JP6108502B1 - Elastic tube and actuator for fluid pressure actuator - Google Patents

Abstract

[PROBLEMS] To improve the wear resistance of an outer peripheral surface by performing a minimum processing on an elastic tube, and to maintain an advantageous feature of a simple structure and light weight, while being low in cost and high in durability. An elastic tube for a fluid pressure actuator and a fluid pressure actuator are provided. An elastic tube serving as a driving force source of a fluid pressure actuator driven by supply or discharge of a fluid such as air or liquid, and a short fiber made of a synthetic resin perpendicularly to the surface. A wear-resistant flocking layer formed by electroplanting is provided, and the wear-resistant flocking layer has a number of strips along the axial direction on the outer peripheral surface of the elastic tube, or a large number of dots on the entire outer periphery of the elastic tube. The synthetic resin short fibers are electrostatically flocked. [Selection] Figure 5

Description

  The present invention relates to an elastic tube used in a hydraulic actuator driven by supplying and discharging a fluid such as air or liquid, and a hydraulic actuator using the elastic tube, and more particularly to a McKibben type hydraulic actuator. .

  Among so-called actuators (driving devices), McKibben type hydraulic actuators have a synthetic resin fiber spiral on the outer periphery of an elastic tube G made of natural rubber or urethane rubber, as shown in FIGS. Covered with a cylindrical sleeve S woven in the mesh, and fixedly sealed at both ends by a pair of terminal portions T having a fluid suction / discharge mechanism such as air or liquid, and an elastic tube G is applied from the outside. The entire length is contracted by expanding with air pressure. As shown in FIG. 4, the sleeve S has a structure in which the angle of the mesh changes like an accordion so that the radius becomes thicker when pushed in the axial direction, and the radius becomes thinner when pulled reversely. When air pressure is applied to the body tube G to expand in the axial direction and the radial direction, the sleeve S takes out the expansion in the radial direction and changes the angle of the mesh, thereby causing the elastic tube G to contract in the axial direction. The principle is to generate.

  The hydraulic actuator is lighter, has a higher output density than the electromagnetic or hydraulic cylinder actuator (a large force is produced even though its own weight is small), and has excellent environmental resistance (resistant to rust and dust). However, it has the advantages of being simple, easy to maintain, highly flexible, close to human muscle characteristics, and low in manufacturing cost. On the other hand, the surface of the elastic tube is damaged due to friction with the sleeve. Or it has the demerit that durability is low because it wears and a hole and a crack are produced.

In order to solve this problem, prior arts as shown in Patent Documents 1 to 3 have been proposed. In the invention described in Patent Document 1, the elastic tube is made to be oriented in the longitudinal direction thereof to contain short fibers such as carbon fiber or glass fiber, thereby enhancing the wear resistance of the elastic tube material itself, and The durability is enhanced by controlling the direction of expansion and contraction. Moreover, in invention of patent document 2, durability is improved by the structure which makes an elastic body tube a double structure, and the abrasion and crack of an outer tube do not propagate to an inner tube. Furthermore, in the invention described in Patent Literature 3, the wear is reduced by arranging a low-friction body having elasticity between the elastic tube and the sleeve.
Japanese Patent Laid-Open No. 2015-180829 Japanese Patent Laid-Open No. 2015-108436 Japanese translation of patent publication No. 2004-085856

  However, when the elastic tube material itself contains short fibers as in the invention described in Patent Document 1, the elasticity of the material such as rubber inevitably changes and the output characteristics of the actuator also change. Therefore, the specification of the material of the elastic tube must be dedicated. In addition, as in the inventions described in Patent Documents 2 and 3, the structure of a double structure of an elastic tube or a structure in which a low friction body is sandwiched between an elastic body tube and a sleeve must be complicated. Therefore, these prior arts all reduce the merit of the hydraulic actuator that the manufacturing cost is low.

  In order to solve the above-described problems of the prior art, the present invention improves the wear resistance of the outer peripheral surface of the conventional elastic tube by performing minimum processing, and has a simple structure and is lightweight. It is an object of the present invention to provide an elastic body tube for a fluid pressure actuator and a fluid pressure actuator which are low in cost and high in durability while maintaining the advantageous characteristics of the above.

In order to solve the above-mentioned problem, the invention described in claim 1 of the present application is an elastic tube as a driving force source of a hydraulic actuator driven by supply and discharge of fluid such as air or liquid, and the elastic body The outer peripheral surface of the tube is provided with an anti-wear flocking layer formed by electrostatically flocking short fibers made of synthetic resin in a strip shape along the axial direction perpendicular to the outer peripheral surface.

  As the synthetic resin short fibers in the present invention, nylon fibers having a high elastic restoring force are suitable, but not limited thereto, synthetic fibers having high wear resistance are used. In electrostatic flocking, a work (flocked object) whose surface is coated with an adhesive in advance is placed in an electrostatic flocking device, and a high voltage is applied to the input short fibers to allow the short fibers to pass through the electric field. While the direction is aligned in parallel with the electric field, it jumps up by electrostatic attraction force and is densely and densely bonded vertically to the adhesive application surface of the workpiece. In the old days, it was widely used in the field of surface processing such as metal heat source covers of amber, various machine tools, daily necessities, etc., and it was used to improve heat insulation, soundproofing, impact resistance, and texture. Technology.

  The flocking layer by electrostatic flocking is highly elastic and is used to modify the surface of rubber. It is also used for various interior parts such as automobile rubber parts and daily necessities, but its purpose is to reduce friction. Smoothing of member operation by sound, sound insulation, airtightness, improvement of texture, etc. For example, electrostatic flocking on rubber packing of automobiles is intended to prevent chatter noise due to friction reduction effect and to facilitate the raising and lowering of window glass, and products with electrostatic flocking inside rubber cooking gloves This is also known for the purpose of preventing stickiness of the glove hand skin and facilitating attachment / detachment. That is, until now, the friction reducing effect of electrostatic flocking has been aimed at facilitating the operation of the contact object, and has not been intended to improve the wear resistance of the flocked body itself.

  On the other hand, the inventor of the present application pays attention to the mechanical wear resistance improving effect of the flocking layer by such electrostatic flocking, and newly requires a relatively high friction coefficient like rubber and requires repeated expansion and contraction. The present invention has been conceived for application to surface protection of an elastic body, that is, durability improvement. Specifically, the layer of short fibers planted at a high density on the rubber surface contacts the inner surface of the sheathed sleeve at the so-called innumerable “points” of the tips of the respective short fibers, so that the rubber surface is in the sleeve. Compared to direct contact with the inner surface, the contact area is greatly reduced. Even when the inner surface of the sleeve presses against the surface due to expansion and contraction of the elastic tube, the individual short fibers are fixed at the root, but the tip of the sleeve is inclined so that it can be freely restored in all directions. Therefore, the side surface of the short fiber linearly contacts the inner surface of the sleeve, so to speak, the inner surface of the sleeve is always “boiled” in all directions to reduce the contact area. By such an action, friction between the surface of the elastic tube and the inner surface of the sleeve is reduced, and damage and wear of the elastic tube surface are suppressed.

  As described above, in the conventional mechanical field, the frictional force is used to smooth the movement of the object in contact with the planted member, protect the human body, reduce the impact sound at the time of contact, or appropriately stop the movement of the object after the contact. Electrostatic flocking has been used for the purpose of increasing the resistance. On the other hand, the present invention is based on the opposite idea of improving the wear resistance of the surface of the elastic tube that expands and contracts by the electrostatic flocking layer and protects it from friction with the inner surface of the rubbing sleeve. As will be described later, as a result of the reciprocating friction test conducted by the inventor, the friction coefficient and the amount of wear material on the surface of the rubber provided with the flocked layer in which short fibers are electrostatically flocked are significantly larger than the rubber surface without the flocked layer. It has been confirmed that the wear resistance is improved by the flocking layer.

Adhesives used for electrostatic flocking include acrylic, urethane, engineered, and vinyl acetate types, and there are emulsion types and solvent types. The adhesive is not particularly limited as long as it has strong adhesion to the rubber surface and has elasticity and flexibility corresponding to the deformation and expansion of the rubber itself. Nylon to rubber elastic tube For example, an acrylic emulsion type or a urethane solvent type is suitable for flocking short fibers. Such an adhesive not only has strong adhesion to rubber, but also has high elasticity of the adhesive layer to be formed, and exhibits high elasticity following the expansion and contraction of the elastic tube. If the elasticity of the adhesive layer is different, cracks may occur in the thin adhesive layer as the expansion and contraction is repeated, and the flocked layer may eventually peel from there.

  In order to prevent the fluff layer from peeling off, it is effective to provide a gap in the flock layer on the rubber surface. If the adhesive layer is not continuous, the influence of stretching of the adhesive layer itself due to the expansion and contraction of the rubber surface is reduced, so that cracks are less likely to occur. As described above, when air pressure is applied to the elastic tube to expand it, the sleeve takes out the expansion in the radial direction and changes the mesh angle to contract the elastic tube in the axial direction. For this reason, the surface of the elastic tube is expanded in the circumferential direction when expanded in the circumferential direction, and cracks are easily generated when the adhesive layer is stretched and stretched. On the other hand, in the axial direction, the tensile force acting on the adhesive layer at the time of expansion is smaller than that in the circumferential direction, so that cracks hardly occur. Further, as shown in FIG. 4, since the mesh of the sleeve is compressed in the axial direction when the elastic tube is expanded, and is expanded when the elastic tube is contracted, the friction between the surface of the elastic tube and the inner surface of the sleeve is smaller than that in the circumferential direction. The axial direction becomes larger. Therefore, if the flocking layer is formed on the outer peripheral surface of the elastic tube in a plurality of strips along the axial direction, the wear resistance against friction in the axial direction can be maintained, and the strips of flocking layers are separated by gaps. Since it is divided, it is possible to prevent the adhesive layer from being cracked by the tensile force in the circumferential direction.

Next, the invention described in claim 2 is an elastic tube as a driving force source of a fluid pressure actuator driven by supply and discharge of a fluid such as air or liquid, and is provided on the entire outer periphery of the elastic tube. It is characterized in that an anti-abrasion flocking layer formed by electrostatically flocking short fibers made of synthetic resin in the form of a large number of dots perpendicular to the outer peripheral surface is provided.

  The elastic tube in the driving Macchiben type hydraulic actuator is contracted in the axial direction and expanded in the circumferential direction when contracted, while operating in the opposite direction when extended, and at the center of the tube and terminals at both ends. In the vicinity, the expansion / contraction rate responds nonlinearly to the applied air pressure. As a result, the direction of expansion and contraction of the elastic tube surface and the direction of friction with the sleeve inner surface also differ depending on the site, so it is more desirable that the flock layer has durability in all directions for expansion and contraction and friction.

  On the other hand, if the flocking layer is provided in high density and equally spaced dots, not only for expansion and contraction in the circumferential direction of the elastic tube, but also for expansion and contraction in all directions. The crack of the adhesive layer can be prevented, and the wear resistance of the elastic tube is further improved. Therefore, the dot arrangement is preferably such that the center of each dot is equidistant from the centers of all adjacent dots. The size of the dots and the distance between the centers of the adjacent dots can be appropriately set according to the diameter of the elastic tube and the expansion / contraction rate, and are not particularly limited. Moreover, in order to provide a uniform space while increasing the density of the flocked layer, the shape of the dots is not limited to a circle, and a square or other rotationally symmetric shape may be repeated in a net shape.

The inventor conducted a reciprocating friction test using a sample piece in which electrostatic flocking was applied to a rubber plate in order to verify the effect of improving the abrasion resistance of the elastic tube surface by electrostatic flocking. The sample piece used was a natural rubber sheet (64 mm square, 3 mm thick) with nylon short fibers (length 0.5 mm, thickness 19 μm) electrostatically flocked by a simple electrostatic flocking device. As an adhesive, an acrylic emulsion type rubber sheet flocking adhesive was applied to a thickness of about 0.1 mm. The object of friction in the reciprocating friction test is a PET (polyethylene terephthalate) sleeve that is generally used for Macchiben type hydraulic actuators, and three PET filament wires with a thickness of about 0.3 mm are arranged in a plane. A sleeve piece cut out of a weave and warp made of twill weave in a mesh with an acute angle (about 35 degrees) and an aperture ratio of about 25% was used. The reciprocating friction test is performed by a surface property measuring machine (friction wear tester) with a weight of 200 g, a speed of 150 mm / min, and a one-way length of 100 mm, each parallel and perpendicular to the sleeve axial direction. Friction of 50 reciprocations was added, and the static friction coefficient, dynamic friction coefficient, and the amount of wear due to the change in the weight of the test piece were measured. As shown in Table 1, the average and standard deviation values were obtained. The “dotted shape” of the “flocked form” is the one in which a circular dot-shaped flocking layer having a diameter of 3 mm is placed on the surface of the sample piece, and flocked on the entire surface of one side of the sample piece with an interval of 6 mm between the centers. did. “Glass piece (reference)” of “Friction object” uses a glass piece with a smooth surface instead of a sleeve as a friction object as a reference test.

  As a result of the test, in the sample piece in which the flock layer is provided on the entire surface of the sample piece without the flock layer, the static friction coefficient and the dynamic friction coefficient are about 80% and about 49% in the parallel direction, respectively, and about 78% in the vertical direction. About 39%. In addition, the wear amount was about 4 mg without the flocked layer, but decreased to 0.1 mg or less with the flocked layer to a measurement error level. This shows that the short fibers implanted under the test conditions were not dropped out at all, and the rubber of the sample piece was prevented from being worn. On the other hand, in the case of a sample piece provided with a dot-like flocked layer, the friction coefficient is about 68% and about 43% in the case of the parallel direction, and about 66% and about 31% in the case of the vertical direction. Although the reduction range of the coefficient was small, the wear amount was still 0.1 mg or less. From the above results, the flocking layer provided on the rubber surface reduces the friction with the sleeve, so that the McKibben type hydraulic actuator can be expected to operate more smoothly, and the wear resistance of the elastic tube can be greatly improved. Was confirmed. When a glass piece is a friction target, a sample piece having a flocking layer provided on the entire surface of a sample piece without a flocking layer has a static friction coefficient and a dynamic friction coefficient of about 89% and about 86%, respectively. In the sample piece provided with the flocking layer, the reduction was about 79% and about 71%. By the way, the standard deviation of the coefficient of friction in the case of the sample piece without the flocking layer is large because the surface of the rubber plate having irregularities due to the manufacturing process is directly contacted with the glass piece and rubbed. It is thought that the variation of the state was reflected.

The invention described in claim 2 is a fluid pressure type actuator having the elastic tube according to claim 1 as a driving force source.

  According to the present invention, damage and wear of the elastic tube due to friction between the outer peripheral surface of the elastic tube and the inner surface of the sleeve, which is a limitation on the durability of the hydraulic actuator, particularly the McKibben actuator, are specially applied to the elastic tube itself. Can be effectively reduced without changing the design. As a result, the durability of the elastic tube as a consumable member can be improved at low cost and the maintenance burden on the actuator can be reduced, which contributes to the promotion of its spread.

(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 5 is a perspective view showing an internal structure of a hydraulic actuator to which an elastic tube (a rubber tube G made of natural rubber in the embodiment) according to the first embodiment of the present invention is applied. FIG. FIG. As shown in the drawing, in the first embodiment, the rubber tube G has a flocking layer F formed by electrostatically flocking nylon short fibers f on the entire outer peripheral surface, and is embedded in the sleeve S. As shown in the schematic diagram (A) of FIG. 7, the sleeve S is formed by weaving a weft and a warp in which three filament wires s made of PET are arranged in a plane with a sharp angle in a mesh, and its inner surface has irregularities. When the rubber tube G not having the flocking layer F is applied and expanded, the inner surface of the sleeve S rubs while directly pressing the surface of the rubber tube G, so that the rubber tube G is worn and damaged by friction. There is a fear.

  On the other hand, in the first embodiment, as shown in the schematic diagram (b) of FIG. 7, the tips of the short fibers f come into contact with the inner surface of the sleeve S as countless “points”, and friction is reduced. . In addition, as shown in the schematic diagram (c) of FIG. 7, each short fiber f is fixed at the root, while its tip is inclined so that it can be freely restored in all directions. The wire linearly contacts the inner surface of the sleeve S, so that the friction is reduced in a so-called “chair” shape in all directions at all times, and damage and wear of the rubber tube G surface are suppressed. Furthermore, if the short fibers f are planted at a sufficiently high density, the short fibers f are supported with each other and are not easily inclined even when pressed against the inner surface of the sleeve S. It serves as a buffer layer between the tube G and the sleeve S.

  The length and thickness of the short fibers f forming the flocking layer F are not particularly limited as long as a sufficient flocking density can be ensured, but a sleeve (diameter of the filament s is 0.3 mm used in a general Macchiben type hydraulic actuator). For example, a short fiber f having a length of about 0.5 mm and a diameter of about 20 μm is implanted at a density of at least 5,000 fibers / square cm. Is preferred. Since the mesh of the sleeve S is repeatedly expanded and contracted by the operation of the actuator, if the short fiber f is too long, the short fiber f that has entered the mesh during expansion may be pinched and pulled out by the mesh at the time of contraction. This is because if the roughness is rough, the filament s bites into the flocked layer F, the friction coefficient increases, and the wear resistance is impaired.

  In addition, it is technically possible to mix the short fibers f having different lengths and form the flocked layer F at a uniform mixing ratio, and it has been practiced. In this case, it is known that the short short fibers support the long short fibers that fall down due to the external pressure on the surface of the flocked layer F, and it is known that the restoring force of the whole flocked layer F is improved. Further, the wear resistance of the flocked layer F can be further increased.

(Second Embodiment)
FIG. 8 is a perspective view showing an internal structure of a fluid pressure actuator to which a rubber tube G according to a second embodiment of the present invention is applied, and FIG. 9 is a sectional view of the same. In the present embodiment, the flocked layer F on the surface of the rubber tube G is formed in a strip shape along the axial direction as shown in the enlarged view of FIG.

  As shown in the schematic diagram of FIG. 11, the flocking layer F is constituted by the adhesive layer a for flocking the short fibers f on the surface of the rubber tube G with an adhesive. If the elasticity of the rubber and the adhesive layer is different even when using an acrylic emulsion type or urethane type solvent type adhesive that exerts its properties, while the rubber tube G repeatedly expands and contracts due to the operation of the actuator, A crack c is generated in the thin adhesive layer a, and there is a possibility that the flocked layer F will eventually peel off from the crack c.

  In the present embodiment, as shown in the enlarged view of FIG. 12, the band-like flocked layer F is formed with a gap g and is not continuous, so that the adhesive layer a itself is stretched by expansion and contraction of the surface of the rubber tube G. Is reduced, and cracks are less likely to occur. In addition, the friction between the flocked layer F and the inner surface of the sleeve S mainly occurs in the reciprocating direction along the axis, and the friction in the circumferential direction is relatively small. Therefore, the flocked layer F is axially disposed on the outer peripheral surface of the rubber tube G. By forming the belt along the belt shape, it is possible to prevent the adhesive layer a from being cracked due to the tensile force in the circumferential direction while maintaining the wear resistance against friction in the axial direction. Will improve. The width and interval of the band of the flocking layer F are not particularly limited, but when applied to the sleeve S used in the above-described general McKibben type hydraulic actuator, a band having a width of about 3 mm is about 1 mm. It is preferable to provide them at intervals.

(Third embodiment)
In the third embodiment of the present invention, the flocked layer F provided on the surface of the rubber tube G is formed in a circular dot shape as shown in the enlarged view of FIG. 13, and the dot arrangement is such that the centers of the dots are adjacent to each other. The center of all dots is equidistant, and other configurations are the same as in the second embodiment. In such a configuration, since the flock layer F has a gap between the adhesive layers a in all directions, even if the surface of the rubber tube G contracts non-linearly with different expansion / contraction ratios depending on the part of the rubber tube G during the operation of the actuator, The possibility that this occurs is reduced, and the durability of the flocked layer F can be further improved as compared with the second embodiment.

  Although the specific configuration of the elastic tube according to the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be improved or changed within the scope of the technical idea of the present invention. They belong to the technical scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be used for a fluid pressure actuator, particularly an elastic tube as a drive body of a McKibben type actuator, and an actuator using the same, and a mechanical device and equipment using such an actuator, particularly with a relatively small required output. It is effective in application to devices such as powered suits (human body-mounted robots), robot prostheses, and prosthetic legs that operate at a high frequency at all times and require a reduction in maintenance burden. According to the present invention, the durability of the elastic tube as a consumable member is improved at low cost, and the burden of maintenance of the actuator is reduced, thereby contributing to the spread of such devices.

Structural perspective view of a general Mackiben type hydraulic actuator Cross section of a general McKibben type hydraulic actuator Diagram showing the operation of a general McKibben type hydraulic actuator Enlarged view of the sleeve of a general McKibben type hydraulic actuator Structural perspective view of a hydraulic actuator to which a rubber tube according to a first embodiment is applied Sectional drawing of the hydraulic actuator which applied the rubber tube which concerns on 1st Embodiment Magnified schematic diagram of contact between rubber tube and sleeve Structural perspective view of a hydraulic actuator to which a rubber tube according to a second embodiment is applied Sectional drawing of the hydraulic actuator which applied the rubber tube which concerns on 2nd Embodiment Magnified schematic diagram of rubber tube surface according to the second embodiment Schematic diagram showing the generation of cracks on the rubber tube surface Schematic diagram of rubber tube surface according to the second embodiment Magnified schematic diagram of rubber tube surface according to the third embodiment

a Adhesive layer D Diameter of hydraulic actuator F Flocked layer f Short fiber G Elastic tube (rubber tube)
g Spacing of flocking layer F L Length of hydraulic actuator S Sleeve s Filament T Terminal

Claims (3)

An elastic tube as a driving force source of a fluid pressure actuator driven by supply and discharge of a fluid such as air or liquid, and the outer peripheral surface of the elastic tube is made of a synthetic resin in a number of strips along the axial direction An elastic tube characterized in that an anti-wear flocking layer is formed by electrostatically flocking the short fibers perpendicular to the outer peripheral surface. An elastic tube as a driving force source of a fluid pressure actuator driven by supply and discharge of a fluid such as air or liquid, and a short fiber made of synthetic resin in a large number of dots on the entire outer periphery of the elastic tube An elastic tube comprising an anti-wear flocking layer formed by electrostatic flocking perpendicular to the outer peripheral surface. A fluid pressure type actuator having the elastic tube according to claim 1 as a driving force source.