JP4185078B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine control device including an intake air amount control means for controlling an intake air amount to an internal combustion engine, and the in-cylinder pressure at the time when the intake valve of the cylinder is fully closed and the intake air sucked into the cylinder The present invention relates to a control device for an internal combustion engine that estimates an air amount before starting fuel injection.

As a method of calculating the amount of intake air into the cylinder of an internal combustion engine, it is conventionally known to install a pressure sensor, an air flow sensor, etc. and calculate the amount of intake air from the detected value.
In this case, there is a cost due to the provision of sensors. In particular, in a multiple throttle system in which a throttle is installed for each cylinder, sensors are also installed for each cylinder, resulting in higher costs.
Therefore, for example, Japanese Patent Application Laid-Open No. 5-222998 (hereinafter referred to as Patent Document 1) estimates the amount of intake air into the cylinder without using a pressure sensor or an airflow sensor, and implements fuel amount control. An intake state detecting device for an internal combustion engine shown in FIG.
In this publication, the throttle valve, the intake valve, and the exhaust valve are regarded as orifices, and the orifice portion is determined based on the fluid dynamics equation based on the flow area of the orifice and the pressure upstream and downstream of the orifice. Estimate the amount of air passing through (orifice passage flow rate). A new throttle downstream pressure is estimated from the estimated throttle portion passage flow rate and intake valve passage flow rate, and a new in-cylinder pressure is estimated from the intake valve passage flow rate and the exhaust valve passage flow rate, and is used for each next passage flow rate estimation. By performing this sequentially according to the crank angle, the throttle downstream pressure, the in-cylinder pressure, and the intake air amount by integrating the intake inflow / outflow amount into the cylinder are estimated. Thus, it is described that the amount of intake air into the cylinder can be estimated and the fuel amount control can be performed without using a pressure sensor, an air flow sensor, or the like.

JP-A-5-222998

In general, the timing of starting fuel injection of the cylinder of the internal combustion engine is about two strokes before the time when the intake valve of the cylinder is fully closed in consideration of the suction time to the cylinder and the time required for atomization of the fuel. This indicates that it is necessary to estimate the amount of intake air into the cylinder about two strokes ahead of the timing at which fuel injection of the cylinder starts.
However, in the prior art of Patent Document 1 described above, the throttle downstream pressure, the cylinder pressure, and the intake air inflow / outflow amount into the cylinder are estimated in real time according to the crank angle, so the intake air amount used for fuel injection control is: For example, the intake air amount of another cylinder that has completed the intake stroke must be used two strokes before the cylinder completes the intake stroke.

The control will be described with reference to FIG.
FIG. 1 shows a stroke table (horizontal axis: time, vertical axis: cylinder number) of each cylinder in a 4-cylinder engine. Symbols and the like in FIG. 1 are as shown in the legend on the right side of FIG.
The control will be described by taking the fuel injection timing α of the fourth cylinder as an example.
Since the fuel injected at the fuel injection timing α of the fourth cylinder is sucked into the cylinder during the intake stroke β of the fourth cylinder, fuel control is performed based on the intake air amount during the intake stroke β of the fourth cylinder. Is desirable. However, as can be seen from FIG. 1, since the fuel injection timing α of the fourth cylinder comes before the intake stroke β of the fourth cylinder, the fuel injection timing α of the fourth cylinder is based on the intake stroke β of the fourth cylinder. Fuel control is not possible. Therefore, in the prior art, the fuel control is performed at the fuel injection timing α of the fourth cylinder based on the intake air amount estimated by the intake stroke γ of the first cylinder.

In this case, especially if the throttle flow path area changes abruptly during transient operation, as shown in FIG. 2, the difference between the actual intake air amount and the intake air amount used in the fuel amount calculation increases. Exhaust gas, fuel consumption, drivability, etc. will be adversely affected.
In addition, in the above prior art, when estimating the downstream pressure of the throttle, the in-cylinder pressure, and the intake inflow / outflow amount to the in-cylinder, the passage flow rate is estimated at three locations of the throttle valve, the intake valve, and the exhaust valve. The calculation load to be implemented is large. If the internal combustion engine speed increases, the allowable calculation time for estimating the flow rate through each part will decrease, so if the calculation load is large, the estimation will not be in time, and it is necessary to install a more sophisticated control unit to avoid it. Occurs. This causes a problem that the cost is increased.

  In order to solve such problems, the inventors have not only estimated the throttle downstream pressure, in-cylinder pressure, and intake air amount in real time according to the crank angle as described in Patent Document 1, but also the cylinder concerned. By predicting and estimating the throttle downstream pressure, in-cylinder pressure, and intake air amount when the intake valve of the cylinder is fully closed prior to the crank angle by the time when the fuel injection is started, the intake into the estimated cylinder is estimated. A method of performing highly accurate fuel injection control using the air amount (hereinafter referred to as intake air amount estimating means 1) is separately proposed.

However, in the intake air amount estimation means 1, when predicting and estimating the throttle downstream pressure, the cylinder pressure, and the intake air amount prior to the crank angle based on the hydrodynamic equation, the intake valve is estimated from the timing when the prediction estimation is started. The actual change in the throttle flow path area is not taken into consideration until the point at which the valve fully closes.
Therefore, in the transient state where the actual throttle flow path area changes greatly from the time when the prediction estimation is started until the time when the intake valve is fully closed, even the intake air amount estimation means 1 does not perform the actual intake. There is a possibility that a deviation between the amount of air and the amount of intake air used in calculating the amount of fuel occurs (see FIG. 2), which may adversely affect exhaust gas, fuel consumption, drivability, and the like.

  The present invention solves the above-mentioned problems, and in an internal combustion engine control device equipped with a throttle for controlling the flow passage area, the throttle downstream pressure, the in-cylinder pressure, and the intake air amount precede the crank angle. Therefore, it is possible to estimate the intake air amount with higher accuracy by eliminating the need to consider the change in the throttle flow path area from the time when the prediction estimation is started to the time when the intake valve is fully closed. An object is to provide a control device for an internal combustion engine.

A control device for an internal combustion engine according to the present invention has a flow path in each of the independent intake pipes, one end of which is connected to the intake valve of each cylinder of the internal combustion engine having a plurality of cylinders, and the other end is connected to a collecting portion of each cylinder. In a control device for an internal combustion engine of a port injection type in which an intake air amount control means for controlling the amount of intake air to the cylinder by controlling the area is provided to perform exhaust stroke injection, the flow path of the intake air amount control means A passage area detecting means for detecting the area; a downstream pressure detecting means for detecting a pressure downstream of the intake air amount control means; and an internal combustion engine speed detecting means, wherein the upstream pressure and the downstream pressure of the intake air amount control means are provided. And the intake valve of the cylinder after the fuel to be injected this time is sucked into the cylinder using the flow area of the intake air amount control means, the internal combustion engine speed, the in-cylinder volume, and the intake air temperature. In-cylinder pressure when the The intake air amount, a time for the internal combustion engine control device that estimates by the time to start the fuel injection, in between time the intake valve as possible and close timing of starting the estimated intake air amount control The flow path area of the means is controlled to be fixed.

  According to the control apparatus for an internal combustion engine of the present invention, the control is performed so as to fix the throttle flow path area from the time when the prediction estimation is started to the time when the intake valve is fully closed, and then the fuel injection of the cylinder is started. Since the intake air amount at the time when the intake valve of the cylinder is completely closed is estimated ahead of the crank angle by the time, the change in the throttle flow area from the time when the prediction estimation is started until the time when the intake valve is fully closed is estimated. Without being affected, highly accurate fuel injection control can be performed particularly during transient operation of the internal combustion engine.

  Also, instead of estimating the flow rate of the throttle part, intake valve, and exhaust valve in total, only the throttle part flow rate is calculated to estimate the throttle downstream pressure, cylinder pressure, and intake air amount. The calculation load is reduced, and the intake air amount can be estimated with a low-cost computing device.

  The present invention is a control device for an internal combustion engine having a throttle for controlling a flow passage area, and the intake air amount estimation means 1 predicts and estimates the throttle downstream pressure, the cylinder pressure, and the intake air amount ahead of the crank angle. In this case, by controlling to fix the throttle flow path area from the time when the prediction estimation is started to the time when the intake valve is fully closed, the time between the time when the prediction estimation is started and the time when the intake valve is fully closed is controlled. This eliminates the need to consider the change in the throttle flow area. Hereinafter, it will be described together with the intake air amount estimation means 1 described above.

The intake air amount estimation means 1 performs control for estimating the throttle downstream pressure, in-cylinder pressure, and intake air amount in real time at predetermined intervals according to the crank angle based on a fluid dynamic equation as in the prior art (hereinafter, real time estimation). Control that predicts and estimates the throttle downstream pressure, in-cylinder pressure, and intake air amount when the intake valve is fully closed by the time fuel injection starts before the crank angle. (Hereinafter referred to as predictive estimation control) is also performed.
The throttle downstream pressure at an arbitrary crank angle in the real-time estimation control and the prediction estimation control is estimated by a recurrence formula such as the following formula (1).

That is, the throttle downstream pressure at an arbitrary crank angle CA-ΔCA is a basis for estimating the throttle downstream pressure at CA.
Predictive estimation control immediately estimates the throttle downstream pressure, the in-cylinder pressure, and the intake air amount when the intake valve is fully closed from a predetermined time (hereinafter referred to as a predetermined time A) before the fuel injection start time. For this purpose, a recurrence formula such as Formula 1 based on a fluid dynamic formula from the throttle upstream pressure and downstream pressure, the throttle flow path area, the cylinder volume, the internal combustion engine speed, and the intake air temperature is used as the crank angle. By repeating until reaching the time when the intake valve is fully closed, the estimation of the throttle downstream pressure, the in-cylinder pressure, and the intake air amount when the intake valve is fully closed is completed.
Hereinafter, for convenience, the throttle downstream pressure and the in-cylinder pressure in the predictive estimation control will be referred to as the predicted estimated downstream pressure and the predicted estimated in-cylinder pressure, respectively, and the predicted estimated downstream pressure and the predicted estimated cylinder when the intake valve is fully closed. The internal pressure is referred to as fuel control downstream pressure and fuel control cylinder pressure. The intake air amount estimated from the in-cylinder volume at the time when the fuel control in-cylinder pressure and the intake valve are fully closed and the intake air temperature is referred to as a fuel control intake air amount. Further, the throttle downstream pressure and the in-cylinder pressure in the real-time estimation control are referred to as an estimated downstream pressure and an estimated in-cylinder pressure, respectively.

In the present invention, in the predictive estimation control, in order to eliminate the need to consider the change in the throttle flow path area from the predetermined time A to the time when the intake valve is fully closed, the time from the predetermined time A to the time when the intake valve is fully closed is eliminated. It controls to fix the throttle flow area between.
Since the throttle channel area depends on the throttle opening, the throttle channel area is controlled to be fixed by controlling the throttle opening (hereinafter referred to as throttle opening fixing control). The throttle opening between the predetermined time A and the time when the intake valve is fully closed is fixed by the above control even during a transient time when the throttle opening suddenly increases. During this period, the throttle flow path area changes greatly, and there is no longer a difference between the actual intake air amount and the intake air amount for fuel control.

FIG. 23 shows an image diagram (horizontal axis: time, vertical axis: throttle opening) of the relationship between the target throttle opening and the actual throttle opening in the present invention.
As shown in FIG. 23, the actual throttle opening changes in an attempt to follow the target throttle opening, but the actual throttle opening is controlled by the throttle opening fixing control from the predetermined timing A to the time when the intake valve is fully closed. Is fixed.
Further, FIG. 3 shows an image of the relationship between the actual throttle downstream pressure, the estimated downstream pressure, and the predicted estimated downstream pressure.

FIG. 3 assumes a multiple throttle system, the upper diagram shows the relationship between the crank angle and the actual throttle downstream pressure, the middle diagram shows the relationship between the crank angle and the estimated downstream pressure and the estimated estimated downstream pressure in the N cycle, and the lower diagram. Shows the relationship between the crank angle and the estimated downstream pressure in the N + 1 cycle.
The upper diagram shows the throttle opening fixing control section.
As shown in FIG. 3, the estimated downstream pressure is estimated for each predetermined period by the real-time estimation control, while the fuel control downstream pressure is estimated by the prediction estimation control from the predetermined time A to the time when fuel injection is started.
The throttle downstream pressure at the predetermined time A is required to start the predictive estimation control. This is estimated by the real time estimation control as shown in FIG. 3, or the pressure sensor is installed in the throttle downstream portion of each cylinder. The throttle downstream pressure value acquired from the pressure sensor or the like when the crank angle reaches the predetermined timing A of the cylinder is used.
In the prior art, the passage downstream flow rate, the in-cylinder pressure, the intake air amount, and the like are estimated by estimating the passage flow rates of the throttle valve, the intake valve, and the exhaust valve, whereas the intake air amount estimation means 1 Then, the calculation load is reduced by estimating only the throttle-passage flow rate and estimating the throttle downstream pressure, in-cylinder pressure, intake air amount, and the like.

Specifically, in a multiple throttle system, an intake valve closed model that models the intake passage from the throttle upstream to the intake valve, and an intake valve open that models the intake passage from the upstream of the throttle to the cylinder in consideration of volume changes. Two intake air quantity estimation models are used.
The intake valve closed model is used to estimate the throttle downstream pressure, the cylinder pressure, the intake air amount, etc. when the intake valve is closed, and the intake valve open model when the intake valve is open.
In addition, by acquiring the downstream pressure for fuel control, the in-cylinder pressure for fuel control, the atmospheric pressure and intake air temperature used when estimating the intake air amount for fuel control, etc. from the sensor, and using those values, higher accuracy is achieved. The fuel control downstream pressure, the fuel control cylinder pressure, and the fuel control intake air amount can be estimated.
Hereinafter, it demonstrates in detail based on embodiment.

Embodiment 1 FIG.
Embodiment 1 of the present invention shows an example when applied to a multiple throttle system in which a throttle is installed for each cylinder.
In the first embodiment, control is performed so as to fix the throttle flow path area from the predetermined time A to the time when the intake valve is completely closed, and then the estimated downstream pressure is estimated at the predetermined time A by real-time estimation control, The intake air amount for fuel control is estimated by predictive estimation control based on the estimated downstream pressure at time A.
Since the throttle flow path area depends on the throttle opening, control is performed to fix the throttle flow path area by performing throttle opening fixing control.
In the first embodiment, in the estimation of the estimated downstream pressure and the intake air amount for fuel control, the intake valve closed model that models the intake passage from the upstream of the throttle to the intake valve, and the in-cylinder that takes into account the volume change from the upstream of the throttle The intake valve open model that models the intake passage up to is used.
The intake valve closed model and intake valve open model are the throttle upstream flow rate, downstream pressure, cylinder pressure, throttle channel area, cylinder volume, internal combustion engine speed, and intake air temperature based on the fluid dynamics formula. And a calculation for estimating new throttle downstream pressure and in-cylinder pressure from the estimated throttle passage flow rate and in-cylinder volume change is performed.
That is, the calculation load is reduced by calculating the passage flow rate of only the throttle part, instead of calculating the passage flow rate of the throttle part, the intake valve part, and the exhaust valve part as in the prior art.
Hereinafter, the first embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 4 shows an example of an overall configuration diagram of Embodiment 1 of the present invention. FIG. 4 shows a multiple throttle system, where only the first cylinder is representatively shown, but the second to fourth cylinders of the engine are similarly configured.
The engine is provided with a throttle valve 1, a fuel injection valve 2, an intake valve 3, an exhaust valve 4, and a crank angle sensor 5 in the engine body for limiting the intake amount for each cylinder.
The throttle valve 1 is driven by a throttle actuator 6 installed for each throttle valve 1, and the throttle valve 1 is electronically controlled by sending a throttle opening control signal to the throttle actuator 6 by the throttle control unit 7.
The throttle actuator 6 is provided with a sensor (hereinafter referred to as TPS) that detects the throttle opening, and transmits a throttle opening detection signal to the throttle control unit 7. In the first embodiment, it is assumed that the throttle control unit 7 is installed for each throttle actuator 6 and each throttle valve 1 is individually controlled.

A throttle opening detection signal is input from the throttle actuator 6 to the throttle control unit 7, and an engine speed signal, a crank angle signal, and a target intake air amount signal are input from the engine control unit 8.
A throttle opening control signal is output from the throttle control unit 7 to the throttle actuator 6, and a fuel control intake air amount signal is output to the engine control unit 8.
In the throttle control unit 7, the throttle opening detection signal, the intake air amount for fuel control, the determination of the target throttle opening degree from the target intake air amount signal, the engine speed signal, the crank angle signal, etc., the intake for fuel control An estimation process such as the amount of air is performed.
In FIG. 4, the throttle downstream pressure is the pressure in the throttle downstream portion 9, and the in-cylinder pressure is the pressure in the cylinder 10.

The engine control unit 8 receives an accelerator depression amount detection signal from the accelerator position sensor and a crank angle detection signal from the crank angle sensor 5.
Then, a fuel injection control signal is output from the engine control unit 8 to the fuel injection valve 2 of each cylinder. The fuel injection valve 2 is injected independently for each cylinder.
The engine control unit 8 detects the engine speed and crank angle from the crank angle detection signal, determines the target intake air amount from the accelerator depression amount and the intake air amount for fuel control, the intake air amount for fuel control and the target air-fuel ratio, etc. From this, the fuel injection amount is determined.

By the way, in the prior art, the flow rate of the throttle valve, the intake valve, and the exhaust valve is estimated to estimate the downstream pressure of the throttle, the in-cylinder pressure, the intake air amount, and the like. In order to reduce the calculation load by estimating only the throttle flow rate and estimating the throttle downstream pressure, cylinder pressure, intake air amount, etc. Two intake air models, an intake valve closed model (Fig. 5) that models the intake passage to the valve, and an intake valve open model (Fig. 6) that models the intake passage from the upstream side of the throttle to the cylinder in consideration of volume changes The quantity estimation model is used after judging the state of the intake valve.
Therefore, the intake valve closing model (FIG. 5) and the intake valve opening model (FIG. 6) used in the first embodiment will be described with reference to the drawings.

The intake valve closed model shown in FIG. 5 is a model for estimating the throttle flow rate when the intake valve is closed and estimating the throttle downstream pressure, intake air amount, etc. It is formed from the throttle downstream part from the throttle part to the intake valve, and the inside of the cylinder is not considered.
Throttle upstream section is composed of the throttle upstream pressure P ₁ and the intake air temperature T _1.
The throttle opening is composed of a throttle flow path area _AT, and the intake air passing through the throttle opening receives pressure from the throttle upstream pressure P ₁ and the throttle downstream pressure P ₂ .
Throttle downstream portion is configured as a throttle downstream pressure P ₂ and the throttle downstream volume V ₂ from the intake air temperature T _1.
Incidentally, the throttle upstream pressure P ₁ is handled as a substantially atmospheric pressure, intake air temperature T ₁ of the treated as constant across.
The estimation of the flow rate through the throttle in this intake valve closing model is estimated from the following equation based on the fluid dynamic equation.

Equations (2) and (3) are divided into cases based on the pressure ratio between the upstream and downstream of the throttle, which is an index as to whether or not the speed of the intake air passing through the throttle becomes the speed of sound. Equation (3) when the speed of the intake air passing through the throttle is less than the sonic speed is the throttle passage flow rate per unit time when the sonic speed is satisfied.
From the throttle flow rate per unit time, the predetermined period, the throttle downstream pressure P ₂ , the throttle downstream volume V _2, and the intake air temperature T ₁ , the throttle downstream pressure after the predetermined period is calculated using the gas state equation. presume. The estimated throttle downstream pressure is further used as a basis for estimating the throttle downstream pressure after a predetermined period.
The above processing is performed at predetermined intervals, and when the intake valve starts to open, the intake valve opening model is switched.

The intake valve opening model shown in FIG. 6 is a model for estimating the throttle passage flow rate when the intake valve is open and estimating the throttle downstream pressure, in-cylinder pressure, intake air amount, and the like. It is formed from the throttle opening, the throttle downstream from the throttle to the intake valve, and the cylinder whose volume changes according to the crank angle.
The throttle upstream portion, the throttle opening portion, and the throttle downstream portion have the same configuration as that of the throttle intake valve closed model, and the intake air temperature is also constant throughout the entire area.
The in-cylinder is composed of in-cylinder pressure P ₃ , in-cylinder volume V _3, and intake air temperature T ₁ , and the in-cylinder volume V ₃ changes according to the crank angle. It is assumed that the in-cylinder pressure P ₃ is in equilibrium with the throttle downstream pressure (P ₂₃ (P ₂ = P ₃ )) except when the intake valve starts to open.

When estimating the throttle passage flow rate at the time when the intake valve begins to open, first, it is necessary to estimate the pressure when the throttle downstream pressure and the in-cylinder pressure at the time when the intake valve starts to open are balanced. The reason for this is that the exhaust stroke is just before the intake valve opens, so the cylinder is at approximately atmospheric pressure. When the intake valve is opened in this state, the cylinder downstream at approximately atmospheric pressure communicates with the throttle downstream that is at negative pressure. This is because the downstream pressure and the in-cylinder pressure are in an equilibrium state.
The throttle downstream pressure and the in-cylinder pressure after pressure equilibrium are estimated from the following equations based on the gas equation of state.

Since the in-cylinder pressure when the intake valve starts to open is substantially atmospheric pressure, the value of P 3 _—IVO is assumed to be equal to the throttle upstream pressure P ₁ .
In addition, when estimating the flow rate through the throttle with the intake valve open model, the difference between the intake valve close model and the intake valve closed model is that the throttle downstream pressure and in-cylinder pressure change due to changes in the in-cylinder volume. It is necessary.
Therefore, when estimating the flow rate through the throttle, it is assumed that there is no flow rate from the throttle during a predetermined period, and the throttle downstream pressure and in-cylinder pressure when the in-cylinder volume changes are estimated (the following formula (5)) and the throttle flow rate is estimated based on the estimated throttle downstream pressure and in-cylinder pressure (the following formulas (6) and (7)).

The above formulas (6) and (7) are the same formulas as the above formulas (2) and (3). Incidentally, at the time the intake valve starts to open on estimating the P _{23_IVO} by formula (4), it is estimated per unit time passing through the throttle flow rate as the P _{23_Old} in equation (5). The throttle flow rate per unit time, the predetermined period, the current throttle downstream pressure and cylinder pressure P ′ _{23_old} (assuming that there is no flow rate from the throttle), the throttle downstream volume V _2, and the current cylinder content From the sum of the products V 3 — _new and the intake air temperature T ₁ , the current throttle downstream pressure and in-cylinder pressure are estimated using the gas equation of state. The estimated throttle downstream pressure and in-cylinder pressure are further used as a basis for estimating the throttle downstream pressure and the in-cylinder pressure after a predetermined period.
When the above processing is performed at predetermined intervals and the intake valve reaches the point where it closes, the amount of intake air into the cylinder is calculated from the cylinder pressure, cylinder volume, and intake air temperature using the gas equation of state. After estimation, switch to the intake valve closed model.

Next, an intake air amount estimation flow 1 performed by the throttle control unit 7 will be described. 7 to 14 show flowcharts of the intake air estimation flow 1. FIG.
In the intake air amount estimation flow 1, as described above, the intake valve closing model and the intake valve opening model of FIGS. 5 and 6 are used.
In addition, the throttle control unit 7 is connected to the throttle upstream pressure P ₁ (= constant), the intake air temperature T ₁ (= constant) value, and the valve timing map of the intake valve using the crank angle as parameters (FIG. 15: for determining whether the intake valve is opened or closed). Use).

The intake air amount estimation flow 1 is performed when a trigger sent from the engine control unit 8 to the throttle control unit 7 is received every predetermined cycle ΔCA based on the crank angle, and the predicted estimated downstream pressure and the predicted estimation are performed by the predicted estimation control. Estimating in-cylinder pressure and intake air amount for fuel control, estimation of estimated downstream pressure and estimated in-cylinder pressure by real-time estimation control, and throttle opening fixing control from a predetermined time A until the intake valve is fully closed To implement.
The intake air amount estimation flow 1 includes control logic (FIGS. 12 to 14) for performing predictive estimation control and control logic (steps s1, s2, and s4 to s20) for performing real-time estimation control (FIG. 7, FIG. 8)) and control logic (steps s23 and s26 (FIG. 9)) for starting and ending the throttle opening fixing control.

Once started, the throttle opening fixing control is controlled to fix the throttle opening until the throttle opening fixing control is finished in step s26.
In the prediction estimation control and the real-time estimation control, the estimated estimated downstream pressure, the intake air amount for fuel control, and the like are calculated using the above equations (2) to (7) and the gas state equation.
In the intake air amount estimation flow 1, based on the throttle passage flow rate per unit time and the gas state equation shown in the above equations (2), (3), (6), and (7), from before ΔCA to the present time The throttle downstream pressure that changes depending on the throttle flow rate is calculated from the following equation.

Further, as explained in the above equation (4), when estimating the throttle passage flow rate when the intake valve starts to open, first, the pressure when the throttle downstream pressure and the in-cylinder pressure when the intake valve starts to open is balanced. It is necessary to estimate.
In the intake air amount estimation flow 1, the pressure at equilibrium is calculated from the following formula based on the formula (4).

Furthermore, as shown in equation (5), when calculating the throttle downstream pressure and in-cylinder pressure in the intake valve opening model, the in-cylinder volume changes assuming that there is no flow rate from the throttle between ΔCA. After that, it is necessary to calculate the throttle downstream pressure and the cylinder pressure.
In the intake air amount calculation flow 1, the downstream pressure of the throttle and the in-cylinder pressure after the in-cylinder volume is changed are calculated by the following equation (10).

The above formulas (8) to (10) are converted into an intake valve closed model (formula (8) only) and an intake valve open model (formula (8),
(10) Then, when the intake valve starts to open, formula (9)) is used properly to estimate or predict the throttle downstream pressure and the in-cylinder pressure when the intake valve is open.
The estimated amount of intake air sucked into the cylinder when the intake valve is fully closed using the gas equation of state from the cylinder pressure, cylinder volume and intake air temperature estimated by predictive estimation I can do it.

Hereinafter, each step will be described. In the intake air amount calculation flow 1, it is assumed that the current crank angle in equations (8) to (10) is CA1, the calculation cycle is ΔCA1, and values are substituted into CA1 and ΔCA1.
First, in FIG. 7, in step s1, it is confirmed whether the engine is operating. If it is operating, the process proceeds to step s2. If it is stopped, the process proceeds to step s3.
When the engine is stopped, the intake flow rate is accumulated in the throttle downstream volume via the throttle, so that the throttle downstream pressure is recovered to the atmospheric pressure. Therefore, in step s3, since the throttle upstream pressure is substantially atmospheric pressure, “P _{2_old} = P ₁ ” is executed, and then the intake air amount calculation flow 1 is terminated and the process waits until the next trigger is received.
When the process proceeds from the s1 step to the s2 step, the engine control unit 8 reads the crank angle, the engine speed, and the throttle opening from the throttle actuator 6, and the process proceeds to the s4 step.

In step s4, it is determined whether or not the intake valve is closed at the present time (crank angle CA) by referring to the valve timing map (FIG. 15) of the intake valve (hereinafter, the time when the intake valve starts to open is IVO, The time when the intake valve is fully closed is called IVC).
If the intake valve is closed, the process proceeds to step s5. If the intake valve is open, the process proceeds to step s12.
When the process proceeds to step s5, it is determined whether the intake valve is closed in the previous cycle (= CA−ΔCA) in the same manner as in step s4.
If closed, go to step s6, and if open, go to step s8.
When the process proceeds to step s6, the estimated downstream pressure is calculated by real-time estimation control using the intake valve closing model up to step s7.
First, in step s6, ΔCA1 = ΔCA and CA1 = CA are performed, and the process proceeds to step s7.
In step s7, intake valve closing model calculation is performed.

The intake valve closing model calculation is composed of s27 to s32 steps as shown in FIG.
First, in step s27, time S is calculated from the engine speed and ΔCA1. Thereafter, the volume term V = V ₂ is implemented in step s28, and the process proceeds to step s29.
In step s29, the speed term H is calculated from (P _{2_old} / P ₁ ) and the speed term map. In step s30, the area term D is calculated from the throttle opening and the area term map, and the process proceeds to step s31.
In step s31, the estimated downstream pressure at CA1 is calculated from equation (8). Thereafter, in step s32, P _{2_old} = P _{2_new} is executed, and the process proceeds to step s21.

If the intake valve is open in the previous cycle (= CA-ΔCA) and the intake valve is closed at the present time (= CA), that is, if the s5 step is advanced from the s5 step, the intake valve open model is used until the s9 step. Then, the estimated downstream pressure and estimated in-cylinder pressure at IVC are calculated by real-time estimation control.
Then, the estimated downstream pressure after IVC is calculated by real-time estimation control from step s10 to step s7 through step s11.
In step s8, ΔCA1 = IVC− (CA−ΔCA) and CA1 = IVC are performed to calculate the estimated downstream pressure and estimated in-cylinder pressure in IVC, and the process proceeds to step s9.

In step s9, intake valve opening model calculation is performed. The intake valve closing model calculation is composed of steps s33 to s41 as shown in FIG.
First, in step s33, a time term S is calculated from the engine speed and ΔCA1.
Thereafter, in step s34, the in-cylinder volume V _{3_new} at CA1 is calculated from CA1 and the in-cylinder volume map, and the volume term V is calculated.
In step s35, the estimated downstream pressure and the estimated in-cylinder pressure at CA1 (assuming that there is no flow rate from the throttle) are calculated using the equation (10) in the intake valve opening model.
In step _s36 , P _{2_old} = P _{2_new} is executed. In step _s37 , the speed term H is calculated from (P _{2_old} / P ₁ ) and the speed term map. In step s38, the area term D is calculated from the throttle opening and the area term map. Calculate and go to step s39.
In step s39, the estimated downstream pressure and estimated in-cylinder pressure at CA1 are calculated from equation (8).
Thereafter, in s40 step, implementing the _V 3_old = V 3_new, in s41 step, proceed to s10 steps performed _P 2_old = P 2_new.

In step s10, the predetermined time A is calculated. This is calculated from the engine speed and a predetermined time A map (FIG. 19: a map using the engine speed as a parameter).
As can be seen from FIG. 19, the predetermined time A is shifted by a predetermined period ΔCA toward the direction where the start of the predictive estimation control is advanced in order to secure the estimated processing time as the rotational speed of the internal combustion engine increases. After calculating the predetermined time A, the process proceeds to step s11.
In step s11, ΔCA1 = CA−IVC and CA1 = CA are performed to prepare for the calculation of the estimated downstream pressure after IVC.
Thereafter, in step s7, the intake valve closing model calculation is performed to calculate the estimated downstream pressure in CA1, and the process proceeds to step s21.

When the intake valve is open at the present time (= CA), that is, when the process proceeds from step s4 to step s12, first, in step s12, it is determined whether the intake valve has already been opened in the previous cycle (= CA−ΔCA). judge.
If it is open, the process proceeds to step s13, and if it is closed, the process proceeds to step s15.
When the process proceeds to step s13, ΔCA1 = ΔCA and CA1 = CA are performed. In step s14, the intake valve opening model calculation described in step s9 is performed, and the estimated downstream pressure and estimated in-cylinder pressure in CA1 are calculated. , Go to step s21.
When the intake valve is closed in the previous cycle (= CA−ΔCA) and the intake valve is open at the present time (= CA), that is, when the process proceeds from step s12 to step s15, the estimated downstream pressure at IVO is increased up to step s16. calculate. Then, the estimated downstream pressure after IVO and the estimated in-cylinder pressure are calculated through steps s17 to s20 and up to step s14.

First, in step s15, ΔCA1 = IVO− (CA−ΔCA) and CA1 = IVO are performed in order to calculate the estimated downstream pressure at IVO, and the process proceeds to step s16.
In step s16, the intake valve closing model calculation described in step s7 is performed to calculate the estimated downstream pressure at IVO.
In step s17, the in-cylinder volume V _{3_new} at IVO is calculated from the IVO and in-cylinder volume map.
In step s18, the pressure when the throttle downstream pressure and the cylinder pressure at IVO are balanced is estimated. This is calculated from equation (9).
After that, _{P2_old} = _{P2_new} is performed in step s19, ΔCA1 = ΔCA and CA1 = CA are performed in step s20, and the intake valve opening model calculation is performed in step s14, and the estimated downstream pressure in CA1 And the estimated in-cylinder pressure is calculated.
Thereafter, the process proceeds to step s21.

After step s21, the predictive estimation control and “start and end of throttle opening fixing control” are performed.
First, in step s21, it is determined whether or not predictive estimation control is to be performed by determining whether or not CA is at a predetermined time A.
If CA = predetermined time A, the process proceeds to step s23 to start the throttle opening fixing control and predictive estimation control, and otherwise proceeds to step s22.

When the process proceeds to step s23, throttle opening fixing control is started, and the process proceeds to step s24.
In step s24, calculation of the intake air amount for fuel control by predictive estimation control is performed.
This is composed of steps s42 to s63 as shown in FIGS.
First, preparations for predictive estimation control are made in steps s42 and s43.
In steps s44 to s61, a predicted estimated downstream pressure and predicted estimated in-cylinder pressure at IVC (= downstream pressure for fuel control and in-cylinder pressure for fuel control) are calculated by predictive estimation control.
In step s62, the fuel control intake air amount is calculated from the fuel control cylinder pressure, and in step s63, the intake air amount calculation flow 1 is completed.

In step s42, CA '= CA is performed. CA ′ is a crank angle used when performing predictive estimation control. In step s43, P _{2_A} = P _{2_old} is executed to store the estimated downstream pressure at the current time (= predetermined time A), and then the process proceeds to step s44.
Steps s44 to s61 are controls that loop until CA ′ reaches IVC.
First, in step s45, CA ′ = CA ′ + ΔCA is executed, and CA ′ is advanced by ΔCA.
Steps s46 to s60 are basically the same as steps s4 to s20, except that CA is CA ′, as can be seen by comparing the flowcharts.
Since each corresponds as follows, detailed description is abbreviate | omitted.
“Steps s4 to 7 (the state where the intake valve is closed in the previous cycle (= CA−ΔCA) and the intake valve is closed at the present time (= CA))” and “steps s46 to 49”
“Steps s4, s12 to s14 (the state where the intake valve is open in the previous cycle (= CA−ΔCA) and the intake valve is open at the present time (= CA))” and “steps s46, s52 to s54”
“After s4, s12, s15 to s20, step s14 (the state where the intake valve is closed in the previous cycle (= CA−ΔCA) and the intake valve is opened at the present time (= CA))” and “s46, s52, s55 S54 step through ~ s60 "

  It should be noted that prediction estimation is performed for “steps s4, s5, s8 to s11, and step s7 (the intake valve is open in the previous cycle (= CA−ΔCA) and the intake valve is closed at the present time (= CA))”. Since it is not necessary to calculate a predicted estimated downstream pressure after IVC in the control, the steps corresponding to steps s7, s10, and s11 of “steps s7, s8, and s7 through steps s4, s5, and s8” are omitted. “Steps s8 and s9” correspond to “steps s46, s47, s50, and s51”.

After executing loop control of steps s44 to 61 to calculate the downstream pressure for fuel control and the in-cylinder pressure for fuel control in IVC, the process proceeds to step s62.
In step s62, the fuel control intake air amount is calculated from the fuel control cylinder pressure, the cylinder volume at IVC, and the intake air temperature using the gas state equation.
Then, after the calculated intake air amount for fuel control is transmitted to the engine control unit 8, the process proceeds to step s63.
In step _s63 , P _{2_old} = P _{2_A} is executed to prepare for real-time estimation control performed after receiving the next trigger.
After processing step s63, the intake air amount calculation flow 1 is terminated, and the process waits until the next trigger is received.

In step s21, it is determined whether or not CA is at a predetermined time A. When CA is not predetermined time A and the process proceeds to step s22, it is determined in step s22 whether throttle opening fixing control is being performed. If the throttle opening fixing control is not performed, the process waits until the intake air amount calculation flow 1 is finished and the next trigger is received.
If the throttle opening fixing control is being performed, the process proceeds to step s25.

In step s25, the completion determination of the throttle opening fixing control is performed.
Since the throttle opening fixing control is performed until CA reaches IVC, if CA reaches IVC, the process proceeds to step s26, and after the throttle opening fixing control is completed, the intake air amount calculation flow 1 is performed. Wait until it finishes and receives the next trigger.
If not reached, the intake air amount calculation flow 1 is terminated as it is, and the process waits until the next trigger is received.

By performing the above processing with the throttle control unit 7 provided for each cylinder during engine operation, in the first embodiment that does not include an airflow sensor or a pressure sensor, the fuel injection is started from the predetermined time A to the time when fuel injection is started. When predicting and estimating the fuel control intake air amount prior to the crank angle, as shown in FIG. 23, the throttle opening fixing control is performed between the predetermined time A and the time when the intake valve is fully closed. The actual throttle opening is fixed.
The above control does not change the actual throttle flow path area from the time when prediction estimation is started until the time when the intake valve is completely closed, so that the accuracy of the estimated intake air amount for fuel control to the cylinder is increased. Highly accurate fuel injection control can be performed.

  According to the first embodiment of the present invention, instead of calculating the passage flow rate of the throttle portion, the intake valve, and the exhaust valve in total, as in the prior art, only the throttle portion passage flow rate is calculated. It is possible to reduce the calculation load by estimating the throttle downstream pressure, the cylinder pressure, and the intake air amount.

  In the first embodiment described above, a system in which the intake air amount is estimated by the throttle control unit 7 and the fuel amount calculation is performed by the engine control unit 8 is shown. The engine control unit 8 may be integrated with the engine control unit 8 to estimate the intake air amount.

Embodiment 2. FIG.
In the first embodiment, control is performed to fix the throttle opening from the predetermined time A to the time when the intake valve is completely closed, and a sensor for detecting the throttle downstream pressure is not installed, and the predetermined time is determined by real-time estimation control. We explained what estimates the throttle downstream pressure at A.
In the second embodiment, the throttle downstream pressure at the predetermined time A is detected by the pressure sensor after controlling to fix the throttle opening from the predetermined time A to the time when the intake valve is completely closed.
That is, based on the throttle downstream pressure at the predetermined time A detected by the pressure sensor, the prediction estimation control performed in the first embodiment is performed, thereby estimating the intake air amount for fuel control. Similarly to the first embodiment, in the second embodiment, in order to reduce the calculation load in the estimation of the estimated downstream pressure and the intake air amount for fuel control as compared with the prior art, the intake valve closing model and the intake valve opening model are used. By using it, the flow rate of only the throttle part is calculated instead of calculating the flow rate of the throttle part, the intake valve part, and the exhaust valve part as in the prior art. In the second embodiment, the control for correcting the throttle upstream pressure and the intake air temperature used in the predictive estimation control with the sensor value is also performed.
The second embodiment will be described below with reference to the drawings.

FIG. 20 shows an overall configuration diagram of Embodiment 2 of the present invention. In the figure, the same reference numerals and the same names as those in FIG. 4 denote the same parts.
In FIG. 20, the control device for the internal combustion engine of the second embodiment is also the same multiple throttle system as that of the first embodiment, and only the first cylinder is shown as a representative. However, the second to fourth cylinders of the engine are also implemented. The configuration is the same as in the first mode.
As can be seen by comparing FIG. 20 with FIG. 4 of the first embodiment, the difference between the two is that each throttle downstream portion 9 is provided with a pressure sensor 11 and that the intake air between the air cleaner 16 and the throttle valve 1 is different. The atmospheric pressure sensor 14 and the temperature sensor 15 are installed in the passage, and the sensor value is input to each throttle control unit 12 and engine control unit 13.
Further, as in the first embodiment, the intake valve closing model and the intake valve opening model used in the second embodiment are the same as those in the first embodiment, such as the configuration and formula, and the description thereof is omitted.

Next, a flowchart of the intake air amount estimation flow 2 performed by the throttle control unit 12 will be described.
FIG. 21 shows a flowchart of the intake air estimation flow 2 implemented in the second embodiment.
In the intake air amount estimation flow 2, since the throttle valve 1 is an individually controlled multiple throttle system, the second embodiment is the same as the first embodiment. The valve opening model will be used. Similarly to the first embodiment, the valve timing map (FIG. 15) of the intake valve using the crank angle as a parameter is incorporated in the throttle control unit 12.

The intake air amount estimation flow 2 is performed when a trigger sent from the engine control unit 13 to the throttle control unit 12 is received every predetermined cycle ΔCA based on the crank angle, and the predicted estimated downstream pressure and the predicted estimated cylinder are received from the predicted estimation control. The estimation of the internal pressure and the intake air amount for fuel control, and the throttle opening fixing control between the predetermined time A and the time when the intake valve is fully closed are performed.
The intake air amount estimation flow 2 includes control logic (s24 step (FIGS. 12 to 14 in the first embodiment) shown in FIG. 12) and control logic (s23, s26) for starting and ending throttle opening fixing control. Step).
As in the intake air amount estimation flow 1, the predictive estimation control in the intake air amount estimation flow 2 includes the equations (8) to (10) shown in the first embodiment, the gas state equations, and various maps (FIG. 15, 16, 18, and 19), the estimated estimated downstream pressure, the fuel control intake air amount, and the like are calculated.

Note that the speed term map shown in FIG. 22 is used for the speed term map used for calculating the speed term of Equation (8). This is because the throttle upstream pressure P ₁ and the intake air temperature T ₁ are corrected based on the sensor value instead of treating the throttle upstream pressure P ₁ and the intake air temperature T ₁ as constants as in the _first embodiment. This is because P ₁ and T ₁ must be handled as parameters of the velocity term H.
The speed term map of FIG. 22 is obtained by using a ratio “P _{2_old} / P ₁ ” between P _{2_old} and the throttle upstream pressure P _{1 and} a ratio “P ₂ ” between the square of the throttle upstream pressure P ₁ and the intake air temperature T _{1. This} is a three-dimensional map with “ ₁ ² / T ₁ ” as a parameter. In the speed term map of FIG. 22, when P ₁ ² / T ₁ is viewed as a fixed parameter (YY ′ axis in FIG. 22), the tendency is the same as in FIG. 17 of the first embodiment, and P _{2_old} / P ₁ is When viewed as a fixed parameter (XX ′ axis in FIG. 22), the increase is proportional.
Further, once the throttle opening degree fixing control is started, the throttle opening degree is controlled to be fixed until the throttle opening degree fixing control is finished in step s26.

Hereinafter, each step will be described. In addition, regarding the s1, s10, and s21 to s26 steps in FIG. 21, the same processing as the s1, s10, and s21 to s26 steps of the first embodiment is performed.
After receiving the trigger from the engine control unit 13, first, it is confirmed in step s1 whether the engine is operating. If it is operating, the process proceeds to step ss1, and if stopped, the intake air amount calculation flow 2 is terminated. Wait until the next trigger is received.
In ss1 step, (assigned to the upstream intake air pressure P ₁₎ from the engine control unit 13 crank angle, engine speed, atmospheric pressure, intake air temperature, reads the throttle downstream pressure from the throttle actuator 6 throttle opening, from the pressure sensor 11, Proceed to step s21.
In step s21, the same process as in step s21 of the first embodiment is performed as described above. If the crank angle CA is not the predetermined time A, the process proceeds to step s22. If CA is the predetermined time A, the throttle opening is fixed. Proceed to step s23 to implement control and predictive estimation control.

If the process proceeds to step s22, thereafter, in the same manner as in the first embodiment, it is first determined whether or not the throttle opening degree fixing control is being performed in step s22. If the intake air amount calculation flow 2 is finished and the control waits until the next trigger is received and the throttle opening fixing control is being performed, it is determined in step s25 whether CA has reached IVC.
If IVC is reached, in step s26, after the throttle opening fixing control is completed, the process waits until the intake air amount calculation flow 2 is completed and the next trigger is received.
If the IVC has not been reached, the intake air amount calculation flow 2 is terminated as it is, and the process waits until the next trigger is received.

When CA is the predetermined time A in step s21 and the process proceeds to step s23, the throttle opening fixing control is started in the same manner as in the first embodiment, and the process proceeds to step s24.
In step s24, the intake air amount for fuel control is calculated by the predictive estimation control shown in FIGS. 12 to 14 (steps s42 to 63) described in the first embodiment.
Note that the map used to calculate the speed term H used in Equation (8) when calculating the intake air amount for fuel control by predictive estimation control is the speed term map shown in FIG.
In step s24, the amount of intake air for fuel control is calculated and transmitted to the engine control unit 13, and then the process proceeds to step s10.
In step s10, the same process as in step s10 of the first embodiment is performed as described above, and a predetermined time A is calculated and transmitted to the engine control unit 13.
After the s10 step processing, the process waits until the intake air amount calculation flow 2 is finished and the next trigger is received.

  By performing the above processing with the throttle control unit 7 provided for each cylinder during engine operation, the intake air amount for fuel control using the pressure sensor 11 can be estimated.

According to the control apparatus for an internal combustion engine of the second embodiment of the present invention, the pressure sensor 11 is provided for each cylinder as compared with the first embodiment, so that the cost is increased.
However, as can be seen by comparing the intake air amount estimation flow 1 and the intake air amount estimation flow 2, in the second embodiment, the intake air amount for fuel control can be estimated with a simpler control logic.

  The throttle downstream pressure at the predetermined time A is detected by the pressure sensor 11, and the atmospheric pressure sensor and the temperature sensor are installed upstream of the throttle valve to correct the atmospheric pressure and the intake air temperature at regular intervals. This makes it possible to estimate the intake air amount for fuel control with higher accuracy than in the first embodiment.

  The atmospheric pressure and intake air temperature correction by the atmospheric pressure sensor and the temperature sensor is performed by installing the atmospheric pressure sensor and the temperature sensor upstream of the throttle valve and incorporating the same correction control as in the second embodiment. But of course it can be implemented.

4 is a stroke table of each cylinder showing a relationship between a timing of starting fuel injection and a reference intake air amount in a conventional four-cylinder engine. FIG. 6 is a diagram showing the relationship between “the amount of intake air used for calculating the fuel amount” and “the actual amount of intake air” during a transition. It is the figure which showed the relationship between actual throttle downstream pressure, estimated downstream pressure, and estimated estimated downstream pressure. 1 is an overall configuration diagram of a control device for an internal combustion engine according to Embodiment 1 of the present invention. It is a figure showing the intake valve closing model in Embodiment 1 of this invention. It is a figure showing the intake valve opening model in Embodiment 1 of this invention. It is a flowchart of the intake air amount estimation flow 1 in Embodiment 1 of this invention. It is a partial flowchart of the intake air amount estimation flow 1 in Embodiment 1 of this invention. It is a partial flowchart of the intake air amount estimation flow 1 in Embodiment 1 of this invention. It is a partial flowchart of the intake air amount estimation flow 1 in Embodiment 1 of this invention. It is a partial flowchart of the intake air amount estimation flow 1 in Embodiment 1 of this invention. It is a partial flowchart of the intake air amount estimation flow 1 in Embodiment 1 of this invention. It is a partial flowchart of the intake air amount estimation flow 1 in Embodiment 1 of this invention. It is a partial flowchart of the intake air amount estimation flow 1 in Embodiment 1 of this invention. It is a valve timing map of an intake valve in Embodiments 1 and 2 of this invention. It is an area term map in Embodiment 1, 2 of this invention. It is a speed term map in Embodiment 1 of this invention. It is a cylinder volume map in Embodiment 1, 2 of this invention. It is the predetermined time A map in Embodiment 1, 2 of this invention. It is a whole block diagram of the control apparatus for internal combustion engines by Embodiment 2 of this invention. It is a flowchart of the intake air amount estimation flow 2 in Embodiment 2 of this invention. It is a speed term map in Embodiment 2 of this invention. It is an image figure which shows the relationship between the target throttle opening and actual throttle opening in this invention.

Explanation of symbols

1: Throttle valve 2: Fuel injection valve 3: Intake valve 4: Exhaust valve 5: Crank angle sensor 6: Throttle actuator 7, 12: Throttle control unit 8, 13: Engine control unit 9: Throttle downstream part 10: Cylinder 11: Pressure sensor 14: Atmospheric pressure sensor 15: Temperature sensor 16: Air cleaner

Claims (13)

Intake into each cylinder of the internal combustion engine having a plurality of cylinders by controlling the flow area to each of the independent intake pipes, one end of which is connected to the intake valve of each cylinder and the other end is connected to the collecting portion of each cylinder In a control device for an internal combustion engine of a port injection type in which an intake air amount control means for controlling an air amount is arranged and exhaust stroke injection is performed,
A flow passage area detecting means for detecting a flow passage area of the intake air amount control means; a downstream pressure detecting means for detecting a pressure downstream of the intake air amount control means; and an internal combustion engine speed detecting means. The fuel to be injected this time is sucked into the cylinder using the upstream pressure and downstream pressure of the control means, the flow passage area of the intake air amount control means, the internal combustion engine speed, the cylinder volume, and the intake air temperature. And a control device for an internal combustion engine that estimates the in-cylinder pressure and the intake air amount sucked into the cylinder at the time when the intake valve of the cylinder is completely closed by the time when the current fuel injection is started , A control apparatus for an internal combustion engine, wherein control is performed so as to fix a flow passage area of the intake air amount control means from a time when the estimation is started to a time when the intake valve is completely closed.   2. The internal combustion engine for an internal combustion engine according to claim 1, wherein the intake air amount sucked into the cylinder until the intake valve is fully closed is estimated based on the in-cylinder pressure when the intake valve is fully closed. Control device When calculating the amount of intake air sucked into the cylinder at the time when the intake valve is fully closed by the time when fuel injection is started to calculate the fuel injection amount of the internal combustion engine, the estimated intake valve is completely closed 3. The control apparatus for an internal combustion engine according to claim 1, wherein the estimated downstream pressure at the time is set to a cylinder pressure at the time when the intake valve is completely closed.   Predetermined estimated downstream pressure, upstream pressure of intake air amount control means, flow path area of intake air amount control means, in-cylinder volume, internal combustion engine speed, intake air temperature The estimated estimated downstream pressure at the time when the intake valve is fully closed is estimated by repeatedly estimating the estimated estimated downstream pressure after a predetermined period from the previous time. Item 4. The control device for an internal combustion engine according to any one of Items 3   The timing for starting the estimation of the estimated estimated downstream pressure is a predetermined timing before the timing for starting the fuel injection, and the predetermined timing is the estimated estimated downstream pressure with respect to the timing for starting the fuel injection as the internal combustion engine speed increases. 5. The control apparatus for an internal combustion engine according to claim 4, wherein the timing for starting the estimation of the engine is shifted earlier. An intake valve closing models the intake passage modeled from inhaled air amount control means upstream to the intake valve, the intake valve open model that models the intake passage from the intake air amount control means upstream to the cylinder in consideration of the volume change The control apparatus for an internal combustion engine according to any one of claims 1 to 5, wherein the two intake air amount estimation models are provided.   The downstream pressure is estimated from the previously estimated downstream pressure, the upstream pressure of the intake air amount control means, the flow passage area of the intake air amount control means, the cylinder volume, the internal combustion engine speed, and the intake air temperature. A control device for an internal combustion engine according to any one of claims 1 to 6.   The control device for an internal combustion engine according to claim 7, wherein the estimation of the downstream pressure is performed at predetermined intervals according to the crank angle.   7. A control device for an internal combustion engine according to claim 1, further comprising a sensor for detecting a downstream pressure, wherein the downstream pressure is based on an output of the sensor.   The control apparatus for an internal combustion engine according to any one of claims 1 to 9, wherein the intake air amount control means is a throttle valve, and the flow passage area is set based on a throttle opening.   The internal combustion engine speed detection means is a sensor capable of detecting a crank angle, and detects the internal combustion engine speed and a cylinder volume set based on the crank angle. 10. The control device for an internal combustion engine according to any one of 10   12. The internal combustion engine having an atmospheric pressure detection means, wherein the upstream pressure of the intake air amount control means is corrected based on the pressure detected from the atmospheric pressure detection means. The control device for an internal combustion engine according to any one of 13. The internal combustion engine having the intake air temperature detection means corrects the intake air temperature based on the intake air temperature detected from the intake air temperature detection means. Control device for internal combustion engine

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