Composite material long variable-pitch rod and forming method of rod body assembly

Abstract

The invention belongs to the field of helicopter rotor systems, and particularly relates to a composite long variable-pitch rod and a forming method of a rod body assembly. By using a high-modulus carbon fiber material and designing a proper connecting structure, the equivalent compression modulus of the variable-pitch rod is slightly greater than the modulus of structural steel, the weight can be greatly reduced, and the critical instability load of the structure is improved.

Description

Technical Field

[0001] The invention belongs to the field of helicopter rotor systems, and in particular relates to a molding method of a composite material long pitch-variable rod and a rod body assembly. Background Art

[0002] The entire control system of an internal-control rotor helicopter is located inside the helicopter rotor shaft. Compared with conventional external-control helicopters, it eliminates the interference of the external control pitch lever on aerodynamics and has a smaller frontal area, which can effectively reduce the drag of the rotor system during flight and improve the performance of the helicopter. Therefore, the internal-control configuration is widely used on different models of helicopters.

[0003] In order to realize the internal control of the rotor, the control command needs to be transmitted to the rotor shaft, so it is necessary to design a long pitch rod for internal control. The long pitch rod in the shaft is more than 2 meters long and bears a large tensile and compressive load, facing serious compression rod stability problems. Due to the limitation of structural size and relatively small outer diameter, conventional aluminum alloy rods cannot meet the root stability requirements, while the structural steel structure is too heavy and does not meet the lightweight requirements. Summary of the invention

[0004] Purpose of the invention: To provide a molding method for a composite material long pitch-variable rod and a rod body assembly, by using high-modulus carbon fiber material and designing a suitable connection structure, the equivalent compression modulus of the pitch-variable rod is slightly larger than the modulus of the structural steel, while the weight can be greatly reduced, thereby increasing the critical instability load of the structure.

[0005] Technical solution:

[0006] A composite material long pitch rod comprises: a rod body assembly 1, a left-handed joint bearing 2, a left-handed locking nut 3, a toothed washer 4, a pressing bushing 5, a right-handed locking nut 6, and a right-handed joint bearing 7, wherein:

[0007] The rod assembly 1 includes: a composite inner tube 11, a composite outer tube 12, a left-handed metal structure 13 and a right-handed metal joint 14, wherein the outer diameter of the end of the composite inner tube 11 is smaller than the outer diameter of the middle section; high-strength carbon fiber material with a strength greater than 300MPa in the 90° direction is wound around the outer sides of both ends of the composite outer tube 12, wherein the 0° direction is axial and the 90° direction is circumferential; the outer contours of the left-handed metal structure 13 and the right-handed metal joint 14 are, from outside to inside, a first outer diameter section, an inverted cone section, and a second cylindrical section, wherein the first outer diameter is equal to the minimum outer diameter of the inverted cylinder, and the second outer diameter is equal to the maximum outer diameter of the inverted cylinder, so as to ensure that the composite outer tube 12 is wound around the outer sides of the composite outer tube 12. When the composite material and the metal joint can be tightly attached, the left-handed metal structure 13 and the right-handed metal joint 14 are provided with an axial through hole, and the axial through hole includes a first inner diameter section and a second inner diameter section from the outside to the inside, the first inner diameter is smaller than the second inner diameter, and the first inner diameter section is designed with a thread inside, and the second inner diameter section is a light hole. The outer sides of the left-handed metal structure 13 and the right-handed metal joint 14 and the inner side of the composite outer tube 12 are coated with structural adhesive to bond the inner and outer sides of the glass cloth, and the end faces of the left-handed metal structure 13 and the right-handed metal joint 14 are provided with a slot; the two ends of the composite inner tube 11 and the second inner diameter of the left-handed metal structure 13 and the right-handed metal joint 14 are connected to the left and right inner diameter sections of the composite inner tube 11. The sections are bonded by structural adhesive; the composite outer tube 12 is arranged on the outside of the composite inner tube 11, the left-handed metal structure 13, and the right-handed metal joint 14 by winding carbon fiber; one end of the clamping bushing 5 has a cylindrical flange, and the end face of the other end is provided with a slot; the left-handed spherical bearing 2 and the right-handed spherical bearing 7 are shank spherical bearings and a groove is provided at the outer diameter of the thread; the toothed washer 4 is divided into an upper toothed washer 41 and a lower toothed washer 42, the inner boss of the upper toothed washer 41 cooperates with the groove of the left-handed spherical bearing 2 or the right-handed spherical bearing 7, and the lower boss of the lower toothed washer 41 cooperates with the slot of the metal joint and the one of the clamping bushing The grooves match, a clamping bushing 5 is sleeved on the left-handed metal structure 13, the left-handed locking nut 3 and the toothed washer 4 are sleeved on the handle of the left-handed spherical bearing 2, the external thread of the left-handed spherical bearing 2 is connected with the internal thread of the left-handed metal structure 13, and the left-handed locking nut 3 is tightened with the external thread of the left-handed spherical bearing 2; another clamping bushing 5 is sleeved on the right-handed metal joint 14, the right-handed locking nut 6 and the toothed washer 4 are sleeved on the handle of the right-handed spherical bearing 7, the external thread of the right-handed spherical bearing 7 is connected with the internal thread of the right-handed metal joint 14, and the right-handed locking nut 6 is tightened with the external thread of the right-handed spherical bearing 7.

[0008] Furthermore, the composite inner tube 11 is axially provided with a through hole of a constant diameter.

[0009] Furthermore, 5-8 layers of high-strength carbon fiber material with a strength greater than 300 MPa in a 90° direction are wound around the outer sides of both ends of the composite outer tube 12 .

[0010] Furthermore, the composite inner tube 11 and the composite outer tube 12 are made of high modulus carbon fiber material with a modulus greater than 400 GPa.

[0011] Furthermore, the cone angle of the inverted cone section is within 20°.

[0012] Furthermore, the first outer diameter sections of the left-handed metal structure 13 and the right-handed metal joint 14 are provided with annular grooves as the cut-off positions for subsequent machining after winding and forming.

[0013] Furthermore, the outer contour of the pressing bushing 5 is a quadrilateral.

[0014] A method for forming the rod assembly, the method comprising:

[0015] Step 1: Curing and forming the composite inner tube 11, and machining after curing to ensure the final drawing size; specifically: laying high modulus carbon fiber materials in an alternating manner of 0° direction and 90° direction, wherein the 0° direction accounts for no less than 90%;

[0016] Step 2: Connecting the two ends of the composite inner tube 11 with the left-handed metal structure 13 and the right-handed metal joint 14 by gluing;

[0017] Step 3: Winding the composite outer tube 12, specifically:

[0018] A layer of glass cloth is laid on the outer surface of the left-handed metal structure 13 and the right-handed metal joint 14, and carbon fiber is wound cyclically, wherein in each cycle, 4-6 sub-cycles of high modulus carbon fiber are first wound, and then a layer of high-strength carbon fiber is wound at 90 degrees;

[0019] Each sub-cycle is as follows: firstly, winding the high modulus carbon fiber at a small angle not greater than 20°; then winding the high modulus carbon fiber at a small angle not less than -20°;

[0020] Step 4: Wrap 5 layers of high-strength carbon fiber material in a 90° direction around both ends of the rod assembly 1 , and after the winding is completed, lay a layer of glass cloth on the outer surface of the composite outer tube 12 .

[0021] Beneficial effects:

[0022] The present invention uses high modulus carbon fiber materials and designs a suitable connection structure, so that the equivalent compression modulus of the pitch change rod is slightly greater than the modulus of the structural steel, and the weight can be greatly reduced, thereby increasing the critical instability load of the structure. It has the characteristics of light weight, high reliability and long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of a composite material long pitch rod;

[0024] Figure 2 is a schematic diagram of the rod assembly;

[0025] Figure 3 It is a schematic diagram of a metal joint;

[0026] Figure 4 It is a compression bushing;

[0027] Figure 5 It is a toothed washer;

[0028] Figure 6 Schematic diagram of locking with toothed washers;

[0029] Among them, 1. composite rod assembly, 2. left-handed spherical bearing, 3. left-handed locking nut, 4. toothed washer, 5. compression bushing, 6. right-handed locking nut, 7. right-handed spherical bearing, 11. composite inner tube, 12. composite outer tube, 13. left-handed metal structure, 14. right-handed metal joint, 41. upper toothed washer, 42. lower toothed washer. DETAILED DESCRIPTION

[0030] The following is a detailed description with reference to the accompanying drawings.

[0031] like Figure 1-6 A composite material long pitch rod of the present invention comprises: a rod body assembly 1, a left-handed spherical bearing 2, a left-handed locking nut 3, a toothed washer 4, a clamping bushing 5, a right-handed locking nut 6, and a right-handed spherical bearing 7.

[0032] The rod assembly 1 comprises: a composite inner tube 11 , a composite outer tube 12 , a left-handed metal structure 13 and a right-handed metal joint 14 .

[0033] The composite inner tube 11 is axially provided with a through hole of a constant diameter, and the wall thickness of the end of the composite inner tube 11 is smaller than the wall thickness of the middle section;

[0034] 5-8 layers of high-strength carbon fiber material (with a strength greater than 300 MPa) in a 90° direction are wound around the outer sides of the two ends of the composite outer tube 12 for circumferential tightening, wherein the 0° direction is axial and the 90° direction is circumferential; a layer of glass cloth is laid on the outermost layer of the composite outer tube 12.

[0035] The composite inner tube 11 and the composite outer tube 12 are made of high modulus carbon fiber material (modulus greater than 400GPa, such as M55J, M40J, etc.). The material has a high elastic modulus and can ensure good straightness after molding. The tie rod assembly can withstand high tensile and compressive loads, can meet the instability requirements of the compression rod of the variable pitch tie rod assembly, and meet the use requirements. At the same time, the tie rod assembly has a lighter weight, which is beneficial to reducing the weight of the entire machine.

[0036] The outer contours of the left-handed metal structure 13 and the right-handed metal joint 14 are, from outside to inside, the first outer diameter section, the inverted cone section, and the second cylindrical section. The cone angle of the inverted cone section is within 20°. The first outer diameter is equal to the minimum outer diameter of the inverted cylinder, and the second outer diameter is equal to the maximum outer diameter of the inverted cylinder, so as to ensure that the composite material and the metal joint can be tightly attached when the composite outer tube 12 is wrapped. The left-handed metal structure 13 and the right-handed metal joint 14 are provided with axial through holes, which include, from outside to inside, the first inner diameter section and the second inner diameter section. The first inner diameter is smaller than the second inner diameter, which is used to increase the connection area and reduce weight at the same time. The first inner diameter section is designed with threads inside, and the second inner diameter section is a smooth hole.

[0037] The outer sides of the left-handed metal structure 13 and the right-handed metal joint 14 and the inner side of the composite outer tube 12 are coated with structural adhesive to adhere the inner and outer sides of the glass cloth, thereby reducing galvanic corrosion between the metal and the composite.

[0038] The first outer diameter sections of the left-handed metal structure 13 and the right-handed metal joint 14 are provided with an annular groove as a cut-off position for subsequent machining after winding molding.

[0039] The end surfaces of the left-handed metal structure 13 and the right-handed metal joint 14 are provided with a slot.

[0040] The axial load of the long tie rod assembly can be carried by the shear strength of the structural adhesive at the connection surface or by the extrusion of the inverted cone area;

[0041] The two ends of the composite inner tube 11 are bonded to the second inner diameter sections of the left-handed metal structure 13 and the right-handed metal joint 14 by means of structural adhesive;

[0042] The composite outer tube 12 is arranged outside the composite inner tube 11, the left-handed metal structure 13, and the right-handed metal joint 14 by winding carbon fibers;

[0043] The outer contour of the compression bushing 5 is a quadrilateral, one end of which has a cylindrical flange, and the flange is matched with the end face of the composite outer tube 12 with a small gap, and a sealant is applied to the matching position for sealing; the end face of the other end is provided with a slot;

[0044] The left-handed spherical bearing 2 and the right-handed spherical bearing 7 are shank spherical bearings and have grooves arranged at the outer diameter of the threads;

[0045] The toothed washer 4 is divided into an upper toothed washer 41 and a lower toothed washer 42. The inner boss of the upper toothed washer 41 cooperates with the groove of the left-handed spherical bearing 2 or the right-handed spherical bearing 7, and the lower boss of the lower toothed washer 41 cooperates with the slot of the metal joint and the slot of the clamping bushing. The toothed washer is used for the anti-loosening design of the three structural parts of the metal joint, the clamping bushing and the metal joint.

[0046] A pressing bushing 5 is sleeved on the left-handed metal structure 13, a left-handed locking nut 3 and a toothed washer 4 are sleeved on the handle of the left-handed spherical bearing 2, the external thread of the left-handed spherical bearing 2 is connected with the internal thread of the left-handed metal structure 13, and the left-handed locking nut 3 is tightened in cooperation with the external thread of the left-handed spherical bearing 2;

[0047] Another clamping bushing 5 is sleeved on the right-handed metal joint 14, the right-handed locking nut 6 and the toothed washer 4 are sleeved on the handle of the right-handed spherical bearing 7, the external thread of the right-handed spherical bearing 7 is connected with the internal thread of the right-handed metal joint 14, and the right-handed locking nut 6 is tightened with the external thread of the right-handed spherical bearing 7.

[0048] Molding method:

[0049] The rod assembly 1 is cured and formed in two steps. The first curing step is: the composite inner tube 11 is cured and formed, and after curing, machining is performed to ensure the final drawing size. The size accuracy after machining is higher and can be well matched with the metal joint.

[0050] The composite inner tube 11 is made of high modulus carbon fiber material. To ensure the axial load-bearing capacity, the composite inner tube 11 is mainly laid in the 0° direction (e.g., 5-6 layers) and supplemented by 90° (1 layer), and the 0° direction accounts for no less than 90%;

[0051] The composite inner tube 11, the left-handed metal structure 13 and the right-handed metal joint 14 are first connected together by gluing, and then wound to form the composite outer tube 12. When the composite outer tube 12 is wound, a layer of glass cloth is laid on the outer surface of the left-handed metal structure 13 and the right-handed metal joint 14 to prevent galvanic corrosion between the metal and the composite material; the composite outer tube 12 is wound with high modulus carbon fiber at a small angle not greater than ±20°. After 4-6 cycles of small-angle winding, a layer of high-strength carbon fiber (such as T800, T300, etc.) is wound at 90°; 5 layers of high-strength carbon fiber material in a 90° direction are wound at both ends of the rod assembly for circumferential tightening. Small-angle winding of high modulus carbon fiber is used to ensure the axial tensile and compressive modulus. High-strength carbon fiber material has good tensile properties and is used for 90° circumferential winding under large winding tension. After winding, a layer of glass cloth is laid on the outer surface of the composite outer tube 12 to protect the internal carbon fiber material and prevent damage to the carbon fiber after collision, which affects the performance of the structure.

[0052] In order to prevent the inner tube from vitrifying after the first curing during the second curing, the second curing temperature should be lower than the first curing temperature. After the second curing, the extra carbon fiber on the outer end of the metal joint is machined to ensure the final joint size. The dimensional accuracy after machining is higher, and it can be well matched with the size of the compression bushing and other structures.

Claims

1. A composite material long pitch rod, characterized in that: include: Rod assembly (1), left-handed spherical bearing (2), left-handed locking nut (3), toothed washer (4), pressing bushing (5), right-handed locking nut (6), right-handed spherical bearing (7), wherein: The rod body assembly (1) comprises: a composite inner tube (11), a composite outer tube (12), a left-handed metal structure (13) and a right-handed metal joint (14); the outer diameter of the end of the composite inner tube (11) is smaller than the outer diameter of the middle section; high-strength carbon fiber material with a strength greater than 300 MPa in a 90° direction is wound around the outer sides of both ends of the composite outer tube (12), wherein the 0° direction is the axial direction and the 90° direction is the circumferential direction; The outer contours of the left-handed metal structure (13) and the right-handed metal joint (14) are, from outside to inside, a first outer diameter section, an inverted cone section, and a second cylindrical section. The first outer diameter is equal to the minimum outer diameter of the inverted cylinder, and the second outer diameter is equal to the maximum outer diameter of the inverted cylinder, so as to ensure that the composite material and the metal joint can be tightly attached when the composite material outer tube (12) is wound. The left-handed metal structure (13) and the right-handed metal joint (14) are provided with an axial through hole. The axial through hole includes, from outside to inside, a first inner diameter section and a second inner diameter section. The first inner diameter is smaller than the second inner diameter. The first inner diameter section is designed with a thread inside, and the second inner diameter section is a light hole. The outer sides of the left-handed metal structure (13) and the right-handed metal joint (14) and the inner side of the composite material outer tube (12) are coated with inner and outer sides of the glass cloth bonded with structural adhesive. The end faces of the left-handed metal structure (13) and the right-handed metal joint (14) are provided with a slot. The two ends of the composite inner tube (11) are bonded to the second inner diameter sections of the left-handed metal structure (13) and the right-handed metal joint (14) by means of structural adhesive; the composite outer tube (12) is arranged on the outside of the composite inner tube (11), the left-handed metal structure (13) and the right-handed metal joint (14) by winding carbon fiber; one end of the clamping bushing (5) is provided with a cylindrical flange, and the end surface of the other end is provided with a straight groove; the left-handed spherical bearing (2) and the right-handed spherical bearing (7) are shank spherical bearings and a groove is provided at the outer diameter of the thread; The toothed washer (4) is divided into an upper toothed washer (41) and a lower toothed washer (42). The inner boss of the upper toothed washer (41) matches with the groove of the left-handed spherical bearing (2) or the right-handed spherical bearing (7). The lower boss of the lower toothed washer (41) matches with the slot of the metal joint and the slot of the clamping bushing. A clamping bushing (5) is sleeved on the left-handed metal structure (13). The left-handed locking nut (3) and the toothed washer (4) are sleeved on the handle of the left-handed spherical bearing (2). The external thread is connected to the internal thread of the left-handed metal structure (13), and the left-handed locking nut (3) is tightened in cooperation with the external thread of the left-handed spherical bearing (2); another pressing bushing (5) is sleeved on the right-handed metal joint (14), the right-handed locking nut (6) and the toothed washer (4) are sleeved on the handle of the right-handed spherical bearing (7), the external thread of the right-handed spherical bearing (7) is connected to the internal thread of the right-handed metal joint (14), and the right-handed locking nut (6) is tightened in cooperation with the external thread of the right-handed spherical bearing (7).

2. The composite material long pitch rod according to claim 1, characterized in that: The composite inner tube (11) is axially provided with a through hole of a constant diameter.

3. The composite material long pitch rod according to claim 1, characterized in that: 5 to 8 layers of high-strength carbon fiber material with a strength greater than 300 MPa in a 90° direction are wound around the outer sides of both ends of the composite outer tube (12).

4. The composite material long pitch rod according to claim 1, characterized in that: The composite inner tube (11) and the composite outer tube (12) are made of high modulus carbon fiber material with a modulus greater than 400 GPa.

5. The composite material long pitch rod according to claim 1, characterized in that: The cone angle of the inverted cone section is within 20°.

6. The composite material long pitch rod according to claim 1, characterized in that: The first outer diameter sections of the left-handed metal structure (13) and the right-handed metal joint (14) are provided with an annular groove as a cut-off position for subsequent machining after winding and forming.

7. The composite material long pitch rod according to claim 1, characterized in that: The outer contour of the pressing bushing (5) is a quadrilateral.

8. A method for forming a rod assembly, characterized in that: The rod body assembly is the rod body assembly according to any one of claims 1 to 7, and the method comprises: Step 1: curing and forming the composite inner tube (11), and machining after curing to ensure the final drawing size; specifically: laying high modulus carbon fiber material in a 0° direction and 90° alternating manner, wherein the 0° direction accounts for no less than 90%; Step 2: connecting the two ends of the composite inner tube (11) with the left-handed metal structure (13) and the right-handed metal joint (14) by gluing; Step 3: Winding the composite outer tube (12), specifically: A layer of glass cloth is laid on the outer surface of the left-handed metal structure (13) and the right-handed metal joint (14), and carbon fiber is wound cyclically, wherein in each cycle, 4 to 6 sub-cycles of high modulus carbon fiber are first wound, and then a layer of high-strength carbon fiber is wound at 90 degrees; Each sub-cycle is as follows: firstly, winding the high modulus carbon fiber at a small angle not greater than 20°; then winding the high modulus carbon fiber at a small angle not less than -20°; Step 4: Five layers of high-strength carbon fiber material in a 90° direction are wound around both ends of the rod assembly (1). After the winding is completed, a layer of glass cloth is laid on the outer surface of the composite outer tube (12).

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