Vehicle Braking Control Device Differential Pressure Management
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Solution Overview
Problem
The existing vehicle braking control systems experience deterioration in brake feeling due to a decrease in pedal reaction force when brake fluid suction occurs, leading to reduced M/C pressure and ineffective brake pedal operation, especially during transitions between regenerative and hydraulic braking forces.
Innovation Solution
Incorporating a differential pressure control valve, a pump, and a motor to manage brake fluid pressure between the master cylinder (M/C) and wheel cylinder (W/C), with control mechanisms that adjust differential pressure to maintain hydraulic braking force and reduce M/C pressure suction, thereby enhancing brake pedal reaction force and feeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the pump significantly increases the pressurization amount to compensate for reduced regenerative braking force, then the hydraulic braking force is improved, but the brake pedal is sucked to the M/C side and the pedal reaction force is reduced
Solution Approach 1:
The control unit performs preliminary pressurization during the ineffective stroke period (before the M/C port closes) to pre-increase the W/C pressure. This preliminary action reduces the need for significant pressurization later when the driver maintains brake pedal depression, thereby preventing excessive brake fluid suction that would cause pedal suction and reduced pedal reaction force.
Solution Approach 2:
The control unit dynamically adjusts the pressurization amount based on the brake pedal stroke amount and the closing state of the M/C port. By making the pressurization amount variable rather than fixed, the system can optimize the balance between generating sufficient hydraulic braking force and minimizing brake fluid suction that would deteriorate brake feeling.
2Force
If the pump increases the W/C pressure by sucking out brake fluid from the M/C, then the hydraulic braking force is improved, but the M/C pressure is reduced and brake feeling deteriorates
Solution Approach 1:
The system performs preliminary pressurization during the ineffective stroke when the M/C port is still open, before significant brake fluid suction occurs. This timing strategy allows the system to build up W/C pressure while minimizing the impact on M/C pressure, thereby maintaining brake feeling while achieving the required hydraulic braking force.
Solution Approach 2:
The control unit utilizes the ineffective stroke period (when the brake pedal is being depressed but the M/C port has not yet closed) as a self-service opportunity to perform pressurization. This period naturally occurs during normal brake operation, allowing the system to prepare the hydraulic pressure without requiring additional driver input or external energy sources.
3Adaptability or versatility
If the amount of pressurization is increased during ineffective stroke to compensate for reduced regenerative braking force, then the switching between braking forces is improved, but the brake pedal suction and pedal reaction force reduction occur
Solution Approach 1:
The control unit performs preliminary pressurization during the ineffective stroke period to prepare the hydraulic braking force before the driver maintains constant brake pedal depression. This timing allows smooth transition from regenerative to hydraulic braking while minimizing the impact on pedal reaction force, as the significant pressurization occurs before the M/C port closes and brake fluid suction begins.
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 suppresses the deterioration in brake feeling by reducing brake pedal suction and maintaining hydraulic braking force, ensuring consistent braking performance during transitions between regenerative and hydraulic braking.
Implementation Method 1
a pump that sucks out brake fluid in an M/C in a state in which the differential pressure is provided by the differential pressure control valve, and increases the W/C pressure by discharging the brake fluid toward a W/C
Implementation Method 2
a differential pressure control valve that forms a differential pressure between an M/C pressure and a W/C pressure
Data Source
AI summary
Taking a stroke within a period from when an operation of a brake operating member is started to when a predetermined stroke operation is performed as an ineffective stroke in which the master cylinder pressure is not generated, a control means controls an amount of differential pressure formed by a differential control valve such that a hydraulic braking force that corresponds to a stroke of the brake operating member is generated during the ineffective stroke, and even after the stroke of the brake operating member exceeds the ineffective stroke, increases the wheel cylinder pressure by performing raising of the amount of differential pressure formed by the differential pressure control valve by a predetermined raising amount with respect to the amount of differential pressure during the ineffective stroke.