Engine management system

Details Engine management system Engine management system

1996-02-28

1998-03-17

Hart, Douglas

Power plants

Internal combustion engine with treatment or handling of...

By means producing a chemical reaction of a component of the...

60300, 1231425E, 12317921, 123549, 123557, F01N 320, F02N 1702

Patent

active

057273847

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to an engine management system for an engine having a rapid heating system for a catalytic converter or a fuel vaporiser.


BACKGROUND OF THE INVENTION

In the following specification, the term "hot operating system" shall mean a catalytic converter or a fuel vaporizer.
For any fast catalyst light off heating system (exhaust gas ignition, external fuel burner, electrically heated catalyst) and fast warm up heating system (glow plug, fuel vaporiser), there is a risk that if the system is operated more than once in close succession damage would occur.
For example, in a vehicle equipped with such a heating system, it is desirable to have the vaporiser or the catalytic converter in full operation within seconds or even a fraction of a second as soon as the car is started, and the heating system should therefore be operated during cold starts. However, if the car stalls and is restarted immediately, the catalyst is already hot, the glow plug is still hot, the fuel vaporiser is already hot, but everything else in the car remains cold. Unless there are temperature sensors measuring these hot elements directly, the engine management microprocessor would have no indication that the second start is any different from the first and would give the heating system another dose of intense heat which could cause damage to the fuel vaporiser or the catalytic converter.
A difficulty currently encountered in complying with statutory regulations is that the temperature sensing elements available do not have the required proven durability and direct temperature measurement is not currently an available solution this problem.
The invention therefore seeks to provide alternative safeguards to protect against damage through overheating.
One possible solution to this problem would be to store in a keep alive memory the coolant temperature at the time the engine is stopped or stalls and to compare the stored reading with a current measurement of the coolant temperature during the attempt to restart the engine. If the engine was hot when switched off and is now cold, then it is safe to operate the heating system but if the engine coolant was cold and is still cold, this suggests that the engine is being restarted after only a very short run and that it is therefore unsafe to operate the heating system.
The problem with this system however is that the time that has elapsed since the engine was switched off is still not known and it is possible that an engine that was run for a very brief period may have been allowed to stand for long enough to cool down fully and in this case the heating system will fail to operate during the next start, even though it should be switched on normally.
Another situation is when the engine is stopped after it has fully warmed. The coolant temperature will continue to rise for a period because of redistribution of heat within the engine when the coolant flow is stopped and will then cool relatively slowly whereas the catalyst or the fuel vaporiser will start to cool immediately after the engine is stopped and will cool more quickly. If the engine is restarted during this period, the engine management system will read the input from the coolant temperature sensor which indicates that the engine is still hot and will prevent activation of the rapid heating system even though the catalyst or the fuel vaporiser is already cold and the heating system should be activated.
U.S. Pat. No. 4,499,879 discloses a management system of an internal combustion engine including a real time clock that continues to operate after the engine has stopped. The engine temperature is estimated based on the elapsed time after engine shutdown and use to determine the fuelling requirements of the engine at restart. The latter patent is not concerned with a heatable catalyst nor a heatable fuel vaporiser, neither of which is mentioned in the patent.
It is also known from DE-A-40 29 811 to control an engine catalyst heater during a restart or warm start as a function of engine tem

REFERENCES:
patent: 5184463 (1993-02-01), Becker
patent: 5390493 (1995-02-01), Fujishita

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