Gear device

Abstract

Gear device (1, 200) comprising: a drive shaft (10, 210) into which power is input; an internal gear (31G, 32G, 243); and an external gear (22, 248A, 248B), wherein the drive shaft (10, 210) comprises: a shaft main body (11); a drive shaft hollow portion (11m, 12m, 211m, 212m) provided in the shaft main body (11) and extending in an axial direction, and an internal gear portion (12A, 212A) engaging a drive pinion (110) which is rotationally driven, wherein the drive pinion (110) internally meshing with the internal gear portion (12A, 212A) is configured not to overlap the drive shaft hollow portion (11m, 12m, 211m, 212m) as viewed in the axial direction, and wherein a bearing (41, 42) supporting the shaft main body (11) is provided, the internal gear portion (12A) is provided at an end portion of the shaft main body (11) in the axial direction, and the internal gear portion (12A) is supported by the bearing (41, 42) in a cantilevered manner.

Description

BACKGROUND OF THE INVENTIONField of the InventionCertain embodiments of the present invention relate to a gear device.Description of the Prior ArtGear devices are known that transmit and output power input from a drive shaft via an internal gear and an external gear. From the gear devices configured in this way, a gear device is known in which the drive shaft has a hollow structure, and in particular a hollow portion extending in an axial direction. The hollow structure may be advantageous in that an elongated member such as a cable or a transmission shaft may be located in the hollow portion of the gear device.FIG. 1 of Japanese Unexamined Patent Publication No. 2014-005900 illustrates a configuration as follows. In an eccentrically oscillating gear device having the hollow structure, internal teeth are disposed on an inner periphery of the hollow portion of the drive shaft (center crankshaft). A gear of a motor internally meshes with the internal teeth of the drive shaft.SUMMARY OF THE INVENTIONAccording to the eccentric oscillating gear device disclosed in Japanese Unexamined Patent Publication No. 2014-005900, the gear of the motor is located in the hollow portion of the drive shaft. Consequently, even if the elongated member needs to be located in the hollow portion, the gear hinders the placement of the elongated member, thereby creating a disadvantage in that the advantage of the hollow structure is reduced.It is desirable to provide a gear device having a hollow structure. In the gear device, a drive pinion internally engages with a drive shaft so that power can be input to the drive shaft, and a drive shaft hollow portion can be effectively used.According to an embodiment of the present invention, there is provided a gear device including a drive shaft to which power is input, an internal gear, and an external gear. The drive shaft has a drive shaft hollow portion extending in an axial direction and an internal gear portion meshing with a drive pinion to be rotationally driven. The internal gear portion is configured such that the drive pinion internally engaged with the internal gear portion and the drive shaft hollow portion do not overlap each other as viewed in the axial direction.According to the embodiment of the present invention, an advantageous effect can be obtained in that it is possible to provide a gear device in which a drive pinion internally engages with a drive shaft so that power can be input to the drive shaft, and in which a drive shaft hollow portion can be effectively used.BRIEF DESCRIPTION OF THE FIGURESFIG. 1 is a sectional view illustrating a gear device according to an embodiment of the present invention. FIG. 2 illustrates a drive shaft and an input-side cover. FIG. 3 is a front view when the gear device in FIG. 1 is viewed from an input side. FIG. 4 is a front view when the gear device in FIG. 1 is viewed from an output side. FIG. 5 is a sectional view illustrating an embodiment in which the present invention is applied to a distribution type eccentric oscillating speed reducer.DETAILED DESCRIPTION OF THE INVENTIONHereinafter, each embodiment of the present invention will be described in detail with reference to the drawings.EMBODIMENT 1FIG. 1 is a sectional view illustrating a gear device according to an embodiment of the present invention. In the present specification, a direction extending along a rotation axis O 1 is defined as an axial direction, a direction perpendicular to the rotation axis O 1 is defined as a radial direction, and a direction rotating about the rotation axis O 1 is defined as a circumferential direction. In the axial direction, a side on which a motor 100 is located is referred to as an input side, and an opposite side thereof is referred to as an output side.A gear device 1 according to the embodiment is a reduction gear, and is specifically a bending mesh gear device. The gear device 1 includes a drive shaft 10 to which power of the motor 100 is input. The drive shaft 10 receives the power of the motor 100 and rotates about the rotation axis O 1. The motor 100 is connected to the gear device 1, and power is transmitted from a drive pinion 110 to be rotationally driven to the drive shaft 10. A pitch circle diameter, the number of teeth, and a size (modulus) of teeth of the drive pinion 110 are set by specifications of the gear device 1. In addition, the drive pinion 110 may be set to be made of metal such as steel.FIG. 2 illustrates the input shaft and an output shaft.The drive shaft 10 is configured such that a shaft main body 11 having a hollow portion 11 mextending in the axial direction and a gear member 12 having a hollow portion 12 mextending in the axial direction are connected to each other. The hollow portion 11 mof the shaft main body 11 and the hollow portion 12 mof the gear member 12 communicate with each other, thereby realizing a hollow structure (drive shaft hollow portion) of the drive shaft 10.The shaft main body 11 includes a shaft generator 11A having a non-round (for example, substantially elliptical) outer shape in a cross section perpendicular to the rotation axis O 1, and shaft portions 11B and 11C respectively disposed on both sides of the shaft generator 11A in the axial direction. The shaft portions 11B and 11C have a circular outer shape in a cross section perpendicular to the rotation axis O 1. The shaft main body 11 has a cylindrical shape, and a bolt hole 11 fextending in the axial direction from an end surface on the input side is disposed in a side wall portion of the shaft main body 11. The bolt holes 11 fare respectively disposed at a plurality of locations in the circumferential direction. The shaft main body 11 is made of metal such as steel. However, without being limited thereto, the shaft main body 11 may be made of an iron-based metal other than steel or made of a metal other than the iron-based metal.The gear member 12 includes an internal gear portion 12A having an internal tooth, a connecting portion 12B to be connected to the shaft main body 11 by a connecting member B 1 such as a bolt, and an inserted portion 12C connected (integrated) between the internal gear portion 12A and the Verbindungsabschnitt12Beingefügtist so as to be mutually connected. The gear member 12 is made of a MaterialmiteinemniedrigerenElastizitätsmodulalseinMaterial of the drive sprocket 110 (for example, a resin or aluminum, but the material is not limited thereto). In the gear member 12, the internal gear portion 12A or the internal tooth portion may be made of a material (resin) having the low elastic modulus, and other portions may be made of metal such as steel.The internal gear portion 12A has an annular shape with internal teeth in the inner peripheral portion. In a state where the internal gear portion 12A and the drive pinion 110 mesh with each other, a shortest distance L 1 from the rotation axis O 1 to a tooth tip of the drive pinion 110 (see FIG. 2 ) is larger than a radius L 2 of the hollow portion 12 m. In this way, the drive pinion 110 and the hollow portions 11 mand 12 mdo not overlap each other as viewed in the axial direction. Further, in a case where a space H 1 (to be described later) is disposed in the internal gear portion 12A, the connection portion 12B partitioning an inner circumferential side of the space H 1 is present inside the drive pinion 110 in the radial direction. In this case, the distance L 1 is larger than a sum of the radius L 2 of the hollow portion 12 mand a thickness L 3 in the radial direction of the connection portion 12B partitioning the inner circumferential side of the space H 1. In addition, as described later, a configuration as follows may be adopted. A through hole 35 hinto which the drive pinion 110 is inserted is disposed in an input-side cover 35, and an oil seal 47 is located between the input-side cover 35 and the connection portion 12B of the gear member 12.The connecting portion 12B has a cylindrical shape, and an insertion hole 12 fextending in the axial direction is disposed at a side wall portion of the connecting portion 12B. The insertion holes 12 fare respectively disposed at plural locations in the circumferential direction and are communicated with the bolt holes 11 fof the shaft main body 11, respectively. the connecting portion 12B is connected to the shaft main body 11 through the connecting member B 1 (bolt). The connection portion 12B and the internal tooth of the internal gear portion 12A overlap each other as viewed in the radial direction.The inserted portion 12C has a shape extending radially in the radial direction, for example, a disk-like shape, and connects the connection portion 12B and the internal gear portion 12A to each other on one side (output side) in the axial direction. In this manner, the internal gear portion 12A, the connection portion 12B, and the inserted portion 12C are integrated with each other. The gear member 12 has a space H 1 (FIG. 2 ) surrounded by the connection portion 12B, the internal gear portion 12A, and the inserted portion 12C in three directions, and which may include the drive pinion 110. A pin member portion 12 p, which is fitted to the shaft portion 11B of the shaft main body 11 in a pin member manner, is disposed inside the inserted portion 12C in the radial direction.FIG. 3 is a front view when the gear device in FIG. 1 is viewed from the input side. FIG. 4 is a front view when the gear device in FIG. 1 is viewed from the output side.As illustrated in FIGS. 1 to 3, the input-side cover 35 closes the input side of the gear device 1 except for the hollow portions 11 mand 12 m. The input-side cover 35 has a cover hollow portion 35 mcommunicated with the hollow portions 11 mand 12 mof the drive shaft 10. The cover hollow portion 35 misterminates the hollow portions 11 mand 12 mof the drive shaft 10 as viewed in the axial direction.The input-side cover 35 further includes a through hole 35 hwhich is located outward in the radial direction from the cover hollow portion 35 m. The through hole 35 hcorresponds to an example of the drive pinion hole according to the present invention. The through hole 35 his disposed at a position in the circumferential direction and is of a size that allows the drive pinion 110 to pass therethrough. An end portion of the motor 100 is inserted into the through hole 35 h, thereby positioning the motor 100. The input-side cover 35 has a screw hole 35 n(FIG. 3 ) for fastening the positioned motor 100 via the connection member such as a screw or a bolt. When the motor 100 is mounted, the drive pinion 110 of the motor 100 engages with the internal gear portion 12A of the drive shaft 10.The input-side cover 35 further includes a protruding portion 35 p(FIG. 2 ) internally fitted to an end of an outer cylinder portion 31B of the first internal gear member 31 in a pin member manner, and a cylindrical protruding portion 35 q(FIG. 2 ) facing the connecting portion 12B of the drive shaft 10 in the radial direction. The input-side cover 35 is fixed to the outer cylinder portion 31B of the first internal gear member 31 at multiple locations in the circumferential direction by the connection member B 2 (FIG. 1 ) such as a bolt. The oil seal 47 seals a portion between the protruding portion 35 qof the input-side cover 35 and the connecting portion 12B of the drive shaft 10 to prevent leakage of lubricant. The oil seal 47, the connecting portion 12B, and the internal gear portion 12A are arranged to overlap each other as viewed in the radial direction.The input-side cover 35 is thicker than a head portion of the connecting member B 1 in the axial direction. The head portion of the connecting member B 1 is enclosed inside the cover hollow portion 35 m, and does not protrude outward from an input-side end surface of the input-side cover 35.As illustrated in FIG. 1, the gear device 1 further includes an external gear 22, two internal gears 31G and 32G, a wave generator bearing 21, a housing 33, an output-side cover 34, an input-side cover 35, bearings 41 and 42, a main bearing 43, stop rings 45 and 46, and oil seals 47, 48, and 49.The external gear 22 is a conformal cylindrical member and has teeth on the outer periphery of the external gear 22.For example, the wave generator bearing 21 is a roller bearing and is located between the wave generator 11A and the external gear 22, so that the wave generator 11A and the external gear 22 are relatively rotatable.The stopper rings 45 and 46 are respectively located on both sides in the axial direction of the external gear 22 and the wave generator bearing 21, and adjust the movement in the axial direction of the external gear 22 and the wave generator bearing 21.The two internal gears 31G and 32G are aligned with each other in the axial direction and mesh with the external gear 22. An internal gear 31G is configured such that teeth are disposed in a portion of the inner periphery of the first internal gear member 31. The other internal gear 32G is configured such that teeth are disposed in a portion of the inner periphery of the second internal gear member 32.The first internal gear member 31 has an annular shape and is connected to the housing 33 by a connecting member B 3 such as a bolt. In addition to the internal gear 31G, the first internal gear member 31 has an extension portion 31A extending to a side opposite to the external gear 22 via the stopper ring 45. The bearing 41 is located between the extension portion 31A and the shaft portion 11B. The first internal gear member 31 further includes an outer cylinder portion 31B extending in a cylindrical shape from the extension portion 31A outward in the radial direction and from the gear member 12 outward in the radial direction. The input-side cover 35 is fitted to an end portion on the input side of the outer cylinder portion 31B.The second internal gear member 32 has an annular shape. In addition to the internal gear 32G, the second internal gear member 32 includes an inner ring portion 32 ithat functions as an inner ring of the main bearing 43, and a flange portion 32 fthat is to be connected to a counterpart member that serves as a power output target.The housing 33 covers the outer circumferential side of the internal gear 32G. The inner peripheral portion of the housing 33 includes an outer ring portion 33 oof the main bearing 43, and the housing 33 rotatably supports the second internal gear member 32 via the main bearing 43.The output side cover 34 is connected to the second internal gear member 32 and covers an engagement portion between the external gear 22 and the internal gear 32G from the output side in the axial direction. The output-side cover 34 and the second internal gear member 32 are connected to a counterpart member for outputting the power. A bearing 42 is provided between the output-side cover 34 and the shaft portion 11C of the drive shaft 10, and the drive shaft 10 is rotatably supported by the output-side cover 34.The oil seal 48 is located on the output side of the main bearing 43 between the housing 33 and the second internal gear member 32, and prevents a possibility that a lubricant flows outward from the portion thereof to the outside of the device therebetween. Another oil seal 49 is located on the output side of the bearing 42 between the output-side cover 34 and the drive shaft 10, and prevents a possibility that the lubricant flows out of the apparatus from the portion therebetween. Speed Reduction OperationWhen the drive pinion 110 is rotated by driving the motor 100, the rotational speed of the rotational movement is reduced by the engagement between the internal gear portion 12A and the drive pinion 110, and the reduced rotational speed is transmitted to the drive shaft 10. The drive pinion 110 internally meshes with the internal gear portion 12A. Accordingly, the number of engaging teeth is larger than a case where the outer teeth externally engage with each other. In this way, noise generated by engagement between the drive pinion 110 and the internal gear portion 12A is reduced. Moreover, the number of meshing teeth between the drive pinion 110 and the internal gear portion 12A is larger, and the gear device 1 has a high reduction ratio. Accordingly, torque transmitted from the drive pinion 110 to the internal gear portion 12A is small. Therefore, for example, a material having a low elastic modulus such as a resin can be adopted as a material for the teeth of the internal gear portion 12A. In this way, noise generated by engagement between the drive pinion 110 and the internal gear portion 12A can be reduced.When the drive shaft 10 rotates, the motion of the wave generator 11A is transmitted to the external gear 22. In this case, the external gear 22 is set to have a shape along the outer circumferential surface of the wave generator 11A, and is bent into an elliptical shape having a long shaft portion and a short shaft portion as viewed in the axial direction. Further, the external gear 22 meshes with the internal tooth of the fixed first internal gear member 31 in the long shaft portion. Therefore, the external gear 22 does not rotate at the same rotation speed as the wave generator 11A, and the wave generator 11A relatively rotates inside the external gear 22, then, in accordance with the relative rotation, the external gear 22 is bent and deformed so that a major axis position and a minor axis position move in the circumferential direction. A period of deformation is proportional to a rotation period of the drive shaft 10.When the external gear 22 is bent and deformed, the main axis position moves. In this way, the engagement position between the external gear 22 and the internal gear 31G is changed in a rotational direction. Here, when the number of teeth of the external gear 22 is 100, and the number of teeth of the internal gear 31G is 102, each time the engagement position rotates by one round, the engaging teeth between the external gear 22 and the internal gear 31G are shifted. In this way, the external gear 22 rotates (refers to). In a case of the above-described number of teeth, the rotational speed of the rotational movement of the drive shaft 10 is reduced at a reduction ratio of 100:2, and the reduced rotational speed is transmitted to the external gear 22.On the other hand, the external gear 22 meshes with the other internal gear 32G. Accordingly, the engagement position between the external gear 22 and the internal gear 32G is also changed in the rotational direction by the rotation of the drive shaft 10. On the other hand, the number of teeth of the internal gear 32G and the number of teeth of the external gear 22 are coincident with each other. Accordingly, the external gear 22 and the internal gear 32G do not rotate relative to each other, and the rotational speed of the rotational movement of the external gear 22 is transmitted to the internal gear 32G at a reduction ratio of 1:1. As a result, the rotational speed of the rotational movement of the drive shaft 10 is reduced at a reduction ratio of 100:2, and the reduced rotational speed is transmitted to the second internal gear member 32 and the output-side cover 34. The rotational movement reduced in speed is then transmitted to a counterpart element.As described above, according to the gear device 1 of the embodiment, the drive shaft 10 has the hollow structure (hollow portions 11 mand 12 m) and the internal gear portion 12A with which the drive pinion 110 internally engages. Further, the internal gear portion 12A has a configuration in which the hollow portions 11 mand 12 mand the drive pinion 110 do not overlap each other as viewed in the axial direction. The power is input from the internally engaging drive pinion 110 to the drive shaft 10. Accordingly, noise generated by the engagement between the teeth when the power is input thereto can be reduced more significantly compared to the engagement between the outer teeth. Moreover, the drive pinion 110 does not block the hollow portions 11m and 12m of the hollow structure. Accordingly, it is possible to achieve an advantage that the hollow structure of the gear device 1 can be effectively utilized. For example, the gear device 1 can be operated using an elongated member through the hollow portions 11m and 12m.According to the gear device 1 of the embodiment, the gear device 1 further includes the input-side cover 35 that closes the input side except for the hollow portions 11 mand 12 m. Further, the input-side cover 35 includes the cover hollow portion 35 mcommunicated with the hollow portions 11 mand 12 mof the drive shaft 10, and the through hole 35 hinto which the drive pinion 110 is inserted. Therefore, a transmission portion of the movement from the drive pinion 110 to the drive shaft 10 can be closed by the input-side cover 35. The closing can significantly reduce the noise generated by the engagement between the teeth when the power is input thereto without hindering the hollow structure. In addition, the engagement portion between the drive pinion 110 and the internal gear portion 12A is closed. Accordingly, it is possible to prevent leakage of lubricant from the engagement portion and entry of dust into the engagement portion.Further, according to the gear device 1 of the embodiment, the internal gear portion 12A with which the drive pinion 110 engages is made of a material having a lower elastic modulus than a material of the drive pinion 110. For example, while the drive pinion 110 is made of metal, the internal gear portion 12A is made of a resin. This configuration can be realized such that the number of engaging teeth is increased by the internally engaging drive pinion 110. According to this configuration, an advantageous effect can then be obtained in that the noise generated by the engagement between these two can be significantly reduced.Further, according to the gear device 1 of the embodiment, the drive shaft 10 is configured such that the shaft main body 11 and the gear member 12 are connected to each other. Further, the gear member 12 is configured to include the connecting portion 12B, the internal gear portion 12A, and the inserted portion 12C that connects both together. The connection portion 12B and the internal gear portion 12A are arranged so as to overlap each other as viewed in the radial direction. According to this configuration, the drive pinion 110 may be located between the connection portion 12B and the internal gear portion 12A. The drive pinion 110 and the internal gear portion 12A may be meshed. Further, compared to a configuration in which the connection portion 12B and the internal gear portion 12A are aligned with each other in the axial direction, a dimension of the gear member 12 in the axial direction can be shortened. Therefore, a dimension of the gear device 1 in the axial direction can be shortened.Further, according to the gear device 1 of the embodiment, the inner peripheral portion of the inserted portion 12C of the gear member 12 and the shaft main body 11 are fitted to each other in a pin member manner. In this way, the shaft main body 11 and the gear member 12 can be aligned with each other very accurately, and vibration or noise generated due to misalignment can be reduced.Further, according to the gear device 1 of the embodiment, the oil seal 47 located between the drive shaft 10 and the input-side cover 35, the connection portion 12B of the gear member 12 in the drive shaft 10, and the internal tooth of the internal gear portion 12A are arranged so as to overlap each other as viewed in the radial direction. In this way, the engagement portion between the drive pinion 110 and the internal gear portion 12A can be sealed so that the lubricant does not leak therefrom. Further, as compared with a configuration in which the oil seal 47 is located by sliding from the connecting portion 12B in the axial direction, an advantageous effect in that the dimension of the gear device 1 in the axial direction can be shortened can be obtained.Modification ExampleIn the embodiment, a configuration in which the present invention is applied to a so-called cylinder-type bending mesh gear device 1 has been described as an example. However, the present invention is applicable to various gear devices. For example, the present invention is similarly applicable to a so-called cup-type or hat-type bending mesh gear device, a simple planetary gear device, and a center crank-type eccentric oscillating reduction gear. Further, the present invention is similarly applicable to a so-called distribution type eccentric oscillating speed reducer in which two or more eccentric body shafts (eccentric planetary shafts) each having an eccentric body are offset from the axis of the gear device.For example, in a case where the present invention is applied as an example to the simple planetary gear device, a sun gear shaft to be integrated with a sun gear is configured to have a large diameter. A hollow portion of the hollow structure extending in the axial direction and communicating with the sun gear shaft is disposed in the simple planetary gear device. Further, the sun gear shaft extends in the axial direction. Similar to the drive shaft 10 according to the embodiment, the internal gear portion that meshes with the drive pinion of the motor is disposed in the drive shaft. In addition, the internal gear portion is configured to have a size at which the hollow portion of the hollow structure and dasAntriebsritzelinderAxialrichtunggesehennichtüberlappen. According to this configuration, even in a case of the simple planetary gear device, the effective use of the hollow structure is not hindered. The drive pinion is caused to internally engage the sun gear shaft. In this way, noise generated by the engaging portion can be significantly reduced.In a case where the present invention is applied to a center-crank type eccentric oscillating speed reducer as illustrated in FIG. 1 disclosed in Japanese Unexamined Patent Publication No. 2014-005900, for example, a hollow portion 33 extending in the axial direction is disposed in a center crankshaft 3 to form the hollow structure. Further, the center crankshaft 3 is elongated in the axial direction. Similar to the drive shaft 10 according to the embodiment, the internal gear portion that meshes with the drive pinion of the engine is disposed in the center crankshaft 3. In addition, the internal gear portion is configured to have a size in which the hollow portion 33 of the hollow structure and the drive pinion do not overlap with each other as viewed in the axial direction. Reference numerals in parentheses in this specification indicate reference numerals in Japanese Unexamined Patent Publication No. 2014-005900. According to this configuration, even in a case of the center crank type eccentric oscillating reduction gear, the effective use of the hollow structure is not hindered. The drive pinion is caused to internally engage the center crankshaft. In this way, noise generated by the engaging portion can be significantly reduced.FIG. 5 is a sectional view illustrating an embodiment in which the present invention is applied to a distribution type eccentric oscillating speed reducer. In a case where the present invention is applied to a distribution type eccentric oscillating speed reducer, a configuration illustrated in FIG. 5 may be adopted as an example. An eccentric oscillating speed reducer 200 in FIG. 5 includes a drive shaft 210 in which a shaft main body 211 and a gear member 212 are connected to each other. The gear member 212 of the drive shaft 210 includes an internal gear portion 212A, a connection portion 212B, and an inserted portion 212C. These are configured similarly to the internal gear portion 12A, the connection portion 12B, and the inserted portion 12C according to the above-described embodiment. The shaft main body 211 of the drive shaft 210 and the gear member 212 are connected to each other by a connection member B 5 via a connection portion 212B.The eccentric oscillating reduction gear 200 further includes an eccentric planetary shaft 246 having eccentric bodies 246 aand 246 b, a first external gear 248A in which the eccentric body 246 ais inserted into an off-axis through hole, and a second external gear 248B in which the eccentric body 246 bis inserted into an off-axis through hole. The respective through holes of the external gear 248A and 248B are arranged at plural locations (for example, three locations) in the circumferential direction. A plurality of eccentric planetary shafts 246 are inserted into the through holes, respectively. The eccentric bodies 246 aand 246 bare respectively located in the through holes of the external gears 248A and 248B so as to be rotatable via a bearing 249A for the eccentric body. The input shaft 210 has a transmission gear 211 garranged in the outer peripheral portion of the input shaft 210, and meshes with a planetary gear 246 gconnected to the eccentric planetary shaft 246.Further, the eccentric oscillating reduction gear 200 includes a carrier 247 supporting a plurality of eccentric planetary shafts 246 via a bearing 249B, and an internal gear 243 meshing with the external gears 248A and 248B. The internal gear 243 includes a plurality of external pins 243B functioning as internal teeth and an annular internal gear main body 243A. The internal gear main body 243A has a pin groove that rotatably holds the plurality of external pins 243B in the inner peripheral portion. The plurality of outer pins 243B are held in the plurality of pin grooves. The carrier 247 is in synchronization with the movement of the revolving component of the external gears 248A and 248B via the eccentric planetary shaft 246.Further, the eccentric oscillating reduction gear 200 includes main bearings 245A and 245B located between the internal gear 243 and the carrier 247 and bearings 262A and 262B located between the drive shaft 210 and the carrier 247. In a case where the internal gear 243 is supported by an external mechanism, the carrier 247 is rotatably supported by the internal gear 243 via the main bearings 245A and 245B. Further, the drive shaft 210 is rotatably supported by the carrier 247 via the bearings 262A and 262B. The carrier 247 is connected, for example, to a counterpart element for delivering the rotation-speed-reduced movement.Further, the eccentric oscillating speed reducer 200 includes an input-side cover 250 that closes the input side of the eccentric oscillating speed reducer 200 except for the hollow portions 211 mand 212 m. The input-side cover 250 is connected to the internal gear main body 243A by a connecting member B 6 such as a bolt, and covers the input side of the eccentric oscillating reduction gear 200 and the outer periphery on the input side of the eccentric planetary shaft 246. The input-side cover 250 includes a cover hollow portion 250 mcommunicated with the hollow portions 211 mand 212 mof the drive shaft 210, and a through hole (equivalent to the drive pinion hole) 250 hinto which the drive pinion 110 of the motor 100 is inserted. The motor 100 is fixed to the input-side cover 250 similarly to the above-described embodiment. In this case, the drive pinion 110 meshes with the internal gear portion 212A of the gear member 212.Further, the eccentric oscillating reduction gear 200 includes an oil seal 265 that seals an input-side AbschnittzwischenderAntriebswelle210unddereingangsseitigen cover 250, an oil seal 266 that seals a portion between the drive shaft 210 and the output-side carrier 247, and an oil seal 267 that seals a portion between the internal gear main body 243A and the carrier 247.According to this configuration, when the drive pinion 110 is rotated by driving the motor 100, the movement is transmitted via the internal gear portion 212A internally meshing with the drive pinion 110, and the drive shaft 210 is rotated about the rotation axis O 1. The power is input through the engagement between the drive pinion 110 and the internal gear portion 212A. In this way, the same operation as in the above-described embodiment is realized. Accordingly, it is possible to significantly prevent generation of noise in a portion to which the power is input.When the drive shaft 210 rotates, the rotational motion is transmitted to the eccentric planetary shaft 246 via the transmission gear 211 gand the planetary gear 246 g. Then, the eccentric bodies 246 aand 246 brotate, thereby causing the external gears 248A and 248B to eccentrically oscillate. Due to the eccentric oscillation, the meshing position between the external gears 248A and 248B and the internal gear 243 is changed in the circumferential direction, and the number of teeth therebetween is different, so that the external gears 248A and 248B rotate (revolvate). The revolving component of the external gears 248A and 248B is output to a counterpart member via the carrier 247.Even in the eccentric oscillating reduction gear 200 thus configured, the effective utilization of the hollow structure of the drive shaft 210 is not hindered. The drive pinion 110 is caused to internally engage the drive shaft 210. In this way, noise generated by the engaging portion can be significantly reduced.The embodiments according to the present invention have been described so far. However, the present invention is not limited to the above-described embodiments. For example, in the above-described embodiment, an example has been described as follows. At least the internal tooth portion of the internal gear portion 12A of the drive shaft 10 is made of a material having the lower elastic modulus than the material of the drive pinion 110, such as a resin. However, without being limited thereto, the internal tooth portion of the internal gear portion 12A may be made of a material whose elastic modulus is equal to or greater than the material of the drive pinion 110. Even in this case, the drive pinion 110 internally engages with the drive shaft 210. In this way, it is possible to reduce noise generated from the engagement portion between the internal gear portion 12A and the drive pinion 110. In addition, a specific example is illustrated and described in the embodiment. However, in the embodiment, configuration elements integrally formed of a single element may be replaced with configuration elements divided into a plurality of elements to be joined or fastened to each other. In addition, configuration elements configured such that a plurality of elements are connected to each other may be replaced with configuration elements integrally formed of a single element. Alternatively, the details described in the embodiments may be appropriately modified within a scope not deviating from the gist of the invention.Brief Description of the Reference Numerals1 Gear device 10 Drive shaft 100 Motor 110 Drive pinion 11 Shaft main body 11 m, 12 m Hohl portion (drive shaft cavity portion) 12 Gear member 12A Internal gear portion 12B Connecting portion 12C Inserted portion 12 f Hole 12 p Zapfen member portion 22 External gear 31G, 32G Internal gear 35 Input-side cover 35 mCover cavity portion 35 hThrough hole (drive pinion hole) 200 Eccentrically oscillating reduction gear 210 Drive shaft 211 Shaft main body 211 g Übertragungs gear 211 m, 212 m Portion (drive shaft cavity portion) 212 Gear member 212A Internal gear portion 212B Connecting portion 212C Inserted portion 243 Internal gear 246 Eccentric planetary shaft 247 Carrier 248A, 248 bout gear 250 input side cover 250 mcover hollow portion 250 hthrough hole (drive pinion hole) 265 oil seal O 1 rotation axis

Claims

A gear device (1, 200) comprising: a drive shaft (10, 210) to which power is input; an internal gear (31G, 32G, 243); and an external gear (22, 248A, 248B), wherein the drive shaft (10, 210) has: a shaft main body (11); a drive shaft concave portion (11m, 12m, 211m, 212m) provided in the shaft main body (11) and extending in an axial direction, and an internal gear portion (12A, 212A) engaged with a drive pinion (110) that is rotationally driven, wherein the drive pinion (110) internally engaged with the internal gear portion (12A, 212A) is configured so as not to overlap the drive shaft concave portion (11m, 12m, 211m, 212m) as viewed in the axial direction, and wherein a bearing (41, 42) supporting the shaft main body (11) is provided, the internal gear portion (12A) is provided at an end portion of the shaft main body (11) in the axial direction, and the internal gear portion (12A) is supported by the bearing (41, 42) in a cantilever manner.The gear device (1, 200) according to claim 1, further comprising: an input-side cover (35) covering at least a portion on an input side of the gear device (1, 200), wherein the input-side cover (35) has: a cover hollow portion (35m) communicating with the drive shaft hollow portion (11m, 12m), and a drive pinion hole (35h) disposed at an outer position of the cover hollow portion (35m) in a radial direction and into which the drive pinion (110) is inserted.The gear device (1, 200) according to claim 1 or 2, wherein the internal gear portion (12A) is made of a material having a lower elastic modulus than a material of the drive pinion (110).The gear device (1, 200) according to any one of claims 1 to 3, wherein the drive pinion (110) is made of metal, and the internal gear portion (12A) is made of a resin.The gear device (1, 200) according to any one of claims 1 to 4, wherein the drive shaft (10) is configured such that a shaft main body (11) and a gear member (12) including the internal gear portion (12A) are connected to each other, wherein the gear member (12) includes: a connection portion (12B) to be connected to the shaft main body (11), and an inserted portion (12C) inserted between the internal gear portion (12A) and the connection portion (12B), and wherein an internal tooth of the internal gear portion (12A) and the connection portion (12B) overlap each other as viewed in a radial direction.The gear device (1, 200) according to claim 5, wherein an inner periphery of the inserted portion (12C) and an outer periphery of the shaft main body (11) are fitted to each other in a pin member manner.The gear device (1, 200) according to claim 5 or 6, further comprising: an oil seal (47) located on an outer periphery of the connection portion (12B), wherein an internal tooth of the internal gear portion (12A), the connection portion (12B), and the oil seal (47) overlap when viewed in the radial direction.

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