Planetary gear device

Abstract

To provide a planetary gear device that is easy to manufacture and can reduce an environmental load.SOLUTION: A planetary gear device 100 comprises: a shaft member 10 that rotates around a rotation axis A; a plurality of pinion gears 20 arranged in a circumferential direction of the shaft member 10; a plurality of pinion shafts 30 that rotatably supports the pinion gears 20; a carrier 40 that rotates together with the shaft member 10 around the rotation axis A while supporting one end of the plurality of pinion shafts 30; and a cover that rotates together with the shaft member 10 around the rotation axis A while supporting the other end of the plurality of pinion shafts 30. The shaft member 10, the carrier 40 and the cover 50 are joined via a common joint part J.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a planetary gear device. [Background technology]

[0002] Patent Document 1 discloses a conventional planetary gear device. This planetary gear device has a rotating shaft that rotates around an axis, a plurality of pinion gears arranged around the rotating shaft, a plurality of pinion shafts that rotatably support each of the plurality of pinion gears, and a first member and a second member that support both ends of the plurality of pinion shafts. The first member and the second member rotate around the axis of the rotating shaft together with the rotating shaft while supporting the plurality of pinion shafts. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-191432 A Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the first member is directly joined to the rotating shaft. In contrast, the second member is integrated with the rotating shaft via the first member. In this case, it was necessary to perform a joining operation separately at each of the two joining portions, the joining portion between the first member and the rotating shaft and the joining portion between the second member and the first member. With such a large number of joining portions, when welding the joining portions, the time and power consumption required for welding increases, and the amount of carbon dioxide emissions also increases.

[0005] Therefore, an object of the present disclosure is to provide a planetary gear device that is easy to manufacture and can reduce the environmental impact. [Means for solving the problem]

[0006] The planetary gear device disclosed herein is a planetary gear device comprising a shaft member that rotates around an axis, a plurality of pinion gears arranged circumferentially around the shaft member, a plurality of pinion shafts that rotatably support the pinion gears, a carrier that supports one ends of the plurality of pinion shafts and rotates around the axis together with the shaft member, and a cover that supports the other ends of the plurality of pinion shafts and rotates around the axis together with the shaft member, wherein the shaft member, the carrier, and the cover are joined via a common joint. Effect of the Invention

[0007] According to the present disclosure, the shaft member, the carrier, and the cover are joined via a common joint, which reduces the number of welded parts compared to the conventional case in which they are joined by separate joints, making manufacturing easier and reducing the environmental impact. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing a planetary gear device according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is a view taken along line II-II of FIG. [Diagram 3] FIG. 3 is a cross-sectional view showing a planetary gear device according to a second embodiment of the present disclosure. [Figure 4] FIG. 4 is a cross-sectional view showing a planetary gear unit according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be listed and described. The planetary gear device of the present disclosure is (1) A planetary gear device comprising: a shaft member that rotates around an axis; a plurality of pinion gears arranged circumferentially around the shaft member; a plurality of pinion shafts that rotatably support the pinion gears; a carrier that supports one ends of the plurality of pinion shafts and rotates around the axis together with the shaft member; and a cover that supports the other ends of the plurality of pinion shafts and rotates around the axis together with the shaft member, wherein the shaft member, the carrier, and the cover are joined via a common joint.

[0010] According to the above configuration, the number of joints can be reduced compared to the conventional case where the joint between the carrier and the cover is separate from the joint with the shaft. This reduces the amount of power consumed and the time required for welding when welding the joints, and suppresses carbon dioxide emissions. In this way, the planetary gear device of the present disclosure is easy to manufacture and reduces the environmental impact.

[0011] (2) The shaft member has a flange portion extending radially, the cover forms an inner circumferential surface facing an outer circumferential surface of the flange portion, at least one of the flange portion and the cover has a recess on a surface facing the carrier, the carrier has a convex portion protruding toward the recess and fitting into the recess, and a fitting interface between the recess and the convex portion is connected to a radial interface formed between the outer circumferential surface of the flange portion and the inner circumferential surface of the cover and forms the joint together with the radial interface.

[0012] According to the above configuration, the position where the joint is to be formed can be determined by fitting of the recesses and protrusions.

[0013] (3) The joint may be formed within the thickness range of the flange portion and the cover. According to the above configuration, a compact joint that fits within the plate thickness range of the flange portion and the cover can be realized.

[0014] (4) The joint may be formed linearly in a plate thickness direction of the flange portion and the cover when viewed in side cross section. According to the above-described configuration, electron beam welding can be easily and accurately performed to form the joint.

[0015] [Details of the embodiment of the present disclosure] Specific examples of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0016] <Embodiment 1> A planetary gear device 100 according to a first embodiment of the present disclosure is provided in a transaxle of an electric vehicle such as a hybrid electric vehicle (HEV) or a plug-in hybrid electric vehicle (PHEV). As shown in Figs. 1 and 2, the planetary gear device 100 includes a shaft member 10, a pinion gear 20, a pinion shaft 30, a carrier 40, and a cover 50.

[0017] The shaft member 10 is supported by a bearing portion (not shown) and rotates around a rotation axis A that is set coaxially with the central axis. A plurality of pinion gears 20 are arranged in the circumferential direction of the shaft member 10. One pinion shaft 30 is provided for each pinion gear 20. Each pinion shaft 30 rotatably supports each pinion gear 20. The carrier 40 rotates around the rotation axis A together with the shaft member 10 while supporting one end of each pinion shaft 30. The cover 50 rotates around the rotation axis A together with the shaft member 10 and the carrier 40 while supporting the other end of each pinion shaft 30. The shaft member 10, the carrier 40, and the cover 50 are joined via a common joint J. In the planetary gear device 100 of this embodiment, the joint J is welded.

[0018] The shaft member 10 is formed by forming by forging and then machining. The shaft member 10 has a cylindrical shape with the direction of the central axis as the longitudinal direction. As shown in Figs. 1 and 2, an oil passage 11 through which lubricating oil flows is formed along the axial direction in the center of the shaft member 10. The oil passage 11 is formed branched so as to open on the outer circumferential surface of the shaft member 10. A plate-shaped flange portion 12 is integrally formed on the outer circumferential surface of one end side of the shaft member 10. The flange portion 12 protrudes radially from the one end side of the shaft member 10.

[0019] As shown in FIG. 2, the pinion gears 20 are arranged in groups of three, equidistantly spaced at 120° around the rotation axis A. The pinion gears 20 are helical gears. The pinion shafts 30 are arranged with their central axes parallel to the rotation axis A. An oil passage 31 is formed in each pinion shaft 30. The oil passage 31 opens at one end of the axial direction of each pinion shaft 30 and extends along the axial direction. The oil passage 31 is bent at the axial center of the pinion shaft 30 and opens on the outer circumferential surface of the pinion shaft 30. A needle bearing 32 is arranged between the outer circumferential surface of the pinion shaft 30 and the inner circumferential surface of the pinion gear 20. The pinion shaft 30 supports the pinion gear 20 via the needle bearing 32.

[0020] Each pinion gear 20 meshes with a sun gear 60 on the inner periphery side and with a ring gear (not shown) on the outer periphery side. The sun gear 60 and the ring gear (not shown) rotate around a rotation axis A so as to be rotatable relative to the shaft member 10. In the planetary gear device 100, the pinion gear 20 is drivingly connected to, for example, an internal combustion engine via the carrier 40 and the shaft member 10. The sun gear 60 and the ring gear (not shown) are drivingly connected to, for example, a rotating electric machine and wheels, respectively. When torque is input from the internal combustion engine to the shaft member 10, for example, the planetary gear device 100 distributes a part of the torque to the rotating electric machine via the sun gear 60 and distributes the remaining torque to the wheels via the ring gear (not shown).

[0021] The carrier 40 and the cover 50 are formed in an annular shape. The carrier 40 and the cover 50 are each formed by forging. The central axes of the carrier 40 and the cover 50 are arranged coaxially with the rotation axis A. As shown in FIG. 1, the carrier 40 and the cover 50 are arranged at a predetermined interval from each other in the plate thickness direction. Each pinion gear 20 is arranged between the carrier 40 and the cover 50.

[0022] The carrier 40 and the cover 50 form a plurality of insertion holes 41, 51 into which the ends of the pinion shafts 30 are inserted. The insertion holes 41 on the carrier 40 side and the insertion holes 51 on the cover 50 side are each formed at the same circumferential position about the rotation axis A. The insertion holes 41, 51 are formed at the same circumferential position about the rotation axis A by machining after the carrier 40 and the cover 50 are joined. Side washers 33 are disposed between both end faces of each pinion gear 20 and the carrier 40 and the cover 50. The side washers 33 have functions such as reducing friction between the pinion gear 20 and the carrier 40 and the cover 50, and maintaining the position of the needle bearings 32.

[0023] 1 and 2, the cover 50 faces the flange portion 12 in the radial direction. The cover 50 has an inner circumferential surface 52 which fits onto the outer circumferential surface 12A of the flange portion 12. The radial boundary surface between the inner circumferential surface 52 of the cover 50 and the outer circumferential surface 12A of the flange portion 12 forms a joint J.

[0024] As shown in FIG. 1 and FIG. 2, the cover 50 has a recess 53. The recess 53 is formed on a surface of the cover 50 facing the carrier 40. The recess 53 is formed to have a certain depth in the axial direction (plate thickness direction). In the present embodiment, the depth of the recess 53 is about half the plate thickness of the cover 50. A plurality of recesses 53 are provided. In the present embodiment, three recesses 53 are provided. The three recesses 53 are formed at equal intervals in the circumferential direction around the rotation axis A. Each recess 53 is formed in an arc shape along the inner peripheral surface 52 in a plan view seen from the axial direction. Each recess 53 is formed between the three pinion gears 20 in the circumferential direction around the rotation axis A. The three recesses 53 are open to the inner peripheral surface 52 on the radially inner side. The recesses 53 are defined by the outer peripheral surface 12A of the flange portion 12 when the inner peripheral surface 52 of the cover 50 faces the outer peripheral surface 12A of the flange portion 12.

[0025] As shown in FIG. 1 and FIG. 2, the carrier 40 has a protrusion 42. The protrusion 42 is formed by drawing, deep drawing, or the like during forging of the carrier 40. When the carrier 40 and the cover 50 face each other, the protrusion 42 protrudes toward the recess 53 and fits into the recess 53. Like the recess 53, the protrusion 42 has an arc shape in a plan view seen from the axial direction. The boundary surface between the protrusion 42 and the recess 53 formed by the fitting is connected to the radial boundary surface between the outer peripheral surface 12A of the flange portion 12 and the inner peripheral surface 52 of the cover 50. A part of the fitting boundary surface between the protrusion 42 and the recess 53 is melted together with the radial boundary surface by welding to the joint J, and forms a part of the joint J.

[0026] A plurality of protrusions 42 are provided corresponding to the recesses 53. In the present embodiment, three protrusions 42 are provided. The three protrusions 42 protrude in the axial direction from the inner edge of the annular carrier 40. The three protrusions 42 are arc-shaped in a plan view seen from the axial direction. The three protrusions 42 are arranged at equal intervals in the circumferential direction around the rotation axis A. The inner circumferential surface 42A of the protrusions 42 is continuous and substantially flush with the inner circumferential surface 52 of the cover 50 when the protrusions 42 and the recesses 53 are engaged with each other. The inner circumferential surface 42A of the protrusions 42 and the inner circumferential surface 52 of the cover 50 are linearly connected along the extension direction of the rotation axis A in the side cross-sectional view shown in FIG. 1.

[0027] The inner circumferential surface 42A of the protrusion 42 faces the outer circumferential surface 12A of the flange portion 12 in a state in which the protrusion 42 and the recess 53 are fitted together and the inner circumferential surface 52 of the cover 50 faces the outer circumferential surface 12A of the flange portion 12. In other words, the carrier 40 is fitted onto the outer circumferential surface 12A of the flange portion 12 at the inner circumferential surfaces 42A of the plurality of protrusions 42. A radial boundary surface constituting a joint J is formed between the inner circumferential surface 42A of the protrusion 42 and the outer circumferential surface 12A of the flange portion 12. In the side cross-sectional view shown in FIG. 1, the radial boundary surface formed by the inner circumferential surface 42A of the protrusion 42 is aligned linearly with the radial boundary surface formed by the inner circumferential surface 52 of the cover 50 along the extension direction of the rotation axis A. As a result, the flange portion 12, the cover 50, and the protrusion 42 are joined by a common joint J that is linear in the side cross-sectional view.

[0028] As shown in Fig. 1, the joint J is formed in a linear shape in a side cross-sectional view. The joint J extends in the plate thickness direction of the flange portion 12 and the cover 50. In other words, the joint J is formed in a linear shape along the extension direction of the rotation axis A. As shown in Fig. 2, the joint J is formed in an annular shape along the circumferential direction of the rotation axis A in a plan view seen from the axial direction.

[0029] As described above, welding is performed on the joint J in this embodiment. Electron beam welding is used for the welding. The welding is performed by emitting an electron beam from the cover 50 side. The bead formed by the welding is formed linearly over the radial boundary surface between the cover 50 and the flange portion 12 and the radial boundary surface between the protrusion 42 and the flange portion 12. The welding is performed over the entire circumferential direction around the rotation axis A.

[0030] The operation of the planetary gear device 100 having the above configuration will be described together with the manufacturing procedure. In the planetary gear device 100, the shaft member 10, the carrier 40, and the cover 50 are each formed by forging and then machining. The shaft member 10, the carrier 40, and the cover 50 formed by forging and machining are joined to the carrier 40 by fitting the protrusion 42 into the recess 53, and the cover 50 and the carrier 40 are joined to the flange portion 12 (shaft member 10) by fitting the inner peripheral surface 52 of the cover 50 and the inner peripheral surface 42A of the protrusion 42 to the outer peripheral surface 12A of the flange portion 12 of the shaft member 10. Note that the procedure for assembling the shaft member 10, the carrier 40, and the cover 50 is not limited to the above procedure.

[0031] Next, welding is performed on the intermediate assembly of the shaft member 10, the carrier 40, and the cover 50 thus assembled. In the welding, an electron beam is emitted from the cover 50 side toward the radial boundary surface between the cover 50 and the flange portion 12 in a plan view seen from the axial direction of the rotation axis A. The electron beam for welding is emitted approximately parallel to the rotation axis A.

[0032] As a result, a continuous weld bead is formed on the radial boundary surface between the cover 50 and the flange portion 12 and on the radial boundary surface between the convex portion 42 and the flange portion 12, which is a boundary surface that is linearly continuous with the radial boundary surface in the axial direction. The welding is performed continuously for one revolution in the circumferential direction about the rotation axis A. In this way, in the planetary gear unit 100, the joining of the shaft member 10, the carrier 40, and the cover 50 is completed by one welding in the circumferential direction about the rotation axis A.

[0033] After the shaft member 10, the carrier 40, and the cover 50 are joined together, the insertion holes 41, 51 are formed in the carrier 40 and the cover 50 by machining. Then, each pinion gear 20 is disposed between the carrier 40 and the cover 50, and in this state, the pinion shaft 30 is inserted into each of the insertion holes 41, 51, thereby completing the manufacture of the planetary gear device 100.

[0034] As described above, in the planetary gear device 100 according to this embodiment, the shaft member 10, the carrier 40, and the cover 50 are joined via a common joint J. Therefore, the planetary gear device 100 can reduce the number of joints compared to conventional cases in which the joints between the carrier and the cover are separate from the joints with the shaft, thereby shortening the manufacturing time, simplifying the process, etc. As a result, the device can be easily manufactured and the environmental impact can be reduced.

[0035] In this embodiment, the shaft member 10 has a flange portion 12 that protrudes in the radial direction. The cover 50 forms an inner peripheral surface 52 that faces the outer peripheral surface 12A of the flange portion 12. A recess 53 is formed in the cover 50, and a protrusion 42 that fits into the recess 53 is formed in the carrier 40. The fitting interface between the recess 53 and the protrusion 42 is connected to a radial interface formed between the outer peripheral surface 12A of the flange portion 12 and the inner peripheral surface 52 of the cover 50, and forms a joint J together with the radial interface. For this reason, the planetary gear unit 100 can determine the position where the joint J is formed by the fit between the recess 53 and the protrusion 42.

[0036] In this embodiment, the joint J is formed within the plate thickness range of the flange portion 12 and the cover 50. In this manner, the planetary gear device 100 can realize a compact configuration by fitting the joint J within the plate thickness range of the flange portion 12 and the cover 50.

[0037] In this embodiment, the joint J is formed in a straight line in the plate thickness direction of the flange portion 12 and the cover 50 when viewed in side cross section. Therefore, when forming a weld bead at the joint J, the planetary gear unit 100 can allow the electron beam to smoothly enter the joint J. As a result, the planetary gear unit 100 can form a weld bead at the joint J easily and accurately.

[0038] In this embodiment, the protrusions 42 are formed on the inner peripheral edge of the carrier 40. Therefore, the planetary gear unit 100 is advantageous in terms of material yield during forming by forging, the amount of plastic deformation of the material during forging, etc., compared to conventional cases in which the protrusions are formed on the outer peripheral edge of the carrier.

[0039] <Embodiment 2> A planetary gear unit 200 according to a second embodiment of the present disclosure is similar to the first embodiment in that a shaft member 210, a carrier 240, and a cover 250 are joined via a common joint J, as shown in Fig. 3. The planetary gear unit 200 differs from the first embodiment in that a convex portion 242 on the carrier 240 fits into a concave portion 213 formed in the shaft member 210. Other configurations that are the same as or equivalent to those in the first embodiment are given the same reference numerals, and duplicated explanations will be omitted.

[0040] As shown in FIG. 3, the recess 213 is formed on a surface of the flange portion 212 of the shaft member 210 facing the carrier 240. The recess 213 is formed to have a certain depth in the axial direction (plate thickness direction). In the case of this embodiment, the depth of the recess 213 is about half the plate thickness of the outer peripheral edge portion of the flange portion 212. The recess 213 is formed on the outer peripheral edge portion of the flange portion 212. As in the first embodiment, three recesses 213 are formed at equal intervals in the circumferential direction around the rotation axis A. Each recess 213 is in the shape of a circular arc along the outer peripheral surface 212A of the flange portion 212. Each recess 213 is opened to the outer peripheral surface 212A on the radial outside. The recess 213 is defined by the inner peripheral surface 252 of the cover 250 in a state in which the outer peripheral surface 212A of the flange portion 212 faces the inner peripheral surface 252 of the cover 250.

[0041] The carrier 240 has a protrusion 242 that fits into the recess 213. The fitting boundary surface between the recess 213 and the protrusion 242 is connected to a radial boundary surface formed between the outer circumferential surface 212A of the flange portion 212 and the inner circumferential surface 252 of the cover 250, and forms a joint J together with this radial boundary surface. In a state where the carrier 240 is fitted into the recess 213, the outer circumferential surface 242A of the protrusion 242 is continuous and substantially flush with the outer circumferential surface 212A of the flange portion 212. The outer circumferential surface 242A of the protrusion 242 and the outer circumferential surface 212A of the flange portion 212 are linearly connected along the extension direction of the rotation axis A in the side cross-sectional view shown in FIG. 3.

[0042] In this manner, in the planetary gear device 200, the flange portion 212 (shaft member 210) and the carrier 240 are joined by the engagement of the recess 213 and the protrusion 242, and the cover 250 and the carrier 240 are joined by the inner peripheral surface 252 of the cover 250 being fitted with the outer peripheral surface 242A of the protrusion 242.

[0043] The protruding portion 242 in this embodiment forms a radial boundary surface between the cover 250 and the protruding portion 242. An outer peripheral surface 242A of the protruding portion 242 faces an inner peripheral surface 252 of the cover 250 in a state in which the protruding portion 242 and the recessed portion 213 are fitted together and the inner peripheral surface 252 of the cover 250 faces an outer peripheral surface 212A of the flange portion 212. In other words, the carrier 240 is fitted inside the inner peripheral surface 252 of the cover 250 at the outer peripheral surface 242A of the protruding portion 242.

[0044] 3, a radial boundary surface formed by outer peripheral surface 242A of protrusion 242 and inner peripheral surface 252 of cover 250 is aligned linearly with a radial boundary surface formed by outer peripheral surface 212A of flange portion 212 and inner peripheral surface 252 of cover 250 in the extension direction of rotation axis A. As a result, flange portion 212, cover 250, and protrusion 242 are joined by a common joint J that is linear in side cross section.

[0045] In the planetary gear device 200 of the second embodiment configured as described above, the flange portion 212 (shaft member 210) and the carrier 240 are joined by fitting the recessed portion 213 with the protruding portion 242, and the cover 250 and the carrier 240 are joined by fitting the outer peripheral surface 242A of the protruding portion 242 into the inner peripheral surface 252 of the cover 250. The joint J of these three members 210, 240, 250 is common. Therefore, the planetary gear device 200 can be easily manufactured in the same manner as in the first embodiment.

[0046] In this embodiment, the protrusion 242 of the carrier 240 fits into the recess 213 formed in the flange portion 212. The fitting boundary surface between the recess 213 and the protrusion 242 is connected to a radial boundary surface formed between the outer circumferential surface 212A of the flange portion 212 and the inner circumferential surface 252 of the cover 250, and forms a joint J together with this radial boundary surface. In this way, the planetary gear unit 200 can also determine the formation position of the joint J by the fit between the recess 213 and the protrusion 242.

[0047] In this embodiment, the joint J is formed within the plate thickness range of the flange portion 212 and the cover 250. In this manner, by locating the joint J within the plate thickness range of the flange portion 212 and the cover 250, the planetary gear device 200 can achieve a compact configuration.

[0048] In the planetary gear unit 200, the shaft member 210, the carrier 240, and the cover 250 are joined by a common joint J that is linear in side cross section. Therefore, in the planetary gear unit 200, similar to the first embodiment, when forming a weld bead at the joint J, the bead can be formed easily and accurately.

[0049] <Embodiment 3> 4, a planetary gear unit 300 according to a third embodiment of the present disclosure is similar to the first embodiment in that a shaft member 310, a carrier 340, and a cover 350 are joined via a common joint J. The planetary gear unit 300 differs from the above-described embodiments in that a protrusion 342 on the carrier 340 fits into a recess 313 formed across the shaft member 310 and the cover 350. Other configurations that are the same as or equivalent to those in the above-described embodiments are given the same reference numerals, and duplicated explanations will be omitted.

[0050] 4, the recess 313 is formed in a state in which the outer peripheral surface 312A of the flange portion 312 of the shaft member 310 and the inner peripheral surface 352 of the cover 350 face each other. The depth of the recess 313 is approximately half the plate thickness of the flange portion 312 and the cover 350, as in the above-described embodiments. As in the above-described embodiments, three recesses 313 are formed at equal intervals in the circumferential direction around the rotation axis A. Each recess 313 is in the shape of a circular arc along the radial boundary surface between the flange portion 312 and the cover 350.

[0051] The carrier 340 has a protrusion 342 that fits into the recess 313. A fitting interface between the recess 313 and the protrusion 342 is connected to a radial interface formed between an outer peripheral surface 312A of the flange 312 and an inner peripheral surface 352 of the cover 350, and forms a joint J together with the radial interface. In a state where the carrier 340 is fitted into the recess 313, one end of the radial interface between the flange 312 and the cover 350 abuts against a tip surface 342A of the protrusion 342. In this manner, in the planetary gear device 300, the flange 312 (shaft member 310), the carrier 340, and the cover 350 are joined together by the fitting of the recess 313 and the protrusion 342.

[0052] In the planetary gear device 300 of the third embodiment having the above configuration, the flange portion 312 (shaft member 310), the carrier 340, and the cover 350 are joined together by fitting the recessed portion 313 into the protruding portion 342. The joint portion J of these three members 310, 340, and 350 is common. Therefore, the planetary gear device 300 can be easily manufactured in the same manner as in the first embodiment.

[0053] In this embodiment, the protrusions 342 of the carrier 340 fit into recesses 313 formed in the flange portion 312 and the cover 350. The fitting interface between the recesses 313 and the protrusions 342 connects to a radial interface formed between the outer circumferential surface 312A of the flange portion 312 and the inner circumferential surface 352 of the cover 350, and forms a joint J together with the radial interface. In this way, the planetary gear unit 300 can also determine the position at which the joint J is formed by the fit between the recesses 313 and the protrusions 342.

[0054] In this embodiment, the joint J is formed within the plate thickness range of the flange portion 312 and the cover 350. In this manner, by locating the joint J within the plate thickness range of the flange portion 312 and the cover 350, the planetary gear device 300 can achieve a compact configuration.

[0055] [Another embodiment of the present disclosure] The embodiments disclosed herein should be considered in all respects as illustrative and not restrictive. In the above embodiment, the joints are welded by electron beam welding. In contrast, in other embodiments, the joints may be welded by other welding methods, such as laser beam welding. In the configuration in which the recess is formed across the flange and the cover, as in the above embodiment 3, for example, in order to more reliably join the protrusions, it is preferable to employ welding that can form a wider bead than electron beam welding, laser beam welding, or the like. When welding is performed on a joint, the depth does not have to be uniform. For example, when a joint is formed as in the above-mentioned embodiments 1 and 2, a deeper weld bead may be formed at the fitting portion between the convex portion and the concave portion, and a shallower weld bead may be formed in other portions. In the above embodiment, three protrusions and three recesses are provided, whereas in other embodiments, for example, two protrusions and two recesses may be provided, or four or more protrusions and three recesses may be provided. In the above embodiment, the number of recesses corresponds to the number of protrusions. In contrast, in another embodiment, one recess may be formed over the entire circumference in the circumferential direction around the rotation shaft. In this case, it is more advantageous in terms of workability than separately forming recesses in the number corresponding to the number of protrusions. In the above embodiment, three pinion gears are provided, but in another embodiment, the number of pinion gears may be four or more. In the above embodiment, the shaft member, the carrier, and the cover are each formed by forging, but in other embodiments, the shaft member, the carrier, the cover, and other members may be formed by other forming methods such as machining or press molding. [Explanation of symbols]

[0056] 10,210,310…Shaft member 12,212,312…Flange section 12A, 212A, 312A...Outer surface of flange 20...Pinion gear 30…Pinion shaft 40,240,340…Career 42,242,342…Convex 50, 250, 350…Cover 52, 252, 352…Inner surface of cover 53,213,313…Concave 100, 200, 300...Planetary gear device J…Joint part

Claims

1. A shaft member that rotates around an axis; A plurality of pinion gears arranged in a circumferential direction of the shaft member; a plurality of pinion shafts that rotatably support the pinion gears; a carrier that supports one ends of the pinion shafts and rotates together with the shaft member about the axis; a cover that supports the other ends of the pinion shafts and rotates together with the shaft member about the axis; A planetary gear device comprising: A planetary gear device, wherein the shaft member, the carrier, and the cover are joined via a common joint.

2. The shaft member has a flange portion that protrudes in a radial direction, The cover defines an inner circumferential surface facing an outer circumferential surface of the flange portion, At least one of the flange portion and the cover has a recess on a surface facing the carrier, the carrier has a protrusion that protrudes toward the recess and fits into the recess, 2. The planetary gear device according to claim 1, wherein a fitting interface between the recess and the protrusion is connected to a radial interface formed between an outer circumferential surface of the flange portion and an inner circumferential surface of the cover, and forms the joint together with the radial interface.

3. The planetary gear device according to claim 2 , wherein the joint portion is formed within a thickness range of the flange portion and the cover.

4. 4. The planetary gear device according to claim 2, wherein the joint portion is formed linearly in a plate thickness direction of the flange portion and the cover when viewed in side cross section.

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