Electric Parking Brake Release Control Using Service Brake Back-Up
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Solution Overview
Problem
The existing vehicle brake mechanism fails to reliably release the parking brake force due to self-locking forces, frictional resistance, and output variations, leading to incomplete release operations.
Innovation Solution
The implementation of release control means that determine a release impossible state by monitoring motor current, perform back-up pressurization using the service brake to reduce load on the electric motor, and drive the motor in reverse to facilitate release, ensuring reliable release operations even with reduced motor output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If the EPB motor output is reduced to achieve size and cost reduction, then the motor size and cost are reduced, but the motor cannot overcome self-locking force and frictional resistance under certain conditions
Solution Approach 1:
The service brake hydraulic system acts as an intermediary to assist the EPB motor during release operations. When the motor current exceeds the threshold indicating high load conditions, the service brake is activated to apply back-up pressurization, which reduces the load on the motor and enables reliable release even with reduced motor output.
Solution Approach 2:
The control device performs preliminary detection of motor current before initiating the release operation. By detecting whether the motor current exceeds the threshold value, the system prepares and activates the service brake in advance to reduce the load on the motor, ensuring the release operation can succeed with the reduced motor output.
2Weight of stationary object
If the EPB motor output is reduced to achieve size and cost reduction, then the motor size and cost are reduced, but the motor cannot reliably release the parking brake force under all conditions
Solution Approach 1:
The service brake hydraulic system serves as a mediator that assists the underpowered motor during release operations. The control device activates the service brake when motor current indicates high load conditions, and the hydraulic pressure from the service brake reduces the frictional resistance, enabling the reduced motor to achieve reliable release.
Solution Approach 2:
The system changes the operating parameters by monitoring motor current and comparing it against a threshold value. When the current exceeds the threshold, the system activates the service brake to alter the load conditions, enabling the reduced motor output to achieve the necessary release force under high-load conditions.
3Reliability
If back-up pressurization is performed using service brake, then the load on the EPB motor is reduced and release operation becomes possible, but the system complexity increases
Solution Approach 1:
The service brake system is utilized for dual purposes: normal braking operations and back-up pressurization for EPB release. By making the service brake multi-functional, the system avoids adding dedicated pressurization equipment, thereby reducing the increase in system complexity while achieving reliable release operations.
Solution Approach 2:
The service brake system serves itself by being activated to assist the EPB release operation. The control device leverages the existing service brake hydraulic infrastructure to provide back-up pressurization, eliminating the need for separate assistance mechanisms and minimizing additional system complexity.
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 enables reliable release of the parking brake force by reducing frictional loads and motor load, improving durability and reducing power consumption, thereby ensuring consistent brake operation.
Implementation Method 1
the service brake that uses hydraulic pressure... the brake fluid pressure in a wheel cylinder is increased... a piston in the W/C is pressed
Implementation Method 2
an electric motor that rotates a friction-applying member... driving the electric motor to rotate in a reverse direction
Implementation Method 3
a friction-applying member... pressing a friction-applying member against a friction-applied member... frictional resistance of a self-locking portion
Data Source
AI summary
An electronic control device for controlling operations of an electric parking brake and a service brake: determines a release impossible state in which release operation cannot be performed, based on a fact that a motor current that is supplied to an electric motor of the electric parking brake during release control is maintained in a state of a locked rotor current; and performs, when the release impossible state is determined, back-up pressurization for pressing the piston by generating a brake fluid pressure in the wheel cylinder using the service brake and for pressing the friction-applying member against the friction-applied member.