JP2004116646A - Resin gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce injection pressure loss without increasing the number of gates for preventing void from being generated regarding a large-bore resin gear used for a power transmission mechanism such as components for automobiles, each kind of industrial equipment, or the like. <P>SOLUTION: In the resin gear 1 that is formed annularly in a large bore by performing the injection molding of resin from a plurality of gates in a peripheral direction at the outer periphery of a large-diameter bracket 2, the resin gear 1 comprises: a boss section 11 that is integrated at the outer periphery of the bracket 2; a web section 12 extended outward in a radial direction from the boss section 11; and a rim section 13 that is formed at the outer periphery of the web section 12 and has a gear tooth section 14 on the outer periphery. A plurality of radial ribs 15 extended in a radial direction, and an annular rib 16 extended in a peripheral direction are formed at the web section 12. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a large-diameter resin gear used in a power transmission mechanism such as a part for an automobile and various industrial devices.
[0002]
[Prior art]
BACKGROUND ART Conventionally, there is a large-diameter resin gear integrally formed by injection molding on the outer periphery of a large-diameter metal bracket (for example, see Patent Document 1).
[0003]
In the case of large-diameter resin gears, the amount of resin increases, so the thickness is designed to be as thin as possible for weight reduction, and a plurality of radial ribs extending in the radial direction are formed to compensate for the lack of strength. Have been.
[0004]
When forming the resin gear on the outer periphery of the bracket, a mold having a plurality of gates in the circumferential direction is used, and the resin is formed by injection molding from the gates. When the injection molding is completed, the resin gear is divided and integrally formed on the bracket.
[0005]
[Patent Document 1]
Japanese Patent Application No. 2001-354652
[Problems to be solved by the invention]
When a large-diameter resin gear is injection-molded, the distance between adjacent gates of the mold increases. Molten resin is injected from each gate and filled into the mold.If the distance between the gates is large, the flow path of the molten resin injected from the gate becomes long, and the formed resin gear is thin. Therefore, the volume of the channel is small. As a result, the resin is in contact with the mold at a low temperature for a long time, and the ratio of the molten resin in contact with the mold is increased, so that the molten resin cools and solidifies during molding, making it difficult for injection pressure to be applied and voids are generated. There is a possibility that.
[0007]
Therefore, it is conceivable to increase the number of gates and shorten the flow path. However, when the number of gates increases, the force required to break the resin at the gates at the time of mold separation increases, causing new problems such as distortion of the resin gears. There is.
[0008]
[Means for Solving the Problems]
The present invention is a resin gear formed into a large-diameter annular shape by injecting a resin from a plurality of gates in a circumferential direction, having a tooth portion on an outer peripheral surface, and a peripheral portion at a radially intermediate portion between the inner and outer circumferences. An annular rib extending in the direction is formed.
[0009]
Specifically, a resin gear is formed on the outer periphery of a large-diameter bracket by injection molding a resin from a plurality of gates in a circumferential direction to form a large-diameter annular ring, and a boss integrally formed on the outer periphery of the bracket. A web portion extending radially outward from the boss portion, and a rim portion formed on the outer periphery of the web portion and having a tooth portion on an outer peripheral surface, and a plurality of radially extending Radial ribs and annular ribs extending in the circumferential direction are formed.
[0010]
The diameter of the large-diameter annular resin gear is 50 to 300 mm. Here, the diameter is the diameter of the inner peripheral surface of the opening of the annular resin gear.
[0011]
The resin gear is injection-molded on a bracket or the like of a CVT transmission ball screw device, and is not integrally formed with a resin gear or a bracket or the like formed integrally with the bracket or the like. For example, a rotary shaft or the like is mounted at the center. A resin gear having an attachment hole may be formed by injection molding alone.
[0012]
The number of annular ribs extending in the circumferential direction may be one, or a plurality of ribs may be formed in the radial direction. Further, the annular rib may be formed on both side surfaces of the resin gear, or may be formed only on one side surface. Furthermore, the position of the annular rib in the radial direction is not limited to substantially the center in the radial direction, and may be formed closer to the inner circumference or the outer circumference.
[0013]
According to the resin gear of the present invention, the annular rib extending in the circumferential direction is formed at the radially intermediate portion, so that when the molten resin injected from the gate flows through the mold during injection molding, the volume of the annular rib is reduced. Flows circumferentially through large spaces. That is, the volume of the flow path in the circumferential direction increases, the time during which the molten resin contacts the low-temperature mold is reduced, the ratio of the molten resin in contact with the mold decreases, and the flowability of the molten resin improves. . Therefore, it is possible to prevent the molten resin from cooling and solidifying in the middle, to easily apply the injection pressure, reduce the injection pressure loss, and prevent the generation of voids.
[0014]
Thus, when injection molding a large-diameter resin gear, it is possible to prevent the occurrence of voids without increasing the number of gates, and to reduce the force required to break the resin at the gate portion during mold splitting. Thus, there is no problem such as distortion of the resin gear.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
A resin gear according to an embodiment of the present invention will be described with reference to the drawings.
[0016]
1 is a front view of the gear device of the present embodiment, FIG. 2 is a sectional view taken along line II-II of FIG. 1, FIG. 3 is a partially enlarged sectional view of FIG. 2, and FIG.
[0017]
In the present embodiment, a resin gear 1 having a large diameter is formed by injection molding a resin from a plurality of circumferential gates formed in a mold on the outer periphery of a large-diameter annular bracket 2. And the resin gear 1 will be referred to as a gear device.
[0018]
The diameter of the resin gear 1 is 50 to 300 mm. Here, the diameter is the diameter of the inner peripheral surface of the opening of the annular resin gear.
[0019]
The resin gear 1 includes a boss portion 11 integrally formed on the outer periphery of the bracket 2, a web portion 12 extending radially outward from the boss portion 11, and a tooth portion 14 formed on the outer periphery of the web portion 12 and on the outer peripheral surface. Rim 13. The axial thickness of the web portion 12 is set smaller than the axial thickness of the boss portion 11 and the rim portion 13 for weight reduction.
[0020]
On both side surfaces of the web portion 12, a plurality of radial ribs 15 extending in the radial direction and an annular rib 16 extending in the circumferential direction are formed at regular intervals. The annular ribs 16 are formed on both side surfaces of the web portion 12 so as to extend between the adjacent radial ribs 15 having the same diameter. The thickness of the annular rib 16 in the axial direction is equal to the thickness of the radial rib 15 in the axial direction.
[0021]
The annular ribs 16 are formed in order to increase the flow rate of the resin in the circumferential direction. The annular ribs 16 are formed on both side surfaces or one side surface of the web portion 12, and the number of the ribs arranged in the radial direction and the position in the radial direction. The thickness dimension in the axial and radial directions is not particularly limited.
[0022]
The resin gear 1 has the bracket 2 disposed in a molding die composed of a fixed die and a movable die, and is positioned at a predetermined interval in a circumferential direction in a cavity of the molding die corresponding to the outer peripheral region of the bracket 2. The resin is integrally formed on the outer periphery of the bracket 2 by injection molding a resin from a plurality of gates. The bracket 2 and the resin gear 1 are provided so as to rotate integrally with each other around the axis, and the tooth portion 14 of the rim portion 13 of the resin gear 1 has a tooth portion of a reduction gear that rotates upon transmission of a driving force from a rotational power source. Are engaged.
[0023]
Examples of the resin material constituting the resin gear include olefin-based resins (eg, polypropylene), fluororesins, styrene-based resins (eg, acrylonitrile-styrene copolymer, ABS resin), acrylic resins (eg, polymethyl methacrylate), Polyester resins (polyalkylene arylates (homopolyesters) such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, copolyesters having alkylene arylate units, polyarylate resins, liquid crystalline polyesters, etc.), polycarbonate resins (bisphenol A) Polycarbonate, etc.), polyamide resins (aliphatic nylon such as nylon 6, nylon 66, nylon 610, aromatic nylon MXD-6, etc.), polyacetal resins, poly Eniren'eteru resins, polyphenylene sulfide resins, polysulfone resins, polysulfone ether resin can be exemplified.
[0024]
The resin material may include a reinforcing fiber. Examples of the reinforcing fibers include inorganic fibers (glass fibers, carbon fibers, metal fibers, potassium titanate, barium titanate, alumina fibers, silica fibers, silicon carbide fibers, silicon nitride fibers, etc.) and organic fibers (aramid fibers, etc.). Can be exemplified.
[0025]
According to the resin gear 1 configured as described above, the annular rib 16 extending in the circumferential direction is formed on the web portion 12, so that when the molten resin injected from the gate flows through the mold during injection molding, the annular rib 16 is formed. Flows in the circumferential direction through a space having a large volume corresponding to. That is, the volume of the flow path in the circumferential direction increases, the time during which the molten resin contacts the low-temperature mold is reduced, the ratio of the molten resin in contact with the mold decreases, and the flowability of the molten resin improves. . Therefore, it is possible to prevent the molten resin from cooling and solidifying in the middle, to easily apply the injection pressure, reduce the injection pressure loss, and prevent the generation of voids.
[0026]
As described above, when injection molding a large-diameter resin gear 1, voids can be prevented without increasing the number of gates, and the force required to break the resin at the gate portion during mold splitting is small. Thus, there is no problem such as occurrence of distortion in the resin gear 1.
[0027]
Further, by forming annular ribs 16 extending in the circumferential direction on the web portion 12 in addition to the plurality of radial ribs 15, strength and rigidity can be improved while reducing the weight of the resin gear 1.
[0028]
Further, the formation of the annular rib 16 can prevent the resin gear 1 from being broken in the radial direction at the weld portion where the molten resin injected from the gate merges. That is, by adding the annular rib 16, the tensile strength in the circumferential direction of the resin gear 1 is improved, the resin gear 1 can be prevented from cracking in the radial direction and opening in the circumferential direction, and the heat shock strength of the welded portion can be prevented. Satisfy the specifications.
[0029]
【The invention's effect】
According to the resin gear of the present invention, the injection pressure loss can be reduced without increasing the number of gates, and the effect that voids can be prevented can be obtained.
[Brief description of the drawings]
FIG. 1 is a front view of a gear device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1. FIG. 3 is a partially enlarged cross-sectional view of FIG. Partial enlarged front view of [Description of symbols]
DESCRIPTION OF SYMBOLS 1 Resin gear 2 Bracket 11 Boss part 12 Web part 13 Rim part 14 Teeth part 15 Radial rib 16 Annular rib

Claims (3)

A resin gear is formed by injection molding a resin from a plurality of gates in a circumferential direction to form a large-diameter annular ring,
A resin gear having a tooth portion on an outer peripheral surface and an annular rib extending in a circumferential direction at a radially intermediate portion between the inner and outer peripheries. A resin gear formed by injection molding resin from a plurality of circumferential gates on the outer periphery of a large-diameter bracket to form a large-diameter annular ring,
A boss portion integrally formed on the outer periphery of the bracket, a web portion extending radially outward from the boss portion, and a rim portion formed on the outer periphery of the web portion and having a tooth portion on an outer peripheral surface,
A resin gear, wherein a plurality of radial ribs extending in a radial direction and an annular rib extending in a circumferential direction are formed on the web portion. 3. The resin gear according to claim 1, wherein the diameter of the resin gear is 50 to 300 mm.

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