Method for manufacturing thermoplastic fiber-reinforced resin wheel

Abstract

According to the present invention, a high-strength resin wheel in which a rim portion and a disc portion are integrated is manufactured with good moldability in an extremely short time.　This resin wheel manufacturing method includes molding, with a mold 31, a material 11 formed of a thermoplastic fiber-reinforced resin, wherein the temperature of the mold 31 is set to a temperature lower than the melting point of a resin matrix of the material 11. A billet-shaped material 13 and a sheet-shaped material 12 are prepared as the material 11, and heated to a temperature higher than the melting points of the resin matrices thereof. The heated billet-shaped material 13 is held inside the mold 31 surrounded by a disc outer surface mold 32 and a rim outer diameter mold 33, and the sheet-shaped material 12 is held on the surface of the rim outer diameter mold 33 on a punch mold 34 side. While forming a rim portion of the wheel by performing molding in which the notch of an outer circumferential part of the sheet-shaped material 12 is closed due to the lowering of the punch mold 34, a disc portion of the wheel is formed by pressing and joining a portion of the sheet-shaped material 12 to the billet-shaped material 13 and compression-molding the billet-shaped material 13.

Description

Method for manufacturing thermoplastic fiber reinforced resin wheels

[0001] The present invention relates to a manufacturing method for molding an automobile wheel having an integrated rim portion and disk portion from a thermoplastic fiber reinforced resin.

[0002] Automobile wheels with an integrated rim and disc structure are generally formed by first aligning all or part of the material, i.e., fiber-reinforced plastics (e.g., FRP (Fiber Reinforced Plastics) or SMC (Sheet Molding Compound)) or a fiber-based material, along the inner surface of a mold. However, because a wheel is made up of an integrated rim and disc, which have different shapes and orientations, the multiple materials that make up at least these parts must be shaped differently and positioned in different positions.

[0003] The wheel disclosed in Patent Document 1 below is made of a thermosetting resin and is manufactured as follows: The material for the rim portion is a sheet-shaped molding compound (SMC) with a high resin content, which is formed into a cylindrical shape and held inside a rim-molding mold. The material for the disk portion is a sheet-shaped molding compound (SMC) with a high fiber volume fraction, which is placed between a lower mold and an upper mold that mold the disk portion. In this example, the cylindrical material for the rim portion is wrapped around the outer periphery of the material for the disk portion to form the resin material for processing.

[0004] The resin material to be processed is placed in a heated mold and then compression molded (heat and cool molding). After heating for a specified time, the resin matrix of the material solidifies through a chemical reaction, and then the material is cooled to complete the molding process.

[0005] Because the wheels are manufactured in this way, it takes time to properly position and shape the material inside the mold and for the resin to harden, making it impossible to complete the molding process in just a few minutes, including the preparation stage.

[0006] A technology for high-speed molding of sheet material made of thermoplastic fiber-reinforced resin rather than thermosetting fiber-reinforced resin is disclosed in the following non-patent document 1. This aims to shorten the cycle time while ensuring sufficient moldability, and employs a method in which the sheet material is heated to a temperature higher than the melting point of the resin matrix, and then sandwiched between molds set at a lower temperature for molding. Manufacturing wheels from thermoplastic fiber-reinforced resin is disclosed in the following non-patent document 2. This uses thermoplastic fiber-reinforced resin, whose reinforcing fibers are chopped material, as the raw material, heated to a predetermined processing temperature, and then placed in a mold for compression molding.

[0007] In this method, a punch is pressed into the blank to compress and form the disk portion, while extruding a portion of the blank into a cylindrical shape to form the rim portion. Because the diameter of the rim portion increases as it extends upward, a larger volume of blank is required to ensure the required thickness. This requires the disk portion to have a larger volume than necessary. Furthermore, for wider rims, the punch must be pressed deeper and harder, dramatically increasing the forming load. Furthermore, because the rim portion is formed by extrusion, the reinforcing fibers tend to align in a specific direction. This increases anisotropy, preventing high strength, making it difficult to mold wheels with wide rims. In other words, even if the reinforcing fibers are isotropic in the blank before molding, their anisotropy increases as they flow upward into the rim, leading to axial strength variations and strength reduction. This imposes limitations on the width of the rim portion.

[0008] To reduce anisotropy, it is conceivable to slow down the molding speed to slow down the flow rate of the reinforcing fibers, but this would increase the molding time and also hinder moldability due to the rapid drop in resin temperature during molding. Thus, while the technology of Non-Patent Document 1 seems to enable molding in a short time with a single compression operation, it is difficult to balance molding speed and molded product performance to satisfy both, and there are also restrictions on the product shape.

[0009] In addition to the quick form molding technique described in Non-Patent Document 2, there is also a technique called HP-RTM (High Pressure Resin Transfer Molding) molding (for example, Patent Document 2).

[0010] In this molding method, for example, dry fiber substrates or fiber substrate laminates that have not been impregnated with resin are manually placed in a molding die and shaped. After the molding die is closed, the pressure inside the die is reduced and a thermosetting resin such as epoxy resin is injected under pressure to impregnate the fiber substrate. The die is then heated to harden the thermosetting resin. Multiple fiber substrates are prepared depending on the application area and manually placed, which has the advantage of ensuring the wheel's strength by increasing the number of layers in areas that need reinforcement.

[0011] However, the process of arranging and shaping the fiber substrate takes time, and a high level of know-how is required to obtain a uniform product.

[0012] As a result, the pre-molding process and molding require a considerable amount of time that cannot be measured in minutes, and the wheels produced in this way are very expensive, so they can only be used on certain special vehicles such as supercars.

[0013] Japanese Patent Publication No. 6-51308 Patent No. 6652523

[0014] 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 August 11, 2018, Version of Record August 11, 2018., Volume 15, pp. 1722-1729. “Carbon Fiber Reinforced Plastic (CFRTP) Automobile Tire Wheels,” Rapit Co., Ltd., Product Catalog, [Retrieved October 3, 2022], Internet <URL: https: / / www.ipros.jp / catalog / detail / 498804>

[0015] The main objective of this invention is to enable the manufacture of wheels made of thermoplastic fiber reinforced resin with good formability in a short time, while also ensuring mechanical performance and enabling the manufacture of wheels with wide rim portions.

[0016] To this end, the present invention provides the following method for manufacturing a thermoplastic fiber reinforced resin wheel.

[0017] Specifically, the method for manufacturing a thermoplastic fiber-reinforced resin wheel involves molding a thermoplastic fiber-reinforced resin material in a mold to produce a wheel with an integrated rim and disk. The material used is a billet-shaped material and a sheet-shaped material. The sheet-shaped material is a deformable sheet with multiple radial notches on its outer periphery, with the contours of the notches meeting each other during molding. The mold is set to a temperature lower than the melting point of the resin matrix, which is a component of the material, and the billet-shaped material and the sheet-shaped material are heated to a temperature higher than the melting point of the resin matrix, which is a component of the material. After heating, the billet-shaped material is held within a mold surrounded by a disk outer surface mold and a rim outer diameter mold, while the sheet-shaped material is held on the punch die side of the rim outer diameter mold, opposite the disk outer surface mold. The punch die and rim outer diameter mold then mold the sheet-shaped material into the rim portion of the wheel, while pressing a portion of the sheet-shaped material against the billet-shaped material to bond them together. At the same time, the billet-shaped material is compression molded using a disk outer surface mold, a rim outer diameter mold, and a punch mold to form the disk portion of the wheel.

[0018] In this configuration, the sheet-shaped material and billet-shaped material, which have different shapes, are plastically deformed in a manner that minimizes strain on each other and conforms to their respective shapes, and are simultaneously joined and integrated with each other during plastic deformation. The deformable sheet, which is the sheet-shaped material, undergoes deformation during molding, closing the notches on the outer periphery and meeting the contours, thereby suppressing the occurrence of wrinkles and reducing the molding load, while enabling the formation of a wide rim portion. Furthermore, compression molding of the billet-shaped material does not require the formation of a rim portion, so excessive volume and molding load are unnecessary. During this molding process, the sheet-shaped material and billet-shaped material are heated to a temperature higher than the melting point of the resin matrix, and then the temperature is reduced while they are plastically deformed into the desired shape quickly within a mold maintained at a predetermined temperature lower than that temperature.

[0019] According to this invention, the molding of sheet-like material and the compression molding of billet-like material are organically combined to smoothly mold and integrate the rim and disc portions in a single operation, allowing for excellent formability and a very short time of minutes. Furthermore, each material is molded in a relatively gentle manner that matches the shape of the material. This facilitates control of the flow of material during molding of the rim and disc portions, and prevents excessive anisotropy of the reinforcing fibers, ensuring mechanical performance. Furthermore, the rim portion is formed by molding a deformable sheet as a sheet-like material having notches with contours that meet during molding, allowing for the formation of a wide rim portion with a small molding load. Furthermore, unlike deep drawing, the rim portion is formed without the risk of fracture of the sheet-like material, resulting in high strength and suppressing the occurrence of wrinkles, resulting in a high-quality appearance. The reduced molding load also contributes to reduced manufacturing costs.

[0020] 6 is a schematic diagram of a method for manufacturing a thermoplastic fiber reinforced resin wheel. A front view of the wheel and its A-A cross section. A perspective view of a sheet-shaped material and a billet-shaped material. A perspective view showing the shape of an easily deformable sheet of the sheet-shaped material. A half-sectional view of the billet-shaped material. A perspective view of a retaining ring holding the sheet-shaped material. A perspective view of the separated state of FIG. 6. A cross-sectional view showing the structure of a mold. A cross-sectional view of a state in which the material is held in the mold. A cross-sectional view showing the molding process. A cross-sectional view of the molded state. A half-sectional view of a billet-shaped material provided with a reinforcing sheet as another example. A plan view of a billet-shaped material provided with a reinforcing sheet. A cross-sectional view showing the molded state using a reinforcing sheet. A front view of a molded product having a reinforcing sheet. A front view of a wheel having a reinforcing sheet.

[0021] An embodiment of the present invention will be described below with reference to the drawings.

[0022] This invention is for manufacturing an automobile wheel (hereinafter referred to as "wheel") having an integrated rim portion and disk portion by molding, and uses a thermoplastic fiber reinforced resin as the molding material (intermediate substrate).

[0023] Thermoplastic fiber reinforced resins include SMC (Sheet Molding Compound), BMC (Bulk Molding Compound), also known as Forged Carbon Sheet or Forged Carbon Fiber Sheet, FRP (Fiber Reinforced Plastic) such as Carbon Fiber Reinforced Plastic, stampable sheets, etc., and are mainly composed of a resin matrix (base material) and reinforcing fibers (reinforcement material).

[0024] Figure 1 shows an outline of the main components of a method for manufacturing an automobile wheel. In this manufacturing method, a prepared material 11 is heated and then molded in a mold 31 to obtain a wheel-shaped molded product. The molded product is then removed from the mold 31 and subjected to post-processing such as cutting to obtain an intermediate wheel product 71 (hereinafter also referred to as "wheel 71") as shown in Figure 2.

[0025] First, the material 11 will be described.

[0026] As shown in Fig. 3, the raw material 11 is roughly divided into two types of shapes: a sheet-shaped raw material 12 having a sheet shape, and a billet-shaped raw material 13 having a billet or bulk shape.

[0027] The sheet material 12 mainly constitutes the rim portion 72 of the wheel 71, and is available in two types: a roughly disk-shaped easily deformable sheet 12a and an annular reinforcing sheet 12b. The easily deformable sheet 12a has an appropriate thickness and is formed in a disk shape that expands in the surface direction, with a through-hole 14 penetrating through the thickness direction at the center of the surface. The through-hole 14 may have a circular shape as shown in the illustration, or may have any other shape.

[0028] Since the deformable sheet 12a is not deep-drawn, it has a plurality of radially extending notches 15 on its outer periphery. The contour lines 16 forming these notches 15 meet each other during forming. In other words, as shown by the imaginary lines in FIG. 4 , when the deformable sheet 12a is formed into a cylindrical outer periphery, the notches 15 close and the contour lines 16 of the notches 15 come into contact with each other, i.e., the notches 15 are formed in such a way that they meet. The shape of the notches 15 can be obtained by analysis using a forming simulation. In the illustrated example, the notches 15 are formed in four equally spaced locations, but the number of notches 15 may be any number other than four.

[0029] The rim portion 72 may be formed using one easily deformable sheet 12a, but is preferably formed using multiple easily deformable sheets 12a. In the illustrated example, three easily deformable sheets 12a are used. The multiple easily deformable sheets 12a are stacked in the thickness direction to prevent them from adhering to each other. When stacking the easily deformable sheets 12a, the orientations of the sheets 12a in the circumferential direction are shifted relative to each other so that the notches 15 are mutually covered.

[0030] The reinforcing sheet 12b is a sheet-like material 12 that moves to a location where the thickness, rigidity, or strength should be increased compared to other locations after deformation of the deformable sheet 12a during molding, and is formed in an annular, more specifically, circular, shape. The location where the thickness, rigidity, or strength should be increased compared to other locations is, for example, the portion forming the inner flange 76 (see FIG. 2). The reinforcing sheet 12b is layered on the deformable sheet 12a while preventing them from adhering to each other. The radial length, i.e., width, of the reinforcing sheet 12b is set according to the size of the location to be reinforced.

[0031] The billet-shaped material 13 mainly constitutes the disk portion 73 of the wheel 71. It is a block of suitable dimensions for compression molding, or a shape of a predetermined size, volume, and bulk. Specifically, it is formed into a short cylindrical shape with a predetermined thickness and diameter to fit the cavity of the mold and a through-hole 17 in the center. It is compression molded during molding. The through-hole 17 may have a circular shape as shown in the illustration, or may have other shapes. In addition to the shape shown in the illustration, the billet-shaped material 13 may have a shape that allows near-net-shape (NNS) molding, i.e., a method of producing a shape close to the finished product without requiring significant post-molding processing. For example, it may have a shape with multiple holes on the inner periphery of a short cylinder, similar to the required number of spokes extending from the inner periphery. This is also true for the sheet-shaped material 12 described above, which may have holes drilled in the areas corresponding to the spokes.

[0032] The reinforcing fibers of the material 11 can be made of chopped material (chopped fiber), chopped sheets, continuous fiber cloth (woven) sheets, etc., with carbon fiber or glass fiber being preferred. In particular, for the easily deformable sheet 12a of the sheet-like material 12, chopped material or chopped sheets can be used, but it is preferable to use one containing continuous fiber as the reinforcing fiber. More preferably, easily deformable sheets 12a made of continuous fiber cross sheets can be used in combination with easily deformable sheets 12a made of chopped material or chopped sheets. In this case, it is possible to layer easily deformable sheets 12a made of chopped material or chopped sheets on both the front and back sides of the easily deformable sheet 12a made of continuous fiber cross sheets. Furthermore, chopped material or chopped sheets are preferred for the reinforcing sheet 12b.

[0033] The billet-shaped material 13 is made quasi-isotropic and contains chopped material (chopped fiber) or chopped sheet as reinforcing fibers, taking into consideration formability during compression molding. In consideration of the rigidity of the molded product in addition to formability, it is more desirable to form the billet-shaped material 13 by stacking multiple SMC 13a, which is a quasi-isotropic random sheet material containing chopped sheet as reinforcing fibers, in the thickness direction as shown in Figure 5. The thickness direction of the SMC 13a is the compression direction during compression molding.

[0034] Since the billet-shaped material 13 is a single mass, it can be handled as a single component from the heating operation to the insertion into the mold 31, and there are no operational problems. However, the sheet-shaped material 12 is in a sheet shape, and the deformable sheet 12a and the reinforcing sheet 12b are stacked in a state where they are prevented from adhering to each other. For this reason, it is necessary to be able to handle the multiple sheet-shaped materials 12 as a single component from the heating operation to the molding.

[0035] To this end, the sheet material 12 is held in a holding ring 18 as shown in FIG. 6 . The holding ring 18 has the function of positioning (centering) the sheet material 12 and the function of holding each sheet material 12 so that it can deform independently. It includes a metal lower ring 81 and an upper ring 82, and the sheet material 12 held between them is heated and formed. As shown in FIG. 7 , the lower ring 81 is made of a circular plate material whose outer diameter corresponds to the outer diameter of the easily deformable sheet 12a and whose inner diameter is smaller than the outer diameter. A plurality of pins 83 are erected at equal intervals on the surface of the lower ring 81. The number of pins 83 is eight, double the number of pins 83, since the easily deformable sheet 12a has four notches 15. The lower ends of the pins 83 protrude a predetermined distance from the underside of the lower ring 81, and the downward protruding portions 83a are used for positioning relative to the mold 31.

[0036] The upper ring 82 has a main ring portion 82a that is the same size as the lower ring 81, and an inner ring portion 82b located on the inner periphery of the main ring portion 82a and having an inner diameter that roughly corresponds to the outer diameter of the reinforcing sheet 12b to be held. The main ring portion 82a and the inner ring portion 82b are integrated via multiple connecting rods 82c. The main ring portion 82a has pin holes 84, the same number as the number of pins 83, formed at equal intervals to insert the pins 83 of the lower ring 81, and the inner ring portion 82b has multiple holding holes 85, formed at equal intervals, to hold the reinforcing sheet 12b. In the illustrated example, four holding holes 85 are formed.

[0037] The central through hole 86 of the upper ring 82, i.e., the hole located more inward than the inner ring portion 82b, is sized to enable molding using the punch die 34 in the die 31 when the retaining ring 18 is placed on the rim outer diameter die 33 in the die 31.

[0038] Such a retaining ring 18 is provided with a spacing member 87 for preventing the sheet-like materials 12 from adhering to each other. The spacing member 87 is made of a metal wire such as a stainless alloy and is composed of an annular main body 87a and multiple anchoring portions 87b extending radially outward from the main body 87a. The size of the main body 87a is formed to be approximately the same as or larger than the through-hole 86 of the upper ring 82. For example, it is preferable to form it larger than the outer diameter of the reinforcing sheet 12b. The anchoring portions 87b are provided in the same number as the number of pins 83 of the lower ring 81 and are arranged at equal intervals. Retaining rings 87c, through which the pins 83 are inserted, are provided at the tips of the anchoring portions 87b.

[0039] To hold the deformable sheet 12a in the retaining ring 18, insertion holes 12c are formed at equal intervals on the outer periphery of the deformable sheet 12a. Because the deformable sheet 12a has four notches 15, it has a structure with four non-notched portions, i.e., four protrusions 15a extending in the circumferential direction. Insertion holes 12c are formed at circumferentially central positions on the outer periphery of these four protrusions 15a. Meanwhile, four insertion holes 12d, the same number as the retaining holes 85 in the inner ring portion 82b of the upper ring 82, are formed at equal intervals on the outer periphery of the reinforcing sheet 12b. Wires 88 inserted through the retaining holes 85 in the inner ring portion 82b are inserted through the insertion holes 12d in the reinforcing sheet 12b, thereby connecting the reinforcing sheet 12b and the upper ring 82 to each other.

[0040] When the sheet material 12 is held on the holding ring 18, first, the lowest deformable sheet 12a is held on the lower ring 81 and a spacing member 87 is placed on top. Next, another deformable sheet 12a is placed on top of that, followed by another spacing member 87, until the required number of deformable sheets 12a are placed one after the other. Thereafter, another spacing member 87 is placed between the upper ring 82 and the lower ring 81, and the upper ring 82 holding the reinforcing sheet 12b is then joined to the lower ring 81. The upper ring 82 is held by inserting the pins 83 of the lower ring 81 into the pin holes 84 of the upper ring 82.

[0041] The resin matrices of the sheet material 12 and the billet material 13 may be any resin that is compatible with each other and can be mixed with each other, and generally the same resin is used, such as a thermoplastic epoxy resin or polyamide.

[0042] Next, the apparatus used in the manufacturing method will be described.

[0043] The manufacturing method involves heating the billet-shaped material 13 and the sheet-shaped material 12 to a temperature higher than the melting point of the resin matrix that constitutes them, and then molding them at high speed in a mold 31 that is set to a temperature lower than the melting point.

[0044] 1, the apparatus includes not only a mold 31 for forming but also heating devices 51 and 52 for heating the sheet-like material 12 and the billet-like material 13, respectively. While the heating devices 51 and 52 may use any suitable heating method, it is preferable to use an IR (infrared) heating method in order to achieve ideal heating without uneven heating inside and outside in a short time. Depending on the shape of the material 11, it may be possible to heat the material in a soaking furnace consisting of a hot air heater. In this case, the heat-retaining pot 56 can be omitted.

[0045] The heating device 51 that heats the sheet material 12 has upper and lower heaters 53, and has an inlet 54 that serves as an entrance to the conveyance path between the heaters 53, and an outlet 55 that serves as an exit. The sheet material 12 is held by a holding ring 18, and is carried in and out by an automatic conveyance device.

[0046] The heating device 52 that heats the billet-shaped material 13 is the same as the heating device 51 that heats the sheet-shaped material 12. A plurality of sheet materials (SMC 13a) that will form a billet when stacked are heated while being conveyed. A heat-retaining pot 56 is provided downstream of the heating device 52. The heat-retaining pot 56 contains the billet-shaped material 13, which is made by stacking sheet materials (SMC 13a), and ensures uniform heating.

[0047] The heating temperature of the sheet-shaped material 12 and the billet-shaped material 13 is higher than the melting point of their resin matrix. If the resin matrix is, for example, polyamide, it is recommended to heat it to about 280°C. This temperature takes into consideration the temperature drop during molding, and is about 30°C to 70°C higher than the melting point.

[0048] The molding die 31 is composed of a disk outer surface die 32, a rim outer diameter die 33, and a punch die 34. The disk outer surface die 32 is a lower die that mainly forms the outer surface of the disk portion 73 of the wheel 71. The rim outer diameter die 33 moves radially on the top surface of the disk outer surface die 32 to form the outer peripheral surface of the rim portion 72 of the wheel 71, and is divided into multiple parts circumferentially. The punch die 34 is an upper die that mainly forms the inner peripheral surface of the rim portion 72 and the inner surface of the disk portion 73, and is supported on the rim outer diameter die 33 from the side opposite the disk outer surface die 32 so that it can move up and down toward the disk outer surface die 32. In addition, a positioning hole 35a is formed in the top surface of a holding die 35 provided on the outer peripheral side of the rim outer diameter die 33, into which the lower end of a pin 83 protruding below the retaining ring 18 is inserted and held.

[0049] Next, the structure of the mold 31 will be described. Wheels 71 come in a variety of shapes, including whether the outer surface of the disk is convex, flat, or concave, as in the case of inset, zeroset, or outset, depending on the distance from the center line of the wheel (rim width) to the mounting surface. The mold 31 also comes in a variety of shapes depending on the wheel shape, and the mold 31 shown in the illustration is one example. The manufacturing method of the present invention is not limited to the illustrated shape.

[0050] 1 and 8, the disk outer diameter mold 32 has a shaft portion 36 in the center that faces vertically upward. The shaft portion 36 is located in a position that corresponds to the center bore 74 of the wheel 71, and the entire circumference of the shaft portion 36 has an undulating surface 37 that corresponds to the outer surface of the disk portion 73. The portion further outward from this is a support surface 38 that supports the rim outer diameter mold 33.

[0051] The tip end of the shank 36 is a fitting portion 36a that fits into the punch die 34, and is formed as the thinnest portion of the shank 36. A large diameter portion 36c is formed below the fitting portion 36a, with a step portion 36b interposed between them. The diameter of the large diameter portion 36c is smaller than the diameter of the through hole 17 in the billet-shaped material 13. The large diameter portion 36c has a base portion, i.e., a sloped portion 36d at the outer periphery at the bottom end, which has a sloped shape that increases in diameter downward like a mountain foot. The diameter of the sloped portion 36d at the bottom end is larger than the diameter of the through hole 17 in the billet-shaped material 13.

[0052] The rim outer diameter mold 33 has a recess 39 at its lower end which forms the portion where the outer flange 75 of the wheel 71 and the outer portion of the tire are assembled. Above the recess 39, an uneven portion 41 which flows in and out along the shape of the rim portion 72 is formed, and at the upper end above the portion 41a which forms the inner flange 76 of the wheel 71, a rounded corner portion 42 is formed.

[0053] The punch die 34 has a fitting recess 43 in the centre of its underside that fits with the fitting portion 36a of the shaft portion 36 of the disc outer surface die 32. It also has an outer peripheral surface 44 shaped to fit inside the rim outer diameter die 33 in the closed state, with a corner gap corresponding to the thickness of the rim portion 72. Of the outer peripheral surface 44, the portion 44a that forms the inner flange 76 of the wheel 71 is particularly shaped so as to form a molding space of the desired shape that takes mechanical performance into consideration between it and the corresponding portion of the rim outer diameter die 33.

[0054] The depth of the fitting recess 43 is set so that a gap d1 is formed between the bottom of the fitting recess 43 and the tip of the shank 36 even when the punch 34 is at the bottom dead center. The dimensions of the periphery of the shank 36 are also designed so that an escape portion 45 that the billet material 13 will not reach when the punch 34 reaches the bottom dead center is formed near the rim of the fitting recess 43.

[0055] The portion outer than the fitting recess 43 is an annular recess 46 that forms the portion outer than the center bore 74 of the wheel 71, and the portion further outer than that is an overhang 47 that forms the spokes 77 of the wheel 71 and the portions corresponding to the window portions 78 between the spokes 77. The overhang 47 protrudes downward from the annular recess 46. The portion of the overhang 47 that corresponds to the window portions 78 is formed so that its thickness after molding is thin between the undulating surface 37 of the disk outer surface mold 32.

[0056] Such a mold 31 is equipped with a temperature control mechanism (not shown) that controls the temperature of the mold 31 to a constant value. The temperature control mechanism is configured with a flow path for flowing a medium such as water, and is configured to maintain a predetermined temperature by monitoring and adjusting the medium flow rate and temperature. The temperature control mechanism can also be configured by inserting a cartridge heater into the mold 31.

[0057] The temperature of the mold 31 is lower than the melting point of the resin matrix of the sheet-like material 12 and the billet-like material 13, and preferably lower than the glass transition temperature. When the resin matrix is ​​a thermoplastic epoxy resin, the recommended molding temperature for thermoplastic epoxy resin is 180°C to 210°C, so the temperature of the mold 31 is specifically 100°C to 130°C, particularly 120°C or lower, and may be 80°C or lower, 75°C, or even about 50°C. As long as the temperature is above a certain required temperature, a lower temperature is preferable because it can suppress adhesion of the resin matrix to the mold 31 and shorten the holding time, thereby shortening the cycle time.

[0058] The above-described apparatus produces the wheel 71 by forming the sheet material 12 and the billet material 13 as follows.

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

[0060] While these preparations are being made, a thermoplastic fiber reinforced resin is cut using a water jet or the like to prepare the sheet material 12 (easily deformable sheet 12a and reinforcing sheet 12b) held in the retaining ring 18, and the sheet material (SMC 13a) for constituting the billet material 13. These are heated to a predetermined temperature using heating devices 51 and 52, and the heated sheet material (SMC 13a) for the billet material 13 is stacked and heated uniformly in a heat-retaining pot 56.

[0061] 9, the punch die 34 is raised to open the die 31, and the billet-shaped material 13 is placed into the die 31. At this time, the shaft portion 36 and the inclined portion 36d of the disk outer surface die 32 align the center of the billet-shaped material 13 with the center of the disk outer surface die 32.

[0062] Immediately after this, the retaining ring 18 holding the sheet material 12 is placed on the upper surface of the rim outer diameter mold 33. The retaining ring 18 is positioned when the downwardly protruding portion 83a of the pin 83 is fitted into the positioning hole 35a on the upper surface of the holding mold 35, and centering is performed to align the center of the sheet material 12 with the center of the mold 31.

[0063] At this time, since the temperature of the mold 31 is lower than the heating temperature of the sheet-like material 12 and the billet-like material 13, the temperatures of the sheet-like material 12 and the billet-like material 13, which decrease in temperature as they leave the heating device 51 and the heat-retaining pot 56, decrease further.

[0064] High-speed forming can be achieved by lowering the punch 34 as shown in FIG. 10 immediately after the sheet-like material 12 and the billet-like material 13 are set in the die 31. Specifically, as the punch 34 descends, the lower end of its protruding portion 47 first contacts the deformable sheets 12a of the sheet-like material 12 and descends to form the rim portion 72. As the punch 34 descends, the multiple deformable sheets 12a, which are prevented from adhering to each other, are drawn into the die 31 and gradually formed along the rim outer diameter die 33 and the punch 34. Through forming, the contours 16 of the notches 15 converge to form the cylindrical rim portion 72. Because the multiple deformable sheets 12a are highly independent of each other, forming in which the contours 16 converge is reliably achieved. Furthermore, the deformable sheets 12a are not held by clamping their outer peripheries but by inserting the pins 83 into the insertion holes 12c, resulting in less constraint and smoother desired forming.

[0065] As this molding is performed, the rim portion 72 cools and solidifies. At this time, as the punch 34 approaches bottom dead center, an upper portion of the outer peripheral surface 44 of the punch 34, which is close to the portion 44a that forms the inner flange 76, presses the reinforcing sheet 12b. The reinforcing sheet 12b is then pressed onto the deformable sheet 12a, and the portion where the reinforcing sheet 12b is located is thickened and reinforced.

[0066] The sheet material 12 pressed down onto the lower end of the protruding portion 47, i.e., the inner peripheral portion of the deformable sheet 12a, comes into contact with the upper surface of the billet material 13 from above and is pressed against the billet material 13 by the punch 34. As a result, the sheet material 12 and the billet material 13 are joined together and continue to deform, and when the punch 34 reaches the bottom dead center, the desired forming of the sheet material 12 and the billet material 13 is completed as shown in FIG.

[0067] At this time, the tip of the shaft portion 36 of the disk outer surface die 32 and the bottom of the fitting recess 43 of the punch die 34 are not in contact with each other, and a space, i.e., an escape portion 45, which the compression-molded billet-shaped material 13 does not reach is formed near the lip of the fitting recess 43. Therefore, although the molding load increases especially after the sheet-shaped material 12 comes into contact with the billet-shaped material 13, an extreme increase in the molding load can be avoided.

[0068] Molding using such a mold 31 can be completed in less than one minute, even if the bottom dead center is held for 15 seconds, depending on the conditions. Furthermore, holding the material 11 in the mold 31 can be done easily and quickly, unlike operations that require precise placement of multiple materials. In particular, since multiple sheets of sheet material 12 are held by a retaining ring 18, the sheet material 12 can be handled as a single component while being prevented from contacting each other. Therefore, the molding process, including removal of the molded product, can be completed in less than one minute. However, with a large-diameter wheel 71, the temperature drop rate is slower, so removal may take longer.

[0069] The molded product removed from the mold 31 is cooled by leaving it to stand at room temperature, and then post-processing is performed, such as cutting out excess parts such as the parts that protrude beyond the inner flange 76 and the window part 78, to form the wheel 71 (see Figure 2).

[0070] As described above, in the molding process using the mold 31, the sheet material 12 is molded and the billet material 13 is compression molded, and the two materials are joined together during each molding process. Moreover, because the inner peripheral portion of the sheet material 12 is pressed down to form a cylindrical shape, the desired rim portion 72 can be easily obtained, and the rim portion 72 can also be made wider. With the billet material 13, only the disk portion 73 is formed, and there is no need to form the rim portion 72, so excessive volume and molding load are not required. As for the molding load, the provision of the relief portion 45 reliably prevents a sudden increase in the molding load.

[0071] This type of molding is, so to speak, an organic combination of molding the sheet-like material 12 and compression molding the billet-like material 13, and the rim portion 72 and disc portion 73 are molded and joined together smoothly in a single operation. This allows the wheel 71 to be molded in an extremely short time, on the order of minutes, with good moldability. Moreover, since molding is performed in a manner that is minimally strained and matches the respective shapes of the sheet-like material 12 and billet-like material 13, it is easy to control the flow of the material 11 during molding. By preventing the reinforcing fibers from excessively increasing anisotropy, the mechanical performance of the wheel can be ensured.

[0072] In particular, the deformable sheet 12a of the sheet-like material 12 has a configuration in which the contour lines 16 meet through the cutouts 15, so that the change in fiber orientation during molding is small, improving strength in the circumferential and width directions. This also reduces the molding load, making it possible to reduce molding costs. Furthermore, wrinkles can be suppressed, resulting in a good appearance quality.

[0073] By optimizing the shape of the material 11 so that it can be formed in NNS, it is possible to reduce the load during forming and the material input load.

[0074] Furthermore, since there is no excessive deformation during molding and the flow of the material 11 is easy to control, partial reinforcement can be performed by using the reinforcing sheet 12b as described above, thereby obtaining sufficient mechanical performance.

[0075] Even in the molding of the disk portion 73, since there is no complicated or excessive deformation, the flow of the billet-shaped material 13 is easy to control, and sufficient mechanical performance can be partially ensured.

[0076] For example, when reinforcing the area between the spokes 77 of the disk portion 73 and the outer flange 75 during molding, the following procedure is carried out.

[0077] That is, when the billet-shaped material 13 is formed by laminating a plurality of SMC 13a, which are quasi-isotropic random sheet materials having chopped sheets as reinforcing fibers, in the thickness direction, a reinforcing sheet 13b is provided between the SMC 13a, as shown in Fig. 12. The reinforcing sheet 13b may be formed of a continuous fiber cross sheet. Alternatively, a braided sheet (quasi-isotropic fabric) such as "QISO" (registered trademark) by A&P Technology may be used as the reinforcing fiber.

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

[0079] This reinforcing sheet 13b moves in the outer circumferential direction as the billet-shaped material 13 is deformed during compression molding, and to enable this movement, it is located on the outer circumferential side of the billet-shaped material 13 and is divided in the circumferential direction.

[0080] FIG. 12(a) shows an example in which the reinforcing sheet 13b is provided on the outer surface side of the disk portion 73, and FIG. 12(b) shows an example in which the reinforcing sheet 13b is provided on both the outer surface side and the inner surface side.

[0081] The reinforcing sheets 13b are formed into an appropriate shape and provided in advance at appropriate positions where reinforcement is required. Specifically, as shown in FIG. 13 , the reinforcing sheets 13b of the billet-shaped material 13 are formed in an approximately fan shape, and multiple reinforcing sheets 13b are arranged at equal intervals to match the number of spokes 77. When the billet-shaped material 13 is placed into the mold 31, the circumferential direction is determined so that the spokes 77 are formed in the portions having the reinforcing sheets 13b. This can be easily achieved by providing a regulating structure between the shaft 36 and the through-holes 17 of the billet-shaped material 13, since the disk outer surface mold 32 has a shaft 36.

[0082] During forming, as shown in Figure 13, when the billet-shaped material 13 is compressed and deformed to expand in both the outer and inner circumferential directions, the reinforcing sheet 13b moves in the outer circumferential direction and becomes positioned between the outer flange 75 and the outer circumferential ends of the spokes 77. Note that Figure 14 illustrates an example in which the billet-shaped material 13 shown in Figure 12(a) has been formed.

[0083] Figure 15 shows a front view of molded product 19. In post-processing of molded product 19, the portion corresponding to window portion 78, including reinforcing sheet 13b, is cut to open window portion 78. As a result, as shown in Figure 16, reinforcing sheet 13b, which is T-shaped when viewed from the front, remains connecting outer flange 75 and spoke 77, improving the strength of this portion.

[0084] The above configuration is one embodiment for carrying out the present invention, and the present invention is not limited to only the above configuration, and other configurations can also be adopted.

[0085] For example, the shape of the reinforcing sheet 12b for padding or reinforcing a portion of the rim portion 72 does not have to be annular as described above, and may be such that partial reinforcement is performed in the circumferential direction. It may also have a shape with a notch like the deformable sheet 12a. Furthermore, the reinforcing sheet 12b may be positioned below the deformable sheet 12a instead of above it as described above, or between the deformable sheets 12a.

[0086] The retaining ring 18 that holds the sheet material 12 may have a configuration other than that described above, and for example may be configured without the upper ring 82. The retaining ring 18 can also be held to the mold 31 by any appropriate method.

[0087] The billet-shaped material 13 may be provided with a reinforcing sheet (not shown) that is not intended to move during molding. The reinforcing sheet may be a continuous fiber cross sheet or a continuous fiber laminated quasi-isotropic cross sheet. In this case, since the reinforcing sheet is not intended to move, it may be formed into a circumferentially continuous annular shape.

[0088] DESCRIPTION OF SYMBOLS 11...Material 12...Sheet-shaped material 12a...Easily deformable sheet 12b...Reinforcing sheet 12c...Insertion hole 13...Billet-shaped material 15...Notch 16...Contour line 18...Retaining ring 31...Mold 32...Disc outer surface mold 33...Rim outer diameter mold 34...Punch mold 71...Wheel intermediate product 72...Rim portion 73...Disc portion 83...Pin 86...Through hole

Claims

1. A method for manufacturing a thermoplastic fiber reinforced resin wheel, in which a material made of thermoplastic fiber reinforced resin is molded in a mold to produce a wheel having an integrated rim portion and disc portion, wherein a billet-shaped material and a sheet-shaped material are used as the material, and the sheet-shaped material is an easily deformable sheet having a plurality of notches radially formed on the outer periphery, with the contours forming the notches meeting each other during molding, the mold is set to a temperature lower than the melting point of the resin matrix which is a constituent element of the material, and the billet-shaped material and the sheet-shaped material are heated to a temperature higher than the melting point of the resin matrix which is a constituent element, and then the billet-shaped material is held in a mold surrounded by a disk outer surface mold and a rim outer diameter mold, while the sheet-shaped material is held on the surface of the rim outer diameter mold on the punch die side opposite to the disk outer surface mold, A method for manufacturing a thermoplastic fiber reinforced resin wheel, comprising: molding the sheet material with the punch die and the rim outer diameter die to form the rim portion of the wheel; pressing a portion of the sheet material against the billet material to join the two; and compression molding the billet material with the disk outer surface die, the rim outer diameter die, and the punch die to form the disk portion of the wheel.

2. A method for manufacturing a thermoplastic fiber reinforced resin wheel as described in claim 1, wherein a plurality of sheets of the sheet material are used, and the plurality of sheets of the sheet material are stacked in the thickness direction with their orientations shifted relative to each other in the circumferential direction, thereby mutually sealing the notches and preventing mutual adhesion and holding the sheets together.

3. A method for manufacturing a thermoplastic fiber reinforced resin wheel as described in claim 1 or claim 2, wherein in addition to the easily deformable sheet, a ring-shaped reinforcing sheet is used as the sheet-like material, which moves to areas where the thickness, rigidity, or strength should be higher than other areas after molding due to deformation of the easily deformable sheet during molding, and the reinforcing sheet is layered on the easily deformable sheet while preventing them from sticking to each other.

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

5. A method for manufacturing a thermoplastic fiber reinforced resin wheel as described in claim 4, wherein the sheet material is held against the retaining ring by inserting a pin provided on the retaining ring into an insertion hole formed on the outer peripheral edge of the sheet material.

6. A method for manufacturing a thermoplastic fiber reinforced resin wheel as described in claim 1 or claim 2, wherein the easily deformable sheet as the sheet-like material is composed of a sheet material having continuous fiber cross sheet, chopped material or continuous fiber laminated pseudo-isotropic cross sheet as reinforcing fibers.

7. A method for manufacturing a thermoplastic fiber reinforced resin wheel as described in claim 2, wherein the sheet-like material is an easily deformable sheet made of a sheet material having a continuous fiber cross sheet as a reinforcing fiber, and an easily deformable sheet made of a sheet material having a chopped material or chopped sheet as a reinforcing fiber.

8. A method for manufacturing a thermoplastic fiber reinforced resin wheel as described in claim 1 or claim 2, wherein the billet-shaped material is constructed by stacking multiple sheet materials having chopped material or chopped sheets as reinforcing fibers in the direction of compression by the punch mold.

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