JP2001323990A - Gear of synthetic resin molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly precise gear to satisfy a highly precise angle transmission error sufficiently and satisfy high precision in strength, rigidity, low noise performance, a shape and a size of an element in each portion of the gear which are requirements in the prior art. SOLUTION: A face width has a ratio of 0.25-0.75 to an addendum circle diameter 1 in this gear, the gear has a cylindrical part of a thickness substantially same to the face width along an outer circumferential direction from an axial center, and has teeth in an outer circumference of the cylinder. The gear is a synthetic resin molding gear molded under the condition where a gate part is kept in a molten state, using a hot runner die.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin molded gear, for example, a copier, a printer, a facsimile,
The present invention relates to a helical gear, a spur gear, and the like of a synthetic resin molded product used as a part of a video, a camera, an automobile, or an OA device.

[0002]

2. Description of the Related Art Conventionally, as a power transmission component of OA equipment such as a copying machine and a printer, a VTR tape drive mechanism,
A spur gear made of a synthetic resin is frequently used for a loading mechanism of a laser disk (registered trademark) player and the like. Also,
When there is a strong demand for low noise performance and high speed performance, a helical gear made of a synthetic resin having a high meshing ratio and transmitting a large force with low noise is used. Conventionally, when designing such synthetic resin gears, considering the noise, transmission efficiency, friction, wear characteristics, strength, high precision in the shape and dimensions of each part of the tooth, etc., the shape of each component of the gear And dimensions.

[0003] Generally, the thickness of a cylindrical rim having teeth outside its outer peripheral surface is about 1.5 times the pitch circle tooth thickness.
Alternatively, the thickness of the disk-shaped web formed about 2.5 times as large as the module and formed in the axial direction from the inner peripheral surface of the rim is designed to be substantially the same as the rim thickness. In addition, for example, the first in the plastic magazine “Plastic molding technology”
Vol. 3, No. 8, page 17 (line 10 to line 18 on the left, FIG. 2 on the right) shows the standard dimensional proportions of the cross-sectional dimensions of a spur gear or a helical gear. The ratio of the pitch circle tooth thickness, rim thickness and web thickness is 1: 1.4: 1.6.

Recently, with the increase in the precision of OA equipment such as printers and copiers, gears for transmitting power and operation of these OA equipments are one of the most important purposes of using gears, the one-axis gears. Accuracy of an angle transmission error for evaluating whether or not to transmit a rotation angle to another axis in inverse proportion to the number of teeth is required.

[0005]

However, as in the case of the conventional resin gear design, an ordinary synthetic resin for gears is used, and the strength, rigidity, low noise performance, and the shape and dimensions of each element of the gear are high. In the design that determines the shape and dimensions of each component of the gear with high precision, for example, in the case of a helical gear using polyacetal resin that is generally used, the actual number of rotations and rotations There is a problem that an angle transmission error occurs for about 10 minutes under torque, and it is difficult to obtain a synthetic resin molded gear having an angle transmission error of about 5 minutes. The present invention sufficiently satisfies the high-precision angle transmission error required by recent OA equipment such as copiers, printers, and facsimile machines, and also has the strength, rigidity, low noise performance, and tooth components that have been conventionally required. It is an object of the present invention to obtain a high-precision gear that sufficiently satisfies high precision in shape and dimensions.

[0006]

SUMMARY OF THE INVENTION In the present invention, a synthetic resin having a specific shrinkage ratio is used to change the shape and dimensions of each component of a synthetic resin molded gear, and at the same time, to measure an angle transmission error. By studying in detail how the rotational speed and rotational torque fluctuate to affect the angle transmission error, and finding out that the above problems can be solved by comprehensively analyzing and studying the results of these studies Thus, the present invention has been completed.

In other words, the synthetic resin molded gear of the present invention has a cylindrical shape having a ratio of a tooth width of 0.25 to 0.75 to a tip diameter of 1 and a thickness substantially the same as the tooth width in the outer circumferential direction from the axis. Having a portion and having teeth on the outer periphery of the cylinder,
It is characterized by being molded using a hot runner mold while keeping the gate portion in a molten state.

The synthetic resin molded gear of the present invention is characterized by using a resin made of a thermoplastic resin and having a shrinkage of 1.0% to 4.0% during molding.

Further, the synthetic resin molded gear of the present invention is a helical gear.

The synthetic resin molded gear of the present invention is a spur gear.

Further, the thermoplastic resin of the synthetic resin molded gear of the present invention is characterized in that it is any one of polyacetal resin, polybutylene terephthalate resin, polyphenylene sulfide resin and polyamide resin.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The synthetic resin molded gear of the present invention has a ratio of a tooth width b of 0.25 to 0.75 to a tooth tip diameter Da, as shown in FIG. A disk-shaped synthetic resin gear having a cylindrical portion having substantially the same thickness as the tooth width b in the outer peripheral direction from the shaft center. And molded using a hot runner mold while maintaining the gate portion in a molten state.

When the tip circle diameter Da is set to 1, the disk-shaped synthetic resin gear having the ratio of the tooth width b to 0.25 to 0.75 with respect to the tip circle diameter Da is obtained when the ratio is less than 0.25. This is because a gear having an angle transmission error with sufficiently high accuracy cannot be obtained even if it exceeds 0.75.

By providing a cylindrical portion having substantially the same thickness as the tooth width b in the outer circumferential direction from the shaft center, the cylindrical portion has no lightening, and is a synthetic resin gear having teeth on the outer periphery of the cylinder. A synthetic resin gear having a web formed in a disk shape thinner than the tooth width b in the outer peripheral direction from the shaft center is a gear having a sufficiently high precision angle transmission error under the rotational speed and rotational torque actually used. Because you cannot get

The synthetic resin gear characterized by using a hot runner mold and molding while keeping the gate portion in a molten state is used when a hot runner mold is not used or when a hot runner mold is used. This is because it is difficult to avoid sinks and voids due to molding shrinkage when molding is performed without maintaining the gate portion in a molten state even when using.

[0016] The synthetic resin molded gear of the present invention, when using a thermoplastic resin having a shrinkage of 1.0% to 4.0% during molding,
This is preferable because the effect is more remarkable. Conventionally, in a resin having a molding shrinkage ratio in this range, a dimensional difference between a molded product obtained by resin shrinkage during molding and a mold shape becomes large, and the shrinkage behavior of the resin is complicatedly changed depending on the molded product shape. Although it has been difficult to obtain a gear having sufficiently high precision angle transmission error, a gear excellent in these characteristics can be obtained by configuring the gear as in the present invention.

The resin used in the present invention is preferably a resin having a shrinkage of 1.0% to 4.0% at the time of molding as described above. Among them, a polyacetal resin (polyoxymethylene resin (PO
M)) or polybutylene terephthalate resin (PB
T) can be particularly preferably used. Further, polyphenylene sulfide resin, polyamide resin and the like are also examples of materials that can be suitably used in the present invention. These may be blended with various additives usually added to the resin,
A resin composition mainly composed of these may be used.

The polyacetal resin as a gear material resin may be either a homopolymer or a copolymer. In the case of a copolymer, a monomer component such as ethylene oxide or dioxolane is randomly copolymerized to stabilize the main chain. Any copolymerized form, such as a polymerized one, a block- or graft-polymerized one, or a further one into which a third component is introduced, may be used. In the case of polybutylene terephthalate, in addition to the usual polybutylene terephthalate resin, as the third or fourth component, an aliphatic or aromatic polybasic acid such as isophthalic acid, naphthalenedicarboxylic acid, adipic acid, or glycol, A copolymer obtained by modification with an alkylene glycol such as ethylene glycol, diethylene glycol or neopentyl glycol or an aromatic alcohol such as bisphenol A as a component may be used.

The gear of the present invention may be a helical gear,
A spur gear may be used, and the twist angle is not limited. These helical gears, spur gears and the like may be single gears or two-stage gears, or may be combined gears arranged in multiple stages from a drive motor to reduce rotational unevenness and reduce speed.

The synthetic resin molded gear of the present invention may be formed by ordinary injection molding or injection compression molding.

[0021]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. Embodiment 1 FIG. 1 shows a helical gear which is a synthetic resin molded gear of the present invention. In a case where a helical gear diameter Da is 1, the helical gear 10 has a tooth with respect to the tooth circle diameter Da. The width b is 0.25 to 0.
A disk-shaped gear having a ratio of 75, having a cylindrical portion 11 having the same thickness as the tooth width b in the outer peripheral direction from the shaft center 12 so that the cylindrical portion 11 is not lightened, and is provided on the outer periphery of the cylinder. Helical teeth 13
have. The cylindrical portion 11 and the helical teeth 13 having the same thickness as the tooth width b are made of a polyacetal resin (polyoxymethylene (POM)), which is a thermoplastic resin, and are integrally formed. As the polyacetal resin, Duracon M270-44 manufactured by Polyplastics Co., Ltd. was used. Such a molding resin does not contain a filler, and the shrinkage during molding is 1.
8%.

The design dimension of the helical gear is the tip circle diameter Da.
Is 30 mm, the tooth width b is 15 mm, and the torsion angle is 20.
In degrees, the module is 1, the number of teeth is 28, and the thickness of the cylindrical portion 11 is the same as the tooth width b, that is, 15 mm.
This dimension has not only the sufficient strength and rigidity required in the related art but also a low noise design and a high degree of precision in the shape and size of each element of the tooth.

Based on the above design dimensions of the helical gear 10,
A mold was prepared by an ordinary method, and was incorporated in a mold 20 for a helical gear of a cut runner shown in FIG. The helical gear mold 20 has a radial rolling bearing 22 inside and outside the nest 21 and a thrust rolling bearing 23 in the mold clamping direction to reduce the rotational resistance of the gear nest 21. The resin is passed through one hot runner gate 25 provided in the cylindrical portion 11 of the gear, and the resin
Pressed into. The position and the number of the hot runner gates 25 are not limited to this.

The helical gear is molded using a usual injection molding machine (J75EP manufactured by Nippon Steel Works) under the following conditions, cylinder temperature: 190 ° C., mold temperature: 60 ° C., injection speed: 17
mm / sec, holding pressure: 100 MPa, injection holding pressure time:
The test was performed for 60 sec and a cooling time of 10 sec. In the hot runner, the gate portion was kept in a molten state under the following conditions, a manifold temperature: 200 ° C., a body temperature: 230 ° C., and a chip heating: 9 A, by using a normal hot runner system (century spear system). The molding was performed as it was.

The angle transmission error was measured using a single-tooth flank meshing tester under the following conditions: the drive-side master gear had a tip circle diameter Da of 50 mm, a tooth width b of 15 mm, and a torsion angle of 20 degrees. , The module is 1 and the rotation speed on the drive side is 15
At 0 rpm, a rotational torque of 15 kg · cm is applied, and the difference between the rotation angle per unit time of the synthetic resin molded gear mounted on the driven side and the rotation angle per unit time of the metal master gear mounted on the drive side is shown. Was measured as an angle transmission error. The angle transmission error result of the synthetic resin molded gear is
As shown in Example 1 of Table 1, it was possible to obtain a synthetic resin molded gear having an extremely small length of 5 minutes. Examples 2 to 3 and Comparative Examples 1 to 9 Next, Examples 2 and 3 and Comparative Examples 1 to 9 will be described. In the first embodiment, the rotation speed on the drive side is set to 150 r.
pm, and a case where the rotational torque is 15 kg · cm. The second and third embodiments are designed in the same manner as in the first embodiment, are molded using the same injection molding machine, and drive the angle transmission error of the synthetic resin gear. The rotational speed and the rotational torque on the side were measured and evaluated under the conditions shown in Table 1.

Further, as shown in Table 1, Comparative Examples 1 to 3 are designed in the same manner as Examples 1 to 3 and use the same injection molding machine, but without using a hot runner mold.
Using a cold runner mold, the angle transmission error of the synthetic resin gear was measured and evaluated under the conditions shown in Table 1 for the number of rotations on the drive side and the rotation torque.

Further, in Comparative Examples 4 to 6, as shown in Table 1, a disk-shaped synthetic resin gear having a ratio of a tooth width of 0.25 to 0.75 to a tooth tip circle diameter 1 was not used. It is an example. That is, the tip circle diameter Da is 15 mm, and the tooth width b is 15
The angular transmission error of the cylindrical synthetic resin gear having a diameter of mm was measured and evaluated under the conditions shown in Table 1 with the number of rotations and the rotation torque on the drive side.

Further, for Comparative Examples 7 to 9,
It is a synthetic resin molded gear that has been generally used, and the thickness of the cylindrical rim having teeth outside its outer peripheral surface is about 1.5 times the pitch circle tooth thickness, or about 2.5 times the module, A disk-shaped web formed in the axial direction from the inner peripheral surface of the rim and having a thickness substantially the same as the rim thickness was used. That is, in the case where the module is 1, the rim thickness and the web thickness are 2.5 mm, and as in the first to third embodiments, the rotation speed and the rotation torque on the drive side are measured under the conditions shown in Table 1 and measured and evaluated. did.

For these examples and comparative examples, molds were prepared, injection molded to prepare synthetic resin gears, and the results of measuring the angle transmission error are shown in Table 1. The synthetic resin molded gear of Example 2 was 3 minutes 30 seconds, the synthetic resin molded gear of Example 3 was 2 minutes 30 seconds, and the synthetic resin molded gears of Comparative Examples 1 to 9 were 10 minutes 30 seconds and more. In contrast, the angle transmission error of the synthetic resin molded gear of the present invention is extremely small, and the most important purpose of using the gear is to change the rotation axis of one shaft to the other shaft in inverse proportion to the number of teeth. This shows that a gear that can transmit correctly has been obtained.

[0030]

[Table 1]

[0031]

As described above, according to the present invention,
A disc-shaped synthetic resin gear that uses a resin with a specific molding shrinkage and has a ratio of tooth width of 0.25 to 0.75 to tooth tip circle diameter 1. A cylinder with the same thickness as the tooth width in the outer circumferential direction from the shaft center By having a portion, there is no lightening in the cylindrical portion, there is a tooth on the outer periphery of the cylinder, using a hot runner mold, and a synthetic resin gear molded with the gate portion kept in a molten state. OA of recent printers, copiers, etc. by using
It is possible to obtain a gear that correctly transmits one rotating shaft, which is the most important purpose in equipment, to another shaft in inverse proportion to the number of teeth.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing Embodiment 1 of a synthetic resin molded gear of the present invention.

FIG. 2 is a sectional view of a mold for forming the gear shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Synthetic resin molded gear 11 Cylindrical part 12 Shaft core 13 Helical tooth Da Tip diameter b Tooth width 20 Mold for helical gear of hot runner 21 Gear insert 22 Radial rolling bearing 23 Thrust rolling bearing 25 Hot runner Gate

Claims (5)

[Claims] 1. A synthetic resin molded gear, wherein the gear has a ratio of a tooth width of 0.25 to 0.75 with respect to a tooth tip diameter of 1, and a thickness substantially the same as the tooth width in the outer circumferential direction from the shaft center. A synthetic resin molded gear having a cylindrical portion and a tooth on the outer periphery of the cylinder, the molded portion being formed using a hot runner mold while keeping the gate portion in a molten state. 2. The synthetic resin molded gear according to claim 1, wherein a thermoplastic resin having a shrinkage ratio of 1.0% to 4.0% during molding is used. 3. The synthetic resin molded gear according to claim 1, wherein the gear is a helical gear. 4. A spur gear according to claim 1, wherein said spur gear is a spur gear.
Or the synthetic resin molded gear according to 2. 5. The synthetic resin molded gear according to claim 1, wherein the thermoplastic resin is any one of a polyacetal resin, a polybutylene terephthalate resin, a polyphenylene sulfite resin, and a polyamide resin. .