Hydraulic Control System
HYDRAULIC CONTROL SYSTEM1. The hydraulic pressure during gear shifting engages the clutches and applies the brakes. It is regulated by the pressure control valve. The hydraulic pressure that works on the pressure control valve is further regulated by the pressure control solenoid valve which functions under the control of the transaxle control module. The transaxle control module controls the solenoid valve using a duty cycle signal, thus providing appropriate regulation of the hydraulic pressure.
2. The transaxle control module decides the timing of the gear-shifting period (during which it performs hydraulic pressure control for gear shifting) according to the change in the kickdown drum rotating speed that it detects. The module identifies the time just before the kickdown brake is applied and uses that as the timing for initiating control of the hydraulic pressure that is to be applied to the kickdown brake.
3. TCM detects torque change ratio (turbine speed change ratio in torque converter). If input torque is larger than the pre-set torque in TCM, TCM controls the duty of PCSV and changes oil pressure. Shift shock will be alleviated due to torque control. Torque change ratio is applied differently according to each pattern.
4. When the transaxle is cold, the fluid viscosity is high, causing slower oil pressure response. In such conditions, the transaxle control module provides a correction for the oil pressure by changing the control duty of the pressure control solenoid valve. This control is performed when the fluid temperature as indicated by the oil temperature sensor is lower than 60°C(140°F).
5. After the engine has been started and the vehicle is in motion, the transaxle control module continues to refine its performance for smoothest possible gear shifting.
The hydraulic control system consists of an oil pump that generates hydraulic pressure for A/T. It also has valves and solenoid valves that control the hydraulic pressure or switch the oil passage. The valves and solenoid valves are all built into the valve body.
For better and smoother shift quality, the rear clutch pressure is controlled independently, 4th-2nd gear skip shift is available and the line pressure at 3rd/4th gear is reduced.
There are 6 solenoid valves are incorporated on the valve body. 2 of those are duty-controlled type and the rest are ON/OFF type.
^ Duty control type: Pressure control solenoid valve A/B, Damper clutch control solenoid valve
^ ON/OFF type: Shift control solenoid valve A/B/C
If the mechanical malfunction such as valve sticking occurred, the fail-safe valve has been adopted to prevent interlock. The line pressure is regulated at the 4th speed to improve the efficiency of power transmission. This function is performed by High-low pressure valve and regulator valve.
OIL PUMP
Oil pump generates pressure for supplying oil to the torque converter, for lubricating frictional parts of the planetary gearing set and the overrunning clutch, etc., and for activating the hydraulic control system.
The pump is one of the inner-teeth engaging trochoid type. It always generates the oil pressure when the engine is running since the drive gear is driven by 2 pawls of the pump drive hub welded at the center of the torque converter shell.
MANUAL VALVE:
PRESSURE CONTROL VALVE-A, B
Pressure control valve A, B regulate the pressure supplied to each clutch under the control of the pressure control solenoid valve A, B to eliminate shock at the time of shifting.
1. Pressure control valve A - Not operated
PRESSURE CONTROL VALVE-A, B
1. Pressure control valve A - Operation
PRESSURE CONTROL VALVE-A B
1. Pressure control valve B - Not Operated
PRESSURE CONTROL VALVE-A, B
1. Pressure control valve B - Operation
The main function of this valve controls the rear clutch independently.
SHIFT CONTROL VALVE(SCV) AND SOLENOID VALVE-A, B, C (SCSV-A,B,C)
The line pressure acting upon the shift control valve is controlled by the two shift control solenoid valves(which are switch ON and OFF according to the shifting gear by the transaxle control module command), and the shift control valve is activated according to the shifting gear, thus switching the oil passages.
The relationship of the shifting gear and the ON-OFF switch of shift control solenoid valve "A", "B" and "C" is shown in the table below.
CONTROL SWITCH VALVE(CSV) & END CLUTCH(E/C) VALVE
^ Function
Switching the pressure of E/C and SA
CONTROL SWITCH VALVE(CSV) & E/C VALVE
^ 2nd Gear
- 2nd pressure is supplied from SA through the CSV.
- SCSV-C maintains OFF as well as 2nd gear.
CONTROL SWITCH VALVE(CSV) & E/C VALVE
^ 2nd - 3rd gear
- SCSV-C maintains OFF as well as 2nd gear.
- The E/C pressure from shift control valve is intercepted at the E/C valve during up-shifting from 2nd to 3rd gear.
- SA pressure is supplied from 1-2 shift valve, but the front clutch and SR pressure is also supplied from the 2-3/43 shift valve, so the both SR and SA pressure will be set off.
CONTROL SWITCH VALVE(CSV) & E/C VALVE
^ 3rd gear
- SCSV-C is changed from OFF to ON.
- The E/C pressure is supplied from 1-2 shift valve at the CSV after finishing the up-shifting from 2nd to 3rd gear.
- SA pressure is supplied from shift control valve, but the front clutch and SR pressure is also supplied from the 2-3/43shift valve, so the both SR and SA pressure will be set off.
4 -> 2 SKIP SHIFT
1. Operating elements
2. Controls
a. R/C engaging duty control
b. E/C releasing duty control
c. Continuous switching to SA
3. Description
a. R/C engaging duty control
b. E/C releasing duty control
4 - 2 Skip shift only (SCSV-C ON)
When releasing the E/C clutch pressure, it is controlled by duty of PCSV-A only in case of 4 - 2 skip shift.
c. Continuous switching to SA
From (SCV) to SA through (CSV)
FAIL SAFE FUNCTION
1. TCM malfunction in 1st or 2nd gear.
CUTTING OFF THE E/C PRESSURE BY E/C VALVE
^ F/C, SR: from 2-3/4-3 shift valve
^ R/C: from PCV-B
^ SA: from 1-2 shift valve
2. TCM malfunction in 1st or 2nd gear.
If the hydraulic pressure is supplied to E/C and the F/C, SR pressure is delayed.
^ R/C, E/C, S/A: interlock