RU2336513C2 - Method of internal combustion engine technical condition estimation - Google Patents

Abstract

FIELD: physics, measurement.

SUBSTANCE: invention is related to equipment for testing in operation conditions with ignition of fuel mixture from compression. Method consists in the following: tests are performed without fuel supply into engine cylinders at start-up rotations, which amount to 150...300 rpm. Sensor of air mass flow rate, for instance, of heat-loss anemometer type, is installed in inlet manifold of engine, the same sensor is installed in engine outlet manifold, both sensors are connected to electronic control unit, which processes signals received from sensors and transmits processed signals to indication unit.

EFFECT: reduction of diagnostics labour intensity in operating conditions.

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Description

The invention relates to a field test technique for internal combustion engines with compression-ignition of a combustible mixture.

Several instrumental methods for diagnosing a cylinder-piston group (CPG) of an engine are known.

A method for evaluating the pneumatic density of each cylinder by the maximum pressure of the compression stroke (compressometer); (see Belsky V.I. Diagnostics of the technical condition and adjustment of tractors. - M .: Kolos, 1973. - 495 s, p. 118).

The "compression" method is simple, affordable, universal. However, professionals are skeptical of him. First, let us evaluate the information content of the method, i.e. the ratio of the magnitude of the change, respectively, structural and diagnostic parameters. If we accept a change in the structural parameter (for example, an increase to the limit value of the tolerance for ovality and conicity of the liner) for 100%, then the change in the diagnostic parameter (compression) for the carburetor and diesel engine will be, respectively, 1.15 MPa-0.9 MPa = 0.25 MPa; 3.2 MPa-2.6 MPa = 0.6 MPa, which in relative units to the upper (nominal) value will be 21.7% and 18.8%. Such informational content of the method is clearly not enough not only to predict the residual life, but also to make a “final diagnosis” about the state of the CPG. But, in addition to informativeness, there is also a methodological error due to the influence of a number of subjective factors. So, the performance of the crankshaft and temperature affect the performance of compression. With a discharged battery, the loss of compression is on average 0.1-0.15 MPa. In addition, factors such as excessive oil or fuel in the cylinders, resistance in the inlet pipe, oil temperature, etc., will have a strong effect on the compression ratios of a worn CPG.

The total methodological error in estimating the CPG by pressure at the end of compression (compression) is 0.1-0.18 MPa, respectively, which, in terms of relative indicators in the parameter variation range (0.25 and 0.6 MPa), is 25 and 30%, respectively . In the presence of such an error, along with low information content, this method can also be safely attributed to the category of indicator (without taking into account the accuracy class of the pressure gauge).

There is a method of assessing the pneumatic density of a particular cylinder by forcing it by crimping with compressed air (the principle of a pneumatic calibrator); (see Belsky V.I. Diagnostics of the technical condition and adjustment of tractors. - M .: Kolos, 1973. - 495 p., p. 120).

The principle of "pneumatic calibrator" implemented in the K-69 device partially eliminates the above-mentioned disadvantages, i.e. allows you to identify a specific faulty cylinder. The piston of the tested cylinder is set when the crankshaft is slowly turned to the working compression or expansion stroke (with valves closed). Compressed air is supplied to the cylinder under a certain pressure, and the pneumatic density of the cylinder is estimated from the time the pressure drops. There is a serious limitation for this method: it can be implemented only in stationary conditions with a source of compressed air. Obviously, with wear or tear on the working surface of the cylinder; wear, coking or breakage of the piston rings; leaks valve seats in the seats, etc. overall cylinder leakage increases, which mainly affects the pressure drop time. Also, the following reasons will affect the accuracy of the diagnosis. Firstly, it is necessary to set the piston in at least two positions - in the middle and at the end of the compression stroke, because the sleeve wears out not only “oval”, but also “conically”. Technically, this operation is quite difficult. Secondly, when checking the last cylinders, ceteris paribus, we get worse results due to leakage at the time of checking part of the oil in the crankcase, which will affect the results of assessing the state of the CPG. Thirdly, only leakages in valves can be reliably estimated by the increased pressure drop intensity and the presence of a “whistle” in the intake or exhaust manifolds. But the main malfunction of the CPG of this cylinder (malfunction of rings or liners) we can not determine by this method.

For the prototype taken A.S. USSR No. 17/4412. A method for diagnosing an internal combustion engine. The method consists in blocking the inlet and outlet channels of the cylinder, cranking the crankshaft at a certain speed, thereby moving the piston of the cylinder being tested from bmw to n.m.t. at the intake stroke, determine the flow rate of air entering the cylinder, then block the air outlet from the cylinder, move the piston at a certain speed from nm to bmw, after a predetermined period of time after this, the air outlet from the cylinder is opened, the flow rate is determined, and the diagnosis is carried out according to the flow ratio. The disadvantages of this method is that it gives a limited information content of the diagnosis, because only the piston-ring-cylinder-engine coupling is evaluated, and the state (leakage) of the valve mechanism is not taken into account.

The technical task is to reduce the complexity of diagnosing in operating conditions.

This is achieved by determining the difference in air flow during start-up at the inlet and outlet, thereby checking the performance of the CPG. The obtained value of the air flow is compared with the standard values of the air flow, on the basis of which they judge the technical condition of the engine.

The method consists in the fact that the tests are carried out without supplying fuel to the engine cylinders at starting revolutions, which are 150 ... 300 rpm.

At the air inlet to the intake manifold, a mass air flow sensor (DMRV) is installed, for example, hot-wire, the same sensor is installed at the air outlet to the exhaust manifold. Both sensors are connected to an electronic control unit (ECU). The computer records the signals from the sensors and, after conversion, provides information to the indicator in the form of a difference in costs.

The drawing shows a diagram for implementing this method, where: the diagnosed engine is 1; mass air flow sensors - 2; electronic control unit - 3; display unit - 4.

The method is as follows:

The above signal pickup devices are connected to the test engine 1. Bring the crankshaft of the engine into rotation with a standard electric starter or starting device. When the crankshaft rotates, the sensors 2 send certain pulses to the electronic control unit 3. The electronic control unit processes the signals from the sensors and transmits the processed signals to the display unit 4.

Claims (1)

The method of assessing the technical condition of internal combustion engines by the amount of air passing through the leaks of the cylinder-piston group and the combustion chamber, which consists in determining the difference in air flow rate at the inlet and outlet, the obtained value is compared with the normative, on the basis of which the technical condition of the cylinder-piston group, different the fact that the determination of the difference in air flow rate at the inlet and outlet is carried out on starting mode.