СИСТЕМА CVT


  1. FUNCTION OF MAIN COMPONENTS

    Component Function
    CVT Fluid Warmer (Transmission Oil Cooler) Warms up the CVT fluid quickly.
    Torque Converter Assembly

    • Transmits engine power to the transaxle.

    • Increases engine torque.
    Oil Pump Assembly Provides oil pressure necessary for the transaxle operation.
    Forward Clutch Connects the input shaft with the sun gear.
    Reverse Brake Keeps the planetary carrier stationary.
    Shift Solenoid Valve SC Used to switch control of the shift solenoid valve SLU for forward and reverse clutch control.
    Shift Solenoid Valve SL Used to switch control of the shift solenoid valve SLU for lock-up clutch control.
    Shift Solenoid Valve SLU Performs forward and reverse clutch control or lock-up clutch control depending on the state of the shift solenoid valves SC and SL.
    Shift Solenoid Valve SLP Controls the oil pressure of the primary pulley in accordance with the vehicle speed and accelerator pedal position signals to control the speed ratio.
    Shift Solenoid Valve SLS Controls the oil pressure of the secondary pulley in accordance with the input shaft torque to control belt clamping force.
    Transmission Revolution Sensor (NIN) Detects the primary pulley speed (input speed).
    Transmission Revolution Sensor (NOUT) Detects the secondary pulley speed (output speed).
    Transmission Revolution Sensor (NT) Detects the forward clutch drum speed (turbine speed).
    CVT Fluid Temperature Sensor Detects the CVT fluid temperature.
    Oil Pressure Sensor Detects the steel belt clamping force.
    Park/Neutral Position Switch Assembly Detects the shift lever position.
    Transmission Control Switch

    • Detects that the shift lever is in M.

    • Detects the driver's upshift and downshift operations when the shift lever is in M.
    Drive Module Switch Assembly Sport Mode Switch Turns the Sport mode on and off.
    ECO Mode Switch Turns the ECO mode on and off.
    ECM

    • Controls engine output and the electronic control of the CVT system.

    • Makes a diagnosis and memorizes the failed section when the ECM detects a malfunction.
    Air Conditioning Amplifier Assembly

    • Transmits the operating state of the air conditioning system to the ECM.

    • Outputs the ECO mode signal to the ECM.
    Center Airbag Sensor Assembly

    • Detects the vehicle's yaw rate.

    • Detects the vehicle's longitudinal and lateral acceleration and deceleration.
    Driving Support ECU Assembly*1 Sends the information about the operation conditions of the dynamic radar cruise control system to the ECM.
    Combination Meter Assembly Shift Position and Gear Range Indicator Indicates the shift position.
    Sport Mode Indicator Light*2 Illuminates when Sport mode is active.
    ECO Mode Indicator Light*2 Illuminates when ECO mode is active.
    MIL Illuminates or blinks to alert the driver that the ECM has detected a malfunction.
    Multi-information Display*3 Displays that Sport or ECO mode is active.
    Buzzer Sounds when the shift-down operation is rejected.

    *1: Models with dynamic radar cruise control system

    *2: Models with analog type combination meter assembly

    *3: Models with Optitron type combination meter assembly

  2. SYSTEM CONTROL

    Electronic Control of CVT
    Control Outline
    Engine-CVT Integrated Control Effects coordinate control of the CVT system and engine control system to ensure both smooth and powerful driving that excels in shift response and fuel economy.
    Automatic Shift Control (Speed Ratio Control) Controls the primary pulley speed to approach the calculated target input rotation speed based on information such as the accelerator pedal position, vehicle speed and stop light switch signals.
    Acceleration Improvement Control Controls the acceleration rate in proportion to the accelerator pedal position, improving the feeling of linear acceleration and expanding the feeling of accelerator pedal input.
    Deceleration Improvement Control Determines a pulley ratio which allows for high engine speed to be maintained during deceleration, thus ensuring adequate engine braking.
    Uphill/Downhill Shift Control Uses the ECM to determine whether the vehicle is traveling uphill or downhill in order to restrict upshifts or provide appropriate engine braking force by restricting downshifts.
    Lock-up Control The ECM sends a current to the shift solenoid valves SC, SL and SLU based on the throttle position sensor signal and vehicle speed signal, and engages or disengages the lock-up clutch.
    Flex Lock-up Control By enhancing the lock-up operation range into the low vehicle speed range, the fuel cut range has been enlarged, achieving improved fuel economy.
    7-speed Sport Sequential Shiftmatic Enables driving in a specific gear range which is selected using the shift lever, providing engine braking force appropriate to each gear range.
    G AI-shift Control Helps to ensure the vehicle proper posture when entering a corner and ensures the driving torque when exiting a corner.

    1. Engine - CVT Integrated Control


      1. To perform fine-tuned control in accordance with driving conditions, various signals are exchanged between the engine control system and the CVT system. As a result, both smooth and powerful driving that excels in shift response and fuel economy has been achieved.

        A01QFGJE01

    2. Automatic Shift Control (Speed Ratio Control)


      1. The ECM judges the driving conditions through each input signal and selects the optimal control to achieve driving which meets the driver's intentions.

        A01QFNIE02

      2. The ECM calculates the target primary pulley speed in accordance with the accelerator pedal position signal, vehicle speed signal, and stop light switch signal, in order to attain an optimal pulley ratio and shifting speed. To allow the actual primary pulley speed (acquired from the primary speed sensor) to match the target primary pulley speed, the ECM actuates the shift solenoid valves SLP and SLS in order to control the pressure of primary pulley and secondary pulley. As a result, optimal pulley ratio and shifting speed have been achieved.

        A01QF8EE05

      3. When the shift lever is in D, the system effects engine integrated control to optimize fuel economy characteristics and driving performance.

        A01QFRKE02

      4. The Sport mode limits the gear step for the acceleration side and maintains the primary pulley speed at high speeds. This produces a moderate engine braking force and provides an excellent shift response.

        A01QF5YE02

      5. 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.

    3. Acceleration Improvement Control


      1. The system determines the driver's acceleration request based on the vehicle speed and the changes in the accelerator pedal position. When the system determines this request, it changes the shift characteristic into one in which the engine speed and vehicle speed increase linearly. This improves the acceleration feeling.

        A01QFLLE01

      2. When Sport mode is on, upshifting time is shortened and engine speed increase rate is improved, thus giving a sportier setting compared to when Sport mode is off.

        A01QFTZE01

    4. Deceleration Improvement Control


      1. During deceleration, the pulley ratio is determined and a high engine speed is maintained, thus ensuring adequate engine braking.

      2. Engine control, which generates driving force quickly, is conducted during re-acceleration.

        A01QFFFE01

      3. When decelerating with Sport mode on, the pulley ratio is fixed in the lower ratio side to achieve a quicker deceleration response and stronger engine braking force compared to when Sport mode is off. In addition, a higher brake pedal force is caused by increasing engine speed when braking hard, and braking downshift control which generates a quick drive force during re-acceleration is used.

        A01QFK9E01

    5. Uphill/Downhill Shift Control


      1. The ECM determines that the vehicle is driving uphill or downhill based on the accelerator pedal position sensor signal and the vehicle speed signal. During uphill driving, the ECM limits upshift to achieve smooth driving. During downhill driving, the ECM downshifts upon detecting brake pedal operation, in order to provide moderate engine braking.

        A01QF0PC01
        *a Without Control *b With Control
        *c Downshift *d Upshift
        *e Restrict Upshift *f Brake Operation

      2. The actual acceleration calculated from the vehicle speed signal is compared with the reference acceleration (based on level road travel) stored in the ECM to determine uphill or downhill travel.

        A01QFO4C01
        *a Smaller *b Greater
        *c Uphill *d Downhill
        A01QFTC Actual Acceleration A01QFNN Reference Acceleration

    6. Lock-up Control


      1. The lock-up operation range has been expanded from that of previous continuously variable transaxles, thus enabling control to start from low speeds.

      2. The lock-up operation range during deceleration has been expanded to the low-speed range. This expands the fuel cut range and achieves excellent fuel economy.

        A01QF4LE02
        *1 Lock-up on
        *2 Throttle Opening Angle
        *3 Vehicle Speed

    7. Flex Lock-up Control


      1. In order to improve the transmission efficiency and also the fuel economy, the shift solenoid valve SLU for lock-up engagement pressure control is employed to deliver flex lock-up control that can provide more precise control than that of a conventional lock-up clutch mechanism.

      2. The flex lock-up control consists of flex start control and flex lock-up control during deceleration.


        1. Flex Lock-up Control during Deceleration


          • Flex lock-up control during deceleration is used to expand the fuel-cut range. It operates the lock-up clutch over the low vehicle speed range when the vehicle decelerates so that minimal speed difference between the engine speed and turbine speed can be maintained.

    8. 7-speed Sport Sequential Shiftmatic


      1. The 7-speed sport sequential shiftmatic is designed to allow the driver to switch the gear step. After moving the shift lever to M, the driver can select the desired gear step by moving the shift lever to "+" (upshift) or "-" (downshift). Thus, the driver is able to select gear steps with a manual-like feel. In addition, engine brake force can be obtained in accordance with each gear step.

      2. Through the engine-CVT integrated control, pulley ratio and engine torque which corresponds to shifting speed are finely controlled, thus improving shifting response and achieving a reduction in shifting shock.

        A01QFTUE06

      3. When the shift lever is in M, this system automatically upshifts or downshifts under the following conditions:

        Condition System Control
        Engine is under-revving. 1 step downshift
        Engine is over-revving. 1 step upshift

      4. When the vehicle is stopped while the shift lever is in M, the transaxle automatically downshifts to M1.

      5. When the accelerator pedal is fully depressed and a kickdown operation is performed, a downshift to a gear step determined according to the vehicle speed is performed.

      6. The ECM will restrict the changing of the shift range if it detects a malfunction in the CVT system.

      7. If the vehicle speed and engine speed exceed or go below a preset level in response to the driver's downshift operation request, changing the gear step will be prohibited. In this case, the buzzer in the combination meter will sound to alert the driver.

    9. G AI-shift Control


      1. G AI-shift control is used. When braking, G AI-shift control performs braking downshift in accordance with the actual braking force, producing appropriate engine braking force. Additionally, while determining a corner condition, G AI-shift control restricts unnecessary shift change and maintains engine speed by detecting a lateral G force, improving acceleration control performance and ensuring the drive torque when exiting a corner.

        A01QF04E01

        Tech Tips


        • G AI-shift control is turned on by pressing the Sport mode switch. When Sport mode is selected, the Sport mode indicator light in the combination meter assembly illuminates. Pressing the Sport mode switch again turns Sport mode off.

        • When the engine is stopped with Sport mode on, Sport mode is turned off.

        • When the shift lever is in M or temporary sport sequential shiftmatic mode is selected, gear range change operation due to mode change is not performed.

        • If a malfunction is detected in the CVT system, transmission control is performed in normal mode.

  3. FAIL-SAFE


    1. This function minimizes the loss of operability when any abnormality occurs in any sensor or shift solenoid valve.

    2. For details, refer to the Repair Manual.

  4. DIAGNOSIS


    1. When the ECM detects a malfunction, it makes a diagnosis and memorizes the failed section. Furthermore, the MIL in the combination meter illuminates or blinks to inform the driver.

    2. At the same time, the Diagnostic Trouble Codes (DTCs) are stored in memory. The DTCs can be read by connecting a Global TechStream (GTS). For details, refer to the Repair Manual.