Diagnosis method for catalytic converter of engine

Abstract

The invention relates to a diagnosis method for a catalytic converter. The method comprises the following steps: after an enabling condition is satisfied, performing fuel oil closed-loop control by only using a downstream oxygen sensor; acquiring a transformation moment T1 when a primary oxygen concentration in an upstream oxygen concentration signal increases, a transformation moment T3 which corresponds to the transformation moment T1 in a downstream oxygen concentration signal, a transformation moment T2 when the primary oxygen concentration in the upstream oxygen concentration signal decreases, a transformation moment T4 which corresponds to the transformation moment T2 in the downstream oxygen concentration signal, a high concentration duration T5 when a primary oxygen concentration in the downstream oxygen concentration signal is continuously high, and a low concentration duration T6 when the primary oxygen concentration is continuously low; computing T31=T3-T1, and T42=T4-T2; acquiring repeatedly, computing the average value of a plurality of numerical values, and comparing the average value with a calibrated limit value in a corresponding critical state of the catalytic converter, wherein the catalytic converter is aged if the average value is smaller than respective calibrated limit value, otherwise, the catalytic converter is normal. The method is easy to implement, and is low in diagnosis cost.

Description

technical field [0001] The invention relates to a method for diagnosing a catalytic converter of an engine, in particular to a method for diagnosing a catalytic converter of an electronically controlled engine. Background technique [0002] The catalytic converter plays a vital role in the control of engine exhaust emissions. In order to effectively use the catalytic converter, the air-fuel ratio needs to be controlled. Once the air-fuel ratio deviates from the theoretical value, the catalytic converter's ability to purify the engine exhaust gas will drop sharply. like figure 1 As shown, the catalytic converter 60 is connected to the exhaust pipe of the engine, an upstream oxygen sensor 72 is installed at the upstream of the catalytic converter 60, and a downstream oxygen sensor 74 is installed at the downstream position. The upstream oxygen sensor 72 is used to detect the oxygen concentration in the exhaust gas of the engine. And according to the rich or lean situation of ...

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Problems solved by technology

[0004] At present, it is usually necessary to design different working conditions to monitor the signal changes of the upstream oxygen sensor 72 and the downstream oxygen sensor 74. For example, under a certain working condition, the air-fuel ratio is constantly changed to change the emission, and then the signal of the upstream oxygen sensor 72 is monitored. Make a judgment, the diagnostic method is relatively complicated, and will increase the cost of diagnosis

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