Helical gear

Abstract

To provide a helical gear capable of ensuring the molding accuracy of an outside rim part while improving releasability from a mold.SOLUTION: The present invention is a helical gear made of resin, comprising: an inside rim part that is connected to a rotational shaft and is circular when viewed from a direction of the rotational shaft; an outside rim part that surrounds the inside rim part at an interval on the radial outside, and in which a plurality of teeth is arranged in a circumferential direction on its outer peripheral part; a web that connects the inside rim part and the outside rim part, and has a dimension in the direction of the rotational shaft smaller than a dimension in the direction of the rotational shaft of the outside rim part; and a locking projection body that protrudes from one surface of the web in the direction of the rotational shaft, and has a thickness dimension in the radial direction and a length dimension in the circumferential direction. The locking projection body has an abutment part at one end in the circumferential direction, and has a gap between itself and the outside rim part in the radial direction.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a helical gear. [Background technology]

[0002] Conventionally, there has been known a helical gear having an outer rim part with a number of teeth on the outer circumferential surface, each of which has a spiral tooth trace. This helical gear is made of resin and is formed by injection molding in which molten resin is injected into a mold (see Patent Document 1).

[0003] The mold used for this injection molding is divided into a plurality of sections when the formed helical gear is removed from the mold. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-13861 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned helical gear, the teeth formed on the outer peripheral surface of the outer rim portion extend in a spiral shape, so when the portion of the mold that forms the teeth (outer rim portion) (tooth forming portion) is removed during injection molding, the tooth forming portion is rotated relative to the helical gear about the rotation axis of the helical gear and moved away in the direction of the rotation axis. However, at this time, the helical gear rotates together with the tooth forming portion, making it difficult to release from the mold.

[0006] Moreover, in recent years, there has been a demand for helical gears with highly precise molding of the outer rim portion in order to improve quietness, transmission efficiency, friction and wear characteristics, and the like.

[0007] Therefore, an object of the present invention is to provide a helical gear that can ensure molding precision of the outer rim portion while improving releasability from a mold. [Means for solving the problem]

[0008] The helical gear according to the present invention has: A resin helical gear, an inner rim portion connected to the rotating shaft and having a circular shape when viewed from the rotating shaft direction; an outer rim portion surrounding the inner rim portion at a distance from the radial outside and having a plurality of teeth arranged in a circumferential direction on an outer periphery thereof; a web connecting the inner rim portion and the outer rim portion and having a dimension in the axial direction smaller than a dimension in the axial direction of the outer rim portion; a locking projection body that protrudes from one surface of the web in the rotation axis direction and has a thickness dimension in the radial direction and a length dimension in the circumferential direction, The locking projection main body has an abutment portion at one end in the circumferential direction, and has a gap between itself and the outer rim portion in the radial direction.

[0009] In this way, the helical gear is provided with a locking projection main body having an abutment portion on the web, and by abutting a part of the mold on the abutment portion in the circumferential direction of the helical gear, co-rotation of the tooth-forming portion of the mold (portion where the teeth are formed) and the tooth-forming portion of the helical gear is prevented when the helical gear is separated from the tooth-forming portion of the mold, thereby improving the releasability of the mold from the helical gear. Moreover, by providing a gap between the locking projection main body and the outer rim portion, deformation of the outer rim portion caused by differences in shrinkage rates between the locking projection main body and the outer rim portion during injection molding is suppressed, and thus sufficient molding precision of the outer rim portion is ensured.

[0010] In the helical gear, The length dimension of the locking projection body may be greater than the thickness dimension.

[0011] In this way, since the length dimension of the locking projection body is greater than the thickness dimension, the strength of the locking projection body against circumferential forces can be ensured, and this makes it possible to suppress deformation of the locking projection body when a part of the mold is abutted against the locking projection body (abutted portion) to prevent the helical gear from rotating together while separating the tooth-forming portions of the mold.

[0012] In addition, in the helical gear, The locking projection may further include a connecting portion extending in the radial direction and connecting the locking projection body and the inner rim portion.

[0013] According to this configuration, the strength of the locking projection body is further improved.

[0014] In addition, in the helical gear, The locking projection bodies are arranged at intervals in the circumferential direction, The abutted portion of each locking projection body may be configured by a surface facing one side in the circumferential direction.

[0015] With this configuration, by abutting the corresponding parts of the die against each of the locking projection bodies from one circumferential side of the helical gear, the number of abutment points between the die and the helical gear in the circumferential direction when the tooth-forming part of the die and the helical gear are separated increases. Moreover, by configuring the abutted parts with a surface facing one circumferential side, it becomes easier to ensure a contact area with the corresponding part of the die. This makes it possible to more reliably prevent co-rotation of the tooth-forming part of the helical gear with the tooth-forming part of the die when the helical gear is separated from the tooth-forming part of the die. Effect of the Invention

[0016] As described above, according to the present invention, it is possible to provide a helical gear that can ensure molding precision of the outer rim portion while improving releasability from a mold. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view of the helical gear according to this embodiment, as viewed from the second gear side. [Diagram 2] FIG. 2 is a perspective view of the helical gear as viewed from the first gear side. [Diagram 3] FIG. 3 is a view of the helical gear as viewed from the other side in the rotation axis direction. [Figure 4] FIG. 4 is a view of the helical gear as viewed from one side in the direction of the rotation axis. [Diagram 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 7 is a diagram for explaining removal of the helical gear from the die, showing the state before the second portion is moved. [Figure 8] FIG. 8 is a diagram for explaining removal of the helical gear from the mold, showing movement of the second portion to one side in the direction of the rotation axis. [Figure 9] FIG. 9 is a view of a helical gear according to another embodiment as viewed from one side in the direction of the rotation axis. [Figure 10] FIG. 10 is a cross-sectional view taken along line XX in FIG. [Figure 11] FIG. 11 is a view of a helical gear according to another embodiment as viewed from one side in the direction of the rotation axis. [Figure 12] FIG. 12 is a cross-sectional view taken along line XII-XII in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, one embodiment of the present invention will be described with reference to FIGS.

[0019] The helical gear according to this embodiment is a resin gear, and is formed by, for example, injection molding. As shown in Figs. 1 to 6, this helical gear H is a two-stage gear in which two gears 1 and 2 with different diameters are arranged in the direction of a rotation axis C (the direction in which the rotation axis C extends: hereinafter also simply referred to as the "axial direction"). Hereinafter, of the two gears 1 and 2 arranged in the axial direction, the gear with the larger diameter is referred to as the first gear 1, and the gear with the smaller diameter is referred to as the second gear 2. This helical gear H has a through hole 3 penetrating in the axial direction at the center when viewed from the axial direction, and is used with the rotation axis C inserted through this through hole 3.

[0020] The helical gear H of this embodiment is made of two types of resin. Specifically, in the helical gear H, the second gear 2 is made of a resin harder than the first gear 1 (see Figs. 3 and 5). In the helical gear H of this embodiment, the second gear 2 is made of polyoxymethylene, and the first gear 1 is made of a thermoplastic polyester elastomer. Of the axial surface of the helical gear H of this embodiment, the inner portion P1 is the second gear 2, and the outer portion P2 is the first gear 1.

[0021] The helical gear H has an inner rim portion 11 connected to a rotation axis C, and the first gear 1 includes an outer rim portion 12 surrounding the inner rim portion 11, a web 13 connecting the inner rim portion 11 and the outer rim portion 12, and a first protrusion (locking protrusion) 14 protruding in the axial direction from one surface 13a of the web 13 in the axial direction. The first gear 1 also includes a second protrusion 15 protruding in the axial direction from the other surface 13b of the web 13 in the axial direction. The first gear 1 of this embodiment includes a plurality of first protrusions 14 and a plurality of second protrusions 15.

[0022] The inner rim portion 11 is a circular portion when viewed from the axial direction. Specifically, the inner rim portion 11 is a disk-shaped portion, and has an annular recess 111 on one axial surface 11a, which is recessed toward the other axial side (upper side in FIG. 5) and surrounds a central portion 110 through which the rotation shaft C is inserted. The inner rim portion 11 also has a circular protrusion 115 protruding toward the other axial side at the center of the other axial surface 11b. The inner diameter α1 of the inner peripheral surface 113 of the annular recess 111 corresponds to the outer diameter α2 of the circular protrusion 115 (more specifically, it is slightly smaller than the outer diameter α2: see FIG. 5). The inner rim portion 11 of this embodiment is composed of an annular inner rim element 22 located in the inner portion P1 of the second gear 2, and an inner rim element 114 of the first gear 1 connected to the inner rim element 22.

[0023] In the present embodiment, the annular recess 111 has a plurality of bottom surface recesses 112a that are recessed deeper toward the other axial side than the surrounding area, formed on the bottom surface 112 of the annular recess 111. These plurality of bottom surface recesses 112a are arranged at intervals in the circumferential direction so as to surround the central portion 110 (see FIG. 4).

[0024] The outer rim portion 12 is a portion that surrounds the inner rim portion 11 at a distance on the radial outside. A plurality of teeth 122 are formed on the outer periphery of this outer rim portion 12 and are aligned in the circumferential direction. Specifically, the outer rim portion 12 has an annular outer rim portion main body 121 that surrounds the inner rim portion 11 when viewed in the axial direction, and a plurality of teeth 122 aligned in the circumferential direction on the outer periphery of the outer rim portion main body 121.

[0025] The outer rim portion main body 121 is a short cylindrical portion extending in the axial direction, and the axial dimension of the outer rim portion main body 121 is the same as the axial dimension of the peripheral portion of the inner rim portion 11 (the portion outside the circular convex portion 115) (see Figure 5).

[0026] Each of the teeth 122 has a spiral tooth trace with the rotation axis C as the spiral center.

[0027] The web 13 connects the outer peripheral surface 11c of the inner rim portion 11 and the inner peripheral surface 12a of the outer rim portion 12, and has an axial dimension γ1 that is smaller than the axial dimension γ2 of the outer rim portion 12 (outer rim portion main body 121) (see FIG. 5). In this embodiment, the axial dimension of the web 13 at each position in a planar direction perpendicular to the axial direction is constant or approximately constant.

[0028] The multiple first protrusions 14 are arranged at intervals in the circumferential direction on one surface 13a of the web 13. The multiple first protrusions 14 in this embodiment are arranged at equal intervals in the circumferential direction (see FIG. 4). Each of the multiple first protrusions 14 protrudes from one surface 13a of the web 13 to one side in the axial direction.

[0029] Specifically, each of the multiple first projections 14 has a first projection body (locking projection body) 141 having a radial thickness dimension β1 and a circumferential length dimension β2 (see FIG. 4). Also, each of the multiple first projections 14 in this embodiment has a first connection portion (connection portion) 145 that connects the first projection body 141 and the inner rim portion 11. An axial dimension (protrusion amount) β3 of each of these first projections 14 is smaller than a dimension β4 in the axial direction from one surface 13a of the web 13 to the end of the outer rim portion 12 (see FIG. 6).

[0030] The first protrusion main body 141 has an abutment portion 142 at one circumferential end, and has a gap γ3 between itself and the outer rim portion 12 in the radial direction (see FIG. 4). In addition to the abutment portion 142, an abutment portion may be provided at one circumferential end of the first connection portion 145.

[0031] The first protrusion body 141 of this embodiment has a rectangular shape that is long in the circumferential direction (in this embodiment, the direction perpendicular to the radial direction and along one surface 13a of the web 13; hereinafter, also referred to as the "longitudinal direction") when viewed from the axial direction (see FIG. 4). That is, in the first protrusion body 141, the length dimension β2 is greater than the thickness dimension β1.

[0032] In this first protrusion main body 141, end faces 142, 143 at both ends in the longitudinal direction each extend in a plane perpendicular to the longitudinal direction. In the first protrusion main body 141 of this embodiment, one of these two end faces 142, 143, the face 142 on one side constitutes the above-mentioned abutted portion. That is, the abutted portion 142 of the first protrusion main body 141 is constituted by a face facing one side in the circumferential direction. In addition, an end face 144 in the protruding direction (axial direction) of the first protrusion main body 141 extends in a plane perpendicular to the axial direction.

[0033] Moreover, in the first protrusion main body 141, the central portion in the longitudinal direction bulges inward and outward in an arc shape when viewed from the axial direction. In the first protrusion main body 141 of this embodiment, the thickness dimension (diameter dimension) β11 of the portion bulging in an arc shape is smaller than the length dimension β2 (see FIG. 4).

[0034] In the first protrusion main body 141 of this embodiment, the portion bulging out in an arc shape is a portion (contact portion 141a: a region indicated by dots on an end face 144 of the first protrusion main body 141 in FIG. 4) that is pressed by an ejector pin when the ejector pin pushes out in the axial direction to release the helical gear H from a mold (second portion 52: see FIGS. 7 and 8) during injection molding described below, and the contact portion 141a has a shape and size corresponding to that of the ejector pin when viewed in the axial direction. This contact portion 141a is disposed in the center of the first protrusion main body 141 in the longitudinal direction.

[0035] By providing the contact portion 141a in this manner, the contact portion 141a can securely receive the ejector pin, and the helical gear H can be reliably released from the mold. Moreover, by arranging the contact portion 141a in the center of the first protrusion main body 141 in the longitudinal direction, the first protrusion main body 141 is less likely to deform when pressed by the ejector pin.

[0036] The first connecting portion 145 protrudes in the axial direction from one surface 13a of the web 13 and extends in the radial direction from the inner rim portion 11 to the first protrusion main body 141. In this embodiment, the first connecting portion 145 is connected to the center portion in the longitudinal direction of the first protrusion main body 141 (more specifically, the portion that bulges out in an arc shape radially inward when viewed from the axial direction). The amount of protrusion in the axial direction of the first connecting portion 145 is the same as the amount of protrusion in the axial direction of the first protrusion main body 141.

[0037] In the multiple first projections 14 each configured as described above, the circumferential distance between the first projection bodies 141 of the circumferentially adjacent first projections 14 (more specifically, the circumferential distance between the central positions of the end faces 142, 143 facing each other in the circumferential direction when viewed from the axial direction) is greater than the length dimension β2. This reduces the longitudinal length (or circumferential length) of the first projection body 141, making it difficult for deformation such as bending to occur in the first projection body 141.

[0038] The second protrusions 15 are arranged at intervals in the circumferential direction on the other surface 13b of the web 13. In the first gear 1 of this embodiment, the number of the second protrusions 15 is the same as the number of the first protrusions 14, and these second protrusions 15 are arranged at positions overlapping the first protrusions 14 when viewed from the axial direction, that is, they are arranged at the same positions as the corresponding first protrusions 14 in the circumferential direction. As a result, the second protrusions 15 are also arranged at equal intervals in the circumferential direction (see FIG. 3). Each of the second protrusions 15 protrudes from the other surface 13b of the web 13 to the other axial side (i.e., the opposite side to the first protrusions 14).

[0039] Specifically, each of the multiple second projections 15 has a second projection body 151 having a radial thickness dimension β5 and a circumferential length dimension β6, and a second connection portion 155 that connects the second projection body 151 to the inner rim portion 11. The axial dimension (protrusion amount) β7 of each of these second projections 15 is smaller than the dimension β4 from the other surface 13b of the web 13 to the end of the outer rim portion 12 in the axial direction (see FIG. 6).

[0040] The second protrusion body 151 has a gap γ4 between itself and the outer rim portion 12 in the radial direction. The second protrusion body 151 of this embodiment has a rectangular shape that is elongated in the circumferential direction (in the example of this embodiment, the long direction) when viewed from the axial direction. That is, in the second protrusion body 151, the length dimension β6 is greater than the thickness dimension β5 (see FIG. 3 ). The thickness dimension β5 of the second protrusion body 151 of this embodiment is the same as the thickness dimension β1 of the first protrusion body 141 (the thickness dimension of the portion excluding the bulging portion), and the length dimension β6 of the second protrusion body 151 is the same as the length dimension β2 of the first protrusion body 141.

[0041] In this second protrusion main body 151, end faces 152, 153 at both ends in the longitudinal direction each extend in a plane perpendicular to the longitudinal direction. In addition, end face 154 in the protruding direction (axial direction) of second protrusion main body 151 extends in a plane perpendicular to the axial direction.

[0042] The second connection portion 155 protrudes in the axial direction from the other surface 13b of the web 13 and extends in the radial direction from the inner rim portion 11 to the second protrusion main body 151. In this embodiment, the second connection portion 155 is connected to the longitudinal center portion of the second protrusion main body 151. The axial protrusion amount of the second connection portion 155 and the axial protrusion amount of the second protrusion main body 151 are the same.

[0043] The second gear 2 extends from the center of the inner rim portion 11 as viewed in the axial direction to the other side along the axial direction. A plurality of teeth 21 are formed on the outer periphery of the second gear 2 and arranged in the circumferential direction. Each of the plurality of teeth 21 has a spiral shape with the rotation axis C as the spiral center. Each tooth 21 of the second gear 2 of this embodiment has a spiral shape that rotates in the opposite direction to each tooth 122 of the first gear 1. The axial dimension α5 of the second gear 2 of this embodiment is larger than the axial dimension α3 at the position of the circular protrusion 115 of the inner rim portion 11 of the first gear 1 (see FIG. 5).

[0044] The helical gear H configured as above is formed by injection molding as described above. In this injection molding, after the resin injected into the mold has solidified to such an extent that it can be released from the first portion 51, when the portion (first portion) 51 forming the teeth 122 (outer rim portion 12) of the first gear 1 is removed from the helical gear H as shown in Figures 7 and 8, the first portion 51 moves relatively to one side in the axial direction (upward in Figure 7) while rotating relatively to the helical gear H about the rotation axis C so as to follow the tooth trace of the first gear 1.

[0045] At this time, a portion (second portion) 52 of the mold located on the other side of the helical gear H in the axial direction has a plurality of abutment portions 521 for preventing the helical gear H from rotating together with the first portion 51.

[0046] These contact portions 521 protrude to one side in the axial direction and are located between the first protrusions 14 adjacent to each other in the circumferential direction of the helical gear H, and contact the contacted portions 142 of the first protrusions 14 in the circumferential direction. More specifically, the contact portions 521 are portions of the second portion 52 that are located between the first protrusions 14 and that face (contact) the contacted portions 142 of the first protrusions 14 in the circumferential direction. As a result, when the first portion 51 moves relatively to one side in the axial direction while rotating relatively around the rotation axis C with the helical gear H, the helical gear H that tends to rotate together with the first portion 51 is prevented from rotating in the circumferential direction relative to the second portion 52 because the contact portions 521 of the second portion 52 contact the contacted portions 142 of the first protrusions 14 from the side opposite to the co-rotation direction in the circumferential direction, and thus the helical gear H is prevented from rotating together with the first portion 51.

[0047] Furthermore, as described above, since the circumferential distance between the first protrusion bodies 141 of circumferentially adjacent first protrusions 14 is greater than the length dimension β2, the circumferential dimension of the abutment portion 521 of the second portion 52 that fits between the circumferentially adjacent first protrusion bodies 141 can be sufficiently secured (i.e., the strength of the abutment portion 521 can be sufficiently obtained).As a result, when the first portion 51 rotates relatively to the helical gear H around the rotation axis C and moves relatively to one side in the axial direction, the abutment portions 521 firmly mesh with the abutted surfaces 142 of each first protrusion body 141, and as a result, the circumferential rotation (co-rotation) of the helical gear H is more reliably prevented.

[0048] The helical gear H described above is a resin helical gear H, and includes an inner rim portion 11 connected to a rotation axis C and circular when viewed from the axial direction (direction of the rotation axis C), an outer rim portion 12 surrounding the inner rim portion 11 with a gap on the radial outside and having a plurality of teeth 122 arranged in the circumferential direction on its outer periphery, a web 13 connecting the inner rim portion 11 and the outer rim portion 12 and having an axial dimension γ1 smaller than the axial dimension γ2 of the outer rim portion 12, and a first protrusion body (locking protrusion body) 141 protruding from one surface 13a of the web 13 in the rotation axis direction and having a radial thickness dimension β1 and a circumferential length dimension β2. The first protrusion body 141 has an abutted portion 142 at one end in the circumferential direction and has a gap γ3 between it and the outer rim portion 12 in the radial direction.

[0049] In this way, the helical gear H includes a first protrusion body 141 having an abutment portion 142 on the web 13, and a part of the mold (the abutment portion of the second portion 52) 521 is abutted against the abutment portion 142 in the circumferential direction of the helical gear H, thereby preventing co-rotation of the first portion 51 of the helical gear H with the first portion (the portion where the teeth 122 are formed) 51 of the mold when the helical gear H is separated from the first portion 51, thereby improving the releasability of the mold (more specifically, the first portion 51) from the helical gear H. Furthermore, since there is a gap γ3 between the first protrusion body 141 and the outer rim portion 12, deformation of the outer rim portion 12 caused by differences in the shrinkage rates between the first protrusion body 141 and the outer rim portion 12 during injection molding, more specifically, during cooling in injection molding, is suppressed, and thus molding precision of the outer rim portion 12 is sufficiently ensured.

[0050] Furthermore, in the helical gear H of this embodiment, the length dimension β2 of the first protrusion main body (locking protrusion main body) 141 is greater than the thickness dimension β1. In this way, the length dimension β2 of the first protrusion main body 141 is greater than the thickness dimension β1, thereby ensuring the strength of the first protrusion main body 141 against circumferential forces. This makes it possible to suppress deformation of the first protrusion main body 141 when the first portion 51 of the mold is separated while preventing the helical gear H from rotating together by abutting a part 521 of the mold (the abutting portion of the second portion 52) against the first protrusion main body 141 (more specifically, the abutted portion 142).

[0051] Moreover, the helical gear H of this embodiment includes a first connection portion (connection portion) 145 that extends in the radial direction and connects the first protrusion body (locking protrusion body) 141 and the inner rim portion 11. This further improves the strength of the first protrusion body 141. For example, the first protrusion body 141 becomes less likely to fall over in the radial direction relative to the web 13.

[0052] In addition, in the helical gear H of this embodiment, multiple first protrusion bodies (locking protrusion bodies) 141 are arranged at intervals in the circumferential direction, and the abutment portion 142 of each first protrusion body 141 is formed by a surface facing one side in the circumferential direction.

[0053] According to this configuration, by abutting the corresponding portion (abutment portion of the second portion 52) 521 of the mold against each first protrusion main body 141 from one circumferential side of the helical gear H, the number of abutment points between the mold (more specifically, the second portion) 52 and the helical gear H in the circumferential direction when the first portion 51 of the mold and the helical gear H are separated increases. Furthermore, by configuring the abutted portion 142 with a surface facing one circumferential side, it becomes easier to ensure the contact area with the corresponding portion 521 of the mold. As a result, it is possible to more reliably prevent co-rotation of the first portion 51 of the helical gear H with the first portion 51 of the mold when the first portion 51 of the mold and the helical gear H are separated.

[0054] It should be noted that the helical gear of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, or part of the configuration of one embodiment can be replaced with the configuration of another embodiment. Furthermore, part of the configuration of one embodiment can be deleted.

[0055] Although the helical gear H in the above embodiment is a double-stage gear, the present invention is not limited to this configuration and the helical gear H may be a single-stage gear.

[0056] In addition, although the helical gear H in the above embodiment is made of two types of resin, the present invention is not limited to this configuration. The helical gear H may be made of one type of resin, or three or more types of resin.

[0057] In addition, in the helical gear H of the above embodiment, the tooth traces of the teeth 122 of the first gear 1 and the tooth traces of the teeth 21 of the second gear 2 are each helical (helical teeth), but the tooth traces of the teeth 21 of the second gear 2 may be straight in the axial direction (i.e., spur gear).

[0058] In the first gear 1 of the above embodiment, the first protrusions 14 are arranged in plurality on the one surface 13a of the web 13, but the present invention is not limited to this configuration. The first protrusion 14 may be arranged in a single number on the one surface 13a of the web 13.

[0059] In the first projection 14 of the first gear 1 in the above embodiment, the first connecting portion 145 is connected to the center of the first projection main body 141 in the circumferential direction, but is not limited to this configuration. The first connecting portion 145 may be connected to a position shifted from the center of the first projection main body 141 in the circumferential direction. Moreover, the first connecting portion 145 may be connected to an end portion of the first projection main body 141 in the circumferential direction, as shown in Figs. 9 and 10.

[0060] Moreover, the first protrusion 14 in the above embodiment has the first protrusion main body 141 and the first connecting portion 145, but is not limited to this configuration. The first protrusion 14 may be configured without the first connecting portion 145, that is, configured only by the first protrusion main body 141. In this case, the first protrusion main body 141 may have a gap formed between it and the inner rim portion 11 and between it and the outer rim portion 12 in the radial direction of the first gear 1. Moreover, the first protrusion main body 141 may be configured without a gap between it and the inner rim portion 11, that is, connected to the inner rim portion 11, as shown in FIG. 11.

[0061] In addition, the axial dimension of each portion of the first protrusion 14 in the above embodiment is constant, but this is not limited to the configuration. The axial dimension of each portion of the first protrusion 14 does not have to be constant. For example, as shown in Figs. 11 and 12, the first protrusion 14 may have a configuration in which the axial dimension gradually decreases as it moves away from the abutted portion 142 in the circumferential direction.

[0062] Further, the specific configuration of the first projection 14 is not limited. The first projection 14 in the above embodiment has a rectangular parallelepiped shape, but may have a columnar shape such as a circular cylinder or a rectangular column extending in the axial direction from one surface 13a of the web 13. Further, the contacted portion 142 of the first projection 14 does not have to be a flat surface perpendicular to the longitudinal direction. The contacted portion 142 may be a curved surface, for example.

[0063] In the first protrusion main body 141 of the above embodiment, the length dimension β2 is greater than the thickness dimension β1, but is not limited to this configuration. In the first protrusion main body 141, the length dimension β2 and the thickness dimension β1 may be the same or approximately the same.

[0064] In the first gear 1 of the above embodiment, the second protrusions 15 are arranged on the other surface 13b of the web 13 at positions corresponding to the first protrusions 14 in the circumferential direction, but this configuration is not limited to this. The second protrusions 15 may not be present on the other surface 13b of the web 13 (see Figs. 10 and 12). The second protrusions 15 may be arranged on the other surface 13b of the web 13 at positions different from the first protrusions 14 in the circumferential direction. [Explanation of symbols]

[0065] 1...first gear, 11...inner rim portion, 11a...one surface, 11b...other surface, 11c...outer peripheral surface, 110...central portion, 111...annular recess, 112...bottom surface, 112a...bottom recess, 113...inner peripheral surface, 114...inner rim element, 115...circular protrusion, 12...outer rim portion, 12a...inner peripheral surface, 121...outer rim portion main body, 122...tooth, 13...web, 13a... One surface, 13b...other surface, 14...first protrusion, 141...first protrusion main body, 141a...contact portion, 142...contacted portion, end surface (surface facing one side in the circumferential direction), 143...surface facing the other side in the circumferential direction, 144...end surface in the protruding direction, 145...first connecting portion, 15...second protrusion, 151...second protrusion main body, 152, 153...end surface in the longitudinal direction, 154...end surface in the protruding direction surface, 155...second connection portion, 2...second gear, 21...tooth, 22...inner rim element, 3...through hole, 51...first portion, 52...second portion, 521...contact portion, C...rotation axis, H...helical gear, P1...inner portion, P2...outer portion, α1...inner diameter of annular recess, α2...outer diameter of circular protrusion, α3...maximum axial dimension of inner rim portion, α5...axial dimension of second gear, β1...thickness dimension of first projection body, β2...length dimension of first projection body, β4...dimension from web to end of outer rim portion in axial direction, β5...thickness dimension of second projection body, β6...length dimension of second projection body, γ1...axial dimension of web, γ2...axial dimension of outer rim portion, γ3...gap between first projection and outer rim portion, γ4...gap between second projection and outer rim portion

Claims

1. A resin helical gear, an inner rim portion connected to the rotating shaft and having a circular shape when viewed from the rotating shaft direction; an outer rim portion surrounding the inner rim portion at a distance from the radial outside and having a plurality of teeth arranged in a circumferential direction on an outer periphery thereof; a web connecting the inner rim portion and the outer rim portion and having a dimension in the axial direction smaller than a dimension in the axial direction of the outer rim portion; a locking projection body that protrudes from one surface of the web in the rotation axis direction and has a thickness dimension in the radial direction and a length dimension in the circumferential direction, the locking projection main body has an abutment portion at one end in the circumferential direction, and has a gap between itself and the outer rim portion in the radial direction.

2. 2. The helical gear according to claim 1, wherein the length dimension of the locking projection body is greater than the thickness dimension of the locking projection body.

3. 3. The helical gear according to claim 1, further comprising a connection portion extending in the radial direction and connecting the locking projection body and the inner rim portion.

4. The locking projection bodies are arranged at intervals in the circumferential direction, 3. The helical gear according to claim 1, wherein the abutted portion of each of the locking projection bodies is formed by a surface facing one side in the circumferential direction.

Images