Variable Damping Hydraulic Unit for Braking Systems
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Solution Overview
Problem
Conventional braking system hydraulic units with constant damping dampers impair pumping efficiency due to excessive fluid displacement and unnecessary damping at low pressures, leading to performance issues like noise, vibration, and harshness.
Innovation Solution
A hydraulic unit with a damper that selectively switches between two damping characteristics based on sensed pressure values, using magneto-rheological fluid and an electro-magnetic coil to adjust viscosity and control damping only at pressure peaks, thereby optimizing noise reduction and system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a large damping chamber is used to provide constant damping, then noise and vibration are reduced, but pumping efficiency is impaired due to excessive fluid displacement
Solution Approach 1:
The damper employs a magneto-rheological fluid whose viscosity can be dynamically adjusted by applying a magnetic field. When the pump is active, the magnetic field is applied to reduce fluid viscosity and minimize damping, thereby maintaining pumping efficiency. When the pump is inactive, the magnetic field is removed and damping is activated to reduce noise and vibration. This dynamic adjustment resolves the contradiction between constant noise reduction and pumping efficiency.
Solution Approach 2:
The damping characteristic is changed by modifying the viscosity parameter of the magneto-rheological fluid through magnetic field application. The fluid transitions between high-viscosity (damping active) and low-viscosity (damping inactive) states, allowing the system to optimize between noise reduction and pumping efficiency based on operational requirements.
2Object-affected harmful factors
If constant damping action is applied, then pressure pulsations are reduced, but system performance is impaired when system pressure is low and damping is not needed
Solution Approach 1:
The system uses a pump controller that monitors pump operation status to control the magnetic field application to the magneto-rheological fluid. When the pump is operating, the controller disables the magnetic field to maintain low viscosity and avoid performance impairment. When the pump is inactive, the controller activates the magnetic field to enable damping of pressure pulsations. This feedback-based control resolves the contradiction between pressure pulsation reduction and system performance.
3Object-affected harmful factors
If a large damping chamber is used, then damping capability is increased, but the volume of fluid displaced increases impairing pumping efficiency
Solution Approach 1:
Instead of increasing the physical size of the damping chamber, the system changes the viscosity parameter of the fluid within the chamber. The magneto-rheological fluid can increase its viscosity by several orders of magnitude when a magnetic field is applied, providing high damping capability without requiring a large chamber volume. This resolves the contradiction between damping capability and fluid volume displaced.
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
The variable damping system effectively reduces noise, vibration, and harshness while maintaining system performance by selectively damping only at high-pressure peaks, improving overall efficiency and reducing unnecessary energy dissipation.
Implementation Method 1
The damper is selectively operable in a first state having a first damping characteristic, and in a second state having a second damping characteristic different from the first damping characteristic
Data Source
AI summary
A hydraulic unit for a braking system of a vehicle includes a body with actuator-side and brake-side ports. Inlet and outlet valves are positioned in the body and operable to selectively supply and relieve hydraulic fluid to/from the wheel cylinder of a brake via the brake-side port. A damper is positioned in the body for damping pressure pulsations in the hydraulic fluid. The damper is selectively operable in a first state having a first damping characteristic, and in a second state having a second damping characteristic different from the first damping characteristic.