Abstract: An LNT (Lean NOx Trap) control method for vehicles increases a purification rate of NOx while preventing an increase in the amount of slip of separated NOx at a relatively low LNT temperature. The method includes a recycle necessity determining step that determines whether to recycle NOx of a LNT in accordance with an amount of adsorbed NOx, a LNT temperature determining step that determines whether a temperature of the LNT is below a predetermined reference temperature, a rich performing step that performs a rich mode when the temperature of the LNT is equal to the reference temperature or above and a pre-rich step that ejects fuel in a rich state when the temperature of the LNT is below the reference temperature.

Abstract: An LNT (Lean NOx Trap) control method for vehicles increases a purification rate of NOx while preventing an increase in the amount of slip of separated NOx at a relatively low LNT temperature. The method includes a recycle necessity determining step that determines whether to recycle NOx of a LNT in accordance with an amount of adsorbed NOx, a LNT temperature determining step that determines whether a temperature of the LNT is below a predetermined reference temperature, a rich performing step that performs a rich mode when the temperature of the LNT is equal to the reference temperature or above and a pre-rich step that ejects fuel in a rich state when the temperature of the LNT is below the reference temperature.

Abstract: An LNT control method for a vehicle may minimize the loss ratio of fuel efficiency while satisfying limits of NOx by changing a rich mode control plan in accordance with the purification rate of NOx in LNT which changes with the degree of deterioration of LNT catalyst.

Abstract: A degradation rate decision method of a lambda sensor, may include an injection step injecting a reducing agent so as to regenerate a nitrogen oxide purification catalyst, a lambda value detection step detecting a lambda value of the lambda sensor from a fuel/air ratio of exhaust gas after injecting the reducing agent, a reaching time decision step determining a time period that the lambda value takes to reach a predetermined criterion value after injecting the reducing agent, and a degradation rate decision step determining that the lambda sensor is degraded when the time period is equal to or longer than a predetermined time period.