Helicopter tail transmission shaft spline self-excited vibration principle tester

Abstract

The present invention belongs to the field of aerospace vibration, and proposes a helicopter tail drive shaft system spline self-excited vibration principle tester. The helicopter tail drive shaft system spline self-excited vibration principle tester includes an active motor, an inner spline shaft, an outer spline shaft, a heating tile, a short shaft, a long shaft, a limit ring, a torque measuring instrument, a passive motor and a sensor; the spline meshing portion between the inner spline shaft and the outer spline shaft is covered with a heating tile, and multiple vibration displacement sensors are arranged in multiple locations to measure the vibration displacement, and the limit rings limit the displacement of the long shaft and the short shaft respectively. The present invention has characteristics similar to the dynamics of an actual helicopter tail drive shaft system, can simulate the vibration characteristics of a helicopter tail drive shaft system, and can realize the appearance and disappearance of the helicopter tail drive shaft system spline self-excited vibration phenomenon and the testing of related vibration reduction measures by adjusting different boundary conditions. It has strong comprehensiveness, high reliability and good repeatability.

Description

Technical Field

[0001] The invention relates to the field of aerospace vibration, and in particular to a self-excited vibration principle tester for a helicopter tail transmission shaft system spline. Background Art

[0002] Splines are commonly used to connect rotor components, transmitting torque through the mating of internal and external splines. Splines are compact, easy to install, minimize stress concentration, and minimally weaken the shaft and hub. They also offer greater compensating power-to-weight ratio, making them irreplaceable in aviation transmissions.

[0003] Helicopter tail drive shafts have large spans and often utilize multiple sets of floating splines and diaphragm couplings to achieve torque transmission. Due to the low bending stiffness and shafting support stiffness of the diaphragm couplings, the shafting often operates near or across multiple critical speeds, rendering the tail drive shafting supercritical. In supercritical tail drive shafting, the weak stiffness of the helicopter's tail boom can lead to complex misalignment of the floating splines. This misalignment can cause a dramatic increase in contact stress and relative slip on grease-lubricated splines, accelerating grease consumption and deterioration, causing the splines to transition from their initial grease-rich lubrication state to grease-lean (boundary lubrication), no lubrication, or even abrasive lubrication.

[0004] When a supercritical tail drive shaft is misaligned and lubricated under special conditions, friction damping within the splines generates forces that induce rotor vortex motion, leading to rotor system instability, a phenomenon known as spline self-excited vibration. This phenomenon causes sudden onset of low-frequency vibrations with a sharp increase in amplitude, making them difficult to eliminate during both acceleration and deceleration. Frequency lock can also occur, ultimately evolving into self-excited oscillations, potentially leading to serious accidents. Exploring the mechanisms of self-excited vibration in floating splines of helicopter tail drive shafts and suppressing their occurrence is of vital importance. However, spline self-excited vibration is highly destructive. Conducting self-excited vibration tests on helicopter tail drive shaft test benches or actual aircraft is costly and inefficient, and cannot simulate the specific spline misalignment conditions and lubrication conditions. Therefore, the development of a principle test bench capable of simulating the dynamic characteristics of helicopter tail drive shafts is urgently needed. Summary of the Invention

[0005] Aiming at the current situation that helicopter tail transmission shaft system dynamics test benches are in short supply and have incomplete functions, the present invention proposes a helicopter tail transmission shaft system spline self-excited vibration principle tester.

[0006] The technical solution of the present invention is a helicopter tail transmission shaft system spline self-excited vibration principle tester, comprising an active motor 1, an inner spline shaft 4, an outer spline shaft 9, a heating tile 5, a short shaft 11, a long shaft 24, a limit ring 16, a torque meter 36, a passive motor 39 and a sensor;

[0007] The output shaft of the active motor 1 is fastened to one end of the internal spline shaft 4 via a connecting disc 2 and an expansion sleeve 3; the inner diameter of the internal spline shaft 4 is larger than the outer diameter of the external spline shaft 9, and the two are meshed by a spline socket, and the socket joint is sealed by an O-ring 6; a heating tile 5 is sleeved on the internal spline shaft 4 at the meshing point; the heating tile 5 includes an upper heating tile 5-1 and a lower heating tile 5-2, the ends of which are connected by bolts 5-3 and respectively sleeved on the upper and lower sides of the meshing point; the heating tile 5 is connected to the system controller 44 via a lead 5-5 for controlling the temperature between the upper heating tile 5-1 and the lower heating tile 5-2; a vibration displacement sensor a7 is installed on the external spline shaft 9 for real-time monitoring of the vibration of the external spline shaft 9; the external spline shaft 9 is connected to one end of the short shaft 11 via a diaphragm coupling 10;

[0008] The stub shaft 11 is connected to multiple stub shaft discs 13 through a stub shaft expansion sleeve 12; a limit ring 16 is provided at the middle position of the stub shaft 11 to prevent excessive vibration of the stub shaft 11; a vibration displacement sensor b14 is installed at the stub shaft limit ring 16 to monitor the vibration amplitude at the middle position of the stub shaft 11; a stub shaft deep groove ball bearing 20 is sleeved on the other end of the stub shaft 11, and the outer ring of the stub shaft deep groove ball bearing 20 is interference fit with the stub shaft elastic ring 19, and they are jointly assembled inside the stub shaft bearing support 18 to support the stub shaft 11; a retaining spring 22 is installed between the stub shaft deep groove ball bearing 20 and the stub shaft 11 to limit the axial displacement of the stub shaft 11; the outer end of the stub shaft deep groove ball bearing 20 is pressed against the stub shaft bearing support 18 through the stub shaft bearing cover 21; a vibration displacement sensor c17 is fixed on the stub shaft bearing support 18 to monitor the displacement of the stub shaft deep groove ball bearing 20;

[0009] One end of the long shaft 24 is connected to the other end of the short shaft 11 through a short shaft diaphragm coupling 23; multiple long shaft discs 26 are fixedly connected to the long shaft 24 through long shaft expansion sleeves 25; a long shaft limiting ring 29 is provided on the long shaft 24; a vibration displacement sensor d27 is fixed at the long shaft limiting ring 29 to monitor the vibration of the long shaft 24; a long shaft bearing 34 is sleeved on the other end of the long shaft 24, and the outer ring of the long shaft bearing 34 and the long shaft elastic ring 32 are interference fit, and the two are installed in the long shaft bearing support 31 to jointly support the long shaft 24; the long shaft bearing cover 33 is fixed to the end face of the long shaft bearing support 31 to limit the axial displacement of the outer end of the long shaft bearing 34; a vibration displacement sensor e30 is fixed on the long shaft bearing support 31 to monitor the vibration displacement of the end of the long shaft 24;

[0010] The torque meter 36 is mounted on a torque meter support 37. One side of the torque meter 36 is connected to the other end of the long shaft 24 via a long shaft diaphragm coupling 35, and the other side is connected to the shaft of the passive motor 39 via a torque meter diaphragm coupling 38. The passive motor 39 and the active motor 1 are connected to the variable frequency speed regulator 42 and the controller 44 via a cable for adjusting and controlling the speed of the experimental platform rotor. The torque meter 36 is used to view the value of the torque transmitted by the system in real time.

[0011] Vibration displacement sensor a7, vibration displacement sensor b14, vibration displacement sensor c17, vibration displacement sensor d27 and vibration displacement sensor e30 are respectively connected to the preamplifier 43 through signal lines, and the preamplifier 43 is connected to the industrial computer 46 through the signal acquisition instrument 45; the operation and stop of the entire system are regulated by the system controller 44.

[0012] The heating tile 5, vibration displacement sensor a7, stop ring 16, long axis stop ring 29, active motor 1, and passive motor 39 are each secured to platform 41 via supports. The short axis bearing support 18 and long axis bearing support 31 are secured to platform 41. The heating tile 5 is secured via heating tile supports 5-4; the vibration displacement sensor a7 is secured via vibration displacement sensor support 8; the stop ring 16 and long axis stop ring 29 are secured via stop ring support 28; and the active motor 1 and passive motor 39 are secured via motor support 40.

[0013] The limiting ring 16 includes an adjusting bolt 16-1, a friction ring 16-2, a friction gasket 16-3 and a preload spring 16-4; the friction ring 16-2 is installed on the short shaft 11, and its end is fixed to the short shaft limiting ring support 15 through the adjusting bolt 16-1; a friction gasket 16-3 is provided at the contact point between the friction ring 16-2 and the adjusting bolt 16-1; an adjusting nut is installed at the end of the adjusting bolt 16-1, and the adjusting bolt 16-1 between the friction ring 16-2 and the adjusting nut is sleeved with a preload spring 16-4. By rotating the adjusting nut, the bolt 16-1 is adjusted to change the distance between the friction ring 16-2 and the adjusting nut.

[0014] The heating tile 5 can control the temperature between the upper heating tile 5-1 and the lower heating tile 5-2 by adjusting the voltage, and control the temperature of the meshing point between the inner spline shaft 4 and the outer spline shaft 9 by the speed of temperature rise between the two, thereby controlling the loss rate of grease and making the system under different boundary conditions; the long axis limit ring 29 has the same structure as the limit ring 16.

[0015] The helicopter tail drive shaft system spline self-excited vibration principle tester operates as follows: When the system operates above the critical speed and the lubrication and boundary conditions of the inner and outer spline surfaces of the inner spline shaft 4 and outer spline shaft 9 reach a certain level, the internal friction damping of the inner and outer spline surfaces 4 causes the system to generate low-frequency vibration. The vibration frequency is approximately the critical natural frequency of the system. At this time, neither acceleration nor deceleration can eliminate the vibration, resulting in frequency lock. At this time, vibration displacement sensors a7, b14, d27, and e30 are used to measure the vibration displacement at different positions of the system. The signal acquisition device 45 and the industrial computer 46 collect and analyze the data to determine the boundary conditions and vibration amplitude of the system's self-excited vibration. In addition, the short axis limit ring 16 and the long axis limit ring 29 control the system's amplitude within an appropriate range and do not damage other system components. By changing different lubrication conditions and boundary conditions, the mechanism of self-excited vibration in the spline system is determined. The speed at which self-excited vibration occurs and the speed at which it disappears are measured to evaluate the impact of different conditions on the system's self-excited vibration.

[0016] The beneficial effects of the present invention are as follows: the present invention has the functions of measuring the characteristics of the self-excited vibration of the helicopter tail transmission shaft system spline under different speed conditions, exploring the influence of different boundary conditions on the self-excited vibration of the system, and measuring the vibration reduction effect of the limit ring on the system. It has strong comprehensiveness, high reliability, good repeatability and high economic benefits.

[0017] 1. Simulate the vibration characteristics of the helicopter tail drive shaft spline system in normal state: test the vibration characteristics of the entire system during the test bench's steady-state operation and transient operation from low speed to high speed.

[0018] 2. Simulate the vibration characteristics of the self-excited vibration state of the helicopter tail drive shaft spline system: Test the vibration characteristics of each position of the system when the system exhibits self-excited vibration.

[0019] 3. Simulate the influence of different boundary conditions on the self-excited vibration of the system: by adjusting the connection angle between the active motor 1 and the platform 41, the misalignment state of the system is changed; the temperature of the heating tile 5 is adjusted to achieve different grease loss rates and control the spline to be in different lubrication states; the mass of the counterweight bolts on the short-axis disk 13 and the long-axis disk 26 is changed to adjust the unbalanced mass of the system. In addition, the different positions of the short-axis disk 13 and the long-axis disk 26 can achieve different critical speeds of the system; when the system self-excited vibration occurs, the above different boundary conditions are changed to explore the influence of internal friction damping on the amplitude of the system self-excited vibration and the speed of generation and disappearance.

[0020] 4. Simulate the influence of different system parameters and structural parameters on the self-excited vibration of the system: adjust the speed difference between the active motor 1 and the passive motor 39 by frequency conversion to achieve the change of torque in the system; replace different internal spline shafts 4 and external spline shafts 9 to realize the influence of different spline structural parameters on the self-excited vibration of the system.

[0021] 5. Simulate the vibration reduction characteristics of the short-axis limit ring 16 and the long-axis limit ring 29 on the self-excited vibration of the system: The short-axis limit ring 16 and the long-axis limit ring 29 installed on the short-axis 11 and the long-axis 24 respectively have a suppressive effect on the self-excited vibration of the system. The suppressive effect of the limit ring on the self-excited vibration of the system is measured by various displacement sensors.

[0022] 6. Simulation comprehensive data measurement, monitoring and analysis function: Through various vibration displacement sensors, preamplifiers 43, signal acquisition instruments 45, and industrial computers 46, vibration testing and monitoring of the experimental device at different speeds can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the helicopter tail transmission shaft system spline self-excited vibration principle tester.

[0024] Figure 2(a) is a schematic diagram of the heating tile structure.

[0025] FIG2( b ) is a schematic cross-sectional view of HH in FIG2( a ).

[0026] Figure 3 It is a schematic diagram of the engagement of internal and external spline shafts.

[0027] Figure 4(a) is a schematic diagram of the limiting ring structure.

[0028] FIG4( b ) is a schematic cross-sectional view of KK in FIG4( a ).

[0029] Figure 5 This is the assembly plan diagram of the short shaft bearing support.

[0030] In the figure: 1-active motor; 2-connecting disc; 3-expansion sleeve; 4-inner spline shaft; 5-heating tile; 6-O-ring; 7-vibration displacement sensor a; 8-vibration displacement sensor support; 9-outer spline shaft; 10-diaphragm coupling; 11-short shaft; 12-short shaft expansion sleeve; 13-short shaft disc; 14-vibration displacement sensor b; 15-short shaft limit ring support; 16-limiting ring; 17-vibration displacement sensor c; 18-short shaft bearing support; 19-short shaft elastic ring; 20-short shaft deep groove ball bearing; 21-short shaft bearing cover; 22-circlip; 23-short shaft diaphragm coupling; 24-long shaft; 25-long shaft expansion sleeve; 26-long shaft disc; 27-vibration displacement sensor d; 28-limiting ring support; 29- Long axis limit ring; 30-vibration displacement sensor e; 31-long axis bearing support; 32-long axis elastic ring; 33-long axis bearing cover; 34-long axis bearing; 35-long axis diaphragm coupling; 36-torque measuring instrument; 37-torque measuring instrument support; 38-torque measuring instrument diaphragm coupling; 39-passive motor; 40-motor support; 41-platform; 42-variable frequency speed regulator; 43-preamplifier; 44-system controller; 45-signal acquisition instrument; 46-industrial computer; 5-1-upper heating tile; 5-2-lower heating tile; 5-3-fixing bolt; 5-4-heating tile support; 5-5-lead; 16-1-adjusting bolt; 16-2-friction ring; 16-3-friction gasket; 16-4-preload spring. DETAILED DESCRIPTION

[0031] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0032] like Figure 1 As shown, the helicopter tail transmission shaft system spline self-excited vibration principle tester of the present invention includes an active motor 1, a connecting disc 2, an expansion sleeve 3, an inner spline shaft 4, a heating tile 5, an O-ring 6, a vibration displacement sensor a7, a vibration displacement sensor support 8, an outer spline shaft 9, a diaphragm coupling 10, a short shaft 11, a short shaft expansion sleeve 12, a short shaft disc 13, a vibration displacement sensor b14, a short shaft limit ring support 15, a limit ring 16, a vibration displacement sensor c17, a short shaft bearing support 18, a short shaft elastic ring 19, a short shaft deep groove ball bearing 20, a short shaft bearing cover 21, a retaining spring 22, a short shaft bearing 23, a short shaft bearing 24, a short shaft bearing 25, a short shaft bearing 26, a short shaft bearing 27, a short shaft bearing 28, a short shaft bearing 29, a short shaft bearing 30, a short shaft bearing 31, a short shaft bearing 32, a short shaft bearing 33, a short shaft bearing 34, a short shaft bearing 35, a short shaft bearing 36, a short shaft bearing 37, a short shaft bearing 38, a short shaft bearing 39, a short shaft bearing 40, a short shaft bearing 41, a short shaft bearing 42, a short shaft bearing 43, a short shaft bearing 44, a short shaft bearing Shaft diaphragm coupling 23, long shaft 24, long shaft expansion sleeve 25, long shaft disc 26, vibration displacement sensor d27, limit ring support 28, long shaft limit ring 29, vibration displacement sensor e30, long shaft bearing support 31, long shaft elastic ring 32, long shaft bearing cover 33, long shaft bearing 34, long shaft diaphragm coupling 35, torque measuring instrument 36, torque measuring instrument support 37, torque measuring instrument diaphragm coupling 38, passive motor 39, motor support 40, platform 41, variable frequency speed regulator 42, preamplifier 43, system controller 44, signal acquisition instrument 45 and industrial computer 46;

[0033] (1) Design and manufacture various components of helicopter tail transmission shaft spline self-excited vibration principle tester according to requirements;

[0034] (2) Assemble all components according to the aforementioned connection and installation relationships;

[0035] (3) Install and debug vibration displacement sensor a7, vibration displacement sensor b14, vibration displacement sensor d27 and vibration displacement sensor e30, preamplifier 43, signal acquisition instrument 45 and industrial computer 46 to ensure the validity and accuracy of speed and displacement measurement signals;

[0036] (4) Install and debug the active motor 1, passive motor 39, variable frequency speed regulator 42, torque measuring instrument 36, etc. to ensure the effectiveness and accuracy of speed and torque regulation, control and measurement;

[0037] (5) According to the experimental requirements, a self-excited vibration simulation test of the helicopter tail transmission shaft spline system will be carried out, and vibration tests and vibration characteristics analysis will be carried out on steady-state vibration and transient vibration under various speed conditions. The principle and frequency of self-excited vibration will be explored, and the characteristics and boundary conditions of self-excited vibration in the system will be analyzed.

[0038] (6) According to the experimental requirements, the influence of different lubrication conditions, different transmission torques, and different misalignment angles on the self-excited vibration of the helicopter tail transmission shaft spline system under the self-excited vibration state is studied to obtain the vibration characteristics and vibration laws under different conditions, and the influence of the limit ring 16 and the long axis limit ring 29 on the self-excited vibration of the system under different conditions is studied;

[0039] (7) Analyze the experimental results to obtain the self-excited vibration characteristics of the helicopter tail drive shaft spline system, providing an experimental basis for the stable operation of the helicopter tail drive shaft;

[0040] (8) After the experiment is completed, the disassembly process of the test bench is carried out in the reverse order of the installation process.

Claims

1. A helicopter tail transmission shaft system spline self-excited vibration principle tester, characterized in that: The helicopter tail transmission shaft system spline self-excited vibration principle tester comprises an active motor (1), an inner spline shaft (4), an outer spline shaft (9), a heating tile (5), a short shaft (11), a long shaft (24), a limiting ring (16), a torque measuring instrument (36), a passive motor (39) and a sensor; The output shaft of the active motor (1) is fastened to one end of the inner spline shaft (4) through a connecting disc (2) and an expansion sleeve (3); the inner diameter of the inner spline shaft (4) is larger than the outer diameter of the outer spline shaft (9), and the two are meshed through a spline sleeve, and the sleeve joint is sealed by an O-ring (6); a heating tile (5) is sleeved on the inner spline shaft (4) at the meshing position; the heating tile (5) includes an upper heating tile (5-1) and a lower heating tile (5-2), and the ends of the two are connected by bolts (5-3) and sleeved on the upper side and the lower side of the meshing position respectively; the heating tile (5) is connected to a system controller (44) through a lead (5-5) for controlling the temperature between the upper heating tile (5-1) and the lower heating tile (5-2); a vibration displacement sensor a (7) is installed on the outer spline shaft (9) for real-time monitoring of the vibration of the outer spline shaft (9); the outer spline shaft (9) is connected to one end of a short shaft (11) through a diaphragm coupling (10); The short shaft (11) is connected to a plurality of short shaft discs (13) via a short shaft expansion sleeve (12); a limiting ring (16) is provided at the middle position of the short shaft (11) to prevent the short shaft (11) from vibrating too much; a vibration displacement sensor b (14) is installed at the short shaft limiting ring (16) to monitor the vibration amplitude at the middle position of the short shaft (11); a short shaft deep groove ball bearing (20) is provided on the other end of the short shaft (11), and the outer ring of the short shaft deep groove ball bearing (20) is interference fit with the short shaft elastic ring (19). The short shaft deep groove ball bearing (20) and the short shaft (11) are assembled together and assembled inside the short shaft bearing support (18) to support the short shaft (11); a retaining spring (22) is installed between the short shaft deep groove ball bearing (20) and the short shaft (11) to limit the axial displacement of the short shaft (11); the outer end of the short shaft deep groove ball bearing (20) is pressed together with the short shaft bearing support (18) through the short shaft bearing cover (21); the vibration displacement sensor c (17) is fixed on the short shaft bearing support (18) to monitor the displacement of the short shaft deep groove ball bearing (20); One end of the long shaft (24) is connected to the other end of the short shaft (11) through a short shaft diaphragm coupling (23); a plurality of long shaft discs (26) are fixedly connected to the long shaft (24) through long shaft expansion sleeves (25); a long shaft limiting ring (29) is provided on the long shaft (24); a vibration displacement sensor d (27) is fixed at the long shaft limiting ring (29) for monitoring the vibration of the long shaft (24); a long shaft bearing (34) is sleeved on the other end of the long shaft (24); the outer ring of the long shaft bearing (34) and the long shaft elastic ring (32) are interference fit, and the two are installed in the long shaft bearing support (31) to jointly support the long shaft (24); the long shaft bearing cover (33) is fixed to the end face of the long shaft bearing support (31) for limiting the axial displacement of the outer end of the long shaft bearing (34); a vibration displacement sensor e (30) is fixed on the long shaft bearing support (31) for monitoring the vibration displacement of the end of the long shaft (24); The torque meter (36) is mounted on a torque meter support (37), one side of which is connected to the other end of the long shaft (24) via a long shaft diaphragm coupling (35), and the other side of which is connected to the shaft of a passive motor (39) via a torque meter diaphragm coupling (38); the passive motor (39) and the active motor (1) are connected to a variable frequency speed regulator (42) and a controller (44) via a cable for adjusting and controlling the speed of the experimental platform rotor; The vibration displacement sensor a (7), the vibration displacement sensor b (14), the vibration displacement sensor c (17), the vibration displacement sensor d (27) and the vibration displacement sensor e (30) are respectively connected to the preamplifier (43) through signal lines, and the preamplifier (43) is connected to the industrial control computer (46) through the signal acquisition instrument (45); The heating tile (5), the vibration displacement sensor a (7), the limiting ring (16), the long axis limiting ring (29), the active motor (1) and the passive motor (39) are respectively fixed on the platform (41) through supports; the short axis bearing support (18) and the long axis bearing support (31) are fixed on the platform (41).

2. The helicopter tail transmission shaft system spline self-excited vibration principle tester according to claim 1, characterized in that: The limiting ring (16) comprises an adjusting bolt (16-1), a friction ring (16-2), a friction washer (16-3) and a preload spring (16-4); the friction ring (16-2) is mounted on the short shaft (11), and its end is fixed to the short shaft limiting ring support (15) through the adjusting bolt (16-1); the friction washer (16-3) is provided at the contact point between the friction ring (16-2) and the adjusting bolt (16-1); an adjusting nut is installed at the end of the adjusting bolt (16-1), and the adjusting bolt (16-1) between the friction ring (16-2) and the adjusting nut is sleeved with a preload spring (16-4); the adjusting nut is rotated to adjust the bolt (16-1), thereby changing the distance between the friction ring (16-2) and the adjusting nut.

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