JPS6050973B2 - Method of controlling fuel-air-mixing ratio or exhaust gas return rate of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the fuel-to-air mixture ratio or the exhaust gas feedback rate of an internal combustion engine, which varies depending on changes in the operating parameters of the internal combustion engine.

Strict exhaust gas regulations and general fuel shortages have made it difficult for internal combustion engines to minimize harmful components of their exhaust gases and/or
Alternatively, methods are being sought to operate within an operating range that minimizes fuel consumption. In order to meet this type of requirement, it has first been proposed to operate the internal combustion engine with a fuel-air mixture as lean as possible, that is, to operate the internal combustion engine at the so-called lean running limit. In this operating range, the harmful components of the exhaust gas are considerably reduced, and a reduction in fuel consumption can also be expected. In this case, first, the variation in pressure inside the cylinder of the internal combustion engine is used as the value for identifying the lean running limit. However, if the above-mentioned problems are considered in more detail, it becomes clear that the pressure characteristics are determined by variations in the uncontrollable operating parameters of the internal combustion engine, such as air excess, charge, turbulence, etc.

If the pressure in the combustion chamber is measured via the instantaneous value of the angular velocity at the crankshaft, other fluctuations such as vibrating objects in the crank mechanism, irregularities in the road of the automobile, or any forces exerted on the engine body of the internal combustion engine can interfere with disturbances. is occurring. The above-mentioned fluctuations, which are superimposed on the normal pressure characteristics in the cylinders of the internal combustion engine and manifest themselves as fluctuations in the angular velocity of the crankshaft, can be avoided by means of a low-pass filter. However, the use of this type of filter is highly problematic. This is because the internal combustion engine must be operated over a wide rotational speed range. Therefore, it is difficult to manufacture a filter suitable for both low and high rotational speeds (frequencies). Starting from the above-mentioned problem, it is an object of the invention to propose a method for controlling an internal combustion engine in such a way that the above-mentioned difficulties or disadvantages do not occur.

According to the invention, the method for the above-mentioned problem is achieved by:
The electrical signals corresponding to the ionic current in successive working cycles are sampled and held to form an electrical signal corresponding to the relative change in the integral value of the ionic current over a respective predetermined time interval as an actual value; The actual value signal is compared with a set value depending on the operating parameters of the internal combustion engine, the deviation is detected and integrated, and the integrated deviation is introduced to the regulating element of the fuel supply system for changing the fuel-air-mixture ratio. The solution is to introduce a regulating element that changes the rate of return of the exhaust gas or the rate of return of the exhaust gas.

Furthermore, an apparatus for carrying out the above-mentioned method, which allows the above-mentioned control to be carried out simply and reliably, will be shown below.

The first objective in this case is that this control device operates reliably even in the case of rough driving of the vehicle and that it is designed so that, if necessary, it can cooperate with the measured value transmitter already installed in the vehicle. It is to be. Furthermore, this device
It must be able to be manufactured at low cost. Next, the method according to the present invention will be explained in detail using the drawings.

With this method, the internal combustion engine is to be operated at least partially in the operating range of the lean running limit. In this case, the so-called lean running limit is the operating range in which the combustion delay first appears. The delay in combustion is caused by the excess air ratio λ=
It only appears when the amount is 5 to 10% greater than 1, that is, when the mixture is clearly lean. In such a predetermined driving limit region, the fuel consumption is generally a fuel-air mixture having a stoichiometric mixture ratio (excess air ratio λ=1).
The fuel consumption is clearly lower than the fuel consumption in the operating range of the internal combustion engine supplied with . When two electrodes are installed in the combustion chamber of an internal combustion engine, an ionic current flows between the two electrodes during the combustion process when the flame reaches both electrodes. This ion current is used to identify the operating region in which the internal combustion engine is operating. In this case, the ion current depends on the excess air ratio λ of the fuel-air mixture supplied to the internal combustion engine. λ can be detected by the relative change in the integrated value of the ion current over one cycle of the piston of the internal combustion engine. This relative change increases with excess air ratio λ.
The graph in FIG. 1 shows the course of the ion current versus time t. In this figure, the first curve belongs to the first cylinder, the second curve belongs to the second cylinder, the third curve belongs to the third cylinder, and the fourth curve belongs to the fourth cylinder. If these ionic currents are integrated in each case over a predetermined time range, or, more suitable for the purpose, over one cycle of the piston of the internal combustion engine, it is possible to generate an electrical signal that varies with the excess air ratio λ. Can be done.
A circuit device shown in the block diagram of FIG. 5, which will be described later, is separately assigned to each of the first to fourth cylinders. FIG. 2 shows the empirically determined relative change rate of ion current τ/d with respect to excess air ratio λ.

In this case, R represents the ionic current in the cylinder, integrated over one cycle of the piston of the internal combustion engine, and T represents the difference between two successive values. From this figure, it can be seen empirically that as the excess air rate increases, the X ton/ton also increases. Corresponding electrical signals can then be used to control the operating characteristics of the internal combustion engine. For example, if λ is too large, either the fuel-air mixture supplied to the internal combustion engine must be adjusted in the direction of enrichment, that is, the air number λ becomes 1 again, or the exhaust gas returned Reduce quantity. The ion current can be detected by, for example, an ion current probe 10 shown in FIG. In this case, the ion current sensor 10 is arranged inside a cylinder head 11 of an internal combustion engine. The spark plug 12 is also installed here. In this case, the ion current sonde 10 is
When detecting the ionic current flowing between the two electrodes during the combustion process, there is no need for special components; the spark plug 12
can have the same configuration. A total of two plugs are therefore installed in the combustion chamber of the internal combustion engine. In this case, the plug 12 is used as a spark plug and the plug 10 is used as an ion current probe. The apparatus shown in FIG. 4 is particularly suitable for measuring ionic currents.

This is because, with this device, it is not necessary to provide additional holes in the cylinder head of the internal combustion engine for mounting the ion current probe. Figure 4 shows two ignition electrodes 16, 17.
A spark plug socket 15 is shown having a. Two further electrodes 18 and 19 are attached to the socket 15, and the ion current flows through the electrode pairs 16 and 17 and the electrode pair 18.
, 19. Both electrodes 16, 17 and 18, 19
The distance between them is only a few millimeters. FIG. 5 shows a block diagram of an embodiment of an apparatus for carrying out the method of the invention.

In the figure, 1 indicates a device for detecting the ionic current during successive working cycles of an internal combustion engine. This detection device 1 corresponds to the ion current probe 10 shown in FIG. 2 indicates a device for converting the detected ionic current into an electrical signal, for example a circuit stage configured as an amplifier.

Reference numeral 3 indicates a sampling and holding circuit which is a circuit stage for forming a signal representing a relative change in the ion current.

4 denotes a memory formed, for example, by a capacitor, which holds this relative change signal.

5 transmits the actual value signal representing the relative change of the ionic current to the operating parameters of the internal combustion engine, such as the rotational speed n, the intake manifold pressure P
A comparator is shown for comparison with a set value that depends on s.

This setpoint value is formed by a setpoint generator indicated at 8. 6 indicates an integrator that integrates the deviation between the set value and the actual value.

Reference numeral 7 designates an adjustment operation member that changes the mixture ratio of fuel-air mixture, such as a solenoid valve, or an adjustment operation member that controls the amount of exhaust gas returned. In this way, the mass ratio of the fuel-air mixture or the amount of exhaust gas returned is controlled depending on the value of the detected deviation. In order to detect relative changes in the ionic current as described above, a sampling and holding circuit, which is known per se, is provided.

This circuit makes it possible to store at least two measured values one after the other. Signals are respectively formed from both measured values to detect changes which can be compared with the set value in the manner described in FIG. Depending on the value of the detected difference, the mass ratio of the fuel-air mixture or the amount of exhaust gas returned is controlled. The sampling and hold circuit is described in, for example, known literature, Data Conversion Handbook, written by Donald B.J. Look, published by Hybrid ● System◆Corporation,
1st edition (DATACONVERSION5HANDBO
OK, byDOnaldB. Bruck, Hybrid
SystemsCOrpOraTlOn, FirstE
ditiOn) 4●1 to 4.7.

[Brief explanation of drawings]

Fig. 1 is a waveform diagram showing the time change of the ion current O current in various cylinders of an internal combustion engine, Fig. 2 is a graph showing the average relative change rate of the ion current with respect to the excess air ratio, and Fig. 3 is a graph showing the average relative change rate of the ion current in various cylinders of an internal combustion engine. A combustion chamber of an internal combustion engine in which an ion current sonde is arranged, FIG. 4 is a front view of a device that integrates a spark plug and an ion current sonde, and FIG. 5 is a block diagram of a circuit device implementing the method of the present invention. It is a diagram. DESCRIPTION OF SYMBOLS 1...Ion current sonde, 2...Circuit stage for converting ion current into an electric signal, 3...Sampling and hold circuit, 4...Storage device, 5...Comparator, 6...Integrator 7... Adjustment member, 8... Operating parameter transmitter, 10... Ion current sonde, 11... Cylinder head, 12... Spark plug, 15... Socket, 1
6, 17... Ignition electrode, 18, 19... Ion current detection electrode.

Claims (1)

[Claims] 1. Detection of ionic currents in successive working cycles of a combustion chamber of an internal combustion engine in a method for controlling the fuel-air-mixture ratio or the exhaust gas return rate of an internal combustion engine that varies depending on changes in operating parameters of the internal combustion engine. Then, sample and hold the electrical signals corresponding to each ion current,
An electrical signal corresponding to the relative change in the integral value of the ionic current over a particular time interval is formed as an actual value, and this actual value signal is compared with a set value that depends on the operating parameters of the internal combustion engine to determine the deviation. and directing the integrated deviation to a regulating member of the fuel supply device for changing the fuel-air mixture ratio or to a regulating member for changing the exhaust gas return rate. A method for controlling the fuel-air-mixing ratio or exhaust gas return rate of an internal combustion engine.