Power drive for coaxial rotor system

Abstract

The invention relates to aviation, specifically to the design of helicopter rotor drives, and can be used for rotary-wing aircraft with a coaxial rotor system, including ultralight ones The power drive of the coaxial rotor system is fixed between the upper and lower rotors of the aircraft on a stationary tubular axis, which is also the axis of rotation of the rotors. The power drive consists of at least two electric motors for the upper rotor drive and two electric motors for the lower rotor drive, arranged around the circumferences of the gear wheels of the upper and lower rotors respectively, rotor drive gears, and electrical wires. The electric motors driving one rotor jointly transmit torque to the gear wheel of the upper or lower rotor respectively. This provides increased safety and the possibility of use in ultralight aircraft due to reduced structural weight.

Description

BACKGROUND OF THE INVENTIONThe invention relates to the field of aviation, specifically to the design of helicopter rotor drives, and can be used for rotary-wing aircraft with a coaxial rotor system, including ultralight ones.In the last decade, there has been a rapid development of electric aircraft, associated with qualitative improvements in electric motor efficiency.Currently, electric motors have high specific power ratings while maintaining compact dimensions and simple design. This has led to electric motors being widely used in drones, paragliders, light aircraft, and they are being considered as an alternative to combustion engines in aircraft weighing up to several tons.The vast majority of applications use direct drive electric motor installations, where the rotor is attached directly to the electric motor rotor. On multicopters sometimes a combination of two such installations is made to improve safety, securing it through a console that fits between the rotors. If one of the electric motors fails then one of the rotors stops, while the remaining rotor can partially compensate for the loss of thrust and maintain the multicopter's controllability. It should be noted that such a combination cannot be used as a lifting system for a coaxial helicopter, as it only works as part of a multi-rotor system.Despite the fact that a direct drive power unit is the simplest and most efficient, its application area is limited by the characteristics of electric motors. The specific power of electric motors decreases at lower RPMs, and currently, electric motors can be effective for aviation at rotation speeds of approximately 2000 rpm and above. At the same time, the maximum rotation speed of a helicopter rotor is inversely proportional to its diameter, so currently it is practical to use direct drive with rotors not exceeding 2 meters in diameter. In the case of helicopters, the upper limit of rotation speed for a single-seat helicopter with a maximum takeoff weight of 250 kg does not exceed 1200-1500 rpm, and the rotor has a diameter of 3.5 meters or more. Therefor, to use electric motors for helicopters capable of carrying loads from 80-100 kg, it is necessary to reduce the rotation speed of the electric motor similar to power units with piston or gas turbine engines.At present, a large number of mass-produced coaxial scheme helicopters are used worldwide, with the weight of the lightest one exceeding 3200 kg, and the main manufacturer is JSC "Kamov". In different countries, there have been numerous attempts to create ultralight 1-2 seat coaxial helicopters, which had flying prototypes, but none of them became a commercially successful product, particularly due to the lack of power units of appropriate weight.A solution is known according to utility model patent No. 144 211 "TWO-ENGINE POWER UNIT FOR DRIVING TWO COAXIAL ROTORS," which presents a two-engine power unit for driving two coaxial rotors designed for use on medium-class attack unmanned aerial vehicles to create thrust for maintaining these aircraft in flight. For use in the power unit, an internal combustion piston engine is proposed (utility model patent No. 133568), which will allow placing two such engines along the axis of their crankshafts facing each other quite compactly (comparable to the dimensions of a single inline four-cylinder engine). The arrangement of two engines along the axis of their crankshafts facing each other makes it possible to obtain rotation of coaxial rotors in opposite directions, which provides the necessary thrust to maintain the aircraft in flight. The use of two engines ensures flight safety in case one of them fails. The use of cylindrical reducers, which are simpler to manufacture than planetary gears, accordingly reduces the cost of the power unit as a whole. The specified patent has entered the public domain.The proposed design of the power drive for a coaxial rotor system of a rotary-wing aircraft allows solving a number of problems of the coaxial rotor system, which is especially relevant for ultralight helicopters in the weight range of 100-1000 kg.SUMMARY OF THE INVENTIONThe technical result of the invention consists in improving safety, increasing economic efficiency by simplifying the design, as well as enabling the use for ultralight aircraft by reducing the weight of the structure.The technical result related to improving flight safety and enabling use for ultralight aircraft is achieved because the proposed system has less design complexity and a large number of redundant elements, which significantly affects the control process and flight of an ultralight helicopter. Typically, a coaxial helicopter control system that allows for safe landing in autorotation during power plant failure includes full rotor control through counter-rotating shafts and additional fin control. These devices add weight and complicate the design, which is critical in the field of ultralight aircraft. The proposed solution eliminates the need for some devices, easily implements the necessary power redundancy in case of failure of some electric motors, which allows for ensuring the required level of safety without using autorotation.The technical result related to increasing economic efficiency is associated with simplifying the design and reducing production costs. The proposed solution does not require mechanical energy input from outside the rotor system; electronic communications and control are supplied through a fixed structure. While in existing solutions, the transmission of mechanical energy to the rotors occurs from engines (gearboxes) located outside the rotors, either through coaxial shafts rotating one inside the other, or through an axial cardan joint with an exit between the rotors and subsequent distribution of rotation to two rotors.The technical result related to simplifying the design and reducing weight is also associated with the use of independent multi-stream power transmission to gears, while it is possible to use simplified principles of coaxial helicopter control due to power redundancy.Figure 1 shows a general view of the claimed power drive. Figure 2 shows a block diagram of the claimed version of the power drive for a coaxial rotor system (hereinafter referred to as PD CRS). In the presented version, the PD CRS consists of the following elements: mounting plates (1B, 1H), rotor drive electric motors (2B, 2H), gear wheels (3B, 3H), rotor drive gears (4B, 4H), rotor hubs (5B, 5H), tubular axis (6), electrical wires (7).DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTThe operation of the presented power drive in the presented version is carried out as follows: The electrical wires (7), laid inside the tubular axis (6), supply electrical energy to the coaxial rotor system in the area between the rotors, where the electric motors are located. The rotor drive electric motors, which are divided into upper rotor drive electric motors (2B) and lower rotor drive electric motors (2H), mounted on the upper (1B) and lower (1H) mounting plates respectively, which are fixed to the tubular axis, transmit rotation to the rotors through gear pairs consisting of upper (4B) and lower (4H) rotor drive gear, as well as the upper (3B) and lower (3H) gear wheels. The gear ratio of the gear pairs is selected based on the parameters of the electric motors and the rotor system.The minimum possible number of electric motors in the redundant drive is four, two for each rotor. The number of electric motors rotating one rotor is determined by the specific technical solution, depending on the characteristics of the electric motors, layout constraints, safety and redundancy requirements, optimization of the gear pairs' service life, and others. The torque is transmitted from the gear wheel to the rotors through the wheels or directly through the main rotor hubs, which rest on the tubular axis via bearings. The main rotor hubs (9), as well as possible systems for controlling the collective and cyclic pitch of the rotors and electric motor controllers (8) are not an integral part of the power drive under consideration.In the preferred embodiment, the calculation of the number of electric motors can be carried out as follows.Initial data:• Required power of one rotor system rotor - NR• Operating rotation frequency of the rotor - nRElectric motors with the following characteristics:• Continuous power of the electric motor - Nconst• Maximum power of the electric motor - Nmax• Rotation frequency of the electric motor - nmIt is required to maintain the operability of the drive, in case of failure of one electric motor.Then the calculation is carried out as follows:Required number of electric motors Zconst per rotor for continuous operation:Zconst ≥ NR / Nconst (1)Required number of electric motors per rotor Zr for meeting power redundancy requirements in case of failure of one electric motor is determined from the relation:(Zr - 1) × Nmax ≥ Zr × Nconst, which getZr ≥ Nmax / (Nmax - Nconst) (2)Then the required number of electric motors ZR per rotor:ZR = Max(Zconst; Zr) (3)Total number of electric motors:Zd = 2 × ZR (4)Required gear ratio:u = nm / nR (5)

Claims

1. A power drive for a coaxial rotor system comprising: at least two fixed upper electric motors with said electric motors driving the upper rotor, at least two fixed lower electric motors with said electric motors driving the lower rotor, and with said four electric motors are located along the circumferences of the gear wheels of the upper and lower rotors respectively, rotor drive gears; and electrical wires; and in which the with said electric motors driving one rotor jointly transmit torque to the gear wheel of the upper or lower rotor respectively, and which is mounted between the upper and lower rotors of an aircraft on a fixed tubular axis, which is also the axis of rotation of the rotors.

2. The power drive as recited in claim 1, in which two mounting plates are used for mounting the electric motors.

3. The power drive as recited in claim 1, in which the transmission of rotation from the gear wheels is carried out by means of hubs.

4. The power drive as recited in claim 1, in which the output shafts of the electric motors of the upper rotor are directed upward towards the upper rotor, and the output shafts of the electric motors of the lower rotor are directed downward.

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