JP2000282926A - Control device of diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance control accuracy of air-fuel ratio by installing a catalyst consisting of a NOx absorbing material in the exhaust passage of an engine and eliminating dispersion in the injection amount, resulting chiefly from the individual difference from injector to injector, in the case where the air-fuel ratio in the engine combustion chamber is controlled so as to become an approx. theoretical air-fuel ratio, when the NOx is released from the catalyst. SOLUTION: When NOx absorbing amount of a catalyst has become excessive, the air-fuel ratio in the combustion chamber of an engine is feedback controlled so that it becomes approx. the theoretical air-fuel ratio on the basis of the output signal from an O2 sensor, and the fuel is split into two and injected. The gear ratio of a CVT is controlled so that the engine is put in the high- load operating condition (SB3 and 4), and the dispersion conditions of the fuel injection amount is learnt on the basis of the output signal from the O2 sensor (SB6-11), and on the basis of the result from learning, the fuel injection amount from injector is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of arranging a NOx absorbent in an exhaust passage of an engine, the NOx absorbent comprising
The present invention relates to a control apparatus for a diesel engine that controls the air-fuel ratio of a combustion chamber of an engine to be approximately in the vicinity of a stoichiometric air-fuel ratio when x is to be released. In the present invention, the air-fuel ratio of the combustion chamber refers to the ratio between the total amount of air filled in the combustion chamber and the total amount of fuel injected in one combustion cycle.

[0002]

2. Description of the Related Art Conventionally, a diesel engine has been operated in a state where the average air-fuel ratio of a combustion chamber is considerably lean (for example, A / F ≧ 18) in all normal operation ranges, and the exhaust gas has a high oxygen concentration. The atmosphere becomes an oxygen-excess atmosphere (for example, an atmosphere having an oxygen concentration of 4% or more). Since it is extremely difficult to sufficiently reduce and purify nitrogen oxides (NOx) in such an atmosphere, a method of removing NOx in exhaust gas is to absorb NOx in the oxygen-excess atmosphere while reducing the oxygen concentration, for example. Less than 3-4% (preferably 1
A technique using a so-called NOx absorbent, which releases the absorbed NOx when it is reduced to less than 2%, is being studied.

[0003] Since the absorption performance of the above-mentioned NOx absorbent gradually decreases as the NOx absorption amount increases, the so-called "refresh" which releases the absorbed NOx and restores the absorption performance before the NOx absorption increases. There is a need to do. Therefore, for example, in the control device disclosed in Japanese Patent Application Laid-Open No. 7-279718, during a certain period of time during operation of the engine,
By switching the air-fuel ratio of the combustion chamber so as to be near the stoichiometric air-fuel ratio or a state richer than the stoichiometric air-fuel ratio, the oxygen concentration in the exhaust gas is reduced to refresh the NOx absorbent. Further, according to this method, when the air-fuel ratio of the combustion chamber is switched to a stoichiometric air-fuel ratio or a state richer than the stoichiometric air-fuel ratio, while reducing the amount of air taken into the combustion chamber, the amount of fuel corresponding to the decrease in the air amount is reduced. The amount of injection is increased to suppress fluctuations in engine output.

[0004]

Generally, in a diesel engine, when the average air-fuel ratio of the combustion chamber is close to the stoichiometric air-fuel ratio, the richer the air-fuel ratio is, the worse the combustion state becomes and the exhaust gas becomes exhausted. However, there is a problem that the amount of smoke emitted by the smoke increases rapidly. On the other hand, in order to effectively refresh the NOx absorbent in the control device as in the conventional example, it is preferable that the oxygen concentration in the exhaust gas be as low as possible. It is necessary to control the air-fuel ratio of the combustion chamber of the engine with extremely high precision.

However, since the diesel engine is configured to inject fuel into the combustion chamber in a high-temperature and high-pressure state by a fuel injection valve, the injection amount variation due to individual differences of the fuel injection valve tends to increase. This is a major obstacle to realizing highly accurate air-fuel ratio control.

[0006] The present invention has been made in view of such a point, and an object of the present invention is to provide a NOx absorbent in the exhaust passage as described above, and when the NOx absorbent is refreshed, In a diesel engine control device that controls the air-fuel ratio of the combustion chamber of the engine to be close to the stoichiometric air-fuel ratio, attention is paid to the injection amount variation mainly caused by the individual difference of the fuel injection valve, and this variation is eliminated. Thus, the control accuracy of the air-fuel ratio is improved.

[0007]

In order to achieve the above object, according to the present invention, there is provided an oxygen concentration detecting means for detecting an oxygen concentration in an exhaust passage upstream of a NOx absorbent. When NOx is to be released from the engine, the air-fuel ratio of the combustion chamber of the engine is feedback-controlled based on the value detected by the oxygen concentration detecting means. At this time, the fuel injection amount is controlled based on the value detected by the oxygen concentration detecting means. To learn the state of variation.

More specifically, according to the first aspect of the present invention, as shown in FIG.
NOx is absorbed in exhaust gas in an oxygen-rich atmosphere having a high oxygen concentration, while the absorbed NOx is reduced due to a decrease in oxygen concentration.
NOx absorbent 22 that emits NOx, and air-fuel ratio control means 35a that controls the air-fuel ratio of the combustion chamber 4 of the engine 1 to be close to the stoichiometric air-fuel ratio when NOx is released from the NOx absorbent 22. It is assumed that the diesel engine control device A is used. The air-fuel ratio control unit 35a includes an oxygen concentration detection unit 17 that detects an oxygen concentration in the exhaust passage 20 upstream of the NOx absorbent 22. The air-fuel ratio control unit 35a determines the air-fuel ratio of the combustion chamber 4 of the engine 1 with the oxygen concentration. Detecting means 17
The feedback control is performed based on the value detected by the air-fuel ratio control means 35a. When the air-fuel ratio is controlled by the air-fuel ratio control means 35a to be close to the stoichiometric air-fuel ratio, the fuel injection amount And a learning unit 35c for learning a variation state of.

With the above configuration, first, the engine 1
When the combustion chamber 4 is operated in a state where the average air-fuel ratio is considerably lean and the exhaust gas becomes an oxygen-excess atmosphere,
NOx in the exhaust gas is absorbed by the NOx absorbent 22 and purified. Then, for example, the NOx of the NOx absorbent 22
When the amount of absorption becomes excessive, the air-fuel ratio control means 35a
The air-fuel ratio of the combustion chamber 4 of the engine 1 is controlled so as to be close to the stoichiometric air-fuel ratio, and NOx is released from the NOx absorbent 22 due to a decrease in the oxygen concentration in the exhaust gas, and the NOx absorbent 22 is refreshed. . At this time, the air-fuel ratio control means 35a feedback-controls the air-fuel ratio of the combustion chamber 4 of the engine 1 based on the value detected by the oxygen concentration detection means 17 provided in the exhaust passage 20, so that the fuel injection valve 5a Even if there is a variation in the injection amount due to individual differences, this variation in the injection amount is absorbed by the feedback correction, and the accuracy of control of the air-fuel ratio is improved.

Further, at this time, the variation state of the fuel injection amount is learned by the learning means 35c based on the value detected by the oxygen concentration detecting means 17. That is, when the air-fuel ratio of the combustion chamber 4 of the engine 1 is close to the stoichiometric air-fuel ratio, the detection accuracy of the oxygen concentration in the exhaust gas by the oxygen concentration detecting means 17 is high. The variation state can be accurately learned.
Therefore, if the basic fuel injection amount by the fuel injection valve 5 is corrected based on the learning result, the dispersion of the injection amount due to the individual difference of the fuel injection valve 5 is eliminated,
The control accuracy of the air-fuel ratio can be further increased.

According to a second aspect of the present invention, in the first aspect of the present invention, an intake air amount detecting means for detecting an amount of air taken into a combustion chamber of the engine, and an exhaust gas recirculating means for recirculating a part of exhaust gas to an intake system of the engine. And an exhaust gas recirculation control unit that controls the amount of exhaust gas recirculated by the exhaust gas recirculation unit based on a value detected by the intake air amount detection unit when the engine is in a predetermined operation range. It is assumed that the variation state of the fuel injection amount is learned when it is in an area other than the predetermined operation area.

Thus, when the engine is in the predetermined operating range, the recirculation amount of the exhaust gas is appropriately controlled by the exhaust gas recirculation control unit based on the actual intake air amount detected by the intake air amount detection unit, and the combustion is reduced. The accompanying generation of NOx is suppressed. On the other hand, in such a state where the exhaust gas is recirculated, the variation in the exhaust gas recirculation amount causes the oxygen concentration in the exhaust gas to fluctuate. It cannot be detected accurately. Therefore, according to the present invention, the learning means learns the state of variation of the fuel injection amount in a region other than the predetermined operation region, that is, in a state in which exhaust gas recirculation is not performed, so that erroneous learning can be prevented.

According to a third aspect of the present invention, in the first aspect of the invention, an intake air amount detecting means for detecting an amount of air taken into a combustion chamber of the engine, and an exhaust gas recirculating means for recirculating a part of exhaust gas to an intake system of the engine. And an exhaust gas recirculation control unit that controls the amount of exhaust gas recirculated by the exhaust gas recirculation unit based on the value detected by the intake air amount detection unit when the engine is in a predetermined operation range. An exhaust gas recirculation prohibiting means for prohibiting the recirculation of exhaust gas by the exhaust gas recirculation means when learning the variation state of the amount is provided.

Thus, similarly to the second aspect of the present invention, an appropriate amount of exhaust gas is recirculated to the combustion chamber of the engine, and generation of NOx accompanying combustion is suppressed. Further, when learning the variation state of the fuel injection amount by the learning means, the recirculation of the exhaust gas is prohibited by the exhaust gas recirculation prohibiting means, whereby erroneous learning can be prevented.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the air-fuel ratio is brought close to the stoichiometric air-fuel ratio by the fuel injection valve for directly injecting the fuel into the in-cylinder combustion chamber of the engine and the air-fuel ratio control means. The fuel injected by the fuel injection valve into two parts, a main injection near the compression top dead center of the cylinder, and a sub-injection from the beginning of the intake stroke to the first half of the compression stroke. An injection control means is provided.

With this configuration, when controlling the air-fuel ratio of the combustion chamber of the engine to be near the stoichiometric air-fuel ratio by the air-fuel ratio control means, first, the sub-injection is performed from the initial stage of the intake stroke of the cylinder to the first half of the compression stroke. Done. Then, the injected fuel spray diffuses substantially uniformly throughout the combustion chamber, is sufficiently vaporized and atomized, and is mixed with air to form a so-called lean premixed gas. In the lean premixed gas, the fuel gas gradually reacts with the surrounding oxygen (cold flame reaction) as the in-cylinder pressure and the in-cylinder temperature rise in the latter half of the compression stroke, and the heat generated by this reaction causes the entire combustion chamber to be heated. Temperature is further increased. Then, when the main injection is performed near the compression top dead center of the cylinder, the fuel spray forms a rich mixture portion in the lean premixture, and explosive combustion starts after a short ignition delay time. Is done.

According to such a combustion state, even if the fuel injection amount is considerably increased so that the air-fuel ratio of the combustion chamber 4 becomes close to the stoichiometric air-fuel ratio, a part of the fuel is injected at an early stage and the lean Since the air-fuel mixture is formed, the fuel spray injected later does not become so fuel-rich, and the vaporization and atomization of the fuel spray is greatly improved by the reaction heat of the lean pre-air-fuel mixture. , The increase in smoke can be sufficiently suppressed. Further, the fuel and oxygen are consumed by the cool flame reaction that gradually progresses in the lean premixed gas, so that the rapid increase in the combustion pressure and the combustion temperature in the initial explosive combustion is moderated. As a result, generation of NOx can be reduced.
In addition, the suppression of the smoke and NOx as described above also occurs when the clothing injection of the fuel is performed during a predetermined period in the initial stage of the expansion stroke after the main injection near the compression top dead center, corresponding to the operating state of the engine. Obtainable.

According to a fifth aspect of the present invention, the air-fuel ratio control means according to the fourth aspect of the present invention causes the air-fuel ratio of the combustion chamber of the engine to be close to the stoichiometric air-fuel ratio when the engine is in a predetermined high load operation state. Control. With this configuration, the engine output can be sufficiently increased by increasing the fuel injection amount so that the air-fuel ratio becomes close to the stoichiometric air-fuel ratio in a high load operation state in which the required output to the engine is high. Also,
Since the fuel injection amount is originally large in the high-load operation state, the air-fuel ratio can be made close to the stoichiometric air-fuel ratio without increasing the fuel injection amount so much, and the fluctuation of the engine output is suppressed.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects of the present invention, a turbocharger for supercharging intake air by exhaust of an engine and a supercharging pressure by the turbocharger are adjusted. And a supercharging pressure adjusting means, wherein the air-fuel ratio controlling means controls the supercharging of the turbocharger by the supercharging pressure adjusting means when controlling the air-fuel ratio of the combustion chamber of the engine to be close to the stoichiometric air-fuel ratio. It is configured to include a supercharging pressure reducing unit that reduces the supply pressure.

In this configuration, when controlling the air-fuel ratio of the combustion chamber of the engine to be close to the stoichiometric air-fuel ratio, the supercharging pressure adjusting means is operated by the supercharging pressure reducing means, and the supercharging of the turbocharger is performed. The pressure is reduced. As a result, the amount of air taken into the combustion chamber decreases and the air-fuel ratio changes to the rich side, so that the air-fuel ratio of the combustion chamber is controlled to be close to the stoichiometric air-fuel ratio without increasing the fuel injection amount too much. It becomes possible. Further, since the engine output decreases due to the decrease in the intake air amount, the increase in the engine output due to the increase in the fuel injection amount can be offset, and as a result, the fluctuation in the engine output can be reduced.

According to a seventh aspect of the present invention, the engine according to any one of the first to fifth aspects is a vehicle-mounted engine,
A continuously variable transmission for continuously changing the output of the engine and transmitting the output to the driving wheels of the vehicle; and controlling the continuously variable transmission when the air-fuel ratio is controlled to be near the stoichiometric air-fuel ratio by the air-fuel ratio control means. Speed ratio control means for controlling the speed ratio of the engine so that the engine is in a predetermined high load operation state.

In this apparatus, when controlling the air-fuel ratio of the combustion chamber of the engine to be close to the stoichiometric air-fuel ratio, the speed ratio of the continuously variable transmission is controlled by the speed ratio control means to forcibly start the engine at a predetermined speed. High load operation state. That is, it is possible to obtain the same operation and effect as in the fifth aspect of the invention by setting the engine to the high load operation state regardless of the running state of the vehicle.

According to an eighth aspect of the present invention, the engine according to any one of the sixth and seventh aspects is mounted on a vehicle having an electric motor for traveling, and the vehicle is driven by at least one of the engine and the electric motor. A driven hybrid vehicle. Thus, the driving of the hybrid vehicle may be performed by at least one of the engine and the electric motor, so that the engine can be controlled to the high-load operation state regardless of the traveling state of the vehicle. Therefore,
The same function and effect as the seventh aspect of the invention can be obtained.

A ninth aspect of the present invention is directed to a diesel engine control apparatus for driving a hybrid vehicle in cooperation with an electric motor for driving, and directly injects fuel into a combustion chamber in a cylinder of the engine. A fuel injection valve, an oxygen concentration detecting means for detecting an oxygen concentration in an exhaust passage of the engine, and an air-fuel ratio of the combustion chamber based on a value detected by the oxygen concentration detecting means. Air-fuel ratio control means for performing feedback control to the air-fuel ratio control means when the air-fuel ratio is controlled to be close to the stoichiometric air-fuel ratio. Fuel injection control means for performing two-split injections, i.e., injection and sub-injection from the beginning of the intake stroke to the first half of the compression stroke, and the air-fuel ratio control means bringing the air-fuel ratio to near the stoichiometric air-fuel ratio When controlled so, a configuration and a learning means for learning the variation state of the fuel injection amount based on a value detected by the oxygen concentration detection means.

With the above-described configuration, a hybrid vehicle normally performs high-efficiency operation by controlling the engine to a high-load low-rotation operation state with excellent fuel efficiency while the vehicle is running. For example, by increasing the fuel injection amount by a small amount by the fuel ratio control means, it is possible to control the air-fuel ratio of the combustion chamber of the engine to be substantially equal to the stoichiometric air-fuel ratio. At this time, the variation state of the fuel injection amount can be accurately learned by the learning means based on the value detected by the oxygen concentration detecting means, as in the first aspect of the present invention. If the basic fuel injection amount by the injection valve is corrected, the variation in the injection amount due to the individual difference of the fuel injection valve can be eliminated, and the control accuracy of the air-fuel ratio can be improved. In addition, the fuel injection control means injects the fuel in two parts: a main injection near the compression top dead center of the cylinder, and a sub-injection from the beginning of the intake stroke to the first half of the compression stroke. The same operation and effect as the invention of claim 4 can be obtained, and even if the air-fuel ratio of the combustion chamber 4 is controlled to be close to the stoichiometric air-fuel ratio, the increase in smoke can be sufficiently suppressed and the generation of NOx can be suppressed. Can be reduced.

A tenth aspect of the present invention is directed to a diesel engine control device for transmitting the output of an on-vehicle engine to a driving wheel side of a vehicle via a continuously variable transmission. A fuel injection valve for directly injecting fuel, an oxygen concentration detecting means for detecting an oxygen concentration in an exhaust passage of the engine, and an air-fuel ratio of the combustion chamber based on a stoichiometric value based on a value detected by the oxygen concentration detecting means. Air-fuel ratio control means for performing feedback control so as to be near the fuel ratio;
Speed ratio control means for controlling the speed ratio of the continuously variable transmission so that the engine is brought into a predetermined high load operation state when the air / fuel ratio is controlled by the air / fuel ratio control means to be close to the stoichiometric air / fuel ratio When controlling the air-fuel ratio to be near the stoichiometric air-fuel ratio by the air-fuel ratio control means, the fuel is injected by the fuel injection valve into the main injection near the compression top dead center of the cylinder and compression from the beginning of the intake stroke. Fuel injection control means for injecting the fuel into two sub-injections up to the first half of the stroke; and oxygen concentration detection means for controlling the air-fuel ratio to near the stoichiometric air-fuel ratio by the air-fuel ratio control means. And a learning means for learning a variation state of the fuel injection amount based on the detection value of

According to the above configuration, when the output of the vehicle-mounted engine is transmitted to the drive wheels via the continuously variable transmission, the operating efficiency of the engine and the power transmission efficiency of the continuously variable transmission are matched during the running of the vehicle. The operation state of the engine and the gear ratio of the continuously variable transmission are controlled so that the efficiency of the entire power train is maximized. That is, since the engine is normally set in a high-load low-speed operation state with excellent fuel efficiency, the control by the air-fuel ratio control means, the fuel injection control means and the learning means is performed in this operation state. The same operation and effect as those of the invention are obtained.

[0028]

(Embodiment 1) FIG. 1 shows an overall configuration of a diesel engine control device A according to Embodiment 1 of the present invention, and 1 is a multi-cylinder diesel engine mounted on a vehicle. This engine 1 has a plurality of cylinders 2, 2,.
A piston 3 is inserted into each cylinder 2 so as to be able to reciprocate, and a combustion chamber 4 is defined in each cylinder 2 by the piston 3. Also,
At substantially the center of the upper surface of the combustion chamber 4, an injector (fuel injection valve) 5 is disposed with the injection hole at the tip end facing the combustion chamber 4, and is opened and closed at a predetermined injection timing for each cylinder. The fuel is directly injected into the combustion chamber 4.

Each of the injectors 5 is connected to a common common rail (accumulator) 6 for storing high-pressure fuel.
The common rail 6 is provided with a pressure sensor 6 a for detecting an internal fuel pressure (common rail pressure), and is connected to a high-pressure supply pump 8 driven by a crankshaft 7. The high-pressure supply pump 8 operates so that the fuel pressure in the common rail 6 detected by the pressure sensor 6a is maintained at a predetermined value or more (for example, about 20 MPa during idle operation, and 50 MPa or more in other operation states). A crank angle sensor 9 for detecting a rotation angle of the crank shaft 7 is provided. The crank angle sensor 9 includes a plate to be detected (not shown) provided at an end of the crank shaft 7 and an outer periphery thereof. And an electromagnetic pickup arranged so as to face each other, and the electromagnetic pickup outputs a pulse signal corresponding to the passage of a projection formed at a predetermined angle on the entire outer peripheral portion of the plate to be detected. Has become.

An intake passage 10 supplies intake air (air) filtered by an air cleaner (not shown) to a combustion chamber 4 of the engine 1. The downstream end of the intake passage 10 is provided with a surge tank (not shown). Each cylinder is branched to a corresponding one of the cylinders, and is connected to a combustion chamber 4 of each cylinder 2 by an intake port. The surge tank is provided with an intake pressure sensor 10a for detecting a supercharging pressure supplied to each cylinder 2.
A hot film type air flow sensor (intake air amount detecting means) 11 for detecting an intake air amount taken into the engine 1 in order from the upstream side to the downstream side in the intake passage 10.
A blower 12 driven by a turbine 21 to compress the intake air, an intercooler 13 for cooling the intake air compressed by the blower 12, and an intake throttle valve 14 for reducing the cross-sectional area of the intake passage 10. ing. The intake throttle valve 14 is formed of a butterfly valve having a cutout so that intake air can flow even in a fully closed state.
As in the case of an EGR valve 24 described later, the magnitude of the negative pressure acting on the diaphragm 15 is adjusted by a negative pressure control electromagnetic valve 16, whereby the opening of the valve is controlled.

Reference numeral 20 denotes an exhaust passage for discharging exhaust gas from the combustion chamber 4 of each cylinder 2. The upstream end of the exhaust passage 20 is branched and each of the cylinders 2 is provided with an exhaust port (not shown).
Are connected to the combustion chamber 4. In this exhaust passage 20,
In order from the upstream side to the downstream side, an O2 sensor 17 (oxygen concentration detecting means) for detecting the oxygen concentration in the exhaust, the turbine 21 rotated by the exhaust flow, and the HC and C in the exhaust
A catalyst 22 capable of purifying O and NOx and particulates is provided.

The O2 sensor 17 is used to detect the air-fuel ratio based on the oxygen concentration in the exhaust gas. When the oxygen concentration in the exhaust gas is approximately 0.5%, that is, when the engine 1 With reference to the case where the air-fuel ratio of the chamber 4 is substantially equal to the stoichiometric air-fuel ratio, the output sharply increases when the air-fuel ratio is richer than this, while the output sharply decreases when the air-fuel ratio is leaner. It has the characteristic that the output changes suddenly at the air-fuel ratio. The catalyst 22 includes a cordierite carrier (not shown) having a honeycomb structure having a large number of through holes extending in parallel with each other along an axial direction (flow direction of exhaust gas). The catalyst layer has two catalyst layers formed thereon. While absorbing NOx in an oxygen-excess atmosphere where the oxygen concentration in the exhaust gas is high, when the oxygen concentration decreases,
It has the property of releasing absorbed NOx and reducing and purifying it.

In other words, the catalyst 22 emits NOx when the air-fuel ratio of the combustion chamber 4 of the engine 1 is in a rich state near the stoichiometric air-fuel ratio or smaller than the stoichiometric air-fuel ratio. NO that absorbs NOx
x-absorbing material, for example, on the wall surface of a carrier, alumina carrying platinum Pt and at least one of alkaline earth metals such as barium Ba as an NOx absorbing material, alkali metal or rare earth metal, A two-layer type in which an inner catalyst layer supporting ceria and an outer catalyst layer supporting a zeolite supporting a noble metal such as platinum Pt is used.

As shown in FIG. 2, the turbocharger 25 comprising the turbine 21 and the blower 12
A plurality of flaps 21b, 21b,... Are provided so as to surround the entire periphery of the turbine 21a in the turbine chamber 21a accommodating the exhaust gas, and each flap 21b is rotated so as to change the nozzle cross-sectional area (A) of the exhaust passage. It is a moving VGT (Variable Geometry Turbo). In the case of this VGT, as shown in FIG. 3A, the exhaust gas flow rate is reduced by positioning the flaps 21b, 21b,. The supercharging efficiency can be improved even in the low rotation range of the engine 1. On the other hand, as shown in FIG.
By increasing the nozzle cross-sectional area (A) by positioning the tips of the nozzles 21b toward the center of the turbine 21, the supercharging efficiency can be increased even in a high rotation range of the engine 1 having a large exhaust flow rate.

The exhaust passage 20 is a portion upstream of the turbine 21 and is branched and connected to an upstream end of an exhaust gas recirculation passage (hereinafter referred to as an EGR passage) 23 for recirculating a part of the exhaust gas to the intake side. The downstream end of the EGR passage 23 is connected to the intake passage 10 downstream of the intake throttle valve 14, and
Near the downstream end in the middle of the EGR passage 23, a negative-pressure-operated exhaust gas recirculation amount control valve (hereinafter, referred to as an EGR valve) 24, whose opening is adjustable, is disposed. While adjusting the flow rate by the EGR valve 24, the intake passage 10
It is designed to reflux. That is, the EGR passage 23 and the EGR valve 24 constitute an exhaust gas recirculation unit.

More specifically, as shown in FIG. 3, the EGR valve 24 is provided with a valve rod 24 on a diaphragm 24a for partitioning a valve box.
b is fixed, and EGR passages 23 are provided at both ends of the valve stem 24b.
A valve body 24c and a lift sensor 26 for linearly adjusting the opening degree are provided. The valve body 24c is urged in the closing direction (downward in the figure) by a spring 24d, while a negative pressure passage 27 is connected to a negative pressure chamber (a chamber above the diaphragm 24a) of the valve box. The negative pressure passage 27 is connected to a vacuum pump (negative pressure source) 29 via a negative pressure control electromagnetic valve 28. The negative pressure passage 27 is controlled by a control signal (current) from an ECU 35 described later. 27, the EGR of the negative pressure chamber
The valve drive negative pressure is adjusted, whereby the opening of the EGR passage 23 is linearly adjusted by the valve body 24c.

The flap 21 of the turbocharger 25
A diaphragm 30 is attached to each of b, 21b,... similarly to the EGR valve 24, and the negative pressure acting on the diaphragm 30 is adjusted by an electromagnetic valve 31 for negative pressure control, so that the flaps 21b, 21b,. The amount of operation of ... is adjusted. These flaps 21b, 21b,
.., The diaphragm 30 and the solenoid valve 31 constitute a supercharging pressure adjusting means for adjusting the supercharging pressure of the turbocharger 25.

The output of the engine 1 as described above is output from a well-known belt-type continuously variable transmission (Continuously Variable Transmission).
on: hereinafter referred to as CVT) to drive wheels of the vehicle. That is, as shown in FIG. 4, a CVT integrally disposed behind the vehicle body of the engine 1.
Reference numeral 40 denotes a drive pulley 41 and a driven pulley 42, and a steel belt 43 wound between the pulleys 41, 42.
a is arranged parallel to the crankshaft 7 of the engine 1, and the torque converter 44 is arranged coaxially with the crankshaft 7.
And a power transmission mechanism including the planetary gear unit 45,
It is drivingly connected to the crankshaft 7. On the other hand, the support shaft 42a of the driven pulley 42 is connected to a drive wheel (not shown) via a speed reduction mechanism 46, a differential gear 47, and the like.

More specifically, the driving pulley 41 and the driven pulley 42 are each constituted by a pair of conical plates.
Further, a hydraulic mechanism (not shown) for adjusting the interval between the conical plates, that is, the width of the pulleys 41 and 42 is provided. When the pulley width is widened by the hydraulic mechanism, the steel belt 43 separates the conical plates from each other. Pull in between the pulleys 41 and 42
The effective diameter is reduced when the pulley width is reduced, while the effective diameter is increased when the pulley width is reduced. If the width of the driving pulley 41 is increased to reduce its effective diameter, and the width of the driven pulley 42 is reduced to increase its effective diameter, the gear ratio of the CVT 40 increases,
Conversely, if the width of the driving pulley 41 is reduced to increase the effective diameter and the width of the driven pulley 42 is increased to decrease the effective diameter, the speed ratio of the CVT 40 is reduced.

Each of the injectors 5, high pressure supply pump 8, intake throttle valve 14, EGR valve 24, turbocharger 25
Are configured to be operated by a control signal from a control unit (hereinafter referred to as an ECU) 35. In addition, the CVT 40
Although not shown, the hydraulic mechanism is provided with an electromagnetic spool valve for supplying engine oil as hydraulic oil, and the spool valve is duty-controlled in response to a control signal from the ECU 35, whereby the CVT 40 Is controlled to be changed.

On the other hand, the ECU 35 supplies an output signal from the pressure sensor 6a, an output signal from the crank angle sensor 9, an output signal from the air flow sensor 11,
(2) An output signal from the sensor 17, an output signal from the lift sensor 26 of the EGR valve 24, and an output from an accelerator opening sensor 32 for detecting an operation amount (accelerator opening) of an accelerator pedal (not shown) by a driver of the vehicle. Signal is input at least.

Then, the fuel injection control by the operation of the injector 5 is performed, the fuel injection amount and the fuel injection timing are controlled according to the operating state of the engine 1, and the common rail pressure by the operation of the high-pressure supply pump 8, ie, the common rail pressure, The fuel injection pressure is controlled. Further, control of the intake air amount by operating the intake throttle valve 14, control of the exhaust gas recirculation amount by operating the EGR valve 24, and control of the flap 21 of the turbocharger 25
, 21b,... (VGT control) are performed,
In addition, the control of the speed ratio of the CVT is performed.

Specifically, a fuel injection amount map in which the optimum fuel injection amount Q experimentally determined according to changes in the accelerator opening and the engine speed is recorded in the memory of the ECU 35 (see FIG. 9). Various control maps such as a fuel injection timing map in which the fuel injection timing is similarly recorded and a basic EGR control map (see FIG. 12) in which the EGR rate (the ratio of the recirculated exhaust gas amount to the total intake air amount) is similarly recorded. Normally, the basic fuel injection amount Qbase is read from the fuel injection amount map based on output signals from the accelerator opening sensor 32 and the crank angle sensor 9, and the basic fuel injection amount Qbase Based on the common rail pressure detected by the pressure sensor 6a, each injector 5
(Excitation time) is determined.

Then, as shown in FIG. 5A, the injector 5 is opened at the end of the compression stroke of the cylinder, and a quantity of fuel corresponding to the target torque of the engine 1 is injected and supplied to the combustion chamber 4, and 1 is operated in a state where the average air-fuel ratio in the combustion chamber 4 is considerably lean (A / F ≧ 18).

The engine 1 is normally operated in a low-load operation region (EGR region: A) as illustrated in FIG. 6, and in this operation region (A), the air flow sensor EGR valve 2 according to the output signal from
4 is controlled to open and close, and a part of the exhaust gas in the exhaust passage 20 is recirculated to the intake passage 10 and supplied to the combustion chamber 6 of the engine 1 together with fresh air.

The NOx absorption amount in the catalyst 22 is estimated, and when the estimated value is equal to or more than the set value and a decrease in the NOx absorption performance is expected, the emptying of the combustion chamber 4 for refreshing the catalyst 22 is performed. The fuel ratio is controlled so as to be substantially equal to the stoichiometric air-fuel ratio, and the fuel is controlled by main injection at the end of the compression stroke of the cylinder and from the beginning of the intake stroke to the first half of the expansion stroke as shown in FIG. 5 (b) or (c). The injection is divided into two times, namely, the sub-injection before the injection.

At this time, the amount of fuel injection by the injector 5 is feedback-corrected based on the output signal from the O2 sensor 17, which is a feature of the present invention. At this time, a predetermined learning condition is satisfied. Then, CVT
By controlling the speed ratio of 40, the operating state of the engine 1 is shifted along the constant horsepower curve shown in FIG. 6 to the operating region (a) set on the high load side, and the engine 1 is operated in this operating region (a). The variation state of the fuel injection amount is learned based on the output signal from the O2 sensor 17.

(Fuel Injection Control) The ECU 35
About the processing operation of the fuel injection control of the engine 1 by
This will be described specifically with reference to the flowcharts of FIGS. 7 and 8. This control is executed independently for each cylinder 2 at a predetermined crank angle before the intake stroke.
May be executed at predetermined time intervals when is in a steady operation state.

First, in the flow shown in FIG. 7, in step SA1 after the start, a crank angle signal, an O2 sensor output, an air flow sensor output, an accelerator opening, and the like are read. In the following step SA2, the basic fuel injection amount Qbase is read from the fuel injection amount map based on the target torque obtained from the accelerator opening and the engine speed obtained from the crank angle signal. In this fuel injection amount map, for example, as shown in FIG. 9, the basic fuel injection amount Qbase is set to increase as the accelerator opening increases and as the engine speed increases.

Subsequently, at step SA3, the NOx absorption amount of the catalyst 22 is estimated. The estimation of the NOx absorption amount of the catalyst 22 may be performed based on, for example, integrating the travel distance of the vehicle and the total injection amount of fuel in the meantime, and based on the integrated value. Alternatively, the operating time of the engine 1 and the total fuel injection amount during that time are integrated, the integrated value is corrected based on the operating state of the engine 1, and the NOx absorption amount is estimated based on the integrated value. It may be. Further, it is possible to more simply estimate the NOx absorption amount based on the total operation time of the engine 1.

In step SA4, the estimated value is compared with a predetermined set value. If the NOx absorption amount is smaller than the set value, the process proceeds to step SA12, while the NOx absorption amount is equal to or larger than the set value. If yes in step SA5, the flow advances to step SA5 to turn on the refresh flag F1 (F1 = 1). The refresh flag F1 controls the air-fuel ratio of the combustion chamber 4 of the engine 1 to be substantially equal to the stoichiometric air-fuel ratio, thereby lowering the oxygen concentration in the exhaust gas. Is a period for refreshing.

Subsequently, at step SA6, the timer value T1 for determining the elapse of the refresh period is incremented, and at subsequent step SA7, it is determined whether or not the timer value T1 is equal to or greater than the set timer value T10. This set timer value T10 indicates the NOx absorbed by the catalyst 22 when the air-fuel ratio of the exhaust gas is controlled to approximately the stoichiometric air-fuel ratio.
Corresponds to the time required to release substantially all of
Note that the set timer value T10 may be corrected according to the operating state of the engine 1, for example, the time during which the engine 1 is continuously operated in the air-fuel ratio lean state or the load state during that time.

At step SA7, the timer value T
If it is determined that 1 is equal to or greater than the set timer value T10, the process proceeds to step SA13. On the other hand, if it is determined that the timer value T1 is no smaller than the set timer value T10, that is, within the refresh period, the process proceeds to step SA8. Proceed to
The fuel is increased and corrected for the basic fuel injection amount Qbase to determine a corrected fuel injection amount Qr0 such that the air-fuel ratio of the combustion chamber 4 becomes substantially equal to the stoichiometric air-fuel ratio. That is, for example, based on the intake air amount obtained from the output of the air flow sensor, the fuel injection amount is calculated such that the air-fuel ratio becomes substantially near the stoichiometric air-fuel ratio with respect to this intake air amount.

Subsequently, in step SA9, a feedback correction coefficient cfb for feedback-correcting the corrected fuel injection amount Qr0 is calculated based on the output signal from the O2 sensor 17. That is, the O2 sensor 17
Is larger than the reference value corresponding to the stoichiometric air-fuel ratio and the air-fuel ratio of the combustion chamber 4 is richer than the stoichiometric air-fuel ratio, the current value of the feedback correction coefficient cfb is The value is obtained by subtracting the predetermined value α. On the other hand, if the output signal from the O2 sensor 17 is equal to or smaller than the reference value, the current value of the feedback correction coefficient cfb is a value obtained by adding a predetermined value α to the previous value.

Next, at step SA10, the fuel injection amount Qr0 after the increase correction and the feedback correction coefficient cfb
Is used to calculate the final total fuel injection amount Qr. That is, Qr = Qr0 × (1 + cfb + clrn) where clrn is a learning correction coefficient for correcting the injection amount variation caused by the individual difference of the injectors 5, which will be described in detail later.

Subsequently, at step SA11, the total fuel injection amount Qr is reduced by 2 to the main injection amount Qr1 and the sub injection amount Qr2.
At the same time, the injection timing is set, and then the process proceeds to step SA16 in FIG. Specifically, the timings of the main injection and the sub-injection are illustrated in FIG. 5, respectively, and the valve opening timing of the injector 5 for the main injection is advanced as the injection amount increases with reference to BTDC5 ° CA. Conversely, the smaller the injection amount is, the more the phase is retarded.

On the other hand, the valve opening timing of the injector 5 for the sub-injection is determined by the pre-injection period (BTDC35 in the illustrated example) from the beginning of the intake stroke to the first half of the compression stroke of the cylinder shown in FIG.
0 ° CA to BTDC 90 ° CA) or a post-injection period from the completion of the main injection to the first half of the expansion stroke as shown in FIG.
C20 ° CA), and is set such that as the engine load is higher, the angle is advanced, and conversely, as the engine load is lower, the angle is advanced. That is, the sub-injection is a pre-injection performed earlier than the main injection when the engine 1 is on the high load side, while the post-injection performed after the main injection is performed when the engine 1 is on the low load side. It is said.

The ratio of the sub-injection amount Qr2 to the main injection amount Qr1 is experimentally determined in advance based on the load condition and the rotation speed of the engine 1 and recorded in a memory as a map. It is supposed to be. In this map, when the sub-injection is the pre-injection, the ratio of the injection amount Qr2 to the main injection amount Qr1 is set to 8 to 23%, and the injection ratio increases as the engine load increases in that range. Is set. On the other hand, when the sub-injection is post-injection, the ratio of the injection amount Qr2 to the main injection amount Qr1 is set to 30 to 50%, and the injection ratio is set to be smaller as the engine load is higher in that range. ing.

As described above, when the NOx absorption amount of the catalyst 22 becomes equal to or more than the set value, and there is a concern that the NOx absorption performance is reduced, the air-fuel ratio of the combustion chamber 4 of the engine 1 becomes substantially the stoichiometric air-fuel ratio. Then, the fuel injection amount is increased and corrected to reduce the oxygen concentration in the exhaust gas, thereby releasing NOx from the catalyst 22 to purify the catalyst 22, thereby refreshing the catalyst 22. Further, at this time, the fuel is divided into two injections, a main injection and a sub-injection, so as to suppress an increase in the amount of smoke generated and the like. Note that the number of fuel injections is not limited to two, and may be divided into a plurality of times. Further, a so-called pilot injection may be performed immediately before the main injection.

On the other hand, in step SA12 where the estimated value of the NOx absorption amount is determined to be no smaller than the set value in step SA4, the process proceeds to step SA12, where it is determined whether the accelerator opening is larger than the set opening. Determine. If the determination result is yes, it is determined that the engine 1 is in the accelerating operation state, and the process proceeds to step SA5 to increase the fuel injection amount and perform the fuel injection division control as described above.
The catalyst 22 is refreshed. On the other hand, if the determination result is n
If it is o, it is determined that the engine 1 is not in the accelerating operation state, the process proceeds to step SA13, the refresh flag F1 is cleared (F1 = 0), and the timer value T1 is reset in the following step SA14 (T1 = 0). . Then, in the subsequent step SA15, the basic fuel injection amount Qbase read in step SA2 is corrected by the learning correction coefficient clrn, and this is directly used as the main injection amount Qr1, and the process proceeds to step SA1 in FIG.
Go to 9.

That is, while the NOx absorption amount of the catalyst 22 is lower than the set value, unless the engine 1 is in an accelerating operation state, the increase correction of the fuel injection amount is not performed and only the normal main injection is performed. As a result, the air-fuel ratio of the combustion chamber 4 becomes lean, and the overall fuel efficiency can be improved while the engine 1 is operating.

When the engine 1 is in an accelerating operation state, the required output to the engine 1 is high. Therefore, the fuel injection amount is increased so that the air-fuel ratio becomes substantially the stoichiometric air-fuel ratio, and the engine output is increased. The catalyst 22 is refreshed. Thereby, the refresh frequency of the catalyst 22 can be increased, and the NOx absorption performance can be maintained higher. In addition, if the air-fuel ratio is switched when the operating state of the engine shifts from the steady operation state to the accelerated operation state, a change in the engine output due to the change in the air-fuel ratio is expected, so the riding feeling is reduced. There is no loss.

Subsequent to step SA11 in FIG. 7, in step SA16 in FIG. 8, it is determined whether or not pre-injection is set. If the sub-injection timing is not set within the pre-injection period, it is determined that there is no pre-injection and the process proceeds to step SA19. If the sub-injection timing is set within the pre-injection period, pre-injection is performed.
It is determined as s, and the process proceeds to Step SA17. In step SA17, it is determined whether or not the set injection timing (pre-injection timing) has come based on the crank angle signal, and it is waited until the pre-injection timing comes (no in step SA17). If the injection timing comes (yes in step SA17), step S
Proceeding to A18, pre-injection is performed.

Subsequently, at step SA19, it is similarly determined whether or not the execution timing of the main injection (main injection) has come based on the crank angle signal, and waits until the main injection timing comes (no at step SA19). If the main injection timing comes (yes in step SA19)
s) Then, the process proceeds to Step SA20 to execute the main injection. Further, in each of the steps SA21 to SA23, it is determined whether or not post-injection is set in the same manner as in the pre-injection, and if so, post-injection is performed when the post-injection timing comes. Execute and return after a while.

On the other hand, in steps SA19 and SA20 following step SA15 in FIG. 7, after executing the main injection, the subsequent step SA20 determines that there is no post-injection and returns.

Steps SA8 to SA8 of the flow shown in FIG.
When it is determined that the amount of NOx absorbed by the catalyst 22 has become excessive or that the engine 1 has entered the accelerated operation state in each of the steps 10,
air-fuel ratio control means 3 for controlling the air-fuel ratio of the combustion chamber 4 of the engine 1 to be substantially the stoichiometric air-fuel ratio when x is to be released
5a is configured.

Further, by the step SA11 and steps SA16 to SA23 of the flow shown in FIG.
When the air-fuel ratio control means 35a controls the air-fuel ratio of the combustion chamber 4 to be substantially equal to the stoichiometric air-fuel ratio, the fuel is injected by the injector 5 at the end of the compression stroke of the cylinder 2;
The fuel injection control means 35b is configured to inject fuel into two parts, i.e., a sub-injection from the beginning of the intake stroke to the first half of the compression stroke.

(Learning Control) According to the fuel injection control described above, when the air-fuel ratio of the combustion chamber 4 of the engine 1 is controlled to be substantially the stoichiometric air-fuel ratio, the fuel injection amount from the O2 sensor 17 is controlled. By performing feedback correction based on the output signal, highly accurate air-fuel ratio control is realized. However, immediately after the air-fuel ratio is switched from the lean state to the substantially stoichiometric air-fuel ratio state, the feedback correction is not sufficiently reflected in the fuel injection amount. The air-fuel ratio of the chamber 4 may temporarily shift to the rich side, and in this case, a sudden increase in the amount of smoke emission and the like will be caused. Therefore, in the control device A according to this embodiment, once the feedback control of the fuel injection amount is performed during the period in which the target air-fuel ratio of the engine 1 is set to substantially the stoichiometric air-fuel ratio, the feedback correction coefficient cfb Injectors 5 based on
Is learned, and the basic fuel injection amount is corrected in accordance with the learning result.

More specifically, as shown in FIG. 10, in step SB1 after the start, it is first determined whether or not the engine 1 is in a steady operation state. If the determination is no and the engine 1 is not in the steady operation state, it is difficult to accurately learn the variation in the injection amount of the injector 5. Therefore, if the determination is yes and the engine 1 is in the steady operation state, Proceeding to step SB2, it is determined whether a predetermined learning condition is satisfied. That is, for example, the refresh flag F1 set in the above-described fuel injection control is on (F1 = 1), and the catalyst 2
In addition, when the engine coolant temperature is sufficiently high, it is determined that the learning condition has been satisfied, and the process proceeds to step SB3. If the determination is no, the process returns.

In step SB3, it is determined whether or not the engine 1 is in the high load side operation region (a) shown in FIG. Then, the engine 1 is in the operating region (a).
If the determination is no, the process proceeds to step SB4,
The speed ratio of the CVT is changed to be small, the engine speed is reduced without changing the running speed of the vehicle, and the target torque of the engine 1 is increased, so that the engine 1 is forcibly operated in the operating region ( Then, the process proceeds to step SB5.
Proceed to. On the other hand, if it is determined in step SB3 that the engine 1 is already in the operating range (a), the process proceeds to step SB5.

In step SB5, the O2 sensor 17
It is determined whether or not the air-fuel ratio of the combustion chamber 4 of the engine 1 is substantially equal to the stoichiometric air-fuel ratio based on the output signal from the engine. If this determination is yes, that is, the O2 sensor output is a predetermined value near the reference value. If the value is in the range, the process proceeds to step SB6, while if the O2 sensor output is outside the predetermined range (no in step SB5), the process waits. Following step SB6
Then, the feedback correction coefficient cfb (see step SA9 in FIG. 7) calculated in the fuel injection control is read from the memory, and the read value is added to the number of samples n and stored in the memory again.

Subsequently, in step SB7, the number of samples n
Is incremented, and in a step SB8, it is determined whether or not the sample number n has reached a preset predetermined number n1. If the determination result is no and the sample number n of the feedback correction coefficient cfb has not reached the set number n1, the process proceeds to step SB12, while the determination result is yes.
When the sample number n of the feedback correction coefficient cfb reaches the set number n1, the process proceeds to step SB9, and the average value of the sampled n1 feedback correction coefficients cfb is calculated as the learning correction coefficient clrn. Then, the following step SB1
The number n of samples is reset to 0 (n = 1), and in the next step SB11, the calculated learning correction coefficient clrn is calculated.
And return after a while.

That is, if a sufficiently large number of feedback correction coefficients cfb can be sampled, the average value thereof will be a value that reflects the variation in the injection amount of the injector 5 with high accuracy. This value is used as the learning correction coefficient clrn. In addition, it is possible to eliminate the variation in the injection amount due to the individual difference of the injector 5.

On the other hand, at step SB8, where it is determined that the number of samples n has not reached the set number n1 and the process proceeds to step SB12, the number of samples n
Is greater than or equal to a predetermined minimum sample number n0. If the result of the determination is no, the number of samples of the feedback correction coefficient cfb is too small, and the process returns without performing the calculation of the learning correction coefficient. If the result of the determination is yes, the number of samples of the feedback correction coefficient cfb is sufficient. Although it is not, some effects are expected. Then, the process proceeds to step SB13, where a provisional learning correction coefficient clrn is calculated based on the value of the sampled feedback correction coefficient cfb, and the process proceeds to step SB1.
Go to 0.

Step SB6 of the flow shown in FIG.
When the air-fuel ratio of the combustion chamber 4 of the engine 1 is controlled by the air-fuel ratio control means 35a so as to become substantially the stoichiometric air-fuel ratio in each of the steps SB11 to SB11, the variation in the fuel injection amount based on the value detected by the O2 sensor 17 The learning means 35c for learning is configured. The learning means 35c
Is designed to learn the variation of the fuel injection amount in an operation region in which exhaust gas recirculation by the EGR passage 23 is not performed.

When the air-fuel ratio is controlled to be substantially the stoichiometric air-fuel ratio by the air-fuel ratio control means 35a in step SB4 of the flow, the speed ratio of the CVT 40 is set to a predetermined high-load operation range. A gear ratio control means 35d for controlling the operation in (a) is configured.

(EGR Control) Hereinafter, the processing operation of the EGR control by the ECU 35 will be specifically described with reference to the flowchart of FIG. This control is executed every predetermined time.

First, in step SC1 after the start, a crank angle signal, an air flow sensor output, an accelerator opening, and the like are read, and in a subsequent step SC2, based on the accelerator opening and the engine speed obtained from the crank angle signal, The basic EGR rate EGRb is read from the basic EGR control map as exemplified in FIG. This map determines experimentally the optimum EGR rate corresponding to the accelerator opening and the engine speed in advance when the engine 1 is in the EGR region (A) shown in FIG. The basic EGR rate EG
Rb is set to increase as the accelerator opening decreases, and to increase as the engine speed decreases. However, since it is necessary to suppress the increase in smoke in a predetermined high-load, low-rotation region of the engine, the EGR rate is set to an extremely small value or zero.

Subsequently, in step SC3, the target fresh air amount q is read from the map based on the accelerator opening and the engine speed in the same manner as in step SC2. here,
The fresh air amount is a value obtained by removing the recirculated exhaust gas from the intake air taken into the combustion chamber 4, and is an intake air amount measured by the air flow sensor 11. The map is also stored in the memory in the same manner as the basic EGR control map. As shown in FIG. 13, the target fresh air amount q increases as the accelerator opening increases, and increases as the engine speed increases. It is set to be large.

In general, in a direct injection diesel engine, the generation of NOx can be suppressed by increasing the amount of exhaust gas recirculation, but on the other hand, as shown in FIG. 14, the amount of exhaust gas recirculation increases. When the air-fuel ratio of the combustion chamber 4 becomes too small, there is a characteristic that the amount of smoke generated increases rapidly. Therefore, both the basic EGR rate EGRb and the target fresh air amount q in the steps SC2 and SC3 are set to be as small as possible within a range where the air-fuel ratio of the combustion chamber 4 of the engine 1 does not rapidly increase in the smoke amount. .

Following step SC3, step S3
At C4, the value of the refresh flag F1 set in the above-described fuel injection control is determined. If the flag is off (F1 = 0), it is determined that the current period is not the refresh period and the process proceeds to step SC6. If it is turned on (F1 = 1), the refresh period is yes
And the process proceeds to Step SC5.

At step SC5, the basic EGR rate EGRb and the target fresh air q
Are corrected so that the air-fuel ratio of the combustion chamber 4 changes to the rich side. That is, the EG corresponding to the engine load
The R rate correction value EGRm is read from the EGR correction map, and the EGR rate correction value EGRm is added to the basic EGR rate EGRb read in step SC2. Further, a new air amount correction value qm corresponding to the engine load is read from the new air amount correction map, and the new air amount correction value qm is subtracted from the target new air amount q read in step SC3. Although not shown, the EGR correction map and the fresh air amount correction map are obtained by experimentally setting correction values corresponding to the load state of the engine 1, and include an EGR rate correction value EGRm and a new air amount correction value q.
m is set to be smaller as the target torque of the engine is larger. The EGR rate correction value EGRm
Is set so as not to cause a misfire due to an excessive amount of exhaust gas recirculation.

Subsequently, in step SC6, the EGR rate feedback correction value EGRf / b is illustrated in FIG. 15 based on the fresh air amount deviation obtained by subtracting the target fresh air amount q from the actual fresh air amount obtained from the air flow sensor output. Read from the map. In this map, when the target fresh air amount q is larger than the actual fresh air amount, the EGR rate feedback correction value EGRf / b becomes smaller as the deviation increases, and the target fresh air amount q becomes smaller than the actual fresh air amount. When the amount is smaller than the amount, the larger the deviation is, the larger is set. However, there is a dead zone where the target fresh air q is close to the actual fresh air.

Subsequently, at step SC7, the basic EGR rate EGRb corrected at step SC5 is added to step SC6.
The target EGR rate EGRt is calculated by adding the EGR rate feedback correction value EGRf / b obtained in the above. Then, in step SC8, an output corresponding to the target EGR rate EGRt is output to the negative pressure control solenoid valve 28, and the EGR valve 24
And returns after a while. The feedback correction in steps SC6 and SC7 may not be performed.

According to such EGR control, during the period in which the refresh flag F1 is on and the catalyst 22 is to be refreshed, the EG is higher than when it is not.
The opening of EGR valve 24 is controlled so that the R ratio increases. Further, the target fresh air amount q is corrected so as to correspond to the decrease in the intake air amount accompanying this. As a result, the air-fuel ratio of the combustion chamber 4 for each cylinder changes to the rich side.
The air-fuel ratio can be controlled to approximately the stoichiometric air-fuel ratio without increasing the fuel injection amount in the above-described fuel injection control. Further, since the engine output decreases due to the decrease in the intake air amount, the increase in the engine output due to the increase in the fuel injection amount can be offset, and as a result, the fluctuation in the engine output can be reduced.

In addition, by circulating the exhaust gas to the combustion chamber 4, the combustion becomes moderately moderate, so that the generation of NOx accompanying the combustion can be suppressed, and the recirculated exhaust gas evaporates and atomizes the fuel and mixes it with air. Is promoted, thereby improving the flammability and thereby suppressing the generation of smoke.

According to each step of the flow shown in FIG. 11, when the engine 1 is in the predetermined operation region (A), the EG
An exhaust gas recirculation control unit 35e that controls the opening degree of the R valve 24 and controls the amount of exhaust gas recirculated through the EGR passage 23 based on the value detected by the air flow sensor 11 is provided.

(VGT Control) Next, the processing operation of the VGT control by the ECU 35 will be specifically described with reference to the flowchart of FIG. This control is also executed at predetermined time intervals.

First, in step SD1 after the start, a crank angle signal, an intake pressure sensor output, an air flow sensor output, an accelerator opening, and the like are read, and the following step S1 is executed.
At D2, the basic nozzle sectional area VGTb is read from the map based on the accelerator opening and the engine speed obtained from the crank angle signal. As shown in FIG. 17, this map determines experimentally the optimum nozzle cross-sectional area of the turbocharger 25 corresponding to the accelerator opening and the engine speed in advance, and stores it in the memory of the ECU 35 electronically. The basic nozzle cross-sectional area VGTb is set to increase as the accelerator opening increases, and to increase as the engine speed increases. As a result, even in the low rotation range of the engine 1 having a small exhaust flow rate, the exhaust flow speed can be increased and the supercharging efficiency can be improved.

Subsequently, in step SD3, the value of the refresh flag F1 set in the above-described fuel injection control is determined, and if the flag is off (F1 = 0),
Determined as no during the refresh period, the basic nozzle cross-sectional area VGTb as it is as the target nozzle cross-sectional area VGTr,
On the other hand, if the flag is turned on (F1 = 1), it is determined that the refresh period is yes, and the process proceeds to step SD4.

In this step SD4, the step S
The target nozzle cross-sectional area VGTr is calculated by adding a preset correction value VA to the basic nozzle cross-sectional area VGTb read in D2. Then, in step SD5, the output corresponding to the target nozzle cross-sectional area VGTr is output to the solenoid valve 3 for negative pressure control.
1 to the flaps 21b, 2b of the turbocharger 25.
1b, and then return.

That is, during the period in which the refresh flag F1 is ON and the catalyst 22 is refreshed, the nozzle cross-sectional area (A) of the turbocharger 25 is increased and the supercharged state is increased. The capacity is reduced so that the amount of fresh intake air is reduced. Then, due to the decrease in the amount of intake air, the aforementioned EG
As with the R control, even if the fuel injection amount is not increased
The air-fuel ratio of the combustion chamber 4 can be controlled so as to be substantially in the vicinity of the stoichiometric air-fuel ratio, and the engine output decreases due to the decrease in the intake air amount. In addition, fluctuations in engine output due to switching of the air-fuel ratio can be reduced. In addition, more simply, the V
The intake air amount may be reduced by forcibly releasing the waste gate (not shown) of the GT 25 to lower the supercharging pressure.

Step SD in the flow shown in FIG.
3 and SD4, when controlling the air-fuel ratio of the combustion chamber 4 of the engine 1 to be substantially the stoichiometric air-fuel ratio, rotating the flaps 21b, 21b,. A boost pressure reducing means 35f for reducing the pressure is provided.

(Operation and Effect) Next, the operation and effect of the first embodiment will be described.

During the operation of the engine 1, the operation shown in FIG.
As shown in (a), at the end of the compression stroke of each cylinder 2, fuel is collectively injected from the injector 5, and the air-fuel mixture is burned in the combustion chamber 4 in each cylinder 2 with a lean air-fuel ratio. The resulting NOx is absorbed by the catalyst 22 in the exhaust passage 20.

Thereafter, when the NOx absorption amount in the catalyst 22 becomes larger than a predetermined amount, the fuel injection amount is increased so that the air-fuel ratio of the combustion chamber 4 becomes substantially equal to the stoichiometric air-fuel ratio.
The intake air amount is reduced by R control, VGT control, or the like. At this time, if the operating state of the engine 1 is on the high load side, as shown in FIG. 5 (b), the fuel is injected in two parts, a pre-injection and a main injection, and the fuel injected in the intake stroke is pre-injected. Is diffused sufficiently uniformly due to an increase in the volume of the combustion chamber 4 due to the downward movement of the piston 3, and a part thereof adheres to the wall surface of the cylinder 2, but most of the gas is sufficiently vaporized and atomized and mixed with air, and A so-called lean premix is formed throughout the chamber 4.

Subsequently, as the pressure in the cylinder and the temperature in the cylinder rise in the latter half of the compression stroke, the fuel adhering to the wall surface of the cylinder 2 is also vaporized and atomized. The reaction proceeds gradually, and the reaction heat is generated by the progress of the so-called cold flame reaction. Then, the temperature of the entire combustion chamber further rises due to the reaction heat, so that the fuel spray of the main injection injected into the combustion chamber 4 in such a high-temperature and high-pressure state is quickly vaporized and atomized. The fuel spray of the main injection does not spread to the entire combustion chamber, and a part of the uniform lean premixture generates a rich mixture that can self-ignite. When the temperature in the cylinder 2 reaches the self-ignition temperature of the fuel just before the compression top dead center, combustion explosively proceeds with the rich mixture portion as a nucleus.

With such a combustion state, even if the total fuel injection amount of the pre-injection and the main injection is considerably increased, the average air-fuel ratio of the combustion chamber 4 becomes substantially the stoichiometric air-fuel ratio. The pre-injected fuel diffuses throughout the combustion chamber 4 to form a lean premixed gas. Since the amount of fuel injected in the main injection is not so large, the excess amount formed by the main injection is small. The rich mixture portion is not so fuel-rich. In addition, the reaction heat of the lean premixed gas greatly improves the vaporization and atomization of the fuel in the rich mixture and the state of mixing with the air, so that the generation of smoke accompanying combustion is sufficiently suppressed.

In the lean premixed fuel, fuel and oxygen are consumed by a gradually progressing cold flame reaction, so that a rapid increase in the combustion pressure and combustion temperature in the initial explosive combustion is moderate. Mitigated, thereby reducing NOx
Is reduced.

On the other hand, if the operating state of the engine 1 is on the low load side, as shown in FIG. 5C, the fuel is injected in two parts, namely, the main injection and the post injection immediately after the completion.
Then, this post-injection is performed immediately after the completion of the main injection, and the fuel is injected into the combustion chamber 4 having an extremely high temperature and pressure, whereby the fuel spray is quickly vaporized and atomized, and most of the fuel is completely burned. This makes it possible to suppress generation of smoke due to incomplete combustion of fuel. In particular, in the low-load operation state, the required output to the engine 1 is low and the total amount of fuel injection is small, so that even if the air-fuel ratio of the combustion chamber 4 is controlled to be substantially close to the stoichiometric air-fuel ratio, no sudden increase in smoke is caused. .

That is, it is possible to control the air-fuel ratio of the combustion chamber 4 of the engine 1 to be substantially equal to the stoichiometric air-fuel ratio without causing adverse effects such as a sudden increase in the amount of smoke in the exhaust gas. To reduce the oxygen concentration of
Ox is released, and the catalyst 22 can be refreshed.

When the catalyst 22 is refreshed by controlling the air-fuel ratio of the combustion chamber 4 to be substantially equal to the stoichiometric air-fuel ratio, the amount of fuel injected by the injector 5 is converted into an output signal from the O 2 sensor 17. Since the feedback correction is performed based on the difference, the variation of the injection amount due to the individual difference of the injector 5 can be absorbed, and the air-fuel ratio of the combustion chamber 4 can be controlled with high accuracy.

Further, while controlling the air-fuel ratio of the combustion chamber 4 to be substantially the stoichiometric air-fuel ratio, the learning correction coefficient clrn is calculated based on the feedback correction coefficient cfb of the fuel injection amount at that time. Therefore, the learning correction coefficient clrn that accurately reflects variations in the individual fuel injection amounts of the injectors 5 can be obtained in combination with the high detection accuracy of the O2 sensor 17 near the stoichiometric air-fuel ratio. By correcting the fuel injection amount with the learning correction coefficient clrn, the air-fuel ratio of the combustion chamber 4 of the engine 1 can be controlled with extremely high accuracy. As a result, even when the air-fuel ratio of the combustion chamber 4 of the engine 1 is switched from the lean state to the substantially stoichiometric air-fuel ratio state, the air-fuel ratio is prevented from shifting to the rich side, and the smoke emission amount increases rapidly. Can be prevented.

When learning the fuel injection amount variation, the engine 1 is operated in the high load side operation region (a) by controlling the speed ratio of the CVT 40. In other words, since the injection amount variation is learned in an operation state in which the exhaust gas is not recirculated,
At the time of the learning, the oxygen concentration in the exhaust gas does not change due to the fluctuation of the recirculated exhaust gas amount, so that erroneous learning can be prevented from occurring.

Further, in the operation region (a) on the high load side, the required output to the engine 1 is high and the fuel injection amount is originally large. Therefore, when the air-fuel ratio is changed so as to be close to the stoichiometric air-fuel ratio. However, the fuel injection amount does not need to be increased so much. In addition, at this time, the supercharging pressure of the turbocharger 25 is reduced to reduce the amount of intake air. Therefore, the increase correction of the fuel injection amount is minimal, and the intake air Since the engine output decreases due to the decrease in the amount, the increase in the output due to the correction of the increase in the fuel injection amount is offset, and the fluctuation in the engine output can be reduced.

In the first embodiment, when the amount of NOx absorbed in the catalyst 22 becomes larger than a predetermined value, the air-fuel ratio of the combustion chamber 4 of the engine 1 is controlled to be substantially equal to the stoichiometric air-fuel ratio. Although NOx is released from the catalyst 22, the present invention is not limited to this, and the air-fuel ratio of the combustion chamber 4 may be controlled so as to be substantially in the vicinity of the stoichiometric air-fuel ratio at every set cycle during the operation of the engine 1. .

In the first embodiment, when the catalyst 22 is refreshed, in all the cylinders 2 of the engine 1, the air-fuel ratio of the combustion chamber 4 is controlled to be substantially the stoichiometric air-fuel ratio. However, the control of the air-fuel ratio may be performed only for a predetermined cylinder.

In the first embodiment, a so-called lambda one sensor whose output greatly fluctuates near the stoichiometric air-fuel ratio is used as the oxygen concentration detecting means. However, the present invention is not limited to this. A type whose output changes linearly can also be used.

Further, in the first embodiment, CVT4
Instead of 0, a normal gear type transmission may be used, and in this case, the torque shock may be suppressed by controlling the fuel injection amount at the time of shifting. Furthermore, when the air-fuel ratio of the combustion chamber 4 of the engine 1 is controlled to be substantially the stoichiometric air-fuel ratio, the engine 1 is operated in a high-load low-speed range. If the amount can be reduced, the operation may be performed at a higher load.

(Embodiment 2) FIG. 18 shows an embodiment in which a diesel engine according to the present invention is mounted on a hybrid vehicle. Note that the overall configuration of the diesel engine control device A according to the second embodiment is the same as that of the first embodiment (see FIG. 1). Is omitted.

As shown in FIG. 18, this embodiment 2
The hybrid vehicle 50 according to the present invention includes a diesel engine 1 and a traveling motor (electric motor) 51 as a power unit that generates a driving force, and the traveling state using only the traveling motor 51 according to the traveling state of the vehicle. ,
The driving state can be switched to a driving state using only the engine 1 or a driving state using both of them.

More specifically, the crankshaft 7 of the engine 1
Is an automatic transmission (A) including a torque converter 44, a planetary gear unit 45, and the like (see FIG. 4) as in the first embodiment.
T) 52 and a power transmission mechanism 53 including a reduction gear and the like, and are connected to the drive wheels 54, 54 so as to be capable of intermittent switching. That is, although not shown, the automatic transmission 52 is provided with a multi-plate clutch or the like for switching the operation state of the planetary gear unit. 53
Side is switched between a power transmission state and a power cutoff state.

The running motor 51 is also connected to the drive wheels 54 via the power transmission mechanism 53, and a general control unit (general ECU) is provided.
Switching to a motor operation or power generation operation state is made by a control signal from 55. That is, the traveling motor 51 receives the electric power supplied from the battery 56 in the motor operating state and drives the drive wheels 54 and 54 via the power transmission mechanism 53, while the power transmission mechanism 53 receives the power in the power generation operation state. The kinetic energy of the vehicle is converted into electric power and supplied to the battery 56. Incidentally, reference numeral 57 in the figure denotes an alternator for charging the battery 56.

The general ECU 55 cooperates with the ECU 30 for controlling the operation of the engine 1 while coordinating with the traveling motor 5.
1 and the alternator 57, as well as the shift control of the automatic transmission 52, the charge and discharge of the battery, and the like. That is, the schematic flow of the overall control is shown in FIG.
First, step S after the start
At E1, it is determined whether or not the ignition switch is turned on. If the ignition switch is turned on (yes in step SE1), the process proceeds to step SE2.

Subsequently, in step SE2, data such as the vehicle speed, the accelerator opening, the number of revolutions of the traveling motor 51, the number of engine revolutions, and the like are inputted. In the following step SE3, the traveling motor 51 is inputted based on the input data. , The engine 1, and the basic operation mode of the clutch of the automatic transmission 52 are set. For example, as shown in Table 1 below, the basic operation modes are set in advance into four modes according to the vehicle speed v and the accelerator opening acc during normal running.

[0116]

[Table 1]

That is, the vehicle speed v is low and the accelerator opening
When acc is small, the engine 1 is stopped, the clutch of the automatic transmission 52 is set in the power cutoff state (off), and the vehicle is driven only by the driving motor 51. Also,
When the vehicle speed v is low but the accelerator opening acc is large, for example, when the vehicle is suddenly started, the engine 1 is started to engage the clutch (ON), and the vehicle is driven by both the engine 1 and the driving motor 51 to drive. .

On the other hand, when the vehicle speed v is high, the vehicle is driven by the output of the engine 1 with the clutch engaged regardless of the accelerator opening acc, and at this time, if the accelerator opening acc is small, the driving motor 51 is turned off. The battery 56 is charged by the power generation operation. Also, the accelerator opening acc
Is large, the traveling motor 51 is brought into a stopped state (idling state) in which neither the motor operation nor the power generation operation is performed.

When the vehicle decelerates, the engine 1 is stopped, the clutch of the automatic transmission 52 is turned off, and the traveling motor 51 is operated to generate electric power by the inertia of the vehicle, thereby regenerating the traveling energy. Further, the battery 56
When the charged amount of the vehicle falls below a predetermined value, the traveling motor 5
1 is stopped, the engine 1 is operated, and the battery 56 is charged by the alternator 57. In this case, if the vehicle is stopped (v = 0), the clutch is turned off.

Following step SE3, step S3 is executed.
At E4, a basic control amount Mb of the traveling motor 51 is calculated,
In a succeeding step SE5, a basic control amount Eb of the engine 1 is calculated. Here, the basic control amount Eb of the engine 1
Is set so that Eb ≧ 0. If Eb = 0, the engine 1 is stopped. The basic control amount Mb of the traveling motor 51 corresponds to the motor operation state if Mb> 0, the stop state if Mb = 0, and the power generation operation state if Mb <0. Further, the basic control amounts Eb and Mb of the engine 1 and the traveling motor 51 are determined by a predetermined high-load low-rotation region (e.g., a diagonal line in FIG. (Operating range). Then, following step SE5, in step SE6, the above-described determination of clutch on / off switching is performed, and the process returns after a while.

(Engine Fuel Injection Control) Next, the processing operation of the fuel injection control of the engine 1 according to the second embodiment will be specifically described with reference to the flowcharts of FIGS. 21 and 22. This control is independently executed for each cylinder 2 by the ECU 35 at a predetermined crank angle before the intake stroke, but may be executed at predetermined intervals when the engine 1 is in a steady operation state. .

First, in the flow shown in FIG. 21, in step SF1 after the start, a crank angle signal, an O2 sensor output, an air flow sensor output, an accelerator opening, and the like are read, and a signal from the overall ECU 55 is input. Subsequently, in step SF2, the overall ECU 55
It is determined whether or not the basic control amount Eb of the engine 1 input from the engine is greater than zero, and if the determination result is no, (E
b = 0), stops the engine 1 and returns. on the other hand,
If the determination result is yes and Eb> 0, step SF
Proceeding to 3, the basic fuel injection amount Qbase and the injection timing ITbase are set in the same manner as in the first embodiment.

Subsequently, in step SF4, a timer value T2 for determining a predetermined learning period for learning the state of variation of the fuel injection amount by the injector 5 is incremented. In the following step SF5, the timer value T2 is set to the first value. It is determined whether or not the value is equal to or greater than the set timer value T20. The first set timer value T20 corresponds to, for example, a time required for the engine 1 to shift to a preset normal operation area (see FIG. 20) after the engine is started and to enter a steady operation state. If the result of this determination is no, step SF in FIG.
Proceed to 21.

On the other hand, if the result of the determination is yes, the process proceeds to step SF6, where it is determined whether the timer value T2 is smaller than the second set timer value T21. The second set timer value T21 is set such that an interval between the second set timer value T21 and the first timer value T20 is a time required for accurate learning of the injection amount variation. If the result of the determination is no, it is determined that the learning period has ended, and step S in FIG.
On the other hand, if the result of the determination is yes, the process proceeds to F19 and it is determined that the learning period has elapsed, and the process proceeds to step SF7. In step SF7, first, the fuel is increased and corrected for the basic fuel injection amount Qbase, and the corrected fuel injection amount Qr0 is determined so that the air-fuel ratio of the combustion chamber 4 becomes substantially equal to the stoichiometric air-fuel ratio. That is, for example, based on the intake air amount obtained from the output of the air flow sensor, the fuel injection amount is calculated such that the air-fuel ratio becomes substantially the stoichiometric air-fuel ratio with respect to this intake air amount.

Subsequently, in step SF8, the fuel injection amount Qr0, which has been increased and corrected, is divided into a main injection amount QT0 and a sub injection amount QL0, and their injection timings are set. Here, the division ratio of the fuel injection amount and the setting of the injection timing are performed in the same manner as in the first embodiment. However, in the second embodiment, since the engine 1 is in the high-load operation state, the sub-injection is performed in the cylinder 2 , And the main injection is a main injection performed near the compression top dead center. Then, the following steps SF9 and SF1
At 0 and SF11, the pre-injection amount QL0 and the main injection amount QT0 obtained as described above are feedback-corrected based on the output signal from the O2 sensor 17, and the process proceeds to step SF12 in FIG.

That is, the output signal E from the O2 sensor 17 is larger than the reference value E1 corresponding to the stoichiometric air-fuel ratio (E
> E1), if the air-fuel ratio of the combustion chamber 4 is richer than the stoichiometric air-fuel ratio (yes in step SF9), the current values of the fuel feedback correction amounts QcL and QcT are respectively predetermined from the previous values. The values a and b are subtracted (step SF10). On the other hand, if the output signal E from the O2 sensor 17 is equal to or less than the reference value E1 (E ≦ E1: no in step SF9), the feedback correction amounts QcL and QcT
Is a value obtained by adding predetermined values a and b to the previous value (step SF11).

Following step SF10 or step SF11 in FIG. 21, step SF12 in FIG.
The final pre-injection amount QL and the main injection amount QT are calculated using the pre-injection amount QL0 and the main injection amount QT0 and the feedback correction amounts QcL and QcT, respectively. That is, QL = QL0 + QcL + Qlrn / 2 QT = QT0 + QcT + Qlrn / 2 where Qlrn is a learning correction amount for correcting the injection amount variation caused by the individual difference of the injectors 5, which will be described in detail later.

Subsequently, in step SF13, it is determined whether or not the set injection timing (pre-injection timing) has been reached based on the crank angle signal.
Wait until the pre-injection timing comes (step S
When the pre-injection timing comes (no in F13) (yes in step SF13), the process proceeds to step SF14 to execute the pre-injection. Steps SF15 and SF16
Then, similarly to the pre-injection, the fuel injection is executed by the injector 5 when the main injection timing comes.

Subsequently, in step SF17, the feedback correction amounts QcL and QcT obtained in steps SF10 and SF11 are added to obtain a learning sample value Qc. In the following step SF18, the learning sample value Qc is set to the number n of samples. (Qc (n)) and store it in the memory, and thereafter return.

That is, during the learning period, the feedback correction amounts QcL and QcT themselves are learned while performing feedback control based on the O2 sensor output so that the air-fuel ratio of the combustion chamber 4 of the engine 1 becomes substantially the stoichiometric air-fuel ratio. The value is sampled.

On the other hand, in step SF6 of FIG. 21, the timer value T2 is not smaller than the second set timer value T21.
When it is determined as o, that is, after a sufficient time has elapsed for learning the injection amount variation of the injector 5 accurately,
If a sufficient number of learning sample values Qc (n) are obtained, subsequently, in step SF19 in FIG.
2 is reset (T2 = 0), and in a succeeding step SF20, a learning correction amount QL is calculated. In the calculation of the learning correction amount QL, first, an average value of the n learning sample values Qc (n) is obtained as a provisional value of the current learning correction amount QL, and the provisional value and the learning value stored in the memory are further determined. The average value of the correction amount QL with the previous value is stored in the memory as the current value of the learning correction amount QL.

Subsequently, in step SF21, it is determined whether or not the basic injection timing (main injection timing) set in step SF3 has come, based on the crank angle signal. (No in step SF21), if the injection timing comes (yes in step SF21), step SF22
Then, the fuel of the basic fuel injection amount Qbase is injected in a lump, and then the process returns.

That is, a sufficiently large number of learning sample values Qc
If (n) is obtained, the average value is a value that reflects the variation in the injection amount of the injector 5 with high accuracy. By using this value as the learning correction amount Qlrn, the injection value caused by the individual difference of the injector 5 can be obtained. The variation in the amount can be eliminated. In addition, since the average with the previous value is calculated, the learning correction amount QL does not become an extremely inappropriate value even if erroneous learning occurs.

Step SF7 of the flow shown in FIG.
The air-fuel ratio control means 35
When the air-fuel ratio of the combustion chamber 4 is controlled by the air-fuel ratio control means 35a to be substantially the stoichiometric air-fuel ratio by each of the steps SF12 to SF16 of the flow shown in FIG. And injector 5
A fuel injection control means 35b is configured to inject fuel into two parts, a pre-injection during the intake stroke of the cylinder 2 and a main injection near the compression top dead center. Further, steps SF17 and SF18 constitute a learning means 35c for learning the state of variation in the fuel injection amount by the injector 5.

Therefore, according to the second embodiment, in the hybrid vehicle 50 in which the diesel engine 1 is normally operated in the high-load-side normal operation region having excellent fuel efficiency, as in the first embodiment, Controlling the air-fuel ratio of the combustion chamber 4 to be substantially the stoichiometric air-fuel ratio while suppressing the adverse effects such as increased smoke by the divided injection of
In this state, the variation state of the fuel injection amount is learned based on the output signal from the O2 sensor 17, and the fuel injection amount is corrected according to the individual learning result. It is possible to eliminate the variation in the amount and improve the control accuracy of the air-fuel ratio.

In the second embodiment, the learning of the fuel injection variation is performed irrespective of the refresh of the catalyst 22. However, similarly to the first embodiment, when the catalyst 22 is refreshed, Learning may be performed at the same time.

Further, an exhaust gas recirculation prohibiting means for prohibiting the recirculation of exhaust gas to the intake system of the engine 1 may be provided when learning the injection amount variation. That is, FIG.
In the fuel injection control flow shown in FIG. 1, when it is determined “yes” in step 6, the EGR valve 24 of the engine 1
May be forcibly closed to prohibit the recirculation of exhaust gas through the EGR passage 23. With this configuration, the gear ratio of the automatic transmission 52 is changed according to the change in the traveling state,
Even if the operating state of the engine 1 is in a region other than the high-load low-speed rotation where the EGR is performed, the variation in the oxygen concentration in the exhaust gas due to the change in the recirculated exhaust gas volume is avoided, and the injection amount variation is prevented. Erroneous learning can be prevented beforehand.

In the second embodiment, the present invention is applied to the hybrid vehicle 50. However, the present invention is not limited to this.
Similarly to the first embodiment, the present invention can be similarly applied to a vehicle equipped with the CVT 40 and in which the engine 1 is normally operated under a high load state during traveling.

(Other Embodiments) The present invention is not limited to the above embodiments, but includes other various embodiments. That is, in each of the above embodiments,
When controlling the air-fuel ratio of the combustion chamber 4 of the engine 1 to be substantially the stoichiometric air-fuel ratio, the fuel injection amount is increased and corrected, and the supercharging pressure is reduced by VGT control to reduce the intake air amount. However, the present invention is not limited to this. For example, when the operating state of the engine 1 is on the low load side, the intake air may be throttled by the intake throttle valve 14 to reduce the amount of intake air to the combustion chamber 4.

[0140]

As described above, according to the control apparatus for a diesel engine according to the first aspect of the present invention, for example,
When the air-fuel ratio of the combustion chamber of the engine is controlled by the air-fuel ratio control means to be close to the stoichiometric air-fuel ratio, and the NOx absorbent is refreshed, the air-fuel ratio of the combustion chamber is determined based on the value detected by the oxygen concentration detection means. By performing the feedback control, even if there is a variation in the injection amount due to the individual difference of the fuel injection valve, the variation can be absorbed and the control accuracy can be improved. Then, at this time, the variation state of the fuel injection amount can be accurately learned by the learning unit based on the value detected by the oxygen concentration detection unit, so that the fuel injection amount is corrected based on the learning result. In addition, it is possible to eliminate the variation in the injection amount due to the individual difference of the fuel injection valve, and to further improve the control accuracy of the air-fuel ratio.

According to the second aspect of the present invention, since the variation state of the fuel injection amount is learned in the operating region in which the exhaust gas is not recirculated to the intake system of the engine, erroneous learning caused by the fluctuation of the exhaust gas recirculation amount is learned. Can be prevented beforehand.

According to the third aspect of the present invention, when the variation state of the fuel injection amount is learned by the learning means, the exhaust gas recirculation prohibiting means prohibits the recirculation of exhaust gas to the intake system of the engine. As in the second invention, erroneous learning of the injection amount variation can be prevented beforehand.

According to the fourth aspect of the present invention, when controlling the air-fuel ratio of the combustion chamber of the engine to be close to the stoichiometric air-fuel ratio, the fuel is divided into two and injected to sufficiently suppress the increase in smoke. And the generation of NOx can be reduced.

According to the fifth aspect of the present invention, when the engine is in a predetermined high load operation state, the air-fuel ratio of the combustion chamber of the engine is controlled to be close to the stoichiometric air-fuel ratio. Fluctuations can be suppressed.

According to the sixth aspect of the invention, when the fuel injection amount is increased, the supercharging pressure reducing means lowers the supercharging pressure of the turbocharger to reduce the amount of intake air. Therefore, it is not necessary to increase the fuel injection amount too much,
In addition, fluctuations in engine output can be reduced.

According to the seventh aspect of the invention, when controlling the air-fuel ratio of the combustion chamber of the engine to be close to the stoichiometric air-fuel ratio, the speed ratio of the continuously variable transmission is controlled by the speed ratio control means. Can be forced to a predetermined high load operation state. Claim 5 irrespective of the running state of the vehicle.
The same effect as that of the invention is obtained.

According to the eighth aspect of the present invention, by mounting the engine on a hybrid vehicle, the same effect as the seventh aspect of the invention can be obtained.

According to the diesel engine control apparatus of the ninth aspect, in the diesel engine mounted on the hybrid vehicle, the air-fuel ratio of the combustion chamber of the engine is controlled to be substantially equal to the stoichiometric air-fuel ratio. Since the variation state of the fuel injection amount can be accurately learned based on the value detected by the oxygen concentration detecting means, the fuel injection amount is corrected based on the learning result, which results in the individual difference of the fuel injection valve. By eliminating the variation in the injection amount, the control accuracy of the air-fuel ratio can be made extremely high. At this time, there is no adverse effect such as an increase in smoke.

According to the control apparatus for a diesel engine according to the tenth aspect of the present invention, the same effects as those of the ninth aspect can be obtained in a vehicle equipped with a continuously variable transmission.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of a diesel engine control device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a part of the turbocharger in a small A / R state (a) or a large A / R state (b).

FIG. 3 is a diagram showing a configuration of an EGR valve and a drive system thereof.

FIG. 4 is a skeleton diagram illustrating a schematic configuration of a CVT.

FIG. 5 is a time chart showing injection timings of pre-injection, main injection, and post-injection.

FIG. 6 shows an EGR region (A) and an effective region of learning control (A) in association with a target torque and an engine speed of the engine.
It is explanatory drawing which illustrated.

FIG. 7 is a flowchart illustrating a first half of a processing procedure of fuel injection control;

FIG. 8 is a flowchart illustrating the latter half of the fuel injection control.

FIG. 9 is a diagram showing an example of a map in which a fuel injection amount is set in association with an accelerator opening and an engine speed.

FIG. 10 is a flowchart illustrating a processing procedure of learning control.

FIG. 11 is a flowchart illustrating a processing procedure of EGR control.

FIG. 12 is a diagram showing an example of a basic EGR control map in which a basic EGR rate is set in association with an accelerator opening and an engine speed.

FIG. 13 is a diagram showing an example of a map in which a target fresh air amount is set in association with an accelerator opening and an engine speed.

FIG. 14 is a graph showing the relationship between the air-fuel ratio of the combustion chamber and the amount of smoke.

FIG. 15 is a diagram illustrating an example of a map in which an EGR feedback correction value is set in association with a fresh air amount deviation.

FIG. 16 is a flowchart illustrating a processing procedure of VGT control.

FIG. 17 is a diagram showing an example of a map in which the nozzle cross-sectional area of the VGT is set in association with the accelerator opening and the engine speed.

FIG. 18 is a schematic configuration diagram of a hybrid vehicle according to a second embodiment.

FIG. 19 is a flowchart illustrating a basic control procedure of a motor, an engine, and the like of the hybrid vehicle.

FIG. 20 is an explanatory diagram showing a normal operation region of an engine mounted on the hybrid vehicle.

FIG. 21 is a flowchart illustrating the first half of a fuel injection control procedure;

FIG. 22 is a flowchart illustrating a second half of the fuel injection control and a learning control.

[Explanation of symbols]

 Reference Signs List A Exhaust gas purification device 1 Diesel engine 2 Cylinder 4 Combustion chamber 5 Injector (fuel injection valve) 20 Exhaust passage 21b VGT flap (supercharging pressure adjusting means) 22 Catalyst (NOx absorber) 23 EGR passage (Exhaust recirculation means) 24 EGR Valve (exhaust gas recirculation means) 25 Turbocharger 30 Diaphragm (supercharge pressure adjustment means) 31 Solenoid valve (supercharge pressure adjustment means) 35 ECU (control unit) 35a Air-fuel ratio control means 35b Fuel injection control means 35c Learning means 35d Gear ratio control means 35e Exhaust gas recirculation control means 35f Supercharging pressure reducing means 40 CVT (Continuously variable transmission) 50 Hybrid vehicle 51 Traveling motor (electric motor)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 21/08 301 F02D 21/08 311B 3G093 311 23/00 E 3G301 23/00 29/00 H 29/00 29/02 D 29/02 41/04 355 41/04 355 41/40 C 41/40 43/00 301N 43/00 301 301R 301W F02M 25/07 570J F02M 25/07 570 570B 570P F02B 37/12 301Q / / B60K 6/00 B60K 9/00 Z 8/00 (72) Inventor Akihiro Kobayashi 3-1, Fuchu-cho, Shinchu, Aki-gun, Hiroshima Mazda F-term (reference) 3G005 DA02 EA04 EA16 FA35 FA37 GA04 GC05 GE01 GE09 HA04 HA05 HA12 HA18 JA26 JA39 JA45 JA51 JB02 3G062 AA01 AA05 BA02 BA04 BA05 CA06 GA04 GA05 GA06 GA15 GA17 3G084 AA01 BA07 BA09 BA13 BA15 BA20 D A04 DA10 DA11 DA21 EB11 EB17 FA07 FA10 FA29 FA33 FA38 3G091 AA14 AA18 AB06 BA11 BA14 CB02 CB07 GA06 GB02Y GB03Y GB04Y GB06W GB09W GB10W GB17X HA36 HB05 3G092 AA02 AA17 AA18 AC02 BA04 EC03 FA01 DB03 FA03 HD05X HD05Z HD07Z HE01Z HE03Z HF08Z HF12Z 3G093 AA06 AA16 AB00 AB01 AB02 BA02 BA20 CA07 DA09 DA11 DB23 EA04 EA05 EB03 FA04 FA09 FA11 FB05 3G301 HA02 HA11 HA13 JA00 JA04 JA17 JA24 JA25 KA09 LA00Z11 PD01 MA01 MA01 PD02 PE01Z PE03Z PF03Z PF07Z

Claims (10)

[Claims] 1. A NOx absorber disposed in an exhaust passage of an engine and absorbing NOx in exhaust gas in an oxygen-rich atmosphere having a high oxygen concentration and releasing the absorbed NOx due to a decrease in oxygen concentration. An air-fuel ratio control means for controlling the air-fuel ratio of the combustion chamber of the engine to be close to the stoichiometric air-fuel ratio when NOx is released from the absorbent; Oxygen concentration detection means for detecting the oxygen concentration in the exhaust passage on the side, the air-fuel ratio control means feedback-controls the air-fuel ratio of the combustion chamber of the engine based on the value detected by the oxygen concentration detection means, When controlling the air-fuel ratio to be near the stoichiometric air-fuel ratio by the air-fuel ratio control means, the fuel based on the value detected by the oxygen concentration detection means is used. Control apparatus for a diesel engine, wherein a learning means for learning the variation state of the injection amount is provided. 2. An engine according to claim 1, wherein an intake air amount detecting means for detecting an amount of air taken into a combustion chamber of the engine, an exhaust gas recirculation means for recirculating a part of exhaust gas to an intake system of the engine, And an exhaust gas recirculation control unit that controls the amount of exhaust gas recirculated by the exhaust gas recirculation unit based on the value detected by the intake air amount detection unit. A control device for a diesel engine, characterized in that it is configured to learn a state of variation of the fuel injection amount when it is in a state. 3. The engine according to claim 1, wherein an intake air amount detecting means for detecting an amount of air taken into a combustion chamber of the engine, an exhaust gas recirculation means for recirculating a part of exhaust gas to an intake system of the engine, Exhaust gas recirculation control means for controlling the amount of exhaust gas recirculated by the exhaust gas recirculation means based on the value detected by the intake air amount detection means. An exhaust gas recirculation prohibiting means for prohibiting the recirculation of exhaust gas by the exhaust gas recirculation means is provided. 4. The fuel injection valve according to claim 1, wherein the fuel injection valve for directly injecting fuel into a combustion chamber in the cylinder of the engine, and the air-fuel ratio control means controls the air-fuel ratio to be close to the stoichiometric air-fuel ratio. Fuel injection control means for injecting fuel by the fuel injection valve into two parts, a main injection near the compression top dead center of the cylinder and a sub-injection from the beginning of the intake stroke to the first half of the compression stroke, is provided. A control device for a diesel engine. 5. The air-fuel ratio control means according to claim 4, wherein the air-fuel ratio of the combustion chamber of the engine is controlled to be close to the stoichiometric air-fuel ratio when the engine is in a predetermined high load operation state. A control device for a diesel engine, comprising: 6. A turbocharger according to any one of claims 1 to 5, for supercharging intake air by exhaust of an engine, and a supercharging pressure adjusting means for adjusting a supercharging pressure by the turbocharger. When the air-fuel ratio control means controls the air-fuel ratio of the combustion chamber of the engine to be close to the stoichiometric air-fuel ratio, the air-fuel ratio control means reduces the supercharging pressure of the turbocharger by the supercharging pressure adjusting means. A control device for a diesel engine, comprising a supply pressure reducing means. 7. The continuously variable transmission according to claim 1, wherein the engine is an on-vehicle engine, and a continuously variable transmission for continuously changing the output of the engine and transmitting the output to the driving wheels of the vehicle. When the control means controls the air-fuel ratio to be close to the stoichiometric air-fuel ratio, there is provided speed ratio control means for controlling the speed ratio of the continuously variable transmission so that the engine is in a predetermined high load operation state. A control device for a diesel engine, comprising: 8. A hybrid according to claim 6, wherein the engine is mounted on a vehicle provided with an electric motor for traveling, and the vehicle is driven by at least one of the engine and the electric motor. A control device for a diesel engine, which is a vehicle. 9. A control device for a diesel engine for driving a hybrid vehicle in cooperation with an electric motor for driving, the fuel injection valve being configured to inject fuel directly into a combustion chamber in a cylinder of the engine. An oxygen concentration detecting means for detecting an oxygen concentration in an exhaust passage of the engine; and an air for feedback-controlling an air-fuel ratio of the combustion chamber to be close to a stoichiometric air-fuel ratio based on a value detected by the oxygen concentration detecting means. Fuel-ratio control means, when the air-fuel ratio control means controls the air-fuel ratio to be close to the stoichiometric air-fuel ratio, the fuel is injected by the fuel injection valve, the main injection near the compression top dead center of the cylinder, the intake stroke Fuel injection control means for injecting the fuel into two sub-injections during the period from the initial stage to the first half of the compression stroke; and controlling the air-fuel ratio to be close to the stoichiometric air-fuel ratio by the air-fuel ratio control means. Come, the control device for a diesel engine, characterized in that it comprises a learning means for learning the variation state of the fuel injection amount based on a value detected by the oxygen concentration detection means. 10. A control device for a diesel engine that transmits the output of an on-vehicle engine to a driving wheel side of a vehicle via a continuously variable transmission, wherein fuel is directly injected into an in-cylinder combustion chamber of the engine. A fuel injection valve, an oxygen concentration detecting means for detecting an oxygen concentration in an exhaust passage of the engine, and an air-fuel ratio of the combustion chamber based on a value detected by the oxygen concentration detecting means so as to be close to a stoichiometric air-fuel ratio. Air-fuel ratio control means for performing feedback control on the air-fuel ratio control means, when controlling the air-fuel ratio to be near the stoichiometric air-fuel ratio, the speed ratio of the continuously variable transmission,
Speed ratio control means for controlling the engine to be in a predetermined high load operation state; and when controlling the air-fuel ratio to be close to the stoichiometric air-fuel ratio by the air-fuel ratio control means, the fuel is injected by the fuel injection valve. Fuel injection control means for performing two-split injections of main injection near the compression top dead center of the cylinder and sub-injection from the beginning of the intake stroke to the first half of the compression stroke; and A control unit for a diesel engine, comprising: a learning unit configured to learn a variation state of a fuel injection amount based on a value detected by the oxygen concentration detecting unit when performing control so as to be near the stoichiometric air-fuel ratio. .