JP4957033B2 - Fuel injection control device - Google Patents

Description

  The present invention relates to an apparatus for controlling fuel injection of an engine.

  In an internal combustion engine, for example, there is a time delay from when an acceleration operation is performed until the amount of intake air actually taken into a cylinder of the engine increases.

  When fuel of the target fuel injection amount calculated from the intake air flow rate detected by the air flow meter provided upstream of the intake throttle and the target air-fuel ratio is injected from the fuel injector, the engine This air-fuel mixture becomes the target air-fuel ratio. However, in transient operation such as acceleration and deceleration, the air-fuel mixture in the cylinder temporarily deviates from the target air-fuel ratio due to a delay in the change in the intake air amount.

Therefore, Patent Document 1 proposes a method for calculating a fuel injection charge so that the air-fuel mixture supplied to the cylinder matches the target air-fuel ratio even during transient operation of the vehicle internal combustion engine. That is, the intake air amount per combustion cycle of the cylinder is calculated from the detected flow rate of the air flow meter, and the fuel injection amount corresponding to the cylinder intake amount is calculated from the intake air amount and the theoretical air-fuel ratio. Furthermore, the prior art is applied at a timing when the fuel injection amount is advanced by 10 milliseconds from the closing of the intake valve.
JP-A-01-305144

  When calculating the intake air amount per combustion cycle of the cylinder from the detected flow rate of the air flow meter, a delay process is performed. In other words, the amount of intake air in the cylinder is calculated before the air is actually drawn into the cylinder. Therefore, the fuel injection amount based on the calculation result can be applied prior to closing the intake valve.

  Regarding the acceleration operation of the internal combustion engine, if the application timing of the fuel injection amount advanced by 10 milliseconds from the closing of the intake valve is before the actual fuel injection timing, the calculated fuel injection amount is reflected in the actual fuel injection Can be made. However, if the timing advanced by 10 milliseconds from the closing of the intake valve is after the injection timing, fuel injection is performed using the fuel injection amount calculated in the previous combustion cycle. In the latter case, when the internal combustion engine is accelerated, it is inevitable that the actual air-fuel ratio of the air-fuel mixture in the cylinder becomes lean.

  In order to solve this problem, the application timing of the calculated value of the fuel injection amount may be greatly advanced. However, since this advance operation is performed as a correction for the delay process when calculating the intake air amount of the cylinder from the detected flow rate of the air flow meter, it cannot be advanced beyond the range of the delay process. More simply, the corresponding fuel injection quantity cannot be calculated before the air flow meter detects an increase in air flow. Therefore, the advance operation of the application timing of the fuel injection amount calculation value is limited to a narrow range, and the effect on the air-fuel ratio control accuracy is also limited.

  The present invention has been made paying attention to such conventional problems, and an object of the present invention is to provide a fuel injection control device that improves the air-fuel ratio control accuracy of an internal combustion engine during transient operation.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

The present invention is provided in an intake passage and is driven by an actuator that operates in response to a control signal to change the intake passage opening area to adjust the amount of air sucked into the cylinder. A fuel injection control device for controlling a fuel injection amount of an engine having an intake throttle (51), provided in an intake passage upstream of the intake throttle and detecting an air flow rate, and a control signal Predicting area calculating means for predicting the opening area of the intake throttle in accordance with the actual opening area calculating means for calculating the actual opening area of the intake throttle, and calculating a ratio of the expected opening area to the actual opening area An area ratio calculating means and a pressure ratio meter for calculating a ratio of an estimated pressure in a downstream portion of the intake passage downstream of the intake throttle to an actual pressure Means, a density ratio calculating means for calculating a density ratio of an expected density to an actual density of air in the intake throttle, and an air flow rate detected by the air flow rate detecting means, the area ratio, the pressure ratio, and the intake throttle is corrected based on the density ratio, and the intake predicted air amount calculating means for calculate the predicted value of the intake air amount the intake throttle is realized, the required injection of calculating the amount of the required fuel injection in accordance with the estimated intake air amount It has quantity calculation means (78), and a fuel injector (52) which injects fuel of the demanded fuel injection quantity at a predetermined timing.

  According to the present invention, an intake air amount adjustment mechanism is realized in an engine having an intake air amount adjustment mechanism that adjusts the amount of air sucked into a cylinder in response to a control signal but has a response delay with respect to the control signal. Since the predicted value of the intake air amount is calculated based on the control signal, the required fuel injection amount is calculated according to the expected intake air amount, and the fuel of the required fuel injection amount is injected at a predetermined timing. The control accuracy of the air-fuel ratio in transient operation such as engine acceleration and deceleration is improved. In addition, since the predicted value of the intake air amount is calculated based on the density ratio particularly in the intake throttle, the intake air amount can be predicted more accurately, and the control accuracy of the air-fuel ratio is further improved.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.
(First embodiment)
FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention.

  In the intake passage 2 of the engine 1 including the intake collector 21, an air flow meter 61, an intake throttle device 51, and a fuel injector 52 are provided from upstream. The intake throttle device 51 includes an intake throttle 51a and a throttle motor 51b. When the driver depresses the accelerator pedal 35, the controller 7 determines a target torque based on a signal from the accelerator position sensor 67, determines a target air amount for realizing the target torque, and obtains this target air amount. Further, the opening degree of the intake throttle 51a is controlled via the throttle motor 51b. Further, for example, if there is a torque request signal for constant speed running by an ASCD (Auto Speed Control Device) or a torque request signal for rotation synchronization control for alleviating the shift shock of the automatic transmission, the controller 7 A target air amount for realizing the target torque is determined, and the opening degree of the intake throttle 51a is controlled via the throttle motor 51b so as to obtain this target air amount. The intake throttle device 51 is not mechanically connected to the accelerator pedal 35, and the throttle motor 51b drives the intake throttle 51a. For this reason, there is a response delay until the actual intake throttle opening coincides with the intake throttle target opening.

A manifold catalyst 31 and an underfloor catalyst 32 are provided in the exhaust passage 3. When the air-fuel ratio of the exhaust gas is in a narrow range centered on the stoichiometric air-fuel ratio, the manifold catalyst 31 and the underfloor catalyst 32 remove hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in the exhaust gas. It is a three-way catalyst that can be removed at the same time. For this reason, the controller 7 determines the basic injection amount from the fuel injector 52 according to the operating conditions, and feedback-controls the air-fuel ratio based on the signal of the O ₂ sensor 64 provided upstream of the manifold catalyst 31.

  The engine 1 is also referred to as a “variable valve event and lift control system” (hereinafter referred to as “VEL mechanism”) that is configured by a multi-node link-like mechanism that continuously and variably controls the lift amount and operating angle of the intake valve 15. ) 41, a variable valve timing mechanism (hereinafter referred to as "valve timing control") that continuously and variably controls the rotational phase difference between the crankshaft 14 and the intake valve camshaft 41a to advance or retard the valve timing of the intake valve 15. 42) (abbreviated as “VTC mechanism”). Since these specific configurations are known from Japanese Patent Application Laid-Open No. 2003-314347, detailed description thereof is omitted.

  The air metered by the intake throttle 51a is stored in the intake collector 21 and then introduced into the cylinders 11 of the respective cylinders via the intake manifold 22. Fuel is intermittently injected and supplied to the intake port 23 at a predetermined timing from a fuel injector 52 disposed in the intake port 23 of each cylinder. Here, the fuel injection amount given to the fuel injector 52 is calculated based on the intake air flow rate detected by the air flow meter 61 (air flow rate detecting means) by the controller 7 and the signal from the crank angle sensors (33, 34). It is calculated according to the engine speed.

  The injected fuel is mixed with the intake air to form an air-fuel mixture. The air-fuel mixture is confined in the cylinder 11 by closing the intake valve 15, compressed by the ascending piston 13, and ignited by the spark plug 17 to burn. The gas pressure due to the combustion works to push down the piston 13, and the reciprocating motion of the piston 13 is converted into the rotational motion of the crankshaft 14. The combusted gas (exhaust gas) is discharged into the exhaust passage 3 when the exhaust valve 16 is opened.

  FIG. 2 is a diagram for explaining the basic concept of the present invention.

  Next, the basic concept of the fuel injection control according to the present invention when the internal combustion engine 1 is accelerated will be described with reference to FIG.

  As shown in FIG. 2A, at time t1, the driver depresses the accelerator pedal 35, and the accelerator pedal depression amount APO starts increasing from the first depression amount APO1 to the second depression amount APO2. As described above, the change in the throttle opening TVO is delayed with respect to the change in the accelerator pedal depression amount APO. Here, the throttle opening TVO starts increasing at time t4.

  As shown in FIG. 2A, when the internal combustion engine 1 is accelerated or decelerated, the intake throttle opening TVO rises as much as the response delay of the intake throttle 51a with respect to the rise of the accelerator pedal depression amount APO. Is delayed. Therefore, the waveform of the intake throttle opening TVO is equal to the waveform of the accelerator pedal depression amount APO translated in the right direction. However, the intake throttle 51a has a first-order lag or a several-order lag with respect to the depression of the accelerator pedal 35, and thus has a waveform as shown in FIG.

  The change in the intake air amount of the cylinder 11 is further delayed with respect to the change in the throttle opening TVO. That is, the intake air that has passed through the intake throttle 51 a is temporarily stored in the collector 21 and then sucked into the cylinder 11. Therefore, the change in the intake air amount of the cylinder 11 is further delayed with respect to the change in the throttle opening TVO. Here, the intake air amount of the cylinder 11 starts to increase at time t5. The amount of air actually sucked into the cylinder 11 is referred to as a cylinder intake actual air amount Qc.

  The subject of the present invention is to improve the control accuracy of the air-fuel ratio by solving the difference between the change in the amount of air actually taken into the cylinder 11 and the change in the fuel injection amount in transient operation including acceleration. . Therefore, in FIG. 2C, the cylinder intake actual air amount Qc and the required injection amount Tpf are drawn at the same height for convenience of explanation. Actually, if the fuel injection amount is 1 at the stoichiometric air-fuel ratio, the intake air amount is 14.7. The unit of the cylinder intake actual air amount Qc is [g / cycle] (gram / cycle), and the unit of the required injection amount Tpf is [msec] (millisecond). Therefore, although the units are different, only the increase timing is a problem here, so the unit differences are ignored to simplify the notation. As a result, the cylinder intake actual air amount Qc and the required injection amount Tpf have the same waveform, and only a time-axis direction deviation exists between them.

  It takes 40 to 50 milliseconds from the start of the change in the accelerator pedal depression amount APO at the time t1 to the start of the change in the throttle opening TVO of the intake throttle 51a at the time t4.

  The basic concept of the present invention is that a signal for controlling the amount of fuel injection instead of the throttle opening TVO (the signal of an accelerator pedal depression amount, a torque request signal for constant speed traveling by ASCD, for example) Or torque request signal for rotation synchronization control to alleviate shift shock of automatic transmission), and as a result, the required injection amount Tpf is calculated prior to the change in throttle opening TVO. it can.

  The response delay from the start of change of the accelerator pedal depression amount APO at time t1 to the start of change of the intake air amount of the cylinder 11 at time t5 will be referred to as dead time T2 in the following description.

  As shown in FIG. 2 (C), the controller 7 performs an advance processing using the dead time T2 until the phase of change in the cylinder intake actual air amount Qc matches the phase of change in the accelerator pedal depression amount APO. The value after processing is assumed as the cylinder intake predicted air amount Qca. The dead time T2 is given in advance as a constant value. The controller 7 further adds a delay process based on the dead time T1 for synchronizing with the injection timing to the cylinder intake predicted air amount Qca to obtain a required injection amount Tpf indicated by a one-dot chain line in FIG.

  Each curve in FIG. 2C indicates a value calculated from a change in the accelerator pedal depression amount APO, and does not consider opening / closing of the intake valve 15. Actually, as shown in FIG. 2B, the intake valve 15 is closed at time t6, so the value Qc1 of the cylinder intake actual air amount Qc at time t6 is the intake actual air amount of the cylinder 11. A value Tpf1 at time t2 of the curve of the required injection amount Tpf is a required injection amount corresponding to the actual intake air amount Qc1. Therefore, the controller 7 actually calculates the required injection amount Tpf1 at time t2.

  In FIGS. 2A to 2C, it is assumed that the rotational speed Ne of the internal combustion engine 1 is constant and the injection timing is a time t2 slightly delayed from the time t0. From time t3 to time t6 is the valve opening period of the intake valve 15, and the injection timing is set immediately before the intake stroke. This relationship is the same for any cylinder 11.

  Since the horizontal axis in FIGS. 2A to 2C is a time axis, the injection timing changes when the engine rotational speed Ne changes. Specifically, when the engine rotational speed Ne decreases, the injection timing is delayed and moves to the right in the figure. When the engine speed Ne increases, the injection timing is advanced and the engine moves to the left in the figure. Along with this, the dead time T1 also changes. That is, the dead time T1 is a function of the engine speed Ne.

  A specific configuration of the controller 7 will be described with reference to FIG.

  The controller 7 calculates the fuel injection amount Ti. The controller 7 includes an air flow meter output delay advance compensation unit 71, a throttle opening predicted area calculation unit 721, a throttle opening actual area calculation unit 722, an area ratio calculation unit 723, a corrected predicted pressure ratio calculation unit 731, a correction Actual pressure ratio calculation unit 732, pressure ratio ratio calculation unit 733, density ratio calculation unit 740, intake predicted air amount calculation unit 74, intake passage downstream portion filling model 75, and cylinder intake prediction per combustion cycle An air amount calculation unit 76, a dead time calculation unit 77, a required injection amount calculation unit 78, a fuel injection amount calculation unit 79, a cylinder intake air amount calculation unit 701, and a cylinder intake air amount equivalent injection amount calculation unit 702 Is provided. Each block shown in FIG. 3 represents each function of the controller 7 as a virtual unit, and each block does not mean physical existence.

  With these calculation units, the controller 7 calculates the fuel injection amount Ti [msec] at intervals of 1 millisecond during the operation of the internal combustion engine 1.

  The air flow meter output compensation unit 71 advances and compensates for the response delay in the signal input from the air flow meter 61, and calculates the air flow meter detected flow rate Qa [g / msec] (gram / millisecond). It is known from Japanese Patent Application Laid-Open No. 2003-314347 to add response delay advance compensation to the signal of the air flow meter 61, and here the method is applied as it is.

Based on the required drive torque Trq or the accelerator pedal depression amount APO detected by the accelerator position sensor 67, the estimated throttle opening area calculation unit 721 calculates a throttle opening area (hereinafter referred to as “predicted throttle opening area”) AAPO [m ² ] (Square meter) is calculated. A specific calculation method will be described later.

The throttle opening actual area calculating unit 722 searches the characteristic map of FIG. 5B stored in the ROM of the controller 7 in advance, and determines the throttle opening from the throttle opening TVO of the intake throttle 51a detected by the throttle opening sensor 36. Calculate the actual area ATVO [m ² ] (square meter).

  The area ratio calculation unit 723 calculates a ratio AAPO / ATVO between the predicted throttle opening area AAPO and the actual throttle opening area ATVO.

The corrected predicted pressure ratio calculation unit 731 calculates a ratio Pma / Pa between a predicted pressure Pma [Pa] (pascal) in the downstream portion of the intake passage, which will be described later, and an atmospheric pressure Pa [Pa] detected by the atmospheric pressure sensor 68, as shown in FIG. A map stored in advance in the ROM of the controller 7 having the characteristics shown in (A) is searched to obtain the corrected predicted pressure ratio PRA.

The corrected actual pressure ratio calculation unit 732 calculates in advance the controller 7 having the characteristics shown in FIG. 6B from the ratio Pm / Pa of the actual pressure Pm [Pa] downstream of the intake passage and the atmospheric pressure Pa [Pa] . The map stored in the ROM is searched for the corrected actual pressure ratio PR.

  The ratio calculation unit 733 of the two pressure ratios calculates a ratio PRR between the corrected predicted pressure ratio PRA and the corrected actual pressure ratio PR.

  The density ratio calculation unit 740 obtains the air density ratio ρtha / ρth in the intake throttle 51a by the following equations (1-1) and (1-2).

  Whether or not it is choking is determined based on the pressure ratio (Pm / Pthf) before and after the intake throttle 51a. That is, when Pm / Pthf <0.53, it is determined that the choke is being performed, and when Pm / Pthf ≧ 0.53, it is determined that the choke is not being performed.

  Further, ρthfa / ρthf is the following equation (2).

Here, a specific method for obtaining Expression (2) will be described with reference to FIG .

  The predicted air amount Qthfa in the upstream portion of the intake passage is expressed by the following equation (3).

  Further, since the air density ρ is the air amount Q / volume V, ρthfa / ρthf is expressed by the following equation.

  Since the volume of the upstream portion of the intake passage is constant (invariable), the following equation (5) is obtained. If equation (3) is substituted for this, equation (2) is obtained.

  The predicted intake air amount calculation unit 74 corrects the air flow meter detected flow rate Qa with the area ratio AAPO / ATVO and the pressure ratio PRR as shown in the following equation (6), and the predicted cylinder intake air amount Qaa [g / msec].

  The cylinder intake predicted air amount Qaa calculated in this way is input to the intake passage downstream portion filling model 75. The intake passage downstream portion filling model 75 calculates an air amount Cma [g] in the intake passage downstream portion, an actual pressure Pm [Pa] in the intake passage downstream portion, and a predicted pressure Pma [Pa] in the intake passage downstream portion.

  The downstream portion of the intake passage refers to a portion of the intake passage that is downstream of the intake throttle 51a. In this embodiment, the intake collector 21, the intake manifold 22, and the intake port 23 are combined. .

  The cylinder intake predicted air amount calculation unit 76 per combustion cycle calculates the cylinder intake predicted air amount Qca [g / cycle] (gram / cycle) per combustion cycle using the air amount Cma in the downstream of the intake passage. To do.

  Detailed configurations of the intake passage downstream portion filling model 75 and the cylinder intake predicted air amount calculation unit 76 per combustion cycle will be described later.

  The dead time calculation unit 77 calculates the dead time T1 by the following equation (7) from the engine speed Ne [rpm] and the dead time T2 of the intake throttle 51a.

  The pre-crank crank angle section X1 corresponds to a crank angle section from the fuel injection start timing to the intake valve closing timing. The pre-crank angle section X1 is a constant value such as 250 degrees when the fuel injection timing is predetermined and the opening / closing timing of the intake valve 15 and the valve lift amount are constant.

  The required injection amount calculation unit 78 is first a known value as shown in FIG. 2C based on the estimated cylinder intake air amount Qca [g / cycle] per combustion cycle and the dead time T1. The cylinder intake predicted air quantity Qca [g / cycle] per combustion cycle at a time point before the dead time T1 from the time t2 is calculated. Since the predicted cylinder intake air amount Qca per combustion cycle given by the calculation unit 76 is a function of time, the time t = t2-T1 is given to this function, and the specific cylinder intake predicted air amount Qca per combustion cycle is specified. The numerical value Qca1 [g / cycle] is calculated. The required injection amount calculation unit 78 further obtains a required injection amount Tpf1 [msec] for realizing the theoretical air-fuel ratio by dividing Qca1 [g / cycle] by the theoretical air-fuel ratio of 14.7 in the following equation (8). The required injection amount Tpf1 is represented by a fuel injection pulse width.

  The fuel injection amount calculation unit 79 uses the required injection amount Tpf1 [msec] calculated by the required injection amount calculation unit 78 to calculate the fuel injection amount Ti [msec] for sequential injection and synchronous injection according to the following equation (9).

  Equation (9) is a known calculation formula for the fuel injection amount by air-fuel ratio feedback correction. The transient correction amount Kathos is a value for wall flow correction. The target equivalent ratio Tfbya is a value corresponding to the target air-fuel ratio. When the theoretical air-fuel ratio is set to the target air-fuel ratio, the target air-fuel ratio Tfbya is 1.0, and when the lean air-fuel ratio is set to the target air-fuel ratio, the target equivalent ratio The ratio Tfbya is a value less than 1.0, and when the rich air-fuel ratio is set to the target air-fuel ratio, the target air-fuel ratio Tfbya is a value greater than 1.0.

  The controller 7 outputs a fuel injection pulse signal corresponding to the fuel injection amount Ti [msec] calculated in this way to the fuel injector 52 at the injection timing.

  The cylinder intake air amount calculation unit 701 calculates a value obtained by delaying the cylinder intake predicted air amount Qca per combustion cycle by a dead time T2 [msec] as a cylinder intake actual air amount Qc [g / cycle].

  The cylinder intake air amount equivalent injection amount calculation unit 702 calculates the injection amount with respect to the cylinder intake predicted air amount Qca per combustion cycle, and retards the value by a dead time T2 [msec] to retard the cylinder intake air amount equivalent injection amount Tp. Calculate [msec]. The injection amount Tp is represented by the fuel injection pulse width.

  The cylinder intake air amount equivalent injection amount Tp calculated by the cylinder intake air amount equivalent injection amount calculation unit 702 and the cylinder intake actual air amount Qc calculated by the cylinder intake air amount calculation unit 701 are calculated for fuel injection control in steady operation. This value is not used for fuel injection control in transient operation.

  Although not shown in FIG. 3, the controller 7 preferably discriminates between the steady operation and the transient operation of the internal combustion engine 1, and in the steady operation, the cylinder intake actual air amount Qc and the cylinder intake air amount are equivalent to the conventional case. The fuel injection amount Ti is calculated using the injection amount Tp, and in the transient operation, the fuel injection amount Ti is calculated using the predicted cylinder intake air amount Qca and the required injection amount Tpf per combustion cycle.

  FIG. 4 is a diagram for explaining the details of the predicted throttle opening area calculation unit 721.

  A predicted throttle opening area calculation unit 721 includes a predicted throttle opening area calculation unit 7211 based on an accelerator depression amount, a predicted throttle opening area calculation unit 7212 based on a torque request signal, a high selection unit 7213, and a throttle opening based on an idle maintenance signal. A predicted area calculation unit 7214 and a throttle opening predicted area calculation unit 7215 are included.

Throttle opening prediction area calculating unit 7211 based on A Kuseru depression amount, based on the accelerator pedal depression amount APO of an accelerator position sensor 67 detects, searches the advance characteristic map of FIG stored in the ROM of the controller 7 5 (A) Thus, the throttle opening prediction area AAPO1 based on the accelerator depression amount APO is calculated.

  A predicted throttle opening area calculation unit 7212 based on the torque request signal calculates a predicted throttle opening area AAPO2 based on the torque request signal Trq. An example of the torque signal is, for example, a torque signal for constant speed running by an ASCD (Auto Speed Control Device) and a torque signal for rotation synchronization control for alleviating a shift shock of the automatic transmission. The estimated throttle opening area calculation unit 7212 based on the torque request signal includes a necessary air amount calculation unit 72121 and a throttle opening area conversion unit 72122. The estimated throttle opening area calculation unit 7212 based on the torque request signal calculates the required air amount based on the torque request signal in the required air amount calculation unit 72121 and opens the throttle opening area conversion unit 72122 to pass the required air amount. Calculate the power throttle area AAPO2.

  The high selection unit 7213 compares the predicted throttle opening area AAPO1 based on the accelerator depression amount with the predicted throttle opening area AAPO2 based on the torque request signal, and sets the larger one as the predicted throttle opening area AAPO0.

  An estimated throttle opening area calculation unit 7214 based on the idle maintenance signal calculates an intake throttle opening area AISC corresponding to an idle torque portion of the engine torque necessary for ensuring idle rotation. Specifically, it is calculated as an opening area corresponding to the torque necessary to maintain the target idle rotational speed in idle rotational speed control (ISC) including auxiliary machine drive torque and the like.

  The estimated throttle opening area calculation unit 7215 calculates the estimated throttle opening area AAPO by adding the idle torque equivalent opening area AISC to the estimated throttle opening area basic value AAPO0.

In the following, an intake passage downstream portion filling model 75, the configuration of the cylinder intake predicted air amount calculation unit 76 per combustion cycle will be described.

A combination of the intake passage downstream portion filling model 75 and the cylinder intake predicted air amount calculation unit 76 per combustion cycle is known from Japanese Patent Application Laid-Open No. 2001-50091. Here, by applying the known technique, the intake passage downstream portion filling model 75 and combustion cycle cylinder intake predicted air amount calculation unit 76 per to configure.

Can be calculated cylinder intake predicted air amount Qca per combustion cycle is advanced phase until it matches the changes in the A Kuserupedaru depression amount APO. That is, in FIG. 2C, a value obtained by advancing the cylinder intake actual air amount Qc per combustion cycle by the dead time T2 is calculated. The value calculated here is the predicted cylinder intake air amount Qca per combustion cycle. As described above, the dead time T2 is given as a constant value in advance.

  Each part will be briefly described.

The following formula (10) is used to calculate the air amount Caa [g] flowing into the downstream portion of the intake passage by multiplying the cylinder intake predicted air amount Qaa by the calculation period Δt, that is, 1 millisecond.

By adding the inflow air amount Caa [g] to the previous value Cma ⁻¹ and subtracting the intake air amount of the cylinder (flowing out from the downstream portion of the intake passage) Cca [g] by the following equation (11), Calculate the air quantity Cma [g] downstream of the intake passage.

The cylinder intake air amount Cca ^{−1 on} the right side of the equation (11) is a cylinder intake predicted air amount (that is, the previous value of Cca) calculated before one control cycle.

The actual pressure calculation unit 753 uses the intake passage downstream portion air amount Cma [g], the intake passage downstream portion temperature Tm [K] detected by the temperature sensor 44, and the intake passage downstream portion volume Vm [m ³ ]. Then, the predicted pressure Pm a [Pa] in the downstream portion of the intake passage is calculated by the following equation (12). Equation (12) is derived from the gas equation of state.

Thus, the intake passage downstream portion pressure Pm were dead time T2 the advance of the intake throttle 51a, the accelerator opening angle intake passage downstream portion pressure Pma [Pa] is Ru is calculated.

The cylinder intake predicted air amount calculation unit 761 uses the intake passage downstream air amount Cma [g], the cylinder volume Vc [m ³ ], and the intake passage downstream portion volume Vm [m ³ ] to The cylinder intake predicted air amount Cca [g] is calculated by Equation (13). Vc and Vm are constant values.

  Equation (13) is obtained as follows. The equation of state of gas is expressed by the following equation (14).

  When this relationship is rewritten, the following equation (15) is obtained.

  By applying this to the cylinder 11, the number of moles of the cylinder 11, that is, the air amount Cc can be obtained by the following equation (16).

  If it is considered that the pressure Pc of the cylinder 11 and the intake passage downstream portion pressure Pm are equal, and the temperature Tc of the cylinder 11 and the intake passage downstream portion temperature Tm are equal, the equation (16) is rewritten into the following equation (17).

  On the other hand, the following equation is derived from the gas equation of state.

  Therefore, the following equation (19) is established in the downstream portion of the intake passage.

  Substituting equation (19) into equation (17) yields the following equation (20).

  When the air amount Cc of the cylinder 11 is replaced with the cylinder intake predicted air amount Cca, the above equation (13) is obtained.

  The predicted cylinder intake air amount Cca calculated by the predicted air amount calculation unit 761 is used by the air amount balance calculation unit 752 in the next calculation cycle. As described above, the predicted air amount calculation unit 761 and the air amount balance calculation unit 752 perform cyclic calculations using the calculated values.

  The weighted average processing unit 762 calculates the weighted average value Ccak [g] of the cylinder intake predicted air amount by performing the weighted average of the cylinder intake predicted air amount Cca using the following equation (21).

  The unit conversion unit 763 uses the engine rotational speed Ne [rpm] to make the weighted average value Ccak [g] of the estimated cylinder intake air amount correspond to the calculation cycle, and thus one combustion cycle, that is, 6 In a cylinder engine, it is converted into a predicted cylinder intake air amount Qca [g / cycle] per 120 degrees of crank angle.

  In this way, the intake passage downstream portion filling model 75 and the cylinder intake predicted air amount calculation unit 76 per combustion cycle are the cylinder intake predicted air amount Qca [g / cycle] per combustion cycle, and the intake passage downstream portion Calculate the actual pressure Pm [Pa] and the predicted pressure Pma [Pa] downstream of the intake passage.

The operation and effect of the present invention will be described with reference to FIG .

  Here, when the driver depresses the accelerator pedal 35 at time t1 to maintain a constant depression amount, that is, when the throttle opening area AAPO is calculated based on the accelerator pedal depression amount APO in the predicted throttle opening area calculation unit 721 of FIG. think about.

As shown in FIG. 8A , when the driver depresses the accelerator pedal 35, the predicted throttle opening area increases from the predicted area AAPO10 before the accelerator pedal is depressed to the predicted area AAPO20 after the depression. This change is more advanced than the change in the actual throttle opening area ATVO.

  Here, a change in the predicted intake air amount Qaa during acceleration of the internal combustion engine 1 will be considered.

  In order to simplify the calculation, the correction pressure ratio PRA = Pma / Pa, and the ratio between the correction pressure ratio PRA and the correction pressure ratio PR is PRR = PRA / PR = Pma / Pm. In this way, equation (6) can be replaced with the following equation (23).

  The area ratio AAPO / ATVO on the right side of Equation (23) increases from the predicted area AAPO10 before the depression until it reaches the estimated area AAPO20 after the depression, and remains constant until the actual intake throttle opening area ATVO rises, and then decreases. Converge to 1.

  The pressure ratio Pma / Pm increases from the first pressure Pm1 before the accelerator pedal is depressed to the second pressure Pm2 until the predicted pressure Pma in the downstream portion of the intake passage reaches the second pressure Pm2, and the actual pressure in the downstream portion of the intake passage It keeps a constant value until Pm rises, then decreases and converges to 1.

The predicted intake air amount Qaa is proportional to the area ratio AAPO / ATVO and the pressure ratio ratio Pma / Pm that change as described above. As a result, the intake predicted air amount Qaa may form a peak abruptly rises at time t1 when, consistent with the air flow meter flow rate Qa then ramps.

  Thus, the predicted intake air amount Qaa is a value obtained by advancing the air flow meter flow rate Qa until the phase of change of the air flow meter flow rate Qa matches the phase of change of the accelerator pedal depression amount APO, that is, the air flow meter flow rate Qa Is a value obtained by advancing the dead time T2 of the intake throttle 51a.

  As described above, according to the configuration of the present invention, since the fuel injection amount is determined based on the accelerator pedal depression amount APO at least during transient operation, the air flow that changes in phase with the throttle opening TVO as in the past. Compared to determining the fuel injection amount based on the detected flow rate of the meter, it is possible to grasp the change in the cylinder intake air amount at an early timing and set the fuel injection amount that matches the change in the cylinder intake air amount early. it can. As a result, the control accuracy of the air-fuel ratio in transient operation such as acceleration or deceleration of the internal combustion engine is improved.

In FIG. 8 , the case where the driver depresses the accelerator pedal has been described. However, the same applies to the case where the torque request signal is generated by ASCD or the like. Will improve.

In the above description, the correction pressure ratio PRR = Pma / Pm is set to simplify the calculation and facilitate understanding, but the actual configuration is PRR = PRA / PR. Correcting the predicted pressure ratio PRA, the pressure ratio Pma / Pa as shown in FIG. 5 (A) is in the vicinity close to 1.0 is set to a small value. Similarly corrected actual pressure ratio PR, pressure ratio Pm / Pa as shown in FIG. 5 (B) is in the vicinity close to 1.0 is set to a small value. The reason for setting in this way is as follows.

That is, the region where the pressure ratios Pma / Pa and Pm / Pa are close to 1.0 corresponds to the high load region of the internal combustion engine 1. The air flow rate in the high load region is smaller than the predicted intake air amount Qaa calculated by Equation (23). Thus, the predicted intake air amount Qaa in the high load region is brought close to the actual air flow rate using the corrected pressure ratios PRA and PR that decrease as the pressure ratios Pma / Pa and Pm / Pa approach 1.0. The characteristics of the corrected pressure ratio PRA shown in FIG. 5 (A) are the same as the characteristics of the corrected pressure ratio PR shown in FIG. 5 (B), and these characteristics depend on the flow rate characteristics of the intake throttle 51a.

By the way, the dead time T1 calculated by the dead time calculating unit 77 using the equation (7) decreases as the engine speed Ne decreases. When the engine speed Ne drops below a certain value, the dead time T1 becomes a negative value. However, the dead time T1 is a delay processing time that the controller 7 adds in order to synchronize the cylinder intake predicted air amount Qca with the injection timing, and cannot take a logical negative value. Therefore, when the dead time T1 becomes a negative value, the controller 7 delays the operation timing of the intake throttle 51a, that is, the change in ATVO in FIG . Specifically, this processing is performed when the condition of the following equation (24) derived from the equation (7) is satisfied.

Expression (24) is further transformed into the following expression (25).

  In this way, the controller 7 delays the operation timing of the intake throttle 51a until the left and right terms of Equation (25) become equal. This increases the dead time T2 and prevents the dead time T1 from becoming a negative value.

(Second Embodiment)
FIG. 9 is a block diagram of the controller of the second embodiment of the fuel injection control device according to the present invention.

  In the following embodiments, the same reference numerals are given to the portions that perform the same functions as those of the above-described embodiments, and overlapping descriptions are omitted as appropriate.

  In this embodiment, instead of the cylinder intake air amount calculation unit 701 and the cylinder intake air amount equivalent injection amount calculation unit 702 of the first embodiment, the intake passage downstream portion filling model 751 and the cylinder air amount per combustion cycle are used. A calculation unit 761, a cylinder intake air amount calculation unit 7011, and a cylinder intake air amount equivalent injection amount calculation unit 7021 are provided.

  The intake passage downstream portion filling model 751 and the cylinder air amount calculation unit 761 per combustion cycle are configured using the known technique disclosed in Japanese Patent Laid-Open No. 2001-50091 described above as it is.

  In the first embodiment, the cylinder intake air amount equivalent injection amount Tp [msec] is calculated from the cylinder intake predicted air amount Qca per combustion cycle, but in this embodiment, from the air flow meter detected flow rate Qa as in the prior art. calculate.

  That is, the intake passage downstream portion filling model 751 and the cylinder air amount calculation unit 761 per combustion cycle calculate the cylinder intake air amount Qck [g / cycle] per combustion cycle from the air flow meter detected flow rate Qa.

 The cylinder intake air amount calculation unit 7011 outputs the cylinder intake air amount Qck per combustion cycle as it is as the cylinder intake actual air amount Qc [g / cycle].

  The cylinder intake air amount equivalent injection amount calculation unit 7021 calculates the cylinder intake air amount equivalent injection amount Tp [msec] by the following equation (26) based on the cylinder intake air amount Qck [g / cycle] per combustion cycle.

  Equation (26) is obtained by replacing the predicted cylinder intake air amount Qca1 per combustion cycle of Equation (8) with the cylinder intake air amount Qck per combustion cycle.

  This embodiment is also exactly the same as the first embodiment in that the fuel injection amount Ti [msec] is calculated based on the cylinder intake predicted air amount Qca1 at least during transient operation, and the air-fuel ratio control accuracy during transient operation is also the same. As for the improvement, the same preferable effect as in the first embodiment can be obtained.

  In summary, according to the present invention, the controller 7 calculates the target intake air amount of the cylinder 11 based on the accelerator pedal depression amount APO or the required drive torque Trq, and provides an intake air amount adjustment mechanism so as to realize the target intake air amount. On the other hand, a predicted value Qca of the intake air amount realized by the control mechanism for the intake air amount after control is calculated based on the accelerator pedal depression amount APO or the required drive torque Trq, and the fuel is supplied to the target fuel injection amount based on the predicted value Qca. The fuel injection amount of the injector 52 is controlled. Therefore, even if fuel injection is performed within the time lag from the change in the accelerator pedal depression amount APO (required drive torque Trq) to the actual intake air amount in the cylinder 11, the fuel based on the predicted value Qca An injection amount of fuel is injected. For this reason, as compared with the conventional fuel injection control that calculates the fuel injection amount based on the actual intake air amount, the responsiveness of the change in the fuel injection amount is increased, and the control accuracy of the air-fuel ratio during acceleration or deceleration is improved.

  The present invention is not limited to the embodiment described above, and various modifications and changes can be made within the scope of the technical idea, and it is obvious that these are equivalent to the present invention.

It is a schematic structure figure showing a 1st embodiment of the present invention. It is a figure explaining the basic concept of this invention. It is a block block diagram of a controller. It is a figure explaining the detail of the throttle opening estimated area calculation unit 721. It is a characteristic map stored in the ROM of the controller. It is a characteristic map stored in the ROM of the controller. FIG. 5 is a diagram illustrating a specific method for obtaining Expression (2). The operation and effect of the present invention will be described. The block block diagram of the controller of 2nd Embodiment of the fuel-injection control apparatus by this invention. It is.

Explanation of symbols

1 Engine 41 VEL mechanism (intake air amount adjustment mechanism / variable valve mechanism)
42 VTC mechanism (intake air amount adjustment mechanism / variable valve mechanism)
51 Intake throttle device (intake air amount adjustment mechanism)
52 Fuel injector 61 Air flow meter (air flow detection means)
71 Airflow meter output delay advance compensation unit 721 Throttle opening predicted area calculation unit (predicted area calculation means)
722 Throttle opening actual area calculation unit (actual opening area calculation means)
723 Area ratio calculation unit (Area ratio calculation means)
731 corrected predicted pressure ratio calculation unit (predicted pressure ratio calculation means)
732 Corrected actual pressure ratio calculation unit (actual pressure ratio calculation means)
733 Pressure ratio ratio calculation unit (pressure ratio ratio calculation means)
74 Inhalation predicted air amount calculation unit (expected intake air amount calculation means)
75 Inlet passage downstream portion filling model 754 Predicted pressure calculation unit (Predicted pressure calculation means)
76 Cylinder intake prediction air amount calculation unit per combustion cycle (Cylinder intake prediction air amount calculation means per combustion cycle)
77 Waste time calculation unit 78 Required injection amount calculation unit (required injection amount calculation means)
79 Fuel injection amount calculation unit 701 Cylinder intake air amount calculation unit 702 Cylinder intake air amount equivalent injection amount calculation unit

Claims (7)

Provided in the intake passage, but by changing the intake passage opening area is driven by an actuator which operates in response to a control signal for adjusting the amount of air taken into the cylinder, an intake throttle with response delay to the control signal A fuel injection control device for controlling a fuel injection amount of an engine comprising:
An air flow rate detection means for detecting an air flow rate, provided in an intake passage upstream of the intake throttle;
Predicted area calculation means for predicting the opening area of the intake throttle according to a control signal;
An actual opening area calculating means for calculating an actual opening area of the intake throttle;
Area ratio calculating means for calculating a ratio of the expected opening area to the actual opening area;
A pressure ratio calculating means for calculating a ratio of an estimated pressure in the downstream portion of the intake passage downstream from the intake throttle to an actual pressure;
Density ratio calculating means for calculating a density ratio of an expected density to an actual density of air in the intake throttle;
The air flow rate detected by said air flow rate detecting means, the area ratio is corrected based on the density ratio in the ratio and the intake throttle of the pressure, predicts values calculated amount of intake air the intake throttle is realized inhalation Expected air volume calculation means,
Required injection amount calculation means for calculating a required fuel injection amount in accordance with the expected intake air amount;
A fuel injector that injects fuel of the required fuel injection amount at a predetermined timing;
A fuel injection control device comprising: The predicted area calculation means is a larger one of a predicted throttle opening area AAPO1 calculated based on an accelerator pedal depression amount signal that is a control signal and a predicted throttle opening area AAPO2 calculated based on a torque request signal that is a control signal. Based on the above, the predicted throttle opening area is calculated,
The fuel injection control device according to claim 1 . The predicted area calculation means is the torque required to maintain the idle rotation speed, whichever is larger of the predicted throttle opening area AAPO1 based on the accelerator pedal depression amount signal and the predicted throttle opening area AAPO2 based on the torque request signal. The opening area of the minute is added to calculate the predicted throttle opening area,
The fuel injection control device according to claim 1 or claim 2, characterized in that. The density ratio calculating means obtains the density ratio ρtha / ρth based on the following formula:
The fuel injection control device according to any one of claims 1 to 3 , wherein the fuel injection control device is a fuel injection control device. A predicted pressure ratio calculating means for calculating a predicted pressure ratio of the predicted pressure in the downstream portion of the intake passage to the atmospheric pressure;
An actual pressure ratio calculating means for calculating an actual pressure ratio of the actual pressure downstream of the intake passage to the atmospheric pressure;
With
The pressure ratio calculation means is a pressure ratio ratio calculation means for calculating a ratio of the predicted pressure ratio to the actual pressure ratio .
The fuel injection control device according to any one of claims 1 to 4 , wherein the fuel injection control device is provided. The predetermined timing is a timing delayed by a dead time T1 with respect to the control signal.
The fuel injection control device according to any one of claims 1 to 5 , wherein the fuel injection control device is a fuel injection control device. The estimated intake air amount calculated by the estimated intake air amount calculation unit further includes calculation means for calculating the expected intake air amount of the cylinder per combustion cycle in consideration of a time delay when flowing through the downstream portion of the intake passage.
The fuel injection control device according to any one of claims 1 to 6 , wherein the fuel injection control device is a fuel injection control device.