JPH06307505A - Differential plant gear transmission - Google Patents

Abstract

PURPOSE:To provide a short and compact gear transmission with a small number of parts. CONSTITUTION:This transmission is provided with a sun gear 21 or a planet ear carrier 25 directly connected to a drive source, one ball bearing 43 installed between the inner periphery of housings 13, 15, 17 and the outer periphery of the planet gear carrier 25, a fixed inner gear 14 meshed with one side of a planet gear 23 formed in the inner periphery of the housing, a rotary inner gear 27 meshed with the other side of the planet gear 23 and having a number of teeth different from that of the fixed inner gear 14, an output shaft 29 formed on the side surface of the rotary inner gear 27 and a cross roller bearing 45 installed between the inner periphery of the housings 13, 15, 17 and the rotary inner gear 27 and the output shaft 29.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential planetary gear speed reducer which is compact and lightweight and has high rotational position accuracy.

[0002]

2. Description of the Related Art Generally, for driving a joint of a robot or the like,
A motor that is a drive source and a speed reducer that converts the rotation of the motor into a large torque are used. Although there are various types of this speed reducer, a differential planetary gear device is assumed to be able to withstand a relatively large load. It has been known.

FIG. 4 is a side sectional view showing such a conventional differential planetary gear device. This differential planetary gear device 100
Rotates the input shaft 101 to rotate the sun gear 103, and, for example, three planetary gears 107 that are equally arranged so that the rotation of the sun gear 103 meshes with both the sun gear 103 and the fixed internal gear 105. It is of a type that revolves around the sun gear 103 while rotating.

Then, each planetary gear 107 is fixed to the fixed internal gear 1
In addition to No. 05, the fixed internal gear 105 is meshed with the rotating internal gear 109 having a slight difference in the number of teeth, and the rotating internal gear 109 rotates the output shaft 111.
Therefore, when each planetary gear 107 revolves around the sun gear 103 while rotating, the rotating internal gear 109 rotates in accordance with the difference in the number of teeth from the fixed internal gear 105, and as a result, the rotating internal gear 109 becomes integrated with the rotating internal gear 109. The output shaft 111 is the input shaft 10
The motor rotates at a reduced speed with respect to one rotation speed.

Incidentally, such a differential planetary gear device 1
In general, as shown in FIG. 5, the fixed internal gear 105 having different numbers of teeth is different from the planetary gear 107.
Since it is necessary to make the rotating internal gear 109 and the rotating internal gear 109 concentric with each other and accurately mesh with each other, the internal gear having the smaller number of teeth, for example, the fixed internal gear 105 is designed to have a large dislocation coefficient. The diameter of the addendum circle 105a of the fixed internal gear 105 and the diameter of the addendum circle 109a of the rotating internal gear 109 (both D _kd ) are respectively obtained from the following equations.

D _kd = {Z _b −2 + 2 (X _b + y)} m (1) However, Z _d ··· The number of teeth of the internal gear X _b ··· The dislocation coefficient y of the planetary gear y ··· Center distance increase factor m ··· Internal gear module As a result, the diameter of the tip circle 105a of the fixed internal gear 105 and the diameter of the tip circle 109a of the rotating internal gear 109 are designed to be equal in size. Has been done. Furthermore, both internal gears 105,
Since the plurality of planetary gears 107 that mesh with the gears 109 are integrated by common gear specifications, both internal gears 105,
The diameters of the addendum circles 107a in the portions that engage with the 109 are all equal.

In such a differential planetary gear device 100,
A large reduction ratio is obtained by the differential according to the difference in the number of teeth of the internal gears 105 and 109, and the internal gears 10 of both
Since the planetary gear 107 that meshes with the gears 5 and 109 is common and integrated as described above, the planetary gear 107 is less deformed, and an output can be obtained directly from the internal rotating gear 109, so that the torsional rigidity is increased. There is. And the above common
Due to the direct output from the integrated planetary gear 107 and the rotating internal gear 109, the differential planetary gear device 100 has a small number of parts and is characterized by being a small and lightweight reducer.

[0008]

As described above, in order to drive the joints of a robot or the like, a drive source that is small and lightweight and has high rotational position accuracy is required, and the example of the prior art was also considered for this purpose. However, the overall length is still long, compactness is not sufficient for driving the end joints of robots, etc., and there are many parts that make up the function.

It is an object of the present invention to provide a gear reduction device having a compact structure, a short overall length, and a small number of parts.

[0010]

A sun gear connected to a drive source, a planet gear supported by a planet gear carrier surrounding the sun gear and meshing with the sun gear, an inner circumference of a housing and an outer circumference of the planet gear carrier. 1 placed between and
Individual rotary bearings, a fixed internal gear that is formed on the inner circumference of the housing and meshes with one side of the planetary gear, and a rotating internal gear that meshes with the other side of the planetary gear and that has a different number of teeth from the fixed internal gear, A differential planetary gear reduction device is constituted by an output shaft formed on the side surface of the rotating internal gear and one cross roller bearing arranged between the inner circumference of the housing and the rotating internal gear and the output shaft. .

Alternatively, in the above gear reduction device,
Remove the sun gear and connect the planet gear carrier directly to the drive source on the input side.

[0012]

The mechanism of power transmission and speed reduction of this differential planetary gear reduction device is the same as that of the above-mentioned prior art. When the sun gear directly connected to the drive source rotates, each planetary gear that meshes with this sun gear also meshes with the internal gear fixed to the housing, revolves around the sun gear while rotating, and the internal gear on the output side The output shaft, which rotates in accordance with the difference in the number of teeth from the fixed internal gear, is integrated with the rotating internal gear, and rotates at a reduced speed with respect to the rotational speed of the input shaft.

Further, in the above-described gear reduction device, even if the planetary gear carrier is directly connected to the drive shaft of the drive motor without passing through the sun gear, each planetary gear meshes with the internal gear fixed to the housing and rotates. The internal gear on the output side revolves and rotates according to the number of teeth difference from the fixed internal gear. In this case, the revolution speed of the planetary gears becomes faster than when the sun gear is present, so a device having a reduction ratio larger than the former is obtained.

The sun gear or the planetary gear carrier is directly connected to a drive source, the planetary gear carrier is supported by one rotary bearing on the outer circumference of a large-diameter flange portion that supports the planetary gear, and the output-side internal gear is one. Since it is supported by the individual cross roller bearings, the axial length of the gear reduction device can be sufficiently shortened by only the size for accommodating the gear mechanism.

[0015]

【Example】

First Embodiment A first embodiment of the present invention will be described with reference to the side sectional views shown in FIGS. A sun gear 21 is fixedly mounted on the drive shaft 11a of the motor 11, and a planetary gear carrier 25 surrounding the sun gear 21 is supported on the inner circumference of the housing 13 coaxially with the sun gear 21 via a ball bearing 43. There is. The planetary gear carrier 25 has a plurality of planetary gear shafts 33.
Are equidistantly arranged on the same circumference and fixed by a seat plate 39 and bolts 41, and the plurality of planetary gears 2 are attached to the planetary gear shaft 33.
3 is supported via a needle bearing 37 so as to freely rotate, and meshes with the sun gear 21 (the number of teeth Z _A ). The plurality of planetary gears 23 are two internal gears that are coaxial and have different numbers of teeth, that is, a fixed internal gear 14 (the number of teeth _Zc ) formed on the inner circumference of the housing 13, and a rotating internal gear 27.
(The number of teeth Z _D ) is meshing at the same time.

Since it is necessary to precisely mesh the same planetary gear 23 with the fixed gear 14 and the rotating internal gear 27 having different numbers of teeth by making them coaxial with each other, the internal gear having the smaller number of teeth, for example, The fixed internal gear 14 has a large dislocation coefficient, and the diameter of the tip circle of the fixed internal gear 14 and the diameter of the tip circle of the rotary internal gear 27 are designed to be equal. The fixed internal gear 14 forms a part of the housing 13, and the housing 13 and the housing 1 are integrally connected by bolts.
5 and the housing 17 constitute the entire housing. A cross roller bearing 45 is fixed by the housing 15 and the housing 17, and the cross roller bearing 45 rotatably supports the output shaft 29. As shown in FIG. 2 (enlarged view of portion A in FIG. 1), the rotating internal gear 27 is welded to the output shaft 29 so as to be integrated with each other by electron beam welding (which hardly causes processing distortion). Output shaft 29
The pin 31 rotates the rotary shaft 3 of the driven machine such as a robot.
3 and the entire reduction gear is attached to the frame 19 of the driven machine at the flange of the housing 17.

When the sun gear 21 (the number of teeth Z _A ) directly connected to the drive shaft of the drive motor 11 rotates, each planet gear 23 becomes
The sun gear 21 meshes with the fixed internal gear 14 and rotates.
Revolving around, the output side internal gear 27 (the number of teeth Z _D )
The output shaft 29 that rotates in accordance with the tooth number difference with the fixed internal gear 14 (the number of teeth Z _c ) fixed to the housing 13 and as a result, the output shaft 29 that is integrated with the rotating internal gear 27 of the sun gear 21 on the input side is It rotates at a reduced speed relative to the rotation speed.

[0018] The reduction ratio is R, the _{R = (1-Z D /} Z c) / (1 + Z A / Z D). The sun gear 21 is directly connected to the drive shaft 11a of the drive motor 11, and the planetary gear carrier 25 is supported by one ball bearing 43 on the outer periphery of the flange portion that supports the planetary gear 37.
Further, since the rotary internal gear 27 integrated with the output shaft 29 is supported by one cross roller bearing 45, the axial length of the gear reduction device is short enough to accommodate the gear mechanism. There is.

On the input side, the drive motor 11 is directly attached to the housing 13, which is a part of the entire housing, and on the output side, the housing 17 is directly connected to the driven machine frame 19. The device is mounted very compactly on a driven machine such as a robot. Second Embodiment A second embodiment of the present invention will be described with reference to the side sectional view of FIG.

In the second embodiment, in the differential planetary gear speed reducer described in the first embodiment, the sun gear 21 is removed and the planetary gear carrier 25 surrounding the sun gear 21 is replaced with a motor serving as a drive source. 11, a planetary gear carrier 51 directly connected to the drive shaft 11a of 11 is provided. That is,
The shaft portion of the planetary gear carrier 51 is directly connected to the drive shaft 11a of the motor 11, the rotation of the motor 11 is directly the revolution of the planetary gear 23, and the planetary gear 23 is meshed with the fixed internal gear 14 and is rotated at the same time. Rotating internal gear 27
The rotation is output by rotating by the difference in the number of teeth of both internal gears.

In the apparatus of the second embodiment, the planetary gear carrier 51 is directly connected to the drive shaft 11a of the motor 11 without passing through the number of sun teeth, and the differential gear mechanism is established. In this case, the first gear is used. A device having a reduction ratio larger than that of the embodiment is obtained. If the number of teeth of the fixed internal gear 14 is Z _{c and the} number of teeth of the rotary internal gear 27 is Z _D reduction ratio R ′, then R ′ = 1−Z _D / Z _c .

[0022]

The differential planetary gear reduction device according to the present invention comprises:
A sun gear or planetary gear carrier directly connected to the drive source,
One ball bearing arranged between the inner circumference of the housing and the outer circumference of the planetary gear carrier, a fixed internal gear formed on the inner circumference of the housing and meshing with one side of the planetary gear, and the other side of the planetary gear. A rotary internal gear that meshes with the fixed internal gear and has a number of teeth different from that of the fixed internal gear, an output shaft formed on a side surface of the rotary internal gear, and an inner peripheral surface of the housing and the rotary internal gear and the output shaft. Having the individual cross roller bearings has the following effects.

Since the axial length of the gear reduction device can be accommodated only by the size for accommodating the gear mechanism, the length is shortened. Further, since the number of functional parts is small, it is possible to make the device lightweight and compact, and it is easy to improve the processing accuracy. Therefore, it is an optimum drive source to be attached to a joint of a robot or the like. Since the presence or absence of the sun gear can be selected, the range of reduction ratio can be widened in the device having the same shape and size.

[Brief description of drawings]

FIG. 1 is a side sectional view of a differential planetary gear speed reducer according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of part A in FIG.

FIG. 3 is a side sectional view of a differential planetary gear speed reducer according to a second embodiment of the present invention.

FIG. 4 is a side sectional view of a conventional differential planetary gear reduction device.

5 is an enlarged view showing a meshing portion between a planetary gear and a fixed internal gear and a rotary internal gear in FIG.

[Explanation of symbols]

 11a Drive shaft 13 Housing 15 Housing 17 Housing 14 Fixed internal gear 27 Rotating internal gear 21 Sun gear 23 Planetary gear 25 Planetary gear carrier 29 Output shaft 43 Ball bearing 45 Cross roller bearing

Claims (2)

[Claims] 1. A sun gear connected to a drive source, a planetary gear supported by a planetary gear carrier surrounding the sun gear and meshing with the sun gear, and between an inner circumference of the housing and an outer circumference of the planetary gear carrier. One rotary bearing arranged, a fixed internal gear formed on the inner circumference of the housing and meshing with one side of the planetary gear, and a rotation that meshes with the other one side of the planetary gear and has a different number of teeth from the fixed internal gear. An internal gear, an output shaft formed on a side surface of the rotary internal gear, and one cross roller bearing arranged between an inner circumference of the housing and the rotary internal gear and the output shaft. Differential planetary gear reducer. 2. A planetary gear carrier connected to a drive source for supporting a planetary gear, one rotary bearing arranged between the inner circumference of the housing and the outer circumference of the planetary gear carrier, and formed on the inner circumference of the housing. A fixed internal gear that meshes with one side of the planetary gear, a rotating internal gear that meshes with the other side of the planetary gear and has a different number of teeth from the fixed internal gear, and an output shaft formed on the side surface of the rotating internal gear. And a cross roller bearing arranged between the inner circumference of the housing and the rotary internal gear and the output shaft.