Hydraulic Brake System for Multi-Axle Trailer with Low-Pressure Accumulator
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Solution Overview
Problem
Current hydraulic braking systems for trailers with multiple axles face challenges in meeting the 0.6s response time requirement under European regulation 2015/68, leading to oversized and expensive energy reserves, as the oil flow from the tractor is limited, necessitating a large hydraulic accumulator to achieve 75% efficiency on the ninth brake stroke.
Innovation Solution
A hydraulic braking system that utilizes a low-pressure line supplied by a pressure amplifier and includes a sequence valve to switch the main hydraulic circuit to the accumulator filling circuit when the first braking group reaches its nominal torque, allowing excess oil to be directed to additional axles, thereby reducing the capacity and cost of the hydraulic accumulator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large hydraulic accumulator is used to ensure sufficient braking energy reserve for multiple braking operations, then the braking efficiency requirement (75% on ninth stroke) is met, but the cost and size of the energy reserve system increases significantly
Solution Approach 1:
The braking system is divided into two independent groups: the first group of axles is supplied directly by the tractor's hydraulic circuit, while the second group is supplied by the trailer's accumulator. This segmentation allows the accumulator to only need to supply the second group, reducing the required capacity while still meeting the requirement of providing sufficient braking energy after the tractor's oil is depleted.
Solution Approach 2:
The accumulator is pre-charged with hydraulic fluid during normal operation when the tractor's brake valve is activated. This preliminary action ensures that the accumulator is ready to provide the required braking energy for the second group of axles when the tractor's oil supply is depleted, without needing to be oversized to handle all braking operations from scratch.
2Reliability
If the stroke of actuators is adjusted to optimize braking performance, then braking efficiency improves, but the cost of the installation increases
Solution Approach 1:
Instead of changing the physical parameters of the actuators (such as stroke length or diameter), the system achieves optimized braking performance by changing the hydraulic circuit configuration and control parameters. The sequence valve and differential connection allow the system to automatically adjust oil distribution based on pressure differentials, achieving optimal braking efficiency with standard actuators.
3Productivity
If the number of actuators is increased to provide braking for multiple axles, then complete axle coverage is achieved, but the oil flow limitation from the tractor (140cm³ in 0.6s) becomes insufficient to meet the 0.6s response time requirement
Solution Approach 1:
The multi-axle braking system is segmented into two groups supplied by different sources. The first group of axles receives hydraulic oil directly from the tractor's brake valve, ensuring immediate response for those axles. The second group is supplied by the trailer's accumulator, which is pre-charged during normal operation. This segmentation allows the system to provide complete axle coverage while maintaining the 0.6s response time requirement, as the accumulator can immediately supply the second group when needed.
Solution Approach 2:
The hydraulic system is designed with multi-functionality: the tractor's brake valve serves both to brake the first group of axles directly and to charge the accumulator during normal operation. The sequence valve automatically switches between these functions based on pressure differentials, allowing the same hydraulic circuit to serve multiple purposes without increasing response time.
4Productivity
If a sequence valve is added to switch the hydraulic circuit to the accumulator filling circuit when the first braking group reaches nominal torque, then excess oil can be directed to additional axles, but the device complexity increases
Solution Approach 1:
The sequence valve is designed to automatically switch the hydraulic circuit based on pressure differentials without requiring external control signals or complex electronic systems. When the first braking group reaches its nominal torque and creates a sufficient pressure differential, the sequence valve automatically directs excess oil to the accumulator filling circuit or to the second group of axles. This self-service mechanism achieves efficient oil distribution while minimizing the increase in device complexity, as the switching action is purely hydraulic and requires no additional control systems.
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 significantly reduces the capacity of the hydraulic accumulator, optimizing oil volume and cost while maintaining the required braking efficiency, allowing for a trailer braking system that meets regulatory standards with a smaller, less expensive energy reserve.
Implementation Method 1
the hydraulic accumulator is supplied by a low pressure line, via a pressure amplifier
Implementation Method 2
One solution already envisaged in an attempt to overcome this difficulty consists in loading a reserve of energy on the trailer. This energy reserve is generally an accumulator pre-inflated with nitrogen.
Data Source
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AI summary
The present invention relates to a hydraulic braking system for at least one axle of a vehicle, in particular an axle of a trailer, comprising two separate braking circuits (40, 110), one (40) of the braking circuits being supplied by a main hydraulic circuit of the vehicle (62), while the other braking circuit is supplied by a hydraulic accumulator (100), characterized in that the hydraulic accumulator (100) is supplied by a low pressure line (72) and the braking circuit (40) supplied by the main hydraulic circuit of the vehicle (62) is supplied by a hydraulic line having a pressure regulating valve (300).