JP2015108436A - Fluid pressure type actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic type actuator having a superior durability while holding some features such as a simple structure and a light weight.SOLUTION: This invention is constituted by comprising: double inner tubes 1 and 5 of which both ends are sealed with rubber plugs 2, 3 and expanded or shrunk through supplying and discharging of fluid; a mesh sleeve 6 covering outer peripheries of these inner tubes 1, 5 and having both ends fastened and fixed to the rubber plugs 2, 3 together with inner tubes 1, 5 through a fastening ring in which diameters are expanded in response to an expansion of the inner tubes to cause an axial length of the actuator to be shortened; and an air supplying or discharging pipe 4 arranged at the rubber plug 2 at one end thereof.

Description

Detailed Description of the Invention

  The present invention relates to a hydraulic actuator that is driven by supply and discharge of a fluid such as air.

In recent years, it has been proposed to use an elastic expansion body (hereinafter referred to as “fluid pressure actuator”) as described in Patent Document 1 to Patent Document 3 as a drive source of equipment.
Conventional hydraulic actuators, such as pneumatic actuators, are constructed by covering the outer periphery of a tube made of rubber or urethane rubber with a non-stretchable mesh-like covering, and supplying air into the tube. When the tube is expanded, since the covering does not have stretchability, the mesh of the covering is expanded in the circumferential direction, and the covering contracts in the length direction. As a result, the length of the actuator is reduced, and a driving force is generated by the reduction of the length. This fluid pressure actuator is characterized by its simple structure and light weight, and is expected to be used in various industrial fields.

  When the pneumatic actuator as disclosed in the above document is repeatedly operated, the friction between the tube as the covering body and the expansion / contraction body is repeated with the increase in the number of operations, so that the vicinity of the wire member at both ends of the tube The side surface of the covering is scraped. For example, when air is supplied to the pneumatic actuator to obtain a driving force, the actuator expands, and the central portion of each of the tube and the covering expands to a diameter larger than the diameter of the plug member. During this expansion, the tube and the cover are slightly displaced in the length direction in the vicinity of the plug member. This misalignment also occurs when the actuator contracts. When this misalignment occurs, the tube is strongly pressed against the cover by internal pressure, and therefore fine cuts are generated on the outside of the tube due to the unevenness of the mesh of the fiber of the cover. For example, according to experiments conducted by the inventors of the present application, in the conventional pneumatic actuators described in Patent Document 1 to Patent Document 3 and the like, when expansion and contraction are repeated at a frequency of 4 times / minute, tens of thousands of times It was found that the tube was damaged, the supplied air leaked, and the function of the actuator was impaired.

  In order to solve this problem, it is proposed in Patent Document 4 that a low friction layer is provided between the covering and the tube.

JP-A-7-24771 JP 2002-103270 A International Publication WO2004 / 085856 International Publication WO2007 / 058085

  However, according to the repeated operation test by the inventors of the present application, it was confirmed that the pneumatic actuator disclosed in Patent Document 4 also breaks when the repeated operation reaches several hundred thousand times. Pneumatic actuators with repeated operation life of hundreds of thousands of times are considered to have sufficient life in fields where usage is infrequent, such as nursing care and welfare. As an actuator used for a device that is frequently used, such as a support device, an actuator having a longer repeated operation life is required.

The present invention has been made to solve the above-described problems, and provides a pneumatic actuator with further improved durability while retaining the characteristics of the pneumatic actuator that is simple and lightweight as described above. The purpose is to do.

  The fluid pressure actuator according to the present invention covers a plurality of layers of expansion / contraction bodies that are inflated / contracted when both ends are sealed by a plug member and fluid is supplied / discharged, and the outer periphery of the expansion / contraction body is covered. A cover body in which the ends of the navel are tightened and fixed, the diameter is expanded in accordance with the expansion of the expansion / contraction body and the length in the axial direction of the actuator is shortened, and the fluid supply / discharge port provided in the plug member is provided. It is a feature.

  According to the present invention, since the auxiliary member is provided, the number of repetitions of expansion / contraction (durability) until the expansion / contraction body is deformed, such as scratches and cracks, is greatly increased, and the application field is further expanded. There is expected.

1 is a longitudinal sectional view of a pneumatic actuator according to a first embodiment of the present invention. Enlarged view The enlarged view of the crimping part of the rubber stopper of the pneumatic actuator by the 2nd Embodiment of this invention The figure which shows the shape of the reinforcement ring used for 2nd Embodiment Diagram showing the durability test method for pneumatic actuators

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a longitudinal sectional view of a pneumatic actuator according to a first embodiment of the present invention. As shown in FIG. 1, a pneumatic actuator according to an embodiment of the present invention includes a first expansion / contraction body (hereinafter referred to as a “first inner tube”) 1 that expands by supplying air, and this. Rubber stoppers 2 and 3 for sealing both ends of the first inner tube 1, and an air supply / exhaust pipe 4 provided so as to penetrate the rubber stopper 2 and reach the internal space of the first inner tube 1; , A second expansion / contraction body (hereinafter referred to as “second inner tube”) 5 covering the outer periphery of the first inner tube 1, and a net-like covering body (hereinafter referred to as “second inner tube”). , 6, and a stopper (caulking ring) for fastening the first inner tube 1, the second inner tube 5, and the mesh sleeve 6 to the rubber plugs 2 and 3 at both ends. 7, 8 and It is al configuration. The air supply / discharge pipe 4 is connected to an air supply / discharge device (not shown), for example, an air supply / discharge device including an air compressor and an electromagnetic valve. By supplying air from the air compressor to the inside of the first inner tube 1 via the air supply / discharge pipe 4 or discharging the air inside the first inner tube 1 via the electromagnetic valve, a pneumatic actuator Is driven.

  The mesh sleeve itself is made of a resin that has a very small elongation with respect to the load, for example, a high-tensile fiber wire (filament) such as nylon fiber or polyester fiber is knitted into a cylindrical shape, and the mesh is in the length direction of the mesh sleeve. It is knitted so as to cross from two directions at a predetermined angle, and when its diameter is expanded, the length (length in the actuator major axis direction) is shortened. The mesh sleeve 6 in the present embodiment has a double structure, but for each mesh sleeve, the material and thickness of the wire (filament) and the number of strands constituting the mesh may be the same. In addition, the diameters of the mesh sleeves having a double structure are strictly different between the inner mesh sleeve and the outer mesh sleeve. Can do.

  The inner tube made of urethane rubber inserted into the mesh sleeve 6 also has a double structure. That is, the inner tube has a double structure of the first inner tube 1 forming an air accommodating space of the actuator and the second inner tube 5 on the side in contact with the inner surface of the mesh sleeve 6. The mesh sleeve 6 and the inner tubes 1 and 5 inserted into the inside thereof have rubber plugs 2 and 3 inserted at both ends in the longitudinal direction thereof, and the caulking ring 7 is formed at the rubber plugs 2 and 3 as shown in the figure. Then, the inner tube and the mesh sleeve are both folded back, and are crimped again by the caulking ring 8 at a position corresponding to the caulking ring 7. By these caulking, the rubber plug, the inner tube, and the mesh sleeve are combined and air leakage from the rubber plug portion is prevented.

  The end portions of the rubber plugs 2 and 3 have a shape that can be connected to a hook attached to a load. As an example, the rubber plug 2 is provided with a fastening bolt 9, and the rubber plug 3 on the other end side is provided with a fastener 10 in which a screw hole is formed. One end of the fastening bolt 9 is prevented from coming off by a washer embedded in the rubber plug 2, and a connecting eye nut or the like can be attached to the outside of the rubber plug. Similarly to the fastening bolt 9, the fastener 10 also has a screw hole formed in the central axis of the metal fastener 10 that is prevented from being removed by a washer embedded in the rubber plug 3, and an eyebolt is formed in the screw hole. Etc. can be attached, and a load is connected. In this embodiment, although the aspect from which a connection tool differs in both ends was illustrated, you may provide the same connection tool in both ends.

  Durability tests were conducted on the pneumatic actuator of the present invention configured as described above and the conventional pneumatic actuator in the manner shown in FIG. That is, the specifications of the pneumatic actuator are as follows: the mesh sleeve material 6 has a rated diameter of 1.5 inches, the outer diameter of the mesh sleeve at no load is about 30 mm, the outer diameter of the mesh sleeve at the maximum load is about 50 mm, The length of the type actuator without load is 300 mm. A 20 kg weight is suspended from this actuator. As an endurance test, the air supply / exhaust device connected to the air supply / exhaust pipe 4 is 4 cycles / minute (air supply to exhaust is defined as one cycle). FIG. 5 (b) shows the time of air supply, and a method of alternately repeating the expansion / contraction operation of the pneumatic actuator was adopted.

  In the conventional pneumatic actuator, since the inner tube constituting the actuator is a single layer, when pressed against the mesh sleeve whose diameter is expanded by the pressure of the air supplied into the tube, the mesh fiber of the expanded fiber of the mesh sleeve is used. Friction occurs between the inner tube and the inner tube, and if the test progresses more than 30,000 times, the outer peripheral surface of the inner tube is locally cut and damaged due to repeated high-pressure air supply thereafter. The cracks suddenly expand and expand, and finally the fine holes penetrate the film thickness of the tube, causing air leakage. And the function of the pneumatic actuator is lost.

  Compared with this, the pneumatic actuator provided with the dual-structure inner tubes 1 and 5 to which the present invention is applied is a double actuator in which both the second inner tube 5 and the first inner tube 1 receive the air pressure and expand and contract. It has a structure. Therefore, even if the repeated operation of the durability test proceeds and a fine crack occurs in the outer second inner tube 5, the first inner tube 1 exists on the inner side, so the first inner tube The pressure of the high-pressure air supplied to 1 is held by the first inner tube 1, stress concentration does not occur in the crack portion generated in the second inner tube 5, and rapid expansion of the crack is prevented. Even if the second inner tube 5 is cracked, the crack does not propagate to the first inner tube 1 provided separately from the second inner tube 5. That is, even if a fine flaw occurs in the second inner tube 5, the flaw does not spread more and more. The pneumatic actuator does not lose its function until the second inner tube 5 is completely frayed, a new crack is generated in the inner first inner tube 1 and a through hole is opened. According to the test results of the inventors of the present application, the pneumatic actuator having the double inner tube of the first embodiment of the present invention has an operating life of 10 to 20 times that of the conventional type. It was confirmed that Details thereof will be described later.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is an enlarged view of a caulked portion between the rubber plug, the mesh sleeve, and the inner tube of the pneumatic actuator according to the second embodiment of the present invention. In this embodiment, the durability of the tightening portion of the rubber plug member is improved. Conventional methods have been used, such as solid hose end fittings. However, since the main use of this actuator is a wearing robot suit, etc., it is desired that the terminal fitting is as light as possible. For this purpose, there is a terminal caulking method shown in the first embodiment, and the actuator has been reduced in weight.

  However, it has been found that due to the duplication of the inner tube, in the structure in which the thin metal ring is crimped to the hexagon, the stress increases at the corner portion of the caulking ring every time air is supplied to the inner tube. As a result, it has been clarified that, when the operation is repeated for 300 to 400,000 cycles, metal fatigue occurs at the corners of the caulking ring and the caulking ring breaks. In order to solve this problem, a circular reinforcing ring 12 is inserted near the center of the caulking rings 7 and 8 in the axial direction of the actuator as an auxiliary member for preventing the stress from increasing at the corners of the caulking rings. The inner diameter of the circular reinforcing ring 11 may be approximately the outer diameter when the inner tube and the mesh sleeve are fitted into the caulked portions of the rubber plugs 2 and 3. As a result, the stress (expansion stress) generated in the caulking portion due to the expansion of the diameters of the mesh sleeve and the inner tube acts on the reinforcing ring 12, and the hexagonal caulking ring is not subjected to any stress to expand it. This eliminates breakage due to repeated metal fatigue of caulking. Since the weight of the ring is about 3 g, the weight increase is negligible. The pneumatic actuator according to the present embodiment was able to obtain durability exceeding that of the first embodiment. The shape of the reinforcing ring 12 may be either a circular shape (12a) or a rectangular shape (12b) with smooth corners in the radial direction.

Table 1 shows the results of durability tests conducted by the inventors.
In the pneumatic actuator of the present invention, the number of repeated operations from the start of the test to the breakage is doubled with that of the conventional single inner tube (Document No. 1 to 3) (Document No. 4 to 4). Compared with 8), it was improved about 10 to 40 times. In addition, the conventional single-layer structure could not be expected when the influence of the cracks would appear, but it became possible to obtain a stable life by making it double, and from this result, the present invention was applied. The superiority of the pneumatic actuator was confirmed.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention can be deform | transformed in the range which does not deviate from the meaning. To summarize the present invention, the present invention provides a means for preventing or suppressing the deformation of the expansion / contraction body that expands / contracts when both ends are sealed with plug members and the fluid is supplied / discharged, such as scratches and cracks. It is characterized by having. As this means, from the first embodiment, the expansion / contraction body (inner tube) has a double structure, but the expansion / contraction body may have a triple structure.

  In the above embodiment, the pneumatic actuator using air as the fluid has been described as an example. However, the fluid supplied to the expansion / contraction body is not limited to air, and water, oil, or the like may be used depending on the application. Various fluids such as gas can be used.

  The fluid pressure actuator according to the prior art has been used as a drive actuator for rehabilitation equipment (for example, CPM (Continuous Passive Motion) device) and nursing care equipment, but the fluid pressure actuator according to the present invention has a durability of 1 million times or more. Therefore, it can be used as a driving actuator for wearable robot suits worn by humans in harsh operating environments such as cargo handling that operates more than 1,000 times a day, that is, as an artificial muscle. Can be used for industrial robots and construction machines. Since the durability of the fluid pressure actuator having such a wide range of applications is improved by the present invention, further expansion of the applications is expected.

DESCRIPTION OF SYMBOLS 1 ... Inner tube 2 ... Rubber plug 3 ... Rubber plug 4 ... Air supply / discharge tube 5 ... Inner tube 6 ... Mesh sleeve 7 ... Caulking ring 8 ... Caulking ring 9 ... Fastening bolt 10 ... Fastener 11 ... Eye bolt 12 ... Reinforcement ring

Claims (2)

  Covers the outer periphery of the expansion / contraction body with both ends sealed with plug members and inflated / contracted when fluid is supplied / discharged, and both ends thereof are clamped and fixed to the plug member. A fluid pressure type actuator comprising: a covering body whose diameter expands in response to expansion of an expansion / contraction body and whose length in the axial direction of the actuator is shortened; and a fluid supply / discharge port provided in the plug member.   2. The hydraulic actuator according to claim 1, wherein an auxiliary member that receives an expansion stress of a covering that has received an internal pressure is inserted into an inner side in an actuator axial direction of a tightening fixing portion of the plug member.

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