Electrohydraulic Brake Actuator with Segmented Pistons
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Solution Overview
Problem
Existing electrohydraulic brake actuators for vehicles require high displacement forces to generate and increase brake pressure, which can be inefficient and slow in activating hydraulic wheel brakes.
Innovation Solution
The electrohydraulic brake actuator employs a piston-cylinder unit with a rotation-translation conversion gear driven by an electric motor, featuring multiple pistons with varying pressure-generating surfaces, allowing for initial rapid displacement with a larger surface area to quickly activate brakes and subsequent pressure increase with reduced force using smaller surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a single piston with constant pressure-generating surface is used, then the structure is simple, but high displacement force is required throughout the entire pressure buildup process
Solution Approach 1:
The piston is divided into multiple segments (first piston, second piston, third piston) with different pressure-generating surfaces. Each segment can be independently displaced to perform different functions: the first piston with large surface area quickly displaces brake fluid to activate brakes, while subsequent pistons with smaller surfaces increase pressure with reduced force requirements.
Solution Approach 2:
The piston structure transitions from static to dynamic by enabling sequential displacement of different piston segments. The system dynamically adjusts which piston segment is active based on the braking phase, allowing the pressure-generating surface to change during operation rather than remaining constant.
2Productivity
If a larger pressure-generating piston surface is used, then brake fluid displacement volume per distance is greater for quick brake activation, but the displacement force required becomes excessively high
Solution Approach 1:
The piston is segmented into multiple functional units with different surface areas. The first piston has a large pressure-generating surface for rapid brake fluid displacement and quick brake activation, while the second and third pistons have smaller surfaces for subsequent pressure increase with lower force requirements.
Solution Approach 2:
The system uses partial action by selectively engaging different piston segments based on braking requirements. The large-surface first piston is used only when rapid brake activation is needed, while smaller-surface pistons handle normal pressure increase, avoiding the continuous high force requirement of a single large piston.
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 design reduces the displacement force required to increase brake pressure, enabling quick activation of hydraulic wheel brakes and efficient pressure buildup, improving the efficiency and speed of brake engagement.
Implementation Method 1
an electric motor 2, a spindle drive 3 and, if applicable, a mechanical reduction gear 5. The spindle drive 3 converts a rotational movement of the electric motor 2 into a displacement
Implementation Method 2
The rotation-translation conversion gear may include a screw drive, for example a spindle drive or a ball screw
Implementation Method 3
The displacement of the piston in the cylinder generates a brake pressure in the cylinder and in one or multiple hydraulic wheel brakes connected to the cylinder
Data Source
AI summary
An electrohydraulic brake actuator for a motor vehicle. The brake actuator has a piston-cylinder unit, whose piston is displaceable by an electric motor via a screw drive. Two pistons are provided, of which initially only a piston having a greater pressure-generating piston surface is displaced in order to build up pressure quickly and subsequently a second piston having a smaller pressure-generating piston surface is displaced in order to increase pressure.