JPH0442522Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a fuel injection device suitable for diesel engines, particularly direct injection diesel engines.

(Prior Art) In a direct injection diesel engine, the area of the nozzle hole of the fuel injection nozzle has a great influence on the performance of the engine, and it is desirable that the area is variable depending on the operating state of the engine. In other words, when the engine is running at low speeds, it is advantageous to have a smaller nozzle area in order to make the fuel spray finer and improve its mixing with the air. Due to the need for spraying, a suitably large area is preferred. Therefore, various fuel injection nozzles having variable area nozzle holes have been proposed, and the representative ones include:
The injection hole part at the tip of the nozzle is made of double cylinders that can rotate relative to each other, and each cylinder is provided with a cooperating elongated hole to change the relative rotational phase between the cylinders. A method in which the effective area of the nozzle hole is made variable by changing the wrap area of the elongated hole has already been disclosed, but this is structurally unreasonable for a fuel injection nozzle that operates in a severe environment of high temperature and high pressure. It was completely impractical.

(Problems to be solved by the invention) This invention does not change the nozzle area of the fuel injection nozzle by a mechanical method that is difficult to put into practice under high temperature and high pressure conditions. It is an object of the present invention to provide a fuel injection device that realizes a substantially variable effective nozzle area using a hydrodynamic method while providing a constant nozzle hole.

(Means for Solving the Problems) The present invention was devised to achieve the above object, in which a plurality of elongated nozzle holes are provided in the nozzle body, and the inflow direction of fuel into the nozzle holes is A hole type nozzle provided with a plurality of different fuel supply passages, and a switching valve that selectively connects any one of the plurality of fuel supply passages to a fuel supply source depending on the operating state of the engine. This article focuses on the characteristic fuel injection device.

(Function) According to the present invention, by changing the inflow direction of fuel into the elongated nozzle hole with a constant area, the flow rate coefficient changes, and the effective nozzle area, that is, the (geometric) (chemical nozzle area x flow rate coefficient) can be changed. The above change in the fuel flow direction can be easily achieved by providing a plurality of fuel passages in the nozzle body and selectively communicating one of the passages with the fuel supply source using a switching valve. can.

(Example) Examples of the present invention will be specifically described below with reference to the accompanying drawings. First, in FIGS. 1 and 2 showing the main parts of a hole-type fuel injection nozzle, reference numeral 10
12 is a nozzle body, 12 is a needle valve slidably fitted in the nozzle body 10, 14 is a nozzle spring that always biases the needle valve 12 in the closing direction, and 16 is provided at the tip of the nozzle body 10. Multiple injection holes, usually 2, 4, or 6 depending on the shape of the engine fuel chamber.
However, in this embodiment, as an example, as shown in the developed views of FIGS. 3 and 4, four are provided, and the shape is a long hole having a long axis in the axial direction of the needle valve 12. I am doing it. Further, within the nozzle body 10, a fuel reservoir 20 is provided which communicates with a cylindrical fuel passage 18 formed on the outer periphery of the needle valve 12. A first fuel supply passage A communicates with the fuel reservoir 20, and the cylindrical fuel passage A communicates with the fuel reservoir 20. shaped fuel passage 18
A second fuel supply passage B is communicated approximately tangentially with.

As shown in FIG. 5, the fuel supply passages A and B are connected to a fuel supply source, such as an inline fuel pump 24, via an electromagnetically actuated switching valve 22.
The switching valve 22 is operated by the controller 26 to selectively connect either the fuel supply passage A or B to the fuel supply source depending on the operating state of the engine. The controller 26 controls the engine rotation speed Ne
and a signal regarding the load L, and as shown in the operability diagram of FIG. 6, in the low speed region and medium speed partial load region b of the engine, the fuel supply passage B is communicated with the fuel supply source 24, In a high-speed, high-load region a of the engine, the switching valve 22 is operated to connect the fuel supply passage A to the fuel supply source 24.

Now, in Figure 1, the fuel supply passage A is the fuel supply source 2.
4, the nozzle spring 14 is overcome by the fuel pressure, and the needle valve 12 is opened (note that the other fuel supply passage B is sealed by the switching valve 22 at this time). However, of course, a check valve may be provided at an appropriate location in the fuel passage from the switching valve 22 to the fuel supply passage B.) In this case, the fuel is transferred to the fuel reservoir 20 as indicated by the arrow α in the figure. The fuel flows in the axial direction inside the cylindrical fuel passage 18, and as shown in the exploded view of FIG.
Since it flows into the same nozzle hole along the long axis of the flow rate coefficient ξ becomes large. Therefore, the injection period is shortened and the injection pressure is kept low. Next, the second
The figure shows a case where the fuel supply passage B is connected to the fuel supply source 24. At this time, the fuel flows while swirling tangentially around the needle valve 12, as shown by the arrow β in the figure, and as shown in the exploded view of FIG. Since it flows into the same nozzle hole along the direction, the flow coefficient ξ becomes small. Therefore, the injection pressure increases, the spray becomes finer, and mixing with air is promoted. That is, according to the above-mentioned configuration, the injection pressure is maintained high in the low speed range and medium speed partial load range of the engine, and the spray becomes finer and mixes better with the air, so the fuel quality is improved. The generation of black smoke and particulate matter is suppressed, resulting in improved fuel efficiency. () In the high-speed, high-load range of the engine, the injection pressure is kept to the minimum necessary, while the injection period is shortened. So the fuel is improved, black smoke,
A reduction in particulate matter and an improvement in fuel efficiency are achieved. Furthermore, since the injection pressure is low, secondary injection and cavitation are prevented, and the durability of the fuel injection pipe and fuel pump is improved. It has the following effects.

In the above embodiment, the nozzle body 10 is provided with two fuel supply passages A and B, but a third fuel supply passage is further provided, and the nozzle body 10 is provided with a third fuel supply passage, which is connected to the longitudinal axis of the nozzle hole 16 in FIGS. 3 and 4. It is obvious that the fuel can be configured to flow into the injection hole at an angle intermediate to that shown in the figure. Further, in the above embodiment, the shape of the nozzle hole 16 is formed of upper and lower circular arc parts and a straight part, but any long hole shape such as an elongated ellipse can be adopted.
Furthermore, their size, number, arrangement, etc. can be changed as appropriate.

(Effects of the invention) As mentioned above, the fuel injection device according to the invention has the following effects:
A hole-type nozzle in which a nozzle body is provided with a plurality of elongated nozzle holes and a plurality of fuel supply passages in which fuel flows into the nozzle holes in different directions, and the plurality of fuel supply passages are arranged according to the operating state of the engine. It is characterized by being equipped with a switching valve that selectively communicates either one of them with a fuel supply source, and can perform fuel injection that is adapted to the operating condition of the engine, thereby reducing emissions such as black smoke and particulate matter. This has the advantage that it is possible to realize a practical fuel injection device that can suppress fuel consumption and improve fuel efficiency.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the mode of fuel flow when fuel is supplied to the first fuel supply passage A of the nozzle body in one embodiment of the present invention, and FIG. Fuel supply passage B
FIG. 3 is a cross-sectional view showing the manner of fuel flow when fuel is supplied to the nozzle hole 16 in the case of FIG. A developed view showing how fuel flows into the nozzle hole 16 in the case of
FIG. 5 is a schematic configuration diagram of the entire fuel injection system including the nozzle bodies shown in FIGS. 1 and 2, and FIG. 6 is a characteristic diagram showing the operating mode of the controller 26 in FIG. 5. 10... Nozzle body, 12... Needle valve, 14... Nozzle spring, 16... Nozzle hole,
22...Switching valve, 24...Fuel supply source, 26...
Controller, A...first fuel supply passage, B...
Second fuel supply passage.

Claims (1)

[Scope of utility model registration request] A hole-type nozzle in which a nozzle body is provided with a plurality of elongated nozzle holes and a plurality of fuel supply passages in which the fuel flows into the nozzle holes in different directions; A fuel injection device comprising a switching valve that selectively connects one of the passages to a fuel supply source.