JP2023117778A - Planetary gear device - Google Patents

Abstract

To provide a planetary gear device that can smoothly rotate planetary gears with respect to a planetary carrier while reducing machining cost.SOLUTION: A planetary gear device 1 comprises: a plurality of planetary gears 2 each having a first gear part 21 and a second gear part 22;, a planetary carrier 3 having a plurality of housing holes 30 holding the planetary gears 2; a sun gear 4 having external teeth 41 engaged with the first gear part 21; and an internal gear 5 having internal teeth engaged with the second gear part 22. The housing holes 30 each have a first hole part 301 housing the first gear part 21, and a second hole part 302 housing the second gear part 22. In the second gear part 22, a part in an axial direction is an engaged part 221 engaged with the internal gear 5, and a non-engaged part 222 is provided between the engaged part 221 and the first gear part 21. An inner surface 302a of the second hole part 302 has a supporting surface 302b supporting the second gear part 22, and an opposed surface 302c opposed to the non-engaged part 222 via a gap.SELECTED DRAWING: Figure 1

Description

The present invention relates to a planetary gear system.

2. Description of the Related Art Conventionally, a planetary gear mechanism is used as a differential for distributing a driving force of a vehicle driving source to a pair of axles (see, for example, Patent Document 1).

The planetary gear mechanism of the differential device described in Patent Document 1 includes a planetary gear (planetary gear) having a large-diameter gear portion and a small-diameter gear portion with different pitch circle diameters, and a planetary gear having a housing support portion that supports the planetary gear so that it can rotate. It has a carrier, a sun gear that meshes with the large-diameter gear portion of the planetary gear, and an internal gear that meshes with the small-diameter gear portion of the planetary gear. The accommodation support portion includes a first accommodation hole that accommodates the large-diameter gear portion and a second accommodation hole that accommodates the small-diameter gear portion. The inner peripheral surface of the first accommodation hole is formed with a first support surface that slidably supports the tooth crest surface of the large-diameter gear portion. The inner peripheral surface of the second housing hole is formed with a second support surface that slidably supports the tip surface of the small-diameter gear portion.

JP 2009-281544 A

In the planetary gear mechanism configured as described above, if the concentricity and parallelism of the first receiving hole and the second receiving hole of the planetary carrier are insufficient, the difference in level between the first receiving hole and the second receiving hole is increased. The corners may come into contact with the planetary gears, resulting in increased wear and frictional force at these parts. For this reason, it is necessary to perform high-precision machining by using a special tool such as a stepped end mill, for example, which increases the machining cost.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a planetary gear device capable of smoothly rotating planetary gears with respect to a planetary carrier while suppressing machining costs.

In order to achieve the above objects, the present invention provides a planetary carrier having a plurality of planetary gears having a first gear portion and a second gear portion arranged in an axial direction, and a plurality of housing holes formed to respectively house the plurality of planetary gears. a sun gear having external teeth that mesh with the first gear portions of the plurality of planetary gears; and an internal gear having internal teeth that mesh with the second gear portions of the plurality of planetary gears, wherein the first gear portion and The second gear portion is a helical gear, the pitch circle diameter of the second gear portion is smaller than the pitch circle diameter of the first gear portion, and the planetary carrier, the sun gear, and the internal gear share a common rotation axis. One axial end surface of the planetary carrier serves as a receiving surface for receiving the thrust force of the sun gear, and the plurality of accommodation holes accommodate the first gear portion and A first hole opening radially inward perpendicular to the rotation axis, and a second hole accommodating the second gear portion and opening radially outward perpendicular to the rotation axis a portion of the second gear portion in the axial direction is a meshing portion that meshes with the internal gear, and a portion between the meshing portion and the first gear portion does not mesh with the internal gear. The inner surface of the second hole is a non-meshing portion, and the inner surface of the second hole portion includes a support surface that receives the meshing reaction force between the meshing portion and the internal gear and supports the second gear portion, and the second gear portion. and a stepped surface between the supporting surface and the opposing surface, wherein the opposing surface is arranged in an axial direction parallel to the rotation axis in the A planetary gear device is provided that is formed between the stepped surface and the receiving surface.

According to the planetary gear device of the present invention, it is possible to smoothly rotate the planetary gears with respect to the planetary carrier while suppressing machining costs.

1 is a cross-sectional view showing a planetary gear device according to an embodiment of the invention; FIG. 2(a) is a cross-sectional view of the planetary gear device taken along line AA of FIG. 1; FIG. 2(b) is a cross-sectional view of the planetary gear device taken along line BB of FIG. 1; FIG. FIG. 3 is a perspective view showing one planetary gear together with a planetary carrier; (a) is a cross-sectional view of a planetary gear device according to an embodiment in which a support surface is formed to be inclined with respect to the axial direction of a planetary carrier. (b) is a cross-sectional view of the planetary gear device according to the embodiment in which the first hole and the second hole are misaligned. (a) is a cross-sectional view of a planetary gear device according to a comparative example in which a support surface is formed to be inclined with respect to the axial direction of a planetary carrier. (b) is a cross-sectional view of a planetary gear device according to a comparative example in which a first hole and a second hole are misaligned.

[Embodiment]
An embodiment of the present invention will be described with reference to the drawings. It should be noted that the embodiment described below is shown as a preferred specific example for carrying out the present invention, and there are portions that specifically illustrate various technically preferable technical matters. , the technical scope of the present invention is not limited to this specific embodiment.

FIG. 1 is a cross-sectional view showing a planetary gear device according to an embodiment of the invention. 2(a) is a cross-sectional view of the planetary gear device taken along line AA of FIG. 1, and FIG. 2(b) is a cross-sectional view of the planetary gear device taken along line BB of FIG. The planetary gear device 1 is mounted on a vehicle, for example, and used as a differential device that distributes the driving force of a driving source such as an engine input from an input shaft to a pair of output shafts while permitting differential rotation.

The planetary gear device 1 includes a plurality of planetary gears 2 having a first gear portion 21 and a second gear portion 22 arranged in the axial direction, and a planetary carrier 3 formed with a plurality of housing holes 30 for housing the plurality of planetary gears 2 respectively. a sun gear 4 having external teeth 41 meshing with the first gear portions 21 of the plurality of planetary gears 2; a bottomed cylindrical internal gear 5 having internal teeth 511 meshing with the second gear portions 22 of the plurality of planetary gears 2; A closing member 6 that closes the opening end of the internal gear 5, and a first thrust bearing 71 and a first thrust washer 72 that are arranged between the first gear portion 21 of the plurality of planetary gears 2 and the closing member 6. , a second thrust bearing 73 arranged between the planetary carrier 3 and the internal gear 5, a second thrust washer 74 arranged between the planetary carrier 3 and the sun gear 4, and the closing member 6. A retainer member 75 for retaining retainer, a first radial bearing 76 fitted in a shaft hole 50 formed in the center of the internal gear 5, and a second radial bearing 77 fitted in the closing member 6. and

In this embodiment, the planetary gear device 1 has eight planetary gears 2, and the same number of receiving holes 30 are formed in the planetary carrier 3 at regular intervals in the circumferential direction. The planetary carrier 3, the sun gear 4, and the internal gear 5 are relatively rotatable around a common rotation axis O. As shown in FIG. Hereinafter, a direction parallel to the rotation axis O will be referred to as an axial direction, and a direction perpendicular to the rotation axis O will be referred to as a radial direction.

In FIG. 1, a first shaft 81 is non-rotatably connected to the planetary carrier 3, a second shaft 82 is non-rotatably connected to the sun gear 4, and a non-rotatable shaft is connected to the internal gear 5. The third shaft 83 is indicated by a phantom line (chain double-dashed line). The first shaft 81 has its distal end supported by the first radial bearing 76 . The second shaft 82 has a cylindrical shape with the first shaft 81 inserted through its center, and is supported by the second radial bearing 77 . The third shaft 83 has a cylindrical shape and is fitted onto the stem portion 53 of the internal gear 5, which will be described later.

When the planetary gear device 1 is used as a differential device for a vehicle, for example, the driving force of the drive source input to the planetary gear device 1 from the first shaft 81 as an input shaft is applied to the second gear device 1 as a pair of output shafts. is distributed to the shaft 82 and the third shaft 83 and output. The second shaft 82 is, for example, a front-wheel-side propeller shaft that transmits driving force to the front wheels of a four-wheel-drive vehicle. The third shaft 83 is, for example, a rear-wheel propeller shaft that transmits driving force to the rear wheels of a four-wheel drive vehicle.

The sun gear 4 has external teeth 41 that mesh with the first gear portion 21 of the planetary gear 2 and are formed in a helical shape so as to be inclined with respect to the axial direction. A spline fitting portion 42 including a plurality of spline teeth 421 extending in the axial direction is formed on the inner peripheral surface of the sun gear 4 . The second shaft 82 is spline-fitted into the spline-fitting portion 42 so as to be non-rotatably connected to the sun gear 4 .

The internal gear 5 includes a cylindrical portion 51, a disc-shaped bottom portion 52 provided inside one axial end portion of the cylindrical portion 51, and a shaft provided protruding from the center portion of the bottom portion 52 in the axial direction. It integrally has a shaped stem portion 53 . The plurality of planetary gears 2 , planetary carrier 3 and sun gear 4 are arranged inside the cylindrical portion 51 . Internal teeth 511 that mesh with the second gear portion 22 of the planetary gear 2 are formed in a spiral shape on the inner peripheral surface of the cylindrical portion 51 so as to be inclined with respect to the axial direction. The internal tooth 511 is formed at a position and in a range where it meshes with a part of the second gear portion 22 of the planetary gear 2 in the axial direction.

A spline fitting portion 54 including a plurality of spline teeth 541 extending in the axial direction is formed on the outer peripheral surface of the stem portion 53 . The third shaft 83 is spline-fitted into the spline-fitting portion 54 so as to be non-rotatably connected to the internal gear 5 .

A male threaded portion 61 formed on the outer peripheral end portion of the closing member 6 is screwed into a female threaded portion 512 formed on the cylindrical portion 51 of the internal gear 5 . The retaining member 75 is press-fitted into the cylindrical portion 51 outside the closing member 6 in the axial direction to retain the closing member 6 .

FIG. 3 is a perspective view showing one planetary gear 2 together with a planetary carrier 3. FIG. In FIG. 3, the planetary carrier 3 is shown in cross-sectional oblique view along the axial direction. In the planetary gear 2, the first gear portion 21 and the second gear portion 22 are helical gears, and the first gear portion 21 and the second gear portion 22 are arranged coaxially. An axial end surface 2 a of the planetary gear 2 on the first gear portion 21 side faces the first thrust washer 72 .

In this embodiment, as an example, the number of teeth of the first gear portion 21 is nine, and nine twisted teeth 210 are spirally formed on the outer peripheral surface of the first gear portion 21 . The number of teeth of the second gear portion 22 is six, and six twisted teeth 220 are spirally formed on the outer peripheral surface of the second gear portion 22 . The twist direction of the twist teeth 210 of the first gear portion 21 and the twist direction of the twist teeth 220 of the second gear portion 22 are the same.

As shown in FIG. 1, the pitch circle diameter _D22 of the second gear portion 22 is smaller than the pitch circle diameter _D21 of the first gear portion. The pitch circle diameter _D21 of the first gear portion is, for example, 1.3 to 1.7 times the pitch circle diameter _D22 of the second gear portion 22. In the illustrated example of FIG. The circle diameter D ₂₁ is 1.5 times the pitch circle diameter D ₂₂ of the second gear portion 22 .

As shown in FIG. 1 , the second gear portion 22 is a meshing portion 221 that partially meshes with the internal teeth 511 of the internal gear 5 in the axial direction. A portion between the meshing portion 221 and the first gear portion 21 is a non-engaging portion 222 that does not mesh with the internal teeth 511 of the internal gear 5 . In the second gear portion 22, a part of the axial direction including the entire meshing portion 221 is a complete gear portion 22a, and a portion closer to the first gear portion 21 than the complete gear portion 22a is an incomplete gear portion 22b. It has become. The incomplete gear portion 22 b is entirely included in the non-meshing portion 222 . FIG. 2(b) shows a cross section of the complete gear portion 22a, and FIG. 2(a) shows a cross section of the incomplete gear portion 22b.

In the complete gear portion 22a, the addendum circle diameter _D1 and the root circle diameter _D2 (see FIG. 2(b)) are constant. In the incomplete gear portion 22b, as shown in FIG. 2(a), the addendum circle diameter _D1 is the same as that of the complete gear portion 22a and is constant, but the root circle diameter _D2 increases toward the first gear portion 21 side. It's getting bigger. That is, in the incomplete gear portion 22b, the tooth bottom surface 220b between the plurality of twisted teeth 220 gradually becomes shallower. The shape of the incomplete gear portion 22b depends on the diameter difference between the first gear portion 21 and the second gear portion 22 and the diameter of the hob cutter when the second gear portion 22 is formed by hobbing using a hob cutter, for example. inevitably occur.

The planetary carrier 3 has a large diameter portion 31 and a small diameter portion 32 having different outer diameters. The sun gear 4 is accommodated inside the large diameter portion 31 . A spline fitting portion 33 including a plurality of spline teeth 331 extending in the axial direction is formed on the inner peripheral surface of the small diameter portion 32 . The first shaft 81 is spline-fitted into the spline-fitting portion 33 so as to be non-rotatably connected to the planetary carrier 3 .

A plurality of accommodation holes 30 are formed over a large diameter portion 31 and a small diameter portion 32, and accommodate a first hole portion 301 that accommodates the first gear portion 21 of the planetary gear 2 and a second gear portion 22 of the planetary gear 2. and a second hole 302 . The first hole portion 301 and the second hole portion 302 are arranged concentrically along the axial direction.

The first hole portion 301 is open radially inward, and the first gear portion 21 of the planetary gear 2 is exposed through this open portion and meshes with the external teeth 41 of the sun gear 4 . The second hole portion 302 is open radially outward, and the second gear portion 22 of the planetary gear 2 is exposed through this open portion and meshes with the internal teeth 511 of the internal gear 5 .

The inner surface 301a of the first hole portion 301 has an arcuate shape with a constant diameter when the planetary carrier 3 is viewed along the rotation axis O from the axial direction. The tooth top surface 210a of the torsion tooth 210 in the first gear portion 21 of the planetary gear 2 which receives the meshing reaction force due to meshing with the external tooth 41 of the sun gear 4 is pressed against the inner surface 301a.

The inner surface 302a of the second hole portion 302 supports the second gear portion 22 of the planetary gear 2 by receiving the meshing reaction force between the meshing portion 221 of the second gear portion 22 of the planetary gear 2 and the internal teeth 511 of the internal gear 5. A supporting surface 302b, a facing surface 302c facing the non-meshing portion 222 of the second gear portion 22 with a gap therebetween, a stepped surface 302d between the supporting surface 302b and the facing surface 302c, and the second gear portion of the planetary gear 2. and a bottom surface 302e facing the axial end surface 2b on the 22 side. The length L of the support surface 302b in the axial direction is equal to or slightly shorter than the length of the meshing portion 221 of the second gear portion 22 .

A support surface 302 b of the second hole portion 302 is formed to have a smaller inner diameter than the first hole portion 301 . When the planetary carrier 3 is viewed from the axial direction along the rotation axis O, the support surface 302b and the opposing surface 302c are arcuate with a constant diameter, as shown in FIGS. 2(a) and 2(b). . The tooth top surface 220a of the torsion tooth 220 in the meshing portion 221 of the second gear portion 22 that receives the meshing reaction force due to meshing with the internal tooth 511 of the internal gear 5 is pressed against the support surface 302b.

A facing surface 302c of the second hole portion 302 has a predetermined gap from the non-meshing portion 222 of the second gear portion 22 and is formed in an arc shape when viewed in the axial direction. The inner diameter of the facing surface 302c is equal to the inner diameter of the first hole 301, and the facing surface 302c and the inner surface 301a of the first hole 301 are formed continuously. The step surface 302d faces the first hole 301 side.

When the planetary gear 2 rotates in the accommodation hole 30, the tooth top surface 210a of the torsion tooth 210 of the first gear portion 21 slides on the inner surface 301a of the first hole portion 301, and the torsion tooth 220 of the second gear portion 22 slides. The tooth top surface 220 a slides on the support surface 302 b of the second hole portion 302 . The frictional force generated by these sliding acts as a rotational resistance against the rotation of the planetary gear 2 , and as a result, acts as a differential limiting force that suppresses the differential between the second shaft 82 and the third shaft 83 .

One end face in the axial direction of the small diameter portion 32 of the planetary carrier 3 serves as a receiving surface 32 a that receives the thrust force of the sun gear 4 generated by the meshing of the planetary gear 2 with the first gear portion 21 . The facing surface 302c of the second hole 302 in the planetary carrier 3 is formed between the stepped surface 302d and the receiving surface 32a in the axial direction of the planetary carrier 3 .

When the planetary carrier 3 rotates in the main direction of rotation (for example, the direction of rotation when the vehicle moves forward), the sun gear 4 is engaged with the first gear portion 21 of the planetary gear 2 to move toward the small diameter portion 32 of the planetary carrier 3. direction axial thrust force is generated. The receiving surface 32 a of the planetary carrier 3 receives this thrust force via the second thrust washer 74 . The second thrust washer 74 is arranged between the receiving surface 32 a of the planetary carrier 3 and the axial end surface 4 a of the sun gear 4 .

In the present embodiment, the second thrust washer 74 is prevented from rotating with respect to the planetary carrier 3 by means of concave-convex fitting, so that when the sun gear 4 and the planetary carrier 3 rotate relative to each other, the axial end surface 4a of the sun gear 4 Slide the second thrust washer 74 . The frictional force generated by this serves as a rotational resistance force against the relative rotation between the sun gear 4 and the planetary carrier 3 , and in turn serves as a differential limiting force that suppresses the differential between the second shaft 82 and the third shaft 83 .

As described above, in the present embodiment, the second hole portion 302 of the planetary carrier 3 has a stepped shape in which the step surface 302d is formed between the support surface 302b and the opposing surface 302c. This stepped shape enables smooth rotation of the planetary gear 2 with respect to the planetary carrier 3 while suppressing machining costs. Next, with reference to FIGS. 4 and 5, the operation and effects of this embodiment will be described.

FIG. 4A shows the planetary carrier 3 according to the present embodiment in which the second holes 302 are formed in a stepped shape, and the supporting surface 302b is inclined away from the rotation axis O toward the first hole 301 side. 1 is a cross-sectional view of a planetary gear device 1 formed by FIG. 4B shows the planetary carrier 3 in which the second hole 302 is formed in a stepped shape, the first hole 301 is biased toward the rotation axis O side from the design value, and the first hole 301 and the first hole 301 FIG. 4 is a cross-sectional view of the planetary gear device 1 when the two holes 302 are formed slightly off-center.

FIG. 5A shows a planetary carrier 3A according to a comparative example in which the second holes 302 are not formed in a stepped shape, in which the supporting surface 302b is inclined away from the rotation axis O toward the first hole 301 side. 1A is a cross-sectional view of a planetary gear device 1A formed by FIG. 5(b) shows that in a planetary carrier 3A in which the second holes 302 are not formed in a stepped shape, the first holes 301 are biased toward the rotation axis O side from the design value, and the first holes 301 and FIG. 11 is a cross-sectional view of a planetary gear device 1A according to a comparative example when a second hole portion 302 is slightly misaligned;

The inclination of the support surface 302b of the second hole 302 and the misalignment between the first hole 301 and the second hole 302 are, for example, separated by cutting the first hole 301 and the second hole 302 using different cutting tools. This may occur, for example, when forming in the step of In addition, in FIGS. 4A and 4B and FIGS. 5A and 5B, for clarity of explanation, the inclination of the support surface 302b and the center between the first hole 301 and the second hole 302 are different. The deviation is exaggerated.

As shown in FIGS. 5A and 5B, when the second hole portion 302 does not have a stepped shape and the support surface 302b is formed up to the position corresponding to the outer periphery of the receiving surface 32a, Compared to the case where the second hole portion 302 has a stepped shape, the corner portion 302f, which is the end portion of the support surface 302b on the side of the first hole portion 301, is located at the non-meshing portion 222 of the second gear portion 22. The tooth crest 220a of the twisted tooth 220 is strongly abutted, and the wear and frictional force at the corner abutting portion are increased.

On the other hand, as shown in FIGS. 4A and 4B, the second hole portion 302 has a stepped shape, and the inner surface 302a of the second hole portion 302 has a gap between the non-meshing portion 222 of the second gear portion 22 and the gap. Even if the corner portion 302g between the opposing surface 302c and the stepped surface 302d contacts the tooth crest surface 220a of the torsion tooth 220 of the second gear portion 22, the contact surface pressure can be made smaller. This allows the planetary gear 2 to rotate smoothly with respect to the planetary carrier 3 .

Further, the machining of the housing holes 30 of the planetary carrier 3 according to the present embodiment is performed by cutting using two end mills having outer diameters corresponding to the inner diameters of the first hole portion 301 and the second hole portion 302, for example. Alternatively, the first hole portion 301 and the second hole portion 302 may be formed by contouring using an end mill having an outer diameter smaller than the inner diameter of the second hole portion 302 . That is, in the planetary carrier 3 according to the present embodiment, the first hole 301 and the second hole 302 can be formed with accuracy that can be achieved by a general processing method using a general-purpose cutting tool. It is possible to reduce costs.

Further, according to the present embodiment, the inner diameter of the facing surface 302c of the second hole 302 of the planetary carrier 3 is equal to the inner diameter of the first hole 301, and the inner surface 301a of the first hole 301 and the facing surface 302c are equal to each other. Since they are formed continuously, the inner surface 301a of the first hole portion 301 and the facing surface 302c of the second hole portion 302 can be formed in the same step using a common cutting tool. This makes it possible to further reduce processing costs.

(Appendix)
As described above, the present invention has been described based on the embodiments, but the embodiments do not limit the invention according to the scope of claims. Also, it should be noted that not all combinations of features described in the embodiments are essential to the means for solving the problems of the invention. In addition, the present invention can be modified appropriately by omitting a part of the configuration, or by adding or replacing the configuration without departing from the gist of the invention.

DESCRIPTION OF SYMBOLS 1... Planetary gear apparatus 2... Planetary gear 21... 1st gear part 22... 2nd gear part 221... Engaging part 222... Non-engaging part 22b... Incomplete gear part 3... Planetary carrier 30... Accommodating hole 301... First hole part 302 Second hole portion 302a Inner surface 302b Support surface 302c Opposing surface 302d Step surface 4 Sun gear 5 Internal gear _D21 Pitch circle diameter _D22 Pitch circle diameter

Claims (3)

a plurality of planetary gears having a first gear portion and a second gear portion arranged in an axial direction; a planetary carrier formed with a plurality of housing holes respectively housing the plurality of planetary gears; and the first gear portions of the plurality of planetary gears. a sun gear having external teeth that mesh with the internal gear, and an internal gear having internal teeth that mesh with the second gear portions of the plurality of planetary gears;
the first gear portion and the second gear portion are helical gears, and the pitch circle diameter of the second gear portion is smaller than the pitch circle diameter of the first gear portion;
the planetary carrier, the sun gear, and the internal gear are relatively rotatable about a common rotation axis;
one axial end surface of the planetary carrier serves as a receiving surface for receiving the thrust force of the sun gear;
The plurality of accommodation holes include a first hole portion that accommodates the first gear portion and is opened inward in a radial direction perpendicular to the rotation axis, and a first hole portion that accommodates the second gear portion and the rotation axis. and a second hole opened radially outward perpendicular to the
A portion of the second gear portion in the axial direction is a meshing portion that meshes with the internal gear, and a portion between the meshing portion and the first gear portion is a non-meshing portion that does not mesh with the internal gear. cage,
The inner surface of the second hole has a support surface that receives a meshing reaction force between the meshing portion and the internal gear and supports the second gear portion, and the non-engagement portion of the second gear portion. and a stepped surface between the supporting surface and the facing surface,
The facing surface is formed between the stepped surface and the receiving surface in an axial direction parallel to the rotation axis,
Planetary gearing. A part of the planetary gear on the first gear part side of the second gear part is an incomplete gear part,
wherein the incomplete gear portion is included in the non-meshing portion;
A planetary gear device according to claim 1. The opposing surface has a predetermined distance from the non-engagement portion and is formed in an arc shape when viewed in the axial direction,
The inner diameter of the facing surface is equal to the inner diameter of the first hole,
The facing surface and the inner surface of the first hole are formed continuously,
A planetary gear device according to claim 1 or 2.

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