Adjustment method for vehicle automatic transmission

An adjustment method for a vehicle automatic transmission that is provided with a hydraulic control circuit including linear solenoid valves which control supply pressures that are supplied to hydraulically-driven friction engagement elements;

• and a valve control unit that outputs drive currents to drive the linear solenoid valves, the adjustment method being used to calculate correction values that are applied to control command values used to adjust the drive currents so that correlations between the drive currents and effective pressures exhibit nominal characteristics, comprising:
• measuring valve characteristics of the linear solenoid valves when the linear solenoid valves are fitted to the hydraulic control circuit, and estimating linear valve characteristics of the linear solenoid valves in isolation state based on the measured valve characteristics using predetermined correlations;
• calculating estimated linear piston-end pressures of the hydraulically-driven friction engagement elements immediately before the hydraulically-driven friction engagement elements are engaged based on the estimated linear valve characteristics, and calculating 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 based on differences between the estimated linear piston-end pressures and nominal piston-end pressures;
• and
• outputting the calculated correction values, wherein:
• the estimated linear piston-end pressures are calculated immediately before the hydraulically-driven friction engagement elements are engaged based on the estimated linear valve characteristics;
• constantly-maintained pressure correction values are calculated based on the differences between the estimated linear piston-end pressures and the predetermined nominal piston-end pressures;
• hydraulic pressure correction values that are applied to the control command values are calculated based on the constantly-maintained pressure correction values so that the correlations between the drive currents and the effective pressures exhibit the nominal characteristics;
• the calculation of the hydraulic pressure correction value comprises calculating multiple first nominal linear pressures set as lattice points of the correction values applied to the control command values, and calculating required linear pressures by making corrections to the first nominal linear pressures using the constantly-maintained pressure correction values;
• the calculated hydraulic pressure correction values are output in a form that is used by an electronic control unit which controls the automatic transmission;
• and
• the drive currents required to achieve the required linear pressures are determined based on the estimated linear valve characteristics, the required control command values are calculated as second nominal linear pressures based on the isolated-state nominal linear pressure characteristics using the drive currents, and the hydraulic pressure correction values, which are pressure differences between the first nominal linear pressures and the second nominal linear pressures, are calculated for the predetermined lattice points.