JPH10274087A - Control unit for diesel engine - Google Patents

Abstract

(57) [Problem] To perform pilot injection prior to main injection at the start of a diesel engine, further enhance ignitability, and promote start. SOLUTION: An EGR passage as a communication passage for communicating an exhaust passage and an intake passage of an engine, an EGR valve for opening and closing the passage, and an injection control means 33 for controlling fuel injection and an operation of the EGR valve are provided. E to control
GR control means 34 is provided. These control means 33,
34, the injection nozzle 3 is controlled so that pilot injection is performed prior to main injection at least during the period from the start of cranking to the complete explosion at the time of cold start of the engine, and the EGR valve is opened. Control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a diesel engine in which fuel injection means performs main injection and pilot injection for injecting a small amount of fuel prior to the main injection when the engine is started. .

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Application Laid-Open No. 62-7504.
As disclosed in Japanese Patent Application Publication No. 7-107, there is known a diesel engine fuel injection device in which pilot injection is performed prior to main injection at the time of engine start. Particularly, in the device disclosed in this publication, first, pilot injection is performed, and it is determined whether or not ignition has been performed by this pilot injection based on a signal from an ignition sensor.If ignition has occurred, main injection is performed. If the ignition is not performed, the main injection is stopped to prevent a large amount of unburned gas from being discharged, and to suppress the generation of white smoke and smoke.

[0003] Further, as disclosed in Japanese Patent Application Laid-Open No. 5-156993, for example, in a diesel engine provided with an exhaust gas purifying device using a catalyst for purifying NOx in exhaust gas in an exhaust passage, NOx by the catalyst is used. In order to improve the purification efficiency, there is also known a device that executes a post-stroke injection of injecting a small amount of fuel at a timing immediately after the exhaust valve is opened after the main injection.

[0004]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 62-7 / 1987
In the device disclosed in Japanese Patent No. 5047, in order to prevent deterioration of emission when a misfire occurs at the start,
The main injection is stopped when it is not ignited by the pilot injection.However, if a misfire occurs, no special measures are taken to enhance the ignitability after that, and it has a sufficient effect on promoting the start. It doesn't work.

The apparatus disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-156993 is intended to improve the NOx purification efficiency of the catalyst by performing post-stroke injection, but does not promote the start-up.

In view of such circumstances, the present invention provides a control apparatus for a diesel engine that can perform pilot injection prior to main injection at the time of starting, further enhance ignitability, and promote starting. The purpose is to do.

[0007]

The invention according to claim 1 is
A control device for a diesel engine that performs a main injection from a fuel injection unit and a pilot injection for injecting a small amount of fuel prior to the main injection at the time of engine start, and connects an exhaust passage and an intake passage of the engine to each other. A communication path and communication path opening and closing means for opening and closing the communication path are provided, and control means for controlling the communication path opening and closing means and the fuel injection means are provided. During the period from the start time to the time point at which the engine speed increases due to the complete explosion, the fuel injection means is controlled so as to perform pilot injection prior to the main injection, and the communication passage opening / closing means is opened. It is intended to be controlled.

According to this configuration, at least during the period from the start of cranking to the complete explosion at the time of cold start of the engine, the pilot injection secures a fire for main combustion by the main injection, thereby improving ignitability. If the misfire still occurs while being improved, the unburned fuel discharged to the exhaust passage is returned from the communication passage to the combustion chamber through the intake passage. The fuel is vaporized and atomized at the compression temperature before being discharged to the exhaust passage, and is sufficiently mixed while passing through the communication passage and the intake passage. Flammable air-fuel mixture is formed, and in the state where the combustible air-fuel mixture exists, the pilot injection in the next stroke is performed, whereby the ignitability is further improved. In this way, starting is promoted.

When combustion is performed, high-temperature exhaust gas is recirculated through the communication passage, that is, high-temperature EG
The introduction of the R gas raises the temperature in the combustion chamber, which also promotes starting.

In the present invention, it is preferable that an end of the communication passage on the exhaust passage side is connected to an exhaust manifold upstream of the exhaust passage or a position near the exhaust manifold.

Further, after the engine speed is increased due to the complete explosion, and when the engine shifts to a cold first idle operation in which the engine speed is higher than the normal idle speed, the control means is used. It is preferable to control the communication passage opening / closing means to a closed state by (claim 3),
In this way, it is possible to avoid deterioration of the combustibility during the first idling operation in which the fuel is increased to increase the engine speed.

According to a fourth aspect of the present invention, there is provided a diesel engine control device for causing a main injection and a pilot injection for injecting a small amount of fuel prior to the main injection from a fuel injection means when the engine is started, EGR means for recirculating high-temperature exhaust gas having a small decrease in temperature in the exhaust passage to the combustion chamber is provided, and control means for controlling the EGR means and fuel injection means is provided. In the period from the time of the initial explosion of the engine during cranking to the time when the engine speed increases due to the complete explosion, the fuel injection means is controlled to perform pilot injection prior to the main injection, and The means is controlled to an operating state.

According to this configuration, during the period from the initial explosion of the engine to the complete explosion during the cold start of the engine, high-temperature exhaust gas is introduced into the combustion chamber to increase the temperature in the combustion chamber. By performing the main injection after the pilot injection is performed, the ignitability is greatly improved, and the start is promoted.

In the present invention, the EGR means includes an EGR passage which connects an intake manifold upstream of the exhaust passage or a position near the exhaust manifold to the intake passage;
An on-off valve for opening and closing the R passage may be provided (claim 5). Alternatively, the EGR means may vary the valve-opening overlap period of the intake / exhaust valve so that the internal EGR is performed during the valve-opening overlap period.

After the engine speed has risen due to the complete explosion, and when the engine shifts to a cold first idle operation in which the engine speed is higher than the normal idle speed, the above-mentioned control means causes It is preferable to stop the operation of the EGR means (claim 7),
In this way, deterioration of the flammability during the first idle operation can be avoided.

In each of the above inventions, a catalyst for purifying exhaust gas is provided in the exhaust passage of the engine, and when the temperature of the catalyst is at or below a predetermined temperature in a catalyst cooling state at least after the engine speed is increased due to complete explosion. Alternatively, control may be performed such that a post-stroke injection for injecting a small amount of fuel is performed during a period from the expansion stroke to the exhaust stroke after the main injection (claim 8).

A ninth aspect of the present invention is a control apparatus for a diesel engine in which a main injection and a pilot injection for injecting a small amount of fuel prior to the main injection are performed by a fuel injection means when the engine is started. In addition, a catalyst for purifying exhaust gas is provided in an exhaust passage of the engine, and control means for controlling the fuel injection means in accordance with the temperature state of the catalyst from the time of starting the engine to after the start is provided. If the temperature of the catalyst is in a catalyst cold state at or below a predetermined temperature after the engine speed is increased due to a complete explosion, in addition to the pilot injection and the main injection, the period from the expansion stroke to the exhaust stroke after the main injection is reduced. The fuel injection means is controlled so as to perform a post-stroke injection for injecting a small amount of fuel.

According to this configuration, when the engine is started, the ignitability is enhanced by the pilot injection to promote the start, and when the engine is cold after the complete combustion of the engine, a small amount of fuel due to the post-stroke injection reacts with the catalyst. The catalyst is warmed up early because it generates heat to accelerate the temperature rise of the catalyst.

In this case, when the catalyst reaches a catalyst warm-up state in which the temperature of the catalyst is higher than a predetermined temperature, control may be performed so as to stop the post-stroke injection (claim 10).

In each of the above inventions, if the interval between the pilot injection and the main injection is controlled to be small after the first explosion of the engine (claim 11), the starting torque can be increased while maintaining good ignitability. This is advantageous.

[0021]

FIG. 1 shows an embodiment of a control system for a diesel engine according to the present invention. In this figure, reference numeral 1 denotes an engine body of a diesel engine,
A plurality of cylinders 2 are provided. A fuel injection device for injecting fuel into the combustion chamber of each cylinder 2 is provided for the engine body 1, and in this embodiment, a so-called common rail type fuel injection device is provided. That is, each cylinder 2 is provided with an injection nozzle (fuel injection means) 3 for performing fuel injection by operating a needle valve by a solenoid in accordance with a control signal, and a high-pressure cylinder. Each of the injection nozzles 3 is connected to a common rail 4 that stores the fuel.

The common rail 4 is connected to a fuel pump 6 via a fuel passage 5, and the pump 6 is connected to a fuel tank (not shown). The high-pressure fuel pumped from the fuel pump 6 is supplied to each injection nozzle 3 via the common rail 4. The fuel passage 5 is provided with a pressure regulating valve 7 as a pressure regulating means for regulating the pressure of the fuel sent to the common rail 4 to regulate the injection pressure of the injection nozzle 3, and the pressure regulating valve according to a control signal. The above operation allows the injection pressure to be changed. Further, a pressure sensor 8 is provided on the common rail 4, and the pressure sensor 8 detects the injection pressure.

The engine body 1 is connected to an intake manifold 11 downstream of the intake passage 10 and an exhaust manifold 13 upstream of the exhaust passage 12. A compressor of the turbocharger 15 is provided in the middle of the intake passage 10, and a turbine of the turbocharger 15 is provided in the middle of the exhaust passage 12.

In the turbocharger 15, the turbine is driven by the energy of the exhaust gas, and the turbocharger 15 supercharges the intake air by the rotation of the compressor in conjunction with the exhaust gas. A variable supercharging pressure turbo is used which has a structure capable of increasing the supercharging performance from a low-speed region to a high-speed region by expanding and contracting the turbine blade according to a state. The turbocharger 15 is provided with a supercharging pressure controller 16 that adjusts a supercharging pressure according to a control signal.

The turbocharger 1 in the intake passage 10
An intercooler 17 for cooling the supercharged air is provided downstream of the compressor No. 5, and an air flow meter 18 for detecting an intake air amount is provided upstream of the compressor. On the other hand, a catalyst 19 for purifying exhaust gas is provided downstream of the turbine of the turbocharger 15 in the exhaust passage 12.

Further, the exhaust passage 12 and the intake passage 10
An EGR passage 20 is provided as a communication passage connecting the two passages, and an EGR valve 23 is provided in the EGR passage 20 as communication passage opening / closing means. The EGR valve 23 is operated by an EGR valve controller 24 to control the EGR amount.

In this embodiment, a first EGR passage 21 and a second EGR passage 22 are formed on the exhaust passage side of the EGR passage 20, and one of the passages 21 and 22 is connected to the intake passage side via the EGR valve 23. , Or both passages are closed. The first E
The GR passage 21 is connected to the exhaust manifold 13 or an upstream portion of the exhaust passage near the exhaust manifold 13 so as to recirculate exhaust gas with a small decrease in temperature in the exhaust passage, and is opened at a cold start or the like as described later. It has become. Further, the second EGR passage 22 is connected to the downstream side of the exhaust passage 12 so as to recirculate relatively low-temperature exhaust gas.

The injection nozzle 3, the pressure regulating valve 7, the supercharging pressure controller 16 and the EGR valve controller 24
Are controlled by a control unit (ECU) 30. The control unit 30 receives detection signals from the pressure sensor 8 and the air flow meter 18, a rotation speed sensor 25 for detecting an engine rotation speed, an accelerator opening sensor 26 for detecting an amount of depression of an accelerator pedal, Detection signals from a water temperature sensor 27 for detecting the engine water temperature, a catalyst temperature sensor 28 for detecting the catalyst temperature, an ignition switch 29a, a starter switch 29b and the like are also input.

FIG. 2 is a functional block diagram showing a control system. In this figure, the control unit 30
Includes a start determination unit 31, a temperature state determination unit 32, an injection control unit 33, and an EGR control unit. Based on the discrimination by the discriminating means 31, 32, the control means 33, 34 at least during the cold start of the engine at least during the period from the start of cranking to the time when the engine speed increases due to complete explosion. In addition, while controlling the injection nozzle 3 so that the pilot injection is performed prior to the main injection, the first EGR passage 2
The EGR valve 23 is controlled so that the valve 1 is opened to the intake passage 10.

More specifically, the start determining means 3
1 determines the starting state based on signals from the ignition switch 29a, the starter switch 29b, the rotation speed sensor 25, and the like. That is, the pole at the time of starting the engine, as shown in FIG. 3, the ignition switch 29a from being the ON (t ₀ time) First, the engine starter by the starter switch 29b is set to ON (t ₁ time) Cranking at low speed is started, and during the cranking, the first explosion of the engine (t
After rising engine speed slightly by ₂ times), further when reaching the complete combustion (t ₃ time points) in the engine speed rapidly increases, rises to the fast idle rotation speed if the engine is cold . The start determination means 31 examines such behavior of the engine, and determines a state before cranking and a state during a period (t _{1 to} t ₃ ) from the start of cranking to the time when the engine speed increases due to complete explosion. And the state after the complete explosion.

The temperature state discriminating means 32 discriminates, based on signals from the water temperature sensor 27 and the catalyst temperature sensor 28, whether the engine is in a cold start or a warm start, and determines whether the catalyst 19 is in a cold state. It is determined whether the engine is in a warm-up state.

The injection control means 33, based on the determination by the start determination means 31 and the temperature state determination means 32,
The injection nozzle 3 is controlled so that pilot injection is performed prior to main injection during a period from the start of cranking to the time when the engine speed increases due to complete explosion. That is, as shown in FIG. 4, as the control of the fuel injection from the start of cranking to the complete explosion, the main injection C is performed at a predetermined timing, and the pilot injection B is performed before this. In this case, at least one pilot injection B may be performed, but a plurality of pilot injections may be performed. In the example shown in the flowchart described later, the pilot injection is performed twice, that is, FIG. In addition to the pilot injection B shown by a solid line, a pilot injection A shown by a broken line (hereinafter, this is referred to as a split injection A) is performed in advance.

The split injection A is performed before the pressure in the combustion chamber rises to a ignitable pressure in the compression stroke.
For example, BTDC 30 ° CA (30 degrees before top dead center at crank angle)
°). Pilot injection B above
Is TDC (top dead center) after BTDC 30 ° CA
Done earlier. Main injection C is started after TDC. Further, the injection amount of the split injection A and the pilot injection B is made smaller than the injection amount of the main injection C, and the injection amount of the pilot injection B is made larger than that of the split injection A. In other words, the injection amount of the split injection A is reduced within a range necessary for forming an air-fuel mixture for premixed combustion as described later in detail, while the pilot injection B
In order to ensure that fuel that can be maintained until the main injection timing is obtained, the injection amount is increased compared to the split injection A.

Further, the injection control means 33 causes the post-stroke injection D to be performed in addition to the injections A, B, and C when the catalyst is in a cold state after the complete combustion of the engine.
A small amount of fuel is injected from the injection nozzle 3 during a period from the expansion stroke to the compression stroke after the main injection C.

The EGR control means 34, based on the discrimination by the start discriminating means 31 and the temperature state discriminating means 32, starts from the start of cranking during the cold start to the time when the engine speed increases due to complete explosion. During the period, the EGR valve controller 24 is controlled so that the first EGR passage 21 is opened to the intake passage 10.

Therefore, in this embodiment, as shown in FIG. 3, from the start of cranking at the time of cold start to the complete explosion, multi-stage injection (split, pilot and main injection) and the first EGR passage 21 are performed. EGR is performed, and multi-stage injection and post-stroke injection are performed until a warm-up state occurs after a complete explosion.

Next, an example of control of fuel injection at the time of startup by the apparatus of the present embodiment will be described with reference to the flowchart of FIG.

The process shown in this flowchart is started by turning on the ignition switch 29a (step S1). First, an engine water temperature and a catalyst temperature are inputted (step S2). It is determined whether the start is a warm start or a warm start (step S3).

When it is determined that the engine is a cold start, it is determined in step S4 that the starter has been turned on. In step S5, the main injection timing T, the required injection amount Q, and the injection pressure at the time of startup are determined. P is determined according to the water temperature and the like, and in step S6, the injection pattern is determined so that the split injection A, the pilot injection B, and the main injection C are performed. That is, each injection A,
The timings of B and C and the injection amounts are determined, and the injections A, B and C are executed. In addition, such fuel injection control is performed, and in step S7, the first EGR
The solenoid of the EGR valve 23 is controlled so that the passage 21 is opened.

Subsequently, in step S8, the engine speed and its angular velocity fluctuation are examined, and based on this, the process proceeds to step S9.
It is determined whether or not a complete explosion has occurred, and the processes of steps S5 to S8 are repeated until the complete explosion is reached.

When it is determined in step S9 that the complete explosion has been reached, the solenoid of the EGR valve 23 is controlled so that the EGR passage is closed in step S10. The injection timing is determined, and the post-stroke injection D is executed in step S11. Further, the catalyst temperature is detected in step S13, and it is determined whether or not the catalyst temperature has risen to a predetermined warm-up temperature in step S14. If the catalyst temperature is lower than the warm-up temperature, the processing in steps S11 to S13 is performed. Repeated. When it is determined in step S14 that the catalyst temperature or the warm-up temperature has been reached, the process proceeds to step S15, in which an idle map operation, which is a control state during normal idle operation, is performed.

On the other hand, if it is determined in step S3 that the engine is warm starting, then in step S16 the starter O is started.
When it is determined that N has been reached, the main injection timing T at the start, the required injection amount Q, and the injection pressure P are determined according to the water temperature and the like in step S17, and in step S18,
The injection pattern is determined so that the split injection A, the pilot injection B, and the main injection C are performed. Then, the fuel injection is controlled based on this injection pattern, and in step S19, the solenoid of the EGR valve 23 is controlled so that the EGR passage is closed.

Subsequently, in step S20, the engine speed and its angular velocity fluctuation are checked, and based on this, the step S20 is executed.
At 21 it is determined whether or not a complete explosion has occurred, and the processes of steps S17 to S20 are repeated until the complete explosion. When it is determined in step S21 that a complete explosion has occurred,
Moving to step S15, an idle map operation, which is a control state during normal idle operation, is performed.

[0044] The control device for a diesel engine such as described above, the period from the start of cranking at the time of engine start until complete explosion (period t ₁ ~t ₃ in FIG. 3)
And at least one pilot injection B and main injection C
Is performed, and the fuel is ignited by pilot injection B, which becomes the ignition source, and main combustion by main injection C is performed. In the present embodiment, the multi-stage injection of the split injection A, the pilot injection B, and the main injection C is performed, so that the ignitability is further improved.

That is, first, the split injection A is performed at a time substantially before the top dead center of the compression stroke. At this time, the cylinder pressure is relatively low and ignition does not occur, and the injected fuel is injected into the piston top. After adhering to the surface or the cylinder wall surface, the mixture gradually evaporates to form a premixed mixture (flammable mixture) in the combustion chamber. Next, pilot injection B is performed. At this point, since the in-cylinder pressure is high, the so-called premixed combustion is performed such that the premixed air that already exists burns relatively rapidly in a short time. The ignitability is enhanced. This premixed combustion is completed in a short time, but using this as a fire, so-called diffusion combustion is performed in which the fuel from the pilot injection B gradually burns and diffuses from an unmixed state, and the combustion period is extended by the diffusion combustion. The combustion continues until after top dead center. Then, by performing the main injection while the combustion by the pilot injection B is sustained, the combustion of the fuel of the main injection is achieved.

In addition, during the period from the cranking to the complete explosion at the time of the cold start, the above-described multi-stage injection is performed. The emission of unburned gas to the fuel cell is suppressed, and the ignitability is further enhanced.

That is, although the ignitability is improved by the multi-stage injection as described above, if the misfire still occurs, the unburned gas is discharged to the exhaust passage 12. In this case, the unburned gas is returned from the first EGR passage 21 to the combustion chamber through the intake passage 10, so that the discharge of the unburned gas to the outside is suppressed, and the gas returned to the combustion chamber is As in the case of split injection A, a premixed gas is formed,
The ignitability in the next step can be further improved.

Further, when the combustion is performed, the relatively high temperature exhaust gas is recirculated from the first EGR 21 and the high temperature EGR gas raises the in-cylinder temperature, so that the effect of promoting the start is obtained.

When shifting to the first idling operation after the complete explosion, the EGR is stopped, so that the deterioration of the combustion characteristics (generation of smoke) due to the EGR during the first idling operation in which the fuel is increased to increase the engine speed. Invitation is avoided.

Further, after the complete explosion during the cold start, the catalyst 1
When the engine 9 is in the cold state, the post-stroke injection in which a small amount of fuel is injected during the period from the expansion stroke to the exhaust stroke after the main injection is performed, so that the warm-up of the catalyst 19 is promoted. In other words, a small amount of fuel due to the post-stroke injection reacts with the catalyst 19 to generate heat, thereby promoting the temperature rise of the catalyst 19, so that the catalyst is warmed up early.

In this way, the start of the engine and the warm-up of the catalyst 19 are promoted, and the time required for the start and the warm-up to be completed is shortened. .

The control of the EGR and the like is not limited to the above embodiment. For example, the first EGR passage 21 may be opened from the start of cranking to the complete explosion even during a warm start.

In the above-described embodiment, the first EGR passage 21 is opened while performing the multi-stage injection during the period from the start of cranking to the complete explosion when the engine is started, but high-temperature EGR gas is introduced into the combustion chamber. As shown in FIG. 6, in order to improve the ignitability of the engine, during the period from the initial explosion of the engine to the complete explosion, the multistage injection (at least one pilot injection and the main injection) and the high-temperature gas injection are performed. E
GR may be performed.

In this case, the initial explosion of the engine can be detected by a change in the number of revolutions or the like. The recirculation of the high-temperature gas may be performed by the external EGR passage 21 shown in FIG. 1, or may be performed by the internal EGR. That is, as shown in FIG. 7, a valve timing variable mechanism (VVT) 41 is provided for changing at least one of the intake valve and the exhaust valve to change the valve opening overlap of the intake and exhaust valves. , VVT control means 40 in control unit 30
The internal EGR may be performed by controlling the variable valve timing mechanism 41 to increase the valve opening overlap during the period from the initial explosion of the engine to the complete explosion.

When the ignitability and the flammability are increased by the temperature rise in the combustion chamber, the combustion speed by the pilot injection is increased, and the pilot interval (the interval between the pilot injection and the main injection) can be reduced. Since the torque by the main injection increases as the pilot interval decreases, the control of the fuel injection at the time of starting the engine may be such that the pilot injection is retarded after the initial explosion to reduce the pilot interval. This way,
After the first explosion, the starting torque is further increased, and the starting is accelerated.

[0056]

According to the present invention, a communication passage and a communication passage opening / closing means for connecting an exhaust passage and an intake passage of an engine are provided, and at least during a period from a cranking start time to a complete explosion at a cold start of the engine. Since the fuel injection is controlled so that the pilot injection is performed prior to the main injection, and the communication passage opening / closing means is controlled to the open state, the main injection is performed by the pilot injection during the period. And the ignitability can be further improved by returning the unburned gas to the combustion chamber in the event of misfire. Therefore, starting can be promoted. In addition, the emission of unburned gas is suppressed to the outside at the time of misfire during the start and the start time is shortened, so that the emission can be significantly improved.

Further, at least at the time of the cold start of the engine, during the period from the initial explosion to the complete explosion of the engine, the fuel injection means is controlled so as to perform the pilot injection prior to the main injection, and the high-temperature exhaust gas is discharged. EG to reflux
If the R means is controlled to the operating state, the temperature in the combustion chamber is increased by introducing high-temperature exhaust gas into the combustion chamber during the above period, and the ignitability is improved by performing pilot injection in this state. , Can help start.

At the time of starting the engine, the pilot injection is performed prior to the main injection.
If the catalyst is cold after the complete engine explosion,
In addition to the pilot injection and the main injection, if a post-stroke injection of injecting a small amount of fuel after the main injection is performed, ignitability at the time of starting the engine is enhanced to promote the starting, and after the engine complete explosion, The catalyst can be warmed up when the catalyst is cold.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing the overall configuration of a diesel engine control device according to the present invention.

FIG. 2 is a functional block diagram showing a configuration inside a control unit.

FIG. 3 is an explanatory diagram showing a change in the rotational speed and a change in a control state after the engine is started.

FIG. 4 is a diagram showing a fuel injection pattern and an injection timing when the engine is started.

FIG. 5 is a flowchart showing a fuel injection control operation at the time of starting the engine.

FIG. 6 is an explanatory diagram showing a change in the rotational speed and a change in a control state after the engine is started according to another embodiment.

FIG. 7 is a functional block diagram of another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine main body 3 Injection nozzle 10 Intake passage 12 Exhaust passage 19 Catalyst 20 EGR passage 23 EGR valve 25 Engine speed sensor 27 Water temperature sensor 29a Ignition switch 29b Starter switch 30 Control unit 31 Start-up determination means 32 Temperature state determination means 33 Injection control means 34 EGR control means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301G 301W F02M 25/07 570 F02M 25/07 570A

Claims (11)

[Claims] 1. A control device for a diesel engine, wherein a main injection from a fuel injection means and a pilot injection for injecting a small amount of fuel preceding the main injection are performed at the time of engine start. A communication path for communicating with the passage; and a communication path opening / closing means for opening / closing the communication path, and a control means for controlling the communication path opening / closing means and the fuel injection means. At the time of starting, during a period from a cranking start time to a time point at which the engine speed increases due to a complete explosion, the fuel injection means is controlled to perform pilot injection prior to main injection, and
A control device for a diesel engine, wherein the communication passage opening / closing means is controlled to an open state. 2. The diesel engine control device according to claim 1, wherein an end of the communication passage on the exhaust passage side is connected to an exhaust manifold upstream of the exhaust passage or a position near the exhaust manifold. 3. The control means according to claim 1, wherein after the engine speed has risen due to a complete explosion, and when the engine shifts to a cold first idle operation in which the engine speed is higher than a normal idle speed. 3. The communication path opening / closing means is controlled to be in a closed state by means of (1) or (2).
A control device for a diesel engine as described. 4. A control device for a diesel engine, wherein a main injection from a fuel injection means and a pilot injection for injecting a small amount of fuel preceding the main injection are performed at the time of engine start, wherein a temperature drop in an exhaust passage is performed. EGR means for recirculating high-temperature exhaust gas having a small temperature into the combustion chamber is provided, and control means for controlling the EGR means and the fuel injection means is provided. During the period from the time of the first explosion to the time when the engine speed rises due to the complete explosion, the fuel injection means is controlled so as to perform pilot injection prior to the main injection, and the EGR means is controlled to an operating state. A control device for a diesel engine, characterized in that: 5. An EGR device comprising: an EGR passage that connects an intake manifold upstream of an exhaust passage or a position near the exhaust manifold to an intake passage; and an on-off valve that opens and closes the EGR passage. Item 5. A control device for a diesel engine according to item 4. 6. The diesel engine according to claim 4, wherein said EGR means varies the valve opening overlap period of the intake / exhaust valve to perform internal EGR during the valve opening overlap period. Control device. 7. When the engine speed is increased due to a complete explosion, and when the engine shifts to a cold first idle operation in which the engine speed is higher than a normal idle speed, the control means is provided. The operation of the EGR means is stopped by means of:
7. The control device for a diesel engine according to any one of 6. 8. An exhaust gas purifying catalyst is provided in an exhaust passage of the engine, and the main injection is performed when the temperature of the catalyst is at or below a predetermined temperature at least after a rise in engine speed due to complete explosion. 8. The fuel injection device according to claim 1, wherein the control device controls the fuel injection device so as to perform a post-stroke injection of injecting a small amount of fuel during a period from a subsequent expansion stroke to an exhaust stroke. Diesel engine control device. 9. A diesel engine control device in which a main injection from a fuel injection means and a pilot injection for injecting a small amount of fuel preceding the main injection are performed at the time of engine start. In addition to providing a catalyst for gas purification, a control means for controlling the fuel injection means in accordance with the temperature state of the catalyst from the start of the engine to after the start is provided, and this control means increases the engine speed at least due to complete explosion. Later, when the temperature of the catalyst is in a catalyst cold state at a predetermined temperature or less, in addition to the pilot injection and the main injection, a subsequent stroke of injecting a small amount of fuel during a period from an expansion stroke to an exhaust stroke after the main injection. A control device for a diesel engine, which controls a fuel injection means so as to perform injection. 10. The fuel injection means is controlled by control means to stop the post-stroke injection when the catalyst reaches a catalyst warm-up state in which the temperature of the catalyst becomes higher than a predetermined temperature. Or a control device for a diesel engine according to item 9. 11. The control device for a diesel engine according to claim 1, wherein an interval between the pilot injection and the main injection is controlled to be small after the initial explosion of the engine.