Fluid pressure actuator and robot hand

Abstract

This paper proposes a structure to prevent slippage between a functional cover and the sealing portion at the tip of a fluid pressure actuator, which constitutes the finger portion of a robot hand, when a functional cover is attached to the actuator. [Solution] A fluid pressure actuator that operates by the fluid pressure supplied into a tube, comprising an inner layer cover that covers at least the tip of the fluid pressure actuator, and an outer layer cover that covers at least the portion that covers the tip of the inner layer cover, A fluid pressure actuator wherein at least the outer surface of the inner layer cover has a higher coefficient of friction than the inner surface of the outer layer cover.

Description

Technical Field

[0001] The present invention relates to a fluid pressure actuator and a robot hand.

Background Art

[0002] In recent years, general-purpose robots that perform operations such as grasping, lifting, transporting, and supporting workpieces have been used in various fields such as manufacturing and logistics. In particular, regarding the robot hand, which is a part of the robot that performs the functions of the palm, various proposals have been made for the part of the robot that is beyond the human wrist and mimics the functions of the palm.

[0003] For example, it is known to use a fluid pressure actuator (also called a "MacKibben-type fluid pressure actuator") that can achieve a desired operation by expanding and contracting a tube covered with a sleeve for the fingers of a robot hand.

[0004] In the above-mentioned robot hand, since it handles a wide variety of workpieces, it is conceivable to cover each finger of the robot hand with a functional cover from the viewpoints of preventing contamination by the oil content of the lubricating oil of the robot hand, preventing wetting by moisture from the workpiece, etc., and preventing contamination by wear powder due to the operation of the robot hand. For example, Patent Document 1 discloses a fluid pressure actuator with a cover covered with a highly oil-resistant cover.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The covered fluid pressure actuator described in Patent Document 1 is fitted with a functional cover, such as an oil-resistant one. However, the sealing portion on the actuator tip side is typically made of metal, and therefore, there was room for improvement in addressing the problem that the functional cover tends to slip against the sealing portion.

[0007] Therefore, the present invention aims to propose a structure for preventing slippage between a functional cover and a sealing portion on the tip side of a fluid pressure actuator when a functional cover is attached to a fluid pressure actuator that constitutes the finger portion of a robot hand. [Means for solving the problem]

[0008] The inventors diligently studied covers for fluid pressure actuators that could solve the above problems and found that it is effective to newly provide an inner layer cover with a higher coefficient of friction than the functional cover between the functional cover and the sealing portion on the actuator tip side. The present invention is derived from the above findings, and its gist is as follows.

[0009] 1. A fluid pressure actuator that operates by the fluid pressure supplied into a tube, comprising an inner layer cover that covers at least the tip of the fluid pressure actuator, and an outer layer cover that covers at least the portion of the inner layer cover that covers the tip, At least the outer surface of the inner layer cover has a higher coefficient of friction (or kinetic friction coefficient or sliding friction coefficient) than the coefficient of friction of the inner surface of the outer layer cover. Fluid pressure actuator.

[0010] 2. The fluid pressure actuator according to paragraph 1, wherein the thickness of the inner layer cover is 1.0 mm or more and 3.0 mm or less.

[0011] 3. The fluid pressure actuator according to claim 1 or 2, wherein the inner layer cover covers only the tip portion of the fluid pressure actuator.

[0012] 4. The fluid pressure actuator according to any one of 1 to 3, wherein the ratio of the outer diameters of the inner layer cover to the outer layer cover is in the range of 1:0.9 to 1:1.1.

[0013] 5. The fluid pressure actuator according to any one of 1 to 4, wherein the outer layer cover has at least one of the functions of waterproofing, oil resistance, and stain resistance.

[0014] 6. A robot hand equipped with a gripping means for grasping a workpiece, The gripping means has a plurality of fingers extending from the hand body of the robot hand, the base end of each of the plurality of fingers is rotatably attached to the hand body, and the spacing between the fingertips of the plurality of fingers is adjustable. The aforementioned finger is a fluid pressure actuator as described in 1 above. Robot hand. [Effects of the Invention]

[0015] According to the present invention, an anti-slip effect is obtained between the functional cover and the fluid pressure actuator, making it possible to attach any functional cover without reducing the workpiece carrying capacity of the robot hand using the fluid pressure actuator. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic perspective view showing a fluid pressure actuator. [Figure 2] This is a schematic diagram of a fluid pressure actuator according to one embodiment of the present invention. [Figure 3] This is a cross-sectional view along line AA in Figure 2. [Figure 4] This figure shows an example of a robot hand and a robot arm to which the robot hand is attached, according to the present invention. [Modes for carrying out the invention]

[0017] A fluid pressure actuator as an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3. Here, FIG. 1 shows a schematic view of the fluid pressure actuator 3. However, in order to explain the basic configuration of the fluid pressure actuator 3, the cover attached to the actuator 3 will be described later, and the cover is omitted in FIG. 1. FIG. 2 is a schematic view of a fluid pressure actuator with a cover according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view taken along the line A-A of FIG. 2.

[0018] [Fluid pressure actuator 3] That is, the fluid pressure actuator 3 shown in FIG. 1 includes a rubber tube 31 in this embodiment, a sleeve 32 of high-strength fibers covering the tube 31, and sealing portions 34 and 35 made of, for example, metal cylinders for sealing both axial ends of the tube 31.

[0019] In addition, the sealing portion 34 on the base end side of the tube 31 has an inlet 36 for introducing the working fluid from the outside. By introducing the working fluid from the inlet 36, as shown by the two-dot chain line in FIG. 1, an operation can be given to bend the axis of the tube 31 toward its tip.

[0020] On the other hand, the sealing portion 35 on the tip side of the tube 31 is formed in a hemispherical shape that tapers toward the tip in this embodiment, and when the actuator is applied to the finger of a robot hand, it realizes a soft contact with the workpiece through a curved surface.

[0021] The fluid pressure actuator 3 according to an embodiment of the present invention includes, as shown in FIG. 2, an inner layer cover 40 that covers at least the sealing portion 35 and an outer layer cover 41 that covers at least the portion overlapping the sealing portion 35 of the inner layer cover 40.

[0022] Both the inner layer cover 40 and the outer layer cover 41 have a vertically long bag-like structure that can expand and contract and have an opening on one side of the end. When attaching the above cover to the fluid pressure actuator 3, the opening is expanded, inserted from the sealing portion 35 of the fluid pressure actuator 3 into the opening, and attached so as to cover the sealing portion 35.

[0023] Figure 3 is a cross-sectional view along line AA in Figure 2. The inner layer cover 40 directly covers the sealing portion 35 and sleeve 32 of the fluid pressure actuator 3. The requirements for the covering area of ​​the inner layer cover 40 will be described later.

[0024] In this embodiment, the outer layer cover 41 completely covers the inner layer cover 40. The requirements for the covering area of ​​the outer layer cover 41 will be described later.

[0025] [Inner cover 40] In this embodiment, it is essential that the inner layer cover 40 has the function of preventing the outer layer cover 41 from slipping against the sealing portion 35 at the interface between the sealing portion 35 and the outer layer cover 41 when the sealing portion 35 is directly covered by the outer layer cover 41. In other words, it is essential that at least the outer surface of the inner layer cover 40 has a higher coefficient of friction (or dynamic friction coefficient or sliding friction coefficient) than the friction coefficient of the inner surface of the outer layer cover 41. By interposing an inner layer cover 40 with such a high coefficient of friction, it is possible to prevent the outer layer cover 41 from slipping against the sealing portion 35.

[0026] The inner layer cover 40 may include, for example, a rubber material such as silicone rubber or nitrile rubber.

[0027] The thickness of the inner layer cover 40 is preferably 1.0 mm or more and 3.0 mm or less. With this configuration, the inner layer cover 40 itself becomes more easily deformed when pressure is applied, which is advantageous in that the contact area increases when gripping the workpiece, thereby improving the gripping force of the robot hand's fingers.

[0028] The inner layer cover 40 is important to cover at least the tip side of the fluid pressure actuator 3, i.e., the sealing portion 35 which is the gripping portion, but as shown in Figure 3, it may also cover the entire fluid pressure actuator 3 (to the extent that it does not reach the inlet 36).

[0029] Furthermore, the inner layer cover 40 may be configured to cover only the sealing portion 35, which is the tip of the fluid pressure actuator 3. This configuration is particularly advantageous when it is sufficient to cover only the sealing portion 35, which is the gripping portion, and it facilitates the attachment of the inner layer cover 40 and the outer layer cover 41.

[0030] However, in order to prevent the inner layer cover 40 from coming off due to some accident or other reason once it has been installed, it is preferable to cover at least up to the upper end of the sealing portion 34.

[0031] [Outer cover 41] In this embodiment, the outer layer cover 41 is formed by dip coating a chemical fiber, such as nylon, with a rubber material, for example. Therefore, in order to impart a desired function to the functional outer layer cover 41, the chemical fiber and / or rubber material should be appropriately selected according to the desired function.

[0032] The desired function of the outer cover 41 means any function such as oil / water resistance, stain prevention, and / or prevention of contamination by wear particles from the operation of the robot hand.

[0033] The outer diameter of the outer layer cover 41 is preferably within a certain range relative to the outer diameter of the inner layer cover 40. That is, as shown in Figure 3, the ratio a:b of the outer diameter a of the inner layer cover 40 to the outer diameter b of the outer layer cover 41 is preferably in the range of 1:0.9 to 1:1.1, and more preferably 1:1. This configuration is advantageous in preventing slippage of the outer layer cover 41 and improving the load-bearing capacity. Although not shown in the figures, the outer diameter a of the inner layer cover 40 and the outer diameter b of the outer layer cover 41 refer to the outer diameters of each cover in a state where they have not undergone any expansion or contraction (before actuator installation).

[0034] It is essential that the outer cover 41 covers at least the portion of the inner cover 40 that covers the tip (sealing portion 35). In other words, since the outer cover 41 is a functional cover, it should be configured to cover the portion of the fluid pressure actuator 3 to which the above-described function is to be applied, namely the sealing portion 35 that corresponds to the fingertip.

[0035] The fluid pressure actuator 3 described above can be applied to the fingers of a robot hand to maintain or improve the gripping ability of the robot hand while allowing the outer cover to function properly. The robot hand to which the fluid pressure actuator 3 is applied is not particularly limited. Typical examples of robot hands to which the fluid pressure actuator 3 is applied will be described below with reference to the drawings.

[0036] The robot hand is attached to the tip of the robot arm for use. The structure of the robot arm is not particularly limited, but for example, the robot arm 1 shown in Figure 4 can be used. This robot arm 1 will be described with reference to Figure 4.

[0037] <Robot Arm 1> Figure 4 is a perspective view of a robot arm 1 having a robot hand 2 according to the present invention. As shown in Figure 4, the robot arm 1 has a base 11 attached to a foundation (not shown), an arm 13a extending from the base 11 via a joint 12a, and an arm 13b extending from the arm 13a via a joint 12b. Thus, the robot hand 2 is attached to the tip of the connected arm 13b via a joint 12c. Next, the robot hand 2 according to the present invention will be described in detail with reference to the drawings.

[0038] <Robot Hand 2> As shown in Figure 4, the robot hand 2 has a gripping means 30 for grasping a workpiece (not shown). The gripping means 30 consists of multiple fingers 30a to 30d attached to the hand body 20, in this embodiment consisting of four fingers 30a to 30d. The fluid pressure actuator 3 described above is applied to these fingers 30a to 30d.

[0039] As shown in Figure 4, the base ends of the fingers 30a to 30d are attached to a frame 3 fixed to the joint 12c of the robot arm 1 described above. The fingers 30a to 30d are rod-shaped bodies that extend uniaxially from their base to their tip. As described above, each of the fingers 30a to 30d in this embodiment is a fluid pressure actuator 3 capable of bending from a state of extending uniaxially as shown in Figure 1 to a direction different from that uniaxial direction.

[0040] By applying the above actions to each finger, the distance between opposing fingers can be varied to enable a strong grip on the workpiece or, conversely, a soft grip using the fingertips. The working fluid is determined appropriately depending on the type of workpiece and fluid pressure actuator, but compressed air is used as an example. [Examples]

[0041] A fluid pressure actuator (inventive example) with a double cover consisting of an inner cover and an outer cover covering the inner cover, as shown in Figures 1-3, and a fluid pressure actuator (comparative example) having the same basic structure as the inventive example but without an inner cover, and covered only with the same outer cover as conventional models, were applied to the fingers of a robot hand shown in Figure 4. Next, a workpiece was gripped by these robot hands, and the limit of the load capacity that could be maintained without the cover coming off was measured. The inner cover was made of silicone rubber, and the outer cover was made of nitrile rubber.

[0042] The results measured according to the above measurement conditions are shown in Table 1. [Table 1]

[0043] According to Table 1, the robot hand with an inner layer cover in this embodiment had a payload capacity of 2.4 kg. In other words, the robot hand with a double-covered fluid pressure actuator as the finger part in this embodiment had a payload capacity that was approximately 1.0 kg greater than that of a conventional robot hand without an inner layer cover. [Industrial applicability]

[0044] This invention relates to a robotic arm. Furthermore, the SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is considered to be a technology that can contribute to "No. 12: Responsible Consumption and Production" and "No. 13: Take urgent action to combat climate change," among others. [Explanation of symbols]

[0045] 1. Robot arm 2. Robot Hand 3. Fluid pressure actuator 4 frames 11 Bass 12a~12c Joints 13a~13b Arm 20 Handheld Body 30a~30d fingers 31 Tubes 32 sleeves 34,35 Sealing section 36 Inlet 40 Inner layer cover 41 Outer cover

Claims

1. A fluid pressure actuator that operates by fluid pressure supplied into a tube, comprising an inner layer cover that covers at least the tip of the fluid pressure actuator, and an outer layer cover that covers at least the portion of the inner layer cover that covers the tip, At least the outer surface of the inner layer cover has a higher coefficient of friction than the inner surface of the outer layer cover. Fluid pressure actuator.

2. The fluid pressure actuator according to claim 1 or 2, wherein the thickness of the inner layer cover is 1.0 mm or more and 3.0 mm or less.

3. The fluid pressure actuator according to claim 1, wherein the inner layer cover covers only the tip portion of the fluid pressure actuator.

4. The fluid pressure actuator according to claim 1, wherein the ratio of the outer diameters of the inner layer cover and the outer layer cover is in the range of 1:0.9 to 1:1.

1.

5. The fluid pressure actuator according to claim 1, wherein the outer layer cover has at least one of the functions of waterproofing, oil resistance, and stain resistance.

6. A robot hand equipped with a gripping mechanism for grasping a workpiece, The gripping means has a plurality of fingers extending from the hand body of the robot hand, the base end of each of the plurality of fingers is rotatably attached to the hand body, and the spacing between the fingertips of the plurality of fingers is adjustable. The aforementioned finger is a fluid pressure actuator according to claim 1. Robot hand.

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