CVT Subtransmission Interlocking for Torque Shock Reduction
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Solution Overview
Problem
Existing continuously variable transmissions experience shock when reducing output shaft torque during vehicle stoppage due to torque amplification in low gear position, leading to uncomfortable shifts and potential driving force deficiencies.
Innovation Solution
Implementing a second speed interlocking condition in the subtransmission mechanism, where both frictional engagement elements of the first and second gear positions are engaged when the vehicle stops, reducing output shaft torque smoothly and alleviating shock during transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the subtransmission mechanism is set in a low gear position during vehicle stoppage to secure sufficient driving force for restart, then the driving force is improved, but shock occurs when reducing output shaft torque during D-N select or N idle control
Solution Approach 1:
The control device reduces the oil pressure supplied to the frictional engagement element before the actual gear position change occurs. By anticipating the upcoming D-N select or N idle control operation, the system pre-reduces torque amplification through controlled pressure reduction, thereby minimizing the shock that would otherwise occur when torque is suddenly reduced from the high amplification state of low gear position.
Solution Approach 2:
The control device changes the oil pressure parameter supplied to the frictional engagement element during vehicle stoppage. By reducing the oil pressure to a specific level before gear position change, the system modifies the torque amplification characteristic of the low gear position, enabling a smoother transition and reducing shock during subsequent gear position changes without compromising restart capability.
2Object-affected harmful factors
If the oil pressure supplied to the frictional engagement element is reduced gently using an orifice and accumulator, then shock is alleviated, but engagement of the frictional engagement element is delayed
Solution Approach 1:
The control device performs preliminary pressure reduction only during vehicle stoppage conditions, before gear position change is needed. By anticipating the timing of D-N select or N idle control operations, the system pre-adjusts the oil pressure to an optimal level that enables both smooth shock reduction and rapid subsequent engagement, eliminating the need for orifice and accumulator components that cause delay.
Solution Approach 2:
The control device dynamically adjusts the oil pressure supplied to the frictional engagement element based on vehicle operating conditions. During stoppage, pressure is reduced to minimize shock; during gear position changes, pressure is maintained or increased to ensure rapid engagement. This dynamic control eliminates the fixed, delay-causing pressure reduction mechanism of orifice and accumulator systems.
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 step in output shaft torque, minimizing shock and ensuring sufficient driving force during restarts, thereby enhancing the driving experience and reducing the likelihood of engagement delays.
Implementation Method 1
a frictional engagement element for realizing the low gear position is disengaged by draining an oil pressure supplied to the frictional engagement element
Implementation Method 2
draining an oil pressure supplied to the frictional engagement element
Data Source
AI summary
When a vehicle stops in a travel range, a transmission controller sets a subtransmission mechanism in a second speed interlocking condition in which a torque input into a continuously variable transmission is transmitted in a second gear position and both a frictional engagement element of a first gear position and a frictional engagement element of the second gear position are engaged, and when a predetermined condition is established while the vehicle is stationary, the transmission controller reduces an output shaft torque of the continuously variable transmission.