Rear Brake Pressure Boost for Directional Stability
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Solution Overview
Problem
Current vehicle brake systems face challenges in maintaining directional stability during heavy loads or trailer towing, as the rear wheels may lock up before the front wheels, leading to increased stopping distances and potential loss of control.
Innovation Solution
A brake system algorithm that boosts rear brake circuit pressure relative to the front brake circuit pressure, using electronically controlled solenoid valves and a microprocessor to monitor wheel speeds and apply incremental pressure increases when necessary, ensuring the front wheels lock up before the rear wheels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If equal hydraulic pressure is applied to both front and rear brake circuits, then the braking force is distributed equally, but the rear wheels may lock up before the front wheels during heavy loads or high friction conditions, causing loss of directional stability
Solution Approach 1:
The patent applies different hydraulic pressures to different parts of the brake system - specifically, higher pressure to the rear brake circuit when rear wheel slip is detected, while maintaining normal pressure to the front brake circuit. This local differentiation resolves the contradiction by allowing the rear brakes to generate sufficient force to prevent lockup during heavy loads, while the front brakes maintain their normal locking characteristics for directional stability.
Solution Approach 2:
The system dynamically adjusts the hydraulic pressure distribution between front and rear brake circuits based on real-time wheel speed sensor feedback. When rear wheel slip is detected during braking, the control algorithm automatically increases rear brake pressure, creating a dynamic response that adapts to changing vehicle loading conditions and maintains optimal brake balance.
2Reliability
If the proportioning valve limits rear brake pressure to ensure front wheels lock before rear wheels, then directional stability is maintained, but stopping distance increases when the vehicle is heavily loaded or towing a trailer
Solution Approach 1:
The patent employs wheel speed sensors that continuously monitor the rotational speed of each wheel and provide feedback to the control algorithm. This feedback mechanism detects rear wheel slip conditions in real-time, allowing the system to distinguish between normal braking and conditions requiring enhanced rear brake pressure, thereby eliminating the need for conservative proportioning valve limitations.
Solution Approach 2:
The system transitions from the static pressure limitation imposed by the proportioning valve to a dynamic pressure control system that adjusts rear brake pressure based on actual wheel slip conditions. This allows the rear brakes to provide maximum force when needed (during heavy loads with wheel slip) while maintaining directional stability when wheel slip is not present.
3Productivity
If the brake system is designed for high friction surfaces with greater vehicle deceleration, then braking performance is improved, but weight transfer from rear to front wheels causes the rear brakes to become insufficient, requiring a proportioning valve that further limits rear brake effectiveness
Solution Approach 1:
The control algorithm uses real-time wheel speed data to detect rear wheel slip that occurs during high-deceleration braking on high friction surfaces. This feedback allows the system to identify when additional rear brake force is needed due to weight transfer, and automatically compensates by increasing rear brake pressure beyond what the proportioning valve would normally allow.
Solution Approach 2:
The system changes the hydraulic pressure parameter in the rear brake circuit dynamically based on detected wheel slip conditions. Rather than using a fixed proportioning valve setting, the algorithm adjusts the rear brake pressure parameter in real-time, allowing the rear brakes to maintain effectiveness even under the extreme weight transfer conditions of high-friction surface braking.
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 enhances braking efficiency and reduces stopping distances by ensuring the front wheels lock up before the rear wheels, maintaining directional stability and improving vehicle control during heavy loads or trailer towing conditions.
Implementation Method 1
Depressing a brake pedal, which is connected by a mechanical linkage to the master cylinder, applies hydraulic pressure through both brake circuits to the brake cylinders at each of the vehicle wheels
Implementation Method 2
The proportioning valve is operative to increase the hydraulic pressure applied to the rear wheel brake cylinders at a slower rate than the rate of increase of the hydraulic pressure applied to the front wheel brake cylinders
Implementation Method 3
many vehicles are equipped with electronically controlled brake systems that include selectively controlled solenoid valves in the front and rear brake circuits to enhance control of the vehicle
Implementation Method 4
an anti-lock brake system which in anti-lock pressure control operation is capable to raise the pressure in the rear brake cylinder above the pressure in the front wheel brake cylinder
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
Under certain operating conditions, the pressure applied to a vehicle rear brake circuit is increased above the pressure applied to the vehicle front brake circuit to enhance stopping of the vehicle.