Multi-stage Transmission Brake Piston Segmentation
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Solution Overview
Problem
Conventional multi-stage transmission brakes experience deteriorated shifting performance due to negative pressure in one of the engagement oil chambers when oil pressure is supplied to only one of the chambers, hindering smooth piston movement.
Innovation Solution
The multi-stage transmission incorporates a brake design with a first and second piston, each with a pressure-receiving and plate-pressing portion, and a return spring, where the pistons define engagement oil chambers to ensure smooth operation by maintaining positive pressure in both chambers, regardless of the oil pressure distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If engagement oil pressure is supplied to only one of the first and second engagement oil chambers, then the brake structure can be simplified and oil consumption reduced, but the pressure inside the other chamber becomes negative which hinders smooth piston movement and deteriorates shifting performance
Solution Approach 1:
The brake is divided into two independent engagement oil chambers (first and second chambers) with separate pressure-receiving portions, allowing each chamber to operate independently without negative pressure effects on the other, thus resolving the contradiction between simplified structure and reliable operation
Solution Approach 2:
The second piston acts as an intermediary that transmits oil pressure from the second engagement oil chamber to the first piston, enabling coordinated operation of both friction engagement plates while maintaining positive pressure in both chambers during engagement
2Device complexity
If a single piston design is used in conventional brakes, then the device complexity is reduced, but the piston movement becomes hindered by negative pressure when oil is supplied to only one chamber
Solution Approach 1:
The single piston is segmented into a first piston and a second piston, where the second piston independently manages the second engagement oil chamber pressure and transmits force to the first piston, eliminating negative pressure hindrance and ensuring smooth movement
Solution Approach 2:
The second piston is positioned within the first piston structure, with the second piston's pressure-receiving portion receiving oil pressure and its piston-pressing portion transmitting force to the first piston, creating a nested arrangement that solves the movement smoothness problem
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 enhances shifting performance by ensuring smooth movement of the pistons and effective engagement of friction plates, regardless of the torque share, thereby improving the overall transmission efficiency.
Implementation Method 1
a return spring that biases the first piston so that the first piston moves away from the first and the second friction engagement plates
Implementation Method 2
engagement oil pressure (hydraulic oil) is supplied to either one of the first and the second oil pressure chambers when the torque share becomes relatively low, and the engagement oil pressure is supplied to both of the first and the second oil pressure chambers when the torque share becomes relatively high
Implementation Method 3
a brake has been known having: one piston that is slidable in a case or a cylinder coupled to the case, and causes friction members and disk plates to engage with and disengage from each other
Data Source
AI summary
A brake of an automatic transmission includes: first and second recessed portions and formed in a center support; a first piston having a first pressure-receiving portion that is disposed in the first recessed portion and defines a first engagement oil chamber and having a plate-pressing portion that presses friction plates and separator plates; a second piston having a second pressure-receiving portion that is disposed in the second recessed portion and defines a second engagement oil chamber and a piston-pressing portion that presses the first piston by supply of oil pressure to the second engagement oil chamber; and a return spring that biases the first piston so that the first piston moves away from the friction plates and the separator plates.