Active variable pitch pull rod for helicopter rotor

Abstract

The invention discloses an active variable pitch pull rod for a helicopter rotor, and relates to the technical field of active vibration reduction of helicopter rotors. While the requirements for supporting and vibration reduction are met, coaxial arrangement of the vibration reduction direction and the center of the piezoelectric actuator is achieved, and various adverse effects caused by unbalanced centrifugal force can be effectively avoided. The active variable-pitch pull rod sequentially comprises an upper hanging lug, an upper cover, an outer sleeve, a wedge-shaped structure part, a spring and a lower hanging lug from top to bottom. The wedge-shaped structure part is connected below the piezoelectric actuator and the outer sleeve; an inner core shaft fixedly connected with the lower hanging lug is further arranged in the spring, the top end of the inner core shaft extends into the wedge-shaped structure part, the wedge-shaped structure part is pressed through the piezoelectric actuator, and therefore the clamping force applied to the top end of the inner core shaft is changed. Through the integrated design, vibration reduction in different flight states is achieved in the application field of the variable pitch pull rod of the helicopter, the vibration reduction effect is good, and the application range is wide.

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 the health of passengers, 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 in forward flight and descent.

[0003] There are basically three types of active control vibration reduction technologies based on helicopter rotors: 1) active trailing edge flap control, 2) active rotor torsion control, and 3) active variable pitch rod. The first two vibration reduction methods are based on blade vibration reduction research, and the active variable pitch rod is a method of using an active control strut device to replace the traditional variable pitch rod to reduce the vibration of the helicopter rotor. This vibration reduction method does not involve blade adjustment and retains the integrity of the blade.

[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. In the application, a pitch rod with a piezoelectric drive as the power source is recorded. 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-implementing parts such as piezoelectric actuators are exposed. Considering that the helicopter faces a complex, harsh and severe flight environment 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 view of the above problems, the present invention proposes an active variable pitch pull rod for a helicopter rotor, which not only meets the requirements of both support and vibration reduction, but also realizes the coaxial arrangement of the vibration reduction direction and the center of the piezoelectric actuator, which can effectively avoid various adverse effects caused by unbalanced centrifugal force.

[0006] The technical solution of the present invention is as follows: the active variable pitch pull rod comprises, from top to bottom, an upper hanging ear 111, an upper cover 110, an outer sleeve 103, a wedge-shaped structure 2, a spring 104 and a lower hanging ear 112; The upper hanging ear 111, the upper cover 110 and the outer sleeve 103 are kept fixedly connected, and a piezoelectric actuator 102 coaxially arranged with the spring 104 is provided inside the outer sleeve 103, the top end of the piezoelectric actuator 102 is fixedly connected with the outer sleeve 103, and the wedge-shaped structure 2 is connected under the piezoelectric actuator 102 and the outer sleeve 103; the bottom end of the spring 104 is fixedly connected with the lower hanging ear 112, and an inner core shaft 115 fixedly connected with the lower hanging ear 112 is also provided inside the spring 104, the top end of the inner core shaft 115 extends into the wedge-shaped structure 2, and the wedge-shaped structure 2 is pressed by the piezoelectric actuator 102, thereby changing the clamping force applied to the top end of the inner core shaft 115; The wedge-shaped structure 2 includes a wedge-shaped movable retaining ring 105 and a wedge ring block 107; The wedge-shaped movable retaining ring 105 is installed at the bottom of the outer sleeve 103 through pre-tightening bolts 108 and pre-tightening nuts 109 that are evenly distributed in the circumference, and the wedge-shaped movable retaining ring is fixedly connected to the top of the spring. A disc spring 113 is also mounted on the pre-tightening bolt 108. The disc spring 113 is pressed between the bottom surface of the wedge-shaped movable retaining ring 105 and the pre-tightening nut 109. The disc spring 113 keeps the wedge-shaped movable retaining ring 105 in a movement trend of fitting with the bottom of the outer sleeve 103; the piezoelectric actuator 102 is extended and contacts with the wedge-shaped movable retaining ring 105, and drives the wedge-shaped movable retaining ring 105 to overcome the force of the disc spring 113 and move downward; The center of the wedge-shaped movable retaining ring 105 is provided with a tapered through hole which is larger at the top and smaller at the bottom; The outer wall of the wedge ring block 107 is in the shape of a cone that is larger at the top and smaller at the bottom, and a wedge ring block groove 301 that runs through from top to bottom is provided on the wedge ring block 107; the lower part of the wedge ring block 107 extends into the conical through hole, and the wedge ring block 107 is fixedly connected to the outer sleeve 103 via a fixed shaft 101 that passes through the center of the piezoelectric actuator 102, and a core shaft accommodating hole is also provided in the center of the wedge ring block 107, and the top end of the inner core shaft 115 extends into the core shaft accommodating hole.

[0007] When the piezoelectric actuator 102 does not contact the wedge-shaped movable retaining ring 105, the wedge ring block 107 is compressed by the disc spring 113, so that the wedge ring block 107 tightens the wedge ring block groove 301 under the action of the conical surface, thereby maintaining the clamping of the top of the inner core shaft 115; when the piezoelectric actuator 102 extends and drives the wedge-shaped movable retaining ring 105 to overcome the force of the disc spring 113 and move downward, the wedge-shaped movable retaining ring 105 will gradually reduce the pressure on the wedge ring block 107, so that the wedge ring block 107 gradually returns to its original position naturally, and then gradually weakens the clamping force on the top of the inner core shaft 115 until there is no clamping force, thereby achieving the purpose of changing the friction force applied to the top of the inner core shaft 115, and then achieving the purpose of adjusting the overall stiffness of the variable pitch pull rod.

[0008] The top of the inner core shaft 115 is provided with an inner core shaft upper end stepped shaft side plane 802, and the inner wall of the core shaft receiving hole is provided with a wedge ring block inner wall friction plane 303, and the wedge ring block inner wall friction plane 303 and the inner core shaft upper end stepped shaft side plane 802 are arranged opposite to each other. On the one hand, it can play an effective anti-rotation role, and on the other hand, the two opposite planes can also ensure that different degrees of clamping force, that is, different degrees of friction force, can be stably applied to the top of the inner core shaft 115 during the process of the wedge ring block 107 gradually returning to its original position.

[0009] In order to adapt to the length of the outer sleeve 103 , there are several piezoelectric actuators 102 , which are all mounted on the fixed shaft 101 , and are connected end to end, and the piezoelectric actuator 102 at the bottom is also empty with the wedge ring block 107 .

[0010] Regarding the sensors required for data acquisition: An acceleration sensor is fixedly mounted on the upper cover 110 to obtain the acceleration of the active variable pitch pull rod; A displacement sensor and an acceleration sensor are fixedly installed on the inner core shaft 115. 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 platform 803 at the lower end of the inner core shaft, and a Hall sensor is connected to the lower end surface 704 of the wedge-shaped movable retaining ring. The fixed magnet provides a magnetic field for the Hall sensor, so that the relative displacement between the bottom end of the wedge-shaped movable retaining ring 105 and the bottom end 803 of the inner core shaft is obtained through the Hall sensor.

[0011] A force sensor is also provided between the piezoelectric actuator 102 and the wedge-shaped movable retaining ring 105 for detecting the magnitude of the output force of the piezoelectric actuator.

[0012] Regarding the specific installation structure used in the helicopter pitch lever: 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.

[0013] The present invention pre-tightens the wedge-shaped structure 2 by adjusting the pre-tightening bolts 108 before working. Since the pre-tightening force is applied, the inner wall of the wedge ring block 107 and the inner core shaft 115 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 actuator 602 generates a micro-displacement under the excitation of the control voltage. Under the push of the piezoelectric actuator 602, the distance between the wedge-shaped movable retaining ring 105 and the wedge ring block 107 increases. At this time, relative movement can be generated between the inner core shaft 115 and the inner wall of the wedge ring block 107. Since the preload force between the inner core shaft 115 and the inner wall of the wedge ring block still exists, there is still friction to hinder the relative movement between the inner core shaft 115 and the outer sleeve 103 and the spring 114, 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 stiffness of the spring; as the output displacement of the piezoelectric actuator 602 continues to increase, the force between the wedge-shaped movable retaining ring 105 and the wedge ring block 107 continues to decrease. When the preload force between the inner core shaft 115 and the inner wall of the wedge ring block 107 disappears, the variable pitch pull rod is equivalent to a spring, which further enhances the vibration reduction effect.

[0014] The present invention effectively overcomes the problem that the stiffness and damping of the traditional pitch rod cannot be adjusted in real time and can only handle noise or vibration under specific flight conditions. It solves the problem that the pitch rod in previous inventions is subjected to large unbalanced centrifugal force when in use and key components are exposed. Through an integrated design, vibration reduction under different flight conditions is achieved in the application field of helicopter pitch rods, and the vibration reduction effect is good and the application range is wide. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1a This is a schematic diagram of the appearance structure of this case; Figure 1b This is a schematic diagram of the internal structure of this case; Figure 2 A connection diagram for realizing the function of the wedge-shaped structure; Figure 3 This is a detailed diagram of the wedge ring block structure; Figure 4 a is the top view of the wedge-shaped movable retaining ring. Figure 4 b is a side view of the wedge-shaped movable retaining ring; Figure 5 a is an oblique view of the outer sleeve. Figure 5 b is a bottom view of the outer sleeve; Figure 6 a is the side view of the piezoelectric actuator. Figure 6 b is the bottom view of the piezoelectric actuator; Figure 7 It is a schematic diagram of the structure of the spring connection; Figure 8 It is a schematic diagram of the inner core shaft structure; Fig. 9 It is a schematic diagram of the spring structure; Fig.10 It is a schematic diagram of the present invention being applied to be installed on a helicopter rotor; In the figure: 101, fixed shaft; 102, piezoelectric actuator; 103, outer sleeve; 104, spring; 105, wedge-shaped movable retaining ring; 107, wedge ring block; 108, pre-tightening bolt; 109, pre-tightening nut; 110, upper cover; 111, upper hanging ear; 112, lower hanging ear; 113, disc spring; 114, bolt; 115, inner core shaft; 116, fixing bolt; 301, wedge ring block groove; 302, upper end face of wedge ring block; 303, friction plane of inner wall of wedge ring block; 401, wedge-shaped movable retaining ring through hole; 402, downward concave stepped platform of wedge-shaped movable retaining ring; 403, upper end face of wedge-shaped movable retaining ring; 404, lower end face of wedge-shaped movable retaining ring Threaded end; 501, through hole at the flange edge at the lower end of the outer sleeve; 502, through hole for connecting the fixed shaft at the upper end of the outer sleeve; 503, through hole for bolts at the upper end of the outer sleeve; 504, lower end surface of the flange edge at the lower end of the outer sleeve; 601, head of the piezoelectric actuator; 602, threaded hole at the bottom end of the piezoelectric actuator; 701, through hole of the spring; 702, nut; 703, stepped shaft surface of the inner core shaft; 704, lower end surface of the wedge-shaped movable retaining ring; 801, through hole at the bottom of the inner core shaft; 802, side plane of the stepped shaft at the upper end of the inner core shaft; 803, platform surface at the lower end of the inner core shaft; 901, threaded inner end of the spring; 902, stepped shaft hole at the upper end of the spring; 903, plane of the through hole at the lower end of the spring; 2 is a wedge-shaped structural part, 1001 is an active variable pitch pull rod, and 1002 is a helicopter rotor. DETAILED DESCRIPTION

[0016] In order to clearly illustrate the technical features of this patent, this patent is elaborated in detail below through a specific implementation method and in combination with its accompanying drawings.

[0017] As shown in Figure 1 to Fig.10 As shown, the active variable pitch rod has two effective stiffness states and one transition stiffness state, and the active variable pitch rod includes an upper hanging ear 111, an upper cover 110, an outer sleeve 103, a wedge-shaped structure 2, a spring 104 and a lower hanging ear 112 from top to bottom; The upper hanging ear 111, the upper cover 110 and the outer sleeve 103 are kept fixedly connected, and a piezoelectric actuator 102 coaxially arranged with the spring 104 is provided inside the outer sleeve 103, the top end of the piezoelectric actuator 102 is fixedly connected with the outer sleeve 103, and the wedge-shaped structure 2 is connected under the piezoelectric actuator 102 and the outer sleeve 103; the bottom end of the spring 104 is fixedly connected with the lower hanging ear 112, and an inner core shaft 115 fixedly connected with the lower hanging ear 112 is also provided inside the spring 104, the top end of the inner core shaft 115 extends into the wedge-shaped structure 2, and the wedge-shaped structure 2 is pressed by the piezoelectric actuator 102, thereby changing the clamping force applied to the top end of the inner core shaft 115; The wedge-shaped structure 2 includes a wedge-shaped movable retaining ring 105 and a wedge ring block 107; The wedge-shaped movable retaining ring 105 is installed at the bottom of the outer sleeve 103 through pre-tightening bolts 108 and pre-tightening nuts 109 that are evenly distributed in the circumference, and the wedge-shaped movable retaining ring is fixedly connected to the top of the spring. A disc spring 113 is also mounted on the pre-tightening bolt 108. The disc spring 113 is pressed between the bottom surface of the wedge-shaped movable retaining ring 105 and the pre-tightening nut 109. The disc spring 113 keeps the wedge-shaped movable retaining ring 105 in a movement trend of fitting with the bottom of the outer sleeve 103; the piezoelectric actuator 102 is extended and contacts with the wedge-shaped movable retaining ring 105, and drives the wedge-shaped movable retaining ring 105 to overcome the force of the disc spring 113 and move downward; The center of the wedge-shaped movable retaining ring 105 is provided with a tapered through hole which is larger at the top and smaller at the bottom; The outer wall of the wedge ring block 107 is in the shape of a cone that is larger at the top and smaller at the bottom, and a wedge ring block groove 301 that runs through from top to bottom is provided on the wedge ring block 107; the lower part of the wedge ring block 107 extends into the conical through hole, and the wedge ring block 107 is fixedly connected to the outer sleeve 103 via a fixed shaft 101 that passes through the center of the piezoelectric actuator 102, and a core shaft accommodating hole is also provided in the center of the wedge ring block 107, and the top end of the inner core shaft 115 extends into the core shaft accommodating hole.

[0018] When the piezoelectric actuator 102 does not contact the wedge-shaped movable retaining ring 105, the wedge ring block 107 is compressed by the disc spring 113, so that the wedge ring block 107 tightens the wedge ring block groove 301 under the action of the conical surface, thereby maintaining the clamping of the top of the inner core shaft 115; when the piezoelectric actuator 102 extends and drives the wedge-shaped movable retaining ring 105 to overcome the force of the disc spring 113 and move downward, the wedge-shaped movable retaining ring 105 will gradually reduce the pressure on the wedge ring block 107, so that the wedge ring block 107 gradually returns to its original position naturally, and then gradually weakens the clamping force on the top of the inner core shaft 115 until there is no clamping force, thereby achieving the purpose of changing the friction force applied to the top of the inner core shaft 115, and then achieving the purpose of adjusting the overall stiffness of the variable pitch pull rod.

[0019] The top of the inner core shaft 115 is provided with an inner core shaft upper end stepped shaft side plane 802, and the inner wall of the core shaft receiving hole is provided with a wedge ring block inner wall friction plane 303, and the wedge ring block inner wall friction plane 303 and the inner core shaft upper end stepped shaft side plane 802 are arranged opposite to each other. On the one hand, it can play an effective anti-rotation role, and on the other hand, the two opposite planes can also ensure that different degrees of clamping force, that is, different degrees of friction force, can be stably applied to the top of the inner core shaft 115 during the process of the wedge ring block 107 gradually returning to its original position.

[0020] In order to adapt to the length of the outer sleeve 103 , there are several piezoelectric actuators 102 , which are all mounted on the fixed shaft 101 , and are connected end to end, and the piezoelectric actuator 102 at the bottom is also empty with the wedge ring block 107 .

[0021] Regarding the sensors required for data acquisition: An acceleration sensor is fixedly mounted on the upper cover 110 to obtain the acceleration of the active variable pitch pull rod; A displacement sensor and an acceleration sensor are fixedly installed on the inner core shaft 115. 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 platform 803 at the lower end of the inner core shaft, and a Hall sensor is connected to the lower end surface 704 of the wedge-shaped movable retaining ring. The fixed magnet provides a magnetic field for the Hall sensor, so that the relative displacement between the bottom end of the wedge-shaped movable retaining ring 105 and the bottom end 803 of the inner core shaft is obtained through the Hall sensor.

[0022] A force sensor is also provided between the piezoelectric actuator 102 and the wedge-shaped movable retaining ring 105 for detecting the magnitude of the output force of the piezoelectric actuator.

[0023] Regarding the specific installation structure used in the helicopter pitch lever: 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.

[0024] About the installation process of the variable pitch pull rod device: With the outer sleeve 103 as a reference, the piezoelectric actuator 102 is placed in and the bottom end of the piezoelectric actuator is fixedly connected to the inner side of the upper end of the outer sleeve with bolts, and then the second piezoelectric actuator is placed in, and then the fixed shaft 101 is inserted. The bottom end of the fixed shaft is provided with a threaded hole, and the fixing bolt 116 can be strung with a gasket to fix the fixed shaft 101 to the upper end of the outer sleeve, and then the upper end face 302 of the wedge ring block 107 is pressed against the lower end face of the fixed shaft, and the wedge-shaped movable baffle ring 105 is covered, and then the spring 104 is connected to the inner core shaft 115, and the inner core shaft is inserted into the spring and then the nut 70 is used to tighten the screw. 2 and bolts 114 to connect the two. After the two are connected, insert the whole into the wedge ring block 107, connect the spring and the wedge-shaped movable retaining ring 105 with internal and external threads, and then fine-tune the fixing bolts 116 to make the gap between the lower end surface of the outer sleeve flange and the wedge-shaped movable retaining ring appropriate when the wedge-shaped movable retaining ring is pressed against the wedge ring block, and then string the disc spring 113 on the pre-tightening bolt 108, and use the pre-tightening nut 109 to pre-tighten and connect. At this time, the whole device is in a rigid rod state, and finally install the upper cover 110, the upper hanging ear 111 and the lower hanging ear 112.

[0025] like Figures 2 to 5 As shown, four or more through holes 401 are provided at the flange edge of the wedge-shaped movable retaining ring 105, and a through hole 501 having the same number and size as the holes on the wedge-shaped movable retaining ring is provided at the flange edge of the lower end of the outer sleeve. After a plurality of pre-tightening bolts 108 are put on the disc spring 113, they pass through the through holes 501 at the flange edge of the lower end of the outer sleeve and the through holes 401 of the wedge-shaped movable retaining ring. The pre-tightening nut 109 is screwed on the pre-tightening bolt 108 and contacts the disc spring 113. When the pre-tightening nut 109 is tightened, the bolt pre-tightening force squeezes the disc spring 113 to cause deformation and at the same time drives the wedge-shaped movable retaining ring 105 to move relative to the fixed wedge ring block 107. The surface groove 301 of the wedge ring block 107 is deformed to provide an initial pre-tightening force for the wedge-shaped structure part 2. The pre-tightening nut 109 adjusts the initial compression amount of the disc spring 113.

[0026] By adjusting the output force / displacement of the piezoelectric actuator head on the lower end of the wedge-shaped movable ring, the initial bolt preload force is changed, thereby changing the friction force between the wedge-shaped structure part 2 and the inner core shaft 115.

[0027] As shown in Figures 3 and 4, the wedge ring block 107 of the wedge-shaped structure 2 is tightly contacted with the wedge-shaped movable retaining ring 105, the lower end 504 of the outer sleeve 103 and the upper end face 403 of the wedge-shaped movable retaining ring are both provided with flange edges, the pre-tightening bolt 108 passes through the flange edge hole 501 at the lower end of the outer sleeve 103 and the flange edge hole 401 at the upper end of the wedge-shaped movable retaining ring 105, and a disc spring 113 is provided between the pre-tightening nut 109 and the lower end face of the flange edge hole of the wedge-shaped movable retaining ring 105. There is a gap between the upper end face 403 of the wedge-shaped movable retaining ring and the lower end face 504 of the outer sleeve flange, so that when the wedge-shaped structure 2 is subjected to bolt pre-tightening force, the wedge-shaped movable retaining ring 105 produces a micro-displacement to press the wedge ring block 107 sleeved therein, and the wedge ring block 107 will not produce axial displacement under the pressing action of the fixed shaft 101, and then the wedge-shaped movable retaining ring squeezes the groove 301 of the wedge ring block in the micro-displacement to produce deformation, thereby holding the inner core shaft 115. The concave stepped platform 402 of the wedge-shaped movable retaining ring is used to receive the output of the piezoelectric actuator 102.

[0028] like Figure 5 As shown, the fixing bolts connect the fixed shaft to the outer sleeve through the fixing through hole 502, and the flange through hole 501 at the lower end of the outer sleeve is used to connect the outer sleeve with the wedge-shaped movable retaining ring and the disc spring. The bolt through hole 503 at the upper end of the outer sleeve is used to fix the piezoelectric actuator 102 after the bolts are installed.

[0029] like Figure 6 As shown, the piezoelectric actuator 102 is composed of a piezoelectric ceramic stack and a piezoelectric actuator head 601. The bottom end of the piezoelectric actuator 102 near the bottom end of the outer sleeve is bolted to the upper end of the outer sleeve 103, and the piezoelectric actuator head 601 near the upper end of the wedge-shaped movable retaining ring is against the upper end surface 403 of the wedge-shaped movable retaining ring.

[0030] like Figure 7 , 8 As shown in FIG. 9 , a through hole 801 is provided at the bottom end of the inner core shaft 115 , which is fixedly connected to the opening 701 at the bottom end of the spring by means of a nut 702 and a bolt 114 .

[0031] The outer thread 404 at the lower end of the wedge-shaped movable retaining ring is screwed into the inner thread 901 on the upper side of the spring for connection, and a stepped hole 902 is opened at the upper end of the spring 104, corresponding to the stepped shaft 703 designed at the upper end of the inner core shaft 115, so as to provide a limiting function for the movement of the spring and the variable pitch pull rod structure device in the transition and elastic states.

[0032] A flat surface 903 is machined at the opening at the lower end of the spring for the end face of the bolt head to contact the end face of the nut.

[0033] The open platform 803 at the lower end of the inner core shaft is connected to a fixed magnet, and the lower end surface 704 of the wedge-shaped movable retaining ring is connected to a Hall sensor. The fixed magnet provides a magnetic field for the Hall sensor, so that the relative displacement between the bottom end of the wedge-shaped movable retaining ring 105 and the bottom end 803 of the inner core shaft is obtained through the Hall sensor.

[0034] like Fig.10 As shown, the active variable pitch rod 1001 of the present invention replaces the traditional variable pitch rod in the application of the helicopter rotor 1002. When used, 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. Without changing the shape of the blade, the vibration of the blade and the vibration transmitted to the helicopter fuselage by the blade are reduced by changing the stiffness of the strut itself.

[0035] Before work, the wedge-shaped structure part in the strut structure used for the helicopter rotor pitch change pull rod is pre-tightened by adjusting the pre-tightening bolts and nuts. Due to the application of pre-tightening force, when the outer sleeve is subjected to external pressure transmitted from the upper cover to the wedge-shaped movable retaining ring, the inner wall of the wedge ring block and the inner core shaft are not easy to move relative to each other due to the friction between the friction surface and the friction plate. At this time, the strut device is equivalent to a rigid rod; when the acceleration sensor detects a large vibration, the control system outputs a control voltage, and the piezoelectric actuator produces a micro-displacement under the excitation of the control voltage. Since the pre-tightening disc spring is not fully compressed, the wedge ring block can be displaced. Therefore, under the push of the piezoelectric actuator, the distance between the wedge ring block and the wedge-shaped movable retaining ring increases, and the force between the inner core shaft and the wedge ring block Reduced, at this time, relative movement can be generated between the inner core shaft and the outer sleeve. Since the pre-tightening force between the inner core shaft and the wedge ring block still exists, during the relative movement of the inner core shaft and the outer sleeve, there is still friction between the friction surface and the friction plate to hinder the relative movement between the inner core shaft and the wedge ring block, thereby achieving the purpose of vibration reduction. At this time, the stiffness of the strut device is between the stiffness of the rigid rod and the stiffness of the spring; as the output force / displacement of the piezoelectric actuator continues to increase, due to the relative movement between the wedge-shaped structural parts, the force between the upper plane surface of the inner core shaft and the wedge ring block continues to decrease. When the groove of the wedge ring block recovers its deformation, that is, the wedge ring block no longer holds the inner core shaft, the strut device is equivalent to a spring, which further enhances the vibration reduction effect. Its stiffness is determined by the spring stiffness.

[0036] An acceleration sensor may be fixed on the upper cover to obtain the acceleration of the active variable pitch pull rod as a whole; a platform is provided at the bottom end of the inner core shaft to place a displacement sensor, an acceleration sensor, etc.

[0037] A fixed magnet is connected to the open platform at the lower end of the inner core shaft, and a Hall sensor is connected to the lower end surface of the wedge-shaped movable baffle ring. The fixed magnet provides a magnetic field for the Hall sensor, so that the relative displacement between the bottom end of the wedge-shaped movable baffle ring and the bottom end of the inner core shaft is obtained through the Hall sensor.

[0038] During the operation of the helicopter, the vibration of the strut device is detected by the acceleration sensor and the displacement sensor, and the collected signal is transmitted to the control system. The control system analyzes the vibration state of the rotor according to the signal detected by the sensor and adjusts the control voltage of the piezoelectric actuator. 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 groove of the wedge ring block can be adjusted by adjusting the control voltage of the piezoelectric actuator, and the stiffness of the variable pitch pull rod can be adjusted to achieve vibration reduction under different flight conditions of the helicopter rotor.

[0039] Considering the safety of the active vibration reduction strut mechanism used in the helicopter rotor pitch rod, when the piezoelectric actuator is suddenly powered off, the piezoelectric actuator has no displacement output and the initial preload of the wedge-shaped structure is restored. At this time, the pitch rod is equivalent to a rigid strut, so the vibration of the rotor will not change suddenly.

[0040] There are many specific implementation ways of the present invention. The above is only the preferred implementation mode 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 principle of the present invention. These improvements should also be regarded as the protection scope of the present invention.

Claims

1. An active variable pitch pull rod for a helicopter rotor, characterized in that: The active variable pitch pull rod comprises, from top to bottom, an upper hanging ear (111), an upper cover (110), an outer sleeve (103), a wedge-shaped structure (2), a spring (104), and a lower hanging ear (112); The upper hanging ear (111), the upper cover (110) and the outer sleeve (103) are fixedly connected, and a piezoelectric actuator (102) coaxially arranged with the spring (104) is provided inside the outer sleeve (103), the top end of the piezoelectric actuator (102) is fixedly connected to the outer sleeve (103), and the wedge-shaped structure (2) is connected below the piezoelectric actuator (102) and the outer sleeve (103); the bottom end of the spring (104) is fixedly connected to the lower hanging ear (112), and an inner core shaft (115) fixedly connected to the lower hanging ear (112) is also provided inside the spring (104), the top end of the inner core shaft (115) extends into the wedge-shaped structure (2), and the wedge-shaped structure (2) is pressed by the piezoelectric actuator (102), thereby changing the clamping force applied to the top end of the inner core shaft (115); The wedge-shaped structural part (2) comprises a wedge-shaped movable retaining ring (105) and a wedge ring block (107); The wedge-shaped movable retaining ring (105) is installed at the bottom of the outer sleeve (103) through pre-tightening bolts (108) and pre-tightening nuts (109) evenly distributed in the circumferential direction, and the wedge-shaped movable retaining ring is fixedly connected to the top of the spring. A disc spring (113) is also mounted on the pre-tightening bolt (108), and the disc spring (113) is pressed between the bottom surface of the wedge-shaped movable retaining ring (105) and the pre-tightening nut (109). The disc spring (113) enables the wedge-shaped movable retaining ring (105) to maintain a movement trend of fitting with the bottom of the outer sleeve (103); the piezoelectric actuator (102) contacts the wedge-shaped movable retaining ring (105) after being extended, and drives the wedge-shaped movable retaining ring (105) to overcome the action force of the disc spring (113) and move downward; A tapered through hole with a larger top and smaller bottom is provided at the center of the wedge-shaped movable retaining ring (105); The outer wall of the wedge ring block (107) is in the shape of a cone with a larger upper portion and a smaller lower portion, and a wedge ring block groove (301) is provided on the wedge ring block (107) and extends from top to bottom; the lower portion of the wedge ring block (107) extends into the conical through hole, and the wedge ring block (107) is fixedly connected to the outer sleeve (103) via a fixed shaft (101) that passes through the center of the piezoelectric actuator (102); a core shaft accommodating hole is also provided in the center of the wedge ring block (107), and the top end of the inner core shaft (115) extends into the core shaft accommodating hole.

2. The active variable pitch pull rod for a helicopter rotor according to claim 1, characterized in that: The top of the inner core shaft (115) is provided with an inner core shaft upper end stepped shaft side plane (802), and the inner wall of the core shaft accommodating hole is provided with a wedge ring block inner wall friction plane (303), and the wedge ring block inner wall friction plane (303) and the inner core shaft upper end stepped shaft side plane (802) are arranged relative to each other.

3. The active variable pitch pull rod for a helicopter rotor according to claim 1, characterized in that: There are a plurality of piezoelectric actuators (102), all of which are sleeved on a fixed shaft (101), and the plurality of piezoelectric actuators (102) are connected end to end, with the piezoelectric actuator (102) at the bottom also being hollowly sleeved on the wedge ring block (107).

4. An active variable pitch pull rod for a helicopter rotor according to any one of claims 1 to 3, characterized in that: An acceleration sensor is fixedly mounted on the upper cover (110) for acquiring the acceleration of the active variable pitch pull rod; A displacement sensor and an acceleration sensor are fixedly mounted on the inner core shaft (115), 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 actuator (102) and the wedge-shaped movable retaining ring (105) for detecting the magnitude of the output force of the piezoelectric actuator.

5. An active variable pitch pull rod for a helicopter rotor according to any one of claims 1 to 3, 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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