Low-Pressure Accumulator Layout for Stable Motor-Driven Braking
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Solution Overview
Problem
Existing brake systems with motor-driven master cylinders face challenges in providing consistent braking performance across varying temperatures and altitudes, particularly in cold temperatures and high altitudes where performance is compromised.
Innovation Solution
The integration of a low pressure accumulator between pairs of wheel brakes, in indirect fluid communication with the reservoir via the master cylinder, helps to provide slip control and attenuate pressure spikes, enhancing braking performance across different conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a motor-driven master cylinder is used to generate brake actuating pressure, then braking performance can be improved through electronic control, but the system becomes vulnerable to performance degradation in cold temperatures and high altitudes
Solution Approach 1:
A low pressure accumulator is introduced as an intermediary component between the motor-driven master cylinder and the wheel brakes. The accumulator stores hydraulic fluid under pressure and provides a supplemental pressure source that compensates for motor-driven cylinder performance degradation in cold temperatures and high altitudes, ensuring consistent braking performance across varying environmental conditions
Solution Approach 2:
The system changes the pressure parameter by introducing a dual-pressure architecture. The low pressure accumulator maintains a baseline pressure (e.g., 50-200 psi) that compensates for the reduced output of the motor-driven master cylinder in adverse environmental conditions, effectively adjusting the system's pressure characteristics to adapt to temperature and altitude variations
2Speed
If hydraulic fluid is directly communicated between the reservoir and wheel brakes, then pressure response is fast, but pressure spikes cause instability and reduced braking performance
Solution Approach 1:
The low pressure accumulator serves as a cushioning element that absorbs pressure spikes before they reach the wheel brakes. By pre-charging the accumulator with hydraulic fluid at a controlled pressure, the system dampens pressure transients and prevents instability, maintaining smooth and stable brake application while preserving fast pressure response
3Reliability
If the low pressure accumulator is placed in indirect fluid communication with the reservoir via the master cylinder, then slip control is improved, but the system complexity increases
Solution Approach 1:
The low pressure accumulator is designed to perform multiple functions within a single component: it provides supplemental pressure for cold temperature and high altitude compensation, dampens pressure spikes to prevent instability, and enables slip control by working in coordination with the motor-driven master cylinder. This multi-functionality reduces the need for separate components for each function, thereby limiting the increase in system complexity
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 configuration improves braking system performance by maintaining desired pressure levels and reducing pressure spikes, even in cold temperatures and high altitudes, while also providing effective slip control.
Implementation Method 1
A low pressure accumulator is interposed hydraulically between the first and second pairs of wheel brakes. The low pressure accumulator is in indirect fluid communication with the reservoir via the first and second MC outputs and the master cylinder.
Implementation Method 2
a motor-driven master cylinder operable during a normal non-failure braking mode by actuation of an electric motor of the master cylinder to generate brake actuating pressure
Implementation Method 3
The secondary brake module includes an electric PTU motor configured to selectively pressurize the hydraulic fluid by transmitting rotary motion to at least two pump pistons
Implementation Method 4
generate brake actuating pressure at first and second MC outputs for hydraulically actuating the first and second pairs of wheel brakes
Data Source
AI summary
A brake system includes a motor-driven master cylinder for generating brake actuating pressure at first and second MC outputs for hydraulically actuating pairs of wheel brakes. A secondary brake module is configured for selectively providing pressurized hydraulic fluid at first and second PTU outputs for actuating the first and second pairs of wheel brakes. A low pressure accumulator is interposed hydraulically between the first and second pairs of wheel brakes. The low pressure accumulator is in indirect fluid communication with the reservoir via the first and second MC outputs and the master cylinder. The low pressure accumulator at least partially provides slip control to the wheel brakes in coordination with the secondary brake module when the brake system is in the normal non-failure braking mode.