CVT Controller Initializing Pulley Ratio for Reliable Pressure Supply
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Solution Overview
Problem
In continuously variable transmissions without a primary pulley pressure sensor, the startability of a vehicle is impeded when the operating position of the step motor at the preceding stopping time is not stored, and a backup power source failure occurs, leading to loss of pulley information and inability to determine primary pulley pressure.
Innovation Solution
A continuously variable transmission system that includes an input side primary pulley and an output side secondary pulley with varying groove widths, a belt looped around them, a speed change control mechanism connected to a step motor, and a controller that sets the primary pulley pressure to zero and increases the secondary pulley pressure to a predetermined level, shifting the pulley ratio to the lowest speed ratio during vehicle activation, allowing reliable primary pulley pressure supply without a primary pulley pressure sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the vehicle uses a continuously variable transmission without a primary pulley pressure sensor and without stored pulley information, then the device complexity is reduced, but the startability of the vehicle deteriorates
Solution Approach 1:
The system performs preliminary actions during vehicle activation by detecting rotation of the primary and secondary pulleys and automatically setting the pulley ratio to the lowest speed ratio before vehicle operation begins. This preliminary setup ensures the primary pulley pressure can be supplied reliably without requiring stored pulley information or a primary pulley pressure sensor, thus resolving the startability issue while maintaining simplified device complexity.
2Reliability
If the backup power source fails, then the loss of information occurs, but the vehicle can still be started if the pulley ratio is reset to the lowest speed ratio
Solution Approach 1:
The system implements self-service by automatically detecting pulley rotation during activation and autonomously resetting the pulley ratio to the lowest speed ratio without requiring stored information or external intervention. This self-service mechanism ensures the vehicle can be started even when backup power source fails and pulley information is lost, as the system independently recovers the necessary operational state.
3Speed
If the step motor is displaced to an operating position corresponding to High speed ratio without confirming primary pulley pressure, then the speed ratio can be maintained, but the primary pulley pressure may not be supplied reliably
Solution Approach 1:
The system performs the action of setting the pulley ratio to the lowest speed ratio as a preliminary step before vehicle operation begins. By establishing this baseline state during activation through rotation detection, the system ensures the primary pulley pressure can be supplied reliably before attempting to maintain any other speed ratio, thus resolving the reliability issue while enabling subsequent speed ratio maintenance.
Data Source
AI summary
When a speed ratio (ip) at a stopping time of the vehicle cannot be stored, an operating position of a step motor (27) is initialized to a home position such that a primary pulley pressure (Ppri) is completely drained, a secondary pulley pressure (Psec) is increased to a predetermined pressure (P1), and a pulley ratio (the speed ratio (ip)) between a non-rotating primary pulley (2) and a non-rotating secondary pulley (3) is set at a lowest speed ratio. As a result, the primary pulley pressure (Ppri) is supplied reliably, and the startability of the vehicle improves.