Electronic Parking Brake Backup Power for Safe-State Switching
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Solution Overview
Problem
Conventional electronic parking brake systems for commercial vehicles face issues with 'greypoint sticking' where the piston remains in an intermediate position, leading to potential braking force loss, especially when the driver is not in the cabin, risking the vehicle to run away.
Innovation Solution
A backup system that includes a detection unit for power failure, a storage device to store energy, a boost circuit for charging and discharging during vehicle standstill and motion, and a switch device to supply power to the electronic parking brake, ensuring it can switch to a safe state even during power failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electronic parking brake system uses a conventional power supply without backup, then the system structure remains simple, but the reliability deteriorates during power failure
Solution Approach 1:
The storage device (capacitor) is pre-charged during vehicle standstill through the boost circuit before power failure occurs. This preliminary energy storage ensures that sufficient power is available to actuate the solenoid valve and switch the parking brake to safe state when power failure is detected, without requiring complex real-time power management during emergency conditions.
Solution Approach 2:
The storage device acts as an intermediary energy buffer between the power supply unit and the electronic parking brake actuator. During normal operation, the boost circuit charges the storage device; during power failure, the storage device rapidly discharges to provide the high current needed by the solenoid valve, isolating the actuator from power supply fluctuations and failures.
2Reliability
If the boost circuit charges the storage device during standstill, then energy is available for power failure, but energy is wasted during vehicle motion
Solution Approach 1:
The charging control is made dynamic by monitoring vehicle motion state. The boost circuit activates to charge the storage device only when the vehicle is detected to be in standstill condition. When motion is detected, the charging operation is automatically suspended, allowing the system to adapt energy management strategy to actual operating conditions and avoid unnecessary energy consumption during vehicle motion.
3Speed
If the storage device rapidly discharges during power failure, then the solenoid valve can be actuated quickly, but the storage device capacity is depleted
Solution Approach 1:
The system operates in periodic cycles: during vehicle standstill, the boost circuit charges the storage device; during vehicle motion, charging is suspended; upon detecting power failure during standstill, the storage device rapidly discharges to actuate the solenoid valve. This periodic charging-discharging pattern ensures the storage device is replenished during normal operation and only depleted during emergency power failure events, maintaining system readiness without permanent capacity loss.
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 system ensures the parking brake can always be switched to a safe state, preventing unintended vehicle movement by rapidly actuating the solenoid valve with stored energy, maintaining safety even during power outages.
Implementation Method 1
a storage device (120) adapted to store sufficient electric power to perform a switch into the safe state
Implementation Method 2
at least one solenoid valve (70) being configured to adjust a pneumatic pressure in the EPB based on control input from the control unit (60)
Implementation Method 3
a relay valve (80) connected to a spring brake chamber at an outlet (84), which is either exhausted through an exhaust (82) (parked state) or is pressurized (drive state)
Data Source
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AI summary
A backup system (100) for an electronic parking brake, EPB, of a commercial vehicle to ensure a safe state even during electric power failure of a power supply unit (50) of the EPB, includes: a detection unit (110) for detecting the power failure; a storage device (120) for storing sufficient electric power to perform a switch into the safe state; a boost circuit (130) configured to charge the storage device (120) during standstill of the vehicle and to discharge the storage device (120) during motion of the vehicle; and a switch device (140) configured to supply the electric power of the storage device (120) to the EPB if the power failure is detected by the detection unit (110).