RU2087886C1 - Method testing detonation in internal combustion engines - Google Patents

Abstract

FIELD: adjustment of internal combustion engines with forced ignition under stationary conditions and in process of repair and operation. SUBSTANCE: method testing detonation in internal combustion engines with forced ignition consists in measurement of ionization current in measurement circuit with burning of fuel-and-air mixture which includes power supply source and is connected to sparking plug. Measurement is conducted under conditions of protection of measurement electric circuit against action of high voltage of sparking plug. With this in mind combination of high-voltage resistor with threshold element is inserted into this circuit. EFFECT: improved efficiency of method. 3 cl, 1 dwg

Description

 The invention relates to the field of knock control in internal combustion engines (ICE) with spark ignition and can be used to adjust the engine in stationary conditions and during repair and maintenance.

 When the internal combustion engine operates in high-voltage conditions under certain conditions, detonation occurs [1, 2], which sharply reduces power and threatens further burnout of the piston and engine destruction; on the other hand, the operation mode near the detonation threshold is most effective in terms of power and economy, therefore, searching for methods and devices , solving the problem of controlling the appearance and determining the detonation intensity, begun back in the 30s, continues to this day.

Known methods for controlling detonation in internal combustion engines can be divided into several groups: mechanical (Midgeley needle); piezoelectric [3] electroacoustic [4, 5] ionization [6, 7]
Most of the known methods of knock control use special sensors located on the cylinder heads of the internal combustion engine, or introduced into them, which requires separate special holes.

 Other disadvantages of the known methods include the following: mechanical methods are archaic due to their low sensitivity. Electro-acoustic methods are characterized by interference from valve seating and from detonation in other cylinders of a multi-cylinder engine. The same interference occurs in piezoelectric methods.

A known method of controlling detonation by measuring the ionization current occurring in the sensor circuit with the arrival of the flame to the ionization sensor introduced into the combustion chamber (CS) of each cylinder. The ionization sensor is connected to a power source and to a measuring circuit that controls the occurrence of detonation [7]
The known method [7] provides a sufficiently high measurement sensitivity, however, this option of ionization control of detonation also requires drilling an additional hole for the sensor in each combustion chamber.

Closest to the proposed method is a method for controlling detonation in internal combustion engines with positive ignition by measuring the ionization current flowing through the spark plug connected through a high voltage resistance to an additional power source and in series with the measuring resistance, while a bulky battery is used as an additional power source voltage of 500 V, and as a measuring resistance low resistance [8]
The known method [8] avoids the need for drilling a special additional hole for the sensor and provides sufficient measurement sensitivity, but it is necessary to use a bulky high-voltage battery and low resistance measuring resistance, which nevertheless does not allow to achieve an optimal ratio of useful signal / interference from a spark.

 The objective of the invention is to provide a method for controlling detonation in an internal combustion engine, which would combine high measurement sensitivity with no need to use a bulky high-voltage battery as an ionization current power source and would significantly improve the useful signal / noise ratio from an ignition spark.

 The solution to this problem is achieved by the proposed method of detonation control in internal combustion engines with positive ignition by measuring the ionization current flowing through the spark plug connected through a high voltage resistance to an additional power source and in series with a measuring resistance, in which an additional power source and measuring resistance are shunted Zener diode, the stabilization voltage of which exceeds the electromotive force power source, and high-resistance resistance is used as a measuring resistance.

 An additional power source and measuring resistance can be bypassed with a neon lamp or dinistor, or thyristor.

The use of the spark plug in the proposed method simultaneously as a probe and as an ignition source requires the fulfillment of two conflicting conditions: protection of the supply battery (B) (see diagram in the drawing), output measuring resistance (R _and ), as well as subsequent circuits processing the resulting the signal from the spark breakdown, on the one hand, and the supply to the spark plug, since it is also a battery voltage sensor B of the order of 10 V on the other.

При протекании ионизационного тока добавляется сопротивление ионизационного промежутка в свече (R_i), тогда величина сигнала ионизации (u) будет равно

а отношение полезный сигнал/помеха

равно:

т. е. для удаления этого отношения в известном способе имеется только одна возможность увеличение напряжения дополнительного источника питания E. При E 500 В [8] отношение u/u¹ в известном способе равно 0,0125.In the known method [8], it is possible to obtain an allowable amount of interference from a spark (u ¹ ) at the measuring resistance R _u only by fulfilling the condition R _u <R _b . With U _{sparks of} 20,000 V and u ¹ 10 V we get:

When the ionization current flows, the resistance of the ionization gap in the candle (R _i ) is added, then the value of the ionization signal (u) will be equal to

and the ratio of the useful signal / interference

equally:

that is, to remove this ratio in the known method there is only one possibility of increasing the voltage of the additional power source E. At E 500 V [8], the ratio u / u ¹ in the known method is 0.0125.

 In the proposed method, the task is solved in another way.

 It is known from the literature that diodes are used to limit pulses, for example [9], but it is difficult to fulfill both of the above requirements using high-voltage poles or diodes or low-inertia switches, and in the latter case it is unsafe for the equipment. At low values of the applied voltage, both the high voltage poles and vacuum diodes have extremely high resistance and will not pass the necessary voltage to the sensor.

 In the proposed method, the problem is solved by replacing the diode with a high voltage resistance and a stabilizer (or a neon lamp). You can use other threshold limiters, such as dinistor or thyristor.

Such a replacement allows not only to limit the interference of the spark, but also to apply the voltage of the battery B to the candle to ensure the ionization current and the isolation of its signal at the measuring resistance during detonation. The purpose of the zener diode (or other threshold elements) is to work with the unlocked diode at the moment of spark supply and be locked by the diode (i.e. high resistance) after it ends so as not to shunt the probe plug when the voltage B from the battery B is applied to it (about 10 V ) The stabilization voltage of the Zener diode U _st should exceed the electromotive force of the battery B. Moreover, u ¹ = U _st .

т. е. по сравнению с известным способом [8] получим увеличение этого отношения в 4 раза при использовании несравнимо меньшего по напряжению и габаритам дополнительного источника питания Б.When the stabilization voltage of the zener diode is 10 V and the voltage of the supply battery B 9 V, the ratio of the useful signal / noise from the spark will be

that is, compared with the known method [8], we obtain an increase in this ratio by 4 times when using an incomparably smaller additional voltage source B. in terms of voltage and dimensions.

 The drawing shows three parts (I, II, III) of the general scheme used in the proposed method. Parts I and II make it possible to obtain an ionization signal characterizing the state of combustion products in the engine CS normal or detonation from the spark plug.

 Notation previously mentioned: Pr interrupter, P spark distributor for cylinders, short circuit ignition coil, 1, 2, 3, 4 spark plugs in the four-cylinder engine CS, P switch connecting part II of the circuit to one of the engine CS, T toggle switch that turns on the plug power probe from battery B.

 The proposed method is as follows.

 Part II of the circuit is connected by a switch P to the CS of the investigated cylinder of the working engine. Toggle switch T.

According to the process conditions in the internal combustion engine, through the spark plug up to 50 times per second (at a speed of up to 6000 1 / min) a spark discharge with a maximum voltage of 30–40 kV passes for a duration of 0.5–2.5 ms [10] after which a few milliseconds there is a burning center with the ionization of combustion products. When ignition by introducing into electrical measuring circuit part II high resistance R _in (of the order of hundreds of kilo-ohms), only a small (less than 1%) proportion of the energy spark branches in the measuring circuit and almost all closed through the zener diode, with the result that only a small part of this fraction (much less than a millionth of the spark energy) passes through the battery B and the measuring resistance R _and into the recording part of the circuit (III) in the form of interference, easily eliminated by it. This fulfills the requirement of protecting the measuring circuit from spark discharge. The second requirement is the supply of the candle probe, the fact that the candle through R _{in is} connected to the battery B. The ionization current arising during the combustion of the fuel mixture of the order of microamperes flows from the plus of the battery B through R _c , the ionized gas in the gap of the candle R _i , the resistor R _and to the minus of the battery. The voltage drop across R _and from the ionization current gives a useful signal containing, in the case of detonation, detonation vibrations, which are used later to control detonation.

Literature
1. B. Lewis, G. Elbe. Burning, flame and gas explosions. M. Mir, 1968, p. 544.

 2. A. S. Sokolik. Self-ignition, flame and detonation in gases. M. Academy of Sciences of the USSR, 1960, p. 244, 234, 389.

 3. A.P. Usachev. Piezo-quartz knock indicator. TVF, 1946, N 2, p. 15.

 4. A.S. Sokolik, A.I. Sokolik, B.K. Shapiro, M.I. Rodman. TVF, 1947, N 5.

 5. M.I. Rodman, E.S. Semenov. Device for detecting detonation in ICE. Auth. St. N 79149, cl. G 01 L 23/08, 1947.

 6. Tauss, Gerlacher and Drexel. Sat ICE, t. III. Under. ed. S.N. Vasilieva, 1987, p. 153.

 7. L.A. Gussak, E.S. Semenov, N.G. Artemov, V.P. Zudin. Clarification of the possibility of using ionization equipment to determine the initial moment, place of occurrence, intensity and frequency of detonation in ICE. Report on the topic N 70001112, I.KhF AN SSSR, 1974.

 8. Application of Germany N 2507286, cl. F 02 P 11/06, 1978.

 9. V.V. Gusev. Impulse formation. M. Military Publishing House, 1958, p. 27.

 10. A. Kh. Sinelnikov. Electronics in the car. M. Radio and communications, p. 7, 21, 39.

Claims (3)

 1. The method of controlling knock in internal combustion engines with positive ignition by measuring the ionization current flowing during the combustion of the air-fuel mixture in a circuit consisting of an additional power source, high voltage resistance, the gap of the spark plug and measuring resistance, characterized in that the measurement of ionization current carried out under conditions of protection of the measuring electric circuit from the action of high voltage using a threshold element through which part of the energy is closed and sparks.  2. The method according to claim 1, characterized in that a zener diode or a neon lamp are used as a threshold element.  3. The method according to claim 1, characterized in that a dynistor or thyristor is used as a threshold element.