JP2013007330A - Air quantity estimation device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the estimation accuracy of a cylinder air quantity of an internal combustion engine including a supercharger.SOLUTION: An air quantity estimation device is applicable to an internal combustion engine equipped with a supercharger including an intake passage for leading air taken from the outside into a cylinder and a compressor for compressing the air in the intake passage, and estimates a cylinder air quantity which refers to a quantity of air led into the cylinder based on a physical model indicating a behavior of the air flowing in the intake passage. In estimating the cylinder air quantity, the air quantity estimation device estimates a compressor flow rate which refers to a quantity of air passing through the compressor, and calculates a back-flow correction value wherein a compressor flow rate estimation value in a region where the compressor flow rate estimation value is a negative value is inverted to a positive value. An intake quantity is estimated according to the back-flow correction value, and in addition, an intake quantity is detected according to an output from an intake quantity sensor. The compressor flow rate estimation value is corrected according to a difference between the estimation value of the intake quantity and the detection value of the intake quantity detected by an air quantity detecting means. The cylinder air quantity is estimated according to the corrected compressor flow rate correction value.

Description

  The present invention relates to an air amount estimation device for an internal combustion engine.

  2. Description of the Related Art An air amount estimation device that estimates an in-cylinder air amount, which is the amount of air introduced into a cylinder of an internal combustion engine equipped with a supercharger, using a physical model representing the behavior of air in an intake passage is known. Yes. For example, in the air amount estimation device described in Patent Document 1, the compressor flow rate is estimated based on the signal of the intake air amount sensor, and the air amount in the intake passage downstream of the compressor is estimated based on the compressor flow rate.

JP 2006-194107 A JP 2010-242893 A JP 2008-106703 A JP 2008-0697707 A JP 2010-270627 A

  The intake air amount sensor detects the air flow rate based on the difference in heat dissipation due to the air flow rate. Therefore, an output corresponding to the flow rate is generated as a positive value regardless of the direction of air flow. Therefore, for example, even when a surge occurs and air flows backward (flows upstream), the flow rate is detected as a positive value. That is, in the region where the surge is generated, a large difference opens between the intake air flow rate detected based on the intake air amount sensor and the actual flow rate.

  As a result, as described in the above publication, in the estimation of the compressor flow rate based on the signal of the intake air amount sensor, there is a large difference between the estimated compressor flow rate and the actual flow rate when a reverse flow occurs due to a surge. It will open, and it is considered that the estimation accuracy of the in-cylinder air amount decreases. In this respect, the air amount estimation device still has room for improvement.

  The present invention has been made to solve the above-described problems, and provides an air amount estimation device for an internal combustion engine that can estimate the in-cylinder air amount with high accuracy in an internal combustion engine including a supercharger. The purpose is to do.

  In order to achieve the above object, the present invention is an air amount estimation device for an internal combustion engine, and includes an intake passage for introducing air taken from outside into a cylinder, and a compressor for compressing air in the intake passage. This is applied to an internal combustion engine equipped with a supercharger, and estimates the in-cylinder air amount that is the amount of air introduced into the cylinder based on a physical model representing the behavior of air flowing in the intake passage. is there.

In the present invention, the air amount estimation device
A flow rate estimating means for estimating a compressor flow rate that is an amount of air passing through the compressor;
Backflow correction means for calculating a backflow correction value obtained by inverting the compressor flow rate estimation value to a positive value in a region where the compressor flow rate estimation value estimated by the flow rate estimation means is a negative value;
An air amount estimating means for estimating an intake air amount in accordance with the backflow correction value;
An air amount detecting means for detecting an intake air amount in accordance with an output of the intake air amount sensor;
A flow rate correcting unit that corrects the estimated compressor flow rate according to a difference between an estimated value of the intake air amount estimated by the air amount estimating unit and a detected value of the intake air amount detected by the air amount detecting unit. When,
In-cylinder air amount estimating means for estimating the in-cylinder air amount according to the compressor flow rate correction value corrected by the flow rate correcting means,
Is provided.

  In addition, the air amount estimation device of the present invention may further include a surge determination unit that determines that a surge has occurred when the estimated compressor flow rate is a negative value.

  According to the first aspect of the invention, it is possible to estimate the intake air amount corresponding to the compressor flow rate reversed to a positive value even when a reverse flow due to a surge occurs. This compares the detected value of the air amount with the intake air amount sensor that always outputs a positive value regardless of the air flow direction and the estimated value of the air amount that is estimated according to the compressor flow rate that is a positive value. The compressor flow rate can be corrected appropriately according to the difference between the two. Therefore, it is possible to estimate the in-cylinder air amount with high accuracy regardless of the presence or absence of backflow due to surge.

  According to the second invention, it is possible to easily detect the occurrence of a surge. In this way, by adopting a mechanism that can detect the occurrence of a surge by a simple method, for example, when the surge is generated, the operation condition of the ABV may be corrected, and the occurrence of the surge can be suppressed. it can.

It is a figure for demonstrating the system configuration | structure of embodiment of this invention. It is the schematic diagram which showed the various models of the air quantity estimation apparatus of embodiment of this invention. It is a figure for demonstrating an example of the estimated value of the compressor flow volume in embodiment of this invention. It is a figure for demonstrating an example of the correction value of the compressor flow volume in the embodiment of this invention, the estimated value of the intake air amount, and the detected value.

Embodiment.
Embodiments of an air amount estimation device for an internal combustion engine according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram for explaining a system configuration according to an embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine 10 and an ECU (Electronic Control Unit) 12 for controlling the internal combustion engine 10. The control device 12 comprehensively controls the entire system of the internal combustion engine 10. Various actuators are connected to the output side of the control device 12, and various sensors are connected to the input side. The control device 12 receives the sensor signal, detects the air-fuel ratio of the exhaust gas, the engine speed, and other various information necessary for the operation of the internal combustion engine 10, and operates each actuator according to a predetermined control program. There are many actuators and sensors connected to the control device 12, but the description thereof is omitted in this specification. In the present embodiment, the control device 12 functions as an air amount estimation device that estimates the amount of air flowing into each cylinder of the internal combustion engine 10.

  Each cylinder of the internal combustion engine 10 is provided with an intake valve 14, an exhaust valve 16, a spark plug 18, and a fuel injector 20. The intake system 30 includes an intake manifold 31, a surge tank 32 communicating with the intake manifold 31, an air filter 33, a compressor 40 a of the supercharger 40, an intercooler 34, and a throttle valve 35. The exhaust system 50 includes an exhaust pipe 51 including an exhaust manifold, a turbine 40b of the supercharger 40 provided in the exhaust pipe 51, and a three-way catalyst device 52 provided in the exhaust pipe 51 downstream of the turbine 40b. And.

  With such an arrangement, the turbine 40b of the supercharger 40 is rotated by the energy of the exhaust gas and drives the compressor 40a. Thereby, the compressor 40a compresses the air in the intake passage. Although not shown, the system according to the present embodiment includes various sensors.

  FIG. 2 is a functional block diagram for explaining the air amount estimation apparatus according to the embodiment of the present invention. As shown in FIG. 2, the air model of the air amount estimation device of the present embodiment divides the intake system of the internal combustion engine into elements such as a compressor, an air flow meter, an intercooler, a throttle valve, an intake pipe, and an intake valve. For each element, the air flow rate is estimated by a physical model constructed based on physical laws such as the energy conservation law, the momentum conservation law, and the mass conservation law. The in-cylinder air amount KLF at the time is estimated.

  More specifically, in the estimation of the cylinder charge air amount KLF, the intercooler pressure Pic and its temperature Tic are estimated in the model M10 of the intercooler section in FIG. The pressure Pic and the temperature Tic are input to the throttle model M20, and the throttle passing air amount mt is estimated. Further, the throttle passage air amount mt is input to the model M30 of the intake pipe section, and the pressure Pm of the air in the intake pipe section and its temperature Tm are estimated. The pressure Pm and the temperature Tm are input to the intake valve model M40, the flow rate of air passing through the intake valve is calculated, and the in-cylinder air amount KLF is estimated.

  In the air amount estimation device of the present embodiment, a compressor flow rate mcp that is a flow rate of air flowing out from the compressor 40a is input to the model M10 of the intercooler unit. The compressor flow rate mcp input to the intercooler unit is the same as the compressor flow rate mcp estimated by the compressor flow rate estimation unit M50, and the intake air amount calculated by the intake air amount estimated by the AFM model M70 and the output of the intake air amount sensor. It is calculated by correcting with the correction value calculated by the amount.

なお、上記式（１）において、ｄＰｉｃ/ｄｔは、インタークーラ圧力センサの出力変化量に応じて求められる。ｍｔはインタークーラ圧力、温度センサと、インタークーラ以降の空気モデルに基づいて算出される。Ｖｉｃはインタークーラの体積、Ｔａは吸気温度、ｋは係数、Ｒは変換率である。 First, in the compressor flow rate estimation unit M50, the compressor flow rate mcp is estimated by the following formula (1) based on the energy conservation formula of the intercooler.

In the above formula (1), dPic / dt is obtained according to the output change amount of the intercooler pressure sensor. mt is calculated based on the intercooler pressure, temperature sensor, and air model after the intercooler. Vic is the volume of the intercooler, Ta is the intake air temperature, k is a coefficient, and R is the conversion rate.

  FIG. 3 shows an example of the compressor flow rate mcp calculated in the present embodiment. In FIG. 3, the horizontal axis represents time, and the vertical axis represents the flow rate. As shown in FIG. 3, the compressor flow rate mcp output from the compressor flow rate estimation unit M50 shows a negative value in a region where a surge occurs and air flows backward.

  FIG. 4 is a diagram comparing air flow rates based on the output of the backflow correction unit M60, the output of the AFM model M70, and the output of the intake air amount sensor in the present embodiment. In FIG. 4, the horizontal axis represents time, and the vertical axis represents the flow rate.

  The compressor flow rate mcp estimated by the compressor flow rate estimation unit M50 is corrected by the backflow correction unit M60. Specifically, the backflow correction unit M60 corrects the compressor flow rate mcp to be an absolute value as shown in FIG. That is, the compressor flow rate mcp in a region where a reverse flow due to a surge is recognized in FIG. 3 is inverted to a positive value.

  Next, the compressor flow rate corrected by the backflow correction unit M60 is input to the AFM model M70, and the amount of air flowing into the compressor 40a, that is, the amount of intake air is estimated as shown in FIG. 4B. In the AFM model M70, an estimated value of the air amount that takes into account the response delay of the intake air amount sensor is output.

  Next, a correction value corresponding to the difference between the intake air amount based on the output of the intake air amount sensor (see FIG. 4C) and the estimated air amount output from the model M70 (FIG. 4B). Is required. The compressor flow rate mcp is corrected according to the correction value. As described above, the corrected compressor flow rate is input to the intercooler model M10.

  Incidentally, as described above, the intake air amount sensor is a sensor that detects a flow rate based on a difference in heat dissipation of the air flow rate. Therefore, the output of the intake air amount sensor outputs a positive output according to the flow rate regardless of the direction of air flow in the intake pipe. Therefore, even in a region where a reverse flow due to a surge occurs and the flow rate should be a negative value, the intake air amount sensor shows an output in the positive direction (the direction of flowing downstream).

  On the other hand, the AFM model M70 receives the compressor flow rate mcp and estimates the air amount. Here, assuming that there is no correction in the backflow correction unit M60, if a backflow occurs, the compressor flow rate mcp that is a negative value is input to the AFM model M70 as it is. In this case, the estimated value of the intake air amount calculated by the AFM model M70 also corresponds to the compressor flow rate that is a negative value. Therefore, when a reverse flow due to surge occurs, there is a large difference between the estimated value of the air amount based on the AFM model M70 and the detected value of the intake air amount based on the output of the intake air amount sensor. For this reason, the correction value obtained by comparing the intake air amount estimated value and the intake air amount detection value is excessively large, and it is considered that the correct correction of the estimated value of the compressor flow rate cannot be performed.

  In this regard, according to the present embodiment, the backflow correction unit M60 corrects the compressor flow rate to a compressor flow rate | mcp | that is a positive value that does not include a directional element. By converting the compressor flow rate mcp to a positive value (absolute value) in this way, even in the region where the reverse flow occurs, the AFM model M70 has an estimated intake air amount value based on the compressor flow rate reversed in the forward direction. Calculated. Thereby, the detected value of the air amount based on the intake air amount sensor and the estimated value of the air amount based on the AFM model M70 do not include a direction element, and both can be appropriately compared. As a result, the compressor flow rate can be corrected appropriately, and the estimation accuracy of the intake air amount and the in-cylinder air amount can be further increased.

  Further, in the present embodiment, the air amount estimation device may have a function of determining a surge in addition to the correction of the compressor flow rate. That is, as shown in FIG. 3, when the compressor flow rate estimated according to the equation (1) becomes negative, it can have a surge determination function for determining the occurrence of surge.

  Note that the calculation method of the flow rate mt, temperature Tic, Ta, pressure Pic, and the like in Equation (1) is not limited to that described in the present embodiment, and may be calculated by another conventional method. For example, the throttle valve flow rate mt has been described with reference to the intercooler pressure or temperature sensor and the air model after the intercooler. It may be.

  In other cases, in the above embodiment, when the number of each element, quantity, quantity, range, etc. is mentioned, unless otherwise specified or clearly specified in principle, that number The invention is not limited to the number mentioned. The structures, steps, and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Control apparatus 30 Intake system 40 Supercharger 40a Compressor 50 Exhaust system M50 Compressor flow rate estimation part M60 Backflow correction part M70 AFM model

Claims (2)

Applied to an internal combustion engine having an intake passage for introducing air taken from outside into a cylinder and a supercharger having a compressor for compressing the air in the intake passage, the behavior of the air flowing in the intake passage is An air amount estimation device for an internal combustion engine that estimates an in-cylinder air amount, which is an amount of air introduced into the cylinder, based on a physical model to be represented,
A flow rate estimating means for estimating a compressor flow rate that is an amount of air passing through the compressor;
Backflow correction means for calculating a backflow correction value obtained by inverting the compressor flow rate estimation value to a positive value in a region where the compressor flow rate estimation value estimated by the flow rate estimation means is a negative value;
An air amount estimating means for estimating an intake air amount in accordance with the backflow correction value;
An air amount detecting means for detecting an intake air amount in accordance with an output of the intake air amount sensor;
A flow rate correcting unit that corrects the estimated compressor flow rate according to a difference between an estimated value of the intake air amount estimated by the air amount estimating unit and a detected value of the intake air amount detected by the air amount detecting unit. When,
In-cylinder air amount estimating means for estimating the in-cylinder air amount according to the compressor flow rate correction value corrected by the flow rate correcting means,
An air amount estimation device for an internal combustion engine, comprising:   The air amount estimation device for an internal combustion engine according to claim 1, further comprising surge determination means for determining that a surge has occurred when the compressor flow rate estimation value is a negative value.

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