JPS61123758A - Fuel injector - Google Patents

Abstract

PURPOSE:To stabilize combustion by providing a bypath for a fuel injection nozzle and returning a portion of injected fuel through the bypath into fuel tank thereby enabling high pressure fuel supply even under low load of engine or low fuel injection. CONSTITUTION:Fuel is fed from a tank 1 through pipe 21 to the intake port 3 of injection pump 2 then compressed and fed through delivery port 4 and a pipe 22 to an injection nozzle 6. Upon pressure rise on the needle 13 due to the fuel filled through the take-in port 7 of injection nozzle 6 to communication paths 8-10 and supply path 11, the needle 13 will lift against a spring 18 to open the seat section 14 thus to inject fuel through an injection port 15. Simultaneously, high pressure fuel is also fed to a bypath 16 and returned through a spring chamber 17, communication path 19, discharge port 20 and bypath 23 into the tank 1. Consequently, large amount of fuel can be fed to the injection nozzle 6 to maintain the fuel injection pressure at high level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection device used in an internal combustion engine such as a diesel engine.

[Prior art] ・ Conventionally, as a device for injecting fuel in an internal combustion-like manner such as in a diesel engine, fuel is pumped from an injection pump, passed through an injection pipe, and sent from an automatic valve type fuel injection nozzle attached to the engine to a cylinder. A fuel injection amount has been proposed in which fuel is injected within the range. As a measure against atomization of injected fuel at low rotation speeds and low loads, a fuel injection device using a nozzle with a throttle mechanism in which the cross-sectional area of the injection port is variable has been proposed.

Furthermore, in the sense of controlling the pressure of a fuel injection valve, a fuel injection valve such as that disclosed in Japanese Utility Model Application Laid-Open No. 58-81375 has been proposed.

[Problems to be Solved by the Invention]However, in the above device, the configuration of the injection device, that is,
In the method of measuring and pumping fuel using an injection pump and injecting it from an injection nozzle, the injection pressure of the fuel injected from the injection nozzle naturally changes depending on the fuel injection amount. especially,
When the injection amount is low, that is, when the engine is under low load, the pressure of the fuel compressed and pumped by the injection pump does not rise sufficiently, and the injected fuel is not atomized enough to mix well with air, resulting in unstable combustion and However, there were drawbacks such as a deterioration in fuel consumption efficiency and the generation of a large amount of exhaust HC.

In view of the above-mentioned conventional drawbacks, an object of the present invention is to introduce high-pressure fuel into an injection nozzle, sufficiently atomize the injected fuel, and obtain stable combustion even when the engine load is low, that is, the fuel injection amount is low. In addition to preventing deterioration of fuel consumption efficiency,
An object of the present invention is to provide a fuel injection device that can suppress HC emissions.

[Means for Solving the Problems] A fuel injection device of the present invention that meets this objective includes an injection pump that delivers fuel at high pressure, a needle tip conical portion, and an inner circumferential conical portion of a nozzle body that abuts the conical portion. A fuel injection nozzle is provided on a seat formed by a bypass passage that encounters the outside when the needle rises and provides flow resistance to the fuel flowing inside the fuel injection nozzle.

[Function] In a device having such a configuration, when the needle is raised, fuel is released from the seat through the bypass passage to the outside, for example, to the fuel tank, separately from the injected fuel, so even under low load conditions where conventionally the amount of fuel supplied was small, , the amount of fuel supplied to the fuel injection nozzle is guaranteed to be at least a certain amount. Furthermore, since the bypass passage has flow path resistance, it is possible to ensure the fuel injection pressure even if the fuel escapes from the bypass passage. This increase in the amount of fuel and the flow resistance of the bypass passage increase the pressure of the supplied fuel, promoting atomization of the injected fuel, and providing a stable combustion state even under low load.

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

FIG. 1 shows a first embodiment of the present invention, in which 1 is a fuel tank, and 2 is an injection pump that sucks fuel from the fuel tank 1 through a vibrator 21 and pumps it under high pressure. Further, an accelerator lever 5 is attached to the injection pump 2 to adjust the amount of fuel from the discharge port 4. Discharge port 4 of injection pump 2
A fuel injection nozzle 6 is connected via a vibrator 22 to the fuel injection nozzle 6 .

This fuel injection nozzle 6 consists of a nozzle body 12 and a needle 13, and a nozzle 15 is opened at the tip thereof.
The seat portion 14 formed by the contact between the tip of the needle 13 and the nozzle body 12 keeps the needle 13 sealed by the spring 18 in the spring chamber 17 normally urging the needle 13 downward in the figure. . Fuel is supplied from the intake lower to the fuel supply passage 11 via the encounter passage 8.9.10, but as the needle 13 rises, it also encounters the fuel bypass passage 16 which opens at the axial center of the needle 13, causing pressure. Encounter route 28 in bottle 27
Fuel is also channeled into the spring cavity 17 via the.

To explain the detailed structure of the nozzle tip with reference to FIG. 2, the nozzle body 12 at the tip of the fuel injection nozzle 6 has a needle 13.
is inserted into the nozzle body 12 so as to abut the tip conical portion 24 of the inner circumferential cone 1! ! 1525 is formed, and the seat portion 14 that blocks the encounter of fuel between the injection port 15 and the fuel supply passage 11 is formed. A fuel bypass passage 16 runs through the center of the needle 13 parallel to the axis and opens at its end into an encounter passage 29 . The encounter path 29 is the seat part 14
When the needle 13 is tightly closed to the seat part 14, the fuel supply passage 11 and the nozzle 15 are opened.
However, when the needle 13 is raised and the seat portion 14 is opened, the encounter path 29 encounters the fuel supply passage 11 and the injection port 15, and the bypass passage 16.
I also encountered it. Therefore, the two encounter passages, the bypass passage 16, the encounter passage 28, the spring chamber 17, the encounter passage 19, the discharge port 20, and the vibe 23 constitute a bypass passage with flow resistance that allows the fuel to escape from the seat portion 14 to the outside. .

The action will be explained below.

Fuel is supplied from the fuel tank 1 to the intake port 3 of the fuel injection pump 2 by a vibrator 21, and after being compressed at high pressure, it is delivered to the discharge port 4.
It is supplied to the injection nozzle 6 by the vibrator 22. When the pressure applied to the needle 13 increases due to the fuel filling the encounter passage 8.9.10 and the fuel supply passage 11 from the intake lower of the injection nozzle 6, and the needle 13 rises against the spring 18, the seat portion 14 is opened, and fuel is injected from the nozzle 15. At the same time, high-pressure fuel is also supplied to the fuel bypass passage 16, and the encounter passage 28 of the pressure bin 27
is introduced into the spring chamber 17 through the encounter path 1.
9, and is returned to the fuel tank 1 via a pipe 23 from an outlet 2o. In this way, since the fuel is released from the bypass passage, a larger amount of fuel is supplied to the injection nozzle 6 than before, and since there is flow resistance in the bypass passage, the fuel injection pressure is maintained at a high pressure. Regarding the fuel 1 escaping from this bypass passage, the flow path resistance of the bypass passage is set so that the total amount supplied to the injection nozzle 6 is approximately 1772, for example.

To explain the above effect using the relationship between the fuel injection amount and the fuel injection pressure shown in Fig. 3, in conventional fuel injection devices, when the fuel injection l is small, the fuel injection pressure at the injection nozzle does not rise sufficiently. , following the changes shown by the broken line in the figure. Therefore, due to insufficient pressure during low fuel injection, the atomization of the injected fuel is impaired, liquid fuel is injected into the cylinder, and there is a region where salt burning becomes worse. Therefore, as described above, in the present invention, the needle 13 moves up to drain the fuel filling the fuel supply passage 11 of the injection nozzle 6 into the seat part 14.
When the injection nozzle 6 is opened, the amount of fuel supplied from the intake lower of the injection nozzle 6 is increased by ejecting it from the injection port 15 and also introducing it into the bypass passage 16 formed in the needle 13 and returning it to the outside. This increases the pressure of the fuel and promotes atomization of the injected fuel in the fuel injection l shown by the hatched area in the figure.

Figure 4 shows the injection pressure waveform when the present invention is applied.Compared to the conventional pressure waveform shown by the broken line in the figure, the present invention shows a very large pressure increase as shown by the solid line in the figure. becomes possible.

Next, FIG. 5 shows a second embodiment of the present invention.
A throttle 26 is added to the passage in which the bypass fuel from the bypass passage 16 of the injection nozzle 6 returns to the fuel tank 1 via the vibrator 23 via the discharge port 20, and the rest is the same as that of the embodiment shown in FIG. The structure is the same.

This throttle 26 serves to maintain the fuel injection pressure value shown in FIG. ! The other functions are the same as those of the first embodiment shown in FIG. 1.

[Effects of the Invention] As is clear from the above description, according to the present invention, a bypass passage is provided in the fuel injection nozzle, and a part of the injected fuel is returned to the fuel tank via the bypass passage. Since the engine is cycled, high-pressure fuel can be supplied even when the engine is under low load, that is, during low fuel injection, and by improving the atomization of the injected fuel, combustion can be stabilized. As a result, it is possible to achieve a significant improvement in fuel consumption efficiency, and at the same time, it is possible to achieve the effect that exhaust HC can be significantly reduced.

[Brief explanation of drawings]

Fig. 1 is an overall system diagram of a fuel injection device according to a first embodiment of the present invention, Fig. 2 is an enlarged sectional view of the tip of the injection nozzle in Fig. 1, and Fig. 3 is an illustration of fuel injection amount and fuel injection pressure. FIG. 4 is a relationship diagram between time and injection pressure waveform, and FIG. 5 is an overall system diagram of a fuel injection device according to a second embodiment of the present invention. 1... Fuel tank 2... Injection pump 3... Intake port 4... Discharge port 5... Accelerator lever 6... ... Fuel injection nozzle 7 ... Intake port 8.9.10 ... Encounter path 11 ... Fuel supply passage 12 ... Nozzle body 13 ... ... Needle 14 ... Seat part 15 ... Nozzle 16 ... Fuel bypass passage 17 ... Spring to 18 ... Spring 19 ... Encounter path 20 ... Discharge port 21.22.23 ... Vibrator 24 ... Conical end portion 25 ... Inner circumferential conical portion 2G...Aperture 27...Pressure bin 28...Encounter path 29...Encounter path Fig. 2 24 Tip cone Fig. 3 Fuel injection amount time

Claims (2)

[Claims] (1) An injection pump that delivers fuel at high pressure, a seat portion formed by a needle tip conical portion and an inner peripheral conical portion of the nozzle body that abuts the conical portion, is placed on the seat portion that meets the outside and the inside when the needle rises. A fuel injection device comprising: a fuel injection nozzle forming a bypass passage that provides flow resistance to fuel flowing through the fuel injection nozzle. (2) The fuel injection device according to claim 1, wherein the bypass passage is provided with a throttle mechanism.