CVT Pulley Piston Area Layout for Lower Electric Pump Output
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Solution Overview
Problem
Existing continuously variable transmission systems do not adequately address the magnitude relationship between the piston areas of primary and secondary pulleys, which affects the output required from the electric oil pump during shifts, leading to inefficiencies and potential downsizing challenges.
Innovation Solution
The solution involves specifying a magnitude relationship between the piston area of the primary pulley and the secondary pulley, with the primary pulley's piston area being set smaller than the secondary pulley's to reduce the output required from the electric oil pump, thereby enabling downsizing of the electric oil pump and reducing the risk of gear rattle noise and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the piston area of the primary pulley is made equal to or larger than the secondary pulley, then the hydraulic pressure control is simplified, but the output required from the electric oil pump increases, preventing downsizing
Solution Approach 1:
The patent applies asymmetry by intentionally making the primary pulley piston area smaller than the secondary pulley piston area. This asymmetric design creates a thrust ratio that is always less than 1, allowing the electric oil pump to operate at lower output levels while maintaining effective shift control through the resulting hydraulic pressure differential.
Solution Approach 2:
The patent changes the parameter of piston area from being equal or larger (conventional) to smaller (invention). This parameter change fundamentally alters the thrust ratio characteristics, enabling the system to achieve effective shift control with reduced pump output requirements.
2Weight of moving object
If the electric oil pump output is reduced for downsizing, then the pump size and weight decrease, but the shift control effectiveness may be compromised
Solution Approach 1:
The asymmetric piston area design ensures that the thrust ratio remains below 1 throughout operation, creating a hydraulic pressure differential that enhances shift control effectiveness. This allows the use of a smaller, lighter pump while maintaining or improving shift control performance.
Solution Approach 2:
The patent leverages the hydraulic pressure differential created by asymmetric piston areas to amplify the control effect, allowing a smaller pump to achieve the same or better shift control effectiveness as a larger pump would provide with symmetric areas.
3Reliability
If the piston areas are made large to ensure sufficient hydraulic pressure, then the shift control is reliable, but the overall transmission size increases
Solution Approach 1:
The asymmetric piston area configuration optimizes the thrust ratio to be less than 1, which allows for reduced piston areas while maintaining sufficient hydraulic pressure for reliable shift control. This reduces the overall transmission volume without compromising reliability.
Solution Approach 2:
By changing the piston area parameter from large and equal to smaller and asymmetric, the system achieves reliable shift control with reduced component sizes, thereby reducing the overall transmission volume.
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 approach reduces the output needed from the electric oil pump, allowing for a smaller electric motor and pump design, while maintaining efficient shift control and preventing gear rattle noise and vibration by ensuring proper hydraulic pressure management.
Implementation Method 1
a shift oil pump configured to control entry and exit of oil in a primary pulley oil chamber
Implementation Method 2
the piston area of the primary pulley is smaller than the piston area of the secondary pulley
Data Source
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AI summary
An object of the present invention is to provide a continuously variable transmission in which a magnitude relationship between a piston area of a primary pulley and a piston area of a secondary pulley is specified. As means for achieving the object, a continuously variable transmission (4) includes: an electric oil pump (123) disposed in an oil path (106) between a piston oil chamber (41c) of a primary pulley (41) and a piston oil chamber (42c) of a secondary pulley (42); and a controlling portion (10) configured to control the entry and exit of oil in the piston oil chamber (41c) of the primary pulley (41) by the electric oil pump (123). A piston area (41c) of the primary pulley (41) in the continuously variable transmission (4) is smaller than a piston area (42c) of the secondary pulley (42).