Vehicle Brake System Thermal Expansion Pressure Control
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Solution Overview
Problem
The accuracy of braking force generation in vehicle brake systems is compromised due to the expansion of brake fluid caused by frictional heat, leading to increased brake fluid pressure and reduced control over braking performance.
Innovation Solution
A brake system with two hydraulic systems and a control unit that manages the communication between these systems and a reservoir, allowing brake fluid to flow between them or into a reservoir when the output characteristic of brake fluid pressure shifts from its basic characteristic, thereby regulating brake fluid pressure and maintaining accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the master-cut valve is closed to shut off brake fluid pressure from the pedal-operated master cylinder, then the hydraulic system becomes a closed system and brake fluid pressure can be generated by the motor cylinder device, but the brake fluid expands due to frictional heat causing brake fluid pressure to become higher than intended, which decreases the accuracy of braking force generation
Solution Approach 1:
The patent extracts the expanded brake fluid from the closed hydraulic system by opening the master-cut valve to allow communication with the pedal-operated master cylinder system, which acts as a reservoir. This removes the harmful thermal expansion effect while maintaining the motor cylinder device's primary control function.
Solution Approach 2:
The system changes the physical state of the hydraulic system from closed to open by adjusting the master-cut valve position. This parameter change allows the system to accommodate thermal expansion of brake fluid while maintaining pressure control accuracy through controlled communication between the two hydraulic systems.
2Ease of operation
If the hydraulic system is kept closed to maintain brake fluid pressure generated by the motor cylinder device, then braking force can be controlled accurately under normal conditions, but when brake fluid temperature rises and expands, the pressure becomes higher than the target pressure, reducing control accuracy
Solution Approach 1:
The master-cut valve dynamically switches between closed and open positions based on system conditions. Under normal conditions, it remains closed to maintain precise pressure control. When thermal expansion occurs, it opens to relieve excess pressure, providing adaptive response to changing system states.
Solution Approach 2:
The control unit monitors brake fluid pressure and temperature conditions, and based on this feedback, controls the master-cut valve to open or close. This feedback mechanism ensures pressure accuracy is maintained by compensating for thermal expansion effects through appropriate valve positioning.
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 solution effectively reduces the decrease in braking force accuracy caused by brake fluid expansion, ensuring consistent and accurate braking performance by adjusting brake fluid pressure to match the basic characteristic, even when the brake fluid temperature rises.
Implementation Method 1
The temperature of the brake fluid rises by heating the brake fluid with the frictional heat, so that the brake fluid expands.
Data Source
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AI summary
Provided is a brake system (10) for a vehicle including an input side hydraulic system (Pin), an output side hydraulic system (Pout), a first and a second shutoff valves (60b, 60a) to shut off flowing of the brake fluid between the input side hydraulic system and the output side hydraulic system when closed, a first and a second out-valves (128, 130) through which the brake fluid flows into a reservoir unit (132) when opened, and a control unit (150) to control a motor cylinder device (16) of the output side hydraulic system to generate the brake fluid pressure (Bp) according to the operational amount of a brake pedal (12). The control unit opens one or both of the first and the second shutoff valves and the first and the second out-valves when output characteristic (Thigh) of the brake fluid pressure generated by the motor cylinder device shifts from basic characteristic (Tstd).