DE102008060929A1 - Method for running-smoothness control of internal combustion engine, involves detecting cylinder internal pressure in each cylinder of internal combustion engine during working cycle of cylinder - Google Patents

Abstract

The method involves detecting cylinder internal pressure (p-i1) in each cylinder of internal combustion engine during a working cycle of the cylinder (Z-i), before a piston reaches a top dead center in the cylinder. Another cylinder internal pressure (p-i2) is detected after the piston reaches the top dead center. A pressure difference is formed for each cylinder by subtracting the former cylinder internal pressure from the latter cylinder internal pressure. Controlled variables (r-i) of a control circuit are formed from the pressure differences for adjusting the fuel injection amount.

Description

The The invention relates to a method for regulating the noise of an internal combustion engine with multiple cylinders and at least one pressure sensor for each Cylinder for determining an in-cylinder pressure in the cylinder, wherein fuel injection amounts corresponding to each cylinder be fed during a work cycle, be aligned with each other by means of a control loop.

at Combustion engines with multiple cylinders carry component tolerances and / or injection quantity error to torque differences between the Cylinders and thus to a rotational nonuniformity, the the smoothness and thus the noise of the internal combustion engine impaired. Furthermore, the mentioned lead Injection quantity error of the individual cylinders to cylinder individual Emission differences and thus to a possible expansion the emission spread of an engine.

It are already devices and procedures for the truancy of a Internal combustion engine with several cylinders known.

From the DE 19945618 A1 For example, a method and a device for controlling a fuel metering system of an internal combustion engine are known. In this case, the activation duration of at least one electrically actuated valve determines the quantity of fuel to be injected. In certain operating states, a minimum drive duration is determined at which fuel is being injected. Starting from a starting value, the activation duration is increased or decreased. The drive time at which a change of the signal occurs is stored as a minimum drive duration. The signal used is a variable that characterizes the rotational uniformity, an output signal of a lambda probe or an output signal of an ion current probe.

From the DE 19741965 C1 is a method for restraining a multi-cylinder internal combustion engine known. An inverse model estimates from state variables of the internal combustion engine, in particular a rotational speed, fuel quantity, operating temperature and / or a supercharging pressure, a characteristic process variable. The estimated value enters the control as a setpoint. The combustion in the individual cylinders of the internal combustion engine is corrected by means of a controller such that an actual value determined by a measuring element, which indicates the rotational acceleration contribution of each cylinder, is brought closer to the nominal value.

Of the Invention is based on the object, an improved, in particular Simplified, method for a rudder control of an internal combustion engine specify with several cylinders.

The The object is achieved by a method solved with the features specified in claim 1.

advantageous Embodiments of the invention are the subject of the dependent claims.

The The purpose of the method according to the invention is to provide a restorative exercise an internal combustion engine with multiple cylinders and at least one pressure sensor for each cylinder for determining a cylinder internal pressure in the cylinder, wherein fuel injection amounts to the individual Cylinders each fed during a work cycle be adjusted by means of a control loop. This is done in each cylinder during a work cycle of the cylinder detects at least a first in-cylinder pressure, before a piston in the cylinder reaches top dead center, and at least one second in-cylinder pressure detected after the Piston in the cylinder has reached the top dead center. For each cylinder is at least one pressure difference by subtraction a first in-cylinder pressure of a second in-cylinder pressure formed and from the pressure differences are controlled variables the control circuit for the adjustment of the fuel injection quantities of Cylinder formed.

When alternative controlled variable is also the middle indicated Pressure of a cylinder of the internal combustion engine suitable, which a definable number of measured cylinder pressure values and a calculated known incremental stroke volume becomes.

there is advantageously exploited that the pressure differences are a measure of the fuel injection amounts respectively supplied to the cylinders are. The higher a cylinder supplied Fuel injection amount is, the higher is the corresponding Pressure difference. Therefore, from the pressure differences controlled variables formed as quantity replacement signals for the Cylinders each supplied fuel injection quantities act.

The Forming such quantity replacement signals has the advantage of being requires only a small computational effort, since the basis of them lying pressure differences by simply subtracting two Cylinder internal pressures are formed. This simple education The control variables also have the advantages that only a short signal chain and a low filtering effort in the Signal processing is needed, reducing the processing time reduced and the accuracy of the control can be increased. Furthermore, the method advantageously requires a small amount of hardware. In particular, no additional sensors are needed if the individual cylinders already have pressure sensors.

embodiments The invention will be described in more detail below with reference to drawings explained.

there demonstrate:

1 schematically a block diagram of a control loop for equalizing fuel injection quantities for cylinders of an internal combustion engine, and

2 a diagram for pressure differences and corrected pressure differences of cylinder internal pressures as a function of an engine speed.

each other corresponding parts are in all figures with the same reference numerals Mistake.

1 shows a control circuit for equalizing fuel injection quantities M _i for cylinder Z _{i of} an internal combustion engine V by means of the method according to the invention. The index i assumes values of 1 to n, where n denotes a cylinder number of the internal combustion engine V.

Each cylinder Z _i has a pressure sensor S _i . By means of the pressure sensor S _i , during a working cycle of the cylinder Z _i, a first in-cylinder pressure p _i1 and a second in-cylinder pressure p _{i2 of} the cylinder Z _i are detected. The first in-cylinder pressure p _i1 is detected before a piston in the cylinder Z _i reaches top dead center, and the second in-cylinder pressure p _i2 is detected after the piston in the cylinder Z _{i has} reached top dead center.

The first in-cylinder pressure p _i1 and the second in-cylinder pressure p _i2 are preferably detected at positions of a crankshaft connected to the piston of the respective cylinder Z _i , which are symmetrical to one another relative to top dead center, so that crankshaft angles of these positions are equal to one crankshaft angle , For example, 80 degrees, deviate from a crankshaft angle corresponding to the top dead center.

From the first in-cylinder pressure p _i1 and the second in-cylinder pressure p _i2 , a controlled variable r _{i of} the control loop is formed for each cylinder Z _i by means of a control unit C, which functions as a set replacement signal for the fuel injection quantity M _i fed to the cylinder Z _i .

For this purpose, a pressure difference Δp _{i is} formed for each cylinder Z _i by subtracting the first in-cylinder pressure p _i1 from the second in-cylinder pressure p _i2 Ap i = p i2 - p i1 , [1]

From the pressure difference Dp _i, a corrected pressure difference Dp _i, formed _c by a is added from a current engine speed D of the internal combustion engine V-dependent correction value p _c of the pressure difference Ap _i, the one stored correction value map for the correction value p _c depending on the Engine speed D is removed. The corrected pressure difference Δp _{i, c} thus results from the pressure difference Δp _i and the correction value p _c according to FIG Ap i, c = Δp i + p c , [2]

By adding the correction value p _c to the pressure difference Δp _i , it is taken into account that the relationship between the fuel injection quantity M _i and the pressure difference Δp _i depends on the engine speed D. This advantageously improves the regulation of the fuel injection quantity M _i via the pressure difference Δp _i .

The corrected pressure differences Δp _{i, c} or the corrected pressure differences Δp _{i, c} multiplied by a scaling factor are used as controlled variables r _i . They are subtracted from a desired value w to equalize the fuel injection quantity M _{i of} the cylinders Z _i , whereby for each cylinder Z _i a deviation value e _{i in} accordance with e i = w - r i [3] is formed.

Of the Setpoint w is in an embodiment of the invention a stored nominal value map for the nominal value in Dependence on at least one operating parameter the internal combustion engine V, for example, the engine speed D and / or a Temperature, taken.

In an alternative embodiment, the desired value w is determined from the controlled variables r _i , for example by forming an average value or a weighted mean value over all cylinders Z _i from the instantaneous values of the controlled variables r _i .

The deviation values e _i are fed to a regulator R, by means of which an injection duration t _{i is} determined for each cylinder Z _i from the deviation value e _i , during which fuel is to be injected into the cylinder Z _i in a following operating cycle.

The injection duration determined by the regulator R for the respective cylinder Z _i t _i is used to control the fuel injection quantity M _i used, which is supplied to the cylinder Z _i, for example, by being used as a control period of an injection nozzle for injecting fuel into the cylinder Z _i , The cylinders Z _i respectively supplied fuel injection quantity M _i are also of sturgeon variables d _i , which are caused by component tolerances of the cylinder Z _i and / or injection quantity errors.

2 shows a diagram for pressure differences Δp _i and corrected pressure differences Δp _{i, c} in dependence on the engine speed D for a combustion engine V with six cylinders Z _i . In this case, the pressure differences .DELTA.p ₁ to .DELTA.p _{6 of} the six cylinders Z ₁ to Z ₆ by trajectories 1.1 to 6.1 and the respectively corrected pressure differences Δp _{1, c,} to Δp _{6, c} by corrected course curves 1.2 to 6.2 represented and for each engine speed D to the average of the corrected pressure differences Δp _{1, c,} to Δp _{6, c} , so that this average forms the zero line of the diagram. The engine speed is given in the unit rpm, which indicates the number of revolutions per minute.

The corrected pressure difference Δp _{i, c} results from the associated pressure difference Δp _i by addition of the dependent on the engine speed D correction value p _c according to equation [2], wherein the correction value p _c a stored correction value map for the correction value p _c as a function of the engine speed D is taken.

A further embodiment of the embodiment provides to detect in each cylinder Z _i during a work cycle a plurality of first _internal cylinder pressures p _i1 at each different positions of the crankshaft before a piston in the cylinder Z _{i reaches} a top dead center, and / or a plurality of second _internal cylinder pressures p _i2 After the piston in the cylinder Z _{i has reached} the top dead center.

Accordingly, for each cylinder Z _{i, a} plurality of pressure differences Δp _{i are formed} by subtracting a first cylinder _internal pressure p _i1 from a second cylinder _internal pressure p _i2 . These pressure differences Ap _i is a dependent on the engine speed correction value D p _c is added in each case. In this case, the added correction value p _c preferably depends on the positions of the crankshaft, in each of which the first _internal cylinder pressure p _i1 and the second _internal cylinder pressure p _{i2 are} determined.

As a result, a plurality of corrected pressure differences Δp _{i, c are} formed for each cylinder Z _i according to equation [2] during a work cycle. From these, a controlled variable r _{i is} formed for each cylinder Z _i by forming an average value or a weighted mean value of the corrected pressure differences Δp _{i, c} determined for the respective cylinder Z _i during a work cycle.

In the case of the formation of a weighted mean value, the weighting can take into account the positions of the crankshaft, in each of which the first _internal cylinder pressure p _i1 and the second _internal cylinder pressure p _{i2 are} determined, from which the respective pressure difference Δp _{i is} formed. Furthermore, in the case of weighting, a corrected pressure difference Δp _{i, c may be} less heavily weighted or completely ignored in the mean value if its value deviates significantly from previously determined values and / or the values of the other determined corrected pressure difference Δp _{i, c} .

Such a formation of the control variables r _i from a plurality of pressure differences Δp _i advantageously makes it possible to compensate for measurement inaccuracies and / or statistical fluctuations in the pressure sockets, thereby improving the quality of the control.

1.1

pressure difference a first cylinder in response to an engine speed

2.1

pressure difference a second cylinder in response to an engine speed

3.1

pressure difference a third cylinder in response to an engine speed

4.1

pressure difference a fourth cylinder in response to an engine speed

5.1

pressure difference of a fifth cylinder depending on one Engine speed

6.1

pressure difference a sixth cylinder in response to an engine speed

1.2

corrected Pressure difference of a first cylinder as a function of an engine speed

2.2

corrected Pressure difference of a second cylinder in dependence from an engine speed

3.2

corrected Pressure difference of a third cylinder in dependence from an engine speed

4.2

corrected Pressure difference of a fourth cylinder in dependence from an engine speed

5.2

corrected Pressure difference of a fifth cylinder in dependence from an engine speed

6.2

corrected Pressure difference of a sixth cylinder in dependence from an engine speed

V

internal combustion engine

M _i

Fuel injection quantity

Z _i

cylinder

n

number of cylinders

S _i

pressure sensor

p _i1

first Cylinder pressure

p _i2

second Cylinder pressure

C

control unit

_i

controlled variable

Δp _i

pressure difference

D

Engine speed

p _c

correction value

Δp _{i, c}

corrected pressure difference

w

setpoint

e _i

deviation value

R

regulator

t _i

Injection duration

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19945618 A1 [0004]
• - DE 19741965 C1 [0005]

Claims (6)

Method for controlling the noise of an internal combustion engine (V) having a plurality of cylinders (Z _i ) and at least one pressure sensor (S _i ) for each cylinder (Z _i ) for determining an internal cylinder pressure in the respective cylinder (Z _i ), fuel injection quantities (M _i ) which are supplied to the individual cylinders (Z _i ) in each case during a working cycle, are adapted to each other by means of a control circuit, characterized in that in each cylinder (Z _i ) during a working cycle of the cylinder (Z _i ) at least one first _internal cylinder pressure (p _i1 ) is detected before a piston in the cylinder (Z _i ) reaches a top dead center, and at least a second in-cylinder pressure (p _i2 ) is detected after the piston in the cylinder (Z _i ) has reached the top dead center, for each cylinder ( Z _i ) at least one pressure difference (Δp _i ) is formed by subtracting a first cylinder _internal pressure (p _i1 ) from a second cylinder _internal pressure (p _i2 ), and from de n pressure differences (Δp _i ) control variables (r _i ) of the control loop to equalize the fuel injection quantities (M _i ) of the cylinder (Z _i ) are formed. A method according to claim 1, characterized in that for forming the controlled variables (r _i ) from the pressure differences (Δp _i ) to each of these pressure differences (Δp _i ) one of a current engine speed (D) of the internal combustion engine (V) dependent correction value (p _c ) is added. A method according to claim 2, characterized in that the correction value (p _c ) is taken from a stored correction value map. Method according to one of the preceding claims, characterized in that the first in-cylinder pressure (p _i1 ) and the second in-cylinder pressure (p _i2 ), from which in each case a pressure difference (Δp _i ) is formed, at positions with the piston of the respective cylinder ( Z _i ) are detected whose crankshaft angle differ by a same crankshaft angle amount from a crankshaft angle corresponding to the top dead center. Method according to one of the preceding claims, characterized in that an average value of the current actual values of the controlled variables (r _i ) is formed over the various cylinders (Z _i ) and in a subsequent run of the control loop for equalizing the fuel injection quantities (M _i ) of the cylinders as Reference variable of this control loop is used. Method according to one of claims 1 to 4, characterized in that a reference variable for the control loop for equalizing the fuel injection quantities (M _i ) of the cylinder (Z _i ) is taken from a stored nominal value map.