Electric Parking Brake Actuation Timing for Brake Gap Fault Detection
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Solution Overview
Problem
In electric parking brake devices, abnormalities in the braking gap automatic adjustment means can lead to an excessively large gap between brake shoes and the brake drum, resulting in inadequate or delayed engagement of the parking brake state.
Innovation Solution
The electric parking brake device includes a control unit that determines the presence of abnormality in the braking gap automatic adjustment means by monitoring the application operation time of the electric actuator and the inrush current generated during operation, using predetermined time and current thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the braking gap automatic adjustment means operates abnormally, then the gap between brake shoes and brake drum becomes excessively larger, but the required parking brake force cannot be obtained or it takes time to obtain the parking brake state
Solution Approach 1:
The control unit performs preliminary abnormality determination by monitoring the application operation time of the electric actuator. Before the parking brake state is fully obtained, the system already detects if the adjustment means is abnormal by checking whether the actuator operation time exceeds a predetermined threshold, enabling early warning and preventive action.
Solution Approach 2:
The control unit establishes a feedback mechanism that continuously monitors the application operation time of the electric actuator and compares it against a predetermined threshold. When the operation time exceeds the threshold, the system determines abnormality in the braking gap automatic adjustment means, providing real-time feedback on system health.
2Reliability
If the application operation time of the electric actuator is monitored to determine abnormality, then the presence or absence of abnormality can be determined at the time of obtaining parking brake state, but the system complexity increases
Solution Approach 1:
The control unit performs multiple functions: it controls the electric actuator operation, monitors the application operation time, determines abnormality of the braking gap automatic adjustment means, and manages the overall parking brake control. By making the control unit multi-functional, the patent avoids adding separate dedicated monitoring devices, thus limiting the increase in system complexity.
3Reliability
If the inrush current detection is used for abnormality determination, then the abnormality can be detected during actuator operation, but the system requires additional current detection means
Solution Approach 1:
The control unit is designed to perform both control functions (controlling the electric actuator) and detection functions (detecting inrush current and determining abnormality) through a single integrated device. This multi-functionality approach allows the system to gain abnormality detection capability without adding separate dedicated detection hardware.
Solution Approach 2:
The control unit utilizes the inrush current that naturally occurs during the normal operation of the electric actuator as a diagnostic signal. By monitoring this existing electrical phenomenon, the system performs self-diagnosis of the braking gap automatic adjustment means without requiring external testing equipment or additional sensors.
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 quick determination of abnormality in the braking gap automatic adjustment means during parking brake engagement, facilitating timely maintenance and differentiating between normal and abnormal inrush currents.
Implementation Method 1
when a detection value by the current detection means of an inrush current generated in response to the start of the operation of the electric actuator has exceeded a predetermined current threshold
Data Source
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AI summary
Provided is an electric parking brake device in which a drum brake includes braking gap automatic adjustment means and a parking brake lever, and the operation of an electric actuator that drives the parking brake lever is controlled by a control unit. When an application operation time of the electric actuator (38) by the time when a parking brake state is obtained has exceeded a predetermined application operation end determination time (T2), the control unit (C) determines that the braking gap automatic adjustment means (18) is abnormal. With this configuration, at the time of obtaining the parking brake state, the presence or absence of abnormality in the braking gap automatic adjustment means can be determined.