Institution

Abstract

The present invention provides a finger mechanism that allows control over the sequence of joint flexion without compromising lightness and ease of control. [Solution] The finger mechanism according to the present disclosure comprises a first link provided at the end, a second link whose tip is rotatably connected to a first joint provided at the base of the first link, a wire fixed to the first link and engaged with the second link, and a spring portion provided at the first joint and the second joint provided at the base of the second link, respectively, which biases the first joint and the second joint to extend, and the first joint and the second joint bend when the wire is pulled, wherein the first joint torque, obtained by subtracting the torque due to the reaction force of the spring portion from the torque due to the tension of the wire at the first joint, is greater than the second joint torque, obtained by subtracting the torque due to the reaction force of the spring portion from the torque due to the tension of the wire at the second joint.

Description

Technical Field

[0001] This disclosure relates to a finger mechanism.

Background Art

[0002] Patent Document 1 discloses a technology related to a passive drive type finger mechanism capable of controlling the order of bending joints by providing electromagnetic brakes at each joint.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding the finger mechanism disclosed in Patent Document 1, the inventor has found the following problems. The finger mechanism as shown in Patent Document 1 has an additional mechanism called an electromagnetic brake in order to bend the joints in the intended order. Therefore, the weight of the joint mechanism increases due to the mounting of the electromagnetic brake, and a control mechanism needs to be provided for the control of the electromagnetic brake. Therefore, the advantages of the passive drive type finger mechanism, such as light weight and ease of control, are not utilized.

[0005] The present invention has been made to solve such problems, and an object thereof is to provide a finger mechanism capable of controlling the order of bending joints without impairing light weight and ease of control.

Means for Solving the Problems

[0006] The finger mechanism according to this disclosure comprises a first link provided at the end, a second link whose tip is rotatably connected to a first joint provided at the base of the first link, a wire fixed to the first link and engaged with the second link, and springs provided at the first joint and the second joint provided at the base of the second link, respectively, and biased to extend the first joint and the second joint, wherein the first and second joints bend when the wire is pulled, and the first joint torque, obtained by subtracting the torque due to the reaction force of the spring from the torque due to the tension of the wire at the first joint, is greater than the second joint torque, obtained by subtracting the torque due to the reaction force of the spring from the torque due to the tension of the wire at the second joint. This makes it possible to control the order in which the joints bend without impairing lightness and ease of control.

[0007] The spring constants of the spring portion in the first joint and the second joint may be set such that the torque of the first joint is greater than the torque of the second joint.

[0008] The shortest distance between the first joint and the second joint and the wire may be set such that the torque of the first joint is greater than the torque of the second joint.

[0009] It may be installed on a robot hand. [Effects of the Invention]

[0010] The present invention provides a finger mechanism that allows control over the sequence of joint flexion without compromising lightness and ease of control. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic cross-sectional view illustrating the configuration of the finger mechanism according to Embodiment 1. [Figure 2] Figure 2 is a schematic cross-sectional view showing the operation process of the finger mechanism according to Embodiment 1. [Figure 3]Figure 3 is a schematic cross-sectional view illustrating the distance relationship between each joint of the finger mechanism according to Embodiment 1 and the wire. [Modes for carrying out the invention]

[0012] The following describes specific embodiments of this disclosure in detail with reference to the drawings. However, this disclosure is not limited to the following embodiments. Also, for clarity, the following descriptions and drawings have been simplified as appropriate.

[0013] (Embodiment 1) <Finger Mechanism Configuration>

[0014] Referring to Figure 1, the configuration of the finger mechanism according to this embodiment 1 will be described. Figure 1 is a schematic cross-sectional view illustrating the configuration of the finger mechanism according to embodiment 1. The finger mechanism 1 is mounted, for example, on a robot hand or a mechanical prosthetic hand. As shown in Figure 1, one or more finger mechanisms 1 are provided on a base F corresponding to the body of the hand. The finger mechanism 1 comprises a plurality of links 10, a plurality of joints 20, a plurality of spring parts 30, one or more guides 40, and a wire 50.

[0015] In the finger mechanism 1 shown in Figure 1, the multiple links 10 include a first link 10a, a second link 10b, and a third link 10c. The first link 10a is provided at the end of the finger mechanism 1. The second link 10b is provided on the root side of the finger mechanism 1 relative to the first link 10a. The third link 10c is provided on the root side of the finger mechanism 1 relative to the second link 10b. In this embodiment, the number of links 10 is set to three, but the number is not limited to this; the number of links 10 can be two or more.

[0016] In the finger mechanism 1 shown in Figure 1, the multiple joints 20 include a first joint 20a, a second joint 20b, and a third joint 20c. In this embodiment, the number of joints 20 is set to three, but the number is not limited to this; the number of joints 20 can be two or more. The first joint 20a is provided at the base of the first link 10a and rotatably connects the base of the first link 10a and the tip of the second link 10b. The second joint 20b is provided at the base of the second link 10b and rotatably connects the base of the second link 10b and the tip of the third link 10c. The third joint 20c is provided at the base of the third link 10c and rotatably connects the base of the third link 10c to the base F.

[0017] The multiple spring sections 30 are, for example, coil springs or leaf springs. Each of the multiple spring sections 30 is provided on each of the multiple joints 20 and biases the multiple links 10 to form a straight line, that is, to extend each of the joints 20. As will be explained in detail later, the multiple spring sections 30 extend or flex as the finger mechanism 1 moves from an initial extended state to a flexed state, and the elastic force increases. As a result, a reaction force is generated in the multiple spring sections 30 that causes each of the joints 20 to extend.

[0018] In the finger mechanism 1 shown in Figure 1, the multiple spring portions 30 include a first spring portion 30a provided at the first joint 20a, a second spring portion 30b provided at the second joint 20b, and a third spring portion 30c provided at the third joint 20c.

[0019] Guide 40 and wire 50 are provided to transmit power from an actuator (not shown) to each joint 20. Wire 50 is fixed to the first link 10a and engages with the second link 10b and the third link 10c via guide 40. Finger mechanism 1 is a sub-driven finger mechanism in which each link 10 rotates and each joint 20 bends when an actuator (not shown) pulls wire 50 toward the base F.

[0020] The guide 40 is provided on the second link 10b and the third link 10c so that the wire 50 does not slack even when the link 10 rotates. As the guide 40, for example, a pulley, a pin, or the like is used.

[0021] <Operation of the finger mechanism> Subsequently, referring to FIG. 2, the operation of the finger mechanism 1 according to the first embodiment will be described. FIG. 2 is a schematic cross-sectional view showing the process of the operation of the finger mechanism according to the first embodiment. The finger mechanism 1 operates in the order of FIGS. 2(a), 2(b), and 2(c) from the initial state of FIG. 1.

[0022] When an actuator (not shown) starts to pull the wire 50, as shown in FIG. 2(a), the first link 10a rotates counterclockwise about the first joint 20a as a fulcrum, and the first joint 20a bends. During and after the rotation of the first link 10a, an elastic force is generated in the first spring portion 30a, and a reaction force is generated to extend the first joint 20a.

[0023] From the state of FIG. 2(a), when the actuator (not shown) further pulls the wire 50, as shown in FIG. 2(b), the second link 10b rotates counterclockwise about the second joint 20b as a fulcrum, and the second joint 20b bends. During and after the rotation of the second link 10b, an elastic force is generated in the second spring portion 30b, and a reaction force is generated to extend the second joint 20b.

[0024] From the state of FIG. 2(b), when the actuator (not shown) further pulls the wire 50, as shown in FIG. 2(c), the third link 10c rotates counterclockwise about the third joint 20c as a fulcrum, and the third joint 20c bends. During and after the rotation of the third link 10c, an elastic force is generated in the third spring portion 30c, and a reaction force is generated to extend the third link 10c.

[0025] As described above, the finger mechanism 1 according to this embodiment 1 bends sequentially from the first joint 20a at the end, which is furthest from the base F, thus enabling a bending motion that is closer to the movement of a human finger. With such a bending motion, a robot hand or prosthetic hand having the finger mechanism 1 can perform actions such as biting the fingertips into a large object or pulling an object into the hand.

[0026] <Setting joint torque> In the case of finger mechanisms used in general robot hands and prosthetic hands, the sliding resistance between the wire 50 and the guide 40 reduces the force transmitted to the first link 10a at the end, thus reducing the torque due to the tension of the wire 50. As a result, bending begins from the third joint 20c on the base F side, where the torque due to the tension of the wire 50 is greater.

[0027] Furthermore, for strength reasons, the third link on the base F side becomes about 10c thicker, and the distance from the center of the joint 20 to the wire 50 becomes about 10c longer. As a result, bending begins from the third joint 20c on the base F side, where the torque due to the tension of the wire 50 is greater.

[0028] To address the above issues, the finger mechanism 1 according to this embodiment 1 sets the joint torque of each joint 20 when the wire 50 is pulled so that the finger bends from the first joint a at the end, which is furthest from the base F. Here, the joint torque is the value obtained by subtracting the torque due to the reaction force of the spring part 30 from the torque due to the tension of the wire 50 at each joint 20. When the wire 50 is pulled, the joints 20 bend in descending order of joint torque.

[0029] In the finger mechanism 1 according to this embodiment 1, the joint torque of the first joint 20a (hereinafter referred to as the first joint torque) is set to be greater than the joint torque of the second joint 20b (hereinafter referred to as the second joint torque), and the second joint torque is set to be greater than the joint torque of the third joint 20c (hereinafter referred to as the third joint torque). As a result, the finger mechanism 1 bends from the first joint 20a, which is furthest from the base F. The following describes how to individually set the joint torque at each joint 20.

[0030] First, one method is to set the spring constant of each spring portion 30 provided at each joint 20. This is because by setting the spring constant, the torque due to the reaction force of the spring portion 30 can be set. For example, by setting the spring constant of the first spring portion 30a to be greater than the spring constant of the second spring portion 30b, and the spring constant of the second spring portion 30b to be greater than the spring constant of the third spring portion 30c, the torque at the first joint can be made greater than the torque at the second joint, and the torque at the second joint can be made greater than the torque at the third joint.

[0031] Another method for controlling the joint torque at each joint 20 is to set the shortest distance ΔD between each joint 20 and the wire 50. As explained above, the joint torque is the value obtained by subtracting the torque due to the reaction force of the spring 30 from the torque due to the tension of the wire 50. Therefore, in order to set the torque due to the tension of the wire 50, it is sufficient to set the distance ΔD between each joint 20 and the wire 50.

[0032] Figure 3 is a schematic cross-sectional view illustrating the distance relationship between each joint and the wire of the finger mechanism according to Embodiment 1. The shortest distance between the first joint 20a and the wire 50 is the first distance ΔD1, the shortest distance between the second joint 20b and the wire 50 is the second distance ΔD2, and the shortest distance between the third joint 20c and the wire 50 is the third distance ΔD3. The torque generated at each joint 20 due to the tension of the wire 50 is determined by the product of the force pulling the wire 50 and the shortest distance ΔD between each joint 20 and the wire 50. Therefore, for example, by setting the first distance ΔD1 to be greater than the second distance ΔD2, and the second distance ΔD2 to be greater than the third distance ΔD3, the torque at the first joint can be made greater than the torque at the second joint, and the torque at the second joint can be made greater than the torque at the third joint.

[0033] As described above, according to the finger mechanism 1 of this embodiment 1, the order in which the joints 20 are bent can be controlled by setting the spring constant of the spring portion 30 provided at each joint 20 and the shortest distance ΔD between each joint 20 and the wire 50. These methods do not require additional mechanisms such as electromagnetic brakes to be provided in the underdriven finger mechanism. Therefore, the finger mechanism 1 can control the order in which the joints 20 are bent without compromising the advantages of the underdriven finger mechanism, namely its lightness and ease of control.

[0034] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. [Explanation of symbols]

[0035] 1 finger mechanism 10 links 10a Link 1 10b Second Link 10c Third Link 20 joints 20a First joint 20b Second joint 20c Third joint 30 Spring section 30a First spring section 30b Second spring section 30c Third spring section 40 Guide 50 wires F base ΔD Shortest distance ΔD1 First distance ΔD2 2nd distance ΔD3 Third distance

Claims

1. The first link located at the end, A second link whose tip is rotatably connected to a first joint provided at the base of the first link, A wire fixed to the first link and engaged with the second link, The first joint and the second joint provided at the base of the second link each have a spring portion that biases the first joint and the second joint to extend, A sub-driven finger mechanism in which the first and second joints bend by pulling the wire, The first joint torque, obtained by subtracting the torque due to the reaction force of the spring from the torque due to the tension of the wire at the first joint, is greater than the second joint torque, obtained by subtracting the torque due to the reaction force of the spring from the torque due to the tension of the wire at the second joint. finger mechanism.

2. The spring constants of the springs in the first and second joints are set such that the torque of the first joint is greater than the torque of the second joint. The finger mechanism according to claim 1.

3. The shortest distance between the first joint and the second joint and the wire is set such that the torque of the first joint is greater than the torque of the second joint. The finger mechanism according to claim 1 or 2.

4. It is installed on the robot hand, The finger mechanism according to claim 1 or 2.

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