Gear device

Abstract

To provide a speed reducing gear (speed increasing gear) that prevents the occurrence of unusual noise and improves durability.SOLUTION: A gear device 100 comprises: a first shaft member 111; an eccentric member 120 comprising a cylindrical surface eccentric with respect to a shaft core of the first shaft member 111, and to be rotated together with the first shaft member 111; a bearing 130 arranged on an outer periphery of the eccentric member 120; a first gear 140 arranged on an outer periphery of the bearing 130, comprising a plurality of external teeth in a circumferential direction, and made of resin; and a fixed gear 150 comprising a plurality of internal teeth engaged with the external teeth of the first gear 140. In an axial direction, a middle position 230 of the length of rolling bodies 131 comprised in the bearing 130 is not located in a first region 241 in which the external teeth and the internal teeth are engaged with each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a gear device that functions as a speed reducer or a speed increaser. [Background technology]

[0002] Conventionally, there are reducers that are equipped with multiple gears to reduce the input rotation angle and output it. For example, Patent Document 1 discloses a reducer in which the gears are made of resin and the bearing outer ring is integrated with the resin gear, thereby suppressing abnormal noise such as rattle noise and reducing the number of parts. In addition, Patent Document 2 describes a reducer that reduces the rotation angle by rotating an external gear with fewer teeth than the internal gear eccentrically around the internal gear. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-8953 [Patent Document 2] JP 2021-113598 A Summary of the Invention [Problem to be solved by the invention]

[0004] As described in Patent Document 1, technology for making gears out of resin is known as a method for reducing abnormal noise. However, if the gears of a reducer such as that shown in Patent Document 2 are simply made out of resin, the stress caused by the meshing of the gears is easily transmitted to the bearing that rotatably holds the external gear, and there is a risk of damage to the portion of the outer ring in particular where the raceway of the rolling elements of the bearing is formed and which is thin in the radial direction, due to its low strength.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a gear device that includes at least one resin gear and can improve durability. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, one gear device of the present invention comprises a first shaft member, an eccentric member having a cylindrical surface eccentric with respect to the axis of the first shaft member and rotating together with the first shaft member, a bearing arranged on the outer periphery of the eccentric member, a resin first gear arranged on the outer periphery of the bearing and having a plurality of external teeth in the circumferential direction, and a fixed gear having a plurality of internal teeth that mesh with the external teeth of the first gear, wherein in the axial direction, the central position of the length of the rolling elements of the bearing is not located in a first region where the external teeth and the internal teeth mesh with each other. Effect of the Invention

[0007] According to the present invention, stress caused by meshing between the first gear and the fixed gear is less likely to affect weak parts of the bearing, and the durability of the gear device can be improved. [Brief description of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing an outline of the configuration of a gear device according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of the gear device with the hatching of FIG. 1 removed. [Diagram 3] FIG. 11 is a cross-sectional view showing the outline of the configuration of a gear device according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of a gear device according to the present invention will be described with reference to the drawings. Note that the following embodiment is an example for explaining the present invention, and is not intended to limit the present invention. For example, the shapes, structures, materials, components, relative positional relationships, connection states, numerical values, mathematical expressions, contents of each step in the method, and the order of each step shown in the following embodiment are examples, and may include contents not described below. In addition, geometric expressions such as parallel and orthogonal may be used, but these expressions do not indicate mathematical strictness, and include substantially permissible errors, deviations, etc. In addition, expressions such as simultaneous and identical also include substantially permissible ranges.

[0010] In addition, the drawings are schematic diagrams in which emphasis, omission, or adjustment of the ratio is appropriately performed in order to explain the present invention, and differ from the actual shapes, positional relationships, and ratios. In addition, the X-axis, Y-axis, and Z-axis that may be shown in the drawings indicate orthogonal coordinates that are arbitrarily set for the explanation of the drawings. In other words, the Z-axis is not necessarily an axis along the vertical direction, and the X-axis and Y-axis are not necessarily present in a horizontal plane.

[0011] In addition, in the following, a plurality of inventions may be collectively described as one embodiment, and some of the contents described below are described as optional components related to the present invention.

[0012] FIG. 1 is a cross-sectional view showing an outline of the configuration of a gear device 100 according to an embodiment. Note that in FIG. 1, the teeth of the gears are omitted. The gear device 100 includes a first shaft member 111, an eccentric member 120, a bearing 130, a first gear 140, and a fixed gear 150. In the present embodiment, the gear device 100 includes a second gear 160, a second shaft member 112, and a housing 170. Note that the shape of the teeth of each gear is not particularly limited, and examples of the shape include an involute tooth profile, a cycloid tooth profile, or a tooth profile that is a combination of these. When the first shaft member 111 is an input shaft member and the second shaft member 112 is an output shaft member, the gear device 100 functions as a reducer, and when the first shaft member 111 is an output shaft member and the second shaft member 112 is an input shaft member, the gear device 100 functions as a speed increaser. In this embodiment, the first shaft member 111 will be described as an input shaft member, and the second shaft member 112 will be described as an output shaft member. The gear device 100 is not particularly limited in its application, but may be used, for example, for power assist in a steering device of a moving body such as an automobile, or for steering drive that generates a force for steering the steered wheels of a moving body.

[0013] The first shaft member 111 is a shaft-shaped structural member that is connected to, for example, an output shaft of a motor, and to which torque is input around an axis 211 of the first shaft member 111. In the case of this embodiment, the first shaft member 111 is a cylindrical member, and is attached to the housing 170 via a second bearing 172 so as to be rotatable around the axis 211.

[0014] The eccentric member 120 has a cylindrical surface on its outer periphery that is eccentric with respect to the axis 211 of the first shaft member 111, and is a member that rotates together with the first shaft member 111. The outer periphery of the eccentric member 120 is circular when viewed from the direction of the axis 211, and the central axis 220 is disposed at a position eccentric with respect to the axis 211. In the case of this embodiment, the eccentric member 120 is molded integrally with the first shaft member 111. Note that the eccentric member 120 and the first shaft member 111 are separate bodies, and may be joined by press fitting or the like.

[0015] The bearing 130 is attached to the outer periphery of the eccentric member 120, and is a member that rotatably holds the first gear 140 relative to the eccentric member 120. The type and shape of the bearing 130 are not particularly limited. The bearing 130 may be a ball bearing with a spherical rolling element 131, or a roller bearing with a cylindrical rolling element 131. In the present embodiment, the bearing 130 includes a spherical rolling element 131, and the length of the outer race 132 of the bearing 130 is longer than the length of the inner race 133 in the direction of the shaft core 211 (the X-axis direction in the figure). The bearing 130 includes only one rolling element 131 in the shaft core direction. That is, the bearing 130 does not include rolling elements 131 arranged in the shaft core direction. Details of the arrangement of the bearing 130 will be described later.

[0016] The first gear 140 is a resin gear attached to the outer periphery of the outer race 132 of the bearing 130 and has an external tooth portion 141 with a plurality of external teeth in the circumferential direction. The first gear 140 revolves together with the eccentric member 120 as the first shaft member 111 rotates. The first gear 140 is rotatably attached to the eccentric member 120 only by one bearing 130, and the bearing 130 has only one rolling element 131 in the axial direction. The shape of the first gear 140 is not limited. In the case of this embodiment, the first gear 140 has an internal tooth portion 142 arranged on the second shaft member 112 side (X-side in the figure) with internal teeth in the axial direction (X-axis direction in the figure) with the external tooth portion 141. The external tooth portion 141 and the internal tooth portion 142 are cylindrical and are arranged so that their axial centers are eccentric to the axial center 211 and coincide with the central axis 220 of the eccentric member 120. The internal teeth portion 142 has a larger diameter than the external teeth portion 141, and is connected to the outer periphery of the external teeth portion 141 such that a part of the external teeth portion 141 and a part of the internal teeth portion 142 overlap in the axial direction. The external teeth portion 141 and the internal teeth portion 142 are integrally molded from resin.

[0017] The fixed gear 150 is a gear having a plurality of internal teeth that mesh with the external teeth of the first gear 140. The fixed gear 150 is cylindrical, and the axis of the fixed gear 150 coincides with an axis 211 that is the rotation axis of the first shaft member 111. The fixed gear 150 has a larger outer diameter than the external teeth portion 141 of the first gear 140, and the number of internal teeth of the fixed gear 150 is greater than the number of teeth of the external teeth portion 141. The first gear 140 revolves around the axis 211 while meshing with the fixed gear 150. In other words, the first gear 140 can be expressed as an internally-engraved planetary gear with the fixed gear 150 as a ring gear.

[0018] There is no limitation on the material of the fixed gear 150. In the present embodiment, the fixed gear 150 is made of metal. The fixed gear 150 is fixedly attached to the inner circumferential surface of the housing 170.

[0019] The second gear 160 is a gear having a plurality of external teeth that mesh with the internal teeth of the first gear 140. The second gear 160 has an inner diameter smaller than the inner diameter of the internally toothed portion 142 of the first gear 140, and the number of external teeth of the second gear 160 is smaller than the number of teeth of the internally toothed portion 142. The material of the second gear 160 is not limited. In this embodiment, the second gear 160 is made of metal. The axis of the second gear 160 coincides with the axis 211 of the first shaft member 111.

[0020] The internal teeth of the first gear 140 revolve around the shaft center 211 while rotating about the central axis 220. The internal teeth portion 142 of the first gear 140 functions as a ring gear and meshes with the internal teeth of the first gear 140. The second gear 160, which functions as a planetary gear, rotates around the shaft center 211 due to the rotation and revolution of the internal teeth portion 142.

[0021] The second shaft member 112 is a shaft-shaped structural member that rotates around the axis 211 together with the second gear 160 and outputs torque around the axis 211 to the outside. In the case of this embodiment, the first shaft member 111 is a cylindrical member, and is attached to the housing 170 via a third bearing 173 so as to be rotatable around the axis 211. In the case of this embodiment, the second shaft member 112 is molded integrally with the second gear 160. Note that the second gear 160 and the second shaft member 112 are separate bodies, and may be joined by press-fitting or the like.

[0022] 2 is a diagram showing a cross section of the gear device 100 without hatching in FIG. 1. As shown in the figure, in the axial direction (X-axis direction in the figure), a center position 230 of the length of the rolling element 131 of the bearing 130 is not located in a first region 241 where the external teeth of the first gear 140 and the internal teeth of the fixed gear 150 mesh. In the case of this embodiment, the rolling element 131 of the bearing 130 is a ball, and the center position 230 of the rolling element 131 in the axial direction is the position of the center of the rolling element 131. In addition, the center position 230 of the rolling element 131 is located such that the entire thin-walled portion 250 where the raceway of the outer race 132 is formed and is thinnest in the radial direction is not located in the first region 241, but is located closer to the second shaft member 112 than the first region 241.

[0023] Further, a second region 242 where the internal teeth of the first gear 140 and the external teeth of the second gear 160 mesh with each other is a region aligned with the first region 241 in the axial direction, and is located closer to the second shaft member 112 than the first region 241. The central position 230 of the rolling element 131 is located between the first region 241 and the second region 242. Further, the entire thin-walled portion 250 is not located within the second region 242.

[0024] Further, the central position 230 of the rolling element 131 of the bearing 130 and the thick portion 143 where the external teeth portion 141 and the internal teeth portion 142 of the first gear 140 are integrally connected overlap in the axial direction.

[0025] The outer race 132 of the bearing 130 is molded integrally with the first gear 140 by, for example, insert molding. In the axial direction, a part of the outer race 132 is disposed in the first region 241. In the case of this embodiment, the end face of the outer race 132 on the first shaft member 111 side (X+ side in the figure) is flush with or nearly flush with the end face of the external teeth portion 141 of the first gear 140. In addition, in the axial direction, the end face of the outer race 132 on the second shaft member 112 side (X- side in the figure) is flush with or nearly flush with the end face of the external teeth portion 141 of the first gear 140. The thin-walled portion 250 of the outer race 132 is disposed at a position biased toward the second shaft member 112 side in the axial direction.

[0026] The inner race 133 of the bearing 130 is attached to the eccentric member 120 by, for example, press fitting. In the axial direction, the end face of the inner race 133 on the first shaft member 111 side (X+ side in the figure) is flush with or nearly flush with the end face of the eccentric member 120. In addition, in the axial direction, the end face of the inner race 133 on the second shaft member 112 side (X- side in the figure) is flush with or nearly flush with the end face of the eccentric member 120.

[0027] The present invention is not limited to the above-described embodiment. For example, the components described in this specification may be combined in any manner, or some of the components may be removed to create another embodiment of the present invention. In addition, the present invention also includes modifications that are made to the above-described embodiment by those skilled in the art without departing from the spirit of the present invention, i.e., the meaning of the words in the claims.

[0028] 3, a cylindrical core metal 180 may be provided that is molded integrally with the first gear 140 on the inner periphery of the internal teeth portion 142 of the first gear 140 with its inner surface exposed. In this case, the bearing 130 may be fitted into the inner periphery of the core metal 180 by press fitting or the like.

[0029] Moreover, the core metal 180 may be entirely covered with the resin of the first gear 140. In other words, the core metal 180 may be embedded inside the first gear 140. This can improve the structural strength of the first gear 140.

[0030] As described above, the gear device 100 of the first aspect of this embodiment comprises a first shaft member 111, an eccentric member 120 having a cylindrical surface eccentric with respect to the axis of the first shaft member 111 and rotating together with the first shaft member 111, a bearing 130 arranged on the outer periphery of the eccentric member 120, a first gear 140 made of resin and arranged on the outer periphery of the bearing 130 and having a plurality of external teeth in the circumferential direction, and a fixed gear 150 having a plurality of internal teeth that mesh with the external teeth of the first gear 140, and in the axial direction, the central position 230 of the length of the rolling element 131 of the bearing 130 is not located in the first region 241 where the external teeth and internal teeth mesh with each other.

[0031] According to the gear device 100 of the first aspect, the resin first gear 140 can reduce abnormal noise caused by meshing with the fixed gear 150. Furthermore, although stress caused by meshing between the external teeth of the first gear 140 and the internal teeth of the fixed gear 150 is directly applied to the inner circumference of the first gear 140, the thin-walled portion 250 of the outer race 132 of the bearing 130 is not located in the first region 241, which is the region where the internal teeth and the external teeth mesh, the effect of the stress on the thin-walled portion 250 can be reduced, and damage to the bearing 130 can be suppressed.

[0032] The second embodiment of the gear device 100 includes the first embodiment, and the first gear 140 has a plurality of internal teeth in the circumferential direction in a second region 242 that is aligned with the first region 241 in the axial direction, and the gear device 100 is provided with a second gear 160 having a plurality of external teeth that mesh with the internal teeth of the first gear 140, and a central position 230 of the rolling element 131 is located between the first region 241 and the second region 242.

[0033] According to the gear device 100 of the second aspect, the balance of the distance between the first region 241 and the second region 242 with respect to the central position 230 in the axial direction can be adjusted, and deformation of the first gear 140 can be suppressed.

[0034] The third embodiment of the gear device 100 includes the first embodiment or the second embodiment, and is provided with a cylindrical core 180 that is molded integrally with the first gear 140 on the inner circumference of the first gear 140, and the bearing 130 is fitted into the inner circumference of the core 180.

[0035] According to the gear device 100 of the third aspect, it is possible to improve the strength of the first gear 140 against stress generated in the first region 241. Furthermore, the metal core 180 can mediate the compatibility of the materials between the resin first gear 140 and the metal bearing 130. Furthermore, even if the outer race 132 of the bearing 130 and the first gear 140 cannot be directly molded integrally, the metal core 180 can be used to reinforce the structural strength of the first gear 140 while ensuring a strong connection between the first gear 140 and the bearing 130.

[0036] The fourth aspect of the gear device 100 includes any of the first to third aspects, and in the axial direction, the outer race 132 of the bearing 130 is longer than the inner race 133, and a portion of the outer race 132 is positioned in the first region 241.

[0037] According to the gear device 100 of the fourth aspect, the outer race 132 can withstand the stress generated in the first region 241 when the internal teeth and external teeth mesh, and deflection of the first gear 140 can be suppressed. [Industrial Applicability]

[0038] The present invention is useful, for example, as a gear device 100 mounted on a moving body such as an automobile or an industrial machine. [Explanation of symbols]

[0039] 100... gear device, 111... first shaft member, 112... second shaft member, 120... eccentric member, 130... bearing, 131... rolling element, 132... outer race, 133... inner race, 140... first gear, 141... external teeth portion, 142... internal teeth portion, 143... thick portion, 150... fixed gear, 160... second gear, 170... housing, 172... second bearing, 173... third bearing, 180... core metal, 211... shaft core, 220... central axis, 230... central position, 241... first region, 242... second region, 250... thin portion

Claims

1. A first shaft member; an eccentric member having a cylindrical surface eccentric with respect to an axis of the first shaft member and rotating together with the first shaft member; a bearing disposed on an outer periphery of the eccentric member; a first gear made of resin and arranged on an outer periphery of the bearing and having a plurality of external teeth in a circumferential direction; a fixed gear having a plurality of internal teeth that mesh with the external teeth of the first gear, In the axial direction, the center position of the length of the rolling elements of the bearing is not located in a first region where the external teeth and the internal teeth mesh with each other. Gear mechanism.

2. The first gear is A second region aligned with the first region in the axial direction has a plurality of internal teeth in a circumferential direction, The gear device comprises: a second gear having a plurality of external teeth that mesh with the internal teeth of the first gear, The center position of the rolling element is located between the first region and the second region.

2. The gear arrangement of claim 1.

3. a cylindrical core metal formed integrally with the first gear at an inner periphery of the first gear, The bearing is fitted onto the inner periphery of the core metal. A gear device according to claim 1 or 2.

4. In the axial direction, the outer race of the bearing is longer than the inner race, and a portion of the outer race is disposed in the first region. A gear device according to claim 1 or 2.

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