JP3550793B2 - Fuel injection nozzle - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a fuel injection nozzle used for diesel injection.
[0002]
[Prior art]
FIG. 4 shows a general fuel injection nozzle in which a needle valve a is housed in a nozzle body b so as to be able to move up and down. The needle valve a has a tapered portion c, which is located in an oil sump e formed in the nozzle body b when the needle valve a closes the injection hole d as shown in the figure. Fuel pumped from a fuel pump (not shown) is supplied to the oil reservoir e through a passage f. The fuel in the oil sump e causes the fuel pressure to act on the tapered portion c to lift the needle valve a against the urging force of the spring g. When the needle valve a is lifted, the injection hole d is opened, and the fuel in the oil sump e is injected after passing through the gap between the needle valve a and the hole h.
[0003]
[Problems to be solved by the invention]
Meanwhile, there is a technique called two-stage injection in which a relatively short and small amount of pilot injection is performed in an initial stage for the purpose of reducing diesel knock, and then main injection (main injection) is performed for a predetermined time and a predetermined amount.
[0004]
In the case of the above nozzle structure, the pressure for lifting the needle valve, that is, the valve opening pressure is determined by the spring constant of the spring. When the fuel pressure in the oil reservoir reaches the valve opening pressure, the needle valve is lifted and injection is performed. Is On the other hand, the spray pressure is also determined by the volume of the oil sump.
[0005]
However, the volume of the oil sump is determined so that the main injection can be uniformly performed at an appropriate spray pressure. In this case, the volume of the oil sump is too large at the time of pilot injection to sufficiently increase the spray pressure. In other words, the fuel in the oil sump absorbs the high fuel pressure sent from the passage, and as a result, atomization of the spray cannot be achieved, resulting in deterioration of smoke.
[0006]
Therefore, the present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a fuel injection nozzle capable of sufficiently increasing the spray pressure at the time of pilot injection.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a fuel injection nozzle according to the present invention is connected to a fuel supply passage, and a small-volume first fuel injection nozzle for lifting a needle valve by fuel pressure supply from the supply passage to perform pilot injection. An oil reservoir is provided separately from the supply passage and the first oil reservoir, and communicates with the first oil reservoir to perform main injection when the needle valve is lifted beyond a pre-lift amount. And a second oil sump.
[0008]
[Action]
At the time of pilot injection, the lift amount of the needle valve is small, and the fuel pressure is supplied only to the small-capacity first oil sump. On the other hand, at the time of the main injection, the lift amount of the needle valve is larger than the pre-lift amount, so that the fuel pressure is also supplied to the second oil reservoir through the first oil reservoir.
[0009]
【Example】
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0010]
FIG. 3 is a longitudinal sectional front view showing the whole of the fuel injection nozzle according to the present invention. As shown in the drawing, the fuel injection nozzle 1 has a holder body 2, and the lower end of the holder body 2 is provided with a retaining nozzle body 3. It is attached by a nut 4. An upper holder body 6 is attached to an upper end of the holder body 2 via an inner body 5. A closing bolt 7 is attached to the upper end of the upper holder body 6.
[0011]
A seat 9, a pressure pin 10, a pilot injection spring 11, a push rod 12, and a shaft holder 13 are sequentially inserted into the center hole 8 of the holder body 2 from above, and these are inserted into the holder body of the inner body 5. The position is fixed by screwing to 2. A pressure piece 15 and a main injection spring 16 are sequentially fitted and inserted into the center hole 14 of the inner body 5 from above. The upper piece 17 is screwed to the inner body 5, and a lock nut 18 is inserted. The position is fixed by fixing with. An introduction passage 19 is formed inside the holder body 2 to introduce high-pressure fuel pumped from a fuel pump (not shown). FIG. 1 is a longitudinal sectional front view showing the inside of the nozzle body 3 of the fuel injection nozzle 1. A center hole 20 is formed inside the nozzle body 3, and a needle valve 21 rises (lifts) in the center hole 20. It is housed so that it can descend. The needle valve 21 has a large-diameter portion 22 formed slightly above the needle valve 21 slidable along the inner wall of the center hole 20. Is pin portion 23 pushes the upper portion of the enlarged diameter portion 22 is formed, push pin portion 23, as shown in FIG. 3, abuts against the pressure pin 10 through the sheet 9. A tapered portion 24 and a reduced diameter portion 25 connected to the tapered portion 24 are formed below the enlarged diameter portion 22, and the reduced diameter portion 25 forms a small gap 26 with the inner wall of the center hole 20.
[0012]
In the state shown in FIG. 1, the needle valve 21 receives the downward pressing force or the urging force of the pilot injection spring 11 and is pressed against the seat 27 at the lower end of the center hole 20 to close the injection hole 28. The nozzle 1 is a hole type mainly used in a direct injection diesel engine, and a plurality of injection holes 28 are provided in a substantially hemispherical hole portion 29 at the lower end of the nozzle body 3.
[0013]
In particular, inside the nozzle body 3, the first oil reservoir 30 opened toward the tapered portion 24 of the needle valve 21, and the lift of the needle valve 21 above the first oil reservoir 30, that is, with respect to the first oil reservoir 30. The second oil reservoirs 31 that are separated from each other and that are open toward the enlarged diameter portion 22 are formed. The first and second oil sumps 30 and 31 are formed in a ring shape along the inner wall of the center hole 20, while their cross sections are such that the first oil sump 30 has an elongated groove shape and the second oil sump 31 has a base. It is formed into a shape. The first oil reservoir 30 and the tapered portion 24 have the same length and the same position at both ends in the longitudinal direction of the needle valve, whereas the length of the second oil reservoir 31 is formed larger than that of the first oil reservoir 30. You. The volume of the first oil sump 30 is smaller than the volume of the second oil sump 31, and the sum of these volumes is set to a value suitable for the main injection as in the above. Therefore, the first and second oil sumps 30 and 31 are obtained by dividing the conventional oil sump at an appropriate ratio.
[0014]
Further, in the present embodiment, a supply passage 32 for supplying fuel to the first oil reservoir 30 by connecting the first oil reservoir 30 to the introduction passage 19 is formed inside the nozzle body 3. The supply passage 32 communicates only with the first oil sump 30 and is completely separated from the second oil sump 31. Therefore, the second oil sump 31 forms a completely independent space.
[0015]
The closing bolt 7 is provided with a leak hole 34 for leaking fuel leaking from the upper end of the center hole 20 and invading upward. The leak hole 34 is connected to the fuel tank by a pipe or the like (not shown).
[0016]
Next, the operation of the present embodiment will be described.
[0017]
The high-pressure fuel pumped from the fuel pump is supplied to the first oil reservoir 30 through the introduction passage 19 and the supply passage 32. When the fuel pressure in the first oil sump 30 reaches a pilot valve opening pressure determined by the spring constant of the pilot injection spring 11, the fuel pressure acts on the tapered portion 24 to resist the urging force of the spring 11. The needle valve 21 is lifted. In this case, the injection hole 28 is opened, and the fuel in the first oil reservoir 30 is injected from the injection hole 28 through the gap 26. At this time, the push rod 12 only moves within the hole 35 of the pressure piece 15, and the needle valve 21 is not pressed by the main injection spring 16.
[0018]
Referring to FIG. 2 as well, especially during the pilot injection, the pressure feeding period is short, so the needle valve 21 rises, that is, the lift amount is small. Specifically, the lift i.e. pre-lift amount h ₁ includes a first oil sump 30 or the tapered section 24, is less than the needle valve longitudinal direction or distance h along the lift direction and the second oil sump 31.
[0019]
Therefore, since the enlarged diameter portion 22 is in close contact with the inner wall of the center hole 20 between the oil sumps 30 and 31 and reliably partitions and does not communicate with each other, the supplied high fuel pressure is applied only to the small oil sump 30. Acts to increase the fuel pressure in the first oil sump 30 in a short time. In this case, the high fuel pressure can be used as the spray pressure, the atomization of the spray can be promoted, and the smoke can be improved.
[0020]
Meanwhile, at the time of main injection, for pumping period of the fuel is longer needle valve 21 also increase the lift amount, the lift amount h ₂ is the distance h greater than the aforementioned.
[0021]
When this occurs, the tapered portion 24 reaches the position of the second oil sump 31. Specifically, the upper end 24 a of the tapered portion 24 exceeds the lower end position 31 a of the second oil sump 31, and the fuel in the first oil sump 30 is shifted to the second oil sump. The fuel pressure flows into the sump 31 or the fuel pressure in the first sump 30 is supplied to the second sump 31. In this case, since the total volume of the oil sumps 30 and 31 is a value suitable for the main injection, a good main injection can be executed as in the related art. At this time, the push rod 12 pushes up the main injection spring 16 via the pressure piece 15.
[0022]
By the way, Japanese Patent Application Laid-Open No. 4-325766 discloses a device in which two oil reservoirs for pilot injection and main injection are provided as in the present embodiment. Since the fuel passage communicates with the oil reservoir, a substantial change in volume cannot be obtained, and the effect of increasing the pressure of the spray cannot be expected. In addition, since a throttle is provided in the passage to the pilot injection oil sump, it is difficult to increase the pressure in a short time, and the responsiveness may be deteriorated. Therefore, from this point as well, the present embodiment can be expected to have more excellent operational effects than those disclosed in the above-mentioned publication.
[0023]
As described above, according to the above-described configuration, it is possible to solve the disadvantages of the related art at the time of the two-stage injection, and it is possible to achieve a good spray state at the time of the pilot and the main injection. In addition, the valve opening pressure can be reached from a stage where the pump pressure is low, and conversely, it is possible to set a high valve opening pressure with a conventional pump. Since the time required to reach the pilot valve opening pressure is also reduced, the responsiveness is improved, and the pilot injection period can be shortened. In addition, since there is only one supply passage 32 communicating with the first oil sump 30, the configuration is simplified and the manufacturing cost can be reduced.
[0024]
In addition to the above embodiments, the present invention can be implemented in various modes.
[0025]
【The invention's effect】
The present invention exhibits the following excellent effects.
[0026]
(1) The spray pressure at the time of pilot injection can be sufficiently increased to achieve atomization of spray and improvement of smoke.
[0027]
(2) The response is improved, and the pilot injection period can be shortened.
[Brief description of the drawings]
FIG. 1 is an enlarged vertical sectional front view showing one embodiment of a fuel injection nozzle according to the present invention.
FIG. 2 is an enlarged view showing the operation of the needle valve.
FIG. 3 is a vertical sectional front view showing the entire fuel injection nozzle.
FIG. 4 is a vertical sectional front view showing a conventional fuel injection nozzle.
[Explanation of symbols]
1 fuel injection nozzle 21 needle valve 30 first oil sump 31 second oil sump

Claims (1)

A small-capacity first oil sump which is communicated with a fuel supply passage , lifts a needle valve by the fuel pressure supply from the supply passage, and performs pilot injection, and the supply passage and the first oil sump. A second oil reservoir which is provided at a distance and communicates with the first oil reservoir to perform a main injection when the needle valve is lifted beyond a pre-lift amount. .

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