Hydraulic Brake System with Controlled Boost and Slip Control
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Solution Overview
Problem
Existing vehicle brake systems face challenges in maintaining precise control, especially under adverse conditions, leading to wheel lock-up and reduced stability, due to the difficulty in dynamically proportioning braking forces between front and rear axles and transitioning between hydraulic and regenerative braking smoothly.
Innovation Solution
A vehicle brake system with a brake pedal unit that includes an input piston for normal and manual push through modes, a hydraulic pressure source, and a hydraulic control unit with a slip control valve and switching base brake valve, which allows for controlled switching between boost pressure and pedal-actuated pressure, providing progressive damping and feedback to the driver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a driver applies excessive braking pressure under adverse conditions, then braking force is increased, but wheel lock-up occurs causing excessive slippage and loss of directional control
Solution Approach 1:
The ABS system continuously monitors wheel rotational speed and provides feedback to the electronic control unit. When wheel deceleration exceeds a threshold indicating impending lock-up, the system automatically modulates brake pressure through apply and dump valves, creating a feedback control loop that maintains wheels at the threshold of lock-up for maximum braking force without actual lock-up
Solution Approach 2:
The system dynamically adjusts brake pressure in real-time based on wheel speed feedback, transitioning between pressure apply, pressure dump, and pressure hold modes. This dynamic control allows the braking force to adapt continuously to changing road conditions and wheel states, preventing wheel lock-up while maintaining optimal braking performance
2Reliability
If ABS valves are used to control braking pressure at each wheel, then wheel lock-up is prevented, but system complexity increases
Solution Approach 1:
The brake system is segmented into independent control circuits for front and rear wheels, with separate ABS valves at each wheel. This segmentation allows independent control of braking pressure at each wheel based on its specific rotational behavior, enabling precise prevention of wheel lock-up while maintaining manageable system complexity through modular architecture
Solution Approach 2:
The ABS valve assembly performs multiple functions: it acts as an apply valve to increase brake pressure, a dump valve to relieve pressure, and a hold valve to maintain constant pressure. This multi-functionality reduces the need for separate components for each function, thereby managing system complexity while achieving reliable wheel lock-up prevention
3Productivity
If brake pressures are proportioned between front and rear brakes to achieve maximum braking forces, then braking performance is optimized, but control complexity increases
Solution Approach 1:
The system implements dynamic rear proportioning that automatically adjusts the distribution of brake pressure between front and rear wheels based on real-time wheel speed feedback and vehicle deceleration rates. This dynamic proportioning optimizes braking performance by ensuring each axle operates at its optimal slip level without requiring complex manual adjustment mechanisms
Solution Approach 2:
The ABS control system automatically manages brake pressure proportioning between front and rear brakes based on sensor feedback from wheel speed monitors. The electronic control unit independently calculates and adjusts the optimal pressure distribution without driver intervention, achieving maximum braking performance while keeping the control system manageable through automated self-regulation
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 enables precise control of braking forces, reduces wheel lock-up, and ensures smooth transitions between braking modes, enhancing vehicle stability and traction control.
Implementation Method 1
The input piston cooperates with a seal mounted in the brake pedal unit to provide for a progressive rate of friction therebetween as the input piston is advanced in the brake pedal unit by the brake pedal
Implementation Method 2
A typical hydraulic booster senses the movement of the brake pedal and generates pressurized fluid which is introduced into the master cylinder
Implementation Method 3
The ABS valves regulate the pressure between the master cylinder and the wheel brakes
Implementation Method 4
The pedal simulator applies an opposing feedback force to the input piston and brake pedal during brake application
Data Source
AI summary
A vehicle brake system includes a brake pedal unit coupled to a vehicle brake pedal. The system includes an input piston connected to operate a pedal simulator during a normal braking mode, and coupled to actuate a pair of output pistons during a manual push through mode. The output pistons are operable to generate brake actuating pressure at first and second outputs of the brake pedal unit. A hydraulic pressure source supplies fluid at a controlled boost pressure. A hydraulic control unit is adapted to be hydraulically connected to the brake pedal unit and the hydraulic pressure source. The hydraulic control unit includes a slip control valve arrangement, and a switching base brake valve arrangement for switching the brake system between the normal braking mode wherein boost pressure from the pressure source is supplied to first and second vehicle brakes, and the manual push through mode wherein brake actuating pressure from the brake pedal unit is supplied to the first and second vehicle brakes. The input piston cooperates with a seal mounted in the brake pedal unit to provide for a progressive rate of friction therebetween as the input piston is advanced in the brake pedal unit by the brake pedal.