Fluid pressure actuator

Abstract

Disclosed is an effective configuration of a bending actuator using a Warsaw-type artificial muscle, and various gripping devices equipped with the actuator are realized. 【Solution means】The configuration of the actuator 10 includes a multi-layer fiber-reinforced tube 11 composed of two layers, a rubber base material layer and a fiber-encapsulated layer, lid members 12A and 12B respectively attached to both ends of the tube 11, a restraining member 20 provided in contact with a part of the side surface of the tube 11 along the axial direction of the tube, an adhesive layer 31 connecting the tube and the member, and tightening bands 13A and 13B. The lid members 12A and 12B are members that close the openings at both ends of the tube 11 and maintain the inside in a sealed state. The tightening bands 13A and 13B are fastened to the outer peripheral surfaces of both ends of the tube 11, and tighten the tube 11 together with the restraining member 20 so that no gap is formed between the lid members 12A and 12B and the tube 11.

Description

Technical Field

[0001] The present invention relates to a hydraulic actuator optimal for end effector applications.

Background Art

[0002] A soft actuator is a material, element, or device that functions as an actuator by deforming a lightweight and flexible material. These soft actuators are also called artificial muscles and have characteristics such as being small and lightweight, having various drive sources, being silent, and being able to operate under extreme conditions such as underwater and in the atmosphere. In recent years, there has been a growing demand for their development as power sources for rehabilitation, caregiving, or wearable robots for work assistance and medical surgery support robots.

[0003] As one example of the practice of an end effector (robot arm) using a soft actuator, a gripping device using an artificial muscle driven by hydraulic pressure can be cited (see Patent Document 1). There are roughly two types of configurations for artificial muscles that operate with hydraulic pressure. One is a configuration consisting of a combination of an inner rubber tube and a braided sleeve, which is called a McKibben type artificial muscle. The other is a configuration called a Walshaw type artificial muscle, which is characterized by bonding a rubber base material tube layer that expands and contracts and a fiber encapsulation layer that encapsulates a thread or fiber for restraining the axial elongation of the rubber tube so as not to separate (see Non-Patent Document 2). The invention of Document 1 adds a restraining member that can be deformed in a direction orthogonal to the axial direction to the above-mentioned McKibben type artificial muscle, thereby constituting an actuator having a mechanism that curves (curls) in the radial direction, which is the direction orthogonal to the axial direction and where the restraining member is on the outer side of the bend, along with the contraction operation of the artificial muscle. By configuring an effector in which a plurality of the actuators are arranged with this bending direction being the direction of contact with the object to be contacted, a gripping device having flexibility is realized.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The content described in the illustration of Document 1 is an application form of a so-called McKibben type artificial muscle in which a sleeve of a braided tube is put on the outside of a rubber tube, that is, the rubber tube that tries to expand in all directions by fluid pressure, the fiber cord that is rubbed while being pressed from the inside of the rubber tube and forms the sleeve of the braided tube. The sleeve of the braided tube has a characteristic of regulating only the axial expansion of the rubber tube by allowing a change in the orientation angle of the cord and not regulating the radial expansion, and a restraint member that is inserted in a form sandwiched between the contact surfaces of the rubber tube and the sleeve of the braided tube and regulates the bending direction. It is a McKibben type artificial muscle actuator that curves and consists of a lid member that connects the rubber tube, the sleeve of the braided tube, and the restraint member at the ends to seal the rubber tube and hold the fluid pressure. In the configuration of the McKibben type artificial muscle, allowing a change in the orientation angle of the fiber cord that forms the sleeve of the braided tube is a prerequisite for the manifestation of the contraction operation of the artificial muscle. Therefore, although the rubber tube and the sleeve of the braided tube are in close contact with each other, the contact surfaces are not fixed to each other, and the rubber tube and the sleeve of the braided tube operate while rubbing against each other at the contact surface. Therefore, pressure transmission loss between the rubber tube and the sleeve of the braided tube due to friction between the contact surfaces and reduction of the product life due to wear of the rubber tube and the sleeve of the braided tube accompanying repeated bending operations may occur.

[0006] The present invention has been made in view of such a situation, By showing an effective configuration of a bending actuator that uses the configuration of a Walshaw type artificial muscle instead of the configuration of a McKibben type artificial muscle, it is intended to achieve high efficiency and long life of pressure transmission of the bending actuator.

Means for Solving the Problems

[0007] The fluid pressure actuator of the present invention for solving the above problems is characterized by combining two elements: a Warshaw type axially contracting artificial muscle tube and a restraint member that converts the contraction operation of the tube into a bending operation.

[0008] According to the basic configuration of the Warshaw type artificial muscle, that is, the axially fiber-reinforced type artificial muscle, there is a two-layer structure composed of a rubber base tube layer and a fiber-encapsulated layer that restricts the axial elongation of the tube layer. When fluid pressure is applied, the tube expands greatly in the radial direction and contracts along the axial direction.

[0009] When the tube becomes substantially spherical due to the application of fluid pressure, the internal volume with respect to the length of the tube becomes maximum, so it does not contract further axially. Here, when the free length (L1) before expansion is 100 mm and the diameter of the tube is 10 mm, the length (L2) in the most contracted case is 68% of the free length (L1). That is, a maximum stroke of 32% can be realized.

[0010] The fluid pressure actuator presented by the present invention is continuously adhered to the outer surface of the tube so as not to separate when the tube contracts from one end side to the other end side in the axial direction of the tube while being in contact with a part of the side surface of the tube. Resisting the radial expansion of the tube with a higher elastic modulus than the rubber base material forming the tube It is characterized in that a restraining member that can be elastically deformed in a direction orthogonal to the axial direction is provided.

[0011] According to the configuration shown in the previous paragraph, the restraining member has a larger flexural modulus than the previous tube. For this reason, in the part where the restraining member is in contact with a part of the side surface of the tube and is continuously adhered to the outer surface of the tube from one end side to the other end side in the axial direction of the tube, even when the internal pressure of the tube increases, the radial expansion is restricted by the restraining member. Therefore, the part that can expand in the radial direction without being restricted, particularly the part facing the restraining member, expands greatly. As a result, the tube expands unevenly due to the application of the fluid pressure, and the entire actuator operates in a curved manner. The direction of this curvature is such that the side where the previous restraining member is adhered and has low expansion is on the outer side of the bend, and the side with high expansion is on the inner side of the bend. Therefore, by arranging the actuator on the end effector so that the direction of this bending operation becomes the direction of contact with the object to be contacted, operations such as pushing, pulling, and grasping the object can be performed.

[0012] As described in paragraph 0009, when the artificial muscle operates to the maximum contraction rate, the tube becomes substantially spherical and the internal volume with respect to the length of the tube becomes maximum. Therefore, the diameter of the tube is approximately equal to the length. For this reason, when the actuator operates in a curved manner, the tube expands greatly and protrudes in the inner direction of the bend, which may cause problems when incorporated into equipment.

[0013] In addition to the configuration shown in Item 0010, the fluid pressure actuator presented by the present invention may also be configured such that one or more ring members that restrain the radial expansion of the tube are provided in contact with the outer surface of the tube in a region from one end side to the other end side in the axial direction of the tube. When one or a plurality of the radial restraint ring members are provided, the tube bulges during expansion due to the ring members. The shape of the tube at the maximum expansion in the radial direction becomes a shape in which substantially spherical bodies are connected by the ring members, and the maximum shrinkage rate is substantially the same as that in the case where there is no ring member, and it operates while curving in the same manner. This configuration solves the problem described in Item 0012.

[0014] Instead of the restraint member described in the configuration shown in Item 0010 being continuously adhered so as not to separate from the outer surface of the tube from one end side to the other end side in the axial direction of the tube, it may be characterized in that the restraint member is embedded in the tube and integrated. Even in the actuator having the configuration shown in this item, in the portion where the restraint member is embedded, even if the internal pressure of the tube increases, the radial expansion is restricted by the restraint member. Therefore, only the portion that can expand in the radial direction and the portion facing the restraint member expand greatly due to the application of the fluid pressure, so the tube expands unevenly, and the entire actuator operates while curving in the same manner as the configuration shown in Item 0010.

[0015] Instead of the restraint member described in the configuration shown in item 0010 being continuously adhered so as not to separate from the outer surface of the tube from one end side to the other end side in the axial direction of the tube, the restraint member may be adhered so as not to separate from the inner surface. Even in the actuator having the configuration shown in this item, at the portion where the restraint member is adhered to the inner surface of the tube, even if the internal pressure of the tube increases, the radial expansion is restricted by the restraint member. Therefore, only the portion that can expand in the radial direction and the portion facing the restraint member expand greatly due to the application of the fluid pressure, so the tube expands unevenly, and the entire actuator operates in a curved manner similar to the configuration shown in item 0010.

Advantages of the Invention

[0016] According to the novel idea of the fluid pressure actuator described above, by using the configuration of a Walshaw type artificial muscle instead of the configuration of a McKibben type artificial muscle, a bending actuator with high efficiency and long life can be realized.

Brief Description of the Drawings

[0017]

Figure 1

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Figure 8-a

Figure 8-b

Figure 9-c

Figure 9-d

Figure 9-e

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Figure 14

Mode for Carrying Out the Invention

[0018] Embodiments are shown below to specifically explain the present invention, but the invention according to the claims is not limited thereto. Also, not all combinations of features described in the embodiments are essential for the solution means of the present invention.

[0019] Figure 1 is a schematic diagram of a fluid pressure actuator system that bends by increasing and decreasing fluid pressure. The actuator 10 and the drive device 30 are connected by a fluid supply and discharge pipe 31. The detailed configuration of the actuator 10 is shown in the side view of Figure 2, the cross-sectional view of Figure 4, the perspective view of Figure 5, and the exploded perspective view of Figure 6.

[0020] It is desirable to select a working fluid for the actuator system that is suitable for the application and use environment of the actuator. Specifically, water, oil, air, steam, generated gas resulting from reactive substances, etc. can be used.

[0021] The configuration of the aforementioned actuator 10 includes a multilayer fiber-reinforced tube 11 composed of two layers, namely a rubber base layer 11a and a fiber-encapsulated layer 11b, lid members 12A and 12B respectively attached to both ends of the tube 11, a restraint member 20 provided in contact with a part of the side surface of the tube 11 along the axial direction of the tube, an adhesive layer 31 connecting the tube and the members, and tightening bands 13A and 13B. The lid members 12A and 12B are members that close the openings at both ends of the tube 11 and maintain the interior in a sealed state. The tightening bands 13a and 13b are fastened to the outer peripheral surfaces of both ends of the tube 11, and tighten the tube 11 together with the restraint member 20 so that no gap is formed between the lid members 12A and 12B and the tube 11. As a result, the tube 11 is maintained in a sealed state by the lid members 12A and 12B and the tightening bands 13A and 13B, and operates when a working fluid is introduced into the sealed space. A hole penetrating inside and outside is opened in the lid member 12B, and a fluid supply and discharge pipe 31 is inserted into the hole. The drive device 20 includes an electromagnetic valve 32a for fluid injection, an electromagnetic valve 32b for fluid discharge, a working fluid supply means 33, and a control means 34, and the fluid supply and discharge pipe 31 is inserted into the electromagnetic valve 32b. The control means 34 controls the opening and closing of the electromagnetic valve 32a for injection and the opening and closing of the electromagnetic valve 32b for discharge to control the bending operation of the actuator.

[0022] The actuator 10 transitions between two states, namely the non-pressurized state shown in Figure 2 and the pressurized state shown in Figure 3, and bends by the supply and discharge of the working fluid through the fluid supply and discharge pipe 31 under the control of the drive device 30.

[0023] The tube 11 has a cylindrical shape with both ends open and is a multi-layer structure composed of one or more layers of each of a rubber base material layer 11a and a fiber-embedded layer 11b. The fiber-embedded layer 11b is formed by forming a fiber sheet 11s in which a plurality of reinforcing fibers 11k are uniformly dispersed in a binder material 11r or evenly attached to the surface into a cylindrical shape (FIGS. 8-a and 8-b). At this time, it should be noted that the orientation direction of the fibers 11k is an angle close to parallel to the axial direction of the tube 11, more specifically, the angle difference from the axial direction is within 5 degrees. The fibers 11k constituting the fiber layer 11b can be made of any material as long as they have a tensile strength capable of withstanding the expansion due to the internal pressure of the tube 11 and restricting the elongation of the tube and are flexible enough not to prevent the expansion force in the tube diameter direction. Specifically, various high-strength fibers such as glass fiber, nylon fiber, aramid fiber, carbon fiber, and piano wire can be selected. Regarding the binder material 11r, it may be a soft material that can hold the reinforcing fibers 11k without separation or displacement and can follow the contraction and expansion of the tube 11. More specifically, it can be selected from natural rubber or synthetic rubber latex, silicone, polyurethane, vinyl polymer, etc.

[0024] Regarding the layer structure of the tube 11, any structure may be used as long as the rubber base material layer 11a and the fiber-embedded layer 11b do not peel off during expansion and contraction. The structure can be selected according to the material of each layer, such as bonding through the tackiness of the 11a layer or 11b layer, or adhesive bonding. For the inside and outside and the number of layers of each layer, an appropriate structure can be selected according to the application. More specifically, either the rubber base material layer 11a or the fiber-embedded layer 11b may be on the inside or outside (FIG. 9-c), multiple layers of the same layer may be stacked (FIG. 9-d), or different layers may be stacked alternately (FIG. 9-e).

[0025] The dimensions of the restraint member 20 can be changed according to the dimensions of the fluid pressure actuator 10, the driving force of the actuator, and the operating stroke, and are not particularly limited. Regarding the selection of the material constituting the restraint member 20, a material having a bending elastic modulus larger than that of the tube 11 made of an elastic rubber material and untwisted fibers is desirable. Specifically, various general-purpose plastics, engineering plastics, glass fiber-reinforced resins, carbon fiber-reinforced plastics, stainless steel for springs, copper alloys for springs, etc., materials that can be used as leaf springs are processed into members having the same length as the tube 11 and used.

[0026] The restraint member 20 is adhered via an outer surface adhesive layer 21 of the tube so as not to separate during the expansion and contraction of the tube 11. It is desirable to select the material of the adhesive layer 21 in consideration of the respective materials of the tube 11 and the restraint member 20. Specifically, it can be selected and used from epoxy resin adhesives, acrylic resin adhesives, styrene-butadiene rubber adhesives, chloroprene rubber adhesives, silicone rubber adhesives, etc.

[0027] So far, among the multiple configurations of the actuator 10 that bends by increasing and decreasing fluid pressure presented by the present invention, the simplest basic configuration has been shown and described in FIGS. 2, 3, 4, 5, 6, and 7. In the said basic configuration, since the expansion in the radial direction of the tube 11 is restricted at the part where the outer surface of the tube 11 and the restraint member 20 are continuously adhered, the part that can expand in the said radial direction without being restricted, particularly the part facing the restraint member 20, expands greatly. This swelling of the tube 11 may become an obstacle to equipment installation.

[0028] Figures 10 and 11 are a side view and a perspective view, respectively, of a configuration of the actuator 10 in which two additional radial restraint ring members 22 are added to a plurality of configurations. FIG. 12 shows the pressurized bending operation state of the actuator of the above configuration. The tube 11 bulges during pressurized expansion due to the ring member 22. Therefore, the shape of the tube 11 at maximum expansion is a shape in which substantially spherical bodies are connected by ring members, and the maximum shrinkage rate is approximately the same as that without the ring member and operates with the same curvature. The thickness of the tube 11 at maximum expansion is suppressed to about 37% compared to the case where the ring member 22 is not added, enabling the actuator 10 to operate with less space. The material of the ring member 22 desirably has tensile strength to withstand the radial expansion of the tube 11. More specifically, it can be selected and used from those in which high-strength fibers are converged in a ring shape, steel hose bands, rubber rings, and the like. The method of attaching the ring member 22 to the actuator 10 can be a method of tightening from the outside of the tube 11 and fixing it by friction, adhering it to the tube 11 or the restraint member 20, or sandwiching it between the tube 11 and the restraint member 20 and fixing it by friction. Any method can be selected as long as it does not come off or shift during the expansion and contraction of the tube 11.

[0029] FIG. 13 is a cross-sectional view taken along line A-A' of a configuration in which the restraint member 20 is embedded in the tube 11 among a plurality of configurations of the above actuator. The restraint member 20 may be embedded in either the rubber base layer 11a or the fiber-encapsulated layer 11b inside the tube 11, or across both layers. Even in the actuator 10 having the configuration of FIG. 13, since the radially outward expansion is restricted by the restraint member 20 at the portion where the restraint member 20 is embedded even when the internal pressure of the tube 11 increases, only the portion facing the restraint member 20 expands greatly, so the tube 11 expands unevenly, and the actuator as a whole operates with the same curvature as the basic configuration.

[0030] FIG. 14 is a cross-sectional view taken along line A-A' of a configuration in which the restraint member 20 is adhered so as not to separate from the inner surface of the tube 11 among the plurality of configurations of the actuator 10. Even in the actuator 10 having the configuration shown in FIG. 14, at the portion where the restraint member 20 is adhered to the inner surface of the tube 11, the radial expansion is restricted by the restraint member 20 even when the internal pressure of the tube 11 increases. Therefore, only the portion facing the restraint member 20 expands greatly, so that the tube 11 expands unevenly, and the entire actuator operates in a curved manner as in the basic configuration.

[0031] Although not described in the above embodiment, it is of course possible to construct an actuator system by combining each configuration of the actuator 10, such as an actuator that combines the configuration of the restraint member embedded type shown in FIG. 13 and the configuration of the ring member constriction type shown in FIG. 10, or an actuator that combines the configuration of the restraint member inner surface adhesion type shown in FIG. 14 and the configuration of the ring member constriction type shown in FIG. 10.

Explanation of Reference Numerals

[0032] 10 Fluid pressure actuator 11 Multilayer fiber-reinforced tube 11a Rubber base material layer 11b Fiber encapsulation layer 11k Reinforcing fiber 11r Binder material 11s Fiber sheet 12A Cover member 12B Supply / discharge pipe side cover member 13A Clamping band 13B Supply / discharge pipe side clamping band 20 Restraint member 21 Adhesive layer 22 Restraint ring member 30 Driving device 31 Fluid supply / discharge pipe 32a Fluid injection solenoid valve 32b Fluid discharge solenoid valve 33 Fluid supply means 34 Control means

Claims

1. A fluid pressure actuator that expands the tube in the radial direction by the pressure of a fluid supplied to a space formed by a multi-layer fiber-reinforced tube that expands and contracts due to fluid pressure and cover members provided on both ends of the tube, and generates a contraction force in the axial direction of the tube, wherein the tube has a multi-layer structure consisting of a combination of one or more layers of a rubber-based tube layer and a fiber-encapsulated layer aligned parallel to the axial direction that restricts the extension of the tube layer in the axial direction, and the multi-layer structure is an integrated cylindrical body in which contact surfaces are bonded together to prevent interlayer peeling and positional displacement when the tube changes shape, such as expanding, contracting, bending, and stretching, and further comprises a pair of cover members that resist the radial expansion of the tube and expand in an orthogonal direction perpendicular to the axial direction. a restraining member which is deformable and has a higher elastic modulus than the rubber base material forming the tube, contacts a portion of the side of the tube and is continuously bonded from one end to the other in the axial direction of the tube so as to prevent displacement of the peeling position when the tube changes shape such as expanding, contracting, bending, and stretching, and therefore, even if the internal pressure of the tube increases due to the application of the fluid pressure, the radial expansion of the tube is partially restricted by the restraining member, resulting in the tube expanding unevenly in the radial direction, and the actuator as a whole operates by curving in a direction such that the side where the restraining member is bonded and which experiences low expansion is on the outside of the bend and the side where high expansion is on the inside of the bend.

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