Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Patent
1992-01-16
1994-01-18
Argenbright, Tony M.
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
123686, F02D 4114, F02D 4106, F02D 4110
Patent
active
052792757
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process for operating an internal combustion engine.
A customary .lambda. adjustment adjusts the mixture of fuel and air to be fed to an internal combustion engine to a stoichiometric ratio. During special operating conditions which require a rich mixture, the .lambda. adjustment must therefore be switched off and its task is assumed by a control.
This process works satisfactorily as long as the control sets the required rich mixture correctly during the special operation. However, maladjustment or corresponding long-term changes may lead to the setting of a lean mixture instead of the required rich mixture. Particularly towards the end of a special operation, when the rich mixture is brought back to a stoichiometric mixture ratio in order to achieve a continuous transition to the subsequent .lambda. adjustment, even small maladjustments of the control in the lean direction lead to an undesirably lean mixture. Since, during control, there is no feedback, this error also remains undetected and manifests itself only in a poorer operating behavior of the engine.
U.S. Pat. No. 4,753,209 discloses a mixture adjustment system for an internal combustion engine with a .lambda. adjustment, the .lambda. probe supplying a linear output signal. Prior to the readiness of the .lambda. probe for operation, temperature-dependent control of a choke valve is carried out. During the warm-up phase of the engine and after the operating temperature of the .lambda. probe has been achieved, coarse .lambda. adjustment takes place via the choke valve and fine .lambda. adjustment via a bypass valve. The use of a .lambda. probe with a linear characteristic ensures that a fuel/air mixture in a range from lean to rich can be set even in the warm-up phase of the internal combustion engine.
SUMMARY OF THE INVENTION
The object of the invention is, in contrast, to improve mixture control during such special operating conditions of the engine.
The solution according to the invention is a process for operating an internal combustion engine with a .lambda. probe and a .lambda. adjuster which adjust the mixture of fuel and air to be fed to the internal combustion engine to a setpoint value as a function of the output signal of the .lambda. probe in the adjusting mode and with a control. During special operating conditions, the fuel/air mixture is set to a mixture value which lies on the rich side, below the setpoint value which the .lambda. adjuster sets outside the special operating conditions. During the special operating conditions, the .lambda. adjuster acts asymmetrically, adjusting the mixture only in the rich direction. In further advantageous developments of the invention the special operating condition can be the warming-up of the internal combustion engine. After the starting of the internal combustion engine and when a special operating temperature is reached, the .lambda. adjuster is switched on with the restricted range of adjustment, and the range of adjustment is enabled without restriction only when a minimum cooling-water temperature is reached. Alternatively, the special operating condition can be the acceleration mode of the internal combustion engine or the full-load mode of the internal combustion engine.
The solution according to the invention consists in switching on the .lambda. adjustment during the control mode as well, but with a restricted range of adjustment. With an unrestricted range of adjustment, the .lambda. adjustment would adjust the rich mixture set by the control back in the lean direction, to a stoichiometric ratio with an air ratio of .lambda.=1. The range of adjustment of the .lambda. adjuster is therefore restricted such that it only adjusts in the rich direction and not in the lean direction. The .lambda. adjustment thus does not intervene when the mixture is rich. If, however, the control erroneously sets a lean mixture, the .lambda. adjustment can intervene in the enriching direction and thus mitigate the error to a tolerable degree.
The war
REFERENCES:
patent: 4096834 (1978-06-01), Norimatsu et al.
patent: 4119072 (1978-10-01), Asano
patent: 4143623 (1979-03-01), Norimatsu et al.
patent: 4753209 (1988-06-01), Hibino et al.
Argenbright Tony M.
Siemens Aktiengesellschaft
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