CVT Shift Control Preventing Engine Overspeed
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Solution Overview
Problem
The challenge in continuously variable transmissions is to prevent over-speeding of internal combustion engines caused by rapid rotation increases during shifts in the subtransmission mechanism, which can lead to unstable engine operation and reduced performance.
Innovation Solution
A control device and method that utilize a rotation speed sensor and shift controller to adjust the speed ratio of the continuously variable transmission mechanism in opposition to the subtransmission mechanism's speed ratio variation, ensuring the overall speed ratio remains constant during shifts, and reducing the shift speed when excess rotation speed exceeds a predetermined value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the speed ratio of the continuously variable transmission mechanism is shifted rapidly to compensate for subtransmission shifts, then the overall speed ratio can be maintained, but the engine rotation speed increases rapidly causing over-speeding
Solution Approach 1:
The control device performs preliminary action by detecting the start of subtransmission upshift before the actual shift occurs, and begins adjusting the variator speed ratio in advance. This anticipatory control prevents rapid engine rotation increase by preparing the speed ratio adjustment beforehand, rather than reacting after the deviation occurs.
Solution Approach 2:
The invention applies dynamics by making the variator speed ratio adjustable and continuous during the shift process. The control device dynamically modifies the speed ratio of the continuously variable transmission mechanism in real-time to compensate for subtransmission speed ratio changes, enabling smooth adaptation without abrupt engine speed changes.
2Reliability
If the speed ratio of the continuously variable transmission mechanism is adjusted to maintain constant overall speed ratio, then engine over-speeding is prevented, but the control complexity increases
Solution Approach 1:
The control device implements feedback control by continuously monitoring the speed ratio of the subtransmission mechanism and adjusting the variator speed ratio accordingly. The control unit receives signals about subtransmission shift status and automatically modifies the continuously variable transmission ratio to maintain constant overall speed ratio, creating a closed-loop control system that ensures engine operation stability.
Data Source
AI summary
A speed ratio of a continuously variable transmission mechanism 20 is increased when a speed ratio of a subtransmission mechanism 30 connected in series to the continuously variable transmission mechanism 20 is switched from a first speed to a second speed. When an excess rotation speed Nb obtained by subtracting a target rotation speed from an engine rotation speed Ne exceeds a determination value Nr1 during this shifting process, a rapid rotation increase in an internal combustion engine 1 is prevented by reducing a shift speed of the continuously variable transmission mechanism 20 (S105A).