DE102015102249A1 - Method and device for determining the power distribution of an internal combustion engine - Google Patents

Abstract

Method for determining the power distribution of an internal combustion engine using the rotational irregularity curve of the crankshaft of the internal combustion engine, characterized in that data belonging to the internal combustion engine for the first time, such as e.g. Masses, spring constants, damping, the firing order of the cylinder and other combustion engine-relevant data are provided in a map in a processing unit and then permanently using the data from the map after the determination of the rotational irregularity curve at the crankshaft, a conversion into the acceleration curve at the measuring point takes place, the acceleration profile of an order analysis is subjected to a calculation of the alternating components of the total torque based on the order analysis is done by the ignition sequence, an assignment of the alternating components to the cylinder and thus determines the percentage power components at a certain speed via a system of equations for the cylinder.

Description

 The invention relates to a method for determining the power distribution of an internal combustion engine. In addition, the invention relates to a device with which the method can be performed.

Presentation of the invention

Due to the increasing demands on internal combustion engines in terms of economy, ecology and safety, the requirements for the operation management of the machines are also increasing. In particular, compliance with the operating parameters specified by the manufacturer and thus the timely detection of deviations from normal operation are becoming increasingly important. Particularly important in this context is the even distribution of the cylinder output. Deviations lead here to increased fuel consumption, to increase pollutant emissions and to an increased load on the components of the internal combustion engine.

The determination of the power distribution of internal combustion engines is usually via the measurement of the cylinder pressure curve of the individual cylinders of the engine and the subsequent calculation of the indicated cylinder power. In the in the DE 10 2010 051 370 A1 disclosed method for determining the indicated torque of an internal combustion engine is used on a cylinder pressure of the guide cylinder to determine the torque of the other cylinders from the measured speed profile. This requires relatively expensive measuring and evaluation technology. Precisely because of this, the advantage offered by the measurement and evaluation of the rotational nonuniformity with its simple and inexpensive measurement and evaluation technology is canceled out. Since many engines no longer have the ability to measure pressure, this method is only partially usable in practice.

Also in the patent DE 10 2006 053 255 B3 A method for determining the internal cylinder pressure of an internal combustion engine from the rotational irregularity curve is presented. In this case, the cylinder internal pressure is determined via an adaptive method, but not the power distribution of the cylinders. For the method, a relatively accurate and therefore expensive internal process model is required, of which a large number of model parameters of the engine must be known. These parameters are often not available in practice. Furthermore, the consideration of an elastic torsional vibration system is dispensed with in the presented method. Thus, this method can only be used on smaller engines with a relatively rigid torsional vibration system. In large diesel engines with elastic torsional vibration systems, this method is too imprecise in practice.

 An assessment of the power distribution using the measured exhaust gas temperatures is very inaccurate. Since the exhaust gas temperature of a cylinder is also heavily dependent on the ignition point in addition to the cylinder output, causing premature or spark ignitions strong distortions of the result.

 Due to the development of sensors and microcontrollers that has been driven forward in recent years, it is possible to measure the rotational irregularity profile on the crankshaft of an internal combustion engine with simple and inexpensive systems. With this measurement, a speed curve is recorded over a cycle of the internal combustion engine. This speed curve is the result of the torques introduced by the individual cylinders. Considering the crankshaft of the internal combustion engine as a rigid system, so caused by the moments angular acceleration and thus the angular velocity at each point of the crankshaft is the same.

 In practice, however, the crankshaft is to be regarded as an elastic system with masses, spring constants and damping. Therefore, the angular velocity measured at one location of the crankshaft is not identical at all locations of the crankshaft. An accurate recalculation of the torques of the individual cylinders with only one measuring point is not directly possible due to the complexity of the torsional vibration systems of multi-cylinder engines.

By way of example several fonts may be mentioned. Such is in the published patent application DE 10 2009 049 544 A1 a method for detecting misfiring in internal combustion engines on the basis of the measurement of rotational irregularity at the crankshaft described. In this method, only the malfunction of a cylinder is evaluated. A determination of the distribution of the power of the cylinder does not take place. In the procedure, further readings, eg from the lambda probe, are required for validation.

In the patent document: DE 41 22 139 C2 described method, the measurement of rotational nonuniformity is used to adjust the injected fuel quantities for optimum concentricity of the engine. A determination of the power distribution is waived. It is an adaptive method to minimize the uneven running, in which only individual sections of the rotational irregularity course are used.

In Scripture DE 10 2006 003 264 A1 A method is presented with which the output from the internal combustion engine torque is determined by measuring the rotational irregularity. In this method, especially the influence of external moments is considered. A determination of the power distribution of the engine is not made here.

 The object of the invention is therefore to provide a method with which the power distribution of internal combustion engines can be determined more accurately and more cost-effectively. In addition, it is an object to provide a device with which the method can be carried out.

 The first object is achieved by the method according to claim 1. The subclaims 2 to 4 represent additional method steps. The second object is solved by the independent claim 5, wherein the subclaims contain 6 to 8 improvements of the device.

 To solve the method, the rotational irregularity curve of the crankshaft is recorded on the internal combustion engine with a suitable measuring device via a working cycle. This measured rotational irregularity curve is converted into the acceleration curve at the measuring point. With the help of an order analysis, the Fourier orders of the acceleration curve are determined. Then, the calculation of the torque curve, for which it is assumed that the individual vibration orders are changed by the torsional vibration system by speed-dependent factors in the amount and by speed-dependent phase rotations in the phase angle. Using these factors and phase angle, the measured acceleration curve can be recalculated into a "rigid crankshaft" acceleration curve, which corresponds to the total torque curve for all cylinders. The speed-dependent factors and phase angle can be determined in advance, for example, by means of torsional vibration calculations and stored in a map. Interpolation methods can be used to determine the parameters required for retroactive accounting for the measured speed.

 By multiplying the recalculated acceleration curve with the mass moment of inertia of the rotating masses, one obtains the alternating parts of the total torque. The mean torque required to determine the total torque must be determined directly from the measurement. For this purpose, various options can be used. For engines with small numbers of cylinders, the amplitude of the first main harmonics may be a measure of the mean torque. For engines with larger numbers of cylinders, the average torque can be determined from direct or indirect measurements and maps.

 From the alternating parts and the average torque, the total torque can be calculated. This total torque is the sum of all introduced at the crankshaft of the internal combustion engine torques. These are essentially the cylinder torques generated by the combustion of the individual cylinders and introduced via the crank drive.

 To determine the power distribution of the internal combustion engine, the cylinder torques must be extracted from the total torque of the crankshaft. For this purpose, it is assumed that the total torque is the sum of the cylinder torques and that the cylinder torques introduced at the crankshaft have a similar course. Since the sum of the compression and expansion work and the sum of the oscillating moments over a working cycle is zero, this course can be considered without compression / expansion work and without oscillating moments of the pistons. This leaves the pure power component of the cylinder.

 In order to determine the proportions of the individual cylinders in the course of the total torque of the internal combustion engine, divided into individual surface sections. The upper dead centers of the cylinders form the boundaries of the individual surfaces. Furthermore, the torque curve of the cylinder is divided into areas with the same limits as the total moment. During the course of the cylinder torque, the proportion of each surface section on the cylinder moment, the total surface of the course, can then be determined.

The area of a section of the overall torque curve is obtained by the sum of the area proportions of the cylinders formed in accordance with the firing order of the internal combustion engine. On this basis, an equation system can be set up, with which the proportions of the cylinders can be calculated on the total torque of the internal combustion engine.

 By normalizing the calculated cylinder components, the power distribution of the internal combustion engine can then be calculated. With accurate determination of the mean torque, it is also possible to calculate the cylinder power.

embodiment

For the determination of the power distribution, the rotational nonuniformity course for a working cycle is to be measured at a suitable point of the crankshaft of the internal combustion engine. From the measured data, the acceleration curve at the measuring point must then be calculated.

 Since the crank mechanism of internal combustion engines is not a rigid system, the overall torque curve can not be calculated directly from the measured acceleration profile. Before that, the changes due to the torsional vibration system have to be calculated back. For this purpose, it is assumed that the individual oscillation orders are changed by a factor in magnitude and by an angle in the phase position. Furthermore, it is assumed that the factor and the phase offset are speed-dependent.

 This allows a speed-dependent factor and a speed-dependent phase angle can be determined for each vibration order with a back calculation on the acceleration curve of the "rigid crankshaft" is possible. For this purpose, the vibration orders of the measured acceleration curve are calculated by means of an order analysis.

M_t

Drehmoment

Θ

Massenträgheitsmoment

α

Winkelbeschleunigung

n

Drehzahl

k_i(n)

drehzahlabhängiger Faktor (i-te Schwingungsordnung)

∆φ_i(n)

drehzahlabhängiger Phasenwinkel (i-te Schwingungsordnung)

Pa_z

Leistungsanteil des Zylinders z

za_b

Flächenanteil Bereich b des Zylinderdrehmomentes

MA_b

Flächenanteil Bereich b des Gesamtdrehmomentes

Pn_z

normierter Leistungsanteil des Zylinder z an der Gesamtleistung in %

The following mathematical explanations can be based on the following formula list:

M _t

torque

Θ

Moment of inertia

α

angular acceleration

n

rotation speed

k _i (n)

speed-dependent factor (ith order of oscillation)

Δφ _i (n)

speed-dependent phase angle (ith order of vibration)

Pa _z

Power share of the cylinder z

za _b

Area ratio range b of the cylinder torque

MA _b

Area ratio area b of the total torque

Pn _z

normalized power component of the cylinder z to the total power in%

With the help of the relationship M _t = Θ · α (1) can be calculated from the angular acceleration, the total torque.

The orders of the total torque are determined according to the following correction equations: | M _ti | = K _i (n) · Θ · | α _i | (2a) γ (M _ti ) = γ (α _i ) + Δφ _i (n) (2b)

 From the individual orders of the moment and the average torque, the total moment characteristic of the internal combustion engine can be calculated with the aid of a Fourier synthesis.

The factors and the phase angles can be determined by means of torsional vibration calculations or through tests and can be used via maps in the calculation of the torque. Furthermore, the determination of the factors and phase angle via torsional vibration calculations is also possible at runtime. The mean torque can be from a direct torque or power measurement or from an indirect determination of suitable maps, such as turbocharger speed, exhaust gas temperatures, charge air pressure, etc., take place. For engines with a few cylinders, the average torque can also be determined from the alternating parts of the Momemtenverlaufes. For this purpose, the amplitude of the first main harmonics can be used.

 The calculated total torque curve is the sum of the individual torques introduced by the cylinders via the crank drive. In order to determine the power distribution, the proportions of the individual moments in the overall torque curve must be determined.

For this purpose, it is divided overall moment course in area proportions, which are limited by the top dead centers of the individual cylinders. The area of the torque curve in each interval is formed by the sum of the partial areas of the individual moments of the cylinders in the same crank angle interval. Since the moment of the compression, the expansion and the oscillating moment in the sum are zero, only the torque from the overpressure component, ie without compression, expansion and oscillating masses, is used in the determination of the partial surfaces of the cylinder torque ( 2 ). Thus, the area of this course is a direct measure of cylinder performance.

 From the area proportions and the partial areas of the individual moments of the cylinder, a system of equations can be set up, taking into account the firing sequence, with the aid of which the proportions of the cylinders can be calculated on the total moment.

The following system shows an example of an engine with the firing order 1-3-5-6-4-2: za ₁ · Pa ₁ + za ₂ · Pa ₂ + za ₆ · Pa ₃ + za ₃ · Pa ₄ + za ₅ · Pa ₅ + za ₄ Pa ₆ = MA ₁ za ₂ · Pa ₁ + za ₃ · Pa ₂ + za ₁ · Pa ₃ + za ₄ · Pa ₄ + za ₆ · Pa ₅ + za ₅ Pa ₆ = MA ₂ za ₃ · Pa ₁ + za ₄ · Pa ₂ + za ₂ · Pa ₃ + za ₅ · Pa ₄ + za ₁ · Pa ₅ + za ₆ Pa ₆ = MA ₃ za ₄ · Pa ₁ + za ₅ · Pa ₂ + za ₃ · Pa ₃ + za ₆ · Pa ₄ + za ₂ · Pa ₅ + za ₁ Pa ₆ = MA ₄ za ₅ · Pa ₁ + za ₆ · Pa ₂ + za ₄ · Pa ₃ + za ₁ · Pa ₄ + za ₃ · Pa ₅ + za ₂ Pa ₆ = MA ₅ za ₆ · Pa ₁ + za ₁ · Pa ₂ + za ₅ · Pa ₃ + za ₂ · Pa ₄ + za ₄ · Pa ₅ + za ₃ Pa ₆ = MA ₆

With the solution of the equation system, the proportions Pa _{i of} the cylinders can be calculated on the total torque of the internal combustion engine.

The percentage of a cylinder's percentage of total momentum can then be calculated using the following equation:

 If the performance or average torque of the engine is measured sufficiently accurately, the cylinder power of each cylinder can be calculated in addition to the power shares of the cylinders.

 The device according to the invention is characterized by a rotary encoder mounted at a position of the crankshaft of an internal combustion engine, with which the relative proportions of the cylinder outputs to the total output and the power distribution of the internal combustion engine can be determined from the measured rotational irregularity profile via the multistage method described. This allows a quick and reliable evaluation of the power distribution and thus of the engine setting by the operator. In particular, malfunctions in the injection system of diesel engines can be recognized quickly and reliably.

Embodiment of the device according to the invention

The invention will be explained in more detail with reference to drawings. Show

1 an internal combustion engine according to the invention, with the individual components of the torsional vibration system

2 : the measured torsional vibration course (dashed line) and the calculated total torque curve (solid line) in a diagram and

3 : a diagram of the torque curve of a cylinder with compression, expansion and oscillating moment (dashed) and moment produced by the combustion (solid).

In the 1 illustrated internal combustion engine comprises a crankshaft 1 , with the cylinder 2 in operative connection. Next to it are on the crankshaft 1 a flywheel 3 and a vibration damper 4 arranged. In addition, the internal combustion engine in the embodiment has a buyer of the generated force, a ship's propeller 9 , The data required for the procedure, for example, by encoders 5 , a power measurement system 6 , An institution 7 for measuring zero crossings and angular passages or a shaft power measuring system 8th levied. In addition, a cylinder pressure measuring device 10 be provided. The data determined at the different locations become a processing unit 11 fed, are stored in the parameters and one or more maps with eg basic data about the internal combustion engine.

The determined data are used to calculate the overall moment course. This can be done as in 2 shown, the torque over the crank angle over the angular acceleration are measured. It turns out that the measured moment, in 2 shown in phantom, a different course shows than the corrected torque for the "rigid crankshaft", shown in solid lines, has. The correction is in the processing unit 11 carried out according to the described method.

In the further course of the procedure then the in 2 shown corrected total moment course divided into areas and distributed proportionally to the individual cylinders. Then the proportions of the cylinder powers are calculated via the equation system described 3 calculated.

As the foregoing embodiments described in detail are exemplary embodiments, they may be modified in a conventional manner to a wide extent by those skilled in the art without departing from the scope of the invention. In particular, the concrete embodiments of 1 in a different form than that described here. Likewise, the [0038] can be configured in another form, if this is necessary for space reasons or designerischen reasons. Further, the use of the indefinite article "on" does not preclude that the features in question may also be duplicated.

LIST OF REFERENCE NUMBERS

1

crankshaft

2

cylinder

3

flywheel

4

vibration

5

encoder

6

Power Meter

7

Facility

8th

Shaft power measurement system

9

ship propellers

10

 Cylinder pressure measuring device

11

 processing unit

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010051370 A1 [0003]
• DE 102006053255 B3 [0004]
• DE 102009049544 A1 [0008]
• DE 4122139 C2 [0009]
• DE 102006003264 A1 [0010]

Claims (8)

Method for determining the power distribution of an internal combustion engine using the rotational irregularity curve of the crankshaft ( 1 ) of the internal combustion engine, wherein the internal combustion engine is a measuring element and a processing unit ( 11 ) and in the method after the determination of the rotational irregularity pattern on the crankshaft with the aid of the measuring element and determination of the average torque, a calculation of the total torque is made, and the relative or absolute power proportions of the cylinder are determined, characterized in that prior to the first execution of the method data relating to the internal combustion engine, such as masses, spring constants, damping, the firing order of the cylinders ( 2 ) and other engine-related data in a map in the processing unit ( 11 ) and then permanently using the data from the map after the determination of the rotational irregularity curve on the crankshaft ( 2 ) a conversion into the course of the acceleration takes place at the measuring point, the acceleration curve is subjected to an order analysis, a calculation of the alternating parts of the total torque takes place on the basis of the order analysis, by the ignition sequence an assignment of the alternating parts to the cylinders ( 2 ) and so the percentage of power at a certain speed for the cylinder ( 2 ) are determined via a system of equations. Method for determining the power distribution of an internal combustion engine according to claim 1, characterized in that the factors required for conversion into the acceleration curve and phase angle for the "rigid wave" by tests or by torsional vibration calculations previously determined or permanently provided by rotary vibration calculations at runtime. Method for determining the power distribution of an internal combustion engine according to one of the preceding claims, characterized in that the mean torque is determined by direct or indirect measurements with a shaft power measuring system ( 8th ), a power measurement system ( 6 ) or cylinder pressure measuring system ( 10 ) is detected. Method Determining the power distribution of an internal combustion engine according to one of the preceding claims, characterized in that the mean torque is determined by determining the amplitude levels of the acceleration curve or the torque curve of the individual cylinder ( 2 ) is determined. Device for carrying out the method according to claim 1 for determining the power distribution in internal combustion engines, characterized in that the internal combustion engine at a suitable position of the crankshaft, a component for determining the rotational nonuniformity and a processing unit ( 11 ), wherein the processing unit ( 11 ) is in electrical connection with the element for determining rotational nonuniformity. Device for determining the power distribution of internal combustion engines according to claim 5, characterized in that the processing unit ( 11 ) carries out the methods of claim 1 to 5 and thus to provide the power distribution of the internal combustion engine. Device for determining the power distribution of internal combustion engines according to claim 5, characterized in that the element for determining the rotational identity is an encoder ( 5 ) on the crankshaft ( 1 ) or on the sheep roll. Device for determining the power distribution of internal combustion engines according to claim 5, characterized in that the element for determining the rotational nonuniformity comprises an element for marking a zero point and for marking a discrete number of angles of an angular graduation and a device ( 7 ) for measuring the zero point crossing and all angular passages.

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