JP2003120401A - Method for modeling friction torque of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a method of determining friction torque of an engine and to provide a method applicable to a variety of engines at a low cost. SOLUTION: The method models the friction torque of the engine in which viscosity of a lubricant used for lubrication of the engine is measured so that the measured viscosity of the lubricant is compared with characteristics in a lubricant viscosity characteristic map in order to determine a viscosity difference, an amount of amendment with respect to the engine friction torque stored in the characteristic map is calculated depending on the viscosity difference, and outputs corrected engine friction torque.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for modeling the friction torque of an engine, as well as a control device and a computer program implementing this method.

[0002]

2. Description of the Related Art In electronic stability programs or anti-slip control of a motor vehicle, for example, a target torque to be generated by an internal combustion engine in the vehicle is calculated. Furthermore, the driver's wishes expressed in the corresponding position of the accelerator pedal are converted into a target torque. The more accurately the actual torque produced by the internal combustion engine matches the target torque, the better the control quality. In the above applications, improved control quality results in safer and more comfortable driving characteristics of the vehicle.

The friction torque necessary to cancel the internal friction of the internal combustion engine is added to the target torque so that the target torque is generated by the internal combustion engine. The target torque including the friction torque forms a so-called "internal torque". In the case of diesel or gasoline engines, for example, the injection quantity, which depends on the operating parameters and thus on the application parameters, corresponds to this internal torque. The conversion of the internal torque to the target injection amount can be done by calculating the engine efficiency.
It is carried out by the control device depending on various operating parameters such as, for example, the speed and temperature of the internal combustion engine, the temperature of the exhaust gas and the humidity of the exhaust gas.

The friction torque of an internal combustion engine is usually determined during resistance tests and is filed in a characteristic map as a function of engine temperature and engine speed.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the method of determining the friction torque of an engine, yet to provide a method that functions inexpensively and is applicable to various engines.

[0006]

The above-mentioned object is to measure the viscosity of a lubricant used for engine lubrication and compare the measured lubricant viscosity with a characteristic value of a characteristic map of the viscosity of the lubricant. Then, a viscosity difference is formed, a correction amount for the engine friction torque stored in the characteristic map is calculated depending on the viscosity difference, and a corrected engine friction torque is output, and the engine friction torque is modeled. Be solved by the method.

[0007] The above problems also include performing the above method,
This is solved by a control device for a fuel injection position of an internal combustion engine and a computer program.

[0008]

The method according to the invention takes into account the actual viscosity of the lubricant used for lubricating the engine, in particular the internal combustion engine, in determining the friction torque. Thereby, the injection amount required for the internal combustion engine to generate the predetermined target torque can be calculated with high accuracy.
Already when the lubricant is in the neutral state, there is already a significant difference in viscosity, depending in particular on the permissible range of viscosities, and the addition causes fuel properties (thixotropy or rheopexy) depending on the tempering time. Therefore, by measuring the fuel viscosity, and by taking this viscosity into account in the present invention when determining the friction torque of the engine, an obviously more accurate friction torque measurement can be performed. The accuracy of the actual torque produced by the internal combustion engine is also improved to the same extent. As a result, the torque limitation necessary for protecting members such as the transmission and the clutch can be performed with a relatively small safety measure cost, and the performance of the vehicle is improved.

Therefore, according to the method of the present invention,
It is readily possible to clearly improve the accuracy of engine control with respect to the engine torque generated.

In essence, the friction torque of the engine is determined by the friction of the oil bearing. In such a system, the magnitude of the friction torque depends on the vertical power, the slip rate and the oil viscosity (Stribeck curve).
The first two parameters are defined by the operating point and the constitutive engine structure, and thus are constant with respect to a reference point in a given engine, whereas the oil viscosity is generally shear rate, tempering time. , Depends on temperature and pressure. Therefore, viscosity is the only parameter that determines the current friction torque at a particular operating point. The dependence on shear rate is generally absent in mineral and synthetic oils (so-called Newtonian fluids), but can be produced by addition. This addition also determines the time response of viscosity under tempering. Finally, the oil viscosity can be increased by applying pressure at the bearing position of the engine.

Furthermore, according to the method according to the invention, deterioration of the lubricant can be taken into account, for example due to dilution of the oil by decomposition of additives or penetration of other media.

With the method according to the invention, all these effects can easily be taken into account for the calculation of the friction torque, and a closed-loop control / control of the generated engine torque is carried out.
Open loop control is improved. For carrying out the method according to the invention, in the simplest case, there is only one viscosity sensor for the engine lubricant and a control device suitable for carrying out the method according to the invention.

According to another variant of the invention, the correction quantity is a correction factor and / or a correction moment, so that, depending on the operating point and the structure of the engine control, the effect of the oil viscosity on the friction torque is adequate. Consideration can be made.

Furthermore, in the characteristic map of the viscosity of the lubricant and / or the characteristic map of the friction torque, the temperature and / or the rotational speed of the engine are taken into consideration.

In an alternative embodiment of the method according to the invention,
Along with other input variables such as lubricant temperature and / or engine speed, the viscosity of the lubricant (η _oel ) is taken into account in modeling the engine friction torque. Advantageously, additional input quantities may be taken into account in the engine friction torque characteristic map.

To further improve the modeling of engine friction torque, the engine may be divided into various components. In an internal combustion engine, for example, a camshaft, a crankshaft, a piston and a cylinder can be divided. Then, for each of these components, the friction torque is modeled according to the method according to the invention, and the output of the corrected friction torque is then made based on the corrected friction torque of the component. This makes it possible to take into account differences in lubricant viscosity from component to component, eg due to different temperatures or different lubricants used. Of course, in order to carry out this method, it is necessary to provide at least one viscosity sensor for each component.

The method according to the invention can be used, inter alia, to determine the desired target torque development of an engine, in particular an internal combustion engine.

To further complement the invention, the method according to the invention may be used to determine the target injection quantity of the internal combustion engine required to produce the desired target torque.

Further advantages and advantageous embodiments of the invention can be understood from the drawings, the description of the drawings and the claims.

[0020]

1 shows a block diagram of a first exemplary embodiment of the method according to the invention. In particular, if it is desired to generate the target torque M _{d, Soll} by the engine which is the internal combustion engine, it is necessary to calculate the so-called internal torque M _{i, Soll} of the engine. Internal torque M
_{i and Sol} cancel the engine friction torque and
This is the torque that must be generated inside the engine in order to be able to generate the desired target torque M _{d, Soll} .

The internal torque M _{i, Soll} is usually not measured but must be calculated from other quantities. If the internal torque M _{i, Soll} is known, the target injection amount me _{, Soll} can be calculated in consideration of the engine speed n _Motor and the efficiency calculation. This target injection amount me _{, Soll} is the target torque M of the internal combustion engine (not shown) which is the basis of the embodiment according to FIGS. 1 and 2.
It is necessary to generate _{d and Sol} .

Engine friction torque M_{r, Basis}Is
It depends on a number of parameters. Not shown
The rotation speed n of the fuel engine is one of the parameters. Another
The parameters of the engine parameters are not shown in FIG.
Lubricant temperature T_oelIs. Rotation speed n and temperature T_oel
And possibly other unspecified parameters
Friction torque against M_{r, Basis}The dependency of
The friction torque characteristic map 3 is stored. This characteristic
Up 3 is a so-called resistance test, preferably with an engine
Required by. During this resistance test, the engine
Constant speed and predetermined temperature T of lubricant_oelDriven under
And friction torque M_{r, Basis}Is required for driving equivalent to
Required torque is stored. The output amount of the characteristic map 3 is friction.
Torque M _{r, Basis}Is.

In the engine control according to the prior art, the negative friction torque M _{r, Basis} is _converted into the target torque M _{d, Soll.}
From which the internal torque M _{i, Soll} is calculated. At that time, the influence of the viscosity of the lubricant is not considered,
As a result, the target torque M _{d, Soll} produced by the engine is no longer accurate. This inaccuracy adversely affects, for example, vehicle stability control or vehicle anti-slip control.

In the method according to the invention according to FIG. 1, at least one viscosity sensor 5 is provided, which preferably _measures the viscosity η _ol of the lubricant at a friction-related position in the oil circuit. taking measurement. In the characteristic map 7 of oil viscosity, various rotation speeds n in different resistance tests are shown.
_And the lubricant viscosity η measured under the lubricant temperature _Toel
oel is stored. The output amount of this characteristic map is the viscosity η _{oel, Basi s} . Measured viscosity η
viscosity eta _oe read from _oel and characteristic map 7
_From the comparison with _{1, Basis} , a viscosity difference Δη _oel is formed. In the embodiment according to FIG. 1, the correction coefficient f _η is calculated in calculation block 9 from this viscosity difference Δη _oel . The correction coefficient f _η is multiplied by the friction torque M _{r, B asis} read from the characteristic map 3 to _obtain the internal torque M
Corrected friction torque M used to calculate _{i and Sol
r, korr} are obtained.

Since _{the effect} of the lubricant viscosity η _oel is taken into account in the corrected friction torque M _{r, korr} , the internal torque M _{i, Soll} can be determined with relatively high accuracy. As a result, the target injection amount _{me, Soll} is also calculated with relatively high accuracy, and the engine target torque M _{d, Soll} is calculated.
Is generated with relatively high accuracy from the engine. This improves vehicle stability control or anti-slip control. In addition, the driveability of the vehicle is usually improved.

Of course, the method according to the invention is not limited to vehicle stability control and anti-slip control, but to any open-loop control in which the engine, in particular the internal combustion engine, produces a predetermined target torque M _{d, Soll.} It can be used for tasks and closed loop control tasks.

FIG. 2 shows a second implementation of the method according to the invention.
An example block circuit diagram is shown. This second embodiment
Then, the correction coefficient f_ηIn parallel with the second calculation block 1
Viscosity difference in 1_oelTo torque difference ΔM_rIs calculated
Corrected friction torque M _{r, korr}Captured in
It As a result, the friction torque M_{r, B
assis}And the correction factor f_ηFriction corrected by product of
Luk M_{r, korr}Formation and / or differential torque Δ
M_rCorrected friction torque M by adding_{r, Ba sis}
Can be corrected. According to this method, the target torque
M_{d, Soll}Further improvement in control quality of
It In particular-according to the structure of the characteristic map 3--correction
Used friction torque M_{r, korr}The correction clerk to ask for
Number f_ηOr correction torque ΔM_rSo that
Good.

FIG. 3 shows a block circuit diagram of a third embodiment of the method according to the invention. In this example,
Friction torque n-dimensional characteristic map (M _r = f (η _oel ,
T _{o el} , n, E ₁ ... E _i ) are provided. Along with the other input quantities E ₁ ... E _i , the lubricant viscosity η _oel is also directly included in the calculation of the friction torque M _r . This friction torque is
As described in FIG. 1, the fuel amount m to be injected m
It may be taken into consideration for the calculation of _{e and soll} .

In the embodiment according to FIG. 4, the engine has j = 1.
... is divided into various components j of n. A characteristic map of friction torque (not shown) is determined for each of these components. As described above, the corrected friction torque M for each component j
_{r, korr, j} are obtained and added at the combining position “+”. As a result, the corrected friction torque M _{r, korr of the} entire engine is obtained. In this example, the friction torque can be modeled in great detail to allow for various effects and operating conditions of the component. As a result, this embodiment further improves the quality of friction torque modeling.

[Brief description of drawings]

FIG. 1 shows a block circuit diagram of a first embodiment of the method according to the invention.

FIG. 2 shows a block circuit diagram of a second embodiment of the method according to the invention.

FIG. 3 shows a block circuit diagram of a third embodiment of the method according to the invention.

FIG. 4 shows part of a block circuit diagram of a fourth embodiment of the method according to the invention.

[Explanation of symbols]

1 Efficiency calculator 3 characteristic map 5 Viscosity sensor 7 characteristic map 9 calculation blocks 11 Calculation block

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Andreas Hoover             Federal Republic of Germany Steinheim             Ugusto-Scholl-Strasse 21 (72) Inventor Dirk Zamuelsen             Ludwigsburg, Germany               Tischendorf Strasse 7 F-term (reference) 3G084 BA02 BA13 DA00 DA25 EB06                       EC04 FA00 FA20 FA33

Claims (12)

[Claims] 1. A method for modeling the friction torque of an engine, for example an internal combustion engine, wherein the viscosity of the lubricant used for lubricating the engine (η
measuring the _OEL), characteristic map characteristic value (7) of the viscosity of the measured lubricant viscosity (eta _OEL) said lubricant (eta _OEL) (eta
_{Oel, Basis} ) and the viscosity difference (Δη _oel = η _oel −
η _{oel, Basis} ) and the engine friction torque (M
_{r, Basis} ) _, a step of calculating a correction amount (f _η , ΔM _r ) depending on the viscosity difference (Δη _oel ), and a step of outputting a corrected engine friction torque (M _{r, korr} ) A method characterized by. 2. The method according to claim 1, wherein the correction amount is a correction coefficient (f _{η oel} ). 3. The method according to claim 1, wherein the correction amount is a correction torque (ΔM _r ). 4. The temperature (T) and / or the engine speed (n) of the engine are included in the characteristic map of the lubricant viscosity (η _oel ).
The method according to any one of claims 1 to 3, wherein 5. The lubricant viscosity (η _oel ), the engine temperature (T) and / or the rotational speed (n) are input in the characteristic map (3) of the friction torque (M _{r, korr} ). Item 5. The method according to any one of Items 1 to 4. 6. The engine friction torque (M
Method according to claim 5, characterized in that a further input quantity (E _i ) is entered in the characteristic map (3) of _{r, korr} ). 7. The engine is divided into various components, for each of which the friction torque is modeled by the method according to any one of claims 1 to 6 and subsequently the friction torque of the component ( _j ) is modeled. The corrected friction torque (M _{r, korr} ) is output based on the corrected friction torque (M _{r, korr, j} ).
The method according to any one of 1. 8. A desired target torque (M
_8. The method according to any one of claims 1 to 7, used to determine the occurrence of _d . 9. A target injection amount (m) of an internal combustion engine required to generate a desired target torque (M _{d, Soll} ).
_{e, Sol} ) used to determine _e.
9. The method according to any one of 1 to 8. 10. A control device for a fuel injection position of an internal combustion engine, characterized in that it is suitable for carrying out the method according to any one of claims 1-9. 11. A computer program, adapted to carry out the method according to any one of claims 1 to 9. 12. The computer program according to claim 11, which can be stored in a storage medium, for example, a CD-ROM.