JP2016183764A - Composite gear and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite gear capable of reducing a difference in a gear shape caused by a difference in filling timing for each gear and suppressing occurrence of welds near a resin merge part.SOLUTION: In a composite gear that is made of a synthetic resin or metal, and comprises an inner cylindrical part or a shaft part, a first member including an outer cylindrical part, and a second member including a gear part formed by a synthetic resin differing from the first member, the second member is filled between the inner cylindrical part or the shaft part, and the outer cylindrical part, and into a through hole punched in the outer cylindrical part, and forms a thick part communicating with the gear part in a direction vertical to the outer peripheral surface between the through hole and the gear part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a compound gear and a method for manufacturing the same, in which materials of a tooth part and other parts are different.

  Resin gears are incorporated as power transmission components in OA equipment such as copiers and printers, consumables such as ink cartridges, and mechanical products of small precision equipment such as digital cameras and video cameras. Conventionally, for resin gears as high-accuracy power transmission components, the accuracy standards of the tip circle size, meshing error (JGMA 116-02) and tooth trace grade (JIS B 1702) depend on the application and purpose. Is set. In particular, resin gears used for high-quality machine products often increase the quality by setting a small range of these accuracy standards. However, recent color printers and color copiers are required to have not only high quality but also functional improvements such as low noise performance during driving and advanced printing performance. In these cases, since it is difficult to satisfy the requirements only by the conventional method of setting the gear accuracy standard width to be small, it is necessary to improve the rotation transmission accuracy (dynamic accuracy) of the gear.

  In order to increase the rotation transmission accuracy of the gear, means such as (1) increasing the meshing rate, (2) preventing gear rattling during rotation driving, and (3) suppressing deformation during rotation driving have been considered.

  Specifically, in the case of (1), when a pair of gear pairs is rotationally driven, the number of teeth that mesh continuously is increased. For example, in the case of a gear having no twist angle, such as a spur gear, the meshing state changes from the start to the end of the meshing. However, this change is reduced by increasing the meshing rate, and power can be transmitted smoothly. Conventionally, in order to increase the meshing rate, there is a means of using a helical gear as a gear. The teeth of the helical gear have a twist, and thus extend helically in the direction of the rotation axis. Therefore, point contact begins at one end of the tooth at the beginning of the working surface, then the contact width of the tooth increases to a maximum and then gradually decreases and meshes with point contact on the opposite side of the tooth width at the end of the working surface. It ends. Therefore, the fluctuation of the force applied to the teeth becomes smooth and the rotation of the gears becomes smooth. In helical gears, the greater the twist angle and tooth width, and the smaller the module, the greater the meshing rate.

  In the case of (2), it is to suppress the impact and vibration generated at the beginning of meshing. Since the gear includes not only the tooth portion but also the shaft portion in a shape error that occurs in the machining process, an interference region is generated in the tooth portion during meshing. The generation of this interference region becomes an impact or vibration and deteriorates the transmission performance of the gear. Conventionally, means such as tooth profile correction, crowning, and end relief have been used to suppress this impact and vibration. Tooth profile correction is a method of thinning the tooth tip and root portion where interference has occurred. In addition, the crowning is one in which an appropriate bulge is added in the tooth line direction in order to prevent tooth interference caused by a gear tooth direction error, a shaft parallel error, a mounting error, and the like. Similarly, the end relief is a method of providing a chamfered relief at the tooth end portion in the tooth line direction.

  In the case of (3), it is to suppress the deformation due to the component force in the thrust direction that occurs when torque is applied to the helical gear. If the tooth is deformed in the thrust direction, the position and angle of the tooth meshing change, and the above-described tooth interference may occur. Conventionally, in a gear manufactured by injection molding a synthetic resin such as polyacetal, the rigidity of the entire gear has been improved by arranging a plurality of ribs.

  However, with the recent improvement in performance of color printers and color copiers, improvement of functions has reached the limit only with such conventional methods. For example, the suppression of the striped pattern due to shading during printing, which is called banding, which requires very high rotation transmission accuracy, is difficult to solve only by the method described above. Therefore, in recent years, compound gears formed of two or more kinds of materials have been devised.

  For example, FIG. 11 shows a conventional example of a compound gear formed of two kinds of materials. Fig.7 (a) is a side view of the conventional compound gear, FIG.11 (b) is a longitudinal cross-sectional view of Fig.11 (a).

  In FIG. 11, the compound gear 70 has a first member 73 and a second member 71. The first member 73 is formed of resin, and is formed on the outer side of the inner cylindrical portion 76 and an inner cylindrical portion 76 that is a boss (shaft support portion) fitted to a shaft (not shown) having an axial center 75. The outer cylindrical portion 77 has a plate-like web that connects the inner cylindrical portion 76 and the outer cylindrical portion 77. The second member is made of a softer material than the first member, and the tooth portion 74 is formed on the outer peripheral surface of the outer cylindrical portion 77. By making the resin material of the second member 71 have a lower elastic modulus than the polyacetal resin normally used for gears, the tooth surfaces can be elastically deformed to increase the actual engagement rate when the gears are engaged. It becomes possible. Further, since the elastic modulus is small, it also serves as a cushioning material, and can suppress the behavior of rattling during rotation driving. That is, (1) and (2) described above can be obtained more effectively. Further, by making the resin material of the first member 73 highly rigid, it is possible to suppress the deformation of the gear during the rotational drive, and the above-described effect (3) is not hindered.

  In general, such a compound gear is manufactured by inserting the first member into a mold and secondarily forming the second member. However, since the second member is formed on the outer peripheral surface of the first member, the gate of the second member must be installed in a limited area. In FIG. 11, which is a conventional example, a method of installing the gate 72 directly on the tooth portion is used, but it is difficult to install the gate due to a lack of space in a small module gear used for OA equipment or the like. In addition, the installation of a gate near the tooth portion causes problems such as deterioration of tooth accuracy due to a difference in contraction rate due to heat and deformation at the time of gate cutting.

  In order to solve such a problem, in the composite gear 80 as shown in FIG. 12, the distance between the outer cylindrical portion 87 and the inner cylindrical portion 88 of the first member 81 that is far from the tooth portion and relatively easy to install the gate is set. A means for providing a gate of the second member in the space 85 is used. In this case, the gate 82 of the second member is installed in the space 85 inside the outer cylindrical portion 87 of the first member, and the injected molten resin passes through the through hole 86 formed in the first member and the tooth portion 84. To be filled. Therefore, not only is the accuracy of the teeth part deteriorated due to heat and deformation, but also the second member is formed inside and outside the first member, so that the effect of firmly bonding each other is also produced.

  For example, in Patent Document 1, the first member rotates at the injection pressure when filling the second member by making the resin flow path of the second member provided in the first member oblique from the radial direction, A technique for minimizing a difference in flow distance generated between teeth is disclosed.

JP2000-843

  When the gate of the second member is provided inside the first member, the resin flow path connecting the inner diameter portion of the first member and the tooth portion of the outer peripheral portion is provided in the first member as shown in FIG. The plurality of through holes 86 are formed.

  However, the flow of the second member branches into a plurality of parts by passing through the through holes and rejoins on the outer peripheral surface of the first member, so that various problems arise. FIG. 13 is a diagram illustrating a state in which the outer peripheral surface of the first member having the plurality of through holes 86 is filled with the second member. In the second member 83 formed on the outer peripheral surface, the thickness Tb of the tooth bottom portion is thinner than the thickness Tt of the tooth tip portion. Therefore, the resin that has passed through the through hole 86 preferentially flows through the tooth portion 87 in the vicinity of the through hole, and is difficult to flow into the adjacent tooth portion. That is, the flow in the circumferential direction is slow, and there is a large difference in the filling timing of the tooth portion 88 located near the middle of the through hole 86 and the tooth portion 87 near the through hole. In such a case, since the solidified state of the second member varies from tooth to tooth, a difference occurs in the pressed state of each tooth, resulting in a difference in tooth shape. Furthermore, in this case, when the angle formed by the two lines when the resin flow direction when the branched resin flow merges again from the two directions near the tooth portion 88 is represented by two lines is α, Since the angle α is small, there is a possibility that a weld is formed and the tooth surface accuracy is significantly deteriorated.

  In Patent Document 1, the resin flow path of the second member provided in the first member is inclined from the radial direction, so that the first member rotates at the injection pressure when filling the second member, and the teeth A technique for minimizing the difference in flow distance between the two is disclosed. However, since this method cannot obtain the effect of reducing the merging angle of the second member, there is a possibility that a weld is formed in the vicinity of the final filling portion. In order to be able to rotate by injection of the first member and the second member, the structure of the mold becomes complicated and the mold cost increases. Furthermore, since the first member rotates during molding, there is a possibility that the cylindrical accuracy such as the coaxiality of the gears may be adversely affected.

  The invention relating to the present application has been made in view of the above-described problems of the prior art. With a simple configuration, the difference in tooth shape caused by the difference in filling timing for each tooth is reduced, and the weld near the resin merging portion is obtained. An object of the present invention is to provide a compound gear capable of suppressing generation.

The composite gear of the present invention is made of synthetic resin or metal, and includes a first member having an inner cylindrical portion or a shaft portion, an outer cylindrical portion, and an outer peripheral surface of the first member. In the composite gear including the second member having tooth portions formed of different synthetic resins, the second member includes the inner cylindrical portion or the shaft portion, the outer cylindrical portion, and the outer outer portion. It is filled in the through hole made in the cylindrical part,
A thick wall portion is formed between the through hole and the tooth portion and communicates with the tooth portion perpendicular to the outer peripheral surface.

  In the method for manufacturing a composite gear according to the present invention, resin is supplied from between the inner cylindrical portion or the shaft portion and the outer cylindrical portion of the first member having the inner cylindrical portion or the shaft portion and the outer cylindrical portion. Injecting and forming a toothed portion on the outer peripheral surface of the outer cylindrical portion by the resin that has passed through the through hole formed in the outer cylindrical portion, the resin that has passed through the through hole is thick The tooth portion is injected from a direction perpendicular to the outer peripheral surface through a meat portion.

  According to the present invention, with a simple configuration, it is difficult for the tooth accuracy to deteriorate due to thermal effects and gate cuts, and the deterioration of fluidity in the circumferential direction can be minimized. Therefore, it is possible to reduce the difference in tooth shape resulting from the filling timing difference for each tooth, and further increase the joining angle at the resin joining portion to suppress the occurrence of welds.

The figure which shows the compound gearwheel in embodiment of this invention The figure which shows the compound gearwheel in embodiment of this invention Detailed view of compound gear in embodiment of the present invention Example of injection mold for forming the second member of the present invention The figure showing the flow of the 2nd member in embodiment of this invention Measurement results showing the relationship between gate position and deformation Measurement results showing accuracy difference for each tooth Experimental results showing the relationship between the thickness Tr of the thick part and the roundness of the tip Experimental results showing the relationship between the thickness Tb of the root and the roundness of the tip Measurement results showing the tendency of roundness of the tip circle The figure which shows the compound gear in a 1st prior art example The figure which shows the compound gear in a 2nd prior art example The figure showing the flow of the 2nd member in the 2nd conventional example

  1, 2 and 3 are drawings which best illustrate the features of the present invention. 1 and 2 are schematic views of a compound gear 10 showing an example of an embodiment of the present invention. FIG. 1 (a) shows a front view, and FIG. 1 (b) shows A in FIG. 1 (a). -A shows a cross-sectional view. Fig.2 (a) shows the side view of the compound gearwheel 10, and FIG.2 (b) shows BB sectional drawing of Fig.2 (a). The compound gear 10 has a first member 11 and a second member 20. The first member 11 has an inner cylindrical portion 15 that is an attachment portion to a shaft (not shown) having an axial center 14 and an outer cylindrical portion 18. The inner cylindrical portion 15 and the outer cylindrical portion 18 are connected to each other, and the spoke portion 111 that divides the space 12 between the inner cylindrical portion 15 and the outer cylindrical portion 18 and a plate-like web 112 that fills the space between the spoke portions are included. . The second member 20 forms a tooth portion 23 on the outer peripheral surface of the outer cylindrical portion 18. Although the example which has the inner side cylindrical part 15 which is an attachment part to a axis | shaft is shown here as the 1st member 11, the axis | shaft may be directly attached to the 1st member 11. FIG. That is, a shaft portion may be provided instead of the inner cylindrical portion 15. The outer cylindrical portion 18 is formed with a plurality of through holes 13 penetrating the inner side (inner peripheral surface) and the outer side (outer peripheral surface). 1 and 2 show an example in which the through holes 13 are provided at eight positions at equal intervals, but the present invention is not limited to this. A gate 21 for injecting resin is formed in the space 12 between the inner cylindrical portion 15 (or the shaft portion) and the outer cylindrical portion 18. The resin injected from the gate 21 passes through the space 12 and the through hole 13 between the inner cylindrical portion 15 (or shaft portion) and the outer cylindrical portion 18, and reaches the outer peripheral surface of the outer cylindrical portion 18 of the first member 11. The tooth part 23 is formed. That is, the tooth portion 23 and the gate 21 are connected by the through hole 13. 29 is a thick part through which the resin that has passed through the through hole 13 passes before forming the tooth part 23, and is formed of the second member. Further, a rim 28 made of the second member is formed between the tooth portion 23 made of the second member and the outer peripheral surface of the outer cylindrical portion 18 made of the first member. The rim 28 is formed so as to straddle the plurality of tooth portions 23 so as to communicate with the bottom portion of the tooth portion 23 in the radial inner direction of the tooth portion 23. The thick portion 29 is formed so as to communicate with the tooth portion in the direction perpendicular to the outer peripheral surface in the lateral direction (parallel to the axis) of the tooth portion 23 and across the plurality of tooth portions 23. . In addition, the rim 28 and the thick part 29 communicate with each other. The thick portion 29 has a thickness Tr in the lateral direction (direction parallel to the axis). The rim 28 has a thickness Tb in the radial direction. The second member 20 is formed by the resin injected from the gate 21. That is, the second member 20 is formed of a resin filled in the space 12 between the inner cylindrical portion 15 and the outer cylindrical portion 18, the through hole 13, the thick portion 29, the rim 28, and the tooth portion 23.

  FIG. 3 is an enlarged view of a DT1 portion of the compound gear 10 shown in FIG. Reference numeral 18 denotes an outer cylindrical portion which is formed of the first member 11. Reference numeral 28 denotes a rim made of a second member having a thickness Tb. The outer cylindrical portion 18 also becomes a part of the rim of the compound gear 10. The rim 28 is formed by the second member 20 concentrically on the outer peripheral surface of the outer cylindrical portion 18. The first member preferably has a higher elastic modulus than the second member. By making the second member a softer material than the first member, it is possible to increase the actual meshing rate by elastically deforming the tooth surface when the gear meshes, and fluctuations in the force applied to the teeth. Becomes smoother, and the rotation of the gears becomes smoother. In addition, since rattling can be suppressed, vibration can be reduced. Moreover, since the resin material of the first member can be made highly rigid, deformation of the gear during rotation driving can be suppressed. Specifically, the first member 11 is manufactured by injection molding using a resin material containing any of polyacetal, polybutylene terephthalate, polyphenylene sulfide, polyamide, nylon, and the like. Alternatively, it is manufactured by cutting, sintering, pressing or the like using a metal material. The second member 20 is manufactured by injection molding using a synthetic resin material including a thermoplastic elastomer.

  1, 2, and 3, the second member has a thick portion that spans a plurality of tooth portions before flowing into the tooth portion through a through hole provided in the first member. Characterized by the point of passing. FIG. 5 is a diagram showing a filling tendency of the second member 20 of the compound gear 10 in the present embodiment shown in FIGS. 1, 2, and 3. In the present embodiment, a thick portion 29 having a thickness Tr is provided between the through hole 13 and the tooth portion 23 so as to extend over a plurality of teeth. Therefore, the second member 20 includes a tooth tip portion and a tooth bottom portion. The effect of flowing in the circumferential direction works without being affected by the thickness difference. Therefore, it becomes easy to flow into adjacent teeth, and as shown in FIG. 5, there is no great difference in filling timing for each tooth. As a result, the difference in the pressure applied to the teeth is reduced, and the difference in tooth shape is less likely to occur. Furthermore, when the direction of the resin flowing from the two directions is represented by lines in the resin merge section, if the angle formed by the two lines is the merge angle α, this merge angle α increases, so that welds are generated. Can be suppressed. In the present embodiment, it is possible to suppress the filling timing difference and suppress the weld without complicating the structure of the mold. Furthermore, the coaxiality of the gear is not impaired.

  As described above, the composite gear 10 of the present embodiment is a first member that can reduce the difference in tooth shape caused by the difference in filling timing for each tooth and can further suppress the occurrence of welds near the resin meeting portion. It is possible to provide a compound gear formed by the second member.

  Next, a method for manufacturing the compound gear according to the embodiment of the present invention will be described. The first member 11 can be manufactured by injection molding using a conventionally used mold. By using a mold including a core piece and a slide piece as the mold 31, it is possible to mold even the first member 11 having a complicated shape having an undercut portion. Further, the first member 11 may be a metal and can be manufactured by metal processing conventionally used.

  FIG. 4 shows an example of means for forming the second member 20 in the embodiment of the present invention. The first member 11 is inserted into the mold 41, and the space formed between the gear piece 42, the cavity piece 43, the core piece 44 and the first member 11 is filled with a synthetic resin such as a thermoplastic elastomer. The second member 20 is formed. A synthetic resin as a material is injected through a sprue runner 49. Further, the gear piece 42 can be installed so as to be rotated by installing parts such as bearings adjacent to each other. By doing so, the composite gear 10 can be taken out so that the second member is not deformed by a release resistance or the like at the time of release.

  Next, examples will be described.

  The compound gear of the present invention shown in FIGS. 1 and 2 was manufactured. As a comparative example, a conventional compound gear shown in FIG. 11 was manufactured.

  As the first member, a polyacetal resin (Tenac (registered trademark) HC750 manufactured by Asahi Kasei Chemicals Corporation) having a tensile elastic modulus of 3200 MPa was used. As the material of the second member, three types of compound gears were manufactured for each of Examples and Comparative Examples using three types of polyester elastomers (Hytrel (registered trademark) 4047, 5557 and 7247 manufactured by Toray DuPont). The Shore hardness of Hytrel 4047 is 40D, 5557 is 55D, and 7247 is 72D. The higher the resin grade number, the higher the hardness. The tensile modulus of Hytrel 4047 is 49.5 MPa, 5557 is 137 MPa, and 7247 is 422 MPa, and increases as the resin grade number increases.

  In the manufacturing method, the first member was first formed with a mold as shown in FIG. Next, the procedure was to insert the first member into the mold shown in FIG. 4 to form the second member. The compound gear was manufactured so that the module m = 0.7, the pressure angle 20 °, the number of teeth 32, the twist angle β = 25 °, and the tooth width t = 10 mm.

The manufactured Example, Comparative Example, and each of the three types of compound gears were each subjected to the measurement of the roundness of the tip circle, the total meshing error measurement, and the tooth profile / tooth trace measurement. In the measurement of the roundness of the tooth tip, the roundness of the tooth tip circle was calculated by extracting and connecting the feature point (tooth tip position) of the gear with a roundness measuring machine. The total meshing error was measured by a method described in JIS (JIS B 1702-2: 1998) using a double-tooth mesh testing machine. Tooth profile and tooth trace were measured by a method described in JIS (JIS B 1702-1: 1998) with a gear measuring machine.
The results are shown in Table 1.

  From Table 1, it was found that there was a large difference between the roundness of the tip circle and the total meshing error value in the example and the comparative example. In both cases, the value of the comparative example is large and the accuracy is poor. This is because, in the comparative example, there is no thick portion that spans a plurality of teeth, which is a feature of the present invention as in the embodiment, so the fluidity in the circumferential direction is deteriorated, and there is a large difference in filling timing for each tooth. This is probably because of this. These tendencies vary slightly depending on the type of the second member, and are somewhat affected by the fluidity of the material, but in any case, the difference in tooth filling timing may be improved by the thick part. all right.

  Further, the tooth profile / tooth line error is large in the value of the comparative example, and the accuracy is deteriorated. This is considered to be because the load at the time of gate cutting was applied to the tooth portion after forming the second member, and the tooth surface accuracy was lowered. FIG. 6 compares the tooth trace measurement results of Comparative Example 3 and Example 1-3 of the present invention. As is apparent from FIG. 6, in Comparative Example 3, the tooth surface is greatly swelled and deformed. Furthermore, in Comparative Example 1 and Comparative Example 2 in which the material of the second member is soft, the accuracy is greatly deteriorated so that the tooth trace measurement becomes impossible. On the other hand, in the embodiment of the present invention, since the gate position is disposed on the inner diameter portion of the first member, it is hardly affected by the gate cut, and the tooth surface accuracy is stably increased regardless of the hardness of the second member. I was able to secure it.

  A composite gear shown in FIGS. 1 and 2 of the present invention is used as a second embodiment, and a composite gear shown in FIG. 12 is used as a comparative example 4, and a second gear provided on a first member as described in Patent Document 1. Compound gears in which the resin flow paths of the members were slanted from the radial direction were manufactured as Comparative Example 5, respectively. As the material of the second member, Hytrel 7247 was used. The compound gear was manufactured such that the module m = 0.7, the pressure angle 20 °, the number of teeth 32, the twist angle β = 25 °, and the tooth width t = 10 mm.

  And the roundness measurement of the tooth tip circle | round | yen, the total meshing error measurement, and the tooth profile and the tooth trace measurement were performed on the manufactured composite gears of Example 2, Comparative Example 4 and Comparative Example 5, respectively. Further, it was visually observed whether or not welds were generated. In the measurement of the roundness of the tooth tip, the roundness of the tooth tip circle was calculated by extracting and connecting the feature point (tooth tip position) of the gear with a roundness measuring machine. The total meshing error was measured by a method described in JIS (JIS B 1702-2: 1998) using a double-tooth mesh testing machine. Tooth profile and tooth trace were measured by a method described in JIS (JIS B 1702-1: 1998) with a gear measuring machine. Weld was confirmed visually with a digital microscope (magnification x 100 or more). The results are shown in Table 2.

  Comparative Example 4 and Comparative Example 5, which are conventional techniques, were worse than Example 2 in all of the roundness of the tooth tip, the total meshing error, the tooth profile error, and the tooth trace error. In particular, tooth profile and tooth trace errors were very bad values. FIG. 7 is a diagram comparing the measurement results of tooth profile errors in Example 2 and Comparative Examples 4 and 5. Among these, it was found that the measurement results of Comparative Example 4 generated teeth whose tooth profile errors deteriorate periodically. This is considered to be caused by the deterioration in the fluidity in the circumferential direction of the second member due to the thickness difference between the tooth tip part and the tooth bottom part of the tooth part. That is, as the fluidity in the circumferential direction deteriorates, the filling of the teeth near the resin joining portion becomes extremely slow, and the tooth profile shape at the same location deteriorates. In Comparative Example 5, the periodic tooth profile error did not deteriorate as in Comparative Example 4, but the tooth profile had an error with waviness in all teeth. In Comparative Example 5, the through hole provided in the first member is slanted, and when the second member is injected, the first member rotates and the tooth portion is filled with resin. For this reason, the mold structure becomes complicated, and the filling property and the pressurized state become unstable. As a result, as shown in FIG. 7, it is considered that the transferability of the tooth portion was lowered and the tooth profile error was deteriorated. On the other hand, in Example 2, since it has the thick part which straddles several teeth, the fluidity | liquidity of the circumferential direction is good, and the difference of the filling timing for every tooth is small. Therefore, there were few defects generated near the resin junction, and teeth with good transferability could be formed as a whole. When the presence or absence of the weld was visually confirmed, it was confirmed that the weld was generated in Comparative Examples 4 and 5, but it was not visually confirmed whether or not the weld was generated in Example 2.

  The compound gear shown in FIGS. 1 and 2 of the present invention was manufactured as Example 3. Hytrel 7247 was used as the second member. The teeth of the compound gear were manufactured so that the module m = 0.7, the pressure angle 20 °, the number of teeth 32, the twist angle β = 25 °, and the tooth width t = 10 mm.

  FIG. 8 shows the result of measuring the roundness of the tooth tip when the thickness Tb of the tooth bottom portion of the compound gear is Tb = 0.2 mm and the thickness Tr of the thick portion is changed. The roundness measurement of the tooth tip was calculated by extracting and connecting the characteristic points (tooth tip positions) of the gears with a roundness measuring machine.

  According to this result, the roundness improved as the thickness Tr of the thick portion increased. In particular, when Tr was 1.5 mm or more, the roundness was stable at 30 μm or less.

  FIG. 9 shows the result of measuring the roundness of the tooth tip when the thickness Tr of the thick portion of the compound gear is Tr = 1.0 mm and the thickness Tb of the bottom portion is changed. Similarly, the roundness measurement of the tooth tip was calculated by extracting and connecting the characteristic points (tooth tip positions) of the gears with a roundness measuring machine.

  According to this result, the roundness improved as the thickness Tb of the tooth bottom increased. In particular, when Tb was 0.7 mm or more, the roundness was stable at 30 μm or less.

  FIG. 10 is a diagram showing a roundness tendency when the value of Tb + Tr is 1.0 mm, 1.4 mm, and 1.7 mm.

  From these results, it was found that when the value of Tb + Tr is 1.7 mm or more, the roundness of the tooth tip circle is 30 μm or less and is particularly stable.

DESCRIPTION OF SYMBOLS 10 Compound gear 11 1st member 12 Inner diameter part 13 Through hole 14 Shaft 15 Boss (shaft support part)
18 Rim (first member)
20 second member 21 gate 23 tooth portion 28 rim (second member)
29 Thick part α Merge angle Tr Thick part thickness Tt Thickness of tooth tip Tb Thickness of bottom part

Claims (10)

It is made of synthetic resin or metal, and is formed of a synthetic resin different from the first member on the first member having the inner cylindrical part or shaft part, the outer cylindrical part, and the outer peripheral surface of the first member. In a compound gear composed of a second member having a tooth portion,
The second member is between the inner cylindrical portion or the shaft portion and the outer cylindrical portion,
The through hole formed in the outer cylindrical portion is filled,
A composite gear formed between the through hole and the tooth portion and having a thick wall portion communicating with the tooth portion in a direction perpendicular to the outer peripheral surface.   The composite gear according to claim 1, wherein a thickness Tb of a rib by a second member between the outer peripheral surface and the tooth portion and a thickness Tr of the thick portion satisfy Tb + Tr ≧ 1.7. .   The compound gear according to claim 1, wherein the first member has a higher elastic modulus than the second member.   The composite gear according to any one of claims 1 to 3, wherein the first member is formed of a material containing any one of polyacetal, polybutylene terephthalate, polyphenylene sulfide, polyamide, and nylon.   The compound gear according to any one of claims 1 to 3, wherein the first member is made of a metal material.   The compound gear according to any one of claims 1 to 5, wherein the second member is made of a material containing a thermoplastic elastomer. Resin is injected from between the inner cylindrical portion or the shaft portion and the outer cylindrical portion of the first member having the inner cylindrical portion or the shaft portion and the outer cylindrical portion, and is opened in the outer cylindrical portion. A method of manufacturing a compound gear that forms a tooth portion on the outer peripheral surface of the outer cylindrical portion by the resin that has passed through the through-hole,
The resin that has passed through the through-hole is injected into the tooth portion from a direction perpendicular to the outer peripheral surface through a thick-wall portion.   8. The method of manufacturing a composite gear according to claim 7, wherein the first member is manufactured by injection molding using a resin material containing any one of polyacetal, polybutylene terephthalate, polyphenylene sulfide, polyamide, and nylon. .   8. The method of manufacturing a composite gear according to claim 7, wherein the first member is manufactured by cutting, sintering, or pressing using a metal material.   The method of manufacturing a composite gear according to any one of claims 7 to 9, wherein the member forming the tooth portion is a synthetic resin material containing a thermoplastic elastomer or the like.