Method for molding annular frame

Abstract

This method for molding an annular frame comprises the following procedures. A plurality of prepregs each formed of reinforcing fibers and a thermoplastic resin are laminated to form an annular or generally annular preform having an opening. In an inner circumferential edge region delimiting the opening of the preform, a restraining process for limiting movement of the laminated prepregs in a direction orthogonal to the lamination direction is performed. In a state in which the restraining process is performed, the preform is shaped by application of heat and pressure.

Description

Method for forming an annular frame

[0001] The present disclosure relates to a method for molding an annular frame formed by laminating a plurality of prepregs made of reinforcing fibers and a thermoplastic resin.

[0002] A method is known in which a preform made of a thermoplastic resin with reinforcing fibers embedded therein is heated and pressurized to form a desired molded product. Patent Document 1 discloses a technique for forming an annular frame to be used as a window frame for an aircraft, in which the preform is stamp-molded to form a bent portion in the preform.

[0003] The preform may be a laminate obtained by heating and pressurizing a plurality of prepregs made of fiber-reinforced thermoplastic resin and cut into ring shapes. The prepregs contain a large number of reinforcing fibers aligned in a predetermined fiber direction. When a preform made of such a prepreg laminate is shaped, the fiber direction may become distorted. In this case, problems may arise, such as the desired strength of the annular frame not being achieved or deformation occurring after molding.

[0004] Japanese Patent Application Laid-Open No. 2023-10612

[0005] An object of the present disclosure is to provide a method for molding an annular frame using a fiber-reinforced thermoplastic resin, which enables the production of an annular frame with excellent strength and quality, and suppresses deformation after molding.

[0006] A method for molding an annular frame according to one aspect of the present disclosure includes stacking a plurality of prepregs composed of reinforcing fibers and thermoplastic resin to form an annular or approximately annular preform having an opening, applying a restraint treatment to the inner peripheral edge region defining the opening of the preform to restrict movement of the stacked prepregs in a direction perpendicular to the stacking direction, and heating and pressurizing the preform while the restraint treatment has been applied to the preform to form it into a shape.

[0007] According to the present disclosure, in a method for molding an annular frame using a fiber-reinforced thermoplastic resin, it is possible to produce an annular frame with excellent strength and quality, and to suppress deformation after molding.

[0008] FIG. 1A is a perspective view of a window frame produced by a method for molding an annular frame according to the present disclosure. FIG. 1B is a cross-sectional view taken along line IB-IB in FIG. 1A. FIG. 2 is a process chart illustrating a method for molding an annular frame according to a first embodiment of the present disclosure. FIG. 3A is a plan view of a prepreg sheet. FIG. 3B is a plan view of a prepreg sheet. FIG. 3C is a plan view of a prepreg sheet. FIG. 4 is a diagram illustrating the process from punching the prepreg to forming a prepreg laminate piece. FIG. 5 is a perspective view showing a state in which a preform is disposed between a lower molding die and an upper molding die. FIG. 6 is a cross-sectional view showing a process for shaping a preform. FIG. 7A is a perspective view of the preform after shaping. FIG. 7B is a perspective view showing the state in which a tab has been cut off from the preform. FIG. 7C is a perspective view of the preform after the tab has been cut off. FIG. 8 is a cross-sectional view showing press molding of a preform and a filler. FIG. 9 is a process chart illustrating a method for molding an annular frame according to a second embodiment of the present disclosure. FIG. 10 is a cross-sectional view showing a shaping die used in the second embodiment. FIG. 11A is a perspective view showing the steps of a method for molding an annular frame according to the second embodiment. FIG. 11B is a perspective view showing the steps of a method for molding an annular frame according to the second embodiment. FIG. 11C is a perspective view showing the steps of a method for molding an annular frame according to the second embodiment. FIG. 11D is a cross-sectional view taken along XID-XID in FIG. 11C. FIG. 12A is a perspective view showing the steps of a method for molding an annular frame according to the second embodiment. FIG. 12B is a perspective view showing the steps of a method for molding an annular frame according to the second embodiment. FIG. 12C is a perspective view showing a portion of the second upper molding die shown in FIG. 12B omitted. FIG. 12D is a cross-sectional view taken along XIID-XIID in FIG. 12B. FIG. 13A is a cross-sectional view of the base portion of a window frame. FIG. 13B is a plan view showing the setting of cut regions in prepreg laminate pieces with a fiber direction of 45°. FIG. 14 is an explanatory diagram showing the necessity of making cuts in prepreg laminate pieces. FIG. 15A is a plan view showing the setting of cut regions in prepreg annular laminate pieces with a fiber direction of 0°. Fig. 15B is a plan view showing the setting of incision regions for a prepreg annular laminate piece with a fiber direction of 90°. Fig. 16A is a plan view showing an example of the arrangement of punched pieces that make up the prepreg laminate piece.16B and 16C are plan views showing examples of the arrangement of punched pieces that make up the prepreg laminate piece.

[0009] A method for molding an annular frame according to the present disclosure will be described below with reference to the drawings. The molding method according to the present disclosure can be applied to the production of various annular frames formed by laminating multiple prepregs. The prepreg used in the present disclosure is a thermoplastic prepreg with a thermoplastic resin matrix. There are no limitations on the "annular" form of the molded annular frame. Examples include a circle with an opening in the central region, an ellipse, a rectangle, and a rectangle with some or all of the corners curved. "Annular" includes not only a completely closed annular form, but also a form that has one or more small openings but can be treated as substantially annular. One example of a preferred annular frame is a window frame for an aircraft. The following embodiment illustrates a method for molding the window frame.

[0010] [Configuration of the window frame] Figure 1A is a perspective view of a window frame 1 produced by a molding method described below, and Figure 1B is a cross-sectional view taken along line IB-IB in Figure 1A. The window frame 1 includes a base portion 11 and a filler 12. The window frame 1 is composed of a pair of semicircular ring portions and a straight portion connecting the ends of the semicircular ring portions, and has a shape similar to the Arabic numeral zero in plan view. In other words, the window frame 1 has an oval shape in plan view, and is shaped like the letter O.

[0011] The base portion 11 includes an upper stage portion 111 and a lower stage portion 112 each having a flat surface, and an S-shaped curved portion 113. The S-shaped curved portion 113 connects the upper stage portion 111 and the lower stage portion 112, which have a difference in height. The S-shaped curved portion 113 has two bent portions: a first bent portion 1A and a second bent portion 1B. The first bent portion 1A is connected to the upper stage portion 111. The second bent portion 1B is connected to the lower stage portion 112. The edge of the lower stage portion 112 is the inner peripheral edge 1C of the window frame 1. The inner peripheral edge 1C defines the opening 13 of the window frame 1. The edge of the upper stage portion 111 is the outer peripheral edge 1D of the window frame 1.

[0012] The method for molding the base portion 11 is roughly as follows: A plurality of prepregs are stacked to form an annular preform having an opening 13. A restraining treatment is applied to the inner peripheral edge 1C of the preform to restrict movement of the stacked prepregs in a direction perpendicular to the stacking direction. With the restraining treatment applied, the preform is heated and pressurized to be shaped to have an S-shaped curved portion 113. The details of the shape of the annular preform are determined according to the shape of the window frame 1 after molding.

[0013] The filler 12 is attached to the upper surface of the lower portion 112. Specifically, the filler 12 is filled in the step portion between the upper portion 111 and the lower portion 112 of the base portion 11. The filler 12 is made of a thermoplastic resin that has affinity with the base portion 11. The filler 12 may be made of the same thermoplastic resin as the matrix of the prepreg that constitutes the base portion 11. The filler 12 may also contain reinforcing elements such as reinforcing fibers. The filler 12 is integrated with the base portion 11 by being heated and heated while stacked on the base portion 11.

[0014] [First embodiment] Figure 2 is a process chart showing a molding method according to a first embodiment of the present disclosure. The process chart is intended to produce the window frame 1 shown in Figure 1A. Figures 3A to 8 are diagrams explaining each step in the process chart. The overall flow of the molding method according to the first embodiment will be explained based on the process chart in Figure 2.

[0015] In step S1, prepreg pieces 25 are punched out from the prepreg sheet 2 shown in Figures 3A to 3C, as shown in Figure 4. The step of punching the prepreg pieces 25 out of the prepreg sheet 2 may be performed by punching using a punching die, or by cutting the prepreg sheet 2 into a predetermined shape. The prepreg pieces 25 are punched out in a shape having tabs 26. The tabs 26 are used during the above-mentioned restraint treatment. In step S2, slitting is performed. This slitting is a process of making required cuts in the prepreg pieces 25. Slitting prevents the prepreg pieces 25 from deforming during the pressing process during shaping, which would be detrimental to the manufacture of the window frame 1.

[0016] In step S3, an annular preform 4 is formed. In this formation, prepreg pieces 25 are first arranged to form prepreg laminate pieces 3. The shape of the prepreg laminate pieces 3 is determined according to the shape of the window frame 1 after molding. The required number of these prepreg laminate pieces 3 are stacked. In step S4, a restraint process is performed on the preform 4. In this embodiment, as shown in Figure 5, step S3A is performed in which steps S3 and S4 are performed simultaneously. Specifically, in step S3A, the prepreg pieces 25 are sequentially placed on a molding lower mold 5 having restraint pins 53. This placement forms the preform 4, and the preform 4 is restrained by inserting the restraint pins 53 into the tabs 26.

[0017] In step S5, as shown in Figure 6, the preform 4 is shaped using an upper molding die 6. In this shaping, the preform 4 is bent in two stages to form an S-shaped curved portion 113. In step S6, as shown in Figure 7B, tabs 26 that are unnecessary for the window frame 1 are cut off. In step S7, the shaped preform 4 and filler 12 are consolidated. This consolidation integrates the preform 4 and filler 12. Each of steps S1 to S7 will be described in detail below.

[0018] <Step S1> Figures 3A to 3C are plan views showing a prepreg sheet 2. The prepreg sheet 2 is composed of a thermoplastic resin 21 matrix and a large number of reinforcing fibers 22. The large number of reinforcing fibers 22 are continuous fibers arranged parallel to a predetermined fiber direction. Figure 3A shows an example where the fiber direction is 0°, Figure 3B shows an example where the fiber direction is ±45°, and Figure 3C shows an example where the fiber direction is 90°. The examples of the fiber direction angles in these Figures 3A to 3C are described with the horizontal direction on the page as 0° and the vertical direction on the page as 90°. For example, a preform 4 having quasi-isotropic properties can be formed by multi-layering three types of prepreg sheets 2 having different fiber directions in three axes, such as 0°, 45°, and 90°.

[0019] Examples of the thermoplastic resin include polyetherketoneketone (PEKK), polyetherimide (PEI), polyamide (PA), polyaryletherketone (PAEK), polyacetal (POM), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), thermoplastic epoxy resin, etc. Examples of the reinforcing fiber 22 that can be used include carbon fiber, glass fiber, ceramic fiber, metal fiber, or organic fiber.

[0020] Figure 4 is a diagram showing the flow from punching out prepreg pieces 25 in step S1 to forming prepreg laminate pieces 3. A predetermined length of prepreg sheet 2 is unwound from a prepreg roll and fed to a punching device equipped with a punch blade. The punch blade punches out prepreg pieces 25 of a predetermined shape. Prepreg piece 25 has tab 26. Fixing holes 27 into which restraining pins 53 are inserted are punched in tab 26. Fixing holes 27 penetrate tab 26 in the stacking direction of prepreg laminate pieces 3. Figure 4 shows an example in which fan-shaped punching portions 23 and linear punching portions 24 are punched in prepreg sheet 2.

[0021] The prepreg pieces 25 punched out from the fan-shaped punching section 23 constitute the curved portions of the prepreg laminate piece 3. The prepreg pieces 25 punched out from the linear punching section 24 constitute the linear portions of the prepreg laminate piece 3. When nesting the prepreg pieces 25 from the prepreg sheet 2, the arrangement of the fan-shaped punching section 23 and the linear punching section 24 relative to the prepreg sheet 2 is determined taking into account the fiber direction of the prepreg sheet 2 and the prepreg pieces 25. This allows the prepreg pieces 25 to be efficiently punched out from the prepreg sheet 2. One layer of the prepreg laminate piece 3 is formed by connecting the fan-shaped and linear prepreg pieces 25 in an annular shape. The prepreg laminate piece 3 includes a frame portion 31 and a tab 26. The frame portion 31 is a constituent part of the base portion 11. The tab 26 protrudes from the inner peripheral edge 31B of the annular prepreg laminate piece 3 toward the inside of the ring. In other words, the shape and number of the prepreg pieces 25 are set and punched out so that the tab 26 of the annular prepreg laminate piece 3 is positioned on the inner peripheral edge 31B.

[0022] <Step S2> In the slitting process of step S2, incisions SL are made in the prepreg laminate piece 3, extending in a predetermined direction from the outer peripheral edge 31A. The incisions SL may be made at an appropriate timing before the prepreg pieces 25 are stacked on the lower molding die 5. For example, the incisions SL may be made individually in the punched prepreg pieces 25, or the incisions SL may be made collectively after joining multiple prepreg pieces 25 into the shape of the prepreg laminate piece 3. The incisions SL do not reach the inner peripheral edge 31B. In other words, the incisions SL do not divide the prepreg laminate piece 3. In this embodiment, a first incision region 32 and a second incision region 33 are provided in the prepreg laminate piece 3. The first incision region 32 is a region in which the incisions SL are made at a predetermined first interval. The second incision region 33 is a region in which the incisions SL are made at a second interval narrower than the first interval. The slitting process in step S2 will be further described below with reference to FIGS.

[0023] <Step S3A> Figures 5 and 6 are diagrams showing the execution status of step S3A. Figure 5 is a perspective view showing a state in which the preform 4 is arranged between the lower molding die 5 and the upper molding die 6. Figure 6 is a cross-sectional view showing a state in which the preform 4 is arranged between the lower molding die 5 and the upper molding die 6. The preform 4 is formed by stacking the required number of prepreg laminate pieces 3. After the preform 4 is formed, the tabs 26 of the prepreg laminate pieces 3 are in a state in which they protrude from the inner peripheral edge of the preform 4 into the opening. Each tab 26 at the same position in the circumferential direction of the preform 4 overlaps so that the fixing holes 27 are in the same position.

[0024] The molding lower die 5 includes a lower die base 50, a lower shaping portion 51, a pressing portion 52, a restraining pin 53, and a positioning pin 54. A plurality of prepreg laminate pieces 3 are placed on the molding lower die 5. The lower die base 50 is a flat plate that serves as the base of the molding lower die 5. The lower shaping portion 51 is a surface with an uneven shape that is shaped relative to the underside of the preform 4. The lower shaping portion 51 has a surface shape that corresponds to the upper step portion 111, the lower step portion 112, and the S-shaped curved portion 113 of the base portion 11. The pressing portion 52 is a convex surface that is received by the molding upper die 6 during pressing. The restraining pin 53 is a cylindrical pin that stands upright from the pressing portion 52 in the vertical direction. The restraining pins 53 are each erected at a position corresponding to the fixing holes 27 of the preform 4 that are arranged circumferentially. The positioning pin 54 is provided vertically from the pressing portion 52 inside the group of annularly arranged restraining pins 53. The positioning pin 54 is used for alignment with the upper forming die 6.

[0025] The preform formation process of step S3 described above is achieved by placing prepreg pieces 25 or prepreg laminate pieces 3 one layer at a time on the lower molding die 5. During this placement, restraint pins 53 are inserted into the fixing holes 27 of the tabs 26. This insertion corresponds to the restraint process of step S4 described above. That is, the position of the tabs 26 is fixed by the restraint pins 53, thereby restricting movement of the prepreg laminate pieces 3 in a direction perpendicular to the stacking direction. In FIG. 6, the direction perpendicular to the stacking direction of the prepreg laminate pieces 3 is the horizontal direction on the paper. In this way, in step S3A, steps S3 and S4 are performed simultaneously. Once the required layers of the prepreg laminate pieces 3 have been placed, the formation of the preform 4 and the restraint of the inner peripheral edge region of the preform 4 are completed. It is also possible to perform lamination of the prepreg laminate pieces 3, that is, formation of the preform 4, at a location separate from the lower molding die 5, and then place the preform 4 on the lower molding die 5 in that state.

[0026] <Step S5> Figure 6 shows the state immediately before shaping in step S6 is performed by the molding upper mold 6. The shaping is performed by pressing the molding upper mold 6 under a predetermined temperature environment. The molding upper mold 6 includes an upper mold base 60, an upper shaping portion 61, a restraining pin hole 62, and a positioning pin hole 63. The upper mold base 60 is a flat plate that serves as the base of the molding upper mold 6. The upper shaping portion 61 is positioned opposite the lower shaping portion 51 of the molding lower mold 5. The upper shaping portion 61 has a surface with an uneven shape that is shaped relative to the upper surface of the preform 4. The restraining pin hole 62 receives the restraining pin 53 of the molding lower mold 5 during the pressing operation. The positioning pin hole 63 receives the positioning pin 54. As the molding upper mold 6 descends from the state shown in Figure 6, the upper shaping portion 61 approaches the lower shaping portion 51. Eventually, the lower shaping portion 51 comes into contact with the lower surface of the preform 4, and the upper shaping portion 61 comes into contact with the upper surface of the preform 4, pressing the preform 4 into the required shape. During shaping, the tabs 26 are restrained by the restraining pins 53, which prevents the reinforcing fibers 22 of each prepreg laminate piece 3 from becoming disordered. As a result, deformation of the preform 4 can be prevented, and the strength of the window frame 1 after molding can be improved.

[0027] The heating temperature of the preform 4 during shaping will be described. The heating temperature is set to a temperature at which the preform 4 can be shaped but at which the stacked prepreg laminate pieces 3 do not weld together. Specifically, when the melting point of the thermoplastic resin 21 that is the matrix of the prepreg sheet 2 is Th [°C], the heating temperature during shaping can be selected from the range of Th [°C] to Th-40 [°C].

[0028] An example will be given in which the thermoplastic resin 21 is polyaryletherketone. The melting point Th of polyaryletherketone is 305°C. In this case, the heating temperature during shaping can be selected within the range of 305°C - 40°C = 265°C to 305°C. A more preferable temperature range is 270°C to 290°C. By selecting such a heating temperature, adjacent prepreg laminate pieces 3 do not weld together during shaping, but slip relative to each other. In other words, prepreg laminate pieces 3 stacked at multiple angles are shaped without interfering with each other. In addition, the incisions SL facilitate the fibers contained in the prepreg laminate pieces 3 to be displaced in the fiber direction. Therefore, even when a press load is applied, a large restraining force is not generated between the layers, suppressing the occurrence of large wrinkles or fiber fluctuations in the prepreg laminate pieces 3. As a result, shaping can be performed while maintaining the angle of the fibers contained in the prepreg laminate pieces 3. The preform 4 can be heated by heating the lower mold 5 and the upper mold 6, or by carrying out shaping in a heating chamber.

[0029] <Step S6> Figure 7A is a perspective view showing the preform 4A after shaping in step S5. Figure 7B is a perspective view showing the state of cutting off the tab 26 of the preform 4A. The tab 26 is a member for restraining the prepreg piece 25 or prepreg laminate piece 3 that constitutes the preform 4 before shaping. The tab 26 is an unnecessary member for the window frame 1, so it is cut off after shaping. For example, the tab 26 can be cut off from the preform 4A by punching using a Thomson blade. Figure 7C is a perspective view showing the preform 4B after the tab 26 has been cut off. The preform 4B corresponds to the base portion 11 shown in Figure 1.

[0030] <Step S7> Figure 8 is a cross-sectional view showing the state of press molding for consolidating the preform 4B and the filler 12. In step S7, a press mold 14 is used. The press mold 14 includes an upper mold 141 and a lower mold 142. A stack is formed by attaching the filler 12 molded in a separate process to the preform 4B shaped in step S6. The stack is sandwiched in the cavity between the upper mold 141 and the lower mold 142. Thereafter, the stack is pressed by the upper mold 141 at a predetermined heating temperature. The shaped preform 4B and the filler 12 are integrated by this pressing.

[0031] The heating temperature in step S7 will be described. Unlike during shaping, the heating temperature is set to a temperature at which the prepreg laminate pieces 3 constituting the preform 4A are welded together. In the state of the preform 4A, the prepreg laminate pieces 3 are in contact with each other to the extent that the preform 4A has shape retention, but are not welded together. In step S7, press molding is performed by selecting a heating temperature that exceeds the melting point Th [°C] of the thermoplastic resin 21. As a condition for selecting the heating temperature, it is also necessary that the heating temperature be equal to or higher than the melting point of the thermoplastic resin constituting the filler 12. By press molding at this heating temperature, the preform 4B and the filler 12 are melted and integrated, and the prepreg laminate pieces 3 can be welded together.

[0032] [Second embodiment] Figure 9 is a process chart showing a molding method according to a second embodiment of the present disclosure. This process chart also assumes the production of the window frame 1 shown in Figure 1A. Figures 10 to 12D are diagrams explaining each step of the process chart. The overall flow of the molding method according to the second embodiment will be explained based on the process chart in Figure 9.

[0033] The punching of the prepreg in step S11 and the slitting in step S12 are substantially the same as steps S1 and S2 in the first embodiment. However, the prepreg in the second embodiment is punched out in a form that does not have tabs 26. In step S13, the required number of prepreg laminate pieces 3 are stacked to form an annular preform 4. As shown in Figures 11A and 11B, the prepreg laminate pieces 3 are sequentially placed on a molding lower mold 5A that has a different form from that in the first embodiment. In step S13, the preform 4 is not restrained.

[0034] In step S14, as shown in Figures 11C and 11D, the first upper molding die 64 of the upper molding die 6A is fitted into the lower molding die 5A. As a result, the inner peripheral edge region of the preform 4 is sandwiched between the fixing surface 642 of the first upper molding die 64 and the lower molding die 5A. In step S15, as shown in Figure 12A, the first upper molding die 64 is urged toward the lower molding die 5A by tightening the spring-loaded bolt 66. In step S15, the preform 4 is restrained at the inner peripheral edge region.

[0035] In step S16, as shown in FIG. 12B, a second upper molding die 65 is set relative to the lower molding die 5A. The second upper molding die 65 has an upper shaping portion 652. In the following step S17, the second upper molding die 65 performs a pressing operation in a predetermined temperature environment. As shown in FIG. 12D, the preform 4 is shaped by pressing the fixing surface 642, the upper shaping portion 652, and the lower shaping portion 51A of the lower molding die 5A. In step S18 after shaping, the preform 4 is removed from the lower molding die 5A. In step S19, the shaped preform 4 and the filler 12 are consolidated. Below, the shaping die used in the second embodiment and each of the steps other than steps S11, S12, and S19, which are substantially the same as those in the first embodiment, will be described in detail.

[0036] <Shaping Mold Structure> Figure 10 is a cross-sectional view showing a shaping mold used in the second embodiment. The shaping mold includes a lower shaping mold 5A, an upper shaping mold 6A, and a spring-loaded bolt 66. The upper shaping mold 6A is composed of a first upper shaping mold 64 and a second upper shaping mold 65. A prepreg piece 25 or a prepreg laminate piece 3 is placed on the lower shaping mold 5A to form the preform 4. The first upper shaping mold 64 restrains the preform 4 and shapes the inner peripheral region of the preform 4. The second upper shaping mold 65 shapes the outer region of the preform 4 other than the inner peripheral region.

[0037] The lower forming die 5A includes a lower die base 50A, a lower shaping portion 51A, a fitting protrusion 55, a plurality of screw holes 56, a plurality of positioning holes 57, and a standing wall 58. The lower die base 50A is a flat plate that serves as the base of the lower forming die 5A. The lower shaping portion 51A is an annular surface with an uneven shape that forms the underside of the preform 4. The fitting protrusion 55 protrudes upward from the inner region of the lower shaping portion 51A on the lower die base 50A. A first upper forming die 64 is fitted into the fitting protrusion 55. A spring-loaded bolt 66 is fastened into the screw hole 56. The positioning hole 57 is used to position the second upper forming die 65.

[0038] The standing wall 58 is erected vertically on the outer periphery of the lower shaping portion 51A. An annular molding space 51B is defined between the inner peripheral surface of the standing wall 58 and the side peripheral surface of the mating protrusion 55. When multiple prepreg laminate pieces 3 are placed on the lower shaping portion 51A, the multiple prepreg laminate pieces 3 are accommodated in the molding space 51B. When the preform 4 is accommodated in the molding space 51B, the standing wall 58 surrounds the outer peripheral edge of the preform 4. This makes it possible to restrict movement of the preform 4 in the radial expansion direction during shaping.

[0039] The first molding upper mold 64 includes a first mold base 640, a first cylindrical portion 641, a fixing surface 642, a first cavity 643, and a plurality of bolt holes 644. The first mold base 640 is a flat plate with an outer periphery larger than that of the fitting protrusion 55 of the molding lower mold 5A. The first cylindrical portion 641 is a sidewall extending downward from the outer periphery of the first mold base 640. The fixing surface 642 is the lower end surface of the first cylindrical portion 641. During shaping, the fixing surface 642 abuts against a region of the inner periphery of the preform 4 from above in the stacking direction of the prepreg laminate piece 3. The first cavity 643 is a space defined by the inner periphery of the first cylindrical portion 641 and the lower surface of the first mold base 640. The fitting protrusion 55 fits into the first cavity 643. The bolt hole 644 is a through-hole in the vertical direction for passing the spring-loaded bolt 66. The bolt hole 644 is drilled at a position that overlaps the screw hole 56 in the vertical direction when the first forming upper die 64 is fitted into the forming lower die 5A.

[0040] The second molding upper die 65 includes a second die base 650, a second cylindrical portion 651, an upper shaping portion 652, a second cavity 653, a bolt relief hole 654, and a positioning pin 655. The second die base 650 is the foundation of the second molding upper die 65. A load is applied to the second die base 650 during shaping. The second cylindrical portion 651 is a side wall extending downward from near the outer periphery of the second die base 650. The upper shaping portion 652 is the lower end surface of the second cylindrical portion 651. The upper shaping portion 652 is an annular molding surface that shapes the outer region of the preform 4 during shaping.

[0041] The second cavity 653 is a space defined by the inner periphery of the second cylindrical portion 651 and the underside of the second mold base 650. The second cavity 653 is a space sized to accommodate the first molding upper die 64. During molding, the first molding upper die 64 is fitted into the second cavity 653, and the underside of the second mold base 650 presses the first mold base 640. The bolt escape hole 654 is a through hole drilled in the second mold base 650. A spring-loaded bolt 66 is inserted into the bolt escape hole 654. The positioning pin 655 is erected downward from the underside of the second mold base 650 at a position corresponding to the positioning hole 57. During molding, the positioning pin 655 is inserted into the positioning hole 57, and the molding upper die 6A is positioned relative to the molding lower die 5A.

[0042] The spring-loaded bolt 66 is fastened to the screw hole 56 through the bolt hole 644, thereby biasing the first forming upper die 64 in a direction toward the forming lower die 5A. The spring-loaded bolt 66 includes a bolt body 661 and a biasing spring 662. The bolt body 661 has a threaded portion at its tip and a screw head at its base end. The biasing spring 662 is a coil spring inserted into the bolt body 661. One end of the biasing spring 662 is supported by the screw head. The other end of the biasing spring 662 abuts against the top surface of the first forming upper die 64. A washer bolt with a disc spring may also be used as the spring-loaded bolt 66.

[0043] <Step S13> Figures 11A and 11B show the implementation of step S13 using a lower molding die 5A. The lower molding die 5A has an annular molding space 51B that matches the shape of the preform 4. The bottom surface of the molding space 51B is a lower shaping portion 51A that abuts against the underside of the preform 4. Prepreg pieces 25 or prepreg laminate pieces 3 are stacked one layer at a time in the molding space 51B. This stacking operation is continued until the required number of layers of the preform 4 is reached. The inner peripheral edge of the formed preform 4 abuts against the side peripheral surface of the mating protrusion 55. The outer peripheral edge of the preform 4 is surrounded by a standing wall 58.

[0044] <Steps S14 and S15> Figures 11C and 11D show the implementation of step S14, and Figure 12A shows the implementation of step S15. In step S14, the first cavity 643 of the first molding upper die 64 is fitted into the fitting convex portion 55 of the molding lower die 5A. The opening size of the first cavity 643 is slightly larger than the outer size of the fitting convex portion 55. As a result of this fitting, as shown in Figure 11D, the inner circumferential surface of the first cylindrical portion 641 comes into contact with or is close to the side circumferential surface of the fitting convex portion 55. The fixing surface 642, which is the lower end surface of the first cylindrical portion 641, comes into contact with or is close to the inner circumferential edge region of the preform 4. The preform 4 is placed on the lower shaping portion 51A. Therefore, the inner peripheral edge region of the preform 4 is sandwiched from above and below between the fixing surface 642 and the inner region of the lower shaping portion 51A.

[0045] The region of the inner peripheral edge of the preform 4 in the second embodiment is an annular region near the inner peripheral edge of the preform 4, and is a partial region of the preform 4 itself. This partial region roughly corresponds to the region of the lower step 112 of the base portion 11 shown in FIG. 1B. In the second embodiment, the region of the lower step 112 is the region that is restrained in the restraining process. In this respect, it differs from the first embodiment, in which the tab 26 that protrudes separately from the main body of the preform 4 is used as the restraining region. The second embodiment has the advantage that it is not necessary to attach a dedicated restraining portion such as the tab 26 to the preform 4.

[0046] In step S15, the spring-loaded bolt 66 is threaded into the threaded hole 56. The bolt hole 644 of the first forming upper die 64 is drilled in alignment with the threaded hole 56 of the forming lower die 5A. By the fitting in step S14, the bolt hole 644 and the threaded hole 56 are aligned vertically. The bolt body 661 of the spring-loaded bolt 66 is inserted into the bolt hole 644 and fastened to the threaded hole 56 of the forming lower die 5A. The biasing spring 662 is compressed by fastening the bolt body 661, generating a biasing force. The first forming upper die 64 is pressed downward by the other end of the biasing spring 662 with the biasing force. As a result, the inner peripheral edge region of the preform 4 is sandwiched and fixed between the fixing surface 642 and the inner region of the lower shaping portion 51A from above and below. In other words, the preform 4 is restrained at its inner peripheral edge region. Since the preform 4 is clamped and fixed with a biasing force, it can be more reliably restrained.

[0047] <Steps S16 to S18> Figures 12B and 12C show the implementation of step S16, and Figure 12D shows the implementation of step S17. Note that Figure 12C is a diagram in which the second die base 650 of the second molding upper die 65 in Figure 12B is omitted. In step S16, the second cavity 653 of the second molding upper die 65 is fitted into the first molding upper die 64. The opening size of the second cavity 653 is slightly larger than the outer size of the first molding upper die 64. The spring-loaded bolt 66 protruding from the top surface of the first molding upper die 64 is inserted into the bolt relief hole 654 of the second molding upper die 65.

[0048] 12D, the fitting in step S16 brings the inner peripheral surface of the second cylindrical portion 651 into contact with or into close proximity to the side peripheral surface of the first cylindrical portion 641. The upper shaping portion 652, which is the lower end surface of the second cylindrical portion 651, comes into contact with or into close proximity to the outer peripheral edge region of the preform 4. The outer peripheral edge region is the remaining portion excluding the inner peripheral edge region, and roughly corresponds to the upper step portion 111 and the S-shaped curved portion 113 region of the base portion 11 shown in FIG. 1B. The upper shaping portion 652 has a mold shape that forms the upper step portion 111 and the S-shaped curved portion 113.

[0049] In step S17, a downward load is applied from the press mechanism to the second molding upper die 65 to shape the preform 4. This load causes the upper shaping portion 652 and the lower shaping portion 51A to shape the outer peripheral edge region of the preform 4, forming the upper step portion 111 and the S-shaped curved portion 113. At the same time, the second molding upper die 65 presses the first molding upper die 64 downward. That is, the first die base 640 fitted into the second cavity 653 is pressed by the second die base 650.

[0050] The inner peripheral edge region of the preform 4 is shaped to a certain extent by sandwiching it between the fixing surface 642 and the inner region of the lower shaping portion 51A in step S15. The pressing in step S17 shaping the inner peripheral edge region of the preform 4 into its final shape. Furthermore, the pressing in step S17 sandwiches the preform 4 between the fixing surface 642 and the inner region of the lower shaping portion 51A, and a greater load is applied to the preform 4. This makes it possible to suppress fiber disordering of the reinforcing fibers 22 of each prepreg laminate piece 3 when the outer peripheral edge region is shaped by the upper shaping portion 652. Furthermore, because the outer peripheral edge of the preform 4 is surrounded by the standing wall 58, it is possible to restrict radially outward movement of the prepreg laminate piece 3.

[0051] As described above, in step S17, the preform 4 is sandwiched between the lower molding die 5A and the first and second upper molding dies 64 and 65, and is shaped by applying heat and pressure. As in the first embodiment, the heating temperature is a temperature at which the preform 4 can be shaped but does not cause the stacked prepreg laminate pieces 3 to weld together. In step S18, the shaping die is disassembled and the shaped preform 4 is removed. Specifically, the load applied by the press mechanism is released, and the second upper molding die 65 is removed from the lower molding die 5A. Next, the spring-loaded bolt 66 is removed, and the first upper molding die 64 is removed. Thereafter, the preform 4 is removed from the molding space 51B. Subsequently, consolidation in step S19 is performed using the same procedure as step S7 in the first embodiment.

[0052] [Regarding Slitting] The slitting performed in steps S2 and S12 above will be described in detail. Slitting is performed to prevent deformation such as wrinkles and tears from occurring in the prepreg pieces 25 or prepreg laminate pieces 3 when shaping the preform 4. Slitting also contributes to maintaining the fiber angle and fiber direction of the prepreg pieces 25 or prepreg laminate pieces 3 when shaping the preform 4. Figure 13A is a cross-sectional view of the base portion 11 of the window frame 1. Note that, contrary to the base portion 11 in Figure 1B, the base portion 11 in Figure 13A has an upper step portion 111 that defines the inner peripheral edge 1C.

[0053] 13B is a plan view showing an example of an incision made in a prepreg laminate piece 3 with a fiber direction of 45°. The portion corresponding to the first bent portion 1A of the base portion 11 is indicated by dotted line A on the prepreg laminate piece 3, and the portion corresponding to the second bent portion 1B is indicated by dotted line B. The portion corresponding to the inner peripheral edge 1C is the inner peripheral line E1 of the prepreg laminate piece 3, and the portion corresponding to the outer peripheral edge 1D is the outer peripheral line E2.

[0054] The prepreg laminate piece 3 includes a first cut region 32 and a second cut region 33. A first cut SL1 is made in the first cut region 32. A second cut SL2 is made in the second cut region 33. The prepreg laminate piece 3 has a fiber direction in one direction. In contrast, the angle between the dotted lines A and B and the fiber direction varies depending on the position on the prepreg laminate piece 3. As a result, when the prepreg laminate piece 3 is bent along the dotted lines A and B during shaping, the direction in which the fibers tend to bend varies depending on the position. The fibers in the prepreg laminate piece 3 are bonded together by a thermoplastic resin, restricting free deformation. As a result, when the prepreg laminate piece 3 is bent along the dotted lines A and B during shaping, relatively large deformation or tearing of the prepreg laminate piece 3 occurs in some locations. By providing the cuts SL1 and SL2 in the prepreg laminate piece 3, the propagation of localized deformation that occurs in the prepreg laminate piece 3 during shaping is suppressed. As a result, it is possible to prevent the above-mentioned relatively large deformation and tearing of the prepreg laminate piece 3. Therefore, it is possible to suppress the occurrence of deformation in the prepreg laminate piece 3 that is detrimental to the manufacture of the window frame 1 during shaping.

[0055] In the prepreg laminate piece 3 with a fiber direction of 45°, a large number of reinforcing fibers 22 are arranged parallel to one another in the thermoplastic resin 21. The first incision SL1 and the second incision SL2 are aligned along the fiber direction of the prepreg laminate piece 3. In other words, the incisions SL1 and SL2 are inclined at 45° with respect to the minor axis or major axis of the annular prepreg laminate piece 3. If the incisions are made in a direction intersecting the fiber direction, the reinforcing fibers 22 will be cut. In contrast, if the incisions are made along the fiber direction, cutting of the reinforcing fibers 22 can be prevented, and a decrease in the strength of the prepreg laminate piece 3 can be suppressed.

[0056] The first cut SL1 extends from the circumferential line E2 to the dotted line A. In other words, the first cut SL1 is a cut that spans from the lower step portion 112 to the region corresponding to the S-shaped curved portion 113. The second cut SL2 extends from the circumferential line E2 to the dotted line B. The second cut SL2 is in the region corresponding to the lower step portion 112. In the first cut region 32, the first cuts SL1 are made at a predetermined first interval. In the second cut region 33, the second cuts SL2 are made at a second interval that is narrower than the first interval.

[0057] The prepreg laminate piece 3 is composed of a pair of opposing straight line portions 3L and a pair of opposing semicircular curved portions 3R. The first and second cut regions 32, 33 are mostly located in the curved portions 3R. The first and second cut regions 32, 33 are regions with a constant width in a direction perpendicular to the fiber direction of the reinforcing fibers 22. Point P1 on the curved portions 3R is the point of contact between a tangent to the inner circumferential line E1 of the curved portions 3R and the inner circumferential line E1. The tangent to the inner circumferential line E1 described here is approximately parallel to the fiber direction of the reinforcing fibers 22. Each of the pair of opposing semicircular curved portions 3R has a tangent to the inner circumferential line E1 and point P1. The area between the two tangents to the inner circumferential line E1, in other words, the area between the two points P1, is defined as the inside of the annular prepreg laminate piece 3 when the fiber direction is 45°. Furthermore, the area that is not inside the annular prepreg laminate piece 3 is defined as the outside of the annular prepreg laminate piece 3 when the fiber direction is 45°. Near point P1, the extension direction of the step wall of the S-shaped curved portion 113 and the fiber direction are approximately parallel. The first cut region 32 and the second cut region 33 are adjacent to each other, with the tangent to the curved portion 3R passing through point P1 as their boundary. The first cut region 32, which has a sparse cut pitch, is located inside the annular prepreg laminate piece 3 from the tangent to the curved portion 3R passing through point P1. The first cut region 32, which has a dense cut pitch, is located outside the annular prepreg laminate piece 3 from the tangent to the curved portion 3R passing through point P1.

[0058] The arrangement of the first cut region 32 and the second cut region 33 described above depends on the susceptibility of deformation, such as wrinkles and tears, of the prepreg laminate piece 3 during shaping. Figure 14 is an enlarged view of the prepreg laminate piece 3 in Figure 13B near point P1. Figure 14 also shows three lines PA1, PA2, and PA3 along the fiber direction. When shaping the preform 4, the reinforcing fibers 22 tend to curve along the step portion 511 of the lower shaping portion 51A along line PA1 of the straight portion 3L away from point P1. This is because the crossing angle between the fiber direction and the extension direction of the step portion 511 is relatively large. In this case, the arrangement of the reinforcing fibers 22 is relatively unlikely to be disrupted.

[0059] In contrast, in the curved portion 3R, the step portion 511 is curved, so the arrangement and angle of the reinforcing fibers 22 are easily disturbed during shaping. In particular, in the line PA2 near point P1, the fiber direction and the extension direction of the step portion 511 are nearly parallel, so the reinforcing fibers 22 are unlikely to curve along the step portion 511. When a load for shaping is applied to such a location, the spaces between adjacent reinforcing fibers 22 may widen, causing large tears GA, or wrinkles LA in which the reinforcing fibers 22 overlap significantly. In other words, the arrangement and angle of the reinforcing fibers 22 are likely to be significantly disturbed. On the other hand, even in the vicinity of point P1, in the line PA3 that does not overlap the step portion 511, the arrangement of the reinforcing fibers 22 is unlikely to be disturbed.

[0060] Considering the deformation of the reinforcing fibers 22 during shaping, no cuts are intentionally made in the straight section 3L. Of course, some cuts may be made. The area of ​​the curved section 3R, excluding the area near point P1, is designated as the first cut region 32, which has coarsely spaced first cuts SL1. By making the first cuts SL1, the deformation force of the prepreg laminate piece 3 during shaping is dispersed through small gaps between the reinforcing fibers 22 and small overlaps between the reinforcing fibers 22. The area surrounding the line PA2 at point P1 is designated as the second cut region 33, which has densely spaced second cuts SL2. By making multiple second cuts SL2 with a small pitch, the deformation force is further dispersed. Furthermore, by making the cut length of the second cuts SL2 shorter than the first cuts SL1, the disorder of the fiber arrangement and angle at the perimeter line E2 of the prepreg laminate piece 3 can be further suppressed. The second cut region 33 is designated in a region where the fiber movement during shaping is greater than that of the first cut region 32. When a cut is made in the prepreg laminate piece 3, the longer the length from the start point to the end point of the cut, the greater the fiber movement at the start point of the cut during shaping. For example, in the first cut region 32 and the second cut SL2 in this embodiment, the fiber movement at the perimeter line E2 is greater. For this reason, if the second cut region 33, which is applied to a portion with greater fiber movement, has the same cut length as the first cut region 32, the fiber arrangement and angle at the perimeter line E2 are likely to become distorted. For this reason, the cut length of the second cut region 33 is set shorter than that of the first cut region 32. This prevents deformation of the prepreg laminate piece 3 that is harmful to the manufacture of the window frame 1. It is not necessary to actively make cuts in the area surrounding the line PA3 at point P1.

[0061] FIG. 15A is a plan view showing an example of incisions made in a prepreg laminate piece 3 with a fiber direction of 0°. As with the prepreg laminate piece 3 with a fiber direction of 45°, the tangent to the inner periphery line E1 of the curved portion 3R is assumed to be approximately parallel to the fiber direction of the reinforcing fibers 22. In this case, point P2, where the tangent to the inner periphery line E1 of the curved portion 3R and the inner periphery line E1 intersect, is located at the circumferential center of the inner periphery line E1 of the curved portion 3R. The first incision region 32 and the second incision region 33 are adjacent to each other, with the tangent to the inner periphery line E1 of the curved portion 3R passing through point P2 as their boundary. Each of a pair of opposing semicircular curved portions 3R has a tangent to the inner periphery line E1 and point P2. The area between the two tangents to the inner periphery line E1, in other words, the area between the two points P2, is defined as the inside of the annular prepreg laminate piece 3 when the fiber direction is 0°. Furthermore, the area that is not inside the annular prepreg laminate piece 3 is defined as the outside of the annular prepreg laminate piece 3 when the fiber direction is 0°. The first incision region 32 having the coarse-pitch first incisions SL1 is provided inside the annular prepreg laminate piece 3 from the tangent to the curved portion 3R that passes through point P2. The second incision region 33 having the fine-pitch second incisions SL2 is provided outside the annular prepreg laminate piece 3 from the tangent to the curved portion 3R that passes through point P2.

[0062] 15B is a plan view showing an example of an incision made in a prepreg laminate piece 3 with a fiber direction of 90°. In this case, the tangent to the inner circumferential line E1 of the annular prepreg laminate piece 3 coincides with the inner circumferential line E1 of the straight section 3L. Point P3, which is the contact point with the tangent, is defined as the circumferential center position of the straight section 3L. Each of a pair of opposing straight sections 3L has a tangent to the inner circumferential line E1 and point P3. The region between the two tangents to the inner circumferential line E1, in other words, the region between the two points P3, is defined as the inside of the annular prepreg laminate piece 3 when the fiber direction is 90°. Furthermore, the region that is not inside the annular prepreg laminate piece 3 is defined as the outside of the annular prepreg laminate piece 3 when the fiber direction is 90°. The first cut region 32 and the second cut region 33 are adjacent to each other, with the boundary being a tangent to the straight portion 3L passing through point P3, i.e., the inner circumferential line E1 of the straight portion 3L. The first cut region 32, which has the coarse-pitch first cuts SL1, is located from the inner circumferential line E1 of the straight portion 3L to the inside of the diameter of the annular prepreg laminate piece 3. The second cut region 33, which has the fine-pitch second cuts SL2, is located from the inner circumferential line E1 of the straight portion 3L to the outside of the diameter of the annular prepreg laminate piece 3.

[0063] [Punching Example of Prepreg Piece] Figure 4 shows an example of a punching pattern for the prepreg piece 25 executed in step S1 of Figure 2. Here, other preferred examples of punching patterns are shown. Figures 16A to 16C are plan views showing an example of the arrangement of punched pieces constituting the annular prepreg laminate piece 3. Figure 16A shows a prepreg laminate piece 3 with a fiber direction of ±45°. The prepreg laminate piece 3 with a fiber direction of ±45° is composed of two first prepreg pieces 25A and two second prepreg pieces 25B joined together. The cutting lines NL of the prepreg pieces 25A and 25B are aligned along the fiber direction of ±45°. The first prepreg piece 25A is a punched piece with a semicircular arc shape including point P1 shown in Figure 13B. The first prepreg piece 25A is slit to form the first cut region 32 and the second cut region 33. The second prepreg piece 25B is a punched piece including a straight portion and an approximately quarter-circular arc portion. The second prepreg piece 25B is slit to form the first cut region 32.

[0064] The two first prepreg pieces 25A have the same shape. The two second prepreg pieces 25B also have the same shape. Therefore, when punching out the prepreg sheet 2 shown in Figures 3A to 4, which is the base material, it is only necessary to punch out two shapes, the first prepreg pieces 25A and the second prepreg pieces 25B. This has the advantage that it is easy to arrange the sector-shaped punching portions 23 and the linear punching portions 24 for punching out the prepreg pieces 25 in the prepreg sheet 2. Furthermore, it is sufficient to prepare two types of cutting patterns for slitting, which simplifies the processing work.

[0065] Figure 16B shows a prepreg laminate piece 3 with a fiber direction of 0°. The prepreg laminate piece 30° with a fiber direction of 0° is composed of two identically shaped third prepreg pieces 25C and two identically shaped fourth prepreg pieces 25D spliced ​​together. Figure 16C shows a prepreg laminate piece 3 with a fiber direction of 90°. The prepreg laminate piece 3 with a fiber direction of 90° is composed of two identically shaped fifth prepreg pieces 25E and two identically shaped sixth prepreg pieces 25F spliced ​​together. The cut lines NL of prepreg pieces 25C and 25D are aligned along the 0° fiber direction. The cut lines NL of prepreg pieces 25E and 25F are aligned along the 90° fiber direction. The concept of minimizing the punching and slitting patterns is the same as for the prepreg laminate piece 3 with a fiber direction of ±45°.

[0066] [Other Modifications] As examples of the restraint process of the present disclosure, the first embodiment shows an example in which the restraint pin 53 is inserted through the tab 26 to restrain it, and the second embodiment shows an example in which the inner peripheral edge portion of the preform 4 itself is clamped between a shaping mold to restrain it. Instead of the restraint pin 53, a configuration in which the tab 26 is clamped and fixed between a shaping mold or other restraining device may be used. Also, a configuration in which the restraint means of the first and second embodiments are used together, that is, a configuration in which restraint using the tab 26 and restraint of the inner peripheral edge portion of the preform 4 are used together may be used.

[0067] [Summary of the Disclosure] The specific embodiments described above include disclosures having the following configurations.

[0068] A method for molding an annular frame according to a first aspect of the present disclosure includes stacking a plurality of prepregs composed of reinforcing fibers and thermoplastic resin to form an annular or approximately annular preform having an opening, applying a restraint treatment to the inner peripheral edge region defining the opening of the preform to restrict movement of the stacked prepregs in a direction perpendicular to the stacking direction, and heating and pressurizing the preform in the restraint state to form it into a shape.

[0069] According to the first aspect, the laminated prepreg is constrained in the inner peripheral region of the preform. Generally, the reinforcing fibers of a prepreg are embedded in a thermoplastic resin in a predetermined arrangement that provides reinforcing effects. Disorders in the arrangement or angle of the reinforcing fibers can reduce the strength of the molded part or cause deformation. The constraining process ensures that the reinforcing fibers in the prepreg also have fixed points in the inner peripheral region. Therefore, even when the preform is heated and pressurized for shaping, the reinforcing fibers are prevented from becoming distorted. The desired fiber orientation and angle of each prepreg are maintained even after aging. As a result, annular frames with the desired strength can be consistently produced. This allows, for example, the design stage to avoid increasing the number of prepreg layers to account for manufacturing variability, ensuring the desired strength even when annular frames are manufactured with a small number of layers. Furthermore, deformations such as warping of the annular frame after molding can also be suppressed.

[0070] A second aspect of the method for molding an annular frame is the molding method of the first aspect, wherein each of the plurality of prepregs includes a tab protruding from the inner peripheral edge at a position that protrudes into the opening after the preform is formed, and the restraint treatment is performed using the tab.

[0071] According to the second aspect, each prepreg has a tab for restraining. The protruding tabs make the restraining position clear during the restraining process, and the tabs can be used to easily restrain each prepreg.

[0072] A third aspect of the method for molding an annular frame is the molding method of the second aspect, wherein the tab has a fixing hole that passes through the tab in the stacking direction and has a plurality of pins that are erected at positions corresponding to the fixing holes, a molding lower mold is prepared on which the plurality of prepregs are placed, and as the restraint process, the pins are inserted into the fixing holes when the prepregs or the preforms are placed on the molding lower mold.

[0073] According to the third aspect, the restraint process can be completed by the simple operation of inserting the pins into the fixing holes of the tabs. If the prepreg is laminated on the lower mold while the pins are inserted into the fixing holes, the restraint process can be performed simultaneously with the formation of the preform. This improves work efficiency. If the preform is formed and then placed on the lower mold, there is the advantage that the operation of inserting the pins into the fixing holes can be performed in a single operation.

[0074] The method for molding an annular frame according to the fourth aspect is the molding method of the first or second aspect, in which a lower molding die on which the plurality of prepregs are placed is prepared, and as the restraint process, a first upper molding die is placed above the preform on the lower molding die, and the lower molding die and the first upper molding die sandwich and fix the inner peripheral edge region of the preform.

[0075] According to the fourth aspect, the inner peripheral edge region of the preform is sandwiched and fixed between the lower molding die and the first upper molding die, thereby simplifying the restraint process. The portion sandwiched and fixed may be a dedicated portion provided for restraining the prepreg, such as the tab. If the original shape portion of the prepreg is sandwiched and fixed, the formation of the dedicated portion can be omitted.

[0076] The molding method for an annular frame according to the fifth aspect is the molding method of the fourth aspect, wherein the first upper molding die has a fixing surface that contacts the inner peripheral edge region from the direction of stacking, and as the restraint process, a biasing mechanism biases the first upper molding die in a direction toward the lower molding die, thereby sandwiching and fixing the inner peripheral edge region of the preform between the lower molding die and the first upper molding die.

[0077] According to the fifth aspect, the inner peripheral edge region of the preform is clamped and fixed by the biasing force, so that the preform can be more reliably restrained.

[0078] The sixth aspect of the method for molding an annular frame is the molding method of the fifth aspect, wherein the first upper molding die has a bolt hole that penetrates in the stacking direction, the lower molding die has a screw hole at a position corresponding to the bolt hole, and the biasing mechanism is a spring-loaded bolt, and in the restraint process, the spring-loaded bolt is inserted into the bolt hole and fastened to the screw hole to bias the first upper molding die in a direction toward the lower molding die.

[0079] According to the sixth aspect, the application of a biasing force to the inner peripheral edge of the preform can be achieved in a simple manner by fastening the spring-loaded bolt into the screw hole.

[0080] The seventh aspect of the molding method for an annular frame is the molding method of the fifth aspect, wherein during the shaping, a second upper molding mold having a molding surface for molding the outer region other than the inner peripheral edge of the preform is used, and the preform is sandwiched between the lower molding mold, the first upper molding mold, and the second upper molding mold, and shaped by applying heat and pressure.

[0081] According to the seventh aspect, the preform can be shaped by sandwiching it between the first upper molding die and the lower molding die, after which the second upper molding die is added. In other words, the transition from the restraining process to the shaping process can be carried out smoothly.

[0082] The method for molding an annular frame according to the eighth aspect is the molding method of the fifth to seventh aspects, in which the lower molding mold uses a mold having a vertical wall that surrounds the outer peripheral edge of the preform and extends in the direction of stacking.

[0083] According to the eighth aspect, since a lower molding die having a standing wall is used, it is possible to restrict movement of the prepreg outward in the radial direction of the annular frame.

[0084] A ninth aspect of the method for molding an annular frame is the molding method of any one of the first to eighth aspects, wherein when the melting point of the thermoplastic resin constituting the prepreg is Th [°C], the heating temperature during the shaping is selected from the range of Th [°C] to Th-40 [°C].

[0085] According to the ninth aspect, the heating temperature during shaping of the preform is set to a temperature at which the thermoplastic resin of the prepreg does not melt. In other words, a temperature range is selected during shaping that does not cause the laminated prepregs to weld together. Therefore, adjacent prepregs can slip during shaping, thereby suppressing the occurrence of wrinkles, etc.

[0086] A tenth aspect of the method for forming an annular frame is the method of any one of the first to ninth aspects, wherein incisions are made in the prepreg before the lamination.

[0087] According to the tenth aspect, the incisions prevent localized deformation in the prepreg from propagating to the surrounding area during shaping, thereby preventing tearing of the prepreg and changes in the fiber angle and fiber direction during shaping.

[0088] The method for molding an annular frame according to the eleventh aspect is the molding method of the tenth aspect, wherein the prepreg has a structure in which a large number of the reinforcing fibers are arranged parallel to a predetermined direction, and multiple incisions are made in the shaping area along the predetermined direction.

[0089] According to the eleventh aspect, since the incisions are made along the arranging direction of the reinforcing fibers, it is possible to prevent the reinforcing fibers from being cut by the incisions, and therefore it is possible to prevent a decrease in strength of the prepreg.

[0090] The method for molding an annular frame according to the twelfth aspect is the molding method according to the eleventh aspect, in which a first cut region in which the cuts are spaced apart by a predetermined first distance and a second cut region in which the cuts are spaced apart by a second distance that is narrower than the first distance are formed.

[0091] According to the twelfth aspect, cuts can be made in the prepreg at appropriate intervals depending on the likelihood of wrinkles or tears occurring in the prepreg during shaping.

[0092] The method for molding an annular frame according to the thirteenth aspect is the molding method according to any one of the first to twelfth aspects, in which after the shaping, a stack is formed by adding a filler made of a thermoplastic resin to the preform, and heating and pressurizing are performed to integrate the stack.

[0093] According to the thirteenth aspect, an integrally molded product of the shaped preform and the filler is produced. By forming the filler into a desired shape, an annular frame with a uniform outer shape can be obtained.

Claims

1. A method for molding an annular frame, comprising stacking a plurality of prepregs composed of reinforcing fibers and thermoplastic resin to form a ring-shaped or approximately ring-shaped preform having an opening, applying a restraint treatment to restrict movement of the stacked prepregs in a direction perpendicular to the stacking direction in the inner peripheral edge region that defines the opening of the preform, and heating and pressurizing the preform in the restrained state to form it into a shape.

2. A method for molding an annular frame as set forth in claim 1, wherein each of the plurality of prepregs includes a tab protruding from the inner peripheral edge at a position that will protrude into the opening after the preform has been formed, and the restraining treatment is performed using the tab.

3. A method for molding an annular frame as set forth in claim 2, wherein the tab has a fixing hole penetrating the tab in the stacking direction, and has a plurality of pins erected at positions corresponding to the fixing holes, a molding lower mold on which the plurality of prepregs are placed is prepared, and as the restraining treatment, the pins are inserted into the fixing holes when the prepregs or the preforms are placed on the molding lower mold.

4. A method for molding an annular frame as described in claim 1, comprising: preparing a lower molding die on which the plurality of prepregs are placed; and as the restraining process, placing a first upper molding die above the preform on the lower molding die, and clamping and fixing the inner peripheral edge region of the preform between the lower molding die and the first upper molding die.

5. A method for molding an annular frame as set forth in claim 4, wherein the first upper molding die has a fixing surface that contacts the inner peripheral edge region from the direction of stacking, and the restraining process involves biasing the first upper molding die in a direction toward the lower molding die by a biasing mechanism, thereby sandwiching and fixing the inner peripheral edge region of the preform between the lower molding die and the first upper molding die.

6. A method for molding an annular frame as set forth in claim 5, wherein the first upper forming die has bolt holes passing through in the stacking direction, the lower forming die has threaded holes at positions corresponding to the bolt holes, the biasing mechanism is a spring-loaded bolt, and in the restraining process, the spring-loaded bolt is inserted into the bolt hole and fastened to the threaded hole, thereby biasing the first upper forming die in a direction toward the lower forming die.

7. A method for molding an annular frame as set forth in claim 5, wherein, during the shaping, a second upper molding die having a molding surface for molding the outer region of the preform other than the inner peripheral edge is used, the preform is sandwiched between the lower molding die, the first upper molding die and the second upper molding die, and the heating and pressurization are carried out to shape the preform.

8. A method for molding an annular frame according to claim 5, wherein the lower molding die is a die having a standing wall surrounding the outer periphery of the preform and extending in the direction of lamination.

9. A method for molding an annular frame according to any one of claims 1 to 8, wherein the heating temperature during the shaping is selected from the range of Th [°C] to Th-40 [°C], where Th [°C] is the melting point of the thermoplastic resin that constitutes the prepreg.

10. A method for forming an annular frame according to any one of claims 1 to 8, wherein before the lamination, incisions are made in the prepreg.

11. A method for molding an annular frame as described in claim 10, wherein the prepreg has a structure in which a large number of the reinforcing fibers are arranged in parallel in a predetermined direction, and a plurality of the incisions are made in the shaping area along the predetermined direction.

12. A method for forming an annular frame as set forth in claim 11, wherein a first cutout region is formed in which the cutouts are spaced a predetermined first distance, and a second cutout region is formed in which the cutouts are spaced a second distance narrower than the first distance.

13. A method for molding an annular frame according to any one of claims 1 to 8, wherein, after the shaping, a stack is formed by adding a filler made of a thermoplastic resin to the preform, and the stack is integrated by heating and pressurizing.

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