Electric Drive Unit Central Brake Integration
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Solution Overview
Problem
Electric drive units in motor vehicles face challenges with high moment of inertia, limited regenerative braking capabilities, and high demands on braking systems due to high-speed electric motors, leading to complex and expensive brake technologies.
Innovation Solution
An electric drive unit with a central brake integrated into the transmission intermediate shaft, allowing optimal matching of speed and torque, and featuring a transmission gear with multiple gear stages, enabling a self-releasing service brake design that can handle high braking forces and reduce the need for elaborate braking systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If direct motor brakes are used on high-speed electric traction motors, then braking torque can be provided, but the braking system becomes too expensive for industrial mass production
Solution Approach 1:
A clutch is introduced as an intermediary component between the electric traction motor and the central brake. This clutch can disconnect the motor from the brake, allowing the brake to operate at reduced speeds when the motor is not directly coupled. This mediation enables the use of less expensive braking components while maintaining the required braking torque capability.
Solution Approach 2:
The braking system employs dynamic speed reduction through the clutch mechanism, allowing the brake to operate at variable speeds rather than the full motor speed. This dynamic adaptation enables the use of more cost-effective brake components that cannot withstand continuous high-speed operation, while still providing adequate braking torque when needed.
2Speed
If central brakes are positioned at the transmission output, then lower speeds are achieved, but the torques present require high forces from the brake actuator
Solution Approach 1:
The system dynamically adjusts the operating speed of the central brake through the clutch mechanism. By disconnecting the high-speed motor from the brake during braking operations, the brake operates at lower speeds that reduce the required actuator forces, making the braking system more efficient and less demanding on actuator components.
Solution Approach 2:
The operating parameters of the brake (speed and torque) are changed by introducing the clutch between the motor and brake. This allows the brake to operate in a different parameter regime (lower speed, reduced torque) compared to direct motor coupling, thereby reducing the forces required from the brake actuator while maintaining effective braking capability.
3Power
If electromechanical or electrohydraulic brakes are used, then braking torque can be controlled, but the brake size becomes relatively large compared to hydraulic brakes
Solution Approach 1:
The clutch serves as a mediator that allows the brake to operate under more favorable conditions (lower speed, reduced torque). This enables the use of more compact brake designs that would not be sufficient if directly coupled to the high-speed motor, while still achieving the required braking torque through the mechanical advantage of the speed reduction.
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 configuration simplifies the construction of central brakes, reduces the size and complexity of braking systems, and allows for efficient energy conversion during braking, while also enabling the use of electromechanical brakes and reducing installation space restrictions.
Implementation Method 1
coping with the high (compared to the internal combustion engine) moment of inertia of the electric traction motor. This torque has to be absorbed when the vehicle is decelerating
Implementation Method 2
braking torque can be provided by operating an electric traction motor as a generator
Implementation Method 3
dynamic braking, in which a separate electrical resistor is connected to the electric traction motor and converts the energy generated by the electric traction motor into heat
Implementation Method 4
The central brake is designed as a wet multi-disc brake
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to an electrical power unit (10) for driving at least two wheels (11) of a motor vehicle, which comprises an exclusively electrically drivable wheel axle (12), wherein the wheel axle (12) is connected to at least one electrical traction motor (13) for transferring a drive torque and a central brake (14) for transferring a braking torque, wherein a transmission (16) having at least two transmission stages (17, 20a, 20b) and at least one transmission intermediate shaft (18, 20) is arranged between the traction motor (13) and the wheel axle (12), wherein the central brake (14) is integrated in a transmission intermediate shaft (18, 30) of the transmission (16).