JP3358449B2 - Exhaust system pressure estimation device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an EGR for an internal combustion engine.
The present invention relates to a technique for estimating an exhaust system pressure required for control and the like.

[0002]

2. Description of the Related Art As a conventional pressure detection method for an intake system and an exhaust system of an internal combustion engine, a sensor for directly detecting these pressures is generally provided. In addition, Japanese Patent Application No. 7-9263
As disclosed in No. 1, there is also a technique of estimating from an output of an air flow meter or the like.

[0003]

However, in the case where the sensor is provided as described above, the cost is of course high. However, in the case of the sensor for detecting the exhaust pressure, the exhaust gas such as EGR is circulated, Due to exposure to the atmosphere, durability is extremely severe. Further, it has been found that when the durability can be ensured, the time constant of the sensor becomes extremely large, and it is difficult to display an accurate value in a transient state, and it is difficult to reflect the value on the control.

[0004] The exhaust temperature which affects the exhaust pressure is:
Since it changes depending on parameters representing the ignition timing such as the injection timing and the air flow in the cylinder, the technique of Japanese Patent Application No. 7-92631 cannot cope with this.

[0005]

Therefore, according to the present invention, as shown in FIG. 1, a fuel injection amount detecting means for detecting an injection amount of fuel injected into an engine, and a fuel injected into the engine. Intake air temperature detecting means for detecting the temperature of the air, fuel injection timing detecting means for detecting the fuel injection timing, intake air flow rate detecting means for detecting the flow rate of the intake air,
And the engine rotational speed detecting means for detecting a rotational speed of the engine, fuel
The basic exhaust temperature is calculated based on the fuel injection amount, and the basic exhaust temperature is calculated.
The intake air temperature, the previously estimated exhaust pressure, and the fuel injection
Calculate the exhaust temperature from the cylinder by correcting with the firing timing,
From the cylinder obtained from the intake air flow rate and the engine speed
Based on the exhaust gas flow rate and the exhaust gas temperature from the cylinder.
Exhaust pressure estimating means for estimating exhaust pressure.

(Operation / Effect) Since the amount of heat generated during combustion is determined by the fuel injection amount detected by the fuel injection amount detecting means, the basic exhaust temperature is determined. Further, when the intake air temperature changes, the combustion temperature changes, so that the exhaust gas temperature also changes.

Further, when the injection timing of the fuel is advanced (the advance amount is increased), the combustion state is improved, and the temperature at the time of discharging the cylinder is lowered. If the timing is delayed, the exhaust gas temperature is affected such that the exhaust gas temperature increases due to the opposite effect. Therefore, the exhaust gas temperature is accurately estimated based on the fuel injection amount, the intake air temperature, and the fuel injection timing.

On the other hand, the exhaust flow rate at the time of cylinder discharge can be obtained based on the intake air flow rate and the engine speed. In the steady state, the flow rate of the intake air (per unit time) substantially matches the flow rate of the exhaust gas discharged from the cylinder, but in the transient state, it differs depending on the volume of the intake system. Therefore, the amount of exhaust per cylinder discharged from the cylinder is calculated based on the intake air flow rate and the engine speed, and then the exhaust flow rate (per unit time) discharged from the cylinder using the engine speed is calculated again. By performing the conversion, the exhaust flow rate can be accurately calculated.

Then, the exhaust pressure can be obtained from Bernoulli's equation based on the estimated exhaust temperature and the calculated exhaust flow rate. Also, when estimating the exhaust gas temperature,
The basic exhaust temperature obtained based on the fuel injection amount is
In addition to the air flow and fuel injection timing, the previously estimated exhaust pressure
However, the exhaust gas temperature is estimated after correction. That is, adiabatic change
As the exhaust pressure rises, the exhaust temperature also increases
, So the correction based on the previous estimated exhaust pressure
Simultaneously, the exhaust gas temperature is more accurately estimated.

[0010]

Further, as shown in FIG. 2, the invention according to claim 2 detects fuel injection amount detecting means for detecting the amount of fuel injected into the engine, and detects the temperature of air taken into the engine. Intake air temperature detecting means, swirl control state detecting means for detecting a swirl control state by a swirl control valve provided in an intake system of the engine, intake air flow rate detecting means for detecting a flow rate of the intake air, and rotation of the engine. Engine speed detection means for detecting the speed and basic based on the fuel injection amount
Calculate the exhaust gas temperature, and calculate the basic exhaust gas temperature as the intake air temperature.
Correction with the estimated exhaust pressure and swirl control state
Calculates the exhaust temperature from the cylinder, and calculates the intake air flow rate and engine
Exhaust flow rate from the cylinder obtained from the rotational speed
Exhaust pressure estimating means for estimating the exhaust pressure based on the exhaust temperature from the cylinder .

(Operation / Effect) In a system having a swirl control valve in the intake system, the swirl control valve controls the swirl intensity and thereby changes the flammability, so that the exhaust gas temperature also changes. Therefore, the control state of the swirl by the swirl control valve is detected, and the exhaust temperature is estimated in consideration of the swirl control state in addition to the fuel injection amount and the intake air temperature. In addition, it goes without saying that the exhaust gas temperature may be estimated including the injection timing, and the estimation accuracy is further improved.

[0013] it is possible to accurately estimate the exhaust pressure on the basis of the exhaust temperature estimated accurately in this manner, the exhaust flow rate determined from the intake air flow rate and the engine rotational speed
You can see that.

Therefore, the basic exhaust temperature corresponding to the calorific value at the time of fuel combustion is obtained from the fuel injection amount, and the basic exhaust temperature is corrected by the intake air temperature, the exhaust pressure estimated last time, and the swirl control state, so that the exhaust gas is accurately discharged. The temperature can be estimated and calculated, and the exhaust temperature can be accurately estimated based on the exhaust flow rate from the cylinder and the exhaust temperature.

Further, the invention according to claim 3 is characterized in that the correction of the basic exhaust gas temperature in the swirl control state is performed by a correction coefficient set based on the opening degree of the swirl control valve and the engine speed. I do. (Operation / Effect) When the swirl control valve opening is large, the effect of the swirl is small even if the engine speed changes, but when the swirl control valve opening is small, an appropriate swirl is effective at low speeds. In the high-speed range, the swirl is too strong and the flammability decreases.
Further, the exhaust gas temperature increases due to a decrease in the cylinder intake air amount due to the throttling action.

Therefore, a correction coefficient for the exhaust gas temperature is set based on the swirl valve opening and the engine speed, and the exhaust gas temperature is corrected using the correction coefficient, thereby further improving the estimation accuracy of the exhaust gas temperature. it can. Further, in the invention according to claim 4 , the correction of the basic exhaust gas temperature by the swirl control state is set based on a swirl flow rate equivalent value calculated from the intake air flow rate, the engine rotation speed, and the opening of the swirl control valve. The correction is performed by using a correction coefficient.

(Operation / Effect) The intake air flow rate when the intake air is taken into the cylinder can be calculated based on the intake air flow rate and the engine rotation speed. By dividing this cylinder intake air flow rate by the opening of the swirl control valve, the swirl can be calculated. A value corresponding to the flow velocity is determined. When the swirl flow velocity is at a certain value, the flammability is improved most and the exhaust temperature is reduced. When the swirl flow velocity is higher or lower, the flammability lowers and the exhaust temperature tends to increase. .

Therefore, a correction coefficient for the exhaust gas temperature is set based on the swirl flow velocity equivalent value calculated from the intake air flow rate, the engine rotation speed, and the opening of the swirl control valve, and the exhaust gas temperature is corrected using the correction coefficient. By doing so, the estimation accuracy of the exhaust gas temperature can be further improved .

[0019]

[0020]

[0021]

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 4 showing the overall configuration of one embodiment, a supercharger 1 is configured to remove air that has been dust-removed by an air filter 2 and that is taken into an intake passage 3 by an intake compressor 1A.
, And is fed into the downstream intake manifold 4.

On the other hand, fuel is distributed to each cylinder from an injection pump 7 and supplied to the fuel injection nozzle 6 mounted in the combustion chamber of the engine (diesel engine) 5 under pressure, and the fuel is supplied from the fuel injection nozzle 6 to the combustion chamber. Fuel is injected toward the fuel, and the injected fuel is ignited and burned at the end of the compression stroke. The EGR is connected to the exhaust manifold 8 and the intake manifold 4.
An EGR passage 10 provided with a control valve 9 is connected. At the time of EGR control, the intake air is throttled to the upstream side of the intake compressor 1A in the intake passage 3 to expand the differential pressure between the exhaust pressure and the intake pressure to perform EGR. A throttle valve 31 is provided for ease of exhaustion, and exhaust is improved mainly at idle or low load.
The EGR control is performed by controlling the opening of the EGR control valve 9 at the same time as the throttle valve 31 is throttled to reduce noise. Specifically, the negative pressure from the vacuum pump 11 is
2 to the diaphragm device 33 through the throttle valve 3
At the same time as reducing the value of 1, the solenoid valve 12 that duty-controls the negative pressure controls the dilution ratio with the atmosphere, thereby controlling the pressure guided to the pressure chamber of the EGR control valve 9, thereby controlling the opening. Thus, the EGR rate is controlled. The EGR rate and the fuel injection control are performed by the control unit 13.

The EGR control valve 9 is provided with a lift sensor 34 for detecting a lift amount of the valve body. After the combustion, the exhaust turbine 1B of the supercharger 1 is driven to rotate by the exhaust manifold 8, and the particulates (exhaust particulates) and the like contained in the exhaust are collected by the filter 14 and silenced by the muffler 15. After being released into the atmosphere.

In the intake passage 3 upstream of the intake compressor 1A of the supercharger 1, an air flow meter 16 for detecting an intake air flow rate is provided, a rotation speed sensor 17 for detecting an engine rotation speed Ne, and the fuel injection. A lever opening sensor 18 for detecting the control lever opening (accelerator opening) of the pump 7, a water temperature sensor 19 for detecting the water temperature, and the like are provided, and the intake system pressure and the exhaust system pressure are detected based on these detected values. Meanwhile, the allowable maximum injection amount of fuel corresponding to the cylinder intake air amount is set as described later.

Hereinafter, various calculations by the control unit 13 will be described. FIG. 5 shows the intake air flow rate Qas
This is shown in the flow of the operation of 0. Step (denoted by S in the figure)
In step 1, the output voltage Us of the air flow meter 16 is read, and in step 2, the intake air flow rate Qas0 is calculated using a characteristic table (voltage-intake air flow rate conversion table) as shown in FIG. Then, the averaging process is performed in step 3, and the process ends as Qas0.

FIG. 7 is a calculation flow of the amount of intake air per one intake stroke drawn into the cylinder, and is calculated at a timing synchronized with the engine rotation. In step 11, the engine rotational speed Ne is read, and in step 12, the intake air amount Qac0 per intake stroke is calculated from the intake air flow rate Qas0 processed in FIG.

In step 13, the process ends with the intake air amount Qac0 calculated a predetermined number of times before as Qacn.
The reason why Qac0 before this predetermined time is Qacn is that there is a transport delay from the measurement position of the air flow meter 16 to the collector inlet. In step 14, a first-order lag process is performed as shown in FIG.
c is calculated and the process is terminated.

FIG. 8 is a flow chart for performing a cycle delay (dead time processing) from the intake and supply to the cylinder to the discharge from the cylinder. The cylinder intake air amount Qac, the actual injection timing ltist, the fuel injection amount Qsol, and the intake air temperature are shown. A dead time process for a predetermined cycle is performed for each Tn. This is performed in order to obtain data before cylinder intake, which is the basis of the exhaust pressure to be obtained.

FIG. 9 is a flow chart for calculating the exhaust pressure using the values obtained as described above. Step 31
Then, based on the fuel injection amount cycle processing value Qsold processed in FIG. 8, the basic exhaust temperature Tehi is searched from the table shown in FIG. Since the amount of combustion heat increases with an increase in the fuel injection amount, the basic exhaust temperature Texhi has a characteristic of proportionally increasing.

In step 32, the exhaust temperature correction coefficient Ktmpn based on the intake air temperature is searched from the table shown in FIG. 11 based on the intake air temperature cycle processing value Tne. When the intake air temperature is high, the exhaust gas temperature is also high. Therefore, the exhaust gas temperature correction coefficient Ktmpn increases with the intake air temperature. In step 33, the exhaust pressure Pexhn-1 of the previous calculation is calculated.
Thus, the exhaust temperature correction coefficient Kkmpp based on the exhaust pressure is calculated from the table shown in FIG. Since the exhaust gas temperature increases as the exhaust pressure increases, the exhaust temperature correction coefficient Ktmppp
Is also such a property.

In step 34, the exhaust temperature correction coefficient Ktmpi based on the injection timing is calculated from the table shown in FIG. 13 based on the actual injection timing cycle processing value ltistd. It should be noted that since the exhaust temperature increases as the injection timing becomes later, for example, the end of combustion is delayed, the exhaust temperature correction coefficient Ktmpi is also set in accordance with the characteristic. In step 35, the basic exhaust gas temperature Texhi obtained in step 31 is
Each exhaust temperature correction coefficient Ktmpn, Ktm obtained in 32, 33, 34
By using pp and Ktmpi, the cylinder discharge temperature Texhc is calculated by correcting the following equation.

Texhc = Texhi × Ktmpn × Ktmpp × Ktmpi In step 36, the cylinder discharge temperature Texhi is
The exhaust temperature Texh is obtained by performing a first-order lag process represented by the following equation. Texh = Texh _n-1 × (1-KO) + Texhc × KO KO is a constant In step 37, the amount of exhaust air per cylinder Qexh,
Engine speed Ne, exhaust temperature Texh and constant KPEX
Using H, OPEXH (a value corresponding to the atmospheric pressure in the standard state), a basic exhaust pressure value Pehb is calculated by the following equation. Pehb = (Qexh × Ne / KC) ² × Texh × KEXH + OPEXH In step 38, the exhaust pressure basic value Pexhb is subjected to a first-order lag process represented by the following equation to obtain the exhaust pressure Pexh.

Pexh = Pexh _n-1 × (1-KP) + Pexhb × KP KP is a constant Next, a second embodiment will be described. In this embodiment, as shown in FIG. 14, a swirl control valve 21 for strengthening the intake swirl at low speed to enhance the combustion performance is interposed at the intake port portion of each cylinder of the intake manifold 4, and the swirl control valve 21 is provided. The opening of control valve 21 is the control unit
The control is performed according to the operating state of the engine by means of 13. In the present embodiment, the swirl control valve 21
The exhaust pressure is corrected and estimated in accordance with the opening degree.

3 to 12 are used in common with the first embodiment. FIG. 15 is a flow for performing a cycle delay (dead time processing) performed in the same manner as in FIG. 8, and includes a cylinder intake air amount Qac, a swirl control valve opening Riscv,
Dead time processing for a predetermined cycle is performed for each of the fuel injection amount Qsold and the intake air temperature Tne.

FIG. 16 is a flowchart for calculating the exhaust pressure.
Steps 41 to 43 correspond to steps 31 to
The description is omitted because it is the same as 33. In step 44, the swirl control valve opening cycle processing value R shown in FIG.
Based on the iscvd and the engine speed Ne, the exhaust temperature correction coefficient Ktm based on the swirl control valve opening is obtained from the table shown in FIG.
Search for psc. When the swirl control valve 21 is fully opened (corresponding to a case where the swirl control valve is not substantially provided)
Is fixed at the exhaust temperature correction coefficient Ktmpsc = 1 (substantially no correction is performed). When the opening degree of the swirl control valve 21 is small, the swirl strength becomes appropriate when the engine is at low speed, and the combustibility is reduced. As a result, the exhaust temperature decreases, but at high engine speeds, the swirl becomes excessive and the combustibility deteriorates.
Further, the exhaust gas temperature rises due to, for example, a decrease in the cylinder intake air amount due to the throttling action. Therefore, the exhaust temperature correction coefficient Ktmpsc is set in accordance with the characteristic.

In step 45, the basic exhaust gas temperature Tex
hi is the exhaust temperature correction coefficient K obtained in steps 42, 43 and 44.
Using the tmpn, Ktmpp, and Ktmpsc, the cylinder discharge temperature Texhc is calculated by correcting the following equation. Texhc = Texhi × Ktmpn × Ktmpp × K
tmpsc Hereinafter, steps 46 to 48 are the same as steps 36 to 38 in FIG.
A first-order lag process is performed on the cylinder discharge temperature Texhi to obtain an exhaust gas temperature Texh. In step 47, a basic exhaust pressure value Pexhb is calculated by an equation shown in the drawing, and in step 48, a first-order lag process is performed on the basic exhaust pressure value Pexhb. To the exhaust pressure Pexh.

In the above-described embodiment, the exhaust temperature correction coefficient Ktmpsc is set by searching the three-dimensional table from the opening degree of the swirl control valve and the engine speed, but the cylinder intake air amount Qac, the engine speed Ne, the swirl The ratio of the intake air flow rate to the swirl valve opening degree, that is, the value Vsc corresponding to the swirl flow velocity is calculated from the valve opening degree Rascv, and the exhaust temperature correction coefficient Ktm is calculated according to the flow velocity equivalent value Vsc.
The psc may be set.

The above embodiment will be described below. FIG. 3 to FIG.
12 is used in common with the first embodiment. Fig. 18
Is a flow for performing a cycle delay (dead time processing) performed in the same manner as in the above-described embodiments, and includes a cylinder intake air amount Qac, a swirl flow velocity Vsc, and a fuel injection amount Qsol.
d, dead time processing for a predetermined cycle is performed for each intake air temperature Tne.

Here, the swirl flow rate Vsc is obtained by dividing the intake air flow rate Qac × Ne in the cylinder portion by the swirl control valve opening Rascv, as shown in the equation in the figure.
FIG. 19 is a flowchart for calculating the exhaust pressure. Step 51 ~
Step 53 is the same as steps 31 to 33, and a description thereof will not be repeated.

In step 54, the exhaust gas temperature correction coefficient Ktm based on the swirl control valve opening is obtained from the cycle processing value Vsc corresponding to the swirl flow velocity in FIG.
Search for psc. This is the swirl flow velocity equivalent value Vsc
At a certain value, the combustion state becomes the best and the exhaust gas temperature decreases, and the exhaust gas temperature rises regardless of the deviation from Vsc.
Is set.

In step 55, the basic exhaust gas temperature Tex
hi is set to each exhaust temperature correction coefficient K obtained in steps 52, 53 and 54.
The cylinder discharge temperature Texhi is calculated by performing correction using the equations shown in the figure using tmpn, Ktmpp, and Ktmpsc. Hereinafter, regarding steps 56 to 58,
9 is the same as steps 36 to 38 in FIG. 9. In step 56, a first-order lag process is performed on the cylinder discharge temperature Texhi to obtain an exhaust temperature Texh. In step 57, a basic exhaust pressure value Pehb is calculated by the illustrated equation. Then step
In step 58, the exhaust pressure basic value Pexhb is subjected to a first-order lag process to obtain the exhaust pressure Pexh.

Next, the intake pressure estimation will be described. FIG.
Shows a functional block diagram of intake pressure estimation, and FIG.
This is a flow for calculating the pressure.
This will be explained. In step 61, a volume efficiency equivalent value basic value Kinb is retrieved from the table shown in FIG. 22 based on the cylinder intake air amount Qac and the engine rotation speed Ne. Steps
In 62, the volume efficiency equivalent value Kin is calculated using the intake air temperature Tint using the equation (Kin = Kinb × TA / Tint) shown in FIG.
Calculate with.

In step 63, the cylinder intake air amount Qa
c, using the volume efficiency equivalent value Kin as a variable, the equation (P
m = Qac / Kin × TA × Ra / VCYL), and the process ends. The constants TA, RA, and VCYL appearing in this flow are the standard state temperature,
Air gas constant and cylinder volume. FIG. 23 is a flowchart for calculating the basic fuel injection amount Qsol1.

In step 71, the engine speed Ne is set, and in step 72, the accelerator opening (control lever opening) CL
Read. In step 73, the basic fuel injection amount Mqdrv is retrieved from the table shown in FIG. 24 based on the engine speed Ne and the accelerator opening CL. In step 74, the basic fuel injection amount Mqdrv is corrected by various correction coefficients such as a water temperature to obtain a basic fuel injection amount Qsol1.

FIG. 25 is a flowchart for calculating the maximum fuel injection amount Qful, which is processed at a timing synchronized with the rotation.
In step 81, the engine rotational speed Ne is read, and in step 82, a limit excess air ratio equivalent value Klamb is retrieved from the table in which values corresponding to the smoke limit shown in FIG. 26 are set from the engine rotational speed Ne.

In step 83, the cylinder intake air amount Qa
c, and at step 84 the equation (Qfull = Qa)
c / Klamb / 14.7) is used to calculate the maximum fuel injection amount Qful, and the process ends. FIG. 26 is a flowchart for finally setting the fuel injection amount, which is executed in synchronization with the engine rotation.

In step 91, the basic fuel injection amount Qs
ol1 is compared with the maximum fuel injection amount Qful, and when the former is large, the routine proceeds to step 92, where the maximum fuel injection amount Qful is used as the fuel injection amount Qsol, and when the former is small, the step is performed.
Proceed to 93 to add the basic fuel injection amount Qso to the fuel injection amount Qsol.
l1 is set and the process ends. Hereinafter, the EGR control performed using the exhaust pressure and the intake pressure estimated according to the present invention will be described.

FIG. 28 is a flowchart for calculating the opening area of the EGR valve. In step 101, a target EGR amount is calculated. This method will be described later. At step 102, the estimated intake pressure Pm is read, and at step 103
Then, the estimated exhaust pressure Pexh is read.

In step 104, the equation [Cqe =
{K (Pexh-Pm)} ^1/2 ; K is a constant]
The GR flow rate equivalent value Cqe is calculated, and in step 105, the required EGR amount Tqek and the EGR flow rate equivalent value Cqe are used to calculate the opening area Aev of the EGR valve by the illustrated equation (Aev = Tqek / Cqe). In step 106, a weight constant Nlk for performing a weighted averaging process on an EGR valve opening area, which will be described later, is searched from the table shown in FIG. 29 based on the EGR flow velocity equivalent value Cqe. The EGR flow rate equivalent value C
When qe is small, the weight constant Nlk is set large, and when the EGR flow velocity equivalent value Cqe is large, the weight constant Nlk is set small. This is because when the flow velocity is small, the required opening area must be largely changed even with a small change in the flow velocity, and the weighted average is increased (heavy) because it becomes difficult to stabilize. In addition, when the flow velocity is high, the opposite phenomenon occurs.In general, the flow velocity increases during a transient (the differential pressure between the intake pressure and the exhaust pressure increases). For this reason, the weighted average constant is set to be small. The reason why the characteristic is inversely proportional is that, as shown in the equation shown in step 104, the flow velocity has a square root characteristic with respect to the differential pressure, and the requirement of the weighted average constant is the reciprocal thereof. is there.

In step 107, using the weight constant Nlk retrieved in step 106, step 10
The weighted average is performed on the opening area Aev obtained in step 5, and the result is set as the target EGR valve opening area Aevf, and the process is terminated. Aevf = Aev / 2 ^Nlk + (1-1 / 2 ^Nlk ) × Ae
vf _n-1 The equations in steps 104 and 105 are theoretical states. The actual EGR valve driving device has a target opening area Aev
f is converted into a command value by the actuator characteristics shown in FIG.

FIG. 31 is a flowchart for calculating the target EGR amount, which is calculated at a timing synchronized with the engine rotation or equivalent. In step 111, the cylinder intake air amount Qa
Read c. In step 112, the target EGR rate Me
Calculate gr. In step 113, the equation (Mqe
The target EGR amount Mqec per intake air is calculated by c = Qac × Megr).

In step 114, the intermediate variable Rqec is calculated by the following equation. Rqec = Mqec × KIN × KVOL + Rqec
_n-1 (1−KIN × KVOL) where KIN is a value corresponding to volumetric efficiency _, KVOL = VE / NC
/ VM, VE is the displacement, NC is the number of cylinders, and VM is the intake system volume. In step 115, advance correction processing is performed by the following equation, and the result is set as Tqec. This expression is
This is a simplified version of the normal advance processing.

Tqec = GKQEC × Mqec− (GK
QEC-1) × Rqec _{n-1 In} step 116, the target EGR amount Tq after the advance processing is performed.
ec is calculated by the following equation as the target EGR amount Tqe per unit time.
After that, the process is terminated. Tqek = Tqec × Ne / KCON FIG. 32 is a flow for calculating the target EGR rate Megr, which is executed at a timing synchronized with the engine rotation.

In step 121, the engine speed Ne, the fuel injection amount Qsol, and the engine coolant temperature Tw are read. In step 122, the engine speed Ne and the fuel injection amount Qso
and the basic target EGR from the table shown in FIG.
Calculate the rate Megr. In step 123, a correction coefficient Kegr for correcting the target EGR rate Megr from the table shown in FIG. 34 based on the engine coolant temperature Tw. tw.

In step 124, the equation (Megr =
Megrb × Kegr tw), the target EGR rate M
Calculate egr. In step 125, it is determined whether or not the state of the engine is a complete explosion state. This method will be described later. If it is determined in step 126 that the explosion is complete, the process is terminated as it is. If it is not determined that the explosion is complete, the process proceeds to step 127, where the target EGR rate Megr is set to 0 and the process is terminated.
In this case, the throttle valve 31 is simultaneously controlled to be fully opened.

FIG. 35 is a flow chart for judging a complete explosion of the engine.
It is executed at a timing synchronized with a time such as 10 msec. In step 131, the engine speed Ne is read, and
In step 132, the complete explosion determination slice level NRPMK
If the engine rotation speed Ne is higher than the above, the routine proceeds to step 133.

In step 133, the counter value Tmrkb after the complete explosion determination based on the engine speed Ne and the predetermined time TM
RKBP is compared, and if Tmrkb is larger, the routine proceeds to step 134, where it is determined that the explosion is complete and the processing is terminated. If it is determined in step 132 that the engine rotation speed Ne is lower, the routine proceeds to step 136, where Tmrkb is cleared, and in step 137, the process is terminated because it is not in the complete explosion state.

If it is determined in step 133 that Tmrkb is smaller, the routine proceeds to step 135, where Tmrkb is incremented. Then, the routine proceeds to step 137, where it is determined that the state is not the complete explosion state, and the processing is terminated. In this process, when the engine speed Ne becomes equal to or higher than a predetermined value (for example, 400 rotations or more), and when a predetermined time has elapsed, it is determined that the combustion state is the complete explosion state.

As described above, according to the present invention, by calculating the exhaust pressure from a signal such as an air flow meter, the durability and the transient response can be improved without increasing the cost. By compensating the pressure estimation, it is possible to correct the exhaust pressure based on the injection timing, ignition timing, swirl control valve opening, and the ratio of the intake flow velocity to the opening area.
The estimation accuracy is improved, and the control accuracy of EGR control and the like is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration and functions of the invention according to claim 1 ;

FIG. 2 is a block diagram showing the configuration and functions of the invention according to claims 2 to 4 ;

FIG. 3 is a function of an intake pressure estimation according to an embodiment of the present invention;
Block Diagram.

FIG. 4 is a diagram showing a system configuration according to an embodiment of the present invention.

FIG. 5 is a flowchart of a routine for calculating an intake air flow rate.

FIG. 6 is a diagram showing a relationship between an output voltage of an air flow meter and an intake air flow rate .

FIG. 7 is a flowchart of a routine for calculating a cylinder intake air amount.

FIG. 8 is a flowchart showing a cylinder cycle delay process.

FIG. 9 is a flowchart of a routine for calculating the exhaust system pressure.

FIG. 10 is a table in which an exhaust temperature correction coefficient according to a fuel injection amount is set.

FIG. 11 is a table in which exhaust temperature correction coefficients according to the intake air temperature are set.

FIG. 12 is a table in which an exhaust gas temperature correction coefficient based on a previous exhaust pressure estimation value is set.

FIG. 13 is a table in which exhaust temperature correction coefficients according to fuel injection timing are set.

FIG. 14 is a diagram illustrating a system configuration according to a second embodiment of the present invention.

FIG. 15 is a flowchart showing a cylinder cycle delay process.

FIG. 16 is a flowchart of a routine for calculating the exhaust system pressure.

FIG. 17 is a table in which exhaust temperature correction coefficients according to the swirl control state are set.

FIG. 18 is a flowchart showing a cylinder cycle delay process.

FIG. 19 is a flowchart of a routine for calculating an exhaust system pressure in another embodiment.

FIG. 20 is a table in which exhaust temperature correction coefficients according to the swirl control state are set.

FIG. 21 is a flowchart of a routine for calculating intake pressure according to another embodiment of the present invention.

FIG. 22 is a table in which basic values for volume efficiency equivalent values are set.

FIG. 23 is a flowchart of a routine for calculating a basic fuel injection amount.

FIG. 24 is a table in which basic fuel injection amounts are set.

FIG. 25 is a flowchart of a routine for calculating a maximum fuel injection amount.

FIG. 26 is also a table in which a limit excess air ratio is set.

FIG. 27 is a flowchart of a routine for similarly setting a fuel injection amount.

FIG. 28 is a flowchart of a routine for calculating an EGR valve opening area in the same manner.

FIG. 29 is a table in which weight constants for calculating a weighted average of the EGR valve opening area are set.

FIG. 30 is a table showing the relationship between the target opening area and the number of steps of the step motor.

FIG. 31 is a flowchart of a routine for similarly setting a target EGR amount.

FIG. 32 is a flowchart of a routine for similarly setting a target EGR rate.

FIG. 33 is a table in which target EGR rates are also set.

FIG. 34 is a table in which a water temperature correction coefficient of the target EGR rate is set.

FIG. 35 is a flowchart showing a complete explosion determination routine.

[Explanation of symbols]

 Reference Signs List 5 diesel engine 6 fuel injection nozzle 7 fuel injection pump 11 vacuum pump 13 control unit 16 air flow meter 17 rotation speed sensor 18 lever opening sensor 19 water temperature sensor 21 swirl control valve 31 throttle valve 34 lift sensor

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-6-229324 (JP, A) JP-A-7-158479 (JP, A) JP-A-5-180057 (JP, A) JP-A-7- 332139 (JP, A) JP-A-2-157438 (JP, A) JP-A-8-10069 (JP, A) JP-A-8-121233 (JP, A) JP-A-1-315635 (JP, A) Japanese Unexamined Patent Publication No. Hei 4-153547 (JP, A) Japanese Unexamined Patent Publication No. Hei 1-27-16473 (JP, A) Japanese Unexamined Patent Publication No. Hei 8-284735 (JP, A) Japanese Unexamined Patent Publication No. Sho 64-53032 (JP, A) Japanese Unexamined Patent Publication No. Hei 9-170480 (JP, A) JP 7-13454 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/00-45/00 F02D 29/00-29/06 F02D 9 / 00-28/00 F01N 9/00-11/00 F01N 3/00-3/38 F02B 31/00-31/02

Claims (4)

(57) [Claims] A fuel injection amount detector for detecting an amount of fuel injected into the engine; an intake air temperature detector for detecting a temperature of air taken into the engine; and detecting an injection timing of the fuel. Fuel injection timing detecting means, intake air flow rate detecting means for detecting the flow rate of the intake air, engine rotational speed detecting means for detecting the rotational speed of the engine , and calculating a basic exhaust temperature based on the fuel injection amount; Basic exhaust
The intake air temperature and the exhaust pressure and fuel estimated previously
Calculate exhaust temperature from cylinder by correcting with injection timing
And the cylinder determined from the intake air flow rate and the engine speed
Based on the exhaust gas flow from the cylinder and the exhaust gas temperature from the cylinder.
An exhaust system pressure estimating device for an internal combustion engine, comprising: exhaust system pressure estimating means for estimating exhaust pressure. And the fuel injection amount detecting means for detecting the amount of fuel injected to 2. A engine, and intake air temperature detecting means for detecting a temperature of air sucked into the engine, provided in an intake system of the engine a swirl control condition detecting means for detecting the swirl control state by the swirl control valve, and the intake air flow rate detecting means for detecting the flow rate of the intake air, and the engine rotational speed detecting means for detecting a rotational speed of the engine, the fuel injection amount The basic exhaust temperature is calculated based on the basic exhaust temperature.
The intake air temperature, the exhaust pressure and the sw
To control the exhaust temperature from the cylinder.
Calculated from the intake air flow rate and the engine speed.
And the exhaust temperature from the cylinder.
An exhaust system pressure estimating means for estimating the exhaust pressure based on the exhaust system pressure. 3. The method according to claim 1, wherein the correction of the basic exhaust gas temperature based on the swirl control state is performed by a correction coefficient set based on the opening degree of the swirl control valve and the engine speed.
An exhaust system pressure estimating device for an internal combustion engine according to claim 2 . Wherein correction by the swirl control state of the basic exhaust gas temperature is carried out by the correction coefficient which is set based on the swirl flow velocity equivalent value calculated from the degree of opening of the intake air flow rate and the engine rotational speed and the swirl control valve Claims characterized by the following :
3. The exhaust system pressure estimation device for an internal combustion engine according to 2 .