Exhaust Brake Torque Control for Vehicle Speed Management
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Solution Overview
Problem
Exhaust brake torque systems for vehicles, particularly diesel engines, face challenges in effectively calculating and controlling exhaust brake torque to supplement braking on varying loads and grades, often requiring mechanical braking assistance, which can lead to overheating issues.
Innovation Solution
A system comprising a controller that calculates current and maximum exhaust brake torque using engine speed and turbine inlet pressure, with a display to show these values and a method to selectively apply mechanical brakes based on setpoints, allowing for efficient modulation of both exhaust brake torque and mechanical braking to maintain vehicle speed on downhill grades.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If exhaust brake torque is used to slow the vehicle, then mechanical brake wear is reduced, but braking efficiency is insufficient for higher loads and downgrades
Solution Approach 1:
The system combines exhaust brake torque with mechanical braking into a unified braking system. The controller integrates both braking sources to work together, allowing the exhaust brake to handle moderate braking needs while mechanical brakes provide supplemental force when required, achieving synergistic braking performance that neither system could achieve alone.
Solution Approach 2:
The system dynamically adjusts the contribution of exhaust brake torque versus mechanical braking based on real-time conditions. The controller modulates mechanical brake application according to the current exhaust brake torque level, creating a dynamic, adaptive braking system that optimizes the mix of braking sources according to vehicle load, grade, and speed conditions.
2Productivity
If mechanical brakes are applied to supplement exhaust brake torque, then braking capability is improved, but brake overheating occurs
Solution Approach 1:
The system employs feedback control where the controller continuously monitors braking conditions and adjusts mechanical brake application based on the current exhaust brake torque level. When exhaust brake torque is sufficient, mechanical brakes are reduced or released; when additional braking is needed, mechanical brakes are applied in a controlled manner. This feedback mechanism prevents excessive mechanical brake usage and associated overheating.
Solution Approach 2:
The controller selectively applies and releases mechanical brakes in periodic cycles rather than continuous application. Mechanical brakes are applied only when exhaust brake torque exceeds the setpoint, then released when it falls below the setpoint minus delta, creating periodic action that allows heat dissipation and prevents thermal buildup.
3Speed
If mechanical brakes are continuously applied to maintain vehicle speed, then vehicle speed control is improved, but energy consumption increases
Solution Approach 1:
The system allows the exhaust brake torque to serve itself as the primary braking source for speed maintenance on downhill grades. The controller only intervenes with mechanical brakes when exhaust brake torque is insufficient to maintain the speed setpoint. This self-service approach minimizes mechanical brake usage and associated energy consumption while maintaining effective speed control.
Solution Approach 2:
The system changes the operational parameters of the braking system by using exhaust brake torque as the primary control variable for speed maintenance. By adjusting the exhaust brake torque setpoint and utilizing its variable torque characteristics, the system achieves speed control with minimal mechanical brake intervention, thereby reducing overall energy consumption compared to continuous mechanical brake application.
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
Enables precise control of vehicle speed on downhill grades by modulating mechanical brakes in conjunction with exhaust brake torque, preventing overheating and optimizing brake usage, thus enhancing braking efficiency and reducing mechanical brake wear.
Implementation Method 1
The exhaust brake torque systems restrict an exhaust path of the diesel engine causing compression of exhaust gases in the exhaust manifold and cylinders of the diesel engine
Implementation Method 2
The flow control device selectively restricts the exhaust system to create the exhaust back pressure, which retards engine speed
Data Source
AI summary
An exhaust brake torque system for a vehicle including an engine includes a controller configured to determine a current exhaust brake torque and a maximum exhaust brake torque. A display is configured to display at least one of the current exhaust brake torque, the maximum exhaust brake torque and a percentage corresponding to the current exhaust brake torque divided by the maximum exhaust brake torque. An engine speed sensor determines an engine speed of an engine. A pressure sensor is configured to sense turbine inlet pressure. The controller is configured to calculate the current exhaust brake torque and the maximum exhaust brake torque in response to the engine speed and the turbine inlet pressure.