Automatic Transmission Line Pressure Control via Oil Temperature
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Solution Overview
Problem
Existing line pressure control devices for automatic transmissions struggle to further improve fuel economy and prevent clutch slipping, as they are limited in adjusting line pressure based on hydraulic oil temperature and torque capacity differences.
Innovation Solution
A line pressure control device that regulates oil pressure by storing hydraulic pressure control characteristics for high and low pressure regions based on engine load and using a hydraulic oil temperature sensor to adjust these characteristics, thereby enlarging the low pressure region and switching mapped data to improve fuel efficiency and prevent clutch slipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If line pressure is switched between high and low pressure regions based on throttle valve opening degree and vehicle speed, then fuel economy can be improved, but clutch slipping may occur due to torque capacity differences
Solution Approach 1:
The patent changes the parameter basis for line pressure control from throttle valve opening degree and vehicle speed to hydraulic oil temperature. This allows dynamic adjustment of pressure characteristics based on actual fluid viscosity changes, enabling fuel economy improvement while maintaining clutch engagement stability across different operating conditions.
Solution Approach 2:
The patent introduces dynamic switching between different pressure characteristics (first and second characteristics) based on hydraulic oil temperature. This dynamic adaptation allows the system to optimize for fuel economy in warm conditions while preventing clutch slipping in cold conditions, resolving the contradiction between energy efficiency and reliability.
2Loss of energy
If low line pressure region is enlarged to improve fuel economy, then friction torque increases and clutch slipping occurs, but maintaining small low pressure region prevents clutch slipping
Solution Approach 1:
The patent changes the defining parameter of the low pressure region from fixed thresholds to temperature-dependent characteristics. By using hydraulic oil temperature as the basis for determining pressure characteristics, the system can safely enlarge the low pressure region in warm conditions (improving fuel economy) while maintaining appropriate pressure in cold conditions (preventing clutch slipping).
Solution Approach 2:
The patent applies preliminary action by pre-defining two sets of pressure characteristics corresponding to different temperature ranges. The system proactively selects the appropriate characteristic set before clutch engagement based on current hydraulic oil temperature, preventing clutch slipping before it can occur rather than reacting after the problem arises.
3Ease of operation
If line pressure is controlled based on mapped data of throttle valve opening degree and vehicle speed, then gear shift shock can be reduced, but fuel economy cannot be further improved
Solution Approach 1:
The patent changes the control parameters from throttle valve opening degree and vehicle speed to hydraulic oil temperature. This fundamental parameter change enables both gear shift smoothness (through gradual pressure transitions between characteristics) and improved fuel economy (through temperature-appropriate pressure optimization that reduces unnecessary friction).
Solution Approach 2:
The patent introduces dynamic switching between first and second pressure characteristics based on hydraulic oil temperature. This allows the system to adapt to changing thermal conditions, maintaining smooth gear shifts while optimizing fuel economy by using lower pressure when the hydraulic system is warm and viscosity is reduced.
Data Source
AI summary
Mapped data of line pressure set to any of high pressure/low pressure regions on the basis of an engine load are stored in a storage section. A determining section 103 determines, on the basis of temperature of the hydraulic oil detected by an ATF temperature sensor 18, whether the mapped data the low pressure region is shifted in an enlarged direction. A state determining section 104 determines whether a throttle valve opening degree TH of the vehicle is totally closed or whether the line pressure is currently set to low line pressure. When the low pressure region is shifted in the enlarged direction and the throttle valve opening degree TH is totally closed or the line pressure is currently set to the low line pressure, a region changing section enlarges the low pressure region of the mapped data stored in the storage section.