Retarder Braking Torque Control via Accelerator Pedal Position
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Solution Overview
Problem
Existing methods for controlling hydrodynamic retarders in vehicles are cumbersome for drivers, requiring manual adjustment of braking torque through separate sensors or pedals, making it difficult to maintain target speed during overrun mode.
Innovation Solution
The method utilizes the accelerator pedal as a control element to adjust retarder braking power, allowing for stepless adjustment by interpreting the driver's foot-off position as a braking torque request, eliminating the need for separate switches or brake pedal actuation, and integrating with electronic accelerator pedal systems for seamless operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate sensors or switches are used for retarder control, then the braking torque can be adjusted, but the operation becomes cumbersome and complex for the driver
Solution Approach 1:
The accelerator pedal is assigned multiple functions: it controls both the drive motor torque request and the retarder braking torque request. When the drive motor torque is negative (overrun mode), the accelerator pedal position is interpreted as a braking torque request signal, eliminating the need for separate control devices and simplifying the overall control system architecture
Solution Approach 2:
The control functions for drive motor torque and retarder braking torque are merged into a single control interface (the accelerator pedal). The evaluation unit integrates both torque requests by combining the drive motor torque request and the retarder braking torque request derived from the same pedal position signal, reducing the number of separate control circuits and sensors needed
2Ease of operation
If manual adjustment of braking torque is required, then the driver has direct control, but the ease of use is reduced and driver workload increases
Solution Approach 1:
The system automatically interprets the accelerator pedal position to generate the appropriate retarder braking torque request without requiring the driver to perform additional manual adjustments. The evaluation unit automatically processes the pedal signal and determines the braking torque based on the negative drive motor torque condition, making the system self-regulating and reducing driver workload
3Ease of operation
If the accelerator pedal is used for both drive torque and braking torque control, then the operation is simplified, but the control precision may be affected
Solution Approach 1:
The system dynamically changes the function of the accelerator pedal signal based on the drive motor torque condition. When the drive motor torque is positive, the pedal position controls drive torque. When the drive motor torque becomes negative (overrun mode), the same pedal position signal is dynamically reinterpreted to control retarder braking torque, allowing precise control adaptation to different operating conditions
Solution Approach 2:
The interpretation of the accelerator pedal position parameter changes based on the drive motor torque state. In overrun mode, the pedal position is transformed into a braking torque request parameter through the evaluation unit, which calculates the appropriate braking torque based on the relationship between the negative drive motor torque and the pedal position, maintaining control precision through parameter transformation
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 approach simplifies the operation of hydrodynamic retarders by allowing intuitive adjustment of braking torque through the accelerator pedal, enhancing ease of use and reducing driver workload, while ensuring efficient braking torque management during overrun mode.
Implementation Method 1
In a hydrodynamic retarder, the mechanical energy of a drive shaft is converted into the kinetic energy of a liquid, usually oil
Implementation Method 2
the rotating rotor takes the oil with it, which is supported on the stator blades by converting kinetic flow energy into heat, which creates a braking effect on the rotor and its driving shaft
Implementation Method 3
The oil is passed through a heat exchanger to cool it down
Data Source
AI summary
The invention relates to a method for actuating a retarder of a motor vehicle, for example a hydrodynamic retarder of a commercial vehicle, in which in coasting mode a request is made by the driver, by means of an operating element, for a braking power of the retarder. In order to implement said method in a simple, convenient and cost-effective manner, the gas pedal of the motor vehicle is utilized as the operating element for requesting the braking power of the retarder, and specifically such that, when the torque of the driving motor of the motor vehicle becomes negative due to the coasting mode, the braking power request is signaled by at least partially releasing the gas pedal.