A helicopter rotor pitch lever with active adjustable stiffness and damping

Abstract

The present invention discloses a helicopter rotor pitch rod with actively adjustable stiffness and damping, which relates to the technical field of active vibration reduction of helicopter rotors. While meeting the requirements of both support and vibration reduction, the coaxial arrangement of the vibration reduction direction and the center of the piezoelectric actuator is achieved, which can effectively avoid various adverse effects caused by unbalanced centrifugal force. The pitch rod comprises an upper hanging ear, an upper cover, an outer sleeve, a spring and a lower hanging ear from top to bottom; a pair of piezoelectric drivers arranged coaxially with the spring are provided inside the outer sleeve, and a wedge-shaped structure is provided between the pair of piezoelectric drivers; the inner core shaft passes through the lower cover, the outer sleeve, the wedge-shaped structure and the pair of piezoelectric drivers, and the wedge-shaped structure is pressed by the piezoelectric driver, thereby changing the clamping force applied to the middle of the inner core shaft. Vibration reduction under different flight conditions is achieved in the application field of helicopter pitch rods through an integrated and integrated design, with good vibration reduction effect and a wide range of applications.

Description

Technical Field

[0001] The invention relates to the technical field of active vibration reduction of helicopter rotors. Background Art

[0002] Currently, helicopters generate excessive noise and vibration during flight, which is harmful to passenger health, the surrounding environment, and the aircraft itself. The source of this noise and vibration is mainly due to the aerodynamic loads experienced by the helicopter rotor blades, and is most prominent during forward flight and descent.

[0003] There are three basic types of active control vibration reduction technologies for helicopter rotors: 1) active trailing-edge flap control, 2) active rotor torsion control, and 3) active pitch control. The first two methods focus on blade-based vibration reduction. Active pitch control utilizes an active control strut device to replace the traditional pitch control rod. This method eliminates blade adjustment and preserves blade integrity.

[0004] On April 25, 2023, the applicant applied for a Chinese invention patent application entitled: A helicopter rotor pitch rod with an active vibration reduction mechanism, with publication number: CN116443247A. The application describes a pitch rod with a piezoelectric driver as the power source. However, this type of structure that replaces the pitch rod has a device that places the piezoelectric actuator perpendicular to the axial direction for its active vibration reduction function, which may cause the overall structure to be subjected to large unbalanced centrifugal forces during dynamic load tests or actual applications. In addition, in this type of structure, key function implementation parts such as piezoelectric actuators are exposed. Considering that helicopters face complex, harsh and adverse flight environments in actual operation, it is also very easy to cause failure or damage to key components such as piezoelectric actuators. Summary of the Invention

[0005] In response to the above problems, the present invention proposes a helicopter rotor pitch rod with actively adjustable stiffness and damping. While meeting the requirements of both support and vibration reduction, it achieves a coaxial arrangement of the vibration reduction direction and the center of the piezoelectric actuator, which can effectively avoid the various adverse effects caused by unbalanced centrifugal force.

[0006] The technical solution of the present invention is as follows: the pitch-variable pull rod comprises, from top to bottom, an upper hanging ear 101, an upper cover 102, an outer sleeve 111, a spring 114 and a lower hanging ear 116;

[0007] The upper hanging ear 101, the upper cover 102, the outer sleeve 111 and the lower cover are fixedly connected, and a pair of piezoelectric drivers 104 arranged coaxially with the spring 114 are provided inside the outer sleeve 111. The pair of piezoelectric drivers 104 are respectively fixedly connected to the outer sleeve 111, and a distance is left between the two. A wedge-shaped structure portion 2 is provided between the pair of piezoelectric drivers 104; the spring 114 is fixedly connected between the lower hanging ear 116 and the lower cover, and an inner core shaft 113 fixedly connected to the lower hanging ear 116 is further provided inside the spring 114. The inner core shaft 113 passes through the lower cover, the outer sleeve 111, the wedge-shaped structure portion 2 and the pair of piezoelectric drivers 104, and the wedge-shaped structure portion 2 is pressed by the piezoelectric driver 104, thereby changing the clamping force applied to the middle part of the inner core shaft 113;

[0008] The wedge-shaped structure 2 includes a wedge-shaped stopper 106 and a pair of symmetrically arranged wedge-shaped heads 105;

[0009] A pair of wedge-shaped plugs 105 are slidably mounted on the middle portion of the inner core shaft 113 and are respectively fixedly connected to a pair of piezoelectric actuators 104. The piezoelectric actuators 104 drive the pair of wedge-shaped plugs 105 to move closer to or away from each other.

[0010] The wedge-shaped stopper 106 is sleeve-shaped, and the upper and lower parts of the inner wall of the wedge-shaped stopper 106 are conical surfaces with a small inner side and a large outer side adapted to the wedge-shaped head 105. The wedge-shaped stopper 106 includes two half-wedge-shaped stoppers, which are separated from each other and connected by a pre-tightening bolt 109 and a pre-tightening nut 110. The pre-tightening bolt 109 is arranged along the radial direction of the wedge-shaped stopper 106, and a disc spring 107 is mounted on the pre-tightening bolt 109. The disc spring 107 is pressed between the pre-tightening nut 110 and the outer wall of the wedge-shaped stopper 106 or between the head of the pre-tightening bolt 109 and the outer wall of the wedge-shaped stopper 106, so that the two half-wedge-shaped stoppers maintain a movement trend of approaching each other.

[0011] A long strip through hole parallel to its axial direction is also provided in the middle of the inner core shaft 113, and the pre-tightening bolt 109 passes through the long strip through hole, and the inner core shaft 113 passes through the wedge-shaped stopper 106; after the piezoelectric driver 104 is extended, it drives a pair of wedge-shaped heads 105 to approach each other, and drives the two half-part wedge-shaped stops to overcome the force of the disc spring 107 and separate.

[0012] When the piezoelectric driver 104 is not extended, the pressure of the disc spring 107 causes the two half wedge-shaped blocks to maintain clamping on the middle part of the inner core shaft 113; when the piezoelectric driver 104 is extended to drive the wedge-shaped head 105 to overcome the force of the disc spring 107 and approach each other, the two half wedge-shaped blocks gradually reduce the pressure on the middle part of the inner core shaft 113, thereby gradually weakening the clamping force on the middle part of the inner core shaft 113, achieving the purpose of changing the friction force applied to the middle part of the inner core shaft 113 until there is no clamping force, thereby achieving the purpose of adjusting the overall stiffness of the variable pitch pull rod.

[0013] The inner core shaft 113 is provided with an inner core shaft middle plane 201 in the middle, and the inner wall of the wedge-shaped stopper 106 is provided with a wedge-shaped stopper inner side plane 305 in the middle. The wedge-shaped stopper inner side plane 305 is arranged opposite the inner core shaft middle plane 201, and a friction plate 108 is provided between them. On the one hand, this effectively prevents rotation, and on the other hand, the two opposing planes ensure that different degrees of clamping force, that is, different degrees of friction, can be stably applied to the middle of the inner core shaft 113 during the gradual relaxation of the two halves of the wedge-shaped stopper.

[0014] Regarding the sensors required for data acquisition:

[0015] An acceleration sensor is fixedly mounted on the upper cover to obtain the acceleration of the active pitch-variable pull rod;

[0016] A displacement sensor and an acceleration sensor are fixedly installed on the inner core shaft. The displacement sensor is used to detect the spring deformation, and the acceleration sensor is used to detect the vibration of the mechanism. Specifically, a fixed magnet is connected to the upper surface of the platform at the lower end of the inner core shaft, and a Hall sensor is connected to the lower end surface of the outer sleeve. The magnet provides a magnetic field for the Hall sensor, so that the relative displacement between the lower surface of the bottom end of the outer sleeve and the upper surface of the bottom end of the inner core shaft can be obtained through the Hall sensor.

[0017] A force sensor is also provided between the piezoelectric driver and the wedge-shaped head for detecting the magnitude of the output force of the piezoelectric driver.

[0018] Regarding the specific installation structure used in the helicopter pitch lever:

[0019] The upper hanging ear is connected to the rotor, and the lower hanging ear is connected to the dynamic ring of the automatic tilt device.

[0020] The present invention pre-tightens the wedge-shaped structure by adjusting the pre-tightening bolts before work. Since the pre-tightening force is applied, the inner wall of the wedge-shaped block connecting the friction plate and the middle lathe plane of the inner core shaft are not prone to relative movement due to the existence of friction. At this time, the variable pitch pull rod is equivalent to a rigid rod. When the acceleration sensor detects a large vibration, the control system outputs a control voltage, and the piezoelectric driver generates a micro-displacement under the excitation of the control voltage. Under the push of the piezoelectric actuator, the gap between the two parts of the wedge block increases. At this time, the friction plate connecting the inner core shaft and the inner wall of the wedge block is no longer in compression contact, and relative movement can be generated. Since the preload force between the inner core shaft and the inner wall of the wedge block still exists, there is still friction that hinders the relative movement between the inner core shaft and the outer sleeve spring, thereby achieving the purpose of vibration reduction. At this time, the stiffness of the variable pitch pull rod is between the stiffness of the rigid rod and the spring; as the output displacement of the piezoelectric driver continues to increase, the preload force between the wedge block and the inner core shaft continues to decrease. When the preload force between the inner core shaft and the inner wall of the wedge block disappears, the variable pitch pull rod is equivalent to a spring, which further enhances the vibration reduction effect.

[0021] The present invention effectively overcomes the problem that the stiffness and damping of traditional pitch rods cannot be adjusted in real time and can only handle noise or vibration under specific flight conditions. It solves the problem in previous inventions that the pitch rod structure is subjected to large unbalanced centrifugal forces when in use and key components are exposed. Through an integrated and integrated design, vibration reduction under different flight conditions is achieved in the application field of helicopter pitch rods, with good vibration reduction effect and a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 a is a schematic diagram of the appearance structure of this case;

[0023] Figure 1 b is a schematic diagram of the internal structure of this case;

[0024] Figure 2 A connection diagram for the wedge-shaped structural function;

[0025] Figure 3 This is a detailed diagram of the wedge-shaped stopper structure;

[0026] Figure 4 This is a detailed diagram of the wedge-shaped head structure;

[0027] Figure 5 a is the side view of the outer sleeve structure, Figure 5 b is a top view of the outer sleeve structure;

[0028] Figure 6 a is the side view of the piezoelectric actuator structure, Figure 6 b is the bottom view of the piezoelectric actuator structure;

[0029] Figure 7a is the side view of the spring structure, Figure 7 b is the front view of the spring;

[0030] Figure 8 a is the installation process diagram of the variable pitch pull rod, Figure 8 b is the installation completion diagram of the pitch rod;

[0031] Figure 9 This is a schematic diagram of the present invention being applied to and installed on a helicopter rotor;

[0032] In the figure: 101, upper hanging ear; 102, upper cover; 103, bolt; 104, piezoelectric driver; 105, wedge-shaped head; 106, wedge-shaped stopper; 107, disc spring; 108, friction plate; 109, pre-tightening bolt; 110, pre-tightening nut; 111, outer sleeve; 112, bolt; 113, inner core shaft; 114, spring; 115, bolt; 116, lower hanging ear; 201, middle plane of inner core shaft; 301, half of wedge-shaped stopper 1; 302, Half of the wedge-shaped stopper; 303, the outer plane of the wedge-shaped stopper; 304, the wedge-shaped stopper gap; 305, the inner plane of the wedge-shaped stopper; 306, the wedge-shaped surface of the wedge-shaped stopper; 401, the internal thread of the wedge-shaped head; 501, the through hole at the bottom end of the outer sleeve; 502, the square hole in the middle of the outer sleeve; 503, the inner shaft hole of the outer sleeve; 601, the threaded hole of the piezoelectric actuator; 602, the external thread of the piezoelectric actuator head; 701, the nut; 702, the through hole at the bottom end of the spring;

[0033] 2 is a wedge-shaped structural part, 901 is an active variable pitch pull rod, and 902 is a helicopter rotor. DETAILED DESCRIPTION

[0034] In order to clearly illustrate the technical features of this patent, this patent is described in detail below through specific implementation methods and in combination with its accompanying drawings.

[0035] like Figures 1 to 9 As shown, the variable pitch rod has two effective stiffness states and one transition stiffness state. The variable pitch rod comprises, from top to bottom, an upper hanging ear 101, an upper cover 102, an outer sleeve 111, a spring 114 and a lower hanging ear 116;

[0036] The upper hanging ear 101, the upper cover 102, the outer sleeve 111 and the lower cover are kept fixedly connected, and a pair of piezoelectric drivers 104 arranged coaxially with the spring 114 are provided inside the outer sleeve 111. The pair of piezoelectric drivers 104 are respectively fixedly connected to the outer sleeve 111, and a distance is left between the two. A wedge-shaped structure portion 2 is provided between the pair of piezoelectric drivers 104; the spring 114 is fixedly connected between the lower hanging ear 116 and the lower cover, and an inner core shaft 113 fixedly connected to the lower hanging ear 116 is further provided inside the spring 114. The inner core shaft 113 passes through the lower cover, the outer sleeve 111, the wedge-shaped structure portion 2 and the pair of piezoelectric drivers 104, and the wedge-shaped structure portion 2 is pressed by the piezoelectric driver 104, thereby changing the clamping force applied to the middle part of the inner core shaft 113;

[0037] The wedge-shaped structure 2 includes a wedge-shaped stopper 106 and a pair of symmetrically arranged wedge-shaped heads 105;

[0038] A pair of wedge-shaped plugs 105 are slidably mounted on the middle portion of the inner core shaft 113 and are respectively fixedly connected to a pair of piezoelectric actuators 104. The piezoelectric actuators 104 drive the pair of wedge-shaped plugs 105 to move closer to or away from each other.

[0039] The wedge-shaped stopper 106 is sleeve-shaped, and the upper and lower parts of the inner wall of the wedge-shaped stopper 106 are conical surfaces with a small inner side and a large outer side adapted to the wedge-shaped head 105. The wedge-shaped stopper 106 includes two half-wedge-shaped stoppers, which are separated from each other and connected by a pre-tightening bolt 109 and a pre-tightening nut 110. The pre-tightening bolt 109 is arranged along the radial direction of the wedge-shaped stopper 106, and a disc spring 107 is mounted on the pre-tightening bolt 109. The disc spring 107 is pressed between the pre-tightening nut 110 and the outer wall of the wedge-shaped stopper 106 or between the head of the pre-tightening bolt 109 and the outer wall of the wedge-shaped stopper 106, so that the two half-wedge-shaped stoppers maintain a movement trend of approaching each other.

[0040] A long strip through hole parallel to its axial direction is also provided in the middle of the inner core shaft 113, and the pre-tightening bolt 109 passes through the long strip through hole, and the inner core shaft 113 passes through the wedge-shaped stopper 106; after the piezoelectric driver 104 is extended, it drives a pair of wedge-shaped heads 105 to approach each other, and drives the two half-part wedge-shaped stops to overcome the force of the disc spring 107 and separate.

[0041] When the piezoelectric driver 104 is not extended, the pressure of the disc spring 107 causes the two half wedge-shaped blocks to maintain clamping on the middle part of the inner core shaft 113; when the piezoelectric driver 104 is extended to drive the wedge-shaped head 105 to overcome the force of the disc spring 107 and approach each other, the two half wedge-shaped blocks gradually reduce the pressure on the middle part of the inner core shaft 113, thereby gradually weakening the clamping force on the middle part of the inner core shaft 113, achieving the purpose of changing the friction force applied to the middle part of the inner core shaft 113 until there is no clamping force, thereby achieving the purpose of adjusting the overall stiffness of the variable pitch pull rod.

[0042] The inner core shaft 113 is provided with an inner core shaft middle plane 201 in the middle, and the inner wall of the wedge-shaped stopper 106 is provided with a wedge-shaped stopper inner side plane 305 in the middle. The wedge-shaped stopper inner side plane 305 is arranged opposite the inner core shaft middle plane 201, and a friction plate 108 is provided between them. On the one hand, this effectively prevents rotation, and on the other hand, the two opposing planes ensure that different degrees of clamping force, that is, different degrees of friction, can be stably applied to the middle of the inner core shaft 113 during the gradual relaxation of the two halves of the wedge-shaped stopper.

[0043] Regarding the sensors required for data acquisition:

[0044] An acceleration sensor is fixedly mounted on the upper cover to obtain the acceleration of the active pitch-variable pull rod;

[0045] A displacement sensor and an acceleration sensor are fixedly installed on the inner core shaft. The displacement sensor is used to detect the spring deformation, and the acceleration sensor is used to detect the vibration of the mechanism. Specifically, a fixed magnet is connected to the upper surface of the platform at the lower end of the inner core shaft, and a Hall sensor is connected to the lower end surface of the outer sleeve. The magnet provides a magnetic field for the Hall sensor, so that the relative displacement between the lower surface of the bottom end of the outer sleeve and the upper surface of the bottom end of the inner core shaft can be obtained through the Hall sensor.

[0046] A force sensor is also provided between the piezoelectric driver and the wedge-shaped head for detecting the magnitude of the output force of the piezoelectric driver.

[0047] Regarding the specific installation structure used in the helicopter pitch lever:

[0048] The upper hanging ear is connected to the rotor, and the lower hanging ear is connected to the dynamic ring of the automatic tilt device.

[0049] About the installation process of the variable pitch pull rod device:

[0050] Taking the outer sleeve 111 as a reference, the two piezoelectric drivers are connected to the wedge-shaped head 105 with internal and external threads respectively. After the piezoelectric driver 104 located on the lower side is placed from the opening at the upper end of the outer sleeve, the bottom end of the piezoelectric actuator is fixedly connected to the opening 501 at the bottom of the outer sleeve by bolts 112. Then, the spring and the outer sleeve are connected by internal and external threads. The inner core shaft is inserted from the lower end of the spring and fixed with bolts and nuts. At this time, the wedge-shaped stopper 106 with a friction plate 108 is placed, and a disc spring 10 is inserted on one side from the square hole 502 in the middle of the outer sleeve. 7, and the other side passes through the outer sleeve and then strings the disc spring 109 on the other side, and screws on the pre-tightening nut 110, then puts in the second piezoelectric driver with a wedge-shaped head, covers the upper cover 102, and the upper cover and the outer sleeve are threaded together, and then screws in the bolts 103 to fix the upper piezoelectric driver to the upper cover, and finally connects the upper hanging ear 101 and the upper cover, and the lower hanging ear 116 and the bottom end of the inner core shaft 113 with internal and external threads. After the overall installation is completed, tighten the pre-tightening bolts 109 and the pre-tightening nut 110. At this time, the device is in a rigid state.

[0051] Regarding the preload force application method of the wedge-shaped structure:

[0052] A square through hole 502 is provided in the middle of the outer sleeve 111, and a pre-tightening bolt 109 passes through one side of the hole. The pre-tightening bolt is pierced with a disc spring 107, a wedge-shaped block 106, a friction plate 108 and a pre-tightening nut 110. When the pre-tightening bolt 109 is tightened, the bolt pre-tightening force squeezes the disc spring 107 to cause deformation and at the same time drives the two parts of the wedge-shaped block 106 to move. The gap 304 between the wedge-shaped blocks is reduced, and the positive pressure between the friction plate 108 and the middle turning plane 201 of the inner core shaft is increased, providing an initial pre-tightening force for the wedge-shaped structure part 2. The pre-tightening bolt 109 and the pre-tightening nut 110 adjust the initial compression of the disc spring 107.

[0053] A square through hole 502 is formed in the middle of the outer sleeve 111, and a pre-tightening bolt 109 passes through one side of the hole. The pre-tightening bolt is pierced with a disc spring 107, a wedge-shaped block 106, a friction plate 108 and a pre-tightening nut 110. When the pre-tightening bolt 109 is tightened, the pre-tightening force of the bolt squeezes the disc spring 107 to cause deformation and simultaneously drives the two parts of the wedge-shaped block 106 to displace. The gap 304 between the wedge blocks is reduced, and the positive pressure between the friction plate 108 and the plane 201 of the middle part of the inner core shaft is increased, providing an initial pre-tightening force for the wedge-shaped structure 2. The pre-tightening bolt 109 and the pre-tightening nut 110 adjust the initial compression of the disc spring 107.

[0054] The described helicopter rotor pitch-changing pull rod structure device with active adjustable stiffness and damping, through open-loop and closed-loop control of the piezoelectric driver 104 in the outer sleeve 111, the piezoelectric actuator head 602 can perform axial telescopic movement, the piezoelectric driver head 602 and the wedge-shaped top 105 are connected through the internal thread 401 on the inner side of the wedge-shaped top and the external thread on the outer side of the piezoelectric driver head 602, and the output force / displacement of the piezoelectric actuator head on the wedge block 106 is adjusted to change the initial bolt preload, thereby changing and adjusting the friction force between the wedge-shaped structure part 2 and the inner core shaft 113.

[0055] The assembly relationship between the inner core shaft 113 and the inner hole of the piezoelectric driver 104, the outer sleeve shaft hole 503, and the inner hole of the spring 114 is a clearance fit, and a platform is provided near the bottom end of the spring to place displacement sensors, acceleration sensors, etc. The piezoelectric driver head end 602 has a wedge-shaped head 105 that presses against the inner wedge surface 306 of the wedge block. The wedge block gap 304 is adjusted by the expansion and contraction of the piezoelectric actuator head 602.

[0056] like Figure 2 、 3 As shown, the wedge-shaped stopper 106 of the wedge-shaped structure portion 2 is in contact with the wedge-shaped head 105. The wedge-shaped stopper 106 of the wedge-shaped structure portion 2 is composed of two parts 301 and 302. When the wedge-shaped stopper 106 is passed through the pre-tightening bolt 109 and the pre-tightening nut 110, it can be tightly contacted with the wedge-shaped head 105. The pre-tightening bolt 109 and the pre-tightening nut 110 are provided with a disc spring 107 between the surface 303 adjacent to the wedge-shaped stopper 106. The inner surface of the wedge stopper 106 is machined with a flat surface 305. The friction plate 108 has a hole in the middle and is welded or adhered to the flat surface 305 on the inner side of the wedge stopper. A gap 304 is left between the two parts 301 and 302 of the block 106 when they are passed through the pre-tightening bolt 109 and the pre-tightening nut 110 with the disc spring 107 and in contact with the friction plate 108 and the inner core shaft 113, so that when the wedge-shaped structure part 2 is subjected to pre-tightening force, the disc spring 107 is compressed and deformed, and the gap 304 between the wedge-shaped block 106 produces a micro-displacement, so that the friction plate 108 on the inner surface 305 of the wedge-shaped retaining ring 106 applies a large positive pressure to the middle turning plane 201 of the inner core shaft, thereby generating friction between the wedge-shaped block 106 and the inner core shaft 113, thereby clamping the inner core shaft 113.

[0057] like Figure 4 As shown, the inner side of the wedge-shaped head 105 is threaded and threadedly connected to the outer thread of the piezoelectric driver head.

[0058] like Figure 5As shown, a square through hole 502 is opened in the middle of the outer sleeve for passing the pre-tightening bolt 109 during installation, and connecting the disc spring and the pre-tightening nut 110 in series. A through hole is turned at the bottom of the outer sleeve for fixing the piezoelectric driver, and the matching relationship between the outer sleeve shaft hole and the inner core shaft is a clearance fit.

[0059] like Figure 6 As shown, the bottom end of the piezoelectric driver has a threaded hole 601 which is fixed to the outer sleeve and the upper cover by bolts, and the internal and external threads of the piezoelectric driver head are connected to the wedge-shaped head 105.

[0060] like Figure 7 As shown, the bottom opening of the inner core shaft is fixedly connected to the bottom opening 702 of the spring through a bolt 115 and a nut 701.

[0061] like Figure 8 As shown, the structure of the present invention involves a specific installation process. With the outer sleeve 111 as a reference, the two piezoelectric drivers are connected to the wedge-shaped head 105 with internal and external threads respectively. After the piezoelectric driver 104 located on the lower side is placed from the opening at the upper end of the outer sleeve, the bottom end of the piezoelectric actuator is fixedly connected to the opening 501 at the bottom of the outer sleeve by bolts 112. Then, the spring and the outer sleeve are connected by internal and external threads, the inner core shaft is inserted from the lower end of the spring and fixedly connected with bolts and nuts, and the wedge-shaped stopper 106 with a friction plate 108 is placed at this time, and the square hole 502 in the middle of the outer sleeve is passed through. Insert the pre-tightening bolt 109 with a disc spring 107 on one side, and then thread the disc spring 109 on the other side after passing through the outer sleeve on the other side, and screw on the pre-tightening nut 110, then put in the second piezoelectric driver with a wedge-shaped head, cover the upper cover 102, and thread the upper cover and the outer sleeve together. Then screw in the bolt 103 to secure the upper piezoelectric driver to the upper cover, and finally connect the upper hanging ear 101 and the upper cover, and the lower hanging ear 116 and the bottom end of the inner core shaft 113 with internal and external threads. After the overall installation is completed, tighten the pre-tightening bolt 109 and the pre-tightening nut 110. At this time, the device is in a rigid state.

[0062] like Figure 9 As shown, the strut device 901 of the present invention replaces the traditional pitch rod in the application of the helicopter rotor 902. When used, the upper ear bearing is connected to the rotor, and the lower ear bearing is connected to the automatic tilt mechanism dynamic ring. Without changing the shape of the blade, the vibration of the blade and the vibration transmitted from the blade to the helicopter fuselage are reduced by changing the stiffness of the strut itself.

[0063] Before work, the wedge-shaped structure is pre-tightened by adjusting the pre-tightening bolts. Since the pre-tightening force is applied, the inner wall of the wedge-shaped block connecting the friction plate and the middle lathe plane of the inner core shaft are not prone to relative movement due to the existence of friction. At this time, the variable pitch pull rod is equivalent to a rigid rod. When the acceleration sensor detects a large vibration, the control system outputs a control voltage, and the piezoelectric driver generates a micro-displacement under the excitation of the control voltage. Under the push of the piezoelectric actuator, the gap between the two parts of the wedge block increases. At this time, the friction plate connecting the inner core shaft and the inner wall of the wedge block is no longer in compression contact, and relative movement can be generated. Since the preload force between the inner core shaft and the inner wall of the wedge block still exists, there is still friction that hinders the relative movement between the inner core shaft and the outer sleeve spring, thereby achieving the purpose of vibration reduction. At this time, the stiffness of the variable pitch pull rod is between the stiffness of the rigid rod and the spring; as the output displacement of the piezoelectric driver continues to increase, the preload force between the wedge block and the inner core shaft continues to decrease. When the preload force between the inner core shaft and the inner wall of the wedge block disappears, the variable pitch pull rod is equivalent to a spring, which further enhances the vibration reduction effect.

[0064] An acceleration sensor may be fixed on the upper cover to obtain the acceleration of the entire pitch rod; a platform is provided at the bottom end of the inner core shaft to place a displacement sensor, an acceleration sensor, etc.

[0065] A fixed magnet is connected to the upper surface of the platform at the lower end of the inner core shaft, and a Hall sensor is connected to the lower surface of the lower end face of the outer sleeve. The magnet provides a magnetic field to the Hall sensor, so that the relative displacement between the lower surface of the bottom end of the outer sleeve and the upper surface of the bottom end of the inner core shaft can be obtained through the Hall sensor.

[0066] During the operation of the helicopter, the vibration of the strut device is detected by acceleration sensors and displacement sensors, and the collected signals are transmitted to the control system. The control system analyzes the vibration state of the rotor according to the signals detected by the sensors and adjusts the control voltage of the piezoelectric driver. Since the output displacement of the piezoelectric actuator is different under different control voltages, the preload force between the inner core shaft and the inner wall of the wedge-shaped block can be adjusted by adjusting the control voltage of the piezoelectric actuator, thereby adjusting the stiffness of the pitch rod to achieve vibration reduction under different flight conditions of the helicopter rotor.

[0067] Considering the safety of the active vibration damping strut mechanism used in the helicopter rotor pitch rod, when the piezoelectric actuator suddenly loses power, the piezoelectric actuator has no displacement output, the preload force of the wedge-shaped structure is restored, and the pitch rod is now equivalent to a rigid strut, so the vibration of the rotor will not change suddenly.

[0068] There are many specific implementation ways of the present invention. The above is only the preferred implementation method of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements can be made without departing from the principles of the present invention. These improvements should also be considered as the scope of protection of the present invention.

Claims

1. A helicopter rotor pitch lever with active adjustable stiffness and damping, characterized in that: The pitch-variable pull rod comprises, from top to bottom, an upper hanging ear (101), an upper cover (102), an outer sleeve (111), a spring (114), and a lower hanging ear (116); The upper hanging ear (101), the upper cover (102), the outer sleeve (111) and the lower cover are fixedly connected, and a pair of piezoelectric drivers (104) arranged coaxially with the spring (114) are provided inside the outer sleeve (111), the pair of piezoelectric drivers (104) are respectively fixedly connected to the outer sleeve (111), and a distance is left between the two, and a wedge-shaped structure portion (2) is provided between the pair of piezoelectric drivers (104); the spring (114) is fixedly connected between the lower hanging ear (116) and the lower cover, and an inner core shaft (113) fixedly connected to the lower hanging ear (116) is also provided inside the spring (114), the inner core shaft (113) passes through the lower cover, the outer sleeve (111), the wedge-shaped structure portion (2) and the pair of piezoelectric drivers (104), and the wedge-shaped structure portion (2) is pressed by the piezoelectric driver (104), thereby changing the clamping force applied to the middle of the inner core shaft (113); The wedge-shaped structural portion (2) comprises a wedge-shaped stopper (106) and a pair of symmetrically arranged wedge-shaped heads (105); A pair of wedge-shaped heads (105) are slidably mounted on the middle portion of the inner core shaft (113) and are respectively fixedly connected to a pair of piezoelectric drivers (104). The piezoelectric drivers (104) drive the pair of wedge-shaped heads (105) to move closer to or farther from each other. The wedge-shaped stopper (106) is sleeve-shaped, and the upper and lower parts of the inner wall of the wedge-shaped stopper (106) are conical surfaces with a smaller inner side and a larger outer side that are adapted to the wedge-shaped head (105). The wedge-shaped stopper (106) includes two half-part wedge-shaped stoppers, which are separated from each other and are connected by a pre-tightening bolt (109) and a pre-tightening nut (110). The pre-tightening bolt (109) is arranged along the radial direction of the wedge-shaped stopper (106), and a disc spring (107) is mounted on the pre-tightening bolt (109). The disc spring (107) is pressed between the pre-tightening nut (110) and the outer wall of the wedge-shaped stopper (106) or between the head of the pre-tightening bolt (109) and the outer wall of the wedge-shaped stopper (106), so that the two half-part wedge-shaped stoppers maintain a movement trend of approaching each other. A long strip through hole parallel to the axial direction is also provided in the middle of the inner core shaft (113), the pre-tightening bolt (109) passes through the long strip through hole, and the inner core shaft (113) passes through the wedge-shaped stopper (106); after the piezoelectric driver (104) is extended, it drives a pair of wedge-shaped heads (105) to approach each other, and drives the two half wedge-shaped stops to overcome the force of the disc spring (107) and separate.

2. The helicopter rotor pitch lever with active stiffness and damping adjustment according to claim 1, characterized in that: The inner core shaft (113) is provided with an inner core shaft middle plane (201) in the middle, and the wedge-shaped stopper (106) inner wall is provided with a wedge-shaped stopper inner turning plane (305) in the middle. The wedge-shaped stopper inner turning plane (305) and the inner core shaft middle plane (201) are arranged opposite to each other, and a friction plate (108) is provided between the two.

3. A helicopter rotor pitch lever with active adjustable stiffness and damping according to claim 1 or 2, characterized in that: An acceleration sensor is fixedly mounted on the upper cover to obtain the acceleration of the active pitch-variable pull rod; A displacement sensor and an acceleration sensor are fixedly mounted on the inner core shaft, the displacement sensor is used to detect the spring deformation, and the acceleration sensor is used to detect the vibration of the mechanism; A force sensor is also provided between the piezoelectric driver and the wedge-shaped head for detecting the magnitude of the output force of the piezoelectric driver.

4. A helicopter rotor pitch lever with active adjustable stiffness and damping according to claim 1 or 2, characterized in that: The upper hanging ear is connected to the rotor, and the lower hanging ear is connected to the dynamic ring of the automatic tilt device.

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