SHIFT CONTROL: System Description: Description

To select the gear ratio that can give the driving force to meet driver's intent or vehicle situation, the vehicle driving condition such as vehicle speed or accelerator pedal position is detected and the most appropriate gear ratio is selected and the shifting method before reaching the speed is determined. The information is output to the primary pressure solenoid valve and secondary pressure solenoid valve to control the line pressure input/output to the pulley, to determine the pulley (movable pulley) position and to control the gear position.

Shift Position Function

• D Position (Normal)

  Gear shifting is performed in all shifting ranges from the lowest to the highest gear ratio.

  Fig 1: Identifying Shift Area (D Position; Normal)

  Courtesy of NISSAN NORTH AMERICA, INC.
• D Position (O/D OFF)

  The gear ratio is generally high by limiting the shifting range on the high side, and this always generates a large driving power.

  Fig 2: Identifying Shift Area (D Position OD OFF)

  Courtesy of NISSAN NORTH AMERICA, INC.
• L Position

  By limiting the shifting range only to the lowest of the gear ratio, a large driving force and engine brake are obtained.

  Fig 3: Identifying Shift Area (L Position)

  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 acceleration performance in re-acceleration by limiting the gear shift range on the high side.

Fig 4: Hill Climbing And Descending Control Function Diagram

Courtesy of NISSAN NORTH AMERICA, INC.

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.

• When the accelerator pedal is depressed 4/8 or more in D position, CVT performs step shifting to allow the vehicle speed and engine speed to increase simultaneously. This improves the feel of acceleration and enables the fuel economy by preventing unnecessary rise in engine speed, compared to the conventional shifting.
  Fig 5: Control In Acceleration Vehicle Speed Or Accelerator Pedal Position

  Courtesy of NISSAN NORTH AMERICA, INC.