Differential Hydraulic Master Cylinder Valve Interconnection
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Solution Overview
Problem
Differential brake master cylinders face challenges in ensuring simultaneous and efficient operation of pressure relief and non-return valves, particularly when these valves are restricted in size, leading to difficulties in smooth transition between chambers and maintaining low pedal effort while achieving desired braking forces.
Innovation Solution
A differential hydraulic master cylinder design where the pressure relief valve and non-return valve are mechanically interconnected, with the non-return valve comprising a piston in a second valve chamber, allowing fluid to flow from the first working chamber to the outlet while preventing reverse flow, and utilizing a valve spool and spring mechanism to ensure quick and reliable opening of the pressure relief valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a large diameter piston and cylinder arrangement is used in the master cylinder, then large volumes of hydraulic fluid can be moved over relatively short travel to take up play during initial brake application, but greater pedal effort is required to produce the high pressures necessary to generate desired braking forces
Solution Approach 1:
The master cylinder is divided into two separate chambers: a first chamber with a first piston for initial brake application and a second chamber with a second piston for subsequent braking. This segmentation allows each chamber to be optimized for its specific function, with the first chamber handling large fluid volumes at low pressure and the second chamber generating high pressure with smaller piston travel
Solution Approach 2:
The system dynamically switches between two different piston-chamber configurations based on operating conditions. During initial brake application, the first chamber with larger piston area is active to move large fluid volumes. After play is taken up and pressure rises, the system transitions to the second chamber with smaller piston area for high-pressure braking, optimizing performance across the entire braking range
2Volume of moving object
If the pressure relief valve and non-return valve are located in the piston assembly, then the valves are compact, but the valves are necessarily restricted in size leading to difficulties in smooth transition between chambers
Solution Approach 1:
The pressure relief valve and non-return valve are extracted from the piston assembly and relocated to the cylinder body. This extraction allows the valves to be significantly larger in size while maintaining a compact overall master cylinder design. The larger valve size enables smoother and more reliable operation during the transition between chambers, eliminating the size-related operational difficulties
3Reliability
If a one-way valve is provided in the fluid passageway to prevent fluid from flowing back into the larger chamber, then reverse flow is prevented, but the transition period increases due to slow response of the lip seal
Solution Approach 1:
The pressure relief valve and non-return valve are merged into a single integrated valve assembly with mechanically interconnected movable members. This combination ensures that both valves respond simultaneously to pressure changes, with the non-return valve's piston directly assisting in opening the pressure relief valve. The unified design eliminates the time delay associated with separate valve operations and lip seal response
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 design ensures a quick and reliable transition between chambers, reducing pedal effort required and maintaining efficient braking performance by mechanically linking the valves to assist in opening and holding the pressure relief valve open, thus improving the overall efficiency and adjustability of the master cylinder.
Implementation Method 1
a pressure relief valve in the first passageway which is arranged to open to connect the first working chamber with said source of ambient pressure when the pressure in the first working chamber reaches a threshold value
Implementation Method 2
the piston carrying a lip seal for contact with the surface of the second valve chamber, the arrangement being such that, in use, fluid is able to flow from the first working chamber over the lip seal to the outlet but is prevented from flowing in the reverse direction by engagement of the lip seal with the surface of the second valve chamber
Implementation Method 3
utilizing a valve spool and spring mechanism to ensure quick and reliable opening of the pressure relief valve
Data Source
Figure 1
AI summary
A differential hydraulic master cylinder (10) has a cylinder body (12) in which is provided a larger diameter first chamber (18) and a smaller diameter second chamber (20). A first fluid passageway (60, 74, 78, 80) connects the first chamber (18) with a source of ambient pressure and contains a pressure relief valve (70) for connecting the first chamber with said source of ambient pressure when the pressure in the first chamber reaches a threshold value. A second fluid passageway (76, 78, 80, 82) connects the first chamber (18) with an outlet (11) and the second chamber (20). A non-return valve (72) is located in the second passageway to prevent hydraulic fluid from flowing from the second chamber (20) to the first chamber (18) at least when the pressure relief valve (70) is open. The non-return valve (72) and the pressure relief valve (70) each have a movable valve member (100, 102, 88; 122) which are mechanically interconnected.