JP7706382B2 - Planetary Gear Unit - Google Patents

Description

The present invention relates to a planetary gear device.

In a planetary gear device, the sun gear portion that meshes with the planetary gear and the male spline portion that is connected to the front shaft are formed on the same sun gear shaft (see, for example, Patent Document 1). In such a planetary gear device, tooth trace modification may be performed on the sun gear shaft to improve the meshing of the sun gear portion.

JP 2014-159814 A

However, simply modifying the teeth of the sun gear shaft may result in the male spline portion being machined as an extension of the sun gear portion, which may result in poor meshing of the male spline portion.

The present invention was made in consideration of the above circumstances, and aims to perform tooth trace modification while suppressing deterioration of the meshing of the male spline portion.

The present invention provides a planetary gear device including a sun gear shaft having a sun gear portion and a planetary gear meshing with the sun gear portion,
the sun gear shaft has a male spline portion for connecting with a front-stage shaft, and each tooth portion of the sun gear portion extends in the axial direction to form the male spline portion,
the sun gear portion has a crowning portion in which the tooth thickness gradually decreases toward both axial ends,
The male spline portion is configured such that the amount of change in tooth thickness in the axial direction is smaller than that of the crowning portion.

The present invention also provides a planetary gear device including a sun gear shaft having a sun gear portion, a planetary gear meshing with the sun gear portion, and a front stage shaft connected to the sun gear shaft,
the sun gear shaft has a male spline portion connected to the front shaft, and each tooth portion of the sun gear portion extends in the axial direction to form the male spline portion,
the sun gear portion has a crowning portion in which the tooth thickness gradually decreases toward both axial ends,
The male spline portion has a tooth thickness that changes continuously from the crowning portion in the axial direction,
The front shaft is configured such that the female spline portion that meshes with the male spline portion has a tooth thickness that changes in the axial direction in accordance with the change in the tooth thickness of the male spline portion in the axial direction.

According to the present invention, it is possible to perform tooth trace modification of the sun gear section while suppressing deterioration of the meshing of the male spline section.

FIG. 1 is a cross-sectional view showing a planetary gear device according to an embodiment. FIG. 2 is an enlarged view of a main part of FIG. 1 . 3A is a view of the teeth of the input shaft of the second planetary gear mechanism as viewed from the axial direction, and FIG. 3B is a cross-sectional view of the teeth taken along line III-III in FIG. FIG. 1A is a cross-sectional view showing a modified example of the teeth of the input shaft of the second planetary gear mechanism, and FIG. 1B is a cross-sectional view showing another modified example of the teeth of the input shaft of the second planetary gear mechanism and the tooth grooves of the female spline portion that meshes with the teeth.

The following describes an embodiment of the present invention in detail with reference to the drawings.

[Overall configuration of the planetary gear device]
FIG. 1 is a cross-sectional view showing a planetary gear device 1 according to this embodiment.
As shown in this figure, the planetary gear device 1 includes a worm reduction mechanism 20 and at least two stages of simple planetary gear mechanisms (a first planetary gear mechanism 30 and a second planetary gear mechanism 40), in this order, on a power transmission path from a motor (not shown).
In the following description, the direction along the central axis Ax of the planetary gear device 1 is referred to as the "axial direction", the direction perpendicular to the central axis Ax is referred to as the "radial direction", and the direction of rotation about the central axis Ax is referred to as the "circumferential direction". In addition, in the axial direction, the side to which the motor is connected (upper side in the figure) is referred to as the "input side", and the side to which the driven member is connected (lower side in the figure) is referred to as the "output side".

A motor (not shown) is connected to the worm reduction mechanism 20. The rotating shaft of the motor is connected to the worm pinion 21 of the worm reduction mechanism 20 via a coupling. The worm pinion 21 meshes with the worm gear 22, changing the direction of power transmission to approximately a right angle. The worm gear 22 is fixed to an intermediate shaft 23. The intermediate shaft 23 is connected to the input shaft 31 of the first planetary gear mechanism 30 via a coupling 24.

The first planetary gear mechanism 30 includes a sun gear portion 33 formed on an input shaft 31, three planetary gears 34 meshing with the sun gear portion 33, a carrier pin 35 that rotatably supports each of the planetary gears 34, and an internal gear 36 with which each of the planetary gears 34 internally meshes. The first planetary gear mechanism 30 extracts the revolutions of the three planetary gears 34 generated by the rotation of the sun gear portion 33 from an output member 37 to which the carrier pin 35 is fixed. The output member 37 is connected to an input shaft 41 of the second planetary gear mechanism 40 via a spline joint.
1 and 2, only one planetary gear 34 and one carrier pin 35 are shown. The same applies to a planetary gear 44 and a carrier pin 45 of a second planetary gear mechanism 40 described later.

The second planetary gear mechanism 40 includes a sun gear section 43 formed on the input shaft (sun gear shaft) 41, three planetary gears 44 that mesh with the sun gear section 43, a carrier pin 45 that rotatably supports each planetary gear 44, and an internal gear 46 with which each planetary gear 44 meshes internally. The second planetary gear mechanism 40 extracts the revolution of the three planetary gears 44 generated by the rotation of the sun gear section 43 from an output member 47 to which the carrier pin 45 is fixed. The output member 47 is connected to an output shaft 49 via a spline joint. An output pinion 49a that meshes with a gear (e.g., a ring gear) provided on a driven member (not shown) is integrally fixed to the end of the output shaft 49.

In the planetary gear device 1 having the above-described configuration, when the rotational force of the motor is input to the worm reduction mechanism 20, it is initially reduced in speed by the meshing of the worm pinion 21 and the worm gear 22, and then transmitted to the input shaft 31 of the first planetary gear mechanism 30.
When the input shaft 31 of the first planetary gear mechanism 30 rotates, the sun gear portion 33 formed on the input shaft 31 rotates, and the planetary gear 34 revolves inside the internal gear 36. This revolution component is taken out from the output member 37 via the carrier pin 35 and transmitted to the input shaft 41 of the second planetary gear mechanism 40 via a spline joint.
The second planetary gear mechanism 40 also performs a speed reduction action similar to that of the first planetary gear mechanism 30, and the revolution of the planetary gears 44 is taken out from the output member 47 and transmitted to the output shaft 49 via a spline joint. When the output shaft 49 rotates, the output pinion 49a also rotates, and the rotational force is transmitted to the driven member connected to the output pinion 49a. In this way, the rotational force reduced by the worm reduction mechanism 20 and the two-stage simple planetary gear mechanism (the first planetary gear mechanism 30 and the second planetary gear mechanism 40) is output to the driven member.

[Tooth Flank Shape of Input Shaft of Second Planetary Gear Mechanism]
FIG. 2 is an enlarged view of a main portion of FIG.
As shown in this figure, an input shaft (sun gear shaft) 41 of the second planetary gear mechanism 40 has a male spline portion 42 and a sun gear portion 43 coaxially arranged therewith.
Of these, the male spline portion (spline shaft) 42 is connected to the output member 37 of the first planetary gear mechanism 30, and has a plurality of first teeth 42a (see FIG. 3(b)) that mesh with the female spline portion (spline hole) 38 of the output member 37. On the other hand, the sun gear portion 43 has a plurality of second teeth 43a (see FIG. 3(b)) that mesh with the planetary gear 44.

The first teeth 42a of the male spline portion 42 and the second teeth 43a of the sun gear portion 43 are formed with the same number of teeth and the same module, and each second tooth 43a of the sun gear portion 43 extends in the axial direction to form the male spline portion 42. In other words, the input shaft 41 has teeth 41a that are axially connected (integrally formed) across the male spline portion 42 and the sun gear portion 43, of which the input side portion is the first teeth 42a that mesh with the female spline portion 38 of the output member 37, and the output side portion is the second teeth 43a that mesh with the planetary gear 44 (see FIG. 3(b)).
Although not particularly limited, the sun gear portion 43 (second teeth 43a) is subjected to a periodically changing load unlike the male spline portion 42 (first teeth 42a), and therefore it is preferable that the surface roughness (e.g., arithmetic mean roughness Ra) of the tooth surface be smaller than that of the male spline portion 42. For example, the sun gear portion 43 is subjected to a more advanced finishing process than the male spline portion 42. For the same reason, it is also preferable that the sun gear portion 43 (second teeth 43a) has a higher hardness of the tooth surface than the male spline portion 42 (first teeth 42a), for example, by performing induction hardening only on the sun gear portion 43.

3A is a view of the teeth 41a of the input shaft 41 as viewed from the axial direction, and FIG. 3B is a cross-sectional view of the teeth 41a taken along line III-III in FIG. 3A.
As shown in FIGS. 3A and 3B, the tooth thickness of the teeth 41a of the input shaft 41 varies in the axial direction (tooth width direction).
Specifically, in this embodiment, the sun gear portion 43 of the input shaft 41 is subjected to tooth lead (tooth surface) modification from a substantially constant tooth thickness state (shown by a broken line) in the axial direction in order to improve tooth contact with the planetary gear 44. The sun gear portion 43 in this embodiment is subjected to crowning as the tooth lead modification. As a result, the sun gear portion 43 has a crowned portion 43b over its entire axial length, in which the tooth thickness gradually decreases toward both axial ends. In the crowned portion 43b, the tooth thickness is distributed substantially symmetrically in the axial direction within the range in which it meshes with the planetary gear 44, and the tooth thickness at both axial ends is substantially the same.
The crowning portion 43b may be at least a part of the sun gear portion 43. In other words, it is sufficient that the sun gear portion 43 has the crowning portion 43b.

On the other hand, no tooth trace modification processing (crowning) is performed on the male spline portion 42 of the input shaft 41. Therefore, the male spline portion 42 has a constant tooth thickness portion 42b in which the tooth thickness is approximately constant in the axial direction.
The constant tooth thickness portion 42b may be at least a part of the male spline portion 42. In other words, it is sufficient that the male spline portion 42 has the constant tooth thickness portion 42b (excluding the chamfered portion if the axial end of the male spline portion 42 is chamfered).

In this manner, in this embodiment, the sun gear portion 43 has the crowning portion 43b, and the male spline portion 42 has the constant tooth thickness portion 42b. This improves the meshing of the sun gear portion 43 without deteriorating the meshing of the male spline portion 42. In other words, the tooth trace modification of the sun gear portion 43 can be performed while suppressing the deterioration of the meshing of the male spline portion 42.
More specifically, in normal tooth trace modification, a grinding wheel is used to process the entire tooth surface along the tooth width direction. In this case, the tooth shape on the male spline side is curved as an extension of the crowning portion, as shown by the two-dot chain line in Figure 3(b), and there is a risk of the meshing between this male spline portion and the female spline portion, which has a small change in tooth thickness, becoming worse (the occurrence of backlash, etc.).
In this regard, in the present embodiment, crowning is performed so that the sun gear portion 43 has a crowning portion 43b and the male spline portion 42 has a constant tooth thickness portion 42b. That is, the tooth trace of the sun gear portion 43 is modified while suppressing deterioration of meshing (occurrence of rattle) of the male spline portion 42. Furthermore, while the occurrence of rattle in the male spline portion 42 causes misalignment in each gear of the planetary reduction portion, and there is a risk of uneven contact of the gears and damage to the tooth surfaces, the occurrence of such misalignment is suppressed in the present embodiment, and the risk of uneven contact and damage to the tooth surfaces can be reduced.

In addition, the male spline portion 42 does not have to have a constant tooth thickness portion 42b, and the tooth thickness change amount in the axial direction may be smaller than that of the crowning portion 43b. Here, the "tooth thickness change amount (in the axial direction)" of the crowning portion 43b refers to the relative tooth thickness change amount ΔS (in the case of one side, twice that amount in the case of both sides) between the axial center of the crowning portion 43b, where the tooth thickness is the largest, and the axial end portion, where the tooth thickness is the smallest. Similarly, the "tooth thickness change amount (in the axial direction)" of the male spline portion 42b refers to the relative tooth thickness change amount between the portion of the male spline portion 42b, where the tooth thickness is the largest, and the portion, where the tooth thickness is the smallest. In this embodiment, since the tooth thickness is constant, the tooth thickness change amount is "0". With such a configuration, the same effect as above can be obtained. Therefore, for example, as shown in FIG. 4(a), the tooth thickness may be uniform from the axial end portion of the sun gear portion 43 (crowning portion 43b) where the crowning processing is completed to the male spline portion 42 side.

[Technical effect of the present embodiment]
As described above, according to the planetary gear device 1 of this embodiment, the input shaft (sun gear shaft) 41 has each tooth portion of the sun gear portion 43 extending in the axial direction to form the male spline portion 42, and the sun gear portion 43 has a crowning portion 43b whose tooth thickness gradually decreases toward both axial ends, and the male spline portion 42 has a smaller amount of change in tooth thickness in the axial direction than the crowning portion 43b.
Therefore, it is possible to perform tooth trace modification of the sun gear portion 43 while suppressing deterioration of the meshing of the male spline portion 42. Furthermore, while the occurrence of rattle in the male spline portion 42 causes misalignment in each gear of the planetary reduction portion, which poses the risk of uneven contact of the gears or damage to the tooth surfaces, the occurrence of such misalignment is suppressed in this embodiment, and the risk of uneven contact and damage to the tooth surfaces can be reduced.

Furthermore, according to the planetary gear device 1 of this embodiment, the male spline portion 42 has the constant tooth thickness portion 42b, the tooth thickness of which is constant in the axial direction.
This makes it possible to perform tooth trace modification of the sun gear portion 43 while further preventing deterioration of the meshing of the male spline portion 42.

[Modification]
In the above embodiment, deterioration of meshing with the female spline portion 38 is suppressed by suppressing changes in the tooth thickness of the male spline portion 42 of the input shaft 41. However, the tooth thickness of the female spline portion 38 may be changed in the axial direction in accordance with (corresponding to) changes in the axial tooth thickness of the male spline portion 42.
More specifically, as shown in Figure 4(b), the tooth thickness of the first tooth 42a of the male spline portion 42 and the width of the tooth groove 38a of the female spline portion 38 that meshes with it may have corresponding axial change rates. Here, the expression "correspondence" between the axial change rates of the tooth thickness of the first tooth 42a and the width of the tooth groove 38a means that these axial change rates are approximately the same (within a predetermined error range) at corresponding axial positions.

In this case, the tooth trace modification of the input shaft 41 (teeth 41a) can be performed by machining the crowning portion 43b and the male spline portion 42 so that the change in tooth thickness in the axial direction is smoothly continuous with each other. For example, the male spline portion 42 may be machined linearly while leaving the tooth thickness change rate of the input side end of the crowning portion 43b unchanged. In other words, the tooth thickness of the crowning portion 43b may change curvilinearly in the axial direction, and the tooth thickness of the male spline portion 42 may change linearly in the axial direction. By keeping the tooth thickness change rate constant (or not changing it significantly), machining can be performed relatively easily.

In this way, even if the tooth thickness of the female spline portion 38 is changed in response to a change in the tooth thickness of the male spline portion 42, the tooth trace of the sun gear portion 43 can be adjusted while suppressing deterioration of the meshing between the male spline portion 42 and the female spline portion 38 (the occurrence of rattle), just as in the above embodiment.

[others]
Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.
For example, in the above embodiment, the present invention has been described as being applied to the input shaft (sun gear shaft) 41 of the second stage second planetary gear mechanism 40, but the present invention can also be applied to the input shaft (sun gear shaft) 31 of the first stage first planetary gear mechanism 30. That is, the intermediate shaft (output shaft) 23 (or the output shaft of the motor) of the worm reduction mechanism 20 and the input shaft 31 of the first planetary gear mechanism 30 may be connected by a spline, and the structure of the present invention may be applied to the spline portion and the sun gear portion 33. In addition, the present invention can be widely applied to planetary gear devices having a sun gear shaft, and there is no particular limitation on the number of stages of the reduction mechanism or the type of reduction mechanism to be combined with it.

In addition, in the above embodiment, a simple planetary gear mechanism is used as an example of the planetary gear mechanism, but the planetary gear device according to the present invention is not limited to a simple planetary gear mechanism and can be widely applied to planetary gear devices (mechanisms) in which the sun gear portion and the spline portion are arranged coaxially.

Furthermore, the planetary gear device according to the present invention can be applied to various types of reducers, such as a yaw drive reducer for a wind power generator, a reducer for a slewing bearing of a shovel, and a planetary reducer for a robot.
In addition, the details shown in the above embodiment can be modified as appropriate without departing from the spirit of the invention.

1 Planetary gear device 30 First planetary gear mechanism (pre-reduction mechanism)
37 Output member (front shaft)
38 Female spline portion 38a Tooth groove 40 Second planetary gear mechanism 41 Input shaft (sun gear shaft)
41a tooth 42 male spline portion 42a first tooth 42b constant tooth thickness portion 43 sun gear portion 43a second tooth 43b crowning portion 44 planet gear Ax central axis ΔS tooth thickness change amount

Claims (9)

A planetary gear device including a sun gear shaft having a sun gear portion and a planetary gear meshing with the sun gear portion,
the sun gear shaft has a male spline portion for connecting with a front-stage shaft, and each tooth portion of the sun gear portion extends in the axial direction to form the male spline portion,
the sun gear portion has a crowning portion in which the tooth thickness gradually decreases toward both axial ends,
The male spline portion has a smaller change in tooth thickness in an axial direction than the crowning portion.
Planetary gear set. The male spline portion has a constant tooth thickness portion having a constant tooth thickness in the axial direction.
2. The planetary gear device according to claim 1. A planetary gear device including a sun gear shaft having a sun gear portion, a planetary gear meshing with the sun gear portion, and a front stage shaft connected to the sun gear shaft,
the sun gear shaft has a male spline portion connected to the front shaft, and each tooth portion of the sun gear portion extends in the axial direction to form the male spline portion,
the sun gear portion has a crowning portion in which the tooth thickness gradually decreases toward both axial ends,
The male spline portion has a tooth thickness that changes continuously from the crowning portion in the axial direction,
the front stage shaft has a female spline portion that meshes with the male spline portion, the tooth thickness of which changes in the axial direction in accordance with the change in the tooth thickness of the male spline portion in the axial direction;
Planetary gear set. The crowning portion has a tooth thickness that changes curvilinearly in the axial direction,
The male spline portion has a tooth thickness that changes linearly in the axial direction.
4. The planetary gear device according to claim 3. The tooth thickness changes in the crowning portion and the male spline portion in the axial direction are smoothly continuous with each other.
The planetary gear device according to claim 3 or 4. The front shaft is an output member of the front reduction mechanism.
The planetary gear device according to any one of claims 1 to 5. The crowning portion has the same tooth thickness at both axial ends of the range in which it meshes with the planetary gear.
The planetary gear device according to any one of claims 1 to 6. the sun gear portion has a tooth surface having a smaller surface roughness than the male spline portion;
A planetary gear device according to any one of claims 1 to 7. the sun gear portion has a tooth surface having a higher hardness than the male spline portion;
A planetary gear device according to any one of claims 1 to 8.

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