JP7573255B2 - Fluid Pressure Actuator - Google Patents

Description

The present invention relates to a fluid pressure actuator that uses gas or liquid to expand and contract a cylindrical body made of an elastic material.

A fluid pressure actuator is known that includes an elastic tube containing fibers inserted along the longitudinal direction and a lid member that seals both longitudinal ends of the elastic tube, and that can generate a contraction force in the longitudinal direction of the elastic tube when a fluid is injected into the elastic tube by restricting the longitudinal expansion of the elastic tube with the fibers inserted into the elastic tube (see Non-Patent Document 1, Non-Patent Document 2, and Patent Document 1).

In such a fluid pressure actuator, it is important to efficiently convert the radial expansion of the elastic tube into a contraction force in the longitudinal direction of the elastic tube when fluid is injected into the elastic tube.

Matsushita: Notes on the manufacturing method of rubber artificial muscle; "Measurement and Control" Vol. 7, No. 12 (December 1968): pp. 110-116 Development of Axially Fiber Reinforced Air Rubber Artificial Muscle; Journal of the Japan Society of Mechanical Engineers, 2007.5, vol. 110, No. 1062: p. 73

Patent No. 5416580

However, in the structure of the fluid pressure actuator described in Non-Patent Document 1 and Non-Patent Document 2, there are some places on the circumference where there are fiber bundles and some places where there are not. Therefore, when the elastic tube is in an expanded state, radial expansion is concentrated in the elastic body at the circumferential places where there are no fiber bundles, and there is a problem that the radial expansion cannot be sufficiently transmitted to axial contraction. In addition, the fluid pressure actuator of Patent Document 1, which is proposed as a method to solve this problem, is capable of sufficiently transmitting radial expansion to axial contraction, but it is difficult to arrange at least three layers, an outer cylindrical member, a fiber layer, and an inner cylindrical member, which are arranged coaxially, with a uniform thickness, and when contraction is repeated, the load is concentrated in the thin parts of the cylindrical member, which may cause damage to the cylindrical member.

The present invention aims to provide a fluid pressure actuator that can efficiently convert the radial expansion of the fluid pressure actuator body into a contraction force in the longitudinal direction, and further, can increase the durability of the actuator body when contraction is repeated.

A fluid pressure actuator according to an embodiment of the present invention includes a cylindrical body made of an elastic body, and a sealing mechanism that seals an opening at an end of the cylindrical body. The cylindrical body includes a plurality of twisted yarns oriented from one end to the other end. The diameter of each of the twisted yarns included in the plurality of twisted yarns is 0.2 mm or more and 0.8 mm or less. The plurality of twisted yarns are arranged at a plurality of radial positions that are offset from each other in the radial direction of the cylindrical body. The plurality of twisted yarns are arranged at equal intervals in the circumferential direction of the cylindrical body at each of the radial positions in the plurality of radial positions. The plurality of radial positions at which the plurality of twisted yarns are arranged include at least a first radial position and a second radial position at which a twisted yarn adjacent in the radial direction of the cylindrical body to the twisted yarn arranged at the first radial position is arranged. Each twisted yarn arranged at the first radial position is arranged offset in the circumferential direction of the cylindrical body from a twisted yarn arranged at the second radial position.

The above configuration makes it possible to efficiently convert the radial expansion of the fluid pressure actuator body into a contraction force in the longitudinal direction, and further provide a fluid pressure actuator that can increase the durability of the actuator body when contracting repeatedly.

FIG. 1 is a side view of a fluid pressure actuator 1 according to this embodiment, with a portion shown in cross section. 2(a) is an end view taken along the line II-II of FIG. 1, and FIG. 2(b) is an enlarged view of a portion of FIG. 2(a). 3(a) and 3(b) are partially enlarged end views of cross sections of cylindrical bodies 100A and 100B according to modified examples, respectively. FIG. 4(a) is an explanatory diagram showing the operation of the fluid pressure actuator 1 according to the embodiment, and is a diagram showing the state before the actuator body 10 starts to operate, and FIG. 4(b) is a diagram showing the state after fluid AR has been injected into the actuator body 10 and the actuator body 10 has contracted. FIG. 5(a) is an end view of a cylindrical body 100C according to another modified example, and FIG. 5(b) is an enlarged view of a portion of FIG. 5(a). FIG. 6 is a side view of an actuator body 10D according to yet another modified example.

The following describes the embodiments with reference to the drawings. Note that identical or similar symbols are used for identical functions and configurations, and descriptions thereof will be omitted as appropriate.

(1) Overall Schematic Configuration of Fluid Pressure Actuator FIG. 1 is a side view of a fluid pressure actuator 1 according to this embodiment, with a portion shown in cross section.

As shown in FIG. 1, the fluid pressure actuator 1 includes an actuator body 10 and a fluid supply/discharge mechanism 500 that supplies fluid to the actuator body 10.

In this embodiment, the actuator body 10 includes a cylindrical body 100 made of an elastic material, and sealing mechanisms 200, 300 that seal the opening at the end of the cylindrical body 100.

The sealing mechanism 200, 300 includes a sealing member 210, 310 that is inserted into the cylindrical body 100 to seal the opening at the end of the cylindrical body 100, and a fastening band 230, 330 that restrains the cylindrical body 100 to the sealing member 210, 310.

Specifically, the sealing members 210, 310 include a body portion (not shown) that is inserted into the cylindrical body 100, and a flange portion 211, 311 that is connected to the body portion in the direction of insertion of the body portion into the cylindrical body 100 and limits the sealing members 210, 310 from being inserted excessively into the cylindrical body 100. In addition, at least one of the sealing members 210 is formed with a connection port 213 that is connected to the flange portion 211 on the opposite side of the body portion and is provided so that the fluid AR can be injected into and discharged from the cylindrical body 100 via the body portion inserted into the cylindrical body 100 and the flange portion 211.

In this embodiment, the actuator body 10 is obtained by inserting the body portion (not shown) of the sealing member 210, 310 into the opening at the end of the cylindrical body 100, and then connecting the cylindrical body 100 to the sealing member 210, 310 by tightening the tightening bands 230, 330 from the outer periphery of the cylindrical body 100 to the part of the cylindrical body 100 where the body portion of the sealing member 210, 310 is inserted.

Furthermore, as shown in FIG. 1, rings 250, 350 are arranged on the outer periphery of the cylindrical body 100 to limit the expansion of the cylindrical body 100 near the tightening bands 230, 330. In this embodiment, the rings 250, 350 are made of a metal such as aluminum.

In this embodiment, the rings 250 and 350 are disposed adjacent to the tightening bands 230 and 330 on the central side of the cylindrical body 100 in the longitudinal direction _DAX .

With this configuration, when fluid is injected and the cylindrical body 100 expands, the portions of the cylindrical body 100 adjacent to the tightening bands 230, 330 are protected by the rings 250, 350, and excessive stress on the elastic body of the cylindrical body 100 can be prevented from being applied by the edges of the tightening bands 230, 330, etc.

As shown in FIG. 1, in this embodiment, the fluid supply/discharge mechanism 500 is composed of a fluid supply device 510 that supplies fluid, a fluid injection/discharge pipe 530 to which a solenoid valve 521 for fluid injection and a solenoid valve 523 for fluid discharge are attached, forming a fluid supply path from the fluid supply device 510 to the inside of the actuator body 10 and a fluid discharge path from the actuator body 10 to the outside of the fluid pressure actuator 1, and a control device 540 that transmits control signals to the solenoid valves 521 and 523 to control the injection/discharge of fluid into the actuator body 10.

A fluid injection/discharge pipe 530 is connected to the connection port 213 of the sealing member 210 in the actuator body 10. A solenoid valve 521 for fluid injection and a solenoid valve 523 for fluid discharge are connected to the fluid injection/discharge pipe 530.

The solenoid valve 521 for fluid injection is connected to the fluid injection/discharge pipe 530 between the portion connected to the fluid supply device 510 and the portion connected to the connection port 213 of the actuator body 10. In other words, the solenoid valve 521 for fluid injection is connected so as to be able to open and close the fluid supply path from the fluid supply device 510 to the actuator body 10.

The solenoid valve 523 for discharging fluid is connected between the part of the fluid injection/discharge pipe 530 that is connected to the connection port 213 of the actuator body 10 and a fluid discharge path (fluid discharge port) to the outside of the fluid pressure actuator 1 that branches off on the actuator body 10 side from the solenoid valve 521 for injecting fluid. In other words, the solenoid valve 523 for discharging fluid is connected so as to be able to open and close the fluid discharge path from the actuator body 10 to the outside of the fluid pressure actuator 1.

The control device 540 is capable of controlling the opening and closing of the solenoid valve 521 for injecting fluid and the solenoid valve 523 for discharging fluid, and controls the injection and discharge of fluid into the actuator body 10.

The fluid supply/discharge mechanism 500 of the fluid pressure actuator 1 is not limited to the configuration of this embodiment.

In other words, as long as the configuration can increase the pressure inside the actuator body by injecting fluid into the actuator body 10 when a contraction force is generated in the actuator body 10, maintain the pressure inside the actuator body when the contraction force generated by the actuator body is to be maintained, and reduce the pressure by discharging the fluid inside the actuator body when the contraction force generated by the actuator body is to be reduced, the configuration is not limited to that of this embodiment.

For example, in this embodiment, both the injection and discharge of fluid into the actuator body 10 are performed via the connection port 213 of the sealing member 210 and the injection/discharge pipe 530. However, the connection port 213 provided in the sealing member 210 of the actuator body 10 may be divided into an injection port and a discharge port, and a fluid injection pipe equipped with a solenoid valve for fluid injection may be connected to the injection port, and a fluid discharge pipe equipped with a solenoid valve for fluid discharge may be connected to the discharge port, thereby providing independent fluid injection paths and fluid discharge paths.

(2) Configuration of the tubular body 100 made of an elastic body In this embodiment, the actuator body 10 includes a tubular body 100 made of an elastic body, the openings at both ends of which are sealed by a pair of sealing mechanisms 200, 300. The tubular body 100 includes a plurality of twisted yarns 130 oriented from one end to the other end thereof, as shown in FIG.

Specifically, in the present embodiment, the tubular body 100 uses rubber as the elastic body that constitutes the tubular body 100. However, the elastic body used in the tubular body 100 is not limited to rubber. For example, it may be an elastic body such as silicone, urethane, or elastomer.

In this embodiment, the tubular body 100 is cylindrical. However, the shape of the tubular body 100 is not limited to a cylindrical shape as long as it is cylindrical. For example, it may be a square cylinder, an elliptical cylinder, etc.

Specifically, in this embodiment, the dimensions of the cylindrical body 100 are a length in the longitudinal direction D _AX of 50 mm to 200 mm, an inner diameter before fluid injection of 15 mm to 30 mm, and a thickness of the cross-sectional rubber layer before fluid injection in a cross section perpendicular to the longitudinal direction D _AX of 1.5 mm to 2.5 mm. However, the shape of the cylindrical body 100 may be appropriately selected depending on the desired output, use conditions, etc.

In this embodiment, the twisted yarn 130 is a twisted yarn made by twisting organic fibers. Examples of organic fibers used in the twisted yarn 130 include polyester cord, nylon cord, PET cord, and aromatic polyamide cord.

Specifically, in this embodiment, the diameter of the twisted yarn 130 is about 0.2 to 0.8 mm. However, the diameter of the twisted yarn 130 may be appropriately selected depending on the desired output, usage conditions, etc.

In this embodiment, the twisted yarn 130 and the elastic body constituting the tubular body 100 are bonded at least at one location on the circumference of the cross section of the twisted yarn 130. Therefore, the tubular body 100 is configured to prevent the twisted yarn 130 from peeling off from the elastic body.

Fig. 2(a) is an end view of the cross section taken along line II-II in Fig. 1. Fig. 2(b) is an enlarged view of a portion of Fig. 2(a). Fig. 2(a) and Fig. 2(b) show the arrangement of multiple twisted yarns 130 in a cross section perpendicular to the longitudinal direction D _AX of the tubular body 100, i.e., the cylindrical axial direction of the tubular body 100 in this embodiment.

As shown in Figures 2(a) and 2(b), the multiple twisted yarns 130 are arranged at multiple radial positions R1, R3 that are offset from each other in the radial direction of the tubular body 100. The multiple twisted yarns 130 are arranged at equal intervals in the circumferential direction of the tubular body 100 at each of the multiple radial positions R1, R3.

Specifically, the twisted yarns 130 are arranged at equal intervals of about 0.8 mm to 2.5 mm in the circumferential direction of the cylindrical body 100. Here, "equally spaced in the circumferential direction of the cylindrical body 100 at each radial position" specifies that the distance between the twisted yarns 131 (133) arranged at a specific radial position R1 (R3), for example, as shown in FIG. 2(b), is equal when the cross-sectional center of each twisted yarn 131 (133) is used as the reference.

The "radial direction" of the cylindrical body 100 refers to the radial direction centered on the cylindrical axis direction, and the "circumferential direction" of the cylindrical body 100 refers to the rotational direction centered on the cylindrical axis direction.

The multiple radial positions R1, R3 at which the multiple twisted yarns 130 are arranged include at least a first radial position R1 and a second radial position R3 at which the twisted yarn 133 is arranged adjacent in the radial direction of the tubular body 100 to the twisted yarn 131 arranged at the first radial position R1.

In this embodiment, as shown in Figures 2(a) and 2(b), the twisted yarn 130 is arranged only at the first radial position R1 and the second radial position R3.

As shown in FIG. 2(b), each twisted yarn 131 arranged at the first radial position R1 is shifted in the circumferential direction of the tubular body 100 from the twisted yarn 133 arranged at the second radial position R3.

The misalignment between the twisted yarns 131 and 133 in the circumferential direction of the tubular body 100 refers to the misalignment when the cross-sectional centers of the twisted yarns 131 and 133 are used as references. Therefore, the twisted yarns 131 and 133 may overlap in the circumferential direction of the tubular body 100 to the extent that they do not come into contact with each other.

The radial distance of the tubular body 100 between the first radial position R1 and the second radial position R3 at which the twisted yarn 130 is arranged may be equal to or greater than the radius of the twisted yarn 130 used, within the range of arrangement where the twisted yarns 130 do not come into contact with each other. Furthermore, if the radial distance of the tubular body 100 between the first radial position R1 and the second radial position R3 at which the twisted yarn 130 is arranged is equal to or less than twice the diameter of the twisted yarn 130 used, the efficiency of converting the radial expansion of the actuator body 10 into a contraction force in the longitudinal direction DAX can be maintained.

Figures 3(a) and 3(b) each show a modified example of the actuator body 10 of this embodiment. Specifically, Figures 3(a) and 3(b) each show an enlarged view of the end cross-section of the cylindrical bodies 100A and 100B in the actuator body.

For example, as shown in Figures 3(a) and 3(b), if each twisted yarn 131A, 131B arranged at the first radial position R1A, R1B is arranged circumferentially offset from the twisted yarn 133A, 133B arranged at the second radial position R3A, R3B of the tubular body 100A, 100B, the distance between the first radial position R1A, R1B and the second radial position R3A, R3B in the radial direction of the tubular body 100A, 100B can be changed.

Specifically, in FIG. 3(a), the distance between the first radial position R1A and the second radial position R3A in the cylindrical body 100A is set to be longer than the distance between the first radial position R1 and the second radial position R3 in the cylindrical body 100 of the embodiment shown in FIG. 2(b).

In FIG. 3(b), the distance between the first radial position R1B and the second radial position R3B in the cylindrical body 100B is set to be shorter than the distance between the first radial position R1 and the second radial position R3 in FIG. 2(b).

2(b), 3(a), and 3(b), the two twisted yarns 133 arranged at the second radial position R3 and the twisted yarn 131 arranged at the first radial position R1 may be arranged to draw an approximately isosceles triangle with the two twisted yarns 133 as the base, as shown by the dashed lines in 3(a) and 3(b). In this case, the thickness of the rubber between each twisted yarn 133, 133A, and 133B arranged at the second radial positions R3, R3A, and R3B and the twisted yarns 131, 131A, and 131B arranged at the first radial positions R1, R1A, and R1B is approximately the same, so that when the cylindrical bodies 100, 100A, and 100B expand in the radial direction, the cylindrical bodies 100, 100A, and 100B can be expanded uniformly around the entire circumference.

In addition, as shown in FIG. 2(a), in this embodiment, the difference in the number of twisted yarns 131, 133 arranged at each of the multiple radial positions R1, R3 is 1 or less. Specifically, in this embodiment, the twisted yarn 131 arranged at radial position R1 of the tubular body 100 and the twisted yarn 133 arranged at radial position R3 are arranged alternately in the circumferential direction of the tubular body 100 as shown in FIG. 2(a) and 2(b).

(3) Actions and Effects Next, the action of the fluid type actuator will be described with reference to FIG. 4(a) and FIG. 4(b).

Figure 4(a) is an explanatory diagram showing the operation of the fluid pressure actuator 1 according to the embodiment, showing the state before the actuator body 10 starts to operate, and Figure 4(b) is a diagram showing the state after fluid AR is injected into the actuator body 10 and the actuator body 10 contracts.

As shown in Fig. 4(b), when the fluid AR is injected into the cylindrical body 100 from the fluid injection/discharge pipe 530 through the connecting port 213 of the sealing member 210, the pressure inside the cylindrical body 100 increases, and the cylindrical body 100 made of an elastic body expands. However, the expansion of the cylindrical body 100 in the longitudinal direction _DAX of the cylindrical body 100 is restricted by the action of the twisted yarn 130 contained in the cylindrical body 100. Therefore, as shown in Fig. 4(b), the cylindrical body 100 contracts in the longitudinal direction _DAX while expanding in the radial direction.

In conventional fluid pressure actuators, the fibers are inserted very densely inside the rubber tube, and the unevenness of the dense fibers in the circumferential direction could reduce the uniformity of the radial expansion of the rubber tube in the circumferential direction.

In contrast, as shown in Figs. 2(a) and 2(b), the fluid pressure actuator 1 of this embodiment has a configuration in which, in the cylindrical body 100 of the actuator main body 10, a plurality of twisted yarns 130 are arranged at a plurality of radial positions R1, R3 that are mutually offset in the radial direction of the cylindrical body 100, the plurality of twisted yarns 130 are arranged at equal intervals in the circumferential direction of the cylindrical body 100 at each of the radial positions R1, R3, the plurality of radial positions R1, R3 at which the plurality of twisted yarns 130 are arranged include at least a first radial position R1 and a second radial position R3 at which a twisted yarn 133 adjacent in the radial direction of the cylindrical body 100 to the twisted yarn 131 arranged at the first radial position R1 is arranged, and each twisted yarn 131 arranged at the first radial position R1 is arranged offset in the circumferential direction of the cylindrical body 100 from the twisted yarn 133 arranged at the second radial position R3.

According to the configuration of this embodiment, it is possible to ensure the circumferential uniformity of the radial expansion of the tubular body 100 while ensuring the elasticity of the elastic body, so that it is possible to efficiently convert the radial expansion of the actuator body 10 into a contraction force in the longitudinal direction _DAX , and further it is possible to provide a fluid pressure actuator 1 that can increase the durability of the actuator body 10 when contraction is repeated.

In this embodiment, the multiple twisted yarns 130 are included in the tubular body 100 in a state where they are oriented from one end to the other. With this configuration, unlike a case where an elastic tube is inserted into an external sleeve, wear and deterioration due to friction between the twisted yarns 130 can be prevented even when the yarns are repeatedly expanded and contracted.

In this embodiment, the tubular body 100 is cylindrical. When the tubular body 100 made of an elastic material is cylindrical, the elastic material stretches evenly when expanded, and no local load is applied to the elastic material. This can improve the durability of the actuator body 10 compared to other shapes such as a rectangular cylinder or an elliptical cylinder.

In this embodiment, rubber is used for the elastic body constituting the tubular body 100, and twisted yarn 130 made of twisted organic fibers is used. When rubber is used for the elastic body constituting the tubular body 100, the adhesion to the twisted yarn 130 is high, so peeling from the twisted yarn 130 arranged inside the tubular body 100 can be suppressed. As a result, the durability of the actuator body 10 can be increased.

The twisted yarn 130 and the elastic body constituting the tubular body 100 are bonded at least at one location on the circumference of the cross section of the twisted yarn 130. With this configuration, even if the tubular body 100 repeatedly expands and contracts, it is possible to prevent the twisted yarn 130 from peeling off from the elastic body. As a result, it is possible to increase the repetitive durability of the actuator body 10.

2(a) and 2(b), in the cylindrical body 100, the twisted yarns 130 are arranged only at a first radial position R1 and a second radial position R3 in a cross section perpendicular to the longitudinal direction _DAX of the cylindrical body 100. With this configuration, it is possible to increase the durability of the actuator body 10 while reducing material costs.

In this embodiment, the difference in the number of twisted yarns 131, 133 arranged at each of the multiple radial positions R1, R3 in the tubular body 100 is one or less, and the twisted yarns 131 arranged at radial position R1 and the twisted yarns 133 arranged at radial position R3 in the tubular body 100 are arranged alternately in the circumferential direction of the tubular body 100. This configuration makes it easier to stably ensure uniformity in the circumferential direction of the radial expansion of the tubular body 100 made of an elastic material.

(4) Other Embodiments The contents of the present invention have been described above in accordance with the embodiments. However, the present invention is not limited to these descriptions, and it will be obvious to those skilled in the art that various modifications and improvements are possible.

5(a) and 5(b) are diagrams showing a modified example of the fluid pressure actuator 1 according to the embodiment. Specifically, Fig. 5(a) is an end view of a cross section perpendicular to the longitudinal direction _DAX of the cylindrical body 100C, and Fig. 5(b) is an enlarged view of a portion of Fig. 5(a).

Figures 5(a) and 5(b) differ from the embodiment shown in Figures 2(a) and 2(b) in that the twisted yarns 135C are also arranged at equal intervals in the circumferential direction of the tubular body 100C at a third radial position R5, where the twisted yarns 135C adjacent to the twisted yarns 133C arranged at the second radial position R3 are arranged on the opposite side of the first radial position R1 in the radial direction of the tubular body 100C.

Even in the modified example configuration shown in Figures 5(a) and 5(b), the twisted yarn 135C arranged at the third radial position R5 of the tubular body 100C and the twisted yarn 133C arranged at the radial position R3 are arranged alternately in the circumferential direction of the tubular body 100C. Therefore, the difference in the number of twisted yarns 131C, 133C, and 135C arranged at each radial position in the multiple radial positions R1, R3, and R5 is one or less.

According to the configuration of the modified example shown in Figures 5(a) and 5(b), the twisted yarns 135C are also arranged at equal intervals at the third radial position R5, which can further suppress the circumferential distortion of the tubular body 100C during expansion from concentrating only on the elastic body of the tubular body 100C. As a result, the durability of the tubular body 100C used in the fluid pressure actuator can be improved.

Figure 6 is a side view of the actuator body 10D according to another modified example.

The modified example shown in FIG. 6 differs from the configuration of the actuator body 10 in the embodiment shown in FIG. 1 in that a ring 150D is disposed on the outer periphery of the cylindrical body 100D to limit the expansion of the cylindrical body 100D when fluid is injected.

In the modified example shown in FIG. 6, the ring 150D is made of a metal such as aluminum. However, the ring 150D may also be made by shrinking a heat shrink tube and fixing it to the outer periphery of the cylindrical body 100D with an adhesive or the like.

In the modified example shown in FIG. 6, the rings 150D are provided at positions 1/3 and 2/3 of the total length of the cylindrical body 100D from one end of the cylindrical body 100D.

According to the configuration of this modified example, the ring 150D limits the radial expansion of the cylindrical body 100D, preventing the elastic body constituting the cylindrical body from expanding excessively and deteriorating.

In this modified example, two rings 150D are provided on the outer periphery of the cylindrical body 100D. However, the number of rings 150D arranged on the outer periphery of the cylindrical body 100D is not limited to this. The rings 150D are members that limit the radial expansion of the cylindrical body 100D when the cylindrical body 100D expands in the radial direction. Therefore, if it is desired to reduce the amount of expansion, the amount of expansion of the cylindrical body 100D may be reduced by increasing the number of rings 150D arranged on the cylindrical body 100D.

As described above, an embodiment of the present invention has been described, but the descriptions and drawings that form part of this disclosure should not be understood as limiting this invention. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure.

1 Fluid pressure actuator 10, 10D Actuator body 100, 100A, 100B, 100C, 100D Cylindrical body 130 Twisted yarn 131, 131A, 131B, 131C Twisted yarn arranged at first radial position 133, 133A, 133B, 133C Twisted yarn arranged at second radial position 135C Twisted yarn arranged at third radial position 200, 300 Sealing mechanism R1, R1A, R1B First radial position R3, R3A, R3B Second radial position R5 Third radial position

Claims (7)

A cylindrical body made of an elastic body;
a sealing mechanism for sealing an opening at an end of the cylindrical body,
The cylindrical body includes a plurality of twisted yarns oriented from one end to the other end,
The diameter of the twisted yarns included in the plurality of twisted yarns is 0.2 mm or more and 0.8 mm or less,
The plurality of twisted yarns are arranged at a plurality of radial positions that are shifted from one another in the radial direction of the cylindrical body,
The plurality of twisted yarns are arranged at equal intervals in the circumferential direction of the cylindrical body at each of the plurality of radial positions,
the plurality of radial positions at which the plurality of twisted yarns are arranged include at least a first radial position and a second radial position at which a twisted yarn adjacent to the twisted yarn arranged at the first radial position in the radial direction of the tubular body is arranged,
A fluid pressure actuator in which each twisted yarn arranged at the first radial position is positioned circumferentially offset from the twisted yarn arranged at the second radial position. The fluid pressure actuator according to claim 1, wherein the difference in the number of twisted yarns arranged at each of the plurality of radial positions is one or less. The fluid pressure actuator according to claim 1 or 2, wherein the twisted yarn is arranged only at the first radial position and the second radial position. The fluid pressure actuator according to any one of claims 1 to 3, wherein the twisted yarn is a twisted yarn made by twisting organic fibers. The fluid pressure actuator according to any one of claims 1 to 4, wherein the elastic body is rubber. A fluid pressure actuator according to any one of claims 1 to 5, in which the twisted yarn and the elastic body are bonded at least at one location on the circumference of the cross section of the twisted yarn. A fluid pressure actuator according to any one of claims 1 to 6, wherein the spacing between adjacent twisted yarns in the radial direction of the cylindrical body is equal to or less than twice the diameter of the twisted yarn.

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