Tail rotor pulling and twisting strip and forming method

Abstract

The invention provides a tail rotor pulling and twisting strip. The tail rotor pulling and twisting strip comprises guide sleeves arranged at the two ends of the pulling and twisting strip, pulling and twisting layers and rubber layers. The tension-torsion layer is made of a steel wire which is wound on the outer side face of the stand column. The rubber layer is made of a polyurethane rubber material and wraps the outer surface of the tension-torsion layer; the guide sleeve and the tension-torsion layer can integrally wrap the tension-torsion layer by the rubber layer through a casting molding process, and the tension-torsion layer is cured and molded into a tension-torsion strip. The tension-torsion strip can meet the use requirements of centrifugal force and variable-pitch torsion of the tail rotor blade, that is, the tension-torsion layer manufactured after winding and heat setting of the steel wire enables the tension-torsion strip to have enough rigidity when bearing the centrifugal force generated by rotation of the tail rotor blade in the transverse direction, and to have small rigidity when the tail rotor blade rotates to generate torsion deformation; and high durability and reliability are achieved. Under the working condition of using the load, the tension-torsion strip has small torsional rigidity and axial displacement. The pulling and twisting strip is light in weight, mature in technology, high in finished product percent of pass and consistency and capable of achieving single-piece interchange.

Description

Technical Field

[0001] The invention relates to the technical field of helicopter structural component design, and in particular to a tail rotor twist strip and a molding method thereof. Background Art

[0002] The tail rotor torsion strip is the main structural load-bearing component of the tail rotor system connecting the tail rotor hub and the tail rotor clamp. It is a main structural load-bearing component commonly used in the tail rotor hub of light helicopters. Its main function is to withstand the centrifugal force generated by the rotation of the tail rotor blades and produce torsional deformation to achieve the variable pitch movement of the tail rotor blades, thereby greatly improving the stress of the axial hinge of the tail rotor hub, making the tail rotor hub structure simple, compact, light, safe to use, and easy to maintain. However, in the prior art, the torsion strip is composed of multiple layers of metal sheets, bushings, and gaskets. Since each layer of metal sheet is subjected to great tension and repeated torsional deformation during work, cracks are prone to appear on the side of the metal sheet, causing the metal sheet to break easily; each layer of metal sheet is an independent individual, and the fit (gap) between the layers after assembly is uneven, resulting in uneven force and deformation of each layer of metal sheet; the selection of metal sheets should take into account both strength and toughness, and low-strength stainless steel sheets are usually used; in the process of pulling and twisting, the metal sheet is prone to breakage and the fit between the metal sheets is uneven. The above defects lead to a low life of the metal laminate torsion strip. Therefore, special attention needs to be paid to the selection of materials and the design of the structure during the design and manufacturing process to improve its durability and reliability.

[0003] Through searching, no patents or documents related to the present invention have been found.

[0004] In summary, how to design a tail rotor torsion strip and a forming method to ensure high durability and reliability when withstanding the centrifugal force and torsional deformation generated by the rotation of the tail rotor blades is a technical problem that needs to be solved urgently. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a tail rotor torsion strip and a forming method in view of the defects existing in the prior art, so as to ensure that the tail rotor can still have high durability and reliability when subjected to the centrifugal force and torsional deformation generated by the rotation of the tail rotor blades.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a tail rotor torsion strip, including guide sleeves arranged at both ends of the torsion strip, including a torsion layer wound on the column of the guide sleeve and a rubber layer wrapping the torsion layer; the torsion layer is made of steel wire, and the steel wire is wound on the outer edge surface of the column; the rubber layer is made of polyurethane rubber material, and the rubber layer is wrapped on the outer surface of the torsion layer; the guide sleeve and the torsion layer as a whole can be formed into a torsion strip by a casting molding process, and the rubber layer wraps the torsion layer and is solidified.

[0007] Furthermore, the steel wire wound around the column in multiple turns can be shaped into a tension-torsion layer by eliminating the internal stress through the shaping device to prevent the steel wire from rebounding.

[0008] Furthermore, the guide sleeve also includes a mounting hole, which passes through the column and the large head, the center line of the mounting hole coincides with the center axis of the column, and the center distance between the two mounting holes matches the installation dimensions set on the tail rotor.

[0009] Furthermore, the tension-twist strip has a torsion angle when twisted, assuming the torsion angle is θ, and the range of θ is -28°≤θ≤28°.

[0010] Furthermore, the guide sleeve also includes two large heads connected to both ends of the column, and the large heads can limit the tension-torsion layer on the column to prevent the tension-torsion layer from falling off the column.

[0011] Furthermore, assuming that the center distance between the two mounting holes of the torsion bar is L, and assuming that the center distance between the mounting holes when the torsion bar is stretched transversely is L1; then L and L1 satisfy: L1-L≤1mm.

[0012] The present invention provides a method for forming a tail rotor twist strip, the forming steps of which are: S1, guide sleeve processing, large head sandblasting, cleaning and drying; S2, winding the steel wire on the outer surface of the guide sleeve column; S3, placing the guide sleeve wound with the steel wire into a shaping device for stress relaxation so that the steel wire is shaped into a tension-twist layer; S4, placing the guide sleeve and the tension-torsion layer as a whole into a mold to cast a rubber layer, and after vulcanization, the rubber layer wraps the tension-torsion layer; S5, demoulding, and then trimming the formed torsion strip.

[0013] Furthermore, the metal wire is tightly wound on the outer surface of the column in multiple turns in a spiral reciprocating manner; the specific operation of S2 is: first clamp the two guide sleeves on the winding tooling, then install the winding tooling on the winding machine, press the end of the metal wire on the column of the guide sleeve, and then start the winding machine, the metal wire is tightly wound on the outer surface of the column in multiple turns in a spiral reciprocating manner, and the winding is stopped when the number of turns of the steel wire reaches the requirement.

[0014] Furthermore, after the steel wire is wound on the guide sleeve, internal stress is eliminated through heat setting to form a tensile-torsion layer; the specific operation is: the guide sleeve and winding tooling with the wound steel wire are removed from the winding machine as a whole and placed in a shaping device, and then the shaping device is turned on, and the steel wire wound on the column is baked at a constant temperature to remove the internal residual stress, thereby shaping the steel wire into a tensile-torsion layer.

[0015] Furthermore, the casting molding step is: placing the guide sleeve, the torsion layer and the winding tooling as a whole into the mold, and then pouring polyurethane rubber into the mold, and then vulcanizing it. After vulcanization, the polyurethane rubber forms a rubber layer that completely wraps the torsion layer.

[0016] The beneficial effects of the present invention are as follows: the torsion strip of the present invention can meet the centrifugal force and pitch-changing torsion requirements of the tail rotor blades, that is, the torsion layer made by winding and hot-setting the steel wire makes the torsion strip have sufficiently large rigidity when it bears the centrifugal force generated by the rotation of the tail rotor blades in the lateral direction, and has smaller rigidity when the tail rotor blades rotate and produce torsional deformation, and has higher durability and reliability; at the same time, it avoids the defects of easy breakage of the metal sheet and uneven fitting between the metal sheets during the torsion process, and prolongs the service life of the torsion strip and reduces the maintenance cost of the torsion strip; the metal wire adopts universal standard specification metal wire, and does not need to be machined, which effectively reduces the manufacturing cost and shortens the production cycle. Under the load condition, the torsion strip has smaller torsional rigidity and axial displacement. The torsion strip is light in weight, mature in technology, has a higher qualified rate and consistency of finished products, and can realize single-piece interchangeability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the three-dimensional structure of the tail rotor twist strip according to an embodiment of the present invention; Figure 2 Schematic cross-sectional view of a tail rotor twist strip according to an embodiment of the present invention; Figure 3 It is a schematic diagram of the overall structure of the guide sleeve and the tension-twist layer of an embodiment of the present invention; Figure 4 It is a cross-sectional schematic diagram of the guide sleeve and the tension-twist layer as a whole according to an embodiment of the present invention; Figure 5 for Figure 2 Schematic diagram of the AA section; Figure 6 A top view of a tail rotor torsion strip according to an embodiment of the present invention; Figure 7 A top view of a tail rotor torsion strip when subjected to a lateral force FN according to an embodiment of the present invention; Figure 8 Schematic diagram of the deformation process when subjected to a torsional force Ft according to an embodiment of the present invention; In the figure: 1. guide sleeve, 11. mounting hole, 12. column, 13. large head, 2. tension-torsion layer, 3. rubber layer. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the invention clearer, the following will be combined with the appended drawings of the embodiments of the invention. Figure 1-8, clearly and completely describe the technical solutions of the embodiments of the invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0019] It should be noted that all directional indications (such as up, down, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship of the components in a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly. Embodiment 1

[0020] like Figure 1 and Figure 2 As shown, the tail rotor torsion strip of the present application includes a guide sleeve 1 arranged at both ends of the torsion strip, a torsion layer 2 wound on the column of the guide sleeve and a rubber layer 3 wrapping the torsion layer; the torsion layer 1 is a steel wire layer formed by winding multiple circles of steel wire; the rubber layer 3 is made of polyurethane rubber, and the guide sleeve 1 and the torsion layer 2 as a whole can be formed into a torsion strip through a casting molding process so that the rubber layer 3 wraps the torsion layer 2 and solidifies.

[0021] like Figure 3 and Figure 4 As shown, the torsion layer 2 is formed by winding multiple turns of steel wire tightly around the columns 12 of the guide sleeves 1 at both ends of the tail rotor torsion strip, so that the torsion layer 1 has both strength and toughness. Since the steel wire layer itself has great rigidity in the lateral direction, the tail rotor torsion strip of the present application has sufficient rigidity to withstand the centrifugal force generated by the rotation of the tail rotor blades; at the same time, the steel wire used has a diameter of 0.1 mm and has multiple turns. When torsion deformation occurs, since the steel wire is thin and slides between the multiple turns, it has less rigidity when the tail rotor blades rotate to generate torsion deformation.

[0022] like Figure 2 As shown, the rubber layer 3 that wraps the tension-torsion layer 2 is made of polyurethane rubber material, and polyurethane rubber has many excellent properties, such as excellent elasticity, adaptability to various deformation requirements, and extremely high wear resistance; high tensile strength and tear strength, and can withstand large external forces and deformations without breaking; good cold resistance, and can still maintain certain elasticity and mechanical properties at low temperatures; resistant to oxygen, ozone and ultraviolet radiation, and can withstand the effects of these environmental factors for a long time without significant aging. It can be seen that the helicopter flight environment is relatively complex, and the polyurethane rubber used in the rubber layer 3 can still have good elasticity, mechanical properties and resistance in a complex flight environment, while also avoiding the occurrence of rust and the like due to direct contact between the tension-torsion layer 2 and the outside world, thereby ensuring the life of the tension-torsion layer 2. By designing the above scheme, it is ensured that it can still have high durability and reliability when it is subjected to the centrifugal force generated by the rotation of the tail rotor blades and the torsional deformation.

[0023] like Figure 3 and Figure 4 As shown, the steel wire wound on the column 12 in multiple turns can be formed into a torsion layer 2 by eliminating the internal residual stress through a shaping device. The shaping device such as a baking oven is used to shape the product. Since there will be residual stress inside the steel wire layer after winding, the steel wire layer after winding may rebound and shrink, making the lateral size of the torsion strip smaller, which is very fatal. Therefore, it is necessary to heat treat the steel wire layer after winding to eliminate the residual stress inside the steel wire layer and avoid the rebound of the steel wire layer affecting the size of the torsion strip.

[0024] like Figure 5 , Figure 6 and Figure 7 As shown, the guide sleeve 1 is preferably provided with a mounting hole 11, the mounting hole 11 passes through the guide sleeve 1, the center line M of the mounting hole 11 coincides with the center axis N of the guide sleeve 1, and the center distance between the two mounting holes 11 matches the mounting dimensions set on the tail rotor. Assuming the center distance between the two mounting holes of the torsion bar is L, and assuming that the center distance between the mounting holes when the torsion bar is subjected to lateral tensile force is L1; then L and L1 satisfy: L1-L≤1mm. The purpose of this setting is that the torsion bar can still maintain its own dimensional accuracy when it is subjected to a large centrifugal force in the lateral direction.

[0025] like Figure 8 As shown, the torsion bar has a torsion angle θ when twisted, and the range of θ is -28°≤θ≤28°. Specifically, when the torsion bar is subjected to the torsional force Ft, the torsion bar will produce a torsion angle θ. In order to satisfy the requirement that the torsion bar has a large lateral stiffness while also satisfying the requirement that the tail rotor blade still has a small stiffness when it is torsionally deformed, the torsion angle θ of this embodiment is in the range of -28°≤θ≤28°. In order to satisfy the requirement that the torsion bar has a large lateral stiffness while also satisfying the requirement that the tail rotor blade still has a small stiffness when it is torsionally deformed, the stress condition of the axial hinge of the tail rotor hub during torsional deformation is improved.

[0026] like Figure 5 As shown, the guide sleeve 1 also includes two large heads 13 connected to the two ends of the column. The large heads 13 can limit the tension-torsion layer 2 on the column 12 to prevent the tension-torsion layer 2 from falling off the column 12.

[0027] The present invention provides a method for forming a tail rotor twist strip, the forming steps of which are: S1, guide sleeve 1 processing, large head sandblasting, cleaning and drying; S2, winding a steel wire on the outer surface of the column 12; S3, placing the guide sleeve 1 wound with the steel wire into a shaping device for stress relaxation so that the steel wire is shaped into a tension-torsion layer 2; S4, placing the guide sleeve 1 and the torsion layer 2 as a whole into a mold to cast the rubber layer 3, and after vulcanization, the rubber layer 3 wraps the torsion layer 2; S5, demoulding, removing the winding tooling, and then trimming the formed torsion strip.

[0028] The steel wire is tightly wound on the outer surface of the column 12 in multiple turns in a spiral reciprocating manner; the specific operation of S2 is: by winding the twisted steel wire on a winding machine and a winding tool, inputting the specified force value, rotation speed, and wire arrangement feed speed into the winding machine, and then installing the two guide sleeves 1 on the winding machine through the winding tool, the end of the metal wire is pressed on the column of the guide sleeve, and then the winding machine is turned on, and the steel wire is tightly wound on the outer surface of the column 12 in multiple layers in a spiral reciprocating manner, and the winding is stopped when the number of turns of the steel wire reaches the requirement.

[0029] After the steel wire is wound around the guide sleeve 1, it is shaped to eliminate the internal stress and form a tension-twist layer 2; the specific operation is: place the guide sleeve 1 with the steel wire wound into the shaping device, then turn on the shaping device, and remove the internal residual stress of the steel wire wound on the column by constant temperature baking, so as to shape the steel wire into a tension-twist layer. After winding, the center hole of the tension-twist strip will shrink due to the residual stress of the steel wire being tightened and wound. The shaping device is used to eliminate the residual stress and air humidity by high-temperature constant temperature baking, thereby improving the mechanical properties, stability and reliability of the steel wire layer. The coil absorbs moisture from the air during the manufacturing process, and baking can remove this moisture to achieve a contracted and stable state, thereby improving the mechanical strength of the coil and enhancing the anti-corrosion and rust performance. Baking can ensure the dimensional stability of the coil and avoid dimensional expansion due to moisture, thereby ensuring the stability and reliability of the coil in use. It can better resist external influences such as moisture and extend its service life.

[0030] The casting molding steps are: placing the guide sleeve 1 and the torsion layer 2 as a whole into a mold, and then pouring polyurethane rubber into the mold, and then vulcanizing it. After vulcanization, the polyurethane rubber forms a rubber layer 3 that completely wraps the torsion layer 2.

[0031] The torsion strip formed by the above method can meet the centrifugal force and pitch-changing torsion requirements of the tail rotor blades. That is, the torsion layer formed by winding the steel wire and then hot-setting makes the torsion strip have sufficient rigidity when it is laterally subjected to the centrifugal force generated by the rotation of the tail rotor blades, and has smaller rigidity when the tail rotor blades rotate and produce torsional deformation, and has higher durability and reliability; at the same time, it avoids the defects of easy breakage of the metal sheets and uneven fitting between the metal sheets during the torsion process, and prolongs the service life of the torsion strip and reduces the maintenance cost of the torsion strip. Under the load condition, the torsion strip has smaller torsional rigidity and axial displacement. The torsion strip is light in weight, has mature technology, has a high qualified rate and consistency of finished products, and can realize single-piece interchangeability.

[0032] The above embodiments are only used to illustrate the present invention, rather than to limit the present invention. Technicians in the relevant technical field may make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also fall within the protection scope of the present invention, and the protection scope of the present invention should be defined by the claims.

Claims

1. A tail rotor torsion bar, comprising guide sleeves arranged at both ends of the torsion bar, characterized in that: It also includes a tension-torsion layer wound around the upright post of the guide sleeve and a rubber layer wrapping the tension-torsion layer; The torsion layer is made of steel wire, which is wound around the outer surface of the column; the rubber layer is made of polyurethane rubber material, which is wrapped around the outer surface of the torsion layer; the guide sleeve and the torsion layer as a whole can be formed into a torsion strip by a casting process in which the rubber layer wraps the torsion layer and is solidified.

2. The tail rotor torsion strip according to claim 1, characterized in that: The steel wires wound around the outer surfaces of the two uprights can be shaped into a tension-torsion layer by eliminating internal stress through a shaping device.

3. The tail rotor twist strip according to claim 2, characterized in that: The guide sleeve also includes a mounting hole, which passes through the column and the large head. The center line of the mounting hole coincides with the center axis of the column, and the center distance between the two mounting holes matches the installation dimensions set on the tail rotor.

4. The tail rotor twist strip according to claim 3, characterized in that: The torsion bar has a torsion angle when twisted. Assuming the torsion angle is θ, the range of θ is -28°≤θ≤28°.

5. The tail rotor twist strip according to claim 4, characterized in that: The guide sleeve also includes two large heads connected to the two ends of the column, and the large heads can limit the tension-torsion layer on the column to prevent the tension-torsion layer from falling off the column.

6. The tail rotor twist strip according to claim 3, characterized in that: Assume that the center distance between the two mounting holes of the torsion bar is L, and assume that the center distance between the mounting holes when the torsion bar is stretched transversely is L1; then L and L1 satisfy: L1-L≤1mm.

7. A method for forming a tail rotor twist strip, characterized in that: The steps for forming the tail rotor twist strip according to claims 1-6 are: S1, guide sleeve processing, large head sandblasting, cleaning and drying; S2, winding steel wire on the outer surface of the column; S3, placing the guide sleeve wound with the steel wire into a shaping device for stress relaxation so that the steel wire is shaped into a tension-twist layer; S4, placing the guide sleeve and the tension-torsion layer as a whole into a mold to cast a rubber layer, and after vulcanization, the rubber layer wraps the tension-torsion layer; S5, demoulding, removing the winding tooling, and then trimming the formed torsion strip.

8. The method for forming a tail rotor twist strip according to claim 7, characterized in that: The steel wire is tightly wound on the outer surface of the column in multiple turns in a spiral reciprocating manner; the specific operation of S2 is: two guide sleeves and winding tools are installed on the winding machine, the end of the metal wire is pressed on the column of the guide sleeve, and then the winding machine is turned on. The metal wire is tightly wound on the outer surface of the column in multiple turns in a spiral reciprocating manner, and the winding is stopped when the number of turns of the steel wire reaches the requirement.

9. The method for forming a tail rotor twist strip according to claim 8, characterized in that: The steel wire is wound on the guide sleeve and then heat-set to eliminate internal stress to form a tensile-torsion layer. The specific operation is: the guide sleeve with the wound steel wire is placed in a shaping device, and then the shaping device is turned on to remove the internal residual stress of the steel wire wound on the column by constant temperature baking, so as to shape the steel wire into a tensile-torsion layer.

10. The method for forming a tail rotor twist strip according to claim 9, characterized in that: The casting molding steps are: placing the guide sleeve, the torsion layer and the winding tooling as a whole into the mold, and then pouring polyurethane rubber into the mold, and then vulcanizing it. After vulcanization, the polyurethane rubber forms a rubber layer that completely wraps the torsion layer.

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