JP3752716B2 - Fuel injection valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection valve capable of adjusting a fuel injection pressure.
[0002]
[Prior art]
In a fuel injection valve of an internal combustion engine, it is known that the injection rate is reduced at the initial stage of injection and the injection rate is increased when the main injection is reached. According to such a fuel injection valve of the two-stage injection type, The ignitability of fuel is improved, and it is effective in reducing noise and preventing harmful components from being discharged.
[0003]
Such a two-stage injection type fuel injection valve is, for example, as shown in Japanese Patent Publication No. 63-502767, Japanese Utility Model Publication No. 4-109467, etc. A small amount of initial injection is performed while the amount is controlled, and when the fuel pressure continues to increase, the needle valve is lifted largely against the first spring and the second spring to cause a large amount of main injection to be performed. It has become.
By the way, in this type of fuel injection valve, the initial valve opening pressure may decrease due to long-term use, and this is often adjusted.
[0004]
[Problems to be solved by the invention]
The fuel injection valve described in the former publication has a structure in which a shim is applied to the intermediate bush to adjust the valve opening pressure. If the initial valve opening pressure is to be adjusted, it must be replaced with a shim with a different thickness. There is. However, in the case of the structure described in this publication, in order to replace the shim, the retaining nut is loosened, the nozzle holder is removed from the nozzle body, and the second spring and intermediate bush incorporated in the spring chamber are taken out. There is a problem that the shim needs to be replaced, and therefore man-hours are extremely long and workability is not good.
[0005]
Further, this is divided into a first chamber in which the spring chamber accommodates the first spring and a second chamber in which the second spring is accommodated, and the first chamber and the second chamber have a level difference. However, since the spring seat is pressed against this step, the first chamber on the upper side has a small diameter. With such a structure, the first spring accommodated in the small chamber becomes small, and there is a drawback that the setting range and the adjustable range of the valve opening pressure are small.
[0006]
On the other hand, in the latter publication, an adjustment screw is screwed into the nozzle body, and the adjustment force is adjusted so that the valve opening pressure can be adjusted by adjusting the spring force of the first spring. Therefore, there is an advantage that the valve opening pressure can be easily adjusted by operating the adjusting screw using a tool such as a screwdriver from the outside. However, this device requires a part such as an adjusting screw, a nut, and a gasket because of a structure for adjusting the valve opening pressure from the outside, resulting in an increase in the number of parts and a manufacturing cost.
[0007]
The present invention has been made based on such circumstances, and an object of the present invention is to provide a fuel injection valve that can easily adjust the valve opening pressure and has a simple structure.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a spring chamber is provided at one end of the nozzle holder, a communication hole communicating with the spring chamber is opened at the other end, and a spring for pushing the needle valve is provided in the spring chamber. accommodated, and the biasing force of the spring is fixed by press-fitting an adjustable bush to the spring chamber, the spring by the bush, press a pressing tool is screwed into the internal thread portion of the communication hole is inserted from the communication hole A fuel injection valve characterized by being moved indoors.
[0009]
According to such a configuration, if the pressing tool is inserted from the outside through the communication hole, and the bush fixed by press-fitting into the spring chamber is pushed and moved by the pressing tool, the urging force of the spring is changed, so that the injection is performed. The valve opening pressure can be adjusted.
[0010]
Therefore, with such a configuration, the valve opening pressure can be adjusted by inserting a pressing tool from the outside. Therefore, the adjustment work is easy, and the troublesome work such as disassembling the nozzle holder is unnecessary. Excellent workability. In addition, no special parts are required for the adjustment work, the number of parts is reduced, and the manufacturing cost is reduced.
[0011]
According to a second aspect of the present invention, in the fuel injection valve according to the first aspect, the first spring for regulating the valve opening pressure at the time of initial injection and the first spring at the time of full injection are provided in the spring chamber. A second spring for setting the valve opening pressure is accommodated, and the first bush and the second bush for adjusting the urging force of the first spring and the second spring are respectively fixed by press fitting, and the first spring The fuel injection valve is characterized in that the bush is movable in the spring chamber by being pressed by the pressing tool inserted through the communication hole and screwed into the female screw portion .
[0012]
According to such a structure, at the initial stage of injection, the lift amount of the needle valve is pushed by the first spring to cause a small amount of initial injection, and when the fuel pressure continues to increase, the first spring and the second spring A large amount of main injection can be performed by largely lifting the needle valve against the spring, resulting in a so-called two-stage fuel injection valve.
[0013]
In this case, since the pressing tool is inserted from the outside to move the first bush, and thereby the force for pressing the needle valve can be adjusted by changing the biasing force of the first spring, the valve opening pressure can be adjusted. Therefore, in this case as well, it can be operated from the outside, so adjustment work is easy, and it is not necessary to disassemble the nozzle holder, so adjustment work is excellent and no special parts are required for adjustment work. Therefore, the number of parts is reduced and the cost is reduced.
[0014]
Furthermore, it is not necessary to provide a step in the spring chamber, and not only is the process easy, but a large spring can be used as the first spring, and the range in which the valve opening pressure can be set and adjusted can be increased. it can.
[0015]
A third aspect of the present invention is the fuel injection valve according to the first or second aspect, wherein the communication hole also serves as a fuel escape hole.
According to such a configuration, since the communication hole also serves as the fuel escape hole, the structure is greatly simplified.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described based on the first embodiment shown in FIG.
In the figure, reference numeral 1 denotes a nozzle holder. A distance piece 2 and a nozzle body 3 are connected to the nozzle holder 1 via a retaining nut 4 in the axial direction.
[0017]
The nozzle holder 1 is formed with a spring chamber 5 opened at one end facing the distance piece 2, and a communication hole 6 communicating with the spring chamber 5 is formed at the other end. The spring chamber 5 and the communication hole 6 are coaxially connected. Therefore, the nozzle holder 1 is penetrated by the spring chamber 5 and the communication hole 6 from one end to the other end. The spring chamber 5 is a circular hole having a uniform inner diameter, and the communication hole 6 is a circular hole having a smaller diameter than the spring chamber 5. The communication hole 6 also serves as a surplus fuel escape hole, and a female screw part 6a into which a nipple (not shown) connected to the surplus fuel return pipe is screwed is formed at the opening of the communication hole 6. Yes. Therefore, the inner diameter of the communication hole 6 may be the same as the lower hole of the female screw portion 6a, and the lower hole and the communication hole 6 are formed by continuous processing.
[0018]
A first bush 7 and a second bush 8 are accommodated in the spring chamber 5 so as to be separated from each other in the axial direction. The first bush 7 and the second bush 8 are fixed in the spring chamber 5 by press fitting, that is, the first bush 7 and the second bush 8 are applied to the inner surface of the spring chamber 5 by a strong frictional force. Is engaged. However, a pressing jig 9 prepared as a service tool is inserted from the outside of the nozzle holder 1 through the communication hole 6, and the first bush 7 is pushed with a pressing force equal to or greater than the frictional force at the tip of the pressing jig 9. The first bush 7 is movable. That is, the first bush 7 is fitted to the inner surface of the spring chamber 6 with a pressure input that can be moved by pressing the first bush 7 with the pressing jig 9. Each of the first bush 7 and the second bush 8 has through-holes 7a and 8a, and has a ring shape.
[0019]
Note that the pressing jig 9 of this embodiment has a nut shape that can be inserted into the communication hole 6, and has a male screw part 9 a that can be screwed into the female screw part 6 a of the communication hole 6. The first bush 7 is pushed forward by screwing.
[0020]
A first spring 10 for setting the valve opening pressure for initial injection is accommodated in the spring chamber 5, and a second spring for setting the valve opening pressure for all injections in cooperation with the first spring 10. A spring 11 is accommodated.
[0021]
The first spring 10 is accommodated between the first bush 7 and the second bush 8, and the second spring 11 is accommodated between the second bush 8 and the distance piece 2. Yes.
[0022]
The first spring 10 has an upper end in contact with the lower surface of the first bush 7 and a lower end in contact with the first spring receiving sheet 12. An upper end of a push rod 13 is connected to the first spring receiving sheet 12 by press fitting or the like, and the push rod 13 slidably penetrates the through hole 8a of the second bush 8 so that the nozzle holder 1 It extends to the lower end.
[0023]
The second spring 11 has an upper end in contact with the lower surface of the second bush 8 and a lower end in contact with the second spring receiving sheet 14. The lower end of the push rod 13 is slidably inserted into the second spring receiving sheet 14 .
[0024]
Further, a fuel supply passage 15 through which high-pressure fuel is sent from a fuel supply pump (not shown) is formed on the side wall of the nozzle holder 1, and one end of the fuel supply passage 15 passes through the inside of the side wall of the nozzle holder 1 and the distance piece. 2 to the nozzle body 3.
[0025]
The distance piece 2 connected to the nozzle holder 1 is formed with a through hole 16 at the center, and the lower portion of the second spring receiving sheet 14 is slidable in the through hole 16. It is penetrated by.
[0026]
The nozzle body 3 connected to the distance piece 2 is provided with a sliding hole 20 in the center, and a fuel reservoir 21 communicating with the sliding hole 20 and the fuel reservoir located at the lower end. An injection hole 22 that continues to 21 is formed. The fuel reservoir 21 communicates with the fuel supply passage 15, so that high pressure fuel is sent to the fuel reservoir 21 from the fuel supply pump through the fuel supply passage 15.
[0027]
A needle valve 25 is slidably inserted into the accommodation hole 20. The needle valve 25 is configured such that a valve portion 26 formed at the lower end contacts and separates a valve seat formed at the lower end of the nozzle body 3 to open and close the injection hole 22. An inclined pressure receiving surface 27 is provided.
[0028]
A small-diameter pressing rod 28 projects integrally from the upper end of the needle valve 25. The upper end of the pressing rod 28 is slidably inserted into the second spring bearing sheet 14 . And the upper end of this press rod 28 and the lower end of the said push rod 13 are contact | abutting so that contact / separation is possible within the 2nd spring receiving sheet | seat 14. FIG.
[0029]
For this reason, the load of the first spring 10 is transmitted to the needle valve 25 via the push rod 13 and the pressing rod 28, so that the needle valve 25 is pushed down by the pressing force of the first spring 10 and its valve portion 26. Is in contact with the valve seat so as to be able to contact and separate.
[0030]
A presser rod 29 is attached to the upper end of the needle valve 25 so as to surround the press rod 28 and lower than the height of the press rod 28. The pressing element 29 faces the lower surface of the second spring receiving sheet 14 .
[0031]
The operation of the embodiment having such a configuration will be described.
High pressure fuel is supplied from a fuel supply pump (not shown) to the fuel reservoir 21 through the fuel supply passage 15, and the fuel pressure in the fuel reservoir 21 acts on the pressure receiving surface 27 formed on the needle valve 25, thereby Pushing force is applied. When the fuel pressure in the fuel reservoir 21 reaches a predetermined initial valve opening pressure, the pushing force applied to the needle valve 25 compresses the first spring 10 through the push rod 28 and the push rod 13. Therefore, the needle valve 25 is lifted, the valve portion 26 is separated from the valve seat, the injection hole 22 is opened, and the fuel in the fuel reservoir portion 21 is injected from the injection hole 22 to an engine (not shown).
[0032]
The lift of the needle valve 25 rises to a position where the pressing element 29 provided at the upper end of the needle valve 25 contacts the lower surface of the second spring receiving sheet 14 , and the pressing element 29 moves to the lower surface of the second spring receiving sheet 14 . When this occurs, the needle valve 25 is temporarily lifted by the needle spring 25 because the pressure of the second spring 11 acts on the needle valve 25 in addition to the pressure of the first spring 10.
[0033]
This state is a pre-lift, and initial injection is performed at this time. After such initial injection, when the fuel pressure in the fuel reservoir 21 further increases and exceeds the valve opening pressure of all injections, the pressing rod 28 pushes the first spring 10 through the push rod 13, because the pushing element 29 pushes up the second spring receiving seat 14, pushes the second spring 11 via the second spring receiving seat 14. Therefore, the needle valve 25 rises against the pressing force of the first and second springs 10 and 11, thereby further opening the injection hole 22. Therefore, the fuel in the fuel reservoir 21 is injected from the injection hole 22 and this state is the total injection.
[0034]
In this full injection, the needle valve 25 is raised until the upper surface of the presser 29 comes into contact with the distance piece 2, that is, the needle valve 25 stops when the full lift is reached.
[0035]
In the configuration as described above, the valve opening pressure of the initial injection is determined by the urging force of the first spring 10, and the initial load of the first spring 10 is determined by the position of the first bush 7. That is, the position of the first bush 7 is determined with high accuracy when the first spring 10 is attached. Similarly, the starting pressure of all injections is determined by the urging force of the first spring 10 and the urging force of the second spring 11, and the initial load of the second spring 11 is determined by the position of the second bush 8. . That is, when the second spring 11 is attached, the position of the second bush 8 is also determined with high accuracy.
[0036]
However, when the valve opening pressure becomes unstable due to a spring sag due to long-term use, it is necessary to adjust the valve opening pressure. According to the present embodiment, the pressing jig 9 is inserted into the communication hole 6 from the outside of the nozzle holder 1, and the male screw portion 9 a of the pressing jig 9 is screwed into the female screw portion 6 a of the communication hole 6. Screw. Then, the tip of the pressing jig 9 pushes the first bush 7, and the first bush 7 is moved downward in the figure against the frictional force. This compresses the first spring 10 and increases the initial load.
[0037]
Therefore, the pressure required for the needle valve 25 to start lifting is increased, and the valve opening pressure can be increased. For this reason, the valve opening pressure of initial injection becomes high, and the start pressure of all injections also becomes high simultaneously.
[0038]
In the configuration of such an embodiment, when adjusting the valve opening pressure, this bushing is inserted by inserting the pressing jig 9 from the outside and pressing the first bushing 7 press-fitted into the spring chamber 5. 7 can be moved against the frictional resistance, so that it is easy to operate and requires troublesome work such as loosening the retaining nut 4 and removing the nozzle body 3 and the distance piece 2 for disassembly. Therefore, the adjustment operation of the valve opening pressure can be performed easily and quickly, and the workability is greatly improved.
[0039]
Moreover, as compared with the conventional type in which the valve opening pressure is adjusted by adjusting the spring force of the first spring by screwing back and forth the adjustment screw integrally screwed into the nozzle body, Special parts such as adjusting screws, nuts and gaskets screwed together are unnecessary, and the number of parts can be reduced, and the manufacturing cost can be reduced.
[0040]
In particular, when the communication hole 6 is also used as a surplus fuel escape hole, the female screw portion 6a can use a female screw for connecting the nipple, the drilling process can be omitted, and a special part other than the pressing jig 9 can be used. No longer need it.
[0041]
Further, in this embodiment, the spring chamber 5 has a uniform diameter throughout, and the space for accommodating the first spring 10 and the space for accommodating the second spring 11 are partitioned by the second bush 8. Since the second bush 8 is also fixed to the spring chamber 5 by press-fitting, no special step is required, and the processing of the spring chamber 5 is easy. Since the space for accommodating the first spring 10 can be formed with the same diameter as the space for accommodating the second spring 11, this room can be enlarged, and a large spring can be used as the first spring to be accommodated in this room. Can be used. For this reason, there is an advantage that the range in which the valve opening pressure can be set and adjusted is increased.
[0042]
Although the first embodiment has been described with respect to the initial injection and the two-stage injection type fuel injection valve that performs the full injection subsequently, the present invention is not limited to this, and the second embodiment shown in FIG. As shown, a single-stage injection type fuel injection valve may be used.
[0043]
In FIG. 2, members having the same functions as those of the first embodiment are designated by the same reference numerals and their description is omitted. In FIG. 2, 30 is a spring, 31 is a bush for setting the biasing force of the spring 30. The bush 31 is fixed to the spring chamber 5 by press fitting.
[0044]
Therefore, the upper end of the spring 30 is in contact with the lower surface of the bush 31. The lower end of the spring 30 is in contact with a spring receiving sheet 34, and the spring receiving sheet 34 is in contact with a pressing rod 28 formed at the upper end of a needle valve (not shown).
[0045]
Even in such a configuration, when the valve opening pressure changes due to the spring sag due to long-term use, the pressing jig 9 is inserted into the communication hole 6 from the outside of the nozzle holder 1 and this pressing is performed. When the male screw portion 9a of the jig 9 is screwed into the female screw portion 6a of the communication hole 6 and the pressing jig 9 is screwed, the tip of the pressing jig 9 pushes the bush 31 and the bush 31 overcomes the frictional force. It is moved downward in the figure. Therefore, since the spring 30 is compressed, the valve opening pressure can be adjusted.
[0046]
Note that the communication hole 6 for inserting the pressing jig 9 and the hole for allowing excess fuel to escape are not necessarily combined, and these holes may be formed separately.
In the present invention, a pressing jig prepared as a service tool in advance may be used as the pressing tool, or a tool such as a driver may be used.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a two-stage injection type fuel injection valve showing a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of a one-stage injection type fuel injection valve showing a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Nozzle holder 2 ... Distance piece 3 ... Nozzle body 5 ... Spring chamber 6 ... Communication hole 7 ... 1st bush 8 ... 2nd bush 9 ... Pressing jig 10 ... 1st spring 11 ... 2nd spring 12 ... first spring receiving sheet 13 ... push rod 14 ... second spring receiving sheet 15 ... fuel supply passage 21 ... fuel reservoir 22 ... injection hole 25 ... needle valve 28 ... pressing rod

Claims (3)

A nozzle holder having a spring chamber opened at one end and a communication hole communicating with the spring chamber at the other end;
A nozzle body having one end connected to the nozzle holder and the other end having a nozzle hole;
A needle valve housed in the nozzle body and lifted to open the nozzle hole when a fuel pressure equal to or higher than a predetermined valve opening pressure is reached;
A spring that is housed in a spring chamber of the nozzle holder, pushes the needle valve to close the nozzle hole, and allows the needle valve to lift when the needle valve receives a fuel pressure higher than a valve opening pressure;
It said movably secured by press-fitting the spring chamber, an adjustable bushing urging force of the upper Symbol spring;
An internal thread formed in the communication hole;
The bush has a shape that can be inserted from the communication hole and has an external thread portion on the outer peripheral portion, and is inserted through the communication hole and screwed into the internal thread portion, so that the bush is formed at the tip portion. A pressing tool that presses and moves the bush to adjust the biasing force of the spring;
A fuel injection valve comprising: 2. The fuel injection valve according to claim 1, wherein a valve opening pressure is set in the spring chamber in cooperation with the first spring that regulates the valve opening pressure at the time of initial injection and the first spring at the time of full injection. The first bush and the second bush for adjusting the urging force of the first spring and the second spring are respectively fixed by press-fitting, and the first bush However , the fuel injection valve is movable in the spring chamber when pressed by the pressing tool inserted through the communication hole and screwed into the female screw portion . 3. The fuel injection valve according to claim 1, wherein the communication hole also serves as a fuel escape hole.

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