Adjusting Solenoid Valve Drive Currents for Automatic Transmission Torque Control
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Solution Overview
Problem
Conventional vehicle automatic transmission test systems fail to accurately control torque transfer by hydraulically-driven friction engagement elements and suppress shift shock due to unaccounted variations in engagement/disengagement characteristics, leading to torque shock and shift shock during gear changes.
Innovation Solution
An adjustment method that calculates correction values for drive currents supplied to linear solenoid valves based on estimated valve characteristics and piston-end pressures, accounting for variations in both valve characteristics and engagement/disengagement characteristics of hydraulically-driven friction engagement elements, ensuring accurate torque control and reduced shift shock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional test systems measure only output pressure from linear solenoid valves, then valve characteristics can be corrected, but torque shock and shift shock occur due to unaccounted variations in friction engagement element characteristics
Solution Approach 1:
The invention introduces feedback by detecting the actual supply pressure at the friction engagement element using a pressure detection portion, and using this feedback to calculate correction values that compensate for variations in both valve characteristics and engagement element characteristics. This closed-loop approach ensures accurate torque control by continuously adjusting based on actual pressure conditions.
Solution Approach 2:
The invention performs preliminary measurement of the pressure difference between output pressure and supply pressure during the test phase, and uses this pre-measured data to calculate correction values before actual operation. This preliminary characterization of the hydraulic circuit allows the system to compensate for pressure losses and variations without requiring real-time sensing during operation.
2Manufacturing precision
If drive currents are adjusted based only on valve characteristics, then valve output pressure varies correctly, but piston-end pressure varies due to friction engagement element variations
Solution Approach 1:
The invention introduces an intermediary measurement approach by detecting the supply pressure at the friction engagement element as an intermediate parameter. This supply pressure measurement serves as a mediator between the valve output pressure and the piston-end pressure, allowing calculation of the pressure difference that accounts for friction engagement element variations.
Solution Approach 2:
The invention changes the measurement parameter from only output pressure to include both output pressure and supply pressure, thereby obtaining the pressure difference parameter. This additional parameter enables calculation of correction values that compensate for variations in friction engagement element characteristics, transforming the control approach to account for real-world variations.
3Ease of manufacture
If pressure difference between output pressure and detected pressure is used for correction, then some compensation is achieved, but correction errors occur due to hydraulic circuit variations
Solution Approach 1:
The invention creates a universal correction method that works for different hydraulic circuits and friction engagement elements by measuring the pressure difference in the actual installed configuration. This approach provides a multi-functional solution that compensates for various sources of variation including hydraulic circuit characteristics, connection sealing, and engagement element variations, making the correction method universally applicable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively controls torque transfer and suppresses shift shock by compensating for variations in engagement/disengagement characteristics, providing precise control of hydraulically-driven friction engagement elements and minimizing shift shock in automatic transmissions.
Implementation Method 1
linear solenoid valves that control the pressures supplied to hydraulically-driven friction engagement elements
Implementation Method 2
hydraulic control circuit including linear solenoid valves that control the pressures supplied to hydraulically-driven friction engagement elements
Implementation Method 3
hydraulically-driven friction engagement elements
Data Source
AI summary
The adjustment method includes an estimation step in which valve characteristics of the linear solenoid valves fitted to the hydraulic control circuit are measured, and estimated linear valve characteristics of the linear solenoid valves in isolation state are estimated based on the measured valve characteristics using predetermined correlations; and a correction value output step in which estimated linear piston-end pressures of the hydraulically-driven friction engagement elements immediately before the hydraulically-driven friction engagement elements are engaged are calculated based on the estimated linear valve characteristics, and the correction values that are applied to the control command values to adjust the drive currents supplied from the valve control unit to the linear solenoid valves are calculated based on differences between the estimated linear piston-end pressures and nominal piston-end pressures, and then output.