Hydraulic actuator

Abstract

The present invention proposes a structure which is for a hydraulic actuator serving as a robot hand finger and which is for reliably and firmly gripping a workpiece as a finger.　Provided is a hydraulic actuator that is activated by the operation of curving in a direction different from the axial direction of a tube by fluid pressure which is supplied into the tube, said hydraulic actuator comprising, at the tip end of the tube, a claw part that extends in the axial direction, and comprising a low rebound part on the tube operation direction side of the claw part.

Description

Fluid pressure actuator

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

[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 the robot hand that is responsible for the part that mimics the function of the palm, which is the part of the robot beyond the human wrist, various proposals have been made.

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

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

[0005] Japanese Patent Application Laid-Open No. 2024-3131051

[0006] Patent Document 1 describes a so-called "McKibben-type fluid pressure actuator" composed of a rubber tube and a sleeve of high-strength fibers surrounding it as a fluid pressure actuator. In the fluid pressure actuator, in order to apply fluid pressure to the tube, both ends of the tube are provided with a sealing portion (sealing member) made of, for example, a metal cylinder to seal the inside of the tube. In a robot hand, when using the actuator as a finger, the portion that sandwiches the workpiece becomes the fingertip, that is, the sealing portion at the tip of the actuator. As described above, since the sealing portion is made of a hard material such as metal, the sealing portion makes point contact with the workpiece and the workpiece is grasped, and in some cases, the grasping strength may decrease depending on the workpiece. Therefore, a device has been devised to increase the grasping strength by attaching a cover made of a material with a high coefficient of friction, for example, to the tip portion of the actuator, but further improvement in grasping strength has been desired. In particular, when the workpiece to be grasped is a heavy object having a relatively soft surface, there remains a problem in that it is difficult to grasp this type of workpiece 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.

[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 is effective. The present invention is based on this finding, and its gist is as follows.

[0009] 1. 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.

[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, wherein 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, the spacing between the fingertips of the plurality of fingers is adjustable, and the fingers are the fluid pressure actuators described in 1 or 2 above.

[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.

[0013] This is a perspective view showing one embodiment of a fluid pressure actuator according to the present invention. These are a top view (a) and a side view (b) of the fluid pressure actuator. This is a cross-sectional view along line A-A in Figure 2. This is an exploded perspective view showing the structure of the sealing tip side of the fluid pressure actuator. This is a diagram showing an example of a robot hand and a robot arm to which the robot hand is attached, according to the present invention. This is a graph showing the results of the investigation of the payload capacity.

[0014] A fluid pressure actuator as one embodiment of the present invention will be described in detail with reference to Figures 1 to 3. Here, Figure 1 is a perspective view of the fluid pressure actuator 3, Figure 2 is a view showing the top and side views, and Figure 3 is a cross-sectional view along the line A-A in Figure 2.

[0015] In other words, the fluid pressure actuator 3 in this embodiment has an actuator body 33 in which a rubber tube 31 is covered with a high-strength fiber sleeve 32, and sealing parts 34 and 35, for example, metal cylinders, for sealing both axial ends of the tube 31 to seal the tube 31.

[0016] Furthermore, an inlet 36 is provided in the sealing portion 34 at the base end of the tube 31 for introducing working fluid from the outside. By introducing working fluid through the inlet 36, the axis of the tube 31 can be made to curve toward its tip, as shown by the dashed line in Figure 1.

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

[0018] Furthermore, a low-rebound portion 38 is provided adjacent to the claw portion 37 in the radial direction (radial direction of the tube 31). The low-rebound portion 38 is a mass of, for example, gel material, extending axially from the arc portion of the tip edge of the sealing portion 35 other than the claw portion 37, and possesses low rebound properties. In other words, it is essential that the low-rebound portion 38 has low rebound force, a slow displacement rate associated with pressure application (for example, when using the actuator as a finger of a robot hand to grip a workpiece), and a slow recovery rate when the pressure decreases. The material constituting the low-rebound portion 38 is not particularly limited as long as it is a material that possesses low rebound properties, but for example, silicone, urethane, etc. can be applied.

[0019] As shown in Figure 3, the low-rebound portion 38 is positioned adjacent to the claw portion 37 on the side of the actuator's operating direction (arrow) described above. Due to this arrangement, when the actuator is used as a finger of a robot hand to grip a workpiece, for example, the workpiece first comes into contact with the low-rebound portion 38. At that time, the low-rebound portion 38, having low rebound properties, gradually deforms in response to the pressure applied during contact, while being supported from behind by the claw portion 37, and the contact area with the workpiece increases. While conventional actuators gripped workpieces at a point contact, the actuator of this embodiment achieves surface contact. As a result, even heavy workpieces with soft surfaces can be gripped firmly and securely.

[0020] In this embodiment, the dimensions of the fluid pressure actuator 3 shown in Figure 3, namely the axial length l1, thickness d1, and (in Figure 4) circumference r1 of the claw portion 37, and the axial length l2, thickness d2, and (in Figure 4) circumference r2 of the low-rebound portion 38, are, for example, within the following ranges, which is particularly effective in increasing the contact area as described above: 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] Furthermore, at least the tip of the actuator, which consists of a claw portion 37 and a low-rebound portion 38, is fitted with a cover 39 made of, for example, silicone rubber, so that at least the claw portion 37 and the low-rebound portion 38 are not exposed to the outside. Note that the cover 39 is shown only in Figure 1 and is omitted in the 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. In this way, 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 fingers 30a-30d are attached to the hand body 20, which is fixed to the joint 12c of the robot arm 1 described above. Each of the fingers 30a-30d is a rod-shaped body that extends in a uniaxial direction from its base end to its tip. As mentioned above, each of the fingers 30a-30d in this embodiment is a fluid pressure actuator that can perform a movement from extending in a uniaxial direction as shown in Figure 1 to bending in a direction different from that uniaxial direction as shown in Figure 2. 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 grip even heavy workpieces with relatively soft surfaces securely and firmly.

[0027] By applying the above actions to each finger, the distance between opposing fingers can be varied, enabling the device to firmly grip the workpiece or, conversely, softly grip it 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.

[0028] A fluid pressure actuator (example of 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. Specifications: McKibben type actuator; Low-rebound part: 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 described above is as follows: 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 measured according to the above measurement procedure are shown in Table 1.

[0031]

[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 was as follows: The robot hand was attached to a collaborative robot, and the robot was taught a gripping posture in which only the low-rebound portion of the McKibben actuator contacted the workpiece. The robot was then taught the robot postures for workpiece gripping, workpiece transport, and workpiece placement, and in addition, the robot was 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, a 0mm pouch is a refillable container used for retort foods, detergents, shampoos, conditioners, etc., with a minimum thickness of 1mm or less; a 60mm box is an acrylic box with an outer diameter of 60mm x 60mm; an 80mm box is an acrylic box with an outer diameter of 80mm x 80mm; a 100mm box is an acrylic box with an outer diameter of 100mm x 100mm; and an onigiri gripper is a soft gel model that mimics the shape of a rice ball.

[0034] 1 Robot arm 2 Robot hand 3 Fluid pressure actuator 11 Base 12a-12c Joints 13a-13c Arm 20 Hand body 30a-30d Fingers 31 Tube 32 Sleeve 33 Actuator body 34, 35 Sealing part 36 Inlet 37 Claw part 38 Low rebound part 39 Cover

Claims

1. 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.

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

3. A robot hand comprising a gripping means for grasping a workpiece, wherein 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, the distance between the fingertips of the plurality of fingers is adjustable, and the fingers are the fluid pressure actuators described in claim 1 or 2.

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