WO2020090819A1

WO2020090819A1 - Small speed reducer

Info

Publication number: WO2020090819A1
Application number: PCT/JP2019/042384
Authority: WO
Inventors: 小川　隆雄; 清水　猛; 樹哉岸野
Original assignee: 日本電産株式会社
Priority date: 2018-11-02
Filing date: 2019-10-29
Publication date: 2020-05-07

Abstract

Provided is a small speed reducer constituted by small and high-precision-molded parts. In a small speed reducer 1, an input gear 33, a first rotating shaft 41, a first planetary carrier 42, a plurality of first planetary shaft members 43, a plurality of first planetary gears 44, and a sun gear 45 are formed from an inorganic whisker-containing resin composition using a thermoplastic resin, such as a polyamide-based resin, as a base resin. In addition, a second rotating shaft 61, a second planetary carrier 62, a plurality of second planetary shaft members 63, a plurality of second planetary gears 64, and a casing 2 including a first internal gear 5 and a second internal gear 7 are formed into sintered bodies by powder compacting or formed by metal injection molding (MIM).

Description

Small reducer

The present invention relates to a small reducer mounted on, for example, a small and thin electronic device.

As a small speed reducer using a planetary gear mechanism, for example, the small speed reducer described in Patent Document 1 is known. This small reduction gear is composed of a fixed internal gear, a movable internal gear, a planetary gear meshed with the fixed internal gear and the movable internal gear, and a planetary gear held by a holder body and a holder retainer, and a motor meshing with the planetary gear. In a small speed reducer including a sun gear directly connected to a shaft, a support beam provided in a holder body and a guide portion provided at a contact portion between a fixed internal gear and a movable internal gear.

Patent Document 2 discloses that components such as a sun gear and a planetary wheel in a small reduction gear are integrally molded products such as resin.

JP-A-4-366046 JP, 2003-130145, A

In the small speed reducer disclosed in Japanese Patent Laid-Open Publication No. Hei 4-366046, some or all of the components are made of synthetic resin, and the transmission efficiency of gears is improved by the low coefficient of friction of synthetic resin. As a synthetic resin material, it is illustrated that a basic resin such as a polyacetal resin or a polyamide resin contains carbon fiber, glass fiber or the like.

Japanese Unexamined Patent Publication No. 2003-130145 describes that a polyacetal resin, a polyamide resin, and a polyester resin are used as a resin material, and carbon fibers, whiskers, glass fibers, mica, and the like are mixed using these as a base polymer. ..

However, even though the conventional resin material configuration described above can reduce the friction coefficient due to the base resin, when a micro gear is molded from the resin material, the surface roughness of the gear is such that the gear unit of the speed reducer is easy to assemble. The effect on the meshing of gears and gears cannot be ignored. As a result, there arises a problem that the transmission efficiency of the gear is reduced.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a small speed reducer that is compact and highly accurately molded, and is composed of parts having high durability and dust resistance.

As one means for achieving the above object and solving the above problems, the present invention has the following configurations. That is, an exemplary invention of the present application is a small reducer that reduces the power from an input shaft and transmits the power to an output shaft, and includes a casing and an annular first first inner peripheral surface of the casing. An internal gear, an annular second internal gear located on a second inner peripheral surface of the casing, an input gear connected to the input shaft, and a first coaxial shaft arranged coaxially with the input shaft in the casing. A first planetary carrier that has a rotating shaft part and a sun gear that rotates together with the first rotating shaft part, and is rotatable around the first rotating shaft part; and the first planetary carrier is rotatably supported by the first planetary carrier. A plurality of first planetary gears that mesh with the input gear and the first internal gear; a second rotating shaft portion that is disposed coaxially with the input shaft in the casing and that is connected to the output shaft; Second A second planetary carrier rotatable about a rolling shaft portion, and a plurality of second gears arranged in the circumferential direction of the sun gear and rotatably supported by the second planetary carrier and meshing with the sun gear and the second internal gear. Second planetary gear, the first planetary carrier, the first rotating shaft portion, and the sun gear are a single member, and the input gear, the first planetary carrier, and the first planetary carrier. The planetary gear is a molded product of a resin composition containing a thermoplastic resin as a base resin and an inorganic whisker as a predetermined functional expression component, and the base resin and the inorganic whiskers in the resin composition. Content of 99.5% by weight or more, the first internal gear is formed of a metal sintered body, and the relationship between the tooth thickness T of the first internal gear and the arithmetic mean roughness Ra is 5. It is characterized in that 0 × 10 ⁻³ ≦ (Ra / T) ≦ 66.7 × 10 ⁻³ is satisfied.

According to the present invention, it is possible to provide a small reduction gear composed of small precision parts with improved moldability, durability, dimensional accuracy, and the like.

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).

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 showing the configuration of a small reducer according to an exemplary 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).

Note that FIG. 1 shows a cross section by 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”.

Also, in the following description, the up-down direction, which is the direction in which the central axis J1 faces, is also called the “axial direction”. The direction of the central axis J1 does not necessarily have to match the direction of gravity. 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, a small speed reducer (hereinafter simply referred to as “speed reducer”) 1 includes a casing 2, an input unit 3, a first rotation assembly 4, a second rotation assembly 6, and a first inner. It includes a Lugear 5, a second internal gear 7, an input shaft (first input shaft) 8, an output shaft 9, and a motor 15 directly connected to the input shaft 8 to reduce the power from the input shaft 8. It can be transmitted to the output shaft 9.

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. As a result, the speed reducer 1 can be made smaller and thinner, and thus can be easily mounted in a device such as a small and thin electronic device. Further, the two-stage configuration of the first rotation assembly 4 and the second rotation assembly 6 can provide the speed reducer 1 that satisfies the mechanical characteristics required for the input side and the output side.

<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. The structure is not particularly limited, and may be a small camera, for 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 the motor shaft of the 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 the direction of the central axis J1 does not necessarily have to coincide with the gravity direction. There is no. 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 part>
The input unit 3 includes an input shaft (second input shaft) 31 and an input gear 33. The input shaft 31 and the input gear 33 are located inside the casing 2.

The input shaft 31 is located on the central axis J1 and is connected to the upper part of the input shaft 8. As a result, the input shaft 31 can rotate around the central axis J1 together with the input shaft 8 in the casing 2. The 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.

A substantially cylindrical or cylindrical input gear 33 is connected to the outer peripheral portion of the input shaft 31. The input shaft 31 and the input gear 33 are arranged on a concentric shaft. As a result, the input gear 33 can rotate around the central axis J1 together with the input shaft 31. The method of fixing the input gear 33 to the input shaft 31 is not particularly limited, and for example, a fixing method using another member, that is, a fixing method using a key and a key groove can be used. Further, although the input shaft 31 and the input gear 33 are configured separately from each other in the illustrated configuration, the present invention is not limited to this and may be a single connected member. For example, it may be composed of one gear member formed integrally.

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 portion 41, a first planet carrier 42, a plurality of first planet shaft members 43, a plurality of first planet gears 44, and a sun gear 45. Further, the first rotation shaft portion 41, the first planetary carrier 42, the plurality of first planetary shaft members 43, the plurality of first planetary gears 44, and the sun gear 45 are located inside the casing 2.

In the first rotating assembly 4, the first rotating shaft portion 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 rotation shaft portion 41, the first planetary carrier 42, and the plurality of first planetary shaft members 43, this support may further include another member.

The first rotation shaft portion 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 portion 41 is coaxial with the input shaft 31 of the input unit 3 and is arranged above the input shaft 33.

A disk-shaped first planetary carrier 42 is arranged concentrically with the first rotation shaft portion 41 below the first rotation shaft portion 41. That is, the first rotation shaft portion 41 is arranged so as to project upward at the center of the disk-shaped first planetary carrier 42. The first planet carrier 42 can rotate around the central axis J1.

At the lower part of the first planet carrier 42, a plurality of first planetary shaft members 43 are arranged radially outside the first planet carrier 42. In other words, on the outer side in the radial direction of the first planetary carrier 42, the plurality of first planetary shaft members 43 are arranged at positions eccentric from the central axis J1. 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. In addition, each first planetary shaft member 43 is in a state of being non-rotatably fixed to the first planetary carrier 42.

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 first planetary shaft members 43 arranged is three, the 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 supported on 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 of the first planetary gears 44 is a spur gear having a cylindrical shape and 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. The outer peripheral teeth 441 of each first planetary gear 44 mesh with the outer peripheral teeth 331 of the input gear 33.

Note that the module of the first planetary gear 44 is preferably 0.2 mm or less, and more preferably 0.05 to 0.2 mm.

The sun gear 45 is concentrically connected to the outer peripheral portion of the first rotating shaft portion 41. As a result, the sun gear 45 can rotate around the central axis J1 together with the first rotation shaft portion 41 in the casing 2. The method for fixing the sun gear 45 to the first rotating shaft portion 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.

Also, the first rotating shaft portion 41, the first planet carrier 42, and the sun gear 45 are composed of a single member that is integrally connected by integral molding. Further, this member and the plurality of first planetary shaft members 43 may be configured as one gear member integrally formed, and such a gear member is also referred to as “C 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 concentrically with the casing 2 inside the casing 2 (on the side of the first inner peripheral surface). The 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.
The first internal gear 5 may be indirectly fixed to the casing 2 via another member, or may be a member that is connected to the casing 2. That is, the first internal gear 5 and the casing 2 may be separate members from each other, or may be a single member by integral molding.

<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 portion 61, a second planet carrier 62, a plurality of second planet shaft members 63, and a plurality of second planet gears 64. The second planet carrier 62, the plurality of second planetary shaft members 63, and the plurality of second planetary gears 64 are located inside the casing 2.

In the second rotating assembly 6, the second rotating shaft portion 61, the second planet carrier 62, and the plurality of second planetary shaft members 63 are supports that support the respective second planetary shaft members 63. In addition to the second rotating shaft portion 61, the second planet carrier 62 and the plurality of second planetary shaft members 63, this support may further include another member.

The second rotating shaft portion 61, the second planetary carrier 62, and the plurality of second planetary shaft members 63 are formed as one gear member by integral molding in this embodiment. That is, the second planet carrier 62 and the plurality of second planetary shaft members 63 are configured as one continuous member, but the present invention is not limited to this, and for example, they are configured as separate bodies, and these separate bodies are coupled to each other. It may be composed of a connected body.

The second rotary shaft portion 61 has a substantially cylindrical shape or a substantially cylindrical shape, and is arranged coaxially with the input shaft 3, that is, the central axis thereof coincides with the central axis J1 like the first rotary shaft portion 41. ing. The second rotary shaft portion 61 projects upward from the upper surface of the casing 2 to the outside of the casing 2 and is connected to the output shaft 9.

A disc-shaped second planet carrier 62 is arranged concentrically with the second rotating shaft portion 61 below the second rotating shaft portion 61. That is, the second rotation shaft portion 61 is arranged so as to project upward at the center of the disk-shaped second planet carrier 62. The second planet carrier 62 can rotate about the central axis J1 (second rotating shaft portion 61).

A plurality of second planetary shaft members 63 are arranged below the second planetary carrier 62 in a radial direction of the second planetary carrier 62, that is, at positions eccentric from the central axis J1. 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). Further, each second planetary shaft member 63 is in a state of being non-rotatably fixed to the second planetary carrier 62.

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.

Further, these 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 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 cylindrical shape and 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.

The module of the second planetary gear 64, like the module of the first planetary gear 44, is preferably 0.2 mm or less, and more preferably 0.05 to 0.2 mm. As a result, the first planetary gear 44 and the second planetary gear 64 are each obtained as a microminiature molded part. Further, by using such a component, it becomes possible to manufacture a precise speed reducer 1 suitable for mounting on another small-sized device, in combination with the outer dimensions of the speed reducer 1 described above.

<Second internal gear>
The second internal gear 7 is annular with the central axis J1 as the central axis. The second internal gear 7 is arranged inside the casing 2 (on the side of the second inner peripheral surface), above the first internal gear 5, and axially separated from the first internal gear 5.

Also, the second internal gear 7 is arranged and fixed concentrically with the casing 2. The 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 71 (hereinafter referred to as “inner peripheral teeth”) 71 protruding from 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.

Note that the second internal gear 7 may be indirectly fixed to the casing 2 via another member, or may be a single connected member. That is, the second internal gear 7 and the casing 2 may be separate members, or may be a single member by integral molding.

<Output shaft>
The output shaft 9 is connected (coupled) to the upper portion (upper end portion) of the second rotating shaft portion 61 on the outside of the casing 2 and can rotate around the central axis J1 together with the second rotating shaft portion 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 portion 61.

Note that the output shaft 9 may be directly connected to the second rotating shaft portion 61 or indirectly, that is, connected via another member. The connecting method between the output shaft 9 and the second rotating shaft portion 61 is not particularly limited, and various methods such as a connecting method using a key and a key groove, a connecting method using a D-cut, a connecting method using a gear component, etc. Methods are available. Further, although the output shaft 9 and the second rotation shaft portion 61 are configured as separate bodies in the present embodiment, the output shaft 9 and the second rotation shaft portion 61 are not limited to this and may be a single connected member. For example, it may be composed of one member formed by integral molding.

<Operation of reducer>
As described above, in the speed reducer 1, the gear ratio between the first rotary assembly 4 and the second rotary assembly 6 is set within a predetermined range.

First, when the motor 15 operates, its power is transmitted to the input gear 33 via the input shaft 8 and the 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.

Moreover, 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.

Also, 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 second planetary gear 64 can rotate in the direction of arrow β2 around the second planetary axis J3, that is, can rotate on its axis.

Also, each second planetary gear 64 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 output shaft 9 outputs decelerated power. The power here refers to a rotational force, but is not limited to this.

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.

[Example 1]
In order to reduce the size and weight of the speed reducer according to the first embodiment, some components such as the first planetary gear are molded with a resin composition containing a thermoplastic resin as a base resin. Further, in the speed reducer according to the first embodiment, the first internal gear is formed by a sintered body formed by powder compacting or a metal injection molding (MIM) method. More specifically, the input gear 33, the first rotation shaft portion 41 that is a component of the first rotation assembly 4, the first planet carrier 42, the plurality of first planetary shaft members 43, and the plurality of first planetary gears. The 44 and the sun gear 45 are, for example, a molded body of a resin composition in which a thermoplastic resin such as a polyamide resin is used as a base resin, and the base resin contains an inorganic whisker.

The inorganic whiskers are, for example, potassium titanate fibers having an aspect ratio of 10 or more. This inorganic whisker is a component in which the first planetary carrier 42, the first planetary gear 44, and the like described above exhibit functionality such as fine moldability, durability, and releasability as a small component. As described above, the potassium titanate fiber has a function of providing not only a high aspect ratio but also high strength and high rigidity in the mixed material with the resin. Further, the potassium titanate fiber has an extremely fine shape because its average fiber length is almost equal to the diameter of glass fiber, carbon fiber and the like. For this reason, in addition to the reinforcing property as the resin filler, the moldability and the like are exerted in the microminiature (microsize) component used in the speed reducer according to the present embodiment.

The total content of the base resin and the inorganic whiskers in the above resin composition is 99.5% by weight or more. Specifically, the content of the base resin is, for example, 59.5 to 94.5% by weight, and the content of the inorganic whiskers is, for example, 5 to 40% by weight. The content of the inorganic whiskers in the resin composition is preferably 15-40% by weight, more preferably 20-30% by weight. The resin composition may contain components that are unavoidably mixed as other components (the balance) in addition to the above components.

When the first planetary carrier 42, the first planetary gear 44, etc. are made of a thermoplastic resin containing an inorganic whisker, they can be molded by using a method such as injection molding. A resin composition containing a polyamide resin containing an inorganic whisker is excellent in strength such as impact resistance and load resistance and in dimensional accuracy, and is therefore suitable as a constituent material for a small precision gear.

Note that, for the thermoplastic resin described above, for example, a polycarbonate resin, an acrylic resin, a polyphenylene resin, a fluorine resin, or the like can be used instead of the polyamide resin. Further, in the inorganic whiskers, instead of potassium titanate fibers, for example, zinc oxide fibers, magnesium oxide fibers, aluminum oxide fibers, calcium sulfate fibers, silicon carbide fibers, silicon nitride fibers, mullite fibers, magnesium borate fibers, borated Titanium fiber or the like can be used.

Therefore, the resin composition can be appropriately selected and combined from the above-mentioned thermoplastic resin and inorganic whiskers. Above all, a configuration in which a polyamide resin and potassium titanate fiber are combined is preferable.

[Example 2]
The speed reducer according to the second embodiment is similar to the first embodiment, in which the input gear 33, the first rotating shaft portion 41, the first planetary carrier 42, the plurality of first planetary shaft members 43, and the plurality of first planetary gears 44 are included. , And the sun gear 45 are formed of a resin composition containing a thermoplastic resin such as a polyamide resin as a base resin and containing an inorganic whisker.

On the other hand, the second rotary shaft portion 61, the second planet carrier 62, the plurality of second planetary shaft members 63, the plurality of second planetary gears 64, and the second internal gear 7, which are the components of the second rotary assembly 6, are It is formed by a powder compacted sintered body or a metal injection molding method (MIM).

[Example 3]
The speed reducer according to the third embodiment includes a plurality of first gears 33, a first rotating shaft portion 41, a first planet carrier 42, a plurality of first planetary shaft members 43, a plurality of first planetary gears 44, and a sun gear 45. The two-planetary gear 64 is formed of a resin composition containing a thermoplastic resin such as a polyamide resin as a base resin and containing an inorganic whisker, as in the first embodiment.

On the other hand, the second rotary shaft portion 61, the second planet carrier 62, the plurality of second planetary shaft members 63, and the second internal gear 7 are formed by a sintered body by compaction molding or a metal injection molding method (MIM). Has been done.

In the third embodiment, the plurality of first planetary gears 44 and the plurality of second planetary gears 64 can be molded with a common mold as a resin molded body, and the cost can be reduced. Further, by using a common mold, the first planetary gear 44 and the second planetary gear 64 have the same tooth thickness, and the same tooth thickness results in the same surface roughness and tooth ratio. Therefore, the effect that it is easy to assemble is obtained.

In the speed reducer according to any of the above embodiments, the gears that form the gear unit are microminiature molded bodies, and in order to obtain good rotation between the gears, the tooth thickness portion of one gear is the tooth of the other gear. Between the teeth and the teeth must be exactly engaged. In this case, if the surface roughness of the teeth is rough, it is difficult for the teeth to mesh, and if the surface roughness is small, it is difficult for the teeth to mesh. Therefore, the ratio between the surface roughness and the tooth thickness of the internal gear is examined below.

For example,
・ Standard circle pitch diameter of planet gear (first planet gear): 1.5mm
・ Number of teeth of planetary gear: 14 ・ Module of planetary gear: standard circle pitch diameter / number of teeth = 0.107
・ Planet gear tooth thickness: π / 2 × module ≈ 0.168 mm
Surface roughness of the internal gear (first internal gear): 1.0 × 10 ⁻³ mm or more and 8.0 × 10 ⁻³ mm or less.

Here, since the tooth thickness of the planetary gear and the tooth thickness of the internal gear that meshes with the planetary gear are the same, the tooth thickness of the internal gear is approximately 0.168 mm as described above. Therefore, it is considered that a reasonable range is 0.12 mm or more and 0.2 mm or less for the tooth thickness of the internal gear by giving a margin to the tooth thickness.

Table 1 shows the ratio (surface roughness / tooth thickness) of the surface roughness Ra to the tooth thickness T that the internal gear can take from the above numerical values. Therefore, from Table 1, the range of the ratio of surface roughness that can be realistically obtained when molding by the metal injection molding method (MIM) is
5.0 × 10 ⁻³ ≦ (Ra / T) ≦ 66.7 × 10 ⁻³
It turns out that

For example, when the tooth thickness T is 0.2 mm, the surface roughness Ra can be 1 × 10 ⁻³ mm. When the tooth thickness T is 0.12 mm, the surface roughness Ra can be 8 × 10 ⁻³ mm.
The relationship between the tooth thickness T and the arithmetic mean roughness Ra described above can be applied to the first internal gear, but can also be applied to the second internal gear.

By defining the relationship between the tooth thickness T of the internal gear and the arithmetic mean roughness Ra as described above, the gear meshing with the internal gear, for example, the meshing with the planet gear that is a molded product of the resin composition is improved. As a result, the planetary gears that form the rotating assembly rotate smoothly. On the other hand, it has been found that when the ratio Ra / T is out of the above numerical range, it is difficult for the internal gear to smoothly mesh with the planetary gear.

As described above, the small reduction gear according to the present embodiment is a small reduction gear that reduces the power from the input shaft and transmits the power to the output shaft, and is located on the casing and the first inner peripheral surface of the casing. A ring-shaped first internal gear, a ring-shaped second internal gear located on the second inner peripheral surface of the casing, an input gear connected to the input shaft, and coaxially with the input shaft in the casing. A first planetary carrier having a first rotating shaft portion arranged and a sun gear that rotates together with the first rotating shaft portion, the first planetary carrier being rotatable around the first rotating shaft portion, and rotating around the first planetary carrier. A plurality of first planetary gears that are movably supported and mesh with the input gear and the first internal gear; and a second rotation that is arranged coaxially with the input shaft in the casing and that is connected to the output shaft. axis Part, a second planetary carrier rotatable about the second rotation shaft part, and arranged in the circumferential direction of the sun gear and rotatably supported by the second planetary carrier. A plurality of second planetary gears meshing with an internal gear, wherein the first planetary carrier, the first rotating shaft portion, and the sun gear are a single member, the input gear, and the first planetary gear. A carrier and the first planetary gear are molded articles of a resin composition containing a thermoplastic resin as a base resin and inorganic whiskers as a predetermined functional expression component, and the base in the resin composition. The total content of the resin and the inorganic whiskers is 99.5% by weight or more, the first internal gear is formed of a metal sintered body, and the tooth thickness T of the first internal gear and the arithmetic mean roughness are Ra Relationship satisfies ^{5.0 × 10 -3 ≦ (Ra /} T) ≦ 66.7 × 10 -3.

Further, according to the small speed reducer according to the present embodiment, the member close to the input shaft of the small speed reducer is a resin molded product that is ultra-small, has a good power transmission rate, and has high impact resistance and load resistance. By configuring and forming the member close to the output shaft from metal, it is possible to realize a small speed reducer having resistance and strength according to an applied load. Further, by adopting the resin, it becomes possible to mass-produce the members and improve the yield, and it is possible to reduce the cost of the speed reducer. In addition, since the member near the input shaft that rotates at high speed is made of resin, it is possible to perform a silent design that reduces noise during operation of the small reducer.

In particular, by using a resin composition containing an inorganic whisker such as potassium titanate fiber in a thermoplastic resin such as a polyamide resin, fine moldability and durability as a small component are improved, and thin wall molding becomes possible. Become. In addition, the mold releasability from the mold is improved, and it is possible to manufacture a small precision gear with a high dimensional accuracy while suppressing burrs. At the same time, when the small parts are molded, the gate of the resin is easily broken.

Further, unlike the conventional speed reducer described above, the base resin does not have a structure in which carbon fibers, glass fibers, etc. are contained, so that the fibers scraped away due to mutual wear of meshing gears become dust or dust. There is no problem of hindering the rotation operation.

The configurations in the above-described embodiment and each example may be appropriately combined unless they contradict each other.

Although the small speed reducer of the present invention has been described above with reference to the illustrated embodiment, the present invention is not limited to this, and each unit constituting the small speed reducer has an arbitrary configuration capable of exhibiting the same function. Can be replaced. In addition, any constituent may be added.

The small reducer according to the present invention can be used in various devices such as small cameras, robots, and other small and thin devices. The small speed reducer according to the present invention can also be used for other purposes.

1 Small speed reducer (speed reducer)
2 casing 3 input section 31 input shaft (second input shaft)
33 input gear 331 outer peripheral teeth 4 first rotating assembly 41 first rotating shaft portion 42 first planet carrier 43 first planetary shaft member 44 first planetary gear 441 outer peripheral teeth 45 sun gear 451 outer peripheral teeth 5 first internal gear 51 Peripheral tooth 6 Second rotating assembly 61 Second rotating shaft portion 62 Second planet carrier 63 Second planetary shaft member 64 Second planetary gear 641 Outer peripheral tooth 7 Second internal gear 71 Inner peripheral tooth 8 Input shaft (first input shaft) )
9 Output shaft 15 Motor J1 Central shaft J2 First planetary shaft J3 Second planetary shaft

Claims

A small reducer that reduces the power from the input shaft and transmits it to the output shaft.
A casing,
An annular first internal gear located on a first inner peripheral surface of the casing;
An annular second internal gear located on the second inner peripheral surface of the casing;
An input gear connected to the input shaft,
A first rotating shaft portion arranged coaxially with the input shaft in the casing;
A first planetary carrier having a sun gear that rotates together with the first rotating shaft portion and rotatable about the first rotating shaft portion;
A plurality of first planetary gears that are rotatably supported by the first planetary carrier and that mesh with the input gear and the first internal gear;
A second rotating shaft portion arranged coaxially with the input shaft in the casing and connected to the output shaft;
A second planetary carrier rotatable about the second rotating shaft portion;
A plurality of second planetary gears arranged in the circumferential direction of the sun gear and rotatably supported by the second planetary carrier, and meshing with the sun gear and the two internal gears;
Equipped with
The first planetary carrier, the first rotating shaft portion, and the sun gear are a single member,
The input gear, the first planetary carrier, and the first planetary gear are molded products of a resin composition containing a thermoplastic resin as a base resin and containing an inorganic whisker as a predetermined functional expression component, and The total content of the base resin and the inorganic whiskers in the resin composition is 99.5% by weight or more,
The first internal gear is formed of a metal sintered body, and the relationship between the tooth thickness T of the first internal gear and the arithmetic mean roughness Ra is
5.0 × 10 −3 ≦ (Ra / T) ≦ 66.7 × 10 −3
Small speed reducer characterized by satisfying.
The small reduction gear according to claim 1, wherein the second planet carrier, the second planet gear, and the second internal gear are formed of a metal sintered body.
The second planetary gear is a molded product of a resin composition containing a thermoplastic resin as a base resin and inorganic whiskers as a predetermined functional expression component, and the base resin in the resin composition and the base resin in the resin composition. The content rate including the inorganic whiskers is 99.5% by weight or more,
The miniature speed reducer according to claim 1, wherein the second planet carrier and the second internal gear are formed of a metal sintered body.
The small speed reducer according to any one of claims 1 to 3, wherein the resin composition contains 15 to 40% by weight of the inorganic whiskers.
The small speed reducer according to claim 4, wherein the resin composition preferably contains 20 to 30% by weight of the inorganic whiskers.
The small speed reducer according to any one of claims 1 to 5, wherein the inorganic whiskers are potassium titanate fibers.
The small speed reducer according to any one of claims 1 to 6, wherein the thermoplastic resin is a polyamide resin.
The compact speed reducer according to claim 1, wherein the module of the first planetary gear and the module of the second planetary gear is 0.2 mm or less.
The small speed reducer according to claim 1, wherein the external dimensions of the small speed reducer are formed to have a volume of 5 mm in width, 5 mm in depth and 20 mm in height or less.
A first rotation assembly in which the input gear, the first planet carrier having the sun gear, the first planetary gear, and the first rotation shaft portion transmit rotational force between the input shaft and the input shaft. And the second planetary carrier, the second planetary gear, and the second rotating shaft portion constitute a second rotating assembly that transmits rotational force between the first rotating assembly. The small reduction gear according to claim 1, wherein