JPH057500Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention can prevent the pump housing and plunger from being damaged by the cut-off jet flowing back through the intake and exhaust hole of the plunger barrel at the end of fuel injection. Regarding fuel injection pumps.

[Prior Art] In general, in fuel injection pumps, when fuel injection ends, high-pressure fuel flows backward through the intake and exhaust holes, which is the so-called cut-off jet, which is unavoidable, and the pump housing is said to be damaged by this cut-off jet. There's a problem. Therefore, various measures have been taken to prevent damage caused by the cut-off jet.

FIG. 3 shows an example of a fuel injection pump in which such measures have been taken. The fuel injection pump shown in this figure uses a plunger 5 to compress fuel sucked from a fuel reservoir 2 of a pump housing 1 through an intake/discharge hole 4 of a plunger barrel 3, and then pumps the compressed fuel to a fuel injection nozzle (not shown). A repulsion screw 8 is screwed and fixed to the part of the pump housing 1 facing the suction and discharge hole 4, and when the lead 6 of the plunger 5 reaches the suction and discharge hole 4, From the compression chamber 9 to the vertical groove (communication path) 7
Also, the pump housing 1 is prevented from being damaged by the cut-off jet flowing into the fuel reservoir chamber 2 through the suction/discharge hole 4.

However, in the above fuel injection pump,
At the end of the suction stroke of the plunger 5, the inside of the suction/discharge hole 4 becomes negative pressure, and bubbles are generated there. This bubble is crushed by the wave reflected by the cut-off jet from the repulsion screw 8. At this time, a shock wave with large energy is generated, and this shock wave causes damage (cavitation erosion) to the outer periphery of the plunger 5 and the inner periphery of the suction/discharge hole 4.

In this regard, the fuel injection pump shown in Fig.
61-175570), a tapered hole portion 4a is formed at the end of the suction/discharge hole 4 on the side of the pump housing 1, and a rectifying deflector 10 having a tapered portion 10a on the tip surface is screwed and fixed to the pump housing 1. 10a is inserted into the tapered hole 4a with a gap 11, and the taper degree of the tapered portion 10a is set smaller than that of the tapered hole 4a. Therefore, the gap 11 between them
gradually increases from the small diameter side to the large diameter side of the tapered hole 4a. Since the gap 11 gradually increases in this way,
While the cut-off jet passes through the gap 11, its injection energy is gradually weakened and furthermore, it is rectified. The weakened jet stream then hits the tip end face of the deflector 10 and is dispersed into the oil reservoir chamber 2. Therefore, the air bubbles generated inside the suction/discharge hole 4 are not crushed, and cavitation erosion can be prevented from occurring.

By the way, in the fuel injection pump shown in FIG. 4, the fuel supply hole (fuel discharge hole) 12 is located 90 degrees in the circumferential direction with respect to the suction and discharge hole 4, as shown by the two-dot chain line.
There is no problem because they are placed at a certain distance apart, but with fuel circulation injection pumps for ships,
Due to the layout of the engine, there are cases where at least one of the fuel supply hole and the fuel injection/discharge hole must be disposed to face the intake/discharge hole. In such a case, if a rectifying deflector is placed in the fuel supply hole or the fuel discharge hole facing the suction and discharge hole, fuel cannot be supplied or discharged. For this reason, it was not possible to use a rectifying deflector.

The fuel injection pump shown in FIG. 5 was developed to cope with such a case, and a pipe body 13 is screwed and fixed to the part of the pump housing 1 facing the suction/discharge hole 4, and the inside thereof is fixed. Fuel supply hole 1
4, and the suction and exhaust hole 4 of the fuel supply hole 14.
A cylinder 15 is attached to the side end. In this fuel injection pump, the cut-off jet flow can be rectified by the cylindrical body 15, so cavitation erosion in the plunger etc. can be reduced compared to a pump simply provided with a repulsion screw. .

[Problems to be Solved by the Invention] However, compared to the one using the rectifying deflector 10, the rectifying effect is low and there is almost no energy reduction effect. For this reason, there has been a problem in that cavitation erosion gradually progresses on the outer periphery of the plunger 5 over a long period of time.

[Purpose of the invention] This invention was made in consideration of the above-mentioned circumstances, and even in cases where the fuel supply hole or fuel discharge hole and the intake and exhaust hole must be placed opposite each other, the fuel It is an object of the present invention to provide a fuel injection pump that can reliably prevent cavitation erosion in the plunger 5 and the suction/discharge hole without interfering with the supply or discharge of fuel.

[Structure of the device] In order to achieve the above object, this device forms a tapered hole portion at the end of the suction/discharge hole on the pump housing side, the diameter of which gradually increases as it goes toward the pump housing side. A stopper is provided in the use hole to close the hole, and a tapered part with a smaller taper than the taper hole is placed on the surface of the stopper facing the intake/exhaust hole so that the gap between the intake/exhaust hole is at the tip of the tapered part. The fuel holes are arranged and formed so as to gradually increase in size from the side toward the proximal end, and one end faces the fuel hole between the plug and the pump housing and at least one of the inside of the plug. A communicating path is formed in which the opening facing the suction/discharge hole is located on an extension along the taper of the tapered hole, and the other end is open in the surface facing the suction/discharge hole. The main feature is that the extended portion of the opening along the communication path is located outside the suction/exhaust hole.

[Function] When the cut-off jet passes through the gap between the taper portion and the taper hole, its injection energy is weakened and the flow is rectified. Therefore, cavitation erosion is prevented.

In addition, the cut-off jet ejected from the suction and exhaust holes is
Although it hits the stopper and is reflected, a part of the cut-off jet flows through the communication path to the fuel because the opening of the communication hole is located on the extension of the tapered hole of the intake and discharge hole. It enters the hole and is attenuated there. The attenuated cutoff jet is reflected inside the fuel hole and passes through the communication path toward the plunger barrel. At this time, since the extended portion of the communicating passage is located outside the suction/discharge hole, the cutoff jet returning from the communication passage does not enter the suction/discharge hole.

Note that fuel flows between the fuel hole and the intake/discharge hole via a communication path.

[Example] An example of this invention will be described below with reference to FIGS. 1 and 2.

In FIGS. 1 and 2, reference numeral 21 indicates a pump housing. This pump housing 21
A cylindrical plunger barrel 22 is inserted inside. This plunger barrel 22 is
Its upper end is sealed by a lid 23 and is fixed to the pump housing 21 with bolts 25 via the lid 23 and valve holder 24 . Furthermore, a fuel reservoir chamber 25 is formed in an upper portion between the plunger barrel 22 and the pump housing 21 by forming an annular recess in the pump housing 21. This fuel storage chamber 25
Two suction/exhaust holes 26, 26, which communicate the fuel reservoir chamber 25 with the inside of the plunger barrel 22, are formed at a distance of 180 degrees in the circumferential direction on the side wall of the plunger barrel 22 facing the fuel storage chamber 25. This suction/discharge hole 26 has an inner straight hole portion 26a and a tapered hole portion 26b whose diameter gradually increases from the inside toward the outside.
It is composed of.

Further, a plunger 27 is slidably inserted into the plunger barrel 22. This plunger 27 is for pressurizing fuel in a compression chamber 28 formed by its upper surface, the lower surface of the lid body 23, and the inner periphery of the plunger barrel 22 and sending it to a fuel injection nozzle (not shown). It is moved upwardly via a tappet 29 by a cam (not shown) and downwardly moved by a plunger spring 30. Further, a lead 27a and a lead 2 are provided on the outer periphery of the plunger 27.
A vertical groove 27 extending from 7a to the tip surface of the plunger 27
b is formed.

Then, when the plunger 27 is moved upward by the cam and the outer periphery of the plunger 27 closes the suction/discharge hole 26, the fuel in the compression chamber 28 is pressurized. When the pressure of the fuel becomes higher than the set pressure of the spring 31a of the check valve mechanism 31 provided in the valve housing 24, the fuel passes through the check valve mechanism 31, the passage 32, and the pipe (not shown) to the fuel injection nozzle. Sent.

During the upward movement of the plunger 27, the lead 2
When 7a faces the suction/discharge hole 26, the fuel in the compression chamber 28 flows out into the suction/discharge hole 26 via the vertical groove 27b and the lead 27a, and then flows from there into the fuel reservoir chamber 25.
It flows out as a cut-off jet. Compression chamber 28
When the fuel inside flows out into the fuel reservoir chamber 25, the substantial pressurization of the fuel by the plunger 27 ends. Note that when the pressure inside the compression chamber 28 decreases due to the outflow of fuel, the fuel inside the pipe etc. mentioned above flows back into the compression chamber 28 via the passage 34 and the check valve mechanism 33, and the inside of the pipe etc. The pressure is reduced to the set pressure by the spring 33a of the check valve mechanism 33.

Further, when the plunger 27 is moved downward by the plunger spring 30, the fuel in the fuel reservoir chamber 25 is drawn into the compression chamber 28 through the intake/discharge hole 26, the lead 27a, and the vertical groove 27b.

Incidentally, the amount of fuel supplied by the plunger 27 is increased or decreased by rotating the plunger 27 forward or backward by a rack 35 via a pinion 36.

By the way, when the cut-off jet flows through the suction/discharge hole 26, the pump housing 21 and the plunger 2
7th class is damaged. Therefore, in this embodiment, damage is prevented by the following configuration.

That is, a deflector 37 is provided on the side wall of the pump housing 21 facing one suction/exhaust hole 26 . The deflector 37 includes a threaded portion 37a screwed and fixed to the pump housing 37, and a protrusion 37b formed on the distal end surface of the threaded portion 37a so that its axis coincides with the axis of the suction/discharge hole 26. At the distal end, there is a tapered part 3 that gradually becomes smaller in diameter as it goes from the proximal end to the distal end.
7c is formed. This tapered portion 37c is
An annular gap 3 is formed in the tapered hole portion 26b of the suction/discharge hole 26.
8, and its degree of taper is set smaller than the degree of taper of the tapered hole portion 26b of the suction/discharge hole 26. Therefore, the gap 38 between the tapered portion 37c and the tapered hole portion 26b is
The size gradually increases from the compression chamber 28 side toward the fuel reservoir chamber 25 side.

Further, a tube body 39 having a bottom portion 39a is screwed and fixed to the side wall of the pump housing 21 facing the other suction/discharge hole 26. This pipe body 39 is for supplying fuel to the fuel storage chamber 28, and its inner hole (fuel hole) 39b is connected to a fuel pump (not shown) through a pipe joint 40 and a pipe (not shown).
It is connected to the. Further, a plug 41 that closes the inner hole 39b is fixed to the opening at the tip of the inner hole 39b by means such as shrink fitting or welding.

This plug body 41 is made of steel, and a blind hole 4 having the same diameter as the inner hole 39b of the tube body 39 is formed on the rear end surface.
1a is formed, and the axis is connected to the suction and exhaust hole 2 on the tip surface.
A protrusion 41b is formed which is aligned with the axis of 6. A tapered portion 41 is provided at the tip of this protrusion 41b.
c is formed. This tapered portion 41c is inserted into the suction/discharge hole 26 with an annular gap 42, and the degree of taper is the same as that of the taper hole portion 26 of the suction/discharge hole 26.
It is set smaller than b. Therefore, the size of the gap 42 (the tapered part 41c and the tapered hole part 26
b) is from the compression chamber 28 side to the fuel reservoir chamber 25
It gradually becomes larger as it goes to the side.
Further, the tip end surface of the plug body 41 has a protrusion 41 extending from the outer circumferential side.
It is gradually concave toward the b side, and a communication hole (communication path) 41d is formed in a portion of the distal end surface adjacent to the protrusion 41b. This communication hole 41d is for communicating the blind hole 41a and the fuel reservoir chamber 25, and in turn, for communicating the inner hole 39b of the tube body 39 and the fuel reservoir chamber 25,
Its axis is inclined with respect to the axis of the suction/discharge hole 26, and if the communication hole 41d is extended along the axis, the extended portion will touch the large diameter side edge of the tapered hole portion 26b or be located outside of it. It is now located in As is clear from this point, in this invention, the extended portion of the communication hole 41d is
6 includes the case where the extended portion of the communication hole 41d touches the suction/discharge hole 26 (the tapered hole portion 26b thereof). Moreover, the opening of the communication hole 41d facing the fuel storage chamber 25 is the tapered hole 26b.
It is arranged so that it is located on the extension along the taper of.

Although not shown, the fuel discharge hole is located in the pipe body 3.
It is formed on the side wall of the pump housing 21 at a distance of 90 degrees in the circumferential direction from the location where the groove 9 is provided.

In the above configuration, the suction/discharge hole 26 on the pipe body 39 side
The cut-off jet flowing through the gap 42 has its injection energy reduced and is rectified while flowing through the gap 42 , and is dispersed into the fuel reservoir chamber 25 when it hits the tip surface of the stopper 41 . Therefore, the pump housing 21, plunger 27, etc. will not be damaged.

Further, a part of the cut-off jet reflected from the tip surface of the plug body 41 enters the suction/discharge hole 26 again, and this point is also taken into consideration in this invention. That is, the cut-off jet ejected from the suction/discharge hole 26 hits the tip surface of the stopper 41 and is reflected, but since the opening of the communication hole 41d is located on the extension of the tapered hole 26b, the cut-off jet is Not all of it is reflected, and some of it is reflected through the communication hole 41d.
and enters into the inner hole 39b. Therefore,
The amount of reflection of the cut-off jet can be reduced,
The plunger 27 is caused by the reflected cut-off jet.
damage can be reduced. Moreover, the cut-off jet that has entered the inner hole 39b through the communication hole 41d is reflected there and tries to head toward the suction and exhaust hole 26 through the communication hole 41d again, but the extended portion of the communication hole 41d is a tapered hole. Part 26b
Since the cut-off jet jet is ejected into the fuel reservoir chamber 25 through the communication hole 41d again, it does not enter into the suction/discharge hole 26. Therefore, damage to the plunger 27 can be more reliably prevented.

In addition, although the inner hole (fuel hole) 39b of the tube body 39 was closed with the plug 41, the communication hole 41 was closed in the plug 41.
d, the plug body 41 does not pose any problem in terms of fuel supply. Note that since the flow of fuel in the inner hole 39b is very slow, no problem will occur even if the communication hole 41d is made smaller than the inner hole 39b.

In the above embodiment, the inner hole 39b serving as the fuel supply hole among the fuel holes is opposed to the suction/discharge hole 26, but the fuel discharge hole for discharging fuel is used as the fuel hole. The fuel discharge hole may face the suction/discharge hole, or both may face the suction/discharge hole. In addition, although the pipe body 39 is screwed and fixed to the pump housing 21 and the plug body 41 is fixed to the inner hole 39b of the pipe body 39, a fuel hole is directly formed in the pump housing and the plug body is attached thereto. You can. Further, although the communication hole 41d is formed inside the plug body 41, a groove may be formed in at least one of the inner periphery of the pipe body and the outer periphery of the plug body to communicate the inner hole and the fuel reservoir chamber. This also applies when the stopper is attached directly to the pump housing.

[Effects of the invention] As explained above, according to the fuel injection pump of this invention, a plug is provided in the fuel hole facing the suction and discharge hole, and a gap is provided in the taper hole of the suction and discharge hole in the plug. While forming a tapered part to be inserted, a communication passage communicating between the inside and outside of the fuel hole is formed between the plug body and the pump housing or inside the plug body, and the opening of the communication hole is formed in the taper hole part. Located on the extension,
In addition, since the communicating passage is arranged so that the extended portion of the communicating passage is separated from the suction/discharge hole, there is no choice but to arrange the fuel supply hole or the fuel discharge hole and the suction/discharge hole to face each other. Also, effects such as being able to reliably prevent cavitation erosion in the plunger and the suction/exhaust hole can be obtained without inhibiting the supply or discharge of fuel in any way.

[Brief explanation of the drawing]

Figures 1 and 2 show an embodiment of this invention, with Figure 1 being an enlarged front sectional view of the main parts, Figure 2 being a front sectional view of the whole, Figures 3, 4, and 2. FIG. 5 is an enlarged front sectional view showing the main parts of a conventional fuel injection pump. 21...Pump housing, 22...Plunger barrel, 26...Suction/exhaust hole, 26b tapered hole portion,
27... Plunger, 27a... Lead, 27b
... Vertical groove, 28 ... Compression chamber, 39b ... Inner hole (fuel hole), 41 ... Plug body, 41c ... Taper part,
41d...Communication hole (communication path), 42...Gap.

Claims (1)

[Scope of utility model registration request] a pump housing having a fuel hole opening on an inner wall surface; a plunger barrel built into the pump housing and having a suction/discharge hole facing the fuel hole formed in a side wall; and a plunger barrel slidably inserted into the plunger barrel. In a fuel injection pump equipped with a plunger having a lead formed on its outer periphery, a tapered hole portion whose diameter gradually increases toward the pump housing side is formed at an end of the suction/discharge hole on the pump housing side, A plug body is provided in the fuel hole to close the hole, and a surface of the plug body facing the suction/discharge hole,
A tapered portion having a smaller taper degree than the tapered hole portion is arranged and formed such that the gap between it and the suction/discharge hole gradually increases from the distal end side to the proximal end side of the tapered portion. , a communication passage between the plug body and the pump housing and at least one of the inside of the plug body, one end of which opens on a surface facing the fuel hole, and the other end opens on a surface facing the suction/discharge hole; , and this communication path,
The opening facing the suction/discharge hole is located on an extension along the taper of the tapered hole, and the extension portion of the opening along the communication path is located on the outside of the suction/discharge hole. fuel injection pump.