Electrified Drivetrain Downhill Braking With Speed-Dependent Generator Torque
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Solution Overview
Problem
Existing electrified drivetrains for work machines face challenges in applying sufficient regeneration and braking torque at high speeds, leading to unintended acceleration when traveling downhill, which can result in excessive speeds and potential damage to the electric motor or brake system.
Innovation Solution
The method involves driving an electric motor coupled to a work machine's wheel, counteracting acceleration torque with generator torque in generator mode, and applying brakes automatically to reduce motor speed until the maximum generator torque matches or exceeds the acceleration torque, thereby preventing further acceleration and reducing the need for continuous use of mechanical brakes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the electric motor operates in generator mode at high speeds to provide regeneration torque, then energy recovery is improved, but the regeneration torque becomes insufficient to prevent unintended acceleration downhill
Solution Approach 1:
The patent combines the electric motor's generator mode with the mechanical friction brake system to create a hybrid braking system. The control unit coordinates both systems so that the friction brake provides additional braking torque when the electric motor's regeneration torque is insufficient at high speeds, while still allowing energy recovery through the generator mode.
Solution Approach 2:
The control unit dynamically adjusts the braking torque of the friction brake based on the operating conditions, particularly the speed of the work machine. At high speeds where regeneration torque is insufficient, the friction brake is activated to provide the necessary additional torque, and the control unit continuously monitors and adjusts the braking parameters to maintain safe speed control.
2Reliability
If the service or parking brake is continuously actuated to prevent acceleration downhill, then speed control is improved, but the brake system may be damaged due to prolonged actuation
Solution Approach 1:
The patent merges the electric motor's regenerative braking capability with the mechanical friction brake system. This combination allows the system to distribute the braking load between the two systems, using the electric motor for energy recovery and the friction brake only when necessary, thereby reducing prolonged actuation of the service or parking brake.
Solution Approach 2:
The patent replaces continuous mechanical brake actuation with a coordinated hybrid system that uses electric motor regeneration primarily and mechanical friction braking only when necessary. This substitution reduces the duration and intensity of mechanical brake actuation, preventing damage while maintaining speed control reliability.
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 approach ensures safe control of the work machine's speed during downhill travel by enhancing generator torque through reduced motor speed, minimizing wear on mechanical brakes, and preventing excessive speeds, thus maintaining drivetrain efficiency and safety.
Implementation Method 1
the electric motor in generator mode, a generator torque counteracting said acceleration torque
Implementation Method 2
applying brakes in an automated manner when the work machine accelerates as a result of the downhill force
Data Source
AI summary
A method for operating an electrified drivetrain for a work machine, including driving an electric motor of the drivetrain being drivingly coupled to at least one wheel of the work machine, the work machine being subjected to a downhill force when traveling downhill, the downhill force bringing about an acceleration torque on the work machine. The method further includes counteracting the acceleration torque with a generator torque of the electric motor in generator mode, a maximum generator torque being dependent on an actual motor speed of the electric motor, and applying brakes in an automated manner when the work machine accelerates as a result of the downhill force. The brakes being applied reduces the actual motor speed until the maximum generator torque at a reduced actual motor speed is at least the same as the acceleration torque.