Transmission Brake Device Piston Nesting for Clutch Clearance Control
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Solution Overview
Problem
Existing brake devices in transmissions, such as automatic and continuously variable transmissions, face challenges in maintaining high responsiveness and reducing clutch clearance volume, leading to increased fuel consumption and power consumption, especially when the One-Way Clutch (OWC) is eliminated.
Innovation Solution
A brake device configuration featuring an engaging piston and a clearance adjusting piston, where the engaging hydraulic chamber is formed by fitting the base part of the engaging piston into a concave portion of the clearance adjusting piston, allowing for precise control of clutch clearance and maintaining a small volume, even when reducing clutch clearance, thereby enhancing responsiveness and reducing viscosity resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the clutch clearance is reduced to improve responsiveness, then the engagement timing and force can be precisely controlled, but the volume of the engaging hydraulic chamber increases
Solution Approach 1:
The engaging piston is nested within the clearance adjusting piston, with the engaging piston disposed inside a concave portion of the clearance adjusting piston. This nesting arrangement allows the engaging hydraulic chamber to be formed within the existing structure of the clearance adjusting piston, thereby reducing the overall volume of the engaging hydraulic chamber while maintaining the ability to reduce clutch clearance for improved responsiveness.
2Loss of energy
If the OWC is eliminated to reduce cost and improve fuel consumption, then the structure is simplified, but the responsiveness and control precision of the brake device must be significantly improved
Solution Approach 1:
The clearance adjusting piston performs preliminary action by reducing the clutch clearance before the engaging piston engages the friction plates. By pre-adjusting the clearance to a minimal value, the system ensures that when engagement occurs, the responsiveness is maximized and the control precision is enhanced, compensating for the elimination of the OWC.
3Speed
If the clutch clearance is reduced to improve engagement control, then the responsiveness increases, but the viscosity resistance of the lubricant increases causing higher fuel consumption
Solution Approach 1:
The system dynamically adjusts the clutch clearance based on operational requirements. The clearance adjusting piston can vary the clearance between fixed and rotatable friction plates, allowing the system to optimize between responsiveness (small clearance during engagement) and fuel consumption (larger clearance during non-engagement to reduce viscosity resistance).
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
The solution enables high responsiveness and precise control of the brake device engagement while maintaining a large clutch clearance for reduced viscosity resistance, improving fuel consumption performance and engine efficiency.
Implementation Method 1
when a hydraulic pressure is supplied into a clearance adjusting hydraulic chamber 570 formed on a back side of the clearance adjusting piston 560, as illustrated in FIG. 13B, the pistons 550 and 560 move forward against the biasing force of the return spring 540
Implementation Method 2
by supplying the hydraulic pressure into the engaging hydraulic chamber 580 on the back side of the engaging piston 550 in this state, the brake device 500 is engaged with high responsiveness
Implementation Method 3
the pistons 550 and 560 are kept at their retreat positions by the biasing force of the return spring 540 in an unengaged state
Implementation Method 4
a resistance that acts on the rotational member 520 due to a viscosity resistance of a lubricant between the fixed friction plate 531 and the rotatable friction plate 532 becomes small
Data Source
AI summary
A brake device of a transmission is provided. The brake device includes a friction plate set including fixed friction plates and rotatable friction plates alternately disposed with each other, an engaging piston, and a clearance adjusting piston. A clearance adjusting hydraulic chamber is formed on a side of the clearance adjusting piston opposite to the friction plate set, and a concave portion is formed in a surface of the clearance adjusting piston on a friction plate set side. A base part of the engaging piston on a side opposite to the friction plate set is slidably fitted into the concave portion of the clearance adjusting piston and an engaging hydraulic chamber is formed by the base part and the concave part.