Electro-hydraulic Actuator Cam Profile for Brake Motor Overheating
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Solution Overview
Problem
Existing electro-hydraulic brake systems, such as 'Brake By Wire,' face issues with overheating under extreme braking conditions due to the need for oversized electric motors to generate high hydraulic pressures, leading to increased manufacturing and operational costs, weight, and dimensions.
Innovation Solution
An electro-hydraulic actuator with a hydraulic thrust unit that optimizes motor torque and power supply by using a converting mechanism with a non-linear ratio between motor torque and piston stroke, allowing for high fluid pressure generation without overheating, where the motor torque increases proportionally in the rear half of the piston stroke and sub-proportionally in the front half, enabling efficient operation under normal and extreme conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric motor is oversized to generate very high fluid pressures under extreme braking conditions, then the braking system can handle extreme conditions, but the motor torque and power supply requirements increase, leading to overheating risk and increased weight and dimensions
Solution Approach 1:
The patent applies dynamics by making the transmission ratio variable through a cam mechanism. The cam profile is specifically designed to provide a first transmission ratio during the first portion of the piston stroke and a second, lower transmission ratio during the second portion. This dynamic adjustment allows the motor to operate at optimal torque levels throughout the braking cycle, preventing overheating while maintaining the capability to generate high pressures when needed.
Solution Approach 2:
The invention changes the transmission ratio parameter dynamically during operation. By using a cam mechanism with a specific profile, the transmission ratio between motor shaft rotation and piston stroke is varied: a first ratio during the initial portion of the stroke and a second, lower ratio during the final portion. This parameter change enables the motor to deliver appropriate torque at different stages, avoiding the need for continuous high torque that would cause overheating.
2Reliability
If the electric motor is oversized to generate very high fluid pressures under extreme braking conditions, then the braking system can handle extreme conditions, but the manufacturing and operational costs increase
Solution Approach 1:
The patent applies dynamics by making the transmission ratio variable through a cam mechanism. The cam profile is specifically designed to provide a first transmission ratio during the first portion of the piston stroke and a second, lower transmission ratio during the second portion. This dynamic adjustment allows the motor to operate at optimal torque levels throughout the braking cycle, preventing overheating while maintaining the capability to generate high pressures when needed.
Solution Approach 2:
The cam mechanism automatically adjusts the transmission ratio based on the piston position without requiring external control systems or sensors. The mechanical design itself provides the optimal torque distribution, allowing the motor to self-regulate its output characteristics throughout the braking cycle, which simplifies control and reduces system complexity.
3Reliability
If the electric motor is oversized to generate very high fluid pressures under extreme braking conditions, then the braking system can handle extreme conditions, but the overall dimensions of the actuator increase
Solution Approach 1:
The patent applies dynamics by making the transmission ratio variable through a cam mechanism. The cam profile is specifically designed to provide a first transmission ratio during the first portion of the piston stroke and a second, lower transmission ratio during the second portion. This dynamic adjustment allows the motor to operate at optimal torque levels throughout the braking cycle, preventing overheating while maintaining the capability to generate high pressures when needed.
4Device complexity
If a constant transmission ratio is used between motor shaft and piston, then the system is simpler, but the motor cannot efficiently generate high fluid pressures without excessive torque and power requirements
Solution Approach 1:
The patent applies dynamics by making the transmission ratio variable through a cam mechanism. The cam profile is specifically designed to provide a first transmission ratio during the first portion of the piston stroke and a second, lower transmission ratio during the second portion. This dynamic adjustment allows the motor to operate at optimal torque levels throughout the braking cycle, preventing overheating while maintaining the capability to generate high pressures when needed.
Solution Approach 2:
The invention changes the transmission ratio parameter dynamically during operation. By using a cam mechanism with a specific profile, the transmission ratio between motor shaft rotation and piston stroke is varied: a first ratio during the initial portion of the stroke and a second, lower ratio during the final portion. This parameter change enables the motor to deliver appropriate torque at different stages, avoiding the need for continuous high torque that would cause overheating.
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 reduces the risk of motor overheating during extreme braking while maintaining suitable operation under standard conditions, allowing for precise control of fluid pressure and efficient energy use, thus optimizing the braking system's performance and reducing costs.
Implementation Method 1
an electric motor (3) with a drive shaft (4)
Implementation Method 2
a converting mechanism (5) connected with the drive shaft (4) and adapted to convert a rotational motion of the drive shaft (4) into a translational motion of a translatable portion (6)
Implementation Method 3
a hydraulic pump (7) connected to the converting mechanism (5) and adapted to generate, in response to the translational movement, an increase in pressure of a hydraulic liquid
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An electro-hydraulic actuator (1) for actuating a brake (2) with a hydraulic thrust unit comprises an electric motor (3), a converting mechanism (5) to convert a rotational motion of the motor (4) into a translational motion, a cylinder (8), and a piston (9) connected to the converting mechanism, wherein the converting mechanism (5) is configured so that, for a given angular speed of the drive shaft (4), the translation speed of the piston (9) decreases from a maximum value in a rear length (14) of the piston stroke to a minimum value in a front length (13) of the piston stroke.