WO2008080679A2

WO2008080679A2 - Method for determining a rotational speed value

Info

Publication number: WO2008080679A2
Application number: PCT/EP2007/062151
Authority: WO
Inventors: Joerg Breuninger; Haris Hamedovic; Franz Raichle; Wolfgang Fischer
Original assignee: Robert Bosch Gmbh
Priority date: 2006-12-27
Filing date: 2007-11-09
Publication date: 2008-07-10
Also published as: DE102006061579A1; WO2008080679A3; EP2104784A2

Abstract

The invention relates to a method for determining a rotational speed value of a signal representing a current rotational speed of a shaft, particularly of a signal of a transmitter associated with a transmitter wheel of a crankshaft of an internal combustion engine, wherein a correction function is applied to the signal, compensating the influence of oscillating masses at least partially.

Description

description

Title Procedure for determining a speed value

State of the art

The present invention relates to a device, a computer program and a method for determining a rotational speed value of a torque representing a torque of a shaft signal, in particular a signal of a transmitter wheel of a crankshaft of an internal combustion engine associated transmitter.

In modern internal combustion engines, the speed signal provides information of central importance for engine control, diagnosis and optimization of the operating behavior with regard to a wide variety of criteria. The speed signal is typically measured by means of a donor wheel mounted on the crankshaft, which has a certain number of markings by alternately attaching teeth and tooth gaps and usually a Geberradlücke. The individual markings are detected by means of a sensor, so that angle increments and a zero position of the crankshaft identified by a transmitter wheel gap or the like can be detected. By measuring the elapsed time between two successive markings, one obtains the so-called tooth sides, which are converted into corresponding speed values.

Fluctuations in the speed signal are primarily due to two factors, namely the gas torque resulting from compression and combustion and the oscillating masses of an internal combustion engine. The oscillating masses of an internal combustion engine are in particular the pistons, piston pins, piston ring packages and the oscillating portion of the connecting rods. Their influence on the angular acceleration depends quadratically on the speed. As a rule, a speed signal u.a. Information about combustion characteristics of the

Internal combustion engine or individual cylinder of the internal combustion engine can be obtained. Therefore, the influence of these oscillating masses for determining the quantities mentioned represents a disturbance that should be taken into account or compensated. From DE 44 456 84 and DE 19 941 171 it is known to calculate the gas torque by the entire torque of the crankshaft is first determined from the speed and then subtracted from this separately calculated torque due to the oscillating masses. However, no method is known in which the influence of oscillating masses is compensated directly on the speed signal.

Disclosure of the invention

An object of the present invention is to compensate for the influence of oscillating masses directly on the speed signal.

This problem is solved by a method for determining a rotational speed value of a signal representing an instantaneous rotational speed of a shaft, in particular a signal of an encoder assigned to a transducer wheel of a crankshaft of an internal combustion engine, wherein a correction function which at least partially compensates for the influence of oscillating masses is applied to the signal , Thus, the speed signal without the detour of a torque calculation by means of a characteristic curve or a characteristic field is directly converted or transformed in such a way that the influence of the oscillating masses in this speed signal is eliminated. This is advantageous since in many functions of today's motor control features such as e.g. Combustion features are calculated directly from the speed signal, that are determined without detour via the torque. The correction function can be any function with which the speed signal is converted. Preferably, it is provided that the signal is determined from an angle-discrete encoder signal and the correction function is angularly discrete, wherein the discretization of the speed signal in the correction function is the same. Under angle discrete is understood in this context that both the

Speed signal and the correction function to discrete crankshaft angles are present. The discretization can also be, for example, an interpolation to crankshaft angles at which there is no signal of a speed sensor exist. The correction function is preferably determined by a simulation of the oscillating masses of the internal combustion engine and stored in the form of a series of numbers in a control unit of the internal combustion engine. As a result, it is not necessary to determine the correction terms online during operation. It is preferably provided that the correction function is a multiplication with a discrete angle-dependent correction factor. The respective speed value or value of the angular speed to a discrete crankshaft angle is thus determined with a constant and from the operating point of the internal combustion engine multiplied independent correction factor. Preferably, it is provided that the correction factor is stored as an angle-dependent series in a memory of a control unit.

In addition, it can be provided that a gas torque of the internal combustion engine is determined from the transformed speed signal. Since the speed signal is compensated for the influence of the oscillating masses, the rotational inertia of the crankshaft is no longer dependent on the crankshaft angle but constant. As a result, the gas torque can be determined directly from the speed signal. If the transformed speed signal is transmitted via e.g. integrated compression torque curve determined from an adiabatic model of the internal combustion engine, in addition, the influence of the compression can be eliminated, so that only the proportion of the torque resulting from the combustion during the power stroke, can be determined.

The problem mentioned at the outset is also solved by a device, in particular control unit or internal combustion engine, which is set up to carry out a method according to the invention and a computer program with program code for carrying out all steps according to a method according to the invention, when the program is executed in a computer.

Brief description of the drawings

Hereinafter, an embodiment of the present invention will be explained in more detail with reference to the accompanying drawings. Showing:

1 is a block diagram of a method according to the invention;

FIG. 2 is a graph of a correction value over the crankshaft angle; FIG.

Fig. 3 is a diagram of a speed signal and a corrected by the correction value of Fig. 2 speed signal.

Embodiment of the invention - A -

For the following exemplary embodiment, it is assumed that an instantaneous speed of a crankshaft of an internal combustion engine is present as a time series at discrete crankshaft angles. Usually, the speed signal is determined by an inductive sensor, for example, which cooperates with a fixedly mounted on the crankshaft sensor wheel. The sender wheel has markings in the form of a sequence of teeth and tooth gaps, wherein the tooth pitch is usually 6 °, the distance between two similarly oriented tooth flanks is therefore 6 ° over the circumferential angle of the encoder disc. Such encoder discs usually have 60-2 = 58 teeth, wherein a Geberradlücke is formed by omitting two teeth. The electrical signal of the encoder, which is transmitted to the control unit, is a rectangular signal representing the geometric course of teeth and tooth spaces on the circumference of the sensor wheel. From the signal of the encoder, an instantaneous speed or a momentary angular speed of the crankshaft to the crankshaft angles, which are associated with a rising or falling edge of the electrical signal of the encoder, can be determined. The speed signal is thus available as an angle-discrete row at defined crankshaft angles.

The angle-discrete signal of the encoder assigned to the sender wheel of the crankshaft of the internal combustion engine is now corrected for the influence of oscillating masses of the crankshaft by multiplying the angle-discrete signal by an angle-dependent correction value K. Oscillating masses of the crankshaft are the pistons of the engine and proportionally the connecting rods between the crankshaft and the piston. The correction value K is determined as angle-dependent to the crankshaft angles, to each of which an instantaneous speed is present, these are in customary in the prior art combinations of encoder wheel and encoder and subsequent signal evaluation of one of the tooth flanks of the encoder wheel associated crankshaft angle, so for example crankshaft angle of 3, 9, 15, 21, etc., crankshaft. The correction value K is calculated offline using a model of the internal combustion engine, which takes into account internal combustion engine parameters such as oscillating and rotating mass fractions and the engine geometry, and stored in a memory of a control unit of the internal combustion engine. The crankshaft angle-dependent correction values K (Cp ₁ ) are advantageously determined periodically over a period of 2π or 360 °. However, it is also possible to determine the correction values via a complete operating cycle of the internal combustion engine, ie 4π or 720 °. So K (Cp ₁ ) = K (cpj + 2π) or K (Cp ₁ ) = K ( _Φl + 4π). Fig. 2 shows at the block diagram of the method for correcting the measured speed values φ _meM (ψ _; ). In a first step 1, an instantaneous value to a crankshaft angle Cp _{1 of} the measured value of the angular velocity φ _mess (φ _; ) is determined. The following embodiment is shown for angular velocities φ, for rotational speeds n the formulation is identical by the relation φ = 2% n up to the constant factor 2π. In a subsequent step 2, the correction value K (Cp ₁ ) is determined for the crankshaft angle φi for which the measured angular velocity φ _mess (ψ _; ) is present. In a step 4, the measured angular velocity φ _meas (φ _; ) multiplied by the correction value K (Cp ₁ ), obtaining a corrected value of the angular velocity (p _kor (φ _; ) in step 3)

Values K (Cp ₁ ) are stored in a memory of the control unit so that they only have to be read out and not have to be calculated online.

FIG. 2 shows an exemplary embodiment of the values of the correction factor K via the crankshaft angle φ. The correction values K (Cp ₁ ) are present at discrete interpolation points which are assigned to the tooth sides of the transmitter wheel, but can also be present at intermediate values, the rotational speed or angular velocity values being interpolated between the crankshaft angles φ determined by the tooth pitch. A correction value of 1 means that the measured speed signal (p _mess (ψ _; ) is multiplied by the factor 1, ie remains unchanged.

Fig. 3 shows as a dashed curve the measured value of the angular velocity φ _mess (φj and as a solid curve the corrected value of the angular velocity

Φ _f o _r _(Ψ:) fö ^r ^ e duration of a working cycle between cp = 0 ° of the crankshaft angle, and cp = 720 ° crank angle. The abscissa of FIG. 3 shows the index of the rotational speed measured values. As previously explained, the speed measurement values for specific interpolation points are, for example, cp = 3 °, 9 °, 15 ° etc., ie with an increment of 6 °. An index of 40 thus means here a crankshaft angle of cp ₀ + 40 x 6 °, with a cp ₀ of 3 ° as in the previously mentioned example of 3 °, 9 °, etc., the index 40 thus corresponds to a crankshaft angle of 243 °. As can be seen from Fig. 3, the measured speed value deviates from the corrected speed value.

Claims

claims

1. A method for determining a speed value of an instantaneous speed of a shaft signal representing, in particular a signal of a donor wheel of a crankshaft of an internal combustion engine associated encoder, characterized in that the signal is applied a correction function that at least partially compensates the influence of oscillating masses.

2. The method according to claim 1, characterized in that the signal is determined from an angle-discrete encoder signal and the correction function is angularly discrete, wherein the discreting the rotational speed signal and the correction function is the same.

3. The method according to claim 1 or 2, characterized in that the correction function is a multiplication with a discrete angle-dependent correction factor.

4. The method according to any one of claims 1 to 3, characterized in that the correction factor is stored as an angle-dependent series in a memory.

5. The method according to any one of claims 1 to 4, characterized in that from the transformed speed signal, a gas torque is determined.

6. The method according to any one of claims 1 to 5, characterized in that the transformed speed signal is integrated via a compression torque.

7. The method according to claim 6, characterized in that the compression torque from a model, in particular an adiabatic model, the internal combustion engine is determined.

8. Device, in particular control unit or internal combustion engine, to carry out a

Method according to one of claims 1 to 7 is set up.

A computer program with program code for carrying out all the steps according to one of claims 1 to 7, when the program is executed in a computer.