JP2014025448A - Intake air amount estimation device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance estimation accuracy of an intake air amount by enhancing accuracy of a physical model, in an intake air amount estimation device of an internal combustion engine for estimating an intake air amount by calculation with a physical model.SOLUTION: An intake air amount estimation device of an internal combustion engine calculates an intake pipe pressure with an intake pipe model having at least an intake pipe diameter and an intake pipe length as physical parameters, and actually measures the intake pipe pressure with a pressure sensor. Then, the intake air amount estimation device compares a calculation value of the intake pipe pressure obtained by the intake pipe model and an actual measurement value of the intake pipe pressure obtained by the pressure sensor, and identifies the physical parameter on the basis of the comparison result.

Description

  The present invention relates to an intake air amount estimation device for an internal combustion engine that estimates an intake air amount into a cylinder by a calculation using a physical model.

  For example, as disclosed in Patent Document 1, there is known a method for estimating the amount of intake air into a cylinder by calculation using a physical model representing the behavior of air in the intake passage. In the intake air amount estimation device (hereinafter referred to as a conventional device) disclosed in Patent Document 1, a plurality of models including an intake pipe model, a cylinder model, an intake valve model, and an exhaust valve model are used. In the calculation using the cylinder model by the conventional apparatus, the cylinder gas pressure is calculated from the intake valve passage gas flow rate calculated by the intake valve model and the exhaust valve passage gas flow rate calculated by the exhaust valve model. In the calculation using the exhaust valve model, the exhaust valve passage gas flow rate is calculated from the in-cylinder gas pressure and the exhaust gas pressure. In the calculation using the intake valve model, the intake valve passage gas flow rate is calculated from the in-cylinder gas pressure and the intake pipe air pressure calculated from the intake pipe model. The cylinder intake air amount is estimated by integrating the intake valve passage gas flow rate.

JP 2007-0779970 A JP 2004-263571 A JP 2007-239484 A

  The amount of intake air estimated by the conventional device depends on the state quantity of each part calculated by each model. The state quantity of each part calculated by each model depends on physical parameters and boundary conditions that characterize each model. For this reason, in order to accurately estimate the intake air amount, it is important to appropriately set the physical parameters and boundary conditions of each model.

  However, in the conventional apparatus, preset values are used for typical physical parameters and boundary conditions in each model. Of course, these setting values may be determined by adaptation using an actual machine, but not all physical parameters and boundary conditions are set optimally.

  In this case, if the physical parameters and boundary conditions can be optimally set in all models, the estimation accuracy of the intake air amount becomes very high. However, if at least a part of the models can optimize any of the physical parameters and the boundary conditions even if not all of the models, it is possible to improve the estimation accuracy of the intake air amount as compared with the conventional device. .

  The present invention has been made in view of such problems. In an intake air amount estimation device for an internal combustion engine that estimates an intake air amount by a calculation using a physical model, the physical parameters of the intake pipe model or the exhaust pipe model are determined. The purpose is to improve the estimation accuracy of the intake air amount by increasing the accuracy.

  The intake air amount estimation device according to the present invention is configured as a device that estimates an intake air amount into a cylinder by a calculation using a physical model. Then, the specific state quantity related to the intake of the internal combustion engine is calculated using the physical model, the specific state quantity is measured using the sensor, and the physical state is calculated based on the comparison result between the calculated value of the specific state quantity and the actual measurement value. It is configured to identify physical parameters of the model.

  In the first embodiment of the intake air amount estimation device according to the present invention, the physical model includes an intake pipe model, the specific state quantity is calculated using the intake pipe model, and the calculated value and the actual measurement value of the specific state quantity are calculated. The physical parameters of the intake pipe model are identified based on the comparison result.

  The intake pipe pressure can be used as the specific state quantity in the first embodiment. An example of the physical parameters identified based on the comparison result between the calculated value of the intake pipe pressure and the actual measurement value is the intake pipe diameter and the intake pipe length. The intake pipe diameter is identified based on the comparison result between the calculated value of the intake pipe pressure amplitude and the actual measurement value, and the intake pipe length is identified based on the comparison result between the calculated value of the intake pipe pressure and the actual measurement value. it can. Preferably, the intake pipe diameter is identified such that the peak value of the intake pipe pressure wave immediately after the intake valve is opened matches the calculated value and the actual measurement value, and the peak of the intake pipe pressure wave immediately before the intake valve is closed. The intake pipe length is identified so that the calculated phase and the measured value coincide with each other.

  The intake air amount can also be used as the specific state amount in the first embodiment. In this case, if the physical parameter of the intake pipe model to be identified is the intake pipe diameter or the intake pipe length, the intake pipe diameter or the intake pipe length is identified based on the comparison result between the calculated value of the intake air amount and the actual measurement value. be able to. If the physical parameter of the intake pipe model to be identified is the surge tank temperature, the surge tank temperature can be identified based on the comparison result between the calculated value of the intake air amount and the actual measurement value. Furthermore, if the physical parameter of the intake pipe model to be identified is the intake port heat transfer coefficient, the intake port heat transfer coefficient can be identified based on the comparison result between the calculated value of the intake air amount and the actual measurement value. .

  In the second embodiment of the intake air amount estimation device according to the present invention, the physical model includes an exhaust pipe model, the specific state quantity is calculated using the exhaust pipe model, and the calculated value and the actual measurement value of the specific state quantity are calculated. Based on the comparison result, the physical parameters of the exhaust pipe model are identified.

  The exhaust pipe pressure can be used as the specific state quantity in the second embodiment. An example of the physical parameter identified based on the comparison result between the calculated value of the exhaust pipe pressure and the actual measurement value is the exhaust pipe diameter and the exhaust pipe length. The exhaust pipe diameter is identified based on the comparison result between the calculated value of the exhaust pipe pressure amplitude and the actual measurement value, and the exhaust pipe length is identified based on the comparison result between the calculated value of the exhaust pipe pressure phase and the actual measurement value. it can. Preferably, the exhaust pipe diameter is identified so that the peak value of the exhaust pipe pressure wave immediately after the exhaust valve is opened matches the calculated value and the measured value, and the peak of the exhaust pipe pressure wave immediately before the exhaust valve is closed. The exhaust pipe length is identified so that the calculated phase and the measured value coincide with each other.

  The intake air amount can also be used as the specific state amount in the second embodiment. In this case, if the physical parameter of the intake pipe model to be identified is the exhaust pipe diameter or the exhaust pipe length, the exhaust pipe diameter or the exhaust pipe length is identified based on the comparison result between the calculated value of the intake air amount and the actual measurement value. be able to.

  According to the present invention, the accuracy of the physical parameter can be improved by identification based on the comparison result between the calculated value and the actual measurement value of the specific state quantity related to the intake air. The estimation accuracy can be increased.

1 is a schematic configuration diagram of a system in which an intake air amount estimation device according to Embodiment 1 of the present invention is applied to an internal combustion engine. It is a functional block diagram which shows the connection relationship between each model which the intake air quantity estimation apparatus which concerns on Embodiment 1 of this invention uses. It is a schematic diagram for demonstrating the content of the intake pipe model which the intake air amount estimation apparatus which concerns on Embodiment 1 of this invention uses. It is a flowchart which shows the routine for the identification of the physical parameter of the intake pipe model and exhaust pipe model which the intake air amount estimation apparatus which concerns on Embodiment 1 of this invention performs. It is a graph for demonstrating the identification method of the physical parameter of an exhaust pipe model by the intake air amount estimation apparatus which concerns on Embodiment 1 of this invention. It is a graph which shows the effect of identification of the physical parameter of the exhaust pipe model by the intake air amount estimation device according to Embodiment 1 of the present invention. It is a graph which shows the effect which the intake air quantity estimation apparatus which concerns on Embodiment 1 of this invention has on the behavior of the air-fuel ratio at the time of a transition. It is a schematic block diagram of the system which applied the intake air amount estimation apparatus which concerns on Embodiment 2 of this invention to the internal combustion engine. It is a functional block diagram which shows the connection relation between each model which the intake air amount estimation apparatus which concerns on Embodiment 2 of this invention uses. It is a flowchart which shows the routine for the identification of the physical parameter of the intake pipe model and exhaust pipe model which the intake air amount estimation apparatus which concerns on Embodiment 2 of this invention performs. It is a flowchart which shows the routine for the identification of the physical parameter of the intake pipe model which the intake air amount estimation apparatus which concerns on Embodiment 3 of this invention performs.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a system in which an intake air amount estimation device according to this embodiment is applied to an internal combustion engine. The internal combustion engine according to the present embodiment is a spark ignition type 4-cycle reciprocating engine. Although only one cylinder is illustrated in FIG. 1, the internal combustion engine according to the present embodiment is a multi-cylinder internal combustion engine having a plurality of cylinders. An intake pipe 1 and an exhaust pipe 7 are connected to each combustion chamber 4 of the internal combustion engine according to the present embodiment. Communication between the combustion chamber 4 and the intake pipe 1 is controlled by the intake valve 5, and communication between the combustion chamber 4 and the exhaust pipe 7 is controlled by the exhaust valve 6. A pressure sensor 3 for measuring the intake pipe pressure and a temperature sensor 2 for measuring the intake pipe temperature are attached to the intake pipe 1. A pressure sensor 8 for actually measuring the exhaust pipe pressure is attached to the exhaust pipe 7. The output values of these sensors 2, 3 and 8 are stored in a memory 10 provided in the ECU 9.

  The intake air amount estimation device according to the present embodiment is realized as part of the function of the ECU 9. A programmed intake air amount estimation model is used for the estimation of the intake air amount into the cylinder by the ECU 9. The intake air amount estimation model is a physical model of the behavior of air in the engine, and its outline is represented by the functional block diagram of FIG.

  As shown in FIG. 2, the intake air amount estimation model according to the present embodiment includes a plurality of element models, that is, an intake pipe model M1, an intake valve model M2, a cylinder model M3, an exhaust valve model M4, and an exhaust pipe model M5. It is composed of Further, the intake air amount estimation model is combined with a memory M6 for storing parameter values calculated by some element models. Hereinafter, an outline of each element model included in the intake air amount estimation model will be described.

  The intake pipe model M1 is a physical model for calculating the intake pipe pressure Pm and the intake pipe temperature Tm, and has at least the intake pipe length and the intake pipe diameter as physical parameters. The contents of the intake pipe model M1 can be described with reference to FIG. As shown in FIG. 3, in the intake pipe model M1, the intake pipe 1 is divided into a plurality of cells having a discretized length dx (in FIG. 3, it is divided into i + 1 cells). The discretization length dx and the number of cells are determined according to the intake pipe length set as a physical parameter in the intake pipe model M1. As will be described later, the intake pipe length of the intake pipe model M1 is variable. For example, when the intake pipe length is increased, the discretization length dx is increased or the number of cells is increased.

In the intake pipe model M1, the density, flow velocity, and energy are calculated for each cell by the one-dimensional Euler equation shown in the following equation (1). Thereby, the pulsation of the intake air in the intake pipe 1 can be reproduced. In addition, Q and E in Formula (1) are represented by Formula (2) and Formula (3), respectively.

  Since δx in equation (1) corresponds to the discretization length dx, the amount of time change of Q changes when the intake pipe length in the intake pipe model M1 is changed. That is, the time variation of the calculated values of density, flow velocity, and energy changes according to the change in the intake pipe length. Each time variation of density, flow velocity, and energy determines the phase of the pressure wave of the intake pipe pressure Pm calculated by the intake pipe model M1. Therefore, in the intake pipe model M1, the phase of the pressure wave of the intake pipe pressure Pm can be arbitrarily adjusted by changing the intake pipe length, which is a physical parameter.

  Further, the cross-sectional area s in the equation (3) is calculated from the intake pipe diameter in the intake pipe model M1. For this reason, if the intake pipe diameter of the intake pipe model M1 is changed, the calculated value of the mass flow rate per unit area changes. The mass flow rate per unit area determines the maximum amplitude of the pressure wave of the intake pipe pressure Pm calculated by the intake pipe model M1. Therefore, in the intake pipe model M1, the maximum amplitude of the pressure wave of the intake pipe pressure Pm can be arbitrarily adjusted by changing the intake pipe diameter, which is a physical parameter.

  The intake valve model M2 is a physical model for calculating the intake valve flow rate (the flow rate of air flowing through the intake valve 5 and flowing into the combustion chamber 4) mi. According to the intake valve model M2, based on an in-cylinder gas pressure Pc and an in-cylinder gas temperature Tc calculated by a cylinder model M3, which will be described later, and an intake pipe pressure Pm and an intake pipe temperature Tm calculated by the intake pipe model M1. Thus, the intake valve flow rate mi is calculated. Note that examples of mathematical formulas that can be used for the intake valve model M2 are known, and are not themselves characteristic features of the present invention, so that specific mathematical formulas for the intake valve model M2 are not described. Omitted.

  The cylinder model M3 is a physical model for calculating the cylinder gas pressure Pc and the cylinder gas temperature Tc. According to the cylinder model M3, an intake valve flow rate mi calculated by the intake valve model M2 and an exhaust valve flow rate calculated by an exhaust valve model M4 described later (air flowing out of the combustion chamber 4 through the exhaust valve 6). The in-cylinder gas pressure Pc and the in-cylinder gas temperature Tc are calculated based on the flow rate (me). Note that examples of mathematical formulas that can be used for the cylinder model M3 are known, and are not themselves feature points in the present invention, so that descriptions of specific mathematical formulas for the cylinder model M3 are omitted. .

  The exhaust valve model M4 is a physical model for calculating the exhaust valve flow rate me. According to the exhaust valve model M4, the in-cylinder gas pressure Pc and the in-cylinder gas temperature Tc calculated by the cylinder model M3 and the exhaust pipe pressure Pe and the exhaust pipe temperature Te calculated by an exhaust pipe model M5 described later are used. Thus, the exhaust valve flow rate me is calculated. Note that examples of mathematical formulas that can be used for the exhaust valve model M4 are known, and are not themselves characteristic features of the present invention, so that specific mathematical formulas for the exhaust valve model M4 are not described. Omitted.

  The exhaust pipe model M5 is a physical model for calculating the exhaust pipe pressure Pe and the intake pipe temperature Te, and has the exhaust pipe length and the exhaust pipe diameter as physical parameters. The contents of the exhaust pipe model M5 are similar to the contents of the intake pipe model M1. That is, in the exhaust pipe model M5, the exhaust pipe 7 is divided into a plurality of cells having a discretized length, and the density, flow velocity, energy for each cell is determined by the one-dimensional Euler equation expressed by the equations (1) to (3). Is calculated. According to the exhaust pipe model M5, the exhaust pulsation in the exhaust pipe 7 can be reproduced. As in the case of the intake pipe model M1, in the exhaust pipe model M5, the phase of the exhaust pipe pressure Pe can be arbitrarily adjusted by changing the exhaust pipe length, which is a physical parameter. Further, the maximum amplitude of the pressure wave of the exhaust pipe pressure Pe can be arbitrarily adjusted by changing the exhaust pipe diameter which is a physical parameter.

  The intake air amount estimation device according to the present embodiment performs the calculation based on each of the element models M1, M2, M3, M4, and M5 at a predetermined calculation cycle, and calculates the intake valve flow rate mi calculated by the intake valve model M2. The cylinder intake air amount is estimated by integration.

  In the intake air amount estimation device according to the present embodiment, the estimation accuracy of the in-cylinder intake air amount depends on the model accuracy of each of the element models M1, M2, M3, M4, and M5. Among these, regarding the intake pipe model M1, the quality of the model accuracy is determined by how precisely the pulsation of the intake air in the intake pipe 1 can be reproduced. Similarly, regarding the exhaust pipe model M5, the quality of the model accuracy is determined by how precisely the exhaust pulsation in the exhaust pipe 7 can be reproduced. However, in the case of a multi-cylinder internal combustion engine such as this embodiment, it is difficult to accurately reproduce the pulsation of intake and exhaust by a physical model. More specifically, in the intake pipe model M1 and the exhaust pipe model M5, the amplitude and phase of the pressure wave are determined by setting the pipe length and pipe diameter, which are physical parameters. However, it is difficult to preset the tube length and tube diameter so that they match the amplitude and phase in actual pulsation.

  Therefore, the intake air amount estimation device according to the present embodiment does not continue to use the preset pipe length and pipe diameter as they are, but the intake pipe pressure measured by the pressure sensors 3 and 8 during operation of the internal combustion engine and Using the exhaust pipe pressure, the pipe length and pipe diameter of each model M1, M5 are identified. More specifically, the intake air amount estimation device according to the present embodiment compares the calculated value of the intake pipe pressure obtained by the intake pipe model M1 with the actual measured value of the intake pipe pressure obtained by the pressure sensor 3, Based on the comparison result, the intake pipe length and the intake pipe diameter of the intake pipe model M1 are identified. Also, the calculated value of the exhaust pipe pressure obtained by the exhaust pipe model M5 is compared with the actual value of the exhaust pipe pressure obtained by the pressure sensor 8, and the exhaust pipe length and exhaust gas of the exhaust pipe model M5 are compared based on the comparison result. Identify the tube diameter. Hereinafter, a method for identifying the tube length and the tube diameter of each model M1, M5 will be described with reference to the drawings.

  FIG. 4 is a flowchart showing a routine executed by the intake air amount estimating apparatus according to the present embodiment. By executing this routine, the intake air estimation device according to the present embodiment identifies the tube lengths and tube diameters of the models M1 and M5. However, although the flowchart of FIG. 4 is written as if the identification of the pipe length and the pipe diameter in both the intake pipe model M1 and the exhaust pipe model M5 is performed simultaneously in one routine, this is the case for convenience of explanation. It is only written in. Actually, the identification of the intake pipe length and the intake pipe diameter of the intake pipe model M1 and the identification of the exhaust pipe length and the exhaust pipe diameter of the exhaust pipe model M5 are performed in different routines. In the following description, it is assumed that the intake pipe length and the intake pipe diameter of the intake pipe model M1 are identified by the routine shown in FIG.

  According to the routine shown in FIG. 4, in step S101, state quantities Pm, Tm, Pc, and the like for each crank angle in each of the element models M1, M2, M3, M4, and M5 are calculated by using the above-described intake air amount estimation model. Tc, Pe, Te, mi, and me are calculated. In the next step S103, the intake pipe pressure Pm (hereinafter, calculated value of the intake pipe pressure) calculated by the intake pipe model M1 among the state quantities calculated in step S101 is stored in the memory M6.

  In parallel with steps S101 and S103, steps S102 and S104 are executed. In step S <b> 102, the actual intake pipe pressure for each crank angle is actually measured by the pressure sensor 3. In the next step S104, the intake pipe pressure actually measured in step S102 (hereinafter, measured value of the intake pipe pressure) is stored in the memory 10.

  Subsequent to steps S103 and S104, step S105 is executed. In step S105, the calculated value of the intake pipe pressure obtained in a certain period after the intake valve 5 is opened is read from the memory M6, and the actual measured value of the intake pipe pressure obtained during the same period is read from the memory 10. . Then, the peak of the pressure wave is specified for each of the calculated value and the actually measured value of the intake pipe pressure during the same period. The peak of the specified pressure wave is a peak immediately after the intake valve 5 is opened and a peak immediately before the intake valve 5 is closed. The identified peaks are compared in steps S106 and S108, and the intake pipe length and the intake pipe diameter of the intake pipe model M1 are identified based on the comparison result.

  In step S106, it is determined whether or not the peak of the calculated value is out of phase with the peak of the actually measured value of the intake pipe pressure. The peak to be compared in this step is the peak immediately before the intake valve 5 is closed. This is because the phase shift between the actually measured value and the calculated value of the intake pipe pressure becomes prominent at the peak immediately before the intake valve 5 is closed, which has a large effect on the phase due to the reflected wave. When there is a phase shift between the peak of the actual measured value of the intake pipe pressure and the peak of the calculated value, specifically, when the phase difference is equal to or greater than the threshold value, the process of step S107 is performed.

  In step S107, the intake pipe length of the intake pipe model M1 is changed in a direction to reduce the phase shift between the actually measured value and the calculated value of the intake pipe pressure. Specifically, when the phase of the calculated value is advanced with respect to the actually measured value of the intake pipe pressure, the intake pipe length is made longer by a predetermined value than the current value. Conversely, when the phase of the calculated value is retarded with respect to the actual measured value of the intake pipe pressure, the intake pipe length is shortened by a predetermined value from the current value. After step S107, the process of this routine returns to the beginning again, and steps S101 to S107 are repeatedly executed until the determination result of step S106 is negative.

  The determination result in step S106 is negative when the phase shift between the actually measured value and the calculated value of the intake pipe pressure is resolved. In that case, the process proceeds to step S108, and it is determined whether the peak value of the calculated value, that is, the amplitude is deviated from the peak value of the actually measured value of the intake pipe pressure. The peak to be compared in this step is a peak immediately after the intake valve 5 is opened. This is because the deviation of the amplitude between the actually measured value and the calculated value of the intake pipe pressure becomes conspicuous at the peak immediately after the intake valve 5 is opened, which greatly affects the amplitude. If there is a deviation in amplitude between the actual measured value and the calculated value of the intake pipe pressure, specifically, if the difference in amplitude is greater than or equal to a threshold value, the process of step S109 is performed.

  In step S109, the intake pipe diameter of the intake pipe model M1 is changed in a direction to reduce the amplitude deviation between the actually measured value and the calculated value of the intake pipe pressure. Specifically, when the amplitude of the calculated value is larger than the actually measured value of the intake pipe pressure, the intake pipe diameter is increased by a predetermined value from the current value. On the contrary, when the amplitude of the calculated value is small with respect to the actually measured value of the intake pipe pressure, the intake pipe diameter is made smaller by a predetermined value than the current value. After step S109, the process of this routine returns to the beginning again, and steps S101 to S106 and steps S108 and S109 are repeatedly executed until the determination result of step S108 becomes negative.

  The determination result in step S108 is negative when the amplitude deviation between the actually measured value and the calculated value of the intake pipe pressure is resolved. In that case, the identification of the intake pipe length and the intake pipe diameter of the intake pipe model M1 is completed, and all the steps of this routine are finished. By identifying the intake pipe length and the intake pipe diameter of the intake pipe model M1 by the method according to this routine, the reproducibility of the pressure wave in the intake pipe 1 by the intake pipe model M1 is improved.

  Also for the exhaust pipe model M5, the exhaust pipe length and the exhaust pipe diameter are identified by the same method as the above-described routine. In the graph of FIG. 5, the exhaust pipe pressure Pe (hereinafter, calculated value of the exhaust pipe pressure) calculated by the exhaust pipe model M5 during the valve opening period of the exhaust valve 6 and the exhaust pipe pressure actually measured by the pressure sensor 8 are shown. (Hereinafter, measured values of exhaust pipe pressure) are also shown. In this graph, the peak of the pressure wave given the number “1” is the peak of the pressure wave immediately after the exhaust valve 6 is opened, and the peak of the pressure wave given the number “2” is the peak of the exhaust wave 6. It is the peak of the pressure wave just before the valve closing.

  In the example shown in the graph of FIG. 5, since the phase of the peak of the pressure wave immediately before closing the exhaust valve 6 does not match the measured value and the measured value, the exhaust pipe model is in a direction to reduce the phase shift. The length of the exhaust pipe of M5 is changed. Specifically, when the phase of the calculated value is advanced with respect to the measured value of the exhaust pipe pressure as in the example shown in this graph, the exhaust pipe length is the amount corresponding to the advance of the phase. Made longer.

  Further, in the example shown in the graph of FIG. 5, since the peak value of the pressure wave immediately after the exhaust valve 6 is opened, that is, the amplitude does not match the measured value and the measured value, the deviation of the amplitude is reduced. The exhaust pipe diameter of the exhaust pipe model M5 is changed in the direction. Specifically, when the amplitude of the calculated value is large with respect to the actually measured value of the exhaust pipe pressure as in the example shown in this graph, the exhaust pipe diameter is increased by an amount corresponding to the excess of the amplitude.

  On the graph of FIG. 6, in addition to the calculated waveforms and the actual measured values of the exhaust pipe pressure shown in the graph of FIG. 5, the exhaust pipe pressure calculated after identifying the exhaust pipe length and the exhaust pipe diameter is shown. The waveform of the calculated value is also shown. As can be seen from this graph, by identifying the exhaust pipe length and the exhaust pipe diameter of the exhaust pipe model M5 by the above-described method, the reproducibility of the pressure wave in the exhaust pipe 7 by the exhaust pipe model M5 is improved.

  As described above, according to the intake air amount estimation device according to the present embodiment, the reproducibility of the pressure wave in the intake pipe 1 by the intake pipe model M1 and the pressure wave in the exhaust pipe 7 by the exhaust pipe model M5. Since both the reproducibility is improved, the estimation accuracy of the intake air amount into the cylinder is improved as compared with the conventional device. Since the estimated value of the intake air amount is used for calculation of the fuel injection amount in the air-fuel ratio control, if the estimation accuracy of the intake air amount is improved, the feasibility of the target air-fuel ratio by the air-fuel ratio control is also improved. Therefore, for example, as shown in FIG. 7, during the transient operation in which the VVT operates on the advance side or the retard side, the intake air amount estimation device (this device) according to the present embodiment uses the conventional device. In comparison, the deviation of the air-fuel ratio from the target air-fuel ratio (A / F = 14.6) is suppressed. That is, according to the intake air amount estimation device according to the present embodiment, it is possible to improve the transient response of the air-fuel ratio.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to the drawings.

  FIG. 8 is a schematic configuration diagram of a system in which the intake air amount estimation device according to the present embodiment is applied to an internal combustion engine. In FIG. 8, elements having the same configuration or function as those of the system according to the first embodiment shown in FIG. The difference between the system according to the present embodiment and the system according to the first embodiment is that a flow rate sensor 11 for actually measuring the intake air amount is attached to the intake pipe 1. The output value of the flow sensor 11 is stored in the memory 10 provided in the ECU 9 together with the output values of the other sensors 2, 3, 8, and is used to calculate the actual value of the intake air amount. The intake air amount is defined as the amount of air per cycle sucked into the cylinder.

  The intake air amount estimation device according to the present embodiment is realized as part of the function of the ECU 9. A programmed intake air amount estimation model is used for the estimation of the intake air amount into the cylinder by the ECU 9. The intake air amount estimation model is a physical model of the behavior of air in the engine, and its outline is represented by the functional block diagram of FIG. In FIG. 9, elements having the same functions as those of the intake air amount estimation model according to Embodiment 1 shown in FIG. The difference between the intake air amount estimation model according to the present embodiment and the intake air amount estimation model according to the first embodiment is that an intake air amount calculation model M7 is provided. The intake air amount calculation model M7 calculates the intake air amount Ga per cycle by using the intake valve flow rate mi calculated by the intake valve model M2 or by using the intake valve flow rate me calculated by the exhaust valve model M4. calculate.

  FIG. 10 is a flowchart showing a routine executed by the intake air amount estimating apparatus according to the present embodiment. By executing this routine, the intake air estimation device according to the present embodiment identifies the tube length or tube diameter of each model M1, M5. However, although the flowchart of FIG. 10 is written as if the identification of the pipe length in both the intake pipe model M1 and the exhaust pipe model M5 and the identification of the pipe diameter in both are performed simultaneously in one routine, This is only written as such for convenience of explanation. Actually, the identification for the intake pipe model M1 and the identification for the exhaust pipe model M5 are performed in different routines. Furthermore, only one of the identification of the intake pipe length and the identification of the intake pipe diameter in each model M1, M5 is performed alternatively. In the following description, it is assumed that the intake pipe length of the intake pipe model M1 is identified by the routine shown in FIG.

  According to the routine shown in FIG. 10, in step S201, the state quantities Pm, Tm, Pc, and the like for each crank angle in each of the element models M1, M2, M3, M4, and M5 are calculated by using the above-described intake air amount estimation model. Tc, Pe, Te, mi, and me are calculated. In the next step S203, the intake air amount Ga per cycle is calculated from the intake valve flow rate mi calculated by the intake valve model M2 among the state quantities calculated in step S201. In the next step S205, the intake air amount calculated in step S203 (hereinafter, the calculated value of the intake air amount) is stored in the memory M6.

  Further, steps S202 and S204 are executed in parallel with steps S201, S203 and S205. In step S202, the flow rate sensor 11 measures the intake air amount per cycle. In the next step S204, the intake air amount actually measured in step S202 (hereinafter, measured value of the intake air amount) is stored in the memory 10.

  Subsequent to steps S205 and S204, step S206 is executed. In step S206, the calculated value of the intake air amount per cycle calculated using the intake air amount estimation model is read from the memory M6, and the actually measured value of the intake air amount in the same cycle is read from the memory 10. Then, the calculated value of the intake air amount is compared with the actual measurement value, and the intake pipe length and the intake pipe diameter of the intake pipe model M1 are identified based on the comparison result.

  In step S207, it is determined whether or not the calculated value is deviated from the actually measured value of the intake air amount. If there is a difference between the actually measured value and the calculated value, specifically, if the difference between the actually measured value of the intake air amount and the calculated value is greater than or equal to the threshold value, the process of step S208 is performed.

  In step S208, the intake pipe length of the intake pipe model M1 is changed in a direction that reduces the deviation between the actually measured value and the calculated value of the intake air amount. Since the relationship between the change direction of the intake pipe length of the intake pipe model M1 and the change direction of the calculated value of the intake air amount is known, the intake pipe length of the intake pipe model M1 is adjusted based on the known relationship. After step S208, the process of this routine returns to the beginning again, and steps S201 to S208 are repeatedly executed until the determination result of step S207 is negative.

  The determination result in step S208 is negative when the difference between the actually measured value and the calculated value of the intake air amount is eliminated. In that case, the identification of the intake pipe length of the intake pipe model M1 is completed, and all the steps of this routine are finished. By identifying the intake pipe length of the intake pipe model M1 by the method according to this routine, the estimation accuracy of the intake air quantity using the intake air quantity estimation model including the intake pipe model M1 is improved.

  In the above routine, the intake pipe length of the intake pipe model M1 is identified, but the intake pipe diameter can be identified instead of the intake pipe length. In that case, in step S208, based on the known relationship between the direction of change in the intake pipe diameter of the intake pipe model M1 and the direction of change in the calculated value of the intake air amount, the difference between the actually measured value and the calculated value of the intake air amount is determined. The intake pipe diameter of the intake pipe model M1 is changed in the direction of decreasing the intake air.

  Also for the exhaust pipe model M5, the exhaust pipe length or the exhaust pipe diameter is identified by the same method as the above-described routine. First, the intake air amount Ga per cycle is calculated from the exhaust valve flow rate me calculated by the exhaust pipe model M5. Then, the actually measured value of the intake air amount in the same cycle is compared with the calculated value of the intake air amount calculated by the exhaust pipe model M5. If there is a deviation between the measured value and the calculated value of the intake air amount, the exhaust pipe length or the exhaust pipe diameter of the exhaust pipe model M1 is changed in a direction to reduce the deviation. By identifying the exhaust pipe length or the exhaust pipe diameter of the exhaust pipe model M5 by such a method, the estimation accuracy of the intake air quantity using the intake air quantity estimation model including the exhaust pipe model M5 is improved.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to the drawings.

  The intake air amount estimation device according to the present embodiment is a device applied to the system shown in FIG. 8 in the same manner as the intake air amount estimation device according to the second embodiment, and the outline thereof is the intake air according to the second embodiment. Similar to the quantity estimation device, it is represented by the functional block diagram of FIG. However, the intake pipe model M1 according to the present embodiment has the surge tank temperature and the intake port heat transfer coefficient as physical parameters in addition to the intake pipe length and the intake pipe diameter.

  FIG. 11 is a flowchart showing a routine executed by the intake air amount estimating apparatus according to the present embodiment. By executing this routine, the intake air estimation device according to the present embodiment identifies the surge tank temperature or intake port heat transfer coefficient of intake pipe model M1. However, the flowchart of FIG. 11 is written as if the identification of the surge tank temperature and the identification of the intake port heat transfer coefficient of the intake pipe model M1 are performed together in one routine, but this is for convenience of explanation. It is just written as follows. Actually, only one of the identification of the surge tank temperature and the identification of the intake port heat transfer coefficient is performed alternatively in the intake pipe model M1. In the following description, it is assumed that the surge tank temperature of the intake pipe model M1 is identified by the routine shown in FIG.

  In the routine shown in FIG. 11, the same reference numerals are given to the steps for performing the same processing as the routine according to the second embodiment shown in FIG. 10. The routine according to the present embodiment and the routine according to the second embodiment are different in processing after it is determined in step S207 that the calculated value is deviated from the actually measured value of the intake air amount. According to the routine according to the present embodiment, when the difference between the actually measured value and the calculated value of the intake air amount is greater than or equal to the threshold value, the process of step S209 is performed.

  In step S209, the surge tank temperature of the intake pipe model M1 is changed in a direction that reduces the difference between the actually measured value and the calculated value of the intake air amount. Since the relationship between the change direction of the surge tank temperature of the intake pipe model M1 and the change direction of the calculated value of the intake air amount is known, the surge tank temperature of the intake pipe model M1 is adjusted based on the known relationship. The After step S209, the process of this routine returns to the beginning, and steps S201 to S209 are repeatedly executed until the determination result of step S207 is negative.

  The determination result in step S209 is negative when the difference between the actually measured value and the calculated value of the intake air amount is eliminated. In that case, the identification of the surge tank temperature of the intake pipe model M1 is completed, and all the steps of this routine are finished. By identifying the surge tank temperature of the intake pipe model M1 by the method according to this routine, the estimation accuracy of the intake air quantity using the intake air quantity estimation model including the intake pipe model M1 is improved.

  In the routine described above, the surge tank temperature of the intake pipe model M1 is identified, but the intake port heat transfer coefficient can also be identified instead of the surge tank temperature. In that case, in step S209, based on a known relationship between the direction of change in the intake port heat transfer coefficient of the intake pipe model M1 and the direction of change in the calculated value of the intake air amount, the actually measured value and the calculated value of the intake air amount are calculated. The intake port heat transfer coefficient of the intake pipe model M1 is changed in a direction to reduce the deviation.

Others.
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the routine shown in FIG. 4, the intake pipe diameter is identified after the identification of the intake pipe length of the intake pipe model M1, but the order may be reversed. The same applies to the exhaust pipe model M5, and the exhaust pipe length may be identified after the exhaust pipe diameter is identified.

  In the first embodiment, the pipe length and the pipe diameter are identified by paying attention to the peak of the pressure wave. However, as long as the calculated value of the pressure wave can be adapted to the actual measurement value, the pipe length and There is no limitation on the tube diameter identification method.

DESCRIPTION OF SYMBOLS 1 Intake pipe 2 Temperature sensor 3 Pressure sensor 4 Combustion chamber 5 Intake valve 6 Exhaust valve 7 Exhaust pipe 8 Pressure sensor 9 ECU
10 Memory 11 Flow sensor

Claims (17)

In an intake air amount estimation device for an internal combustion engine that estimates an intake air amount into a cylinder by a calculation using a physical model,
Calculation means for calculating a specific state quantity related to intake of the internal combustion engine using the physical model;
Actual measurement means for actually measuring the specific state quantity using a sensor;
Identification means for identifying physical parameters of the physical model based on a comparison result between the calculated value and the actual measurement value of the specific state quantity;
An intake air amount estimation device for an internal combustion engine, comprising: The physical model includes an intake pipe model,
The calculation means calculates the specific state quantity using the intake pipe model,
2. The intake air amount estimation device for an internal combustion engine according to claim 1, wherein the identification means identifies a physical parameter of the intake pipe model.   The intake air amount estimation device for an internal combustion engine according to claim 2, wherein the specific state amount is an intake pipe pressure.   The intake air amount estimation device for an internal combustion engine according to claim 3, wherein the physical parameters of the intake pipe model include at least an intake pipe diameter and an intake pipe length.   The identification means identifies the intake pipe diameter based on a comparison result between the calculated value of the intake pipe pressure amplitude and the actual measurement value, and based on a comparison result between the calculated value of the intake pipe pressure phase and the actual measurement value. The intake air amount estimation device for an internal combustion engine according to claim 4, wherein the intake pipe length is identified.   The identification means identifies the intake pipe diameter such that the peak value of the intake pipe pressure wave immediately after the intake valve is opened matches the calculated value and the measured value, and the intake pipe pressure immediately before the intake valve is closed. 6. The intake air amount estimation device for an internal combustion engine according to claim 5, wherein the intake pipe length is identified so that the phase of the wave peak matches between the calculated value and the actually measured value.   The intake air amount estimation device for an internal combustion engine according to claim 2, wherein the specific state amount is an intake air amount. The intake pipe model physical parameters include at least the intake pipe diameter or the intake pipe length,
8. The intake air amount estimation device for an internal combustion engine according to claim 7, wherein the identification unit identifies the intake pipe diameter or the intake pipe length based on a comparison result between a calculated value and an actual measurement value of the intake air amount. . The physical parameters of the intake pipe model include surge tank temperature,
8. The intake air amount estimation device for an internal combustion engine according to claim 7, wherein the identification unit identifies the surge tank temperature based on a comparison result between a calculated value and an actual measurement value of the intake air amount. The intake pipe heat transfer coefficient is included in the physical parameters of the intake pipe model,
8. The intake air amount estimation device for an internal combustion engine according to claim 7, wherein the identifying means identifies the intake port heat transfer coefficient based on a comparison result between a calculated value and an actual measurement value of the intake air amount. The physical model includes an exhaust pipe model;
The calculation means calculates the specific state quantity using the exhaust pipe model,
2. The intake air amount estimation device for an internal combustion engine according to claim 1, wherein the identification means identifies a physical parameter of the exhaust pipe model.   The intake air amount estimation device for an internal combustion engine according to claim 11, wherein the specific state amount is an exhaust pipe pressure.   The intake air amount estimation device for an internal combustion engine according to claim 12, wherein the physical parameters of the exhaust pipe model include at least an exhaust pipe diameter and an exhaust pipe length.   The identification means identifies the exhaust pipe diameter based on a comparison result between the calculated value of the exhaust pipe pressure amplitude and the actual measurement value, and based on the comparison result between the calculation value of the exhaust pipe pressure and the actual measurement value. 14. The intake air amount estimation device for an internal combustion engine according to claim 13, wherein an exhaust pipe length is identified.   The identification means identifies the exhaust pipe diameter such that the peak value of the exhaust pipe pressure wave immediately after the exhaust valve is opened matches the calculated value and the measured value, and the exhaust pipe pressure immediately before the exhaust valve is closed. 14. The intake air amount estimation device for an internal combustion engine according to claim 13, wherein the exhaust pipe length is identified so that the phase of the wave peak matches between the calculated value and the actually measured value.   12. The intake air amount estimation device for an internal combustion engine according to claim 11, wherein the specific state amount is an intake air amount. The exhaust pipe model physical parameters include at least the exhaust pipe diameter or the exhaust pipe length,
17. The intake air amount estimation device for an internal combustion engine according to claim 16, wherein the identifying means identifies the exhaust pipe diameter or the exhaust pipe length based on a comparison result between a calculated value and an actual measurement value of the intake air amount. .

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