RU2247259C2 - Method of automatic determination and optimum timing of ignition of fuel-air mixture in internal combustion engine - Google Patents

Abstract

FIELD: mechanical engineering; internal combustion engines.

SUBSTANCE: invention relates to ignition timing control systems. It is aimed at optimization of process of conversion of energy of combusted fuel-air mixture into mechanical energy of engine crankshaft rotation. Proposed invention makes it possible to determine automatically and time optimum ignition moment of fuel-air mixture in any internal combustion engine irrespective of its condition, grade of fuel and environment. According to invention, commencement of moment of ignition of fuel-air mixture is regulated by results of end of burning. Burning process of fuel-air mixture is monitored by light-sensitive flame pickup, and after each cycle actual and preset time of burning of entire amount of fuel-air mixture is compared. Basing of obtained data, ignition timing for following cycle is corrected.

EFFECT: increased efficiency of internal combustion engine.

2 dwg

Description

The invention relates to systems for controlling the moment of ignition of the air-fuel mixture in an internal combustion engine.

The prior art methods for correcting the ignition moment, based on adjusting the delay of the beginning of the ignition moment relative to a strictly defined control law (the dependence of the ignition timing on engine revolutions) using electronic devices, randomly select a reference point, and then the microprocessor computing unit according to various signals sensors changes the delay time of the ignition moment, thereby changing the ignition timing.

In this method, the optimum start time for ignition of the air-fuel mixture (FA) is preliminarily determined on a special bench by a test method on a reference engine, and the multiple values obtained for the start of the moment of ignition are realized on serial engines with a mechanical device or an electronic microprocessor system in which the law of change in the ignition timing (in depending on various parameters: engine speed, quantity, composition and temperature of the air-fuel mixture) is written as mat matic matrix in the microprocessor memory. During engine operation, the microprocessor calculates and sets the reference reference ignition start time in accordance with the values of the above parameters determined by special sensors.

The disadvantages of this method is the mismatch of the installation of the reference value of the ignition moment to the required one, since the burning time of the air-fuel mixture depends on the pressure, temperature, quantity and quality of the air-fuel mixture, the quality of gasoline on a particular engine. In other words, existing methods involve correcting the ignition timing of the air-fuel mixture of one engine relative to the initial setting of the ignition timing of another reference engine.

The prototype of the invention is a method of combating detonation, the most similar to the claimed, in which the correction of the ignition moment is carried out using an ionization sensor. The essence of the method is to correct the ignition moment after comparing the actual time of passage of the flame front from the spark plug to the ionization sensor with the set one, when detonation occurs, this time decreases sharply and the system introduces a delay in the ignition moment until the engine detonation disappears (see, for example, US patent No. 4308519 IPC F 02 B 77/08, publ. 12/29/1981).

The disadvantage of the prototype is that the method is applicable only in the presence of detonation, as well as the low accuracy of determining the magnitude and sign of the correction of the ignition timing due to the complexity and uneven propagation of the flame front in the combustion chamber due to the chaotic turbulence of the air-fuel mixture, which leads to a large spread of the magnitude correction of ignition timing.

The problem to which the invention is directed, is to automatically determine and set the optimum ignition timing of the air-fuel mixture in a particular internal combustion engine, regardless of the technical condition of the engine, grade of fuel and environmental conditions.

The technical result of the invention is to increase the efficiency of the internal combustion engine by optimizing the working process of converting the thermal energy of the burned air-fuel mixture into the mechanical energy of rotation of the engine crankshaft.

The technical result is achieved by controlling the start of the moment of ignition of the air-fuel mixture according to the results of the end of its combustion. In this case, the combustion process of the air-fuel mixture is monitored by a photosensitive flame sensor, and after each cycle, the actual and predetermined burning times of the entire air-fuel mixture are compared. Then, the delay time of the ignition moment of the next cycle is adjusted. In this case, the beginning of combustion of the air-fuel mixture is adjusted so that its end occurs at a given point, which corresponds to the position of the piston 10-15 ° after the top dead center. At the end of the combustion process at this point, the work performed by the working fluid (burnt air-fuel mixture) is maximum. Based on this, when using the proposed method, each duty cycle of the internal combustion engine is controlled by a photosensitive flame sensor. The beginning of the combustion process (the optimum ignition time) in each subsequent cycle is adjusted according to the result of the end of the combustion process of the previous cycle, while the computing unit of the microcontroller determines the magnitude and sign of the correction depending on the difference between the actual moment of completion of the combustion process and the set one. The inventive method allows to implement the "ideal" theoretical curve of the law of variation of the ignition timing depending on engine speed.

Obtaining the technical result of the invention is possible only when applying the correction of the ignition start moment after comparing the actual moment of the end of the combustion process (variable value) and the given moment of the end of combustion (constant value) of the entire air-fuel mixture by adjusting the delay time of the ignition moment by the microcontroller’s computing unit while monitoring the combustion process by a light-sensitive sensor flame.

New significant features of the invention, differing from analogues and prototypes, are:

- correction of the beginning of the moment of ignition by the computing unit of the microcontroller of each subsequent cycle according to the results of comparing the set and actual moments of the end of the combustion process of the entire air-fuel mixture in the combustion chamber in the previous cycle by the computing unit of the microcontroller,

- the use of a photosensitive flame sensor to control the combustion process.

The introduction of new essential features allows you to automatically set the optimum value of the ignition moment in the engine cylinder, regardless of the variation in engine operating parameters (pressure, temperature, quantity and quality of the air-fuel mixture) and the mismatch of the type of gasoline, since the ignition moment is corrected in a specific cylinder, under specific conditions and during the combustion of a specific type of fuel (while existing methods involve the correction of the moment of ignition of a fuel-air mixture of one engine relative to the initial installation of the ignition moment of another reference engine), that is, "direct control of the combustion process" is carried out. The use of a photosensitive flame sensor eliminates the ambiguity in the correction of the ignition moment, since the duration of the light flux of all burning gases does not depend on the general pattern of the propagation of the flame front in the combustion chamber, but only indicates the presence of combustion or its absence. Correction of the start of the ignition moment at the moment of completion of the fuel assembly combustion prevents the occurrence of detonation in all engine operation modes by automatically reducing the ignition timing with the slightest reduction in the fuel assembly burning time from the set one.

The invention is illustrated by drawings, where

- figure 1 presents a diagram of a model of a microprocessor ignition system that implements a method for automatically determining and setting the optimum ignition timing of the air-fuel mixture in an internal combustion engine;

- figure 2 presents the timing diagram of the computing unit of the microcontroller system.

In accordance with the invention, the system comprises (see figure 1):

- sensor for starting the delay time of the ignition timing 1;

- sensor for a given piston position (corresponds to a predetermined end moment of fuel assembly burning) 2;

- photosensitive flame sensor 3;

- the computing unit of the microcontroller 4,

- standard ignition unit 5.

The system operates as follows (see figure 1 and figure 2).

In the compression stroke during the passage of the piston of a conditionally set reference point "a", the signal of the sensor 1 starts the following time counters in the computing unit of the microcontroller 4:

- a counter of the delay time of the ignition 11 from the reference to the moment of issuing the voltage pulse D to the ignition unit 5;

- time counter of a given moment of the end of the combustion process;

- time counter of the actual moment of the end of the combustion process.

After counting by the delay time counter 11, the computing unit of the microcontroller provides signal D to the standard ignition unit 5 and then through the distributor to the spark plugs. The air-fuel mixture ignites and the combustion process G begins in the engine's operating cycle.

The computing unit of the microcontroller 4 awaits the arrival of signals from the sensor of the preset piston position (corresponding to the specified end time of the combustion of the air-fuel mixture) 2 and from the sensor of the actual moment of completion of the combustion of the air-fuel mixture 3. After the signals B and B arrive, the corresponding time counters stop, comparing the set and actual moments the end of the combustion of the air-fuel mixture, determining the correction value for the delay time Δτ and the formation of a new delay time that plugs 11 'in the random access memory of the microcontroller unit for computing the corrected reference time retarding ignition timing in a subsequent operating cycle, and therefore, a new air-fuel mixture combustion time.

Thus, the operation of the device is reduced to continuous monitoring and change (correction) of the moment of the beginning of burning (time delay of the ignition moment in the random access memory of the computing unit of the microcontroller) through feedback at the time of its completion.

Claims (1)

A method for automatically determining and setting the optimum ignition time of the air-fuel mixture in an internal combustion engine, which consists in controlling the start of the moment of ignition of the air-fuel mixture according to the results of its combustion, the process of burning the air-fuel mixture by a light-sensitive flame sensor is controlled and, after each cycle, the actual and predetermined burning time are compared the entire air-fuel mixture, and then make the correction of the delay time of the ignition moment after cycle.

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