Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual — part 1842

7A1-30 CONSTRUCTION AND FUNCTION

LINE PRESSURE CONTROL

•

Either the throttle opening, vehicle speed, turbine rotational speed, ATF temperature or speed-change

range signal appropriate under the situation is issued from the TCM. The ON/OFF type line pressure
solenoid is actuated and switches the line pressure to high or low pressure.

•

The line pressure generated by the oil pump acts on the point A of the pressure regulator valve. When

the pressure control solenoid is turned ON by the signal from the TCM, the solenoid pressure does not
act. The line pressure is adjusted to match the spring force acting on the right side of the pressure
regulator valve.

•

When the pressure control solenoid is turned OFF, the solenoid pressure acts so that the line pressure is

adjusted to match the spring force acting on the right side of the pressure regulator valve.

•

As a result, the line pressure is adjusted to be low when the pressure control solenoid is ON and to be

high when the pressure control solenoid is OFF.

•

In the D, 3, 2 and L range, the line pressure through the oil pressure circuit acts onto the point B of the

pressure regulator valve and the pressure regulator valve moves so as to increase the pressure to be
drained, so that the line pressure is adjusted to be lower than the P, N, and R range by the difference of
area at the point B.

Figure 50. Line Pressure Control

LOCK-UP CONTROL

•

The lock-up solenoid adjusts the pressure and controls the lock-up based on the pre-set lock-up point,

according to the vehicle speed, throttle opening, engine rotations, turbine rotations and ATF temperature
input signal, based on the signal from the TCM.

•

Smooth lock-up control is employed to engage or disengage the clutch smoothly at the time of lock-up.

•

When the oil temperature is low (below 20

°

C) or high (over 128

°

C), lock-up is disengaged even though

the vehicle is at the lock-up speed.

•

The lock-up is disengaged also when the throttle is closed.

•

When the TCM determines the lock-up engagement, the DUTY ratio to supply power to the lock-up

solenoid is gradually increased (5% to 95%) and the oil between the lock-up piston and converter cover is
gradually

drained.

As a result, the lock-up piston is fitted slowly under pressure to the converter cover securing smooth lock-
up engagement.

CONSTRUCTION AND FUNCTION 7A1-31

Figure 51. Lock-up Control

DIRECT ELECTRIC SHIFT CONTROL (DESC)

Feature

•

Based on the each switch signals (low & reverse brake pressure, 2-4 brake pressure & high clutch

pressure) and sensors signals (turbine sensor, speed sensor, engine speed signal & throttle position
signal), duty cycle type solenoid adjusts the clutch pressure to match the engine load and vehicle
traveling condition. By this result, controlling the engagement and disengagement of the clutch and brake
pressure is directly and accurately controlled via TCM, which is not realized in previous accumulator type.

Operation

•

Instead of the previous system (on/off type of shift solenoid and shift valve), the combination of duty cycle

type solenoid and amplifier (Amp) valve are used to adjust the clutch pressure to match the engine load
and vehicle traveling condition based on the signal from the TCM, and the pressure switch provided in the
oil passage of the control valve transmits the oil pressure condition at that time to TCM, thus controlling
the engagement and disengagement of the clutch and brake directly and finely.

•

When the gear is shifted from the 2nd to 3rd, 3rd to 4th (O/D), 4th (O/D) to 3rd and 3rd to 2nd, the clutch

pressure on the engagement side and that on the disengagement side are simultaneously controlled.

As a result, engine racing or clutch drag is prevented securing smooth and quick speed change response

7A1-32 CONSTRUCTION AND FUNCTION

Direct Electric Shift Control

Previous Model

Figure 52. Direct Electric Shift Control (DESC)

CONSTRUCTION AND FUNCTION 7A1-33

LEARNING CONTROL

•

Oil pressure control timing is optimally corrected at the time of clutch engagement and disengagement

and controlled to bring the speed-change time to the value preset to the TCM and compensate the
changes of the engine performance and changes of the transmission with time.

•

When the gear is shifted, the clutch pressure

2

is optimally corrected so that the speed-change time is as

near as the target value

1

preset to the TCM and the changes in the engine performance and the

changes of the transmission with time can be compensated based on the past speed-change results.

•

When the clutch is operated to shift the gear, the time of the clutch oil pressure release timing

4

on the

disengagement side is optimally corrected so that the changes of the engine rpm

3

is optimum.

Note:

•

When the battery terminal is disconnected, contents of learning are cleared and resultantly the speed

change shock may increase. After the vehicle has traveled, learning is repeated and the shock
decreases gradually.

Figure 53. Learning Control