Master Cylinder Valve Pressure Adjustment for Pedal Feel
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Solution Overview
Problem
Conventional vehicle braking systems with master cylinders struggle to provide a good pedal feel over a larger range due to limitations in hydraulic pressure, especially when the booster fails, leading to insufficient braking force and poor pedal response.
Innovation Solution
A vehicle braking system with a master cylinder, booster, and pressure-intensifying means, where a pressure-reducing valve is activated when the hydraulic pressure in the small-diameter pressure chamber exceeds 500 N, and the pressure-intensifying means compensates for hydraulic pressure using a different source, ensuring adequate braking force even in booster failure scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the pressure-reducing valve is opened at low hydraulic pressure during initial stage of stroke to compensate for ineffective fluid amount, then the pedal stroke is shortened in limited extent, but the pedal feel cannot be maintained over a larger hydraulic pressure range
Solution Approach 1:
The patent changes the opening pressure parameter of the pressure-reducing valve from conventional low pressure (within ineffective fluid amount compensation range) to high pressure (2-10 MPa). This parameter change allows the valve to remain closed during initial stroke, enabling pedal feel to be maintained across the entire hydraulic pressure range while still achieving stroke shortening through fast fill mechanism
2Adaptability or versatility
If the pressure-reducing valve is set to open at high hydraulic pressure (2-10 MPa), then the pedal feel is maintained over larger range, but the hydraulic pressure in large-diameter pressurized chamber cannot be reduced to atmospheric pressure along with pressure increase after valve opening
Solution Approach 1:
The patent applies preliminary action by pre-filling the small-diameter pressure chamber with brake fluid from the large-diameter pressurized chamber before the pressure-reducing valve opens. This fast fill occurs during initial piston movement when the valve is still closed, preparing the system for high-pressure operation without requiring the valve to reduce pressure to atmospheric levels
3Length of moving object
If the master cylinder compensates for ineffective fluid amount during initial stage of stroke, then the pedal stroke is shortened, but the predetermined hydraulic pressure is set within low hydraulic-pressure region limiting the compensation range
Solution Approach 1:
The patent changes the pressure parameter at which the pressure-reducing valve operates from low pressure region to high pressure region (2-10 MPa). This allows the fast fill mechanism to operate effectively across the entire hydraulic pressure range, not just in the low pressure region, thereby maintaining pedal feel throughout the full operating range
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 enhances the braking system's ability to maintain a good pedal feel and sufficient braking force by adjusting hydraulic pressure dynamically, ensuring deceleration rates and pedal stroke optimization across various operating conditions.
Implementation Method 1
a pressure-reducing valve for reducing a hydraulic pressure in the large-diameter pressurized chamber (70) along with an increase in hydraulic pressure after the valve is opened
Implementation Method 2
a booster (BS) having a full-load point, for assisting an input of a brake pedal
Implementation Method 3
pressure-intensifying means for compensating for a hydraulic pressure supplied to wheel cylinders with a hydraulic pressure generated by a hydraulic pressure source different from the master cylinder
Data Source
AI summary
Provided are a vehicle braking system and a master cylinder which are capable of providing a good pedal feel. A valve-opening pressure for a pressure-reducing valve of the master cylinder is set higher than a hydraulic pressure which is obtained with a pressing force on a brake pedal being 500 N and lower than a hydraulic pressure obtained at a time when a booster reaches a full-load point in case of failure of the booster so as to be specialized for improving pedal feel. Required performance in case of failure of the booster is realized by a pressure-intensifying unit.