Electric Parking Brake Control Apparatus Sensor Failure Handling
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Solution Overview
Problem
The existing electric parking brake mechanism fails to prevent excessive braking force application when the wheel speed sensor fails, leading to incorrect calculation of the vehicle's running state, resulting in inappropriate braking force application.
Innovation Solution
A brake control apparatus with a pressing member and a control portion that adjusts the thrust force of the pressing member at a lower time rate of change when the vehicle's running state cannot be calculated, using an electric motor and a pressing member holding mechanism to manage the braking force effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the existing electric parking brake mechanism is activated based on wheel speed sensor data, then the braking force can be controlled according to vehicle running state, but when the wheel speed sensor fails, the system cannot detect slip rate and applies excessive braking force
Solution Approach 1:
The control portion dynamically adjusts the thrust force of the pressing member based on whether the running state can be calculated. When wheel speed sensor data is unavailable, the system transitions from normal braking control to a restricted mode where the thrust force changes at a lower time rate of change, preventing excessive braking force application while maintaining basic braking functionality.
Solution Approach 2:
The system changes the control parameter of thrust force rate of change based on the availability of running state data. When the wheel speed sensor fails and running state cannot be calculated, the control portion imposes a lower time rate of change on the thrust force, effectively limiting the maximum braking force that can be applied and preventing wheel locking.
2Productivity
If the control portion rapidly increases thrust force for quick braking response, then braking efficiency is improved, but when running state is unknown, this causes wheel locking and loss of control
Solution Approach 1:
The control portion dynamically adjusts the thrust force increase rate based on the availability of running state information. When the running state can be calculated from wheel speed sensors, the system allows rapid thrust force increase for efficient braking. When the running state cannot be calculated, the system automatically reduces the thrust force increase rate to maintain stability and prevent wheel locking.
Solution Approach 2:
The control portion changes the time rate of change parameter of the thrust force based on the running state calculation availability. This parameter adjustment ensures that when sensor data is unavailable, the thrust force increases more gradually, maintaining braking force stability within safe limits while still providing responsive braking capability.
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 solution effectively prevents or reduces excessive braking force application, ensuring stable braking even when the vehicle's running state cannot be determined, thereby improving braking force stability and preventing wheel locking.
Implementation Method 1
an electric motor as a brake apparatus mounted on a vehicle
Implementation Method 2
a braking member configured to press a braking target member rotating together with a wheel
Data Source
AI summary
A parking brake control apparatus 20 drives an electric motor 43B to advance a piston 39 according to an application request signal from a parking brake switch 19. The parking brake control apparatus 20 includes a running state detection portion that calculates a running state about whether a vehicle is running or stopped based on a wheel signal from a wheel speed sensor 18. When the running state cannot be calculated by the running state detection portion, the parking brake control apparatus 20 controls the electric motor 43B in such a manner that the thrust force of the piston 39 changes at a lower time rate of change than when the running state can be calculated.