Vehicle Brake Servo Pressure Control for Fluid Hammering Noise Reduction
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Solution Overview
Problem
The existing vehicle brake device experiences significant hydraulic pressure variation and vibration due to large pressure differences across the holding and pressure decreasing valves during ESC and TRC control, leading to fluid hammering noise.
Innovation Solution
The vehicle control device adjusts the target servo pressure to be incrementally increased, setting it to a value smaller than the maximum output pressure of the servo pressure generating device, and dynamically adjusts the target wheel cylinder pressure to minimize pressure differences across the valves, thereby reducing vibrations and fluid hammering noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the target servo pressure is set to a relatively high pressure during ESC control or TRC control, then the service life of the pressure decreasing valve and pressure increasing valve is extended, but the pressure difference between the master cylinder side and the wheel cylinder side becomes large, causing hydraulic pressure variation, vibration, and fluid hammering noise
Solution Approach 1:
The invention dynamically adjusts the target servo pressure based on the rising inclination of the target wheel cylinder pressure maximum value. When the rising inclination is steep, the target servo pressure is set to the target wheel cylinder pressure maximum value; when the rising inclination is gentle, the target servo pressure is set to a predetermined value smaller than the maximum output pressure. This dynamic adjustment resolves the contradiction by adapting the pressure setting to the specific control conditions.
Solution Approach 2:
The invention changes the parameter of target servo pressure from a fixed high value to a variable value that depends on the rising inclination of target wheel cylinder pressure. This parameter change allows the system to optimize between valve service life and suppression of hydraulic pressure variation and noise by selecting appropriate pressure levels based on real-time conditions.
2Speed
If the target servo pressure is set to the maximum output pressure of the servo pressure generating device, then the wheel cylinder pressure can be quickly supplied, but the pressure difference across the holding valve and pressure decreasing valve becomes large, generating vibration and noise
Solution Approach 1:
The invention changes the target servo pressure parameter from a fixed maximum value to a dynamically adjusted value based on the rising inclination of target wheel cylinder pressure. This allows the system to maintain fast pressure supply when needed while reducing pressure differences that cause vibration and noise when the rising inclination is gentle.
Solution Approach 2:
The system dynamically adjusts the target servo pressure based on the calculated rising inclination of target wheel cylinder pressure maximum value. When the rising inclination indicates urgent pressure supply is needed, the maximum pressure is applied; when the inclination is gentle, a lower predetermined pressure is used to avoid noise and vibration.
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 minimizes fluid pressure variations and vibrations, ensuring stable operation and reducing noise in the brake actuator by maintaining a lower master pressure and optimizing valve operations.
Implementation Method 1
a servo pressure generating device formed by a high pressure source 431, a pressure increasing control valve 42 disposed between the high pressure source and the servo chamber for controlling a flow of a brake fluid from the high pressure source to the servo chamber and a first pressure decreasing control valve 41 disposed between a low pressure source and the servo chamber for controlling the flow of the brake fluid from the servo chamber to the low pressure source
Implementation Method 2
a master cylinder 1 wherein master pistons 113 and 114 are driven to move by a servo pressure in a servo chamber and by the movement of the master pistons, master pressure in the master chambers 132 and 136 changes
Implementation Method 3
a pressure sensor 74 which detects the servo pressure
Implementation Method 4
a brake actuator 53 which performs an ABS control and an ESC control and so on
Data Source
AI summary
In a vehicular brake device, while a brake operating member is not operated and a wheel cylinder pressure supplying control is executed to supply the target wheel cylinder pressure to the respective wheel cylinders individually, the vehicle control device sets the target servo pressure to a first predetermined target servo pressure which is a value smaller than a maximum output pressure of the servo pressure generating device. When the execution of the wheel cylinder pressure supplying control starts, the vehicle control device sets the target servo pressure to be the target wheel cylinder maximum value when a firstly occurred rising inclination of the target wheel cylinder maximum value is equal to or more than a minimum increment of an output of the servo pressure generating device per unit time and at the same time when the target wheel cylinder pressure is smaller than the first determined target servo pressure.