GB2329040A

GB2329040A - Apparatus for estimating pressure in intake system and exhaust system of internal combustion engine

Info

Publication number: GB2329040A
Application number: GB9825391A
Authority: GB
Inventors: Hiroyuki Itoyama; Hiroyuki Aizawa
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1996-06-03
Filing date: 1997-06-03
Publication date: 1999-03-10
Anticipated expiration: 2017-06-03
Also published as: GB2329040B; GB9825391D0

Abstract

The pressure in the exhaust system and in the intake system is estimated on the basis of engine speed, intake air flow, and intake air temperature. The estimation of the pressure in the exhaust system additionally takes into account (a) fuel injection volume and (b) fuel injection timing or swirl control state. The estimated pressures can be used in the control of EGR.

Description

APPARATUS FOR ESTIMATING PRESSURE IN INTAKE SYSTEM AND EXHAUST SYSTEM OF INTERNAL COMBUSTION ENGINE The present invention relates to the estimation of pressures in intake and discharge systems of an internal combustion engine which are required for controlling EGR (exhaust gas recycling).

In conventional methods of detecting pressures in intake and exhaust systems of internal combustion engine, it is popular to provide a sensor for directly detecting the pressures. Further, there is a technique disclosed in Japanese Patent Application Laid-Open No. 8-284735, in which the pressure is estimated from the output from an air flow meter and the like.

However, in the case that a sensor is provided in the above manner, high cost is required, and in the case of a sensor for detecting the exhaust pressure, the sensor is exposed to a high temperature atmosphere, durability is a very severe problem. In the case of securing durability, the time constant of the sensor is extremely large and an accurate value can not be displayed in a transient state, so that it is difficult to apply feedback control.

Further, since the exhaust temperature affecting to the exhaust pressure is changed by parameters such as injection timing and/or air flow within a cylinder, the above described technique disclosed in Japanese Patent Application Laid-Open No. 8-284735 can not solve this problem.

The present invention is made by taking the above described conventional problems into consideration.

It would be desirable to be able to optimize control of a volume for injecting fuel oil and an amount of EGR. It would also be desirable to be able to provide apparatus for accurately estimating pressures in an intake system and an exhaust system of an internal combustion engine without using a pressure sensor.

In accordance with one aspect of the present invention, there is provided an internal combustion engine having means for detecting engine speed; means for detecting intake air flow; means for detecting intake air temperature; and means for estimating the pressure in the exhaust system and/or the intake system on the basis of the engine speed, intake air flow, and intake air temperature, wherein the estimation of the pressure in the exhaust system takes into account fuel injection volume and fuel injection timing or the swirl control state of a swirl control valve.

Furthermore, in accordance with another aspect of the invention (as shown in Fig. 35), there is provided an estimating apparatus for estimating a pressure in an exhaust system for an internal combustion engine comprising: injection volume detecting means for detecting an injecting amount of a fuel injected to the engine; intake air temperature detecting means for detecting a temperature of an air sucked to the engine; fuel injection timing detecting means for detecting an injection timing of the fuel; intake air flow detecting means for detecting a flow of intake air; engine speed detecting means for detecting an engine speed; and exhaust system pressure estimating means for estimating a pressure in e. exhaust system on the basis of the fuel injection volume., the intake air temperature, the fuel injection timing, the intake air flow and the engine speed.

Since a calorific value is determined by a volume :

detected by the fuel injection volume detecting means, a standard exhaust temperature can be defined. Since the combustion temperature is changed due to the change of the temperature of the intake, the temperature of the exhaust gas is changed. Further, when the injection timing is advanced (an advance value is made large) in the injection timing of the fuel, combustion state is improved and the temperature in discharging the cylinder is lowered so that the temperature in the exhaust gas. is lowered, while when the injection timing is delayed, the temperature in the exhaust gas rises in the inverse manner of the above case.

Thus, the temperature in the exhaust gas can be accurately estimated on the basis of the fuel injection volume, the temperature in the intake air, and the fuel injection timing.

In contrast to this, the exhaust air flow volume can be determined on the basis of the intake air flow volume and the engine speed. In a stationary state, the intake air volume (per unit tile) substantially equals to an exhaust volume discharged from the cylinder: however, in a transient states is different due to the volume and the like in the intake system.

Thus, after the exhaust volume per cycle discharged from the cylinder is determined on the basis of the intake air flow volume and the engine speed, the exhaust volume is again converted to the exhaust flow volume ( per unit time discharged from the cylinder by using the engine speed so that the exhaust flow volume can be accurately calculated.

Then, the pressure in the exhaust gas can be determined by using Bernoulli's equation on the basis of the estimated temperature in the exhaust gas and calculated volume of the exhaust flow.

the exhaust system pressure estimating means calculates the standard exhaust temperature on the basis of the X fwel~ injection vole, calculates the temperature in the exhaust ges discharged from the cylinder by adjusting the standard exhaust temperature by the temperature in the intake air, the preceding estimated pressure in the exhaust system, and the fuel injection timing, and estimates the pressure in the exhaust system on the basis of the exhaust gas flow volume determined by the intake air volume and the engine speed and the temperature in the exhaust yas discharged from the cylinder.

In accordance with this aspect, as mentioned above, the standard exhaust temperature is determined on the basis of the - - fhel injection value and the temperature in the exhaust qat is estimated by adjusting the standard exhaust temperature by the intake air volume, the preceding estimated pressure in the exhaust system,and the fuel injection timing.

Since, due to abiabatic change, the temperature in the exhaust gas rises at a predetermined rate when the pressure in the exhaust system rises, adjustment by using the preceding estimated pressure in the exhaust system is performed at the same time, thereby estimating the temperature in the exhaust temperature more precisely.

The pressure in the exhaust system can be estimated on the basis of the volume of the exhaust flow determined by the intake air volume and the engine speed and the temperature in the exhaust Further, in accordance with another aspect of the invention (as shown in Fig.36), there is provided an estimating apparatus for estimating a pressure in an exhaust system for an internal combustion engine comprising: ~ injectipft uolMe detecting means for detecting an injection amount of a fuel injected to the engine; intake air temperature detecting means for detecting a temperature of air sucked to the engine: swirl control state detecting means for detecting a swirl control state by a swirl control valve provided in an w.t ake system of the engine; intake air flow detecting means for detecting a flow of the intake airt engine speed detecting means for detecting an engine speed; and exhaust system pressure estimating means for estimating a pressure in Uie exhaust system on the basis of the * U!el injection vol Wnt, the intake air temperature, the swirl control state, the intake air flow and the engine speed.

Since swirl strength is controlled by the swirl control valve in the structure provided with the swirl control valve in the intake air system, by which combustibility is changed, the temperature in the exhaust 31s is changed. In this structure, the temperature in the exhaust gas is estimated by detecting the swirl control state by the swirl control valve and taking the swirl control state in addition to the volume for injecting fuel oil and the temperature in the intake air into consideration. The temperature in the exhaust gas may be estimated by adding the injection timing as the element for estimation in this case, the accuracy in estimation is further improved.

The pressure in the exhaust system can be accurately estimated on the basis of the temperature in the exhaust estimated in such an accurate manner, the temperature in the intake air and the exhaust flow volume determined by the engine speed.

the exhaust system pressure estimating means calculates the standard exhaust temperature on the basis of the fuel injection volume, calculates the temperature in the exhaust gas discharged from the cylinder by adjusting the standard exhaust temperature. by the temperature in the intake air, the preceding estimated pressure in the exhaust system and the swirl control state and estimates the pressure in the exhaust system on the basis of the exhaust gas flow volume determined by the intake air volume and the engine speed and the temperature in the exhaust discharged from the cylinder.

In accordance with this aspect, the standard exhaust temperature in accordance with the calorific value is determined by the fuel injection invention vol at the time of fuel injection and the temperature in the exhaust sas is accurately estimated by adjusting the standard exhaust temperature by the intake air temperature, the preceding estimated pressure in the exhaust system and the swirl control state.

the adjustment by using the swirl control state in the standard exhaust temperature is performed by an adjustment coefficient set by the opening degree of the swirl control valve and the engine speed.

When the opening degree of the swirl control valve is large, the swirl gives only a small effect to all the range in changing the engine speed; however, when the opening degree of the swirl control valve is small, in the low speed range, the combustibility is improved due to suitable swirl generation so that the temperature in the exhaust gas falls and in contrast with this, in the high speed range, the combustibility is reduced due to excess swirl strength and the intake air volume to the cylinder is reduced by throttling effect so that the temperature in the exhaust gas is increased.

Then, the adjustment coefficient of the temperature in the exhaust sas is set on the basis of the opening of the swirl valve and the engine speed and the temperature in the exhaust rs is adjusted by using the adjustment coefficient, thereby improving the accuracy in estimating the temperature in the exhaust sas.

the adjustment by using the swirl control state in the standard exhaust temperature is performed by an adjustment coefficient set on the basis of a swirl flow speed correspondence value calculated by the intake air volume, the opening degree of the swirl control valve and the engine speed.

In accordance with this aspect, the intake air volume at a time of being sucked to the cylinder can be calculated by using the intake air volume and the engine speed and the intake air volume to the cylinder is divided by the opening degree of the swirl control valve so that the value corresponding to the swirl flow speed can be determined. when the swirl flow speed is a certain value, the combustibility is best improved tolower the temperature in the exhaust gas, and when the swirl flow speed is over the certain value or below the certain value, the combustibility tends to be reduced to raise the temperature in the exhaust Then, the adjustment coefficient of the temperature in the exhaust gas is set on the basis of the swirl flow speed correspondence value calculated by the intake air volume, the opening of the swirl valve, and the engine speed, and the temperature in the exhaust as is adjusted by using the adjustment coefficient, thereby further improving the accuracy in estimating the temperature in the exhaust Still further, in accordance with another aspect of the invention(as shown in Fig.37), the present invention provides an estimating apparatus for estimating a pressure in an intake system for an internal combustion engine comprising: intake air flow volume detecting means for detecting an air flow volume sucked to the engine; engine speed detecting means for detecting an engine speed; intake air temperature detecting means for detecting a temperature of the intake air; and intake system pressure estimating means for estimating a pressure in an intake system on the basis of the intake air flow volume, the engine speed,and the intake air temperature.

wince the volume of (mass) air at a intake stroke to the cylinder is determined on the basis of the intake air flow volume and the engine speed and a value corresponding to volumetric efficiency in the case of constant temperature can be determined on the basis of the intake air volume to the cylinder and the engine speed, a value corresponding to volumetric efficiency in accordance with the temperature in the intake air can be determined by adjusting the value by the temperature in the intake air.

Then, since the volume of air sucked to the cylinder is determined by the value corresponding to volumetric efficiency and the cylinder volume, the pressure in the intake system can be estimated by using an equation of state on the basis of the volume and the temperature in the intake air.

In accordance with a preferred aspect the intake system pressure estimating means calculates an intake air volume per cylinder on the basis of the intake air flow volume and the engine speed, calculates a standard value corresponding to volumetric efficiency on the basis of the intake air volume per cylinder and the engine speed, calculates a value corresponding to volumetric efficiency by adjusting the standard volumetric efficiency correspondence value by the intake air temperature, and estimates the pressure in the intake system on the basis of the intake air volume per cylinder and the volumetric efficiency correspondence value by using a following equation: Pm = Qac/Kin X TA X RA X VCYL, in which Pm means a pressure in the intake system, Qac means an intake air volume per cylinder, Kin means a corresponding value to a volumetric efficiency, TA means temperature in a standard state, RA means a constant of air and gastand VCYL means a cylinder volume.

The nature, principle, and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, In the accompanying drawings: Fig.l is a standard block diagram of an EGR control apparatus for an internal combustion engine; Fig.2 is a flow chart showing procedures for calculating a standard ei injection worse; Fig.3 is a drawing showing a map for the standard rues injection volume; Fig.4 is a flow chart showing procedures for setting a fuel injection timing; Fig.5 is a drawing showing a map for the injection timing; Fig.6 is a flow chart showing procedures for

calculating a #opening area of the EGR valve; Fig.7 is a graph showing a relation between a value corresponding to an EGR flow speed and a weight constant; Fig.8 is a graph showing an actuator characteristic; Fig.9 is a flow chart showing procedures for calculating a target EGR value; Fig.10 is a flow chart showing procedures for calculating an intake air volume sucked to a cylinder; Fig.ll is a flow chart showing procedures for calculating an intake air volume; Fig.12 is a graph showing a table for conversion between a voltage and an intake air volume; Fig.13 is a flow chart showing procedures for calculating a target EGR rate; Fig.14 is a graph showing an example of a map for a target EGR rate; Fig.15 is a graph showing an example of a table for adjustment coefficient between a target EGR rate and a water temperature; Fig.16 is a flow chart showing procedures for determining whether or not the +el is completely burned; Fig.17 is a flow chart showing procedures for calculating an injection timing error adjusting coefficient; Fig. 18 is a graph showing an example of a table between an injection timing error and an adjustment rate; Fig.19 is a standard block diagram of a control apparatus for an internal combustion engine; Fig.20 is a systematic view in relation to the control apparatus; - Fig.21 is a flow chart showing procedures for calculating an intake EGR value sucked to the cylinder; Fig.22 is a flow chart showing procedures for calculating a maximum volume for injecting fuel oil; Fig.23 is a graph showing a table for limit air excess rate in a non-oversupply; Fig.24 is a graph showing a table for a relation between the limit air excess rate and a pressure adjusting value; Fig.25 is a flow chart showing procedures for setting a volume for injecting fuel oil; Fig.26 is a flow chart showing procedures for calculating (adjusting) a target EGR rate; Fig.27 is a graph showing a table for a setting value of an accelerator opening degree; Fig.28 is a flow chart showing a second example of procedures for calculating (adjusting) a target EGR rate; Fig.29 is a graph showing a table for an adjustment coefficient; Fig.30 is a flow chart showing a third example of procedures for calculating (adjusting) a target EGR rate; Fig.31 is a graph showing a map for an adjustment coefficient; Fig.32 is a flow chart showing a fourth example of procedures for calculating (adjusting) a target EGR rate; Fig.33 is a graph showing a map for an adjustment coefficient; Fig.34 is a flow chart showing a fifth example of procedures for calculating (adjusting) a target EGR rate; Fig.35 is a standard block diagram of an estimation apparatus in an exhaust system for an internal combustion engine in accordance with the present invention; Fig.36 is a standard block diagram of an estimation apparatus for estimating a pressure in an exhaust system for an internal combustion engine in accordance with the present invention; Fig.37 is a standard block diagram of an estimation apparatus for estimating a pressure in an intake system for an internal combustion engine in accordance with the present invention; Fig.38 is a drawing showing a total structure of an estimation apparatus for estimating pressures in intake and exhaust systems for an internal combustion engine in accordance with the present invention; Fig. 39 is a flow chart showing procedures for operating a delay in cylinder cycles; Fig.40 is a flow chart showing procedures for calculating an exhaust pressure; Fig.41 is a graph showing a table between an operation value for a volume for injecting fuel oil cycle and a standard exhaust air temperature; Fig.42 is a graph showing a table between an operation value for an intake air temperature cycle and an adjustment coefficient for an exhaust air temperature; Fig.43 is a graph showing a table between an exhaust air pressure calculated in a preceding time and an adjustment coefficient for an exhaust air temperature; Fig.44 is a graph showing a table between an operation value for an actual injection timing cycle and an adjustment coefficient for an exhaust air temperature; Fig.45 is a drawing showing a second example of a total structure of an estimation apparatus for estimating a pressure in intake and exhaust systems for an internal combustion engine in accordance with the present invention; Fig.46 is a flow chart showing procedures for operating a delay in cylinder cycles; Fig.47 is a flow chart showing procedures for calculating an exhaust pressure; Fig.48 is a graph showing a table between an engine speed and an adjustment coefficient for an exhaust air temperature; Fig.49 is a flow chart showing procedures for operating a delay in cylinder cycles; Fig.50 is a flow chart showing procedures for calculating an exhaust air pressure; Fig.51 is a graph showing a table between a value corresponding to a swirl flow speed and an adjustment coefficient for an exhaust air temperature; Fig.52 is a flow chart showing procedures for calculating an intake air pressure; Fig.53 is a graph showing a table for a standard value corresponding to volumetric efficiency with respect to an engine speed and an intake air volume to a cylinder; Fig.54 is a flow chart showing procedures for calculating a maximum volume for injecting fuel oil; and Fig.55 is a graph showing a table between an engine speed and a value corresponding to a limit air excess rate.

A control apparatus for controlling EGR in an internal combustion engine will be explained below with reference to the drawings.

Fig. 1 is a block diagram which shows a control structure.

First, the structure will be explained. The EGR control apparatus in accordance with the present invention comprises: driving condition detecting means 1 for detecting engine speed, the opening of an accelerator (accelerator opening degree), and an engine operating condition such as a water temperature; injection volume of fuel oil calculating means 2 for calculating a nominal or Standard" injection volume as a standard amount from outputs from the driving condition detecting means 1; target injection timing setting means 3 for setting a target fuel injection timing from outputs from the driving condition detecting means 1 and the volume calculating means 2; actual injection timing detecting means 4 for detecting an actual fuel injection timing; standard target EGR rate calculating means 5 for calculating nominal or standard target EGR rate from outputs from the driving condition detecting means 1 and the volume calculating means 2; target EGR rate adjustment amount calculating means 6 for calculating an amount of adjustment of the target EGR rate from outputs from the volume calculating means 2, the target injection timing setting means 3, and the actual injection timing detecting means 4; target EGR rate setting means 7 for setting an adjusted target EGR rate from outputs from the standard target EGR rate calculating means 5 and the target EGR rate adjustment amount calculated means 6; and EGR valve control means 8 for controlling an EGR valve according to the output from the setting means 7.

Next, an operation of the EGR control apparatus having the above structure will be explained.

Figs. 2 to 18 show flow charts in accordance with a preferred embodiment and tables and maps required for them.

Fig. 2 is a flow chart for calculating a "standard" volume ~~~~~~~~~~~~ for injection and this operation is performed in a synchronized timing with the engine speed by making a signal from a sensor for a crank angle a trigger. This flow chart corresponds to the standard injecti volume calculating means In a step S21, an engine speed Ne which is calculated on the basis of a cycle of a signal from a sensor for sensing a crank angle is read in.

In a step S22, an opening degree Cl of an accelerator which is detected on the basis of a signal from a sensor for sensing an opening degree of the accelerator is read in.

In a step S23, a standard volume for injecting fuel oil Mqdrv is set by the engine speed Ne and the accelerator opening degree Cl with reference to a map for a standard volume for injecting fuel oil as shown in Fig.3.

In a step S24, various adjustments including a water temperature adjustment are performed with respect to the standard volume for injecting fuel oil Mqdrv, thereby obtaining an adjusted standard volume for injecting fuel oil Qsoll,and t'heoperation is completed.

Fig.4 is a flow chart for setting a fuel injection timing.

In a step S41, the engine speed Ne and the adjusted volume for injecting fuel oil Qsoll are read in and in a step S42, a standard fuel injection timing Mit is calculated from, for example, a map for an injection timing as shown in Fig.5.

In a step S43, various adjustments are performed to the standard fuel injection timing Mit, thereby setting a final taraet iniection timina Itsol and theoPeration is completed.

Fig.6 is a tiow cnart tor caicujating a Opening area of the EGR valve.

In a step S61, a target EGR amount is calculated. This method is described hereinafter.

In a step S62, an intake pressure Pm is read in, and in a step S63, an exhaust pressure Pexh is read in.

In a step S64, a value Cqe corresponding to an EGR flow speed is calculated by using the shown equation (Cqe = (K(Pexh - Pm) )1,2,in which K is a constant ), and in a step S65, an opening area of the EGR valve Aev is calculated from the shown equation (Aev = Tqek/Cge) by using a required EGR amount Tqek and the EGR flow speed corresponding value Cqe.

In a step S66, a weight constant Nlk for performing a weighted average operation of the opening area of the EGR valve described hereinafter is searched by the EGR flow speed corresponding value Cqe by using a table shown in Fig.7. In this case, the weight constant Nlk is set large when the EGR flow speed corresponding value Cqe is small and the weight constant Nlk is set small when the EGR flow speed corresponding value Cqe is large. This is because when the flow speed is small, the required opening area should be changed largely so that it is difficult to obtain a stable operation even if the flow speed is slightly changed so that the weighted average value is set to be much (heavy).

When the flow speed is large, an inverse phenomenon occurs, that is, since the flow speed generally becomes large (a differential pressure between an intake pressure and an exhaust pressure is large) in a transition period, it is desirable not to perform a weighted average operation due to a following characteristic in a transition period so that the weighted average constant is set to be small. In this case, a characteristic like an inverse proportion is applied because the flow speed has a characteristic of a square root with respect to the differential pressure as shown in the equation in the step S64 so that the weighted average constant is required to be an inverse number thereof.

In a step S67, a weighted average operation is performed to the opening area Aev determined in the step S65 by the following equation by using the weight constant Nlk searched in the step S66, the result is determined as a target EGR valve opening area Aevf,and the operation is completed: Aevf = Aev/2Nlk + (1 - 1/2Nlk) X Aevfn-1 In this case, the equations in the steps S64 and S65 are those in a theoretical state. To an actual EGR valve driving apparatus, the target opening area Aevf is converted to a command value by an actuator characteristic shown in Fig.8.

Fig.9 is a flow chart for calculating the target EGR amount and the amount is calculated at a timing of the engine revolution or the corresponding timing.

In a step S91, an amount Qac of an intake air to the cylinder is read in.

In a step S92, A target EGR rate Megr is calculated.

In a step S93, a target EGR amount Mgec for an intake stroke is calculated by using the shown equation (Mqec = Qac X Megr).

In a step S94, an intermediate variable Rqec is calculated by using the following equation: Rqec = Mqec X KIN X KVOl + Rqecnl - KIN X KVOl), in which KIN means a volumetric efficiency corresponding and the calculation is performed at a timing corresponding to the engine revolution.

In a step S101, an intake air amount QasO is read in.

In a step 5102, the engine speed Ne is read in.

In a step S103, the intake air amount QasO is converted into an intake air amount QacO per intake stroke by using the following equation: QacO = (QasO/Ne) X KC, in which KC is a constant.

In a step 5104, a delay operation in correspondence to a feed delay from an air flow meter to a collector is performed by using the following equation. Accordingly, a value QaaOn,L which corresponds to a QacO L times before is read out and this is defined as Qacn.

Qacn = QacOnL in which L is a constant.

In step S105, a delay operation in correspondence to the dynamics within the collector is performed by using the following equation, thereby obtaining an intake air amount to the cylinder Qac and the operation is completed.

Qac = Qacnl X (1 - KV) + Qacn X KV, in which KV is a constant.

Fig.11 is a flow chart for calculating the intake air amount QasO, which is calculated every 4 milliseconds.

In a step S111, an output voltage of detecting means for detecting the intake air amount of the air flow meter and the like is read in, in step S102, detecting means as shown in Fig.12 is converted by using a characteristic table (a table for converting between voltage and intake air amount), and in step 103, QasO is determined by an averaging operation so that the operation is completed.

Fig.13 is a flow chart for calculating target EGR rate Megr, which is calculated at each timing corresponding to the engine speed.

At first, in a step S131, the engine speed Ne, the volume for injecting fuel oil Qsoll, a engine coolant temperature Tw, a target injection timing Itsol,and an actual injection timing Itist are read in. The actual injection timing Itist is obtained by detecting a starting time of lifting or an average between a starting time and an ending time by using an output of a sensor for sensing a needle valve lifting provided in a injection nozzle.

In a step S132, a map as shown in Fig.14 is searched from the engine speed Ne and the volume for injecting fuel oil Qsoll and a standard target EGR rate Megrb calculated.

In step S133, Kegr-tw is determined by searching a coefficient table for adjusting the target EGR rate from Tw with respect to the engine water temperature, for example, as shown in Fig.15. In a step S134, an ignition timing error adjusting coefficient Kegrit is calculated. A calculating method will be explained hereinafter with reference to Fig.17 and 18. Ae

target EGR rate Megr is calculated by using an equation as shown in a step S135. Inastep 5136, whether or not the engine is in a state of complete burn; is determined. This method will be explain hereinafter by using Fig.16. When in the step S136, complete burning is determined, the operation is finished as it is, and when . complete burning is not

determined, in a step 5137, theltarget EGR rate Megr is set to 0 and the operation is finished.

Fig.16 is a flow chart for determining complete burning in the engine and the calculation is performed every 10 milliseconds.

At first, in a step S161, the engine speed Ne is read in and in a step S162, the value is compared with a complete burning determination slice level NRPMK and when the value Ne is larger, the step is advanced to a step S163. In the step S163, the value is compared with a counter Tmrkb after determination of complete burning by revolution and a predetermined time period TMRKBP and when the value is larger, the step is advanced to a step S164 and the operation is finished as determining complete burning. When the value Ne is smaller in the step S162, the step is advanced to a step S166, the value Tmrkb is cleared and the operation is finished as determining not-complete burning. In the step S163, when the value Tmrkb is smaller, the step is advanced to a step 5165, the value Tmrkb is increased to advance to a step S167 and the operation is finished as determining not-complete burning.

In this operation, the determination in which complete burning is determined when the engine speed becomes equal to or more than a predetermined value (for example, not less than 400 revolution per minute) and a predetermined time period has passed is performed.

Fig.17 is a flow chart for calculating an injection timing error adjusting coefficient Kegrit.

At first, in a step S171, a difference Dit between an actual injection timing Itist and a target injection timing Itsol is calculated. In a step S172, madjustment rate Regd with respect to the injection timing error is set, for example, by searching from a table as shown in Fig.18. In a step 5173, the ignition timing error adjusting coefficient Kegrit is calculated from the value Regd and the volume for injecting fuel oil Qsoll by using a equation shown in the drawing. In a step S174, the operation is completed by limiting the value Kegrit to a range between 0 and 1. This limiting is for the purpose of not being over the standard target value even when the adjustment gain is increased by increasing the injection amount.

As explained above, since the adjustment sensitivity can be changed with respect to the load by changing the adjustment rate by the load such as the injection amount when the EGR is adjusted with respect to the difference between the target value and the actual value of the injection timing, the required EGR can be faithfully supplied in correspondence to the injection timing error value. Further, the control pfot re is effectively applied to a system having a high exhaust emission sensibility with respect to a range of required EGR amount, the EGR and the injection timing.

Next, an embodiment of a control apparatus for an internal combustion engine will be explained.

Fig.20 is a system drawing in connection with the control apparatus for the internal combustion engine.

A fuel injection pump 51 is provided with a control sleeve (not shown) as a volume for injecting fuel oil control means inside thereof, and the control sleeve is driven through a motor and the like in response to a signal from a control unit 53 so that the volume for injecting fuel oil can be controlled.

An EGR control valve 52 is provided in an EGR passage communicating the exhaust system for the engine with the intake system, and is driven by a signal from the control unit 53 through an electromagnetic valve for controlling a negative pressure in the case of a negative pressure operating type or through a stepping motor in the case of a direct drive type, thereby serving as an EGR amount control means so as to control the EGR amount to a target EGR rate.

In the control unit 53, signals from various kinds of driving state detecting means are input.

Concretely, the signals are . crank angle 54, accelerator opening degree - . 55, air flow 56, EGR flow 57, water temperature .58, intake air pressure 59, and vehicle speed 60.

In this, the control unit 53 performs a calculating operation by a built-in micro computer in accordance with a below described flow chart and controls the fuel injection pump 51 and the EGR control valve 52.

Fig.21 is a flow chart for calculating an intake EGR amount to cylinder (an EGR amount sucked to the cylinder) and the calculation is performed at a corresponding timing to the engine revolution.

In a step S211. an EGR amount Qe detected on the basis of the signal from the EGR flow meter 57 is read in. The EGR amount Qe may be obtained by a suitable estimating means.

In a step S212, the engine speed Ne is read in.

in a step S213, the EGR amount Qe is converted into an EGR amount Qec per 1 intake stroke in accordance with the following equation: Qecn = (Qe/Ne) X KC, in which KC is a constant.

In a step S214, a delay operation corresponding toehe dynamics in the collector is performed, thereby obtaining the intake EGR amount to cylinder Qec, and the operation is completed.

Qec = Qecnl X (1 - KV) + Qecn X KV, in which KV is a constant.

Fig.22 is a flow chart for calculating a maximum volume for injecting fuel oil and the calculation is performed at a timing corresponding to the engine revolution. The flow chart corresponds to maximum volume for injecting fuel oil calculating means.

In a step S221, the engine speed Ne is read in.

in a step S222, a limit air excess rate (a rich limit) Klaabn is set from the engine speed Ne with reference to a table for the limit air excess rate in a no-supercharging state as shown in Fig.23.

In a step S223, an intake air pressure Pm is read in.

In a step S224, a limit air excess rate pressure adjusting value Klambp is set from the intake air pressure Pm with reference to a table for the limit air excess rate pressure adjusting value as shown in Fig.24.

In a step S225, the limit air excess rate Klambn is adjusted by the pressure adjusting value Klambp thereof in accordance with the following equation so that a final limit air excess rate Klamb is calculated: Klamb = Klambn X Klambp.

In this case, the table in Fig.24 is on the basis of a characteristic that the limit air excess rate (rich limit) becomes worse because the air utilization rate is reduced by that a complete penetration force of the fuel spray is relatively reduced when the air density becomes high together with increasing the intake air pressure Pm.

In a step S226, the intake air amount to cylinder Qac in accordance with the flow chart in Fig.10 is read in.

In a step S227, the intake EGR amount to cylinder Qec in accordance with the flow chart in Fig.21 is read in.

In a step S228, a maximum volume for injecting fuel oil Qful is calculated on the basis of the intake air amount Qac, the intake EGR amount to cylinder Qec and the limit air excess rate Klamb by using the following equation and the operation is completed: Qful = (Qac + Qec X KOR)/(Klamb X 14.7), in which KOR is a constant.

Fig.25 is a flow chart for setting the volume for injecting fuel oil and the setting is performed at a timing corresponding to the engine revolution. This flow chart corresponds to the volume for injecting fuel oil setting means.

In a step S251, the standard volume for injecting fuel oil Qsoll in accordance with the flow chart in Fig.12 and the maximum volume for injecting fuel oil Qful in accordance with the flow chart in Fig.22 are read in and these values are compared with each other.

As a result of comparison, when Qsoll < Qful, the step is advanced to a step S252, the Qsoll is selected, the volume for injecting fuel oil Qsol = Qsoll is set and the operation is completed.

Inversely, when Qsoll 2 Qful, the step is advance to a step S253, the Qful is selected, the volume for injecting fuel oil Qsol = Qful is set and the operation is completed.

As described above, a smaller one is set to a final volume for injecting fuel oil Qsol by comparing the standard volume for injecting fuel oil Qsoli with the maximum volume for injecting fuel oil Qful. The volume for injecting fuel oil to the engine is controlled by the fuel injection pump in accordance with the final volume for injecting fuel oil Qsol.

Fig.26 is a flow chart for calculating (adjusting) the target EGR rate and the calculation is performed at a timing corresponding to the engine revolution. The flow chart corresponds to the target EGR rate adjusting means.

In a step S261, an opening degree Cl of the accelerator is read in.

In a step S262, the engine speed Ne is read in.

In a step S263, an accelerator opening degree setting value Clegrc is determined from the engine speed Ne with reference to a table for the accelerator opening degree setting value as shown in Fig.27. In this, the Clegrc is set smaller the lower the engine revolution is.

In a step S264, the accelerator opening degree C1 is compared with the setting value thereof Clegrc.

As a result of comparison, when C1 < Clegrc, in a step

S265, the # target EGR rate Megr = Megrbils set and the operation is completed.

Inversely, when C1 2 Clegrc, in a step S266, the

tttarget EGR rateMegr - 0 is set and the operation is completed.

When the#target EGR rate Megr is set in the above manner, the EGR amount is controlled by the EGR valve so as to obtain

the# target EGR rate Megr. In this control, when the accelerator opening degree Cl is equal or more than the

setting value clegrc, the#target EGR rate Megr is adjusted to O and the EGR is stopped.

Fig.28 shows a second example of a flow chart for calculating (adjusting) a target EGR rate and is performed in place of the flow chart in Fig.26.

In a step S281, a standard volume for injecting fuel oil Nqdrv which is determined by the engine speed Ne and the accelerator opening degree C1 in the flow chart in Fig.2 is read in.

In a step S282, a final volume for injecting fuel oil Qsol in accordance with the flow chart in Fig.25 is read in.

In a step S283, a adjusting rate Qfh for the volume for injecting fuel oil is calculated as a ratio between the standard volume for injecting fuel oil Mqdrv and the final volume for injecting fuel oil Qsol.

Qfh = Qsol/Mqdrv In a step 5284, a adjustment coefficient K is set from the adjusting rate Qfh for the volume for injecting fuel oil with reference to a table for the adjustment coefficient as shown in Fig.29. In this case, it is assumed that the adjustment coefficient K = the adjusting rate for the volume for iniectina fuel oil Qfh.

In a step S285, K farget EGR rate Megr is calculated by multiplying the adjustment coefficient K (= the adjusting rate for the volume for injecting fuel oil Qfh) to the standard target EGR rate Negrbin accordance with the flow chart in Fig.13, as shown in the following equation: Meqr = MeqrbX K.

As mentioned above, thetarget EGR rate ;egrb is adjusted to be reduced in correspondence to the adjusting rate for the volume for injecting fuel oil Qfh, that is, in correspondence to the degree of limiting the volume for iniectina fuel oil.

When the;target EGR rate Megr is set, the EGR amount

IS controlled by the EGR valve so as to obtain tfletarget EGR rate Megr.

Fig.30 shows a third example of a flow chart for calculating (adjusting) a target EGR rate and is performed in place of the flow chart in Fig.26.

Steps S301 to S303 are the same as the steps S281 to S283, which calculate the adjusting rate for the volume for injecting fuel oil Qfh = Qsol/Mqdrv as a ratio between the standard volume for injecting fuel oil Mqdrv and the final volume for injecting fuel oil Qsol.

In a step S304, the accelerator opening degree C1 is read in.

in a step S305, the adjustment coefficient K is set from the adjusting rate Qfh for the volume for injecting fuel oil and the accelerator opening degree C1 with reference to a map for the adjustment coefficient as shown in Fig.31.

In this case, the adjustment coefficient K is set smaller so as to adjust to reduce the target EGR rate together with increasing the accelerator opening degree Cl.

In a step S306, farget EGR rate flegr = Megzb X K is calculated by multiplying the adjustment coefficient K to the standard target EGR rate Megr.

Fig.32 shows a fourth example of a flow chart for calculating (adjusting) a target EGR rate and is performed in place of the flow chart in Fig.26.

Steps S321 to S323 are the same as the steps S281 to S283, which calculate the adjusting rate for the volume for injecting fuel oil Qfh = Qsol/Mgdrv as a ratio between the standard volume for injecting fuel oil Nqdrv and the final volume for injecting fuel oil Qsol.

In a step S324, the accelerator opening degree C1 is read in.

In a step S325, the acceleration Acc is calculated as a changing value of the accelerator opening degree by subtracting the accelerator opening degree L times before from the now accelerator opening degree in accordance with the following equation: Acc - C1 - ClflL in which L is a constant.

In a step S326, the adjustment coefficient K is set from the adjusting rate for the volume for injecting fuel oil Qfh and the acceleration Acc with reference to a map for the adjustment coefficient as shown in Fig.33.

In this case, the adjustment coefficient K is set smaller so as to adjust to reduce the target EGR rate together with increasing the acceleration Acc.

In a step S327, k target EGR rate Megr = MegrbX K is calculated by multiplying the adjustment coefficient K to the standard target EGR rate Megrb.

Fig.34 shows a fifth example of a flow chart for calculating (adjusting) a target EGR rate and is performed in place of the flow chart in Fig.26.

This flow chart substantially corresponds to the flow chart shown in Fig.32 and only steps S344 and S345 for detecting the acceleration Aco are different.

In a step S344, a vehicle speed Vsp which is detected on the basis of a signal from the vehicle speed sensor is read in.

In a step S345, the acceleration Ace is calculated as a changing value of the vehicle speed by subtracting the vehicle speed L times before from the now vehicle speed in accordance with the following equation: Acc = Vsp in which L is a constant.

Accordingly, in the case of detecting the acceleration by the changing value of the vehicle speed, the same effect can also be obtained.

Next, an embodiment of an estimation apparatus for estimating pressure in intake and exhaust systems of an internal combustion engine in accordance with the present invention will be explained.

In Fig.38 which shows a main structure of apparatus in accordance with the present invention, a supercharger 61 pressurizes and supercharges air, which is freed or dusts in an air filter 62 and sucked into an intake passage 63, by an intake air compressor 61A and thereafter feeds the air to an intake manifold 64 disposed in a downward side.

While to a fuel injection nozzle 66 mounted to a combustion chamber in an engine (a diesel engine) 65, fuel oil is supplied in a pressurized state and in a divided condition to each cylinder from a fuel injection pump 51. The fuel oil is injected from the fuel injection nozzle 66 toward the combustion chamber and the injected fuel oil is ignited at a final timing of a pressurized stroke and burned Further, an EGR passage 70 having an EGR control valve 52 is connected so as to connect an exhaust manifold 68 with the intake manifold 64 and a throttle valve 91 is arranged in an upward side of an intake air compressor 61A in the intake passage 63 so as to enlarge a differential pressure between an exhaust pressure and an intake pressure by throttling the intake air at the time of an EGR control and so as to easily perform an EGR. Accordingly, the EGR control is performed in such a manner as to throttle the throttle valve 91 for the purpose of improvement of exhaust air and reduction of noise mainly at a time of idling or low load and at the same time to control the opening degree of the EGR control valve 52.

Concretely speaking, at the same time that the throttle valve 91 is throttled by introducing a negative pressure from a vacuum pump 71 to a diaphragm device 93 through an electromagnetic valve 92, an electromagnetic valve 72 which is duty controlled the negative pressure controls a dilution ratio to an atmosphere so that a pressure introduced to a pressure chamber in the EGR control valve 52 is controlled, thereby controlling an EGR rate due to control of the opening degree. The control for these EGR rate and fuel injection is performed by a control unit 53.

The EGR control valve 52 is provided with a lift sensor 94 for detecting a lift amount of a valve body.

After an exhaust turbine 61B of the super charger 61 is rotated by the exhaust manifold 68, particulate (exhaust fine particles) contained in an exhaust air after combustion are collected to a filter 74. Then the exhaust air is discharged to the atmosphere through a muffler 75 in which noise is arrested.

In the intake passage 63 disposed in an upward of the intake compressor 61A in the super charger 61, an air flow meter 76 for detecting an intake air flow is provided and further a speed sensor 77 for detecting the engine speed Ne, a lever opening degree sensor 78 for detecting an opening degree of a control lever (accelerator opening degree) in the fuel injection pump 51, a water temperature sensor 79 for detecting water temperature and the like are provided. An allowable maximum injection amount of fuel oil corresponding to the intake air amount to cylinder is set by detecting a pressure in the intake system and a pressure in the exhaust system on the basis of the above detected values in a manner mentioned below.

Various kinds of operations by the control unit 53 are explained below.

The flow chart for calculating the intake air flow QasO is shown in Fig.10. Further, the flow chart for calculating the intake air amount per intake stroke sucked to the cylinder is shown in Fig.ll.

Fig.39 is a flow chart for performing a cycle delay (a dead time operation) after sucked to the cylinder and supplied to the cylinder before discharged, in which the dead time operation for a predetermined cycle is performed to each of the intake air amount to cylinder Qac, the actual injection timing Itist, the volume for injecting fuel oil Qsol,and the intake air temperature Tn. This is performed for the purpose of obtaining data before sucking to the cylinder which is a base of the exhaust pressure to be determined.

Fig.40 is a flow chart for calculating the exhaust pressure by using the respective values determined in the above manner.

In a step S401, a standard exhaust air temperature Tehi is searched from the volume for injecting fuel oil cycle operation value Qsold which is operated in the Fig.39 by using a table shown in Fig.41. In this case, the standard exhaust air temperature Texhi has a characteristic of proportionally increasing since a combustion calorie increases together with increase of the volume for injecting fuel oil.

In a step S402, an exhaust air temperature adjustment coefficient Ktmpn due to the intake air temperature is searched by the intake air temperature cycle operation value Tne by using a table shown in Fig.42. In this case, the exhaust air temperature adjustment coefficient Ktmpn has a characteristic of increasing together with increase of the intake air temperature since the temperature in the exhaust air is high when the temperature in the intake air is high.

In a step 5403, an exhaust air temperature adjustment coefficient Ktmpp due to the exhaust air pressure is searched by the exhaust pressure Pexhn-l calculated in the preceding time by using a table shown in Fig.43. The exhaust air temperature adjustment coefficient Ktmpp has a suitable characteristic for that the temperature in the exhaust air increases together with increase of the exhaust air pressure.

In a step S404, an exhaust air temperature adjustment coefficient Ktmpi due to the injection timing is calculated by the actual injection timing cycle operation value Itistd by using a table shown in Fig .44. The exhaust air temperature adjustment coefficient Ktmpi has a suitable characteristic for that the temperature in the exhaust air increases together with delay of the injection timing because of delay in the combustion finish.

In a step S405, an exhaust temperature from cylinder Texho is calculated by adjusting the standard exhaust air temperature Texhi which is determined in the step S401 by using the respective exhaust air temperature adjustment coefficient Ktmpn, Ktmpp,and Ktmpi which are determined the respective steps 8402, S403,and S404 in accordance with the following equation: Texhc = Texhi X Ktmpn X Ktmpp X Ktmpi.

In a step S406, an exhaust air temperature Texh is determined by performing a primary delay operation as shown in the following equation with respect to the exhaust temperature from cylinder Texhi: Texh = Texhnl X (1 - KO) + Texhc X KO, in which KO is a constant.

In a step S407, an exhaust pressure standard value Pehb is calculated by using the exhaust air amount per cylinder Qexh, the engine speed Ne, the exhaust air temperature Texh, and the constants KPEXH and OPEXH (which is a value corresponding to an atmosphere pressure in a standard state) in accordance with the following equation: Pehb = (Qexh X Ne/KC)2 X Texh X KPEXH + OPEXH.

In a step S408, an exhaust air pressure Pexh is determined by performing a primary delay operation as shown in the following equation with respect to the exhaust pressure standard value Pexhb: Pexh = Pexhnl X (1 - KP) + Pexhb X KP in which KP is a constant.

Next, a second example will be explained. In this example, a swirl control valve 81 which strengthens intake swirl in low speed driving so as to improve the combustion characteristic is provided in an intake port portion of each of the cylindenof the intake manifold64 as shown in Fig.45.

The opening degree of the swirl control valve 81 can be controlled by the control unit 53 in accordance with the operating condition of the engine. In the present examp the opening degree of the swirl control valve Riscv, the volume for injecting fuel oil Qsold and the intake air temperature Tne.

Fig.47 is a flow chart for calculating the exhaust air pressure.

Steps S471 to S473 are the same as the steps S401 to S403 described above so that the explanation thereof is omitted.

In a step S474, an exhaust temperature adjustment coefficient Ktmpse due to the opening degree of the swirl control valve is searched by the swirl control valve opening degree cycle operation value Risovd in the above Fig.46 and the engine speed Ne in accordance with a table shown in Fig. 48.

In this case, when the swirl control valve 81 is full open (which substantially corresponds to the case where the swirl control valve is not provide), the exhaust temperature adjustment coefficient Rtspsc equals to 1 and is constant (in which the adjustment is not substantially performed). When the opening degree of the swirl control valve 81 is small, in a low engine speed condition, a suitable swirl strength can be obtained and the combustibility can be improved so that the exhaust air temperature is lowered. However, in a high engine speed condition, due to an excessively large swirl strength the combustibility becomes worse and the intake air amount to cylinder is reduced due to throttling operation so that the exhaust air temperature is risen. Accordingly, the exhaust temperature adjustment coefficient Ktmpso is set so as to be in conformity with the above characteristics.

In a step S475, an exhaust temperature from cylinder Texho is calculated by adjusting the standard exhaust air temperature Texhi by using the respective exhaust temperature adjustment coefficient Ktmpn, Ktmpp,and Rtmpsc which are respectively determined in the steps S472, S473,and S474 in accordance with the following equation: Texhc = Texhi X Ktmpn X Ktmpp X Ktmpsc.

Steps S476 to S478 are the same as the steps S406 to S408 in the above Fig.40. In the step S476, a primary delay operation is performed to the exhaust temperature from cylinder Texhi so as to determine the exhaust air temperature Texh, in the step S477, the exhaust air pressure standard value Pehb is calculated in accordance with the described equation and in the step S478, a primary delay operation is performed to the exhaust air pressure standard value Pexhb so as to determine the exhaust air pressure Pexh.

Though in the above described embodiment, the exhaust temperature adjustment coefficient Ktmpse is set by searching from a three dimension table by using the opening degree of the swirl control valve and the engine speed, the exhaust temperature adjustment coefficient Rtmpsc may be set such that a ratio of the intake air flow with respect to the opening degree of the swirl valve, that is, a value Vsc corresponding to the swirl flow speed is calculated by the intake air flow to cylinder Qac, the engine speed Ne, and the opening degree of the swirl valve Rasov, and the exhaust temperature adjustment coefficient Ktmpso is determined to be in correspondence with the swirl flow speed corresponding value Vsc.

The following is an embodiment described above.

Fig.49 is a flow chart for performing a cycle delay (dead time operation) in a similar manner to the above described embodiments and the dead time operation for a predetermined cycle is performed with respect to each of the intake air amount to cylinder Qac, the swirl flow speed Vsc, the volume for injecting fuel oil Qsold,and the intake air temperature Tne.

In this case, the swirl flow speed Vsc is determined by dividing the intake air flow Qac X Ne in the cylinder portion as shown in the described equation by the opening degree Rascv of the swirl control valve.

Fig.50 is a flow chart for calculating the exhaust air pressure.

Steps S501 to S503 are the same as the steps S401 to S403 and the explanation thereof is omitted.

In a step S504, an exhaust temperature adjustment coefficient Rtmpsc due to the opening degree of the swirl control valve is searched by using the cycle operation value Vec corresponding to the swirl flow speed in Fig.49 in accordance with a table shown in Fig.51. In this case, the exhaust temperature adjustment coefficient Ktmpso is set to satisfy the characteristic such that when the swirl flow speed corresponding value Vsc is a certain value, the combustion state is best and the exhaust air temperature is lowered so that the exhaust air temperature rises in a change to both direction from the Vsc.

In a step S505, an exhaust temperature from cylinder Texhi is calculated by adjusting the standard exhaust air temperature Texhi by using each of the exhaust temperature adjustment coefficient Ktmpn, Ktmpp, and Ktmpsc which are determined in the steps 8502, 8503, and 8504 in accordance with the described equation.

Steps S506 to S508 are the same as the steps S406 to S408 in the above Fig.40. In the step S506, a primary delay operation is performed to the exhaust temperature from cylinder Texhi so as to determine the exhaust air temperature Texh, in the step S507, the exhaust air pressure standard value Pobb is calculated in accordance with the described equation and in the step S508, a primary delay operation is performed to the exhaust air pressure standard value Pexhb so as to determine the exhaust air pressure Pexh.

Next, an embodiment for estimating the intake air pressure in accordance with the present invention will be explained.

Fig.52 is a flow chart for calculating the intake air pressure In a step S521, a standard value corresponding to a volumetric efficiency Kinb is searched from a table shown in Fig.53 by using the intake air amount to cylinder Qac and the engine speed Ne.

In a step S522, the volumetric efficiency corresponding value Kin is calculated by using the intake air temperature Tint in accordance with a described equation (Kin = Kinb X-TA/Tint).

In a step S523, an intake air pressure Pm is calculated in accordance with a described equation (Pm = Qac/Kin X TA X Ra/VCYL) by using the intake air amount Qac and the volumetric efficiency corresponding value Kin as variables and the operation is finished. In this case, the constant TA, RA, and VCYL in this flow chart respectively mean a temperature in a standard state, an air gas constant, and a cylinder volume.

The standard volume for injecting fuel oil Qsoll is calculated by the flow chart shown in Fig.2.

Fig.54 is a flow chart for calculating a maximum volume for injecting fuel oil Qful and the operation is performed at a timing corresponding to the revolution.

In a step S541, the engine speed Ne is read in and in a step S542, a value Klamb corresponding to a limit air excess rate is searched from a table in which a value corresponding to a smoke limit as shown in Fig.55 is set by the engine speed Ne.

In a step S543, the intake air amount to cylinder Qac is read in, in step S544, the maximum volume for injecting fuel oil Qful is calculated in accordance with the described equation (Qful = Qac/Klamb/14.7) and the operation is finished.

The volume for injecting fuel oil is finally set in accordance with the flow chart shown in Fig.25 mentioned above.

The EGR control by using the exhaust air pressure and the intake air pressure estimated by the present invention is performed in a similar manner to the above mentioned manner.

Accordingly, tne-target h;GR rate negr is calculated in accordance with the flow chart shown in Fig.13 and the complete buming of the engine is determined by the flow chart show n in Fig.

16.

As explained above, in accordance with the present invention, estimation of pressure which suffers no cost increase and assures durability and transient response can be performed by calculating an exhaust air pressure and an intake air pressure from signals from an air flow meter and the like. Further, an accuracy for estimation is improved and an accuracy for control such as an EGR control is improved by adjusting the exhaust air pressure according to Injection timing, ignition timing, opening of a swirl control valve and ratio of intake flow speed with respect to an opening area.

Attention Is directed to our co-pending application No. 9711483.9 (Publication No. 2313 927) from which this application has been divided and which daims: (1) Apparatus for controlling EGR in an internal combustion engine, comprising: driving condition detecting means for detecting at least the engine speed, the opening degree of an accelerator, and the intake air amount, as engine operating conditions; means for calculating a fuel oil injection volume on the basis of at least the engine speed and the accelerator opening degree; means for setting a target fuel injection timing on the basis of the engine speed and the calculated injection volume; means for detecting the actual fuel injection timing; means for calculating a nominal target EGR rate on the basis of the engine speed, the intake air amount and the calculated injection volume; means for calculating an amount of adjustment of the target EGR rate on the basis of the calculated injection volume, the target fuel injection timing, and the actual fuel injection timing; means for setting an adjusted target EGR rate on the basis of the calculated nominal target EGR rate and the calculated adjustment amount; and means for controlling the EGR on the basis of the adjusted target EGR rate.

(2) Apparatus for controlling EGR in an internal combustion engine, comprising: driving condition detecting means for detecting at least the engine speed, the opening degree of an accelerator, the intake air amount, and the EGR amount, as engine operating conditions; means for calculating a fuel oil injection volume on the basis of at least the engine speed and accelerator opening degree; means for calculating a possible maximum injection volume on the basis of the intake air amount and the EGR amount; means for setting an injection volume by comparing the calculated injection volume and the calculated maximum injection volume and selecting the smaller one; means for controlling the injection volume in accordance with the set injection volume; means for calculating a nominal target EGR rate on the basis of the engine speed, the intake air amount and the calculated injection volume; means for adjusting the nominal target EGR rate in accordance with at least the ratio of the said set injection volume with respect to the calculated injection volume so as to obtain an adjusted target EGR rate; and means for controlling the EGR amount in accordance with the adjusted target EGR rate.

Claims

Claims:

1. An internal combustion engine having means for detecting engine speed; means for detecting intake air flow; means for detecting intake air temperature; and means for estimating the pressure in the exhaust system andlor the intake system on the basis of the engine speed, intake air flow, and intake air temperature, wherein the estimation of the pressure in the exhaust system takes into account fuel injection vdume and fuel injection timing or the swirl control state of a swirl control valve.

2. An internal combustion engine as claimed in claim 1, further having means for controlling EGR on the basis of intake pressure and exhaust pressure.

3. Apparatus for estimating a pressure in an exhaust system of an internal combustion engine, comprising: injection volume means for detecting an injection amount of fuel injected to the engine; intake air temperature detecting means for detecting a temperature of air sucked into the engine; fuel injection timing detecting means for detecting an injection timing of the fuel; intake air flow detecting means for detecting a flow of intake air; engine speed detecting means for detecting an engine speed; and exhaust system pressure estimating means for estimating a pressure in the exhaust system on the basis of the injection volume, the intake air temperature, the fuel injection timing, the intake air flow, and the engine speed.

4. Apparatus as claimed in claim 3, wherein the exhaust system pressure estimating means calculates a standard exhaust temperature on the basis of the injection volume, calculates the temperature in the exhaust gas discharged from a cylinder by adjusting the standard exhaust temperature according to the intake air temperature, the preceding estimated pressure in the exhaust system, and the fuel injection timing, and estimates a pressure in the exhaust system on the basis of the exhaust gas flow volume determined by the intake air volume and the engine speed and the calculated temperature in the exhaust gas discharged from a cylinder.

5. Apparatus for estimating a pressure in an exhaust system of an internal combustion engine, comprising injection volume detecting means for detecting an injection amount of fuel injected to the engine; intake air temperature detecting means for detecting a temperature of air sucked into the engine; swirl control state detecting means for detecting the swirl control state of a swirl control valve provided in an intake system of the engine; intake air flow detecting means for detecting a flow of intake air; engine speed detecting means for detecting engine speed; and exhaust system pressure estimating means for estimating a pressure in the exhaust system on the basis of the injection volume, the intake air temperature, the swirl control state, the intake air flow, and the engine speed.

6. Apparatus as claimed in claim 5, wherein the exhaust system pressure estimating means calculates a standard exhaust temperature on the basis of the injection volume, calculates the temperature in the exhaust gas discharged from a cylinder by adjusting the standard exhaust temperature according to the intake air temperature, the preceding estimated pressure in the exhaust system, and the swirl control state, and estimates a pressure in the exhaust system on the basis of the exhaust gas flow volume determined by the intake air volume and the engine speed and the calculated temperature in the exhaust gas discharged from a cylinder.

7. Apparatus as daimed in daim 6, wherein the adjustment of the standard exhaust temperature is performed by an adjustment coefficient set on the basis of the opening degree of the swirl control valve and the engine speed.

8. Apparatus as claimed in daim 6, wherein the adjustment of the standard exhaust temperature is performed by an adjustment coefficient set on the basis of a swirl flow speed correspondence value calculated from intake air volume, the opening degree of the swirl control valve, and the engine speed.

9. Apparatus for estimating a pressure in an intake system of an internal combustion engine, comprising: intake air flow detecting means for detecting an air flow sucked into the engine; engine speed detecting means for detecting an engine speed; intake air temperature detecting means for detecting a temperature of the intake air; and intake system pressure estimating means for estimating a pressure in the intake system on the basis of the intake air flow volume, the engine speed, and the intake air temperature.

10. Apparatus as daimed in claim 9, wherein the intake system pressure estimating means calculates an intake air volume per cylinder on the basis of the intake air flow and the engine speed, calculates a standard value of volumetric efficiency on the basis of the intake air volume per cylinder and the engine speed, calculates a value of volumetric efficiency by adjusting the standard volumetric efficiency value according to the intake air temperature, and estimates a pressure in the intake system on the basis of the calculated intake air volume per cylinder and the calculated volumetric efficiency correspondence value by using following equation: Pm = Qac/Kin x TA x RA x VCYL, in which Pm is the pressure in the intake system Qac is the intake air volume per cylinder, Kin is the volumetric efficiency value, TA is the temperature in a standard state, RA is a constant of air and gas, and VCYL is cylinder volume.

11. An internal combustion engine substantially as described with reference to Figure 32 or Figure 45 of the accompanying drawings.

12. Apparatus for estimating a pressure in an exhaust system of an intemal combustion engine, substantially as described with reference to Figures 40 to 44 or Figures 50 and 51 of the accompanying drawings.

13. Apparatus for estimating a pressure in an intake system of an intemal combustion engine, substantially as described with reference to Figure 52 of the accompanying drawings.