Fluid pressure actuator

Abstract

This paper proposes a structure for a fluid pressure actuator, intended to function as a finger in a robot hand, that ensures a secure and firm grip on a workpiece. [Solution] A fluid pressure actuator that operates by bending in a direction different from the axial direction of the tube due to the fluid pressure supplied into the tube, wherein the tip of the tube has a claw portion extending in the axial direction, and the claw portion has a low-rebound portion on the side of the tube that is in the direction of operation of the tube.

Description

Technical Field

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

Background Art

[0002] In recent years, in various fields such as manufacturing and logistics, general-purpose robots that perform operations such as grasping, lifting, transporting, and supporting objects are being used. In particular, regarding robot hands that are responsible for the part beyond the human wrist and mimic the function of the palm among the parts of the robot, various proposals have been made.

[0003] Now, in recent logistics where various workpieces with different shapes and sizes are handled, when applying a robot hand, it is required to securely grip various workpieces. For example, a fluid pressure actuator is used for the fingers of a robot hand having a gripping means by a plurality of fingers.

[0004] For example, Patent Document 1 discloses a fluid pressure actuator applicable to a robot hand.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Patent Document 1 describes a so-called "McKibben-type fluid pressure actuator" as a fluid pressure actuator, which consists of a rubber tube and a high-strength fiber sleeve surrounding it. In a fluid pressure actuator, in order to apply fluid pressure to the tube, both ends of the tube are provided with sealing parts (sealing members), for example, made of metal cylinders, to seal the inside of the tube. When the actuator is used as a finger in a robot hand, the part that grips the workpiece is the fingertip, i.e., the sealing part at the tip of the actuator. As described above, since the sealing part is made of a hard material such as metal, the sealing part makes point contact with the workpiece when gripping the workpiece, and the gripping strength may decrease depending on the workpiece. For this reason, measures have been taken to increase the gripping strength by attaching a cover made of a material with a high coefficient of friction to the tip of the actuator, for example, but there has been a desire for further improvement in gripping strength. In particular, when the workpiece to be gripped is a heavy object with a relatively soft surface, there remains a problem in that it is difficult to grip such workpieces reliably and firmly.

[0007] Therefore, the present invention aims to propose a structure for a fluid pressure actuator used as a finger of a robot hand, which ensures that the finger can reliably and firmly grip a workpiece. [Means for solving the problem]

[0008] The inventors diligently studied the structure of a fluid pressure actuator that could solve the above problems and found that providing a low-rebound section at the tip of the actuator's tube was effective. The present invention is derived from the above findings, and its gist is as follows.

[0009] 1. A fluid pressure actuator that operates by bending the tube in a direction different from the axial direction due to the fluid pressure supplied into the tube, A fluid pressure actuator having a claw portion extending in the axial direction at the tip of the tube, and a low-rebound portion on the side of the claw portion that is in the operating direction of the tube.

[0010] 2. The fluid pressure actuator according to 1, wherein the low-rebound portion is made of gel material.

[0011] 3. 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 or 2 above. Robot hand. [Effects of the Invention]

[0012] According to the present invention, a fluid pressure actuator that serves as a finger of a robot hand can be provided with a structure that allows it to reliably and firmly grip a workpiece. Therefore, by applying the fluid pressure actuator of the present invention to the fingers of a robot hand, it becomes possible to provide a robot hand that can reliably and firmly grip a wide variety of workpieces. [Brief explanation of the drawing]

[0013] [Figure 1] This is a perspective view showing one embodiment of a fluid pressure actuator according to the present invention. [Figure 2] These are top view (a) and side view (b) of a fluid pressure actuator. [Figure 3] This is a cross-sectional view along line AA in Figure 2. [Figure 4] This is an exploded perspective view showing the structure of the sealing tip side of the fluid pressure actuator. [Figure 5] 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. [Figure 6] This graph shows the results of the payload survey. [Modes for carrying out the invention]

[0014] A fluid pressure actuator according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3. Here, FIG. 1 is a perspective view of the fluid pressure actuator 3, FIG. 2 is a view showing the upper surface and the side surface, and FIG. 3 is a cross-sectional view taken along the line A-A of FIG. 2.

[0015] That is, the fluid pressure actuator 3 includes an actuator body 33 in which a rubber tube 31 is covered with a high-strength fiber sleeve 32 in the present embodiment, and sealing portions 34 and 35 made of, for example, metal cylinders for sealing each of the axial end portions of the tube 31 to seal the tube 31.

[0016] Further, an inlet 36 for introducing the working fluid from the outside is provided in the sealing portion 34 on the base end side of the tube 31. By introducing the working fluid from the inlet 36, as shown by the two-dot chain line in FIG. 1, an operation of curving the axis of the tube 31 toward its tip can be given.

[0017] On the other hand, the sealing portion 35 on the tip side of the tube 31 has a metal claw portion 37, for example, made of aluminum or the like, extending axially from the tip of the sealing portion 35. As shown in FIG. 4 as an exploded perspective view of the structure on the tip side of the sealing portion 35, the claw portion 37 is a fitting extending axially from, for example, a semi-arc portion at the tip edge of the sealing portion 35, and its tip is formed in a curved shape without corners, for example, an arc shape.

[0018] Furthermore, a low-rebound portion 38 is provided adjacent to the claw portion 37 in the radial direction (the radial direction of the tube 31). The low-rebound portion 38 is, for example, a mass of gel material extending axially from an arc portion other than the claw portion 37 at the tip edge of the sealing portion 35 and has low rebound properties. That is, it is important that the low-rebound portion 38 has low rebound force, a slow displacement speed accompanying pressure application (for example, when the actuator is used as a finger of a robot hand to grip a workpiece), and a slow restoration speed when the pressure decreases, that is, has low rebound properties. The material constituting the low-rebound portion 38 is not particularly limited as long as it has low rebound properties, and for example, silicon, urethane, etc. can be applied.

[0019] As shown in FIG. 3, the low-rebound portion 38 is disposed adjacent to the actuator's operating direction (arrow) side of the claw portion 37. Due to this arrangement relationship, for example, when the actuator is used on the finger of a robot hand to grip a workpiece, the workpiece will first come into contact with the low-rebound portion 38. At that time, since the low-rebound portion 38 that contacts the workpiece has low rebound characteristics, in a state where it is supported by the claw portion 37 at the back, it will gradually deform as the pressure is applied during contact, and the contact area with the workpiece will increase. In contrast to the previous actuator where workpiece gripping was point contact, surface contact is realized with the actuator of this embodiment. As a result, strong and reliable gripping becomes possible even for workpieces that are, for example, heavy objects with a soft surface.

[0020] Here, in this embodiment, the fluid pressure actuator 3 has dimensions as shown in FIG. 3, that is, the axial length l1, thickness d1, (circumference r1 in FIG. 4) of the claw portion 37, the axial length l2, thickness d2, (circumference r2 in FIG. 4) of the low-rebound portion 38 are, for example, within the following ranges, which is particularly effective for expanding the above-mentioned contact area. l1: 14.3 to 15.3 mm Thickness d1: 2.3 to 5.3 mm Circumference r1: 10.3 to 16.7 mm l2: 14.3 to 15.3 mm Thickness d2: 5.3 to 8.3 mm Circumference r2: 16.7 to 23.0 mm

[0021] In addition, at least the tip of the actuator, which is composed of the combination of the claw portion 37 and the low-rebound portion 38, is covered with a cover 39 made of, for example, silicon rubber, and at least the claw portion 37 and the low-rebound portion 38 are not exposed on the outside. The cover 39 is shown only in FIG. 1 and is omitted in other figures.

[0022] The fluid pressure actuator 3 described above can significantly improve the gripping ability of a robot hand by being applied to the fingers of the robot hand. The robot hand to which the fluid pressure actuator 3 is applied is not particularly limited. A typical example of a robot hand to which the fluid pressure actuator 3 is applied will be described below with reference to the drawings.

[0023] 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 5 can be used. This robot arm 1 will be described with reference to Figure 5.

[0024] <Robot Arm 1> Figure 5 is a perspective view of a robot arm 1 having a robot hand 2 according to the present invention. As shown in Figure 1, 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.

[0025] <Robot Hand 2> As shown in Figure 5, 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 described above is applied to these fingers 30a to 30d.

[0026] [Fingers 30a~30d] As shown in Figure 5, the base ends of the fingers 30a to 30d are attached to the hand body 20, which is fixed to the joint 12c of the robot arm 1 described above. The fingers 30a to 30d are rod-shaped bodies that extend in a uniaxial direction from their base end to their tip. As mentioned above, each of the fingers 30a to 30d in this embodiment is a fluid pressure actuator capable of bending from a state of extending in a uniaxial direction as shown in Figure 2, as shown in Figure 1, to a direction different from that uniaxial direction. By applying the fluid pressure actuator of this embodiment as the fluid pressure actuator, the gripping ability of the robot hand is greatly improved. In particular, it is possible to reliably and firmly grip even heavy workpieces with relatively soft surfaces.

[0027] 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]

[0028] A fluid pressure actuator (example of the invention) having the following specifications according to the structure shown in Figure 3 was applied to the finger of a robot hand shown in Figure 5, and the contact area when gripping a workpiece was investigated according to the following procedure. Specifically, the gripping operation involved pressing the actuator against a light-transmitting plate representing a workpiece, and the contact area of ​​the actuator tip on the light-transmitting plate was investigated. The pressing force was measured using a load cell. Note • McKibben type actuator • Low-rebound section: Silicone or urethane

[0029] For comparison, a fluid pressure actuator having the same basic structure as the above-described example, but with the sealing portion covered by a silicone rubber cover without a low-rebound portion on the tip side of the sealing portion, was also applied to the finger of the robot hand shown in Figure 5, and the contact area was measured when gripping a workpiece according to the same procedure.

[0030] The procedure for measuring the contact area is as follows: Specifically, internal pressure is applied to the McKibben-type actuator to press its tip against the light-transmitting plate. The distance from the low-rebound portion of the actuator tip (the tip in the comparative example) to the light-transmitting plate is defined as the pressing distance. The contact area is measured using a surface area measuring device from an image of the actuator tip pressed against the light-transmitting plate. The measurement results are shown as the ratio of the contact area measurement value X of the comparative example to the contact area measurement value X of the comparative example. The results of the measurements performed according to the above procedure are shown in Table 1.

[0031] [Table 1]

[0032] Furthermore, the payload capacity was investigated when gripping and transporting various workpieces using a robot hand to which the above-described examples of inventions and comparative examples were applied. The procedure for measuring the payload capacity is as follows. Specifically, a robot hand is attached to the collaborative robot, and the robot is taught a gripping posture such that only the low-rebound portion of the McKibben actuator contacts the workpiece. The robot is taught the robot postures for workpiece gripping, workpiece transport, and workpiece placement, and in addition, the robot is taught to move between these postures at a TCP speed of 250 mm / s as defined in the collaborative robot safety standards.

[0033] The results of measurements taken according to the above procedure are shown in Figure 6. In Figure 6, 0mm pouch refers to a refillable container used for retort foods, detergents, shampoos, conditioners, etc., with a minimum thickness of 1mm or less; 60mm BOX refers to an acrylic box with outer dimensions of 60mm x 60mm; 80mm BOX refers to an acrylic box with outer dimensions of 80mm x 80mm; 100mm BOX refers to an acrylic box with outer dimensions of 100mm x 100mm; and Onigiri Grab refers to a soft gel model that mimics the shape of a rice ball. [Explanation of Symbols]

[0034] 1. Robot arm 2. Robot Hand 3. Fluid pressure actuator 11 Bass 12a~12c Joints 13a~13c Arm 20 Handheld Body 30a~30d fingers 31 Tubes 32 sleeves 33 Actuator body 34,35 Sealing section 36 Inlet 37 Claw 38 Low-rebound section 39 Cover

Claims

1. A fluid pressure actuator that operates by bending the tube in a direction different from the axial direction due to the fluid pressure supplied into the tube, A fluid pressure actuator having a claw portion extending in the axial direction at the tip of the tube, and a low-rebound portion on the side of the claw portion that is in the operating direction of the tube.

2. The fluid pressure actuator according to claim 1, wherein the low-rebound portion is made of gel material.

3. 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 or 2. Robot hand.

Images