JP6076202B2 - Synthetic resin injection molded products - Google Patents

Description

The present invention relates to a synthetic resin molded product such as a gear and a pulley formed by synthetic resin injection molding. In particular, a shaft (such as a boss) is formed in the center of the molded product, and a force transmission portion (such as a tooth portion in a gear) is provided on the outer periphery of the molded product. The present invention relates to a synthetic resin molded product connected by the web.

Such resin gears and pulleys have come to be widely used as driving parts for, for example, electronic copying machines and printer devices. In these fields of use, the resin gears and pulleys have very high dimensions in order to improve printing quality. Accuracy (for example, roundness of the outer peripheral portion) is required. Such resin gears and pulleys are usually manufactured by injection molding of synthetic resin, and various techniques have been developed so that these resin molded products can be efficiently manufactured while improving accuracy. ing.

On the other hand, these resin molded products are often used as gears, pulleys, etc. to transmit force, moment, and movement. In that case, the torque transmitted and the local force applied to the force transmission part In order to withstand, it is necessary to have a predetermined strength. In addition, when injection molding a disc-shaped synthetic resin molded product, resin is often injected with a plurality of pin gates arranged on a predetermined circle. In this case, welds are generated between adjacent pin gates. Cheap. Generally, the weld has low strength, and the resin molded product may be damaged starting from the weld.

A technique for increasing the strength of a molded product by controlling the occurrence of welds on gears and pulleys is known.
For example, Patent Document 1 relates to a resin gear having a tooth portion on the outer periphery, and adjusts the number and position of gates so that a weld (joint portion) comes to a tooth crest portion, thereby providing high mechanical strength. It is disclosed to form a gear.

Japanese Patent Laid-Open No. 08-121574

In the technique disclosed in the above-mentioned patent document, the circumferential position of the pin gate is adjusted in order to place the weld on the tooth crest portion (tooth tip portion). On the other hand, there is a demand to arrange the gates at equal intervals in the circumferential direction in order to increase the roundness of the outer periphery of the gear. Therefore, if the weld generation position is controlled by the above-mentioned prior art, the gate position cannot be adjusted well when the number of teeth is not a multiple of the number of gates (the number of teeth cannot be divided by the number of gates). As in the example shown in FIG. 5, it may be difficult to place the weld on the tooth crest.

Accordingly, an object of the present invention is to increase the degree of freedom in adjusting the position where the weld is generated in a synthetic resin molded product such as a resin gear or a resin pulley manufactured by injection molding, and the force transmitting portion in which the weld is on the outer periphery of the resin molded product. It is in providing the resin molded product arrange | positioned at the convex part of this, and raising the intensity | strength of a synthetic resin molded product.

As a result of intensive studies, the inventor has found that even if a pin gate is used, the circumferential position and angle of the weld generated between the gates can be changed by changing the positions of the adjacent gates in the radial direction. It discovered and came to complete this invention.

The present invention is a synthetic resin injection molded product that is integrally molded with a resin, has a shaft portion serving as a rotating shaft, and a disc-shaped web, and is provided with a force transmission portion on the outer peripheral side of the web. In the transmission portion, a plurality of convex portions and concave portions are alternately provided in the circumferential direction, a plurality of gate traces are arranged on the web so as to surround the shaft portion, and between the gate traces adjacent to each other in the circumferential direction. All the generated welds are arranged so as to pass through the convex portion of the force transmission unit, and at least one set of gate marks is adjacent to each other in the circumferential direction, and one gate mark is more than the other gate mark. It is a synthetic resin injection-molded product that is disposed so as to be located radially inward, and the weld generated between the pair of gate marks is inclined with respect to the radial direction of the web on the outer peripheral side of the gate marks. . (First invention)

In the first aspect of the present invention, the first gate mark and the second gate mark are the first gate mark and the second gate mark that is arranged inside the first set of gate marks. It is preferable that the weld generated during the period is inclined so as to approach the first gate mark side in the circumferential direction as it goes outward in the radial direction of the web (second invention). In the second aspect of the invention, it is preferable that Z is the number of convex portions provided on the force transmission portion, N is the number of gate marks provided on the web, and Z is not divisible by N (first 3 invention). Further, in the third invention, it is preferable that the gate marks are arranged on the web at equal intervals in the circumferential direction so that the central angles between the adjacent gate marks are equally divided (fourth invention).

Alternatively, in the first invention, it is preferable that the synthetic resin injection-molded product is a gear, the force transmission part is a tooth part, the convex part is a tooth tip, and the concave part is a tooth bottom (fifth invention). Alternatively, in the first invention, it is preferable that 3 to 10 gate marks are arranged on the web (sixth invention).

According to the present invention, since the position and inclination of the weld generated between the gates can be adjusted by adjusting the radial position of the gate mark, all the welds have the convex portions of the force transmission portion (tooth tips in the resin gear). The length of the weld can be increased, and the strength of the synthetic resin molded product is improved.

Furthermore, according to the present invention, even if the number Z of convex portions of the force transmission portion and the number N of gate marks are not divisible by N as in the third invention, according to the present invention, all the welds It can pass the convex part of a transmission part, and can contribute to the strength improvement of a synthetic resin molded product. Further, as in the fourth invention, when the gate marks are arranged at equal intervals in the circumferential direction, the roundness of the outer peripheral shape of the molded product can be improved.

It is a front view of the resin gear of a 1st embodiment of the present invention. It is a figure explaining arrangement | positioning of the gate and the weld in the resin gear of 1st Embodiment. It is a front view of the resin gear of a 2nd embodiment of the present invention. It is a front view of the resin gear of a 3rd embodiment of the present invention. It is a figure which shows the gate position and the weld generation | occurrence | production location of the conventional resin gear.

Hereinafter, an embodiment of the present invention will be described using a resin gear as an example. 1 and 2 are views showing the shape of a resin gear 1 according to the first embodiment of the present invention. That is, in the first embodiment, the synthetic resin molded product is a resin gear. FIG. 1 shows a front view of the resin gear 1. The resin gear 1 is formed by injection molding of a synthetic resin and is used for a gear transmission mechanism such as a printer, a copier, or a meter.

Spur gear teeth 12 are formed on the outer periphery of the resin gear 1. The tooth portion 12 transmits a force along the circumferential direction of the gear and plays a role of transmitting the torque of the gear. That is, in the first embodiment, a portion (hereinafter referred to as “force transmission portion”) provided on the outer peripheral portion of the resin molded product and transmitting force and torque is the tooth portion 12. In the present embodiment, the number of teeth Z of the tooth portion 12 is 19.
Further, a boss 13 is provided at a shaft portion provided in the central portion of the resin gear 1, and a rotation shaft of the resin gear 1 is configured by fitting a shaft (not shown) on the inner peripheral surface of the boss 13. The shaft portion (boss 13) and the tooth portion 12 are connected and integrated with each other by a substantially disc-shaped web 14. That is, the resin gear (synthetic resin molded product) 1 includes a shaft portion serving as a rotation shaft and a disk-shaped web 13, and a tooth portion 12 (force transmission portion) is provided on the outer peripheral side of the web.

In the present embodiment, the tooth portion 12 formed on the outer peripheral portion of the web 14 is provided integrally with a ring-shaped rim along the outer periphery of the web. Then, the rim and the tooth portion 12 are thicker in the gear shaft direction than the web 14. The rim may be omitted, and the tooth portion 12 may be provided with the same thickness as the web 14 in the gear shaft direction. Moreover, you may provide a rib and meat stealing in the web 14. FIG. The ribs can be provided radially or concentrically. In addition to forming the boss 13, the shaft portion may have other configurations such as insert molding of the shaft or integral molding of the shaft with resin.

On one surface of the web 14, there are a plurality of traces (gate traces 161, 162) of the gate portion that injected the resin when the resin gear 1 is injection molded. The gate traces 161, 162 are formed on the surface of the web 14, It arrange | positions so that the axial part 13 may be surrounded. In the present embodiment, the three gate marks 161 and 162 are arranged at equal intervals in the circumferential direction around the gear central axis. Of the gate marks, the two gate marks 161 are arranged on the same circle centered on the gear central axis. The other gate mark 162 is arranged such that the radial distance from the gear central axis is larger than the gate mark 161. That is, the gate mark 161 is arranged so as to be inside the gate mark 162. In the following description, what is arranged on the inner side is described as the first gate mark 161, and what is arranged on the outer side is described as the second gate mark 162.

The resin gear (synthetic resin molded product) 1 has a weld (weld line) 17 generated during injection molding. The weld 17 extends between the gate marks adjacent to each other in the circumferential direction at an angle close to the radial direction of the molded product. In the resin gear 1, all the welds 17 and 17 are arranged so as to pass through the tooth tip portions of the teeth 12.

Also, a set of gate traces that are adjacent to each other in the circumferential direction and that one is positioned radially inward of the other (in this embodiment, a set of the first gate trace 161 and the second gate trace 162). The weld 17 generated during the period extends in a direction inclined with respect to the radial direction of the gear 1. In particular, the weld 17 is inclined on the outer peripheral side of the gate mark. More specifically, the weld formed between the first gate mark 161 arranged on the inner side and the second gate mark 162 arranged on the outer side is a first gate in the circumferential direction as it goes radially outward of the web. It inclines so that the mark 161 side may be approached.

The resin gear 1 is formed of a thermoplastic resin suitable for injection molding, for example, a general-purpose synthetic resin such as polyethylene resin, polypropylene resin, or polyamide resin, or engineering plastic such as polyacetal resin or polybutylene terephthalate resin. A filler or reinforcing fiber may be kneaded into these resin materials.

The resin gear 1 is formed by resin injection molding in which a molten resin is injected into a cavity using a mold capable of forming a cavity that matches the outer shape of the gear. The resin is injected through a plurality of pin gates provided at positions corresponding to the gate marks 161 and 162 of the molded product.

The function and effect of the present invention will be described. In the present invention, the adjacent gate marks 161 and 162 are arranged at different positions in the radial direction, i.e., one is arranged inward of the other, so that the weld 17 is inclined so as to be inclined with respect to the radial direction. Can do. Accordingly, by adjusting the position of the gate mark in the radial direction of the molded product, all the welds 17 and 17 can be arranged so that the welds pass through the tooth tips 121. If all the welds can pass through the tip portion, the strength of the gear can be increased.

The arrangement of the gate marks 161 and 162 and the position and inclination where the weld occurs will be described.
FIG. 2 is a schematic diagram showing the relationship between the gate marks 161 and 162 and the weld 17 generated between them in the resin gear 1, and shows an enlarged upper left half of the resin gear in FIG. FIG. 5 shows the position of the weld W when the gate marks G (corresponding to the gate at the time of injection molding) are arranged on the same circle at equal intervals in the circumferential direction as a conventional technique.

The resin injected from the pin gate at the time of injection molding flows toward the outer peripheral direction and the inner peripheral direction while spreading in the cavity forming the web, but generally between the adjacent gates, the adjacent pin gates Along the vertical bisector between the two, the resin flows from the gates on both sides merge to generate welds. Therefore, in the prior art, as shown in FIG. 5, when the gate marks G and G are arranged on the same circle, the welds W and W are arranged along the radial direction (radial direction and Occur in parallel). Then, as illustrated in FIG. 5, the number of teeth Z is not divisible by the number of gates N as in the case where the number of teeth Z is 19 and the number of gates N is 3 (that is, Z is an integral multiple of N). If the gate G can be disposed so that some of the welds W pass through the tooth tips 221, it is easy for the remaining welds W to pass through the roots 222.

If the radial positions of adjacent gate marks are different as in the resin gear 1 of the first embodiment, the direction and position where the weld is generated can be adjusted, and the weld can pass through the tooth tip. That is, as shown in FIG. 2, if gate traces are arranged on the same circle in the radial direction at equal intervals in the circumferential direction (virtual gate traces 161S and 162S), the resulting weld 17S (virtual weld) is It is assumed that the tooth bottom 122 is passed along the radial direction (weld arrangement according to the prior art).

In such a case, the gate arrangement is arranged at a position rotated by an angle a around the middle part of the virtual gates 161S and 162S. In the present embodiment, the angle a is rotated counterclockwise. That is, on the side to be the first gate mark 161, the gate mark 161 is provided radially inward of the virtual gate 161S, and on the side to be the second gate mark 162, the gate mark 162 is set to the radial direction of the virtual gate 162S. Provide outside. Then, the weld referred to between these gate marks 161 and 162 is inclined by an angle a (counterclockwise) in general with respect to the radial direction so as to approach the first gate mark side in the circumferential direction toward the outer side in the radial direction. As a result, the weld generation position on the outer peripheral portion of the gear also changes, and the weld 17 can be inclined so as to pass through the tooth tip 121.
In particular, since the weld can be generated by being inclined with respect to the radial direction in a region radially outward from the gate trace, the tooth portion 12 can be formed only by relatively changing the radial position of the gate traces 161 and 162. The circumferential position of the generated weld can be adjusted.

Specifically, the circumferential position of the weld gear outer peripheral portion generated between adjacent gates is set to be closer to the first gate mark 161 side (the gate located radially inward than the center position in the circumferential direction of both gate marks. It can be placed close to the mark side.

In this way, if the radial positions of the adjacent gate marks are sequentially adjusted, all the welds can pass through the tooth tips.

In particular, when the number of teeth Z is not divisible by the number of gates N (that is, Z is not an integer multiple of N), even in the prior art, some welds can be arranged to pass through the tooth tips. However, according to the present invention, by adjusting the position of the gate mark in the radial direction, all the welds are connected to the teeth regardless of the relationship between the number of teeth Z and the number of gates N. You can get ahead.

Further, according to the present invention, the weld 17 generated between the pair of gate traces 161 and 162 whose radial positions are different from each other is arranged obliquely as compared with the case where the weld is generated parallel to the radial direction. As a result, the total length of the weld increases. If the total length of the weld is increased, it becomes easier to disperse and bear the force applied to the weld, which contributes to the improvement of the strength of the weld portion.

The arrangement of the gate traces in the circumferential direction is not particularly limited. However, as shown in the above embodiment, the gate traces are equally spaced in the circumferential direction (the central angle between adjacent gate traces is equally divided. As is preferred).
When the gate marks are arranged at equal intervals in the circumferential direction, the roundness of the outer peripheral shape of the resin gear (resin molded product) can be increased.

In the present invention, the radial position does not necessarily have to be different in all adjacent gate traces. In the set of adjacent gate traces, the same position in the radial direction (that is, the same circle) There may be a set (for example, a set of gate 161 and gate 161 in FIG. 1) in which gate marks are arranged. Between the pair of gate marks thus formed, a weld is generated in parallel with the radial direction as in the prior art. Therefore, if the circumferential position of the gate mark is set so that the weld passes through the tooth tip 121. Good.

In the present invention, a plurality of gate marks, that is, two or more gate marks are provided, and it is particularly preferable that three or more gate marks are provided. When there are three or more gate traces, the circumferential interval between the gate traces is reduced, and the weld generation position and angle can be adjusted more accurately. The number of gate marks is preferably 3 or more and 10 or less, and particularly preferably 3 to 6.

The present invention is not limited to the above embodiment, and can be implemented with various modifications. Other embodiments of the present invention will be described below. However, in the following description, portions different from the above embodiment will be mainly described, and detailed descriptions of the same portions will be omitted.

In FIG. 3, the resin gear 2 which is the 2nd Embodiment of this invention is shown. In this embodiment, the point where four gate marks are provided and the specific arrangement thereof are different from those of the first embodiment, but are substantially the same in other points. In the present embodiment, the number of teeth Z of the tooth portion 22 is 18. The four gate marks 271 and 272 are arranged at equal intervals in the circumferential direction (four equal parts in the circumferential direction). Two of the gate marks (first gate marks 271 and 271) are arranged radially inward of the other two (second gate marks 272 and 272). The first gate mark and the second gate mark are alternately arranged in the circumferential direction in the order of the first gate mark 271, the second gate mark 272, the first gate mark 271, and the second gate mark 272. Yes.

Also in this embodiment, the weld 17 generated between the gate marks adjacent to each other is arranged so that all the welds pass through the tooth tips 221 of the tooth portion 22. Specifically, the weld 17 between the first gate mark 271 and the second gate mark 272 having different radial positions is inclined with respect to the radial direction, and both pass through the tooth tip 221 of the tooth portion 22. Has been.

As in the present embodiment, four or more gate marks may be provided. Preferably, as in the present embodiment and the first embodiment, the arrangement of the gate traces on the web may be a mirror image arrangement (a symmetrical arrangement) or a rotationally symmetrical arrangement with respect to the axis on the web. preferable. In this way, the gate arrangement can be designed and adjusted more easily.

In FIG. 4, the resin gear 3 which is the 3rd Embodiment of this invention is shown. The third embodiment is different from the other embodiments in that gate marks are not provided at equal intervals in the circumferential direction. In the third embodiment, the number of teeth Z of the tooth portion 32 of the resin gear 3 is 26, and the number of gates N is five. One of the five gate marks is a first gate mark 371 disposed relatively inside. In addition, four of the five gate marks are second gate marks 372 and 372 that are disposed relatively outside, and these gate marks are disposed at the same position in the radial direction (that is, on the same circle). Yes.

The four second gate marks 372 and 372 are provided on a radius connecting the central axis of the gear and the tooth bottom 322 so as to be separated from each other by five tooth pitches. Therefore, the weld generated between the second gate marks 372 and 372 is generated in parallel with the radial direction of the gear and passes through the tooth tip 2.5 pitches away from the tooth bottom where the gate mark is located in the circumferential direction. Placed in.

The first gate marks 371 are arranged such that the circumferential distance between the adjacent second gate marks 372 and 372 is 5.5 tooth pitches. Also in this embodiment, since the radial positions of the first gate mark 371 and the second gate mark 372 are different from each other, the weld generated between these gate marks extends in a direction inclined with respect to the radial direction. In addition, the outer peripheral side end portion of the weld 17 can pass through the tooth tip 321 of the tooth portion 32. As described above, the gate marks may be equally arranged in the circumferential direction as in the first embodiment or the second embodiment, but may not be equally arranged as in the third embodiment. . In addition, it is more preferable that the gate traces are equally arranged in the circumferential direction from the viewpoint of increasing the roundness of the outer periphery of the resin gear (resin molded product).

The present invention can be applied to various resin gears manufactured by injection molding. As the type of gear, in addition to the spur gear described in the above embodiment, the present invention can be applied to other types of resin gears such as a helical gear, a toothed gear, and a worm hole.

In the description of the above embodiment, the case where the number Z of teeth of the resin gear is not divisible by the number N of gate marks has been described, but the present invention is also applied to the case where Z is divisible by N. In this case, all the welds are allowed to pass through the tooth tips, and the specific weld is inclined at a predetermined angle with respect to the radial direction, so that the strength of the gear is increased.

In addition, the synthetic resin molded product according to the present invention is not limited to the resin gear, and may be another form, for example, a resin pulley that provides a force transmitting portion on the outer periphery. That is, the present invention is applicable to a synthetic resin molded product having a force transmission portion. The present invention can be applied to a rigid resin molded product in which convex portions and concave portions are alternately provided in the force transmission portion. If the synthetic resin molded product is a resin gear, the tooth tip portion of the tooth portion corresponds to the convex portion of the force transmission portion, and the tooth bottom portion corresponds to the concave portion of the force transmission portion. If the synthetic resin molded product is a toothed resin pulley used for a cogged belt, the portion where the convex portion and the concave portion that are engaged with the cogged belt are connected to each other corresponds to the force transmitting portion. In this invention, it can arrange | position so that all the welds may pass through the convex part of a force transmission part, and can improve the intensity | strength of a resin molded product.

According to the present invention, when a resin pulley or a resin gear is formed by injection molding, all the welds can pass through the convex portion of the force transmission portion (the tooth tip in terms of a gear), and thus obtained. The strength of the resin molded product can be improved. The obtained resin molded product can be used as a component of a gear transmission mechanism or a belt transmission mechanism, and has high industrial utility value.

1 Resin gear (synthetic resin molded product)
12 Tooth part (force transmission part)
121 tooth tip (convex)
122 tooth bottom (concave)
13 Boss 14 Web 161, 162 Gate mark 17 Weld 161S, 162S Virtual gate mark 17S Virtual weld 2, 3 Resin gear (synthetic resin molded product)
22, 32 Tooth part (force transmission part)
221 and 321 tooth tip (convex part)
222, 322 Tooth bottom (concave)
271, 371 First gate mark 272, 372 Second gate mark

Claims (6)

It is a synthetic resin injection molded product that is integrally molded with resin, has a shaft portion that becomes a rotating shaft and a disc-shaped web, and a force transmission portion is provided on the outer peripheral side of the web,
The force transmission portion is provided with a plurality of convex portions and concave portions alternately in the circumferential direction,
A plurality of gate marks are arranged on the web so as to surround the shaft part, and all the welds generated between the gate marks adjacent to each other in the circumferential direction are arranged so as to pass through the convex part of the force transmission part,
At least one set of gate traces is arranged adjacent to each other in the circumferential direction, and one gate trace is located radially inward of the other gate trace,
A synthetic resin injection molded product in which welds generated between the pair of gate marks are inclined with respect to the radial direction of the web on the outer peripheral side of the gate marks. Of the one set of gate marks, the one arranged on the inside is the first gate mark, and the one arranged on the outside is the second gate mark,
2. The composition according to claim 1, wherein the weld generated between the first gate mark and the second gate mark is inclined so as to approach the first gate mark side in the circumferential direction as it goes outward in the radial direction of the web. Resin injection molded product. The synthetic resin injection-molded article according to claim 2, wherein Z is a number that is not divisible by N, where Z is the number of convex portions provided on the force transmission portion, N is the number of gate marks provided on the web. The synthetic resin injection molded product according to claim 3 , wherein the gate traces are arranged on the web at equal intervals in the circumferential direction so that the central angles between the adjacent gate traces are equally divided . The synthetic resin injection molded product according to claim 1, wherein the synthetic resin injection molded product is a gear, the force transmitting portion is a tooth portion, the convex portion is a tooth tip, and the concave portion is a tooth bottom. The synthetic resin injection molded product according to claim 1, wherein 3 to 10 gate marks are arranged on the web.

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