JP2864896B2 - Control unit for diesel engine - Google Patents

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.

[0002]

2. Description of the Related Art In order to suppress the generation of NOx, which is a harmful component in exhaust gas, a so-called EGR (Exhaust Gas) in which inert exhaust gas is recirculated through an intake pipe.
Recirculation devices are well known. In this EGR device, an EGR valve is mounted on an EGR passage (a passage for returning a part of exhaust gas to an intake pipe), and an EGR valve is provided.
The EGR valve is opened in the area where the required amount of exhaust gas (E
The maximum temperature during combustion is lowered by mixing GR gas) with the intake air.

When the EGR rate (= (EGR amount / fresh air amount) × 100) [%] increases, the smoke emission concentration increases. For this reason, in JP-A-60-162018, the swirl is strengthened as the EGR rate increases.

[0004] The reason is that when the EGR rate increases, the swirl is strengthened to improve the mixing of air and fuel during combustion, thereby reducing smoke.

[0005]

However, with the above-described apparatus, it is difficult to suppress the increase in smoke when the EGR rate is significantly increased.

[0006] For example, FIG.
When the EGR rate increases, the NOx concentration sharply decreases, whereas the smoke concentration sharply increases. In this case, if the swirl ratio SR is increased, the smoke density can be generally reduced. However, even in a region where the EGR rate is high, the smoke density exceeds the limit value. The effect of reducing the smoke concentration by swirl can be obtained by increasing the diffusion speed of air and fuel during diffusion combustion, so that high EG
When the oxygen concentration is low due to the R rate, the effect is not so large due to lack of oxygen in the air.
Note that the swirl ratio SR is a value defined by SR = Vc / N where Vc; swirl flow cutting direction rotation speed N; engine rotation speed.

When the swirl ratio SR is increased, N
The Ox concentration has also increased.

Accordingly, the present invention reduces the combustion temperature.
When the means are activated, the heat release pattern will be in the form of a single stage combustion.
By prolonging beyond common sense ignition delay period so that, to achieve new combustion system, and an object thereof to both reduce the NOx and smoke. In addition, JP-A-63-
Japanese Patent No. 21335 discloses an idle state or a low speed load.
When operating in a loaded state, the exhaust
The one that performs the retard control of the injection timing according to
No. 61-6255 discloses that injection is performed during EGR in a predetermined region.
Some have been proposed to delay the timing. This place
At first glance, the “means for lowering the combustion temperature” is EG
R, and "means to extend the ignition delay period"
If it is considered that the injection timing is delayed, the present invention and the above
Seems to be similar to the prior art
In addition, both conventional technology, NOx and smoke
(PM) is disclosed as a technology for simultaneous reduction
You. However, the prior art of NOx and SM
The trade-off relationship of the network (reducing one will increase the other)
It is not a simultaneous reduction technology that breaks down. In particular
Smoke is generated during the operation of EGR, which is a NOx reduction means.
It is a technology that minimizes, in other words,
Exhaust that finds a matching point (compromise) within the framework of "method"
It's just an improvement technique.

[0009]

SUMMARY OF THE INVENTION The first aspect of the present invention, as shown in FIG. 1, the means 81 for reducing the combustion temperature of the engine according to operating conditions of the engine, lowering the combustion temperature
When the heating means is activated, the heat generation pattern
Means 82 for significantly increasing the ignition delay period so that
And provided.

A second invention is <br/> means 81 which causes lowering the combustion temperature is a means for reducing the oxygen concentration of the intake air.

The third invention greatly reduces the ignition delay period.
The lengthening means 82 is means for delaying the fuel injection timing until after the top dead center.

In a fourth aspect based on the third aspect, a means for supercharging the intake air is provided when the fuel injection timing is delayed until after the top dead center.

In a fifth aspect based on the third aspect, a means for enhancing swirl is provided when the fuel injection timing is delayed until after the top dead center.

According to a sixth aspect of the present invention, the oxygen concentration reducing means according to the second aspect of the present invention comprises an oxygen removal filter for removing oxygen from intake air flowing through at least one of the branch pipes, and a branch provided with the filter. It comprises a flow control valve for adjusting the flow rate of intake air to the passage, and means for controlling the control valve according to operating conditions.

[0015]

[Function] According to the “conventional combustion method”, the combustion temperature is lowered
Although the NOx concentration decreases during the operation of the
The smoke concentration rises sharply.

During this same operation , heat is generated according to the first invention.
If the ignition delay period is significantly lengthened so that the raw pattern becomes a single-stage combustion mode , not only the NOx concentration but also the smoke concentration decreases. This is called “the traditional combustion method.
The combustion according to the formula is the initial combustion in which the premixed gas formed during the ignition delay period burns at a stretch, and the combustion that follows the combustion, and the combustion speed is limited by the diffusion speed of fuel and air (main combustion). However, if the ignition delay period is greatly extended beyond the common sense, it is considered that most of the combustion becomes premixed combustion, and smoke is less likely to be generated.

In the second invention, if the oxygen concentration of the intake air is lowered, the combustion temperature is lowered. If the fuel injection timing is extremely delayed until after the top dead center in the third invention, the ignition delay period is greatly increased. become longer.

In the third aspect of the invention, if the fuel injection timing is delayed until after the top dead center, the oxygen concentration of the intake air is reduced, and both the NOx concentration and the smoke concentration can be reduced in an operating range where the combustion temperature is low. On the other hand, since the absolute amount of oxygen is insufficient, the HC concentration tends to increase.

On the other hand, in the fourth invention, when the intake air is supercharged, the oxygen concentration is reduced, but the absolute amount of oxygen is secured, and in the fifth invention, the swirl is strengthened to improve the combustion. Therefore, the HC concentration is greatly reduced.

In the second invention, the oxygen concentration of the intake air is set to E
If reduced by the GR device, the intake valve may stick due to carbon in the exhaust gas.

On the other hand, according to the sixth aspect, the EG
Since there is no need to recirculate exhaust gas into the intake air unlike the R device, sticking of the intake valve due to carbon in the exhaust gas can be prevented, and an increase in NOx concentration due to an increase in the intake air temperature due to high-temperature exhaust gas can be suppressed. Is done.

[0022]

In FIG. 2, 21 is an engine body, 23 is an intake pipe, 25 is an exhaust pipe, 26 is an exhaust pipe 25 and an intake pipe 23.
An EGR passage 27 communicates with the diaphragm, and a diaphragm type EGR valve 27 that responds to the control negative pressure.

Reference numeral 28 denotes a negative pressure control valve which adjusts a constant negative pressure from a negative pressure source in three stages according to a duty signal from the control unit 31. For example, when the OFF duty (OFF time ratio of a constant cycle) to the negative pressure adjusting valve 28 is the maximum value and a constant negative pressure is directly introduced into the EGR valve 27, 50% of the exhaust gas is recirculated. This corresponds to an EGR rate of 100%. When the OFF duty decreases stepwise, the control negative pressure to the EGR valve 27 decreases and E
The degree of opening of the GR valve decreases, and the EGR flow rate decreases. That is, each time the OFF duty is reduced, the EGR rate decreases to 60% and 30%.

The three-stage EGR rates thus obtained are set as shown in FIG. 3 with respect to the operating conditions. In the figure, the EGR rate is 100% in the middle rotation / medium load region and the low rotation full load region. This is because, in these operating ranges, the generation of smoke is suppressed to almost zero, and therefore, even if the EGR rate is increased, sticking of the intake valve caused by the flow of the smoke into the intake pipe 23 does not occur. On the other hand, in the high rotation speed / high load range, the combustion period is long and the generation of smoke cannot be completely suppressed. Therefore, the intake air temperature increases due to the increase in the exhaust gas temperature and the EGR flow rate, To reduce the effect of NOx reduction by EGR, the EGR rate is gradually reduced to 60% and 30%.

In order to control the EGR rate in accordance with the operating conditions of the engine, a control unit 3 comprising a microcomputer
1, a control unit 31 includes a sensor 32 for detecting an accelerator opening (accelerator pedal opening);
The EGR flow rate is controlled stepwise based on a signal from the air flow meter 33 and a reference pulse and a scale pulse described later.

In order to obtain the characteristics of the EGR rate (target EGR rate) shown in FIG. 3 with respect to the torque generated by the engine and the engine speed, the accelerator opening (engine load equivalent) Acc and the engine speed Ne are obtained. Is set as a parameter, and the map is looked up to find the target EGR rate at that time. The EGR flow rate is calculated from this and the air flow meter flow rate (new air flow rate) as follows: EGR flow rate = air flow meter flow rate × target EGR rate... You do it.

On the other hand, FIG. 4 shows a specific structure of the fuel injection pump 20, which is a well-known distribution type fuel injection pump in which the fuel injection timing and the fuel injection amount are electronically controlled.

In FIG. 4, reference numeral 4 denotes a drive shaft connected to the output shaft of the engine 21, and reference numeral 2 denotes a vane-type feed pump driven by the drive shaft 4, which is sucked from a fuel inlet (not shown) by the feed pump 2. The fuel is supplied to a pump chamber 5 in the housing 1, and is supplied to a plunger chamber 1 of the plunger pump 3 through a suction passage 6 opened to the pump chamber 5.
Sent to 2.

A nail 9a of a face cam 9 fixed to the left end of the plunger 7 is slidably connected to one end (right end in the figure) of the drive shaft 4 in the axial direction.
The face cam 9 and the plunger 7 are located on the same axis as the drive shaft 4, and the plunger 7 is configured to be displaceable in the axial direction.

A roller holder 1 carrying a plurality of rollers 11 is provided on the outer periphery of the connection between the drive shaft 4 and the face cam 9.
0 is arranged concentrically with the drive shaft 4, and the face cam 9 has a cam surface 9b having a number of unequal speed cams corresponding to the number of cylinders.
The cam surface 9b is provided with a spring 15
To press the roller 11.

The plunger 7 has the same number of suction grooves 8 at its tip as the number of cylinders of the engine, and the cam surface 9b rotates with the drive shaft 4 so as to ride over the roller 11 provided on the roller holder 10 and to reach a predetermined position. When the cam lift reciprocates, the fuel sucked into the plunger chamber 12 from the suction groove 8 is pressure-fed to the injection nozzle from a distribution port for each cylinder (not shown) communicating with the plunger chamber 12 through a delivery valve.

A fuel return passage 13 communicates the plunger chamber 12 with the low-pressure pump chamber 5.
Reference numeral 3 denotes a high-speed responsive solenoid valve driven in accordance with the operating conditions of the engine by a signal (drive pulse) from a drive circuit.
4 are interposed. The solenoid valve 14 is provided for fuel control, and is operated during the compression stroke of the plunger 7.
When the valve 4 is closed, fuel injection is started, and when the solenoid valve 14 is opened, the fuel injection ends. That is, the fuel injection start timing is controlled by the valve closing timing of the electromagnetic valve 14, and the injection amount is controlled by the valve closing period.

When the EGR rate is increased, NOx
Although the concentration can be reduced, the smoke concentration sharply increases. In this case, if measures are merely taken to improve the mixing during diffusion combustion by strengthening the swirl, the smoke concentration at a high EGR rate will be reduced only insufficiently.

In order to cope with this, the control unit 31 delays the fuel injection timing until after the top dead center so that the ignition delay period becomes extremely long in the high EGR rate operation range. FIG. 5 shows the characteristics of the fuel injection timing in comparison with the characteristics of the EGR rate (FIG. 3). In the operation range from a medium load to a high load in a low rotation speed range, the injection timing is changed after the top dead center (+4 ATDC). And + 2ATDC). This is due to a significant delay in the injection timing, making the intake air cooler and increasing the proportion of premixed combustion,
This is for suppressing the generation of smoke.

In FIG. 5, when the engine speed is changed from medium rotation to high rotation in the middle to high load range, the injection timing is advanced as the engine speed increases. This is because even if the ignition delay time is constant, the ignition delay crank angle (the value obtained by converting the ignition delay time into a crank angle) increases in proportion to the increase in the engine speed. Is maintained at a substantially constant value, the injection timing is advanced as the rotational speed increases. For example, at 1200 rpm, 1 msec is equivalent to a crank angle of 7.2 °, but tripled to 3600.
At rpm, 1 msec is a crank angle of 2.4 °. That is, in order to make the ignition timing the same at 1200 rpm and 3600 rpm, 1 is required at a rotation speed of 3600 rpm.
It is necessary to advance the injection timing by about 5 ° from 200 rpm.

On the other hand, in FIG. 5, the injection timing is advanced from the high load region in order to suppress the occurrence of smoke in the low load region where smoke does not occur and to suppress the rapid increase of hydrocarbon HC. This is because, when the injection timing is the same as that in the high load region in the low load region where the combustion chamber wall temperature is low, the ignition timing is delayed due to the longer ignition delay period, and the combustion temperature is lowered. It is.

In order to obtain the injection timing shown in FIG.
The control unit 31 controls the opening timing (equivalent amount of injection timing) of the solenoid valve 14 in FIG.

FIG. 6 is a flowchart for controlling the fuel injection timing and the injection period (injection amount), which are executed at a constant cycle.

First, the engine speed Ne, accelerator opening Acc, cooling water temperature TW and fuel temperature TF are read (step 1 in FIG. 6). The engine speed Ne is
Reference pulse (1 per rotation of injection pump 20)
) And a scale pulse (36 pulses per revolution of the injection pump 20). Cooling water temperature TW
And the fuel temperature TF are detected by the respective sensors 34 and 35.

Based on the read engine speed Ne and the accelerator opening Acc, the maps of the basic fuel injection timing Itm and the basic fuel injection period Avm are respectively looked up and obtained (step 2 in FIG. 6).

The map of the basic injection timing Itm is a map (not shown) in which the accelerator opening Acc and the engine speed Ne are defined as parameters so as to obtain the injection timing characteristics of FIG. As shown in FIG. 7, the basic injection period Avm becomes longer as the accelerator opening Acc increases.

On the other hand, an injection timing correction amount ΔItm is obtained from the fuel temperature TF and the cooling water temperature TW.
The injection timing is corrected by adding to tm (see FIG. 6).
Steps 3 and 4).

The injection timing correction amount ΔItm has two correction amounts Δ
FIG. 8 shows the fuel temperature correction amount ΔI as the sum of Itm ₁ and ΔItm ₂ .
Characteristics of tm _1, FIG. 9 is a characteristic of the water temperature correction amount ΔItm _2. In any of the characteristics, the reason why the advance angle correction amount is increased as the temperature becomes lower is that the combustion speed becomes lower as the temperature becomes lower. In other words, temperature compensation is performed.

The injection timing IT (= Itm + Δ) thus obtained
Itm) and the basic injection period Avm are stored at predetermined addresses (step 5 in FIG. 6). The solenoid valve 14 is closed at the injection timing IT, and the solenoid valve 14 is opened at a timing when the basic injection period Avm has elapsed from the closing timing.

Here, the operation of this example will be described with reference to FIG.

FIG. 3 shows the NOx and smoke concentration characteristics with respect to the EGR rate when the fuel injection timing is before the top dead center and after the top dead center, and shows the injection timing (IT
= −4ATDC), the NGR increases as the EGR rate increases.
Although the Ox concentration decreases, the smoke concentration increases in a sharp curve.

On the other hand, the injection timing after the top dead center (IT
= + 4ATDC), there is a tendency to decrease to smoke concentration. As can be seen from the heat generation pattern shown in the figure, the combination of the extreme delay of the injection timing and the high EGR rate significantly increases the ignition delay period, and the combustion concentration is reduced. This is probably because most of the fuel was premixed gas combustion. That is, EG
If the injection timing is delayed until after the top dead center in the conventional example in which the R rate is not so high, the tendency of the smoke concentration to increase cannot be suppressed as shown in FIG. 11, but in this example, most of the combustion is performed. Is premixed gas combustion, so that the smoke concentration can be significantly reduced even in an operation region with a high EGR rate.

FIG. 10 shows an example in which the crank angle after the top dead center is 4 degrees. However, since the critical points of the premixed gas combustion and the diffusion combustion differ depending on the type of engine, the number of times after the top dead center increases. This is determined by matching for each engine.

FIG. 12 shows the characteristics of the fuel consumption rate. In this example, although the isovolume is deteriorated due to the delay of the injection timing, the cooling loss is greatly reduced due to the decrease in the combustion temperature. However, delaying the injection timing does not deteriorate the fuel consumption rate. The equivalent volume means the work conversion efficiency, and the work conversion efficiency is: work conversion efficiency = work shown / heat generation = working efficiency / (1−
Cooling loss).

Further, in this example, as the fuel temperature or the cooling water temperature becomes lower, the injection timing is advanced to correct the temperature, so that the temperature is compensated, so that the same ignition timing can be obtained even at a low temperature as at a high temperature.

FIG. 13 shows a second embodiment in which, in addition to the EGR device, a supercharging device 41 comprising a mechanical supercharger 42 and a variable pulley 43 and a device for controlling the swirl ratio are provided. Things.

The supercharger 42 provided in the intake passage 23 after the EGR gas merges has a pulley 45 fixed to the crankshaft of the engine, a variable speed pulley 43, and a belt 44 wound around the two pulleys. When the variable speed pulley 43 changes the pulley outer shape via an actuator (not shown) according to a signal from the control unit 51, the engine 21 and the supercharger 4 are connected.
The speed ratio of 2 becomes larger or smaller.

The control unit 51 controls the speed ratio between the two to maintain a substantially constant supercharging pressure of 400 to 500 mmHg over the entire rotation range. FIG. 14 shows the characteristics of the speed ratio. As shown in FIG. 14, when the engine speed is low, the supercharging pressure is increased by increasing the speed ratio to 3: 1 and increasing the speed of the supercharger 42. , The EGR rate decreases, the HC concentration decreases, and the maximum cylinder pressure also increases.
The boost pressure should not be increased by reducing the pressure to one.

The intake air containing the exhaust gas is supplied to the turbocharger 4
When the gas flows into the cylinder 2, a stick is generated due to carbon or the like in the exhaust gas. To prevent this, a screw type having a high blade rigidity and being in line with the casing is used for the supercharger 42.

On the other hand, as shown in FIGS. 15 and 16, the swirl control device of the rotary blade type has a so-called helical intake port 46 (a substantially straight intake passage 46a and a spiral passage 46b around the intake valve axis). Formed spiral path 46b
Rotatable blade 4 that is rotatably provided near the
7, and a link mechanism 49 connected to the blade 47,
The swirl ratio can be adjusted at the rotational position of the blade 47 by an actuator 48 that drives the link mechanism 49. For example, the swirl ratio is high at the blade position in FIG. 15, and the swirl ratio is low when the blade 47 reaches the position in FIG. This rotating blade system has a quick response and enables swirl control over a wide range. Therefore, it is suitable for controlling HC that is sensitive to the swirl ratio.

FIG. 1 shows the characteristics of the swirl ratio with respect to the operating conditions.
As shown in FIG. 7, the swirl ratio increases as the rotation speed decreases. In the high rotation range, the volume efficiency decreases with the high swirl ratio, and the improvement of combustion by increasing the injection pressure weakens the necessity of swirl, so the swirl ratio gradually decreases as the rotation speed increases. It is.

The variable swirl actuator 4
Numeral 8 denotes a diaphragm type actuator (not shown) having a two-stage spring, and a negative pressure control valve for producing a control negative pressure in three stages by diluting the atmosphere to a constant negative pressure from a negative pressure source. .

In the control unit 51, the engine speed N is adjusted so that the swirl ratio shown in FIG. 17 is obtained.
Look up a map (not shown) of the swirl ratio (basic swirl ratio) allocated to e and the accelerator opening Acc to obtain the basic swirl ratio, and according to this swirl ratio, the opening Vb of the negative pressure control valve. Is read and stored at a predetermined address (steps 11 to 14 in FIG. 18).

FIG. 19 shows the concentration characteristics of HC, smoke, and NOx with respect to the EGR rate. Symbols R, R shown in the figure
+ C, R + C + S are: R; fuel injection timing delayed after top dead center (corresponding to the previous embodiment), R + C; R supercharged, R +
C + S; R is obtained by adding supercharging and swirl control. However, the supercharging pressure is 400 to 500 mmHg and the swirl ratio is an example of 5.

Although HC has not been described in the previous embodiment, the combustion temperature is lowered by the combination of the high EGR rate and the extreme delay of the injection timing, and both the NOx concentration and the smoke concentration can be greatly reduced. The absolute amount of oxygen is insufficient, and the HC concentration tends to increase as shown by R in FIG. In order to suppress this increase in the HC concentration, in the previous embodiment, as shown in FIG. 2, an oxidation catalyst 40 conventionally used had to be mounted on the exhaust pipe 25.

On the other hand, in this embodiment, in addition to the NOx and smoke concentrations, the HC concentration can be greatly reduced in the high EGR rate operation region as shown in FIG. That is, in this embodiment, the oxidation catalyst 40 mounted in the previous embodiment is not required. In addition to securing the absolute amount of oxygen by supercharging in the low speed range, and improving the combustion by strengthening the swirl, the HC concentration is greatly increased to a level that can clear the regulation value without using an oxidation catalyst. It can be reduced to

FIG. 20 shows a third embodiment.
Instead of reducing the oxygen concentration in the intake air by introducing inert EGR gas into the intake pipe by the GR device, the oxygen concentration in the intake air is reduced by using an oxygen removal filter (also called an oxygen-depleted membrane). It was made.

In FIG. 20, the intake passage 23 is branched into two downstream of the mechanical supercharger 42,
1 is provided with an oxygen removal filter 63. It is known that the oxygen removing filter 63 has a structure in which oxygen is passed but nitrogen is not passed due to a difference in molecular size between nitrogen and oxygen, for example, using a hollow fiber. Filter 6
The oxygen removed by 3 is discarded to the exhaust passage 25 via the communication passage 64.

In order to adjust the flow rate of the intake air flowing through the branch passage 61 on the side where the filter 63 is provided, a flow control valve 65 is provided at the branch portion. The flow control valve 65 includes a butterfly valve (not shown) and an electromagnetic valve that adjusts the opening position of the butterfly valve in three stages according to a signal from the control unit 71. When the butterfly valve is at the fully closed position, The entire amount of intake air is guided to the branch passage 51, and the flow rate of intake air guided to the branch passage 51 decreases as the opening of the butterfly valve increases. That is, when 100% of the intake air flows through the branch passage 51, the oxygen concentration of the intake air becomes 15%, and the branch passage 5
By increasing the intake air flow to be bypassed to 2, 17
% And 19%, the oxygen concentration of the intake air increases stepwise (the oxygen concentration in the atmosphere is 21%).

The three levels of oxygen concentration thus obtained are set as shown in FIG. 21 with respect to the operating conditions. The step characteristics of the oxygen concentration correspond to the step characteristics of the EGR rate (FIG. 3). The states where the oxygen concentration is 15%, 17%, and 19% correspond to the EGR rates of 100%, 60%, and 30%, respectively.

For this reason, the amount of the film of the oxygen removal filter 63 is set so that the oxygen concentration can be reduced to 15% under a supercharging pressure of 400 mmHg. Needless to say, the supercharging pressure is controlled to be constant using the supercharger 42 so that the inlet pressure of the oxygen removal filter 63 becomes 400 mmHg.

According to this example, the oxygen removal filter 63
And the flow control valve 65 operate similarly to the EGR device of the second embodiment. The difference from the EGR device is that it is not necessary to recirculate the exhaust gas into the intake air. For this reason, the intake valve and the supercharger 42 do not stick due to carbon in the exhaust gas, and an increase in NOx due to an increase in the intake air temperature due to the high-temperature exhaust gas can be suppressed.

In order to lower the combustion temperature, it is conceivable to reduce the oxygen concentration of the intake air by using an EGR device or an oxygen removal filter, to reduce the compression ratio, or to cool the intake air in advance.

[0069]

EFFECTS OF THE INVENTION] A first aspect of the present invention, the means for reducing the combustion temperature of the engine in response to operating conditions of the engine, the fuel
When the means for lowering the baking temperature is activated, the heat generation pattern
Means to greatly increase the ignition delay period so as to form a single-stage combustion are provided, which is completely different from the conventional combustion method
A new combustion system can be realized, which enables the conventional combustion system
Simultaneous reduction of NOx and smoke, which was impossible in the above, can be realized .

[0070] For the second invention, <br/> means causes decrease of the combustion temperature is a means for reducing the oxygen concentration of the intake air,
Contributes to significantly extending the ignition delay period beyond common sense
Can be done .

In the third invention, the ignition delay period is greatly reduced.
Because the means for lengthening the fuel is a means for delaying the fuel injection timing until after the top dead center, the ignition delay period exceeds the common sense and greatly
It can contribute to lengthening .

According to a fourth aspect, in the third aspect, a means for supercharging the intake air is provided when the fuel injection timing is delayed until after the top dead center.
The concentration can also be significantly reduced.

According to a fifth aspect of the present invention, in the third aspect, a means for enhancing the swirl is provided when the fuel injection timing is delayed until after the top dead center, so that the NOx concentration can be increased without increasing the smoke concentration and the HC concentration. Can be reduced.

According to a sixth aspect of the present invention, the oxygen concentration reducing means according to the second aspect of the present invention comprises an oxygen removing filter for removing oxygen from intake air flowing through at least one of the branch pipes, and a branch provided with the filter. A flow control valve that adjusts the flow rate of intake air to the passage, and means for controlling this control valve according to operating conditions can prevent sticking of the intake valve due to carbon in the exhaust gas, and can reduce the intake air temperature due to the high-temperature exhaust gas. The increase in NOx concentration due to the increase in NO can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to a claim of the first invention.

FIG. 2 is a schematic configuration diagram of one embodiment.

FIG. 3 is a characteristic diagram of an EGR rate.

FIG. 4 is a sectional view of a fuel injection pump.

FIG. 5 is a characteristic diagram of injection timing.

FIG. 6 is a flowchart for explaining control of an injection timing and an injection period in the embodiment.

FIG. 7 is a characteristic diagram of a basic injection period Avm.

8 is a characteristic diagram of a fuel temperature correction amount ΔItm _1.

FIG. 9 is a characteristic diagram of a fuel temperature correction amount ΔItm ₂ .

FIG. 10 is a graph showing each concentration characteristic of smoke and NOx with respect to the EGR rate.

FIG. 11 is a graph showing the respective concentration characteristics of smoke and NOx with respect to the injection timing.

FIG. 12 is a characteristic diagram of a cooling loss, an equal volume, and a fuel consumption rate with respect to an EGR rate.

FIG. 13 is a schematic configuration diagram of a second embodiment.

FIG. 14 is a characteristic diagram of a speed ratio with respect to an engine speed.

FIG. 15 is a perspective view showing the position of the rotating blade when the swirl is high.

FIG. 16 is a perspective view showing the position of the rotating blade when the swirl is low.

FIG. 17 is a characteristic diagram of a swirl ratio.

FIG. 18 is a flowchart for explaining control of a swirl ratio.

FIG. 19 is a diagram showing concentration characteristics of HC, smoke, and NOx with respect to an EGR rate.

FIG. 20 is a schematic configuration diagram of a third embodiment.

FIG. 21 is a characteristic diagram of oxygen concentration with respect to operating conditions.

FIG. 22 shows smoke and NOx relative to the EGR rate in a conventional example.
FIG. 4 is a density characteristic diagram of FIG.

[Explanation of symbols]

 Reference Signs List 20 fuel injection pump 23 intake pipe 25 exhaust pipe 26 EGR passage 27 EGR valve 28 negative pressure control valve 31 control unit 41 supercharger 42 mechanical supercharger 47 rotating blade 48 actuator 51 control unit 61, 62 branch passage 63 oxygen removal Filter 65 Flow control valve 71 Control unit 81 Combustion temperature lowering means 82 Ignition delay period increasing means

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301R 301U F02M 25/07 570 F02M 25/07 570J 33/00 33/00 Z

Claims (6)

(57) [Claims] And 1. A means for reducing the combustion temperature of the engine according to operating conditions of the engine, during the operation of the means for reducing the combustion temperature of this ignition delay period, as the heat generation pattern is in the form of a single-stage combustion A control device for a diesel engine, comprising: Wherein means for causing lowering the combustion temperature, the control device for a diesel engine according to claim 1, characterized in that the means for reducing the oxygen concentration of the intake air. 3. The control device for a diesel engine according to claim 1, wherein the means for significantly lengthening the ignition delay period is means for delaying the fuel injection timing until after the top dead center. 4. The diesel engine control device according to claim 3, further comprising means for supercharging the intake air when the fuel injection timing is delayed until after the top dead center. 5. The control system for a diesel engine according to claim 3, further comprising means for strengthening the swirl when the fuel injection timing is delayed until after the top dead center. 6. The oxygen concentration reducing means adjusts an oxygen removal filter for removing oxygen from intake air flowing through one of at least two branch pipes, and an intake flow rate to a branch passage provided with the filter. 3. The control device for a diesel engine according to claim 2, comprising a flow control valve and means for controlling the control valve in accordance with operating conditions.