JP2010196860A - Reduction gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reduction gear capable of stabilizing the number of revolution of an output shaft and the output torque, obtaining a large reduction gear ratio. <P>SOLUTION: This reduction gear includes: a driving shaft 1 connected to a drive source so as to be rotated around the shaft center by drive of a drive source; an eccentric shaft 2 connected to the driving shaft at an eccentric position relative to the shaft center of the driving shaft so as to be rotated around the shaft center of the driving shaft with rotation of the driving shaft; a first external gear 3 rotatably provided in the eccentric shaft; a first internal gear 4 fixed at a predetermined position so as to be engaged with the first external gear; a second external gear 5 rotatably provided in the eccentric shaft and arranged in parallel with the first external gear in the shaft center direction of the eccentric shaft; a second internal gear 6 engaged with the second external gear; and an output shaft 7 connected to the second internal gear so as to be rotated around the same shaft center as the driving shaft. A difference of the number of teeth between the first external gear and the first internal gear and a difference of the number of teeth between the second external gear and the second internal gear are set equal to each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reduction gear.

In order to transmit the rotation of a drive source that rotates at a high speed to a device that rotates at a low speed, a speed reducer in which a plurality of gears are combined is used.
When a relatively large reduction ratio is required with respect to the rotational speed of a motor or the like that is a driving source, it is difficult to reduce the size if a plurality of reduction gears having a small reduction ratio are used. For this reason, a speed reduction device in which an external gear meshes with an internal gear is known as a speed reduction device capable of obtaining a large reduction ratio in one stage (see, for example, Patent Document 1).
In the reduction gear described in Patent Document 1, two eccentric shafts are provided on the rotating shaft, planetary gears are provided on the eccentric shafts, and the internal gears are provided so as to mesh with the planetary gears. A sliding hole is formed in the two planetary gears, a sliding pin of a rotating wheel is passed through the sliding hole, and an output shaft is provided on the rotating wheel.
With this configuration, when the planetary gear rotates once, the rotation angle advances by the difference in the number of teeth between the fixed internal gear and the two planetary gears, and the output shaft rotates by the difference in this rotation angle. And a large reduction ratio can be realized.

JP 2007-315581 A

  However, in Patent Document 1 described above, the output shaft rotates following the rotation of the planetary gear, and thus cannot rotate about the rotation axis and the coaxial axis. For this reason, there has been a problem that the rotational speed and output torque of the output shaft vary depending on the position of the planetary gear with respect to the internal gear, and the rotational speed and output torque of the output shaft are not stable. In addition, there has been a desire to obtain a large reduction ratio with a simple structure while solving such problems.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a speed reducer that can obtain a large speed reduction ratio and can stabilize the rotational speed and output torque of an output shaft.

The present invention is a reduction gear,
A drive shaft coupled to the drive source and rotated about an axis by the drive source;
An eccentric shaft coupled to the drive shaft at a position eccentric with respect to the axis of the drive shaft and rotating about the axis of the drive shaft together with the rotation of the drive shaft;
A first external gear rotatably provided on the eccentric shaft;
A first internal gear fixed to a predetermined position and meshing with the first external gear;
A second external gear provided rotatably on the eccentric shaft, and arranged so as to be aligned in the axial direction of the first external gear and the eccentric shaft;
A second internal gear meshing with the second external gear;
An output shaft connected to the second internal gear and rotating about the same axis as the drive shaft;
The difference in the number of teeth between the first external gear and the first internal gear and the difference in the number of teeth between the second external gear and the second internal gear are made equal. And

  According to the present invention, a large reduction ratio can be obtained, and the rotational speed and output torque of the output shaft can be stabilized.

The disassembled perspective view of a reduction gear. The schematic diagram which looked at each gearwheel from the axial center direction in order to demonstrate the mechanism of the deceleration by a reduction gear. The schematic diagram which looked at each gear from the side orthogonal to an axial center, in order to demonstrate the mechanism of the deceleration by a reduction gear.

Hereinafter, embodiments of a speed reducer according to the present invention will be described. The reduction gear is provided so as to connect a drive source that rotates at high speed and a device that rotates at low speed in each device.
<Configuration of reduction gear>
As shown in FIG. 1, the speed reduction device 100 includes a drive shaft 1, an eccentric shaft 2, a first external gear 3, a first internal gear 4, a second external gear 5, Two internal gears 6 and an output shaft 7 are provided.
The drive shaft 1 is connected to a motor shaft of a motor that is a drive source, and rotates around the axis by driving the motor. A mounting base 10 for mounting the eccentric shaft 2 is provided at the tip of the drive shaft 1. The mounting base 10 is a plate material having a surface larger than the cross section orthogonal to the axial direction of the drive shaft 1, and the drive shaft 1 is attached to one surface.
The eccentric shaft 2 is attached to the other surface of the mounting base 10. The eccentric shaft 2 is provided on the mounting base 10 at a position where the shaft center is eccentric with respect to the axis of the drive shaft 1. As a result, when the drive shaft 1 rotates around the axis, the eccentric shaft 2 rotates in the same direction around the axis of the drive shaft 1 as the drive shaft 1 rotates.

The first external gear 3 is rotatably provided on the eccentric shaft 2 so that the rotation axis thereof is coaxial with the axis of the eccentric shaft 2. The first external gear 3 has teeth with the number of teeth Z ₃ along its outer periphery.
The 1st internal gear 4 is being fixed to the apparatus main body in which the speed reducer 100 is provided. The first internal gear 4, the teeth number Z ₄ along the inner periphery of the body formed in an annular shape is formed.
The first external gear 3 is disposed so as to mesh with the first internal gear 4.

The second external gear 5 is rotatably provided on the eccentric shaft 2 so as to be aligned in the axial direction of the first external gear 3 and the eccentric shaft 2. The second external gear 5, the teeth number Z ₅ are formed along the outer periphery. The second external gear 5 is installed so that one surface thereof overlaps one surface of the first external gear 3, and the first external gear 3 and the second external gear 5 are connected to each other. It is provided so as to be united in appearance.
The second internal gear 6 is arranged so as to mesh with the second external gear 5. The second internal gear 6, the teeth number Z ₆ along the inner circumference of the body formed in an annular shape is formed. The second internal gear 6 is not fixed to the apparatus main body like the first internal gear 4 and can rotate about the drive shaft 1 and the same axis. A connection member 6a (for example, a plate material as shown in FIG. 1) for connecting the second internal gear 6 and the output shaft 7 is attached to the end surface of the second internal gear 6 on the output shaft 7 side. It has been.
The output shaft 7 is connected to a connection member 6 a attached to the second internal gear 6, and rotates about the same axis as the second internal gear 6.
Here, each of the gears 3, 4, 5, 6 has a difference in the number of teeth Z ₄ −Z ₃ between the first external gear 3 and the first internal gear 4, and the second external gear 5. The difference between the number of teeth Z ₆ −Z ₅ with the second internal gear 6 is made equal.

<Deceleration mechanism>
Next, the mechanism of deceleration by the reduction gear 100 will be described with an example.
As shown in FIGS. 2 and 3, the difference in the number of teeth Z ₄ −Z ₃ between the first external gear 3 and the first internal gear 4 is set to 3 teeth, and the second external gear 5 and the first external gear 5 If the difference in the number of teeth Z ₆ -Z ₅ from the internal gear 6 of No. ₂ is three, Z ₃ = Z ₄ -3 and Z ₅ = Z ₆ -3.

Here, if the gear module is m, the pitch circle diameter is D, and the number of teeth is Z,
D = mZ (1)
Since but satisfied, as shown in FIG. 2, the eccentric amount d ₅ relative to the drive shaft 1 of the eccentricity d ₃ and a second external gear 5 relative to the drive shaft 1 of the first external gear 3,
d ₃ = {Z ₄ × m− (Z ₄ −3) × m} / 2 (2)
d ₅ = {Z ₆ × m− (Z ₆ −3) × m} / 2 (3)
Can be obtained.

When formulas (2) and (3) are arranged,
d ₃ = d ₅ = m × 3/2 (4)
It becomes.

That is, the eccentricity d ₃ of the first external gear 3 is determined by the difference in the number of teeth “3” between the first external gear 3 and the first internal gear 4 and the module m, and the second external gear The eccentricity d ₅ of ₅ is determined by the difference in the number of teeth “3” between the second external gear 5 and the second internal gear 6 and the module m. Therefore, if the difference in the number of teeth is made the same at 3 as described above, the eccentric amounts of the external gears 3 and 5 can be matched and can be provided on one eccentric shaft 2, thus causing a problem in the transmission of the drive. Absent.

On the other hand, when the eccentric shaft 2 is rotated by one rotation about the axis of the drive shaft 1, i.e., the first rotational speed R ₃ and second outer external gear 3 when the drive shaft 1 as an input to rotate 1 The rotational speed R ₅ of the toothed gear 5 is
R ₃ = Z ₄ / Z ₃ = Z ₄ / (Z ₄ -3) (5)
R ₅ = Z ₆ / Z ₅ = Z ₆ / (Z ₆ −3) (6)
It becomes.

Here, if the number of teeth of the first internal gear 4 is Z ₄ = 20, the number of teeth of the second internal gear 6 is Z ₆ = 25, and the number of teeth of both the internal gears 4 and 6 is changed, The rotational speeds R ₃ and R ₅ of both external gears 3 and ₅ are:
R ₃ = 20 / (20-3) ≈1.176 (7)
R ₅ = 25 / (25-3) ≈1.136 (8)
It becomes.

Since the first internal gear 4 is fixed, the difference ΔR between the rotational speeds R ₃ and R ₅ of the external gears 3 and ₅ is:
ΔR = 1.176−1.136 = 0.040 (9)
It becomes.

  This rotational speed difference ΔR becomes the rotational speed of the second internal gear 6 when the eccentric shaft 2 makes one rotation around the axis of the drive shaft 1.

Therefore, the reduction ratio S in this case is
S = 1 / 0.04 = 25 (10)
Thus, a large reduction ratio can be realized.

<Effects of Embodiment>
Thus, according to the reduction gear 100, when the drive shaft 1 rotates around the axis by driving the drive source, the eccentric shaft 2 coupled to the drive shaft 1 rotates around the axis of the drive shaft 1. When the eccentric shaft 2 rotates about the axis of the drive shaft 1, the first external gear 3 and the second external gear 5 provided on the eccentric shaft 2 also follow the internal gears 4 and 6 that mesh with each other. And rotate around the axis of the drive shaft 1.
Since the first external gear 3 meshes with the first internal gear 4, the first external gear 3 tries to rotate the first external gear 3 by the rotation of the first external gear 3. Since the internal gear 4 is fixed, the first external gear 3 rotates around the axis of the eccentric shaft 2 and revolves around the axis of the drive shaft 1.

Here, the difference in the number of teeth between the first external gear 3 and the first internal gear 4 and the difference in the number of teeth between the second external gear 5 and the second internal gear 6 are made equal. The first external gear 3 and the second external gear 5 have the same eccentric amount with respect to the axis of the drive shaft 1 and can be provided on one eccentric shaft 2.
Furthermore, since the first external gear 3 and the second external gear 5 are provided on the same eccentric shaft 2, the second external gear 5 follows the first external gear 3 and follows the eccentric shaft. 2 rotates around the axis of 2 and revolves around the axis of the drive shaft 1. Due to the revolution of the second external gear 5, the second internal gear 6 that meshes with the second external gear 5 rotates around the axis of the drive shaft 1. Due to the rotation of the second internal gear 6, the output shaft 7 rotates around the axis, and the rotational speed of the drive shaft 1 can be reduced and output.

Here, since the first external gear 3 and the second external gear 5 have different numbers of teeth, the first external gear 3 when the eccentric shaft 2 makes one rotation around the axis of the drive shaft 1. And the second external gear 5 have different rotational speeds.
Accordingly, the difference in rotational speed between the external gears 3 and 5 becomes the rotational speed of the second internal gear 6 when the eccentric shaft 2 makes one rotation around the axis of the drive shaft 1.

Thereby, since the output shaft 7 can be rotated around the coaxial axis with the drive shaft 1, the rotational speed and output torque of the output shaft 7 depend on the position of the second external gear 5 with respect to the second internal gear 6. The fluctuation does not occur, and the rotation speed and output torque of the output shaft 7 can be stabilized.
Further, as shown in the above example, a large reduction ratio can be realized only by a combination of the two external gears 3 and 5 and the two internal gears 4 and 6.
Therefore, a large reduction ratio can be obtained while reducing the size and weight of the reduction gear 100, and the number of parts can be reduced and the cost can be reduced.

The present invention is not limited to the above embodiment. For example, the speed reduction device 100 may use the output shaft 7 as an input side by connecting the output shaft 7 to a drive source, and the drive shaft 1 as an output side. In this case, the rotation direction is opposite to that in the above embodiment.
The number of internal gears and external gears is not limited to two, and three or more may be used.

DESCRIPTION OF SYMBOLS 1 Drive shaft 2 Eccentric shaft 3 1st external gear 4 1st internal gear 5 2nd external gear 6 2nd internal gear 7 Output shaft 100 Reduction gear

Claims (1)

A drive shaft coupled to the drive source and rotated about an axis by the drive source;
An eccentric shaft coupled to the drive shaft at a position eccentric with respect to the axis of the drive shaft and rotating about the axis of the drive shaft together with the rotation of the drive shaft;
A first external gear rotatably provided on the eccentric shaft;
A first internal gear fixed to a predetermined position and meshing with the first external gear;
A second external gear provided rotatably on the eccentric shaft, and arranged so as to be aligned in the axial direction of the first external gear and the eccentric shaft;
A second internal gear meshing with the second external gear;
An output shaft connected to the second internal gear and rotating about the same axis as the drive shaft;
The difference in the number of teeth between the first external gear and the first internal gear and the difference in the number of teeth between the second external gear and the second internal gear are made equal. A reduction gear.

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