JPH0722942B2 - Synthetic resin gear - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a gear that is injection-molded using a synthetic resin as a material, and particularly to a gear that is formed of two types of resins each having different characteristics.

(Prior Art) Conventionally, a resin-molded gear is generally manufactured by injection molding a synthetic resin material such as polyacetal or nylon, but it has a drawback of large molding shrinkage and poor dimensional accuracy.

Therefore, the gear is composed of a primary molded product part and a secondary molded product part, the primary molded product part is made of a resin with a small shrinkage ratio such as polycarbonate, and the secondary molded product part has high strength such as polyacetal and nylon. It has been proposed to form a resin having excellent oil lubricity (Japanese Patent Publication No. 54-21903).

(Problems to be Solved by the Invention) However, in the above-described gear, the resin material forming the primary molded product part and the secondary molded product part does not have compatibility and does not fuse, and therefore, the rotational torque may vary. There was a problem of peeling at the material boundary surface.

Further, there is a disadvantage that both the boss portion and the tooth profile portion of the gear, which are required to have oil lubricity, cannot be formed as the secondary molded product portion with the same material, for example, a resin having self-lubricating property.

The present invention has been made in view of such circumstances,
Due to the fact that the primary molded part and the secondary molded part are firmly connected and do not separate even when a large rotational torque is applied, and the boss part and the tooth profile part are formed of the same material by injection molding. An object of the present invention is to provide a synthetic resin gear which has advantages and eliminates adverse effects due to molding shrinkage and has high accuracy.

(Means for Solving the Problem) The present invention comprises a resin molded gear composed of a primary molded product part and a secondary molded product part, and the primary molded product part has an inner peripheral surface to an outer peripheral surface within its wall thickness. In addition to forming a through hole to reach, the secondary molded part is formed by injection molding on both inner and outer sides of the primary molded part using the through hole as a resin passage.
The tooth profile part is composed of a primary molded product part that forms the tooth profile main body and a secondary molded product part that forms the tooth surface part, and the tooth surface part is formed by a uniform thin-walled resin layer injection-molded on the outer periphery of the tooth profile main body part. It features a synthetic resin gear.

(Operation) In the present invention, since the integrated secondary molded product portion is provided on both sides of the inner periphery and the outer periphery of the primary molded product portion through the through hole inside the primary molded product portion, Due to the molding shrinkage of the secondary molded product portion, the primary molded product portion can be clamped and fixed from both the inner and outer peripheral surfaces thereof, so that the connection between the two becomes strong.

Further, since the tooth profile portion and the boss portion of the gear can be formed of the same resin, it is possible to secure the lubricity of both the above parts by forming the secondary molded product portion with a resin having a high lubricity.

Furthermore, if the outer peripheral surface of the tooth profile main body (primary molded product) is covered with a uniform thin tooth surface (secondary molded product), the fitting condition between the primary molded product and the secondary molded product is better. In addition to being strong, there is no anisotropy in molding shrinkage due to the uniform thickness of the tooth surface, and it is easy to predict molding shrinkage, and a highly accurate gear can be obtained.

(Embodiment) An embodiment of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 is a front view of a gear according to the present invention, and FIG. 2 is its X-
It is an X-ray sectional view.

This gear has a primary molded product portion A and a secondary molded product portion B that are fitted and integrated with each other. A part of the boss 1 as the primary molded product portion 1, the plate-like arm portion 2 and the rim A part 3 is formed, and the remaining part 5 of the boss and the remaining part 6 of the rim serve as the secondary molded product part B.
And a tooth profile 7 is formed.

Through-holes 4 extending from the inner peripheral surface of the boss part 1 to the outer peripheral surface of the rim part 3 are formed in the thick part of the primary molded part A at appropriate intervals along the circumferential direction (this embodiment In the example, 8 holes are provided, and the through hole 4 is filled with resin 8 as a resin passage for forming the secondary molded product.

In molding the primary molded part A, the molded product obtained by injection molding may be provided with the through hole 4 by cutting, or the through hole 4 may already be formed at the time of molding by using a hollow pin. The injection-molded product obtained may be obtained, and the primary-molded product portion does not necessarily have to be an injection-molded product, and may be obtained by another molding method.

In molding the secondary molded product part B, the primary molded product part A is cooled and sufficiently contracted, and then set in an injection molding die, and a cavity in the mold is filled with a resin material. Usually, it is injected through a plurality of pinpoint gates arranged in the circumferential direction on the inner peripheral side of the primary molded product part A, and this injected resin material is first part of the boss of the primary molded product part A. 1 is formed with the remaining portion 5 of the boss, and then the through hole 4 inside the primary molded product portion A is sequentially filled as a resin passage, and then the remaining portion of the rim is formed on the outer periphery of the part 3 of the rim of the primary molded product portion A. 6 and tooth profile 7 are formed.

The injection-molded secondary molded part B is cooled and hardened over time, so that the tooth profile 7 and the remaining portion 6 of the rim are molded and shrunk in the inner peripheral direction, and the remaining portion 5 of the boss is molded and contracted in the outer peripheral direction. The primary molded product portion A is sandwiched by the secondary molded product portion B from the inner and outer peripheral surfaces.

As the resin material forming the primary molded product part A and the secondary molded product part B, arbitrary materials can be combined, but the primary molded product part A includes thermosetting resin, ABS resin, polycarbonate, etc. It is preferable to use a resin having a small shrinkage ratio and a small strain, and a resin having high strength and excellent lubricity such as nylon and polyacetal for the secondary molded product part B.

FIG. 3 and FIG. 4 are a front view and a sectional view taken along the line YY showing another embodiment of the present invention.

In this embodiment, the primary molded product portion C and the secondary molded product portion D are fitted and integrated in the same manner as in the above-described embodiment, but a part 11 of the boss as the primary molded product portion C, the plate -Shaped arm part 12, rim part
13 and the tooth profile main body 14 are formed, and the remaining portion 16 of the boss as the secondary molded product portion D and the tooth surface portion 17 are formed,
In addition, a plurality of (8 in this embodiment) through holes 15 extending from the inner peripheral surface of the part 11 of the boss to the outer peripheral surface of the tooth profile main body 14 are bored in the wall thickness of the primary molded part C. Different from the previous embodiment.

The primary molded product portion C and the secondary molded product portion D are molded by the same method and resin material as in the above-mentioned embodiment, and the through hole 15 is formed.
Is filled with resin as a resin passage for forming the secondary molded part.
To be done. The tooth surface 17 of the secondary molded product D has a wall thickness of 0.5 to 1.0 mm.
The outer circumference of the tooth profile main body 14 is covered with a thin and uniform resin layer so to speak.

Then, as in the above-described embodiment, the primary molded product portion C is clamped and fixed from the inner and outer peripheral surfaces by the molding shrinkage of the secondary molded product portion D.

(Effects of the Invention) As described above, in the invention according to claim 1 of the above-mentioned claims, in the gear molded from the dissimilar resin material that is not compatible and cannot be fused, the primary molded part Since the latter partly penetrates the inside of the former and is integrally formed on both the inner and outer surfaces of the former, and the latter is molded and contracted from both the inside and outside of the former, the connection between the two It can be tightly integrated and made very strong, and durability can be improved without peeling at the boundary surface of different materials even when a large rotating torque is applied.

Further, since the tooth tip portion and the boss portion of the gear can be formed of the same material, for example, by selecting a material having a good self-lubricating property, it is possible to impart excellent oil lubricity to both the parts, and the inner peripheral surface of the gear The same performance based on the same material can be given to the outer peripheral surface.

Further, in the invention according to claim 2, in addition to the above effects, the tooth profile main body portion and the tooth surface portion of the tooth profile portion are fitted and adhered in an uneven shape, and the primary molded product portion and the secondary molded product In addition to a stronger bond with the toothed part, the tooth surface part is a thin layer with a uniform thickness, so it is possible to accurately design molding shrinkage and design gears and molds, greatly improving dimensional and shape accuracy. Can be improved.

[Brief description of drawings]

1 is a front view showing an embodiment of the present invention, FIG. 2 is a sectional view taken along the line XX, FIG. 3 is a front view showing another embodiment, and FIG. 4 is a sectional view taken along the line YY. It is a figure. A, C …… Primary molded part, B, D …… Secondary molded part 1,11 …… Part of boss, 2,12 …… Plate arm part, 3 …… Part of rim, 4, 15 …… through hole, 5,16 …… rest of boss, 6…
… Remaining part of rim, 7 …… Tooth profile part, 13 …… Rim part, 14 …… Tooth profile body part, 17 …… Tooth surface part.

Claims (2)

[Claims] 1. A gear comprising a primary molded product part and a secondary molded product part, wherein the primary molded product part has a through hole extending from an inner peripheral surface to an outer peripheral surface in a thickness thereof, A synthetic resin gear, in which a molded product part is injection-molded on both inner and outer sides of the primary molded product part with the through hole as a resin passage. 2. The tooth profile portion is composed of a primary molded product portion forming a tooth profile main body portion and a secondary molded product portion forming a tooth surface portion, and the tooth surface portion is injection-molded uniformly on the outer periphery of the tooth profile main body portion. The synthetic resin gear according to claim 1, wherein the synthetic resin gear is formed of a thin resin layer.