RU2293206C2 - Device for diagnosing condition of fuel devices of diesel engines - Google Patents

Abstract

FIELD: mechanical engineering; diesel engines.

SUBSTANCE: invention relates to devices for measuring difference of two and more pressure values and it can be used for checking fuel equipment of diesel engines both at test stands and directly on operating diesel engines. Proposed device contains stand base on which fuel injection pump to be tested, nozzles, measuring cylinders, fuel distributor, upper and lower fuel tanks, stand feed pump, fuel filter, pressure gauge damper, pressure gauge are mounted and fuel cylinder is introduced additionally through which high-pressure fuel is fed. Fuel cylinder is connected with fuel high-pressure accumulator and with fuel cylinder fuel hydraulic vibrations damper. Disk with fitted-on permanent magnet to control opening of spool of fuel hydraulic vibration damper and permanent magnet of first cylinder top dead center marker is arranged on shaft of fuel injection pump under testing. Device contains also electric circuit for recording changes of fuel pressure in high-pressure fuel line including fuel pressure pickup arranged in fuel cylinder and connected by switch and electric circuits with current amplifier, analog-digital converter, port and computer which is connected with display. Electric circuit of first cylinder top dead center marker contains electric coil arranged on housing of fuel-injection pump and connected through electric circuit with electric unit. Spool control electric circuit communicating fuel cylinder with fuel hydraulic vibration damper consists of electric coil secured on housing of fuel-injection pump, dc current amplifier and electric coil of spool communicating fuel cylinder with fuel hydraulic vibration damper interconnected by electric circuit.

EFFECT: reduced time taken for testing fuel-injection pump and nozzles, provision of automatic recording of fuel feed process to get date for reliable evaluation of fuel equipment tested on stand or directly on engine.

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Description

The invention relates to devices for measuring the difference of two or more pressure values and can be used to check the fuel equipment of diesel engines both on stands and directly on running engines.

A device for checking plunger pairs and discharge valves of sections of a high pressure fuel pump (TNVD) on a diesel engine [1]. To check the condition of the plunger couples and the tightness of the pressure valves, the KI-4802 GOSNITI device is used. It consists of a pressure gauge and a handle. A damper and a safety valve are mounted in the handle, which is adjusted to a pressure of 300 kgf / cm ² (30 MPa).

The device is connected by a high-pressure fuel line (high-pressure fuel line) to the tested section of the high-pressure fuel pump and the crankshaft of the diesel is cranked by the starting engine or starter. If the plunger pair does not develop a pressure of 300 kgf / cm ² (30 MPa) or more, it should be replaced.

The tightness of the discharge valve is checked by creating a pressure of 150 kgf / cm ² (15 MPa) in the pump section. Then the fuel supply is stopped and the time of pressure drop in the fixture system is detected from the stopwatch from 150 to 130 kgf / cm ² (from 15 to 13 MPa). If the pressure drop time does not exceed 10 s, then the discharge valve is rejected.

In the absence of the KI-4802 device, the technical condition of the plunger couples and the operation of the discharge valves can be checked using a pressure gauge connected by a tee to the nozzle that plays the role of a safety valve.

However, this device does not provide simultaneous simultaneous verification of high-pressure fuel pumps and injectors; it requires considerable labor costs when the condition of the above-mentioned devices of the diesel power system is not fully estimated.

A device for checking the operation of the nozzle on a diesel engine [1]. To check the nozzle, a diesel operation mode is established in which interruptions are most clearly audible. Then, in turn, loosen the nuts securing the high pressure fuel lines. If the speed of the crankshaft does not change after loosening the nut, the nozzle under test is faulty. If the nozzle does not work due to a violation of the pressure regulation of the fuel injection start, then it can be adjusted using a maximeter or a control nozzle. Having fixed the maximeter on the injection pump nozzle, they connect the tested nozzle to it, crank the crankshaft with a starter and achieve the simultaneous start of fuel injection with the maximeter and nozzle. In the absence of a maximeter, the tested nozzle is connected to the control using a tee. Having connected the tee with the injection pump nozzle, crank the diesel crankshaft with a starter and achieve simultaneous start of fuel injection at the control and adjustable nozzles.

This device also does not provide an objective assessment of the state of the nozzle, since it does not allow to determine the maximum pressure of fuel injection, the moment the nozzle needle fits into the saddle and the duration of the fuel injection process by the nozzle.

Known stands for checking, adjusting and testing fuel injection pumps and nozzles SDTA-1 and SDTA-2 [2], which provide the measurement of the following parameters: the amount of fuel supplied by each section of the injection pump, the lead angle of the beginning of fuel injection, the duration of the fuel injection process, the pressure of the beginning of opening discharge valves.

However, when using the SDTA-1 and SDTA-2 stands, considerable time is required to check the diesel fuel equipment due to the need to perform a large number of auxiliary operations. For example, to check the lead angle of the beginning of fuel injection by the injection pump section, it is necessary to remove the high pressure pipe from the fitting of the first section and install a glass tube (momentoscope) on this fitting. After that, the camshaft of the high-pressure fuel pump is rotated before the fuel starts moving in the momentoscope and the lead angle of the fuel injection start is determined on the scale of the movable disk.

The absence of reliable test data in the form of a diagram obtained with a device that automatically registers the fuel supply process in a diesel engine during testing of the high-pressure fuel pump and injectors does not allow an objective assessment of the state of the fuel equipment at various high-pressure fuel pump operating modes (starting flow, flow at maximum idle speed , intermediate feeds at different crankshaft speeds). In addition, at these stands it is impossible to verify the simultaneous joint operation of all sections of the injection pump and nozzles.

However, the stands SDTA-1 and SDTA-2 are closest in essence to the claimed invention and are taken as a prototype.

The technical result is aimed both at reducing the time of testing fuel injection pumps and injectors, and at automating the registration of the fuel supply process in order to obtain data allowing an objective assessment of the state of fuel equipment being tested at the stand or directly on the engine.

The technical result is achieved by the fact that in the developed device containing the base of the stand, on which the tested injection pump, nozzles, graduated cylinders, fuel distributor, upper and lower fuel tanks, booster pump, fuel filter, pressure gauge damper, pressure gauge are placed, an additional fuel cylinder is introduced through which high-pressure fuel lines (HPTs) pass, moreover, the fuel cylinder is connected to a high-pressure fuel accumulator and to a damper for hydraulic oscillations of the fuel in the fuel qi the cylinder, and on the shaft of the tested high-pressure fuel pump there is a disk with a permanent magnet for controlling the opening of the damper of the hydraulic oil vibration damper and a permanent magnet of the top dead center marker (TDC) of the first cylinder mounted on it, while the following are also entered into the diagnostic device:

- an electric circuit for detecting changes in fuel pressure in a fuel engine containing a fuel pressure sensor located in the fuel cylinder and connected by a switch and electric circuits to a current amplifier, analog-to-digital converter (ADC), a port and a computer, the computer being connected to the display;

- an electric circuit of the TDC marker of the first cylinder, containing an electric coil placed on the high pressure fuel pump housing and connected through an electric circuit to an electric unit;

- an electric control circuit for the control valve of the fuel cylinder with the damper of hydraulic vibrations of the fuel, consisting of an electric coil mounted on the injection pump housing, a direct current amplifier and an electric coil of the valve of the fuel cylinder with the damper of hydraulic vibrations of the fuel, interconnected by an electric circuit.

Distinctive features of the prototype is that an additional fuel cylinder is introduced into it through which the theater passes; moreover, the fuel cylinder is connected to a high-pressure accumulator of fuel and a damper for hydraulic vibrations of the fuel in the fuel cylinder, and a disk is installed on the shaft of the tested injection pump with it installed a permanent magnet controlling the opening of the damper damper of hydraulic vibrations of fuel and a permanent magnet of the top dead center marker (TDC) of the first cylinder, while in the device for Diagnostics are also introduced:

- an electric circuit for detecting changes in fuel pressure in a fuel engine containing a fuel pressure sensor located in the fuel cylinder and connected by a switch and electric circuits to a current amplifier, analog-to-digital converter (ADC), a port and a computer, the computer being connected to the display;

- an electric circuit of the TDC marker of the first cylinder, containing an electric coil placed on the high pressure fuel pump housing and connected through an electric circuit to an electric unit;

- an electric control circuit for the control valve of the fuel cylinder with the damper of hydraulic vibrations of the fuel, consisting of an electric coil mounted on the injection pump housing, a direct current amplifier and an electric coil of the valve of the fuel cylinder with the damper of hydraulic vibrations of the fuel, interconnected by an electric circuit.

Figure 1 and 2 shows a device for diagnosing fuel equipment of diesel engines, figure 3 is a diagram of the change in fuel pressure in a theater, depending on the angle of rotation of the camshaft.

A device for diagnosing fuel equipment of diesel engines (Fig. 1) contains the base of stand 1, on which the test pump 2 is located, nozzles 3, graduated cylinders 4, fuel distributor 5, upper 6 and lower 7 fuel tanks, a booster pump 8, fuel filter 9, pressure gauge damper 10, pressure gauge 11. A fuel cylinder 12 is installed above the high-pressure fuel pump 2 through which the turbine engine 13 passes. The fuel cylinder 12 is connected by a pipe 14 to a fuel high pressure accumulator 15, and by a pipe 16 to a hydraulic shock absorber of fuel 17 in a cylinder 12. Acc High pressure fuel stimulants 15 is designed to maintain the fuel in the cylinder 12, excess fuel pressure of 150 MPa. Such a value of excess pressure eliminates both erosive destruction of the external surfaces of the theater 13 due to the elimination of the occurrence of cavitation [3], and to increase the rate of transmission of fuel pressure from the theater to the pressure sensor and to increase the response speed of the electric circuit for registering pressure in the theater.

The damper of hydraulic vibrations of the fuel 17 is made in the form of a ball connected by a pipe 16 to the fuel cylinder 12 through an opening 18 (Fig. 2) made in the spool 19. The spool 19 is designed to communicate the damper of hydraulic vibrations 17 with the fuel cylinder 12 at intervals between fuel supplies separate sections of fuel injection pump 2.

A return spring 21 is placed above the spool 19 in its housing 20, and an electric coil 22 forming a solenoid is installed over another part of the spool 19. The electric coil 22 of the solenoid is connected by electric lines 23 and 24 through a DC rectifier 25 with an electric coil 26 mounted on the front of the injection pump 2. At the front end of the cam shaft 27 of the injection pump 2, a movable disk 28 is mounted together with four permanent magnets 29 mounted on it.

For a four-cylinder four-stroke diesel engine, the angles φ ₁ , φ ₂ , φ ₃ , φ ₄ between the permanent magnets 29 are 20 ° of the camshaft, since it is known that the duration of the full supply of diesel engines does not exceed 40 ° of the crankshaft rotation or 20 ° of the camshaft rotation [ 3]. Angles φ ₅ , φ ₆ , φ ₇ , φ ₈ are 70 ° of the camshaft. This value corresponds to the rotation angles of the camshaft of the injection pump 2 in the intervals between the fuel supply to the nozzles 3 by separate sections of the injection pump 2.

An electric coil 26 together with permanent magnets 29, a DC amplifier 25, electric circuits 23 and 24, and an electric coil 22 of the solenoid form an electric circuit for detecting changes in fuel pressure in a fuel assembly containing a strain gauge fuel pressure sensor 30 located in the fuel cylinder 12. Strain gauges Compared with other types of sensors (piezometric, capacitive), they have better dynamic qualities, less insulation requirements and measuring equipment, have a simpler device and cost.

The sensor 30 is connected by electrical circuits 31, 32, 33 and 34 with a current amplifier 35, an ADC 36, a port 37, a computer 38 and a display 39.

A device for diagnosing diesel fuel equipment also includes a TDC meter circuit of the first cylinder, consisting of an electric coil 42 connected by electric circuits 40, 32, 33 and 34 to ADC 36, port 37, computer 38 and display 39.

All three electrical circuits are included in the operation using the switch 41.

The device operates as follows: fuel is supplied to the high-pressure fuel pump 2 from the lower fuel tank 7 through the valve 5 and the fuel filter 9 using the fuel priming pump 8. The high-pressure fuel pump 2 delivers fuel to the nozzles 3 under high pressure through the high-pressure fuel pump 13.

To diagnose the technical condition of the high-pressure fuel pump 2, nozzles 3 and high pressure fuel pump 13, it is necessary to close the contacts of the switch 41. In this case, the electric control circuits for controlling the spool of the fuel cylinder 12 with the damper for hydraulic oscillations of the fuel 17, registering the change in fuel pressure in the theater 13 and the TDC of the first cylinder will work.

The electrical control circuit of the spool of communication of the fuel cylinder 12 with the damper of hydraulic oscillations of the fuel 17 operates as follows.

When fuel flows through the theater 13 with a variable pressure, they are subject to vibrations that are transmitted to the fuel in the fuel cylinder 12. Under the influence of the vibrations of the theater 13, wave phenomena occur in the fuel that adversely affect the operation of the fuel pressure sensor 30. This occurs due to resonance the addition of oscillations caused by vibrations of the fuel assembly 13, through which fuel is supplied to the nozzles.

When the movable disk 28 is rotated by an angle of 45 °, the permanent magnet 29 moves at the turns of the electric coil 26, in which an electric current occurs. The electric current through the electric circuits 24 and 23 through the current amplifier enters the electric coil 22. Under the influence of the electric field arising in the coil 22, the spool 19 moves to the left, compressing the return spring 21. In this case, the hole 18 in the spool 19 is aligned with the hole of the pipe 16. In this case, part of the fuel from the fuel cylinder 12 will flow into the ball 17, in which there is air. Due to the periodic compression of the air in the ball 17, the wave oscillations in the cylinder 12 are rapidly damped. When the cam shaft is turned at angles φ ₁ , φ ₃ , φ ₄ and φ ₂ , fuel is supplied to the first, third, second, and fourth sections of the high-pressure fuel pump 2 and to the first , third, second and fourth nozzles, respectively. However, the damper 17 does not work. At time intervals corresponding to the angles φ ₅ , φ ₆ , φ ₇ and φ ₈ , the ball 17 through the hole 18 in the spool 19 communicates with the fuel cylinder 12, in which the hydraulic oscillations in the fuel are damped.

Thus, the damping of wave phenomena arising in the fuel cylinder 12 due to vibrations of the fuel assembly 13 occurs in the time intervals between the fuel supply of the injection pump 2 to the nozzles 3.

The principle of operation of the electrical circuit for detecting changes in fuel pressure in the fuel assembly 13 is that the pressure change is detected by the fuel pressure sensor 30, the electrical signal from the sensor 30 is amplified by a current amplifier 35 and fed to the ADC 36, which converts the analog signal to its corresponding code . This code through port 37 enters a computer (computer) 38, the output of which is connected to a display 39, which displays information about the change in fuel pressure in the theater 13.

When the camshaft 27 of the fuel injection pump 2 rotates, the fuel is pumped in sections under high pressure in the order of the diesel cylinders through the theater 13 to the nozzles 3. When the fuel flows through the section of the theater 13 located in the fuel cylinder 12, the fuel pressure pulse is transmitted through the walls of the theater 13 and fuel, under pressure 150 MPa [3] in the fuel cylinder 12, to the pressure sensor 30, from which the electric signal is supplied through an electric circuit 31 to a current amplifier 35 and ADC 36. The accuracy of recording the fuel supply process is determined by the amplitude-frequency bubbled characteristics of measuring instruments, by which is generally understood dependence transformation coefficient on the frequency of the signal [5]. The idea of the necessary frequency spectrum describing the processes in the fuel equipment with a given accuracy can be obtained on the basis of triangular and rectangular pulses, the shape of which is close to the oscillograms of the processes studied in the fuel equipment (for example, the curve of the change in fuel injection pressure depending on the angle of rotation of the cam shaft Injection pump 2).

The limits of the necessary spectrum can be established by the example of the analysis of a triangular impulse described by a function in the form of a series [5]:

where A ₀ is the magnitude of the input signal;

a is the wavelength of the input signal;

k is the order of the considered harmonic.

When registering the fuel supply process with steep fronts, the necessary spectrum can be determined by the magnitude of the phase shift caused by the fact that the amplitude of the transmission pulse does not reach the nominal value immediately, but after some period φ _n , which is usually called the rise time.

The largest increase in the fuel supply front is observed for pulses approaching rectangular in shape, and is described by the following expression in the form of a series [5]:

The signal from the ADC 36 is supplied through electrical circuits 32, 33 and 34 to port 37, computer 38 and to the display 39 as a graphical representation of the change in fuel pressure in the fuel assembly 13 from the angle of rotation of the camshaft of the injection pump 2 (Fig. 3).

In the case of fuel supply by the first section of the injection pump 2, the electric circuit of the TDC marker of the first cylinder is triggered, since when the permanent magnet 39 moves near the electric coil 42, a magnetic flux Φ occurs in the gap between these parts, and at some point in time τ it reaches a maximum, and then decreases. In accordance with the change in magnetic flux, the magnitude of the EMF created in the coil 42, determined by the formula:

, между которыми кривая ЭДС проходит через ВМТ. Электрический импульс от электрической катушки 42 передается по электрическим цепям 40, 32, 33 и 34 на дисплей 39 в виде импульса 8 (фиг.3).In accordance with expression (3), the EMF reaches its maximum value at maximum

between which the EMF curve passes through the TDC. The electric pulse from the electric coil 42 is transmitted through electrical circuits 40, 32, 33 and 34 to the display 39 in the form of a pulse 8 (figure 3).

On the diagram of the change in pressure of fuel injection into the engine cylinders [4] depending on the angle of rotation of the camshaft (Fig. 3), point 1 corresponds to the beginning of the increase in pressure, which coincides with the rise of the discharge valve. At point 2, the fuel pressure reaches a value at which the torque of the nozzle spring is overcome, the needle breaks away from its seat, and injection occurs. In section 3-4, there is a decrease in the rate of increase in injection pressure due to an increase in the volume in the atomizer when the nozzle needle is raised. At point 5, the injection pressure reaches its maximum value. Point 6 corresponds to the moment the nozzle needle fits into the saddle, and at point 7 the pressure valve fits into the saddle.

The diagram (Fig. 3) shows, by way of example, changes in the pressure of fuel injection into the cylinders in one working cycle of a four-stroke four-cylinder diesel engine. These diagrams can be compared with reference design diagrams and determine malfunctions in the operation of the injection pump sections and nozzles both on the stand and on the engine mounted on the stand or on the vehicle. For example, figure 3 shows that the injection pump section of the third cylinder has low pressures at points 1 and 7, which indicates a loose fit of the discharge valve in the seat and wear of the plunger pair. The section of the fourth cylinder has an insufficient tightening of the nozzle needle spring, which therefore rises earlier. The pressure at point 5 of this section does not reach the maximum value. This will lead to a deterioration in atomization of the fuel in the combustion chamber and to a deterioration in the flow of the combustion process.

The volume of fuel injected by the nozzles 3 (figure 1) is determined using graduated cylinders 4.

Thus, the claimed design of a device for diagnosing fuel equipment of diesel engines allows you to get a diagram of the pressure change of fuel injection in a fuel engine depending on the angle of rotation of the camshaft of the injection pump. The resulting diagrams allow you to obtain objective data about the technical condition of the high-pressure fuel pump, high pressure fuel pump and nozzles, and detect malfunctions in their operation. A device for diagnosing fuel equipment has only one fuel pressure sensor. This simplifies the design of the device and reduces its cost.

Information sources

1. NK Bakhtiyarov et al. Fuel equipment of tractor and combine engines. - M .: Kolos, 1980 .-- 160 p.

2. GI Trubnikov and others. Workshop on automotive engines. - M .: Kolos, 1975 .-- 190 p.

3. TMBashta and others. Hydraulics, hydraulic machines and drives. - M.: Mechanical Engineering, 1982.- 422 p.

4. P.M. Belov and others. Engines of army vehicles, part 1. Theory. - M .: Military Publishing, 1971. - 508 p.

5. B.N. Fainleb. Fuel equipment of automotive diesel engines. - L .: Engineering, 1974. - 263 p.

Claims (1)

A device for diagnosing diesel fuel equipment, comprising a stand base, on which the tested high pressure fuel pump (TNVD) is located, nozzles, graduated cylinders, fuel distributor, upper and lower fuel tanks, booster pump, fuel filter, pressure gauge damper, pressure gauge, characterized the fact that a fuel cylinder is additionally introduced into the device through which the high pressure fuel lines (HPT) pass, moreover, the fuel cylinder is connected to the high pressure fuel accumulator and with a damper for hydraulic vibrations of the fuel in the fuel cylinder, and a disk with a permanent magnet for controlling the opening of the damper damper for hydraulic vibrations of the fuel and a permanent magnet of the top dead center marker (TDC) of the first cylinder mounted on it is mounted on the shaft of the tested injection pump; an electric circuit was introduced for detecting changes in fuel pressure in a fuel engine, containing a fuel pressure sensor located in the fuel cylinder and connected by a switch and an electric circuits with a current amplifier, analog-to-digital converter (ADC), a port and a computer, the computer being connected to the display; an electric circuit of the TDC marker of the first cylinder, comprising an electric coil located on the high pressure fuel pump housing and connected through an electric circuit to an electric unit; an electric control circuit for controlling a valve of a fuel cylinder with a damper for hydraulic vibrations of fuel, consisting of an electric coil mounted on the injection pump housing, a direct current amplifier and an electric coil for connecting a valve of a fuel cylinder with a damper for hydraulic vibrations of fuel connected by an electric circuit.

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