Multi-Piston Master Cylinder for Slip Control Boost Braking
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Solution Overview
Problem
Electric-hydraulic braking systems face issues with pressure differentials and flow rate problems during urgent operations, particularly when secondary braking subsystems are actuated, and are susceptible to failure if isolation valves become inoperable or if hydraulic leaks occur, with multi-chamber master cylinders facing packaging constraints and gas entrapment issues.
Innovation Solution
A braking system utilizing a multi-piston and multi-chamber master cylinder with a specific housing configuration and secondary pistons to manage pressure and flow, including a high-pressure accumulator and electro-hydraulic pilot operated boost valve, which allows for controlled hydraulic boost and manual push-through operations, and incorporates a bleed valve system to purge entrapped gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation valves are used to allow manual push-through operation from master cylinder to brake actuators, then manual braking capability is provided during electrical or hydraulic failure, but the system becomes susceptible to failure if the isolation valves become inoperable or if hydraulic leaks occur
Solution Approach 1:
The patent removes the isolation valves from the hydraulic circuit between the master cylinder and brake actuators. Instead of using valves to control manual push-through operation, the system directly connects the master cylinder to the brake actuators through a simplified hydraulic path, eliminating the single point of failure associated with isolation valves while maintaining manual braking capability during electrical or hydraulic failures
Solution Approach 2:
The system incorporates a backup hydraulic path that is always available and does not depend on the operational status of isolation valves. By designing the circuit so that manual braking can occur directly from the master cylinder to the brake actuators without passing through potentially failed valves, the system provides beforehand protection against valve failure or hydraulic leaks
2Volume of moving object
If a multi-chamber and multi-piston master cylinder is used to optimize packaging constraints, then the system achieves compact size within the engine compartment, but gas may become entrapped in the segregated braking module which must be purged
Solution Approach 1:
The master cylinder is divided into multiple chambers with multiple pistons, each chamber being independently sealable. This segmentation allows gas to be trapped in isolated chambers rather than the entire system, enabling targeted purging of specific chambers while maintaining braking function in other chambers. The segregated design achieves compact packaging while managing gas entrapment through chamber-level isolation
Solution Approach 2:
The system includes a purging mechanism that allows entrapped gas to be removed from the braking module. By providing a dedicated purging path and mechanism, the system can discard the harmful gas bubbles from the hydraulic circuit, restoring proper braking function without requiring system disassembly or complex bleeding procedures
3Power
If electro-hydraulic braking system operates with secondary braking subsystems during urgent actuation, then braking performance is enhanced, but pressure differentials and flow rate issues occur
Solution Approach 1:
The master cylinder is designed to serve multiple functions: it provides hydraulic pressure for both normal braking operations and manual push-through operations during failures. The same master cylinder chambers and pistons that generate pressure during electro-hydraulic braking also enable manual braking, eliminating the need for separate pressure generation systems and reducing pressure differential conflicts between different braking modes
Solution Approach 2:
The patent introduces a direct hydraulic connection path that acts as an intermediary between the master cylinder and brake actuators, bypassing the electro-hydraulic control circuitry during manual operation. This intermediary path allows pressure to equalize more effectively between different parts of the system during urgent actuation, reducing pressure differentials and flow rate issues while maintaining enhanced braking performance
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 system provides reliable hydraulic boost and manual braking capabilities, minimizes pressure differentials, and effectively manages gas entrapment, ensuring consistent braking performance and reduced packaging size, while allowing for efficient purging of entrapped gas.
Implementation Method 1
a high-pressure accumulator in fluid communication with the electro-hydraulic braking module
Implementation Method 2
an electro-hydraulic pilot operated boost valve in fluid communication with the master cylinder
Implementation Method 3
the bleed valve allows pressurized hydraulic fluid to flow from the first intermediate chamber to the second intermediate chamber to purge entrapped gas
Data Source
AI summary
A master cylinder includes a housing and a first secondary piston disposed in the housing. The first secondary piston cooperates with the housing to define a first secondary chamber which changes volume as the first secondary piston moves in the housing. A second secondary piston is disposed in the housing and cooperates with the housing to define a second secondary chamber which changes volume as the second secondary piston moves in the housing. A stepped primary piston is disposed in the housing. The primary piston cooperates with the housing to define a primary chamber which changes volume as the primary piston moves in the housing. The primary piston defines an abutment surface which can be driven into abutment with the first secondary piston and the second secondary piston to move the first secondary piston and the second secondary piston. A primary piston spring maintains a restorative force on the primary piston when actuated.