Dual Piston Automatic Transmission Brake Control
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Solution Overview
Problem
Current power delivery devices for automatic transmissions face inefficiencies due to uncontrolled operating speed and coupling force, leading to reduced brake performance and potential damage from repeated high coupling force applications, as well as drag loss when releasing the brake.
Innovation Solution
A power delivery device utilizing dual pistons to rapidly control the gap between friction members, providing quick responsiveness and sufficient coupling force, and a return spring to minimize drag loss and prevent brake damage, with hydraulic pressure control initiated above the spring force threshold to stabilize valve operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single piston is used to operate the brake, then the structure is simple, but the operating speed and coupling force cannot be precisely controlled for each operating stage
Solution Approach 1:
The single piston is divided into two separate pistons: a first piston responsible for rapid gap closure and a second piston responsible for applying coupling force. This segmentation allows independent control of operating speed and coupling force, resolving the contradiction between control precision and structural simplicity.
Solution Approach 2:
The system transitions from a static single-piston design to a dynamic two-piston system where each piston can be independently actuated based on operating conditions. The control unit dynamically controls hydraulic pressure to each piston, enabling precise control at different operating stages.
2Productivity
If great coupling force is repeatedly applied to the brake plate with quick operating speed, then power delivery is efficient, but the brake may be damaged due to accumulated fatigue
Solution Approach 1:
The brake operation is segmented into two phases: a first phase with quick operating speed for rapid engagement, and a second phase with great coupling force for secure power delivery. This prevents excessive force during the engagement phase, reducing fatigue damage while maintaining power delivery efficiency.
Solution Approach 2:
The dual-piston system enables periodic control of hydraulic pressure, allowing the brake to be operated in controlled intervals. The control unit can modulate pressure application to prevent continuous high-stress conditions that lead to fatigue damage.
3Measurement precision
If hydraulic pressure is controlled at low-pressure region, then fine control is possible, but control reliability deteriorates due to unstable valve operation
Solution Approach 1:
The system introduces a spring element as an intermediary between the hydraulic pressure source and the piston. The spring provides a force threshold that stabilizes valve operation by ensuring the hydraulic pressure always overcomes a minimum spring force, preventing unstable low-pressure operation while allowing fine control above this threshold.
4Speed
If the brake releases quickly, then responsiveness is improved, but drag loss occurs during brake release
Solution Approach 1:
The brake release process is segmented into two stages: first piston releases to reduce pressure quickly, then second piston releases to complete the release. This staged approach minimizes the time the brake is in a partial engagement state, reducing drag loss while maintaining quick overall responsiveness.
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
Enhances power delivery efficiency, reduces brake damage, and improves control reliability by precisely managing the gap between friction members and minimizing drag loss, while maintaining stable hydraulic pressure control.
Implementation Method 1
a return spring mounted between the spring retainer and the second piston and applying restoring force to the first and second pistons
Implementation Method 2
a first piston having an external circumferential portion closely contacting the external circumferential portion of the brake drum and an internal circumferential portion closely contacting the internal circumferential portion of the brake drum, and being movable toward the brake in the axial direction by receiving hydraulic pressure
Data Source
AI summary
A power delivery device configured for an automatic transmission may include a brake disposed between a rotation element connected to a brake hub and a transmission housing, and a piston device disposed corresponding to the brake and operating the brake by hydraulic pressure, wherein the power delivery device configured for an automatic transmission selectively connects the rotation element to the transmission housing by use of dual pistons.