Internal-combustion engines – Engine speed regulator – Idle speed control
Patent
1992-07-06
1994-01-25
Nelli, Raymond A.
Internal-combustion engines
Engine speed regulator
Idle speed control
F02M 300
Patent
active
052807720
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process for controlling the speed of an internal combustion engine after starting, and until reaching an idling speed.
The starting process is terminated when the engine which has been disconnected from the starter continues to run under its own power and has reached a specific minimum speed. After this, the so-called after-start phase begins, during which the engine runs up to its predetermined idling speed. This idling speed is usually controlled in modern engine controls by means of an idling speed regulator.
During this after-start phase, there is still no stable operating state present. The speed usually increases very rapidly within approximately 0.3 to 1 second, from approximately 200 revolutions per minute after the start, to the temperature-dependent idling speed of approximately 600 revolutions per minute at approximately 20.degree. C. A slightly enriched mixture adjustment and early ignition angle values are usually provided here in order to ensure reliable running up.
However, the rapid increase in speed also causes the speed firstly to rise beyond the predetermined idling speed and only then to be subsequently controlled back to the idling speed by the idling speed regulator. As a result of this overshooting of the speed over the idling speed, increased exhaust gas emissions arise which are in any case already increased by the rich mixture setting and therefore by the not yet possible lambda control during the after-start phase.
SUMMARY OF THE INVENTION
The invention is therefore based on the object of avoiding this overshoot with the associated higher exhaust gas emissions without thereby adversely affecting the reliable running up of the engine.
In general terms the present invention is a process for controlling the speed of an internal combustion engine after starting and until reaching an idling speed. The speed of the internal combustion engine is continuously detected and the idling speed is dependent on the cooling water temperature. Starting from a specific engine speed threshold, the ignition angle is adjusted in the retarded direction as a function of the rate of change of the speed for a specific time period. After this time period has elapsed the ignition angle is adjusted back to the normal ignition angle in accordance with a predetermined function.
The following are advantageious developments of the present invention. An idling speed control can be provided which adjusts the engine speed of the idling speed. The engine speed threshold can be dependent on the idling speed. The return control function can be linear or the return control function can be progressive. A still existing adjustment in the retarded direction of the ignition angle can be reversed if the idling operating state is departed from.
The invention is based on the recognition that the degree of overshoot is dependent on the rate of variation of the speed, that is to say on the acceleration during the starting phase. Therefore, the higher this rate of variation of the speed the greater is the degree of intervention that is necessary. However, each such intervention unavoidably causes the running of the motor to be impaired, since a power limitation must take place in some form or another although, particularly during the after-start phase, this power is necessary for reliable operation of the engine. Therefore, according to the invention, the power is reduced only above a specific engine speed threshold. This engine speed threshold is determined individually for each engine type during driving trials so that, on the one hand, the engine no longer dies, and on the other hand, the overshooting of the speed can still be avoided. The intervention consists of abruptly adjusting the ignition angle in the retarded direction above this engine speed threshold, as a function of the rate of charge of the engine speed and controlling it back to the ignition angle, which is normal for the idling speed, only after a specific time period has elapsed. The time period and t
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Krebs Stefan
Weber Gerald
Nelli Raymond A.
Siemens Aktiengesellschaft
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