Planetary gear device

Abstract

To modify a tooth trace of a sun gear part while suppressing deterioration of meshing of a male spline part.SOLUTION: A planetary gear device 1 comprises a sun gear shaft 41 having a sun gear part 43, and a planetary gear 44 meshing with the sun gear part 43. The sun gear shaft 41 has a male spline part 42 for coupling with a front stage shaft, and each tooth part of the sun gear part 43 extends in an axial direction to form the male spline part 42. The sun gear part 43 has a crowning part 43b whose tooth thickness gradually decreases toward both end parts in the axial direction. The male spline part 42 has a change in the tooth thickness in the axial direction smaller than a tooth thickness change amount of the crowning part 43b.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an epicyclic gear device.

Background Art

[0002] In an epicyclic gear device, a sun gear portion that meshes with a planet gear and a male spline portion that is connected to a front shaft are formed on the same sun gear shaft (see, for example, Patent Document 1). In such an epicyclic gear device, tooth flank dressing may be performed on the sun gear shaft to improve the meshing of the sun gear portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, if the tooth flanks of the sun gear shaft are simply dressed, the male spline portion may be machined as an extension of the sun gear portion, etc., and the meshing of the male spline portion may deteriorate.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to perform tooth flank dressing while suppressing deterioration of the meshing of the male spline portion.

Means for Solving the Problems

[0006] The present invention is an epicyclic gear device including a sun gear shaft having a sun gear portion and a planet gear that meshes with the sun gear portion, the sun gear shaft has a male spline portion for connecting to a front shaft, and the male spline portion is configured by extending each tooth portion of the sun gear portion in the axial direction, 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.

[0007] The present invention also relates to 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 stage shaft, and the male spline portion is formed by each tooth portion of the sun gear portion extending in the axial direction, the sun gear portion has a crowning portion whose tooth thickness gradually decreases toward both axial ends, the tooth thickness of the male spline portion changes continuously in the axial direction from the crowning portion, the front stage shaft is configured such that the female spline portion meshing with the male spline portion changes its tooth thickness in the axial direction in accordance with the change in the axial tooth thickness of the male spline portion.

Advantages of the Invention

[0008] According to the present invention, it is possible to perform tooth streak dressing of the sun gear portion while suppressing deterioration of the meshing of the male spline portion.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] [Overall Configuration of Planetary Gear Device] FIG. 1 is a cross-sectional view showing a planetary gear device 1 according to the present embodiment. As shown in this figure, the planetary gear device 1 includes a worm reduction mechanism 20 and at least two-stage simple planetary gear mechanisms (first planetary gear mechanism 30, second planetary gear mechanism 40) in this order on the 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 rotational direction centered on the central axis Ax is referred to as the "circumferential direction". Also, among the axial directions, the side to which the motor is connected (the upper side in the figure) is referred to as the "input side", and the side to which the driven member is connected (the lower side in the figure) is referred to as the "output side".

[0012] 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 and changes the power transmission direction by approximately 90 degrees. The worm gear 22 is fixed to the 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.

[0013] The first planetary gear mechanism 30 includes a sun gear portion 33 formed on the input shaft 31, three planetary gears 34 that mesh with the sun gear portion 33, carrier pins 35 that rotatably support each planetary gear 34, and an internal gear 36 with which each planetary gear 34 meshes internally. The first planetary gear mechanism 30 extracts the revolution of the three planetary gears 34 generated by the rotation of the sun gear portion 33 from the output member 37 to which the carrier pin 35 is fixed. The output member 37 is connected to the input shaft 41 of the second planetary gear mechanism 40 via a spline joint. In FIGS. 1 and 2, only one planetary gear 34 and carrier pin 35 are shown. The same applies to the planetary gear 44 and carrier pin 45 of the second planetary gear mechanism 40 described later.

[0014] The second planetary gear mechanism 40 includes a sun gear portion 43 formed on an input shaft (sun gear shaft) 41, three planetary gears 44 that mesh with the sun gear portion 43, carrier pins 45 that rotatably support the respective planetary gears 44, and an internal gear 46 with which the respective planetary gears 44 mesh internally. The second planetary gear mechanism 40 extracts the revolution of the three planetary gears 44 generated by the rotation of the sun gear portion 43 from an output member 47 to which the carrier pins 45 are 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 (for example, a ring gear) provided on a driven member (not shown) is integrally fixed to an end of the output shaft 49.

[0015] In the planetary gear device 1 having the above configuration, when the rotational force of the motor is input to the worm reduction mechanism 20, it is first-stage decelerated by the meshing of the worm pinion 21 and the worm gear 22 and 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 revolving component is extracted 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. Also in the second planetary gear mechanism 40, a deceleration action similar to that of the first planetary gear mechanism 30 is performed, the revolution of the planetary gear 44 is extracted 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 a driven member connected to the output pinion 49a. In this way, the rotational force decelerated by the worm reduction mechanism 20 and the two-stage simple planetary gear mechanisms (the first planetary gear mechanism 30 and the second planetary gear mechanism 40) is output to the driven member.

[0016] [Tooth surface shape of the input shaft of the second planetary gear mechanism] FIG. 2 is an enlarged view of the main part of FIG. 1. As shown in this figure, the 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. Among 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.

[0017] 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 the male spline portion 42 is configured by extending each second tooth 43a of the sun gear portion 43 in the axial direction. That is, 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. Among them, 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, since a periodically changing load acts on the sun gear portion 43 (second teeth 43a), which is different from the male spline portion 42 (first teeth 42a), it is preferable that the surface roughness of the tooth surface (for example, the arithmetic mean roughness Ra) is smaller than that of the male spline portion 42. For example, the sun gear portion 43 is subjected to a higher finishing process than the male spline portion 42. Also, for the same reason, it is preferable that the sun gear portion 43 (second teeth 43a) has a higher tooth surface hardness than the male spline portion 42 (first teeth 42a), for example, by performing induction hardening only on the sun gear portion 43.

[0018] FIG. 3(a) is a view of the teeth 41a of the input shaft 41 as seen from the axial direction, and FIG. 3(b) is a cross-sectional view of the teeth 41a taken along line III-III in FIG. 3(a). As shown in FIGS. 3(a) and 3(b), the tooth thickness of the teeth 41a of the input shaft 41 changes in the axial direction (tooth width direction). Specifically, in the present embodiment, for the sun gear portion 43 of the input shaft 41, for the purpose of improving the tooth contact with the planetary gear 44, tooth flank (tooth surface) dressing is performed from a tooth thickness state that is substantially constant in the axial direction (shown by a dashed line). The sun gear portion 43 of the present embodiment is subjected to crowning as the tooth flank dressing. As a result, the sun gear portion 43 has a crowning portion 43b in which the tooth thickness gradually decreases toward both axial ends over the entire axial length thereof. In the crowning portion 43b, within the range of meshing with the planetary gear 44, the tooth thickness is distributed substantially symmetrically in the axial direction, and the tooth thicknesses at both axial ends are substantially the same as each other. Note that the crowning portion 43b only needs to be at least a part of the sun gear portion 43. That is, it is sufficient if the sun gear portion 43 has the crowning portion 43b.

[0019] On the other hand, the male spline portion 42 of the input shaft 41 is not subjected to tooth flank dressing (crowning) processing. Therefore, the male spline portion 42 has a constant tooth thickness portion 42b in which the tooth thickness is substantially constant in the axial direction. Note that the constant tooth thickness portion 42b only needs to be at least a part of the male spline portion 42. That is, it is sufficient if the male spline portion 42 has the constant tooth thickness portion 42b (when there is chamfering at the axial end of the male spline portion 42, that chamfered portion is excluded).

[0020] In this way, in the present embodiment, the sun gear portion 43 has the crowning portion 43b, and the male spline portion 42 has the constant tooth thickness portion 42b. As a result, the meshing of the sun gear portion 43 is improved without deterioration of the meshing of the male spline portion 42. That is, it is possible to perform tooth flank dressing of the sun gear portion 43 while suppressing deterioration of the meshing of the male spline portion 42. More specifically, in normal tooth flank dressing, the entire tooth surface is machined along the tooth width direction using a grinding wheel. In this case, as shown by the two-dot chain line in FIG. 3(b), the tooth shape on the male spline side becomes a curved shape that is an extension of the crowning portion. Therefore, there is a possibility that the meshing between this male spline portion and the female spline portion with a small tooth thickness change deteriorates (play or the like occurs). In this regard, in the present embodiment, crowning is performed such 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, while suppressing the deterioration of the meshing of the male spline portion 42 (the occurrence of backlash), the tooth flanks of the sun gear portion 43 are dressed. As a result, misalignment occurs in each gear of the planetary reduction portion due to the occurrence of backlash in the male spline portion 42, and there is a risk of tooth contact and tooth surface damage. In the present embodiment, the occurrence of such misalignment is suppressed, and the risk of tooth contact and tooth surface damage can be reduced.

[0021] Note that the male spline portion 42 does not necessarily have a constant tooth thickness portion 42b, and it is sufficient that the amount of tooth thickness change in the axial direction is smaller than that of the crowning portion 43b. Here, the "amount of tooth thickness change (in the axial direction)" of the crowning portion 43b refers to the relative amount of tooth thickness change ΔS (in the case of one side; twice that in the case of both sides) between the axial center of the crowning portion 43b with the largest tooth thickness and the axial end with the smallest tooth thickness. Similarly, the "amount of tooth thickness change (in the axial direction)" of the male spline 42b refers to the relative amount of tooth thickness change between the portion of the male spline portion 42b with the largest tooth thickness and the portion with the smallest tooth thickness. In the present embodiment, since the tooth thickness is constant, the amount of tooth thickness change is "0". With such a configuration, the same effect as described above can be obtained. Therefore, for example, as shown in Fig. 4(a), the side of the male spline portion 42 may have a uniform tooth thickness starting from the axial end of the sun gear portion 43 (crowning portion 43b) where the crowning process is completed.

[0022] [Technical Effects of the Present Embodiment] As described above, according to the planetary gear device 1 of the present embodiment, in the input shaft (sun gear shaft) 41, the male spline portion 42 is formed by extending each tooth portion of the sun gear portion 43 in the axial direction. 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 an amount of tooth thickness change in the axial direction that is smaller than that of the crowning portion 43b. Therefore, while suppressing the deterioration of the meshing of the male spline portion 42, the tooth flanks of the sun gear portion 43 can be dressed. As a result, misalignment may occur in each gear of the planetary reduction gear due to the play generated in the male spline portion 42, leading to the risk of gear interference and tooth surface damage. However, in this embodiment, the occurrence of such misalignment can be suppressed, and the risk of interference and tooth surface damage can be reduced.

[0023] Further, according to the planetary gear device 1 of the present embodiment, the male spline portion 42 has a constant tooth thickness portion 42b with a constant tooth thickness in the axial direction. Thereby, while further suppressing the deterioration of the meshing of the male spline portion 42, the tooth flanks of the sun gear portion 43 can be dressed.

[0024] [Modification Example] In the above embodiment, the deterioration of the meshing with the female spline portion 38 is suppressed by suppressing the change 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 according to (corresponding to) the change in the axial tooth thickness of the male spline portion 42. More specifically, as shown in FIG. 4(b), the axial change rates of 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 meshing therewith may correspond to each other. Here, the axial change rates of the tooth thickness of the first tooth 42a and the width of the tooth groove 38a being "corresponding" means that these axial change rates substantially coincide (within a predetermined error range) at the axially corresponding positions.

[0025] In this case, in the tooth flank dressing of the input shaft 41 (tooth 41a), the tooth thickness changes in the axial direction may be processed so as to be smoothly continuous with each other in the crowning portion 43b and the male spline portion 42. For example, the male spline portion 42 may be linearly processed with the tooth thickness change rate of the input side end portion of the crowning portion 43b remaining unchanged. That is, the crowning portion 43b may have a curvilinear change in tooth thickness in the axial direction, and the male spline portion 42 may have a linear change in tooth thickness in the axial direction. By keeping the tooth thickness change rate constant (or not changing it significantly), the processing can be performed relatively easily.

[0026] Thus, even when the tooth thickness of the female spline portion 38 is changed in response to the change in the tooth thickness of the male spline portion 42, it is possible to perform tooth streak dressing of the sun gear portion 43 while suppressing deterioration of the meshing (generation of backlash) between the male spline portion 42 and the female spline portion 38, as in the above-described embodiment.

[0027] [Others] As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above-described embodiments. For example, in the above-described embodiment, the case where the present invention is applied to the input shaft (sun gear shaft) 41 of the second planetary gear mechanism 40 in the second stage has been described, but the present invention is also applicable to the input shaft (sun gear shaft) 31 of the first planetary gear mechanism 30 in the first stage. That is, the intermediate shaft (output shaft) 23 of the worm reduction mechanism 20 (or the output shaft of the motor) 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. Further, the present invention is widely applicable to a planetary gear device having a sun gear shaft, and the number of stages of the reduction mechanism and the combination with any reduction mechanism are not particularly limited.

[0028] Further, in the above-described embodiment, a simple planetary gear mechanism has been described 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 is widely applicable to a planetary gear device (mechanism) in which a sun gear portion and a spline portion are arranged coaxially.

[0029] Further, the planetary gear device according to the present invention is applicable to various reduction mechanisms such as a yaw drive reduction mechanism for a wind power generator, a swing bearing reduction mechanism for an excavator, and a planetary reduction mechanism for a robot. In addition, the details shown in the above-described embodiment can be appropriately changed without departing from the gist of the invention.

Explanation of Reference Numerals

[0030] 1 Planetary gear device 30 First planetary gear mechanism (front-stage reduction mechanism) 37 Output member (front-stage shaft) 38 female spline part 38a tooth groove 40 second planetary gear mechanism 41 input shaft (sun gear shaft) 41a teeth 42 male spline part 42a first teeth 42b constant tooth thickness part 43 sun gear part 43a second teeth 43b crowning part 44 planetary gear Ax central axis ΔS tooth thickness change amount

Claims

1. A planetary gear device comprising a sun gear shaft having a sun gear portion and a planetary gear meshing with the sun gear portion, wherein the sun gear shaft has a male spline portion for connecting to a front-stage shaft, and the male spline portion is formed by each tooth portion of the sun gear portion extending in the axial direction, the sun gear portion has a crowning portion where the tooth thickness gradually decreases toward both axial ends, and the change amount of the tooth thickness in the axial direction of the male spline portion is smaller than that of the crowning portion. A planetary gear device.

2. The male spline portion has a constant tooth thickness portion where the tooth thickness is constant in the axial direction. The planetary gear device according to Claim 1.

3. A planetary gear device comprising 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, wherein the sun gear shaft has a male spline portion for connecting to the front-stage shaft, and the male spline portion is formed by each tooth portion of the sun gear portion extending in the axial direction, the sun gear portion has a crowning portion where the tooth thickness gradually decreases toward both axial ends, the tooth thickness of the male spline portion changes continuously in the axial direction from the crowning portion, and in the front-stage shaft, the female spline portion meshing with the male spline portion has a tooth thickness that changes in the axial direction according to the change in the axial tooth thickness of the male spline portion. A planetary gear device.

4. The crowning portion has a tooth thickness that changes curvilinearly in the axial direction, and the male spline portion has a tooth thickness that changes linearly in the axial direction. The planetary gear device according to Claim 3.

5. In the crowning portion and the male spline portion, the changes in the tooth thickness in the axial direction are smoothly continuous with each other. The planetary gear device according to Claim 3 or Claim 4.

6. The front-stage shaft is an output member of a front-stage speed reduction mechanism. The planetary gear device according to any one of Claims 1 to 5.

7. In the crowning portion, the tooth thicknesses at both axial ends within the range meshing with the planetary gear are the same. The planetary gear device according to any one of Claims 1 to 6.

8. The tooth surface of the sun gear portion has a smaller surface roughness than that of the male spline portion. The planetary gear device according to any one of Claims 1 to 7.

9. The tooth surface of the sun gear portion has a higher hardness than that of the male spline portion. The planetary gear device according to any one of Claims 1 to 8.

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