JPH025710A - Fuel injection device for direct injection diesel engine - Google Patents

Abstract

PURPOSE:To aim at smoke reduction by providing a pilot nozzle and a multiple nozzle hole type main nozzle and directing the injecting direction of the pilot nozzle to the neighborhood of the main nozzle between main nozzle injection holes. CONSTITUTION:A pilot nozzle 11 and a multiple nozzle hole type main nozzle 12 are provided at a combustion chamber 4. The injecting direction of the pilot nozzle 11 is directed to the neighborhood of the main nozzle between the injection nozzles of the main nozzle 12. At the time of high load, a pilot injection time and a main injection time are overlapped each other. At this time, fuel atomizing from the pilot nozzle does not overlap fuel atomizing from the main nozzle. Accordingly, air utilization factor is improved to be able to reduce the generation of smoke.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection device for a direct injection diesel engine, and particularly to an improvement in a fuel injection device for performing so-called pilot injection.

(Prior art) Conventionally, as a fuel injection device for a direct injection diesel engine,
For example, as disclosed in Japanese Unexamined Patent Publication No. 59-165856, a plurality of plunger-type fuel injection pumps are provided for each cylinder, and these fuel injection pumps are connected to a nozzle. By forming the cam shape appropriately, the pump can be used only for pilot injection, and when the load is low,
It is known that the pilot injection-only pump performs pilot injection from the nozzle, and another pump performs main injection following the pilot injection from the nozzle. If the pilot injection is performed before the main injection in this manner, the ignitability of the main injected fuel can be improved by combustion of a small amount of the pilot injected fuel.

(Problem to be solved by the invention) By the way, if pilot injection is performed even under high load, the fuel injection amount will increase and the swirl will become stronger at high load, so the fuel spray from the pilot nozzle and the main nozzle will be different. There are reports that the air-fuel mixture overlaps with the fuel spray, causing the air-fuel mixture to become locally overrich, resulting in poor air utilization and increased smoke.

The present invention has been made in view of the above, and its purpose is to improve the ignition performance at low loads by pilot injection, while also reducing the amount of fuel spray from the pilot nozzle and the fuel spray from the main nozzle during combustion. The objective is to improve the air utilization efficiency by preventing the two from overlapping each other, and to prevent smoke from increasing even when pilot injection is performed under high load.

(Means for Solving the Problems) In order to achieve the above object, the present invention directs the injected fuel from the pilot nozzle to the vicinity of the main nozzle where fuel injected from the main nozzle is difficult to diffuse, and when the load is high, the fuel injected from the pilot nozzle The fuel injection timing of the main nozzle and the fuel injection timing of the main nozzle should not be separated from each other.

Specifically, the solution taken by the present invention is to provide a pilot nozzle and a multi-nozzle main nozzle facing the combustion chamber in which a swirl is formed, and to supply fuel to the pilot nozzle and the main nozzle. The present invention is based on a fuel injection system for a direct injection diesel engine, which is equipped with a fuel injection pump and performs fuel injection by pilot injection from a pilot nozzle and main injection from a main nozzle.

In response to this, the fuel injection direction from the pilot nozzle is directed to the vicinity of the main nozzle between the main nozzle nozzle holes, and a load detection means for detecting the load of the engine, and receiving the output of the load detection means, The fuel injection pump is configured to include a control means for controlling the fuel injection pump so that the pilot injection timing is delayed during load so that the pilot injection period overlaps with the main injection period.

(Function) With the above configuration, in the present invention, not only pilot injection is performed at low load to improve ignition performance, but also pilot injection is performed at high load to improve output.

In that case, since the fuel injection direction from the pilot nozzle is directed to the vicinity of the main nozzle between the main nozzle nozzle holes, the fuel injected from the pilot nozzle is directed to the vicinity of the main nozzle where fuel injected from the main nozzle is difficult to diffuse.
During combustion, the fuel spray from the pilot nozzle and the fuel spray from the main nozzle do not overlap, improving the air utilization rate during high loads and reducing smoke.

Moreover, when the engine has a high load detected by the load detection means, the control means controls the fuel injection pump to delay the pilot injection timing so that the pilot injection period overlaps with the main injection period, so that the fuel spray from the pilot nozzle The fuel is injected from the main nozzle before it has yet diffused, which reliably prevents fuel spray from both nozzles from overlapping, further improving air utilization under high loads and reducing smoke.

(Example) Embodiments of the present invention will be described below based on the drawings.

1 and 2 show a four-cylinder direct injection diesel engine equipped with a fuel injection device according to a first embodiment of the present invention. In these figures, 1 is an engine, cylinders 2, 2... are formed in the engine 1, and a piston 3 is slidably fitted into each cylinder 2, and the piston 3 forms a combustion chamber 4 within the cylinder 2. Further, the engine 1 is provided with an intake port 5 for supplying fresh air to each combustion chamber 4 and an exhaust boat 6 for discharging exhaust gas from each combustion chamber 4. The intake boat 5 is formed at a swirl port to form a swirl in the combustion chamber 4. Further, an intake valve 7 for opening and closing the intake port 5 is provided at the opening of the intake boat 5 to the combustion chamber 4, and an exhaust valve 8 for opening and closing the exhaust port 6 is provided for the opening of the exhaust boat 6 to the combustion chamber 4. Each is provided.

Further, the engine 1 is provided with a single-hole pilot nozzle 11 and a multi-hole (for example, four-hole) main nozzle 12 facing each combustion chamber 4 for each cylinder 2. The pilot nozzle 11 and the main nozzle 12 are each connected to a fuel injection pump 20 via a high pressure pipe 26.

As shown in FIG. 2, the fuel injection pump 20 includes a number of plungers 21, 21, . . . corresponding to the number of pilot nozzles 11 and main nozzles 12. A drive shaft 22 driven by the engine is pivotally supported on the fuel injection pump 20, and the drive shaft 22 includes pilot injection cams 23, 23, etc. as shown in FIG.
・Main injection cam 24.24・as shown in Fig. 4
... is formed, and each pilot injection cam 2
3 drives the plunger 21 connected to the pilot nozzle 11 to forcefully feed fuel to the pilot nozzle 11, and the main injection cam 24 drives the plunger 21 connected to the pilot nozzle 11.
main nozzle 1 by driving plunger 21 connected to main nozzle 1.
The fuel is pumped to 2. Further, each of the high-pressure pipes 26 of the pilot nozzle 11 is provided with a high-speed electromagnetic valve 27, and fuel injection is performed by the pilot by force-feeding fuel to the pilot nozzle 11 only when the high-speed electromagnetic valve 27 is open. This is carried out by a pilot injection from the nozzle 11 and a main injection from the main nozzle 12 following the pilot injection. Note that 25 is a timer provided on the drive shaft 22 for adjusting the fuel injection timing. Each plunger 21, timer 25 and high-speed solenoid valve 27 are connected to the control unit 3.
Controlled by 0.

Furthermore, 31 is a needle valve lift sensor provided in the pilot nozzle 11 and detects the lift of the needle valve, 32 is a needle valve lift sensor provided in the main nozzle 12 and detects the lift of the needle valve, and 33 is a needle valve lift sensor provided in the main nozzle 12 to detect the lift of the needle valve. 34 is an accelerator opening sensor serving as a load detection means for detecting the engine load based on the accelerator opening; 35 is a water temperature sensor provided in the water jacket of the engine 1 and detects the cooling water temperature; 36 is the engine 1; a crank angle sensor 37 for detecting the top dead center position of each cylinder 2;
38 is an ignition sensor that detects ignition in the combustion chamber 4; 38 is an intake sensor that is installed in the intake passage and detects intake air temperature; 39
is an atmospheric pressure sensor that detects atmospheric pressure. Output signals from each of these sensors 31 to 39 are input to the control unit 30. Thus, the control unit 30 controls the fuel injection amount, fuel injection rate, and fuel injection timing of pilot injection and main injection, respectively, depending on the operating state of the engine.

Further, as shown in FIG. 5, the main nozzle 12 is arranged slightly offset from the center of the combustion chamber 4.

The volumes of the combustion chambers between the nozzle holes are equalized to prevent fuel spray from each nozzle hole from overlapping. Further, the pilot nozzle 11 is arranged slightly apart from the main nozzle 12. The fuel injection direction t1 from the pilot nozzle 11 is set so as to direct toward the vicinity of the main nozzle 12 between the main nozzle 12 nozzle holes beyond the fuel injected from a specific nozzle hole of the main nozzle 12 (fuel injection direction T+). There is.

Next, to explain the operation control of the control unit 30, when the engine is under low load, pilot injection is performed from the pilot nozzle 11 as shown in FIG. Fuel is injected from each nozzle hole. Since the pilot injection is performed in this way, the ignition performance at low loads is improved and HC is reduced.

On the other hand, when the engine is under high load, the pilot injection period is delayed and overlapped with the main injection period so that the pilot injection period is completely included in the main injection period, as shown in FIG.

In this way, pilot injection is performed not only when the engine is under low load, but also when the engine is under high load, so it is possible to improve the output under high loads, and to prevent carbon from adhering to the pilot nozzle 11 and causing clogging. be able to.

In that case, since the fuel injection direction from the pilot nozzle 11 is directed to the vicinity of the main nozzle 12 between the main nozzle 12 nozzle holes, the fuel injected from the pilot nozzle 11 and the fuel injected from the main nozzle 12 are difficult to diffuse into the main nozzle. Pilot nozzle 1 faces toward the vicinity of nozzle 12 during combustion.
Since the fuel spray from the main nozzle 1 and the fuel spray from the main nozzle 12 do not overlap, the air utilization rate during high loads is improved and smoke is reduced.

Moreover, when the engine has a high load detected by the accelerator opening sensor 34 (load detection means), the fuel injection pump 20 is controlled so that the pilot injection timing is delayed so that the pilot injection period overlaps with the main injection period. Fuel is injected from the main nozzle 12 before the fuel spray from the nozzle 11 is diffused, and overlapping with the fuel spray from both nozzles 11 and 12 is reliably prevented, thereby improving the air utilization rate during high loads. Further improvement and smoke reduction.

In that case, the fuel injection direction t1 from the pilot nozzle 11 is different from the fuel injection direction t1 from the specific nozzle hole of the main nozzle 12 (
The fuel injection period is set so as to be oriented near the main nozzle 12 between the main nozzle 12 nozzle holes across the fuel injection direction T+), and the pilot injection period is set so as to be completely included in the main injection period. Since the fuel spray from the pilot nozzle 11 and the fuel spray from the main nozzle 12 are combined, the fuel spray is at t2, which is approximately halfway between the fuel injection directions T1 and tl.
I will be heading to

This control unit 30 controls the load detection means (
The control means receives the output of the accelerator opening sensor 34) and controls the fuel injection pump 20 so that the pilot injection period is overlapped with the main injection period by delaying the pilot injection timing when the load is high.

Furthermore, FIGS. 8 and 9 show a second embodiment. In the first embodiment, when the pilot injection period is overlapped with the main injection period at high load, the pilot injection period is completely included in the main injection period.
In this embodiment, as shown in FIG. 9, the second half of the pilot injection period is set to span the main injection period.

As a result, in the first half of the pilot injection period, the fuel spray from the pilot nozzle 11 is directed in the fuel injection direction t1 without being influenced by the fuel spray from the main nozzle 12,
In the second half of the pilot injection period, the fuel injection direction is directed to t2, which is approximately halfway between the fuel injection directions T1 and tl, as in the first embodiment. As a result, the fuel spray from the pilot nozzle 11 is effectively diffused in the vicinity of the main nozzle 12, and the fuel spray from the pilot nozzle 11 and the fuel spray from the main nozzle 12 are prevented from overlapping, and the fuel spray from the pilot nozzle 11 and the fuel spray from the main nozzle 12 are prevented from overlapping. Improves air utilization and reduces smoke.

Further, FIG. 10 shows a third embodiment. In this embodiment, the pilot nozzle 11 is arranged at the end of the combustion chamber 4, and the fuel injection direction t1 from the pilot nozzle 11 is directed to the vicinity of the main nozzle 12 between the nozzle holes of the main nozzle 12 and in a direction opposite to the swirl. This is the setting. Figures 11 and 12 show the injection timing and injection period at low load, and the injection timing at high load, respectively.
Indicates injection period.

Furthermore, FIG. 13 shows a fourth embodiment. In this embodiment, the pilot nozzle 11 is arranged at the end of the combustion chamber 4 as in the third embodiment, and the fuel injection direction t1 from the pilot nozzle 11 is directed to the vicinity of the main nozzle 12 between the nozzle holes of the main nozzle 12. It is set in the direction along the swirl.

(Effects of the Invention) As described above, according to the fuel injection device for a direct injection diesel engine of the present invention, the fuel injection direction from the pilot nozzle is directed to the vicinity of the main nozzle between the main nozzle nozzle holes, and By controlling the fuel injection pump so that the pilot injection period overlaps with the main injection period, the pilot injection timing is delayed and the fuel injection pump is controlled so that the pilot injection period overlaps with the main injection period. This improves ignition performance at low loads, and also reduces the amount of fuel spray from the piston nozzle during combustion. By preventing the fuel spray from the main nozzle from overlapping with each other, it is possible to improve the air utilization rate and reduce smoke during high loads.

[Brief explanation of the drawing]

1 to 7 illustrate a first embodiment of the present invention, FIG. 1 is an overall schematic explanatory diagram, FIG. 2 is a side view including a partial cross section of the fuel injection pump, and FIG. 3 is a pilot injection Figure 4 is a characteristic diagram of the cam for main injection, Figure 5 is an explanatory diagram showing the direction of fuel injection from the pilot nozzle and the direction of fuel injection from the main nozzle, and Figure 6 is an illustration of the characteristics of the cam for main injection. An explanatory diagram showing the main nozzle fuel injection timing, fuel injection period, and pilot nozzle fuel injection timing, fuel injection period during low load, and Fig. 7 shows the main nozzle fuel injection timing, fuel injection period, and fuel injection period during high engine load. It is an explanatory view showing fuel injection timing of a pilot nozzle, and a fuel injection period. 8 is a diagram corresponding to FIG. 5 in the second embodiment, and FIG. 9 is a diagram corresponding to FIG. 7 in the second embodiment. 10th
The figure is a diagram corresponding to Figure 5 in the third embodiment, and Figure 11 is a diagram equivalent to Figure 5 in the third embodiment.
FIG. 6 is a diagram corresponding to the embodiment, and FIG. 12 is a diagram corresponding to FIG. 7 in the third embodiment. FIG. 13 is a diagram corresponding to FIG. 5 in the fourth embodiment. 4... Combustion chamber, 11... Pilot nozzle, 12.
・・Main nozzle, 20・・Fuel injection pump, 30・
...Control unit (control means), 34...Accelerator opening sensor (load detection means).

Claims (1)

[Claims] (1) A pilot nozzle and a multi-nozzle main nozzle are provided facing the combustion chamber where a swirl is formed, and a fuel injection pump is provided to supply fuel to the pilot nozzle and the main nozzle, and the fuel injection is performed in a pilot manner. In a fuel injection device for a direct injection diesel engine that performs pilot injection from a nozzle and main injection from a main nozzle, the fuel injection direction from the pilot nozzle is directed to the vicinity of the main nozzle between the main nozzle nozzle holes, and , a load detection means for detecting the load of the engine, and a control means for receiving the output of the load detection means and controlling the fuel injection pump so that the pilot injection period is delayed so that the pilot injection period overlaps the main injection period when the load is high. A fuel injection device for a direct injection diesel engine, characterized by comprising: