RU2727737C1 - Method of chips detecting in oil and device for its implementation - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to machine building, particularly, to lubrication systems of mechanical devices. Chip signaling system in oil contains a scoreboard "Chip in a signaling device" and "Chip in oil", an electromagnetic chip detector, automatic control and monitoring unit with a device for analyzing signals coming from the electromagnetic chip signaling device, connected by means of signal transmission channels with the display and the electromagnetic chip detector, wherein signal analysis device performs processing of at least three serially received actuation signals of electromagnetic chip signaling device, "Chip in a signaling device" signal generation during first actuation of chip electromagnetic signaling device and formation of "Chip in oil" signal with the "Chip in a signaling device" signal not registered and reduction of diagnostics reliability to the level P<1-α, where αis a given false triggering probability.

EFFECT: technical result consists in simplification of design and reduction of probability of false alarm system operation.

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Description

The invention relates to mechanical engineering, namely to lubrication systems for mechanical devices, such as gearboxes, in particular to devices for signaling the presence of metal particles in the lubrication system of the main helicopter gearboxes, and allows you to diagnose the onset of destruction of gearbox parts with a given reliability, excluding false alarms, when shavings in oil.

Known magnetic plug-signaling device (RU 2460006), consisting of magnetic and non-magnetic electrodes, in the gap between which accumulates metal magnetic chips, closing the electrical circuit of the board "Chips in oil". This signaling device does not exclude false alarms during the running-in process of unit parts.

Known is a magnetic plug with a pre-alarm function (RU 2483221), which includes two magnetic electrodes and an intermediate, preferably non-magnetic, electrode. This design allows you to give a preliminary signal about the presence of chips in the oil, but does not allow to exclude false alarms due to the closure of a single hair-like shavings that arose during the running-in process.

Known is a magnetic signaling device for shavings of an engine oil system (SU 1719954), which has two or more magnetic contacts connected to a serial electrical circuit with a signal board. The signaling device is triggered only in the event of a chip closure of all magnetic contacts, excluding the closure of some of them with a single hair-like chip. In this case, despite the complexity of the design of the signaling device, the intensity of the actuation of the magnetic contacts is not recorded.

Known technical solution (RU 2312240) reduces the likelihood of false alarms by using the oil temperature as an additional diagnostic feature that increases the reliability of the alarm. However, the inertia of a significant volume of oil in the oil system does not allow to reveal the timely correlation of signs at the early stages of the destruction of parts, because the running-in period is associated with increased friction in the units and, consequently, an increased oil temperature.

The closest adopted as a prototype is a technical solution implemented in signaling chips of a gas turbine engine TV7-117ST, which includes an electromagnetic chip signaling device and an automatic control and monitoring unit for the engine, which generates a signal "Chips in oil" when triple sequential operation within a certain time interval chip alarm. The disadvantage of this solution is due to the insufficient reliability of the device, which does not allow, due to the use of a deterministic signal processing approach, to cut off false alarms of the chip alarm.

The aim of the invention is to diagnose the incipient destruction of gearbox parts with a given reliability, excluding false alarms not associated with the destruction of parts. The technical result consists in simplifying the design and reducing the likelihood of false triggering of the alarm system by using a non-deterministic approach to the analysis of signals coming from the chip alarm.

The specified technical result is achieved by the fact that according to the invention, the chip-in-oil alarm system contains the "Chips in the signaling device" and "Chips in oil" displays, an electromagnetic chip signaling device, an automatic control and monitoring unit with a device for analyzing signals coming from the electromagnetic chip signaling device connected by signal transmission channels with a board and an electromagnetic chip signaling device, and the signal analysis device processes at least three successively received signals of operation of the electromagnetic chip signaling device, generates the signal "Chips in the signaling device" at the first actuation of the electromagnetic chip signaling device and generates the signal "Chips in oil" when not removed from the register of the signal "Chips in the signaling device" and a decrease in the reliability of diagnosis to the level P <1-α, where α is the given probability of a false alarm.

The functioning of the proposed alarm system is as follows.

When the electrical resistance in the electromagnetic chip detector (CC) falls below the set value R1, the automatic regulation and control unit (BARK) detects this drop and removes power from the CC electromagnet, the CC core is demagnetized and the chips are washed off by the oil flow. After increasing the resistance in the SS above the preset value R2, the BARK again supplies power to the SS electromagnet. If an increase in the SS resistance to a predetermined value R2 does not occur within a predetermined time t _CM , the BARK generates a signal "Chips in the detector" and fixes the time t _i at which the SS resistance dropped. If in a given time interval Δt after the formation of the signal "Chips in the signaling device" there is no next drop in resistance, then the BARK removes this signal from the account. Thus, false alarms of the SS are excluded:

- due to the closure of the contacts by a single hair-like shaving, which is eliminated by washing it off with an oil flow when the CC core is demagnetized;

- associated with a constant frequency of operation (no increase in the rate of chip formation).

Let us consider the operation of the alarm system with a given probability of false alarms α using the example of three successive actuations of the electromagnetic SS at times t ₁ <t ₂ <t ₃ , between which the power supply from the SS electromagnet is removed for a short time so that the oil flow will carry away the adhered particles by cleaning the SS contacts for the next trigger.

The SS is triggered with the accumulation of wear products or destruction of engine parts, which is a relatively rare event characterized by Poisson flow. In this case, the time intervals between events are considered exponentially distributed. Similar signaling devices for shavings of main gearboxes of helicopters have more extensive statistics of operations, during the processing of which the exponential distribution law is reliably identified.

As a criterion for triggering the chip-in-oil alarm device, the ratio

Then the distribution of the random criterion δ is the result of the following theorem.

0≤t<∞ и параметром λ. И пусть составлен вариационный ряд t₁≤t₂≤t₃. Тогда плотность распределения отношения

имеет видTheorem. Let independent random variables t ₁ , t ₂ , t ₃ be equally distributed exponentially with the density

0≤t <∞ and parameter λ. And let the variation series be composed t ₁ ≤t ₂ ≤t ₃ . Then the distribution density of the ratio

has the form

Evidence. The joint distribution density of ordered random variables t ₁ ≤t ₂ ≤t _{3 is} as follows:

Let us introduce the transformation of variables

Inverse transformations

The Jacobian of this transformation is

Then the joint distribution density of random variables δ ₁ , δ ₂ , δ ₃

After integration over the variables δ ₂ , δ ₃ and the transition to the variable δ = δ _{1, the} density takes the form

The theorem is proved.

Normalized distribution function

Formula (8) was verified by the method of statistical tests with the number N = 10 ⁶ .

который показывает, что достигнутый уровень значимости р=0,75 не дает оснований для того, чтобы отвергнуть гипотезу о равномерном распределении случайной величины R.FIG. 1 shows the result of checking the uniformity of the distribution of the random variable

which shows that the achieved level of significance p = 0.75 does not provide grounds for rejecting the hypothesis of a uniform distribution of the random variable R.

In turn, this means that there is also no reason to reject the hypothesis about the distribution of the random variable δ according to the law with density (7). The density (7) is shown in Fig. 2.

Distribution with density (7) belongs to the class of power distributions, a feature of which is independence from the parameter of the initial distribution λ, which characterizes the criterion δ for the exponential law as nonparametric.

The power-law distribution is used to describe non-equilibrium systems prone to catastrophic behavior under certain conditions. These are fast, unstable, multidimensional, and therefore poorly controlled processes.

The function of the analysis device is to control the fulfillment of the inequality P≥1-α. Or taking into account (4) and (8)

Expression (9) was verified by a simulation experiment with the number of realizations N = 10 ⁶ .

As a result of repeated repetition of the experiment, it was found that the relative deviation of the number of simulated false alarms from the given level α does not exceed 0.2%, which indicates the statistical reliability of the proposed alarm device triggering scheme.

Simulation modeling was carried out with the number of tests N = 5000. As a result of several iterations, the relative deviation of the number of signal formations "Chips in oil" from the specified level α averaged 0.2%.

Thus, the proposed device allows, with a given probability of false triggering α, to timely issue a signal on the signaling board about the presence of chips. The choice of the value of α is based on the recommendations of GOST R 51901.12-2007 when analyzing the types and consequences of failures using a criticality matrix.

The algorithm of the analysis device is shown in Fig. 3.

The input signals are the "Start" signal, which starts the timers T ₁ , T ₂ , T ₃ and the signals from the triggered chip alarm.

When the chip alarm is first triggered, a signal X ₁ is generated at the output of the counter-decoder, which stops timer T ₁ and generates the "Chips in the alarm" signal. The value of t ₁ from the output of the timer T _{1 is} fed to the input of the comparison circuit.

At the second triggering of the chip signaling device, a signal X ₂ is generated at the output of the counter-decoder, which stops the timer T ₂ . The value of t ₂ from its output is also fed to the input of the comparison circuit.

When the chip alarm is triggered for the third time, a signal X ₃ is generated at the output of the counter-decoder, which stops the timer T ₃ . The value of t ₃ from its output is also fed to the input of the comparison circuit.

и не снятом с учета сигнале "Стружка в сигнализаторе" формируется сигнал "Стружка в масле".The comparison circuit checks the likelihood of chip formation. With probability

and an unregistered signal "Chips in the signaling device", the signal "Chips in oil" is generated.

Claims (2)

1. A method for signaling chips in oil, including processing at least three successively received signals of operation of the electromagnetic chip signaling device, generating the signal "Chips in the signaling device" at the first actuation of the electromagnetic chip signaling device and generating the signal "Chips in oil" if the signal is not removed from the register " Chips in the signaling device "and a decrease in the diagnostic reliability to the level P <1-α, where α is the given probability of a false alarm. 2. A device for implementing the method according to claim 1, including the display "Chips in the signaling device" and "Chips in oil", the electromagnetic signaling device of the chips and the automatic regulation and control unit connected by means of signal transmission channels with the board and the electromagnetic signaling device of the chips, containing the signal analysis device coming from an electromagnetic chip alarm.

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