#
LINE PRESSURE CONTROL DESCRIPTION [JA5A-EL]

BME051718901T05

## Outline

### Features

  • Line pressure is hydraulic pressure for operating friction elements such as the multiple disc clutches, multiple disc brakes, and the brake band.
  • To adjust to optimal line pressure according to engine load conditions and vehicle driving conditions, continuous variable line pressure control from the pressure control solenoid is used.
  • The line pressure control includes the basic control, line pressure control when shifting, backup control, and other.

### Construction (System diagram)

## Basic Line Pressure Control

• Control at vehicle-start or during normal driving. The pressure control solenoid is controlled so that the line pressure is optimal according to the throttle opening angle.
The pressure characteristic is as shown in the graph at below. During normal driving (only in shift ranges for forward travel), the line pressure is set lower than that of at vehicle-start; this is called "cutback."

• Though the cutback control is selected in each driving pattern, it is not operated in the fail-safe mode. In the fail-safe mode, the pressure before the cutback is retained and so the pressure is higher than that during normal driving.

## Line Pressure Control When Shifting

• Line pressure is controlled when shifting the transaxle to reduce shift shock. Line pressure is adjusted only during shifting so that it is optimal at each shifting according to the driving conditions. During the control, engine output torque is also reduced.

## Backup Control

• When shifting down to employ engine braking during high-speed driving, line pressure is gradually increased, thus increasing clutch capacity.
The backup control is operated regardless of the driving range when the engine brake is operated in 1GR or when shifting down to 2GR-4GR.

## Line Pressure Control at Extremely Low Temperatures

• When the ATF temperature is approximately -30 °C {-22 °F} or below, the period when the pressure control solenoid is ON (duty ratio) is set at 3 % to maintain line pressure at maximum regardless of the throttle opening angle. Thus delay in clutch or brake operation due to high viscosity of ATF is prevented when the ATF temperature is extremely low.

## Pressure Control Solenoid Stop Control

• When the vehicle is stopped at ATF temperatures approximately -30 °C {-86 °F} or below and the accelerator pedal is released, the operation (duty ratio) of the pressure control solenoid is set at 3 %, regardless of the driving range. Due to this, AT noise is reduced when the vehicle is stopped at extremely low ATF temperatures.