Joint unit
The joint unit design with biased intermediate gears and elastic members addresses backlash and noise issues in complex gear structures, achieving smooth operation and reduced wear.
Patent Information
- Application Number
- JP2024001878
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-01-10
- Publication Date
- 2025-07-23
- Estimated Expiration
- 2044-01-10
AI Technical Summary
Existing joint units with large gaps (backlash) between gears cause noise and vibration due to collisions between teeth, and their complex structures exacerbate this issue.
A joint unit design featuring two opposing bevel gears, an intermediate bevel gear, a shaft, bearings, and an elastic member that biases the intermediate gear along a specific axis to reduce backlash and prevent collisions.
The design effectively suppresses backlash and associated noise and vibration while maintaining a simple gear structure, ensuring smooth operation and reduced wear.
Smart Images
Figure 2025108156000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a joint unit.
Background Art
[0002] Patent Document 1 below discloses a joint unit capable of moving an arm of a robot or the like. The joint unit has a pair of gears that are two bevel gears facing each other, and an intermediate gear that is a bevel gear disposed between the two pair of gears. The teeth of the intermediate gear mesh with the teeth of the two pair of gears. The two pair of gears receive the power of different motors and are rotatable independently of each other. When the two pair of gears rotate in different directions (for example, when one rotates clockwise and the other rotates counterclockwise), the intermediate gear rotates about the axis of the intermediate gear. Also, when the two pair of gears rotate in the same direction (for example, when both of the two gears rotate clockwise, or when both of the two gears rotate counterclockwise), the intermediate gear rotates and moves about the axis of the pair of gears. By these two types of movements of the intermediate gear, it is possible to move a member such as an arm connected to the intermediate gear in two directions (for example, the front-rear direction and the left-right direction).
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] When there is a large gap (backlash) between the teeth of the opposing gear and the intermediate gear, when the opposing gear starts to rotate, a collision occurs between the teeth of the opposing gear and the teeth of the intermediate gear. This causes noise and vibration. In this regard, in the configuration of Patent Document 1 described above, the member constituting the inner peripheral portion of the opposing gear can be separated from the member constituting the outer peripheral portion of the opposing gear. Then, an elastic member is disposed between these members, and by biasing the member constituting the inner peripheral portion of the opposing gear with the elastic member, an increase in the backlash between the opposing gear and the intermediate gear is suppressed. However, the opposing gear is composed of two members, and the structure of the opposing gear is complex.
[0005] An object of the present disclosure is to suppress an increase in backlash with a gear having a simple structure.
Means for Solving the Problem
[0006] The joint unit may include two opposing gears that are two opposing bevel gears, an intermediate gear that is a bevel gear meshing with both of the two opposing gears, a first shaft that rotatably supports a first gear that is any one of the two opposing gears and the intermediate gear, a bearing disposed between the first gear and the first shaft, and an elastic member. The first gear may have an opposing surface that opposes the bearing in a direction along a first axis defined by the first shaft. The elastic member may bias the opposing surface in a direction along the first axis via the bearing. According to this, an increase in backlash with a gear having a simple structure can be suppressed.
Brief Description of the Drawings
[0007]
Figure 1
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Figure 10
[0008] [1. First Embodiment] First, a first embodiment proposed in the present disclosure will be described with reference to the drawings. FIG. 1 is a perspective view showing a joint unit 1A according to the first embodiment. FIG. 2 is a front view of the joint unit 1A. FIG. 3 is a partially enlarged view of FIG. 2 and shows two opposing gears 2 (2A, 2B) provided in the joint unit 1A and an intermediate gear 3. In the following description, X1 and X2 shown in each figure are referred to as the left and right respectively, Y1 and Y2 are referred to as the front and rear respectively, and Z1 and Z2 are referred to as the upper and lower respectively.
[0009] [1-1. Outline of Joint Unit] The joint unit 1A may be attached to a robot in order to move the arm of the robot. The joint unit 1A is attached to, for example, a robot imitating a human or an animal and functions as a joint for moving the arm, leg, neck, waist, etc. of the robot.
[0010] As shown in FIGS. 1 and 2, the joint unit 1A may have two opposing gears 2 (2A and 2B) which are two bevel gears facing each other, and an intermediate gear 3 which is a bevel gear meshing with both of these two opposing gears 2. In the example shown in FIGS. 1 and 2, the two opposing gears 2 face each other in the left - right direction. And the intermediate gear 3 is disposed between the two opposing gears 2 in the left - right direction. The opposing gear 2A is located to the left of the intermediate gear 3. The opposing gear 2B is located to the right of the intermediate gear 3. Not limited to this, the two opposing gears 2 may face each other in the up - down direction with the intermediate gear 3 in between, or may face each other in the diagonal direction of left - right and up - down.
[0011] As shown in FIG. 3, each of the two opposing gears 2 may have a bevel gear portion 21 provided at its end with a plurality of teeth 21a arranged along the rotational direction of each opposing gear 2. The intermediate gear 3 may also have a bevel gear portion 31 provided at its end with a plurality of teeth 31a arranged along the rotational direction of the intermediate gear 3. The width of the plurality of teeth 21a provided on the bevel gear portion 21 of each opposing gear 2 may gradually increase toward the outer periphery of the bevel gear portion 21. The width of the plurality of teeth 31a provided on the bevel gear portion 31 of the intermediate gear 3 may also gradually increase toward the outer periphery of the bevel gear portion 31.
[0012] The intermediate gear 3 may be rotatable about the first axis Ax1 shown in FIG. 1. Also, the two opposing gears 2 may be rotatable about the second axis Ax2 shown in FIG. 1. In the example shown in FIG. 1, the first axis Ax1 extends in the front - rear direction, and the second axis Ax2 extends in the left - right direction. In the example shown in FIG. 1, the first axis Ax1 and the second axis Ax2 intersect perpendicularly. Not limited to this, the first axis Ax1 and the second axis Ax2 may be in a twisted position. Also, the angle formed by the first axis Ax1 and the second axis Ax2 does not necessarily have to be 90 degrees.
[0013] As shown in FIG. 1, the joint unit 1A may have two motors 4 (4A and 4B). In the example shown in FIG. 1, the motor 4A drives the opposing gear 2A, and the motor 4B drives the opposing gear 2B. The joint unit 1A has drive gears 22 respectively fixed to the two opposing gears 2, and the motor 4 is connected to each drive gear 22. Thereby, the two opposing gears 2 can receive the power of different motors 4 and rotate independently of each other about the second axis Ax2.
[0014] The two opposing gears 2 may both be able to rotate in the same direction or may rotate in opposite directions to each other. Also, the two opposing gears 2 may rotate while having different rotational speeds from each other while rotating in the same direction. Further, while one of the two opposing gears 2 is stopped, only the other may rotate. Here, "the two opposing gears 2 rotate in the same direction" means that both of the two opposing gears 2 rotate in the direction indicated by R1 in FIG. 3 or rotate in the direction indicated by R2 in FIG. 3. Also, "the two opposing gears 2 rotate in opposite directions to each other" means that one of the two opposing gears 2 rotates in the direction indicated by R1 in FIG. 3 and the other gear rotates in the direction indicated by R2 in FIG. 3.
[0015] When the two opposing gears 2 rotate in opposite directions to each other, the intermediate gear 3 rotates about the first axis Ax1. Also, when the two opposing gears 2 rotate in the same direction, the intermediate gear 3 moves (rotates) about the second axis Ax2. As shown in FIG. 1, the intermediate gear 3 may be fixed to the connecting member 71 by a fixture such as a screw. The intermediate gear 3 may have a bevel gear portion 31 at one end and a base portion 32 at the other end. The connecting member 71 may be fixed to the base portion 32 of the intermediate gear 3.
[0016] The connecting member 71 to which the intermediate gear 3 is fixed may rotate or move together with the intermediate gear 3. The articulated unit 1A provided with the intermediate gear 3 may rotate or move relative to the connecting member 71. The articulated unit 1A can move relative to the member fixed to the connecting member 71 about the first axis Ax1 when the two opposing gears 2 rotate in opposite directions to each other. Such movement of the articulated unit 1A is referred to as a roll motion. Further, the articulated unit 1A can move relative to the member fixed to the connecting member 71 about the second axis Ax2 when the two opposing gears 2 rotate in the same direction. Such movement of the articulated unit 1A is referred to as a pitch motion. The articulated unit 1A can perform a roll motion, a pitch motion, and a combined motion of the roll motion and the pitch motion.
[0017] For example, a member of a robot (e.g., an arm or a body) (hereinafter referred to as a first member), not shown, may be fixed to the connecting member 71. By the connecting member 71 rotating about the first axis Ax1 or the connecting member 71 moving together with the intermediate gear 3 about the second axis Ax2, the first member fixed to the connecting member 71 can move about the first axis Ax1 and the second axis Ax2. Further, an articulated unit 1A may be provided at an end of the first member. In this case, the connecting member 71 may be fixed to a second member which is a member of a robot different from the first member. Also by the connecting member 71 moving or rotating with respect to the second member, the first member can move about the first axis Ax1 and the second axis Ax2.
[0018] [1-2. Internal Structure] FIG. 4 is a cross-sectional view showing a cross-section along line IV-IV (a line overlapping with the second axis Ax2) of FIG. 2. As shown in FIG. 4, the joint unit 1A may have a shaft 5 (an example of the first axis) that rotatably supports two opposing gears 2 and an intermediate gear 3. The shaft 5 may have a T-shaped configuration and may have a first shaft portion 51 extending along the first axis Ax1 and a second shaft portion 52 extending along the second axis Ax2. The first axis Ax1 may intersect the second axis Ax2. The first axis Ax1 may intersect the second axis Ax2 perpendicularly. The first shaft portion 51 may extend along the first axis Ax1 from a central position in the direction along the second axis Ax2 of the second shaft portion 52.
[0019] Also, as shown in FIG. 4, the joint unit 1A may have a bearing 61 disposed between the intermediate gear 3 and the shaft 5 (more specifically, the first shaft portion 51), and a bearing 62 disposed between each opposing gear 2 and the shaft 5 (more specifically, the second shaft portion 52). The bearings 61, 62 allow relative rotation of the two opposing gears 2 and the intermediate gear 3 with respect to the shaft 5. The bearings 61, 62 may be radial bearings. In the example shown in FIG. 4, the joint unit 1A has two bearings 61 arranged along the first axis Ax1 and in contact with each other in this direction, and two bearings 62 arranged along the second axis Ax2 and in contact with each other in this direction. The number of the bearings 61, 62 is not limited to two, and may be one or a plurality of three or more.
[0020] As shown in FIG. 4, each opposing gear 2 may have a cylindrical portion 23 extending along the second axis Ax2. The bearing 62 may be housed inside the cylindrical portion 23. An bevel gear portion 21 (see FIG. 3) may be formed at one end of the cylindrical portion 23 of each opposing gear 2, and a drive gear 22 connected to the motor 4 may be formed at the other end. In each opposing gear 2, the bevel gear portion 21, the drive gear 22, and the cylindrical portion 23 may be integrally formed.
[0021] Further, as shown in FIG. 4, the intermediate gear 3 may have a cylindrical portion 33 extending along the first axis Ax1, and a bearing 61 may be housed inside the cylindrical portion 33. An bevel gear portion 31 may be formed at one end of the cylindrical portion 33, and a base portion 32 may be formed at the other end. The base portion 32 may have a diameter larger than that of the cylindrical portion 33 in the circumferential direction of the first axis Ax1. In the intermediate gear 3, the bevel gear portion 31, the base portion 32, and the cylindrical portion 33 may be integrally formed.
[0022] FIG. 5 is a partially enlarged view of FIG. 4. As shown in FIG. 5, the intermediate gear 3 may have a facing surface 33a facing the bearing 61 in a direction along the first axis Ax1 defined by the shaft 5 (more specifically, the first shaft portion 51). The facing surface 33a may be in contact with the bearing 61. The facing surface 33a may be formed inside the cylindrical portion 33.
[0023] Further, as shown in FIG. 5, the articulation unit 1A may have an elastic member 80. The elastic member 80 may bias the bearing 61 in a direction along the first axis Ax1. The elastic member 80 may bias the bearing 61 in a direction in which the bevel gear portions 21 of the two opposed gears 2 are arranged (along the first axis Ax1 and facing the intersection of the first axis Ax1 and the second axis Ax2. This direction is hereinafter also simply referred to as the direction of the opposed gear 2). Thereby, the elastic member 80 can bias the facing surface 33a in a direction along the first axis Ax1 (more specifically, the direction of the opposed gear 2) via the bearing 61. That is, the elastic member 80 can bias the intermediate gear 3 in which the facing surface 33a is formed in a direction along the first axis Ax1 (more specifically, the direction of the opposed gear 2).
[0024] By biasing the intermediate gear 3 in the direction of the opposed gear 2 in this way, the teeth 31a of the bevel gear portion 31 of the intermediate gear 3 can be pushed in so as to fill the gap between two adjacent teeth 21a in the bevel gear portion 21 of each opposed gear 2 shown in FIG. 3. Thereby, backlash, which is the gap between the teeth 21a of the bevel gear portion 21 of the opposed gear 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3, can be reduced, and the generation of noise and vibration caused by the backlash can be suppressed.
[0025] In the examples shown in FIGS. 4 and 5, the elastic member 80 is a coil spring disposed on the first shaft portion 51 of the shaft 5 and surrounding the outer periphery of the first shaft portion 51. However, the elastic member 80 is not limited to this, and any member that biases the bearing 61 (see FIG. 4) in the direction along the first axis Ax1 may be used, and it may be a spring of a type different from a coil spring. Further, the elastic member 80 may be attached to a member different from the shaft 5.
[0026] As shown in FIG. 5, the bearing 61 may have an inner peripheral portion 61a in contact with the shaft 5 (more specifically, the first shaft portion 51) and an outer peripheral portion 61b in contact with the intermediate gear 3. Between the inner peripheral portion 61a and the outer peripheral portion 61b, spherical balls or cylindrical rollers may be disposed. Thereby, the inner peripheral portion 61a and the outer peripheral portion 61b can rotate independently of each other about the first axis Ax1. Further, the inner peripheral portion 61a and the outer peripheral portion 61b may be able to move integrally in the direction along the first axis Ax1.
[0027] As shown in FIG. 5, the elastic member 80 may bias the inner peripheral portion 61a of the bearing 61. And the bearing 61 may face the opposing surface 33a at the outer peripheral portion 61b, and the outer peripheral portion 61b may bias the opposing surface 33a. By doing so, the outer peripheral portion 61b of the bearing 61 can rotate relative to the inner peripheral portion 61a biased by the elastic member 80 about the first axis Ax1. The elastic member 80 can bias the opposing surface 33a of the intermediate gear 3 rotating about the first axis Ax1 without rotating about the first axis Ax1. Thereby, while suppressing the generation of friction between the elastic member 80 and other members (for example, a fixing member 53 described later), the intermediate gear 3 can be biased in the direction of the opposing gear 2 by the elastic member 80.
[0028] As shown in FIG. 5, the joint unit 1A may be attached to the shaft 5 (more specifically, the first shaft portion 51) and have a fixing member 53 (an example of the first fixing member) fixed to the shaft 5. The fixing member 53 may be fixed to the end of the first shaft portion 51 by a fixture 54 such as a screw. The fixture 54 may be inserted into the fixing member 53 and the shaft 5 along the first axis Ax1.
[0029] Also, as shown in FIG. 5, the elastic member 80 may be disposed between the fixing member 53 and the bearing 61 in the direction along the first axis Ax1. The fixing member 53 may be formed in a cylindrical shape including an inner space S1. And the elastic member 80 may be housed in the inner space S1 of the fixing member 53. In the space S1, the end portion of the elastic member 80 may contact the fixing member 53. The elastic member 80 may bias the bearing 61 in a direction away from the fixing member 53.
[0030] As shown in FIG. 4, one end of the connecting member 71 may be fixed to the base portion 32 of the intermediate gear 3, and a lid member 72 may be attached to the other end of the connecting member 71. Also, the connecting member 71 may be formed in a cylindrical shape including an inner space S2. And the fixing member 53 and a sensor fixing portion 111 described later may be housed in the inner space S2 of the connecting member 71.
[0031] The intermediate gear 3 and the bearing 61 may be allowed to move only at a distance shorter than the deformation amount of the elastic member 80 (for example, the difference between the length of the elastic member 80 in a state where no load is generated in the elastic member 80 and the length of the elastic member 80 when the elastic member 80 is most compressed) in the direction along the first axis. By doing so, the backlash, which is the gap between the teeth 21a of the bevel gear portion 21 of the opposed gear 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3, can be made appropriate.
[0032] As shown in FIG. 5, the fixing member 53 may have a fixed portion 53a fixed to the end of the shaft 5 and an extending portion 53b extending from the fixed portion 53a toward the bearing 61. Here, the distance that the intermediate gear 3 and the bearing 61 can move in the direction along the first axis Ax1 (for example, the distance that can move in the direction opposite to the direction of the opposing gear 2) may be limited by the end face 53c of the extending portion 53b. By doing so, the backlash, which is the gap between the teeth 21a of the bevel gear portion 21 of the opposing gear 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3, can be made appropriate.
[0033] As shown in FIG. 5, the articulated unit 1A may have a movable member 90 disposed between the fixing member 53 (more specifically, the end face 53c of the extending portion 53b) and the bearing 61. The movable member 90 may be a washer attached to the first shaft portion 51 of the shaft 5 and surrounding the outer periphery of the first shaft portion 51. Also, the movable member 90 may be able to move in the direction along the first axis Ax1. The movable member 90 may be able to move in the direction of the opposing gear 2 by being pushed by the elastic member 80. Also, the movable member 90 may be able to move in the direction in which the fixing member 53 is disposed by being pushed by the intermediate gear 3 and the bearing 61.
[0034] As shown in FIG. 5, the diameter W1 in the circumferential direction of the first axis Ax1 of the movable member 90 may be larger than the diameter W2 in the same direction of the space S2 formed in the fixing member 53. Thereby, the end face 90a of the movable member 90 may face the end face 53c of the fixing member 53 in the direction along the first axis Ax1. Also, a gap D1 may be provided between the end face of the movable member 90 and the end face 53c of the fixing member 53. And the distance that the intermediate gear 3 and the bearing 61 can move in the direction along the first axis Ax1 (for example, the distance that can move in the direction opposite to the direction of the opposing gear 2) may be limited within the range of the gap D1 between the end face 53c of the fixing member 53 and the movable member 90. By doing so, the backlash, which is the gap between the teeth 21a of the bevel gear portion 21 of the opposing gear 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3, can be made appropriate.
[0035] Further, as shown in FIG. 5, a facing surface 51a may be formed on the first shaft portion 51 so as to face the inner peripheral portion 61a of the bearing 61 in the direction along the first axis Ax1. Here, a gap D2 may be provided between the inner peripheral portion 61a and the facing surface 51a in the direction along the first axis Ax1. The distance that the intermediate gear 3 and the bearing 61 can move in the direction along the first axis Ax1 (for example, the distance that they can move in the direction of the counter gear 2) may be limited within the range of this gap D2. By doing so, the backlash, which is the gap between the teeth 21a of the bevel gear portion 21 of the counter gear 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3, can be made appropriate.
[0036] As shown in FIG. 5, the joint unit 1A may have a first rotation sensor 110 that detects the relative rotation angle of the intermediate gear 3 with respect to the shaft 5 (more specifically, the first shaft portion 51) in the circumferential direction of the first axis Ax1. The first rotation sensor 110 may have a sensor fixing portion 111 fixed to the end portion of the first shaft portion 51, and a sensor rotating portion 112 that faces the sensor fixing portion 111 in the direction along the first axis Ax1 and rotates together with the intermediate gear 3 in the circumferential direction of the first axis Ax1. As described above, a fixing member 53 may be fixed to the end portion of the first shaft portion 51. The sensor fixing portion 111 may be fixed to this fixing member 53. That is, the fixing member 53 may support the sensor fixing portion 111. Further, the sensor rotating portion 112 may be fixed to a lid member 72 that covers the connecting member 71.
[0037] The first rotation sensor 110 may be a magnetic angle sensor that detects rotation by utilizing a change in magnetic flux. The sensor fixing portion 111 may be a magnet. The sensor rotating portion 112 may be a sensor substrate on which a Hall IC is mounted and that outputs a signal corresponding to the change in magnetic flux caused by the rotation of the sensor fixing portion 111. However, it is not limited to this, and the sensor fixing portion 111 may be a sensor substrate and the sensor rotating portion 112 may be a magnet.
[0038] As shown in FIG. 4, the joint unit 1A may have a second rotation sensor 120 that detects the relative rotation angle of the counter gear 2 with respect to the shaft 5 (more specifically, the second shaft portion 52) in the circumferential direction of the second axis Ax2. Similar to the first rotation sensor 110, the second rotation sensor 120 may include a sensor fixing portion 121 fixed to the end portion of the second shaft portion 52, and a sensor rotating portion 122 facing the sensor fixing portion 121 in the direction along the second axis Ax2. The sensor fixing portion 121 may be a magnet. The sensor rotating portion 122 may be a sensor substrate that outputs a signal corresponding to the rotation of the sensor fixing portion 121. However, the present invention is not limited to this, and the sensor fixing portion 121 may be a sensor substrate, and the sensor rotating portion 122 may be a magnet.
[0039] As described above, in the joint unit 1A, the elastic member 80 may bias the opposing surface 33a of the intermediate gear 3 in the direction along the first axis Ax1 (more specifically, the direction of the counter gear 2) via the bearing 61. Thereby, the intermediate gear 3 having the opposing surface 33a can be biased in the direction along the first axis Ax1 (more specifically, the direction of the counter gear 2). By doing so, the backlash, which is the gap between the teeth 21a of the bevel gear portion 21 of the counter gear 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3, can be reduced, and the generation of noise and vibration caused by the backlash can be suppressed.
[0040] Further, in the joint unit 1A, the fixing member 53 fixed to the end portion of the shaft 5 may have an extending portion 53b extending along the first axis Ax1 toward the bearing 61. The end surface 53c of the extending portion 53b may limit the distance that the intermediate gear 3 and the bearing 61 can move in the direction along the first axis Ax1. By doing so, the backlash, which is the gap between the teeth 21a of the bevel gear portion 21 of the counter gear 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3, can be made appropriate.
[0041] [2. Second Embodiment] Next, a second embodiment proposed in the present disclosure will be described. FIG. 6 is a perspective view showing a joint unit 1B according to the second embodiment. As shown in FIG. 6, the joint unit 1B may also have two opposing gears 2 that rotate about a second axis Ax2 and an intermediate gear 3 that rotates about a first axis Ax1, similar to the joint unit 1A described in the first embodiment.
[0042] As shown in FIG. 6, in the joint unit 1B, a connecting member 271 may be fixed to the intermediate gear 3. Thereby, the joint unit 1B can also rotate or move relative to the connecting member 271. For example, when the two opposing gears 2 rotate in the same direction, the joint unit 1B can move relative to a member such as an arm fixed to the connecting member 271 about the second axis Ax2. Also, when the two opposing gears 2 rotate in opposite directions, the joint unit 1B can move relative to a member such as an arm fixed to the connecting member 271 about the first axis Ax1.
[0043] FIG. 7 is a cross-sectional view showing a cross-section of the joint unit 1B at the first axis Ax1 and the second axis Ax2. The cutting position of the cross-section shown in FIG. 7 corresponds to the cutting position of the cross-section shown in FIG. 4. As shown in FIG. 7, the joint unit 1B may have a first shaft 210 that rotatably supports the intermediate gear 3 and a second shaft 220 that rotatably supports the two opposing gears 2. The first shaft 210 may extend along the first axis Ax1. The second shaft 220 may extend along the second axis Ax2. In the joint unit 1B, the first axis Ax1 may intersect the second axis Ax2. The first axis Ax1 may intersect the second axis Ax2 perpendicularly.
[0044] Figures 8 and 9 are partial enlarged views of Figure 7. Figure 8 shows one end of the first shaft 210, and Figure 9 shows the other end of the first shaft 210. As shown in Figure 9, the second shaft 220 may have a storage portion 221 which is a hole or notch formed along the first axis Ax1 and houses a part of the first shaft 210. The first shaft 210 may penetrate the second shaft 220 in the storage portion 221. Thereby, the first shaft 210 may be able to move in a direction along the first axis Ax1 with respect to the second shaft 220.
[0045] As shown in Figures 7 and 8, a first fixing member 230 may be fixed to the end of the first shaft 210. As shown in Figure 8, mounting holes 231 may be formed in the first fixing member 230 in a direction perpendicular to and intersecting the first axis Ax1. And a fixture 240 such as a screw may be inserted into the mounting holes 231 of the first fixing member 230. Thereby, the first fixing member 230 may be fastened to the end of the first shaft 210 and may be able to move in a direction along the first axis Ax1 with respect to the second shaft 220 together with the first shaft 210.
[0046] As shown in Figure 8, the first fixing member 230 may be located on the opposite side of the opposing surface 33a formed on the intermediate gear 3, sandwiching the bearing 61 in the direction along the first axis Ax1. The first fixing member 230 may have an opposing surface 232 facing the bearing 61 in the direction along the first axis Ax1. The opposing surface 232 may be in contact with the bearing 61 in the direction along the first axis Ax1.
[0047] As shown in Figures 7 and 9, the joint unit 1B may have an elastic member 250. The elastic member 250 may be a coil spring disposed on the first shaft 210 and surrounding the outer periphery of the first shaft 210. The elastic member 250 may be disposed at the end of the first shaft 210. The elastic member 250 may be disposed at the end opposite to the end where the first fixing member 230 is fixed.
[0048] A space S3 may be formed at an end of the storage portion 221, which is a hole or notch formed in the second shaft 220. The elastic member 250 may be stored in this space S3. The diameter W3 of the space S3 in the circumferential direction of the first axis Ax1 may be larger than the diameter W4 of the storage portion 221 in the same direction.
[0049] Here, the elastic member 250 may bias the first shaft 210. As described above, the first fixing member 230 may be fixed to the first shaft 210. By the elastic member 250 biasing the first shaft 210, the first fixing member 230 fixed to the first shaft 210 can be biased. Further, the first fixing member 230 is located on the opposite side of the opposing surface 33a of the intermediate gear 3 across the bearing 61 and may be aligned with the bearing 61 in the direction along the first axis Ax1. Thereby, by biasing the first fixing member 230 in the direction along the first axis Ax1 (more specifically, in the direction of the opposing gear 2), the bearing 61 and the opposing surface 33a can be biased in the same direction. As a result, the intermediate gear 3 having the opposing surface 33a formed thereon can be biased in the direction of the opposing gear 2. In this way, the elastic member 250 may bias the opposing surface 33a of the intermediate gear 3 via the first shaft 210, the first fixing member 230, and the bearing 61.
[0050] By doing so as well, the elastic member 250 can bias the intermediate gear 3 having the opposing surface 33a formed thereon in the direction of the opposing gear 2. Thereby, the backlash, which is the gap between the teeth 21a of the bevel gear portion 21 of the opposing gear 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3, can be reduced, and the generation of noise and vibration caused by the backlash can be suppressed.
[0051] As shown in FIGS. 7 and 9, the joint unit 1B may have a second fixing member 260 fixed to the first shaft 210. The second fixing member 260 may be fixed to the end of the first shaft 210 by a fixture 270 (see FIGS. 6 and 9) such as a screw. As shown in FIG. 7, the second fixing member 260 may be fixed to the end of the first shaft 210 opposite to the end where the first fixing member 230 of the first shaft 210 is attached. As shown in FIG. 9, the second fixing member 260 may be a washer. In this case, the second fixing member 260 may have a hole or notch with a diameter smaller than the diameter of the first shaft 210. Further, the fixture 270 may be inserted into the hole or notch of the second fixing member 260 and the mounting hole formed along the same direction on the first shaft 210 along the first axis Ax1.
[0052] As shown in FIG. 7, the second fixing member 260 may be disposed on the opposite side of the first fixing member 230 with the bearing 61 interposed therebetween in the direction along the first axis Ax1. And the elastic member 250 may bias the second fixing member 260 in a direction away from the bearing 61. By doing so, the first shaft 210 and the first fixing member 230 can be biased in the direction of the counter gear 2. Thereby, the bearing 61 and the opposing surface 33a of the intermediate gear 3 can be biased in the direction of the counter gear 2.
[0053] As shown in FIG. 9, in the direction along the first axis Ax1, the end face of the second fixing member 260 fixed to the first shaft 210 may face the edge 222 of the space S3 in which the elastic member 250 is housed in the housing portion 221 formed in the second shaft 220. Also, the diameter W5 of the second fixing member 260 in the circumferential direction of the first axis Ax1 may be larger than the diameter W3 of the space S3. Here, a gap D3 may be provided between the edge 222 of the housing portion 221 formed in the second shaft 220 (more specifically, the edge 222 of the space S3) and the second fixing member 260. The distance that the intermediate gear 3 and the bearing 61 can move in the direction along the first axis Ax1 (for example, the distance that can move in the direction opposite to the direction of the counter gear 2) may be limited within the range of this gap D3. By doing so, the backlash, which is the gap between the teeth 21a of the bevel gear portion 21 of the counter gear 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3, can be made appropriate.
[0054] Also, as shown in FIG. 8, a convex portion 211 protruding in the circumferential direction of the first axis Ax1 may be formed on the first shaft 210. The convex portion 211 formed on the first shaft 210 may face an edge 223 (the edge on the side opposite to the edge 222 shown in FIG. 9) of the housing portion 221 formed on the second shaft 220 in the direction along the first axis Ax1. Here, a gap D4 may be provided between the convex portion 211 and the edge 223 in the direction along the first axis Ax1. The distance that the intermediate gear 3 and the bearing 61 can move in the direction along the first axis Ax1 (for example, the distance that they can move in the direction of the counter gear 2) may be limited within the range of this gap D4. By doing so, the backlash, which is the gap between the teeth 21a of the bevel gear portion 21 of the counter gear 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3, can be made appropriate.
[0055] As shown in FIG. 7, a connecting member 271 may be fixed to the base portion 32 of the intermediate gear 3 by a fixture such as a screw. This connecting member 271 may be fixed to a robot arm or a member different from the robot arm. Further, the connecting member 271 may be formed in a cylindrical shape, and a lid member 272 may be attached to an end portion thereof. A space S4 for housing the first fixing member 230 may be provided inside the connecting member 271 formed in a cylindrical shape.
[0056] In the present embodiment, the first fixing member 230 shown in FIG. 8 is attached to the end portion of the first shaft 210 instead of the fixing member 53 shown in FIG. 5. Here, the elastic member 250 for biasing the intermediate gear 3 is disposed inside the space S3 formed in the second shaft 220. Therefore, it is not necessary to provide a space for housing the elastic member 250 in the first fixing member 230. As a result, the first fixing member 230 can be made smaller than the fixing member 53 in which the space S2 for housing the elastic member 80 shown in FIG. 5 is formed. Along with this, the connecting member 271 housing the first fixing member 230 can also be made smaller than the connecting member 71 housing the fixing member 53.
[0057] Further, as shown in FIG. 7, the joint unit 1B may also have a first rotation sensor 110 that detects the relative rotation angle of the intermediate gear 3 with respect to the first shaft 210 in the circumferential direction of the first axis Ax1, similar to the joint unit 1A. The first rotation sensor 110 may have a sensor fixing portion 111 fixed to the end of the first shaft 210, and a sensor rotating portion 112 that faces the sensor fixing portion 111 in the direction along the first axis Ax1 and rotates together with the intermediate gear 3 in the circumferential direction of the first axis Ax1. The sensor fixing portion 111 may be fixed to the first fixing member 230. The first fixing member 230 may support the sensor fixing portion 111. The sensor rotating portion 112 may be attached to the lid member 272, similar to the example shown in FIG. 5.
[0058] As described above, in the joint unit 1B according to the present embodiment, the elastic member 250 biases the first shaft 210 (more specifically, the second fixing member 260 fixed to the first shaft 210) in the direction along the first axis Ax1, so that the bearing 61 can be biased in the direction of the counter gear 2 via the first fixing member 230 fixed to the first shaft 210. By doing so, the intermediate gear 3 having the opposing surface 33a can also be biased in the direction of the counter gear 2 by the elastic member 250 and the bearing 61. As a result, the backlash, which is the gap between the teeth 21a of the bevel gear portion 21 of the counter gear 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3, can be reduced, and the generation of noise and vibration caused by the backlash can be suppressed.
[0059] Also, in the joint unit 1B, the distance that the intermediate gear 3 and the bearing 61 can move in the direction along the first axis Ax1 may be limited within the range of the gap D3 between the edge 222 of the storage portion 221 formed in the second shaft 220 (more specifically, the edge 222 of the space S3) and the second fixing member 260. By doing so, the backlash, which is the gap between the teeth 21a of the bevel gear portion 21 of the counter gear 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3, can be made appropriate.
[0060] [3. Modification Example] The present invention is not limited to the joint units 1A and 1B described above, and various modifications may be made. For example, in the first and second embodiments, an example of reducing the backlash between the intermediate gear 3 and the two opposed gears 2 by biasing the intermediate gear 3 in the direction along the first axis Ax1 with an elastic member was described. However, not limited to this, the two opposed gears 2 may be biased in the direction along the second axis Ax2 (more specifically, the direction in which the bevel gear portion 31 of the intermediate gear 3 is arranged) with an elastic member, thereby reducing the backlash, which is the gap between the teeth 21a of the bevel gear portions 21 of the two opposed gears 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3.
[0061] FIG. 10 is a cross-sectional view showing a cross-section of a part of a joint unit according to a modified example. As shown in FIG. 10, each of the two opposed gears 2 may have an opposing surface 23a that opposes the bearing 62 in the direction along the second axis Ax2. The opposing surface 23a may contact the bearing 62 in the direction along the second axis Ax2. The bearing 62 may have an inner peripheral portion 62a and an outer peripheral portion 62b similar to the bearing 61. The opposing surface 23a may oppose and contact only the outer peripheral portion 62b of the inner peripheral portion 62a and the outer peripheral portion 62b of the bearing 62. Further, each opposed gear 2 may have a cylindrical portion 23 extending along the second axis Ax2, and the opposing surface 23a may be formed inside the cylindrical portion 23.
[0062] Here, an elastic member (not shown) may bias the opposing surface 23a in the direction along the second axis Ax2 (more specifically, the direction in which the bevel gear portion 31 of the intermediate gear 3 is arranged) via the bearing 62. Thereby, the opposed gear 2 having the opposing surface 23a formed thereon can be biased in the direction in which the bevel gear portion 31 of the intermediate gear 3 is arranged. The elastic member may be arranged, for example, on the opposite side of the opposing surface 23a with the bearing 62 interposed therebetween. By doing so, the backlash, which is the gap between the teeth 21a of the bevel gear portions 21 of the two opposed gears 2 and the teeth 31a of the bevel gear portion 31 of the intermediate gear 3, can be reduced.
[0063] Further, the elastic member may press only the inner peripheral portion 62a of the bearing 62 out of the inner peripheral portion 62a and the outer peripheral portion 62b of the bearing 62. By doing so, the elastic member can bias the opposing surface 23a of the opposing gear 2 that rotates about the second axis Ax2 without rotating about the second axis Ax2. Thereby, while suppressing the generation of friction between the elastic member and other members, the opposing gear 2 can be biased by the elastic member in the direction in which the bevel gear portion 31 of the intermediate gear 3 is arranged.
[0064] [4. Summary] (1) As described above, the articulation unit described in the present disclosure may include two opposing gears that are two opposing bevel gears, an intermediate gear that is a bevel gear meshing with both of the two opposing gears, a first shaft that rotatably supports a first gear that is any one of the two opposing gears and the intermediate gear, a bearing disposed between the first gear and the first shaft, and an elastic member. The first gear may have an opposing surface that opposes the bearing in a direction along a first axis defined by the first shaft. The elastic member may bias the opposing surface in a direction along the first axis via the bearing. According to this, it is possible to suppress an increase in backlash in a gear having a simple structure.
[0065] (2) In the articulation unit of (1) above, the bearing may have an inner peripheral portion in contact with the first shaft and an outer peripheral portion in contact with the first gear. The elastic member may bias the inner peripheral portion of the bearing. The outer peripheral portion of the bearing may bias the opposing surface.
[0066] (3) The articulation unit of (1) or (2) above may further include a first fixing member fixed to the first shaft. The elastic member may be disposed between the first fixing member and the bearing.
[0067] (4) Any of the joint units (1) to (3) may further include a second shaft that rotatably supports a second gear, which is a gear different from the first gear among the two opposed gears and the intermediate gear, and a first fixing member fixed to the first shaft. The first axis may intersect the second axis defined by the second shaft. The first fixing member may be located on the opposite side of the facing surface across the bearing in the direction along the first axis. The first shaft and the first fixing member may be movable in the direction along the first axis with respect to the second shaft. The elastic member may bias the first shaft.
[0068] (5) The joint unit of (4) above may further include a second fixing member fixed to the first shaft. The second fixing member may be arranged on the opposite side of the first fixing member across the bearing in the direction along the first axis. The elastic member may be arranged between the bearing and the second fixing member. The elastic member may bias the second fixing member in a direction away from the bearing.
[0069] (6) In any of the joint units (1) to (5) above, the first gear and the bearing may be allowed to move only by a distance shorter than the deformation amount of the elastic member in the direction along the first axis. By doing so, the backlash between the opposed gear and the intermediate gear can be made appropriate.
[0070] (7) In the joint unit of (3) above, the first fixing member may include a fixed portion fixed to an end of the first shaft and an extending portion extending from the fixed portion toward the bearing. The distance that the first gear and the bearing can move in the direction along the first axis may be limited by an end surface of the extending portion.
[0071] (8) In the joint unit of the above (7), a movable member may be further provided, which is disposed between the end face and the bearing and can move along the first axis between the end face and the bearing. The distance that the first gear and the bearing can move in the direction along the first axis may be limited within the range of the gap between the end face and the movable member.
[0072] (9) The joint unit of the above (7) or (8) may further include a rotation sensor that detects the relative rotation angle of the first gear with respect to the first axis. The rotation sensor may include a sensor fixing portion fixed to the end of the first axis, and a sensor rotating portion that faces the sensor fixing portion in the direction along the first axis and rotates together with the first gear. The first fixing member may support the sensor fixing portion.
[0073] (10) In the joint unit of any one of the above (7) to (9), the first fixing member may have a recess that opens in the direction in which the bearing is disposed. The elastic member may be housed in the recess.
[0074] (11) In the joint unit of the above (5), the second shaft may have a hole portion that houses a part of the first shaft. The distance that the first gear and the bearing can move in the direction along the first axis may be limited within the range of the gap between the edge of the hole portion and the second fixing member.
[0075] (12) In the joint unit of any one of the above (1) to (11), the first gear may be the intermediate gear. The elastic member may bias the intermediate gear toward the two opposing gears.
Explanation of Reference Numerals
[0076] 1A and 1B joint units, 2, 2A, and 2B opposing gears, 3 intermediate gear, 4, 4A, and 4B motors, 21 and 31 bevel gear parts, 21a and 31a teeth, 22 drive gear, 32 base, 23 and 33 cylindrical parts, 23a, 33a, 51a, and 232 opposing surfaces, 5 shaft, 51 first shaft part, 52 second shaft part, 53 fixing member, 53a fixed part, 53b extending part, 53c and 90a end faces, 54, 240, and 270 fixtures, 61 and 62 bearings, 61a and 62a inner circumferential parts, 61b and 62b outer circumferential parts, 71 and 271 connecting members, 72 and 272 cover members, 80 and 250 elastic members, 90 movable member, 110 first rotation sensor, 120 second rotation sensor, 111 and 121 sensor fixing parts, 112 and 122 sensor rotating parts, 210 first shaft, 211 convex part, 220 second shaft, 221 housing part, 222 and 223 edges, 230 first fixing member, 231 mounting hole, 260 second fixing member, Ax1 first axis, Ax2 second axis, D1, D2, D3, D4 gaps, S1, S2, S3, S4 spaces, W1, W2, W3, W4, W5 diameters.
Claims
1. Two opposing gears which are two opposed bevel gears, An intermediate gear which is a bevel gear meshing with both of the two opposing gears, A first shaft rotatably supporting a first gear which is any one of the two opposing gears and the intermediate gear, A bearing disposed between the first gear and the first shaft, An elastic member, and having, The first gear has an opposing surface opposing the bearing in a direction along a first axis defined on the first shaft, The elastic member biases the opposing surface in a direction along the first axis via the bearing Articulation unit.
2. The bearing has an inner peripheral portion in contact with the first shaft and an outer peripheral portion in contact with the first gear, The elastic member biases the inner peripheral portion of the bearing, The outer peripheral portion of the bearing biases the opposing surface The articulation unit according to claim 1.
3. Further having a first fixing member fixed to the first shaft, The elastic member is disposed between the first fixing member and the bearing The articulation unit according to claim 1.
4. A second shaft rotatably supporting a second gear which is a gear different from the first gear among the two opposing gears and the intermediate gear, A first fixing member fixed to the first shaft, and further having, The first axis intersects a second axis defined on the second shaft, The first fixing member is located on the opposite side of the opposing surface across the bearing in a direction along the first axis, The first shaft and the first fixing member can move in a direction along the first axis with respect to the second shaft, The elastic member biases the first shaft The articulation unit according to claim 1.
5. Further having a second fixing member fixed to the first shaft, The second fixing member is disposed on the opposite side of the first fixing member across the bearing in a direction along the first axis, The elastic member is disposed between the bearing and the second fixing member, The elastic member biases the second fixing member in a direction away from the bearing The articulation unit according to claim 4.
6. The first gear and the bearing are allowed to move only at a distance shorter than the deformation amount of the elastic member in a direction along the first axis The articulation unit according to claim 1.
7. The first fixing member has a fixed portion fixed to an end of the first shaft and an extending portion extending from the fixed portion toward the bearing. The distance that the first gear and the bearing can move in a direction along the first axis is limited by an end face of the extending portion. The joint unit according to claim 3.
8. It further has a movable member disposed between the end face and the bearing and capable of moving along the first axis between the end face and the bearing. The distance that the first gear and the bearing can move in a direction along the first axis is limited within a range of a gap between the end face and the movable member. The joint unit according to claim 7.
9. It further has a rotation sensor for detecting a relative rotation angle of the first gear with respect to the first shaft. The rotation sensor has a sensor fixing portion fixed to an end of the first shaft, and a sensor rotating portion facing the sensor fixing portion in a direction along the first axis and rotating together with the first gear. The first fixing member supports the sensor fixing portion. The joint unit according to claim 7.
10. The first fixing member has a recess that opens in a direction in which the bearing is disposed. The elastic member is housed in the recess. The joint unit according to claim 7.
11. The second shaft has a hole portion that houses a part of the first shaft. The distance that the first gear and the bearing can move in a direction along the first axis is limited within a range of a gap between an edge of the hole portion and the second fixing member. The joint unit according to claim 5.
12. The first gear is the intermediate gear. The elastic member biases the intermediate gear toward the two opposing gears. The joint unit according to claim 1.
Citation Information
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