US-12623414-B2 - Method for producing composite material molded article, method for producing retainer and rolling bearing, and method for producing gearbox constituent component

Abstract

A method for producing a composite material molded article includes a process of, from a solution in which reinforcing fibers with an average fiber length of 0.5 mm or more and thermosetting resin are dispersed and mixed in a solvent, removing the solvent by paper-making to form a preform, and a process of press molding the obtained preform using a mold set at a temperature equal to or higher than a curing temperature of the thermosetting resin to form the composite material molded article.

Inventors

• Takuya Tsunemasu
• Tomoaki Matsumoto

Assignees

• NSK LTD.

Dates

Publication Date

20260512

Application Date

20220513

Priority Date

20210514

Claims (8)

1. 1 . A method for producing a retainer for use in a rolling bearing, the retainer including: a pair of annular portions that face each other in an axial direction; and a plurality of columnar portions that connect the pair of annular portions, rolling elements being housed in regions surrounded by the pair of columnar portions arranged to face each other in a circumferential direction and the pair of annular portions facing each other in the axial direction, the method comprising: to obtain the columnar portions, from a solution in which reinforcing fibers with an average fiber length of 0.5 mm or more and thermosetting resin are dispersed and mixed in a solvent, removing the solvent by paper-making to form a reference preform in which the reinforcing fibers are formed at a first bulk density; to obtain the annular portions, from the solution in which the reinforcing fibers and the thermosetting resin are dispersed and mixed in the solvent, removing the solvent by paper-making to form a high density preform in which the reinforcing fibers are formed at a second bulk density higher than the first bulk density; placing the high density preform in a cavity of a mold at a portion where the annular portions to be molded; placing the reference preform in the cavity at a portion where the columnar portions to be molded; and clamping and heating the mold and injecting a molten resin into the cavity to perform resin molding.
2. 2 . The method according to claim 1 , wherein the first bulk density is 0.4 g/cm 3 or more and 1.0 g/cm 3 or less.
3. 3 . The method according to claim 1 , wherein the thermosetting resin is mixed between the reinforcing fibers in the reference preform and the high density preform.
4. 4 . The method according to claim 1 , wherein the reinforcing fiber is at least one selected from carbon fiber, aramid fiber, glass fiber, cellulose fiber, polyarylate fiber, and polyparaphenylene benzbisoxazal fiber.
5. 5 . The method according to claim 1 , when the retainer is molded, thermoplastic resin, containing the reinforcing fibers in an amount of 10% by mass or more and 60% by mass or less, is formed.
6. 6 . The method according to claim 1 , wherein the thermosetting resin is at least one selected from epoxy resin, bismaleimide resin, polyaminoamide resin, polyimide resin, and phenol resin.
7. 7 . The method according to claim 1 , wherein the thermosetting resin is in powder form.
8. 8 . A method for producing a rolling bearing, comprising producing a rolling bearing using the retainer produced by the method according to claim 7 .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a National Phase Entry of PCT International Application No. PCT/JP2022/020276 filed on May 13, 2022, which claims priority to Japanese Patent Application No. 2021-082611 filed on May 14, 2021, and Japanese Patent Application No. 2022-071024 filed on Apr. 22, 2022, the contents of all of which are incorporated herein by reference in their entirety. TECHNICAL FIELD The present disclosure relates to a method for producing a composite material molded article, a method for producing a retainer and a rolling bearing, and a method for producing a gear box component. BACKGROUND ART Generally, cylindrical roller bearings, angular ball bearings, and the like are used as bearings for a main shaft of a machine tool. For retainers of such bearings, retainers made by cutting phenol resin reinforced with cotton cloth, and so-called plastic retainer (synthetic resin retainer) made of 66 nylon resin reinforced with glass fibers or carbon fibers, polyphenylene sulfide resin, polyetheretherketone resin, and the like, are used. The plastic retainers are advantageous for high speed rotation because plastic retainers have characteristics of being lightweight, having small centrifugal force during rotation, and having excellent self-lubrication. For example, Patent Literature 1 proposes a method of reinforcing the rigidity of a retainer by forming a retainer main body of the retainer from a compression molded body of a resin material and integrally molding metal ring plates on both end surfaces of the retainer main body. Patent Literature 2 proposes a method of molding a high strength, high rigidity retainer by impregnating and coating a carbon fiber woven fabric with thermosetting resin and compressing the fabric in an annular axial direction. An electric power steering device is known that transfers auxiliary output from an electric motor to a steering mechanism of a vehicle via a reduction gear mechanism. A gear box that houses the reduction gear mechanism of the electric power steering device includes gear box components such as a gear box and a cover, and such components are generally molded of metal such as an aluminum alloy. In recent years, there has been a demand for improved fuel efficiency of automobiles to save resources, save energy, and reduce CO2 emissions, and electric power steering devices are also required to be even lighter. Therefore, efforts have been made to reduce the weight of gear boxes for electric power steering devices, but to achieve such goal, the materials and structures that form the devices had to be significantly changed. For example, it is conceivable to form a metal gear box from a resin material with a smaller specific gravity, but the resin material has lower impact resistance, creep properties, and rigidity than the metal material, and it is difficult to ensure the same quality as the related-art articles by simply changing the material to the resin material. In the resin structure, it is not easy to ensure dimensional stability equivalent to that of the metal structure. Under such circumstances, examples in which a gear box (housing) of an electric power steering device is made of a resin material are disclosed in Patent Literatures 3 and 4. In the electric power steering device of Patent Literature 3, the housing is entirely made of resin material. In the electric power steering device disclosed in Patent Literature 4, a housing made of a resin material is coated with a metal plating film. Accordingly, it is aimed to achieve weight reduction while keeping characteristics equivalent to those of a metal housing. CITATION LIST Patent Literature Patent Literature 1: JP2015-232382APatent Literature 2: JP2015-135153APatent Literature 3: JP2009-298246APatent Literature 4: JP2012-20647A SUMMARY OF INVENTION Technical Problem In recent years, there has been an increasing demand for machine tools with improved cutting capabilities and short machining time, which resulted in a noticeable tendency to increase the rotational speed of the main shaft. Therefore, in rolling bearings that support the main shaft rotating at high speed, when the centrifugal force exerted on the retainer increases and the retainer is used under severe conditions, there is a risk that the retainer may deform and come into contact with the outer ring, causing wear, or that the retainer may break due to high hoop stress. In Patent Literature 3 discussed above, the sensor housing and the gear housing are entirely formed of a polyamide resin material or polyamide resin filled with reinforcing fibers, and are integrated by laser welding. Therefore, to laser weld both, it is necessary to lower the fiber content, making it difficult to maintain physical properties such as high temperature strength, impact resistance, creep properties, and rigidity over a long period of time. Regarding the method of coating the housing with the metal plating film in Patent Literature 4, alth