JPH09242645A - Fuel injection nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the eccentric abrasion of the sliding surface of a needle due to an eccentric load while attempting compatibility between a decrease in the diameter of a fuel injection nozzle and high pressure resistance thereof by eccentrically arranging a pressure pin. SOLUTION: A pressure pin 25 and a spring 28 are eccentrically arranged in a holder body 23 so as to form a thick part 30 in the holder body 23, and a high pressure fuel passage 31 is formed in this thick part 30 so as to attempt compatibility between the decrease of the diameter of a fuel injection nozzle and high pressure resistance thereof. A pushing/pressing projection 37 is integrally projected in a position concentric with a needle 35 in a large diametral part 25a at the lower end of the pressure pin 25, and brought in contact with the center of the upper end surface of the needle 35. Hereby, a pushing/pressing load from the pressure pin 25 can be applied to the center of the upper end surface of the needle 35, so that a large eccentric load can be prevented from being applied to the needle 35, and the eccentric abrasion of the sliding surface of the needle 35 can be prevented, and pulsation characteristics can be excellently retained for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection nozzle used in a diesel engine and having a structure in which a pressure pin for pressing a needle for opening and closing an injection hole is eccentrically arranged with respect to the needle. Is.

[0002]

2. Description of the Related Art In recent years, in order to make a fuel injection nozzle smaller in diameter and higher in pressure resistance at the same time, as shown in JP-A-7-63137 (see FIG. 7), a pressure pin 12 and a spring are provided in a holder body 11. There is one in which 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 by eccentrically arranging 13 and 13. In this structure, the flange 16 and the pressing protrusion 17 are formed at the lower end of the pressure pin 12, and the lower end of the pressing protrusion 17 presses the upper end surface of the needle 18 to move the lower end of the needle 18 to the lower end of the nozzle body 19. A sheet portion (not shown) around the injection hole is pressed to close the injection hole.

The fuel pumped into the fuel injection nozzle from an injection pump (not shown) is sent to an oil reservoir (not shown) of the nozzle body 18 through the high-pressure fuel passage 15, and the fuel pressure is set to a predetermined value. When the valve opening pressure becomes higher than the valve opening 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 due to this fuel injection, the needle 18 is pushed down by the pressure pin 12, the injection hole is closed, and the fuel injection ends.

[0004]

In the above-mentioned structure, the pressing projection 17 at the lower end of the pressure pin 12 is displaced from the axial center of the needle 18 as the pressure pin 12 is eccentrically arranged, and the pressing projection 17 is The corner of the upper end surface of the needle 18 is pressed. Therefore, the pressing protrusion 1
The pressing load from the needle 7 to the needle 18 becomes an unbalanced load, which causes the sliding resistance between the needle 18 and the nozzle body 19 to increase, resulting in uneven wear on the sliding surface of the needle 18 and sliding of the needle 18. The dynamic performance (responsiveness at the time of opening / closing valve) is deteriorated, and the sealing property (oil tightness) between the needle 18 and the seat portion around the injection hole, which is the most important characteristic of the fuel injection nozzle, is deteriorated. Schneal characteristics (pressure pulsation characteristics) deteriorate.

The present invention has been made in consideration of the above circumstances, and therefore an object thereof is to eccentrically dispose a pressure pin to achieve both a small diameter of a fuel injection nozzle and a high withstand pressure while achieving an eccentric load. An object of the present invention is to provide a fuel injection nozzle that can prevent uneven wear of the sliding surface of the needle due to the above, and can maintain excellent responsiveness at the time of opening / closing, oil tightness of the seat portion, and Schneal characteristics for a long period of time. .

[0006]

In order to achieve the above object, in the fuel injection nozzle according to claim 1 of the present invention, the pressure pin is arranged eccentrically from the axial center of the needle,
Both the small diameter and high withstand pressure of the fuel injection nozzle are achieved, and the pressing load is applied to the needle from the pressure pin through the load acting position adjusting means, so that the pressing load is substantially concentric or even with respect to the needle. To act on. As a result, a large unbalanced load does not act on the needle, uneven wear on the sliding surface of the needle can be prevented, and responsiveness at the time of opening / closing the valve, oil tightness of the seat portion, and Schneal characteristics are maintained well for a long period of time. be able to.

In this case, according to the second aspect, as the load acting position adjusting means, a pressing projection provided between the pressure pin and the needle in a position substantially concentric with the needle is used, and the pressing load from the pressure pin uses the pressing projection. It is designed to act almost concentrically on the needle. Here, the pressing protrusion may be integrally formed on either one of the pressure pin and the needle, or the pressing protrusion formed by another piece may be fixed to either one of the pressure pin and the needle. The point is that the pressing protrusions may be provided substantially concentrically with the needles, whereby a large unbalanced load can be prevented from acting on the needles, and uneven wear of the sliding surface of the needles can be prevented.

According to the present invention, as the load acting position adjusting means, a load transmitting member provided between the pressure pin and the needle so as to cover substantially the entire end face of the needle is used. The load acts on almost the entire end face of the needle via the load transmitting member. In this case, since the pressing load acts on almost the entire end surface of the needle, the pressing load acts substantially evenly on the entire end surface of the needle, and a large unbalanced load is prevented from acting on the needle. Here, the load transmission member may be formed as a separate piece and may be interposed between the pressure pin and the needle, or may be fixed to or integrally formed with either one.

Further, according to 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. The distal end portion of the pressure pin is slidably inserted into the tubular portion. Then, 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 comes into contact with the lower end of the tubular portion of the spring seat in the first stage, and the load transmission in the second stage. A member simultaneously pushes up both the pressure pin and the spring seat 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.

In this structure, since the tubular portion of the spring seat is slidably fitted in the sliding hole formed in the packing, the vertical movement of the spring seat is guided by the sliding hole of the packing and smoothed. To be done. Moreover, since the pressure pin is slidably inserted into the tubular portion of the spring seat, the sliding area between the pressure pin and the spring seat is increased, and wear between the two is reduced.

On the other hand, in claim 5, a large diameter portion is formed at the lower end portion of the pressure pin, and the entire lower end surface of this 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 transmitting member is enlarged, and the eccentric load that acts on the load transmitting member from the pressure pin is reduced.

[0012]

DETAILED DESCRIPTION OF THE INVENTION A first embodiment of the present invention will be described below with reference to FIGS. First, a schematic configuration of the entire fuel injection nozzle will be described based on FIG. The nozzle body 21 is attached to the holder body 23 by a retaining nut 22. The pressure pin 2 is inserted into the vertical hole 24 formed at the eccentric position in the holder body 23.
5 is housed via a bearing member 26 so as to be vertically slidable. Further, a first spring 27 is housed just above the pressure pin 25 in the holder body 23, and the elastic force of the first spring 27 urges the pressure pin 25 downward. This pressure pin 25 has
The second spring 28 and the annular spring seat 29 are inserted, and the spring seat 29 is biased downward by the elastic force of the second spring 28.

These pressure pin 25 and spring 2
By forming the vertical hole 24 for accommodating 7, 28 in the holder body 23 in an eccentric manner, the thick portion 30 is formed in the holder body 23.
And a high-pressure fuel passage 31 is formed in the thick portion 30. Then, the holder body 23 and the nozzle body 21
A packing 32 is sandwiched between and, and these three members are fastened and fixed by a retaining nut 22. Packing 3
Both 2 and the spring seat 29 are made of bearing metal.

The packing 32 and the nozzle body 21 are formed with high-pressure fuel passages 33 and 34 which communicate with the high-pressure fuel passage 31 of the holder body 23, and the fuel pumped from a fuel pump (not shown) is supplied to the high-pressure fuel passage 31, 33,34
It is designed to be fed through an oil reservoir (not shown) at the bottom of the nozzle body 21 through. A needle 35 to which a downward pressure load is applied by a pressure pin 25 is housed in the nozzle body 21 in a vertically slidable manner, and the lower end of the needle 35 is formed at the lower end of the nozzle body 21. A sheet portion (not shown) around the hole is pressed to close the injection hole.

Next, a structure for applying a pressing load from the pressure pin 25 to the needle 35 will be described with reference to 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 arranged at a position deviated from the axis of the needle 35. A large diameter portion 25a is integrally formed at a lower end portion of the pressure pin 25, and the large diameter portion 25a is vertically slidably fitted in a sliding hole 36 formed in the packing 32. On the lower end surface of the large diameter portion 25a, a pressing protrusion 37 (load acting position adjusting means) is integrally formed downward at a position concentric with the needle 35, and the pressing protrusion 37 is continuous with the packing 32 and the sliding hole 36. The pressing projection 37 is inserted into the insertion hole 38 formed in this way, and abuts on the central portion (axial center portion) of the upper end surface of the needle 35.

In this case, the large diameter portion 2 of the pressure pin 25
By making the vertical dimension of 5a smaller than the depth dimension of the sliding hole 36 of the packing 32 and setting the vertical dimension of the pressing protrusion 37 larger than the vertical dimension of the insertion hole 38, the pre-lift amount PHD and the maximum lift amount HD are set. And are secured.

When the valve is closed, as shown in FIG. 1, the spring seat 29 is in contact with the upper end surface of the packing 32, and a pre-lift amount is provided between the spring seat 29 and the upper end surface of the large diameter portion 25a of the pressure pin 25. A gap corresponding to PHD is secured. When the valve is closed, the pressing protrusion 37
The needle 3 protruding downward from the lower end surface of the packing 32.
By pushing down 5, the gap corresponding to the maximum lift amount HD is secured between the lower end surface of the packing 32 and the upper end surface of the needle 35.

When the fuel pressure in the oil reservoir 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 needle 35 to move. The lower end is brought into pressure contact with the sheet portion around the injection hole to hold the injection hole in a closed state. After that, when the fuel pressure in the oil pool becomes higher than the first valve opening pressure, the needle 35 overcomes the pressing force from the pressing protrusion 37 and ascends, and the upper end surface of the large diameter portion 25a of the pressure pin 25 is below the packing 32. The end face is brought into contact with the end face, the injection hole is opened, and the fuel is injected.
The lift amount of the needle 35 at this time is the pre-lift amount PH.
D.

When the fuel pressure in the oil sump is equal to or higher than the first valve opening pressure and equal to or lower than the second valve opening pressure, the lift amount of the needle 35 is held at the pre-lift amount PHD, but the fuel pressure in the oil sump is reduced. When it becomes higher than the second valve opening pressure, the pressure pin 2
The needle 35 ascends while pushing up the spring seat 29 against the second spring 28 at the large diameter portion 25a of No. 5, and the upper end surface of the needle 35 comes into contact with the lower end surface of the packing 32. The lift amount of the needle 35 at this time becomes the maximum lift amount HD.

When the fuel pressure in the oil pool decreases due to the fuel injection, the needle 35 is pushed down by the pressing force from the pressing protrusion 37 of the pressure pin 25, and the lower end of the needle 35 comes into pressure contact with the seat portion around the injection hole. hand,
The injection hole is closed. An example of the change in the lift amount of the needle 35 described above with time is shown in FIG.

According to the fuel injection nozzle described above, the pressure pin 25 and the spring 2 are provided in the holder body 23.
7 and 28 are eccentrically arranged to form a thick portion 30 in the holder body 23, and the high pressure fuel passage 3 is formed in the thick portion 30.
By forming No. 1, the fuel injection nozzle has both a small diameter and a high pressure resistance. In this way, the pressure pin 2
Although the position of the pressure pin 25 deviates from the axial center of the needle 35 with the eccentric arrangement of 5, the lower end portion (large diameter portion 25a) of the pressure pin 25 has a pressing projection 37 at a position concentric with the needle 35. , The pressing load from the pressure pin 25 can be applied to the axial center of the needle 35 by the pressing protrusion 37, and a large unbalanced load can be prevented from acting on the needle 35.
As a result, uneven wear of the sliding surface of the needle 35 can be prevented, durability of the needle 35 can be improved, responsiveness at the time of opening and closing the valve (sliding property of the needle 35), oil tightness of the seat portion Thus, the schnarl characteristics can be maintained well over a long period of time.

In the above embodiment, the pressure pin 2 is used.
Although the pressing protrusion 37 is integrally provided on the lower end portion (large diameter portion 25a) of 5, the pressing protrusion formed by another piece is fitted into the hole formed in 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. The pressing protrusion may be provided on 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 limited to the exact concentric position, but it is sufficient if the amount of deviation from the concentric position is small (that is, it is good if it is close to the concentric position). Even in this case, the eccentric load acting on the needle 35 is smaller than in the conventional case, and the eccentric wear of the sliding surface of the needle 35 is reduced.

Next, a second embodiment of the present invention will be described with reference to FIG. However, the same parts as those of the first embodiment will be designated by the same reference numerals and the description thereof will be omitted, and only different parts will be designated by different reference numerals. In the second embodiment, a tubular portion 29a is integrally provided so as to project downward at the center of the spring seat 29, and the tubular portion 29a is provided with a packing 32.
It is slidably fitted in a sliding hole 39 formed in the lower end of the pressure pin 25, and the lower end of the pressure pin 25 is slidably inserted in the tubular portion 29a. The lower end of the pressure pin 25 has a first
The large-diameter portion 25a and the pressing protrusion 37 as in the above embodiment are not formed.

On the other hand, in the packing 32, a large diameter hole 40 is eccentrically formed below the sliding hole 39. The needle 35 and the tubular portion 29a of the spring seat 29 project into the large-diameter hole 40, and the lower end of the pressure pin 25 projects from the tubular 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 vertically slidably fitted in the large diameter hole 40 of the packing 32. There is. Then, the entire lower end surface of the pressure pin 25 contacts the upper end surface of the load transmitting member 41, the entire upper end surface of the needle 35 contacts the lower end surface of the load transmitting member 41, and the pressing load of the pressure pin 25 is applied to the load transmitting member 41. It is adapted to be transmitted to the entire upper end surface of the needle 35 via.

In this case, the tubular portion 29a of the spring seat 29 projects into the large diameter hole 40 of the packing 32, and further,
The lower end of the pressure pin 25 projects from the tubular portion 29a to secure the pre-lift amount PHD and the maximum lift amount HD.

When the fuel pressure in the oil reservoir 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 portion of the needle 35 to move. The sheet around the injection hole is brought into pressure contact with the sheet to keep the injection hole closed. After that, when the fuel pressure in the oil pool becomes higher than the first valve opening pressure, the needle 35 overcomes the pressing force from the load transmitting member 41 and ascends, and the upper end surface of the load transmitting member 41 has a cylindrical portion of the spring seat 29. The lower end surface of 29a is brought into contact with the lower surface, the injection hole is opened, and fuel is injected. The lift amount of the needle 35 at this time becomes the pre-lift amount PHD.

When the fuel pressure in the oil sump is equal to or higher than the first valve opening pressure and equal to or lower 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 in the oil sump is reduced. When the pressure becomes higher than the second valve opening pressure, the load transmission member 41
The needle 35 ascends while pushing up the spring seat 29 against the second spring 28, and the upper end surface of the load transmission member 41 comes into contact with the upper end surface of the large diameter hole 40 of the packing 32. The lift amount of the needle 35 at this time becomes the maximum lift amount HD. In this way, by setting the relationship between the valve opening pressure and the needle lift amount in two stages, the valve opening characteristic can be adapted to the load characteristic and the injection characteristic.

When the fuel pressure in the oil pool decreases due to the fuel injection, the needle 35 is pushed down by the pressing force from the load transmission member 41, and the lower end of the needle 35 comes into pressure contact with the seat portion around the injection hole, The injection hole is closed.

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,
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 the. Therefore, the pressing load acts substantially evenly on the upper end surface of the needle 35, the uneven load acting on the needle 35 is reduced, and the uneven wear of the sliding surface of the needle 35 is prevented.

Further, the sliding hole 3 formed in the packing 32
Since the tubular portion 29a of the spring seat 29 is slidably fitted to the spring 9, the vertical movement of the spring seat 29 is smoothly guided by the sliding hole 39 of the packing 32, and the response at the time of opening and closing the valve. It improves the sex. Moreover, since the pressure pin 25 is slidably inserted into the tubular portion 29a of the spring seat 29, the sliding area between the pressure pin 25 and the spring seat 29 is increased, and the wear between the two is reduced.

In the second embodiment described above, the load transmitting member 41 is provided between the pressure pin 25 and the needle 35.
, The load transmitting member 41 is fixed to either one of the pressure pin 25 and 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 from the load transmitting member 41 to the upper end surface of the needle 35 is increased. Therefore, the unbalanced load acting on the needle 35 can be reduced.

Next, a third embodiment of the present invention will be described with reference to FIG. The third embodiment is a partial modification of the structure of the second embodiment. That is, as the spring seat 29, the one without the cylindrical portion 29a is used as in the first embodiment, 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 vertically slidably fitted in a sliding hole 36 formed in the packing 32. The sliding hole 36 of the packing 32 is continuous with the large diameter hole 40 into which the load transmission member 41 is vertically slidably fitted, and the large diameter portion of the pressure pin 25 protruding 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 transmission member 41.

In this structure, the pre-lift 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 determined by the load transmission member 41. It is regulated by the gap between the upper end surface of the and the upper end surface of the large diameter hole 40 of the packing 32.

In the third embodiment described above, the entire lower end surface of the large diameter portion 25a formed at the lower end portion of the pressure pin 25 is brought into contact with the upper end surface of the load transmitting member 41,
The contact area between the pressure pin 25 and the load transmission member 41 can be increased, and the eccentric load acting on the load transmission member 41 from the pressure pin 25 can also be reduced. As a result, the eccentric load that acts on the pressure pin 25 from the load transmitting member 41 can be further reduced as compared with the second embodiment.

[Brief description of drawings]

FIG. 1 is an enlarged vertical sectional view of a main portion of a fuel injection nozzle showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line AA of FIG.

FIG. 3 is a partially cutaway sectional view of a fuel injection nozzle.

FIG. 4 is a time chart showing a lift operation of a needle.

FIG. 5 is an enlarged vertical cross-sectional view of the main part of the fuel injection nozzle showing the second embodiment of the present invention.

FIG. 6 is an enlarged vertical cross-sectional view of a main part of a fuel injection nozzle showing a third embodiment of the present invention.

FIG. 7 is an enlarged vertical sectional view of a main part of a conventional fuel injection nozzle.

[Explanation of reference numerals] 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, 30 ...
Thick wall portion, 31 ... High-pressure fuel passage, 32 ... Packing, 33,
34 ... High-pressure fuel passage, 36 ... Sliding hole, 37 ... Pressing projection (load acting position adjusting means), 38 ... Insertion hole, 39 ... Sliding hole, 40 ... Large diameter hole, 41 ... Load transmitting member (Load acting position) Adjusting means).

Claims (5)

[Claims] 1. A nozzle body having an injection hole at its tip,
In a fuel injection nozzle including a needle housed in the nozzle body so as to open and close the injection hole, and a pressure pin that presses the needle in a direction of closing the injection hole, the pressure pin is the axial center of the needle. The fuel injection nozzle is characterized in that it is eccentrically disposed from the pressure pin, and is provided with load acting position adjusting means for causing a pressing load from the pressure pin to the needle to act substantially concentrically or substantially evenly on the needle. 2. The load acting position adjusting means is a pressing protrusion provided between the pressure pin and the needle at a position substantially concentric with the needle, and a pressing load from the pressure pin passes through the pressing protrusion. 2. The fuel injection nozzle according to claim 1, wherein the fuel injection nozzle acts substantially concentrically on the needle. 3. The load acting position adjusting means is a load transmitting member provided between the pressure pin and the needle so as to cover substantially the entire end surface of the needle, and the pressing load from the pressure pin. The fuel injection nozzle according to claim 1, wherein the fuel injection nozzle acts on substantially the entire end surface of the needle via the load transmission member. 4. A tubular 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. At the same time, the tip end portion of the pressure pin is slidably inserted into the tubular portion, and when the valve is opened, the pressure pin is held until the load transmission member comes into contact with the lower end of the tubular portion of the spring seat in the first step. 4. The needle is pushed up to raise the needle to a pre-lift position, and in the second stage, the load transmission member pushes up both the pressure pin and the spring seat at the same time to raise the needle to the maximum lift position. The fuel injection nozzle according to. 5. 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. The fuel injection nozzle described.