Power drive for coaxial rotor system

Abstract

The present application relates to the field of aviation, in particular to the structural design of a helicopter rotor driving device, which can be applied to a rotor aircraft with a coaxial rotor system, including an ultralight aircraft. The power driving device of the coaxial rotor system is integrally installed on a fixed tubular shaft between the upper rotor and the lower rotor of the aircraft, which simultaneously serves as the rotation axis of the rotors. The power driving device is composed of at least two motors for driving the upper rotors, at least two motors for driving the lower rotors, rotor driving gears, and electric wires. The four motors are arranged along the circumferences of the upper rotor gear rings and the lower rotor gear rings, respectively. The motors driving the same rotor cooperatively transmit torque to the corresponding upper rotor gear ring or lower rotor gear ring. The present application realizes the improvement of safety by reducing the structural self-weight, and has the feasibility of being used on ultralight aircrafts.

Description

Technical Field

[0001] This invention relates to the field of aviation, specifically to the structural design of a helicopter rotor drive device, which can be applied to rotorcraft with coaxial rotor systems, including ultralight aircraft. Background Technology

[0002] Over the past decade, thanks to the improvement in motor efficiency, electric aircraft have developed rapidly.

[0003] Current electric motors have high specific power parameters, as well as a compact structure and simple design, which makes them widely used in the fields of drones, paragliders, and light aircraft. They are also regarded as a replacement for internal combustion engines in aircraft with takeoff weights of several tons.

[0004] Most existing applications employ a direct-drive motor system, where the rotor is directly mounted on the motor rotor. In multirotor aircraft, sometimes two direct-drive systems are combined and mounted on a cantilever support between the rotors to improve safety. When one motor fails, the corresponding rotor stops operating, and the remaining rotor can partially compensate for the thrust loss, maintaining the multirotor aircraft's maneuverability. However, it's important to note that this type of combined structure cannot be used as a lift system for coaxial helicopters; it can only operate within the framework of a multirotor system.

[0005] Although direct-drive power units have the simplest structure and highest efficiency, their applicability is still limited by the characteristics of the motor itself. The specific power of a motor decreases as the speed decreases; currently, motors suitable for aviation applications operate at speeds above approximately 2000 rpm. Furthermore, the maximum operating speed of a helicopter rotor is inversely proportional to its diameter; therefore, current direct-drive solutions can only be used with rotors no larger than 2 meters in diameter. For single-seat helicopters with a maximum takeoff weight of 250 kg, the maximum operating speed of the rotor is no more than 1200-1500 rpm, and the rotor diameter is generally over 3.5 meters. Therefore, to apply a motor to a helicopter capable of carrying a load of 80-100 kg, the motor's output speed must be reduced, similar to piston or gas turbine engine power units.

[0006] Currently, a large number of coaxial helicopters are in mass production and in use worldwide, with the lightest model having a takeoff weight exceeding 3200 kg. The mainstream manufacturer is Kamov JSC. Several countries have attempted to develop ultralight coaxial helicopters with 1-2 seats, and some designs have even produced test-flown prototypes. However, due to the lack of power units suitable for their weight, none of them have ultimately achieved commercialization.

[0007] The existing known solution is Utility Model Patent No. 144211, "Dual-Engine Power Unit for Driving Two Coaxial Rotors," which discloses a dual-engine coaxial rotor drive power unit adapted to a medium-sized attack UAV, providing thrust to sustain flight. This power unit uses a piston internal combustion engine (corresponding to Utility Model Patent No. 133568), with two engines arranged facing each other along the crankshaft axis, achieving an overall compactness comparable to a single inline four-cylinder engine. The structure of the two engines facing each other along the crankshaft axis drives the coaxial rotors to rotate in opposite directions, providing the thrust required for flight; the dual-engine configuration also ensures flight safety in the event of a single engine failure. The cylindrical reducer used in this solution is less difficult to manufacture than planetary gears, reducing the overall manufacturing cost of the power unit. The aforementioned patent is currently in the public domain.

[0008] The proposed power drive structure for coaxial rotor systems can solve a series of existing problems of coaxial rotor systems, and is especially suitable for use in ultralight helicopters with a weight range of 100-1000kg. Summary of the Invention

[0009] The technical effects of this invention are reflected in the following aspects: by simplifying the structure, safety and economy are improved, and by reducing the structural weight, the feasibility of its use in ultralight aircraft is realized.

[0010] The technical effects related to improved flight safety and adaptability to ultralight aircraft are achieved by reducing system structural complexity and incorporating numerous redundant components. These two characteristics significantly impact the control procedures and flight safety of ultralight helicopters. Typically, coaxial helicopters require a full-range rotor control mechanism with a counter-rotating axis and an additional tail control mechanism to ensure safe landing in the event of power unit failure, relying on autorotation. These components increase overall weight and structural complexity, a problem particularly pronounced in the ultralight aircraft field. The solution proposed in this invention eliminates some of these components, conveniently achieving the required power redundancy in the event of partial motor failure, and meeting the required safety level without relying on autorotation.

[0011] The technological benefits related to improved economic efficiency stem from structural simplification and reduced production costs: This solution eliminates the need for external mechanical power input to the rotor system, requiring only the transmission of electrical and control signals through a fixed structure; while existing solutions require the mechanical energy output from the externally mounted engine (gearbox) to be transmitted to the rotor either through a nested coaxial drive shaft or through an axial universal joint extending out of the rotor area before distributing the rotational power to the two rotors.

[0012] The technical effects related to simplified structure and reduced weight also stem from the use of an independent multi-path power transmission structure to transmit power to gears. At the same time, relying on the power redundancy characteristics, a simplified coaxial helicopter control principle can be adopted. Attached Figure Description

[0013] Figure 1 An overall view of the power drive unit for which protection is required is shown; Figure 2 A schematic block diagram of the claimed coaxial rotor system power drive unit (hereinafter referred to as PD CRS) is shown.

[0014] In the illustrated embodiment, the PD CRS includes the following components: mounting plate (IB, IH), rotor drive motor (2B, 2H), gear ring (3B, 3H), rotor drive gear (4B, 4H), rotor hub (SB, SH), tubular shaft (6), and wire (7). Detailed Implementation

[0015] The operating procedure of this power drive device is as follows: Electrical energy is transmitted to the coaxial rotor system area between the rotors via wires (7) running inside the tubular shaft (6), where the motor is located. The rotor drive motor is divided into an upper rotor drive motor (2B) and a lower rotor drive motor (2H), which are respectively mounted on the upper mounting plate (1B) and the lower mounting plate (1H) fixed to the tubular shaft. The rotational power is transmitted to the rotors through a gear pair consisting of the upper rotor drive gear (4B), the lower rotor drive gear (4H), and the upper gear ring (3B) and the lower gear ring (3H). The transmission ratio of the gear pair is selected according to the motor parameters and the rotor system parameters.

[0016] The minimum number of motors available under redundant drive configuration is 4, with 2 configured for each rotor; the total number of drive motors for a single rotor can be adjusted according to the specific technical solution, taking into account factors such as motor characteristics, layout limitations, safety and redundancy requirements, and gear pair service life optimization indicators. The torque of the gear ring is transmitted directly to the rotor through the wheel body, or it can be transmitted through the main rotor hub, which is supported on a tubular shaft by bearings. The main rotor hub (9), rotor collective pitch and cyclic pitch control system, and motor controller (8) are not components of this power drive device.

[0017] In this preferred embodiment, the method for calculating the number of motors is as follows.

[0018] Initial parameters: Power required for a single rotor —

[0019] Rotor operating speed —

[0020] Motor characteristic parameters: Continuous output power of motor —

[0021] Maximum output power of the motor —

[0022] Motor speed —

[0023] Design requirement: The drive unit should still be able to operate normally after any motor fails.

[0024] Calculation process: Number of motors required for a single rotor to meet continuous operation requirements

[0025] (1) The number of motors required for a single rotor to meet the power redundancy requirements after the failure of a single motor. From the relation The derivation yields (2) The final number of motors required for a single rotor

[0026] (3) Total number of motors in the whole machine (4) Required transmission ratio (5)

Claims

1. A power drive device for a coaxial rotor system, comprising: At least two fixed upper motors are provided for driving the upper rotor. At least two fixedly mounted lower motors are used to drive the lower rotor. The four motors are arranged circumferentially along the upper rotor gear ring and the lower rotor gear ring, respectively. Rotor drive gear; And electrical wires; Among them, each of the motors driving the same rotor cooperates to transmit torque to the corresponding upper rotor gear ring or the lower rotor gear ring; The power drive unit is integrally mounted on a fixed tubular shaft between the upper rotor and the lower rotor of the aircraft, and the fixed tubular shaft also serves as the rotation axis of the rotor.

2. The power drive device for a coaxial rotor system according to claim 1, characterized in that, Two mounting plates are used to mount the motor.

3. The power drive device for a coaxial rotor system according to claim 1, characterized in that, The gear ring outputs rotational power through the propeller hub.

4. The power drive device for a coaxial rotor system according to claim 1, characterized in that, The output shaft of the motor of the upper rotor is arranged toward the upper rotor, and the output shaft of the motor of the lower rotor is arranged toward the lower rotor.

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