System Description

System Diagram 

Courtesy of NISSAN NORTH AMERICA, INC.

• Pre-crash seat belt system integrates control unit and motor in driver and passenger seat belt retractors.
• Provides a sense of ease when pre-crash seat belt control unit judges the emergency braking operation, the intelligent brake assistance operating status, the continuous ABS operating status, the emergency steering wheel operation, the excessive vehicle inclination status, or the lateral slippage status during cornering.

  The motor immediately retracts the seat belt and suppresses change in occupant posture.

• Even in a situation where a collision is unavoidable, effects of other safety devices, like the air bag, are maximized and damages are reduced.
• Motor retracts seat belt when unfastening and extracts seat belt when fastening to reduce the feeling of pressure. (comfort function)

FUNCTION DESCRIPTION 

Pre-crash seat belt system operates under the following conditions.

• During emergency brake operation
• When ABS continuously operates
• When intelligent brake assistance operates
• When lateral slippage during cornering occurs
• When steering wheel is rotated for emergency
• When the vehicle inclined excessively
• When comfort function operates

OPERATION CONDITION 

Operation while driving

• Operation start and stop conditions of pre-crash seat belt system are as shown in the following table.
• The activation and deactivation conditions of pre-crush seat belt are as per the following.

Operation item	Operation start condition	Operation stop condition
During emergency brake operation	Vehicle speed is 15 km/h (9 MPH) or more Emergency braking status is detected	During acceleration When stopped
When ABS continuously operates	ABS continuously operates for 2 seconds or more Brake pedal is in depressed state
When intelligent brake assistance operates	System detects that intelligent brake assistance is in operating status	2 seconds after operation start
When lateral slippage during cornering occurs	Vehicle speed is 30 km/h (19 MPH) or more System detects that the vehicle is in lateral slippage state System detects that the vehicle is driving on a curve	Vehicle stopped 1 second or more after maintaining steering wheel angle in straight driving state
When steering wheel is rotated for emergency	Vehicle speed is 60 km/h (36 MPH) or more Steering wheel angle is 90 degrees or more System detects that steering wheel is rotated for emergency
When the vehicle inclined excessively	Vehicle speed is 30 km/h (19 MPH) or more System detects that the vehicle inclined excessively	During acceleration Vehicle stopped

Comfort function 

• Seat belt is retracted and the looseness is reduced in the state as shown in the following table.
• Operation start and stop conditions of pre-crash seat belt system are as shown in the following table.

  Operation item	Activating condition	Deactivating condition
  Door open	Seat belt is in not fastened state Door is operated to open from closed Vehicle stopped	Seat belt retract is complete 13 seconds after start retracting
  Seat belt is fastened	When door is closed Seat belt is fastened	Seat belt is unfastened 1 second after operation
  Seat belt is release	Seat belt is unfastened	Seat belt retract is complete 10 seconds after start retracting

Operation Prohibited Condition 

Pre-crash seat belt system does not operate in the following conditions.

• When seat belt is not fastened (only the seat belt that is not fastened does not operate)
• When motor is overheat due to contentious operation*1
• When the system is in fail-safe mode

  *1: System operation is temporarily deactivated to avoid overheating, when comfort function is continuously operated (18 times or more) during a short period of time by fastening and unfastening seat belts or opening and closing doors.

MALFUNCTION WARNING 

When system malfunction is detected, comfort function is deactivated to warn customer of system malfunction.