3, the bush support 5, the slurry diffusion pin 7, and the hollow lower compression die 2 are configured to be movable upward, but the hollow upper compression die 4 and the pressing member 8 move downward. The structure to do may be sufficient.
When the metal bush 31 is sandwiched between the bush support 5 and the slurry diffusion pin 7, as shown in FIG. 3B, the slurry diffusion pin 7 is placed on the bush and the weight of the slurry diffusion pin 7 is set. The metal bush 31 is sandwiched.

As shown in FIG. 3B, the slurry formed by dispersing the short fibers in the dispersion medium seals the cylindrical mold 3 and the slurry injection upper mold 20 and is supplied from the slurry injection hole 21.
The slurry is supplied toward the slurry diffusion pin 7 from above, whereby the short fibers are spread evenly distributed around the slurry diffusion pin 7.

<Step (b)>
In the step (b), the same dispersion medium or water as the dispersion medium used in the step (a) is poured toward the slurry diffusion pin from above, and the short fibers attached to the slurry diffusion pin are dropped.
After adding the slurry in the step (a), the fibers adhere to the upper part of the slurry diffusion pin 7 and remain. When fibers remain in the slurry diffusion pin 7, in the step of compressing the fiber assembly during or after the dispersion medium is discharged in the following steps (c) and (d), In the meantime, the base material bite that bites the short fibers is generated, the mold is damaged, and continuous production cannot be performed. Therefore, after the slurry is introduced, the same dispersion medium or water as the slurry dispersion medium is injected from the slurry injection hole 21, and the short fibers remaining on the upper part of the slurry diffusion pin 7 are washed away.
The injection start timing of the dispersion medium or water for washing out the short fibers is preferably added at a timing when the liquid level of the slurry in the mold reaches the upper surface of the fiber assembly accumulated in the mold.
The amount of the dispersion medium or water to wash out the short fiber is surely added by adding a small amount so that the dispersion medium or water does not overflow from the mold, and the number of injections of the dispersion medium or water is two times or more (multiple times). In addition, the short fibers remaining on the top of the slurry diffusion pin 7 can be washed away.
The interval when the dispersion medium or water is injected two or more times is preferably set so that the level of the previously injected dispersion medium or water is lowered to the upper surface of the fiber assembly accumulated in the mold.

<Steps (c) and (d)>
In the step (c), the dispersion medium is discharged from the cylindrical mold to form a fiber assembly in which short fibers are accumulated in the cylindrical mold.
In the step (d), a step of compressing the fiber assembly is performed.
More specifically, as shown in FIG. 3 (B), the inside of the cylindrical mold is vacuum-sucked, and the liquid component is discharged from a plurality of discharge ports 12 provided in the hollow lower compression mold 2. Thus, the fiber assembly 38 surrounding the periphery of the metal bush 31 is produced.
When the bush support 5 and the slurry diffusion pin 7 are used in this way, the metal bush 31 can be positioned and supported easily.

The shape of the outer peripheral surface of the fiber assembly 38 is determined by the shape of the inner peripheral surface of the cylindrical mold 3. Therefore, by making the inner peripheral surface of the cylindrical mold 3 into a gear shape, it is possible to form gear-shaped irregularities on the outer peripheral surface of the fiber assembly 38.
If it is a metal mold | die used with the above-mentioned papermaking compression apparatus, when the fiber assembly 38 is compressed with the hollow upper compression mold 4 and the hollow lower compression mold 2, both the inner side and the outer side in the radial direction of the metal bush 31 are used. It is possible to reliably prevent the short fibers from flowing out.

After the liquid is discharged from the plurality of discharge ports 12 provided in the hollow lower compression mold 2, the bush support 5, the slurry diffusion pin 7, and the hollow lower compression mold 2 are moved upward as shown in FIG. Moving. Then, first, the slurry diffusion pin 7 and the pressing member 8 come into contact with each other, and the metal bush 31 is fixed by the force of the upper elastic body 9 and the lower elastic body 6. In the structure shown in FIG. 3, springs having the same spring constant are used as the upper and lower elastic bodies.
Further, the bush support 5, the slurry diffusion pin 7, and the hollow lower compression mold 2 are raised, and the step 10 provided on the bush support 5 and the hollow lower compression mold 2, the pressing member 8, and the hollow upper compression mold 4 are provided. The step portion 11 is brought into contact with the hollow upper compression mold 2 and the hollow upper compression mold 4 so that the distance is not reduced (see FIG. 3D).

Here, the thickness of a fiber base material is demonstrated in detail using FIG.
As shown in FIG. 4A, the thickness of the metal bush 31: T1 and the thickness of the fiber base 35 determined by the stepped portions 10 and 11 (see FIG. 3) (thickness during compression): T2. The relationship can be arbitrarily selected from three patterns: (A) T1 = T2, (B) T1> T2, and (C) T1 <T2.
Further, the relationship between the distance T3 from the lower surface of the metal bush 31 to the lower surface of the fiber base material 35 during compression and the distance T4 from the upper surface of the metal bush 31 to the upper surface of the fiber base material 35 during compression is: (D) It can be arbitrarily selected from three patterns of T3 = T4, (e) T3> T4, and (f) T3 <T4, which are the heights L3 and L4 of the stepped steps 10 and 11 (FIG. 4). It becomes possible by changing (see (B)).
Furthermore, it is also possible to have a specification combining (a) to (c) and (d) to (f) described above.

The compression time and temperature can be arbitrarily changed depending on the type of short fiber to be used. At the time of compression, a heater is attached to the hollow upper compression mold 4 and compressed in a heated state, so that the fiber base after paper making The time for removing the liquid component contained in the material 35 can be shortened, and the change with time of the thickness of the fiber base material 35 after compression can be suppressed. Preferably, the fiber base material 35 having almost no change with time in thickness can be obtained by compressing for 0.1 to 10 minutes at a temperature higher than the boiling point of water: 100 to 180 ° C. in this example, at a temperature equal to or higher than the boiling point of water. it can.
Moreover, at the time of the said compression, the time which removes the liquid component contained in the fiber base material 35 after papermaking can be shortened by compressing in the state vacuum-sucked from the discharge port 12 of the hollow lower compression type | mold 2.

In addition, a process (c) and a process (d) may be performed simultaneously, or a process (d) may be performed after performing a process (c).
When performed in order, the dispersion medium and the fiber base material can be sufficiently separated first. Therefore, when the upper mold is heated during the compression in the step (d), the fiber is compressed by reducing the temperature drop of the upper mold. I can do it.
When performed at the same time, the process for one process can be reduced, so that the fiber substrate can be produced in a shorter time.

<Process (e)>
The step of impregnating and curing the resin in step (e) will be described below.
As shown in FIG. 5, after the resin rotating body forming material 40 provided with the fiber base material 35 is placed in the mold 41, a liquid resin is injected into the mold 41 to add the resin to the fiber base material 35. Impregnation and then curing are performed to form a resin rotating body provided with a resin molded body.
The mold 41 includes a fixed mold 42, a movable mold 43 that is disposed at the center of the fixed mold 42 and is displaced in the vertical direction, and holds the metal bush 31 in pairs with the movable mold 43. A mold 44 is provided.

When the pressing portion 44 </ b> A of the upper mold 44 is inserted into the fixed mold 42 and presses the metal bush 31, the moving mold 43 is displaced downward according to the amount of insertion of the upper mold 44.
After the upper mold 44 completely closes the opening of the fixed mold 42, the liquid resin is injected into the fixed mold 42. At this time, the liquid resin can be quickly injected by evacuating the fixed mold 42.
After that, when the resin is cured, the resin rotating body including the resin molded body formed with the fiber base material 35 as the core material is taken out from the mold 41 to complete the manufacture of the resin rotating body.

The resin to be impregnated into the fiber base material 35 may be any of thermosetting resin, thermoplastic resin, and the like. Epoxy resin, polyaminoamide resin, phenol resin, unsaturated polyester resin, polyimide resin, polyether sulfone resin, poly A combination of at least one resin selected from ether ether ketone resin, polyamideimide resin, polyamide resin, polyester resin, polyphenylene sulfide resin, polyethylene resin, polypropylene resin, and the like, and a curing agent according to the type of the selected resin. Things can be used.
Among these, a polyaminoamide resin is preferable from the viewpoint of the strength and heat resistance of the cured resin, and a mixture 100 of 2,2 ′-(1,3 phenylene) bis-2-oxazoline and an amine curing agent having excellent heat resistance and strength. It is preferable to use, for example, a resin containing 5 parts by mass or less of n-octyl bromide as a curing accelerator for the catalyst with respect to parts by mass. If this catalyst is added in an amount exceeding 5 parts by mass, the curing time is shortened, and the resin is cured before the fiber substrate 35 is sufficiently impregnated with the resin. It becomes easy to do.

<Step (f)>
In the step (f), the gear cutting process for the outer peripheral portion of the fiber base material impregnated and cured with resin will be described below.
The teeth can be added at the time of mold forming or can be added by cutting after the mold forming. However, since the accuracy can be increased, it is preferable to provide the teeth by cutting.

Moreover, it is preferable to divide the cutting process into three stages and perform a first process of the outer peripheral portion, a second process of tooth profile creation, and a third process of tooth surface finishing.
The first process is described in more detail. A lathe process is performed, and the outer peripheral surface and the inner diameter part are cut and processed to a predetermined dimension. At this stage, teeth are not produced, and simple circumferential processing is performed.
To describe the second processing in more detail, it is processed into a tooth profile with a hobbing machine. As the hobbing machine, for example, GE15A (trade name) manufactured by Mitsubishi Heavy Industries, Ltd. can be used.
To describe the third process in more detail, the tooth surface is finished with a shaving machine. As the shaving machine, for example, FE30A (trade name) manufactured by Mitsubishi Heavy Industries, Ltd. can be used. In addition, since the shaving process is a final finishing process, the cutting amount is small and is about 20 to 150 μm.

Examples of the present invention will be described below.
[Example 1]
In order to produce a slurry, a tank filled with an amount of water in which the short fiber dispersion concentration is 4 g / liter is prepared. And the short fiber of the quantity from which the total amount of the short fiber in a resin molding becomes 40 volume% is put in this tank. Specifically, as a short fiber, a single fiber fineness of 1.7 dtex, a fiber length: 3 mm long para-aramid short fiber (“Technora (Teijin Corporation trademark)” manufactured by Teijin Limited) is 45% by mass, 50% by mass of a meta-aramid short fiber (“Conex (Teijin Limited)” manufactured by Teijin Limited) having a fiber fineness of 2.2 dtex and a fiber length: 3 mm, and “Kevlar (DuPont Limited) manufactured by DuPont Co., Ltd. "Trademark) Pulp" is fibrillated to a freeness value of 300 ml. Next, the water in the tank is stirred with a stirrer to disperse the short fibers to prepare a slurry.

Next, using the paper making compression device shown in FIG. 3A, the metal bush 31 is positioned on the bush support 5 and the slurry diffusion pin 7 is placed on the metal bush 31 so as not to be displaced. The metal bush 31 is sandwiched. Note that the angle of the conical portion that protrudes upward from the slurry diffusion pin 7 is 90 °.
The shape of the protrusion 33 and the recess 34 of the metal bush 31 to be used (see FIG. 2) is h1 = 2 mm and h2 = 0.5 mm, and is an undercut shape. Is 20 °.
Here, the position of the hollow lower compression mold 2 was a position where the distance from the axial center of the metal bush 31 to the upper surface of the bottom member 39 was 40 mm.

The slurry injection upper mold 20 and the cylindrical mold 3 shown in FIG. 3B are brought into close contact with each other, and the slurry is put into the papermaking compression apparatus. Then, vacuum suction is performed in the cylindrical mold to drain water from the plurality of outlets 12 provided in the hollow lower compression mold 2, thereby separating the short fibers and the water to obtain a cylindrical fiber assembly 38. . After separating the short fibers and water by vacuum suction, water is injected from the slurry injection hole 21 to wash away the short fibers remaining on the upper side of the slurry diffusion pin 7. The slurry injection hole 21 is disposed immediately above the slurry diffusion pin 7.
In order to prevent short fibers from flowing out from the discharge port 12 during drainage, a bottom member 39 is disposed on the hollow lower compression mold 2. As the bottom member 39, a metal: 100 mesh wire mesh was used.

  Next, compression is performed in order to make the short fiber bite into the detent portion of the metal bush 31 more firmly. As shown in FIG. 3C, the hollow lower compression mold 2 and the cylindrical mold are moved to a position where the distance from the axial center of the metal bush 31 to the lower surface of the hollow upper compression mold 4 heated to 150 ° C. is 40 mm. 3. The bush support 5, the metal bush 31, the slurry diffusion pin 7, and the fiber assembly 38 are raised together with the base 1. This position is a position where the metal bush 31 is located in the center between the hollow upper compression mold 4 and the hollow lower compression mold 2.

As shown in FIG. 3D, the pedestal 1 is raised at a speed of 1 to 5 mm / s while the metal bush 31 is located at the center between the hollow upper compression mold 4 and the hollow lower compression mold 2. The fiber assembly 38 is compressed until the thickness becomes 10 mm.
And it compressed for 2 minutes in the heated state, and the resin-made rotary body shaping | molding raw material integrated with the metal bush 2 was obtained.
In addition, at the time of the said compression, it compresses in the state vacuum-sucked from the through-hole 32 of the hollow lower compression type | mold 2. 4B, the length of the bush support base 5: L7 = 100 mm, the length of the slurry diffusion pin 7: L6 = 70 mm, the length of the pressing member 8: L5 = 30 mm, the metal bush 31 Thickness: T1 = 10 mm, height L3 and L4: L3 = L4 = 100 mm of the step portions of the hollow upper compression mold 4 and the hollow lower compression mold 2.

<Production of fiber substrate>
Ten fiber base materials were produced using the paper-making compression apparatus and slurry mentioned above.

[Comparative Example 1]
A fiber substrate was prepared in the same manner as in Example 1 except that the remaining short fibers attached to the slurry diffusion pin 7 were not washed away.

  After slurry injection by the method shown in Example 1 and Comparative Example 1 described above, the number of short fibers remaining on the slurry diffusion pin 7 was measured (the number of remaining fibers during ten fiber substrate preparations). The measurement results are shown in Table 1 below.

  From Table 1, in Comparative Example 1 in which the short fibers were not washed away, the short fibers remained on the slurry diffusion pin 7 out of 10 times, whereas in Example 1 in which cleaning water was added, the slurry diffusion pin was It was 0 times out of 10 that fibers remained on 7. Therefore, in comparison with Comparative Example 1, in the present invention including the step of washing away the remaining short fibers attached to the slurry diffusion pin in the step (b), there is no fiber remaining on the slurry diffusion pin 7, and thus the amount of fibers in each product varies. There is little and no mold damage occurs, so continuous production is possible.

DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Hollow lower compression type, 3 ... Cylindrical metal mold, 4 ... Hollow upper compression type, 5 ... Bush support stand, 6 ... Lower elastic body, 7 ... Slurry diffusion pin, 8 ... Pushing member, 9 ... Upper elastic body, 10 ... step portion, 11 ... step portion, 12 ... discharge port, 13 ... paper making compressor, 20 ... slurry injection upper die, 21 ... slurry injection hole, 30 ... resin gear, 31 ... metal bush, 32 ... Through hole, 33 ... Projection, 34 ... Recess, 35 ... Fiber base material, 36 ... Outer peripheral part, 37 ... Resin molded body, 38 ... Fiber assembly, 39 ... Bottom member, 40 ... For molding resin rotating body 41, mold, 42 ... stationary mold, 43 ... transfer mold, 44 ... upper mold, 44A ... pressing part,

Claims (7)

By preparing a slurry in which short fibers are dispersed in a dispersion medium, putting the slurry into a cylindrical mold and discharging the dispersion medium from the cylindrical mold to accumulate the short fibers in the cylindrical mold And the manufacturing method of the fiber base material manufactured by the following processes.
(A) A step of throwing slurry into the cylindrical mold from above toward a slurry diffusion pin having a conical or pyramid shape that is arranged at the center of the cylindrical mold and has a sharp top.
(B) After the step (a), a step of pouring the same dispersion medium or water as the dispersion medium from above toward the slurry diffusion pin to drop the short fibers attached to the slurry diffusion pin.
(C) A step of discharging the dispersion medium from the cylindrical mold to form a fiber assembly in which short fibers are accumulated in the cylindrical mold.   2. The method for producing a fiber base material according to claim 1, wherein (c) a step of compressing the fiber aggregate is further performed during or after discharging the dispersion medium.   The method for producing a fiber base material according to claim 1 or 2, wherein the dispersion of (c) is separated in a reduced-pressure atmosphere.   4. The method for producing a fiber base material according to claim 2, wherein the step (d) of compressing the fiber assembly is performed while applying heat.   The method for producing a fiber base material according to any one of claims 1 to 4, wherein the fiber assembly is provided with a gear shape in a cylindrical mold.   The manufacturing method of the resin-made rotary body which performs the process which the fiber base material manufactured by the method in any one of Claims 1-5 impregnates and hardens (e) resin.   7. The method of manufacturing a resin rotating body according to claim 6, wherein after the step of (e) impregnating and curing the resin, (f) a gear cutting step is performed on the outer peripheral portion of the fiber base impregnated and cured.

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