Electronic Component Description
Electronic Component Description
General
The electronic control system of the MVB 4-speed automatic transaxle consists of the controls listed below.
Construction
The configuration of the electronic control system in the U341E automatic transaxle is as shown in the following chart.
Layout of Main Components
Shift Indicator
Solenoid Valve
Construction and Operation of Main Components
ATF Temperature Sensor
* The ATF temperature sensor is installed in the lower valve body for direct detection of the fluid temperature.
* The ATF temperature sensor is used for correction of clutch and brake pressures to keep smooth shift quality every time.
Speed Sensor NT
The speed sensor NT detects the input speed of the transaxle. The forward clutch (C1) drum is used as the timing rotor for this sensor. Thus, the ECM can detect shift timing of the gears and appropriately control the engine torque and hydraulic pressure in response to the various conditions.
Solenoid Valves
Clutch Pressure Control
Clutch to Clutch Pressure Control
This control is used for shifting from the 3rd to 4th gear, and from the 4th to 3rd gear. It actuates solenoid valves ST and SLT in accordance with the signals from the ECM, and guides this output pressure directly to 4-3 shift timing valve and 3-4 shift timing valve in order to regulate the line pressure that acts on the B1 brake and C1 clutch. As a result, compact B1 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 speed sensor NT, allowing solenoid valve SLT 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
Through the use of the 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 controlled minutely in accordance with the engine output, traveling condition, and ATF temperature, thus realizing smooth shift characteristics and optimizing the workload in the oil pump.
Shift Control in Uphill/Downhill Traveling
General
This control helps minimize the gear shifting when the driver operates the accelerator pedal while driving on a winding uphill or downhill road in order to ensure a smooth drive.
Shift Control in Uphill Traveling
When the engine ECU detects uphill travel, it prohibits upshifting to the 4th after downshifting to the 3rd.
Shift Control in Downhill Traveling
If a signal indicating that the driver has operated the brake pedal is input while the ECM detects downhill travel, it downshifts from the 4th to 3rd.
Uphill/Downhill Judgment
The actual acceleration calculated from the speed sensor signal is compared with the reference acceleration (based on level road travel) stored in the ECM to determine uphill or downhill travel.
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 the solenoid valve SLU as an intermediate mode between the ON and OFF operation of the lock-up clutch.
* The flex lock-up clutch control operates during acceleration, in the 3rd and 4th gears in the D position, and during deceleration, in the 3rd and 4th gears in the D position, and in the 3rd gear in the 3 position.
* 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, fuel-cut area is expanded and fuel economy is improved.
Flex Lock-up Timing
Diagnosis
* When the ECM detects a malfunction, the ECM makes a diagnosis and memorizes the failed section. Furthermore, the MIL (Malfunction Indicator Lamp) in the combination meter illuminates or blinks to inform the driver.
* At the same time, the DTCs (Diagnosis Trouble Codes) are stored in memory.
Fail-safe
This function minimizes the loss of operability when any abnormality occurs in each sensor or solenoid.
