Gear, robot and gear manufacturing method

Abstract

A gear (10) formed from a resin containing a filler is provided with a plurality of recesses formed in an axial end surface (11) when a plurality of points on the axial end surface (11) of the gear (10) corresponding to a plurality of needle gates in a one-to-one manner are each set as gate points. And a plurality of needle-shaped sprues, each extending from one side to the other side of a straight line extending from the corresponding sprue point to the radial outer side of the gear (10), each having an asymmetric shape with respect to the straight line, the plurality of needle-shaped sprues being used for injecting resin during molding of the gear (10).

Description

Technical Field

[0001] The present disclosure relates to a gear, a robot and a gear manufacturing method. Background Art

[0002] Patent document 1 discloses a gear formed of a resin containing reinforcing fibers. In the gear, a resin flow rate adjustment groove is formed. According to Patent document 1, when the gear is molded, the flow rate of the resin injected from the pinpoint gate toward the radial outside is controlled and made uniform by a protrusion for the resin flow rate adjustment groove protruding in the cavity to form the resin flow rate adjustment groove. As a result, the orientation of the reinforcing fibers in the resin is uniform in the radial direction over the entire circumference.

[0003] Patent Document 2 discloses a gear that is molded using a molding material in which reinforcing fibers are blended into a base resin. According to Patent Document 2, when the gear is molded, the mold and the shaft are rotated relative to each other, thereby causing the molding material filled in the cavity area corresponding to the tooth bottom to flow. As a result, the orientation of the reinforcing fibers in the molding material at the tooth bottom is disturbed.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2004-358665

[0007] Patent Document 2: Japanese Patent Application Publication No. 2019-218994 Summary of the invention

[0008] Problems to be solved by the invention

[0009] When the fiber orientation is controlled by the shape of the gear rather than by the molding method, if the fiber orientation is locally uniform in the radial direction, local deformation and stress are likely to occur, and there is a concern that dimensional accuracy and strength may be reduced.

[0010] An object of the present disclosure is to provide a gear that is less susceptible to local deformation or stress.

[0011] Methods for solving problems

[0012] Several aspects of the present disclosure are shown below.

[0013] [Method 1]

[0014] A gear, formed of a resin containing a filler, the gear having a plurality of recessed portions, the plurality of recessed portions being formed on the axial end surface when a plurality of points on the axial end surface of the gear corresponding one-to-one to a plurality of needle-shaped gates are respectively set as gate points, and each of the recessed portions extends from one side to the other side of a straight line extending radially outward from the corresponding gate point to the gear, and each of the recessed portions has an asymmetric shape relative to the straight line, wherein the plurality of needle-shaped gates are used to inject the resin when the gear is molded.

[0015] [Method 2]

[0016] A gear as described in method 1, wherein at least a portion of each recess existing on one side of the straight line has a shape such that the radial width of the gear increases from a first end existing on one side of the straight line among the two ends of each recess in the circumferential direction of the gear toward a second end existing on the other side of the straight line.

[0017] [Method 3]

[0018] The gear according to aspect 2, wherein the first end is formed into an acute angle shape when viewed from an end face in the axial direction of the gear.

[0019] [Method 4]

[0020] The gear according to aspect 2 or aspect 3, wherein the second end is formed into an acute angle when viewed from the end face in the axial direction of the gear.

[0021] [Method 5]

[0022] The gear according to any one of the first to fourth aspects comprises: an annular rim formed with a plurality of teeth, and a web formed with the plurality of recessed portions and adjacent to the inner periphery of the rim,

[0023] At least a portion of each recessed portion that is present on the other side of the straight line extends to the outer periphery of the web that is connected to or opposed to the inner periphery of the rim.

[0024] [Method 6]

[0025] The gear according to any one of aspects 1 to 5, wherein, when the number of gate points is n, the plurality of recessed portions have an n-fold symmetrical shape when viewed from an end surface in the axial direction of the gear.

[0026] [Method 7]

[0027] The gear according to any one of aspects 1 to 6, wherein the plurality of recessed portions have a shape that is symmetrical with respect to a center point of the axial end surface.

[0028] [Method 8]

[0029] The gear according to any one of aspects 1 to 7, wherein the number of recesses included in the plurality of recesses is a multiple of the number of gate points.

[0030] [Method 9]

[0031] The gear as described in any one of Modes 1 to 8, wherein the filler is a fibrous filler.

[0032] [Method 10]

[0033] The gear according to any one of aspects 1 to 9, wherein the resin is a polyarylene sulfide resin.

[0034] [Method 11]

[0035] A robot comprising the gear described in any one of aspects 1 to 10.

[0036] [Method 12]

[0037] A method for manufacturing a gear, comprising:

[0038] melting a resin containing a filler; and

[0039] In a mold cavity of a gear molding mold having a plurality of needle-shaped gates, a resin gear is molded by injecting molten resin from the plurality of needle-shaped gates. The mold has a plurality of protrusions, each of which extends from one side to the other side of a straight line extending radially outward from the corresponding needle-shaped gates of the mold, and each has an asymmetric shape relative to the straight line.

[0040] Effects of the Invention

[0041] According to the present disclosure, a gear that is less susceptible to local deformation or stress can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a perspective view of a gear according to an embodiment of the present disclosure.

[0043] Figure 2 is an annotated top view of a gear of an embodiment of the present disclosure.

[0044] Figure 3 is a bottom view of a gear according to an embodiment of the present disclosure.

[0045] Figure 4 It is a perspective view of a gear molding die according to an embodiment of the present disclosure.

[0046] Figure 5 This is another perspective view of the gear molding die according to the embodiment of the present disclosure.

[0047] Figure 6 It is an annotated top view of a gear molding die according to an embodiment of the present disclosure.

[0048] Figure 7 Detailed description of the invention is given in conjunction with a flowchart of a gear manufacturing method according to an embodiment of the present disclosure.

[0049] Figure 8 It is a graph showing the dimensional accuracy evaluation results of Comparative Example 1 and Example 1.

[0050] Fig. 9 It is a graph showing the durability test results of Comparative Example 1 and Example 1.

[0051] Fig.10 It is a figure which shows the welding state of Comparative Example 1.

[0052] Fig.11 This is a diagram showing the welding state of Example 1. DETAILED DESCRIPTION

[0053] Hereinafter, one embodiment of the present disclosure will be described with reference to the drawings.

[0054] In each figure, the same or corresponding parts are denoted by the same reference numerals. In the description of the present embodiment, the description of the same or corresponding parts will be omitted or simplified as appropriate.

[0055] Reference Figures 1 to 3 , the structure of the gear 10 of this embodiment is described.

[0056] In each figure, the plane parallel to the top and bottom of the gear 10 is taken as the XY plane, and the axis parallel to the central axis of the gear 10 is taken as the Z axis. Figure 2 and Figure 3 The surfaces shown are respectively the upper surface and the bottom surface, but may be viewed as the bottom surface and the upper surface conversely, or may be viewed as the side surface and the opposite side surface.

[0057] The gear 10 is formed of a resin containing a filler. As the resin, any resin can be used, but in this embodiment, a polyarylene sulfide (PAS) resin such as a polyphenylene sulfide (PPS) resin is used. Anisotropy is imparted to the resin by adding a filler. As the filler, any filler can be used, but in this embodiment, a fibrous filler such as glass fiber or carbon fiber is used.

[0058] The gear 10 has a plurality of recesses. Each recess is formed on the axial end face 11 of the gear 10. When a plurality of points on the axial end face 11 corresponding one-to-one to a plurality of pin gates for injecting resin when the gear 10 is molded are respectively set as gate points, each recess extends from one side of a straight line extending radially outward from the corresponding gate point to the other side, and has an asymmetric shape relative to the straight line. The number of recesses can be any number, but is preferably a multiple of the number of gate points, and in this embodiment, is the same number as the number of gate points. In this embodiment, since the number of gate points is 4, the number of recesses is also 4. That is, the gear 10 has 4 recesses 20A, 20B, 20C, and 20D as a plurality of recesses.

[0059] like Figure 2 As shown, the recess 20A extends from the corresponding gate point PA to the other side of the straight line LA extending radially outward from the gear 10, and has an asymmetric shape with respect to the straight line LA. Similarly, the recess 20B extends from the corresponding gate point PB to the other side of the straight line LB extending radially outward from the gear 10, and has an asymmetric shape with respect to the straight line LB. Similarly, the recess 20C extends from the corresponding gate point PC to the other side of the straight line LC extending radially outward from the gear 10, and has an asymmetric shape with respect to the straight line LC. Similarly, the recess 20D extends from the corresponding gate point PD to the other side of the straight line LD extending radially outward from the gear 10, and has an asymmetric shape with respect to the straight line LD.

[0060] According to such a configuration, when the gear 10 is molded, the speed of movement of the resin injected from the plurality of pin-shaped gates toward the radially outer side is different on one side and the other side of a straight line extending from the gate point corresponding to each pin-shaped gate toward the radially outer side of the gear 10. As a result, the orientation of the filler contained in the resin is inconsistent and disordered in the radial direction, so that local deformation or stress is less likely to occur, the dimensional accuracy and strength are improved, and the performance of the gear 10 is improved.

[0061] The gear 10 may be any type of gear, but in this embodiment, it is a spur gear, and includes an annular rim 12, a web 13 adjacent to the inner periphery of the rim 12, and a cylindrical hub 14 connected to the rim 12 via the web 13. A plurality of teeth 15 are formed in the rim 12. Four recesses 20A, 20B, 20C, and 20D are formed as a plurality of recesses in the web 13. A shaft hole 16 for mounting a shaft is formed in the hub 14.

[0062] like Figure 3As shown, the axial end face 17 on the opposite side of the axial end face 11 of the gear 10 does not have a recess formed on the axial end face 11, but as a variation of the present embodiment, multiple recesses similar to the recesses 20A, 20B, 20C, and 20D may be formed on the axial end face 17.

[0063] The gear 10 can be applied to a gear for a robot, for example. That is, according to the present embodiment, a robot including the gear 10 can be provided.

[0064] Reference Figures 4 to 6 , the structure of the gear forming die 30 of this embodiment is described.

[0065] The mold 30 may be a two-plate mold composed of a fixed side plate and a movable side plate, but in the present embodiment, it is a three-plate mold composed of a combination of a middle plate in addition to the fixed side plate and the movable side plate. Figure 4 This is a diagram showing a fixed side plate of the mold 30 as viewed obliquely from the side opposite to the side where the cavity 33 is formed. Figure 5 This is a diagram of the fixed side plate of the mold 30 viewed obliquely from the side forming the mold cavity 33. Figures 4 to 6 In the figure, a part of the mold 30 is omitted or simplified.

[0066] In the mold 30, a plurality of runners and a plurality of pin gates are formed. The number of runners and the number of pin gates can be any number, but in this embodiment, they are four. That is, in the mold 30, four runners 31A, 31B, 31C, and 31D are formed as a plurality of runners, and four pin gates 32A, 32B, 32C, and 32D are formed as a plurality of pin gates. The runners 31A, 31B, 31C, and 31D are connected to the pin gates 32A, 32B, 32C, and 32D, respectively.

[0067] The mold 30 has a plurality of protrusions for forming a plurality of recesses in the gear 10. Each protrusion extends from one side of a straight line extending radially outward from the corresponding needle gate to the other side of the mold 30, and has an asymmetric shape relative to the straight line. The number of protrusions can be any number, but is preferably a multiple of the number of needle gates, and in the present embodiment, is the same number as the number of needle gates. In the present embodiment, since the number of needle gates is 4, the number of protrusions is also 4. That is, the mold 30 has four protrusions 40A, 40B, 40C, and 40D as a plurality of protrusions. When the gear 10 is molded, recesses 20A, 20B, 20C, and 20D are formed in the gear 10 by the protrusions 40A, 40B, 40C, and 40D, respectively.

[0068] like Figure 6As shown, the convex portion 40A extends from one side of the straight line MA extending radially outward from the corresponding pin-shaped gate 32A to the other side of the mold 30, and has an asymmetric shape with respect to the straight line MA. Similarly, the convex portion 40B extends from one side of the straight line MB extending radially outward from the corresponding pin-shaped gate 32B to the other side of the mold 30, and has an asymmetric shape with respect to the straight line MB. Similarly, the convex portion 40C extends from one side of the straight line MC extending radially outward from the corresponding pin-shaped gate 32C to the mold 30 to the other side, and has an asymmetric shape with respect to the straight line MC. Similarly, the convex portion 40D extends from one side of the straight line MD extending radially outward from the corresponding pin-shaped gate 32D to the mold 30 to the other side, and has an asymmetric shape with respect to the straight line MD.

[0069] With such a configuration, when the gear 10 is molded, the speed of movement of the resin injected from the plurality of pin-shaped gates toward the radially outer side is different on one side and the other side of the straight line extending from each pin-shaped gate toward the radially outer side of the mold 30. As a result, the orientation of the filler contained in the resin is not uniform and is disordered in the radial direction, so that local deformation or stress is less likely to occur, and the dimensional accuracy and strength are improved, thereby improving the performance of the gear 10.

[0070] Main reference Figure 2 and Figure 6 , details of the recessed portions 20A, 20B, 20C, and 20D of the gear 10 will be described.

[0071] The recessed portions 20A, 20B, 20C, and 20D are respectively arranged near the gate points PA, PB, PC, and PD and at positions radially outward from the gate points PA, PB, PC, and PD. Therefore, when the gear 10 is molded, the convex portions 40A, 40B, 40C, and 40D of the mold 30 corresponding to the recessed portions 20A, 20B, 20C, and 20D can change the flow direction of the resin near the needle gates 32A, 32B, 32C, and 32D, respectively, to prevent the fibers from being linearly oriented in the radial direction.

[0072] The first portion 21A, which is a portion of the recess 20A existing at least on one side of the straight line LA, has a shape in which the width of the gear 10 in the radial direction increases from the first end 23A existing on one side of the straight line LA to the second end 24A existing on the other side of the straight line LA, of the two ends of the recess 20A in the circumferential direction of the gear 10. The first portion 21B, which is a portion of the recess 20B existing at least on one side of the straight line LB, the first portion 21C, which is a portion of the recess 20C existing at least on one side of the straight line LC, and the first portion 21D, which is a portion of the recess 20D existing at least on one side of the straight line LD, also have the same shape. Of course, the portions of the convex portions 40A, 40B, 40C, 40D of the mold 30 corresponding to the first portions 21A, 21B, 21C, 21D have shapes corresponding to the shapes of the first portions 21A, 21B, 21C, 21D, respectively. That is, the portion of the convex portion 40A existing at least on one side of the straight line MA has a shape in which the width of the mold 30 in the radial direction increases from the circumferential direction end 43A of the convex portion 40A existing on one side of the straight line MA toward the circumferential direction end 44A existing on the other side of the straight line MA. The portion of the convex portion 40B existing at least on one side of the straight line MB, the portion of the convex portion 40C existing at least on one side of the straight line MC, and the portion of the convex portion 40D existing at least on one side of the straight line MD also have the same shape.

[0073] With such a configuration, when the gear 10 is molded, the speed of movement of the resin injected from the plurality of pin gates toward the radially outer side differs according to the circumferential position of the gear 10, at least on the side of the straight line extending from the gate point corresponding to each pin gate toward the radially outer side of the gear 10. For example, on the side of at least the straight line corresponding to the straight line LA in the cavity 33 of the mold 30, that is, the straight line MA extending toward the radially outer side from the pin gate 32A, the movement of the resin injected from the pin gate 32A toward the radially outer side is delayed by the convex portion 40A as the position is farther from the circumferential end 43A of the convex portion 40A of the mold 30 corresponding to the first end 23A of the concave portion 20A. As a result, it becomes increasingly difficult for the orientation of the filler contained in the resin to be uniform in the radial direction, and thus it becomes more difficult for local deformation or stress to occur.

[0074] In the present embodiment, the second portion 22A, which is the portion of the recess 20A existing on the other side of the straight line LA, also has a shape in which the width of the gear 10 in the radial direction increases from the first end 23A to the second end 24A of the recess 20A only in a partial region adjacent to the first portion 21A. The second portion 22B, which is the portion of the recess 20B existing on the other side of the straight line LB, the second portion 22C, which is the portion of the recess 20C existing on the other side of the straight line LC, and the second portion 22D, which is the portion of the recess 20D existing on the other side of the straight line LD, also have the same shape. Of course, the portions of the convex portions 40A, 40B, 40C, 40D of the mold 30 corresponding to the second portions 22A, 22B, 22C, 22D have shapes corresponding to the shapes of the second portions 22A, 22B, 22C, 22D, respectively. That is, the portion of the convex portion 40A existing on the other side of the straight line MA also has a shape in which the width in the radial direction of the mold 30 increases from the circumferential end 43A of the convex portion 40A to the circumferential end 44A only in a partial region adjacent to the portion existing on one side of the straight line MA. The portion of the convex portion 40B existing on the other side of the straight line MB, the portion of the convex portion 40C existing on the other side of the straight line MC, and the portion of the convex portion 40D existing on the other side of the straight line MD also have the same shape.

[0075] With such a configuration, when the gear 10 is molded, the speed of movement of the resin injected from the plurality of pin gates toward the radially outer side also partially differs depending on the circumferential position of the gear 10 on the other side of the straight line extending from the gate point corresponding to each pin gate toward the radially outer side of the gear 10. For example, on the other side of the straight line MA extending toward the radially outer side from the pin gate 32A at least corresponding to the straight line LA in the cavity 33 of the mold 30, the movement of the resin injected from the pin gate 32A toward the radially outer side is partially delayed by the convex portion 40A at a position farther from the circumferential end 43A of the convex portion 40A of the mold 30 corresponding to the first end 23A of the concave portion 20A. As a result, it becomes increasingly difficult for the orientation of the filler contained in the resin to be uniform in the radial direction, and thus it becomes more difficult for local deformation or stress to occur.

[0076] When the gear 10 is viewed from the axial end face, the first end 23A of the recess 20A is formed into an acute angle. Figure 2 The axial end face 11 is viewed along the axial direction of the gear 10. For example, the recess 20A is formed into a polygon such as a triangle with at least one vertex being an acute angle. Figure 2 As shown in FIG. 1 , it is preferred that one or more sides of the polygon be curved convexly outward in the radial direction. The recessed portions 20B, 20C, and 20D are also similar to the recessed portion 20A.

[0077] In the present embodiment, the second end 24A of the recess 20A is also formed into an acute angle when viewed from the end face in the axial direction of the gear 10. For example, the recess 20A is formed into a polygon such as a triangle with at least two vertices being acute angles. The recesses 20B, 20C, and 20D are also formed in the same manner as the recess 20A.

[0078] Since the resin flows easily in a large flow path, setting a large curved flow path is more effective than setting a plurality of small curved flow paths. In this embodiment, each recess is formed into a polygon with at least one, preferably at least two, vertices being acute angles, and the arrangement is as follows: Figure 2 The large curved flow path shown enables the resin to easily flow in the desired direction.

[0079] At least the second portion 22A of the recess 20A, at least the second portion 22B of the recess 20B, at least the second portion 22C of the recess 20C, and at least the second portion 22D of the recess 20D extend to the outer periphery of the web 13 connected to the inner periphery of the rim 12. In the present embodiment, since each recess continuously extends in the radial direction from the vicinity of the corresponding gate point to the vicinity of the tooth tip, the area of ​​the web 13 can be effectively utilized, and the recess area for obtaining the desired fiber orientation can be ensured. In the present embodiment, the rim 12 and the web 13 are connected without a gap, but, for example, there may be a gap between the rim 12 and the web 13. In such a modified example, at least the second portion 22A of the recess 20A, at least the second portion 22B of the recess 20B, at least the second portion 22C of the recess 20C, and at least the second portion 22D of the recess 20D may extend from the inner periphery of the rim 12 to the outer periphery of the web 13 opposite to each other through the gap.

[0080] When the number of gate points is n, the recesses 20A, 20B, 20C, and 20D have an n-fold symmetric shape as a whole when viewed from the end face in the axial direction of the gear 10. That is, the recesses 20A, 20B, 20C, and 20D have a rotational symmetry of 360° / number of gates as a whole. In the present embodiment, since the number of gate points is 4, the shapes of the recesses 20A, 20B, 20C, and 20D when viewed along the axial direction of the gear 10 are 4-fold symmetric. For example, the number of gate points may be 3, and in such a modified example, a plurality of recesses may be formed in a manner that is 3-fold symmetric.

[0081] The recesses 20A, 20B, 20C, and 20D as a whole have a shape that is point-symmetrical with respect to the center CT of the axial end face 11. For example, the recesses 20A, 20B, 20C, and 20D as a whole are formed in a windmill shape. Therefore, when the gear 10 is molded, the protrusions 40A, 40B, 40C, and 40D of the mold 30 corresponding to the recesses 20A, 20B, 20C, and 20D become easy to bend the flow direction of the resin. By bending the flow direction of the resin, the pressure of the resin in the flow becomes uneven. As a result, even if a special molding method for controlling the fiber orientation is not adopted, the fiber orientation can be disturbed.

[0082] The large flow path shape has a great influence on the warpage deformation, and the symmetry of the warpage deformation becomes important in a rotating body such as the gear 10. For the symmetry of the warpage deformation, if the large curved flow path is set symmetrically with respect to the gate, the fibers are aligned at the confluence of the flow path, thereby offsetting the effect of the curved flow path disturbing the fiber orientation. In this embodiment, although it is asymmetrical with respect to the gate, if the number of gates is set to n, it is n-fold symmetric. More specifically, by forming a flow path that is point-symmetrical with respect to the center CT, the symmetry of the warpage deformation can be improved. As a result, the roundness of the gear 10 is improved.

[0083] Reference Figure 7 , describing the gear manufacturing method of this embodiment.

[0084] First, step S1 of melting the resin containing the filler is performed. As a method for melting the resin, a known method can be used.

[0085] Next, step S2 is performed to inject the molten resin into the cavity 33 of the mold 30 through the plurality of runners from the plurality of needle gates to form the resin gear 10. As a method for injecting the resin into the cavity 33 of the mold 30 to form the gear 10, the same method as the known method of injecting the resin into the cavity of the mold to form a known gear can be used.

[0086] In the present embodiment, a resin containing a filler is used to mold the gear 10. Therefore, the gear 10 of the present embodiment corresponds to a molded product of the resin containing a filler, and the gear manufacturing method of the present embodiment corresponds to a manufacturing method of the molded product.

[0087] The resin used in the present embodiment is preferably a thermoplastic resin. The thermoplastic resin is not particularly limited, but examples thereof include polyolefin resins such as polypropylene, polyethylene, and polybutene; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyamide resins or aromatic polyamide resins such as nylon-6 or nylon 6,6; thermoplastic polyimide resins; polyamide-imide resins; polystyrene resins such as polystyrene, syndiotactic polystyrene, acrylonitrile-styrene copolymer resins, or acrylonitrile-butadiene-styrene copolymer resins; polyarylene sulfide resins such as polyphenylene sulfide; polyphenylene ether resins; polyurethane resins; polylactic acid; polyetheretherketone resins; polyetherimide resins; polyketone resins; polyarylate resins such as amorphous polyarylate or liquid crystalline polyarylate; liquid crystal polyester resins, etc.

[0088] Among them, as the thermoplastic resin that can be used in the present embodiment, thermoplastic polyimide resins, polyamide-imide resins, polyarylene sulfide resins, polyphenylene ether resins, polyetheretherketone resins, polyetherimide resins, polyketone resins, polyarylene ester resins and liquid crystalline polyester resins, which are so-called engineering plastics or super engineering plastics excellent in heat resistance and mechanical properties, are preferred. From the viewpoints of chemical resistance, heat resistance and mechanical properties, polyarylene sulfide resins are more preferred, and among polyarylene sulfide resins (hereinafter also referred to as "PAS resin"), polyphenylene sulfide (hereinafter also referred to as "PPS resin") resins are particularly preferred.

[0089] In the present embodiment, the above-mentioned resin can also be used alone, or can also be used in the form of a polymer alloy (Polymer Alloy) mixed with a plurality of the above-mentioned resins. In addition, the resin containing filler in the present embodiment can be in the form of a composition containing any of the following added components (colorant, antistatic agent, antioxidant, heat stabilizer, ultraviolet stabilizer, ultraviolet absorber, foaming agent, flame retardant, flame retardant aid, rust inhibitor, coupling agent, silane coupling agent, thermoplastic elastomer or synthetic resin) as needed as long as it contains the filler and the above-mentioned resin described later.

[0090] The polyarylene sulfide resin has a resin structure having a structure in which an aromatic ring and a sulfur atom are bonded as a repeating unit, and specifically, a resin having a structural part represented by the following general formula (1) and, if necessary, a trifunctional structural part represented by the following general formula (2) as repeating units.

[0091]

[0092] In formula (1), R 1 and R 2 Each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a nitro group, an amino group, a phenyl group, a methoxy group, or an ethoxy group.

[0093]

[0094] The trifunctional structural part represented by formula (2) is preferably in the range of 0.001 to 3 mol %, particularly preferably in the range of 0.01 to 1 mol %, based on the total molar number of other structural parts.

[0095] Here, from the viewpoint of the mechanical strength of the PAS resin, the structural part represented by the general formula (1), especially R in the formula 1 and R 2 It is preferably a hydrogen atom, and in this case, examples thereof include a structural part bonded at the para position as represented by the following formula (3) and a structural part bonded at the meta position as represented by the following formula (4).

[0096]

[0097] Among them, from the viewpoint of heat resistance and crystallinity of the PAS resin, the sulfur atom and the aromatic ring in the repeating unit are preferably bonded at the para position as represented by the general formula (3).

[0098] The PAS resin may contain not only the structural part represented by the general formula (1) or (2) but also structural parts represented by the following structural formulas (5) to (8) in an amount of 30 mol% or less of the total of the structural parts represented by the general formula (1) and (2).

[0099]

[0100] In particular, in the present embodiment, from the viewpoint of heat resistance and mechanical strength of the PAS resin, the structural parts represented by the general formulae (5) to (8) are preferably 10 mol% or less. When the PAS resin contains the structural parts represented by the general formulae (5) to (8), the combination thereof may be any of a random copolymer and a block copolymer.

[0101] The PAS resin may have a naphthyl sulfide bond or the like in its molecular structure, but the amount thereof is preferably 3 mol% or less, particularly preferably 1 mol% or less, based on the total molar number of other structural parts.

[0102] In addition, the physical properties of the PAS resin are not particularly limited as long as the effects of the present embodiment are not impaired, but are as follows.

[0103] (Melt viscosity)

[0104] The melt viscosity of the PAS resin is not particularly limited, but in view of a good balance between fluidity and mechanical strength, the melt viscosity (V6) measured at 300°C is preferably in the range of 2 Pa·s or more, preferably in the range of 1000 Pa·s or less, more preferably in the range of 500 Pa·s or less, and further preferably in the range of 200 Pa·s or less. The melt viscosity (V6) is measured by using a flow tester CFT-500D manufactured by Shimadzu Corporation for the polyarylene sulfide resin at 300°C and a load of 1.96×10 6 Pa, L / D = 10 (mm) / 1 (mm) after 6 minutes of holding. This is the measured value of the melt viscosity.

[0105] (Non-Newtonian index)

[0106] The non-Newtonian index of the PAS resin is not particularly limited, but is preferably in the range of 0.90 to 2.00. In the case of using a linear polyarylene sulfide resin, the non-Newtonian index is preferably in the range of 0.90 or more, more preferably in the range of 0.95 or more, and preferably in the range of 1.50 or less, more preferably in the range of 1.20 or less. Such polyarylene sulfide resins have excellent mechanical properties, fluidity, and wear resistance. Among them, in the present embodiment, the non-Newtonian index (N value) is a value calculated using the following formula by measuring the shear rate (SR) and shear stress (SS) using a capillary rheometer (Capillograph) under the conditions of melting point + 20°C, ratio of pore length (L) to pore diameter (D), L / D = 40. The closer the non-Newtonian index (N value) is to 1, the closer it is to a linear structure, and the higher the non-Newtonian index (N value), the more advanced the branching structure.

[0107] SR=K·SS N

[0108] Where SR is the shear rate (seconds-1), SS is the shear stress (dynes / cm 2 ), and K represents a constant.

[0109] As fillers, well-known and commonly used materials can also be used as long as the effects of the present embodiment are not impaired, for example, fibrous fillers, or fillers of various shapes such as granular or plate-like non-fibrous fillers, etc. can be listed. Specifically, fibrous fillers such as glass fiber, carbon fiber, silane glass fiber, ceramic fiber, polyaramid fiber, metal fiber, potassium titanate, silicon carbide, calcium silicate, wollastonite, and natural fiber can be used, and non-fibrous fillers such as glass beads, glass fragments, barium sulfate, clay, pyrophyllite, bentonite, sericite, mica, mica, talc, attapulgite, ferrite, calcium silicate, calcium carbonate, glass beads, zeolite, milled fiber, and calcium sulfate can also be used.

[0110] In the present embodiment, the content of the filler is not particularly limited as long as it does not damage the effect of the present embodiment. As the amount of the filler, for example, relative to 100 parts by mass of the resin, it is preferably 1 part by mass or more, more preferably 10 parts by mass or more, and preferably 600 parts by mass or less, more preferably 200 parts by mass or less. Within this range, the resin shows good mechanical strength and moldability, so it is preferred.

[0111] The resin used in the present embodiment may be combined with a silane coupling agent as an optional component as needed. As a silane coupling agent, there is no particular limitation as long as the effect of the present embodiment is not impaired, but as a preferred silane coupling agent, a silane coupling agent having a functional group that reacts with a carboxyl group, such as an epoxy group, an isocyanate group, an amino group or a hydroxyl group can be listed. As such a silane coupling agent, for example, alkoxysilane compounds containing epoxy groups such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane can be listed; γ-isocyanatopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, γ-isocyanatopropylmethyldimethoxysilane, γ-isocyanatopropylmethyldiethoxysilane, γ-isocyanatopropylethyldimethoxysilane can be listed. Alkoxysilane compounds containing isocyanate groups such as γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, etc.; Alkoxysilane compounds containing amino groups such as γ-hydroxypropyltrimethoxysilane, γ-hydroxypropyltriethoxysilane, etc. Alkoxysilane compounds containing hydroxy groups such as γ-hydroxypropyltrimethoxysilane and γ-hydroxypropyltriethoxysilane. In this embodiment, the silane coupling agent is not an essential component, but when it is matched, its amount is not particularly limited as long as it does not damage the effect of this embodiment, but relative to 100 parts by mass of the resin, it is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less. Within this range, the resin has good corona resistance and moldability, especially demoulding, and the molded product has excellent bonding with the epoxy resin, and the mechanical strength is further improved, so it is preferred.

[0112] In the resin used in the present embodiment, a thermoplastic elastomer can be optionally contained as an arbitrary component. As a thermoplastic elastomer, polyolefin elastomer, fluorine elastomer or silicone elastomer can be listed, wherein, as a preferred thermoplastic elastomer, a polyolefin elastomer can be listed. In the case of adding these elastomers, the amount thereof is not particularly limited as long as it does not damage the effect of the present embodiment, but relative to 100 parts by mass of resin (A), preferably more than 0.01 parts by mass, more preferably more than 0.1 parts by mass, and preferably less than 10 parts by mass, more preferably less than 5 parts by mass. Within this range, the impact resistance of the resulting resin is improved, so it is preferred.

[0113] For example, the polyolefin elastomer may include a homopolymer of α-olefin, a copolymer of two or more α-olefins, or a copolymer of one or more α-olefins and an ethylene-based polymerizable compound having a functional group. In this case, the α-olefin may include ethylene, propylene, 1-butene, and other α-olefins having a carbon number ranging from 2 to 8. In addition, the functional group may include a carboxyl group, an acid anhydride group (-C(=O)OC(=O)-), an epoxy group, an amino group, a hydroxyl group, a mercapto group, an isocyanate group, an oxazoline group, and the like. Furthermore, examples of the above-mentioned ethylene-based polymerizable compounds having a functional group include vinyl acetate; α,β-unsaturated carboxylic acids such as (meth) acrylic acid; alkyl esters of α,β-unsaturated carboxylic acids such as methyl acrylate, ethyl acrylate, and butyl acrylate; metal salts of α,β-unsaturated carboxylic acids such as ionomers (metals are alkali metals such as sodium, alkaline earth metals such as calcium, and zinc); glycidyl esters of α,β-unsaturated carboxylic acids such as glycidyl methacrylate; α,β-unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; and derivatives (monoesters, diesters, and anhydrides) of the above-mentioned α,β-unsaturated dicarboxylic acids, and one or more thereof. The above-mentioned thermoplastic elastomers may be used alone or in combination of two or more thereof.

[0114] Furthermore, in the resin used in the present embodiment, in addition to the above-mentioned components, polyester resin, polyamide resin, polyimide resin, polyetherimide resin, polycarbonate resin, polyphenylene ether resin, polysulfone resin, polyethersulfone resin, polyetheretherketone resin, polyetherketone resin, polyarylene resin, polyethylene resin, polypropylene resin, polytetrafluoroethylene resin, polyvinylidene fluoride resin, polystyrene resin, ABS resin, phenol resin, carbamate resin, liquid crystal polymer and other synthetic resins (hereinafter referred to as synthetic resins) can be further appropriately mixed as an arbitrary component according to the purpose. In the present embodiment, the above-mentioned synthetic resin is not an essential component, but when mixed, the mixing ratio thereof is not particularly limited as long as it does not damage the effect of the present embodiment. In addition, it is different according to each purpose and cannot be generally specified, but as the ratio of the synthetic resin mixed in the resin of the present embodiment, for example, relative to 100 parts by mass of the resin, the range of 5 parts by mass or more and the range of 15 parts by mass or less can be listed. In other words, the ratio of the resin (A) to the total of the resin (A) and the synthetic resin is preferably in the range of (100 / 115) or more, and more preferably in the range of (100 / 105) or more, based on mass.

[0115] In addition, the resin used in the present embodiment may also contain, as required, well-known conventional additives such as colorant, antistatic agent, antioxidant, heat stabilizer, UV stabilizer, UV absorber, foaming agent, flame retardant, flame retardant aid, rust inhibitor and coupling agent as arbitrary components. These additives are not essential components, for example, relative to 100 parts by mass of resin, preferably in the range of 0.01 parts by mass or more, preferably in the range of 1000 parts by mass or less, and can be used according to purpose or use to suitably adjust without damaging the effect of the present embodiment.

[0116] The method for producing the resin used in the present embodiment will be described in detail below.

[0117] The resin used in the present embodiment is formed by matching each essential component and other optional components as needed. There is no particular limitation on the method for manufacturing the resin used in the present embodiment, and examples include a method of matching the essential components and optional components and performing melt kneading, and more specifically, a method of uniformly performing dry mixing with a tumbler or Henschel mixer as needed, and then putting it into a twin-screw extruder and performing melt kneading.

[0118] Melt kneading can be carried out by heating the resin temperature to a temperature range above the melting point of the resin, preferably a temperature range above the melting point + 10°C, more preferably above the melting point + 10°C, further preferably above the melting point + 20°C, and preferably below the melting point + 100°C, more preferably below the melting point + 50°C.

[0119] As the above-mentioned melt kneader, from the viewpoint of dispersibility or productivity, a twin-screw kneading extruder is preferred. For example, it is preferred to perform melt kneading while appropriately adjusting the discharge amount of the resin component in the range of 5 to 500 (kg / hr) and the screw rotation number in the range of 50 to 500 (rpm). It is further preferred to perform melt kneading under the condition that their ratio (discharge amount / screw rotation number) is in the range of 0.02 to 5 (kg / hr / rpm). In addition, the addition and mixing of each component to the melt kneader can be carried out simultaneously or separately. For example, when adding additives to the above-mentioned components, it is preferred to feed the extruder from the side feeder of the above-mentioned twin-screw kneading extruder from the viewpoint of dispersibility. Regarding the position of the side feeder, the ratio of the distance from the extruder resin input part (top feeder) to the side feeder to the total length of the screw of the twin-screw kneading extruder is preferably 0.1 or more, more preferably 0.3 or more. In addition, the ratio is preferably 0.9 or less, more preferably 0.7 or less.

[0120] The resin of the present embodiment obtained by melt kneading in this way is a molten mixture containing the above-mentioned essential components and optional components added as needed and components derived from them. After the melt kneading, it is preferably subjected to preliminary drying at a temperature range of 100 to 150° C. by a known method, such as extruding the molten resin into a strand shape, processing it into the form of pellets, chips, granules, powder, etc., as needed.

[0121] The molded product of this embodiment is formed by molding a resin. In addition, the method for manufacturing the molded product of this embodiment includes the step of melt-molding the above-mentioned resin.

[0122] The resin used in this embodiment can be used for injection molding. There is no particular limitation on the various molding conditions, and molding can be performed by common methods. For example, in an injection molding machine, the resin temperature is in a temperature range above the melting point of the resin, preferably in a temperature range above the melting point + 10°C, more preferably in a temperature range of melting point + 10°C to melting point + 100°C, and further preferably in a temperature range of melting point + 20 to melting point + 50°C. After the step of melting the above resin, it can be injected into the mold from the resin discharge port for molding. At this time, the mold temperature can be set in a known temperature range, such as room temperature (23°C) to 300°C, preferably 120 to 180°C.

[0123] Hereinafter, the gear 10 of the present embodiment is actually manufactured as Example 1, and a gear not having a plurality of recessed portions like the gear 10 of the present embodiment is manufactured as Comparative Example 1, and the results of dimensional accuracy evaluation and durability test of each of Example 1 and Comparative Example 1 are described.

[0124] Comparative Example 1 and Example 1 are both spur gears formed of a resin containing 15 wt% of a fibrous filler. The dimensional accuracy of Comparative Example 1 and Example 1 was evaluated. The results are as follows: Figure 8 As shown, it can be confirmed that in Comparative Example 1, bulging deformation due to welding is observed at 4 locations, whereas in Example 1, the deterioration of dimensional accuracy due to such deformation can be suppressed. Regarding the JGMA grade, the result of Comparative Example 1 is that 1 pitch meshing is grade 6 or above, and full tooth meshing is grade 5, whereas the result of Example 1 is that 1 pitch meshing is grade 5, and full tooth meshing is grade 3. "JGMA" is the abbreviation of Japan Gear Manufacturers Association.

[0125] Comparative Example 1 and Example 1 are both spur gears with a module of 1 mm and 31 teeth. For the durability test of Comparative Example 1 and Example 1, a pair of gears of the same material were used and the test was carried out under the conditions of a torque of 20 kgf·cm and a rotation speed of 1000 rpm. The results are as follows Fig. 9 As shown in the figure, the test was stopped after 2 hours in Comparative Example 1 due to thermal deformation of the tooth top, while the test in Example 1 was able to continue for more than 16 hours. This is believed to be because in Comparative Example 1, due to poor dimensional accuracy, a portion with excessive load was generated at the contact point between the gears, and this portion melted due to heat. If melting proceeds, the gears will not mesh with each other and will idle, so in the example Fig. 9 In the graph shown, the tooth surface temperature of Comparative Example 1 dropped sharply after 2 hours.

[0126] Fig.10 and Fig.11 The parts of Comparative Example 1 and Example 1 were observed with an optical microscope, and the images obtained were combined and processed into a picture showing the welding state. Fig.10 As shown, in Comparative Example 1, at 4 locations in the circumferential direction, the fiber orientation from the shaft hole to the tooth top is consistent and fusion occurs. Fig.11 As shown in the figure, in Example 1, the fiber orientation is not uniform as in Comparative Example 1, and "no welding (weldless)" is achieved. That is, in Example 1, by making the flow path from the gate into an asymmetric tornado shape, the welded junction is moved from the center, thereby achieving "no welding", thereby improving dimensional accuracy and durability time. By making the flow path shape into a wing shape and configuring the wing-shaped flow path to be rotationally symmetrical, the deterioration of true roundness accuracy caused by warping deformation is also suppressed.

[0127] The present disclosure is not limited to the above-described embodiments, and modifications may be made without departing from the spirit of the present disclosure.

[0128] Explanation of symbols

[0129] 10 Gears

[0130] 11,17 Axial end face

[0131] 12 Rim

[0132] 13. Belly Plate

[0133] 14 wheels

[0134] 15 teeth

[0135] 16 shaft holes

[0136] 20A, 20B, 20C, 20D concave part

[0137] 21A, 21B, 21C, 21D Part 1

[0138] 22A, 22B, 22C, 22D Part 2

[0139] 23A first end

[0140] 24A Second terminal

[0141] 30 molds

[0142] 31A, 31B, 31C, 31D runner

[0143] 32A, 32B, 32C, 32D needle gate

[0144] 33 Cavity

[0145] 40A, 40B, 40C, 40D convex part

[0146] 43A, 44A Circumferential end

Claims

1. A gear, formed of a resin containing a filler, the gear having a plurality of recessed portions, The plurality of recesses are formed on the axial end surface when a plurality of points on the axial end surface of the gear corresponding one-to-one to the plurality of needle gates are respectively set as gate points, and each of the recesses extends from one side to the other side of a straight line extending radially outward from the corresponding gate point to the gear, and each has an asymmetric shape with respect to the straight line, wherein: The plurality of pin gates are used to inject the resin when molding the gear.

2. The gear according to claim 1, wherein: At least a portion of each recess existing on one side of the straight line has a shape in which the radial width of the gear increases from a first end existing on one side of the straight line among the two ends of each recess in the circumferential direction of the gear toward a second end existing on the other side of the straight line.

3. The gear according to claim 2, wherein: The first end is formed into an acute angle shape when viewed from an end surface in the axial direction of the gear.

4. The gear according to claim 2, wherein: The second end is formed in an acute angle shape when viewed from an end surface in the axial direction of the gear.

5. The gear according to claim 1, comprising: an annular rim formed with a plurality of teeth, and a web formed with the plurality of recessed portions and adjacent to an inner periphery of the rim, At least a portion of each recessed portion that is present on the other side of the straight line extends to the outer periphery of the web that is connected to or opposed to the inner periphery of the rim.

6. The gear according to claim 1, wherein: When the number of gate points is n, the plurality of recessed portions have an n-fold symmetrical shape when viewed from an end surface in the axial direction of the gear.

7. The gear according to claim 1, wherein: The plurality of recessed portions have a shape that is point-symmetrical with respect to the center of the axial end surface.

8. The gear according to claim 1, wherein: The number of the recesses included in the plurality of recesses is a multiple of the number of the gate points.

9. The gear according to claim 1, wherein: The filler is a fibrous filler.

10. The gear according to claim 1, wherein: The resin is polyarylene sulfide resin.

11. A robot comprising the gear according to any one of claims 1 to 10.

12. A method for manufacturing a gear, comprising: Melting the resin containing the filler; as well as In a mold cavity of a gear molding mold having a plurality of needle-shaped gates, a resin gear is molded by injecting molten resin from the plurality of needle-shaped gates. The mold has a plurality of protrusions, each of which extends from one side to the other side of a straight line extending radially outward from the corresponding needle-shaped gates of the mold, and each has an asymmetric shape relative to the straight line.

Images