JP4455353B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine provided with an exhaust gas recirculation device that recirculates a part of exhaust gas to an intake system, and more particularly to a device that controls fuel injection by an injector.

  Patent Document 1 discloses an internal combustion engine in which a relatively large amount of exhaust gas is recirculated to an intake system to reduce the combustion temperature in the combustion chamber in order to reduce the amount of NOx in the exhaust gas. In this internal combustion engine, the exhaust gas recirculation rate is set higher than usual, and a relatively large amount of recirculated exhaust gas is supplied into the combustion chamber. As a result, the temperature of the fuel in the combustion chamber and the surrounding gas is suppressed to a temperature lower than the temperature at which soot is generated, so that generation of soot is prevented and NOx emission is reduced.

Japanese Patent No. 3116876

  The low temperature combustion shown in Patent Document 1 is possible only when the engine load is low, so the engine control mode, particularly the fuel injection control mode by the injector, is changed as the engine load increases. There is a need to. However, Patent Document 1 does not disclose a control method for fuel injection when the engine load increases or when the engine is shifted from a high load state to a low load state where low temperature combustion is possible.

  The present invention smoothly changes the fuel injection control mode accompanying increase / decrease in engine load, and suppresses excessive switching of the control mode caused by a slight load change and fluctuation of torque accompanying the switching of the control mode. An object of the present invention is to provide a control device for an internal combustion engine.

In order to achieve the above object, according to the first aspect of the present invention, air is sucked into the cylinder (3a) through the intake system (4), and the fuel injected from the injector (6) is put into the cylinder (3a). In the control device for an internal combustion engine that supplies and recirculates a part of the exhaust gas discharged from the internal combustion engine (3) to the intake system (4) as recirculated exhaust gas by the exhaust gas recirculation device (14), the intake system (4) Intake air amount control means (2, 7) for controlling the amount of intake air sucked into the cylinder (3a) via the intake air amount detection means (27) for detecting the intake air amount (Fa), Recirculation exhaust gas flow rate estimating means (2) for estimating the flow rate (Fe) of the recirculated exhaust gas by the exhaust gas recirculation device (14), the detected intake air amount (Fa), and the estimated recirculated exhaust gas flow rate (Fe) Based on the inside of the cylinder In-cylinder oxygen amount estimating means (2) for estimating the amount of oxygen (mo2) present, speed detection means (22) for detecting the engine speed (Ne), and the detected engine speed (Ne) And a fuel injection parameter determining means (2) for determining a fuel injection parameter (Q *) by searching a fuel injection parameter map according to the estimated in-cylinder oxygen amount (mo2). On the basis of the fuel injection parameter (Q *), the injector control means (2) for controlling the injector (6) and the air adjustment parameter (A *) for controlling the intake air amount (Fa) engine operating condition (Ne, AP) and an air adjustment parameter calculating means (2) which is calculated by searching an air adjustment parameter map according to the fuel injection parameter map, the engine Low-temperature combustion fuel injection parameter map (Q * O2LTC map) corresponding to the low load operation region, and normal combustion fuel injection parameter map (Q * O2STD map) corresponding to the operation region on the higher load side than the low load operation region And the fuel injection parameter determination means switches the fuel injection parameter map to be used from the low temperature combustion fuel injection parameter map (Q * O2LTC map) to the normal combustion fuel injection parameter map (Q * O2STD map). or wherein when the normal combustion fuel injection parameter map (Q * O2STD map) switches the fuel injection parameter map for the low temperature combustion (Q * O2LTC maps), the switching have rows with a hysteresis, the intake air amount control means (2, 7) is the calculated air conditioning parameter (A *) Accordingly, the intake air amount (Fa) is controlled, and the air adjustment parameter map includes a low temperature combustion air adjustment parameter map (A * LTC map) corresponding to the low load operation region, and an operation region on the high load side. When the air conditioning parameter calculation means uses the low temperature combustion air conditioning parameter map (A * LTC map), the normal combustion air conditioning parameter map (A * STD map) corresponding to When the in-cylinder oxygen amount (mo2) reaches the first threshold value (Oxy1), switching to the normal combustion air adjustment parameter map (A * STD map) is performed while the normal combustion air adjustment parameter map ( A * STD map) is used, the in-cylinder oxygen amount (mo2) is larger than the first threshold value (Oxy1), and the engine When the output torque reaches the second threshold value (Oxy2) smaller than the output torque (TH) corresponding to the first threshold value, the line switching to the low-temperature combustion air adjustment parameter map (A * LTC map) Ukoto It is characterized by.

According to a second aspect of the present invention, in the control apparatus for an internal combustion engine according to the first aspect , the fuel injection parameter determining means uses the low temperature combustion fuel injection parameter map (Q * O2LTC map). When the air conditioning parameter map is switched to the normal combustion air conditioning parameter map (A * STD map), the in-cylinder oxygen amount (mo2) is greater than the second threshold value (Oxy2). When the fuel injection parameter (Q *) is determined so that the output torque of the engine becomes substantially constant until reaching Oxy3), and the in-cylinder oxygen amount (mo2) reaches the third threshold (Oxy3), The normal combustion fuel injection parameter map (Q * O2STD map) is switched to the normal combustion fuel injection parameter map (Q * O2STD map). When the air conditioning parameter map is switched to the low temperature combustion air conditioning parameter map (A * LTC map), the in-cylinder oxygen amount (mo2) is set to the first threshold ( The fuel injection parameter (Q *) is determined so that the output torque of the engine becomes substantially constant until a fourth threshold value (Oxy4) smaller than Oxy1) is reached, and the in-cylinder oxygen amount (mo2) is set to the fourth threshold value. When (Oxy4) is reached, switching to the low temperature combustion fuel injection parameter map (Q * O2LTC map) is performed.

According to the first aspect of the present invention, by searching the low-temperature combustion fuel injection parameter map or the normal combustion fuel injection parameter map according to the detected engine speed and the estimated in-cylinder oxygen amount, A fuel injection parameter is determined. When switching the fuel injection parameter map to be used from the low temperature combustion fuel injection parameter map to the normal combustion fuel injection parameter map, or when switching from the normal combustion fuel injection parameter map to the low temperature combustion fuel injection parameter map Switching is performed with hysteresis. Therefore, excessive switching of the fuel injection parameter map due to a slight engine load change is suppressed. Further, an air conditioning parameter for controlling the intake air amount of the engine is calculated by searching a low temperature combustion air conditioning parameter map or a normal combustion air conditioning parameter map according to the engine operating state. When the low-temperature combustion air adjustment parameter map is used, when the in-cylinder oxygen amount reaches the first threshold, the normal combustion air adjustment parameter map is switched to the normal combustion air adjustment parameter map. When the parameter map is used, low temperature combustion occurs when the in-cylinder oxygen amount is larger than the first threshold and the engine output torque reaches a second threshold smaller than the output torque corresponding to the first threshold. Switching to an air conditioning parameter map is performed. Therefore, it is possible to prevent the air adjustment parameter map used for calculating the air adjustment parameter from being excessively switched due to a slight engine load change.

According to the second aspect of the present invention, when the low-temperature combustion fuel injection parameter map is used, when the air adjustment parameter map is switched to the normal combustion air adjustment parameter map, the in-cylinder oxygen amount is The fuel injection parameter is determined so that the output torque of the engine becomes substantially constant until the third threshold value which is larger than the second threshold value is reached, and when the in-cylinder oxygen amount reaches the third threshold value, the fuel injection parameter for normal combustion On the other hand, when the normal combustion fuel injection parameter map is used, when the air conditioning parameter map is switched to the low temperature combustion air conditioning parameter map, the in-cylinder oxygen amount is changed to the map. The fuel injection parameters are determined so that the engine output torque is substantially constant until a fourth threshold value less than one threshold value is reached. When the in-cylinder oxygen amount reaches the fourth threshold value, switching to the low-temperature combustion fuel injection parameter map is performed, so that torque fluctuations associated with switching between the air adjustment parameter map and the fuel injection parameter map to be used are suppressed. Can do.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
An internal combustion engine (hereinafter referred to as “engine”) 3 shown in FIG. 1 is a diesel engine of, for example, four cylinders (only one is shown) mounted on a vehicle (not shown). A combustion chamber 3d is formed between the piston 3b and the cylinder head 3c of each cylinder 3a. An intake pipe 4 (intake system) and an exhaust pipe 5 are connected to the combustion chamber 3d, and an intake valve and an exhaust valve (both not shown) are provided in the intake port and the exhaust port, respectively. Yes. A fuel injection valve (hereinafter referred to as “injector”) 6 and an in-cylinder pressure sensor 21 are attached to the cylinder head 3c so as to face the combustion chamber 3d.

  The injector 6 is disposed at the center of the cylinder head 3c and is connected to a high-pressure pump (both not shown) via a common rail. Fuel in a fuel tank (not shown) is boosted by a high-pressure pump, then sent to the injector 6 through the common rail, and injected from the injector 6 into the combustion chamber 3d. The injection pressure Pe, injection time (valve opening time) De, and injection timing (valve opening timing) TMe of the injector 6 are controlled by control signals from an electronic control unit (hereinafter referred to as “ECU”) 2 shown in FIG. . In the following description, FIG. 2 is also referred to.

  The in-cylinder pressure sensor 21 (combustion state detection means) is, for example, of the piezoelectric element type, and a piezoelectric element (not shown) is provided in accordance with a change in pressure (hereinafter referred to as “in-cylinder pressure”) P in the combustion chamber 3d. By displacing, a detection signal indicating the change amount ΔP of the in-cylinder pressure P is output to the ECU 2. The ECU 2 obtains the in-cylinder pressure P by integrating this detection signal.

  A magnet row 22 a is attached to the crankshaft 3 e of the engine 3. The magnet rotor 22a and the MRE pickup 22b constitute a crank angle sensor 22 (rotational speed detection means). The crank angle sensor 22 outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 2 as the crankshaft 3e rotates.

  The CRK signal is output every predetermined crank angle (for example, 30 degrees). The ECU 2 obtains the rotational speed Ne (hereinafter referred to as “engine rotational speed”) Ne of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston 3b of each cylinder is at a predetermined crank angle position near the TDC (top dead center) at the start of the intake stroke, and in this example of the four-cylinder type, every crank angle of 180 degrees. Is output.

  A throttle valve 7 (intake amount control means) is provided on the upstream side of the intake manifold 4a of the intake pipe 4 and an actuator 8 for driving the throttle valve 7 is connected to the throttle valve 7. The actuator 8 is composed of a motor, a gear mechanism (not shown) or the like, and the operation of the actuator 8 is controlled by a control signal from the ECU 2 so that the opening of the throttle valve 7 (hereinafter referred to as “throttle valve opening”). TH) changes, and the amount of intake air taken into the combustion chamber 3d is controlled accordingly. The throttle valve opening TH is detected by a throttle valve opening sensor 23, and the detection signal is output to the ECU 2.

  The intake manifold 4a is provided with an intake pressure sensor 24 and an intake air temperature sensor 25. The intake pressure sensor 24 detects a pressure (hereinafter referred to as “in manifold pressure”) Pi in the intake manifold 4a. ) Ts is detected, and those detection signals are output to the ECU 2. An engine water temperature sensor 26 is attached to the main body of the engine 3. The engine water temperature sensor 26 is composed of a thermistor or the like, detects the temperature (hereinafter referred to as “engine water temperature”) Tw of the coolant circulating in the main body of the engine 3, and outputs a detection signal to the ECU 2.

  The intake pipe 4 is provided with a supercharging device 9. The supercharger 9 includes an evening charger-type supercharger 10, an actuator 11 connected thereto, and a vane opening control valve 12. The supercharger 10 includes a rotatable compressor blade 10a provided upstream of the throttle valve 7 of the intake pipe 4, a turbine blade 10b provided in the middle of the exhaust pipe 5, and a plurality of rotatable variable vanes. 10c (only two are shown) and a shaft 10d for integrally connecting these blades 10a and 10b. The turbocharger 10 performs a supercharging operation when the compressor blade 10a integrated with the turbine blade 10b is rotationally driven by the exhaust gas in the exhaust pipe 5 as the turbine blade 10b is rotationally driven.

  Each variable vane 10 c is connected to the actuator 11, and its opening degree (hereinafter referred to as “vane opening degree”) VO is controlled via the actuator 11. The actuator 11 is of a diaphragm type that operates by negative pressure, and is connected to a negative pressure pump (not shown), and the vane opening control valve 12 is provided in the middle thereof. The negative pressure pump operates using the engine 3 as a power source and supplies the generated negative pressure to the actuator 11. The vane opening degree control valve 12 is configured by an electromagnetic valve, and the negative pressure supplied to the actuator 11 changes when the valve opening degree is controlled by a control signal from the ECU 2. The supercharging pressure is controlled by changing the vane opening VO of the engine 10c.

An air flow sensor 27 (intake air amount detection means) is provided upstream of the supercharger 10 in the intake pipe 4. The air flow sensor 27 detects the intake air amount Fa flowing in the intake pipe 4 and outputs a detection signal to the ECU 2.
Further, the intake manifold 4a of the intake pipe 4 is divided into a swirl passage 4b and a bypass passage 4c from the collecting portion to the branch portion. The bypass passage 4c is provided with a swirl device 13 for generating a swirl in the combustion chamber 3d. The swirl device 13 includes a swirl valve 13a, an actuator 13b for driving the swirl valve 13a, and a swirl control valve 13c. The actuator 13b and the swirl control valve 13c are respectively configured similarly to the actuator 11 and the vane opening control valve 12 of the supercharging device 9, and the swirl control valve 13c is connected to the negative pressure pump. With the above configuration, when the valve opening degree of the swirl control valve 13c is controlled by the control signal from the ECU 2, the negative pressure supplied to the actuator 13b changes, and the opening degree SVO of the swirl valve 13a changes. The strength of the swirl is controlled.

  Further, an exhaust gas recirculation pipe (hereinafter referred to as “EGR pipe”) 14a is connected between the portion of the collecting portion of the swirl passage 4b of the intake manifold 4a and the downstream side of the oxidation catalyst 15 described later of the exhaust pipe 5. The EGR pipe 14a and the exhaust gas recirculation control valve (hereinafter referred to as “EGR control valve”) 14b provided in the middle thereof constitute an exhaust gas recirculation device (hereinafter referred to as “EGR device”) 14. A part of the exhaust gas from the engine 3 is recirculated to the intake pipe 4 as recirculated exhaust gas through the EGR pipe 14a. The EGR control valve 14b is composed of a linear electromagnetic valve, and its opening degree (hereinafter referred to as “EGR valve opening degree”) LE is controlled in accordance with a control signal from the ECU 2, whereby the recirculated exhaust gas flow rate Fe is reduced. Be controlled. The EGR valve opening degree LE is detected by the EGR valve opening degree sensor 28, and the detection signal is output to the ECU 2.

  Further, an oxidation catalyst 15 and a NOx absorption catalyst 16 are provided in order from the upstream side of the exhaust pipe 5 on the downstream side of the supercharger 10. The oxidation catalyst 15 oxidizes HC and CO in the exhaust gas and purifies the exhaust gas. Further, the NOx absorption catalyst 16 absorbs NOx in the exhaust gas in a lean oxidizing atmosphere and reduces the absorbed NOx in a rich reducing atmosphere.

  Further, an oxygen concentration sensor 29 is provided between the supercharger 10 and the oxidation catalyst 15 in the exhaust pipe 5. The oxygen concentration sensor 29 linearly detects the oxygen concentration λ in the exhaust gas and outputs the detection signal to the ECU 2. The ECU 2 calculates the air-fuel ratio A / F of the gas burned in the combustion chamber 3d based on the oxygen concentration λ. The ECU 2 further detects from the accelerator opening sensor 30 (accelerator depression amount detecting means) the depression amount (hereinafter referred to as “accelerator opening”) AP of the accelerator pedal (not shown) of the vehicle driven by the engine 3. A signal is output.

  In this embodiment, the ECU 2 is a part of intake air amount control means, recirculation exhaust gas flow rate estimation means, in-cylinder oxygen amount estimation means, rotation speed detection means, fuel injection parameter determination means, injector control means, and air adjustment parameter calculation. Configure the means. The ECU 2 is composed of a microcomputer including an I / O interface, CPU, RAM, ROM, and the like, and according to the detection signals from the various sensors 21 to 30 described above, various types of ECU 2 are performed according to a control program stored in the ROM. Perform arithmetic processing. Specifically, the operating state of the engine 3 is determined from the detection signal, and the combustion mode of the engine 3 is determined based on the determination result, and the throttle valve opening TH is determined according to the determined combustion mode. Thus, the intake air amount is controlled, and the fuel injection by the injector 6 is controlled.

  The combustion mode of the engine 3 is roughly divided into a low temperature combustion mode and a normal combustion mode other than that. The low-temperature combustion mode is executed in a low load region after the warm-up of the engine 3 is finished. On the other hand, the normal combustion mode is executed in a higher load region. In both combustion modes, a lean operation in which the air-fuel ratio is controlled to be leaner than the stoichiometric air-fuel ratio is normally performed, and NOx absorbed by the NOx absorption catalyst 16 is reduced or attached to the NOx absorption catalyst 16. In order to desorb the sulfur in the fuel, a rich operation for making the air-fuel ratio richer than the stoichiometric air-fuel ratio is appropriately performed. In the low-temperature combustion mode, fuel injection control (hereinafter referred to as “O2 reference LTC control”) mainly based on the in-cylinder oxygen amount and the engine speed Ne described below is executed, and in the normal combustion mode, the throttle valve opening TH and EGR are controlled. On the low load side where the intake air amount can be controlled by changing the valve opening LE, fuel injection control (hereinafter referred to as “O2 standard STD control”) based mainly on the in-cylinder oxygen amount and the engine speed Ne is executed, and the throttle Fuel injection control (hereinafter referred to as “pedal reference STD control”) based on the accelerator opening AP and the engine speed Ne is executed on the high load side where the valve 7 is fully opened and the EGR control valve 14b is fully closed.

  Hereinafter, the process performed by ECU2 is demonstrated. The ECU 2 searches the A * map shown in FIG. 3 according to the engine speed Ne and the accelerator pedal opening AP, and determines the air conditioning parameter A *. The air adjustment parameter A * is a vector whose elements are the target throttle valve opening THR, the target EGR valve opening LER, the target vane opening VOR, and the target swirl valve opening SVOR. A grid point at addresses i and j on the A * map includes a target throttle valve opening degree THR, a target EGR valve opening degree LER, a target vane opening degree VOR and a target that are suitable for the corresponding engine speed Ne and accelerator opening degree AP. A swirl valve opening SVO is set. Then, the ECU 2 drives the corresponding actuator so that the actual throttle valve opening TH, EGR valve opening LE, vane opening VO, and swirl valve opening SVO become the target opening retrieved from the A * map. To do. Thus, the intake air amount, the recirculated exhaust gas flow rate, the supercharging pressure, and the swirl are controlled in accordance with the engine speed Ne and the accelerator pedal opening AP.

  The A * map is provided corresponding to each of the above-described O2 reference LTC control, O2 reference STD control, and pedal reference STD control, and for each of these controls, a normal lean operation map, PM (Particulate Matter) An oxidation map, a NOx reduction map, and a sulfur desorption map are set. The set air-fuel ratio when using the normal lean operation map, PM oxidation map, NOx reduction map, and sulfur desorption map are A / FLN, A / FLP, A / FRN, and A / FRS, respectively. A / FLN> A / FLP> A / FRS> A / FRN is established.

  Next, fuel injection control by the ECU 2 will be described. FIG. 4 shows a calculation process of the in-cylinder state parameter [O2] used for the O2 reference LTC control and the O2 reference STD control. This in-cylinder state parameter [O2] represents the state in the cylinder 3a immediately before fuel injection, and is a total of three parameters: the in-cylinder oxygen amount mo2, the in-cylinder inert gas amount mint, and the actual intake manifold temperature Ti. Composed. The in-cylinder oxygen amount mo2 represents the amount of oxygen existing in the cylinder 3a before fuel injection, and the in-cylinder inert gas amount mint is an inert gas (oxygen) present in the cylinder 3a before fuel injection. The actual intake manifold temperature Ti represents the actual temperature of the intake manifold 4a. Of these, the in-cylinder oxygen amount mo2 is a main parameter that has a major influence on combustion. On the other hand, the in-cylinder inert gas amount mint and the actual intake manifold temperature Ti are sub-parameters that complement the in-cylinder oxygen amount mo2, and in the steady state of the engine 3, are almost uniquely determined according to the in-cylinder oxygen amount mo2. At the same time, in the transient state, it is used to correct the in-cylinder oxygen amount mo2 as described later.

In this process, first, the actual intake manifold temperature Ti is calculated by the following equation (1) from the intake manifold temperature Ts detected by the intake air temperature sensor 25 (step 31).
Ti = Ts (τo · s + 1) (1)
Where τo: intake air temperature sensor time constant
s: Laplace transform operator By such calculation, the actual intake manifold temperature Ti can be correctly estimated in real time while compensating for the response delay based on the detection result of the intake air temperature sensor 25.

  Next, the cylinder oxygen amount mo2 is calculated by estimation (step 32). This calculation is based on the intake air amount Fa detected by the airflow sensor 27, the intake manifold pressure Pi detected by the intake pressure sensor 24, and the actual intake manifold temperature Ti estimated in step 31, and using an EGR model to be described later. The following procedure is performed.

A. B. Estimation of EGR rate Ri Estimation of cylinder oxygen amount mo2 Estimation of EGR Rate Ri The basic equation of the EGR rate Ri is given by the following equation (2).
Ri = Fe_hat / Fi (2)
Here, Fi is a total gas flow rate flowing into the cylinder, Fe_hat is a predicted value of the recirculation exhaust gas flow rate (estimated recirculation exhaust gas flow rate) flowing into the cylinder 3a, and EGR in a transient state between the lean operation and the rich operation. It is obtained in consideration of the response delay of the device 14.

The total gas flow Fi in the equation (2) is calculated by the following equation (3) from a well-known speed density equation.
Fi = Ne · Vd · Pi · ηv / (60 × 2R · Ti) (3)
Where Ne: engine speed (rpm)
Vd: Engine displacement
Pi: In manifold pressure
ηv: Volumetric efficiency of the engine
R: Gas constant
Ti: Intake manifold temperature Note that the volume efficiency ηv is obtained, for example, from a map set in advance based on the experimental result, in accordance with the engine speed Ne and the intake manifold pressure Pi, and the obtained map value is obtained from the actual intake manifold. It is calculated | required by correct | amending according to temperature Ti.

On the other hand, when the ideal gas law is applied to the intake manifold 4a under a constant temperature condition, the following equation (4) is established between the recirculated exhaust gas flow rate Fe, the intake air amount Fa, and the total gas flow rate Fi. A relationship is established.
dPi / dt = (R · Ti / Vi) · (Fe + Fa−Fi) (4)
When Vi: intake manifold volume equation (4) is solved for the recirculated exhaust gas flow rate Fe, the following equation (5) is obtained.
Fe = (dPi / dt) · Vi / (R · Ti) −Fa + Fi (5)

Further, when the Laplace transform operator s is introduced (dPi / dt = sPi) and the equation (5) is rewritten, the following equation (6) is obtained.
Fe = s · Pi · Vi / (R · Ti) −Fa + Fi (6)
On the other hand, the predicted value Fe_hat of the recirculated exhaust gas flow rate is expressed by the following equation (7) in consideration of the first-order lag of the response of the EGR device 14.
Fe_hat = (1 / (τs + 1)) · Fe (7)

Therefore, the predicted value Fe_hat of the recirculated exhaust gas flow rate is obtained from both equations (6) and (7) as in the following equation (8).
Fe_hat = (s · Pi / (τs + 1)) (Vi / (R · Ti))
− (1 / (τs + 1)) · Fa + (1 / (τs + 1)) · Fi
(8)
Here, s · Pi / (τs + 1) is an approximate value of dPi / dt using the numerical difference filter s / (τs + 1), and the time constant τ is determined based on experimental results.

Therefore, by substituting the total gas flow rate Fi calculated by the equation (3) and the predicted value Fe_hat of the recirculated exhaust gas flow rate in the transient state calculated by the equation (8) into the equation (2), the EGR in the transient state is obtained. The rate Ri can be calculated.
In the steady state, the following equation (9) holds, so
Fe_hat = Fe = Fi-Fa (9)
From the equations (9) and (2), the EGR rate Ri in the steady state is calculated by the following equation (10).
Ri = (Fi−Fa) / Fi (10)

B. Estimation of In-Cylinder Oxygen Mo2 Next, the in-cylinder oxygen amount mo2 is estimated based on the total gas flow rate Fi and the EGR rate Ri obtained as described above.

The basic equation of the cylinder oxygen amount mo2 is given by the following equation (11).
mo2 = ma × φ (O2) a + me × φ (O2) e (11)
Where ma is the amount of air flowing into the cylinder in each combustion cycle
me: Amount of recirculated exhaust gas flowing into the cylinder in each combustion cycle
φ (O2) a: oxygen concentration in air (constant)
φ (O2) e: oxygen concentration in the recirculated exhaust gas The air amount ma and the recirculated exhaust gas amount me in the equation (11) are calculated by the following equations (12) and (13) from the total gas flow rate Fi and the EGR rate Ri, respectively. .
ma = (Fi × (1-Ri) × 60 × 2) / (Ne × ncyl) (12)
me = (Fi × Ri × 60 × 2) / (Ne × ncyl) (13)
Where ncyl: number of engine cylinders

ここで、ｉは燃焼サイクルを表す添え字であり（累乗を意味するものではない）、ａ0，ａ1，ａ2，…ａnは、実験結果に基づき、エンジン３の運転状態および排気マニホルドの容積によって決定される重み係数である。 Further, the oxygen concentration φ (O2) e in the recirculated exhaust gas can be calculated by the following equation (14) in consideration of the response delay of the EGR device 14.

Here, i is a subscript representing the combustion cycle (not meaning a power), and a0, a1, a2,..., An are determined by the operating state of the engine 3 and the volume of the exhaust manifold based on the experimental results. Weighting factor.

ここで、ｍf は気筒に噴射される燃料量、Ｌstは、燃料のタイプに応じて決定される理論空燃比である。すなわち、式（１５）中のｍf×Ｌst×φ(Ｏ２)a は、リーン運転において噴射燃料量ｍf の完全燃焼により消費される酸素量に相当する。なお、式（１４）（１５）によれば、還流排ガス中の酸素濃度φ(Ｏ２)e を算出するには、排ガス中の酸素濃度φ(Ｏ２)exh の初期値が必要である。このφ(Ｏ２)exh の初期値は、例えば、エンジン３の始動直後にＥＧＲ動作を停止するという条件が設定されている場合には、φ(Ｏ２)e ＝０であることから、そのときの吸入空気量Ｆａおよび燃料噴射量ｍf などに応じ、式（１４）などを用いて求めることができる。 Φ (O2) exh is the oxygen concentration in the exhaust gas, and is calculated by the following equation (15) in the lean operation.

Here, mf is the amount of fuel injected into the cylinder, and Lst is the stoichiometric air-fuel ratio determined according to the type of fuel. That is, mf × Lst × φ (O2) a in the equation (15) corresponds to the amount of oxygen consumed by complete combustion of the injected fuel amount mf in the lean operation. According to the equations (14) and (15), in order to calculate the oxygen concentration φ (O2) e in the recirculated exhaust gas, the initial value of the oxygen concentration φ (O2) exh in the exhaust gas is required. The initial value of φ (O2) exh is, for example, φ (O2) e = 0 when the condition that the EGR operation is stopped immediately after the start of the engine 3 is set. Depending on the intake air amount Fa, the fuel injection amount mf and the like, it can be obtained using the equation (14).

  Therefore, the oxygen concentration φ (O2) e in the recirculated exhaust gas calculated by the equation (14), the air amount ma and the recirculated exhaust gas amount me calculated by the equations (12) and (13) are substituted into the equation (11). Thus, the in-cylinder oxygen amount mo2 in the lean operation can be calculated. Further, in the rich operation, since the in-cylinder oxygen is completely consumed by the combustion, φ (O2) exh = 0, so that by substituting this into the equation (14), the oxygen concentration φ in the recirculated exhaust gas (O2) e is obtained, and the in-cylinder oxygen amount mo2 can be calculated.

Returning to FIG. 4, in step 33 following step 32, an in-cylinder inert gas amount mint is calculated. As described above, since the in-cylinder inert gas is a gas other than oxygen among the gases present in the cylinder 3a, the in-cylinder inert gas amount mint is the in-cylinder oxygen amount mo2 obtained in step 32. Is calculated by the following equation (16).
mint = (ma + me) -mo2 (16)

  Next, the in-cylinder state parameter [O2] is determined by setting the actual intake manifold temperature Ti, the in-cylinder oxygen amount mo2 and the in-cylinder inert gas amount mint estimated in steps 31 to 33, respectively (step 34), and the present process. Exit.

  As is apparent from the above, in the calculation process of the in-cylinder state parameter [O2], the intake air amount Fa detected by the airflow sensor 27, the intake manifold pressure Pi detected by the intake pressure sensor 24, and the intake air temperature sensor 25 are detected. The in-cylinder oxygen amount mo2, the in-cylinder inert gas amount mint, and the actual intake manifold temperature Ti are estimated in all operating states including a transient state using the intake manifold temperature Ts and the EGR model. Then, with these three parameters as one set, an in-cylinder state parameter [O2] representing a state in the cylinder 3a immediately before fuel injection is determined. Since the in-cylinder state parameter [O2] represents the state in the cylinder 3a immediately before fuel injection as described above, the engine water temperature Tw may be included in this.

  FIG. 5 shows the Q * i, j map setting process. This Q * i, j map defines the optimum fuel injection parameter Q * i, j for the in-cylinder state parameter [O2] and the engine speed Ne in a steady state. The fuel injection parameter Q * i, j is composed of a total of three control parameters: the injection pressure Pe of the injector 6, the injection time De, and the injection timing TMe. The subscript i indicates the address of the engine speed Ne and the subscript j. Represents the address of the in-cylinder state parameter [O2]. This setting process is executed in advance in a bench test (benchmark test).

  In this process, first, the fuel injection parameter Q *, that is, the injection pressure Pe, the injection time Te, is controlled while the accelerator opening AP, the opening of the vane opening control valve 12, the EGR valve opening LE, and the like are controlled to certain values. Then, the injection timing TMe is tuned (adjusted) (step 41). Next, in this state, it is determined whether or not the combustion state has become optimal (step 42). This determination is performed based on one appropriate predetermined criterion, for example, a criterion such as a minimum NOx emission amount (NOx best), a best fuel consumption (fuel consumption best), or a maximum output (output best). Alternatively, determination may be made for each of the plurality of criteria, and the fuel injection parameter Q * may be set.

  When the answer to step 42 is YES and the combustion state becomes optimum, the fuel injection parameter Q * at that time is assigned to the addresses i and j corresponding to the engine speed Ne and the in-cylinder state parameter [O2] at that time. Is assigned (step 43). Thereby, one fuel injection parameter Q * i, j is determined. Next, it is determined whether or not the assignment of the fuel injection parameter Q * is completed for all addresses i and j of the Ne value and the [O2] value (step 44). When the answer is NO, the steps 41 to 43 are repeated, and when the answer is YES, the process is terminated. As a result, a Q * i, j map as shown in FIG. 6 is obtained, and the fuel injection parameter Q * i for all addresses i, j corresponding to the engine speed Ne and the in-cylinder state parameter [O2]. , j is assigned.

  Accordingly, if the engine speed Ne and the in-cylinder state parameter [O2] are obtained in the steady state of the engine 3, the fuel injection parameters Q * i, j corresponding to the addresses i, j are represented in the Q * i, j map. By reading from, it is possible to uniquely determine the optimum fuel injection parameter Q * for the state of the combustion chamber 3d at that time, that is, the injection pressure Pe, the injection time Te, and the injection timing TMe. When the fuel injection parameter Q * i, j is determined, the torque T of the engine 3 obtained at that time is also uniquely determined using the address i, j as a function. The determined torque Ti, j is Ti , j map (not shown).

  The Q * i, j map and Ti, j map are set separately for lean operation and rich operation. As the lean operation map, a normal lean operation map and a PM (Particulate Matter) oxidation map are provided, and as the rich operation map, a NOx reduction map and a sulfur desorption map are provided. The set air-fuel ratio when using the normal lean operation map, PM oxidation map, NOx reduction map, and sulfur desorption map are A / FLN, A / FLP, A / FRN, and A / FRS, respectively. A / FLN> A / FLP> A / FRS> A / FRN is established.

Further, in the engine control of the present embodiment, all control parameters including the fuel injection parameter Q * and the torque T are set based on the addresses i and j.
The above Q * i, j map is set on the assumption that the engine 3 is in a steady state. This is because, in a steady state, the in-cylinder inert gas amount mint and the actual intake manifold temperature Ti are determined almost uniquely with respect to a certain cylinder oxygen amount mo2, and the relationship between the three components can be regarded as substantially constant. This is because the optimum fuel injection parameter Q * is also uniquely determined for the state of the combustion chamber 3d represented by these three parties. However, in the transient state, the relationship between the three is shifted from the steady state. For example, even if the in-cylinder oxygen amount mo2 is the same, the in-cylinder inert gas amount mint and the actual intake manifold temperature Ti are not in the steady state. Since the values are different, the combustion state changes accordingly. For this reason, in the transient state, the optimum fuel injection parameter Q * cannot be obtained only by referring to the Q * i, j map.

From the above viewpoint, in order to quantitatively compensate for the influence of the deviation of the in-cylinder inert gas amount mint and the actual intake manifold temperature Ti on the combustion in the transient state, the correction function f (α , Β) i, j is introduced.
f (α, β) i, j = (mint / mints) ^{−αi, j} × (Ti / Tis) ^{βi , j} (17)
This correction function f (α, β) i, j is obtained by changing the actual in-cylinder oxygen amount mo2 in the transient state to the in-cylinder oxygen amount (hereinafter ““ It is used to convert to mo2v (referred to as “virtual cylinder oxygen amount”).
mo2v = mo2 × f (α, β) i, j (18)

In the equation (17), mints and Tis are the in-cylinder inert gas amount and the actual intake manifold temperature in the steady state, respectively. Further, mint and Ti in the equation are the actual in-cylinder inert gas amount and the actual intake manifold temperature in the transient state calculated by the above-described method, respectively. That is, the first term (mint / mints) ^{-αi, j} in the ^equation represents the degree of influence on combustion due to the displacement of the in-cylinder inert gas amount, and the second term (Ti / Tis) ^{βi, j} is Indicates the degree of influence on combustion due to the intake manifold temperature difference. Αi, j and βi, j are correction variables for defining the degree of influence. For this reason, the correction variable α is set to the value 0 in the operating state in which the EGR device 14 is stopped and it is considered that there is no influence of the in-cylinder inert gas amount.

  FIG. 7 shows a process for setting correction variables αi, j, βi, j. This process is executed in advance in the bench test in the same manner as the Q * i, j map setting process described above. In this process, first, the opening degree of the vane opening degree control valve 12 and / or the EGR valve opening degree LE is changed from a steady state in which the engine 3 is operated at a constant engine speed Ne and in-cylinder state parameter [O2]. By doing so, only the in-cylinder inert gas amount mint is offset (a small amount is changed) (step 61). Next, in this offset state, it is determined whether or not the combustion state has become optimal while tuning the fuel injection parameter Q * (step 62). This determination is made based on the same standard as the above-described standard used for setting the Q * i, j map.

  When the answer to step 62 is YES, the combustion state in the steady state closest to the combustion state at that time is selected as the virtual combustion state from the Q * i, j map (step 63). For this selection, for example, an approximate function of the heat generation rate at each address i, j on the Q * i, j map is obtained in advance, and the address i at that time corresponds to the engine speed Ne before the offset. This is done by specifying an address j having an approximate function value closest to the heat release rate. When the addresses i and j are specified in this manner, the in-cylinder state parameter [O2] is also specified, and the in-cylinder oxygen amount mo2 is obtained as the virtual cylinder oxygen amount mo2v.

Next, a correction variable α is calculated (step 64). This calculation is performed as follows. That is, in step 63, the virtual cylinder oxygen amount mo2v is obtained, and the cylinder oxygen amount mo2 is calculated from Equation (11) at any time. Therefore, from these mo2v value, mo2 value and Equation (18), The correction function f (α, β) i, j is obtained from the equation (19).
f (α, β) i, j = mo2v / mo2 (19)

On the other hand, the in-cylinder inert gas amount mint in the equation (17) is calculated at any time by the equation (16), and the in-cylinder inert gas amount mints in the steady state is known from the address j before the offset, Ti / Tis is equal to the value 1 because the actual intake manifold temperature Ti is not offset. Therefore, the following equation (20) is established, and the correction variable α can be calculated from the equations (20) and (19).
f (α, β) i, j = (mint / mints) ^{−αi, j} (20)

  Subsequently, in order to calculate the correction variable β, only the actual intake manifold temperature Ti is offset by changing the opening degree of the vane opening degree control valve 12 and / or the EGR valve opening degree LE from the steady state (step) 65). Thereafter, similarly to steps 62 to 64, it is determined whether or not the combustion state has become optimum (step 66), and the steady state combustion state closest to the optimum combustion state is selected as the virtual combustion state (step 67). ) And a correction variable β is calculated from the selected virtual combustion state and equations (17) and (18) (step 68). As described above, the correction functions α and β are set for one address i and j. Next, it is determined whether or not the calculation of the correction functions α and β is completed for all addresses i and j of the Ne value and the [O2] value (step 69). When this answer is NO, the above steps 61 to 68 are repeated, and when it becomes YES, this processing is ended. As described above, the correction variables α and β are set for all the addresses i and j, stored as α i, j map and β i, j map, and the correction function f according to α i, j and β i, j. (Α, β) i, j is set.

  FIG. 8 determines the fuel injection parameter Q * i, j during operation of the engine 3 using the Q * i, j map and the correction function f (α, β) i, j set in advance as described above. Indicates processing. First, it is determined whether or not the engine 3 is in a transient state (step 71). When the answer is NO and the engine 3 is in a steady state, the above-described method is applied to the in-cylinder state parameter [O2] s (in-cylinder oxygen amount mo2s, in-cylinder inert gas amount mints, and actual intake manifold temperature Tis in the steady state. ) Is calculated (step 72). Next, an address i, j corresponding to the engine speed Ne and the calculated in-cylinder state parameter [O2] is determined (step 73), and a fuel injection parameter Q * i, j corresponding to the determined address i, j is determined. Is determined from the Q * i, j map and determined as the fuel injection parameter Q * (step 74). Further, the correction variables α and β are determined by searching the α i, j map and β i, j (step 75).

  If the answer to step 71 is YES and the engine 3 shifts from the steady state to the transient state, the in-cylinder state parameters [O2] (mo2, mint and Ti) in the transient state are calculated (step 76). Then, using the calculated mint value and Ti value, the mints value and Tis value in the steady state calculated in step 72, and the correction variables α and β determined in step 75, the correction function f (α , Β) is calculated (step 77). Next, using the calculated correction function f (α, β) and the in-cylinder oxygen amount mo2 calculated in step 76, the virtual in-cylinder oxygen amount mo2v is calculated by equation (18) (step 78). As a result, the actual in-cylinder oxygen amount mo2 in the transient state is converted into the virtual in-cylinder oxygen amount mo2v in the steady state. Next, on the same address i, an in-cylinder state parameter [O2] including the in-cylinder oxygen amount mo2 closest to the calculated virtual cylinder oxygen amount mo2v is selected, and the corresponding addresses i and j are assigned to the virtual address i, It is determined as jv (step 79). As a result, as shown in FIG. 9, the address of the in-cylinder state parameter [O2] moves from j in the steady state to the virtual address jv on the Q * i, j map. Then, the fuel injection parameter Q * i, jv corresponding to the virtual address i, jv is read from the Q * i, j map and determined as the fuel injection parameter Q * (step 80). When the fuel injection parameter Q * i, jv is determined, the torque T of the engine 3 obtained at that time can be determined as T = Ti, jv from the Ti, j map.

  FIG. 10 shows the control regions corresponding to the two combustion modes of the engine 3, that is, the low temperature combustion mode and the normal combustion mode, on the coordinate plane defined by the required torque Td according to the engine speed Ne and the accelerator pedal opening AP. It is shown. An O2 reference LTC control region, an O2 reference STD control region, and a pedal reference STD control region are set in order from the low load side. That is, the O2 reference LTC control region, the O2 reference STD control region, and the pedal reference STD control region correspond to the low load operation region, the medium load operation region, and the high load operation region of the engine 3, respectively. The O2 reference LTC control region corresponds to the low temperature combustion mode, and the O2 reference STD control region and the pedal reference STD control region correspond to the normal combustion mode. A curve LTH shown in FIG. 10 corresponds to a state in which the throttle valve 7 is fully open and the EGR valve 14b is fully closed, that is, a state in which the intake air amount cannot be further increased by changing the air adjustment parameter A *. Yes.

  In the O2 reference LTC control region and the O2 reference STD control region, the fuel injection parameter Q * is calculated based on the engine speed Ne and the in-cylinder state parameter [O2] described above. In the following description, the fuel injection parameter calculation map used in the O2 reference LTC control region is referred to as “Q * O2LTC map”, and the fuel injection parameter calculation map used in the O2 reference STD control region is referred to as “Q * O2STD map”. That's it. In the O2 reference LTC control region and the O2 reference STD control region, a map for calculating the air adjustment parameter A * corresponding to these control regions is set, and the air adjustment used in the O2 reference LTC control region is set. The parameter calculation map is referred to as “A * LTC map”, and the air adjustment parameter calculation map used in the O2 reference STD control region is referred to as “A * STD map”. The A * LTC map is set so that the EGR rate is larger than the A * STD map.

  In the pedal reference STD control region, a fuel injection parameter calculation map corresponding to the engine speed Ne and the accelerator pedal opening AP is used. Hereinafter, this map is referred to as a “Q * PDSTD map”.

  The Q * O2LTC map, the Q * O2STD map, and the Q * PDSTD map are set so that the air-fuel ratios realized by the fuel injection according to the set values of the respective maps are different from each other.

  Next, the transition control when shifting from the O2 reference LTC control to the O2 reference STD control and the shift control when shifting from the O2 reference STD control to the O2 reference LTC control will be described. FIG. 11 is a diagram for explaining this transition control. When the O2 reference LTC control is executed, as indicated by the solid line L1, as the required torque Td (accelerator opening AP) increases, FIG. When the in-cylinder oxygen amount mo2 increases, when the in-cylinder oxygen amount mo2 reaches the first A * switching threshold value Oxy1, a map for calculating the air conditioning parameter A * is obtained from the A * LTC map by A * STD. Switch to the map. The in-cylinder oxygen amount mo2 is increased while maintaining the output torque of the engine 3 at a substantially constant value TH. At this time, the fuel injection parameter Q * is determined using the Q * O2LTC map so that the output torque becomes a substantially constant value TH.

  When the in-cylinder oxygen amount mo2 increases and reaches the first Q * map switching threshold value Oxy3 (> Oxy1), the map for calculating the fuel injection parameter Q * is switched from the Q * O2LTC map to the Q * O2STD map.

  On the other hand, when the O2 standard STD control is executed, as shown by the broken line L2, when the in-cylinder oxygen amount mo2 decreases as the required torque Td decreases, the in-cylinder oxygen amount mo2 becomes the output torque. When the second A * switching threshold value Oxy2 corresponding to the output torque TL smaller than TH is reached, the map for calculating the air conditioning parameter A * is switched from the A * STD map to the A * LTC map. The in-cylinder oxygen amount mo2 is decreased while maintaining the output torque of the engine 3 at a substantially constant value TL. At this time, the fuel injection parameter Q * is determined using the Q * O2STD map so that the output torque becomes a substantially constant value TL. Here, the second A * switching threshold value Oxy2 is set to a value smaller than the first Q * map switching threshold value Oxy3.

  When the in-cylinder oxygen amount mo2 decreases and reaches the second Q * map switching threshold value Oxy4 (<Oxy2), the map for calculating the fuel injection parameter Q * is switched from the Q * O2STD map to the Q * O2LTC map. Here, the second Q * switching threshold value Oxy4 is set to a value smaller than the first A * switching threshold value Oxy1.

  Thus, in the present embodiment, when shifting from the O2 reference LTC control to the O2 reference STD control, the air adjustment parameter A * is calculated when the in-cylinder oxygen amount mo2 reaches the first A * switching threshold value Oxy1. When the map to be used is switched and then the cylinder oxygen amount (intake air amount) is increased while maintaining the engine output torque substantially constant, and the cylinder oxygen amount mo2 reaches the first Q * switching threshold value Oxy3, the fuel The map used for calculating the injection parameter Q * is switched. When the O2 reference STD control is shifted to the O2 reference LTC control, the map used for calculating the air adjustment parameter A * is switched when the in-cylinder oxygen amount mo2 reaches the second A * switching threshold value Oxy2. Next, when the engine output torque is maintained substantially constant, the in-cylinder oxygen amount (intake air amount) is decreased, and when the in-cylinder oxygen amount mo2 reaches the second Q * switching threshold value Oxy4, the fuel injection parameter Q * is calculated. The map to be used is switched. As a result, the transition from the O2 standard LTC control to the O2 standard STD control can be smoothly performed without torque fluctuation, and excessive control mode switching due to slight accelerator operation can be prevented. .

  The first and second A * switching threshold values Oxy1, Oxy2 and the first and second Q * switching threshold values Oxy3, Oxy4 are set to optimum values by a bench test. In order to shorten the time required to increase the in-cylinder oxygen amount mo2 from the first A * switching threshold value Oxy1 to the first Q * switching threshold value Oxy3, the air conditioning parameter A * is changed with a moderate overshoot. It is desirable. The same applies to the case where the time required to reduce the in-cylinder oxygen amount mo2 from the second A * switching threshold value Oxy2 to the second Q * switching threshold value Oxy4 is shortened.

Next, transition control between the O2 standard STD control and the pedal standard STD control will be described.
FIG. 12A is a diagram for explaining the transition control (transition control during acceleration) from the O2 reference STD control to the pedal reference STD control. The O2 reference STD control area and the pedal reference STD control area A first transition control area is set between them. In the first transition control region, the fuel injection parameter Q * is basically calculated using a first transition control reference map (hereinafter referred to as “Q * O2PD map”) indicated by a solid line L3. The Q * O2PD map is a map set according to the engine speed Ne and the accelerator pedal opening AP, and the accelerator from the reference accelerator pedal opening APB corresponding to the point P1 to the zero EGR opening APEGRZ corresponding to the point P2. The opening degree AP is set. The reference accelerator opening APB is the accelerator opening AP at which the cylinder oxygen amount mo2 becomes the critical oxygen amount mo2c in the reference engine operation state (hereinafter referred to as “reference operation state”), and the zero EGR opening APEGRZ is In the reference operation state, the accelerator opening AP is set so that the EGR valve 14b is fully closed. The critical oxygen amount mo2c is the maximum in-cylinder oxygen amount mo2 in the O2 reference STD control region, and the fuel injection parameter Q * corresponding to the critical oxygen amount mo2c is the critical fuel injection parameter Q * c.

  Since the actual engine operating state deviates from the standard operating state, the accelerator opening (hereinafter referred to as “critical accelerator opening”) APc at which the in-cylinder oxygen amount mo2 reaches the critical oxygen amount mo2c is shown in FIG. As described above, the value is different from the reference accelerator opening APB. Therefore, in this case, the Q * O2PD map indicated by the solid line L3 cannot be referred to as it is. Therefore, in the present embodiment, the accelerator opening AP in the first transition control region is converted into the map search opening APM, and the Q * O2PD map is searched according to the map search opening APM and the engine speed Ne. Like to do. This is substantially equivalent to using the correction map indicated by the broken line L4.

Specifically, the detected accelerator opening AP is converted into a map search opening APM by the following equation (21), for example, and the fuel injection parameter Q * is calculated by searching the Q * O2PD map. . When the accelerator opening AP reaches the zero EGR opening APEGRZ, the fuel injection control is switched from the first transition control to the pedal reference STD control.

  According to the first transition control, it is possible to smoothly transition from the O2 standard STD control to the pedal standard STD control during acceleration when the accelerator pedal is depressed. Further, the detected accelerator opening AP is converted into a map search opening APM according to the critical accelerator opening APc that is the accelerator opening when the in-cylinder oxygen amount mo2 becomes the critical oxygen amount mo2c. Since the Q * O2PD map search is performed, smooth transition is possible even if the engine operating state deviates from the reference operating state.

  FIG. 12B is a diagram for explaining the transition control from the pedal reference STD control to the O2 reference STD control (transition control at the time of deceleration). The O2 reference STD control area and the pedal reference STD control area A second transition control area is set between them. In this second transition control region, the fuel injection parameter Q * is basically calculated using a second transition control reference map (hereinafter referred to as “Q * PDO2 map”) indicated by a solid line L5. The Q * PDO2 map is a map set according to the engine speed Ne and the in-cylinder oxygen amount mo2, from the reference zero EGR oxygen amount mo2EGRB corresponding to the point P3 to the critical oxygen amount mo2c corresponding to the point P4. The in-cylinder oxygen amount mo2 is set. The reference zero EGR oxygen amount mo2EGRB is the in-cylinder oxygen amount mo2 when the accelerator opening AP is the zero EGR opening APEGRZ in the reference operation state.

  Since the actual engine operating state deviates from the reference operating state, the in-cylinder oxygen amount (hereinafter referred to as “zero EGR oxygen amount”) mo2EGRZ when the accelerator opening AP becomes the zero EGR opening APEGRZ is, for example, shown in the figure. Thus, a value different from the reference zero EGR oxygen amount mo2EGRB is obtained. Therefore, in this case, the Q * PDO2 map indicated by the solid line L5 cannot be referred to as it is. Therefore, in the present embodiment, the in-cylinder oxygen amount mo2 in the second transition control region is converted to the map search oxygen amount mo2M, and the Q * PDO2 map is changed according to the map search oxygen amount mo2M and the engine speed Ne. I try to search. This is substantially equivalent to using the correction map indicated by the broken line L6.

Specifically, the calculated in-cylinder oxygen amount mo2 is converted into a map search oxygen amount mo2M by the following equation (22), for example, and the fuel injection parameter Q * is calculated by searching the Q * PDO2 map. To do. When the in-cylinder oxygen amount mo2 reaches the critical oxygen amount mo2c, the fuel injection control is switched from the second transition control to the O2 reference STD control.

  According to the second transition control, it is possible to smoothly shift from the pedal reference STD control to the O2 reference STD control during deceleration when the accelerator pedal is being returned. Also, the in-cylinder oxygen amount mo2 calculated from time to time is converted into the map search oxygen amount mo2M according to the zero EGR oxygen amount mo2EGRZ which is the in-cylinder oxygen amount when the accelerator opening AP becomes the zero EGR opening APEGRZc. Then, since the Q * PDO2 map search is performed, even if the engine operating state deviates from the reference operating state, a smooth transition is possible.

  When the accelerator pedal stops during execution of the first transition control or the second transition control, the fuel injection parameter Q * at the time of the stop is held, and when the accelerator pedal starts to move next, the accelerator opening AP The direction of the subsequent transition control is determined according to the polarity of the time differential value. That is, if the accelerator pedal stops during execution of the first transition control and then the accelerator opening AP starts to increase again, the transition control toward the point P2 is continued, while the accelerator opening AP starts to decrease after the stop. If so, the transition control to return to the point P1 is executed. Further, if the accelerator pedal stops during execution of the second transition control, and then the accelerator opening AP starts to decrease again, the transition control toward the point P4 is continued, while the accelerator opening AP starts to increase after the stop. If so, the transition control to return to the point P3 is executed.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, the fuel injection parameter Q * is configured by the injection time De, the injection timing TMe, and the injection pressure Pe, but may be one or two of these. Furthermore, although the example which applied this invention to control of the diesel engine was shown in embodiment mentioned above, this invention is applicable also to control of a gasoline engine.

  The present invention can also be applied to control of a marine vessel propulsion engine such as an outboard motor having a crankshaft as a vertical direction.

It is a figure which shows roughly the control apparatus to which this invention is applied with an internal combustion engine. It is a block diagram which shows a control apparatus. It is a figure which shows an A * map. It is a flowchart which shows the calculation process of an in-cylinder state parameter. It is a flowchart which shows the setting process of a Q * i, j map. It is a figure which shows Q * i, j map. It is a flowchart which shows the setting process of correction variable (alpha) i, j and (beta) i, j. It is a flowchart which shows the setting process of fuel parameter Q *. It is a figure explaining the method of calculating | requiring the virtual address i and jv. It is a figure which shows the control area | region of fuel-injection control. It is a figure for demonstrating the transition control between oxygen reference low temperature combustion control and oxygen reference normal combustion control. It is a figure for demonstrating transfer control between oxygen reference | standard normal combustion control and pedal reference | standard normal combustion control.

Explanation of symbols

2 Electronic control unit (intake air amount control means, recirculation exhaust gas flow rate estimation means, in-cylinder oxygen amount estimation means, fuel injection parameter determination means, injector control means, air adjustment parameter calculation means)
3 Internal combustion engine 3a Cylinder 4 Intake pipe (intake system)
6 Injector 7 Throttle valve (intake air amount control means)
14 Exhaust gas recirculation device 22 Crank angle sensor (rotational speed detection means)
27 Air flow sensor (intake air volume detection means)
30 accelerator opening sensor (accelerator depression amount detection means)

Claims (2)

Air is sucked into the cylinder through the intake system, fuel injected from the injector is supplied into the cylinder, and part of the exhaust gas discharged from the internal combustion engine is returned to the intake system as recirculated exhaust gas by the exhaust gas recirculation device. In a control device for an internal combustion engine,
Intake air amount control means for controlling the amount of intake air taken into the cylinder via the intake system;
An intake air amount detection means for detecting the intake air amount;
Recirculation exhaust gas flow rate estimating means for estimating the flow rate of recirculated exhaust gas by the exhaust gas recirculation device;
In-cylinder oxygen amount estimation means for estimating the amount of oxygen present in the cylinder based on the detected intake air amount and the estimated recirculated exhaust gas flow rate;
A rotational speed detecting means for detecting the rotational speed of the engine;
Fuel injection parameter determination means for determining a fuel injection parameter by searching a fuel injection parameter map according to the detected engine speed and the estimated in-cylinder oxygen amount;
Injector control means for controlling the injector based on the determined fuel injection parameter ;
An air adjustment parameter calculating means for calculating an air adjustment parameter for controlling the intake air amount by searching an air adjustment parameter map according to the engine operating state ;
The fuel injection parameter map includes a low temperature combustion fuel injection parameter map corresponding to a low load operation region of the engine and a normal combustion fuel injection parameter map corresponding to an operation region on a higher load side than the low load operation region. Become
The fuel injection parameter determining means switches the fuel injection parameter map to be used from the low temperature combustion fuel injection parameter map to the normal combustion fuel injection parameter map, or from the normal combustion fuel injection parameter map. when switching the injection parameter map, you have rows switching with a hysteresis,
The intake air amount control means controls the intake air amount according to the calculated air adjustment parameter,
The air conditioning parameter map is composed of a low temperature combustion air conditioning parameter map corresponding to the low load operation region and a normal combustion air conditioning parameter map corresponding to the high load side operation region,
In the case where the low temperature combustion air adjustment parameter map is used, the air adjustment parameter calculation means switches to the normal combustion air adjustment parameter map when the in-cylinder oxygen amount reaches a first threshold value. On the other hand, when the normal combustion air adjustment parameter map is used, the in-cylinder oxygen amount is larger than the first threshold value, and the output torque of the engine is smaller than the output torque corresponding to the first threshold value. It becomes when it reaches the second threshold value, the control apparatus for an internal combustion engine, characterized in row Ukoto the switching to the low-temperature combustion air adjustment parameter map. The fuel injection parameter determination means uses the low temperature combustion fuel injection parameter map, and when the air adjustment parameter map is switched to the normal combustion air adjustment parameter map, the in-cylinder oxygen amount is The fuel injection parameter is determined so that the output torque of the engine becomes substantially constant until a third threshold value greater than the second threshold value is reached, and the normal combustion is performed when the in-cylinder oxygen amount reaches the third threshold value. When the normal combustion fuel injection parameter map is used, when the air adjustment parameter map is switched to the low temperature combustion air adjustment parameter map, the cylinder is Until the internal oxygen amount reaches the fourth threshold value which is smaller than the first threshold value, the output torque of the engine is almost equal to one. Determining the fuel injection parameter so that, when said cylinder oxygen amount reaches the fourth threshold value, according to claim 1, characterized in that for switching to the low temperature combustion fuel injection parameter map Control device for internal combustion engine.

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