SHIFT CONTROL: System Description: Description

The shift control sets the shifting method conforming to the intention of the driver and gear ratio, providing traction force suitable to the vehicle conditions.

Gear ratio setting

• The TCM detects the driving status of vehicle according to the vehicle speed and the throttle position, and then the TCM calculates the most suitable gear ratio (target gear ratio) for driving the vehicle.
• The TCM calculates the actual gear ratio of the transaxle according to each sensor signal of the primary speed sensor, secondary speed sensor and, etc.
• The TCM transmits the drive signal to the step motor and the secondary pressure solenoid valve, so that the actual gear ratio becomes identical to the target gear ratio. Upon receipt of the drive signal, the step motor and the secondary pressure solenoid valve control the shift control valve and the secondary valve so that the outwards flow and the inward flow of the operating pressure to the primary pulley and the secondary pulley is controlled. By this operation, the variable position of the primary pulley and the secondary pulley is changed and the gear ratio is controlled to become identical to the target gear ratio.

"D" Position

• Gear shifting is performed in all shifting ranges from the lowest to the highest gear ratio.
• Multiple shift schedules are set for D position. TCM automatically selects a shift schedule with consideration given to the balance between fuel economy and driving performance, according to drive conditions and driving tendencies.
  Fig 1: Primary Pulley Speed Versus Vehicle Speed Graph (D Position)

  Courtesy of NISSAN NORTH AMERICA, INC.

"M" Position

When the selector lever is put in the manual shift gate side, the fixed changing gear line is set. By moving the selector lever to + side or - side, the manual mode switch is changed over, and shift change like M/T becomes possible following the changing gear set line step by step.

Manual Mode Information

The TCM transmits the manual mode shift refusal signal to the combination meter if the TCM refuses the transaxle from the driving status of vehicle when the selector lever shifts to "UP (+ side)" or "DOWN (- side)" side. The combination meter blinks shift position indicator on the combination meter and sounds the buzzer to indicate the driver that the shifting is not performed when receiving this signal. However, the TCM does not transmit the manual mode shift refusal signal in the conditions as per the following.

• When the selector lever shifts to "DOWN (- side)" side while driving in M1.
• When the selector lever shifts to "UP (+ side)" side while driving in M6.

Blipping Control

Using engine torque, the blipping control enables a faster and more responsive gear shifting by compensating inertia torque generated from the rotational change during gear shifting in real time.

Operation

• The blipping control is activated when shifting up/down in manual mode.
  NOTE: The blipping control is not activated when the vehicle is in the following conditions:

  • When CAN communication is abnormal.
  • During the retard inhibit signal transmission from ECM within the engine-CVT integrated control.
  • Engine coolant temperature is less than 20°C (68°F).
  • CVT fluid temperature is more than 120°C (248°F).
  • Vehicle speed is less than 20 km/h (13 MPH).
  • When ABS, TCS or VDC is active.
  • During wheel spin.
• ECM selects blipping control or normal shift control according to the gear position, the selector lever position, etc.
• The blipping control is activated when ECM judges it controllable after receiving a control permit signal from TCM.
• ECM controls engine torque, based on generated inertia torque.
  Fig 3: Engine Speed And CVT Output Torque Characteristics Curves

  Courtesy of NISSAN NORTH AMERICA, INC.

Hill Climbing And Descending Control

If a downhill is detected with the accelerator pedal is released, the system performs downshift to increase the engine brake force so that vehicle may not be accelerated more than necessary. If a climbing hill is detected, the system improves the driving performance in climbing hill by limiting the gear shift range on the high side.

Control In Acceleration

From change of the vehicle speed or accelerator pedal position, the acceleration request level of the driver or driving scene is evaluated. In start or acceleration during driving, the gear shift characteristics with linearity of revolution increase and vehicle speed increase are gained to improve the acceleration feel.