JP2000008883A - Fuel injection device and control device for diesel engine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce the size of an apparatus. A pressure accumulator chamber (7) stores fuel supplied from a pump (1) for supplying fuel in a high pressure state, and a fuel supply from the accumulator chamber (7) is received by a nozzle chamber (12) of an injector (11). In the injector 11, when the needle valve 16 is lifted and the nozzle seat portion 16a is opened, fuel is injected from the injection hole 20 at the nozzle tip. In this case, the lift speed of the needle valve 16 is configured to be controllable (piezo actuator 32, control unit 2
2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection device and a control device for a diesel engine.

[0002]

2. Description of the Related Art As an injector of an accumulator type fuel injection device, there is one disclosed in Japanese Patent Application Laid-Open No. 9-58811. The basic configuration of this injector will be described with reference to FIG.

In FIG. 16, high-pressure fuel in a pressure accumulating chamber 7 is guided from a supply passage 151 to a nozzle chamber 12, and also to a pressure chamber 14 above a nozzle piston 13 via a charging orifice 18.

An electromagnetic valve 152 for connecting the pressure chamber 14 to the drain side
When is closed, needle valve 16 is seated. When the solenoid valve 152 is opened from this state, the pressure in the pressure chamber 14 decreases through the discharge orifice 17, so that the needle valve 16 is lifted upward by the fuel pressure acting on the nozzle chamber 12, and fuel is injected. You. When the solenoid valve 152 closes, the pressure chamber 14 is filled with high-pressure fuel through the filling orifice 18, and the nozzle piston 13 whose pressure receiving area is set to be larger than the pressure receiving area of the needle valve 12.
As a result, the needle valve 16 is pushed down and seated, and fuel injection stops.

A return spring 19 is provided to prevent the fuel in the nozzle chamber 12 from leaking into the combustion chamber when the engine is stopped or the like.
16, contracted by the hydraulic pressure applied to the nozzle piston 13,
The needle valve 16 and the nozzle piston 13 always move integrally.

In such an injector, the force in the valve closing direction, which is the product of the pressure in the pressure chamber 14 and the cross-sectional area of the sliding portion of the nozzle piston 13, is the product of the pressure in the nozzle chamber 12 and the pressure receiving area of the needle valve 16. The movement of the needle valve 16 is determined by the balance of the forces in a certain valve opening direction. In this case, since the nozzle chamber 12 is always in communication with the pressure accumulating chamber via the supply passage 151, the pressure is substantially constant, whereas the pressure in the pressure chamber 14 is greatly changed by opening and closing the solenoid valve 152. . The hydraulic pressure received by the nozzle piston 13 depends on the effective flow path area of the filling orifice 18 and the discharge orifice 17 and the pressure receiving area of the nozzle piston 13 when the solenoid valve 152 is opened, and on the filling orifice 18 when the solenoid valve 152 is closed.
And the pressure receiving area of the nozzle piston 13. Thus, the filling orifice 18 and the discharge orifice 17
By changing the three parameters of each effective flow path area and the diameter of the nozzle piston 13, it is possible to change the respective rising and falling speeds of the needle valve 16, that is, the injection rate.

[0007] The injection rate is reduced to reduce the combustion noise due to the reduction of the injection amount during the ignition delay period at the beginning of injection and to suppress the emission of NOx, to make the rising slope gentle, and to suppress the smoke emission at the end of injection. Because it is common to increase the slope on the descending side (“Internal combustion engine” Vol. 31 N
o.393 1992.7 p.21 to p.29), the ascending speed of the needle valve 16 is decreased and the descending speed is increased by matching the above three parameters.

[0008]

By the way, since the quality of the spray greatly affects the combustion state, it was examined what actually happens to the spray injected from the injector of the accumulator type fuel injection system. For the first time. Explaining this, in the above-described injector, the rising speed of the needle valve 16 is slowed, so at the beginning of the injection, the needle valve lift is low, and after the fuel has passed through the very narrow clearance of the nozzle seat at high speed. It flows into the nozzle orifice.

FIG. 3 shows a cross-sectional view of the nozzle tip portion. This type shows the nozzle seat portion 16 of the needle valve 16 when the needle valve 16 is seated.
Since the injection hole is closed by a, the VCO
(Valve Covered Orifice) type.

Here, looking at the fuel flow velocity distribution in a cross section perpendicular to the axis of the injection hole 20, an ideal nozzle is symmetrical with respect to the central axis of the needle valve 16 as shown in FIG. A weak flow occurs. This is because the fuel firstly flows into the upper portion of the injection hole 20 from the nozzle sheet portion.

However, in an actual nozzle,
The needle valve 16 is slightly eccentric due to the play of the needle valve sliding portion and the problem of manufacturing accuracy. For example, when the eccentricity to the left is generated as shown in FIG. 5 (a view taken along the line AA in FIG. 3), the circumferential flow toward the right is vertically symmetrical in the nozzle sheet portion (indicated by an arrow). Occurs. In such a case, the inside of the injection holes 20a and 20b located at the site where the flow is fast is shown in FIG.
A strong swirling flow is generated as shown in FIG. 5 (viewed along the line BB) and FIG. 6B (viewed along the line CC in FIG. 5).

The swirling flow in the plane perpendicular to the axis of the injection hole becomes stronger when the needle valve lift is lower and when the nozzle chamber pressure is higher. This is because the nozzle sheet portion is narrow and the fuel flow rate in the circumferential direction of the nozzle sheet portion increases, and the higher the pressure in the nozzle chamber, the higher the fuel flow rate in the nozzle sheet portion. When the swirling flow in the plane perpendicular to the axis of the injection hole is large, the spray has a wide spray cone angle for its injection rate, a weak penetration, and an atomized spray (ie, ignition Good spray). Such a phenomenon is particularly remarkable in a VCO type nozzle.

[0013] In such a spray having good ignitability, evaporation and mixing with the ambient air are promoted, so that the ignition delay period is shorter than that in the conventional spray of a jerk type fuel injection device. Therefore, there is an advantage that the amount of premixed combustion at the beginning of combustion is reduced, and combustion noise and NOx emission are suppressed. However, on the other hand, in the operating range where the excess air ratio is small, such as in the high load range, the premixed combustion ratio is reduced, and in addition, near the center of the combustion chamber where the flow is weak, the spray that is initially injected and the weak spray of the penetration remains. Therefore, there is a demerit that the generation of smoke increases.

This concludes the description of the inventor's first knowledge.

On the other hand, in the jerk type fuel injection device, the fuel is rapidly pressurized by a plunger, the generated pressure wave is guided to a nozzle chamber through a fuel injection pipe, and the fuel pressure in the nozzle chamber is changed to a substantially mountain shape. The pressure lifts the needle valve against the force of the return spring in the needle valve seating direction,
It is configured to inject fuel. In such a jerk type fuel injection device, since the nozzle chamber pressure in the initial stage of injection is low and the needle valve is rapidly lifted, the period during which fuel is injected with the low needle valve lift is short, so that the high load Has low smoke emission, but has the disadvantage of high combustion noise and NOx emission. In addition, since the ignitability is lower than the spray obtained by the accumulator type fuel injection device, it is necessary to further advance the injection timing at the time of cooling in order to suppress misfire particularly at the time of cooling, and NOx emission at the time of cooling is reduced. There is also a disadvantage that there are many.

As described above, the fuel injection devices of the accumulator type and the jerk type each have advantages and disadvantages. Therefore, in order to obtain sprays having different requirements, two fuel injection devices are provided, and two fuel injection devices are provided according to the requirements. One of the two fuel injection devices is selected and used, but providing two fuel injection devices independently increases not only the cost but also the size of the device.

Accordingly, the present invention provides a needle valve ascending speed (needle valve lifting speed) of an injector used in an accumulator type fuel injection device.
Alternatively, it is a first object to reduce the size of the device by configuring the maximum lift of the needle valve to be controllable.

Further, a spray having good ignitability obtained by lifting (raising) the needle valve at a low speed (or reducing the maximum lift of the needle valve), and a spray at a high speed of the needle valve (or the maximum lift of the needle valve). Which one of the sprays having poor ignitability obtained by increasing the size is required depends on the operating conditions.

For example, even in an operation range where the excess air ratio is small, such as a high load range, when the spray having good ignitability obtained by lifting the needle valve at a low speed is used, the generation of smoke increases.

In addition, low-temperature premixed combustion, in which a large amount of EGR is performed to reduce the oxygen concentration and fuel injection is terminated during the ignition delay period so that the combustion is performed at a low temperature mainly by premixed combustion, is performed. There is a method for performing this operation (see JP-A-7-4287). In order to realize this low-temperature premixed combustion, it is convenient for the ignition delay period to be appropriately long, and for the spray having good ignitability obtained by the accumulator type fuel injection, the ignition delay period becomes short and the ignition delay period becomes short. Since it is difficult to inject all the fuel into the exhaust gas, the operating range in which exhaust particulates and NOx can be simultaneously reduced by low-temperature premixed combustion is narrowed. Therefore, in this case, in the low temperature premixed combustion region, a spray having poor ignitability obtained by lifting the needle valve at high speed is more preferable.

Accordingly, the present invention variably controls the needle valve lift speed (or the maximum needle valve lift) in accordance with the specific requirements for the quality of the spray, so that [1] smoke and the like are reduced in the region where the excess air ratio is small. Suppress the emission of exhaust particulates,
[2] Prevent misfire when the engine is cold; [3] For low temperature premixed combustion, expand the range of low temperature premixed combustion so as to maximize its effect,
[4] A second object is to prevent adverse effects when the pressure of the accumulator deviates from the target value, and [5] to perform highly accurate control of the injection amount during pilot injection and post injection.

[0022]

According to a first aspect of the present invention, a pump 1 for supplying fuel, a pressure accumulation chamber 7 for storing the supplied fuel in a high pressure state, and a fuel supply from the pressure accumulation chamber 7 are received by a nozzle chamber 12. An injector that injects fuel from the injection hole 20 at the nozzle tip when the needle valve 16 lifts and the nozzle seat portion 16a opens.
In the diesel engine fuel injection device provided with 11, the lift speed of the needle valve 16 or the maximum lift of the needle valve 16 can be controlled.

According to a second aspect, in the first aspect, the nozzle has a shape in which the needle valve 16 covers the injection hole inlet when the needle valve is seated.

As shown in FIG. 17, a third aspect of the present invention provides a pump 71 for supplying fuel, a pressure accumulation chamber 72 for storing the supplied fuel in a high pressure state, a fuel supply from the pressure accumulation chamber 72, and a needle valve. The injector 73 injects fuel from the injection hole at the tip of the nozzle when the nozzle seat is opened by lift, and also controls the lift speed of the needle valve or the maximum lift of the needle valve.
Means 141 for determining whether or not the high load region and the high rotation region, the needle valve lifts at high speed in the determined high load region and the high rotation region or the maximum lift of the needle valve is large And a means 142 for controlling the injector 73 so that the needle valve lifts at a low speed in a region other than the high load region and the high rotation region or the maximum lift of the needle valve is reduced.

As shown in FIG. 18, a fourth aspect of the present invention provides a pump 71 for supplying fuel, a pressure accumulation chamber 72 for storing the supplied fuel in a high pressure state, a fuel supply from the pressure accumulation chamber 72, and a needle valve. The injector 73 injects fuel from the injection hole at the tip of the nozzle when the nozzle seat is opened by lift, and also controls the lift speed of the needle valve or the maximum lift of the needle valve.
Means 74 for directly or indirectly detecting the excess air ratio of the engine, and when the detected excess air ratio is equal to or more than a predetermined value, the needle valve lifts at a low speed or the maximum lift of the needle valve And means 75 for controlling the injector 73 so that the needle valve lifts at a high speed or the maximum lift of the needle valve increases when the excess air ratio is less than a predetermined value. Was.

As shown in FIG. 19, a fifth aspect of the present invention provides a pump 71 for supplying fuel, a pressure accumulating chamber 72 for storing the supplied fuel in a high pressure state, a fuel supply from the pressure accumulating chamber 72, and a needle valve. The injector 73 injects fuel from the injection hole at the tip of the nozzle when the nozzle seat is opened by lift, and also controls the lift speed of the needle valve or the maximum lift of the needle valve.
Means 81 for detecting the cooling water temperature of the engine, and the injector 73 so that the needle valve lifts at a low speed or the maximum lift of the needle valve decreases when the detected cooling water temperature is a predetermined value or less. And means 82 for controlling

As shown in FIG. 20, a sixth aspect of the present invention provides a pump 71 for supplying fuel, a pressure storage chamber 72 for storing the supplied fuel in a high pressure state, a fuel supply from the pressure storage chamber 72, and a needle valve. The injector 73 injects fuel from the injection hole at the tip of the nozzle when the nozzle seat is opened by lift, and also controls the lift speed of the needle valve or the maximum lift of the needle valve.
Means 91 for controlling the combustion rate, and in some operating conditions, the control means 91 is used to reduce the combustion rate, and to terminate the fuel injection within the ignition delay period to perform low-temperature premix combustion. Means 92, means 93 for determining whether or not the temperature is in the low-temperature premixed combustion zone, and the needle valve is lifted at high speed or the maximum lift of the needle valve is increased in the determined low-temperature premixed combustion zone. Injector
A means 94 for controlling 73 is provided.

In the seventh invention, the means for controlling the combustion speed in the sixth invention is means for controlling the EGR amount.

As shown in FIG. 21, the eighth aspect of the present invention provides a pump 71 for supplying fuel, a pressure accumulation chamber 72 for storing the supplied fuel in a high pressure state, a fuel supply from the pressure accumulation chamber 72, and a needle valve. The injector 73 injects fuel from the injection hole at the tip of the nozzle when the nozzle seat is opened by lift, and also controls the lift speed of the needle valve or the maximum lift of the needle valve.
Means for controlling the injector 73 in accordance with the demand for the needle valve lift speed or the needle valve maximum lift
101, the needle valve lifts at a low speed, or the needle valve lifts at a low speed when different requests occur for the needle valve lift speed or the needle valve maximum lift under the same engine speed and fuel injection amount conditions. Means 102 for setting the target accumulator chamber pressure higher when controlling to reduce the maximum lift of the needle valve than when controlling the needle valve to lift at a high speed or to increase the maximum lift of the needle valve. And means 103 for controlling the pressure of the accumulator so that the target pressure of the accumulator is set higher.

As shown in FIG. 22, the ninth aspect of the present invention provides a pump 71 for supplying fuel, a pressure accumulation chamber 72 for storing the supplied fuel in a high pressure state, a fuel supply from the pressure accumulation chamber 72, and a needle valve. The injector 73 injects fuel from the injection hole at the tip of the nozzle when the nozzle seat is opened by lift, and also controls the lift speed of the needle valve or the maximum lift of the needle valve.
Means 111 for determining whether or not the load is in a high load range or a high rotation range, and the needle valve lifts at a high speed in the determined high load range or the high rotation range or the maximum lift of the needle valve is large. Means 112 for controlling the injector 73 is provided.

According to a tenth aspect, in any one of the third to ninth aspects, the nozzle has a shape in which the needle valve covers the injection hole inlet when the needle valve is seated.

In the eleventh invention, as shown in FIG. 23, a pump 71 for supplying fuel, a pressure accumulation chamber 72 for storing the supplied fuel in a high pressure state, and a fuel supply from the pressure accumulation chamber 72,
When the needle valve is lifted and the nozzle seat is opened, fuel is injected from the injection hole at the tip of the nozzle, and an injector 73 that can control the lift speed of the needle valve or the maximum lift of the needle valve.
A means 121 for setting the needle valve lift speed or the needle valve maximum lift in accordance with operating conditions; a means 122 for detecting the fuel pressure of the accumulator 72; and the detected accumulator pressure being higher than a target value. Is also larger than a predetermined value, the means 123 for correcting the needle valve lift speed under the current operating condition to a side that decreases the needle valve lift speed or the needle valve maximum lift under the operating condition at that time to a side that reduces the needle valve lift speed. Means 124 for controlling the injector 73 so that the corrected needle valve lift speed or needle valve maximum lift is provided.

According to a twelfth aspect, as shown in FIG. 24, a pump 71 for supplying fuel, a pressure storage chamber 72 for storing the supplied fuel in a high pressure state, and a fuel supply from the pressure storage chamber 72,
When the needle valve is lifted and the nozzle seat is opened, fuel is injected from the injection hole at the tip of the nozzle, and an injector 73 that can control the lift speed of the needle valve or the maximum lift of the needle valve.
A means 121 for setting the needle valve lift speed or the needle valve maximum lift in accordance with operating conditions; a means 122 for detecting the fuel pressure of the accumulator 72; and the detected accumulator pressure being higher than a target value. Is also smaller than a predetermined value, a means 131 for correcting the needle valve lift speed under the operating condition to a higher side or increasing the needle valve maximum lift under the operating condition, and a corrected needle Means 114 for controlling the injector 73 so that the valve lift speed or the needle valve maximum lift is provided.

In a thirteenth aspect, in any one of the third to twelfth aspects, when a small amount of fuel is injected (pilot injection) prior to the main fuel injection, the needle valve is lifted at a low speed. Alternatively, the maximum lift of the needle valve is reduced.

According to a fourteenth aspect of the present invention, in any one of the third to thirteenth aspects, in order to supply HC required for NOx reduction to the NOx reduction catalyst provided in the exhaust passage, the latter stage of the combustion stroke or the exhaust stroke is performed. When a small amount of fuel is injected (post-injection) in the stroke, the needle valve is lifted at a low speed or the maximum lift of the needle valve is reduced.

[0036]

According to the first and second aspects of the present invention, the lift speed of the needle valve or the maximum lift of the needle valve can be controlled without separately providing two fuel injection devices of the accumulator type and the jerk type. The configuration makes it possible to control the quality of the spray. (If the needle valve is lifted at a low speed or the maximum lift of the needle valve is reduced, a spray having good ignitability can be obtained. If the maximum lift of the needle valve is increased, a spray with poor ignitability can be obtained.) Therefore, compared with the case where the accumulator type fuel injection device and the jerk type fuel injection device having the constant needle valve lift speed are independently provided, Can be reduced in size.

According to the third aspect of the invention, there is a correlation between the generation of smoke and the operating conditions determined from the load and the rotation.
The needle valve lift speed or needle valve maximum lift is switched and controlled according to whether it is in the high-load region and high-rotation region or in the high-load region and the high-rotation region. It can be controlled optimally.

According to the fourth aspect of the invention, the correlation between the generation of smoke and the excess air ratio is very high, and the smaller the excess air ratio is, the more the smoke discharge increases. Since the lift speed or the maximum lift of the needle valve is switched, the excess air ratio can be accurately determined by following changes in weather conditions such as air pressure and temperature, or changes in supercharging pressure in transient engine conditions. This makes it possible to optimally control the ignitability of the spray even when the weather conditions such as the atmospheric pressure and the temperature are different, and even before the supercharging pressure rises transiently.

According to the fifth aspect of the present invention, even when the engine is cold, misfire can be suppressed without applying measures such as advancing the injection timing greatly, and a spray having good ignitability can be obtained. The supply can also suppress combustion noise and NOx emissions.

In each of the sixth and seventh aspects of the present invention, the needle valve is lifted at a high speed in the low-temperature premixed combustion region or the maximum lift of the needle valve is increased to obtain a spray having poor ignitability. Exhaust particulates and NO from low-temperature premix combustion
x, the effect of simultaneously reducing combustion noise can be enhanced, and the operating range in which low-temperature premix combustion can be performed can be expanded.

According to the eighth aspect, the needle valve is lifted at a low speed (or the maximum lift of the needle valve is reduced) under the same conditions of the engine speed and the fuel injection amount, and If both high-speed lift (or increase the maximum lift of the needle valve) occurs,
During the low-speed needle valve lift (or when the maximum lift is small), the injection period is not extended by increasing the pressure in the accumulator chamber than during the high-speed needle valve lift (or when the maximum lift is large). The gradient becomes steeper, and the injection period is shortened accordingly, whereby it is possible to suppress the smoke and the deterioration of exhaust particulates due to the injection period being extended with the low-speed lift of the needle valve (or the operation of reducing the maximum lift).

According to the ninth aspect of the invention, when the needle valve is lifted at a low speed or the maximum lift of the needle valve is reduced in a high load range or a high rotation range, smoke in an operating range which cannot be dealt with by an increase in the pressure of the accumulator or the like. And increase in emission of exhaust particulates can be prevented.

According to the tenth aspect, a spray having better ignitability can be obtained as compared with the case where a nozzle with a suck is used.

In the eleventh and twelfth inventions, the needle valve lift speed and the needle valve maximum lift are corrected so that the injection period does not change even when the actual accumulator pressure deviates from the target value.
It is possible to prevent any increase in smoke and emission of exhaust particles due to an increase in the injection period due to a decrease in the actual pressure of the accumulator, and to prevent deterioration of NOx and combustion noise due to a decrease in the injection period due to an increase in the pressure of the actual pressure.

A so-called pilot injection is performed by using an injector capable of controlling a needle valve lift speed or a maximum lift, and a so-called pilot injection is performed to supply HC required for NOx reduction to a NOx reduction catalyst provided in an exhaust passage. When performing post-injection, if the needle valve is lifted at a high speed or the maximum lift of the needle valve is increased in the minute injection amount region where the pilot injection or post-injection is performed, the sensitivity of the injection amount with respect to the needle valve lift time is increased. And it becomes difficult to control the injection amount with high accuracy.
According to the fourth aspect, such a problem can be prevented.

[0046]

FIG. 1 shows the configuration of a fuel supply system. The fuel supply pump 1 includes a plunger 3 that reciprocates by a cam 2 that is driven to rotate in synchronization with engine rotation.
As the plunger 3 reciprocates, fuel is sucked from the suction passage 4 and stored in the pressure accumulating chamber 7 via the check valve 5 and the discharge passage 6 in a high pressure state.

The suction passage 4 is provided with an effective stroke control valve 8 for the plunger 3, and when the effective stroke control valve 8 is closed during the compression stroke of the plunger 3, fuel pumping is started, and the pump discharge is accordingly performed. The amount is determined. The pressure accumulating chamber 7 is provided with a pressure sensor 9 for detecting a fuel pressure.
The high-pressure fuel in the accumulator 7 passes through the supply passage 10 and the injector 11
And injected from the nozzle into the cylinder of the engine.

A control unit 22 is provided for adjusting the fuel pressure of the accumulator 7, and the opening / closing timing of the effective stroke control valve 8 is controlled by a signal from the control unit 22 in accordance with the pressure detected by the pressure sensor 9. Then, the discharge amount of the fuel supply pump 1 is changed.

When the fuel is sucked, the effective stroke control valve 8
That is, when the plunger 3 is descending, it is opened, and when the plunger 3 is ascended to discharge fuel (compression stroke), it is closed by a necessary stroke, thereby controlling the fuel discharge amount. If the fuel pressure in the pressure accumulating chamber 7 drops below the target value, the pressure is recovered by increasing the effective stroke amount. Conversely, if the fuel pressure is high, the pressure can be reduced by decreasing the effective stroke amount.

The control unit 22 receives signals from a sensor 23 for discriminating the engine cylinder, a sensor 24 for detecting the engine speed, a crank angle, a sensor 25 for detecting the accelerator opening, and the like. A target pressure accumulation chamber pressure, a target fuel injection amount, and a target injection timing are searched based on the opening degree and the engine speed, and the opening / closing timing of the control valve 15 is determined so that the target fuel injection amount and the injection timing are obtained. At the same time, the opening / closing timing of the effective stroke control valve 8 is controlled so that the fuel pressure in the accumulator 7 becomes the target pressure.

FIG. 2 is a schematic sectional view of the fuel injection injector. The high-pressure fuel in the accumulator 7 is guided to the nozzle chamber 12 via the supply passage 10 and the supply passage 151 of the injector 11, and is guided to the pressure chamber 14 above the nozzle piston 13 via the charging orifice 18.

Reference numeral 15 denotes an actuator (piezo actuator) in which a valve 31 and a piezoelectric element are stacked in the needle valve lift direction.
The pressure receiving area of the nozzle piston 13 is set to be larger than the pressure receiving area of the needle valve 16. When the piezo actuator 32 is energized and the valve 31 is seated, the force in the valve closing direction applied to the nozzle piston 13 becomes larger than the force in the valve opening direction of the needle valve 16, the needle valve 16 is seated, and fuel is injected. Not done. When the energization to the piezo actuator 32 is stopped (the energization voltage value is set to 0) or the energization voltage is reduced, the piezo actuator 32 contracts and the valve 31 lifts.

In this case, when the energization voltage is lowered without stopping the energization, the lift of the valve 31 becomes small,
31 The discharge orifice
The same effect as when the diameter of 17 is reduced is produced. That is, since the pressure drop rate of the pressure chamber 14 decreases and the pressure of the pressure chamber 14 after the stabilization determined by the diameters of the filling orifice 18 and the discharge orifice 17 increases, the power supply is stopped (see the thick solid line in the lower part of FIG. 7). 7, the rising speed of the needle valve 16 becomes slower (see the thin solid line in the lower part of FIG. 7). At this time, when the comparison is made with the same injection amount, the injection period is longer than in the case where the energization is stopped.

As described above, by selectively switching the energizing voltage to the piezo actuator 32 from the seated state of the valve 31, the rising speed (lift speed) of the needle valve 16 can be controlled in two stages. Thus, the characteristic of the fuel injection rate shown in the upper part of FIG. 7 is obtained. That is, at the time of the needle valve high-speed lift, the gradient of the rise of the injection rate becomes steep, whereas at the time of the needle valve low-speed lift, the gradient of the rise of the injection rate becomes gentler than at the time of the needle valve high-speed lift. According to the accumulator-type fuel injection device of the present invention, by increasing the pressure of the accumulator at the time of the low-speed needle valve lift, it is possible to perform injection in the same injection period as at the time of the high-speed needle valve lift (broken line in FIG. 7). reference).

The present invention is not limited to the two-step control of the needle valve lift speed. By making it possible to control the energizing voltage to the piezo actuator 32 steplessly (the lower the energizing voltage to the piezo actuator 32 is, the higher the needle valve lift speed is), the needle valve lift speed can be controlled steplessly.

Here, the operation of the configuration of the present invention shown in FIGS. 1 and 2 will be described. The needle valve 16 is controlled by a piezo actuator 32 and a control unit 22 as a means for controlling a voltage applied to the piezo actuator 32. Of the needle valve 16
By spraying the needle valve at low speed, a spray having good ignitability can be obtained, and by lifting the needle valve at high speed, spray having poor ignitability can be obtained.

That is, while the needle valve lift speed is constant in the conventional accumulator type fuel injection device, the needle valve lift speed is configured to be controllable in the present invention. It is possible to reduce the size of the device and to switch the ignitability of the spray as compared with a case where the pressure-accumulation chamber type fuel injection device and the jerk type fuel injection device each having a constant value are independently provided.

Now, using the accumulator type fuel injection device having the structure shown in FIGS. 1 and 2, the smoke in the high load region is suppressed while suppressing the combustion noise and NOx emission in the operation region where smoke emission is not a problem. In order to suppress the emission, when a predetermined area map is searched from the engine speed and the fuel injection amount (corresponding to the engine load) to determine that the area is in a high load area, it is determined that the area is where smoke is generated, It is conceivable to perform switching control from a state in which the valve 16 lifts at a low speed to a state in which the needle valve 16 lifts at a high speed.

However, the region where smoke is generated does not always correspond to the operation region determined by the rotational speed and the fuel injection amount. In other words, since the mass flow rate of the intake air changes even if the rotation speed and the fuel injection amount are the same, the temperature, the atmospheric pressure, and the supercharging pressure when matching the above-described area maps are used. When used, there is a region where a spray having poor ignitability without smoke is generated, or a spray having good ignitability when smoke is generated.

To cope with this, the first embodiment of the present invention focuses on the fact that the correlation between the occurrence of smoke and the excess air ratio is extremely high, and regards the case where the excess air ratio is less than a predetermined value as the smoke generation region. Let me judge.

The details of the control executed by the control unit 22 will be described in detail with reference to the flowchart of FIG. 8. This control is executed at regular time intervals (or in synchronization with engine rotation).

First, in step 1, the engine speed Ne,
Accelerator opening Acc, EGR valve lift Legr, intake pressure Pi
nt, exhaust pressure Pexh, and intake air amount Qair are read.

Here, the EGR valve lift Legr, the intake pressure Pint, the exhaust pressure Pexh, and the intake air amount Qair are sensor detection values. For example, in FIG. 9, the overall configuration is shown. High-pressure fuel in the accumulator 7 is injected into a cylinder of the diesel engine 41 by an injector 11 provided in each cylinder. The intake passage 43 connected to the intake manifold 42 has an exhaust passage 44
The EGR passage 45 is connected to the EGR passage 45 and is controlled by an EGR valve 46 interposed therebetween so that the EGR amount becomes an optimum value according to the engine speed and the accelerator opening. In addition, a turbocharger 47 that pressurizes intake air using exhaust energy is provided. In this case, an intake pressure sensor 48 is provided in the intake passage 43, an exhaust pressure sensor 49 is provided in the exhaust passage 44, and E
A lift sensor (not shown) is provided for the GR valve 46, and an air flow meter 51 is provided downstream of the air filter 50.

Returning to FIG. 8, in step 2, a predetermined map is searched from the accelerator opening Acc and the engine speed Ne to determine the target fuel injection amount Qs.

In step 3, the excess air ratio λ is calculated as follows. First, since the EGR flow rate is obtained by the product of the square root of the differential pressure across the EGR valve and the effective area of the EGR valve,

[0066]

[Number 1] Qegr = f (Legr) × calculates the (Pexh-Pint) EGR flow rate Qegr by formula ^0-5.

Here, f (Legr) on the right side of Expression 1 is E
The effective area of the GR valve is experimentally obtained and is a function of the EGR valve lift Legr as shown in step 3 of FIG. 8 and is stored in the control unit in advance.

Next, since the oxygen concentration in the EGR gas is the same as the oxygen concentration in the exhaust gas,

[0069]

DO2egr = 0.21−Cl × Qs / (Qair / Ne) where 0.21: oxygen concentration of air Cl: oxygen concentration in the exhaust gas determined by the equation It is calculated as the density DO2egr.

Here, the second term on the right side of Expression 2 is the oxygen concentration consumed by combustion, and the oxygen concentration of air (21%)
By subtracting this value from the above, the oxygen concentration in the exhaust gas can be calculated.

Next, since the intake air is a mixture of fresh air and EGR gas, the oxygen amount QO2 in the intake air in which fresh air and EGR gas are mixed is determined.

[0072]

## EQU3 ## Calculated by the formula of QO2 = 0.21 × Qair + DO2egr × Qegr.

Here, the excess air ratio is the ratio of intake oxygen amount / fuel injection amount per cylinder, one cycle (two rotations).
Since it is proportional to ((2 × (QO2 / Ne)) / number of cylinders) / Qs,

[0074]

Λ = C2 × (QO2 / Ne) / Qs where the excess air ratio λ can be calculated by the equation of C2: proportionality constant.

The excess air ratio λ obtained in this manner is compared with a predetermined value in step 4, and when λ is equal to or larger than the predetermined value, the process proceeds to step 5, in which the needle valve 16 is lifted at a low speed (piezoelectric injection during fuel injection). When λ is smaller than a predetermined value, needle valve 16 is lifted at a high speed (power supply to piezo actuator 32 during fuel injection is stopped).

Here, since the smoke emission characteristics vary from engine to engine, a predetermined value for comparison with λ is set for each engine and according to the smoke emission level.

As described above, in the first embodiment of the present invention, the correlation between the generation of smoke and the excess air ratio λ is very high, and the smaller the excess air ratio λ is, the larger the smoke discharge is. The excess air ratio is calculated from the number, the target fuel injection amount, the EGR valve lift, the intake pressure, the exhaust pressure, and the intake air amount, and the needle valve lift speed is switched and controlled in accordance with the calculated excess air ratio (the excess air ratio is The needle valve is lifted at a low speed when the air pressure is equal to or more than a predetermined value, and the needle valve is lifted at a high speed when the excess air ratio is less than the predetermined air pressure. It is possible to accurately obtain the excess air ratio λ by following the change of the supercharging pressure in the air conditioner. Optimum spray ignitability It has become possible to Gosuru.

In the first embodiment, the excess air ratio λ is calculated using the engine speed, the target fuel injection amount, the EGR valve lift, the intake pressure, the exhaust pressure, and the intake air amount. The calculation method is not limited to this,
For example, <1> a method using an intake pressure sensor and an intake temperature sensor, and <2> a method using an air-fuel ratio sensor provided in an exhaust passage may be used.

To explain this, for simplicity, EGR
Think in case you do not do. At this time, the above equation 3 is QO
Since 2 = 0.21 × Qair,

[0080]

Λ = C2 × (QO2 / Ne) / Qs = C3 ×
(Qair / Ne) / Qs Here, in the case of <1>, the volume efficiency is determined by the engine speed Ne, and this volume efficiency is hardly affected by the intake pressure and the intake temperature. Therefore, the filling efficiency can be obtained by storing the relationship between the volume efficiency and the rotational speed in advance and correcting the volume efficiency with the intake pressure and the intake temperature. Since this filling efficiency is proportional to Qair / Ne,
Λ can be obtained by using equation (5).

In the case of <2>, the reciprocal of the air-fuel ratio detected by the sensor is proportional to λ.
Can be requested.

On the other hand, when performing EGR, <1>,
Also in the case of <2>, it is necessary to obtain and correct the EGR flow rate from Legr, Pexh, and Pint as described above.

Next, FIG. 10 is a flowchart of the second embodiment of the present invention.

Misfire is more likely to occur when the engine is cold than when the engine is completely warmed up. Therefore, in the second embodiment, when the engine is in a cold state, the needle valve is lifted at a low speed to suppress misfire, thereby supplying a spray having good ignitability.

More specifically, first, at step 11, the cooling water temperature Tw detected by the water temperature sensor is read, and this cooling water temperature Tw is compared with a predetermined value at step 12. Tw
Is less than the specified value (the engine is cold),
Proceed to step 13 to lift the needle valve at a low speed,
Is higher than a predetermined value (the engine is in a warm-up completed state), the routine proceeds to step 14, where the needle valve is lifted at a high speed.

As described above, in the second embodiment of the present invention,
It is determined whether the engine is in a cold state, and in the cold state of the engine, the needle valve is lifted at a low speed to suppress misfire, so that a spray that is more ignitable than in the warm-up completed state is supplied. Even when the engine is cold, misfires can be suppressed without applying measures such as significantly increasing the injection timing, and combustion noise and NOx emissions can be suppressed by supplying ignitable spray. .

The switching control of the needle valve lift speed shown in FIG. 8 may be performed instead of step 14 in FIG.

FIG. 11 is a control area diagram of the needle valve lift speed according to the third embodiment of the present invention. In this embodiment, switching control of the needle valve lift speed is performed based on the cooling water temperature (second embodiment). Is assumed.

According to the second embodiment, when the engine is cold, the needle valve is lifted at a low speed even in a high load range or a high rotation range. If the pressure is lifted, the injection period is prolonged, which causes smoke and the emission of exhaust particulates to deteriorate, and there is a limit in increasing the pressure of the accumulator.

Therefore, in the third embodiment of the present invention, the needle valve is constantly lifted at a high speed in the prohibition region with the high rotation region or the high load region as the prohibition region of the switching control of the needle valve lift speed. The control for switching the needle valve lift speed shown in FIG. 11 is performed in this permission region as the control permission region for the valve lift speed.

As described above, in the third embodiment of the present invention, it is prohibited to lift the needle valve at a low speed in a high load range or a high rotation range even when the engine is cold. In addition, when the needle valve is lifted at a low speed in a low engine speed and in a high engine speed region, it is possible to prevent an increase in smoke and an increase in the emission of exhaust particulates in an operating region that cannot be handled due to an increase in the pressure of the accumulator.

FIG. 12 is a map characteristic diagram of the fourth embodiment used for switching control of the needle valve lift speed. This embodiment is based on the assumption that low-temperature premix combustion is performed.

A method for performing low-temperature premixed combustion is known as a means for simultaneously suppressing NOx and combustion noise in addition to exhaust particulates (see Japanese Patent Application Laid-Open No. 7-4287). In addition to reducing the oxygen concentration in the intake air by performing the so-called EGR, the ignition delay period is set longer by setting the fuel injection timing to the vicinity of the compression top dead center and the fuel is completely injected during the ignition delay period. This can be achieved.

However, even if this low-temperature premixed combustion is attempted in a high load region, the excess air ratio becomes extremely small, and smoke is generated due to lack of oxygen.
Because of the large amount of fuel injection, it is difficult to terminate the injection of fuel during the ignition delay period. Therefore, the operation range in which low-temperature premix combustion can be performed is in the low rotation range and low load range (regions hatched in the figure). ).

In order to realize low-temperature premixed combustion, it is convenient that the ignition delay period is appropriately long. In the case of a spray having good ignitability obtained by lifting the needle valve at a low speed, the ignition delay period is short. Since it becomes shorter and it becomes difficult to inject all the fuel during the ignition delay period, the operating range where simultaneous reduction of exhaust particulates and NOx by low-temperature premixed combustion is narrowed.

Therefore, in the fourth embodiment of the present invention, FIG.
The needle valve is lifted at high speed so as to obtain a spray having poor ignitability in a region where low-temperature premix combustion is performed (low rotation region and low load region). Poor ignitability of the spray increases the ignition delay period, so that a large amount of fuel can be injected during the ignition delay period, and mixing and evaporation of the injected fuel is also promoted. NOx,
The effect of simultaneously reducing combustion noise is increased, and the operating range in which low-temperature premixed combustion can be realized is widened.

As described above, in the fourth embodiment of the present invention,
By raising the needle valve at high speed in the region where low-temperature premixed combustion is performed, a spray with poor ignitability is obtained, so the effect of simultaneous reduction of exhaust particulates, NOx, and combustion noise by low-temperature premixed combustion is improved. It is possible to expand the operation range where low-temperature premix combustion can be performed.

In the fourth embodiment, the generation of smoke is suppressed by lifting the needle valve at high speed even in a high load range or a high rotation range. When the region map of FIG. 12 is searched from the engine speed and the fuel injection amount to determine whether or not the vehicle is in a high load region or a high rotation region, and when the determined high load region or high rotation region is regarded as a smoke generation region, However, the above-described problem may occur. (When the temperature, the atmospheric pressure, and the supercharging pressure at the time of matching the area map of FIG. 12 are used, even if the area map of FIG. There is an area where the spray is inferior, or conversely, a spray is generated with good ignitability due to the generation of smoke.) However, when the area map in FIG. At the same time, no problem arises with such a configuration.

FIG. 13 is a characteristic diagram of the target accumulator pressure according to the fifth embodiment of the present invention.

While the engine speed and the fuel injection amount are the same, depending on the intake air amount and the cooling water temperature of the engine, both the state in which the needle valve is lifted at a low speed and the state in which the needle valve is lifted at a high speed are determined. May occur.

For example, when the intake air amount decreases, the excess air ratio decreases. Therefore, when the switching control of the needle valve lift speed is performed based on the excess air ratio (first embodiment),
Before the intake air amount was reduced under the same engine speed and fuel injection amount conditions, the needle valve was lifted at a low speed because the excess air ratio was equal to or higher than a predetermined value. When the rate falls below a predetermined value, the needle valve is lifted at a high speed. In addition, when the switching control of the needle valve lift speed is performed based on the cooling water temperature (second,
In the third embodiment), the needle valve is lifted at a low speed when the engine is cold under the same engine speed and fuel injection amount conditions. When this happens, the needle valve will be lifted at high speed.

In this case, if the accumulator pressures are equal,
When the needle valve is lifted at a low speed, the injection period is extended, which leads to an increase in smoke and exhaust particulates (see FIG. 7).

Therefore, in the fifth embodiment, as shown in FIG. 13, the target accumulator pressure is set to be higher when the needle valve is lifted at a low speed than when the needle valve is lifted at a high speed. It is set.

As described above, in the fifth embodiment of the present invention,
When both the state where the needle valve is lifted at low speed and the state where the needle valve is lifted at high speed occur under the same conditions of the engine speed and the fuel injection amount, the needle valve high speed By increasing the pressure of the accumulator from the time of the lift to prevent the injection period from extending, the slope of the injection rate rises steeply and the injection period is shortened, and the injection period is thereby shortened with the low-speed lift of the needle valve. It is possible to suppress smoke and deterioration of exhaust particulates due to the extension.

As shown by the dashed line in FIG. 7, in comparison with the case where the injection periods are made equal, the needle valve is more lifted than when the needle valve is lifted at a high speed without increasing the pressure of the accumulator (see the thick solid line). When the needle valve is lifted at a low speed without increasing the pressure of the pressure accumulator, because the atomization of the spray is promoted in a region where the needle valve lift is low, because the pressure is increased at a low speed and the pressure of the pressure accumulator is increased. It is possible to supply a spray having better ignitability than (see the thin solid line).

In each of the five embodiments described above,
By using the above-mentioned VCO type nozzle, the effect when the needle valve is lifted at a low speed is enhanced. This is because the velocity vector on the plane perpendicular to the nozzle orifice is larger than that of the sack-equipped nozzle, and the ignitability of the spray during the needle valve low-speed lift is higher.

FIG. 14 is a flowchart of the sixth embodiment of the present invention.

When the actual pressure of the accumulator becomes lower than the target value, the injection period is extended, thereby increasing the amount of smoke and the amount of exhaust fine particles. Conversely, when the actual accumulator pressure becomes higher than the target value, NOx and combustion noise deteriorate.

In this embodiment, the needle valve lift speed is corrected when the actual pressure of the accumulator deviates from the target value by a predetermined value or more.

More specifically, in step 21, the engine speed Ne and the accelerator opening Acc are read, and in step 22, the actual accumulator pressure Pri detected by the sensor 9 is read, and the engine speed Ne and the accelerator opening Acc are calculated from these values. Step 2
In step 3, the target fuel injection amount Qs is searched, and based on the target fuel injection amount Qs and the engine speed Ne, step 2 is executed.
In step 4, the target pressure accumulation chamber pressure Prs is searched.

In steps 25 and 26, the actual pressure in the accumulator chamber Pri
And a predetermined value is compared with the difference between the target accumulator pressure Prs and the actual accumulator pressure Prs. If the actual accumulator pressure Pri is greater than or equal to the target accumulator pressure Prs by a predetermined value or more, the routine proceeds to step 28, where the needle valve lift speed is corrected to a lower speed.

Here, the needle valve lift speed is corrected by controlling the voltage applied to the piezo actuator 32. However, in each of the first to fifth embodiments, two-stage switching is performed to stop energization of the piezo actuator 32 or to reduce the energization voltage, whereas in the sixth embodiment, the piezo actuator 32 The voltage that can be applied to the power supply is controlled steplessly. According to the injector that can control the energization voltage steplessly, the needle valve lift speed increases as the energization voltage to the piezo actuator 32 decreases, so that the needle valve lift speed needs to be corrected to the higher side. To reduce the current supply voltage up to that point by a predetermined value and conversely correct the needle valve lift speed to a lower side, the current supply voltage up to that point is raised by a predetermined value.

As described above, in the sixth embodiment of the present invention, the needle valve lift speed is corrected so that the injection period does not change even when the actual accumulator pressure deviates from the target value. Accordingly, it is possible to prevent any increase in smoke and emission of exhaust particulate due to an increase in the injection period, or deterioration of NOx and combustion noise due to a decrease in the injection period due to an increase in the actual pressure of the accumulator.

By the way, the injector 11 shown in FIGS. 1 and 2 is used to perform a so-called pilot injection for injecting a small amount of fuel prior to the main injection of the fuel in order to reduce combustion noise and NOx, or to perform an exhaust passage. In order to supply HC required for NOx reduction to the NOx reduction catalyst provided in the above, so-called post-injection in which a small amount of fuel is injected in a later stage of a combustion stroke or an exhaust stroke can be performed. When the needle valve 16 is lifted at a high speed in the minute injection amount region where the post injection is performed, the sensitivity of the injection amount with respect to the piezo actuator operation time increases, and it becomes difficult to control the injection amount with high accuracy.

Therefore, in the seventh embodiment, when performing pilot injection or post-injection using an injector capable of variably controlling the needle valve lift speed, the needle valve is lifted at a low speed to solve such a problem. To prevent

When it is desired to inject the main injection fuel in a short period of time, the needle valve can be lifted at a high speed by the main injection after the pilot injection, so that the injection can be performed in a short period.

FIG. 15 is a schematic sectional view of an injector 11 according to an eighth embodiment of the present invention, and corresponds to FIG. 2 of the first embodiment. 2 are given the same reference numerals.

The injector 11 shown in FIG. 15 is configured such that the needle valve 16 is directly driven by the piezo actuator 61. In such an injector 11, when the energization voltage to the piezo actuator 61 is reduced during fuel injection, the maximum lift of the needle valve 16 is smaller than when the energization is stopped. That is, the maximum lift of the needle valve 16 changes in two stages.

Therefore, in the eighth embodiment, the injector 11 capable of controlling the maximum lift of the needle valve 16 in two stages is used, and in each of the first to seventh embodiments described above, the needle valve 16 is used.
So that the maximum lift of the needle valve 16 is reduced under the condition that the needle valve 16 is lifted at a low speed, and the maximum lift of the needle valve 16 is increased under the condition that the needle valve 16 is lifted at a high speed. By controlling the energizing voltage,
The same operation and effect as those of the first to seventh embodiments can be obtained.

In the embodiment, the VCO type nozzle in which the nozzle orifice is closed by the needle valve when the needle valve is seated has been described.
A nozzle with a sack may be used.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a fuel supply system according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of an injector.

FIG. 3 is a cross-sectional view of a tip portion of a VCO type nozzle.

FIG. 4 is a diagram showing a fuel flow velocity distribution in an injection hole of an ideal nozzle.

FIG. 5 is a view taken along line AA of FIG. 3;

FIG. 6 is a view taken along line BB and CC of FIG. 5;

FIG. 7 is a characteristic diagram of a needle valve lift and a fuel injection rate.

FIG. 8 is a flowchart of a control operation according to the first embodiment.

FIG. 9 is a schematic configuration diagram showing the entire configuration of the first embodiment.

FIG. 10 is a flowchart of a control operation according to the second embodiment.

FIG. 11 is a region diagram of a needle valve speed according to a third embodiment.

FIG. 12 is a region diagram of a needle valve speed according to a fourth embodiment.

FIG. 13 is a characteristic diagram of a target accumulator pressure according to the fifth embodiment.

FIG. 14 is a flowchart of a control operation according to a sixth embodiment.

FIG. 15 is a schematic cross-sectional view of a fuel injection injector according to an eighth embodiment.

FIG. 16 is a schematic cross-sectional view of a conventional injector of the accumulator type fuel injection device.

FIG. 17 is a diagram corresponding to claims of the third invention.

FIG. 18 is a diagram corresponding to claims of the fourth invention.

FIG. 19 is a diagram corresponding to a claim of the fifth invention.

FIG. 20 is a diagram corresponding to a claim of the sixth invention.

FIG. 21 is a view corresponding to a claim of the eighth invention.

FIG. 22 is a view corresponding to a claim of the ninth invention.

FIG. 23 is a view corresponding to claims of the eleventh invention.

FIG. 24 is a view corresponding to claims of the twelfth invention.

[Explanation of symbols]

 1 Fuel supply pump 7 Fuel accumulator 11 Injector 15 Control valve 16 Needle valve 22 Control unit 32 Piezo actuator 61 Piezo actuator

Continued on front page F-term (reference) DC18 DC19 3G301 HA02 HA06 HA13 JA23 JA24 JA25 KA09 KA25 LB12 LB17 LC01 LC05 MA15 MA27 NC02 ND03 ND04 NE01 NE06 PA01Z PA07Z PB03A PB08Z PD14Z PD15Z PE01Z PE05Z PE08Z PF03Z

Claims (14)

[Claims] A pump for supplying fuel, a pressure accumulating chamber for storing the supplied fuel in a high pressure state, a fuel supply from the pressure accumulating chamber being received by a nozzle chamber, a needle valve being lifted to open a nozzle seat portion. A fuel injection device for a diesel engine, comprising: an injector for injecting fuel from an injection hole at a nozzle tip, wherein the lift speed of the needle valve or the maximum lift of the needle valve is configured to be controllable. Fuel injection device. 2. The fuel injection device for a diesel engine according to claim 1, wherein the nozzle has a shape in which the needle valve covers the injection hole inlet when the needle valve is seated. 3. A pump for supplying fuel, a pressure accumulating chamber for storing the supplied fuel in a high pressure state, and a fuel supply from the pressure accumulating chamber. An injector that injects fuel from an injection hole and controls the lift speed of the needle valve or the maximum lift of the needle valve; a means for determining whether the engine is in a high load range and a high rotation range; The needle valve lifts at a high speed in a high speed range and a high rotation range or the maximum lift of the needle valve increases, and the needle valve lifts at a low speed in a high load range and a region other than the high rotation range, or Means for controlling the injector such that the maximum lift of the needle valve is reduced. 4. A pump for supplying fuel, a pressure accumulating chamber for storing the supplied fuel in a high pressure state, and a fuel supply from the pressure accumulating chamber. An injector for injecting fuel from the injection hole and controlling the lift speed of the needle valve or the maximum lift of the needle valve, a means for directly or indirectly detecting the excess air ratio of the engine, and the detected excess air The needle valve lifts at a low speed when the rate is equal to or more than a predetermined value or the maximum lift of the needle valve decreases, and when the excess air rate is less than a predetermined value, the needle valve lifts at a high speed. Or means for controlling the injector so that the maximum lift of the needle valve is increased. 5. A pump for supplying fuel, a pressure accumulating chamber for storing the supplied fuel in a high pressure state, and a fuel supply from the pressure accumulating chamber. An injector that injects fuel from the injection holes and controls the lift speed of the needle valve or the maximum lift of the needle valve, a means for detecting the temperature of the engine coolant, and a device for detecting the coolant temperature below a predetermined value. Means for controlling the injector such that the needle valve lifts at a low speed or the maximum lift of the needle valve decreases. 6. A pump for supplying fuel, a pressure accumulating chamber for storing the supplied fuel in a high pressure state, and a fuel supply from the pressure accumulating chamber. An injector that injects fuel from the injection holes and controls the lift speed of the needle valve or the maximum lift of the needle valve, a means for controlling the combustion speed, and a method for reducing the combustion speed using this control means under some operating conditions. Means for performing low-temperature premixed combustion by terminating the fuel injection within the ignition delay period; means for determining whether or not the low-temperature premixed combustion area; and Means for controlling the injector so that the needle valve lifts at a high speed or the maximum lift of the needle valve increases. . 7. The diesel engine control device according to claim 6, wherein the means for controlling the combustion speed is means for controlling an EGR amount. 8. A pump for supplying fuel, a pressure accumulating chamber for storing the supplied fuel in a high pressure state, a fuel supply from the pressure accumulating chamber, and a needle valve lifts to open the nozzle seat when the needle valve is lifted to open the nozzle seat. An injector that injects fuel from an injection hole and controls a lift speed of the needle valve or a maximum lift of the needle valve, and a unit that controls the injector in accordance with a request for the needle valve lift speed or the needle valve maximum lift. If a different request is made for the needle valve lift speed or the needle valve maximum lift under the same engine speed and fuel injection amount conditions, the needle valve lifts at a low speed or the needle valve The target pressure is higher when controlling the lift to be smaller than when controlling the needle valve to lift at a high speed or to increase the maximum lift of the needle valve. A control device for a diesel engine, comprising: means for setting the chamber pressure high; and means for controlling the pressure of the pressure storage chamber so as to attain the target pressure of the pressure storage chamber set high. 9. A pump for supplying fuel, a pressure accumulating chamber for storing the supplied fuel in a high pressure state, a fuel supply from the pressure accumulating chamber, and a needle valve lifts to open the nozzle seat when the needle valve lifts to open the nozzle seat. An injector that injects fuel from an injection hole and controls the lift speed of the needle valve or the maximum lift of the needle valve, means for determining whether the engine is in a high load range or a high rotation range, and the determined high load Control means for controlling the injector such that the needle valve lifts at a high speed in a high speed range or a high rotation range or a maximum lift of the needle valve is increased. 10. The diesel engine control device according to claim 3, wherein the nozzle has a shape in which the needle valve covers the injection hole inlet when the needle valve is seated. 11. A pump for supplying fuel, a pressure accumulating chamber for storing the supplied fuel in a high pressure state, and a fuel supply from the pressure accumulating chamber. An injector that injects fuel from an injection hole and that can control the lift speed of the needle valve or the maximum lift of the needle valve; a means for setting the needle valve lift speed or the needle valve maximum lift in accordance with operating conditions; Means for detecting the fuel pressure in the accumulator, and when the detected accumulator pressure is greater than the target value by a predetermined value or more, the needle valve lift speed under the operating conditions at that time is decreased or at that time Means for correcting the needle valve maximum lift to a side that reduces the needle valve maximum lift under the operating conditions of: and means for controlling the injector so that the corrected needle valve lift speed or needle valve maximum lift is obtained. Control device for a diesel engine, characterized by comprising. 12. A pump for supplying fuel, a pressure accumulating chamber for storing the supplied fuel in a high pressure state, and a fuel supply from the pressure accumulating chamber. An injector that injects fuel from an injection hole and that can control the lift speed of the needle valve or the maximum lift of the needle valve; a means for setting the needle valve lift speed or the needle valve maximum lift in accordance with operating conditions; Means for detecting the fuel pressure of the accumulator, and when the detected accumulator pressure is smaller than the target value by a predetermined value or more, the needle valve lift speed under the operating condition is increased or the operating condition is increased. Means for correcting the needle valve maximum lift to a larger side, and means for controlling the injector such that the corrected needle valve lift speed or needle valve maximum lift is provided. Control device for a diesel engine characterized. 13. The needle valve according to claim 3, wherein a small amount of fuel is injected before the main injection of the fuel, the needle valve is lifted at a low speed or the maximum lift of the needle valve is reduced. The control device for a diesel engine according to any one of the above. 14. When a small amount of fuel is injected in a later stage of a combustion stroke or an exhaust stroke to supply HC necessary for NOx reduction to a NOx reduction catalyst provided in an exhaust passage.
14. The valve according to claim 3, wherein the needle valve is lifted at a low speed or the maximum lift of the needle valve is reduced.
The control device for a diesel engine according to any one of the above.