Electronic Component Description
Electronic Component Description
General
The electronic control system of the MVD 5-speed automatic transaxle consists of the control listed below.
Construction
The configuration of the electronic control system in the U250E automatic transaxle is as shown in the following chart.
Layout of Main Components
Shift Indicator
Solenoid Valves
Solenoid Valves SL1, SL2, SL3 and SLT
* In order to provide a hydraulic pressure that is proportion to current that flows to the solenoid coil, the solenoid valves SL1, SL2, SL3, and SLT linearly control the line pressure and clutch and brake engagement pressure based on the signals received from the ECM.
* The solenoid valves SL1, SL2, SL3, and SLT have the same basic structure.
Solenoid Valves SR, S4 and DSL
* The solenoid valves SR, S4, and DSL use a three-way solenoid valve.
* The solenoid valve SR controls the solenoid relay valve. Accordingly, the fluid passages from the solenoid valves DSL and S4 have been changed.
* The solenoid valve S4, when set to ON, controls the 4-5 shift valve to establish the 5th by changing over the fluid pressure applied to B3 brake and C3 clutch.
* The solenoid valve DSL controls the B2 control valve via the solenoid relay valve when the transaxle is shifted in the R or L position. During lock-up, the lock-up relay valve is controlled via the solenoid relay valve.
Apply Orifice Control
This control is effected by the B3 orifice control valve. The B3 orifice control valve has been provided for the B3 brake, which is applied when shifting from 5th to 4th. The B3 orifice control valve is controlled by the amount of the line pressure in accordance with shifting conditions, and the flow volume of the fluid that is supplied to the B3 brake is controlled by varying the size of the orifice in the control valve.
Construction and Operation of Main Components
ATF Temperature Sensor
* The ATF temperature sensor is installed in the valve body for direct detection of the fluid temperature.
* The ATF temperature sensor is used for the revision of clutch and brake pressures to maintain a smooth shift quality every time.
Speed Sensors
* The automatic transaxle uses an input turbine speed sensor (for the NT signal) and a counter gear speed sensor (for the NC signal). Thus, the ECM can detect the timing of the shifting of the gears and appropriately control the engine torque and hydraulic pressure in response to the various conditions. These speed sensors are the pick-up coil type
* The input turbine speed sensor detects the input speed of the transaxle. The direct clutch (C2) drum is used as the timing rotor for this sensor.
* The counter gear speed sensor detects the speed of the counter gear. The counter drive gear is used as the timing rotor for this sensor.
Clutch Pressure Control
Clutch to Clutch Pressure Control
* This control is used for shifting from the 2nd to 3rd gear, and from the 3rd to 4th gear.
* Solenoid valves SL1, SL2, and SL3 are actuated in accordance with the signals from the ECM, and this output pressure is guided directly to the control valves B1, C0, and C1 in order to regulate the line pressure that acts on the B1 brake, C0 and C1 clutches. As a result, compact B1, C0 and C1 accumulators without a back pressure chamber have been realized.
Clutch Pressure Optimal Control
The ECM monitors the signals from various types of sensors such as the input turbine speed sensor, allowing shift solenoid valves SL1, SL2, and SL3 to minutely control the clutch pressure in accordance with engine output and driving conditions. As a result, smooth shift characteristics have been realized.
Line Pressure Control
The line pressure is controlled by using solenoid valve SLT. Through the use of solenoid valve SLT, the line pressure is optimally controlled in accordance with the engine torque information, as well as with the internal operating conditions of the torque converter and the transaxle. Accordingly, the line pressure can be accurately controlled in accordance with the engine output, traveling condition, and ATF temperature, thus realizing smooth shift characteristics and optimizing the workload of the oil pump.
Shift Control in Uphill/Downhill Traveling
General
This control helps minimize the shifting of gears when the driver operates the accelerator pedal while driving on a winding road with ups and downs, in order to ensure a smooth drive.
Shift Control in Uphill Traveling
* When the ECM determines uphill travel, it prohibits the transaxle from shifting up into 5th after the transaxle has shifted down below 4th.
* When the ECM determines uphill travel with a steeper grade, it prohibits the transaxle from shifting up into 4th after the transaxle has shifted down below 3rd.
Shift Control in Downhill Traveling
* When the ECM determines downhill travel, it shifts down the transaxle from 5th to 4th in accordance with the brake operation signal that is input when the driver operates the brake pedal.
* When the ECM determines downhill travel with a steeper grade, and a brake operation signal is input again, the ECM shifts the transaxle down from 4th to 3rd.
Uphill/Downhill Judgment
The actual acceleration calculated from the speed sensor signal is compared with the reference acceleration stored in the ECM to judge uphill or downhill traveling.
Flex Lock-up Clutch Control
* In addition to the conventional lock-up timing control, flex lock-up clutch control is used.
* This flex lock-up clutch control regulates solenoid valve SL2 as an intermediate mode between the ON and OFF operations of the lock-up clutch.
* The flex lock-up clutch control operates during acceleration, in the 4th and 5th gears in the D position and S5 range, and during deceleration, in the 4th and 5th gears in the D position and S5 range, and in the 4th gear in the S4 range.
* During acceleration, the partition control of the power transmission between the lock-up clutch and torque converter greatly boosts the transmission efficiency in accordance with the driving conditions, improving the fuel economy.
* During deceleration, the lock-up clutch is made to operate. Therefore, the fuel-cut area is expanded and fuel economy is improved.
Flex Lock-up Timing
Multi-Mode Automatic Transmission
General
In the multi-mode automatic transmission, an S mode position is provided on the side of the D position. By moving the shift lever to the front ("+" position) or to the rear ("-" position), the driver can select the desired shift range position. Thus, the driver is able to shift gears with a manual-like feel.
* The multi-mode automatic transmission is designed for switching the gear range; not for fixing in one gear.
* An S mode indicator light which illuminates when the S mode position is selected and a shift range and shift position indicator, which indicates the shift range, have been provided in the combination meter
Operation
* The driver selects the S mode position by engaging the shift lever. At this time, the shift range position selects the 4 range. However, if the driver changes quickly the shift lever from the P, R, or N position to the S mode position while the vehicle is stopping, default shift range position selects the 5 range. Then, the shift range positions change one at a time, as the driver moves the shift lever to the front ("+" position) or to the rear ("-" position). If the driver pushes the select lever to the front ("+" position) for a long time, shift range position selects the 5 range.
* Under this control, the ECM effects optimal shift control within the usable gear range that the driver has selected. As with the ordinary automatic transmission, it shifts to the 1st gear when the vehicle is stopped.
* When the shift lever is in the S mode position, the S mode indicator in the combination meter illuminates. The shift range and shift position indicator indicates the state of the shift range position that the driver has selected.
Transmission Shift Positions
Diagnosis
* When the ECM detects a malfunction, the ECM makes a diagnosis and memorizes the information related to the fault. Furthermore, the MIL (Malfunction Indicator Lamp) in the combination meter illuminates or blinks to inform the driver of the malfunction.
* At the same time, the DTC (Diagnosis Trouble Code) is stored in the memory.
Fail-Safe
This function minimizes the loss of operability when any abnormality occurs in each sensor or solenoid.
