Plastic molded gears

Abstract

To align the orientation of resin fibers and reduce costs of manufacturing of a resin molded gear in a resin molded gear formed by insert molding.SOLUTION: The present invention comprises a resin molded gear 1 and a gear-shaped insert 2. The insert 2 has a web part 21 and a tooth part 22, and the tooth part 22 has a tooth bottom part 22a opposing a tooth bottom 12a of the resin molded gear 1, and a tooth tip part 22c opposing a tooth tip 12c of the resin molded gear 1. An annular first flow path 23 is formed on a surface of the web part 21, and an outer edge of the first flow path 23 is provided with an outlet port 23a that causes a molten resin 31 to flow out to the tooth bottom part 22a.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, in resin-molded gears, a technique of insert molding is known in which an insert member is placed in a mold, and molten resin is injected into a cavity formed between the insert member and the mold to perform resin molding. For example, Patent Document 1 proposes a technique of preventing the formation of weld lines on the tooth surface and improving the durability of the gear by providing a guide path for the molten resin in the insert and guiding the molten resin to a portion corresponding to the tooth bottom surface using the guide path. Also, Patent Document 2 proposes a resin-molten gear in which a flow path is formed to guide the molten resin injected into a gear-shaped insert to the tooth portion via the inside of the insert member, and the open end of the flow path is provided at the tooth bottom of the tooth portion. Patent Document 3 proposes a technique of suppressing retention of the molten resin and suppressing resin cracking and peeling of the molded product by pretreating the surface of the insert and heating the insert. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-154463 A [Patent Document 2] International Publication WO2021 / 049533 [Patent Document 3] International Publication WO2005 / 046957 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to ensure the strength of resin-molded gears, it is desirable to use fiber-reinforced resin, and it is desirable that the fiber orientation of the resin portion covering the tooth surface be aligned along the tooth surface. In addition, it is preferable that the weld line of the resin is not formed in the tooth shape portion, but is formed outside the tooth surface where contact friction due to gear power transmission does not occur. In resin gears molded by inserting a metal gear, the strength of the tooth base is reinforced by the metal insert, so it is not an issue for the durability of the gear, but the friction and wear of the resin on the tooth surface greatly affects the durability of the gear. For this reason, it is preferable to use fiber-reinforced resin by blending carbon fiber or the like with super engineering plastics, which have excellent friction and wear characteristics. However, such resins are very expensive, and the cost has been a major issue in practical use. In this regard, according to the techniques of Patent Documents 1 and 2, there are problems in that the flow path of the molten resin becomes complicated, increasing the manufacturing cost of the insert, and the amount of molten resin used increases, resulting in an increase in material cost. In addition, according to the technique of Patent Document 3, there is a problem in that temperature control is time-consuming.

[0005] Therefore, an object of the present disclosure is to provide a resin-molded gear in which the fiber orientation can be adjusted from the bottom of the teeth toward the tip of the teeth, a weld line can be formed so as to coincide with the center line of the tip of the teeth, and the flow path of the molten resin formed in the insert is simple. [Means for solving the problem]

[0006] In order to solve the above problems, the resin molded gear of the present disclosure has the following features.

[0007] (1) An insert-molded resin-molded gear comprising a resin-molded gear and a gear-shaped insert, the insert including a web portion, a tooth portion, and a flow path for flowing molten resin into the web portion or the tooth portion, the tooth portion including a tooth bottom portion facing the tooth bottom of the resin-molded gear and a tooth tip portion facing the tooth tip of the resin-molded gear, a first annular flow path is formed on the surface of the web portion, and an outlet is provided on the outer edge of the first flow path for flowing molten resin into the tooth bottom portion.

[0008] (2) In the resin-molded gears of (1), the insert is made of metal.

[0009] (3) In the resin-molded gear of (1) or (2), the resin portion covering the insert shall be made of fiber-reinforced resin. Effect of the Invention

[0010] According to the resin molded gear of the present disclosure, an outlet is provided at the outer edge of the first flow path for allowing the molten resin to flow out to the tooth bottom, so that the molten resin flowing out from the first flow path to the tooth bottom flows along the tooth surface of the tooth in the cavity and merges at the center line of the tooth tip. Therefore, the fiber orientation is arranged from the tooth bottom to the tooth tip of the gear tooth, and a weld line is formed at the center line of the tooth tip of the gear tooth. In addition, since an 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 be reduced. In addition, since the metal insert can suppress the shrinkage of the resin, a high-precision resin gear can be manufactured with the mold accuracy of the resin tooth shape portion, and since the metal insert itself does not require the precision required for a metal gear, the manufacturing cost can be reduced. [Brief description of the drawings]

[0011] [Figure 1] 1A and 1B are a plan view and a bottom view, respectively, of a resin molded gear according to an embodiment of the present disclosure. [Diagram 2] FIG. 2A is a perspective view of the resin molded gear in FIG. 1 as seen from the top side, and FIG. 2B is a perspective view of the resin molded gear as seen from the bottom side. [Diagram 3] (a) is a plan view and (b) is a bottom view of the insert. [Figure 4] FIG. 2A is a perspective view of the insert as seen from the top side, and FIG. 2B is a perspective view of the insert as seen from the bottom side. [Diagram 5] (a) Cross-sectional view along line AA, (b) Cross-sectional view along line BB. [Figure 6] 1A to 1C are schematic diagrams illustrating a method for manufacturing a resin molded gear. [Figure 7] FIG. 2 is a schematic diagram showing fiber orientation and weld lines in a resin-molded gear. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] An embodiment of a resin molded gear according to the present disclosure will be described below with reference to the drawings. As shown in FIGS. 1 to 5, the resin molded gear 1 is a resin molded gear formed by insert molding. The resin molded gear 1 is composed of an insert 2 and a resin member 3. The resin molded gear 1 also 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 tip 12c. In the following description, the upper side of the drawing refers to the front side of the resin molded gear 1 and the insert 2, and the lower side of the drawing refers to the back side of the resin molded gear 1 and the insert 2.

[0013] Insert molding is a manufacturing method in which molten resin 31 is injected between a mold 4 and an insert 2. Here, it is preferable to select a metal material for the insert 2. This is because it is possible to suppress deformation due to heat when injecting the molten resin 31 and to mold a resin-molded gear 1 with high precision that is closer to the design dimensions. On the other hand, there is also an advantage to making a resin-molded gear by covering it with resin rather than making the gear only from metal. This is because resin is quieter than metal, so covering the gear teeth with resin can suppress operating noise.

[0014] Specifically, the material of the insert 2 can be selected from metals such as aluminum alloys, magnesium alloys, and iron alloys, and resins such as thermoplastic resins and thermosetting resins. The insert 2 is formed by sintering, metal injection molding (MIM), forging, and press molding. In particular, forming the insert 2 by MIM is advantageous in terms of freedom of design and economy.

[0015] Specifically, the material of the resin member 3 may be a synthetic resin material such as polyether ether ketone (PEEK), polyamide imide (PAI), polyimide (PI), polyethersulfone (PES), liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polyphthalamide (PPA), polyarylate (PAR), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytetramethylene adipamide (PA46), polyhexamethylene adipamide (PA66), polynonamethylene terephthalamide (PA9T), polydecamethylene terephthalamide (PA10T), or polydodecamethylene terephthalamide (PA12T). It is also possible to reinforce the resin member 3 with carbon fiber, glass fiber, aramid fiber, or the like, or to compound it with a lubricant such as a fluororesin such as polytetrafluoroethylene (PTFE), silicone resin, molybdenum disulfide, or graphite to impart frictional properties.

[0016] 3 to 5, the insert 2 is provided in a gear shape roughly similar to that of the resin molded gear 1 and is composed of a web portion 21 and a teeth portion 22. The teeth portion 22 has a tooth bottom portion 22a facing the tooth bottom 12a of the resin molded gear 1, a tooth surface portion 22b facing the tooth surface 12b of the resin molded gear 1, and a tooth tip portion 22c facing the tooth tip 12c of the resin molded gear 1.

[0017] A first flow passage 23 is formed in an annular shape on the surface of the web portion 21, and an outlet 23a for causing the molten resin 31 to flow out to the tooth bottom portion 22a is provided on the outer edge of the first flow passage 23. The flow passage width w1 of the first flow passage 23 can be appropriately selected, but it is preferable to make it narrower in order to suppress the amount of the molten resin 31.

[0018] A second flow path 24 is formed in an annular shape on the back surface of the web portion 21. The web portion 21 is also provided with a through hole 25 penetrating from the front surface to the back surface of the web portion 21. An opening 25a of the through hole 25 is disposed in the first flow path 23, and an opening 25b (see FIG. 5) is disposed in the second flow path 24. The provision of the through hole 25 and the second flow path 24 makes it possible to prevent the insert 2 from falling off from the resin molded gear 1 when the resin member 3 filled in the through hole 25 and the second flow path 24 hardens. The injection port 13 for the molten resin 31 is preferably disposed vertically above the opening 25a. The number of injection ports 13 can be changed as appropriate.

[0019] Here, the depth d of the first flow passage 23 (see FIG. 5), the flow passage width w1 of the first flow passage 23, the width w2 of the outlet 23a, and the recess width w3 of the outlet 23a (see FIG. 3) are greater than the thickness w0 of the resin member 3 covering the tooth surface portion 22b (see FIG. 1), i.e., "d>w0, w1>w0, w2>w0, w3>w0". Since the d, w1, w2, and w3 of the first flow passage 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 portion 22a can be suppressed. Therefore, the occurrence of resin welds on the tooth surface 12b of each gear tooth 12 can be prevented. In other words, the flow balance of the molten resin 32 on the tooth surface portion 22b can be uniformly adjusted, and the weld line 33 can be reliably formed on the tooth tip 12c of each gear tooth 12.

[0020] The flow path width w1 of the first flow path 23 is greater than the width w3 of the outlet 23, i.e., "w1>w3". This allows the circumferential flow of the molten resin 3 to be prioritized, reducing delay of the molten resin 3 to the gear teeth 12 far from the injection port 13, and making the quality of the gear teeth 12 more uniform. The recess width W3 of the outlet 23 can also be set to 1 / 2 the flow path width w1 or less. In this case as well, the circumferential flow of the molten resin 3 can be prioritized, reducing delay of the molten resin 31 to the gear teeth 12 far from the injection port 13, and making the quality of the gear teeth 12 more uniform.

[0021] Next, a manufacturing method of the resin molded gear 1 having the above configuration will be described with reference to Fig. 6. When 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 portion 22a from the outlet 23a of the first flow path 23. The molten resin 31 that flows into the tooth bottom portion 22a flows in the thickness direction of the insert 2 along the tooth bottom portion 22a. At this time, the molten resin 31 flows in the cavity 5 that forms the gear teeth 12, from the tooth bottom portion 22a toward the tooth tip portion 22c, crawling along the tooth surface portion 22b.

[0022] Thereafter, when the molten resin 31 hardens, a resin member 3 is formed, which is made of resin fibers 32 oriented in the flow direction of the molten resin 31, i.e., from the tooth bottom 12a to the tooth tip 12c, as shown in Fig. 7. Also, a weld line 33 is formed so as to coincide with the center line of the tooth tip 12c.

[0023] Meanwhile, the molten resin 31 injected from the injection port 13 flows inside the through hole 25 from the opening 25a on the front surface of the web portion 21 toward the back surface, 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 2. When the molten resin 31 subsequently hardens, the resin member 3 that has penetrated 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 2 from falling off.

[0024] Therefore, according to the resin molded gear 1 of the present disclosure, the outlet 23a for causing the molten resin 31 to flow into the tooth bottom 22a is provided on the outer edge of the first flow passage 23, so that the molten resin 31 flowing through the first flow passage 23 can be caused to flow directly into the tooth bottom 22a and can be directed from the tooth bottom 12a to the tooth tip 12c within the cavity, thereby aligning the resin from the tooth bottom 12a to the tooth tip 12c. Furthermore, since the insert 2 has a simple structure in which the outlet 23a for causing the molten resin 31 to flow directly into the outer edge of the first flow passage 23 is provided, there are effects that the manufacturing cost of the insert 2 can be reduced, and the amount of molten resin 31 can be reduced, thereby reducing the material cost.

[0025] The present disclosure is not limited to the above-described embodiments, and the shape and configuration of each part can be appropriately modified within the scope of the present disclosure, for example, by changing the shape and number of teeth of the gears, or by changing the thickness of the resin member 3. [Explanation of symbols]

[0026] 1 Plastic molded gears 2 Insert 3 Resin parts 4. Mold 5 Cavity 11. Web 12 Gear teeth (a: tooth root, b: tooth surface, c: tooth tip) 13 Inlet 21 Web Department 22 Tooth portion (a: tooth bottom portion, b: tooth surface portion, c: tooth tip portion) 23 First flow path (a: outlet) 24 Second Flow Stream 25 Through hole (a: opening on the front surface, b: opening on the back surface) 31 Molten Resin 32 Resin Fiber 33 Weld Line

Claims

1. A resin-molded gear that is insert-molded, The resin molded gear and a gear-shaped insert are provided, the insert includes a web portion and a teeth portion; the tooth portion includes a tooth bottom portion facing a tooth bottom of the resin molded gear and a tooth tip portion facing a tooth tip of the resin molded gear, the web portion includes a first surface on a side where an injection port for a molten resin is formed, and a second surface which is a reverse surface of the first surface, A first flow passage for flowing a ring-shaped molten resin is formed on a surface of the first surface web portion, an outlet for causing molten resin to flow out to the tooth bottom is provided at an outer edge of the first flow path; A resin molded gear, characterized in that the outlet is formed by cutting out the tooth bottom portion from the first surface in the thickness direction of the insert, and removing the tooth bottom portion on the first surface side down to the bottom surface of the first flow path.

2. The resin molded gear according to claim 1 , further comprising a through hole that connects the first flow passage and the second surface via an inside of the web portion.

3. a second annular flow passage formed in the second surface; The resin molded gear according to claim 2 , wherein the second flow passage is connected to the first flow passage via the through hole.

4. a tooth tip coated with a resin member formed by hardening the molten resin, The resin member is a fiber reinforced resin, 2. The resin molded gear according to claim 1, wherein the fibers of the fiber-reinforced resin are oriented toward the tooth tips.

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