Rotorcraft Drive Unit with Tiltable Propellers for Passive Lift Balance
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Solution Overview
Problem
Existing rotary-wing aircraft drive units are complex and costly, with systems for cyclically changing the angle of attack of rotor blades being intricate and costly.
Innovation Solution
A drive unit with two propellers rotating in opposite directions, each tiltable relative to their axis, and an electric drive module with a specific diameter-to-axial distance ratio, allowing passive adjustment of the angle of attack based on airflow velocity and lift imbalance, eliminating the need for complex active systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a swashplate system is used to cyclically change the angle of attack of rotor blades, then the lift distribution is balanced during forward flight, but the device complexity and cost increase significantly
Solution Approach 1:
The patent removes the swashplate mechanism entirely from the rotor system. Instead of using a complex mechanical system to cyclically change blade angles, the invention uses rigid blades with fixed geometric angles combined with a tilted rotation axis that is offset from the vertical axis by a specific angle (typically 30-45 degrees). This extraction of the angle-changing mechanism simplifies the device while maintaining lift balance through the geometric configuration of the tilted axis.
Solution Approach 2:
The patent changes the geometric parameters of the rotor system by tilting the rotation axis at a specific angle relative to the vertical axis. This parameter change (the tilt angle) allows the rigid blades to experience cyclic angle of attack variations passively as they rotate, achieving lift balance without active mechanical control systems. The specific tilt angle is optimized to compensate for the lift difference between advancing and retreating blades during forward flight.
2Productivity
If variable-angle rotor blades with cyclical angle changes are implemented, then forward flight performance is improved, but the manufacturing cost and system complexity increase
Solution Approach 1:
The patent extracts the variable-angle mechanism from the blade design itself, using instead rigid blades with fixed angles. The angle variation is achieved not by changing blade geometry but by tilting the rotation axis, which is a simpler structural modification that reduces manufacturing complexity and cost.
Solution Approach 2:
Instead of making the blades variable in angle (complex), the invention inverts the approach by making the rotation axis tilted (simple). This inversion transfers the complexity from the blade structure to the support structure, where it is easier and cheaper to implement.
3Stability of the object's composition
If complex angle adjustment systems are used to compensate for lift differences, then flight stability is improved, but the device complexity and maintenance requirements increase
Solution Approach 1:
The patent implements a self-regulating system where the tilted rotation axis automatically provides the necessary angle of attack variations as the blades pass through different positions in their rotation. The system serves itself by using the rotation motion and gravity to create the lift-balancing effect, eliminating the need for external control mechanisms, actuators, or complex adjustment systems that would require maintenance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a simple, cost-effective design that passively adjusts the angle of attack, ensuring stable flight and reducing bending moments, while eliminating the need for a tail rotor and enabling efficient maneuverability in urban environments.
Implementation Method 1
the flow velocity resulting from the rotation of the rotor overlaps with the approach flow velocity resulting from the forward movement of the helicopter at the rotor or propeller blades
Implementation Method 2
the tilt axis causes the propeller to rotate about its longitudinal axis as it pivots around the tilt axis. This rotation results in a change in the angle of attack
Implementation Method 3
a first propeller and a second propeller which rotates in the opposite direction to the first propeller
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A drive unit (12) for a rotary-wing aircraft (10) is specified, having a first propeller (22) and a second propeller (24) which runs oppositely to and is axially spaced apart from the first propeller (22), having a first drive shaft (26) and a second drive shaft (28), which is arranged coaxially with respect to the first drive shaft (26), for the propellers (22, 24), wherein the two propellers (22, 24) are each rigid and are mounted so as to be tiltable relative to the axis of rotation of the drive shafts (26, 28) thereof, wherein the tilting axis (K) of each propeller (22, 24) runs in a plane perpendicular to the axis of rotation of the drive shafts (26, 28) and is oriented at a non-90° angle (α) relative to the longitudinal axis of the propeller (22, 24), and having an electric drive module (30) with at least two rotors (36) which are coupled to a respective one of the drive shafts (26, 28), wherein the ratio of the diameter of the propellers (22, 24) to the axial spacing between the propellers (22, 24) is between 4:1 and 12:1. A rotary-wing aircraft (10) having a drive unit is also specified.