JPH0763243A - Diffrential type internal meshing planetary gear structure - Google Patents

Abstract

PURPOSE:To achieve miniatuarization, weight reduction, low cost, low noise, low vibration on the assumption that a high reduction gear ratio is obtained by internally meshing both external gears with an integrated internal gear, respectively, and rotatably supporting this internal gear by means of a casing. CONSTITUTION:Since a first external gear 110 and a second external gear 112 are ocsillating (eccentrically) rotated in the opposite direction into the center of an input shaft 102, respectively, active unbalance caused by individual oscillating-rotation is offset. Moreover, since there is not provided with a crank- like inner pin, there is few number of parts, and also there is no concern of generation of inconvenience of this part. As for the reduction gear ratio, when the rotational speed of the input shaft 102 is N1, and when the rotational speed of the output shaft 104 is taken as N2, the formula; N2={1-(S2.P1)/(S1.P2)}N1 holds. And when the value of N. is positive, the rotation in the same direction as that of the input rotation is output, while, when the value is negative, the rotation in the reverse direction to the input rotation is output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internally meshing planetary gear structure, and more particularly to an internally meshing planetary gear structure utilizing a differential action (a concept including sum operation is the same except for the above).

[0002]

2. Description of the Related Art Conventionally, for example, in Japanese Unexamined Patent Publication No. 3-272348, there has been proposed a speed reducer adopting an internally meshing planetary gear structure as shown in FIG.

In this speed reducer, all the members are made of plastic, and the rotation of the input shaft 1 is taken out as the decelerated rotation of the output shaft 8 (pinion gear 9).

An eccentric body 2 is integrally formed with the input shaft 1, and an external gear 3 is rotatably supported on the eccentric body 2.

The external gear 3 is integrally provided with external teeth 3a having a trochoidal tooth shape on the outer periphery thereof, and a plurality of cylindrical inner pins 3b are integrally formed on the circumference coaxial with the input shaft 1 so as to project therefrom. .

The external gear 3a of the external gear 3 is included in the internal gear 4.
The circular arc tooth profile 4a that meshes with the inner side is integrally formed.
This internal gear 4 also serves as the main casing,
Therefore, the speed reducer is in a fixed state.

A disk-shaped flange portion 8 is provided at the end of the output shaft 8.
d is integrally formed. This flange part 8d has
An inner pin hole 8a is formed in which the inner pin 3b is loosely fitted.

The output shaft 8 is supported by the support portion 7a of the support cover 7, and the input shaft 1 is rotatably supported in a bearing hole 8c formed at the end of the output shaft 8. Further, a pinion gear 9 is provided on the opposite shaft end of the output shaft 8 from the output shaft 8.
It is assembled to the rotation fixing and the pull-out fixing.

Next, the operation of this speed reducer will be briefly described. When the input shaft 1 makes one revolution, the eccentric body 2 makes one revolution.
The external gear 3 tries to oscillate around the input shaft 1 by one rotation of the eccentric body 2. However, since the rotation of the external gear 3 is restricted by the internal gear 4, the external gear 3 is rotated by the internal gear 4. Almost only swinging is performed while inscribed in the tooth gear 4.

Now, for example, when the number of teeth of the external gear 3 is N and the number of teeth of the internal gear 4 is N + 1, the difference in the number of teeth is 1. Therefore, each time the input shaft 1 rotates once, the external gear 3 is displaced (rotated) by one tooth with respect to the (fixed) internal gear 4. This means that the rotation of the input shaft 1 is reduced to -1 / N rotation of the external gear 3 (minus indicates reverse rotation).

The rotation component of the external gear 3 is absorbed by the swinging component of the inner pin 3b and the inner pin hole 8a, and only the rotation component is transmitted to the output shaft 8 through the inner pin 3a. As a result, a reduction ratio of -1 / N is eventually achieved.

The rotation of the output shaft 8 is transmitted to a pinion gear 9 fixed to the shaft end portion of the output shaft 8. The pinion gear 9 meshes with the gear W of the mating machine to transmit the output to the mating machine.

The internally meshing planetary gear structure shown in FIG. 7 can secure a relatively large reduction ratio under the condition that the input shaft 1 and the output shaft 8 are coaxial, but the external gear rotates eccentrically. Therefore, there is a problem that vibration is likely to occur during operation due to unbalance of rotation.

Therefore, as shown in FIG. 8, many proposals have been made to incorporate a pair of external gears 3, 3 whose phases in the eccentric direction are shifted by 180 °. If the eccentric phase of the pair of external gears 3, 3 deviates by 180 ° with respect to the input shaft 1 as described above, the rotational balance as a whole is secured and vibration during operation is considerably suppressed. be able to.

By the way, in the speed reducer shown in FIG. 7 or FIG. 8, it is not possible to increase the speed reduction ratio indefinitely from the practicality of the size (module) of the gear. When the outer diameter of the reducer is 60 mm,
The upper limit is approximately a reduction ratio of around 80.

On the other hand, in order to establish a higher reduction ratio (for example, a reduction ratio of several hundreds or more), the above-described inscribed meshing planetary gear structures A and B are stacked in two stages (FIG. 9).
(See) or a differential type has been proposed.

FIG. 10 shows a differential type planetary gear structure disclosed in Japanese Utility Model Laid-Open No. 4-1111947. In this structure, the eccentric direction (phase difference of the crank portion 14) of the external gears 11 and 12 with respect to the input shaft 13 is set to 180 °,
One external gear 11 is meshed with an internal gear 16 fixed to a casing 15, and the other external gear 12 is used as an internal gear 19 formed on a peripheral portion of a disc 18 integrated with an output shaft 17. The external gears 11 and 12 are connected to each other by a crank-shaped inner pin 20 so as to be meshed with each other.

According to this structure, a reduction ratio of several hundreds or more can be obtained by the differential of the external gears 11 and 12 and the internal gears 16 and 19.

[0019]

However, in the differential type internally meshing planetary gear structure according to this prior art,
The following defects still remained.

1) The crank-shaped inner pin 20 is required as a separate component (three in the disclosed text), and the number of components increases accordingly.

2) If the assembling error when actually assembling each crank-shaped inner pin 20 is not within a predetermined value, a smooth differential cannot be drawn out, resulting in a decrease in efficiency and noise. Will become larger. Therefore, each is manufactured with high dimensional accuracy, and high quality control is required, resulting in an increase in cost.

3) Each crank-shaped inner pin 20 receives the load from both external gears 11 and 12 as a couple during operation and also rotates on its own axis in synchronism with the rotation of the input shaft crank portion 14. In order to suppress the torque and obtain smooth differential rotation, the bearings 21 and 22 are required to have appropriate accuracy and strength, and appropriate measures are required to maintain the initial assembly performance for a long period of time. Becomes Therefore, also in this aspect, the cost or weight is increased.

The present invention has been made in view of such conventional problems, and on the premise of obtaining a high reduction gear ratio, it is possible to reduce the size, weight, cost and noise as much as possible.
Alternatively, it is an object of the invention to provide a differential type internally meshing planetary gear structure capable of achieving low vibration and the like.

[0024]

According to the first aspect of the present invention, a casing, an input shaft and an output shaft rotatably supported by the casing, and a phase difference of 180 ° between the input shaft and the input shaft are provided. First and second eccentric bodies fixed side by side in the axial direction, and a plurality of first eccentric bodies rotatably provided on the outer circumferences of the first and second eccentric bodies and penetrating themselves in the axial direction,
First and second external gears each having a second internal pin hole,
While being rotatably supported by the casing, the first,
First and second internal gears that are intermeshingly meshed with the second external gear and integrated with each other, and projecting from the casing and loosely fitted in the first internal pin holes of the first external gear; A first internal pin that restrains the rotation of the first external gear and allows the oscillation of the first external gear caused by the rotation of the first eccentric body; and a second external gear that projects from the output shaft. And a second inner pin that loosely fits into the second inner pin hole and absorbs the swing component of the second outer gear while transmitting only the rotation component of the second outer gear to the output shaft. The above object is achieved.

In the second invention, the casing, the input shaft and the output shaft rotatably supported by the casing, and the input shaft are arranged in the axial direction with a phase difference of 180 °. A fixed first and second eccentric body, and a first and second eccentric body each having a plurality of first and second inner pins rotatably provided on the outer periphery of the first and second eccentric bodies and projecting in the axial direction. First and second externally toothed gears, which are rotatably supported by a casing, are inwardly meshed with the first and second externally toothed gears, respectively, and are integrated with each other. A casing formed to engage with the first inner pin of the first external gear with play, restrain the rotation of the first external gear, and generate the first external member by rotation of the first eccentric body. A first inner pin hole that allows the tooth gear to swing and a shaft formed on the output shaft A second internal gear which engages with the second internal pin of the two external gear with play and absorbs the swing component of the second external gear while transmitting only the rotation component of the second external gear to the output shaft. By providing the pin hole, the above-mentioned object is also achieved.

In the third aspect of the invention, the casing, the input shaft and the output shaft rotatably supported by the casing, and the input shaft are arranged in the axial direction with a phase difference of 180 °. Fixed first and second eccentric bodies, and a first externally toothed gear rotatably provided on the outer periphery of the first eccentric body and having a plurality of first internal pin holes penetrating itself in the axial direction,
While being rotatably provided on the outer periphery of the second eccentric body,
A second external gear having a plurality of second internal pins protruding in the axial direction, and a second external gear that is rotatably supported by the casing and internally meshes with the first and second external gears and is integral with each other. The first and second internal gears that are made into a single piece, and project from the casing and are loosely fitted in the first internal pin holes of the first external gear,
A first for restraining the rotation of the external gear and allowing the swing of the first external gear caused by the rotation of the first eccentric body.
The inner pin engages with the second inner pin of the second external gear, which is formed on the output shaft, with play, and absorbs the swing component of the second external gear while rotating the second external gear. By having the second inner pin hole that transmits only the component to the output shaft,
Similarly, the above-mentioned object is achieved.

In the fourth invention, the casing, the input shaft and the output shaft rotatably supported by the casing, and the input shaft are arranged in the axial direction with a phase difference of 180 °. A fixed first and second eccentric body, a first external gear provided rotatably on the outer periphery of the first eccentric body, and having a plurality of first inner pins protruding in the axial direction; A second external gear that is rotatably provided on the outer circumference of the eccentric body and has a plurality of second internal pin holes that penetrate the eccentric body in the axial direction; , First and second internal gears respectively internally meshed with the second external gear and integrated with each other, and engaged with the first internal pin of the first external gear formed in the casing with play. The rotation of the first external gear and restrain the rotation of the first eccentric body. A first inner pin hole to allow the swinging of the first external gear caused I, the projects from the output shaft 2
A second inner pin that is loosely fitted in the second inner pin hole of the external gear and that transmits only the rotation component of the second external gear to the output shaft while absorbing the swing component of the second external gear. By providing the same, the above-mentioned object is also achieved.

[0028]

In the first aspect of the present invention, one of the two external gears (the first external gear) is constrained from rotating by the first inner pin protruding from the casing and is allowed to swing only. I chose The other external gear (second external gear) absorbs the swing of the second external gear by the second internal pin protruding from the output shaft side, and only its rotation component is transmitted to the output shaft. I was able to communicate.

Then, both external gears were internally meshed with the integrated internal gears, and the internal gears were rotatably supported by the casing. As a result, the output shaft can obtain a reduction ratio of −several tens to ∞ to + several tens with respect to the positive rotation of the input shaft. Here, “−” indicates reverse rotation with respect to input rotation, and “+” indicates forward rotation. In addition, the fact that the reduction ratio can be set to infinity means that the output shaft rotational speed can be zero regardless of the input shaft rotational speed.

In the second to fourth inventions, the members forming the first and second inner pins and the first and second inner pin holes are replaced with each other, and the same effect as in the first invention can be obtained. .

According to the structure of the present invention, the two external gears are oscillated and rotated by shifting the phase by 180 °.
Dynamic balance can be achieved and vibration generation during operation can be suppressed.

Further, since the crank-shaped inner pin or the like is not required, the manufacturing cost can be reduced, the size can be reduced, or the noise can be easily reduced.

Further, since the conventional structure in which the crank-shaped inner pin portion receives a couple of forces during operation is improved, it is possible to maintain the rigidity much more easily than the conventional structure.

[0034]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIGS. 1 and 2 show a differential internal gearing planetary gear structure according to the present invention applied to a plastic internal gearing planetary gear reducer. Further, FIG. 3 is a skeleton diagram of the speed reducer shown in FIGS. 1 and 2, focusing on the power transmission system thereof, and FIG. 4 is a matrix of obtained reduction ratios.

In this embodiment, the rotation of the input shaft 102 is taken out as the decelerated rotation of the output shaft 104.

The input shaft 102 made of plastic is integrally molded with the first and second eccentric bodies 106 and 108, and their eccentric directions (phases) are deviated by 180 ° (that is, opposite directions). The first and second eccentric bodies 106 and 108
In the illustrated example, is directly formed integrally with the input shaft 102, but it may be formed as a separate body and later assembled to be integrated.

The first and second external gears 110 and 112 are also made of plastic and are rotatably assembled to the outer circumferences of the first and second eccentric bodies 106 and 108, respectively. This first,
The second external gears 110 and 112 have trochoidal external teeth 110a and 112a on the outer circumference thereof. Further, each of the first and second external gears 110, 112 has a plurality of first and second inner pin holes 111, 113 penetrating in the axial direction.
Is provided.

The first and second external teeth 110a and 112a of the first and second external gears 110 and 112 are the first and second internal teeth (arcs) of the plastic first and second internal gears 114 and 116, respectively. (Tooth profile) 114a, 116a are intermeshed with each other.
The first and second internal gears 114, 116 are rotatable in a guide portion 118b formed inside a first casing 118 (in the illustrated example, integrally formed from the beginning) while being integrated with each other. Supported by.

A hole 108a for rotatably supporting the input shaft 102 and a guide portion 108b (described above) for rotatably supporting the first and second internal gears 114 and 116 are provided on the inner periphery of the first casing 118. And a first inner pin 122 that is inserted into the first inner pin hole 111 of the first external gear 110 is integrally formed to project.

In the second casing 120, the output shaft 104
A hole 120a for rotatably supporting is formed. The first casing 118 and the second casing 120 are concentrically fitted and integrated with each other.

The output shaft 104 is also made of plastic. The output shaft 104 is provided with a center port 104a for rotatably supporting the input shaft 102, and a second inner pin 124 inserted into the second inner pin hole 113 of the second external gear 112 is integrated. Are formed so as to protrude. This output shaft 1
04 is rotatably supported by the second casing 120.

The operation of this embodiment will be described below with reference to the skeleton diagram of FIG.

In FIG. 3, the first external gear 110 and the second external gear 110
Since the external gear 112 swings (eccentrically) rotates in the directions opposite to each other with respect to the center of the input shaft 102, the dynamic imbalance caused by each swing rotation is canceled.

Since it does not have a crank-shaped inner pin,
The number of parts is so small, and there is no concern about the occurrence of defects in this part.

Regarding the reduction ratio, if the rotation speed of the input shaft 102 is N1 and the rotation speed of the output shaft 104 is N2, then N
2 = 1-{(S2.P1) / (S1.P2)} N1.

Here, P1 and P2 are the first and the second, respectively.
The numbers of teeth of the external gears 110 and 112, and S1 and S2 indicate the numbers of teeth of the first and second internal gears 114 and 116, respectively. If the value of N2 is positive, the rotation in the same direction as the input rotation is output, and if the value of N2 is negative, the rotation in the opposite direction to the input rotation is output.

As is clear from the above equation, when the first system and the second system have the same number of teeth, the reduction ratio becomes infinite and the output rotation becomes zero.

Here, the relationship in which the input rotation is decelerated to the output rotation will be described using specific numbers. The deceleration is performed at the same time by the overall movement of each part, but for convenience, it will be described by dividing it into parts.

Now, the number of teeth of each gear is P1 = 29, P2
= 30, S1 = 30, S2 = 31. Input shaft 102
1 makes one rotation, the first external gear 110, whose rotation is restricted by the first inner pin 122 formed in the first casing 118, makes one swing rotation. As a result, the first internal gear 114 that meshes with the first external gear 110 becomes (S1−
P1) / S1, ie, 1/30 rotation, rotates in the same direction as the input shaft 102.

On the other hand, assuming that the second internal gear 116 does not rotate on its own axis, when the input shaft 102 is rotated once, the second external gear 112 (as in the first system) has a-(S2-P2).
/ P2, i.e., -1/30 rotation, rotates in the direction opposite to the input shaft 102. However, in reality, the second internal gear 116 is integrated with the first internal gear 114,
Only 1/30 rotation rotates in the same direction as the input shaft 102. Therefore, the rotational speed of the input shaft 102 with respect to the meshing of the gears of the second system is 1-1 / 30 rotation, and the actual second external gear 112 is-(1/30) × (1-1 / 1). 30),
That is, -1 / 31.0348277 ... Rotates only in the opposite direction to the input shaft.

As a result, the final output rotational speed is the sum (or difference) of the rotational speeds of the first internal gear 114 and the second external gear 112.
1 / 30-1 / 31.034448277 ... = 1/9
00 rotations is the number of rotations on the output shaft for one rotation of the input shaft 102. This is nothing but achieving a reduction ratio of 900.

With respect to the reduction ratio, the smaller the difference in the number of teeth between the first external gear 110 and the second external gear 112 is, the larger the reduction ratio is obtained (in the above calculation example, the difference in the number of external teeth and internal teeth is obtained). = 1 is the maximum reduction ratio).

When the difference in the number of teeth between the external gear and the internal gear is 1, that is, P + 1 = S, the number of gear teeth (P1, P
Fig. 4 shows a calculation example of the combination of 2) and the obtained reduction ratio.
Note that all the slashes show that the reduction ratio is infinite (∞) and the output rotation is zero regardless of the input rotation. A major feature of this speed reducer is that various reduction ratios can be obtained with the same outer diameter size by only slightly changing the number of teeth of each gear.

Next, FIG. 5 shows an embodiment of a differential type internally meshing planetary gear reducer in which a small DC motor is directly connected.

In this embodiment, the motor shaft (corresponding to the input shaft)
The rotation of 202 is taken out as the decelerated rotation of the output shaft 204. The small DC motor 200 includes the first casing 21.
8 is assembled concentrically and rotationally fixed by a motor coupling screw 232. A first eccentric body 206 and a second eccentric body 208 made of plastic are integrated with the motor shaft 202 by press fitting (or known D-cut coupling).

The eccentric directions of the first and second eccentric bodies 206 and 208 are deviated from each other by 180 ° (in opposite directions). First,
Although the second eccentric bodies 206 and 208 are integrated from the beginning in the illustrated example, they may be formed separately and then integrated. The first and second casings 218 and 220 are
The outer diameter is set to be substantially the same as the outer diameter of the DC small motor 200, and as a result, it can be delivered to the user as if it were a single ultra-low speed DC small motor.
Since other configurations are the same as those of the first embodiment, the same or similar parts are denoted by the same last two digits in the drawings, and duplicated description will be omitted.

Although each member of the speed reducer is made of plastic in the above embodiment, the material of each member is not necessarily limited to plastic in the present invention.

In the first and second embodiments, the first inner pin holes 111, 211 are provided on the first external gear 110, 210 side.
To the first casing 118, 218 in the first inner pin 12
2 and 222 are provided respectively, the first inner pin 122 and 222 and the first inner pin hole 111 and 211 are provided.
Even if they are formed so as to be replaced with each other on the mating member side, the same effect as the above description can be obtained (FIG. 6 (a)).

Similarly, the second inner pins 124, 224 and the second inner pins 124, 224
Even if the inner pin holes 113 and 213 are formed so as to be exchanged with each other on the mating member side, the same effect as the above description can be obtained (FIG. 6 (b)).

[0061]

As described above, according to the present invention,
The structure is simple, a large reduction ratio can be obtained with a small number of parts, and by combining the number of gear teeth, various reduction ratios can be obtained even with the same outer diameter dimension. can get.

The eccentric direction of the two external gears is 180 °
Because they are displaced, the internal load during operation is balanced,
The generation of vibration can be suppressed.

Furthermore, since there is no crank-shaped inner pin required for manufacturing precision or assembling precision, the cost can be reduced accordingly, and there is no fear of damage or noise generation at this portion, and even The load on the crank bearing portion due to the force action is not increased.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of a speed reducer to which a differential type internally meshing planetary gear structure according to the present invention is applied.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a skeleton diagram focusing on the power transmission system of the above embodiment.

FIG. 4 is a diagram showing an example of a reduction ratio obtained when the number of teeth of each gear is changed in the above embodiment.

FIG. 5 is a differential internal meshing planetary gear structure D according to the present invention.
Sectional drawing which shows the Example applied to the output part of C small motor

FIG. 6 is a first inner pin and a first inner pin hole, and a second inner pin and a second inner pin.
Partial enlarged view showing the state in which the inner pin holes are replaced

FIG. 7 is a cross-sectional view showing an example of a speed reducer to which a conventional internally meshing planetary gear structure is applied.

8 is a skeleton diagram showing an example in which two external gears are used in the structure shown in FIG.

9 is a skeleton diagram showing a configuration in which the structure of FIG. 8 is stacked in two stages to obtain a large reduction ratio.

FIG. 10 is a skeleton diagram showing an example of an internally meshing planetary gear structure of a differential type for obtaining a large reduction ratio.

[Explanation of symbols]

 102, 202 ... Input shafts 104, 204 ... Output shafts 106, 206 ... First eccentric bodies 108, 208 ... Second eccentric bodies 110, 210 ... First external gears 111, 211 ... First inner pin holes 112, 212 ... 2nd external gear 113, 213 ... 2nd internal pin hole 114, 214 ... 1st internal gear 116, 216 ... 2nd internal gear 118, 218 ... 1st casing 120, 220 ... 2nd casing 122, 222 ... First inner pin 124, 224 ... Second inner pin

[Procedure amendment]

[Submission date] March 29, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction content]

Regarding the reduction ratio, if the rotation speed of the input shaft 102 is N1 and the rotation speed of the output shaft 104 is N2, then N
2 = {1- (S2.P1) / (S1.P2)} N1.

Claims (4)

[Claims] 1. A casing, an input shaft and an output shaft rotatably supported with respect to the casing, and a first fixed to the input shaft side by side in the axial direction with a phase difference of 180 °. A second eccentric body, and a plurality of first and second eccentric bodies rotatably provided on the outer circumferences of the first and second eccentric bodies and axially penetrating themselves.
First and second externally toothed gears each having an inner pin hole, and rotatably supported by the casing, and
First and second internal gears that are internally meshed with the second external gear and integrated with each other, and projecting from the casing and loosely fitted in the first internal pin holes of the first external gear, A first internal pin that restrains the rotation of the first external gear and also allows the first external gear to swing due to the rotation of the first eccentric body; and a second external gear that projects from the output shaft. A second inner pin that is loosely fitted in the second inner pin hole and transmits only the rotation component of the second outer tooth gear to the output shaft while absorbing the swing component of the second outer tooth gear. Differential type internally meshing planetary gear structure. 2. A casing, an input shaft and an output shaft rotatably supported with respect to the casing, and a first fixed to the input shaft side by side in the axial direction with a phase difference of 180 °. A second eccentric body, and first and second external teeth rotatably provided on the outer circumferences of the first and second eccentric bodies and respectively having a plurality of first and second inner pins protruding in the axial direction. The gear is rotatably supported by the casing, and the first,
First and second internal gears that are internally meshed with the second external gear and integrated with each other, and are formed in a casing and engage with the first internal pin of the first external gear with play. A first internal pin hole that restrains the rotation of the first external gear and allows the swing of the first external gear caused by the rotation of the first eccentric body; and a first internal pin hole formed in the output shaft. A second internal gear which engages with the second internal pin of the two external gear with play and absorbs the swing component of the second external gear while transmitting only the rotation component of the second external gear to the output shaft. A differential type internally meshing planetary gear structure characterized by comprising pin holes. 3. A casing, an input shaft and an output shaft rotatably supported with respect to the casing, and a first fixed to the input shaft aligned in the axial direction with a phase difference of 180 °. A second eccentric body, and a first eccentric body rotatably provided on the outer periphery of the first eccentric body and having a plurality of first inner pin holes penetrating itself in the axial direction.
An external gear, and rotatably provided on the outer periphery of the second eccentric body,
A second external gear having a plurality of second internal pins protruding in the axial direction; rotatably supported by a casing;
First and second internal gears that are internally meshed with the second external gear and integrated with each other, and projecting from the casing and loosely fitted in the first internal pin holes of the first external gear, A first internal pin that restrains the rotation of the first external gear and that allows the first external gear to swing due to the rotation of the first eccentric body; and a second external gear formed on the output shaft. A second inner pin hole that engages with the second inner pin with play and absorbs the swing component of the second outer gear and transmits only the rotation component of the second outer gear to the output shaft; A differential type internally meshing planetary gear structure characterized by being provided. 4. A casing, an input shaft and an output shaft rotatably supported with respect to the casing, and a first fixed to the input shaft arranged side by side in the axial direction with a phase difference of 180 °. A second eccentric body, a first external gear provided rotatably on the outer periphery of the first eccentric body and having a plurality of first inner pins protruding in the axial direction, and an outer periphery of the second eccentric body. It is provided rotatably,
A second external gear having a plurality of second internal pin holes penetrating itself in the axial direction; and a first external gear that is rotatably supported by the casing and
First and second internal gears that are internally meshed with the second external gear and integrated with each other, and engage with the first internal pin of the first external gear with play, with play. A first internal pin hole that restrains the rotation of the first external gear and allows the swing of the first external gear caused by the rotation of the first eccentric body; A second inner pin that is loosely fitted in the second inner pin hole of the external gear and that transmits only the rotation component of the second external gear to the output shaft while absorbing the swing component of the second external gear; A differential type internally meshing planetary gear structure characterized by being provided.