CVT Clutch Synchronization with Upshift Timing
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Solution Overview
Problem
Continuously variable transmission (CVT) systems in vehicles experience noise, vibration, and harshness issues due to shifting patterns and clutch engagement, which can be unpleasant for drivers and affect the overall propulsion system performance.
Innovation Solution
A control system that synchronizes the application state of a torque converter lockup clutch with changes in pulley ratio and engine speed, using a method to determine impending CVT upshifts and alter clutch engagement state after a delay to mask engine speed drops and blend them with turbine acceleration changes, ensuring a single engine note and imperceptible clutch engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a torque converter lockup clutch is engaged during CVT operation, then torque transfer efficiency is improved, but noise and vibration increase due to clutch engagement harshness
Solution Approach 1:
The control system determines impending continuous upshifts before they occur and times the clutch engagement to coincide with the natural engine speed drop from the upshift. This preliminary timing action ensures the clutch engages when engine speed is already changing, masking the engagement harshness and reducing perceived noise and vibration while maintaining torque transfer efficiency.
2Adaptability or versatility
If clutch engagement state is altered independently of CVT shift pattern, then clutch control flexibility is improved, but noise and vibration harshness increases due to unsynchronized engagement
Solution Approach 1:
The control system continuously monitors CVT pulley ratio changes and engine speed to detect impending continuous upshifts. This feedback mechanism allows the system to synchronize clutch engagement with the natural engine speed changes from upshifts, maintaining clutch control flexibility while eliminating unsynchronized engagement harshness and reducing noise and vibration.
3Ease of operation
If CVT pulley ratio changes continuously, then transmission smoothness is improved, but engine speed fluctuations increase causing audible noise
Solution Approach 1:
The control system merges the clutch engagement event with the engine speed drop caused by CVT continuous upshifts. By timing the clutch engagement to coincide with the natural engine speed changes from pulley ratio variation, the system combines two events that would otherwise be separate and audible, creating a single masked engagement event that reduces overall noise while maintaining transmission smoothness.
Data Source
AI summary
A continuously variable transmission, a control system, and a method is provided for synchronizing a clutch application state change and a continuous upshift in a motor vehicle propulsion system having a continuously variable transmission (CVT). The control system and method are configured to determine whether a continuous upshift of the CVT is impending. The continuous upshift is defined as a pulley ratio change exceeding a predetermined threshold for a predetermined pulley ratio change period. If a continuous upshift is impending, the control system and method are configured to alter a clutch engagement state after a predetermined delay period to synchronize the change in clutch engagement state with an engine speed change.