Device and method for diagnosing the condition of a probe upstream from a catalytic converter
AssigneeRENAULT s.a.s.
InventorsEric Marcheguet, Vasco Afonso, Francois Ratinet
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Abstract
An apparatus and method for diagnosing the condition of a sensor in an internal combustion engine upstream from the catalytic converter. The diagnosis utilizes a signal from a second non-linear probe downstream from the catalytic converter. This signal is processed to give a signal that is filtered. The filtered signal is in turn compared with maximum and minimum values. The upstream probe is considered to be correct if the signal falls between these two values or faulty if it falls outside the values.
Claims14
A device for diagnosis of the condition of a nonlinear sensor disposed upstream from a catalytic converter associated with a fuel injected internal combustion engine controlled by an electronic computer, the engine containing a first control loop, including said nonlinear sensor, to deliver to the computer a first signal for correction of a quantity of fuel injected, and a second control loop, including a second nonlinear sensor disposed downstream from the catalytic converter, to deliver a second signal for correction of the quantity of fuel injected, said diagnostic device comprising:
- a filter circuit to which there is applied the second correction signal in order to deliver a filtered signal,
- a measuring circuit to which there is applied an output of the upstream sensor in order to determine the mean value of the period of correction of the first control loop, and
- a logic circuit to determine, as a function of the values of the filtered signal and of the mean period, whether the condition of the upstream sensor is good or defective.
A process for diagnosis of the condition of a nonlinear sensor disposed upstream from a catalytic converter associated with a fuel injected internal combustion engine controlled by an electronic computer, the engine containing a first control loop, including the nonlinear sensor, to deliver to the computer a first signal for correction of a quantity of fuel injected, and a second control loop, including a second nonlinear sensor disposed downstream from the said catalytic converter, to deliver a second signal for correction of the quantity of fuel injected, the diagnostic process comprising the steps of:
- filtering the second correction signal to obtain a filtered signal,
- calculating the mean value of the period of the output signal of the upstream sensor,
- comparing the filtered signal with predetermined maximum and minimum values of the filtered signal, to determine whether the condition of the upstream sensor is correct or defective, according to whether the filtered signal is respectively within the limits defined by the maximum and minimum values,
- or outside predetermined limits for the value of the mean period.
Dependencies are inferred from the claim text.