GB2102165A

GB2102165A - Method of controlling an internal combustion engine

Info

Publication number: GB2102165A
Application number: GB08219073A
Authority: GB
Inventors: Dusan Gruden
Original assignee: Dr Ing HCF Porsche AG
Current assignee: Dr Ing HCF Porsche AG
Priority date: 1981-07-17
Filing date: 1982-07-01
Publication date: 1983-01-26
Also published as: JPS5825547A; IT1190855B; GB2102165B; FR2509797B1; IT8221733A0; DE3128245A1; FR2509797A1

Abstract

The optimum values of combustion chamber pressure of engine 1 are experimentally determined as a function of the crankshaft angle and are stored as set values in the memory of an electronic control unit (3). The actual pressure in the combustion chamber is continually measured by sensor 2 and fed to the control unit (3) where it is compared with the set value. Deviations between the actual and set values are rectified by modifying the air/fuel mixture (4) or ignition timing (5) of the internal combustion engine. Other characteristics of the combustion process may be used instead of pressure. <IMAGE>

Description

SPECIFICATION Method of controlling the combustion sequence in internal combustion engines The invention concerns a method of controlling the combustion sequence in internal combustion engines, especially Otto cycle engines.

In the combustion process in internalcombustion engines which is reflected, for example, in the variation of the combustion chamber pressure as a function of the crankshaft angle (Figure 1), three phases can be distinguished. In the initial phase of combustion approximately between 400 to 200 before top dead centre (TDC) a turbulent flame core forms in the proximity of the spark plug. In order for this phase, referred to as ignition delay, to be able to move into the second phase, called the main phase, the flame core must reach the dimensions of the turbulent flame region. In the main phase occurs the expansion of the turbulent flame through the combustion chamber, which results in combustion of the main portion of the combustible mixture.The final phase of the combustion, from approximately 100 after top dead centre (TDC), consists of post-combustion of the mixture behind the flame front. The duration and development of the individual phases depend on the ignition conditions, mixture composition, turbulence intensity, pressure, temperature and chemical characteristics of the fuel.

These three phases of mixture combustion reoccur in each operating cycle. The successive combustion sequences, which at any given time can be recorded by a pressure-crankshaft angleindicator diagram, exhibit considerable variations under constant operating conditions. The nonuniformity of the operating cycles reduces the indicated effective mean pressure and thus the efficiency of the internal-combustion engine, particularly when it is operated in an excess air range (amount of air actually required exceeds theoretical amount to burn fuel). In addition, because of these cyclic variations, the emission of the legally restricted quantities of the exhaust components NO, HC and CO increases.

Based on these physical facts, the purpose of the invention is to increase the efficiency of the internal combustion engines and to reduce the harmful exhaust emissions by eliminating cyclic variations in the combustion sequence.

The present invention consists in a method of controlling the combustion sequence in an internal combustion engine, wherein the optimum values of the combustion characteristic (of the combustion chamber pressure) are determined as functions of the crankshaft angle and are stored in an electronic control unit, the actual combustion characteristic in the combustion chamber being continually measured and compared with the set values stored in the control unit and the deviations between the actual and set values are rectified by intervening into the formation of the mixture and/or the ignition system of the internal combustion engine.

By regulation according to this invention, on the one hand, successive combustion sequences will be made comparable and, on the other, adjustment to the experimentally determined and stored optimum values will be accomplished. The controlled variable is preferably the combustion chamber pressure, the variation of which, when at variance with the electronically stored set value, is adjusted as a function of the crankshaft angle by altering the mixture composition or ignition timing point. For each operating phase of the performance characteristics, from the idling speed to the maximum output, the optimum set value curves are recorded and stored in the electronic control unit.

In the accompanying drawings:- Fig. 1 is a graph showing cylinder pressure/crank angle relationship of an internal combustion engine, and Fig. 2 is a block diagram showing the control circuit for carrying out the present invehtion.

Referring to Fig. 2, in the internal combustion engine 1 the actual combustion chamber pressure is continually determined by an indicator device 2 and, as an actual value signal, it is sent to an electronic control unit 3 which contains optimum curve traces of the combustion chamber pressure as the set value. When a deviation between the actual and the set value occurs, an adjustment signal is sent to a mixing device 4 and/or to the ignition system 5 of the engine 1, which are appropriately adjusted and thus the combustion chamber pressure is adjusted to the proper set value.

In this way in Otto cycle engines an increase in specific work or output of approximately 6% can be reached which means at the same time an improvement in actual efficiency. In the excess air range, the NO emission can be reduced by 30% to 50%. These advantages far outweigh the additional costs of the control unit and guarantee an extraordinarily economical operation of an Otto cycle engine which is equipped with this unit.

1. A method of controlling the combustion sequence in an internal combustion engine, wherein the optimum values of the combustion characteristic (of the combustion chamber pressure) are determined as functions of the crankshaft angle and are stored in an electronic control unit, the actual combustion characteristic in the combustion chamber being continually measured and compared with the set values stored in the control unit and the deviations between the actual and set values are rectified by intervening into the formation of the mixture

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Method of controlling the combustion sequence in internal combustion engines The invention concerns a method of controlling the combustion sequence in internal combustion engines, especially Otto cycle engines. In the combustion process in internalcombustion engines which is reflected, for example, in the variation of the combustion chamber pressure as a function of the crankshaft angle (Figure 1), three phases can be distinguished. In the initial phase of combustion approximately between 400 to 200 before top dead centre (TDC) a turbulent flame core forms in the proximity of the spark plug. In order for this phase, referred to as ignition delay, to be able to move into the second phase, called the main phase, the flame core must reach the dimensions of the turbulent flame region. In the main phase occurs the expansion of the turbulent flame through the combustion chamber, which results in combustion of the main portion of the combustible mixture.The final phase of the combustion, from approximately 100 after top dead centre (TDC), consists of post-combustion of the mixture behind the flame front. The duration and development of the individual phases depend on the ignition conditions, mixture composition, turbulence intensity, pressure, temperature and chemical characteristics of the fuel. These three phases of mixture combustion reoccur in each operating cycle. The successive combustion sequences, which at any given time can be recorded by a pressure-crankshaft angleindicator diagram, exhibit considerable variations under constant operating conditions. The nonuniformity of the operating cycles reduces the indicated effective mean pressure and thus the efficiency of the internal-combustion engine, particularly when it is operated in an excess air range (amount of air actually required exceeds theoretical amount to burn fuel). In addition, because of these cyclic variations, the emission of the legally restricted quantities of the exhaust components NO, HC and CO increases. Based on these physical facts, the purpose of the invention is to increase the efficiency of the internal combustion engines and to reduce the harmful exhaust emissions by eliminating cyclic variations in the combustion sequence. The present invention consists in a method of controlling the combustion sequence in an internal combustion engine, wherein the optimum values of the combustion characteristic (of the combustion chamber pressure) are determined as functions of the crankshaft angle and are stored in an electronic control unit, the actual combustion characteristic in the combustion chamber being continually measured and compared with the set values stored in the control unit and the deviations between the actual and set values are rectified by intervening into the formation of the mixture and/or the ignition system of the internal combustion engine. By regulation according to this invention, on the one hand, successive combustion sequences will be made comparable and, on the other, adjustment to the experimentally determined and stored optimum values will be accomplished. The controlled variable is preferably the combustion chamber pressure, the variation of which, when at variance with the electronically stored set value, is adjusted as a function of the crankshaft angle by altering the mixture composition or ignition timing point. For each operating phase of the performance characteristics, from the idling speed to the maximum output, the optimum set value curves are recorded and stored in the electronic control unit. In the accompanying drawings:- Fig. 1 is a graph showing cylinder pressure/crank angle relationship of an internal combustion engine, and Fig. 2 is a block diagram showing the control circuit for carrying out the present invehtion. Referring to Fig. 2, in the internal combustion engine 1 the actual combustion chamber pressure is continually determined by an indicator device 2 and, as an actual value signal, it is sent to an electronic control unit 3 which contains optimum curve traces of the combustion chamber pressure as the set value. When a deviation between the actual and the set value occurs, an adjustment signal is sent to a mixing device 4 and/or to the ignition system 5 of the engine 1, which are appropriately adjusted and thus the combustion chamber pressure is adjusted to the proper set value. In this way in Otto cycle engines an increase in specific work or output of approximately 6% can be reached which means at the same time an improvement in actual efficiency. In the excess air range, the NO emission can be reduced by 30% to 50%. These advantages far outweigh the additional costs of the control unit and guarantee an extraordinarily economical operation of an Otto cycle engine which is equipped with this unit. CLAIMS

1. A method of controlling the combustion sequence in an internal combustion engine, wherein the optimum values of the combustion characteristic (of the combustion chamber pressure) are determined as functions of the crankshaft angle and are stored in an electronic control unit, the actual combustion characteristic in the combustion chamber being continually measured and compared with the set values stored in the control unit and the deviations between the actual and set values are rectified by intervening into the formation of the mixture and/orthe ignition system of the internal combustion engine.

2. A method of controlling the combustion sequence in an internal combustion engine substantially as descrbed with reference to Fig. 2 of the accompanying drawings.