EP0254005B1 - Method for the improvement of the regularity with a piston engine and engine running according to this method - Google Patents

Description

The present invention relates to a method for improving the synchronism with a three- or multi-cylinder reciprocating piston internal combustion engine in the stationary operating state, in which the indicated mean pressure of at least one cylinder is changed, and to a reciprocating piston internal combustion engine for practicing the method.

The control and monitoring of the synchronism of such reciprocating internal combustion engines, such as, for example, diesel engines, has hitherto been carried out by monitoring the speed of the output shaft or the shaft of a machine driven by the engine. The regulation itself is carried out by changing the injection quantity of all injection pumps, which are connected to the individual cylinders in a certain cycle.

This known type of control takes into account and regulates the constancy of the speed in the sense that with the change in the injection quantity, this is changed in the same way for all cylinders if it is assumed that the injection quantity in each cylinder is the same. The publication C33 / 85 of the Institution of Mechanical Engineers Conference 1985-2, page 15-24, (Mechanical Engineering Publications Limited, London) shows with the article "Vehicle Condition Monitoring and Fault Diagnosis" a measurement model and the possibility to detect a failed cylinder multi-cylinder diesel engine in the steady state of a crankshaft deal. Speed fluctuations are observed using Fourier analysis.

Another type of speed control is described in EP-A 0 113510 in that the speed deviation or the time difference for a predetermined rotation angle interval is measured on the motor shaft based on an average operating speed, this speed deviation is cyclically allocated to a specific cylinder with the firing sequence and in the opposite way A control system acts on the deviation of the speed on the injection time and thus the injection quantity on the allocated cylinders, in order to achieve an equally large speed fluctuation over all rotation angle intervals measured on the engine shaft.

Such regulations hardly take into account the torsional vibrations of the shaft system involved and their effects on the driven units, which are therefore not taken into account in the previously known speed control.

There are cases where this type of control is not sufficient and in which the speed differences resulting from torsional vibrations of the shafts or changes in the angular velocity resulting therefrom can be disruptive within one revolution. For example, this uneven running caused by torsional vibrations in diesel-powered electrical machines, such as generators, can have a disruptive effect. In systems of this type, which are driven with slow-running two-stroke diesel engines (e.g. 80 to 120 / min), the excitation frequency for torsional vibrations of the first and second order of the shaft (single or double rotational frequency) is in many cases close to the electrical natural frequency of the generator . The case may arise that the amplitudes of the torsional vibrations of these orders are dynamically increased several times, with the mechanical shaft system as a whole vibrating against the rigid interconnected network in combined operation, which can lead, for example, to power fluctuations. In an independent network (stand-alone operation), this can result in flickering light. The invention provides a remedy here and ensures that the reciprocating piston internal combustion engine has a significantly improved synchronism behavior in this respect. According to the invention, such a method for improving the synchronism of a three- or multi-cylinder reciprocating piston internal combustion engine is characterized in that the torsional vibrations of at least one order of the drive shaft system are minimized by:

in a first method step, the torsional vibrations on the drive shaft or on a shaft kinematically connected to the drive shaft are measured with a torsional vibration measuring device,

in a second process step, the measured torsional vibrations are subjected to a Fourier analysis for torsional vibrations,

in a third method step in a computer, correction factors for the change in the indicated mean cylinder pressure of at least two cylinders are determined from the determined amounts and phase positions of the torsional vibration amplitudes and from the comparison with predetermined torsional vibrations caused by the individual cylinders,

in a fourth method step, the correction factors cause a change in the injection quantity per injection process of the injection pump in at least one of these two cylinders.

The invention further relates to a reciprocating piston internal combustion engine according to claim 5 for carrying out the method and advantageous special embodiments of the method and the reciprocating piston internal combustion engine.

• Fig. 1 schematisch einen sechszylindrigen Dieselmotor mit Generator und erfindungsgemässer Anlage für die Verbesserung des Gleichlaufs des Dieselmotors;
• Fig. 2, 2A, 2B, 2C je schematisch einen sechszylindigen Schiffsdieselmotor mit nebengeschaltetem Bordnetz-Generator und erfindungsgemisser Anlage für die Verbesserung des Gleichlaufs des Dieselmotors;
• Fig. 3 das Poldiagramm der Torsionsschwingungen erster Ordnung der Welle eines Sechszylinder-Dieselmotors bzw. einer vom Dieselmotor angetriebenen Welle.

The invention is explained in more detail using the example of the drawings. Show it:

• Figure 1 shows schematically a six-cylinder diesel engine with generator and system according to the invention for improving the synchronism of the diesel engine.
• 2, 2A, 2B, 2C each schematically show a six-cylinder marine diesel engine with a connected on-board electrical system generator and a system according to the invention for improving the synchronism of the diesel engine;
• 3 shows the pole diagram of the torsional vibrations of the first order of the shaft of a six-cylinder diesel engine or of a shaft driven by the diesel engine.

The six-cylinder two-stroke diesel engine 1 with turbocharger 11 and with the shaft 12 drives a generator 2, the rotor of the generator, such as drawn, mounted directly on the extension of the shaft 12 or the rotor shaft can be coupled to the shaft 12 of the diesel engine 1. The torsional vibrations or their amplitudes and angular position are continuously measured with the torsional vibration meter 3 at the shaft end 123 and fed to the Fourier analyzer 4. In the Fourier analyzer 4, the Fourier decomposition of the torsional vibrations into members of different orders is carried out.

• 1. welcher oder welche der Zylinder 161, 162, 163, 164, 165, 166 die Anregung der Torsionsschwingungen dieser Ordnung verursachen und
• 2. welche Korrektur der Einspritzmenge in welchen Zylindem erforderlich ist, um die Torsionsschwingungen dieser Ordnung zu minimieren.

For the time being, the injection pumps 61, 62, 63, 64, 65, 66, each of which is assigned to a cylinder 161, 162, 163, 164, 165, 166, inject predetermined, equal amounts of fuel into the cylinders. As soon as the diesel engine has reached the steady-state operating state, the switch 45 is closed and the Fourier signals from the Fourier analyzer now arrive at the injection pump control 5, which comprises a computer which, for example, uses the first and second order terms based on, for example, the crank star method 3 and is determined by comparison with a target state:

• 1. Which or which of the cylinders 161, 162, 163, 164, 165, 166 cause the excitation of the torsional vibrations of this order and
• 2. Which correction of the injection quantity in which cylinders is required in order to minimize the torsional vibrations of this order.

Since the cranking method is a simple approximation method, for example, the torsional vibrations are minimized iteratively, i.e. in several cycles or steps. Correction signals are generated at each step and are supplied to the relevant injection pumps 61, 62, 63, 64, 65, 66. Due to the corrections, a new steady state is established in the course of the diesel engine 1. After this has been reached, the torsional vibrations are measured and analyzed again in a further control cycle, and other correction signals are generated on the basis of the analysis results and the torsional vibrations are further minimized.

As a rule, a favorable steady-state operating condition with minimal torsional vibrations that are no longer disruptive, e.g. First and second order of the shaft 12 or higher orders achieved after a few control cycles of the type described.

The control cycle advantageously extends over the time of several working cycles (revolutions) of the diesel engine 1. This ensures that the stochastic changes in the indicated cylinder mean pressure from ignition to ignition of the individual cylinders 161, 162, 163, 164, 165, 166 are the ones to be evaluated Only negligibly affect the torsional vibration signal.

For the detection of the torsional vibrations e.g. a device available on the market under the name angle encoder (optical incremental encoder, type G 70 from Litton). An injection pump that is suitable for changing the injection quantity is e.g. described in DE-OS 31 00 725.2-13. Fourier analyzers are also known and commercially available (e.g. CAT 2515 from Genrad).

The two-stroke diesel engine 1 from FIG. 2 with the six cylinders 161 to 166 drives the marine propeller 7 via the shaft 22. The other end of the crankshaft 22 of the diesel engine is connected via a clutch 18 to a transmission gear 8, which drives a hydraulic pump 81 . This pump 81 is part of a hydrostatic transmission which, together with the hydrostatic motor 82, forms a closed hydraulic pressure medium circuit. The supply of this circuit with hydrostatic pressure medium, e.g. Oil is carried out by the low pressure station 83, which contains a pressure medium reservoir, a feed pump, an overflow line with an overflow valve, filter, etc. The hydrostatic motor 82 drives the electric generator 9 via a shaft 89. The speed of the shaft 89 and thus of the generator 9 is monitored by the sensor 84, from which the measured actual value is fed to the speed controller 85 and in which the actual value is also included the specified target value is compared. The generator delivers the electrical energy to the vehicle electrical system 100. In the event of deviations from the actual and target values, the quantity of pressure medium flowing through the hydrostatic motor 82 is prevented by the control signals being fed via the signal line 86 to an actuator in the motor 82. In this example, the torsional vibration meter 3 measures the torsional vibrations of the shaft of the generator 9. The determination of the correction signals which are fed to the injection pumps 61, 62, 63, 64, 65, 66 are carried out in the same way as for the system from FIG. 1 described, determined. The torsional vibrations generated by the diesel engine 1 are partially transmitted to the engine 82 and the shaft of the generator via the hydrostatic circuit.

2A, the shaft 17 drives the diesel engine 1 via the coupling 71 and shaft 73 the adjustable ship propeller 72. The shaft 17 of the diesel engine 1 on the other side of the diesel engine drives the generator 9 via a transmission 91, which outputs the electrical current to the electrical system 100. The torsional vibrations or their amplitudes and angular position are measured with the torsional vibration meter 3 on the shaft of the generator and continuously fed to the Fourier analyzer 4. The Fourier decomposition of the torsional vibrations into links of different orders is carried out in the Fourier analyzer 4 and a comparison with predefined target values then takes place. The correction signals for the change in the injection quantity of the injection pumps 61, 62, 63, 64, 65, 66 are in the injection pump controller 5, which comprises a computer, on the basis of, for example, the elements of the first and second order, e.g. determined by the Kurbeister method, which is explained with reference to FIG. 3.

2B, the shaft 17 of the diesel engine drives over the Coupling 71, the shaft 73 with the adjustable ship propeller 72. The gear 92 is connected as a secondary gear to the shaft of the diesel engine 1 and drives the generator 9 via a coupling 94. The generator supplies electrical energy to the vehicle electrical system 100. Here, too, the torsional vibrations of the Shaft of the generator with the torsional vibration meter 3 continuously determined according to amplitude and angular position and fed to the Fourier analyzer 4. Here, too, the torsional vibrations are broken down into links of different orders in the Fourier analyzer 4 and then compared with predetermined target values.

In the marine diesel system shown in FIG. 2C, the shaft 17 of the diesel engine 1 drives the shaft 73 with the adjustable ship propeller 72 via the coupling 71. In this system, the transmission 93 is driven directly by the shaft 73 and in turn drives the generator via the coupling 94 9. The generator 9 supplies electrical energy to the vehicle electrical system 100. Again, the amplitude and angular position of the torsional vibrations are continuously measured on the shaft of the generator 9 and fed to the Fourier analyzer 4. In the Fourier analyzer 4, the torsion vibrations are broken down into the members of different orders, and then a comparison with predetermined target values takes place. The correction signals for the injection pumps 61, 62, 63, 64, 65 and 66 can be determined in the systems of FIGS. 2A, 2B and 2C in the same way as described for FIG. 1.

Improving the synchronism of the diesel engine 1 and also the generators 9 driven by the diesel engine requires that the diesel engine is essentially in a stationary operating state. This is generally the case with marine diesel systems, and increasingly with marine diesel systems with adjustable marine propellers, when operating for longer periods. The hydraulic or mechanical gears 91, 92, 93 are able, for example, to keep the speed of the rotor constant within certain limits of speed changes, as can be the case with ship drives with a non-adjustable ship propeller. Since a ship has several on-board generators, the group driven by the drive diesel engine is often only connected to the on-board electrical system when driving on the open sea, where the drive engine runs at constant speed.

It is also possible to place the rotor of the generator 9 directly on the shaft 73 and to design the generator for a specific speed which corresponds to the speed of the diesel engine during continuous operation. The transmission 93 and the clutch 94 would then be omitted, for example in a system, as shown in FIG. 2C. In this case, the torsional vibrations would be measured with the torsional vibration meter 3 on the shaft 73 or on the shaft 17.

• - der mittlere indizierte Zylinderdruck eines Zylinders nicht mehr als 5 % vom Soll-Wert abweicht;
• - sich die Störamplitude linear mit der Störung ändert und die Phase gleich bleibt;
• - die gemessene Störung, d.h. eine gemessene Torsionsschwingung durch Korrektur des mittleren indizierten Zylinderdrucks von zwei oder in Sonderfällen einem Zylinder minimiert werden kann, d.h. die Störung durch die entsprechenden Zylinder erzeugt wird.

The crank star method for determining the correction factors for correcting the injection quantity for minimizing the first-order torsional vibrations is explained with reference to FIG. 3. In the crank star method, for example, the simplifying assumptions are made that

• - the average indicated cylinder pressure of a cylinder does not deviate from the target value by more than 5%;
• - the interference amplitude changes linearly with the interference and the phase remains the same;
• - The measured disturbance, ie a measured torsional vibration can be minimized by correcting the mean indicated cylinder pressure of two or, in special cases, one cylinder, ie the disturbance is generated by the corresponding cylinder.

The firing order of the engine is 1, 6, 2, 4, 3, 5. In pole diagram 19, the calculated torsional vibration vectors 191 to 196 are first order of the shaft of a six-cylinder engine for all six cases that one of the cylinders has a 5% reduction in yields mean indicated cylinder pressure, shown in dashed lines. These vectors 191 to 196 form the so-called first-order correction crank stars. The ends of these vectors 191 to 196 lie on a circle whose center M does not lie in the zero point P of the pole diagram, but is shifted by a vector 190. This vector 190 corresponds to the ideal torsional vibration vector, i.e. fully balanced engine.

If you subtract this vector 190 from the individual vectors 191 to 196, you get the shifted correction curve modifiers 191 'to 196'.

This calculated Kurbeistern 191 'to 196' is now used to determine the corrections to the mean indicated cylinder pressure in one or two cylinders.

If, for example, a torsional vibration S (amplitude and phase) is measured on the shaft and the vector is drawn in the shifted correction crank star, S lies between two vectors of the shifted correction crank star, in our example between vectors 191 'and 196' or falls in the direction one of the vectors 191 'to 196'. The decomposition of the amplitude vector S into the two vectors s _i and s ₆ in the direction of the two vectors of the correction crank star is thus interpreted as a disturbance of the two cylinders 1 and 2. Since the correction curve is based on the assumption of underperformance of the disturbed cylinders, but the cylinders could also perform too much, this decomposition must be calculated in the correct vector basis. This basis is a pair of the vectors z _i , zε, z ₃ and z ₄ . The correction factor for the two cylinders of a pair combination thus results directly from the correction curve correction.

In reality one or more cylinders can be disturbed. The simplified assumption that each fault can be attributed to two faulty cylinders, for example, generally makes it necessary to carry out the iteration iteratively, ie in several steps. A single correction factor for only one cylinder results when the Vek the measured disturbance coincides with one of the vectors 191 'to 196'.

Although the calculation of the correction factors for the first-order disturbances has been explained here for the sake of clarity using a graphic example, it is expedient to calculate the correction factors in the injection pump control 5 arithmetically, i.e. to be determined numerically. The correction factors for minimizing the second-order torsional vibrations can also be determined in an analogous manner.

The described way of minimizing the torsional vibrations has proven to be very favorable in practice. The invention is in no way limited to the exemplary embodiments described, but rather comprises any method for improving the synchronism of reciprocating piston internal combustion engines, in which correction factors acting on the indicated medium pressure are determined in a different way.

The invention has been explained on the basis of examples relating to diesel engines. In principle, however, the method can be used for any reciprocating piston internal combustion engine with a volumetric fuel supply to the cylinders.

Claims (11)

1. Method of evening out the steady-state running of a reciprocating internal combustion engine having three or more cylinders, wherein the mean indicated pressure of at least one cylinder is varied, characterised in that at least one order of the torsional vibrations of the drive system is minimized by: in a first step of the method: measuring the torsional vibrations at the drive shaft or at a shaft (12, 22) connected kinematically to the drive shaft, by means of a torsional vibration meter (3), in a second step of the method: subjecting the measured torsional vibrations to a Fourier analysis for torsional vibrations, in a third step of the method: determining correction factors for the variation of the mean indicated cylinder pressure of at least two cylinders in a computer from the ascertained amounts and phase positions of the torsional vibration amplitudes and from comparison of predetermined torsional vibrations produced by the individual cylinders (161, 162, 163, 164, 165, 166), in a fourth step of the method; the correction factors effect a variation of the amount injected per injection step of the injection pump (61, 62, 63, 64, 65, 66) at at least one of these two cylinders.

2. A method according to claim 1, characterised in that the fundamental frequency and the second harmonic of the torsional vibrations are minimized.

3. A method according to claim 1 or 2 characterised in that the torsional vibrations are minimized lit- eratively in a number of steps.

4. A method according to any of claims 1-3, characterised in that the torsional vibrations are measured on the shaft (123) of an electricity generator (2, 9; 91-93) which is driven by the shaft (12) of engine (1) either directly or through a transmission (8, 81-83) or which is an extension (123) of the engine shaft (12), and the torsional vibrations of the shaft (12) of the engine are minimized with the minimization of the torsional vibrations of the generator shaft (123, 89).

5. A reciprocating internal combustion engine for the practice of the method according to claim 1, characterised by; a meter (3) for mesuring torsional vibrations of the engine shaft or of a further shaft coupled therewith; a Fourier analyser (4) supplied with the measured values of torsional vibration; a computer (5) which determines correction signals for the injected quantity of fuel of at least one cylinder from the phase and amplitude of elements of the Fourier analysis and from comparison with predetermined torsional vibrations; and characterised by an injection device (61-66) which is supplied with the correction signals and which injects into the cylinders the quantity of fuel varied in accordance therewih and, therefore, varies the mean indicated cylinder pressure thereof.

6. An engine according to claim 5, characterised in that it has from 3 to 12 cylinders.

7. An engine according to claim 5 or 6, characterised in that it is a slowrunning two-stroke diesel engine.

8. An engine according to any of claims 5-7, characterised in that an axial prolongation of the engine shaft is operative as the shaft of an electricity generator and the torsional vibration meter (3) is adapted to mesure torsional vibrations of the generator shaft (123).

9. An engine according to any of claims 5-8, characterised in that a transmission (8, 81-83; 91-93) is disposed between the main (12) of the engine (1) and a secondary shaft (89) and in that the torsional vibration meter (3) is adapted to measure torsional vibrations of the secondary shaft (9, 89).

10. An engine according to any of claims 5-9, characterised in that a common computer is provided for Fourier analysis of the torsional vibrations and for comparison with programmed set values and for determining the correction signal for varying the injection step of the injection device (61-66).

11. An engine according to any of claims 5-10, characterised in that a transmission is disposed between the main shaft (12) of the engine (1) and a secondary shaft and in that the torsional vibration meter is adapted to measure the torsional vibrations of the secondary shaft (9, 89).

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