JP2552348Y2 - Diesel engine fuel injection system - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for a diesel engine which injects fuel into a combustion chamber and supplies the fuel.

[0002]

2. Description of the Related Art Normally, one cylinder of a diesel engine is provided with one injection nozzle, and fuel is injected into a fuel chamber from an injection hole of the injection nozzle. The injected fuel is heated by the compression heat of the air in the combustion chamber and self-ignites and burns.
It is greatly affected by the particle size of the fuel spray and the quality of the mixture of air and fuel, and affects the performance of the engine.

[0003] The particle size of the fuel spray is affected by the speed and temperature of fuel injection from the injection nozzle, and the fuel injection speed is determined by the injection pressure and the diameter of the injection hole.

[0004]

Since the size of the injection hole of the injection nozzle is determined based on the maximum injection amount of fuel supplied to the combustion chamber, when the diesel engine is in the idling operation range. In this case, the injection hole becomes too large compared to the fuel injection amount.
For this reason, in the idling operation range, the amount of premixed fuel mixed with air increases before the ignition of the fuel. As a result, when the injected fuel ignites thereafter, the fuel burns rapidly, and the combustion noise, that is, the combustion noise during idling operation becomes large.

[0005] For this reason, it is conceivable to narrow the injection hole of the injection nozzle, in this case, the maximum output point, etc.
In the high-speed high-speed range , the maximum injection amount cannot be injected within a predetermined injection period, so that the required maximum output cannot be secured. The present invention has been made based on the above-described circumstances, and an object of the invention is to provide a diesel engine fuel capable of securing the required maximum output and reducing combustion noise in an idle operation range. An object of the present invention is to provide an injection device.

[0006]

According to the present invention, a fuel injection device for a diesel engine includes a first injection nozzle for injecting fuel into a combustion chamber of one cylinder when the engine is in an operation range other than an idle operation range; A second injection nozzle for injecting fuel into the combustion chamber when the engine is in an idle operation range, wherein the second injection nozzle has an injection hole area smaller than the injection hole area of the first injection nozzle; And a nozzle needle whose lift amount is small and limited.

[0007]

According to the fuel injection device described above, when the diesel engine is in the idling operation range, the second injection nozzle is opened with the lift of the nozzle needle kept small, and the second injection nozzle is opened from the small injection hole. Fuel is injected. On the other hand, when the diesel engine is in an operation range other than the idle operation range, fuel is injected from the large injection hole of the first injection nozzle. Therefore, the fuel injection device according to the present invention has the first and second fuel injection devices according to the operating condition of the engine.
The proper use of the injection nozzle will be performed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG.
Part of one cylinder is shown. This diesel engine includes a cylinder block 1, and a cylinder bore 2 is formed in the cylinder block 1. A piston 4 is slidably fitted to the cylinder bore 2 via a cylinder liner 3, and a combustion chamber 6 is defined between the top surface of the piston 4 and the cylinder head 5. In this embodiment, an annular recess 7 is formed on the top surface of the piston 4 as shown.

A first injection nozzle 8 is attached to the cylinder head 5 such that a front end thereof faces the combustion chamber 6. The front end of the first injection nozzle 8 is located substantially at the center of the combustion chamber 6. It is positioned. Furthermore, a second injection nozzle 9 is attached to the cylinder head 5 in the vicinity of the first injection nozzle 8, and the tip of the second injection nozzle 9 also faces the combustion chamber 6.

In this embodiment, the first and second injection nozzles 8 and 9 are connected to respective fuel injection pumps via solenoid valves 20 to supply high-pressure fuel sent from the fuel injection pumps. In response, the fuel is injected into the combustion chamber 6. The solenoid valve 20 is composed of a direction switching valve, and its switching operation is controlled by a controller 21. The controller 21 has a load sensor 22 for detecting a load on the diesel engine and a rotational speed of the diesel engine. The rotational speed sensors 23 to be detected are respectively connected.

The first and second injection nozzles 8, 9 are of the hole type as shown in FIG. 2, and their structures are substantially the same. That is, each injection nozzle is configured by slidably fitting a nozzle needle 11 in the nozzle body 10, and this nozzle needle 11 is urged in a valve closing direction by a nozzle spring, though not shown. .

When the high-pressure fuel delivered from the above-described fuel injection pump is led to the fuel reservoir 13 through the fuel passage 12 in the nozzle body 10, the fuel reservoir 13
Is applied to the tapered surface 14 of the nozzle needle 11, and the nozzle needle 11 is lifted. As a result, when the nozzle needle 11 is opened, the nozzle body 1 is opened.
Fuel is respectively injected from the injection holes 15 and 16 formed at the leading end of the zero.

FIG. 2 shows one side of each of the first and second injection nozzles 8 and 9 at the same time. The injection hole 15 is the injection hole of the first injection nozzle 8, and this injection hole 15 is shown in FIG. As shown, several fuel cells are provided in the circumferential direction so as to uniformly inject fuel over the entire area of the combustion chamber 6. On the other hand, the injection hole 16
Is an injection hole of the second injection nozzle 9, and this injection hole 16
As shown in FIG. 4, in the combustion chamber 6, the fuel is positioned so as to be injected toward the side opposite to the injection hole 16 side, and the number is one to three. .
3 and 4, white arrows indicate swirl flows of air generated in the combustion chamber 6.

Here, as shown in FIG.
Assuming that the hole diameter of D5 is D1 and the hole diameter of the injection hole 16 is D2, the relationship between these hole diameters D1 and D2 is set to D1> D2. If the injection hole area of all injection holes 15 is A1 and the injection hole area of all injection holes 16 is A2, the injection hole area A2 is, for example, A2 ≦ 0.3.
・ It is set to be A1. Further, as shown in FIG. 5, the nozzle needle 1 of the second injection nozzle 9
When the valve 1 is lifted and opened, the lift amount H is
The second injection nozzle 9 is set so that, for example, H ≦ 0.3 · Hmax with respect to the original maximum lift amount Hmax of the nozzle needle 11. Therefore, when the second injection nozzle 9 is opened, the opening of the annular valve port 17 shown in FIG. 6 is limited to a small value.

When the lift amount H of the nozzle needle 11 is limited in the second injection nozzle 9 as described above, the injection period θL becomes the maximum lift amount Hmax as shown in FIG. In this case, the injection period is set longer than the injection period θS, so that the injection amount is constant. FIG. 8 shows the lift of the nozzle needle in the first injection nozzle 8.

Next, referring to FIG. 9, the first and second injection nozzles 8,
9 is shown in a flowchart, and the flowchart will be described below. When this flowchart is executed, first, in step S1
Then, the engine rotation speed Ne of the diesel engine is read based on the signal from the rotation speed sensor 23 described above, and in the next step S2, the load L of the diesel engine is read based on the signal from the load sensor 22. To step S3.

In step S3, the engine speed Ne is calculated.
Is near the idle rotation speed Nei and the load L is near zero. That is, the following equation is evaluated. Ne ≒ Ne and L ≒ 0 If the determination result of step S3 is positive (YES), it is determined that the diesel engine is in the idling operation range, and the process proceeds to step S4. In this step, it is set so that fuel is injected only from the second injection nozzle 9. Specifically, the electromagnetic valve 20 paired with the second injection nozzle 9 is opened, and the second injection nozzle 9 is connected to the fuel injection pump, whereas the electromagnetic valve 20 paired with the first injection nozzle 8 is Valve 2
0 is closed, so that the fuel pumping from the fuel injection pump to the first injection nozzle 8 is stopped.

From step S3, returning to step S1, the above-described steps are repeatedly performed. Therefore, as long as the diesel engine is in the idle operating range,
Fuel injection is performed using only the second injection nozzle 9. On the other hand, from the state described above, the engine speed Ne
Rises and the load L increases, the step S
The determination result of No. 3 is negative (NO). In this case, it is determined that the diesel engine is in the operating range outside the idle operating range, and the process proceeds to the next step S5. In this step, instead of the second injection nozzle 9, the first injection nozzle 8
Is used, and fuel is injected only from the first injection nozzle 8. The process returns from step S4 to step S1, and the steps after this step are repeatedly performed.

As apparent from the above description, when the diesel engine is in the idling operation range, that is, in FIG.
As is clear from the switching map of FIG. 5, when the operation state is in the region shown by hatching, the second injection nozzle 9
Only the first injection nozzle 8 is used when the diesel engine is in an operating range other than the idle operating range. That is, in the case of the diesel engine of the present invention, the first and second injection nozzles 8 and 9 can be selectively used according to the operation state.

Therefore, as described above, the second injection nozzle 9
If the injection hole 16 of the first injection nozzle 8 is smaller than the injection hole 15 of the first injection nozzle 8, the particle size of the fuel injected from the second injection nozzle 9 into the combustion chamber 6 when the diesel engine is in the idling operation range. That is, the particle size of the spray becomes sufficiently small, and the mixing of fuel and air in the combustion chamber 6 is promoted,
As shown in FIG. 7, the ignition delay of the fuel can be shortened. Moreover, if the lift amount H of the nozzle needle 11 in the second injection nozzle 9 is also limited to a small value, the nozzle
Since the sheet portion of the needle 11 is also squeezed , the injection period becomes longer.

Therefore, the injection of fuel does not end before the time of ignition of the fuel. As a result, the amount of premixed fuel mixed with air before ignition is also reduced,
This prevents abrupt combustion of the injected fuel and significantly reduces combustion noise in the idling operation range. on the other hand,
When the diesel engine is in an operation range other than the idle operation range, fuel can be injected from the large injection hole 15 of the first injection nozzle 8, so that desired fuel can be injected in a short time,
The required maximum output can be sufficiently obtained.

This invention is not limited to the above-described embodiment, and various modifications are possible. For example, in one embodiment, whether or not the diesel engine is in the idle operation range is determined based on signals from the engine rotation speed sensor and the load sensor, but using a sensor other than these sensors, It is also possible to make that determination. Further, in one embodiment, the fuel injection pump is provided for each of the first and second injection nozzles. However, based on the operating state of the engine, the fuel delivered from one fuel injection pump is supplied to the first and second injection nozzles. You may make it distribute and supply to a nozzle.

[0023]

As described above, according to the diesel engine fuel injection device of the present invention, two cylinders can be used in one cylinder.
The number of injection nozzles, that is, the first and second injection nozzles, is set, and the injection hole of the second injection nozzle is set smaller than the injection hole of the first injection nozzle, while the lift amount of the nozzle needle is limited. Therefore, by using the second injection nozzle only when the diesel engine is in the idling operation range, the combustion noise in the idling operation range can be significantly reduced. Further, in an operation range other than the idle operation range, fuel can be injected from the first injection nozzle,
There is an advantage that the maximum output of the diesel engine can be sufficiently secured.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a part of a diesel engine.

FIG. 2 is a cross-sectional view showing a tip portion of an injection nozzle.

FIG. 3 is a diagram showing a spray flow injected from a first injection nozzle.

FIG. 4 is a diagram showing a spray flow injected from a second injection nozzle.

FIG. 5 is a sectional view showing a lift of a nozzle needle in a second injection nozzle.

FIG. 6 is a sectional view showing a valve port of the nozzle needle of FIG. 5 when the nozzle needle is lifted.

FIG. 7 is a graph showing the lift of the second injection nozzle and the amount of heat generated in the combustion chamber during the lift.

FIG. 8 is a graph showing a lift of a nozzle needle in a first injection nozzle.

FIG. 9 is a flowchart showing a procedure for switching use of first and second injection nozzles.

FIG. 10 is a graph showing an injection nozzle switching map determined by the flowchart of FIG. 9;

[Explanation of symbols]

 Reference Signs List 1 cylinder block 4 piston 5 cylinder head 6 combustion chamber 8 first injection nozzle 9 second injection nozzle 11 nozzle needle 15, 16 injection hole D1, D2 hole diameter

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-171264 (JP, A) JP-A 64-29265 (JP, U) JP-A 62-141679 (JP, U) JP-A 60-29 63068 (JP, U) Japanese Utility Model Showa 58-139579 (JP, U) Japanese Utility Model Showa 58-113872 (JP, U)

Claims (1)

(57) [Scope of request for utility model registration] 1. A first method for injecting fuel into a combustion chamber of one cylinder when an engine is in an operating range other than an idle operating range.
When the injection nozzle and the engine are in idle operating range,
A second injection nozzle for injecting fuel into the combustion chamber,
The fuel injection device for a diesel engine, wherein the second injection nozzle has an injection hole area smaller than the injection hole area of the first injection nozzle and a nozzle needle whose lift amount is limited to a small amount.