RU2729582C1 - Diagnostic method of fuel-feed system and low pressure loop of injector ice - Google Patents

Abstract

FIELD: engine building.SUBSTANCE: invention relates to diagnostics of fuel systems of internal combustion engines (ICE). Disclosed is a method of diagnosing fuel injection system (FFS) of injector ICE, including measurement of such current values of diagnostic parameters, as current pressure and fuel efficiency in FFS systems of discrete and continuous fuel injection into inlet channel, as well as current pressure and fuel output in low-pressure loop (LPL) of direct fuel injection system and supply of low-pressure electric fuel pumps included in FFS and LPL, determination of calculated values of said parameters in function of ICE rated power, fuel temperature and air temperature at inlet, comparing calculated values with measured current values and determining technical diagnosis of FFS and LPL.EFFECT: invention enables to diagnose all types of fuel feed systems (FFS) and low-pressure loops (LPL) of injector ICE in the absence of standard and reference values of diagnostic parameters and provides simple and fast determination of reliable technical diagnosis of FFS and LPL.1 cl, 4 dwg

Description

The technical field to which the invention relates

The proposed method relates to the field of control and technical diagnostics of fuel supply equipment for automobile internal combustion engines (ICE) equipped with gasoline injection systems, which, according to the heading of the International Patent Classification MPK-2019.01, belongs to the class F02M 65/00 - testing of equipment for liquid fuel supply systems for engines, working from fuel combustion in general.

The object of diagnostics (OD) is the fuel supply system (STP) of the fuel injection system (SVT) into the intake tract (BT) or the low pressure circuit (LPC) of the direct injection system (STP) of fuel into the internal combustion engine cylinders. The main component of the OD is an electric low pressure fuel pump (LPP), which creates a pressure (an increment of mechanical energy of the fuel mass between the inlet and outlet of the LPP), sufficient to provide the required pressure and performance of the STP in the fuel rail (TP), and LPC - in the high pressure (injection pump). The low pressure fuel pump, as a rule, is built into the fuel tank, less often into the fuel line (TM), consisting of a suction line (BM; before entering the pump), pressure head (NM; between the pump outlet and the fuel pressure regulator (RD)) and supply (PM); between taxiway and TR / injection pump) highways.

Hydrocarbons contained in gasoline are a source of chemical energy that is converted in the cylinders of the internal combustion engine into thermal energy, and then, through the cylinder-piston group and the crank mechanism, into mechanical energy, which determines the torque on the crankshaft (KB), which in turn depends on the pressure, taking into account the compensation of the inevitable losses in the fuel injection pump itself, lines, filters and other components of the STP / LPC, therefore, the technical condition of the STP / LPC is one of the factors that decisively affects the characteristics of the internal combustion engine. During operation, the STP / LPC components are continuously exposed to intense wear, a decrease in pressure, flow and productivity, an increase in energy losses from leaks, impurities, contaminants, steam and gas generation and cavitation, which negatively affects fuel metering, toxicity of exhaust gases (OG), the functioning of high pressure fuel pumps, nozzles, etc. ICE as a whole, therefore, improving the means and methods for diagnosing STF and LPC is a very urgent need.

State of the art

The technical result of the diagnosis is to quickly determine a reliable technical diagnosis of OD without dismantling and disassembling it, with TM disconnection. Diagnostics includes: determination of current values of diagnostic parameters and signs by connecting measuring instruments to standard connectors and taps, TM disconnection points; recognition of the type of technical condition of the OD and its components; definition and localization of the defect; diagnosis. Recognition consists in comparing the current values of parameters and features with standard values, on the basis of which a conclusion is made about the most plausible their compliance, and referring the technical state of the OD and its components to the established type (serviceable or not, serviceable or not, functioning or not).

The diagnostic parameters of the STP / LPC are pressure, fuel performance, fuel pump feed; diagnostic sign - steam-gas bubbles and plugs in the fuel flow (BOSCH. Gasoline engine control systems. Translated from German - 1st Russian edition. - M .: LLC "Book publishing house" Za rulem ", 2005, p. 132 , 133, 138). The normative values of the parameters are contained in the normative and technical documentation on the STP / KND. In their absence, the reference values of the parameters of a workable standard, a sample similar to the OD, are used, and if they are absent, then the calculated values, which are determined by means of physical and mathematical calculations.

As a rule, the standard values of fuel pressure are always known, and the OD has special hydraulic outlets and connectors for connecting a pressure gauge, which ensures the determination of the current pressure value. However, a reliable diagnosis of OD, like any source of energy, is possible in at least two parameters: for the assessment of STF and LPC, the second necessary parameter is productivity, and for the assessment of LPP - the supply, the normative and reference values of which are most often unknown, due to which resort to determining their calculated values using analogues of the invention. Since both productivity and feed depend primarily on the required cyclic feed, effective power and engine displacement, such analogs are the well-known physical and mathematical relationships set forth in numerous sources devoted to the theory, technical device and design of internal combustion engines and fuel equipment, where mathematically justified the required amount of fuel (Automotive engines. Ed. by M. Khovaha. M., "Mechanical Engineering", 1977, pp. 150, 151; BOSCH. Gasoline engine control systems. Transl. from German. - 1st Russian edition - M .: LLC "Book publishing house" Behind the wheel ", 2005, pp. 132 ÷ 435, 138, 139; Khrulev A.E. Repair of engines of foreign cars. Production and practical edition. - M .: Publishing house - in "Behind the wheel", 1998, p. 126; BOSCH. Automobile directory: Translated from English - 2nd ed., revised and additional - M .: ZAO "KZH" Za rulem ", 2004, p. 424; BOSCH. Diesel engine control systems. Translated from German C40. 1st Russian edition - M .: KZHI "Za rulem" LLC, 2004, p. 60 and many others etc.). The prototype of the invention for calculating the supply of low-pressure fuel pump Q is the expression (Erokhov V.I. Injection systems of gasoline engines (design, calculation, diagnostics). Textbook for universities. - M: Hotline - Telecom, 2011, p. 132), volume / time:

where k _zap is the fuel supply safety factor;

z is the number of engine cylinders;

Q _max - maximum cyclic feed for the cylinder;

τ _max is the duration of the control pulse at the maximum cycle feed;

T _min is the minimum period of the following cycle feeds;

n _max is the maximum rotational speed of the CV;

Q _рд - minimum fuel consumption through taxiway.

However, in practice, the calculated flow calculated according to (1) does not correspond to the normative one, since the actual duration of the injection differs from the duration of the control pulse τ _max due to the inertia of the moving parts of the injectors, which can be neglected only in individual injection systems equipped with fast-acting injectors. The prototype is not suitable for diagnostics of continuous injection systems, in which the control impulse and injection cyclicity are absent in principle. The internal combustion engine develops the nominal effective power N _nom , as a rule, not at the maximum n _max , but at the nominal speed n _nom (BOSCH. Gasoline engine control systems. Translated from German - 1st Russian ed. - M .: OOO " Za Rulem book publishing house, 2005, p. 23, fig. 1). The mass of the fuel in the temperature range of -20 ÷ + 80 ° C changes by more than 25%, but the prototype does not take into account the influence of the fuel temperature and air temperature at the inlet. Also, the return of fuel through the control valve (KP) in the high pressure circuit (HPC) of the SNV is not taken into account, which does not allow calculating the performance of the _LPC Q _knd . Considerable difficulties are caused by calculating the maximum cyclic feed Q _max with acceptable accuracy. The calculation of the effective cycle feed Q _e for the internal combustion engine is possible through the effective engine power (BOSCH. Automobile reference book: Translated from English - 2nd ed., Revised and added. - M .: ZAO "KZH" Za rulem ", 2004, p. 424; BOSCH. Diesel engine control systems. Translated from German C40. 1st Russian edition - M .: LLC "KZH" Za rulem ", 2004, p. 60), mm ³ / cycle:

where N _e - effective engine power, kW;

b _e - specific effective fuel consumption, g / kWh;

n - frequency of rotation KB, min ^-1 ;

ρ _b - density of gasoline, mg / mm ³ .

It is possible to increase the accuracy of calculations by rechecking the result found by means of (2) through the engine displacement; for a 4-stroke internal combustion engine (IV Alekseev et al. Textbook on course design of internal combustion engines, Part 1. Technique for performing thermal calculation. M .: 2004, Rotaprint MADI (GTU), according to (9.1), p. 40) by means of an analogue:

where p _e is the average effective pressure in the cylinder, MPa;

V _H - engine displacement, l.

A significant drawback of (2) and (3), which prevents the achievement of the technical result of diagnosis, is the unknown normative and reference values of p _e and b _{e of a} particular diagnosed engine, as a result of which they resort to the reference air mass in the air-fuel mixture (FA), and since it is more often everything is not known, then to the determination of its calculated value (M_STEP. MPI - multipoint injection system, p. 2-13) at the nominal power mode N _nom (n _nom ); for a 4-stroke engine:

where m _in - air mass;

μ is the cylinder filling factor;

p _W - pressure in the inlet tract;

R is the gas constant;

t _in - intake air temperature.

Excess air coefficient λ (Khrulev A.E. Repair of engines of foreign cars. Industrial and practical ed. - M .: Publishing house "Behind the wheel", 1998, p. 7):

where L ₀ = 14.7 - stoichiometric ratio of air mass to fuel mass;

m _t - fuel mass.

From (3) and (4) follows the volumetric fuel consumption of the engine Q _p at the nominal power mode, volume / time:

where k _v = 1 + ε ^-1 is the utilization factor of the engine displacement;

ε is the compression ratio;

ρ _in - inlet air density;

η _b = Q _e / (Q _e + Q _p ) is the utilization rate of the volume of gasoline;

Q _p is the cycle consumption of gasoline for blowing the cylinders and losses due to droplet formation.

Considering that in fuel assemblies at rated power mode, the excess air factor λ = 0.85 (BOSCH. Gasoline engine control systems. Transl. From German. - 1st Russian edition. - M .: LLC "Book publishing house" Behind the wheel ", 2005, p. 40, fig. 1):

In (7), as a rule, standard values of V _H , n _nom and ε are known from the technical databases (BTC) of cars. In full throttle mode, you can take p _W = 1.

The value of ρ _in at sea level at air temperature t _in , ° С, kg / m ³ :

where ρ _0v - standard air density, kg / m ³ ;

П _в - temperature correction of air density.

The value of ρ _{b is} determined by measuring with a hydrometer or calculated depending on its temperature, kg / m ³ :

where ρ _0b is the standard density of gasoline (European standard EN 228; GOST R 51866-2002. Motor fuels. Unleaded gasoline. Table 1, p. 13), kg / m ³ ;

P _b - temperature correction of the density of gasoline (Grigorieva N.A. et al. Determination of the density of petroleum products. M .: ITs Russian State University of Oil and Gas (NRU) named after I.M. Gubkin, 2016, p. 3, 4);

t _b - gasoline temperature, ° С.

At the same time, a significant drawback (7) is the unknown normative and reference values of μ and η _{b of a} particular diagnosed engine, which significantly complicates, and most often prevents, the achievement of the technical result of diagnostics.

Thus, the listed disadvantages prevent the achievement of the technical result of STF and LPC diagnostics, due to which the prototype (1), in conjunction with a known nominal, reference or calculated value of fuel pressure, in practice, ensures the determination of the calculated value of the low pressure fuel pump feed and the performance of only the STP of the discrete fuel injection system, equipped with high-speed nozzles, and in the presence of exact values of p _e and b _e or μ and η _b .

The invention eliminates the disadvantages of the prototype and takes into account the needs of practical diagnostics of STP / LPC. The proposed method for determining the calculated values of the diagnostic parameters of the low-pressure fuel pump, the STP and the LPC allows achieving the technical diagnostic result. The method is not known from the prior art, for a specialist does not follow from the prior art explicitly, and can be applied in the automotive service industry, due to which it is a new, industrially applicable invention having an inventive step.

According to the invention, a method is proposed for diagnostics of the fuel supply system (STF) of injection internal combustion engines (ICE), which includes the measurement of such current values of diagnostic parameters as the current pressure and fuel performance in the STP of discrete and continuous fuel injection systems into the intake tract, as well as the current fuel pressure and performance in the low pressure circuit (LPC) of the direct fuel injection system and supply of electric low pressure fuel pumps included in the STP and LPC, determination of the calculated values of the specified parameters as a function of the rated power of the internal combustion engine, fuel temperature and intake air temperature, comparison of the calculated values with measured current values and determination of the technical diagnosis of STP and LPC.

Disclosure of invention

The essence of the invention lies in the implementation of a diagnostic model (GOST 20911-89. Technical diagnostics. Terms and definitions, table. 1, p. 20), reflecting the regulatory requirements for the STP and LPC for the continuous provision of an operating internal combustion engine with such a fuel flow, current values of pressure, feed and whose performance is within the tolerances of the standard values:

where t is the current time;

q (t) - current feed of low pressure fuel pump;

Q - normative feed of low-pressure fuel pump;

q _od (t) - current productivity of OD;

Q _od - standard performance of OD;

p (t) - current pressure;

Р - standard pressure;

ΔР - standard pressure tolerance;

p _tr (t) is the current pressure in the fuel rail of the recirculation STP;

U _W - standard vacuum in the intake tract;

p _max ^_ current maximum pressure;

P _max ^_ standard maximum pressure.

In the general case, the fuel flow OD includes the flow rate and two return flows (to the fuel tank through the taxiway in the STP / LPC and through the KR in the HPC).

Accordingly, the current supply q (t) includes the current effective flow rate q _p (t) (consists of the indicator flow rate q _and (t) and losses q _p (t) for condensation, blowdown, etc.), the current return q _p ( t) OD and current HPC return q _cr (t), volume / time:

where the current performance of the OD:

The ratio of the normative, reference and calculated feed Q, productivity Q _od , flow Q _p and returns Q _rd and Q _{cr of} STP and LPC is similar, but taking into account the requirement to create a fuel stock in k _zap times, volume / time.

where OD performance:

where β is the proportionality coefficient between the flow rate and the return through the KP.

The value of N _{nom is} indicated in all BTC and the technical passport of the car.

Based on the analysis of the above information sources, the characteristics of the internal combustion engine, given in the BTC (Autodata 3.38, "Autodata Limited", 2012, etc.) and manuals for repair and maintenance (Volkswagen Passat / Variant 1988-1996. Manual for repair, operation and maintenance service. P .: Mashservis, 2002, pp. 80-81 and many others), taxiway operating points, flow continuity, gasoline stock in the high-pressure fuel pump, the practice of constructing the STP and LPC and statistical data accumulated in the process of practical diagnostics, it was established what:

Where

a , c, d, x, y are constant coefficients.

From (2) and (16) it follows for a 4-stroke engine, l / min:

Taking into account the redistribution of fuel flows in full throttle mode in the direction of increasing consumption and decreasing return, Q _rd = 0.36 l / min can be accepted by default; k _zap = 1.1; β = 0.1; a = -0.374; c = 94.95; d = 286580; x = 0.335; y = -0.665. In supercharged engines b _{e is} higher (IV Alekseev et al. Textbook on course design of internal combustion engines, Part 1. Methodology for performing thermal calculation. M .: 2004, Rotaprint MADI (GTU), p. 54) for by increasing the rated power of the internal combustion engine by 10 ÷ 40% in comparison with a similar internal combustion engine without pressurization.

Upper P ⁺ and lower P ^{are the} boundaries of the design pressure range of any STP are determined according to (10) by the technical characteristics or the operating pressure of the taxiway:

и нижняя

границы диапазона расчетного давления между входом и выходом форсунок распределенной СВТ, оснащенной тупиковой СТП, определяется техническими характеристиками, (19) и разрежением воздуха U_вт во впускном тракте; по умолчанию на режиме холостого хода U_вт= 65 кПа, полной нагрузки U_вт=0 кПа:Upper

and lower

the boundaries of the design pressure range between the inlet and outlet of the nozzles of a distributed SVT equipped with a dead-end STP, is determined by the technical characteristics, (19) and the air rarefaction U _W in the intake tract; by default at idle mode U _w = 65 kPa, full load U _w = 0 kPa:

и нижняя

границы диапазона расчетного давления между входом и выходом форсунок распределенной СВТ, оснащенной рециркуляционной СТП:Upper

and lower

the limits of the design pressure range between the inlet and outlet of the nozzles of the distributed CBT equipped with a recirculation STP:

и нижняя

границы диапазона расчетного давления в топливной рампе рециркуляционной СТП системы распределенного впрыска:Upper

and lower

limits of the range of the design pressure in the fuel rail of the recirculation STP of the distributed injection system:

и нижняя

границы диапазона расчетного давления в топливной рампе тупиковой СТП системы распределенного впрыска:Upper

and lower

limits of the range of the design pressure in the fuel rail of the dead-end STP of the distributed injection system:

In LPC, the upper P ⁺ and lower P ^{are the} boundaries of the design pressure range are determined according to (10) by the technical characteristics or the working pressure of the taxiway:

The calculated maximum pressure of the low pressure fuel pump P _max exceeds the working pressure P _rd :

Thus, in contrast to the prototype, by means of the invention, not only the values of the low-pressure fuel pump feed and the output of the STP of the discrete fuel injection system equipped with fast-acting nozzles are calculated, but also the calculated values of the performance of the STP of the continuous injection system, the LPC of the direct injection system equipped with any them LPND as a function of the rated power of the internal combustion engine, the temperature of the fuel and air at the inlet, which provides the technical result of diagnosing the STP and LPC of all types.

Brief Description of Drawings

FIG. 1. Algorithm No. 1 for calculating the values of the parameters of the LPC.

FIG. 2. Algorithm # 2 for calculating the values of the parameters of the recirculation STP of the central injection system.

FIG. 3. Algorithm No. 3 for calculating the values of the parameters of the recirculation STP of the distributed injection system.

FIG. 4. Algorithm No. 4 for calculating the values of the parameters of the dead-end STP of the distributed injection system.

Implementation of the invention

The diagnostic model is implemented by applying formulas (8), (9), (13) ÷ (24), according to algorithms No. 1 ÷ 4 (Fig. 1 ÷ 4), determining the calculated values of the parameters of the LPC, recirculation and dead-end STP distributed and central SVT in naturally aspirated and supercharged internal combustion engines.

The achieved technical result is confirmed by experimental data obtained during repeated practical diagnostics of STP and LPC.

Example 1. Diagnosis of LPC of a Mitsubishi Pajero 3.5 GDI 2004, engine code 6G74, naturally aspirated. Rated engine power 149 kW. Fuel pressure 3.29 bar. Direct injection system. Fuel return via pressure regulator 0.4 l / min. Fuel temperature + 40 ° С. Inlet air temperature + 30 ° С.

The calculated values of the LPC parameters are determined according to algorithm No. 1 (Fig. 1):

Due to the inaccessibility of the pressure main for measuring the flow, this LPC is unsuitable (GOST 20911-89. Technical diagnostics. Terms and definitions, table. 1, p. 14), and therefore measure the current values p (t) = 3.4 bar and q _cnd (t) = 1.48 l / min and compare them with the corresponding calculated values of P ⁺ , P ^- and Q _cnd : P ⁺ ≤p (t) ≤P ^- , which satisfies the requirement (7), but q _cnd (t) <Q _cnd , which indicates the inoperability of the LPC. Diagnosis: clogged fuel filters / lines or increased wear of the low pressure fuel pump. When dismantling the fine filter, it was found that it is operational; it is necessary to dismantle the fuel pump module from the fuel tank. After dismantling the low-pressure fuel pump, it was found that the high-pressure fuel pump does not provide the required flow due to clogging of the coarse filter, which needs to be replaced.

Example 2. Diagnostics of the recirculation STP of a Volkswagen Golf sedan 1.4 l 1993, engine code ABD, naturally aspirated. Rated engine power 44 kW. Central injection system. Fuel pressure 0.8 ÷ 4.2 bar. Fuel return via pressure regulator 0.42 l / min. Fuel temperature + 35 ° С. Inlet air temperature + 30 ° С.

The calculated values of the STP parameters are determined according to algorithm No. 2 (Fig. 2):

This STP is controllable (there is access to the pressure line), therefore, the current values p (t) = 0.95 bar, p _max = 3.9 bar and q (t) = 1.06 l / min are measured and compared with the corresponding calculated the values of P _in , P _in , P _max and Q.

Р ⁺ ≤p (t) ≤Р ^- , which satisfies the requirement (7), but q (t) <Q, which indicates a defect in the low pressure fuel pump or clogged fuel filters and / or lines. But since p _max > P _{max, the} TNND is efficient. Diagnosis: STP is inoperative, replacement of fuel filters and cleaning of lines is required.

Example 3. Diagnostics of the recirculating STP of the car BMW 520i 2.0 l 1984 rengine code 20 6 ЕВ, naturally aspirated. Rated engine power 92 kW. Distributed injection system. Fuel pressure 2.5 ± 0.05 bar. Fuel return via pressure regulator 0.36 l / min. Temperature: fuel + 20 ° С; inlet air + 15 ° С.

The calculated values of the STP parameters are determined according to algorithm No. 3 (Fig. 3):

This STP is traceable (there is access to the pressure main); measure the current values p (t) = 2.5 bar, q (t) = 1.67 l / min, p _max = 5.6 bar, p _tr (t) = 1.83 bar at idle, which meets the requirement (ten). Diagnosis: STP is functional, the defect takes place in another engine system.

Example 4. Diagnostics of the recirculation STP of the Geely MK sedan 1.5 l 16 cl. 2013, engine code Toyota 5A-FE, naturally aspirated. Rated engine power 94 HP Distributed injection system. Fuel pressure 3.5 bar. Fuel temperature + 38 ° С. Intake air temperature + 32 ° С.

Rated motor power in kW: 69.14.

The calculated values of the STP parameters are determined according to algorithm No. 3 (Fig. 3):

This STP is controllable (there is access to the pressure line), therefore, the current values of pressure p (t) = 3.5 bar, pressure in the rail at idle speed p _tr (t) = 3.1 bar and flow q (t) = 1 are measured , 97 l / min and compare them with the corresponding calculated values: p _tr (t) does not meet the requirement (10), which indicates an incorrect adjustment of the fuel pressure by the pressure regulator. Diagnosis: STP is inoperative, fuel pressure regulator defect.

Example 5. Diagnostics of a dead-end STP of the car LADA Granta sedan 1.6 l 16 cl. 2019, 5 MT, engine code 21127, dynamic boost. Rated engine power 78 kW. Distributed injection system. Fuel pressure 3.8 ÷ 4.0 bar. Fuel return via pressure regulator 0.45 l / min. Fuel temperature + 30 ° С. Inlet air temperature + 26 ° С.

The calculated values of the STP parameters are determined according to algorithm No. 4 (Fig. 4):

Since this STP is uncontrollable (there is no access to the pressure line), then the current values are measured at idle speed p (t) = 3.95 bar and when emulating a full load q (t) = 1.63 l / min and compare them with the corresponding calculated values, which satisfies the requirement (10) and indicates the operability of the STP. Diagnosis: STP is functional, the defect is located in another engine system.

Example 6. Diagnosis of a dead-end STP of a Subaru Forester 2.5 Turbo, engine code EJ255, turbocharging. The rated power of the engine is 169 kW. Distributed injection system. Fuel pressure 4.0 bar. Fuel return via pressure regulator 0.46 l / min. Fuel temperature + 36 ° С. Intake air temperature + 28 ° С.

The calculated values of the STP parameters are determined according to algorithm No. 4 (Fig. 4):

Since this STP is uncontrollable (there is no access to the pressure line), then the current values are measured at idle p (t) = 3.8 bar, while emulating a full load q _stp (t) = 1.15 l / min and compare them with the corresponding calculated values, which does not satisfy the requirement (10), indicates an inoperative state of the STP and requires dismantling the fuel module from the fuel tank, as a result of which an inoperative state of the low pressure fuel pump is established. Diagnosis: STP is inoperative, requires replacement of TNND.

The obtained experimental data confirm the compliance of the technical result of diagnostics with the claimed purpose of the invention.

Claims (1)

A method for diagnostics of the fuel supply system (STF) of injection internal combustion engines (ICE), including the measurement of such current values of diagnostic parameters as the current pressure and fuel performance in the STF systems of discrete and continuous fuel injection into the intake tract, as well as the current pressure and fuel performance in the low pressure circuit (LPC) of the direct fuel injection system and the supply of electric low pressure fuel pumps included in the STP and LPC, determination of the calculated values of these parameters as a function of the rated power of the internal combustion engine, fuel temperature and intake air temperature, comparison of the calculated values with the measured current values and determination of the technical diagnosis of STP and LPC.

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