Self-weight compensation mechanism, lifting device, and robot

Abstract

To suppress an increase in weight of a self-weight compensation mechanism.SOLUTION: The self-weight compensation mechanism includes at least one first device, a first member, a second member, and a lifting unit fixed to the first member and the second member. The at least one first device includes a first shaft, and a first rotor, a second rotor and a biasing member provided on the first shaft. The first rotating body and the second rotating body are rotatable relative to each other and have different outer diameters. The biasing member connects the first rotating body and the second rotating body. The first member is wound around the first rotating body, and the second member is wound around the second rotating body. The lifting unit is fixed to the first member and the second member and moves together with the first member and the second member in a second direction intersecting a first direction parallel to a central axis of the first shaft.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a weight compensation mechanism, a lifting device, and a robot. [Background technology]

[0002] There is known a weight compensation mechanism that compensates for the weight of a driven body that has been driven to a desired position. For example, Patent Document 1 describes a device that includes a stage that is movable in the direction of gravity, a counterweight, a connecting member that connects the counterweight and the stage, a pulley that wraps around and supports the connecting member to compensate for the weight of the entire stage, and a counterweight guide that allows the counterweight to move only in the direction of gravity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 2003-84087 Summary of the Invention [Problem to be solved by the invention]

[0004] In the device described in Patent Document 1, the counterweight is configured to balance the weight of the entire stage, including the stage and any loads on the stage. However, depending on the counterweight, there is a risk that the weight of the entire device will increase. [Means for solving the problem]

[0005] The present disclosure has been made to solve the above-mentioned problems, and can be realized, for example, in the following aspects.

[0006] According to a first aspect of the present disclosure, there is provided a weight compensation mechanism. The weight compensation mechanism includes at least one first device, a first member, a second member, and a lifting unit. The at least one first device includes a first shaft, a first rotating body, a second rotating body, and a biasing member. The first rotating body and the second rotating body are provided on the first shaft. The first rotating body and the second rotating body are rotatable. The first rotating body and the second rotating body are configured to be rotatable relative to each other. The outer diameter of the first rotating body is different from the outer diameter of the second rotating body. The biasing member connects the first rotating body and the second rotating body. The first member is hung across the first rotating body. The second member is hung across the second rotating body. The lifting unit is fixed to the first member and the second member. The lifting unit is configured to move together with the first member and the second member in a second direction intersecting a first direction parallel to the central axis of the first shaft. According to a second aspect of the present disclosure, there is provided a lifting device, the lifting device including the weight compensation mechanism.

[0007] According to a third aspect of the present disclosure, there is provided a robot, the robot including the lifting device and a robot arm attached to the lifting section. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a robot system including a robot. [Figure 2] FIG. 3 is an explanatory diagram of a weight compensation mechanism in the first embodiment. [Figure 3] FIG. 3 is an explanatory diagram of a weight compensation mechanism in the first embodiment. [Figure 4] 10 is a diagram for explaining a weight compensation force that is generated in response to the lifting section being moved in the −Z-axis direction from the position of the dashed line E1. FIG. [Figure 5] 10 is a diagram for explaining a weight compensation force that is generated in response to the lifting section being moved in the −Z-axis direction from the position of the dashed line E1. FIG. [Figure 6]FIG. 10 is a diagram for explaining setting of a weight compensation force. [Figure 7] FIG. 10 is an explanatory view showing a part of a weight compensation mechanism in a second embodiment. [Figure 8] FIG. 10 is an explanatory diagram of a weight compensation mechanism in the third embodiment. [Figure 9] FIG. 10 is an explanatory diagram of a weight compensation mechanism in the third embodiment. [Figure 10] FIG. 10 is an explanatory view showing a part of a weight compensation mechanism in a fourth embodiment. [Figure 11] FIG. 13 is an explanatory view showing a part of a weight compensation mechanism in a fifth embodiment. [Figure 12] FIG. 13 is an explanatory view showing a part of a weight compensation mechanism in a sixth embodiment. [Figure 13] FIG. 13 is an explanatory diagram of a weight compensation mechanism in the seventh embodiment. [Figure 14] FIG. 13 is an explanatory diagram of a weight compensation mechanism in the eighth embodiment. [Figure 15] FIG. 13 is an explanatory diagram of a weight compensation mechanism in the ninth embodiment. [Figure 16] FIG. 23 is an explanatory diagram of a weight compensation mechanism in the tenth embodiment. [Figure 17] FIG. 23 is an explanatory diagram of a weight compensation mechanism in the eleventh embodiment. [Figure 18] FIG. 23 is an explanatory diagram of a weight compensation mechanism in the twelfth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] First Embodiment FIG. 1 is a schematic diagram showing a robot system 100 including a robot 1 according to an embodiment of the present disclosure. The robot system 100 includes the robot 1 and a control device 9 that controls the robot 1. The robot 1 performs, for example, a pick-and-place operation in which a workpiece W placed at a transfer source is transported to a transfer destination. In FIG. 1, the robot 1 picks up a workpiece W from a first container C1 placed on a shelf S and transfers the workpiece W to a second container C2.

[0010] The shelf S has a plurality of shelf boards s1 arranged at intervals in the vertical direction. The first container C1 is placed on the shelf boards s1. On the shelf S, a work space H into which the robot arm 4 can enter is present between the first container C1 and the shelf board s1 located above the first container C1.

[0011] The robot 1 comprises a cart 11, a lifting device 2 placed on the cart 11, a robot arm 4 attached to the lifting device 2, a robot wrist 7 attached to the tip of the robot arm 4, and a hand 8 attached to the tip of the robot wrist 7.

[0012] The robot 1 moves by traveling on a carriage 11. The carriage 11 is, for example, an AVG (Automated Guided Vehicle). The carriage 11 includes a box-shaped main body 110. The main body 110 has an upper surface 111 and a recess 112 recessed downward from the upper surface 111. The upper surface 111 also functions as a mounting surface for a container or the like. In the example shown in FIG. 1, a second container C2 is loaded on the upper surface 111.

[0013] The lifting device 2 raises, lowers, and rotates the robot arm 4. The lifting device 2 includes a housing 200 extending in the vertical direction, a rotation mechanism 30, and a weight compensation mechanism 20. The central axis of the housing 200 is also referred to as the lifting axis U. The housing 200 is attached to the carriage 11 so as to be rotatable around the lifting axis U. In the example shown in FIG. 1 , the housing 200 is attached to a recess 112 of the carriage 11. The rotation mechanism 30 includes various actuators configured to rotate the robot arm 4 around the lifting axis U. The weight compensation mechanism 20 is configured to compensate for the weight of the robot arm 4 and move the robot arm 4 along the lifting axis U. The weight compensation mechanism 20 will be described in detail below.

[0014] The robot arm 4 is a linear-acting telescopic arm. The robot arm 4 telescopes in the direction of a forward / backward axis V that intersects with the elevation axis U. The robot arm 4 moves the robot wrist 7 and hand 8 by telescoping.

[0015] The control device 9 includes a processor such as a CPU that performs various arithmetic operations, and a storage device. The storage device includes, for example, a nonvolatile memory and a volatile memory. The CPU controls the robot 1 by expanding and executing various programs stored in the memory. The control device 9 outputs commands to the robot control device 10 included in the robot system 100, for example, to move a lifting section 201 (described below) of the lifting device 2 in a direction parallel to the lifting axis U or to rotate the lifting device 2. The robot control device 10 includes a processor such as a CPU that performs various arithmetic operations, and a storage device. The storage device includes, for example, a nonvolatile memory and a volatile memory. The CPU of the robot control device 10 expands and executes various programs stored in the memory, thereby controlling various actuators of the robot 1 in accordance with commands from the control device 9.

[0016] In FIG. 1, the Z-axis direction is shown as a direction parallel to the lifting axis U. Within the Z-axis direction, the direction away from the carriage 11 is also referred to as the +Z-axis direction, and the opposite direction is also referred to as the -Z-axis direction. In this embodiment, the Z-axis direction is the vertical direction. The +Z-axis direction is the vertically upward direction, and the -Z-axis direction is the vertically downward direction.

[0017] 2 and 3 are schematic diagrams of the weight compensation mechanism 20. The weight compensation mechanism 20 is a mechanism for holding and moving a heavy object, and cancels or reduces the effect of the weight of the object. The weight compensation mechanism 20 includes at least one first device 21, a first member 27, a second member 28, and a lifting / lowering unit 201 fixed to the first member 27 and the second member 28. The weight compensation mechanism 20 compensates for the weight of the lifting / lowering unit 201 and an object attached to the lifting / lowering unit 201. The object is, for example, a robot arm 4. As shown in FIG. 2, in this embodiment, the weight compensation mechanism 20 is supported by frames 202 and 203 extending in the Z-axis direction. The frames 202 and 203 are spaced apart in the X-axis direction, which is perpendicular to the Z-axis direction. The frames 202 and 203 are fixed to a housing 200. The weight compensation mechanism 20 may be directly supported by the housing 200. Hereinafter, within the X-axis direction, the direction from frame 202 to frame 203 will also be referred to as the +X-axis direction, and the opposite direction will also be referred to as the -X-axis direction. Figure 3 also shows the Y-axis direction, which is perpendicular to the X-axis and Z-axis directions.

[0018] The weight compensation mechanism 20 of this embodiment includes one first device 21. The first device 21 includes a first shaft 210, a first rotating body 211 and a second rotating body 214 provided on the first shaft 210, and a biasing member 22 provided on the first shaft 210. In this embodiment, the first shaft 210 is supported by a frame upper end 206, which is the end of the frames 202 and 203 in the +Z-axis direction. The weight compensation mechanism 20 further includes a second shaft 250, and a third rotating body 253 and a fourth rotating body 254 provided on the second shaft 250. The second shaft 250 is supported by a frame lower end 207, which is the end of the frames 202 and 203 in the -Z-axis direction. In Figure 2, in order to explain the arrangement of the frames 202, 203, the shafts 210, 250 in the weight compensation mechanism 20, and the rotating bodies 211, 214, 253, 254, the first member 27 and the second member 28 are shown with dashed lines, and the rotating bodies 211, 214, 253, 254 and the shafts 210, 250 are shown in cross section parallel to the Z-axis direction.

[0019] The first device 21 will be described in detail. The first shaft 210 included in the first device 21 extends in a direction intersecting the Z-axis direction. In this embodiment, the central axis (axis line) AX1 of the first shaft 210 is parallel to the X-axis direction. In this embodiment, the first shaft 210 is fixed to the frames 202 and 203.

[0020] The first rotating body 211 and the second rotating body 214 are each rotatable freely and can rotate relatively to each other. The fact that the first rotating body 211 and the second rotating body 214 can rotate relatively to each other means that the first rotating body 211 can rotate independently of the second rotating body 214, and the second rotating body 214 can rotate independently of the first rotating body 211. In this embodiment, the first rotating body 211 and the second rotating body 214 are rotatably mounted on the first shaft 210 via bearings 212 and 215, thereby allowing them to rotate relatively to each other.

[0021] 3, the outer diameter D1 of the first rotating body 211 is different from the outer diameter D2 of the second rotating body 214. The outer diameter is also referred to as diameter. In this embodiment, the outer diameter D1 of the first rotating body 211 is smaller than the outer diameter D2 of the second rotating body 214. The first rotating body 211 and the second rotating body 214 are spaced apart in the X-axis direction.

[0022] The biasing member 22 is an elastic body having a spring constant against torsion. The biasing member 22 directly or indirectly connects the first rotating body 211 and the second rotating body 214. In this embodiment, the biasing member 22 is disposed between the first rotating body 211 and the second rotating body 214. The biasing member 22 includes a main body 220 through which the first shaft 210 is inserted, a first end 221 connected to the first rotating body 211, and a second end 224 connected to the second rotating body 214. In this embodiment, the biasing member 22 is a torsion spring. The first end 221 and the second end 224 are also called arms or legs of the torsion spring. As will be described in detail later, the first member 27 and the second member 28 are fixed to the lifting unit 201, and therefore the first member 27 and the second member 28 are displaced (rotated, moved) by the same amount of displacement. At this time, a difference (radial difference) between the outer diameter D1 of the first rotating body 211 and the outer diameter D2 of the second rotating body 214 causes a difference in the amount of rotation between the first rotating body 211 and the second rotating body 214. When the first member 27 and the second member 28 are displaced by the same amount in the −Z axis direction, the first rotating body 211 and the second rotating body 214 rotate in the second rotation direction R2 about the central axis AX1, causing the urging member 22 to wind. When the first member 27 and the second member 28 are displaced by the same amount in the +Z axis direction together with the elevating unit 201, the first rotating body 211 and the second rotating body 214 rotate in the first rotation direction R1, which is opposite to the second rotation direction R2, causing the urging member 22 to unwind.

[0023] The second shaft 250, the third rotor 253, and the fourth rotor 254 provided at the frame lower end 207 will now be described. In this embodiment, the second shaft 250 is rotatably supported by the frames 202 and 203 via bearings 251 and 252. The central axis AX2 of the second shaft 250 is parallel to the central axis AX1 of the first shaft 210. The position of the central axis AX2 of the second shaft 250 in the Y-axis direction is the same as the position of the central axis AX1 in the Y-axis direction.

[0024] The third rotating body 253 is provided on the second shaft 250 and rotates integrally with the second shaft 250. The fourth rotating body 254 is rotatably provided on the second shaft 250 via a bearing 255. Therefore, the third rotating body 253 and the fourth rotating body 254 rotate relative to each other. The positions of the third rotating body 253 and the fourth rotating body 254 in the X-axis direction are the same as the positions of the first rotating body 211 and the second rotating body 214 in the X-axis direction, respectively. In this embodiment, the outer diameter of the third rotating body 253 and the outer diameter of the fourth rotating body 254 are different. The outer diameter of the third rotating body 253 is equal to the outer diameter D1 of the first rotating body 211. The outer diameter of the fourth rotating body 254 is equal to the outer diameter D2 of the second rotating body 214.

[0025] The first member 27 is stretched between the first rotating body 211 and the third rotating body 253. The second member 28 is stretched between the second rotating body 214 and the fourth rotating body 254. In this embodiment, the first member 27 and the second member 28 are formed in an endless shape (loop shape). The third rotating body 253 and the fourth rotating body 254 cooperate with the first rotating body 211 and the second rotating body 214 to function as supports that rotate and support the first member 27 and the second member 28, respectively. In this embodiment, the first rotating body 211, the second rotating body 214, the third rotating body 253, and the fourth rotating body 254 are sprockets. The first member 27 and the second member 28 are roller chains.

[0026] The lifting / lowering unit 201 is fixed by a fixing member 204 to the +Y-axis direction side of the extending portions of the first member 27 and the second member 28 along the Z-axis direction. The lifting / lowering unit 201 is configured to allow an object such as the robot arm 4 to be attached and detached. In this embodiment, the frames 202 and 203 are formed like rails extending in the Z-axis direction, and the frames 202 and 203 are provided with slide members 205 that slide in the Z-axis direction. An end portion of the lifting / lowering unit 201 in the +X-axis direction and an end portion of the lifting / lowering unit 201 in the −X-axis direction are slidably supported by the frames 202 and 203 by the slide members 205.

[0027] As shown in FIG. 2, the weight compensation mechanism 20 further includes an electric motor 29. The motor 29 is operably connected to the second shaft 250. When the motor 29 is driven, the third rotor 253 rotates integrally with the second shaft 250. This drives (rotates) the first member 27. The motor 29, the second shaft 250, and the third rotor 253 also function as a drive unit in the weight compensation mechanism 20. Note that the fourth rotor 254 is provided on the second shaft 250 via a bearing 255, and therefore does not rotate directly when the second shaft 250 rotates.

[0028] The operation of each part of the weight compensation mechanism 20 and the weight compensation force generated in the weight compensation mechanism 20 will be described below. As described above, in this embodiment, the first member 27 rotates when the second shaft 250 and the third rotating body 253 are rotated by the power of the motor 29. Furthermore, as the first member 27 rotates, the first rotating body 211 rotates around the axis AX1 of the first shaft 210. At this time, the lifting / lowering unit 201 moves (displaces) in the Z-axis direction as the first member 27 rotates. Because the second member 28 is fixed to the lifting / lowering unit 201 by the fixing member 204, the second member 28 rotates as the lifting / lowering unit 201 moves in the Z-axis direction. As a result, the second rotating body 214 rotates around the axis AX1. The fourth rotating body 254 rotates around the axis AX2 following the rotation of the second member 28.

[0029] In the first device 21, when the first rotating body 211 and the second rotating body 214 rotate in the first rotation direction R1, the first member 27 and the second member 28 move the lifting / lowering unit 201 in the +Z axis direction. When the first rotating body 211 and the second rotating body 214 rotate in the second rotation direction R2, the first member 27 and the second member 28 move the lifting / lowering unit 201 in the -Z axis direction. In other words, the first rotation direction R1 is the rotation direction of the first rotating body 211 and the second rotating body 214 when the first member 27 and the second member 28 move the lifting / lowering unit 201 in the +Z axis direction. The second rotation direction R2 is the rotation direction of the first rotating body 211 and the second rotating body 214 when the first member 27 and the second member 28 move the lifting / lowering unit 201 in the -Z axis direction.

[0030] 4 and 5 show the state in which the lifting unit 201 of the weight compensation mechanism 20 has been moved in the −Z-axis direction from the position indicated by the dashed line E1. As described above, as the first member 27 and the second member 28 move in the −Z-axis direction, the first rotating body 211 and the second rotating body 214 rotate in the second rotation direction R2. Because the outer diameter D1 of the first rotating body 211 and the outer diameter D2 of the second rotating body 214 are different, when the first member 27 and the second member 28 are displaced by the same amount in the −Z-axis direction, a difference occurs between the amount of rotation of the first rotating body 211 and the amount of rotation of the second rotating body 214. The amount of rotation is the degree of rotation. The amount of rotation can also be referred to as the number of rotations or the angle of rotation. Here, the amount of rotation θ1 of the first rotating body 211 is expressed by the following equation (1) using the diameter D1 of the first rotating body 211 and the amount of movement Δz of the lifting unit 201 in the Z-axis direction. The rotation amount θ2 of second rotating body 214 is expressed by the following formula 2 using diameter D2 of second rotating body 214 and movement amount Δz in the Z-axis direction of elevating section 201. Furthermore, the difference in rotation amount Δθ is expressed by the following formula (3) using formulas (1) and (2).

[0031]

number

[0032]

number

[0033]

number

[0034] The force acting on the biasing member 22 when the lifting unit 201 is moved in the −Z-axis direction from the position indicated by the dashed line E1 will be described. The first end 221 of the biasing member 22 rotates (turns, displaces, moves) as the first rotating body 211 rotates in the second rotation direction R2 due to the displacement (Δz) of the first member 27. Similarly, the second end 224 of the biasing member 22 rotates (turns, displaces, moves) as the second rotating body 214 rotates in the second rotation direction R2 due to the displacement (Δz) of the second member 28. At this time, a difference in rotation amount Δθ between the first end 221 and the second end 224 also occurs due to a difference in rotation amount Δθ between the first end 221 and the second end 224. This difference Δθ twists the biasing member 22. As a result, spring torques are generated in opposing directions between the first end 221 and the second end 224. For example, a spring torque is generated at the first end 221 in the direction indicated by arrow T1 in FIG. 4, and a spring torque is generated at the second end 224 in the direction indicated by arrow T2. The spring torque in the direction indicated by arrow T1 and the spring torque in the direction indicated by arrow T2 are balanced. This spring torque can be expressed by the spring constant Kθ of the biasing member 22 and the difference in rotation amount Δθ. Therefore, the spring torque generated at the first rotating body 211 can be expressed by the following equation (4) using the spring constant Kθ, the difference in rotation amount Δθ, the tension F1 generated at the first member 27, and the radius (D1 / 2) of the first rotating body 211. The spring torque generated at the second rotating body 214 can be expressed by the following equation (5) using the spring constant Kθ, the difference in rotation amount Δθ, the tension F2 generated at the second member 28, and the radius (D1 / 2) of the second rotating body 214.

[0035]

number

[0036]

number

[0037] The difference ΔF between the tension F1 calculated from equation (4) and the tension F2 calculated from equation (5) is the force in the Z-axis direction acting on the lifting unit 201 via the first member 27 and the second member 28, i.e., the weight compensation force. As shown in the following equation (6), the weight compensation force ΔF can be expressed as the value obtained by multiplying the movement amount Δz by the spring constant Kz of the spring that has a biasing force in the Z-axis direction, which in this embodiment is the vertical direction. The spring constant Kz can be expressed by the following equation (7) using the relationships from equations (1) to (6).

[0038]

number

[0039]

number

[0040] In this way, although the weight compensation mechanism 20 of this embodiment does not directly use a spring having a vertical spring constant, it can apply a spring force in the +Z axis direction to the lifting section 201 by using a spring having a vertical spring constant Kz.

[0041] Next, setting of the weight compensation force in weight compensation mechanism 20 will be described with reference to Fig. 6. Fig. 6 shows an image diagram illustrating the relationship between the number of times n that lifting / lowering unit 201, more specifically the position of the upper end of lifting / lowering unit 201, is moved from position E1 to position E2, and the magnitude Fn of the weight compensation force generated in lifting / lowering unit 201. In setting the weight compensation force, after lifting / lowering unit 201 is moved from position E1 to position E2, fixing of lifting / lowering unit 201 to first member 27 and second member 28 by fixing member 204 is released, and lifting / lowering unit 201 is returned to position E1 again without displacing first member 27 and second member 28, and then the next movement is performed.

[0042] With respect to the hatched region Fn1, the width w of the region Fn1 at a predetermined position in the Z-axis direction indicates the magnitude of the weight compensation force at that predetermined position. This is also true for the other regions Fn2, Fn3, and FnN. During the first movement (n=1) of the lifting / lowering unit 201, the weight compensation force at position E1 is 0 (zero), but the weight compensation force increases according to the amount of movement Δz in the Z-axis direction. The weight compensation force at position E1 and the weight compensation force at position E2 increase according to the number of movements from position E1 to position E2. Therefore, a desired weight compensation force can be obtained by moving the lifting / lowering unit 201 in the Z-axis direction a desired number of times. Furthermore, as can be seen from a comparison of the regions Fn1, Fn2, Fn3, and FnN, as the number of movements n increases, the ratio between the weight compensation force at position E1 and the weight compensation force at position E2 decreases. Therefore, by increasing the number of movements, the amount of change in the magnitude of the weight compensation force relative to the amount of movement Δz can be reduced. In this way, a desired weight compensation force can be set in the weight compensation mechanism 20 in advance.

[0043] As described above, in the weight compensation mechanism 20 of this embodiment, a biasing force in the Z-axis direction (vertical direction) can be generated by utilizing the fact that the biasing member 22 is twisted around the first shaft 210 due to the diameter difference between the first rotating body 211 and the second rotating body 214. Therefore, the weight of the lifting unit 201 can be compensated for by this vertical biasing force.

[0044] Furthermore, according to this embodiment, compared to a configuration in which a counterweight is used to compensate for the weight, the overall weight of the weight compensation mechanism 20 can be reduced and the size of the weight compensation mechanism 20 can be prevented from increasing. Furthermore, for example, when the weight compensation mechanism 20 is applied to the robot 1 shown in FIG. 1, the power required to raise and lower the robot arm 4 can be reduced. In other words, the weight compensation mechanism 20 of this embodiment contributes to power saving.

[0045] Furthermore, the first end 221 and the second end 224 of the biasing member 22 rotate in the same rotational direction due to the rotation of the first rotating body 211 and the second rotating body 214, and are rotated by different rotational amounts due to the difference in diameter between the first rotating body 211 and the second rotating body 214. Therefore, compared to a configuration in which a constant force spring is used to compensate for the weight, even if the rotational amount of the biasing member 22 is relatively small, a biasing force can be applied to the biasing member 22 and the durability of the biasing member 22 can be improved. As a result, the durability of the weight compensation mechanism 20 can be improved.

[0046] The weight compensation mechanism 20 of this embodiment further includes a slide member 205 fixed to the lifting / lowering unit 201. The slide member 205 is slidably mounted on frames 202 and 203 formed in the shape of rails extending in the Z-axis direction. This allows the lifting / lowering unit 201 to move smoothly in the Z-axis direction.

[0047] As described above, spring torques are generated in the first rotating body 211 and the second rotating body 214 in opposing directions, and the tension F1 of the first member 27 and the tension F2 of the second member 28 act in different directions. In this embodiment, the tension F1 of the first member 27 acts in the +Z-axis direction, and the tension F2 of the second member 28 acts in the -Z-axis direction. Therefore, as shown in FIG. 4, a rotational moment M is generated in the lifting / lowering unit 201, causing the lifting / lowering unit 201 to rotate around an imaginary axis parallel to the Y-axis direction. However, in this embodiment, the lifting / lowering unit 201 is supported by the slide member 205 on rail-shaped frames 202 and 203 extending in the Z-axis direction. Therefore, rotation of the lifting / lowering unit 201 due to the rotational moment M is suppressed.

[0048] In the first embodiment, the first member 27 and the second member 28 are driven by rotating the second shaft 250 and the third rotor 253, which rotates integrally with the second shaft 250, using the power of the motor 29. The manner in which the first member 27 and the second member 28 are driven is not limited to that of the first embodiment and can be changed as appropriate. In the following second and third embodiments, a weight compensation mechanism will be described in which the manner in which the first member 27 and the second member 28 are driven differs from that of the first embodiment.

[0049] Second Embodiment FIG. 7 shows a portion of the weight compensation mechanism 20a according to the second embodiment. In the following embodiments, the same reference numerals are used for components similar to those in the above-described embodiments, and descriptions thereof will be omitted where appropriate. In this embodiment, the first shaft 210a of the first device 21a is rotatably supported by the frames 202 and 203 via bearings 216 and 217. The first rotor 211a is fixed to the first shaft 210a, and the second rotor 214 is mounted on the first shaft 210a via a bearing 215. Therefore, the first rotor 211a and the second rotor 214 are rotatable relative to each other. In this embodiment, the motor 29 is operably connected to the first shaft 210a. Although the outer diameters D1 and D2 are not shown in the drawings, the outer diameter D1 of the first rotor 211a is smaller than the outer diameter D2 of the second rotor 214. This also applies to the following third to ninth embodiments.

[0050] In this embodiment, when the motor 29 is driven, the first shaft 210a and the first rotor 211a rotate around the axis AX1. This causes the first member 27 to rotate. In the second embodiment, the motor 29, the first shaft 210a, and the first rotor 211a function as a drive unit. The remaining configuration of the weight compensation mechanism 20a is the same as that of the weight compensation mechanism 20 of the first embodiment. Therefore, this embodiment also achieves the same effects as the first embodiment.

[0051] <Third embodiment> 8 and 9 show a weight compensation mechanism 20b according to a third embodiment. The first device 21 in the weight compensation mechanism 20b has the same configuration as in the first embodiment. In this embodiment, the motor 29 is operably coupled to a second shaft 250b provided at the frame lower end 207. This embodiment differs from the above-described embodiments in that the outer diameters of the third and fourth rotors 253b and 254b are equal and that the third and fourth rotors 253b and 254b are fixed to the second shaft 250b. Although not shown in FIG. 8, as shown in FIG. 9, the weight compensation mechanism 20b further includes a third shaft 260b, and a fifth and sixth rotors 261 and 262 rotatably provided on the third shaft 260b. The fifth rotating body 261 and the sixth rotating body 262 are provided so that the first member 271 and the second member 28 extend in the +Y-axis direction parallel to the frames 202 and 203 having rails. The central axis AX3 of the third shaft 260b is parallel to the X-axis direction. The first member 27 is hung across the first rotating body 211, the third rotating body 253b, and the fifth rotating body 261. The second member 28 is hung across the second rotating body 214, the fourth rotating body 254b, and the sixth rotating body 262. The fifth rotating body 261 and the sixth rotating body 262 are driven by the rotation of the first member 27 and the second member 28, respectively.

[0052] When the motor 29 is driven, the third rotor 253b and the fourth rotor 254b rotate integrally with the second shaft 250b around the axis AX2. This causes the first member 27 and the second member 28 to rotate. In this embodiment, the motor 29, the second shaft 250b, the third rotor 253b, and the fourth rotor 254b function as a drive unit that applies power to the first member 27 and the second member 28. The remaining configuration of the weight compensation mechanism 20b is the same as that of the weight compensation mechanism 20 of the first embodiment. Therefore, this embodiment also achieves the same effects as the first embodiment.

[0053] <Fourth embodiment> FIG. 10 shows a portion of a weight compensation mechanism 20c according to the fourth embodiment. In this embodiment, a first shaft 210c of a first device 21c is rotatably supported by the frames 202 and 203 via bearings 216 and 217. A first rotating body 211c is fixed to the first shaft 210c and rotates integrally with the first shaft 210c. A second rotating body 214c is attached to the first shaft 210c via a bearing 215. Therefore, the first rotating body 211c and the second rotating body 214c are rotatable relative to each other. In this embodiment, the first rotating body 211c, the second rotating body 214c, and the biasing member 22c are arranged on the first shaft 210c in this order in the +X-axis direction. The second rotating body 214c can also be said to be disposed between the first rotating body 211c and the biasing member 22c. Because the first rotor 211c and the second rotor 214c are adjacent to each other on the first shaft 210c, the distance between the first rotor 211c and the second rotor 214c in the X-axis direction is shorter than in the above-described embodiment, and therefore the distance between the first member 27 and the second member 28 in the X-axis direction is shorter than in the above-described embodiment.

[0054] In this embodiment, the biasing member 22c is a spiral spring. A first end 221c of the biasing member 22c is fixed to the first shaft 210c. Because the first rotating body 211c is fixed to the first shaft 210c, it can be said that the first end 221c is connected to the first rotating body 211c via the first shaft 210c. A second end 224c of the biasing member 22c is connected to the second rotating body 214c via a case 223c. The case 223c is coupled to the second rotating body 214c and configured to rotate integrally with the second rotating body 214c. The spiral spring serving as the biasing member 22c is wound around the central axis AX1 when the first rotating body 211c and the second rotating body 214c rotate in the second rotation direction R2. The remaining configuration of the weight compensation mechanism 20c in this embodiment is similar to that of the weight compensation mechanism 20 in the first embodiment. Therefore, this embodiment also achieves the same effects as the above-described embodiment. In addition, because first rotating body 211c and second rotating body 214c are adjacent to each other in the X-axis direction, the distance in the X-axis direction between first member 27 and second member 28 can be shortened. Therefore, the moment M acting on lifting / lowering unit 201 can be reduced. As a result, it is possible to simplify the configuration for suppressing rotation of lifting / lowering unit 201, for example, by reducing the size of slide member 205.

[0055] Fifth Embodiment FIG. 11 shows a weight compensation mechanism 20d according to the fifth embodiment. In this embodiment, a first shaft 210d of a first device 21d is rotatably supported by the frames 202 and 203 via bearings 216 and 217. As in the fourth embodiment, a first rotor 211d is fixed to the first shaft 210d and rotates integrally therewith. A second rotor 214d is provided on the first shaft 210d via a bearing 215. Therefore, the first rotor 211c and the second rotor 214c are rotatable relative to each other. In this embodiment, a seventh rotor 219d is further provided on the first shaft 210d. The seventh rotor 219d is fixed to the first shaft 210d and rotates integrally therewith. The outer diameter of the seventh rotor 219d is equal to the outer diameter D1 of the first rotor 211c.

[0056] The weight compensation mechanism 20d further includes a third member 26. The third member 26 is suspended between a rotor (not shown) provided at the frame lower end 207 and a seventh rotor 219d. The lifting unit 201 is fixed to the first member 27, the second member 28, and the third member 26 by a fixing member 204.

[0057] In this embodiment, the distance between the second rotating body 214d and the first rotating body 211d in the X-axis direction is approximately equal to the distance between the second rotating body 214d and the seventh rotating body 219d. The seventh rotating body 219d is disposed symmetrically with the first rotating body 211d with respect to an imaginary plane P that passes through the center of the second rotating body 214d in the X-axis direction and is parallel to the YZ plane. Furthermore, the third member 26 is disposed symmetrically with the first member 27 with respect to the imaginary plane P.

[0058] With the above configuration, as the first rotor 211d rotates, the seventh rotor 219d rotates integrally with the first shaft 210d. Therefore, the third member 26 is displaced in the Z-axis direction in synchronization with the first member 27. Because the first end 221c is fixed to the first shaft 210d, the spring torque of the biasing member 22c acts on the first rotor 211d and the seventh rotor 219d. Therefore, the tension F1 described in the first embodiment is distributed to the first member 27 and the third member 26. Therefore, the rotational moment M acting on the lifting unit 201 can be reduced.

[0059] Furthermore, in this embodiment, the third member 26 is disposed symmetrically to the first member 27 with respect to the virtual plane P, and therefore the tension F1 described in the first embodiment is equally distributed to the first member 27 and the third member 26. As a result, the rotational moment M acting on the lifting unit 201 is canceled.

[0060] Sixth Embodiment FIG. 12 shows a weight compensation mechanism 20e according to the sixth embodiment. As in the fifth embodiment, a first rotating body 211e, a second rotating body 214e, and a seventh rotating body 219e are provided on a first shaft 210e in this order in the +X-axis direction. The first shaft 210e is rotatably supported by the frames 202 and 203 via bearings 216 and 217. The first rotating body 211e is fixed to the first shaft 210e and rotates integrally with the first shaft 210e. The second rotating body 214e is provided on the first shaft 210e via a bearing 215. Therefore, the first rotating body 211e and the second rotating body 214e are rotatable relative to each other. Furthermore, the second rotating body 214e and the seventh rotating body 219e are rotatable relative to each other.

[0061] The first device 21e includes two biasing members 22e and 23e. In this embodiment, the biasing members 22e and 23e are torsion springs. The biasing member 22e is disposed between the first rotor 211c and the second rotor 214e. A first end 221e of the biasing member 22e is connected to the first rotor 211e, and a second end 224e of the biasing member 22e is connected to the second rotor 214e. Therefore, similar to the above-described embodiment, the biasing member 22e is twisted around the axis AX1 of the first shaft 210e due to the radial difference between the first rotor 211e and the second rotor 214e. The biasing member 23e is disposed between the second rotor 214e and the seventh rotor 219e. A first end 231e of the biasing member 23e is connected to the seventh rotating body 219e, and a second end 234e of the biasing member 23e is connected to the second rotating body 214e. Therefore, the biasing member 23e is twisted around the first shaft 210e due to the difference in diameter between the second rotating body 214e and the seventh rotating body 219e. The remaining configuration of the weight compensation mechanism 20e is the same as that of the fifth embodiment described above.

[0062] Similar to the weight compensation mechanism 20d of the fifth embodiment, the weight compensation mechanism 20e of the present embodiment can cancel the rotational moment M acting on the lifting unit 201 by using the seventh rotor 219e and the third member 26. Furthermore, the weight compensation mechanism 20e includes a biasing member 22e connected to the first rotor 211c and the second rotor 214c, and a biasing member 23e connected to the second rotor 214c and the seventh rotor 219d. Therefore, compared to the above-described embodiments, the tension acting in the +Z axis direction can be increased, and as a result, the weight compensation force can be increased.

[0063] Seventh Embodiment FIG. 13 shows a weight compensation mechanism 20f according to the seventh embodiment. The weight compensation mechanism 20f according to the present embodiment includes a plurality of first devices 21 arranged in the Z-axis direction. The plurality of first devices 21 are arranged at positions corresponding to the range of movement of the lifting unit 201 in the Z-axis direction. The configuration of the first devices 21 according to the present embodiment is the same as that according to the first embodiment. As shown in FIG. 13, the orientation of the biasing member 22 in each first device 21 is opposite to that of the adjacent first device 21 in the Z-axis direction. The orientation of the biasing member 22 in each first device 21 is the direction in which a biasing force is applied to the biasing member 22 by the rotation of the first rotating body 211 and the second rotating body 214.

[0064] The frame lower end 207 is provided with a second shaft 250f, and a third rotor 253f and a fourth rotor 254f fixed to the second shaft 250f. As in the third embodiment, the second shaft 250f is rotatable relative to the frames 202 and 203 and is operably connected to a motor 29 (not shown). The outer diameters of the third rotor 253f and the fourth rotor 254f are equal. The frame upper end 206 is provided with a third shaft 260f. The third shaft 260f is provided with a fifth rotor 261f and a sixth rotor 262f. The fifth rotor 261f and the sixth rotor 262f are rotatable relative to the third shaft 260f. The first member 27 spans each of the first rotors 211, the third rotor 253f, and the fifth rotor 261f in the multiple first devices 21. The second member 28 is stretched across each second rotor 214, a fourth rotor 254f, and a sixth rotor 262f in the plurality of first devices 21. The manner in which the first member 27 and the second member 28 are driven is the same as in the third embodiment. The fifth rotor 261f and the sixth rotor 262f are driven by the rotation of the first member 27 and the second member 28, respectively.

[0065] According to this embodiment, the weight compensation mechanism 20f includes a plurality of first devices 21, which allows the biasing force of the weight compensation mechanism 20f to be increased. Furthermore, by arranging the plurality of first devices 21 at positions according to the range of movement of the lifting / lowering unit 201 in the Z-axis direction, the biasing force can be increased without increasing the size of the weight compensation mechanism 20f. Furthermore, since the weight compensation mechanism 20f includes a plurality of first devices 21, even if the biasing force of one biasing member 22 is unintentionally reduced, the other biasing members 22 can prevent the lifting / lowering unit 201 from falling. This improves the safety of the weight compensation mechanism 20f. In other words, the weight compensation mechanism 20f of this embodiment can achieve a fail-safe.

[0066] Eighth Embodiment FIG. 14 shows a weight compensation mechanism 20g according to the eighth embodiment. The weight compensation mechanism 20g of this embodiment includes a plurality of first devices 21c arranged in the Z-axis direction. The configuration of the first devices 21c is the same as that of the fourth embodiment. The other configurations of the weight compensation mechanism 20g are the same as those of the weight compensation mechanism 20f of the seventh embodiment. As in the seventh embodiment, the orientation of the biasing member 22c in each first device 21c is opposite to that of the adjacent first device 21c in the Z-axis direction. The orientation of the biasing member 22c in each first device 21c is such that a biasing force is applied to the biasing member 22c by rotation of the first rotating body 211c and the second rotating body 214c.

[0067] According to this embodiment, the weight compensation mechanism 20g includes multiple first devices 21c, and therefore, similar to the seventh embodiment, the biasing force of the weight compensation mechanism 20g can be increased without increasing the size of the weight compensation mechanism 20g. Furthermore, the weight compensation mechanism 20g can achieve a fail-safe. Furthermore, similar to the fourth embodiment, in each first device 21c, the first rotating body 211c and the second rotating body 214c are adjacent to each other in the X-axis direction. Therefore, the distance between the first member 27 and the second member 28 in the X-axis direction can be shortened. Therefore, the moment M acting on the lifting unit 201 can be reduced.

[0068] Ninth Embodiment FIG. 15 shows a weight compensation mechanism 20h according to the ninth embodiment. The weight compensation mechanism 20h differs from the first embodiment in that a first member 27h and a second member 28h cooperate with the lifting / lowering unit 201 to form an endless (loop-shaped) structure. The first member 27h includes an end 271h and an end 272h. The end 271h is fixed to the end of the lifting / lowering unit 201 in the -Z-axis direction, and the end 272h is fixed to the end of the lifting / lowering unit 201 in the +Z-axis direction. Similarly, the second member 28h includes an end 281h and an end 282h. The end 281h is fixed to the end of the lifting / lowering unit 201 in the -Z-axis direction, and the end 282h is fixed to the end of the lifting / lowering unit 201 in the +Z-axis direction. The endless structure is realized by the second member 28h and the lifting / lowering unit 201. Other configurations of the weight compensation mechanism 20h are the same as those in the first embodiment, so the present embodiment also provides the same effects as those in the first embodiment.

[0069] Tenth Embodiment 16 shows a portion of the weight compensation mechanism 20i according to the tenth embodiment. In this embodiment, a first shaft 210i of a first device 21i is rotatably supported by frames 202 and 203 via bearings 216 and 217. A first rotating body 211i is fixed to the first shaft 210i and rotates integrally with the first shaft 210i. A second rotating body 214i is provided on the first shaft 210i via a bearing 215. Therefore, the first rotating body 211i and the second rotating body 214i are rotatable relative to each other.

[0070] The biasing member 22i is a torsion spring. A first end 221i of the biasing member 22i is fixed to the first shaft 210i. Since the first rotor 211c is fixed to the first shaft 210i, it can be said that the first end 221i is connected to the first rotor 211i via the first shaft 210i. A second end 224i of the biasing member 22i is connected to the second rotor 214i. The remaining configuration of the weight compensation mechanism 20i in this embodiment is the same as that of the weight compensation mechanism 20 in the first embodiment. Therefore, this embodiment also achieves the same effects as the above-described embodiments.

[0071] Eleventh Embodiment 17 shows a portion of a weight compensation mechanism 20j according to the eleventh embodiment. In this embodiment, the first device 21j includes a leaf spring as a biasing member 22j. The biasing member 22j is not provided on the first shaft 210. A first end 221j of the biasing member 22j is connected to the first rotor 211, and a second end 224j of the biasing member 22j is connected to the second rotor 214. The remaining configuration of the weight compensation mechanism 20j is the same as that of the weight compensation mechanism 20 according to the first embodiment. Therefore, this embodiment also achieves the same effects as those of the above-described embodiments.

[0072] <Twelfth embodiment> FIG. 18 shows a portion of a weight compensation mechanism 20k according to the twelfth embodiment. In this embodiment, the first device 21k includes a rubber-like elastic body as a biasing member 22k. The biasing member 22k is formed in a hollow cylindrical shape with a hollow portion 222k, and an upper surface 221k and a bottom surface 224k are connected to the first rotor 211 and the second rotor 214, respectively. The upper surface 221k and the bottom surface 224k can be regarded as a first end and a second end of the biasing member 22k. The remaining configuration of the weight compensation mechanism 20k is the same as that of the weight compensation mechanism 20 according to the first embodiment. Therefore, this embodiment also achieves the same effects as the above-described embodiments.

[0073] <Correspondence> The correspondence between each component (feature) of the above embodiment and each component (feature) of the present disclosure or invention is shown below. However, each component of the embodiment is merely an example and does not limit each component of the present disclosure or invention.

[0074] The weight compensation mechanisms 20, 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, and 20k are examples of "weight compensation mechanisms." The first devices 21, 21a, 21c, 21d, 21e, 21i, 21j, and 21k are examples of "at least one first device." The first shafts 210, 210a, 210c, 210d, 210e, and 210i are examples of the "first shaft." The first rotating bodies 211, 211a, 211c, 211d, 211e, 211i, and the seventh rotating body 219e are examples of the "first rotating body." The second rotating bodies 214, 214c, 214d, 214e, and 214i are examples of the "second rotating body." The biasing members 22, 22e, 23e, 22i, 22j, and 22k are examples of the "biasing member." The first ends 221, 221c, 221e, 231e, 221i, 221j, and the top surface 221k are an example of the "first end." The second ends 224, 224c, 224e, 234e, 224i, 224j, and the bottom surface 224k are examples of the "second end." The first members 27 and 27h are examples of the "first member." The second members 28 and 28h are examples of the "second member." The lifting unit 201 is an example of an "lifting unit." The X-axis direction is an example of a "first direction." The Y-axis direction is an example of a "second direction." The +Y-axis direction and the -Y-axis direction are examples of an "upward direction" and a "downward direction," respectively. The rotation directions R1 and R2 are examples of a "first rotation direction" and a "second rotation direction", respectively. The frames 202 and 203 and the rail shapes provided on the frames 202 and 203 are an example of a "guide rail." The slide member 205 is an example of a "slide member." The third member 26 is an example of the "third member." The seventh rotating bodies 219d and 219e are an example of the "rotating body." The motor 29, the second shaft 250, and the third rotor 253 are an example of a "drive unit that drives the first member or the second member." The motor 29, the second shaft 250b, the third rotor 253b, and the fourth rotor 254b are an example of a "drive unit that drives the first member and the second member." The motor 29, the second shaft 250f, the third rotor 253f, and the fourth rotor 254f are an example of a "drive unit that drives the first member and the second member." The first shaft 210a is an example of a "drive shaft." The second shafts 250, 250b, and 250f are examples of the "second shaft." The third rotating bodies 253, 253b, and 253f are examples of the "third rotating body." The fourth rotating bodies 254, 254b, and 254f are examples of the "fourth rotating body." The housing 200 is an example of a "housing." The lifting device 2, the robot arm 4, and the robot 1 are examples of an "lifting device," a "robot arm," and a "robot," respectively.

[0075] The weight compensation mechanism according to the present disclosure is not limited to the above-described embodiment. For example, the following non-limiting examples are possible. Furthermore, at least one of these modifications may be adopted in combination with the weight compensation mechanisms 20 to 20k of the embodiments and at least one of the features described in the claims.

[0076] A single guide rail may be provided between frame 202 and frame 203, and slide member 205 may be supported by the guide rail. Note that the slide member and guide rail may be omitted as appropriate, for example, when the rotation moment M of the lifting unit is canceled.

[0077] In the first to third, sixth, seventh, and ninth embodiments described above, a torsion spring is used as the biasing member, but a spiral spring may also be used. Similarly, in the fourth, fifth, and ninth embodiments, a spiral spring is used as the biasing member, but a torsion spring may also be used. Alternatively, a leaf spring or a rubber-like elastic body may also be used as the biasing member. The biasing members 22, 22c, 22e, 23e, 22i, 22j, and 22k in the above embodiments may be elastic bodies having a torsional spring constant.

[0078] In the various embodiments described above, the Z-axis direction is the vertical direction, but the Z-axis direction may be a substantially vertical direction, which may be a direction whose angle with the vertical direction is within a range of -10° to +10°.

[0079] The outer diameter D1 of the first rotating bodies 211, 211a, 211c, 211d, 211e, and 211i and the outer diameter D2 of the second rotating bodies 214, 214c, 214d, 214e, and 214i may be different. As in the above embodiment, the outer diameter D1 may be smaller than the outer diameter D2. Alternatively, the outer diameter D1 may be larger than the outer diameter D2.

[0080] In the above embodiment, the second members 28, 28h may function as the "first member" of the present disclosure, and the first members 27, 27h may function as the "second member" of the present disclosure. In this case, the second rotating bodies 214, 214c, 214i function as the "first rotating body" of the present disclosure, and the first rotating bodies 211, 211c, 211i function as the "second rotating body" of the present disclosure.

[0081] In the weight compensation mechanism according to the above embodiment, the configuration for rotating (driving) the first and second rotating bodies can be modified as needed, as long as the first and second rotating bodies are rotatable and configured to rotate relative to each other. In the weight compensation mechanism, if the outer diameters of the third and fourth rotating bodies are different, one of the third and fourth rotating bodies may be fixed to the second shaft, and the other may be rotatably mounted on the second shaft. In other words, if the outer diameters of the third and fourth rotating bodies are different, the drive unit may be configured so that the third and fourth rotating bodies rotate relative to each other. Furthermore, if the outer diameters of the third and fourth rotating bodies are equal, the drive unit may be configured so that the third and fourth rotating bodies rotate relative to each other, or so that the third and fourth rotating bodies rotate synchronously (integrally).

[0082] In the third embodiment described above, the third rotating body 253b and the fourth rotating body 254b may be configured as a single rotating body. In this case, the portion of the single rotating body around which the first member is hung is an example of the "third rotating body" of the present disclosure, and the portion around which the second member is hung is an example of the "fourth rotating body" of the present disclosure.

[0083] Each of the rotating bodies in the above embodiment may be a sprocket or a pulley. The first members 27, 27h, the second members 28, 28h, and the third member 26 may be a chain or a belt.

[0084] The weight compensation mechanism can be applied to various mechanisms that require weight compensation. The weight compensation mechanism 20 to 20g has excellent durability, making it more suitable for mechanisms that move up and down frequently. For example, the weight compensation mechanism is not limited to elevators that raise and lower robot arms, but may also be applied to forklifts, balancers, etc.

[0085] The weight compensation force of the weight compensation mechanism may be obtained by moving the lifting unit 201 in the −Z axis direction by manual operation by an operator, etc. The motor 29 is not an essential component.

[0086] The present disclosure is not limited to the above-described embodiments and can be realized in various forms without departing from the spirit thereof. For example, the present disclosure can also be realized in the following aspects. The technical features in the above embodiments corresponding to the technical features in each aspect described below can be appropriately replaced or combined to solve some or all of the problems of the present disclosure or to achieve some or all of the effects of the present disclosure. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0087] (1) According to a first aspect of the present disclosure, there is provided a weight compensation mechanism. The weight compensation mechanism includes at least one first device, a first member, a second member, and an elevating unit. The at least one first device includes a first shaft, a first rotating body, a second rotating body, and an urging member. The first rotating body and the second rotating body are provided on the first shaft. The first rotating body and the second rotating body are rotatable. The first rotating body and the second rotating body are configured to be rotatable relative to each other. The outer diameter of the first rotating body and the outer diameter of the second rotating body are different. The urging member connects the first rotating body and the second rotating body. The first member is hung across the first rotating body. The second member is hung across the second rotating body. The elevating unit is fixed to the first member and the second member. The lifting section is configured to move together with the first member and the second member in a second direction that intersects with a first direction that is parallel to the axis of the first shaft. According to this configuration, the first and second members are fixed to the lifting / lowering unit, and therefore the first and second members are displaced (rotated, moved) by the same displacement amount (amount of rotation, amount of movement). Because the outer diameters of the first and second rotating bodies are different, a difference in the amount of rotation occurs between the first and second rotating bodies. Therefore, a biasing force (elastic energy) is applied to the biasing member connecting the first and second rotating bodies. This biasing force can compensate for the weight of the lifting / lowering unit. Furthermore, because the weight of the lifting / lowering unit can be compensated for using the first and second rotating bodies mounted on the first shaft and the biasing member connecting the first and second rotating bodies, the overall weight of the weight compensation mechanism can be reduced compared to a configuration in which weight is compensated for using a counterweight, and the size of the weight compensation mechanism can be prevented from increasing. In this embodiment, connecting the biasing member to the first rotating body and the second rotating body includes a case where the biasing member is directly connected (fixed, coupled) to the first rotating body and a case where the biasing member is indirectly connected to the first rotating body, and also includes a case where the biasing member is directly connected (fixed, coupled) to the second rotating body and a case where the biasing member is indirectly connected to the second rotating body.

[0088] (2) In the weight compensation mechanism described in the above aspect (1), the second direction may be a substantially vertical direction. The first rotating body and the second rotating body may be rotatable in a first rotational direction about the central axis and a second rotational direction about the central axis, the second rotational direction being opposite to the first rotational direction. The first rotational direction may correspond to a rotational direction of the first member and the second member when the lifting / lowering unit moves upward in the second direction. The second rotational direction may correspond to a rotational direction of the first member and the second member when the lifting / lowering unit moves downward in the second direction, opposite to the upward direction. The at least one first device may be configured to urge the lifting / lowering unit upward by rotating the urging member in the second rotational direction about the central axis due to rotation of the first rotating body and the second rotating body in the second rotational direction. According to this aspect, by rotating the first rotating body and the second rotating body in the second rotation direction, a biasing force can be applied to the biasing member, and the lifting section can be biased upward.

[0089] (3) In the weight compensation mechanism described in the above aspect (2), the biasing member may have a first end connected to the first rotating body and a second end connected to the second rotating body. The at least one first device may be configured to bias the lifting unit in the upward direction by rotating the first end and the second end around the central axis in the second rotation direction due to rotation of the first rotating body and the second rotating body in the second rotation direction. According to this embodiment, when the first and second rotors rotate in the second rotation direction, a difference in the amount of rotation occurs between the first end connected to the first rotor and the second end connected to the second rotor, and a biasing force is applied to the biasing member, which biases the lifting unit upward. In this embodiment, the connection of the first end to the first rotating body includes both a direct connection (fixed, coupled) and an indirect connection of the first end to the first rotating body. Similarly, the connection of the second end to the second rotating body includes both a direct connection (fixed, coupled) and an indirect connection of the second end to the second rotating body.

[0090] (4) In the weight compensation mechanism according to any one of the above aspects (1) to (3), the biasing member may be an elastic body having a spring constant against torsion. According to this aspect, a biasing force can be applied to the biasing member provided on the first shaft by utilizing the fact that the biasing member is twisted around the central axis due to the diameter difference between the first rotor and the second rotor. The elastic body having a spring constant against torsion may be, for example, a torsion spring, a spiral spring, or a member made of synthetic resin such as rubber.

[0091] (5) The weight compensation mechanism according to any one of the above aspects (1) to (4) may further include a guide rail extending in the second direction and a slide member. The slide member may be provided on the guide rail so as to be slidable in the second direction. The lifting unit may be fixed to the slide member. According to this aspect, the lifting / lowering unit can be moved smoothly in the second direction. Since the lifting / lowering unit is supported on the guide rail by the slide member, the lifting / lowering unit can be prevented from rotating around an imaginary axis perpendicular to the first direction and the second direction due to the difference in tension between the first member and the second member.

[0092] (6) In the gravity compensation mechanism described in any of the above embodiments (1) to (5), one of the first rotating body and the second rotating body may be arranged between the other of the first rotating body and the second rotating body and the biasing member in the first direction. According to this embodiment, the distance in the first direction between the first rotating body and the second rotating body can be shortened, so that the rotational moment acting on the lifting section due to the difference between the tension of the first member and the tension of the second member can be reduced. When one of the first rotating body and the second rotating body is positioned between the other of the first rotating body and the second rotating body and the biasing member in the first direction, the first rotating body and the second rotating body may be adjacent to each other in the first direction.

[0093] (7) In the weight compensation mechanism according to any one of the above aspects (1) to (6), the at least one first device may be a plurality of first devices arranged in the second direction. According to this embodiment, the biasing force of the weight compensation mechanism is increased, and a fail-safe function can be realized in the weight compensation mechanism. In this embodiment, the plurality of first devices may be arranged in the second direction so as to correspond to extensions of the first member and the second member in the second direction. According to this embodiment, the biasing force, that is, the weight compensation force, can be increased without increasing the size of the weight compensation mechanism.

[0094] (8) In the weight compensation mechanism according to any one of the above aspects (1) to (7), the first shaft may be rotatable. The first rotor or the second rotor may be provided on the first shaft so as to rotate integrally with the first shaft. In this embodiment, one of the first rotating body and the second rotating body may rotate integrally with the first shaft, and the other of the first rotating body and the second rotating body may be rotatable relative to the first shaft. When this mode (8) is applied to the weight compensation mechanism described in mode (7) above, for example, the first rotating body may rotate integrally with the first shaft, and the second rotating body may be rotatably mounted on the second shaft. Furthermore, the first end may be fixed to the first shaft and connected to the first rotating body via the first shaft, and the second end may be connected to the second rotating body. According to this mode, the distance in the first direction between the first rotating body and the second rotating body can be shortened through rational arrangement, and as a result, the rotational moment acting on the lifting unit can be reduced.

[0095] (9) The weight compensation mechanism according to any one of the above aspects (1) to (8) may further include a third member fixed to the lifting unit. The at least one first device may further include a third rotor provided on the first shaft and around which the third member is suspended. According to this embodiment, the third member can reduce the rotational moment acting on the lifting unit. In this embodiment, the third rotor may be provided on the opposite side of the first rotor with respect to the second rotor in the second direction. Also, the weight compensation mechanism may be configured so that the third rotor and the first rotor rotate synchronously. The third member may be configured to move in the second direction in synchronization with the first member. The outer diameter of the first rotating body may be equal to the outer diameter of the third rotating body. Furthermore, in the second direction, the distance between the third rotating body and the second rotating body may be equal to the distance between the first rotating body and the second rotating body. According to this embodiment, the rotational moment acting on the lifting section can be canceled by the third member.

[0096] (10) The weight compensation mechanism according to any one of the above aspects (1) to (9) may further include a drive unit that drives the first member or the second member. The first rotor and the second rotor may be configured to be rotatable relative to the first shaft. According to this embodiment, the drive unit drives the first member or the second member, thereby rotating the first rotating body. Furthermore, the first member moves the lift unit in the second direction, thereby rotating the second member, and the second rotating body can be rotated in response to the rotation of the second member. Alternatively, the second member moves the lift unit in the second direction, thereby rotating the first member, and the first rotating body can be rotated in response to the rotation of the first member. In this form, when the drive unit rotates the first member, (i) the first rotating body rotates, (ii) the first end rotates in conjunction with the rotation of the first rotating body, (iii) the lifting unit moves in the second direction, (iv) the second member and the second rotating body rotate in conjunction with the movement of the lifting unit in the second direction, and (v) the second end rotates in conjunction with the rotation of the second rotating body. Alternatively, in this form, when the drive unit rotates the second member, (i) the second rotating body rotates, (ii) the second end rotates in conjunction with the rotation of the second rotating body, (iii) the lifting unit moves in the second direction, (iv) the first member and the first rotating body rotate in conjunction with the movement of the lifting unit in the second direction, and (v) the first end rotates in conjunction with the rotation of the first rotating body. In this embodiment, the drive unit may include a motor, a second shaft operably connected to the motor, and a third rotating body that rotates integrally with the second shaft and has the first member suspended therearound.

[0097] (11) The weight compensation mechanism according to any one of the above aspects (1) to (9) may further include a drive unit that drives the first member and the second member. The first rotating body and the second rotating body may be rotatable relative to the first shaft. According to this embodiment, the drive unit drives the first member and the second member to rotate the first rotating body and the second rotating body, thereby rotating the first end and the second end around the central axis. In this form, when the drive unit rotates the first member and the second member, (i) the lifting unit moves in the second direction, (ii) the first rotating body rotates, and the first end rotates in conjunction with the rotation of the first rotating body, and (iii) the second rotating body rotates, and the second end rotates in conjunction with the rotation of the second rotating body. In this embodiment, the drive unit may include a motor, a second shaft operably connected to the motor, and third and fourth rotors fixed to the second shaft. The third rotor and the fourth rotor may have the same outer diameter. The first member may span the first rotor and the third rotor, and the second member may span the second rotor and the fourth rotor.

[0098] (12) In the weight compensation mechanism according to any one of the above aspects (1) to (9), the first shaft may be a drive shaft. The first rotor may rotate integrally with the first shaft, and the second rotor may be rotatable relative to the first shaft. According to this aspect, by driving the first shaft, the first rotor and the second rotor can be rotated relatively around the central axis. In this embodiment, the weight compensation mechanism may include a motor operably connected to the first shaft, and the motor, the first shaft, and the first rotating body may function as a drive unit.

[0099] (13) The weight compensation mechanism according to any one of the above aspects (1) to (12) may further include a second shaft extending parallel to the first direction, and a third rotating body and a fourth rotating body provided on the second shaft, each of which is rotatable. The first member and the second member may be endless. The first member may span between the first rotating body and the third rotating body. The second member may span between the second rotating body and the fourth rotating body. According to this embodiment, in a weight compensation mechanism having a first member stretched across the first rotating body and the third rotating body, and a second member stretched across the second rotating body and the fourth rotating body, the weight of the lifting section fixed to the first member and the second member can be compensated for.

[0100] (14) According to a second aspect of the present disclosure, there is provided a lifting device including the weight compensation mechanism according to any one of the above aspects (1) to (13). The lifting device may include the weight compensation mechanism and a housing that accommodates the weight compensation mechanism. In this embodiment, the lifting device may further include a motor that moves the lifting section up and down.

[0101] (15) According to a third aspect of the present disclosure, there is provided a robot including the lifting device according to the above aspect (14) and a robot arm attached to the lifting section. According to this aspect, the robot arm can be moved in the second direction while the weight of the robot arm is compensated for by the weight compensation mechanism. [Explanation of symbols]

[0102] 1: robot, 4: robot arm, 7: robot wrist, 8: hand, 9: control device, 10: robot control device, 11: cart, 110: main body, 111: top surface, 112: recess, C1: first container, C2: second container, H: working space, S: shelf, s1: shelf board, U: lifting axis, V: forward / backward axis, W: workpiece, 100: robot system, 2: lifting device, 30: rotation mechanism, 200: housing, 20, 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k: weight compensation mechanism, 2 1, 21a, 21c, 21d, 21e, 21i, 21j, 21k: first device, 22, 22c, 22e, 23e, 22i, 22j, 22k: biasing member, 220: main body, 221, 221c, 221e, 231e, 221i, 221j, 221k: first end, 224, 224c, 224e, 234e, 224i, 224j, 224k: second end, 222k: hollow portion, 223c: case, 27, 27h: first member, 28, 28h: second member, 26: third member, 271h, 272h: end, 281h, 282h: end, 2 9: motor, 201: lifting unit, 202, 203: frame, 206: upper end of frame, 207: lower end of frame, 204: fixed member, 205: slide member, 210, 210a, 210c, 210d, 210e, 211i: first shaft, 211, 211a, 211c, 211d, 211e, 211i: first rotating body, 212, 215, 216, 217: bearing, 214, 214c, 214d, 214e, 214i: second rotating body, 219d, 219e: seventh rotating body, 250, 250b, 250f: second shaft , 251, 252, 255: bearings, 253, 253b, 253f: third rotating body, 254, 254b, 254f: fourth rotating body, 260b, 260f: third shaft, 261, 261f: fifth rotating body, 262, 262f: sixth rotating body, AX1, AX2, AX3: central axis, D1, D2: diameter, E1, E2: position, F1, F2: tension, Fn1, Fn2, Fn3, FnN: area, M: rotation moment, P: virtual plane, R1: first rotation direction, R2: second rotation direction, ΔF: weight compensation force, Δz: movement amount, θ1, θ2: rotation amount

Claims

1. A weight compensation mechanism, at least one first device, A first shaft; a first rotating body and a second rotating body provided on the first shaft, each of which is rotatable and relatively rotatable, the first rotating body and the second rotating body having different outer diameters; a biasing member connecting the first rotating body and the second rotating body; At least one first device comprising: a first member stretched across the first rotor; a second member stretched across the second rotating body; a lifting unit that is fixed to the first member and the second member and moves together with the first member and the second member in a second direction that intersects with a first direction that is parallel to the central axis of the first shaft, Dead weight compensation mechanism.

2. 2. The weight compensation mechanism according to claim 1, the second direction is a substantially vertical direction, the first rotating body and the second rotating body are rotatable in a first rotation direction about the central axis and in a second rotation direction opposite to the first rotation direction, the first rotation direction corresponds to a rotation direction of the first member and the second member when the lifting unit moves in an upward direction in the second direction, the second rotation direction corresponds to the rotation direction of the first member and the second member when the lifting unit moves in the downward direction, which is opposite to the upward direction in the second direction, and the at least one first device is a gravity compensation mechanism that urges the lifting unit in the upward direction by rotating the urging member in the second rotation direction around the central axis due to the rotation of the first rotating body and the second rotating body in the second rotation direction.

3. 3. The weight compensation mechanism according to claim 2, the biasing member has a first end connected to the first rotating body and a second end connected to the second rotating body; The at least one first device is a gravity compensation mechanism that urges the lifting section upward by rotating the first rotating body and the second rotating body in the second rotation direction, causing the first end and the second end to rotate around the central axis in the second rotation direction.

4. 2. The weight compensation mechanism according to claim 1, A weight compensation mechanism in which the biasing member is an elastic body having a spring constant against torsion.

5. The weight compensation mechanism according to claim 1, further comprising: a guide rail extending in the second direction; a slide member provided on the guide rail so as to be slidable in the second direction, The lifting unit is fixed to the slide member.

6. 2. The weight compensation mechanism according to claim 1, A gravity compensation mechanism, wherein the at least one first device is a plurality of first devices arranged in the second direction.

7. 2. The weight compensation mechanism according to claim 1, a weight compensation mechanism in which one of the first rotating body and the second rotating body is disposed between the other of the first rotating body and the second rotating body and the biasing member in the first direction.

8. 2. The weight compensation mechanism according to claim 1, the first shaft is rotatable; A weight compensation mechanism in which the first rotating body or the second rotating body is provided on the first shaft so as to rotate integrally with the first shaft.

9. 2. The weight compensation mechanism according to claim 1, a third member fixed to the lifting section; The at least one first device further includes a rotating body provided on the first shaft and around which the third member is suspended.

10. 2. The weight compensation mechanism according to claim 1, further comprising a drive unit that drives the first member or the second member, a weight compensation mechanism in which the first rotating body and the second rotating body are rotatable relative to the first shaft;

11. 2. The weight compensation mechanism according to claim 1, further comprising a drive unit that drives the first member and the second member, a weight compensation mechanism in which the first rotating body and the second rotating body are rotatable relative to the first shaft;

12. 2. The weight compensation mechanism according to claim 1, the first shaft is a drive shaft; a gravity compensation mechanism in which the first rotating body rotates integrally with the first shaft, and the second rotating body is rotatable relative to the first shaft;

13. 2. The weight compensation mechanism according to claim 1, a second shaft extending parallel to the first direction; a third rotor and a fourth rotor provided on the second shaft, The first member and the second member are endless, the first member is stretched across the first rotating body and the third rotating body, a weight compensation mechanism, wherein the second member is suspended between the second rotating body and the fourth rotating body;

14. The weight compensation mechanism according to claim 1; a housing that accommodates the weight compensation mechanism.

15. The lifting device according to claim 14; a robot arm attached to the lifting section.

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