JPH11159385A - Control unit for diesel engine - Google Patents

Abstract

(57) Abstract: While detecting an actual fuel injection period and an ignition delay period, the fuel injection pressure and the supercharging pressure are controlled so that the ignition delay period becomes longer than the fuel injection period.
x and PM can be simultaneously reduced. In a diesel engine that performs low-temperature premix combustion, a sensor (61) that detects a start time and an end time of fuel injection from a fuel injection valve (1), a sensor (62) that detects a start time of combustion of injected fuel, When the fuel injection period is calculated from the detected values of the start time and the injection end time, and the ignition delay period is calculated from the detected values of the fuel injection start time and the combustion start time, and when the ignition delay period is shorter than the injection period Then, the fuel injection pressure is corrected so as to shorten the fuel injection period. When a supercharger is provided, the supercharging pressure is reduced and corrected so that the ignition delay period is also longer.

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 diesel engine which reduces NOx (nitrogen oxide) and PM (particulate matter).

[0002]

2. Description of the Related Art NO emitted from a diesel engine
An exhaust gas recirculation system that recirculates part of the exhaust gas into the intake air is effective in reducing the x amount, but on the other hand, when the exhaust gas recirculation rate is increased, the PM tends to increase accordingly. Therefore, the exhaust gas recirculation rate could not be made so large to suppress PM.

On the other hand, low-temperature premixed combustion of a diesel engine has attracted attention as a method for simultaneously reducing NOx and PM in a trade-off relationship.

[0004] This simultaneously realizes reduction of NOx by low-temperature combustion and reduction of PM by premix combustion.
By recirculating a part of the exhaust gas into the intake air, the maximum combustion temperature is suppressed and the generation of NOx is suppressed, while increasing the chance of contact between as much fuel spray and air (oxygen) as possible before ignition. In order to increase the contact time, the gas flow in the combustion chamber is increased, and the ignition delay period from fuel injection to ignition is made as long as possible.

In particular, in this low-temperature premixed combustion, as shown in FIG. 5, when the ignition delay period becomes longer than the fuel injection period, the amount of PM emitted for the same exhaust gas recirculation rate tends to sharply decrease. In this case, even in a region where the exhaust gas recirculation rate is large, the absolute value of the PM emission amount can be suppressed to a small value, and simultaneous reduction of NOx and PM can be achieved.

[0006]

However, the ignition delay period of a diesel engine is determined substantially depending on the fuel injection timing and the operating conditions of the engine at that time, and conventionally, the ignition delay period is specially controlled. That was not done.

[0007] As a fuel injection system for a diesel engine, there is a common rail type injection device capable of injecting a plurality of times during one cycle, and stores high-pressure fuel in a fuel storage chamber called a common rail. It supplies high-pressure fuel to the fuel injection valve of a cylinder, and has a feature that fuel injection can be freely controlled by adjusting the opening and closing timing and period of the fuel injection valve (see Japanese Patent Application Laid-Open No. 62-258160).

Even when such a common rail type fuel injection device is used, the ignition delay period described above is
At that time, the common rail pressure (fuel injection pressure), fuel temperature,
Due to fluctuations in the specific gravity of the fuel and precise variations in the fuel injection valve, the exhaust gas recirculation control valve, etc., the target ignition delay period is set with high accuracy, that is, the ignition delay period is always longer than the fuel injection period, and maintained It was very difficult to do.

For this reason, in low-temperature premixed combustion, attempts to reduce PM simultaneously with NOx by lengthening the ignition delay period are naturally limited, and satisfactory results have not always been obtained. .

In particular, in a high load region where the fuel injection amount is large and the injection period is long, it is difficult to make the ignition delay period longer than the injection period, and during transition, the PM greatly deteriorates and the combustion noise increases. There were also problems.

The present invention has been proposed in order to solve such a problem. The fuel injection is performed so that the fuel injection period is shorter than the ignition delay period while detecting the actual fuel injection period and the ignition delay period. By controlling the pressure or the supercharging pressure, the ignition delay period is relatively increased, so that the NOx and the PM having a trade-off relationship can be simultaneously reduced.

[0012]

According to a first aspect of the present invention, there is provided a fuel accumulator for storing high-pressure fuel pumped from a fuel pump, and means for controlling a fuel pressure of the fuel accumulator to a target value corresponding to an operation state. A fuel injection valve connected to the fuel accumulator and injecting fuel into each cylinder, an injection control means for variably controlling the opening / closing timing and the lift amount of the fuel injection valve, and an injection amount and an injection timing according to an operation state. Start of fuel injection from the fuel injection valve in a diesel engine provided with control means for driving the injection control means so that exhaust gas recirculation control means for introducing a part of exhaust gas into intake air and suppressing combustion temperature. Means for detecting the timing and end time, means for detecting the combustion start time of the injected fuel, and a fuel injection period calculation means for calculating the fuel injection period from the detected values of the fuel injection start time and the injection end time. An ignition delay period calculating means for calculating an ignition delay period from each of the detected values of the fuel injection start time and the combustion start time, and when the fuel injection period is longer than the calculated ignition delay period, the same fuel injection amount is used. And an adjusting means for increasing and correcting the fuel injection pressure so that the injection period is shorter than the ignition delay period.

In a second aspect based on the first aspect, the adjusting means sets a fuel injection period when the fuel injection pressure is at a maximum value to a minimum injection period for the same fuel injection amount, and When the delay period is longer than the minimum injection period, the fuel injection pressure is configured to be increased and corrected within the range of the maximum value.

In a third aspect based on the second aspect, the adjustment means is configured to calculate a correction value of the injection pressure according to a difference between the ignition delay period and a minimum injection period.

In a fourth aspect based on the second or third aspect, the adjusting means causes the pilot injection to be performed separately from the main fuel injection when the ignition delay period is shorter than the minimum injection period. It is composed of

In a fifth aspect based on the fourth aspect, the adjusting means is arranged such that when the ignition delay period is shorter than the minimum injection period and shorter than a preset value.
It is configured to stop the pilot injection.

According to a sixth aspect of the present invention, there is provided a fuel accumulator for storing high-pressure fuel pumped from a fuel pump, means for controlling a fuel pressure in the fuel accumulator to a target value corresponding to an operation state, and a fuel accumulator. A fuel injection valve for connecting and injecting fuel into each cylinder, an injection control means for variably controlling the opening / closing timing and the lift amount of the fuel injection valve, and the injection control so as to obtain an injection amount and an injection timing according to an operation state. Control means for driving the means, exhaust recirculation means for recirculating a part of the exhaust gas into the intake air to suppress the combustion temperature, and a supercharger capable of adjusting the exhaust inflow speed and variably controlling the supercharging pressure of the intake air. A diesel engine provided with a means for detecting a start time and an end time of fuel injection from the fuel injection valve, a means for detecting a start time of combustion of the injected fuel, and detecting each of a fuel injection start time and an injection end time. From the value Fuel injection period calculation means for calculating the fuel injection period, ignition delay period calculation means for calculating the ignition delay period from the detected values of the fuel injection start timing and the combustion start timing, and the fuel more than the calculated ignition delay period An adjusting means for reducing the supercharging pressure by the supercharger so that the ignition delay period is longer when the injection period is longer.

In a seventh aspect based on the sixth aspect, the adjusting means is provided when the ignition delay period is shorter than a fuel injection period and the fuel injection amount is smaller than a predetermined reference injection amount. It is configured to perform pressure reduction correction of the supercharging pressure.

In an eighth aspect based on the first to seventh aspects, the means for detecting the fuel injection start timing and the fuel injection timing comprises a lift sensor for detecting a lift of the fuel injection valve.
The means for detecting the combustion start timing is constituted by a cylinder pressure sensor.

[0020]

In the first invention, the injection period is obtained from the actual fuel injection start timing and the actual fuel injection start timing, and the ignition delay period from the fuel injection to the ignition is determined from the fuel injection start timing and the ignition start timing. Is calculated. The actual ignition delay period calculated in this way is compared with the fuel injection period,
When the ignition delay period is shorter than the fuel injection period, the fuel injection pressure injected from the fuel injection valve is increased. Control is performed such that the fuel injection period required to inject the same amount of fuel is shortened, and the ignition delay period is relatively increased.

Therefore, even if the fuel injection pressure, the fuel temperature, the fuel specific gravity, and the like fluctuate, and the fuel injection valve and the exhaust gas recirculation control valve and the like vary with accuracy, the ignition delay period is always equal to the fuel injection period. Is controlled to be larger than that, so that good low-temperature premixed combustion can always be maintained,
It is possible to reduce PM simultaneously with reduction of NOx.

In the second invention, when the ignition delay period is longer than the minimum injection period, the injection period is shortened by increasing the fuel injection pressure within the range of the maximum value, thereby shortening the ignition delay period. The fuel injection period can be controlled to be longer than the fuel injection period, so that the fuel injection pressure does not need to be increased more than necessary.

In the third aspect, the fuel injection pressure is corrected in accordance with the deviation from the minimum injection period, so that the fuel injection pressure can always be controlled appropriately and responsively.

In the fourth aspect of the invention, when the ignition delay period is shorter than the minimum injection period, the fuel injection period cannot be shortened further. Therefore, the pilot injection is performed separately from the main injection to make the combustion characteristics smooth. Thus, an increase in PM and combustion noise can be suppressed.

In the fifth invention, when the ignition delay period is very short, which is equal to or shorter than the set value, control such as the fuel injection period is stopped, pilot injection is not performed, and engine output performance is emphasized.

In the sixth invention, when the ignition delay period calculated in the same manner as in the first invention is shorter than the fuel injection period, the ignition delay period is increased by controlling the supercharging pressure. By reducing the supercharging pressure, the compression temperature relatively decreases, and the ignition delay period from injection of fuel to ignition increases.

Therefore, when the actual ignition delay period is shorter than the injection period, the boost pressure is corrected to reduce the pressure, and the ignition delay period is increased. Thereby, good low-temperature premixed combustion is realized, and NOx and PM can be simultaneously reduced.

In the seventh aspect, when the fuel injection amount is smaller than a predetermined reference amount, the boost pressure is reduced, the ignition delay period is increased, and good low-temperature premixed combustion is maintained.

According to the eighth aspect, detection of the fuel injection start timing, end timing, ignition timing, and the like can be performed reliably and easily.

[0030]

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

FIG. 1 shows the overall structure, in which 51 is a diesel engine main body, 52 is an exhaust passage, 53 is an intake passage, and an exhaust recirculation passage 54 for recirculating a part of exhaust gas to the intake passage 53. Is provided, and an exhaust gas recirculation control valve 55 for controlling the amount of exhaust gas recirculation is interposed in the middle of this.
In addition, 57 is a supercharger that pressurizes intake air.

A fuel injection valve 1 for directly injecting fuel into the engine combustion chamber 56 is provided.
As described later, a common rail (high-pressure fuel accumulator) 26
And high pressure fuel is supplied.

In order to realize low-temperature premixed combustion while recirculating a part of the exhaust gas into the intake air, although not shown, a swirl is generated in the combustion chamber 56 to generate a gas flow for promoting the mixing of fuel and air. Control means and the like are provided.

In order to control the ignition delay period in the low-temperature premixed combustion to be longer (longer) than the fuel injection period, the actual ignition delay period and the fuel injection period are calculated, and the ignition delay period is shorter. Sometimes, the controller 60 controls the common rail pressure, that is, the fuel injection pressure, so as to shorten the fuel injection period.

The fuel injection period required to inject the same amount of fuel becomes shorter as the fuel injection pressure becomes larger. Therefore, by variably controlling the fuel injection pressure, the fuel injection period with respect to the ignition delay period is reduced. It becomes possible to make it relatively small.

For this reason, the controller 60 includes a signal from the lift sensor 61 as a means for detecting the fuel injection start time and the fuel end time of the fuel injection valve 1 and an in-cylinder pressure as a means for detecting the combustion start time. A signal from the sensor 62 is input, a fuel injection period and an ignition delay period are calculated based on these signals, and the common rail pressure is variably controlled as described later.

The controller 60 also controls the fuel injection timing and the injection amount of the fuel injection valve 1 to optimal values according to the operating state. For this reason, the accelerator opening, the engine speed signal, and the cooling water temperature are controlled. Signals etc. are input. Further, the opening degree of the exhaust gas recirculation control valve 55 is controlled in accordance with the operation state, so that the exhaust gas recirculation amount is increased in a partial load region or the like, and the exhaust gas recirculation amount is reduced or stopped in a high load region.

Next, FIG. 2 shows the details of the fuel injection valve 1 and FIG. 3 shows the details of the fuel injection system.

In FIG. 2, the fuel injection valve 1 comprises an injection nozzle holder 2, an injection nozzle 3, and an injection valve drive unit 4. The injection nozzle holder 2 and the injection nozzle 3 are integrated by a retaining nut 5. Have been. A needle valve sliding hole 6 and a fuel reservoir 7 are formed in the injection nozzle 3, and a nozzle hole 8 communicating with the fuel reservoir 7 is formed at the tip.

The large diameter portion 10 of the needle valve 9 is slidably fitted in the needle valve sliding hole 6. The large diameter portion 10 of the needle valve 9 has a connecting portion 11 formed therein, and a small diameter portion 12 and a valve body portion 13 are integrally formed at a lower end portion. The valve portion 13 opens and closes the seat portion X, and turns on / off the fuel injection from the nozzle hole 8.

A push rod 14 is in contact with the distal end of the connecting portion 11 of the needle valve 9 and is further urged by a spring 16 in a valve closing direction. The pins 17 position the injection nozzle 3 and the injection nozzle holder 2. The push rod 14 is slidably fitted in a cylinder 15 formed in the injection nozzle holder 2.

An injection valve driving unit 4 for driving the needle valve 9 and the push rod 14 is disposed above the injection nozzle holder 2, and a solenoid valve 22 is disposed in the injection valve driving unit 4; Control current is supplied via 23.

The solenoid valve 22 has a valve body 22a in accordance with the energized state.
And opens and closes a communication passage 39 that communicates the back pressure chamber 38 of the push rod 14 with the low pressure chamber 20 on the fuel outlet 24 side.
When the energization of the solenoid valve 22 is released, the valve body 22a is pulled up by the return spring 21 and the communication passage 39 is opened. Thereby, the back pressure chamber 38 of the push rod 14
Pressure is released.

A fuel supply passage 19 for high-pressure fuel is formed in the injection nozzle holder 2, one end of which is provided at the injection nozzle holder 2.
, And the other end is connected to the fuel storage chamber 7.
And also to the back pressure chamber 38. The high-pressure fuel of the common rail 26 is supplied to the fuel storage chamber 7 and the back pressure chamber 38 via the inlet 18 and the fuel supply passage 19. Leaked fuel in the fuel injection valve 1
4, the leaked fuel in the fuel injection valve 1 is returned to the fuel tank through the fuel outlet 24, and the needle valve 9 is normally closed by the push rod 14 receiving the pressure of the back pressure chamber 38. The solenoid valve 2
When the power supply to the fuel tank 2 is released, the communication path 39 is opened, the pressure in the back pressure chamber 38 is reduced, and the pushing force of the push rod 14 from the back is reduced. The needle valve 9 lifts and opens, and fuel is injected.

When the energization of the solenoid valve 22 is stopped, the valve 2
2a closes the communication path 39, the pressure in the back pressure chamber 38 rises,
At this time, since the pressure receiving area in the direction of pushing down the push rod 14 is large, the needle valve 9 is pushed down against the spring 16 and closed, and the fuel injection is stopped.

Therefore, by controlling the energizing interval and timing of the solenoid valve 22, the fuel injection amount and the injection timing can be freely controlled. Can be controlled freely.

Next, in FIG. 3, the fuel injection valve 1 for each cylinder is connected via an injection pipe 27 to a high-pressure accumulator pipe common to each cylinder, a so-called common rail 26. A high-pressure supply pump 30 is connected to the common rail 26 via a supply pipe 28 and a check valve 29. This high pressure supply pump 3
Numeral 0 controls the pressure of the fuel sucked through the fuel feed pump 33 from the fuel tank 31 via the fuel filter 32 to a predetermined high pressure. In this case, the drive shaft 34 having the cam rotates in synchronization with the engine rotation, the piston in the high-pressure supply pump 30 reciprocates, and the fuel from the fuel feed pump 33 is pressurized.
Supplied to Further, the high-pressure supply pump 30 is provided with a discharge amount control solenoid valve 35 for always controlling the common rail pressure to a desired pressure.

Further, a pressure sensor 37 for detecting the fuel pressure (common rail pressure) in the common rail is provided on the common rail 26. The controller 60 determines that the detected pressure is an optimum value set in advance according to the load and the engine speed. In such a manner, the discharge amount is feedback-controlled via the electromagnetic valve 35.

The above-described control executed by the controller 60 will be described in detail with reference to the flowchart shown in FIG.

This flowchart is repeated in synchronization with the engine speed. In step S1, the engine speed Ne, the engine load Q, and the cooling water temperature Tw are read.

In step S2, the basic fuel injection amount, the basic injection timing (advance value), the basic exhaust gas recirculation rate (EGR rate), and the basic common rail pressure according to the operation state determined based on the above are calculated, for example, as shown in FIG. ) To (D).

In step S3, in order to obtain the basic injection amount thus obtained, a minimum injection period, which is an injection period obtained when the basic common rail pressure is maximized, is calculated at the read engine speed. . This is calculated based on a characteristic as shown in FIG. 7 when the fuel injection amount is changed, for example.

The common rail pressure corresponds to the fuel injection pressure. In order to obtain the same injection amount, the higher the fuel injection pressure, the shorter the fuel injection period.

In step S4, the outputs of the in-cylinder pressure sensor and the needle valve lift sensor of the fuel injection valve are read, and in step S5, the ignition delay period and the fuel injection period are calculated.

The ignition delay period is a period from the start of fuel injection to the start of combustion. As shown in FIG. 8, the combustion start timing, that is, the ignition timing, is the output of the in-cylinder pressure sensor. It can be determined from the differential value, and the injection start timing can be determined from the rise of the output of the lift sensor. The fuel injection period is a period from the start to the end of fuel injection, and can be determined from the output of the lift sensor.

Next, in step S6, the magnitudes of the ignition delay period and the fuel injection period are determined. If the ignition delay period is longer, the control is terminated.

On the other hand, if the ignition delay period is shorter, the process proceeds to step S7, where the ignition delay period is compared with the minimum injection period obtained as described above.

This minimum injection period is the minimum injection period obtained when the common rail pressure is maximized. If it is determined that the ignition delay period is longer than the minimum injection period, the minimum injection period will be shorter than the current state. Since the fuel injection period can be shortened by increasing the pressure, the process proceeds to step S8, and the increase correction amount of the common rail pressure is calculated according to the difference as shown in FIG.

In step S9, the common rail pressure is obtained by adding the correction pressure to the basic common rail pressure, and the control is terminated.

In this case, the higher the common rail pressure, the shorter the fuel injection period for achieving the same injection amount, and the longer the ignition delay period.

On the other hand, if it is determined in step S7 that the ignition delay period is shorter than the minimum injection period, the fuel injection period is made shorter than the ignition delay period even if the common rail pressure is increased to the allowable maximum value. It is not possible.

At that time, the process proceeds to step S10, and it is determined whether or not the ignition delay period is longer than a set value determined according to the operation state. When it is determined that the ignition delay period is shorter than the set value, the control for the further fuel injection period ends.

When the ignition delay period is longer than the set value, pilot injection is set in step S11. That is, the pilot injection is performed separately from the main injection, and the pilot injection amount and the injection timing for this purpose, and the injection amount and the injection timing of the main injection changed accordingly are set in advance according to the operation state. Determine based on characteristics.

This is the case where the ignition delay period does not become shorter than the present time. In this case, pilot injection is performed prior to main injection, the combustion characteristics are made smooth, and combustion noise and the like are improved. .

The configuration is as described above. Next, the overall operation will be described.

The opening degree of the exhaust gas recirculation control valve 55 is controlled in accordance with the operation state of the diesel engine, and the exhaust gas is recirculated. As a result, the maximum combustion temperature decreases. Decrease.

On the other hand, the PM in the exhaust gas increases as the exhaust gas recirculation rate increases. As shown in FIG. 5, this PM decreases as the ignition delay period becomes shorter than the fuel injection period at the same exhaust gas recirculation rate.

During the ignition delay period, the fuel particles are premixed with air, and as the degree of premixing advances, in other words, the longer the ignition delay period, the less PM is generated during combustion.

Therefore, the fuel injection start timing and the fuel end timing of the fuel injection valve 1 are detected, the injection period is calculated from the difference between them, and the combustion start (ignition) timing is detected. Then, the ignition delay period corresponding to the period from the actual injection of fuel to the start of ignition is calculated. When the ignition delay period is shorter than the fuel injection period, the common rail pressure is increased so as to shorten the fuel injection period.

The higher the common rail pressure, that is, the higher the fuel injection pressure, the shorter the injection period required to inject the same amount of fuel. As a result, the ignition delay period can be relatively longer than the fuel injection period, and the longer the ignition delay period, the lower the PM emission amount.

As described above, according to the present invention, the fuel injection period is controlled by adjusting the common rail pressure so that the ignition delay period is longer than the fuel injection period while detecting the actual ignition delay period and the fuel injection period. Therefore, the ignition delay period is always made longer than the fuel injection period to achieve good low-temperature premixed combustion, and the trade-off relationship between NOx and PM can be improved.

In this case, even if the fuel injection pressure, the fuel temperature, the fuel specific gravity and the like fluctuate, and even if the fuel injection valve 1, the exhaust gas recirculation control valve 55, and the like have a precise variation,
The actual ignition delay period can be made longer than the fuel injection period, ensuring that good low-temperature premixed combustion is maintained.
And PM at the same time.

Further, when the fuel injection period cannot be made longer than the ignition delay period due to the operating conditions, that is, when the fuel injection amount is large and the load is high, the fuel injection period does not increase even if the common rail pressure is increased to the allowable maximum value. In some cases, the ignition delay period cannot be shorter than the ignition delay period. In such a case, the pilot injection is performed separately from the main injection.

Mainly during such a transient state, the pilot injection moderates the rise in combustion pressure due to this pilot injection.
Not only can the generation of M be suppressed, but also the increase in combustion noise can be suppressed.

Next, another embodiment shown in FIG. 10 will be described.

In the first embodiment described above, the fuel injection period is corrected and controlled with respect to the ignition delay period. However, in this embodiment, the ignition delay period is controlled in order to realize good low-temperature premixed combustion. Is directly corrected and controlled.

In this case, a turbocharger is provided as the supercharger 57, and the turbocharger is provided with a variable nozzle capable of changing the inflow area at the turbine inlet. By controlling the position (opening) of the variable nozzle, the supercharging pressure changes, thereby changing the ignition delay period. Specifically, for example, when the opening degree of the variable nozzle is increased, the speed of exhaust gas flowing into the turbine decreases, the supercharging pressure decreases, and the ignition delay period increases. The supercharging pressure control is described in a new manual of Nissan Leopard F31 type car (issued in February 1986).

The controller 60 controls the supercharging pressure and controls the ignition delay period so that the detected ignition delay period is longer than the fuel injection period as follows.

In FIG. 10, steps S1 to S5 are substantially the same as those in FIG. 4, except for reading the basic nozzle position and calculating the minimum injection period.

In step S2, the basic nozzle position and the like are read from FIG.

If the ignition delay period is longer than the injection period in step S5, the control is terminated, but if the ignition delay period is shorter, the process proceeds to step S6 where the basic injection amount is compared with the set injection amount. As shown in FIG. 12, the set injection amount is set to a characteristic that decreases as the engine speed increases.

When the basic injection amount is smaller than the set injection amount, in step S7, the position correction amount of the variable nozzle is read from FIG. 13 according to the difference. Then, in step S, this correction amount is added to the basic nozzle position (therefore, the nozzle opening is increased) to obtain a set nozzle position.

When the basic injection amount is equal to or larger than the set injection amount in step S6, the control is terminated.

As described above, when the ignition delay period is shorter than the fuel injection period and the fuel injection amount at that time is equal to or less than the set value and the load is not so large, the variable nozzle of the turbocharger is not used. Is corrected to the enlargement side. As a result, the supercharging pressure of the diesel engine decreases, the rise in intake air temperature during the compression stroke becomes relatively low, and the ignition delay period becomes longer.

Since the ignition delay period is longer than the fuel injection period, low-temperature premixed combustion is improved, and PM and N
Simultaneous reduction of Ox can be achieved.

In this case, since the ignition delay period can be increased while maintaining the common rail pressure at the basic value,
The increase in the driving torque of the fuel injection pump can be suppressed by the amount by which the common rail pressure is not increased.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a sectional view of the fuel injection valve.

FIG. 3 is a configuration diagram of a fuel supply system.

FIG. 4 is a flowchart showing a control operation.

FIG. 5 is an explanatory diagram showing a relationship between an ignition delay period and a PM emission amount.

FIG. 6 is an explanatory diagram showing characteristics in an operation state, where A indicates fuel injection amount characteristics, B indicates fuel injection timing characteristics, C indicates exhaust gas recirculation characteristics, and D indicates common rail pressure characteristics.

FIG. 7 is an explanatory diagram showing characteristics of a minimum injection period.

FIG. 8 is an explanatory diagram showing a relationship between in-cylinder pressure and an output of a needle valve lift sensor.

FIG. 9 is an explanatory diagram showing a correction characteristic of a common rail pressure.

FIG. 10 is a flowchart illustrating a control operation according to another embodiment.

FIG. 11 is an explanatory diagram showing characteristics in an operating state, where A indicates fuel injection amount characteristics, B indicates fuel injection timing characteristics, C indicates exhaust gas recirculation characteristics, and D indicates nozzle opening characteristics.

FIG. 12 is an explanatory diagram showing characteristics of a set injection amount.

FIG. 13 is an explanatory diagram showing a correction characteristic of a nozzle position (opening degree).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel injection valve 22 Solenoid valve 26 Common rail 51 Diesel engine 55 Exhaust recirculation control valve 60 Controller 61 Lift sensor 62 In-cylinder pressure sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 21/08 301 F02D 21/08 301D 23/00 23/00 N 41/38 41/38 AB 41/40 41/40 R 45/00 364 45/00 364N 364P 368 368S

Claims (8)

[Claims] 1. A fuel storage chamber for storing high-pressure fuel pumped from a fuel pump, means for controlling a fuel pressure of the fuel storage chamber to a target value corresponding to an operating state, and each cylinder connected to the fuel storage chamber A fuel injection valve for injecting fuel into the fuel injection valve; an injection control means for variably controlling an opening / closing timing and a lift amount of the fuel injection valve; Control means, and exhaust gas recirculation control means for introducing a part of the exhaust gas into the intake air to suppress the combustion temperature, wherein a means for detecting fuel injection start timing and end timing from the fuel injection valve, Means for detecting the combustion start time of the injected fuel; fuel injection period calculation means for calculating the fuel injection period from the detected values of the fuel injection start time and the injection end time; and fuel injection start time An ignition delay period calculating means for calculating an ignition delay period from each detected value of the combustion start timing; and when the fuel injection period is longer than the calculated ignition delay period, the injection period at the same fuel injection amount is longer than the ignition delay period. Control means for increasing the fuel injection pressure so as to reduce the fuel injection pressure. 2. The adjusting means sets a fuel injection period when a fuel injection pressure is a maximum value to a minimum injection period for the same fuel injection amount, and the ignition delay period is longer than the minimum injection period. 2. The control device for a diesel engine according to claim 1, wherein the fuel injection pressure is occasionally increased and corrected within a range of its maximum value. 3. The control device for a diesel engine according to claim 2, wherein said adjusting means calculates a correction value of the injection pressure in accordance with a difference between the ignition delay period and a minimum injection period. 4. The control device for a diesel engine according to claim 2, wherein said adjusting means causes the pilot injection to be performed separately from the main fuel injection when the ignition delay period is shorter than the minimum injection period. 5. The diesel engine control according to claim 4, wherein said adjusting means stops said pilot injection when said ignition delay period is shorter than said minimum injection period and shorter than a preset value. apparatus. 6. A fuel accumulator for storing high-pressure fuel pumped from a fuel pump, means for controlling a fuel pressure of the fuel accumulator to a target value corresponding to an operation state, and each cylinder connected to the fuel accumulator. A fuel injection valve for injecting fuel into the fuel injection valve; an injection control means for variably controlling an opening / closing timing and a lift amount of the fuel injection valve; A diesel engine comprising: a control unit; an exhaust gas recirculation unit that recirculates a part of the exhaust gas into the intake air to suppress a combustion temperature; In the engine, means for detecting a start time and an end time of fuel injection from the fuel injection valve, means for detecting a start time of combustion of the injected fuel, and fuel from each detected value of the fuel injection start time and the injection end time Jet Fuel injection period calculation means for calculating a period, ignition delay period calculation means for calculating an ignition delay period from each detected value of fuel injection start timing and combustion start timing, and a fuel injection period longer than the calculated ignition delay period A controller for reducing the supercharging pressure by the supercharger so that the ignition delay period is longer when the ignition timing is longer. 7. The supercharger according to claim 1, wherein the adjusting means corrects the supercharging pressure when the ignition delay period is shorter than the fuel injection period and when the fuel injection amount is smaller than a predetermined reference injection amount. Item 7. A control device for a diesel engine according to item 6. 8. The means for detecting the fuel injection start time and the end time comprises a lift sensor for detecting a lift of the fuel injection valve, and the means for detecting the combustion start time comprises a cylinder pressure sensor. The control device for a diesel engine according to any one of claims 1 to 7.