JP4860650B2 - Synthetic resin molded product - Google Patents

Description

The present invention relates to a synthetic resin molded article such as a synthetic resin gear or a pulley used for OA equipment. In particular, the present invention relates to a synthetic resin molded product having a deformed portion such as a keyway at the central shaft portion of the molded product.

In recent years, plastic gears, pulleys, and other disk-shaped synthetic resin molded products that are injection-molded by engineering plastics, which are widely used as metal substitutes, require strict accuracy in the roundness and runout of the outer and inner peripheral surfaces. Yes. In order to injection-mold a plastic molded product having such a substantially circular outer periphery with high accuracy, consideration is usually given to arranging a plurality of gates at substantially equal intervals on the concentric circles of the molded product. The molten resin material is injected into the cavity and molding is performed.

In Patent Document 1, the hollow boss portion formed on the inner periphery is not a uniform cylindrical shape over the entire circumference, and when a deformed portion such as a key groove is formed in a part of the circumferential direction, It is disclosed that the accuracy of the outer peripheral shape of the synthetic resin molded product can be improved by moving the gate at a position corresponding to the deformed portion in the radial direction.

Patent Document 2 discloses an embodiment in which a large number of ribs are provided in a radial direction in a resin gear provided with a key receiving portion in a boss portion, and the strength is improved by devising the peripheral shape of the key receiving portion. It is described that it can be achieved.
JP 2001-341167 A JP 2004-308731 A

However, in the gears described in Patent Document 1 and Patent Document 2, the boss portion has a deformed portion such as a key groove or a key receiving portion, and is not uniform in the circumferential direction. There is a possibility that the accuracy of the outer peripheral surface of the molded product may be lowered.

For example, when the wall portion constituting the key receiving portion formed in the boss portion is relatively thick, the resin injected into the mold is delayed from solidifying in the key receiving portion. The amount of shrinkage of the key receiving part is relatively large compared to other parts. As a result, even in the outer peripheral surface shape of the resin molded product, the part located on the outer periphery of the key receiving part tends to be recessed radially inward. In some cases, the accuracy deteriorated.

Conversely, in resin molded products in which a relatively large key groove is formed in a notch shape from the boss part to the web part, the resin around the key groove hardens relatively quickly, so the shrinkage around the key groove As a result, the amount of the outer peripheral surface of the resin molded product may be less accurate than the other parts, resulting in a deterioration in accuracy that tends to cause the part located on the outer periphery of the keyway to bulge outward in the radial direction.

In view of the above, it is an object of the present invention to produce a synthetic resin molded product in which a deformed portion is formed on a part of a boss portion by injection molding with high dimensional accuracy.

As a result of intensive investigations, the inventor of the present invention makes the thickness and spacing of the rib member extending radially adjacent to the boss portion different between the rib adjacent to the deformed portion of the boss and the other rib. As a result, it was found that the non-uniformity of shrinkage due to the deformed portion of the boss portion can be compensated and the above-mentioned problems can be solved, and the present invention has been completed.

The present invention comprises an annular rim formed on the outer peripheral portion, a boss provided concentrically with the rim on the inner peripheral portion, a web connecting the rim and the boss, and a rib extending in the radial direction. An integrally molded synthetic resin molded product, wherein the boss is formed with a deformed portion whose radial cross-sectional shape is changed in the circumferential direction, and ribs connected to the deformed portion are different from other ribs. It is a synthetic resin molded product characterized by being made thick.

In the synthetic resin molded product, in the radial cross section of the synthetic resin molded product, if the cross-sectional area of the boss deformed portion is larger than the cross-sectional area of the boss that is not the deformed portion, a rib connected to the deformed portion is provided. Preferably, the rib is thinner than the other ribs (Claim 2), or when the cross-sectional area of the boss deformed portion is smaller than the cross-sectional area of the boss that is not the deformed portion, the rib connected to the deformed portion is the other rib. It is preferable to make it thicker than the rib.

The present invention also provides an annular rim formed on the outer peripheral portion, a boss provided concentrically with the rim on the inner peripheral portion, a web connecting the rim and the boss, and a rib extending in the radial direction. And the boss is formed with a deformed portion whose radial cross-sectional shape is changed over the circumferential direction, and the interval between the ribs connected to the deformed portion is other than It is a synthetic resin molded product provided at different intervals with respect to the interval between ribs. (Claim 4).

In the synthetic resin molded product, when the cross-sectional area of the boss deformed portion is larger than the cross-sectional area of the boss that is not the deformed portion in the radial cross section of the synthetic resin molded product, the boss deformed portion is connected. It is preferable that the interval between the ribs is provided at a wider interval than the interval between the other ribs (Claim 5), or the cross-sectional area of the boss deformed portion is smaller than the cross-sectional area of the boss that is not the deformed portion. It is preferable that the interval between the ribs connected to the deformed portion of the boss is narrower than the interval between the other ribs.

According to the synthetic resin molded product of the present invention, there is an effect that a molded product having a highly accurate outer peripheral shape can be manufactured by injection molding even if the molded product has a deformed portion in the boss portion.
In the aspect of Claim 1, Claim 2 or Claim 3, by adjusting the thickness of the rib, in the aspect of Claim 4, Claim 5 or Claim 6, by adjusting the interval of the rib. The effect of the present invention can be obtained.

Hereinafter, an embodiment of the present invention will be described based on a synthetic resin gear as an example based on the drawings.
FIG. 1 is a front view showing a synthetic resin gear 1 according to a first embodiment of the present invention. 2 is a cross-sectional view taken along the line XX of FIG.

The synthetic resin gear 1 is a disc-shaped gear, and a plurality of tooth portions 2 and 2 are provided on the outer peripheral portion thereof. The tooth portion 2 is integrated with an annular rim 3. A boss 4, which is a shaft portion of the gear by fitting a shaft (not shown) on its inner peripheral surface, is provided concentrically with the rim 3 at the central portion of the synthetic resin gear 1. The rim 3 and the boss 4 are connected by a disc-shaped web 5. As shown in the cross section of FIG. 2, the rim 3, the boss 4, and the web 5 form a shape in which a thick disk is thinned. Furthermore, on the web 5, ribs 6 and 6 extend in the radial direction so as to connect the rim 3 and the boss 4 to each other. The tooth portion 2, the rim 3, the boss 4, the web 5, and the rib 6 are formed integrally with each other.

The synthetic resin gear of the present invention can be manufactured by an injection molding method using an engineering plastic such as a polyacetal resin or a thermoplastic resin such as a polyamide resin.

A shaft (not shown) that is inserted and fitted into the inner peripheral hole of the boss 4 is provided with a key, and the boss 4 has a side wall 43 so that a key receiving portion 42 for storing the key is formed. Is provided. By providing the key receiving portion 42 and the side wall 43, the cross-sectional shape around the boss 4 is constant in the circumferential direction with respect to the cross section in the plane including the gear axis and the radial direction of the synthetic resin gear 1 (hereinafter referred to as the radial cross section). In other words, the cross-sectional shape changes corresponding to the key receiving portion 42 and the side wall 43. In the present embodiment, particularly when the radial cross section includes the side wall 43, the cross-sectional area around the boss tends to increase. In other words, the boss 4 is provided with a portion corresponding to the key receiving portion 42 and having a radial cross-sectional shape that changes in the circumferential direction of the gear, that is, a deformed portion. The cross-sectional area, that is, the amount of resin around the boss is increased.

The ribs 6 and 6 that connect the boss 4 and the rim 3 in the radial direction are provided with different thicknesses and intervals depending on whether or not the boss 4 is connected to a deformed portion (key receiving portion or side wall). It has been. That is, the ribs 6a and 6a (ribs provided in the section a in the drawing) connected to the deformed portion are thinner (that is, ta <tb) than the other ribs 6b and 6b (ribs provided in the section b in the drawing). And the interval Wa between the ribs 6a, 6a connected to the deformed portion is wider than the interval Wb between the other ribs 6b, 6b (Wa> Wb). Here, the thickness and interval of the ribs 6 mean the thickness and interval in the circumferential direction, as shown in FIG.

Hereinafter, the operation and effect of the synthetic resin molded product of the present invention will be described.
By the injection molding method, the molten resin is injected into the cavity of the mold, and the pressure is held and cooled to produce the synthetic resin gear of the present invention. In this embodiment, the key receiving portion is provided around the boss 4. Since the amount of resin in the deformed portion corresponding to 42 is increased, the cooling of the deformed portion is delayed around the boss, and as a result, the shrinkage amount of the deformed portion tends to be larger than the other portions around the boss. Is produced. On the other hand, since the ribs 6a and 6a connected to the deformed portion are provided thinner than the other ribs 6b and 6b, the area where the ribs 6a and 6a are provided is more than the area where the ribs 6b and 6b are provided. However, the cooling of the resin is promoted, and the shrinkage amount of the resin is reduced. As a result, the non-uniformity of the resin shrinkage due to the deformed portion is compensated by the resin shrinkage of the portion where the rib is provided, so that the entire synthetic resin gear has a uniform shrinkage in the circumferential direction. The accuracy of the outer peripheral portion of the gear can be improved.

Similarly, the ribs 6a and 6a are also provided when the interval (Wa) between the ribs 6a and 6a connected to the deformed portion is wider than the interval (Wb) between the other ribs 6b and 6b. The region has a tendency that the cooling of the resin is promoted more than the region where the ribs 6b and 6b are provided, and the shrinkage amount of the resin tends to be small. Similarly, the ribs provide unevenness of the resin shrinkage amount due to the deformed portion. The accuracy of the outer peripheral portion of the gear can be improved by compensating the amount of shrinkage of the resin in the portion so that the entire synthetic resin gear has a uniform amount of contraction in the circumferential direction. That is, the adjustment by the ribs 6 and 6 may be to adjust only the thickness of the ribs or to adjust only the interval between the ribs.

Other embodiments are shown below.
FIG. 3 is a front view showing a synthetic resin gear 1 ′ according to the second embodiment of the present invention. 4 is a sectional view taken along line XX in FIG. In the description of the present embodiment, the description will mainly focus on parts that are different from the first embodiment, and description of the parts that are the same will be omitted.

In the present embodiment, a key groove 7 is provided in the central portion of the synthetic resin gear together with the boss 4 '. The keyway 7 is provided so as to cut out a part of the boss 4 ′ and a part of the web 5. In this embodiment, the portion corresponding to the key groove 7 constitutes a deformed portion, and the cross-sectional area of the radial cross section around the boss portion is smaller in the deformed portion than in other portions, and the resin around the boss portion The amount of is decreasing.

The ribs 6 'and 6' that connect the boss 4 'or the periphery of the key groove 7 and the rim 3 in the radial direction may or may not be connected to the deformed portion (key groove peripheral portion) on the inner peripheral side. It is provided with different intervals. That is, the ribs 6a 'and 6a' (ribs provided in the section a shown in the figure) connected to the deformed portion are thicker than the other ribs 6b 'and 6b' (ribs provided in the section b shown in the figure) (that is, ta). The distance between the ribs 6a 'and 6a' connected to the deformed portion is narrower than the distance between the other ribs 6b 'and 6b' (that is, Wa '<Wb'). It has been.

In the present embodiment, since the amount of resin in the deformed portion corresponding to the key groove 7 is reduced around the boss 4 ′, cooling of the deformed portion is accelerated, and as a result, the contraction amount of the deformed portion. Tends to be smaller than other parts around the boss. On the other hand, since the ribs 6a ′ and 6a ′ connected to the deformed portion are provided thicker than the other ribs 6b ′ and 6b ′, the region where the ribs 6a ′ and 6a ′ are provided is the rib 6b. The cooling of the resin is slower than the region where “, 6b” is provided, and the amount of shrinkage of the resin increases. As a result, non-uniformity in the amount of resin shrinkage caused by the deformed portion (key groove) is compensated by the amount of resin shrinkage in the portion where the ribs are provided, and the entire synthetic resin gear has a uniform shrinkage amount in the circumferential direction. In this way, the accuracy of the outer peripheral portion of the gear can be improved.

Similarly, the interval between the ribs 6a ′ and 6a ′ connected to the deformed portion is provided narrower than the interval between the other ribs 6b ′ and 6b ′ (Wa ′ <Wb ′). The non-uniformity of the resin shrinkage caused by the deformed part is compensated by the resin shrinkage of the part where the ribs are provided, and the synthetic resin gear as a whole has a uniform shrinkage in the circumferential direction. The accuracy of the part can be improved.

Although the embodiments of the present invention have been described above, the present invention can be implemented with the following modifications.

In the above-described embodiment, the synthetic resin gear having the tooth portions 2 and 2 has been described as an example of the synthetic resin molded product. However, it is not necessarily a gear, and a pulley having no tooth portion may be used. is there.

In addition, although an example in which the synthetic resin molded product has a disk shape has been shown, the present invention is not limited to a disk-shaped molded product having a relatively small axial thickness compared to the diameter of the outer circumferential circle. The present invention also includes a synthetic resin molded product having a shape (so-called cylindrical shape) in which the axial thickness is relatively larger than the diameter of the resin.

Further, in the embodiment, an example in which there is one deformed portion in the circumferential direction is shown. However, even in a molded product having a plurality of deformed portions, the rib thickness and interval corresponding to each deformed portion are shown. The present invention can be carried out by adjusting.

Further, as shown in the first embodiment, when the deformed portion exists only on one side of the molded product, it is more preferable to adjust the thickness and interval of the ribs only on the side where the deformed portion exists. By doing so, it is possible to compensate for the tendency of the disk-shaped molded product to warp to the one side due to the influence of the deformed portion existing only on the molded product one side, and to obtain a highly accurate gear with little deflection.

According to the present invention, even a disc-shaped synthetic resin molded product in which a deformed portion is formed on a part of the boss portion can be manufactured by injection molding with high dimensional accuracy.

The front view which shows 1st Embodiment of the synthetic resin gear of this invention. XX sectional drawing of FIG. The front view which shows 2nd Embodiment of the synthetic resin gear of this invention. XX sectional drawing of FIG.

Explanation of symbols

1 Synthetic resin gear 2 Tooth part 3 Rim 4 Boss 42 Key receiving part 43 Side wall 5 Web 6 Rib 7 Keyway

Claims (6)

An annular rim formed on the outer peripheral portion, a boss provided concentrically with the rim on the inner peripheral portion, a web connecting the rim and the boss, and a rib extending in the radial direction are integrally formed. A synthetic resin molded product,
The boss is formed with a deformed portion whose radial cross-sectional shape is changed over the circumferential direction,
A synthetic resin molded product characterized in that ribs connected to the deformed portion have different thicknesses relative to other ribs. The radial cross section of the synthetic resin molded product is characterized in that a cross-sectional area of the boss deformed portion is larger than a cross-sectional area of a boss that is not a deformed portion, and a rib connected to the deformed portion is thinner than other ribs. The synthetic resin molded product according to claim 1. In the radial cross section of the synthetic resin molded product, the cross-sectional area of the boss deformed portion is smaller than the cross-sectional area of the boss that is not the deformed portion, and the rib connected to the deformed portion is thicker than the other ribs. The synthetic resin molded product according to claim 1. An annular rim formed on the outer peripheral portion, a boss provided concentrically with the rim on the inner peripheral portion, a web connecting the rim and the boss, and a rib extending in the radial direction are integrally formed. A synthetic resin molded product,
The boss is formed with a deformed portion whose radial cross-sectional shape is changed over the circumferential direction,
A synthetic resin molded product, characterized in that the interval between ribs connected to the deformed portion is different from the interval between other ribs. In the radial cross section of the synthetic resin molded product, the cross-sectional area of the boss deformed portion is larger than the cross-sectional area of the boss that is not the deformed portion, and the interval between the ribs connected to the deformed portion of the boss is the interval between the other ribs. The synthetic resin molded product according to claim 4, wherein the synthetic resin molded product is provided at a wide interval. In the radial cross section of the synthetic resin molded product, the cross-sectional area of the boss deformed portion is smaller than the cross-sectional area of the boss that is not the deformed portion, and the interval between the ribs connected to the deformed portion of the boss is the interval between the other ribs. The synthetic resin molded product according to claim 4, wherein the synthetic resin molded product is provided at a narrow interval.

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