Control Module: Description and Operation
PURPOSE/OPERATIONThe Transmission Control Module (TCM) receives various sensor signals and determines the running conditions of the vehicle. It then sends control signals to each solenoid according to the preset gearshift characteristic data lockup operation data and transfer clutch torque data (duty ratio).
CONTROL SYSTEM
SYSTEM DIAGRAM
SHIFT CONTROL
Gearshifting is controlled in response to driving conditions, according to the shift point characteristic data, as shown in the diagram, stored in the Transmission Control Module (TCM). Solenoids are operated at the proper time corresponding to the shift pattern, throttle position, and vehicle speed for smooth shifting.
When oil temperature is below approximately 10°C (50°F), the Vehicle can not be shifted to the 4th range.
1. Control module activates both solenoids 1 and 2 in response to throttle and vehicle speed signals.
2. Shift valve moves in response to solenoid operation, supplying/interrupting Clutch pressure to the line.
3. Gears are shifted by "ON"-"OFF" operation of both Solenoids as indicated in Table.
3-2 TIMING CONTROL
- When shifting from 3rd to 2nd, the high clutch is disengaged. At the same time, oil pressure (which releases the brake band) is also released from the servo piston 3rd release chamber (3R).
- At this point, the servo piston moves to release oil pressure from the 3rd release chamber (3r) and apply oil pressure to the 2nd apply chamber. This causes the brake band to be applied. In other words, high clutch "release" and brake band "application" are properly timed by electronic control. This eliminates engine revving up under no load or hesitation.
- When the 3-2 Timing Valve conducts, oil pressure applied to the 3rd release chamber is quickly released through passage (A).
- When the 3-2 timing valve does not conduct, oil pressure applied to the 3rd release chamber is slowly released through passage (B) (provided with an orifice).
LOCK-UP CONTROL
- The lock-up engaging and disengaging conditions are set for each gear shift range, gear position and shift pattern and correspond to the throttle position and vehicle speed, and the duty solenoid is electronically controlled by the Transmission Control Module (TCM) controls the lock-up clutch. The lock-up clutch engagement and disengagement are controlled by the lock-up control valve.
- When engaging and disengaging:
The shuttle shift valve d is actuated by the hydraulic pressure from the shift valve A. It controls the position of the lock-up control valve for engaging or disengaging the lock-up clutch.
1. Non-Lock-up Operation (1st, N, R, and P range).
- Since no operating pressure is generated from the shift valve a, the shuttle shift valve D sets the lock-up control valve in the 'disengaging" position.
- The lock-up operating pressure (torque converter clutch regulator pressure) acts on the lock-up clutch disengaging circuit, while the engaging circuit communicates with the oil cooler circuit. Accordingly, the lock-up clutch is disengaged by the pressure difference.
2. Lock-Up Operation (4th speed of D range).
- The operating pressure generated by the shift valve a is applied to the shuttle shift valve D, which pushes the lock-up control valve to the "engaging" position. Since the lock-up operating pressure is applied to the engaging side circuit while the disengaging circuit is drained, the lock-up clutch is engaged by the pressure difference.
- Smooth Control.
The duty solenoid B is controlled by the Transmission Control Module (TCM) and controls the operation of the lock-up control valve. Because the lock-up operating pressure is controlled by the lock-up control valve, the force applied to the lock-up clutch is controlled for smooth clutch operation. When locking up, the clutch is set in the half-engaged state beforehand. After this, the lock-up operating pressure is gradually increased to achieve smooth locking up.
LINE-PRESSURE CONTROL
1. The oil pump delivery pressure (line pressure) is regulated to the constant pilot pressure by the pilot valve.
2. The pilot pressure applied to the pressure modifier valve is regulated by the line pressure controlling duty solenoid A and changed into the pressure modifier pressure.
3. The pressure modifier valve is an auxiliary valve for the pressure regulator valve, and it creates a signal pressure (pressure modifier pressure) for regulating the line pressure to an optimum pressure corresponding to the driving conditions.
4. This pressure modifier pressure is applied to the pressure regulator valve to control the oil pump delivery pressure.
5. The delivery pressure of the oil pump is regulated to an appropriate pressure (line pressure) corresponding to the driving condition to reduce the loss in the oil pump driving time and acceleration shock.
6. The pressure modifier pressure regulated by the pressure modifier valve is smoothed by the pressure modifier accumulator and pulsation in the line pressure is eliminated.
LINE-PRESSURE SHIFTING CONTROL
- Oil pressure which engages shift clutches (to provide 1st through 4th speeds) is electronically controlled to meet varying operating conditions. In other words, line pressure decreases to match the selected shift position, minimizing shifting shock.
- Electronic control of clutch oil pressure in summary.
a. Solenoids activate through the Transmission Control Module (TCM) which receives various control signals (throttle signal, etc.)
b. Control signals are converted into throttle pressure, which is transmitted to the pressure regulator valve.
c. The pressure regulator valve optimally regulates line pressure (built-up by oil pump) in response to throttle pressure, matching varying operating conditions.
SHIFT PATTERN SELECT CONTROL
Shift pattern is selectable automatically between a normal pattern suitable for ordinary economy running and a power pattern suitable for climbing uphill or rapid acceleration.
In the power pattern, the shift down point and shift up point are set higher than those of the normal pattern.
1. Normal Pattern to Power Pattern.
Depending on throttle opening and Vehicle speed, 16 areas as shown in the figure are set. Accelerator depression speed for pattern change over is set for each area.
When the accelerator depression speed exceeds this set value, the pattern changes from normal to power.
2. Power Pattern to Normal Pattern.
The power pattern is shifted to the normal pattern, depending on car speed. Shifting to the normal pattern is determined by the throttle position as shown. Time lag in shifting is also determined by car speed. The maximum time lag is 3 seconds.
ENGINE BRAKE CONTROL
The Transmission Control Module (TCM) controls the shift solenoid corresponding to such input signals as throttle position, vehicle speed, shift range, and cruise control signals to automatically control the operation of the overrunning clutch and for positive application of engine brake.
1. In range D or 3, the overrunning clutch is kept inoperative by the action of the shuttle shift valve S when the throttle position is large. With small Throttle valve opening, the overrunning clutch is engaged by the action of shift solenoid 3.
2. In range 2, the overrunning clutch is engaged by the operation of shift solenoid 3.
3. In range 1, the overrunning clutch is engaged irrespective of the operation of shift solenoid 3.
AWD TRANSFER CLUTCH CONTROL
TRANSFER CONTROL
- The transfer hydraulic pressure control module is fitted with the transfer valve body attached to the side face of the extension case via gasket and separate plate.
- The hydraulic oil of the transfer hydraulic pressure control module is led from the oil pump delivery pressure circuit on the transmission case front to the transmission case rear. from there it is further led to the extension case where it is fed to the hydraulic circuit of the transfer valve body.
- The hydraulic oil pressure (line pressure) is regulated by the transfer pilot valve, duty solenoid c and transfer control valve for obtaining optimum rear torque distribution corresponding to the driving conditions.
1. The line pressure regulated to a proper pressure corresponding to the driving condition is further regulated to a constant pilot pressure by the transfer pilot valve.
2. The pilot pressure is regulated to the transfer duty pressure by the duty solenoid c whose duty ratio is controlled by the Transmission Control Module (TCM) corresponding to the driving condition. (The transfer duty pressure varies with the degree of duty control.)
3. The transfer duty pressure is applied to the transfer control valve.
4. The line pressure is led also to the transfer control valve where the pressure is regulated to the transfer clutch pressure by the transfer duty pressure. (The transfer clutch pressure varies with the transfer duty pressure.)
5. The transfer clutch pressure is applied to the transfer clutch and causes the clutch to be engaged. In this way, the transfer clutch pressure is varied so that optimum rear torque distribution can be achieved which corresponds to the vehicle driving conditions.