Joint unit

Abstract

To suppress an increase in backlash by a gear having a simple structure in a joint unit.SOLUTION: Joint units (1A, 1B) may include: first shafts (5, 210) which rotatably support a first gear to be one of two facing gears (2) and an intermediate gear (3), a bearing (61) which is arranged between the first gear and the first shafts (5, 210), and elastic members (80, 250). The first gear may have a facing surface (33a) facing the bearing (61) in a direction along a first axis line (A x 1) stipulated in the first shafts (5, 210). The elastic members (80, 250) may bias the facing surface (33a) in the direction along the first axis line (A x 1) through the bearing (61).SELECTED DRAWING: Figure 1

Description

Technical Field

[0004] , ,

[0001] The present invention relates to a joint unit.

Background Art

[0002] Patent Document 1 below discloses a joint unit that can move 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 pairs of gears. The teeth of the intermediate gear mesh with the teeth of the two pairs of gears. The two pairs of gears receive the power of different motors and can rotate independently of each other. When the two pairs 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 pairs 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. Due to 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-back 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 the gap between the teeth (backlash) between the opposing gear and the intermediate gear is large, a collision occurs between the teeth of the opposing gear and the teeth of the intermediate gear when the opposing gear starts to rotate. This causes noise and vibration. In this regard, the configuration of Patent Document 1 described above allows the member constituting the inner circumference of the opposing gear to be separated from the member constituting the outer circumference of the opposing gear. An elastic member is then placed between these members, and the member constituting the inner circumference of the opposing gear is biased by the elastic member, thereby suppressing an increase in backlash between the opposing gear and the intermediate gear. However, the opposing gear is composed of two members, making the structure of the opposing gear complex.

[0005] The purpose of this disclosure is to suppress the increase in backlash in gears with a simple structure. [Means for solving the problem]

[0006] The joint unit may include two opposing gears, which are two opposing bevel gears; an intermediate gear, which is a bevel gear that meshes with both of the two opposing gears; a first shaft that rotatably supports a first gear, which is one of the two opposing gears or 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 faces the bearing in a direction along a first axis defined on the first shaft. The elastic member may bias the opposing surface in a direction along the first axis via the bearing. This makes it possible to suppress large backlash in a gear with a simple structure. [Brief explanation of the drawing]

[0007] [Figure 1] This is a perspective view showing a joint unit according to the first embodiment proposed in this disclosure. [Figure 2] This is a front view showing a joint unit according to the first embodiment. [Figure 3] This is a magnified view of a portion of Figure 2. [Figure 4]Figure 2 is a cross-sectional view showing the cross-section along line IV-IV. [Figure 5] This is a magnified view of a portion of Figure 4. [Figure 6] This is a perspective view showing a joint unit according to the second embodiment proposed in this disclosure. [Figure 7] This is a cross-sectional view showing a cross-section of the joint unit according to the second embodiment. [Figure 8] This is a magnified view of a portion of Figure 7. [Figure 9] This is a magnified view of a portion of Figure 7. [Figure 10] This is a cross-sectional view showing a portion of the joint unit involved in the modification. [Modes for carrying out the invention]

[0008] [1. First Embodiment] First, the first embodiment proposed in this disclosure will be described with reference to the drawings. Figure 1 is a perspective view showing the joint unit 1A according to the first embodiment. Figure 2 is a front view of the joint unit 1A. Figure 3 is a partially enlarged view of Figure 2, showing two opposing gears 2 (2A, 2B) and an intermediate gear 3 provided on the joint unit 1A. In the following description, X1 and X2 shown in each figure will be referred to as the left and right, respectively, Y1 and Y2 will be referred to as the front and rear, respectively, and Z1 and Z2 will be referred to as the top and bottom, respectively.

[0009] [1-1. Overview of Joint Units] The joint unit 1A may be attached to a robot to move the robot's arm. The joint unit 1A may be attached to a robot that mimics a human or animal, for example, and function as a joint to move the robot's arms, legs, neck, waist, etc.

[0010] As shown in Figures 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 that meshes with both of these opposing gears 2. In the example shown in Figures 1 and 2, the two opposing gears 2 face each other in the left-right direction. The intermediate gear 3 is positioned between the two opposing gears 2 in the left-right direction. Opposing gear 2A is located to the left of the intermediate gear 3. Opposing gear 2B is located to the right of the intermediate gear 3. However, the two opposing gears 2 may also face each other in the vertical direction with the intermediate gear 3 in between, or they may face each other in diagonal directions both left-right and vertically.

[0011] As shown in Figure 3, each of the two opposing gears 2 may have a bevel tooth portion 21 at its end, which has a plurality of teeth 21a arranged in the direction of rotation of each opposing gear 2. The intermediate gear 3 may also have a bevel tooth portion 31 at its end, which has a plurality of teeth 31a arranged in the direction of rotation of the intermediate gear 3. The width of the plurality of teeth 21a provided on the bevel tooth portion 21 of each opposing gear 2 may gradually increase toward the outer circumference of the bevel tooth portion 21. The width of the plurality of teeth 31a provided on the bevel tooth portion 31 of the intermediate gear 3 may also gradually increase toward the outer circumference of the bevel tooth portion 31.

[0012] The intermediate gear 3 may rotate around the first axis Ax1 shown in Figure 1. The two opposing gears 2 may also rotate around the second axis Ax2 shown in Figure 1. In the example shown in Figure 1, the first axis Ax1 extends in the front-to-back direction, and the second axis Ax2 extends in the left-to-right direction. In the example shown in Figure 1, the first axis Ax1 and the second axis Ax2 intersect perpendicularly. However, the first axis Ax1 and the second axis Ax2 may be in a twisted position. Furthermore, the angle between the first axis Ax1 and the second axis Ax2 does not necessarily have to be 90 degrees.

[0013] As shown in Figure 1, the joint unit 1A may have two motors 4 (4A and 4B). In the example shown in Figure 1, motor 4A drives the opposing gear 2A, and motor 4B drives the opposing gear 2B. The joint unit 1A has drive gears 22 fixed to each of the two opposing gears 2, and a motor 4 is connected to each drive gear 22. As a result, the two opposing gears 2 can rotate independently of each other around the second axis Ax2, powered by different motors 4.

[0014] The two opposing gears 2 may both rotate in the same direction, or they may rotate in opposite directions. Alternatively, the two opposing gears 2 may rotate in the same direction but at different speeds. Furthermore, one of the two opposing gears 2 may be stationary while the other rotates. Here, "the two opposing gears 2 rotating in the same direction" means that both opposing gears 2 rotate in either the direction indicated by R1 in Figure 3 or the direction indicated by R2 in Figure 3. Also, "the two opposing gears 2 rotating in opposite directions" means that one gear rotates in the direction indicated by R1 in Figure 3, and the other gear rotates in the direction indicated by R2 in Figure 3.

[0015] When the two opposing gears 2 rotate in opposite directions, the intermediate gear 3 rotates around the first axis Ax1. When the two opposing gears 2 rotate in the same direction, the intermediate gear 3 moves (rotates) around the second axis Ax2. As shown in Figure 1, the intermediate gear 3 may be fixed to the connecting member 71 by fasteners such as screws. The intermediate gear 3 may have a bevel tooth 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 articulation unit 1A provided with the intermediate gear 3 may rotate or move relative to the connecting member 71. The articulation 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 articulation unit 1A is referred to as a roll motion. Also, the articulation 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 articulation unit 1A is referred to as a pitch motion. The articulation 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 (e.g., an arm or a body) of a robot (not shown) (hereinafter referred to as a first member) 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 7 can move about the first axis Ax1 and the second axis Ax2. Also, an articulation 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 that is a member of a robot different from the first member. Even when the connecting member 71 moves or rotates with respect to this 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 the 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 include 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 bearings 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] Furthermore, as shown in Figure 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 this cylindrical portion 33. An umbrella tooth 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 larger diameter than the cylindrical portion 33 in the circumferential direction of the first axis Ax1. In the intermediate gear 3, the umbrella tooth portion 31, the base portion 32, and the cylindrical portion 33 may be formed integrally.

[0022] Figure 5 is a partially enlarged view of Figure 4. As shown in Figure 5, the intermediate gear 3 may have an opposing surface 33a facing the bearing 61 in a direction along the first axis Ax1 defined on the shaft 5 (more specifically, the first shaft portion 51). The opposing surface 33a may be in contact with the bearing 61. The opposing surface 33a may be formed on the inside of the cylindrical portion 33.

[0023] Furthermore, as shown in Figure 5, the joint 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 the direction in which the bevel teeth 21 of the two opposing gears 2 are arranged (a direction along the first axis Ax1 and toward the intersection of the first axis Ax1 and the second axis Ax2. This direction will also be simply referred to as the direction of the opposing gears 2 below). As a result, the elastic member 80 can bias the opposing surface 33a via the bearing 61 in a direction along the first axis Ax1 (more specifically, the direction of the opposing gears 2). That is, the elastic member 80 can bias the intermediate gear 3 on which the opposing surface 33a is formed in a direction along the first axis Ax1 (more specifically, the direction of the opposing gears 2).

[0024] In this way, by biasing the intermediate gear 3 toward the opposing gear 2, the teeth 31a of the bevel tooth portion 31 of the intermediate gear 3 can be pushed in to fill the gap between two adjacent teeth 21a in the bevel tooth portion 21 of each opposing gear 2 shown in Figure 3. This reduces the backlash, which is the gap between the teeth 21a of the bevel tooth portion 21 of the opposing gear 2 and the teeth 31a of the bevel tooth portion 31 of the intermediate gear 3, thereby suppressing the generation of noise and vibration caused by backlash.

[0025] In the examples shown in Figures 4 and 5, the elastic member 80 is a coil spring positioned on the first shaft portion 51 of the shaft 5 and surrounding the outer circumference of the first shaft portion 51. However, the elastic member 80 is not limited to this; it can be any type of spring that biases the bearing 61 (see Figure 4) in the direction along the first axis Ax1, and may be a different type of spring than a coil spring. Furthermore, the elastic member 80 may be attached to a member other than the shaft 5.

[0026] As shown in Figure 5, the bearing 61 may have an inner circumferential portion 61a that contacts the shaft 5 (more specifically, the first shaft portion 51) and an outer circumferential portion 61b that contacts the intermediate gear 3. A spherical ball or a cylindrical roller may be placed between the inner circumferential portion 61a and the outer circumferential portion 61b. This allows the inner circumferential portion 61a and the outer circumferential portion 61b to rotate independently of each other about the first axis Ax1. Furthermore, the inner circumferential portion 61a and the outer circumferential portion 61b may move integrally in the direction along the first axis Ax1.

[0027] As shown in Figure 5, the elastic member 80 may bias the inner circumference 61a of the bearing 61. The bearing 61 may also face the opposing surface 33a at its outer circumference 61b, and the outer circumference 61b may bias the opposing surface 33a. In this way, the outer circumference 61b of the bearing 61 can rotate relative to the inner circumference 61a, which is 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, which rotates about the first axis Ax1, without rotating about the first axis Ax1 itself. This allows the elastic member 80 to bias the intermediate gear 3 towards the opposing gear 2 while suppressing friction between the elastic member 80 and other members (for example, the fixing member 53 described later).

[0028] As shown in Figure 5, the joint unit 1A may have a fixing member 53 (an example of a first fixing member) attached to the shaft 5 (more specifically, the first shaft portion 51) and fixed to the shaft 5. The fixing member 53 may be fixed to the end of the first shaft portion 51 by a fastener 54 such as a screw. The fastener 54 may be inserted into the fixing member 53 and the shaft 5 along the first axis Ax1.

[0029] Furthermore, as shown in Figure 5, the elastic member 80 may be positioned between the fixed member 53 and the bearing 61 in a direction along the first axis Ax1. The fixed member 53 may be formed in a cylindrical shape with a space S1 inside. The elastic member 80 may be housed in the space S1 inside the fixed member 53. In space S1, the end of the elastic member 80 may be in contact with the fixed member 53. The elastic member 80 may bias the bearing 61 in a direction away from the fixed member 53.

[0030] As shown in Figure 4, the connecting member 71 may be fixed to the base 32 of the intermediate gear 3 at one end, and a cover member 72 may be attached to the other end of the connecting member 71. The connecting member 71 may also be formed in a cylindrical shape with a space S2 inside. The fixing member 53 and the sensor fixing part 111, which will be described later, may be housed in the space S2 inside the connecting member 71.

[0031] The intermediate gear 3 and the bearing 61 may only be allowed to move in the direction along the first axis over a distance shorter than the amount of deformation of the elastic member 80 (for example, the difference between the length of the elastic member 80 when no load is applied to it and the length of the elastic member 80 when it is most compressed). In this way, the backlash, which is the gap between the teeth 21a of the bevel tooth portion 21 of the opposing gear 2 and the teeth 31a of the bevel tooth portion 31 of the intermediate gear 3, can be properly controlled.

[0032] As shown in Figure 5, the fixing member 53 may have a fixed portion 53a fixed to the end of the shaft 5 and an extended 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 they can move in the direction opposite to that of the opposing gear 2) may be limited by the end face 53c of the extended portion 53b. In this way, the backlash, which is the gap between the teeth 21a of the bevel tooth portion 21 of the opposing gear 2 and the teeth 31a of the bevel tooth portion 31 of the intermediate gear 3, can be properly adjusted.

[0033] As shown in Figure 5, the joint unit 1A may have a movable member 90 positioned between the fixed member 53 (more specifically, the end face 53c of the extension 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 circumference of the first shaft portion 51. The movable member 90 may also be able to move in a 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. The movable member 90 may also be able to move in the direction in which the fixed member 53 is positioned by being pushed by the intermediate gear 3 and the bearing 61.

[0034] As shown in Figure 5, the diameter W1 of the movable member 90 in the circumferential direction along the first axis Ax1 may be larger than the diameter W2 of the space S2 formed in the fixed member 53 in the same direction. This allows the end face 90a of the movable member 90 to face the end face 53c of the fixed member 53 in the direction along the first axis Ax1. A gap D1 may also be provided between the end face of the movable member 90 and the end face 53c of the fixed member 53. 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 they can move in the direction opposite to that of the opposing gear 2) may be limited to within the range of the gap D1 between the end face 53c of the fixed member 53 and the movable member 90. In this way, the backlash, which is the gap between the teeth 21a of the bevel tooth portion 21 of the opposing gear 2 and the teeth 31a of the bevel tooth portion 31 of the intermediate gear 3, can be properly controlled.

[0035] Furthermore, as shown in Figure 5, the first shaft portion 51 may have an opposing surface 51a that faces the inner circumference 61a of the bearing 61 in the direction along the first axis Ax1. Here, a gap D2 may be provided between the inner circumference 61a and the opposing 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 they can move in the direction of the opposing gear 2) may be limited to within the range of this gap D2. By doing so, the backlash, which is the gap between the teeth 21a of the bevel tooth portion 21 of the opposing gear 2 and the teeth 31a of the bevel tooth portion 31 of the intermediate gear 3, can be properly controlled.

[0036] As shown in Figure 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 axis 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 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 mentioned above, a fixing member 53 may be fixed to the end 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. The sensor rotating portion 112 may be fixed to a cover 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 changes in magnetic flux. The sensor fixing part 111 may be a magnet. The sensor rotation part 112 may be a sensor board on which a Hall IC is mounted that outputs a signal corresponding to the change in magnetic flux caused by the rotation of the sensor fixing part 111. However, it is not limited to this, and the sensor fixing part 111 may be a sensor board and the sensor rotation part 112 may be a magnet.

[0038] As shown in Figure 4, the joint unit 1A may have a second rotation sensor 120 that detects the relative rotation angle of the opposing gear 2 with respect to the axis 5 (more specifically, the second shaft portion 52) in the circumferential direction of the second axis Ax2. The second rotation sensor 120, like the first rotation sensor 110, may have a sensor fixing portion 121 fixed to the end of the second shaft portion 52 and a sensor rotation 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 rotation portion 122 may be a sensor board that outputs a signal corresponding to the rotation of the sensor fixing portion 121. However, it is not limited to this, and the sensor fixing portion 121 may be a sensor board and the sensor rotation 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, in the direction of the opposing gear 2) via the bearing 61. This allows the intermediate gear 3, on which the opposing surface 33a is formed, to be biased in the direction along the first axis Ax1 (more specifically, in the direction of the opposing gear 2). By doing so, the backlash, which is the gap between the teeth 21a of the bevel tooth portion 21 of the opposing gear 2 and the teeth 31a of the bevel tooth portion 31 of the intermediate gear 3, can be reduced, and the generation of noise and vibration caused by backlash can be suppressed.

[0040] Furthermore, in the joint unit 1A, the fixing member 53 fixed to the end of the shaft 5 may have an extension portion 53b that extends along the first axis Ax1 toward the bearing 61. The end face 53c of this extension 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. In this way, the backlash, which is the gap between the teeth 21a of the bevel tooth portion 21 of the opposing gear 2 and the teeth 31a of the bevel tooth portion 31 of the intermediate gear 3, can be properly adjusted.

[0041] [2. Second Embodiment] Next, a second embodiment proposed in this disclosure will be described. Figure 6 is a perspective view showing a joint unit 1B according to the second embodiment. As shown in Figure 6, the joint unit 1B, like the joint unit 1A described in the first embodiment, may have two opposing gears 2 that rotate about a second axis Ax2 and an intermediate gear 3 that rotates about a first axis Ax1.

[0042] As shown in Figure 6, in the joint unit 1B, a connecting member 271 may be fixed to the intermediate gear 3. This allows the joint unit 1B to rotate or move relative to the connecting member 271. For example, by rotating the two opposing gears 2 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. Alternatively, by rotating the two opposing gears 2 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] Figure 7 is a cross-sectional view showing the joint unit 1B along the first axis Ax1 and the second axis Ax2. The cutting positions of the cross-sections shown in Figure 7 correspond to the cutting positions of the cross-sections shown in Figure 4. As shown in Figure 7, the joint unit 1B may have a first axis 210 that rotatably supports the intermediate gear 3 and a second axis 220 that rotatably supports the two opposing gears 2. The first axis 210 may extend along the first axis Ax1. The second axis 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 enlarged sections 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 housing portion 221, which is a hole or notch formed along the first axis Ax1 and houses a portion of the first shaft 210. The first shaft 210 may pass through the second shaft 220 in the housing portion 221. This allows the first shaft 210 to move relative to the second shaft 220 in a direction along the first axis Ax1.

[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, a mounting hole 231 may be formed in the first fixing member 230 in a direction perpendicular to the first axis Ax1. A fastener 240, such as a screw, may be inserted into the mounting hole 231 of the first fixing member 230. In this way, the first fixing member 230 may be fastened to the end of the first shaft 210 and may move together with the first shaft 210 in a direction along the first axis Ax1 relative to the second shaft 220.

[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, with the bearing 61 in between in the direction along the first axis Ax1. The first fixing member 230 may have an opposing surface 232 that faces 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 positioned on the first shaft 210 and surrounding the outer circumference of the first shaft 210. The elastic member 250 may be positioned at the end of the first shaft 210. The elastic member 250 may be positioned at the end opposite to the end to which the first fixing member 230 is fixed.

[0048] A space S3 may be formed at the end of the storage portion 221, which is a hole or notch formed in the second shaft 220. An elastic member 250 may be housed 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 mentioned 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 also be biased. Furthermore, the first fixing member 230 may be located on the opposite side of the opposing surface 33a of the intermediate gear 3, with the bearing 61 in between, and aligned with the bearing 61 in the direction along the first axis Ax1. In this way, 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 on which the opposing surface 33a is formed can be biased in the direction of the opposing gear 2. Thus, 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] In this way, the elastic member 250 can bias the intermediate gear 3, on which the opposing surface 33a is formed, toward the opposing gear 2. This reduces the backlash, which is the gap between the teeth 21a of the bevel tooth portion 21 of the opposing gear 2 and the teeth 31a of the bevel tooth portion 31 of the intermediate gear 3, thereby suppressing the generation of noise and vibration caused by backlash.

[0051] As shown in Figures 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 fastener 270 such as a screw (see Figures 6 and 9). As shown in Figure 7, the second fixing member 260 may be fixed to the end of the first shaft 210 opposite to the end to which the first fixing member 230 is attached. As shown in Figure 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. The fastener 270 may be inserted along the first axis Ax1 into the hole or notch of the second fixing member 260 and into a mounting hole formed in the first shaft 210 along the same direction.

[0052] As shown in Figure 7, the second fixing member 260 may be positioned on the opposite side of the first fixing member 230, with the bearing 61 in between, in a direction along the first axis Ax1. The elastic member 250 may then bias the second fixing member 260 away from the bearing 61. In this way, the first shaft 210 and the first fixing member 230 can be biased toward the opposing gear 2. This allows the opposing surfaces 33a of the bearing 61 and the intermediate gear 3 to be biased toward the opposing gear 2.

[0053] As shown in Figure 9, in the direction along the first axis Ax1, the end face of the second fixing member 260 fixed to the first axis 210 may face the edge 222 of the space S3 in which the elastic member 250 is housed in the housing 221 formed on the second axis 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 221 formed on the second axis 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 they can move in the direction opposite to the direction of the opposing gear 2) may be limited to within the range of this gap D3. In this way, the backlash, which is the gap between the teeth 21a of the bevel tooth portion 21 of the opposing gear 2 and the teeth 31a of the bevel tooth portion 31 of the intermediate gear 3, can be properly adjusted.

[0054] Furthermore, as shown in Figure 8, the first shaft 210 may have a protrusion 211 that projects in the circumferential direction of the first axis Ax1. The protrusion 211 formed on the first shaft 210 may face the edge 223 of the housing portion 221 formed on the second shaft 220 (the edge opposite to the edge 222 shown in Figure 9) in the direction along the first axis Ax1. Here, a gap D4 may be provided between the protrusion 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 they can move in the direction of the opposing gear 2) may be limited to within the range of this gap D4. By doing so, the backlash, which is the gap between the teeth 21a of the bevel tooth portion 21 of the opposing gear 2 and the teeth 31a of the bevel tooth portion 31 of the intermediate gear 3, can be properly controlled.

[0055] As shown in Figure 7, a connecting member 271 may be fixed to the base 32 of the intermediate gear 3 by fasteners such as screws. This connecting member 271 may be fixed to the robot arm or to a member other than the robot arm. The connecting member 271 may be formed in a cylindrical shape, and a cover member 272 may be attached to its end. Inside the cylindrical connecting member 271, a space S4 for housing the first fixing member 230 may be provided.

[0056] In this embodiment, a first fixing member 230, shown in Figure 8, is attached to the end of the first shaft 210 instead of the fixing member 53 shown in Figure 5. Here, the elastic member 250 for biasing the intermediate gear 3 is located inside the space S3 formed in the second shaft 220. Therefore, the first fixing member 230 does not need to have a space for housing the elastic member 250. As a result, the first fixing member 230 can be made smaller than the fixing member 53, which has a space S2 for housing the elastic member 80 shown in Figure 5. Consequently, 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] Furthermore, as shown in Figure 7, the joint unit 1B, like the joint unit 1A, 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. The first rotation sensor 110 may have a sensor fixing part 111 fixed to the end of the first shaft 210, and a sensor rotating part 112 that faces the sensor fixing part 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 part 111 may be fixed to a first fixing member 230. The first fixing member 230 may support the sensor fixing part 111. The sensor rotating part 112 may be attached to a cover member 272, similar to the example shown in Figure 5.

[0058] As described above, in the joint unit 1B according to this embodiment, the bearing 61 may be biased toward the opposing gear 2 via the first fixing member 230 fixed to the first shaft 210, by biasing the first shaft 210 (more specifically, the second fixing member 260 fixed to the first shaft 210) in a direction along the first axis Ax1 using the elastic member 250. In this way, the intermediate gear 3, on which the opposing surface 33a is formed, can be biased toward the opposing gear 2 by the elastic member 250 and the bearing 61. This reduces the backlash, which is the gap between the teeth 21a of the bevel tooth portion 21 of the opposing gear 2 and the teeth 31a of the bevel tooth portion 31 of the intermediate gear 3, and suppresses the generation of noise and vibration caused by backlash.

[0059] Furthermore, 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 to within the range of the gap D3 between the edge 222 of the housing portion 221 formed on the second axis 220 (more specifically, the edge 222 of space S3) and the second fixing member 260. By doing so, the backlash, which is the gap between the teeth 21a of the bevel tooth portion 21 of the opposing gear 2 and the teeth 31a of the bevel tooth portion 31 of the intermediate gear 3, can be properly controlled.

[0060] [3. Variant] 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 was described in which the backlash between the intermediate gear 3 and the two opposing gears 2 is reduced by biasing the intermediate gear 3 in a direction along the first axis Ax1 with an elastic member. However, the backlash, which is the gap between the teeth 21a of the bevel teeth 21 of the two opposing gears 2 and the teeth 31a of the bevel teeth 31 of the intermediate gear 3, may also be reduced by biasing the two opposing gears 2 in a direction along the second axis Ax2 with an elastic member (more specifically, in the direction in which the bevel teeth 31 of the intermediate gear 3 is located).

[0061] Figure 10 is a cross-sectional view showing a portion of the joint unit according to a modified example. As shown in Figure 10, each of the two opposing gears 2 may have an opposing surface 23a facing the bearing 62 in the direction along the second axis Ax2. The opposing surface 23a may be in contact with the bearing 62 in the direction along the second axis Ax2. The bearing 62 may have an inner circumference 62a and an outer circumference 62b, similar to the bearing 61. The opposing surface 23a may face only the outer circumference 62b of the bearing 62, and may be in contact only with the outer circumference 62b. In addition, each opposing gear 2 may have a cylindrical portion 23 extending along the second axis Ax2, and the opposing surface 23a may be formed inside this cylindrical portion 23.

[0062] Here, an elastic member (not shown) may bias the opposing surface 23a via the bearing 62 in a direction along the second axis Ax2 (more specifically, in the direction in which the bevel teeth 31 of the intermediate gear 3 are located). This allows the opposing gear 2, on which the opposing surface 23a is formed, to be biased in the direction in which the bevel teeth 31 of the intermediate gear 3 are located. The elastic member may, for example, be positioned on the opposite side of the opposing surface 23a, with the bearing 62 in between. Doing so also reduces backlash, which is the gap between the teeth 21a of the bevel teeth 21 of the two opposing gears 2 and the teeth 31a of the bevel teeth 31 of the intermediate gear 3.

[0063] Furthermore, the elastic member may press only the inner circumference 62a of the bearing 62, rather than the outer circumference 62b. In this way, the elastic member can bias the opposing surface 23a of the opposing gear 2, which rotates around the second axis Ax2, without rotating itself around the second axis Ax2. This allows the elastic member to bias the opposing gear 2 in the direction in which the bevel teeth 31 of the intermediate gear 3 are positioned, while suppressing friction between the elastic member and other members.

[0064] [4. Summary] (1) As described above, the joint unit described in this disclosure may include two opposing gears, which are two opposing bevel gears; an intermediate gear, which is a bevel gear that meshes with both of the two opposing gears; a first shaft that rotatably supports a first gear, which is one of the two opposing gears or 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 faces the bearing in a direction along a first axis defined on the first shaft. The elastic member may bias the opposing surface in a direction along the first axis via the bearing. This makes it possible to suppress large backlash in a gear with a simple structure.

[0065] (2) In the joint unit described in (1) above, the bearing may have an inner circumferential portion in contact with the first shaft and an outer circumferential portion in contact with the first gear. The elastic member may bias the inner circumferential portion of the bearing. The outer circumferential portion of the bearing may bias the opposing surface.

[0066] (3) The joint unit described in (1) or (2) above may further include a first fixing member fixed to the first axis. The elastic member may be disposed between the first fixing member and the bearing.

[0067] (4) Any of the joint units described in (1) to (3) above may further include a second shaft that rotatably supports a second gear which is a gear different from the first gear among the two opposing gears and the intermediate gear, and a first fixing member fixed to the first shaft. The first axis may intersect the second axis defined on the second shaft. The first fixing member may be located on the opposite side of the opposing surface, sandwiching the bearing in a direction along the first axis. The first shaft and the first fixing member may be movable relative to the second shaft in a direction along the first axis. The elastic member may bias the first shaft.

[0068] (5) The joint unit described in (4) above may further include a second fixing member fixed to the first axis. The second fixing member may be positioned on the opposite side of the first fixing member, sandwiching the bearing in a direction along the first axis. The elastic member may be positioned 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 described in (1) to (5) above, the first gear and the bearing may be allowed to move in the direction along the first axis only over a distance shorter than the deformation of the elastic member. This allows for proper control of backlash between the opposing gear and the intermediate gear.

[0070] (7) In the joint unit described in (3) above, the first fixing member may have a fixed portion fixed to the end of the first shaft and an extended 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 the end face of the extended portion.

[0071] (8) The joint unit of (7) described above may further include 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 the direction along the first axis may be limited to within the range of the gap between the end face and the movable member.

[0072] (9) The joint unit described in (7) or (8) above may further include a rotation sensor for detecting the relative rotation angle of the first gear with respect to the first axis. The rotation sensor may have a sensor fixing portion fixed to the end of the first axis 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 may support the sensor fixing portion.

[0073] (10) In any of the joint units described in (7) to (9) above, the first fixing member may have a recess that opens in the direction in which the bearing is located. The elastic member may be housed in the recess.

[0074] (11) In the joint unit described in (5) above, the second axis may have a hole that houses a portion of the first axis. The distance that the first gear and the bearing can move in the direction along the first axis may be limited to within the range of the gap between the edge of the hole and the second fixing member.

[0075] (12) In any of the joint units described in (1) to (11) above, the first gear may be the intermediate gear. The elastic member may bias the intermediate gear toward the two opposing gears. [Explanation of symbols]

[0076] 1A,1B Joint unit, 2,2A,2B Opposing gear, 3 Intermediate gear, 4,4A,4B Motor, 21,31 Umbrella tooth section, 21a,31a Teeth, 22 Drive gear, 32 Base section, 23,33 Cylinder section, 23a,33a,51a,232 Opposing surfaces, 5 Axis, 51 First shaft section, 52 Second shaft section, 53 Fixing member, 53a Fixed section, 53b Extending section, 53c,90a End face, 54,240,270 Fixing device, 61,62 Bearing, 61a,62a Inner circumference section, 61b,62b Outer circumference section, 71,271 Connecting member, 72,272 Cover member, 80,250 Elastic member, 90 Movable member, 110 First rotation sensor, 120 Second rotation sensor, 111,121 Sensor fixing part, 112,122 Sensor rotation part, 210 First axis, 211 Protrusion, 220 Second axis, 221 Storage part, 222,223 Edge, 230 First fixing member, 231 Mounting hole, 260 Second fixing member, Ax1 First axis, Ax2 Second axis, D1,D2,D3,D4 Gap, S1,S2,S3,S4 Space, W1,W2,W3,W4,W5 Diameter.

Claims

1. Two opposing gears, which are two bevel gears, An intermediate gear, which is a bevel gear that meshes with both of the two opposing gears, A first shaft rotatably supports a first gear, which is one of the two opposing gears and the intermediate gear, A bearing is disposed between the first gear and the first shaft, Elastic member and A second shaft rotatably supports a second gear, which is a gear different from the first gear among the two opposing gears and the intermediate gear, It comprises a first fixing member fixed to the first shaft, The first gear has an opposing surface that faces the bearing in a direction along the first axis defined on the first shaft, The elastic member biases the opposing surface in a direction along the first axis via the bearing, The first axis intersects the second axis defined in the second axis, The first fixing member is located on the opposite side of the opposing surface, sandwiching the bearing in a direction along the first axis, The first shaft and the first fixing member can move relative to the second shaft in a direction along the first axis. The elastic member biases the first shaft. Joint unit.

2. Two opposing gears, which are two bevel gears, An intermediate gear, which is a bevel gear that meshes with both of the two opposing gears, A first shaft rotatably supports a first gear, which is one of the two opposing gears and the intermediate gear, A bearing is disposed between the first gear and the first shaft, Elastic member and It comprises a first fixing member fixed to the first shaft, The first gear has an opposing surface that faces the bearing in a direction along the first axis defined on the first shaft, The elastic member is positioned between the first fixing member and the bearing, and biases the opposing surface in a direction along the first axis via the bearing. The first fixing member has a fixed portion that is fixed to the end of the first shaft and an extended portion that extends 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 the end face of the extension portion. Joint unit.

3. The bearing has an inner circumference that is in contact with the first shaft and an outer circumference that is in contact with the first gear. The elastic member biases the inner circumference of the bearing, The outer circumference of the bearing biases the opposing surface. The joint unit according to claim 1 or 2.

4. It further comprises a second fixing member fixed to the first shaft, The second fixing member is positioned on the opposite side of the first fixing member, sandwiching the bearing in a direction along the first axis, The elastic member is positioned between the bearing and the second fixing member. The elastic member biases the second fixing member in a direction away from the bearing. The joint unit described in claim 1.

5. The first gear and the bearing are permitted to move in the direction along the first axis only over a distance shorter than the deformation of the elastic member. The joint unit according to claim 1 or 2.

6. The present invention further comprises a movable member that is positioned between the end face and the bearing and is 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 to the range of the gap between the end face and the movable member. The joint unit according to claim 2.

7. The system further includes a rotation sensor for detecting the relative rotation angle of the first gear with respect to the first axis, The rotation sensor has a sensor fixing portion fixed to the end of the first shaft, and a sensor rotation portion that faces the sensor fixing portion in a direction along the first axis and rotates together with the first gear. The first fixing member supports the sensor fixing portion. The joint unit according to claim 2.

8. The first fixing member has a recess that opens in the direction in which the bearing is located, The elastic member is housed in the recess. The joint unit according to claim 2.

9. The second shaft has a hole that houses a portion of the first shaft, The distance that the first gear and the bearing can move in a direction along the first axis is limited to the range of the gap between the edge of the hole and the second fixing member. The joint unit according to claim 4.

10. 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 or 2.

11. The elastic member is a coil spring. The joint unit according to claim 1 or 2.

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