AUTOMATIC TRANSAXLE SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    No. 1 Clutch (C1) Connects the intermediate shaft and the Ravigneaux planetary rear sun gear.
    No. 2 Clutch (C2) Connects the intermediate shaft and the Ravigneaux planetary ring gear.
    No. 1 Brake (B1) Prevents the Ravigneaux planetary front sun gear and the underdrive planetary carrier from turning clockwise or counterclockwise.
    No. 2 Brake (B2) Prevents the Ravigneaux planetary ring gear from turning clockwise or counterclockwise.
    No. 3 Brake (B3) Prevents the underdrive planetary ring gear from turning clockwise or counterclockwise.
    No. 1 1-way Clutch (F1) Prevents the Ravigneaux planetary ring gear from turning counterclockwise.
    Planetary Gears Change the route through which driving force is transmitted in accordance with the operation of each clutch and brake in order to increase or reduce the input and output speed.
    Shift Solenoid Valve SL1 Controls the No. 1 clutch (C1) pressure.
    Shift Solenoid Valve SL2 Controls the No. 2 clutch (C2) pressure.
    Shift Solenoid Valve SL3 Controls the No. 1 brake (B1) pressure.
    Shift Solenoid Valve SL4 Controls the No. 3 brake (B3) pressure.
    Shift Solenoid Valve SLU
    • Controls the lock-up clutch pressure.

    • Controls the No. 2 brake (B2) pressure.

    Shift Solenoid Valve SLT Controls line pressure.
    Shift Solenoid Valve SL
    • Switches the lock-up relay valve.

    • Switches the B2 apply control valve and the reverse sequence valve.

    Transmission Revolution Sensor Output Speed Sensor NC Detects the speed of the counter gear.
    Input Speed Sensor NT Detects the input speed of the transaxle.
    ATF Temperature Sensor Detects the ATF temperature.
    Engine Coolant Temperature Sensor Detects the engine coolant temperature.
    Throttle Body with Motor Assembly Throttle Position Sensor Detects the opening angle of the throttle valve.
    Crank Position Sensor Detects the engine speed.
    Intake Mass Air Flow Meter Sub-assembly Mass Air Flow Meter Directly detects the intake air mass.
    Accelerator Pedal Sensor Assembly Detects the accelerator pedal opening angle.
    Air Conditioning Amplifier Assembly Transmits the operating state of the air conditioning system to the ECM.
    ATF Pressure Switch Monitors the output fluid pressure of the shift solenoid valve.
    Park/Neutral Position Switch Assembly Detects the shift lever position.
    Shift Lever Assembly (Shift Lock Control Unit Assembly) Transmission Control Switch
    • Detects that the shift lever is in S.

    • Detects the driver's upshift and downshift operations when the shift lever is in S.

    Combination Switch Assembly ECO MODE Switch Sends the ECO MODE switch operation signal to the airconditioning amplifier assembly.
    Stop Light Switch Assembly Detects when the brake pedal is depressed.
    TCM
    • Controls each shift solenoid valve in response to a signal from each sensor and switch.

    • Makes a diagnosis and memorizes the failed section when the TCM detects a malfunction.

    ECM Controls engine output in response to signals from the TCM.
    Combination Meter Assembly Malfunction Indicator Lamp (MIL) Illuminates to inform the driver when the ECM detects a malfunction.
    Multi-information Display
    • Displays the shift lever position.

    • Indicates the shift range (S1 to S6).

    • Displays the ECO MODE.

    Buzzer
    • Sounds when the downshift operation is rejected.

    • Warns the driver by sounding when a message is shown on the multi-information display.

  2. SYSTEM CONTROL


    1. The electronic control system of the U660E automatic transaxle uses the controls listed below.

      Control Outline
      Shift Timing Control The TCM sends current to shift solenoid valves SL1, SL2, SL3, SL4, SL and/or SLU based on signals from various sensors, in order to shift the gears.
      Clutch to Clutch Pressure Control Controls the pressure that is applied directly to the C1, C2 clutches and B1, B3 brakes by actuating the shift solenoid valves (SL1, SL2, SL3 and SL4) in accordance with TCM signals.
      Line Pressure Control Actuates shift solenoid valve SLT to control the line pressure in accordance with information from the TCM and the operating conditions of the transaxle.
      Lock-up Timing Control The TCM sends current to shift solenoid valves SL and SLU based on signals from various sensors to engage or disengage the lock-up clutch.
      Flex Lock-up Clutch Control Controls shift solenoid valve SLU, provides an intermediate mode between the on and off states of the lock-up clutch, and increases the operating range of the lock-up clutch to improve fuel economy.
      Powertrain Cooperative Control Controls both shift control and engine output control in an integrated way, achieving excellent shift characteristics and drivability.
      Deceleration Downshift Control To prevent engine speed from decreasing and thereby maintain fuel cut, the TCM performs downshifts before fuel cut ends.
      Direct Downshift Control Direct downshift control is used. This makes it possible to skip unnecessary shifts, enabling the vehicle to downshift directly from 6th to 3rd or from 5th to 2nd, enhancing downshift response when the accelerator pedal is depressed quickly.
      Artificial Intelligence Shift Control (AI-shift Control) Based on the signals from various sensors, the TCM determines the road conditions and the intention of the driver. Thus, an appropriate shift pattern is automatically determined, improving drivability.
      Multi-mode Automatic Transmission The TCM appropriately controls the automatic transaxle in accordance with the range selected while the shift lever is in S.
      Fail-safe If a malfunction is detected in the sensors or solenoids, the TCM performs fail-safe control to prevent the vehicle drivability from being affected significantly.
      Diagnosis When the TCM detects a malfunction, the TCM records the malfunction and memorizes the information that relates to the fault.
    2. Clutch to Clutch Pressure Control


      1. Clutch to clutch pressure control is used for shift control. As a result, shift control in 2nd gear or above is possible without using a 1-way clutch, making the automatic transaxle lightweight and compact.

      2. Based on the information about transmission input and output speed, engine torque and other items, the TCM controls each clutch and brake accordingly with the optimum fluid pressure and timing, in order to shift the gears. The TCM changes gears using fluid pressure circuits which enable the clutches and brakes (C1, C2, B1 and B3) to be controlled independently, and using high flow SL1, SL2, SL3 and SL4 shift solenoid valves which directly control the line pressure. As a result, highly responsive and excellent shift characteristics have been realized.

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    3. Line Pressure Control


      1. The line pressure is controlled using shift solenoid valve SLT.

      2. Through the use of shift solenoid valve SLT, the line pressure is appropriately controlled in accordance with the engine torque information, as well as with the internal operating conditions of the torque converter and the transaxle.

      3. Accordingly, the line pressure can be accurately controlled in accordance with the engine output, traveling condition, and the ATF temperature, thus realizing smooth shift characteristics and regulating the workload of the oil pump (reducing unnecessary parasitic losses).

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    4. Lock-up Timing Control


      1. The TCM uses lock-up timing control in order to improve the fuel economy in 4th gear or higher when the shift lever is in D, or when the S6, S5 or S4 range has been selected.

        Figure 1. Lock-up Operating Range in Each Gear

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        Lock-up Operation
        Gear Shift Lever Position or Range
        D or S6 S5 S4
        1st X X X
        2nd X X X
        3rd X X X
        4th
        5th -
        6th - -

        ○: Operates

        X: Does not operate

        -: Not applicable

        ▲: Only operates while AI-shift control is being performed.

    5. Flex Lock-up Clutch Control


      1. During acceleration, the partial 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.

      2. Even when the vehicle is decelerating (the accelerator pedal is released), flex lock-up clutch control operates. Therefore, the fuel-cut area of the engine has been expanded and fuel-economy has been improved.

      3. By allowing flex lock-up clutch control to continue operating during gearshifts, smooth torque transmission has been obtained. As a result, fuel economy and drivability have been improved.

      4. For flex lock-up control, H infinity (H∞) control theory is used to achieve a high level of system stability and response to various characteristic changes.

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      5. The flex lock-up operating range has been expanded. Flex lock-up begins operating once the vehicle starts moving to lower engine speed and improve fuel economy.

        Figure 2. Flex Lock-up Operating Range

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        Flex Lock-up Operation
        Gear Shift Lever Position or Range
        D or S6 S5 S4
        1st X X
        2nd X X
        3rd X X
        4th ○* ○* ○*
        5th ○* ○* -
        6th ○* - -

        ○: Operates

        X: Does not operate

        -: Not applicable

        *: Flex lock-up clutch control also operates when the vehicle decelerates.

    6. Powertrain Cooperative Control


      1. The engine output is appropriately controlled with Electronic Throttle Control System-intelligent (ETCS-i) in real-time according to the transient force from the torque converter when the vehicle is launched. This achieves a "high response and smooth acceleration", ensuring excellent launch performance.

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      2. The TCM determines the gear that is to be selected when the accelerator pedal is released (released completely) in accordance with the way the accelerator pedal is released (quickly or slowly) during deceleration. In this way, unnecessary upshifts are prevented during deceleration, matching the driver's intentions. In addition, unintended downshifts are prevented when accelerating the vehicle again, achieving smooth acceleration.

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      3. Through cooperative control with Electronic Throttle Control System-intelligent (ETCS-i) and Electronic Spark Advance (ESA), and electronic control of the engagement and release speed of the clutch and brake hydraulic pressures, quick response and shift shock reduction have been achieved.

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      4. ECO mode changes the transmission characteristics to ones which prioritize fuel efficient driving to ensure low fuel consumption compared to those of NORMAL mode. This drive mode provides optimal fuel efficiency.

    7. Deceleration Downshift Control


      1. The TCM performs downshift control to help prevent the engine speed from decreasing, thus keeping fuel cut control operating for as long as possible. In this way, fuel economy is improved.

      2. For this control, when the vehicle is in 6th gear and starts decelerating, the transaxle downshifts from 6th to 5th and then 5th to 4th before fuel cut control ends so that fuel cut continues uninterrupted.

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    8. Direct Downshift Control


      1. For conventional downshift control, when shifting from 6th to 3rd or 5th to 2nd, downshifts use an intermediate gear, in order to achieve smooth acceleration response. In addition to conventional control, direct downshift control is used for this vehicle. This control skips unnecessary shifts, enabling the vehicle to downshift directly from 6th to 3rd or from 5th to 2nd.

      2. When the accelerator pedal is depressed quickly, direct downshift control enables direct downshifts with a quick shift response, skipping unnecessary shifts. Direct downshift control places the emphasis on reducing the time required to achieve the target gear. Conventional downshift control is used when the accelerator pedal is depressed slowly, providing smooth acceleration response. As a result, this logic achieves downshift responsiveness in accordance with the driver's intentions.

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    9. Artificial Intelligence Shift Control (AI-shift Control)


      1. The automatic transaxle gear is determined by the shift pattern, which uses the vehicle speed and throttle valve opening angle.

      2. Additionally, AI-shift control enables the TCM to estimate the road conditions and the driver's intention in order to automatically control the shift pattern in the manner. As a result, a comfortable ride has been achieved.

      3. AI-shift control includes road condition support control and driver's intention support control.

      4. AI-shift control determines transaxle control based on input signals and automatically changes the shift pattern.

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      5. Under road condition support control, the ECM determines the throttle opening angle and the vehicle speed in addition to whether the vehicle is being driven uphill or downhill. To achieve the drive force required while driving uphill, this control prevents unnecessary upshifts. To achieve engine braking while driving downhill, this control automatically performs downshifts.

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      6. The TCM estimates the driver's intention based on the accelerator pedal operation and vehicle operating conditions to select a shift pattern that is well-suited to each driver, without the need to operate the shift pattern select switch used on conventional models.

    10. Multi-mode Automatic Transmission


      1. A multi-mode automatic transmission is designed to allow the driver to switch between gear ranges. By moving the shift lever to S and then moving the shift lever toward "+" or "-", the driver can select the desired shift range. Thus, the driver is able to shift gears with a manual-like feel.

      2. This Multi-mode Automatic Transmission is designed to allow the driver to switch gear ranges; it is not for manually selecting single gears.

      3. When the vehicle is being driven at a speed that is higher than the maximum safe speed for a downshift, any attempt to shift to a lower range by operating the shift lever will not be performed. This is done in order to protect the automatic transaxle. In this case, the ECM sounds the buzzer in the combination meter assembly twice to alert the driver.

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      4. The driver can select S mode by moving the shift lever to S. At this time, the 4th or 5th shift range will be selected according to the vehicle speed (during AI-shift control, however, the 3rd shift range may be selected).

      5. Under this control, the TCM performs shift control within the usable gear range that the driver selects. As with an ordinary automatic transaxle, it shifts to 1st gear when the vehicle is stopped.

      6. The shift lever position and the shift range are indicated by the shift indicator light in the combination meter assembly (the shift range is shown only when the shift lever is in S, and it is not shown when the shift lever is in P, R, N or D).

      7. When the shift lever is in S, the S mode indicator light in the combination meter illuminates. The shift indicator light indicates the shift range that the driver has selected.

      8. Holding the shift lever toward "+" with the shift lever in S will change the shift range to the S6 range regardless of the current range (S1 to S5).

      9. In order to prevent excessive engine speed, a function is adopted that automatically selects a higher shift range before engine speed becomes excessive.

      10. In order to protect the automatic transmission, a function is adopted that automatically selects a higher shift range when the fluid temperature is high.

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        *a Transition of Shift Ranges *b Shift Pattern
        B006JXV Default Shift Range - -
        Usable Gear Chart
        Shift Range Shift Indicator Light Usable Gear
        S6 6 1st to 6th
        S5 5 1st to 5th
        S4 4 1st to 4th
        S3 3 1st to 3rd
        S2 2 1st to 2nd
        S1 1 1st
  3. FAIL-SAFE


    1. This function minimizes the loss of operability when an abnormality occurs in a sensor or solenoid. For details, refer to the Repair Manual.

  4. DIAGNOSIS


    1. When the TCM detects a malfunction, the TCM records the malfunction and memorizes the information related to the fault. Furthermore, the TCM illuminates the Malfunction Indicator Lamp (MIL) in the combination meter assembly to inform the driver.

    2. The TCM will also store Diagnostic Trouble Codes (DTCs) of the malfunctions. The DTCs stored in the TCM are output to the Global TechStream (GTS) via the ECM and the DLC3.

    3. For details, refer to the Repair Manual.