Vehicle Control Device Switching Hydraulic to Electric Parking Brake
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Solution Overview
Problem
The existing vehicle control systems face challenges in maintaining reliable vehicle wheel braking during extended periods of inactivity, leading to potential discomfort for drivers due to unstable timing in canceling brake hold control and engaging frictional elements when starting, resulting in reduced starting performance and discomfort.
Innovation Solution
A vehicle control device that includes a neutral control unit, a brake hold control unit, and a switching control unit, which manage the engagement and disengagement of frictional elements and braking forces between hydraulic and electric parking brake systems to ensure smooth transitions and stable starting conditions by prioritizing the engagement of frictional elements before brake hold control cessation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brake hold control is executed using hydraulic brake device for a long period during vehicle stop, then braking force is maintained, but fluid pressure gradually decreases leading to unreliable braking state and increased energy consumption from electric pump pressurization
Solution Approach 1:
The system preliminarily switches from hydraulic brake device to electric parking brake device before fluid pressure depletion occurs, preventing the need for continuous electric pump operation and maintaining braking reliability without excessive energy consumption
2Loss of energy
If switching from hydraulic brake device to electric parking brake device is performed during brake hold control, then energy consumption is reduced and heat generation is minimized, but timing instability in canceling brake hold control and engaging frictional elements causes starting performance degradation
Solution Approach 1:
The frictional engagement element is preliminarily engaged before canceling brake hold control, ensuring that starting performance is not degraded by timing instability between these two operations
Solution Approach 2:
The system prepares the frictional engagement element in advance to cushion against potential starting performance issues that would arise from unstable timing in the coordination of brake release and engagement operations
3Speed
If both cancellation of electric parking brake device braking and engagement of frictional engagement element are performed simultaneously when driver requests vehicle start, then system response is efficient, but unstable timing between these operations reduces starting performance
Solution Approach 1:
The frictional engagement element is engaged in advance before the driver's start request is fully processed, ensuring that when the electric parking brake is released, the transmission is already ready to transmit torque effectively, eliminating starting performance degradation
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 configuration reduces driver discomfort and improves starting performance by ensuring the frictional engagement element is fully engaged before starting, minimizing overlapping operations and fluid pressure changes, thus maintaining a stable vehicle state during transitions.
Implementation Method 1
a hydraulic brake device provided at each of all vehicle wheels of the vehicle and providing braking force to each vehicle wheel by fluid pressure
Implementation Method 2
an electric parking brake device provided at each of at least some of all vehicle wheels and providing braking force to the at least some of the vehicle wheels by driving of an electric actuator
Implementation Method 3
an automatic transmission to which torque generated at the drive source is input, the automatic transmission having a frictional engagement element engaged upon starting of the vehicle
Data Source
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AI summary
A vehicle control device (a control unit 100) includes a neutral control unit (100b), a brake hold control unit (100c), and a switching control unit (100d) configured to switch, when a predetermined switching condition is satisfied during execution of brake hold control by the brake hold control unit (100c), application of braking force to at least a drive wheel by execution of the brake hold control to application of the braking force to at least some vehicle wheels by an electric parking brake device. The neutral control unit (100b) stops execution of neutral control upon switching by the switching control unit (100d).