Resin molded gear

Abstract

In an insert-molded resin-molded gear, the orientation of resin fibers is adjusted, and the manufacturing cost of the resin-molded gear is reduced. The gear is provided with a resin molded gear (1) and a gear-shaped insert (2). The insert (2) has a web portion (21) and a tooth portion (22), and the tooth portion (22) has a tooth bottom portion (22a) facing a tooth bottom portion (12a) of the resin molded gear (1) and a tooth top portion (22c) facing a tooth top portion (12c) of the resin molded gear (1). An annular first flow path (23) is formed on the surface of the web part (21), and an outflow port (23a) through which the molten resin (31) flows out to the tooth bottom part (22a) is provided on the outer edge part of the first flow path (23).

Description

Technical Field

[0001] The present disclosure relates to an insert-molded resin molded gear. Background Art

[0002] In the past, in resin molded gears, the following insert molding technology is known: an insert component is arranged in a mold, and molten resin is injected into a cavity formed between the insert component and the mold to perform resin molding. For example, the following technology is proposed in Patent Document 1: a guide path for molten resin is provided in the insert component, and the molten resin is guided to a portion corresponding to the bottom surface of the tooth using the guide path, thereby preventing the formation of a weld line on the tooth surface and improving the durability of the gear. In addition, the following resin molded gear is proposed in Patent Document 2: a flow path is formed to guide the molten resin injected into the gear-shaped insert component to the tooth portion through the inside of the insert component, and the open end of the flow path is set at the tooth bottom of the tooth portion. The following technology is proposed in Patent Document 3: by pre-treating the surface of the insert component while heating the insert component, the retention of molten resin is suppressed, and the resin cracking or peeling of the molded product is suppressed.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-154463

[0006] Patent Document 2: International Publication No. WO2021 / 049533

[0007] Patent Document 3: International Publication No. WO2005 / 046957 Summary of the invention

[0008] Problems to be solved by the invention

[0009] In order to ensure the strength of the resin molded gear, it is preferred to use a fiber-reinforced resin, and it is preferred to make the fiber orientation of the resin portion covering the tooth surface consistent along the tooth surface. In addition, it is preferred that the weld line of the resin is not formed in the tooth-shaped portion, but is formed outside the tooth surface where contact friction caused by the gear power transmission does not occur. In the resin gear molded by embedding the metal gear, since the strength of the tooth root is reinforced by the metal insert, it will not be a problem in terms of the durability of the gear, but the friction and wear of the resin on the tooth surface will have a greater impact on the durability of the gear. Therefore, it is preferred to use a fiber-reinforced resin obtained by combining super engineering plastics with excellent friction and wear characteristics with carbon fibers. However, such resins are very expensive, and the cost becomes a big issue when they are put into practical use. In this regard, according to the technology of patent documents 1 and 2, in addition to the complication of the flow path of the molten resin and the increase in the manufacturing cost of the insert, there is also the problem of increased use of molten resin and increased material cost. In addition, according to the technology of patent document 3, there is a problem of time-consuming temperature management.

[0010] Therefore, an object of the present disclosure is to provide a resin molded gear that can adjust the fiber orientation from the tooth bottom toward the tooth top, can form a weld line to coincide with the center line of the tooth top, and has a simple flow path for molten resin formed in an insert.

[0011] Technical solutions to solve problems

[0012] In order to solve the above-mentioned problems, the resin molded gear of the present disclosure has the following features.

[0013] (1) A resin molded gear is a resin molded gear formed by insert molding, wherein the resin molded gear and a gear-shaped insert are provided, the insert including a web portion, a tooth portion, and a flow path for allowing molten resin to flow toward the web portion or the tooth portion, the tooth portion including a tooth bottom portion opposite to the tooth bottom of the resin molded gear and a tooth top portion opposite to the tooth top of the resin molded gear, an annular first flow path is formed on the surface of the web portion, and a flow outlet is provided at the outer edge of the first flow path for allowing molten resin to flow out to the tooth bottom portion.

[0014] (2) In the resin molded gear of (1), the insert is made of metal material.

[0015] (3) In the resin molded gear of (1) or (2), the resin portion covering the insert member is a fiber-reinforced resin.

[0016] Effects of the Invention

[0017] According to the resin molded gear disclosed in the present invention, since a flow outlet for allowing molten resin to flow out to the bottom of the tooth is provided at the outer edge of the first flow path, the molten resin flowing out from the first flow path to the bottom of the tooth flows along the tooth surface of the tooth portion in the cavity and merges at the center line of the tooth top. Therefore, the fiber orientation is configured from the root of the gear tooth toward the tooth top, and the weld line is formed on the center line of the tooth top of the gear tooth. In addition, since the flow outlet is provided at the outer edge of the first flow path, the flow path is simplified, the amount of molten resin can be reduced, and the manufacturing cost of the insert itself can also be suppressed. In addition, since the metal insert can be used to suppress the shrinkage of the resin, a high-precision resin gear can be manufactured with the mold accuracy of the resin tooth-shaped portion, and since the metal insert itself does not require the accuracy required for the metal gear, the manufacturing cost can also be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 (a) is a top view and (b) is a bottom view showing a resin molded gear according to an embodiment of the present disclosure.

[0019] Figure 2 yes Figure 1 (a) A stereoscopic view of a resin molded gear as viewed from the plane side, and (b) a stereoscopic view as viewed from the bottom side.

[0020] Figure 3 (a) a top view and (b) a bottom view of the insert.

[0021] Figure 4 (a) is a perspective view of the insert member as viewed from the plane side, and (b) is a perspective view of the insert member as viewed from the bottom side.

[0022] Figure 5 (a) is the AA line cross-sectional view, and (b) is the BB line cross-sectional view.

[0023] Figure 6 This is a schematic diagram showing a method for manufacturing a resin molded gear.

[0024] Figure 7 This is a schematic diagram showing the fiber orientation and weld lines of a resin-molded gear. DETAILED DESCRIPTION

[0025] Hereinafter, an embodiment of the present disclosure as a resin molded gear will be described based on the drawings. Figures 1 to 5As shown, the resin molded gear 1 is an insert molded resin molded gear. The resin molded gear 1 is composed of an insert 2 and a resin member 3. In addition, the resin molded gear 1 has a web 11 and gear teeth 12. The gear teeth 12 are composed of a tooth bottom 12a, a tooth surface 12b, and a tooth top 12c. In the following, the upper side of the drawing is regarded as the surface of the resin molded gear 1 and the insert 2, and the lower side of the drawing is regarded as the back side of the resin molded gear 1 and the insert 2.

[0026] Insert molding is a method of injecting molten resin 31 between a mold 4 and an insert 2. Here, the insert 2 is preferably made of metal. This is because when the molten resin 31 is injected, deformation caused by heat can be suppressed, thereby forming a high-precision resin-molded gear 1 that is closer to the design size. On the other hand, compared with a gear made of only metal, forming a resin-molded gear by coating with resin also has advantages. This is because resin is more silent than metal, so when the gear teeth are coated with resin, the working sound can be suppressed.

[0027] Specifically, the material of the insert part 2 can be selected from metals such as aluminum alloy, magnesium alloy, and iron alloy, and resins such as thermoplastic resin and thermosetting resin. In addition, the insert part 2 is formed by sintering, metal injection molding (MIM: Metal Injection Molding), forging, and press molding. In particular, when the insert part 2 is formed by MIM, the design freedom and economic efficiency of the insert part 2 are excellent.

[0028] Specifically, the material of the resin component 3 can be a synthetic resin material such as polyetheretherketone (PEEK), polyamideimide (PAI), polyimide (PI), polyethersulfone (PES), liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polyphthalamide (PPA), polyarylate (PAR), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polybutylene adipamide (PA46), polyhexamethylene adipamide (PA66), polynonane terephthalamide (PA9T), polydecane terephthalamide (PA10T), polydodecyl terephthalamide (PA12T), etc. The resin component 3 can also be reinforced with carbon fiber, glass fiber, aramid fiber, etc., or a lubricant such as fluororesin such as polytetrafluoroethylene (PTFE), silicone resin, molybdenum disulfide, graphite, etc. can be added to give the resin component 3 friction characteristics.

[0029] like Figures 3 to 5As shown, the insert 2 is provided in a gear shape substantially similar to the resin molded gear 1, and is composed of a web portion 21 and a tooth portion 22. The tooth portion 22 has a tooth bottom portion 22a opposed to the tooth bottom 12a of the resin molded gear 1, a tooth face portion 22b opposed to the tooth face 12b of the resin molded gear 1, and a tooth top portion 22c opposed to the tooth top 12c of the resin molded gear 1.

[0030] The first flow path 23 is formed in an annular shape on the surface of the web portion 21, and an outflow port 23a for allowing the molten resin 31 to flow out to the tooth bottom 22a is provided at the outer edge of the first flow path 23. The flow path width w1 of the first flow path 23 can be appropriately selected, but is preferably set to be narrower in order to reduce the amount of the molten resin 31.

[0031] A second flow path 24 is formed in an annular shape on the back side of the web portion 21. In addition, a through hole 25 is provided in the web portion 21, which passes from the front side of the web portion 21 to the back side. The opening 25a of the through hole 25 is arranged in the first flow path 23, and the opening 25b (see Figure 5 ) is arranged in the second flow path 24. Since the through hole 25 and the second flow path 24 are provided, when the resin member 3 filled in the through hole 25 and the second flow path 24 is solidified, the insert 2 can be prevented from falling off from the resin molded gear 1. In addition, the injection port 13 of the molten resin 31 is preferably arranged vertically above the opening 25a. In addition, the number of the injection ports 13 can be appropriately changed.

[0032] Here, the depth d of the first flow path 23 (see Figure 5 ), the flow path width w1 of the first flow path 23, the width w2 of the outlet 23a, and the recess width w3 of the outlet 23a (see Figure 3 ) is greater than the thickness w0 (refer to Figure 1 ) is larger, that is, it is set to "d>w0, w1>w0, w2>w0, w3>w0". Since d, w1, w2, w3 of the first flow path 23 are set larger than the thickness w0 of the resin member 3 covering the tooth surface 12b, the arrival time difference of the molten resin 31 reaching each tooth bottom 22a can be suppressed. Therefore, in each gear tooth 12, the occurrence of resin welding on the tooth surface 12b can be prevented. That is, the flow balance of the molten resin 32 in the tooth surface portion 22b can be uniformly adjusted, and the weld line 33 can be reliably formed on the tooth top 12c of each gear tooth 12.

[0033] In addition, the flow path width w1 of the first flow path 23 is larger than the width w3 of the outflow port 23, that is, it is set to "w1>w3". Therefore, the circumferential flow of the molten resin 3 can be prioritized, and the delay of the molten resin 3 to the gear teeth 12 away from the injection port 13 can be reduced, thereby making the quality of the gear teeth 12 more uniform. In addition, the recessed width W3 of the outflow port 23 can also be set to be less than 1 / 2 of the flow path width w1. In this case, the circumferential flow of the molten resin 3 can also be prioritized, and the delay of the molten resin 31 to the gear teeth 12 away from the injection port 13 can be reduced, thereby making the quality of the gear teeth 12 more uniform.

[0034] Next, based on Figure 6 The manufacturing method of the resin molded gear 1 of the above structure is described. When the molten resin 31 is injected into the injection port 13, the molten resin 31 flows in the circumferential direction along the first flow path 23 and flows into the tooth bottom 22a from the outflow port 23a of the first flow path 23. The molten resin 31 that has flowed into the tooth bottom 22a flows in the thickness direction of the insert 2 along the tooth bottom 22a. In addition, at this time, the molten resin 31 flows from the tooth bottom 22a to the tooth top 22c in the cavity 5 for forming the gear tooth 12 along the tooth face 22b.

[0035] Afterwards, when the molten resin 31 solidifies, Figure 7 As shown, the resin member 3 is formed of resin fibers 32 with the fiber orientation from the tooth bottom 12a toward the tooth top 12c in the flow direction of the molten resin 31. In addition, the weld line 33 is formed to coincide with the center line of the tooth top 12c.

[0036] On the other hand, the molten resin 31 injected from the injection port 13 flows from the opening 25a on the surface of the web portion 21 toward the back surface inside the through hole 25, and flows into the second flow path 24 from the opening 25b on the back surface. The molten resin 31 that has flowed into the second flow path 24 flows in the circumferential direction along the second flow path 24 on the back surface of the insert part 2. Thereafter, when the molten resin 31 solidifies, the resin member 3 that penetrates the inside of the resin-molded gear 1 and the annular resin member 3 formed on the back surface of the resin-molded gear 1 can prevent the insert part 2 from falling off.

[0037] Therefore, according to the resin molded gear 1 of the present disclosure, since the outflow port 23a for allowing the molten resin 31 to flow out to the tooth bottom 22a is provided at the outer edge of the first flow path 23, the molten resin 31 flowing in the first flow path 23 can be directly flowed into the tooth bottom 22a, and the molten resin 31 can be directed from the tooth bottom 12a to the tooth top 12c in the cavity, so that the resin orientation can be adjusted from the tooth bottom 12a to the tooth top 12c. In addition, since the insert 2 has a simple structure in which the outflow port 23a for allowing the molten resin 31 to flow out directly is provided at the outer edge of the first flow path 23, there is an effect that the manufacturing cost of the insert 2 can be reduced, and the amount of the molten resin 31 can be reduced to reduce the material cost.

[0038] It should be noted that the present disclosure is not limited to the above-mentioned embodiment, and can be implemented by appropriately changing the shape and structure of each part, for example, by changing the shape and number of teeth of the gear or changing the thickness of the resin member 3, without departing from the scope of the present disclosure.

[0039] Description of symbols

[0040] 1 Resin molded gear;

[0041] 2 Inserts;

[0042] 3. Resin components;

[0043] 4. Mould;

[0044] 5. Cavity;

[0045] 11 belly plate;

[0046] 12 gear teeth (a: tooth bottom, b: tooth surface, c: tooth top);

[0047] 13 injection port;

[0048] 21 belly part;

[0049] 22 tooth part (a: bottom of tooth, b: face of tooth, c: top of tooth);

[0050] 23 First flow path (a: outlet);

[0051] 24 second flow path;

[0052] 25 Through hole (a: opening on the surface, b: opening on the back);

[0053] 31 molten resin;

[0054] 32 resin fiber;

[0055] 33 Weld line.

Claims

1. A resin molded gear, which is a resin molded gear formed by insert molding, characterized in that: The resin molded gear comprises the resin molded gear and a gear-shaped insert. The insert comprises a web portion and a tooth portion, The tooth portion includes a tooth bottom portion facing the tooth bottom of the resin molded gear and a tooth top portion facing the tooth top of the resin molded gear. An annular first flow path is formed on the surface of the web portion. An outflow port for allowing molten resin to flow out to the tooth bottom portion is provided at an outer edge portion of the first flow path.

2. The resin molded gear according to claim 1, wherein: The insert is made of a metal material.

3. The resin molded gear according to claim 1, wherein: The resin molded gear includes a resin member covering the insert part. The resin member is a fiber-reinforced resin.

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