Electric Parking Brake Control Device Motor Current Timing
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Solution Overview
Problem
Existing electric parking brake systems face challenges in maintaining braking force due to thermal expansion of brake pads and disc rotors, leading to inefficient power consumption and inaccurate timing for re-driving the electric motor, resulting in reduced braking force and increased power consumption.
Innovation Solution
An electric parking brake control device that measures motor current supply time and adjusts waiting times between re-clamp operations based on this measurement to ensure consistent braking force, using a current supply unit, supply time measurement unit, waiting time setting unit, and control unit to optimize motor current supply and re-clamp timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric motor is re-driven at regular time intervals to compensate for braking force loss, then the braking force can be maintained, but electric current is uselessly supplied when braking force does not decrease much, degrading power consumption efficiency
Solution Approach 1:
The patent applies dynamics by making the waiting time between motor re-drives variable rather than fixed. The control device dynamically adjusts the waiting time based on the measured motor current supply time from previous operations. When the motor requires longer supply time to reach target current, indicating higher pad temperature and greater braking force loss, the waiting time is shortened. Conversely, when supply time is shorter, waiting time is extended or re-drives are terminated, optimizing power consumption while maintaining braking force.
Solution Approach 2:
The patent implements feedback by measuring the motor current supply time from previous re-clamp operations and using this measurement to determine the waiting time for subsequent operations. The control device continuously monitors the actual current supply time, compares it against predetermined thresholds, and adjusts the waiting time accordingly, creating a closed-loop control system that adapts to changing brake component temperatures.
2Productivity
If the temperature of the pad is estimated based on vehicle state to determine re-drive timing, then re-clamp operations can be scheduled, but the temperature estimation is inaccurate due to various affecting factors, resulting in inappropriate re-drive timing
Solution Approach 1:
The patent uses motor current supply time as an intermediary parameter to indirectly measure pad temperature. Instead of directly estimating temperature from unreliable vehicle state parameters, the system measures the time required for the motor to reach target current, which serves as a more accurate proxy for pad temperature. This intermediary measurement provides a reliable basis for determining appropriate waiting times between re-clamp operations.
Solution Approach 2:
The patent replaces the unreliable thermal estimation approach with an electrical measurement approach. By substituting the thermal model (which estimates temperature from vehicle state) with an electrical measurement (motor current supply time), the system achieves more precise and reliable data for controlling re-clamp timing, eliminating the inaccuracies inherent in thermal estimation methods.
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 solution effectively maintains braking force by adjusting waiting times based on motor current supply time, reducing unnecessary power consumption and ensuring appropriate re-clamp timing, thereby improving the efficiency and reliability of the electric parking brake system.
Implementation Method 1
an electric parking brake (EPB) is employed, which drives an electric motor to generate or release a braking force
Implementation Method 2
the pad and the disc rotor included in the parking brake are thermally expanded by heat generated by braking
Data Source
AI summary
An EPB-ECU is an electric parking brake control device which generates a braking force by driving an electric motor to press pads and to a disc rotor. The EPB-ECU includes a current supply unit for supplying a motor current to the electric motor and stopping the supply of the motor current when the motor current reaches a predetermined target current value, a supply time measurement unit for measuring a supply time of the motor current, a waiting time setting unit for setting a waiting time from when the supply of the motor current is stopped to when the supply of the motor current is restarted next time on the basis of the measured motor current supply time, and a control unit for instructing the current supply unit to supply the motor current according to the set waiting time.