JP2016205521A - Backlash-less planetary gear device - Google Patents

Backlash-less planetary gear device Download PDF

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JP2016205521A
JP2016205521A JP2015088132A JP2015088132A JP2016205521A JP 2016205521 A JP2016205521 A JP 2016205521A JP 2015088132 A JP2015088132 A JP 2015088132A JP 2015088132 A JP2015088132 A JP 2015088132A JP 2016205521 A JP2016205521 A JP 2016205521A
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gear
planetary gear
planetary
counterclockwise
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JP2015088132A
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水野 博
Hiroshi Mizuno
博 水野
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水野 博
Hiroshi Mizuno
博 水野
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Abstract

PROBLEM TO BE SOLVED: To provide a planetary gear device having a less amount of backlash.SOLUTION: A conventional planetary gear device and a 3K type magical planetary gear device are operated in such a manner that the planetary gear kept under a state described below is commonly present when it is fixed after an input rotating part is stopped and a backlash is reduced. As to the planetary gear with a clockwise dead point, it can be revolved in a counter-clockwise direction, but cannot be revolved in a clockwise direction. As to the planetary gear with a counter-clockwise dead point, it can be revolved in a clockwise direction, but cannot be revolved in a counter-clockwise direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for removing backlash from a planetary gear set.

Conventionally, the gear mechanism is provided with a certain amount of backlash (backlash) so that it can operate smoothly.
In recent years, cases where high stop accuracy is required have increased, and various methods have been adopted to reduce the amount of backlash.
Conventionally, it has been considered to be roughly divided into a method of improving accuracy and a method of guiding a gear to a counter gear.
The former has a limited effect because backlash is necessary for smooth operation.
A typical example of the latter is a method in which a counter gear is sandwiched between a wave gear (trade name Harmonic Drive) and two gears connected by elasticity such as a spring represented by a scissor gear.
The wave gear is a mechanism that moves and meshes with a movable internal gear by bending a movable gear (flex spline).

Among the latter uses of elasticity, there are the following methods that are relatively similar in structure and action to the present invention.

Japanese Patent Laid-Open No. 2007-170459 This utilizes the elastic force caused by the twisting of the two-stage planetary gear to remove the backlash by sandwiching the internal gear.

However, the wave gear device (trade name Harmonic Drive) requires special processing and is expensive. Further, since the thin flexspline is bent, there is a difficulty such as torsion, or difficult to apply to a large torque, and to make a reduction ratio of less than 30.
Scissor gears are difficult to adapt to small objects and have problems such as spring deterioration and breakage.
In Patent Document 1, since the torsional force is generated by elasticity, there is a problem of how to control the restoring force. Further, the elastic force depends on the physical properties of the elastic body, and it is very difficult to ensure the performance stably in consideration of the variation of the material, temperature change, change with time, and the like.
The present invention improves the above problems and provides a backlash-less planetary gear that can be miniaturized with a simple structure and is low in manufacturing cost.

A sun gear (number of teeth Z1) and a plurality of planetary gears (number of teeth Z2) around it, a fixed internal gear (number of teeth Z3) on the outer periphery, and a carrier that supports each planetary gear so that it can rotate and revolve. This was applied to a conventional planetary gear device having
When the sun gear was stopped and then fixed, the following planetary gears were allowed to coexist.
Clock side dead center planetary gear: Counterclockwise transmission surface of sun gear (surface transmitting power when sun gear is rotated counterclockwise) and clock side forced surface of fixed gear (clockwise revolution of planetary gear) It is in contact with the surface to be suppressed.
Counterclockwise dead center planetary gear: Clock transmission surface of sun gear (surface transmitting power when sun gear is rotated clockwise) and counterclockwise forced surface of fixed gear (counterclockwise revolution of planetary gear) Is in contact with the surface to suppress.

The outline is shown in FIG.
It is a planetary type which gives input rotation to the sun gear 7 and outputs it from the carrier supporting each planetary gear. After the input rotation is stopped, the sun gear 7 is fixed by the action of the servo motor or the stepping motor.
The planet gear B at the 3 o'clock position in this figure is the counterclockwise dead center planet gear. In this state, an external force can be applied to the carrier to revolve the planetary gear clockwise. However, even if the planetary gear B is rotated counterclockwise, the fixed sun gear 7 and the internal gear 6 are obstructed and cannot be rotated.
On the other hand, the planetary gear D at the 9 o'clock position becomes the clockwise dead center planetary gear. In this state, an external force can be applied to the carrier to revolve the planetary gear D counterclockwise. However, even if the planetary gear D is to be rotated in the clockwise direction, the fixed sun gear 7 and the internal gear 6 are obstructed and cannot be rotated.
By simultaneously coexisting the clock-side dead center planetary gear and the counter-clockwise dead center planetary gear, the carrier supporting both of them cannot be rotated clockwise or counterclockwise. That is, despite the backlash between the individual gears, the entire planetary gear device can create a zero backlash state.
Although the planetary type has been described, the same effect can be obtained with a solar type or a star type.
Thus, claim 1 is obtained.

In order to mesh each planetary gear with the sun gear and the internal gear in such a plane, the number of planetary gear teeth may be an odd number.
Until now, the number of teeth of the sun gear and the number of teeth of the internal gear have been almost an integer multiple of the number of planetary gears. In that case, the sun gear 7 and the internal gear 6 mesh with only one of the clock side and the counterclockwise side.
In order to make both dead center planetary gears and establish them as planetary gears,
Z1 is not the number of planetary gears × natural number. Z3 must be the number of planetary gears × natural number.
Many conventional backlash reduction methods require highly accurate machining. In this method,
Even with low accuracy, the intended contact can be obtained by setting the number of teeth, and the object can be achieved.

A sun gear (number of teeth Z1) and a plurality of planetary gears (number of teeth Z2) around it, a fixed internal gear (number of teeth Z3) that cannot be rotated on the outer periphery thereof, and an output internal gear (number of teeth Z4) that can rotate In a so-called 3K-type wonder planetary gear device having a carrier that supports each planetary gear so as to be capable of rotating and revolving, the following is performed.
The following planetary gears coexist when the sun gear is stopped and then fixed.
Counterclockwise dead center planetary gear: Counterclockwise transmission surface of sun gear (surface transmitting power when sun gear is rotated counterclockwise) and clock-side forced surface of fixed internal gear (clockwise side of planetary gear) The surface that suppresses revolution) and the clockwise transmission surface of the output internal gear (the surface that transmits the clockwise rotation to the output gear).
Clock side dead center planetary gear: Clock side transmission surface of sun gear (surface that transmits power when sun gear is rotated clockwise) and counterclockwise forced surface of fixed gear (counterclockwise revolution of planetary gear) The surface to be suppressed is in contact with the counterclockwise transmission surface of the output internal gear (the surface transmitting the counterclockwise rotation to the output gear).
This is the third aspect.

On the fixed side, the structure and the principle of operation are the same as the planetary type of an ordinary planetary gear device, so the method adopted in claim 1 can be used as it is.
Therefore, as an output side corresponding to FIG. 1, consider Z4 = Z3-4 (number of planetary gears) = 23 (FIG. 2).
Or it is good also as Z4 = Z3 + number of planetary gears. By setting the number of teeth in this way, both the backlash reduction condition and the magic planetary gear formation condition are satisfied.

Due to the action of the fixed side, the carrier cannot be rotated in either direction. Further, it is obvious that the planetary gear B and the planetary gear D at 3 o'clock and 9 o'clock in FIG. 2 cannot rotate.
That is, these gears mesh with the output internal gear 11 in a locked state. In this state, even if the output internal gear 11 is to be rotated clockwise, the planetary gear B at the 3 o'clock position becomes an obstacle and cannot be rotated.
If you try to turn it counterclockwise, the planetary gear D at 9 o'clock will become an obstacle and cannot be turned.
The output internal gear 11 is in a 0 backlash state.
In this case, unlike the carrier output of claim 1, the gear at the 3 o'clock position is a planetary gear on the clock side dead center,
The gear at 9 o'clock is the counterclockwise dead planet gear.

Backlash may occur not only in the gear portion but also between the shafts for rotating the carrier and the planetary gear. One method is to eliminate the gap by elastically deforming the bearing. This is the third aspect.

Another method is to place an elastically deformable member between the bearing for rotating the planetary gear and the hole of the carrier. This is the fourth aspect.
However, both of claims 3 and 4 are not perfect methods because a displacement due to elastic deformation occurs if a large force is applied to the output portion.

Heat generation due to friction occurs during gear operation. In addition, wear is caused by long-term use. Even if these are present, the backlash reduction effect is not lost as long as they mesh with the intended surface. However, the stop position deviates from the design value. Suppresses the tooth profile by using a Cornu curve with low friction instead of an involute curve. This is the fifth aspect.

The phase angle of the sun gear is defined as shown in FIG. 0 to 180 degrees is a clockwise transmission surface, and 180 to 360 degrees is a counterclockwise transmission surface.
The phase angle of the internal gear is defined as shown in FIG. The direction of the positive direction is different from that of the sun gear because the direction of the meshing surface is taken into account when the sun gear is input and rotated clockwise. When the number of planetary gear teeth is an odd number, the phase angle between the sun gear and the internal gear is shifted by 180 degrees. In the 3K type mysterious planetary gear, it is considered that the output internal gear is guided to the same phase angle as the fixed internal gear, and the phase angles of both are the same. Clock-side forced surface of internal gear fixed at 0 to 180 degrees, counter-clockwise transmission surface of output internal gear, counter-clockwise forced surface of internal gear fixed at 180-360 degrees, clock side of output internal gear It is a transmission surface.

According to the first aspect, a backlash-less state can be generated in the entire planetary gear device while backlash required for smooth operation is present between the individual gears.
Due to its extremely simple structure and principle, it is suitable for downsizing, can be manufactured at low cost, and has a low risk of trouble such as breakdown.
Conventionally, a low backlash is possible even in a plastic gear that requires a large backlash.

According to the second aspect, the backlash can be reduced with respect to the 3K-type wonder planetary gear device.
The 3K-type planetary gear is a mechanism that can obtain a large torque and a high resolution. However, compared with the carrier output type of claim 1, since the influence of backlash between the carrier and the planetary shaft is reduced, higher stopping accuracy is obtained. Is possible.

According to the third and fourth aspects, the influence of play between the carrier and the planetary shaft is reduced.

According to the fifth aspect of the present invention, the stop position closer to the design value can be obtained with less adverse effects of wear and heat generation due to the characteristics of the Cornu tooth type.

(Example 1) The gear was selected as follows. It is shown in FIG.
Tooth shape Cornu curve Sun gear Number of teeth 9
Planetary gear Number of teeth 9
Fixed internal gear Number of teeth 27
Number of planetary gears 4
The reduction ratio is 4.

Let X be the phase angle at which the sun gear 7 meshes with the planetary gear A. The phase angle of each part is as follows.
Planetary gear A Planetary gear B Planetary gear C Planetary gear D
Sun gear X X + 270 X + 180 X + 90
Fixed internal gear X + 180 X + 90 X X + 270
That is, each planetary gear can only be either a dead-point planetary gear or a gear that is in the vicinity of a mountain or valley and is not meshed.
Also, it is numerically impossible to make all the planetary gears non-meshing gears.
And, if one of the opposing gears becomes a clock side planetary gear, like the planetary gears A and C and the planetary gears B and D, the other becomes a counterclockwise planetary gear.
From the above, both dead center planetary gears are always present.
In this case, Z1 = number of planetary gears × n + 1, but the same holds true even when Z1 = number of planetary gears × n−1.

The state of the planetary shaft is shown in FIG. As the resin bearing, the trade name Luron is used, and not only the planetary shaft but also the carrier hole is press-fitted.

(Example 2) The gears were selected as follows. (Fig. 5)
Tooth type Cornu curve Sun gear Number of teeth 10
Planetary gear teeth number 17
Internal gear Number of teeth 44
Number of planetary gears 33

The phase angle at each meshing position of the sun gear is expressed as follows.
Planetary gear E Planetary gear F Planetary gear G
X X + 240 X + 120
If everything is on the watch side, the following holds, but there is no such X. Therefore, it never comes to the watch side.
0 <X <180
0 <X + 240 <180 or 360 <X + 240 <540
0 <X + 120 <180 or 360 <X + 120 <540
Similarly, it does not come all counterclockwise.
If any of them is near a mountain (180 degrees) or a valley (0 degree), the other gears are
The phase angle is shifted by 120 degrees and -120 degrees.
That is, it is meshed with both the timepiece and the counterclockwise.
From the above, both dead center planetary gears are always present.
In this case, the relationship is Z1 = 3n + 1 (n is a natural number), but the same holds true even when Z1 = 3n + 2. This is because the arrangement of the planetary gears has changed.

The state of the planetary shaft is shown in FIG. The planetary shaft 15 is in a caulking state with the carrier A and the carrier B and does not rotate. It also has a spacer function. The elastic bearing is made of resin and is press-fitted without a gap.
The reduction ratio is 5.4, and when connected to a stepping motor with 200 pulses per rotation, the output angle becomes 3 pulses per 1 degree, which can correspond to all integer angles.
Suitable for machine tools.

(Example 3) The gears were selected as follows.
Sun gear 7 Number of teeth 11
Planetary gear teeth number 29
Internal gear Number of teeth 67
Output internal gear Number of teeth 70
Number of planetary gears 3
The reduction ratio is 184.6.
High stopping accuracy and large torque or high resolution can be obtained.
The state of the planetary shaft is shown in FIG. A metal bearing is used, and the gap with the carrier hole is filled with an elastic member. A silicon adhesive was used as the elastic member.

1 is a diagram illustrating a state of Example 1. FIG. It is a figure which shows the output side of a 3k type mysterious planetary gear when Example 1 is made into the fixed side. It is a figure which shows the phase angle of a sun gear. It is a figure which shows the phase angle of an internal gearwheel. 6 is a state diagram of Example 2. FIG. It is a figure which shows the planetary shaft part of Example 1. FIG. It is a figure which shows the planetary shaft part of Example 2. FIG. It is a figure which shows the planetary shaft part of Example 3. FIG. It is a figure which shows the whole planetary gear apparatus. It is a figure which shows the 3K type mysterious planetary gear whole.

1 planetary gear device 2 planetary gear A
3 Planetary gear B
4 Planetary gear C
5 Planetary gear D
6 internal gear 7 sun gear 8 spacer 9 kamiai point 10 3K-type wonder planetary gear device 11 output internal gear 12 planetary gear E
13 Planetary gear F
14 Planetary gear G
15 Planetary shaft 16 Elastic body bearing 17 Carrier A
18 Carrier B
19 Elastic body bearing 20 Planetary shaft part 21 Bearing 22 Case A
23 Case B
24 Motor 25 Motor output shaft

Claims (5)

  1. A sun gear (number of teeth Z1), a plurality of planetary gears (number of teeth Z2) around it, an inner gear (number of teeth Z3) on the outer periphery, and a carrier that supports each planetary gear so that it can rotate or revolve. A planetary gear device having the following planetary gear coexisting when the sun gear or the internal gear is stopped and then fixed.
    Clock side dead center planetary gear: There is no problem in turning the output part counterclockwise, but the output part is turned to the clock side.
    When turning, the fixed gear becomes an obstacle and cannot be turned.
    Counterclockwise dead center planetary gear: There is no problem in turning the output part clockwise, but the output part is clockwise.
    When turning, the fixed gear becomes an obstacle and cannot be turned.
  2. A sun gear (number of teeth Z1) and a plurality of planetary gears (number of teeth Z2) around it, a fixed internal gear (number of teeth Z3) that cannot be rotated on the outer periphery thereof, and an output internal gear (number of teeth Z4) that can rotate And a carrier that supports each planetary gear so that it can rotate and revolve, and when the sun gear is stopped and then fixed, the following planetary gear coexists with the 3K type mysterious planetary gear device. .
    Counterclockwise dead center planetary gear: Counterclockwise transmission surface of sun gear (surface transmitting power when sun gear is rotated counterclockwise) and clock-side forced surface of fixed internal gear (clockwise side of planetary gear) The surface that suppresses revolution) and the clockwise transmission surface of the output internal gear (the surface that transmits the clockwise rotation to the output gear).
    Clock side dead center planetary gear: Clock side transmission surface of sun gear (surface that transmits power when sun gear is rotated clockwise) and counterclockwise forced surface of fixed gear (counterclockwise revolution of planetary gear) The surface to be suppressed is in contact with the counterclockwise transmission surface of the output internal gear (the surface transmitting the counterclockwise rotation to the output gear).
  3. The planetary gear device according to claim 1, wherein a bearing for rotating the planetary gear is elastically deformed.
  4. 3. The planetary gear device according to claim 1, wherein a member capable of elastic deformation is interposed between a bearing for rotating the planetary gear and the hole of the carrier.
  5. The planetary gear device according to claim 1 or 2, wherein the tooth profile is a Cornu curve.
JP2015088132A 2015-04-23 2015-04-23 Backlash-less planetary gear device Pending JP2016205521A (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63231036A (en) * 1987-03-16 1988-09-27 Masanori Mochizuki Epicyclic gear unit
JPH01108447A (en) * 1987-10-21 1989-04-25 Takashi Takahashi Controlling transmission
JP2005180636A (en) * 2003-12-22 2005-07-07 Nsk Ltd Bearing for planetary gear
WO2006109838A1 (en) * 2005-04-08 2006-10-19 Tsutomu Miyaoku Gear with cornu's spiral tooth profile
JP2010151269A (en) * 2008-12-26 2010-07-08 Thk Co Ltd Rotating and driving device, articulation structure of robot and robot arm
JP2015001289A (en) * 2013-06-17 2015-01-05 株式会社島津製作所 Planetary gear mechanism

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63231036A (en) * 1987-03-16 1988-09-27 Masanori Mochizuki Epicyclic gear unit
JPH01108447A (en) * 1987-10-21 1989-04-25 Takashi Takahashi Controlling transmission
JP2005180636A (en) * 2003-12-22 2005-07-07 Nsk Ltd Bearing for planetary gear
WO2006109838A1 (en) * 2005-04-08 2006-10-19 Tsutomu Miyaoku Gear with cornu's spiral tooth profile
JP2010151269A (en) * 2008-12-26 2010-07-08 Thk Co Ltd Rotating and driving device, articulation structure of robot and robot arm
JP2015001289A (en) * 2013-06-17 2015-01-05 株式会社島津製作所 Planetary gear mechanism

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