KR101064197B1 - Method for estimating indicated mean effective pressure using cylinder pressure - Google Patents

Abstract

The present invention relates to a method for estimating the city average effective pressure of an internal combustion engine using a cylinder pressure that can reduce the amount of computational work by using a small number of cylinder pressure data and can estimate the city average effective pressure simply and accurately. A method for estimating the urban mean effective pressure of an internal combustion engine using a cylinder pressure according to the present invention estimates the average mean effective pressure in a cylinder for an internal combustion engine including a cylinder and a piston reciprocating linearly in the cylinder. The method of claim 1, wherein the sum of the detected pressure which is the difference between the cylinder internal pressure when combustion occurs and the internal pressure of the cylinder when combustion does not occur, and the city average effective pressure inside the cylinder using the sum of the detected pressures Estimating.

Urban average effective pressure (IMEP), motoring pressure, combustion pressure, detection pressure (DP), internal combustion engine

Description

Method for estimating indicated mean effective pressure using cylinder pressure}

The present invention relates to a method of estimating the urban average effective pressure of an internal combustion engine, and more particularly, to a method of estimating the urban average effective pressure which is widely used as a measure of the performance of an internal combustion engine.

The engine of an internal combustion engine, for example a motor vehicle, comprises a cylinder and a piston reciprocating linearly in the cylinder, and when fuel burns in the cylinder, dedicated work is produced. And, the illustrated work is transmitted to each drive unit through the crank shaft connected to the piston, so that the vehicle can be driven.

On the other hand, the multi-cylinder automobile engine is provided with a plurality of cylinders, and combustion occurs in a predetermined order in the plurality of cylinders, and the cylinder pressure is continuously converted to the rotation day of the crankshaft. The torque generated on the crankshaft has a great influence on the drivability of the vehicle. By design, the same size torque is generated in each cylinder, but in reality, there is a difference in the amount of fuel burned or the amount of air sucked into the cylinder due to various factors such as production tolerances and aging of engine parts. This difference causes a difference in the torque generated in each cylinder.

The difference in torque generated for each cylinder is obtained by measuring the torque coming out of the crankshaft directly. However, the torque sensor for measuring torque has a problem that durability is not only being verified, but also expensive, and that reliability of torque data measured by the torque sensor is still being verified, and the method disclosed in Korean Patent No. 510,804 is a map. It required a lot of tests when constructing the engine and moreover it was very vulnerable to aging and disturbance of engine parts.

In addition to this, there is a method of using the city average effective pressure as a method of measuring torque variation for each cylinder. Since the city average effective pressure is derived from the cylinder pressure which immediately shows combustion information, it is most suitable for calculating the city torque. In particular, the pressure sensor for measuring the cylinder pressure includes atmospheric pressure, mass airflow, and camshaft sensor. Since it is possible to replace a sensor such as a (torque sensor), measuring or estimating the city average effective pressure using a cylinder pressure is more accurate and economical than using a torque sensor. The urban average effective pressure is calculated by the following equation.

Here, n ₁ and n ₂ are integration periods, the initial and the last of the crank angle, Δθ are the resolution of the crank angle, V _S is the displacement of the cylinder, p is the cylinder pressure.

However, since the cylinder pressure data for the entire cycle is required to calculate the city average effective pressure, 720 data are required for one cylinder when sampling the cylinder pressure for each 1 degree of the crank. Thus, for a four-cylinder engine, 2880 data sampling and calculations must be completed in one cycle. Such an excessive amount of calculation has a problem that a high performance controller as well as a commercial engine controller are difficult to perform in real time. And, in order to reduce the workload of the controller, which was proposed in 1996 by Brunt and Empire, an error is obtained when obtaining a city average effective pressure (Coarse IMEP) with a wider sampling interval of cylinder pressure. A new problem arises that is increased.

Therefore, the necessity of researching a new method for measuring the urban mean effective pressure has emerged.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to reduce the amount of computational work by using a small number of cylinder pressure data, and furthermore to obtain a cylinder pressure which can estimate the city average effective pressure simply and accurately. It is to provide a method for estimating the urban average effective pressure of an internal combustion engine.

In order to achieve the above object, the urban mean effective pressure estimation method of an internal combustion engine using a cylinder pressure according to the present invention is a city average effective inside the cylinder with respect to an internal combustion engine comprising a cylinder and a piston reciprocating linearly in the cylinder. A method for estimating a pressure (indicated mean effective pressure), comprising: obtaining a sum of a detected pressure which is a difference between an internal pressure of a cylinder when combustion occurs and an internal pressure of the cylinder when combustion does not occur, and the detected pressure Estimating a city average effective pressure inside the cylinder by using the sum of.

According to the present invention, the city average effective pressure can be estimated simply and accurately by using the difference pressure integral (DPI). In particular, unlike the conventional method, since the number of cylinder pressure data is used, the number of data measurement and the amount of calculation work can be reduced, and as a result, the city average effective pressure can be estimated in real time even with a mass production engine controller.

1 is a graph for explaining the detection pressure, Figure 2 is a photograph of the diesel engine used in the experiment, Figure 3 is a graph showing the correlation between DPI and IMEP.

Hereinafter, a method for estimating the city average effective pressure of an internal combustion engine using a cylinder pressure according to a preferred embodiment of the present invention will be described with reference to FIGS. 1 to 3.

First, the present invention relates to a method for estimating the average mean effective pressure (IMEP) of an internal combustion engine having a piston and a cylinder. As described above, in the conventional case, the city average effective pressure was measured using the pressure of the cylinder at each crank angle as a variable. In order to solve this problem, it is necessary to have a close correlation with the urban average effective pressure and to estimate the urban average effective pressure with a small number of data. In this embodiment, the city average effective pressure is estimated using the sum of the detected pressures as the variable.

The detection pressure (DP) refers to a difference between the combustion pressure P _{firing which} is the cylinder pressure when combustion occurs and the _motoring pressure P _{motoring which} is the cylinder pressure when combustion does not occur. At this time, the combustion pressure and the motoring pressure are measured by a pressure sensor installed in the cylinder. In addition, the sum of the detection pressures (DPI: Difference Pressure Integral) is a value (integrated value), that is, the sum of the detection pressures while the crank angle is rotated by 180 ° based on the top dead center (TDC), that is, colored in FIG. Means part.

On the other hand, an experiment was conducted to establish a correlation between the sum of the detected pressures (DPI) and the urban mean effective pressure (IMEP).

In the experiment, the diesel engine shown in FIG. 2, that is, a 2-liter in-line four-cylinder common-rail direct injection diesel engine having a turbocharger and an intercooler, was used. As the engine control system, a commercially available general-purpose controller, that is, a commercial off-the-shelf (COTS) rapid control prototyping (RCP) platform and a MicroAutoBox was used. Fuel injection timing, injection duration and common rail pressure were adjusted for each experiment. Cylinder pressure was measured using a piezo pressure transducer suitable for the glow plugs. Details of the experimental apparatus are shown in Table 1 below.

TABLE 1

After configuring the experimental device as shown in <Table 1>, at the engine rotational speed of 2000 RPM, start the fuel injection command (SOE: Start Of Energizing) at a crank angle of 4 ° (4 ° BTDC) before 24 ° ( The experiment was conducted in the form of checking the correlation between DPI and IMEP according to fuel injection amount by varying 4 ° to 24 ° BTDC), and the results are shown in FIG. 3.

Referring to FIG. 3, it can be seen that the IMEP and the DPI have a very linear relationship. Therefore, the correlation between the IMEP and the DPI may be set as in Equation 1 below.

<Equation 1>

IMEP = a × DPI + b

Here, a and b are constants determined according to operating conditions of the internal combustion engine such as SOE, RPM, and fuel injection amount, and particularly, a and b are closely related to the conditions of SOE and RPM. Therefore, in the present embodiment, as shown in Equation 2, a and b are set as functions of SOE and RPM.

<Equation 2>

a = f _a (SOE, RPM) = a ₁ SOE ² + a ₂ SOE + a ₃ RPM + a ₄

b = f _b (SOE, RPM) = b ₁ SOE + b ₂ RPM + b ₃

Here, a ₁ , a ₂ , a ₃ , a ₄ , b ₁ , b _2, and b ₃ are constants that change depending on the shape of the engine, and nonlinear curve fitting based on data obtained through experiments and simulations. Is set by

On the other hand, a simulation was performed to confirm the accuracy of the IMEP estimated by the above-described urban average effective pressure estimation method of the internal combustion engine, and the results are shown in FIGS. 4 to 7.

4 shows the measured values of IMEP and the estimated IMEP by simulation when the SOE is changed by 4 ° from 4 ° BTDC to 24 ° BTDC at engine speed of 1500 RPM and the fuel injection amount is changed from 10mg to 40mg by 10mg. Graph showing values. 5 to 7 are graphs showing the values of the IMEP estimated using the measured DPI and the measured DPI while the engine is repeatedly rotating the cycle at 1500 RPM, 1750 RPM, and 2000 RPM.

Referring to FIG. 4, it can be seen that an error between the actually measured IMEP value and the estimated IMEP value falls within an error range of about 0.3 bar. 5 to 7, at the time when the operating conditions (fuel injection amount) are changed (0.5s and 1.8s in FIG. 5, 0.5s and 1.7s in FIG. 6 and 0.5s and 1.5s in FIG. 7). In the cycle of, the error is slightly large, and the error of the measured IMEP value and the estimated IMEP value from DPI are small. In other words, the IMEP value actually measured and the IMEP value estimated by the simulation are generally identical, and therefore, it can be seen that the IMEP value can be accurately estimated by the urban mean effective pressure estimation method of the internal combustion engine according to the present embodiment.

As described above, when the urban mean effective pressure estimation method of the present embodiment is used, the city average effective pressure can be accurately estimated using the sum of the detected pressures (DPI), where the sum of the detected pressures is a crank after the top dead center. This can be obtained by sensing the pressure of the cylinder until the angle rotates 180 °. Therefore, the amount of data (pressure) to be measured in order to estimate the city average effective pressure is reduced to about 1/4 as compared with the conventional art, and the computational load for processing the data is greatly reduced. Therefore, the city average effective pressure can be estimated in real time even in the engine controller currently used.

In addition, since the effect of the aging of the engine or the production tolerance of the engine is reflected in the combustion result, when using a detection pressure that is directly related to the combustion result as in the present embodiment, the engine may be aged or the production tolerance may be Even if it is, the city average effective pressure can be estimated accurately.

In addition, by using the city average effective pressure estimated as described above, it is possible to accurately estimate the city day in real time, and thus the output of the engine can be controlled to meet the target driving conditions over the entire operating area. The reduction effect of exhaust gas, noise, and vibration can be aimed at.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific preferred embodiments described above, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

1 is a graph for explaining the detection pressure.

Figure 2 is a photograph of the diesel engine used in the experiment.

3 is a graph showing the correlation between DPI and IMEP.

4 shows the measured values of IMEP and the estimated IMEP by simulation when the SOE is changed by 4 ° from 4 ° BTDC to 24 ° BTDC at engine speed of 1500 RPM and the fuel injection amount is changed from 10mg to 40mg by 10mg. Graph showing values.

5 to 7 are graphs showing the values of the measured IMEP and the estimated IMEP using the measured DPI while the engine is repeatedly rotating the cycle at 1500 RPM, 1750 RPM and 2000 RPM, respectively.

Claims (4)

A method for estimating the mean mean effective pressure inside a cylinder for an internal combustion engine comprising a cylinder and a piston reciprocating linearly in the cylinder, Obtaining a sum of a detection pressure which is a difference between the cylinder internal pressure when combustion occurs and the internal pressure of the cylinder when combustion does not occur; And Estimating a city average effective pressure inside the cylinder by using the sum of the detected pressures; In the estimating the city average effective pressure, the city average effective pressure is estimated by Equation 1 below. A and b in Equation 1 are functions of the fuel injection command point SOE and the rotational speed RPM of the internal combustion engine, and are determined by Equation 2 below. Method of estimating the city mean effective pressure <Equation 1> IMEP = a × DPI + b <Equation 2> a = a ₁ SOE ² + a ₂ SOE + a ₃ RPM + a ₄ , b = b ₁ SOE + b ₂ RPM + b ₃ Where IMEP is the estimated city average effective pressure, DPI is the sum of the detected pressures, a and b are constants determined according to the operating conditions of the internal combustion engine, and a ₁ , a ₂ , a ₃ , a ₄ , b ₁ , b ₂ and b ₃ are constants determined by nonlinear curve fitting. delete delete delete

Images