Geared motor
The geared motor design addresses the challenges of cost and accuracy by using an elastic support system to maintain zero backlash, enabling cost-effective production with plastic gears while ensuring smooth operation.
Patent Information
- Application Number
- PCT/JP2024/037214
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-11-15
- Filing Date
- 2024-10-18
- Publication Date
- 2025-05-22
AI Technical Summary
Geared motors face challenges in reducing manufacturing costs while maintaining high dimensional accuracy, and existing designs often struggle with backlash issues.
A geared motor design featuring a reduction gear mechanism with gears arranged to achieve zero backlash, supported by elastic members that allow radial displacement of the first support shaft and output gear, enabling smooth operation without increasing dimensional accuracy requirements.
This design achieves low manufacturing costs and high dimensional accuracy by eliminating the need for precise gear alignment and allowing the use of plastic gears, which reduces production costs further.
Smart Images
Figure JP2024037214_22052025_PF_FP_ABST
Abstract
Description
geared motor
[0001] The present invention relates to a geared motor.
[0002] Patent Document 1 describes a motor actuator including a worm formed on a rotating shaft of a motor, a wheel gear that meshes with the worm, and a reduction gear that meshes with the wheel gear. The motor is held inside an inner case by an O-ring. More specifically, the motor is held so that it can move in the axial direction of the rotating shaft due to elastic deformation of the O-ring but cannot move in a direction perpendicular to the rotating shaft.
[0003] Japanese Patent Application Publication No. 8-154358
[0004] Geared motors are required to have reduced manufacturing costs and improved dimensional accuracy.
[0005] A geared motor according to one embodiment includes a motor, a reduction mechanism including a first gear rotatably supported by a first support shaft, and a second gear rotatably supported by a second support shaft and meshing with the first gear. The first gear and the second gear are arranged at a center distance such that backlash is zero. Both ends of the first support shaft are supported by elastic members. The first support shaft and the first gear are radially displaceable by elastic deformation of the elastic members.
[0006] According to one embodiment, a geared motor with low manufacturing costs and high dimensional accuracy is realized.
[0007] FIG. 1 is a perspective view showing the appearance of a geared motor. FIG. 2 is a plan view showing the structure of a geared motor. FIG. 3 is a cross-sectional view showing the structure of a geared motor. FIG. 4 is another cross-sectional view showing the structure of a geared motor. FIG. 5 is a perspective view showing the inside of a cover that constitutes a case. FIG. 6 is a perspective view showing the inside of a main body that constitutes a case. FIG. 7 is a plan view showing the center distance between an output gear and an intermediate gear. FIG. 8 is an explanatory diagram schematically showing the displacement of the output gear.
[0008] An example of an embodiment of the present invention will be described in detail below with reference to the drawings. In all drawings used to explain the embodiment, the same reference numerals are used for the same or substantially the same configurations and elements. Furthermore, as a general rule, once a configuration or element has been explained, it will not be explained again.
[0009] <Overview> Fig. 1 is a perspective view showing the appearance of a geared motor 1A according to this embodiment. Fig. 2 is a plan view showing the structure of the geared motor 1A. Figs. 3 and 4 are cross-sectional views showing the structure of the geared motor 1A. The cross section shown in Fig. 3 is taken along line A-A in Fig. 2, and the cross section shown in Fig. 4 is taken along line B-B in Fig. 2.
[0010] The geared motor 1A is not particularly limited in its application, but may be used in a robot arm, for example.
[0011] The geared motor 1A includes a motor 10, a reduction mechanism 20, and a case 30. The reduction mechanism 20 is housed in the case 30, and a portion of the motor 10 is also housed in the case 30. From another perspective, the motor 10 and the reduction mechanism 20 are housed in the common case 30 and are unitized.
[0012] The rotational driving force output from the motor 10 is reduced in rotation speed by the speed reducing mechanism 20, and the rotational force is increased and output.
[0013] <Motor> The motor 10 is a brushed DC motor and has a rotating shaft 12 with one end protruding from a motor case 11. Although not shown, a stator, a rotor, etc. are housed within the motor case 11, and the rotating shaft 12 rotates integrally with the rotor.
[0014] A worm 13 is provided on one end of the rotating shaft 12 protruding from the motor case 11. From another perspective, a cylindrical pinion gear is provided on one end of the rotating shaft 12 protruding from the motor case 11, and the pinion gear has a series of gear teeth extending in a spiral shape.
[0015] <Reduction Mechanism> <Gears> The reduction mechanism 20 is made up of a first gear 21, a second gear 22, and a third gear 23. The first gear 21 is a single-stage gear, whereas the second gear 22 and the third gear 23 are double-stage gears.
[0016] More specifically, the second gear 22 has a coaxial large gear 22a and a coaxial small gear 22b, and the third gear 23 has a coaxial large gear 23a and a coaxial small gear 23b. The first gear 21, the large gear 22a, the coaxial small gear 22b, and the coaxial small gear 23b are all spur gears. On the other hand, the large gear 23b is a helical gear.
[0017] The third gear 23 is interposed between the worm 13 and the second gear 22 and meshes with these two gears. More specifically, the large gear 23 a of the third gear 23 meshes with the worm 13, and the small gear 23 b of the third gear 23 meshes with the large gear 22 a of the second gear 22.
[0018] The second gear 22 is interposed between the third gear 23 and the first gear 21 and meshes with these two gears. More specifically, the small gear 22b of the second gear 22 meshes with the first gear 21.
[0019] As a result, the rotational driving force output from the motor 10 is transmitted in the following order: worm 13 → third gear 23 → second gear 22 → first gear 21. In other words, the third gear 23 (large gear 23 a) is the input gear of the reduction mechanism 20, and the first gear 21 is the output gear of the reduction mechanism 20.
[0020] Therefore, in the following description, the third gear 23 may be referred to as the "input gear 23," and the first gear 21 may be referred to as the "output gear 21." Also, the second gear 22 may be referred to as the "intermediate gear 22." From another perspective, the third gear 23 meshing with the worm 13 is a worm wheel.
[0021] <<Support Shafts>> The input gear 23, the intermediate gear 22, and the output gear 21 are each rotatably supported within the case 30. More specifically, the output gear 21 is rotatably supported by a first support shaft 41, and the intermediate gear 22 is rotatably supported by a second support shaft 42. In addition, the input gear 23 is rotatably supported by a third support shaft 43.
[0022] The first support shaft 41, the second support shaft 42, and the third support shaft 43 are fixed to the case 30. As shown in Fig. 3, the first support shaft 41 passes through the center of the output gear 21, and both ends thereof are fixed to the case 30. More specifically, one end (lower end 41a) of the first support shaft 41 is fixed to the main body 31 of the case 30, and the other end (upper end 41b) of the first support shaft 41 is fixed to the cover 32 of the case 30.
[0023] 4, the lower end 42a of the second support shaft 42 is fixed to the main body 31 of the case 30, and the upper end 42b of the second support shaft 42 is fixed to the cover 32 of the case 30. As shown in FIG. 3, the lower end 43a of the third support shaft 43 is fixed to the main body 31 of the case 30, and the upper end 43b of the third support shaft 43 is fixed to the cover 32 of the case 30.
[0024] The structure for fixing the first support shaft 41, the second support shaft 42, and the third support shaft 43 to the case 30 will be described later.
[0025] <Case> The main body 31 and cover 32 of the case 30 are made of resin. The main body 31 and cover 32 are butted together and fixed with screws 33 (FIG. 1). However, the material of the case 30 is not limited to resin. The main body 31 and cover 32 may also be made of different materials. Furthermore, the main body 31 and cover 32 may also be fixed using a snap fit, adhesive, or the like.
[0026] Fig. 5A is a perspective view showing the inside of the cover 32, and Fig. 5B is a perspective view showing the inside of the main body 31. In Figs. 5A and 5B, dot patterns are applied to the mating surfaces of the cover 32 and the main body 31.
[0027] A space for accommodating the motor 10 and the reduction mechanism 20 is provided inside the case 30. More specifically, when the cover 32 and the main body 31 are combined, a recess provided on the inside of the cover 32 and a recess provided on the inside of the main body 31 are butted together, and a space for accommodating the motor 10 and the reduction mechanism 20 is formed inside the case 30.
[0028] <Bearings> Both ends of the first support shaft 41, the second support shaft 42, and the third support shaft 43 of the reduction gear mechanism 20 are inserted into bearings provided in the case 30 and are held non-rotatably.
[0029] As shown in Figure 5B, the main body 31 of the case 30 is provided with a bearing portion 51a into which the lower end portion 41a of the first support shaft 41 is inserted, a bearing portion 52a into which the lower end portion 42a of the second support shaft 42 is inserted, and a bearing portion 53a into which the lower end portion 43a of the third support shaft 43 is inserted.
[0030] As shown in Figure 5A, the cover 32 of the case 30 is provided with a bearing portion 51b into which the upper end portion 41b of the first support shaft 41 is inserted, a bearing portion 52b into which the upper end portion 42b of the second support shaft 42 is inserted, and a bearing portion 53b into which the upper end portion 43b of the third support shaft 43 is inserted.
[0031] The lower end 42a of the second support shaft 42 is press-fitted into the bearing portion 52a, and the upper end 42b of the second support shaft 42 is inserted into the bearing portion 52b (see FIG. 4). Similarly, the lower end 43a of the third support shaft 43 is press-fitted into the bearing portion 53a, and the upper end 43b of the third support shaft 43 is inserted into the bearing portion 53b (see FIG. 3).
[0032] As a result, the second support shaft 42 and the third support shaft 43 cannot be displaced in the radial direction. From another perspective, the intermediate gear 22 supported by the second support shaft 42 and the input gear 23 supported by the third support shaft 43 cannot be displaced in the radial direction.
[0033] On the other hand, the first support shaft 41 is displaceable in the radial direction, and the output gear 21 supported by the first support shaft 41 is also displaceable in the radial direction.
[0034] <Elastic Member> The bearings 52a and 52b are round holes having substantially the same diameter as the second support shaft 42. The bearings 53a and 53b are round holes having substantially the same diameter as the third support shaft 43.
[0035] However, the diameter of bearing portion 52b is slightly larger than the diameter of bearing portion 52a. Also, the diameter of bearing portion 53b is slightly larger than the diameter of bearing portion 53a. From another perspective, there is a slight gap between the inner peripheral surface of bearing portion 52b and the outer peripheral surface of upper end portion 42b. Similarly, there is a slight gap between the inner peripheral surface of bearing portion 53b and the outer peripheral surface of upper end portion 43b.
[0036] On the other hand, the bearings 51a and 51b are circular holes with a diameter sufficiently larger than the diameter of the first support shaft 41. That is, when the lower end 41a of the first support shaft 41 is inserted into the bearing 51a, an annular gap is created between them. Similarly, when the upper end 41b of the first support shaft 41 is inserted into the bearing 51b, an annular gap is created between them.
[0037] 3, an elastic member 61 is disposed in the gap between the bearing portion 51a and the lower end portion 41a of the first support shaft 41 inserted into the bearing portion 51a. Also, an elastic member 62 is disposed in the gap between the bearing portion 51b and the upper end portion 41b of the first support shaft 41 inserted into the bearing portion 51b.
[0038] From another perspective, an elastic member 61 is interposed between the bearing portion 51a and the lower end portion 41a of the first support shaft 41, and an elastic member 62 is interposed between the bearing portion 51b and the upper end portion 41b of the first support shaft 41.
[0039] The elastic members 61, 62 are formed in an annular shape from synthetic rubber. That is, the elastic members 61, 62 are rubber O-rings. Although the material of the elastic members 61, 62 is not particularly limited, the elastic members 61, 62 in this embodiment are formed from nitrile rubber.
[0040] The elastic members 61 and 62 have outer diameters that are the same as or approximately the same as the diameters of the bearings 51 a and 51 b, and are fitted into the bearings 51 a and 51 b, so that the outer periphery of the elastic member 61 contacts the inner periphery of the bearing 51 a, and the outer periphery of the elastic member 62 contacts the inner periphery of the bearing 51 b.
[0041] The elastic members 61, 62 have an inner diameter that is the same as or approximately the same as the diameter of the first support shaft 41. The lower end 41a of the first support shaft 41 is press-fitted into the elastic member 61 that is fitted into the bearing portion 51a. The upper end 41b of the first support shaft 41 is press-fitted into the elastic member 62 that is fitted into the bearing portion 51b.
[0042] As a result, the inner periphery of the elastic member 61 contacts the outer periphery surface of the lower end portion 41 a of the first support shaft 41 , and the inner periphery of the elastic member 62 contacts the outer periphery surface of the upper end portion 41 b of the first support shaft 41 .
[0043] That is, both ends of the first support shaft 41 are supported by the elastic members 61, 62. More specifically, the lower end 41a of the first support shaft 41 inserted into the bearing portion 51a is supported by the elastic member 61. Furthermore, the upper end 41b of the first support shaft 41 inserted into the bearing portion 51b is supported by the elastic member 62.
[0044] 6 is a plan view showing the center distance L between the output gear 21 and the intermediate gear 22. The illustrated center distance L is set to a length at which backlash is zero. In other words, there is no backlash between the output gear 21 and the intermediate gear 22, and the gear teeth of the output gear 21 and the intermediate gear 22, which are meshed with each other, are in contact with each other.
[0045] As already mentioned, the output gear 21 is capable of being displaced in the radial direction.
[0046] When the output gear 21 and the intermediate gear 22, which have zero backlash, mesh together, a radial load is applied to the first support shaft 41 and the second support shaft 42. This causes elastic deformation of the elastic members 61 and 62 that support both ends of the first support shaft 41. As a result, the first support shaft 41 moves in a direction away from the second support shaft 42, and the output gear 21 also moves in a direction away from the intermediate gear 22.
[0047] In other words, the center distance L (FIG. 6) temporarily increases. However, the elastically deformed elastic members 61, 62 generate a force (elastic restoring force) that resists the radial load. Therefore, no gap is generated between the output gear 21 and the intermediate gear 22.
[0048] Thereafter, when the radial load is removed or reduced, the elastic members 61, 62 return to their original shapes, the center distance L (FIG. 6) returns to its initial length, and the first support shaft 41 and the output gear 21 return to their original positions.
[0049] As described above, in the geared motor 1A according to this embodiment, the center distance L between the output gear 21 and the intermediate gear 22 is set to a length that eliminates backlash. However, the output gear 21 is able to move radially in response to elastic deformation of the elastic members 61, 62 that support the first support shaft 41. As a result, the gear teeth of the output gear 21 and the intermediate gear 22 do not interfere with each other, allowing the output gear 21 and the intermediate gear 22 to rotate smoothly.
[0050] From another perspective, in the geared motor 1A according to this embodiment, the center distance L between the output gear 21 and the intermediate gear 22 can increase or decrease as the elastic members 61 and 62 are elastically deformed.
[0051] In the geared motor 1A according to this embodiment, there is no need to increase the dimensional accuracy of the output gear 21 and the intermediate gear 22 in order to reduce backlash, and therefore the motor can be manufactured at low cost.
[0052] Furthermore, backlash is sufficiently reduced even when resin gears, which have lower dimensional accuracy than metal gears, are used for the output gear 21 and the intermediate gear 22. From another perspective, the manufacturing cost of the geared motor 1A can be further reduced by using resin gears, which can be mass-produced at low cost.
[0053] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit and scope of the present invention. For example, the radial displacement of the first support shaft 41 (output gear 21) can be increased or decreased as appropriate. The radial displacement of the first support shaft 41 (output gear 21) can be increased or decreased, for example, by changing the hardness or cross-sectional area of the elastic members 61, 62.
[0054] Not only the first support shaft 41, but also the second support shaft 42 and the third support shaft 43 may be supported by an elastic member so as to be displaceable. On the other hand, if the second support shaft 42 and the third support shaft 43 are made immovable, they may be molded integrally with the case 30 (main body 31).
[0055] The specifications of the geared motor 1A, including the center distance L (the center distance L when the output gear 21 and the intermediate gear 22 are not rotating), can be changed as appropriate.
[0056] The number of reduction stages and the reduction ratio of the reduction mechanism 20 can be changed as needed. The motor 10 is not limited to a brushed DC motor. In addition, a sensor (for example, a rotary encoder or a Hall IC) for detecting the rotation speed and rotation angle of the motor 10 may be added.
[0057] The present invention can be configured as follows.
[0058] (1) A geared motor having: a motor; and a reduction mechanism including a first gear rotatably supported by a first support shaft; and a second gear rotatably supported by a second support shaft and meshing with the first gear, wherein the first gear and the second gear are arranged at a center distance such that backlash is zero, both ends of the first support shaft are supported by elastic members, and the first support shaft and the first gear are radially displaceable by elastic deformation of the elastic members.
[0059] (2) A geared motor as described in (1), having a case that houses the reduction mechanism, wherein the two end portions of the first support shaft are inserted into two bearing portions provided in the case, respectively, and the elastic member is interposed between each of the bearing portions and the end portion of the first support shaft that is inserted into the bearing portion.
[0060] (3) The geared motor described in (2), wherein the elastic member is annular, the outer periphery of the elastic member is in contact with the inner periphery of the bearing portion, and the inner periphery of the elastic member is in contact with the outer periphery of the end of the first support shaft.
[0061] (4) The geared motor according to any one of (1) to (3), wherein the elastic member is made of synthetic rubber.
[0062] (5) The geared motor according to any one of (1) to (4), wherein the reduction mechanism includes a third gear interposed between a worm provided on a rotary shaft of the motor and the second gear.
[0063] (6) The geared motor according to (5), wherein the third gear is an input gear of the reduction mechanism, and the first gear is an output gear of the reduction mechanism.
[0064] DESCRIPTION OF SYMBOLS 1A...geared motor, 10...motor, 11...motor case, 12...rotating shaft, 13...worm, 20...reduction mechanism, 21...first gear (output gear), 22...second gear (intermediate gear), 22a...large gear, 22b...small gear, 23...third gear (input gear), 23a...large gear, 23b...small gear, 30...case, 31...main body, 32...cover, 41...first support shaft, 41a...lower end, 41b...upper end, 42...second support shaft, 42a...lower end, 42b...upper end, 43...third support shaft, 43a...lower end, 43b...upper end, 51a, 51b...bearing portion, 52a, 52b...bearing portion, 53a, 53b...bearing portion, 61, 62...elastic member
Claims
1. A geared motor comprising: a motor; a reduction mechanism including a first gear rotatably supported by a first support shaft; and a second gear rotatably supported by a second support shaft and meshing with the first gear, wherein the first gear and the second gear are arranged at a center distance such that backlash is zero, both ends of the first support shaft are supported by elastic members, and the first support shaft and the first gear are radially displaceable by elastic deformation of the elastic member.
2. A geared motor as described in claim 1, further comprising a case that houses the reduction mechanism, wherein both ends of the first support shaft are inserted into two bearing portions provided in the case, respectively, and the elastic member is interposed between each of the bearing portions and the end of the first support shaft inserted into the bearing portion.
3. A geared motor as described in claim 2, wherein the elastic member is annular, the outer periphery of the elastic member is in contact with the inner periphery of the bearing portion, and the inner periphery of the elastic member is in contact with the outer periphery of the end of the first support shaft.
4. The geared motor according to claim 1, wherein the elastic member is made of synthetic rubber.
5. A geared motor as claimed in claim 1, wherein said reduction mechanism includes a third gear interposed between said second gear and a worm provided on a rotating shaft of said motor.
6. A geared motor according to claim 5, wherein the third gear is an input gear of the reduction mechanism, and the first gear is an output gear of the reduction mechanism.
Citation Information
Patent Citations
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