JP2009281283A - Engine intake air flow rate detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine intake air flow rate detection device enabling accurate fresh air flow rate detection by quickly correcting detection error of an air flow sensor. <P>SOLUTION: A fresh air flow rate detection part 40 detects fresh air flow rate of an engine 1 as detected fresh air flow rate Gs based on detection signal of the air flow sensor 16, and a fresh air flow rate estimation part 42 estimates fresh air flow rate of the engine 1 as estimated fresh air flow rate G1m based on fuel supply quantity Qf and excess air ratio λs of exhaust gas detected by a λ sensor 32. A correction coefficient operation part 44 determines a correction coefficient R by comparing the detected fresh air flow rate Gs and estimated fresh air flow rate BG1m, and a fresh air flow rate correction part 46 determined true fresh air flow rate Ga of the engine 1 by correcting the detected fresh air flow rate Gs by the correction coefficient R. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a device for detecting a flow rate of fresh air sucked into an engine, and more particularly to an intake air flow rate detection device that detects a fresh air flow rate based on a detection signal of an air flow sensor provided in an intake passage.

2. Description of the Related Art Conventionally, it is required to accurately detect the flow rate of fresh air sucked into an engine in order to properly control the operation of the engine.
For example, in engine EGR control, a target excess air ratio is set as an excess air ratio that can suppress the generation of NOx (nitrogen oxide) without deteriorating the combustion state in each combustion chamber of the engine, and actual excess air When the exhaust gas recirculation amount to the intake side is controlled so that the rate becomes equal to the target excess air rate, the fresh air flow rate detected using the air flow sensor is used. Specifically, the actual excess air ratio of the engine is obtained from the fresh air flow rate detected using the air flow sensor, the amount of fuel supplied to the engine, and the amount of air in the recirculated exhaust gas. In addition, the amount of air in the exhaust gas that is recirculated is the difference between the theoretical air supply amount to each cylinder of the engine and the fresh air flow rate detected using the air flow sensor, and the excess air amount that has been determined so far. It is calculated based on the rate. Therefore, if the detection accuracy of the fresh air flow rate detected using the air flow sensor is low, the actual excess air rate cannot be obtained accurately, and the excess air rate of the engine can be matched with the target excess air rate. Disappear. As a result, there arises a problem that exhaust characteristics deteriorate due to an increase in NOx emission amount of the engine.

Therefore, Patent Document 1 proposes a control device that improves the detection accuracy of a fresh air flow rate using an air flow sensor. In the control device of Patent Document 1, the exhaust gas recirculation amount is controlled so that the fresh air flow rate detected using the air flow sensor becomes the target fresh air flow rate set in accordance with the target EGR rate. At this time, the target oxygen concentration is set corresponding to the target EGR rate, and an air flow sensor is used according to the magnitude relationship between the actual oxygen concentration detected by the air-fuel ratio sensor provided in the exhaust passage and the target oxygen concentration. By correcting the detected fresh air flow rate, the detection accuracy of the fresh air flow rate is improved. That is, if the actual oxygen concentration is higher than the target oxygen concentration, the new air flow rate is corrected by subtracting a predetermined value from the fresh air flow rate detected using the air flow sensor, while the actual oxygen concentration is higher than the target oxygen concentration. When it is lower than the oxygen concentration, the fresh air flow rate is corrected by adding a predetermined value to the actual fresh air flow rate detected using the air flow sensor.
JP 2002-70654 A

  When the fresh air flow rate is corrected by adding or subtracting a constant value to the fresh air flow rate detected using the air flow sensor as in the control device of Patent Document 1, the correct fresh air flow rate is obtained. Because it is corrected gradually by a predetermined value toward the time, it takes time until an accurate fresh air flow rate can be obtained, and control using the fresh air flow rate until an accurate fresh air flow rate is obtained There is a problem in that the accuracy of the engine is lowered and the operating performance and exhaust performance of the engine are lowered.

Further, if the engine operating environment changes greatly while such correction is performed, the correction may not be performed properly, and an accurate fresh air flow rate may not be obtained.
The present invention has been made in view of such problems, and an object of the present invention is to provide an engine intake flow rate detection device capable of detecting a new air flow rate with high accuracy by quickly correcting a detection error. There is to do.

  In order to achieve the above object, an engine intake flow rate detection device of the present invention is provided in an intake passage of an engine, and outputs an detection signal corresponding to a fresh air flow rate sucked into the engine, and the air flow sensor Based on the detection signal, a fresh air flow rate detecting means for detecting a fresh air flow rate sucked into the engine as a detected fresh air flow rate, and a λ that is provided in the exhaust passage of the engine and detects an excess air ratio of the exhaust gas of the engine A fresh air flow rate estimating means for estimating a fresh air flow rate sucked into the engine as an estimated fresh air flow rate based on a sensor, an excess air ratio of exhaust gas detected by the λ sensor and a fuel supply amount of the engine; Compensation is performed by comparing the detected fresh air flow detected by the fresh air flow detection means with the estimated fresh air flow estimated by the fresh air flow estimation means. A correction coefficient calculating means for obtaining a positive coefficient and a detected fresh air flow detected by the fresh air flow detecting means are corrected by a correction coefficient obtained by the correction coefficient calculating means to obtain a true fresh air flow of the engine. And a fresh air flow rate correction means to be obtained (claim 1).

  According to the engine intake flow rate detecting apparatus configured as described above, the fresh air flow rate detection means detects the fresh air flow rate sucked into the engine as the detected fresh air flow rate based on the detection signal of the air flow sensor, while The flow rate estimating means estimates the fresh air flow rate sucked into the engine as the estimated fresh air flow rate based on the excess air ratio of the exhaust detected by the λ sensor and the fuel supply amount of the engine. The correction coefficient calculating means obtains a correction coefficient by comparing the detected fresh air flow with the estimated fresh air flow, and the fresh air flow correcting means corrects the detected fresh air flow using the correction coefficient obtained by the correction coefficient calculating means. To find the true fresh air flow of the engine.

  The estimated fresh air flow rate is a fresh air flow rate estimated based on the actual excess air ratio of the exhaust gas, and can be regarded as a relatively high accuracy fresh air flow rate. Therefore, the correction coefficient has an appropriate value for correcting the detected fresh air amount to an accurate value, and if there is a difference between the detected fresh air flow rate and the estimated fresh air flow rate, this difference is immediately Reflected in the correction coefficient, the detected fresh air flow is immediately corrected to an accurate value corresponding to the difference between the detected fresh air flow and the estimated fresh air flow.

  Further, in the engine intake flow rate detecting device, the fresh air flow rate detecting means repeatedly detects the detected fresh air flow rate based on a detection signal of the air flow sensor, and the correction coefficient calculating means is the fresh air flow rate estimating means. The detected fresh air flow detected by the fresh air flow detection means a predetermined number of times corresponding to a response delay until the fresh air sucked into the engine is discharged as exhaust. The correction coefficient is obtained by making a comparison using the air flow rate (claim 2).

  According to the engine intake flow rate detection device configured as described above, the detected fresh air flow rate to be compared with the estimated fresh air flow rate when the correction coefficient calculation means obtains the correction coefficient is predetermined from the latest detected fresh air flow rate at that time. The detected fresh air flow rate detected by the fresh air flow rate detection means a number of times before is used. The estimated fresh air flow rate is obtained based on the excess air ratio of the exhaust, and the exhaust at this time corresponds to the fresh air sucked into the engine before the timing when the latest detected fresh air flow rate is detected. Yes. The predetermined number of times corresponds to a response delay until the fresh air sucked into the engine is discharged as exhaust and reaches the λ sensor, and is therefore a detection target of the excess air ratio when obtaining the estimated fresh air flow rate. The detected fresh air flow rate for the fresh air from which the exhaust is generated can be used for comparison.

More specifically, in the engine intake air flow rate detection device, the correction coefficient calculation means changes the predetermined number corresponding to the response delay in accordance with the engine speed. 3).
The response delay until the fresh air sucked into the engine reaches the λ sensor as exhaust becomes shorter as the engine speed increases. By configuring the engine intake flow rate detection device in this way, the engine speed can be reduced. The detected fresh air flow rate of the fresh air from which the exhaust gas that has been the target of detection of the excess air ratio when obtaining the estimated fresh air flow rate over a wide range can be used for comparison with the estimated fresh air flow rate.

  Further, in the engine intake air flow detection device, the fresh air flow detection means uses a detection signal of the air flow sensor as an input value, and converts a conversion curve approximated by a predetermined adaptive parameter coefficient and a polynomial represented by the input value. And a degree of correction of the detected fresh air flow rate by the signal converting unit for detecting the detected fresh air flow rate by converting the detection signal of the air flow sensor and the fresh air flow rate correcting means is greater than a predetermined degree. A conversion curve correction unit that identifies the adaptive parameter and corrects the conversion curve by performing an operation by the successive least squares method using the estimated fresh air flow estimated by the fresh air flow estimation means. (Claim 4).

  According to the engine intake flow rate detecting device configured as described above, in the fresh air flow rate detection means, the signal conversion unit obtains a detected fresh air flow rate corresponding to the detection signal of the air flow sensor using the conversion curve. The conversion curve is approximated by a predetermined adaptive parameter coefficient and a polynomial represented by the input value using the detection signal of the air flow sensor as an input value, and the degree of correction of the detected fresh air flow by the fresh air flow correcting means is determined in advance. If the degree is greater than the specified degree, the conversion curve correction unit sequentially performs an operation by the least square method using the estimated fresh air flow, thereby identifying the adaptive parameter and correcting the conversion curve.

Therefore, when it becomes necessary to largely correct the detected fresh air flow rate, the conversion curve itself for converting the detection signal of the air flow sensor into the detected fresh air flow rate is corrected. Calculation load such as flow rate correction means is reduced.
Also, when the same airflow sensor is applied to different intake passages or engines, the conversion curve is corrected in the same manner, so that it is not necessary to obtain the conversion curves individually for different intake passages or engines.

  According to the engine intake flow rate detection device of the present invention, the detected new air flow rate based on the detection signal of the air flow sensor and the estimated new air flow rate based on the exhaust excess air ratio are detected with a correction coefficient obtained by comparison. By correcting the air flow rate, the true fresh air flow rate of the engine is obtained. Therefore, even if a detection error occurs in the air flow sensor due to secular change or air flow sensor assembly error, the detected fresh air flow rate and the estimated fresh air flow rate Corresponding to the difference between the detected fresh air flow rate, the detected fresh air flow rate is immediately corrected to an accurate value.

Therefore, it is possible to detect the fresh air flow rate quickly and accurately without causing a delay as in the control device of Patent Document 1 described above. As a result, it is possible to prevent a decrease in engine operation performance and exhaust performance due to a decrease in the detection accuracy of the fresh air flow rate.
According to the engine intake flow rate detection device of claim 2, the excess air when the estimated fresh air flow rate is obtained in response to the response delay until the fresh air drawn into the engine is exhausted and reaches the λ sensor. Since the detected fresh air flow rate for the fresh air from which the exhaust gas was detected is compared with the estimated fresh air flow rate, a correction coefficient is obtained, so that the detected fresh air flow rate can be corrected more accurately. it can.

  Further, according to the engine intake flow rate detection device of claim 3, the response delay until the fresh air sucked into the engine is discharged as exhaust gas is repeatedly detected in response to the increase in the engine speed. Since the detected fresh air flow to be compared with the estimated fresh air flow is selected from the detected fresh air flow, it is possible to correct the detected fresh air flow with high accuracy using a correction coefficient over a wide range of engine speeds. .

According to the engine intake flow rate detection device of claim 4, when it is necessary to largely correct the detected fresh air flow rate, the conversion curve itself for converting the detection signal of the air flow sensor into the detected fresh air flow rate is provided. Since the correction is made, it is possible to reduce a calculation load such as a fresh air flow correction means required for correction by the correction coefficient.
Also, when the same airflow sensor is applied to different intake passages or engines, the conversion curve is corrected in the same manner, so that it is not necessary to obtain the conversion curves individually for different intake passages or engines.

Hereinafter, an engine intake flow rate detection device according to an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an overall configuration diagram of an engine system to which an engine intake flow rate detection device according to an embodiment of the present invention is applied. The configuration of the engine system will be described based on FIG.
The engine 1 is a four-cylinder diesel engine, and includes a high-pressure accumulator chamber (hereinafter referred to as a common rail) 2 common to each cylinder. High-pressure fuel supplied from a fuel injection pump (not shown) and stored in the common rail 2 is supplied to the injectors 4 provided in the respective cylinders, and injected from the injectors 4 into the respective cylinders.

  The intake pipe (intake passage) 6 is equipped with a turbocharger 8, and intake air drawn from an air cleaner (not shown) flows from the intake pipe 6 into the compressor 8 a of the turbocharger 8. The intake air supercharged by the compressor 8a is introduced into the intake manifold 14 via the intercooler 10 and the intake control valve 12, and is supplied to each cylinder of the engine 1 via an intake port (not shown).

  An air flow sensor 16 for detecting the flow rate of air sucked into the engine 1 from the atmosphere, that is, fresh air, is provided upstream of the compressor 8a of the intake pipe 6. The air flow sensor 16 outputs, as a detection signal, a voltage that changes in accordance with the flow rate of fresh air drawn into the engine 1. Between the intake control valve 12 and the intake manifold 14, an intake pressure sensor 18 that detects the intake pressure and an intake temperature sensor 20 that detects the intake air temperature are provided for intake air of the engine 1.

  On the other hand, an exhaust port (not shown) through which exhaust is discharged from each cylinder of the engine 1 is connected to an exhaust pipe (exhaust passage) 24 via an exhaust manifold 22. An EGR passage 28 is provided between the exhaust manifold 22 and the intake manifold 14 through the EGR cooler 25 and the EGR valve 26 so that the exhaust manifold 22 and the intake manifold 14 communicate with each other. The exhaust gas recirculation amount from the exhaust manifold 22 to the intake manifold 14 can be adjusted by changing the degree.

The exhaust pipe 24 is connected to the exhaust aftertreatment device 30 after passing through the turbine 8 b of the turbocharger 8. Further, the rotating shaft of the turbine 8b is mechanically connected to the rotating shaft of the compressor 8a, and the turbine 8b receives the exhaust flowing in the exhaust pipe 20 and rotates to drive the compressor 8a. .
The exhaust aftertreatment device 30 renders harmful components such as particulates and NOx contained in the exhaust of the engine 1 harmless, and includes a particulate filter, a catalyst device (none of which are shown), and the like.

The exhaust pipe 24 upstream of the exhaust aftertreatment device 30 is provided with a λ sensor 32 that detects an excess air ratio of the exhaust flowing in the exhaust pipe 24. The λ sensor 32 outputs a detection signal that continuously changes in response to a change in the excess air ratio of the exhaust gas.
The ECU 34 is a control device for performing comprehensive control including operation control of the engine 1, and includes a CPU, a memory, a timer counter, and the like. The ECU 34 calculates various control amounts and based on the control amounts. Controls various devices.

  On the input side of the ECU 34, in order to collect information necessary for various controls, in addition to the air flow sensor 16, the intake pressure sensor 18, the intake air temperature sensor 20, and the λ sensor 32 described above, a rotation speed sensor 36 that detects the engine speed. And various sensors such as an accelerator opening sensor 38 for detecting the depression amount of an accelerator pedal (not shown) are connected, and the injector 4 of each cylinder is controlled on the output side based on the calculated control amount. Various devices such as the intake control valve 12 and the EGR valve 26 are connected.

  The ECU 34 also performs calculation of the fuel supply amount to each cylinder of the engine 1 and control of fuel supply from the injector 4 based on the calculated fuel supply amount. The fuel supply amount necessary for the operation of the engine 1 is read out from a map stored in advance based on the engine speed detected by the speed sensor 36 and the accelerator pedal depression amount detected by the accelerator opening sensor 38. Determined. The amount of fuel supplied to each cylinder is adjusted by the valve opening time of the injector 4, and each injector 4 is driven to open in a driving time corresponding to the determined fuel supply amount, and fuel injection is performed to each cylinder. As a result, the amount of fuel necessary for the operation of the engine 1 is supplied.

  Further, the ECU 34 executes EGR control, adjusts the opening degree of the EGR valve 26 provided in the EGR passage 28 and controls the amount of exhaust gas recirculated from the exhaust manifold 22 to the intake manifold 14, whereby the air of the engine 1 is controlled. The excess rate is controlled to the target excess air rate. This target excess air ratio is an EGR control based on the number of revolutions of the engine 1 and the amount of fuel supplied to the engine 1 in advance as an excess air ratio that can suppress the generation of NOx without deteriorating the combustion state in each combustion chamber of the engine 1. It is stored as a map.

  In addition to the fresh air flow rate that the engine 1 inhales detected based on the detection signal of the airflow sensor 16, the ECU 34 supplies the fuel supply amount injected from the injector 4 into the combustion chamber and the exhaust gas recirculated through the EGR passage 28. Based on the amount of air contained, the actual excess air ratio is repeatedly calculated. At this time, the amount of air contained in the exhaust gas recirculated through the EGR passage 28 is detected based on the detection signal of the air flow sensor 16 from the theoretical air supply amount that is the amount of gas that can be supplied to the combustion chamber of the engine 1. It is obtained based on the exhaust gas recirculation amount obtained by reducing the intake fresh air flow rate of the engine 1 and the actual excess air ratio calculated last time. Further, the theoretical air supply amount used in such calculation is the charging efficiency of the engine 1 determined according to the operating state such as the rotation speed and load of the engine 1, the intake pressure detected by the intake pressure sensor 18, and the intake air pressure. It is obtained based on the intake air temperature detected by the air temperature sensor 20.

The ECU 34 adjusts the exhaust gas recirculation amount through the EGR passage 28 by controlling the opening degree of the EGR valve 26 so that the actual excess air ratio thus obtained becomes equal to the target excess air ratio. By controlling the excess air ratio of the engine 1 to the target excess air ratio in this way, the NOx emission amount from the engine 1 is suppressed satisfactorily.
Here, the ECU 34 executes fresh air flow rate detection control in order to detect the fresh air flow rate of the engine 1 with high accuracy based on the detection signal of the air flow sensor 16. Hereinafter, the fresh air flow rate detection control will be described in detail.

FIG. 2 is a control block diagram showing the processing of the ECU 34 in the fresh air flow rate detection control. The ECU 34 repeatedly performs the fresh air flow rate detection control at a predetermined control period according to the control block diagram of FIG. Execute.
The air flow sensor 16 outputs a detection signal whose voltage changes corresponding to the fresh air flow rate sucked into the engine 1, but as shown in FIG. 2, in the new air flow rate detection control, the detection signal of the air flow sensor 16 is detected. The voltage Vs is input to the fresh air flow rate detection unit 40. The fresh air flow rate detection unit 40 has a function of converting the detection signal voltage Vs of the air flow sensor 16 into a fresh air flow rate and outputting it as a detected fresh air flow rate Gs detected by the air flow sensor 16. Specifically, the fresh air flow rate detection unit 40 uses a conversion curve that is set in advance, and a signal conversion unit 40a that repeatedly converts the detection signal voltage Vs of the air flow sensor 16 into a detected fresh air flow rate Gs every control cycle. The function includes a conversion curve correction unit 40b described later.

The conversion curve used by the signal conversion unit 40a is a characteristic curve indicating the relationship between the detection signal voltage Vs and the detected fresh air flow rate Gs as indicated by the solid line in FIG. ing.
On the other hand, the excess air ratio λs of the exhaust detected by the λ sensor 32 and the fuel supply amount Qf to the engine 1 calculated by the ECU 34 are repeatedly input to the fresh air flow rate estimation unit 42 every control cycle. The fresh air flow rate estimation unit 42 uses the excess air ratio λs and the fuel supply amount Qf and the theoretical air-fuel ratio Lth stored in advance, and calculates the fresh air flow rate sucked into the engine 1 by the following equation (1). The estimated fresh air flow rate Glm is repeatedly calculated and estimated every control cycle.

Glm _(c) = λs _(c) · Qf _(c−a) · Lth (1)
In addition, the subscript (c) in the above formula (1) indicates the latest value among the repetitive calculations or inputted values, and Qf ₍ ca ₎ is _a predetermined number of times from the latest fuel supply amount Qf _(c). The fuel supply amount obtained before a is shown. The definition of the subscript is the same in each expression shown below. However, in FIG. 2, the addition of these subscripts is omitted.

As described above, the fuel supply amount Qf _(c−a) obtained a predetermined number of times a before the latest fuel supply amount Qf _(c) in the formula (1) is used when the fuel is supplied to the engine 1. This is to cope with the fact that there is a time delay between the time when the fuel is combusted and the exhaust gas reaches the λ sensor 32. That is, the fuel supply amount Qf _(c−a) of the fuel that is the generation source of the exhaust gas that is the detection target of the excess air ratio λs _(c) used in the equation (1) is used in the equation (1). The predetermined number of times a is set in advance. In this way, by considering the time delay from the fuel supply to the arrival of the exhaust to the λ sensor 32, the estimated fresh air flow rate Glm corresponding to the exhaust excess air ratio λs can be calculated and estimated with high accuracy.

Since the time delay decreases as the engine speed increases, in the present embodiment, the time delay decreases according to the increase in the engine speed Ne according to the engine speed Ne detected by the engine speed sensor 36. The predetermined number of times a is changed. Thus, the estimated fresh air flow rate Glm can be calculated and estimated with high accuracy over a wide range of engine speeds.
The detected fresh air flow rate Gs obtained by the fresh air flow rate detection unit 40 and the estimated fresh air flow rate Glm obtained by the fresh air flow rate estimation unit 42 are input to the correction coefficient calculation unit 44. The correction coefficient calculation unit 44 can store a plurality of detected fresh air flows Gs that are repeatedly input, and the detected fresh air flow Gs _(c−) that is obtained and input a predetermined number of times before. _b) is compared with the latest estimated fresh air flow rate Glm _(c), and the correction coefficient R is obtained by the following equation (2).

R = Glm _(c) / Gs _(c−b) (2)
The estimated fresh air flow rate Glm is a fresh air flow rate estimated based on the actual excess air ratio λs of the exhaust gas, and can be regarded as a relatively accurate fresh air flow rate. Therefore, by obtaining the correction factor R by comparing the detected as described above fresh air flow rate Gs and _(c-b) and the estimated fresh air flow rate Glm _(c), detecting the fresh air flow rate Gs of the _(c-b) An appropriate correction coefficient R for correcting to an accurate value can be obtained.

The reason why the detected fresh air flow rate Gs _(c−b) obtained a predetermined number of times before the latest detected fresh air flow rate Gs _{(c )} is used after the fresh air is inhaled into the engine 1 is used. This is because it corresponds to the time delay that is used for the combustion of fuel to reach the λ sensor 32 as exhaust gas. That is, the detected fresh air flow rate Gs _{(c−b) of the} fresh air that is the generation source of the exhaust gas that is the detection target of the estimated fresh air flow rate Glm _(c) used in the equation (2) is used in the equation (2). As described above, the predetermined number b is set in advance. In this way, the correction coefficient R can be obtained with high accuracy by considering the time delay from the intake of fresh air to the arrival of the exhaust gas at the λ sensor 32.

Since the time delay decreases as the engine speed increases, in the present embodiment, the time delay decreases according to the increase in the engine speed Ne according to the engine speed Ne detected by the engine speed sensor 36. The predetermined number of times b is changed. As a result, the correction coefficient R can be obtained with high accuracy over a wide range of the engine speed.
The correction coefficient R obtained in this way by the correction coefficient calculation unit 44 is input to the fresh air flow correction unit 46 together with the detected fresh air flow rate Gs obtained by the fresh air flow rate detection unit 40. The fresh air flow correction unit 46 obtains the true fresh air flow rate Ga _(c) of the engine 1 by correcting the latest detected fresh air flow rate Gs _(c) with the correction coefficient R using the following equation (3). .

Ga _(c) = R · Gs _(c) (3)
The true fresh air flow rate Ga obtained by the fresh air flow rate correcting unit 46 is used for various controls of the engine 1 including the aforementioned EGR control executed by the ECU 34.
In this way, the latest detected fresh air flow rate Gs _(c) is corrected by the correction coefficient R to obtain the true fresh air flow rate Ga, so that the air flow sensor 16 has a detection error due to secular change or an assembly error of the air flow sensor 16. In response to the difference between the detected fresh air flow rate Gs and the estimated fresh air flow rate Glm, the latest detected fresh air flow rate detected using the air flow sensor 16 is immediately corrected to an accurate value. Is done. Therefore, it is possible to improve the accuracy of the control using the fresh air flow rate including the EGR control. As a result, for example, in EGR control, the excess air ratio of the engine 1 can be appropriately controlled, and the exhaust performance of the engine 1 can be maintained well.

  The correction coefficient R obtained by the correction coefficient calculation unit 44 is input not only to the fresh air flow correction unit 46 but also to the conversion curve correction unit 40b. When the absolute value | R−1 | of the value obtained by subtracting 1 from the correction coefficient R is larger than the predetermined reference value α, the conversion curve correcting unit 40 b, that is, the detected fresh air flow rate Gs performed by the fresh air flow rate correcting unit 46. When the degree of correction is greater than a predetermined degree, the conversion curve used in the signal conversion unit 40a is corrected.

The conversion curve used by the signal conversion unit 40a is a characteristic curve indicating the relationship between the detection signal voltage Vs of the air flow sensor 16 and the detected fresh air flow rate Gs as shown by the solid line in FIG. Is preset. This conversion curve is expressed by the following n-order polynomial (4) using _n predetermined adaptive parameters (k ₀ , k ₁ , k ₂ ,..., K _n ) using the detection signal voltage Vs as an input value. These adaptive parameters are approximated and stored in the fresh air flow rate detector 40.

_{Gs = k 0 + k 1 ·} Vs + k 2 · Vs 2 + ··· + k n · Vs n ··· (4)
Here, when the adaptive parameter vector K and the input value vector P are respectively defined as the following equations (5) and (6), the n-order polynomial (4) is expressed as the following equation (7).
K = [k ₀ , k ₁ , k ₂ ,..., K _n ] (5)
P = [1, Vs, Vs ² ,..., Vs ⁿ ] (6)
Gs = K · P ^T (7)
Note that P ^T in the above equation (7) is a transposed matrix of the input value vector P.

When the absolute value | R-1 | is greater than the predetermined reference value α, the conversion curve correcting unit 40b determines the latest estimated fresh air flow rate Glm _(c) and the fresh air flow rate obtained from the conversion curve used at that time. And the adaptive parameter vector K used in the equation (7) corresponding to the nth order polynomial (4) is updated by performing the operation of the successive least squares method according to the following equation (8) using the Identify the adaptation parameters of 4).

_{K (c) = K (c} -1) + δ · (Glm (c) -K (c-1) · P (c) T) · P (c) ··· (8)
In Equation (8), δ is an adaptive gain, K _(c) represents the latest, that is, the updated adaptive parameter vector, and K _(c−1) represents the previous, that is, the updated adaptive parameter vector. Represents. K _(c-1) · P _(c) ^T corresponds to the fresh air flow rate obtained from the conversion curve before update.

  The conversion curve correction unit 40b corrects the conversion curve used in the signal conversion unit 40a based on the adaptive parameter vector K thus updated. As a result, the conversion curve is corrected, for example, as indicated by a broken line in FIG. In the modification shown in FIG. 3, a larger fresh air flow rate is obtained for the same detection signal voltage Vs after the modification than before the modification, but this is an example, Depending on the calculation result of Expression (8), the correction may be made so that a smaller fresh air flow rate is obtained for the same detection signal voltage Vs after the correction.

As described above, when it is necessary to largely correct the detected fresh air flow rate Gs, the conversion curve itself for converting the detection signal voltage Vs of the air flow sensor 16 into the detected fresh air flow rate Gs is corrected. Calculation loads such as the correction coefficient calculation unit 44 and the fresh air flow rate correction unit 46 required for correction by the coefficient R can be reduced.
In addition, when the airflow sensor 16 is applied to an intake pipe 6 or an engine having different specifications, the conversion curve used in the signal conversion unit 40a is appropriately corrected as described above. There is no need to obtain a conversion curve for each engine individually. As a result, engine system development and manufacturing costs can be reduced.

This is the end of the description of the engine intake flow rate detection device according to one embodiment of the present invention, but the present invention is not limited to the above embodiment.
For example, in the above embodiment, when the degree of correction of the detected fresh air flow rate in the fresh air flow rate correction unit 46 is large, the conversion curve correction unit 40b corrects the conversion curve used in the signal conversion unit 40a. The correction may be omitted. In this case, the effect of correcting the conversion curve as described above cannot be obtained, but the latest detected fresh air flow rate Gs detected using the airflow sensor 16 is immediately corrected to an accurate value by the correction coefficient R, The effect that the accuracy of the control using the fresh air flow including EGR control can be improved can be obtained in the same manner as in the above embodiment.

  In the above embodiment, the conversion curve is corrected by determining whether the degree of correction of the detected fresh air flow rate Gs is large based on the correction coefficient R obtained by the correction coefficient calculation unit 44. The method of determining whether or not the degree of correction with respect to the detected fresh air flow rate Gs is large is not limited to this. For example, it may be determined whether or not the degree of correction for the detected fresh air flow rate Gs is large based on the deviation between the true fresh air flow rate Ga obtained by correction and the detected fresh air flow rate Gs before correction.

  In the above embodiment, both the detected fresh air flow rate Gs and the estimated fresh air flow rate Glm are repeatedly obtained for each control period of the fresh air flow rate detection control. However, these calculation cycles are not necessarily limited to the fresh air flow rate detection control. It is not necessary to match the control period, and the calculation may be performed with independent control periods. Also in this case, what is added with the subscript (c) in each arithmetic expression described above indicates the latest value at that time as in the above embodiment, and each value before the predetermined number of times is also The value obtained previously by the predetermined number of times is indicated.

  In the above embodiment, the engine 1 is a four-cylinder diesel engine. However, the number of cylinders and the type of the engine 1 are not limited thereto, and the present invention is applied to engines having various cylinders or types. be able to.

1 is an overall configuration diagram of an engine system to which an engine intake flow rate detection device according to an embodiment of the present invention is applied. It is a control block diagram which shows the process of ECU in a fresh air flow rate detection control. It is a graph which shows an example of the conversion curve used by fresh air flow rate detection control.

Explanation of symbols

1 Engine 6 Intake pipe (intake passage)
16 Air flow sensor 24 Exhaust pipe (exhaust passage)
32 λ sensor 34 ECU
40 Fresh air flow rate detector (fresh air flow rate detection means)
40a Signal conversion unit 40b Conversion curve correction unit 42 Fresh air flow estimation unit (fresh air flow estimation means)
44 Correction coefficient calculation unit (correction coefficient calculation means)
46 New air flow correction unit (new air flow correction means)

Claims (4)

An air flow sensor provided in an intake passage of the engine and outputting a detection signal corresponding to a flow rate of fresh air sucked into the engine;
A fresh air flow rate detecting means for detecting a fresh air flow rate sucked into the engine as a detected fresh air flow rate based on a detection signal of the air flow sensor;
A λ sensor provided in an exhaust passage of the engine for detecting an excess air ratio of the exhaust of the engine;
A fresh air flow estimation means for estimating a fresh air flow rate sucked into the engine as an estimated fresh air flow rate based on an excess air ratio of the exhaust detected by the λ sensor and a fuel supply amount of the engine;
A correction coefficient calculation means for obtaining a correction coefficient by comparing the detected fresh air flow detected by the fresh air flow detection means and the estimated fresh air flow estimated by the fresh air flow estimation means;
A fresh air flow correcting means for correcting the detected fresh air flow detected by the fresh air flow detecting means with a correction coefficient obtained by the correction coefficient calculating means to obtain a true fresh air flow of the engine. Engine intake flow rate detection device characterized by. The fresh air flow rate detecting means repeatedly detects the detected fresh air flow rate based on the detection signal of the air flow sensor,
The correction coefficient calculating means responds to a response delay until fresh air sucked into the engine is exhausted and reaches the λ sensor with respect to the estimated fresh air flow estimated by the fresh air flow estimating means. 2. The engine intake flow rate detection device according to claim 1, wherein the correction coefficient is obtained by performing comparison using the detected fresh air flow rate detected by the fresh air flow rate detection means a predetermined number of times before.   3. The engine intake flow rate detection device according to claim 2, wherein the correction coefficient calculation means changes the predetermined number of times corresponding to the response delay according to the engine speed. The fresh air flow rate detecting means is
Using the detection signal of the air flow sensor as an input value and using a conversion curve approximated by a polynomial expressed by a predetermined adaptive parameter coefficient and the input value, the detected fresh air flow rate is converted by converting the detection signal of the air flow sensor. A signal converter for detecting
When the degree of correction of the detected fresh air flow rate by the fresh air flow rate correcting unit is greater than a predetermined level, the estimated fresh air flow rate estimated by the fresh air flow rate estimating unit is used to sequentially perform the least square method. The engine intake flow rate detection device according to claim 1, further comprising: a conversion curve correction unit that identifies the adaptive parameter and corrects the conversion curve by performing an operation.

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