WO2020116370A1

WO2020116370A1 - Gear manufacturing method and reduction gear

Info

Publication number: WO2020116370A1
Application number: PCT/JP2019/046944
Authority: WO
Inventors: 樹哉岸野; 清水　猛; 小川　隆雄
Original assignee: 日本電産株式会社
Priority date: 2018-12-05
Filing date: 2019-12-02
Publication date: 2020-06-11

Abstract

Provided are a gear manufacturing method with which a gear having superior mechanical strength and shape stability can be manufactured with high yield, and a reduction gear comprising a gear manufactured by said gear manufacturing method. In this gear manufacturing method, a gear is manufactured using a resin composition containing a crystalline resin and a filler. The gear manufacturing method comprises: a step for melting the resin composition; a step for supplying the resin composition in a molten state to a molding die set to a temperature 5-25°C lower than the glass transition temperature of the crystalline resin so as to obtain a molded body having a shape corresponding to the gear; and a step for heat treating the molded body at a temperature higher than the crystallization temperature of the crystalline resin so as to obtain the gear.

Description

Gear manufacturing method and reduction gear

The present invention relates to a gear manufacturing method and a speed reducer.

BACKGROUND ART Conventionally, a speed reducer using a planetary gear mechanism has been known (for example, see Patent Document 1). In this speed reducer, the planetary gear is manufactured by a metal injection molding (MIM) method, and the output gear and the fixed gear are manufactured by using a resin composition containing an additive. However, when the gear is manufactured by the MIM method, the dimensional accuracy of the obtained gear is low, and it is difficult to increase the yield. On the other hand, in the case of manufacturing a gear using a resin composition, if glass fibers or carbon fibers are mixed as an additive, depending on the size of the gear, manufacturing conditions, etc., insufficient filling of the resin composition or deterioration of gate disconnection may occur. May occur.

Japanese Laid-Open Publication: JP-A-2010-091095

The present invention has been made in view of the above problems, and an object thereof is to manufacture a gear that is excellent in mechanical strength and shape stability at a high yield, and a method for manufacturing such a gear. It is to provide a speed reducer including a gear.

An exemplary invention of the present application is a method for producing a gear using a resin composition containing a crystalline resin and a filler, the step of melting the resin composition, and the resin composition in the molten state. To a molding die set at a temperature lower by 5 to 25° C. than the glass transition temperature of the crystalline resin to obtain a molded body having a shape corresponding to the gear, and A heat treatment at a temperature higher than the crystallization temperature of the resin to obtain the gear. ‥

Another exemplary invention of the present application is a casing having a central axis, a first internal gear and a second internal gear that are arranged in the casing and are separated from each other in a direction along the central axis, and the casing. An input gear that is disposed inside and rotates about the central axis, a first rotation assembly that transmits a rotation force to and from the input gear, and a rotation force is reduced between the first rotation assembly and the first rotation assembly. A second reduction gear assembly for transmitting, wherein the first rotation assembly is arranged in a circumferential direction of the input gear between the first internal gear and the input gear, and has outer teeth. A plurality of first planetary gears meshing with the inner peripheral teeth of the first internal gear and the outer peripheral teeth of the input gear; and a first planetary shaft facing each of the plurality of first planetary gears in a direction along the central axis. A first planetary carrier that is rotatably supported about the center, a first rotating shaft part that is connected to the first planetary carrier, and has the central axis at the center, and the first rotating shaft part about the central axis. A rotating sun gear, wherein the first planet carrier, the first rotating shaft portion and the sun gear are a single gear member, and the second rotating assembly comprises the second internal gear and the sun. A plurality of second planetary gears, which are arranged in the circumferential direction of the sun gear between the gears and have outer peripheral teeth meshing with inner peripheral teeth of the second internal gear and outer peripheral teeth of the sun gear; A second planet carrier that rotatably supports each of the planetary gears around a second planet shaft that is oriented along the central axis, and a second planet carrier that is connected to the second planet carrier and that has the central shaft at the center. The rotating shaft portion, and at least one of the gear member, the plurality of first planetary gears, the plurality of second planetary gears, and the input gear, according to any one of claims 1 to 7. It is a speed reducer comprising a gear obtained by a gear manufacturing method.

According to the exemplary invention of the present application, it is possible to manufacture a gear having excellent mechanical strength and shape stability.

FIG. 1 is a vertical cross-sectional view of a small reducer according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA and the line BB in FIG. 1 (reference numerals are shown in parentheses). 2 is an electron microscope (SEM) photograph showing appearances of molded articles of Example 1 and Comparative Example 2.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a vertical cross-sectional view of a small reducer according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line AA and the line BB in FIG. 1 (reference numerals are shown in parentheses). It should be noted that FIG. 1 shows a cross section of a plane including the central axis J1 of the small reduction gear 1 (hereinafter also simply referred to as a reduction gear). Further, hereinafter, for convenience of description, the upper side in FIG. 1 is referred to as “upper” or “upper”, and the lower side is referred to as “lower” or “lower”. Further, in the following description, the up-down direction, which is the direction in which the central axis J1 faces, is also referred to as the “axial direction”. Further, in the following description, the circumferential direction centering on the central axis J1 is simply referred to as “circumferential direction”, and the radial direction centering on the central axis J1 is simply referred to as “radial direction”. ‥

As shown in FIG. 1, the speed reducer 1 includes a casing 2, an input unit 3, a first rotation assembly 4, a second rotation assembly 6, a first internal gear 5, and a second internal gear 7. , An input shaft 8, an output shaft 9, and a motor 15 directly connected to the input shaft 8. The speed reducer 1 has a planetary gear mechanism having a two-stage structure including a first rotation assembly 4 and a second rotation assembly 6, and is formed to have an outer dimension of, for example, a width of 5 mm, a depth of 5 mm, and a height of 20 mm or less. ing. ‥

<Motor> The motor 15 serves as a drive source of a structure (not shown) on which the speed reducer 1 is mounted, that is, a power source. Note that the structure is not particularly limited, and a small camera can be given as an example. Further, as the motor 15, for example, various motors are appropriately selected according to the usage of the structure. The input shaft 8 is also a motor shaft of a motor 15 that is rotationally driven about the central axis J1. ‥

<Casing> The casing 2 is arranged and fixed on the upper side of the motor 15. The casing 2 has a substantially cylindrical shape centered on the central axis J1. Inside the casing 2, the input unit 3, the first rotation assembly 4, a part of the second rotation assembly 6, the first internal gear 5, and the second internal gear 7 are housed. In FIG. 1, the second rotation assembly 6 side is the upper side and the first rotation assembly 4 side is the lower side along the central axis J1, but it is not necessary to make the direction of the central axis J1 coincide with the gravity direction. Absent. Further, the gear ratio between the first rotary assembly 4 and the second rotary assembly 6 is appropriately set depending on the usage of the structure. Thereby, the power from the motor 15 can be decelerated and output from the output shaft 9. ‥

<Input Unit> The input unit 3 includes a second input shaft 31 and an input gear 33. The second input shaft 31 is connected to the upper portion of the input shaft 8 and can rotate together with the input shaft 8 about the central axis J1. The second input shaft 31 has a substantially cylindrical shape or a substantially cylindrical shape, and its outer diameter is smaller than the outer diameter of the input shaft 8. An input gear 33 is concentrically fixed to the outer peripheral portion of the second input shaft 31. Thereby, the input gear 33 can rotate around the central axis J1 together with the second input shaft 31. The method of fixing the input gear 33 to the second input shaft 31 is not particularly limited, and for example, a fixing method using a key and a key groove can be used. Further, although the second input shaft 31 and the input gear 33 are configured separately from each other in the illustrated configuration, the configuration is not limited to this, and may be configured by one gear member integrally molded, for example. .. As shown in FIG. 2, the input gear 33 is a spur gear having a plurality of teeth (hereinafter referred to as “outer peripheral teeth”) 331 protruding on the outer peripheral portion thereof. ‥

<First Rotation Assembly> The first rotation assembly 4 includes a first rotation shaft member 41, a first planet carrier 42, a plurality of first planet shaft members 43, a plurality of first planet gears 44, and a sun. And a gear 45. In the first rotating assembly 4, the first rotating shaft member 41, the first planetary carrier 42, and the plurality of first planetary shaft members 43 are supports that support the respective first planetary gears 44 and the sun gears 45. In addition to the first rotating shaft member 41, the first planetary carrier 42, and the plurality of first planetary shaft members 43, this support may further include another member. The first rotating shaft member 41, the first planetary carrier 42, and the plurality of first planetary shaft members 43 are configured as one gear member by integral molding in the present embodiment, but the present invention is not limited to this and, for example, is It may be configured as a separate body, and may be configured as a connected body in which these separate bodies are connected. ‥

The first rotation shaft member 41 has a substantially cylindrical shape or a substantially columnar shape, and its central axis coincides with the central axis J1. The first rotation shaft member 41 is arranged above the second input shaft 31 of the input unit 3. A disk-shaped first planetary carrier 42 is arranged concentrically with the first rotating shaft member 41 below the first rotating shaft member 41. That is, the first rotation shaft member 41 is arranged so as to project upward at the center of the disk-shaped first planet carrier 42. ‥

Below the first planetary carrier 42, a plurality of first planetary shaft members 43 are arranged on the outer peripheral side of the first planetary carrier 42, that is, at positions eccentric from the central axis J1 (first rotating shaft member 41). .. The plurality of first planetary shaft members 43 have the same substantially cylindrical shape, and are arranged with their longitudinal directions oriented along the central axis J1 (hereinafter, also referred to as “along the central axis J1”). There is. Note that the number of first planetary shaft members 43 arranged is three in the configuration shown in FIG. 2, but is not limited to this, and may be two or four or more. The first planetary shaft members 43 are arranged at equal angular intervals around the central axis J1. For example, as shown in FIG. 2, when the number of arranged first planetary shaft members 43 is three, these first planetary shaft members 43 are arranged at 120° intervals around the central axis J1. In the following description, the central axis of each first planetary shaft member 43 is referred to as "first planetary shaft J2". ‥

A first planetary gear 44 is rotatably (rotatably) supported by each first planetary shaft member 43. As a result, each first planetary gear 44 can rotate about the first planetary axis J2, that is, can rotate on its axis. Further, each of the first planetary gears 44 can rotate, that is, revolve around the central axis J1. As described above, each of the first planetary gears 44 is a planetary gear (also referred to as “P gear”) that rotates about the first planetary axis J2 and revolves around the central axis J1. Each first planetary gear 44 is a spur gear having a plurality of teeth (hereinafter, referred to as “outer peripheral teeth”) 441 protruding on the outer peripheral portion thereof. The first planetary gears 44 are arranged radially outside the input gear 33 along the circumferential direction thereof, and the outer peripheral teeth 441 mesh with the outer peripheral teeth 331 of the input gear 33. ‥

The sun gear 45 is concentrically fixed to the outer peripheral portion of the first rotating shaft member 41. Accordingly, the sun gear 45 can rotate around the central axis J1 together with the first rotation shaft member 41. The method of fixing the sun gear 45 to the first rotating shaft member 41 is not particularly limited, and for example, a fixing method using a key and a key groove can be used. The sun gear 45 is a spur gear having a plurality of teeth (hereinafter, referred to as “outer peripheral teeth”) 451 protruding on the outer peripheral portion thereof. Further, although the first rotary shaft member 41 and the sun gear 45 are configured separately from each other in the illustrated configuration, the invention is not limited to this, and for example, they may be configured by one gear member integrally molded. Good. Therefore, the first rotating shaft member 41, the first planetary carrier 42, the plurality of first planetary shaft members 43, and the sun gear 45 may be configured as a single gear member formed by integral molding. Also called "gear".

<First Internal Gear> The first internal gear 5 has an annular shape with the central axis J1 as the central axis. The first internal gear 5 is arranged and fixed inside the casing 2 concentrically with the casing 2. This fixing method is not particularly limited, and for example, a fixing method by fitting can be used. In this case, intermediate fitting is preferred. As shown in FIG. 2, the first internal gear 5 is an internal gear having a plurality of teeth (hereinafter referred to as “inner peripheral teeth”) 51 protruding on the inner peripheral portion thereof. The inner peripheral teeth 51 mesh with the outer peripheral teeth 441 of each first planetary gear 44 at different positions in the circumferential direction. ‥

<Second Rotation Assembly> The second rotation assembly 6 is arranged above the first rotation assembly. The second rotation assembly 6 includes a second rotation shaft member 61, a second planet carrier 62, a plurality of second planet shaft members 63, and a plurality of second planet gears 64. In the second rotation assembly 6, the second rotation shaft member 61, the second planet carrier 62, and the plurality of second planet shaft members 63 are supports that support the respective second planet shaft members 63. In addition to the second rotation shaft member 61, the second planet carrier 62 and the plurality of second planet shaft members 63, this support may further include another member. The second rotating shaft member 61, the second planetary carrier 62, and the plurality of second planetary shaft members 63 are configured as one gear member by integral molding in the present embodiment, but the present invention is not limited to this, and, for example, one another It may be configured as a separate body, and may be configured as a connected body in which these separate bodies are connected to each other.

The second rotating shaft member 61 has a substantially cylindrical shape or a substantially columnar shape, and its central axis coincides with the central axis J1 like the first rotating shaft member 41. The second rotating shaft member 61 projects upward from the upper surface of the casing 2 to the outside of the casing 2. A disk-shaped second planet carrier 62 is arranged concentrically with the second rotating shaft member 61 below the second rotating shaft member 61. That is, the second rotation shaft member 61 is arranged so as to project upward at the center of the disk-shaped second planet carrier 62. ‥

A plurality of second planetary shaft members 63 are arranged below the second planetary carrier 62 at the outer peripheral side of the second planetary carrier 62, that is, at a position eccentric from the central axis J1 (second rotary shaft member 61). .. The plurality of second planetary shaft members 63 have the same substantially cylindrical shape, and are arranged with their longitudinal directions oriented along the central axis J1 (along the central axis J1). The number of the second planetary shaft members 63 arranged is three in the configuration shown in FIG. 2, but is not limited to this and may be two or four or more, and particularly the first planetary shaft member 43. It is preferable that the number is the same as the number of arrangements. The second planetary shaft members 63 are arranged at equal angular intervals around the central axis J1. For example, as shown in FIG. 2, when the number of the second planetary shaft members 63 arranged is three, these second planetary shaft members 63 are arranged at 120° intervals around the central axis J1. In the following description, the central axis of each second planetary shaft member 63 is referred to as "second planetary shaft J3". ‥

A second planetary gear 64 is rotatably (rotatably) supported on each second planetary shaft member 63. As a result, each second planetary gear 64 can rotate about the second planetary axis J3, that is, can rotate on its axis. In addition, each second planetary gear 64 can rotate about the central axis J1, that is, can revolve. As described above, each second planetary gear 64 is a planetary gear (also referred to as “P gear”) that rotates about the second planetary axis J3 and revolves around the central axis J1. Each second planetary gear 64 is a spur gear having a plurality of teeth (hereinafter, referred to as “outer peripheral teeth”) 641 protruding on the outer peripheral portion thereof. The second planetary gears 64 are arranged radially outward of the sun gear 45 along the circumferential direction thereof, and the outer peripheral teeth 641 mesh with the outer peripheral teeth 451 of the sun gear 45. ‥

<Second Internal Gear> The second internal gear 7 has an annular shape with the central axis J1 as the central axis. The second internal gear 7 is arranged inside the casing 2, above the first internal gear 5, and apart from the first internal gear 5 in the axial direction. Further, the second internal gear 7 is arranged and fixed concentrically with the casing 2. This fixing method is not particularly limited, and for example, a fixing method by fitting can be used. In this case, intermediate fitting is preferred. The second internal gear 7 is an internal gear having a plurality of teeth (hereinafter referred to as “inner peripheral teeth”) 71 protruding on the inner peripheral portion thereof. The inner peripheral teeth 71 mesh with the outer peripheral teeth 641 of each second planetary gear 64 at different positions in the circumferential direction. ‥

<Output Shaft> The output shaft 9 is connected to the upper part of the second rotary shaft member 61 outside the casing 2 and can rotate around the central axis J1 together with the second rotary shaft member 61. The output shaft 9 has a substantially cylindrical shape or a substantially cylindrical shape, and its outer diameter is the same as the outer diameter of the second rotating shaft member 61. ‥

<Operation of Reduction Gear> As described above, in the reduction gear 1, the gear ratio between the first rotation assembly 4 and the second rotation assembly 6 is set within a predetermined range. First, when the motor 15 operates, the power thereof is transmitted to the input gear 33 via the input shaft 8 and the second input shaft 31 in order. As a result, as shown in FIG. 2, the input gear 33 rotates about the central axis J1 in the arrow α1 direction. Then, the rotational force of the input gear 33 is transmitted to each first planetary gear 44 that meshes with the input gear 33. As a result, as shown in FIG. 2, each first planetary gear 44 can rotate in the direction of the arrow α2 around the first planetary axis J2, that is, can rotate on its axis. ‥

Further, each first planetary gear 44 also meshes with the first internal gear 5 fixed to the casing 2. As a result, as shown in FIG. 2, each first planetary gear 44 can transmit its rotational force to the first internal gear 5 when the first planetary gear 44 rotates in the direction of the arrow α2, and thus the arrow about the central axis J1. It can also rotate in the α3 direction, that is, can revolve. By this revolution, the sun gear 45 can be rotated around the central axis J1 in the arrow β1 direction. ‥

Further, each second planetary gear 64 meshes with the sun gear 45. As a result, when the sun gear 45 rotates in the direction of arrow β1, the rotational force is transmitted to each second planetary gear 64. Then, by this transmission, as shown in FIG. 2, each of the two planetary gears 64 can rotate in the direction of the arrow β2 around the second planetary axis J3, that is, rotate on its axis. ‥

Each second planetary gear 64 also meshes with the second internal gear 7 fixed to the casing 2. As a result, as shown in FIG. 2, each second planetary gear 64 can transmit its rotational force to the second internal gear 7 when the second planetary gear 64 rotates in the direction of arrow β2. It can rotate in the β3 direction, that is, can revolve. By this revolution, the output shaft 9 can be rotated around the central axis J1 in the same direction as the arrow β1 direction. ‥

Due to the force transmission as described above, the decelerated power is output from the output shaft 9. In the configuration described above, the direction along the central axis J1 means a direction substantially parallel to the central axis J1 (axial direction), and does not need to be strictly parallel to the axial direction. That is, the first planetary axis J2 and the second planetary axis J3 may be parallel to the central axis J1 or may be inclined by a small angle with respect to the central axis J1. ‥

<Gear Manufacturing Method> In the speed reducer 1 configured as described above, preferably, a gear that rotates (rotates and/or revolves) is manufactured by the gear manufacturing method of the present invention. The method for producing a gear of the present invention is a method for producing a gear using a resin composition containing a crystalline resin and a filler. The gear manufacturing method of the present embodiment comprises: [1] a first step of preparing a resin composition containing a crystalline resin and a filler; [2] a second step of melting the resin composition; [3] The molten resin composition is supplied to a mold set to a temperature lower by about 5 to 25° C. than the glass transition temperature of the crystalline resin to obtain a molded product having a shape corresponding to the gear to be manufactured. And [4] a step of heat-treating the molded body at a temperature higher than the crystallization temperature of the crystalline resin to obtain a gear. ‥

[1] First step First, a resin composition containing a crystalline resin and a filler is prepared. Here, the crystalline resin refers to a thermoplastic resin having a melting peak when performing a differential scanning calorimetry (DSC) according to JIS K 7121:2012 (Plastic transition temperature measuring method). Examples of the crystalline resin include polyamide, polyolefin, polyester, polyether, polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyacetal (POM), polyimide, and fluoropolymer. Incidentally. These resins may be used alone or in combination of two or more. Of these, polyamide is preferable as the crystalline resin. The use of polyamide can improve the mechanical strength, rigidity and wear resistance of the gear. ‥

Polyamides are generally classified into aliphatic polyamides (non-aromatic polyamides), semi-aromatic polyamides and wholly aromatic polyamides, but semi-aromatic polyamides are preferred. Semi-aromatic polyamides are preferable because they are easily melted and easily crystallized. The semi-aromatic polyamide is a copolymer of dicarboxylic acid and diamine, one of which has an aromatic group and the other has an aliphatic group. ‥

Examples of the aliphatic dicarboxylic acid include HOOC-(CH ₂ ) _n- COOH (n is 0 to 12), dimethylmalonic acid, 3,3-diethylsuccinic acid, 2,2-dimethylglutaric acid, 2-methyladipine Acids, chain-like aliphatic dicarboxylic acids such as trimethyladipic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, cycloheptanedicarboxylic acid, cyclooctanedicarboxylic acid And alicyclic dicarboxylic acids such as cyclodecane dicarboxylic acid. On the other hand, examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenic acid and 4,4′-biphenyl. Examples thereof include dicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid and diphenylsulfone-4,4'-dicarboxylic acid.

Examples of the aliphatic diamine include linear aliphatic diamines such as NH ₂ —(CH ₂ ) _m —NH ₂ (m is 0 to 12), 1-butyl-1,2-ethanediamine, 1,1-dimethyl-1,4-butanediamine, 1-ethyl-1,4-butanediamine, 1,2-dimethyl-1,4-butanediamine, 2-methyl-1,5-pentanediamine, 3- Methyl-1,5-pentanediamine, 2,5-dimethyl-1,6-hexanediamine, 2,4-dimethyl-1,6-hexanediamine, 2,2-dimethyl-1,6-hexanediamine, 1, Branching such as 3-dimethyl-1,8-octanediamine, 2,4-dimethyl-1,8-octanediamine, 2,2-dimethyl-1,8-octanediamine, 5-methyl-1,9-nonanediamine Examples thereof include alicyclic diamine such as aliphatic diamine, cyclohexanediamine, methylcyclohexanediamine, isophoronediamine, norbornenedimethylamine, and tricyclodecanedimethyldiamine. On the other hand, as the aromatic diamine, for example, p-phenylenediamine, m-phenylenediamine, p-xylylenediamine, m-xylylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 4 , 4'-diaminodiphenyl ether and the like.

Examples of the semi-aromatic polyamide include polyamide MXD6 (PAMXD6), polyamide 9T (PA9T), polyamide 4T (PA4T), polyamide 6T (PA6T), polyamide 10T (PA10T), and the like. Examples of other polyamides include polyamide 6 (PA6), polyamide 11 (PA11), polyamide 12 (PA12) polyamide 66 (PA66), polyamide 610 (PA610), polyamide 612 (PA612), polyamide 410 (PA410). Etc. ‥

Examples of the polyolefin include polyethylene (PE) and polypropylene (PP). Examples of polyesters include polyethylene terephthalate (PET), polybutadiene terephthalate (PBT), polylactic acid (PLA), and the like. Examples of the polyether include polyetheretherketone (PEEK), polyetherketone (PEK), polyetherketoneketone (PEKK), polyaryletherketone (PAEK), and the like. The melting point of the crystalline resin depends on its type, but is preferably about 165 to 390°C, more preferably about 175 to 375°C, and even more preferably about 185 to 360°C. ..

The filler is mixed with the crystalline resin for the purpose of improving the moldability and releasability of the resin composition, or the durability (mechanical strength, rigidity, wear resistance) of the obtained gear. It is a component. Therefore, the filler is appropriately selected depending on the purpose and is not particularly limited. The filler includes an inorganic filler and an organic filler, but for the above purpose, it is preferable to use the inorganic filler. Examples of the inorganic fillers include fibrous inorganic fillers, particle (powder) inorganic fillers, non-fibrous inorganic fillers such as flaky inorganic fillers, and the like. ‥

Examples of the fibrous inorganic filler include glass fiber, carbon fiber, asbestos fiber, inorganic whiskers (potassium titanate fiber, zinc oxide fiber, magnesium oxide fiber, aluminum oxide fiber, calcium sulfate fiber, silicon carbide fiber, silicon nitride fiber). , Silicon nitride fibers, mullite fibers, magnesium borate fibers, titanium boride fibers, etc.) and the like. Examples of the particulate inorganic filler include silica powder, quartz powder, glass beads, kaolin, clay, diatomaceous earth, wollastonite and the like. Examples of the plate-like inorganic filler include mica, talc, various metal pieces, and the like.

These inorganic fillers are appropriately selected and used according to the size of the gear. For example, when manufacturing a micro gear having a module of 0.2 mm or less, preferably inorganic whiskers are used, and more preferably potassium titanate fibers are used. The inorganic whisker has an aspect ratio of 10 or more, but its average fiber length is almost equal to the diameter of glass fiber, carbon fiber, etc., and has an extremely fine shape. For this reason, when manufacturing a micro gear having a module of 0.2 mm or less, it is possible to improve characteristics such as mechanical strength of the gear, and when the resin composition is molded, protrusions are formed on the gate portion of the molded body. Are difficult to form (that is, the occurrence of defects such as gate breakage is prevented and the moldability of the gear is improved). Therefore, when manufacturing a micro gear having a module of 0.2 mm or less, it is preferable to use a resin composition containing polyamide and potassium titanate fiber. ‥

The amount of the filler contained in the resin composition is not particularly limited, but is preferably about 10 to 40% by mass, more preferably about 20 to 30% by mass. When the resin composition containing the filler in such an amount is used, the effect of improving the characteristics of the obtained gear and the effect of improving the moldability of the resin composition are exhibited in a well-balanced manner. A resin composition is obtained by mixing these crystalline resins and a filler. Various mixers such as a blender, a kneader, a roll, and an extruder can be used for this mixing. [2] Second step Next, the obtained resin composition is melted by heating it to a temperature higher than the melting point of the crystalline resin. The heating temperature is preferably about 5 to 20° C. higher than the melting point of the binder resin, and more preferably about 5 to 15° C. higher. ‥

[3] Third step Next, the resin composition in a molten state is supplied to a molding die by, for example, an injection molding method to obtain a molded body having a shape corresponding to the gear to be manufactured. The present invention is characterized in that the temperature of the molding die is set to a predetermined temperature. Specifically, the temperature of the mold is set to a temperature lower by about 5 to 25° C. than the glass transition temperature (Tg) of the crystalline resin. Conventionally, when forming a molded product containing a crystalline resin, in order to promote crystallization of the crystalline resin, the temperature of the mold is slightly lower than the melting point of the binder resin (much higher than the Tg of the crystalline resin. High temperature). In this case, according to the studies by the present inventors, the resin composition is likely to be stretched, resulting in defective gate disconnection, resulting in a phenomenon in which unnecessary protrusions are formed on the molded body, and the edge of the molded body. It was also found that the shape of the part (particularly, the shape of the edge of the tooth tip) becomes unstable. Further, since the temperature is relatively high (about 130 to 150° C.), it takes time (about 30 to 40 seconds) until the resin composition is solidified, including the crystallization time of the crystallization resin. It took a long time to mold the molded body. ‥

Therefore, in the present invention, the temperature of the mold is set to a temperature lower by about 5 to 25° C. than the glass transition temperature (Tg) of the crystalline resin. Since the preset temperature is sufficiently lower than the preset temperature of the conventional mold, when the resin composition is supplied to the mold, the resin composition is rapidly solidified into a molded body. For this reason, the resin composition is less likely to expand, the gate breakage is good, and the shape (contour shape) of the edge portion of the molded body is also stabilized. Further, the releasability of the molded body from the molding die is also enhanced. From the above, according to the present invention, the time required for forming the molded body can be sufficiently shortened (about 10 to 15 seconds) as compared with the conventional case. Therefore, the yield in the production of the molded body can be improved, and the number of installed facilities for manufacturing the molded body can be significantly reduced. The mold temperature to be set may be a temperature about 5 to 25° C. lower than the Tg of the crystalline resin, but a temperature about 10 to 20° C. is more preferable. By setting the molding die at such a temperature, the above effect can be further improved. At this point, the crystallization of the crystallized resin has not substantially progressed. ‥

[4] Fourth Step Next, the molded body is taken out of the molding die and heat-treated (annealed) at a temperature higher than the crystallization temperature of the crystalline resin to obtain a gear. At this time, as a result of crystallization of the crystalline resin in the molded body, the crystallinity of the molded body increases. Here, the crystallization temperature refers to an exothermic peak temperature that accompanies crystallization acceleration of the crystallized resin when the differential scanning calorimetry is performed on the crystalline resin under a temperature rising condition of 10° C./min. The temperature of the heat treatment may be higher than the crystallization temperature of the crystalline resin, but is 5 to 25° C. higher than the maximum temperature (hereinafter, also referred to as “actual use temperature”) when the Kia is actually used. The temperature is preferably, and more preferably about 10 to 20° C. higher than the actual use temperature. By performing the heat treatment at such a temperature, it is possible to ensure dimensional stability when the gear is used. In the case of the gear used in the speed reducer 1, the actual operating temperature thereof is preferably about 110 to 140°C, more preferably about 120 to 130°C. ‥

Examples of the method of this heat treatment include a method of heating with a heater in a heating furnace, a method of irradiating infrared rays, a method of blowing hot air, and the like. The heating furnace may be a batch furnace or a continuous furnace. The pressure of the atmosphere of the heat treatment may be any of reduced pressure, normal pressure and increased pressure. The heat treatment time is not particularly limited, but is preferably about 30 to 120 seconds, more preferably about 45 to 100 seconds. The gear is manufactured through the above steps. ‥

The gear module to be manufactured is not particularly limited, but is preferably 0.2 mm or less, and more preferably about 0.1 to 0.2 mm. According to the gear manufacturing method of the present invention, even such a minute gear can be manufactured accurately and in a short time (high yield). In addition, since the obtained resin has the crystalline resin sufficiently crystallized therein, the gear has excellent properties such as mechanical strength, rigidity, and abrasion resistance, and high shape stability. Further, it is preferable that the micro gear has a reference circle pitch diameter of about 1.2 to 1.7 mm, a number of teeth of about 8 to 18 and a tooth thickness of about 0.15 to 0.32 mm. As described above, the gear manufactured by the gear manufacturing method of the present invention is preferably used as a gear that rotates (rotates and/or revolves). Therefore, in the speed reducer 1 shown in FIG. 1 and the like, at least one of the input gear 33, the C gear (gear member), and the plurality of P gears (the first planetary gear 44 and the second planetary gear 64) is replaced by the main gear. It is preferable that the gear is manufactured by the gear manufacturing method of the invention. In particular, since the input gear 33 arranged close to the motor 15 is easily affected by the heat generation of the motor 15, it may be made of a gear manufactured using a resin composition containing a semi-aromatic polyimide. preferable. ‥

Although the gear manufacturing method and the speed reducer of the present invention have been described above based on the preferred embodiments, the present invention is not limited thereto. Further, the gears obtained by the gear manufacturing method of the present invention include, for example, parts for industrial machines such as small cameras and robot hands, as well as parts for automobiles, parts for bicycles, parts for railway vehicles, parts for ships, and aircraft. Parts, parts for transportation equipment such as parts for space transportation equipment, parts for personal computers, parts for electronic equipment such as parts for mobile terminals, parts for electric equipment such as refrigerators, washing machines, air conditioners, parts for plants Used for parts for watches, etc.

Next, examples of the present invention will be described. 1. Production of Gear (Example 1) [A] First, a semi-aromatic polyamide (PAMXD6) as a crystalline resin and potassium titanate fiber as an inorganic whisker were mixed with a blender to obtain a resin composition. The Tg of the aromatic polyamide was about 100° C., and the amount of potassium titanate fiber in the resin composition was 30% by mass. [B] Next, this resin composition was supplied to a mold set to about 80° C. to obtain a molded body having a shape corresponding to the gear to be manufactured. After confirming that the molded body was solidified, 11 minutes after the resin composition was supplied to the molding die, the molded body was taken out from the molding die. An electron microscope (SEM) photograph of this molded body is shown in FIG. ‥

[C] Next, the obtained molded body was heat-treated in a heating furnace at 150° C. for 60 seconds to obtain a gear. The target gear had a reference circle pitch diameter of 1.3 mm, a module of 0.2 mm, 14 teeth, and a tooth thickness of 0.4 mm. ‥

(Comparative Example 1) A gear was obtained in the same manner as in Example 1 except that the step [C] (heat treatment) was omitted. That is, the gear of Comparative Example 1 was a molded product before heat treatment, and the semi-aromatic polyamide was not crystallized. ‥

Comparative Example 2 [A′] First, in the same manner as in Example 1, a resin composition was obtained. [B'] Next, this resin composition was supplied to a mold set to about 130°C to obtain a molded body. After confirming that the molded body was solidified, 35 seconds after supplying the resin composition to the molding die, the molded body was taken out of the molding die. An electron microscope (SEM) photograph of this molded body is shown in FIG. Then, this molded body was used as a gear. The target shape of the sintered gear is the same as in Example 1. ‥

2. Evaluation As shown in FIG. 3(a), in the molded product of Example 1, the resin composition had good gate breakage, unnecessary protrusions were not formed in the molded product, and the shape of the edge portion of the molded product was stable. Was. The molded product of Comparative Example 1 was also formed because it was formed under the same conditions as in Example 1. On the other hand, as shown in FIG. 3(b), in the molded body of Comparative Example 2, the resin composition was defective in gate disconnection, unnecessary protrusions were formed on the molded body, and the edge portion of the molded body was formed. The shape was also unstable and it could not be used as a gear. Therefore, in the following, the durability obtained by using the gears obtained in Example 1 and Comparative Example 1 was evaluated. ‥

Using the gears obtained in Example 1 and Comparative Example 1 as the input gear, the speed reducer shown in FIG. 1 and the like was manufactured. Then, the operation of fixing the other end of the string having a 200 g weight attached to one end to the output shaft of the reduction gear and winding the string around the output shaft was repeated. As a result, the speed reducer using the gear of Example 1 could perform the winding operation 300,000 times without any problem. On the other hand, in the speed reducer using the gear of Comparative Example 1, the input gear started to idle after the winding operation of 150,000 times. When the speed reducer was disassembled and the shape of the input gear was confirmed, the teeth were bent and deformed.

1... Reduction gear, 2... Casing, 3... Input part, 4... 1st rotation assembly, 5... 1st internal gear, 51... Teeth, 6... 2nd rotation assembly, 7... 2nd internal gear, 71... Tooth, 8... Input shaft, 9... Output shaft, 15... Motor, 31... Second input shaft, 33... Input gear, 331... Tooth, 41... First rotating shaft member, 42... First planet carrier, 43... 1 planetary shaft member, 44... 1st planetary gear, 441... Tooth, 45... Sun gear, 451... Tooth, 61... 2nd rotation member, 62... 2nd planet carrier, 63... 2nd planetary shaft member, 64... 2 planetary gears, 641... Tooth, J1... Central axis, J2... 1st planetary axis, J3... 2nd planetary axis.

Claims

A method of manufacturing a gear using a resin composition containing a crystalline resin and a filler, the step of melting the resin composition, and the resin composition in the molten state, the glass of the crystalline resin Supplying to a mold set at a temperature 5 to 25° C. lower than the transition temperature to obtain a molded body having a shape corresponding to the gear; and the molded body having a temperature higher than the crystallization temperature of the crystalline resin. And a step of heat-treating to obtain the gear.
The method for manufacturing a gear according to claim 1, wherein the temperature of the heat treatment is a temperature higher by 5 to 25° C. or more than the maximum temperature when the gear is actually used.
The method for manufacturing a gear according to claim 1 or 2, wherein the amount of the filler contained in the resin composition is 10 to 40% by mass.
The gear manufacturing method according to any one of claims 1 to 3, wherein the gear module has a size of 0.2 mm or less.
The gear manufacturing method according to claim 4, wherein the filler is an inorganic whisker.
The method of manufacturing a gear according to claim 5, wherein the inorganic whiskers are potassium titanate fibers.
7. The gear manufacturing method according to claim 1, wherein the crystalline resin is polyamide.
The gear manufacturing method according to claim 7, wherein the polyamide is a semi-aromatic polyamide.
A casing having a central axis, a first internal gear and a second internal gear that are arranged in the casing and are spaced apart from each other in a direction along the central axis, and are arranged in the casing and rotate about the central axis. And a second rotating assembly for decelerating and transmitting the rotational force with the first rotating assembly, and a first rotating assembly for transmitting the rotating force with the input gear. The first rotation assembly is disposed in the circumferential direction of the input gear between the first internal gear and the input gear, and the outer peripheral teeth of the first rotary gear are the same as the inner peripheral teeth of the first internal gear. A plurality of first planetary gears that mesh with the outer peripheral teeth of the gears, and a first planetary carrier that rotatably supports each of the plurality of first planetary gears around a first planetary axis that is oriented along the central axis. A first planetary carrier connected to the first planetary carrier and having a central axis centered on the central axis; and a sun gear that rotates together with the first rotational axis about the central axis. The carrier, the first rotating shaft portion, and the sun gear are a single gear member, and the second rotating assembly is disposed between the second internal gear and the sun gear in the circumferential direction of the sun gear. A plurality of second planetary gears that are arranged and have outer peripheral teeth meshing with the inner peripheral teeth of the second internal gear and the outer peripheral teeth of the sun gear, and the plurality of second planetary gears in the direction along the central axis. A second planetary carrier rotatably supported around a second planetary axis facing the second planetary carrier; and a second rotary shaft portion connected to the second planetary carrier and having the central shaft at the center thereof, the gear member, the At least one of the plurality of first planetary gears, the plurality of second planetary gears, and the input gear is composed of a gear obtained by the gear manufacturing method according to any one of claims 1 to 7. A speed reducer characterized by that.
The speed reducer according to claim 9, wherein the input gear is a gear obtained by the method for manufacturing a gear according to claim 8.