CVT Sheave Origin Learning for Smooth Vehicle Start
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Solution Overview
Problem
Existing vehicle transmission systems, particularly those with continuously variable transmissions, face challenges in providing a stable transmission ratio and smooth start-up, as they require time to correct upper and lower limit values upon engine start, potentially leading to delayed vehicle initiation.
Innovation Solution
A vehicle equipped with a belt-drive continuously variable transmission, an actuator, a control unit, a sheave position sensor, and an origin location learning mechanism that allows the movable sheave body to be moved to its origin position without interfering with engine start-up, enabling immediate vehicle start-up and maintaining a stable transmission ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control unit corrects the upper limit value and lower limit value of the transmission ratio each time the engine is started, then a stable transmission ratio is achieved, but the vehicle cannot start immediately and smooth start is prevented
Solution Approach 1:
The control unit performs origin location learning control in advance when the main switch is turned OFF and the driving force is not transferred to the drive wheel. This preliminary action positions the movable sheave body at the origin location before the driver attempts to start the vehicle, so that when the engine is started, the transmission ratio is already stable and no additional correction time is needed during vehicle start-up.
2Reliability
If the movable sheave body is moved to the origin location by the actuator, then a stable transmission ratio is obtained, but the movement interferes with the start of the vehicle
Solution Approach 1:
The origin location learning control is extracted from the vehicle start-up process and performed separately when the main switch is OFF and the driving force is not transferred to the drive wheel. By separating these operations in time, the movable sheave body can be positioned at the origin location without interfering with the driver's ability to start the vehicle smoothly when needed.
Solution Approach 2:
The control unit dynamically determines whether to perform origin location learning control based on the state of the main switch and whether the driving force is being transferred to the drive wheel. This dynamic control allows the system to adapt to different operating conditions, performing the sheave positioning only when it will not conflict with vehicle start-up operations.
3Ease of operation
If the origin location learning control is performed when the main switch is turned OFF, then the vehicle can start smoothly, but the transmission ratio may be unstable during operation
Solution Approach 1:
The control unit uses feedback from the sheave position sensor to detect the position of the movable sheave body and determines when it has reached the origin location. This feedback mechanism ensures that the origin location learning control is completed accurately, providing a stable foundation for subsequent transmission ratio control during vehicle operation.
Data Source
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AI summary
To provide a vehicle capable of obtaining a stable transmission ratio and a smooth start of the vehicle as desired by a driver, the vehicle includes an engine, a transmission including a stationary sheave body and a movable sheave body, a drive wheel to which a driving force of the engine is transferred, a motor for moving the movable sheave body, an ECU 7 for controlling the motor, a sheave position sensor 40 for detecting the position of the movable sheave body, and a main switch 33. The ECU 7 includes a memory 7b for storing an origin location P0 of the movable sheave body, a traveling state determination unit 131, an origin location moving unit 121 for controlling movement of the movable sheave body towards the origin location P0 when detecting or estimating that the main switch 33 is turned OFF and the driving force of the engine is not transferred to the drive wheel, and an origin location setting unit 122 for causing the memory 7b to store a new origin location P0' detected by the sheave position sensor 40.