KR100292876B1 - Method for measuring moment of rotating inertia in engine - Google Patents

Abstract

PURPOSE: A measuring method of a moment of a rotating inertia for an engine is provided to contribute to studies about the moving characteristic, the power efficiency and the vibrating direction of the engine by measuring the moment of the rotating inertia. CONSTITUTION: An IMEP(Indicated Mean Effective Pressure) and a sum are detected through a piezoelectric sensor in a plug. A BMEP(Brake Mean Effective Pressure) is detected through a dynamometer. A correlation between the IMEP and the BMEP is set by calculating an inclination and a coefficient between the IMEP and the BMEP. A braking torque is calculated by calculating the sum of the IMEP in an idle status of an engine(10). A moment of a rotating inertia of the engine is calculated based on the calculated value and the inertia of the engine. The moments of the rotating inertia are compared and analyzed by accelerating the engine in the idle status based on the calculated moment and measuring the moment per RPM. Thereby, errors are reduced and the characteristic of the engine is found out easily.

Description

How to measure the moment of rotational inertia of an engine

The present invention relates to a method of measuring the rotational moment of inertia of an engine, and in detail, by measuring the cylinder pressure and the speed of the engine without disassembling the engine, it is possible to experimentally measure the rotational moment of inertia of the engine. It relates to a measuring method.

In general, the rotational moment of inertia of the engine is a result of the torque of the engine generated by the pressure of the cylinder, which is calculated through a constant relationship from the average pressure of the cylinder measured by the crank angle.

In addition, the average pressure of the cylinder is divided into the city average pressure (IMEP), the pumping average pressure (PMEP), the braking average pressure (BMEP), and the friction average pressure (FMEP). Can be calculated.

In addition, a spark plug type piezoelectric sensor, which is generally used to measure the pressure of the cylinder, is attached to the spark plug to be coupled to the engine with the spark plug to measure the pressure in the engine cylinder.

In addition, a braking average pressure can be measured from dynamo meta.

However, to obtain the pumping average pressure for each cylinder of the engine, a pressure curve of the intake and exhaust process is required, and the spark plug type piezoelectric sensor prevents obtaining reliable values due to the low resolution in the low pressure region and the temperature difference between the piezoelectric sensors. In a real vehicle situation, no suitable way to measure the average friction pressure of the engine was found.

Therefore, conventionally, a systematic research method for obtaining the rotational moment of inertia of the engine has not been proposed due to the above problems. In some cases, the rotational moment of inertia is calculated by numerical calculation according to the drawings, but the calculation method is complicated and As a result, a large error was generated and various difficulties were found in related fields because the obtained results were not sufficiently verified.

That is, in the related art, a systematic research and measurement method for obtaining the rotational moment of inertia of an engine from a real vehicle has not been presented, and the rotational moment of inertia of an engine calculated from the drawings is complicated and does not sufficiently verify the results obtained. There was a problem that caused difficulties in the field of research.

Accordingly, the present invention has been made in order to solve the above problems, by presenting a method for measuring the rotational inertia moment of the engine according to various measurement criteria from the actual vehicle, as well as in the related fields as well as the dynamic characteristics of the engine and The purpose is to provide a method of measuring the moment of rotational inertia of an engine that can significantly contribute to the study of power performance and vibration direction.

1 is a test state diagram showing the test equipment and configuration to which the present invention is applied.

2 is a graph and a relation showing the relationship between the average pressure and the braking average pressure as a precondition for measuring the rotational moment of inertia of the present invention.

3 is a graph and a relational diagram showing the average city pressure according to the engine speed when the engine is idle according to the present invention.

Figure 4 is a graph showing the comparison between the results and theoretical values measured mass moment of inertia by the present invention.

** Explanation of Signs of Major Parts of Drawings **

10: engine 20: E.C.U.

30: charge amplifier 40: transmission

50: CP senser (of ring gear)

60: Data Acquisition (DSP) 70: Computer (PC)

80: wheel speed meta 90: operation circuit (DVIDING CIRCUIT)

100: Wheel

Accordingly, the present invention is to measure and calculate the various average pressure of the cylinder from the measurement equipment and equipment configured as shown in Figure 1 to measure the rotational moment of inertia of the engine, but through the piezoelectric sensor attached to the plug shown in the average And a preliminary step of studying the correlation between the city average pressure and the braking mean pressure by detecting the sum and detecting the braking average pressure through the dynameta and calculating the slope and the constant through the respective relational expressions. A braking torque calculation step of detecting a sum of city average pressures in an unloaded state, i.e., in an unloaded state without an engine, and calculating a braking torque based on a result and a relational expression; The transient and transient transmission of torque generated by the results obtained in the calculation step and the combustion pressure Calculating the rotational moment of inertia based on the inertia of the engine involved in the calculation and calculating the rotational moment of inertia through the relation, and accelerating the engine under no load based on the analyzed moment of inertia for each revolution It is characterized in that it comprises a comparison / analysis step of measuring the rotational moment of inertia of the engine and comparing and analyzing it by calculating the theoretical rotational moment of inertia through a relationship.

When described step by step with reference to the drawings illustrating a method of the present invention for achieving the above object is as follows.

Figure 1 of the illustrated drawings is a test state diagram showing the test equipment and configuration to which the present invention is applied, Figure 2 is a prerequisite for measuring the rotational moment of inertia of the present invention to test the relationship between the average pressure and the average braking pressure Fig. 3 shows a graph prepared from the results and a corresponding relation, and Fig. 3 is fitted by a fifth order based on the test results and results of the city average pressure according to the engine speed obtained at idle (no load) of the engine according to the present invention. Figure 4 is a graph and corresponding relations, Figure 4 is a graph showing the comparison between the theoretical value and the result of measuring the mass moment of inertia by the present invention.

That is, the present invention is to measure and calculate the various average pressure of the engine cylinder for the actual vehicle from the measurement equipment and equipment configured as shown in FIG. 1 to measure the rotational moment of inertia of the engine, attached to the plug as a precondition The average piezoelectric sensor is used to detect the average urban pressure and its sum, the average brake pressure is detected through the dynamometer, and the slope and the constant are calculated from each detected result and various relations. It has a premise stage to study the correlation of braking mean pressure.

The indicated mean effective presser (IMEP) and break mean effective presser (BMEP) detected in the preliminary step are specified in terms of their slopes and constants by the following relationship.

BMEP = atIMEPgross-b

b = atIMEPgross.idle

BMEP = at (IMEPgross-IMEPgross.idle)

Therefore, it can be seen that in the real vehicle state, the constant b increases but the slope a will not change than illustrated in FIG. 2, and specifying a no-load IMEP_gross (i.e., BMEP = 0) gives a larger constant b than in the target as in the second equation The braking torque of the engine can be calculated by the third equation.

Also, a braking torque calculation step of detecting the sum of the average city pressures in the no-load state, i.e., the state where there is no load on the engine, based on the result analyzed in the preliminary step, and calculating the braking torque through the obtained result and the relational expression Have

The braking torque calculation step is to measure the sum of the average city pressure in the no-load state, the no-load state can be easily made by stepping on the clutch only, the engine speed is adjusted by the accelerator pedal, the measurement is made when the engine speed is kept constant The results can be obtained as shown in Fig. 3, where the points of each data are the average values of 50 cycles, and the solid line is fitted by the fifth order from the obtained results, The sum is calculated as a function of engine speed, and the braking average pressure can be found by substituting this value and the slope of the fitted equation in Fig. 2, the test result, in the third equation.

When the braking average pressure is obtained from the third equation, the brake torque of the engine can be calculated by the following equation (2).

MEP (kPa) = 6.28nRT (Nm) / Vd (dm3)

In addition, the rotation based on the result obtained in the preliminary step and the braking torque calculation step, the torque transfer process generated by the combustion pressure, and the inertia of the engine involved in the transient state, and calculating the rotational inertia moment of the engine through the relational expression. Has a step of calculating the moment of inertia.

The calculation step of the rotational moment of inertia will be described in detail as follows.

When the torque is transmitted from the manual vehicle to the clutch, the torque generated by the cylinder combustion pressure is released by some friction in the normal state, and the torque is transmitted to the clutch. In transient state, this is the inertia of the engine. If this is expressed as an expression, it is as follows.

Tbrake-IEta = Tclutch

T _brake : Engine braking torque I _E : Engine moment of inertia

a: _Angular acceleration of the engine T _clutch : Torque transmitted to the clutch

Since no torque is transmitted when the clutch pedal is pressed, the right inertia of the above equation becomes 0, so that only the braking torque and the angular acceleration of the engine can be known to calculate the rotational moment of inertia of the engine. Since the engine torque obtained in Equation 2 is a cycle average value, the inertia of the engine can be obtained every cycle by reconfiguring the above equation into the following equation and the energy equation.

IE = 2t4 π tTi, brake / (O1.22-O1.12)

BMEPi = 1.08t (IMEPi, 1gross + IMEPi, 2gross + IMEPi, 3gross + IMEPi, 4gross-4tIMEPgross, idle)

T _{i, brake} : Cycle average engine braking torque Ω ₁ , Ω ₂ : Engine speed at the beginning and end of the cycle

IMEP _{i, k_gross} : GROSS IMEP of cylinder K

In addition, a comparison / analysis step of measuring the rotational inertia moment of each engine by the number of revolutions based on the analyzed rotational moment of inertia and accelerating the engine under no load, and comparing and analyzing the theoretical moment of inertia by calculating a theoretical rotational moment of inertia through a relational equation. Has

This can be obtained by measuring and calculating the values shown in FIG. 4 by performing the measurement while accelerating the engine (pressing the accelerator pedal) while pressing the clutch as in the previous step. Figure in each cycle due to an error on the measurement of the moment of inertia variation can be seen, and showed the error of ± 2% compared to the average mean is 0.175kg.m ^2.

Therefore, the rotational moment of inertia of the engine can be measured using the method of the present invention, so that the measured values can be used in various studies to study the dynamic characteristics and power performance of the engine, and to distinguish the engine's front and rear vibration directions. You can do it.

As described above, the method of measuring the rotational inertia moment of the engine according to the present invention can reduce the error than the conventional rotational inertia moment calculated through the drawings, and the calculation method and the process are processed to facilitate the tester, and the theoretical values and the results of the test. Being able to compare the values graphically makes it easy to identify the various characteristics of the engine from various angles, contributing to your engine research.

Claims (1)

The urban average pressure and the braking average are detected by detecting the average urban pressure and its sum through a piezoelectric sensor attached to the plug, and the braking average pressure through the dynamometer, and calculating the slope and constant through the respective relations. Preliminary steps to correlate pressure, A braking torque calculation step of detecting a sum of city average pressures in an unloaded state, i.e., in an idle state with no load on the engine, and calculating braking torque based on a result and a relational expression, based on the result analyzed in the preliminary step; Rotational inertia moment based on the results obtained in the preliminary step and the braking torque calculation step, the torque transfer process generated by the combustion pressure, and the inertia of the engine involved in the transient state, and the rotational inertia moment of the engine is calculated through the relation With the calculation step, Based on the analyzed moment of inertia and by accelerating the engine under no load, the moment of inertia is measured at each rotational speed and the comparison / analysis step of comparing and analyzing the theoretical moment of inertia by calculating the relation is included. Method of measuring the moment of rotation inertia of the engine, characterized in that.

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