JP2011252785A - Air intake volume correction method for internal combustion engines - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the accuracy of measuring air intake volumes by correcting detection errors of an air flow meter in a time series.SOLUTION: A correction method, using a thin film type air flow meter for measuring air intake volumes of internal combustion engines, measures air intake volumes on the basis of output signals from the air flow meter; calculates the ripple factor of the air intake volume on the basis of the output signals of the air flow meter; sets an error rate, which is a ratio of any measurement error of the air intake volume arising from an increase in ripple factor to a reference air intake volume figured out on the basis of a ripple-free output signal from the air flow meter having measured the intake volume of ripple-free air; and corrects the measured air intake volume on the basis of the calculated ripple factor and the set error rate.

Description

  The present invention relates to a method for correcting an intake air amount in an internal combustion engine having a thin film type air flow meter.

  Conventionally, for example, in an internal combustion engine mounted on an automobile, an air flow meter is used to measure an intake air amount. As an air flow meter which is frequently used in recent years, a thermal type is known. A thermal air flow meter has a bridge circuit that combines a heating resistor and a temperature-compensating resistor at a position where the intake air flowing in the intake passage hits, and the temperature of the heating resistor is deprived by the intake air. The resistance value changes and the current flows through the bridge circuit to measure the intake air amount.

  In such an air flow meter, in addition to the intake air flowing toward the combustion chamber of the internal combustion engine, the output is actually sucked by the intake pulsation generated by the intake air flowing outside the engine, in other words, toward the air cleaner. It tends to be larger than the amount of air. In order to eliminate such a problem, for example, in Patent Document 1, the detection error of the air flow meter is compensated based on the opening degree of the throttle valve, the engine speed, the opening degree of the swirl control valve, and the cam angle. The coefficient is set, and the output is corrected by multiplying the output of the air flow meter by the coefficient.

  By the way, in recent internal combustion engines, exhaust gas recirculation control (hereinafter referred to as EGR control) in which a part of the exhaust gas is mixed into the intake air is performed. However, in the above configuration, the EGR control is performed. When accelerating, the state of pulsation changes from the steady operation state and the case where EGR control is not performed. For this reason, as described above, even if the output of the air flow meter is corrected by a coefficient set based on the opening degree of the throttle valve, the engine speed, etc., the correction is excessive or insufficient, and the accuracy of measuring the intake air amount is reduced. It became.

Japanese Patent Laid-Open No. 2004-19450

  Therefore, the present invention focuses on the above points and aims to improve the measurement accuracy of the intake air amount by correcting the measurement error of the air flow meter in time series.

  That is, the intake air amount correction method for an internal combustion engine according to the present invention includes a thin film type air flow meter for measuring the intake air amount, and the intake air amount is calculated based on an output signal output from the air flow meter. Measures the pulsation rate of the intake air amount based on the output signal of the air flow meter, and measures the intake air amount measurement error that occurs when the pulsation rate increases. Intake air measured based on the calculated pulsation rate and the set error rate by setting an error rate that is a ratio to the reference intake air amount measured based on the no-pulsation output signal output from the air flow meter. It is characterized by correcting the amount.

  According to such a configuration, it is possible to detect the backflow air amount by using a thin film type air flow meter, and according to the pulsation of the intake air amount generated during the operation of the internal combustion engine including the backflow air. It is possible to set the error rate including these factors in the measurement error that occurs. In addition, the measurement error of the air flow meter due to fluctuations in the pulsation rate can be corrected with a correction amount that takes into account the time series based on the pulsation rate and the error rate. For example, when EGR control is being executed or when transient Even at times, it is possible to improve the measurement accuracy of the intake air amount.

  The present invention is configured as described above. By taking into account the error rate of the measurement error when the intake air amount pulsates, the intake air amount can be accurately determined following the change in the pulsation rate of the intake air. Can be measured.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows the cross-section of one cylinder in embodiment of this invention, and shows the whole engine structure schematically. The flowchart which shows the control procedure in the same embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  A multi-cylinder engine 100, for example, a two-cylinder engine 100 schematically showing the configuration of one cylinder in FIG. 1 is mounted on, for example, an automobile. The engine 100 includes an intake system 1 and an exhaust system 2. The intake system 1 is provided with a throttle valve 3 that opens and closes in response to an accelerator pedal (not shown). An air flow meter 22 for measuring the amount of intake air is upstream of the throttle valve 3, and downstream thereof. An intake manifold 5 having an integrated surge tank 4 is attached. The air flow meter 22 is a thin film type that can also measure the air that flows back in the intake system 1.

A spark plug 8 is attached to the ceiling portion of the combustion chamber 7 formed in the upper part of the cylinder 6. A fuel injection valve 10 is attached to the intake port side end 9 of the intake manifold 5. The fuel injection valve 10 is controlled by an electronic control device 11 described later. Further, an exhaust gas recirculation device (hereinafter referred to as an EGR device) 15 is connected between the surge tank 4 and the exhaust system 2 including the O ₂ sensor 12, the three-way catalyst 13 and the exhaust manifold 14.

  The EGR device 15 is connected to an exhaust gas recirculation pipe (hereinafter referred to as EGR) having one end connected so as to communicate with the surge tank 4 and the other end connected to an exhaust manifold 14 downstream of the three-way catalyst 13. And an exhaust gas recirculation control valve (hereinafter referred to as an EGR valve) 17 that is provided in the EGR pipe 16 and controls the flow rate of the exhaust gas that passes through the EGR pipe 16. Is done. The flow rate of the exhaust gas to be recirculated (hereinafter referred to as EGR gas) depends on the opening degree of the EGR valve 17, and the opening degree of the EGR valve 17 is controlled by the electronic control unit 11.

  The electronic control device 11 includes a microcomputer 18, a memory 19, an input interface 20, and an output interface 21. The microcomputer 18 executes various programs described below stored in the memory 19 to control the operation of the engine 100. Information necessary for operation control of the engine 100 is input to the microcomputer 18 via the input interface 20, and the microcomputer 18 controls the fuel control valve 10, the EGR valve 17, the spark plug 8, and the like. Are output via the output interface 21.

Specifically, the input interface 20 outputs an air flow rate signal a output from the air flow meter 22 for measuring the air flow rate flowing into the intake manifold 5 and an output from the rotation speed sensor 23 for detecting the engine speed. A rotation speed signal b, a vehicle speed signal c output from the vehicle speed sensor 24 for detecting the vehicle speed, an LL signal e output from the idle switch 25 for detecting the open / closed state of the throttle valve 3, and cooling of the engine 100 A water temperature signal f output from the water temperature sensor 26 for detecting the water temperature, a voltage signal h output from the O ₂ sensor 12, and the like are input. On the other hand, the output interface 21 outputs an ignition signal m to the spark plug 8, a fuel injection signal n to the fuel control valve 10, an open / close signal o to the EGR valve 17, and the like.

  In such a configuration, the electronic control unit 11 is set according to the operating state with the air flow rate signal a output from the air flow meter 22 and the rotation speed signal b output from the rotation speed sensor 23 as main information. The fuel injection amount is calculated using a coefficient to determine the fuel injection time corresponding to the fuel injection amount, that is, the energization time for the fuel injection valve 10, and the fuel injection valve 10 is controlled by the determined energization time to Is injected into the intake system 1. Such fuel injection control itself may apply what is known in this field.

  Further, an EGR control program for controlling the opening degree of the EGR valve 17 and performing EGR control according to the operating state of the engine 100 is stored in the electronic control unit 11. This EGR control program may be widely known in this field.

  Further, the electronic control device 11 stores an intake air amount correction control program. This intake air amount correction control program is executed every predetermined time, calculates the pulsation rate G of the intake air amount based on the air flow rate signal a which is the output signal of the air flow meter 22, and increases the pulsation rate G. An error rate, which is a ratio of the measurement error of the intake air amount caused by the above, to the reference intake air amount measured based on the non-pulsation output signal output from the air flow meter 22 of the intake air amount of the intake air in which no pulsation occurs It is set and programmed to correct the measured intake air amount based on the calculated pulsation rate and the set error rate. The intake air amount correction program will be described with reference to FIG.

  First, in step S1, the intake air amount is measured based on the air flow rate signal a output from the air flow meter 22. The intake air amount is obtained by A / D converting the air flow rate signal a output from the air flow meter 22 at the time of executing this intake air amount correction program, and referring to the map with the obtained digital signal, and the intake air at that time Measure the amount.

  Next, in step S2, the maximum value Gmax and the minimum value Gmin of the amplitude of the air flow rate signal a in one crank period are measured. The measured maximum value Gmax and minimum value Gmin are temporarily stored in order to calculate the average value Gave of the amplitude of the air flow signal a and the pulsation rate G of the intake air amount which will be described next.

  In step S3, the air flow rate signal a is determined based on a plurality of predetermined maximum values Gmax and minimum values Gmin stored up to this point, including the maximum value Gmax and minimum value Gmin measured in step S2. The average value Gave of the amplitudes is calculated. The average value Gave of the amplitude is a moving average value calculated including the latest maximum value Gmax and minimum value Gmin.

In step S4, the pulsation rate G of the intake air amount is calculated by the following equation based on the maximum value Gmax and minimum value Gmin of the amplitude of the air flow rate signal a obtained in step S2 and the average value gave. Therefore, the pulsation rate G is a value calculated every crank cycle (one rotation of the crankshaft).
G = 100 × (Gmax−Gmin) / Gave (1)

  In step S5, the error rate of the measurement error of the intake air amount is set based on the pulsation rate G obtained by the equation (1). The error rate is obtained by searching a map in which a value corresponding to a typical pulsation rate G, which is produced before the engine 100 is mounted on the vehicle, is set, and there is no pulsation rate G corresponding to the map. Are set by performing interpolation calculation. The map corresponds to the pulsation rate with a representative value of the error rate obtained by actually measuring the pulsation rate for each different engine speed and actually measuring the intake air amount measurement error using the measured pulsation rate and the engine speed as variables. Is set.

  A measurement error always occurs when pulsation occurs in the intake air, and the pulsation always occurs because the intake air is intermittent during the operation of the engine 100. Therefore, the air flow rate signal a output from the air flow meter 22 includes an error during the operation of the engine 100.

  The error rate is determined by measuring the reference intake air amount based on the air flow rate signal output from the air flow meter 22, that is, the non-pulsation output signal, when measuring the intake air amount in which no pulsation occurs, and measuring the measured reference intake air amount. It is obtained by calculating the ratio of the measurement error of the intake air amount with respect to. The reference intake air amount is to measure the flow rate of air corresponding to the intake air before the air flow meter 22 is attached to the engine 100, that is, the air flow meter 22 alone.

  In step S6, a correction amount is calculated based on the pulsation rate calculated in step S3 and the error rate calculated in step S4, and the intake air amount measured in step S1 is corrected with the calculated correction amount. The correction amount is set by, for example, an average value of the variation based on the error rate obtained from the pulsation rate.

  In such a configuration, during operation of the engine 100, Steps S <b> 1 to S <b> 6 are executed every predetermined time, and the intake air amount measured based on the air flow rate signal a output from the air flow meter 22 is converted into a pulsation rate. And correction based on the error rate. Since the correction is performed based on the pulsation rate in one crank cycle and the error rate based on the pulsation rate, the intake air amount corresponding to the pulsation that changes with time during operation of the engine 100 reflects the measurement error due to the pulsation. To be. Therefore, the correction accuracy of the intake air amount can be improved.

  That is, in correcting the intake air amount, the pulsation rate G is calculated for each crank period, and the error rate for each operating state of the engine 100 is set from the obtained pulsation rate G, so the correction amount of the intake air amount Can be set in time series. In addition, since the error rate is the ratio of the measurement error to the reference intake air amount, an error caused by variations among engines can be suppressed, so that the error included in the corrected intake air amount can be reduced. .

  In addition, the error rate is due to the performance of the air flow meter 22 alone, and the error rate is set in correspondence with the pulsation rate due to the operating state of the engine 100. For example, intake air such as an intake manifold is taken into account. It does not depend on the structure of the system. Therefore, even if a part of the intake system is changed due to repair or the like, it is not necessary to change the map for performing the adaptation again and setting the error rate.

  In addition, this invention is not limited to the above-mentioned embodiment.

  In addition, the specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  As an application example of the present invention, the present invention can be applied to a gasoline engine that includes an EGR device, a variable valve timing mechanism, and the like and has a small number of cylinders and easily generates pulsation.

DESCRIPTION OF SYMBOLS 11 ... Electronic control unit 18 ... Microcomputer 19 ... Memory 20 ... Input interface 21 ... Output interface 22 ... Air flow meter

Claims (1)

The internal combustion engine includes a thin film type air flow meter for measuring the amount of intake air, and measures the amount of intake air based on an output signal output from the air flow meter,
Calculate the pulsation rate of the intake air amount based on the output signal of the air flow meter,
This is the ratio of the measurement error of the intake air amount caused by the increase in the pulsation rate to the reference intake air amount measured based on the non-pulsation output signal output from the air flow meter. Set the error rate,
An intake air amount correction method for an internal combustion engine that corrects an intake air amount measured based on a calculated pulsation rate and a set error rate.

Images