Twin Piston Caliper EPB Segmentation
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Solution Overview
Problem
Current electric parking brake (EPB) caliper applications are limited to single piston hydraulic calipers, which restrict the maximum vehicle weight that can utilize EPB, as larger vehicles require twin piston calipers for hydraulic braking, leading to costly special mechanisms and packaging issues with larger pistons.
Innovation Solution
A twin piston caliper design that separates the EPB mechanism from hydraulic pistons, using high pressure overlay to preload the housing and pads, allowing a separate EPB apply mechanism with its own friction pad to clamp against the rotor, independent of hydraulic fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a single large diameter piston is used for EPB in larger vehicles, then the EPB clamp force is sufficient, but the packaging space is insufficient and the piston overhangs the brake pad
Solution Approach 1:
The patent divides the single large piston into two separate smaller pistons (e.g., two 45mm or two 51mm pistons) that work together to provide the required EPB clamp force. This segmentation allows the EPB mechanism to fit within the available caliper packaging space while still generating sufficient clamping force through the combined action of multiple pistons.
Solution Approach 2:
The patent combines the EPB mechanism with the hydraulic braking system by integrating two EPB pistons into the twin piston caliper assembly. The EPB pistons are positioned to work in conjunction with the hydraulic pistons, sharing the same caliper body and brake pad interface, thereby eliminating the need for a separate large single piston while achieving the required clamp force.
2Adaptability or versatility
If special mechanisms and gearing are added to achieve clamping of two pistons, then the EPB functionality is achieved in twin piston calipers, but the cost increases
Solution Approach 1:
The patent designs the twin piston caliper so that the same caliper body and basic mechanism serve both hydraulic braking and EPB functions. The two EPB pistons utilize the existing caliper structure, mounting points, and brake pad interface, eliminating the need for separate specialized mechanisms or gearing systems. This multi-functional design achieves EPB capability in twin piston calipers without increasing manufacturing complexity or cost.
3Force
If a 72 mm piston diameter is used, then the EPB clamp force is sufficient for larger vehicles, but the effective radius of the caliper is reduced and piston overhang increases
Solution Approach 1:
The patent segments the required clamp force generation from a single 72mm piston into two smaller pistons (e.g., two 45mm or two 51mm pistons). This segmentation reduces the individual piston diameter, thereby reducing piston overhang and increasing the effective radius of the caliper, while the combined force output of both pistons maintains the required EPB clamp force for larger vehicles.
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 enables higher EPB clamp force, improved lubrication, easier sealing, reduced service braking noise, and increased friction capabilities without the limitations of hydraulic fluid, allowing EPB functionality in larger vehicles.
Implementation Method 1
The caliper would utilize high pressure overlay (HPO) to preload the housing and pads thereby increasing the nominal clamp force for parking.
Implementation Method 2
The EPB apply mechanism shall use its own 'small' EPB friction brake pad to clamp against the brake rotor.
Data Source
AI summary
A twin piston caliper with an electric parking brake and method of operating such a twin piston caliper with an electric parking brake. The twin piston caliper housing comprises two separate inner brake pads for each of the two pistons; one outer brake pad at the outer housing finger area; an electric parking brake mechanism configured to be incorporated in between the two pistons so that it is not embedded in the hydraulic piston and not the hydraulic brake fluid; and wherein the electric parking brake mechanism uses its own electric parking brake friction brake pad to clamp against the brake rotor. The method of operating the twin piston caliper with the electric parking brake comprising the following steps: using hydraulic pressure, preferably high pressure overlay, to clamp up inner brake pads and the outer brake pad against a brake rotor; applying the electric parking brake mechanism to clamp an electric parking brake friction brake pad against the brake rotor; releasing the hydraulic pressure to unclamp the two inner brake pads whereby the electric parking brake mechanism maintains the clamp between the outer brake pad and the electric parking brake friction brake pad.