Method for manufacturing fiber-reinforced thermoplastic resin wheel rim

Abstract

This invention provides a method for manufacturing a fiber-reinforced thermoplastic resin wheel rim, which can integrate the rim and disc portions in a short time to produce a high-strength resin wheel rim with excellent formability. The method involves molding a fiber-reinforced thermoplastic resin material into a resin wheel rim using a mold, with the mold temperature set below the melting point of the resin matrix. During manufacturing, block-shaped and sheet-shaped materials are prepared and heated to a temperature above the melting point of the resin matrix. After heating, the block-shaped material is held within the mold, surrounded by the outer surface mold of the disc portion and the outer diameter mold of the rim, while the sheet-shaped material is held on the side of the outer diameter mold near the punching mold. The punching mold is then lowered, closing the notch on the outer periphery of the sheet-shaped material to form the rim portion of the wheel rim. A portion of the sheet-shaped material pushes against the block-shaped material to join them, compressing the block-shaped material to form the disc portion of the wheel rim.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a wheel rim made of fiber-reinforced thermoplastic resin, wherein the method involves molding the rim portion and the disc portion of the automotive wheel rim into a single piece using fiber-reinforced thermoplastic resin. Prior Technology

[0002] A car wheel rim, where the rim and disc are integrated into a single structure, is essentially formed by holding and shaping all or part of the material—fiber-reinforced plastics (FRP), SMC (sheet molding compound)—along the inner surface of a mold. However, because the wheel rim integrates the rim and disc portions, which have different shapes and orientations, at least a plurality of materials constituting these portions must be arranged in different positions with different shapes.

[0003] The wheel rim disclosed in Patent Document 1, described later, is made of thermosetting resin. It is manufactured by using sheet molding compound (SMC) with a high resin content as the material for the rim portion, forming it into a cylindrical shape and holding it inside the rim molding mold. The material for the disc portion is sheet molding compound (SMC) with a high fiber volume ratio, which is placed between the lower and upper molds for molding the disc portion. In this embodiment, the cylindrical material constituting the rim portion is wound around the outer periphery of the material constituting the disc portion as the resin material for processing.

[0004] The resin material for processing is placed into a heated mold for compression molding (hot / cold forming). After heating for a specific time, a chemical reaction occurs, causing the resin matrix of the material to solidify. After cooling, the molding process is complete.

[0005] Since the wheel rims are manufactured through the above process, which involves time-consuming material placement, shaping, and waiting for resin to harden within the mold, it is impossible to complete the forming process, including the preparation stage, in just a few minutes.

[0006] Non-Patent Document 1, described later, discloses a technology for high-speed forming of sheet materials, wherein the sheet material is a fiber-reinforced thermoplastic resin rather than a fiber-reinforced thermosetting resin. This technology can shorten cycle time and ensure sufficient formability. The method involves heating the sheet material at a temperature higher than the melting point of the resin matrix, then clamping it in a mold set at a temperature lower than that melting point and forming it. Non-Patent Document 2, described later, discloses a wheel rim manufactured from fiber-reinforced thermoplastic resin. The material is a fiber-reinforced thermoplastic resin with scrap material as reinforcing fibers, which is heated to a specific processing temperature and then placed in a mold for compression forming.

[0007] The aforementioned method involves punching holes in the material and compressing it to form the disc portion, thereby pushing a portion of the material into a cylindrical shape to form the rim portion. The diameter of the rim portion increases as it extends upwards; to ensure the rim width, a larger volume of material is required, thus the volume on the disc side must be greater than the required volume. Furthermore, when the rim width is large, the punching must be intensified to deepen the holes, resulting in a rapid increase in forming load. Moreover, because the rim is formed by punching and stacking, the reinforcing fibers tend to align in a specific direction. Since increasing anisotropy does not improve strength, it is difficult to form a rim with a large width. In other words, even if the reinforcing fibers are isotropic in the material stage before forming, they easily become anisotropic as they flow upwards towards the rim portion, resulting in uneven or low axial strength, thus limiting the width of the rim portion.

[0008] To reduce anisotropy, one could consider slowing down the molding speed to reduce the flow rate of the reinforcing fibers, but this would lengthen the molding time and hinder moldability due to the rapid drop in resin temperature during molding. In view of this, the technology in Non-Patent Document 1 seems to be able to form in a short time through a single compression action, but it is difficult to achieve a balance between molding speed and molded product performance, which not only fails to achieve the best of both worlds but also limits the shape of the product.

[0009] In addition, there are techniques such as Quick Form molding (as described in Non-Patent Document 2) and so-called HP-RTM (High Pressure Resin Transfer Molding) molding techniques (e.g., Patent Document 2).

[0010] In the above molding method, for example, a dry fiber substrate or a laminate of fiber substrate without resin impregnation is manually placed in a forming mold for shaping. After the mold is closed, the pressure inside the mold is reduced and then increased to inject a thermosetting resin such as epoxy resin, impregnating the fiber substrate. The mold is then heated to harden the thermosetting resin. Because multiple fiber substrates are prepared according to the applicable areas and arranged manually, the strength of the wheel rim can be ensured simply by increasing the number of laminates at the locations requiring reinforcement; this is an advantage of the above method.

[0011] However, the preparation and shaping of fiber substrates is time-consuming and requires excellent technical skills to obtain products with stable quality.

[0012] Therefore, because the pre-forming work and forming process are very time-consuming and cannot be shortened to a few minutes, the manufactured wheels are very expensive and can only be used on a few special vehicles such as sports cars.

[0013] Patent Document 1: Japanese Patent Publication No. H6-51308; Patent Document 2: Japanese Patent No. 6652523.

[0014] Non-patent document 1: Sachihiro Isogawa, Yoshio Enomoto, Hisao Kobayashi, Shougo Nasu, "High cycle deep drawing of PA6 matrix carbon fiber reinforced thermoplastics by servo-driven screw press", "Procedia Manufacturing", Available online 11 August 2018, Version of Record 11 August 2018., Volume 15, p.1722-1729. Non-Patent Document 2: Rapid, Inc., "CFRTP-manufactured Automobile Tires and Wheels", Product Catalog, [Search Results as of October 3, 2022], Website<URL: https: / / www.ipros.jp / catalog / detail / 498804> Summary of the Invention

[0015] The main objective of this invention is to provide a wheel rim that can be manufactured in a short time with good formability made of fiber-reinforced thermoplastic resin, while ensuring the mechanical properties of the wheel rim, and can also manufacture a wheel rim with a wider rim section.

[0016] The present invention provides a method for manufacturing wheel rims made of fiber-reinforced thermoplastic resin.

[0017] The manufacturing method of the fiber-reinforced thermoplastic resin wheel rim of the present invention involves integrally forming the rim portion and the disc portion of the wheel rim. Both the rim portion and the disc portion are formed from fiber-reinforced thermoplastic resin material through a mold, using both block and sheet materials. The sheet material is a deformable sheet with multiple radially arranged notches on its outer periphery, and the outlines of the notches converge during forming. The mold temperature is set below the melting point of the resin matrix, which is a constituent element of the material. The block and sheet materials are heated to a temperature higher than the melting point of the resin matrix. After heating, the block material is held in the mold within a position surrounded by the disc outer surface mold and the rim outer diameter mold, while the sheet material is held on the side of the rim outer diameter mold near the punching mold, which is opposite to the disc outer surface mold. Next, the sheet material is shaped using a punching die and a wheel rim outer diameter die to form the wheel rim portion. A portion of the sheet material is then pressed onto the block material to join the two together. Simultaneously, the block material is compressed using a disc outer surface die, a wheel rim outer diameter die, and a punching die to form the disc portion of the wheel rim.

[0018] According to the above structure, sheet-like and block-like materials of different shapes undergo plastic deformation in a manner consistent with their shapes, joining together to form a single unit during the plastic deformation process. The easily deformable sheet-like material, by closing the notches at its outer periphery during molding to bring the contour lines together, suppresses wrinkle formation, reduces molding load, and forms a wide rim section. Furthermore, the compression molding of the block-like material does not require the formation of a rim section, thus eliminating the need for extra volume or molding load. In the aforementioned molding process, after the sheet-like and block-like materials are heated to a temperature higher than the melting point of the resin matrix, they undergo rapid plastic deformation into a specific shape within a mold at a specific temperature below that temperature, and the temperature is then lowered.

[0019] According to the invention, the forming of the rim and disc portions is organically combined with the compression forming of sheet materials, allowing for smooth forming and joining of the rim and disc portions in a continuous motion. This enables rim forming in an extremely short time (in minutes) and provides excellent formability. Furthermore, the forming of each material is carried out in a manner consistent with its shape. Therefore, the material flow in the rim and disc portions is easily controlled during forming, and excessive anisotropy of the reinforcing fibers can be suppressed, thereby ensuring mechanical performance. Moreover, the rim portion is formed from a deformable sheet material. During forming, the outline of this sheet material merges and has gaps, allowing for a wider rim portion to be formed with a smaller forming load. Additionally, since the rim portion is not deep-drawn, a high-strength molded product can be obtained, preventing the sheet material from cracking and suppressing wrinkles, resulting in good appearance quality. The low forming load also reduces manufacturing costs. Simple Explanation of the Diagram

[0020] Figure 1 is a schematic diagram of the manufacturing method of fiber-reinforced thermoplastic resin wheel rims. Figure 2 shows the front view of the wheel rim and its cross-sectional view along line AA. Figure 3 shows a three-dimensional view of the sheet-like material and the block-like material. Figure 4 is a perspective view showing the shape of a deformable sheet in a sheet-like material. Figure 5 is a cross-sectional view of one side of the block material. Figure 6 is a three-dimensional view of the retaining ring that holds the sheet-like material. Figure 7 is a three-dimensional view of the separated state of Figure 6. Figure 8 is a cross-sectional view showing the mold structure. Figure 9 is a cross-sectional view showing the material being held in the mold. Figure 10 is a cross-sectional view showing the forming process. Figure 11 is a cross-sectional view of the formed state. Figure 12 is a cross-sectional view of one side of a block material containing reinforcing sheets in another embodiment. Figure 13 is a plan view of the block material containing the reinforcing sheet. Figure 14 is a cross-sectional view showing the forming state of the reinforcing sheet. Figure 15 is a front view of a molded article with reinforcing sheets. Figure 16 is a front view of a wheel rim with reinforcing slabs. Implementation

[0021] The following description, with reference to the relevant figures, illustrates one embodiment of the present invention.

[0022] The present invention relates to an automobile wheel rim (hereinafter referred to as "wheel rim") in which the rim and disc are integrated, which is manufactured by molding, and the molding material (intermediate substrate) is fiber-reinforced thermoplastic resin.

[0023] Fiber-reinforced thermoplastic resins, such as SMC (Sheet Molding Compound), BMC (Bulk Molding Compound), or FRP (Fiber Reinforced Plastic), or Stampable Sheet, are mainly composed of a resin matrix (base material) and reinforcing fibers (reinforcing material).

[0024] Figure 1 shows a schematic diagram of the main parts in the automobile wheel rim manufacturing method. In this manufacturing method, the prepared material 11 is heated and formed into a wheel rim shape using a mold 31. Then, the molded part removed from the mold 31 is subjected to subsequent processing such as cutting to obtain an intermediate product of wheel rim 71 as shown in Figure 2 (hereinafter also referred to as "wheel rim 71").

[0025] First, let's explain material 11.

[0026] The two shapes shown in Figure 3 are used as material 11. One is a sheet-like material 12, and the other is a block-like or large block-like material 13.

[0027] The sheet-like material 12 mainly constitutes the rim portion 72 of the wheel rim 71, and has two types: a slightly circular plate-shaped easily deformable sheet 12a and a ring-shaped reinforcing sheet 12b. The easily deformable sheet 12a has a suitable thickness, is formed into a circular plate shape in the surface direction, and has a through hole 14 in the center of the surface that extends through the thickness direction. The through hole 14 can be in any shape other than the circular shape shown in the embodiment.

[0028] The deformable sheet 12a is not deep-drawn, but has multiple radial notches 15 on its outer periphery. The outlines 16 forming these notches 15 meet during forming. That is, as shown by the dotted lines in FIG4, when the deformable sheet 12a is formed into a cylindrical shape on its outer periphery, the notches 15 close and the outlines 16 of the notches 15 contact each other, so that the notches 15 form a meeting shape. The shape of the notches 15 can be obtained through forming simulation analysis. In the embodiment shown in the figure, four notches 15 are formed at equal intervals, but the number of notches 15 can also be more than four.

[0029] The rim portion 72 can be formed using a single deformable sheet 12a, but it is preferable to use multiple deformable sheets 12a. The embodiment shown in the figures uses three deformable sheets 12a. The multiple deformable sheets 12a overlap in the thickness direction to prevent them from fitting together. Furthermore, when overlapping the deformable sheets 12a, the circumferential gaps 15 are staggered so that they overlap.

[0030] The reinforcing sheet 12b is formed in a ring shape, specifically a circular ring. It is a sheet material 12 that deforms during the forming of the easily deformable sheet 12a and moves to a portion where its thickness, rigidity, or strength must be higher than other parts. For example, the portion where the thickness, rigidity, or strength must be higher than other parts is the portion forming the inner flange 76 (see Figure 2). The reinforcing sheet 12b overlaps the easily deformable sheet 12a and prevents them from fitting together tightly. The length, or width, of the reinforcing sheet 12b in the diametrical direction is sized to match the portion requiring reinforcement.

[0031] The block material 13 mainly constitutes the disc surface portion 73 of the rim 71, and during compression molding, it becomes a block of appropriate size, or a shape of a specific size, volume, and height. Specifically, the mold groove, which mates with the mold, has a specific thickness and a specific diameter, forming a short cylindrical shape with a through hole 17 in the center. The forming process is compression molding. The through hole 17 can be circular in addition to the shape shown in the embodiment, or other shapes. In addition to the shape shown in the embodiment, the block material 13 can also be formed using near-net-shape (NNS), which is a method that requires minimal processing after forming to achieve a shape close to the finished product. For example, the required number of spokes can be extended on the inner circumference of the short cylindrical shape to form multiple openings. This can also be applied to the aforementioned sheet material 12, for example, the portion between the corresponding spokes can be designed as an opening shape.

[0032] The reinforcing fiber of material 11 can be a material containing short fibers or flakes, or a continuous fiber cross-woven (woven) sheet, etc., and it is preferable to use fibers containing carbon fiber or glass fiber. In particular, regarding the deformable sheet 12a in the sheet-like material 12, although short fibers or flakes can be used, it is preferable to use a material containing continuous fibers as the reinforcing fiber. It is even more preferable to use a deformable sheet 12a composed of continuous fiber cross-woven sheets and a deformable sheet 12a composed of short fibers or flakes in combination. In this case, it is possible to consider overlapping the deformable sheet 12a composed of short fibers or flakes on both the inner and outer surfaces of the deformable sheet 12a composed of continuous fiber cross-woven sheets. Furthermore, the reinforcing sheet 12b is suitable to be made of short fibers or flakes.

[0033] Considering the formability during compression molding, the block material 13 is a quasi-isotropic material with fragments (short fibers) or thin flakes as reinforcing fibers. In addition to formability, considering the rigidity of the molded article, it is preferable to overlap multiple sheets of quasi-isotropic random series of thin sheets SMC 13a with thin flakes as reinforcing fibers in the thickness direction to form the block material 13, as shown in Figure 5. The thickness direction of SMC 13a is the compression direction during compression molding.

[0034] The block material 13 is a single block, and from the heating process to its placement in the mold 31, it can be considered as a single component, thus posing no operational problems. However, the sheet material 12 is sheet-like, and the sheet 12a is easily deformable, along with the reinforcing sheet 12b to prevent overlapping and tight contact. Therefore, from the heating process to the forming process, multiple sheet materials 12 must be considered as a single component.

[0035] Therefore, the sheet material 12 is held on the retaining ring 18 as shown in FIG. 6. The retaining ring 18 has the functions of positioning (aligning) the sheet material 12 and keeping each sheet material 12 independent and deformable. The retaining ring 18 includes a lower ring 81 and an upper ring 82 made of metal, which are constructed for heating and shaping the sheet material 12 held therebetween. As shown in FIG. 7, the outer diameter of the lower ring 81 is the same as the outer diameter of the deformable sheet 12a, and the inner diameter is made of a ring-shaped plate with a smaller outer diameter. On the surface of the lower ring 81, a plurality of pins 83 are erected at equal intervals. Since the deformable sheet 12a has 4 notches 15, the number of pins 83 is twice that of the notches, which is 8. The lower end of the pin 83 protrudes from the bottom of the lower ring 81 by a certain length, and the protruding part 83a is used for positioning the mold 31.

[0036] The upper ring 82 has a body ring portion 82a of the same size as the lower ring 81, and an inner ring portion 82b with an inner diameter is included on the inner circumference side of the body ring portion 82a at a position almost the same as the outer diameter of the reinforcing sheet 12b being held. The body ring portion 82a and the inner ring portion 82b are integrated through a plurality of connecting rods 82c. On the body ring portion 82a, the same number of pin holes 84 as the number of pins 83 are formed at equal intervals, through which the pins 83 of the lower ring 81 are inserted; on the inner ring portion 82b, a plurality of retaining holes 85 are formed at equal intervals to retain the reinforcing sheet 12b. Four retaining holes 85 are formed in the figure.

[0037] The through hole 86 in the center of the upper ring 82, which is a hole located on the inner circumference side even more than the inner ring part 82b, is the size that can be formed by the punching die 34 of the mold 31 when the retaining ring 18 is placed in the outer diameter mold 33 of the mold 31.

[0038] The aforementioned retaining ring 18 has a separating member 87 to prevent the sheet-like materials 12 from sticking together. The separating member 87 is made of metal wire such as stainless steel alloy and includes a circular body portion 87a and a plurality of fixing portions 87b extending radially outward from the body portion 87a. The size of the body portion 87a is formed to be equal to or larger than the through hole 86 of the upper ring 82. For example, it can be formed to be larger than the outer diameter of the reinforcing sheet 12b. The fixing portions 87b are arranged at equal intervals, with the same number as the pins 83 of the lower ring 81. The front end of the fixing portion 87b is provided with a retaining ring 87c for inserting the pin 83.

[0039] To maintain the retaining ring 18, through holes 12c are formed at equal intervals on the outer periphery of the deformable sheet 12a. The deformable sheet 12a has four notches 15, and the non-notch portion has a structure of four protrusions 15a along the outer periphery. Through holes 12c are formed at the center position of the outer periphery of these four protrusions 15a in the circumferential direction. Furthermore, four through holes 12d are formed at equal intervals on the outer periphery of the reinforcing sheet 12b, the same number as the retaining holes 85 of the inner ring portion 82b of the upper ring 82. Metal wires 88, which pass through the retaining holes 85 of the inner ring portion 82b, are inserted into the through holes 12d of the reinforcing sheet 12b, thereby connecting the reinforcing sheet 12b and the upper ring 82.

[0040] When the sheet material 12 is held relative to the retaining ring 18, firstly, the bottommost deformable sheet 12a is held and the separating member 87 is placed on the lower ring 81. Next, other deformable sheets 12a are placed on top, and then other separating members 87 are placed in the same manner, and so on, until the required number of deformable sheets 12a are placed. Then, the separating member 87 is positioned between and engaged with the upper ring 82 and the lower ring 81, which hold the reinforcing sheet 12b. The upper ring 82 is held by inserting the pin 83 of the lower ring 81 into the pin hole 84 of the upper ring 82.

[0041] The resin matrix for both the sheet material 12 and the block material 13 can be a material with good compatibility with each other; generally, the same resin is used. Examples of resins include thermoplastic epoxy resin or polyamide.

[0042] Secondly, the manufacturing method of the device will be explained.

[0043] The manufacturing method involves heating the block material 13 and the sheet material 12 to a temperature higher than the melting point of the resin matrix of these constituent elements, and then forming them at high speed using a mold 31 set to a temperature lower than the melting point.

[0044] Therefore, as shown in the schematic diagram of Figure 1, the device includes heating devices 51 and 52, in addition to the forming mold 31, for heating the sheet material 12 and the block material 13 respectively. The heating devices 51 and 52 can be devices using suitable heating methods; from the viewpoint of achieving ideal heating in a short time and ensuring uniform heating inside and out, IR (infrared) heating is preferable. Depending on the shape of the material 11, a homogenizing furnace consisting of a heat exchanger can also be used for heating. In this case, the heat preservation tank 56 can be omitted.

[0045] The heating device 51 for heating the sheet material 12 has heaters 53 at the top and bottom, an inlet 54 serving as the inlet for the conveying path between the heaters 53, and an outlet 55 serving as the outlet. The sheet material 12 is held on a retaining ring 18 and fed or discharged by an automatic conveying device.

[0046] The heating device 52 for heating the block material 13 is the same as the heating device 51 for heating the sheet material 12. Multiple sheets (SMC 13a) that have been stacked and heated are conveyed and heated to form a block. The rear section of the heating device 52 has a heat-insulating tank 56. The heat-insulating tank 56 holds the block material 13 composed of laminated sheet materials (SMC 13a) and heats it uniformly.

[0047] The heating temperature of the sheet material 12 and the block material 13 is higher than the melting point of the resin matrix. Assuming the resin matrix is ​​polyamide, it can be heated to about 280°C. This temperature is set to approximately 30°C to 70°C higher than the melting point, taking into account the temperature drop during molding.

[0048] The forming die 31 includes a disc outer surface die 32, a rim outer diameter die 33, and a punching die 34. The disc outer surface die 32 is the lower die, primarily used to form the outer surface of the disc portion 73 of the rim 71. The rim outer diameter die 33 moves diametrically above the disc outer surface die 32, forming multiple circumferential sections for forming the outer peripheral surface of the rim portion 72 of the rim 71. The punching die 34 is the upper die, primarily used to form the inner peripheral surface of the rim portion 72 and the inner surface of the disc portion 73. The rim outer diameter die 33 is supported on the opposite side of the disc outer surface die 32 and can move up and down toward the disc outer surface die 32. Furthermore, a positioning hole 35a is formed on the retaining die 35 on the outer peripheral side of the rim outer diameter die 33, which allows the lower end of a pin 83 protruding below the retaining ring 18 to be inserted and held.

[0049] The construction of mold 31 will be described next. Wheel rims 71 come in various shapes. For example, based on the distance from the center line of the rim (rim width) to the mounting surface, they can be classified as positive offset, zero offset, negative offset, etc. The outer surface shape of the disc also varies, including convex, flat, and concave shapes. Therefore, mold 31 also has various shapes corresponding to the shape of the wheel rim. The mold 31 in the illustrated embodiment is only one example, and the manufacturing method of the present invention is not limited to the shape shown in the illustration.

[0050] As shown in Figures 1 and 8, the outer surface mold 32 of the disc has a vertically upward-facing shaft portion 36 at its center. The shaft portion 36 is located at the center hub 74 of the corresponding rim 71, and the entire periphery of the shaft portion 36 has an undulating surface 37 corresponding to the outer surface of the disc portion 73. The portion further outward from the undulating surface 37 is the support surface 38 that supports the outer diameter mold 33 of the rim.

[0051] The front end of the shaft portion 36 is a fitting portion 36a that engages with the punching die 34, forming the thinnest part of the shaft portion 36. Below the fitting portion 36a, a large-diameter portion 36c is formed through a step portion 36b. The diameter of the large-diameter portion 36c is smaller than the diameter of the through hole 17 of the block material 13. The base of the large-diameter portion 36c has an inclined shape portion 36d, the lower outer periphery of which resembles a foothills, with the diameter increasing towards the bottom. The diameter at the lower end of the inclined shape portion 36d is larger than the diameter of the through hole 17 of the block material 13.

[0052] The outer diameter mold 33 of the wheel rim has a recess 39 at its lower end, which is used to form the portion on the outer flange 75 of the wheel rim 71 where the outer side of the tire is mounted. The recess 39 forms an inward and outward concave-convex shape 41 along the shape of the wheel rim portion 72, while the upper end of the portion 41a of the inner flange 76 of the wheel rim 71 forms a corner curved surface 42.

[0053] The punching die 34 has a fitting recess 43 at its lower center that fits into the fitting portion 36a of the shaft portion 36 of the outer surface die 32. Furthermore, an outer peripheral surface 44 is formed inside the wheel rim outer diameter die 33 in the closed state, with a gap equivalent to the thickness of the wheel rim portion 72. The portion 44a of the outer peripheral surface 44 used to form the inner flange 76 of the rim 71, particularly between the portions corresponding to the outer diameter die 33, forms a forming space of the desired shape to meet mechanical performance considerations.

[0054] The depth of the fitting recess 43 is set such that even when the punching die 34 reaches the bottom dead center, a gap d1 can be left between the bottom of the fitting recess 43 and the front end of the shaft portion 36. In addition, the dimensions around the shaft portion 36 are designed such that when the punching die 34 reaches the bottom dead center, the clearance portion 45, which is inaccessible to the block material 13, can approach the opening edge of the fitting recess 43.

[0055] The outermost portion of the fitting recess 43 is an annular recess 46, which is used to form the portion of the rim 71 that is further outward than the center hub 74. The portion further outward than the annular recess 46 is a protrusion 47, which is used to form the spokes 77 of the rim 71 and the corresponding window portions 78 between the spokes 77. The lower part of the protrusion 47 protrudes further than the annular recess 46. The portion of the protrusion 47 corresponding to the window portions 78 is formed between the undulating surfaces 37 of the outer surface mold 32 of the disc, and its thickness will be thinner after forming.

[0056] The mold 31, constructed as described above, includes a temperature regulating mechanism (not shown in the figure) for adjusting the temperature of the mold 31 to a constant level. The temperature regulating mechanism has a flow channel for the flow of media such as water, and monitors and adjusts the flow rate and temperature of the media to maintain a specific temperature. Alternatively, the temperature regulating mechanism can be configured by inserting a heater into the mold 31.

[0057] The temperature of mold 31 is lower than the melting point of the resin matrix of sheet material 12 and block material 13, preferably lower than the glass transition temperature. When the resin matrix is ​​thermoplastic epoxy resin, the recommended molding temperature of thermoplastic epoxy resin is 180℃~210℃, and the temperature of mold 31 is specifically 100℃~130℃, especially below 120℃ is preferred, and below 80℃, 75℃ or around 50℃ are also acceptable. As long as the temperature is maintained above the required temperature, the lower temperature can inhibit the resin matrix from adhering to mold 31, and at the same time shorten the holding time, thus shortening the cycle time.

[0058] The above-mentioned device performs the following forming steps on the previously described sheet material 12 and block material 13 to manufacture wheel rim 71.

[0059] The mold 31 is closed, and its temperature is set to a specific temperature lower than the melting point of the resin matrix of the material 11.

[0060] While carrying out the aforementioned preparations, the fiber-reinforced thermoplastic resin is cut using tools such as a water jet, and sheet-like materials 12 (deformable sheet 12a and reinforcing sheet 12b) are prepared to be held in the retaining ring 18, as well as sheet material (SMC 13a) constituting the block material 13. These materials are placed in heating devices 51 and 52 and heated to a specific temperature. For the block material 13, the heated sheet material (SMC 13a) is stacked and homogenized in the heat-insulating tank 56.

[0061] Next, as shown in Figure 9, the punching die 34 is raised to open the die 31, and the block material 13 is inserted into the die 31. At this time, the shaft portion 36 and the inclined shape portion 36d of the outer surface die 32 are aligned with the center of the block material 13 and the center of the outer surface die 32.

[0062] Immediately afterwards, the retaining ring 18 holding the sheet material 12 is placed on the outer diameter mold 33 of the wheel rim. The retaining ring 18 is positioned by inserting the protruding part 83a below the pin 83 into the positioning hole 35a on the retaining mold 35, thereby aligning the center of the sheet material 12 with the center of the mold 31.

[0063] At the same time, the temperature of the mold 31 is lower than the heating temperature of the sheet material 12 and the block material 13, which further reduces the temperature of the sheet material 12 and the block material 13 as they leave the heating device 51 or the heat preservation tank 56.

[0064] After the sheet material 12 and the block material 13 are placed into the mold 31, the punching mold 34 is immediately lowered as shown in Figure 10 for high-speed forming. That is, when the punching mold 34 lowers, the lower end of its protrusion 47 first abuts against the deformable sheet 12a in the sheet material 12 and then lowers to form the rim portion 72. In other words, as the punching mold 34 lowers, multiple deformable sheets 12a that prevent each other from sealing are pulled into the mold 31 and formed along the outer diameter of the rim mold 33 and the punching mold 34. Through forming, the outline of the notch 15 converges to form a cylindrical rim portion 72. Because the multiple deformable sheets 12a are highly independent, the convergence of the outline 16 is reliably achieved. Furthermore, the deformable sheets 12a are not held by clamping the outer periphery, but are held by inserting the pin 83 into the through hole 12c, thus requiring less constraint and achieving the desired forming smoothly.

[0065] During the above forming process, the rim portion 72 is cooled and solidified. At this time, when the punching die 34 approaches the bottom dead center, a reinforcing sheet 12b is applied to the upper part of the outer peripheral surface 44 of the punching die 34, that is, at the position close to the portion 44a where the inner flange 76 is formed. Then, the reinforcing sheet 12b is added to the deformable sheet 12a, so that a portion of the reinforcing sheet 12b is thickened and reinforced.

[0066] The sheet material 12, which is the inner peripheral portion of the easily deformable sheet 12a, pressed down by the lower end of the protrusion 47, contacts the top of the block material 13 from above and is pressed onto the block material 13 through the punching die 34. Therefore, the sheet material 12 and the block material 13 are joined together and continue to deform. When the punching die 34 reaches the bottom dead center, the desired sheet material 12 and block material 13 are formed as shown in FIG11.

[0067] At this time, the front end of the shaft portion 36 of the outer surface mold 32 and the bottom of the fitting recess 43 of the punching mold 34 do not contact each other. Therefore, a space that the compressed block material 13 cannot reach can be obtained near the opening of the fitting recess 43, which is the clearance portion 45. Therefore, especially when the sheet material 12 contacts the block material 13, increasing the forming load can avoid the forming load from being increased too much.

[0068] The forming process using this mold 31, while varying depending on conditions, will not exceed one minute even if held at the bottom dead center for 15 seconds. Furthermore, the holding of the material 11 is simpler and faster than with the mold 31, unlike operations requiring precise arrangement of numerous materials. In particular, holding multiple sheet-like materials 12 with the holding ring 18 allows them to be considered as a single component even if they are not tightly fitted together. Therefore, the forming operation, including removing the molded product, can be completed within one minute. However, in the case of large-diameter rims 71, the removal time may be delayed due to the slower rate of temperature drop.

[0069] After the molded product is taken out of the mold 31 and cooled by standing at room temperature, the excess parts such as the protruding part of the inner flange 76 or the window 78 are removed by post-processing such as cutting to form the wheel rim 71 (see Figure 2).

[0070] During the forming process of the aforementioned mold 31, the sheet material 12 is formed while the block material 13 is compressed and formed, and they join together during their respective forming processes. Furthermore, because the sheet material 12 is pressed down on its inner circumference to form a cylindrical shape, the desired rim portion 72 can be smoothly obtained, thus widening the width of the rim portion 72. The block material 13 only forms the disc portion 73; since it does not need to form the rim portion 72, there is no extra volume or forming load. The clearance portion 45 also reliably prevents a sudden increase in forming load.

[0071] This forming process means that the forming of the sheet material 12 and the compression forming of the block material 13 are organically combined, and the rim portion 72 and the disc portion 73 are smoothly formed and joined together in a series of actions. Therefore, the rim 71 can be formed in a short time, measured in minutes, with excellent formability. Furthermore, because the forming is carried out in a more reasonable manner that conforms to the shapes of the sheet material 12 and the block material 13 respectively, the flow of the material 11 during forming is easily controlled. Excessive anisotropy of the reinforcing fibers is suppressed, thus ensuring the mechanical properties of the rim.

[0072] In particular, the easily deformable sheet 12a of the sheet material 12, through molding, creates a notch 15 in the converging contour line 16, resulting in minimal change in fiber orientation during molding and improved strength in both the circumferential and width directions. Furthermore, it reduces molding load and lowers molding costs. Additionally, it suppresses wrinkle formation, resulting in good appearance quality.

[0073] By optimizing the shape of material 11 for NNS molding, the load during molding or the load of the material being fed in can be reduced.

[0074] Furthermore, during molding, it is easy to control the flow of the material 11 to prevent excessive deformation. By using the reinforcing sheet 12b as described above, local reinforcement can be performed, thereby obtaining sufficient mechanical properties.

[0075] The forming of the disc portion 73 does not involve complex and excessive deformation, making it easy to control the flow of the block material 13 and ensuring sufficient mechanical properties.

[0076] For example, when it is desired to reinforce the relationship between the spokes 77 and the outer flange 75 of the disc portion 73 during forming, the following method shall be used.

[0077] In other words, when the block material 13 is a quasi-isotropic random series of sheet materials SMC 13a with fragmented thin sheets as reinforcing fibers, and multiple sheets are stacked in its thickness direction, as shown in Figure 12, a material with reinforcing sheets 13b is used between the SMC 13a. The reinforcing sheets 13b can be composed of continuous fiber cross sheets. Alternatively, braided sheets (quasi-isotropic material) of, for example, "QISO" (registered trademark) from A&P Technology Co., Ltd., can be used as reinforcing fibers.

[0078] The reinforcing sheet 13b has the same thickness as the SMC 13a and is sandwiched between the SMC 13a.

[0079] When the block material 13 is compressed and formed, the reinforcing sheet 13b moves outward in the direction of deformation. In order to achieve such movement, it is located on the outer periphery of the block material 13 and is divided in the circumferential direction.

[0080] Figure 12(a) shows an example of a reinforcing sheet 13b on the outer surface side of the disk portion 73, and Figure 12(b) shows an example of a reinforcing sheet 13b on the inner surface side in addition to the outer surface side.

[0081] The reinforcing sheet 13b is pre-formed into a suitable shape and placed at the appropriate location where reinforcement is needed. Specifically, as shown in Figure 13, the reinforcing sheet 13b of the block material 13 is roughly fan-shaped, with multiple sheets evenly spaced to match the number of spokes 77. When the block material 13 is placed into the mold 31, the spokes 77 are formed on the portion with the reinforcing sheet 13b, thus determining the circumferential direction. This is because the mold 32 on the outer surface of the disc has a shaft portion 36, which facilitates the construction by regulating the relationship between the shaft portion 36 and the through hole 17 of the block material 13.

[0082] Furthermore, during the forming process, as shown in FIG13, when the block material 13 is compressed and expands and deforms in both the outer and inner peripheral directions, the reinforcing sheet 13b moves in the outer peripheral direction and is located between the outer flange 75 and the outer peripheral end of the spoke 77. Also, FIG14 shows a forming example of the block material 13 shown in FIG12(a).

[0083] Figure 15 shows a front view of the molded article 19. In the post-processing of the molded article 19, the portion corresponding to the reinforcing sheet 13b and the window 78 is cut to create the window 78. In this way, as shown in Figure 16, a T-shaped reinforcing sheet 13b is left connecting the outer flange 75 and the spoke 77, increasing the strength of this part.

[0084] The above structure is one embodiment of the present invention. The present invention is not limited to the above structure and other structures may also be used.

[0085] For example, the shape of the reinforcing sheet 12b used to thicken or reinforce a portion of the rim portion 72 does not have to be the annular shape described above; it can be a shape for local reinforcement in the circumferential direction. It can also be a shape like the deformable sheet 12a with a notch. Furthermore, the reinforcing sheet 12b is not positioned above the deformable sheet 12a as described above; it can be positioned below the deformable sheet 12a or between each other.

[0086] The retaining ring 18 holding the sheet material 12 can be a configuration other than that described above, for example, it can be a configuration without the upper ring 82. The mold 31 holding the retaining ring 12 is also performed in a suitable manner.

[0087] The block material 13 may also have reinforcing sheets (not shown) that do not require movement during forming. Continuous fiber cross sheets or continuous fiber laminated quasi-isotropic cross sheets can be used on the reinforcing sheets. Since movement is not required, they can have a continuous annular shape in the circumferential direction.

[0088] 11:Material 12: Thin sheet material 12a: Easily deformable thin sheet 12b: Reinforcing sheet 12c, 12d: Through holes 13: Block material 13a:SMC 13b: Reinforcing sheet 14, 17: Through holes 15: Gap 15a: lenticel 16: Outline 18: Keep the ring 19: Molded products 31: Mold 32: Mold for the outer surface of the disc 33: Wheel rim outer diameter mold 34: Punching Die 35: Keep the mold 35a: Positioning hole 36: Shaft 36a: Fitting part 36b: Step difference part 36c: Large diameter part 36d: Inclined shape 37: Undulating Shape Surface 38: Supporting aspects 39: Alcove 41: Concave-convex shape part 41a: Part 42: Corner Curved Face 43: Fitting recess 44: Outer Peripheral Surface 44a: Part 45: Avoidance section 46: Annular recess 47: Protrusion 51, 52 Heating devices 53: Heater 54: Served at the entrance 55: Output port 56: Insulation tank 71: Wheel rim 72: Wheel rim 73: Chart Section 74: Center Hub 75: Outer flange 76: Inner flange 77: Wheel spokes 78: Window 81: Lower Ring 82: IUD insertion 82a: Body ring part 82b: Inner ring 82c: Connecting rod 83: Sales 83a: Prominent part 84: Pin Hole 86: Through hole 87: Separate components 87a: Main body 87b: Fixing part 87c: Retaining ring 88: Metal wire d1: Gap

Claims

1. A method for manufacturing a fiber-reinforced thermoplastic resin wheel rim, comprising integrally forming a rim portion and a disc portion of a wheel rim, wherein the rim portion and the disc portion are formed from a fiber-reinforced thermoplastic resin material through a mold, the manufacturing method comprising: The material is made using a block-shaped material and a thin sheet-shaped material; A deformable sheet is used as the sheet material. The deformable sheet has multiple radial notches on its outer periphery, and the outlines of the notches converge during molding. The temperature of the mold is set below the melting point of a resin matrix, which is a constituent element of the material. The block material and the sheet material are heated to a temperature higher than the melting point of the resin matrix. After heating, the block material is held in the mold in a position surrounded by a disc outer surface mold and a wheel rim outer diameter mold, and the sheet material is held on the side of the wheel rim outer diameter mold near a punching mold, which is opposite to the disc outer surface mold. The thin sheet material is shaped using the punching die and the outer diameter die of the wheel rim to form the wheel rim portion. A portion of the thin sheet material is then pressed onto the block material to join the two together. Simultaneously, the block material is compressed and shaped using the outer surface die of the disc, the outer diameter die of the wheel rim, and the punching die to form the disc portion of the wheel rim.

2. The method for manufacturing a fiber-reinforced thermoplastic resin wheel rim as described in claim 1, wherein the sheet material is made of multiple sheets, and the multiple sheets of the sheet material are held in the following state: staggered from each other in the circumferential direction, overlapping in the thickness direction so that the gaps are covered by each other and preventing them from sealing together.

3. The method for manufacturing a fiber-reinforced thermoplastic resin wheel rim as described in claim 1 or 2, wherein the sheet material is made by using a deformable sheet plus a ring-shaped reinforcing sheet, the reinforcing sheet overlapping the deformable sheet but preventing them from being tightly fitted together, the reinforcing sheet deforming during the forming of the deformable sheet, and moving to a part whose thickness, rigidity, or strength must be higher than other parts after forming.

4. A method for manufacturing a fiber-reinforced thermoplastic resin wheel rim as described in claim 1 or 2, wherein the sheet material has a through hole in the center and is held by a retaining ring, the through hole allowing the punching die to pass through, and the retaining ring is placed on the outer diameter die of the wheel rim.

5. The method for manufacturing a fiber-reinforced thermoplastic resin wheel rim as described in claim 4, wherein the retaining ring is provided with a pin that is inserted into a through hole formed on the outer periphery of the sheet material to retain the sheet material.

6. The method for manufacturing a fiber-reinforced thermoplastic resin wheel rim as described in claim 1 or 2, wherein the deformable sheet of the sheet material is composed of a sheet material having a reinforcing fiber, wherein the reinforcing fiber is a continuous fiber cross sheet, a fragment material, or a continuous fiber laminated isotropic cross sheet.

7. The method for manufacturing a fiber-reinforced thermoplastic resin wheel rim as described in claim 2, wherein the sheet material is either a deformable sheet composed of a sheet material having continuous fiber cross-laminated sheets as reinforcing fibers, or a deformable sheet composed of a sheet material having fragmented material or broken sheets as reinforcing fibers.

8. A method for manufacturing a fiber-reinforced thermoplastic resin wheel rim as described in claim 1 or 2, wherein the block material is formed by laminating multiple thin sheets through the punching die in the compression direction, and the thin sheets have fragments or flakes as reinforcing fibers.

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