JP2022142462A - Injection molded body - Google Patents

Abstract

To provide an injection molded body that has high dimensional accuracy in shape and excellent quietness.SOLUTION: An injection molded body includes a central part, a body part and an outer peripheral part, where the body part connects the central part to the outer peripheral part. The body part includes: a gate mark generated at the time of injection molding; and a groove part that is provided while extending in a circumferential direction in a position different from the gate mark in a radial direction and has a depth that varies in the circumferential direction.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an injection molded article such as a gear.

2. Description of the Related Art Conventionally, as a gear used in various mechanical devices, a resin gear manufactured by injection molding or insert molding and provided with teeth on the outer circumference is known. Compared to metal gears, resin gears have the advantages of less noise, better wear resistance, and better chemical resistance. They are also lighter than metal gears, and can be mass-produced with precision molding. is possible.

Resin gears are designed to control the flow of the molten resin material in the cavity in order to improve the dimensional accuracy of the shape, such as the roundness, which affects the accuracy of rotation transmission.

For example, in Patent Document 1, in a resin gear formed by connecting an annular rim on the outer periphery of a molded product and a shaft portion in the center of the molded product with a disc-shaped web, the gate provided on the web is positioned closer to the outer peripheral portion than the gate. A configuration is disclosed in which ribs are erected to control the flow of molten resin material.

In Patent Document 1, the volume of resin flowing into the space forming the rib increases, and the timing at which the flow of the molten resin material reaches the rim portion on the outer periphery of the resin gear is delayed. As a result, the resin is uniformly filled from the gate to the outer rim portion, and the roundness of the molded product as a resin gear is improved.

Japanese Patent No. 5443089

However, in the resin gear of Patent Document 1, the ribs are erected on the outer peripheral side of the gate of the web in the axial direction to adjust the flow of the molten resin. growing. As a result, it is conceivable that they interfere with the meshing partner of the resin gear, and it is necessary to change the external dimensions of the meshing partner depending on the arrangement position of the resin gear.

In addition, since the ribs are formed by storing resin in the extending direction thereof, there is a problem in that it tends to flow in the extending circumferential direction, and it is difficult to fill the ribs with high accuracy and uniformity in the radial direction.

In particular, when resin gears are molded, if welds are formed on the teeth of the outer peripheral portion when the outer peripheral portion is filled with molten resin, the rotation transmission accuracy will be affected by the single pitch error. It is known to generate noise.

For this reason, there is a demand for a gear that is evenly filled with a molding material such as resin up to the outer peripheral portion with high accuracy, is less likely to cause a single pitch error, and is excellent in quietness.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an injection-molded article having high dimensional accuracy and excellent quietness.

One embodiment of the injection molded article of the present invention is
having a central portion, a main body portion, and an outer peripheral portion, wherein the central portion and the outer peripheral portion are connected by the main body portion;
The main body includes a gate mark at the time of injection molding,
and grooves extending in the circumferential direction at positions different from the gate mark in the radial direction and having different depths in the circumferential direction.

As described above, according to the present invention, it is possible to realize an injection-molded article having high dimensional accuracy and excellent quietness.

1 is a perspective view showing a gear as an injection-molded body according to one embodiment of the present invention; FIG. It is a bottom view of the same gear. It is a top view of the same gear. FIG. 4 is a cross-sectional view taken along the line AA of FIG. 3; 4 is a cross-sectional view taken along line BB of FIG. 3; FIG. 4 is a cross-sectional view taken along line CC of FIG. 3; FIG. It is a figure where it uses for description of the dimensional accuracy of the gear as an injection molded object of one embodiment which concerns on this invention. It is a figure where it uses for description of the dimensional accuracy of the gear as an injection molded object of one embodiment which concerns on this invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing a gear as an injection molded body according to one embodiment of the present invention, and FIG. 2 is a bottom view of the same gear.

The gear 1 as an injection-molded body shown in FIGS. a rim portion 4;

An injection-molded body is formed by injecting and filling a molding material into a space to be a product by injection molding into a mold for the product, and is rotatable. The injection molded body is, for example, a rotation transmission member that rotates and transmits its rotational force or external driving force to another rotating body. The injection-molded article may be formed, for example, by insert molding or the like in which a member is placed in a mold in advance and a molding material is filled around the member.

The injection-molded body may not have teeth on the outer peripheral portion, and may have a configuration in which the outer peripheral surface of the rim portion 4 slides on the outer peripheral surface of another injection-molded body. Further, the injection molded body may be provided with a concave portion extending in the circumferential direction on the outer peripheral surface to form a pulley. The injection-molded body preferably has a portion that extends in the circumferential direction and has high dimensional accuracy, and is formed in the shape of a disc or column (which may be hollow) that rotates around the shaft. Injection moldings such as gears and pulleys are preferred. In the present embodiment, the gear 1 is used as an example of an injection-molded body, so the main body will be referred to as a gear main body 3 for the sake of convenience.

The shaft portion 2 is provided in the central portion of the gear 1 and is provided with the central axis of rotation of the gear 1 . The shaft portion 2 has a shaft hole 21 penetrating in the axial direction (thickness direction) of the gear 1 , and the shaft portion constituting the rotating shaft of the gear 1 is inserted through the shaft hole 21 .

In this embodiment, the injection-molded gear 1 is provided with teeth 6 that require high dimensional accuracy on the outer peripheral surface of the rim portion 4 provided on the outer peripheral portion of the gear body portion 3 . The tooth portion 6 is formed integrally with the gear body portion 3, is provided at a position different from the gate marks G1 to G3 in the radial direction, and is an outer peripheral portion that engages with another mechanical part (for example, another gear) during use. correspond to

The gear main body 3 has gate traces G and grooves 5 on one side surface (upper surface) spaced apart in the axial direction. That is, the gear main body 3 has the gate traces G1 to G3 and the groove 5 on the same end surface. The gear main body 3 has a flat inner surface (surface on the bottom surface side) and has a shape with a different height on the other surface (top surface in the drawing).

The gear body portion 3 has a first web 31, a second web 32, a groove portion 5, and a third web 33 arranged in order from the shaft hole 21 side as the shaft portion 2 toward the outer peripheral side. The rim portion 4 is connected to the outer periphery of 33 .

In this embodiment, the rim portion 4 is provided so as to protrude vertically from the outer peripheral portion of the gear main body, that is, the outer periphery of the third web 33 which is the outer peripheral web.

The gate traces G1 to G3 are gate traces formed when the gear 1 is molded by injection molding or the like. A gate is a resin inlet into the space formed by the core and cavity of the mold. Specifically, when the gear 1 is molded using a mold (core and cavity), the gate marks G1 to G3 are formed by filling a molding material (for example, molten resin) from the gate to form a molded product (gear 1 ) is formed when the molded product (gear 1) is removed from the cavity. It is preferable that the gate marks G1 to G3 are arranged at positions such that the molding material preferably flows over the entire molded article as a product within the cavity.

The molten resin, which is the molding material for forming the gear 1 of the injection molded body, is, for example, a thermoplastic resin suitable for injection molding, such as a general-purpose synthetic resin such as polyethylene resin, polypropylene resin, or polyamide resin (polyamide 66, etc.). , engineering plastics such as polyacetal resin (POM) and polybutylene terephthalate resin. Moreover, it is good also as a material which kneaded a filler, a reinforcing fiber (glass fiber, carbon fiber), etc. into these resin materials. Metal powder may also be used as the molding material. In this embodiment, for example, POM containing reinforcing fibers such as glass fibers as a reinforcing resin is used as the molten resin.

In this embodiment, the gate marks G1 to G3 are provided on the second web 32 at equal intervals in the circumferential direction.

FIG. 3 is a plan view of the same gear of one embodiment according to the present invention, and FIGS. 4 is a sectional view taken along the line CC of FIG. 3. FIG. As shown in FIGS. 1 and 3 to 6, the groove portion 5 is provided adjacent to the gate marks G1 to G3 in the radial direction outside.

The portion of the core that becomes the groove 5 has the function of temporarily blocking the radial flow of the molten resin injected from the gate marks G1 to G3 into the cavity during molding of the gear 1. The groove portion 5 is filled with the molten resin flowing in the radial direction from the gate by being adjusted and made to flow uniformly.

The portion of the core that becomes the groove 5 dams up the molten resin from the gate traces G1 to G3, and controls the flow time over the portion that becomes the groove 5 in the radial direction, for example, to the outer peripheral side. The groove portion 5 extends in the circumferential direction and has different depths in the circumferential direction.

The portion of the core that becomes the groove portion 5 controls the molten resin flowing throughout the gear 1 so that it flows uniformly. By making the depths of the grooves 5 different, the molten resin flowing in the cavity from the gate in the radial direction (e.g., radial direction) at the time of molding flows beyond the grooves 5 depending on the depth of the grooves 5. The time to flow radially outward to the outer periphery is adjusted. As a result, the molten resin uniformly flows over the entire outer peripheral portion and uniformly flows over the entire injection-molded body.

In the present embodiment, as shown in FIGS. 1, 3 and 4, the groove portion 5 is formed in a ring shape in a plan view surrounding the shaft hole 21 as the shaft portion 2. As shown in FIG.

The deepest portion 52 of the groove portion 5 is adjacent to each of the gate traces G1 to G3 on the outer peripheral side of the gear body portion 3 and is arranged on a radial line passing through the gate traces G1 to G3. In addition, the groove portion 5 is formed extending in the circumferential direction from the deepest portion 52 (52-1, 52-2, 52-3).

In addition, the shallowest portion 54, which is the shallowest portion of the groove portion 5, is arranged in the intermediate portion between the deepest portions 52-1, 52-2, and 52-3 which are spaced apart in the circumferential direction in the groove portion 5. there is

In the present embodiment, the bottom of the groove portion 5 is gradually shallowed from the deepest portions 52-1, 52-2, 52-3 to the shallowest portions 54-1, 54-2, 54-3. sloped. In this configuration, as shown in FIGS. 3 and 6, in the groove portion 5, the deepest portions 52-1, 52-2, 52-3 and the shallowest portions 54-1, 54-2, 54-3 are adjacent to each other. The intermediate portions 56-1, 56-2, 56-3 have the same height.

The injection-molded body has a disk-shaped or columnar main body, for example, a web portion, provided with gate marks, and the main body is radially spaced from the gate marks so as to be separated from other machine parts during use. The outer peripheral portion to be engaged has a portion that requires high dimensional accuracy. The outer peripheral portion is formed integrally with the main body portion and provided at a position different from the gate mark in the radial direction.

As for the injection-molded body, grooves extending in the circumferential direction and having different depths in the circumferential direction are provided in the main body at positions between the outer peripheral portion and the gate marks in the radial direction. Just do it. The groove may be arranged radially adjacent to the gate mark on the outer peripheral side.

In addition, the groove has portions with different depths in the circumferential direction so that the outer peripheral portion is uniformly filled with the molten resin, which is the molding material. For example, it is assumed that the injection-molded body has, as the outer peripheral portion, a portion that requires dimensional accuracy on the outer peripheral portion (rim portion 4) of the main portion (gear main portion 3), such as the tooth portion 6 of the gear 1. In this case, in the injection-molded body, the groove portion 5 is a flat surface extending in the gear body portion 3 while gradually becoming shallower in the circumferential direction, with the deepest portion being the portion adjacent to the gate traces G1 to G3 in the radial direction. It may be formed in an arc shape when viewed.

That is, if the injection-molded article has a configuration in which welds are less likely to occur in a portion such as the tooth portion 6 that requires high dimensional accuracy by uniformly flowing the molten resin in the cavity, the groove portion 5 will not cause gate marks. It does not have to be a ring shape that surrounds the shaft part adjacent to the part side of G. Further, the groove portion 5 may have a flat inclined surface whose depth is gradually different in the circumferential direction, a stepped bottom surface, or a curved inclined surface.

According to the configuration of the gear 1 of the present embodiment, the circumferential It has grooves 5 with different depths in different directions.

Thus, when the gear 1 is molded, the molten resin as the molding material filled from the gate is blocked by the height of the groove 5 in the core, and the flow rate of the molten resin can be adjusted. Control is performed such that the liquid flows in the circumferential direction along the portion forming the groove portion 5 of the cavity. For example, when the groove portion 5 is formed adjacent to the gate mark G, the control can be performed immediately after injecting the molten resin into the mold through the gate. Therefore, it is possible to uniformly fill the teeth 6, which require high dimensional accuracy, with the molten resin by controlling the flow of the molten resin such that the portion closer to the gate is normally filled faster than the portion farther from the gate.

Welds are less likely to occur in a portion requiring high dimensional accuracy, for example, the tooth portion 6, the occurrence of a single pitch error in the tooth portion 6 can be reduced, the injection molded body rotates, and the rotational force is applied to mesh. Therefore, it is possible to ensure quietness when transmitting to other parts. Furthermore, since the generation of welds is suppressed in the tooth portion 6, the reduction in strength caused by the welds is less likely to occur.

7 and 8 are diagrams for explaining the dimensional accuracy of a gear as an injection-molded article according to one embodiment of the present invention. 7A shows the gear 1 of this embodiment, and FIG. 7B shows a gear 100 manufactured by injection molding in the same manner as the gear 1 but having no groove 5 unlike the gear 1. The location where the pitch error was measured is shown. Further, FIG. 8 shows a single pitch error at the same position measured in each tooth portion of the gear 1 of the present embodiment and the gear 100 as a comparative example. In FIG. 8, the numbers arranged in the circumferential direction are the numbers of the tooth portions, and the numbers arranged in the radial direction indicate the error of each tooth portion based on 0 (no error).

As shown in FIGS. 7A and 7B, a plurality (six) of each of the gear 1 of the present embodiment and the gear 100 of the comparative example were manufactured. In both the gear 1 manufacturing method and the gear 100 manufacturing method, a similar molding material (for example, POM containing reinforcing fibers such as glass fibers as a reinforcing resin) was used. In addition, in any manufacturing method, the same mold for forming the groove was used which was detachable. Further, in any manufacturing method, the gear 1 and the gear 100 were manufactured under the same conditions such as the temperature of the molding material and the environmental conditions.

Single pitches on the right and left flanks of the tooth portions 6A, 60 of the respective gears 1, 100 shown in FIG. 7 were measured and shown in FIG.

8A and 8B show the measurement results of a single pitch of the right tooth flank and the left tooth flank in the tooth portion 6A (see FIG. 7A) of a plurality of gears 1. FIG. 8C and 8D show the measurement results of a single pitch on the right and left flanks of the tooth portion 60 (see FIG. 7B) of a plurality of gears 100. FIG.

As shown in FIGS. 7 and 8, when comparing the gear 1 of the present embodiment and the gear 100 of the comparative example, in the tooth portion 60 of the gear 100, both the left and right tooth flanks have dimensional errors. , especially the single pitch error caused by the weld.

On the other hand, in the gear 1 of the present embodiment having the grooves 5, in the tooth portion 6A of the gear 1, there is little dimensional error between the left and right tooth flanks, and there is no or a small single pitch error due to weld.

As a result, in the injection-molded body such as the gear 1, by providing the groove portion 5 adjacent to the gate mark in the radial direction and extending in the circumferential direction and having different depths in the circumferential direction, comparison Compared to the example, it was found to be a gear with high dimensional accuracy and excellent quietness.

In the present embodiment, there are three gates (that is, gate traces G1 to G3), but the depth of the groove portion 5 allows the molten resin to be uniformly filled in the cavity of the injection molded body. It may be a single gate as long as it can be controlled to In this case, there is one gate trace. Also, the number of gates may be two or four or more, and in this case, the number of gate traces is two or four or more.

In addition, although the configuration is such that the groove portion 5 is provided adjacent to the outer peripheral side of the gate mark G, it is not limited to this. If there is a portion, a groove portion may be provided adjacent to the inner peripheral side of the gate mark.

Further, in this embodiment, the gear main body 3 has the gate traces G1 to G3 and the groove 5 on the same end surface. As a result, when the injection-molded body is molded by injection molding or the like, the core can be easily removed from the cavity and the molding can be performed with high accuracy.

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and range of equivalents of the scope of the claims. That is, the above description of the configuration and the shape of each part is an example, and it is clear that various modifications and additions to these examples are possible within the scope of the present invention.

INDUSTRIAL APPLICABILITY The injection-molded article according to the present invention has high dimensional accuracy in shape and excellent quietness, and is useful as a gear.

1 gear 2 shaft 3 gear main body (main body)
4 rim portion 5 groove portion 6 tooth portion (peripheral portion)
21 axial hole 31 first web 32 second web 33 third web 52, 52-1, 52-2, 52-3 deepest portion 54, 54-1, 54-2, 54-3 shallowest portion 56-1, 56-2, 56-3 Intermediate part G1, G2, G3 Gate marks

Claims (7)

An injection molded body having a central portion, a body portion and an outer peripheral portion,
The central portion and the outer peripheral portion are connected by the body portion,
The main body includes a gate mark at the time of injection molding,
a groove portion extending in the circumferential direction at a position different from the gate mark in the radial direction and having a different depth in the circumferential direction;
Injection molding. the deepest part of the groove is arranged at a radial position passing through the gate mark;
The injection molded article according to claim 1. The depth of the groove portion gradually decreases in the circumferential direction from the deepest portion,
The injection molded article according to claim 2. The groove has a ring shape surrounding the shaft,
The injection molded article according to any one of claims 1 to 3. The outer peripheral portion is provided on an annular rim portion connected to the outer periphery of the main body portion,
The groove is provided adjacent to the gate trace on the outer peripheral side of the gate trace.
The injection molded article according to any one of claims 1 to 4. A gear tooth portion is provided on the outer peripheral surface of the rim portion,
The injection molded article according to claim 5. the main body has the gate mark and the groove on the same end surface,
The injection molded article according to any one of claims 1 to 6.

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