Vehicle Control Apparatus for CVT Hesitation
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Solution Overview
Problem
The existing control apparatus for vehicles with internal combustion engines and belt-type continuously variable transmissions experiences hesitation during engine restart due to premature idling stop caused by high brake pedal force, leading to improper transmission ratio and delayed oil pressure recovery.
Innovation Solution
A control apparatus with oil pressure control, automatic stop control, transmission ratio detection, and continuable time period setting means, which adjusts the engine stop duration based on detected transmission ratio and oil temperature to ensure proper restart timing, independent of the transmission ratio and road conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the idling stop is performed based on predetermined conditions (vehicle speed = 0, brake pedal depressed), then fuel economy is improved, but the transmission ratio may not have returned to maximum transmission ratio, causing hesitation during vehicle start
Solution Approach 1:
The control apparatus performs preliminary actions by monitoring the transmission ratio before allowing idling stop to terminate. The ECU determines whether the transmission ratio has returned to the maximum transmission ratio (or within a predetermined range) before permitting engine restart, ensuring the CVT is in the optimal state for vehicle start. This preliminary check prevents hesitation during start-up while maintaining fuel economy benefits of idling stop.
2Speed
If the brake pedal depressing force is large, then vehicle stopping is achieved quickly, but the transmission ratio does not return to maximum transmission ratio, causing delayed oil pressure recovery and hesitation
Solution Approach 1:
The control apparatus implements feedback control by continuously monitoring the transmission ratio and using this information to determine when to terminate the idling stop. The ECU receives feedback about the transmission ratio from the CVT control device and adjusts the engine restart timing accordingly. This feedback mechanism ensures that even under high brake pedal force conditions, the engine restarts only after the transmission ratio has recovered to the maximum value, preventing hesitation and ensuring proper oil pressure recovery.
3Loss of time
If the engine is restarted immediately after idling stop, then time is saved, but the operation oil pressure may not have recovered sufficiently, causing belt slippage and hesitation
Solution Approach 1:
The control apparatus performs preliminary verification of the transmission ratio before allowing engine restart. The ECU determines whether the transmission ratio has returned to the maximum transmission ratio (or within a predetermined range) as a preliminary condition for terminating the idling stop. This preliminary action ensures that the CVT is in the optimal state for vehicle start, preventing belt slippage and hesitation while minimizing the time delay for restart.
Data Source
AI summary
A control apparatus controls a vehicle provided with an internal combustion engine, an oil pump actuated by the engine for pressurizing operation oil, and a belt-type continuously variable transmission to which the pressurized operation oil is supplied. An automatic stop of the engine is performed when a predetermined condition is satisfied. A transmission ratio of the continuously variable transmission is detected, and a continuable time period of the automatic stop of the engine is set according to the detected transmission ratio upon automatically stopping the engine. The automatic stop is controlled to end when a continuation time period of the automatic stop of the engine expires. Good vehicle start performance can be obtained when restarting the engine after the automatic stop, regardless of the brake operation manner and the like upon stopping the vehicle.