JP2007092723A - Fuel injection quantity control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection quantity control device of an engine effectively inhibiting abnormal combustion such as preignition even in the control using an air model. <P>SOLUTION: The fuel ignition quantity control device is constructed in the engine equipped with an electronic throttle system so that a later throttle opening is estimated based on an opening command value of a throttle valve calculated from an operating amount of an accelerator pedal and a fuel injection quantity is controlled based on a cylinder-filled air volume estimated from the throttle opening. At sudden acceleration wherein the opening is larger than a predetermined value and a variation is larger than a predetermined value by excessive depressing operation of the accelerator pedal, the fuel injection quantity based on the cylinder filled air volume of a corresponding cylinder (a second cylinder #2) estimated from the later throttle opening based on the opening command value of the throttle valve calculated from the operation amount of the acceleration pedal at that time is corrected at decreasing timing beginning at the time of depressing the acceleration pedal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection amount control device for an internal combustion engine having an electronic throttle system that controls a throttle opening by driving a throttle valve with a throttle actuator, and more specifically, abnormal combustion such as knocking or pre-ignition during sudden start. It relates to measures to prevent.

  Recently, the intake system of an internal combustion engine is divided into elements such as a throttle valve, an intake pipe, an intake valve, etc., and each element is modeled and expressed by a mathematical expression to express the intake air quantity (in-cylinder charged intake quantity) of the engine. An intake air amount of an internal combustion engine is estimated by using a so-called air model obtained by calculation.

  In the intake air amount estimation device using such an air model, for example, as will be described later, it is possible to calculate the in-cylinder charged intake amount based only on the engine speed and the throttle opening in addition to the atmospheric pressure and the atmospheric temperature. Become. Further, since the in-cylinder charged intake amount can be calculated by calculation using a model formula, it is possible to calculate the intake air amount with high responsiveness even during transient operation where the change rate of the throttle opening is large.

On the other hand, in an internal combustion engine equipped with a so-called electronic throttle system that can control the throttle valve opening independently of the amount of operation of the accelerator pedal by the driver, the throttle is set to the target throttle opening determined by the amount of operation of the accelerator pedal. When controlling the opening, the air model is used to accurately predict the in-cylinder charged air amount, and the fuel injection amount is controlled based on the in-cylinder charged air amount predicted from the throttle opening. Is conventionally known (see, for example, Patent Document 1).
JP 2002-201998 A

  By the way, during the normal operation of the internal combustion engine, although the fuel injection amount is smoothly controlled based on the in-cylinder charged air amount accurately predicted by using the air model, the accelerator pedal operation amount (depression amount) is At the time of a transition that exceeds a predetermined value, the fuel injection amount based on the in-cylinder charged air amount of the corresponding cylinder predicted when controlling the throttle opening to the target throttle opening determined from the operation amount of the accelerator pedal is It is necessary to correct at the timing of reduction starting from the operation time (change time) of the throttle opening that is changed based on the throttle valve opening command value calculated from the operation amount of the accelerator pedal.

  However, in the control using the air model as described above, the throttle opening is controlled to the target throttle opening determined from the operation amount of the accelerator pedal, and therefore, as shown in FIG. If the fuel injection amount is corrected at the timing to reduce the amount of fuel that is injected, the fuel is injected immediately after the accelerator pedal is depressed during low-speed / high-load operation of the internal combustion engine that starts suddenly due to excessive depression of the accelerator pedal. There is a possibility that a delay occurs in the correction of the fuel injection amount based on the in-cylinder charged air amount of the cylinder (the first cylinder # 1 in the figure) and a pre-ignition signal is generated when the cylinder (the first cylinder # 1) is ignited. In addition, the control using the air model cannot effectively suppress abnormal combustion such as plague during the low rotation / high load operation of the internal combustion engine.

  The present invention has been made in view of the above points, and an object of the present invention is to inject fuel in an internal combustion engine that can effectively suppress abnormal combustion such as plague even in control using an air model. It is to provide a quantity control device.

  In order to achieve the above object, in the present invention, in an internal combustion engine equipped with an electronic throttle system that controls the throttle opening by driving the throttle valve with a throttle actuator, the throttle valve opening calculated from the operation amount of the accelerator pedal. A fuel injection amount control for an internal combustion engine that predicts the subsequent throttle opening based on the command value and controls the fuel injection amount based on the in-cylinder charged air amount of the corresponding cylinder predicted from the throttle opening. Assume equipment. Then, at the time of a sudden start when the accelerator pedal operation amount is greater than or equal to a predetermined value after the vehicle is stopped, the throttle valve opening command value calculated from the accelerator pedal operation amount at that time is used to calculate the subsequent throttle opening. The fuel injection amount based on the predicted cylinder air charge amount of the corresponding cylinder is corrected at a reduction timing starting from the time when the accelerator pedal is operated.

  Based on this specific matter, based on the throttle valve opening command value calculated from the amount of operation of the accelerator pedal at the time of low speed / high load operation of the internal combustion engine that starts suddenly by excessive depression of the accelerator pedal Therefore, the fuel injection amount based on the in-cylinder charged air amount of the corresponding cylinder predicted from the subsequent throttle opening is corrected at the reduction timing starting from the time when the accelerator pedal is operated. There is no delay like the one that corrects the fuel injection amount of the corresponding cylinder at the timing of reduction, and the correction of the fuel injection amount of the corresponding cylinder is sufficiently in time even when the internal combustion engine is operated at low speed and high load. become. Thereby, even if it is control using an air model, it becomes possible to suppress abnormal combustion, such as a plague, effectively.

  Here, the fuel injection amount corrected at the reduction timing starting from the accelerator operation time point is based on the in-cylinder charged air amount of the corresponding cylinder predicted from the subsequent throttle opening based on the throttle valve opening command value. When the fuel injection amount is continuously corrected until the fuel injection amount is corrected based on the actual opening of the throttle valve, the corresponding cylinder in the low rotation / high load operation of the internal combustion engine The correction of the fuel injection amount is continuously performed smoothly, and it becomes possible to more effectively suppress abnormal combustion such as pre-ignition due to air model control.

  In short, when the internal combustion engine that starts suddenly is operating at low speed and high load, the value predicted from the subsequent throttle opening based on the throttle valve opening command value calculated from the operation amount of the accelerator pedal at that time By correcting the fuel injection amount based on the in-cylinder charged air amount of the cylinder to be reduced at a reduction timing starting from the time when the accelerator pedal is operated, the fuel injection amount is corrected to correct the fuel injection amount during low-speed / high-load operation of the internal combustion engine. Abnormal combustion such as plague can be effectively suppressed even in the case of control using the air model sufficiently in time without causing a delay.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an entire control system of an in-line four-cylinder engine 1 (hereinafter simply referred to as an engine) as an internal combustion engine mounted on an automobile. In FIG. 1, an air cleaner 12 is mounted on the upstream side of the intake pipe 11 of the engine 1, and an air flow meter 13 for measuring the intake air amount is installed on the downstream side thereof. This air flow meter 13 has a built-in hot wire and intake air temperature detecting element that are arranged in the flow of intake air, so that the temperature difference between the hot wire cooled by the intake air and the intake air temperature is kept constant. The supply current is controlled. As a result, the supply current to the heat wire changes according to the heat radiation amount of the heat wire that changes according to the intake air flow rate, and a voltage signal corresponding to this supply current is output as the intake air flow rate signal.

  A throttle valve 14 is provided on the downstream side of the air flow meter 13, and a motor 15 (throttle actuator) such as a DC motor is connected to a rotating shaft 14 a of the throttle valve 14. The opening of the throttle valve 14 (throttle opening) is controlled by the driving force of the motor 15, and the actual throttle opening of the throttle valve 14 is detected by the throttle opening sensor 16.

  In this case, even during idle operation, the throttle opening is controlled by the driving force of the motor 15, thereby controlling the intake air amount during idle operation and feedback control so that the engine speed matches the target idle speed. To do. This throttle control during idling is idle rotation speed control (ISC). In the idle speed control, an idle speed control valve (ISC valve) is provided in a bypass passage that bypasses the throttle valve 14, and the amount of bypass air is controlled by controlling the opening of the idle speed control valve during idle operation. (The amount of intake air during idle operation) may be controlled.

  On the other hand, an intake pressure sensor 17 for detecting the intake pressure is installed on the downstream side of the throttle valve 14. A fuel injection valve 19 is attached to an intake manifold 18 that introduces intake air that has passed through the throttle valve 14 into each cylinder of the engine 1, and a spark plug 20 is attached to the cylinder head of each cylinder of the engine 1. It has been. A crank angle sensor 23 is installed facing the outer periphery of the signal rotor 22 fitted to the crankshaft 21 of the engine 1, and the pulse of the engine rotation speed signal Ne output from the crank angle sensor 23 is sent to an electronic control unit (ECU 3), and the engine speed is detected based on the frequency of generation of the engine speed signal Ne.

  Then, the depression amount (accelerator operation amount) of the accelerator pedal 24 is detected by the accelerator sensor 25, and a voltage signal corresponding to the accelerator operation amount is taken into the electronic control unit 3 via the A / D converter 31. The outputs of various sensors such as the air flow meter 13, the intake pressure sensor 17, and the throttle opening sensor 16 are also taken into the electronic control unit 3 via the A / D converter 31.

  The electronic control unit 3 is mainly composed of a microcomputer including a CPU 32, a ROM 33, a RAM 34, and the like. By executing various throttle control programs stored in the ROM 33 by the CPU 32, during normal throttle control, The motor 15 is feedback-controlled by PID control or the like via the motor drive circuit 35 in accordance with the opening command value (target throttle opening) set based on the accelerator operation amount, etc. The degree is controlled to the opening command value. In addition, a safety circuit 26 comprising a relay or the like is provided in the energization path from the motor drive circuit 35 to the motor 15, and when the electronic throttle system is abnormal, this safety circuit 26 is activated to cut off the energization to the motor 15. It is supposed to be.

  Further, the electronic control unit 3 executes the routines of FIG. 9 to FIG. 16 stored in the ROM 33 by the CPU 32, so that the throttle opening degree at the intake valve closing timing (timing for determining the in-cylinder charged air amount) is set. Predicting the cylinder filling air amount based on the predicted throttle opening, calculating the fuel injection amount based on the predicted cylinder filling air amount, and calculating the injection pulse having a pulse width corresponding to the calculation result. It outputs to the injector drive circuit 36 and controls the injection time (fuel injection amount) of the fuel injection valve 19.

  A method of calculating the fuel injection amount by the electronic control unit 3 will be described with reference to FIGS. FIG. 2 is a block diagram showing an outline of a method for predicting the in-cylinder charged air amount. During engine operation, the accelerator operation amount is detected by the accelerator sensor 25, and the opening command value (target throttle opening) is set by a map or the like according to the accelerator operation amount by the opening command value calculation means. This opening command value is output to the motor drive circuit 35 of the electronic throttle system. In this case, the time Tinj from the calculation timing of the fuel injection amount TAU (prediction timing of the in-cylinder charged air amount) to the intake valve closing timing becomes shorter as the engine speed increases.

  On the other hand, the opening command value φtotal set by a map or the like according to the accelerator operation amount or the like by the opening command value calculating means is input to the electronic throttle model. As shown in FIG. 3, the electronic throttle model is composed of an electronic throttle dynamic characteristic model section and a change amount calculation section. This electronic throttle dynamic characteristic model section simulates the response delay characteristic of the electronic throttle system with a second-order lag element [ω2 / (s2 + 2ζωs + ω2)], and simulates the limit characteristic of the drive speed of the throttle valve 14 with a speed limiter. The predicted throttle opening θf is calculated from the degree command value φtotal. The two integral elements (1 / s) of the second-order lag element are rectangular integrals. In order to simplify the arithmetic processing, a primary delay element may be used instead of the secondary delay element.

  The electronic throttle model change amount calculation unit includes a differential element (d / dt) and an integral element (∫), and the differential element (d / dt) outputs the output of the electronic throttle dynamic characteristic model unit (predicted throttle opening). Degree) sampling time Ts is obtained, and this difference is integrated by an integration element (∫), thereby calculating the predicted change amount Δθ of the throttle opening. At this time, the time for integrating the difference with the integral element (∫) is the time Tinj from the calculation timing of the fuel injection amount TAU (predicted timing of the in-cylinder charged air amount) to the intake valve closing timing. Thus, the predicted change amount Δθ of the throttle opening output from the change amount calculation unit becomes the predicted change amount of the throttle opening until the intake valve closing timing.

  The electronic throttle model adds the predicted change amount Δθ of the throttle opening output from the change amount calculation unit to the current throttle opening θ (the output of the throttle opening sensor 18), and the predicted throttle opening at the intake valve closing timing. The degree θf is obtained, and the predicted throttle opening degree θf is output to the intake system model.

  As shown in FIG. 4, the intake system model includes a predicted throttle passage air amount calculation unit, a predicted intake pressure calculation unit, and a predicted in-cylinder charged air amount calculation unit. The estimated throttle opening air amount Gin is calculated from the predicted throttle opening degree, etc., assuming that the throttle opening through which the valve passes is an orifice. The predicted intake pressure calculation unit calculates a predicted intake pressure Pm from the predicted throttle passage air amount Gin, and the predicted in-cylinder charged air amount calculation unit calculates a predicted in-cylinder charged air amount Gcf from the predicted intake pressure Pm. The predicted throttle passage air amount calculation unit is expressed by the following orifice equation.

ここで、ｆ（Ｐm／Ｐa）は、上式により演算しても良いが、演算処理を簡略化するために、Ｐm／Ｐaをパラメータとするテーブルから算出すると良い。ｆ（Ｐm／Ｐa）のテーブルは、最大値を１として正規化すると、図５に示すような曲線で表される。このｆ（Ｐm／Ｐa）は、上記（３）式、（４）式から明らかなように、物理的には負の値にならないため、図６の例では、Ｐm／Ｐa＞１のときに、ｆ（Ｐm／Ｐa）＝０に設定している。

Here, f (Pm / Pa) may be calculated by the above formula, but in order to simplify the calculation process, it is preferable to calculate it from a table using Pm / Pa as a parameter. The table of f (Pm / Pa) is represented by a curve as shown in FIG. As apparent from the above equations (3) and (4), f (Pm / Pa) is not physically negative. Therefore, in the example of FIG. 6, when Pm / Pa> 1, , F (Pm / Pa) = 0.

  However, if f (Pm / Pa) = 0 when Pm / Pa> 1, as shown in FIG. 7, the calculated value (throttle throttle) of the intake system model during high load operation in which Pm / Pa fluctuates around 1. Hunting tends to occur due to vibration of the passing air amount Gin, the predicted intake pressure Pm, and the predicted in-cylinder charged air amount Gcf. This is because the rate of change of f (Pm / Pa) increases in the region where Pm / Pa is near 1 and f (Pm / Pa) every time Pm / Pa becomes 1 or more in calculation during high load operation. This is because the change in f (Pm / Pa) during high-load operation becomes irregular because is guarded at 0.

  As a countermeasure, in this embodiment, a table of f (Pm / Pa) is set as shown in FIG. That is, f (Pm / Pa) = positive value when Pm / Pa <1, f (Pm / Pa) = 0 when Pm / Pa = 1, and f (Pm / Pa when Pm / Pa> 1. Pa) = a negative value is set. As a result, the f (Pm / Pa) table has a symmetrical change characteristic in which ± is reversed with Pm / Pa = 1 as a boundary.

  When the f (Pm / Pa) table having the change characteristics as shown in FIG. 6 is used, the change in f (Pm / Pa) becomes regular during high load operation in which Pm / Pa varies around 1. Therefore, by averaging the calculated values of the intake system model (throttle passage air amount Gin or predicted intake pressure Pm or predicted in-cylinder charged air amount Gcf), as shown in FIG. The model output (predicted in-cylinder charged air amount Gcf) can be stabilized, and hunting can be prevented.

  As the intake pressure Pm input to the predicted throttle passage air amount calculation unit, the previous predicted intake pressure Pm (i−1) calculated by the predicted intake pressure calculation unit is used, but the output of the intake pressure sensor 17 is used. Also good.

  Further, the throttle opening effective sectional area A used for calculating the predicted throttle passing air amount Gin may be calculated by substituting the throttle opening θ into the above equation (2). However, in this embodiment, the calculation process is simplified. In order to achieve this, the multiplication value μ · A of the flow coefficient μ and the throttle opening effective sectional area A is calculated from a table using the predicted throttle opening as a parameter.

  Next, a method for calculating the predicted intake pressure Pm and the predicted in-cylinder charged air amount Gcf will be described.

When the law of conservation of mass is applied to the flow of intake air flowing through the intake passage (hereinafter referred to as “throttle downstream intake passage”) from the throttle valve 14 to the intake port of the engine 1, the relationship expressed by the following equation (5) is obtained. can get.
d / dt · Qm = Gin−Gcf (5)
Here, Qm is the amount of air in the throttle downstream intake passage, d / dt · Qm is the amount of change in the amount of air in the throttle downstream intake passage, Gin is the predicted throttle passage air amount, and Gcf is the predicted in-cylinder charged air amount. .

When the gas equation of state is applied to the throttle downstream intake passage, the relationship expressed by the following equation (6) is obtained.
Gcf = η · (Ne / 2) · Vc · (Qm / VIM) (6)
η: Volumetric efficiency, Ne: Engine speed, Vc: Cylinder volume, VIM: Inner volume of the throttle downstream intake passage Here, the volumetric efficiency η varies depending on the intake air flow rate, and therefore has a correlation with the intake air flow rate. Is set by a map or the like based on the engine speed Ne and the intake pressure Pm. Pm used here is the previous value Pm (i-1) of the predicted intake pressure.
η = f (Ne, Pm)
The model time constant τIM of the intake system model is expressed by the following equation (7).
τIM = 2 ・ VIM / (Vc ・ η ・ Ne) (7)
The following formula (8) is derived from the above formulas (5) to (7).
d / dt · Qm = Gin−Qm / τIM (8)
Since the above equation (8) is a continuous equation, it is discretized as follows so that the electronic control unit 3 can perform arithmetic processing.
{Qm (i) -Qm (i-1)} / Ts = Gin (i) -Qm (i-1) / τIM (9)
Here, Ts is a sampling time.

When this equation (9) is arranged, an equation for calculating the air amount Qm in the throttle downstream intake passage is derived as follows.
Qm (i)
= {Gin (i) -Qm (i-1) /. Tau.IM} .Ts + Qm (i-1) [kg] (10)
Further, when the gas state equation is applied to the throttle downstream intake passage, an equation for calculating the predicted intake pressure Pm is derived from the air amount Qm in the throttle downstream intake passage as follows.
Pm = Qm * R * T / VIM [Pa] (11)
R: gas constant, T: intake air temperature The predicted intake pressure calculation unit of the intake system model calculates the predicted intake pressure Pm using the above equations (10) and (11).

From the above equations (11) and (6), an arithmetic expression for the predicted in-cylinder charged air amount Gcf expressed by the following equation (12) is derived.
Gcf = η · Vc · Pm / (2 · R · T) [kg / rev] (12)
The predicted in-cylinder charged air amount calculation unit of the intake system model calculates a temporary predicted in-cylinder charged air amount Gcf using the above equation (12).

  As shown in FIG. 2, the output of the intake system model (temporary predicted in-cylinder charged air amount Gcf) is input to a differential element (d / dt), and a difference between sampling times ts is obtained, and the difference is integrated. Integrated with element (∫). The integration time is a time Tinj from the calculation timing of the fuel injection amount TAU (prediction timing of the in-cylinder charged air amount) to the intake valve closing timing. The value integrated by the integration element (∫) is a value corresponding to the predicted change amount ΔGc of the in-cylinder charge air amount until the intake valve closing timing, and the base in-cylinder charge obtained by calculating this predicted change amount ΔGc by the base intake system model. The final predicted in-cylinder charged air amount Gc (cylinder charged air amount determined at the intake valve closing timing) is obtained by adding to the air amount Gbase.

  Next, a method for calculating the base cylinder charge air amount will be described.

  This base cylinder charge air amount is the current cylinder charge air amount calculated based on the output of the air flow meter 13 (intake air flow rate). Therefore, the amount of air charged in the cylinder does not include the amount of change in the amount of air charged in the cylinder due to the change in the throttle opening from the present to the intake valve closing timing (timing for determining the amount of air charged in the cylinder). In general, the method of calculating the in-cylinder charged air amount from the output of the air flow meter 13 has an advantage that the calculation accuracy of the in-cylinder charged air amount is good because the intake air flow rate = in-cylinder charged air amount in a steady state. However, there is a response delay of the air flow meter 13 at the time of transition (for example, in the case of a thermal air flow meter 13, there is a response delay due to the heat mass of the sensor part of the air flow meter 13), so the response at the time of transition is poor. There are drawbacks.

Therefore, in this embodiment, in order to improve the response at the time of transition, the response delay of the output of the air flow meter 13 is compensated by a response delay compensation element (phase advance compensation element), and the output of this response delay compensation element is used as a base. A base cylinder charge air amount Gbase, which is an output of the base intake system model, is input to the intake system model. The transfer function of this base intake system model is expressed by the following first-order lag equation.
Gbase = 1 / (1 + τIM · s)
Gbase: Base cylinder charge air amount, τIM: Time constant The time constant τIM of this base intake system model is expressed by the following equation.
τIM = 2 ・ VIM / (Vc ・ η ・ Ne)
VIM: inner volume of the intake passage on the downstream side of the throttle, Vc: cylinder volume, η: volumetric efficiency Ne: engine rotational speed Here, the volumetric efficiency η varies depending on the intake air flow rate, and is therefore correlated with the intake air flow rate. A map or the like is set based on the engine speed Ne and the intake pressure P (the output of the intake pressure sensor 17), which are parameters.

  The base in-cylinder charged air amount Gbase calculated by such a base intake system model and the estimated change amount ΔGc of the in-cylinder charged air amount calculated from the predicted throttle opening etc. are integrated to obtain the final predicted in-cylinder charging. An air amount Gc (in-cylinder charged air amount determined at the intake valve closing timing) is obtained, and a fuel injection amount is set according to the predicted in-cylinder charged air amount Gc, the engine speed, and the like.

  The functions of the blocks in FIG. 2 described above are realized by the routines in FIGS. The processing contents of each routine will be described in detail below.

[Main routine]
The main routine of FIG. 9 is executed at a predetermined cycle after the ignition switch is turned on. When this routine is started, first, in step ST1, a predicted in-cylinder charged air amount calculation routine of FIG. 10 described later is executed, and the predicted in-cylinder charged air amount Gc (in-cylinder charged air amount determined at the intake valve closing timing) is executed. ) Is calculated.

  Thereafter, the routine proceeds to step 2, where a basic injection amount calculation routine (not shown) is executed, and the basic injection amount Tp is calculated by a map or the like according to the predicted in-cylinder charged air amount Gc and the engine rotational speed Ne. Thereafter, the routine proceeds to step 3 where an injection amount correction routine of FIG. 16 described later is executed, and various correction coefficients Kc such as a fuel correction coefficient Kload (acceleration / deceleration correction coefficient), an air-fuel ratio feedback correction coefficient, a water temperature correction coefficient, etc. with respect to the load fluctuation. Is multiplied by the basic injection amount Tp to obtain the final fuel injection amount.

[Predicted in-cylinder charged air amount calculation routine]
The predicted in-cylinder charged air amount calculation routine of FIG. 10 is a subroutine executed in step S1 of the main routine of FIG. 9, and plays a role of calculating the predicted in-cylinder charged air amount in the claims.

When this routine is started, first, in step S11, a predicted intake pressure calculation routine of FIG. 11 described later is executed to calculate a predicted intake pressure Pm (intake pressure at the intake valve closing timing). Thereafter, the process proceeds to step S12, and the predicted in-cylinder charged air amount Gcf (i) is calculated by the following equation using the predicted intake pressure Pm.
Gcf (i) = η · Vc · Pm / (2 · R · T) [kg / rev]
η: Volumetric efficiency, Vc: Cylinder volume, R: Gas constant, T: Intake air temperature Thereafter, the process proceeds to step S13, and the predicted change amount ΔGc of the cylinder charge air amount from the calculation timing of the fuel injection amount to the intake valve closing timing Is set to 0.

Then, the process proceeds to step S14, where a base in-cylinder charged air amount calculation routine (not shown) is executed, and the base in-cylinder charged air amount Gbase is calculated by the following transfer function.
Gbase = 1 / (1 + τIM · s)
Here, τIM is a time constant.

  In order to simplify the explanation, the above formula represents the calculation formula for the amount of air charged in the base cylinder in a continuous system. The air amount Gbase is calculated.

Thereafter, the process proceeds to step S15, and the final predicted in-cylinder charged air amount Gc is obtained by adding the predicted change amount ΔGc in step S13 to the base in-cylinder charged air amount Gbase.
Gc = Gbase + ΔGc
[Predicted intake pressure calculation routine]
The predicted intake pressure calculation routine of FIG. 11 is a subroutine executed in step S11 of the predicted in-cylinder charged air amount calculation routine of FIG. When this routine is started, first, in step S111, a predicted throttle passage air amount calculation routine of FIG. 12 described later is executed to calculate a predicted throttle passage air amount Gin. Thereafter, the routine proceeds to step 112, where an intake system model time constant calculation routine of FIG. 14 described later is executed to calculate a model time constant τIM of the intake system model. Thereafter, the process proceeds to step S113, and the air amount Qm in the throttle downstream intake passage is calculated by the following equation.
Qm (i) = {Gin (i) -Qm (i-1) /. Tau.IM} .Ts + Qm (i-1)
Here, Qm (i) is the amount of air in the current throttle downstream intake passage, Qm (i-1) is the amount of air in the previous throttle downstream intake passage, and Ts is the sampling time.

Thereafter, the process proceeds to step S114, and the predicted intake pressure Pm is calculated from the air amount Qm in the throttle downstream intake passage according to the following equation.
Pm = Qm ・ R ・ T / VIM
Here, R is a gas constant, T is the intake air temperature, and VIM is the internal volume of the throttle downstream intake passage.

Thereafter, the process proceeds to step S115, and the predicted intake pressure Pm is averaged by calculating an average value of the current predicted intake pressure Pm (i) and the previous predicted intake pressure Pm (i-1).
Pm (i) = {Pm (i) + Pm (i-1)} / 2
[Predicted throttle passage air amount calculation routine]
The predicted throttle passage air amount calculation routine of FIG. 12 is a subroutine executed in step S111 of the predicted intake pressure calculation routine of FIG. When this routine is started, first, in step S121, a predicted throttle opening degree calculation routine of FIG. 13 to be described later is executed to calculate a predicted throttle opening degree θf of the intake valve closing timing. Thereafter, the process proceeds to step S122, and the atmospheric pressure Pa, the intake air temperature T, and the previous predicted intake pressure Pm (i-1) are read.

  Thereafter, the process proceeds to step S123, and the predicted throttle passage air amount Gin is calculated by the following equation.

この際、μ・Ａは、予測スロットル開度θfをパラメータとするテーブルから算出し、ｆ（Ｐm／Ｐa）は、Ｐm／Ｐaをパラメータとする図６のテーブルから算出する。吸気圧Ｐmは、前回の予測吸気圧Ｐm（ｉ−１）が用いられ、大気圧Ｐaと吸気温度Ｔは、それぞれセンサの検出値が用いられる。尚、大気圧Ｐaは標準大気圧（固定値）を用いても良い。

At this time, μ · A is calculated from a table using the predicted throttle opening θf as a parameter, and f (Pm / Pa) is calculated from the table of FIG. 6 using Pm / Pa as a parameter. The previous predicted intake pressure Pm (i-1) is used as the intake pressure Pm, and the detected values of the sensors are used as the atmospheric pressure Pa and the intake air temperature T, respectively. The atmospheric pressure Pa may be a standard atmospheric pressure (fixed value).

[Predicted throttle opening calculation routine]
The predicted throttle opening calculation routine of FIG. 13 is a subroutine executed in step S121 of the predicted throttle passage air amount calculation routine of FIG. 12, and plays a role as a predicted throttle opening calculation.

When this routine is started, first, in step S131, the opening command value φtotal is set according to the accelerator operation amount and the like. At this time, the opening command value φtotal is obtained by integrating various required openings such as the required opening φpedal corresponding to the accelerator operation amount and the required opening φisc by idle rotation speed control (ISC).
φtotal = φpedal + φisc
Thereafter, the process proceeds to step S132, the current throttle opening .theta. Detected by the throttle opening sensor 16 is read, and then the process proceeds to step S133, in which the electronic throttle dynamic characteristic model part and the change amount calculation of the electronic throttle model shown in FIG. The predicted change amount Δθ of the throttle opening is calculated using the opening command value φtotal. This predicted change amount Δθ is a predicted change amount of the throttle opening during the time Tinj from the calculation timing of the fuel injection amount TAU (prediction timing of the in-cylinder charged air amount) to the intake valve closing timing.

Then, the process proceeds to step S134, and the predicted throttle opening θf is obtained by adding the predicted change amount Δθ to the current throttle opening θ.
θf = θ + Δθ
The predicted throttle opening degree θf is a predicted throttle opening degree at the intake valve closing timing.

[Intake system model time constant calculation routine]
The intake system model time constant calculation routine of FIG. 14 is a subroutine executed in step S112 of the predicted intake pressure calculation routine of FIG. When this routine is started, first, in step S141, a volumetric efficiency calculation routine of FIG. 15 described later is executed to calculate volumetric efficiency η. Thereafter, the process proceeds to step S142, and the model time constant τIM is calculated by the following equation.
τIM = 2 · VIM / (VC · η · Ne / 60)
Here, VIM is the internal volume (fixed value) of the throttle downstream intake passage, VC is the cylinder volume (fixed value), and Ne is the engine speed (rpm).

[Volume efficiency calculation routine]
The volumetric efficiency calculation routine of FIG. 15 is a subroutine executed in step S141 of the intake system model time constant calculation routine of FIG. When this routine is started, first, in step S151, the previous intake pressure Pm (i-1), atmospheric pressure Pa, intake air temperature T, engine speed Ne, valve timing VVT, and cooling water temperature THW are read.

  Thereafter, the process proceeds to step S152, where a volumetric efficiency map using Pm / Pa, engine rotational speed Ne, and valve timing VVT as parameters is retrieved to calculate a basic volumetric efficiency ηr corresponding to the current engine operating state. The volumetric efficiency ηr is corrected with a correction value corresponding to the cooling water temperature THW to obtain the volumetric efficiency η.

[Injection amount correction routine]
The injection amount correction routine of FIG. 16 is a subroutine executed in step S3 of the main routine of FIG. 9, and serves as a fuel injection amount calculation means together with a basic injection amount calculation routine (not shown).

  When this routine is started, first, in step S31, it is determined whether or not there is a load fluctuation (fluctuation in the in-cylinder charged air amount) due to an accelerator operation. The determination is made based on whether or not the amount of change in the accelerator operation amount is equal to or greater than a set value. If it is determined that the load is changed due to the accelerator operation, the process proceeds to step S32, and the fuel correction coefficient Kload for the load change (change in the in-cylinder charged air amount) is set to a small value K1. The reason for this is that, in the method for calculating the in-cylinder charged air amount of the present embodiment, the load fluctuation (fluctuation in the in-cylinder charged air quantity) due to the accelerator operation can be accurately predicted, and therefore the correction for the fuel injection quantity is reduced. Because it can.

  In this case, the control of the fuel injection amount in the traveling state excluding the low rotation / high load operation state of the internal combustion engine that suddenly starts by excessive depression of the accelerator pedal 24 is performed by the throttle valve calculated from the operation amount of the accelerator pedal. The subsequent throttle opening is predicted based on the opening degree command value, and this is performed based on the in-cylinder charged air amount predicted from the throttle opening. The correction to the fuel injection amount at this time is based on the opening command value of the throttle valve 14 calculated from the depression amount (accelerator operation amount) of the accelerator pedal 24 in the traveling state excluding the low rotation / high load state. It is executed at the timing starting from the operation time (change time) of the changed throttle opening.

  On the other hand, when it is determined that there is no load fluctuation due to the accelerator operation (for example, when the automatic transmission is shifted from the neutral range to the drive range, or when the load fluctuation is caused by power steering, brake, air conditioner, etc.), the process proceeds to step S33. Then, the fuel correction coefficient Kload for the load fluctuation is set to a large value K2. The reason for this is that load fluctuations due to factors other than the accelerator operation cannot be predicted from the accelerator operation amount, and therefore it is desirable to increase the correction to the fuel injection amount for load fluctuations due to factors other than the accelerator operation. .

As described above, after determining the fuel correction coefficient Kload for load fluctuation in step S32 or S33, the process proceeds to step S34, and various fuel correction coefficients Kc (for example, air-fuel ratio feedback correction coefficient, water temperature, etc.) for factors other than load fluctuation. Correction coefficient, learning correction coefficient, etc.) are calculated, and in the next step S35, the final fuel injection amount (injection pulse width) TAU is calculated by the following equation using the basic injection amount Tp and the fuel correction factors Kload, Kc. Calculate.
TAU = Tp × Kload × Kc
An example of the behavior of the predicted throttle opening calculated by each routine described above and the predicted in-cylinder charged air amount is shown in the time chart of FIG. During engine operation, the opening command value φtotal is set according to the accelerator operation amount and the like.

  Based on this opening command value φtotal, a predicted change amount Δθ of the throttle opening is calculated by the electronic throttle model of FIG. 3, and this predicted change amount Δθ is converted to the current throttle opening θ (output of the throttle opening sensor 16). The predicted throttle opening θf at the intake valve closing timing is obtained by addition. Then, using this predicted throttle opening θf, a temporary predicted in-cylinder charged air amount Gcf is calculated by the intake system model of FIG. 4, and this is differentiated and integrated to obtain the in-cylinder charged air amount up to the intake valve closing timing. The predicted change amount ΔGc is calculated. This predicted change amount ΔGc is added to the base in-cylinder charged air amount Gbase calculated by the base intake system model to obtain the final predicted in-cylinder charged air amount Gc (cylinder charged air amount determined at the intake valve closing timing). Ask. As a result, the cylinder charge air amount Gc can be accurately predicted, and the air-fuel ratio control accuracy at the time of transition can be improved.

  As a characteristic part of the present invention, as shown in FIG. 18, in the low rotation / high load operation state of the engine 1 that suddenly starts by excessive depression of the accelerator pedal 24, the accelerator operation amount at that time is detected. In-cylinder to the second cylinder # 2 and the first cylinder # 1 of the next point predicted from the subsequent throttle opening based on the opening command value of the throttle valve 14 calculated from the voltage signal from the accelerator sensor 25 The fuel injection amount based on the charged air amount is corrected at a reduction timing starting from the depression point P (operation point) of the accelerator pedal 24 at the time of sudden start.

  Here, a procedure for correcting the fuel injection amount in the low rotation / high load operation state of the engine 1 that suddenly starts when the accelerator pedal 24 is excessively depressed will be described with reference to the flowchart of FIG.

  First, in step ST51 of the flowchart of FIG. 19, it is determined whether or not the engine 1 is in an idle state and is in a stopped state such as waiting for a signal at which the speed becomes 0 km / h. If the determination in step ST51 is YES, ie, when the vehicle is stopped such as waiting for a signal, in step ST52, the opening of the accelerator pedal 24 is larger than a predetermined value and the change amount of the accelerator pedal 24 is larger than a predetermined value. It is determined whether or not the vehicle is large, that is, whether or not the vehicle is suddenly started by excessive depression of the accelerator pedal 24. If the determination in step ST52 is YES indicating a sudden start, the value of the weight reduction execution counter is set to 2 in step ST53.

  Thereafter, in step ST54, when the determination in step ST51 is NO when the vehicle is not stopped, such as waiting for a signal, and when the determination in step ST52 is NO, the fuel injection valve 19 of any cylinder is at the fuel injection timing. If it is not the fuel injection timing, the control is terminated as it is. If the fuel injection valve of any cylinder is the fuel injection timing, the process proceeds to step ST55.

  In step ST55, it is determined whether or not the value of the weight reduction execution counter is not zero. If the determination in step ST55 is YES when the value of the reduction execution counter is not 0, the fuel of the fuel injection valve 19 of the corresponding cylinder (the fuel injection valve 19 of the second cylinder # 2 in FIG. 18) is determined in step ST56. After correcting the injection amount by a predetermined amount and performing fuel injection, the value of the reduction execution counter is decremented by one in step ST57. In this case, since the value of the decrease execution counter is decremented by 1 to 1, the process proceeds again from step ST51 to step ST54 and step ST55, and then in step ST56, the first cylinder # 1 corresponding to the second cylinder # 2 is applied. After the fuel injection amount is corrected by reducing the fuel injection amount of the fuel injection valve 19 by a predetermined amount, the value of the reduction execution counter is decremented by 1 in step ST57 to zero.

  On the other hand, if the determination in step ST55 is NO where the value of the decrease execution counter is 0, in step ST58, fuel is injected at the normal fuel injection amount without performing the correction for decreasing the fuel injection amount.

  Therefore, in the above embodiment, at the time of sudden start when the opening degree is larger than the predetermined value and the change amount is larger than the predetermined value due to excessive depression of the accelerator pedal 24, the operation amount of the accelerator pedal 24 at that time Based on the calculated throttle valve opening command value, the fuel injection amount based on the in-cylinder charged air amount of the corresponding cylinder (second cylinder # 2 in FIG. 18) predicted from the subsequent throttle opening is determined by the accelerator pedal 24. Since the correction is made at the reduction timing starting from the depression time, there is no delay as in the case of correcting the fuel injection amount of the corresponding cylinder at the reduction timing starting from the operation time of the throttle opening. Even during the low rotation / high load operation, the correction of the fuel injection amount of the corresponding cylinder is sufficiently in time. Moreover, the value of the weight reduction execution counter is set to 2 at the time of sudden start, and the fuel injection valve 19 of the corresponding cylinder (second and first cylinders # 2, # 1) is subtracted one by one until it becomes zero. Correction for reducing the fuel injection amount by a predetermined amount is performed. Thereby, even if it is control using an air model, abnormal combustion, such as a plague, can be controlled effectively.

  In addition, this invention is not limited to the said embodiment, The other various modifications are included. For example, in the above-described embodiment, the value of the weight reduction execution counter is set to 2 at the time of sudden start, and the corresponding cylinder (second and first cylinders # 2, # 1) is subtracted one by one until it becomes zero. The fuel injection amount of the fuel injection valve 19 is corrected by a predetermined amount, but the fuel injection amount corrected at the timing of reduction starting from the accelerator operation point is based on the throttle valve opening command value. The number of corresponding cylinders is increased until the fuel injection amount based on the in-cylinder charged air amount of the corresponding cylinder predicted from the subsequent throttle opening becomes the fuel injection amount corrected based on the actual throttle valve opening. You may be allowed to continue to lose weight as many times as you like. In this case, the correction of the fuel injection amount of the corresponding cylinder is performed smoothly and smoothly during low-speed / high-load operation of the engine, so that abnormal combustion such as plague due to air model control can be more effectively suppressed. It becomes possible.

1 is a schematic configuration diagram of an entire engine control system including a fuel injection amount control device according to an embodiment of the present invention. It is a block diagram which shows the function of an electronic control unit. It is a block diagram which shows an electronic throttle model. It is a block diagram which shows an intake system model. It is a figure which shows notionally the table of f (Pm / Pa). It is a figure which shows notionally the table of f (Pm / Pa). FIG. 6 is a characteristic diagram showing the behavior of a predicted in-cylinder charged air amount Gcf calculated using the f (Pm / Pa) table of FIG. 5 during high load operation. FIG. 8 is a characteristic diagram showing the behavior of a predicted in-cylinder charged air amount Gcf calculated using the f (Pm / Pa) table of FIG. 7 during high load operation. It is a flowchart figure which shows the flow of a process of a main routine. It is a flowchart figure which shows the flow of a process of cylinder filling air amount calculation routine. It is a flowchart figure which shows the flow of a process of a prediction intake pressure calculation routine. It is a flowchart figure which shows the flow of a process of a prediction intake pressure calculation routine. It is a flowchart figure which shows the flow of a process of prediction throttle passage air amount calculation routine. It is a flowchart figure which shows the flow of a process of an intake system model time constant calculation routine. It is a flowchart figure which shows the flow of a process of a volumetric efficiency calculation routine. It is a flowchart figure which shows the flow of a process of the injection quantity correction routine. It is a time chart which shows an example of the behavior of the prediction throttle opening at the time of acceleration computed with each model, and the prediction cylinder air charge amount. It is a time chart which illustrates the fuel injection amount decreasing timing at the time of sudden start. It is a flowchart figure which shows the correction | amendment procedure of the fuel injection quantity at the time of sudden start. It is a time chart which illustrates the reduction timing of the fuel injection quantity at the time of the sudden start concerning a prior art example.

Explanation of symbols

1 engine (internal combustion engine)
14 Throttle valve 15 Motor (throttle actuator)
24 Accelerator pedal

Claims (2)

In an internal combustion engine equipped with an electronic throttle system that controls the throttle opening by driving the throttle valve with a throttle actuator, the subsequent throttle opening is determined based on the throttle valve opening command value calculated from the operation amount of the accelerator pedal. A fuel injection amount control device for an internal combustion engine, which predicts and controls the fuel injection amount based on the in-cylinder charged air amount of the corresponding cylinder predicted from the throttle opening,
Predicted from the subsequent throttle opening based on the throttle valve opening command value calculated from the accelerator pedal operation amount at the time of sudden start when the accelerator pedal operation amount from the vehicle stop state exceeds a predetermined value A fuel injection amount control device for an internal combustion engine, wherein the fuel injection amount based on the cylinder air charge amount of the corresponding cylinder is corrected at a reduction timing starting from the time when the accelerator pedal is operated. In the fuel injection amount control device for an internal combustion engine according to claim 1,
The fuel injection amount corrected at the reduction timing starting from the accelerator pedal operation time is the fuel based on the in-cylinder charged air amount of the corresponding cylinder predicted from the subsequent throttle opening based on the throttle valve opening command value. A fuel injection amount control device for an internal combustion engine, wherein the fuel injection amount is continuously corrected until the fuel injection amount is corrected based on the actual opening of the throttle valve.

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