JP2020143733A - Resinous gear and multi-layer molding method of gear - Google Patents

Abstract

To accurately manufacture a resinous gear.SOLUTION: A resinous gear 10 is composed of a ring portion 11 and a disc portion 12, and has an outside member 14 and an inside member 21. The outside member 14 comprises an outside ring portion 16 provided with a tooth-shaped portion 15, and an outside disc portion 17. The inside member 21 comprises an inside ring portion 23 provided with a projection 22 projecting outward in a diametrical direction toward the tooth-shaped portion 15 and joined with the inside in the diametrical direction of the outside ring portion 16, and an inside disc portion 24 integrally provided with a boss portion 25 at a center portion in the diametrical direction. The ring portion 11 is formed by the outside ring portion 16 and the inside ring portion 23, and the disc portion 12 is formed by the outside disc portion 17 and the inside disc portion 24.SELECTED DRAWING: Figure 1

Description

The present invention relates to a resin gear having a ring portion provided with external teeth and a disc portion integrated on one end side of the ring portion, and a multi-layer molding method thereof.

External gears provided with teeth on the outer peripheral surface include spur gears, helical gears, screw gears, and the like. A spur gear is a gear in which the tooth muscle is parallel to the rotation axis, and a helical gear is a gear in which the tooth muscle is obliquely oriented in the circumferential direction with respect to the rotation axis. A screw gear is a gear that is provided with a screw-shaped tooth surface and is used to transmit power between staggered shafts.

Such an outer gear is molded by a double molding method having a step of molding the outer shell portion on which the tooth portion is formed with resin and a step of molding the inner portion arranged inside the outer shell portion with resin. The synthetic resin molded product obtained is described in Patent Document 1. The double molding method includes a form in which the inner part is molded and then the outer part is formed and the outer part is joined to the inside, and a form in which the outer part is molded and then the inside is formed and the inner part is joined to the outer part. .. In Patent Document 1, in order to mold the inside after molding the outer shell portion, the outer shell portion and the inner portion are subsequently molded by one molding die.

Patent Document 2 discloses a resin gear including a peripheral edge portion which is a surface layer portion of a tooth profile portion and a main body portion arranged inside the peripheral portion. This gear has a process of molding the main body with a metal or resin boss, that is, a collar as an insert member by an injection molding die for primary molding, and a secondary body with the collar integrated as an insert member. It is molded by the step of molding the peripheral portion with an injection molding die for molding.

JP-A-63-165113 Japanese Unexamined Patent Publication No. 2004-52791

As described in Patent Document 1, in a resin gear in which an inner flat outer peripheral surface and a flat inner peripheral surface of an outer shell portion are joined, the external force in the rotational direction between the inner and outer shell portions is applied. The strength cannot be increased. On the other hand, as described in Patent Document 2, when the tooth core portion provided on the outer peripheral portion of the main body portion is arranged inside the tooth profile portion of the peripheral portion, the tooth core portion enters the tooth profile portion. Since it is molded with, the strength in the rotation direction between the main body portion and the peripheral portion can be increased.

However, in Patent Document 2, the boss portion is manufactured in advance from metal or resin, and in addition to this manufacturing process, a step of molding the main body portion using the boss portion as an insert member and a main body portion having a pair of collars are inserted. Gears are manufactured by a step of forming a peripheral portion as a member, and the number of manufacturing steps is increased. Further, the main body portion and the boss portion are only in contact with each other on a cylindrical surface, and the strength against an external force in the rotation direction cannot be increased.

An object of the present invention is to enable efficient production of high-precision resin gears.

The resin gear of the present invention is a resin gear including a ring portion provided with external teeth and a disc portion integrated with one end of the ring portion, and is an outer ring portion provided with a tooth profile portion and the outer side. An outer member having an outer disk portion integrated with one end of the ring portion, and an inner ring provided with a protrusion protruding radially outward toward the tooth profile portion and joined to the radial inside of the outer ring portion. It has an inner member having a portion and an inner disc portion integrated with one end of the inner ring portion and integrally provided with a boss portion at a radial center portion and joined to the inner surface of the outer disk portion. The ring portion is formed by the outer ring portion and the inner ring portion, and the disc portion is formed by the outer disc portion and the inner disc portion.

The multi-layer molding method for a resin gear of the present invention is a multi-layer molding method for a resin gear including a ring portion provided with external teeth and a disc portion integrated with one end of the ring portion, and is a radial outer multi-layer molding method. A primary molding step of molding an inner member including an inner ring portion provided with a protrusion protruding from the inner ring portion and an inner disc portion integrated with one end portion of the inner ring portion and integrally provided with a boss portion at a radial center portion. An outer ring portion provided with a tooth profile portion corresponding to the protrusion and arranged radially outward of the inner ring portion, and an outer disc portion integrated with one end of the outer ring portion and joined to the inner disc portion. It has a secondary molding step of molding an outer member comprising.

The multi-layer molding method for a resin gear of the present invention is a multi-layer molding method for a resin gear including a ring portion provided with external teeth and a disc portion integrated with one end of the ring portion, and the tooth profile portion is provided. A primary molding step of molding an outer member including an outer ring portion to be formed and an outer disc portion integrated with one end of the outer ring portion, and a protrusion protruding outward in the radial direction toward the tooth profile portion are provided. The inner ring portion to be joined radially inside the outer ring portion and the boss portion integrally provided at one end of the inner ring portion and integrally provided at the radial center portion are joined to the inner surface of the outer disc portion. It has a secondary molding step of molding an inner member including an inner member including an inner disk portion.

The ring portion of the resin gear includes an outer ring portion of the outer member and an inner ring portion of the inner member, and since the outer ring portion and the inner ring portion are joined, the rotation between the boss portion and the outer teeth The strength against external force in the direction is increased. Further, it is possible to obtain a resin gear in which the thickness of the outer ring portion in the direction along the circumferential direction is uniform and the tooth surface of the outer tooth is highly accurate.

The multi-layer molding method for resin gears includes a form in which the inner member is primarily molded and the inner member is placed in a molding die to secondarily mold the outer member, and the outer member is primarily molded and the outer member is molded in a molding die. In both cases, the outer ring portion and the inner ring portion are joined by the secondary molding, so that the outer ring portion and the inner ring portion are joined by the secondary molding, so that the external force in the rotational direction between the boss portion and the outer tooth is applied. The strength is increased. It is possible to mold a resin gear having a highly accurate outer tooth surface.

In the form of secondary molding of the outer member, if the outer member is secondary molded after the primary molded inner member is thermally contracted and deformed, the amount of cooling shrinkage of the secondary molded outer member can be significantly reduced. It is possible to manufacture a resin gear having a high degree of tooth surface accuracy of the external teeth.

In the form of secondary molding of the inner member, if the inner member is secondary molded before the primary molded outer member undergoes heat shrinkage deformation, the molten resin for molding the inner member presses the outer ring portion from the inside. Since the gears are pressed outward in the radial direction, the tooth surface accuracy of the external teeth can be improved, and a resin gear having a high tooth surface accuracy of the external teeth can be manufactured.

(A) is a perspective view of the resin gear according to the embodiment as viewed from one side, and (B) is a sectional view taken along line AA in (A). It is a perspective view which looked at the resin gear shown in FIG. 1 from the other side. It is a perspective view which shows the inner member of the resin gear shown in FIG. 1 and FIG. (A) is a plan view showing one surface of the inner member, and (B) is a front view of (A). It is a perspective view which shows the outer member of the resin gear shown in FIG. 1 and FIG. (A) is a plan view showing one surface of the outer member, and (B) is a front view of (A). A molding die according to an embodiment is shown, and is a cross-sectional view taken along the line BB in FIG. FIG. 7 is a plan view of FIG. FIG. 8 is a sectional view taken along line CC in FIG. (A) is an enlarged cross-sectional view showing a cavity of a primary molding die in the molding die shown in FIGS. 7 to 9, and (B) is an enlarged cross-sectional view showing a state in which the cavity is filled with molten resin. .. (A) is an enlarged cross-sectional view showing a cavity of a secondary molding die in the molding die shown in FIGS. 7 to 9, and (B) is an enlarged cross-sectional view showing a state in which the cavity is filled with molten resin. is there. A molding die according to another embodiment is shown, and is a cross-sectional view taken along the line DD in FIG. It is a plan view of FIG. It is a right side view of FIG. (A) is an enlarged cross-sectional view showing a cavity of a primary molding die in the molding die shown in FIGS. 12 to 14, and (B) is an enlarged cross-sectional view showing a state in which the cavity is filled with molten resin. .. (A) is an enlarged cross-sectional view showing a cavity of a secondary molding die in the molding die shown in FIGS. 12 to 14, and (B) is an enlarged cross-sectional view showing a state in which the cavity is filled with molten resin. is there. It is a top view which shows the resin gear which is another embodiment. FIG. 17 is a cross-sectional view taken along the line EE in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The resin gear 10 shown in FIGS. 1 and 2 includes a ring portion 11 and a disc portion 12 integrated with one end portion in the axial direction of the ring portion 11, and external teeth 13 are provided on the outer peripheral portion of the ring portion 11. Is provided. The resin gear 10 has an outer member 14 and an inner member 21, and the outer member 14 is integrated with an outer ring portion 16 provided with a plurality of tooth profile portions 15 and an axial end portion of the outer ring portion 16. It is provided with an outer disc portion 17.

On the other hand, the inner member 21 has an inner ring portion 23 in which a plurality of protrusions 22 projecting outward in the radial direction toward each tooth profile portion 15 are provided at regular intervals in the circumferential direction, and an axial direction of the inner ring portion 23. An inner disc portion 24 integrated with one end portion is provided, and a boss portion 25 is integrally provided at the radial center portion of the inner disc portion 24. The boss portion 25 is provided with a mounting hole 25a, and the outer disk portion 17 is also provided with a mounting hole 25a. A shaft (not shown) is attached to the attachment hole 25a. When only one of the outer member 14 and the inner member 21 is resin-molded and then the other is resin-molded, the other is insert-molded while being arranged in the cavity of the mold. As a result, the inner ring portion 23 is joined to the inner surface of the outer ring portion 16 in the radial direction, and the inner disc portion 24 is joined to the inner surface of the outer disc portion 17.

The protrusion 22 has a triangular serrated cross-sectional shape and protrudes outward at an acute angle in the radial direction, and the radial dimensions of the side surfaces on both sides in the circumferential direction are the same. The tip portion 22a of each protrusion 22 is located at the center of the tooth profile portion 15 in the circumferential direction, that is, the center in the width direction. On the inner peripheral surface of the outer ring portion 16, a meshing protrusion 19 that enters a groove between the protrusions 22 is provided. Therefore, the outer ring portion 16 and the inner ring portion 23 are in mesh with each other.

A plurality of tooth profile portions 15 are provided on the outer ring portion 16 of the outer member 14 at intervals in the circumferential direction, and a tooth groove portion 18 is formed between adjacent tooth profile portions 15. The external tooth 13 is formed by the plurality of tooth profiles 15 and the tooth groove 18. As shown in the figure, the resin gear 10 is a helical gear in which the tooth muscle of the tooth profile portion 15 is inclined in the circumferential direction with respect to the rotation center axis O, assuming that the rotation center axis is O. The tip portion 22a of the protrusion 22 is also inclined in the circumferential direction with respect to the rotation center axis O so as to correspond to the tooth profile portion 15 of the helical gear. Therefore, the tip portion 22a of the protrusion 22 is located at the central portion in the circumferential direction of the tooth profile portion 15 in the entire width along the axial direction.

As shown in FIG. 1, a plurality of reinforcing ribs 26 extending in the radial direction from the inner peripheral surface of the inner ring portion 23 toward the boss portion 25 are provided on the inner member 21. Each reinforcing rib 26 has a radial inner portion 27 and a branch portion 27a branched from the radial inner portion 27 in the circumferential direction and connected to the inner peripheral surface of the inner ring portion 23, and has an inner disc portion. It is integrated with 24, and three are provided at equal intervals in the circumferential direction. By providing the inner disc portion 24 with a plurality of reinforcing ribs 26 in this way, the strength of the inner disc portion 24 can be increased.

A space 28 is provided between the reinforcing rib 26 and the boss portion 25. In this way, when the space 28 is provided to block the boss portion 25 and the reinforcing rib 26, when the inner member 21 is resin-molded, even if the reinforcing rib 26 heat shrinks in the radial direction, the heat shrinkage is caused by the inner ring. A high-precision resin gear 10 can be formed without affecting the roundness of the portion 23. Further, when the resin gear 10 is used, the member can be arranged in the space 28.

Since the inner disk portion 24 is joined to the outer disk portion 17 and the protrusion 22 on the outer peripheral portion of the inner ring portion 23 meshes with the inner peripheral portion of the outer ring portion 16, the bonding strength between the outer member 14 and the inner member 21 is increased. .. As a result, the strength against an external force in the rotational direction between the external teeth 13 and the boss portion 25 is increased. However, the reinforcing rib 26 may not be provided, and the resin gear 10 may be provided with the inner member 21 having the inner disc portion 24, the inner ring portion 23, and the boss portion 25, and the reinforcing rib 26 may be the boss portion 25. A resin gear 10 having an inner member 21 connected to the inner ring portion 23 may be used.

As shown in FIG. 1, if the radius from the rotation center axis O of the protrusion 22 to the tip is R1 and the radius of the tooth bottom of the tooth groove portion 18 is R2, is the inner ring radius R1 substantially the same as the tooth bottom radius R2? , Is set slightly smaller. As described above, the inner ring radius R1 is a length such that the protrusion 22 does not penetrate into the tooth profile portion 15. Therefore, the thickness of the outer ring portion 16 which is zigzag along the circumferential direction can be set uniformly in the circumferential direction. That is, the thickness of the tooth profile portion 15 and the meshing protrusion 19 connected to the adjacent tooth profile portion 15 can be made uniform. As a result, when the outer member 14 is resin-molded, the high-precision resin gear 10 can be molded without affecting the roundness of the outer ring portion 16 at the time of heat shrinkage of the resin.

Further, when the protrusion 22 is inserted into the tooth profile portion 15 like the resin gear 10, the dimension between the tooth profile portion 15 and the protrusion 22 becomes smaller, and the molten resin is formed in the cavity of the tooth profile portion 15 during resin molding. It becomes difficult to flow into. On the other hand, since the protrusion 22 does not enter the tooth profile portion 15, the molten resin can be reliably filled in the cavity of the tooth profile portion 15 during resin molding, and the tooth surface shape of the tooth profile portion 15 is molded with high accuracy. At the same time, the manufacturing yield of the resin gear 10 can be increased.

Next, the method for forming the above-mentioned resin gear 10 in multiple layers will be described. 7 to 9 show a molding die 30a which is one embodiment. In this molding die 30a, the inner member 21 shown in FIGS. 3 and 4 is primarily molded, and the outer member 14 shown in FIGS. 5 and 6 is secondarily formed with the inner member 21 arranged in the mold. Mold. The outer member 14 and the inner member 21 are joined by secondary molding, which is insert molding.

The molding die 30a has a fixed die 31 and a movable die 32 that can move away from each other as shown by an arrow, and the mold matching surface 32a of the movable die 32 is a mold of the fixed die 31. It is abutted against the mating surface 31a. In FIG. 7, the movable mold 32 is shown to move in the vertical direction for convenience according to the orientation of the resin gears shown in FIGS. 1 and 2, but the molding mold 30a is horizontal. It is installed in the direction, and in the installed state, the movable mold 32 moves in the horizontal direction. Therefore, the molding die 30a is installed in a state of being rotated by 90 degrees about the direction perpendicular to the paper surface in FIG. 7.

The fixed mold 31 includes a mounting plate 33 on the base end side, and a fixed mold plate 35 attached via a runner plate 34a and a receiving plate 34b, and an inner member 21 is formed on the fixed mold plate 35. The fixed mold 36 and the fixed mold 37 that molds the outer member 14 are attached side by side. Molding rings 38 and 39 are attached to the fixed molding dies 36 and 37, respectively. The front surface of the fixed mold plate 35 constitutes the mold matching surface 31a of the fixed mold 31 described above.

The movable mold 32 includes a mounting plate 41 on the base end side, and a movable mold plate 43 that is attached to the mounting plate 41 via the connecting block 42a and the connecting plate 42b. An anchor ring 44 that is abutted against the molding ring 38 is attached to the movable template 43, and a guide ring 45 fixed to the movable template 43 is abutted against the anchor ring 44. The ejector ring 46 is mounted so as to be movable in the axial direction inside the guide ring 45 facing the fixed molding die 36, and the molding pin 47 is arranged inside the ejector ring 46.

The anchor ring 44, the ejector ring 46, and the forming pin 47 constitute the movable forming die 48, and the movable forming die 48 and the fixed forming die 36 form the inner member 21 as shown in FIG. 10 (A). A cavity 50 corresponding to the shape is formed. In order to inject the molten resin into the cavity 50 from the outside, three runners 49 for guiding the resin are formed in the fixed mold 31. The runner 49 opens in the radial center of the inner disk portion 24 of the inner member 21 in the cavity 50. FIG. 7 shows one runner 49, and the opening of the runner 49 is shown in a state of being closed by the plug member 49a.

A gear ring 51 abutting against the molding ring 39 is attached to the movable template 43, and a guide ring 52 fixed to the movable template 43 is abutted against the gear ring 51. The ejector ring 53 faces the fixed molding mold 37 and is mounted inside the guide ring 52 so as to be movable in the axial direction. The ejector ring 53 is provided with a forming pin 57 for forming the boss portion 25.

The gear ring 51 and the ejector ring 53 constitute a movable molding die 54, and the movable molding die 54 and the fixed molding die 37 form a cavity corresponding to the shape of the outer member 14 as shown in FIG. 11 (A). 55 is formed. In order to inject the molten resin into the cavity 55 from the outside, eight runners 56 for guiding the resin are formed in the fixed mold 31. The runner 56 opens in the radial center of the outer disk portion 17 of the outer member 14 in the cavity 55. In FIG. 7, two runners 56 are shown, and the opening of the runner 56 is shown in a state of being closed by a plug member.

In the molding die 30a, the movable mold 48 and the fixed mold 36 for molding the inner member 21 constitute a primary molding mold, and the movable mold 54 and the fixed mold 37 for molding the outer member 14 are formed. Consists of a secondary molding die, and a primary molding die and a secondary molding die are provided in the molding die 30a. In this way, in the molding die 30a, after the cavity 50 for primary molding is filled with molten resin to form the inner member 21, the molded inner member 21 is conveyed into the cavity 55 for secondary molding. By filling the cavity 55 with molten resin, a resin gear 10 composed of an inner member 21 and an outer member 14 integrated therein is formed in multiple layers.

7 to 9 show the molding dies 30a in a molded state, and the movable dies 32 are driven in the horizontal direction by a driving means (not shown). When the movable mold 32 is moved closer to the fixed mold 31 and the mold matching surface 32a is abutted against the mold matching surface 31a, as shown in FIG. 7, the molding die 30a has a cavity for primary formation. 50 and a cavity 55 for secondary molding are formed. When the outer member 14 is secondarily molded, the primarily molded inner member 21 is arranged upside down in the cavity 55.

From the inner member 21 formed of the molten resin filled in the cavity 50 for primary molding, the inner member 21 formed of the molten resin filled in the cavity 55 for secondary molding, and the outer member 14 integrated therein. The resin gear 10 is taken out from the molding die 30a by driving the ejector rings 46 and 53. In order to drive the ejector rings 46 and 53, an ejector plate (not shown) is incorporated in the molding die 30a.

In the molding die 30 described above, the cavity 50 is formed by the fixed molding die 36 on the fixed side and the movable molding die 48 on the movable side, and the cavity 55 is formed by the fixed molding die 37 on the fixed side and the movable molding on the movable side. Although it is formed by the mold 54, the movable molding dies 48 and 54 may be on the fixed side, and the fixed molding dies 36 and 37 may be on the movable side.

Next, a method of multi-layer molding of the resin gear 10 by the molding die 30a will be described with reference to FIGS. 10 and 11.

As shown in FIG. 10A, the movable mold 32 is abutted against the fixed mold 31 and compacted, so that the cavity 50 corresponding to the shape of the inner member 21 is formed in the molding mold 30a. Under this state, as shown in FIG. 10B, by injecting the molten resin into the cavity 50, the primary molding step is executed and the inner member 21 is molded. The runner 49 is opened in the radial center of the inner disk portion 24 of the cavity 50, and the molten resin filled in the cavity 50 is diffused radially outward in the cavity 50. It flows and flows to the inner ring portion 23. As shown in FIGS. 3 and 4, the inner member 21 has an inner ring portion 23 provided with a plurality of protrusions 22 and an inner disc portion 24 integrated with one end portion of the inner ring portion 23 in the axial direction. A boss portion 25 is integrally formed at the radial center of the inner disc portion 24, and three reinforcing ribs 26 are integrally formed with the inner ring portion 23 and the inner disc portion 24.

The inner member 21 is taken out from the molding die 30a by separating the movable mold 32 from the fixed mold 31 and opening the mold. When the inner member 21 is cooled to a temperature lower than that at the time of molding, the inner member 21 is deformed due to heat shrinkage. However, although the three reinforcing ribs 26 have a relatively large volume, since a space 28 is provided between the reinforcing ribs 26 and the boss portion 25, the inner member 21 is deformed due to heat shrinkage of the reinforcing ribs 26. The amount can be reduced.

In order to perform the secondary molding step by injecting the molten resin into the cavity 55, the inner member 21 molded in the primary molding step is arranged in the cavity 55 as shown in FIG. 11A. At this time, the front and back surfaces of the inner member 21 are inverted and arranged in the cavity 55. As shown in FIG. 11B, by injecting the molten resin into the cavity 55, the outer member 14 is molded and the outer member 14 is integrated with the inner member 21. The runner 56 is open in the radial center of the outer disk portion 17 of the cavity 55, and the molten resin filled in the cavity 55 is diffused radially outward in the cavity 55. It flows and flows to the outer ring portion 16. By the secondary molding step, as shown in FIGS. 1 and 2, the outer ring portion 16 is arranged and integrated on the radial outer side of the inner ring portion 23, and the outer disk portion 17 is integrated with the outer ring portion 16. Is joined to the inner disk portion 24.

The injection of the molten resin into the cavity 55 is performed after the inner member 21 is cooled and thermally contracted and deformed, that is, in a state where sink marks are generated. As described above, when the outer member 14 is molded after the cooling deformation, that is, the sink mark occurs, only the heat shrinkage deformation of only the outer member 14 is obtained, and the cooling shrinkage amount of the secondary molded outer member can be significantly reduced. Therefore, it is possible to manufacture a resin gear having a high precision of the tooth surface of the external tooth, and it is possible to significantly improve the roundness of the resin gear 10.

After molding the inner member 21, in order to arrange the inner member 21 in the cavity 55 on the secondary side after cooling and deforming the inner member 21, a cooling stage (not shown) is arranged adjacent to the molding die 30a. Is preferable. The inner member 21 formed by the primary molding is carried out to this cooling stage, cooled to a predetermined temperature, and then carried into the cavity 55 on the secondary side.

By carrying the inner member 21 from the cooling stage into the cavity 55 on the secondary side, the molding of the inner member 21 by the cavity 50 on the primary side and the molding of the outer member 14 by the cavity 55 on the secondary side can be performed at the same time. it can.

The inner member 21 that is primarily formed and the outer member 14 that is secondarily formed may be molded from the same resin material, or the resin material may be different between the inner member 21 and the outer member 14. When different, in order to increase the tooth surface strength, the resin material of the outer member 14 may be stronger than the resin material of the inner member 21.

12 to 14 show a molding die 30b which is another embodiment. In this molding die 30b, unlike the molding die 30a, the outer member 14 shown in FIGS. 5 and 6 is primarily molded, and the inner member 21 shown in FIGS. 3 and 4 is formed on the molding die 30b. Secondary molding is performed with the outer member 14 arranged on the surface. The outer member 14 and the inner member 21 are joined by secondary molding, which is insert molding.

The molding die 30b has the same basic structure as the molding die 30a, and has a fixed die 31 and a movable die 32 that can move away from each other as shown by an arrow, and the movable die 32. The mold matching surface 32a of the above is abutted against the mold matching surface 31a of the fixed mold 31. In FIG. 12, similarly to FIG. 7, the movable mold 32 is shown to move in the vertical direction, but in the state where the molding mold 30b is installed, the movable mold 32 is in the horizontal direction. Move to.

The fixed mold 31 includes a mounting plate 33 on the base end side, and a fixed mold plate 35 attached via a runner plate 34a and a receiving plate 34b, and an inner member 21 is formed on the fixed mold plate 35. The fixed mold 36 and the fixed mold 37 that molds the outer member 14 are attached side by side. A molding ring 38 on the fixed side is attached to the fixed molding die 36. The front surface of the fixed mold plate 35 is the mold matching surface 31a of the fixed mold 31 described above.

The movable mold 32 includes a mounting plate 41 on the base end side, and a movable mold plate 43 that is attached to the mounting plate 41 via the connecting block 42a and the connecting plate 42b. A movable molding ring 44a abutting against the molding ring 38 is attached to the movable mold plate 43, and a movable molding die 46a is attached to the movable mold plate 43 facing the fixed molding mold 36. A molding pin 47 is arranged inside the movable molding die 46a.

The forming ring 44a, the movable forming die 46a, and the forming pin 47 constitute the movable forming die 48, and the movable forming die 48 and the fixed forming die 36 form a resin gear as shown in FIG. 16 (A). A cavity 50 corresponding to the shape of 10 is formed. In order to inject the molten resin into the cavity 50 from the outside, three runners 49 for guiding the resin are formed in the fixed mold 31. The runner 49 opens in the radial center of the inner disk portion 24 of the inner member 21 in the cavity 50.

A gear ring 51a abutting against the fixed molding mold 37 is attached to the movable mold plate 43, and the movable molding mold 53a is attached to the movable mold plate 43 so as to face the fixed molding mold 37. The gear ring 51a and the movable molding die 53a constitute the movable molding die 54, and the movable molding die 54 and the fixed molding die 37 correspond to the shape of the outer member 14 as shown in FIG. 11 (A). The cavity 55 is formed. In order to inject the molten resin into the cavity 55 from the outside, eight runners 56 for guiding the resin are formed in the fixed mold 31. The runner 56 opens in the radial center of the outer disk portion 17 of the outer member 14 in the cavity 55.

In the molding die 30b, the movable molding die 54 and the fixed molding die 37 for molding the outer member 14 constitute a secondary molding die, and the movable molding die 48 and the fixed molding die 48 for molding the inner member 21 are formed. Reference numeral 36 denotes a secondary molding die, and the primary molding die and the secondary molding die are provided in the molding die 30b as in the molding die 30a. As described above, in the molding die 30b, after the cavity 55 for primary molding is filled with molten resin to form the outer member 14, the molded outer member 14 is conveyed into the cavity 50 for secondary molding. By filling the cavity 50 with molten resin, a resin gear 10 composed of an outer member 14 and an inner member 21 integrated therein is formed in multiple layers.

12 to 14 show the molding dies 30b in a molded state, and the movable dies 32 are driven in the horizontal direction by a driving means (not shown). When the movable mold 32 is moved closer to the fixed mold 31 and the mold matching surface 32a is abutted against the mold matching surface 31a, as shown in FIG. 12, the molding die 30b has a cavity for primary formation. 55 and a cavity 50 for secondary molding are formed.

As shown in FIG. 12, the ejector plate 58 is incorporated in the movable mold 32, and the movable molding dies 46a and 53a are driven by driving the ejector plate 58. As a result, the resin gear 10 composed of the outer member 14 formed of the molten resin filled in the cavity 55 and the inner member 21 integrated with the outer member 14 by the molten resin filled in the cavity 50 is an ejector. By driving the ejector ring with the plate 58, it is taken out from the molding die 30b.

Regarding the molding die 30b, the cavity 50 is formed by the fixed molding die 36 on the fixed side and the movable molding die 48 on the movable side, and the cavity 55 is formed by the fixed molding die 37 on the fixed side and the movable molding die 54 on the movable side. However, the movable molding dies 48 and 54 may be on the fixed side, and the fixed molding dies 36 and 37 may be on the movable side.

Next, a method for forming the resin gear 10 in multiple layers by the forming die 30b will be described with reference to FIGS. 15 and 16.

As shown in FIG. 15A, the movable mold 32 is abutted against the fixed mold 31 and fastened, so that the cavity 55 corresponding to the shape of the outer member 14 is formed in the molding mold 30b. Under this state, as shown in FIG. 15B, by injecting the molten resin into the cavity 55, the primary molding step is executed and the outer member 14 is molded. The runner 56 opens in the radial center of the outer disk portion 17 of the cavity 55, and the molten resin filled in the cavity 55 flows radially outward in the cavity 55 and the outer ring. It flows to the part 16 part. As shown in FIGS. 5 and 6, the outer member 14 has an outer ring portion 16 provided with a tooth profile portion 15 and an outer disc portion 17 integrated with one end portion in the axial direction of the outer ring portion 16. ing.

The outer member 14 is taken out from the molding die 30b by separating the movable mold 32 from the fixed mold 31 and opening the mold. The outer member 14 is quickly placed in the cavity 50 before the removed outer member 14 is cooled and solidified. FIG. 16A shows a state in which the outer member 14 is placed in the cavity 50 and then the movable mold 32 is brought into contact with the fixed mold 31 to be molded.

In the state where the outer member 14 that has been molded in the primary molding step and before being cooled and solidified is arranged in the cavity 50, the molten resin is injected and injected into the cavity 50 to execute the secondary molding step. As a result, as shown in FIG. 16B, the inner member 21 is formed and the inner member 21 is integrated with the outer member 14. The runner 49 opens in the radial center of the inner disk portion 24 of the cavity 50, and the molten resin filled in the cavity 50 flows in the cavity 50 while diffusing radially outward in the radial direction. It flows to the inner ring portion 23. As a result, as shown in FIGS. 1 and 2, the outer ring portion 16 is arranged and integrated on the radial outer side of the inner ring portion 23, and the outer disk portion 17 integrated with the outer ring portion 16 is an inner disk. It is joined to the portion 24.

The primary-formed outer member 14 and the secondary-formed inner member 21 may be molded from the same resin material, or the resin material may be different between the outer member 14 and the inner member 21. When different, in order to increase the tooth surface strength, the resin material of the outer member 14 may be stronger than the resin material of the inner member 21.

In the secondary molding step, the portion of the inner ring portion 23 of the molten resin injected into the outer ring portion 16 of the outer member 14 before cooling and solidifying pressurizes the outer ring portion 16 outward in the radial direction. As a result, the tooth surface shape of the tooth profile portion 15 of the outer ring portion 16 accurately corresponds to the tooth surface shape formed in the mold, and the molding accuracy and roundness of the tooth profile portion 15 can be improved.

The molding dies 30a and 30b described above are both provided with a primary molding die and a secondary molding die, but the primary molding die and the secondary molding die may be separated from each other.

FIG. 17 is a plan view showing a resin gear 10a according to another embodiment, and FIG. 18 is a sectional view taken along line EE in FIG. In these figures, the same reference numerals are given to the members having commonality with the above-mentioned members.

The resin gear 10a has an outer member 14 and an inner member 21 like the resin gear 10. The outer member 14 includes an outer ring portion 16 provided with a plurality of tooth profile portions 15 and an outer disc portion 17 integrated with one end portion in the axial direction of the outer ring portion 16. The inner member 21 is integrated with an inner ring portion 23 in which a plurality of tooth-shaped protrusions 22 that enter into each tooth profile portion 15 are provided at regular intervals in the circumferential direction, and an axial end portion of the inner ring portion 23. The inner disc portion 24 is provided, and the boss portion 25 is integrally provided at the radial center portion of the inner disc portion 24.

In the resin gear 10a, the protrusion 22 of the inner ring portion 23 has a tooth profile, and the outer ring portion 16 covers the outer peripheral surface of the tooth profile protrusion 22 with an overall uniform thickness. When the outer ring portion 16 is formed in layers in this way, even if the resin material of the inner member 21 is a high-strength resin or a resin containing powder such as glass powder inside, it can be used with other gears. The outer peripheral surface of the inner ring portion 23 can be covered by the outer ring portion 16 that engages and contacts. This makes it possible to prevent the other gears that mesh with the outer ring portion 16 from being worn.

The reinforcing rib 26 described above is not provided on the inner member 21 of the resin gear 10a. Further, in the tooth profile portion 15 formed by the protrusion 22 and the outer ring portion 16 covering the outer peripheral surface thereof, the tooth muscle is parallel to the rotation center axis, and the resin gear 10a is a spur gear.

The resin gear 10a can also be multi-layered by the above-mentioned molding dies 30a and 30b, respectively, and can be manufactured with high accuracy.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist thereof. The resin gear 10 is a helical gear, and the resin gear 10a is a spur gear. However, if it is made of resin, a gear such as a screw gear may be formed.

10, 10a Resin gear 11 Ring part 12 Disc part 13 External tooth 14 Outer member 15 Tooth profile part 16 Outer ring part 17 Outer disk part 18 Tooth groove part 21 Inner member 22 Protrusion 23 Inner ring part 24 Inner disc part 25 Boss part 26 Reinforcement Rib 28 Space 30a, 30b Molding mold 31 Fixed mold 32 Movable mold 35 Fixed mold plate 36, 37 Fixed molding mold 43 Movable mold plate 48 Movable molding mold 49 Runner 50 Cavity 55 Cavity 56 Runner

Claims (9)

A resin gear consisting of a ring portion provided with external teeth and a disc portion integrated with one end of the ring portion.
An outer member including an outer ring portion provided with a tooth profile portion and an outer disc portion integrated with one end portion of the outer ring portion.
An inner ring portion that is provided with a protrusion that projects radially outward toward the tooth profile portion and is joined to the radial inner side of the outer ring portion, and one end portion of the inner ring portion that is integrated and has a boss at the radial center portion It has an inner member having a portion integrally provided and an inner disc portion joined to the inner surface of the outer disc portion.
The ring portion is a resin gear formed by the outer ring portion and the inner ring portion, and the disc portion is formed by the outer disc portion and the inner disc portion. In the resin gear according to claim 1,
The inner ring radius from the rotation center axis of the inner ring portion to the tip of the protrusion is a length such that the protrusion does not penetrate into the inside of the tooth profile portion. In the resin gear according to claim 1,
The protrusion of the inner ring portion is a resin gear having a tooth profile that penetrates into the tooth profile portion. In the resin gear according to any one of claims 1 to 3.
A resin gear in which a plurality of reinforcing ribs extending in the radial direction from the inner peripheral surface of the inner ring portion toward the boss portion are provided on the inner member, and a space is provided between the reinforcing ribs and the boss portion. A multi-layer molding method for resin gears consisting of a ring portion provided with external teeth and a disc portion integrated with one end of the ring portion.
A primary for forming an inner member including an inner ring portion provided with a protrusion protruding outward in the radial direction and an inner disk portion integrated with one end portion of the inner ring portion and integrally provided with a boss portion at the radial center portion. Molding process and
An outer ring portion provided with a tooth profile portion corresponding to the protrusion and arranged radially outward of the inner ring portion, and an outer disc portion integrated with one end of the outer ring portion and joined to the inner disc portion. Secondary molding process for molding the outer member
A method for forming multiple layers of gears. In the multi-layer molding method for gears according to claim 5.
A multi-layer molding method for gears, in which the outer member is molded in the secondary molding step after the inner member is thermally contracted and deformed. A multi-layer molding method for resin gears consisting of a ring portion provided with external teeth and a disc portion integrated with one end of the ring portion.
A primary molding step of molding an outer member including an outer ring portion provided with a tooth profile portion and an outer disc portion integrated with one end portion of the outer ring portion.
An inner ring portion that is provided with a protrusion that projects radially outward toward the tooth profile portion and is joined to the radial inner side of the outer ring portion, and one end portion of the inner ring portion that is integrated and has a boss at the radial center portion A secondary molding step of molding an inner member including an inner member having an inner disk portion integrally provided with the portions and joined to the inner surface of the outer disk portion.
A method for forming multiple layers of gears. In the multi-layer molding method for gears according to claim 7.
A multi-layer molding method for gears, in which the inner member is molded in the secondary molding step before the outer member is cooled and solidified. In the multi-layer molding method for gears according to any one of claims 5 to 8, when the inner member is molded, the molten resin injected from a plurality of runners is radially out of the inner disk portion. Diffuse radially toward the inner ring and fill the inner ring.
A multi-layer molding method for gears, in which molten resin injected from a plurality of runners is radially diffused outward in the radial direction from the outer disk portion to fill the outer ring portion when the outer member is molded.

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