Centrifugal Differential Locking for Uneven Wheel Torque Distribution
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Solution Overview
Problem
Modern vehicle drive systems with electric machines face challenges in achieving uneven torque distribution between wheels, particularly when one wheel is on a slippery surface, as conventional wheel brakes are omitted, making it difficult to implement differential locking effectively.
Innovation Solution
A differential system with a rotatable cage, driven gears, a compensating gear, and a flywheel mass that moves radially to actuate a clutch, allowing for adjustable locking levels based on rotational speed, enabling high locking at high speeds and low locking at low speeds, mimicking an open differential for tight turning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wheel brakes are used to achieve uneven torque distribution, then torque can be effectively distributed to wheels on slippery surfaces, but the device complexity increases and wheel brakes cannot be omitted in modern electric vehicle drive systems
Solution Approach 1:
The patent combines the braking function with the differential locking function by integrating a clutch mechanism into the differential assembly. The clutch can lock the differential to achieve uneven torque distribution, replacing the need for separate wheel brakes in certain applications. This merging of functions reduces overall system complexity while maintaining the ability to handle slippery surface conditions.
Solution Approach 2:
The differential assembly is designed with multi-functionality, serving both as a torque distributing mechanism and a braking mechanism. The clutch mechanism within the differential can engage to lock the differential, providing the torque distribution function traditionally associated with wheel brakes. This universal design allows the same component to perform multiple functions, reducing the need for separate braking systems.
2Reliability
If a differential locking mechanism is implemented to achieve uneven torque distribution, then torque can be effectively distributed, but the ease of operation deteriorates due to automatic engagement at high speeds
Solution Approach 1:
The differential locking mechanism is designed to operate automatically based on operating conditions rather than requiring manual intervention. The clutch engages and disengages based on the rotational speed difference between the output shafts, automatically providing differential locking when needed and open differential operation when appropriate. This self-service mechanism eliminates the need for manual control while maintaining reliable torque distribution.
Solution Approach 2:
The differential locking mechanism incorporates feedback through the rotational speed difference between the two output shafts. When a significant speed difference is detected (indicating one wheel is slipping), the clutch automatically engages to lock the differential and redistribute torque. When the speed difference decreases (indicating both wheels have traction), the clutch disengages to allow free differential operation. This feedback mechanism ensures reliable torque distribution without manual intervention.
3Stability of the object's composition
If the differential is locked at high rotational speeds, then vehicle stability is improved during cornering, but the adaptability decreases for low-speed maneuvers requiring open differential behavior
Solution Approach 1:
The differential locking mechanism is designed to be dynamic rather than static, automatically adjusting the locking level based on operating conditions. The clutch engagement is proportional to the rotational speed difference between the output shafts, providing partial or full locking as needed. This dynamic behavior allows the differential to adapt to varying driving conditions, maintaining vehicle stability at high speeds while preserving the ability to perform low-speed maneuvers requiring open differential operation.
Solution Approach 2:
The differential locking level is changed as a parameter based on the rotational speed difference between the output shafts. When the speed difference is large (high-speed cornering or slipping), the clutch engages to increase the locking level and improve stability. When the speed difference is small (low-speed maneuvering), the clutch disengages to decrease the locking level and allow free differential operation. This parameter-based control provides both stability and adaptability across different operating conditions.
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
This design achieves a stabilizing effect during high-speed cornering and on slippery surfaces by varying the locking level of the differential, enhancing vehicle stability without the need for wheel brakes.
Implementation Method 1
A flywheel mass is therefore mounted on the cage to be displaceable in a radial direction, i.e., perpendicularly to the first axis of rotation about which the cage is rotatable. At a high rotational speed of the cage, the flywheel mass is moved radially outwards, i.e., away from the first axis of rotation
Data Source
AI summary
A differential for a vehicle. The differential includes a cage, which is rotatable about a first axis of rotation and has a drive interface, a first driven gear, mounted in the cage to be rotatable about the first axis of rotation, a second driven gear, mounted in the cage to be rotatable about the first axis of rotation, a compensating gear, which is mounted in the cage about a second axis of rotation extending perpendicularly to the first axis of rotation and meshes with the first and the second driven gear, a flywheel mass, coupled to the cage and locked against rotation with respect to the first axis of rotation and displaceable in a radial direction perpendicularly to the first axis of rotation, and a clutch, which, as a result of an outward movement of the flywheel mass in the radial direction, is movable into a locking state.