CVT Gearbox Control Unit for Optimal Transmission Ratio
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Solution Overview
Problem
Centrifugally controlled CVT transmissions lack controllability and optimality, leading to suboptimal fuel consumption, emissions, and vehicle dynamics, particularly during acceleration phases.
Innovation Solution
A CVT transmission system with a control unit that adjusts the position of an axially movable conical disk using an actuating device, allowing for intervention in the transmission ratio based on primary and secondary speeds, motor torque, and adjustment speed, incorporating a PD controller and characteristic map for optimal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a centrifugal governor is used to adjust the belt position on conical pulleys, then the transmission ratio can be automatically adjusted based on speed, but controlled or regulated intervention in the transmission ratio becomes impossible
Solution Approach 1:
The patent combines the centrifugal governor mechanism with an additional actuating device that can be controlled by a control unit. This merging allows the system to maintain the automatic speed-based adjustment capability of the centrifugal governor while adding the ability for controlled intervention through the actuator, which can override or supplement the centrifugal forces based on control signals.
Solution Approach 2:
The system dynamically switches between two control modes: passive centrifugal governor control for normal operation and active controlled intervention when the control unit activates the actuating device. This dynamic capability allows the transmission ratio to be adjusted both automatically based on speed and through controlled regulation when needed.
2Device complexity
If a centrifugal governor controls the CVT transmission, then the system structure remains simple, but the transmission cannot operate at optimal points leading to increased fuel consumption and emissions
Solution Approach 1:
The control unit receives feedback about the actual transmission ratio and operating conditions, then activates the actuating device to adjust the transmission ratio toward optimal values. This feedback control enables the system to operate at optimal points for fuel efficiency while maintaining a relatively simple structure by only adding controlled adjustment capability when needed.
3Device complexity
If a centrifugal governor is used for transmission ratio adjustment, then the system is easy to implement, but vehicle dynamics and acceleration performance are suboptimal
Solution Approach 1:
The control unit can predict optimal transmission ratio adjustments based on driving conditions and activate the actuating device in advance to prepare the transmission for upcoming acceleration demands. This preliminary action allows the system to maintain simple centrifugal governor hardware while achieving improved acceleration performance through proactive control.
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
Significantly improves fuel efficiency, reduces emissions, and enhances driving performance by enabling operation at optimal points, achieving up to 10% fuel savings and 17% improved acceleration between 0-60 km/h and 19% improved elasticity between 20-50 km/h compared to traditional centrifugally controlled CVT transmissions.
Implementation Method 1
Depending on the speed, centrifugal weights of the centrifugal governor shift their radial position, as a result of which an axial distance between two conical disks is changed and the transmission ratio is thereby changed.
Data Source
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AI summary
The invention relates to a CVT gearbox having a first pair of cone pulleys (2) comprising a locationally-fixed cone pulley (20) and an axially-displaceable cone pulley (21), an output element (25), particularly a second pair of cone pulleys, a belt means (12) which connects the first pair of cone pulleys (2) to said output element (25), an adjustment device (5) for adjusting the axially-displaceable cone pulley (21) by means of an actuator (50), and a control unit (6) that is configured to actuate the adjustment device (5) in order to adjust said axially-displaceable cone pulley (21).