JP4025536B2 - Resin gear - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resin gear in which tooth portions are integrally formed by injection molding on an outer peripheral portion of a resin gear such as a bracket gear, in particular, an insert such as a large-diameter metal bracket, and a manufacturing method thereof.
[0002]
[Prior art]
A resin gear having a resin tooth portion formed on the outer periphery of a metal bracket is usually manufactured by insert molding. In particular, when the diameter of the metal bracket is large, the tooth portion is formed by injecting the resin composition from a plurality of gate portions arranged at equal intervals in the circumferential direction. Such resin gears are required to have high dimensional stability and roundness, mechanical strength, wear resistance, and the like.
[0003]
However, since the orientation direction of the reinforcing fiber of the resin composition is different between the vicinity of the gate portion and the weld portion where the molten resin joins, it is difficult to mold the resin gear with high dimensional accuracy. That is, since the resin composition is injected from the gate portion in the thickness direction and flows in the circumferential direction, the axial direction of the reinforcing fibers is easily oriented in the circumferential direction along the flow direction of the resin in the vicinity of the gate portion. On the other hand, in the weld portion located between the adjacent gate portions, the molten resin joins while spreading in the radial direction, so that the axial direction of the reinforcing fiber is easily oriented in the radial direction. That is, in the weld portion, the reinforcing fibers are oriented in a direction that suppresses shrinkage of the resin in the radial direction. For this reason, the uniform thermal shrinkage of the resin is inhibited at the gate portion and the weld portion, and the roundness and dimensional accuracy of the outer peripheral surface of the gear are lowered.
[0004]
Furthermore, since the injection molding is performed in the outer peripheral area of the bracket, the position of the gate portion is biased outward. Therefore, the weld portion is clearly formed, and the strength of the weld portion is greatly reduced.
[0005]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a resin gear that can be molded with high dimensional accuracy and can effectively reinforce a weld portion even if a resin tooth portion is formed on the outer periphery of a disk-like or ring-like insert by injection molding, and its It is to provide a manufacturing method.
[0006]
Another object of the present invention is to provide a resin gear having a high dimensional accuracy and roundness and having a highly reinforcing tooth portion and a method for manufacturing the same, even if the disc-shaped or ring-shaped insert has a large diameter. It is to provide.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above-mentioned problems, the present inventors have formed ribs on the gate part and the weld part in accordance with injection molding, and adjusted the wall thickness and / or width so that they are larger than the gate part. When a rib having high reinforcing properties is formed in the weld portion, a resin composition containing reinforcing fibers from a plurality of gate portions located in the circumferential direction may be injection-molded in the thickness direction in the outer peripheral region of the large-diameter disk-shaped insert. The inventors have found that the degree of heat shrinkage can be made uniform to improve dimensional accuracy and roundness, and that the weld portion can be effectively reinforced, thereby completing the present invention.
[0008]
That is, the resin gear of the present invention is a gear in which a tooth portion is formed by injection molding a resin composition containing reinforcing fibers from a plurality of circumferential gate portions on the outer periphery of a disc or ring-shaped insert such as a metal bracket. The tooth portion includes a boss portion formed integrally with an outer peripheral portion of the disc or the ring-shaped insert, a web portion extending in a radial direction from the boss portion, and a ring shape extending in a radial direction from the web portion. It is composed of a rim portion and a plurality of teeth formed in the circumferential direction of the rim portion. At least the gate portion of the web portion and a weld portion where the resin composition injected from the gate portion merges rib extending in the radial direction is formed, the thickness and / or width of the rib portion of the weld portion than the rib part of the gate portion is formed larger. The number of ribs can be appropriately selected as long as the reinforcing property is not impaired. For example, when the number of gate portions is n, the number of ribs may be n × (1 to 6). The ratio (W2 / W1) between the width W2 of the rib portion of the weld portion and the width W1 of the rib portion of the gate portion is the former / the latter = 110/100 to 200/100 depending on the shrinkage amount of the resin composition. You can choose from a range of degrees. The ratio (T2 / T1) between the tooth thickness T2 and the web thickness T1 can be selected from the range of the former / the latter = 1.5-5.
[0009]
The present invention is useful for forming a tooth portion with respect to a large-diameter insert. For example, the inner diameter (or outer diameter of the insert) D1 of the tooth portion is about 50 to 300 mm, and the outer diameter D2 and the inner diameter of the tooth portion. (Or the outer diameter of the insert) D1 may be about the former / the latter = 110/100 to 150/100, and the ratio between the outer diameter D2 of the tooth portion and the inner diameter D3 of the rim portion (D2 / D3). ) May be about 120/100 to 103/100. Furthermore, the module (the diameter of the pitch circle (mm) / the number of teeth) representing the size of the gear teeth may be about 0.5 to 3.5.
[0010]
The present invention is a gear manufacturing method in which a resin composition containing reinforcing fibers is injection-molded in the thickness direction from a plurality of gate portions located in the circumferential direction on the outer periphery of a disc or ring-shaped insert to form a tooth portion. A boss part formed integrally with the outer peripheral part of the disc or ring-shaped insert, a web part extending in a radial direction from the boss part, and a ring-shaped rim part extending in a radial direction from the web part And a plurality of teeth formed in the circumferential direction of the rim portion, and extends in a radial direction to at least the gate portion of the web portion and a weld portion where the resin composition injected from the gate portion merges. forming a rib portion, the manufacturing method of the resin gear formed increase the thickness and / or width of the rib portion of the weld portion than the rib part of the gate portion comprises.
[0011]
In the present invention, even if the diameter is large, when the resin composition containing reinforcing fibers is injection-molded in the thickness direction from a plurality of gate portions located in the circumferential direction in the outer peripheral region of the disc-shaped insert, Although the degree of shrinkage of the resin is small depending on the orientation direction of the reinforcing fibers compared to the vicinity, the amount of shrinkage at the weld is larger than that near the gate because the weld rib is thick and / or wide. The amount of contraction of the teeth can be made uniform. In addition, since ribs having a large thickness and / or wide width are formed in the weld portion, the reinforcement in the weld portion can be improved.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the accompanying drawings as necessary. FIG. 1 is a partially cutaway schematic side view showing an example of the resin gear of the present invention, and FIG. 2 is a schematic plan view showing the resin gear of FIG.
[0013]
In this example, the resin gear is formed by injection-molding a large-diameter disk or ring-shaped metal insert 1 having an outer diameter of about 50 to 300 mmφ and a resin composition containing reinforcing fibers in the outer peripheral region of the insert. It is comprised with the tooth | gear part 2 integrally formed by insert molding.
[0014]
The tooth portion 2 includes a boss portion (or a thick annular strip portion) 3 formed integrally with the outer peripheral portion of the metal insert 1, a radial web portion 4 extending from the boss portion, and a thin wall portion 4. A ring-shaped rim portion (or thick annular portion) 5 extending radially from the web portion and a plurality of teeth 6 formed at a predetermined pitch in the circumferential direction of the rim portion.
[0015]
In the resin gear of this example, the ratio (D2 / D1) between the outer diameter D2 of the tooth portion and the inner diameter (or outer diameter of the insert) D1 is formed to be about the former / the latter = 125/100 to 135/100. The ratio (D2 / D3) between the outer diameter D2 of the tooth portion 2 and the inner diameter D3 of the rim portion 5 is about 105/100 to 115/100. Further, the module (the diameter of the pitch circle (mm) / the number of teeth) representing the size of the gear teeth 6 is about 1.5 to 2.3.
[0016]
The tooth portion 2 has a metal insert placed in a molding die 8 composed of a fixed die and a movable die, and in a cavity (not shown) corresponding to the outer peripheral area of the metal insert in the molding die. The resin composition containing reinforcing fibers is formed by injection molding from a plurality of gate portions 7 positioned at predetermined intervals in the circumferential direction. In this example, the resin composition is injected from eight gate portions 7 every 45 degrees in the circumferential direction.
[0017]
In such a resin gear, each of the gate portions 7 and a weld portion (not shown) located between the adjacent gate portions 7 and where the molten resin joins are respectively injection-molded with the resin composition. Accordingly, rib portions 9 and 10 extending in the radial direction are formed. In particular, in the web portion 4, a rib portion 9 extending in the radial direction is formed in the gate portion 7 with a narrow width W1, and a rib portion 10 extending in the radial direction is formed in the weld portion with a wide width W2 (W2>). W1) The ratio (W2 / W1) between the width W1 of the rib portion 9 of the gate portion 7 and the width W2 of the rib portion 10 of the weld portion is set to “100” when the width of the rib portion 9 of the gate portion 7 is “100”. It is formed in the order of 110/100 to 150/100. Furthermore, the ratio (T2 / T1) between the width (thickness) T2 of the tooth 6 and the thickness T1 of the web portion 4 is formed to be about 2.3 to 3. In this example, the number of rib portions 9 and 10 is n × 4 = 32 while the number of gate portions 7 is n = 8.
[0018]
In the manufacture of such a resin gear, when a resin composition containing reinforcing fibers is injection-molded from a plurality of gate portions 7, the welded rib portion 10 is formed wider than the rib portion 9 of the gate portion 7. As described above, the amount of heat shrinkage at the wide rib portion 10 is large. Therefore, by expanding the width of the rib portion 10 of the weld portion, the thermal shrinkage suppressed by the orientation of the reinforcing fiber can be offset by the thermal contraction of the wide rib portion 10, and the suppressed thermal contraction amount of the weld portion can be reduced. 7 equal to the amount of heat shrinkage in the rib portion 9 and its peripheral region, the dimensional accuracy in the rib portion 10 and its peripheral region can be increased, and the roundness can also be improved. Furthermore, by increasing the width of the rib portion 10 in the weld portion, the weld portion that causes a decrease in mechanical strength can be effectively reinforced. Reference numeral 11 is a through hole (air hole) for cooling by ventilation while using the gear.
[0019]
In addition, this invention is applicable to the various gearwheel which formed the tooth | gear part in the outer periphery of the disk-shaped or ring-shaped insert from the several gate part of the circumferential direction. For example, the insert is not limited to metal (made of steel such as stainless steel, aluminum metal such as aluminum, magnesium alloy, titanium alloy, etc.), but may be ceramic. The outer peripheral part of the insert is usually ring-shaped, and the insert has a wheel with an arm part extending in the radial direction (particularly in the radial direction) from the central or central boss toward the outer peripheral part, and the boss and the outer peripheral part. It may be a wheel-like insert having a web portion formed between them.
[0020]
The present invention can be applied to resin gears of various sizes, but it is effective to apply to a large-diameter resin gear. For example, the present invention can be applied to a resin gear having a tooth part inner diameter (or insert outer diameter) D1 of about 50 to 300 mm. In such a resin gear, the ratio (D2 / D1) between the outer diameter D2 and the inner diameter D1 of the tooth portion is usually about 110/100 to 150/100 depending on the type of resin. Furthermore, the ratio (D2 / D3) between the outer diameter D2 of the tooth portion 2 and the inner diameter D3 of the rim portion 5 is usually the former / the latter = 125/100 to 103/100, preferably about 120/100 to 105/100. It is. The module representing the size of the gear teeth 6 (the diameter of the pitch circle (mm) / the number of teeth) is usually about 0.5 to 3.5, preferably about 1.5 to 2.5.
[0021]
The rib portions respectively formed in the gate portion and the weld portion usually extend in the radial direction, but may be extended in the radial direction as long as the reinforcing property is not impaired. When the tooth portion is composed of a boss portion, a web portion, a rim portion, and teeth, the thickness of the web is usually larger and uniform than the boss portion and the rim portion, but is thicker in the radial direction. May increase or decrease gradually and may be different. Further, instead of the web portion, a wide or narrow arm portion may be formed.
[0022]
Further, in order to control the amount of heat shrinkage and the reinforcing property, the rib of the weld portion only needs to be thicker and / or wider than the rib of the gate portion, and the rib width and / or thickness of the weld portion and the gate The ratio of the rib width and / or wall thickness of the part is about the former / the latter = 110/100 to 200/100. Further, the ratio (T2 / T1) between the width (thickness) T2 of the teeth 6 and the thickness T1 of the web portion 4 is usually the former / the latter = 1.5-5, preferably about 2-3.
[0023]
In the manufacturing method of the present invention, the gate portions are usually positioned at substantially equal intervals on the fixed die constituting the forming die in order to increase the dimensional accuracy and roundness. The number n of gate portions is not particularly limited, and is about n = 3-18. Further, the number of ribs is usually n × (1 to 6), preferably about n × (2 to 5) with respect to the number n of gate portions.
[0024]
The tooth | gear part of the resin gear of this invention can be formed with a various resin composition. Preferred teeth are usually made of engineering plastic. Examples of the resin include olefin resins (polypropylene, etc.), fluororesins, styrene resins (acrylonitrile-styrene copolymer, ABS resin, etc.), acrylic resins (polymethyl methacrylate, etc.), polyester resins (polyethylene, etc.). Polyalkylene arylates (homopolyesters) such as terephthalate, polybutylene terephthalate, polyethylene naphthalate, copolyesters having an alkylene arylate unit, polyarylate resins, liquid crystalline polyesters, etc., polycarbonate resins (such as bisphenol A type polycarbonate), Polyamide resin (Nylon 6, Nylon 66, Aliphatic nylon such as nylon 610, Aromatic nylon MXD-6, etc.), Polyacetal resin, Polyphenylene ether Resins, polyphenylene sulfide resins, polysulfone resins, polysulfone ether resin can be exemplified. These resins may be used alone or in combination of two or more as a polymer blend or a polymer alloy.
[0025]
Reinforcing fibers include, for example, inorganic fibers and organic fibers (for example, aramid fibers). Examples of inorganic fibers include glass fibers, carbon fibers, metal fibers, potassium titanate, barium titanate, alumina fibers, Examples thereof include silica fiber, silicon carbide fiber, and silicon nitride fiber. The inorganic fiber may be a whisker. These reinforcing fibers can be used alone or in combination of two or more.
[0026]
Reinforcing fibers are usually used as short fibers. The average fiber diameter of the reinforcing fibers is 0.05 to 50 μm, preferably about 0.1 to 25 μm (for example, 1 to 20 μm), and the average fiber length is 0.1 to 5 mm, preferably 0.2 to 3 mm. More preferably, it is about 0.5 to 2 mm.
[0027]
The content of the reinforcing fiber can be selected according to the type of the resin, for example, 1 to 50 parts by weight, preferably 5 to 40 parts by weight, more preferably about 10 to 40 parts by weight with respect to 100 parts by weight of the resin. It is.
[0028]
If necessary, the resin composition may be a particulate reinforcing agent or filler (calcium carbonate, titanium oxide, talc, etc.), stabilizer (ultraviolet absorber, antioxidant, heat stabilizer, etc.), flame retardant, A lubricant, a lubricant, a plasticizer, an antistatic agent, a dispersant, a colorant, and the like may be contained.
[0029]
The present invention has a high unity between the insert and the tooth part, and the tooth part is made of resin. Therefore, the noise reduction is high, and the parts constituting the power transmission mechanism using gears, for example, automobile parts, etc. It is valid.
[0030]
【The invention's effect】
In the present invention, since the thickness and / or width of the rib portion of the weld portion is increased, even if the resin tooth portion is formed on the outer periphery of the disk-like or ring-like insert by injection molding, with high dimensional accuracy. A resin gear can be molded and the weld portion can be effectively reinforced. Furthermore, even if the disc-shaped or ring-shaped insert has a large diameter, it is possible to form a tooth portion having high dimensional accuracy and roundness and high reinforcement.
[Brief description of the drawings]
FIG. 1 is a partially cutaway schematic side view showing an example of a resin gear of the present invention.
FIG. 2 is a schematic plan view showing the resin gear of FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Metal insert 2 ... Tooth part 3 ... Boss part (or thick annular belt part)
4 ... Web part 5 ... Rim part (or thick annular part)
6 ... Teeth 7 ... Gate part 8 ... Mold 9, 10 ... Rib part

Claims (7)

A gear having a tooth portion formed by injection molding a resin composition containing reinforcing fibers from a plurality of circumferential gate portions on the outer periphery of a disc or ring-shaped insert, wherein the tooth portion is a disc or ring shape A boss portion formed integrally with the outer peripheral portion of the insert, a web portion extending in a radial direction from the boss portion, a ring-shaped rim portion extending in a radial direction from the web portion, and a circumferential direction of the rim portion A rib portion extending in a radial direction is formed in at least the gate portion of the web portion and a weld portion where the resin composition injected from the gate portion merges; parts resin gear thickness and / or width of the rib portion of the weld portion than the rib portion is formed to be larger in. The resin gear according to claim 1, wherein a ratio (W2 / W1) between a width W2 of the rib portion formed in the weld portion and a width W1 of the rib portion formed in the gate portion is 110/100 to 200/100. . The ratio of the thickness T1 of the thickness T2 and the web portion of the tooth (T2 / T1) is a resin gear according to claim 1, wherein 1.5 to 5.   The inner diameter (or outer diameter of the insert) D1 of the tooth portion is 50 to 300 mm, and the ratio (D2 / D1) between the outer diameter D2 of the tooth portion and the inner diameter (or outer diameter of the insert) D1 is 110/100 to 150. The resin gear according to claim 1, which is / 100. Teeth ratio of the inner diameter D3 of the outer diameter D2 and the rim portion (D2 / D3) is 120/100 to 103/100 resin gear according to claim 1, wherein.   The resin gear according to claim 1, wherein a module representing a tooth size of the gear is 0.5 to 3.5. A method of manufacturing a gear, wherein a tooth part is formed by injection molding in the thickness direction from a plurality of gate parts positioned in the circumferential direction on a circumference of a disk or a ring-shaped insert from a plurality of gate parts located in the circumferential direction. A boss formed integrally with the outer periphery of the disk or ring-shaped insert, a web extending radially from the boss, a ring-shaped rim extending radially from the web, and the rim A plurality of teeth formed in the circumferential direction of the portion, and forming a rib portion extending in the radial direction at least at the gate portion of the web portion and a weld portion where the resin composition injected from the gate portion merges And the manufacturing method of the resin gear which forms the thickness and / or width | variety of the rib part of the said weld part larger than the rib part of the said gate part.

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