Foldable quad-blade seesaw rotor structure

Abstract

This invention discloses a foldable four-bladed seesaw rotor structure, including blades 1, 2, 3, and 4, a power motor, an upper hub, and a lower hub. The upper hub, blades 1 and 3 form an upper seesaw assembly, and the lower hub, blades 2 and 4 form a lower seesaw assembly. The upper seesaw assembly is bolted to the power motor via a flange. The blades form a seesaw structure in pairs, releasing the degree of freedom in the flapping direction and avoiding hub fatigue caused by asymmetrical aerodynamic loads on a rigid rotor. The rotor has high solidity and uniform load distribution. The seesaw structure effectively reduces rotor excitation force and system vibration response. Damping struts ensure that the rotor does not collide with nearby structures due to abnormal operating conditions during flight, and also prevent impacts on people or objects below the rotor from random environmental loads when the rotor is stationary on the ground. During level flight, the blades fold in the direction of the airflow, effectively reducing drag and increasing flight time and range.

Description

Technical Field

[0001] This invention relates to a foldable four-bladed seesaw rotor structure, belonging to the field of four-bladed seesaw rotor technology. Background Technology

[0002] Currently, mainstream tiltrotor eVTOLs are divided into semi-tilt and full-tilt configurations. In the full-tilt configuration, all rotors can tilt; during vertical takeoff and landing, the rotors provide vertical thrust, and during level flight, they provide directional thrust. This configuration utilizes battery power most efficiently. In the semi-tilt configuration, only some rotors can tilt, with the remaining rotors providing thrust only during vertical takeoff. Compared to the full-tilt configuration, the semi-tilt configuration has higher technological maturity. During the tilt transition, the probability of safety accidents due to turbulence between the rotors and the incoming airflow is lower, resulting in lower transition flight risk and superior safety.

[0003] In a semi-tilt configuration, the rotor that only provides lift and does not participate in tilting is called a lift rotor. Common lift rotors include three-bladed, four-bladed, and five-bladed rotors rigidly connected to the hub. Because the blades and hub are rigidly connected, a large bending moment is generated at the blade root when subjected to asymmetrical aerodynamic loads from the advancing and retreating blades. This makes the hub prone to fatigue failure and has poor vibration resistance. During level flight, the lift rotor becomes a drag force, wasting energy and flight time, and shortening the range. Alternatively, some designs use two-bladed rotors in a seesaw configuration. While this releases the degree of freedom of the hub root and solves the hub fatigue problem, such lift rotors have low solidity, low aerodynamic efficiency, and significant noise issues. Summary of the Invention

[0004] The purpose of this invention is to provide a foldable four-bladed seesaw rotor structure to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: The present invention discloses a foldable four-bladed seesaw rotor structure, including blade No. 1, blade No. 2, blade No. 3, blade No. 4, a power motor, an upper hub, and a lower hub. The upper hub, blade No. 1, and blade No. 3 form an upper seesaw assembly, and the lower hub, blade No. 2, and blade No. 4 form a lower seesaw assembly. The upper seesaw assembly and the power motor are fixedly connected by bolts through a flange.

[0006] Preferably, the upper propeller hub is connected to the main shaft via a pin and an upper bushing, and the two ends of the left and right damping support rods are respectively connected to the double lugs on the upper propeller hub and the double lugs on the bushing.

[0007] Preferably, the left damping limiting support assembly consists of a left fisheye joint bearing, a right fisheye joint bearing, a central guide shaft, a rectangular cross-section spring, and an outer shell. The left and right fisheye joint bearings are installed at both ends of the outer shell, and the rectangular cross-section spring is fitted onto the central guide shaft inside the outer shell.

[0008] Preferably, the lower propeller hub consists of a left damping strut, a right damping strut, a lower seesaw structure bushing, a shoulder baffle, a lower bushing with triangular splines, and a locking mechanism. The lower seesaw structure bushing is fitted onto the outer diameter of the upper bushing. The protruding round shaft on the side wall of the lower seesaw structure bushing is connected to the lower propeller hub through the shoulder baffle. The lower seesaw structure bushing and the lower bushing with triangular splines transmit torque through the triangular splines. A slot is cut on the side wall of the splined sleeve, and bolts on both sides are used to axially position the splined sleeve and the lower seesaw structure bushing relative to each other. A locking mechanism is installed on the outer side of the lower bushing with triangular splines.

[0009] Preferably, the locking mechanism and the lower bushing with triangular splines form a ratchet and pawl drive, the lower bushing rotates synchronously with the main shaft, and the locking mechanism is fixedly connected to the stator of the power motor and remains stationary.

[0010] Preferably, a preloaded torsion spring is positioned and installed at the lower end of the lower bushing with triangular splines.

[0011] Preferably, the locking mechanism consists of a mounting base, a locking shaft, a shaft end mounting washer, a torsion spring, a pawl, and a washer. The mounting base and the pawl are positioned and installed. The mounting base is fixedly connected to the power motor. The locking shaft and the mounting base are fitted with a shaft hole. A torsion spring is sleeved on the locking shaft. The shaft end mounting washer and the washer are installed at the upper and lower ends of the locking shaft.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] The upper rotor hub is connected to the main shaft via a pin and an upper bushing. The upper bushing is connected to the upper rotor hub's double lugs via a left damping limit support assembly and a right damping limit support assembly. Blade 1 and blade 3 are fixedly connected to the rotor hub via two sets of hinged bolts. The main shaft, rotor hub, and bushing are connected to each other via pins. This connection only retains rotational motion around the pin axis and restricts freedom in other directions, thus forming a seesaw structure. The four blades form two sets of seesaws, and the motion of the two sets of seesaws is decoupled from each other and does not affect each other.

[0014] The upper shaft sleeve has two protruding shoulders on its lower end face, which are arranged opposite each other at a 180° phase on the circumference. The lower shaft sleeve also has two protruding shoulders on its upper end face, which are arranged opposite each other at a 180° phase on the circumference. Through the mutual contact of the upper and lower protruding shoulders, the torque transmitted from the power motor is transmitted from the shaft sleeve to the lower shaft sleeve. At this time, the rotor is in working state. When the upper shaft and the lower shaft sleeve rotate 90° relative to each other, the rotor is in the locked state.

[0015] The left damping limit support assembly consists of a left fisheye joint bearing, a right fisheye joint bearing, a central guide shaft, a rectangular section spring, and an outer shell. To prevent the blades from being subjected to random loads such as ground winds when parked on the ground, and thus from hitting other surrounding structures, two sets of damping limit support assemblies are arranged. The two damping struts are arranged symmetrically to achieve a balanced mass distribution and prevent abnormal vibration caused by mass imbalance in a single damping strut.

[0016] The lower rotor hub consists of a left damping strut, a right damping strut, a lower seesaw structure bushing, a front convex shoulder baffle, a rear convex shoulder baffle, a lower bushing with triangular splines, and a locking mechanism. The protruding round shaft on the side wall of the bushing is connected to the rotor hub through the front and rear convex shoulder baffles, retaining only the degree of freedom of rotor flapping and restricting other degrees of freedom. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the foldable four-bladed seesaw rotor structure of the present invention.

[0018] Figure 2 This is a schematic diagram of the mounting structure of the propeller hub of the present invention;

[0019] Figure 3 This is a schematic diagram of the structure of the damping limiting support component of the present invention;

[0020] Figure 4 This is a schematic diagram showing the composition and connection relationship of the lower seesaw structure of the lower propeller hub of the present invention;

[0021] Figure 5 This is a schematic diagram of the structure of the lower propeller hub of the present invention;

[0022] Figure 6 This is a schematic diagram of the partial connection relationship of the propeller hub in this invention;

[0023] Figure 7 This is a schematic diagram of the mounting structure of the upper bushing of the present invention;

[0024] Figure 8 This is a schematic diagram of the connection relationship of the locking mechanism of the present invention;

[0025] Figure 9 This is a schematic diagram of the locking mechanism of the present invention;

[0026] Figure 10 This is a schematic diagram illustrating the rotor deployment principle of the present invention;

[0027] Figure 11 This is a schematic diagram illustrating the principle of rotor folding in this invention.

[0028] In the diagram: 1. Blade No. 1; 2. Blade No. 2; 3. Blade No. 3; 4. Blade No. 4; 5. Power motor; 6. Upper hub; 7. Lower hub; 6.1. Bushing; 6.2. Main shaft; 6.3. Left damping limit support assembly; 6.4. Right damping limit support assembly; 6.5. Pin; 6.3.1. Left fisheye spherical bearing; 6.3.2. Right fisheye spherical bearing; 6.3.3. On the central guide shaft; 6.3.4. Rectangular cross-section spring. 6.3.5. Outer shell; 7.1. Left damping strut; 7.2. Right damping strut; 7.3. Lower seesaw structure bushing; 7.4. Front shoulder baffle; 7.5. Rear shoulder baffle; 7.6. Lower bushing with triangular spline; 7.7. Locking mechanism; 7.7.1. Mounting base; 7.7.2. Locking shaft; 7.7.3. Shaft end mounting washer; 7.7.4. Torsion spring; 7.7.5. Pawl; 7.7.6. Washer. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0030] like Figures 1-9 As shown, a foldable four-bladed seesaw rotor structure includes blade 1, blade 2, blade 3, blade 4, motor 5, upper hub 6, and lower hub 7. The upper hub 6, blade 1, and blade 3 form an upper seesaw assembly, and the lower hub 7, blade 2, and blade 4 form a lower seesaw assembly. The upper seesaw assembly and the motor 5 are fixedly connected by bolts through a flange.

[0031] The upper rotor hub 6 is connected to the main shaft 6.2 via pin 6.5 and upper bushing 6.1. The two ends of the left damping support rod 6.4 and the right damping support rod 6.3 are connected to the double lugs on the rotor hub 6 and the double lugs on the bushing 6.1, respectively. The blades 1 and 3 are fixedly connected to the rotor hub via two sets of hinged bolts. The main shaft 6.2, rotor hub, and upper bushing 6.1 are connected to each other via pin 6.5. This connection only retains rotational motion around the pin axis, restricting freedom in other directions, thus forming a seesaw structure. The four blades form two sets of seesaws, and the movements of the two sets of seesaws are decoupled and do not affect each other.

[0032] The left damping limiting support assembly 6.3 consists of a left fisheye joint bearing 6.3.1, a right fisheye joint bearing 6.3.2, a central guide shaft 6.3.3, a rectangular section spring 6.3.4, and an outer shell 6.3.5. The left fisheye joint bearing 6.3.1 and the right fisheye joint bearing 6.3.2 are installed at both ends of the outer shell 6.3.5. The rectangular section spring 6.3.4 and the two fisheye joint bearings are fitted inside the central guide shaft 6.3.3 inside the outer shell 6.3.5. The bearings restrict only 3 translational degrees of freedom, while the 3 rotational degrees of freedom are released. The length of the damping strut can be adjusted by the engagement length of the thread at the bearing rod end, which facilitates assembly.

[0033] The lower propeller hub 7 consists of a left damping strut 7.1, a right damping strut 7.2, a lower seesaw structure bushing 7.3, a front shoulder baffle 7.4, a rear shoulder baffle 7.5, a lower bushing 7.6 with triangular splines, and a locking mechanism 7.7. The lower seesaw structure bushing 7.3 is fitted onto the outer diameter of the upper bushing 6.1. The protruding round shaft on the side wall of the lower seesaw structure bushing 7.3 is connected to the lower propeller hub 7 through the front shoulder baffle 7.4 and the rear shoulder baffle 7.5. The lower seesaw structure bushing 7.3 and the lower bushing 7.6 with triangular splines transmit torque through triangular splines. A slot is cut on the side wall of the spline sleeve, and bolts on both sides are used to axially position the spline sleeve and the lower seesaw structure bushing 7.3 relative to each other. A locking mechanism 7.7 is installed on the outside of the lower bushing 7.6 with triangular splines. The upper bushing 6.1 has two protruding shoulders on its lower end face, arranged 180° apart on the circumference. The lower seesaw structure bushing 7.3 also has two protruding shoulders on its upper end face, arranged 180° apart on the circumference. Through the contact between the upper and lower protruding shoulders, the torque transmitted from the power motor is transferred from the upper bushing 6.1 to the lower seesaw structure bushing 7.3. At this time, the rotor is in working condition. When the upper bushing 6.1 and the lower seesaw structure bushing 7.3 rotate 90° relative to each other, the rotor is in a locked state. The raised circular shaft on the side wall of the bushing is connected to the rotor hub through the front protruding shoulder baffle 7.4 and the rear protruding shoulder baffle 7.5, which only retains the degree of freedom of rotor flapping and restricts other degrees of freedom.

[0034] The locking mechanism 7.7 and the lower bushing 7.6 with triangular splines form a ratchet and pawl drive. The lower bushing 7.6 rotates synchronously with the main shaft 6.2. The locking mechanism 7.7 is fixedly connected to the stator of the power motor 5 and remains stationary. In this way, the lower bushing 7.6 and the entire lower rotor hub can only rotate in one direction along the rotor shaft axis and cannot rotate in the opposite direction.

[0035] A preloaded torsion spring 7.6.1 is positioned at the lower end of the lower bushing 7.6 with triangular splines to prevent relative rotation between the main shaft 6.2 and the lower bushing 7.6.

[0036] The locking mechanism 7.7 consists of a mounting base 7.7.1, a locking shaft 7.7.2, a shaft end mounting washer 7.7.3, a torsion spring 7.7.4, a pawl 7.7.5, and a washer 7.7.6. The mounting base 7.7.1 and the pawl 7.7.5 are positioned and installed. The mounting base 7.7.1 is fixedly connected to the power motor 5. The locking shaft 7.7.2 is installed in a shaft hole with the mounting base 7.7.1. The torsion spring 7.7.4 is fitted on the locking shaft 7.7.2. The shaft end mounting washer 7.7.3 and the washer 7.7.6 are installed at the upper and lower ends of the locking shaft 7.7.2.

[0037] Specific usage instructions:

[0038] The working principle of the 4-bladed propeller seesaw: Because the upper hub is connected to the upper bushing and main shaft via a pin, and the blades are fixed to the hub via bolts, these two blades form a seesaw structure, swinging around the axis of the pin to create a flapping motion. Blades 2 and 4 are fixedly connected to the hub, and the hub is connected to the lower bushing via two shoulder baffles forming a revolute joint. Blades 2 and 4 rotate freely around the common axis formed by the two shoulder baffles, creating the flapping motion of the lower seesaw structure. The flapping motions of the two seesaw structures are independent and do not affect each other. Because of the added damping strut assembly, it ensures that there is no collision or interference with other aircraft structures when the aircraft is stationary on the ground or when the blades rotate abnormally.

[0039] Folding Paddle Lock Mechanism Principle: From Figure 10 work status Figure 11 The working principle of the folding and locking propeller state is explained as follows: After the flight control computer issues a propeller locking command, the power motor, based on the zero position specified by its own servo system encoder, rotates the lower seesaw rotor assembly, consisting of blades 2 and 4, the hub, and the lower bushing, to the direction of the airflow. Then, the flight control issues a command to rotate the power motor 90° in the opposite direction, causing the upper seesaw structure, consisting of blades 1 and 3, the hub, the bushing, and the shaft, to rotate in the opposite direction to the position of the airflow. Due to the action of the pawl in the locking mechanism, the rotation of the upper seesaw assembly will not cause frictional contact between the upper and lower seesaw assemblies, preventing the lower seesaw assembly, which is already aligned with the airflow, from rotating.

[0040] Upon arrival Figure 11 When all four blades of the upper seesaw are aligned with the airflow, the motor activates the electromagnetic brake, limiting the rotation of the upper seesaw assembly. The lower seesaw is limited by a shoulder at the top and simultaneously by the pawl of the locking mechanism rotating in the anti-return direction. This limits the lower seesaw assembly's movement to its two extreme positions at 90° rotation lock, ensuring... Figure 11 The reliability of the folding lock paddle.

[0041] If from Figure 11The position of the lock paddle Figure 10 In its operating state, when the flight control computer issues a command to the power motor, the power motor drives the upper seesaw structure, composed of blades 1 and 3, the hub, the bushing, and the main shaft, to rotate to the 90° open position. Due to the contact between the two protruding shoulders, the upper and lower blade assemblies rotate synchronously. This first transmits the power from the power motor to the upper blade assembly, and then, through the two protruding shoulders, transmits the power from the upper blade assembly to the lower blade assembly. The spline sleeve rotates synchronously with the lower blade assembly. A rotary motion in the drive direction of the ratchet and pawl is formed between the spline sleeve and the locking mechanism. The preloaded torsion spring and the torsion spring continuously force the ratchet on the spline sleeve and the pawl on the locking mechanism to be in the working position, ensuring the stability of the ratchet and pawl transmission. This ensures that... Figure 10 The stable operating state of the propeller blades shown will not be affected by external factors, thus ensuring flight safety.

[0042] To address the aforementioned drawbacks of multi-bladed rotors and seesaw-structure rotors, this invention provides a foldable seesaw-style four-bladed rotor structure, such as... Figure 10 As shown. The technical problems solved by this invention are:

[0043] 1) The four-bladed rotor has a seesaw structure between the blades, which releases the degree of freedom in the flapping direction and avoids hub fatigue caused by asymmetrical aerodynamic loads on rigid rotors; the rotor has a large solidity and the load is evenly distributed. The seesaw structure effectively reduces the excitation force on the rotor and reduces the vibration response of the system.

[0044] 2) During vertical takeoff and landing, the rotor deployment is... Figure 1 Rotation generates thrust; during initial flight, the rotor acts like... Figure 11 The fold shown is aligned with the direction of the incoming airflow, minimizing the frontal area, which effectively reduces flight drag, saves battery energy, and increases flight time and range. It also requires minimal storage space during relocation and transport.

[0045] 3) The arrangement of the damping struts ensures that during flight, the rotor will not collide with other nearby structures due to abnormal operating conditions, and also ensures that when the aircraft is parked on the ground, it will not be hit by random environmental loads that could cause people or objects to be struck below the rotor.

[0046] The above description is a preferred embodiment of the present invention. For those skilled in the art, any changes, modifications, substitutions, and variations made to the implementation methods without departing from the principles and spirit of the present invention will still fall within the protection scope of the present invention.

Claims

1. A foldable four-bladed seesaw rotor structure, characterized in that, It includes blade 1 (1), blade 2 (2), blade 3 (3), blade 4 (4), motor (5), upper hub (6), and lower hub (7). The upper hub (6) together with blade 1 (1) and blade 3 (3) forms an upper seesaw assembly, and the lower hub (7) together with blade 2 (2) and blade 4 (4) forms a lower seesaw assembly. The upper seesaw assembly and the motor (5) are fixedly connected by bolts through a flange.

2. The foldable four-bladed seesaw rotor structure according to claim 1, characterized in that: The upper rotor hub (6) is connected to the main shaft (62) via a pin (6.5) and an upper bushing (6.1). The two ends of the left damping support rod (6.4) and the right damping support rod (6.3) are respectively connected to the double ears on the upper rotor hub (6) and the double ears on the bushing (6.1).

3. The foldable four-bladed seesaw rotor structure according to claim 2, characterized in that: The left damping limiting support assembly (6.3) consists of a left fisheye joint bearing (6.3.1), a right fisheye joint bearing (6.3.2), a central guide shaft (6.3.3), a rectangular section spring (6.3.4), and an outer shell (6.3.5). The left fisheye joint bearing (6.3.1) and the right fisheye joint bearing (6.3.2) are installed at both ends of the outer shell (6.3.5). The rectangular section spring (6.3.4) is fitted inside the central guide shaft (6.3.3) of the outer shell (6.3.5).

4. The foldable four-bladed seesaw rotor structure according to claim 1, characterized in that: The lower propeller hub (7) consists of a left damping strut (7.1), a right damping strut (7.2), a lower seesaw structure bushing (7.3), a front shoulder baffle (7.4), a rear shoulder baffle (7.5), a lower bushing with a triangular spline (7.6), and a locking mechanism (7.7). The lower seesaw structure bushing (7.3) is fitted onto the outer diameter of the upper bushing (6.1). The protruding round shaft on the side wall of the lower seesaw structure bushing (7.3) passes through... The front shoulder baffle (7.4) and rear shoulder baffle (7.5) are connected to the lower propeller hub (7). The lower seesaw structure bushing (7.3) and the lower bushing with triangular splines (7.6) transmit torque through triangular splines. The spline bushing is slotted on the side wall and the spline bushing and the lower seesaw structure bushing (7.3) are axially positioned relative to each other by bolts on both sides. A locking mechanism (7.7) is installed on the outside of the lower bushing with triangular splines (7.6).

5. The foldable four-bladed seesaw rotor structure according to claim 4, characterized in that: The locking mechanism (7.7) and the lower bushing (7.6) with triangular spline form a ratchet and pawl drive. The lower bushing (7.6) rotates synchronously with the main shaft (6.2). The locking mechanism (7.7) is fixedly connected to the stator of the power motor (5) and remains stationary.

6. The foldable four-bladed seesaw rotor structure according to claim 4, characterized in that: A preloaded torsion spring (7.6.1) is positioned at the lower end of the lower bushing (7.6) with triangular splines.

7. The foldable four-bladed seesaw rotor structure according to claim 4, characterized in that: The locking mechanism (7.7) consists of a mounting base (7.7.1), a locking shaft (7.7.2), a shaft end mounting washer (7.7.3), a torsion spring (7.7.4), a pawl (7.7.5), and a washer (7.7.6). The mounting base (7.7.1) and the pawl (7.7.5) are positioned and installed. The mounting base (7.7.1) is fixedly connected to the power motor (5). The locking shaft (7.7.2) and the mounting base (7.7.1) are fitted with a shaft hole. The torsion spring (7.7.4) is fitted on the locking shaft (7.7.2). The shaft end mounting washer (7.7.3) and the washer (7.7.6) are installed at the upper and lower ends of the locking shaft (7.7.2).

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