KR100490930B1 - Method for calculating the torque of an internal combustion engine - Google Patents

Abstract

According to the invention, a) forming, for each phase in the combustion of a mixture of air and fuel in each cylinder of an internal combustion engine, a defined viewing window defined by predetermined angular positions of the crankshaft of the engine, b) said Measuring through the window a series of time intervals ΔT _i for dividing the movement of the crankshaft into the predetermined angular position, and c) two linear combinations of the time intervals ΔT _i ∑a _i ΔT _i And Σb _i ΔT _i ) and select the coefficients a _i and b _i of the combination to measure the corresponding time interval ΔT _i with the observation window in the first and second operating modes of the engine. during the step and, d) for amplifying the change in the AC component of the crankshaft angular velocity been phase-shifted with respect to each other by a predetermined angle is applied to the two linear combinations, the average time interval cubic (ΔT ³⁾ measured in the predetermined window, It indicated a step leading to an evaluation of the torque from the value of the rule.

Description

Calculation method of internal combustion engine torque {METHOD FOR CALCULATING THE TORQUE OF AN INTERNAL COMBUSTION ENGINE}

TECHNICAL FIELD The present invention relates to a method for calculating torque transmitted by an internal combustion engine, and more particularly, to a method for calculating torque performed based on observation of a change in rotational speed of an engine crankshaft.

When the engine of an internal combustion engine is used to power a motor vehicle, the torque transmitted by the internal combustion engine is an important parameter that can characterize, in particular, the operating state and performance of the engine. Devices known as "torque meters" measure the torque transmitted by the internal combustion engine during a bench test. It is practically impossible to mount such a device inside a vehicle, especially in terms of cost. Therefore, various methods have been proposed today to measure torque by measuring the instantaneous engine speed transmitted by a sensor installed inside a vehicle. Such automotive engines are controlled by a computer provided with a variety of signals, including those provided by speed sensors. In this regard, publication SAE 890885 to the Society of Automotive Engineers, "Applications of Precise Crankshaft Position Measurements for Engine Testing, Control," and 1989 publication by WB RIBBENS and G. RIZZONI. The publication deduces the absolute value of the torque for each cylinder from the instantaneous speed measurement during each engine cycle, and as a result, the instantaneous speed measurement during each engine cycle to detect any abnormal change in torque. A method comprising performing a matrix algebra on a value. Such calculations are complex and require powerful computational means that cannot be installed in vehicles at present. Also, according to the publication, this method is only available at low speeds (up to 3500 rpm).

Other torque calculation methods involve observing changes in engine speed within a time “horizon” covering the combustion phase of several successive air / fuel mixtures in different cylinders of the engine. Is done. For example, if abnormal combustion occurs, such as incomplete combustion occurring in one of the observing cylinders, this substantially disturbs the overall observation and thus makes it difficult to calculate from this observation.

In European Patent Application No. 532 419, filed under the name Regie, Nationale des Usines Renault SA, the average "gas generated every time the mixture burns inside the cylinder of an internal combustion engine. Methods and apparatus are known for calculating numerical values indicative of "average" gas "torque. This method uses a " primary " value representing the duration of the passage in front of the sensor of each of a plurality of reference marks disposed on a ring integrally formed with the crankshaft or flywheel of the engine. generating a " primary " value, and manipulating this primary value to determine the projection of the mark above the phase reference line in relation to the angular combustion cycle and the average angular velocity of the reference mark during the combustion cycle of the engine and Obtaining two secondary values each representing an alternating component of the instantaneous angular velocity, and combining the two secondary values to obtain a value representing the desired torque.

This method can provide satisfactory results as follows. 1) The "combustion center", ie the maximum pressure in the cylinder during combustion, remains substantially set at a fixed angular position of the crankshaft. 2) The average speed of the engine hardly changes between two top dead centers (indicated by PMH in FIGS. 1 and hereinafter).

1 attached to this specification shows, for example, the pressure inside a cylinder in which combustion occurs between two top dead centers (PMH) continuously reached by two pistons operating within two cylinders of a four-cylinder engine. The change in P) and the corresponding change in angular speed (Ω) are shown. When a normal concentration of air / fuel mixture is provided at high speed, the center of pressure (P _{0 max} ) is the first quarter of the angular interval (two quarters one point) dividing two consecutive top dead centers (PMH). In the experiment, it was confirmed that the center of gravity is maintained at a fixed position relative to the top dead center (PMH). Has a maximum value (Ω _{0 max)} at substantially the end of the corresponding wave of the second quarter (4 branching point 2) between the top dead center is represented as Ω ₀ (PMH) to the interval of the engine's angular velocity.

On the other hand, in other modes of operation of the engine, for example when a sparse air / fuel mixture is provided at low or average speeds, the pressure peak is 45 ° of crankshaft rotation with respect to the pressure center P _{0 max} . Up to the P _max position). And the corresponding phase shift corresponding to at the angular velocity (Ω ₉₀₎ to (phase shift) observation, the angular velocity (Ω ₉₀₎ corresponding to the case for almost sine wave velocity (Ω ₀₎ at the frequency of the top dead center (PMH) Phase shifted by π / 2.

In addition to these operating modes, an intermediate phase shift ΔΦ of Ω relative to Ω ₀ between 0 and π / 2 is observed.

In all possible modes of operation of the engine, algorithms for calculating torque measurements of internal combustion engines that do not take into account the maximum angular velocity of the crankshaft or the displacement of the peak may not be able to satisfactorily calculate the torque in all possible modes of operation of the engine.

1 is a collection of graphs useful for understanding the method according to the invention.

It is an object of the present invention to provide a reliable torque calculation method in all situations regardless of the engine operating mode and regardless of the rate of change of the average speed of the engine.

This object is achieved by further details, which will be described below, as well as a method of calculating the torque transmitted by the internal combustion engine from a change in the rotational speed of the engine crankshaft. The present invention comprises the steps of: a) defining, for each phase in the combustion of a mixture of air and fuel in each cylinder of an internal combustion engine, an observation window bounded by predetermined angular positions of the crankshaft of the engine; b) measuring, at each observation window, a series of time intervals ΔT _i for dividing the movement of the crankshaft into the respective predetermined positions; and c) corresponding time intervals ΔT _i at the observation windows. During the measurement of, select the coefficients a _i and b _i for amplifying the change in the alternating current component of the angular velocity of the crankshaft which is phase shifted relative to each other by a predetermined angle in each of the first and second operating modes of the engine, the selected coefficients and the time intervals (ΔT _i) two linear combinations calculating (Σa _i ΔT _i and Σb _i ΔT _i) and d) the two linear combination of the norm (norm) and the predetermined applied in Within the observation window Obtaining a calculation of torque from a value expressed in cubes of measured average time intervals ΔT ³ .

As can be seen from the description below, the present invention enables the accurate calculation of the torque generated by the engine while the engine is operating in all modes, the operating mode of the engine being an average or improved rotational speed, a low rotational speed or They operate at moderate rotational speeds with low strength.

Further features and advantages of the present invention will be understood from the following description and the accompanying drawings.

As shown in the figure, the present invention is mainly based on the observation of the effect of combustion of air and fuel mixture in the internal combustion engine cylinder at the angular velocity (Ω) of the crankshaft of the engine. The mixture, after ignition, the internal cylinder pressure, at normal speed or high speed, reaching a maximum pressure (P _{0 max)} immediately after the top dead center or, for example, as described earlier in this specification, the maximum pressure value in the low speed (P _{0 max)} is slightly delayed in reaching the maximum value (P _max position) than the. The gas then expands in the cylinder, which continues until the other pistons in succession reach top dead center in sequence during a standard four stroke cycle. For clarity, only the four-cylinder internal combustion engine will be described below.

According to FIG. 1, each of the angular velocity maxima (Ω _{0 max} and Ω _{90 max} ) corresponding to the maximum pressures P _{0 max} and P _max , respectively, separates the continuous movement of the two pistons of the engine with respect to top dead center. Nearly centered at the end and midpoint of the first quarter of the time interval. It can be seen from the figure that the change in the angular velocity of the engine crankshaft is similar to a sinusoidal curve with a frequency equal to the frequency at which the cylinders of the engine continuously move to top dead center. It will be appreciated that the change in the angular speed of the crankshaft is a change in the alternating component (also including the direct current component) of the angular speed of the engine. This change in alternating current component corresponds to a change in engine speed N, ΔN, which is shown in the figure as a change in the slope of the axis of the curve in Ω.

According to the invention, for each combustion phase of the fuel / air mixture in each cylinder of the engine, in order to fully observe the acceleration and deceleration phase of the crankshaft due to the combustion of the fuel / air mixture in the cylinder of the engine, A wider viewing window is defined than the angular space separating the two consecutive movements of the piston to top dead center. However, this viewing window is preferably less than or equal to 1.5 times the angular space. Thus, the angular positions of the seven crankshafts that are continuously reached at a particular moment (t ₀ to t ₆ ) are defined, these moments being the time interval (ΔT _i = t _{i + 1} − t _i (i = 0 to 5)) Divided into The seven angular positions are spaced apart from one another at an angle. Therefore, there are four time intervals between the two top dead centers, and the limits of these time intervals substantially coincide with the characteristic points of the waveform of the angular velocity, thus matching either the maximum, minimum or zero intersection point. do. Note that the first time interval ΔT ₀ and the last time interval ΔT ₅ are each located within the interval between the top dead centers adjacent to the point where the observation of the change in angular velocity is based.

Before continuing, the time intervals ΔT _{n + 1} and ΔT _n , which are bounded by three equally spaced angular positions, that have reached a certain instant (t _n-1 , t _n , t _{n + 1} ) When is measured, the instantaneous torque at a particular instant (t _{n + 1} ) is:

J represents the moment of inertia of the rotating part of the engine, and α represents the constant angular deviation of two successive angular positions.

J and α are constants, so torque and ratio ( There is a proportional relationship with). Where ∑ (= ΔT _{n + 1} -ΔT _n ) is the linear combination of measured time intervals, ΔT ³ is the cube of the measured average time, and ΔT _n is ΔT _{n + 1} during observation of the time interval within the same measurement window. Wow Almost no difference.

According to the invention, the measurement of torque is based on the presence of the same type of proportional relationship between the ratio and the torque, wherein? Expressed in the ratio is modified to ensure accurate measurement of the torque regardless of the operating mode of the engine. For this reason, this equation must take into account the potential spatial displacement of the waveform of the change in angular velocity, which can occur between any of the positions shown in the figures (at Ω ₀ and Ω ₉₀ ).

To this end, according to the present invention, two linear combinations of the time intervals (ΔT _i) (Σa _i ΔT _i · and Σb _i · ΔT _i) are calculated. The coefficients a _i and b _i are related to the fluctuations in the angular velocities Ω ₀ and Ω ₉₀ , respectively, and are determined from the first operating mode and the first operating mode at a constant speed at which the combustion peak occupies the most suitable position. In the second operation mode in which the angular velocity is phase shifted by an angle Φ ₀ , it is selected as a value that amplifies the change in the AC component of the crankshaft angular velocity observed in the observation window.

The first linear combination yields a kind of "projection" for the change in velocity (Ω) along the phase "axis" of the curve (Ω ₀ ).

The second linear combination yields a pseudoprojection over the phase axis of the curve representing the velocity at which the phase is displaced.

This phase shift Φ ₀ is preferably selected in such a manner as φ ₀ = π / 2. In fact, two linear combinations by calculating a value of (Σa _i ΔT _i · and Σb _i · ΔT _i), the value of the Euclidean norm (euclidean norm) or quadratic _{[(Σa i · ΔT i)} 2 + (∑b _i · ΔT _i ) ² ] ^1/2 Therefore, in order to calculate the instantaneous torque transmitted by the engine, the calculated norm may be substituted into the above formula (1), which is replaced with the linear combination ΔT _{n + 1} − ΔT _n .

However, especially if the mark formed on the ring or "target" integral with the flywheel of the engine makes it impossible to set to a phase shift of π / 2, the selected phase shift Φ ₀ may be different from π / 2. . In this case, the computed norm is somewhat complicated as follows:

[(∑a _i · ΔT _i ) ² + (∑b _i · ΔT _i ) ² + 2∑a _i ΔT _i · ∑b _i ΔT _i cosΦ ₀ ] ^1/2

In only exemplary and non-limiting embodiments, the method of calculating the coefficients a _i and b _i used in a given norm as described above is described below.

First, ignoring the change in engine speed (ΔN) with a change in the average angular velocity of the engine, the instantaneous angular velocity centered between two top dead centers, i.e. one combustion, is calculated to calculate the engine torque delivered by combustion. Only changes in need to be observed. Thus, in the embodiment shown in FIG. 1, the reduced observation window [t ₁ , t ₅ ] corresponding to a single interval between single combustion and top dead center, except for the direct current component (average speed N of the engine). It is possible to be limited to a linear combination of four coefficients acting on the time interval (ΔT _i ) measured between the instants t ₁ and t ₅ to amplify the peak-to-peak change in velocity within. Do.

In this case, the coefficient a _i or b _i is positive (e.g., +1) or negative (e.g. -1, depending on whether the instantaneous speed Ω is above or below the average speed. ). In accordance with the present invention, a _i (or b _i ) is selected such that Σa _i (or Σb _i ) becomes “zero” in order to eliminate the influence of the direct component.

According to the present invention, as shown in the figure for Ω, in order to eliminate the influence of the change of the average speed (ΔN) on the average speed (or speed (N)) of the engine, the movement period to the top dead center (PMH) is It is preferable to select observation windows [t ₀ and t ₆ ] which can be enlarged by 1.5 times. This window is centered in the middle (t ₃ ) of the gap between two consecutive top dead centers (PMH). In addition, each coefficient (a _i , b _i ) is a _i = a ' _i + a " _i , and is defined as the sum of 2 coefficients, such as b _i = b ' _i + b " _i . The coefficients a' _i and b ' _i are defined within four time intervals ΔTi in the interval [t _0, t ₄ ]. And coefficients a " _i and b" _i are defined within time intervals of interval [t _2, t ₆ ], each of which has a duration approximately equal to the duration of the interval between two consecutive top dead centers. Total ∑a ' _i , ∑a " _i , Σb ' _i and Σb " _i are both null as described above to eliminate the influence of the direct current component.

Thus, the effect of the change ΔN on the first combination ∑a ' _i ΔT _i is the same for the second combination ∑a " _i ΔT _i , but with the opposite indication, because the window [t ₂ , t ₆ ] Because the change in Ω has a phase opposite to that observed in the window [t ₀ , t ₄ ], so this effect is the sum calculated as the term against the corresponding time interval (ΔT _i ) ( a _i = a ' _i + a " _i ) The same applies to the coefficient b ₁ of the linear combination? B _i ΔT _i . Furthermore Σb _i ΔT _i has been selected to generate the same amplification and Σa _i ΔT _i.

As such, the influence of the change of the engine speed N ΔN is to classify each coefficient a _i , b _i as two sums of coefficients a ' _i + a "_i;b' _i + b" _i . By removing each coefficient (a ' _i , a " _i , b' _i , The sequence of b " _i ) has a sum of zero and each sequence pair (a ' _i , a"_i;b' _i , b " _i ) are removed from each other by elimination of the coefficients associated with the time intervals symmetric to the time intervals of the other sequences for the intermediate instant t ₃ of the observation window [t ₀ , t ₆ ] in each sequence.

The figure illustrates a method of calculating the coefficients a _i , b _i . It is to be understood that a number of other computational methods are also contemplated, but not restrictive, and are feasible by practitioners in the field.

For the coefficient a _i , the method starts with the form of two rectangular wavelengths (a ' _i , a " _i ), each with an interval [t ₀ , t ₄ ] and [t ₂ , t ₆ ] along the angular velocity (Ω ₀ ), the shape of these wavelengths varies between -1 and +1, respectively. The shape of each wavelength moves along the angular velocity within four time intervals. For each interval ΔT _i , by adding the levels reached by the form of the two wavelengths, a series of coefficients a _i can be obtained for a _i in the graph of the figure. here,

a ₀ = -1, a ₁ = -1, a ₂ = +2, a ₃ = +2, a ₄ = -1, a ₅ = -1.

The same applies to the coefficient b _i = b ' _i + b " _i ,

b ₀ = 1, b ₁ = -1, b ₂ = -2, b ₃ = +2, b ₄ = +1, b ₅ = -1

Thus, according to the invention the influence of a sufficient time interval ΔT _i is input into the torque calculation irrespective of the position of the velocity waveform in the observation window. This is you entered this effect, if close to the curve of ₀ Ω and Σa _i ΔT _i, the sum (Σb _i ΔT _i) different in this case is minimized by the coefficient (b _i). If the shape of the wavelength is shifted towards the curve of Ω ₉₀ , the opposite phenomenon can be seen. Whatever the mode of operation of the engine, a valid linear combination is entered into the torque calculation.

When the method of the present invention is implemented in a motor vehicle, no computer hardware is required other than that which is generally installed for electronically monitoring the engine's control parameters such as timing angle and injection time during ignition. To this end, conventionally used electronic computers receive signals from a variety of sensors, including sensors for detecting the passage of teeth formed on the periphery of the wheels integral with the output shaft of the engine, wherein the computer is at an angle of the crankshaft of any temporary engine. Analyze the signals supplied by the sensors to determine the position and phase of the various cylinders in the engine. Therefore, these signals and the appropriate program enable the computer to execute the torque calculation method according to the present invention using only one software. This is a particularly economical solution for the huge production system of the automotive industry.

In addition to the practical advantage of the present invention that it is possible to provide a reliable calculation of the torque transmitted by the engine in any mode of operation, even if the average angular velocity of the crankshaft changes rapidly in the interval between two top dead centers (PMH), respectively. It can be seen that the calculations produced at the moment include only acceleration and deceleration due to the combustion of the fuel / air mixture in only one of the cylinders of the engine. In the prior art, the measuring window used several consecutive combustions that were normally covered, and as a result were exhausted from each other, impairing the accuracy of the calculation of the torque transmitted by the engine.

While one embodiment according to the present invention has been described above, the present invention is not limited only to the above-described embodiment. Therefore, the present invention is not limited to use only in four cylinders, but can be easily applied to five or six cylinder engines by those skilled in the art.

Claims (11)

In the method for calculating the torque generated by the internal combustion engine based on the change in the rotational speed of the engine crankshaft, a) defining, for each phase in the combustion of air and fuel mixtures in each cylinder of the internal combustion engine, an observation window delimited by predetermined angular positions of the crankshaft of the engine; b) measuring a series of time intervals ΔT _i for dividing the movement of the crankshaft into the predetermined angular position in the observation window; c) amplifying the change in the alternating current component of the angular velocity of the crankshaft which is phase shifted relative to each other by a predetermined angle in each of the first and second operating modes of the engine during the measurement of the corresponding time interval ΔT _i in the observation window. and the step of selecting the coefficients (a _i and b _i) for, calculate two linear combinations (Σa _i ΔT _i and Σb _i ΔT _i) of the selected coefficients and the time intervals (ΔT _i), d) calculating said torque from a value expressed as a cube (ΔT ³ ) of the mean time interval measured in said predetermined observation window and the norm to which said two linear combinations are applied, How to calculate the torque of an internal combustion engine. The method of claim 1, Defining the first mode of operation at a substantially constant speed, wherein the combustion peak is in the most convincing position, How to calculate the torque of an internal combustion engine. The method of claim 2, Forming the second mode of operation at a combustion peak phase shifted by approximately Φ ₀ = 90 ° relative to the combustion peak of the first mode of operation, How to calculate the torque of an internal combustion engine. The method of claim 1, Forming an observation window covering an angular space separating two consecutive movements to the top dead center of the two cylinders of the engine, the observation window having a width less than or equal to 1.5 times the angular space; It is characterized in that for overlapping any one of both sides of the angular space, How to calculate the torque of an internal combustion engine. The method of claim 4, wherein The internal combustion engine is a four-cylinder engine, the time interval corresponding to a constant angular deviation equals one quarter (one quarter) of the angular space separating two consecutive top dead centers, the observation window having six angles To cover the deviation, How to calculate the torque of an internal combustion engine. The method of claim 5, The limitation of several successive angular deviations is characterized by coinciding with the ground point of the waveform of the alternating current component (Ω ₀ , Ω ₉₀ ) of the angular velocity of the engine between two consecutive top dead centers. How to calculate the torque of an internal combustion engine. The method of claim 6, And selecting the ground point from a group consisting of a highest point, a lowest point, and a zero intersection point. How to calculate the torque of an internal combustion engine. The method of claim 7, wherein Sum by selecting the coefficients to a zero method _(i Σa and Σb _i) further comprising the step of removing the influence of a direct current component of the angular velocity (Ω) of the engine, How to calculate the torque of an internal combustion engine. The method of claim 8, The amount of change in the rotational speed N of the engine by classifying each of the coefficients a _i and b _i into two coefficient sums a ' _i + a "_i;b' _i + b" _i which is a sequence of coefficients ( ΔN), and the sum of each of the coefficients (a ' _i , a "_i;b' _i , b" _i ) of the coefficients is zero, and each sequence pair (a ' _i , a " _i b ' _i , b " _i ) is removed from each other by elimination in each sequence of coefficients associated with a time interval symmetrical with the time interval of the other sequence with respect to the intermediate instant (t ₃ ) of the observation window [t ₀ , t ₆ ] in each sequence Characterized in that How to calculate the torque of an internal combustion engine. The method of claim 9, The coefficient a _i is a ₀ = -1, a ₁ = -1, a ₂ = +2, a ₃ = +2, a ₄ = -1, a ₅ = -1, and the coefficient b _i Is b ₀ = +1, b ₁ = -1, b ₂ = -2, b ₃ = +2, b ₄ = +1, b ₅ = -1, How to calculate the torque of an internal combustion engine. The method of claim 1, Further comprising the step of applying the Euclidean norm in the linear combinations (Σa _i ΔT _i and Σb _i ΔT _i), How to calculate the torque of an internal combustion engine.