JP7714915B2 - Manufacturing method of composite structure rotating body and composite structure rotating body - Google Patents

Description

One aspect of the present invention relates to a method for manufacturing a composite structure rotating body and a composite structure rotating body.

One example of technology related to composite structure rotating bodies is the gear described in Patent Document 1. The gear described in Patent Document 1 includes a metal ring-shaped body (metal ring-shaped member) with teeth formed on its outer periphery, an annular metal bushing, and a resin web (resin ring-shaped member) that connects the metal ring-shaped body and the metal bushing.

JP 2017-61059 A

When molding a composite structure rotating body such as the one described above, cracks can occur at the joints between the metal and resin due to the difference in thermal contraction between the metal annular member and metal bushing, which are made of metal, and the resin web, which is made of resin. The occurrence of cracks can cause a problem in that the strength of the molded composite structure rotating body is reduced.

Technologies for suppressing the aforementioned cracks have been proposed in the past. For example, one technique involves annealing or curing a composite rotating body immediately after molding to suppress cracking. However, because such treatment must be carried out before the molded product cools, equipment modifications are required to enable such rapid processing. Furthermore, crack suppression through annealing, which promotes hardening and improves physical properties, cannot be expected when using thermoplastic resins, so the effectiveness of such treatments is limited. Another technique for suppressing cracking is to chamfer the edges of the joint between metal and resin. However, depending on the shape of the joint, the processing of the chamfer can be complicated. Furthermore, the effectiveness of such techniques in suppressing cracking is limited. As such, conventional crack suppression techniques have not been able to sufficiently suppress the reduction in strength of composite rotating bodies due to cracks.

One aspect of the present invention was made in consideration of the above situation, and aims to suppress the reduction in strength of composite structure rotors due to the effects of cracks.

One aspect of the present invention relates to a method for manufacturing a composite-structure rotating body having a metal annular member with teeth formed on its outer periphery, an annular metal bushing, and a resin annular member connecting the metal annular member and the metal bushing. The method includes the following steps: a first step of applying a second thermoplastic resin having a lower melting point than the first resin constituting the resin annular member to a plurality of first protruding anti-rotation portions formed at predetermined intervals circumferentially on the inner circumferential surface of the metal annular member; a second step of, after the first step, injecting the first resin between the metal annular member and the metal bushing while the metal annular member and the metal bushing are set in a molding machine to integrally mold the metal annular member, the metal bushing, and the resin annular member by injection molding; and a third step of, after the second step, removing the integrally molded metal annular member, the metal bushing, and the resin annular member from the molding machine and cooling them.

In one embodiment of the present invention, a manufacturing method for a composite rotating body includes a first step in which a thermoplastic second resin having a lower melting point than the first resin constituting the resin annular member is applied to multiple first anti-rotation portions formed on the inner circumferential surface of the metal annular member, prior to a second step in which the metal annular member, metal bushing, and resin annular member are integrally molded by injection molding. In the second step in which injection molding is performed, cracks may occur at the joint between the metal and the resin due to the difference in thermal contraction between the metal annular member and metal bushing, which are made of metal, and the resin annular member, which is made of resin. Such cracks are particularly likely to occur around the first anti-rotation portions that protrude into the resin annular member, which are the joint on the metal annular member side where the first resin is filled late. In this regard, by applying a thermoplastic second resin with a lower melting point than the first resin to the first anti-rotation portion prior to injection molding, the second resin melts due to heat during injection molding. Therefore, if cracks occur around the first anti-rotation portion after molding, the molten second resin will penetrate the cracks. In this case, when the second resin that has penetrated the cracks solidifies upon cooling in the subsequent third step, the cracks are filled with the second resin, thereby preventing a decrease in the strength of the composite rotating body due to the effects of cracks. As described above, the manufacturing method for a composite rotating body according to one aspect of the present invention prevents a decrease in the strength of the composite rotating body due to cracks by filling any cracks that occur, rather than by preventing cracks from occurring.

In the first step, the second resin may be applied to the entire surface of the inner circumferential surface of the metal annular member that comes into contact with the resin annular member. In this way, by applying the second resin to the entire surface of the inner circumferential surface of the metal annular member that comes into contact with the resin annular member, the second resin can be applied to areas where the timing of filling the first resin is delayed and cracks are likely to occur, and the penetration of the second resin into cracks when they occur can be more appropriately promoted. This makes it possible to further suppress a decrease in strength of the composite structure rotating body due to the effects of cracks.

In the first step, a second resin may be applied to multiple convex second anti-rotation portions formed at predetermined intervals circumferentially on the outer surface of the metal bushing. Although not as susceptible to cracks as the joint between the metal annular member and the resin annular member (the outer surface of the metal bushing), cracks are also likely to occur at the joint between the metal bushing and the resin annular member. At the joint between the metal bushing and the resin annular member, cracks are particularly likely to occur around the second anti-rotation portions that protrude into the resin annular member. In this regard, applying the second resin to the second anti-rotation portions allows the second resin to be applied to areas of the joint between the metal bushing and the resin annular member that are particularly susceptible to cracking, thereby more appropriately promoting the penetration of the second resin into cracks when they occur. This further reduces the strength reduction of the composite structure rotating body due to cracks.

In the first step, the second resin may be applied to the entire surface of the outer periphery of the metal bushing that comes into contact with the resin annular member. In this way, applying the second resin to the entire surface of the outer periphery of the metal bushing that comes into contact with the resin annular member can more appropriately promote the penetration of the second resin into cracks that occur at the joint between the metal bushing and the resin annular member. This can further reduce the reduction in strength of the composite structure rotating body due to the effects of cracks.

A composite structure rotating body according to one aspect of the present invention is a composite structure rotating body comprising a metal annular member having teeth formed on its outer periphery, an annular metal bushing, and a resin annular member connecting the metal annular member and the metal bushing. The metal annular member has a plurality of convex first anti-rotation portions formed on its inner periphery at predetermined intervals in the circumferential direction, and the first anti-rotation portions are coated with a thermoplastic second resin having a lower melting point than the first resin constituting the resin annular member. In the composite structure rotating body according to one aspect of the present invention, the plurality of convex first anti-rotation portions formed on the inner periphery of the metal annular member are coated with a thermoplastic second resin having a lower melting point than the first resin constituting the resin annular member. In such a composite structure rotating body, a thermoplastic second resin with a lower melting point than the first resin is applied to the first anti-rotation portion, which is prone to cracking. Therefore, if cracks occur around the first anti-rotation portion after molding, the molten second resin penetrates the cracks. The second resin that has penetrated the cracks solidifies upon cooling, filling the cracks. This prevents strength reduction due to cracks. As described above, the composite structure rotating body according to one aspect of the present invention effectively prevents strength reduction due to cracks. Furthermore, in the composite structure rotating body according to one aspect of the present invention, the second resin has a lower melting point than the first resin (melts at a relatively low temperature), is relatively elastically deformable near room temperature, and has high viscosity. Therefore, vibration can be effectively reduced.

In the above-described composite structure rotating body, the second resin may be applied to the entire inner circumferential surface of the metal annular member that comes into contact with the resin annular member. In this way, by applying the second resin to the entire inner circumferential surface of the metal annular member that comes into contact with the resin annular member, the second resin can be applied to areas where the timing of filling the first resin is delayed and cracks are likely to occur, thereby more appropriately promoting the penetration of the second resin into cracks when they occur. This further reduces the reduction in strength due to the effects of cracks.

In the composite structure rotating body, the metal bushing may have a plurality of convex second anti-rotation portions formed on its outer surface at predetermined intervals in the circumferential direction, and the second anti-rotation portions may be coated with a second resin. Although not as susceptible to cracks as the joint between the metal annular member and the resin annular member, cracks are also likely to occur at the joint between the metal bushing and the resin annular member (the outer surface of the metal bushing). At the joint between the metal bushing and the resin annular member, cracks are particularly likely to occur around the second anti-rotation portions that protrude into the resin annular member. In this regard, by coating the second anti-rotation portions with the second resin, the second resin can be applied to areas of the joint between the metal bushing and the resin annular member that are particularly susceptible to cracking, thereby more appropriately promoting the penetration of the second resin into cracks when they occur. This further reduces strength reduction due to cracks.

In the above-described composite structure rotating body, the second resin may be applied to the entire surface of the outer periphery of the metal bushing that comes into contact with the resin annular member. In this way, applying the second resin to the entire surface of the outer periphery of the metal bushing that comes into contact with the resin annular member can more appropriately promote the penetration of the second resin into cracks that occur at the joint between the metal bushing and the resin annular member. This can further reduce the reduction in strength due to the effects of cracks.

According to one aspect of the present invention, it is possible to suppress a decrease in the strength of a composite structure rotor due to the effects of cracks.

FIG. 1 is a front view and a cross-sectional view of a composite structure gear according to an embodiment. FIG. 2 is a perspective view of a metal bushing included in the composite structure gear of FIG. FIG. 3 is a perspective view of a metallic annular member included in the composite structural gear of FIG. FIG. 4 is a diagram illustrating the molding process of the composite structure gear of FIGS. 1(a) and 1(b). FIG. 5 is a diagram illustrating the application of the low melting point resin in the molding process.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the description of the drawings, identical or equivalent elements will be designated by the same reference numerals, and duplicate explanations will be omitted.

Figure 1 shows a front view (Figure 1(a)) and a cross-sectional view (Figure 1(b)) of a composite structure gear 1 according to an embodiment. As shown in Figures 1(a) and 1(b), the composite structure gear 1 is a so-called hybrid gear made of resin and metal, and is used, for example, as a gear for vehicles and industrial applications. The composite structure gear 1 is a composite structure rotating body including a metal bushing 3, a resin annular member 5, and a metal annular member 7. The composite structure gear 1 is, for example, a helical gear. The composite structure gear 1 may also be a spur gear. Note that Figures 1(a) and 1(b) omit the illustration of a low-melting-point resin 90 (see Figure 5), which will be described later. Here, the configuration other than the low-melting-point resin 90 (see Figure 5) will be described.

The metal bushing 3 is a component attached to, for example, a rotating shaft (not shown). Figure 2 is a perspective view of the metal bushing 3 included in the composite structure gear 1 of Figure 1. As shown in Figures 1(a), 1(b), and 2, the metal bushing 3 is annular. The metal bushing 3 is formed of a metal such as stainless steel. The metal bushing 3 has a through hole 3h. The through hole 3h passes through the metal bushing 3 in the axial direction. A rotating shaft is inserted into the through hole 3h. The metal bushing 3 has a plurality of convex anti-rotation portions 31 (second anti-rotation portions) formed on its outer circumferential surface at predetermined intervals. The anti-rotation portions 31 are embedded in the resin annular member 5. The anti-rotation portions 31 function to prevent the resin annular member 5 from rotating relative to the metal bushing 3 and from coming loose.

The resin annular member 5 is disposed between the metal bushing 3 and the metal annular member 7, connecting the two. The resin annular member 5 is a member that damps vibrations propagating between the metal annular member 7 and the metal bushing 3, for example. Vibrations include those caused by impacts generated when the composite gear 1 meshes with other gears. The resin annular member 5 absorbs and damps vibrations through its elastic deformation. The resin annular member 5 is annular and coaxial with the metal bushing 3. The resin annular member 5 is disposed around the metal bushing 3. Here, the resin annular member 5 is disposed so as to contact the outer surface of the metal bushing 3. Note that "disposed around the metal bushing 3" does not only mean that the resin annular member 5 is disposed so as to contact the metal bushing 3, but also includes that the resin annular member 5 is disposed around the metal bushing 3 via another member.

The resin ring member 5 is manufactured by resin molding. The resin 80 (first resin) constituting the resin ring member 5 may be, for example, a thermoplastic resin such as acrylonitrile butadiene styrene, acrylonitrile styrene acrylate, cycloolefin copolymer, cycloolefin polymer, ethylene acrylic acid resin, ethylene vinyl acetate, liquid crystal polymer, polyamide, polybutylene terephthalate, polycarbonate, polyethylene, polyether ether ketone, polyetherimide, polyethersulfone, polyethylene terephthalate, perfluoroalkoxyalkane, polymethyl methacrylate, polyoxymethylene, polypropylene, polyphenylene ether, polyphenylene sulfide, polyphenylsulfone, polystyrene, polysulfone, polyvinyl chloride, polyvinylidene fluoride, styrene acrylonitrile, styrene butadiene, styrene butadiene styrene, or styrene ethylene butadiene styrene. Alternatively, the resin 80 may be, for example, a thermosetting resin such as unsaturated polyester resin, epoxy resin, liquid silicone rubber, phenolic resin, or polyurethane. Furthermore, the resin 80 (first resin) that constitutes the resin annular member 5 may be a fiber-reinforced resin. The end face of the resin annular member 5 is seamlessly connected to the end face of the metal bushing 3.

The metal annular member 7 is a member that meshes with other gears. Figure 3 is a perspective view of the metal annular member 7 included in the composite structure gear 1 of Figure 1. As shown in Figures 1(a), 1(b), and 3, the metal annular member 7 is annular and coaxial with the metal bushing 3. The metal annular member 7 is formed of a metal such as stainless steel. The metal annular member 7 is provided around the metal bushing 3 and, by extension, around the resin annular member 5. Here, the metal annular member 7 is provided so as to contact the outer surface of the resin annular member 5. Note that being provided around the resin annular member 5 includes not only being provided so as to be in direct contact with the resin annular member 5, but also being provided around the resin annular member 5 via another member. Tooth profiles 7a are formed on the outer periphery of the metal annular member 7. Multiple tooth profiles 7a are formed at predetermined intervals around the circumferential direction of the metal annular member 7. The tooth profiles 7a are formed obliquely with respect to the rotation axis.

The metal annular member 7 has multiple convex anti-rotation portions 71 (first anti-rotation portions) formed at predetermined intervals circumferentially on its inner surface. The anti-rotation portions 71 are recessed into the resin annular member 5. The anti-rotation portions 71 function to prevent the resin annular member 5 from rotating relative to the metal annular member 7 and from coming loose. The end face of the metal annular member 7 is seamlessly connected to the end face of the resin annular member 5.

Next, the molding process (manufacturing method) for the composite structure gear 1 will be described with reference to Figure 4. Figure 4 is a diagram illustrating the molding process for the composite structure gear of Figures 1(a) and 1(b). Note that Figure 4 omits the illustration of the low-melting-point resin 90 (see Figure 5), which will be described later. Here, steps other than the step related to applying the low-melting-point resin 90 (see Figure 5) will be described. Figure 4(a) shows the flow of the molding process. Figure 4(b) shows the injection molding machine 100 before injection.

The composite structure gear 1 is molded by injection molding. As shown in Figure 4(b), the injection molding machine 100 includes a mold 101 in which the metal bushing 3 and metal annular member 7 are set, a hopper 102 into which the resin 80 that forms the resin annular member 5 is poured, a cylinder 103 that heats and melts the resin 80 poured into the hopper 102, and a nozzle 104 that injects the molten resin 80.

In this injection molding machine 100, as shown in FIG. 4(a), the mold 101 is first preheated (step S1) and filled (step S2). In this state, as shown in FIG. 4(b), the metal bushing 3 is set in the mold 101, and the metal annular member 7 is set outside the position in the mold 101 where the metal bushing 3 is set. With the metal bushing 3 and metal annular member 7 set, the anti-rotation portion 31 of the metal bushing 3 extends toward the metal annular member 7, and the anti-rotation portion 71 of the metal annular member 7 extends toward the metal bushing 3.

As shown in FIG. 4(a), resin 80 that will form the resin annular member 5 is poured into a hopper 102 (step S1), the resin 80 is heated and melted in a cylinder 103 (step S12), and the resin 80 is measured (step S13). In this state, the resin 80 is ready to be injected from a nozzle 104, as shown in FIG. 4(b).

Then, with the metal bushing 3 and metal annular member 7 set in the mold 101 of the injection molding machine 100, resin 80 is poured between the metal bushing 3 and the metal annular member 7, and the metal bushing 3, metal annular member 7, and resin annular member 5 are integrally molded by injection molding (second step). More specifically, as shown in FIG. 4(a), the injection process of pouring the resin 80 (step S21), the pressure holding process (step S22), and the hardening or solidification process (step S23) are carried out sequentially. In step S23, if the resin 80 is a thermosetting resin, a hardening process is carried out, and if it is a thermoplastic resin, a solidification process is carried out.

Figure 4(c) shows the injection molding machine 100 during injection molding. Figure 4(d) shows an enlarged view of a portion of Figure 4(c). As shown in Figure 4(c), resin 80 injected from the nozzle 104 passes through a flow path 101a in the mold 101. Then, as shown in Figure 4(d), the resin 80 flows from the circumferential disk gate 101b into the area between the metal bushing 3 and the metal annular member 7, filling the area between the metal bushing 3 and the metal annular member 7. The resin 80 is filled so as to contact, for example, the entire outer surface of the metal bushing 3 (including the area of the anti-rotation portion 31) and the entire inner surface of the metal annular member 7 (including the area of the anti-rotation portion 71).

Once the integral molding by injection molding is completed, as shown in FIG. 4(a), the resin annular member 5, which is composed of the integrally molded metal bushing 3, metal annular member 7, and resin 80, is removed from the injection molding machine 100 and allowed to cool naturally (step S31, third process). Finally, an annealing process or curing process is performed as necessary. For example, if the resin 80 is a thermosetting resin, an annealing process is performed (step S41).

During the molding process described above, cracks may occur at the joints between the metal and resin due to the difference in thermal contraction between the metal bushing 3 and metal annular member 7, which are made of metal, and the resin annular member 5, which is made of resin. In other words, cracks may occur at the joints between the metal bushing 3 and resin annular member 5, and between the metal annular member 7 and resin annular member 5. The occurrence of cracks may reduce the strength of the molded composite structure gear 1.

To solve the above-mentioned problems, in the molding process (manufacturing method) for the composite structure gear 1 according to this embodiment, before injection molding (the second process described above), a thermoplastic low-melting-point resin 90 (second resin) with a melting point lower than that of resin 80 is applied to the joint between the metal and resin, which is prone to cracking. The reason for applying low-melting-point resin 90 will be described later. Low-melting-point resin 90 may be, for example, acrylonitrile butadiene styrene, polyethylene, polypropylene, polystyrene, polyvinyl chloride, or the like, and is selected appropriately depending on the heat resistance of resin 80. Low-melting-point resin 90 is applied to a thickness of, for example, several millimeters.

Specifically, prior to injection molding, the low-melting-point resin 90 described above is applied to at least the anti-rotation portion 71 of the metal annular member 7 (first step). Preferably, in the first step, the low-melting-point resin 90 is applied to the entire surface of the inner circumferential surface of the metal annular member 7 that comes into contact with the resin annular member 5. Even more preferably, in the first step, the low-melting-point resin 90 is applied to the anti-rotation portion 31 of the metal bushing 3. Even more preferably, in the first step, the low-melting-point resin 90 is applied to the entire surface of the outer circumferential surface of the metal bushing 3 that comes into contact with the resin annular member 5.

Figure 5 illustrates the application of low-melting-point resin 90 during the molding process. Figure 5(a) shows an example in which low-melting-point resin 90 is applied to the entire inner surface of metal annular member 7 (including anti-rotation portion 71) in the first step, and low-melting-point resin 90 is applied to the entire outer surface of metal bushing 3 (including anti-rotation portion 31) in the first step, and then injection molding (second step) is performed. In this case, when injection molding (second step) is completed, low-melting-point resin 90 will be applied to the entire surface of the inner surface of metal annular member 7 that comes into contact with resin 80 (resin annular member 5), and the entire surface of the outer surface of metal bushing 3 that comes into contact with resin 80 (resin annular member 5).

Figure 5(b) is an enlarged view of a portion of Figure 5(a) and shows the state of the area around the anti-rotation portion 71 after injection molding (step 2). Assume that low-melting-point resin 90 is applied to the entire inner surface of the metal annular member 7, including the anti-rotation portion 71, and that the low-melting-point resin 90 is in contact with the resin 80 (resin annular member 5). Here, the low-melting-point resin 90 is melted by heat during injection molding. Therefore, as shown in Figure 5(c), if a crack 300 occurs in the resin 80 (resin annular member 5) around the anti-rotation portion 71 after injection molding, the molten low-melting-point resin 90 will penetrate the crack 300. In this case, when the composite structure gear 1 is cooled in the subsequent step 3, the low-melting-point resin 90 that has penetrated the crack 300 will solidify, and the crack 300 will be filled with the low-melting-point resin 90. This effectively prevents a decrease in the strength of the composite structure gear 1 due to the effects of the crack 300, even if the crack 300 occurs.

In the composite structure gear 1 formed in this manner, the anti-rotation portion 71 of the metal annular member 7 is coated with a thermoplastic low-melting-point resin 90 having a lower melting point than the resin 80 constituting the resin annular member 5. Preferably, in the composite structure gear 1, the low-melting-point resin 90 is coated over the entire surface of the inner circumferential surface of the metal annular member 7 that comes into contact with the resin annular member 5. Even more preferably, in the composite structure gear 1, the low-melting-point resin 90 is coated over the anti-rotation portion 31 of the metal bushing 3. Even more preferably, in the composite structure gear 1, the low-melting-point resin 90 is coated over the entire surface of the outer circumferential surface of the metal bushing 3 that comes into contact with the resin annular member 5.

Next, we will explain the effects of the manufacturing method for the composite structure gear 1 according to this embodiment.

The manufacturing method for the composite structure gear 1 according to this embodiment is a manufacturing method for a composite structure gear 1 having a metal annular member 7 with a tooth profile 7a formed on its outer periphery, an annular metal bushing 3, and a resin annular member 5 connecting the metal annular member 7 and the metal bushing 3. The manufacturing method includes the following steps: a first step of applying a thermoplastic low-melting-point resin 90 having a lower melting point than the resin 80 constituting the resin annular member 5 to a plurality of convex anti-rotation portions 71 formed at predetermined intervals circumferentially on the inner circumferential surface of the metal annular member 7; a second step of, after the first step, pouring resin 80 between the metal annular member 7 and the metal bushing 3 while the metal annular member 7 and the metal bushing 3 are set in a mold 101 of an injection molding machine 100 to integrally mold the metal annular member 7, the metal bushing 3, and the resin annular member 5 by injection molding; and a third step of, after the second step, removing the integrally molded metal annular member 7, the metal bushing 3, and the resin annular member 5 from the injection molding machine 100 and cooling them.

In the manufacturing method for the composite structure gear 1 according to this embodiment, a process (first process) is carried out in which a thermoplastic low-melting-point resin 90, which has a lower melting point than the resin 80 constituting the resin annular member 5, is applied to the multiple anti-rotation portions 71 formed on the inner circumferential surface of the metal annular member 7, prior to a process (second process) in which the metal annular member 7, the metal bushing 3, and the resin annular member 5 are integrally molded by injection molding. In the second process in which injection molding is carried out, cracks may occur at the joint between the metal and the resin due to the difference in thermal contraction between the metal annular member 7 and the metal bushing 3, which are made of metal, and the resin annular member 5, which is made of resin. Such cracks are particularly likely to occur around the anti-rotation portions 71 that protrude into the resin annular member 5, which are the joint on the metal annular member 7 side, where the resin 80 is filled late (because it is located on the outside). In this regard, because low-melting-point resin 90 is applied to anti-rotation portion 71 before injection molding, the low-melting-point resin 90 melts due to heat during injection molding. Therefore, if cracks occur around anti-rotation portion 71 after molding, the molten low-melting-point resin 90 will penetrate the cracks (see FIG. 5(c)). In this case, when the low-melting-point resin 90 that has penetrated the cracks solidifies upon cooling in the subsequent third step, the cracks are filled with low-melting-point resin 90, thereby preventing a decrease in strength of composite structure gear 1 due to the effects of cracks. As described above, the manufacturing method for composite structure gear 1 according to this embodiment can prevent a decrease in strength of composite structure gear 1 due to the effects of cracks.

In the first step described above, low-melting-point resin 90 may be applied to the entire surface of the inner circumferential surface of metal annular member 7 that contacts resin annular member 5. By applying low-melting-point resin 90 to the entire surface of the inner circumferential surface of metal annular member 7 that contacts resin annular member 5 in this way, low-melting-point resin 90 can be applied to areas where the timing of resin 80 filling is delayed and cracks are likely to occur, and low-melting-point resin 90 can be more appropriately promoted to penetrate cracks when they occur. This can further suppress a decrease in strength of the composite structure gear 1 due to the effects of cracks.

In the first step described above, low-melting-point resin 90 may be applied to multiple protruding anti-rotation portions 31 formed at predetermined intervals circumferentially on the outer circumferential surface of the metal bushing 3. Although not as susceptible to cracks as the joint between the metal annular member 7 and the resin annular member 5, cracks are also likely to occur at the joint between the metal bushing 3 and the resin annular member 5 (the outer circumferential surface of the metal bushing 3). At the joint between the metal bushing 3 and the resin annular member 5, cracks are particularly likely to occur around the anti-rotation portions 31 that protrude into the resin annular member 5. In this regard, applying low-melting-point resin 90 to the anti-rotation portions 31 allows the low-melting-point resin 90 to be applied to areas of the joint between the metal bushing 3 and the resin annular member 5 that are particularly susceptible to cracking, thereby more appropriately promoting the penetration of the low-melting-point resin 90 into cracks when they occur. This further reduces the strength reduction of the composite structure gear 1 due to cracks.

In the first step described above, low-melting-point resin 90 may be applied to the entire surface of the outer periphery of the metal bushing 3 that comes into contact with the resin annular member 5. By applying low-melting-point resin 90 to the entire surface of the outer periphery of the metal bushing 3 that comes into contact with the resin annular member 5 in this way, the low-melting-point resin 90 can be more appropriately promoted to penetrate into cracks that occur at the joint between the metal bushing 3 and the resin annular member 5. This makes it possible to further suppress a decrease in strength of the composite structure gear 1 due to the effects of cracks.

1...Composite structure gear, 3...Metal bushing, 5...Resin annular member, 7...Metal annular member, 7a...Tooth profile, 31...Anti-rotation portion (second anti-rotation portion), 71...Anti-rotation portion (second anti-rotation portion), 80...Resin (first resin), 90...Low-melting-point resin (second resin), 100...Injection molding machine (molding machine).

Claims (8)

A method for manufacturing a composite structure rotating body having a metal annular member having teeth formed on an outer periphery thereof, an annular metal bushing, and a resin annular member connecting the metal annular member and the metal bushing, comprising:
a first step of applying a thermoplastic second resin having a lower melting point than the first resin constituting the resin annular member to a plurality of first protruding anti-rotation portions formed at predetermined intervals in the circumferential direction on the inner peripheral surface of the metal annular member;
a second step after the first step, in which the metal annular member and the metal bush are set in a molding machine, the first resin is poured between the metal annular member and the metal bush, and the metal annular member, the metal bush, and the resin annular member are integrally molded by injection molding;
a third step of removing the integrally molded metal annular member, the metal bushing, and the resin annular member from the molding machine after the second step and cooling them. The method for manufacturing a composite structure rotating body according to claim 1, wherein in the first step, the second resin is applied to the entire surface of the inner circumferential surface of the metal annular member that contacts the resin annular member. A method for manufacturing a composite structure rotating body according to claim 1 or 2, wherein in the first step, the second resin is applied to a plurality of convex second anti-rotation portions formed at predetermined intervals in the circumferential direction on the outer circumferential surface of the metal bushing. The method for manufacturing a composite structure rotating body according to claim 3, wherein in the first step, the second resin is applied to the entire surface of the outer circumferential surface of the metal bushing that contacts the resin annular member. A composite structure rotating body including a metal annular member having teeth formed on an outer periphery thereof, an annular metal bushing, and a resin annular member connecting the metal annular member and the metal bushing,
the metal annular member has a plurality of first anti-rotation portions formed on an inner peripheral surface thereof at predetermined intervals in the circumferential direction,
A composite structure rotating body, wherein the first anti-rotation portion is coated with a thermoplastic second resin having a melting point lower than that of the first resin constituting the resin annular member. A composite structure rotating body as described in claim 5, wherein the second resin is applied to the entire surface of the inner circumferential surface of the metal annular member that contacts the resin annular member. the metal bushing has a plurality of second anti-rotation portions formed on its outer circumferential surface at predetermined intervals in the circumferential direction,
7. The composite structure rotating body according to claim 5, wherein the second anti-rotation portion is coated with the second resin. A composite structure rotating body as described in claim 7, wherein the second resin is applied to the entire surface of the outer circumferential surface of the metal bushing that contacts the resin annular member.