Brake Assist Device Servomotor Dynamics for Pressure Jump Control
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Solution Overview
Problem
Current brake-assist devices for motor vehicles cannot differentiate between driving modes, requiring similar braking force from drivers with sporty and relaxed driving styles, leading to ineffective feedback and pressure jumps in the master cylinder.
Innovation Solution
A brake-assist device with a servomotor that adjusts the stiffness of a spring and the position of a plunger piston relative to a moving part based on the driver's selected or detected driving mode, using a sensor and control unit to vary the striking force and pressure jump, allowing for distinct feedback experiences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the servomotor is activated to overcome the return spring resistance, then the braking force is generated, but a pressure jump occurs in the master cylinder due to axial play between the plunger piston and moving part
Solution Approach 1:
The control unit activates the servomotor before the driver applies force on the brake pedal to eliminate axial play between the plunger piston and moving part. This preliminary action ensures that when braking force is applied, the pressure jump is minimized and the force transmission is smooth and continuous.
Solution Approach 2:
A force sensor measures the force applied by the driver on the brake pedal and sends information to the control unit. The control unit uses this feedback to determine when to activate the servomotor and adjust the moving part position to eliminate axial play, thereby controlling the pressure jump in the master cylinder.
2Device complexity
If the same braking force is required for both sporty and relaxed driving modes, then the device structure is simple, but the driver feedback is ineffective and does not differentiate between driving styles
Solution Approach 1:
The control unit dynamically adjusts the position of the moving part relative to the plunger piston based on the detected driving mode. In sporty mode, the moving part is positioned to provide stronger feedback, while in relaxed mode, it is positioned to provide gentler feedback. This dynamic adjustment allows the same physical device to adapt to different driving styles and provide appropriate feedback.
Solution Approach 2:
The system changes the physical parameter of the moving part position based on the driving mode. By adjusting the initial position of the moving part, the system modifies the mechanical feedback characteristics to the driver, enabling differentiation between sporty and relaxed driving modes without changing the overall device structure.
3Force
If the moving part is positioned closer to the plunger piston, then the striking force is reduced for relaxed driving mode, but the pressure amplification effect is diminished
Solution Approach 1:
The control unit dynamically adjusts the position of the moving part based on the detected driving mode. When relaxed mode is detected, the moving part is positioned closer to the plunger piston to reduce the striking force. When sporty mode is detected, the moving part is positioned farther away to increase the striking force and pressure amplification effect.
Solution Approach 2:
The system changes the position parameter of the moving part to achieve different force characteristics. By adjusting this parameter, the system can reduce the striking force for relaxed driving while maintaining the ability to provide sufficient pressure amplification when needed in sporty mode.
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 better feedback and reduced pressure jumps by dynamically adjusting the striking force and pressure amplification based on driving mode, improving hysteresis and reducing the force required for braking, especially in calm driving modes.
Implementation Method 1
a spring compressed between the plunger piston and the moving part
Implementation Method 2
an electric servomotor having a ball-screw assembly that transforms a rotational movement of the ball forming the rotor of the electric motor into a translational movement of the screw that moves a moving part in the direction of a master cylinder
Data Source
AI summary
A brake-assist device for a motor vehicle having a servomotor is described. A servomotor has a plunger piston, a moving part, and an arrangement to move the moving part into position with respect to the plunger piston. The servomotor is actuated by a control rod. The control rod has a first end that presses upon the plunger piston and a second end to receive a force exerted by a brake pedal intended to be moved by a driver of the vehicle. The servomotor includes a sensor interposed in a contact space between the plunger piston and the moving part. A spring is compressed between the plunger piston and the moving part. The servomotor includes an arrangement for displacing the plunger piston in the contact space based on the driving mode. A stiffness of the spring is sufficiently high for an onset of braking to occur only with a striking force that is significantly higher during a reactive driving mode than it is during a calm driving mode.