Method and arrangement for checking the aging condition of a catalyzer

• US 5,267,439 A
• Filed: 12/13/1991
• Issued: 12/07/1993
• Est. Priority Date: 12/13/1990
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Schnaibel, Eberhard, Raff, Lothar
• Primary Examiner(s): Hart, Douglas
• Application Number:
  US07/806,309
• Time in Patent Office: 725 Days
• Field of Search: 60/276, 60/277, 60/274, 123/691
• US Class Current: 60/274
• CPC Class Codes: F01N 11/007 the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

The invention is directed to a method for checking the aging condition of a catalyzer by utilizing a lambda probe rearward of the catalyzer. For a transition from lean to rich which takes place within a pregiven time span, a check is made if an overshoot of the probe signal occurs which exceeds a pregiven amplitude. A conclusion is drawn as to the aging condition of the catalyzer from an overshoot when the latter occurs. Transitions between lean and rich and vice versa take place especially during the transition from overrun operation to controlled operation of the engine. Transitions of this kind have large swings of the signals of the lambda probes and this permits reliable measurements. In contrast, conventional methods operate exclusively when the engine to which the catalyzer belongs is lambda controlled. The relatively small signal amplitudes occurring thereby lead to a signal/noise ratio which is considerably poorer than in the methods according to the invention.

Claims

1. A method for checking the state of deterioration of a catalytic converter by utilizing a lambda probe arranged rearward of the catalytic converter, the method comprising the steps of:

monitoring the output signal of said lambda probe during a transition taking place within a pregiven time span from a lean mixture composition, which is indicated by a low-level of said output signal, to a rich mixture composition, which is indicated by a high-level of said output signal;

checking said output signal while passing from said low-level to said high-level to determine if an overshoot occurs in the form of an excessive jump in said output signal which departs for a short time from the expected trace of said output signal;

determining if the amplitude of said overshoot exceeds a pregiven threshold amplitude; and

,

determining the state of deterioration of said catalytic converter from the occurrence of said overshoot having an amplitude exceeding said threshold amplitude.

2. The method of claim 1, the method comprising the further steps of:

for a transition from rich to lean, which takes place within a pregiven time span, investigating if a forward swing of the probe signal occurs which exceeds a pregiven amplitude; and

,

determining the state of deterioration of the catalytic converter from said forward swing upon the occurrence thereof.

3. A method for checking the state of deterioration of a catalytic converter by utilizing a lambda probe arranged rearward of the catalytic converter, the method comprising the steps of:

monitoring the output signal of said lambda probe during a transition taking place within a pregiven time span from a lean mixture composition, which is indicated by a low-level of said output signal, to a rich mixture composition, which is indicated by a high-level of said output signal;

checking if an overshoot occurs in the trace of said output signal in the form of a local maximum (OS) as said output signal moves from said low-level to said high-level;

determining if the amplitude of said overshoot exceeds a pregiven threshold amplitude; and

,

determining the state of deterioration of said catalytic converter from the occurrence of said overshoot having an amplitude exceeding said threshold amplitude.

4. A method for checking the state of deterioration of a catalytic converter by utilizing a lambda probe arranged rearward of the catalytic converter, the method comprising the steps of:

monitoring the output signal of said lambda probe during a transition taking place within a pregiven time span from a lean mixture composition, which is indicated by a low-level of said output signal, to a rich mixture composition, which is indicated by a high-level of said output signal;

checking if said output signal has an overshoot in the form of a short-term excessive increase at the start of the phase having said high-level;

determining if the amplitude of said overshoot exceeds a pregiven threshold amplitude; and

,

determining the state of deteriorations of said catalytic converter from the occurrence of said overshoot having an amplitude exceeding said threshold amplitude.

5. An arrangement for checking the aging condition of a catalyzer, the arrangement comprising:

a lambda probe supplying a probe signal and being mounted rearward of the catalyzer;

comparator means connected to said lambda probe for monitoring the probe signal of said lambda probe during a transition taking place within a pregiven time span from a lean mixture composition, which is indicated by a low-level of said probe signal, to a rich mixture composition, which is indicated by a high-level of said probe signal;

said comparator means being adapted for comparing the amplitude of an overshoot of said probe signal to a pregiven threshold amplitude while said probe signal moves between said low-level and said high-level during a transition from lean to rich within a pregiven time span;

said overshoot being in the form of an excessive jump in said probe signal which departs for a short time from an expected trace of said probe signal;

said comparator means being adapted to emit an overshoot signal in the event an amplitude of said overshoot exceeds said pregiven amplitude; and

,

an aging condition detector configured to determine the aging condition of the catalyzer based on said overshoot signal when said overshoot signal occurs.

6. An arrangement for checking the aging condition of a catalyzer, the arrangement comprising:

a lambda probe supplying a probe signal and being mounted rearward of the catalyzer;

comparator means connected to said lambda probe for monitoring the probe signal of said lambda probe during a transition taking place within a pregiven time span from a lean mixture composition, which is indicated by a low-level of said probe signal, to a rich mixture composition, which is indicated by a high-level of said probe signal;

said comparator means being adapted for comparing the amplitude of an overshoot of said probe signal to a pregiven threshold amplitude while said probe signal moves between said low-level and said high-level during a transition from lean to rich within a pregiven time span;

said overshoot occurring in the trace of said probe signal in the form of a local maximum (OS) as said probe signal moves from said low-level to said high-level;

said comparator means being adapted to emit a forward swing signal in the event said local maximum (OS) exceeds said pregiven amplitude; and

,

an aging condition detector configured to determine the aging condition of the catalyzer based on a forward swing signal when said forward swing signal occurs.