JP3750697B2 - Fuel injection nozzle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection nozzle used in a diesel engine, and relates to a fuel injection nozzle having a structure in which a pressure pin that presses a needle that opens and closes an injection hole is arranged eccentric to the needle.
[0002]
[Prior art]
In recent years, in order to achieve both a reduction in the diameter of the fuel injection nozzle and an increase in pressure resistance, as shown in Japanese Patent Laid-Open No. 7-63137 (see FIG. 7), the pressure pin 12 and the spring 13 are arranged eccentrically in the holder body 11. As a result, a thick portion 14 is formed in the holder body 11, and a high pressure fuel passage 15 is formed in the thick portion 14. In this configuration, a flange 16 and a pressing projection 17 are formed at the lower end of the pressure pin 12, and the upper end surface of the needle 18 is pressed by the lower end of the pressing projection 17. The injection hole is closed by being brought into pressure contact with a sheet portion (not shown) around the injection hole.
[0003]
The fuel pressure-fed from the injection pump (not shown) into the fuel injection nozzle is sent to the oil sump (not shown) of the nozzle body 18 through the high-pressure fuel passage 15, and the fuel pressure reaches a predetermined valve opening. When the pressure exceeds the pressure, the needle 18 is pushed up by the fuel pressure, the injection hole is opened, and the fuel is injected. When the fuel pressure becomes lower than the valve opening pressure by this fuel injection, the needle 18 is pushed down by the pressure pin 12, the injection hole is closed, and the fuel injection is completed.
[0004]
[Problems to be solved by the invention]
In the above configuration, as the pressure pin 12 is eccentrically arranged, the pressing projection 17 at the lower end of the pressure pin 12 is displaced from the axis of the needle 18, and the pressing projection 17 moves the corner of the upper end surface of the needle 18. Will be pressed. For this reason, the pressing load from the pressing projection 17 to the needle 18 becomes an unbalanced load, and this causes an increase in sliding resistance between the needle 18 and the nozzle body 19, causing uneven wear on the sliding surface of the needle 18. As a result, the slidability of the needle 18 (responsiveness at the time of the on-off valve) is deteriorated, and the seal (oil tightness) between the needle 18 most important in the characteristics of the fuel injection nozzle and the seat portion around the injection hole is poor. Thus, the schnar characteristics (pressure pulsation characteristics) representing the valve performance are deteriorated.
[0005]
The present invention has been made in consideration of such circumstances. Accordingly, the object of the present invention is to provide an eccentric load for the needle by the eccentric load, while the pressure pin is eccentrically arranged to make the fuel injection nozzle smaller in diameter and higher in pressure resistance. It is an object of the present invention to provide a fuel injection nozzle that can prevent uneven wear of the sliding surface and can maintain the responsiveness at the time of the on-off valve, the oil tightness of the seat portion, and the schnarl characteristics well over a long period of time.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the fuel injection nozzle according to claim 1 of the present invention achieves both a reduction in the diameter of the fuel injection nozzle and an increase in pressure resistance by disposing the pressure pin eccentrically from the axis of the needle. together, by exerting a pressing load to the needle via the load acting position adjusting means from the pressure pin, the pressure load with respect to the needle same mental Wakashi Ku exerts on evenly. As a result, a large unbalanced load does not act on the needle, the uneven wear of the sliding surface of the needle can be prevented, and the responsiveness at the time of the on-off valve, the oil tightness of the seat portion, and the schnar characteristics are maintained well over a long period of time. be able to.
[0007]
In this case, the claim 1, as a load acting position adjusting means, using a pressing projection provided on the needle and the heart position between the pressure pin and the needle, the pressing load from the pressure pin via the pressing protrusion needle We have to act the same mind to to. Here, the pressing protrusion may be formed integrally with either the pressure pin or the needle, or the pressing protrusion formed with another piece may be fixed to either the pressure pin or the needle. In short, may be provided a pressing projection to the needle and the heart position, whereby it can be prevented that a large offset load on the needle acts, prevents uneven wear of the sliding surface of the needle. It should be noted that the positional relationship between the pressing protrusion and the needle need not be exactly the concentric position, as long as the amount of deviation from the concentric position is small (that is, as long as it is close to the concentric position). What is necessary is just to provide in a concentric position. Even in this case, the unbalanced load acting on the needle becomes smaller than before, and the unbalanced wear on the sliding surface of the needle is reduced.
[0008]
Further, in claim 2, the load acting position adjusting means, using a load transmission member that is provided so as to cover the entire surface of the end face of the needle between the pressure pin and the needle, load pressure load from pressure pin and so as to act on the entire surface of the end face of the needle through the transmission member. In this case, since the pressure load is applied to the entire surface of the end face of the needle, the pressure load on the entire end surface of the needle acts substantially uniformly, a large unbalanced load to the needle is prevented from acting. Here, the load transmission member may be formed as a separate piece, interposed between the pressure pin and the needle, or may be fixedly or integrally formed with either one.
[0009]
According to a third aspect of the present invention , the tubular portion of the spring seat urged downward by the spring is slidably fitted into the sliding hole formed in the packing interposed between the nozzle body and the holder body. In addition, the tip portion of the pressure pin is slidably inserted into the cylindrical portion. When the valve is opened, the pressure pin is pushed up to raise the needle to the pre-lift position until the load transmission member contacts the lower end of the cylindrical portion of the spring seat in the first stage, and the load transmission is performed in the second stage. A member pushes up both the pressure pin and the spring seat simultaneously to raise the needle to the maximum lift position. Thereby, the relationship between the valve opening pressure and the needle lift amount can be set in two stages, and the valve opening characteristic can be adapted to the load characteristic and the injection characteristic.
[0010]
In this configuration, since the cylindrical portion of the spring seat is slidably fitted into the sliding hole formed in the packing, the vertical movement of the spring seat is guided smoothly by the sliding hole of the packing. . In addition, since the pressure pin is slidably inserted into the cylindrical portion of the spring seat, the sliding area between the pressure pin and the spring seat increases, and wear between them decreases.
[0011]
On the other hand, in claim 4 , a large-diameter portion is formed at the lower end portion of the pressure pin, and the entire lower end surface of the large-diameter portion is brought into contact with the upper end surface of the load transmitting member. With this configuration, the contact area between the pressure pin and the load transmission member is expanded, and the uneven load acting on the load transmission member from the pressure pin is reduced.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. First, a schematic configuration of the entire fuel injection nozzle will be described with reference to FIG. The nozzle body 21 is attached to the holder body 23 by a retaining nut 22. A pressure pin 25 is accommodated in a vertical hole 24 formed at an eccentric position in the holder body 23 via a bearing member 26 so as to be slidable up and down. Further, a first spring 27 is housed immediately above the pressure pin 25 in the holder body 23, and the pressure pin 25 is urged downward by the elastic force of the first spring 27. A second spring 28 and an annular spring seat 29 are inserted into the pressure pin 25, and the spring seat 29 is biased downward by the elastic force of the second spring 28.
[0013]
A vertical hole 24 for accommodating the pressure pin 25 and the springs 27, 28 is formed eccentrically in the holder body 23, thereby forming a thick portion 30 in the holder body 23, and forming a high-pressure fuel passage 31 in the thick portion 30. ing. A packing 32 is sandwiched between the holder body 23 and the nozzle body 21, and these three members are fastened and fixed by a retaining nut 22. Both the packing 32 and the spring seat 29 are formed of bearing metal.
[0014]
The packing 32 and the nozzle body 21 are formed with high-pressure fuel passages 33 and 34 communicating with the high-pressure fuel passage 31 of the holder body 23, and fuel pressure-fed from a fuel pump (not shown) is fed into the high-pressure fuel passages 31, 33 and 34. It is sent to the oil sump (not shown) at the bottom of the nozzle body 21 through. In addition, a needle 35 to which a downward pressing load is applied by a pressure pin 25 is accommodated in a central portion in the nozzle body 21 so as to be slidable up and down, and a lower end portion of the needle 35 is formed at the lower end of the nozzle body 21. The injection hole is closed by pressing against a sheet portion (not shown) around the hole.
[0015]
Next, a structure for applying a pressing load from the pressure pin 25 to the needle 35 will be described based on FIG. 1 showing a state when the valve is closed. As described above, in order to form the thick portion 30 (high pressure fuel passage 31) in the holder body 23, the pressure pin 25 is disposed at a position shifted from the axis of the needle 35. A large-diameter portion 25a is integrally formed at the lower end portion of the pressure pin 25, and the large-diameter portion 25a is fitted in a sliding hole 36 formed in the packing 32 so as to be slidable in the vertical direction. On the lower end surface of the large-diameter portion 25a, a pressing projection 37 (load acting position adjusting means) is integrally formed downward at a position concentric with the needle 35. The pressing projection 37 is continuous with the packing 32 and the sliding hole 36. The pressing protrusion 37 is in contact with the center portion (axial center portion) of the upper end surface of the needle 35 through the insertion hole 38 formed as described above.
[0016]
In this case, the vertical dimension of the large-diameter portion 25 a of the pressure pin 25 is set to be smaller than the depth dimension of the sliding hole 36 of the packing 32, and the vertical dimension of the pressing protrusion 37 is set to be larger than the vertical dimension of the insertion hole 38. Thus, the pre-lift amount PHD and the maximum lift amount HD are secured.
[0017]
When the valve is closed, as shown in FIG. 1, the spring seat 29 comes into contact with the upper end surface of the packing 32, and between the spring seat 29 and the upper end surface of the large diameter portion 25a of the pressure pin 25, it corresponds to the prelift amount PHD. A gap is secured. When the valve is closed, the pressing protrusion 37 protrudes downward from the lower end surface of the packing 32 to push down the needle 35, so that a gap corresponding to the maximum lift amount HD is formed between the lower end surface of the packing 32 and the upper end surface of the needle 35. It is secured.
[0018]
When the fuel pressure of the oil sump below the nozzle body 21 is lower than the first valve opening pressure (corresponding to the pressing force from the pressure pin 25), the pressing force from the pressing protrusion 37 of the pressure pin 25 causes the lower end of the needle 35 to move. It is brought into pressure contact with the sheet portion around the injection hole to hold the injection hole in a closed state. Thereafter, when the fuel pressure of the oil pool becomes higher than the first valve opening pressure, the needle 35 rises overcoming the pressing force from the pressing protrusion 37, and the upper end surface of the large diameter portion 25 a of the pressure pin 25 is below the packing 32. The fuel comes into contact with the end face and the injection hole is opened to inject fuel. The lift amount of the needle 35 at this time becomes the prelift amount PHD.
[0019]
When the fuel pressure of the oil sump is not less than the first valve opening pressure and not more than the second valve opening pressure, the lift amount of the needle 35 is maintained at the pre-lift amount PHD, but the fuel pressure of the oil sump is the second valve opening pressure. When the valve opening pressure becomes higher, the needle 35 rises while the spring seat 29 is pushed up against the second spring 28 by the large diameter portion 25 a of the pressure pin 25, and the upper end surface of the needle 35 becomes the lower end surface of the packing 32. It comes into contact. The lift amount of the needle 35 at this time is the maximum lift amount HD.
[0020]
When the fuel pressure in the oil pool is reduced by the fuel injection, the needle 35 is pushed down by the pressing force from the pressing projection 37 of the pressure pin 25, and the lower end portion of the needle 35 comes into pressure contact with the seat portion around the injection hole. The injection hole is closed. An example of the change over time of the lift amount of the needle 35 described above is shown in FIG.
[0021]
According to the fuel injection nozzle described above, the thick portion 30 is formed in the holder body 23 by disposing the pressure pin 25 and the springs 27 and 28 in the holder body 23 eccentrically, and the high pressure fuel passage is formed in the thick portion 30. By forming 31, the fuel injection nozzle can have both a small diameter and a high pressure resistance. Thus, as the pressure pin 25 is eccentrically arranged, the position of the pressure pin 25 deviates from the axis of the needle 35, but the lower end portion (large diameter portion 25 a) of the pressure pin 25 is concentric with the needle 35. Since the pressing protrusion 37 is integrally provided at the position of FIG. 5, the pressing load from the pressure pin 25 can be applied to the axial center portion of the needle 35 by the pressing protrusion 37, and a large offset load is applied to the needle 35. Can be prevented. Thereby, uneven wear of the sliding surface of the needle 35 can be prevented, the durability of the needle 35 can be improved, responsiveness at the time of the on-off valve (slidability of the needle 35), and oil tightness of the seat portion In addition, the schnar characteristics can be maintained well over a long period of time.
[0022]
In the above embodiment, the pressing protrusion 37 is integrally provided at the lower end portion (large diameter portion 25a) of the pressure pin 25. However, the pressing protrusion formed as a separate piece is connected to the lower end portion (large diameter portion 25a) of the pressure pin 25. For example, the pressing protrusion of another piece may be fixed to the pressure pin, such as by fitting into the hole formed in (1). The pressing protrusion may be provided at the upper end of the needle 35. In short, the pressing protrusion may be provided at a position substantially concentric with the needle 35. Further, the positional relationship between the pressing protrusion and the needle 35 is not required to be precisely the concentric position, but it is sufficient if the deviation amount from the concentric position is small (that is, close to the concentric position). Even in this case, the unbalanced load acting on the needle 35 becomes smaller than the conventional one, and the uneven wear of the sliding surface of the needle 35 is reduced.
[0023]
Next, a second embodiment of the present invention will be described based on FIG. However, the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted, and only different parts are denoted by different reference numerals. In the second embodiment, a cylindrical portion 29 a is integrally projected downward at the center portion of the spring seat 29, and the cylindrical portion 29 a is slidably fitted into a sliding hole 39 formed in the packing 32. The lower end portion of the pressure pin 25 is slidably inserted into the cylindrical portion 29a. At the lower end of the pressure pin 25, the large-diameter portion 25a and the pressing protrusion 37 as in the first embodiment are not formed.
[0024]
On the other hand, a large-diameter hole 40 is formed eccentrically in the packing 32 below the sliding hole 39. In the large diameter hole 40, the needle 35 and the cylindrical portion 29a of the spring seat 29 protrude, and the lower end of the pressure pin 25 protrudes from the cylindrical portion 29a of the spring seat 29. A load transmitting member 41 (load acting position adjusting means) is sandwiched between the pressure pin 25 and the needle 35, and the load transmitting member 41 is fitted into the large-diameter hole 40 of the packing 32 so as to be slidable up and down. Yes. The entire lower end surface of the pressure pin 25 abuts on the upper end surface of the load transmitting member 41, the entire upper end surface of the needle 35 abuts on the lower end surface of the load transmitting member 41, and the pressure load on the pressure pin 25 is applied to the load transmitting member 41. It is transmitted to the entire upper end surface of the needle 35 via the.
[0025]
In this case, the cylindrical portion 29a of the spring seat 29 protrudes into the large-diameter hole 40 of the packing 32, and the lower end of the pressure pin 25 protrudes from the cylindrical portion 29a, so that the pre-lift amount PHD and the maximum lift amount HD. And ensure.
[0026]
When the fuel pressure of the oil sump below the nozzle body 21 is lower than the first valve opening pressure (corresponding to the pressing force from the pressure pin 25), the pressing force from the load transmitting member 41 causes the lower end of the needle 35 to surround the injection hole. The sheet is pressed against the sheet portion and the injection hole is held closed. Thereafter, when the fuel pressure in the oil pool becomes higher than the first valve opening pressure, the needle 35 rises overcoming the pressing force from the load transmission member 41, and the upper end surface of the load transmission member 41 is the cylindrical portion of the spring seat 29. It will be in the state contact | abutted to the lower end surface of 29a, an injection hole will be open | released, and fuel will be injected. The lift amount of the needle 35 at this time becomes the prelift amount PHD.
[0027]
When the fuel pressure of the oil sump is not less than the first valve opening pressure and not more than the second valve opening pressure, the lift amount of the needle 35 is maintained at the pre-lift amount PHD, but the fuel pressure of the oil sump is the second valve opening pressure. When higher than the valve opening pressure, the needle 35 rises while pushing up the spring seat 29 against the second spring 28 by the load transmission member 41, and the upper end surface of the load transmission member 41 is in the large-diameter hole 40 of the packing 32. It will be in the state contact | abutted to the upper end surface. The lift amount of the needle 35 at this time is the maximum lift amount HD. Thus, the valve opening characteristic can be adapted to the load characteristic and the injection characteristic by setting the relationship between the valve opening pressure and the needle lift amount in two stages.
[0028]
When the fuel pressure in the oil pool is reduced by fuel injection, the needle 35 is pushed down by the pressing force from the load transmitting member 41, the lower end portion of the needle 35 is pressed against the seat portion around the injection hole, and the injection hole is Closed.
[0029]
In the second embodiment described above, the load transmission member 41 that covers the entire upper end surface of the needle 15 is interposed between the pressure pin 25 and the needle 35, and the pressure load from the pressure pin 25 is applied to the load transmission member 41. It acts on the entire upper end surface of the needle 35 via For this reason, the pressing load acts on the upper end surface of the needle 35 substantially evenly, the uneven load acting on the needle 35 is reduced, and the uneven wear of the sliding surface of the needle 35 is prevented.
[0030]
Further, since the cylindrical portion 29 a of the spring seat 29 is slidably fitted in the sliding hole 39 formed in the packing 32, the vertical movement of the spring seat 29 is guided to the sliding hole 39 of the packing 32. It is performed smoothly and the responsiveness when opening and closing is improved. Moreover, since the pressure pin 25 is slidably inserted into the cylindrical portion 29a of the spring seat 29, the sliding area between the pressure pin 25 and the spring seat 29 is increased, and wear between both is reduced.
[0031]
In the second embodiment described above, the load transmitting member 41 is sandwiched between the pressure pin 25 and the needle 35. However, the load transmitting member 41 is fixed to either the pressure pin 25 or the needle 35. Alternatively, they may be integrally formed. Further, a part of the upper end surface of the needle 35 may not be in contact with the load transmitting member 41. Even in this case, the area where the pressing load is applied to the upper end surface of the needle 35 from the load transmitting member 41 is enlarged. This can reduce the unbalanced load acting on the needle 35.
[0032]
Next, a third embodiment of the present invention will be described based on FIG. In the third embodiment, the structure of the second embodiment is partially changed. That is, the spring seat 29 is the same as that of the first embodiment, but has no cylindrical portion 29a, and the large-diameter portion 25a is integrally formed at the lower end portion of the pressure pin 25 as in the first embodiment. The large diameter portion 25a is fitted in a sliding hole 36 formed in the packing 32 so as to be slidable in the vertical direction. The sliding hole 36 of the packing 32 is continuous with the large-diameter hole 40 into which the load transmitting member 41 is slidably fitted, and the large-diameter portion of the pressure pin 25 protrudes downward from the sliding hole 36 of the packing 32. The entire lower end surface of 25a is in contact with the upper end surface of the load transmitting member 41.
[0033]
In this configuration, the prelift amount PHD is regulated by the size of the gap between the upper end surface of the large diameter portion 25a of the pressure pin 25 and the lower end surface of the spring seat 29, and the maximum lift amount HD is the upper end surface of the load transmitting member 41. And a clearance dimension between the upper end surface of the large-diameter hole 40 of the packing 32 and the upper end surface of the packing 32.
[0034]
In the third embodiment described above, the pressure pin 25 and the load transmission member 41 are brought into contact with the upper end surface of the load transmission member 41 by bringing the entire lower end surface of the large diameter portion 25a formed at the lower end portion of the pressure pin 25 into contact with the upper end surface. The contact area between the pressure pin 25 and the load transmission member 41 can be reduced. Thereby, the eccentric load which acts on the pressure pin 25 from the load transmission member 41 can further be reduced rather than 2nd Embodiment.
[Brief description of the drawings]
FIG. 1 is an enlarged longitudinal sectional view of a main part of a fuel injection nozzle showing a first embodiment of the present invention. FIG. 2 is a transverse sectional view taken along line AA in FIG. FIG. 4 is a partially cutaway sectional view of FIG. 4. FIG. 5 is a time chart showing the needle lift operation. FIG. 5 is an enlarged vertical sectional view of the main part of the fuel injection nozzle showing the second embodiment of the invention. FIG. 7 is an enlarged longitudinal sectional view of a main part of a fuel injection nozzle showing a third embodiment. FIG. 7 is an enlarged longitudinal sectional view of a main part of a conventional fuel injection nozzle.
21 ... Nozzle body, 22 ... Retaining nut, 23 ... Holder body, 25 ... Pressure pin, 25a ... Large diameter part, 27 ... First spring, 28 ... Second spring, 29 ... Spring seat, 29a ... Cylindrical part, DESCRIPTION OF SYMBOLS 30 ... Thick part, 31 ... High pressure fuel passage, 32 ... Packing, 33, 34 ... High pressure fuel passage, 36 ... Sliding hole, 37 ... Pressing protrusion (load action position adjustment means), 38 ... Insertion hole, 39 ... Sliding Moving hole, 40... Large diameter hole, 41... Load transmission member (load action position adjusting means).

Claims (4)

In a fuel injection nozzle comprising a nozzle body having an injection hole at the tip, a needle housed in the nozzle body so as to open and close the injection hole, and a pressure pin for pressing the needle in a direction to close the injection hole.
Wherein the pressure pin while arranged shaft is sincerely eccentricity of the needle, the load acting position adjusting means for applying a pressing load to the Ku same mental Wakashi with respect to the needle is evenly from the pressure pin into the needle set,
The load acting position adjusting means is a pressing protrusion provided concentrically with the needle between the pressure pin and the needle, and the pressing load from the pressure pin is concentric with the needle through the pressing protrusion. A fuel injection nozzle that acts on the fuel. The load acting position adjusting means, wherein a load transmission member that is provided so as to cover the entire surface of the end face of the needle between the pressure pin and said needle, said load transfer member pressing force from the pressure pin the fuel injection nozzle according to claim 1, characterized in that acting on the entire surface of the end face of the needle through the. A cylindrical portion of a spring seat urged downward by a spring is slidably fitted in a sliding hole formed in a packing interposed between the nozzle body and the holder body. The tip of the pressure pin is slidably inserted into the part,
When the valve is opened, the pressure pin is pushed up to raise the needle to the pre-lift position until the load transmission member contacts the lower end of the cylindrical portion of the spring seat in the first stage, and the load transmission member is moved to the pre-lift position in the second stage. The fuel injection nozzle according to claim 2 , wherein both the pressure pin and the spring seat are simultaneously pushed up to raise the needle to a maximum lift position. The fuel injection nozzle according to claim 2 , wherein a large diameter portion is formed at a lower end portion of the pressure pin, and an entire lower end surface of the large diameter portion is in contact with an upper end surface of the load transmitting member. .

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