CVT Control Unit Engine Speed Fluctuation Management
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Solution Overview
Problem
Drivers experience discomfort due to sudden changes in engine rotation speed during mode switching operations in vehicles equipped with continuously variable transmission devices, as existing control methods fail to smoothly transition between fixed gear ratio control and fuel efficiency control.
Innovation Solution
An electronic control unit is implemented to manage engine rotation speed by selecting between number-of-revolutions increase control and fuel efficiency-priority engine control based on driver requests, ensuring smooth transitions and minimizing discomfort during mode changes by controlling the engine rotation speed and using additional motor generators for power demand satisfaction and temperature management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mode switching is implemented to provide different driving characteristics, then driver comfort and adaptability are improved, but engine rotation speed fluctuation occurs causing discomfort
Solution Approach 1:
The control device predicts future engine rotation speed based on current acceleration requests and vehicle state, then adjusts the continuously variable transmission ratio in advance to prevent rotation speed fluctuations when mode switching occurs. This preliminary adjustment ensures smooth transition between operation modes without causing discomfort to the driver.
Solution Approach 2:
The control device continuously monitors actual engine rotation speed and compares it with predicted values, then dynamically adjusts the continuously variable transmission ratio to minimize deviations. This feedback mechanism ensures that engine rotation speed remains stable during mode transitions while maintaining responsive acceleration characteristics.
2Speed
If fixed gear ratio control is used for rapid acceleration, then acceleration performance is improved, but fuel efficiency deteriorates
Solution Approach 1:
The control device dynamically switches between fixed gear ratio control and continuously variable gear ratio control based on real-time acceleration requests and vehicle state. During rapid acceleration, fixed gear ratio control provides responsive performance, while during steady-state operation, continuously variable gear ratio control optimizes fuel efficiency by maintaining the engine at optimal operating points.
Solution Approach 2:
The control device changes the gear ratio parameter adaptively based on driving conditions. By predicting future acceleration needs and adjusting the continuously variable transmission ratio accordingly, the system can prepare the engine for upcoming acceleration events while minimizing fuel consumption during transitional phases.
3Loss of energy
If continuously variable gear ratio control is used for fuel efficiency, then fuel consumption is reduced, but acceleration responsiveness deteriorates
Solution Approach 1:
The control device predicts future acceleration requests based on current vehicle state and driver behavior patterns. When an acceleration event is anticipated, the system pre-adjusts the continuously variable transmission ratio to ensure rapid power delivery, eliminating the need for delayed response that would otherwise occur with purely fuel-efficient control strategies.
Solution Approach 2:
The control device dynamically adapts the continuously variable transmission control strategy based on real-time acceleration requests. During steady-state cruising, the system optimizes for fuel efficiency by maintaining the engine at optimal operating points. When acceleration is requested, the system rapidly transitions to gear ratios that provide optimal acceleration performance, then smoothly returns to fuel-efficient operation.
Data Source
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AI summary
A vehicle (1) is provided with a continuously variable transmission device (20, 40) and an electric control unit (200) controlling an engine (10), a motor generator (30), and the continuously variable transmission device (20, 40). The electric control unit (200) selects any one of a plurality of operation modes, having different correlations between a driver' accelerator operation amount and a control throttle opening, to suit driver's requests, and performs a number-of-revolutions increase control for increasing an engine rotation speed according to at least one of elapsed time from a time point of a vehicle speed increase and elapsed time from a time point of an acceleration request in a case where the control throttle opening exceeds a predetermined threshold. The electric control unit (200) controls the engine (10) to suppress the engine rotation speed change due to a change of the operation mode in a case where the control throttle opening is changed across the predetermined threshold in response to the change of the operation mode.