Vehicle Downhill Braking Control System for Retarder and Service Brake Coordination
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Solution Overview
Problem
Heavy motor vehicles, especially those with automatic or semi-automatic transmission, face challenges in maintaining a constant speed downhill due to the limitations of auxiliary braking devices like retarder brakes, which may not provide sufficient braking action, especially during gear shifting, potentially leading to engine damage and increased wear on service brakes.
Innovation Solution
A braking control system that calculates the need for auxiliary and service frictional braking device activation based on driving conditions, including speed, gear shifting, and total braking torque, to ensure reliable braking and prevent excessive engine revolutions by activating the service brakes when the auxiliary braking device alone cannot maintain the required braking action.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the auxiliary braking device (retarder brake) is used alone for downhill braking, then service brake wear is reduced, but braking reliability is insufficient at low speeds and during gear shifting
Solution Approach 1:
The system dynamically switches between auxiliary braking mode and combined braking mode based on real-time operating conditions. The braking control means activates service brakes when detecting low vehicle speeds or gear shifting operations, while relying on the auxiliary braking device during steady-state downhill driving at higher speeds, optimizing both brake longevity and reliability.
Solution Approach 2:
The system changes the braking configuration parameter based on operating conditions. When vehicle speed falls below a threshold or gear shifting is detected, the system transitions from using only the auxiliary braking device to activating the service frictional braking device, thereby adapting the braking system's characteristics to match the required performance level.
2Duration of action of stationary object
If the auxiliary braking device is used alone during gear shifting, then service brakes are saved, but engine speed may exceed safe limits causing damage
Solution Approach 1:
The braking control means detects gear shifting operations in advance and proactively activates the service frictional braking device before the gear change completes. This preliminary action ensures that the service brakes are already engaged when needed, preventing engine speed from rising to dangerous levels during the gear shifting transition.
Solution Approach 2:
The system continuously monitors gear position and vehicle speed, using this feedback to determine when service brake activation is necessary. When gear shifting is detected or engine speed approaches unsafe thresholds, the feedback loop triggers service brake engagement to counteract the auxiliary braking device's insufficient performance during these transient conditions.
3Reliability
If the service frictional braking device is activated frequently to assist the auxiliary braking device, then braking reliability is improved, but service brake wear increases
Solution Approach 1:
The system dynamically adjusts the proportion of braking force provided by each braking device based on real-time conditions. During steady-state downhill driving, the auxiliary braking device provides the majority of braking force, minimizing service brake usage. During transient conditions like gear shifting or low-speed operation, the service brakes are activated only when necessary, optimizing the balance between reliability and wear.
Solution Approach 2:
The system applies partial service brake activation rather than full braking force during conditions where auxiliary braking is insufficient. This partial action provides just enough additional braking force to maintain reliability during critical transitions, while avoiding excessive service brake engagement that would accelerate wear.
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 system ensures consistent braking action during downhill driving, reduces service brake wear, and prevents engine damage by strategically activating both auxiliary and service brakes, maintaining speed control and torque levels during gear shifting.
Implementation Method 1
The retarder brake is a hydraulic brake, which acts upon a driven wheel axle of the vehicle for instance by acting on the output shaft of a gear box of the vehicle
Implementation Method 2
a retarder brake acting upon a driven wheel axle or an output shaft of a gearbox for obtaining a braking action
Implementation Method 3
The exhaust brake also indirectly acts upon the driven wheel axle of the vehicle by causing a resistance to the rotation of the output shaft of the engine of the motor vehicle by regulating the flowing resistance of exhaust gases from the engine
Data Source
Figure 1
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AI summary
A system for controlling braking of a motor vehicle during downhill driving, in which the vehicle is provided with a service frictional braking device (18) and an auxiliary braking device (25), comprising a retarder brake (26) and a lever (40) for activating the retarder brake by the driver of the vehicle, comprises means (29) adapted to, upon activation of said retarder brake (26) by actuating said lever (40) by the driver for applying a braking action to the vehicle when driving downhill, based upon values of parameters of the driving conditions of the vehicle, calculate whether the auxiliary braking device is able to alone obtain said braking action to be applied to the vehicle. The braking control means (28) is adapted to activate the service frictional braking device to assist said auxiliary braking device when said calculation states that the auxiliary braking device is not able to alone obtain said braking action to be applied to the vehicle. (Fig 1).