Self-adaptive variable pitch mechanism and method

Abstract

The invention provides a self-adaptive variable-pitch mechanism and method. The self-adaptive variable-pitch mechanism comprises a centrifugal force driving assembly and a tension-torsion coupling flat spring, and the centrifugal force driving assembly comprises a balancing weight, a bearing and a propeller shaft sleeve. One end of the tension-torsion coupling flat spring is fixed on the propeller hub, the other end of the tension-torsion coupling flat spring is connected with a balancing weight of the centrifugal force driving assembly, and the root of the blade is rigidly connected with the balancing weight. During working, centrifugal force and lift force generated by rotation of the propeller enable the flat spring to generate specific stretching and torsional deformation under the coupling action of stretching force and torsional moment, the balancing weight is driven to move outwards and twist, the higher the rotating speed is, the larger the centrifugal force and lift force are, the larger the pitch angle adjusting amplitude is, and precise adaptation of the rotating speed and the pitch angle is achieved. External energy input is not needed, the structure is simple, the weight is light, different flight working conditions can be automatically adapted, the aerodynamic efficiency is improved, and the adjusting precision is ensured through the pull-torsion coupling design.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aircraft propeller variable pitch control, and particularly relates to a self-adaptive variable pitch mechanism and method. BACKGROUND

[0002] Currently, the thrust and rotation speed demand of an aircraft propeller varies significantly with flight conditions (such as take-off, cruising, and landing). The traditional fixed-pitch propeller cannot balance the efficiency and performance under different conditions due to the fixed pitch, resulting in energy waste or insufficient thrust. In recent years, the electric variable pitch mechanism drives the gear set to achieve pitch adjustment through a servo motor, but it has problems such as complex control system, significant weight increase, and the need for additional power supply; the hydraulic variable pitch mechanism uses a hydraulic cylinder to push the propeller shaft, which has large thrust but has a risk of leakage; the mechanical linkage variable pitch uses a linkage mechanism to transmit the displacement of the flight control lever to the propeller, which has a simple structure but a limited adjustment range, cannot respond to rotation speed changes autonomously, and has poor adaptability. The current mainstream research focuses on simplifying the mechanism and reducing energy consumption, but the existing schemes still rely on external energy input and cannot achieve completely self-adaptive pitch adjustment. SUMMARY

[0003] To solve the problem that the conventional fixed-pitch propeller cannot adapt to the thrust and rotation speed demand of an aircraft under different flight conditions, and the existing variable pitch mechanism relies on external energy or manual intervention and cannot achieve self-adaptive adjustment based on rotation speed, the application provides a self-adaptive variable pitch mechanism and method, which uses the centrifugal force and lift generated by the rotation of the propeller as driving force, and realizes self-adaptive adjustment of the pitch angle through a pull-torsion coupling structure, to accurately correspond the specific rotation speed to the specific pitch angle.

[0004] To achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0005] A self-adaptive variable pitch mechanism driven by centrifugal force to automatically match the pitch angle and rotation speed, comprising a centrifugal force driving assembly and a pull-torsion coupling sheet spring.

[0006] A self-adaptive variable pitch mechanism driven by centrifugal force to automatically match the pitch angle and rotation speed, comprising a centrifugal force driving assembly, a pull-torsion coupling sheet spring, the centrifugal force driving assembly comprising a counterweight, a bearing, and a propeller shaft sleeve, the pull-torsion coupling sheet spring being fixed at one end to a propeller hub and at the other end to the counterweight, so that the counterweight and the propeller hub always maintain elastic pull-torsion coupling, the counterweight being able to only slide radially and rotate circumferentially relative to the propeller hub along the axis of the bearing, the centrifugal force and lift generated by the rotation of the propeller acting on the counterweight, forcing the sheet spring to produce tensile deformation and torsional deformation at the same time, and driving the counterweight to move outward and twist, and further driving the propeller blade root to rotate synchronously, to realize one-way change of the pitch angle with the rotation speed.

[0007] Further, the counterweight is rigidly connected with the blade root, so that the blade, the counterweight and the leaf spring form a same torsional rigid body, and the torsional angle of the leaf spring is one-to-one corresponding to the pitch angle.

[0008] Further, the counterweight is made of a material that provides maximum centrifugal force in a limited volume.

[0009] Further, the tensile-torsional coupling leaf spring is a high-strength single-piece structure with a thickness of 1.5 mm, so as to ensure that the tensile-torsional stiffness is in a predetermined range.

[0010] Further, the tensile-torsional coupling leaf spring is made of carbon fiber sheet, so as to reduce the moment of inertia.

[0011] Further, the tensile-torsional coupling leaf spring is made of rubber elastomer, so as to improve the torsional flexibility.

[0012] Further, the counterweight is replaced by a centrifugal pendulum, the pendulum axis of the centrifugal pendulum is connected with the input end of the gear set, and the change of the swing angle directly drives the gear set to change the pitch, so as to eliminate the sliding friction.

[0013] Further, a damper is further included, one end of the damper is connected with the centrifugal pendulum, and the other end of the damper is connected with the hub, so as to suppress the high-speed swing.

[0014] Further, the counterweight is made of carbon steel and has a hollow structure.

[0015] The application also provides an adaptive variable pitch method of the adaptive variable pitch mechanism, and the method comprises the following steps:

[0016] Step 1, the tensile-torsional coupling leaf spring is fixed at both ends with the hub and the counterweight, so as to form a pre-tensioned and pre-torsional elastic loop;

[0017] Step 2, the bearing and the shaft sleeve are assembled, and only the radial sliding and circumferential rotation degrees of freedom are reserved between the bearing, the shaft sleeve and the counterweight;

[0018] Step 3, the blade root is rigidly connected with the counterweight, so as to ensure that the blade, the counterweight and the tensile-torsional coupling leaf spring are synchronously torsioned;

[0019] Step 4, when the propeller rotates, the centrifugal force and the lift force synchronously increase, so as to drive the counterweight to move outward and be torsioned, the tensile-torsional coupling leaf spring reaches a new force balance under the tensile-torsional coupling effect, and the blade root is synchronously rotated, so as to realize that the pitch angle is unidirectionally increased with the rotation speed;

[0020] Step 5, the pitch angle is checked at the maximum design rotation speed, if the target value is not reached, the initial pre-torsion angle of the tensile-torsional coupling leaf spring or the mass of the counterweight is adjusted, and step 4 is repeated until the checking is qualified.

[0021] Beneficial effects:

[0022] The self-adapting variable pitch mechanism is driven by centrifugal force without external energy input, has simple structure and light weight, can automatically adapt to different flight working conditions, automatically matches the pitch angle and the rotating speed, improves the aerodynamic efficiency under different working conditions, avoids over-regulation through the pull-torsion coupling design, ensures the regulation accuracy, and is suitable for the fields of unmanned aerial vehicles and the like. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 An assembly principle diagram of the self-adapting variable pitch mechanism;

[0024] Figure 2 A working principle flow chart of the self-adapting variable pitch mechanism;

[0025] Figure 3 A structure diagram of the self-adapting variable pitch mechanism;

[0026] Figure 4 A sectional view of the self-adapting variable pitch mechanism.

[0027] Wherein, the reference signs are: a propeller shaft sleeve 1, a propeller hub 2, a pull-torsion coupling sheet spring 3, a propeller blade 4, a counterweight 5, and a bearing 6. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0029] As shown in Figure 3 , Figure 4 A self-adapting variable pitch mechanism of the present application includes a centrifugal force driving assembly, a pull-torsion coupling sheet spring 3, a propeller blade 4 and a propeller hub 2.

[0030] The centrifugal force driving assembly includes a counterweight 5, a bearing 6 and a propeller shaft sleeve 1. The counterweight 5 is connected to the pull-torsion coupling sheet spring 3 and slides and twists through the bearing 6 under the driving of the pull-torsion coupling sheet spring 3. The propeller hub 2 is arranged in the propeller shaft sleeve 1.

[0031] The pull-torsion coupling sheet spring 3 is made of high-strength steel sheet, one end of which is fixed to the counterweight 5, and the other end of which is connected to the hub 2, the pull-torsion coupling sheet spring 3 is subjected to tensile force and torsional force to produce torsional and tensile deformation when the propeller works; the root of the blade 4 is rigidly connected with the counterweight 5, and the hub 2 is installed on the engine.

[0032] Specifically, the self-adaptive variable pitch mechanism mainly relies on the lift generated by the blade 4 during rotation to change the pitch.

[0033] Specifically, the pull-torsion coupling sheet spring 3 is fixed at two ends to the counterweight 5 and the hub 2 respectively.

[0034] Specifically, the bearing 6 and the propeller shaft sleeve 1 are installed on the counterweight 5 to ensure that the counterweight 5 slides radially and twists without jamming;

[0035] Specifically, after the blade 4 is installed, it is necessary to check whether the pitch angle at the maximum rotating speed meets the standard.

[0036] Specifically, the counterweight 5 is made of carbon steel, and a hollow structure can be used to reduce the mass of the counterweight 5, or a solid structure and an increased length of the counterweight 5 can be used to increase the mass.

[0037] Specifically, the thickness of the high-strength steel is 1.5 mm.

[0038] Specifically, the pull-torsion coupling sheet spring 3 can be replaced by carbon fiber sheet to reduce weight, or can be replaced by rubber elastomer to increase flexibility.

[0039] As shown in Figure 1 The assembly process of the self-adaptive variable pitch mechanism is as follows: the two ends of the pull-torsion coupling sheet spring 3 are fixed to the hub 2 and the counterweight 5 respectively; the bearing 6 and the propeller shaft sleeve 1 are assembled to ensure that the counterweight 5 slides radially and twists without jamming under the limitation of the assembled bearing 6 on the inner wall of the propeller shaft sleeve 1; after the blade 4 is installed, it is necessary to check whether the pitch angle at the maximum rotating speed meets the standard.

[0040] As shown in Figure 2As shown, the working principle of the adaptive variable pitch mechanism of the present application is as follows: when the propeller rotates, the blade 4 and the counterweight 5 are subjected to centrifugal force, the counterweight 5 moves outward, and the sheet spring is subjected to tensile force; the higher the rotational speed, the greater the centrifugal force, and the greater the tensile force; at the same time, the lift generated by the rotation of the blade 4 causes the blade 4 to be subjected to a torsional force in the radial direction of the hub, and the torsional force is transmitted to the sheet spring through the counterweight 5; the higher the rotational speed, the greater the lift, and the greater the torsional force; under the coupling action of tensile force and torsional force, the sheet spring is subjected to tensile and torsional deformation and reaches equilibrium; at this time, the torsion of the sheet spring drives the counterweight 5 to twist, changing the pitch angle of the blade 4. The higher the rotational speed of the propeller, the greater the centrifugal force and the lift, and the greater the pitch angle adjustment range, realizing the rotational speed-pitch angle correspondence, thereby realizing adaptive adjustment based on rotational speed.

[0041] Those skilled in the art will readily understand that the above description is only the preferred embodiment of the present application and is not intended to limit the present application, and any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. An adaptive pitch mechanism, characterized by, The application relates to a propeller driven by centrifugal force, which can automatically match the pitch angle with the rotating speed, and comprises a centrifugal force driving component and a pull-torsion coupling sheet spring. The centrifugal force driving component comprises a counterweight, a bearing and a propeller shaft sleeve. The pull-torsion coupling sheet spring is fixed at one end of a propeller hub and at the other end of the counterweight, so that the elastic pull-torsion coupling between the counterweight and the propeller hub is maintained. The counterweight can only slide radially and rotate circumferentially relative to the propeller hub along the axis of the bearing. The centrifugal force generated by the rotation of the propeller and the lift force jointly act on the counterweight, so as to force the pull-torsion coupling sheet spring to simultaneously generate tensile deformation and torsional deformation, drive the counterweight to move outward and twist, and drive the root of the propeller blade to synchronously rotate, so as to realize the synchronous one-way change of the pitch angle with the rotating speed.

2. An adaptive pitch mechanism according to claim 1, characterized in that, The counterweight is rigidly connected with the root of the propeller blade, so that the propeller blade, the counterweight and the sheet spring form a same torsional rigid body, and the torsional angle of the sheet spring is one-to-one corresponding to the pitch angle.

3. A self-adapting pitch mechanism according to claim 1 or 2, characterized in that, The counterweight is made of a material which can provide the maximum centrifugal force in a limited volume.

4. A self-adapting pitch mechanism according to claim 1 or 2, characterized in that, The pull-torsion coupling sheet spring is a high-strength single sheet structure with a thickness of 1.5 mm, so as to ensure that the tensile-torsional rigidity is in a predetermined range.

5. A self-adapting pitch mechanism according to claim 1 or 2, characterized in that, The pull-torsion coupling sheet spring is made of carbon fiber sheet, so as to reduce the moment of inertia.

6. An adaptive pitch mechanism according to claim 1 or 2, characterized in that The pull-torsion coupling sheet spring is made of rubber elastomer, so as to improve the torsional flexibility.

7. An adaptive pitch mechanism according to claim 1, characterized in that, The counterweight is replaced by a centrifugal pendulum, the pendulum shaft of the centrifugal pendulum is connected with the input end of a gear set, and the change of the swing angle directly drives the gear set to change the pitch, so as to eliminate the sliding friction.

8. An adaptive pitch mechanism according to claim 7, characterised in that, Further comprising a damper, one end of the damper is connected with the centrifugal pendulum, and the other end of the damper is connected with the propeller hub, so as to inhibit the high-speed swing.

9. An adaptive pitch mechanism according to claim 1, characterized in that, The counterweight is made of carbon steel and has a hollow structure.

10. An adaptive pitch method of an adaptive pitch mechanism as claimed in claim 1, characterized by, The application further comprises the following steps: Step 1, fixing the pull-torsion coupling sheet spring at both ends of the propeller hub and the counterweight to form a pre-tensile pre-torsional elastic loop; Step 2, assembling the bearing and the propeller shaft sleeve, and only leaving the radial sliding and circumferential rotation freedom between the counterweight; Step 3, rigidly connecting the root of the propeller blade with the counterweight to ensure that the propeller blade, the counterweight and the pull-torsion coupling sheet spring are synchronously twisted; Step 4, when the propeller rotates, the centrifugal force and the lift force synchronously increase, drive the counterweight to move outward and twist, the pull-torsion coupling sheet spring reaches a new force balance under the tensile-torsional coupling effect, drives the root of the propeller blade to synchronously rotate, and realizes the one-way increase of the pitch angle with the rotating speed; Step 5, checking the pitch angle at the maximum design rotating speed, if the target value is not reached, adjusting the initial pre-torsional angle of the pull-torsion coupling sheet spring or the mass of the counterweight, and repeating step 4 until the check is qualified.

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