RU2473067C1 - Method of diagnosing internal combustion engine - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: proposed method consists in exciting electromagnetic oscillations of fixed-wavelength in combustion chamber to define amplitude of received signal. I diagnosing, electromagnetic wave wavelength is selected to be smaller than combustion chamber minimum size with piston in TDP.

EFFECT: higher accuracy.

3 dwg

Description

The present invention relates to tests and diagnostics of internal combustion engines (ICE). It is based on the control of processes in the combustion chamber of the internal combustion engine and allows you to adjust the parameters of the internal combustion engine.

Known methods for diagnosing internal combustion engines, in which the combustion chamber is considered as a volume resonator of variable volume (Viktorov V.A., Lunkin B.V., Sovlukov A.S. Radio wave measurements of process parameters. - M .: Energoatomizdat. 1989. S. 189-192). The disadvantages of these methods is the simultaneous excitation in the combustion chamber of a variable volume when the piston moves simultaneously several types of electromagnetic waves, which makes it difficult to obtain useful information.

,A technical solution is also known (SU 1281956, 01/07/1987), which, by technical nature, is closest to the proposed method and is adopted as a prototype. This prototype method consists in the excitation of electromagnetic waves of a given fixed wavelength using a microwave generator in a waveguide located in the area of the combustion chamber, and registration of the characteristics of the field of a standing electromagnetic wave in this waveguide when moving the piston. In this case, the wavelength (selected from the condition

,

where D is the inner diameter of the cylinder, N is the displacement of the piston from the bottom dead center (BDC) to the top dead center (TDC); h - the gap between the piston bottom and the cylinder head when the piston is at top dead center.

Such a choice of the wavelength A ensures the operation of the devices implementing this method on the left slope of the resonance curve — the dependence of the amplitude of the detected signal on the position of the piston in the cylinder, that is, on the section within which the amplitude does not yet reach the maximum value corresponding to the resonance. In this case, a unique continuous determination of the operating parameters of the internal combustion engine is possible.

However, this method has a significant drawback, consisting in the low accuracy of diagnosis. This is due to the fact that for the implementation of the method it is necessary to provide a given electromagnetic wavelength with high accuracy. Only in this case, the recorded amplitude corresponding to the operating point on the slope of the resonance curve corresponds to the true position of the piston in the cylinder. This, in turn, requires a very high degree of stability of the frequency of the microwave generator, which is difficult to achieve in practice.

The technical result of the present invention is to improve the accuracy of diagnosis.

The technical result in the proposed method for diagnosing an internal combustion engine is achieved by the fact that electromagnetic waves of a fixed wavelength are excited in the combustion chamber and the amplitude of the received signal is determined, while the electromagnetic wave length is chosen much smaller than the minimum size of the combustion chamber that occurs when the piston is at top dead center .

The proposed method is illustrated by drawings. Figure 1 shows a diagram of a device for implementing the proposed method. Figure 2 shows a graph of the amplitude of the received signal, and figure 3 is a time graph of the amplitude of the received signal in the vicinity of the TDC when the piston moves in the cylinder of the combustion chamber.

The device of figure 1 contains a microwave generator 1, a circulator 2, a waveguide 3, a spark plug 4, a combustion chamber 5, a piston 6, a detector 7, a recorder 8.

The essence of the proposed method is as follows.

When choosing the length of the electromagnetic wave λ is much smaller than the characteristic size D of the cavity (combustion chamber): λ << D (or λ ³ << V ₀ , where V ₀ is the volume of the cavity). In this case, the resonance phenomena on individual types of oscillations are weakly manifested, since the distance between adjacent resonant frequencies is less than the width of the resonance curves on the frequency axis determined by dielectric losses, while the integral Q-factor of the cavity is high. In this case, the cavity - the combustion chamber - can be considered as a non-resonant cavity. In this case, the mixing of the excited electromagnetic waves occurs both due to the choice of a small wavelength in comparison with the characteristic size of the cavity and the movement of the piston in the combustion chamber.

The reception of power after multiple scattering and re-reflections of electromagnetic waves in the cavity can be carried out using an antenna, in particular the open end of the waveguide or horn antenna connected to the cavity through an opening in its wall. In this case, the function of such a transceiver antenna is performed by a spark plug, existing or modified to ensure the passage of electromagnetic waves into the combustion chamber. In this case, processes related directly to the operation of the internal combustion engine are not violated.

The _received power P _rad depends on the density ρ = W / V _{0 of the} electromagnetic energy stored in the cavity upon excitation of oscillations from the electromagnetic energy source in it by means of an antenna. The value of this energy density can be expressed as

where Q is the quality factor of the cavity resonator; P _East - the power of the signal exciting electromagnetic waves in the cavity; ω = 2πс / λ is the circular frequency of the excited oscillations; c is the speed of light.

Here, the Q factor Q - the integral Q factor averaged over all types of excited oscillations can be characterized as the ratio of the electromagnetic energy stored in the cavity W to the energy dissipated during the oscillation period.

We obtain a relation connecting the received power P _rad with the volume volume V _{0 of the} cavity. The value of P _{rad is} characterized by the energy output from the cavity per unit time through the aperture with the effective surface S in the solid angle Ω of the radiation pattern of the receiving antenna

Here, it is taken into account that the quantity ΔW passing during the time Δt through the indicated aperture of electromagnetic energy is

In this formula, the coefficient is 4 (in the denominator of the right-hand side corresponds to the full solid angle (in radians).

In this case

which follows from the uniform distribution of the energy of the electromagnetic field inside the cavity, the unity of the average value of the directional coefficient D = 4πS / λ ^{2 of the} receiving antenna and the reception of the part Ω / 4π of the electromagnetic energy dissipated in the cavity.

Hence

In accordance with the definition of Q, taking into account (5), we can write the following expression for the cavity under consideration:

Here on the right side in the denominator the power of the source of electromagnetic energy is recorded, which is legitimate, since all this power is spent on compensating for losses in the resonator and on maintaining undamped oscillations in it. The same post P _ist correct and the right side of formula (1).

Thus, by measuring the received power P _rad or the ratio P _rad / P _arg , it is possible to determine the variable volume V _{0 of the} cavity (combustion chamber) and, therefore, the position of TDC and BDC of the piston in the combustion chamber: V ₀ = sl, where s is the transverse area section of the combustion chamber, l is its length, determined by the position of the piston, as well as the quality factor Q and the functionally attenuation of electromagnetic oscillations depending on the physical properties of the substance (plasma) during the combustion process, to control the operation of the internal combustion engine as a whole at various stages of its operation.

Electromagnetic vibrations from a microwave generator 1 of a fixed wavelength, at which the condition λ << D (or λ ³ << V ₀ ), are passed through the circulator 2 and waveguide 3 to the antenna, the function of which is performed by the spark plug 4, into the cavity of the combustion chamber 5, which is a cavity of variable volume due to movement of the piston 6 in it (Fig. 1). A useful signal carrying information about the position of the piston 6 is received with the help of a spark plug 4. The received vibrations are transmitted through the waveguide 3 and circulator 2 to the detector 7, to the output of which a recorder 8 is connected. Its output signal is a unique function of the position of the piston in the combustion chamber, in particular top dead center and bottom dead center.

Taking into account the actual dimensions of the combustion chambers, the wavelength of electromagnetic waves excited in the combustion chamber is advisable to choose in the millimeter wavelength range, for example, λ = 1 mm, 2 mm, 4 mm or 8 mm.

It follows from (5), measuring the volume V ₀ capacitance variable configuration - a combustion chamber with a movable piston therein - received power P _rad, and therefore, the amplitude A of the received detected signal is inversely proportional to the measured volume V ₀ and hence variable the length l of the combustion chamber, determined by the position of the piston. Figure 2 shows a (qualitatively) graph of the dependence A (l), and figure 3 is a graph of the dependence of the amplitude A on time t in the vicinity of TDC with a forward, towards TDC (left slope of the curve) and reverse, from TDC, (right slope of the curve) piston movement in the cylinder of the combustion chamber. Here, the peak of the curve corresponds to the position of the piston in TDC and has this form due to a change in the direction of the piston in TDC.

In the device diagram of figure 1 there is no moving element for mixing the types of vibrations. In this case, it is not necessary, since, firstly, the position of the movable wall (piston) of the cavity is strictly defined, and secondly, mixing of the types of vibrations takes place when the piston moves.

Such a scheme can be, in particular, applied to ICEs with a pre-chamber ignition torch, where there is a narrow communication channel between the combustion chamber and the pre-chamber. It is fundamentally impossible to introduce electromagnetic energy from a generator at a frequency below the critical frequency of excitation of propagating electromagnetic waves in the combustion chamber; This corresponds to the well-known technical solution (SU 1666935, 07/30/1991). Such ICEs are installed, for example, on the GA3-3102 car, in many types of foreign cars. According to the proposed method, the working wavelength 2 can be selected here in the millimeter range, which ensures the fulfillment of the condition λ ³ << V _min , where V _min is the volume of the combustion chamber when the piston is in TDC. For example, for a VA3-2101 automobile, the combustion engine of an internal combustion engine has the following parameters: volume of the combustion chamber V = 1197 cm ³ ; diameter D = 76 mm; the position of the piston bottom in TDC h = 8.2 mm; piston stroke 66 mm. It follows that V _min = 148.7 cm ³ . Therefore, choosing a wavelength of 2 = 1 mm, 2 mm, 4 mm or 8 mm, it is possible to ensure that the required condition λ ³ << V _min . So, with λ = 8 mm we will have: λ ³ = 0.512 cm ³ , which is significantly less than the value of V _min = 148.7 cm ³ .

The amplitude of the recorded signal can be used to judge the position of the piston in the combustion chamber, including the coordinates of the upper and lower dead points, the physical properties of the substance in the combustion chamber at various stages of the internal combustion engine.

Thus, this method allows you to accurately diagnose internal combustion engines by measuring the amplitude of the recorded signal when choosing an electromagnetic wavelength that is much smaller than the minimum size of the combustion chamber that occurs when the piston is at top dead center.

Claims (1)

A method for diagnosing an internal combustion engine, in which electromagnetic waves of a fixed wavelength are excited in the combustion chamber and the amplitude of the received signal is determined, characterized in that the electromagnetic wave length is chosen smaller than the minimum size of the combustion chamber that occurs when the piston is at top dead center.

Images