Hybrid Transmission Oil Pump Control Under High Line Pressure
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Solution Overview
Problem
In hybrid vehicles, the electric oil pump's lower maximum discharge pressure can lead to erroneous failure determination and increased fuel consumption when the line pressure is high, causing the mechanical oil pump to solely supply hydraulic oil, which deteriorates fuel efficiency.
Innovation Solution
A vehicle control device that adjusts the minimum rotation speed of the drive source and executes control strategies like automatic downshift, idle reduction, and coast stop based on the drive current value and line pressure, preventing erroneous determination of the electric oil pump failure and ensuring appropriate hydraulic oil supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the electric oil pump is used to supply hydraulic oil when line pressure is high, then the discharge pressure capability is improved, but the drive current value exceeds the maximum value and causes erroneous failure determination
Solution Approach 1:
The control device dynamically adjusts the minimum rotation speed of the drive source based on the drive current value of the motor. When the drive current exceeds the maximum value, the system increases the minimum rotation speed to reduce the load on the motor, thereby preventing erroneous failure determination while maintaining the ability to supply required hydraulic oil.
Solution Approach 2:
The system changes the operating parameters by adjusting the minimum rotation speed of the drive source in response to the drive current value. This parameter adjustment allows the electric oil pump to operate safely under high line pressure conditions without triggering false failure detections.
2Productivity
If the mechanical oil pump solely supplies hydraulic oil when electric oil pump failure is determined, then the required flow rate is secured, but fuel consumption deteriorates
Solution Approach 1:
The control device continuously monitors the drive current value of the motor and uses this feedback to determine whether the electric oil pump is actually failed or merely overloaded. This feedback mechanism prevents premature switching to the mechanical oil pump, thereby avoiding unnecessary fuel consumption while ensuring adequate hydraulic oil supply.
Solution Approach 2:
By dynamically adjusting the minimum rotation speed of the drive source based on real-time drive current monitoring, the system maintains electric oil pump operation under high load conditions, preventing erroneous failure determination and avoiding the fuel consumption penalty associated with relying solely on the mechanical oil pump.
3Reliability
If the minimum rotation speed of the drive source is increased to prevent motor overload, then the electric oil pump can continue operating, but the fuel consumption increases due to higher engine load
Solution Approach 1:
The system changes the minimum rotation speed parameter of the drive source based on the drive current value. This controlled parameter change allows the electric oil pump to continue operating reliably under high line pressure conditions while minimizing the increase in fuel consumption by only adjusting the rotation speed when necessary.
Data Source
AI summary
In a vehicle control device for controlling the vehicle, when automatic downshift control for automatically downshifting a speed ratio of the transmission is executed in the case where a drive current value of the motor obtained when the second oil pump is driven is larger than a maximum value of the drive current value of the motor obtained when the second oil pump is driven in a normal drive state, the vehicle control device increases a minimum rotation speed of the drive source compared to a case where the drive current value of the motor is equal to or less than the maximum value, and when the automatic downshift control is executed in the case where a line pressure generated by a hydraulic pressure supplied from the first oil pump and the second oil pump is larger than a predetermined value, the vehicle control device does not increase the minimum rotation speed of the drive source even in the case where the drive current value of the motor obtained when the second oil pump is driven is larger than the maximum value.