Gear, robot and method for manufacturing gear

Abstract

To provide a gear in which local deformation or stress is unlikely to occur.SOLUTION: A gear 10 formed of a resin containing a filler comprises a plurality of recess parts that are formed on an axial end surface 11, each of which corresponds one-to-one to a plurality of pin gates used to inject resin when molding the gear 10, and that, when each of a plurality of points on the axial end surface 11 of the gear 10 is a gate point, extend from one side to the other side of a straight line of the gear 10 extending radially outward from the corresponding gate point on the axial end surface 11, each of which has an asymmetric shape with respect to the straight line.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Patent Document 1 discloses a gear made of resin containing reinforcing fibers. This gear has a resin flow speed adjustment groove. According to Patent Document 1, when molding the gear, the radial outward flow speed of the resin injected from the pinpoint gate is controlled and made uniform by a resin flow speed adjustment groove protrusion that protrudes into the cavity to form the resin flow speed adjustment groove. As a result, the orientation of the reinforcing fibers in the resin is aligned in the radial direction over the entire circumference.

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

[0004] [Patent Document 1] JP 2004-358665 A [Patent Document 2] JP 2019-218994 A Summary of the Invention [Problem to be solved by the invention]

[0005] When fiber orientation is controlled by the gear shape rather than by the molding method, if the fiber orientation becomes locally aligned in the radial direction, local deformation and stress are likely to occur, which may result in reduced dimensional accuracy and strength.

[0006] An object of the present disclosure is to provide a gear that is less susceptible to localized deformation or stress. [Means for solving the problem]

[0007] Several aspects of the present disclosure are set forth below. [Aspect 1] A gear formed of a resin containing a filler, a gear having a plurality of recesses formed on an axial end face of the gear, the recesses extending from one side to the other side of a straight line extending radially outward of the gear from a plurality of points on the axial end face of the gear corresponding one-to-one to a plurality of pin gates used to inject the resin during molding of the gear, the recesses having shapes asymmetric with respect to the straight line. [Aspect 2] A gear of embodiment 1, wherein the portion of each recess that is on at least one side of the straight line has a shape in which the width in the radial direction of the gear increases from a first end that is on one side of the straight line to a second end that is on the other side of the straight line, among both ends of each recess in the circumferential direction of the gear. [Aspect 3] The gear according to aspect 2, wherein the first end is formed at an acute angle when viewed from an end surface in the axial direction of the gear. [Aspect 4] The gear according to aspect 2 or 3, wherein the second end is formed at an acute angle when viewed from an end surface in an axial direction of the gear. [Aspect 5] an annular rim having a plurality of teeth formed thereon; A web adjacent to an inner periphery of the rim, the web having the plurality of recesses formed therein; Equipped with A gear according to any one of aspects 1 to 4, wherein at least a portion of each recess on the other side of the straight line extends to an outer periphery of the web that is connected to or faces an inner periphery of the rim. [Aspect 6] A gear according to any one of Aspects 1 to 5, wherein the plurality of recesses have an n-fold symmetric shape in an end view in the axial direction of the gear, where n is the number of gate points. [Aspect 7] The gear according to any one of the first to sixth aspects, wherein the plurality of recesses have shapes that are point-symmetric with respect to a center of the axial end face. [Aspect 8] 8. The gear of 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. [Aspect 9] The gear according to any one of the first to eighth aspects, wherein the filler is a fibrous filler. [Aspect 10] A gear according to any one of Aspects 1 to 9, wherein the resin is a polyarylene sulfide resin. [Aspect 11] A robot comprising the gear of any one of embodiments 1 to 10. [Aspect 12] Melting a resin containing a filler; A gear molding die having a plurality of pin gates formed therein, the die having a plurality of protrusions each having an asymmetric shape with respect to a straight line extending radially outward from the corresponding pin gate, the plurality of protrusions each having an asymmetric shape with respect to the straight line, and a resin gear is molded by injecting molten resin through the plurality of pin gates into a cavity of the die. A gear manufacturing method comprising: Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a gear in which local deformation or stress is unlikely to occur. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a gear according to an embodiment of the present disclosure. [Diagram 2] FIG. 1 is an annotated plan view of a gear according to an embodiment of the present disclosure. [Diagram 3] FIG. 13 is a bottom view of a gear according to an embodiment of the present disclosure. [Figure 4] FIG. 1 is a perspective view of a gear molding die according to an embodiment of the present disclosure. [Diagram 5]FIG. 13 is another perspective view of a gear molding die according to an embodiment of the present disclosure. [Figure 6] FIG. 1 is an annotated plan view of a gear molding die according to an embodiment of the present disclosure. [Figure 7] 1 is a flow chart illustrating a gear manufacturing method according to an embodiment of the present disclosure. [Figure 8] FIG. 1 is a diagram showing the results of evaluation of dimensional accuracy of Comparative Example 1 and Example 1. [Figure 9] 1 is a graph showing the results of durability tests of Comparative Example 1 and Example 1. [Figure 10] FIG. 1 is a diagram showing a weld state in Comparative Example 1. [Figure 11] FIG. 2 is a diagram showing a welded state in Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0011] In each drawing, the same or corresponding parts are denoted by the same reference numerals. In the description of this embodiment, the description of the same or corresponding parts will be omitted or simplified as appropriate.

[0012] The configuration of a gear 10 according to this embodiment will be described with reference to FIGS.

[0013] In each drawing, the planes parallel to the top and bottom faces of gear 10 are designated as the XY plane, and the axis parallel to the central axis of gear 10 is designated as the Z axis. For ease of explanation, the faces of gear 10 shown in Figs. 2 and 3 are designated as the top and bottom faces, respectively, but they may be regarded conversely as the bottom and top faces, or as the side and opposite side faces.

[0014] The gear 10 is formed of a resin containing a filler. Any resin may be used as the resin, but in this embodiment, a polyarylene sulfide (PAS) resin such as a polyphenylene sulfide (PPS) resin is used. The resin is given anisotropy by adding a filler. Any filler may be used as the filler, but in this embodiment, a fibrous filler such as glass fiber or carbon fiber is used.

[0015] The gear 10 has a plurality of recesses. Each recess is formed on an axial end surface 11 of the gear 10. When a plurality of points on the axial end surface 11, which correspond one-to-one to a plurality of pin gates used to inject resin when molding the gear 10, are taken as gate points, each recess extends from one side of a line extending radially outward of the gear 10 from the corresponding gate point to the other side, and has an asymmetric shape with respect to the line. The number of recesses may be any number, but is preferably a multiple of the number of gate points, and is the same as the number of gate points in this embodiment. In this embodiment, the number of gate points is four, so the number of recesses is also four. That is, the gear 10 has four recesses 20A, 20B, 20C, and 20D as a plurality of recesses.

[0016] As shown in FIG. 2, the recess 20A extends from one side to the other side of a straight line LA extending from the corresponding gate point PA to the radially outward side of the gear 10, and has an asymmetric shape with respect to the straight line LA. Similarly, the recess 20B extends from one side to the other side of a straight line LB extending from the corresponding gate point PB to the radially outward side of the gear 10, and has an asymmetric shape with respect to the straight line LB. Similarly, the recess 20C extends from one side to the other side of a straight line LC extending from the corresponding gate point PC to the radially outward side of the gear 10, and has an asymmetric shape with respect to the straight line LC. Similarly, the recess 20D extends from one side to the other side of a straight line LD extending from the corresponding gate point PD to the radially outward side of the gear 10, and has an asymmetric shape with respect to the straight line LD.

[0017] With this configuration, when molding the gear 10, the speed at which the resin injected from the multiple pin gates moves radially outward differs between one side and the other side of a line extending from the gate points corresponding to each pin gate to the radially outward side of the gear 10. As a result, the orientation of the filler contained in the resin is not uniform in the radial direction and is disturbed, making it difficult for local deformation or stress to occur, improving the dimensional accuracy and strength, and ultimately improving the performance of the gear 10.

[0018] 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 circumference of the rim 12, and a cylindrical hub 14 connected to the rim 12 by the web 13. The rim 12 is formed with a plurality of teeth 15. The web 13 is formed with a plurality of recesses, four recesses 20A, 20B, 20C, and 20D. The hub 14 is formed with a shaft hole 16 for mounting a shaft.

[0019] As shown in FIG. 3, the axial end face 17 opposite the axial end face 11 of the gear 10 does not have any recesses formed therein like those formed in the axial end face 11. However, as a modified example of this embodiment, the axial end face 17 may also have a plurality of recesses similar to the recesses 20A, 20B, 20C, and 20D formed therein.

[0020] The gear 10 can be applied to, for example, a gear for a robot. That is, according to the present embodiment, a robot including the gear 10 can be provided.

[0021] The configuration of a gear molding die 30 according to this embodiment will be described with reference to FIGS.

[0022] The mold 30 may be a two-plate mold formed by combining a fixed-side plate and a movable-side plate, but in this embodiment, it is a three-plate mold formed by combining a fixed-side plate, a movable-side plate, and an intermediate plate. Fig. 4 is a view of the fixed-side plate of the mold 30 viewed obliquely from the side opposite to the side where the cavity 33 is formed. Fig. 5 is a view of the fixed-side plate of the mold 30 viewed obliquely from the side where the cavity 33 is formed. For convenience of explanation, parts of the mold 30 are omitted or simplified in Figs. 4 to 6.

[0023] The mold 30 has a plurality of runners and a plurality of pin gates. The number of the runners and the number of the pin gates may be any number, but are four in this embodiment. That is, the mold 30 has four runners 31A, 31B, 31C, and 31D as the plurality of runners, and four pin gates 32A, 32B, 32C, and 32D as the plurality of pin gates. The runners 31A, 31B, 31C, and 31D are connected to the pin gates 32A, 32B, 32C, and 32D, respectively.

[0024] The die 30 has a plurality of protruding parts for forming a plurality of recessed parts in the gear 10. Each protruding part extends from one side of a straight line extending from the corresponding pin gate to the radially outward side of the die 30, and has an asymmetric shape with respect to the straight line. The number of protruding parts may be any number, but is preferably a multiple of the number of pin gates, and is the same number as the number of pin gates in this embodiment. In this embodiment, since the number of pin gates is four, the number of protruding parts is also four. That is, the die 30 has four protruding parts 40A, 40B, 40C, and 40D as the plurality of protruding parts. When the gear 10 is molded, the protruding parts 40A, 40B, 40C, and 40D form the recessed parts 20A, 20B, 20C, and 20D in the gear 10, respectively.

[0025] As shown in FIG. 6, the protrusion 40A extends from one side to the other side of a straight line MA extending from the corresponding pin gate 32A to the radially outer side of the mold 30, and has an asymmetric shape with respect to the straight line MA. Similarly, the protrusion 40B extends from one side to the other side of a straight line MB extending from the corresponding pin gate 32B to the radially outer side of the mold 30, and has an asymmetric shape with respect to the straight line MB. Similarly, the protrusion 40C extends from one side to the other side of a straight line MC extending from the corresponding pin gate 32C to the radially outer side of the mold 30, and has an asymmetric shape with respect to the straight line MC. Similarly, the protrusion 40D extends from one side to the other side of a straight line MD extending from the corresponding pin gate 32D to the radially outer side of the mold 30, and has an asymmetric shape with respect to the straight line MD.

[0026] With this configuration, when molding the gear 10, the speed at which the resin injected from the multiple pin gates moves radially outward differs between one side and the other side of the straight line extending from each pin gate to the radially outward side of the mold 30. As a result, the orientation of the filler contained in the resin is not uniform in the radial direction and is disturbed, making it difficult for local deformation or stress to occur, improving the dimensional accuracy and strength, and ultimately improving the performance of the gear 10.

[0027] The recesses 20A, 20B, 20C, and 20D of the gear 10 will be described in detail mainly with reference to FIGS.

[0028] The recesses 20A, 20B, 20C, and 20D are disposed near the gate points PA, PB, PC, and PD, respectively, and at positions radially outward from the gate points PA, PB, PC, and PD. Therefore, when molding the gear 10, the protrusions 40A, 40B, 40C, and 40D of the mold 30 corresponding to the recesses 20A, 20B, 20C, and 20D change the direction of resin flow near the pin gates 32A, 32B, 32C, and 32D, respectively, thereby preventing linear fiber orientation in the radial direction.

[0029] The first portion 21A, which is a portion of the recess 20A that exists at least on one side of the straight line LA, has a shape in which the width in the radial direction of the gear 10 increases from the first end 23A, which exists on one side of the straight line LA, to the second end 24A, which exists on the other side of the straight line LA, among both 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 that exists at least on one side of the straight line LB, the first portion 21C, which is a portion of the recess 20C that exists at least on one side of the straight line LC, and the first portion 21D, which is a portion of the recess 20D that exists at least on one side of the straight line LD, also have the same shape. Naturally, the portions of the protrusions 40A, 40B, 40C, and 40D of the mold 30 that correspond to the first portions 21A, 21B, 21C, and 21D have shapes that correspond to the shapes of the first portions 21A, 21B, 21C, and 21D, respectively. That is, at least a portion of the protrusion 40A on one side of the straight line MA has a shape in which the width in the radial direction of the mold 30 increases from a circumferential end 43A of the protrusion 40A on one side of the straight line MA to a circumferential end 44A on the other side of the straight line MA. At least a portion of the protrusion 40B on one side of the straight line MB, at least a portion of the protrusion 40C on one side of the straight line MC, and at least a portion of the protrusion 40D on one side of the straight line MD also have similar shapes.

[0030] With this configuration, when molding the gear 10, the radially outward movement speed of the resin injected from the pin gates differs depending on the circumferential position of the gear 10, at least on one side of the straight line extending from the gate points corresponding to each pin gate to the radially outward direction of the gear 10. For example, at least on one side of the straight line corresponding to the straight line LA, i.e., the straight line MA extending radially outward from the pin gate 32A, in the cavity 33 of the mold 30, the radially outward movement of the resin injected from the pin gate 32A is delayed by the protrusion 40A of the mold 30 the farther the position is from the circumferential end 43A of the protrusion 40A corresponding to the first end 23A of the recess 20A. As a result, the orientation of the filler contained in the resin becomes less uniform in the radial direction, and local deformation or stress is further unlikely to occur.

[0031] In this embodiment, the second portion 22A, which is a portion of the recess 20A on the other side of the straight line LA, has a shape in which the width in the radial direction of the gear 10 increases from the first end 23A to the second end 24A of the recess 20A only in a part of the region adjacent to the first portion 21A. The second portion 22B, which is a portion of the recess 20B on the other side of the straight line LB, the second portion 22C, which is a portion of the recess 20C on the other side of the straight line LC, and the second portion 22D, which is a portion of the recess 20D on the other side of the straight line LD, also have the same shape. Naturally, the portions of the protrusions 40A, 40B, 40C, and 40D of the mold 30 that correspond to the second portions 22A, 22B, 22C, and 22D have shapes that correspond to the shapes of the second portions 22A, 22B, 22C, and 22D, respectively. That is, the portion of the protrusion 40A 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 protrusion 40A toward the circumferential end 44A, but only in a partial region adjacent to the portion on one side of the straight line MA. The portion of the protrusion 40B on the other side of the straight line MB, the portion of the protrusion 40C on the other side of the straight line MC, and the portion of the protrusion 40D on the other side of the straight line MD also have similar shapes.

[0032] With this configuration, when molding the gear 10, the radially outward movement speed of the resin injected from the pin gates differs partially depending on the circumferential position of the gear 10, even on the other side of the straight line extending radially outward from the gate points corresponding to the pin gates. For example, even on the other side of at least the straight line corresponding to the straight line LA, that is, the straight line MA extending radially outward from the pin gate 32A, in the cavity 33 of the mold 30, the radially outward movement of the resin injected from the pin gate 32A is partially delayed by the protrusion 40A of the mold 30 at a position farther from the circumferential end 43A of the protrusion 40A corresponding to the first end 23A of the recess 20A. As a result, the orientation of the filler contained in the resin becomes less and less uniform in the radial direction, and local deformation or stress is further unlikely to occur.

[0033] The first end 23A of the recess 20A is formed at an acute angle in end view in the axial direction of the gear 10. End view in the axial direction refers to the axial end face 11 of the gear 10 viewed along the axial direction as shown in FIG. 2. For example, the recess 20A is formed in a polygonal shape such as a triangle with at least one apex having an acute angle. As shown in FIG. 2, this polygon preferably has one or more sides curved convexly outward in the radial direction. The recesses 20B, 20C, and 20D are similar to the recess 20A.

[0034] In this embodiment, the second end 24A of the recess 20A is also formed to have an acute angle when viewed from an end surface in the axial direction of the gear 10. For example, the recess 20A is formed to have a polygonal shape, such as a triangle, with at least two vertices having acute angles. The recesses 20B, 20C, and 20D are similar to the recess 20A.

[0035] Since resin flows easily in a large flow path, it is more effective to set a large curved flow path than to set multiple small curved flow paths. In this embodiment, each recess is formed into a polygonal shape with at least one, and preferably at least two, acute apexes, to provide a large curved flow path as shown in Fig. 2, which makes it easier for resin to flow in a desired direction.

[0036] 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 that connects to the inner periphery of the rim 12. In this embodiment, each recess extends continuously in the radial direction from the vicinity of the corresponding gate point to the vicinity of the tooth tip, so that the region of the web 13 can be effectively utilized to ensure a recess region for obtaining a desired fiber orientation. In this 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 to the outer periphery of the web 13 that faces the inner periphery of the rim 12 via a gap.

[0037] When the number of gate points is n, the recesses 20A, 20B, 20C, and 20D as a whole have a shape that is n-fold symmetrical in the end view in the axial direction of the gear 10. That is, the recesses 20A, 20B, 20C, and 20D as a whole have a rotational symmetry of 360° / number of gates. In this embodiment, since the number of gate points is four, the recesses 20A, 20B, 20C, and 20D have a shape that is four-fold symmetrical when viewed along the axial direction of the gear 10. For example, the number of gate points may be three, and in such a modified example, the multiple recesses may be formed to have three-fold symmetry.

[0038] The recesses 20A, 20B, 20C, and 20D are generally symmetrical with respect to the center CT of the axial end surface 11. For example, the recesses 20A, 20B, 20C, and 20D are generally formed in a windmill shape. Therefore, when molding the gear 10, the protrusions 40A, 40B, 40C, and 40D of the mold 30 corresponding to the recesses 20A, 20B, 20C, and 20D tend to bend the flow direction of the resin. Bending the flow direction of the resin makes the resin pressure during flow uneven. As a result, the fiber orientation can be disturbed without employing a special molding method for controlling the fiber orientation.

[0039] A large flow passage shape has a large effect on warpage, and the symmetry of warpage becomes important for a rotating body such as the gear 10. If a large curved flow passage is set symmetrically with respect to the gate in order to obtain symmetry of warpage, the fibers will be aligned at the junction of the flow passages, which will cancel out the effect of the curved flow passage disrupting the fiber orientation. In this embodiment, the flow passage is asymmetric with respect to the gate, but is n-fold symmetric if the number of gates is n, or more specifically, point-symmetric with respect to the center CT, thereby improving the symmetry of warpage. As a result, the roundness of the gear 10 is improved.

[0040] The gear manufacturing method according to this embodiment will be described with reference to FIG.

[0041] First, step S1 is carried out to melt the resin containing the filler. As a method for melting the resin, a known method can be used.

[0042] Next, step S2 is performed in which molten resin is injected through multiple pin gates via multiple runners into cavity 33 of mold 30 to mold resin gear 10. The method of injecting resin into cavity 33 of mold 30 to mold gear 10 can be the same as a known method of injecting resin into a mold cavity to mold a known gear.

[0043] In this embodiment, a resin containing a filler is used to mold the gear 10. Thus, the gear 10 according to this embodiment corresponds to a molded product of a resin containing a filler, and the gear manufacturing method according to this embodiment corresponds to a manufacturing method of the molded product.

[0044] 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 and nylon 6,6; thermoplastic polyimide resins; polyamideimide resins; polystyrene resins such as polystyrene, syndiotactic polystyrene, acrylonitrile-styrene copolymer resins, and acrylonitrile-butadiene-styrene copolymer resins; polyarylene sulfide resins such as polyphenylene sulfide; polyphenylene ether resins; polyurethane resins; polylactic acid; polyether ether ketone resins; polyetherimide resins; polyketone resins; polyarylate resins such as amorphous polyarylate and liquid crystal polyarylate; and liquid crystal polyester resins.

[0045] Among these, the thermoplastic resins used in this embodiment are preferably so-called engineering plastics or super engineering plastics that are excellent in heat resistance, mechanical properties, etc., such as thermoplastic polyimide resins, polyamideimide resins, polyarylene sulfide resins, polyphenylene ether resins, polyether ether ketone resins, polyetherimide resins, polyketone resins, polyarylate resins, and liquid crystalline polyester resins. From the viewpoints of chemical resistance, heat resistance, and mechanical properties, polyarylene sulfide resins are more preferable, and among polyarylene sulfide resins (hereinafter also referred to as "PAS resins"), polyphenylene sulfide (hereinafter also referred to as "PPS resins") resins are particularly preferable.

[0046] In this embodiment, the above resin may be used alone, or may be used in the form of a polymer alloy in which a plurality of the above resins are mixed. The filler-containing resin according to this embodiment may be in the form of a composition containing the filler and the above resin described below, and may be in the form of a composition containing any of the following additive components (colorant, antistatic agent, antioxidant, heat stabilizer, UV stabilizer, UV absorber, foaming agent, flame retardant, flame retardant assistant, rust inhibitor, coupling agent, silane coupling agent, thermoplastic elastomer, or synthetic resin) as necessary.

[0047] The polyarylene sulfide resin has a resin structure having a repeating unit in which an aromatic ring and a sulfur atom are bonded. Specifically, the polyarylene sulfide resin is a resin having a repeating unit of a structural portion represented by the following general formula (1) and, if necessary, a trifunctional structural portion represented by the following general formula (2).

[0048] [ka] 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.

[0049] [ka] The trifunctional structural moiety represented by formula (2) is preferably present in an amount of 0.001 to 3 mol %, particularly preferably 0.01 to 1 mol %, based on the total number of moles including other structural moieties.

[0050] Here, the structural portion represented by the above general formula (1) is particularly R 1 and R 2 is preferably a hydrogen atom from the viewpoint of the mechanical strength of the PAS resin, and in that case, examples include those bonded at the para position represented by the following formula (3) and those bonded at the meta position represented by the following formula (4).

[0051] [ka] Among these, a structure in which the bond of the sulfur atom to the aromatic ring in the repeating unit is bonded at the para position represented by the above general formula (3) is particularly preferred in terms of the heat resistance and crystallinity of the PAS resin.

[0052] In addition, the PAS resin may contain not only the structural moieties represented by the above general formulas (1) and (2), but also the structural moieties represented by the following structural formulas (5) to (8) in an amount of 30 mol % or less of the total of the structural moieties represented by the above general formulas (1) and (2).

[0053] [ka] In particular, in this embodiment, the structural moieties represented by the above general formulae (5) to (8) are preferably 10 mol % or less in terms of the heat resistance and mechanical strength of the PAS resin. When the PAS resin contains the structural moieties represented by the above general formulae (5) to (8), the bonding mode thereof may be either a random copolymer or a block copolymer.

[0054] In addition, the PAS resin may have naphthyl sulfide bonds or the like in its molecular structure, but the amount of such bonds is preferably 3 mol % or less, and particularly preferably 1 mol % or less, relative to the total number of moles including other structural portions.

[0055] The physical properties of the PAS resin are not particularly limited as long as they do not impair the effects of this embodiment, and are as follows.

[0056] (Melt Viscosity) The melt viscosity of the PAS resin is not particularly limited, but in order to obtain 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 even more preferably in the range of 200 Pa·s or less. However, the melt viscosity (V6) is measured by using a Shimadzu Corporation flow tester, CFT-500D, at 300°C, load: 1.96×10 6 The melt viscosity is measured after holding the sample for 6 minutes at a pressure of 1 Pa and L / D = 10 (mm) / 1 (mm).

[0057] (Non-Newtonian Exponents) The non-Newtonian index of the PAS resin is not particularly limited, but is preferably in the range of 0.90 or more to 2.00 or less. When a linear polyarylene sulfide resin is used, the non-Newtonian index is preferably in the range of 0.90 or more, more preferably in the range of 0.95 or more to preferably in the range of 1.50 or less, more preferably in the range of 1.20 or less. Such a polyarylene sulfide resin is excellent in mechanical properties, fluidity, and abrasion resistance. However, in this 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 capillograph under the conditions of melting point +20°C and the ratio of the orifice length (L) to the orifice diameter (D) L / D=40. The closer the non-Newtonian index (N value) is to 1, the closer the structure is to a linear structure, and the higher the non-Newtonian index (N value), the more branched the structure is.

[0058]

number

[0059] As the filler, any known or commonly used material can be used as long as it does not impair the effect of this embodiment, and examples of such fillers include fillers of various shapes, such as fibrous ones and non-fibrous ones such as granular or plate-like ones. Specifically, fibrous fillers such as glass fiber, carbon fiber, silane glass fiber, ceramic fiber, aramid fiber, metal fiber, potassium titanate, silicon carbide, calcium silicate, wollastonite, and natural fibers can be used, and non-fibrous fillers such as glass beads, glass flakes, barium sulfate, clay, pyrophyllite, bentonite, sericite, mica, talc, attapulgite, ferrite, calcium silicate, calcium carbonate, glass beads, zeolite, milled fiber, and calcium sulfate can also be used.

[0060] In this embodiment, the content of the filler is not particularly limited as long as it does not impair the effect of this embodiment. The amount of the filler to be blended is, for example, 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, relative to 100 parts by mass of the resin. In this range, the resin exhibits good mechanical strength and moldability, which is preferable.

[0061] The resin used in this embodiment can be mixed with a silane coupling agent as an optional component as necessary.The silane coupling agent is not particularly limited as long as it does not impair the effect of this embodiment, but the silane coupling agent having a functional group that reacts with a carboxyl group, such as an epoxy group, an isocyanato group, an amino group or a hydroxyl group, is preferably mentioned. Examples of such silane coupling agents include epoxy group-containing alkoxysilane compounds such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; isocyanato group-containing alkoxysilane compounds such as γ-isocyanatopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, γ-isocyanatopropylmethyldimethoxysilane, γ-isocyanatopropylmethyldiethoxysilane, γ-isocyanatopropylethyldimethoxysilane, γ-isocyanatopropylethyldiethoxysilane, and γ-isocyanatopropyltrichlorosilane; amino group-containing alkoxysilane compounds such as γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, and γ-aminopropyltrimethoxysilane; and hydroxyl group-containing alkoxysilane compounds such as γ-hydroxypropyltrimethoxysilane and γ-hydroxypropyltriethoxysilane. In this embodiment, the silane coupling agent is not an essential component, but when it is blended, the blending amount is not particularly limited as long as it does not impair the effect of this embodiment, and 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, relative to 100 parts by mass of the resin. In this range, the resin has good corona resistance and moldability, especially releasability, and the molded product exhibits excellent adhesion to the epoxy resin while further improving mechanical strength, which is preferable.

[0062] The resin used in this embodiment may contain a thermoplastic elastomer as an optional component, if necessary. Examples of the thermoplastic elastomer include polyolefin-based elastomers, fluorine-based elastomers, and silicone-based elastomers, among which polyolefin-based elastomers are preferred. When these elastomers are added, the amount of the elastomers is not particularly limited as long as it does not impair the effects of this embodiment, but is preferably in the range of 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, to preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of resin (A). In this range, the impact resistance of the resulting resin is improved, which is preferable.

[0063] For example, the polyolefin-based elastomer may be a homopolymer of an α-olefin, a copolymer of two or more α-olefins, or a copolymer of one or more α-olefins and a vinyl polymerizable compound having a functional group. In this case, the α-olefin may be an α-olefin having 2 or more to 8 or less carbon atoms, such as ethylene, propylene, or 1-butene. In addition, the functional group may be a carboxy group, an acid anhydride group (-C(=O)OC(=O)-), an epoxy group, an amino group, a hydroxyl group, a mercapto group, an isocyanate group, or an oxazoline group. Examples of the vinyl polymerizable compound having the functional group include one or more of 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 include alkali metals such as sodium, alkaline earth metals such as calcium, and zinc, etc.), 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 of the above α,β-unsaturated dicarboxylic acids (monoesters, diesters, and acid anhydrides). The above-mentioned thermoplastic elastomers may be used alone or in combination of two or more.

[0064] Furthermore, in addition to the above components, the resin used in this embodiment may further contain synthetic resins such as 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, polydifluoroethylene resin, polystyrene resin, ABS resin, phenol resin, urethane resin, and liquid crystal polymer as optional components depending on the application. Although the above synthetic resin is not an essential component in this embodiment, when it is added, the ratio of the synthetic resin to be added is not particularly limited as long as it does not impair the effects of this embodiment, and it differs depending on each purpose and cannot be generally defined, but the ratio of the synthetic resin to be added in the resin according to this embodiment is, for example, in the range of 5 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the resin. In other words, the ratio of resin (A) to the total of 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, on a mass basis.

[0065] The resin used in this embodiment may contain other known and commonly used additives as optional components, such as colorants, antistatic agents, antioxidants, heat stabilizers, UV stabilizers, UV absorbers, foaming agents, flame retardants, flame retardant assistants, rust inhibitors, and coupling agents, etc. These additives are not essential components, and may be used, for example, in an amount of preferably 0.01 parts by mass or more and preferably 1000 parts by mass or less relative to 100 parts by mass of the resin, with appropriate adjustment depending on the purpose and application so as not to impair the effects of this embodiment.

[0066] The method for producing the resin used in this embodiment will be described in detail below.

[0067] The resin used in this embodiment is made by blending each essential component and other optional components as necessary. The method for producing the resin used in this embodiment is not particularly limited, but includes a method of blending the essential components and optional components as necessary and melt-kneading them, more specifically, a method of uniformly dry-mixing them in a tumbler or Henschel mixer as necessary, and then feeding them into a twin-screw extruder and melt-kneading them.

[0068] The melt kneading can be carried out by heating the resin to a temperature range in which the resin temperature is equal to or higher than the melting point of the resin, preferably equal to or higher than the melting point + 10°C, more preferably equal to or higher than the melting point + 10°C, even more preferably equal to or higher than the melting point + 20°C, preferably equal to or lower than the melting point + 100°C, more preferably equal to or lower than the melting point + 50°C.

[0069] The melt kneader is preferably a twin-screw kneading extruder from the viewpoint of dispersibility and productivity. For example, it is preferable to melt knead while appropriately adjusting the discharge amount of the resin component in the range of 5 to 500 (kg / hr) and the screw rotation speed in the range of 50 to 500 (rpm), and it is more preferable to melt knead under the condition that the ratio (discharge amount / screw rotation speed) 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 may be performed simultaneously or in portions. For example, when an additive is added among the above components, it is preferable to feed the additive into the extruder from a side feeder of the twin-screw kneading extruder from the viewpoint of dispersibility. The position of the side feeder is preferably such that the ratio of the distance from the extruder resin input part (top feeder) to the side feeder to the total screw length of the twin-screw kneading extruder is 0.1 or more, more preferably 0.3 or more. In addition, such a ratio is preferably 0.9 or less, more preferably 0.7 or less.

[0070] The resin according to the present embodiment obtained by melt kneading in this manner is a molten mixture containing the above-mentioned essential components, optional components added as necessary, and components derived therefrom. After the melt kneading, it is preferable to process the molten resin by a known method, for example, by extruding the resin in a strand shape, and then processing it into a form such as pellets, chips, granules, powder, or the like, and then pre-drying it at a temperature in the range of 100 to 150°C as necessary.

[0071] The molded article of the present embodiment is produced by molding a resin containing a filler. The method for producing the molded article of the present embodiment includes a step of melt-molding the resin. The method will be described in detail below.

[0072] The resin used in this embodiment is subjected to injection molding. The various molding conditions are not particularly limited, and molding can be performed by a general method. For example, in an injection molding machine, the resin is melted at a temperature range of the melting point of the resin or higher, preferably at a temperature range of the melting point +10°C or higher, more preferably at a temperature range of the melting point +10°C to the melting point +100°C, and even more preferably at a temperature range of the melting point +20 to the melting point +50°C, and then the resin is injected into a mold from a resin discharge port and molded. At that time, the mold temperature may be set to a known temperature range, for example, room temperature (23°C) to 300°C, preferably 120 to 180°C.

[0073] In the following, a gear 10 according to the present embodiment was actually produced as Example 1, and a gear not having the multiple recesses as provided in gear 10 according to the present embodiment was actually produced as Comparative Example 1. The results of evaluating the dimensional accuracy and carrying out a durability test for each of Example 1 and Comparative Example 1 will be described.

[0074] Both Comparative Example 1 and Example 1 are spur gears formed of a resin containing 15 wt% of fibrous filler. When the dimensional accuracy of each of Comparative Example 1 and Example 1 was evaluated, as shown in FIG. 8, bulging deformation due to welds was observed in four places in Comparative Example 1, whereas it was confirmed that deterioration of dimensional accuracy due to such deformation was suppressed in Example 1. The JGMA grades of Comparative Example 1 were grade 6 or non-grade for one pitch mesh and grade 5 for all teeth mesh, whereas the results of Example 1 were grade 5 for one pitch mesh and grade 3 for all teeth mesh. "JGMA" is an abbreviation for Japan Gear Manufacturers Association.

[0075] Both Comparative Example 1 and Example 1 are spur gears with a module of 1 mm and 31 teeth. Durability tests for Comparative Example 1 and Example 1 were conducted using a pair of gears made of the same material under conditions of a torque of 20 kgf·cm and a rotation speed of 1000 rpm. As shown in FIG. 9, the test was stopped after 2 hours in Comparative Example 1 due to thermal deformation of the tooth tips, whereas the test could be continued for more than 16 hours in Example 1. This is believed to be because Comparative Example 1 has poor dimensional accuracy, which causes excessive loads to be applied to the contact points between the gears, and these parts melt due to heat. As the melting progresses, the gears no longer mesh with each other and spin freely, so in the graph shown in FIG. 9, the tooth surface temperature of Comparative Example 1 drops sharply after 2 hours.

[0076] 10 and 11 are images of Comparative Example 1 and Example 1 observed by optical microscope, respectively, and the images were pasted together to show the weld state. As shown in FIG. 10, in Comparative Example 1, the fiber orientation is aligned at four points in the circumferential direction from the shaft hole to the tooth tip, and welds are generated. On the other hand, as shown in FIG. 11, in Example 1, the fiber orientation is not aligned as in Comparative Example 1, and "weldless" is achieved. That is, in Example 1, the shape of the flow path from the gate is made asymmetrical tornado-shaped, and the weld meeting part is moved from the center to achieve "weldless", thereby improving the dimensional accuracy and durability. By making the shape of the flow path wing-shaped and arranging this wing-shaped flow path rotationally symmetrically, the deterioration of the circularity accuracy due to warpage deformation is also suppressed.

[0077] The present disclosure is not limited to the above-described embodiment, and may be modified without departing from the spirit and scope of the present disclosure. [Explanation of symbols]

[0078] 10 Gears 11,17 Axial end face 12 Rims 13. Web 14. Hub 15 teeth 16 Shaft hole 20A, 20B, 20C, 20D Recess 21A, 21B, 21C, 21D 1st part 22A, 22B, 22C, 22D 2nd part 23A 1st end 24A 2nd end 30 Mold 31A, 31B, 31C, 31D Runner 32A, 32B, 32C, 32D Pin Gate 33 Cavity 40A, 40B, 40C, 40D Convex part 43A,44A Circumferential end

Claims

1. A gear formed of a resin containing a filler, a gear having a plurality of recesses formed on an axial end face of the gear, the recesses extending from one side to the other side of a straight line extending radially outward of the gear from a corresponding gate point, the recesses each having an asymmetric shape with respect to the straight line, when each of a plurality of points on the axial end face of the gear corresponds one-to-one to a plurality of pin gates used to inject the resin when molding the gear is defined as gate points.

2. 2. A gear according to claim 1, wherein a portion of each recess which is on at least one side of the straight line has a shape in which a width in a radial direction of the gear increases from a first end which is on one side of the straight line to a second end which is on the other side of the straight line, among both ends of each recess in a circumferential direction of the gear.

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

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

5. an annular rim having a plurality of teeth formed thereon; A web adjacent to an inner periphery of the rim, the web having the plurality of recesses formed therein; Equipped with 2. The gear according to claim 1, wherein at least a portion of each recess on the other side of the straight line extends to an outer periphery of the web that is connected to or faces an inner periphery of the rim.

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

7. 2. The gear according to claim 1, wherein the filler is a fibrous filler.

8. 2. The gear according to claim 1, wherein the resin is a polyarylene sulfide resin.

9. A robot comprising the gear according to any one of claims 1 to 8.

10. Melting a resin containing a filler; A gear molding die having a plurality of pin gates formed therein, the die having a plurality of protrusions each having an asymmetric shape with respect to a straight line extending radially outward from the corresponding pin gate, the plurality of protrusions each having an asymmetric shape with respect to the straight line, and a resin gear is molded by injecting molten resin through the plurality of pin gates into a cavity of the die. A gear manufacturing method comprising:

Images