JP7799537B2 - Method for manufacturing fiber-reinforced resin pipe body - Google Patents

Description

The present invention relates to a method for manufacturing a fiber-reinforced resin pipe body used, for example, as a power transmission shaft in a vehicle.

A power transmission shaft (propeller shaft) mounted on a vehicle has a tubular body extending in the longitudinal direction of the vehicle, and this tubular body transmits power generated by the prime mover and reduced in speed by the transmission to the final drive unit. Tubes used in such power transmission shafts include those made of fiber-reinforced plastic manufactured using a mandrel (see Patent Document 1 below).

Methods of winding material around a mandrel include the filament winding method, in which resin-impregnated continuous fibers are wound, and the sheet winding method, in which prepreg (a sheet made of fibers impregnated with resin) is wound. Patent Document 2 discloses the multi-fiber winding method, in which carbon fibers are wound around a mandrel, and the resin injection molding method, in which resin is impregnated inside a mold. According to these methods, the tube is molded between the mandrel and the mold by pressurizing and expanding the inside of a mandrel formed from resin or the like, conforming to the inner surface of the mold. This method reduces the diameter of the tube at the ends to avoid enlarging the joint, while expanding the diameter toward the center, thereby increasing the tube's bending resonance point.

Japanese Patent Application Publication No. 3-265738 Patent No. 6873369

The tube is formed with a diameter that expands from the end toward the center, but during the manufacturing process, the orientation angle of the carbon fiber wound around the mandrel outside the mold changes as it expands from the inside inside the mold. This can result in the tube not achieving the desired performance.

The present invention was created to solve these problems, and its objective is to provide a method for manufacturing a fiber-reinforced resin pipe that allows the fiber orientation angle to be suitably set.

According to the present disclosure, there is provided a method for manufacturing a fiber-reinforced resin pipe body, the method including: an arrangement step of winding fibers around the outer peripheral surface of a cylindrical mandrel; an expansion step of expanding the mandrel on which the fibers are arranged; and a curing step of impregnating the fibers arranged on the outer peripheral surface of the mandrel with a thermosetting resin and curing it, wherein in the arrangement step, the fibers are arranged at a position shifted from a predetermined orientation angle so that the orientation angle of the fibers after the expansion step becomes a predetermined orientation angle; in the expansion step, the mandrel on which the fibers are wound is expanded so as to conform to the inner peripheral surface of a molding device; and the orientation angle of the fibers in the arrangement step is set based on the outer diameter of the mandrel before expansion, the radial dimension of the fibers, and the inner diameter of the inner peripheral surface of the molding device .

This invention makes it possible to manufacture fiber-reinforced resin pipes with fibers wound at a suitable orientation angle.

FIG. 1 is a cross-sectional view schematically showing a mandrel according to a first embodiment of the present invention. 1 is a diagram schematically illustrating a power transmission shaft manufactured using a mandrel according to a first embodiment of the present invention. FIG. 1 is a cross-sectional view schematically showing a power transmission shaft according to a first embodiment of the present invention. 1A to 1C are schematic views for explaining a method for manufacturing a power transmission shaft according to a first embodiment of the present invention. 1A to 1C are schematic views for explaining a method for manufacturing a power transmission shaft according to a first embodiment of the present invention. 1A to 1C are schematic views for explaining a method for manufacturing a power transmission shaft according to a first embodiment of the present invention. 3 is a flowchart illustrating a method for manufacturing a power transmission shaft according to a first embodiment of the present invention. 1A to 1C are schematic views for explaining a method for manufacturing a power transmission shaft according to a first embodiment of the present invention. 1A is a schematic diagram showing the inner peripheral surface of a carbon fiber layer before expansion, and FIG. 1B is a schematic diagram showing the inner peripheral surface of a carbon fiber layer after expansion. 1A is a schematic diagram showing the orientation angle of the carbon fiber layer before expansion, and FIG. 1B is a schematic diagram showing the orientation angle of the carbon fiber layer after expansion. 5A and 5B are schematic diagrams showing changes in the radial position of a carbon fiber layer before and after expansion. 10 is a flowchart illustrating a method for manufacturing a power transmission shaft according to a second embodiment of the present invention. 5A to 5C are schematic views for explaining a method for manufacturing a power transmission shaft according to a second embodiment of the present invention. 10A to 10C are schematic views for explaining a method for manufacturing a power transmission shaft according to a third embodiment of the present invention.

An embodiment of the present invention will be described in detail with reference to the drawings, taking as an example the case of manufacturing a vehicle power transmission shaft (propeller shaft), which is an example of a fiber-reinforced resin tube, using carbon fiber-reinforced plastic. In the following description, identical elements will be assigned the same reference numerals, and duplicate explanations will be omitted. The drawings referred to have been exaggerated for clarity.

First Embodiment
As shown in FIG. 1, the mandrel 1 according to the first embodiment is used to manufacture a fiber-reinforced resin pipe 40 (see FIG. 2), and includes a mandrel body 10 and an inner fitting member 20.

<Mandrel body>
The mandrel body 10 is a cylindrical resin member. In this embodiment, the mandrel body 10 is removed from the interior of the fiber-reinforced resin pipe 40, but it can also remain inside the fiber-reinforced resin pipe 40 and function as a core material for the fiber-reinforced resin pipe 40. The mandrel body 40 can be made of a material that can withstand the heat generated during resin curing in the fiber-reinforced resin pipe 40. Examples of such materials include PP (polypropylene resin), PET (polyethylene terephthalate resin), and SMP (shape memory polymer). The mandrel body 10 integrally includes a large-diameter section 11 in an axially intermediate portion, a tapered section 12 and a medium-diameter section 13 formed at one axial end, and a step section 14 and a small-diameter section 15 formed at the other axial end. In this embodiment, a protrusion 16 having a diameter smaller than that of the medium-diameter section 13 is formed at one axial end of the medium-diameter section 13. The protrusion 16 is a portion onto which the first metal member 30 is fitted.

<Inner fittings>
The inner fitting member 20 is a cylindrical metal member that is fitted into the small-diameter portion 15, which is the other axial end of the mandrel body 10. The inner fitting member 20 prevents the small-diameter portion 15 from deforming radially inward, and has a flow path 20a formed therein for filling the mandrel body 10 with a pressurizing fluid F (see FIG. 8 ) (e.g., pressurized air). In this embodiment, the pressurizing fluid F is used to pressurize and expand the mandrel body 10 within the molding apparatus 100. The pressurizing fluid F also serves as a heating fluid for heating and curing a thermosetting resin (resin 44, described below) arranged on the outer circumferential surface of the mandrel body 10 within the molding apparatus 100, described below.

<Power transmission shaft>
2 and 3, the power transmission shaft 2 manufactured using the mandrel 1 (see FIG. 1) is a shaft that extends in the fore-and-aft direction of a vehicle and transmits power generated by a power source as rotation about an axis. The power transmission shaft 2 includes a fiber-reinforced resin pipe body 40, a first metal member 50, and a second metal member 60.

<Fiber reinforced resin tube body>
The fiber-reinforced resin pipe 40 is a resin-containing fiber layer formed in a tubular shape to fit along the outer peripheral surface of the mandrel body 10. The fiber-reinforced resin pipe 40 is formed to fit along the outer peripheral surfaces of the large-diameter section 11, the tapered section 12, and the medium-diameter section 13 of the mandrel body 10, one axial end of the first metal member 50, and the other axial end of the second metal member 60. As shown in FIGS. 4 to 6 , the fiber-reinforced resin pipe 40 includes, as carbon fiber layers, a first carbon fiber layer 41, a second carbon fiber layer 42, and a third carbon fiber layer 43, in this order from the radially inner side (the mandrel body 10 side). Note that only a portion of the carbon fiber layers 41, 42, and 43 are shown in FIGS. 4 to 6 . In addition, the outer peripheral surface of one axial end of the first metal member 50 (the end located opposite the mandrel body 10) and the outer peripheral surface of the other axial end of the second metal member 60 (the end located opposite the mandrel body 10) are not covered by the fiber-reinforced resin pipe body 40 and protrude from the fiber-reinforced resin pipe body 40.

<First carbon fiber layer>
4, the first carbon fiber layer 41 is composed of a plurality of carbon fibers that are arranged on the outer peripheral surface of the mandrel body 10 or the like so as to cover the mandrel body 10. More specifically, a carbon fiber aggregate is formed by bundling a plurality of carbon fibers into a strip or bundle, and the first carbon fiber layer 41 is formed by arranging the plurality of carbon fiber aggregates in different phases. The carbon fibers in the first carbon fiber layer 41 extend parallel to the axial direction of the mandrel body 10. That is, the orientation angle of the carbon fibers in the first carbon fiber layer 41 with respect to the axis X of the mandrel body 10 is 0°.

<Second carbon fiber layer>
As shown in Figure 5, the second carbon fiber layer 42 is provided radially outward of the first carbon fiber layer 41 and is composed of a plurality of carbon fibers that are provided to cover the first carbon fiber layer 41. More specifically, a carbon fiber aggregate is formed by bundling a plurality of carbon fibers into a strip or bundle, and the second carbon fiber layer 42 is formed by arranging a plurality of carbon fiber aggregates with different phases. The carbon fibers in the second carbon fiber layer 42 are wound around one or more turns at an angle of 45° with respect to the axial direction of the mandrel body 10 and extend in a spiral with respect to the axial direction of the mandrel body 10. That is, the orientation angle of the carbon fibers in the second carbon fiber layer 42 with respect to the axis X of the mandrel body 10 is 45°.

<Third carbon fiber layer>
As shown in Figure 6, the third carbon fiber layer 43 is provided radially outward of the second carbon fiber layer 42 and is composed of a plurality of carbon fibers that are provided to cover the second carbon fiber layer 42. More specifically, a carbon fiber aggregate is formed by bundling a plurality of carbon fibers into a strip or bundle, and the third carbon fiber layer 43 is formed by arranging the plurality of carbon fiber aggregates in different phases. The carbon fibers in the third carbon fiber layer 43 are wound one or more times at an inclination of -45° with respect to the axial direction of the mandrel body 10 and extend in a spiral with respect to the axial direction of the mandrel body 10. That is, the orientation angle of the carbon fibers in the third carbon fiber layer 43 with respect to the axis X of the mandrel body 10 is -45°.

As shown in Figures 2 and 3, the fiber-reinforced resin tube 40 has a tapered section 40b formed at one axial end, which tapers from the large-diameter section 40a at the axial center toward the small-diameter section 40c at one axial end. The large-diameter section 40a is a main section whose shape follows the outer peripheral surface of the large-diameter section 11 of the mandrel body 10. The tapered section 40b follows the outer peripheral surface of the tapered section 12 of the mandrel body 10. The small-diameter section 40c is an end whose shape follows the outer peripheral surfaces of the medium-diameter section 13 of the mandrel body 10 and part of the first metal member 50.

<First Metal Member>
The first metal member 50 is a member (shaft) having a substantially cylindrical shape. As shown in Figure 6 and other figures, during the manufacturing process, one axial end of the first metal member 50 located away from the mandrel body 10 protrudes from the mandrel body 10, and the other axial end of the first metal member 50 located on the mandrel body 10 side is fitted (externally fitted) to the mandrel body 10.

As shown in Figures 1 and 2, the other axial end of the first metal member 50 is formed with a bottomed hole 50a into which the protrusion 16 of the mandrel body 10 can be inserted.

The first metal member 50 is one component of the plunge joint assembly on the power transmission shaft 2. The plunge joint assembly is formed by assembling a boot and plunge joint (both not shown) to the first metal member 50.

<Second Metal Member>
The second metal member 60 is a member having a substantially cylindrical shape. As shown in Figure 6 and other figures, during the manufacturing process, the other axial end of the second metal member 60 located away from the mandrel body 10 protrudes from the mandrel body 10, and one axial end of the second metal member 60 located on the mandrel body 10 side is fitted (externally fitted) to the mandrel body 10.

The second metal member 60 is one component of the yoke assembly on the power transmission shaft 2. The yoke assembly is formed by assembling a spider, needle bearing, and yoke (all not shown) to the second metal member 60.

<Manufacturing method>
Next, a method for manufacturing a power transmission shaft 2 using a mandrel 1 according to a first embodiment of the present invention will be described with reference to the flowchart of FIG. 7 . The method for manufacturing the power transmission shaft 1 includes a mandrel body forming step (step S1), an inner fitting member installation step (step S2) performed after the mandrel body forming step, a first connecting step (step S3) performed after the inner fitting member installation step, and a second connecting step (step S4) performed after the first connecting step. The method for manufacturing the power transmission shaft 2 also includes a fiber installation step (steps S5A to S5C) performed after the second connecting step, and a mold installation step (step S6) performed after the fiber installation step. The method for manufacturing the power transmission shaft 2 also includes an expansion step (step S7) performed after the mold installation step, and a molding step (step S8) performed after the expansion step. The method for manufacturing the power transmission shaft 2 also includes an extraction step (step S9) performed after the molding step, and a joint assembly step (step S10) performed after the extraction step.

Step S1 is a process of forming the resin mandrel body 10 shown in Figure 1 using a molding device (not shown).

Following step S1, in step S2, the inner fitting member 20 is press-fitted into the small diameter portion 15 of the mandrel body 10. During press-fitting, a lubricant may be applied between the outer surface of the inner fitting member 20 and the outer surface of the small diameter portion 15. Note that step S2 may be performed before step S8.

Following step S2, in step S3, a first metal member 50 is provided on one axial end of the mandrel body 10. In step S3, the other axial end of the first metal member 50 is first fitted (externally attached) to the protruding portion 16 of the mandrel body 10. Next, an adhesive layer (not shown) is provided on the outer peripheral surface of the other axial end of the first metal member 50. In step S3, the first metal member 50 is fitted onto the protruding portion 16 of the mandrel body 10.

Following step S3, in step S4, a second metal member (collar) 60 is provided at the other axial end of the mandrel body 10. In step S4, the second metal member 60 is fitted onto the stepped portion 14 of the mandrel body 10. The order of steps S3 and S4 can be changed as appropriate; step S4 may be performed first, or steps S3 and S4 may be performed simultaneously.

Following step S4, in step S5A, a first carbon fiber layer 41 is formed on the outer peripheral surfaces of the mandrel body 10, the first metal member 50, and the second metal member 60, as shown in FIG. 4. Following step S5A, in step S5B, a second carbon fiber layer 42 is formed on the outer peripheral surfaces of the first carbon fiber layer 41 of the mandrel body 10, the first metal member 50, and the second metal member 60, as shown in FIG. 5. Following step S5B, in step S5C, a third carbon fiber layer 43 is formed on the outer peripheral surfaces of the second carbon fiber layer 42 of the mandrel body 10, the first metal member 50, and the second metal member 60, as shown in FIG. 6. In steps S5 to S7, carbon fiber layers 41 to 43 are formed on the axial ends of the first metal member 50 and the second metal member 60 opposite the mandrel 10, so that no fibers are present.

In steps S5A to S5C, the carbon fiber layers 41 to 43 are not resin-impregnated fibers but are raw silk. The carbon fiber layers 41 to 43 are arranged on the outer peripheral surfaces of the other axial ends of the mandrel body 10, first metal member 50, and second metal member 60 using a multi-fiber filament winding method. The carbon fiber layers 41 to 43, which are fed using the multi-fiber filament winding method, are independent layers that are not woven together, creating a so-called non-crimp structure.

In steps S5A to S5C, the carbon fiber layers 41 to 43 are arranged on the outer peripheral surface of the mandrel body 10 or the like by a device (not shown). This device is capable of appropriately setting and adjusting the orientation angles of the carbon fiber layers 41 to 43. The orientation angles of the carbon fiber layers 42 and 43 in steps S5B and S5C are calculated and set based on the outer diameter of the mandrel body 10 before expansion, the radial dimensions of the carbon fiber, and the inner diameter of the inner peripheral surface of the molding device 100. The calculation of the orientation angle of the second carbon fiber layer 42 in step S5B is performed at least before step S5B. The calculation of the orientation angle of the third carbon fiber layer 43 in step S5C is performed at least before step S5C. The method for calculating these orientation angles will be described below.

Following step S5C, in step S6, the assembly of the mandrel 1, first metal member 50, second metal member 60, and each carbon fiber layer 41-43 is placed in the molding device (mold) 100, as shown in FIG. 8.

Following step S6, in step S7, the mandrel body 10 is expanded. As shown in FIG. 8 , the molding apparatus 100 of the first embodiment has a communication passage 104 that connects to the inside of the mandrel body 10 via the flow path 20a. In step S7, the hollow portion of the mandrel body 10 is filled with pressurizing fluid F (e.g., pressurized air at 140°C or higher) via the communication passage 104, which is connected to a supply device (not shown). The mandrel body 10, heated by the high-temperature pressurizing fluid F, softens when it reaches a temperature lower than the temperature at which the resin 44 hardens (its transformation temperature of 80°C). Pressurized from the inside by the pressurizing fluid F, the mandrel body 10 expands and deforms to conform to the inner circumferential surface of the molding apparatus 100. This pressurization prevents the mandrel body 10 from being deformed in a radial direction by the filled resin 44. Furthermore, this pressurization reduces the amount of resin 44 filled, preventing an increase in the weight of the finished fiber-reinforced resin pipe 40.

Following step S7, resin 44 is supplied into the molding device 100. This allows the carbon fiber layers 41-43 arranged on the outer circumferential surface of the mandrel body 10 to be impregnated with the resin 44. Heat is then applied to the molding device 100 to harden the resin 44, forming the fiber-reinforced resin pipe 40, and the fiber-reinforced resin pipe 40, first metal member 50, and second metal member 60 are integrally molded (step S8, molding process). The resin 44 is, for example, a thermosetting resin. In this embodiment, the mold of the molding device 100 is divided into multiple sections. In step S9, heat is applied to the assembly, and a mold closing operation is performed to close the mold of the molding device 100. Subsequently, a mold clamping operation is performed to apply pressure to the closed mold, thereby increasing the pressure within the mold and promoting the hardening of the resin 44. Note that in this embodiment, the mold is divided into multiple sections, and therefore the mold closing operation and mold clamping operation are performed, but the mold clamping operation is not required. Furthermore, if the mold is not divided into multiple sections, such mold closing and clamping operations are not required. Within the molding device 100, a space (resin pool 102) is formed on the outlet side of the gate 101, through which the molten resin 44 is introduced. The resin 44 introduced into the molding device 100 is stored in the resin pool 102, located to the side of one axial end of the carbon fiber layers 41-43. The resin 44 stored in the resin pool 102 moves in the axial direction of the mandrel body 10 by vacuum suction from a suction port 103 formed on the opposite side of the gate 101 in the arrangement direction of the carbon fiber layers 41-43 (on the outer peripheral surface side of the other axial end of the carbon fiber layers 41-43), and impregnates the carbon fiber layers 41-43. With the resin 44 impregnated into the carbon fiber layers 41-23, heat is applied to the molding device 100, and pressure is further applied within the molding device 100, thereby forming the fiber-reinforced resin pipe 40.

Following step S8, in step S9, the molded assembly, i.e., the intermediate body, is removed from the molding apparatus 100. Following step S9, in step S10, a plunge joint assembly is attached to the first metal member 50 of the intermediate body, and a yoke assembly is attached to the second metal member 60.

It is also possible to carry out a mandrel removal process between steps S9 and S10. This mandrel removal process involves removing the mandrel 1 from the end opening side of the second metal member 60 to the outside of the fiber-reinforced resin pipe body 20. During this process, the mandrel 1 is removed from the inside of the fiber-reinforced resin pipe body 40 by, for example, deforming, melting, decomposing, destroying, or eluting it, depending on the material used. This achieves a reduction in the weight of the power transmission shaft 2.

Furthermore, when deforming the mandrel 1 and removing it from the end opening side of the second metal member 60, a method can be used in which, for example, the hollow portion of the mandrel body 10 is depressurized to shrink the mandrel 1 so that it is smaller than the end opening, and then the mandrel 1 can be removed from the fiber-reinforced resin pipe body 40.

When performing the mandrel removal process, the hollow portion of the mandrel body 10 can be depressurized via the communication passage 104 connected to a vacuum pump (not shown).

This mandrel removal process can be more effectively carried out by plasticizing the mandrel body 10, which is made of, for example, a thermoplastic resin, by heating or other means. It can also be effectively carried out on a mandrel body 10 made of, for example, a diamond-cut aluminum thin plate.

In the expansion step of step S7, the values of the wound fiber layer before and after expansion are represented by the following variables.
d _A : inner diameter of the fiber layer before expansion (see FIG. 9( a) and FIG. 11)
d _B : inner diameter of the fiber layer after expansion (see FIG. 9( b) and FIG. 11)
θ _A : Orientation angle of the fibers before expansion (see FIG. 10( a))
θ _B : Orientation angle of the fibers after expansion (see FIG. 10( b ))
L: Axial dimension of the fiber-wrapped region before expansion (see Figure 6)
n: Number of turns of fiber (how many times the fiber is wound around the mandrel 1, etc.)
l: Amount of reduction in the axial dimension per turn of the fiber layer due to expansion; α: Total amount of reduction in the axial dimension of the fiber layer due to expansion (see FIG. 10(b)).

Here, θ _B is calculated by the following formulas (1) and (2): and α is calculated by the following formulas (3), (4), and (5).

Here, the outer diameter of the mandrel body 1 etc. before expansion is D _A , the outer diameter of the mandrel body 1 etc. after expansion is D _B , and the diameter (inner diameter) of the inner circumferential surface of the molding apparatus 100 is D _C. Also, the radial dimension of the first carbon fiber layer 41 is b ₄₁ , the radial dimension of the second carbon fiber layer 42 is b ₄₂ , and the radial dimension of the third carbon fiber layer 43 is b _43. The relationship between D _B and D _C is expressed by the following formula (6).

For the second carbon fiber layer 42, θ _A is calculated so that θ _B becomes 45°, and in step S5B, the second carbon fiber layer 42 is wound around the outer peripheral surface of the first carbon fiber layer 41 at this orientation angle θ _A. As a result, the orientation angle θ _B of the second carbon fiber layer 42 after step S7 is performed becomes 45°. Here, d _A and d _B of the second carbon fiber layer 42 are calculated by the following formulas (7) and (8).

For the third carbon fiber layer 43, θ _A is calculated so that θ _B is −45°, and in step S5C, the third carbon fiber layer 43 is wound around the outer peripheral surface of the second carbon fiber layer 42 at this orientation angle θ _A. As a result, the orientation angle θ _B of the third carbon fiber layer 43 after step S7 is performed is −45°. That is, the orientation angles of the carbon fiber layers 42, 43 arranged on the outer peripheral surface of the mandrel body 10, etc. in the arrangement step are changed by the expansion step to become predetermined orientation angles. Here, d _A and d _B of the third carbon fiber layer 43 are calculated using the following equations (9) and (10).

Equations (1) to (10) assume that the mandrel body 10, on which the carbon fiber layers 41 to 43 are arranged, has a constant outer diameter along the axial direction, and that the inner circumferential surface of the molding device 100 also has a constant inner diameter along the axial direction, and apply to the range in which the mandrel body 10 expands to fit the inner circumferential surface of the molding device 100. In cases such as when the inner circumferential surface of the molding device 100 has a barrel shape with a maximum diameter at the middle of the axial direction, correction coefficients, etc. are incorporated into equations (1) to (10) as appropriate.

A manufacturing method for a fiber-reinforced resin pipe body 40 (power transmission shaft 2) according to a first embodiment of the present invention includes an arrangement step of winding and arranging fibers on the outer peripheral surface of a cylindrical mandrel 1 (mandrel body 10), an expansion step of expanding the mandrel on which the fibers are arranged, and a curing step of impregnating the fibers arranged on the outer peripheral surface of the mandrel with a thermosetting resin and curing it, in which the fibers are arranged at a position shifted from a predetermined orientation angle in the arrangement step so that the orientation angle of the fibers after the expansion step becomes a predetermined orientation angle.
According to this manufacturing method for the fiber-reinforced resin pipe body 40, the fibers (carbon fiber layers 42, 43) are arranged taking into consideration the change in the fiber orientation angle that occurs with the expansion of the mandrel 1 (mandrel body 10). This makes it possible to suitably set the fiber orientation angle after the mandrel 1 expands, and to manufacture a fiber-reinforced resin pipe body 40 (power transmission shaft 2) with the desired performance (torsional strength, etc.).

In addition, in the manufacturing method of the fiber-reinforced resin pipe body 40 (power transmission shaft 2), in the expansion step, the mandrel 1 (mandrel body 10) around which the fibers are wound is expanded so as to conform to the inner peripheral surface of the molding device 100, and the orientation angle of the fibers (carbon fiber layers 42, 43) in the arrangement step is set based on the outer diameter of the mandrel 1 (mandrel body 10) before expansion, the radial dimension of the fibers (carbon fiber layers 41 to 43), and the inner diameter of the inner peripheral surface of the molding device 100.
According to this manufacturing method for the fiber-reinforced resin pipe body 40, the fibers (carbon fiber layers 42, 43) are arranged taking into consideration the outer diameter of the mandrel 1 before expansion, the radial dimensions of the fibers (carbon fiber layers 41 to 43), and the inner diameter of the inner surface of the molding device 100, so that the orientation angle of the fibers after expansion of the mandrel 1 can be suitably set.

Second Embodiment
Next, a method for manufacturing a power transmission shaft 2 according to a second embodiment of the present invention will be described, focusing on differences from the method for manufacturing a power transmission shaft 2 according to the first embodiment.

As shown in FIG. 12, the method for manufacturing a power transmission shaft 2 according to the second embodiment of the present invention includes a fiber fixing step (step S5D) that is performed between the fiber setting step and the mold placement step. As shown in FIG. 13, in the fiber fixing step, one end of each carbon fiber layer 41-43 is fixed to the mandrel 1 (in this embodiment, the first metal member 50) by a fixing member 71. Also, in the fiber fixing step, the other end of each carbon fiber layer 41-43 is fixed to the mandrel 1 (in this embodiment, the second metal member 60) by a fixing member 72.

The first fixing member 71 and the second fixing member 72 are annular members (rings, tapes, etc.) made of resin or metal, and are fitted onto the third carbon fiber layer 43 to fix each of the carbon fiber layers 41-43 to the mandrel 1 (first metal member 50 and second metal member 60).

The strength with which one end of each of the carbon fiber layers 41-43 is fixed by the first fixing member 71 is greater than the strength with which the other end of each of the carbon fiber layers 41-43 is fixed by the second fixing member 72. As a result, during the expansion process, one end of each of the carbon fiber layers 41-43 is fixed, and the other end moves closer to the one end as the mandrel body 10 expands. Here, because the tapered portion 40b is formed on the first fixing member 71 side, the carbon fiber layers 41-43 on the first fixing member 71 side are less likely to move in the axial direction. In this embodiment, the fixing strength of the first fixing member 71 is set greater than the fixing strength of the second fixing member 72, so the second fixing member 72 side of the carbon fiber layers 42, 43 moves favorably toward the first fixing member 71 as the mandrel body 10 expands.

The first fixing member 71 and the second fixing member 72 may be configured to melt when heated during the molding process.

The manufacturing method of the fiber-reinforced resin pipe body 40 (power transmission shaft 2) according to the second embodiment of the present invention includes, between the arrangement step and the expansion step, a fixing step of fixing both ends of the fibers (carbon fiber layers 42, 43) arranged on the outer peripheral surface of the mandrel 1 (mandrel body 10), and the fixing strength of one end side of the fibers is greater than the fixing strength of the other end side of the fibers.
According to this manufacturing method for the fiber-reinforced resin pipe body 40, the direction of the fiber displacement due to the expansion of the mandrel 1 can be determined, so that the position of the fiber after the expansion of the mandrel 1 can be suitably set, and a fiber-reinforced resin pipe body having the desired performance (torsional strength, etc.) can be manufactured.

Third Embodiment
Next, a method for manufacturing a power transmission shaft 2 according to a third embodiment of the present invention will be described, focusing on differences from the method for manufacturing a power transmission shaft 2 according to the second embodiment.

In this embodiment, the positions of the other ends of the carbon fibers 42, 43 in the placement step are calculated and set based on the outer diameter of the mandrel body 10 before expansion, the radial dimensions of the carbon fibers 41, 42, 43, and the inner diameter of the inner circumferential surface of the molding apparatus 100. More specifically, as shown in FIG. 14 , in the fiber placement step, each carbon fiber layer 42, 43 is positioned so that its other end is axially outward by the aforementioned α from its position (predetermined position) after the expansion step. As a result, in the expansion step, one end of each carbon fiber layer 42, 43 is fixed, and the other end moves closer to the one end as the mandrel body 10 expands, moving to the predetermined position. In other words, the positions of the other ends of the carbon fiber layers 42, 43 placed on the outer circumferential surface of the mandrel body 10, etc., in the placement step are changed to predetermined positions by the expansion step. The position of the other end of the first carbon fiber layer 41 remains unchanged before and after expansion, and is therefore aligned with the position of the other end of the expanded carbon fiber layers 42, 42.

In the manufacturing method of the fiber-reinforced resin pipe body 40 (power transmission shaft 2) according to the third embodiment of the present invention, the other end of the fiber (carbon fiber layers 42, 43) is positioned in the positioning step so that the position of the other end side of the fiber after the expansion step is a predetermined position.
According to this manufacturing method for the fiber-reinforced resin pipe body 40, the carbon fibers are positioned taking into consideration the displacement of the fibers that occurs as the mandrel 1 expands, so that the position of the fibers after the mandrel 1 expands can be suitably set, and a fiber-reinforced resin pipe body having the desired performance (strength against collisions, strength against torsion, etc.) can be manufactured.

Furthermore, in the manufacturing method of the fiber-reinforced resin pipe body 40 (power transmission shaft 2), in the expansion process, the mandrel 1 (mandrel body 10) around which the fiber is wound is expanded so as to conform to the inner surface of the molding device 100, and the position of the other end of the fiber in the placement process is set based on the outer diameter of the mandrel 1 (mandrel body 10) before expansion, the radial dimension of the fiber (carbon fiber layers 41 to 43), and the inner diameter of the inner surface of the molding device 100.
According to this manufacturing method for the fiber-reinforced resin pipe body 40, the fibers are positioned taking into consideration the outer diameter of the mandrel 1 before expansion, the radial dimensions of the fibers, and the inner diameter of the inner surface of the molding device 100, so that the position of the other end of the fiber after expansion of the mandrel 1 can be suitably set.

While the above describes an embodiment of the present invention, the present invention is not limited to the above embodiment and can be modified as appropriate without departing from the spirit and scope of the present invention. For example, the large-diameter portion (main body portion) 11 of the mandrel body 10 may expand into a barrel shape with a diameter that decreases from the center of the large-diameter portion 11 to both ends, or into a cylindrical shape with a constant diameter along the axial direction. Such an expanded shape can be appropriately set depending on the shape of the inner circumferential surface of the molding device (mold) 100 where the large-diameter portion 11 is installed. Furthermore, the fluid flowing into and filling the mandrel body 10 may not only pressurize the inside of the mandrel body 10, but also heat the thermosetting resin disposed on the outer circumferential surface of the mandrel body 10 to harden it. Note that if such a fluid is a pressurizing fluid that does not perform heating, the thermosetting resin is heated by a separate heat source.

Alternatively, the mandrel 1 may be removed from the molded fiber-reinforced resin pipe 40 between steps S9 and S10. The mandrel body 10 may be melted and removed by the heat of the resin 44 or the molding device (mold) 100 in step S8. It is also possible to melt and remove the mandrel body 10 using other forms of energy, such as heat, electricity, or vibration. The carbon fiber layers 41-43 may be interwoven with one another, forming a so-called crimped structure. The fiber material is not limited to carbon fiber, and may be any fiber material capable of reinforcing the resin layer (e.g., glass fiber, cellulose fiber, etc.).

REFERENCE SIGNS LIST 1 Mandrel 2 Power transmission shaft 10 Mandrel body 20 Inner fitting member 40 Fiber reinforced resin pipe body 50 First metal member 60 Second metal member

Claims (5)

an arrangement step of winding and arranging fibers on an outer peripheral surface of a cylindrical mandrel;
an expansion step of expanding the mandrel on which the fibers are disposed;
a curing step of impregnating the fibers arranged on the outer peripheral surface of the mandrel with a thermosetting resin and curing the resin;
Including,
In the arranging step, the fibers are arranged so as to be shifted from the predetermined orientation angle so that the orientation angle of the fibers after the expanding step becomes the predetermined orientation angle;
In the expanding step, the mandrel around which the fiber is wound is expanded so as to conform to the inner circumferential surface of a molding device,
an orientation angle of the fibers in the arranging step is set based on the outer diameter of the mandrel before expansion, the radial dimension of the fibers, and the inner diameter of the inner circumferential surface of the molding device;
A method for manufacturing a fiber-reinforced resin pipe body. a fixing step of fixing both ends of the fibers arranged on the outer circumferential surface of the mandrel between the arranging step and the expanding step,
The fixing strength of one end side of the fiber is greater than the fixing strength of the other end side of the fiber.
The method for manufacturing the fiber-reinforced resin pipe according to claim 1 . an arrangement step of winding and arranging fibers on an outer peripheral surface of a cylindrical mandrel;
an expansion step of expanding the mandrel on which the fibers are disposed;
a curing step of impregnating the fibers arranged on the outer peripheral surface of the mandrel with a thermosetting resin and curing the resin;
Including,
In the arranging step, the fibers are arranged so as to be shifted from the predetermined orientation angle so that the orientation angle of the fibers after the expanding step becomes the predetermined orientation angle;
a fixing step of fixing both ends of the fibers arranged on the outer circumferential surface of the mandrel between the arranging step and the expanding step,
The fixing strength of one end side of the fiber is greater than the fixing strength of the other end side of the fiber.
A method for manufacturing a fiber-reinforced resin pipe body. In the arranging step, the other end of the fiber is arranged so as to be shifted from the predetermined position so that the position of the other end side of the fiber after the expanding step will be the predetermined position.
The method for manufacturing a fiber-reinforced resin pipe according to claim 2 or 3 . In the expanding step, the mandrel around which the fiber is wound is expanded so as to conform to the inner circumferential surface of a molding device,
a position of the other end of the fiber in the arranging step is set based on an outer diameter of the mandrel before expansion, a radial dimension of the fiber, and an inner diameter of an inner circumferential surface of the molding device;
The method for manufacturing the fiber-reinforced resin pipe according to claim 4.