Hydraulic actuator

Abstract

A sleeve 26 of a hydraulic actuator 20 has a first group WA and a second group WE and is formed by alternately crossing respective yarn materials W in the first group WA and the second group WE. In each yarn material W, when the pressure of fluid applied to a tube 24 is at a maximum, a length X1 of the yarn material W in a direction φ orthogonal to an extension direction θ and a radial direction R is not more than 4 times a length Y1 in the radial direction R.

Description

Fluid Pressure Actuator

[0001] The present disclosure relates to fluid pressure actuators.

[0002] Japanese Patent Application Laid-Open Publication No. 2021-088999 discloses a fluid pressure actuator that includes a cylindrical tube that expands and contracts due to fluid pressure, an elastic structure made of woven fiber cords oriented in a predetermined direction, a sleeve that covers the outer surface of the tube, and a sealing member that seals the axial end of the tube, and includes a restraining member that is provided inside the sleeve from one end to the other end in the axial direction, and the restraining member resists compression along the axial direction and is deformable in an orthogonal direction perpendicular to the axial direction.

[0003] In the configuration described in JP 2021-088999 A, when the fluid pressure actuator is repeatedly deformed from an axially extended state in a direction intersecting the axial direction, the fluid pressure actuator is likely to acquire a fixed shape after deformation. In this case, once the fluid pressure actuator has acquired a fixed shape after deformation, even if the fluid pressure applied to the fluid pressure actuator is removed, the fluid pressure actuator is unlikely to return to the axially extended shape.

[0004] Here, the discloser of the present disclosure has discovered that by applying the technical matters disclosed below to a fluid pressure actuator, it is possible to obtain a fluid pressure actuator that easily returns to its axially extended shape even when the fluid pressure actuator is repeatedly deformed from an axially extended state in a direction intersecting the axial direction.

[0005] The present disclosure aims to provide a fluid pressure actuator that easily returns to an axially extended shape even when the fluid pressure actuator is repeatedly deformed from an axially extended state in a direction intersecting the axial direction.

[0006] a pair of sealing members that seal the ends of the tube on one side and the other side in the axial direction, respectively, and have insertion portions into which the tube is inserted; wherein the sleeve has a group of thread material oriented in one direction and a group of other thread material oriented in another direction intersecting the group of thread material, and the thread materials in the group of thread material and the group of other thread material are formed by alternatingly intersecting each other; and wherein, when the pressure of the fluid applied to the tube is at a maximum, the length of each of the thread material in the extension direction of the thread material and in the direction perpendicular to the radial direction is four times or less than its length in the radial direction.

[0007] The fluid pressure actuator according to the present disclosure has a sleeve formed of thread materials intertwined with each other. Furthermore, when the pressure of the fluid applied to the tube is at its maximum, the length of each thread material in a direction perpendicular to the extension direction and radial direction is no more than four times its radial length. In other words, in the fluid pressure actuator according to the present disclosure, when the pressure of the fluid applied to the tube is at its maximum, the ratio of the length of the thread material in a direction perpendicular to the extension direction and radial direction to its radial length is no more than four. Therefore, the thread materials are less likely to slide against each other due to bending deformation, and the relative positions of the intersections of the thread materials in the sleeve are less likely to change.

[0008] Therefore, in the fluid pressure actuator according to the present disclosure, even if the fluid pressure actuator is repeatedly deformed from an axially extended state in a direction intersecting the axial direction, the fluid pressure actuator easily returns to its axially extended shape.

[0009] A fluid pressure actuator of a third aspect is the fluid pressure actuator according to the first or second aspect, wherein the thread material has a twist coefficient of 100 or more.

[0010] This fluid pressure actuator prevents the yarn material from becoming biased due to repeated operations, thereby achieving the effect of suppressing curling.

[0011] A fluid pressure actuator of a fourth aspect is the fluid pressure actuator according to any one of the first to third aspects, wherein the thread material has a thickness of 1000 dtex or more.

[0012] This fluid pressure actuator has the effect of preventing breakage due to wear caused by the thread material being too thin and preventing curling due to unevenness of the thread material during repeated operations.

[0013] According to the present disclosure, a fluid pressure actuator can be provided that easily returns to an axially extended shape even when the fluid pressure actuator is repeatedly deformed from an axially extended state in a direction intersecting the axial direction.

[0014] 6A is a side view of a fluid pressure actuator according to an embodiment; FIG. 7 is a partially exploded perspective view of the fluid pressure actuator; FIG. 8 is a cross-sectional view of the fluid pressure actuator; FIG. 9 is an enlarged view of a portion E of the sleeve in FIG. 2; FIG. 10 is a view showing the portion of FIG. 4 in a state in which the fluid pressure actuator has been bent and then restored to an extended state; FIG. 11 is a cross-sectional view illustrating the deformation of the sleeve when the fluid pressure actuator has been bent and deformed, as seen from the extension direction of the thread material, which is direction 4A-4A in FIG. 4; FIG. 12 is a plan view illustrating the deformation of the sleeve when the fluid pressure actuator has been bent and deformed, as a continuation of FIG. 6A; FIG. 13 is a view showing the results of comparing the relationship between the number of times maximum pressure has been applied to a tube and the bending angle after restoration, for each aspect ratio of the thread material when maximum pressure has been applied to the tube; and FIG. 14 is a view showing the results of comparing the relationship between the number of times maximum pressure has been applied to a tube and the bending angle after restoration, for each number of twists of the thread material.

[0015] Hereinafter, embodiments for realizing the technology of the present disclosure will be described in detail with reference to the drawings.

[0016] In addition, components and processes that perform the same actions and functions are given the same reference numerals throughout the drawings, and duplicated explanations may be omitted as appropriate. Furthermore, the present disclosure is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present disclosure.

[0017] In each drawing, arrow S indicates the direction in which the fluid pressure actuator extends. Arrow X indicates a direction perpendicular to arrow S and indicates the direction that becomes the inner side of the curve when the fluid pressure actuator is bent. Arrow R indicates a direction perpendicular to arrow S and indicates the radial direction of the sleeve in the fluid pressure actuator. Arrow θ1 indicates the direction in which the first group of thread materials that make up the sleeve in the fluid pressure actuator are oriented relative to the direction in which the fluid pressure actuator extends, and arrow θ2 indicates the direction in which the second group of thread materials that make up the sleeve in the fluid pressure actuator are oriented.

[0018] In the following description, the term "initial state" refers to a state in which the fluid pressure actuator has never been bent or deformed after assembly. In the following description, the term "bent state" refers to a state in which the internal pressure of the tube of the fluid pressure actuator has increased and the fluid pressure actuator has been bent or deformed. In the following description, the term "restoration" refers to a state in which the pressure inside the tube of a bent or deformed fluid pressure actuator is reduced to atmospheric pressure, thereby eliminating the bend. In the following description, the term "extended state" refers to a state in which the fluid pressure actuator has passed from the initial state to a bent state, and has then been restored to its original state and no longer bent.

[0019] <Configuration of Fluid Pressure Actuator> A fluid pressure actuator 20 according to the present disclosure is shown in Fig. 1. The fluid pressure actuator 20 includes an actuator main body 22, a first sealing portion 30A, and a second sealing portion 30B.

[0020] As shown in FIG. 2 , the actuator main body 22 includes a tube 24, a sleeve 26, and a restraining member 28. The tube 24 is cylindrical and elastically deformable, expanding and contracting with changes in the pressure of the fluid inside. The axial direction of the tube 24 is designated as the "axial direction S." The tube 24 may be made of an elastic material such as butyl rubber. Air may be used as the fluid supplied to the tube 24, in which case the fluid pressure actuator 20 becomes a pneumatic actuator. Note that when the fluid pressure actuator 20 is hydraulically driven, it is preferable to use at least one rubber selected from the group consisting of highly oil-resistant NBR (nitrile rubber), hydrogenated NBR, chloroprene rubber, and epichlorohydrin rubber.

[0021] It is preferable to use fiber cords made of aromatic polyamide (aramid fiber) or polyethylene terephthalate (PET) as the cords constituting the sleeve 26. However, the cords are not limited to these types of fiber cords, and other high-strength fiber cords such as PBO fiber (polyparaphenylene benzobisoxazole) may also be used.

[0022] The restraining member 28 is provided between the tube 24 and the sleeve 26. The restraining member 28 is in the form of a long plate, and is arranged such that its longitudinal direction is along the axial direction of the tube 24. The restraining member 28 covers part of the outer periphery of the tube 24 and is arranged from one end of the tube 24 to the other end.

[0023] The restraint member 28 is formed of a material that does not expand or contract when pressurized, and is capable of flexural deformation in the direction in which its ends approach each other. A so-called leaf spring can be used as the restraint member 28. The dimensions of the leaf spring are determined according to the size of the fluid pressure actuator 20, the required output, and other factors. The material of the leaf spring is not particularly limited, but typically, any material that is easily flexurally deformed and resistant to compression, such as a metal such as stainless steel, may be used. Alternatively, the leaf spring may be formed of a thin plate of carbon fiber reinforced plastic (CFRP).

[0024] The first sealing portion 30A includes a first sealing member 32, a locking ring 34, and a crimping member 36.

[0025] The first sealing member 32 has an integrally molded lid portion 32A and an insertion portion 32B. The lid portion 32A is shaped like a hexagonal pillar with a diameter larger than the outer diameter of the tube 24. The insertion portion 32B extends in the axial direction S from the center of one end of the lid portion 32A. The insertion portion 32B has a so-called bamboo shoot shape and is inserted into one end of the tube 24 inside the sleeve 26. An attachment portion 38 is formed on the side of the lid portion 32A opposite the insertion portion 32B. The attachment portion 38 has an attachment hole 38A formed therethrough in a direction perpendicular to the axial direction S. While a metal such as stainless steel can be suitably used as the first sealing member 32, the first sealing member 32 is not limited to such a metal and may also be made of a hard plastic material.

[0026] 3, the first sealing member 32 has a flow path F. The flow path F is formed in the radial center of the insertion portion 32B and extends in the axial direction, and is connected to a connection hole H on the side surface of the cover portion 32A. An air supply hose (not shown) is connected to the connection hole H, and compressed air is supplied to the connection hole H.

[0027] The locking ring 34 is ring-shaped and is disposed on the outside of the sleeve 26 so as to sandwich the sleeve 26 between itself and the insertion portion 32B, thereby locking the sleeve 26 to the first sealing member 32. The sleeve 26 is folded back onto the outer periphery via the locking ring 34. The locking ring 34 may be made of a material such as metal, hard plastic, fiber, or rubber.

[0028] The crimping member 36 is disposed on the outer periphery of the actuator body 22 so as to cover the portion into which the insertion portion 32B is inserted, and crimps the actuator body 22 to the first sealing member 32. This fixes the actuator body 22 to the first sealing member 32. The crimping member 36 can be made of a metal such as aluminum alloy, brass, or iron.

[0029] The second sealing portion 30B has a second sealing member 33, a locking ring 34, and a crimping member 36. The second sealing member 33 is similar to the first sealing member 32 of the first sealing portion 30A, except that the connection hole H and the flow path F are not formed in the second sealing member 33, and the tip of the lid portion 33A is rounded.

[0030] The sleeve 26 is cylindrical and covers the outer periphery of the tube 24. The sleeve 26 is an elastic structure in which fiber cords oriented in a predetermined direction are woven, and the oriented cords intersect with the axial direction S at a predetermined angle.

[0031] More specifically, as shown in Figure 4, the sleeve 26 has a first group WA, which is a group of thread material W oriented in a first direction θ1, and a second group WE, which is a group of thread material W oriented in a second direction θ2 that intersects the first direction θ1. In other words, the first direction θ1 is a direction that winds clockwise toward the axial direction S as viewed from the axial direction S, and the second direction θ2 is a direction that winds counterclockwise toward the axial direction S as viewed from the axial direction S. The first direction θ1 and the second direction θ2 are symmetrical to each other with respect to the axial direction S. The first group WA is an example of a "group of thread material oriented in one direction" in this embodiment, and the second group WE is an example of a "group of other thread material oriented in another direction" in this embodiment.

[0032] The thread material W of the first group WA and the thread material W of the second group WE alternately intersect at a predetermined angle with respect to the axial direction S, thereby forming the sleeve 26. The interval M at which the thread material W of the first group WA and the thread material W of the second group WE intersect is set appropriately depending on the specifications of the fluid pressure actuator 20. Because the sleeve 26 has such a shape, it deforms like a pantograph that changes its angle, and follows the contraction and expansion of the tube 24 while regulating the contraction and expansion of the tube 24.

[0033] In this embodiment, the thread material W of the first group WA and the thread material W of the second group WE are both formed by twisting a plurality of filaments together. The twist coefficient of this thread material W is, for example, 100 or more, but preferably 120 or more. The thickness of the twisted thread material W is, for example, 700 dtex or more, but preferably 1000 dtex or more.

[0034] The twist factor can be calculated using the following formula:

[0035]

[0036] In the above formula (1), C is the twist coefficient, Tw is the number of twists (T / m), and Th is the thickness of the yarn material (dtex).

[0037] <Operation of Fluid Pressure Actuator> The fluid pressure actuator 20 is used with the first sealing portion 30A on one end side fixed by the attachment portion 38 and the second sealing portion 30B on the other end side being a free end.

[0038] As shown in FIG. 3 , when compressed air is introduced into the tube 24 through the connection hole H, the pressure inside the fluid pressure actuator 20 increases. The increase in internal pressure causes the tube 24 to elastically deform and expand, and the sleeve 26 deforms so as to increase the angle between the oriented strands W, exerting a force in a direction that shortens the length L0 (length when unshortened) of the actuator main body 22. At this time, because the outer peripheral side wall of the actuator main body 22 on which the restraining member 28 is disposed is restricted from shortening, the outer peripheral wall of the actuator main body 22 on the side where the restraining member 28 is not disposed, as viewed from the axial direction S, shortens. This causes the restraining member 28 to flex and deform, and the entire actuator main body 22 bends in the direction of arrow X, as indicated by the two-dot chain line in FIG. 3 . The force that bends the actuator main body 22 in the direction of arrow X is determined by the internal pressure of the tube 24.

[0039] The maximum internal pressure of the fluid applied to the tube 24, as determined in the specifications of the fluid pressure actuator 20, is referred to as the "maximum pressure."

[0040] (Deformation of Sleeve 26 and Thread Material W) Fig. 5 shows enlarged views of the weave of the sleeve 26 before and after bending and deforming the actuator body 22. Note that the two-dot chain lines in Fig. 5 indicate the positions of the thread material W of the first group WA and the second group WE when the actuator body 22 is in the initial state.

[0041] 5, even when the actuator body 22 is restored to its original shape after being bent and deformed, the intersection C may move in the direction of the arrow X by a distance D. The reason why the intersection C moves is thought to be as follows.

[0042] First, when the internal pressure of the tube 24 in the fluid pressure actuator 20 increases, the tube 24 and the sleeve 26 expand in the radial direction R. In other words, the circumferential spacing of the intersections C between the strands W in the sleeve 26 expands.

[0043] However, the fluid pressure actuator 20 according to this embodiment has a restraining member 28 between the tube 24 and the sleeve 26 on the opposite side of the arrow X direction (the right side in FIG. 3 ), so the sleeve 26 is less likely to expand circumferentially on the opposite side of the arrow X direction. Then, due to the expansion of the sleeve 26 in the radial direction R on the arrow X side, the thread material W in the sleeve 26 tends to move toward the arrow X side. Furthermore, if the thread materials W tend to slide against each other at intersections C where the thread materials W intersect, then apart from pantograph deformation, the intersections of the thread materials W tend to shift, and intersections C tend to move toward the arrow X direction.

[0044] Therefore, when the sleeve 26 expands in the radial direction R and the circumferential direction, the intersection C between the thread material W of the first group WA and the thread material W of the second group WE tends to move in the direction of the arrow X on the sleeve 26. In other words, when the fluid pressure actuator 20 is curved and deformed, the intersection C tends to move in the direction of the arrow X.

[0045] If the inflow of compressed air is stopped and the pressure inside the tube 24 is reduced, the fluid pressure actuator 20 will return to the extended state. The restoring force required for the fluid pressure actuator 20 to return from the curved state to the extended state is the force with which the restraint member 28 returns from the curved state to the extended state, and the force with which the tube 24 contracts in the radial direction R and circumferential direction due to rubber elasticity. As a result, the arrow X side of the tube 24 (the left side in FIG. 4 ) extends in the axial direction S, and the fluid pressure actuator 20 returns to its extended state shape.

[0046] On the other hand, when attention is focused on the sleeve 26, the tube 24 expands in the axial direction S, and therefore the pantograph-deformed sleeve 26 also contracts in the radial direction R and the circumferential direction. However, because the intersection points C of the thread materials W of the sleeve 26 are misaligned, it is thought that even if a force is applied in a direction that eliminates the pantograph deformation, the sleeve 26 will not completely return to its original intersection position.

[0047] 5, in the sleeve 26 in which the intersection C of the thread material W is shifted in the direction of arrow X, the position of the intersection C is unlikely to return to the position in the extended state even if the pressure in the tube 24 is reduced, and it is likely to remain shifted by a length D in the direction of arrow X from the extended state. Furthermore, since the intersection C moves in the direction of arrow X with each bending deformation, the amount of movement of the intersection C in the direction of arrow X accumulates when the actuator main body 22 is repeatedly bent and deformed.

[0048] Furthermore, the movement of the intersection point C described above can occur anywhere within the range of the length L0 of the sleeve 26 in the axial direction S. In other words, by repeatedly undergoing bending deformation, the fluid pressure actuator 20 becomes accustomed to a shape that is difficult to return to the shape extended in the axial direction S.

[0049] FIG. 6 shows the cross-sectional shapes of the thread material W before and after the bending deformation of the actuator main body 22, i.e., before and after the expansion in the radial direction R of the sleeve 26. In FIG. 6, arrow θ indicates the extension direction of the thread material W, which is the direction 4A-4A in FIG. 4, indicated by arrow θ1 for the thread material W of the first group WA or by arrow θ2 for the thread material W of the second group WE. Arrow φ indicates a direction perpendicular to arrow θ and arrow R, which is the radial direction R of the sleeve 26. In FIGS. 6A and 6B, diameter X0 is the length of the thread material W in the direction of arrow φ in the stretched state, and diameter Y0 is the length of the thread material W in the radial direction R in the stretched state. In this embodiment, diameter X0 and diameter Y0 of the thread material W in the stretched state are approximately equal, and the cross section may be considered to be circular.

[0050] First, when the sleeve 26 expands, the thread material W receives a deformation load from the inside in the radial direction R. In this state, both ends of the sleeve 26 in the axial direction S are restricted by the crimping members 36, so deformation of the thread material W in the extension direction is restricted. Therefore, the thread material W deforms into a flattened shape as if crushed in the radial direction R, as shown in FIG. 6A .

[0051] 6, when the sleeve 26 expands in the radial direction R, the major axis length X1, which is the length of the thread material W in the direction of the arrow φ, increases. In other words, when the fluid pressure actuator 20 is in a curved state, the contact area between the thread materials W that intersect at the intersection C increases. This reduces the pressure at which the thread materials W contact each other, making it easier for the thread materials W to slide against each other, and making it easier for the intersection C to move in the direction of the arrow X.

[0052] The major axis length X1, which is the length of the thread material W in the direction of the arrow φ after the actuator body 22 has been curved and deformed, tends to be longer than the diameter X0 in the stretched state. Also, the minor axis length Y1, which is the length of the thread material W in the radial direction R after the actuator body 22 has been curved and deformed, tends to be shorter than the diameter Y0 in the stretched state.

[0053] Furthermore, because the cross-sectional area of ​​the thread material W is unlikely to change before and after the actuator body 22 is bent and deformed, the cross section of the thread material W after the actuator body 22 is bent and deformed can be considered to be an ellipse. Therefore, if the values ​​of the diameter X0 and diameter Y0 in the stretched state are determined in advance, the minor axis length Y1 can be determined by measuring the major axis length X1 after the actuator body 22 is bent and deformed. That is, for the thread material W after the actuator body 22 is bent and deformed, the aspect ratio, which is the ratio of the major axis length X1 to the minor axis length Y1 of the thread material W, can be determined by measuring the major axis length X1 of the thread material W from the outside in the radial direction R of the sleeve 26 as shown in Figure 6B.

[0054] As described above, it can be said that as the aspect ratio of the cross section of the thread material W increases, the frictional force decreases between the thread materials W that intersect within the sleeve 26 and between the thread material W and the tube 24. In other words, as the aspect ratio increases, when the actuator main body 22 is curved and deformed, the intersection C is more likely to shift in the direction of arrow X, which is the inside of the bend, and the fluid pressure actuator 20 is more likely to become flexed.

[0055] The major axis length X1 can be considered to be the "length in the direction perpendicular to the extension direction and radial direction of the thread material" in this embodiment, and the minor axis length Y1 can be considered to be the "radial length" in this embodiment. Also, the aspect ratio can be considered to be the size of "the length in the direction perpendicular to the extension direction and radial direction of the thread material relative to the radial length" in this embodiment.

[0056] (Conditions for Suppressing Movement of Intersection C) As described above, the state in which intersection C is likely to move in the direction of arrow X is when the ratio of the major axis length X1 to the minor axis length Y1 in the cross section of the thread material W becomes large when the actuator main body 22 is curved and deformed. The present inventors conducted the following various tests to confirm the conditions under which the above-mentioned curling is likely to occur. The conditions and results of each test example conducted by the present inventors will be described with reference to FIGS. 7 and 8.

[0057] In the following description, the "deformed angle" refers to the angle of the fluid pressure actuator 20 that is deformed from its initial state after restoration (the degree of deformation of the fluid pressure actuator 20).

[0058] Furthermore, in each test, if the bending angle is 30° or less after the fluid pressure actuator 20 has been repeatedly bent and deformed 100,000 times, it is considered that the performance is sufficient as a product specification. In other words, 100,000 times is the target number of bending times in each test example.

[0059] [Test 1] In Test 1, the relationship between the number of times the tube 24 was bent and deformed when maximum pressure was applied and the set angle after restoration was compared for each aspect ratio of the thread material W when the fluid pressure actuator 20 was bent and deformed.

[0060] In this test, the bending angle when the maximum pressure was applied to the tube 24 and the fluid pressure actuator 20 was bent and deformed was 90°.

[0061] The specifications of the fluid pressure actuator 20 used in this test are as follows: The fluid pressure actuators 20 used in the following tests were all the same except for the sleeve 26 .

[0062]

[0063] The conditions for this test are as follows:

[0064]

[0065] FIG. 7 shows the relationship between the number of times of bending deformation and the bending angle after restoration, which was measured for the fluid pressure actuator 20 using the sleeve 26 according to Test Example 1 and Test Example 2.

[0066] 7, this test confirmed that movement of the intersection C in the direction of the arrow X is suppressed when the ratio of the major axis length X1 to the minor axis length Y1 in the cross section of the thread material W is 4 or less. In particular, when the fluid pressure actuator 20 of each test example repeated the bending deformation 100,000 times, which is the target number of bending times, the bending angle exceeded 30° in test example 1, but was 30° or less in test example 2, so it can be determined that performance was improved.

[0067] [Test 2] In Test 2, the relationship between the number of times of bending deformation at rated output and the set angle after restoration was compared for each twist coefficient of the yarn material W.

[0068]

[0069] 8 shows the relationship between the number of times of bending deformation and the set angle after restoration, measured for the fluid pressure actuator 20 using the sleeve 26 according to Test Example 3 to Test Example 6. Note that in this test, although bias in the thread material in the sleeve 26 was observed in Test Example 3, no bias in the thread material was confirmed in Test Example 4 to Test Example 6.

[0070] As shown in Figure 8, this test confirmed that when the twist coefficient of the thread material W is set to 100 or more, deviation of the thread material due to repeated operations is prevented, thereby achieving the effect of suppressing curling. In particular, when the fluid pressure actuator 20 of each test example repeated bending deformation 100,000 times, which is the target number of bending times, the curling angle exceeded 30° in test example 3, but was 30° or less in test examples 4 to 6, and therefore it can be determined that performance has improved.

[0071] [Test 3] In Test 3, the fluid pressure actuator 20 of Test Example 7 was manufactured using a 760 dtex thread material that was even thinner than that of Test Example 6, and the relationship between the number of times it was bent at rated output and the set angle after restoration was measured. As a result, in the fluid pressure actuator of Test Example 6, the thread material wore out and the sleeve broke before 100,000 operations. In other words, the fluid pressure actuator 20 of Test Example 7 was unable to bend 100,000 times, which was the target number.

[0072] This test confirmed that if the thickness of the thread material W is 1000 dtex or more, it is possible to prevent breakage due to wear caused by the thread material being too thin during repeated operations, and to prevent the thread material from becoming distorted due to bias.

[0073] The above describes an embodiment of the present disclosure with reference to the accompanying drawings. However, it is clear that a person with ordinary knowledge in the field of technology to which the present disclosure pertains can conceive of various modifications or applications within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0074] The disclosure of Japanese Patent Application No. 2023-208782, filed on December 11, 2023, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A fluid pressure actuator comprising: a cylindrical tube that expands and contracts in response to fluid pressure; a sleeve that covers the outer peripheral surface of the tube and expands the tube radially while restricting its elongation in the axial direction as the tube expands; a plate-shaped restraining member that is provided radially inside the sleeve from one side in the axial direction to the other side, resisting compression along the axial direction and being deformable in a direction intersecting the axial direction; and a pair of sealing members that seal the one and other axial ends of the tube, respectively, and have an insertion portion into which the tube is inserted, wherein the sleeve has a group of thread material oriented in one direction and a group of other thread materials oriented in another direction intersecting the group of thread materials, and the thread materials in the group of thread materials and the group of other thread materials are formed by alternatingly intersecting each other, and when the pressure of the fluid applied to the tube is at a maximum, the length of each of the thread materials in the direction perpendicular to the extension direction of the thread material and the radial direction is four times or less than its length in the radial direction.

2. The fluid pressure actuator according to claim 1, wherein the thread material has a twist factor of 100 or more.

3. The fluid pressure actuator according to claim 1 or 2, wherein the thread material has a thickness of 1000 dtex or more.

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