JP2002030979A - Diesel engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote warming-up of a direct injection type diesel engine 1, and to reduce vibrations and noise, without causing misfire or substantial deterioration in fuel consumption, during idle operation of the non-warmed diesel engine 1. SOLUTION: When the engine 1 is in an idle operation state, while an injector 5 conducts pilot injection to improve ignition stability and a combustion property of main injected fuel, an intake air throttle valve 22 is closed to reduce vibrations and noise. A recirculation rate of exhaust is controlled by air flow feedback controlling, and the necessary amount of fresh air to fuel injection amount is ensured even if the intake air throttle valve 22 is closed. In a non- warmed state, as compared with a state after warming-up, a target air/fuel ratio A/Fsol in the air flow feedback controlling is made to have a value in a lean side, and the intake air throttle valve 22 is relatively wide opened. According to a rise of engine water temperature thw, the intake air throttle valve 22 is closed so as to make intake negative pressure generally constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a direct-injection diesel engine, and more particularly, to promoting warm-up and reducing noise and vibration when the engine is not warmed up after a cold start. It concerns measures to achieve both.

[0002]

2. Description of the Related Art Generally, a diesel engine having high thermal efficiency has a low temperature state of a combustion chamber in an idling operation state and a large ignition delay of fuel injected into the combustion chamber. Is known to rise sharply and generate harsh combustion noise. In addition, there is a demand that the engine speed be reduced as much as possible in order to reduce fuel consumption during idling after warm-up. However, the lower the engine speed, the greater the angular speed fluctuation of the crankshaft. Situation.

To cope with such problems of engine vibration and noise, a sub-chamber diesel engine has conventionally been provided with an intake throttle valve in an intake passage, and the idle throttle valve is substantially omitted during idling operation after warm-up. Control so that it is fully closed,
By forcibly reducing the intake air amount to the cylinder,
There is one that reduces vibration and noise of an engine (for example, see Japanese Patent Application Laid-Open No. 8-284700).

It is known that in a direct injection diesel engine, performing so-called pilot injection is particularly effective in reducing noise (for example, Japanese Patent Application Laid-Open No. H11-21-211).
No. 47703). That is, a small amount of fuel is pilot-injected by the fuel injection valve prior to the main injection, and the combustion of this fuel raises the temperature state of the combustion chamber and forms a flame kernel (fire type). The ignition delay can be greatly reduced, and the combustion noise can be reduced.

Further, for example, in the direct injection type diesel engine disclosed in Japanese Patent Application Laid-Open No. 11-93735, the main injection is performed by increasing the pilot injection amount as the engine water temperature is lower in the idle operation state of the unheated engine. The temperature of the combustion chamber when the fuel is ignited is set to be substantially the same as that after warm-up even in a non-warmed state to prevent misfire and reduce combustion noise.

[0006]

By the way, when the engine is idling with the engine not warmed up, the engine speed is usually controlled to be higher than after the engine is warmed up (hereinafter also referred to as idle-up control). Although it is advantageous for vibration isolation, it is rather disadvantageous for fuel economy. Further, when the fuel is not warmed up, the vaporization of the fuel becomes extremely poor, so that the ignitability and combustibility of the fuel are reduced, and the possibility of misfiring is increased.

In this regard, when the intake throttle valve is closed to restrict the intake air to the cylinder as in the first conventional example (Japanese Patent Laid-Open No. 8-284700), the mixing of fuel and air is thereby reduced. Because the condition will worsen,
As described above, in the unwarmed state in which the vaporization of the fuel is poor, there is a very strong risk of misfiring. In addition, since the amount of generated heat is reduced due to the deterioration of the combustibility, there is a problem that the warm-up of the engine is delayed.

On the other hand, the second and third conventional examples (JP-A-11-247703 and JP-A-11-93735)
As described above, when trying to improve the ignitability and combustibility of the main injection fuel by pilot injection, in the unwarmed state where the temperature state of the combustion chamber is low as described above, it is not necessary to perform pilot injection of a considerable amount of fuel. Therefore, there is a situation that the fuel consumption is significantly deteriorated due to this.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and an object thereof is to provide a direct injection type diesel engine mainly in a state of exhaust gas recirculation and an intake throttle when the engine is in an idle operation state in which the engine is not warmed up. An object of the present invention is to devise control of the amount and the like so as to achieve both the promotion of engine warm-up and the reduction of vibration and noise without causing a misfire or a significant deterioration in fuel efficiency.

[0010]

In order to achieve the above object, according to the present invention, while the ignition stability is increased by pilot injection while the engine is idling, the intake throttle valve is closed to reduce vibration noise. In particular, when the engine is not warmed up, the amount of intake air relative to the amount of fuel supplied is relatively increased as compared to the state after warming up, so that fuel vaporization and mixing with air are promoted.

Specifically, the invention according to claim 1 comprises a fuel injection valve facing a combustion chamber in a cylinder of an engine, and an intake throttle valve for restricting intake air to the combustion chamber, wherein the throttle valve is provided in accordance with a load state of the engine. While controlling the fuel injection amount by the fuel injection valve,
It is assumed that the control device of the diesel engine is such that the intake throttle valve is closed at least in an idle operation state after the engine is warmed up. An exhaust gas recirculation passage for recirculating a part of the exhaust gas to an intake passage downstream of the intake throttle valve; an exhaust gas recirculation amount control valve for adjusting the amount of exhaust gas recirculated by the exhaust gas recirculation passage; Exhaust recirculation control means for controlling the opening degree of the valve to indirectly adjust the amount of intake air to the combustion chamber so that the average air-fuel ratio of the combustion chamber becomes a predetermined target value; A pilot injection control means for pilot-injecting a small amount of fuel prior to the main injection of fuel by the fuel injection valve; and Idle-up control means for controlling the air-fuel ratio to be higher than that in the idle operation state. The target value was assumed to have a target air-fuel ratio setting unit for setting to a value leaner than in the idling state after warm-up.

With the above configuration, first, during idle operation of the engine, the intake throttle valve is closed, the amount of air taken into the combustion chamber is reduced, and the compression pressure in the cylinder is reduced, thereby reducing vibration and noise. Is achieved. At this time, the high-temperature burned gas (exhaust gas) is recirculated to the combustion chamber by the exhaust gas recirculation passage, and the pilot injection is performed before the main injection of the fuel by the fuel injection valve, so that the main injection is performed before the main injection is performed. The temperature and pressure conditions of the combustion chamber are increased, and a flame nucleus serving as a fire is formed, so that the ignitability and combustibility of the main injection fuel are greatly improved. Thus, the generation of NOx is suppressed by relaxing the initial combustion, and the increase in smoke is suppressed by improving the overall flammability.

When the engine is not warmed up and idling, the idle-up control means controls the engine speed to be relatively high.
The target air-fuel ratio setting section of the exhaust gas recirculation control means sets the target value of the air-fuel ratio to a value on the lean side as compared to after the warm-up. Lean air-fuel ratio means that the amount of air supply relative to the amount of fuel supply is relatively large, so even if the engine is not warmed up, the fuel vaporization and the state of mixing with air deteriorate. It is suppressed and the injected fuel can be more effectively burned. Thus, in combination with the effect of the pilot injection, misfire can be reliably prevented even when the engine is not warmed up. In addition, since the amount of heat generated by combustion increases, the engine speed becomes relatively low. In combination with the high cost, it is possible to sufficiently promote the warm-up of the engine.

According to the second aspect of the present invention, the intake throttle valve controls the opening degree of the intake throttle valve to be larger than in the idle operation state after the engine is warmed up when the engine is in the idle operation state with the engine not warmed up. It is configured to include control means. As a result, when the engine is not warmed up, compared to after warming up,
The opening degree of the intake throttle valve is relatively increased, and the amount of intake air to the cylinder itself increases. As a result, the air flow in the in-cylinder combustion chamber is increased, and the compression pressure of the intake air is increased, so that the ignition stability of the injected fuel is further improved. Along with this, the combustibility is also improved, and the warm-up of the engine is further promoted.

According to a third aspect of the present invention, there is provided a state quantity detecting means for detecting a state quantity relating to the air-fuel ratio of the combustion chamber, and the exhaust gas recirculation control means is controlled by the opening degree of the exhaust gas recirculation control valve by the state quantity detecting means. Feedback control is performed based on the detected value. Thus, the air-fuel ratio state of the combustion chamber can be accurately controlled by feedback-controlling the opening of the exhaust gas recirculation amount control valve by the exhaust gas recirculation control means based on the value detected by the state quantity detection means, Even if the intake throttle valve is closed, it is possible to secure air required for combustion and prevent misfire.

According to a fourth aspect of the present invention, the idle-up control means in the second aspect of the invention controls the engine rotational speed to decrease as the temperature of the unwarmed engine increases. The throttle valve control means performs control such that the opening degree of the intake throttle valve decreases as the temperature state of the engine increases.

As a result, the engine speed is decreased as the temperature of the engine is increased, so that the deterioration of fuel efficiency due to the warm-up operation is suppressed. In addition, the intake air flow per unit time naturally decreases with a decrease in the engine rotation speed, but in response to this, the opening degree of the intake throttle valve is reduced by the intake throttle valve control means, The negative pressure in the intake passage does not suddenly change, thereby preventing sudden changes in the magnitude of vibration and noise during warm-up of the engine and preventing the driver from feeling uncomfortable.

According to a fifth aspect of the present invention, when the engine is in an idling state in which the engine is not warmed up, a fuel increase correction means for intermittently increasing the amount of fuel injected by the fuel injection valve from the expansion stroke to the exhaust stroke of the cylinder. Shall be provided.

That is, in general, when the engine is cold started, the temperature state of the exhaust gas purifying catalyst is low, that is, in a so-called inactive state. Therefore, according to the present invention, when the engine is in the idling operation state in which the engine is not warmed up, the fuel increase correction means intermittently increases the fuel injection amount from the expansion stroke of the cylinder to the exhaust stroke to raise the temperature state of the exhaust, The temperature of the catalyst can be increased. In addition, by intermittently increasing the amount of fuel, it is possible to suppress deterioration in fuel efficiency due to the increase in fuel.

According to a sixth aspect of the present invention, there is provided a post-injection control system in which the fuel increase correction means according to the fifth aspect of the present invention uses the fuel injection valve to intermittently inject a small amount of fuel immediately after the main fuel injection during the cylinder expansion stroke. Means. With this,
Since part of the fuel injected immediately after the main injection of fuel burns and contributes to the driving force of the engine,
Deterioration of fuel efficiency due to an increase in fuel can be minimized. Further, since the unburned fuel is also thermally decomposed at a high temperature, the reaction of the unburned fuel with the catalyst becomes active, and the temperature rise of the catalyst is further promoted.

According to a seventh aspect of the present invention, the fuel increase correction means in the fifth aspect of the invention intermittently increases the main injection amount of fuel by the fuel injection valve. That is, the main injection time of the combustion is extended, and the fuel injection amount in the expansion stroke of the cylinder is increased, so that the temperature state of the exhaust gas is increased.

According to an eighth aspect of the present invention, the idle-up control means in the second aspect of the invention controls the engine speed so as to decrease as the temperature state of the unwarmed engine increases. The throttle valve control means controls the opening of the intake throttle valve so that the negative pressure in the intake passage is substantially constant while the temperature state of the engine is lower than a set temperature, while the temperature state of the engine is lower than the set temperature. When the temperature becomes equal to or higher than the temperature, the opening degree of the intake throttle valve is controlled so that the negative pressure in the intake passage gradually increases until the warm-up of the engine is completed.

With this, the engine speed is reduced as the temperature of the engine becomes higher, so that the deterioration of fuel efficiency during the warm-up operation is suppressed. In addition, the intake air flow per unit time naturally decreases with a decrease in the engine rotation speed.At this time, until the temperature state of the engine reaches the set temperature, the intake air flow decreases according to the decrease in the intake air flow.
The opening degree of the intake throttle valve is gradually reduced by the intake throttle valve control means so that the negative pressure in the intake passage becomes substantially constant.
In other words, when the temperature of the engine is relatively low, priority is given to promoting warm-up, and while the opening of the intake throttle valve is kept relatively large, changes in the magnitude of vibration and noise during that time are prevented. can do.

Then, when the temperature state of the engine reaches the set temperature, the intake throttle valve is immediately closed with priority given to the reduction of vibration and noise thereafter. On this occasion,
By closing the intake throttle so that the negative pressure in the intake passage gradually increases in accordance with the rise in the temperature of the engine, the magnitude of vibration and noise can be changed smoothly, which allows the driver to It can prevent you from feeling uncomfortable.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

(Overall Configuration) FIG. 1 shows the overall configuration of a diesel engine control device A according to an embodiment of the present invention.
Reference numeral 1 denotes a multi-cylinder diesel engine mounted on a vehicle. The engine 1 has a plurality of cylinders 2, 2,... (Only one is shown), and a piston 3 is inserted into each cylinder 2 in a reciprocating manner. The combustion chamber 4 is partitioned. Also, piston 3
An injector (fuel injection valve) 5 is disposed on the ceiling of the combustion chamber 4 facing the top surface of the fuel cell so that the front end faces the combustion chamber 4 and extends along the cylinder center line. An injection nozzle is integrally provided at a distal end of each of the injectors 5, while a base end is connected to a common pipe 6 for storing fuel in a predetermined high pressure state by branch pipes 6 a, 6 a,.
(Only one is shown). When the needle valve of the injection nozzle is opened and closed at a predetermined timing for each cylinder, the common rail 6 is opened.
The high-pressure fuel supplied from the combustion chamber 4 is directly injected into the combustion chamber 4. The common rail 6 has a fuel pressure sensor 7 for detecting the internal fuel pressure (common rail pressure).
Are arranged.

The common rail 6 is connected to a high-pressure supply pump 9 by a fuel supply pipe 8. The high-pressure supply pump 9 is connected to a fuel tank by a fuel supply system (not shown), and is connected to a crankshaft 10 by a toothed belt or the like.
The fuel is sucked up while filtering the fuel in the fuel tank with a fuel filter, and the fuel is fed to the common rail 6 by a jerk type feeding system. The high-pressure supply pump 9 is provided with an electromagnetic valve for returning a part of the fuel sent out by the pressure supply system to the fuel supply system and adjusting the discharge amount of the pump. By being controlled in accordance with the value detected by the pressure sensor 7, the common rail pressure is maintained at a predetermined state corresponding to the operating state of the engine 1.

The engine 1 includes a crank angle sensor 11 for detecting a rotation angle of a crank shaft 10 and a valve operating system cam shaft 1.
A cam angle sensor (not shown) for detecting the rotation angle of
An engine water temperature sensor 13 for detecting the temperature of the cooling water is provided. Although not shown in detail, the crank angle sensor 11 includes a plate to be detected provided at the end of the crankshaft and an electromagnetic pickup disposed so as to face the outer periphery thereof. A pulse signal is output each time the projections formed at equal intervals pass through. The cam angle sensor has the same configuration.

An intake passage 16 for supplying air filtered by an air cleaner 15 to the combustion chamber 4 of each cylinder 2 is connected to one side (the right side in the figure) of the engine 1. A surge tank 17 is provided at a downstream end of the intake passage 16. Each of the passages branched from the surge tank 17 communicates with the combustion chamber 4 of each cylinder 2 through an intake port. An intake pressure sensor 18 for detecting a pressure state of intake air is provided.

A hot film type air flow sensor 19 (state quantity detection) for detecting a flow rate of air (fresh air) taken into the engine 1 from the outside in order from the upstream side to the downstream side is provided in the intake passage 16. Means), a blower 20 driven by a turbine 27 described below to compress the intake air,
An intercooler 21 for cooling the intake air compressed by the blower 20, and an intake throttle valve 2 comprising a butterfly valve;
2 are provided. The intake throttle valve 22 is configured such that the valve shaft is rotated by a stepping motor 23 to be in an arbitrary state from fully closed to fully opened. A gap is left between the peripheral wall and the peripheral wall for air to flow even in the fully closed state.

On the other hand, an exhaust passage 26 is connected to a side surface on the opposite side (left side in the figure) of the engine 1 so as to discharge burned gas (exhaust gas) from the combustion chamber 4 of each cylinder 2. The upstream end of the exhaust passage 26 is an exhaust manifold that branches off for each cylinder 2 and communicates with the combustion chamber 4 through an exhaust port. The exhaust passage 26 downstream of the exhaust manifold has an upstream side to a downstream side. , A turbine 27 that is rotated in response to the exhaust gas flow and a catalytic converter 28 that can purify harmful components (unburned HC, CO, and NOx) in the exhaust gas are provided.

The turbocharger 30 composed of the turbine 27 and the blower 20 in the intake passage 16 changes the cross-sectional area (nozzle cross-sectional area) of the exhaust flow path to the turbine 27 by movable flaps 31, 31,. A variable turbo (hereinafter referred to as VGT),
Are respectively driven and connected to the diaphragm 32 via a link mechanism (not shown).
The magnitude of the negative pressure acting on the flaps is adjusted by the negative pressure control solenoid valve 33, whereby the rotational position of the flaps 31, 31,... Is adjusted, and the nozzle cross-sectional area changes. I have.

Although not shown in detail, the catalytic converter 28 has a cordierite carrier having a honeycomb structure having a large number of through-holes extending in parallel with each other in the exhaust gas flow direction. A catalyst layer of a so-called lean NOx catalyst is formed on each through hole wall surface. This lean NOx catalyst can reduce and purify NOx in exhaust gas even when the oxygen concentration in the exhaust gas is high, that is, in a lean state in which the average air-fuel ratio of the combustion chamber 4 is larger than the stoichiometric air-fuel ratio. In addition, it works as a three-way catalyst near the stoichiometric air-fuel ratio.

More specifically, as the lean NOx catalyst, for example, a catalyst in which a catalyst layer formed by carrying platinum Pt on zeolite in a dry state and supported on the carrier by a binder is used. Lean NO
The purification performance of NOx in exhaust gas by the x catalyst exhibits temperature dependence as shown in an example in FIG. That is, the NOx purification rate of exhaust gas by this catalyst is extremely high in a temperature range of about 250 to 400 ° C. (predetermined temperature range), but when the temperature is lower (inactive state), the lower the temperature, the lower the temperature. The NOx purification rate also decreases rapidly. Conversely, when the temperature of the catalyst becomes 400 ° C. or higher, the NOx purification rate decreases as the temperature rises.

Further, the exhaust passage 26 is provided in the turbine 2
7 and is branched and connected to an upstream end of an exhaust gas recirculation passage (hereinafter, referred to as an EGR passage) 34 for recirculating a part of the exhaust gas to the intake side at a position upstream of the exhaust gas. The downstream end of the EGR passage 34 is connected to the intake passage 16 between the intake throttle valve 22 and the surge tank 17, and a part of the exhaust gas extracted from the exhaust passage 26 is returned to the intake passage 16. ing. Further, an exhaust gas recirculation amount control valve (hereinafter, referred to as an EGR valve) 35 whose opening degree can be adjusted is disposed near the downstream end in the middle of the EGR passage 34. The EGR valve 35 is of a negative pressure responsive type, and the flaps 31 and
As in the case of 31, 31, the magnitude of the negative pressure on the diaphragm is adjusted by the solenoid valve 36, so that the EGR passage 3
4 is adjusted linearly to adjust the flow rate of the exhaust gas recirculated to the intake passage 16.

The injectors 5, the high-pressure supply pump 9, the intake throttle valve 22, the VGT 30, the EGR valve 35, etc.
All control units (Electronic Control
It operates in response to a control signal from a unit (hereinafter referred to as ECU) 40. On the other hand, the ECU 40 receives output signals from the fuel pressure sensor 7, the crank angle sensor 11, the cam angle sensor, the engine water temperature sensor 13, the intake pressure sensor 18, the air flow sensor 19, and the like.
An accelerator opening sensor 41 for detecting an operation amount (accelerator opening) of an accelerator pedal (not shown), a neutral switch 42 (neutral SW) for detecting whether a transmission selector lever is at a neutral position, and presence / absence of a clutch pedal operation. Output signals from a clutch switch 43 (clutch SW) for detecting the operation of the brake pedal, a brake switch 44 (brake SW) for detecting the presence or absence of a depressing operation of the brake pedal, a parking brake switch 45 (PBSW) for detecting the operation state of the parking brake, and the like. Is to be entered.

As the basic control by the ECU 40, the target fuel injection amount is determined mainly based on the accelerator opening, and the fuel injection amount and the injection timing are controlled by controlling the operation of the injector 5; The operation control of the supply pump 9 controls the common rail pressure, that is, the fuel injection pressure. Further, the intake throttle valve 22 and the EGR valve 35
, The intake air amount is adjusted directly and indirectly so that the average air-fuel ratio of the combustion chamber 4 becomes the target value. Further, the flaps 31, 3 of the VGT 30
The supercharging efficiency of the intake air is improved by the operation control (VGT control) of 1,.

(Fuel Injection Control) Specifically, the fuel injection control basically includes a compression top dead center (TDC) for each cylinder.
In accordance with the load state of the engine 1 in the vicinity, fuel is directly injected and supplied to the combustion chamber 4 by the injector 5 (hereinafter, referred to as main injection). During the compression stroke of the cylinder 2 prior to the injection, the injector 5 is operated to inject a small amount of fuel into the combustion chamber 4 (hereinafter referred to as pilot injection: see FIG. 6).

More specifically, the basic configuration of the fuel injection control unit in the ECU 40 is shown in the functional block diagram of FIG. In the figure, reference numeral 40a denotes an engine rotation speed obtained from an accelerator opening Acc detected by the accelerator opening sensor 41 and an output signal of the crank angle sensor 11.
A target torque calculation unit that calculates a target torque Trq corresponding to the required output of the engine 1 based on ne. The target torque Trq calculated by the target torque calculation unit 40a
And the fresh air amount Ai measured by the air flow sensor 19
On the basis of the r and the engine speed ne, the basic target fuel injection amount Q is referred to in the target injection amount calculating section 40b by referring to a three-dimensional control map (fuel injection amount map) on the memory.
b is calculated.

This fuel injection amount map records the optimum fuel injection amount Qb experimentally determined according to changes in the target torque Trq of the engine 1 and the engine speed ne. For example, the value of Qb is The larger the target torque Trq,
In addition, it is set and recorded so as to increase as the engine speed ne increases. This target injection amount calculation unit 40
In b, the basic target fuel injection amount Qb obtained as described above is further corrected according to the engine coolant temperature thw, the intake pressure p, and the like.

Further, based on the accelerator opening Acc and the engine speed ne, the basic injection timing setting section 40c refers to a control map (basic injection timing map) on the memory to obtain the basic injection timing ITb of the injector 5. Is calculated. The basic injection timing ITb is a timing at which the main injection operation of the injector 5 ends and the needle valve closes (crank angle position). Further, the injection timing map is obtained by experimentally obtaining and recording basic injection timings corresponding to the engine water temperature thw, the common rail pressure CRp, the engine rotation speed ne, and the like. The advance is set and recorded as thw is lower, the common rail pressure is lower, and the engine speed ne is higher.

Subsequently, the target fuel injection amount Qb determined by the target injection amount calculating section 40b and the engine speed n
Based on e, the injection ratio calculation unit 40d refers to a control map (injection ratio map) on the memory, and refers to a pilot injection ratio which is a ratio of the pilot injection amount of fuel by the injector 5 to the basic fuel injection amount Qb. Rp is calculated. This injection ratio map is expressed by the target fuel injection amount Q
The pilot injection ratio Rp is set so as to correspond to b and the engine rotation speed ne.For example, the pilot injection ratio Rp increases as the fuel injection amount decreases and the load decreases, while the load state and the rotation speed ne. Is set so that the number gradually decreases as the number increases. Note that when the engine 1 is in the idling operation state, the pilot injection ratio Rp calculated as described above is corrected according to the exhaust gas recirculation state in the EGR passage 34 and the like.

Further, based on the target fuel injection amount Qb and the engine speed ne, the injection stop interval calculating section 40e calculates the injection stop interval Tp by referring to a control map (injection interval map) in the memory. You. The injection stop interval Tp is determined from the time when the pilot injection operation of the injector 5 is completed and the needle valve is fully closed.
Is the time interval before the start of opening for the main injection operation. In the injection interval map, an injection stop interval Tp is set so as to correspond to the target fuel injection amount Qb and the engine rotation speed ne. For example, the injection stop interval Tp is set when the engine 1 is in an idle operation state. At some point, it is set to be the shortest, while gradually becoming longer as it shifts to the high load side or the high rotation side. Note that when the engine 1 is in the idling operation state, the injection stop interval Tp is corrected according to the state of exhaust gas recirculation through the EGR passage 34 and the like.

Then, the target fuel injection amount Qb, basic injection timing ITb, pilot injection ratio Rp, injection stop interval T
p, the common rail pressure CRp detected by the fuel pressure sensor 7, and the like are input to the injection control unit 40f, and the injection control unit 40f performs pilot injection and main injection operation of the injector 5 based on those input values. The start time and the excitation time in each injection operation are determined. That is, first, the target fuel injection amount Qb is distributed based on the pilot injection ratio Rp, and the pilot injection amount Qp and the main injection amount Qm of the fuel are obtained.

Qp = Rp × Qb, Qm = (1−Rp) × Qb
However, 0 ≦ Rp <1 Subsequently, based on the pilot injection amount Qp, the main injection amount Qm, and the common rail pressure CRp, the excitation time in the pilot injection and the main injection operation of the injector 5 is obtained, respectively. The start timing of the main injection operation (main injection timing ITm) is set based on the excitation time at the time and the basic injection timing ITb, and the main injection timing ITm, the injection stop interval Tp, and the excitation time of the pilot injection operation are set. Based on the above, the start timing of the sub main injection operation (pilot injection timing ITp) is set. Then, the crank angle sensor 11
When it is determined that the pilot injection timing ITp or the main injection timing ITm has been reached for each of the cylinders 2 based on the signal from the ECU 2, a control signal is output from the injection control unit 40f to the injector 5 for each of the cylinders 2. As a result, the operation of the injector 5 is controlled.

Further, when the engine 1 is in the idling state, the engine speed is mainly determined, as will be described later in detail.
ISC control unit 40g based on ne and engine water temperature thw
As a result, idle speed control control (hereinafter referred to as ISC control) for maintaining the engine rotation speed ne at the preset idle rotation speed is performed, and especially when the engine is not warmed up, the catalyst converter 28 in the exhaust passage 26 rises. In order to promote the temperature, the post injection control is intermittently performed by the post injection control unit 40h.

In the block diagram shown in FIG. 3, the injection ratio calculation unit 40d, the injection stop interval calculation unit 40e, and the injection control unit 40f perform fuel injection by the injector 5 when the engine 1 is at least in the low speed and low load region. It corresponds to pilot injection control means for pilot-injecting a small amount of fuel prior to the main injection.

(Control of Intake Air Amount) FIG.
FIG. 3 is a functional block diagram showing a configuration of control of an EGR valve 35 and an intake throttle valve 22 in the first embodiment. In FIG.
Is based on the target torque Trq calculated by the target torque calculation unit 40a and the engine speed ne.
A target air-fuel ratio calculation unit that calculates a target air-fuel ratio A / Fsol common to all the cylinders 2 with reference to a target air-fuel ratio map set experimentally in advance. This target air-fuel ratio A / Fsol is a control target value for determining the recirculation amount of exhaust gas so as to achieve both reduction of NOx and smoke in exhaust gas,
In the target air-fuel ratio map, the target air-fuel ratio A / Fsol is set to a value on the rich side as much as possible before the smoke starts to increase sharply in consideration of the demand for the fuel efficiency and output of the engine 1.

Reference numeral 40j in the figure denotes a product of the target air-fuel ratio A / Fsol calculated by the target air-fuel ratio calculator 40i and the target fuel injection amount Qb obtained by the target injection amount calculator 40b. The target fresh air amount calculating unit calculates the amount of fresh air required for the target fuel injection amount Qb (target fresh air amount Airsol). Then, based on a deviation between the target fresh air amount Airsol calculated by the target fresh air amount calculation unit 40j and the actual intake air amount into the combustion chamber 4 of each cylinder 2 obtained based on the output of the airflow sensor, The opening degree of the EGR valve 35 is determined by the EGR valve control unit 40k so that the deviation is reduced, and a control signal is output from the EGR valve control unit 40k to the electromagnetic valve 36 for controlling the negative pressure of the EGR valve 35. It has become.

That is, the EGR control according to this embodiment adjusts the recirculation amount of exhaust gas for each cylinder 2 so that the combustion chamber 4
And controlling the average air-fuel ratio of the in-cylinder combustion chamber 4 to a target value by changing the intake amount of fresh air into the cylinder.
Hereinafter, this specification will be referred to as airflow feedback control.

On the other hand, reference numeral 40L in the figure denotes a target fuel injection amount Qb obtained by the target injection amount calculating section 40b.
The throttle valve 2 is determined by referring to a throttle valve opening degree map that is experimentally set in advance based on the engine throttle speed ne and the engine speed ne.
An intake throttle valve control unit that calculates a target opening degree thsol of 2. According to the throttle valve opening map, when the engine 1 is in a predetermined low-rotation low-load operation region including an idle operation state, the required amount of exhaust gas can be recirculated by the airflow feedback control as described above. In order to generate a negative pressure in the intake passage 16 by closing the intake throttle valve 22, the target opening degree thsol is set to a relatively small value. On the other hand, in other operating states, the target opening degree thsol is set such that the intake throttle valve 22 is substantially fully opened.

Further, when the engine 1 is in the idling operation state, the target air-fuel ratio A / Fsol calculated by the target air-fuel ratio calculator 40i is mainly determined by the target air-fuel ratio corrector 40m, as will be described in detail later. In addition to the correction based on thw, the target opening thsol of the intake throttle valve 22 determined by the intake throttle valve control unit 40L is corrected by the intake throttle valve opening correction unit 40n based on the engine coolant temperature thw. That is, in this embodiment, if the engine 1 is in an idling operation state after warm-up, the target air-fuel ratio A / Fsol is set to substantially the stoichiometric air-fuel ratio, and the intake throttle valve 22 is closed to near the fully closed state. Has become. On the other hand, if the engine 1 is not warmed up, the target air-fuel ratio A / Fs
ol is a value leaner than the stoichiometric air-fuel ratio,
The intake throttle valve 22 is controlled so that its opening becomes larger than after warm-up.

The VGT 30 is controlled by rotating the flaps 31, 31,... So as to reduce the nozzle cross-sectional area in the low rotation range of the engine 1 having a small exhaust flow rate, so that the exhaust gas to the turbine 27 is exhausted. Increase supercharging efficiency by increasing flow rate and pressure. On the other hand, in the high rotation range of the engine 1 having a large exhaust flow rate, the flaps 31, 31,... Are rotated to the open side so as to increase the nozzle cross-sectional area, thereby preventing an increase in exhaust resistance.

In the block diagram shown in FIG. 4, a target air-fuel ratio calculator 40i, a target fresh air calculator 40j, an EGR
The valve opening control unit 40k and the target air-fuel ratio correcting unit 40m determine the opening of the EGR valve 35 based on the value detected by the airflow sensor 19, and determine the average air-fuel ratio of the combustion chamber 4 of each cylinder 2 as the target air-fuel ratio. Exhaust gas recirculation control means for performing feedback control so as to achieve A / Fsol is provided. In particular, the target air-fuel ratio calculation unit 40i and the target air-fuel ratio correction unit 40m
It corresponds to a target air-fuel ratio setting unit that sets the target air-fuel ratio A / Fsol to a value closer to the lean side than when the engine 1 is in an idle operation state after warm-up when the engine 1 is in an idling operation state before warm-up. ing.

Further, when the engine 1 is in a low rotation and low load state including an idle operation state, the intake throttle valve 2 is controlled by the intake throttle valve control section 40L and the intake throttle valve opening correction section 40n.
2 is closed, and when the engine 1 is in an idle operation state in which the engine 1 is not warmed up, an intake throttle valve control means for controlling the opening degree of the intake throttle valve 22 to be larger than in the idle operation state after warming up is configured. Have been.

(Control During Idle Operation) Next, control when the engine 1 is in an idle operation state will be described. At this time, the pilot injection control of the fuel and the ISC control are performed as described above, and the air flow feedback control and the intake throttle control are performed.
That is, first, in accordance with the operating state of the engine 1, an amount of fuel necessary to maintain the rotation speed ne of the engine 1 at the idle rotation speed is read from the idle operation region of the fuel injection amount map, and the basic fuel injection is performed. The basic fuel injection amount Qb is divided into a pilot injection amount Qp and a main injection amount Qm, and is set in the fuel injection control unit 40f. On the other hand, based on the accelerator opening Acc and the engine speed ne, the ISC control unit 40g determines whether or not the engine 1 is in an idling operation state. The main injection amount Qm is feedback-corrected in accordance with a deviation from a preset idle rotation speed so as to reduce the deviation.

Here, the idle speed is as follows:
When a plurality of different values are set according to the external load of the engine 1 and the like, and when the engine coolant temperature thw is lower than the first determination temperature corresponding to the unwarmed state of the engine 1, the plurality of idle rotation speeds are set. The set values are respectively corrected and calculated by the ISC control unit 40g according to the engine coolant temperature thw. As a result, the idle speed increases as the temperature state of the engine 1 decreases, and conversely, decreases as the temperature state of the engine 1 increases. . When the engine 1 is in a warm-up state, the idling rotational speed is constant at approximately 650 rpm unless there is an external load. That is, in the block diagram of the fuel injection control shown in FIG.
Corresponding to idle-up control means for controlling the engine rotational speed ne to be higher than in the idle operation state after warm-up and in accordance with the engine water temperature thw when the engine is in the idling operation state before warm-up. I have.

When the engine 1 is in the idling state in which the engine 1 is not warmed up, the fuel injection control unit 40f injects a predetermined amount of fuel immediately after the main injection in addition to the pilot injection amount Qp and the main injection amount Qm. The post-injection amount Qpo for performing this is set by the post-injection control unit 40h, and the injector 5 intermittently performs post-injection at a rate of, for example, one out of ten combustion cycles. That is,
The post-injection control unit 40h intermittently post-injects a small amount of fuel after the main injection of the fuel by the fuel injection valve during the expansion stroke of the cylinder 2 when the engine 1 is in the idle operation state in which the engine 1 is not warmed up. It corresponds to the control means.

Incidentally, the ratio of one combustion cycle to ten combustion cycles is, for example, from a first cylinder to a third cylinder, a fourth cylinder, a second cylinder, a first cylinder, a third cylinder in a four-cylinder engine. Assuming that fuel injection is performed in the order of the cylinders,..., If post-injection is performed first in the first cylinder, the next post-injection is performed in the eleventh fourth cylinder, and the next post-injection is performed in the 21st. Is intermittently repeated as in the first cylinder.

Further, when the engine 1 is in the idling operation state, the intake throttle valve controller 40L controls the intake throttle valve 2L.
2 is closed, the amount of air taken into each cylinder 2 is forcibly reduced, thereby reducing combustion noise and
Compression pressure of cylinder 2 (maximum pressure in cylinder during compression stroke)
Is reduced and the rotation fluctuation of the crankshaft 10 is reduced, so that the exciting force from the crankshaft 10 to the engine 1 is reduced. For example, FIG. 5 shows that when the intake throttle valve 22 is closed and the negative pressure in the intake passage 16 increases, that is, when the intake pressure p detected by the intake pressure sensor 13 decreases, the engine 1 decreases accordingly. In the figure, if the intake pressure p becomes equal to or less than a predetermined value p0 (p ≦ p0), the excitation force to the engine 1 is sufficiently reduced by a decrease in the secondary angular speed fluctuation. Will be.

On the other hand, when the amount of intake air is reduced as described above, the flow of intake air in the combustion chamber 4 becomes weak, so that the mixing state of air and fuel tends to deteriorate. On the other hand, in this embodiment, the fuel injection pressure is increased by the so-called common rail type fuel injection system even in the idle operation state, and the fuel injection pressure during the idle operation of the engine 1 is, for example, in the range of approximately 20 to approximately 40 MPa. It has been. Thereby, atomization of fuel and mixing with air are promoted by high-pressure injection.

Further, by performing the pilot injection as described above, even if the intake throttle valve 22 is closed, the ignition stability of the main injection fuel can be improved, and the premixed combustion can be moderately moderated. . That is, as shown schematically in FIG. 6, when a small amount of fuel is pilot-injected by the injector 5 in the compression stroke of the cylinder 2, the combustion of this fuel raises the temperature and pressure of the combustion chamber 4 and increases the ignition type. Is formed. Then, when the main injection of the fuel is performed by the injector 5, most of the main injected fuel has good diffusion from the beginning, in combination with the extremely good atomization characteristics of the fuel spray by the high-pressure fuel injection. It becomes a combustion state.

As a result, the rise of the initial combustion of the main injection fuel is greatly reduced as compared with the case where the pilot injection is not performed (shown by a broken line in the figure), the combustion noise is reduced, and the NOx at this time is reduced. Is also suppressed. On the other hand, the diffusion combustion rate is rather high, and the heat generation rate in the latter stage of combustion is maintained at the same high level as the peak in the early stage of combustion, so that the combustion is completed in a shorter combustion period than in the case without pilot injection. And the generation of smoke in the latter stage of combustion is also suppressed.

Further, in this embodiment, necessary fresh air can be secured by the above-described air flow feedback control even if the intake throttle valve 22 is closed as described above. That is, since the exhaust gas that flows through the EGR passage 34 and is recirculated is sucked out of the exhaust passage 26 by a pressure difference between the intake passage 16 and the exhaust passage 26, when the intake throttle valve 22 is closed as described above, Then, the recirculation amount of the exhaust gas becomes too large, which may cause a misfire.

Specifically, as shown in FIG. 7, when the intake throttle valve 22 is gradually closed, the EGR valve 35 is temporarily closed.
Is constant, the amount of fresh air sucked into the combustion chamber 4 and the amount of recirculation of exhaust gas both gradually decrease as the intake pressure p decreases, as is clear from FIG. In addition, the ratio of the exhaust gas recirculation amount to the fresh air amount tends to increase as the intake pressure p decreases. Therefore, in this case, before the intake pressure p reaches the predetermined value p0 (see FIG. 5), the amount of fresh air is insufficient, and a semi-misfire state occurs.
The intake throttle valve 22 cannot be closed sufficiently.

On the other hand, in the air flow feedback control of this embodiment, the opening of the EGR valve 35 is controlled by the combustion chamber 4.
8, the feedback control is performed so that the average air-fuel ratio becomes the target value. Therefore, as shown in an example in FIG. While the amount gradually decreases, the required fresh air amount is secured, so that misfire can be avoided even if the intake air is throttled until the intake pressure p becomes equal to or less than the predetermined value p0. Further, if the intake throttle valve 22 is closed even after the intake pressure p has fallen below the predetermined value p0, the intake pressure p
When p = p1, the EGR valve 35 is fully closed and exhaust gas recirculation is not performed. Thereafter, as the intake throttle valve 22 is closed, the fresh air amount decreases. In this case, the average air-fuel ratio of the combustion chamber 4 becomes richer than the target value. However, since the ignitability of the main injection fuel is enhanced by the pilot injection, no misfire occurs immediately.

That is, in this embodiment, when the engine 1 is in the idling operation state, the pilot injection control of the fuel and the air flow feedback control of the air-fuel ratio are performed, whereby the intake throttle valve 22 is closed. As a result, the fresh air required for good combustion can be secured while sufficiently reducing the vibration and noise of the engine 1, whereby it is possible to reliably prevent a misfire from occurring after the engine is warmed up. Things.

However, when the engine 1 is in an idling operation state in which the engine 1 is not warmed up, the vaporization of the fuel is greatly deteriorated as compared to after the warming up.
Is largely closed, the decrease in ignitability cannot be sufficiently compensated even by pilot injection or the like. Particularly, as the temperature state of the engine 1 becomes lower, there is a strong possibility that a misfire may occur.

Further, since the amount of heat generated decreases with the deterioration of the combustion performance, the warm-up of the engine 1 is delayed, and furthermore, the pilot injection improves the ignitability and the combustion performance of the main injection fuel. In an unwarmed state in which the temperature of the combustion chamber 4 is low, a considerable amount of fuel must be pilot-injected. Therefore, various problems such as a marked decrease in fuel efficiency due to this are required. The points are as described above.

To solve such a problem, in this embodiment, when the engine 1 is not warmed up, the target air-fuel ratio A / Fsol
Is set to a value on the lean side, the intake air amount relative to the fuel supply amount is relatively increased, and the opening degree of the intake throttle valve 22 is relatively increased to increase the intake air amount itself. Even in the state, it is possible to achieve both the promotion of warm-up of the engine 1 and the reduction of vibration and noise without causing a misfire or a significant deterioration in fuel efficiency.

The control procedure for the injector 5, the intake throttle valve 22, and the EGR valve 35 by the ECU 40 in the idle operation state after the cold start of the engine will be specifically described with reference to the flowchart of FIG.

First, in step S1 after the start, the engine speed ne, accelerator opening Acc, fuel injection amount Q, intake air amount Air, crank angle, engine water temperature thw, and the like are input. Subsequently, in step S2, it is determined whether or not the engine is in an idling operation state after the engine is started based on the engine speed ne, the accelerator opening Acc, an ignition on / off signal, and the like. That is, after the ignition switch is turned on and the engine 1 blows up to a complete explosion state, the engine speed ne is maintained at or below a predetermined idling determination speed and the accelerator opening
When Acc is substantially zero except for a very short-time fluctuation, that is, when the accelerator pedal is held in a substantially fully closed state, YES is determined, and the process proceeds to step S3.
On the other hand, if the state is other than the above, the determination is NO, and the process proceeds to a control routine not shown.

Subsequently, at step S3, the engine water temperature
Based on thw, it is determined whether or not the engine 1 is not warmed up. That is, if the engine coolant temperature thw is equal to or higher than the first determination temperature (for example, 80 ° C.) set in advance, the engine 1 is not in the unwarmed state NO (warming has been completed).
While the control proceeds to the control procedure of step S13 and thereafter, which will be described later, if the engine water temperature is lower than the first determination temperature, it is determined that the engine 1 is not warmed up and the process proceeds to step S4. In this step S4, it is determined whether or not the engine 1 is in a semi-warmed state. That is, if the engine water temperature is equal to or higher than the second determination temperature set in advance (for example, 40 ° C.), it is determined that the engine 1 is in a semi-warmed state, and the process proceeds to step S9.
If the engine water temperature is lower than the second determination temperature, it is determined that the engine 1 is not in the semi-warmed state, and the process proceeds to step S5.

Then, in step S5, the intake throttle valve 22, which was substantially fully opened during the start of the engine 1, is closed.
The opening is controlled to increase as the engine water temperature thw decreases. That is, the target opening thsol obtained from the intake throttle opening map of the ECU 40 is corrected in accordance with the engine coolant temperature thw, and the opening of the intake throttle valve 22 is controlled based on the corrected target opening thsol. By doing so, when the engine 1 warms up and the engine water temperature thw gradually rises, the intake pressure p (intake negative pressure) in the intake passage 16 corresponds to the decrease in the engine rotation speed ne accompanying this. Is kept substantially constant, the intake throttle valve 22 is gradually closed.

Subsequently, in step S6, the target air-fuel ratio A / Fsol is set to a value leaner than the stoichiometric air-fuel ratio, and to a value leaner as the engine water temperature thw is lower. Average excess air ratio λ of combustion chamber 4 in 2
Is larger than 1 (λ> 1), the opening of the EGR valve 35 is controlled by airflow feedback control. Thus, when the engine 1 warms up and the engine water temperature thw gradually increases, the target air-fuel ratio A / Fso
l is gradually changed to approach the stoichiometric air-fuel ratio as the engine water temperature thw increases.

Then, in step S7, the injector 5 causes the pilot injection and the main injection to be performed for each cylinder 2 at a predetermined injection timing, and in the subsequent step S8, the injector 5 causes the injector 5 to perform intermittent post-injection. To return. Here, it is preferable that the timing of the post-injection is performed, for example, in a crank angle range up to 35 ° CA after the compression top dead center (ATDC) in the expansion stroke of each cylinder 2. In this way, a part of the post-injected fuel burns and contributes to the driving force of the engine 1. Therefore, it is possible to minimize the deterioration of the fuel consumption and to reduce the remaining fuel. Is also pyrolyzed at a high temperature and supplied to the catalytic converter 28 in the exhaust passage 26, so that the reaction of the unburned fuel in the catalytic converter 28 becomes active and promotes an early temperature rise of the catalytic converter 28. it can.

According to the control procedure of steps S5 to S8, as shown in the time chart of FIG. 10, the engine water temperature thw gradually increases after the cold start of the engine 1, and the second determination temperature (the example in FIG. 10). Until the temperature reaches 40 ° C. (t0 to t1), the average air-fuel ratio of the combustion chamber 4 in each cylinder 2 of the engine 1 becomes leaner than the stoichiometric air-fuel ratio, and the intake throttle valve 22 The opening is kept relatively large as the idling operation state.

That is, while the engine water temperature thw until the engine 1 enters the semi-warmed state after the cold start is particularly low,
The total amount of intake air including the fresh air and the recirculated exhaust gas into the combustion chamber 4 of each cylinder 2 is relatively large, whereby the compression pressure of the intake air in the combustion chamber 4 is increased and the air flow is increased. Thus, the ignition stability and combustibility of the injected fuel are improved. Further, since the amount of fresh air is relatively large with respect to the fuel injected into the combustion chamber 4, deterioration of the fuel vaporization and the state of mixing with air is suppressed even in the unwarmed state,
The ignition stability of the injected fuel is further improved, and the fuel is more effectively burned.
Warm-up is also promoted.

Further, during this time, the engine rotation speed ne decreases with an increase in the engine water temperature thw, so that the intake air flow per unit time naturally decreases. That is, the opening degree of the intake throttle valve 22 is gradually reduced so that the intake pressure p in the intake passage 16 becomes substantially constant.
The magnitude of vibration and combustion noise from the engine 1 does not change much.

When the engine 1 warms up and the engine water temperature becomes equal to or higher than the second determination temperature, the routine proceeds to step S.
In step 4, it is determined that the engine 1 is in a semi-warmed state, and the process proceeds to step S9. This time, as the engine water temperature thw rises, the intake throttle valve is set to slightly exceed the degree of decrease in the engine speed ne accompanying this. 22 is gradually closed. By doing so, as the warm-up of the engine 1 progresses, the negative pressure in the intake passage 16 gradually increases (the intake pressure p gradually decreases), and the compression pressure in each cylinder 2 gradually decreases. During this time, the magnitude of vibration and combustion noise from the engine 1 gradually and smoothly decreases.

Subsequently, in step S10, the target air-fuel ratio A / Fsol is set to a value leaner than the stoichiometric air-fuel ratio and close to the stoichiometric air-fuel ratio with an increase in the engine water temperature. EGR valve 3
5 is controlled. Then, in step S11, similarly to step S7, the injector 5 causes the pilot injection and the main injection to be performed for each cylinder 2 at a predetermined injection timing, and in step S12, the post injection is performed intermittently. I do.

According to the control procedure of steps S9 to S12, as shown in the time chart of FIG. 10, half the time from when the engine coolant temperature thw becomes equal to or higher than the second judgment temperature to when it reaches the first judgment temperature. In the warm-up state (t
1 to t2), the change in the opening degree of the intake throttle valve 22 with respect to the change in the engine rotation speed ne is made relatively larger than before, and as the intake negative pressure increases, the vibration and combustion noise from the engine 1 gradually decrease. Become smaller. That is, the engine 1
When the ignitability and the flammability are maintained to some extent by the semi-warmed state, the intake throttle valve 22 is closed immediately thereafter, so that the vibration and the noise can be sufficiently reduced.

Further, even when the intake throttle valve 22 is quickly closed in this manner, the opening degree of the intake throttle valve 22 is made to gradually decrease in accordance with the rise of the engine water temperature thw. In addition, the magnitude of vibration and noise can be gradually and smoothly reduced, so that the driver can be prevented from feeling uncomfortable.

When the engine 1 warms up further and the engine coolant temperature thw becomes equal to or higher than the first determination temperature, that is, when the engine 1 is warmed up, the process proceeds from step S3 to step S13, where the intake throttle The valve 22 is kept in a substantially fully closed state, and in the subsequent step S14, the target air-fuel ratio
Fsol is set to substantially the stoichiometric air-fuel ratio (λ = 1) to perform airflow feedback control. In the following step S15, pilot injection and pilot injection are performed for each cylinder 2 at a predetermined injection timing by the injector 5 in the same manner as in steps S7 and S11. The main injection is performed, and then the process returns.

That is, when the engine 1 is warmed up,
If the temperature state of the combustion chamber 4 in each cylinder 2 becomes sufficiently high, misfire can be reliably prevented by pilot injection or the like thereafter. Therefore, the intake throttle valve 22 is set to a substantially fully closed state, and vibration and combustion from the engine 1 are set. We try to reduce noise as much as possible. After the engine 1 is warmed up, the target air-fuel ratio A / Fsol
Is set to substantially the stoichiometric air-fuel ratio, and the EGR valve 35 is fully closed, so that exhaust gas is not recirculated to the combustion chamber 4.

As shown in the time chart of FIG. 11, the period from the cold start of the engine 1 to the completion of warm-up (t0
To t2), EGR is performed by airflow feedback control.
The ratio of the exhaust gas recirculated through the passage 34 (EGR rate) gradually decreases so as to correspond to the change in the target air-fuel ratio A / Fsol, and in accordance with the change in the EGR rate, the pilot injection amount Q of the fuel.
p and the injection stop interval Tp also gradually decrease. That is, as the warm-up of the engine 1 progresses, the pilot injection amount Qp becomes smaller, and accordingly, the pilot injection timing is changed to the retard side, and the combustion of the pilot injection fuel and the combustion of the main injection fuel are performed. And become appropriately continuous. Thus, the effect of improving the ignitability and combustibility of the main injection fuel by the pilot injection can always be appropriately obtained.

As shown in FIG. 11, the basic injection timing ITb is changed to the retard side as the engine rotational speed ne decreases, and the common rail pressure CRp, that is, the fuel injection pressure by the injector 5 is reduced. , Engine speed
As ne decreases and the opening degree of the intake throttle valve 22 decreases, it gradually decreases.

Therefore, according to the diesel engine control apparatus A of this embodiment, first, when the engine 1 is in the idling operation state, the intake throttle valve 22 is closed,
While reducing vibration and noise from the engine 1,
By ensuring high-temperature exhaust gas is recirculated to the combustion chamber 4 of each cylinder 2 and pilot injection is performed by the injector 5 while securing necessary fresh air by airflow feedback control, sufficient combustion stability is provided after warm-up. Nature can be secured. In addition, the pilot injection reduces the initial combustion of the main injection fuel, which also reduces vibration and noise.

Here, when the engine 1 is not warmed up after the cold start, the engine rotation speed ne is controlled by the ISC control.
And the air-fuel ratio state of the combustion chamber 4 in each cylinder 2 is made relatively lean by airflow feedback control, and the air amount with respect to the injected fuel is made relatively large. Even so, it is possible to suppress the deterioration of the vaporization of the fuel and the mixing state with the air, and to more effectively burn the fuel.

Further, when the temperature of the engine 1 is particularly low before the engine 1 enters the semi-warmed state, the opening degree of the intake throttle valve 22 is relatively increased to increase the total amount of intake air to the combustion chamber 4 in the cylinder 2. By doing so, the ignition stability and combustibility of the fuel can be further improved. Thus, in combination with the ignitability improvement effect of the pilot injection, misfire can be reliably prevented even in a low temperature state. In addition, the increase in the amount of heat generated by the combustion, combined with the relatively high engine rotation speed ne, can sufficiently promote the warm-up of the engine 1.

On the other hand, when the engine 1 is in a semi-warmed state,
If the ignitability and combustibility of the fuel become high to some extent, thereafter, the intake throttle valve 22 responds to an increase in the engine water temperature thw.
Is relatively large, that is, the intake throttle valve 2
By rapidly closing 2, vibration and noise from engine 1 can be sufficiently reduced.

At this time, during the period until the half-warm-up state, the intake throttle valve 22 is controlled so as to correspond to the decrease in the engine speed ne.
Is closed relatively slowly so that the negative pressure in the intake passage 16 is kept substantially constant, so as not to change the magnitude of vibration and noise during the period, and during the period from the semi-warming up to the completion of warming up, While the intake throttle valve 22 is closed relatively early, the intake throttle valve 22 is gradually closed so that the negative pressure in the intake passage 16 gradually increases in accordance with the rise of the engine coolant temperature thw. And the magnitude of the noise are changed smoothly, so that the magnitude of the vibration and the noise does not suddenly change during the warm-up operation of the engine 1, and therefore,
It is possible to prevent the driver from feeling uncomfortable.

In addition, in this embodiment, when the engine 1 is not warmed up, the post injection is intermittently performed by the injector 5 so as to increase the exhaust gas temperature while minimizing deterioration of fuel efficiency. ing. That is, generally, when the engine 1 is cold started, the catalytic converter 2
Since the temperature state of No. 8 is also low (see FIG. 2) and is in a so-called inactive state, the emission of harmful exhaust components at this time becomes a problem. Therefore, in the present invention, the temperature of the exhaust gas is increased by the intermittent post-injection control as described above, whereby the early temperature rise of the catalytic converter 28 can be effectively promoted.

(Other Embodiments) The configuration of the present invention is not limited to the above-described embodiment, but includes other various configurations. That is, in the above-described embodiment, the intake throttle valve 22 closes relatively slowly until the engine 1 is half-warmed, and closes relatively quickly until the warm-up is completed, but is not limited thereto. The intake throttle valve 22 may be closed immediately after the cold start of the engine 1 such that the intake negative pressure gradually increases as the temperature state increases.

Alternatively, as shown in FIG. 12, a first set period immediately after the cold start (in the example shown in FIG.
Until the temperature reaches 0 ° C.), the opening degree of the intake throttle valve 22 is kept substantially constant, during which the temperature state of the engine 1 is raised as quickly as possible. Approximately 60 ° after thw is approximately 30 ° C or more
Until C), the intake throttle valve 22 may be closed at a substantially constant rate. With this configuration, the warm-up promotion of the engine 1 is given top priority in the first set period, and the change in the magnitude of the vibration or noise from the engine 1 is smoothly absorbed in the second set period thereafter. , Gradually reduce the vibration and noise, and then until the warm-up of the engine 1 is completed
Vibration and noise can be reduced as much as possible.

Further, as indicated by a phantom line in the graph of the target intake throttle valve opening degree of FIG. 12, the intake throttle valve 22 is operated from immediately after the cold start of the engine 1 until the second set period ends. The opening may be kept substantially constant. This is not the one in which the intake throttle valve 22 is finely operated by the stepping motor 23 as in the above-described embodiment, but the one in which the intake throttle valve 22 is driven by a diaphragm like the flaps 31, 31, ... of the VGT 30. Especially effective.

The control of the EGR valve 35 is not limited to the air flow feedback control as in the above-described embodiment. For example, an air-fuel ratio sensor is provided in the exhaust passage 26, and based on a signal from this air-fuel ratio sensor. The feedback control may be performed so that the average air-fuel ratio of the combustion chamber 4 becomes the target value. Further, so-called feedforward control may be performed.

Furthermore, in the above-described embodiment, the post-injection is executed intermittently when the engine 1 is not warmed up, thereby prompting the early rise of the temperature of the catalytic converter 28. However, the present invention is not limited to this. Instead, the amount of main injection performed near the TDC of the predetermined cylinder 2 may be intermittently increased as the fuel increase correction means. That is, by extending the time of the main injection operation by the injector 5 and increasing the fuel injection amount in the expansion stroke, the temperature state of the exhaust gas can be increased.

[0099]

As described above, according to the control apparatus for a diesel engine according to the first aspect of the present invention, first,
The intake throttle valve is closed while performing pilot injection control when the engine is in an idling operation state to reduce vibration and noise. When the engine is not warmed up, the engine speed is controlled to be higher than after warming up, and the average air-fuel ratio state of the combustion chamber is controlled to be leaner than after warming up. As a result, the deterioration of the fuel vaporization and mixing with air can be suppressed, and the injected fuel can be burned more effectively. Warm-up can be promoted sufficiently.

According to the second aspect of the invention, when the engine is in the idling operation state in which the engine is not warmed up, the opening degree of the intake throttle valve is controlled to be larger than in the idling operation state after warming up. Thus, the occurrence of misfire can be reliably prevented, and the warm-up of the engine can be further promoted.

According to the third aspect of the invention, the air-fuel ratio state of the combustion chamber can be accurately controlled based on the value detected by the state quantity detecting means. The necessary air can be secured to prevent misfire.

According to the fourth aspect of the present invention, the engine speed is reduced as the engine temperature increases when the engine is not warmed up, and the intake throttle valve is adapted to cope with the engine speed reduction. By preventing the driver from feeling uncomfortable, it is possible to prevent the magnitude of vibration and noise from suddenly changing during warm-up of the engine.

According to the fifth aspect of the present invention, when the engine is in the idling state in which the engine is not warmed up, the amount of fuel injected by the fuel injection valve from the expansion stroke of the cylinder to the exhaust stroke is increased intermittently, and the exhaust gas is exhausted. By raising the temperature of the catalyst, it is possible to promptly raise the temperature of the catalyst.

According to the sixth aspect of the present invention, the fuel injection valve intermittently performs post-injection immediately after the main injection to correct the increase in fuel, thereby minimizing deterioration in fuel efficiency due to fuel increase. The temperature state of the exhaust gas can be increased while suppressing the temperature.

According to the seventh aspect of the present invention, the temperature of the exhaust gas can be increased by intermittently increasing the main injection amount of the fuel by the fuel injection valve and performing the increase correction of the fuel.

According to the eighth aspect of the present invention, the engine speed is reduced as the engine temperature increases while the engine is not warmed up, and the engine speed is reduced while the engine temperature is relatively low. The intake throttle valve is closed relatively slowly to respond to the decrease in temperature, and priority is given to promoting the warm-up of the engine. As soon as possible, vibration noise can be reduced as much as possible. In the meantime, it is possible to prevent the magnitude of vibration and noise from changing suddenly, thereby preventing the driver from feeling uncomfortable.

[Brief description of the drawings]

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

FIG. 2 is a graph showing an example of a temperature-dependent characteristic of a NOx purification rate by a catalyst.

FIG. 3 is a functional block diagram illustrating a configuration of fuel injection control.

FIG. 4 is a functional block diagram showing a configuration of EGR control and intake throttle control.

FIG. 5 is a graph showing a correspondence relationship between a decrease in intake pressure and a change in engine excitation force accompanying the decrease in intake pressure.

FIG. 6 is an explanatory diagram showing, in comparison with each other, changes in the heat generation rate and the cylinder internal pressure when pilot injection is performed and when pilot injection is not performed.

FIG. 7 is a diagram showing the correspondence between fresh air and exhaust gas recirculation amounts and intake pressure when the opening of the EGR valve is constant.

FIG. 8 is a diagram corresponding to FIG. 7 when airflow feedback control is performed.

FIG. 9 is a flowchart illustrating a control procedure of an intake throttle valve, an EGR valve, and an injector in an idle operation state after a cold start of the engine.

FIG. 10 shows changes in engine water temperature and engine speed after a cold start of the engine, the state of control of the air-fuel ratio and intake throttle opening, and the changes in total intake air amount and intake pressure associated therewith. It is a time chart figure.

FIG. 11 shows an EGR rate, a pilot injection amount, an injection stop interval, a basic injection timing, and a common rail pressure.
FIG.

FIG. 12 is a diagram corresponding to FIG. 10 relating to an engine water temperature, an engine rotation speed, a target air-fuel ratio, an intake throttle valve opening, and an EGR rate according to another embodiment.

[Explanation of symbols]

A Diesel engine control device 1 Engine 4 Combustion chamber 5 Injector (fuel injection valve) 19 Air flow sensor (State quantity detection means) 34 EGR passage (Exhaust recirculation passage) 35 EGR valve (Exhaust recirculation amount control valve) 40 Control unit 40d Injection Ratio calculation unit (pilot injection control unit) 40e Injection stop interval calculation unit (pilot injection control unit) 40f Injection control unit (pilot injection control unit, post injection control unit) 40g ISC control unit (idle up control unit) 40h post injection control Section (post injection control means) 40i target air-fuel ratio calculation section (exhaust recirculation control means, target air-fuel ratio setting section) 40j target fresh air amount calculation section (exhaust recirculation control means) 40k EGR valve opening degree control section (exhaust recirculation control means) ) 40L intake throttle valve control unit (intake throttle valve control means) 40m Shimegisora ratio correction unit (target air-fuel ratio setting portion) 40n intake throttle valve opening degree correction section (intake throttle valve control means)

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) F02D 9/02 305 F02D 9/02 305D 3G301 305M 305R 21/08 301 21/08 301B 301D 301E 41/06 355 41/06 355 360 360 380 380A 385 385Z 41/16 41/16 G K P 45/00 320 45/00 320A F02M 25/07 570 F02M 25/07 570E 570J 580 580H 45/02 45/02 45/04 45/04 F Terms (reference) 3G062 AA01 BA06 CA02 CA03 CA06 ED03 FA09 GA08 GA21 3G065 AA00 AA01 CA00 CA14 DA02 DA06 EA02 EA03 FA03 FA11 GA01 GA05 GA07 GA10 GA46 KA36 3G066 AA07 AA11 AA13 AB02 AC09 AD12 BA03 DC14 DC DC09 DC11 DC14 DC18 DC19 DC26 3G084 AA01 BA05 BA09 BA13 BA15 BA20 CA02 CA03 DA02 DA12 DA39 EA11 EB08 EB11 FA08 FA10 FA11 FA20 FA36 FA38 3G092 AA02 AA06 AA17 BA06 BB05 BB06 BB13 BB14 DC03 DC09 DG06 EA01 EA07 EA09 EC01 EC09 FA14 FA15 FA24 GA02 GA04 HA01Z HA05Z HB03Z HE03Z HE08Z HF08Z 3G301 HA02 HA04 HA11 HA13 JA02 JA23 JA37 KA05 KA08 LA00 LA03 LB11 LC04 LC07 MA01 MA15 MA19 MA23 MA26 NA08 NC02 NP01Z03 NE03 NE01 Z03

Claims (8)

[Claims] 1. A fuel injection valve facing an in-cylinder combustion chamber of an engine, and an intake throttle valve for restricting intake air to the combustion chamber, wherein a fuel injection amount by the fuel injection valve is controlled according to a load state of the engine. A diesel engine control device that closes the intake throttle valve at least in an idle operation state after the engine is warmed up, the exhaust recirculation for recirculating a part of exhaust gas to an intake passage downstream of the intake throttle valve. A passage, an exhaust gas recirculation amount control valve that adjusts an amount of exhaust gas recirculated by the exhaust gas recirculation passage, and an opening degree of the exhaust gas recirculation amount control valve to control an average air-fuel ratio of the combustion chamber to a predetermined target value. Exhaust recirculation control means for indirectly adjusting the amount of air taken into the combustion chamber so that the fuel injection valve supplies a small amount of fuel prior to the main injection of fuel when the engine is in an idle operation state. Pilot injection control means for performing a lot injection, and idle-up control means for controlling the engine rotational speed to be higher than when the engine is in an idle operation state after warm-up when the engine is in an idle operation state before warm-up. The exhaust recirculation control means sets the target air-fuel ratio so that the target value of the air-fuel ratio becomes leaner than that in the idle operation state after the warm-up when the engine is in the idle operation state with the engine not warmed up. A diesel engine control device having a fuel ratio setting unit. 2. The intake throttle valve according to claim 1, wherein the opening degree of the intake throttle valve is controlled to be larger when the engine is in an idling operation state before warming up than in an idle operation state after warming up. A control device for a diesel engine, comprising a control means. 3. The exhaust gas recirculation control means according to claim 1, further comprising a state quantity detecting means for detecting a state quantity relating to an air-fuel ratio of the combustion chamber, wherein the exhaust gas recirculation control means sets the opening degree of the exhaust gas recirculation amount control valve to the state. A control device for a diesel engine, wherein feedback control is performed based on a value detected by an amount detecting means. 4. The engine according to claim 2, wherein the idle-up control means controls the engine rotation speed to decrease as the temperature state of the unwarmed engine increases. And a control unit for controlling the opening degree of the intake throttle valve to decrease as the temperature state of the engine increases. 5. The fuel supply system according to claim 1, wherein the amount of fuel injected by the fuel injection valve from the expansion stroke to the exhaust stroke of the cylinder is intermittently set when the engine is in an idling state with the engine not warmed up. A control device for a diesel engine, comprising a fuel increase correction means for increasing the amount of fuel. 6. The fuel injection amount correcting means according to claim 5, wherein the fuel increase correction means is a post injection control means for intermittently injecting a small amount of fuel by the fuel injection valve immediately after the main injection of the fuel during the expansion stroke of the cylinder. Diesel engine control device. 7. The diesel engine control device according to claim 5, wherein the fuel increase correction means intermittently increases the main injection amount of fuel by the fuel injection valve. 8. The idle-up control means according to claim 2, wherein the idle-up control means controls the engine rotation speed to decrease as the temperature state of the unwarmed engine increases. While the temperature state of the engine is lower than the set temperature, the opening degree of the intake throttle valve is controlled so that the negative pressure of the intake passage is substantially constant, while the temperature state of the engine becomes higher than the set temperature. And a control unit for controlling the opening of the intake throttle valve so that the negative pressure in the intake passage gradually increases until the engine is completely warmed up.