Method for manufacturing a composite structure rotating body and composite structure rotating body

Abstract

To suppress a deterioration of strength of a composite structure rotor due to an influence of crack.SOLUTION: A manufacturing method for a composite structure rotor 1 includes: a first step of applying a thermoplastic low-melting-point resin 90 having a lower melting point than a resin 80 constituting a resin annular member 5 to a plurality of convex non-turnover portions 71 formed at predetermined intervals in a circumferential direction on an inner circumference of a metal annular member 7; a second step of integrally molding the metal annular member 7, a metal bush 3, and the resin annular member 5 by injection molding, by pouring the resin 80 between the metal annular member 7 and a metal bush 3, with the metal annular member 7 and the metal bush 3 set in a mold 101 of an injection molding machine 100, after the first step; and a third step of taking out the metal annular member 7, the metal bush 3, and the resin annular member 5 integrally molded from the injection molding machine 100 and cooling them, after the second step.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] One aspect of the present invention relates to a method for manufacturing a composite structure rotating body and a composite structure rotating body.

Background Art

[0002] As a technology related to a composite structure rotating body, for example, a gear described in Patent Document 1 is known. The gear described in Patent Document 1 includes a metal annular body (metal annular member) having teeth formed on its outer peripheral portion, an annular metal bush, and a resin web (resin annular member) that connects the metal annular body and the metal bush.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, when molding a composite structure rotating body as described above, cracks may occur at the joint portion of the metal and the resin due to the difference in thermal shrinkage between the metal annular member and the metal bush formed of metal and the resin web formed of resin. The problem is that the strength of the molded composite structure rotating body decreases due to the occurrence of cracks.

[0005] Conventionally, techniques for suppressing the above-described cracks have been proposed. For example, there is a technique for suppressing the occurrence of cracks by performing annealing treatment or curing treatment on a composite structure rotating body immediately after molding. However, for such treatment, it must be carried out before the molded product is cooled, so changes in equipment, etc. that enable such rapid treatment are required. Also, crack suppression by promoting curing and improving physical properties by annealing cannot be expected when using a thermoplastic resin, so the effect of the above treatment is limited. As another technique for suppressing cracks, for example, there is a technique for suppressing the occurrence of cracks by chamfering the R surface of the edge of the joint portion between metal and resin. However, depending on the shape of the joint portion, the above R chamfering process becomes complicated. Also, the effect of suppressing crack generation by such a technique is limited. Thus, with conventional techniques for suppressing cracks, the strength reduction of the composite structure rotating body due to the influence of cracks has not been sufficiently suppressed.

[0006] One aspect of the present invention has been made in view of the above circumstances, and an object thereof is to suppress the strength reduction of a composite structure rotating body due to the influence of cracks.

Means for Solving the Problems

[0007] A method for manufacturing a composite structure rotating body according to an aspect of the present invention is a method for manufacturing a composite structure rotating body having a metal annular member with a tooth shape formed on an outer peripheral portion, an annular metal bush, and a resin annular member connecting the metal annular member and the metal bush, the method including: a first step of applying a thermoplastic second resin having a melting point lower than that of a first resin constituting the resin annular member to a plurality of convex first anti-rotation portions formed at predetermined intervals in the circumferential direction on an inner peripheral surface of the metal annular member; a second step of, after the first step, pouring the first resin between the metal annular member and the metal bush in a state where the metal annular member and the metal bush are set in a molding machine, and integrally molding the metal annular member, the metal bush, and the resin annular member by injection molding; and a third step of, after the second step, taking out and cooling the integrally molded metal annular member, metal bush, and resin annular member from the molding machine.

[0008] In the method for manufacturing a composite structure rotating body according to one aspect of the present invention, prior to the step (second step) of integrally molding a metal annular member, a metal bush, and a resin annular member by injection molding, a thermoplastic second resin having a melting point lower than that of the first resin constituting the resin annular member is applied to a plurality of first anti-rotation portions formed on the inner peripheral surface of the metal annular member (first step). In the second step where injection molding is performed, cracks may occur at the joint portion between the metal and the resin due to the difference in thermal shrinkage between the metal annular member and the metal bush formed of metal and the resin annular member formed of resin. Such cracks are particularly likely to occur around the first anti-rotation portion that protrudes into the resin annular member at the joint portion on the metal annular member side where the timing of filling the first resin is late. In this regard, since the second resin is applied to the first anti-rotation portion before injection molding and the second resin melts due to heat during injection molding, when cracks occur around the first anti-rotation portion after molding, the molten second resin penetrates into the cracks. In this case, when the second resin that has penetrated into the cracks solidifies by being cooled in the subsequent third step, the cracks are filled with the second resin, so that it is possible to suppress a decrease in the strength of the composite structure rotating body due to the influence of the cracks. As described above, according to the method for manufacturing a composite structure rotating body according to one aspect of the present invention, instead of the idea of suppressing the occurrence of cracks, the idea of filling the generated cracks can suppress a decrease in the strength of the composite structure rotating body due to the influence of the cracks.

[0009] In the first step, the second resin may be applied to the entire area of the surface of the inner peripheral surface of the metal annular member that contacts the resin annular member. Thus, by applying the second resin to the entire area of the surface of the inner peripheral surface of the metal annular member that contacts the resin annular member, the second resin can be applied to the region where the filling timing of the first resin is late and cracks are likely to occur, and the penetration of the second resin into the cracks when cracks occur can be more appropriately promoted. This can further suppress a decrease in the strength of the composite structure rotating body due to the influence of the cracks.

[0010] In the first step, a second resin may be applied to convex second anti-rotation portions formed at predetermined intervals in the circumferential direction on the outer peripheral surface of the metal bush. Although it is not the joint portion between the metal annular member and the resin annular member, cracks are likely to occur also at the joint portion between the metal bush and the resin annular member (the outer peripheral surface of the metal bush). Among the joint portions between the metal bush and the resin annular member, cracks are particularly likely to occur around the second anti-rotation portions protruding so as to enter the resin annular member. In this regard, since the second resin is applied to the second anti-rotation portions, the second resin can be applied to a region where cracks are particularly likely to occur among the joint portions between the metal bush and the resin annular member, and penetration of the second resin into the cracks when cracks occur can be more appropriately promoted. By this, a decrease in the strength of the composite structure rotating body due to the influence of cracks can be more suppressed.

[0011] In the first step, the second resin may be applied to the entire area of the surface of the outer peripheral surface of the metal bush that contacts the resin annular member. In this way, since the second resin is applied to the entire area of the surface of the outer peripheral surface of the metal bush that contacts the resin annular member, penetration of the second resin into the cracks when cracks occur at the joint portion between the metal bush and the resin annular member can be more appropriately promoted. By this, a decrease in the strength of the composite structure rotating body due to the influence of cracks can be more suppressed.

[0012] The composite structure rotating body according to one aspect of the present invention is a composite structure rotating body including a metal annular member having a tooth shape formed on its outer peripheral portion, an annular metal bush, and a resin annular member connecting the metal annular member and the metal bush. The metal annular member has a plurality of convex first anti-rotation portions formed at predetermined intervals in the circumferential direction on its inner peripheral surface, and a thermoplastic second resin having a melting point lower than that of the first resin constituting the resin annular member is applied to the first anti-rotation portions. In the composite structure rotating body according to one aspect of the present invention, a thermoplastic second resin having a melting point lower than that of the first resin constituting the resin annular member is applied to a plurality of convex first anti-rotation portions formed on the inner peripheral surface of the metal annular member. In such a composite structure rotating body, since a thermoplastic second resin having a melting point lower than that of the first resin is applied to the first anti-rotation portions where cracks are likely to occur, when cracks occur around the first anti-rotation portions after molding, the molten second resin penetrates into the cracks, and the second resin that has penetrated into the cracks solidifies by cooling, so that the cracks are filled with the second resin. As a result, a decrease in strength due to the influence of cracks is suppressed. As described above, in the composite structure rotating body according to one aspect of the present invention, a decrease in strength due to the influence of cracks is effectively suppressed. Further, in the composite structure rotating body according to one aspect of the present invention, a second resin having a melting point lower than that of the first resin (melting at a relatively low temperature), being relatively easily elastically deformed near room temperature and having a high viscosity, is applied to the first anti-rotation portions on the inner peripheral surface of the metal annular member, so that vibration can be effectively reduced.

[0013] In the above composite structure rotating body, the second resin may be applied to the entire surface of the inner peripheral surface of the metal annular member that contacts the resin annular member. In this way, by applying the second resin to the entire surface of the inner peripheral surface of the metal annular member that contacts the resin annular member, the second resin can be applied to a region where the filling timing of the first resin is late and cracks are likely to occur, and the penetration of the second resin into the cracks when cracks occur can be more appropriately promoted. By this, a decrease in strength due to the influence of cracks can be further suppressed.

[0014] In the above composite structure rotating body, the metal bush has a plurality of convex second anti-rotation portions formed at predetermined intervals in the circumferential direction on its outer peripheral surface, and the second resin may be applied to the second anti-rotation portions. Although it is not the joint portion between the metal annular member and the resin annular member, cracks are likely to occur also at the joint portion between the metal bush and the resin annular member (the outer peripheral surface of the metal bush). Among the joint portions between the metal bush and the resin annular member, cracks are particularly likely to occur around the second anti-rotation portion that protrudes so as to enter the resin annular member. In this regard, by applying the second resin to the second anti-rotation portion, the second resin can be applied to the region where cracks are particularly likely to occur among the joint portions between the metal bush and the resin annular member, and the penetration of the second resin into the cracks when cracks occur can be more appropriately promoted. By this, the reduction in strength due to the influence of cracks can be more suppressed.

[0015] In the above composite structure rotating body, the second resin may be applied to the entire area of the surface of the outer peripheral surface of the metal bush that contacts the resin annular member. In this way, by applying the second resin to the entire area of the surface of the outer peripheral surface of the metal bush that contacts the resin annular member, the penetration of the second resin into the cracks when cracks occur at the joint portion between the metal bush and the resin annular member can be more appropriately promoted. By this, the reduction in strength due to the influence of cracks can be more suppressed.

Advantages of the Invention

[0016] According to one aspect of the present invention, it is possible to suppress a reduction in strength of the composite structure rotating body due to the influence of cracks.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0019] FIG. 1 is a front view (FIG. 1(a)) and a cross-sectional view (FIG. 1(b)) of a composite structure gear 1 according to an embodiment. As shown in FIGS. 1(a) and 1(b), the composite structure gear 1 is a so-called hybrid gear made of resin and metal, and is used as a gear for vehicles, industries, etc., for example. The composite structure gear 1 is a composite structure rotating body including a metal bush 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 be a spur gear. In FIGS. 1(a) and 1(b), the illustration of the low melting point resin 90 (see FIG. 5) described later is omitted. Here, the configuration other than the low melting point resin 90 (see FIG. 5) will be described.

[0020] The metal bush 3 is a member attached to a rotating shaft (not shown), for example. FIG. 2 is a perspective view of the metal bush 3 included in the composite structure gear 1 of FIG. 1. As shown in FIGS. 1(a), 1(b) and FIG. 2, the metal bush 3 is annular. The metal bush 3 is formed of a metal such as stainless steel, for example. The metal bush 3 is provided with a through hole 3h. The through hole 3h penetrates the metal bush 3 in the axial direction. A rotating shaft is inserted into the through hole 3h. The metal bush 3 has a plurality of convex anti-rotation portions 31 (second anti-rotation portions) formed at predetermined intervals in the circumferential direction on its outer peripheral surface. The anti-rotation portions 31 fit into the resin annular member 5. The anti-rotation portions 31 have the function of preventing the resin annular member 5 from rotating and coming off with respect to the metal bush 3.

[0021] The resin annular member 5 is provided between the metal bush 3 and the metal annular member 7 and connects the metal bush 3 and the metal annular member 7. The resin annular member 5 is a member that attenuates vibrations, for example, vibrations propagating between the metal annular member 7 and the metal bush 3. The vibrations include those caused by the impact generated when the composite structure gear 1 meshes with other gears. The resin annular member 5 absorbs and attenuates the vibrations by its elastic deformation. The resin annular member 5 is annular and coaxial with the metal bush 3. The resin annular member 5 is provided around the metal bush 3. Here, the resin annular member 5 is provided so as to be in contact with the outer peripheral surface of the metal bush 3. Note that being provided around the metal bush 3 includes not only being provided so as to be in contact with the periphery of the metal bush 3 but also being provided around the metal bush 3 via other members.

[0022] The resin annular member 5 is manufactured by resin molding. The resin 80 (first resin) constituting the resin annular 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, polyether imide, polyether sulfone, polyethylene terephthalate, perfluoroalkoxy alkane, polymethyl methacrylate, polyoxymethylene, polypropylene, polyphenylene ether, polyphenylene sulfide, polyphenyl sulfone, 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 an unsaturated polyester resin, an epoxy resin, a liquid silicone rubber, a phenol resin, or a polyurethane. Further, the resin 80 (first resin) constituting the resin annular member 5 may be a fiber-reinforced resin. The end face of the resin annular member 5 is continuous with the end face of the metal bush 3 without a step.

[0023] The metal annular member 7 is a member that meshes with other gears. FIG. 3 is a perspective view of the metal annular member 7 included in the composite structure gear 1 of FIG. 1. As shown in FIGS. 1(a), 1(b), and 3, the metal annular member 7 is annular and coaxial with the metal bush 3. The metal annular member 7 is formed of a metal such as stainless steel, for example. The metal annular member 7 is provided around the metal bush 3 and thus around the resin annular member 5. Here, the metal annular member 7 is provided so as to contact the outer peripheral 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 directly contact around the resin annular member 5 but also being provided around the resin annular member 5 via other members. Tooth profiles 7a are formed on the outer peripheral portion of the metal annular member 7. A plurality of tooth profiles 7a are formed at predetermined intervals in the circumferential direction of the metal annular member 7. The tooth profiles 7a are formed obliquely with respect to the rotation axis.

[0024] The metal annular member 7 has a plurality of convex anti-rotation portions 71 (first anti-rotation portions) formed at predetermined intervals in the circumferential direction on its inner peripheral surface. The anti-rotation portions 71 penetrate into the resin annular member 5. The anti-rotation portions 71 have the function of preventing the resin annular member 5 from rotating and coming off with respect to the metal annular member 7. The end surface of the metal annular member 7 is continuous with the end surface of the resin annular member 5 without a step.

[0025] Next, with reference to FIG. 4, the molding process (manufacturing method) of the composite structure gear 1 will be described. FIG. 4 is a diagram for explaining the molding process of the composite structure gear of FIGS. 1(a) and 1(b). Note that in FIG. 4, the illustration regarding the low melting point resin 90 (see FIG. 5) described later is omitted. Here, the processes other than the process related to the application of the low melting point resin 90 (see FIG. 5) will be described. FIG. 4(a) shows the flow of the molding process. FIG. 4(b) shows the injection molding machine 100 before injection.

[0026] The composite structure gear 1 is formed by injection molding. As shown in Fig. 4(b), the injection molding machine 100 includes a mold 101 in which the metal bush 3 and the metal annular member 7 are set, a hopper 102 into which the resin 80 constituting the resin annular member 5 is charged, a cylinder 103 for heating and melting the resin 80 charged into the hopper 102, and a nozzle 104 for injecting the melted resin 80.

[0027] In such an injection molding machine 100, as shown in Fig. 4(a), first, the preheating process (step S1) and the mold filling process (step S2) of the mold 101 are performed. In this state, as shown in Fig. 4(b), the metal bush 3 is set in the mold 101, and the metal annular member 7 is set outside the position where the metal bush 3 is set in the mold 101. In the state where the metal bush 3 and the metal annular member 7 are set, the anti-rotation portion 31 of the metal bush 3 extends toward the metal annular member 7, and the anti-rotation portion 71 of the metal annular member 7 extends toward the metal bush 3.

[0028] Then, as shown in Fig. 4(a), the resin 80 constituting the resin annular member 5 is charged into the hopper 102 (step S1), the resin 80 is heated and melted in the cylinder 103 (step S12), and the metering of the resin 80 is performed (step S13). In this state, as shown in Fig. 4(b), the resin 80 can be injected from the nozzle 104.

[0029] Then, with the metal bush 3 and the metal annular member 7 set in the mold 101 of the injection molding machine 100, the resin 80 is poured between the metal bush 3 and the metal annular member 7, and the metal bush 3, the metal annular member 7, and the resin annular member 5 are integrally formed by injection molding (second step). More specifically, as shown in Fig. 4(a), the injection process (step S21) of pouring the resin 80, the pressure holding process (step S22), and the hardening or solidifying process (step S23) are sequentially performed. In step S23, when the resin 80 is a thermosetting resin, the hardening process is performed, and when the resin 80 is a thermoplastic resin, the solidifying process is performed.

[0030] Figure 4(c) shows the injection molding machine 100 during injection molding. Figure 4(d) shows a partially enlarged view of Figure 4(c). As shown in Figure 4(c), the resin 80 injected from the nozzle 104 passes through the flow path 101a in the mold 101. Then, as shown in Figure 4(d), the resin 80 flows into the region between the metal bush 3 and the metal annular member 7 from the disk gate 101b on the circumference and is filled in the region between the metal bush 3 and the metal annular member 7. The resin 80 is filled so as to contact the entire outer peripheral surface of the metal bush 3 (including the region of the anti-rotation portion 31) and the entire inner peripheral surface of the metal annular member 7 (including the region of the anti-rotation portion 71), for example.

[0031] When the integral molding by injection molding is completed, as shown in Figure 4(a), the resin annular member 5 composed of the integrally molded metal bush 3, metal annular member 7, and resin 80 is taken out from the injection molding machine 100, and these are naturally cooled (step S31, the third step). Finally, an annealing treatment or a curing treatment is carried out as necessary. For example, when the resin 80 is a thermosetting resin, an annealing treatment is carried out (step S41).

[0032] Here, in the molding process described above, cracks may occur at the joint portion of the metal and the resin due to the difference in thermal shrinkage between the metal bush 3 and the metal annular member 7 formed of metal and the resin annular member 5 shaped by the resin. That is, cracks may occur at the joint portion between the metal bush 3 and the resin annular member 5 and at the joint portion between the metal annular member 7 and the resin annular member 5. The occurrence of cracks may reduce the strength of the molded composite structure gear 1.

[0033] In order to solve the above-described problems, in the molding process (manufacturing method) of the composite structure gear 1 according to the present embodiment, before injection molding (the second step described above), a thermoplastic low melting point resin 90 (second resin) having a melting point lower than that of the resin 80 is applied to the joint portion of the metal and the resin where cracks are likely to occur. The reason for applying the low melting point resin 90 will be described later. The low melting point resin 90 may be, for example, acrylonitrile butadiene styrene, polyethylene, polypropylene, polystyrene, or polyvinyl chloride, etc., and is appropriately selected according to the heat resistance of the resin 80. The low melting point resin 90 is applied, for example, with a thickness of about several millimeters.

[0034] Specifically, before injection molding, at least on the retaining portion 71 of the metal annular member 7, the above-described low melting point resin 90 is applied (first step). Preferably, in the first step, the low melting point resin 90 is applied to the entire area of the surface of the inner peripheral surface of the metal annular member 7 that contacts the resin annular member 5. More preferably, in the first step, the low melting point resin 90 is applied to the retaining portion 31 of the metal bush 3. Even more preferably, in the first step, the low melting point resin 90 is applied to the entire area of the surface of the outer peripheral surface of the metal bush 3 that contacts the resin annular member 5.

[0035] FIG. 5 is a diagram for explaining the application of the low melting point resin 90 in the molding process. In FIG. 5(a), in the first step, the low melting point resin 90 is applied to the entire area of the inner peripheral surface of the metal annular member 7 (including the retaining portion 71), and the injection molding (second step) is shown in a state where the low melting point resin 90 is applied to the entire area of the outer peripheral surface of the metal bush 3 (including the retaining portion 31). In this case, in the state where the injection molding (second step) is completed, the low melting point resin 90 is applied to the entire area of the surface of the inner peripheral surface of the metal annular member 7 that contacts the resin 80 (resin annular member 5), and the entire area of the surface of the outer peripheral surface of the metal bush 3 that contacts the resin 80 (resin annular member 5).

[0036] Fig. 5(b) is a partially enlarged view of Fig. 5(a), showing the state around the rotation prevention portion 71 after injection molding (second step). Now, it is assumed that a low melting point resin 90 is applied to the entire inner peripheral surface of the metal annular member 7 including the rotation prevention portion 71, and the low melting point resin 90 is in contact with the resin 80 (resin annular member 5). Here, at the time of injection molding, the low melting point resin 90 is melted by heat. Therefore, as shown in Fig. 5(c), if a crack 300 occurs in the resin 80 (resin annular member 5) around the rotation prevention portion 71 after injection molding, the molten low melting point resin 90 will penetrate into the crack 300. In this case, when the composite structure gear 1 is cooled in the subsequent third step, the low melting point resin 90 that has penetrated into the crack 300 solidifies, and the crack 300 is filled with the low melting point resin 90. As a result, even when the crack 300 occurs, it is possible to effectively suppress the decrease in the strength of the composite structure gear 1 due to the influence of the crack 300.

[0037] In the composite structure gear 1 formed in this way, a thermoplastic low melting point resin 90 having a melting point lower than that of the resin 80 constituting the resin annular member 5 is applied to the rotation prevention portion 71 of the metal annular member 7. Preferably, in the composite structure gear 1, the low melting point resin 90 is applied to the entire surface of the inner peripheral surface of the metal annular member 7 that contacts the resin annular member 5. More preferably, in the composite structure gear 1, the low melting point resin 90 is applied to the rotation prevention portion 31 of the metal bush 3. Even more preferably, in the composite structure gear 1, the low melting point resin 90 is applied to the entire surface of the outer peripheral surface of the metal bush 3 that contacts the resin annular member 5.

[0038] Next, the operation and effect of the manufacturing method of the composite structure gear 1 according to the present embodiment will be described.

[0039] The manufacturing method of the composite structure gear 1 according to this embodiment is a manufacturing method of the composite structure gear 1 having a metal annular member 7 with a tooth shape 7a formed on the outer peripheral portion, an annular metal bush 3, and a resin annular member 5 that connects the metal annular member 7 and the metal bush 3. The method includes a first step of applying a thermoplastic low melting point resin 90 having a melting point lower than that of the resin 80 constituting the resin annular member 5 to a plurality of convex anti-rotation portions 71 formed at predetermined intervals in the circumferential direction on the inner peripheral surface of the metal annular member 7, a second step of, after the first step, pouring the resin 80 between the metal annular member 7 and the metal bush 3 in a state where the metal annular member 7 and the metal bush 3 are set in the mold 101 of the injection molding machine 100 and integrally molding the metal annular member 7, the metal bush 3, and the resin annular member 5 by injection molding, and a third step of, after the second step, taking out and cooling the integrally molded metal annular member 7, metal bush 3, and resin annular member 5 from the injection molding machine 100.

[0040] In the manufacturing method of the composite structure gear 1 according to this embodiment, prior to the step (second step) of integrally molding the metal annular member 7, the metal bush 3, and the resin annular member 5 by injection molding, a step (first step) is carried out in which a thermoplastic low melting point resin 90 having a melting point lower than that of the resin 80 constituting the resin annular member 5 is applied to a plurality of anti-rotation portions 71 formed on the inner peripheral surface of the metal annular member 7. In the second step where injection molding is carried out, due to the thermal shrinkage difference between the metal annular member 7 and the metal bush 3 formed of metal and the resin annular member 5 formed of resin, cracks may occur at the joint portion between the metal and the resin. Such cracks are likely to occur particularly around the anti-rotation portion 71 that protrudes into the resin annular member 5 at the joint portion on the side of the metal annular member 7 because the timing of filling the resin 80 is late (since it is arranged on the outside, the filling timing is late). In this regard, since the low melting point resin 90 is applied to the anti-rotation portion 71 before injection molding, the low melting point resin 90 melts due to heat during injection molding. Therefore, when cracks occur around the anti-rotation portion 71 after molding, the molten low melting point resin 90 will penetrate into the cracks (see Fig. 5(c)). In this case, when the low melting point resin 90 that has penetrated into the cracks solidifies by being cooled in the subsequent third step, the cracks will be filled with the low melting point resin 90, so it is possible to suppress a decrease in the strength of the composite structure gear 1 due to the influence of the cracks. As described above, according to the manufacturing method of the composite structure gear 1 according to this embodiment, it is possible to suppress a decrease in the strength of the composite structure gear 1 due to the influence of cracks.

[0041] In the above-described first step, the low-melting-point resin 90 may be applied to the entire surface of the inner peripheral surface of the metal annular member 7 that contacts the resin annular member 5. Thus, by applying the low-melting-point resin 90 to the entire surface of the inner peripheral surface of the metal annular member 7 that contacts the resin annular member 5, the low-melting-point resin 90 can be applied to the region where the filling timing of the resin 80 is slow and cracks are likely to occur, and the penetration of the low-melting-point resin 90 into the cracks when the cracks occur can be more appropriately promoted. By this, the decrease in the strength of the composite structure gear 1 due to the influence of cracks can be more suppressed.

[0042] In the above-described first step, the low-melting-point resin 90 may be applied to the convex anti-rotation portions 31 formed at predetermined intervals in the circumferential direction on the outer peripheral surface of the metal bush 3. Although it is not as much as the joint portion between the metal annular member 7 and the resin annular member 5, cracks are also likely to occur at the joint portion (the outer peripheral surface of the metal bush 3) between the metal bush 3 and the resin annular member 5. Among the joint portions between the metal bush 3 and the resin annular member 5, cracks are particularly likely to occur around the anti-rotation portions 31 that protrude so as to enter the resin annular member 5. In this regard, since the low-melting-point resin 90 is applied to the anti-rotation portions 31, the low-melting-point resin 90 can be applied to the region where cracks are particularly likely to occur among the joint portions between the metal bush 3 and the resin annular member 5, and the penetration of the low-melting-point resin 90 into the cracks when the cracks occur can be more appropriately promoted. By this, the decrease in the strength of the composite structure gear 1 due to the influence of cracks can be more suppressed.

[0043] In the above-described first step, the low-melting-point resin 90 may be applied to the entire surface of the outer peripheral surface of the metal bush 3 that contacts the resin annular member 5. Thus, by applying the low-melting-point resin 90 to the entire surface of the outer peripheral surface of the metal bush 3 that contacts the resin annular member 5, the penetration of the low-melting-point resin 90 into the cracks when the cracks occur at the joint portion between the metal bush 3 and the resin annular member 5 can be more appropriately promoted. By this, the decrease in the strength of the composite structure gear 1 due to the influence of cracks can be more suppressed.

Explanation of Reference Numerals

[0044] 1…Composite structure gear, 3…Metal bush, 5…Resin annular member, 7…Metal annular member, 7a…Tooth shape, 31…Anti-rotation part (second anti-rotation part), 71…Anti-rotation part (second anti-rotation part), 80…Resin (first resin), 90…Low melting point resin (second resin), 100…Injection molding machine (molding machine).

Claims

1. A method for manufacturing a composite structure rotating body, comprising a metal annular member having a tooth shape formed on its outer peripheral portion, an annular metal bush, and a resin annular member connecting the metal annular member and the metal bush, a first step of applying a thermoplastic second resin having a melting point lower than that of a first resin constituting the resin annular member to a plurality of convex first anti-rotation portions formed at predetermined intervals in the circumferential direction on the inner peripheral surface of the metal annular member; a second step of, after the first step, pouring the first resin between the metal annular member and the metal bush with the metal annular member and the metal bush set in a molding machine, and integrally molding the metal annular member, the metal bush, and the resin annular member by injection molding; a third step of, after the second step, taking out and cooling the integrally molded metal annular member, metal bush, and resin annular member from the molding machine. A method for manufacturing a composite structure rotating body comprising these steps.

2. 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 peripheral surface of the metal annular member that contacts the resin annular member.

3. The 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 peripheral surface of the metal bush.

4. 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 peripheral surface of the metal bush that contacts the resin annular member.

5. A composite structure rotating body comprising a metal annular member having a tooth shape formed on its outer peripheral portion, an annular metal bush, and a resin annular member connecting the metal annular member and the metal bush, wherein the metal annular member has a plurality of convex first anti-rotation portions formed at predetermined intervals in the circumferential direction on its inner peripheral surface, and a thermoplastic second resin having a melting point lower than that of a first resin constituting the resin annular member is applied to the first anti-rotation portions. A composite structure rotating body.

6. The composite structure rotating body according to claim 5, wherein the second resin is applied to the entire surface of the inner peripheral surface of the metal annular member that contacts the resin annular member.

7. The metal bush has a plurality of convex second anti-rotation portions formed at predetermined intervals in the circumferential direction on its outer peripheral surface. The composite structure rotating body according to claim 5 or 6, wherein the second resin is applied to the second anti-rotation portion. **Claim 8** The composite structure rotating body according to claim 7, wherein the second resin is applied to the entire area of the surface of the outer peripheral surface of the metal bush that contacts the resin annular member.

Images