Resin gear and method for manufacturing the same

Abstract

To provide a resin gear excellent in dimensional accuracy.SOLUTION: In the method for manufacturing a resin gear, a cavity 90C of a mold die 90 for molding the resin gear is provided with: a tooth row molding section 930 in which a central axis molding section 919 for molding a central axis, a tooth tip molding section 933 for molding a tooth tip section, and a tooth bottom molding section for molding a tooth bottom section are alternately arranged in a circumferential direction, and a gate 915 which is located closer to the central axis molding section than the tooth row molding section in a radial direction and into which a resin material is injected; and a cavity 90C which is located between the tooth row molding section and the gate in the radial direction, and in which the cavity 90C is formed in the mold die 90. And a flow adjustment part 920 in which a main flow passage part 921 and a throttle flow passage part having a thickness smaller than that of the main flow passage part are alternately arranged along the circumferential direction, and a center part of the tooth tip forming part is located on the radially front side of the main flow passage part, or a center part of the tooth bottom forming part is located on the radially front side of the main flow passage part.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a gear containing a resin as a material, and a method for manufacturing the same. [Background technology]

[0002] In order to reduce the weight of various devices, the gears used in the devices are also required to be lightweight.

[0003] In order to reduce the weight of the gear, it is considered effective to thin out the gear by reducing the thickness of a part of the gear or by providing a through-hole in the gear (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-098906 Summary of the Invention [Problem to be solved by the invention]

[0005] As mentioned above, it is believed that hollowing out the gear is an effective way to reduce the gear weight. In addition, it is believed that using resin as the gear material can further reduce the gear weight.

[0006] Because gears require high strength, gear materials preferably contain various fillers such as glass fiber and carbon fiber in addition to resin. In this specification, unless otherwise specified, materials containing resin and filler are referred to as resin-containing materials. Furthermore, unless otherwise specified, gears manufactured using such resin-containing materials are referred to as resin gears.

[0007] A suitable method for manufacturing a resin gear is to inject a flowable resin-containing material into the cavity of a mold and mold the resin-containing material into a shape that conforms to the mold surface of the mold. Hereinafter, the resin-containing material that has become flowable may be referred to as a flowable molding material, as needed.

[0008] In a resin molded product obtained by the above-mentioned molding method, most of the filler is oriented along the flow direction of the fluid molding material during molding. The resin molded product shrinks when cooled after molding, and if the orientation of the filler is uneven in each part of the resin molded product, the degree of shrinkage also becomes uneven in each part of the resin molded product. A resin molded product in which the degree of shrinkage is uneven in each part cannot be said to have high dimensional accuracy.

[0009] When a resin-containing material is used to mold a hollowed-out gear as described in the aforementioned Patent Document 1, the flow paths of the flowable molding material in the mold cavity branch into many branches and many confluences are also formed. As a result, the flow direction and flow rate of the flowable molding material in the cavity become biased, which in turn causes bias in the orientation of the filler in the cavity, and thus bias in the orientation of the filler in the resin gear molded in the cavity.

[0010] A typical gear has rows of teeth that are arranged alternately along the circumferential direction, with tooth portions extending radially outward from the central axis and tooth roots that are located radially closer to the central axis than the tooth tips of the tooth portions.

[0011] In gears, it is important that the shape and positional relationship of each tooth and tooth root fall within a predetermined tolerance range in order for the gear to function properly, and gears with low dimensional accuracy are useless. Therefore, as mentioned above, resin gears with uneven filler orientation and poor dimensional accuracy are also difficult to say are useful.

[0012] For this reason, there is a demand for resin gears with excellent dimensional accuracy.

[0013] The present disclosure has been made in consideration of the above circumstances, and an object to be achieved is to provide a resin gear with excellent dimensional accuracy. [Means for solving the problem]

[0014] A method for manufacturing a resin gear according to a first aspect of the present disclosure that solves the above problem includes: A resin-containing material containing a resin and a filler is used, A central axis and A method for manufacturing a resin gear having a tooth row in which tooth portions extending radially outward from the central axis and tooth roots located radially closer to the central axis than tooth tips of the tooth portions are alternately arranged along a circumferential direction, The cavity of the mold for molding the resin gear is a central shaft forming portion that forms the central shaft; a tooth row forming portion, in which tooth tip forming portions for forming the tooth tips and tooth bottom forming portions for forming the tooth bottoms are alternately arranged along the circumferential direction, and which forms the tooth row; a gate for injecting a resin material, the gate being located closer to the central shaft molding portion than the tooth row molding portion in the radial direction; a flow adjustment section that is located between the tooth row forming section and the gate in the radial direction, and in which a main flow path section and a throttle flow path section that is thinner than the main flow path section are alternately arranged along the circumferential direction, In the method for manufacturing a plastic gear, the circumferential center of each of the tooth tip forming portions is located radially outside each of the main flow path portions.

[0015] A method for manufacturing a resin gear according to a second aspect of the present disclosure that solves the above problem includes: A resin-containing material containing a resin and a filler is used, A central axis and A method for manufacturing a resin gear having a tooth row in which tooth portions extending radially outward from the central axis and tooth roots located radially closer to the central axis than tooth tips of the tooth portions are alternately arranged along a circumferential direction, The cavity of the mold for molding the resin gear is a central shaft forming portion that forms the central shaft; a tooth row forming portion, in which tooth tip forming portions for forming the tooth tips and tooth bottom forming portions for forming the tooth bottoms are alternately arranged along the circumferential direction, and which forms the tooth row; a gate for injecting a resin material, the gate being located closer to the central shaft molding portion than the tooth row molding portion in the radial direction; a flow adjustment section that is located between the tooth row forming section and the gate in the radial direction, and in which a main flow path section and a throttle flow path section that is thinner than the main flow path section are alternately arranged along the circumferential direction, In the method for manufacturing a plastic gear, the circumferential center of each of the tooth bottom forming portions is located radially outside each of the main flow path portions.

[0016] A resin gear according to a third aspect of the present disclosure that solves the above problems is as follows: made of a resin-containing material including a resin and a filler; A central axis and a tooth row in which tooth portions extending radially outward from the central axis and tooth bottom portions located radially closer to the central axis than tooth tips of the tooth portions are alternately arranged along the circumferential direction; a gate mark formed by injection of a resin material, the gate mark being located closer to the central axis than the tooth row in the radial direction; a connecting portion that is located between the tooth row and the gate mark in the radial direction, and that includes a main connecting portion and a plurality of narrowing portions that are thinner than the main connecting portion and are alternately arranged along the circumferential direction, The resin gear has a circumferential center of each of the tooth tips located radially outward of each of the main connecting portions.

[0017] A fourth aspect of the present disclosure that solves the above problem is a plastic gear, made of a resin-containing material including a resin and a filler; A central axis and a tooth row in which tooth portions extending radially outward from the central axis and tooth bottom portions located radially closer to the central axis than tooth tips of the tooth portions are alternately arranged along the circumferential direction; a gate mark formed by injection of a resin material, the gate mark being located closer to the central axis than the tooth row in the radial direction; a connecting portion that is located between the tooth row and the gate mark in the radial direction, and that includes a main connecting portion and a plurality of narrowing portions that are thinner than the main connecting portion and are alternately arranged along the circumferential direction, The resin gear has a circumferential center of each of the tooth roots located radially outward of each of the main connecting portions. [Effects of the Invention]

[0018] According to the method for manufacturing a resin gear of the present disclosure, it is possible to manufacture a resin gear with excellent dimensional accuracy. Furthermore, the resin gear of the present disclosure has excellent dimensional accuracy. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is an explanatory diagram illustrating the resin gear of the first embodiment as viewed from above. [Figure 2] FIG. 2 is an explanatory diagram illustrating the resin gear of the first embodiment as viewed from above and from the side. [Figure 3] 3 is an explanatory view for schematically explaining a state in which the plastic gear of the first embodiment is cut at the position XX in FIG. 2. FIG. [Figure 4] 3 is an explanatory view for schematically explaining a state in which the resin gear of the first embodiment is cut at the YY position in FIG. 2. FIG. [Figure 5] 3 is an explanatory view for explaining a schematic view of the forming die in the manufacturing method of Example 1 cut at the same position as position XX in FIG. 2. FIG. [Figure 6] 3 is an explanatory view for explaining a schematic view of the forming die in the manufacturing method of Example 1 cut at the same position as position YY in FIG. 2. FIG. [Figure 7] FIG. 10 is an explanatory diagram illustrating a plastic gear according to a second embodiment as viewed from above. [Figure 8] FIG. 10 is an explanatory diagram illustrating the resin gear of the second embodiment as viewed from above and from the side. [Figure 9] 9 is an explanatory view for schematically explaining a state in which the plastic gear of the second embodiment is cut at the position XX in FIG. 8. FIG. [Figure 10] 9 is an explanatory view for schematically explaining a state in which the plastic gear of the second embodiment is cut at the YY position in FIG. 8. FIG. [Figure 11] 9 is an explanatory view for explaining a schematic view of the forming die in the manufacturing method of Example 2 cut at the same position as position XX in FIG. 8. FIG. [Figure 12] 9 is an explanatory view for explaining a schematic view of the forming die in the manufacturing method of Example 2 cut at the same position as position YY in FIG. 8. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] The resin gear and the manufacturing method thereof according to the present disclosure will be specifically described below.

[0021] Unless otherwise specified, the numerical ranges "x to y" described in this specification include the lower limit x and the upper limit y. These upper and lower limit values, as well as the numerical values ​​listed in the embodiments, can be arbitrarily combined to form a numerical range. Furthermore, the upper and lower limit values ​​can be arbitrarily selected from within the numerical range.

[0022] The method for manufacturing a resin gear according to the present disclosure includes: A resin-containing material containing a resin and a filler is used, A central axis and The method for manufacturing a plastic gear has a tooth row in which tooth portions extending radially outward from the central axis and tooth bottom portions located radially closer to the central axis than the tooth tips of the tooth portions are alternately arranged along the circumferential direction.

[0023] The cavity of the mold for molding the resin gear is: a central shaft forming portion that forms the central shaft; a tooth row forming portion, in which tooth tip forming portions for forming the tooth tips and tooth bottom forming portions for forming the tooth bottoms are alternately arranged along the circumferential direction, and which forms the tooth row; a gate for injecting a resin material, the gate being located closer to the central shaft molding portion than the tooth row molding portion in the radial direction; The flow adjustment section is located between the tooth row forming section and the gate in the radial direction, and is equipped with a main flow path section and a throttle flow path section that is thinner than the main flow path section, which are arranged alternately along the circumferential direction.

[0024] The main flow path is a part of the flow adjustment section of the cavity that is thicker than the throttle flow path. Therefore, the flow molding material that flows into the flow adjustment section during molding is preferentially distributed through the main flow path. In other words, the flow velocity of the flow molding material that flows into the flow adjustment section during molding is faster in the main flow path than in the throttle flow path.

[0025] Therefore, the main flow path portion functions as a main flow path for the fluid molding material flowing into the tooth row forming portion in the flow adjusting portion.

[0026] It can also be said that the main flow path portion of the flow adjusting portion functions as a so-called flow leader, and the throttle flow path portion functions as a so-called flow deflector.

[0027] In the method for manufacturing a plastic gear according to the first aspect of the present disclosure, the circumferential center of each of the tooth tip forming portions is located on the radial tip side of each of the main flow path portions.

[0028] In the method for manufacturing a resin gear according to the first aspect, most of the flow molding material flowing from the flow adjusting portion into the tooth row forming portion passes through the main flow passage portion and flows into the circumferential center of the tooth tip forming portion.

[0029] The fluid molding material that has flowed into the circumferential center of the tooth tip forming portion further flows toward each of the circumferential ends of the tooth tip forming portion. Therefore, in the resin gear obtained by the resin gear manufacturing method of the first aspect, the orientation direction of the filler in the portion of each tooth near the tooth tip is symmetrical with respect to the circumferential center of the tooth tip.

[0030] Furthermore, in the cavity, into the bottom forming portion between adjacent tooth tip forming portions, the flow molding material flows from each of the adjacent main flow passage portions and joins at the circumferential center of the bottom forming portion. Therefore, in the resin gear obtained by the resin gear manufacturing method of the first aspect, the orientation direction of the filler in the portion near each bottom portion is symmetrical with respect to the circumferential center of the corresponding bottom portion.

[0031] As described above, the resin gear manufacturing method of the first aspect can reduce bias in the orientation direction of the filler during molding. As a result, in the resin gear obtained by the resin gear manufacturing method of the first aspect, the orientation direction of the filler in the portions near each tooth tip can be made symmetrical about the circumferential center of the tooth tip. Also, the orientation direction of the filler in the portions near each tooth bottom can be made symmetrical about the circumferential center of the tooth bottom.

[0032] As a result, according to the method for manufacturing a resin gear of the first aspect, the orientation of the filler in each tooth portion can be made substantially uniform, and a resin gear with excellent dimensional accuracy can be manufactured.

[0033] The manufacturing method of the plastic gear of the second embodiment of the present disclosure differs from the manufacturing method of the plastic gear of the first embodiment described above in that the circumferential center of each bottom forming portion is located radially outside the main flow path portion, but otherwise is the same as the manufacturing method of the plastic gear of the first embodiment.

[0034] In the second embodiment of the resin gear manufacturing method, the fluid molding material that flows from the main flow passage into the circumferential center of the tooth bottom forming portion further flows toward each of the circumferential ends of the tooth bottom forming portion. Therefore, in the resin gear obtained by the second embodiment of the resin gear manufacturing method, the orientation direction of the filler in the vicinity of each tooth bottom portion is symmetrical with respect to the circumferential center of the tooth bottom portion.

[0035] Furthermore, the flow molding material that flows into adjacent bottom molding portions in the cavity flows toward the tip molding portion between the bottom molding portions and joins together at the circumferential center of the tip molding portion. Therefore, in the resin gear obtained by the resin gear manufacturing method of the second aspect, the orientation direction of the filler in the portion of each tooth portion near the tip is symmetrical with respect to the circumferential center of the tip.

[0036] In this way, the method for manufacturing a resin gear of the second aspect can also reduce bias in the orientation direction of the filler during molding. As a result, in the resin gear obtained by the method for manufacturing a resin gear of the second aspect, the orientation direction of the filler in the portions near each tooth tip can be made symmetrical around the circumferential center of the tooth tip. Furthermore, the orientation direction of the filler in the portions near each tooth bottom can be made symmetrical around the circumferential center of the tooth bottom.

[0037] As a result, the resin gear manufacturing method of the second aspect also makes it possible to make the orientation of the filler in each tooth portion substantially uniform, and to manufacture a resin gear with excellent dimensional accuracy.

[0038] A resin gear according to a third aspect of the present disclosure includes: made of a resin-containing material including a resin and a filler; A central axis and a tooth row in which tooth portions extending radially outward from the central axis and tooth bottom portions located radially closer to the central axis than tooth tips of the tooth portions are alternately arranged along the circumferential direction; a gate mark formed by injection of a resin material, the gate mark being located closer to the central axis than the tooth row in the radial direction; The groove is located radially between the tooth row and the gate mark and comprises a main connecting portion and a plurality of narrowing portions having a thickness smaller than that of the main connecting portion, which are arranged alternately along the circumferential direction.

[0039] Of these, the gate mark can be said to be a mark left by the gate in the cavity. Furthermore, the main communication section can be said to be a portion formed in the main flow path section of the cavity, and the throttle section can be said to be a portion formed in the throttle section of the cavity. Therefore, the communication section in which the main communication section and the throttle section are alternately arranged in the circumferential direction can be said to be a portion formed in the flow adjustment section of the cavity.

[0040] In the resin gear of the third aspect, the circumferential center of each of the tooth tips is located radially outward of each of the main connecting portions. Such a resin gear of the third aspect can be said to be manufactured by the manufacturing method of the resin gear of the first aspect.

[0041] In the resin gear of the third aspect, the orientation of the filler in each tooth portion is approximately uniform, and the resin gear has excellent dimensional accuracy, similar to the resin gear obtained by the resin gear manufacturing method of the first aspect.

[0042] The fourth embodiment of the plastic gear of the present disclosure differs from the third embodiment in that the circumferential center of each tooth bottom portion is located radially outside each main connecting portion, but otherwise is identical to the third embodiment of the plastic gear. Such a resin gear of the fourth aspect can be said to be manufactured by the manufacturing method of the resin gear of the second aspect.

[0043] The resin gear of the fourth aspect, like the resin gear obtained by the resin gear manufacturing method of the second aspect, has a substantially uniform filler orientation in each tooth portion and is excellent in dimensional accuracy.

[0044] Hereinafter, the resin gear and the manufacturing method thereof according to the present disclosure will be described for each of its components.

[0045] In this specification, the method for manufacturing a resin gear according to the first embodiment may be referred to as the manufacturing method according to the first embodiment, and the method for manufacturing a resin gear according to the second embodiment may be referred to as the manufacturing method according to the second embodiment, as needed. Furthermore, the manufacturing methods according to the first embodiment and the second embodiment may be collectively referred to as the manufacturing method of the present disclosure.

[0046] As described above, the resin gear of the third embodiment is a resin gear manufactured by the manufacturing method of the first embodiment. Therefore, in this specification, as necessary, a resin gear manufactured by the manufacturing method of the first embodiment may be referred to as a resin gear of the third embodiment. Similarly, a resin gear manufactured by the manufacturing method of the second embodiment may be referred to as a resin gear of the fourth embodiment. Furthermore, the resin gear of the third embodiment and the resin gear of the fourth embodiment may be collectively referred to as a resin gear of the present disclosure.

[0047] In the manufacturing method of the present disclosure, the axial, radial, and circumferential directions of the cavity and each part that constitutes the cavity refer to the axial, radial, and circumferential directions of the resin gear of the present disclosure that is located within the cavity in the manufacturing method of the present disclosure. Hereinafter, as necessary, the axial, radial, and circumferential directions of the resin gear of the present disclosure, and the axial, radial, and circumferential directions of the cavity and each part constituting the cavity in the manufacturing method of the present disclosure may be abbreviated simply as the axial, radial, and circumferential directions, respectively.

[0048] In the resin gear and the manufacturing method thereof according to the present disclosure, a resin-containing material is used as the material for the resin gear. The resin-containing material may be any material containing a resin and a filler.

[0049] The type of resin is not particularly limited, and may be appropriately selected depending on the application of the resin gear.

[0050] The filler may also be selected appropriately depending on the application of the resin gear. For example, to improve the strength of the resin gear, it is preferable to select a reinforcing material such as glass fiber or carbon fiber. The shape of the filler is also not particularly limited, and various shapes such as fibrous, scale-like, and granular shapes can be used.

[0051] As described above, the resin gear and manufacturing method of the present disclosure can reduce bias in filler orientation, and therefore the effects of the present disclosure are more pronounced when the shape of the resin gear is such that the filler is easily oriented, specifically, when the shape is elongated or thin with an aspect ratio of 1.5 or more.

[0052] The resin-containing material in the resin gear and manufacturing method of the present disclosure may consist of only a resin and a filler, or may contain other additives such as a stabilizer or a flame retardant in addition to the resin and the filler.

[0053] The resin and filler contents in the resin-containing material are not particularly limited, but when the entire resin-containing material is taken as 100% by volume, it is preferable that the resin-containing material contains 5% by volume or more of filler and 60% by volume or more of resin, 10% by volume or more of filler and 70% by volume or more of resin, or 10% by volume or more of filler and 80% by volume or more of resin. This is because when the resin and filler contents in the resin-containing material are within the above ranges, manufacturing a resin gear using a typical resin molding method is likely to result in biased filler orientation, making it difficult to manufacture a resin gear with high dimensional accuracy.

[0054] The resin gear of the present disclosure includes a central shaft, a tooth row, a gate trace, and a connecting portion. The central axis means the center of rotation of the resin gear, and may be a real axis or a virtual axis.

[0055] The plastic gear of the present disclosure may be any type of gear, including, but not limited to, spur gears, helical gears, bevel gears, and crossed screw gears.

[0056] The tooth row in the resin gear of the present disclosure is an alternating arrangement of tooth portions extending radially outward from the central axis and tooth bottom portions located radially closer to the central axis than the tooth tips of the tooth portions along the circumferential direction. The plastic gear of the present disclosure may also be said to have a plurality of teeth extending radially from a central axis.

[0057] The tooth tip is the radially outer end of the tooth, and the tooth root is the radially inner end of the tooth or the base end of the tooth. The number and shape of the teeth and tooth tips in the tooth row are also not particularly limited.

[0058] The gate is an injection port for injecting a fluid molding material into a cavity for manufacturing a plastic gear in the manufacturing method of the present disclosure, and the gate mark is a mark of the gate formed on the plastic gear of the present disclosure. The gate mark can be said to be the portion of the resin gear of the present disclosure that is located most upstream in the direction of flow of the fluid molding material.

[0059] The components constituting the resin gear of the present disclosure are arranged in the following order from the inside to the outside in the radial direction: the central axis, the connecting portion, and the tooth row. In the radial direction, the gate mark is located closer to the central axis than the tooth row, and there is a connecting portion between the tooth row and the gate mark. Therefore, it can be said that the gate mark is located closer to the central axis than the connecting portion.

[0060] Such a gate mark may be located, for example, between the connecting portion and the central axis, or on the central axis, or, if the central axis is hole-shaped, on the inner circumferential surface of the central axis.

[0061] The connecting portion is located between the tooth row and the gate mark in the radial direction, and is made up of a plurality of main connecting portions and a plurality of narrowing portions, each thinner than the main connecting portions, arranged alternately in the circumferential direction.

[0062] The main communication portion is a portion of the resin gear of the present disclosure that is molded in the main flow path portion of the cavity in the manufacturing method of the present disclosure. The throttle portion is a portion of the resin gear of the present disclosure that is molded in the throttle flow path portion of the cavity in the manufacturing method of the present disclosure.

[0063] Here, the thickness of the main connecting portion or the throttle portion refers to the length of the main connecting portion or the throttle portion in the axial direction of the plastic gear. The connecting portion can also be described as a portion in which thick and thin portions are alternately arranged along the circumferential direction of the plastic gear. The same applies to the thickness of the main flow passage portion and the throttle flow passage portion, which will be described later.

[0064] In the resin gear of the third aspect, the circumferential center of each tooth tip is located radially outward of each main connecting portion. In the resin gear of the fourth aspect, the circumferential center of each tooth bottom is located radially outward of each main connecting portion. The positional relationship of each part referred to here may be the positional relationship in a radial cross section of the plastic gear, i.e., in a cross section obtained by cutting the plastic gear along a plane perpendicular to its axial direction. For example, if the plastic gear of the present disclosure is a helical gear, the position of its tooth tips varies in the axial direction. However, even in such a case, in the plastic gear of the third embodiment, the circumferential center of each tooth tip is located radially outside the main connecting portion in the radial cross section. Similarly, in the plastic gear of the fourth embodiment, the circumferential center of each tooth root is located radially outside the main connecting portion in the radial cross section.

[0065] In addition, each of the components of the resin gear of the present disclosure, such as the tooth portion, tooth bottom portion, main connecting portion, and choke portion, has an axisymmetric shape in the radial cross section of the resin gear, with the circumferential center line serving as the axis of symmetry.

[0066] In the resin gear of the third embodiment, the number of main connecting portions is the same as the number of tooth tips.

[0067] In the resin gear of the third aspect, in its radial cross section, the corresponding main connecting portions and tooth tip portions are linearly arranged along the radial direction, and the circumferential center line of the main connecting portions and the circumferential center line of the tooth tip portions are collinear. In other words, in the resin gear of the third embodiment, in the radial cross section, each main connecting portion extends toward the circumferential center of the corresponding tooth portion.

[0068] In the resin gear of the fourth embodiment, the number of the main connecting portions is the same as the number of the tooth roots.

[0069] In the resin gear of the fourth aspect, in its radial cross section, the corresponding main connecting portions and tooth roots are linearly arranged along the radial direction, and the circumferential center line of the main connecting portions and the circumferential center line of the tooth roots are collinear. In other words, in the resin gear of the fourth embodiment, in the radial cross section, each main connecting portion extends toward the gap between two adjacent tooth portions.

[0070] The thickness of the drawn portion needs only to be smaller than the thickness of the main connecting portion. In the plastic gear of the present disclosure, the ratio of the thickness of the drawn portion to the thickness of the main connecting portion is not particularly limited, but it is preferable that the thickness of the drawn portion be 2 / 3 or less, 1 / 2 or less, or 1 / 3 or less of the thickness of the main connecting portion.

[0071] The thickness of the constricted portion may or may not be constant in the radial direction. Similarly, the thickness of the constricted portion may or may not be constant in the circumferential direction. If the thickness of the constricted portion is not constant in the radial direction and / or circumferential direction, the thickness of the thinnest part of the constricted portion may be considered to be the thickness of the constricted portion.

[0072] Similarly, the thickness of the main connecting portion may or may not be constant in the radial direction. Also, the thickness of the main connecting portion may or may not be constant in the circumferential direction. If the thickness of the main connecting portion is not constant in the radial and / or circumferential directions, the thickness of the thinnest part of the main connecting portion can be considered to be the thickness of the main connecting portion.

[0073] The narrowed portion may or may not have a thickness. In other words, the narrowed portion of the communication portion may be in the form of a blind hole or a through hole.

[0074] In the plastic gear of the present disclosure, the axial position of the throttle portion is not particularly limited, but it is preferable that the throttle portion be located in the axial center of the connecting portion. In other words, the bottom of the blind-hole-shaped throttle portion may be located anywhere in the axial direction in the connecting portion, but it is preferable that it be located in the axial center.

[0075] In the manufacturing method of the present disclosure, a fluid molding material is injected into a cavity of a mold to mold the resin gear of the present disclosure. Specifically, a known resin molding method such as injection molding or injection press molding may be used as the manufacturing method of the present disclosure. If necessary, an insert may be used to inject the fluid molding material into the cavity in which the insert is placed.

[0076] In the manufacturing method of the present disclosure, the cavity of a mold for molding the resin gear of the present disclosure includes a center shaft molding portion, a teeth row molding portion, a gate, and a flow adjustment portion.

[0077] Of these, the central shaft molding portion is, as the name suggests, a portion that molds the central shaft of the resin gear of the present disclosure. The tooth row forming portion is a portion that forms the tooth row in the resin gear of the present disclosure, and has a tooth tip forming portion that forms the tooth tips of the resin gear and a tooth bottom forming portion that forms the tooth bottom of the resin gear. There are multiple tooth tip forming portions and multiple tooth bottom forming portions, and they are arranged alternately in the circumferential direction.

[0078] The shapes and positional relationships of the tooth tip and bottom forming portions may be appropriately designed according to the shapes and positional relationships of the tooth tip and bottom portions of the resin gear of the present disclosure to be manufactured by the manufacturing method of the present disclosure.

[0079] As described above, the gate is an injection port for injecting the fluid molding material into the cavity, and can be said to be located on the most upstream side of the cavity in the direction of flow of the fluid molding material.

[0080] In the manufacturing method of the present disclosure, the respective parts constituting the cavity are arranged in the order of the central axis forming part, the flow adjusting part, and the teeth row forming part from the inside to the outside in the radial direction. In the radial direction, the gate is located closer to the central axis forming portion than the tooth row forming portion, and the flow adjusting portion is located between the tooth row forming portion and the gate. Therefore, it can be said that the gate is located closer to the central axis forming portion than the flow adjusting portion.

[0081] Such a gate may be located, for example, between the flow control section and the central shaft forming section, or on the central shaft forming section, or, if the central shaft is hole-shaped, the gate may be located in the part of the cavity that forms the inner circumferential surface of the central shaft.

[0082] In either case, in order to make the flow rate and flow speed of the fluid molding material flowing into the flow adjustment section uniform or approximately uniform around the entire circumference of the flow adjustment section, it is preferable to distribute the fluid molding material injected into the cavity from the gate circumferentially before it flows into the flow adjustment section.

[0083] In consideration of this, it is preferable that the region of the cavity where the gate is located, or at least a portion of the region between the gate and the flow control section, be shaped to be continuous in the circumferential direction and allow the flow of the molding material in the circumferential direction. Hereinafter, this region of the cavity will be referred to as the "distribution section" as necessary. The thickness of the distribution section is preferably greater than the thickness of the throttle flow path section, and is more preferably 70% or more, 80% or more, or 90% or more, and particularly preferably 100%, of the thickness of the main flow path section taken as 100%.

[0084] In the manufacturing method of the present disclosure, the number of gates is not particularly limited. For example, the number of gates may be the same as the number of main flow path portions, may be greater than the number of main flow path portions, or may be less than the number of main flow path portions.

[0085] Immediately after molding, the resin gear has a burr at the gate mark location, which is formed by solidifying the fluid molding material remaining at the gate. By cutting and removing the burr, the gate mark is formed, and the resin gear of the present disclosure is obtained.

[0086] In the manufacturing method of the present disclosure, in order to reduce the cost required for the molding die and the cost of cutting and removing burrs, it is better to have a smaller number of gates, and it is preferable that the number of gates be smaller than the number of main flow path sections. When the number of gates is smaller than the number of main flow path portions, or when the number of gates is larger than the number of main flow path portions, it is more preferable to provide the above-mentioned distributor in the cavity.

[0087] The flow adjustment section is a portion of the cavity located between the tooth row forming section and the gate in the radial direction, and is made up of a plurality of main flow passage sections and a plurality of throttle flow passage sections, each thinner than the main flow passage sections, alternately arranged in the circumferential direction.

[0088] In the manufacturing method of the first embodiment, the circumferential center of each tooth tip forming portion is located radially outward of each main flow passage portion. In the plastic gear of the second embodiment, the circumferential center of each tooth bottom forming portion is located radially outward of each main connecting portion. The positional relationship of each part here may be the positional relationship of each part in a radial cross section of the cavity, similar to the positional relationship of each part in the above-mentioned plastic gear. The radial cross section refers to a cross section of the cavity cut in the radial direction of the plastic gear inside the cavity.

[0089] In the manufacturing method of the present disclosure, each of the components of the cavity, such as the tooth tip forming portion, the tooth root forming portion, the main flow path, and the throttle flow path, has an axisymmetric shape in a radial cross section, with the circumferential center line as the axis of symmetry. If the portion of the cavity that forms the teeth of the resin gear is defined as the tooth forming portion, then the tooth forming portion can also be said to have an axisymmetric shape in a radial cross section, with the circumferential center line as the axis of symmetry.

[0090] In the manufacturing method of the first embodiment, the number of main flow passage portions is the same as the number of tooth tip forming portions.

[0091] In the manufacturing method of the first embodiment, in the radial cross section, the corresponding main flow path portions and tooth tip forming portions are arranged linearly along the radial direction, and it can also be said that the circumferential center line of the main flow path portion and the circumferential center line of the tooth tip forming portion are collinear. In other words, in the manufacturing method of the first embodiment, it can be said that in the radial cross section, each main flow path portion extends toward the circumferential center of the corresponding tooth forming portion.

[0092] In the manufacturing method of the first aspect, due to the positional relationship between the main flow path section and the tooth tip forming section and the positional relationship between the main flow path section and the tooth forming section as described above, most of the fluid molding material that flows from the main flow path section into the tooth row forming section flows toward the tooth tip forming section of the tooth forming section, and as a result, the orientation direction of the filler in the tooth row forming section near the tooth tip forming section becomes symmetrical around the circumferential center of the tooth tip forming section. The orientation direction of the filler in the vicinity of the tooth bottom forming portion of the tooth row forming portion is symmetrical with respect to the circumferential center of the tooth bottom forming portion.

[0093] As a result, according to the manufacturing method of the first aspect, it is possible to reduce bias in the orientation direction of the filler during molding, and it is possible to make the orientation of the filler in each tooth portion of the resin gear obtained by this manufacturing method approximately uniform, and ultimately it is possible to manufacture resin gears with excellent dimensional accuracy.

[0094] In the manufacturing method of the second embodiment, the number of main flow passage portions is the same as the number of bottom forming portions.

[0095] In the second embodiment of the manufacturing method, in the radial cross section, the corresponding main flow path portions and bottom forming portions are arranged linearly along the radial direction, and it can also be said that the circumferential center line of the main flow path portion and the circumferential center line of the bottom forming portion are collinear. In other words, in the manufacturing method of the second embodiment, it can be said that in the radial cross section, each main flow path portion extends toward the gap between two adjacent teeth forming portions.

[0096] In the second manufacturing method, the positional relationship between the main flow passage section and the tooth bottom forming section and the positional relationship between the main flow passage section and the tooth forming section are as described above, so that most of the fluid molding material that flows from the main flow passage section into the tooth row forming section flows toward the tooth bottom forming section of the tooth forming section, and as a result, the orientation direction of the filler in the tooth row forming section near the tooth bottom forming section becomes symmetrical around the circumferential center of the tooth tip forming section. The orientation direction of the filler in the vicinity of the tooth tip forming portion of the tooth row forming portion is symmetrical with respect to the circumferential center of the tooth tip forming portion.

[0097] As a result, the manufacturing method of the second aspect also reduces bias in the orientation direction of the filler during molding, and the resin gear obtained by this manufacturing method can also have a substantially uniform filler orientation in each tooth portion, thereby enabling the manufacturing of resin gears with excellent dimensional accuracy.

[0098] The thickness of the throttle flow path portion needs only to be smaller than the thickness of the main flow path portion. In the manufacturing method of the present disclosure, the ratio between the thickness of the throttle flow path portion and the thickness of the main flow path portion is not particularly limited, but it is preferable that the thickness of the throttle flow path portion be 2 / 3 or less, 1 / 2 or less, or 1 / 3 or less of the thickness of the main flow path portion. The throttle flow path portion may or may not have a thickness. In other words, the flow control portion of the cavity may form a narrow flow path in the throttle flow path portion, or may be closed.

[0099] The thickness of the throttle passage portion may or may not be constant in the radial direction. Similarly, the thickness of the throttle passage portion may or may not be constant in the circumferential direction. When the thickness of the throttle passage portion is not constant in the radial direction and / or the circumferential direction, the thickness of the narrowest part of the throttle passage portion may be regarded as the thickness of the throttle passage portion.

[0100] Similarly, the thickness of the main flow passage portion may or may not be constant in the radial direction. Furthermore, the thickness of the main flow passage portion may or may not be constant in the circumferential direction. When the thickness of the main flow passage portion is not constant in the radial and / or circumferential directions, the thickness of the thinnest portion of the main flow passage portion can be regarded as the thickness of the main flow passage portion.

[0101] In the manufacturing method of the present disclosure, the axial position of the throttled flow path section is not particularly limited, but the throttled flow path section is preferably located in the axial center of the flow adjustment section. In other words, the throttled flow path section that forms the narrow flow path may be located at any axial position in the flow adjustment section, but is preferably located in the axial center.

[0102] The present disclosure can also be regarded as an invention of a manufacturing apparatus.

[0103] Specifically, the manufacturing apparatus according to the fifth embodiment of the present disclosure is expressed as follows. A resin-containing material containing a resin and a filler is used, A central axis and An apparatus for manufacturing a resin gear having a tooth row in which tooth portions extending radially outward from the central axis and tooth bottom portions located radially closer to the central axis than tooth tips of the tooth portions are alternately arranged along a circumferential direction, a molding die for molding the resin gear, The cavity of the mold is a central shaft forming portion that forms the central shaft; a tooth row forming portion, in which tooth tip forming portions that form the tooth tips and tooth bottom forming portions that form the tooth bottoms are alternately arranged along the circumferential direction, and which forms the tooth row; a gate for injecting a resin material, the gate being located closer to the central shaft molding portion than the tooth row molding portion in the radial direction; a flow adjustment section that is located between the tooth row forming section and the gate in the radial direction, and in which a main flow path section and a throttle flow path section that is thinner than the main flow path section are alternately arranged along the circumferential direction, The manufacturing device for plastic gears, wherein the circumferential center of each of the tooth tip forming portions is located radially outward of each of the main flow path portions.

[0104] The manufacturing apparatus according to the sixth embodiment of the present disclosure is expressed as follows. A resin-containing material containing a resin and a filler is used, A central axis and An apparatus for manufacturing a resin gear having a tooth row in which tooth portions extending radially outward from the central axis and tooth bottom portions located radially closer to the central axis than tooth tips of the tooth portions are alternately arranged along a circumferential direction, a molding die for molding the resin gear, The cavity of the mold is a central shaft forming portion that forms the central shaft; a tooth row forming portion, in which tooth tip forming portions that form the tooth tips and tooth bottom forming portions that form the tooth bottoms are alternately arranged along the circumferential direction, and which forms the tooth row; a gate for injecting a resin material, the gate being located closer to the central shaft molding portion than the tooth row molding portion in the radial direction; a flow adjustment section that is located between the tooth row forming section and the gate in the radial direction, and in which a main flow path section and a throttle flow path section that is thinner than the main flow path section are alternately arranged along the circumferential direction, The manufacturing device for plastic gears, wherein the circumferential center of each of the tooth bottom forming portions is located radially outside of each of the main flow path portions.

[0105] Hereinafter, the resin gear and the manufacturing method thereof according to the present disclosure will be described using specific examples.

[0106] Example 1 The resin gear of Example 1 is the resin gear of the third aspect, and the manufacturing method of Example 1 is the manufacturing method of the first aspect.

[0107] Fig. 1 is an explanatory diagram illustrating a resin gear of Example 1 as viewed from above, and Fig. 2 is an explanatory diagram illustrating a resin gear of Example 1 as viewed from above and to the side. Fig. 3 is an explanatory diagram illustrating a resin gear of Example 1 cut at position XX in Fig. 2, and Fig. 4 is an explanatory diagram illustrating a resin gear of Example 1 cut at position YY in Fig. 2. Fig. 5 is an explanatory diagram illustrating a mold in the manufacturing method of Example 1 cut at the same position as position XX in Fig. 2. Fig. 6 is an explanatory diagram illustrating a mold in the manufacturing method of Example 1 cut at the same position as position YY in Fig. 2.

[0108] The manufacturing method of Example 1 is a method of injection molding the resin gear of Example 1. In the manufacturing method of Example 1, the resin-containing material contains polyacetal as a resin and glass fiber as a filler. When the entire resin-containing material is taken as 100% by volume, the resin is contained at 90% by volume and the filler is contained at 10% by volume. The filler is fibrous, and its aspect ratio is about 5 on average.

[0109] As shown in FIGS. 1 and 2, the resin gear 1 of the first embodiment is a helical gear.

[0110] The plastic gear 1 of Example 1 includes a central shaft portion 10, a shaft connecting portion 11, an annular portion 13, a connecting portion 20, a tooth connecting portion 14, and a tooth row 30. The respective portions of the plastic gear 1 are arranged in the following order from the radially inner side to the radially outer side: central shaft portion 10, shaft connecting portion 11, annular portion 13, connecting portion 20, tooth connecting portion 14, and tooth row 30.

[0111] The central shaft portion 10 has a cylindrical shape extending in the axial direction. Inside the central shaft portion 10, a central shaft 19 is formed as a through-hole extending in the axial direction, which is an imaginary axis of the resin gear 1.

[0112] The shaft connecting portion 11 is annular and is a portion that is continuous with the central shaft portion 10 on the radially outer side of the central shaft portion 10. The shaft connecting portion 11 extends radially outward from the entire outer circumferential surface of the central shaft portion 10 in part of the axial direction of the central shaft portion 10. The thickness of the shaft connecting portion 11 in the circumferential direction is approximately constant. As shown in Figures 3 and 4, the thickness of the shaft connecting portion 11 in the radial direction gradually decreases from the central shaft portion 10 toward the radially outer side, and is approximately constant at its radially outer end.

[0113] 1 and 2, the annular portion 13 is annular and is a portion that is continuous with the shaft connecting portion 11 on the radially outer side of the shaft connecting portion 11. As shown in FIGS. 3 and 4, the thickness of the annular portion 13 is greater than the thickness of the shaft connecting portion 11, and the shaft connecting portion 11 and the annular portion 13 are connected in a stepped manner. The annular portion 13 extends radially outward from the entire outer circumferential surface of the shaft connecting portion 11. The thickness of the annular portion 13 is approximately constant in the circumferential and radial directions.

[0114] 1, a plurality of gate marks 15 are formed in the annular portion 13. The number of gate marks 15 is smaller than the number of main connecting portions 21 and the number of tooth portions 31. The gate marks 15 are formed on one end face of the resin gear 1 in the axial direction, and are arranged at approximately equal intervals in the circumferential direction.

[0115] The connecting portion 20 is a portion that is continuous with the annular portion 13 on the radially outer side of the annular portion 13, and has a generally annular shape. As shown in FIGS. 1 to 4, the connecting portion 20 is formed by alternately arranging a plurality of main connecting portions 21 and a plurality of throttle portions 22 having a thickness smaller than that of the main connecting portions 21 in the circumferential direction.

[0116] The thickness T1 of the main connecting portion 21 is approximately constant in the radial direction and the circumferential direction, and is approximately the same as the thickness of the annular portion 13.

[0117] The throttle portion 22 is formed in the shape of a blind hole, and the thickness of the throttle portion 22 is constant in the circumferential direction but is not constant in the axial direction. The thickness T2 of the throttle portion 22 is smaller than the thickness of the annular portion 13 and the thickness of the main connecting portion 21, and the throttle portion 22 is connected to the annular portion 13 in a stepped manner. The thickness T2 of the throttle portion 22 is approximately constant on the annular portion 13 side and gradually increases radially outward. The throttle portion 22 smoothly connects to the tooth connecting portion 14. The thickness T2 of the narrowed portion 22, that is, the thickness of the thinnest portion of the narrowed portion 22, is about ¼ of the thickness of the annular portion 13 and the thickness T1 of the main connecting portion .

[0118] The tooth connecting portion 14 is annular and is a portion that continues to the connecting portion 20 on the radially outer side of the connecting portion 20. The thickness of the tooth connecting portion 14 is approximately the same as the thickness of the main connecting portion 21, and is also approximately the same as the thickness of the radially outer end of the constricted portion 22. The tooth connecting portion 14 extends radially outward from the entire outer circumferential surface of the connecting portion 20. The thickness of the tooth connecting portion 14 is approximately constant in the circumferential and radial directions.

[0119] The tooth row 30 is a portion that continues to the tooth connecting portion 14 on the radially outer side of the tooth connecting portion 14, and is generally annular. The tooth row 30 has a plurality of tooth portions 31 and a plurality of tooth root portions 32 arranged alternately in the circumferential direction.

[0120] Each tooth 31 extends radially outward from the central axis 19. The radially outer end of each tooth 31, in other words, the outer peripheral end face of each tooth 31, is a tooth tip 33. Each tooth bottom 32 is an end surface formed between adjacent teeth 31 and extending in the circumferential and axial directions. The tooth bottom 32 can also be referred to as the outer peripheral end surface of the tooth connection portion 14. The tooth bottom 32 and the tooth tip 33 are spaced apart in the radial direction.

[0121] In the resin gear 1 of the first embodiment, the circumferential center of each tooth tip portion 33 is located radially outward of each main connecting portion 21 .

[0122] The resin gear 1 of Example 1 is a helical gear, and as shown in Figure 2, each tooth portion 31 extends obliquely with respect to the axial direction L, i.e., in a direction intersecting the axial direction L. Therefore, the tooth bottom portion 32 and the tooth tip portion 33 also extend obliquely with respect to the axial direction L. The main connecting portion 21 and the throttle portion 22 of the connecting portion 20 also extend obliquely with respect to the axial direction L.

[0123] The resin gear 1 of the first embodiment is manufactured by the manufacturing method of the first embodiment.

[0124] The molding device 9 of the first embodiment for manufacturing the resin gear 1 of the first embodiment includes a molding die 90 for molding the resin gear 1 of the first embodiment.

[0125] 5 and 6, cavity 90C of molding die 90 includes a central shaft portion molding portion 910, a shaft connection molding portion 911, a first distribution portion 913, a flow adjustment portion 920, a second distribution portion 914, and a teeth row molding portion 930. The respective portions of cavity 90C are arranged in the following order from the radially inner side to the radially outer side: central shaft portion molding portion 910, shaft connection molding portion 911, first distribution portion 913, flow adjustment portion 920, second distribution portion 914, and teeth row molding portion 930.

[0126] Central shaft portion molding portion 910 is a portion of cavity 90C that is used to mold central shaft portion 10, and has a mold surface that corresponds to central shaft portion 10. The mold surface located inside central shaft portion molding portion 910 is central shaft molding portion 919 that is used to mold central shaft 19.

[0127] The shaft coupling molding portion 911 is a portion of the cavity 90C for molding the shaft coupling portion 11, has a mold surface corresponding to the shaft coupling portion 11, and is continuous with the central shaft molding portion 919 radially outward.

[0128] The first distribution portion 913 is a portion of the cavity 90C that forms the annular portion 13. The first distribution portion 913 is a region of the cavity 90C where the gate 915 is located, and the thickness of the first distribution portion 913 is approximately constant in the circumferential and radial directions.

[0129] The flow adjustment section 920 is a portion of the cavity 90C that molds the communication section 20, has a mold surface that corresponds to the communication section 20, and is continuous with the first distribution section 913 on the outside in the radial direction.

[0130] The flow adjustment section 920 is configured such that a plurality of main flow path sections 921 and a plurality of throttle flow path sections 922 each having a smaller thickness than the main flow path sections 921 are alternately arranged in the circumferential direction.

[0131] Of these, the thickness of the main flow path section 921 is approximately the same as the thickness of the first distribution section 913. The main flow path portion 921 is a portion of the flow adjustment portion 920 that forms the main communication portion 21. The thickness of the main flow path portion 921 is approximately constant in the circumferential and radial directions.

[0132] The throttle flow path section 922 is a portion of the flow adjustment section 920 where the throttle section 22 is formed. The thickness of the throttle flow path portion 922 is about ¼ of the thickness of the main flow path portion 921. The thickness of the throttle flow path portion 922 is constant in the circumferential direction but is not constant in the axial direction L. The thickness of the throttle flow path section 922 is smaller than the thickness of the first distribution section 913 and the thickness of the main flow path section 921, and the throttle flow path section 922 is connected to the first distribution section 913 in a stepped manner. The thickness of the throttle flow path section 922 is approximately constant on the first distribution section 913 side and gradually increases radially outward, and then smoothly continues to the second distribution section 914.

[0133] The second distribution section 914 is a portion of the cavity 90C that forms the tooth connecting portion 14, and is a portion that is continuous with the flow adjustment section 920 on the radially outer side of the flow adjustment section 920. The thickness of the second distribution section 914 is approximately the same as the thickness of the main flow path section 921, and is also approximately the same as the thickness of the radially outer end of the throttle flow path section 922. The thickness of the second distribution section 914 is approximately constant in the circumferential and radial directions.

[0134] The tooth row forming portion 930 is a portion of the cavity 90C for forming the tooth row 30, and is continuous with the second distribution portion 914 on the radially outer side of the second distribution portion 914. The tooth row forming portion 930 is formed by alternately arranging a plurality of tooth tip forming portions 933 and a plurality of tooth bottom forming portions 932 in the circumferential direction. Of the tooth row forming portion 930, the region from the tooth tip forming portion 933 to the tooth bottom forming portion 932 adjacent to the tooth tip forming portion is a tooth forming portion 931 for forming the tooth portion 31.

[0135] In the manufacturing method of Example 1, the circumferential center of each tooth tip forming portion 933 is located radially outside each main flow path portion 921 .

[0136] Each tooth forming portion 931 extends radially outward from the central axis 19. The tooth tip forming portion 933 is located radially outward of the tooth bottom forming portion 932.

[0137] Since the resin gear 1 of Example 1 is a helical gear, the tooth forming portion 931 extends obliquely with respect to the axial direction L, and the tooth bottom forming portion 932 and the tooth tip forming portion 933 also extend obliquely with respect to the axial direction L. Similarly, the main flow path portion 921 and the throttle flow path portion 922 of the flow adjustment portion 920 also extend obliquely with respect to the axial direction L.

[0138] 5 and 6, the molding die 90 in the molding apparatus 9 of Example 1 is divided into a plurality of split dies 940 to 942. Of these, the split die 940 is a fixed die, and the split dies 941 and 942 are movable dies. Furthermore, the split die 941 is a tooth core for molding the tooth portion 31. The molding die 90 can be opened along a parting line PL.

[0139] The mold 90 is connected to an injection molding machine (not shown).

[0140] When manufacturing the resin gear 1 of Example 1 by the manufacturing method of Example 1, first, a resin-containing material is fed into a feeder of an injection molding machine (not shown). The resin-containing material is supplied from the feeder to the molding machine, heated and softened, and becomes a flowable molding material.

[0141] The fluid molding material injected from the injection molding machine into the cavity 90C of the mold 90 flows through the gate 915 into the cavity 90C. The fluid molding material first flows into the first distribution section 913 of the cavity 90C, and then flows in the circumferential direction as shown by the dashed line in Figure 1, before flowing into the flow adjustment section 920. As a result, the flow rate and flow velocity of the fluid molding material flowing into the flow adjustment section 920 become approximately uniform around the entire circumference of the flow adjustment section 920.

[0142] The fluid molding material that flows into the flow adjustment section 920 flows preferentially into the main flow path section 921 of the flow adjustment section 920, and most of the fluid molding material that flows from the flow adjustment section 920 into the tooth row forming section 930 passes through the main flow path section 921 and flows into the circumferential center of the tooth tip forming section 933.

[0143] The fluid molding material that has flowed into the circumferential center of the tooth tip forming portion 933 further flows toward both circumferential ends of the tooth tip forming portion 933. Therefore, in the resin gear 1 of Example 1, the orientation direction of the filler in the portion of each tooth 31 that is located near the tooth tip 33 is approximately symmetrical with respect to the circumferential center of the tooth tip 33.

[0144] Furthermore, the fluid molding material flows into the bottom forming portion 932 of the cavity 90C from each of the main flow passage portions 921 adjacent to the bottom forming portion 932. The fluid molding material meets at the circumferential center of the bottom forming portion 932. Therefore, in the resin gear 1 of Example 1, the orientation direction of the filler in the portion near each bottom portion 32 is approximately symmetrical with respect to the circumferential center of the bottom portion 32.

[0145] As described above, the manufacturing method of Example 1 can reduce bias in the orientation direction of the filler during molding. Therefore, in the resin gear 1 of Example 1, the orientation direction of the filler in the vicinity of each tooth tip 33 can be symmetrical about the circumferential center of the tooth tip 33. Furthermore, the orientation direction of the filler in the vicinity of each tooth bottom 32 can be symmetrical about the circumferential center of the tooth bottom 32.

[0146] As a result, according to the manufacturing method of Example 1, it is possible to suppress unevenness in the degree of shrinkage between portions of the resin gear, and to manufacture the resin gear 1 of Example 1 having excellent dimensional accuracy.

[0147] Example 2 The resin gear of Example 2 is the resin gear of the fourth embodiment, and the manufacturing method of Example 2 is the manufacturing method of the second embodiment. The manufacturing method of Example 2 is roughly the same as that of Example 1, except for the positional relationship between the main flow path portion 921 and the tooth tip forming portion 933 in the radial direction, and the positional relationship between the main flow path portion 921 and the tooth bottom forming portion 932 in the radial direction. Furthermore, the plastic gear 1 of Example 2 is substantially the same as the plastic gear 1 of Example 1, except for the positional relationship between the main connecting portion 21 and the tooth tip portion 33 in the radial direction, and the positional relationship between the main connecting portion 21 and the tooth bottom portion 32 in the radial direction.

[0148] Fig. 7 is an explanatory diagram schematically illustrating the appearance of the resin gear of Example 2 as viewed from above, and Fig. 8 is an explanatory diagram schematically illustrating the appearance of the resin gear of Example 2 as viewed from above and to the side. Fig. 9 is an explanatory diagram schematically illustrating the appearance of the resin gear of Example 2 cut at position XX in Fig. 8, and Fig. 10 is an explanatory diagram schematically illustrating the appearance of the resin gear of Example 2 cut at position YY in Fig. 8. Fig. 11 is an explanatory diagram schematically illustrating the appearance of the molding die in the manufacturing method of Example 2 cut at the same position as position XX in Fig. 8, and Fig. 12 is an explanatory diagram schematically illustrating the appearance of the molding die in the manufacturing method of Example 2 cut at the same position as position YY in Fig. 8.

[0149] The resin gear 1 of the second embodiment and the manufacturing method thereof will be described below, focusing on the differences from the resin gear 1 of the first embodiment and the manufacturing method thereof.

[0150] 7 and 8, in the resin gear 1 of Example 2, a tooth bottom portion 32 is located radially outside the main connecting portion 21. Otherwise, the resin gear 1 of Example 2 is substantially the same as the resin gear 1 of Example 1.

[0151] 11 and 12, in the manufacturing method of Example 2, a tooth bottom forming portion 932 is provided radially outside the main flow path portion 921. Other than that, the manufacturing method of Example 2 is generally the same as the manufacturing method of Example 1.

[0152] When the resin gear 1 of Example 2 is manufactured by the manufacturing method of Example 2, the fluid molding material injected into the cavity 90C of the mold 90 through the gate 915 from the injection molding machine (not shown) first flows into the first distribution section 913, and then flows in the circumferential direction as shown by the dashed line in Figure 7, before flowing into the flow adjustment section 920. As a result, even in the manufacturing method of Example 2, the flow rate and flow speed of the fluid molding material flowing into the flow adjustment section 920 are approximately uniform all around the circumference of the flow adjustment section 920.

[0153] The fluid molding material that flows into the flow adjustment section 920 flows preferentially into the main flow path section 921 of the flow adjustment section 920. As shown in Fig. 12, in the manufacturing method of Example 2, a tooth bottom forming section 932 is located radially outside the main flow path section 921. Therefore, most of the fluid molding material that flows from the flow adjustment section 920 into the tooth row forming section 930 passes through the main flow path section 921 and flows into the circumferential center of the tooth bottom forming section 932.

[0154] The fluid molding material that has flowed into the circumferential center of the bottom forming portion 932 then flows toward each of the circumferential ends of the bottom forming portion 932. Therefore, as shown in Figures 7 and 8, in the resin gear 1 of Example 2 obtained by the manufacturing method of Example 2, the orientation direction of the filler in the portion near each bottom portion 32 is approximately symmetrical with respect to the circumferential center of the bottom portion 32.

[0155] Furthermore, the flowable molding material that flows into each of the adjacent bottom forming portions 932 in the cavity 90C flows toward the tooth tip forming portion 933 between the bottom forming portions 932 and joins together at the circumferential center of the tooth tip forming portion 933. Therefore, in the resin gear 1 obtained by the manufacturing method of the resin gear 1 of Example 2, the orientation direction of the filler in the portion near each tooth tip portion 33 is approximately symmetrical with respect to the circumferential center of the tooth tip portion 33.

[0156] In this way, the manufacturing method of Example 2 can also reduce bias in the orientation direction of the filler during molding. As a result, in the resin gear 1 of Example 2, the orientation direction of the filler in the vicinity of each tooth tip 33 can be made symmetrical about the circumferential center of the tooth tip 33. In addition, the orientation direction of the filler in the vicinity of each tooth bottom 32 can be made symmetrical about the circumferential center of the tooth bottom 32.

[0157] As described above, the manufacturing method of Example 2 can reduce bias in the orientation direction of the filler during molding. Therefore, in the resin gear 1 of Example 2, the orientation direction of the filler in the vicinity of each tooth bottom portion 32 can be symmetrical about the circumferential center of the tooth bottom portion 32. Furthermore, the orientation direction of the filler in the vicinity of each tooth tip portion 33 can be symmetrical about the circumferential center of the tooth tip portion 33.

[0158] As a result, the manufacturing method of Example 2 can also suppress unevenness in the degree of shrinkage among portions of the resin gear 1, and can manufacture the resin gear 1 of Example 2 with excellent dimensional accuracy.

[0159] Although the present invention has been described above, the present invention is not limited to the above-described embodiments, etc., and it is possible to implement the present invention by appropriately extracting and combining elements described in the embodiments, etc., and to make various modifications within the scope that does not deviate from the spirit of the present invention. Furthermore, the specification of the present invention discloses not only the citation relationships of the claims at the time of filing but also the technical idea of ​​appropriately combining the matters described in the claims. [Explanation of symbols]

[0160] 1: Plastic gear 19: Central axis 15: Gate marks 20: Liaison Department 21: Main Contact 22: Diaphragm 30:Dentition 31: Teeth 32: Tooth bottom 33: Tooth tip 90: Molding mold 90C: Cavity 915: Gate 919: Central shaft molding part 920: Flow adjustment section 921:Main flow section 922: Throttle flow passage 930: Tooth arch molding section 932:Tooth bottom molding part 933: Tooth tip molding part

Claims

1. A resin-containing material containing a resin and a filler is used, A central axis and A method for manufacturing a resin gear having a tooth row in which tooth portions extending radially outward from the central axis and tooth roots located radially closer to the central axis than tooth tips of the tooth portions are alternately arranged along a circumferential direction, The cavity of the mold for molding the resin gear is a central shaft forming portion that forms the central shaft; a tooth row forming portion, in which tooth tip forming portions that form the tooth tips and tooth bottom forming portions that form the tooth bottoms are alternately arranged along the circumferential direction, and which forms the tooth row; a gate for injecting a resin material, the gate being located closer to the central shaft molding portion than the tooth row molding portion in the radial direction; a flow adjustment section that is located between the tooth row forming section and the gate in the radial direction, and in which a main flow path section and a throttle flow path section that is thinner than the main flow path section are alternately arranged along the circumferential direction, A method for manufacturing a plastic gear, wherein the circumferential center of each of the tooth tip forming portions is located radially outside each of the main flow path portions.

2. A resin-containing material containing a resin and a filler is used, A central axis and A method for manufacturing a resin gear having a tooth row in which tooth portions extending radially outward from the central axis and tooth roots located radially closer to the central axis than tooth tips of the tooth portions are alternately arranged along a circumferential direction, The cavity of the mold for molding the resin gear is a central shaft forming portion that forms the central shaft; a tooth row forming portion, in which tooth tip forming portions that form the tooth tips and tooth bottom forming portions that form the tooth bottoms are alternately arranged along the circumferential direction, and which forms the tooth row; a gate for injecting a resin material, the gate being located closer to the central shaft molding portion than the tooth row molding portion in the radial direction; a flow adjustment section that is located between the tooth row forming section and the gate in the radial direction, and in which a main flow path section and a throttle flow path section that is thinner than the main flow path section are alternately arranged along the circumferential direction, A method for manufacturing a plastic gear, wherein the circumferential center of each of the tooth bottom forming portions is located radially outside each of the main flow path portions.

3. 3. The method for manufacturing a plastic gear according to claim 1, wherein the thickness of the throttle flow passage portion is equal to or less than half the thickness of the main flow passage portion.

4. The method for manufacturing a resin gear according to claim 1 or 2, wherein the number of the gates is smaller than the number of the main flow passage portions.

5. made of a resin-containing material including a resin and a filler; A central axis and a tooth row in which tooth portions extending radially outward from the central axis and tooth bottom portions located radially closer to the central axis than tooth tips of the tooth portions are alternately arranged along the circumferential direction; a gate mark formed by injection of a resin material, the gate mark being located closer to the central axis than the tooth row in the radial direction; a connecting portion that is located between the tooth row and the gate mark in the radial direction, and that includes a main connecting portion and a plurality of narrowing portions that are thinner than the main connecting portion and are alternately arranged along the circumferential direction, a circumferential center of each of the tooth tips is located radially outward of each of the main connecting portions.

6. made of a resin-containing material including a resin and a filler; A central axis and a tooth row in which tooth portions extending radially outward from the central axis and tooth bottom portions located radially closer to the central axis than tooth tips of the tooth portions are alternately arranged along the circumferential direction; a gate mark formed by injection of a resin material, the gate mark being located closer to the central axis than the tooth row in the radial direction; a connecting portion that is located between the tooth row and the gate mark in the radial direction, and that includes a main connecting portion and a plurality of narrowing portions that are thinner than the main connecting portion and are alternately arranged along the circumferential direction, a circumferential center of each of the tooth roots located radially outward of each of the main connecting portions;

7. 7. The plastic gear according to claim 5, wherein the thickness of said drawn portion is equal to or less than half the thickness of said main connecting portion.

8. 7. The plastic gear according to claim 5, wherein the throttle portion is located at the axial center of the connecting portion.

Images