Electronic Brake Pressure Distribution Using Threshold Detection
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Solution Overview
Problem
Conventional brake systems in commercial vehicles face issues with brake pressure distribution, particularly when the front axle brake circuit fails, leading to premature limitation of rear axle brake pressure and reduced braking power, due to reliance on expensive pressure sensors and inadequate consideration of mechanical failures.
Innovation Solution
A method where the rear axle brake pressure is limited only when the pressure value falls below a predetermined threshold, using a pressure switch to generate an activation signal for electronic control, ensuring full braking pressure is maintained when the threshold is exceeded, and utilizing existing ABS components for cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the electronic brake force distribution (EBV) function uses ABS pressure control valves to implement automatic load-dependent braking based on differential slip between front and rear axles, then the need for a load valve is eliminated and braking force distribution is improved, but in the event of front axle brake circuit failure, the system incorrectly limits rear axle brake pressure resulting in underbraking and extended braking distance
Solution Approach 1:
The patent applies preliminary anti-action by introducing a pressure switch that detects front axle brake pressure before the EBV function activates pressure limitation. When the pressure switch detects insufficient front axle pressure (below threshold), it generates an activation signal that prevents the EBV function from limiting rear axle brake pressure, thereby counteracting the potential harmful effect of incorrect pressure limitation before it occurs.
Solution Approach 2:
The patent introduces a pressure switch as an intermediary component between the front axle brake circuit and the EBV control logic. This pressure switch acts as a mediator that monitors front axle brake pressure and communicates the brake circuit status to the electronic control, enabling the system to distinguish between normal braking conditions and failure conditions before making pressure limitation decisions.
2Measurement precision
If a pressure sensor is used to detect front axle brake pressure for determining EBV activation, then accurate detection of brake circuit status is achieved, but production costs increase significantly
Solution Approach 1:
The patent replaces the expensive pressure sensor with a significantly cheaper pressure switch. The pressure switch uses a simple mechanical or electrical threshold-based detection mechanism rather than the complex sensing electronics of a pressure sensor, dramatically reducing component cost while still providing sufficient functionality for determining brake circuit status and controlling EBV activation.
Solution Approach 2:
The patent changes the detection parameter from continuous pressure measurement (pressure sensor) to threshold-based pressure detection (pressure switch). This parameter change simplifies the detection mechanism, reducing complexity and cost while maintaining adequate performance for the specific application of determining whether front axle brake pressure is sufficient to prevent incorrect EBV activation.
3Stability of the object's composition
If the rear axle brake pressure is continuously limited based on differential slip threshold, then rear wheel locking is prevented, but braking power is reduced when front axle brake circuit fails
Solution Approach 1:
The patent applies preliminary action by having the pressure switch detect and signal front axle brake pressure status before the EBV function executes pressure limitation. This advance detection allows the system to prepare for or prevent incorrect pressure limitation by activating an inhibition signal when front axle brake circuit failure is detected, ensuring full braking power is available when needed.
Solution Approach 2:
The patent inverts the conventional EBV logic by introducing a default state where rear axle brake pressure limitation is activated, but can be deactivated by a specific condition (pressure switch signal indicating front axle brake failure). This inversion ensures that under failure conditions, the system defaults to providing full braking power rather than incorrectly limiting it, reversing the harmful effect of the original logic.
Data Source
Figure 1
AI summary
The invention relates to a method for electronically regulating the braking force distribution in a pressure medium-activated brake system (1) of a vehicle having at least one front axle brake circuit which is assigned to a front axle (2) and at least one rear axle brake circuit which is assigned to at least one rear axle (8), wherein when the brake system (1) is actuated a rear axle brake pressure acting in the at least one rear axle brake circuit is regulated with the objective of preventing locking of the rear wheels before locking of the front wheels. According to the invention there is provision that the brake pressure at the rear axle (8) is limited only for as long as a pressure value acting in the rear axle brake circuit is below a predefined pressure threshold value but the brake pressure at the rear axle (8) is not limited if the pressure value acting in the rear axle brake circuit is equivalent to or higher than the predefined brake threshold value. As a result, a higher braking performance is achieved if the front axle brake circuit fails.