Pressure-Balanced Brake-by-Wire Piston for Stable Brake Blending
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Solution Overview
Problem
Existing brake-by-wire systems face challenges in efficiently blending regenerative braking torque with driver-requested braking torque, requiring hydraulic brakes to supply the difference, which complicates the system's functionality and reliability.
Innovation Solution
The proposed electro-hydraulic brake system incorporates a pressure supply unit (PSU) with a pressure-balanced piston, an electric motor, and a pedal feel emulator to manage brake pressure and simulate pedal feel, enabling efficient blending of braking torques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If regenerative braking is used to recharge batteries, then energy efficiency is improved, but the input torque is not consistent with driver input function requiring complex hydraulic brake blending
Solution Approach 1:
The patent replaces the traditional mechanical linkage between brake pedal and master cylinder with an electro-hydraulic system. The brake pedal is decoupled from direct mechanical connection to the master cylinder, and instead uses sensors (travel and/or force sensors) to detect driver intent and sends signals to an ECU that controls the PSU, eliminating the need for complex mechanical brake blending mechanisms.
Solution Approach 2:
The patent introduces a pedal feel emulator (PFE) as an intermediary device between the brake pedal and the master cylinder. The PFE includes a pedal feel emulator piston that simulates the mechanical feel of traditional brakes while allowing independent control of hydraulic pressure through the PSU, enabling complex brake blending functions without direct mechanical coupling.
2Adaptability or versatility
If brake pedal is isolated from directly applying master cylinder to wheel brakes, then regenerative brake blending capability is improved, but pedal feel simulation becomes more complex
Solution Approach 1:
The patent introduces a pedal feel emulator (PFE) as an intermediary device between the brake pedal and the master cylinder. The PFE includes a pedal feel emulator piston that simulates the mechanical feel of traditional brakes while allowing independent control of hydraulic pressure through the PSU, enabling complex brake blending functions without direct mechanical coupling.
Solution Approach 2:
The patent uses hydraulic fluid to transmit force and pressure through the PFE system. The PFE piston is movable through a PFE bore and separates an upper chamber from a lower chamber, with fluid paths connecting to the master cylinder and PSU, using hydraulic principles to simulate pedal feel while enabling independent pressure control.
3Power
If pressure supply unit provides pressurized fluid for wheel brakes, then braking performance is improved, but pressure consistency and reliability may be compromised without pressure balancing
Solution Approach 1:
The patent employs a pressure-balanced piston in the PSU that uses counterbalancing forces to maintain pressure consistency. The piston is acted upon by forces from both the electric motor and hydraulic pressure, creating a balanced system that reliably converts electrical signals into consistent hydraulic pressure output for the wheel brakes.
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 enhances the system's efficiency and reliability by ensuring consistent brake pressure application and simulating the feel of a traditional brake system, thereby improving the overall braking experience.
Implementation Method 1
an electric motor coupled to an actuator rod
Implementation Method 2
a piston bore including a terminal end opposite the electric motor, and a PSU piston disposed within the piston bore and movable by the actuator rod through the piston bore
Implementation Method 3
a check valve configured to allow fluid flow from the second chamber of the PSU to the first chamber of the PSU and to block fluid flow in an opposite direction
Implementation Method 4
The PSU piston includes a balance piston extending into the balance bore and having a cross-sectional area equal to a cross-sectional area of the actuator rod
Implementation Method 5
The lower chamber of the PFE is fluidly coupled to the second chamber of the PSU to convey fluid from the lower chamber of the PFE to the second chamber of the PSU in response to a compression of the PFE
Data Source
AI summary
An electro-hydraulic brake system includes a master cylinder (MC) fluidly coupled to an MC fluid passageway and configured to supply fluid into the MC fluid passageway in response to pressing force on a brake pedal. A pressure supply unit (PSU) includes an electric motor and a PSU piston disposed within a piston bore, the PSU piston is movable through the piston bore by the electric motor and divides the piston bore into a first chamber and a second chamber. A pedal feel emulator (PFE) includes a PFE piston movable through a PFE bore and separating an upper chamber from a lower chamber. Fluid is conveyed from the lower chamber of the PFE to the second chamber of the PSU in response to a compression of the PFE. The MC fluid passageway provides a fluid path from the master cylinder into the upper chamber of the PFE.