JP2004332846A - Inscribed engagement planetary gear structure with eccentric cam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the performance and durability of a speed reducer with an inscribed engagement planetary gear structure by facilitating the installation and loading capacity of the eccentric body or an external gear of the planetary gear structure. <P>SOLUTION: Rolling elements comprise a first sliding surface S1 on the eccentric bodies 103a and 103b side and a third sliding surface S3 on the external gear side (S1 = S3), and are formed in a convex shape in a plane including the axis O1 of an input shaft 101. The second sliding surface S2 of the external gear slidably moving on the first sliding surface S1 is formed in a convex shape. On the other hand, the fourth sliding surface S4 of the eccentric bodies 103a and 103b slidably moving on the third sliding surface S3 is formed in a convex shape on the eccentric bodies 103a and 103b side. The radius of curvature of the convex shape on the fourth sliding surface S4 is slightly smaller than the radius of curvature of the convex shape on the third sliding surface S3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４３】
（１）、（２）式において、Σρは、（３）式で与えられる曲率和である。
【００４４】
Σρ＝ρｘ１＋ρｘ２＋ρｙ１＋ρｙ２ （３）
ここでρｘ１、ρｘ２、ρｙ１、ρｙ２は、曲率半径ｒｘ１、ｒｘ２、ｒｙ１、ｒｙ２に対応する曲率（ｒｘ１、ｒｘ２、ｒｙ１、ｒｙ２の逆数）である。
【００４５】
（１）式、（２）式の係数μと係数νは、ｃｏｓτを補助係数とし、該補助係数ｃｏｓτの値からヘルツの誘導によってそれぞれ予め与えられている係数である。補助係数ｃｏｓτは、（４）式に従って求められる。
【００４６】
ｃｏｓτ＝（ρｘ１−ρｘ２＋ρｙ１−ρｙ２）／ Σρ ・・・（４）
【００４７】
即ち、（４）式に従って、補助係数ｃｏｓτの値が求められると、ヘルツによって誘導された換算表に基づいて係数μと係数νが求められる。
【００４８】
（１）、（２）式より、接触面積Ｆは（５）式のようになる。
【００４９】
【数２】

【００５０】
押付け力がＱの場合、平均接触面圧Ｐは、Ｑ／Ｆ、最大ヘルツ接触面圧Ｐｍａｘは、１．５Ｑ／Ｆとなる。
【００５１】
以上の理論を本実施形態に具体的に適用するべく、今、図５（Ａ）、（Ｂ）に示すように、外歯歯車１０５ａ、１０５ｂの第２の摺動面Ｓ２の接触部付近の入力軸１０１の軸Ｏ１を含む面における曲率半径をｒｇ１、これと直角の面における摺動部付近の曲率半径をｒｇ２、転動体１０４ａ、１０４ｂの第１（第３）摺動面Ｓ１（Ｓ３）の接触部付近の入力軸１０１の軸心Ｏ１を含む面における曲率半径をｒｃ１、これと直角の面における摺動部付近の曲率半径をｒｃ２、偏心体１０３ａ、１０３ｂの第４の摺動面Ｓ４の接触部付近の入力軸１０１の軸心Ｏ１を含む面における曲率半径をｒｅ１、これと直角の面における摺動部付近の曲率半径をｒｅ２とし、該曲率半径ｒｇ１、ｒｇ２、ｒｃｌ、ｒｃ２、ｒｅ１、ｒｅ２のそれぞれの曲率をρｇ１、ρｇ２、ρｃ１、ρｃ２、ρｅ１、ρｅ２と定義する。
【００５２】
すると、外歯歯車１０５ａ、１０５ｂと転動体１０４ａ、１０４ｂとの間の接触については、
Σρ１＝ρｇ１＋ρｃ１＋（−ρｇ２）＋ρｃ２ ・・・・・・・・（６）
ｃｏｓτ１＝（ρｇ１−（−ρｇ２）＋ρｃ１−ρｃ２ ・・・・・（７）
となり、Ｆ１は（８）式のようになる
【００５３】
【数３】

【００５４】
接触面積Ｆ１が求まると、最大接触面積Ｐ１は（９）式のように求められる。
【００５５】
Ｐ１＝１．５・Ｑ／Ｆ１ ・・・・・・・・・・・・・・・・・・・（９）
【００５６】
一方、偏心体１０３ａ、１０３ｂと転動体１０４ａ、１０４ｂとの間の接触についても、同様に、
Σρ２＝ρｃ１＋（−ρｅ１）＋ρｃ２＋ρｅ２ ・・・・・・・・・（１０）
ｃｏｓτ２＝｛ρｃ１−ρｃ２＋（−ρｅ１）−ρｅ２｝／Σρ２ ・（１１）
となり、Ｆ２は（１２）式のようになる
【００５７】
【数４】

【００５８】
接触面積Ｆ２が求まると、最大接触面圧Ｐ２は（１３）式のように求められる。
【００５９】
Ｐ２＝１．５・Ｑ／Ｆ２ ・・・・・・・・・・・・・・・・・・・（１３）
【００６０】
本実施形態では、Ｐ２がＰ１とほぼ同等かやや大きくなる程度、即ち、０．８倍〜１．６倍程度の範囲に収まるように、各曲率半径ｒｇ１、ｒｇ２、ｒｃ１、ｒｃ２、ｒｅ１、ｒｅ２を決定する。
【００６１】
次に、この減速機の作用を説明する。
【００６２】
所定の減速比を得るための減速機自体の基本的な動力伝達機能は、特に従来と異なることはない。
【００６３】
しかしながら、上記実施形態においては、外歯歯車１０５ａ、１０５ｂの第２の摺動面Ｓ２を入力軸１０１の軸心Ｏ３を含む面内において直線又は凸状に形成することにより、偏心体１０３ａ、１０３ｂの組立を容易化でき、製造コストを低減できる。また、組み立てが容易にできるため、ラジアル隙間をより小さく設定することができ、その分転動体１０４ａ、１０４ｂを数多く組み込むことができる。したがって減速機全体の性能、耐久性をより改善できる。
【００６４】
即ち、外歯歯車１０５ａ、１０５ｂと転動体１０４ａ、１０４ｂとの摺動は、入力軸１０１の軸心Ｏ３と直角の面内においては、凹と凸との摺動となっているため、該軸心Ｏ３を含む面内において外歯歯車１０５ａ、１０５ｂの第２の摺動面Ｓ２を直線あるいは凸状に設定したとしても、強度的になお余裕がある。そのため、この実施形態では、偏心体１０３ａ、１０３ｂと転動体１０４ａ、１０４ｂとの間の最大接触面圧Ｐ２が外歯歯車１０５ａ、１０５ｂと転動体１０４ａ、１０４ｂとの間の最大接触面圧Ｐ１とほぼ同等かやや大きくなる程度、即ち、０．８倍〜１．６倍程度の範囲に収まるように、各曲率半径ｒｇ１、ｒｇ２、ｒｃ１、ｒｃ２、ｒｅ１、ｒｅ２を決定するようにしている。換言するならば、外歯歯車１０５ａ、１０５ｂと転動体１０４ａ、１０４ｂとの間の耐久性が、偏心体１０３ａ、１０３ｂと転動体１０４ａ、１０４ｂとの間の耐久性に対して、相対的に過剰品質となるのを抑制し、この過剰品質分を組付けの容易性の向上の方に振り向けるようにしている。
【００６５】
そのため、結果として耐久性をむしろ向上させることができる上に、組付けコストを低減できる。
【００６６】
更に、本実施形態に係る減速機Ｇにおいては、偏心体１０３ａ、１０３ｂの第４の摺動面Ｓ４を凹面で形成し、かつ転動体１０４ａ、１０４ｂの第３の摺動面Ｓ３をこの第４の摺動面Ｓ４の凹面の曲率半径ｒｅ１よりも僅かに小さな曲率半径ｒｃ１となるように設定している。これにより、偏心体１０３ａ、１０３ｂと転動体１０４ａ、１０４ｂとの摺動を、入力軸１０１の軸心Ｏ３を含む面内において凹と凹の摺動とすることができ、両者の接触面圧低減することができる上に、製造誤差や弾性変形によるミスアライメントを吸収して片当りによる局所的な方面初が発生するの防止することができる。この結果、偏心体１０３ａ、１０３ｂ及び転動体１０４ａ、１０４ｂの摺動をより円滑化でき、両者の耐久性を一層向上させることができる。
【００６７】
なお、上記実施形態において、転動体として、樽形・ころ形状の転動体１０４ａ、１０４ｂ（第１の摺動面Ｓ１＝第３の摺動面Ｓ３、ｒｃ１≠ｒｃ２の転動体）が採用されていたが、本発明における転動体は、ころ形状の転動体に限定されるものではなく、例えば、球（ボール）形状の転動体、即ち、第１の摺動面Ｓ１＝第３の摺動面Ｓ３、ｒｃ１＝ｒｃ２の転動体でも同様の作用効果が得られる。
【００６８】
又、上記実施形態では、入力軸の外周に偏心体（偏心カム）が配置され、その外周に転動体及び外歯歯車が組み込まれる構造の内接噛合遊星歯車構造が示されていたが、本発明は、例えば、入力軸から歯車を介して複数の偏心体軸に動力を振り分け、該偏心体軸にそれぞれ装着された同位相の複数の偏心体を介して外歯歯車を複数箇所において同時に偏心駆動するような振分けタイプの内接噛合遊星歯車構造であっても適用可能であり、同様の効果が得られる。
【００６９】
又、外歯歯車１０５ａ、１０５ｂの第２の摺動面Ｓ２、偏心体（偏心カム）１０３ａ、１０３ｂの第４の摺動面Ｓ４を、それぞれ外歯歯車１０５ａ、１０５ｂ、偏心体１０３ａ、１０３ｂに直接形成するようにしていたが、別体の部材を介在させ、該別体の部材に第２の摺動面Ｓ２、あるいは第４の摺動面Ｓ４を形成するようにしてもよい。
【００７０】
【発明の効果】
本発明によれば、偏心体、或いは外歯歯車の組付けを容易化し、結果として偏心カム〜外歯歯車の動力伝達の負荷能力を向上させ、ひいては、この種の歯車構造を有する減速機の性能及び耐久性の向上を図ることができるという優れた効果が得られる。
【図面の簡単な説明】
【図１】本発明の実施形態が適用された減速機の転動体付近の要部拡大断面図
【図２】上記実施形態における偏心体（偏心カム）と転動体との摺動付近を拡大して示す断面図
【図３】本発明の他の実施形態を示す図１相当の要部拡大断面図
【図４】ヘルツの接触理論のモデルを示す斜視図
【図５】図１に示した実施形態に対してヘルツの接触理論を適用する際の各要素の曲率半径を示す（Ａ）概略正断面図、及び（Ｂ）概略側断面図
【図６】内接噛合遊星歯車構造が適用された従来の減速機の一例を示す画面図
【図７】図６の矢視ＶＩＩ−ＶＩＩ線に沿う端面図
【符号の説明】
１０１…入力軸
１０３ａ、１０３ｂ…偏心体（偏心カム）
１０４ａ、１０４ｂ…転動体
１０５ａ、１０５ｂ…外歯歯車
１２０…内歯歯車
Ｓ１〜Ｓ４…第１〜第４の摺動面[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an internally meshing planetary gear structure.
[0002]
[Prior art]
Conventionally, an input shaft, an eccentric cam, and an external gear and an internal gear having a small difference in the number of teeth are provided, and the external gear rotates eccentrically with respect to the axis of the input shaft via the eccentric cam. Meanwhile, an internally meshing planetary gear structure having an eccentric cam configured to internally mesh with the internal gear is widely known (for example, see Patent Document 1).
[0003]
6 and 7 show examples in which this structure is applied to a speed reducer.
[0004]
Eccentric bodies (eccentric cams) 3a and 3b are fitted to the input shaft 1 with a predetermined phase difference (180 ° in this example). The eccentric bodies 3a and 3b are respectively eccentric with respect to the input shaft 1 (axial center O1) by an eccentric amount e (center O2). Two external gears 5a, 5b are attached to each eccentric body 3a, 3b in a double row via roller-shaped rolling elements 4a, 4b. The external gears 5a and 5b are provided with a plurality of inner roller holes 6a and 6b, and the inner pin 7 and the inner roller 8 are fitted therein.
[0005]
The reason why the number of external gears is two (double row) is mainly to increase transmission capacity, maintain strength, and maintain rotational balance. On the outer periphery of the external gears 5a and 5b, external teeth 9 such as a trochoid tooth shape and an arc tooth shape are provided. The external teeth 9 are internally meshed with an internal gear 10 fixed to a casing 12. Specifically, the internal teeth of the internal gear 10 have a structure in which the outer pin 11 is loosely fitted into the outer pin hole 13 and held so as to be easily rotated. The inner pin 7 penetrating the external gears 5a, 5b is fixed or fitted to the output shaft 2.
[0006]
When the input shaft 1 makes one rotation, the eccentric bodies 3a and 3b make one rotation. One rotation of the eccentric bodies 3a and 3b causes the external gears 5a and 5b to oscillate around the input shaft 1. However, since the rotation of the external gears 5a and 5b is restricted by the internal gear 10, the external gear 5a 5b perform almost only swing while inscribed in the internal gear 10.
[0007]
Now, for example, when the number of teeth of the external gears 5a and 5b is N and the gear of the internal gear 10 is N + 1, the difference in the number of teeth is 1. Therefore, the external gears 5a and 5b are shifted (rotated) by one tooth with respect to the internal gear 10 fixed to the casing 12 for each rotation of the input shaft 1. This means that one rotation of the input shaft 1 has been reduced to -1 / N rotation of the external gears 5a and 5b. A minus sign indicates that the rotation of the external gears 5a and 5b is opposite to the rotation of the input shaft 1.
[0008]
The rotation of the external gears 5a and 5b is absorbed by the gap between the inner roller holes 6a and 6b and the inner pin 7 (the inner roller 8), and only the rotation component is transmitted to the output shaft 2 via the inner pin 7. Is communicated. As a result, a speed reduction of -1 / N is achieved.
[0009]
The above-mentioned internal meshing planetary gear structure is currently applied to various reduction gears or speed-up gears. For example, it is possible to constitute a speed reducer by fixing the output shaft 2 and using the internal gear 10 as an output shaft instead, with exactly the same structure. Further, by reversing the input / output shaft, a “speed increasing device” can be configured.
[0010]
Furthermore, in addition to the above-described inscribed mesh planetary gear structure, for example, power is distributed to a plurality of eccentric shafts from an input shaft via gears, and a plurality of eccentric bodies of the same phase mounted on the eccentric shafts, respectively. There is also known a distributing type internally meshing planetary gear structure in which external gears are simultaneously driven eccentrically at a plurality of locations.
[0011]
By the way, when the input shaft 1 is rotated, the eccentric bodies 3a and 3b rotate, and the rotation of the eccentric bodies 3a and 3b causes the two external gears 5a and 5b to oscillate through the rolling elements 4a and 4b. At this time, a torque transmission load (load) is generated between the external gears 5a, 5b and the rolling elements 4a, 4b and between the rolling elements 4a, 4b and the eccentric bodies 3a, 3b.
[0012]
Since the rolling elements 4a and 4b are assembled to the eccentric bodies 3a and 3b fitted to the input shaft 1, when a load is generated on the rolling elements 4a and 4b, the rolling elements 4a and 4b are applied to the input shaft 1 via the eccentric bodies 3a and 3b. A moment is generated, and the input shaft 1 tilts (misalignment). When the input shaft 1 is inclined, the entire eccentric bodies 3a and 3b fitted thereto are inclined, and as a result, the eccentric bodies 3a and 3b, the rolling elements 4a and 4b, and the external gears 5a and 5b apply a load to each other in an inclined state. The rotation will be transmitted while exerting influence. If this state continues, one-sided contact occurs, so that the life of the rolling elements 4a and 4b is shortened, and it becomes impossible to cope with a high load.
[0013]
Conventionally, in order to shorten the service life due to this one-sided contact, crowning or special heat treatment is performed on the outer peripheral end surfaces of the rolling elements 4a and 4b to avoid the occurrence. However, the misalignment can be absorbed by the crowning. The amount was naturally limited, and it was not possible to cope with further higher load capacity.
[0014]
To cope with such a problem, in Patent Document 1, the rolling element interposed between the eccentric body and the external gear has a single radius of curvature, and the outer circumference of the eccentric body and the internal circumference of the external gear have the rolling element. There is disclosed an example configured with a shape that follows the curvature.
[0015]
[Patent Document 1]
JP 2000-249200 A
[Problems to be solved by the invention]
However, in this method, since it was necessary to install the rolling element in the space sandwiched between the concave surfaces, there was a problem that it was difficult to assemble each member, and the assembling cost was increased. . Also, because of the difficulty in assembling, it is necessary to increase the radial clearance of the rolling elements, which limits the number of rolling elements that can be incorporated, resulting in a small number of rolling elements having a load. However, there is a problem that the performance and the life cannot be sufficiently improved.
[0017]
In addition, since the sliding portions of the rolling elements are formed of surfaces having the same curvature, one-side contact does not occur in the design, but it is actually manufactured at the end of the rolling elements. There is also a concern that a one-sided contact occurs due to the error, which causes an edge stress.
[0018]
SUMMARY OF THE INVENTION The present invention has been made in order to solve such a conventional problem, and it is easy to assemble the respective members and has a high power transmission load capability. It is an object of the present invention to obtain an internally meshing planetary gear structure capable of improving the performance and durability of a machine or the like.
[0019]
[Means for Solving the Problems]
The present invention includes an input shaft, an eccentric cam, an internal gear, and an external gear having a slight difference in the number of teeth from the internal gear, wherein the external gear has an axis of the input shaft via the eccentric cam. In an internally meshing planetary gear structure having an eccentric cam configured to mesh internally with the internal gear while eccentrically swinging, a rolling element is provided between the eccentric cam and the external gear. A first sliding surface on the external gear side of the rolling element, which is formed in a convex shape in a plane including the axis of the input shaft, and wherein the external gear slides on the first sliding surface; The second sliding surface on the side is formed as either a straight line parallel to the axis or a convex shape in the plane including the axis of the input shaft, and the third sliding surface on the eccentric cam side of the rolling element. A moving surface is formed in a convex shape in a plane including the axis of the input shaft, and the eccentric cam side sliding on the third sliding surface. 4 the sliding surface of, by forming a concave in a plane containing the axis of the input shaft is obtained by solving the above problems.
[0020]
The sliding surface between the rolling element and the external gear has a convex and concave contact mode in consideration of a contact in a plane perpendicular to the input shaft. For this reason, the sliding load in this portion is not originally so high, and is originally advantageous in terms of the contact surface pressure. On the other hand, the sliding surface between the rolling element and the eccentric cam has a convex and convex sliding mode in a plane perpendicular to the input shaft, and is in a more severe condition in terms of durability.
[0021]
In consideration of such a situation, the present invention makes it possible to rationalize the advantage of the sliding condition of the sliding surface of the rolling element on the side of the external gear (without maintaining excessive quality) while ensuring the durability. It can be said that it was aimed at the ease of assembly in a targeted and aggressive manner.
[0022]
That is, according to the present invention, the first sliding surface of the rolling element and the second sliding surface on the side of the external gear have a linear or convex contact form in a plane including the axis of the input shaft. And a convex contact mode. With this configuration, it is extremely easy to assemble the rolling elements. This has been confirmed by actual assembly tests. In addition, since the assembling is facilitated, it is not necessary to increase the radial gap between the rolling elements, the number of rolling elements that can be incorporated can be increased, and the rotation performance and durability can be improved.
[0023]
On the other hand, the sliding surface on the side of the rolling element and the eccentric cam, which is in a severe situation in terms of durability, maintains the concave and convex contact mode in the plane including the axis of the input shaft, and the occurrence of one side contact As a result, the generation of edge stress is reliably prevented, and smooth rotation can be ensured and durability can be improved.
[0024]
The second sliding surface may be formed on the external gear itself, or may be formed by another member.
[0025]
When the radius of curvature of the fourth sliding surface is smaller than the radius of curvature of the third sliding surface, there is no one-sided contact caused by a manufacturing error or the like. Misalignment due to elastic deformation during transmission can also be absorbed. Therefore, it is possible to more reliably prevent locally high edge stress from being generated due to the occurrence of the one-sided contact, and it is possible to further ensure smooth rotation and improve durability.
[0026]
Note that the contact surface pressure between the third sliding surface and the fourth sliding surface is 0.8 to 1.... Of the contact surface pressure between the first sliding surface and the second sliding surface. It is preferable to set the radius of curvature of each sliding surface so as to fall within the range of 6 times (described later).
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0028]
FIG. 1 is an enlarged view of a main part of a speed reducer to which an embodiment of the present invention is applied. The reduction gear G includes an input shaft 101, eccentric bodies (eccentric cams) 103a and 103b, an internal gear (not shown), and external gears 105a and 105b having a slight difference in the number of teeth from the internal gear. An eccentric body 103a, wherein the external gears 105a and 105b are configured to mesh with the internal gear while eccentrically swinging with respect to the axis O3 of the input shaft 101 via the eccentric bodies 103a and 103b; An internally meshing planetary gear structure having 103b is provided.
[0029]
Note that the configuration other than the sliding configuration between the eccentric bodies 103a, 103b and the external gears 105a, 105b is basically not particularly different from the configuration of the conventional speed reducer described above, and therefore, redundant description is omitted. .
[0030]
A plurality of rolling elements 104a, 104b are interposed between the eccentric bodies 103a, 103b and the external gears 105a, 105b. Each of the rolling elements 104a and 104b has a barrel-shaped roller shape, has a first sliding surface S1 on the external gears 105a and 105b side, and has a third sliding surface on the eccentric bodies 103a and 103b side. S3.
[0031]
However, since the rolling elements 104a and 104b in this embodiment rotate between the eccentric bodies 103a and 103b and the external gears 105a and 105b, the first and third sliding surfaces S1 and S3 are Actually, they are the same (single) sliding surface (S1 = S3), and both are formed in a convex shape in a plane including the axis O3 of the input shaft 101.
[0032]
The axis of each of the rolling elements 104a and 104b is parallel to the axis O3 of the input shaft 101.
[0033]
The second sliding surfaces S2 of the external gears 105a and 105b sliding on the first sliding surfaces S1 of the rolling elements 104a and 104b are formed in a convex shape in a plane including the axis O3 of the input shaft 101. ing.
[0034]
On the other hand, the fourth sliding surface S4 of the eccentric bodies 103a, 103b sliding on the third sliding surface S3 of the rolling elements 104a, 104b is formed in a concave shape in a plane including the axis O3 of the input shaft 101. 2, and the radius of curvature (rc1) of the third sliding surface S3 is slightly smaller than the radius of curvature (-re1) of the fourth sliding surface S4. Is set to a value.
[0035]
The definition or significance of the radii of curvature rc1 and -re1 will be described later in detail.
[0036]
The shape of the second sliding surface S2 may be formed as a straight line in a plane including the axis O3 of the input shaft 101, as shown in FIG. That is, in this example, the second sliding surfaces S20 of the external gears 205a and 205b are formed as straight lines (cylindrical surfaces).
[0037]
The radius of curvature of each member, including the problem of whether the second sliding surface S2 (S20) is formed by a cylindrical surface, a convex surface, or a radius of curvature when formed by a convex surface. Is based on the Hertzian contact theory described below, "The contact surface pressure between the rolling elements 104a, 104b and the eccentric bodies 103a, 103b is equal to the contact surface pressure between the rolling elements 104a, 104b and the external gears 105a, 105b. It is set to be substantially equal or slightly larger (about 0.8 to 1.6 times). "
[0038]
That is, the contact surface pressure between the rolling elements 104a, 104b and the eccentric bodies 103a, 103b and the contact surface pressure between the rolling elements 104a, 104b and the external gears 105a, 105b are based on the Hertzian point contact theory as follows. You can ask.
[0039]
According to Hertz's point contact theory, as shown in FIG. 4, when two spheroids X and Y are pressed against each other by a pressing force Q, it is assumed that the contact surface becomes an ellipse having a major axis 2a and a minor axis 2b. The relationship between each element is modeled.
[0040]
The spheroids X and Y have two main curvature surfaces P1 and P2 orthogonal to each other, and the spheroid X has a minimum radius of curvature rx1 and a maximum radius of curvature rx2 in the main curvature planes P1 and P2 near the contact portion. Have. On the other hand, the spheroid Y has a minimum radius of curvature ry1 and a maximum radius of curvature ry2 in the same main curvature planes P1 and P2 near the contact portion. If the center of the radius of curvature is inside the object (in the case of a convex surface), the sign of + is added, and if the center of the radius of curvature is outside the object (in the case of a concave surface), the sign of-is specified.
[0041]
When the contact surface is an ellipse, its area (contact area) F is πab. Regarding a and b, Hertz states that Young's modulus E of two spheroids X and Y is equal to Poisson's ratio 1 / m. Expressions (1) and (2) are given under the condition
[0042]
(Equation 1)

[0043]
In the expressions (1) and (2), Σρ is the curvature sum given by the expression (3).
[0044]
Σρ = ρx1 + ρx2 + ρy1 + ρy2 (3)
Here, ρx1, ρx2, ρy1, ρy2 are the curvatures (reciprocals of rx1, rx2, ry1, ry2) corresponding to the radii of curvature rx1, rx2, ry1, ry2.
[0045]
The coefficients μ and ν in the equations (1) and (2) are coefficients which are given in advance by the induction of Hertz from the value of the auxiliary coefficient cosτ with cosτ as the auxiliary coefficient. The auxiliary coefficient cosτ is obtained according to the equation (4).
[0046]
cosτ = (ρx1−ρx2 + ρy1−ρy2) /／ ρ (4)
[0047]
That is, when the value of the auxiliary coefficient cosτ is obtained according to the equation (4), the coefficient μ and the coefficient ν are obtained based on a conversion table derived by Hertz.
[0048]
From the expressions (1) and (2), the contact area F is as shown in the expression (5).
[0049]
(Equation 2)

[0050]
When the pressing force is Q, the average contact surface pressure P is Q / F, and the maximum Hertz contact surface pressure Pmax is 1.5 Q / F.
[0051]
In order to specifically apply the above theory to the present embodiment, as shown in FIGS. 5A and 5B, the vicinity of the contact portion of the second sliding surface S2 of the external gears 105a and 105b is now described. The radius of curvature of the surface including the axis O1 of the input shaft 101 is rg1, the radius of curvature near the sliding portion in a plane perpendicular to this is rg2, and the first (third) sliding surface S1 (S3) of the rolling elements 104a and 104b. The radius of curvature of the surface including the axis O1 of the input shaft 101 near the contact portion is rc1, the radius of curvature near the sliding portion on the surface perpendicular to this is rc2, the fourth sliding surface S4 of the eccentric bodies 103a and 103b. The radius of curvature on the surface including the axis O1 of the input shaft 101 near the contact portion is re1, and the radius of curvature near the sliding portion on the surface perpendicular to this is re2, and the curvature radii rg1, rg2, rcl, rc2, re1 , Re2 each curvature g1, ρg2, ρc1, ρc2, ρe1, is defined as ρe2.
[0052]
Then, regarding the contact between the external gears 105a and 105b and the rolling elements 104a and 104b,
Σρ1 = ρg1 + ρc1 + (− ρg2) + ρc2 (6)
cosτ1 = (ρg1 − (− ρg2) + ρc1−ρc2 (7)
And F1 is as shown in equation (8).
[Equation 3]

[0054]
When the contact area F1 is obtained, the maximum contact area P1 is obtained as in the equation (9).
[0055]
P1 = 1.5 · Q / F1 (9)
[0056]
On the other hand, also for the contact between the eccentric bodies 103a, 103b and the rolling elements 104a, 104b, similarly,
Σρ2 = ρc1 + (− ρe1) + ρc2 + ρe2 (10)
cosτ2 = {ρc1−ρc2 + (− ρe1) −ρe2} /｝ ρ2 (11)
, And F2 becomes as expressed by the equation (12).
(Equation 4)

[0058]
When the contact area F2 is obtained, the maximum contact surface pressure P2 is obtained as shown in Expression (13).
[0059]
P2 = 1.5 · Q / F2 (13)
[0060]
In the present embodiment, each radius of curvature rg1, rg2, rc1, rc2, re1, re2 is set so that P2 is substantially equal to or slightly larger than P1, that is, within a range of about 0.8 to 1.6 times. To determine.
[0061]
Next, the operation of the speed reducer will be described.
[0062]
The basic power transmission function of the speed reducer itself for obtaining a predetermined reduction ratio is not particularly different from the conventional one.
[0063]
However, in the above embodiment, the eccentric bodies 103a, 103b are formed by forming the second sliding surfaces S2 of the external gears 105a, 105b linearly or convexly in a plane including the axis O3 of the input shaft 101. Can be easily assembled and the manufacturing cost can be reduced. Further, since the assembling can be easily performed, the radial gap can be set smaller, and the rolling elements 104a and 104b can be incorporated by a corresponding amount. Therefore, the performance and durability of the entire reduction gear can be further improved.
[0064]
That is, the sliding between the external gears 105a and 105b and the rolling elements 104a and 104b is a sliding between a concave and a convex in a plane perpendicular to the axis O3 of the input shaft 101. Even if the second sliding surfaces S2 of the external gears 105a and 105b are set to be linear or convex in the plane including the center O3, there is still room for strength. Therefore, in this embodiment, the maximum contact surface pressure P2 between the eccentric bodies 103a, 103b and the rolling elements 104a, 104b is equal to the maximum contact surface pressure P1 between the external gears 105a, 105b and the rolling elements 104a, 104b. The curvature radii rg1, rg2, rc1, rc2, re1, and re2 are determined so as to be substantially equal or slightly larger, that is, within a range of about 0.8 to 1.6 times. In other words, the durability between the external gears 105a, 105b and the rolling elements 104a, 104b is relatively excessive with respect to the durability between the eccentric bodies 103a, 103b and the rolling elements 104a, 104b. The quality is suppressed, and the excess quality is directed toward improving the ease of assembly.
[0065]
Therefore, as a result, the durability can be rather improved, and the assembly cost can be reduced.
[0066]
Further, in the speed reducer G according to the present embodiment, the fourth sliding surface S4 of the eccentric bodies 103a and 103b is formed as a concave surface, and the third sliding surface S3 of the rolling elements 104a and 104b is formed as the fourth sliding surface S3. The radius of curvature rc1 is set slightly smaller than the radius of curvature re1 of the concave surface of the sliding surface S4. Thereby, the sliding between the eccentric bodies 103a, 103b and the rolling elements 104a, 104b can be concave and concave in the plane including the axis O3 of the input shaft 101, and the contact surface pressure between them can be reduced. In addition to the above, it is possible to absorb a misalignment due to a manufacturing error or an elastic deformation and to prevent the first local area from occurring due to the one-side contact. As a result, the sliding of the eccentric bodies 103a and 103b and the rolling elements 104a and 104b can be made smoother, and the durability of both can be further improved.
[0067]
In the above embodiment, barrel-shaped / roller-shaped rolling elements 104a and 104b (first sliding surface S1 = third sliding surface S3, rolling elements of rc1 ≠ rc2) are employed as rolling elements. However, the rolling element in the present invention is not limited to a roller-shaped rolling element, and may be, for example, a spherical (ball) -shaped rolling element, that is, a first sliding surface S1 = third sliding surface. The same operation and effect can be obtained with a rolling element of S3, rc1 = rc2.
[0068]
Further, in the above embodiment, the eccentric body (eccentric cam) is arranged on the outer periphery of the input shaft, and the internal meshing planetary gear structure in which the rolling element and the external gear are incorporated on the outer periphery is shown. The present invention, for example, distributes power from an input shaft to a plurality of eccentric shafts via gears, and simultaneously eccentric external gears at a plurality of locations via a plurality of eccentric bodies of the same phase mounted on the eccentric shafts. The present invention can be applied to a split-type internally meshing planetary gear structure that can be driven, and the same effects can be obtained.
[0069]
Also, the second sliding surface S2 of the external gears 105a and 105b and the fourth sliding surface S4 of the eccentric bodies (eccentric cams) 103a and 103b are respectively connected to the external gears 105a and 105b and the eccentric bodies 103a and 103b. Although formed directly, a separate member may be interposed, and the second sliding surface S2 or the fourth sliding surface S4 may be formed on the separate member.
[0070]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, assembling of an eccentric body or an external gear is facilitated, and as a result, the load capacity of the power transmission of an eccentric cam-an external gear is improved, and, as a result, the reduction gear which has this kind of gear structure An excellent effect that performance and durability can be improved can be obtained.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view of a main part in the vicinity of a rolling element of a speed reducer to which an embodiment of the present invention is applied. FIG. 2 is an enlarged view of the vicinity of sliding between an eccentric body (eccentric cam) and a rolling element in the above embodiment. FIG. 3 is an enlarged sectional view of an essential part corresponding to FIG. 1 showing another embodiment of the present invention. FIG. 4 is a perspective view showing a model of Hertzian contact theory. FIG. 5 is an embodiment shown in FIG. (A) Schematic front sectional view and (B) Schematic sectional side view showing the radius of curvature of each element when applying the Hertzian contact theory to the form. [FIG. 6] An internally meshing planetary gear structure is applied. FIG. 7 is a screen view showing an example of a conventional speed reducer. FIG. 7 is an end view taken along line VII-VII of FIG.
101: input shafts 103a, 103b: eccentric body (eccentric cam)
104a, 104b rolling elements 105a, 105b external gear 120 internal gears S1 to S4 first to fourth sliding surfaces

Claims (4)

An input shaft, an eccentric cam, an internal gear, and an external gear having a small difference in the number of teeth from the internal gear, wherein the external gear is eccentric to the axis of the input shaft via the eccentric cam. An internally meshing planetary gear structure having an eccentric cam configured to mesh internally with the internal gear while swinging,
A rolling element is provided between the eccentric cam and the external gear,
A first sliding surface on the external gear side of the rolling element is formed in a convex shape in a plane including the axis of the input shaft, and
A second sliding surface on the side of the external gear that slides with the first sliding surface is formed as a straight line or a convex shape parallel to an axis in a plane including the axis of the input shaft. ,and,
A third sliding surface on the eccentric cam side of the rolling element is formed in a convex shape in a plane including the axis of the input shaft, and
An inscribed cam having an eccentric cam, wherein a fourth sliding surface on the eccentric cam side that slides on the third sliding surface is formed in a concave shape in a plane including the axis of the input shaft. Meshing planetary gear structure. An input shaft, an eccentric cam, an internal gear, and an external gear having a small difference in the number of teeth from the internal gear, wherein the external gear is eccentric to the axis of the input shaft via the eccentric cam. An internally meshing planetary gear structure having an eccentric cam configured to mesh internally with the internal gear while swinging,
A rolling element is provided between the eccentric cam and the external gear,
A first sliding surface on the external gear side of the rolling element is formed in a convex shape in a plane including the axis of the input shaft, and
A second sliding surface on the side of the external gear that slides with the first sliding surface is formed as a straight line or a convex shape parallel to an axis in a plane including the axis of the input shaft. The sliding surface on the eccentric cam side of the rolling element is defined as a third sliding surface, and the sliding surface on the eccentric cam side sliding on the third sliding surface is defined as a fourth sliding surface. sometimes,
The contact surface pressure between the third sliding surface and the fourth sliding surface is 0.8 to 1 of the contact surface pressure between the first sliding surface and the second sliding surface. 6. An internally meshing planetary gear structure having an eccentric cam, wherein the radius of curvature of each sliding surface is set so as to fall within a range of 6 times. In claim 1 or 2,
An internally meshing planetary gear structure having an eccentric cam, wherein the second sliding surface is formed of a member different from the external gear. In any one of claims 1 to 3,
An internally meshing planetary gear structure having an eccentric cam, wherein a radius of curvature of the third sliding surface is smaller than a radius of curvature of the fourth sliding surface.

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