RU2390746C1 - Method of in-place diagnostics of ice con rod bearing wear - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: method of in-place diagnostics of ICE con rod bearing wear consists in measuring amplitude of pressure pulsations in central ICE oil line in the section between filter and crankshaft bearing. Measuring amplitude of pressure pulsations in central ICE is performed for eight rpm values. Pressure pulsation amplitude is plotted as a function of engine rpm. From plotted graph, the point of pressure increase amplitude non-linearity start and rpm corresponding to said point are determined. Numerical value of said point are compared with reference function preset for new engine. From the results of comparison, degree of wear in any con rod bearing is defined.

EFFECT: higher accuracy of diagnostics.

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Description

The invention relates to the field of operation of machines and can be used to diagnose the degree of wear of the connecting rod bearings of internal combustion engines (ICE).

A number of known methods for diagnosing the degree of wear of ICE bearings.

In accordance with SU No. 328364, publ. 01/01/1972, the size of the gaps is determined by the amplitude-phase parameters of the pulsations of the oil flow in the channels of the lubrication system. When determining the gaps, a sensor is installed in the channel of the lubrication system, the microsensor pulses are measured at a certain thermal mode, and the gap value is determined from the calibration dependencies.

The disadvantage of this method is the need to take the engine out of operation for inspection, preparation for the sensor, a large investment of time for diagnostics.

The method according to SU No. 1134897, publ. 01/15/1985, used for in-place diagnosis. It provides for connecting a hydraulic accumulator with a throttle device to the engine at the time of the experiment and determining the intensity of the pressure drop in it using two pressure gauges in certain modes. However, this method also requires the installation of bulky devices.

The method according to RU No. 2259549, publ. 08/27/2005, used for in-place diagnostics of the technical condition of the internal combustion engine. It provides for the installation of two oil pressure gauges at the inlet and outlet of the filter. When using the method, the operating modes of the engine are set, the state indicators of the diagnosed engine systems are measured, the deviations of the state indicators are determined, the calculations are carried out, and the technical condition of the engine is estimated from the results. Moreover, as indicators of the state take the parameters of the pulsations of the pressure of the medium. The method is characterized in that the pressure pulsation curve at the inlet and outlet of the filter element of the diagnosed system is laid out in a harmonic series. The amplitude and phase frequency characteristics are built in a given frequency range, and the comparison is carried out in the range of the highest sensitivity of the measured frequencies, as a result, the magnitude and speed of deviation of the amplitude and phase frequency characteristics from the reference ones obtained under the condition of the most effective operation of the system are determined, and the residual engine service life.

This method does not allow to determine the malfunction of individual connecting rod bearings of the crankshaft. With the mutual combination of faults of individual main and connecting rod bearings, this method allows you to determine only the general trend of wear, while the wear of the bearings is often not the same. In addition, the forecast of the real engine life is difficult, since the law of the change in the technical condition of individual bearings is unknown.

Adopted as a prototype method - patent RU No. 20066811, publ. 01/30/1994, - used for in-place diagnostics of the degree of wear of bearings of an internal combustion engine. The method consists in measuring the pressure in the central oil line of the internal combustion engine and comparing the obtained pressure values with the reference values determined for the new engine. Compared to determine the degree of wear of the bearings. In this case, the pressure is measured at least at two points of the engine lubrication system, the first of which is located at the outlet of the pressure pump, converting these pressures and comparing them with the reference values. As a second pressure measuring point, a point is taken at the inlet to the diagnosed portion of the engine. For a reference engine, the relationship between the ratio of the magnitude of the first pressure to the magnitude of the second on the degree of wear of the bearings or the ratio of the difference in the magnitude of the first and second pressures to the magnitude of the second on the degree of wear is determined. On an idle engine with clean filters, the ratio of the difference between the values of the first and second pressures to the value of the second pressure is determined and the value of this ratio is compared with a reference dependence on the degree of bearing wear. Moreover, the growth of this ratio corresponds to an increase in the degree of wear.

However, this method, despite its simplicity, does not allow to determine the wear of a particular connecting rod bearing, i.e. select the wear signal of the corresponding connecting rod bearing. And an increase in the ratio of pressure values is possible from the wear of any of the main or connecting rod bearings, as well as other elements lubricated in the internal combustion engine.

An analysis of the known methods shows the feasibility of finding a method for assessing the technical condition of the ICE connecting rod bearings, while preserving the advantages of previously existing methods and the possibility of determining the technical condition of any ICE connecting rod bearings, regardless of its location in the oil path.

The aim of the invention is to determine the degree of wear of any connecting rod bearing of the internal combustion engine, regardless of its location in the oil path, and to increase the accuracy of assessing the technical condition of the engine.

This goal is achieved by the fact that in the proposed method of in-place diagnostics of the degree of wear of the internal combustion engine bearings, the pressure pulsation amplitude is measured in the central oil line from the filter to the crankshaft bearings. In contrast to the prototype, the measurement of the amplitude of the pulsations of the pressure value is performed for eight values of the engine speed. The dependence of the amplitude of the pulsations of the pressure on the engine speed is built. From the dependence, the point of the beginning of the nonlinearity of growth of the pressure amplitude and revolutions corresponding to this point is found. The found numerical value of the point of the beginning of the nonlinearity of the growth of the pressure amplitude and revolutions corresponding to this point is compared with the reference dependence defined for the new engine. By comparison, the degree of wear of any of the diagnosed connecting rod bearings is determined.

Figure 1 presents the functional diagram of the engine lubrication system;

figure 2 presents a diagram of the supply of oil to the connecting rod bearings at the stage corresponding to the range of engine operation with a minimum crankshaft speed;

figure 3 presents a diagram of the supply of oil to the connecting rod bearings at the stage corresponding to the range of the engine when the dynamic locking;

figure 4 presents a waveform of pressure in the Central oil line;

figure 5 presents the oscillogram of the pressure in the Central oil line of the engine ZMZ-406;

figure 6 presents the dependence of the amplitude of the pulsations of the pressure on the engine speed for the first connecting rod journal;

Fig.7 shows the dependence of the pressure amplitude on engine speed for various gaps in the main and connecting rod journals.

The discharge pump 1 picks up the oil from the oil pan 2 and through the filter 3 directs it to the bearings of the engine 4, from where it flows into the oil pan. The IPD2-0.6 strain-gauge pressure sensor and the MIC-400 measuring complex, indicated by 5 in Fig. 1, measure the amplitude of the pulsations of the pressure in the central oil line of the engine in the form of an oscillogram of pressure pulsations, in the area from the filter to the crankshaft bearings when diagnosed connecting rod bearings.

During the operation of the connecting rod journal, three stages of its operation can be distinguished: 1 - the stage corresponding to the engine speed range from n = 880 rpm to 1500 rpm; 2 - stage at n = 1500-1900 rpm; 3 - stage at n> 1900 rpm.

The three stages indicated during the operation of the connecting rod neck are illustrated in the diagram for supplying oil to the connecting rod bearings, FIGS. 2, 3. The diagram for supplying oil to the connecting rod bearings has the following designations: r _K is the radius of the main neck; r _W - radius of the connecting rod journal; 6 - an annular groove; 7 - channel in the root neck; 8 - entrance to the feed channel to the connecting rod journal; 9 - inclined feed channel; 10 - crank cavity.

Oil is supplied sequentially from the oil pump to the annular groove 6, from the annular groove 6 to the channel in the main neck 7, from the channel in the main neck 7 to the entrance to the supply channel to the connecting rod neck 8, from the entrance to the supply channel to the connecting rod neck 8 to the inclined channel supply 9, from the inclined supply channel 9 to the connecting rod cavity 10 and then through the gap in the connecting rod journal to the engine oil pan.

When operating the connecting rod journal at the first stage with a minimum crankshaft rotation speed (n = 880 rpm to 1500 rpm), FIG. 2, the centrifugal forces acting on the oil flow in the inclined feed channel 9 are negligible. In this case, the amount of oil supplied to the inclined conduit 9 of the connecting rod journal depends on the pressure created by the oil pump P ₁ , as well as the clearance in the main journal. If the clearance in the main neck has an acceptable value, then the pressure developed by the oil pump P ₁ and communicated to the oil flow is sufficient for a constant supply to the connecting rod journals. The maximum clearance for the main bearing already in this mode creates unfavorable conditions for the lubrication of the connecting rod bearing: most of the oil goes into the increased clearance in the main neck.

At the second stage, in the process of increasing the crankshaft speed from 1500 rpm to 1900 rpm, the action of centrifugal forces on the moving oil flow in the connecting rod journal gains significant significance. On the one hand, at points 7 and 8 (the channel in the root neck and the entrance to the supply channel to the connecting rod neck), a centrifugal force P _{2 of} FIG. 3 arises, acting on the supplied oil along the radius r _K and directed from the center of the root neck, tending to lead to a dynamic locking the incoming oil at point 7 (channel in the root neck). On the other hand at a point 9 (inclined feed channel) of an oil flow is accelerated by the inertial force F ₃ directed toward the point 10 (crank chamber) by the radius r _W. The opposite effect of these inertial forces P ₂ and P ₃ tends to break the continuity of the oil flow in the inclined conduit 9 of the connecting rod journal. In this regard, at the first stage (n = 880 rpm to 1500 rpm), a linear increase in the pressure amplitude in the main oil line is observed. At the second stage (n = 1500 to 1900 rpm), the condition of dynamic locking under the action of the inertial force P ₂ appears. And also an oppositely acting inertia force P ₃ appears, which tends to push the oil flow to the connecting rod cavity 10. The combined effect of these inertial forces leads to a violation of the linearity of pressure growth in the oil line. When observing a change in the amplitude of the oil pressure in the main oil line with an increase in engine speed of more than 1500 rpm to 1900 rpm, a moment was observed corresponding to the maximum decrease in pressure (the point of greatest pressure drop or the point of greatest deviation of the linearity of pressure increase). With a further increase in engine speed of more than 1900 rpm at the third stage, the pressure in the oil line P ₁ increased due to an increase in the oil supply by the oil pump and contributed to an increase in the oil supply to the inclined supply channel 9. Now, with an increase in the oil supply to the inclined supply channel 9, the centrifugal the force P ₃ acting on the oil flow grew, but the relative leaks into the crank pin clearance were limited by the cross section of the gap itself in the crank pin. As a result, the inclined channel was filled with oil and a linear increase in the amplitude of the oil pressure was observed (there was no discontinuity in the flow).

Thus, the strain gauge pressure sensor IPD2-0.6 and the measuring complex MIC-400 measure the amplitude of the pulsations, the pressure in the form of a pressure waveform in the central oil line, Fig.4.

The pressure oscillogram in the central oil line of Fig. 4 shows: I - channel (1-V) - waveform of pressure pulsations P, kgf / cm ² in the central oil line depending on time t, ms; II - channel (3 V) - waveform of pulses for opening the nozzle U, V (voltage in volts) from the electronic control unit depending on time t, ms; A ₁ , A ₂ , A ₃ - the amplitude of the pressure pulsations corresponding to the moments from the action of the combustion forces, kgf / cm ₂ ; a ₁ , a ₂ , a ₃ - the length of time the injection nozzle, ms; in ₁ , in ₂ , in ₃ - the length of time before the combustion cycle, ms; 11, 12, 13 - moments of pressure change from the action of combustion forces.

The pressure oscillogram in the Central oil line in figure 4 was obtained under the conditions: engine speed n = 880 rpm, oil temperature 90 ° C.

Using the pressure waveform in the central oil line in Fig. 4, the amplitude of the pulsations of the pressure value A _{1 is} measured.

Next, pressure oscillograms are measured in the central oil line for eight engine speeds: 880, 1300, 1400, 1500, 1600, 1700, 1800, 2500 rpm for one crank pin. They measure the amplitude of the pulsations of the pressure A ₁ for 1300 rpm ... A ₁ , for 2500 rpm for one connecting rod neck.

Measure the pressure oscillograms in the central oil line for other connecting rod journals, also for eight engine speeds. Figure 5 presents the oscillogram of the pressure in the Central oil line in accordance with the order of operation of the cylinders 1-3-4-2 of the ZMZ-406 engine, explaining a diagram for measuring pressure amplitudes of all four connecting rod journals of the engine.

On the pressure waveform in the Central oil line in accordance with the order of operation of the cylinders 1-3-4-2 of the ZMZ-406 engine, Fig.5, you can see the values of the amplitudes of the pulsations of the pressure for all four connecting rod journals in the order of operation of the engine cylinders 1-3- 4-2. All designations in Fig. 5 are similar to Fig. 4. The pressure waveform in the Central oil line in figure 5 was obtained under the conditions: engine speed n = 880 rpm, oil temperature 90 ° C.

Next, build the dependence of the amplitude of the pulsations of the pressure A ₁ , kgf / cm ² , from the engine speed n, rpm Fig.6.

Figure 6 shows the dependence of the amplitude of the pulsations of the pressure on the engine speed for the first connecting rod journal. The dependence was obtained under the conditions: the gap in the first root neck is 0.15 mm, the gap in the first crank pin is 0.10 mm, the oil temperature is 90 ° C.

6, the point of the beginning of the nonlinearity of the growth of the pressure amplitude and speed corresponding to this point is found. In Fig.6, the start point of nonlinearity is observed at engine speeds n = 1300 rpm. The larger the gap in the connecting rod journal, the lower the speed at which the point of onset of nonlinearity is observed.

For a new engine, the dependence of the pulsation amplitude of the pressure value A ₁ , kgf / cm ² , on the engine speed n, rpm, for eight values of the engine speed is built. The found numerical value of the point of the beginning of the nonlinearity of the growth of the pressure amplitude and revolutions corresponding to this point is compared with the reference dependence defined for the new engine. Figure 7 shows two dependences of the pressure amplitude A ₁ , kgf / cm ² , on engine revolutions n, rpm: 14 - for the gap in the root neck - 0.09 mm and the gap in the connecting rod neck - 0.03 mm; 15 - for a gap in a radical neck - 0,15 mm and a gap in a connecting rod neck - 0,10 mm. When comparing the two dependences, it is seen that the point of the beginning of the nonlinearity of the increase in pressure amplitude for the first dependence corresponds to 1700 rpm and for the second dependence - 1300 rpm Moreover, the start point of the non-linearity of the increase in pressure amplitude for the second dependence shifted toward lower revolutions of the engine crankshaft (by 400 rpm).

Comparing the measured and reference dependencies, the degree of wear of any of the diagnosed connecting rod bearings is determined.

Therefore, determining the degree of wear of any connecting rod bearing, an accurate estimate of the remaining engine life is made.

The technical result consists in increasing the accuracy of assessing the technical condition of individual connecting rod bearings of an internal combustion engine.

Using the proposed method for assessing the technical condition of the internal combustion engine allows you to correctly and timely determine the malfunction of the connecting rod bearings of the crank mechanism, as well as to predict the time of trouble-free operation of the engine.

Claims (1)

The method of in-place diagnostics of the degree of wear of the connecting rod bearings of an internal combustion engine, which consists in measuring the amplitude of pressure pulsations in the central oil line from the filter to the crankshaft bearings, moreover, the pressure pulsation amplitude is measured for eight values of the engine speed, the dependence is built from them the amplitude of the pulsations of the pressure value from the engine speed, find the dependence of the start point of the nonlinearity of the growth of the pressure amplitude and speed, corresponding to this point, and they compare the found numerical value of the start point of the nonlinearity of the growth of the pressure amplitude and revolutions corresponding to this point with the reference dependence defined for the new engine, and compare the degree of wear of any of the diagnosed connecting rod bearings.

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